US2921559A

US2921559A - Piston engine provided with control valve

Info

Publication number: US2921559A
Application number: US763538A
Authority: US
Inventors: Herrmann Helmut
Original assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Current assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Priority date: 1957-10-08
Filing date: 1958-09-26
Publication date: 1960-01-19
Anticipated expiration: 1977-01-19

Description

Jan. 19, 1960 H. HERRMANN PISTON ENGINE PROVIDED wrm CONTROL VALVE Filed Sept. 26. 1958 IN VEN TOP ,W M MW 5 f H a T W HB/ W 6 however also depends on the frequency.

United States Patent Ofihce 2,921,559 Patented Jan. 19, 1960 PISTON ENGINE PROVIDED WITH CONTROL VALVE Helmnt Hermann, Altlunen, Germany, assignor to Gewerkschaft Elsenhutte Westfalia, Wethmar, bei Lunen, Westphalia, Germany, a corporation of Germany Application September 26, 1958, Serial No. 763,538

Claims priority, application Germany October 8, 1957 Claims. (Cl. 121-16) This invention relates to piston engines such as, for example, are employed to impart vibration to vibrating apparatus. More particularly, the invention relates to the manner in which motive medium, such as air, is supplied to such engines.

In the case of free piston engines which serve f instance as drives for vibrating machines and in connection with which elastic interception of the piston is effected by air buffers, it is not possible to make the control of the operating air positively dependent upon the piston movement. This is due to the fact that the engine housing effects different strokes with respect to the piston, depending on the load. If the engine for instance is installed on a vibrating apparatus, then as is known, the one swinging mass is the piston and the second the engine housing, with the moving parts of the vibrating device. The mass of the piston, however, is as a rule very much less than the rest of the mass. As long as no work is given off toward the outside by the vibrating apparatus, the two masses swing about their common center of gravity. If however work is given off, then the common center of gravity is displaced. This displacement of the center of gravity has a relatively smaller effect on the piston movement, since the piston stroke is considerably larger, corresponding to the mass ratio, than the swinging path of the housing. On the other hand, the piston stroke If, namely, in the case of steady-state operation of the engine, the initial pressure in the compression spaces is constant, then the piston stroke will be greater the more the frequency increases. This in turn makes automatic control of such a piston swinging engine diflicult.

The present invention proposes effecting the control of the working air by a freely moving slide valve which is guided in a borehole lying in the axial direction of the piston. The feeding of the working air can be effected from the connecting connection connected to the housing through an annular space in the housing or on the periphso developed that the working air is conducted through an annular groove and corresponding radial bores, de-

pending on the position of the slide, to one side or the other of the working surface of the swinging piston, depending on the position of the slide.

When the elastic intercepting of the piston in its end positions is effected by air buffers, the working surfaces of this piston are ordinarily made annular shape and arranged on both sides of a disk shaped step in the center of the piston. Since the slide valve is also ax'ially approximately in the center of the piston, the

air is in this way introduced over the shortest path into the one operating space and discharged from the other. The leading away of the spent air from the one side is effected in this connection by the central opening of the slide valve.

In order to avoid unnecessary stresses, it is advisable to intercept the control slide, in a manner similar to the piston in its two end positions elastically, for instance by rubber buffers or in a similar manner.

In connection with the development described, the acceleration of the piston at the commencement of its movement is the greatest. It decreases with increasing speed of the piston, reaching a value of zero, approximately in the central position. Upon movement beyond the central position, a delay takes place since the air buifer which intercepts the piston enters into action. Since the slide valve is guided in a freely swinging manner in the direction of swing in the engine, it imparts the acceleration thereof at the beginning of the piston stroke until reaching the central position. From then on, the slide valve swings automatically with respect to the swinging piston and thereby experiences the relative displacement with respect to the swinging piston.

which in accordance with the invention is used to control the working air, advisedly the fresh air as well as the spent air.

Since the piston is arranged in a freely swinging manner in its housing, there is no preferred position of the piston with respect to the housing in which the former comes to a stop upon the shutting off of the working air. This must be taken into consideration also in connection with the development of the slide valve.

