This invention relates to combined electric motor and pump units.

In the development of combined electric motor and pum units separated electric motor units and pump units were initially provided and interconnected with a common drive shaft. To prevent loss of pumped liquids the pump unit required a gland seal for the drive shaft. Subsequently in order to reduce axial length, the separate units were combined together in a single housing. Initially in these combined units the electric motor was axially connected to the pump by a common drive shaft but subsequently the pump was located axially within the moto thereby rendering the combination axially compact. However in these combined units the problem of interactio of the pumped liquid with the electric motor is dealt wit by the provision of specialised seals and mechanical barriers in the form of an impermeable sleeve between the stator and rotor of the electric motor leading to a complicated mechanical construction for the combined unit and a reduced electromagnetic efficiency for the electric motor. Typically the impermeable sleeve is made of stainless steel.

According to the present invention there is provided a combined electric motor and pump unit having a casing provided with inlet and outlet ports for liquids to be pumped, and wherein the motor comprises a stator and a rotor and the pump comprises a fluid reaction member which forms part of the rotor and is located in a principal transmission path for pumped liquids, the rotor and stator of the motor being separated radially by a clearance which forms a secondary transmission path for pumped liquids, and the electrical windings of the motor being insulated with materials which are inert to the pumped liquids.

The insulating materials for the windings may be PVC or PTFE or polyurethane or suitable resin encapsulations.

By virtue of the present invention the motor does not have an impermeable sleeve between its stator and rotor so that the gap between the rotor and the stator can be minimised and the electromagnetic efficiency of the motor is therefore greatly increased thereby rendering the combined unit more compact than hitherto for the same pumping duty. Additionally, the mechanical construction of the unit is simpler than hitherto and the rotor is hydrodynamically lubricated. Because the rotor is hydrodyna ically lubricated and there is no impermeable sleeve between the stator and rotor substantially less heat is generated in the motor so that the operational life of the motor is greater than hitherto.

The pump may be arranged for axial flow, centrifugal flow or mixed flow or it may be a gear pump and it may incorporate a plurality of fluid reaction members. The electric motor may be of the squirrel cage type or salient pole type (for example a variable reluctance motor) .

The rotor may comprise a plurality of rotor units mounted coaxially. Alternate rotor units may be formed with their fluid reaction members of opposite hand. The rotor units may be arranged to rotate in opposite directions by the arrangement of the stator windings in a polyphase motor or by appropriate arrangement of the starter coils for each rotor unit in a single phase motor.

Preferably, a single stator is common to all rotor units, the rotors having stator vanes positioned between them. Alternatively, each rotor unit may operate with a separate stator unit, enabling the production of different rotational speeds and/or power to the different rotor units.

Preferably, the rotor extends beyond the stator, the rotor being formed with radially extending passages,

enabling the unit to operate as a centrifugal pump. Fo example, in such a construction the stator may comprise two units with a fluid inlet at each end of the casing, the outlet being positioned centrally between the pair o stators. Such an arrangement would balance hydraulic a magnetic thrusts independently.

Preferably, the stator units are connected to individual supplies of alternating current at variable frequencies and/or different voltages.

Alternatively, the windings of the individual stator units may be arranged to provide different numbers of poles.

Different rotor units may have different lengths and/or diameters and several rotors and stators may be arranged one within the other.

The rotors may be formed with several sets of helical passages, each set being concentric with the axis of the rotor but being at different radial distances from the axis. Also, different sets of passages may be connectible to different fluids to be pumped. Alternatively in a reflex arrangement, fluid leaving one set of helical passages may be directed to another set of helical passages in the same rotor. The various passage in the rotor may be of circular or non-circular cross section and may be of non-constant area depending on the use to which the pu pis to be put.

A rotor external to the stator and rotatable about th stator may be formed with radially projecting vanes the rotor and the stator being enclosed in an eccentric position within a circular casing having entry and discharge ports whereby the unit may be capable of functioning as a liquid ring pump. Such a pump may be formed as a self-contained roller unit by forming the rotor external to the stator with an external roller surface thus eliminating external gears and couplings.

When the motor is of the variable reluctance type and the pump is of the centrifugal type it is particularly advantageous for the gap between stator and rotor to lie on the surface of a cone the axis of which is the rotational axis of the rotor so that the cross-sectional outline of the rotor follows the shape of the main transmission passageway for liquids extending through the rotor and having small and large diameter impellers at respective ends.

When the pump is of the swash plate type having a plurality of piston and cylinder units mounted with a radial offset from the axis of a support body, the piston being interconnected with a swash plate which is inclinde at an angle to that axis, either the swash plate or the support body may function ε_ the rotor of the electric motor, although the latter is preferred to permit variabl inclination of the swash plate. Liquids to be pumped ar of course transmitted to and from the cylinders by a conventional swash-plate-pump manifold..

