Pump

Abstract

A pump system 2 has a drive unit 4 and removable pump units 8, 10. The pump units have a body 22,26 having a pump cavity 24 and a rotary pump element 34 arranged to rotate in the pump cavity about an axis. Vanes 42 drive fluid from inlet 28 to outlet 30. A magnetic coupling is provided between magnets 40 in the rotary pump element 34 and magnets 16 in drive unit 4. A magnetic disk 48 provides an opposed axial force to axially balance the force between magnets 40 and magnets 16.

Description

FIELD OF INVENTION

The invention relates to a pump, and in embodiments to a vane pump having axially movable vanes.

RELATED ART

An important application for pumps is in the medical field. Where the fluid being processed is a bodily fluid such as blood or peritoneal fluid, pumps need to avoid cross-contamination of fluid of one patient with another. For this reason, medical equipment frequently uses pumps in which fluid flows through a flexible tube and is urged forwards by rollers outside the tube. The flexible tube can then be replaced for each patient.

However, such pumps are not suitable in all circumstances. For example, in some applications there is a need for a portable pump. It is also useful if the pump can be quiet, and low power, for example battery powered.

SUMMARY OF INVENTION

According to the invention there is provided a pump system, comprising a drive unit, comprising a housing, at least one motor and at least one magnetic coupling drive connected to a respective motor to be rotated by the motor; and at least one removable pump unit, the or each removable pump unit comprising: a body having a pump cavity with an inlet and an outlet, a rotary pump element arranged to rotate in the pump cavity about an axis, and a magnetic coupling coupled to the rotary pump element magnetically coupling the rotary pump element with the magnetic coupling drive, and a plurality of drive vanes for pumping fluid from the inlet to the outlet.

In embodiments, the pump system reduces or minimises the risk of contamination by providing removable units. The use of a magnetic drive avoids the need to have an axle or spindle passing through the body into the pump cavity and hence increases reliability and ease of manufacture since no drive shaft seal is required. The rotary pump element may simply be contained by and rotate in the pump cavity.

Importantly, the removable pump units may be manufactured relatively cheaply and yet reliably. This is particularly important in medical use, where the removable pump units may need to be replaced for each patient.

The pump system may be a portable, micro pump system. Accordingly, in embodiments the thickness of the body does not exceed 2 cm and the maximum dimension of the body does not exceed 5 cm.

The pump system may be suitable for use as a portable pump. Accordingly, the pump system may be driven by external batteries which allow for the pump unit to be used even where mains power is not available. As an alternative, batteries may be incorporated in the housing.

The pump system may contain one or more of a number of design features designed to allow the system to operate as a small, portable system without requiring too much power.

In particular, the pump system may further comprise a magnetic compensation unit arranged on the opposite side of the magnetic coupling to the magnetic coupling drive to compensate for the axial force between the magnetic coupling and the magnetic coupling drive. One problem with a magnetic coupling is that the magnetic coupling between drive unit and rotary pump elements must be relatively strong in order for sufficient rotational coupling to take place to drive the pump against a back pressure. However, such a strong force also causes axial force which forces the rotary pump element against the inside of the pump cavity and hence causes significant friction.

By providing an opposing magnetic force in the opposite direction to the force between the magnetic coupling drive and the magnetic coupling of the rotary pump element this axial force is compensated for and reduced. This can reduce the friction and hence the power needed to drive the system as well as increase the reliability.

Conveniently, the magnetic compensation unit may be a disk of ferroelectric material arranged on the opposite side of the magnetic coupling to the magnetic drive unit.

In one embodiment, the body comprises a base piece arranged to face the drive unit; and a cover having the inlet and the outlet and channels to link the inlet and the outlet to the pump cavity, the base piece and the cover cooperating to define the pump cavity. Such a body is relatively easy to manufacture.

The magnetic compensation unit may be incorporated in the cover.

The drive unit may further comprise a movable lid which in a closed position cooperates with the housing to contain the or each removable pump unit and in an open position allows the or each removable pump unit to be removed. In such an embodiment, the magnetic compensation unit may be incorporated in the lid, or in the cover.

The rotary pump unit may have a plurality of slits circumferentially arranged and the drive vanes are arranged to be axially displaceable in respective slits.

To provide a sufficient drive, the magnetic drive unit may comprise a plurality of magnets circumferentially arranged on a drive disk, and the magnetic coupling comprises a corresponding plurality of magnets circumferentially arranged around the rotary pump element to match the drive disk.

The rotary pump element may contain a plurality of axial holes, and the magnets of the magnetic coupling may be provided in the axial holes.

To provide a reliable coupling, the circumferentially arranged magnets of the drive disk and the corresponding plurality of magnets of the rotary pump element are arranged to have alternating polarity. In this way, the alternating magnets also serve to locate the position of the rotary pump element.

