GYRATING PISTON MACHINE

Abstract: In a piston machine, that functions as a fluid pump or motor, of the kind in which rotary inner and outer cylindrical piston members (1, 2) of different sizes are rigidly interconnected by a barrier member (4) so as to be rotatable about their common longitudinal axis (6) and a third cylindrical piston member (3) of an intermediate size is rotatable between the members (1, 2) about an off-set axis (5) with edges (9) of the third member (3) sealingly but movably contacting opposite sides of the barrier member (4) and said member (3) sealingly contacting (7, 8) both the member (1) and the member (2), the first and second members (1, 2) are fixed to a rotary plate member (19) and the third piston member (3) to a rotary plate member (20), the piston members (1, 2) and the plate member (19) are caused to rotate by driven motion of the plate member (20) and third piston member (3), the substantial sealing engagement between the free edges of the piston members (1, 2, 3) and the surfaces of the plate members (19, 20) involving orbital rubbing motion which greatly reduces wear and consequent fluid leakage in these regions.

Description: ;Gyrating piston machine.; This invention relates to piston machines of the kind in which, during use, substantially continuously changing working volumes are contained between the surfaces of a first cylindrical piston member, a concentric second cylindrical piston member of smaller diameter which is fixed in position relative to the first piston member and a third cylindrical piston member of intermediate diameter, the axis of rotation of the latter being off-set so that its outer periphery seals against the inner periphery of the first cylindrical piston member and its inner periphery seals against the outer periphery of the second cylindrical piston member, there being first and second plate members having radial surfaces which close against the end edges of the cylindrical piston members and a barrier member which interconnects the first and second cylindrical piston members, the barrier member passing through a gap in the third cylindrical member, ports also being provided at relatively opposite sides of the barrier member for the inlet and outlet of a fluid. The first, second and third cylindrical piston members and the barrier member all rotate during the use of such a known machine and this rotation takes place relative to at least one of the plate members with the result that frictional energy loss and consequent wear are somewhat high often leading to leakage of fluid in this region of the machine. An object of the present invention is very significantly to reduce the leakage that is caused in this way and, accordingly, the present invention provides a piston machine of the kind set forth, characterised in that the first and second cylindrical piston members are fixed to one of said first and second plate members whilst the third cylindrical piston member is fixed to the other plate member, driven rotation of one plate member during the use of the machine resulting in rotation of the other plate member and the cylindrical piston member(s) corresponding thereto. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a somewhat diagrammatic sectional side view of a piston machine in accordance with the present invention, Figure 2 is a similarly diagrammatic cross-sectional view of the piston machine of Figure 1, and Figure 3 is a somewhat diagammatic sectional side view of an alternative form of piston machine in accordance with the invention. Referring to Figures 1 and 2 of the drawings, the piston machine which is illustrated comprises first, second and third cylindrical piston members 1, 2 and 3 respectively, each of these members 1, 2 and 3 being of circular cross-section' and being rotatable, during the use of the machine, about its own longitudinal axis. The first cylindrical piston member 1 has the largest diameter of the three and the second cylindrical piston member 2 has the smallest diameter of the three, being arranged co-axially inside the first member 1 to which it is fixedly connected by a substantially radially extending barrier member 4. The third cylindrical piston member 3 has a diameter which is intermediate between that of the first and second members 1 and 2 and extends longitudinally parallel to both of the latter at a variable location between them. In fact, the axis of rotation 5 of the third cylindrical piston member 3 is parallel to, but off-set from, the common axis of rotation 6 of the first and second members 1 and 2 to such an extent that, during operation, the convex outer surface or periphery of the member 3 makes a sealing substantially linear contact with the inner concave surface or periphery of the largest cylindrical piston member 1, this variable location being indicated by the reference 7 in Figure 2 of the drawings. Similarly, the inner concave surface or periphery of the third cylindrical piston member 3 makes a sealing and substantially linear contact with the outer convex surface or periphery of the innermost second cylindrical piston member 2, the variable postion of this location being indicated by the reference 8 in Figure 2 of the drawings. There is an axially extending gap in the wall of the third cylindrical piston member 3, the opposite edges of this gap being provided with cylindrical elements 9 that extend parallel to each other and to the axes 5 and 6 at opposite sides of the barrier member 4. In addition to the cylindrical elements 9, the third cylindrical piston member 3 is formed, alongside each of those elements 9 and thus