AU2004256150A1 - A hydraulic machine - Google Patents

Description

WO 2005/005782 PCT/AU2004/000951 1 A HYDRAULIC MACHINE Field of the Invention This invention relates to a hydraulic machine. In particular, the invention 5 relates to a hydraulic machine that may be used as a rotary vane pump or a rotary vane motor. Background to the Invention Hydraulic vane pumps are used to pump hydraulic fluid in many different 10 types of machines for different purposes. Such machines include, for instance, earth moving, industrial and agricultural machines, waste collection vehicles, fishing trawlers, cranes, and vehicle power steering systems. Hydraulic vane pumps typically have a housing with a chamber formed therein. A rotor is rotatably mounted in the housing. The rotor is typically of generally 15 cylindrical shape and the chamber has a shape such that one or more rise and fall regions are formed between the walls of the rotor and the walls of the chamber. In the rise regions, a relatively large space opens between the outer wall of the rotor and the inner wall of the chamber. On the leading side of the rise region, there exists a region which is substantially a dwell, although in usual practice there exists a small amount of fall. This is sometimes 20 called a major dwell or major dwell region. The major dwell is followed by a fall region, in which the space between the rotor and the chamber decreases. Outside of the rise, fall and major dwell regions, the space between the outer wall of the rotor and the inner wall of the chamber is small. In practice, this is usually a true dwell of zero vane extension and is sometimes called the minor dwell. The rotor normally has a number of slots and movable 25 vanes are mounted in the slots. As the rotor rotates, centrifugal forces cause the vanes to move to an extended position as they pass through the rise regions. As the vanes travel along the fall regions, the vanes are forced to move to a retracted position by virtue of the rotors contacting the inner wall of the chamber as they move into the region of restricted clearance between the rotor and chamber. Hydraulic fluid lubricates the vanes and the inner 30 wall of the chamber. Hydraulic vane pumps are usually coupled to a drive, such as to a rotating output shaft of a motor or an engine and, in the absence of expensive space invasive clutches or other disconnecting means, continue to pump hydraulic fluid as long as the WO 2005/005782 PCT/AU2004/000951 2 motor or engine continues to operate. A rotor of the pump also usually has a rotational speed determined by the rotational speed of the motor or engine. A problem with known hydraulic vane pumps is that they continuously pump hydraulic fluid, regardless of whether or not a hydraulic system of a machine is being 5 utilised in a working mode of the machine. That is, a machine may be idle or may be in the process of being driven from one job location to another (i.e. in a non-working mode), yet the pump may continue to consume energy in pumping fluid excessively or unnecessarily. A related problem is that hydraulic hoses, pipes and valves of hydraulic systems of machines such as waste collectors and hydraulic cranes tend to be larger than 10 actually required in order for the machines to carry out lifting in their working mode. That is, lifting may be normally carried out at moderate engine speeds, yet the machines may attain high engine speeds when being driven from one location to another. Consequently, larger and more expensive hydraulic hoses, pipes and valves are required in order to accommodate the higher fluid pressures generated by the pump at high engine speeds. 15 A problem with some known hydraulic vane motors is that, like with hydraulic vane pumps, in the absence of expensive space invasive clutches or other disconnecting means, hydraulic vane motors may also be worked by the hydraulic fluid incessantly and excessively. US patent number 3,421,413 to Adams et al describes a sliding vane pump in 20 which hydraulic pressure is applied to each vane in order to maintain the vanes in optimum engagement with a cam surface that encircles the rotor which carries the vanes. This patent is directed towards ensuring that the vanes remain in optimum contact with the encircling cam. US patent number 3,586.466 to Erickson describes a rotary hydraulic motor 25 having a slotted rotor and a movable vane located in each slot. The rotor is journalled in a chamber that defines three circumferentially spaced crescent-shaped pressure chamber sections. The hydraulic motor includes a valve control means and associated passages to be able to selectively control the flow of pressurised fluid to the pressure chamber sections. This allows pressurised fluid to be supplied to one, two or all three pressure chamber 30 sections. When pressurised fluid is delivered to all three pressure chamber sections, low speed, high torque operation occurs. When pressurised fluid is delivered to two pressure chamber sections, higher speed but lower torque operation occurs. When pressurised fluid is delivered to only one pressure chamber section, even higher speed but lower torque operation of the motor occurs.

WO 2005/005782 PCT/AU2004/000951 3 The hydraulic motor of Erickson also includes an arrangement of passages that allow pressurised fluid to impart radially outward movement to the vanes adjacent the inlet passages to the pressurized chamber sections and to impart radially inward movement to the vanes adjacent the outlet passages of the pressurized chamber sections. Thus, each 5 vane is fluid pressure urged radially outwardly into sealing engagement with the concavity or concave surface of each pressurized chamber section during initial movement of the vane circumferentially across the pressurized chamber section, the vane being moved radially inwardly by fluid pressure at the circumferentially opposite end of the pressurized chamber section, to reduce the frictional load between each vane and the inner peripheral surface 10 portions of the chamber at areas wherein there is little or no circumferential pressure applied to the vanes (see column 4, lines 55 to 72). The entire contents of US 3,421,413 and US 3,586,466 are expressly incorporated herein by cross reference. 15 Brief Description of the Invention It is therefore an object of the present invention to provide a hydraulic machine that overcomes or minimises at least one of the problems referred to above, or to provide the public with a useful or commercial choice. According to a first aspect, the present invention provides a hydraulic 20 machine having: a body having a chamber, an inlet for introducing hydraulic fluid into the chamber, an outlet through which hydraulic fluid leaves the chamber, a rotor rotatable within the chamber, 25 the chamber and the rotor being shaped to define one or more rise, fall and dwell regions between walls of the chamber and the rotor, a shaft extending from the rotor, the rotor having a plurality of slots, a plurality of vanes located such that each slot of the rotor has a vane located 30 therein, each vane being movable between a retracted position and an extended position wherein in the retracted position, the vane is unable to work the hydraulic fluid introduced into the chamber and in the extended position the vane is able to work the hydraulic fluid introduced into the chamber, and WO 2005/005782 PCT/AU2004/000951 4 vane retaining means being selectively actuable such that, when activated, the vane retaining means retains the vanes in the retracted position. Preferably, the hydraulic machine further comprises an under vane passage for selectively receiving pressurised hydraulic fluid to facilitate moving the vanes located in 5 a dwell region from the retracted position to the extended position. Although the vanes of a hydraulic pump are likely to automatically move from the retracted position to the extended position as they enter a rise region after inactivation of the vane retaining means, use of an under vane passage to supply pressurised hydraulic fluid to under the vanes will assist in this movement and also minimise the likelihood of a vane sticking in the retracted position. 10 For hydraulic motors, inclusion of under vane passages can be used to actively drive the vanes to the extended position. Conventional hydraulic motors use springs to drive the vanes to the extended position. The under vane passages can either complement or replace such springs. The under vane passage may also function to allow hydraulic fluid located 15 under the vanes to drain away from under the vanes as the vanes move from the extended position to the retracted position. In some instances, the vanes may have a vane pin located underneath each vane. The vane pins typically can move in a vane pin duct. In such embodiments, the under vane passage may include a passage located under the vane pin. 20 Preferably, the vane retaining means can be selectively actuated to retain all of the vanes in the retracted position. Preferably, the vane retaining means can retain the vanes in the retracted position for at least an entire revolution of the rotor. The inlet may be branched and may have one or more openings into the chamber, adjacent a start of each rise region. An end of the inlet at a periphery of the body 25 may be attached to a hydraulic line. The outlet may be branched and may have one or more openings from the chamber, adjacent an end of each fall region. An end of the outlet at a periphery of the body may be attachable to a hydraulic line. The under vane passages may extend from under each of the vanes to the 30 outlet and the under vane passages may be pressurised with hydraulic fluid from the outlet. Alternatively, the under vane passages may be pressurised with pressurised hydraulic fluid from a pilot source of pressurised hydraulic fluid.

