RADIAL PISTON PUMPS

Abstract

A radial piston pump comprising a rotor mounted for rotation on a pintle. The rotor comprises a plurality of piston chambers, a piston being mounted in each of said chambers for reciprocal movement. The pump comprises a supply flow path which connects the piston chambers to a supply of low-pressure fluid, an exit flow path via which high-pressure fluid from the piston chambers leaves the pump, and an auxiliary flow path which connects another component of the pump to the piston chambers. The pintle comprises a plurality of flow galleries comprising a supply flow gallery forming part of the supply flow path, an exit flow gallery forming part of the exit flow path, and an auxiliary flow gallery forming part of the auxiliary flow path. The radial piston pump uses the pintle as a fluid manifold providing fluid to or from the pistons.

Claims

1. A radial piston pump comprising a rotor mounted for rotation on a pintle, the rotor comprising a plurality of piston chambers, a piston being mounted in each of said chambers for reciprocal movement, the pump comprising: at least one supply flow path which, in use, connects one or more of the piston chambers to a supply of low-pressure fluid; at least one exit flow path via which, in use, high-pressure fluid from one or more of the piston chambers leaves the pump, and at least one auxiliary flow path which connects another component of the pump to one or more of the piston chambers, wherein the pintle comprises a plurality of flow galleries, said plurality comprising at least one supply flow gallery forming part of the supply flow path, at least one exit flow gallery forming part of the exit flow path and at least one auxiliary flow gallery forming part of the auxiliary flow path.

2. A radial piston pump according to claim 1, further comprising a return flow path connected to an outlet of said another component of the pump such that, in use, fluid leaves said another component and/or the pump via the return flow path and the plurality of flow galleries comprises at least one return flow gallery forming part of the return flow path.

3. A radial piston pump according to claim 1, wherein the plurality of flow galleries are integrally formed with the pintle.

4. A radial piston pump according to claim 1, wherein said plurality of flow galleries are present at the same axial position on the pintle.

5. A radial piston pump according to claim 1, wherein said another component of the pump is a control valve, and the auxiliary flow path is, in use, connected to a pressure inlet of the control valve.

6. A radial piston pump according to claim 5, wherein the control valve is a servo valve, for example a three-way or four-way servo valve, and the pump is configured to provide a first and/or second service flow to an actuator or other hydraulic component connected to the pump.

7. A method of operating a radial piston pump comprising a rotor mounted for rotation on a pintle, wherein: the rotor comprises a plurality of piston chambers, a piston being mounted in each of said chambers for reciprocal movement; fluid flows along at least one supply flow path from a supply of low-pressure fluid to one or more of the piston chambers; high-pressure fluid from one or more of the piston chambers leaves the pump via at least one exit flow path; high-pressure fluid from one or more of the piston chambers flows to another component of the pump via at least one auxiliary flow path and is used in the operation of the component; and fluid on the at least one supply flow path, at least one exit flow path and at least one auxiliary flow path flows through one or more flow galleries in the pintle.

8-28. (canceled)

29. A hydraulic power pack comprising a radial piston pump according to claim 1.

30. A hydraulic power pack according to claim 29, further comprising a reservoir and an accumulator, the power pack being configured such that, in use, low-pressure fluid from the reservoir is supplied to the pump and high-pressure fluid from the pump is supplied to the accumulator.

31. A hydraulic power pack according to claim 29, further comprising: a fluid reservoir piston which defines, at least in part, the fluid reservoir; and an accumulator piston which defines, at least in part, the accumulator, wherein the fluid reservoir piston, the accumulator piston and the rotor are concentric.

32. A hydraulic power pack according to claim 31, wherein the rotor is mounted for rotation on a pintle and at least a portion of the fluid reservoir piston and/or accumulator piston is received within a piston recess formed within the pintle.

33. A hydraulic power pack according to claim 29, configured such that force generated by the high-pressure fluid in the accumulator is transmitted to the low-pressure fluid in the reservoir via the fluid reservoir piston.