Embodiments of the present invention will now be described, by way of example, with reference to accompanying drawings in which:-

Fig. 1 shows a combined electric motor and gear pump in accordance with the present invention;

Fig. 2 shows a combined electric motor and mixed flow pump in accordance with the present invention;

Fig. 3 shows a combined electric motor and axial flow pump in accordance with the present invention; and

Fig. 4 shows another form of combined electric motor and mixed flow pump in accordance with the present invention.

The drawings show combined electric motor and pump units comprising a casing 4 having a pump inlet 5, 12, 18 and 29 and a pump outlet 6, 13, 19 and 30 connected by a principal transmission path for pumped liquids, a fluid

reaction member 3, 10, 16 and 23 positioned in the principal transmission path, and an electrical stator and rotor arrangement, the rotor 2, 9, 15 and 21 being united with the reaction member 3, 10, 16 and 23. The electrical windings of the stator 2,9,15,21 are insulated with materials which are inert to the pumped liquids, PTFE wrappings being preferred, and a secondary liquid transmission path is provided through the motor via the clearance between the rotor and stator. An impermeable sleeve is not provided between the rotor and stator. The rotor is hydrodynamically lubricated by the pumped liquids in the transmission paths.

Fig. 1 shows a combined unit in the form of a gear pump comprising two stators 1 each having electrical windings 8 and a rotor 2 in the form of a ring which is rotatable around the exterior of the stator 1. Each rotor has conductor bars 7 and also is formed with externally projecting gear teeth 3. The two rotors 2 mesh with one another and are disposed without bearings within a.close fitting casing 4 having entry and discharge passages 5 and 6 for pumped liquids. Because there are two motors a greater pump output is achieved than would be the case if one of the rotors 2 did not form part of an electric motor.

When in use, liquid enters the input passage 5 and is carried by the gear teeth 3, around to the discharge passage 6 so that a principal transmission path is formed around the periphery of the casing 4. Additionally however, a secondary transmission path for pumped liquid is formed by the spaces between the ends of the rotors 2 and the casing 4 which are interconnected by the annular clearance between the rotors 2 and the pertaining stators 1 and liquid which permeates into the secondary transmission path provides hydrodynamic lubrication of the rotors 2.

Fig. 2 shows a mixed flow pump comprising an annular stator 1 with windings 8 which rotatably receives a rotor 9 with conductor bars 7. The rotor is formed with an axial passageway and is supported for rotation on axially separated bearings 11 by hub units having generally radially-extending arms which are hydrodynamically profiled to form axially separated sets of impeller blade 10. The casing 4 comprises an inlet 12, and an outlet 1 which forms part of a volute. Thus the principal transmission path is axially through the rotor 9 which provides for hydrodynamic lubrication of the bearings 11 but the secondary transmission path is through the clearance between the stator and rotor and the end clearances between the rotor 9 and the casing.

Fig. 3 shows a linear pump comprising a casing 4 within which there is located an annular stator 14 with windings 8 which receives a rotor 15 with conductor bars 7. The rotor 15 has an axial passageway in which is formed a central impeller 16 which at its periphery is united with the rotor and which is mounted on axially-separated journals 17 carried by axially-separate hub units forming part of the casing 4.

The casing 4 has an inlet port 18 for delivery of liquid to be pumped to the principal transmission path axially through the rotor 15, and an outlet port 19 in which is located a set of static vanes to provide for flo straightening of the pumped liquids. Pumped liquids in the principal transmission path provide hydrodynamic lubrication of the journal bearings. The secondary transmission path is formed by the spaces between the rotor 15 and the casing 4 and the stator 14.

Fig. 4 shows a second embodiment of the mixed flow pump having a stator 20. A tube 22 mounted at each end on bushes 25 externally carries a magnetically active annulus so as to form a rotor 21 and internally carries

impeller blading 23 which projects from a hub 23A. A static flow straightening bladed diffuser 24 having its blades projecting from a hub 24A is mounted on an end flange 26 of the casing at the output port 30 and project into the tube 22. Bushes 25 are hydrodynamically lubricated by liquids traversing the secondary transmission path between the stator 20 and the rotor 21.

In each of the embodiments of the pump the impeller 3, 10, 16 and 23 can be designed such that a flow of fluid through the unit induces rotation of the impeller 3, 10, 16 and 23 which in turn causes rotation of the rotor 2, 9, 15 and 21. With a suitable electrical design, the unit may then be made to act as an electrical generator.