US2829731A - Combination muffler and exhaust gas after-burner and method of burning exhaust gases - Google Patents

Description

April 8, 1958 w. CLAYTON 2,329,733

COMBINATION MUFFLER AND EXHAUST GAS AFTER-BURNER AND METHOD OF BURNING EXHAUST GASES 5 Sheets-Sheet 1 Filed Dec. 20, 1954 INVENTOR. WILLIAM CLAYTON fl w ATTORNEYS Apnl 8, 1958 w. CLAYTON 2,29,731 COMBINATION MUFFLER AND EXHAUST-GAS AFTER-BURNER AND METHOD OF BURNING EXHAUST GASES Filed Dec. 20, 1954 5 Sheets-Sheet 2 ATTORNEYS 5T pm? MINI/TE VELOCITY IN COMBINATION MUFFLER AND EXHAUST GAS AFTER-BURNER AND METHOD OF BURNING EXHAUST GASES 5 Sheets-Sheet 3 Apr-ii 8, 1958 w. CLAYTON 2,829,?33

Fil ed Dec. 20, 1954 HORSEPO WER SEC DARY Al RE VOLUT/ONS PER MINUTE V 2/ INVENTOR.

/ WILLIAM CLAYTON l8 ZMW/ 247M141 ATTOR NEYS W. CLAYTON COMBINATION MUFFLER AND EXHAUST GAS AFTER-BURNER AND METHOD OF BURNING EXHAUST GASES 5 Sheets-Sheet 4 Filed Dec. 20, 1954 l I E TN l zetumn Efimat RN 0 m T V C M m L L W ATTORN EYS w. CLAYTON 2,829,731

ND EXHAUST GAS AFTER-BURNER April s, 1958 COMBINATION MUFFLER A 7 AND METHOD OF BURNING EXHAUST GASES 5 Sheets-Sheet 5 Filed Dec. 20, 1954 INVENTOR ATTORNEYS III United States Patent COMBINATION MUFFLER AND EXHAUST GAS AFTER-BURNER AND METHOD OF BURNING EXHAUST GASES William Clayton, El Monte, Calif.,. assignor, by mesne assignments, to Barkelew Manufacturing Company, Los Angeles, Calif., acorporation of California Application December 20, 1954, Serial No. 476,137

24 Claims.- (Cl. 183-6) The present invention relates to engine mufflers, and, more particularly, to a muffler construction including a mufiler section for deadening the noiseof the explosions of the enigne, and an after-burner section for efiecting substantially complete combustion of the combustible constituents of the exhaust gases before dischargingthe same to the atmosphere.

The invention further relates to a method of disposing of the unburned combustible constituents of exhaust gases.

The present application is a continuation-in-part of my prior application, Serial No. 437,964, filed June 21, 1954, now abandoned.

The exhaust gases discharged from internal combustion engines, for example, include carbon dioxide,v carbon monoxide, hydrogen, Water'vapor, partially oxidized hydrocarbons, and, occasionally, some free carbon. Among the constituents enumerated, carbon monoxide and the partially unburned hydrocarbons are the most objectionable, the former because it is extremely poisonous to humans and other animal life, and the latter because of their unpleasant odor. The unburned hydrocarbons are also detrimental to vegetation, and, in View of the fact that they react with nitrogen and ozone, are believed to be, at least in part, responsible for causing the formation of an obnoxious atmospheric condition currently prevailing in some cities and referred to as smog or acid vapor.

Free carbon, carbon monoxide and the partially oxidized hydrocarbons found in exhaust gases are combustible and the principal object of the present invention is to prevent their discharge into the atmosphere and thereby alleviate the smog condition referred to above. This is accomplished by mixing the exhaust gases with the proper amount of air to eflect complete burning of the combustible constituents ofthe exhaust gases so that the discharge from the mufller is in the form of a 'gas that is harmless to animals as well as vegetable life. In this connection, the present method comprises the segregation of a minor portion of the total of the exhaust gases discharged from the engine, and the mixing of primary air with the segregated exhaust gases to form a pilot flame by spontaneous combustion, and the mixing of the remainder of the exhaust gases with secondary air in the presence of the pilot flame in order to efiect complete combustion thereof.

it has been found that, although the exhaust gases from motor vehicle engines contain varying amounts of combustible constituents, depending uponload conditions, acceleration, deceleration, etc., it is possible with the present combination muifler and after-burner to satisfactorily dispose of the combustible constituents, even under engine idling conditions, provided the exhaust gases are sufliciently hot. To this end, the mufller is designed so that the primary air to be mixed with the segregated portion of the exhaust gases is preferably pre-heated before being mixed with the segregated gases so that a pilot flame is formed that is adequate for eflecting flame propagation sufficient to cause burning of the remainder of the exhaust gases upon mixing with a proper amount of secondary air. The principal factor in connection with the burning of the combustible constituents in the exhaust gases is to bring the initial temperature of the primary air and gas mixture to a point that is high enough for combustion to support itself, namely, about 940 1100 E, whereupon the flame will rapidly proceed through the mixture and will be sustained once it has been initiated and proper temperature conditions are maintained.

It has been proposed to dispose of the unburned combustible constituents of exhaust gases by employing spark plugs, igniters, permanent fuel-sustained pilot flames, catalysts, etc., but none of these expedients alone has proved to be effective in actual practice for their intended purposes. The present invention solves the problem by segregating a minor portion of the exhaust gases and utilizing the velocity thereof to induce the flow of primary air to the point of discharge of the segregated gases to effect the spontaneous combustion of the mixture and thus provide a pilot flame. "Phevelocity of the remainder of theexhaust gases is utilized to induce the flow of secondary air for mixture therewith to effect ignition of such mixture by the pilot flame. In the present mumer construction, both the primary air and secondary air are induced to enter the mufller by venturi action produced by suitable primary and secondary injector nozzle constructions embodied within the mulfler casing. The invention also contemplates pro-heating of the. primary and/or secondary air by heat derived from the exhaust gases themselves, and'the imparting of turbulence to the exhaust gases and/or air to produce a more thorough mixture of the same.

The invention further involves the discovery that the pilot flame can be established' and maintained at a lower temperature with less primary air than with the stoichiornetric' air-fuel'ratio for complete combustion. For example, by limiting the primary air for the pilot flame to about one-third the stoichiometric air-fuel ratio, the pilot flame'can' beestablished at a temperature of about to 200 F. below that required to initiate combustion of the" secondary air and exhaust gases in the afterburner section of the muffler. The establishment of the pilot flame is further facilitated by the use of any suitable catalytic material.

In order to" increase the effectiveness of the present mufiler device during periods when the exhaust gases are not hot enough to support spontaneous combustion, an

automatic electrical ignition device may be'incorporated therewith. Thus, the invention further contemplates the use of a spark plug in the after-burner section, which is subject'to thermostatic control. in one form, the spark plug provides a continuous spark from the time the engine is started until the exhaust gases in the after-burner section reach a temperature of about 1200 F., which is higher than necessary to provide a pilot flame by spontaneous combustion. In another form, the spark plug is maintained inactive after the engine is started until the engine exhaust gases reach a temperature of about 400 F, and is again rendered inactive when the temperature reaches about 1200 F. This delay in spark initiation prevents the hazard of explosion that might otherwise exist in certain mufflers during a cold start, due to a rich'exhaust, i. e., a large proportion of raw gasoline in the exhaust gases. On the other hand, in the interest of air pollution control, it is desirable to effect complete burning of the exhaust gases as soon as possible, Without the delay incident to the exhaust gases reaching a temperature'highenough to be burned by a pilot flame produced by spontaneous combustion.

While, as indicated, combustion of the burnable com stituents of engine exhaust gases may be effected spontaneously under nearly all operating conditions, it is desirable, as when the engine idles for prolonged periods, particularlyin cool weather, to employ positive means as a precautionary measure to insure ignition of said constituents. It is also desirable in certain instances to provide positive ignition means which will be continuously operative Whenever the temperature of the gases in the after-burner section falls below about 1200 F, although, as previously stated, spontaneous combustion of the burnable material present in the exhaust gases can be effected at temperatures as low as 940*1100" F. A spark plug controlled by a thermostat switch that is normally closed until a gas temperature of about 1200 F. is reached, or a thermostat switch that will close at about 400 F. and open at about 1200 F., will provide the desired results. Such switch is preferably connected in circuit with the engine ignition switch so that no current is wasted through the muffler spark plug after the engine ignition switch has been opened to stop the engine.

