Cross-Reference to Related Applications

This application claims priority to, and the benefit of, U.S. Provisional Patent

Application No. 61/735,872, filed on December 11, 2012, and U.S. Patent Application No. 13/841,029, filed on March 15, 2013, which are incorporated herein by reference in their entirety.

Field

This disclosure relates to various types of pumps that are magnetically driven. More specifically, it pertains to pumps in which a rotary element, such as a pump gear, or rotary- reciprocating element, such as a piston, is connected to a driven magnet housed in a magnet housing ("magnet cup") in which the magnet is wetted by the fluid being pumped by the pump.

Background

Integrated-drive pumps are particularly advantageous for pumping systems that must operate under severe conditions, handle hazardous fluids, or operate trouble-free for extremely long periods of time. Such pumps often incorporate a magnetically coupled pump-drive mechanism in which a pump element, such as a pair of interdigitating gears or lobes, is connected to a driven magnet housed in a magnet housing or "magnet cup." The driven magnet is caused to rotate by a rotating magnetic field induced by a stator or other mechanism situated outside the magnet cup. This arrangement allows the driven magnet to be immersed in the fluid being pumped while isolating the rest of the system and eliminating the leak-prone hydraulic seals that would otherwise be required around the pump-drive shaft. Operation of the stator typically requires an electronic circuit for provision of power and control logic.

In addition to the electronic circuits required for operation of the pump, integrated-drive pumps are often incorporated into hydraulic systems that require sensors or indicators of any of various parameters such as pressure, temperature, conductivity, etc., of the fluid flowing in the system. A sensor usually includes a transducer or the like that converts the parameter being sensed {e.g., pressure or temperature) into a corresponding signal {e.g., an electronic or optical signal). The sensor usually also includes or is connected to an electronic circuit that receives data directly from the transducer and processes the data for use by other electronics for, e.g. , providing a measure of the parameter or for use in control circuits. It is possible that the sensor(s) not actually include or function as a transducer. As used herein, the term "sensor" encompasses both transducer-based sensors as well as sensors not utilizing a transducer.

In hydraulic systems including a pump, the pump is typically a discrete stand-alone component, by which is meant that the pump is manufactured and sold separately to original equipment manufacturers (OEMs) for incorporation into the OEM's own system. The trend in many OEM hydraulic systems requiring a pump is toward miniaturization, particularly with respect to the aspect ratio of a pump assembly (i.e. , the ratio of a pump assembly's axial length as compared to its diameter) without sacrificing performance or reliability. Thus, the electronic circuitry for operating both the pump and the sensors ideally must be self-contained (i.e. , located on or within the housing or enclosure of a pump-driver portion), and incorporated into a pump assembly that is as small and compact as possible.

However, the circuitry needed to operate the stator in an integrated-drive pump is often required to operate at a much higher voltage and/or current than the circuitry for operating the sensors due to the higher electrical power requirements of the stator relative to the sensors. Additionally, each respective circuit type requires numerous circuit elements which can vary in size. The disparity in power requirements, the relatively large number and size of the circuit elements, and the space constraints imposed by the pump-driver portion often necessitate that the stator and sensor elements be operated on two or more independent electrical circuits.

Moreover, these independent electrical circuits must often be laid out on multiple printed circuit boards that fully extend the full transverse dimension of the enclosure of the pump-driver portion (or be located outside the enclosure) to accommodate the required circuit elements. This, in turn, blocks access to the magnet cup, complicates sensor location, precludes a flow- through pump configuration, and requires a large pump-driver portion that negatively impacts the size of the pump assembly.

