EP0189452A1 - Improvements in piston machines - Google Patents

Abstract

A piston machine of the kind in which an assembly (1) of cylinders is arranged equidistantly around a first axis of rotation (x) and a corresponding piston assembly (4) is arranged equidistantly around a second axis of rotation rotation (y) which is fixed or variably inclined relative to the first axis of rotation (x), each piston (4) comprising a ring (4A) being able to move laterally with respect to the piston itself so that the ring (4A) can move substantially rectilinearly with respect to the corresponding cylinder while the piston itself moves on a curved path relative to the latter. Each cylinder (1) communicates, via a conical or stepped portion (15) thereof, with an annular surface (14) of a non-rotating support device (3) of the assembly (1) of cylinders so that, when a positive or negative pressure exists in the working volume defined by each cylinder (1) and each corresponding piston (4), the thrust reaction is largely transferred to the annular surface (14) of the support device (3 ). Each piston (4) has a through passage (11) which communicates repeatedly, during use of the machine, with the inlet and outlet ducts (13) by means of banana-shaped lights (10) arranged in the sealing surface (9) between a rotor (5) which carries the pistons (4) and an enclosure (7) of the machine. Resilient elements (4B) are interposed between the rings (4A) and the pistons themselves which they surround to prevent periodic shocks occurring during operation.

Description

IMPROVEMENTS IN PISTON MACHINES

This invention relates to piston machines of the kind in which an assembly of cylinders is arranged equidistantly around a first axis of rotation and a co-operating assembly of corresponding pistons is arranged equidistantly around a second axis of rotation that is fixedly or variably inclined to the first axis of rotation. Piston machines of this known kind can function either as pumps or motors and examples thereof are described in GB-A-1511232 and other prior documents. In piston machines known from GB-A-1511232, each piston is formed with a groove that accommodates a piston ring exhibiting an outer part-spherical surface whose diameter is substantially equal to that of the co-operating cylinder, the ring being movable laterally in the groove to enable it to be displaced rectilinearly in the cylinder whereas the piston which carries it follows an arcuate curvilinear path. According to the present invention, there is provided a piston machine in which an assembly of cylinders is arranged equi-distantly around a first axis of rotation and an assembly of corresponding pistons is arranged equi-distantly around a second axis of rotation that is fixedly or variably inclined to the first axis of rotation , each piston comprising a ring member that is displaceable laterally of the piston itself to enable that ring member to move substantially rectilinearly of the corresponding cylinder whilst the piston itself moves through a curved path relative thereto, characterised in that the working volume defined by each piston and corresponding cylinder communicates via an open end of that cylinder or via a passage through the piston itself, with a surface relative to which the piston or the cylinder is movable during the use of the machine, whereby, during such use, positive or negative fluid pressure on that piston or cylinder is at least partially transferred to said surface.

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 view of a piston machine in accordance with the invention which could be used as either a pump or as a motor, and

Figure 2 is a somewhat diagrammatic sectional side elevation illustrating one piston, its co-operating cyli'nder and adjacent parts of an alternative piston machine constructed in accordance with the invention.

It will be assumed that the basic construction and mode of operation of a machine of the kind to which the invention is applicable is known to a reader of this document but, in the absence of such knowledge, reference may be made to GB-A-1511232 or to corresponding US-A-4138930 both of which documents full}, and clearly provide any details of basic construction and mode of operation that may be needed.

Referring now to Figure 1 of the accompanying drawings, an assembly of cylinders in the form of a cylinder block 1 is rotatably mounted around a first axis x that is defined by a spigot 2 formed centrally of an angularly displaceable but non-rotatable carrier 3. The assembly of cylinders in the cylinder block 1 comprises a plurality of those cylinders that are spaced by equal distances from the first axis x and that are equi-angularly spaced apart from one another considered rotationally around that axis x.

A plurality of pistons 4 whose number is equal to that of the cylinders in the block 1 have their base ends fixedly secured to a rotor 5 that is integral with, or fixedly secured to, a shaft 6 which is rotatable, together with the pistons 4, around a second axis v chat is both co-planar with, and usually, for operation, non-perpendicularl inclined co , th first axis x. A housing 7 surrounds the cylinder block 1, the assembly of pistons 4, the rotor 5 and part of the shaft 6, bearings 8 rotatably mounting the shaft 6 in the housing 7 so that the left hand end of that shaft 6, as seen in Figure 1, projects from the housing 7 to be driven, if the piston machine is a pump, or to provide drive if the piston machine is a motor.

Each piston 4 has a body formed with a broad circumscribing groove in which a ring member 4A is received. The ring member 4A is^" in the shape of a thick equatorial slice of spherical external curvature and always makes sealing contact with the interior of the corresponding straight-sided cy.linder 1, during operation, even though each piston 4, as a whole, moves through a curvilinear path relative to that cylinder 1. This is possible because the diameter of the groove in the piston body is significantly less than is the internal diameter of the ring member 4A thus allowing said ring member 4A to move laterally in that groove. This lateral movement is, however, restricted by providing a resilient element 4B around the interior of each ring member 4A or, alternatively, around the base of each groove that receives one of the ring members 4A. The resilient element 4B may be a layer of a resilient elastomeric material or a resiliently constructed ring. The resilient elements 4B considerably reduce, if not entirely eliminate, the shock loading which takes place during the periodic take-up of drive torque by each piston 4 in turn. Preferably, at any instant during operation, at least one of the ring members 4A is always in drive-transmitting contact with its piston 4 via the respective resilient element 4B.

