US2728299A

US2728299A - Variable capacity rotary hydraulic pump or motor

Info

Publication number: US2728299A
Application number: US257447A
Authority: US
Inventors: Johnson Edward Harry
Original assignee: Keelavite Co Ltd
Current assignee: Keelavite Co Ltd
Priority date: 1951-11-21
Filing date: 1951-11-21
Publication date: 1955-12-27
Anticipated expiration: 1972-12-27

Description

Dec. 27, 1955 E. H. JOHNSON 2,728,299

\ VARIABLE CAPACITY ROTARY HYDRAULIC PUMP 0R MOTOR Filed Nov. 21, 1951 5 Sheets-Sheet l I nventor snumm 0mm 'Swmu Attorney Dec. 27, 1955 E. H. JOHNSON 2,728,299

VARIABLE CAPACITY ROTARY HYDRAULIC PUMP OR MOTOR Filed Nov. 21, 1951 5 Sheets-Sheet 2 F/GZ.

Inventor ivwnab ARVN TuANsoN Attorney Dec. 27, 1955 E. H. JOHNSON 2,723,299

VARIABLE CAPACITY ROTARY HYDRAULIC PUMP OR MOTOR Filed Nov. 21, 1951 5 Sheets-Sheet 5 Inventor A ttorney 1955 E. H. JOHNSON 2,728,299

VARIABLE CAPACITY ROTARY HYDRAULIC PUMP OR MOTOR Filed Nov. 21, 1951 5 Sheets-Sheet 4 Inventor A tlorney Dec. 2 7, 1955 E, H. JOHNSON 2,728,299

VARIABLE CAPACITY ROTARY HYDRAULIC PUMP OR MOTOR Filed Nov. 21, 1951 5 Sheets-Sheet 5 I nventor Em mm mum To\-\\-\$0N y an, M v Mm Attorney VARIABLE CAPACITY ROTARY HYDRAULIC PUMP OR MOTOR Edward Harry Johnson, Coventry, England, assignor to The Keelavite Company Limited, Coventry, England, a company of Great Britain Application November 21, 1951, Serial No. 257,447

11 Claims. (Cl. 103-120) This invention relates to variable capacity rotary hydraulic pumps and motors of the kind comprising an annular working chamber in which rotate blades carried by a rotor rotating about the axis of the working chamher and making a sealing fit with the inner and outer circumferential walls of the working chamber, and an abutment extending across the working chamber beween inlet and outlet ports and making sealing engagement with the inner and outer circumferential walls of the Working chamber, the abutment or the blades being rotatable about axes parallel to but displaced from the axis of the rotor and being provided with one or more recesses which come into position at the appropriate times to permit the blades to pass the abutments, while maintaining the required fluid seal between the abutment and the inner and outer circumferential walls of the blade chamber.

In ortary pumps and motors of the kind referred to variation in the capacity of the pump or motor is eflected by moving one end wall of the working chamber axially relatively to the other to vary the axial length of the blade chamber and the corresponding effective length of the abutment and simultaneously moving the blades axially relatively to one end wall so that the axial length of the working chamber and the lengths of the parts of the abutment and of the parts of the blades which extend across the blade chamber are simultaneously and similarly varied by the relative axial movement of the parts referred to.

In variable capacity pumps and motors of the kind referred to, therefore, there are chambers the capacities of which are varied during the operation of changing the capacity of the pump or motor. Moreover, over certain parts of the cycle of operation of the pump or motor one or other of such chambers are closed except for the working clearances between the parts forming them. Assuming, therefore, that it is desired to change the capacity of the pump or motor during operation, such changes will tend to take place in a series of jerks, the stationary periods between which represent the times when the chambers whose capacity changes are closed. Moreover, if it is desired to change the capacity of such a pump or motor when not in operation and the parts happen to be in a position in which one of the chambers whose ca pacity has to be changed is closed, the change can only be effected slowly and with the exercise of considerable force since fluid has to be forced or drawn through working clearances.