Summary

Disclosed embodiments of the present invention provide compact integrated-drive pumps that address the deficiencies of known integrated-drive pumps. Certain embodiments of the present invention concern a pump assembly, comprising a magnetically driven pump-head subassembly and a pump-driver subassembly coupled to the pump-head subassembly. The pump-head subassembly comprises a rotatable magnet contained in a magnet cup, which comprises a distal-end wall and extends into the pump-driver enclosure. The pump-driver subassembly also comprises at least one printed circuit board and a stator adjacent to the printed circuit board. The stator coaxially surrounds the magnet cup. The printed circuit board includes a stator-driving circuit and at least one signal-processing circuit. The printed circuit board also defines a void that is situated relative to the distal-end wall so as to expose at least half of the distal-end wall. In addition, the pump-driver enclosure has an aspect ratio of no greater than one (unity).

Another representative embodiment concerns a pump assembly, comprising a pump- head portion including a pump housing defining a pump cavity. The pump assembly comprises a pump-driver portion, a movable pumping member situated inside the pump housing, a driven magnet connected to the pumping member so that induced motion of the driven magnet causes corresponding induced motion of the pumping member, and a magnet cup. The magnet cup is a respective portion of the pump cavity and contains the driven magnet so that the induced motion of the driven magnet occurs in the magnet cup as the driven magnet and interior of the magnet cup are being wetted by fluid being pumped by induced motion of the pumping member. The magnet cup also comprises a distal-end wall. The pump assembly further comprises a magnet- driver situated outside the magnet cup but within the pump-driver portion, the magnet-driver being magnetically coupled to the driven magnet such that a changing magnetic field produced by the magnet-driver induces corresponding motion of the driven magnet and hence of the pumping member. The pump assembly further comprises a fitting mounted to the distal-end wall of the magnet cup, a circuit board, and at least one sensor located in the pump-driver portion. The sensor is located on, aside, or at least partially in the distal-end wall, the circuit board is electrically connected to the magnet-driver and to the at least one sensor. The circuit board comprises a high-current circuit and a low-current circuit, the high-current circuit providing electrical power to the magnet-driver, and the low-current circuit providing electrical power to the at least one sensor. The circuit board extends orthogonally to the axial length around the magnet cup while defining a void allowing access through the circuit board to the distal-end wall of the magnet cup. In another representative embodiment, a hydraulic pump system comprises a fluid reservoir containing fluid to be pumped, and a pump assembly in fluid communication with the fluid reservoir. The pump assembly comprises a pump-driver portion coupled to a magnetically- driven pump-head portion, the pump-head portion comprising a rotatable magnet coupled to a rotatable pumping member and contained in a magnet cup extending into the pump-driver portion. The pump-driver portion comprises a stator coaxially surrounding the magnet cup and a circuit board, the circuit board allowing access to at least 50% of the surface area of a distal-end wall of the magnet cup. The pump-driver portion has an aspect ratio of no greater than one. The hydraulic pump system further comprises a fluid-utility unit in fluid communication with the pump-head portion and configured to receive fluid pumped by the pump-head portion.

In another representative embodiment concerns a pump assembly, comprising a pump- head portion including a pump housing defining a pump cavity, a pump-driver portion coupled to the pump-head portion and having an axial length and a transverse dimension, a movable pumping member situated inside the pump cavity, and a driven magnet connected to the pumping member so that induced motion of the driven magnet causes corresponding induced motion of the pumping member. The pump assembly further comprises a magnet cup having a distal-end wall, and that is a respective portion of the pump cavity. The magnet cup contains the driven magnet so that the induced motion of the driven magnet occurs in the magnet cup as the driven magnet and the interior of the magnet cup are wetted by fluid being pumped by induced motion of the pumping member. The pump assembly further comprises a magnet-driver situated outside the magnet cup and coupled to the pump-driver portion, the magnet-driver being magnetically coupled to the driven magnet such that a changing magnetic field produced by the magnet-driver induces corresponding motion of the driven magnet and hence of the pumping member. The pump assembly further comprises a circuit board defining a central void, a first sensor situated adjacent to the distal-end wall and connected to the circuit board, and a second sensor mounted to the circuit board and being situated relative to an outside wall of the magnet cup such that the distal-end wall of the magnet cup is exposed by the central void of the circuit board.