There is a sealing surface 9 between the housing 7 and the rotor 5 and so-called banana ports 10 formed in the housing 7 communicate- regularly with a passage 11 formed axially throuσh the centre of each piston 4. Eacn banana port 10 is in communication with an inlet or outlet duct 13 that serves for the inlet or outlet of a fluid to, or fluid from, the working volumes defined between the successive pistons 4 and corresponding cylinders depending upon whether the piston machine is used as a motor or as a pump. The right-hand end of each cylinder, as seen in Figure 1 of the drawings, is in open communication with an annular surface 14 of the angularly displaceable but non-rotatable carrier 3, such communication being by way of a frusto-conically tapered or, alternatively, stepped, portion 15 of the cylinder concerned. Thus, each piston 4 and corresponding cylinder are movable relative to this surface 14 during the use of the machine and consequently, during such use, a major portion of any positive or negative pressure i.n the cylinder is transferred to said surface 14. In an alternative construction which is not illustrated, the passages 11 through the pistons 4 are omitted and the supply of fluid to and from the working volumes defined by the pistons 4 and co-operating cylinders is achieved by way of passages formed through the carrier 3 itself. It is particularly noted that, in the construction shown in Figure 1, whilst a major portion of any pressure in each cylinder acts directly upon the annulaϊ surface 14, a minor portion of that force tends to move the cylinder block I to the right, as seen in Figure 1 of the drawings, into contact with the carrier 3 due to the component of the force exerted on the frusto-conically tapering or stepped portion 15 which is effective in that direction. The axes x and y_ intersect at a point 16 and external means which is not illustrated is employable to displace the carrier 3 angularly, but not rotatably, about an axis which contains the point 16 and that is perpendicular tc the plane of Figure 1, the cylinder block 1 which is rotatably mounted on the carrier 3 having its plane of rotation similarly moved by any angular displacement of the carrier 3. Such aisolacement changes the inclination of the first axis x to that of the second axis y_ and thus enables the working or swept volumes defined by the pistons 4 and their co-operating cylinders to be varied between a maximum value and a minimum value of non-displacement when, in a central position ^the axis x coincides with the axis v. Angular displacement in the opposite direction is possible so that the effective rotation of the piston machine may be reversed. Whilst it is greatly preferred to have the carrier 3 angularly displaceable in this way to enable the action of the machine to be easily adjusted, this is not absolutely essential and, if desired for any particular purpose, the angle and direction of inclination of the axis x to the axis y_ may be fixed. Referring now to Figure 2 of the drawings, a single composite piston 17A and a co-operating single cylinder 18 are illustrated, the composite piston 17A comprising a larger cup member that is indicated 17 and a co-operating smaller cup member 21 which together surround a principally spherical ball 19 at one end of a tubular piston rod 20. Each piston 17A also comprises a surrounding straight-sided ring member 24 which is a close axially slidable fit in the co-operating straight-sided cylinder 18. It will be seen from Figure 2 that the ring member 24 has an end wall in which a central aperture 25 is formed and that, towards its opposite end and around the piston rod 20, a thrust washer 22, whose external diameter is the same as the internal diameter of the ring member 24, is maintained in position by an internal circlip 23 whose external edge is entered in a groove in the internal surface of the member 24. The cup members 17 and 21 of the single composite piston are trapped between the end wall of the casing 24 and one side of the thrust washer 22 but have a common external diameter which is significantly less than the internal diameter of the ring member 24 thus allowing them to snift laterallv msid tne rinσ member 24. The amount of clearance is sufficient to enable the external surfaces of the ring members 24 to move laterally of the corresponding balls 19 to the extent required to allow for the rectilinear movements of the ring members 24 in the cylinders 18 as compared with the curvilinear movements of the cup members 17 and 21 that surround the balls 19. The cylindrical outer surfaces of the cup members 17 and 21 are provided with a resilient element 29 considerably to reduce, if not entirely eliminate, the shock loading which would otherwise take place due to the periodic take-up of drive torque by each piston in turn.

With the arrangement described, at any instant during operation, at least one r-ing member 24 is in drive-transmitting contact with its piston via the respective resilient element 29 which latter may be a resilient elastomeric layer or a resiliently constructed ring.

