BACKGROUND OF THE INVENTION It is amongst the objects of embodiments of the present invention to obviate or mitigate at least one of the disadvantages associated with known fluid machines, in particular hydraulic tools such as motors and pumps, and disadvantages associated with known clutches.

SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided a fluid machine comprising: a shaft rotatable about a main shaft axis; a sleeve located around the shaft and having a main sleeve axis offset from the main shaft axis, the sleeve being movably mounted on the shaft such that, in use, the main sleeve axis follows a path extending around the main shaft axis; and wherein the machine further comprises means for allowing one of converting movement of a fluid through the machine to a rotational motion of the shaft via said movement of the sleeve, a rotational motion of the shaft to movement of a fluid through the machine via said movement of the sleeve, a rotational motion of the sleeve to a rotational motion of the shaft and a rotational motion of the shaft to a rotational motion of the sleeve,

respectively.

According to a second aspect of the present invention, there is provided a fluid machine comprising a motor, the motor comprising: a shaft rotatable about a main shaft axis; a sleeve located around the shaft and having a main sleeve axis offset from the main shaft axis, the sleeve being movably mounted on the shaft such that, in use, the main sleeve axis follows a path extending around the main shaft axis; and wherein the motor further comprises means for converting movement of a fluid through the motor to a rotational motion of the shaft via said movement of the sleeve.

According to a third aspect of the present invention, there is provided a fluid machine comprising a pump, the pump comprising: a shaft rotatable about a main shaft axis ; a sleeve located around the shaft and having a main sleeve axis offset from the main shaft axis, the sleeve being movably mounted on the shaft such that, in use, the main sleeve axis follows a path extending around the main shaft axis; and wherein the pump further comprises means for converting a rotational motion of the shaft to movement of a fluid through the pump via said movement of the sleeve.

According to a fourth aspect of the present invention, there is provided a fluid machine comprising a clutch, the clutch comprising: a shaft rotatable about a main shaft axis ; a sleeve located around the shaft and having a main sleeve axis offset from the main shaft axis, the sleeve being movably mounted on the shaft such that, in use, the main sleeve axis follows a path extending around the main shaft axis; and

wherein the clutch further comprises means for converting a rotational motion of the sleeve to a rotational motion of the shaft.

The fluid machine of the present invention is particularly advantageous in that embodiments of the invention provide a motor, pump and\or a clutch. The motor, pump and\or clutch are preferably of the type suitable for use in the oil and gas industries. In particular, the motor may be of the type suitable for use in downhole drilling applications; the pump may be of the type suitable for downhole applications, subsea or surface pumping applications; and the clutch may be suitable for use in controlled tightening of, for example, lengths of tubing such as joints of drill tubing or well casing. The fluid machine is preferably a hydraulic tool, however, it will be understood that the fluid machine may equally be a pneumatic tool. It will be further understood where the fluid machine comprises a pump, the pressure of the fluid moved through the pump is raised. Furthermore, where the fluid machine comprises a clutch, the converting means may alternatively be for converting a rotational motion of the shaft to a rotational motion of the sleeve. Thus it will be understood that the clutch may be operated in reverse, if desired.

It will be noted that references herein to the main sleeve axis being"offset"from the main shaft axis are to the main sleeve axis being disposed laterally, that is not coaxially with, the main shaft axis, but being substantially parallel thereto.

The fluid machine may further comprise a housing, which may take the form of a crankcase, for receiving the shaft, which shaft may take the form of a crankshaft. The shaft may be selectively rotatable in the housing and\or with the housing. Conveniently, the shaft may be hollow to allow the passage of fluid therethrough, such as drilling

fluid. The shaft may include a collar, shoulder, or preferably an eccentric portion on which the sleeve is movably mounted. The eccentric portion may have an axis located substantially coaxially with the main sleeve axis.

Thus the eccentric axis may follow a common path around the main shaft axis with the main sleeve axis when the sleeve is moved as described above. It will be understood that the eccentric portion axis is substantially coaxial with the main sleeve axis in that the eccentric portion axis must be disposed with respect to the main sleeve axis such that rotation of the shaft relative to the sleeve is allowed. The eccentric portion may be formed on and thus integral with the shaft, or may be formed as a separate member for coupling to the shaft. The eccentric portion may allow said movement of the sleeve to rotate the shaft, or rotation of the shaft to so move the sleeve. It will be understood that it is the provision of the eccentric portion on the shaft and the location of the sleeve on the eccentric portion, such that the main sleeve axis and the eccentric portion axis are offset from the main shaft axis, which may allow the shaft to rotate relative to the sleeve.