Accordingly, the principal object of the invention is to provide a mutiler construction that will eliminate the discharge of objectionable gases into the atmosphere.

Another object is to provide a muffler of the character mentioned that will function satisfactorily and produce substantially complete combustion of the burnable constituents in the exhaust gases under various engine operating conditions, without creating undue back pressure on the engine.

A further object is to provide a combined muffler and after-burner for exhaust gases, including means for adjusting the supply of primary air for maintaining a suitable pilot flame and for also adjusting the secondary air to effect substantially complete combustion of the unburned gases, whereby to meet the operating requirements of different engines.

A still further object is to provide a muffler for motor vehicle engines, wherein the possiblity of explosion of the gases in the mufller is eliminated either by positive ignition means and/ or by automatically maintaining a pilot flame that is attainable even under engine idling or deceleration conditions for igniting any rich mixture of exhaust gases that enters the muffler.

Still another object is to provide a combined mufiler and after-burner for exhaust gases, which may be easily assembled and taken apart for cleaning or for repair or replacement of parts.

Yet another object is to provide a combined muffler and after-burner for exhaust gases which will positively insure complete combustion of the burnable constituents in the exhaust gases of an internal combustion engine, regardless of variations in the exhaust gas temperature.

A further object is to provide a combined mufller and after-burner for exhaust gases which will positively ignite the burnable constituents of said gases under conditions incapable of maintaining a pilot flame by spontaneous combustion.

A still further object is to provide automatic means for igniting the combustible constituents of exhaust gases which is rendered inactive when said gases reach a temperature high enough to provide a pilot flame by spontaneous combustion.

Other and further objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Fig. l is a longitudinal sectional view through one form of mufiier constructed in accordance with the principles of the present invention, and wherein the primary air is heated by the exhaust gases and the secondary air is relatively unheated;

Fig. 2 is a left end elevational view of the mufller shown in Fig. 1, and, particularly illustrating the damper construction for varying the volume of primary air drawn into the mutfler;

Fig. 3 is a vertical sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is a vertical sectional view taken on the hue 4-4 of Fig. l, and, particularly illustrating the ports in the muffler through which secondary air is admitted, together with an adjustable damper ring for adjusting the volume of secondary air admitted to the mufller;

Fig. 5 is an exterior view of the muffler shown in Fig. 1;

Fig. 6 is an enlarged fragmentary sectional view of a modification of the muffler shown in Fig. 1 and including vanes for imparting centrifugal turbulence to the secondary air;

Fig. 7 is a fragmentary sectional view taken on the line 7-7 of Fig. 6;

Fig. 8 is a graph illustrating the relativevelocity of the primary and secondary air that is drawn into the muffler at various horsepower loads and engine speeds;

Fig. 9 is a longitudinal sectional view through a moditied form of mufller in which both the primary and secondary air are pre-heated;

Fig. 10 is a vertical sectional view taken on the line 10-10 of Fig. 9;

Fig. 11 is a fragmentary sectional view of a further modification of the muflier shown in Fig. 9;

Fig. 12 is a fragmentary sectional view of still another modified form of mufiler of the type shown in Fig. 9, but wherein the secondary air is introduced into the mufiler without any substantial pre-heating;

Fig. 13 is a fragmentary, enlarged, end elevational view of a further modified form of muffler including an electrical igniter;

Fig. 14 is a staggered longitudinal sectional view taken on the line 14-14 of Fig. 13 looking in the direction of the arrows;

Fig. 15 is an enlarged sectional view taken on the line 15-15 of Fig. 14;

Fig. 16 is a diagrammatic view of one type of circuit which may be employed to effect automatic control of the electrical igniter so that it is deenergized upon attainment of a predetermined maximum temperature in the after-burner section of the mufller; and

Fig. 17 is a similar view of another circuit which may be employed to effect automatic control of the electrical igniter so that it is energized upon attainment of a predetermined minimum temperature and deenergized upon attainment of a predetermined maximum temperature.

Referring now to Figs. 1 to 5, inclusive, of the drawings, the combination mufller and after-burner is generally identified by the numeral 1 and includes a cylin drical sheet metal casing 2 closed at its inlet end by an end plate 3 and closed at its outlet end by an end plate 4. The end plate 3 has a central opening in which an inlet member 5 is mounted for connecting the same to an engine exhaust connection 6 shown in dot and dash lines. The end plate 4 also has a central opening in which an outlet member 7 of relatively larger diameter than the inlet member 5 is mounted, and which serves as a means for connecting the muffler to a tail pipe 8 shown in dot and dash lines. The member 7 extends a short distance inwardly beyond the end plate 4 and has a flared portion 9 to facilitate the exit of gases from the mufiler.

A frusto-conical member 10 is mounted in the casing 2 at a point approximately medially of the length thereof. The cone or shell 10 cooperates with the end plate 3 to provide a chamber 11 in the mufller 1 to receive hot exhaust gases through the inlet 5. A second frustoconical member 12 is mounted in the casing 2 in longitudinally spaced relation to the cone 10 and has a cylindrical extension 13 of substantially larger diameter than the adjacent open end 14 of the cone 10. The cone 12 cooperates with the end plate 4 to provide a combustion chamber 15, in which substantially complete combustion of the exhaust gases takes place. The chamber 11 is adapted to contain conventional or suitable baflies (not shown) for silencing the explosions of the engine, the bafile means being omitted from the drawings in the interest of simplicity. As indicated in Fig. 1 the muffler 1 includes a mufller section that extends from the end plate 3 to the cone 10, and an after-burner section that extends from the cone to the end plate 4.

The end plate 3 is provided with a suitable number of openings, depending upon the size of the mulfler, in which one end of one or more primary air conduits or tubes 16 is secured. In the present device three conduits 16 are shown, but it is to be understood that any required number of tubes may be employed to supply ample air for combustion of a segregated portion of the exhaust gases to maintain a pilot flame by spontaneous combustion, as will be explained more fully hereinafter. The opposite end of the conduits 16 extend into suitable openings in a cylindrical shroud 17 surrounding a portion of a tapered or converging ram-type tube 18. The tube 18 is actually in the form of an elongated frustoconical shell and is connected with the shroud 17 in such manner that it is maintained in concentric relation with the mufller inlet 5. A nozzle member 19 projects rear- Wardly from the shroud 17 and includes a cylindrical portion 20 that merges into a converging portion 21 adjacent the inner or discharge end 22 of the tube 18. The portion 21 is frusto-conical and generally complemental in shape to the conical shell member 10. The member 19 also has a relatively small cylindrical portion 23 spaced a short distance from the discharge end 22 of the tube 18. The portion 23 has an inner cylindrical nozzle surface 24 that merges into an outwardly flaring nozzle surface 24a which terminates within the cylindrical extension 13 of the cone 12. A dilfuser D is mounted on the shroud 17 and comprises an annular member having vanes d twisted to an angle of about 45 relative to the axis of the mutfler and imparting turbulence to the exhaust gases as they flow through the chamber 11 toward the cone outlet 14.

A damper plate 25 is mounted upon the end plate 3 and is provided with primary air inlet openings 26, one for each tube 16. The damper plate 25 is further provided with arcuate slots 27 for the reception-of screws 28 that are threaded into suitable openings in the end plate 3. The damper plate 25 is rotatable upon the inlet member 5 so that it can be angularly adjusted to control the amount of primary air that enters the conduits 16 through the openings 26. The slots 27 provide for the desired adjustment and the screws 28 are adapted to be tightened to lock the damper plate 25 in any se lected position of adjustment. The plate 25 is preferably adjusted so that less air is admitted than required to effect complete combustion of the exhaust gases segregated by the tube 18, so that the air-fuel mixture is rich, as will be explained more fully hereinafter.

The casing 2 is provided with a series of circumferentially spaced openings 29 for admitting secondary air into a space 30 between the conical shells 10 and 12. The amount of secondary air entering the space 30 is regulated by a damper ring 31 rotatably mounted upon the exterior of the casing 2 and provided with openings 32 which can be positioned to overlap the casing openings 29. The damper ring 31 is provided with a pair of ears 33 and a bolt 34 extends through holes in said ears for tightly clamping the damper ring 32 in any desired position of adjustment. that the amount of secondary air permitted to enter the casing openings 29 can be controlled by simply adjusting the damper ring 32 circumferentially relative to the casing 2. The ring 32 is preferably adjusted so that a substantial excess of air is admitted to assure a lean mixture and to effect complete combustion.

