Patent Application
20120134865
The invention relates to a rotary mechanism, such as a pump, for propelling fluid. The rotary mechanism can also be driven by the fluid and in this arrangement acts as a motor.
There are many types of pump that are known in the art, for example, centrifugal, impeller, piston and gerotor pumps. Another common type of pump is a gear pump. A gear pump typically includes two spur gears located in a casing having an inlet and an outlet. As the gears rotate they separate on the intake side of the pump creating a void and suction, which draws fluid into the casing. Fluid is carried from the inlet by the gear teeth to the outlet where the fluid is discharged by the meshing of the gear teeth. Gear pumps have very tight tolerances and high operational speeds to prevent fluid from leaking back to the inlet side of the pump.
An example of a gear pump is disclosed in GB381,148. That pump includes upper and lower meshed gear elements, wherein the lower gear element includes an arrangement of bores that connect the outer extremity of the gear teeth and the troughs formed between the teeth to the interior of the gear wheel. The pump also includes an adjustable valve member in the interior of the gear wheel. Fluid is fed to the gear pump from a tangentially arranged fluid inlet port and exits the pump via a tangentially arranged fluid output port.
The arrangement is such that fluid from the high pressure side of the pump can enter the radial passages to enter the interior of the gear member and the adjustable valve member is arranged to redirect the fluid, for example to the low pressure side of the pump. The purpose of this device is to enable fluid trapped between the meshing teeth to be returned to the low pressure side of the pump without heating the fluid by compression, which normally occurs when the radial passageways are not provided in a standard gear pump. Alternatively, the trapped fluid can be directed to a secondary circuit, however this provides a very limited feed since the quantity of fluid trapped between the gear teeth is small. This is in part because the gear teeth are of the involute type, which does not provide a well sealed meshing arrangement. Although the direction of flow of fluid entering the gear pump is substantially tangential to the gear wheels, it is in a direction that is opposite to the direction of rotation of the gear wheels. This is not an optimised arrangement.
Accordingly, the invention seeks to provide a new type of pump/and or motor device that to mitigate at least one of the aforementioned problems, or to at least provide an alternative arrangement to known pumps.
According to a first aspect of the invention there is provided a rotary mechanism arranged to propel fluid, such as a pump, and/or to be driven by a fluid, such as a motor, said rotary mechanism including: a rotor assembly having a plurality of piston members distributed about its periphery; a rotary member in peripheral engagement with the rotor assembly, said rotary member having a plurality of piston receiving formations in its periphery for receiving the piston members, the arrangement being such that during rotation of the rotor assembly the piston members move into and out of the piston receiving formations, and a plurality of conduits arranged to connect peripheral portions of the rotary member to an interior portion thereof; a flow separation device including an inlet port for receiving fluid into the rotary mechanism and an outlet port for enabling fluid to exit the rotary mechanism, a first passageway for connecting the inlet port with the interior side of at least one of the conduits formed in the rotary member and a second passageway for connecting the outlet port with the interior side of at least one of the conduits formed in the rotary member wherein the arrangement is such that, in use, the action of withdrawing the piston members from the piston receiving formations draws fluid into the rotary mechanism from the fluid inlet; and wherein the rotary member is rotatable relative to the flow separation device and at least some of the rotary member conduits periodically align with the first and second passageways formed in the flow separation device thereby enabling the fluid received from the inlet to flow outwards towards a first peripheral portion of the rotary member, wherein it is transported to a second peripheral portion of the rotary member by the rotor assembly, and for the fluid to flow away from the second peripheral portion of the rotary member to the outlet port, wherein the flow separation device is constructed and arranged to separate the incoming and outgoing flows.
The invention provides a significant advantage over gear pumps because each of the pistons propels a relatively large volume of fluid into the piston receiving formations, which provides a large throughput of fluid. Since the inlet and outlet ports are formed in the flow separation device the arrangement allows for the inlet and outlet to be arranged substantially axially with respect to the rotary member.
The primary inlet and outlet flows pass through the rotary member and the separation device.