This may be achieved by causing the sleeve to be moved such that the main sleeve axis and eccentric portion axis follows a substantially circular path around the main shaft axis.

The fluid machine may further comprise a bearing, typically a roller bearing such as a needle bearing, between the shaft and the sleeve to allow rotation of the shaft relative to the sleeve. Alternatively, the fluid machine may further comprise a bearing member such as a ring mounted on the shaft to allow said movement. The bearing member may comprise a Beryllium Copper or other suitable material ring. Where a bearing member such as a ring is provided, this may be advantageous in that this member, which may wear in use, may be relatively easy to

replace and may reduce or prevent wear of the eccentric portion.

The converting means may comprise at least one piston mounted for movement in a cylinder defined by the housing to transfer a force to or from the sleeve. It will be understood that references herein to a cylinder and to a piston cylinder do not imply any dimensional restrictions on the cylinder, which may be of any suitable shape in cross-section, for example, circular or square. The\each piston may be disposed radially in the housing and is\are preferably disposed on a radius centred on the main shaft axis. This may allow the\each piston to exert a force upon the sleeve to move the sleeve such that the main sleeve axis may follow the path extending around the main shaft axis; this may be achieved by the main sleeve axis being offset from the main shaft axis and by the piston being on the radius centred on the main shaft axis. Preferably, there are at least three pistons spaced substantially equidistantly around the shaft. Most preferably, there are seven or more pistons. This may advantageously allow a sequenced operation of the pistons to achieve a smooth desired movement of the sleeve, or transfer of movement from the sleeve to the pistons, causing or transferring rotation of the shaft. The\each cylinder may be provided in a wall of the housing and an end cap may be secured to the housing to define a piston chamber. The converting means may further comprise a load transmitting member, preferably a gudgeon pin, coupled to the\each piston.

The\each gudgeon pin may be rotatably mounted to the\each respective piston, may be substantially cylindrical, and may include a shaped face for abutting an outer surface of the sleeve. So shaping the gudgeon pins may advantageously reduce the Hertzean or cyclical stresses which would otherwise be imparted on the sleeve, which may otherwise reduce the maximum forces applicable to the sleeve and thus

limit torque and power of the fluid machine. It will be understood that the gudgeon pins are not however limited to including such a shaped face.

The fluid machine may further comprise fluid supply means including a source of fluid, for supplying fluid to the machine, for converting movement of the fluid through the machine to a rotational motion of the shaft via said movement of the sleeve; for converting a rotational motion of the sleeve to a rotational motion of the shaft; and a rotational motion of the shaft to a rotational motion of the sleeve, respectively. The\each piston cylinder may include a fluid inlet and a fluid outlet for allowing fluid to be supplied to and exhausted from the\each cylinder.

Where the fluid machine comprises a motor, there may conveniently be provided a combined inlet\outlet for the\each cylinder and the fluid supply means may include a conduit coupled to the inlet\outlet for the\each cylinder for allowing fluid communication. This may allow fluid to be supplied to/exhausted from the/each cylinder.

Alternatively, there may be provided a separate inlet and outlet for the\each cylinder. The inlet may be connected in a closed loop to the outlet through the\each cylinder for providing a defined volume of fluid.

Where the fluid machine comprises a clutch, there may be provided a separate inlet and outlet for the\each cylinder, each coupled in a closed loop by conduits for allowing fluid communication, and in particular, for allowing supply\exhaust of fluid, respectively. The fluid supply means may further comprise a manifold connecting the outlet to the inlet of the\each cylinder, with at least one fluid flow restriction therein. Preferably, there are two fluid flow restrictions which may be provided in parallel, one of which creates a greater restriction to flow than the other. Provision of the flow restrictions creates a restriction to flow of fluid through the\each cylinder;

where the restriction to fluid flow is greater, this may serve to increase the back pressure of the fluid in the\each cylinder. This may in turn cause the\each piston to grip the sleeve. Connecting the fluid machine to, for example, a"top"drive on a drilling rig may therefore allow the fluid machine to be rotated, and causing the\each piston to grip the sleeve in this fashion allows rotation of the fluid machine to be transferred to the sleeve to rotate the shaft together with the sleeve. This is because the sleeve is firmly gripped by the\each piston. It will be understood that the gripping force exerted on the sleeve by the\each piston depends upon the back pressure of fluid in the\each piston and therefore upon the relative flow restriction. Thus the flow restriction may be sized to achieve a desired back pressure and consequent gripping force. Provision of two flow restrictions may allow two back pressures and thus gripping forces to be provided.