34. A brake system for a vehicle, the brake system comprising a radial piston pump in accordance with claim 1.

35. A brake system according to claim 34, further comprising a brake pad and an actuator configured to move the brake pad from a first position to a second position in order to effect braking of a wheel of the vehicle and a fluid reservoir for storing low-pressure fluid, and wherein the brake system is configured such that in use, low-pressure fluid from the reservoir is supplied to the pump and high-pressure fluid from the pump is supplied to the actuator.

36. An active suspension system for a vehicle, the active suspension system comprising a radial piston pump in accordance with claim 1.

37. An active suspension system according to claim 36, the system comprising an actuator, the actuator being configured to exert a force on a wheel and/or chassis of a vehicle, and wherein the active suspension system is configured such that in use, high-pressure fluid from the pump is supplied to the actuator.

38. A flight control system for an aircraft, the flight control system comprising a radial piston pump in accordance with claim 1.

39. A flight control system according to claim 38, further comprising an actuator and a control surface, the actuator being configured to move the control surface from a first position to a second position in order to change the aerodynamic performance of the control surface, and wherein the flight control system is configured such that in use, high-pressure fluid from the pump is supplied to the actuator.

40. A method of manufacturing a radial piston pump according to claim 1, wherein the method comprises producing one or more of the rotor, pintle and/or spool using an additive manufacturing process.

41. A method of manufacturing a radial piston pump according to claim 40, wherein the method comprises finishing a rotor, pintle and/or spool produced using an additive manufacturing process using a subtractive manufacturing process.

Description

DESCRIPTION OF THE DRAWINGS

[0141] Embodiments of the present disclosure will now be described by way of example only with reference to the accompanying schematic drawings of which:

[0142] FIG. 1 shows a section view of a prior art radial piston pump;

[0143] FIG. 2 shows a perspective section view of the radial piston pump and motor assembly according to a first embodiment of the disclosure:

[0144] FIGS. 3a and 3b show perspective section views of the radial piston pump of FIG. 2:

[0145] FIG. 4 shows a perspective view of the pintle of the radial piston pump of FIG. 2:

[0146] FIGS. 5a and 5b shows cross-section views of the pintle of FIG. 5:

[0147] FIGS. 6a and 6b show cross-section views of the pintle of FIG. 5:

[0148] FIG. 7 shows a perspective view of the spool of the radial piston pump of FIG. 2:

[0149] FIG. 8 shows a perspective view of the rotor of the radial piston pump of FIG. 2:

[0150] FIG. 9 shows a schematic diagram of a brake system comprising a radial piston pump in accordance with an embodiment of the disclosure:

[0151] FIGS. 10a and 10b show cross sectional views of a power pack according to an embodiment of the disclosure:

[0152] FIG. 11 shows a cross sectional view of the pintle of the power pack of FIG. 10;

[0153] FIG. 12 shows a schematic diagram of an active suspension system comprising a radial piston pump in accordance with an example embodiment of the disclosure; and

[0154] FIG. 13 shows a schematic diagram of a flight control system comprising a radial piston pump in accordance with an example embodiment of the disclosure.

DETAILED DESCRIPTION

[0155] FIGS. 2 and 3 are cross sectional views of a radial piston pump and motor assembly 1. FIGS. 3a and 3b are both cross section plan views of the radial piston pump and motor assembly 1 of FIG. 2. The assembly 1 comprises a rotor, shown in detail in FIG. 9, 2 mounted on a pintle 4 (which is shown as partially transparent in FIG. 2 in order to aid understanding). A spool 6, shown in detail in FIG. 6, is concentrically located within a cavity 8 defined by an inner surface 10 of the pintle 4. In the present embodiment the spool 6 is an elongate body having a generally circular cross-section, but the surface of the spool is flattened in several regions to provide an indented surface 7. In other embodiments the spool may comprise one or more lands or grooves. One end 59 of the spool 6 protrudes from the pintle 4 and is connected to a control motor 12. In the embodiment of FIG. 2 the control motor 12 comprises a plurality of control motor permanent magnets 14 mounted on splines 56 of the spool 6 for rotation therewith and a plurality of control motor coils 16, said control motor permanent magnets 14 being concentrically located within control motor coils 16. While the present embodiment has permanent magnets concentrically located within an annular array of coils it will be appreciated that other control motor arrangements may be used, for example the coils may be mounted on the rotor, and the permanent magnets on the housing of the pump.