As a general proposition, due to the various combustible constituents of the exhaust gases, such as nitrogen, hydrogen, ethane, ethylene, methane, acetylene, etc., the stoichiometric air-fuel ratio, or the ratio of air to fuel It will be understood required for complete oxidation ot said combustible constituents to carbon dioxide and water is about 14.7:1 to 16:1. If the pressure is one atmosphere and a rich mixture exists wherein the air-fuel ratio is about 4.121 to 6.5: or approximately one-third the stoichiometric air volume, the ignition temperature is about 940 to 970 F. If the mixture is changed to one that is very lean through the presence of excessive air, say to a mixture where the air-fuel ratio is about 25:1 to 33.5: 1, or about twice the stoichiometric air volume, the ignition temis increased to about 1110-1150 F. Thus, as the mixture of air and exhaustgases varies from a rich mixture to .a very lean mixture the ignition temperature will correspondingly vary. Hence, by adjusting the primary air so that a rich mixture is produced with the gases segregated by the tube 18, a pilot flame F can be provided that is initiated at a temperature well below that required to initiate the main flame in the chamber 15 in the presence of a lean mixture.

The temperature of the exhaust gases entering the muffler 1 will vary from 550 F. to 1400 F. even during idling of the engine. A temperature of about 940 F. is required if the mixture of primary air and exhaust gases is rich, as noted above, to effect spontaneous combustion thereof to provide a pilot flame F. On the other hand, if the air-fuel ratio is lean, i. e., an excess of air is present, a substantially higher temperature of about 1100 F. is required in order to produce a pilot flame by spontaneous combustion. Accordingly, it is highly advantageous to restrict the air supply so that it is insuflicient to effect complete combustion of the minor portion of segregated exhaust gas, but is suflicient to support and maintain the pilot flame F. In the construction described hereinbefore, the tube 18 is surrounded by the incoming exhaust gases so that it does not lose heat by radiation, but, on the contrary, is itself maintained in a heated condition by the exhaust gases in contact with both the interior and exterior thereof. Moreover, the conduits 16 are also heated by those exhaust gases which do not pass through the tube 18. Thus, the primary air in the conduits 16 is heated to a temperature as high as possible and the portion of the exhaust gases segregated by the tube 18 isalso maintained at as high a temperature as possible.

The volume of exhaust gases that are segregated and passed through the tube 13 under various engine operating conditions is controlled by the diameter of the discharge end 22 of said tube. This diameter is preferably such that it provides a cross sectional areas that is equal to about 10% of the cross sectional area of the inlet opening 5. This ratio theoretically provides for segregation of about 10% of the exhaust gases for flow through the tube 18 with the remaining passing through the chamber 11 around the outside of the tube 18 and constituting a substantial reservoir of heat for keeping the tube 18 hot and for heating the primary air entering through the conduits 16. However, gas flowing over the end of the nozzle portion 23 produces a secondary jet and also assists in inducing flow of primary air through the conduits 16. Both the primary and secondary jets cooperate with the conical members 10 and 12 to induce the entrance of secondary air through the openings 29 and 32 into the space 30, so that the mixture of exhaust gases and secondary air thus produced can be ignited by the pilot flame F. Complete combustion of the combustible constituents of the exhaust gases then occurs in the chamber 15 of the after-burner section.

The tapered tube 18 utilizes the ram-eifect of the exhaust gases to induce the entrance of air into the mufiier and makes it possible to accomplish more positive pressure and velocity control at the discharge end 22 of the tube 18. The structure shown is particularly useful in maintaining consistent performance with smaller engines.

In actual operation, the pilot flame F is present at the nozzle portion 23 during partial or full load engine con ditions. Flash burning takes place at the nozzle portion 23 and in the combushion chamber under deceleration conditions or at any other time when the exhaust gases are rich in unburned hydrocarbons. Flame propagation and continuous burning occurs after deceleration and dur ing extended periods of idling. Such burning occurs notwithstanding that the temperature of the exhaust gases entering the muffler may drop from 1400 F. to about 550 F. during the idling period. Under actual test with an exhaust gas entrance temperature of about 600 F., and exit temperatures of about as high as 1400 F. has been pro duced as a result of reignition or after-burning of the exhaust gases in the chamber 15. Thus, it will be seen that under nearly all operating conditions no difiiculty is experienced in maintaining temperatures at the discharge of the nozzle 19 and in the chamber 15, sufiiciently high to maintain spontaneous ignition of the exhaust gases during idling and deceleration.

During acceleration, the exhaust gases are not so rich in combustible hydrocarbons as during conditions of deceleration, and even when the exhaust gas temperatures drop below that required to maintain the pilot flam F. Nevertheless, the flame is quickly restored since the temperature of the gases increases very rapidly when the engine is under load. During actual tests, carbon monoxide measurements have been made with an M. S. P. mine analyzer, under partial load, full load, deceleration, acceleration and idling conditions, and established that no detectable carbon monoxide was present, thereby indicating that substantially complete combustion was effected. The significance of the foregoing will be more fully appreciated in the light of the wide range of average hydrocarbon values in standard engine exhaust systems as furnished by the Air Pollution Board of Los Angeles, California. Thus, under engine acceleration the hydrocarbon present is 275 (parts per million); with the engine operating from cruising speed to full load, 225 to 250 p. p. m.; engine deceleration 5000 p. p. m.; and engine idling 750 to 1500 p. p. m. (depending on carburetor setting). It will thus be observed that the greatest proportion of the hydrocarbon is present in the exhaust gases during conditions of engine deceleration. Actual observation has shown that after deceleration, both the pilot flame F and burning of the exhaust gases in chamber 15 will continue for periods of 10 to minutes, depending on the initial temperature at the start of deceleration and the rapidity with which the exhaust gases entering the muffler cool down.

One of the important features of the present mufiler construction is that it is capable of functioning satisfactorily under extreme variations in engine operating conditions, that is, from idling with exhaust gas temperatures at about 550 to substantially full load conditions with temperatures at l500, without creating undue back pres sure on the engine, as well as inducing the introduction of the required volume of primary air and secondary air, notwithstanding the variations in the volume and velocity of the exhaust gases under such wide variations in engine operating conditions.

Fig. 8 is a graph which indicates the variation in the velocity, and hence volume of the primary air and secondary air induced to support combustion of the pilot flame and to support combustion of the major portion of the exhaust gases, respectively, at various engine speeds in R. P. M. It will be noted that the secondary air curve shows a very high increase in velocity as the R. P. M. of the engine is increased. For example, with an increase in engine speed from 1450 to 1700 R. P. M., the velocity of the primary air increased only from 100 to 198 feet per minute, whereas the velocity of the secondary air increased from 540 to 1865 feet per minute. The graph also includes a curve marked Horsepower to show the relative power that was developed at the various engine speeds. It will also be understood from the graph that the relative percentage of the total of the exhaust gases segregated by the tube 18 varies correspondingly to the induced air.

Figs. 6 and 7 illustrate a modified form of muflier construction diflering from that shown in Figs. 1 to 5 by the addition of radial vanes V disposed on an angle of 45 from the vertical between the conical shell members 10 and 12 for imparting a centrifugal, rotary motion to the secondary air as it is pulled into the chamber 15 by the action of the primary and secondary exhaust gas jets. More thorough mixing of the secondary air with the exhaust gases is effected as a result of the turbulence imparted to the secondary air before it is mixed with the exhaust gases. Fig. 6 also illustrates a catalyst C mounted in the nozzle portion 23 and consisting of a fine platinum or palladium wire provided for the purpose of facilitating initiation of the pilot flame F.

Figs. 9 and 10 illustrate a modified form of mufiier construction in which the secondary air is pre-heated before it reaches the combustion chamber or after-burner section. As is here shown, a casing 2' is closed at one end by an end plate 3 and at its opposite end by an end plate 4'. The end plate 3 has a central opening in which a cylindrical inlet member 5' is mounted and the end plate 4 has a cylindrical opening in which an outlet 7' is mounted, the latter including a flared portion 9 disposed inwardly of the end plate 4 and extending to the inner periphery of the casing 2, to facilitate the discharge of gases from the casing 2.

A cylindrical shell S having a conical end portion 10 is mounted within the casing 2 in concentric relation with the inlet 5. The shell S cooperates with the end plate 3' to provide a chamber 11 to receive hot exhaust gases from the engine (not shown). A frusto-conical shell member 12 is mounted in the casing 2 in longitudinally spaced relation to the conical portion 10, and has a cylindrical extension 13' of substantially larger diameter than the adjacent end 14' of the shell portion 10'. As in the previous forms of the invention described herein, the shell 12 cooperates with the end plate 4' to provide a combustion chamber 15' in which substantially complete combustion of the exhaust gases takes place. Also, chamber 11' is adapted to contain conventional or suitable bafiles (not shown) for reducing the noise level of the engine.

