Ball pump

Abstract

A fluid pump includes a cam plate defining an inner cam surface having an eccentric portion and a narrow portion. A hub rotates within the inner cam surface and has a piston chamber connected to an inlet port and an outlet port. A piston member is operably accommodated within the piston chamber to define a suction phase within the eccentric portion and a pressure phase within the narrow portion. The piston member is biased outward by rotation of the hub. During the suction phase, the piston member is biased away from the piston chamber to define a flow chamber for extracting fluid from the inlet port. During the pressure phase, the piston member is biased into the flow chamber by the narrow portion to push the fluid from the flow chamber to the outlet port.

Description

Technical Field

[0001] The present invention relates generally to fluid pumps and, more particularly, to a fluid pump having one or more piston members that operate to move fluid through a rotating hub. Background Art

[0002] Various pumps are used to move fluids from one location to another. These fluid pumps use changes in pressure to generate suction and pressure, thereby moving the fluid from an inlet to an outlet. Summary of the Invention

[0003] According to one aspect of the present invention, a fluid pump includes a cam plate defining an inner cam surface having an eccentric portion and a narrow portion. A hub rotates within the inner cam surface and has a piston chamber connected to an inlet port and an outlet port. A piston member is operably housed within the piston chamber to define a suction phase within the eccentric portion and a pressure phase within the narrow portion. The piston member is biased outwardly by rotation of the hub. During the suction phase, the piston member is biased away from the piston chamber to define a flow chamber for extracting fluid from the inlet port. During the pressure phase, the piston member is biased into the flow chamber by the narrow portion to push the fluid from the flow chamber to the outlet port.

[0004] According to another aspect of the present invention, a fluid pump includes a cam plate having an inner cam surface that defines alternating eccentric sections and narrow sections. A wheel hub rotates within the inner cam surface and includes a piston chamber connected to an inlet port and an outlet port. Piston members are positioned in the piston chambers to define a flow chamber therebetween. Rotation of the wheel hub generates centrifugal force that biases the piston members toward the inner cam surface and away from the axis of rotation of the wheel hub. The alternating eccentric sections and narrow sections define respective suction and pressure phases for each piston member. Each suction phase biases the piston member outward to expand the flow chamber. The suction phase draws fluid from the inlet port into the flow chamber. Each pressure phase biases the piston member into its respective piston chamber to compress the flow chamber and discharge the fluid from the flow chamber toward the outlet port. The inlet port is aligned with the eccentric section, and the outlet port is aligned with the narrow section.

[0005] According to another aspect of the present invention, a fluid pump includes an end assembly having a fluid inlet and a fluid outlet. A fluid path extends between the fluid inlet and the fluid outlet. The fluid path has a centrifugal section and a centripetal section for moving fluid through the fluid path. The cam disc includes an inner cam surface that defines the centrifugal section and the centripetal section. The hub assembly rotates around a rotational axis. The hub assembly includes a plurality of piston members and a central hub. The hub assembly limits the radial movement of each piston member through the rotation of the centrifugal section and the centripetal section. The plurality of piston members operate in a radially outward direction in the centrifugal section to expand the corresponding flow chamber that extracts fluid from the inlet port. The plurality of piston members operate in a radially inward direction in the centripetal section to compress the flow chamber and push the fluid out of the flow chamber and toward the outlet port.

[0006] Those skilled in the art will understand and appreciate these and other aspects, objects and features of the present invention from a study of the following specification, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the diagram:

[0008] Figure 1 is a side perspective view of one aspect of a ball pump;

[0009] Figure 2 yes Figure 1 Another side perspective view of the ball pump;

[0010] Figure 3 yes Figure 1 Side view of the ball pump;

[0011] Figure 4 yes Figure 2 Side view of the ball pump;

[0012] Figure 5 yes Figure 1 An exploded perspective view of a ball pump;

[0013] Figure 6 yes Figure 1 Another exploded perspective view of the ball pump;

[0014] Figure 7 It is taken along line VII-VII Figure 1 Cross-sectional view of a ball piston pump;

