US3100401A - Pressure retaining means for double-acting piston engines - Google Patents

Description

Aug. 13, 1963 A. M. CADDELL PRESSURE RETAINING MEANS FOR DOUBLE-ACTING PISTON ENGINES Filed May 2, 1960 2 Sheets-Sheet 1 Aug. 13, 1963 A. M. CADDELL PRESSURE RETAINING MEANS FOR DOUBLE-ACTING PISTON ENGINES 2 sheets-sheet 2"! Filed May 2, 1960 United States Patent 3,100,401 PRESSURE RETAINING MEANS FOR DOUBLE- ACTNG PISTON ENGiNES Alfred M. Caddell, 1318 W. Hunting Park Ave., Philadelphia 40, Pa. Filed May 2, 1960, Ser. No. 26,212 3 Claims. (Cl. 74-36) This continuation-impart application carries the same title as the application entitled Pressure Retaining Means -for Double-Acting Piston Engines, filed June 16, 1959, Serial No. 820,685, which is now abandoned.

The invention is appropriate for either steam or internal combustion engines. it is described herein as applicable to the latter,- with the possibility of its use in the compression ignition field standing out prominen-tly. Basically, it has to do with an operating cycle that is totally different from that employed in conventional practice.

As in the former case, the main object of .the invention is to obtain a large increase in power from an engine having two power strokes per revolution of the crankshaft. This is accomplished :by permitting the release of energy only through a :favorable leverage range on each of the power strokes, `such release commencing at a point in the respective cycles, as an example, 30 degrees past top center on the rst stroke and 30 degrees past bottom center on the second stroke. By virtue of such energy application, anti-leverage pounding on the crankshaft, such as presently occurs in an engine operating under the conventional cycle, is prevented. -For one thing, this anti-leverage pounding constitutes a major drawback that preventsk wider use of diesel engines.

Another objective is Arelated -to the foregoing one, name- 1y, to prevent the intense vibration that accompanies the build-up of energy before the crank arrives at top center, which build-up results in broken crankshafts, the blowing off of cylinder heads and many other engine troubles.

A third objective is to make it possible to construct an engine having smaller cylinder capacity and also operate it at lower r.p.m. compared to the cubic inch displacement and high r.p.m. now necessary -to attain a stated power out- ,n

put; and, coupled with this objective, the achievement of a very considerable saving in fuel for the horespower developed.

Although from the standpoint of a pran'cally unmeasurable period of time, the travel of -a piston in an engine actually stops twice during a single revolution of the crank assembly, namely, at top dead center and at bottom dead center, at which centers the motion Vof the piston becomes reversed. For the next fe-w degrees of the crankthrow past either top or bottom center the movement of the piston in its cylinder is comparatively slight, and it is not until approximately 30 degrees has been reached on the power stroke of the crank-throw that its travel speed commences to materially increase. From zero speed at -top center to maximum at 90 degrees of the l.

by employing a new type of crank assembly that incorpo-v rates a crankpin having, relative to any position of the crank-arms, an angularly disposed cam centrally and integrally formed on the crankpins surface; also, a rod having a wrist pin connection with a crosshead on one end and :a merged housing Vappendage on the other. This into power.

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appendage spans and encompasses a structure that is mounted :uponV and rotates freely around the crankpin which is integrated by means of crankarms with the crankshaft.