The end plate 3' is provided With a suitable number of openings in which one end of one or more primary air conduits 16' is secured. Three conduits 16' are presently employed, as best shown in Fig. 10, but it is to be understood that the number of conduits employed will vary with the size and requirements of a given mufiler. The opposite end of the conduits 16 extend into suitable openings in a circular plate 17a mounted upon a cylindrical tube 18. The tube 13 has a passageway 18 of uniform diameter extending therethrough and one end of said tube projects slightly into the inlet 5 and has a chamfered entrance 18a; whereas, its opposite end 22 terminates close to the entrance 13 of the combustion chamber 15'. The tube 18' is disposed concentric with the axis of the inlet 5' and is relatively thick-walled compared with the thickness of the casing 2., etc. Thus, the tube 18 has substantial body for retaining the heat of the exhaust gases so that heat may be stored in the tube and made available to maintain the pilot flame F by spontaneous combustion when the temperature of the exhaust gases is relatively low, as when the engine is idling. A nozzle member 19 includes a cylindrical portion 17 in which the plate 17a is mounted. The cylindrical portion 17' is substantially larger in diameter than the tube 18, whereby to provide a chamber 17b surrounding the inner end of the tube 18'. The cylindrical portion 17 merges into a relatively thick walled portion 19a including a cylindrical orifice 24 having a converging wall portion 21' on one side thereof and a flaring wall portion 24 on the opposite side thereof. The tube 18 has a tapered portion 18b confronting the converging wall portion 21. The

g nozzle member 19 terminates within the cylindrical section 13 of the shell 12.

The casing 2 is provided with air inlet openings 29 disposed adjacent the end wall 3', and a damper ring 31, similar to the ring 31 and having openings 32 is provided to adjust the volume of secondary air that enters an annular space A between the exterior of the shell S and the interior of the casing 2. The annular space A communicates with a conical space 30', disposed between the conical shell portions 10' and 12'. A damper ring 25', similar to the damper ring 25 is adjustably mounted upon the end wall 3' by screws 28 to adjust the amount of primary air that can enter the conduits 16.

The cross sectional area of the passageway 18" in the tube 18 is equal to about 10% of the cross sectional area of the inlet 5. The tube 18' cooperates with the nozzle member 19 in a manner similar to that described in connection with the tube 18' and nozzle member 19 of Fig. 1 for producing a jet for inducing the flow of primary air through the conduits 16'. The exhaust gases flowing through the chamber 11' and discharging through the end 14' of the shell S provide another jet for inducing a flow of secondaryair through the openings 29' and 32 intothe spaces A and 30' to provide secondary air to support combustion of the major portion of the exhaust gases upon ignition by the pilot flame F. It will be noted that the secondary airpassing through the annular space A is pro-heated by contact with the hot shell' S through which the major portion of the hot ex-' haust gases flow toward the chamber 15' in the afterburner' section'of the muffl'er 1. The preheating of the secondary air has the advantage of avoiding the delivery of relatively cool air in the vicinity of the pilot flame F and facilities combustion of the major portion of the exhaust gases.

The muffler shown in Figs. 9 and 10; functionsin substantially thesame manner to maintain a pilot flame F to effect substantially complete combustion of the combustible constituents of the exhaust gasespassing through the mufiler 1', in substantially the same manner described in connection with the mufller disclosed in Figs. 1 to 5.

Fig. 11 illustrates amodification of the muflier construction shown in Fig. 9, in that it includes vanes V between the conical portions 10 and 12, similar to the vanes V, for imparting turbulence to'the secondary air before it is mixed with the exhaust gases.

Fig. 11 also illustrates wire meshor perforated supports mounted in the nozzle portion 24" and'carrying cata-' lytic material C thereon for facilitating initiation of the pilotflame F through contact of the mixed air and exhaust gases therewith. Such material-may be copper oxide, iron oxide, manganese dioxide, cerium dioxide, or any other known suitable catalyst for promoting the oxidation of hydrocarbons.

Fig. 12 illustrates a further modification of the muffler construction shown in Fig. 9 in that it combines with the tube 18' and nozzle member 19, secondary air inlet means of the character embodied in the muffler disclosed in Fig. 1. In the interest of brevity the corresponding parts of Figs. 1 and 9 have been identified by the same reference numerals. It will be obvious from Fig. 12 that the primary nozzle jet produced by the exhaust gases passing through the tube 18 into the nozzle 19' will deliver primary air through the conduits 16' to support spontaneous combustion of the pilot flame F, and the secondary jet provided by the exhaust gases flowing through the opening 14' in the conical member 10 willinduce the flow of secondary air through the openings 29 and 32 into the space 30 between the conical shell members 10 and 12. The mufller shown in Fig. 12 thus combines the feature of pre-heating the primary air together with a tube and nozzle such as is shown in Fig. 9 with the introduction of relatively unheated secondary air into the combustion chamber 15, in the same manner as is embodied inthe muflier shown in Fig. 1.

Figs. 13 through 17 illustrate a combined muffler and after-burner, which incorporates an electrical ignition aid to insure ignition of theburnable constituents of the exhaust gases even under the extreme conditions mentioned earlier. This embodiment is constructed so that it may be quickly and easily assembled and disassembled for cleaning purposes or to remove and repair or replace parts.

Referring particularly to Fig. 14, the combination muffler and after-burrier is generally designated by the numeral 40 and includes a cylindrical forwardly located Section X and a rearwardly located Section Y secured together in telescoped relation. Section X comprises a cylindrical sheet metal casing 41 and a cylindrical shell 42 provided with a plurality of perforations 43 mounted within the casing 41 in concentric relation therewith, the shell 42 extending slightly beyond the casing 41 at its rearward end. A spacer ring 44 is secured, as by welding, between the casing 41 and shell 42 at their forward ends and a spacer ring 46 is similarly secured between the rearward end of casing 41 and the portion of the outer surface of shell 42 in vertical alignment therewith leaving an unperforated cylindrical portion 47 of shell 43 extending beyond spacer ring 46.

A plurality of evenly spaced bolts 48 pass through apertures in ring 44 and are provided with enlarged head portions 49 which abut the inner face of spacer ring 44 to which they may be secured by welding. A plurality of bolts 51 are mounted on spacer ring 46 in a similar manner. Intermediate spacer rings 52 are secured between casing 41 and perforated shell 42 to provide compartments or dead air spaces 53, 54, and 56, which have a sound-deadening or mufllng effect.

The forward end of Section X is closed by an end plate 57 having a central opening in which an inlet member 58 is mounted by welding or other suitable means for connection to the engine exhaust connection 6 shown in dot and dash lines. End plate 57 is detachably secured to Section X by passing the bolts 48 through apertures therein and threading nuts 59 on said bolts.

The rearward end of Section X is closed by a cylindrical member 61 having a conical end portion 62 provided with a central opening concentric with the opening in end plate 57. Cylindrical member 61 is proportioned so as to telescope over the end portion 47 of shell 42 and is provided with an attaching flange 63 detachably secured to spacer ring 46 by passing bolts 51 through apertures in said flange and threading nuts 64 on said bolts.

End plate 57, and conical end portion 62 of cylindrical member 61 cooperate to form a chamber 66 which receives hot exhaust gas through the inlet 58. The end plate 57 is provided with a plurality of openings 67 in each of which is secured one end of a plurality of primary air conduits 68. As before, three such conduits have been shown, but it is to be understood that the number and size of these conduits can be varied without departing from the principles of the invention, as they will vary with the size and requirements of a given muffler. The opposite ends of the conduits 68 are secured, as by welding 69 about openings 70, to a cylindrical tube 71 so that the tube 71 is concentrically mounted within the shell 42. Tube 71 is internally threaded at its rearward end to receive a nozzle member 72 including a cylindrical orifice 73 having a converging wall portion 74 and a flaring wall portion 76 on the opposite sides thereof. The nozzle member 72 extends a short distance beyond the conical portion 62 of cylindrical member 61 and the extending portion is provided with a converging wall portion 75.

The forward end of tube 71 is closed by an end wall 77, having a threaded central opening to receive a threaded portion 78 of a relatively thick walled tube 79 so as to concentrically mount the same with respect to the outer cylindrical tube 71. The tube 79 has a passageway 81 of uniform diameter extending therethrough and one end of tube 79 projects slightly into the inlet 58 and has a flared entrance 82 to receive a portion of the exhaust gases emerging from the exhaust connection 6.