WO 2005/005782 PCT/AU2004/000951 5 The under vane passage may also communicate with the inlet such that when the vane retaining means is actuated, hydraulic fluid drained from under the vanes is directed to the inlet, to allow the vanes to be retained in the retracted position. A control valve, such as a pressure sensitive spring loaded spool valve, may 5 be located within the under vane passage or in fluid communication with the under vane passages. The control valve may direct hydraulic fluid from the outlet to under the vanes when the vane retaining means is not actuated, and may direct hydraulic fluid from under the vanes to the inlet when the vane retaining means is actuated. The vane retaining means is selectively actuable to retain the vanes in the 10 retracted position. The vane retaining means suitably utilises pressurised hydraulic fluid to retain the vanes in the retracted position. In one embodiment, the vane retaining means comprises an engagement member movable between a disengaged position and an engaged position in which the engagement member contacts the vane to retain the vane in the retracted position. The engagement member may be an engagement pin or an engagement 15 ball that engages with a side wall of the vane. More preferably, the engagement member is an engagement pin or an engagement ball that engages with a recess in the vane to retain the vane in the retracted position. In another embodiment, the vanes may be affixed to the rotor by a vane pin, which vane pin moves with the vane as the vane moves between the retracted and extended 20 positions and the engagement member may be an engagement pin or ball that engages with the vane pin to thereby retain the vane in the retracted position. The engagement member is suitably moved from the disengaged position to the engaged position by pressurised hydraulic fluid. The pressurised hydraulic fluid may be selectively applied to the engaging means when it is desired to retain the vanes in the 25 retracted position. The engagement member may be provided with a biasing means, such as a return spring, to disengage the engagement member when maintaining the vanes in the retracted position is no longer required. Alternatively, hydraulic pressure may be used to move the engagement member to a disengaged position. As a further alternative, the 30 engagement member may be arranged such that centrifugal forces cause the engagement member to move to the disengaged position when the engagement member is inactivated. In another embodiment, the vane retaining mean comprises a vane retaining passage for receiving pressurised hydraulic fluid, the vane retaining passage directing the pressurised hydraulic fluid to at least one face of the vane such that the pressurised WO 2005/005782 PCT/AU2004/000951 6 hydraulic fluid forces (i.e. clamps) the vane against at least one face of the respective slot. For instance, a respective groove extending longitudinally along a radially extending face of each vane may provide a section of the vane retaining passage, a respective groove extending along a radially extending face of each slot may provide a section of the vane 5 retaining passage, or the vane retaining passage may extend through the rotor and direct hydraulic fluid onto a radially extending face of each vane. The vane retaining passage may extend from each of the vanes to a port at a periphery of the body. The port may be attached to a hydraulic line. Preferably, concentric annular sections of the vane retaining passage and 10 under vane passage communicate hydraulic fluid to each of the vanes. In one mode of operation, the hydraulic machine may function as a pump. In another mode of operation the hydraulic machine may function as a motor. When operated as a pump, the drive shaft may be coupled to an output shaft of an engine or motor. The slotted rotor may be splined to fit the drive shaft. When operated as a motor, the drive shaft 15 may be coupled to another hydraulic machine such as a pump. The machine may have any suitable number of vanes and preferably the machine has 10 or 12 vanes. The vanes may be of any suitable shape and size. Each vane may have an enlarged base, each slot may have an enlarged portion within which the base may move when the vane is extending or retracting, and each slot may have a restriction 20 through which the base may not move when the vane is extending. The machine may have a safety pressure relief valve, a solenoid valve (mechanically, piloted or electrically actuated) for selecting whether the pump vanes are to be retained in the retracted position or not, and a pressure responsive shuttle valve. The machine may have features of known hydraulic vane pumps or motors, 25 such as the Vickers® V10 or V20 or VMQ series of rotary vane pumps. For instance, the body may have ball bearings and bushings for supporting opposing ends of the drive shaft and to centre the slotted rotor within the chamber. The body may comprise two or more attachable pieces. An O-ring may be used to provide a fluid tight seal when connecting the body pieces together. 30 Any suitable type of hydraulic fluid may be used. Pilot values of three to four litres per minute and 10 to 15 bar pressure may be suitable for pressurising the vane retaining passage, to clamp the vanes and to activate the control valve such that hydraulic fluid from under the vanes is directed to the inlet.

