FIELD OF THE INVENTION

The present invention relates to an apparatus for controlling movement of a fluid. In one aspect the invention relates to a rotary vane motor, whereby a flow of pressurised fluid is used to generate a power output from the apparatus.

It should be appreciated that the components which utilise the torque generated by the rotary vane motor, such as a drivetrain of a vehicle, or the components that are used to convert the torque generated by the rotary vane motor into a useable or storable source of power, or any power input components, will not be described in detail since they form part of the common general knowledge.

BACKGROUND OF THE INVENTION

There are numerous types of rotary motors and drive units that use a flow of fluid, either being liquid or gas, along a flow path to generate a power output. These types of motors include pneumatic vane motors and hydraulic vane motors.

Generally rotary motors comprise a bore or chamber having inlet and outlet ports and a rotor located typically eccentric within the bore or chamber. The rotor is caused to rotate by a flow of pressurised fluid that enters in through the inlet port. The rotor is used to convert the hydraulic or pneumatic pressure and flow into torque, which is then used to undertake work or is converted into a useable or storable source of power.

The pressurised fluid is held within working compartments that are

temporarily formed between adjacent vanes, the outer surface of the rotor and the inner wall of the bore or chamber, as the fluid moves between the inlet port and outlet port. A force differential produced by the unbalanced force of the pressurized fluid on the vanes causes the rotor to spin in one direction. In this way the pressurised fluid acts upon the vanes to thereby generate torque in the rotor.

Typically vane motors disclosed in the prior art have a number of rigid vanes that are slidably held within slots of a rotor. The rotor being positioned within a casing having an elliptical shaped bore or the rotor may be offset or eccentric within a circular bore. In these designs, as the pressurised fluid turns the rotor, centrifugal forces, internal pusher rods or pressurized fluid, cause the vanes to move outward within their respective slots such that an end of each vane bears against the wall of the bore or chamber thereby forming the working compartment. The area between adjacent vanes, the outer surface of the rotor and the inner surface of the bore delineate each working compartment. Typically, these types of motors include multiple radial working compartments that are repeatedly and temporarily formed as the rotor is rotated.

There are a number of problems with existing vane motors, for instance the requirement for minimal clearances and wearing of the components results in enlarged gaps through which liquid or gas can pass, thereby reducing efficiency. Other problems with existing vane motors include the formation of cavitation in the liquid, corrosion caused by the fluid properties, leakage along the rotating shaft and pulsations at the inlet or outlet ports.

The skilled addressee will appreciate that generally speaking, similar configurations can be used as rotary vane pumps and similar issues occur with the analogous components.

For the purposes of discussion it should be appreciated that the term "fluid" refers to both liquid and gas and therefore the rotary motor/pump discussed may be either pneumatic or hydraulic. It should be appreciated that any discussion of the prior art throughout the specification is included solely for the purpose of providing a context for the present invention and should in no way be considered as an admission that such prior art was widely known or formed part of the common general knowledge in the field as it existed before the priority date of the application. SUMMARY OF THE INVENTION

It could be broadly understood that the invention resides in an apparatus for fluid flow control, including a housing having a chamber connected to an exterior of the housing by an inlet port and an outlet port, a rotor being rotatably held within said chamber and attached to a shaft, the rotor including at least two slots extending outwardly therethrough, a cam rigidly held within said chamber, intermediate of an annular shaped portion of the vane and said shaft, and respective vanes slidably held within each of said at least two slots, wherein each of the respective vanes can simultaneously abut or be positioned adjacent both an outer surface of said cam and a wall of said chamber during rotation of said rotor to thereby delineate a working compartment for passage of a fluid through the apparatus.

In one aspect of the invention, but not necessarily the broadest or only aspect, there is proposed a rotary vane motor, including:

a housing having an internal chamber wherein an inlet and an outlet extend between said internal chamber and an exterior of said housing;

a rotor being rotatably held within said internal chamber and attached to a drive shaft that extends through said housing, wherein the rotor having an annular shaped portion spaced apart from said drive shaft, the annular shaped portion including at least two slots extending outwardly therethrough;

a cam rigidly held within said internal chamber, intermediate of the annular shaped portion of the rotor and said drive shaft; and

a slidable vane held within each of said at least two slots, wherein each said slidable vane can simultaneously abut or be positioned adjacent both an outer surface of said cam and a wall of said internal chamber during rotation of said rotor, to thereby form working compartments delineated by said wall of the internal chamber, an outer surface of said annular shaped portion of the rotor and adjacent slidable vanes, wherein a differential force produced by the unbalanced force of a pressurized fluid on opposite sides of the slidable vanes causes the rotor to rotate.