The tube 79 has a tapered rearward end portion 83 which terminates just short of the cylindrical orifice 73 in nozzle member 72 so as to confront the converglng wall portion 74, and it is apparent that adjustments 1n the distance between the end of tube 79 and converging wall portion 74 may be made by screwing tube 79 in or out with respect to tube 71. A spacer ring 84 is located between tubes 71 and 79 just forward of the openings 69 and with the tubes 71 and 79 forms a chamber 36 to receive primary air from tubes 68 and direct it to nozzle 72 where it mixes with the exhaust gases segregated by tube 79 causing burning of the combustible materials therein to form a pilot flame F".

As shown particularly in Fig. 13, the amount of primary air supplied is controlled in the same manner as was the case with the device illustrated in Figs. 1 through 7. A damper plate 87 is mounted on the end plate 57 and is provided with primary air inlets 88, one for each tube 68. The damper plate 87 is further provided with arcuate slots 89 for the reception of screws 91 that are threaded in suitable openings in the end plate 57. The damper plate 87 is rotatable upon the inlet member 58 so that it can be angularly adjusted to control the amount of primary air that enters the conduits 68 through the openings 88. The slots 89 provide for the desired adjustment and the screws 91 may be tightened to lock the damper plate 87 in any selected position of adjustment.

As in the embodiment illustrated by Figs. 1 through 7, the present embodiment is provided with a diffuser 92 comprising a plurality of vanes 93 located at the point Where the cylindrical member 61 merges into the conical end portion 62 and arranged at an angle of about 45 relative to the axis of the mufller to impart turbulence to the exhaust gases as they flow through chamber 66 toward the opening in the conical portion 62. Vanes 93 may be secured at one end as by welding to either the cylindrical member 61 or nozzle member 72, but not to both as there must be relative movement between these members to permit assembly of the parts.

Section Y of the present form of mufiier is provided with a cylindrical casing 94, the forward end of which may be split as shown at 96, Figs. 13 and 14, so that after being telescoped over the rearward end of the casing 41 of Section X, it may be secured firmly in place by a conventional clamping ring 97, which is provided with a pair of ears 98. A bolt 99 extends through holes in the ears and receives a nut for tightening the ring 97 about the casing 94.

Cylindrical casing 94 is provided with an end plate 102 having a central opening in which an outlet member 103 of relatively larger diameter than the inlet member 58 is mounted. Outlet member 103 serves as a means for connecting the mufiler to the tail pipe 8, shown in dot and dash lines.

A frusto-conical member 104 is mounted in the casing 94 at a point such that when the casing 94 is clamped on the casing 41, the frustoconical member is spaced a slight distance longitudinally of the conical end portion 62 of cylindrical member 61. Frusto-conical member 104 has a cylindrical extension 106 of substantially larger diameter than the adjacent open end of the conical end portion 62 of cylindrical member 61, the cylindrical extension 106, preferably begins at a point which will lie closely adjacent a vertical plane defined by the end of nozzle member 72 when the casing 94 is clamped on the casing 41.

Cylindrical member 61 and frusto-conical member 104 cooperate to form a chamber 107 for receiving secondary air entering through a large rectangular inlet opening 108 in the casing 94. The air entering opening 103 may be conveniently regulated by a sleeve 109 slidably mounted on the casing 94 and provided with a flange 110 for enabling said sleeve to be easily shifted. In order that sleeve 109 may be firmly secured in adjusted position, it is provided, as shown in Fig. 15, with a pair of ears 111. A bolt 112 extends through appertures in the cars so that through cooperation with a nut 113 the sleeve 109 may be clamped tightly upon casing 94 To provide for even distribution of the secondary air, a relatively large spacer element 114 is mounted between the lower portion of cylindrical casing 94 and the cylindrical member 61 at the inlet end of chamber 197. A pair of smaller similarly located spacer elements 116 are provided in angularly disposed relation to spacer element 114 and cooperate therewith to provide arcuate openings 117 through which the secondary air must enter to pass through the chamber 107 to later mix with the unsegregated portion of the exhaust gas leaving the chamber 66 in a highly turbulent state after passing through the diffuser 92. Here the burnable material in the main body of the exhaust gas is ignited by the pilot flame F" and burns in the main combustion chamber 118 of the afterburner which is formed between the frusto-conical member 104 and end plate 102. If desired, the space between frusto-conical member 104 and the casing 94 may be filled with insulating material 119 to prevent dissipation of heat and insure a maximum temperature in the region of the pilot flame F".

To insure ignition of the burnable material in the exhaust gas, even under the most extreme conditions when the pilot flame F" is not propagated by spontaneous combustion of the burnable material in the minor segregated portion of the exhaust gas, the present combination mufher and after-burner is provided with a conventional igniter 121 of the spark plug type. Igniter 121 is mounted in the opening formed by the cylindrical extension 106 of the frusto-conical member 104 and for this purpose, an internally threaded sleeve 122 may be mounted about an opening 123 in cylindrical casing 94 and secured in place as by welding 124. The electrodes of the igniter 121 pass through the opening 123 and the corresponding openings 126 in the insulating material 119 and 127 in the cylindrical extension 106.

Automatic control of the igniter 121, so that it will be deenergized at a temperature above which it may be certain that spontaneous combustion of the burnable constituents of the exhaust gas will take place, for instance, at 1200 F., is effected by a conventional thermostatically actuated switch 128. The switch 128 may be one of two types, both of which will effect deenergization of the spark at the desired temperature, but one of which Will provide for immediate energization of the igniter upon starting of the engine, and the other of which will delay energization until a predetermined minimum temperature, say about 400 F., is attained in the combustion chamber 118, the switch 128 being mounted in eflicient heat exchange relationship With this chamber.

The two forms of thermostatic switch and a convenient electrical circuit incorporating each are shown diagrammatically in Figs. 16 and 17. Referring particularly to Fig. 16, it will be seen that the circuit includes a suitable source of electrical energy 129, and this conveniently may be the vehicle battery if its motor employs an electrical ignition system. A conductor 130 connects the ungrounded terminal of the battery 129 to one terminal of a manual switch 131, which may be the ignition switch of the engine. The other terminal of switch 131 is connected by a conductor 132 to contact 133 of a pair of normally closed contacts of a thermostatically actuated switch 128. As shown, the contact 133 may be mounted on a resilient arm 136 of conducting material and the other contact 137 may be mounted on an arm 138, the arms being mounted in side by side relationship in a block of insulating material. 139. The arm 136 extends outwardly beyond contact 133 to provide the extended portion 141 which is not obstructed by the arm 138 and is adapted to be contacted by a pin 142 mounted on a bimetallic strip 143, which may also be secured to the block.

13 of insulating material 139. The pin 142 is normally out of contact with the extended portion ll ill of arm 136, but will contact the same and force the electrical contacts 133 and 137 apart upon the attainment of a predetermined maximum temperature which, as stated earlier, may be in the neighborhood of l200 F.

The contact 137 is connected by a conductor 144 to a terminal 145 on the primary side of a suitable induction coil 3.46, which will furnish a voltage sufiiciently high for operation of the spark plug 121. A conductor 147 connects the terminal 148 on the secondary side of the induction coil 146 with the nongrounded electrode 121a of the spark plug 121.

The induction coil 146 may be the ordinary ignition coil of an internal combustion engine employing an electrical ignition system, but when the present combination mufiier and after-burner is mounted on a motor of the compression ignition type, such as a Diesel engine, it is obvious that a separate electrical circuit will have to be provided for the igniter 121.

it will be seen that in the use of a device incorporating the positive electrical igniting system, diagrammatically illustrated in Fig. 16, the spark plug 121 will be energized as soon as the switch 131 is closed and an attempt is made to start the engine. As soon as the proper mixture of air and burnable material is obtained in the region of the electrodes of the spark plug 121, it will be ignited so that there is no delay until the conditions necessary tor spontaneous combustion of the burnable material 9 in the exhaust gas are reached. The spark plug 121 will remain in operation until a temperature of approximately 1200 F. is obtained in the main combustion chamber 1. .8, which is more than high enough to maintain the pilot flame F to assure the continued burning of the combustible constituents. At this time, the bimetallic strip 143 will open the contacts 133 and 137, thereby interrupting the current and deenergizing the spark plug 121 and thus effecting a saving in electrical energy. If later, under adverse operating conditions, the temperature in the combustion chamber 118 falls below 1200 F., the bimetallic strip 143 will immediately move in a direction to permit closing of contacts 133 and 137, and reestablish the circuit to the spark plug 121 so that there is no danger of the temperature reaching such a low value that spontaneous ignition of the burnable materials of the exhaust gas would not occur. It will be understood that the combustion of the exhaust gas initiated by electrical ignition will quickly heat the chamber 118 to a temperature adequate to reestablish spontaneous combustion, whereupon operation of the spark plug will be cut out.

