US2211875A - Compressor control system - Google Patents

Description

Aug. 2, 1 B. s. AIKMAN COMPRESSOR CONTROL SYSTEM Original File i Dec; 18, 1936 2 Sheets-Sheet 1 mQ Q Q Q VQ NTN A R I- R w NSWR E 0 mm W MA R U 5m Aug.'20, 1940- B. s. AIKMAN COMPRESSOR CONTROL SYSTEM Original Filed Dec. 18, 193$ 2 Sheets-Sheet 2 V///I/IIIIIIIII mWr gm M wow m h\ WM bor how m w N \9 mom N o .1 T EKQQQN ,1 gm R mbw .U B Qma M mow mmm w 5m @2 ATTORNEY Patented Aug. 20, 1940 a ent I Q F COMPRESSOR CONTROL SYSTEM Burton S. Aikman, Wilkinsburg, Pa, assignor to The Westinghouse Air Brake Company, Wilmerding, Pa, a, corporation of Pennsylvania Original application December 18,1936, Serial 116,473. Divided and this application October 19, 1938, Serial No. 235,830

12 Claims.

This invention relates to compressor anddriving motor equipments, and more particularly to means responsive to the pressure of fluid delivered by a compressor for simultaneously controlling the unloading thereof and the operation of the driving motor, the present application pertaining to subject matter divided out of my copending application for improvements in Compressor control systems, which was filed .in the United States Patent Office December 18, 1936, Serial No. 116,473, and for which Patent Number 2,148,719 was issued on February 28,,

A further object of the invention is to provide I a compressor control system incorporating means to vary the volumetric efliciency of the compressor in accordance with the pressure of fluid compressed thereby.

Another object of my invention is to provide an improved control system for a fluid compressor driven by a variable speed motor, and including means for varying t1 e speed of the motor in accordance with variations in the pressure of fluid compressed by the compressor.

Another object of the invention is to provide a compressor control system of the above type which operates to maintain the compressor unloaded until the driving motor has reached substantially its normal speed, and to effect unloading of the compressor in the event the motor ceases to drive the compressor.

Other objects of the invention and features of' novelty will be apparent from the following description taken in connection with the accompanying drawings, in which,

Fig. l is an elevational view showing a compressor and driving motor therefor equipped with a preferred form of control system embodying my invention;

Fig. 2 is an enlarged sectional view showing a portion of the control mechanism and of th compressor shown in Fig. 1;

Fig.3 isan enlarged sectional'view of a por tion of a compressor shown in Fig. l; and

Fig. 4 is a sectional view taken substantially along the line 4+4 of Fig. 2. g

' Description Referring to l of the drawings, there is 1 illustrated therein a compressor I 0|, which is driven. by an'internal combustion engine I02 and 7 compresses fluid into a reservoir I91...

The engine W2 may be of any well known construction and has an inlet manifold through which fuel is'supplied to the cylinders of the engine froma carburetor I05, which may also be of a well known construction. I A throttle valve m3 is interposed in the passage. through the inlet manifold M4 at apoint intermediate the carburetor and the engine, While'a choke I valve H6 is provided to control theflow of air from the atmosphere to the carburetor.

. The control system provided by this invention comprises a control device indicated generally by the reference numeral IIZand operative in response to variations in the pressure of the fluid in the inlet manifold HM, and to variations in the pressure of the; lubricant in the lubricating system of the compressor IM. for controlling the throttle valve I08, the choke valve Hi1, and for also controlling operation of the unloading means for the cylinders of the compressor IOI.

g The control system provided by thisvi nven tion includes, in addition, a control device indicated generally by'the reference numeral H4 for controlling the supply of fluid from the at'-- mosphere to the inlet chamber of the compressor.

Theconstruction of the control device Il2'is best shown in Fig. 2 of the drawings, and, as illustrated, comprises a body having a boretherein in which is mounted a piston I29, which is subject at one face to the atmosphere, and at the other face to the press'ureo-f the fluid in acham ber I22, which is constantly connected by Way of a pipe lid with the inlet manifold I64 of the engine 182., A spring I is mounted in the chamber I22 and yieldingly urges the piston to the right, as viewed in Fig. 2 of the drawings, until, further movement of the piston is prevented by a stop, not shown.

The choke valve H8 is secured on a shaft on which is secureda lever I26. The lever I26 carries a pin I28, which extends into a slot I30 in the-free end 'ofra lever I32, which is pivotally supported from the body of the control device II2 by means of a pin I34.

As is best shown in Fig. 1 of the drawings, the lever I32 has a slot I86 formed therein into which extends a pin I38 carried by an arm I40 formed on the piston I28.

The throttle valve I08 is secured by means of a shaft to a lever I42, one face of which is engageable with the arm M0 of the piston I29 at certain times, as will hereinafter more fully appear.