Advantageously the input port can be arranged substantially parallel to the axis of the rotary member and/or rotor assembly. Advantageously the first passage way formed in the flow separation device is constructed and arranged to redirect the incoming flow of fluid through approximately 90 degrees. The flow changes from a substantially axial direction to a substantially radial direction. The flow separation device includes a substantially cylindrical body and the input port is located in an end face thereof and the first passage way is arranged to redirect the incoming flow through the body to exit substantially radially at a first aperture formed in the curved surface of the substantially cylindrical body. Preferably the first aperture formed in the curved surface of the body is sized to simultaneously align with a plurality of conduits formed in the rotary member, and more preferably still to simultaneously align with n conduits, wherein n is in the range two to four conduits. Advantageously the orientation of the separation device is fixed. The rotary member is mounted thereon and is arranged to rotate about the separation device.
Advantageously the output port can be arranged substantially parallel to the axis of the rotary member and/or rotor assembly. Advantageously the second passage way formed in the flow separation device is constructed and arranged to redirect the outgoing flow of fluid through approximately 90 degrees. The flow changes from a substantially radial direction to a substantially axial direction. The output port can be located in either of the end faces of the substantially cylindrical body, but preferably is located in the same end face as the input port. The second passageway includes a second aperture formed in the curved surface of the substantially cylindrical body and directs the outgoing flow to the outlet port. Preferably the second aperture formed in the curved surface of the body is sized to simultaneously align with a plurality of conduits formed in the rotary member, and more preferably still to simultaneously align with n conduits in the range two to four conduits.
Advantageously the flow separation device can be arranged to direct the incoming fluid towards the rotor assembly such that the incoming fluid impinges on the rotor assembly in a substantially tangential direction in the direction of rotation of the rotor assembly.
The piston receiving formations are preferably substantially U-shaped slots. The U-shaped slots are formed in the periphery of the rotary member with the open part facing radially outwards. The piston receiving formations include at least one pair of substantially parallel sides. Preferably the fit between the recess side walls and the piston member is tight, with the clearance being typically in the range 0.01 to 0.03 mm.
Advantageously the piston receiving formations are evenly distributed about the periphery of the rotary mechanism. Each adjacent pair of piston receiving formations is separated by a radially extending protrusion. Advantageously each piston receiving formation is connected with the interior of the annular rotary member by at least one conduit. Advantageously each radially extending protrusion is connected with the interior of the annular rotary member by at least one conduit. Preferably each conduit is substantially rectilinear and is arranged along a substantially radial path. Preferably each conduit has a substantially circular cross-section. The action of withdrawing the piston members from the piston receiving formations draws fluid into the rotary mechanism from the fluid inlet, along the first passageway into at least one of the conduits formed in the rotary member thereby filling the piston receiving formation and flowing outwards into the low pressure side of the mechanism for transportation by the rotor assembly to the high pressure side. The action of the piston members moving towards and into the piston receiving formations forces the outgoing fluid through the conduits, into the second passageway and to exit the rotary mechanism via the outlet port.
The rotary mechanism includes a casing assembly for housing the rotor assembly, the rotary member and the flow separation device. Advantageously the casing assembly includes a part having an inner profile that substantially matches the plan of the outer profiles of the rotor assembly and the rotary member, thus providing an inner profile similar to the outer profile of the numeral “8”. The inner profile sets a boundary thereby restricting the radial flow of the fluid. The casing includes front and rear covers, which prevent fluid flowing axially out of the piston receiving formations. The part of the casing that includes the inner profile preferably includes at least first and second parts that can be separated from each other in order to enable the rotor assembly to be mounted therein.
Each piston member comprises a body having a substantially cylindrical or substantially spherical portion. Having cylindrical members is particularly advantageous since it provides a structurally simple arrangement and also allows for a very small clearance between the piston members and the inner periphery of the casing, which is typically approximately 0.000035 to 0.0001 mm. The rotor assembly described is different from the involute gears used in gear pumps.