The fluid supply means may further comprise a flow control, such as a valve, which may be opened and closed to cause flow to be directed through a selected flow restriction, to thus achieve a desired gripping force.

Where the fluid machine comprises a pump, the means for supplying fluid may comprise a separate inlet and outlet for the\each cylinder, the inlet comprising a suction inlet for drawing a fluid into the\each cylinder of the pump for exhaust through the\each cylinder outlet.

This may allow the pump to be used to, for example, move a fluid through a borehole.

The fluid machine may further comprise valve means for regulating the flow of the fluid therethrough, which may form part of the fluid supply means. Such valve means may in particular be provided where the fluid machine comprises a motor. The valve means may further comprise a rotary valve assembly coupled to the shaft for rotation therewith.

The rotary valve assembly may be coupled to a fluid source

for selectively supplying and exhausting fluid to and from the\each cylinder. The rotary valve assembly may thus include a fluid inlet, fluid outlet and at least one piston communication port for selective communication with the one or more cylinder. The rotary valve assembly may further comprise a rotary valve mounted in part of a housing of the fluid machine, conveniently by bearings, for rotation with the shaft. The piston communication ports may be selectively aligned with an inlet\outlet of the\each cylinder on rotation of the rotary valve assembly. Where the fluid machine includes more than one piston, the rotary valve may allow at least one communication port and preferably up to half the communication ports plus one to be open for fluid communication with selected ones of the piston cylinders, and at least one fluid communication port and preferably up to half the fluid communication ports plus one to be closed to prevent the communication with the piston cylinders. Most preferably, where the fluid machine comprises a motor, the fluid machine includes seven pistons, with seven corresponding fluid communication ports, at any one time, between three and four of the fluid communication ports being open and between three and four being closed. As the rotary valve assembly and the shaft rotates, the rotary valve also rotates through a mechanical connection, selectively opening and closing respective fluid communication ports.

Where the fluid machine comprises a motor, the fluid may be water such as sea water, allowing the motor to be used underwater and in particular in offshore environments, where the water acts to rotate the shaft. This may have particular uses with underwater excavation apparatus, such as the applicant's T\Y-shaped dredger, disclosed in International Patent Publication No. W098\27286, where advantageously the motor may be run on pressurised seawater and wherein the spent seawater is thereafter discharged

into the sea with no environmental impact or risk of lost of hydraulic fluid, such as oil, into the sea.

Furthermore, use of seawater in this fashion as the drive fluid also saves on the need to compensate for pressure in deep-water applications.

According to a fifth aspect of the present invention, there is provided a fluid machine assembly comprising two or more fluid machines as defined above in any one of the first to fourth aspects of the present invention.

According to further aspects of the present invention, there are provided methods of converting movement of a fluid to a rotational motion of a shaft via movement of a sleeve ; a rotational motion of a shaft to movement of a fluid via movement of a sleeve; a rotational motion of a sleeve to a rotational motion of a shaft; and a rotational motion of a shaft to a rotational motion of a sleeve, respectively, using one of the fluid machines of the first to fifth aspects of the present invention.

BRIEF DESCRIPTION OF DRAWINGS Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1A is a longitudinal cross-sectional view of a fluid machine in the form of a motor, in accordance with a preferred embodiment of the present invention; Figure 1B is a cross-sectional view of the motor shown in Figure 1A, taken along line A-A of Figure 1A ; Figure 1C is a perspective view of a rotary valve assembly forming part of the motor of Figure 1A, shown in a first rotary position of a valve of the valve assembly; Figure 1D is a view of the valve assembly shown in Figure 1C, sectioned along line A'-A'of Figure 1C and showing the rotary valve in a second rotary position; Figure 1E is a perspective view of the rotary valve

