US2494573A

US2494573A - Free piston compressor and control therefor

Info

Publication number: US2494573A
Application number: US748591A
Authority: US
Inventors: Jr George A Mueller
Original assignee: LIMA HAMILTON CORP
Current assignee: LIMA HAMILTON CORP; LIMA-HAMILTON Corp
Priority date: 1947-05-16
Filing date: 1947-05-16
Publication date: 1950-01-17
Anticipated expiration: 1967-01-17

Description

0 e. A. MUELLER, JR 2,494,573

FREE PISTON COMPRESSOR AND QONTR OL THEREFOR Filed May 16, 1947 2 Sheets-Sheet 1 INVENTOR. GEunQzAMusLLzn, J12.

ATTYS.

1950 G. A. MUELLER, JR 2,494,573

FREE PISTON COMPRESSOR AND CONTROL THEREFOR Filed llay 16, 1947 2 Sheets-Sheet 2 I Q *l IN VEN TOR.

IE1 LT Saunas A. MUELLER, JR.

"QMQM Patented Jan. 17, 1950 I 2,494,573

UNITED STATES PATENT OFFICE 2.494573 FREE PISTON GODIPRESSOR AND CONTROL THEREFOR George A. Mueller, Jr., Hamilton, Ohio. "signer, by Inesne assignments, to Lima-Hamilton Corporation. Hamilton, Ohio, a corporation of Application Mil! 16, 1947, Serial No. 748,591 12 Claims. (Cl. 123-48) This invention relates to free piston internal merits by racks 28-29 which extend toward each combustion engines and is particularly directed to other from connectors 30 on each crosshead l2. a combined engine-compressor unit and a control The racks are thus of short length and are so distherefor. posed that they do not pass between chambers The primary object oi the invention is to procontaining air at diirerent pressures. The necesvide a free-piston engine-compressor and a consity for packing glands around the racks is thus trol therefor which results in the extent of the eliminated. The usual synchronizin pinion 32 stroke or the power and compressor pistons remeshes with both racks and reciprocates on a maining substantially constant over the operathub or shaft 34 extending from the center oi the ingrange. m exterior oi the power cylinder or at some other Another object of the invention is to provide a convenient location. ontrol for a free-pi on n ineompr or ni Air is drawn into the unit to be compressed for in Which p e hydraulic 11 e ay are scavenging the engine cylinder as well as for use ope a ed y an engine r at the e ds of a strok in the receiver 6. A common intake manifold of p e in e l e e ay n n 0 36 is provided which communicates with the at- 8 the amount sv imparted o the mosphere through appropriate filters (not shown) cy l a ch e d of he stroke of the pis n and with both ends oi the cylinder in which com- Still another object of the invention is to propressor pistons It operates. This cylinder is, as vide a device of the above character in which the above stated, divided into an inner part 22 in load n the engine parts added y h control e which scavenging air is compressed, and an outer ments s n zed and w h is pensive to part 24 in which air is compressed and led to the construct and maintain. receiver 6. The passage between the intake Other objects and advantages of the invention manifold and the scavenging air compressing will become app ent m the fol w n s cicylinder is designated 38 and a plurality oi simfication, reference being had to the accompanying ilar, self contained check valves Ill control the drawings in which: passage of air from manifold to cylinder. At one ure l is a dia mm c S e elevation a side the check valves 40 open toward the cylinder free piston engine-compressor unit with par s to admit air on the intake stroke, and at the other broken away to show he rel ive po itions occuside or the cylinder, valves 4| control the outward pied by the several control elem x. 3 18 flow of air from the cylinder 22 to a scavenging rammatic View, partly in c the unit airheader 2 which communicates with the power c nve y p rated. and 8- 3 s a omposite Air is drawn into the compressor cylinder diagrammatic sectional view oi the several conthrough i t k ports 44 and discharged through trol elements. ports 46 to the header 2 on the rearward stroke Referring to the dra nae. nd rti r y o of compressor piston It. From the compressor Figs. 1 and 2, the present inven n 1 h wn apheaders the air passes check valve 8 and enters p d to Iree piston compressor unit 01' the opreceiver 6 from which it may be utilized in any posed piston type. At the ends or the unit are known manner, headers 2 and l which communicate with a com- Bounce cylinders 26 operate as chambers in men compressed air trunk I and, thereby. wi which energy is stored during the outward stroke a receiver an inwardly ning check Valv l of the pistons to be utilized to cause return of the being disposed at the entrance to the receiver. pistons to firing position. The major portion 0t Each of the opposed pistons comprises a power the air in these chambers is preIerabLv contained piston Ill, 01' appropriate diameter, then a stem in annular side chambers 21, although a straight, or crosshead portion 12 to which is connected a continuous chamber may be used. The bounce compressor piston N and finally a bounce piston chambers are closed spaces to which air is added it. Cylinders of the proper diameter are assoor withdrawn as hereinafter described. It will be ciated with each of the piston sections and in 50 appreciated that the extent of the inward stroke ignated 22; the compressor cylinder 24 and the stroke may be lengthened or shortened by changbounce cylinder 26. ing the quantity 01 air in the bounce chambers The pistons are synchronized in their moveas and its initial pressure.