Advantageously the geometry of the piston members and the piston receiving formations can be such that interaction between pistons and the piston receiving formations periodically accelerates and decelerates the rotary member. This leads to a non-constant speed of rotation thereby producing a pulsed output. This can be achieved, for example by having piston members that each include a substantially cylindrical part and piston receiving formations that are each substantially U-shaped and have substantially parallel sides.
The nominal ratio between the number of piston members and the number of piston receiving formations is typically in the range 4:1 to 1:4, but is not restricted to these ranges. The rotor assembly can include n piston members, wherein n is in the range 1 to 20, preferably 2 to 15 and more preferably still 3 to 12. The rotor assembly can include any practicable number of piston members.
The rotor assembly can include a support member for supporting each of the piston members, the arrangement being such that the piston members are located about the periphery of the support member and are arranged to rotate with the support member about a first axis, wherein at least one of the piston members is arranged to rotate relative to the support member about a second axis. Preferably the second axis is the longitudinal axis of the piston member, which enables the piston members to wear more evenly. Advantageously the first axis is substantially parallel to the second axis. Advantageously each piston is arranged to rotate relative to the support member about its own axis, wherein each piston axis is arranged substantially parallel to the first axis.
Advantageously the rotary mechanism can include a plurality of rotor assemblies in peripheral engagement with the rotary member. Advantageously each rotor assembly can be configured according to any configuration of rotor assembly described herein. Advantageously the rotary mechanism can include any practicable number of rotor assemblies. Preferably the rotary mechanism includes n rotor assemblies in peripheral engagement with the rotary member, wherein n is in the range 2 to 10, preferably in the range 2 to 6, and more preferably still in the range 2 to 4.
The flow separation device can include a plurality of inlet ports and/or a plurality of outlet ports. Advantageously the flow separation device can include an inlet port and an outlet port for each rotor assembly. This enables each rotor assembly to serve separate fluid circuits and/or to combine at least some of the outlet flows into a single fluid circuit. In this arrangement, the flow separation device includes separate passageways for connecting each inlet and each outlet port to the conduits. Advantageously each inlet and outlet port can be similarly arranged to those described above. Advantageously at least one of the inlet and outlet ports can be connected to at least one passageway in the separation device that has at least first and second outlets for connecting with the conduits. For example, the flow separation device can be arranged to include a single inlet port, a plurality of inlet apertures formed in the curved surface of the substantially cylindrical body, preferably one for each rotor assembly, and an inlet passageway connecting each of the inlet apertures to the inlet port; and/or a single outlet port, a plurality of outlet apertures formed in the curved surface of the substantially cylindrical body, preferably one for each rotor assembly, and an outlet passageway connecting each of the outlet apertures to the outlet port.
Advantageously the rotary mechanism can include a gear set for synchronising the rotation of the or each rotor assembly and the rotary member. The gear set can include a first gear pair comprising first and second gear elements, wherein each of said first and second gear elements includes meshing zones and non-meshing zones formed in its periphery and the first gear element is arranged to rotate with the second gear element; and a second gear pair including third and fourth gear elements, wherein each of the third and fourth gears elements includes a plurality of meshing zones and non-meshing zones formed in its periphery and the third gear element is arranged to rotate with the fourth gear element; wherein the first and second gear pairs are in meshing engagement such that the first gear element meshes with the third gear element and the second gear element meshes with the fourth gear element, and drive between the first and second gear pairs is transmitted alternately between the first and third gears and the second and fourth gears.
A gear set arranged in this manner enables the generation of peak acceleration curves having no dwell and an abrupt reversal of acceleration. Advantageously the first gear pair can be coupled to the rotor assembly and the second gear pair can be coupled to the rotary member. This type of gear set is used to synchronise the rotor assembly and the rotary member wherein the geometry is such that it provides pulsed rotation, that is, where acceleration and deceleration occur during a full rotation.