While the above described system is quite satisfactory for many types of engines, there is some danger with others of mutller and exhaust system explosions occurring from the ignition of raw gas emitted into the mufiier during a cold start, particularly when the carburetor choke is closed and before there is sufiicient volume, temperature, or velocity of exhaust gas to induce spontaneous combustion. This situation is undesirable and the electrical spark igniter system shown diagrammatically in Fig. 17, has been devised to prevent the occurrence of such hazard. The electrical system of Fig. 17 is identical with that of Fig. 16, with the exception of the type of thermostatically operated switch 128 employed and, therefore, like parts of the two systems have ben given the same numbers. Only the construction and operation of the particular type of thermostatic switch 128 of Fig. 17, therefore, need be described. The thermostatic switch 12$ of Fig. 17 includes a block of insulating material 149 in which is mounted a spring arm 151 carrying an electrical contact 152 spaced inwardly of its outer end. Below the spring arm 151, there is mounted in the insulating block M9 a U-shaped member 156 of conducting material including a shorter leg portion 15? carrying an electrical contact adapted to normally contact the electrical contact 152 on spring arm 151, with the end of leg portion 153 terminatingshort of the end of spring arm 151. U-shaped member also includes a relatively longer leg portion 156, which is provided adjacent its outer end with an upwardly projecting pin 157 normally out of contact with, but underlying the outer end portion of spring arm 151. The leg portion 156 is also provided with an electrical contact 158 on the side opposite that carrying the button 157. Also, mounted in insulating block 149 is a spring arm 159 carrying an electrical contact 161 in confronting relationship to the electrical contact 158 but normally out of contact therewith. The insulating block 149 will also conveniently carry a bimetallic strip 162 having mounted adjacent its outer end a pin M3 normally spaced from the underside of spring arm 159 but adapted to move toward it when the temperature is increased.

It will, thus, be seen that the above described thermostatically operated switch provides a pair of normally closed contacts 152 and 154 and a pair of normally open contacts 158 and 161 arranged in series. It will be obvious that when the manual switch 131 is closed, there will be no current flow to effect energization of the spark igniter 121. However, very soon after starting of the engine, when a predetermined minimum temperature of, say, about 400 F. is obtained in the combustion chamber 118, the pin 163 of bimetallic strip 162 willcontact spring arm 159 and force contact 16E into engagement with the contact 15-55, thus, closing the electrical circuit to the spark igniter 121 and effecting its energization. By this time, however, there will be a sufiicient volume and velocity of exhaust gas flowing through the mufiier to prevent any explosion.

ignition or" the burnable constituents in the exhaust gas by the spark plug "121 will aid in the rapid attainment of higher temperatures in the combustion chamber 118, and

when a temperature of approximately l200 has been reached, the bimetallic strip 162 will have moved a distance sufficient to have forced the pin 157 to contact the over hanging portion of spring arm 151i and continued movement wili open the contacts 152 and 1554 again interrupting the circuit to the spark plug 121 and bringing about its deenergization. If the temperature in the combustion chamber 113 should subsequently fall to a low point at which spontaneous combustion of the burnable constituents in the exhaust gas is not assured, the pin 157 will move downwardly a sufficient distance to permit reengagement of the normally closed pair of contacts 152 and 15 5, again closing the electrical circuit to the spark plug 123., since the bimetallic strip 162 has not cooled sumciently to move a distance great enough to permit opening of the pair of contacts 153 and 161. It is thus assured that complete combustion of all of the burnable constituents of the exhaust gas will occur.

It is to be understood that aside from the electrical ignition feature, the functioning of the embodiment of the invention illustrated by Figs. l3 to 15 is similar to that of the other embodiments shown and described and that the relative dimensioning of the parts is also similar to provide comparable proportions of exhaust gases segregated, and proportions of exhaust gas to primary and secondary air.

It will be further understood that except Where otherwise specified, the parts of the various forms of mufflers disclosed herein may be secured together by welding, or by any other suitable means.

it will be also understood that various changes may be made in the details of construction and in the arrangement of the parts of the various mufllers disclosed herein without departing from the principles of the invention or the scope of the annexed claims.

I claim:

1. A muflier construction, comprising in combination; a casing having a muffier section provided with an inlet for hot engine exhaust gases and an after-burner section adjacent thereto and having an outlet; a tube in said it? Q mulfier section having an inlet and adjacent said casing inlet and having a discharge end extending into said afterburner section, said tube segregating and providing for flow of a portion of the exhaust gases therethrough; primary air supply conduit means; means actuated by the flow of the segregated portion of the exhaust gases for inducing the flow of primary air toward said after-burner section through said last-mentioned means and for mixture with the segregated portion of the hot exhaust gases prior to discharge into said after-burner section; means for admitting the remainder of the exhaust gases into said after-burner section; means responsive to the flow of the remainder of said exhaust gases for inducing the flow of secondary air into said after-burner section for mixture with said remainder of said exhaust gases; and means for separately controlling the volumes of the primary and secondary air flows.

2. In devices for oxidizing the unconsumed residual matter carried by the exhaust gases of internal combustion engines or the like; the combination of an elongated casing having an inlet for hot engine exhaust gases at one end thereof and an outlet at the opposite end thereof; two generally frusto-conical members disposed in said casing in concentric, axially spaced relation; means including an injector nozzle having its outlet within at least one of said frusto-conical members for conducting only a portion of the exhaust gases from the inlet of said casing to said frusto-conical members and for inducing the flow of primary air into at least one of said frusto-conical members to support spontaneous combustion of the exhaust gases discharging from said injector nozzle; means constituting second injector nozzle having its outlet within at least one of said frusto-conical members and through which the remainder of said exhaust gases flow to said frusto'conical members and for inducing the flow of secondary air into said casing in the space between said two frusto-conical members for mixture with said remainder of said exhaust gases.

3. A mufiler construction, comprising in combination: a casing; means in said casing dividing the same into a mulfier section and an after-burner section, said casing having an inlet for hot engine exhaust gases at one end thereof communicating with said muffler section and having an outlet at its other end communicating with said after-burner section, said mutlier section having an exit and said after-burner section having an entrance adjacent thereto; means in said muffler section for segregating and conducting a small portion of the exhaust gases from the mufiler entrance toward the inlet of said afterburner section; means also in said muflier section for conducting primary air through said muffier section to be pre-heated by the exhaust gases for mixture with the segregated exhaust gases to burn therewith adjacent the entrance to said after-burner section; means for delivering secondary air to the entrance of said after-burner section; and means for directing the remainder of the exhaust gases to said after-burner section to be mixed with said secondary air.

4. The combination defined in claim 3 and including also a pair of hollow frusto-conical members disposed in the casing in longitudinal spaced relation and forming the means dividing the casing into the two said sections, said frusto-conical members having central openings forming the exit of the mufller section and the entrance to the after-burner section; said means for delivering secondary air to the entrance of the after-burner section comprising means for admitting air to the space between the two frusto-conical members; and veins between the two frusto-conical members for imparting tunbulence to the air as it passes between said members.

5. A muiiler construction, comprising in combination: a casing; means in said casing dividing the same into a muffler section and an after-burner section, said casing having an inlet at one end communicating with said mufiler section and an outlet at its other end communicating with said after-burner section, said muffler section having an exit and said after-burner section having an entrance adjacent thereto; a tube extending from said inlet of said casing to a point adjacent the entrance to said after-burner section for conducting a minor portion of the exhaust gases from said mufiler section toward said after-burner section; means including a primary air supply conduit positioned in said mufller section to be heated by the remainder of said exhaust gases and arranged to deliver pre-heated primary air adjacent the discharge end of said tube for mixture with said minor portion of said exhaust gases; means for delivering secondary air to the entrance of said after-burner section; and means for directing the remainder of the exhaust gases to said afterburner section to be mixed with said secondary air.