angers control m- The present invention provides a working tem which is actuated by th pistons, through the synchronizing racks and m to be described. that controls the supply of fuel to the firing cylinder and the air in the bounce chambers in such a manner that the stroke of the pistons remains substantially constant throughout the working range.

A dump valve ii is provided. either in the compressed air trunk i or in a by-pass conduit II leading from the trunk to a convenient location. Valve II may be operated by any suitable means such as a piston 52 working in a cylinder 51 against the tension of a spring Bl. A pilot valve 55 operated by air from the receiver admits air at receiver pressure to the front face of piston 52 whenever the receiver pressure reaches a predetermined level which may be adjusted by varying the force of a spring 58 against which pilot valve it moves toward open position. Suitable air passages are provided in the valve body to admit and exhaust air to and from cylinder 53, the vent passage being designated 51 and the passage by which air enters from the receiver 58. These passages are, of course, opened and closed by the pilot valve 55. It will thus be apparent that when the receiver is charged with air at its intended pressure the dump valve is opened and the load on the compressor is reduced to only that required to maintain the pistons in operation, nearly all of the energy taken from the cycle on the outstroke of the pistons being stored in the air in the bounce chambers and returned to the cycle by expansion on the next succeeding instroke. During the period that the receiver is full of air at its intended pressure, check valve 8 functions to prevent this pressure from acting against the compressor and prevents the escape of air from the receiver.

Fuel control is accomplished by a device operating in response to the extent of the outstroke of the pistons. The engine fuel pump is shown diagrammatically at 60 and includes the usual adjusting rack 62 to which is connected a piston 64 operating in a cylinder 68 and biased to the o position by a spring 08. Pressure at the rear of the piston moves the rack in a direction such that more fuel is iniected at each stroke of the fuel pump plunger. An adjustable needle valve III is inserted in the bleed passage from cylinder 69 so that the rate of response of the fuel control may be changed at the selection of the operator. The fuel pump may be operated in any suitable manner as by a cam ii rocked by a rod Bl.

Shaft ill on which the synchronizing pinion is mounted is continued out from the side of the engine and carries a second pinion 12 which cooperates with an arcuate rack ll formed on the end of a lever I6 pivoted at 18 and carrying adjustable actuating members an, 8| at its short end. It will thus be seen that as pinion 12 rotates the actuating members 8|! and 8! reciprocate about pivot point III with the extent of their reciprocation determined by the extent of the rotation of pinion 12. Rod 63 may be operated by lever 16 to move fuel cam 6|.

Actuating member 8|, in its reciprocation, abuts against a stem 82 of a piston type valve 83 the enlarged rear end of which operates in a dash pot cylinder M, the valve being biased to open position by a spring 85. Valve 83 controls the flow of oil or other actuating fluid between a conduit 86 and a conduit 88. Conduit It is fed with oil under pressure by a pump I and conduit ll communicates with cylinder II at the fuel pump. Thus. as valve ll moves to such a position that its reduced area. designated 82, opens communication between conduits It and 88 a small quantity of oil will pass the valve and enter cylinder 6. While the valve remains closed cylinder 68 tends to driiin into a bleed passage 9! around needle valve II. In the normal operation of the engine the stroke is adjusted so that valve 88 opens periodically in an amount suflicient to move the fuel rack 62 to the proper adjusted position. If the engine stroke is too long at the outer end. valve 8 is closed by abutment of actuating member it against stem 82 and less fuel is injected at the W next stroke since the supply of oil is cut off to cylinder 65 and the rack tends to drift toward the off position. The sensitivity of the device can be changed by adjustment of needle valve Ill so that persistent trends are followed rather than individual overstrokes.