In order to effect with certainty, at every possible position of the piston, a control of the air corresponding to this piston position, it is provided in accordance with the invention that the slide valve is moved with a supplementary device which brings it, upon the shutting off of the air, into its one dead center position and upon reconnection of the drive guides the slide valve, advisedly with reduced speed, once over its entire control path so that it definitely also passes through the control position corresponding to the position of the piston, in its instantaneous position with respect to the housing or engine cylinder, and the piston is fed working air on one side or the other.

As a suitable device for the obtaining of the said displacement of the control piston upon the shutting off of the working air and upon reconnection thereof, there can be used for instance a piston which is predominantly in communication with the compressed air line and which is struck on the opposite side by a force of such magnitude that when the compressed air is connected, it is forced into its one end position while when the air is disconnected it is forced by the counterforce into its other end position. This auxiliary piston can for instance be developed as a differential piston, in which case the necessary counterforce is achieved by the fact that the smaller piston surface on the rear side of the piston is struck by the same fresh air via a non-return valve.

This auxiliary piston can for instance be detachably connected via a coupling rod with the slide valve in the manner that the coupling of the two parts is effected when the auxiliary control piston, as well as the slide valve is moved back upon the shutting off of the drive from one dead-center position into the opposite end position. Upon the connecting of the working air which only acts in throttled state on the auxiliary piston, the control slide is pushed over into its opposite end position. Since in this connection the auxiliary piston moves over a larger path than the control piston can move over, the resilient coupling between the coupling rod and the 3 control slide is positively loosened and the control slide is now left to itself.

One embodiment by wayof example of the invention is shown in the drawing in which: I a

Fig. 1 is a longitudinal section through the engine;

Fig. 2 is a cross-section along the line 22 of Fig. 1; and

Fig. 3 is a cross-section along the line 33 of Fig. l.

A piston engine according to the invention includes an engine cylinder having an engine piston slideably mounted therein so as to form a piston-cylinder arrangement, and means are disposed on each side of the piston so as to provide a working space within the cylinder on each side of the piston. Further, means are provided for communicating first one and then the other of the working spaces with a source of relatively high pressure and simultaneously, respectively communicating said other space and then said one space with a source of relatively low pressure for reciprocating the piston relative to the cylinder. This means for reciprocating the piston includes a tubular axially extended space within the piston and a tubular slide valve slideably mounted in the tubular space for axial movement therein in response to reciprocation of the piston. During this movement, the slide valve reciprocates *between a first position and a second position. The slide valve has an outer peripheral annular space disposed intermediate the ends thereof and within said tubular space of the piston. This outer peripheral annular space is hermetically sealed from the balance of the tubular space by the sliding engagement of the ends of the slide valve and the tubular space. Means are provided for communicating the tubular space with a first pressure source and means are provided for communicating the peripherial annular space with a second pressure source. Additionally, radially extending passageways communicate the tubular space with the engine working space so as to communicate one working space with the first pressure source and the other working space with the second pressure source, with the slide valve in its first position and reversing the communication of the working spaces with the first and second pressure sources with the slide valve in its second position. The slide valve is freely slideable in the tubular space within the piston, and hence, in response to reciprocation of the piston, the slide valve is shuttled between the first and second positions and provides control valve action for the engine.

The construction, according to the invention, is advantageously employed in combination with piston engine provided with means for pneumatically arresting each working stroke "of the piston. Conveniently, pneumatically arresting of'the working strokes is provided for by including at each axially disposed end of the engine a cylinder extension which slideably receives a piston extension developed so as to form the engine working spaces as annular working spaces. Means, such as end walls are arranged at the outwardly disposed end of each cylinder extension and the length of the cylinder extension exceeds the throw of the piston extension. Means are provided for maintaining a body of gas in the cylinder extension, and thus arrest reciprocation of the piston. The piston extensions alternately compress and expand gas within the cylinder extension and provide the desired pneumatic arresting action.

According to the invention, there is provided a slide valve positioner for suitably positioning the slide valve with respect to the piston to coordinate the valve and piston upon starting the engine. The positioner includes a hook which is moveable axially within the tubular space disposedin the piston, and a catch which is secured to the slide valve. Means are provided which are responsive to disconnection of the engine from the source of relatively high pressure employed to motivate the engine, and efiective to move the hook axially in the tubular space, relative to the slide valve and engage the catch of the slide valve. Further, means are provided which are responsive to connection of the engine to the source of relatively high pressure, and this means is effective to move the slide valve by the hook relative to the piston to coordinate the position of the piston and slide valve and after effecting the coordination, to disengage the hook and catch and thereby release the slide valve from the hook.

