US3072103A

US3072103A - Piston impact motor and control therefor

Info

Publication number: US3072103A
Application number: US50034A
Authority: US
Inventors: Herrmann Helmut
Original assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Current assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Priority date: 1959-09-09
Filing date: 1960-08-16
Publication date: 1963-01-08
Anticipated expiration: 1980-01-08

Description

Jan. 8, 1963 H. H ERRMANN 3,072,103

PISTON IMPACT MOTORAND CONTROL THEREFOR Filed Aug. 16, 1960 Fig./

a 33 3 a 20 g /4 INVENTOR HEL MLlT HERE N N United States Patent Oflice 3,@7Z,ifl3 Patented Jan. 8, 1963 3,072,103 PISTON IMPACT MOTOR AND CONTROL THEREFOR Helmut Herrmann, Alflunen, Germany, assignor to Gewerhschaft Eisenhiitte Westfaiia, Westphalia, Germany, a corporation of Germany Filed Aug. 16, 1960, Ser. No. tl,tl34 Claims priority, application Germany Sept. 9, 1959 13 Claims. (Cl. 12122) The present invention relates to a piston impact motor and more particularly to a piston impact motor having control means rotatably disposed within the piston for d recting the incoming pressure fluid to each side of the piston and alternatively for conducting the exhausted pressure fiuid to an outlet.

Conventional piston impact motors have been used heretofore wherein a free flying piston driven by compressed air oscillates back and forth within the motor cylinder in order to produce longitudinal mechanical oscillations for working oscillating conveyors and the like. In these devices, the control of the motor is carried out by means of auxiliary apparatus in dependence upon the action of the motor whereby the pressure fluid used as working power is first conducted to one end of the cylinder and then to the other to force the piston back and forth therewithin.

German Patent 810,678 describes a piston impact motor wherein the inlet and exhaust for the compressed air used to drive the motor is controlled by means of an auxiliary rotary slide positioned adjacent the cylinder of the motor. The rotary slide is operated by the compressed air being exhausted wherein a scoop wheel is employed.

It is an object of the invention to provide a simple and eificient control means for operating a piston impact motor which is rotatably disposed within the piston.

Other and further objects of the invention will become apparent from a study of the within specification and accompanying drawing in which,

FIG. 1 is a sectional view taken along the line 1-1 of FIG. 2,

FIG. 2 is a schematic side view of the piston impact motor of the invention wherein certain details are indicated in phantom, and

FIG. 3 is an enlarged fragmentary schematic sectional view of the imbalance member illustrating v-ar-ious details of construction.

In accordance with the present invention, it has been found that a piston impact motor of simple construction and high efliciency in control of the pressure fluid to and from the motor cylinder may be provided which comprises a motor cylinder, an oscillating piston moveable back and forth within the cylinder, and a control means rotatably disposed within the piston on an axis transverse to the piston axis. The control means is rotationally imbalanced for effecting rotation thereof during the oscillating movement of the piston. Two separate flow passages are defined within the control means. Conduit means are provided in the piston for alternately flow communicating the end portions of the cylinder adjacent the corresponding ends of the piston with one of the flow passages and thence with an exhaust outlet means during rotation of the control means. Moreover, inlet means are provided for communicating pressure fluid from a source to the other of said flow passages and then alternately through the conduit means to the corresponding end portion of the cylinder during the rotation of the control means. Thus, pressure fluid from a source is in flow communication with one of the end portions of the cylinder via the inlet means, the other flow passage, and the conduit means while the other end portion of the i the rotation of the hollow cylinder.

cylinder is in separate flow communication with the exhaust outlet via the conduit means and the one flow passage during each half cycle of oscillating movement of the piston.

The inlet means is additionally in alternate unilateral fiow communication with the end portions of the cylinder. The inlet means generally includes an inlet annular passage deflned on each side of the control means by a corresponding groove in the piston and the adjacent wall portion of the cylinder as well as a corresponding bore passage in the piston fiow communicating each inlet annular passage with the other of said flow passages.

The exhaust outlet means includes an exhaust annular passage intermediate the inlet annular passages defined by a groove in the piston and the adjacent wall portion of the cylinder, such that the exhaust outlet means flow communicates the one flow passage of the control means with the exterior of the motor by means of a port defined in the adjacent wall portion of the cylinder.