In alternative embodiments, the magnetic coupling elements may be magnetic material, such as a ferromagnet, for example soft iron, but not a magnet as such. Such ferromagnetic materials may reliably couple to the magnets in the drive unit.

The removable pump units may include a single unit with one rotary pump element and a dual unit with a pair of rotary pump elements.

In another aspect, the invention relates to a removable pump unit for a pump system comprising: a base piece defining the pump cavity; a cover having an inlet and the outlet and channels to link the inlet and the outlet to the pump cavity; one or more rotary pump elements in the form of a disk with a plurality of slits and a plurality of axial holes contained in the pump cavity without a spindle or axle, a plurality of magnets in the axial holes to act as a magnetic coupling; a plurality of vanes in the slits; and means fixing the cover to the base piece.

Such a system may be relatively straightforward to manufacture and yet reliable.

The removable pump unit can include a ferromagnetic disk in the cover as a magnetic compensation unit.

Alternatively, the removable pump unit can be designed without such a disk and the magnetic compensation unit may be included in a lid of a drive unit.

For a better understanding of the invention, an embodiment will now be described, purely by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of a pump system according to an embodiment;

FIG. 2 is a side section through the pump system of FIG. 1, and

FIG. 3 is a detail perspective view of the underside of the cover of a removable pump unit shown in FIGS. 1 and 2.

The figures are schematic.

Referring to FIGS. 1 and 2, a pump system 2 includes a drive unit 4 having a housing 6 and a first, single removable pump unit 8 and a second, dual removable pump unit 10. In the following description, the removable pump unit 8 and corresponding drive will be described. The removable pump unit 10 is of corresponding design, except that there are two of every component to deliver two pumps.

The drive unit 4 includes a motor 12, an electric motor, and a magnetic coupling drive 14 in the form of a disk coupled to the motor 12 and having six axial through holes 18 for containing permanent magnets 16. The permanent magnets 16 are arranged with the direction of the magnetic flux along the axial direction, and alternating around the through holes so that the polarities of the magnets alternate. In other words, the magnets are arranged with magnets having the N pole facing up alternating with magnets having the S pole facing up.

A hinged lid 20 is provided which closes (shown in FIG. 2) to contain the drive elements 8, 10 and opens (shown in FIG. 1) to allow the elements to be replaced.

The drive unit 4 is arranged to drive the removable pump units 8,10.

The removable pump unit 8 has a body comprising a base 22 defining a pump cavity 24 and a cover 26 arranged to cover the pump cavity 24. The cover has an inlet 28 and outlet 30. The underside of the cover (FIG. 3) has channels 32 which connect the inlet 28 and outlet 30 to the pump cavity 24.

A rotary pump element 34 in the form of a disk having through holes 36 and slits 38 is sized to rotate in the pump cavity 24. A plurality of permanent magnets 40 are arranged in the through holes 36, alternating to correspond to the permanent magnets 16 in the drive unit. FIG. 2 shows how magnets 40 correspond to magnets 16.

A plurality of vanes 42 are provided in the slits 38. The vanes are not fixed, but are free to move axially in the slits 38. In use, the vanes move out by centrifugal force to engage the inner circumference of the pump cavity.

A magnetic compensation unit in the form of a disk 48 of iron, a ferromagnet, is mounted in recess 46 in the cover 26. The distance from the disk 48 to the rotary pump element 34 is less than the distance from the rotary pump element 34 to the magnets 16 in the drive unit. This is because the coupling of the magnets 40 in the rotary pump element 34 is stronger with the permanent magnets 16 than with the iron disk 48. The goal is to balance out the axial forces on the rotary pump element. Without the disk 48, the strong magnetic attraction between the magnets 40 and permanent magnets 16 would cause a large amount of force urging the rotary pump element 34 axially towards the drive unit 4 and so cause significant problems with friction. The disk 48 provides an axial force in the opposite direction and so greatly reduces the force of pump element 34 against the inside of the pump cavity 24 and so greatly reduces friction and hence frictional loss. Preferably, the resulting axial force from both permanent magnets 16 and magnetic compensation disk 48 on the magnets 40 of pump element 34 is no more than 20%, preferably 10%, of the axial force on the pump element 34 caused by the interaction of permanent magnets 16 on magnets 40 alone.

In the embodiment shown, a blocking element 54 is used two functions. It is a separate piece that supports disk 48 as well as extending into the chamber 24 as a spindle to locate the rotary pump element 34.

Note that in this description the term “axis” is used to describe a nominal axis in its thickness direction.

In alternative embodiments, the disk 48 may be a ring with a central hole. The blocking element 54 may then be replaced with a spindle element passing through the disk 48, the cover 26 and the rotary pump element 34 to act as the axle of the rotary pump element 34.