The rotor in one form is of a substantially annular shape and is attached to or forms part of, a co-axially aligned rotatable drive shaft, wherein the drive shaft extends through an aperture in the housing. The aperture includes a correspondingly shaped sealing member to inhibit movement of said fluid therethrough. In another form the rotor is cup shaped and includes an annular shaped portion and a base through which the drive shaft extends. In still another form an annular shaped rotor is attached to a generally planar annular projection that extends outwardly from the drive shaft.

A flow of pressurised fluid acts on said slidable vanes to thereby rotate the rotor to generate torque. This torque can be used to undertake work, such as turning a wheel, or be converted via the drive shaft into a useable or storable source of power. Accordingly, the drive shaft may be attached to or engage with a drivetrain of a vehicle, or a device for converting the torque into a usable or storable source of power. The shaft may be attached to magnetic, electrical, or electromagnetic components or devices that enable, through linear or rotary induction of a magnetic fields, the production of electrical energy.

Therefore the apparatus, in one form, could be described as a pneumatic or hydraulic vane motor, wherein the flow of pressurised fluid enters through said inlet port such that is acts on the vanes to rotate said rotor and thereby produce torque in the shaft.

The ports that extend through the housing can be used as either inlet ports or outlet ports depending upon the direction of rotation of the rotor. Pipes or conduit can be connected to the inlet and outlet ports for conveying the fluid to, or away from, the apparatus. In form the housing includes outwardly extending annular protrusions coaxially aligned with respective inlet or outlet ports for connection of said pipes or conduit.

The distance between the outer surface of the cam and the wall of the chamber along radial lines, which extend outwardly from a centre point of the chamber, may be generally constant throughout the chamber. The length of the vanes in one form may be the same as said distance between the outer surface of the cam and the wall of the chamber. This means that the vanes are generally in constant contact with the outer surface of the cam and wall of the chamber as the vanes orbit around the cam. The housing in one form may comprise an annular shaped body portion attached to generally planar end covers that thereby define an internal chamber. Accordingly, in one form the chamber has two substantially flat-sided walls formed by the end covers.

The end covers are sealably attached to opposite ends of the main body portion and maintain the gases/liquid pressure within said housing. In one form the cam is rigidly connected to one of the end covers such that its position relative said housing does not change. The end covers each include an aperture for the drive shaft to extend therethrough, wherein each aperture includes a sealed ring-shaped bearing that is configured to hold said shaft and prevent leakage of said fluid. An inner end of each vane may include a roller that bears against and follows a designated path around the surface of the cam. Alternatively, a slide member may be located at the first end of the vane. An outer end of each vane is configured to bear against the wall of the chamber and may include a slide or seal to inhibit movement of the fluid thereover, except possibly adjacent the ports. The vanes may also be spaced apart from the cam or wall of the chamber at other regions during rotation of the rotate, such as, but not limited to, where the vanes are not forming a side of the working or pumping compartments.

The surface of the cam is preferably scaled from the wall of said chamber, wherein the vanes are configured to retract back inwardly of the annular shaped portion of the rotor after performing its work. As the rotor rotates, the vanes are in contact with the wall of the chamber and the surface of the cam. The reader should appreciate that this configuration could be described as a double cam or dual cam system. Therefore the wall of the chamber could be understood as forming a second or inverse cam.

The rotor may comprise an end attached to the drive shaft and an annular portion extending outwardly from said end and extending over a part of said shaft wherein an inner surface of the annular portion is spaced apart from said shaft. The slots may extend radially between an inner surface and an outer surface of said annular portion of the rotor. Alternatively, the rotor and shaft may be of unitary construction and include an inwardly extending annular shaped gap to accommodate the cam. The wall of the chamber may be shaped such that the outer end of each vane does not contact the wall of the chamber adjacent the inlet port and the outlet port, thereby permitting some flow of the fluid over said outer end of the vane.