at opposite sides of the barrier member 4, with ports 10 and 11, respectively. The port 10 is in open communication with a port 12 formed through the wall of the innermost third cylindrical piston member 3 and that port 12, in turn, is in communication with at least one of a plurality of window ports 13 formed in a hollow shaft 14 through which fluid to be pumped by the piston machine is introduced into the latter when said machine is, in fact, operating as a pump. It is particularly noted that, by introducing fluid under ¬ pressure into the machine, it can function as a fluid motor instead of as a fluid pump. The port 11 is in open communication with one of the two chambers that are formed between the innermost cylindrical piston member 2 and the surrounding cylindrical piston member 3, the port 11 being located alongside a port 15 through the wall of the largest cylindrical piston member 1 and the latter port, in turn, communicating by way of a surrounding chamber 16 with an exit port 17 through a casing 18 of the piston machine. A first substantially circular plate member 19 carries the first and second cylindrical piston members 1 and 2 by having corresponding curved edges of those members 1 and 2 integrally or rigidly secured thereto. A second plate member 20 has one edge of the third cylindrical piston member 3 rigidly or integrally secured to one side thereof whilst the opposite side thereof is rigidly or integrally secured to a shaft 21 whose longitudinal axis/axis of rotation coincides with the axis 5 and also with the centre of the substantially circular second plate member 20. During operation of the piston machine as either a pump, as illustrated, or as a motor, the shaft 21, both plate members 19 and 20 and the cylindrical piston members that are connected to the latter all revolve in the same direction which is indicated by an arrow in a bottom right-hand region of Figure 2 of the drawings. When acting as a pump, the shaft 21 is a driving shaft and driven rotation of the second plate member 20 by that shaft 21 results in rotation of the first plate member 19 and the piston members 1 and 2 that are secured thereto by virtue of the engagement of the barrier member 4 in the gap between the two cylindrical elements 9. A third plate member 22 that is parallel to both the first and second plate members 19 and 20 closes the circular opening that is defined by the free edge of the second cylindrical piston member 2 that lies adjacent to the second plate member 20 and it will be seen from Figure 1 of the drawings that this third plate member 22 lies alongside the second plate member - 20 and is in open communication, through the hollow shaft 14, at least one of the window ports 13 and the port 12, with said inlet port 10. The relatively low inlet pressure acts upon the third plate member 22, whilst the right side (in Figure 1) of said plate member Jj is subject to the higher exhaust or outlet pressure in the manifold chamber 16 that surrounds the cylindrical piston member 1. The 1 result is that the free edge of the first cylindrical piston member 1 is urged towards the second plate member 20 whilst the free edge of the third cylindrical piston member 3 is effectively urged towards the first plate ' 5 member 19. Sealing contact thus tends to be maintained, rather than broken, but the rate of wear in the sealing regions is quite low because, during operation of the machine, many of the parts located internally of the ported casing 18 are rotating in the same direction that 10 is indicated by an arrow near the bottom right of Figure 2 of the drawings, so that movements between the free edges of the cylindrical piston members 1 and 3 and the surfaces of the second and first plate members 20 and 19, respectively, are orbital rubbing movements rather than 15 rotation of one member relative to another non-rotary member as takes place in prior art constructions which are consequently subject to a much faster rate of wear. There is a seal 23 between the rotary first plate member 19, the non-rotary casing 18 and the non-rotary 20 hollow shaft 14 which acts as a fluid inlet, when the piston machine is functioning as a pump, or which would act as an Outlet if the rotation of the drive shaft 21 were to be reversed. The diameter of the seal 23 governs the effective area of the first plate member 19 which is 25 subject to the pressure existing in the manifold chamber 16. It will be noted that the interior of the second cylindrical piston member 2 is rotatably mounted on the inner end of the hollow shaft 14 which exhibits the window ports 13, those window ports 13 being flanked, at 30 both axial sides, by unwindowed shaft portions that co-operate with registering locations disposed internally of the second cylindrical piston member 2 in the manner of plain bearings. In an alternative construction which is not illustrated, the exterior surface or periphery of 35 the first cylindrical piston member 1 rotates, by way of plain bearings , in a surrounding bearing member that may be rigid with the casing 18. The basic operation of a piston machine of this general kind as either a pump or as a motor is known. For operation as a pump, a liquid or gas is drawn inwardly through the hollow shaft 14 to pass through at least one window port 13, the port 12 and the port 10 into the chambers that are defined between the cylindrical piston members 1, 2 and 3. The direction of rotation is such that the substantially continuously changing working volumes of the chambers defined between the piston members 1, 2 and ' 3 causes suction at the port 12 and pressure at the