WO1993008373A1

WO1993008373A1 - Rotary machine

Info

Publication number: WO1993008373A1
Application number: PCT/AU1992/000578
Authority: WO
Inventors: Gosta Ingvald Hook; Kevin Barrett
Original assignee: Gosta Ingvald Hook; Kevin Barrett
Priority date: 1991-10-25
Filing date: 1992-10-26
Publication date: 1993-04-29

Abstract

A rotary machine, primarily for use as an air compressor, comprises a shaft (15) defining a first axis of rotation (20) and a second axis of rotation (22) offset with respect to the first axis (20). A casing (41) is mounted on the shaft (15) for rotation about the first axis (20). A rotor assembly (50) is mounted on the shaft (15) for rotation about the second axis (22). The rotor assembly (50) comprises a plurality of radially disposed cylinders and a piston (61) mounted for reciprocation in each cylinder. Each piston (61) is coupled to the casing (41) whereby the piston (61) is caused to reciprocate within the cylinder upon rotation of the casing (41). A control means (71), provided for accommodating relative movement between the rotor assembly (5) and the casing (41) arising from the eccentricity between the axes (20, 22), comprises a plurality of eccentric connections (73) between the casing (41) and the rotor assembly (50).

Description

"Rotary Machine"

TECHNICAL FIELD

THIS INVENTION relates to a rotary machine having radial pistons.

DISCLOSURE OF THE INVENTION

In one form the invention resides in a rotary machine comprising a shaft defining a first axis of rotation and a second axis of rotation offset with respect to the first axis, a casing, the casing and the shaft being rotatable relate to each other about the first axis, and a rotor assembly, the rotor assembly and the shaft being rotatable relative to each other about the second axis, the rotor assembly comprising a cylinder disposed generally radially with respect to the second axis and a piston mounted for reciprocation in the cylinder, the piston being coupled to the casing whereby the piston is caused to reciprocate within the cylinder upon relative rotation between the shaft and the casing, and a control means for controlling movement of the rotor assembly relative to the casing.

In one arrangement, the machine may operate as a pump or compressor in which case rotational torque applied to the casing causes reciprocation of the piston within the cylinder thereby doing work on a fluid introduced into a working chamber defined between the piston and the cylinder. In another arrangement, the machine may operate as a motor in which case an expanding fluid acting on the piston causes relative rotation between the casing and the shaft. Preferably, the control means comprises a plurality of eccentric connections between the casing and the rotor assembly. The eccentric connections accommodate relative movement between the rotor assembly and the casing arising from the eccentricity between the first axis of rotation about which the casing and the shaft rotate relative to each other and the second axis of rotation about which the rotor assembly and the shaft rotate relative to each other.

The eccentric connections may each comprise a crank pin having a first pin section which defines a first axis and a second pin section which defines a .second axis eccentric to the first axis, the first pin section being rotatably mounted on an end wall of the casing and the second pin section being rotatably mounted onto the rotor assembly. Alternatively, each eccentric connection may comprise a roller mounted on the rotor assembly and received within a circular recess formed within an end wall of the casing, the circular recess defining a circular path around which the roller can travel. As an alternative to the latter arrangement, the roller may be mounted on an end wall of the casing and the circular recess may be provided on the rotor assembly.

The piston is preferably coupled to the casing by way of a connecting rod one end of which is pivotally connected to the piston and the other end of which is pivotally connected to the casing.

The rotor assembly may comprise a control plate onto which said eccentric connections are mounted.

Preferably, there is at least one further cylinder and associated piston provided in the rotor assembly. Desirably, the rotor assembly comprises three cylinders each having a respective piston.

Preferably the casing comprises a cylindrical side wall co-axial with said first axis and two side walls at the ends of the cylindrical side wall.

Preferably, the casing is adapted to contain a fluid such as oil for the purposes of lubrication and cooling of the rotary machine. The cooling is achieved by oil splashing onto the various parts of the machine as they rotate about the shaft, so extracting heat therefrom. Each cylinder is preferably provided with cooling fins to assist in this regard.

As indicated above, each piston and cylinder defines a working chamber the volume of which varies according to reciprocation of the piston within the cylinder.