Each cylinder 18 has a closed end which provides a surface 26 that is in communication with the working volume defined by that cylinder 18 and the co-operating composite piston and that working volume (which is shown in the position illustrated in Figure 2 as being at a minimum) also communicates via the central aperture 25 in the ring member 24 with a tubular passage through the piston rod which passage is designated 27 in Figure 2. As in the embodiment of Figure 1 of the drawings, this passage 27 periodically communicates, when the machine is in use, with ducts for the supply of fluid to, and the exhaust of fluid from, the working volume defined by each cylinder 18 and the corresponding composite piston 17A. As in the preceding embodiment, each piston rod 20 could be solid and means could be provided for the supply and exhaust of fluid through ports in the end walls of the cylinders 18 and through a surrounding non-rotatable block or housing 28. It will be apparent that each composite piston and corresponding cylinder 18 communicate via an ooen end of that cylinder (as iust 1 described) , or via the passage 27 through the composite piston 17A itself, with the surface 26 relative to which both the composite piston 17A and the cylinder 18 are movable during the use of the machine, whereby, during 5 such use, thrust reaction on at least the composite piston 17A is largely transferred to said surface 26.

It will be apparent to persons skilled in this art that a piston machine in accordance with the invention might have, as regards the embodiment of Figure 1 of the 1 . drawings, an assembly of pistons rotatably mounted on the carrier 3 and an assembly of cylinders fixedly mounted on the rotor 5. Such an embodiment would operate in substantially the same way as has been described, only minor re-arrangements of fluid supply and outlet ducts, 15 and so on being required and the details of such arrangements already being available by reference to published prior art documents.

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Claims

CLAIMS : -

1. A piston machine in which an assembly (15 of cylinders is arranged equi-distantly around a first axis of rotation (x) and an assembly of corresponding pistons (4) is arranged equi-distantly around a second axis of rotation (y_) that is fixedly or variably inclined to the first axis of rotation (x) , each piston (4) comprising a ring member (4A) that is displaceable laterally of the piston itself to enable that ring member (4A) to move substantially rectilinearly of the corresponding cylinder whilst the piston itself moves through a curved path relative thereto, characterised in that the working volume defined by each piston (4) and corresponding cylinder (1) communicates via an open end of that cylinder (1) or via a passage (11) through the piston (4) itself, with a surface (14) relative to which the piston (4) or the cylinder (1) is movable during the use of the machine, whereby, during such use, positive or negative fluid pressure on that piston (4) or cylinder (1) is at least partially transferred to said surface (14) .

2. A piston machine according to claim 1, characterised in that each cylinder (1) is in open communication with said surface (14) by way of a portion (15) of said cylinder which tapers, or is stepped, towards the surface (14) whereby, during use of the machine, any positive fluid pressure within the cylinder (1) will produce a force urging that cylinder (1) towards said surface (14) due to a component thereof which acts upon the tapering or stepped portion (15) of the cylinder (1).

3. A piston machine according to claim 1 or 2, wherein a non-rotary carrier (3) upon which the cylinders (1) or the pistons (4) are rotatably mounted is angularly adjustable about an axis containing a point (16) at which said first and second axes (x) and (v) intersect one another and means is provided to effect such angular displacement, when required, to vary the working or swept volume defined b each cylinder (1) and corresponding piston (4) during each rotation about the first and second axes (x) and (v) .

4. A piston machine according to claim 3, characterised in that said carrier (3) is angularly adjustable through a central position in which said first and second axes (x) and (γ_) substantially coincide, the operating effect of the machine being relatively reversed by angular displacement of the carrier (3) to a position at one side, or the other side, of this central position.

5. A piston machine according to any preceding claim, characterised in that said pistons (4) are secured to a rotor (5) which can revolve, together with a shaft (6) , about said second axis (y) , each piston (4) being formed with a passage (11) therethrough which passage also extends through said rotor (5) to a sealing surface (9) between the rotor (5) and a relatively stationary housing (7), the passage (11) through each piston (4) and the rotor (5) communicating periodically, during the use of the machine, with inlet and outlet ducts (13) in said housing (7) which ducts (13) communicate with said passages (11), when in register therewith, by way of banana ports (10) opening across said sealing surface.

6. A piston machine according to any preceding claim characterised in that each piston (17A) is of composite construction comprising a ball (19) upon which cup members (17) and (21) are movably mounted, said cup members (17) and (21) being surrounded by a ring member (24), and characterised in that said ring member (24) has a cylindrical outer surface and surrounds the cup members (17) and (21) with sufficient clearance to enable the ring member (24) to move rectilinearly in the corresponding cylinder (18), during operation of the machine, whilst the cup members (17) and (21) are displaced laterally in said member (24) due to their curvilinear paths of movement. . A piston machine according to any preceding claim characterised in that a resilient element ( 4B , 29) is interposed between a ring member^' (4A, 24) and a body of the corresponding piston to ensure that, at any instant during operation, at least one piston (4,17A) is in drive-transmitting relationship with the respective cylinder (1,18) by way of its resilient element (4B,29) . 8. A piston machine according to claim 7, wherein the resilient element (4B,29⁾ is in the form of either a layer of a resilient material or a ring. . A piston machine according to claim 6, characterised in that each assembly of two cup members (17) and (21) and a thrust member (22) is maintained in interconnected relationsliip by an internal circlip (23) whose outer edge is received in a groove in the internal surface of the corresponding ring member (24) .