[0015] Figure 8 It is taken along line VIII-VIII Figure 2 Cross-sectional view of a ball piston pump;

[0016] Figure 9 It is taken along line IX-IX Figure 1 Cross-sectional view of a ball piston pump;

[0017] Figure 10 is an exploded perspective view of one aspect of a ball pump; and

[0018] Figure 11 is a schematic cross-sectional view of one aspect of the hub and inner cam surface. DETAILED DESCRIPTION

[0019] For the purpose of this description, the terms "upper", "lower", "right", "left", "rear", "front", "vertical", "horizontal" and their derivatives will refer to the following: Figure 1 The present invention is oriented in a manner similar to that described in the accompanying claims. However, it should be understood that the present invention may adopt various alternative orientations unless expressly specified to the contrary. It should also be understood that the specific devices and processes shown in the drawings and described in the following specification are merely exemplary embodiments of the inventive concepts defined in the appended claims. Therefore, unless the claims expressly state otherwise, specific dimensions and other physical characteristics related to the embodiments disclosed herein should not be considered limiting.

[0020] like Figures 1 to 11 As illustrated, reference numeral 10 generally refers to a ball pump having a cam member 12, which includes an inner cam surface 14 that mates with a rotating hub 16 having a plurality of piston members 18. The piston members 18 are positioned in pairs within various apertures defined within the hub 16, such as within a piston cavity 20. As the hub 16 rotates within the inner cam surface 14, a centrifugal force 22 caused by the rotation of the hub 16 within the cam member 12 induces a biasing force that moves the piston members 18 in an outward direction 24 and outside of the piston cavity 20. As the piston members 18 move outside of the piston cavity 20, a suction force 26 is generated that passes through one or more inlet ports 60 and draws fluid 28 into the piston cavity 20, wherein a flow cavity 38 is defined between the piston members 18 and the flow cavity 38. As the hub 16 rotates, the piston members 18 and the piston cavity 20 align with the narrowed portion 32 of the inner cam surface 14, causing the inner cam surface 14 to bias the piston members 18 into the piston cavity 20 due to the centripetal force 36. This movement of the piston member 18 into the piston cavity 20 contracts the flow cavity 38, with the piston member 18 now occupying the piston cavity 20. In this manner, the movement of the piston member 18 pushes the piston member 18 into the piston cavity 20 and, in turn, pushes the fluid 28 out of the piston cavity 20 and into one or more corresponding outlet ports 62.

[0021] Refer to the figure again Figures 4 to 11, the rotational operation of the hub 16 and the piston member 18 within the inner cam surface 14 generates a uniform centrifugal force 22 applied to the piston member 18. The centrifugal force 22 biases the piston member 18 away from the piston cavity 20. At the same time, the inner cam surface 14 generates a relative centrifugal force 36. Through these relative centrifugal forces 22 and centripetal forces 36, the movement of the piston member 18 follows the path defined by the inner cam surface 14. As discussed above, the piston member 18 is allowed to move outside the piston cavity 20 in the eccentric portion 50 or expanded portion of the inner cam surface 14. During this suction phase 40, the flow cavity 38 between the piston member 18 and the corresponding piston cavity 20 expands to generate the suction force 26. This suction force 26 draws fluid into the flow cavity 38. As the hub 16 rotates relative to the inner cam surface 14, the piston member 18 reaches the narrow portion 32 of the inner cam surface 14. Movement of piston member 18 and piston chamber 20 through narrowed portion 32 defines a pressure stage 42, wherein piston member 18 is biased by centripetal force 36 and enters piston chamber 20. This movement of piston member 18 into piston chamber 20 pushes piston member 18 into flow chamber 38 to generate a pressure 44 that pushes fluid from flow chamber 38 toward fluid outlet 34.

[0022] The centrifugal force 22 that biases the piston members 18 in the outward direction 24 is counteracted by the centripetal force 36 generated by the inner cam surface 14. The eccentric portion 50 allows controlled movement of the piston members 18 in the outward direction. Conversely, the centripetal force 36 generated in the narrow portion 32 overcomes the centrifugal force 22 and biases the piston members 18 back into the piston chambers 20. Thus, the rotational movement of the hub 16 within the inner cam surface 14 generates an oscillating motion 52 of each piston member 18 relative to the corresponding piston chamber 20. In operation, as the hub 16 rotates about the rotational axis 54 of the hub 16, the piston members 18 follow a path defined by the inner cam surface 14.