[0156] The rotor 2 comprises a plurality of radially extending piston chambers 18, and in use each cavity has a piston 20 located therein. The pistons 20 (and piston chambers 18) are arranged in two layers, the pistons 20a of a first layer being spaced apart from the pistons 20b of a second layer along the longitudinal axis of the rotor 2. At the distal end of each of the pistons 20 is a cam follower 22. The cam followers 22a of the pistons 20a of the first layer are arranged to roll along a first cam surface and the cam followers 22b of the pistons 20b of the second layer are arranged to roll along the second cam surface. The first cam surface and a second cam surface extend circumferentially around and face towards the outside of the rotor 2. The first cam surface and the second cam surface are profiled so that the radial distance between each cam surface 24 and the rotor 2 varies with location around the circumference of the rotor 2. The first cam surface and the second cam surface therefore have distal regions 26 which are further from the outer surface of the rotor 2 than proximal regions 28. In some embodiments the cam surfaces may have the same profile, in other embodiments the profile of the cam surfaces may differ with respect to each other. While the present embodiment comprises two layers of pistons and two cam surfaces it will be appreciated that in other embodiments more than two layers and/or cam surfaces may be present. A plurality of permanent magnets 30 are mounted on splines 58 and spaced apart around the circumference of the rotor 2 at a location spaced apart along the longitudinal axis of the rotor 2 from the pistons 20. The permanent magnets 30 form part of a motor 32. The motor 32 also comprises an annular array of coils 34, the permanent magnets 30 being concentrically located within the array of coils 34. It will be appreciated that while the present embodiment describes a motor in which the stator comprises a plurality of coils and the rotor comprises an array of permanent magnets other types or motor may be used in embodiments in accordance with the present disclosure provided that the motor comprises a rotor and a stator.

[0157] Formed within the pintle 4 (see FIGS. 4 to 6) are: inlet-to-spool flow galleries 36 which provide a flow path between the inlets 38 of the pump (the inlets 38 are located at the opposite end of the pintle 4 to the control motor 12) and the spool 6: spool-to-piston flow galleries 40 which provide a flow path between the spool 6 and a first and/or second piston inlet aperture 42a, 42b: piston-to-outlet flow galleries 44 which provide a flow path between a first and/or second piston outlet aperture 46a, 46b and the outlets 48 of the motor-pump-valve assembly 1 (the outlets 48 are located at the opposite end of the pintle 4 to the control motor 12): and return flow galleries which provide a flow path between the spool 6 and outlets 48. Each of the first and second piston inlet apertures 42a, 42b is in the form of a slot or groove that extends around a portion of the outer circumference of the pintle 4 at the same axial location as the first or second layer of pistons 20a, 20b respectively. Each of the first and second piston outlet apertures 46a, 46b is in the form of a slot or groove that extends around a different portion of the outer circumference of the pintle 4 to the first and second piston inlet apertures 42a, 42b, but again at the same axial location as the first or second layer of pistons 20a, 20b respectively. Each of the first and second piston inlet apertures 42a, 42b are located opposite a distal region 26 of the first and second cam surfaces 24 respectively. Each of the first and second piston outlet apertures 46a, 46b are located opposite a proximal region 28 of the first and second cam surfaces 24 respectively. In the present embodiment, each cam surface 24, comprises two distal regions 26 and two proximal regions 28, the regions being equally spaced in an alternating manner around the outer circumference of the piston. Each layer of the pump comprises two piston inlet apertures 42, and two piston outlet apertures 46, each of said apertures occupying slightly less than ninety degrees of the circumference of the surface of the pintle 4, with like apertures being located on opposite sides of the pintle 4. For the sake of clarity, not all flow galleries are shown in FIGS. 2 and 3.

[0158] The components described above are located within a housing 50, the interior of the housing 50 being divided into two concentric portions along the entirety of its length by an interior wall 52. The interior wall 52 extends circumferentially around the rotor 2, separating the rotor 2 (including the permanent magnets 30 and pistons 20) and cam surfaces 24 from the coils 34 and control motor coils 16. Within the housing 50, on the exterior side of interior wall 52, there are wires/cables 54 which are capable of transmitting power and/or control signals to the control motor 12 and the motor 32.