shown in the position of Figure ID ; Figure 1F is a view similar to that of Figure 1D of the rotary valve assembly sectioned along line A'-A', but showing the rotary valve in the position of Figure 1C; Figure 1G is a perspective view of the rotary valve shown in the positions of Figures 1C and 1F ; Figures 2A to 2F are views of the motor, similar to Figure 1B, but showing the motor in various positions during rotation of a shaft and sleeve of the motor, in use; Figure 3 is a schematic illustration of the motor in the position shown in Figure 1B, illustrating the order of operation of pistons of the motor, in use; Figure 4A is a view, similar to Figure 1A, of a fluid machine in the form of a pump, in accordance with an alternative embodiment of the present invention ; Figure 4B is a view, similar to Figure 1B, of the pump of Figure 4A, taken along line B-B of Figure 4A; Figure 5A is a view, similar to Figure 1A, of a fluid machine in the form of a clutch, in accordance with a further alternative embodiment of the present invention ; and Figure 5B is a view, similar to Figure 1B, of the clutch of Figure 5A, taken along line C-C of Figure 5A.

DETAILED DESCRIPTION OF DRAWINGS Referring firstly to Figure 1A, there is shown a longitudinal cross-sectional view of a fluid machine in accordance with a preferred embodiment of the present invention. In Figure 1A, the fluid machine takes the form of a motor, in particular a hydraulic motor driven by a fluid, as will be described in more detail below. However, it will be understood that the motor may equally be a pneumatic motor, driven by a gas. It will be understood that the structure of the motor of Figures 1A and 1B is similar to the pump of Figures 4A and 4B and the clutch of

Figures 5A and 5B, therefore the following description of the motor structure and indeed its method of operation applies in part also to the pump and clutch to be described below.

Figure 1B is a cross-sectional view of the motor 10 shown in Figure 1A, taken along line A-A of Figure 1A.

Thus referring to Figures 1A and 1B, the motor 10 generally comprises a shaft 12, rotatable about a main shaft axis 14; a sleeve in the form of a ring 16, located around the shaft 12 and having a main sleeve axis 18, offset from the main shaft axis 14; and converting means, indicated generally by reference numeral 20. In the motor 10, the converting means 20 converts movement of a fluid through the motor 10 to a rotational motion of the shaft 12. This is achieved by moving the sleeve 16 such that the main sleeve axis 18 follows a path extending around the main shaft axis 14.

This will be described in more detail with reference to Figures 2A to 2F below.

The motor 10 has particular application in downhole drilling applications, where it may be used for rotating a drill string or a drill bit (not shown) to carry out a desired drilling operation. The shaft 12, which forms a rotor of the motor 10, is coupled to the drill string which is to be rotated by a threaded connection 24. This allows rotation of the shaft 12 to be transferred to the string.

In more detail, the motor 10 includes a housing in the form of a crankcase 22, which is generally hollow and which houses the shaft 12. The shaft 12 includes an integral eccentric portion 26 which extends from the main body of the shaft 12 and which has an axis which is coaxial with the main sleeve axis 18. The sleeve 16 is mounted on the eccentric portion of the shaft 12, and a rolling bearing in the form of a needle bearing 28 is provided between the eccentric portion 26 and the sleeve 16. This allows for rotation of the eccentric portion 26 (and thus the shaft

12) relative to the sleeve 16.

The converting means 20 is shown in more detail in Figure 1B, and generally comprises, in this embodiment, seven pistons, indicated generally by reference numeral 30.

The pistons are each denoted by the reference numerals a to g, respectively. Each of the pistons 30a to 30g are substantially identical, and are aligned on respective radii 31 centred on axis 14. The crankcase 22 defines a number of cylinders 32, extending through a wall 34 of the crankcase 22, in which the pistons 30 are located and sealed by piston-ring seals 37. End caps 38 seal the cylinders 32, and define chambers 40 to which a fluid may be supplied\exhausted to move the pistons 30. Each piston 30 includes a combined inlet\outlet 41 through which fluid is supplied to\exhausted from the chambers 40. The converting means 20 also includes a load transmitting member in the form of gudgeon pins 42, rotatably mounted in an end of each piston 30. The gudgeon pins 42 are substantially cylindrical, and include a shaped face 44 for abutting the sleeve 16. As will be described, this reduces the Hertzean or cyclical stresses which would otherwise be imparted on the sleeve in use.