With existing arrangements, therefore, not only is it impossible to provide for sensitive control of the capacity owing to the different resistance offered to changes in capacity at different points in the rotation of the rotor but rapid changes in capacity both during operationand for certain positions of the rotor during idle periods may be impossible.

The object of the present invention is to reduce or eliminate this difliculty and to provide an arrangement in which the control of capacity will tend to be easier nited States Patent It has already been proposed in variable capacity pumps and motors of the kind referred to, to provide the pump or motor with a fluid tight pressure casing in which a pressure having a value between the pressures respectively on the high and low pressure sides of the pump or motor is automatically maintained by an automatic valve sensitive to the relationship between such pressures and arranged to automatically admit fluid under pressure from the high pressure side of the pump to the casing or permit escape of fluid to the low pressure side of the pump or motor from the casing in such manner as to maintain the desired predetermined relationship between the pressures on the high and low pressure sides of the pump or motor and the pressure in the casing. Such an automatic valve had the effect incidentally of permitting flow of fluid to and from the casing when the pressure therein is varied by reason of the application to the parts of the pump or motor which are moved to vary the capacity thereof of a force tending to effect such movement since in such pumps and motors the parts which move axially into and out of the working chamber to effect the changes in capacity also cause a corresponding but opposite displacement of fluid out of or into the closed casing.

The present invention is applicable to variable capacity pumps and motors of the kind referred to whether they have a pressure casing as described above or not or motor, and automatic valve apparatus controlling the flow of fluid through the exit and admission passages in such manner as to permit outflow of fluid through the said passages only when the pressure in the chambers exceeds the pressure on the high pressure side of the pump or motor and to enable fluid to flow in through said passages only when the pressure in the chambers is less than the fluid pressure on the low pressure side of the pump or motor.

In a preferred arrangement the automatic valve apparatus includes an automatic outflow non-return valve through which each of the chambers is connected to the high pressure side of the pump or motor and an auto-p matic inflow non-return valve by which each of the chambers is connected automatically to a source of relatively low pressure when the pressure in each of the chambers is reduced below the pressure on the low pressure side of the pump or motor. Thus, in one such arrangement each inflow passage is connected through its associated non-return valve to a pressure-responsive valve which, when the pressure in the inflow passage drops below the pressure on the low pressure side of the pump or motor, moves automatically to admit fluid from the source of relatively low pressure. The source of relatively low pressure in such an arrangement, when the invention is applied to a pump or motor of the kind having a pressure casing as above described may be the interior of the casing or a passage in communication therewith.

Moreover, in any case automatic change-over valve apparatus responsive to the relationship between the pressures respectively at the two sides of the pump or motor may be provided whereby, whichever of the two sides of the pump or motor happen to be respectively the high and low pressure sides at any moment, the appropriate passages and parts of the valve apparatus will automatically be connected respectively to the high and low pressure sides, so that the valve apparatus will function correctly irrespective of the direction of rotation of the pump or motor and of whether the device is in fact at the moment acting as a pump or motor.

When the invention is applied to a pump or motor having a pressure casing as above described the automatic change-over valve apparatus referred to may be similar to that hitherto used in conjunction with such a pump to maintain the pressure in the casing correct irrespective of which of the two sides of the pump or motor happens at the moment to be the high pressure side and may in fact be the same change-over valve apparatus as performs this function.

The invention may be carried into practise in various ways but one arrangement according to the invention and a modification of that arrangement are illustrated by way of example in the accompanying drawings, in which:

Figure l is a sectional side elevation of a pump or motor to which the invention is applied,

Figure 2 is a diagrammatic illustration of the pump or motor shown in Figure l with the associated automatic valve apparatus, with the pump shown in cross section in the plane 2-2 of Figure 1, and with the parts thereof in one position,

Figure 3 is diagrammatic cross section through the pump or motor similar to that included in Figure 2 but with the parts shown in a different position,

Figure 4 is an elevation of the casing enclosing the automatic valve apparatus as used in the pump or motor shown in Figure 1 looking towards the face of the casing which is normally clamped to a corresponding face of the pump or motor casing,

Figure 5 is a side elevation of the casing enclosing the automatic valve apparatus as used in the pump or motor shown in Figure 1,

Figure 6 is a sectional plan on the line 6-6 of Figure 5, and

Figure 7 is a similar view to Figure 3 showing diagrammatically a modified arrangement of the automatic valve apparatus which may be used in some cases.