WO 2005/005782 PCT/AU2004/000951 7 According to a second aspect of the present invention, there is provided a method for retaining vanes of a hydraulic vane pump or motor in a retracted position within a slotted rotor of the pump or motor, the pump or motor including a chamber and a rotor mounted for rotation within the chamber, the chamber and the rotor being shaped to define 5 one or more rise, fall and dwell regions between walls of the chamber and the rotor, the rotor having a plurality of slots and a plurality of vanes located such that each slot of the rotor has a vane located therein, each vane being movable between a retracted position and an extended position wherein in the retracted position, the vane is unable to work the hydraulic fluid introduced into the chamber and in the extended position the vane is able to 10 work the hydraulic fluid introduced into the chamber wherein the method includes the steps of: operating the pump or motor such that the vanes move to the extended position when passing through the rise regions and the vanes move towards or into the retracted position when passing along the fall regions and selectively actuating vane 15 retaining means to retain the vanes in the retracted position. Suitably, the vanes are retained in the retracted position by the vane retaining means for at least an entire revolution of the rotor. Preferably, the method further includes the step of draining hydraulic fluid from under the vanes as the vanes move towards the retracted position. In some instances, 20 the vanes may be provided with vane pins positioned under the vanes and the step of draining hydraulic fluid from under the vanes includes draining hydraulic fluid from under the vane pins. The method may further include releasing the retaining means to allow the vanes to move to the extended position as the vanes enter the rise regions. 25 Most suitably, the method comprises applying hydraulic fluid pressure to activate the vane retaining means to retain each of the vanes in the retracted position. Brief Description of the Drawings Preferred embodiments of the invention will now be described by way of 30 reference to the accompanying drawings in which: Figure 1 shows a side view, partly in cross-section, of a hydraulic pump in accordance with an embodiment of the present invention; Figure 2 shows a front view, partly in cross-section, of a hydraulic pump in accordance with an embodiment of the present invention; WO 2005/005782 PCT/AU2004/000951 8 Figure 3 is a cross-sectional front view of the rotor used in the hydraulic pump of Figure 2; Figure 3a is a side view of the rotor shown in Figure 3. Figure 3a is provided to show the line of section I-I for the cross sectional view shown in Figure 3; 5 Figure 4 is an enlargement of detail J shown in Figure 3; Figure 5 is a front view of the rotor shown in Figure 3; Figure 6 is a sectional side view taken along line H-H of Figure 5; Figure 7 is a three dimensional perspective view, partly in cross-section, showing detail of the rotor of Figure 5; 10 Figure 8 is a detailed front view an assembly used in a hydraulic machine according to an embodiment of the invention; Figure 9 is a detailed front view of another part of a hydraulic machine that is connected to the assembly shown in Figure 8, according to an embodiment of the invention; Figure 10 is a detailed side view of Figure 9; 15 Figure 11 is a cross-sectional side view of the machine part shown in Figure 9 and taken from the other side to that shown in Figure 10; Figure 12 shows an enlarged fragmentary perspective view of one embodiment of a retaining means for use in the hydraulic machine shown in Figures 8 to 11; Figure 13 shows part of a hydraulic circuit for the machine shown in the 20 preceding figures, when used as a pump, according to an embodiment of the invention; Figure 14 shows part of a hydraulic circuit for the machine shown in Figures 8 to 13, when used as a motor, according to an embodiment of the invention; Figure 15 shows an enlarged fragmentary perspective view of another embodiment of a retaining means for use in the hydraulic machine shown in Figures 8 to 11; 25 Figure 15a shows a perspective view of a rotor slot with the vane removed to show more detail of the rotor groove of the embodiment of Figure 15; Figure 16 shows an enlarged fragmentary perspective view of yet another embodiment of a retaining means for use in the hydraulic machine shown in Figures 8 to 11; Figure 16a shows a perspective of a vane removed from the rotor to show 30 more detail of the vane groove on the vane of the embodiment of Figure 16 Figure 17 shows an enlarged fragmentary perspective view of a further embodiment of a retaining means for use in the hydraulic machine shown in Figures 2 to 7; Figure 18 is a front view of a rotor for use with another embodiment of the present invention; WO 2005/005782 PCT/AU2004/000951 9 Figure 19 is a cross-sectional view of the rotor shown in Figure 18, with the cross section taken along line F-F of Figure 19a; Figure 19a is a side view of the rotor of Figure 18, with Figure 19a being provided to show the section line along which the sectional view of Figure 19 is shown; 5 Figure 20 is an enlarged view of detail G of Figure 19; Figure 21 is a cross-sectional view taken along line E-E of Figure 18; Figure 22 is a perspective view, partly in cross-section, of the rotor shown in Figure 18; Figure 23 is a perspective view of a cross-section of a rotor for use with 10 another embodiment of the present invention; Figure 24 is an enlarged view of part of the rotor of Figure 23; Figure 25 is a view similar to that of Figure 24, but with an engagement pin shown in the engaged position; Figure 26 is a front view of a rotor in accordance with another embodiment 15 of the present invention; Figure 27 is a cross-sectional view taken along line A-A of Figure 26; Figure 28 is a three dimensional view of the cross-section shown in Figure 27; Figure 29 is a three dimensional view, on enlarged scale, similar to that 20 shown in Figure 28 but with the engagement pin in an engaged position; Figure 30 is a three dimensional view of the embodiment shown in Figure 29 but with the engagement pin in a disengaged position; Figure 31 is a front view of a rotor for use with another embodiment in accordance with the present invention; 25 Figure 32 is a cross-section taken along line D-D of Figure 31; Figure 33 is a three dimensional view of part of the cross-section shown in Figure 32; Figures 34 is an enlarged three dimensional view of the embodiment shown in Figure 33. Figures 34 shows positioning of the spool valve when the retaining means are 30 disengaged, respectively; Figure 35 has been deliberately omitted; Figure 36 is a three dimensional cross-sectional view showing part of a rotor for use in accordance with another embodiment of the present invention; WO 2005/005782 PCT/AU2004/000951 10 Figure 37 is a front view of a rotor for use in a further embodiment of the present invention; Figure 38 is an enlarged sectional view taken along line K-K in Figure 37; Figure 39 is a perspective view of Figure 38; 5 Figure 40 is a fragmentary side view, in cross section, of a rotor for use in another embodiment of the present invention; Figure 41 is a perspective view of the part of the rotor shown in Figure 40; Figure 42 is an enlargement of detail L shown in Figure 40; Figure 43 is a side view, partly in cross-section, of a power steering pump in 10 accordance with another embodiment of the present invention; Figure 44 is a schematic flow diagram showing control of the power steering pump shown in Figure 40; and Figure 45 is a plot of pump flow against engine speed for the power steering pump shown in figure 37. 15 Detailed Description of the Drawings In the figures, like reference numerals refer to like features. In moving vane hydraulic machines, normal operation requires venting of under vane fluid. There are numerous such venting arrangements know to the person skilled in the art and the hydraulic 20 machines in accordance with the present invention may incorporate any known under vane venting technologies. Such under vane venting is not part of the inventive concept of the present invention and need not be described in great detail Figure 1 shows a side view, partly in cross-section, of one embodiment of a hydraulic pump in accordance with the present invention. The pump 10 of Figure 1 25 comprises a housing 12 having a first part 14 attached to a second part 16, for example by bolts or the like. An O-ring 18 is positioned between first part 14 and second part 16 of the housing to ensure a fluid tight seal is obtained between the housing parts. The housing 12 includes an inlet 20 for hydraulic fluid (often referred to in this art as a suction port) and an outlet 22 for hydraulic fluid (often referred to in this art as a pressure port). 30 The housing 12 defines an inlet chamber 24 that receives hydraulic fluid via inlet 20. A drive shaft 26 is journaled into housing 12 by bearings 28. The drive shaft includes a splined section 30. The splined section of the driveshaft 26 is in fluid communication with the inlet of the hydraulic machine. Thus, the splined section of the WO 2005/005782 PCT/AU2004/000951 11 driveshaft is a region containing low pressure hydraulic fluid. The splined section 30 of the drive shaft 26 is splined into a complementary spline formed or press fitted into an opening through a rotor (not shown) inside ring 32. Further details of the rotor will be provided with reference to the other drawings attached to this specification. Ring 32 defines a chamber 5 that will be described in more detail in later Figures and a rotor (hidden in Figure 1) is mounted in the ring 32. Ring 32 is mounted between front cartridge 34 and rear cartridge 38 in a fashion that enables the rotor to rotate within the housing. The pump 10 further includes a rear pressure plate 36 which is attached to rear cartridge 38. Rear cartridge 38 receives the rear end 40 of drive shaft 26. It will be understood that the rotor rotates relative to the rear 10 pressure plate 36 and rear cartridge 38. The housing 12 includes a pilot line entry 42 in the form of a nipple that allows a pilot line to be connected thereto. The pilot line entry 42 is provided to enable pressurised hydraulic fluid to travel down the pilot line into the housing. The pilot line 42 is in fluid communication with a fluid slot 44 formed in the pressure plate 36. Although 15 Figure 1 shows slot 44 in the rear pressure plate, the slot could be in a front pressure plate with pilot hydraulic fluid being delivered via the front pressure plate. Figure 2 is a detailed front view of part of an hydraulic pump, in particular the ring, rotor, vanes and pressure plate of a hydraulic punmp, in accordance with an embodiment of the invention. The front view shown in Figure 2 is partly in cross section. 20 Some details of the pump shown in Figure 2 have been deleted for clarity. The pump 50 shown in Figure 2 comprises a body 52. The body 52 may be made from two or more parts joined together in a fluid tight manner. The body 52 has a chamber having walls 54. As can be seen from Figure 2, chamber 54 is an elliptical chamber. The body 52 is also provided with appropriate bolt holes 55, 56, 57, 58 which 25 allow for assembly of the parts of the body. A rotor 60 is rotatably mounted within the chamber defined by chamber walls 54. Rotor 60 is of generally cylindrical shape. As the rotor 60 is generally cylindrical, and as the chamber defined by chamber walls 54 is generally elliptical, two rise regions 61,63, two major dwell regions 62, 64 and two fall regions 63,65 are formed in the 30 space between the outer walls of the rotor 60 and the chamber walls 54. In the major dwell regions 62, 64, a significant space exists between the outer walls of the rotor 60 and the chamber walls 54. Outside of the major dwell regions 62, 64, the clearance between the wall of the chamber and the rotor 60 is either expanding or decreasing. However, along the minor dwell regions 67, 69, there is only a small clearance between the wall of the rotor 60 WO 2005/005782 PCT/AU2004/000951 12 and the chamber wall 54. This is well known and is conventional in the sliding vane pump and motor art. The body 52 includes two hydraulic fluid inlets 70, 72 through which hydraulic fluid passes into entry to the rise regions 61, 63. The body also includes fluid 5 outlets at 66, 68 through which pressurised hydraulic fluid leaves the fall regions of the chamber. A drive shaft 82 is splined to rotor 60. In this regard, rotor 60 has a central passage passing therethrough. An appropriate spline connection is fitted into the passage passing through the rotor 60, for example by press fitting, or the spline is formed on the 10 passage, to enable the splined drive shaft 82 to be splined to the rotor. The rotor 60 has a plurality of radially extending slots, some of which are referred to by reference numeral 84. Radial slots 84 each house a vane 86. Respective vane pins 87 are positioned under the vanes 86. In conventional pumps that are generally similar to that shown in Figure 2 (often referred to as vane pumps) the vanes can move from a 15 retracted position in which the vane is essentially fully located within its respective slot to an extended position in which the vane extends out of its respective slot. As will be appreciated from viewing Figure 2, as the rotor 60 rotates, typically at speeds well in excess of 1000 rpm, each vane will move into a rise region. As the space between the outer wall of the rotor and the chamber walls increases in the rise region, centrifugal force and any force 20 imparted by pressure acting on the bottom of pin 87 or any pressure acting directly on the bottom of vane 86 forces the vanes to move outwardly along the slot so that contact between the end of the vane and the chamber wall is maintained (it being appreciated that a thin film of hydraulic fluid will be present between the end of the vane and the chamber wall to provide lubrication). As the vane rotates through the fall region, the space between the 25 outer wall of the rotor and the chamber walls starts to decrease. As a result, the vane is pushed back into the rotor. When the vane is along the minor dwell regions 67, 69, contact between the end of the vane and the chamber wall keeps the vane in a retracted position. When the vane is free to move in its slot, i.e. extend or retract, the vane can work the hydraulic fluid as necessary. If the hydraulic machine is being used as a pump, the 30 collapsing chamber volume associated with the fall regions and the system resistance act to pressurise the hydraulic fluid. If the hydraulic machine is being used as a motor, the hydraulic fluid is pumped through the chamber and the hydraulic fluid interacts with the extended vanes to cause the rotor to rotate.

WO 2005/005782 PCT/AU2004/000951 13 In conventional hydraulic machines of the general type similar to that shown in Figure 2, the position of the vanes is controlled only by the relative positioning between the rotor and the chamber. When the vanes are travelling through the rise and fall regions, the vanes are in an extending or collapsing position. When the vanes have passed into the 5 minor dwell region, they are in the retracted position. As a result, the vanes in the rise and fall regions are always working the hydraulic fluid. The present inventor has realised that significant efficiency gains can be made if the vanes can be held in the retracted position (or slightly below the minor dwell diameter) throughout the entire rotation of the rotor if working of the hydraulic fluid by the 10 vanes is not required. To this end, the present inventor has proposed that the hydraulic machine be provided with retaining means for selectively retaining the vanes in the retracted position. The retaining means are capable of retaining the vanes in the retracted position even as the vanes pass through the rise regions, the major dwell regions and the fall regions. The retaining means are also selectively actuable. In the embodiment shown in Figure 2, the 15 retaining means include a number of engagement pins 88 (these may also be referred to as detent pins). Detent pins 88 are mounted in passageways 90 that intersect with the radially extending slots 84 at an angle. Passageways 90 may suitably formed by machining or drilling a passage through the rotor from the outside wall and fitting a plug 92 into passageway 90. Passageway 90 is in fluid communication with a further passageway 96 20 that opens at an end face of the rotor 60. As shown in Figure 2, the end of longitudinal passageway 96 comes into register with slot 98 that is connected to a pilot source of a pressurised hydraulic fluid (not shown). If it is desired to retain the vanes in the retracted position, a signal may be sent to a control valve to pass pressurised fluid through the pilot feed line. When the end of 25 passageway 96 comes into register with slot 98, pressurised fluid enters passageway 96 and travels along passageway 96 and into passage 90. The pressurised hydraulic fluid then pushes the engagement pin 88 into engagement with the side of the vane 86. As best shown in Figures 3 and 4, the end of engagement pin 88 extends into a complementarily shaped recess formed in the side of vane 86 to thereby retain the vane 86 in the retracted position. 30 Although Figure 1 shows a single slot 98 which will excite gallery 96 when the vanes are in one minor dwell region, this slot 98 may be replicated to excite galleries 96 in the other minor dwell region of the pump. Whilst the pilot line is supplying pressurised hydraulic fluid to the slot 98, the vanes 86 will remain in the retracted position for the entire revolution of the rotor 60.

