GB2126017A - Improvements in or relating to electric machines serving as drives for circulating pumps - Google Patents

Abstract

An electric machine, particularly for a circulating pump, comprises a hemispherically shaped rotor 5 and an annular stator 1 which when in operation induces a voltage therein and which has a concave, spherically shaped recess in which the rotor is located with a spherically shaped air gap which extends around an imaginary sphere and in which there is disposed a hemispherically shaped non-magnetic member 4 which separates the stator space from the rotor space, and a ball pin 8 which is located at the centre point of the sphere for mounting the rotor so as to permit tumbling movements. The stator of the electric machine is manufactured from a continuous edgewise wound soft iron strip whose mutually adjacent turns form obtuse- angled conical surfaces and incorporate slots which are in alignment with one another and in which a two- or multi-strand winding is inserted. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electric machines, serving as drives for circulating pumps The present invention relates to electric machines, serving particularly as drive motors for circulating pumps.

One kind of drive motor has a generally hemispherical rotor and an annular stator which when in operation induces a voltage therein and which has a concave, generally spherical recess in which the rotor is located opposite the stator with a generally spherical air gap which extends on an imaginary sphere and in which is disposed a hemispherical ly-shaped non-magnetic member which separates the stator space from the rotor space, and a ball pin located in the centre point of the sphere for mounting the rotor so as to permit tumbling movements of the rotor.

Electric machines which have spherically shaped air gap and which are structurally combined with such pumps, are known from German Patent Specifications Nos. 1,463,800 and 1,538,715.

Jamming of the rotor after a long inoperative period is a relatively frequent source of trouble in commercially available circulating pumps for domestic heating systems and domestic water supplies. The reasons for trouble of this kind are small foreign bodies which are deposited in the magnetic air gap when the pump is not operating.

In a circulating pump having a rotor shaped as a segment of a sphere, the rotor can execute tumbling movements about its spherical bearing pin located in the centre point of the sphere when the pump is switched on, and can thus remove foreign bodies from the region of the air gap. During unobstructed running, the rotor is stabilised in its preferred magnetic position by magnetic forces.

According to the present invention there is provided an electric machine particularly for a circulating pump, having a hemispherically shaped rotor and an annular stator which when in operation induces a voltage therein and which has a concave, spherically shaped recess in which the rotor is located opposite the stator with a spherically shaped air gap which extends on an imaginary sphere and in which there is disposed a hemispherically shaped non-magnetic member separating the stator space from the rotor space, and a ball pin located at the centre point of the sphere for the purpose of mounting the rotor so as to allow tumbling movements, in which the stator comprises a continuous edge-wise wound sheet metal strip whose mutually adjacent turns form obtuse-angled conical surfaces and include a plurality of slots which are distributed in the direction of rotation and which are open towards the air gap and which are punched out of the strip before the winding operation and each of which contains a strand, passing through the stator over its entire axial thickness, of its two- or multi-strand winding which serves to induce a rotating electromagnetic field when in operation.

An electric machine embodying the present invention is suitable for driving a circulating pump and which, with small spatial requirements and satisfactory electrical-mechanical efficiency, can invdlve only a low expenditure on stator iron.

The invention will be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial longitudinal section of one embodiment of the invention, and Figure 2 shows a modification of the rotor of the embodiment of Figure 1.

The electric motor illustrated has a rotor shaped as a segment of a sphere and comprises a stator 1 having a multi-strand winding 2 which is embedded in slots 3. The stator 1 is of annular configuration and is made from a continuous soft iron strip (not illustrated in detail) which is wound edge-wise on a core indicated at 20.