The apparatus shown in Figures 1 to 6 inclusive comprises a hydraulic pump or motor, hereinafter for convenience called a motor, including a casing A having formed within it two intersecting parallel cylindrical bores A1 and A2 parts of the lengths of which constitute respectively the outer circumference of an annular blade chamber B and the surface of the larger abutment recess in known manner. Mounted to slide within the bore A1 and making a close working fit therewith is an axially movable member C having a part annular end face C1 constituting one end wall of the blade chamber B beyond which end wall projects a part C2 constituting the inner circumferential wall C3 of the blade chamber and having a part cylindrical recess C4 therein which is concentric with the surface of the larger abutment recess A2 and forms therewith the circumferential wall of the abut merit chamber D.

Rigidly mounted within one end portion of the bore A2 and within the corresponding end portion of the recess C4 so as to form one end wall D1 of the abutment chamber D is a part E in bearings in which is mounted an abutment shaft F carrying at one end an abutment F1 having two blade-receiving recesses F2 and at its other end a gear wheel F3. The end wall of the abutment chamber D remote from the end wall Di is formed by a plate G extending across the interior of the casing A and having therein a bore G1 which is concentric with and of the same diameter as that of the outer circumferential surface A1 of the blade chamber so as to form in effect a continuation of that circumferential surface but making a complete cylinder instead of terminating where the abutment chamber overlaps the blade chamber.

Supported in bearings in the axially movable member C is a rotor shaft H carrying at one end a rotor H1 supported in a bearing H2 and at its other end a gear wheel H3 meshing with the gear wheel F3. The rotor H1 is of known type including two blades H4 which extend axially through and make a close lit with the bore G1 and with the circumference of an internal plate I secured to the adjacent end of the part C2, the blades H4 lying partly and sliding with close sealing fits within axial slots K1 in a rotary cylindrical member K which is mounted at one end on a shaft K2 coaxially with the rotor H1 and whose other end lies within the annular space between the surface of the bore G1 and that of the plate I and makes a close sealing fit with these two surfaces so as to form the left hand end wall of the blade chamber.

The shaft K2 is supported in bearing K3 in an end plate U rigidly secured within the casing A and projects through such bearings and through a fluid tight gland A3 in the casing to form the means by which the rotation is transmitted from the moving parts of the motor.

Inlet and outlet ports L and M are formed in the casing A and communicate with the parts of the blade chamber respectively on opposite sides of the abutment F1 in known manner while means including a lever N acting on the end of the part C are provided for moving this part, and therefore the rotor H1 axially to vary the effective length of the blade chamber and hence the capacity of the motor, also in known manner.

The two blade-receiving recesses F2 in the abutment F1 communicate with one another by way of a passage F4 as shown while formed in the circumferential surface of the abutment between the blade receiving recesses are grooves F7 each of the same circumferential width as each of the recesses F2 with each of the grooves communicating with its diametrically opposite groove through a passage F5 or F6. This arrangement and operation of a motor of the construction so far described is well known and is described in example in the specification of United States Patent No. 2,483,705 and will not therefore be further described herein.

It will be seen that during the periods in the cycle of operation of the motor when the chamber B is completely enclosed by two blades H4 as shown in Figure 2 the axial movement of the part C and hence of the blades H4 and end wall C1 to decrease or increase the capacity of the motor will only be possible with corresponding How of working liquid out of or into the chamber. Similarly during'periods in the cycle when each of the blade receiving recesses F2 is completely closed by engagement with the smaller abutment recess C4 as shown in Figure 3 the movement of the part C and hence of the blades H4 can only take place with flow of working liquid into or out of such blade receiving recess F2.