Means are provided for intaking a fluid into each working chamber and exhausting a fluid from the working chamber. In the case where the machine is a compressor or a pump, the fluid exhausted from each working chamber is the same as the fluid introduced into the working chamber other than it has had work performed on it. In the case where the rotary machine is an internal combustion engine, the fluid introduced into each working chamber may comprise an air-fuel mixture and the fluid exhausted from the working chamber may comprise the products or combustion.

The intake and exhaust means may comprise an intake port provided within the shaft and communicating with an intake passage formed within the shaft. Similarly, the intake and exhaust means may comprise a discharge port communicating with a discharge passage also formed in the shaft in isolation from the intake passage. For preference, the intake passage extends from one end of the shaft and the discharge passage extends to the other end of the shaft.

Preferably, the machine is provided with an oil scavaging system for removing excess oil which may enter the casing as a result of, for example, leakage from the working chambers. The scavaging system may comprise an oil scavaging disc rigidly mounted on the shaft within the casing. The disc is preferably provided with at least one oil passage extending between the outer periphery of the disc and the inner periphery thereof for communication with the intake passage formed within the shaft. The oil passage is preferably inclined at its outer end to face oncoming oil rotating within the casing.

In another form the invention resides in a rotary machine comprising a first axis of rotation and a second axis of rotation offset with respect to the first axis, a casing mounted for rotation about the first axis, and a rotor assembly mounted for rotation about the second axis, the rotor assembly comprising a cylinder disposed generally radially with respect to the second axis and a piston mounted for reciprocation in the cylinder, the piston being coupled to the casing whereby the piston is caused to reciprocate within the cylinder upon rotation of the casing, and a control means for controlling movement of the rotor assembly relative to the casing.

In still another form the invention resides in apparatus for supplying compressed air, said apparatus including a rotary machine as set forth hereinbefore. Preferably, said apparatus further comprises an accumulator for receiving compressed air from the rotary machine, the accumulator having provision for separating oil from the compressed air delivered to it.

Preferably, the accumulator comprises a cylindrical side wall and an internal wall positioned within the side wall so as to define an annular space therebetween into which compressed air from the rotary machine is delivered, the internal wall defining an outlet passage the bottom of which opens into the lower region of the accumulator and the top of which communicates with an outlet line.

Preferably, oil trapped within the accumulator is recirculated to the rotary machine for lubrication purposes. This may be done by way of an oil return line which has an inlet located at or in close proximity to the bottom of the accumulator so that it is immersed in oil accumulated therein and having an outlet communicating with the intake passage formed within the shaft. With this arrangement, oil may be forced along the oil return line to the intake passage under the influence of fluid pressure within the accumulator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the following description of two specific embodiments thereof as shown in the accompanying drawings in which:-

Fig. 1 is a perspective view of a rotary machine according to the first embodiment, with part of the machine casing removed to reveal some of the internal workings of the machine; Fig. 2 is a front elevational view of the rotary machine in the condition shown in Fig. 1;

Fig. 3 is a cross-sectional view of the machine;

Figs. 4, 5 and 6 reveal the internal workings of the machine in operation;

Fig. 7 is a front elevational view showing the internal workings of the machine with one cylinder operating in an intake cycle;

Fig. 8 is a view similar to Fig. 7 with the exception that the cylinder is shown at the completion of the intake cycle;

Fig. 9 is also a view similar to Fig. 7 with the exception that the cylinder is shown operating in a discharge cycle;

Fig. 10 is a perspective view of the shaft of the rotary machine;

Fig. 11 is a schematic sectional view showing the rotary machine incorporated into an apparatus for supplying compressed air on demand;

Fig. 12 is a sectional view of an oil control valve employed in the apparatus of Fig. 11;

Fig. 13 is a sectional view of an air intake control valve employed in the apparatus of Fig. 11;

Fig. 14 is a cross-sectional view of an eccentric connection forming part of a rotary machine according to a second embodiment; and

Fig. 15 is an elevational view of the eccentric connection of Fig. 14.

BEST MODES OF CARRYING OUT INVENTION

The first embodiment, which is shown in Figs. 1 to 13, is directed to a rotary machine 11 which operates as an air compressor. The rotary machine is incorporated into an apparatus 13 (as shown in Fig. 11) for supplying compressed air on demand to a device operated by air such as a shearing hand-piece (also not shown).