For each of the first and second gear elements, the non-meshing zones are arranged alternately with the meshing zones, the first and second gear elements are arranged substantially co-axially such that the meshing zones of the first gear element are rotationally offset from the meshing zones of the second gear element. Each of the first and second gear elements can include a central portion and a plurality of lobes distributed around the periphery of the central portion, wherein each lobe includes a peripheral portion having meshing means formed therein. Advantageously the periphery of each lobe is substantially part elliptical.
For each of the third and fourth gear elements the non-meshing zones are arranged alternately with the meshing zones, the third and fourth gear elements are arranged substantially co-axially such that the meshing zones of the third gear element are rotationally offset from the meshing zones of the fourth gear element. Each of the third and fourth gear elements includes concave portions formed in its periphery, wherein alternate concave portions including meshing means formed therein. Advantageously the concave portions are substantially part elliptical.
Typically the meshing means includes involute gear teeth.
Advantageously the gear set can be arranged such that the minimum speed occurs at the handover of meshing engagement from at least one of the first and third gear elements to the second and fourth gear elements and from the second and fourth gear elements to the first and third gear elements; and/or the maximum speed occurs when either the first or second gear element pair are fully engaged.
Advantageously the first and second gear pairs are arranged such that the second gear element meshes with the fourth gear element before the first gear element fully disengages the third gear element. Advantageously the first and second gear pairs are arranged such that the first gear element meshes with the third gear element before the second gear element fully disengages the fourth gear element.
According to another aspect of the invention there is provided a pump and/or a motor including a rotor assembly having a plurality of piston members distributed about its periphery and a rotary member in peripheral engagement with the rotor assembly, said rotary member including a plurality of formations in its periphery for receiving the piston members, the arrangement being such that during rotation of the rotor assembly and rotary member the piston members move into and out the piston receiving formations. Each piston comprises a body having a substantially cylindrical or substantially spherical portion. Thus the rotor assembly described has a different structure to the gears used in gear pumps.
Advantageously the rotary member according to the second aspect of the invention can be arranged in accordance with any configuration described herein of the first aspect of the invention.
The rotor assembly includes a support member for supporting each of the piston members, the arrangement being such that the piston members are arranged to rotate with the support member about a first axis, wherein at least one of the pistons is arranged to rotate relative to the support member about a second axis. Advantageously the first axis is substantially parallel to the second axis. Advantageously each piston is arranged to rotate relative to the support member about its own axis, wherein each piston axis is arranged substantially parallel to the first axis.
Advantageously the rotary member can be a valve member that is arranged to block fluid flowing from a high pressure side to a low pressure side.
Advantageously the rotor assembly can be arranged such that it only periodically engages the rotary member during a full 360 revolution. This enables the rotor assembly to move the valve to a blocking position, wherein the interaction of the rotary assembly and rotary member blocks the flow of fluid from the high pressure side to the low pressure side, so that the next piston member can drive the fluid out of the pump via the outlet. The piston member then engages the rotary member and rotates it through a predetermined angle as the piston member moves to the low pressure side of the pump, thereby resetting the valve member to another blocking orientation to prevent fluid being driven by the next piston member from crossing to the inlet side.
Advantageously the rotary mechanism can include a gear set for synchronising the rotation of the rotor assembly and the rotary member. Advantageously the rotor assembly and the rotary member can be arranged such that they rotate at substantially constant speed throughout a full 360 revolution for any given nominal speed. In this arrangement, the gear set can include standard gears for synchronising rotation. The gear set ensures that the rotary member is continuously rotated when the rotor assembly rotates even when the rotor assembly is not in engagement with the rotary member.
Advantageously the input and output ports can be arranged substantially parallel to the axis of the rotor assembly and/or the rotary member. Alternatively, the input and output ports can be arranged substantially radial or tangential to the rotor assembly.