To control the extent of the instroke of the pistons a valve 86 provided with an abutment I8 is provided to control the fiow of oil between passages Hill and MI. Passage ill communicates with pump 90 and passage lti communicates with a bounce air governor I02. Valve Ii may be conveniently controlled by a spring ill acting on its rear end and working in a I05. The valve passage is designated I" and, as in the case of valve 83, the unit is biased to open position and is moved to cut-oi! position by abutment of actuating element against stem 98.

The bounce air governor I02 may take any suitable form by which air under pressure is admitted to or bled from the direct bounce chambers II. A common passage ma leads to these chambers and enters the body of governor Hit in a common conduit llfl. Air under pressure is supplied to the governor ill: by a conduit III which connects to an air storage bottle H4 having the usual shut-01f valve H5 at its outlet. A vent pipe H6 is also connected in the governor body.

Governor 802 contains a slide valve I20 of the piston type urged in one direction by a spring ill and in the opposite direction by oil under pressure entering from conduit HH and acting against the face of the piston valve In. Oil thus entering bleeds past an adjustable needle valve in to a drain passage I24 so that the rate of bleed. and thus the rate of actuation of the valve I, may be easily controlled. It will be seen that in the position to which the valve I" is urged. in i the absence of pressure on its face, communication is opened between passage lill which leads to the direct bounce cylinders and the vent passage IIB through an upper communicating passage IIB formed in the body N12. The pressure in the direct bounce chambers is thus reduced.

when oil under pressure enters through pipe ltl and acts on the face of valve I20 moving it against its spring, the vent passage H6 is closed and communication is opened between air line I I 2 and the charging bottle H4 and passage lit to the direct bounce chambers thus increasing the pressure of air in these chambers. As the pressure of the air in the direct bounce chambers increases the extent of the instroke of the pistons is increased and, conversely the lower pressure in the direct bounce chambers permits a shorter lnstroke of the pistons to be made. The control thus results in valve I20 hunting between a position of charging and venting the direct bounce dash-pot cylinder asses-rs chambers, with the rate of change being governed largely by the setting of needle valve III. Persistent trends toward an increase or decrease in the length of stroke of the pistons will be followed where individual diflerences in the strokes do not necessarily result in a change 'in the pressure in the direct bounce chambers.

In operation the compressor works against a predetermined receiver pressure and so long as the dump valve in the receiver line remains closed the compressor is under load and suilicient fuel is injected to cause the pistons to compress air to a pressure high enough to overcome the check valve 8 in the compressed air header. When the dump valve opens by reason of the desired receiver pressure being attained, the check valve 0 remains closed and the compressor idlesat full stroke and just enough fuel is iniected to maintain the proper stroke length. Should the compressor begin to understroke the fuel will be increased by reason of the movement of valve 03 to a position such that oil passes into conduit 88 and hence to cylinder 66 adjacent the fuel rack.

Should the compressor then tend to overstroke' the supply of oil to conduit 00 is cut off. the contents of cylinder 66 bled past valve 10 to line 94 and the rack 62 drifts toward cut-oi! position.

At the inner end of the stroke the proper piston position is maintained by increasing or decreasing the pressure in the direct bounce chambers. As the load on the compressor increases and the amount of fuel injected at each stroke is, therefore, increased the pressure on the direct bounce chambers tends to build up and thus forces the pistons closer together at the exact compression strokes. If this tendency goes objectionably far. actuating element 00 strikes the stem 98 of valve 96 which then operates to cut off communication between passages I00 and IN so that fluid operating against the front face of piston valves I20 can bleed past needle valve I22 into the drain line I24. The valve I20 then drifts to the left under the influence of spring III and opens communication, through passage I28, between the direct bounce line I I0 and the vent line I It. The direct bounce spaces are thus vented to a. lower pressure and the pistons urged together less forcibly. The balance of operation is thus restored and succeeding end strokes of the pistons will be of the proper length. This venting continues until actuating element 00 no longer strikes stem 98 and communication to the oil pressure line I00 is again restored and valve I20 moved to a position such that the venting of the direct bounce chambers is stopped. Continued understroking causes valve I20 to move to charging position and the direct bounce chamber pressure is increased.

It will be seen that the present invention provides a control balance which is capable of precise adjustment so that the length of stroke of the pistons will remain substantially constant, varying between limits which can be easily determined and maintained.

While the invention has been described in connection with a particular form and disposition of the parts it should be appreciated that numerous modifications and changes may be made without departing from the spirit of the appended claims.