6. A muffler construction, comprising in combination: a substantially cylindrical casing having an end wall at one end thereof provided with an inlet for hot engine exhaust gases and having an end wall at the opposite end thereof provided with an outlet; a hollow frusto-conical member mounted in said casing and cooperating with said first mentioned end wall to provide a muffler section; a second hollow frusto-conical member in said casing spaced longitudinally from said first-mentioned frustoconical member and cooperating with the second-neutioned end wall to provide an after-burner section, each of said frusto-conical members having a central opening; a tube in said casing having its outer end disposed adjacent said casing inlet and having its inner end disposed adjacent said first mentioned frusto-conical member; means for admitting primary air into said casing; nozzle means surrounding said inner end of said tube and including a portion extending through the openings in and across the space between said hollow frusto-conical members, said nozzle means being operable by the flow of only a portion of the exhaust gases therethrough to induce the flow of primary air into said nozzle means to effect mixing of said primary air and said portion of said exhaust gases prior to discharge thereof into said after-burner section; and means for admitting secondary air into the space between said frusto-conical members, said nozzle means being operable by the flow of the remainder of said exhaust gases through the openings in said frusto-conical members to induce flow of secondary air through said last-mentioned means for mixture thereof with said remainder of said exhaust gases prior to discharge thereof into said after-burner section; and adjustable means for controlling the volume of primary air and secondary air introduced into said casing.

7. A muffier construction, comprising in combination: a substantially cylindrical casing having one end wall pro vided with an inlet for hot engine exhaust gases and another end wall having an outlet; a shell member disposed concentrically within and spaced from said casing and extending from said one end wall toward the other end wall and terminating at its inner end in a hollow frusto-conical portion; a hollow frusto-conical member mounted in said casing in axially spaced relation to the frusto-conical portion of said shell member, the portion of said casing between said frusto-conical member and said other end wall forming an after-burner chamber, said one end wall having openings for admitting primary air into said shell, said casing having air inlet openings for admitting secondary air into the space between said casing and shell; a tube in said casing having its outer end disposed adjacent the inlet of said casing and having its inner end disposed within the 'frusto-conical portion of said shell member; a 1102- zle member surrounding the inner end of said tube and including a portion extending across the gap between the frusto-conical portion of said shell member and said 'frusto-conical member and communicating with said after-burner chamber; conduit means for primary air extending from the openings in said one end wall to said nozzle portion for conducting primary air to the delivery end of said tube, said tube serving to segregate a portion 1? of the exhaust gases and cooperating with said nozzle member to induce the flow of primary air through said conduit means for admixture with the segregated exhaust gases prior to discharge into said after-burner section, said nozzle member also cooperating with said shell member and the exhaust gases passing through said shell member to induce the flow of secondary air into the space between said frusto-conical portion of said shell member and said frusto-conical member for mixture with the remainder of the exhaust gases prior to discharge into said after-burner section.

8. In devices for oxidizing the unconsumed residual matter carried by the exhaust gases of internal combustion engines or the like; the combination of a casing having an inlet for hot engine exhaust gases usually containing sufficient heat to initiate spontaneous combustion, said casing also having an outlet; means in said casing for effecting mixing of primary air with a portion of the hot exhaust gases to effect and support spontaneous combustion thereof in the form of a pilot flame; means in said casing for normally effecting mixing of secondary air with the remainder of the exhaust gases in the presence of said pilot flame to eifect ignition and combustion thereof; electrical ignition means located in the region of said pilot flame to insure ignition of said exhaust gases under temperature conditions inadequate for their spontaneous combustion; and thermostatic switch means mounted in heat exchange relationship with said exhaust gases in the region of their combustion, effecting energization of said electrical ignition means when the temperature of said exhaust gases falls below a predetermined temperature insuring spontaneous combustion thereof, and effecting deenergization of said ignition means when said predetermined temperature is exceeded.

9. In devices for oxidizing the unconsumed residual matter carried by the exhaust gases of internal com bustion engines or the like; the combination of a casing having an inlet for hot engine exhaust gases usually containing sufficient heat to initiate spontaneous combustion, said casing also having an outlet; means in said casing for effecting mixing of primary air with a portion of the hot exhaust gases to effect and support spontaneous combustion thereof in the form of a pilot flame; means in said casing for effecting mixing of secondary air with the remainder of the exhaust gases in the presence of said pilot flame to effect ignition and combustion thereof; electrical ignition means located in the region of said pilot flame to insure ignition of said exhaust gases under temperature conditions inadequate for their spontaneous combustion; and thermostatic switch means mounted in heat exchange relationship with said exhaust gases in the region of their combustion effecting energization of said electrical ignition means between a predetermined minimum temperature above which exhaust explosions in the mufller will not occur on cold starting and a predetermined maximum temperature insuring spontaneous combustion of said exhaust gases, said thermostatic switch means effecting deenergization of said electrical ignition means at temperatures below said predetermined minimum temperature and above said predetermined maximum temperature.

lO. A muflier comprising in combination: a first section including a substantial cylindrical casing; an end plate detachably secured to said casing at its forward end, said end plate having a central opening and a plurality of primary air inlet openings; an inlet member mounted in said central opening in said end plate adapted to be mounted on the exhaust connection of an internal combustion engine; means controlling the amount of air entering said primary inlet openings; 2. first cylindrical tubular member concentrically mounted within said casing in spaced relation thereto, said tubular member being closed at its forward end by a closure member having a central opening therein, said tubular member being proy ided with a plurality of openings for said primary air; a

plurality of conduits, each conduit communicating at one end with one of said primary openings in said end plate and at its other end with one of said primary air openings in said tubular member; a nozzle member detachably secured to the rearward end of said tubular member; a second tubular member detachably secured in the central opening of said closure member of said first tubular member so as to be concentrically mounted in said first tubular member in spaced relation thereto, said second tubular member having its forward end positioned to receive a minor portion of the exhaust gases supplied to said inlet member, said second tubular member having its rearward end projecting into said nozzle member, said primary air mixing with said minor portion of said exhaust gases in said nozzle member prior to discharge from the outlet thereof; and a cylindrical member detachably secured to the rearward end of said casing and extending outwardly 'therebeyond, said cylindrical member terminating in a conical portion having a central opening located adjacent the rearward end of said nozzle member, said end plate and said conical end portion of said cylindrical member forming between them a chamher for the passage of the major portion of said exhaust gases; and a second section including a second cylindrical casing detachably secured at its forward end to the rearward end of said casing of said first section in spaced concentric relation to said cylindrical member, said second casing having an opening therein for admitting secondary air to the space between said second casing and said cylindrical member; means controlling the amount of secondary air admitted; an end plate having a central opening secured to the rearward end of said second casing; an outlet member in said last mentioned opening adapted to be secured to the tail pipe of the exhaust of. said internal combustion engine; and a frusto-conical member mounted in said second casing in axially spaced relation to said conical portion of said cylindrical memher, said frusto-conical member having a central opening therein adjacent the rearward end of said nozzle member, said frustoconical member and said end plate of said second casing forming between them a combustion chamber for the major portion of said exhaust gases which is mixed with said secondary air in the region of the outlet of said nozzle member.

11. A mufl'ler, comprising in combination: a first section including a substantially cylindrical casing; an end plate detachably secured to said casing at its forward-end, said end plate having a central opening and a plurality of primary air inlet openings; an inlet member mounted in said central opening in said end plate adapted to be mounted on the exhaust connection of an internal combustion engine; damper means mounted on said end plate for controlling the amount of air entering said primary air inlet openings; a first cylindrical tubular member concentrically mounted within said casing in spaced relation thereto, said tubular member being closed at its forward end by a closure member having a central opening therein, said tubular member being provided with a plurality of openings for said primary air; a plurality of conduits, each conduit communicating at one end with one of said primary air openings in said end plate and at its other end with one of said primary air openings in said tubular member; a nozzle member detachably secured-to the-rearward end of said tubular member; a second tubular member detachably and adjustably secured in the central opening of said closure member of said first tubular member so as to be concentrically mounted in said first tubular member in spaced relation thereto, said second tubular member having its forward end adjacent said inlet member to receive a minor portion of the exhaust gases delivered thereto, said second tubular member having its rearward end projecting into said nozzle member, said primary air mixing with said minor portion of said exhaust gases in said nozzle member prior to discharge from the outlet thereof; a cylindrical member detachabiy secured to the rearward end of said casing and extending outwardly therebeyond, said cylindrical member terminating in a conical portion having a central opening located adjacent the rearward end of said nozzle member, said end plate and said conical end portion of said cylindrical member forming between them a chamber for the passage of the major portion of said exhaust gases; and a plurality of vanes disposed at an angle to the axis of said casing located between said cylindrical member and said nozzle member imparting turbulence to the exhaust gases passing through said chamber; and a second section including a second cylindrical casing detachably secured at its forward end to the rearward end of said casing of said first section in spaced concentric relation to said cylindrical member, said second casing having an opening therein for admitting secondary air to the space between said second casing and said cylindrical member; a damper movably mounted on said casing over said opening controlling the amount of secondary air admitted; an end plate having a central opening secured to the rearward end of said second casing; and an outlet member mounted in said last-mentioned opening adapted to be secured to the tail pipe of the exhaust of said internal combustion engine; and a frusto-conical member mounted in said second casing in axially spaced relation to said conical portion of said cylindrical member, said frustoconical member terminating in a cylindrical portion extending rearwardly of said nozzle member, with said frusto-conical member and said end plate of said second casing forming between them a combustion chamber for the major portion of said exhaust gases which is mixed with said secondary air in the region of the outlet of said nozzle member.