The conduit means includes a separate conduit from each end of the piston alternatingly communicating with the said fiow passages. The end of each conduit remote from the one flow passage terminates in a recess defined in the corresponding end of the piston. The end portions of the cylinder have corresponding projections adapted to be slidably received within the recesses of the pistons to form a working chamber with said recesses in each instance. The corresponding end portions of the cylinder adjacent the projections define with the correspondingly adjacent ends of the piston, a compression chamber in unilateral separate flow communication with the source of pressure fluid by means of a corresponding unilateral bore conduit connecting each compression chamber with the correspondingly adjacent inlet annular passage.

Specifically, the control means is constructed as a hollow cylinder positioned Within the piston on hearing means at each end of the hollow cylinder. The hollow cylinder has an intermediate wall dividing the interior thereof into two separate flow passages. The first of the flow passages, for instance, is in flow communication with the inlet means and with the conduit means to alternately communicate pressure fluid from a source to the corresponding end portions of the motor cylinder during In the same way, the second of the flow passages is in communication with the conduit means and the exhaust outlet means to alternately communicate pressure medium from the end portions of the motor cylinder adjacent the corresponding ends oi the pistons to the exhaust outlet means during the rotation of the hollow cylinder. The hollow cylinder is provided at one end with a radially position imbalance member rotatable with the hollow cylinder for rotationally imbalaneing the mass of the hollow cylinder. The im- F balance member is provided with a suitable bore channel defined therein which communicates the first flow passage with the exhaust outlet means.

The channel within the imbalance member is provided with a centrifugal force responsive closure valve, which may move from a normally open position at rest, to a closed position upon the rotation of the hollow cylinder. The channel suitably terminates at the exhaust outlet means in a direction tangential to the path of rotation of the imbalance member and accordingly of the hollow cylinder.

In accordance with this feature of the invention, in order to start the piston impact motor, a portion of the pressure medium passed from the inlet means to the first flow passage is conducted through the channel and the valve whereby the same passes out of the channel to the exhaust outlet deans in a tangential direction. This causes the imbalance member and the hollow cylinder to start rotating due to the jet effect of the pressure medium exiting from the outer end of the channel.

Thus, the construction of the invention permits eflicient control of the pressure fluid to and from the end chambers of the cylinder on either side of the piston such that desirably with each full oscillation of the piston back and forth a full rotation of the control means and imbalance member takes place. During the first half turn of the control means, the piston moves from one end of the cylinder to the other, such that one end chamber of the cylinder is in flow communication with the inlet pressure fluid while the other end chamber of the cylinder is in flow communication with the exhaust outlet for the pressure fluid. During the reverse movement of the piston, the second half of one full rotation of the control means is effected whereby the connections of the end portions of the cylinder with the inlet and outlet means are reversed.

It will be appreciated that during the oscillation of the piston within the cylinder, the presence of the imbalance of the control means will cause the control means to be rotated due to the acceleration forces of the piston. Conveniently, the imbalance may be provided as adjustable on the control means axis by means of a clamping device of conventional design so that the imbalance portion may be placed at any peripheral point of the control means. The bore channel defined within the imbalance portion suitably effects the starting of the control for the piston impact motor by causing the initial rotation of the control means due to the jet exhaust of pressure fluid in a tangential direction. Of course, as the piston continues to oscillate back and forth within the cylinder, the acceleration forces generated thereby maintain the control means in continuous motion because of the imbalance portion whereby the control means is rotated one half cycle during each movement of the piston from one end of the cylinder to the other.

As opposed to previous conventional constructions, the control means, in accordance with the invention, is provided in the interior of the piston whereby the acceleration forces of the oscillating piston are used to advantage to impart the desired rotation of the imbalance mass of the control means. The compressed air or other pressure fluid incoming and outgoing is thus readily controlled. Since during the idling of the piston impact motor, without load, the piston and cylinder execute a sinus-curve oscillation, the approximately uniform rotation of the imbalance and in turn of the control means is assured. Nevertheless, even with a load, as for example, operating the piston impact motor to convey material along a conveyor device or the like, while the cylinder may be darnpened due to the load, the piston maintains the approximately sinus-curve oscillation even though the cylinder and the conveyor device reflect interrupted rather than continuous oscillating motion.