[0023] As illustrated herein, the inner cam surface 14 can include a generally elliptical profile having opposing eccentric portions 50 and opposing narrow portions 32. These eccentric portions 50 and narrow portions 32 generate a generally elliptical motion of the piston members 18 relative to the inner cam surface 14. This, in turn, generates an oscillating motion 52 of each piston member 18 relative to the corresponding piston cavity 20. Modifications to the shape of the inner cam surface 14 can be used to generate various patterns of eccentric portions 50 and narrow portions 32 for managing the flow of fluid 28 through the piston pump 10.

[0024] The shape of the inner cam surface 14 aligns with corresponding inlet ports 60 and outlet ports 62 located within a port portion 64 of an end assembly 66 of the piston pump 10, such as within a manifold. Typically, the inlet port 60 aligns with the eccentric portion 50 of the inner cam surface 14. Conversely, the outlet port 62 within the port portion 64 of the end assembly 66 aligns with the narrow portion 32 of the inner cam surface 14. In this manner, the oscillating motion 52 of the piston member 18 relative to the piston cavity 20 and the corresponding expansion and compression of the flow cavity 38 occur simultaneously with the motion of each piston member 18 between the outlet port 62 located at the narrow portion 32 and the inlet port 60 located at the eccentric portion 50 of the inner cam surface 14.

[0025] The design of the hub 16 having the piston member 18 and piston cavity 20 disposed therein and rotating within the internal cam surface 14 can be used to move fluids 28 having higher viscosities. Fluids 28 having higher viscosities can generally include more viscous fluids 28, or fluids 28 that are more viscous at lower temperatures. As an example, during the start-up conditions of a vehicle, a particular fluid 28 can have a higher viscosity. The operation of the piston pump 10 disclosed herein can be used to move these higher viscosity fluids 28 through the piston pump 10. Additionally, as the viscosity of the particular fluid 28 decreases, the fluid 28 generally warms up, and the piston pump 10 remains effective in moving the fluid 28 through the ball pump 10.

[0026] The shape of the inner cam surface 14 can be any of a variety of shapes, including, but not limited to, an ellipse, a circular geometry, or other similar circular geometries having multiple axes of symmetry. As discussed above, these various geometries of the inner cam surface 14 are shaped to include various eccentric portions 50 and narrow portions 32 aligned with the inlet port 60 and outlet port 62, respectively. In certain aspects of the device, the inner cam surface 14 can adopt an egg-shaped geometry, wherein the egg-shaped geometry includes a single eccentric portion 50 and a single narrow portion 32 relative to the rotational axis 54 of the hub 16. This egg-shaped geometry of the inner cam surface 14 defines a single-fill fluid pump having a single inlet port 60 and a single outlet port 62. Typically, the inner cam surface 14 will include a geometry having multiple axes of symmetry, making dual-fill or multi-fill configurations possible. Dual-fill or multi-fill configurations, such as a generally elliptical profile, generally provide for balanced pressure 44 about the rotational axis 54, such that the fluid bore 110 of the piston chamber 20 is balanced about the rotational axis 54 of the hub 16 and within the inner cam surface 14. The cam member 12 tends to maintain the hub 16 aligned with the rotational axis 54 of the ball pump 10 .

[0027] Depending on aspects of the device, the hub 16 can include various numbers of piston members 18 and piston chambers 20. As illustrated herein, six piston members 18 can operate within six piston chambers 20. It is contemplated that additional or fewer piston members 18 and piston chambers 20 can be incorporated into the hub 16. As an example and not limitation, piston members 18 of specific sizes can be incorporated to produce a more viscous fluid flow. Piston members 18 of different sizes and configurations can be incorporated to handle fluid flows with different viscosities and time-varying viscosities. In addition, the number and shape of the narrow portion 32 and the eccentric portion 50 of the inner cam surface 14 can be modified to take into account fluids with different viscosities. Changes in the number and configuration of piston members 18, piston chambers 20, and inner cam surface 14 can also be used to handle a wide range of piston pumps 10 to produce various flow rates.