According to another aspect of the invention there is provided a gear set for synchronising the rotation of first and second rotary members, said gear set including, a first gear pair comprising first and second gear elements, wherein each of said first and second gear elements includes meshing zones and non-meshing zones formed in its periphery and the first gear element is arranged to rotate with the second gear element; and a second gear pair including third and fourth gear elements, wherein each of the third and fourth gears elements includes a plurality of meshing zones and non-meshing zones formed in its periphery and the third gear element is arranged to rotate with the fourth gear element; wherein the first and second gear pairs are in meshing engagement such that the first gear element meshes with the third gear element and the second gear element meshes with the fourth gear element, and drive between the first and second gear pairs is transmitted alternately between the first and third gears and the second and fourth gears. The gear set enables the generation of peak acceleration curves having no dwell and an abrupt reversal of acceleration. Therefore the gear set can be used to synchronise first and second rotary members that are in meshing engagement for at least part of a full revolution wherein the geometry is such that each member does not rotate at a constant speed through a full revolution. Thus the gears can provide synchronisation of the rotor assembly and the rotary member in the rotary mechanism described herein. Having a double gear arrangement provides a strong structure.
Advantageously the first gear pair can be coupled to the rotor assembly and the second gear pair can be coupled to the rotary member. This type of gear set is used to synchronise the rotor assembly and the rotary member wherein the geometry is such that it provides pulsed rotation, that there is acceleration and deceleration during a full rotation.
For each of the first and second gear elements, the non-meshing zones are arranged alternately with the meshing zones, the first and second gear elements are arranged substantially co-axially such that the meshing zones of the first gear element are rotationally offset from the meshing zones of the second gear element. Each of the first and second gear elements can include a central portion and a plurality of lobes distributed around the periphery of the central portion, wherein each lobe includes a peripheral portion having meshing means formed therein. Advantageously the periphery of each lobe is substantially part elliptical.
For each of the third and fourth gear elements the non-meshing zones are arranged alternately with the meshing zones, the third and fourth gear elements are arranged substantially co-axially such that the meshing zones of the third gear element are rotationally offset from the meshing zones of the fourth gear element. Each of the third and fourth gear elements includes concave portions formed in its periphery, wherein alternate concave portions including meshing means formed therein. Advantageously the concave portions are substantially part elliptical.
Typically the meshing means includes involute gear teeth.
Advantageously the gear set can be arranged such the minimum speed occurs at the handover of meshing engagement from at least one of the first and third gear elements to the second and fourth gear elements and from the second and fourth gear elements to the first and third gear elements; and/or the maximum speed occurs when either the first or second gear element pair are fully engaged.
Advantageously the first and second gear pairs are arranged such that the second gear element meshes with the fourth gear element before the first gear element fully disengages the third gear element. Advantageously the first and second gear pairs are arranged such that the first gear element meshes with the third gear element before the second gear element fully disengages the fourth gear element.
According to another aspect of the invention there is provided a gear set for synchronising the rotation of first and second rotary members in a rotary mechanism, said gear set including, a first gear pair comprising first and second gear elements, wherein each of said first and second gear elements includes meshing zones and non-meshing zones formed in its periphery such that the non-meshing zones are arranged alternately with the meshing zones, and wherein the first and second gear elements are arranged substantially co-axially such that the meshing zones of the first gear element are rotationally offset from the meshing zones of the second gear element, and the first gear element is arranged to rotate with the second gear element.
According to another aspect of the invention there is provided a pump and/or motor including a gear set according to any one of the preceding claims.
Embodiments of the invention will now be described by way of example only, with reference to the accompanying Figures, wherein:
a-8k are views of optional gear elements for driving and synchronising rotation of the piston rotor and piston receiving wheel;
The rotor assembly 5 is arranged to transfer fluid from a lower pressure side of the pump to a high pressure side and includes a drive shaft 15, an annular support member 17, two piston carrier plates 19, six piston elements 21, front and rear seals 23 and front and rear bearings 25. The support member 17 and piston carrier plates 19 are keyed to the drive shaft 15 and are arranged for rotation therewith. The piston carrier plates 19 include six through holes 25 that are each arranged to receive one of the piston elements 21. The piston elements 21 are evenly distributed about the support member 17, the arrangement being such that the angles subtended between the centres of two adjacent piston elements 21 is approximately 60° (see angle α in
The rotor assembly 5 is arranged in meshing engagement with the piston receiving wheel 7. The piston receiving wheel 7 includes a substantially annular body having twelve recesses formed in its outer periphery. The recesses 27 are substantially U-shaped in cross section, with each side wall 29 of the recess 27 being substantially parallel to a radial centre line and hence to each other (see
The piston receiving wheel 7 is mounted on a substantially cylindrical splitter member 13. The splitter member 13 is mounted on pegs (not shown) the arrangement being such that its position is fixed relative to the casing 3. The piston receiving wheel 7 is arranged to rotate freely about the splitter element 13.