The operation of this crank Vassembly is as follows:

A cam follower as A is mounted in the end of the connecting rod within the confines of the housing appendage. Also, a cam follower identified as B is mounted diametrically opposite cam follower A in the base of the appendage. Upon the piston arriving at top center of the crankthrow the crankpin cam follower contacts cam A, thereby temporarily lending its radial projection length to the connecting rod which prolongs the heighth of the pis-ton at top center throughout the first 30 degrees of the first power stroke. Thereupon, the crankpin cam contacts cam follower B at bottom center and it, in turn, lends the length of its radial projection to the housing appendage, maintaining a temporary prolonged botto-m cen-ter during 30 4degrees on the second power stroke. Thus, the motion of the piston becomes momentarily halted at top and -at bottom centers respectively and the pressure of the Working fluid becomes applicable only after the apex of the crankpin cam passes in ysequence the apexes of cam followerA and B during the rotation of the crankpin. It will be seen, therefore, that instead of a power stroke commencing at zero leverage, it actually commences 30 degrees past top and 30 degrees past bottom centers where leverage exerts its powerful and ever-increasing influence to the -degree positionl of each of the cycles before it tapers off until the BO-deg'ree position has again been reached on the next succeeding cycle.

The crankpin of this invention has a recess formed therein on the side directly opposite lits cam formation so lthat when cam follower A is lengaged by `the crankpin cam, cam 'follower B will move into this recess and, in turn, when cam follower B is engaged by the crankpin cam, cam lfollower A will occupy the recess. This recess serves a d ua-l purpose: One, as a repository for .the cam follower not at the moment being engaged by the crankpin cam and, two to permit cam followers A and B plosive impulse per revolution of the crankshaft if the` engine is of the two-cycle design or every other revolution if it is of the four-cycle type.

In conventional Otto cycleengines, the power stroke covers a range from 0 degrees (top center) -to approximately `degrees on the power stroke, during which range only the lag of the explosive impulse becomes translated In contrast, in the power cycles of this invention, the range of piston travel commences at the 30- degree position past top or bottom center on the respective ystro-ke and may extend with perfect safety throughout a range of degrees on each stroke before the exhaust valve -is caused to open, thus lassuring maximum expansion pressure through 125 degrees in the most favorable leverage ran-ges of piston travel. Obviously, the greater the expansion force throughout said ranges, the greater in proportion the turning effort at the crankshaft and, by means of lappropriate gearing, the greater the power output per -vpound of fuel will be.

In single-acting internal combustion engines ofthe aviation type, the fuel-air mixture is fired from -30 to 45 degrees before top center so that combustion pressure will build up .to itsmaximum at the. point of maximum compression pressure, which tis attop center. Although the employment of energy yin an anti-leverage position of the crankvthrowf'is contrary to the law of physics, in conventional Ainternal combustionengines' such build-'up of .pressureV is essential for maximum power output.V Thisparadoxical situation is due to the slowness of flame travelcompared Y to the speed ofthe crank-throw throughout 'its rotation;V

Cylinders shown V`in FIG. and in FIG.. 8 may also be noted.

As an example of such comparative slowness, in an Y aviation engine-having a- 6-incl1 bore and ignition taking place l30 degrees before Vtop center, the flame travels from the igniter across-the bore through said 30Vdegrees to top center at a speed of approximately 75 feet per second which, as will be observed from Vthe following` p table, is considerably slower than they travel of the crankpin throughout an equivalentrnumber of degrees` Crankshaft Time required for Crankshaft revolurevolutions crankpin to travel v tions per minute per through 30 of the Y vsecond 360 revolution, ses.

.Which micro-second periods of time focusattention on the speed at Whichchemical reaction takes place upon the fuel-air mixture beingtlred and the critical relation Y existing between maximum combustion pressure build-up and the Vaforesaid speeds of crankpin rotation.

' In the drawings:

FIG. 11 shows the center of the crankpin at a 30- degree-before-top-center position in the crankthrow, with the lapexes of cam -follower A and cam follower B riding the rounded surface'of the crankpin.

`FIG. 9 is an enlarged end view of the crankpin showing Vthe integrally formed cam thereon and directly opposite thereto Vthe recess for accommodating the momentary housing of cam follower B while the crankpin cam makes contact with cam follower A, and vice versa.