The motor 10 also includes a rotary valve assembly, indicated generally by reference numeral 46. The rotary valve assembly 46 is mounted in a valve housing 48, which is coupled to the crankcase 22, and includes a rotary valve 50. The rotary valve assembly 46 is shown in more detail in Figures 1C to 1G, where Figure 1C is a perspective view of the rotary valve assembly 46 shown in a first rotary position of the valve 50. Figure 1D is a view of the valve assembly 46 shown in Figure 1C, sectioned along line A'-A' and showing the rotary valve 50 in a second rotary position. Figure IF is a view similar to Figure 1D but showing the rotary valve 50 in the position of Figure 1C.

Figures 1E and 1G are perspective views of the rotary valve

50 in the respective positions of Figures 1D and 1F.

As shown in Figure 1C, the rotary valve 50 is mounted in the valve housing 48 and includes a key 51 which is engaged by the shaft 12 for rotation therewith, as will be described. In Figure 1D, it will be noted that the valve 50 is located and sealed in a chamber 52 defined by the housing 48. A roller bearing 54 and seals 55 mount the rotary valve 50 in the chamber 52 for rotation therein.

The valve 50 is shown in more detail in Figure 1E, in the position of Figure 1D, and it will be noted that the valve 50 is generally elongate and partially cylindrical.

The valve 50 includes two spaced flat portions 57a and 57b and two spaced channels 59a and 59b which extend around the partial circumference of the valve 50 in the region of the respective flats 57a and 57b.

As shown in Figures 1C, 1D and 1F, the housing 48 includes a number of ports 61a and 61b. As shown in Figure 1A, in this embodiment of the fluid machine, the ports 61a are sealed by a plug, whilst the ports 61b are coupled through hydraulic conduits 56 to the pistons 30. Fluid flow to and from the rotary valve 50 is controlled by inlet/outlet ports 77a and 77b (Figures 1C to 1F), respectively. These enable fluid supply to and exhaust from the valve 50 through chambers defined between the valve 50 and the chamber 52 in the region of the flats 57a and 57b.

This is shown in particular in Figure 1F where the valve 50 has been rotated through 90°. In this position, fluid flows to selected ones of the pistons 30 through port 77a, the chamber defined between flat 57a and chamber 52, a connecting conduit 47 and the respective ports 61b. In a similar fashion, as the valve 50 rotates, fluid exhausts selectively from the respective pistons 30 through the respective ports 61b, the space defined between the flat 57b and the chamber 52, and the port 77b. The rotary valve

50 thus selectively allows fluid supply to the pistons 30 through the coupling conduits 56 and inlet\outlet 41 of the pistons 30, as the rotary valve 50 rotates, as will be described below.

The shaft 12 is mounted in the crankcase 22 by tapered roller bearings 58 and 60. A lower end of the shaft 12 is sealed to the crankcase 22 by rotor pressure seals 63, a rotor 0-ring 65 (mounted by a seal locator 67), and by a rotor scraper seal 69 (mounted by a seal holder 71 and seal spacer 73). Movement of the sleeve 16 to cause the main sleeve axis 14 to follow a path extending around the main shaft axis is achieved by selectively supplying fluid to the chambers 40 of the pistons 30 and allowing fluid to exhaust from the chambers 40 in a desired sequence, controlled by the rotary valve assembly 46. It will be understood that as fluid is supplied to the chamber 40, each piston 30 is moved from the position of the piston 30a shown in Figure 1B, where fluid had been exhausted from the chamber, to the position of the piston 30e, where fluid has been supplied to the chamber and the piston 30e has reached the extent of its travel. This exerts a force upon the sleeve 16 to achieve the desired movement.

Referring now to Figures 2A to F, there are shown views of the motor 10, similar to the view of Figure 1B but illustrating the motor 10 in various positions during rotation of the shaft 12. The motor 10 is initially in the position of Figure 1B. In this position, the pistons 30e and 30d have reached the extent of their travel, whilst the piston 30a is at the limit of its movement away from the sleeve 16. Fluid is then supplied initially to the pistons 30b, 30c and 30d, as indicated in the schematic illustration of Figure 3. The schematic illustration of Figure 3 shows the flow ports 61b, numbered 1 to 7, of the rotary valve assembly 46. In the position of Figure 1B shown, fluid flow to pistons 30b, 30c and 30d is allowed

from the space defined by flat 57a, through ports 2,3 and 4 of the flow ports 61b, whilst flow to pistons 30a to 30d through ports 1,5,6 and 7 is prevented by shoulder 75a.