[0028] According to various aspects of the device, the drive shaft 90 of the piston pump 10 can extend from the motor 92 to the hub 16. When the motor 92 is running, the drive shaft 90 rotates the hub 16 in the inner cam surface 14. The motor 92 can usually be operated at a speed of about 4,000 revolutions per minute or lower, wherein the fluid 28 has a higher viscosity or a desired lower flow rate. When the desired fluid 28 has a lower viscosity or a higher flow rate, a higher rotational speed can be used. A higher rotational speed can be about 10,000 revolutions per minute. It should be understood that the motor 92 and the hub 16 can be operated at a rotational speed greater than or less than the wide range of rotational speeds mentioned herein. The rotational speed used is usually calibrated to generate a centrifugal force 22 of sufficient size on the piston member 18 to produce the continuous engagement of the piston member 18 with the inner cam surface 14.

[0029] The piston pump 10 disclosed herein may be used in applications having higher viscosity fluids 28 or fluids 28 that are more viscous at cooler temperatures. Such applications may include, but are not limited to, vehicle transmissions, vehicle differentials, and other similar applications where higher viscosity fluids 28 are used and where the fluids 28 have higher viscosities at the cooler temperatures seen when a particular mechanism is actuated.

[0030] like Figures 4 to 11As illustrated, the individual inlet ports 60 and outlet ports 62 contained within the port portion 64 of the end assembly 66 can be configured to extend to a common inlet passage 100 and a common outlet passage 102, respectively. In such a configuration, the end plate 104 of the end assembly 66 can include a fluid inlet passage 100 extending between each of the inlet ports 60 of the port portion 64 of the end assembly 66. Similarly, the fluid outlet passage 102 can include a path extending between the individual fluid outlet ports 62 of the port portion 64 of the end assembly 66. Using the fluid inlet passage 100 and the fluid outlet passage 102, a single inlet path and a single outlet path can be defined within the end assembly 66 of the piston pump 10.

[0031] Reference again Figures 4 to 11 , the hub 16 may include various piston cavities 20 that house piston members 18 that operate as pendulum members in an oscillating motion 52 relative to the inner cam surface 14. These piston members 18 may be in the form of spheres, cylinders, or other geometric shapes that can be configured to operate in an oscillating motion 52 or piston-like manner relative to the piston cavities 20 defined within the hub 16.

[0032] Reference again Figures 1 to 11 , the fluid delivery piston pump 10 may include a cam member 12, such as a cam plate having an inner cam surface 14 that defines an eccentric portion 50 and a narrow portion 32. These eccentric portions 50 and narrow portions 32 may be configured as alternating eccentric segments 120 and narrow segments 122, such that a plurality of eccentric segments 120 and narrow segments 122 may be included within the eccentric portion 50 and narrow portion 32. The hub 16 rotates within the inner cam surface 14 and includes a piston cavity 20 that communicates with an inlet port 60 and an outlet port 62. The piston members 18, typically in the form of spherical pistons, are respectively positioned within the piston cavities 20 to define a flow cavity 38 therebetween.

[0033] Rotation of hub 16 generates centrifugal force 22, which biases piston member 18 toward inner cam surface 14 and away from hub 16's axis of rotation 54. Alternating eccentric sections 120 and narrow sections 122 define respective suction stages 40 and pressure stages 42 for each piston member 18. Each suction stage 40 biases piston member 18 outward to expand its respective flow cavity 38. Suction stage 40 serves to draw fluid 28 from inlet port 60 into flow cavity 38. Thus, the expansion of flow cavity 38 generates suction force 26 that draws fluid 28 into flow cavity 38. Each pressure stage 42 biases piston member 18 back into its respective piston cavity 20 to compress flow cavity 38. This compression of flow cavity 38 generates pressure 44, which serves to expel fluid 28 from flow cavity 38 and move fluid 28 toward outlet port 62. Inlet port 60 is aligned with eccentric section 120, and outlet port 62 is aligned with narrow section 122. According to various aspects of the device, each eccentric section 120 may include a corresponding inlet port 60 , and each narrow section 122 may include a corresponding outlet port 62 .