Referring to the drawing, cylinder is shown within which piston 11 is slidably received. From the

end walls

12 and 13 of cylinder 10,

cylindrical projections

14 and 15 are provided which are slidably received within

recesses

18 and 19 in the corresponding end portions of piston 11. Thus,

annular buffer chambers

16 and 17 are formed as well as central working chambers 20 and 21. Rotary slide or hollow control cylinder 22 is provided in the interior of piston 11 positioned perpendicularly with respect to the piston axis. Hollow cylinder 22 is provided in its interior with a partition 23 and is mounted within piston 11 by means of

bearings

24 and 25 within which the shaft ends 26 are conveniently received. The imbalance member 27 is clamped on to the upper end of shaft 26 and is preferably adjustahly positioned so that the same may be fixed at any peripheral position on hollow cylinder 22 with respect to the partition 23.

, Piston 11 is provided with

inlet grooves

28 and 29 running around the circumference of the piston as well as with a central outlet groove 3% similarly extending around piston 11. Both

inlet grooves

28 and 29 are connected by means of

bore passages

31 and 32 with the upper flow passage of hollow cylinder 22 and alternately with

conduits

34 and 33 and in turn working chambers 21 and 20 respectively. By means of

bore channels

35 and 36,

bufler chambers

16 and 17 are unilaterally flow connected with

inlet grooves

28 and 29 of piston 11.

Bore channels

35 and 36 are provided with

check valves

37 and 33 which open toward the

buffer chambers

16 and 17.

The imbalance member 27 positioned on the hollow cylinder axis or shaft 26 is provided with a channel 39 flow communicating with the upper flow passage of hollow cylinder 22 and with the outlet channel 30. The imbalance member 27 may be used to start the motor control upon passage of pressure fluid to one of the working chambers by means of the upper flow conduit in hollow cylinder 22. A portion of this pressure fluid escapes by means of bore or channel 39 in a direction tangential to he path of rotation of the imbalance member 27 and hollow cylinder 22. The exhausting gases exert the jet effect causing a reactive movement of the imbalance 27 imparting rotary motion to hollow cylinder 22.

With respect to the operation of the piston impact motor of the invention, pressure fluid, such as compressed air, passes through line at to each side of the cylinder into the inlet

annular passages

28 and 29 and thence through the

corresponding bore passages

31 and 32 to the rotary slide or hollow cylinder 22. Simultaneously, a portion of the compressed air passes through the channels 35 and as, past the corresponding unilateral check valves 37 and 3d, and enters the

buffer chambers

16 and 17. In this manner, a constant pressure is present in

chambers

16 and 17 which is at least equal to or even higher than the prevailing working pressure. Upon the decline of pres sure in

chambers

16 and 17, further compressed air will constantly flow therewithin through

passages

35 and 36,- which are under the constant pressure flowing into the system via line 40. Check

valves

37 and 38 prevent the escape of air during the compression stroke of piston 11.-

A portion of the incoming pressure fluid, such as compressed air, which enters the upper flow passage of hollow cyiinder 22, from

bore passages

31 and 32 enters the bore channel 3%, defined inthe axle shaft 26 of hollow cylinder 22 and exits from bore channel 39 in the im balance member 27. Since bore channel 39 extends through imbalance member 27, tangentially outwardly, the reaction force produced by the out-flowing compressed air urges the imbalance member 27 and in turn the hollow cylinder 22 into rotational movement in the direction of arrow 41 as may be seen in FIG. 2, i.e. about the longitudinal axis of cylinder 22 (which is transverse to the longitudinal axis of piston 11).

At the same time, the remainder of the compressed air which enters the upper flow passage of hollow cylinder 22 from

bore passages

31 and 32 passes through conduit 34 into working chamber 21. This compressed air which enters chamber 21 forces piston 11 in the opposite direction as shown by arrow 42 in FIG. 1. The incoming compressed air for moving piston 11 back and forth within cylinder 10 is now controlled by rotary slide or hollow cylinder 22 in such a manner that in a first phase of operation the compressed air passes through bore passage 34 into working chamber 21, while simultaneously the compressed air in working chamber 20 is exhausted therefrom via conduit 33, the lower flow passage of hollow cylinder 22, the hollow opening through the lower end of axle shaft 26 and outlet annular passage 30 which is flow connected with the atmosphere at port 43. The inflowing compressed air is represented by dark arrows while the outflowing compressed air is represented by light arrows (see FIG. 1). 7

During the next phase of operation, the compressed air passes through the upper passage of hollow cylinder 22.; now rotated one-half turn and entersworking chamber 2% by means of conduit 33. At the same time, the compressed air in working chamber 21 is placed in connection with the atmosphere by means of conduit 34, the lower flow passage of hollow cylinder 22, the passage through the hollow lower axle shaft 26, the exhaust annular passage 30, and the port 43. Thus, by means of the alternating supply of compressed air to either side of piston 11, the piston is placed into oscillating movement back and forth within cylinder 10.