The casing A is closed and filled with working liquid and automatic valve apparatus is provided not only for maintaining a pressure in the casing approximately midway between the pressures respectively in the inlet and outlet ports but also for permitting the required entry of working liquid into and escape of such liquid from the closed chambers referred to above as being formed at certain periods in the cycle of operations if and when the part C is moved axially to change the capacity of the motor.

This apparatus is shown diagrammatically in Figure 2 of the drawings and in a constructional form in Figures 4, 5 and 6, and comprises a piston valve having a truncated valve member P, P1 the two parts P and P1 of which lie respectively within the two parts P2, P3 of a correspondingly formed valve chamber. The smaller diameter end P3 of the valve chamber communicates through a passage Q with one port of an automatic change over valve R having three further ports two of which communicate con1 tinuously respectively with passages R1, R2 leading respectively to the inlet and outlet ports L and M of the motor, while the third communicates through a passage R3 with a non-return valve S. The non-return valve forms one of a pair of valves S and S1 arranged to control the how of liquid respectively from and to a passage S2 which is in continuous communication with ports S3 and S4 formed respectively in the outer circumferential wall A1 of the blade chamber midway between the inlet and outlet ports L and M and adjacent to the plate G and in the larger abutment recess A2 at a point midway between the inlet and outlet ports L and M. It will thus be seen that the port S3 always communicates with the interior of the blade chamber while the port S4 will communicate directly with one blade receiving recess F2 and indirectly through the passage F4 with the interior of the other blade receiving recess F2 (which would otherwise be completely closed) when the parts are in the position shown in Figure 3. These ports S3 and S4 are thus available for the required flow of working liquid to and from the blade chamber and the blade receiving recesses during the period of the cycle during which axial movement of the part C at any appreciable speed to adjust the capacity of the motor would otherwise be prevented due to the only entry or escape paths for the liquid being the normal working clearances between the parts of the motor.

The larger diameter end P2 of the valve chamber communicates through a passage T with the interior of the casing A while a port P4 at an intermediate point in the wall of the smaller diameter part P3 ofthe valve chamber also communicates with the interior of the casing A. The annular chamber P5 lying between the smaller and larger diameter parts of the valve chamber communicates through a passage P6 with a passage P7 with which also communicates a port P8 formed at an intermediate point in the length of the larger diameter part P2 of the valve chamber.

The passage P7 communicates with the inlet sides of two non-return valves R4, R5 the outlet passage R6 of one of which communicates directly with the passage R1 while the outlet passage R7 of the other communicates directly with the passage R2. The passage P7 also communicates with the outlet side of the non-return valve S1.

The operation of the apparatus is as follows. During operation of the motor the valve R will move so as to close the port leading to the passage R1 or the port leading to the passage R2 automatically according to whether the port M or the port L respectively happens to be at the higher pressure whereby that one of these two ports which is at the moment at the higher pressure is always connected through the passage Q to the smaller diameter end P3 of the valve chamber. Moreover if the port L is at higher pressure then the valve R4 will be maintained on its seat by the pressure in the passage R1 while the valve R5 will be maintained open by any pressure in the passage P7 higher than the pressure in the port M. Similarly if the port M is at higher pressure the valve R5 will be maintained on its seat while the valve R4 will be maintained open by any pressure in the pipe P7 higher than the pressure in the port L. In practice this means that while the pipe Q is always subject to the pressure in that one of the ports L and M which at the momentis at higher pressure, the passage P7 is always subject tothe pressure in the one of the two ports L and M which is at the moment at lower pressure. The valve P so controls the ports P4- and P8 as to maintain within the casing A of the pump at all times a pressure approximately midway between the pressures in the ports L and M, because the righthand end of the valve P is of approximately twice the area of the lefthand end and the chamber P5 is always at the pressure in the lower pressure port. Therefore if and when the pressure in the casing and therefore acting on the righthand face of the valve drops below the mean of the pressures in P3 and PS the valve P will be moved to the right so as to open the port P4 and admit additional working liquid from the end P3 of the valve chamber to the casing until the pressure therein has been built up to the mean between the pressures in P3 and P5. Similarly if for any reason the pressure in the casing exceeds the mean of the pressures in P3 and PS, the valve P will move to the left to open the port P8 and thus permit escape of liquid from the casing through the pipe P7 and the appropriate valve R4 or R5 until the pressure 6 in the casing is again the mean of the pressure in P3 and P5.