The body of the control device H2 is further provided with a bore having mounted therein a piston I94, which is subject on one face to the pressure of fluid in a chamber I48 constantly communicating by way of a pipe I43 with the lubricating system of the compressor IOI, and at the other face to the opposing force exerted by a spring I50. The piston I 48 has formed integral therewith a stem I5I which extends through and is guided by a bore in the end wall of the body of the control device. The stem I5I has a shoulder I52 formed thereon and adapted to engage the body of the control device to limit movement of the piston I44 against the spring The stem I5! has a bore in the end thereof in which is inserted a member I58 which is secured to the arm I42 by means of a pin I5 1. The member I55 has a shoulder'l55 formed thereon and adapted. to engage the end of the stem I5I to limit leftward movement of the member I53 relative to the stem I 5!, as viewed in Fig. 2 of the drawings.

The body of the control device II2 has, in addition, a bore therein in which is mounted a valve I56 in the form of a tube having an annular groove I58 cut therein, which in one position of the valve is adapted to establish communication between a pipe I leading to the unloading means for the compressor IOI, and a passage I62 leading from the chamber I22. The valve I56 is adapted also to control communication between the atmosphere and abranch passage I64 leading from the pipe I60.

A member I66 is secured to the stem I5I of the piston I84 and has a reduced portion extending through a longitudinal bore of the valve I56 and carrying a head I91 engageable with the valve. The member I66 has movement relative to the valve I56 and is operable to shift the valve along its bore in either direction. A spring I58 extends between the member I66 and the arm I42 associated with the throttle valve I08, and yieldingly urges the arm I42 against the arm I00 on the piston I28. The spring I68 is proportioned, however, so that it will not exert sufficient force on the piston I20 to move it against the spring I25, nor cause movement of the piston I44 against the spring I50.

As shown in Fig. 4 of the drawings, each of the cylinders of the compressor IOI has associated therewith unloading means indicated generally by the reference numeral I10. The compressor IOI has secured thereto a cylinder head I'II' having formed therein an inlet chamber I12, which is common to both of the cylinders of the compressor, andwhich is constantly connected with the crankcase chamber I16 of the compressor by way of a passage I14 having a restricted portion or choke I15.

The portion of the cylinder head I1I above each of the cylinders has a suitable passage formed therein for receiving a seat member I18, which isheld in position against a shoulder on the cylinder head I1I by means of a hollow member I19. Each of the seat members for the respective compressor cylinders has associated therewith an inlet valve I80 adapted to engage a seat on the seat member, each of which inlet valves has a stem which carries a spring seat ISI. A spring I82 is interposed between the seat member I18 and the spring seat I8I and yieldingly presses the inlet valve toward its seat.

Each member I19 has openings I83 extending through the wall thereof to permit fluid to flow from the inlet chamber I12 to the chamber within the member, and thence past the inlet valve I80 to the compression chamber in the cylinder with which the inlet valve is associated. Mounted in a suitable bore formed in the member I19 is a piston I84, which is adapted to engage the spring seat I8I on the stem of the valve I80 and is yieldingly pressed into engagement therewith by means of a spring I85 mounted in a chamber I86. The spring I85 is proportioned so that the force exerted thereby on the piston I8 1 is great enough to move the piston I84 and the valve I88 against the opposing force of the spring I82. The piston I84 is subject on one face to the pressure of fluid in the inlet chamber I12, and is subject on the other face to the pressure of fluid in the chamber I86, which is constantly connected by way of a passage I81 with the area within an annular gasket I88 which is clamped between the member I19 and a cover section I 89. The cover section I89 has a, passage therein forming communication from the area within the annular gasket I88 to the pipe I60 leading from the control device H2. in the cover section I89 engages the upper wall of the member I19 and operates through this member to press the seating member I18 into engagement with a shoulder on the head I10.

The control device II l shown in Fig. 4, which in effect constitutes an unloader common to all the compressor cylinders, comprises a body which is secured to the face of the body of the compressor IOI surrounding a passage I92 leading from the inlet chamber I12 through a central passage in the body of the control device II4 to the atmosphere, the central passage being controlled by a balanced valve device indicated generally by the reference numeral I 95.

The valve device I95 comprises a stem I96 1 having reduced end portions which are slidable in aligned bores in the body of the control device H 1, to which stem is secured a valve disc I91 that is disposed in the central atmospheric passage in the body and is adapted to engage a seat on the body of the control device H4. The stem I96 also has secured thereto a valve disc I98 which is mounted in the passage I92 and is adapted to engage a seat on the body of the control device II 4. Both valves I91 and I98 are thus adapted for simultaneous operation to control the flow of fluid from the atmosphere to the passage I92.

The stem I96 has a slot extending therethrough adjacent the middle thereof and into which extends the rounded end portion 200 of a lever 28I, which is pivotally supported from the body of the control device II'4 by means of a pin 203.

The control device H4 has associated therewith a movable abutment in the form of a flexible diaphragm 205, which is clamped between confronting flanges formed on a cover section 206 and on a body portion 208 carried by the casing of the control device. The diaphragm 205 has at one face thereof a chamber 2I0, which is con- A set screw I98 secured 5 stantly connected by way of a pipe 2l2 with the reservoir I03.