[0034] refer to Figures 4 to 11 , an inlet port 60 and an outlet port 62 are defined within the end assembly. Typically, the inlet port 60 and the outlet port 62, or a plurality of inlet ports 60 and outlet ports 62, are defined within a manifold or port portion 64 of the end assembly 66. The end assembly 66 includes a fluid inlet 30 in communication with the inlet port 60 and a fluid outlet 34 in communication with the outlet port 62. The fluid inlet 30 and the fluid outlet 34 are typically positioned at an exterior surface 130 of the end assembly 66 for engagement with various components of an external fluid flow path 132. The external fluid flow path 132 can transport the fluid 28 into the piston pump 10 and also transport the fluid 28 away from the piston pump 10. Within the end assembly 66, an inlet passage 100 extends between the fluid inlet 30 and the inlet port 60. Similarly, an outlet passage 102 extends between the fluid outlet 34 and the outlet port 62. As discussed above, the inlet passage 100 can also be used to provide fluid communication between the various inlet ports 60 so that a consistent flow of the fluid 28 from the fluid inlet 30 through the inlet passage 100 and through the various inlet ports 60 can be maintained to provide the fluid 28 to the eccentric section 120 of the piston pump 10. Similarly, the outlet passage 102 can extend to the plurality of outlet ports 62 for delivering the fluid 28 from the various outlet ports 62 to the fluid outlet 34. In this manner, a consistent flow of the fluid 28 from the narrow section 122 of the piston pump 10 to the fluid outlet 34 can be achieved. The positioning of the inlet ports 60 and the outlet ports 62 can be defined within a flow surface 134 of the end assembly 66. Typically, the flow surface 134 is defined within the port portion 64 of the end assembly 66.

[0035] Reference again Figures 4 to 9 , the eccentric portion 50 of the inner cam surface 14 may include a first eccentric section 150 and a second eccentric section 152 positioned relative to each other. The first narrow section 154 and the second narrow section 156 may also be positioned relative to each other so that the eccentric section 120 and the narrow section 122 create a continuous and alternating pattern of narrow sections 122 and eccentric sections 120. This alternating pattern of narrow sections 122 and eccentric sections 120 produces an oscillating motion 52 of the piston member 18 within the piston cavity 20 to produce expansion and compression of the flow cavity 38. This expansion and compression of the flow cavity 38 produces the suction 26 and pressure 44 that move the fluid 28 from the fluid inlet 30 through the flow cavity 38 and then to the fluid outlet 34.

[0036] To achieve consistent flow of the fluid 28 from the fluid inlet 30 and to each eccentric segment 120, a pressure relief passage 170 can be positioned within the port portion 64. The pressure relief passage 170 can extend between the opposing first and second eccentric segments 150, 152 and function to equalize the suction force 26 between the eccentric segments 120 within the inner cam surface 14. Using the pressure relief passage 170, consistent flow of the fluid 28 can be maintained within the inner cam surface 14 and within each flow cavity 38 defined between the piston member 18 and the piston cavity 20 of the piston pump 10.

[0037] To remove fluid 28 from the inlet port 60 to the flow chamber 38 and from the flow chamber 38 to the outlet port 62, each piston chamber 20 includes a fluid aperture 110 that extends to a port surface 180 of the hub 16. Typically, the port portion 64 or manifold is positioned adjacent to the hub 16 and the cam member 12. In this configuration, the port surface 180 of the hub 16 faces the flow surface 134 of the port portion 64. During operation of the hub 16, the fluid apertures 110 of each piston chamber 20 alternately align with the inlet port 60 and the outlet port 62 in a sequential alignment pattern during operation of the hub 16. Thus, the oscillating motion 52 of the piston member 18, which generates the suction 26 and pressure 44 of the fluid 28 within the piston pump 10, can provide a substantially continuous flow of the fluid 28 through the piston pump 10. With this configuration, operation of each piston member 18 between the suction phase 40 and the pressure phase 42 moves fluid 28 from the inlet port 60 into the flow cavity 38 and then toward the outlet port 62 via the fluid aperture 110 of each piston cavity 20 .