Conveniently, the slide valve positioning means can include a diiferential piston axially mounted in the engine piston for sliding movement therein, and the annular chamber of the differential piston and the outer side of the large piston of the differential piston are communicated with a high pressure source and the outer side of the smaller piston of the differential piston is communicated with a low pressure source. The annular chamber is communicated with the high pressure source through a check valve which permits flow into the annular chamber. The differential piston is arranged to reciprocate in the engine piston upon the engine being started and stopped so that the differential piston completes a stroke in one direction upon the starting of the engine and completes a stroke in the other direction upon the stopping of the engine. The hook is secured to the difierential piston for movement axially through the tubular space upon movement of the differential piston and the catch is secured to the slide valve for engagement by the hook when the differential piston moves in the engine piston upon stopping of the engine, and the catch is also arranged for moving the slide valve with the differential piston upon starting the engine. The stroke of the differential piston is coordinated with the stroke of the slide valve between the first and second position of the slide valve. Suitable means are provided for disengaging the hook and catch after coordination of the slide valve and piston.

Referring to the drawing, the engine there shown comprises an engine cylinder 10 having slideably mounted therein an engine piston 11. The engine cylinder is provided with cylinder extensions 51 and 52, which in- Ielude respectively, cylinder extension end-walls, 53 and 54, and have slideably mounted therein piston exten- I sions 55 and 56.

The piston annular disk 12 arranged approximately in the longitudinal center extends into the widened space 13 of the cylinder 10. In this connection, there result the two working spaces 14 and 15. Furthermore, the two piston discs 16 and 17 of piston extensions extend into the completely enclosed spaces 18 and 19 at the ends of the cylinder 10. The spaces 18 and 19 are the butter spaces for the elastic interception of the swinging piston at the end of one or the other movement stroke. The feeding of the working air is effected through the connecting member 20 which is arranged on the housing 10. Through this connecting member, the air passes through the outer annular channel 21 and the radial boreholes 22 into the annular space 23 which, in the embodiment shown schematically, is reached by an annular groove 23 in the piston 11. The length of this annular groove 23 corresponds to the motion stroke of the piston 11 relative to the housing 10. The compressed air therefore passes continuously from space 23 through the longitudinal channels 24 into the annular space 25 which surrounds the axial control borehole of the piston 11 in its center. From the annular space 23, however, compressed air at the same time continuously passes via the channel 26 and the non-return valve 27 into the buffer space 19'. The buffer space 18 is filled through the axial conduit 28 branching ofl? from the annular space 25 and via the non-return valve 29. The leading away of the spent air is effected through the axial borehole 30 of the piston 11 and through the radial boreholes 31, the annular chamber 32 and the exhaust openings 33. In the drawing the parts are shown in such a position that the working space 14 communicates with the exhaust 33. At the same time, due to, the annular control slide 34 whichis provided on its periphery with a circumferential groove 35, the working space 15 is connected by radial channels and the annular space 35 of the control slide 34 with the chamber 25 which is continuously in communication with the fresh air connection 20.

The control slide 34 is displaceable in its longitudinal direction with respect to the reciprocating piston 11. The path of displacement is limited by two stops. The blow is softened in this connection by buffering means 36 which can be rubber bumpers. 1 The displacement of the slide 34 at the beginning of its motion stroke takes place positively upon the displacement of the swinging piston 11 since the slide 34, first of all, for instance in the piston shown in Fig. 1, rests via its right end edge against thereciprocating piston. When, however, the swinging piston 11 is delayed after movement beyond its central position, the control slide 34 moves away from the swinging piston 11 and carries out, under the influence of the kinetic energy inherent in it, a relative movement with respect to the piston 11.

I By this relative movement, there is then at the same time obtained the desired reversal of the driving medium. The annular space 35 of the control slide 34 then connects the fresh air chamber 25 with the working space 14 of the piston. The piston is therefore struck in opposite direction. At the same time the second working space 15 is now connected via the central opening 37 of the control slide 34 with the exhaust channel 30. By this switching of the driving medium, the desired reversal of the swinging piston 11 is thus positively produced. Upon the next movement stroke of the piston 11, a new reversal of the control piston 34 then again automatically takes place with the eflfect that the engine which is once in operation remains operating as long as the compressed air is not shut off. It is important that the switching take place independently of the position assumed by the swinging pistion 11 in the swinging hous ing 10.