Accordingly, in one form the configuration of the chamber and cam ensures that there is a small sector during the rotation of the rotor wherein the vanes are not in contact with the wall of the chamber and/or the surface of the cam, thereby allowing some of the fluid to flow over an outer end of the vane to inhibit pulsations in the fluid flow at the inlet or outlet ports. Therefore preferably some bi-pass of gases/fluids occurs over the outer end of the vanes adjacent to the inlet/outlet ports to inhibit said pulsations. The inlet and outlet ports may be of any diameter, shape, size or location through the housing and can have the same, or different designs, for each of the ports on opposite sides of apparatus. The cam may include a central bore through which the shaft is configured to pass. The inner surface of said central bore is preferably spaced apart from an outer surface of the shaft. The vane rollers may be generally in constant contact with cam.

The apparatus can be used in either open or closed loop circuits and the vanes follow a generally orbital pathway around the surface of the cam. The wall of the chamber, which is contacted by outer ends of the vanes, acts as an inverted cam and may have two radii or curved surfaces connected by two spaced apart planar surfaces. Accordingly, the skilled addressee will appreciate that the apparatus of the present invention is a dual cam system with an inner cam and the wall of the chamber acting as a second or inverted cam.

The distance between the inner surface of the chamber and outer surface of the cam is generally constant and equal to the length of the vanes to ensure that opposite ends of each vane are generally in constant contact, except possibly adjacent the inlet and outlet ports. In another form the wall of the chamber comprises multiple curved portions with generally flat portions intermediate thereof.

Preferably four vanes are used, which are positioned within corresponding slots in the rotor. Each slot is perpendicular to an adjacent slot. In another form, multiple vanes may be used that are each positioned within a corresponding slot radially spaced apart around the rotor.

The fluid is therefore moved through the apparatus from the inlet port to the outlet port by way of radial working compartments that are formed between the wall/s of the chamber, outer surface of the annular portion of the rotor and adjacent vanes.

The skilled addressee will however appreciate that by connecting the drive shaft to a driving device, such as an electric motor, the same configuration as described above could be used to pump a fluid through the apparatus. Accordingly the reader will appreciate that the apparatus can be used as either a transfer device for moving said fluid, or alternatively it can be used for generating torque from a pressurised flow of said fluid.

In another aspect of the invention there is proposed a fluid flow control apparatus being a rotary vane pump including:

a housing having an internal chamber wherein an inlet port and an outlet port extend between said internal chamber and an exterior of said housing; a rotor being rotatably held within said chamber and attached to, or engaging with a driving shaft that extends through said housing, wherein the rotor having an annular shaped portion spaced apart from said driving shaft, the annular shaped portion including at least two slots extending outwardly therethrough, the driving shaft being attached to an input device;

a cam rigidly held within said chamber, intermediate of the annular shaped portion of the rotor and said driving shaft; and

slidable vanes respectively held within said at least two slots, wherein each of the slidable vanes can simultaneously abut or be positioned adjacent both an outer surface of said cam and a wall of said chamber during rotation of said rotor to thereby form pumping compartments each of which being delineated by said wall of the chamber, an outer surface of said annular shaped portion of the rotor and adjacent slidable vanes for conveying a fluid between the inlet port and the outlet port. The rotary vane pump may be a positive displacement vacuum pump that does not require priming.

The rotor of the above rotary vane pump may be reversible such that the fluid can be pumped in opposite directions. The driving shaft could be understood to be an input shaft when the apparatus is used as a rotary vane pump. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of the invention and, together with the description and claims, serve to explain the advantages and principles of the invention. In the drawings,

Figure 1 is an exploded view of a first embodiment of the apparatus of the present invention;

Figure 2 is a schematic cross-sectional view through A-A of Figure 1 ;

Figure 3 perspective view of the rotor of Figure 1 ;

Figure 4 is a perspective view of the vanes of Figure 1 illustrating the rollers; Figure 5 is a perspective view of the cam of Figure 1 ;

Figure 6 is a perspective view of the front and rear covers of Figure 1 ; Figure 7 is a perspective view of the housing of Figure 1 ;

Figures 8a-d are various views of the assembled apparatus of Figure 1 ;

Figures 9a-d are various views of the housing of Figure 7;

Figures 10a-d are various views of the front and rear covers of Figure 6;

Figures 1 1 a-d are various views of the cam of Figure 5;

Figures 12a-d are various views of the vanes of Figure 4;

Figures 13a-d are various views of a second embodiment of the rotor;

Figures 14a-d are schematic views of the relative positions of the housing, rotor vanes and cam;

Figure 15 is a rear exploded view of the apparatus of Figure 1 ;