The body 208 has a bore therein in which is mounted a plunger 214 which engages a face of the diaphragm 2%. The plunger 2! is yieldingly pressed into engagement with the diaphragm 265 by means of a coil spring 2l6, which is interposed between the plunger and an adjustable spring seat 2| 8. I The plunger 2! has secured thereto a rod 220, which extends through a bore in the spring seat 2? and is pivotally connected to the end of the lever 2M by means of a pin 222.

The compressor It i is provided with a pressure lubricating system, the construction of which is shown in Fig. 3 of the drawings. The compressor has a crankshaft 225, which is mounted in the crankcase chamber lit, and is supported by suitable bearings on the body of the compressor.

The crankshaft 225 has cranks on which are journaled connecting rods to which are secured the pistons of the compressor cylinders.

The crankshaft 225 has, in addition, an eccentric 227 formed thereon on which is journaled a piston 228 having a passage 23B therein, which communicates with an annular groove 232 in the face of the eccentric 221. A passage indicated at 2% communicates with the groove 232 and extends through the crankshaft 225 to the faces of the bearings of the connecting rods which are secured on the crankshaft.

The piston 228 extends into a piston bore in a body 2536, which is pivotally supported on the lower wall of the crankcase chamber il'fi by means T i of brackets 238 and 239. Positioned in the lower body 2236, and at one point in its range of movement the member M2 is positioned above a passage 2515, which communicates with the lower portion of the crankcase chamber H6 and with the bore in the body 236. At another point in the. range of movement of the piston 228, the

member 242 is located adjacent the end of the piston bore in the body 238 so as to cut ofi communication thereto from the passage 245. A passage EtS is formed in the body 236 and communicates with the piston bore therein at a point adjacent the end thereof, and this passage also communicates through a choke M9 with a passage 256 to which is connected the pipe M8 leading to the control device H2.

A pressure release valve device indicated generally by the reference numeral 252 is provided for controlling the pressure of the fluid inthe lubricating system of the compressor. The valve device 352 comprises a seat member having a pas age therein which communicates With the passage 24% in the member 236. The passage in the seat member is surrounded by a seat adapted to be engaged by a ball valve element which is yieldingly pressed to the seated position by a coil spring 256.

The compressor is! has associated therewith, in. addition, a pressure regulating valve device indicated generally by the reference numeral 260 and comprising a body having a bore in which is mounted a piston 262, which is subject on one face to the pressure of the lubricant in a chamber 264, which is constantly connected by way of a passage 266 with the passage 250. The piston 262 has a valve formed integral therewith and engageable with a seat on the body of the valve device surrounding a passage 258 through which lubricant may be discharged from the chamber 26 to the compressor crankcase chamber H6.

The piston 262 is subject on the other face to the force exerted by a coil spring 2753, and to the pressure of the fluid in a chamber Hi2, which is constantly connected to the crankcase chamber HE by way of a passage 2'54.

The equipment is shown in Fig. 2 of the drawings in the position which it assumes when the compressor It?! and the driving engine Hi2 are idle, and the pressure of the fluid compressed by the compressor is less than that which the control system is adapted to maintain.

At this time the spring 2H3 maintains the diaphragm 2B5 inengagement with projections 2t! on the cover 2836, and also maintains the balanced valve device 95 in its full open position.

As the. compressor is idle, no pressure is exerted on the lubricant in the compressor lubricating system, while the piston led of the con trol device H2 is held at one end of its range of movement by the spring $50 so as to hold the throttle valve Hi3 substantially in its closed position, and to holdthe valve 655 in a position to establish communication between the passage I64 and the atmosphere.

As the passage N54 is connected to the atmosphere, the unloading means for the cylinders of the compressor iii! are connected to the atmosphere, and the springs 585 operate through the respective pistons lSfl to hold the inlet valves H30 away from their seats and thereby unload the compressor cylinders.

At this time, as the engine M2 is not being operated, the pressure of the fluid in the inlet manifold [El i thereof will be substantially at atmosphere, and fluid at this pressure will also be present in the chamber I22 of the control device H2 with the result that the spring !25 holds the piston IEil in theposition determined by the stop, not shown, associated therewith.

In this position of the piston I25 the arm M thereon engages the lever M2 and holds it in a position to hold the throttle valve Hi8 slightly open, as shown in Fig. 2 of the drawings. With the lever M2 so positioned the shoulder 555 on the member E53 is spaced from the end of the is at the same time such as to cause the lever l32 to maintain the choke valve H0 in the closed position.

Initial starting operation If it is desired to start the engine I02, it may be started readily at this time as the carburetor is choked and the throttle valve is open slightly, while the compressor is unloaded with the result that the load on the engine is at the minimum.

As soon as the engine is started there is a reduction in the pressure of the fluid in the inlet manifold H34 of the engine and a corresponding reduction in the pressure of the fluid in the chamber I22 on the valve device H2. On a reduction in the pressure of the fluid in the chamber E22, thepiston lZfl is moved by the higher pressure of the atmosphere against the spring I 25, and on this movement of the piston I20 force is exerted through the pin I38 to move the lever I32, and. the slotted end portion of the lever I32 moves the pin I28 and the arm I26 so that the choke valve I I0 is moved from the closed position to the open position.