port 15 whereby the liquid or gas that is being pumped is caused to move in the direction of the arrows shown in Figures 1 and 2 of the drawings, such liquid or gas entering the chamber 16 and being delivered therefrom through the exit port 17. The piston machine will operate as a fluid motor, to rotate the shatt 21, upon supplying fluid under pressure into the hollow shaft 14. Pumping or motoring operation in an opposite direction is effected by reversing the drive to the shaft 21 or supplying fluid under pressure to the port 17 instead of to the interior of the hollow shaft 14. It will be apparent that the first plate member 19 and the first and second cylindrical piston members 1 and 2 could be directly driven by the shaft 21 and the third piston member 3 and the second plate member 20 be rotated as a consequence merely by reversing the described and illustrated arrangement. Figure 3 of the drawings illustrates a piston machine in accordance with the invention in which several parts of the machine are similar, or identical, in construction and/or function to parts that have already been described with reference to Figures 1 and 2 of the drawings. Accordingly, an unnecessary repetition of a full description of such parts will not be given and they are indicated in Figure 3 of the drawings by the same references as are employed in Figures 1 and 2 thereof. In this embodiment, a "double" construction is employed. the shaft 21 carrying, at its inner end, a perpendicular flange 24 which, in turn, is secured to -the first cylindrical piston member 1 and to the second cylindrical piston member 2 both of which are concentric around the axis 6. The first and second cylindrical piston members 1 and 2 are rigidly interconnected by the flange 24 and also by a barrier member that is equivalent to the previously described barrier member 4 but that is not visible in Figure 3 of the drawings. The third cylindrical piston members 3, like the first and second members 1 and 2, are of "double" construction and extend movably at either side of the flange 24 being driven, during the use of the piston machine, by the barrier member that cannot be seen in Figure 3 but that rigidly interconnects the first and second piston members 1 and 2 in substantially the same way as does the barrier member 4 of the first embodiment. It will be noted that rings 25 which are rigid with the third cylindrical piston members 3, and whose, centres are coincident with the axis 5, are rotatably mounted, in the manner of plain sealing bearings, around internal bosses of the casing 18. The boss at the side of the casing 18 remote from the shaft 21 is hollow and acts as an inlet port for fluid to be pumped by the machine or for fluid under pressure when the machine is to function as a motor. This fluid passes through a central opening 26 in the adjacent first plate member 19 and thence into two chambers 27 and 28 formed at opposite sides of the central flange 24 carried by the shaft 21, this flange being formed with a number of ports 29 so that the pressure in the chambers 27 and 28 will be the same. The fluid then passes through the chambers defined by the cylindrical piston members 1, 2 and 3 at the opposite sides of the flange 24 in much the same way as has been briefly described with reference to Figures 1 and 2 of the drawings although the various ports and the barrier member cannot be seen in Figure 3, jthe fluid eventually reaching the surrounding chamber 16 and passing under pressure through the exit port 17. An important feature possessed by the embodiment of Figure 3 of the drawings, is that the two systems defined at opposite sides of the flange 24 are arranged to operate substantially, and preferably exactly, 180 out of phase with one another with the result that, at any instance during operation, potentially damaging forces produced by one system and each acting in one direction are substantially exactly counterbalanced by forces produced by the other system and acting in opposite directions. The chamber 16 surrounds the two systems in the form of a manifold which is subject to the outlet or delivery pressure whereas the internal chambers 27 and 28 form a manifold with is subject to the inlet pressure. A pressure difference is produced which tends to bring the free edges of the various cylindrical piston members 1, 2 and 3 into sealing engagement with the second plate member, afforded by the flange 24, or into sealing engagement with one, or the other, of the two, in this embodiment, first plate members 19. This pressure difference is determined by the diameters of the rings 25 which afford plain bearings that seal the manifold chamber 16 from communication with the manifold chamber 27 and 28. It has been found that an improved sealing contact between the curved surfaces or peripheries of the cylindrical piston members 1, 2 and 3 can be attained by initially coating those surfaces or peripheries with a selectively abradable material, such as a mixture of a polyester with aluminium or other metal, or with an elastomer. As an alternative, the curved surfaces or peripheries of the cylindrical piston members 1, 2 and 3 may be either longitudinally grooved or be shotblasted to increase the resistance thereof to the leakage of gas or liquid between such curved surfaces or peripheries when the latter are in substantial contact with one another at linear locations such as the locations 7 and 8 that are shown in Figure 2 of the drawings. It will be understood that there will not always be full contact at such locations, a film of the working fluid and/or a lubricant often intervening.