[0038] As illustrated, the hub 16 includes six piston cavities 20 and six corresponding piston members 18. During one rotation of the hub 16, each of these pairs of piston members 18 and piston cavities 20 experiences multiple oscillations and multiple occurrences of the pressure phase 42 and suction phase 40 of the piston pump 10. Likewise, the rotation of the hub 16 within the inner cam surface 14 creates a consistent or substantially consistent flow of fluid 28 through the eccentric section 120 and the narrow section 122 of the piston pump 10.

[0039] Reference again Figures 4 to 9 , within the inner cam surface 14 and the manifold, the two narrow sections 122 of the inner cam surface 14 correspond to the two outlet ports 62, and the two eccentric sections 120 of the inner cam surface 14 correspond to the two inlet ports 60 of the port portion 64. As discussed above, the two inlet ports 60 are fluidly connected via the inlet channel 100, and the two outlet ports 62 are fluidly connected via the outlet channel 102. Thus, multiple inlet ports 60 and multiple outlet ports 62 can be coupled to the fluid inlet 30 and the fluid outlet 34 via a single inlet channel 100 and a single outlet channel 102, respectively.

[0040] Reference again Figures 1 to 11 , the fluid delivering piston pump 10 includes an end assembly 66 having a fluid inlet 30 and a fluid outlet 34. A fluid path 190 extends between the fluid inlet 30 and the fluid outlet 34. The fluid path 190 also includes various centrifugal and centripetal sections that move the fluid 28 through the fluid path 190. The centrifugal sections correspond to the eccentric sections 120, wherein the centrifugal force 22 generated by the rotation of the hub 16 causes the piston member 18 to move outward in an oscillating motion 52. The centripetal sections may correspond to the narrow sections 122, wherein the centripetal force 36 generated by the inner cam surface 14 biases the piston member 18 into the corresponding piston cavity 20. As discussed above, these oscillating motions 52 of the piston member 18 produce the suction phase 40 and the pressure phase 42 of the piston pump 10.

[0041] Reference again Figures 1 to 11 , the hub assembly 196 rotates about the rotation axis 54. The hub assembly 196 includes a plurality of piston members 18 and a central hub 16. The hub assembly 196 limits the radial movement or oscillating motion 52 of each piston member 18 through the rotation of the centrifugal section and the centripetal section. The piston members 18, respectively positioned within the corresponding piston chambers 20, define a flow chamber 38 therebetween. The rotation of the hub 16 generates a centrifugal force 22 that biases the piston members 18 toward the inner cam surface 14 and away from the rotation axis 54 of the hub 16. At the same time, the inner cam surface 14 generates a centrifugal force 22 that maintains the outward position of each of the piston members 18. The outward position of the piston members 18 is consistent with the shape or contour of the inner cam surface 14, within which the hub assembly 196 rotates.

[0042] The plurality of piston members 18 operating in the radially outward direction 24 and within the centrifugal section serve to expand the corresponding flow chamber 38, which generates the suction force 26 for drawing the fluid 28 from the inlet port 60. The plurality of piston members 18 operating in the radially inward direction are present within the centripetal section and operate to compress the flow chamber 38. This compression of the flow chamber 38 generates a pressure 44 that pushes the fluid 28 out of the flow chamber 38 and toward the outlet port 62. As discussed herein, the centrifugal and centripetal sections sequentially define the suction stage 40 and pressure stage 42, respectively, of the piston members 18. Operation of the piston members 18 between the suction stage 40 and the pressure stage 42 serves to move the fluid 28 from the inlet port 60 into the flow chamber 38, and then toward the outlet port 62.