When the engine I02 is operated the crankshaft 225 of the compressor IllI is rotated and the piston 220 of the compressor lubricant pump is reciprocated in the member 236. On upward movement of the piston 220, as viewed in Fig. 3 of the drawings, as the member 242 uncovers the end of the passage 245, lubricant from the lower portion of the crankcase chamber I16 is drawn into the bore in the member 236, and on subsequent downward movement of the piston 223 the member 242 cuts off communication between the bore in the member 236 and the passage 245, while the lubricant contained in the bore in the member 236 is subjected to pressure, with the result that the ball check valve 244 is moved against the spring 246 to permit fluid to flow through the passage in the member 242, and thence through the choked passage in the member 240 to the passage 230 leading to the amiular groove 232 and the passage 234 in the crankshaft 235, through which lubricant flows to the portions of the compressor to be lubricated.

The pump is proportioned so that its capacity exceeds by a substantial amount the volume of lubricant required to lubricate the compressor, and lubricant placed under pressure by the piston 220 flows through the restricted passage 249 to the passage 250, and thence by way of the pipe I48 to the chamber I46 at the face of the piston I44 of the control device H2.

In addition, lubricant supplied to the passage 250 flows therefrom by way of the passage 266 to the chamber 264 at the face of the piston 262 of the pressure regulating valve device 260. Normally the valve carried by the piston 262 is held in seated position by the spring 216 to prevent the release of lubricant from the chamber 264 to the compressor crankcase I16, but if the lubricant pump supplies lubricant in a volume in excess of that required to lubricate the compressor and to operate the control device N2, the pressure of the lubricant in the chamber 264 will increase and the lubricant will move the piston against the spring 210 to release lubricant from the passage 250 and thereby reduce the pressure of the lubricant in this passage to the value determined by the spring 210.

Similarly, if the pressure of the lubricant in the passage 248 increases above a predetermined value because of the rapid supply of lubricant thereto by the pump, and the restricted flow of lubricant therefrom through the choke 249, the ball valve 254 will be moved against the spring 256 to permit the release of lubricant from the passage 248 until the pressure therein is reduced to a predetermined value.

The pressure release valve device 252 is adjusted so that it operates to prevent the release of lubricant from the passage 240 until the pressure of the lubricant therein is slightly greater than is required to move the piston 262 of the valve device 260 against the spring 210 when the fluid in the crankcase chamber I16 is at substantially atmospheric pressure, while the valve device 262 is adjusted so that with the crankcase chamber I16 substantially at atmospheric pressure, it will not release lubricant from the passage 250 until the pressure therein is slightly greater than is required to' move the piston I44 of the control device II 2 to the end of its range of movement against the spring I50.

Fluid is supplied to the chamber I46 in the control device H2 at a restricted rate because of the restricted flow capacity of the choke 249, and as a result, the piston I44 is moved slowly against the spring I56. On this movement of the piston I44 the end of the stem I5I engages the shoulder I55 on the member I53 so that force is exerted on the lever I42 to move the throttle valve I08 towards the open position. As the throttle valve is moved slowly, the engine will accelerate gradually, and the engine and the compressor driven thereby will not be subjected to severe strains.

011 movement of the piston I44, the member W6 is also moved. The member I66 is initially moved relative to the valve I56, and when the piston I 54 is moved almost to the end of its range of movement, the head I61 carried by the member I66 engages the valve I56 so that on further movement of the piston I54 the valve I56 is moved in the bore in which it is mounted to a position in which it cuts off communication between the passage I64 and the atmosphere, while the annular groove I58 in the valve I56 establishes communication between the passage I62 leading to the chamber I22, and the pipe I60 leading from the unloading means I10 for the compressor cylinders.

When the valve I56 is moved to this position, communication is established between the inlet manifold I04 of the engine and the unloading means I10 for the compressor cylinders and fluid flows to the inlet manifold from the chambers I86 of the unloading means. On a reduction in the pressure of the fluid in the chambers I86, the pistons I84 are moved upwardly against the springs I85 by the pressure of the atmosphere present in the inlet chamber 112, while the inlet valves I are moved to their seated positions by the springs I82 to load the compressor.

The compressor is now operated in the usual manner to compress fluid under pressure into the reservoir I03, while fluid to be compressed is drawn into the inlet chamber I12 past the open balanced valve device I95.

Restriction of air delivery and, reduction in speed in accordance with increase in reservoir pressure On an increase in the pressure of the fluid in the reservoir I63 there is a corresponding increase in the pressure of the fluid in the chamber 2I0 at the face of the diaphragm 205 of the control device II4. On an increase in the pressure of the fluid in the chamber 2I0 force is exerted through the diaphragm 265 upon the plunger 2I4 to move it against a spring 2I6, while movement of the plunger 2M is transmitted through the stem 220 to move the arm ZllI about the pin 203.