WO 2005/005782 PCT/AU2004/000951 14 When supply of the pressurised pilot fluid to the slot 98 is ceased, and preferably the slot 98 is placed in fluid communication with low pressure hydraulic fluid as the ends of passageways 96 come into register with slot 98, the pressurised hydraulic fluid in passageways 96 and 90 is released in those passageways. Consequently, the pressurised 5 fluid no longer acts on engagement pin 88. Return spring 100 (see Figure 4) then acts to return the engagement pin 88 such that its rear face comes into contact with plug 92. In this position, the engagement pin 88 is no longer in engagement with the vane 86. Consequently, the vane 86 can move (under centrifugal force) to the extended position when the vanes pass through the rise regions. Although a spring 100 is shown in Figure 4 to return 10 the engagement pin to the non-engaged position, it may be possible to orient the engagement pin such that centrifugal force causes the engagement pin to return without having to provide a return spring. Although the vanes will typically move from the retracted position to the extended position automatically, by virtue of centrifugal force caused by rotation of the 15 rotor, when the engagement pins 88 are withdrawn, it may be advantageous to provide some means to assist in or facilitate movement of the vanes from the retracted position to the extended position. In usual practice, such means takes the form of hydraulic pressure acting on a vane or, more frequently, on a pin which then acts on a vane. For example, an oil gallery 102 may be provided around the drive shaft (see Figure 3). Oil gallery 102 may be 20 provided by fitting, such as by means of press fitting, a sleeve having an appropriate gallery space preformed therein into the central aperture of the rotor. Oil gallery 102 is in fluid communication with the underneath part of the vane pins 87 (refer Figures 2 and 5). Oil gallery 102 is also in communication with outlet pressure or some other elevated pressure source. 25 In normal use of the hydraulic machine shown in Figures 2 to 7, with the vanes extending as they enter the rise regions and retracting as enter the fall regions, the fluid in the undervane passages associated with the vanes that are retracting is compressed and is forced into oil gallery 102. At the same time, the vanes that are extending have the pressure in their undervane passages decreasing. Consequently, hydraulic fluid is drawn out 30 of the oil gallery into those undervane passages. Generally, during normal use, an equal number of vanes are extending and retracting at any one time, thereby maintaining a generally equilibrated pressure in oil gallery 102. at outlet pressure or some other elevated pressure level.

WO 2005/005782 PCT/AU2004/000951 15 When it is desired to maintain the vanes in the retracted position, the control system associated with the hydraulic machine supplies pressurised pilot hydraulic fluid to slot 98 which, in turn, activates the retaining means as described above. As the vanes are retracted by rotation through the fall regions, the engagement pins 88 are activated to retain 5 the vanes in the retracted position. When it is desired to operate the hydraulic machine such that the vanes work the hydraulic fluid as they pass through the rise and fall regions, the engagement pins 88 are disengaged Figures 8 to 11 show a hydraulic machine in accordance with another 10 embodiment of the present invention. Figure 8 shows a front view of a ring rotor, vane and pressure plate assembly of the pump. In Figure 8, the assembly 201 of a hydraulic pump includes a body 202, an elliptical chamber 203 located within the body 202, inlets 204 through which hydraulic fluid may be introduced into the chamber 203, outlets 205 from which hydraulic fluid may leave the chamber 203, a slotted rotor 206 rotatable within the 15 chamber 203, a drive shaft 207 extending through the rotor 206, a plurality of vanes 208 (only some of which have been labelled) located within each slot 209 (only some of which have been labelled) of the slotted rotor 206, and openings 210 for bolts. Passages 211 are located under each vane 208. The assembly 201 includes an inlet for hydraulic fluid (not shown) that can be connected to an appropriate hydraulic line, in accordance with 20 conventional practice in this art. Figures 9 to 11 show another part 220 of the hydraulic pump. Assembly 201 and part 220 are joined together to form the hydraulic pump. For clarity, some details have been omitted from Figures 8 to 11, althought the omitted parts relate to features known to the person skilled in this art.. Part 220 has bolt openings 210 in the body 202 that coincide 25 with the openings 210 of assembly 201 so that part 220 may be bolted face to face to the assembly shown in Figure 8 in a fluid tight manner. Part 220 has an outlet 223 that is threaded for attachment to a hydraulic line (not shown). Outlet 223 communicates with branched fluid passages 205a, 205b which, in turn, communicate with kidney shaped openings 222a, 222b. Openings 222a, 222b are 30 positioned in register with respective openings 205 on the pump assembly 201 shown in Figure 8 when assembly 201 and part 220 are joined together. Part 220 includes kidney shaped recesses 224a, 224b that are in fluid communication with the inlet of the machine and in fluid communication with the suction quadrants 212a and 212b of assembly 201.

WO 2005/005782 PCT/AU2004/000951 16 Since the chamber 203 is elliptical and the rotor is generally cylindrical, the space between the inner wall of the chamber and the outer wall of the rotor defines two lobes that form the rise, fall and major dwell regions 260a and 260b (see Figure 8). Each vane 208 is movable between a retracted position and an extended position relative to a 5 respective slot 209. The vanes 208 can only extend whilst within the rise regions. Vanes 290 and 291, for example, are in the extended position. Vanes 292 and 293, for example, are the retracted position. In the retracted position the vane 208 is unable to work hydraulic fluid introduced into the chamber 203, whereas in the extended position the vane 208 is able to work hydraulic fluid introduced into the chamber 203. The rotor includes under vane 10 passages 211 under each of the vanes. A circular groove 231 in part 220 is in fluid communication with high pressure fluid in accordance with conventional practice to deliver pressurised hydraulic fluid to passage 211. This assists in moving the vanes to the extended position during normal operation of the machine. A spool valve 250 is provided to allow venting of the under vane pressure by 15 allowing passage 232 to communicate with inlet recess 224b when it is desired to retain the vanes in the retracted position. This is achieved by pilot pressure from pilot inlet 216 passing along passage 242 and exciting spool valve 250 to allow fluid communication between passage 232and inlet recess 224b. When pilot pressure is released, spring return 234 returns spool valve to a position where passage 232 is in fluid communication with 20 pressurised fluid. As will be understood, this also disconnects fluid communication between passage 232 and recess 224b. The machine shown in Figures 8 to 11 also includes a gallery 230 that prevents the spool moving to a position where passage 232 can communicate with the inlet recess 224b when under normal operation. This feature is optional. The machine has a communication gallery 240 for selectively delivering 25 hydraulic fluid to the vane retaining passage 241 to operate the retaining means associated with each of the vanes 208. When the vane retaining passage 241 is pressurised with hydraulic fluid, for example by pressurised hydraulic fluid delivered from a pilot line via pilot inlet 216 and the vanes 208 are in a minor dwell section 260 of the chamber 203, the fluid clamps the vanes 208 within the respective slots 209. The mechanism for achieving 30 this will be described in more detail with reference to Figures 12, 15 and 16. When the vane retaining passage 241 is pressurised, hydraulic fluid is directed to a face of the vane 208 and forces the vane 208 against one or more surfaces defining the slot 209. This retains the vanes in the retracted position. More specific details WO 2005/005782 PCT/AU2004/000951 17 of how the vanes are retained in the retracted position will now be described with reference to Figures 12, 15, 16 and 17. In one embodiment shown in Figure 12, a passage 263 extends through the rotor 206 into passage 264 to a surface defining each slot 209. The rear end 263a of passage 5 263 can be placed in fluid communication with vane retaining passage 241 to create pressurised hydraulic fluid against a side face of vane 208 to force vane 208 against slot 209 to restrain the vane 208 against slot 209. In the embodiment shown in Figure 15, a respective groove 262 extends longitudinally along a surface defining each slot 209 and the vane retaining passage 241 supplies each groove 262 with hydraulic fluid. In the 10 embodiment shown in Figure 16, a respective groove 261 extends longitudinally along a face of each vane 208 (only some of which have been labelled) and the vane retaining passage 241 supplies each groove 261 with hydraulic fluid via passages 263, 264. When pressurised hydraulic fluid is supplied to passages 263,264 shown in Figures 12, 15 and 16, the pressurised hydraulic fluid applies a force against the side of the vane 208 and this force 15 acts to clamp the vane in the retracted position. The grooves 261, 262 shown in Figures 15 and 16 act to increase the area on which the hydraulic force acts, thereby increasing the retaining effect. Grooves 261 and 262 suitably extend along the entire axial extent of the vane and slot, respectively as shown in Figures 15a and 16a. Figures 12, 15 and 16 have many features in common and like parts are denoted by like reference numerals. 20 In one mode of operation the hydraulic machine may be used as a pump. In another mode of operation the hydraulic machine may be used as a motor. A hydraulic circuit showing how the machine may be used as a pump is shown in Figure 13. The figure shows a safety pressure relief valve 280 (V1) for the clamping pressure supply, a solenoid valve 281 (V2) which selects whether the pump is on 25 or off (i.e. whether the vanes are extended or retracted and clamped), spool valve 250 (V3) which is controlled by remote pilot fluid (oil), a pressure responsive shuttle valve 282 (V4), rotor 206, an enlarged view of a section of the rotor, 206, a slot 209, section 262 of passage 240, and section 234 of passage 230. In order to turn the pump on such that fluid may be circulated, pilot hydraulic 30 fluid is directed by solenoid valve 281 (V2) (in a spring offset mode) to under vane passage 230, 234 for introducing hydraulic fluid under each of the vanes 208, so as to move the vanes 208 to the extended position when located in a dwell section 260. In order to prevent circulation of the fluid, solenoid valve 281 (V2) is armed (mechanically, piloted or electrically), hydraulic fluid is directed to passage 240, 262, valve 250 moves to a spring WO 2005/005782 PCT/AU2004/000951 18 return position, hydraulic fluid is drained from under the vanes 208 and the vanes 208 are clamped within the slots 209 once the vanes 208 leave the dwell sections 260. When solenoid valve 281 (V2) is disarmed the spring offset condition returns the vanes 208 to the extended position under moderate pressure to prevent shock. When the setting pressure of 5 valve 250 is reached, then the valve 250 is reset to allow the main pump pressure to be directed under the vanes 208 when the main pump pressure exceeds the low pilot and clamping pressure. Pressure responsive shuttle valve 282 (V4) prevents loss of the under vane pressure. It will be appreciated that hydraulic pumps may not necessarily require hydraulic pressure to be applied under the vanes (or under the vane pins) because 10 centrifugal force typically causes the vanes to extend when the retaining means are released. A hydraulic circuit showing how the machine may be used as a motor is shown in Figure 14. The figure shows a safety pressure relief valve 280 (Vl) for vane retaining passage 240, a solenoid valve 281 (V2) which selects whether the pump is on or off, valve 250 (V3) which is controlled by pilot hydraulic fluid, pressure responsive shuttle 15 valves 282 (V4), 283, rotor 206, an enlarged view of a section of the rotor, 206, a slot 209, section 262 of passage 240, and section 234 of passage 230. The motor operates basically the same way as the pump in Figure 13. For convenience, Figures 13 and 14 show drain and an under vane pressure source. Figure 17 shows another embodiment of the pin retaining means that can be 20 used with the hydraulic machine shown in Figures 2 to 7. In Figure 17, the rotor 206 is provided with a plurality of slots 1710 that have an enlarged slot portion 1711 and a narrower outer slot portion 1712. Vanes 1701 are positioned in each slot. Each vane 1701 has an enlarged lower portion 1701a that fits into enlarged slot portion 1711. The enlarged vane portion 1701a prevents removal of the vane from the slot by movement in the radial 25 direction. As can be seen from Figure 17, a chamber 1703 is formed between the upper surface of the enlarged portion 1701a of the vane and the surface 1714 of the enlarged portion of the slot. Another chamber 1704 is formed between the floor of the enlarged portion 1711 of the slot and the lower surface of the vane 1701. The rotor 206 has a passage 1710 formed therein. Passage 1710 can come 30 into register with a source of pressurised pilot hydraulic fluid. Passage 1710 is in fluid communication with another passage 1706 that, in turn, is in fluid communication with another passage 1715. Plugs 1716 and 1717 close respective ends of passages 1706 and 1715.