FIG. 1,0 is aside view-of the housing appendage of4 .the connecting rod showing its encompassment of the structure identied as 16, also the longitudinally disposed l. bearingassemblies to permit reciprocaltravel of the appendage-relative to said structure; also, the radial ball bearings `that permit rotation of the appendage and struc- Y ture around the crankpin and the views of cam followers A and B and the .'crankarms integrated with the crankshaft.` l Y Y ,Y Y

(FIG. 11v is an enlarged end view of the crankpin in its relation' to structure 16, showing the radial sweep of its cam and the radial ball bearing assembly that permits rotary movement of the crankpin relative to said structure which is carried by the crankpin throughout the crankthrow.

FIGS. 1, 2, 3, 7 and 8 show cylinder 1 wherein doubleacting piston .2 reciprocates in the well-known manner. This cylinder is surrounded by a jacket 3 and has channels i 4 extending through its top and bottom heads and around FIG. 2 shows the center ofV the` crankpinV in direct line with the top center of the cranktb'row and also the wrist pin in the crosshead, with the base Dof the crankpin cam commencing to make contact withcam follower A and camfollower R in the cranlrpin.v v

FIG..3 shows the crankpin camfully engaging cam follower A at the` 30-degree-after-top-center position and 'cam follower B occupying the aforesaid. crankpin recess.

FIG. 4 is a three-quarter view of the crankpin secured to crankarms which may be integrally formed with a crankshaft, not shown. In thisview, Vthe outlines'V of the crankpin (CP) cam are made clear as is'alsotherrecess R formedpdirectly opposite said cam. Y

FIG. 5. is aview, looking downward, of the structure. identified at 16 taken on the line 5 5, FIG. 10, in whichV view is shown the vopeningfin the top of said structure lfor permitting the in-.and-out movement of cam followv er A for it yto be contacted by the CP cam. An identical opening is provided in the bottom of the structure.

FIG. 6 is a side view of structure lshowing perpendicular ball bearing assemblies that permit, relative to said structure, anti-frictional reciprocation of the housing ap- Babout to occupy recess forV accommodating similar movements of cam follower its sides to permitcirculation of Y a heat-absorbing uid therethrough. Each head in each ofthe above figures has an intake valveS and an exhaust valve 6 for admitting and discharging respectively a working fluid into top chamber 7 and bottom chamber 8. The source of the working Huid and, accessories associated therewith are not shown. v, f Y

' Piston 2 vis connectedl lto lcrosshead assembly 9 by means of tie rod 2A which has a shoulder 2B for seating of the piston thereon, locknut 2C securing the rod to the piston at its top. Crossheadlassembly 9 reciprocates with V,the piston on trackways 10 which may be of an apchamber 8, which chamber is shown clearly in FIGS.

7 and 8.

Connectingrod 14 is movably connected to crosshead 9 by conventional wrist pin 15 and extends centerwise to merge into housing 14A that encompasses twinhalf structure 16 which, in turn, movablyV encompasses cranltpin 17, shown individually in FIGS. 4 and 9 and in position .in FIGS. l, 2, 3, 7 and 8 and also in FIGS. 10and 1l. .As shown `in FIGS, 1, 2, 3, 7 and 8, connecting rod 14 carries in its base cam follower A, which l' is removably secured thereto by screw bolts 18 and which pendage and, of course, the-connecting rod; also, the ball kbearing assembly which permits rotation of the assembly, of'which the 'crankpin is a part and the bolts that secure the halves of structure 16 to each other.

FIG. 7 shows the cranlrpin cam about to make Yccfntact with cam follower B at bottom center of the crank- Vthrow and vcam follower A` about to occupy vrecess R.

gFIG. 8 showsV the crankpin cam fully engaging cam followerB at the 30-degree-pastabottom-center position and cram follower A occupying recess R. As .will be seen, the position of the. cam engagement in the second cycle is directly opposite the position of engagementshown in FIG. 3.y The respective positionsv of the piston in the normally rides, as shown in FIG. 1, on the rounded surface of crankpin 17. Cam `rfollower A is a Ycontact point for the connecting rod, crosshead and piston, and upon being acted .upon by the CP cam, gradually pushes the piston upward the Vfull distance of the radialprojection of the cam. f