On this movement of the arm 2ilI the valves I91 and I98 are moved toward their seats to restrict the rate of flow of fluid to the inlet chamber I12.

On this reduction in the rate of flow of fluid to the inlet chamber I12, as the compressor continues to be operated, there will be a reduction in the pressure of the fluid in the inlet chamber I12, and fluid will flow thereto at a restricted rate from the crankcase chamber I 16 through the passage I14 and the choke I15, thus producing a corresponding reduction in the pressure of the gas present in the crankcase chamber I16.

On this reduction in the pressure of the gas in (ill the crankcase chamber I15, there is a corresponding reduction in the force exerted on the piston 262 of the pressure regulating valve device 260 in opposition to the force exerted thereon by the lubricant under pressure in the chamber 268. The piston 2 52 will thereupon be moved upwardly against the spring 21! and will open communication from the chamber 25 through the passage 268 to release lubr cant from the passage 255i until the'pressure of the lubricant remaining therein has been reduced by an amount substantially equal to the reduction in the pressure of the gas in the crankcase chamber I16.

On this reduction in the pressure of the lubricant in the passage 2% there is a corresponding reduction in the pressure of the lubricant in the chamber hit at the face of the piston M4, and the piston t l is moved by the spring i5 3 until the spring has expanded sufficiently to equalize the force exerted thereby on the piston Hi l with the reduced pressure of lubricant in the chamber M6.

On this movement of the piston I44, the throttle valve iilil is moved away from the full open position toward the closed position to reduce the rate of flow of fuel to the engine, and thereby to reduce the rate at. which the engine drives the compressor. Atthe same time, the member I68 is moved relatively to the valve I55, which remains in the position in which the groove I58 therein establishes communication be tween the passage M52 and the pipe 159 with the result that the compressor continues to be loaded. The compressor, therefore, will continue to be loaded and will be driven by the engine,

but the speed of the engine and of the comcrankcase chamber 115, will be varied in accordance with the pressure of the fluid in the reservoir Hi3.

The rate at which the engine I82 is supplied with fuel past the throttle valve W8 is governed by the pressure of the lubricant in the chamber 5%, and this is controlled by the pressure regulating valve device 280 in accordance with changes in the pressure of the gas in the crankcase chamber I16 It will be seen, therefore, that the degree of reduction in the supply of fuel to the engine will be in accordance with the increase in the pressure of the fluid in the reservoir I93.

On the reduction in the pressure of the fluid in the inlet chamber I12 as a result of operation of the balanced Valve device 195, there is a reduction in the force exerted on the pistons I84 of the unloading means I18] and tending to hold them against the springs I82. The various parts of the equipment are arranged and proportioned, however, so that the pistons I84 will not be moved downwardly by the springs I82, assuming that the chambers I86 remain connected 104, until the pressurepiston I44 to be moved substantially to the end of its range of movement by the spring I50, and move the valve l56 to a position to connect the pipe ISO to the atmosphere.

The unloading means i168 associated with the compressor cylinders will not, therefore, be directly operated to unload the compressor in response to a reduction in the pressure of the fluid in the inlet chamber I12, but will be operated to unload the compressor only as a resultof operation of the pressure regulating valve device 260 and of the control device lit in response to a reduction in the pressure of the fluid in the'inlet chamber H12.

At this time, however, as the flow of air from the atmosphere to the inlet chamber I12 is restricted, and as there is a reduction in the pressure of the fluid in the inlet chamber I12, a reduced amount of fluid will be supplied to the compression chambers of the compressor cylinders, thereby reducing the volumetric efiiciency of the compressor, and also reducing the power required to drive the compressor. I

As the supply of fuel to the engine, and the speed of the engine are reduced at this time, the power developed by the engine is reduced, but as the power required to drive the compressor is reduced, there is no danger that the engine will stall or be unable to operate the compressor.

Proportionate increase in speed in response to loaded If while the compressor continues to be 0p.- erated there'is a reduction in the pressure of the fluid in the reservoir I03, the balanced valve device E95 will be operated by the diaphragm .285 and the spring 216 to permit an increase in the rate of How of fluid from the atmosphere to the inlet chamber I12. There will, therefore, be an increase in the pressure of the fluid in this chamber, and a corresponding increase in the pressure of the ,gas in the crankcase chamber I16, while the pressure regulating valve device 266 will be operated to increase the pressure maintained on the lubricant in the passage 250 and the chamber M6, and the piston M l will be moved against the spring Hill to further open the throttle valve I438 and increase the rate at which the engine drives the compressor,

As a result of the increased flow of fluid from the atmosphere to the inlet chamber I12, there will be an increase in the supply of fluid to the compressor cylinders and a corresponding increase in the volumetric efliciency of the compressor, while more power will be required to drive the compressor. As the rate of supply of fuel to the engine is increased at this time, the engine develops more power and is able to carry the increased load, and the compressor is operated to compress fluid into'the reservoir I83 at a more rapid rate.