Another representative embodiment concerns a pump assembly, comprising a pump- head portion including a pump housing defining a pump cavity, a pump-driver enclosure coupled to the pump-head portion and having an axial length and a transverse dimension, and a movable pumping member situated in the pump cavity. The pump assembly further comprises a driven magnet connected to the pumping member so that induced motion of the driven magnet causes corresponding induced motion of the pumping member, and a magnet cup. The magnet cup has a distal-end wall, is a respective portion of the pump cavity, and contains the driven magnet so that the induced motion of the of the driven magnet occurs in the magnet cup as the driven magnet and the interior of the magnet cup are being wetted by fluid being pumped by induced motion of the pumping member. The pump assembly further comprises a magnet- driver situated outside the magnet cup but inside the pump-driver enclosure. The magnet-driver is magnetically coupled to the driven magnet such that a changing magnetic field produced by the magnet-driver induces corresponding motion of the driven magnet and hence of the pumping member. The pump assembly further comprises a flexible printed circuit electrically connected to the magnet-driver and at least one sensor, the flexible printed circuit and the at least one sensor being located in the pump-driver enclosure. The sensor is located on, aside, or at least partially in the distal-end wall, and the flexible printed circuit is mounted within the pump-driver enclosure such that the flexible printed circuit at least partially surrounds the magnet cup while leaving the distal-end wall exposed.

The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

Brief Description of the Drawings

FIG. 1 is a side-elevational section of an embodiment of an integrated-drive pump assembly.

FIG. 2 is a top view of a printed circuit board used in the embodiment of FIG. 1.

FIG. 3A is a schematic depiction of an integrated-drive pump assembly having a pump- driver enclosure with an aspect ratio of approximately 0.4.

FIG. 3B is a schematic depiction of an integrated-drive pump assembly having a pump- driver enclosure with an aspect ratio of approximately 0.7.

FIG. 4 is a side-elevation cross-sectional view of an embodiment of an integrated-drive pump assembly having a sensor. FIG. 5 is a side-elevational section of an embodiment of an integrated-drive pump assembly including a fitting mounted to the distal-end wall of the magnet cup.

FIG. 6A is a perspective view of an exemplary configuration of a flexible printed circuit. FIG. 6B is an elevational section showing the printed circuit of FIG. 6A and nearby portions of the magnet cup and stator.

FIG. 7 is an elevational view of a portion of a pump-driver assembly situated relative to the magnet cup.

FIG. 8 is a section through a portion of the head of an embodiment of a piston pump as an alternative pump -head.

FIG. 9 is a schematic diagram of an exemplary hydraulic circuit including an integrated- drive pump assembly.

FIG. 10A is a partial cross-sectional view of a pump-driver portion and a pump-head portion releasably attached by threads.

FIG. 10B is an isometric view of a pump-driver portion and a pump-head portion releasably attached by bayonet mount.

FIG. IOC is an isometric view of a pump-driver portion and a pump-head portion releasably attached by a ball and detent system,

FIG. 10D is a partial cross-sectional view of a pump-driver portion and a pump-head portion releasably attached by a fastener and having an O-ring therebetween.

FIG. 10E is a partial cross-sectional view of a pump-driver portion and a pump-head portion releasably attached by threads and having an O-ring therebetween.

Detailed Description

This disclosure is set forth in the context of representative embodiments that are not intended to be limiting in any way.

As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Additionally, the term "includes" means

"comprises." Further, the term "coupled" encompasses mechanical as well as other practical ways of coupling or linking items together, and does not exclude the presence of intermediate elements between the coupled items. The things and methods described herein should not be construed as being limiting in any way. Instead, this disclosure is directed toward all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with one another. The disclosed things and methods are not limited to any specific aspect or feature or combinations thereof, nor do the disclosed things and methods require that any one or more specific advantages be present or problems be solved.

Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed things and methods can be used in conjunction with other things and method. Additionally, the description sometimes uses terms like "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art.