It will be appreciated that the oscillating movement of piston 11 brings about a counter-acting vibratory movement of cylinder 14 Simultaneously,

compression chambers

16 and 17 are compressed and exhausted with compressed air during the back and forth movement of piston 11. The air present in

chambers

16 and 17 acts as a buflfer whereby the stroke or thrust of piston 11 is elastically intercepted by the air cushion in

chambers

16 and 17 respectively so that piston 11 will be urged back once more in opposite direction upon reversal of the incoming compressed air and exhaust systems. Accordingly, hard or violent strokes of piston 11 and in turn hard or violent vibrations of cylinder are avoided during the operation of the motor in accordance with the invention.

The compressed air in

compression chambers

16 and 17 transmits the oscillating movement of piston 11 to cylinder 10 in a cushion-like manner. Since cylinder 10 is generally to be fixedly connected with the device to be operated by the motor, eflicient oscillations may be imparted to the device free from violent vibrations which would otherwise tend to cause premature wear and tear on the working parts.

It will be appreciated that once the hollow cylinder 22 and imbalance member 27 have been urged into rotational movement by means of the compressed air exiting from bore channel 39, a suitable centrifugal valve, normally open when imbalance member 27 is stationary and normally closed when imbalance member 27 is rotating, will in fact close preventing the further escape of compressed air through bore channel 39. The centrifugal control valve may consist of a spring-urged ball movable from a position out of blocking engagement with a valve seat in bore channel 39 to a position into blocking and sealing engagement with a valve seat in the same upon rotational movement of imbalance member 27. Specifically, as shown in FIG. 3, bore channel 35 of imbalance member 27 is provided with a valve seat 44 against which spring-urged ball 45 may be positioned. Spring 46, attached to the wall 47 of bore channel 39, resists the seating of ball 45 against the valve seat 44 and is overcome by the opposing centrifugal force generated after the start of the motor. The ball 45 may be moved from a position out of blocking engagement with valve seat 44 to a position into blocking and sealing engagement therewith, and vice versa, in the direction of arrow 48. Accordingly, it will be appreciated that a centrifugal valve is provided by the construction of FIG. 3 which will close dependent upon the reaching of a certain number of revolutions per minute of the imbalance member. The centrifugal force generated as imbalance member 27 revolves will cause ball 45 to be radially outwardly urged against the action of spring 46 to close the valve.

As the piston 1!; begins to move back and forth within cylinder 19 in response to the incoming and exhausting compressed air as controlled independently by the rotational movement of hollow cylinder 22, the hollow cylinder 22 will be moved back and forth within cylinder 10 simultaneously with piston 11. Each forward movement of piston 11 will cause the imbalance member 27 to turn the hollow cylinder 22 one-half turn so that imbalance member 27 is placed in the opposite direction. In this way, hollow cylinder 22 will turn one-half cycle reversing the incoming and exhausting compressed air flowing to and. from hollow cylinder 22 by means of

bore channels

31 and 32 as well as one of

conduits

33 and 34 on the one hand, and by means of the other one of

conduits

33 and 34, lower hollow shaft 26, exhaust annular passage 30, and port 43 on the other hand. Upon the return movement of piston 11, imbalance member 27 and in turn hollow cylinder 22 will rotate the second half of the cycle reversing once more the connection of the inlet and exhausting compressed air.