Unloading of compressor in response to high reservoir pressure If the pressure of the fluid in the reservoir I03 increases to a predetermined relatively high value, the force exerted by the fluid under pressure in the chamber 2st at the face of the diaphragm 265 will be great enough to move the di-- aphragm 205 and the plunger 2M against the spring 2I6 far enough to cause the valves 191 and I98 to be moved adjacent to their seats to greatly restrict the flow of fluid from the atmosphere to the passage I92 and the inlet chamber I12,

thereby producing a substantial reduction in the pressure'of the fluid in the inlet chamber I12 and in the crankcase chamber I16.

During this reduction in the pressure of the as in the crankcase chamber I15 there will be a corresponding reduction in the force exerted on the piston 252 of the pressure regulating valve device 256 in opposition to the force exerted thereon by the lubricant in the chamber 254, and the piston 262 will thereupon be moved against the spring 210 so as to open communication through the passage 268 to permit the release of lubricant from the passage 256 to the crankcase chamber until the pressure of the lubricant in the passage 250 is reduced a substantial amount.

As there has been a substantial reduction in the pressure of the gas in the crankcase chamber l'iS, the pressure regulating valve device 2 51! will permit the pressure of the lubricant in the passage 255 to reduce a substantial amount. The pressure of the lubricant in the passage 2552 will be permitted to reduce to a value such that the lubricant under pressure in the chamber M5 at the face of the piston I44 is unable to hold this piston against the opposing force of the spring E59, and the piston will be moved to the left, as viewed in Fig. 2, substantially to the end of its range of movement by the spring I55.

After the piston has moved a predetermined amount in this direction, the member I it engages the valve I56 and moves it to a position in which the annular groove I58 therein no longer establishes communication between the passage I62 and the pipe I60, and in which the valve opens communication between the passage I64 and the atmosphere.

Fluid from the atmosphere will thereupon flow through the passage E64 and the pipe I63 to the unloading means I associated with the compressor cylinders, and on an increase in the pressure of the fluid supplied to the unloading means, the pistons I84 thereof will be moved downwardly, and will engage the ends of the stems of the intake valves I86 to move them against the springs I32 away from their seats so as to unload the compressor.

On this movement of the piston I44 force is exerted through the spring I58 to move the arm I42 and close the throttle valve 108. At this time, as the engine IE2 is running, the piston its is held in its inner position against the spring I25, and the arm I4EI thereon does not oppose movement of the arm I42 by the spring E58. The shoulder I55 on the member I53 is maintained in engagement with the end of the stem I5! of the piston I34, therefore, and the arm M2 is moved farther toward the throttle closed position than the position in which it is shown in Fig. 2 of the drawings, while the throttle valve Hi8 will be more nearly in the closed position. Ihe rate of supply of fuel to the engine will be reduced to the minimum, therefore, but the engine will not stall as the compressor IIlI will be unloaded before the supply of fuel to the engine is reduced to the minimum rate.

It will be understood that by this time the high pressure of fluid in the reservoir I03 will have effected operation of the control device II l substantially to cut off the flow of atmospheric air by way of the passage I92 to the inlet passage I12 of the compressor, assuming that no fluid under pressure has meanwhile been withdrawn from the reservoir I03. Since the operation of the compressor has already created a partial vacuum in the'inlet passage as hereinbefore explained, it will be apparent that the sub-atmospheric pressure likewise prevailing in the crankcase chamber I16 of the compressor causes continued operation of the lubricant pressure regulating device 260 to maintain the reduced pressure of lubricant in the passage 25B and consequently in the chamber I25 of the control device II2. The control device H2 thus continues to cause engine I52 to operate the unloaded COIl'lpressor Itl at the minimum speed as long as the pressure of fluid in the reservoir I03 remains at a value high enough to hold the balanced valve device I95 in closed position.

Operation upon reduction in reservoir pressure with compressor unloaded If at this time there is a reduction in the pressure of the fluid in the reservoir I03 as a result of. the withdrawal of fluid under pressure therefrom, the diaphragm 265 and the plunger 2 I 4 will be moved downwardly by the spring 216, while the valves I91 and I98 will be moved away from their seats. The compressor IUI will continue to be unloaded, however, as the inlet valves thereof are held away from their seats by the unloading means associated therewith.

On movement of the valves I91 and I53 away from their seats fluid from the atmosphere is permitted to flow to the passage I92, and thence to the inlet chamber I12, from which it flows by way of the passage I14 and the choke Il5 to the crankcase chamber I15 to increase the pressure of the gas in the crankcase chamber I 16.

On an increase in the pressure of the gas in the crankcase chamber I16 there is an increase in the force exerted on the piston 252 of the pressure regulating valve device 250 to move it towards the seated position to restrict the release of lubricant from the passage 253 to the crankcase chamber. This results in an increase in the pressure of the lubricant in the passage 250 corresponding to the increase in the pressure of the gas in the crankcase chamber I16, while there is a corresponding increase in the pressure of the lubricant in the chamber I46 at the face of the piston I44 of the control device I I2.