WO 2005/005782 PCT/AU2004/000951 19 Passage 1715 opens into chamber 1703. Passage 1705 opens into chamber 1704. Ball 1709 acts a a shuttle valve in a manner known to the person skilled in the art. In particular, if there is high pressure in passage 1705 and low pressure in orifice plug 1707, then ball 1709 is held against the seat of orifice 1707 as a check and fluid can move from 5 chamber 1704 to chamber 1703. If high pressure is applied to orifice 1707 via passage 1710 (such as would occur when it is desired to actuate the retaining means), the ball 1709 sits against the seat of gallery 1705 and pressure is applied to chamber 1703 to retain the vane in the retracted position (and potentially to drive the vane into the retracted position). 10 In the embodiment of Figure 17, the vane retaining passages are progressively and sequentially actuated as the vanes of each passage move into the minor dwell region. This is shown in Figure 17, which shows vane 1723 being fully retracted and clamped by the vane retaining means, vane 1721 moving through the fall region (and hence being retracted) but not yet clamped and vane 1719 moving through the major dwell region. 15 To achieve this, a slot of relatively small circumferential extent, similar to slot 98 shown in Figure 2, is used to pressurise the vane retaining passages with pressurised pilot fluid. In normal operation when the retaining means are not operated, fluid flows from chamber 1704 to chamber 1703 through passages 1705 and 1706 to maintain hydraulic balance and ensure that the force on the top of the vane is not increased due to the larger 20 base of vane 1701, as is known in this art. Figures 18 to 22 show another embodiment of the present invention using a different retaining means to retain the vanes in the retracted position. The embodiment shown in Figures 18 to 22 has a number of features similar to the embodiment shown in Figures 2 to 7. For convenience, like reference numerals will be used to denote like parts 25 and further description of those parts will not be provided. The embodiment shown in Figures 18 to 22 does not use a movable engagement pin or detent pin to retain the vanes in the retracted position. Instead, the embodiment shown in Figures 18 to 22 uses hydraulic fluid pressure to hydraulically clamp the vanes in the retracted position. To this end, the rotor 60 has a plurality of passages 30 drilled therein. As best seen in Figure 20, the passages include a passage 300 that opens in a side wall of slot 84. As can be seen from Figure 20, passage 300 extends obliquely to the radially extending slot 84. Passage 300 is in fluid communication with another passage 302 that extends inwardly in a generally radial direction. A check valve 304 is mounted in an inner part of passage 302. Check valve 304 allows oil to flow through passage in 302 in the WO 2005/005782 PCT/AU2004/000951 20 direction towards passage 300. However, oil flow in the reverse direction is not permitted by the check valve 304. Check valve 304 acts as a non-return valve in a manner known to the person skilled in the art. Suitable check valves may be purchased from many suppliers. An inner part of passage 302 is in fluid communication with a longitudinal 5 passage 306 (best shown in Figures 21 and 22). Passage 306 comes into register with a slot that communicates pressurised pilot hydraulic fluid when it is desired to retain the vanes in the retracted position. Passage 300 is plugged by plug 308 and passage 302 is plugged by plug 310. When it is desired to retain the vanes in the retracted position, pressurised 10 pilot hydraulic fluid is provided to passages 306, 302 and 300. The pressurised hydraulic fluid attempts to leave passage 300 and, in doing so, comes into contact with a sidewall of the vane 86. The pressurised pilot hydraulic fluid applies a force against the vane 86, normal to the face of the vane. As a result, the vane 86 is pressed against the opposed wall of the slot 84. This acts to retain the vane in the retracted position. 15 When the pressurised pilot hydraulic fluid is removed from passage 300, the hydraulic clamping force is removed and the vanes can again operate normally. The embodiment shown in Figures 18 to 22 is suitable for use with smaller hydraulic pumps and motors because the centrifugal force acting on the vanes in smaller pumps and motors is lower. The embodiment of Figures 18 to 22 is also similar to the 20 embodiment of Figures 8 to 17, except that the embodiment of Figures 8 to 17 does not include under vane pins. Figures 23 to 25 show a further embodiment of the present invention. The embodiment shown in Figures 23 to 25 has a number of features in common with the embodiment shown in Figures 2 to 7. For convenience, like reference numerals will be used 25 to refer to like parts and further description of those like parts will not be provided. In the embodiments shown in Figures 23 to 25, the vanes 86 are mounted to the rotor 60 by use of an undervane pin 340. Undervane pin 340 is slidably mounted in pin opening 342. The lower end of pin opening 342 is in fluid communication with oil gallery 102.. Undervane pin 340 includes a T-shaped head 344 that is fitted into a complementary 30 shaped recess formed in vane 86. In this fashion, vane 86 and undervane pin 342 move together. As best shown in Figure 24, undervane pin 342 is provided with a recess 346. Recess 346 is particularly a tapered recess having walls that taper outwardly.