[0043] Using the piston pump 10, fluids of various viscosities and fluids 28 of varying viscosity can be moved from the fluid inlet 30, through the flow chamber 38, and then to the fluid outlet 34. As discussed above, under certain conditions, the viscosity of the fluid 28 can change over time to become less or more viscous. The operation of the ball pump 10 can accommodate these varying viscosities and fluctuating viscosities during operation of a particular device requiring the fluid 28 to flow therethrough.

[0044] It will be understood that changes and modifications may be made in the foregoing constructions without departing from the inventive concepts, and it will be further understood that such concepts are intended to be covered by the appended claims unless such claims by their language expressly state otherwise.

Claims

1. A fluid pump comprising: a cam plate defining an inner cam surface having an eccentric portion and a narrow portion; a hub that rotates within the inner cam surface and has a piston cavity in communication with an inlet port and an outlet port; as well as a piston member operably received within the piston cavity to define a suction phase within the eccentric portion and a pressure phase within the narrow portion, wherein the piston member is biased outwardly by rotational operation of the hub, wherein: During the suction phase, the piston member is biased away from the piston chamber to define a flow chamber that draws fluid from the inlet port; During the pressure phase, the piston member is biased by the narrow portion into the flow chamber to push the fluid from the flow chamber toward the outlet port; The eccentric portion includes opposing first and second eccentric sections of the inner cam surface, and The narrow portion includes opposing first and second narrow sections of the inner cam surface; and The cam plate at least partially defines a pressure relief passage extending between the opposing first and second eccentric sections, and the pressure relief passage equalizes suction pressure within the first and second eccentric sections. 2 . The fluid pump of claim 1 , wherein the inlet port and the outlet port are defined within an end assembly. 3 . The fluid pump of claim 2 , wherein the tip assembly has a fluid inlet in communication with the inlet port and a fluid outlet in communication with the outlet port. 4 . The fluid pump of claim 3 , wherein the fluid inlet and the fluid outlet are positioned at an exterior surface of the end assembly.

5. The fluid pump of claim 4, wherein the inlet port and the outlet port are defined within a flow surface of the tip assembly. 6 . The fluid pump of claim 5 , wherein an inlet passage extends between the fluid inlet and the inlet port, and an outlet passage extends between the fluid outlet and the outlet port.

7. The fluid pump of claim 6 , wherein the end assembly includes a manifold plate positioned between the cam disc and an end plate of the end assembly, the manifold plate having the inlet port extending between the eccentric portion and the inlet passage, and the outlet port extending between the narrow portion and the outlet passage.

8. The fluid pump of claim 6, wherein each piston cavity includes a fluid aperture extending to a port surface of the hub, wherein during operation of the hub, the fluid apertures are alternately aligned with the inlet channel and the outlet channel.

9. The fluid pump of claim 8, wherein operation of the piston member between the suction phase and the pressure phase moves the fluid from the inlet port into the piston cavity and toward the outlet port.

10. A fluid pump according to any one of claims 1 to 9, wherein the piston member is biased against the inner cam surface at least by centrifugal forces generated during rotation of the hub.

11. A fluid pump comprising: a cam plate having an inner cam surface defining alternating eccentric and narrow segments; a hub that rotates within the inner cam surface and has a piston cavity in communication with an inlet port and an outlet port; as well as piston members, the piston members being respectively positioned within the piston chambers to define a flow chamber therebetween, wherein Rotation of the hub generates a centrifugal force that biases the piston member toward the inner cam surface and away from the axis of rotation of the hub, wherein: The alternating eccentric and narrow sections define respective suction and pressure phases for each piston member; Each suction stage biases the piston member outward to expand the flow chamber, the suction stage drawing fluid from the inlet port into the flow chamber; Each pressure stage biases the piston member into a respective piston cavity to compress the flow cavity and expel the fluid from the flow cavity and toward the outlet port; The inlet port is aligned with the eccentric section, and the outlet port is aligned with the narrow section; the inner cam surface comprising a generally elliptical profile having two eccentric sections corresponding to the two inlet ports and two narrow sections corresponding to the two outlet ports; and A pressure relief passage extends between the two eccentric sections to equalize the suction force between the two eccentric sections. 12 . The fluid pump of claim 11 , wherein the two inlet ports are fluidly connected via an inlet channel, and the two outlet ports are fluidly connected via an outlet channel.