Figure 16 is a front exploded view of the apparatus of Figure 1 ;

Figure 17 is a perspective view of a separate rotor attached to a shaft having an annular projection;

Figure 18 is a perspective view of the shaft of Figure 17;

Figure 19 is a schematic view of the vanes, with roller positioned around the cam;

Figure 20 is an end view of the rotor;

Figure 21 is an end view of the rotor of Figure 20 with a vane positioned within one of the slots;

Figure 22 is a schematic view illustrating the relative positions of the housing, vanes and cam with the rotor removed;

Figure 23 is a schematic view of another embodiment of the housing and cam illustrating the generally equal distances 'X' therebetween; and

Figure 24a-d are a series of schematic views of the apparatus illustrating the

temporary formation of the working compartments and movement of the fluid. DETAILED DESCRIPTION OF THE ILLUSTRATED AND EXEMPLIFIED

EMBODIMENTS

Similar reference characters indicate corresponding parts throughout the drawings. Dimensions of certain parts shown in the drawings may have been modified and/or exaggerated for the purposes of clarity or illustration.

Referring to the drawings for a more detailed description, there is illustrated an apparatus 10 for controlling movement of fluid, demonstrating by way of examples, arrangements in which the principles of the present invention may be employed. The skilled addressee should appreciate that the apparatus 10 will be discussed as being used as a rotary vane motor, however the apparatus could also be used as a vane pump by connecting the shaft 12 to a power input device.

As illustrated in Figures 1 , 15 and 16, the apparatus 10 includes a rotatable shaft 12, a generally annular rotor 14 or a rotor having an annular portion, and slidable vane or vanes 16. The rotor 14 is located within a chamber 18 formed by a housing 19 comprising a main body portion 20 and end covers 22 and 24. Ports 26, 28 extend through the main body portion 20 and can be used as either inlet ports or outlet ports depending upon the direction of rotation of the rotor 14. In the present embodiment port 26 is an inlet port and port 28 is an outlet port. Pipes 30 can be connected to the ports 26 and 28 for conveying the fluid to or away from the apparatus 10. It should however be appreciated that ports may also extend through end covers 22 and 24.

The movement of the fluid through the apparatus 10 occurs by way of working compartments 40 that are formed between the walls 34, 36, 38 of the chamber 18, outer surface 41 of the rotor 14, and adjacent vanes 16 as illustrated in Figure 2. One end of each vane 16, as illustrated in Figures 4, 12a-12d and 19, includes a roller 43 that is used to follow a designated path around a cam 44. The rollers 43 are accommodated within recess 42 of the rotor 14 that is illustrated in Figure 3. In another embodiment the vanes 16 do not have rollers and engage with a rotor that does not include a recess as illustrated in Figures 13a to 13d. The reader should however appreciate that a slide member may be used instead of the roller. As further illustrated in Figures 3 and 13a-13d. the shaft 12 is attached to components 45 such as, but not limited to, a drivetrain of a vehicle when the apparatus is being used as a rotary vane motor, or an input drive when the apparatus is being used as a rotary vane pump.

Figures 5, 1 1 a-1 1 d and 14b-14d illustrate the cam 44 having an outer surface 46 scaled from the wall 34 of chamber 18. Accordingly, the reader will appreciate that there is in essence an inner cam member and the wall 34 of the chamber acts as a second or inverted cam. The invention is therefore a dual cam or double cam system in contrast to the prior art. Each vane 16 retracts back towards the centre of the rotor 14 after performing its work. As illustrated in Figure 8a each roller 43 is housed generally within an enlarged end or recess 42 of a corresponding slot 32, wherein an inner region of the roller 43 engages with or abuts the cam 44.

As the rotor 14 rotates, the vane 16 is in contact with the inverted cam/wall 34 of the chamber 18 and the outer surface 46 of the cam 44, by way of the roller 43. This keeps volume pressure from escaping over the vane 16 while still keeping the contact friction to a minimum, which improves efficiency. The apparatus' efficiency is not affected by the direction of rotation and the volume pressure (psi) is only limited by the fatigue strength of the materials.

The chamber 18 and rotor 14 are designed whereby the forces acting against the vane 16 cannot by-pass the vane. This design allows substantially all of the volume/pressure to act on the leverage through the centre of the shaft 12 attached to the rotor 14. In this way the volume and pressure (psi) calculations are easy to formulate. It should be appreciated that although the generally annular shaped rotor 14 is attached to the annular protrusions 52 of the shaft 12 in the present

embodiment, as illustrated in Figures 17 and 18, the rotor and shaft may alternatively be unitary in construction or the rotor may include a base portion and annular portion wherein the shaft extends through and is attached to the base portion of the rotor.