Thus, it will be appreciated that hollow cylinder 22 operates independently of piston 11 in cylinder 10 but during each movement back and forth within cylinder it} of piston 11, a first half rotation and thereafter a second haif rotation of hollow cylinder 22 will take place due to the concentration of the weight mass in imbalance member 27. A compact, etficient, internal control for the driving of the piston by compressed air is thus attained in accordance with the construction of the invention wherein a control means, such as a hollow cylinder, having two flow passages is placed within the piston to alternate the incoming and exhausting pressure fluid to and from the motor. No complicated auxiliary control equipment is required on the exterior of the motor but instead the piston force itself is used to operate the control of pressure fluid to one working chamber, and thence to the other by a control means, simple in construction and requiring a minimum of operating parts. Suitably, the imbalance member 27 may be adjustably mounted on shaft 26 by means of a set screw arrangement, for instance, so that imbalance member 27 may be placed at any rotational angle with respect to partition 23, as desired. The piston impact motor of the invention, therefore, may be conveniently started by merely passing pressure fluid to the hollow cylinder 22 in the normal way whereby the jet action of the exiting compressed air from bore channel 39 begins the rotation of hollow cylinder 22, and thereafter the movement of piston 11 will serve to maintain the rotation of imbalance member 27 and hollow cylinder 22 such that with each full oscillation of piston ill back and forth one full rotation of the hollow cylinder 22 will be coordinated. The centrifugal control valve means in imbalance member 27 may be conveniently produced such that the valve will close after the imbalance member 27 has reached a specific number of revolutions per minute.

What is claimed is:

1. Piston impact motor which comprises a motor cylinder, an oscillating piston movable back and forth within said cylinder, a control means rotatably disposed within said piston on an axis transverse to the piston axis, said control means being rotationally imbalanced for efiecting rotation thereof during the oscillating movement of said piston and having two separate flow passages therein, conduit means for alternately flow communicating the end portions of said cylinder adjacent the corresponding ends of said piston with one of said flow passages and thence with an exhaust outlet means during the rotation of said control means, and inlet means for communicating pressure fluid from a source to the other of said flow passages and thence alternately through said conduit means to the corresponding end portion of said cylinder during the rotation of said control means, said pressure fluid from a source being in flow communication with one of said end portions of said cylinder via said inlet means, said other flow passage and said conduit means and the other end portion of said cylinder being in separate flow communication with said exhaust outlet via said conduit means and said one flow passage during each half cycle of oscillating movement of said piston.

2. Motor according to claim 1 wherein said inlet means is additionally in alternate unilateral flow communication with said end portions of said cylinder.

3. Motor according to claim 2 wherein said inlet means includes an inlet annular passage defined on each side of said control means by a corresponding groove in said piston and the adjacent wall portion of said cylinder and a corresponding bore passage in said piston flow communicating each inlet annular passage with said other: flow passage.

4. Motor according to claim 3 wherein each of said. inlet annular passages is in separate flow communication, with pressure fluid from a source by means of a crresponding inlet opening defined in the wall of said cylinder adjacent the inlet annular passage.

5. Motor according to claim 4 wherein the exhaust outlet means includes an exhaust annular passage intermediate the inlet annular passages defined by a groovein said piston and the adjacent wall portion of said cylinder, said exhaust outlet means flow communicating said. one fiow passage of the control means with the exterior of the motor by means of a port defined in the adjacent wall portion of said cylinder.

6. Motor according to claim 5 wherein said conduit means includes a separate conduit from each end of said piston alternately communicating with said one flow passage, the end of each conduit remote from said one flow passage terminating in a recess defined in the correspond ing end of said piston, the end portions of said cylinder having corresponding projections adapted to be slidably received within the recesses of said piston to form a. working chamber with said recess, the corresponding end portions of said cylinder adjacent said projections defining with the correspondingly adjacent ends of said piston a compression chamber in unilateral separate fiow communication with the source of pressure fluid by means of a corresponding unilateral bore conduit connecting each compression chamber with the correspondingly adjacent inlet annular passage.

7. Motor according to claim 1 wherein said control means is a hollow cylinder positioned within said piston on hearing means at each end of said hollow cylinder, said hollow cylinder having an intermediate wall dividing the interior thereof into two separate flow passages, a first of said flow passages being in flow communication with said inlet means and with said conduit means to alternately communicate said pressure fluid from a source to the corresponding end portions of the motor cylinder during the rotation of said hollow cylinder, and the second of said flow passage-s being in communication with said conduit means and said exhaust outlet means to alternately communicate pressure medium from the end portions of the motor cylinder adjacent the corresponding ends of said piston to said outlet means during the rotation of said hollow cylinder.

8. Motor according to claim 7 wherein said hollow cylinder is provided at one end with a radially positioned imbalance member rotatable with said hollow cylinder for rotationally imbalancing the mass of said hollow cylinder, said imbalance member having a channel defined therewithin communicating said first flow passage with said exhaust outlet means.