In the following description, certain terms may be used such as "up," "down,", "upper," "lower," "horizontal," "vertical," "left," "right," and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But, these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an "upper" surface can become a "lower" surface simply by turning the object over. Nevertheless, it is still the same object.

Referring to FIG. 1, there is shown a cross-sectional view of an embodiment of an integrated-drive pump assembly 10 having a pump-head portion 12 and a pump-driver portion 14. The pump-head portion 12 includes an inlet 16, an outlet 18, a driving gear 20, a driven gear 22, a shaft 24, a driven magnet 26, and a magnet cup 28. The magnet cup 28 extends into the pump-driver portion 14. The magnet cup 28 has side walls 28a and a distal-end wall 30 that surround and are coaxial with the driven magnet 26. The side walls 28a and the distal-end wall 30 separate the driven magnet 26 from electrical parts of the assembly that are kept dry (i.e., not wetted by the fluid being pumped). Meanwhile, the pump-head portion 12 comprises a pump housing 23 (usually a sealed housing) that defines a pump cavity 25. The pump cavity 25 is generally bathed in the fluid being pumped. In other words, the pump cavity 25 is defined by the fluid- wetted interiors of the pump-head portion 12 and the magnet cup 28. Thus, the driven magnet 26 and gears 20, 22 are situated in the pump cavity 25. Coaxially surrounding the magnet cup 28 is a stator 32 that is a respective component of the pump-driver potion 14. The stator 32 is located outside the pump cavity 25 and is magnetically coupled to the driven magnet 26 across the side walls 28a of the magnet cup. In the embodiment shown, the stator 32 is contained in a pump-driver enclosure 34. The pump-driver enclosure 34, being outside the pump cavity 25, is dry. In the embodiment shown in FIG. 1, the pump-driver enclosure 34 and pump-head portion 12 are mounted end-to-end so that a large part of the pump-head portion 12 extends from the pump-driver portion 14.

In this embodiment, the pump-driver potion 14 further comprises a printed circuit board (PCB) 36 that is located within the pump-driver enclosure 34 immediately above and substantially adjacent the stator 32, as shown in FIG. 1. The PCB 36 of this embodiment has a substantially annular shape and defines a central hole (i.e., void) 46 coaxial with and having a diameter substantially equal to or slightly larger than the outside diameter of the magnet cup 28 (see FIG. 2). Mounted to the PCB 36 are an electrical connector housing 38 for providing electrical power to the pump assembly and a plurality of circuit elements 40, as shown in FIGS. 1-2. The PCB 36 is electrically connected to the stator 32 and to one or more sensors 42 (FIG. 4) for sensing any of a variety of respective parameters (e.g. , pressure, temperature, etc.) of the fluid being pumped.

The PCB 36 contains one or more electronic circuits that, for example, provide controlled electrical power (i.e. , electrical power, logical control, signal conditioning, signal processing, etc.) to the stator 32 and to the one or more sensors 42. For example, the PCB 36 of this embodiment comprises a high-current electrical circuit for operating the stator 32 and at least one low-current electrical circuit for operating the one or more sensors 42. Desirably, the PCB 36 accommodates all the circuit elements 40 of the circuits required to operate the stator 32 and the one or more sensors 42 such that only a single printed circuit board is required. In this manner, all the electrical components are contained on or within the pump-driver enclosure 34 such that all that is required from outside (i.e. , from the OEM system) is electrical power input. The integrated-drive pump assembly 10 can also include an output for signals to or from the sensors 42 for use by, for example, OEM systems that are located remotely from the pump assembly.

Alternatively, the necessary electronic circuits can be laid out on two or more PCBs (not necessarily of similar size) substantially adjacent one another (e.g. , coaxially "stacked") or otherwise in close proximity within the pump-driver enclosure 34. Also, the PCB 36 need not be annular, but can comprise any shape that would fit in the pump-driver enclosure 34 and allow access to the distal-end wall 30 of the magnet cup 28 for location of sensors or fittings. For example, the PCB 36 can comprise one or more semi-annular printed circuit boards configured and arranged within the pump-driver enclosure 34 such that the distal-end wall 30 of the magnet cup 28 is accessible.