On this increase in the pressure of the lubricant in the chamber I46, the piston I44 is moved against the spring I55 so as to move the throttle valve towards the open position to increase the rate of supply of fuel to the engine, and increase the rate at which the engine drives the compressor.

When the pressure of the fluid in the reservoir I 03 has reduced to a predetermined relatively low value, the balanced valve device I95 will be operated to supply fluid from the atmosphere to the inlet chamber I12 and the crankcase chamber I16, thereby increasing the pressure of the fluid in the chamber I15 sufiiciently to operate the pressure regulating valve device 260 for permitting creation of a pressure in the passage 25!), and in the chamber I46, high enough to cause the piston I44 and member I66 to move the valve I56 to a position to again eifect loading of the compressor. The compressor will thereupon be loaded in the manner described in detail above, and will thus again operate to compress fluid under pressure into the reservoir M3 to increase the pressure of the fluid therein.

When the engine I02 is stopped and does not drive the compressor IDI, the lubricant pump of the compressor is not operated and will not supply lubricant under pressure to the passage 25!],

and the lubricant under pressure present therein will leak therefrom until the pressure 'of the lubricant remaining is at a relativelylow value. On this reduction in the pressure of the lubricant in the passage 2543 there is a similar reduction in the pressure of the lubricant in the chamber M6 at the face of the piston Md, and this piston is moved to the left to the end of its rangeof movement by the spring ii'aii, while the member 1% engages the valve ilit and moves it to a position to open communication between the atmosphere and the passage ltd so that air from the atmosphere may flow to the unloading means of the compressor to effect unloading of the cylinders of the compressor.

In'addition, when the engine N32 is not operated, the pressure of the fluid in the intake manifold IM thereof will increase to atmospheric pressure, and there Will be a similar increase in the pressure of the fluid in the chamber Hit of the control device l 52 with the result that the spring I25 will move the piston I29 to the right until its movement is prevented by engagement with. the stop, not shown. The member Mil willengage the lever .142 and move it to open the throttle valve 3 a small amount, while the piston iZll will operate through the lever i3? to move the choke H U to the closed position. As the choke is automatically closed as soon the engine ceases to operate. the choke will be nthe position to facilitate starting of engine when it is desired to again operate the engine.

It will be seen that the throttle valve m8 of the engine, and the means for unloading the com.- pressor are controlled by the piston IM of the control device l !2, and. that this piston is subject to lubricant supplied from the lubricating system of the compressor. On a reduction in the pressure of the lubricant supplied thereto this piston moves to a position to reduce the rate of supply of fuel to the engine to the minimum, and thereby causes theengine to be operated at the idling speed, and at the same time conditions the unloading means to unload the compressor. As a result, therefore, if the lubricating system of the compressor should fail for any reason, the compressor will be automatically unloaded to relieve it of work at a time when it is not properly lubricated, while the engine will be operated at the idling speed.

While one embodiment of the improved compressor control system provided by this invention has been illustrated and described in detail, it

should be understood that the invention is not limited to these details of construction, andthat numerous changes and modifications may be made without departing from the scope of the following claims. I

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In combination, an internal combustion engine having a carburetor associated therewith, the engine having an inlet passage through which fluid is supplied from the carburetor to the engine, a throttle valve controlling communication through said inlet passage, a choke valve controlling the flow of fluid from the atmosphere to the carburetor, and means subject to and operated on a predetermined increase in the pressure of the fluid in the inl t passage for closing said choke valve and for partially opening said throttle valve.

2. In combination, a fluid compressor having an inlet passage associated therewith through which fluid to be compressed is supplied to the compressor, an internal combustion engine for driving the compressor, said engine having a fuel supply device associated therewith, a movable member for controlling the rate of supply of fuel to the engine by said device, a liquid circulating system operated in accordance with the speed of the compressor, means responsive to the pressure of the liquid in. said system for controlling the movable member, means responsive to the pressure of the fluid compressed by the compressor for controlling the rate of supply of fluid to said inlet passage thereof, and means responsive to the pressure of the fluid in said inlet passage for controlling the pressure of liquid in said circulating system.

3. In combination, a fluid compressor having an inlet passage associated therewith through which fluid to be compressed is supplied to the compressor, an internal combustion engine. for driving the compressor, said engine having a fuel supply device associated therewith, a movable member for controlling the rate of supply of fuel to the engine by said device, unloading means for the compressor, a liquid circulating system operated in accordance with the speed of the compressor, means responsive to the pressure of the liquid in said system for controlling said movable member and for also controlling said unloading means, means responsive to the pressure of the fluid compressed by the compressor for controlling the rate of supply of fluid to said compressor inlet passage, and means responsive to the pressure of the fluid in said inlet passage for controlling the pressure of the liquid in said circulating system.