[0159] In use, liquid at low pressure enters the pump-motor-valve assembly 1 at inlets 38 and travels via one or more inlet-to-spool flow galleries 36 in pintle 4 to the cavity 8 containing the spool 6. The spool 6 is rotated between different positions by the control motor 12, with the positioning of the spool 6 controlling the flow of fluid by selectively providing one or more flow paths for the fluid across the surface of the spool 6 via indented surfaces 7. Depending on the position of the spool 6, fluid may be directed from the cavity 8 to (i) the pistons 20a of the first layer but not the pistons 20b of the second layer, (ii) the pistons of the first and second layers 20a, 20b, (iii) the pistons of the first and second layers 20a, 20b and the outlets 38 of the pump, or (iv) the outlets 38 of the pump. In the case of (i) and (ii) the spool 6 is positioned such that a flow path is created from inlet-to-spool flow galleries 36 to spool-to-piston flow galleries 40. In the case of (iii) the spool 6 is positioned such that a flow path is created from inlet-to-spool flow galleries 36 to spool-to-piston flow galleries 40 and return flow galleries 49. In the case of (iv) the spool 6 is positioned such that a flow path is created from inlet-to-spool flow galleries 36 to return flow galleries 49. In other embodiments, the spool may be arranged such that for a given position fluid is directed from the cavity 8 to the pistons 20b of the second layer but not the pistons 20a of the first layer.

[0160] In the present embodiment, the provision of electric current to the coils 34 in the presence of the magnetic field produced by permanent magnets 30 generates an electromotive force in the conventional manner, the electromotive force causing the permanent magnets 30 and the rotor 2 to which they are attached to rotate. This rotation of the rotor 2 drives reciprocal motion of the pistons 20 as the motion of the rotor 2 causes cam followers 22 to move along the cam surfaces 24. As the radial distance between the cam surface 24 and the rotor 2 decreases, the cam followers 22 and the pistons 20 to which they are attached are pushed inwards, expelling fluid from the piston chamber 18 via the first and second piston outlet apertures 46a, 46b to the piston-to-outlet flow galleries 44. As the radial distance between the cam surface 24 and the rotor 2 increases, the pistons 20 (which are biased towards an extended position) move outwards and fluid is drawn into the piston chamber 18 via the first and second piston inlet apertures 42a, 42b from the spool-to-piston flow galleries 40. In this way, the pressure of the fluid is increased by the action of the pump.

[0161] The present embodiment provides a variable displacement pump, where the flow rate from the pump can be varied by controlling whether one or both layers of the pump are in operation. In this way, pumps in accordance with the present disclosure may provide additional flexibility and/or may allow for more efficient operation over a wider range of operating conditions. Additionally and/or alternatively, pumps in accordance with the present embodiment may provide this advantage while being compact and/or mechanically simple in comparison to prior art pumps.

[0162] Each cam surface of the present embodiment comprises two proximal regions and two distal regions, resulting in two cycles of motion of the piston for each rotation of the rotor. However, in some embodiments, the number of proximal regions may differ as between different layers of pistons. Further, the profile of the cam surface as between different layers may differ in other ways, for example by having a larger maximum distance between the rotor and cam surface and/or a steep rate of change in said distance. Thus, pumps in accordance with embodiments of the disclosure may allow for a pump to have different characteristics depending on which layer of the pump fluid passes through thereby increasing the flexibility of the pump and/or the efficiency of the pump across a broad range of operating conditions.

[0163] Controlling the flow of fluid to the pistons using a spool valve (as in the present embodiment) may facilitate the provision of a more compact pump for a given flow rate and/or allow for a reduction in the part count of the pump thereby reducing weight and/or cost. Additionally or alternatively, use of a spool valve may provide a more responsive pump as the (relatively lightweight) spool can be quickly and precisely displaced to control flow through the pump. However, it will be appreciated that the multi-layer pump can be used with different control systems, either integral with or separate to the motor-pump assembly, provided said control systems are capable of appropriately controlling the flow of fluid to the pistons.