The rotary machine 11 comprises a shaft 15 supported adjacent its ends on stands 17. The shaft 15 includes a first section 19 which defines a first axis of rotation 20, a second section 21 which defines a second axis of rotation 22, and a third section 23 which is coincident with the first section.

The shaft 15 has an air intake passage 25 extending inwardly from an opening 27 in the end face of the shaft to an intake port 31 provided in the second section 21. The intake port 31 extends radially of the shaft from the intake passage 25 to the periphery of the shaft and diverges radially in the outward direction, as best seen in Fig. 10 of the drawings. The shaft is also provided with an air discharge passage 33 which extends from a discharge port 35 provided within the second portion 21 of the shaft to an outlet opening 37 in the other end face of the shaft. The discharge port 35 extends between the air discharge passage 33 and the periphery of the second portion of the shaft and also diverges in the outward direction, as best seen in Fig. 10. The inlet port 31 and the outlet port 35 are axially spaced along the second section 21 of the shaft.

A casing 41 is mounted on the first and third sections the shaft 15 for rotation about the first axis 20. The casing 41 is defined by a cylindrical side wall 43 and two end walls 45, 47 at the ends of the cylindrical side wall. The end wall 45 is integral with the cylindrical side wall 43 and the end wall 47 is selectively removable to provide access to the interior of the casing. Cooling fins (not shown) are provided on the exterior surface of the cylindrical side wall 43.

The second portion 21 of the shaft 15 is accommodated within the casing and rotatably supports a rotor assembly 50 for rotation about the second axis 22.

The rotor assembly comprises a rotor 51 and a plurality of cylinders 53 (there being three in this embodiment) securely mounted on the rotor. The cylinders 53 are disposed radially with respect to .the second axis 22 about which they rotate in unison with the rotor. The exterior of each cylinder is provided with cooling fins 55.

Each cylinder 53 extends into the rotor 51 and has a cylinder port 57 at its inner end which opens onto the inner face of the rotor and which can communicate sequentially with the intake and delivery ports 31 and 35 respectively formed in the shaft.

A piston 61 is mounted for reciprocation within each cylinder 53. Each piston in association with its respective cylinder defines a working chamber 63 which varies in volume according to reciprocation of the piston within the cylinder. The pistons are each connected to the casing 41 by a connecting rod 65 one end of which is pivotally connected to the respective piston at 67 and the other end of which is pivotally connected to the casing at 69.

Because the casing 41 and the cylinders 53 respectively rotate about the first and second axis 20 and 22 which are eccentric to each other, the pistons are caused to reciprocate within the cylinders upon rotation of the casing.

A drive means (not shown) is provided for rotating the casing. The drive means may comprise an electric motor drivingly coupled to the casing in any suitable means such as a belt and pulley arrangement.

If the connecting rods 65 were to provide the only connection between the casing and the rotor assembly, the latter would rotate erratically within the casing upon rotation of the casing with the probable result that the pistons would jam within the cylinders. To avoid this problem, a control means 71 is provided for controlling movement of the rotor assembly relative to the casing. The control means 71 comprises a plurality of eccentric connections 73 between the casing and the rotor assembly. The eccentric connections 73 accommodate relative movement between the rotor assembly and the casing arising from the eccentricity between the first axis of rotation 20 about which the casing rotates and the second axis of rotation 22 about which the rotor assembly rotates. In other words, the eccentric connections function to control the movement of the rotor assembly relative to the casing.

In this embodiment, each eccentric connections 73 comprises a crank pin 75 having a first pin section 77 which defines a first axis and a second pin section 79 which defines a second axis eccentric to the first axis. The first pin section 77 is rotatably mounted on the end wall 45 of the casing. In particular, the first pin section 77 is rotatably supported within a bearing 81 which is accommodated within a recessed bearing housing 83 formed in the end wall 45 of the casing. The second pin section 79 is rotatably mounted on a control plate 85 which is rigidly mounted on the rotor 51 thereby to form part of the rotor assembly. The control plate 85 extends beyond the rotor and is provided with a bearing housing 87 which accommodates a bearing for rotatably supporting the second pin section 79.