FIG. 2 shows the center ofthe crankpin at top center ofthe crankthrow, with the CP cam about to contact cam follower A. FIG. 3 shows the center of the crankpin at 30 degrees .past top center on the crankthrow and the apexvof the CP cam riding on the apex of cam follower A, the added distance brought Vinto being by the linear dimension of said CP cam being temporarily added to the length ofthe connecting rod thus making Vpossible re- .tention of the' piston, as shown in FIG. 3, at the same Vheights in the cylinder asthe heighth attained by the piston when the center ofthe crankpn, as shown in FIG.

2, was at top center of the crankthrow. The length, or radial projection, of the CP cam thus compensates for what normally would be the travel distance of the piston between top center of the crankthrow and the aforesaid 30 degrees on the power stroke.

In connection with this double-acting piston, a doubleacting cam follower arrangement is provided. That is, just as the aforesaid cam follower A responded to the contact made -by the CP cam, just so is provision made to cause retention of the piston when the crankpin arrives at bottom center of the crankthrow at the commencement of the second cycle. For this purpose, cam follower B, which is mounted in the base of housing appendage 14A and secured thereto by bolts 19, is provided. As shown in the various ligures, particularly FIG. 7, this `cam follower is positioned in said appendage directly opposite cam follower A, in which figure it will be seen that cam follower B is about to be acted upon by the CP cam, the center of the crankpin being at the lSO-degree position of the crankthrow.

By referring particularly to FIG. 9, which is an end view of crankpin 17, it will be seen that a recess R is formed in the underside thereof directly opposite its cam. In FIG. 2, the immediacy of the CP cam contacting cam follower A and cam follower B about to enter the crankpins recess, will be observed. In FIG. 7, the opposite cam follower action takes place. The walls comprising recess R have rounded `corners to smoothen the in-and-out movements of cam yfollowers A and B.

The halves of twin-half structure -16 are made secure to each other by bolts 20. This structure carries in its sides a plurality of bearing assemblies which contact the inner Iwalls of appendage 14A and thereby eliminate most of the friction that otherwise would occur during the rapid reciprocal movements of the appendage relative to the non-reciprocal movement of structure 16. v

Radial bearing assemblies 22 are mounted between twin-half structure 16 and longitudinal bearing assemblies 21. Assemblies 22 permit rotation of structure 16 and all with which it is associated around crankpin 17 throughout the crankthrow. As shown in FIG. l0, crankarms Z3 are made integral with crankpin 17 on each end thereof, which arms are, in turn, made integral with crankshaft 24. Balance weights 25, secured by bolts 26, are positioned on these crankarms for effecting a smooth running balance of the engine.

Dotted line 27 -between FIGS. l and 2 shows the difference in travel of the piston from the 30-degree-beforetop-center position and the top center position in FIG. 2, and dotted line 2S between FIGS. 2 and 3 indicates the artificial heighth of the piston made possible by the CP cam contacting cam follower A. Dotted line 29 between FIGS. 7 and 8 shows the position of the piston in the cylinder relative to the center of the crankpin at bottom center and at the 30-degree-after-bottom-center position on the second power stroke respectively. Dotted line 30 in FIGS. 7 and 8 indicate the extent of reciprocal travel of the housing appendage in accordance with the dictates of the CP cam.

Should this invention be employed in a steam engine, a set of operating conditions different from those employable in an internal combustion engine would naturally obtain. Steam introduced against a piston follows it in its cylinder at constant pressure throughout as many degrees as desired before the steam is cut olf. Therefore, by halting the pistons travel as herein described until the 30-degree position on each power stroke has been reached there would result a great saving in steam for the power developed. The points of introduction and cut-off are all important in steam engine economy.