[0164] In the present embodiment, the spool 6 is mounted for rotation, and therefore a rotary spool valve, but in other embodiments the spool may move axially.

[0165] The rotor 2 of the present embodiment is both the rotor of the motor 32 and the rotor of a radial piston pump comprising pistons 20. Use of such a common rotor in a combined motor-pump may allow for a more compact pump design and/or a more responsive pump. Additionally or alternatively, use of a common rotor may reduce the number of parts in the pump, not only because the pump and motor rotor are integrally formed by because there is no need for shafts and/or gearing to transmit the rotational motion generated by the motor to the rotor of the pump.

[0166] In the present embodiment, one or more orifices (not shown) are formed in the surfaces of the pintle. In use, fluid that has been pressurised by the action of the pistons 20 is forced out of these orifices and forms a hydrostatic bearing between the pintle and the rotor. Thus, pumps in accordance with the present embodiment may suffer lower loses due to friction and/or have a longer operational life.

[0167] Locating the inlet and outlet to the pump at the same end of the pintle (as in the present embodiment) may facilitate connection of the motor and pump assembly to a hydraulic system. However, it will be appreciated that in other embodiments the inlet and/or outlet may have different locations.

[0168] In some embodiments, the interior wall 52 (and associated seals, if necessary) form a water-tight barrier within the housing 50. This allows fluid to flow through and around the rotor 2 while keeping coils 34 and control motor coils 16 dry thereby increasing reliability and simplifying construction of the motor-pump by removing the need to individually protect electrical components from contact with the working fluid.

[0169] In some embodiments, a small amount of fluid leaks from piston chambers 18 when the pump is in use. The interior wall 52 may contain features and/or flow galleries that direct this fluid around and/or over the rotor 2 thereby providing a cooling effect. Thus, assemblies in accordance with the present disclosure may allow for improved cooling for the pump and/or motor. Additionally or alternatively, such a cooling effect may be achieved without significantly reducing the efficiency of the pump by taking advantage of the fluid leaking from piston chambers 18.

[0170] In an embodiment of the disclosure shown schematically using the customary symbols in FIG. 9, a radial piston pump and motor assembly 101 similar to that described above in connection with FIG. 2 (except where described as otherwise below) is used in a disc brake system 160. Similar components as between FIG. 2 and FIG. 9 are indicated in FIG. 9 with the reference numeral incremented by 100, e.g. the spool 6 of FIG. 2 is indicated with the reference number 106 in FIG. 9. The disk brake system 160 comprises radial piston pump and motor assembly 101 connected via inlets 138 to a fluid reservoir 161, and via outlets 148 to a brake caliper and pad assembly 162 adjacent a brake disk 164. In FIG. 9 a single brake caliper and pad 162 is shown, but it will be appreciated that in other embodiments a brake caliper may be located on both sides of the brake disk. As for FIG. 2, the radial piston pump and motor assembly 101 comprises a spool 106 mounted for rotation in cavity 108 (not shown in FIG. 9) to form a spool valve indicated with reference numeral 109 in FIG. 9. Motion of the spool 106 is provided by control motor 104. Pistons 122a of the first layer and pistons 122b of the second layer, along with the associated cam followers etc. form first and second pumps 123a, 123b driven by the motor 132. In contrast to the arrangement of FIG. 2, in the radial piston pump and motor assembly 101 of FIG. 10 the spool valve 109 of FIG. 9 is located downstream of the first and second pumps 123a, 123b.

[0171] As shown in FIG. 9 in the standard schematic manner, the spool valve 109 has four positions (each position corresponding to a different rotational position of the spool 106 within cavity 108). Those positions are labelled I, II, III and IV in FIG. 9. Flow galleries (indicated by lines in FIG. 9) connect (i) the fluid reservoir 161 to each of the first and second pumps 123a, 123b, (ii) each of the first and second pumps 123a, 123b to the spool valve 109 and (iii) the spool valve 109 to the fluid reservoir 161 and the brake caliper and pad assembly 162. While the flow galleries are shown schematically as straight lines in FIG. 9 in practice the flow galleries may be curvilinear and extend around and surround a portion of the brake caliper and pad assembly 162.