It will moreover be seen that if at any time the axially movable part C of the motor is moved to the left in Figure 1 to decrease the capacity of the motor, liquid will be able to escape from the working chamber B during the period when the parts are in and about the position indicated in Figure 2 through the port S3 and the valve S provided that the force applied to the part C is such as to create a pressure in the working chamber B in excess of that at the moment existing in the higher pressure port L or M; while similarly during the period when the parts are in and about the position shown in Figure 3 liquid can be drawn into the blade receiving recess F2 sealed by the abutment recess C4 through the passage F4, the other recess F2, the port S4, the passage S2 and the valve S1 provided that the pressure in the blade receiving recesses F2 is reduced by the force applied to the part C below the pressure in the pipe P7.

Similarly if the axially movable part C is moved to the right in Figure l to increase the capacity of the motor, liquid can be drawn in through the port S3 and the valve S1 from the pipe P7 when the parts are in the position shown in Figure 2 provided the pressure in the working chamber is reduced below that in the pipe P7, while when the parts are in and about the position shown in Figure 3 working liquid can be forced out of the recesses F2 through the port S4, the passage S2 and the valve S provided that the pressure in the recesses F2 is caused to be greater than that in the pipe R3.

It will moreover be seen that any flow into the working chamber B when the parts are in the position shown in Figure 2 or into the recesses F2 when the parts are in the position shown in Figure 3 due to axial movement of the part C will take place through the pipe P7 first to a small extent from the chamber P5 whereupon the movement of the valve P thus caused to the left will cause the further flow to take place through the port P8 whereby in effect the flow into the working chamber B or recesses F2 takes place at least principally from the casing A. This is advantageous since during movement of the part C any change in the free volume of the blade chamber or blade receiving recesses corresponds to an equal and opposite change in the free volume within the casing A enclosing the working parts so that in effect a mere displacement of liquid from one chamber to another occurs without flow from the low pressure port. Similarly on movement of the port C such as to cause outflow of liquid from the blade chamber when the parts are in the position shown in Figure 2 or from the blade receiving recesses F2 when the parts are in the position shown in Figure 3 will cause a change in the relative pressure in P3 and P2 such as to cause the valve P to move to the right whereby in efiect the liquid displaced from the blade chamber or recesses F2 passes into the casing A to fill the space being vacated by the axially moving parts.

In the modification shown in Figure 7 the arrangement and operation are generally similar to those shown and described with reference to Figure 2 but instead of the two ports S3 and S4 being connected to one another so that flow of liquid to or from them when appropriate can take place through the valves S1 and S respectively the port S3 communicates through a passage S5 with the valves S and S1 while the port S4 communicates with a passage S6 having a separate pair of non-return valves S7 and S8 therein through which fluid can flow under suitable conditions respectively from or to the passages P7 and R3.

In the arrangement shown in Figure 7 therefore the valves S and S1 in the arrangement shown in Figure 2 may be regarded as duplicated so as to provide a separate pair of valves associated with each of the ports S3 and S4.

It will be seen that the operation of the apparatus shown in Figure 7 is substantially identical with that of mares the apparatus shown in Figure 2 except that flow to or from the ports S3 and S4 from or to the passages P7 and R3 takes place through the same valves S1 and S in one case and through diflerent valves S1, S and S7, S8 in the other case.