WO 2005/005782 PCT/AU2004/000951 21 An engagement pin 348 is positioned inside passageway 350. Passageway 350 comes into register with a slot that provides for fluid communication of pressurised pilot hydraulic fluid. A screw plug 352 having an opening therethrough is screwed into the end of passage 350 in order to retain the engagement pin 348 in passageway 350. A return 5 spring 354 is mounted between the engagement pin 348 and a shoulder 356 formed near the end of passageway 350. A further passage 358 having a check valve 360 and a screw in plug 362 is provided to enable hydraulic fluid to move from either the chamber at system pressure or underneath the vane 86 into the oil gallery 102 positioned under the under vane pins 340. 10 This allows the oil gallery 102, which is located under the under vane pins and hence under the vanes, to always contain pressurised hydraulic fluid during use of the machine. The machine is preferably arranged such that a check valve is always positioned in fluid communication with the pressurised regions of the chamber during normal use. In this manner, system hydraulic pressure acts on pin 340 to provide appropriate pressure balance 15 on the vane and to ensure that the vane remains in contact with the chamber wall whilst travelling along the rise regions. Other known arrangements, such as using annular grooves, may also be used to supply system hydraulic pressure to under the vane pins 340. Figure 24 shows operation of the apparatus in the normal mode in which the vanes can move between the retracted and extended positions. Figure 25 shows the 20 apparatus in the mode of operation where the vanes are retained in the retracted position. In order to retain the vanes in the retracted position, the control system is actuated to pass pressurised pilot hydraulic fluid through plug 352 to passage 350. The pressurised pilot hydraulic fluid forces the engagement pin 348 to move against the bias of the return spring 354 and into recess 346 in the undervane pin 340. Due to the complementary tapered 25 shape of the recess in 346 and the engagement pin 348, it can be ensured that the vane is retracted below the diameter of the minor dwell. It is advantageous to retract the vane below the minor dwell diameter to ensure that the vane never contacts the chamber wall while pinned in place. If it did, it would gouge the chamber wall. The taper assists in retracting the vane below the minor diameter so contact with the chamber wall while pinned can never 30 occur. A further advantageous feature arising from the complementary tapered shape of the recess 346 and the engagement pin 348 is that the vane 86 does not need to be in a fully retracted position in order to be properly retained. If the vane 86 is not in the fully retracted position, the tapered head of engagement pin 348 engages with the tapered wall of recess 346. As the engagement pin 348 is driven into the recess 346 by virtue of the pressurised WO 2005/005782 PCT/AU2004/000951 22 pilot hydraulic fluid, the undervane pin 340 is forced to move downwardly, which consequently forces the vane 86 to move downwardly to the fully retracted position. A groove (not shown) on pin 340 allows oil to escape from the spring side of the engagement pin 348 upon actuation. If the groove runs towards the T-head side of the pine 340, the 5 pump can be unloaded at high working pressures. If the groove runs to the other end of pin 340 it can be unloaded only at low working pressure. Alternately, holes could be drilled through rotor 60 to achieve the same effect. When the pressurised pilot hydraulic fluid is removed from passageway 350, the return spring 354 causes the engagement pin 348 to be moved out of engagement with 10 the undervane pin 340. Thus, the vane 86 is then free to move to the extended position as the rotor passes into the rise regions. Figures 26 to 30 show an embodiment that has a number of similarities to that shown in Figures 23 to 25. For convenience, like features will be denoted by like reference numerals. 15 Figure 26 shows an end view of a rotor 60 in accordance with the further embodiment of the invention. As best shown in Figures 27 to 30, vanes 86 are slidably affixed in slots 84 by use ofundervane pins 340 having a T-shaped head 344. The body of the rotor 60 is also provided with a first passage 380 and a second passage 382. An engagement pin 384 is positioned in first passage 380. 20 Engagement pin 340 is provided with a bore 386 that passes through the engagement pin 340. Bore 386 defines, at one end, a tapered recess 388 that engages with a complementary shaped tapered head on the engagement pin 384. As can be seen from Figures 27 to 30, engagement pin 384 is not provided with a return spring. In order to retain the vanes 86 in the retracted position, pressurised pilot 25 hydraulic fluid is supplied via passage 380. This forces the engagement pin 384 to move such that its tapered head fits into the tapered recess 388 on undervane pin 340. In order to disengage the engagement pin 384, the pressurised pilot hydraulic fluid flow to passage 380 is stopped and pressurised pilot hydraulic fluid then sent to passage 382. The pressurised hydraulic fluid travels along passage 382, through bore 386 and thereafter engages with the 30 head of engagement pin 384. This causes engagement pin 384 to move out of the tapered recess 388. This then allows the vane 86 to move between the retracted and extended position. Travel of the pin 384 away from undervane pin 340 is limited by appropriate shaping of the passage 380. The shape of passage 380, together with the engagement pin WO 2005/005782 PCT/AU2004/000951 23 384, acts as a check valve to prevent flow of pressurised hydraulic fluid from passage 382 through all of passage 380. Figures 31 to 35 show an embodiment of the invention that includes alternative means for draining hydraulic fluid from the undervane passages, in particular 5 from the passages under the under vane pins. In this regard, it will be appreciated that, as all the vanes of the rotor become locked down when it is desired to retain the vanes in the retracted position, any hydraulic fluid positioned under the vane pins must be able to be vented from under the vane pins. The embodiment of Figures 31 to 35 provides one way of achieving this. As shown in Figure 31, the rotor 60 having a plurality of radially extending 10 slots 84 also defines a plurality of raised lands 400 positioned between the slots 84. As best shown in Figure 33, oil gallery 102 is positioned to receive oil from the undervane pin passages in accordance with description provided hereinabove in this specification. When all of the vanes progressively move to the retracted position and are 15 locked down when the hydraulic machine shown in Figures 31 to 35 is operated in a mode where all of the vanes are retracted, pressure will build up in oil gallery 102 as each of the vanes moves to and is retained in the retracted position. If the oil in gallery 102 is not vented from the undervane pin passages sufficiently quickly enough, damage to the vanes, the detent pins and/or the chamber could occur. To this end, the raised land 400 as shown in 20 Figures 32 to 35 is provided with a passage 402 that has a plug 404 at its outer end. A further passage 406 having a plug 408 at its outer end is also provided, with passages 402 and 406 being in fluid communication. A further passage 410 is formed in the rotor in the space between the vanes. Passage 410 is in fluid communication with the spline oil gallery, which opens into and drains to a low pressure region of the pump such as the splined section 25 of the drive shaft in most pumps. The spline may have a slot formed therein or have one or more splines removed to enable oil to flow along the splined section of the drive shaft. Passage 410 includes an enlarged portion 412. In this section a spool valve 414 is provided. Spool valve 414 includes a closed head 416, a passage 418 and another passage 420. Passage 420 is generally in alignment with passage 410. As can be seen from 30 Figure 33, passages 418 and 420 are in fluid communication with each other. A spool plug 422 closes the enlarged portion 412 of passage 410. A further passage 424 is provided, which passage 424 can move into register with a source of pressurised pilot hydraulic fluid. Passage 424 is in fluid communication with passage 426. A plug 428 closes the outer end of passage 426. A further passage 430 WO 2005/005782 PCT/AU2004/000951 24 extends from passage 426 and opens into the enlarged region 412 of passage 410. Passage 430 is closed by plug 431. When no pressurised pilot hydraulic fluid is applied to passage 424, the spool valve adopts the position shown in Figure 34 due to centrifugal or spring force. In this 5 position, passage 406, which is in fluid communication with the undervane oil gallery 102, is closed by the body of spool valve 414. Thus, no fluid can flow from the undervane pin gallery 102 to the spline gallery. Indeed, in normal operation, this is not required because the number of vanes moving into the retracted position is equalled by the number of vanes moving out of the retracted position, thereby maintaining an essentially constant volume of 10 undervane pin passages in contact with the undervane pin oil gallery 102. However, as the vanes are locked in the retracted position, the number of vanes moving into the retracted position progressively increases until all vanes are in the retracted position. It will be understood that this has the effect of reducing the combined volume of the undervane oil gallery 102 and the undervane passages (by virtue of the vanes 15 moving down to reduce the volume of the undervane passages). Thus, it is necessary to vent some of the oil contained in the undervane passages. When the vanes are to be moved into the retracted position, pressurised pilot hydraulic fluid is supplied to actuate the retaining means, which may be any of the retaining means described in this specification. At the same time, pressurised hydraulic fluid is 20 supplied to passage 424. Due to the configuration of passages 424, 426 and 430, pressurised pilot hydraulic fluid impinges on the closed head 416 of spool valve 414 and forces the spool valve to move from the position shown in Figure 34 to the position shown in Figure 35. As a consequence, passage 420 through the spool valve 414 comes into register with passage 406. This also has the effect of opening passage 410 to the flow of 25 hydraulic fluid from the undervane oil gallery 102. Thus, the excess volume of oil in the undervane pin passages can be vented through passages 402, 406, 420, 418 and 410 into the oil gallery of the spline. As mentioned above, the splined section of the drive shaft is in fluid communication with the inlet region of the machine and thus the splined section of the drive shaft is a region of low pressure. If the spool 416 is of constant diameter as shown, the 30 pump can only be put into neutral mode if the pilot pressure exceeds the oil gallery 102 pressure which is usually very near outlet pressure. In certain applications it would be desirable to neutral the pump while it is under load. To that end, the spool 416 may have a T-shaped cross section with the larger diameter pointing radially outward and on which, the pilot pressure acts. If gallery 102 pressure is prevented from acting on the top side (the WO 2005/005782 PCT/AU2004/000951 25 larger diameter) be some means such as a simple o-ring seal, then the pilot pressure needed to actuate spool 416 could be significantly lower than outlet pressure, dependent on the areas of the spool diameters. When pressurised pilot hydraulic fluid is removed from passage 424, the 5 spool valve 414 can move from the position shown in Figure 35 to the position shown in Figure 34 by centrifugal force. Alternatively, a return spring may be provided. Figure 36 shows an alternative embodiment that is similar to that shown in Figures 23 to 25 but in which the position of the check valve is different. In Figure 36, a passage 440 is drilled in the raised land 400 of rotor 60 located between adjacent radial slots 10 84 of the rotor. A check valve 442 is mounted in passage 440 and a check plug 444 is positioned to maintain the check valve 442 in place. Check valve 442 may be any check valve known to the skilled person to be suitable for use in hydraulic vane machines. Check plug 444 has an opening 446 therethrough. Check valve 442 allows hydraulic fluid to flow downwardly and into oil gallery 102 (not shown) but it does not allow hydraulic fluid to 15 flow in the reverse direction. Other features of the embodiment of Figure 36 that are not shown in Figure 36 may be the same as shown in Figures 23 to 25. Figures 37-39 show a further alternative embodiment of the present invention. In the apparatus shown in Figures 37-39, engagement pin 600 is mounted in passage 602 formed in the rotor 60. Passage 602 has a screw in plug 604 positioned in an 20 end thereof to retain the engagement pin 600 in the passage. A return spring 606 is used to bias the engagement pin 600 away from the undervane pin 340. Undervane pin 340 includes a tapered recess 346 that is adapted to receive a complementary shaped tapered head on pin 600. When it is desired to actuate the engagement pin 600 to retain the vanes 86 in 25 the retracted position, pressurised pilot hydraulic fluid is supplied to passage 602, which forces engagement pin 606 to move into tapered recess. 346 in undervane pin 340. At the same time, bore 608 in the engagement pin 600 comes into alignment with bore 610 formed in the rotor. Bore 610 has a plug 611 closing its outer end. In this fashion, pressurised fluid in undervane pin gallery 102 can be vented from the undervane pin gallery 102. 30 Figures 40 to 42 show a further embodiment in accordance with the present invention. In these figures, vane pin 340 has a T-shaped head 344 that fits into a complementarily-shaped recess 702 in vane 86 to thereby affix the vane 86 to the vane pin 340.