Simultaneously, exhaust from pistons 30e, 30f and 30g is allowed from the space defined by flat 57b, through ports 5,6 and 7 whilst exhaust from pistons 30e to 30g is prevented by shoulder 75b.

This causes the respective pistons 30b to 30d to move inwardly directed along respective radii 31. As the main sleeve axis 18 (and the eccentric portion 26 axis) is offset from the main shaft axis 14, this causes the sleeve 16 to begin to move from the position of Figure 1B in an anti-clockwise direction indicated by the arrow D and shown in Figure 2A. It will be noted that there is no rotation of the sleeve 16 about its axis 18, thus the rotational orientation of the sleeve 16 does not alter. The sleeve 16 is effectively displaced, as shown in Figs. 2A to 2F.

This movement of the sleeve 16 causes the main sleeve axis 18 to move in a generally circular path about the main shaft axis 14, as described above. This causes the eccentric portion 26, and thus the shaft 12, to rotate about the main shaft axis 14. The gudgeon pins 42 rock or "wobble"in the ends of their respective pistons 30 during movement of the sleeve, as clearly shown in Fig. 1A and Figs. 2A to 2F.

Thus it will be understood that fluid supplied to the pistons 30 in this fashion may produce a rotation of the shaft 12 to provide a drive force to a drill string or the like. As also shown in Figure 3, whilst fluid is supplied to the pistons 30b to 30d, fluid is allowed to exit from the pistons 30e, 30f and 30g. As soon as the sleeve 16 begins to move, the inlet flow port 1 connecting the rotary valve 50 to the piston 30a is opened, allowing fluid to begin to be supplied to the piston 30a. This therefore causes the piston 30a to begin to move, to impart a force

on the sleeve 16. This process continues as the shaft 12 rotates, whereby the rotary valve assembly 46 selectively opens and closes fluid communication to the pistons 30a to 30g in a defined order. This causes the pistons 30 to selectively move, as shown in Figures 2B to 2F, to rotate the shaft 12 in the anti-clockwise direction. The sleeve 16 is eventually moved to the position of Figure 2F, and from there to the position of Figure 1B, where the shaft 12 has performed a complete 360 rotation. This process may be continued as desired to provide a drive force as required. In the motor 10 shown in Figures 1A and 1B, a single hydraulic conduit 56 is provided both for supplying and exhausting fluid to and from the pistons 30.

The motor 10 may have further particular uses in subsea applications with, for example, underwater excavation apparatus, such as to provide power for the applicant's T\Y-shaped dredgers, disclosed in International Patent Publication No. W098\27286. Furthermore, the fluid machine, for example the motor 10, may include multiple banks of pistons 30 and may operate on a shaft 12 having multiple eccentric portions 26. Where two such banks of pistons 30 are provided, the eccentric portions 26 would be 180 out of phase, and with three banks of pistons 30, the eccentrics 26 would be 120 out of phase. Fluid machines\motors of this type could be connected in parallel, where the inlets of the two banks of pistons are connected to one common inlet and the outlets to one common outlet, to increase torque supplied and horsepower.

Typical materials for parts including the seals, gudgeon pins 42, bearing 28, sleeve 16, piston end caps 38, rotary valve 50, and bearings of the valve assembly 46 of the motor 10 may be plastics material, such as polyethylethylketone, metal such as copper alloys, or stainless steels.

Referring now to Figure 4A, there is shown a fluid

machine in the form of a pump, indicated generally by reference numeral 100. The pump 100 converts rotational motion of the shaft 112 to movement of a fluid through the pump 100. Like components of the pump 100 with the motor 10 of Figure 1A and 1B share the same reference numerals incremented by 100. Thus it will be noted that the pump 100 is of a similar structure to the motor 10 of Figure 1A, except that it does not include the rotary valve assembly 46 of the motor 10. Each piston 130 of the pump 100 includes separate inlets and outlets 64 and 66, rather than a single, combined inlet\outlet 41 as in the case of the pistons of the motor 10. Each of the piston inlets 64 are connected through a manifold 68 which includes non-return valves 70 (one shown) to prevent fluid egress from the pistons 130 through the inlets 64. Inlet ports 72 on the manifold 68 act as suction ports to allow fluid to be drawn into the pump 100 in use.

The outlets 66 of each piston 130 are, in a similar. fashion, connected to a manifold 74 including non-return valves 76, to prevent fluid flowing into the pistons 130 through the outlets 66. Outlet ports 78 provide for fluid to be exhausted from the pistons 130 to a desired location.