12. A mufiler, comprising in combination: a first section including a substantially cylindrical casing; a perforated shell located concentrically within and spaced from said casing, said shell extending rearwardly a slight distance beyond said casing: a plurality of spacer rings dividing the space between said casing and said shell into a plurality of sound-mufiiing compartments, one of said spacer rings being secured to the forward ends of said casing and said shell and another of said spacer rings being attached to the rearward end of said casing and to said shell adjacent its rearward end but spaced slightly therefrom to leave an unobstructed cylindrical portion; an end plate detachably secured to said one of said spacer rings, said end plate having a central opening and a plurality of primary air inlet openings; an inlet member mounted in said central opening in said end plate adapted to be mounted on the exhaust connection of an internal combustion engine; a first cylindrical tubular member concentrically mounted Within said shell in spaced relation thereto, said tubular member being closed at its forward end by a closure member provided with a central threaded opening, said tubular member being provided with a plurality of openings, for said primary air; a plurality of conduits, each conduit communicating at one end with one of said primary air openings in said end plate and at its other end with one of said primary air openings in said tubular member; a nozzle member releasably secured to the rearward end of said tubular member, said nozzle member including a cylindrical orifice portion and portions provided with converging walls and flaring walls on opposite sides of said cylindrical portion; a second tubular member threadedly secured in the central opening of said closure member of said first tubular member so as to be concentrically mounted in said first tubular member in spaced relation thereto, said second tubular member having its forward end projecting into said inlet member to receive a minor portion of the exhaust gases delivered thereto, said second tubular member having its rearward end slightly spaced from but in confronting relation to the converging wall portion of said nozzle member, said primary air mixing with said minor portion of. said exhaust gas in said nozzle member I prior to discharge from the outlet thereof; damper means,

mounted on said end plate for controlling the amount of primary air admitted to said conduits; and a cylindrical member mounted on said unobstructed cylindrical portion of said shell member and provided with an attaching flange releasably secured to said spacer ring secured to.

the rearward end of said casing, said cylindrical member terminating in a conical portion having a central opening therein located adjacent but spaced forwardly of the rearward end of said nozzle member, said end plate and said conical end portion of said cylindrical member forming between them a chamber for the passage of the major portion of said exhaust gases; and a second section including a second cylindrical casing having its forward end detachably secured in telescoping relation over said casing of said first section in spaced concentric relation to said cylindrical member, said second casing having an opening therein for admitting secondary air to the space between said second casing and said cylindrical member; a damper movably mounted on said casing over said opening for controlling the amount of said secondary air admitted; an end plate having a central opening secured to the rearward end of said second casing; an outlet member mounted in said last-mentioned opening adapted to be secured to the tail pipe of the exhaust of said internal combustion engine; and a frusto-conical member mounted in said second casing in axially spaced relation to said conical portion of said cylindrical member, said frusto-conical member terminating in a cylindrical portion extending rearwardly of said nozzle member,

and said frusto-conical member and said end plate of said second casing forming between them a combustion chamber for the major portion of said exhaust gases which is mixed with said secondary air in the region of the outlet of said nozzle member.

13. A mutfler as defined in claim 3, including means for positively igniting the mixture of air and exhaust gases.

14. The method of oxidizing unconsumed residual matter carried in the hot exhaust gases from internal combustion engines and the like, said method comprising the combination of the following steps: segregating a portion of the hot exhaust gases from the remaining body of exhaust gases and maintaining said segregated portion at substantially the original temperature of the exhaust gases, heating primary air by heat exchange from substantially only the remaining body of exhaust gases, forming a mixture of said heated primary air with the hot segregated portion of the exhaust gases and their carried unconsumed matter, burning said unconsumed matter in said mixture and thereby producing a pilot flame, forming a mixture of secondary air with the remaining body of exhaust gases, and contacting said last named mixture with the pilot flame and thereby raising its temperature and causing oxidation of the unconsumed matter in said last named mixture.

15. The method defined in claim 14 and in which the segregated portion of the hot exhaust gases is a minor portion of said gases.

16. The method defined in claim 14, and in which the amount of primary air is regulated to be less than the stoichiometric amount required for complete combustion of the unconsumed matter carried in the segregated portion of the exhaust gases.

17. The method defined in claim 16 and in which the segregated portion of the hot exhaust gases is a minor portion of said gases.

18. The method defined in claim 16, and in which the amount of secondary air is regulated to be more than the stoichiometric amount required for complete oxidation of the unconsumed matter in said remaining body of exhaust gases.

19. The method defined in claim 18 and in which the segregated portion of the hot exhaust gases is a minor portion of said gases. 1

20. The method of oxidizing unconsumed residual matter carried in the hot exhaust gases from internal combustion engines and the like, said method comprising the combination of the following steps: segregating a portion of the hot exhaust gases from the remaining body of exhaust gases and maintaining said segregated portion at substantially the original temperature of the exhaust gases, forming a rich mixture of said hot segregated portion of the exhaust gases with primary air regulated in amount to be less than the stoichiometric amount required for complete combustion of the unconsumed matter carried in said segregated portion, burning the unconsumed matter in said mixture and thereby producing a pilot flame, forming a lean mixture of secondary air with the remaining body of exhaust gases, said secondary air being regulated in amount to be more than the stoichiometric amount required for complete oxidation of the unconsumed matter in said remaining body of exhaust gases, and contacting said last named lean mixture with the pilot flame and thereby raising its temperature and cansing oxidation of the unconsumed matter in said last named mixture and completing the oxidation of the unburned matter in the segregated portion of the exhaust gases.

21. The method defined in claim 20 and in which the segregated portion of the hot exhaust gases is a minor portion of said gases.

22. In devices for oxidizing the unconsumed residual matter carried by the exhaust gases of internal combustion engines or the like; the combination of a casing enclosing a combustion chamber, primary gas passage means adapted to segregate and pass a primary stream consisting exclusively of a segregated portion only of the total exhaust gas volume, said passage means having a terminal end discharging its stream into the combustion chamber, primary air passage means conducting a primary stream of air to the terminal discharge end of the gas passage means for admixture with the segregated gas stream at a point down-stream of said terminal discharge end, and secondary air and gas passage means discharging secondary air and the remaining portion of the exhaust gases into the combustion chamber at a 22 point down-stream of the mixing point of the primary streams of gas and air.

23. The combination defined in claim 22 and including also a catalyst positioned in the path of the mixture of the primary air and the segregated gas for facilitating the establishment of a pilot flame.

24. In devices for oxidizing the unconsumed residual matter carried by the exhaust gases of internal combustion engines or the like; the combination of a casing enclosing an outer exhaust gas passage and having an intake opening at one end to receive the exhaust gases, and having an outlet opening at the opposite end, and enclosing a combustion chamber adjacent the outlet, a tubular inner gas passage Within the outer gas passage and having an open intake end, located substantially in the intake opening of the casing, and a discharge end, said inner gas passage taking a primary gas stream comprising a portion of the total exhaust gas volume and discharging said stream at its discharge end into the combustion chamber, primary air passage means in heat exchange relation to the exhaust gas in the outer exhaust gas passage and discharging a primary air stream to the discharge end of the inner tubular gas passage for admixture with the gas stream at a point down-stream of said discharge end, and passage means directing secondary air and exhaust gas from the outer exhaust passage into the combustion chamber at a point downstream of the mixing point of the primary streams of gas and air.

References Cited in the file of this patent UNITED STATES PATENTS 1,934,596 Fogas et a1. Nov. 7, 1933 2,167,183 Naab et al. July 25, 1939 2,217,241 Tendler Oct. 8, 1940 2,377,497 Hopkins June 5, 1945 2,729,301 Ekstrow Jan. 3, 1956 FOREIGN PATENTS 631,736 France Sept. 20, 1927

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