The chamber 18 has a small section in which the vanes 16 are not in contact or positioned directly adjacent the second cam/wall 34 of the chamber 18. As illustrated in Figures 2, 14a-14d and 20-22, this configuration allows some of the fluid (gases/liquids) to flow over the outer end 48 of the vane 16a and inhibits pulsations in the fluid flow at the ports. This occurs at both inlet port 26 and outlet port 28.

As some volume of the fluid goes over the outer end 48 of a particular vane 16 there is another vane 16 perpendicular to and ahead which stops the fluid exiting through outlet port 28. The fluid can therefore travel in a uniform flow, which is important for some applications and has a lower stress and fatigue factor on the components, materials and/or prime motor source (when used as a pump).

The inlet and outlet ports 26, 28 are not restricted to any diameter, shape, size or location and can have the same or different designs of each port on either side of apparatus 10 for different applications.

The shaft 12 is held within the housing by sealed bearings 50 on both front and rear covers 22 and 24 of the apparatus as illustrated in Figures 1 , 6, 8a, 8c, 15, and 16. The shaft 12 extends through the central bore 54 of the cam 44, but does not touch the sides of the central bore. The rotor 14 and shaft 12 are joined together, such as by welding or may be unitary in construction. The apparatus 10 can be adjusted in height, width, length and scale, to suit volume/psi requirements to suit different applications. It should be appreciated that the shaft 12 may be either an input shaft when the apparatus is used as a pump or a drive shaft when the apparatus is used as a motor.

The apparatus 10 can be made small in size but still delivers high

volume/pressure at a low rpm, although high rpm could also be used. The apparatus can be used in either open or closed loop circuits.

When the apparatus 10 is being used as a motor, high-pressure pneumatic - gases/hydraulic - liquids, steam etc., from an outside source can enter one port (either 26 or 28) on a first side and exit the other port (either 26 or 28) on the opposite side to thereby rotate the shaft 12 in either an open or closed loop circuit. The apparatus can be controlled (outside control) to rotate shaft 12 in either direction, reciprocate (forward/backward) movement or by locking the shaft 12 from rotating (gradual or fast).

The apparatus 10 can be used for a wide range of applications including aviation, automotive, pharmaceuticals, chemical, oil and gas, as well as the medical field. It should however be appreciated that the invention is not limited to these applications. The apparatus can be used to control the flow of a range of liquids and gases including both low and high viscosity liquids, non-lubricating or lubricating liquids, such as solvents, fuel, oils, gasoline, refrigerants, and liquefied gas. The vanes 16 slide inside slots 32 in rotor 14. The vanes 16 follow a generally orbital pathway around an outer surface 46 of the cam 44. In one embodiment the vanes 16 include respective rollers 43 to reduce friction, however other slide means may be used on the inner end or the vane may simply bear against the surface if the cam 44. Typically the pressurised fluid cannot bi-pass the vanes 16 due to the contact with the inner wall 34 of main body portion 20 at one end and the outer surface 46 of the cam 44 at the opposite end. There may however be brief periods during rotation that the vane 16 does not contact the inner wall 34 of main body portion 20, such as when the vane 16 passes adjacently and over the inlet or outlet port 26, 28, to thereby inhibit pulsations in the flow of fluid. The outer end 48 of the vanes 16 may however be held slightly adjacent the wall 34 of the chamber 18 to reduce friction and permit a slight flow of fluid thereover.

As illustrated in Figures 7 and 9a-9d, the main body portion 20 has an inner surface 34 that forms a wall of the chamber 18, which is contacted by outer ends of the vanes 16. The inner surface 34 acts as an inverted cam. The input and output ports 26 and 28 are positioned on either side of main body portion 20.

As further illustrated in Figures 9a and 9c, the wall 34 of chamber 18 has two radii joined together by parallel generally planar surfaces. These radii can be varied in dimensions to increase or decrease the face height, which affects the face width and leverage radii, but not the volume. The chamber 18 has two substantially flat- sided walls 36, 38 formed by end covers 22, 24 to contain the fluid.