It will be understood that suitable conduits are coupled to the inlet ports 72 and outlet ports 78 to allow fluid to be drawn through the pump 100. The pump 100 essentially operates in reverse fashion to the motor 10 of Figure 1A and 1B, in that the shaft 112 of the pump 100 (which is coupled to a separate drive, such as a motor, through a threaded connection 124) acts to move the pistons 130 to move a fluid through the pump. It will be understood that, rather than the pistons 130 exerting a force upon the sleeve 116 to move the sleeve 116, the sleeve 116 is moved in the fashion described above with reference to the motor 10, by rotation of the shaft 112 and the eccentric portion 126 on the shaft 112. Thus, the sleeve 116 moves the

pistons 130 through the gudgeon pins 142, which are maintained in contact with the sleeve 116 by positively pressurising the pistons 130 in the respective cylinders 132. Alternatively, there may be a spring (not shown) for urging the gudgeon pins into contact with the sleeve 116.

Thus, it will be understood that when the pistons 130d and 130e are in the positions shown in Figure 4B, the pistons 130 are at the their fully extended positions, such that the piston chambers 140 define a maximum volume of the fluid to be discharged from the pistons 130d and 130e. As the shaft 112 rotates, in a similar fashion to that shown in Figures 2A to 2F, the sleeve 116 acts against the pistons 130 sequentially, such that the pistons 130d and 130e are moved through the positions shown in Figures 2C and 2D, where the fluid is exhausted from the chambers 140, through the manifolds 74 and outlet ports 78 to a desired location. Further fluid is then drawn in through the inlet ports 72 and manifold 68 through the inlets 64 of the pistons 130, to replenish the fluid in the piston chambers 140 as the shaft 112 is rotated.' In a similar fashion to the motor 10 of Figures 1A and 1B, a fluid machine such as the pump 100 may be provided with multiple banks of pistons 130 connected either in parallel or in series. This may be achieved simply by coupling a number of such pumps 100 together. When connected in parallel, the volume of the pump overall increases, but the pressure of the fluid is unchanged.

When connected in series, the outlets of a first pump are connected to the inlets of a second pump, such that a second pump increases the pressure of the fluid, but the volume remains the same as a single bank of pistons.

Referring now to Figure 5A, there is shown a fluid machine in the form of a clutch, indicated generally by reference numeral 200. Like components of the clutch 200 with the motor 10 of Figures 1A and 1B share the same

reference numerals incremented by 200. The clutch 200 allows for conversion of a rotational motion of a sleeve 216 to a rotational motion of a shaft 212 of the clutch 200, as will be described below. The clutch 200 is also somewhat similar to the pump 100 of Figures 4A and 4B, therefore like components of the clutch 200 with the pump 100 share the same reference numerals incremented by 200.

It will be noted that the clutch 200 includes pistons 230a to 230g, and that each piston 230 includes fluid inlets 264 and outlets 266, in a similar fashion to the pump 100. A manifold 268 having inlet ports 272, and a manifold 274 having outlet ports 278, are connected in a closed loop by a fluid supply manifold 80, through a first conduit 82. A second conduit 84 branches off the first conduit 82 and includes a flow restriction 86 and a valve in the form of a ball valve assembly 88, movable between open and closed positions to selectively allow fluid flow through the second conduit 84. The ball valve assembly is shown in Figure 5A in an open position. A flow restriction 90 is similarly defined in the first conduit 82, and the flow restriction 90 creates a greater restriction to flow than the flow restriction 86, when fluid flow is constrained to flow through the first conduit 82, by closing the ball valve assembly 88.

The crankcase 222 has a housing 92 secured thereto, which is, in turn, coupled to a top drive (not shown) for example, on a drilling rig, by a female threaded"box" connection 94, to allow the clutch 200 to be rotated. The shaft 212 is secured for rotation with respect to the housing 92 by a sleeve 96 and bearing 98. A lower end of the shaft 212 includes a connector sub 202 for connecting the shaft 212 to a length of tubing, such as drilling tubing or well casing. This length of drilling tubing/ casing is for coupling to a string of such tubing/casing and is to be"torqued-up"by the top drive, through the

clutch 200, to a desired mating torque with an upper end of the string. It will be understood by persons skilled in the art that such casings are typically used for lining a borehole of an oil or gas well.