Claims: Claims : 1 . A piston machine in which, during use, substantially continuously changing working volumes are contained between the surfaces of a firs,t cylindrical piston member (1), a concentric second cylindrical piston member (2) of smaller diameter which is fixed in position relative to the first piston member, and a third cylindrical piston member (3) of intermediate diameter, the axis of rotation (5) of the latter (3) being off-set so that its outer periphery seals (7) against the inner periphery of the first cylindrical piston member (1) and its inner periphery seals (8) against the outer periphery of the second cylindrical member (2), there being first (19) and second (20) plate members having radial surfaces which close against the end edges of the cylindrical piston members and a barrier member (4) which interconnects the first (1) and second (2) cylindrical piston members-, the barrier member (4) passing through a gap in the third cylindrical piston member (3), ports (10,11,12,15) also being provided at relatively opposite sides of the barrier member (4) for the inlet and outlet of a fluid, characterised in that the first (1) and second (2) cylindrical piston members are fixed to one of said first and second plate members (19) whilst the third cylindrical piston member (3) is fixed to the other plate member (20), driven rotation of one plate member (20) during the use of the machine resulting in rotation of the other plate member (19) and the cylindrical piston member(s) (1,2) corresponding thereto. 2. A piston machine according to claim 1, characterised in that one of said first and second plate members (19) is fixed to at least one of the cylindrical piston members (1,2) and has opposite radial surfaces which are subject, when the machine is in use, to a pressure differential whereby said plate member (19) tends to be displaced axially towards sealing contact with the neighbouring edge surfaces of the or each cylindrical piston member (3) corresponding to the other one (20) of said first and second plate members. 3. A piston machine according to claim 2, characterised in that a space (16) communicating with either said inlet or said outlet port is also in communication with the side of said plate member (19) that is remote from the side thereof that is urged, during use of the machine, towards sealing contact with the cylindrical piston member(s) (3) corresponding to the other plate member (20). 4. A piston machine according to claim 3, characterised in that a third plate member (22) is located alongside said other plate member (20) and is in open communication with either said inlet or said outlet port (14) . 5. A piston machine according to any preceding claim, characterised in that the fixedly interconnected first (1) and second (2) cylindrical, piston members are rotatably mounted either by way of the outer surface or periphery of the first cylindrical piston member (1) or the inner surface or periphery of the second cylindrical piston member (2). 6. A piston machine according to any one of claims 2 to 4, characterised in that parts (25) which form seals between manifolds (16,27,28) communicating with said ports (26,17) have sizes which are such that, during use of the machine, a pressure difference is produced between one manifold (16) and working volumes defined between the cylindrical piston members (1,2,3) which pressure difference tends to bring the free edges of those cylindrical piston members into sealing engagement with the co-operating plate members (19,24). 7. A piston machine according to any preceding claim, characterised in that one of said first and second plate members (24) supports cylindrical piston members (1,2) of two separate systems which systems are arranged to operate substantially or exactly 180° ou t of phase with each other at opposite sides of that plate member (24). 8. A piston machine according to any preceding claim, characterised in that one of said ports (15) is formed through said first cylindrical piston member (1). 9. A piston machine according to any preceding claim, characterised in that the surfaces or peripheries of said cylindrical piston members (1,2,3) are coated with an abradable material or with an elastomer to improve sealing contact therebetween during operation of the machine. 10. A piston machine according to any one of claims 1 to 8, characterised in that the surfaces or peripheries of the cylindrical piston members (1,2,3) are longitudinally grooved or are shotblasted to increase the resistance to the leakage of fluid between such surfaces or peripheries when they are in substantial contact.

Inventors: SEARLE RUSSELL JOHN, SEARLE, RUSSELL, JOHN
Applicants: SEARLE RUSSELL JOHN, SEARLE, RUSSELL, JOHN
Application year: 1985
Main classification: F01C1
IPC codes: F01C1, F01C19