The eccentric connections 73 establish a rotational link between the rotor assembly and the casing and serve to control relative movement there between on rotation of the casing about its axis of rotation 20 and rotation of the rotor assembly about its axis of rotation 22. This relationship can be seen in Figs. 4, 5 and 6 of the drawings from which it will be noted that the relationship between the first pin section 77 and the second pin section 79 of each eccentric connection 73 remains constant as the casing rotates about the first axis and the rotor assembly rotates about the second axis 22. This relationship is such that the first pin section remains vertically above the second pin section during rotation, as can be seen in the drawings.

As previously mentioned, the eccentricity between the first axis 20 and the second axis 22 causes the pistons 61 to reciprocate within their cylinders 53. This causes the working chambers 63 to undergo expansion and compression strokes, as illustrated in Figs. 7, 8 and 9 of the drawings where a working chamber can be seen to move between an expansion stroke and a compression stroke as it rotates about the second axis 22.

As each working chamber 63 rotates about the second axis 22 defined by the second section 21 of the shaft 15, the cylinder port 57 at inner end of the cylinder communicates sequentially with the intake port 31 and the discharge port 35. The timing of rotation is such that each working chamber 63 communicates with the intake port 31 during an expansion stroke of the chamber (as shown in Fig. 7) and communicates with the discharge port 35 during a compression stroke of the working chamber (as shown in Fig. 9 of the drawings). With this arrangement, each working chamber can receive a charge of air (with oil entrained therein as will be explained later) via the air intake passage 25 and intake port 31 within the shaft during the intake stroke. Once the cylinder port 57 moves out of communication with the intake port 31, the timing is such that the working chamber commences a compression stroke to compress the air contained therein. At this stage the working chamber is in the position shown in Fig. 8 of the drawings where it communicates with neither the intake port 31 nor the discharge port 35. As the working chamber continues to rotate air contained therein is further compressed until such time as the cylinder port 57 is exposed to the discharge port 35 whereupon the air under pressure within the working chamber discharges through the discharge port 35 and into the discharge passage 33 for further processing, as will be explained later.

A fluid such as oil is contained within the casing 41 for the purposes of lubrication and cooling of the rotary machine. The cooling is achieved by oil splashing onto the pistons, cylinders and related parts as they rotate about the shaft, so extracting heat therefrom. The heat extracted by the oil is dissipated through the casing 41 to the surrounding air. This heat dissipation is assisted by the exterior cooling fins (not shown) on the cylindrical side wall 43 of the casing. The splashing oil serves a lubrication function which is supplemented by a lubrication system 91 which introduces oil into the intake air. The oil is introduced into the intake air as it flows along air intake passage 25 and is subsequently removed form the air after compression. The manner in which oil entrained in the compressed air is removed therefrom will be explained later. The presence of the oil in the air is beneficial not only for lubrication but also for cooling purposes. In this regard, the oil extracts heat from the air during compression in the working chambers 63 and so assists in keeping the compression temperature down. An oil scavenging system 92 is provided for removing excess oil which may enter the casing 43 as a result of leakage from the working chambers. The scavenging system 92 comprises an oil scavenging disc 93 rigidly mounted on the first portion 19 of the shaft within the casing. Because the disc 93 is rigidly mounted on the shaft, it does not rotate with the casing and the rotor assembly. The oil contained within the casing rotates with the casing owing to friction between the oil and the casing, and under the influence of centrifugal forces forms in a rotating annular body against the cylindrical wall of the casing. The depth of the rotation body of oil is controlled by the scavenging disc. When there is the correct amount of oil in the casing, the rotating body of oil does not contact the scavenging disc. Where, however, leakage has occurred and there is excess oil in the casing, the rotating body of oil does contact the disc.

For the purpose of controlling the oil level, the disc 93 is provided with a plurality of circumferentially spaced oil passages 95 which extend between the outer periphery of the disc and a circumferential recess 97 at the inner periphery of the disc. The recess 97 co-operates with a complementary recess in the periphery of the shaft to define a circumferential oil passage 99 into which oil can flow via the oil passages 95. The oil passages 95 are inclined at their outer ends to face oncoming oil rotating with the casing. Because the outer ends of the oil passages 93 face the oncoming oil rotating with the casing, excess oil is scooped into the passages 93 and forced there along to the circumferential passage 99.

A radial oil passage 101 in the shaft extends between the circumferential passage 99 and the air intake passage 25 such that oil can be delivered into incoming air flowing the working chambers 63. The oil delivered into the air is removed from the air at a subsequent stage, as will be explained later.