In the embodiment shown, the PCB 36 is configured such that the distal-end wall 30 of the magnet cup 28 is at least partially exposed through the central hole 46 of the PCB 36 when the PCB 36 is located above the stator 32 (i.e. , at least a portion of the distal-end wall 30 of the magnet cup 28 can be accessed through the annular-shaped PCB 36), as best shown in FIGS. 1- 2. In this manner, the distal-end wall 30 of the magnet cup 28 can be accessed and used for sensor location, as shown in FIG. 4, or for location of a fitting 44 in a flow-through pump, as shown in FIG. 5. In this application, a "flow-through pump" refers to a pump configured such that the fluid being pumped enters an inlet 16 defined in or on the pump cavity 25 and exits through an outlet 18 in the form of a hydraulic fitting 44 or the like located on the distal-end wall 30 of the magnet cup 28. The hydraulic fitting 44 mounted on the distal-end wall 30 of the magnet cup 28 allows pumped fluid to follow a flow path extending substantially in an axial direction with respect to the integrated-drive pump assembly 10 (note axis A and flow lines 52), as shown in FIG. 5. Alternatively, the hydraulic fitting 44 can be mounted on the side wall 28a of the magnet cup 28 and the fluid can follow a flow path that extends through the pump-driver portion 14 in a direction substantially normal to the axis A of the integrated-drive pump assembly 10. In the embodiment shown, desirably between approximately 50% to

approximately 100% of the surface area of the distal-end wall 30 is exposed through the central hole 46 of the PCB 36. Most desirably, 75% or more of the surface area of the distal-end wall 30 is exposed.

In an alternative embodiment, the PCB 36 is configured as a flexible printed circuit sheet or "board", such as a polymeric substrate in/on which circuit wiring is printed and circuit elements are mounted. The flexible printed circuit can be configured as a looped strip or ribbon 50, as shown in FIG. 6A. The ribbon 50 is bent or urged into a substantially cylindrical loop that is mountable inside the pump-driver enclosure 34. Thus, the ribbon 50 at least partially surrounds the magnet cup 28 while leaving the distal-end wall 30 exposed. A flexible printed circuit can reduce the volume of the circuitry required to operate the integrated-drive pump assembly 10, thereby reducing the size of the pump-driver enclosure 34. A flexible printed circuit can also provide enhanced possibilities for locating circuitry inside the pump-driver enclosure 34 without compromising access to the distal-end wall 30 of the magnet cup 28. For example, a flexible printed circuit, such as the ribbon 50, could be used in combination with the PCB 36 in the manner shown in FIG. 6B. As shown in FIG. 6B, the ribbon 50 can be urged into a substantially cylindrical loop with the PCB 36 (shown in phantom) located above and substantially adjacent the ribbon 50 such that the distal-end wall 30 of the magnet cup 28 is exposed. In other embodiments the printed circuit has characteristics of both a looped ribbon and an annulus.

Referring to FIG. 7, the PCB 36 can be configured such that certain sensor(s), such as

Hall sensors 60, are connected to one face 64a of the PCB 36 while other sensor(s) 42 are connected (via conductors 62) to the opposite face 64b of the PCB. This places the Hall sensors 60 advantageously relative to the side wall 28a of the magnet cup 28 for sensing rotation of the magnet 26, while placing other sensors 42 advantageously relative to the distal-end wall 30 of the magnet cup. Similarly, other electronic components mounted to the PCB 36 need not all be located on one face of the PCB (e.g. , opposite face 64b); rather, both faces 64a, 64b of the PCB can be used for mounting components as conditions and/or size constraints dictate.