When it is desired to connect a further section of tubing/casing to the string, the clutch 200 is coupled to the top drive, and the length of casing to be connected is coupled to the connector sub 202 by a threaded pin 204.

The top drive rotates the clutch 200 at a defined rotational velocity, and initially, the ball valve assembly 88 is open, allowing fluid to flow through the second conduit 84. It will be understood that it is desired to transfer rotational motion of the crankcase 222, through the sleeve 216, to the shaft 212, to torque-up the length of casing to a desired mating torque with the string.

If the outlets 266 of the pistons 230 were connected to the inlets 264 without restriction, rotation of the crankcase 222 would cause fluid to flow through the piston chambers 240 without imparting any force on the pistons 230. Accordingly, there would be no force exerted upon the sleeve 216, and the shaft 212 would remain stationary whilst the crankcase 222 rotated. However, when the ball valve assembly 88 is open, fluid flows through the orifice 86, typically creating a restriction developing a 5000 Ft\lb torque. Forcing the fluid to pass through the restriction 86 creates a back pressure in the piston chambers 240 of the pistons 230a to 230g as the crankcase 222 is rotated with respect to the shaft 212.

This back pressure in the chambers 240 causes the pistons 230 to be selectively moved to abut and exert a force upon the sleeve 216. This tends to grip the sleeve 216, such that the sleeve 216 is rotated together with the crankcase 222. This causes the shaft 212 to rotate by an interaction with the eccentric portion 226.

When the sleeve 216 and shaft 212 are rotated in this

fashion, there is little or no fluid flow through the pistons 230, and they are substantially retained in the position shown in Figure 5B. However, when the length of casing has been torqued-up to 5000 Ft\lb, slippage of the shaft 212 and thus the sleeve 216 (with respect to the crankcase 222) occurs. This happens when the length of casing has been initially tightened, but requires further tightening before the casing can be run downhole. The ball valve assembly 88 is then closed, constraining fluid to flow through the restriction orifice 90, which develops, for example, a 50,000 Ft\lb torque. This causes a much larger back pressure in the chambers 240 of the pistons 230, causing renewed grip of the sleeve 216 by the pistons 230. This once again causes the sleeve 216 and shaft 212 to be rotated with the crankcase 222, to further torque-up the length of casing. This continues until the length of casing is torqued-up to 50,000 Ft\lb, when slippage occurs once more. This prevents the length of casing from being over-torqued beyond the preset 50, OOOFt\lb limit, which is preset by bringing the flow restriction 90 on-line.

The clutch therefore allows precise control of mating torques applied to lengths of such casing when a casing string is being made-up. Furthermore, a torque applied, and thus the gripping force of the pistons 230, can be varied by adjusting the ball valve 88 between the open and closed positions, to cause flow to be, if desired, partly through the flow restriction 86 and partly through the flow restriction 90.

Following such torquing-up, the clutch 200 is disconnected from the length of casing before a further length is connected to the connector sub 202 for the operation to be repeated as required.

Use of the clutch 200 with such a top drive is particularly advantageous because the rotational velocity of such top drives may be reliably set to a desired value.

This allows operating parameters of the clutch 200 to be matched to the power of the clutch, when acting as a pump (during slippage of the shaft 212 and sleeve 216).

Specifically, the horsepower of the clutch is equal to the rotational velocity (rpm) multiplied by the desired torque in ft. lbs and divided by a known constant (5252). The power of the fluid machine, when acting as a pump, is equal to the pressure (in psi) of fluid passing through the pump, multiplied by the volume of fluid (in US gallons) and divided by a further constant (1714). Thus where the rotational velocity, pressure and volume, together with the two constants are known, a desired torque may be selected for those particular values. In other words, a desired torque to be applied to the length of casing can be preset, if the rotational velocity of the clutch crankcase 222, pressure of the fluid and fluid volume are known. As noted above, the rotational velocity may be precisely set by the top-drive, and the pump volume is a known, determined factor. The pressure is adjusted as determined by the flow restrictions 86 and 90 and adjustable by the ball valve assembly 88, as also noted above. This is particularly advantageous over, for example, known mechanical clutches which cannot provide such precise determination of the mating torque.

It will be understood that, if desired, the clutch may be operated in reverse, to transfer a rotational motion of the shaft 212 to the crankcase 222.

Various modifications may be made to the foregoing within the scope of the present invention.