As previously mentioned, the rotary machine according to the embodiment forms part of apparatus 13 shown in Fig. 11 of the drawings.

The apparatus 13 includes an accumulator 111 which receives compressed air from the rotary machine 11. The accumulator 111 also has provision for separating oil from the compressed air which is delivered into it from the rotary machine. The accumulator 111 comprises a cylindrical side wall 112 and an internal cylindrical wall 113 positioned within the side wall 112 so as to define an annular space 115 there between. The internal cylindrical wall 113 is supported from the top wall 117 of the accumulator and terminates above the bottom wall 119 of the accumulator. The internal cylindrical wall 113 defines an outlet passage 114 the bottom of which opens onto the lower region of the accumulator and the top of which communicates with an outlet line 120. A fluid line 121 couples the outlet end of the outlet passage 33 of the rotary machine with the accumulator 111. The fluid line 121 opens into the annular passage 115 at a location near the top thereof. The outlet end of the fluid line 121 is so arranged that air with oil entrained therein entering the annular space 115 via the line 121 has a generally tangential path with respect to the annular space 115 such that a spiralling flow is generated as the air travels downwardly towards the bottom of the accumulator from where it can flow upwardly through the central outlet passage 114 defined by the cylindrical wall 113 to the outlet line 120. As the air with oil entrained therein spirals downwardly through the annular space 115, the one component is separated from the air and accumulates on the inner face of the outer wall 111 from where it runs downwardly and collects in the bottom of the accumulator. A sight gauge 125 is provided to offer a visual indication of the level of oil within the accumulator.

A check valve 126 is incorporated in the fluid line 121 to close the fluid line against return flow [and hence loss of air pressure in the accumulator (11)] when the rotary machine has stopped rotating.

Oil within the accumulator is recirculated for lubrication of the rotary machine. This is done by way of the lubrication system 91 which is provided with an oil return line 127 which has an inlet 129 spaced close to the bottom of the accumulator so that it is immersed in oil accumulated therein. The oil return line terminates at a oil entry port 131 which opens into the air intake passage 25. Oil is forced along the oil return line 127 to the air intake passage 25 because of fluid pressure within the accumulator. In circumstances where the apparatus 13 has stopped (and so the rotary machine is not rotating) there could possibly be an excessive amount of oil returned to the rotary machine and an oil control valve 133 is provided to prevent such a situation. The oil control valve is shown in Fig. 12 of the drawings and comprises a body 135 defining a control chamber 137 for exposure to the interior of the accumulator and an operating chamber 139. A piston 141 is slidably mounted within the body, the piston having a first piston head 143 disposed in the control chamber 137 and a second piston head 145 disposed in the operating chamber 139. The first piston head 143 co-operates with a seat 147 to selectively block the return line 127 against oil flow. A biassing means such as a spring 147 acts between the second piston head 145 and a wall of the chamber 139 so as to bias the piston into a position in which the first piston head 143 is in sealing engagement with the seat 147. A fluid pressure line 151 extends between the fluid line 121 (at a location upstream of the check valve 126) and the chamber 139 in the oil control valve 133 so as to expose the second piston 145 to fluid pressure on the side thereof opposite the biassing means 147. With this arrangement, fluid pressure in the fluid line 121 is transferred to the chamber 139 by the line 151. If the fluid pressure acting on the second piston head 145 exceeds the pressure provided by the spring 137 and together with fluid pressure on the face 144 of the first piston head (the face 144 being exposed to air pressure in the accumulator), the piston is caused to move into a position in which the first piston head 143 is out of engagement with the seat 145 with the result that oil return line 129 is open so that oil from the accumulator can be delivered to the air passage 25 in the shaft. On the other hand, in circumstances where fluid pressure acting on the second piston 145 via the line 151 does not exceed the pressure acting on the piston 141 by way of the spring 147 and fluid pressure acting on face 144, the piston 141 is maintained in the position shown in Fig. 12 in which the second piston head 143 is in sealing contact with the seat 147 so closing the oil return line 129.

A particular useful feature of the apparatus shown in Fig. 11 is that the rotary machine can be allowed to free wheel when there is sufficient accumulated air in the accumulator 111. This avoids the need for the rotary machine to be continually started and stopped according to the amount of accumulated air, as is the case with conventional air compressor systems.