What I claim is:

1. A free piston compressor of the class described comprising, axially aligned power, compressor and bounce cylinders, and pistons working therein, a compressed air receiver, means to control the quantity of fuel entering said power cylinder. mean to vary the pressure of air in said bounce cylinders, a member reciproeated by said pistons, and spaced valves operated by said member at each end of its stroke, one valve operating to actuate said fuel control means and the other valve operating said bounce air control means, whereby the stroke of said pistons remains substantially constant.

2. A free piston compressor of the class described comprising axially aligned power, compressor and bounce cylinders, and pistons working therein, means to control the quantity of fuel entering said power cylinder, a vent for' said bounce cylinders, a source of high pressure air for said bounce cylinders, fluid operated means to place said bounce cylinders either in communication with said vent to lower the pressure therein or with said high pressure air source to increase the pressure in said cylinders, a member reciprocated by said pistons, and spaced valves operated by said member at each end of its stroke, one valve operating to actuate said fuel control means and the other valve operating said bounce air control means, whereby the stroke of said pistons remains substantially constant.

3. A free piston compressor of the class described comprising axially aligned power, compressor and bounce cylinders, and pistons working therein, a fuel injector, fluid operated means to control said injector to increase or decrease the quantity of fuel entering said power cylinder, a vent for said bounce cylinders, a source of high pressure air for said bounce cylinders, fluid operated means to place said bounce cylinders either in communication with said vent to lower the pressure therein or with said high pressure air source to increase the pressure therein, a member reciprocated by said pistons, and spaced valves operated by said member at each end of its stroke, one valve operating to actuate said injector control means and the other valve operating said bounce air control means, whereby the stroke of said pistons remains substantially constant.

4. A free piston compressor of the class described comprising axially aligned power, compressor and bounce cylinders, and pistons working therein, a compressed air receiver in communication with said compressor cylinders, a check valve controlling the passage of air to said compressed air receiver and preventing return from the receiver to said compressor cylinders, a by-pass to atmosphere on the compressor side of said check valve, means to open said by-pass when the receiver pressure reaches a predetermined level so that the compressor operates thereafter against a substantially atmospheric pressure, means to control the quantity of fuel entering said power cylinder, means to vary the pressure of air in said bounce cylinders, a member reciprocated by said pistons, and spaced valves operated by said member at each end of its stroke, one valve operating to actuate said fuel control means and the other valve operating said bounce air control means, whereby the stroke of said pistons remains substantially constant.

5. A free piston compressor of the class described comprising, axially aligned power, compressor and bounce cylinders, and pistons working therein, a compressed air receiver in communication with said compressor cylinders, a check valve controlling the passage of air to said compressed air receiver and preventing return from the receiver to said compressor cylinders, a by-pass to atmosphere on the compressor side of said check valve, means to open said by-pass when the receiver pressure reaches a predetermined level so that the compressor operates thereafter against a substantially atmospheric pressure, a fuel injector, fluid operated means to control said injector to increase or decrease the quantity of fuel entering said power cylindenmeans to vary the pressure of air in said bounce cylinders, a member reciprocated by said pistons, and spaced valves operated by said member at each end of its stroke, one valve operating to actuate said fuel injector control and the other valve operating said bounce air control means, whereby the stroke of said pistons remains substantially constant.

6. A free piston compressor of the class described comprising, axially aligned power, compressor and bounce cylinders, and pistons working therein, a compressed air receiver in communication with said compressor cylinders, a check valve controlling the passage of air to said compressed air receiver and preventing return from the receiver to said compressor cylinders, a by-pass to atmosphere on the compressor side of said check valve, means to open said by-pass when the receiver pressure reaches a predetermined level so that the compressor operates thereafter against a substantially atmospheric pressure, means to control the quantity of fuel entering said power cylinder, a vent for said bounce cylinders, a source of high pressure air for said bounce cylinders, fluid operated means to place said bounce cylinders either in communication with said vent to lower the pressure therein or with said high pressure air source to increase the pressure in said cylinders, a member reciprocated by said pistons and spaced valves operated by said member at each end of its stroke, one valve operating to actuate said fuel control means and the other valve operating said bounce air control means, whereby the stroke of said pistons remains substantially constant.