The splitter element 13 includes an end face 37 having an inlet opening 9 and an outlet opening 11. The inlet and outlet openings 9,11 extend substantially parallel to the longitudinal axis of the substantially cylindrical splitter element 13 to around 60% of the depth of the splitter element (see
The casing 3 includes a front plate 47, a rear plate 49 and a centre section comprising a lower part 51 and an upper part 53. The upper and lower parts 53,51 are separable in the directions marked A in
The pump 1 is driven by a drive source (not shown) for example an electric motor. The electric motor drives the drive shaft, and hence the rotor assembly 5, either directly or indirectly, for example via a gear set or a flexible drive system such as a belt drive system. The piston receiving wheel 7 is driven by the rotor assembly 5 as it rotates. When the casing 3 is fully assembled, the recesses 27 are effectively piston chambers and the piston elements 21 move into and out of the piston chambers 27 reciprocally as the rotor assembly 5 rotates through an angle of approximately 60°, with the maximum extent of movement within the piston chamber 27 being reached after approximately 30° of rotation.
In the embodiment shown in
In order to take account of the change in speed of the rotor assembly 5 the inventor has developed a new gear set that can be used to drive the rotor assembly 5 and the piston receiving wheel 7 synchronously. The gears are optional since the rotation of the rotor assembly 5 and piston receiving wheel 7 is automatically synchronised since there is always at least one piston element 21 in engagement with the piston receiving wheel 7, however they can improve the quality of drive even when not strictly required.
The shape of the gears can be seen in
The second gear wheel 69 is similar to the first gear wheel 67. The first gear pair 63 comprises the first and second gears 67,69 arranged coaxially with their lobes rotationally oriented 60° out of phase (see
The second gear wheel pair 65 includes third and fourth gears 79,81. The third gear 79 comprises a substantially annular body that includes twelve concave sides 83 formed in its periphery, thus giving it a modified dodecagon appearance, wherein alternate concave sides 83 include involute spur gear teeth 85. Each concave side 83 follows a part elliptical profile. Each side 83 of the third gear 79 subtends an angle of approximately 30° (see angle θ in
The fourth gear 81 is similar to the third gear 79. The second pair of gears 65 comprises the third and fourth gears 79,81 arranged substantially coaxially but orientated 30° out of phase (see
When the pump 1 uses the first and second gear pairs 63,65 to synchronise the rotation of the rotor assembly 5 and piston receiving wheel 7, the first gear pair 63 is coupled to the drive shaft 15 and the second gear pair 65 is coupled to the piston receiving wheel 7, the arrangement being such that the first and second gear pair 63,65 are in mesh (see
b-c show first and third gears 67,79 engaging and the third and fourth gears 69,81 disengaging.
Thus when the first and third gears 67,79 are fully meshed, the second and fourth gears 69,81 are not meshed and when the third and fourth gears 69,81 are fully meshed, the first and third gears 67,79 are not meshed. The double pulse gear system ensures uninterrupted synchronised drive of the rotor assembly 5 and piston receiving wheel 7 at varying speeds during each revolution.
The operation of the pump 1 will now be described. The following description of the operation of the pump 1 is applicable to pumps 1 whether or not they include the synchronisation gear sets 63,65 as described above.