WO 2005/005782 PCT/AU2004/000951 26 An engagement pin 348 is used to selectively retain the vane 86 in the retracted position. The engagement pin essentially operates along the same principle as the engagement pin of Figures 23 to25. Accordingly, like reference numerals to those used in Figures 23 to 25 will be used in Figures 40 to 42 in relation to the engagement pin operation 5 and arrangement and further description of these features need not be given. The embodiment of Figures 40 to 42 differs from that of Figures 23 to 25 in that passage 358 and ancillary fittings of Figures 23 to 25 are not included in the embodiment of Figures 40 to 42. Instead, vane pin 340 is provided with a passage 700 extending therethrough. The lower opening of passage 700 opens into under vane pin 10 gallery 102. As vane 86 moves from the extended position to the retracted position, especially when the retaining means are operating to retain all of the vanes in the retracted position (whether all vanes are retracted at once or in sequence), pressurised oil in pin gallery 102 can escape via passage 700. When pressure in slot 708 exceeds the pressure in gallery 102, fluid flow is restricted by means of the head 344 and recess 702 acting as a 15 check valve. Thus, fluid in the gallery 102 cannot be vented via passage 700 when the vane is in the inlet or suction region of the pump. Similarly, pressurised hydraulic fluid can be supplied to the gallery 102 to assist in extending vanes 86. Normal operation of a pump similar to that shown in Figures 40 to 42 but without retaining means is well known to the person skilled in the art. 20 During extension of engagement pin 348, hydraulic fluid in chamber 704 that surrounds the tapered head of engagement pin 348 will become pressurised and require venting. To this end, a slot 706 is formed, which slot 706 extends from chamber 704 to slot 708 formed in rotor 60. Slot 706 is preferably formed by recessing the side of the vane pin 340. Alternatively, slot 706 may be formed in the side wall of the vane pin duet that houses 25 the vane pin 340. Figure 43 shows a side view schematic diagram of a power steering pump in accordance with the present invention. Figure 43 is typical of many power steering pumps in that it includes two rotors. In particular, the power steering pump 500 includes a first rotor 502 and a second rotor 504. Rotors 502, 504 are splined via splines 506, 508 to a 30 drive shaft 510. Drive shaft 510 includes a further spline or gear 512 to enable a drive shaft 510 to be driven. The drive shaft 510 is journaled in bearings 514 and 515. The power steering pump 500 includes a first inlet 516 and a second inlet 518. A bypass 520 is provided, which bypass feeds hydraulic fluid back to the inlet.

WO 2005/005782 PCT/AU2004/000951 27 In the power steering pump 500 shown in Figure 43, one rotor operates as a conventional rotary vane pump in which the vanes continuously move between the retracted and extended positions. The other rotor is configured in accordance with the present invention and it allows for the possibility of locking down the vanes into the retracted 5 position when either the power steering pump is running at a speed that will deliver more flow than is required to operate the steering of the vehicle or when the vehicle is operating in a mode where it does not require much flow from the pump to operate the steering (e.g. when the vehicle is driving along a straight road). However, when the power steering pump is required to provide extra flow, the vanes on one of the rotors can be released so that they 10 work the hydraulic fluid and provide the extra flow required. Figure 44 shows a schematic flow and control diagram for controlling operation of the power steering pump 500 shown in Figure 43. In Figure 43, the main pump Pl, which includes rotor 502, has an inlet 518 and an outlet 520. Second pump P2, which includes rotor 504 has an inlet 516 and an outlet 522. 15 Outlet line 520 from main pump P1 has a flow orifice 524. As fluid flows along outlet line 520, it passes through flow orifice 524. Flow orifice 524 causes a pressure drop. The pressure in outlet line 520 measured before the orifice is designated by pressure PR10. The pressure in the outlet line after the flow orifice is designated by pressure PR8. The control system for controlling the operation of the second pump P2 20 includes a spool valve 526. One end 528 of the spool valve detects pressure PR10. The other end 530 of spool valve 526 detects pressure PR8. Additionally, end 530 of spool valve 526 has a spring 532 mounted thereto. Spring 532 has a weight or strength that sets the pressure drop where the second pump cuts in. In operation, as the flow through outlet 520 from the main pump P1 25 increases, for example by virtue of increasing engine revolutions of the motor vehicle, the pressure drop across restriction orifice 524 increases. When the pressure drop across orifice 524 increases to a level where pressure PR10 is greater than the combined pressure PR8 plus the force of spring 532, pressure PR10 in line 534 moves the spool valve 526 to the left against the biasing force of the spring 532. This then results in pressurised pilot hydraulic 30 fluid being provided to the pressurised pilot hydraulic fluid gallery 534 of the second pump P2. This actuates the vane retaining means and the vanes on pump P2 become locked down in the retracted position. A non-return valve 536 is provided in the relevant fluid line. If the flow through outlet 520 drops to a level where the pressure PR10 is less than the total of pressure PR8 plus the biasing force of spring 532 the spool valve 526 WO 2005/005782 PCT/AU2004/000951 28 moves to the right. In this position, the pressurised pilot hydraulic fluid is no longer supplied to gallery 534 and the retraction means are thereby released. At the same time, pilot fluid travels via line 538 to the undervane passages 540. This assists or facilitates movement of the vanes from the retracted position to the extended position as the vanes 5 move into rise regions inside the pump. The flow circuit shown in Figure 44 also includes a phasing valve 540. This valve operates such that as second pump commences pumping operation (by virtue of the vanes moving to the extended position from the locked retracted position), a portion of the outlet fluid from second pump is diverted via line 542 back to inlet 516. This assists in 10 providing a softer start up that imposes less shock on the components. The flow circuit shown in Figure 44 also includes a non-return valve 544 in the outlet line 522 from the second pump P2 and a flow cover or relief 546 that allows for bypass of excess flow from the pump. The flow and control circuit shown in Figure 44 allows for automatic control 15 and operation of the power steering pump shown in Figure 43. In order to demonstrate the benefits of the power steering pump shown in Figures 43 and 44 a modelling study was conducted which shows a graph of flow from the power steering pump plotted against engine speed. As can be seen from Figure 45, the flow from the theoretical standard pump increases with increasing engine speed. This theoretical 20 pump comprises an 11 gallon pump having two rotors. The ideal flow line of Figure 45 represents the minimum flow required to satisfactorily operate the steering of the vehicle. It can be seen, the theoretical standard pump provides flow in excess of the ideal flow from above or approximately 600 rpm engine speed. In comparison, the power steering pump in accordance with the present 25 invention can be operated such that the second pump P2 can effectively be switched off by retaining the vanes in the retracted position once engine speed gets above approximately 1200 rpm. The flow arising from this operation is shown in Figure 45 as single flow P1 only. The area between that line and the theoretical standard pump represents the power savings provided by the power steering pump in accordance with the present invention. 30 Table 1 demonstrates the calculations conducted with respect to the power steering pump in accordance with the present invention. The following assumptions were made when calculating the savings figures: - power steering pump is running 1:1 relative to engine speed; - engine consumes 0.35 gallons per horse power hour; WO 2005/005782 PCT/AU2004/000951 29 - 6.6 lbs in I US gallon; - the pump will be running an average efficiency of 75% - rotors are 6 gallon primary ring and 5 gallon secondary ring - pressures and engine speed data referenced from Mack Truck 5 consultant; - standard power steering pump (comparator) will pump 11 GPM at 1200 rpm running an average efficiency of 75%. Results and Comparison Shown in Table 1, the power steering pump in accordance with the present 10 invention will provide an average saving of 2.2 horsepower (typical highway truck). This power saving will equate to approximately 120 US gallons per 1000 hours of operation for each truck it is fitted to. This is under the assumption that the pump in accordance with the present invention will be replacing a positive displacement pump running 11 GPM at 1200 rpm. 15 Case Study (national per 4000 hours) 7 million trucks running in North America, each truck running approximately 4000 hours per year (average). If the pump power steering pump in accordance with the present invention is fitted to only 25% of these trucks, the annual fuel saving would be 840 million gallons of fuel per annum. 20 Case Study (per vehicle per 4000 hours) USA based on the fuel saving figures will be $480. Australia based on the fuel saving figures will be $1080. Europe based on the fuel saving figures will be $2000. The present invention provides a hydraulic machine that can be operated in 25 an economical mode in situations where conventional hydraulic machines would be consuming unnecessary power. The hydraulic machine of the present invention can be manufactured using existing manufacturing facilities. The hydraulic machine of the present invention allows for selectively retaining the vanes in the retracted position. The retaining means most suitably interact with the vanes when the vanes are in the retracted position to 30 maintain the vanes in the retracted position. The retaining means are capable of retaining the vanes in the retracted position even as the vanes pass through the rise regions, the major dwell regions and the fall regions. Most suitably, the retaining means interact with the vanes as hydraulic fluid passages that operate the retaining means associated with each vane each come into fluid communication with a source of pressurised hydraulic fluid. The retaining WO 2005/005782 PCT/AU2004/000951 30 means may be selectively actuable by an operator of the hydraulic machine or by an automatic control means that responds to situations where low flow or low power is required.. Preferred embodiments of the machine also allow for positive driving of the vanes from the retracted position to the extended position in the dwell regions by virtue of 5 applying pressurised hydraulic fluid to the undervane passages. For start-up, known hydraulic vane motors typically require an external force to extend the vanes. Springs are normally used for initial start-up and then system pressure is directed under the vanes to maintain pressure equilibrium. In the present invention, however, the remote pilot fluid extends the vanes and eliminates the need for springs. 10 In this way, the hydraulic machine of the present invention may be operated such that hydraulic fluid is not pumped excessively or unnecessarily, in the absence of expensive space invasive clutches or other disconnecting means. The hydraulic pump or motor is suitable for use in, for example, earth moving, industrial and agricultural machines, waste collection vehicles, fishing trawlers, 15 cranes, and vehicle power steering systems, as well as in air compressors and air conditioners.