It may in some applications even possible that there is no axle or spindle at all. The inventors have discovered that it is possible to use a magnetic coupling vane pump even without the use of an axle or spindle to locate the rotary pump element and even though the pump element 34 must be smaller than the pump cavity 24 so that it does not engage the rim of the pump cavity at all to allow space for the free axially movable vanes.

The use of alternating magnets in this embodiment is sufficient to locate the rotary pump element and provide enough drive without requiring an axle or spindle extending from the cavity 24 to the drive unit 4.

Screws 52 couple together the cover 26 and base piece 22. Alternatively, glue may be used.

The motors 12 are located within a cavity 50 inside housing 6.

In the embodiment shown, there is provided a single removable unit 8 and a dual unit 10. This may be changed for other applications if required—there may be one or more single, dual, triple units or more as required.

The drive unit 4 may use battery power or power from an external source. Thus, in an alternative embodiment a battery may be provided in the housing 6.

Instead of mounting the disk 48 in the removable unit, it may instead be mounted in the lid 20.

Any suitable inlet and outlet 28, 30 may be used. The form shown in the drawings is suitable for tubular connecting pipes, but other forms may be required in other applications.

Although the pump described is a vane pump, alternative pumps may be used. For example, in some applications a gear pump may be more suitable, in which two rotary elements are provided in an intermeshed form, rotating in a pump cavity 24 in the form of an approximate figure of “8” to drive fluid. The skilled person will also be aware of yet further pump types that may be used.

Claims

1. A pump system, comprising:

a drive unit, comprising a housing, at least one motor and at least one magnetic coupling drive connected to a respective motor to be rotated by the motor; and

at least one removable pump unit,

the or each removable pump unit comprising:

a body having a pump cavity with an inlet and an outlet,

a rotary pump element arranged to rotate in the pump cavity about an axis, and

a magnetic coupling coupled to the rotary pump element magnetically coupling the rotary pump element with the magnetic coupling drive, and

a plurality of drive vanes for pumping fluid from the inlet to the outlet.

2. A pump system according to claim 1, further comprising a magnetic compensation unit arranged on the opposite side of the magnetic coupling to the magnetic coupling drive to compensate for the axial force between the magnetic coupling and the magnetic coupling drive.

3. A pump system according to claim 1, wherein the magnetic compensation unit is a disk of ferroelectric material arranged on the opposite side of the magnetic coupling to the magnetic drive unit.

4. A pump system according to claim 1, wherein the body comprises:

a base piece arranged to face the drive unit; and

a cover having the inlet and the outlet and channels to link the inlet and the outlet to the pump cavity;

the base piece and the cover cooperating to define the pump cavity.

5. A pump system according to claim 4 wherein the magnetic compensation unit is incorporated in the cover.

6. A pump system according to claim 2 wherein the drive unit further comprises a movable lid which in a closed position cooperates with the housing to contain the or each removable pump unit and in an open position allows the or each removable pump unit to be removed,

wherein the magnetic compensation unit is incorporated in the lid.

7. A pump system according to claim 1, wherein the rotary pump unit has a plurality of slits circumferentially arranged and the drive vanes are arranged to be axially displaceable in respective slits.

8. A pump system according to claim 1, wherein the magnetic drive unit comprises a plurality of magnets circumferentially arranged on a drive disk, and the magnetic coupling comprises a corresponding plurality of magnets circumferentially arranged around the rotary pump element to match the drive disk.

9. A pump system according to claim 8, wherein the rotary pump element contains a plurality of axial holes, and wherein the magnets of the magnetic coupling are provided in the axial holes.

10. A pump system according to claim 8, wherein the circumferentially arranged magnets of the drive disk and the corresponding plurality of magnets of the rotary pump element are arranged to have alternating polarity.

11. A pump system according to claim 1, wherein the removable pump units include a single unit with one rotary pump element and a dual unit with a pair of rotary pump elements.

12. A pump system according to claim 1, further comprising an electric battery for providing drive power to the motor.

13. A removable pump unit for a pump system comprising:

a base piece defining the pump cavity;

a cover having an inlet and the outlet and channels to link the inlet and the outlet to the pump cavity;

one or more rotary pump elements in the form of a disk with a plurality of slits and a plurality of axial holes contained in the pump cavity without a spindle or axle,

a plurality of magnets in the axial holes to act as a magnetic coupling;

a plurality of vanes in the slits; and

means fixing the cover to the base piece.

14. A removable pump unit for a pump system according to claim 13 comprising a magnetic compensation unit in the form of a ferromagnetic disk in the cover.

15. A removable pump unit for a pump system according to claim 13 wherein the thickness of the base piece and cover does not exceed 2 cm and the maximum lateral dimension of the base piece and the cover does not exceed 5 cm.

16. A pump system according to claim 3 wherein the drive unit further comprises a movable lid which in a closed position cooperates with the housing to contain the or each removable pump unit and in an open position allows the or each removable pump unit to be removed,

wherein the magnetic compensation unit is incorporated in the lid.