, 9. Motor according to claim 8 wherein said channel is provided with a centrifugal force responsive closure valve moving from a normally open position at rest to a closed position upon the rotation of said hollow cylinder, said channel terminating at said exhaust outlet means in a direction tangential to the path of rotation of said imbalance member, whereby to start said motor a portion of the pressure medium passed from said inlet means to said first flow passage is conducted through said channel and said valve and out of said channel to said exhaust outlet means in tangential direction causing said imbalance member and said hollow cylinder to start rotating.

it). in a piston impact motor having a motor cylinder, an oscillating piston movable back and forth Within said motor cylinder in response to pressure iluid passed alternateiy to two end chambers, each defined by an end or said motor cylinder and the corresponding end of the piston adjacent thereto, the improvement which comprises providing a control means rotatably disposed within the piston on an axis transverse to the piston axis, said control means being rotationally imbalanced for effecting rotation thereof during the oscillating movement of said piston and having two separate fiow passages therein, the first of said flow passages flow communicating pressure fluid passed from a source to said first flow passage via inlet means with conduit means and thence alternately with a. corresponding end chamber during the rotation of said control means, and the second of said flow passages flow communicating pressure fluid passed alternately from a corresponding end chamber to said second flow passage via conduit means with exhaust outlet means during the rotation of said control means, each of said end chambers being in separate fiow communication with said first flow passage and said inlet means via said conduit means and alternately in separate flow communication with said second flow passage and said outlet means via said conduit means during the rotation of said control 11. Improvement according to claim 10 wherein said control means includes a radially positioned imbalance portion rotatable therewith for rotationally imbalancing the mass of said control means.

12, Improvement according to claim 11 wherein said imbalance portion is provided with a channel communicating said first flow passage with said exhaust outlet means, said channel terminating at its outer end in tangential direction to the path of rotation of said imbalance portion.

13. Improvement according to claim 12 wherein said channel is provided with a closure valve closable in response to centrifugal force generated upon rotation of said imbalance portion.

References (Cited in the tile of this patent UNITED STATES PATENTS 2,857,143 Kraeckel et al Oct. 21, 1958 2,944,520 Swanson July 12, 196i) FOREIGN PATENTS 810,678 Germany Aug. 13, 1951

Claims

1. PISTON IMPACT MOTOR WHICH COMPRISES A MOTOR CYLINDER, AN OSCILLATING PISTON MOVABLE BACK AND FORTH WITHIN SAID CYLINDER, A CONTROL MEANS ROTATABLY DISPOSED WITHIN SAID PISTON ON AN AXIS TRANSVERSE TO THE PISTON AXIS, SAID CONTROL MEANS BEING ROTATIONALLY IMBALANCED FOR EFFECTING ROTATION THEREOF DURING THE OSCILLATING MOVEMENT OF SAID PISTON AND HAVING TWO SEPARATE FLOW PASSAGES THEREIN, CONDUIT MEANS FOR ALTERNATELY FLOW COMMUNICATING THE END PORTIONS OF SAID CYLINDER ADJACENT THE CORRESPONDING ENDS OF SAID PISTON WITH ONE OF SAID FLOW PASSAGES AND THENCE WITH AN EXHAUST OUTLET MEANS DURING THE ROTATION OF SAID CONTROL MEANS, AND INLET MEANS FOR COMMUNICATING PRESSURE FLUID FROM A SOURCE TO THE OTHER OF SAID FLOW PASSAGE AND THENCE ALTERNATELY THROUGH SAID CONDUIT MEANS TO THE CORRESPONDING END PORTION OF SAID CYLINDER DURING THE ROTATION OF SAID CONTROL MEANS, SAID PRESSURE FLUID FROM A SOURCE BEING IN FLOW COMMUNICATION WITH ONE OF SAID END PORTIONS OF SAID CYLINDER VIA SAID INLET MEANS, AND THE OTHER END PORTION OF SAID CYLINDER BEING IN SEPARATE FLOW COMMUNICATION WITH SAID EXHAUST OUTLET VIA SAID CONDUIT MEANS AND SAID ONE FLOW PASSAGE DURING EACH HALF CYCLE OF OSCILLATING MOVEMENT OF SAID PISTON.