4. In combination, a fluid compressor, an internal combustion engine for driving said compressor, said engine having a carburetor associated therewith and having an inlet passage through which fluid is supplied to said engine from the carburetor, a throttle valve controlling communication through said inlet passage, a choke valve controlling the flow of air from the atmosphere to said carburetor, means subject to and operated on a predetermined increase in the pressure of the fluid in said engine inlet passage for closing said choke valve and for partially opening the throttle valve, and means responsive to the pressure of the fluid compressed by the compressor for also opening said throttle valve.

5. In combination, a fluid compressor, an internal combustion engine for driving said compressor, said engine having acarburetor associated therewith and having an inlet passage through which fluid is supplied to said engine from the carburetor, a throttle valve controlling communication through said inlet passage, a choke valve controlling the flow of fluid from the atmosphere to said carburetor, means subject to and operated on a predetermined increase in the pressure of the fluid in said engine inlet passage for closing said choke valve and for partially opening the throttle valve, and means responsive to the pressure of the fluid compressed by the compressor for also opening said throttle valve'without affecting the position of the choke valve.

6. Automatic control apparatus for a compressor and an internal combustion engine arranged to operate said compressor to deliver fluid under pressure to a receiving reservoir, said apparatus comprising means operative in accordance with variations in the pressure of fluid in the reservoir to vary the volumetric efliciency of the compressor, and means responsive to variations in said volumetric efliciency to effect corresponding variations in the rate of supply of fuel to said engine.

'7. In an internal combustion engine of the class having an intake manifold through which fuel may be supplied to the engine cylinders by a carburetor device, a throttle valve controlling communication through said intake manifold and a choke valve controlling the supply of air to the carburetor; a control mechanism comprising automatic means for operating the throttle valve including a spring adapted normally to bias said valve toward its closed position, and movable abutment means subject to variations in fluid pressure in the intake manifold and operative by the partial vacuum maintained therein when the engine is running to open said choke valve, said abutment means being operative when the fluid pressure in said manifold is increased upon stopping of the engine to close said choke valve and to hold said throttle valve in partially open position.

8. In a fluid compressing equipment including a compressor having a fluid intake passage, a variable speed driving motor therefor, and a receiving reservoir, the combination of valve means responsive to the pressure of fluid in the reservoir for controlling admission of fluid to said compressor intake passage, control mechanism operable to govern the speed of operation of said motor, and fluid pressure responsive means controlled in accordance with variations in the fluid pressure in said compressor intake passage for controlling operation of said control mechanism.

9. In a fluid compressing equipment including a compressor having a fluid intake passage, a variable speed driving motor therefor, and a receiving reservoir, the combination of unloader means for unloading the compressor, valve means responsive to the pressure of fluid in the reservoir for controlling admission of fluid to said compressor intake passage, control mechanism operable to condition said unloader means to load or unload the compressor and to govern the speed of operation of said motor simultaneously, and fluid pressure responsive means controlled in accordance with variations in the fluid pressure in said compressor intake passage for controlling operation of said control mechanism.

10. In a fluid compressor having an inlet passage and means for compressing fluid supplied therethrough into a reservoir, the combination therewith of a fluid inlet control device comprising a casing having a supply chamber communi taneous movement toward or away from said seats to control admission of fluid to said inlet passage, the seating face of one of said valve discs being subject to fluid pressure in said supply chamber while the seating face of the other valve disc is subject to fluid pressure in said inlet passage for balancing said valve discs against pressure variations, and fluid pressure operated means responsive to an increase in the pressure of fluid in the reservoir for moving said valve discs toward seated position to reduce the volumetric efliciency of the compressor.

11. In a fluid compressing equipment including a compressor, a variable speed driving motor therefor and a receiving reservoir, in combination, a primary unloader device operative in accordance with an increase or a decrease in the pressure of fluid in the receiving reservoir for gradually unloading or loading the compressor, a secondary unloading means cooperative with the compressor independently of said primary unloader device, mechanism controlling the speed of operation of said motor and operative in accordance with the degree of loading or unloading effected by said primary unloader device for correspondingly increasing or reducing the speed, and control means operable by said mechanism to control said secondary unloading means, said control means being operated to maintain said secondary unloading means in compressor loading position upon operation of said mechanism to increase the motor speed to a maximum, and to maintain said secondary unloading means in unloading position upon operation of said mechanism to decrease the motor speed to a minimum.

12. In a fluid compressing equipment including a compressor, a variable speed driving motor therefor and a receiving reservoir, in combination, a valve device operative in accordance with an increase or a decrease in the pressure of fluid in the receiving reservoir for gradually restricting or increasing inlet flow of fluid to the compressor, unloading means associated with the compressor, mechanism controlling the speed of operation of said motor and operative in accordance with the decrease or increase in inlet flow of fluid effected by operation of the valve device for correspond-' ingly increasing or reducing the speed, and con trol means operable by said mechanisni'to control said unloading means, said control means being operated to maintain said unloading means in compressor loading position upon operation of said mechanism to increase the' motor speed to a' maximum, and to maintain said unloading means in unloading position upon operation of said mechanism to decrease the motor speed to a minimum.

BURTON S; AIKMAN.

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