[0172] Mode I may be referred to as a passive mode. In Mode I, the inlet 138, outlet 148 and first and second pumps 123a, 123b are all connected so that fluid can flow freely via the spool valve 109 between the pumps 123a, 123b, the reservoir 161 and the brake caliper and pad 162. Mode I may be used when the brake is disengaged and, more particularly, while the motor 132 is spinning up one or both of pumps 123a, 123b prior to the brake being engaged to allow for faster transmission of hydraulic power to the brake caliper and pad 162 when the brake is eventually engaged (Modes III and IV). Mode I may be used where there is advanced warning that a user is going to brake hardfor instance if a signal is received that a throttle pedal has been sharply disengaged or if a sensor on the car has detected an obstacle. The pumps 123a, 123b and motor 132 have a greater inertia than the spool valve 109 so may take several milliseconds to spin up to full speed, in contrast the spool valve 109 can switch positions almost instantaneously. By taking advantage of the responsiveness of the spool valve, to switch between a passive and active modes, pumps in accordance with the present embodiment may allow for more responsive braking. It will be appreciated that this mode of operation may be used in other systems, apart from braking systems that would similarly benefit from faster provision of hydraulic power.

[0173] Mode II may be referred to as a bypass mode. In Mode II the spool 109 provides a flow path between both first and second pumps 123a, 123b and the fluid reservoir 161. When the motor 132 drives one or both of the first and second pumps 123a, 123b fluid is pumped back to the reservoir 161, but not to the brake caliper and pad assembly 162. The resulting flow of fluid may be used to cool the brake system 160 when the brake is not engaged.

[0174] Mode III may be referred to as partial operation. In Mode III the spool provides a flow path between the first pump 123a and the brake caliper and pad assembly 162 but not between the second pump 123b and the brake caliper and pad assembly 162, with the second pump 123b being connected to the reservoir 161. Thus, in Mode III only a single layer of the radial piston pump and motor assembly 101 is providing hydraulic power to the brake system 160.

[0175] Mode IV may be referred to as full operation. In mode IV the spool provides a flow path between both the first and second pumps 123a, 123b and the brake caliper and pad assembly 162. No flow path between the pumps 123a, 123b and the reservoir 161 is provided. Thus, in Mode IV both layers of the radial piston pump and motor assembly 101 are providing hydraulic power to the brake system 160. Mode IV is used when more hydraulic power is required than can be provided in Mode III. The ability to selectively use the layers of the radial piston pump and motor assembly 101 allows the assembly 101 to achieve high flows when necessary, but to operate more efficiently at lower flows.

[0176] FIG. 12 shows a variation of the embodiment of FIG. 9, where a radial piston pump and motor assembly 101 similar to that described above in connection with FIG. 2 (except where described as otherwise below) is used in an active suspension system 170. Similar components as between FIG. 9 and FIG. 12 are indicated in FIG. 12 with the same reference numeral. Only those aspects of the FIG. 12 embodiment which differ with respect to the FIG. 9 embodiment are discussed here. In FIG. 12, the suspension system 170 comprises radial piston pump and motor assembly 101 connected via inlets 138 to a fluid reservoir 161, and via outlets 148 to an actuator 171 concentrically located with a coil spring 172. The actuator 171 is connected to the chassis 174 (indicated schematically in FIG. 12) of a car (not shown) at one end and to a wheel 176 (indicated schematically in FIG. 12) of the car at the other end. In other embodiments coil spring 172 may be absent.

[0177] In use, power is supplied to actuator 171 so that actuator 171 can be used to vary the damping of the movement between chassis 174 and wheel 176. Mode I (passive mode) may be used when a sensor detects an obstacle on the road and allows the pump to be spun up so that power draw from the engine may be more effectively managed. Modes III and IV are used depending on how much power is required by the actuator (e.g. the amount of damping required) and Mode II may be used to cool the pump when the system is not engaged.