7. A free piston compressor of the class described comprising, axially aligned power, compressor and bpunce cylinders, and pistons working therein, a compressed air receiver in communication with said compressor cylinders, a check valve controlling the passage of air to said compressed air receiver and preventing return from the receiver to said compressor cylinders, a bypass to atmosphere on the compressor side 01' said check valve, means to open said by-pass when the receiver pressure reaches a predetermined lever so that the compressor operates thereafter against a substantially/atmospheric pressure, a fuel injector, fluid operated means to control said iniector to increase or decrease the quantity of fuel entering said power cylinder, a vent for said bounce cylinders, a source of high pressure air for said bounce cylinders, fluid operated means to place said bounce cylinders either in communication with said vent to lower the pressure therein or with said high pressure air source to increase the pressure therein, a member reciprocated by said pistons and spaced valves operated by said member at each end of its stroke, one valve operating to actuatesaid injector control means and the other valve operating said bounce air control means, whereby the stroke of said pistons remains substantially cons ant.

8. A free piston compressor of the class described comprising axially aligned power, and bounce cylinders and pistons working therein, means to control the quantity oi. fuel entering said power cylinder, means to vary the pressure of air in said bounce cylinders. each of said pistons comprising a trunk portion between the power and compressor cylinders, a rack connected to said trunk ortion of each piston and extending toward the center of the compressor, a synchronizing pinion connecting each of said racks, a mounting shaft for said pinion, a second pinion on said mounting shaft, a rocking lever moved by said second pinion and having abutting members at each end thereof, and spaced valves operated by said abutting members at each end of the stroke of said locking lever, one valve operating to actuate fuel control means and the other valve operating said bounce air control means whereby the stroke of said pistons remains substantially constant.

9. A free piston compressor of the class described comprising axially aligned power, compressor and bounce cylinders and pistons working therein, a fuel injector, fluid operated means to control said injector to increase or decrease the quantity of fuel entering said power cylinder, means to vary the pressure of air in said bounce cylinders, each of said pistons comprising a trunk portion between the power and compressor cylinders, a rack connected to said trunk portion of each piston and extending toward the center of the compressor, a synchronizing pinion connecting each of said racks, a mounting shaft for said pinion, a second pinion on said mounting shaft, a rocking lever moved by said second pinion and having abutting members at each end thereof, and spaced valves operated by said abutting members at each end of the stroke of said rocking lever, one valve operating to actuate fuel control means and the other valve operating said bounce air control means whereby the stroke of said pistons remains substantially constant.

10. A free piston compressor of the class described comprising axially aligned power, and bounce cylinders and pistons working therein, means to control the quantity of fuel entering said power cylinder, a vent for said bounce cylinders, a source of high pressure air for said bounce cylinders, each of said pistons comprising a trunk portion between the power and compressor cylinders, a rack connected to said trunk portion of each piston and extending toward the center of V the compressor, a synchronizing'pinion connecting each of said racks, a mounting shaft for said pinion, a second pinion on said mounting shaft, a rocking lever moved by said second pinion and having abutting members at each end thereof,

55 and spaced valves operated by said abutting members at each end of the stroke of said rocking lever, one valve operating to actuate fuel control means and the other valve operating said bo air control means whereby the stroke of said so tons remains substantially constant.

, 11. A free piston compressor of the class described comprising axially aligned power, con;- pressor and bounce cylinders, and pistons working therein, a fuel injector, fluid operated means to control said injector to increase or decrease the quantity of fuel entering said power cylinder, a vent for said bounce cylinders, a source of high pressure air for said bounce cylinders, fluid operated means to place said bounce cylinders either in communication with said vent to lower the pressure therein or with said high prmnre air source to increase the pressure therein, each of said pistons comprising a trunk portion between the power and compressor cylinders, a rack iliconnectedtosaidtrunkportionof eachpiston eans and extending toward the center of the compressor, a synchronizing pinion connecting each of said racks, a mounting shaft for said pinion, a second pinion on said mounting shaft, a rocking lever moved by said second pinion and having abutting members at each end thereof, and spaced valves operated by said abutting members at each end of the stroke 01' said rocking lever, one valve operating to actuate fuel control means and the other valve operating said bounce air control means whereby the stroke of said pistons remains substantially constant.

12. A tree piston compressor of the class described comprising axially aligned power, compressor and bounce cylinders, and pistons working therein, said compressor cylinder being closed at both ends and having intake and exhaust valves at each side of the piston therein, a compressed air receiver in communication with one end of the compressor cylinder, a scavenging receiver header in communication with the opposite end oi said compressor cylinder, means to control the quantity of fuel entering said power cylinder, means to vary the pressure of air in REFERENCES CITED The following references are of record in the file of patent:

UNITED STATES PATENTS Number Name Date 2,075,133 Pateras-Pescara Mar. 30, 1937 2,200,892 Pateras-Pescara May 14, 1940 FOREIGN PATENTS Number Country Date 855,700 France 1939