It will no doubt be obvious that a position other than that of 30 degrees past top and bottom center-s of the crankthrow may prove more advantageous than the example selected, in which case differently sized and differently shaped cam followers may be employed, the selection thereof depending largely upon the speed of engine operation desired.

Having described my invention, I claim:

1. The combination with a rotatable crank assembly and a reciprocating crosshead, of a rod and associated construction mov-ably connecting said crosshead with the crank assembly for permitting halts for a period of time in the movements of said crosshead, said assembly establishing a irst anda second crankthrow cycle having a top and a bottom center respectively, said crank assembly including a crankpin having a center and a rounded surface and a cam having a base andan apex projecting radially therefrom, a cam follower mounted in the rod at the end opposite said crosshead and having an apex for normally contacting said rounded surface, an enveloping structure forming part of said construction mounted on said crankpin and carrying radial bearings positioned on each side of the crankpin cam -for permitting, relative to said structure, uninterrupted rotation of the crankpin, said rod terminating in an appendage having sides and a base and carrying bearings for permitting simultaneously with said rotation reciprocal movement of said structure, a second cam follower mounted in the base of said appendage, said second ycam follower having an apex for normally contacting the rounded surface of said crankpin, the base of said crankpin cam during the first crankthrow cycle contacting the apex of the rod Acam follower at said top center and subsequently lending its radial length thereto for halting said crosshead at said top center until the apex of said crankpin `cam passes the vapex of said rod cam follower at a location in the cycle past top center, the base of said crankpin cam during said second cycle thereafter contacting the apex of said second follower cam follower at bottom center and subsequently lending its radial length thereto for halting the crosshead at said bottom center until the apex of said crankpin cam passes the apex of said second lfollower at a location in the cycle past bottom center.-

2. The combination with a rotatable crank assembly and a reciprocating crosshead of a rod and associated construction rnovably connected to said crosshead and to the crank assembly for permitting periodic halts in the movements of the crosshead, said assembly having a crankshaft and a 'crankpin for establishing a first and a second cycle during every revolution of the assembly, a top and a bottom center of said cycles, said crankpin having a rounded surface, a cam having a base and an apex integrally formed on and extending radially from said surface, a iirst `carn follower having an apex and being mounted in the end of the rod opposite said crosshead for momentarily contacting said rounded surface, said rod terminating in an appendage `comprising a housing, a second cam follower mounted in said appendage and having an apex =for momentarily contacting the lrounded surface of the crankpin, the latter apex being positioned opposite to and facing the apex of the rst follower, the base of said crankpin cam during the first of said cycles making contact with the apex of the first follower at said top center and subsequently lending thereto its radical length until the apex of the crankpin cam passes the apex of the first follower at a location in the cycle past top center, the base of said crankpin lcam thereafter making contact with the apex of the second cam :follower at said bottom center and subsequently lending thereto its radial length until the apex of said crankpin cam passes the apex of the second follower at a location past bottom `center in said second cycle.

3. The combination with a rotatable crank assembly functioning in a rst and a second cycle together with a reciprocating crosshead, of a rod and associated construction movably connected to said crosshead and to the crank assembly for permitting halts in the movements of the crosshead while said assembly rotates uninterruptedly through said cycles, said assembly having a crankshaft, crankarm-s and a crankpin for establishing a top and a bottom'center of said cycles, said Vcrankgpin har/inge rounded surface and bein-,g integrated with; said crankpin, said construction also havingan appendage comprisi ing' ahousing having sidesjand a lhase and means for antifrctionally encompassing said structure, a cam follower' vmounted in the yend of therod opposite said crosshead and terminatingl in an apex for momentarily contacting said rounded surface, a second cam follower mounted in the base of said appendage and being positioned opposite the apex of said rod cam follower, the base of said crankpin `cam establishing contact with the apex of said rod Y cam follower when the center of the cranlipin is in line with the centerof said crankshaft and said top center for permitting retention of said crosshead at top center until the apex of said rod canifollower cornes-in line the center of said crankpin cam at a position in'said rst cycle Va number :ofy degrees past the top center thereof, the base of said crankpin earn thereafter establishing contact with the yapex ofsaidsecond `cam follower when the center. of said erankpin is in V`line With theV center of said crankshaft andcsaid bot-tom -center for permitting retention of said orosshead at bottom center until the apex of said sec-ond cam follower cornes in line with the center of said Ycranlipin cam at a position in said second cycle ia ynumber of degrees past bot-tom center, a recess orinedtin saidcrankpin'diametrically opposite Vthe cam thereof for alternately and sequentially serving as a repository for said rod'cam follower and said second cam follower during each revolution of thecranli assembly, said envelopingstructure being comprised of twin halves, eans for'securing said halves tov each other, each half lhavingan' aperture for permitting the apex of the rod cam follower and the apex of the second cam follower to Contact the rounded surface of said crankpin when said followers are not beingV engaged by said crankpin cam.