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Claims (31)

1. A hydraulic machine having: a body having a chamber, an inlet for introducing hydraulic fluid into the chamber, 5 an outlet through which hydraulic fluid leaves the chamber, a rotor rotatably mounted within the chamber, the chamber and the rotor being shaped to define one or more rise regions, fall regions and dwell regions between walls of the chamber and the rotor, a shaft extending from the rotor, 10 the rotor having a plurality of slots, a plurality of vanes located such that each slot of the rotor has a vane located therein, each vane being movable between a retracted position and an extended position wherein in the retracted position, the vane is unable to work the hydraulic fluid 15 introduced into the chamber and in the extended position the vane is able to work the hydraulic fluid introduced into the chamber, and vane retaining means being selectively actuable such that, when actuated, the vane retaining means retains the vanes in the retracted position.

2. A hydraulic machine as claimed in claim 1 further including an under vane 20 passage for selectively receiving pressurised hydraulic fluid to facilitate moving the vanes located in a dwell region from the retracted position to the extended position.

3. A hydraulic machine as claimed in claim 1 wherein the vane retaining means are selectively actuatable to retain all of the vanes in the retracted position.

4. A hydraulic machine as claimed in claim 3 wherein the vane retaining means 25 retain the vanes in the retracted position for at least an entire revolution of the rotor.

5. A hydraulic machine as claimed in claim 1 the vane retaining means utilises pressurised hydraulic fluid to retain the vanes in the retracted position.

6. A hydraulic machine as claimed in claim 5 wherein the vane retaining means comprises an engagement member movable between a disengaged position and an engaged 30 position in which the engagement member contacts the vane to retain the vane in the retracted position.

7. A hydraulic machine as claimed in claim 6 wherein said engagement member is moved from the disengaged position to the engaged position by pressurised hydraulic fluid. WO 2005/005782 PCT/AU2004/000951 33

8. A hydraulic machine as claimed in claim 6 wherein the engagement member comprises an engagement pin that engages with a side wall of the vane or an engagement ball that engages with a side wall of the vane.

9. A hydraulic machine as claimed in claim 8 wherein the engagement pin or 5 engagement ball engages with a recess in the vane to retain the vane in the retracted position.

10. A hydraulic machine as claimed in claim 5 wherein the vane retaining mean comprises a vane retaining passage for receiving pressurised hydraulic fluid, the vane retaining passage directing the pressurised hydraulic fluid to at least one face of the vane 10 such that the pressurised hydraulic fluid forces the vane against at least one face of the respective slot.

11. A hydraulic machine as claimed in claim 10 wherein the vane retaining passage comprises a passage extending through the rotor and directing hydraulic fluid onto a radially extending face of each vane. 15

12. A hydraulic machine as claimed in claim 11 wherein the vane retaining passage extends from each of the vanes to a port at a periphery of the body.

13. A hydraulic machine as claimed in claim 5 wherein the vanes are affixed to the rotor by a vane pin and the vane retaining means comprises an engagement member movable between a disengaged position and an engaged position in which the engagement 20 member contacts the vane pin to retain the vane in the retracted position.

14. A hydraulic machine as claimed in claim 13 wherein the engagement member comprises an engagement pin that engages with the vane pin or an engagement ball that engages with the vane pin.

15. A hydraulic machine as claimed in claim 2 wherein the under vane passage 25 extends from under each of the vanes to the outlet and the under vane passage is pressurised with hydraulic fluid from the outlet.

16. A hydraulic machine as claimed in claim 2 wherein the under vane passage communicates with the inlet such that when the vane retaining means is actuated, hydraulic fluid drained from under the vanes is directed to the inlet to allow the vanes to be retained in 30 the retracted position.

17. A hydraulic machine as claimed in claim 2 wherein the under vane passage is pressurised with pressurised hydraulic fluid from a pilot source of pressurised hydraulic fluid. WO 2005/005782 PCT/AU2004/000951 34

18. A hydraulic machine as claimed in claim 1 wherein the inlet is branched and has one or more openings into the chamber, adjacent a start of each dwell region.

19. A hydraulic machine as claimed in claim 1 wherein the outlet is branched and has one or more openings from the chamber, adjacent an end of each dwell region. 5

20. A hydraulic machine as claimed in claim 2 further comprising control means to control flow of pressurised hydraulic fluid to the under vane passage.

21. A hydraulic machine as claimed in claim 20 wherein the under vane passage comprises an under vane pin passage.

22. A hydraulic machine as claimed in claim 4 further comprising flow control 10 means to control flow of pressurised hydraulic fluid to the vane retaining means.

23. A hydraulic machine as claimed in claim 22 wherein the control means includes a control valve for directing hydraulic fluid from the outlet to under the vanes when the vane retaining means is not actuated, and directing hydraulic fluid from under the vanes to the inlet when the vane retaining means is actuated. 15

24. A hydraulic machine as claimed in claim 1 wherein each vane has an enlarged base, each slot has an enlarged portion within which the base may move when the vane is extending or retracting, and each slot has a restriction through which the base may not move when the vane is extending.

25. A hydraulic machine as claimed in claim 1 wherein the body comprises two 20 or more attachable pieces

26. A method for retaining vanes of a hydraulic vane pump or motor in a retracted position within a slotted rotor of the pump or motor, the pump or motor including a chamber and a rotor mounted for rotation within the chamber, the chamber and the rotor being shaped to define one or more dwell regions between walls of the chamber and the 25 rotor, the rotor having a plurality of slots and a plurality of vanes located such that each slot of the rotor has a vane located therein, each vane being movable between a retracted position and an extended position wherein in the retracted position, the vane is unable to work the hydraulic fluid introduced into the chamber and in the extended position the vane is able to work the hydraulic fluid introduced into the chamber wherein the method includes 30 the steps of: operating the pump or motor such that the vanes move to the extended position when passing through the dwell regions and the vanes move towards or into the retracted position when passing out of the dwell regions and selectively actuating vane retaining means to retain the vanes in the retracted position. WO 2005/005782 PCT/AU2004/000951 35

27. A method as claimed in claim 26 wherein the vanes are retained in the retracted position by the vane retaining means for at least an entire revolution of the rotor.

28. A method as claimed in claim 26 further including the step of draining hydraulic fluid from under the vanes as the vanes move towards the retracted position. 5

29. A method as claimed in claim 26 further comprising releasing the retaining means to allow the vanes to move to the extended position as the vanes enter the dwell regions.

30. A method as claimed in claim 26 further comprising applying hydraulic fluid pressure to activate the vane retaining means to retain each of the vanes in the retracted 10 position.

31. A method as claimed in claim 28 wherein the step of draining hydraulic fluid from under the vanes as the vanes move towards the retracted position comprises draining hydraulic fluid from under pins positioned under the vanes. 15 DATED this 15th day of July 2004 Norman Ian Mathers By His Patent Attorneys 20 CULLEN & CO.