Further with respect to sensor location, one or more sensors 42 can be located on or relative to the distal-end wall 30 of the magnet cup 28 and electrically connected to the PCB 36, as shown in FIG. 4 (see also FIG. 7). In some embodiments, the one or more sensors 42 can also be integrally formed with the distal-end wall 30 of the magnet cup 28 (i.e. , a portion of the distal-end wall 30 can be configured to act as, or as a portion of, the sensor 42). As a result, the sensor 42 is not actually wetted by the fluid. However, if the parameter being sensed requires that the sensor(s) 42 be wetted by the fluid (e.g., conductivity sensors, pH sensors, etc.), then the one or more sensors 42 can also be sealingly mounted to the distal-end wall 30. (See, e.g. , U.S. Patent Application No. 13/151,188, incorporated herein by reference.) In this application, "sealingly mounted" means that the sensor 42 or other element being mounted is held in a position so as to maintain contact with at least a portion of the mounting surface at one or more contact points at which a static seal prevents fluid from passing through or across the surface. The static seal may take the form of, for example, the surface itself, an o-ring, an absorbent material, an adhesive material, or the like. In this manner, one or more sensors 42 can extend through the distal-end wall 30 of the magnet cup into the pump cavity 25, where they can be wetted by the fluid, without leakage into the pump-driver enclosure 34. Similarly, with respect to the location of a fitting 44, the fitting 44 can be sealingly mounted to the distal-end wall 30 of the magnet cup 28 such that the pump 10 can be configured as a flow-through pump.

The pump-driver enclosure 34 desirably is cylindrical, with an axial length dimension a and a transverse or radial dimension β, as shown in FIGS. 3A-3B, such that an aspect ratio of the pump-driver enclosure 34 can be defined by the expression α / 2β. Desirably, the aspect ratio of the pump-driver enclosure 34 is as low as practicable to accommodate the necessary driver components and stator while allowing the pump 10 to be incorporated into ever smaller OEM hydraulic systems. As a practical matter, the radial dimension β is limited by the diameter of the driven magnet 26 and by the diameter of the stator 32, which must surround the driven magnet 26 to cause axial rotation of the magnet. Similarly, the axial length dimension a is limited by the need to accommodate the axial length of the driven magnet 26 and hence the stator 32, the PCB 36 and other necessary electronic circuitry thereon, the one or more sensors 42 and/or the fitting 44, and the electrical-connector housing 38. Thus, the aspect ratio of the enclosure 34 is generally limited to between approximately 0.25 and 1, depending upon the dimensions and orientation of the components that must be accommodated.

For example, the axial length dimension a can be reduced by configuring the pump- driver enclosure 34 such that the hydraulic fitting 44 extends through a distal-end wall 48 of the pump-driver enclosure 34, or by configuring the electrical-connector housing 38 with an angular (e.g., right-angular) bend. Alternatively, the pump-driver assembly need not include an electrical-connector housing 38 (i.e., the electrical connection facilitated by the electrical- connector housing 38 can be made by, e.g., soldering or otherwise making a hard connection of the associated electrical leads directly to the PCB 36). In this alternative configuration, where proximal ends of electrical leads are hard-connected to the PCB, the distal ends of the electrical leads can terminate with one or more connectors that connect to circuitry elsewhere. Desirably, the aspect ratio can be between approximately 0.4 and 0.7, as shown in FIGS. 3A and 3B, respectively. Most desirably, the aspect ratio can be approximately 0.5 or less, as shown in FIGS. 4-5. In alternative embodiments the pump-driver enclosure 34 is not cylindrical, but rather has an appropriate shape with sufficient interior volume to accommodate the components necessary to operate the pump assembly. For example, the pump-driver enclosure 34 could be square or rectangular, and could have an aspect ratio defined by the expression a / β, where a is an axial dimension and β is a transverse dimension.

In further alternative embodiments, the pump-driver portion 14 need not include a pump- driver enclosure. In these alternative embodiments, the aspect ratio of the pump-driver portion 14 can be defined by the dimensions of the respective components associated with the pump- driver portion. For example, the axial length dimension a can correspond to the height of the components of the pump-driver portion (i.e., the stator 32, the PCB 36, fittings, etc.) and the height of components of the pump cavity 25 that extend into the pump-driver portion (e.g., the magnet cup 28). Similarly, the transverse dimension β can correspond to the diameter of the driven magnet 26 and the stator 32, as described above.