Before the winding operation, the slots 3 of equal cross section are punched into the strip, taking into account the change in the diameter of the core. The winding operation for the stator strip commences in the immediate vicinity of a plane 21 defining the hemispherical shape of the core 20. The individual turns of the strip winding are closely contiguous to one another and form conical surfaces which form an angle a of approximately 1 50 to 250, preferably approximately 1 50 to 17.50, with the hemispherical plane 21, such that an obtuse angle of taper of 180-2 a = 1400 to 1500 ensues.It is at the same time ensured that the stator surrounds a recess which follows the hemispherically shaped outer contour of the core 20 and in which a rotor 5, also having a hemispherically shaped outer surface, is also accommodated. When in the illustrated, stabilised operation position, the rotor 5 mounted upon a ball pin 8, rotates about the axis of rotation A and, if required, can perform tumbling movements about the centre of the ball pin 8 located at the point of intersection of the plane 21 and the axis A, and can thereby remove any foreign bodies from the spherically shaped air gap between the rotor 5 and the stator 1.

A hemispherically shaped member 4 of nonmagnetisable shell metal or plastics material is disposed in the spherically shaped air gap between the stator 1 and the rotor 5 and separates the interior space 6 of the electric motor on the rotor side from the interior space 7 of the electric motor on the stator side.

The rotor 5 forms a structural unit together with the centrifugal plate 25 of a centrifugal circulating pump (not illustrated in detail) shown only in half section. In the embodiment illustrated in Figure 1, the rotor 5 contains a stack 11 of sheet iron disc shaped laminators which, in the manner of a short-circuited rotor, contains a short-circuited or squirrel edge winding 26 cast from aluminium.

When a rotating magnetic field is induced in the stator 1 having the two- or multi-strand winding 2, the rotor 5 can be carried along the magnetic field, thereby driving the circulating pump.

In the embodiment of Figure 1, the width of the stator 1, measured in the direction of the axis A, is approximately 55 to 60% of the spherical radius, indicated at r, of the recess in the stator 1. By virtue of the construction of the stator 1 in accordance with the invention, there is only a slight overhang of the electric machine in the direction of the axis A, and the stator, although it is of a size similar to that in known drive motors having a spherical rotor, is substantially more compact and is only slightly inferior to the stator of electric motors of machines constructed with a drum-shaped, nontumblable armature.

In the embodiment of Figure 2, the rotor 5 includes a sheet iron stack 12 which is continuously wound from a strip and which is wound onto the spherically shaped outer surface 27 of the rotor and in the continuous slots of which is provided an integrally cast short-circuited or squirrel cage winding.

It is also conceivable to construct the rotor as a hysteresis rotor.

Claims (6)

1. An electric machine, particularly for a circulating pump, having a hemispherically shaped rotor and an annular stator which when in operation induces a voltage therein and which has a concave, spherically shaped recess in which the rotor is located opposite the stator with a spherically shaped air gap which extends on an imaginary sphere and in which there is disposed a hemispherically shaped non-magnetic member separating the stator space from the rotor space, and a ball pin located at the centre point of the sphere for the purpose of mounting the rotor so as to allow tumbling movements, in which the stator comprises a continuous edge-wise wound sheet metal strip whose mutually adjacent turns form obtuse-angled conical surfaces and include a plurality of slots which are distributed in the direction of rotation and which are open towards the air gap and which are punched out of the strip before the winding operation and each of which contains a strand, passing through the stator over its entire axial thickness, of its two- or multi-strand winding which serves to induce a rotating electromagnetic field when in operation.

2. An electric machine as claimed in claim 1, in which the conical surfaces form an angle of taper of 1800--2 a, a lying between 100 and 250, preferably approximately 15 to 17.50.

3. An electric machine as claimed in claim 1 or 2, in which the strip forming the stator is wound onto a hemispherically shaped core, and the coiled strip extends in an axial direction across the region of the hemispherically shaped non-magnet member and has from a plane defining the hemisphere an axial length which is approximately 55% to 60% of the spherical radius.

4. An electric machine as claimed in claim 1, 2 or 3, in which the rotor has a core comprising a stack of disc shaped laminator of magnetic material and a short-circuit or squirrel cage winding in slots therein.

5. An electric machine as claimed in claim 1, 2 or 3, in which the rotor has a core of edgewise wound sheet magnetic strip and a short circuit or squirrel cage winding in slots therein.

6. An electric machine, constructed and arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.