kReferences Cited inthe le of this patent UNITED STATES'PATENTS- 1,512,649 Stockrnan Oct. 2l, 1924 1,574,573 Hale Feb. 23, 1926 2,179,185 Jerrell et al. Nov. 7, 1939 2,317,167 Baer Apr. 2o, 194s 2,328,918 McManus Sept. 7, 1943 2,625,048 Vissat Jan. 13, 1953

Claims (1)

1. THE COMBINATION WITH A ROTATABLE CRANK ASSEMBLY AND A RECIPROCATING CROSSHEAD, OF A ROD AND ASSOCIATED CONSTRUCTION MOVABLY CONNECTING SAID CROSSHEAD WITH THE CRANK ASSEMBLY FOR PERMITTING HALTS FOR A PERIOD OF TIME IN THE MOVEMENTS OF SAID CROSSHEAD, SAID ASSEMBLY ESTABLISHING A FIRST AND A SECOND CRANKTHROW CYCLE HAVING A TOP AND A BOTTOM CENTER RESPECTIVELY, SAID CRANK ASSEMBLY INCLUDING A CRANKPIN HAVING A CENTER AND A ROUNDED SURFACE AND A CAM HAVING A BASE AND AN APEX PROJECTING RADIALLY THEREFROM, A CAM FOLLOWER MOUNTED IN THE ROD AT THE END OPPOSITE SAID CROSSHEAD AND HAVING AN APEX FOR NORMALLY CONTACTING SAID ROUNDED SURFACE, AN ENVELOPING STRUCTURE FORMING PART OF SAID CONSTRUCTION MOUNTED ON SAID CRANKPIN AND CARRYING RADIAL BEARINGS POSITIONED ON EACH SIDE OF THE CRANKPIN CAM FOR PERMITTING, RELATIVE TO SAID STRUCTURE, UNINTERRUPTED ROTATION OF THE CRANKPIN, SAID ROD TERMINATING IN AN APPENDAGE HAVING SIDES AND A BASE AND CARRYING BEARINGS FOR PERMITTING SIMULTANEOUSLY WITH SAID ROTATION RECIPROCAL MOVEMENT OF SAID STRUCTURE, A SECOND CAM FOLLOWER MOUNTED IN THE BASE OF SAID APPENDAGE, SAID SECOND CAM FOLLOWER HAVING AN APEX FOR NORMALLY CONTACTING THE ROUNDED SURFACE OF SAID CRANKPIN, THE BASE OF SAID CRANKPIN CAM DURING THE FIRST CRANKTHROW CYCLE CONTACTING THE APEX OF THE ROD CAM FOLLOWER AT SAID TOP CENTER AND SUBSEQUENTLY LENDING ITS RADIAL LENGTH THERETO FOR HALTING SAID CROSSHEAD AT SAID TOP CENTER UNTIL THE APEX OF SAID CRANKPIN CAM PASSES THE APEX OF SAID ROD CAM FOLLOWER AT

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