What I claim as my invention and desire to secure by Letters Patent is:

l. A variable capacity rotary fluid pressure machine of the character described having high and low pressure sides including a housing having chambers whose capacity changes with relative axial movement between the housing and parts which are moved axially to vary the capacity of the machine, said housing having exit and admission ports communicating with said low and high pressure sides and having open connections to said chambers during the periods when they are otherwise closed, and automatic valve apparatus in said connections controlling the flow' of fluid due to said relative axial movement through the said exit and admission ports having means including passages permitting outflow of fluid through said exit and admission ports only when the pressure in the said chambers is higher than the pressure on the high pressure side of the fluid pressure machine and permitting inflow of fluid through the said exit and admission ports only when the pressure in the said chambers is below that on the low pressure side of the fluid pressure machine.

2. A variable capacity rotary pump or motor as claimed in claim 1, in which the valve apparatus comprises an automatic non-return valve through which each of the chambers is connected to the high pressure side of the pump or motor and an automatic non-return inflow valve by which each of the chambers is connected automatically to a source of relatively low pressure fluid when the pressure in each of the chambers is reduced below the pressure on the low pressure side of the pump or motor.

3. A variable capacity rotary pump or motor as claimed in claim 2, in which each inflow passage is connected through its associated non-return valve to a pressure responsive valve which when the pressure in the inflow passage drops below the pressure on the low pressure side of the pump or motor, moves to admit fluid from a source of intermediate pressure.

4. A variable capacity rotary fluid pressure machine of the kind referred to as claimed in claim 1 including an automatic change over valve arranged between the said automatic valve apparatus and passages leading respectively to the two sides of the fluid pressure machine and serving to connect the two sides of the fluid pressure machine to the automatic valve apparatus so that fluid can flow through said automatic valve apparatus only to the high pressure side of the fluid pressure machine and from the low pressure side of said machine.

5. A hydraulic system as claimed in claim 1 including a casing enclosing the fluid pressure machine and formed to contain working fluid under pressure, an automatic pressure responsive valve controlling flow of working fluid to the casing from the high pressure side of the machine and from the casing to the low pressure side of the machine to maintain the pressure in the casing intermediate between the inlet and outiet pressures of the machine and a connection between the admission passage and the chamber in the pressure responsive valve which is subject to the pressure on the low pressure side of the machine.

6. A hydraulic system as claimed in claim 5 including a change-over valve which automatically changes over the connections between the various valves and the two sides of the machine to maintain the appropriate passages and chambers always in communication respectively with the high pressure and low pressure sides of the machine irrespective of which side of the machine is at any moment at higher pressure.

'7. A variable capacity rotary fluidpressure machine of the character'dcscribed having high and low'pressure 8 sides and a working chamber housed in a easing into which open working clearances between parts of the fluid pressure machine which rotate relatively to one another and are subject to the workingpressures in the working chamber of the fluid pressure machine, said casing containing exit and admission passages communicating with the working chamber whose capacities change with relative axial movement between the parts which are moved axially to vary the capacity of the fluid pressure machine, and valve apparatus in said passages including a pressure control valve device responsive to the inlet and outlet pressures of the fluid pressure machine and controlling flow of fluid respectively from the high pressure side of the fluid pressure machine into the casing and out of the casing to the low pressure side of the fluid pressure machine to maintain a fluid pressure in the casing intermediate between the pressures respectively on the high and low pressure sides of the fluid pressure machine, the exit passage communicating with a valve chamber in the pressure control device which is subject to the high pressure side of the fluid pressure machine while the admission passage communicates with a valve chamber in the pressure control valve device which is subject to the low pressure side thereof, and automatic nonreturn valve devices arranged to permit flow only respectively to the exit passage from each of the said valve chambers and from the admission passage to each of the said valve chambers.

8. A variable capacity rotary fluid pressure machine 013 the kind referred to as claimed in claim 7 including an automatic change-over valve responsive to the fluid pressures respectively on the two sides of the fluid pressure machine and serving automatically to maintain the exit passage in communication with the high pressure side of the fluid pressure machine irrespective of which side that may be and automatically to maintain the appropriate chambers of the pressure control valve device respectively in communication with the high and low pressure sides of the fluid pressure machine whichever side may be at the higher pressure at any time.