13. The fluid pump of claim 11, wherein the hub comprises six piston cavities, and the piston member comprises six piston members operably positioned within the six piston cavities.

14. The fluid pump of claim 13, wherein each piston member is rotationally operated about the rotation axis of the hub and sequentially operates the suction stage and the pressure stage with respect to the inlet port and the outlet port.

15. The fluid pump of claim 11, wherein the pressure relief passage is positioned within a manifold plate positioned adjacent to the hub and the cam plate.

16. The fluid pump of claim 15, wherein the inlet passage and the outlet passage are positioned within an end plate, wherein the port plate is positioned between the cam plate and the end plate.

17. The fluid pump of claim 11, wherein each piston cavity comprises a fluid hole extending to a port surface of the hub, wherein each fluid hole is sequentially aligned with one of the two inlet ports, one of the two outlet ports, the other of the two inlet ports, and the other of the two outlet ports.

18. The fluid pump of any one of claims 11 to 17, wherein the inlet port and the outlet port are defined in a manifold plate positioned adjacent the hub and the cam plate.

19. A fluid pump comprising: a tip assembly having a fluid inlet and a fluid outlet, wherein a fluid path extends between the fluid inlet and the fluid outlet, the fluid path having a centrifugal section and a centripetal section that move fluid through the fluid path; a cam plate having an inner cam surface defining the centrifugal section and the centripetal section; as well as A hub assembly, the hub assembly rotating about a rotation axis, the hub assembly comprising a plurality of piston members and a central hub, wherein: The hub assembly limits the radial movement of each piston member by rotating between the centrifugal section and the centripetal section; The plurality of piston members operate in a radially outward direction in the centrifugal section to expand corresponding flow cavities that draw fluid from the inlet port; the plurality of piston members operating in a radially inward direction in the centripetal section to compress the flow cavity and force the fluid out of the flow cavity and toward an outlet port; and The tip assembly includes a pressure relief passage extending between the centrifugal sections to equalize suction forces within the centrifugal sections.

20. The fluid pump of claim 19, wherein the end assembly includes an end plate and a manifold plate, wherein the inlet port and the outlet port are defined in the manifold plate, the manifold plate being positioned adjacent the cam plate and the hub assembly.

21. The fluid pump of claim 20, wherein the end plate has an inlet channel communicating with the inlet port and an outlet channel communicating with the outlet port.

22. The fluid pump of claim 21, wherein the fluid inlet and the fluid outlet are positioned at an outer surface of the end plate.

23. The fluid pump of claim 21, wherein the inlet passage and the outlet passage extend to a flow surface of the end plate, wherein the manifold plate engages the flow surface.

24. The fluid pump of claim 19, wherein the inlet port extends to the fluid inlet through an inlet passage, and the outlet port extends to the fluid outlet through an outlet passage.

25. The fluid pump of claim 19, wherein the piston members are operably disposed within respective piston cavities of the central hub, wherein the respective piston cavities direct travel of the piston members in radially outward and radially inward directions during rotational operation of the hub.

26. The fluid pump of claim 19, wherein each respective piston cavity includes a fluid aperture extending to a port surface of the hub assembly, wherein operation of the hub assembly sequentially aligns the fluid apertures with the inlet port and the outlet port.

27. The fluid pump of claim 19, wherein each of the piston members is biased into elliptical motion about the axis of rotation of the hub assembly, wherein the elliptical motion is defined by centrifugal forces generated during rotation of the hub and centripetal forces exerted by the inner cam surface.

28. A fluid pump according to claim 19, wherein the centrifugal section and the centripetal section sequentially define a suction phase and a pressure phase of the piston member, respectively, wherein operation of the piston member between the suction phase and the pressure phase moves the fluid from the inlet port into the flow chamber and toward the outlet port.

29. The fluid pump of claim 25 or 26, wherein the flow chamber is defined between the piston member and the corresponding piston chamber.

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