This feature is achieved by way of a control valve (as shown in Fig. 13) provided at the inlet end of the air passage 25. The control valve comprises a body 151 having a control chamber 153 and an operating chamber 155. The control chamber 153 communicates with the air passage 25 by way of an elbow pipe section 157. A valve seat 159 is defined at the entry end of the elbow section 157. The body 151 is provided with a pair of ports 161 through which air can enter the control chamber 153.

The chamber 155 communicates with the accumulator 111 by way of fluid line 163 which opens into the upper end of the chamber.

A piston assembly 165 is mounted within the body 151. The piston assembly 165 has a first piston head 167 which is adapted to co-operate with the valve seat 159 and a second piston head 169 which divides the chamber 155 into a first sub-chamber 171 and a second sub-chamber 172. The fluid line 163 opens into the first sub-chamber 171 and a resilient means such as a compression spring 175 is positioned within the second sub-chamber 172 to act between the second piston head and a wall of the sub-chamber. The spring serves to bias the piston into a position in which the first piston head 167 is out of engagement with the valve seat 159. When the piston is in this position, air can enter the valve body 151 from the surroundings through the port 161 and flow into the air passage 25 via the pipe elbow 157. In circumstances where the pressure within the accumulator is at a prescribed maximum, fluid pressure exerted on the second piston 169 is sufficient to overcome the biassing effect of the spring 175 so as to move the piston in a direction towards the valve seat 159 and eventually move the first piston 157 into sealing engagement with the valve seat. At this stage, further air is prevented from entering the air chamber and so the rotary machine free wheels; by this it is meant that the rotary machine continues to operate but there is no air delivered to the working chambers for compression and subsequent delivery to the accumulator. Although no air is delivered to the working chambers as the machine freewheels, the lubrication system 91 continues to deliver oil via port 131 for lubrication purposes. The air pressure within the accumulator will eventually drop as a result of use of an air operated device (such as a shearing hand-piece) coupled to the outlet line 120 of the accumulator and when the drop is sufficient to allow the spring 175 to overcome the fluid pressure in the first sub- chamber 171, the spring will move the piston away from the valve seat 159 and so move the first piston head 167 out of engagement with the valve seat. This allows air to again enter the valve body 151 through the ports 161 and so compression of air can recommence. The second embodiment is similar to the first embodiment with the exception that the eccentric connections 73 between the casing 41 and the rotor assembly 50. Referring to Figs. 14 and 15, each eccentric connection 73 comprises a roller 161 mounted on the control plate 85. The roller 161 is received within a circular recess 163 formed within the end wall 45 of the casing. The circular recess 163 defines a circular path 165 along which the roller can travel. The circular recess 163 has a central axis 164 which is equivalent to the axis of the first section of the eccentric pin of the first embodiment and the roller has an axis of rotation 169 which is equivalent to axis of the second section of the crank pin. Planetary movement of the axis 169 of the roller about the axis 164 of the circular recess 163 provides motion equivalent to that of the crank pin of the first embodiment. This then allows the eccentric connections to control motion of the rotor assembly relative to the casing upon rotation of the rotor assembly and the casing about their respective axis 22 and 20.

It should be appreciated that the scope of the invention is ot limited to the scope of the two embodiments described.

Claims

THE CLAIMS defining the invention are as follows:-

1. A rotary machine comprising a shaft defining a first axis of rotation and a second axis of rotation offset with respect to the first axis, a casing, the casing and the shaft being rotatable relate to each other about the first axis, and a rotor assembly, the rotor assembly and the shaft being rotatable relative to each other about the second axis, the rotor assembly comprising a cylinder disposed generally radially with respect to the second axis and a piston mounted for reciprocation in the cylinder, the cylinder and piston defining a working chamber which varies in volume according to reciprocation of the piston of the cylinder. The piston being coupled to the casing whereby the piston is caused to reciprocate within the cylinder upon relative rotation between the shaft and the casing, and a control means for controlling movement of the rotor assembly relative to the casing.

2. A rotary machine according to claim 1 wherein the control means comprises a plurality of eccentric connections between the casing and the rotor assembly.