9. A hydraulic system comprising a variable capacity hydraulic fluid pressure machine of the character described having a casing having inlet and outlet ports, and chambers in said casing which during parts of the cycle of operation of the machine are closed except for working clearances and have their capacities varied by longitudinal movement of the relatively longitudinally movable parts the longitudinal movement of which changes the capacity oi the machine, inflow and outflow ports being formed in the walls of these chambers where they will open into'the chambers at least during the periods when the chambers are otherwise closed, admission and exit passages leading. from said inflow and outflow ports respectively to areas within. said casing subject to the pressures in the inlet and outlet ports and non-return valves arranged between each inflow and outflow port and the exit and admission passages to permit fluid flow from each inflow and outflow port only to the exit passage and from the admission passage.

10; A variable capacity rotary fluid pressure machine of the character described having high and low pressure sides and comprising an annular working chamber having inlet and outlet ports and a movable end wall, a rotor rotating about the axis of the working chamber and including blades which extend across the working chamber and make a sealing fit with the inner and outer circumferential walls of the working chamber, and an abutment extending across the working chamber between the said inlet and outlet ports and making a sealing engagement with the inner and outer circumferential walls' of the working chamber, the abutment being rotatable in a cylindrical chamber about an axis parallel to but displaced from the axis of the rotor and including one or more rece'sseswhich come intop'osition' at the appropriate times I to perinifthe blades to pass the ab'utme'ntwhile main taining the required fluid seal between the abutment and the inner and outer circumferential walls of the working chamber, and means for moving said end wall of the working chamber axially to provide for variation in the capacity of the working chamber and thereby of the machine; wherein the rotary fluid pressure machine includes exit and admission ports communicating with said working and abutment chambers during the periods when they are otherwise closed, and automatic valve apparatus including means controlling the flow of fluid through the said exit and admission ports, said means permitting outflow of fluid through said exit and admission ports only when the pressure in the said working and abutment chambers is higher than the pressure on the high pressure side of the fluid pressure machine and inflow of fluid through the said exit and admission ports only when the pressure in the said working and abutment chambers is below that on the low pressure side of the fluid pressure machine.

11. A variable capacity rotary fluid pressure machine of the character described, having high and low pressure sides and comprising an annular working chamber having inlet and outlet ports, blades mounted to rotate in the working chamber, a rotor carrying the blades and rotating about the axis of the working chamber, the blades making a sealing fit with the inner and outer circumferential walls of the working chamber, an abutment extending across the working chamber between the inlet and outlet ports and making sealing engagement with the inner and outer circumferential walls of the working chamber, the abutment and blades being rotatable relatively to each other about parallel axes, the abutment being rotatable about an axis displaced from the axis of the rotor and being formed with at least one recess which comes into position at the appropriate times to permit passage of the blades past the abutment while maintaining the required fluid seal between the abutment and the inner and outer circumferential walls of the blade chamher, one end wall of the blade chamber being movable axially relatively to the other to vary the capacity of the working chamber, exit and admission ports arranged to communicate with the part of the working chamber which during operation is intermittently cut off from the inlet and outlet ports, and automatic valve apparatus controlling the flow of fluid through the said exit and admission ports and permitting outflow of fluid through said exit and admission ports only when the pressure in the part of the working chamber with which said ports communicate is higher than the pressure on the high pressure side of the fluid pressure machine and inflow of fluid through the said exit and admission ports only when said working chamber pressure is below that on the low pressure side of the fluid pressure machine.

References Cited in the file of this patent UNITED STATES PATENTS 788,848 Riegel May 2, 1905 1,190,139 Ford July 4, 1916 1,467,837 Colebrook Sept. 11, 1923 1,697,041 Balsiger Jan. 1, 1929 1,742,215 Pigott Jan. 7, 1930 1,990,750 Pigott Feb. 12, 1935 2,052,419 Moore et al Aug. 25, 1936 2,344,879 Johnson Mar. 21, 1944 2,483,705 Levetus et a1. Oct. 4, 1949