[0178] FIG. 13 shows a variation of the embodiment of FIG. 9, where a radial piston pump and motor assembly 101 similar to that described above in connection with FIG. 2 (except where described as otherwise below) is used in a flight control system 180. Similar components as between FIG. 9 and FIG. 13 are indicated in FIG. 13 with the same reference numeral. Only those aspects of the FIG. 13 embodiment which differ with respect to the FIG. 9 embodiment are discussed here. In FIG. 13, the flight control system comprises radial piston pump and motor assembly 101 connected via inlets 138 to a fluid reservoir 161, and via outlets 148 to an actuator 181 connected to a control surface 182 mounted on a portion of a wing 184 of an aircraft (not shown).

[0179] In use, fluid is provided to actuator 181 so that actuator 181 an move control surface 182 thereby changing the aerodynamic performance of wing 184. Mode I (passive mode) may be used to spin up the pump in advance of a manoeuvre so that power requirements within the aircraft can be managed efficiently. Modes III and IV are used depending on how much power is required by the actuator to move the flight control surface 182, and Mode II may be used to cool the pump when the system is not engaged.

[0180] FIGS. 10a and 10b show a cross-sectional view of a hydraulic power pack 270 in accordance with an example embodiment of the disclosure in (a) a reservoir empty/accumulator full configuration and (b) a reservoir full/accumulator empty configuration. Similar components as between FIG. 2 and FIG. 10 are indicated in FIG. 10 with the reference numeral incremented by 200, e.g. the rotor 2 of FIG. 2 is indicated with the reference number 202 in FIG. 10. The power pack housing 250 contains a pintle 204, with a rotor 202 mounted thereon. The pintle 204 is connected to the housing 250 by an interior wall 252 that extends radially inward from the housing 250 to the pintle 204 and appears dome-shaped when viewed in cross section in FIG. 10, with the convex surface of the dome facing towards the right hand side of FIG. 10 and the distal end of the pintle 204 being on the left hand side of FIGURE. Located concentrically with and outside the rotor 202 is the stator 233 of motor 232. The rotor 202 comprises a plurality of pistons (not shown) that together with rotor 202 form a radial piston pump 223 (for example having multiple layers of pistons as described in FIG. 1 or having only a single layer of pistons). In contrast to the FIG. 2 embodiment, the hydraulic power pack does not have a spool configured to control the flow of fluid in the pump. Extending through an axial through-hole 272 in pintle 204 is the stem 274 of a fluid reservoir piston 276. At one end (the left hand end of FIG. 10) of the stem 274 is a reservoir piston head 278 which fits within a cylindrical portion of housing 250 to form a fluid reservoir 280 on the far side of the reservoir piston head 278 to the motor stator 233 and rotor 202 between the reservoir piston head 278 and an end portion of housing 250. At the other of the stem 274 is a circumferential flange 282 which extends radially outward from the stem 274. A recess 284 extends into the stem 274 along its longitudinal axis from the end of the stem having the circumferential flange 282. The stem 286 of an accumulator piston 288 is located in the recess 284. The accumulator piston 288 has an accumulator piston head 290 at one end of the stem 286 (the end located on the right hand side of FIG. 10) which fits within a cylindrical portion of the housing 250 to form a pressure accumulator 292 on the near side of the accumulator piston head 290 to the to the motor stator 233 and rotor 202 (i.e. between the convex surface of the interior wall 252 and the piston head 290). On the far side of the accumulator piston head 290, relative to the motor stator 233 and rotor 202, a gas reservoir 294 is formed between the accumulator piston head 290 and an end portion of housing 250. Control valves 296 are located between the reservoir piston head 278 and the motor stator 233 and rotor 202, and between the inner wall 252 and the motor stator 233 and rotor 202. In FIG. 10(a) the fluid reservoir 280 is empty and the accumulator is substantially full: the reservoir piston head 278 is immediately adjacent the end portion of housing 250 and accumulator piston head 290 is adjacent the opposite end portion of housing 250 such that the volume of gas reservoir 294 is relatively small. In FIG. 10(b) the fluid reservoir 280 is full and the accumulator is empty: the reservoir piston head 278 is spaced apart from the end portion of housing 250 that defines the fluid reservoir 280 and the accumulator piston head 290 is adjacent inner wall 52 such that the volume of gas reservoir 294 is relatively large. A membrane wall 295 provides a fluid-tight barrier separating the motor stator 233 and rotor 202.