3. A rotary machine according to claim 2 wherein the eccentric connections each comprise a crank pin having a first pin section which defines a first axis and a second pin section which defines a second axis eccentric to the first axis, the first pin section being rotatably mounted on an end wall of the casing and the second pin section being rotatably mounted onto the rotor assembly.

4. A rotary machine according to claim 1 or 2 wherein the eccentric connections each comprise a roller mounted on the rotor assembly and received within a circular recess formed within an end wall of the casing, the circular recess defining a circular path around which the roller can travel.

5. A rotary machine according to claim 1 or 2 wherein the eccentric connections each comprise a roller mounted on an end wall of the casing and received within a circular recess formed within the rotor assembly, the circular recess defining a circular path around which the roller can travel.

6. A rotary machine according to .claims 2, 3 or 4 wherein the rotor assembly further comprises a control plate onto which said eccentric connections are mounted.

7. A rotary machine according to any one of the preceding claims wherein the piston is coupled to the casing by way of a connecting rod one end of which is pivotally connected to the piston and the other end of which is pivotally connected to the casing.

8. A rotary machine according to any one of the preceding claims wherein the rotor assembly comprises at least one further cylinder and respective piston.

9. A rotary machine according to claim 8 wherein the rotor assembly comprises three cylinders each having a respective piston.

10. A rotary machine according to any one of the preceding claims wherein the casing comprises a cylindrical side wall co-axial with said first axis and two side walls at the ends of the cylindrical side wall.

11. A rotary machine according to any one of the preceding claims wherein the casing is adapted to contain a fluid such as oil for the purposes of lubrication and cooling of the rotary machine.

12. A rotary machine according to any one of the preceding claims further comprising means for in taking a fluid into each working chamber and exhausting a fluid from the working chamber.

13. A rotary machine according to claim 12 wherein the intake and exhaust means comprises an intake port provided within the shaft and communicating with an intake passage formed within the shaft.

14. A rotary machine according to claim 13 wherein the intake and exhaust means further comprises a discharge port communicating with a discharge passage also formed in the shaft in isolation from the intake passage.

15. A rotary machine according to claim 14 wherein the intake passage extends from one end of the shaft and the discharge passage extends to the other end of the shaft.

16. A rotary machine according to anyone of the preceding claims further comprising an oil sea system for removing excess oil which may enter the casing.

17. A rotary machine according to claim 16 wherein the sea system comprises an oil sea disc rigidly mounted on the shaft within the casing.

18. A rotary machine according to claim 17 wherein the disc is provided with at least one oil passage extending between the outer periphery of the disc and the inner periphery thereof for communication with the intake passage formed within the shaft.

19. A rotary machine according to claim 18 wherein the oil passage is inclined at its outer end to face oncoming oil rotating within the casing.

20. A rotary machine comprising a first axis of rotation and a second axis of rotation offset with respect to the first axis, a casing mounted for rotation about the first axis, and a rotor assembly mounted for rotation about the second axis, the rotor assembly, comprising a cylinder disposed generally radially with respect to the second axis and a piston mounted for reciprocation in the cylinder, the piston being coupled to the casing whereby the piston is caused to reciprocate within the cylinder upon rotation of the casing, and a control means for controlling movement of the rotor assembly relative to the casing.

21. Apparatus for supplying compressed air, said apparatus including a rotary machine as claimed in any one of the preceding claims.

22. Apparatus according to claim 21 further comprising an accumulator for receiving compressed air from the rotary machine, the accumulator having provision ^• for separating oil from the compressed air delivered to it.

23. Apparatus according to claim 22 wherein the accumulator comprises a cylindrical side wall and an internal wall positioned within the side wall so as to define an annular space therebetween into which compressed air from the rotary machine is delivered, the internal wall defining an outlet passage the bottom of which opens into the lower region of the accumulator and the top of which communicates with an outlet line.

24. Apparatus according to claim 22 or 23 further means for recirculating oil trapped within the accumulator to the rotary machine for lubrication purposes.

25. Apparatus according to claim 24 wherein the recirculating means has an inlet located at or in close proximity to the bottom of the accumulator so that it is immersed in oil accumulated therein and having an outlet communicating with the intake passage formed within the shaft.

26. A rotary machine substantially as herein described with reference to the accompanying drawings.

27. Apparatus for supplying compressed air substantially as herein described with reference to the accompanying drawings