Although the foregoing embodiments include one or more sensors for sensing pump parameters (such as temperature, pressure, etc.) and/or Hall sensors 60 for sensing rotation of the driven magnet 26, alternative embodiments need not include such sensors or include any sensors at all. For example, it is possible to use a brushless direct current (BLDC) motor controller wherein the stator is driven by a circuit that does not require Hall sensors. Similarly, depending upon the requirements of the OEM system into which the integrated-drive pump assembly 10 is incorporated, the pump assembly need not include any parameter sensing. However, in such alternative embodiments, the distal-end wall 30 of the magnet cup 28 desirably remains exposed, thereby preserving the ability to mount sensors on the distal-end wall 30.

The range of candidate pump-heads is not limited to gear pumps. Exemplary alternative types of pump-head, without intending to be limiting, are valved or valveless piston pumps. A valveless piston pump is disclosed in, for example, U.S. Patent Publication No. 2007-0237658, incorporated herein by reference. See particularly FIG. 11 of this reference and accompanying discussion on pages 9- 14 thereof.

Reference is now made to FIG. 8, depicting a portion of a piston pump-head 200, including a piston 212, a housing 214, a liner 216, an inlet port 228, and an outlet port 230. The piston 212 is coupled to a driven magnet (not shown). As the magnet rotates as described above, the piston 212 moves in a reciprocating manner (arrows 222) in a bore 224 defined in the housing 214.

In some embodiments, the pump-head portion 12 and the pump-driver portion 14 can be configured to be releasably attachable to one another. For example, with reference to FIGS. 10A-10E, the pump-head portion 12 and the pump-driver portion 14 can be releasably attached by pipe threads 70 (FIG. 10A), a twist-lock or bayonet mount 72 (FIG. 10B) having one or more protrusions 74 and associated slots 76, a ball 78 and detent 79 system (FIG. IOC), or one or more fasteners 80 (see, e.g., FIGS. 1 and 10D). In some embodiments, seals 82 (FIGS. 10D and 10E) can be located between the pump-head portion 12 and the pump-driver portion 14 to prevent leakage of the pumped fluid out of the pump cavity 25 (however, a pipe thread 70 does not normally require a seal). Suitable seals can include, for example, one or more O-rings, gaskets, etc. In the manner of any of these embodiments, the pump-driver portion 14 and the pump-head portion 12 can be quickly and easily assembled together and separated to facilitate, e.g., servicing, replacement of parts, or replacement of the pump-head portion and/or the pump- driver portion.

Another aspect of this disclosure pertains to hydraulic circuits (i.e., hydraulic pump systems) comprising a pump such as any of the embodiments described above. An embodiment of a circuit 100 is shown in FIG. 9, which includes a pump and pressure sensor 102 having an inlet 104 and an outlet 106. The pump and pressure sensor 102 can be as denoted by the pump assembly 10 described hereinabove, or any other embodiment. The inlet 104 is situated downstream of a filter 108, which is situated downstream of a fluid reservoir (i.e., tank) 110 serving as a reservoir for fluid to be pumped by the pump 102. The outlet 106 is hydraulically connected to a downstream fluid utility unit 112 (e.g., an injector, print head, or other component) from which pumped fluid is discharged from the circuit. If desired, the circuit 110 can include a return line 114 for returning fluid to the fluid reservoir 110 that is not actually discharged from the fluid utility unit 112.

It will be understood that this disclosure is directed not only to pump assemblies including pump head, stator, and pump driver, but also to "pump-driver" assemblies comprising the stator mounted to a PCB to which other electronic components are also mounted. Both types of assemblies represent convenient OEM- supplied products. In view of the many possible embodiments to which the principles of the disclosed invention may be applied, one of ordinary skill in the art will recognize that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of this disclosure. Rather, the spirit and scope of the invention is defined by the following claims.