' In order to make possible the starting of the engine in any position of the swinging piston 11 in the swinging housing 10, there is provided an auxiliary device which draws the control slide 34 upon the shutting all of the working air always into the position shown diagramniatically in Fig. l, the auxiliary device being connected with the control slide. If the compressed air feed is again opened, it slowly displaces the control slide 34 over its entire movement stroke up to its other end position, where the control slide 34 is positively disconnected from the auxiliary device. The control slide in this connection passes through all possible control positions and therefore also the position in which the compressed air is so controlled thatthe piston 11 in the position which it has just assumed is acted upon by compressed air, either on one side or on the other side, and therefore is displaced in one direction or the other. This first acceleration of piston 11, as already mentioned, results however in an automatic reversal of the control flldeML;

In the embodiment shown in the drawing, the auxiliary device consists of the stepped piston 38, the larger piston disk 39 of which moves in a bore 40 of the piston 11, while the smaller disc 41 moves in the cylinder 42 of small diameter. The cylinder space 40 communicates via the narrow bore 43 with the 'fresh air channel 26. A non-return valve 44 leads a part of this compressed air into the annular chamber 45 between the two

piston disks

39 and 41. The differential piston 38 bears in its axial extension a rod 46 having a reinforced head 47. This rod passes through the ring 48 borne by the slide 34, on which ring there are arranged the springs 49 which surround the rod-head 47 when the parts assume a corresponding position with respect to each other.

In Fig. 1 of the drawing, the control slide 34, as well as the auxiliary piston 38, is shown in the position which of the parts shown, the parts immediately act on the working space and thus displace the swinging piston 12 toward the left. Furthermore, however, the larger piston surface 39 of the auxiliary piston 38 is acted upon and the control slide 34 moved positively toward the left into its end position. Sincethe auxiliary piston 38 can move a larger distance toward the left, when the lefthand end position of the'control slide 34 is reached, the rod head 47 is forced out of the spring 49. The working space 14 is now acted upon and upon further operation, the control slide 34 can freely follow the acceleration forces of the piston 11, while the auxiliary piston 38 remains in its left end position. In any event the auxiliary device sees to it that the control slide, upon the connecting of the working air, is automatically displaced once over its entire path of movement so that it passes through all possible control positions.

What is claimed is:

l. A piston engine comprising an engine cylinder hav- V ing an engine piston slidably mounted therein forming a piston-cylinder arrangement, means disposed on each side of the piston providing a working space within the cylinder on each side of the piston, operating means for communicating first one and then the other of said working spaces with a source of relatively high pressure and simultaneously respectively communicating said other space and then said one space with a source of relatively low pressure for reciprocating the piston relative to the cylinder, said operating means including means defining a tubular axially extending space within the piston, and a tubular slide valve slidably mounted in said space for axial movement therein in response to reciprocation of the piston between a first position and a second position, said slide valve having means defining an outer peripheral annular space intermediate the ends thereof and disposed within said tubular space and hermetically sealed from the balance of said tubular space, means for communicating said tubular space with a first pressure source, means for communicating said peripheral annular space with a second pressure source, mean defining radially extending passageways communicating said tubular space with the working spaces for communicating one working space with said first pressure source and the other working space with said second pressure source with the slide valve in said first position and reversing the communication of the working spaces with the first and second pressure sources with the valve in said second position, whereby in response to reciprocation of the piston the slide valve is shuttled between said first and second positions and provides control valve action for the" engine.

2. A piston engine according to claim 1 including means for elastically arresting the movement of the slide valve into the first position and the second position.

3. A piston engine according to claim 1, wherein said working space is an annular working space.

4. A piston engine according to claim 1 including means for pneumatically arresting each working stroke of the engine piston.

5. A piston engine according to claim 1 including at each axially disposed end of the engine a cylinder extension slidably receiving a piston extension, means closing the outwardly disposed end of the cylinder extensions, the length of said cylinder extensions exceeding the throw of said piston extensions, and means for maintaining a body of gas in said cylinder extensions whereby each working stroke of the engine piston can be pneumatically arrested.

