GB2113306A

GB2113306A - Rotary positive-displacement fluid-machines

Info

Publication number: GB2113306A
Application number: GB08200366A
Authority: GB
Inventors: Lloyd Garnet Knight
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1982-01-07
Filing date: 1982-01-07
Publication date: 1983-08-03
Also published as: GB2113306B

Abstract

A pump has a rotor 6 in the form of a cylindrical permanent magnet within which the flux is orientated axially thereof so that it can be rolled along the inner peripheral wall of a pumping chamber within a stator 1 by a rotating magnetic-field produced by a polyphase winding (not shown) in the latter. Fluid is thereby displaced by the rotor from an inlet port 2 to an outlet port 3. The magnetic field may be a "stepping" one, instead of rotating. Alternatively, the rotor revolves around the chamber without rotating about its own axis, a spring- loaded vane 5 then being replaced with a flexible vane attached to both the rotor and the stator, Figure 2 (not shown). <IMAGE>

Description

SPECIFICATION Fluid pump This invention relates to a fluid pump having a simple integral pump and motor construction.

A well known type of fluid pump is one using an eccentric rotor in a cylinder which is provided with separate inlet and outlet ports between which is a spring loaded sliding vane making contact with the rotor. The rotor is conventionally driven by an external motor.

According to the present invention there is provided a fluid pump comprising an axially magnetised permanent magnet rotor placed within a polyphase multi-coil laminated cylindrical stator having a greater internal diameter than the external diameter of the rotor, the stator being provided with closely angularly spaced separate inletloutlet ports and a vane extending radially inwards from between the ports to make sealing contact with the rotor.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figs. 1(a)-i (d) illustrate a pump having a freely rotatable rotor, and Figs. 2(a)-2(c) illustrate a pump having an oscillating rotor.

The invention utilises the so-called "Steromotor" principle. This is described in Electric Motors Handbook, Chapter 18, "Special Motors" by R. W. Pearce, Edited by G. G. Weaver, Product Journals Limited, 1 968. Essentially the Steromotor consists of an axially magnetised permanent magnet rotor within a-polyphase multi-coil laminated stator. When the stator is energised a rotating magnetic field is generated and interacts with the rotor which is free to roll around the stator bore. The rotor aligns itself with the rotating magnetic field in the stator and describes a hypocyclic path around the stator bore.The slow hypocyclic motion of the rotor has an angular velocity given by the expression: D-d Nccw.--- d where w=angular velocity to the rotating field, D=stator bore diameter, d=effective rotor diameter.

In the pump illustrated in Fig. 1 a stator 1 is provided with closely angularly spaced inlet and outlet ports 2, 3. Extending inwardly from a slot 4 between the ports 2, 3 is a vane 5 which is urged into continuous sealing contact with a rotor 6 by means of a spring arrangement 7. As the rotor rolls around the stator bore the inlet port 2 is uncovered, admitting fluid into a chamber 8 bounded by the stator bore between the point of contact with the rotor and the sealing vane, the corresponding portion of the rotor circumference, and the vane 5 which effectively seals this inlet chamber from an outlet chamber 9 communicating with port 3. As the rotor continues to roll around the stator the volume of the inlet chamber increases causing the admittance of further fluid.At the same time fluid contained in the outlet chamber is expelled through port 3 as the outlet chamber decreases in size. Evenually a point is reached when the point of contact between the rotor and the stator passes across inlet port 2. At this moment, what had been an increasing volume inlet chamber now becomes an outlet chamber of decreasing volume. At the same time a fresh inlet chamber is created.

When pumping viscous liquids or slurries it may be advantageous to prevent slip between the rotor and the stator by providing toothed engagement therebetween. The Steromotor principle provides a high torque at slow speeds, making it suitable for pumping difficult liquids.

Furthermore, there are no conventional bearings, therefore no bearing wear occurs. Nor is any gearbox needed and so gearbox wear is eliminated. The only point at which friction wear occurs is where the spring loaded vane 5 contacts the rotor, and low friction hard wearing materials are obtainable to minimise wear at this point.

Finally, the pumping action can be simply reversed by reversing the direction of rotation.

This is easily achieved by changing the polarity of one of the two stator phases. It is to be noted that no directional valves are required in this construction.

The steromotor principle lends itself to the construction of so-called "stepping" motors, in which dc pulses are fed in sequence to the stator coils. This results in defined incremental rotation of the rotor. Such an operation allows the construction of an oscillating pump as shown in Fig. 2. As in the previous embodiment the stator 11 is provided with two closely spaced ports 12, 1 3. The rotor 1 6 in this case however comprises a major sector only of a cylinder. Instead of the sliding vane of the previous construction a fixed vane 1 5 extends radially inwards from a point midway between the ports 12, 13 and is attached to the rotor at its axis, i.e. at the apex of the cutout minor sector.The vane 1 5 is either rigid with resilient attachment to the stator and a flexible portion 1 spa attached to the rotor, or the entire vane is flexible yet inelastic. If the stator is energised to cause rotation in one direction, as indicated in Fig. 2(a), fluid will be admitted via port 12 into one chamber 18 and expelled via port 1 3 from a second chamber. When the rotor reaches the position shown in Fig. 2(c) the energising of the stator is changed to reverse the direction of rotation. Fluid is now expelled via port 12 from the first chamber and admitted via port 1 3 into the second chamber. the pulsing action imposed on the fluid can be converted into unidirectional flow by a suitable arrangement of external directional valves (not shown). With appropriate dimensioning of the rotor relative to the stator bore a high throughput of fluid can be obtained compared with that obtainable from the pump of Fig. 1.

Claims

1. A fluid pump comprising an axially magnetised permanent magnet rotor placed within a polyphase multi-coil laminated cylindrical stator having a greater internal diameter than the external diameter of the rotor, the stator being provided with closely angularly spaced separate inlet/outlet ports and a vane extending radially inwards from between the ports to make sealing contact with the rotor.

2. A pump according to Claim 1 wherein the rotor is a freely rotatable cylinder and the vane is a spring loaded vane slidably mounted in an axial slot in the stator.

3. A pump according to Claim 1 wherein the rotor is a major sector of a cylinder and the vane extends to the axis of the cylinder.

4. A pump according to any preceding claim wherein the rotor is in toothed engagement with the stator.

5. A fluid pump substantially as described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.

6. Afluid pump comprising an electric motor having a rotor driven by the steromotor principle and wherein the chamber in which the rotor moves is adapted to form a fluid pumping chamber with angularly spaced inlet and outlet ports for the fluid communicating with the chamber.