[0181] FIG. 11 shows a cross-sectional schematic view of pintle 204 of FIG. 10. At the centre of pintle 204 is axial through-hole 272 having stem 274 of fluid reservoir piston 276 and stem 286 of accumulator piston 288 received therein. A number of flow galleries which appear substantially circular when viewed in cross-section in FIG. 11 are formed along the longitudinal axis of pintle 204. These include (in order travelling clockwise from a 12 o'clock position in FIG. 11): ancillary pressure flow gallery 281, pump outlet flow gallery 283, control valve return flow gallery 285, pump inlet flow gallery 287, control valve pressure flow gallery 281, pump outlet flow gallery 283 and pump inlet flow gallery 287, with flow galleries of the same type being located opposite each other around the circumference of the pintle 204. Pump inlet flow galleries 287 are also present in stem 274 of fluid reservoir piston 276. Two pump inlet flow apertures 241 (denoted with a dashed line in FIG. 11) are formed in the outer circumference of the pintle 204 and are connected to pump inlet flow gallery 287 at a plane spaced apart from the plane of cross section in FIG. 11. The cross-sectional shape of each pump inlet flow gallery 287 changes in the region adjacent to pump inlet flow aperture 241, expanding from a circle to meet aperture 287 which extends around 80 degrees along the outer circumference of the pintle 204. A pump outlet aperture 243 is similarly connected to each pump outlet flow gallery 283. An anti-rotation device 297 and rotation sensor 299 are also located in the pintle 204.

[0182] In use, fluid at low pressure is held in the fluid reservoir 280. Fluid from the fluid reservoir 280 is drawn through pump inlet flow galleries 287 in the reservoir piston head 278 and stem 274, and in pintle 204 (see FIG. 11) to the pump 223 via pump inlet flow apertures 241. Rotation of the pump is caused by supplying current to the coils (not shown) of the motor stator 233. The fluid is pressurised in pump 223 by the action of reciprocating pistons (as described above for FIG. 1) and then passes through pump outlet apertures 243 to pump outlet flow galleries 283 in pintle 204 and inner wall 252 to the pressure accumulator 292. The accumulation of pressurised fluid in pressure accumulator 292 exerts a pressure on accumulator piston head 290 causing the accumulator piston 288 to move towards the right hand side of FIG. 11 and to compress the gas in gas reservoir 294. Fluid in pressure accumulator 292 also exert a force on the surface of circumferential flange 282 that causes fluid reservoir piston 276 to move towards the left hand side of FIG. 10 thereby compressing and increasing the pressure of the fluid in the fluid reservoir 280. Pressurised fluid from pump 223 is also supplied to control valves 296 via ancillary pressure flow galleries 281, and fluid from control valves 296 is returned to fluid reservoir 280 via, control valve return flow gallery 285.

[0183] The use of a common rotor for the pump and motor of a hydraulic power pack may allow for a more compact power pack in comparison to power packs of similar capacity. Additionally or alternatively, use of the pintle to provide flow galleries connecting the reservoir, accumulator and pump of the hydraulic power pack may allow for a more compact power pack in comparison to power packs of similar capacity.

[0184] In the present example embodiment, the pintle acts as a fluid manifold connecting the reservoir, accumulator and pump, which may provide a more compact power pack in comparison to power packs of similar capacity. In the present example embodiment, the pintle further acts as a fluid manifold for control valves present within the hydraulic power packs due to the inclusion of pressure and return flow galleries for such valves within the pintle. This may provide a more compact power pack in comparison to power packs of similar capacity and/or allow for provision of a self-contained control unit for the hydraulic system to which the power pack is connected, said self-contained control unit being able to provide both a flow of pressurised fluid and control flows. By retaining the smart elements of the hydraulic system in the self-contained control unit, design of the hydraulic system may be simplified.

[0185] In the same or yet further embodiments the pintle may act as a fluid manifold for control valves located outside the hydraulic power pack and/or other auxiliary systems of the hydraulic system.

[0186] While the present disclosure has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the disclosure lends itself to many different variations not specifically illustrated herein.

[0187] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, while of possible benefit in some embodiments of the disclosure, may not be desirable, and may therefore be absent, in other embodiments.