6. A piston engine according to claim 1 including a slide valve positioner for suitably positioning the slide valve with respect to. the piston to coordinate the valve and piston upon starting the. engine, said positionerineluding a hook movable within said tubular. space anda catch secured to said slidervalve, meansrresponsive to disconnection from theengine of said source of: relatively highpressureandeffective to move the hook axially in said tubular spacerelative to the slideyalve and en.- gage said catch and means responsive to: connection of the engine to said. source of relatively high pressure. and effective to move'the slide valve by said hook relative to the piston to coordinate the position of the piston and slide valve and thereafter; disengage the hook. and catch and thereby release the slide valve.w

7. A piston engine according to claim 1 including. a slide valve positioner' for suitably positioning the slide valvewith respect .totheipiston to coordinate the valve and piston upon starting the engine, said. positioner including a differential piston axially mounted in saidv engine piston for sliding movement therein, the annular chamber of the differential piston and the outer side of the large piston of the differential piston being communicated with a high pressures source and the outer side of the smaller piston of; the differential. piston being communicated with a low pressure source, said annular chamber being communicated. with said high pressure source through a check valve permitting flow into the: annular chamber, sm'd differential piston being arranged to reciprocate in the engine piston upon the engine being started and stopped completing a stroke in one direction upon startingof the engine and completing a stroke in the other direction upon stopping of the engine, a. hook secured to said differential piston for movement. axially through the tubular space upon movement of the differential piston, a catch secured to said slide valve for engagement by said hook when the differential piston. moves in the piston upon stopping the engine and for. moving the slide valve with the differential piston upon starting the engine, the stroke of the differential piston being coordi mated with the stroke of the slide valve between said first and second positions thereof to coordinate the position of the slide valve and the piston by operation of the difierens tial piston upon starting the engine, and means for'dis-' engaging the hook and catch after coordination of the slide valve and piston.

8. A piston engine according to claim 1, said means for communicating the tubular space with a first pressure source and the peripheral annular space with a second pressure source each comprising a groove disposed in the outer surface of the piston of axial length at least equal to the stroke of the piston, means defining an opening in the engine cylinder communicating the groove and the outside of the cylinder throughout the stroke of the engine piston, and a radially extending passageway in the cylinder communicating with the groove.

9. A piston engine according to clairn- 1, including means for pneumatically arresting each working stroke of the engine piston, and further including a slide valve positioner for suitably positioning the slide valve with:

respect to the. piston to coordinate the valve ,andipiston: uponzstarting theengine, saidpositioner including audit; ferentialpiston axially mounted in saidiengine-pi'ston for sliding movement therein,v the annular chamber of the differential piston and the outer side of the large piston of'the differential piston being communicated with a high pressure source and the outer side of the smaller piston lofthe differential piston being communicated with a low pressure source, said annular chamber being cornmunicated :with said high pressure source through. a check valve permitting flow into the annular chamber; said differential piston being arranged to reciprocate in the engine piston upon the engine being started and stopped completing a stroke in one direction upon starting of theengine and completing a stroke in the other direction upon stopping of the engine, a hook secured to said differential piston for movement axially through the tubular spaceupon movement of the differential piston, a catch secured to said slide valve for engagement by said hook when the dilferential piston moves in the piston upon stopping the engine and for moving the slide valve with the "differential piston upon starting the engine, the stroke of the differential piston being coordinated with the stroke of the slide valve between said first and second positions thereof to coordinate the position of the slide valve and the piston by operation of the differential piston upon starting'the engine, and means for disengaging the hook and catch after coordination of the slide valve and piston, said means for communicating the tubular space with a first pressure source and the peripheral annularspace with a second pressure source each comprising a groove disposed in the outer surface of the piston of axial length at least equal to the stroke of the piston, means defining an opening in the engine cylinder communicating the groove and the outside of the cylinder throughout the stroke of the engine piston,- and a radially extending passageway in the. cylinder communication With the groove, means for elastically arresting the movement, of the slide valve into the first position and the second position.

10. A piston engine according to claim 9, said outer peripheral annular space of the slide valve being communicated with the source of relatively high pressure and the portion of said tubular space hermetically sealed from the outer peripheral annular space being cot-n municated with the source of relatively low pressure.

References Cited inthe file of this'patent UNITED STATES PATENTS Great Britain Dec. 15,1954