The inlet opening 9 of the pump is connected to an incoming fluid supply line (not shown) and the outlet 11 of the pump 1 is connected to an outgoing fluid supply line (not shown). When the pump is switched on by actuating the drive source the rotor assembly 5 begins to rotate and the piston element 21 that is currently located in the piston receiving recess 27 creates a partial vacuum as the piston element 21 withdraws from the piston receiving recess 27 thereby drawing fluid into the pump 1 through the inlet 9, and via the first slot 39 into the adjacent piston recess 27 and the interior of the pump via the passages 33,35. The pump is essentially self-priming in that the suction force created is sufficiently large to flood the piston receiving recess 27 and at least part of the low pressure side 61. The fluid is sucked towards the rotor assembly 5 tangentially in a manner that is substantially in the direction of rotation of the rotor assembly. The fluid is pushed around the inner periphery 57 of the casing by the piston elements 21 and is delivered to the outlet 11 by the piston elements pushing fluid through the passageways 33,35 on the high pressure side 59. The fluid flows through the second slot 41 in the splitter element 13 and out of the outlet 11. As shown in
The pump 1 is fully reversible in that the present inlet 9 can become the outlet 11 and the present outlet 11 can become the inlet 9 simply by reversing the direction of operation of the drive source. This is due to the symmetry of the pump. It should be noted that gear pumps cannot do this since the seals in them are arranged in a directional fashion. If the user of the gear pump wants to reverse the direction, it is necessary to strip the gear pump down and reset the seals to enable flow in the opposite direction. This is not the case for the current pump 1. This is a significant advantage over standard gear pumps.
It has been found by the inventors that the pump described above has significant advantages over known gear pumps. In particular a greater volume of liquid can be moved for a particular operating speed and a greater suction can be produced. With regards to known piston pumps, there is a reduced pulsing of flow and a less complex arrangement
The advantage of having a second rotor assembly is that two separate circuits can be supplied by the pump 201 or alternatively the outputs can be combined to feed the same circuit. If the same circuit is supplied, having two smaller piston rotors as shown on a 1:2 nominal ratio can pump a greater volume of liquid than a single piston rotor having the same sized piston elements but having a 1:1 ratio (i.e. twelve piston elements).
The splitter element 313 includes six apertures in its curved surface. The arrangement is such that each inlet 309 is in fluid communication with one of the apertures (similar to slot 39 in
A fourth embodiment is shown in
It will be appreciated, by the skilled person that modifications can be made to the above embodiments that are within the scope of the invention, for example a pump having any practical number of rotor assemblies can be included, for example between one and eight rotor assemblies, preferably one to four and more preferably still, one to three.
The nominal ratio between the or each rotor assembly and the piston receiving wheel can be adjusted to suit the application. For example, the nominal ratio can be 1:1, 1:2, 1:3, 2:1, 3:1, etc. The number of piston elements 21 and piston receiving recesses 27 can be increased or decreased as required.
For embodiments having a plurality of rotor assemblies, each rotor assembly can have its own first gear pair that is arranged to rotate about the second gear pair. For example, for the third and fourth embodiments, which include three rotor assemblies, the gear set includes three “first gear pairs”, one coupled with each rotor assembly, and one second gear pair, which is coupled with the piston receiving wheel. The pump can be driven by coupling one of the drive shafts to a drive source or alternatively mounting the piston receiving wheel and the second gear pair onto a drive shaft and coupling that drive shaft to the drive source. Using gears when there are multiple rotor assemblies is desirable since it spreads the drive load.
Whenever there is an arrangement having sufficiently few piston elements such that the piston receiving wheel 7 is fully disengaged by the rotor assembly, gears such as those shown in
The splitter element 413 can be adapted to for use in the second and third embodiments, for example by reducing the number of apertures formed in the curved surface of the splitter element.
A fifth embodiment is shown in
It will be appreciated by the skilled person that each of the above-embodiments can operate as fluid motors when fluid is supplied to the inlet under pressure. Useful work can be obtained from the motor, for example via the drive shaft.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0905071.7 | Mar 2009 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2010/000536 | 3/23/2010 | WO | 00 | 12/6/2011 |