The covers 22 and 24 are located at the front and rear of main body portion 20, as illustrated in Figures 8a to 8d. The covers 22 and 24 seal and contain the gases/liquid within chamber 18. The front cover 22 has a flat inner surface in contact with rotor 14 and vanes 16 and rigidly connects and locates the cam 44. As illustrated in Figures 6 and 10a-10d, the covers 22 and 24 include bearings 50 to hold shaft 12.

The outer surface of the cam 44 is parallel to the inside of the housing. The cam 44 is fixed with respect to the main body portion 20 and attached only to the front cover 22. The cam has a central bore 54 through which the shaft 12 is configured to pass. The surface 56 of the central bore 54 is spaced apart from the shaft 12, as illustrated by the broken lines in Figure 1 1 a. The centre shaft 12 therefore passes through the centre of cam 44 but does not touch it. The vane rollers 44 or inner end of the vane 16 is generally in constant contact with cam 44.

The rotor 14 has slots 32 that allow the vanes 16 to slide therewithin. The slots 32 in the rotor 14 are open at both inner and outer surfaces. The vanes 16 can slide totally out of the slots when the apparatus is disassembled which assists in the replacement of worn parts. The vanes 16 are held in place by following the inner wall of the chamber and outer surface of the cam. In the present embodiment four vanes are used that are each set perpendicular to an adjacent vane 16. It should however be appreciated that multiple vanes could be used that are each positioned within a corresponding slot in the rotor and are spaced apart radially around the rotor.

Figure 23 illustrates an alternate embodiment of the main body portion 20 and cam 44. As illustrated the inner surface 34 of the main body portion 20 that forms the chamber 18 includes three generally flat portions 58, 60, 62 that are joined by curved portions 64, 66, 68. The configuration of the surface is reflected on the outer surface 46 of the cam 44 such that the distance 'X', which corresponds to the length of the vanes, remains constant throughout the chamber 18, except maybe, as previously discussed, adjacent the inlet and outlet ports or at other regions.

Figures 24a to 24d illustrate four separate periods during the movement of a pressurised fluid between the inlet 26 and the outlet 28. The reader will appreciate that the fluid will follow the same path whether the apparatus is being used as a vane pump or a vane motor, however the direction of the fluid can be reversed as previously discussed. For the purpose of discussion each of the four vanes in Figures 24a to 24d have been designed references 16a to 16d and the working compartments have been designed references 40a to 40d. Figure 24a illustrates movement of the fluid indicated by the broken arrow, in through the inlet port 26 and into the compartment 40a that has been newly formed by the rotation of the rotor 14 in the direction of the solid arrow. It will be appreciated that fluid may be contained within working compartments 40b, 40c and 40d however the movement of the fluid will not be discussed. Figure 24b illustrates the movement of the vane 16a in an anticlockwise direction, which increases the size of the compartment 40a into which fluid is drawn or impelled. In the rotary vane motor the pressure differential produced by the unbalanced force of the pressurized fluid on opposite sides of the vanes 16 causes the rotor 14 to rotate.

The rotor 14 continues to rotate in an anticlockwise direction as illustrated Figure 24c, such that vane 16d is positioned adjacent the inlet 26. Once the vane 16d passes the inlet 26, it forms the end of the compartment 40a thereby preventing backflow of the pressurized fluid.

As the rotor 14 further rotates in the direction of the solid arrow the vane 16a passes the outlet 28, as illustrated in Figure 24d, thereby opening the compartment 40a and permitting the fluid therein to flow out through outlet 28.

The skilled addressee will now appreciate the advantages of the illustrated invention over the prior art. In one form the invention provides an apparatus that delivers maximum pressure over leverage and can be used to drive, or be driven by, a gas or liquid. The apparatus of the present invention could be understood to be a dual cam system with an inner cam and the wall of the chamber acting as a second or inverted cam. The apparatus 10 can be made compact in size, if required and has only a few simple parts which means weight can be reduced to a minimum. The configuration of the apparatus furthermore means that it is relatively easy to calculate volume and horsepower (hp). Furthermore, the apparatus reduces pulsations in the fluid at the outlet port, can operate at low pressures, as well as accurately controlling the volumetric flow rate and also operate in both directions.

Various features of the invention have been particularly shown and described in connection with the exemplified embodiments of the invention, however it must be understood that these particular arrangements merely illustrate the invention and it is not limited thereto. Accordingly the invention can include various modifications, which fall within the spirit and scope of the invention.