GB2231730A - Securing and insulating element for the stator of an electric motor - Google Patents

Description

:2 2:3 1 7:3 0 1 INSULATING ELEMENT FOR THE STATOR SPACES OF AN ELECTRIC

MOTOR The present invention concerns the insulation for the stator of an electric motor, in particular insulation of the internal walls of the spaces provided in the body of the stator.

It is known that the stator of an electric motor is substantially formed by a pack of identical plates of ferromagnetic material which are tightly clamped together in such a way as to form a single body.

Those packs of plates may assume a wide variety of shapes but all must provide a space within which the rotor is disposed in such a way as to close the magnetic circuit formed by the stator and the rotor.

To generate the desired magnetic flux, provided in the body of the stator is a defined number of ducts or spaces within which the turns of the electrical supply winding of the motor are inserted or wound.

Normally the interior of each space is completely filled with the turns of the winding to produce the maximum possible magnetic flux and thus electromagnetic force.

Once the array of turns has been formed in the spaces in the stator, the state of the art teaches locking that array of turns both to ensure that the structure thereof does not loosen with vibrations of the motor and to keep the electromagnetic characteristics of the stator constant.

It is thus known art to provide for binding of the array of turns over the entire extent thereof thereby to maintain geometrical compactness thereof and definitively to hold it tightly to the pack of plates, thus providing the finished stator.

Those modes of construction are universally known and are not illustrated further herein.

2 Before the turns of electrical wire are inserted into the individual spaces, the latter must be insulated from contact with the wire itself.

Insulation is required by virtue of having to separate the bare electrical wire from the pack structure of the stator which is normally conductively connected to the external frame structure of the motor. It is also necessary to insulate the front part of the coil, that is to say the zone which faces towards the internal opening of the space, to eliminate the danger of a wire becoming detached from the remainder of the coil and by projecting from the space, coming into contact with the rotor.

To achieve that insulation effect, the known art provides two types of processes which are briefly recalled hereinafter: the first process comprises separately moulding an elongated shell member of rigid plastics material, being of a cross-section substantially with the same dimensions and shape as the space to be insulated. The shell member is introduced from one of the two sides of the space and is caused to slide along the entire length thereof, so that at the end of that movement the internal surface of the space is entirely covered by the shell member.

The second process comprises cutting small strips from sheets of flexible insulting material; the strips, which are suitably shaped and dimensioned, are fitted into the opening of each space and are then caused to adhere to the whole of the wall of the space in such a way as to insulate the internal surface thereof completely.

The coil is then wound on the pack of plates using the conventional method and finally the front zone of the coil which is disposed within the space is closed with a further strip which, inserted over the coil through the opening of the space, will complete the insulation for the coil in relation to all the surfaces around same.

The above described procedures make it possible to v 3 provide a product which, even if it is reliable and can be produced automatically, is however fairly costly and of a complicated construction by virtue of the numerous moulding, assembly and binding operations or by virtue of insertion into each space separately of the associated insulating strips.

The aim therefore of the present invention is to overcome the abovediscussed disadvantages and to provide a stator with a particularly simple and economical construction in regard to insulation for the coil in a space and fixing of said coil to the stator pack.

According to the present invention, there is provided an electric motor comprising a stator and a rotor, said stator being formed by a pack of ferromagnetic plates which are superposed and clamped together and having passing therethrough a multiplicity of spaces for containing the coils, said spaces having their surface protected by an insulating element, wherein said insulating element is formed by a continuous layer of plastics material which is injected and moulded on the surface of said spaces.

The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which:- Figure 1 is a diagrammatic view in section of the stator and the upwardly extended locking band in accordance with the invention, Figure 2 shows a detail of the invention with the coil fitted, and Figure 3 shows the same detail with the coil fitted and with the locking band tightened.

The features of the invention are set forth in following claims 1 to 5.

With reference to figure 1, the following components can be observed therein; a pack 1 of identical plates in superposed relationship, spaces 2 in which the 4 wires forming the coil are conventionally inserted, openings 3 through which the wires are passed into the respective spaces, a layer of plastics material which is moulded on the interior of each space, and a clamping band 5.

In a stator according to the present invention the strip of insulating material within the.space is replaced by a layer of plastics or equivalent material which is applied to the internal surface of each individual space, preferably by a hot moulding operation.

The operation of applying the layer of plastics material is effected on the pAck of plates when it has already been formed but not yet consolidated so that in that phase the plates are simply disposed in superposed relationship but are not rigidly locked together.

The operation of simultaneously moulding in the interior of all the spaces thus has the double aim of providing the required insulation and at the same time constituting the means for supporting and locking the plates together, thus completely replacing the means which are conventionally used in the art for that purpose (normally through bolts, welds, rivets or hooping bands).

Thus, with a single moulding operation, that provides both the desired insulation in respect of all the spaces and the formation of the consolidated pack, which enormously increases the speed and economy of the entire production procedure.

This figure shows a section on an enlarged scale of a single space which involves a simple way of replacing the bindings of the coil as described above.

It will be seen that the insulating layer 4 is extended. at an edge of the space, in the form of a free band 5 which is produced simultaneously with the operation of moulding the insulating layer. The band 5 is of a length such as to be able to pass around and bind the coil.

Referring to figure 2 shown therein is the mutual arrangement of the coil 6 and the band 5.

An alternative form of design of the band 5 is afforded by the option of producing it separately and subsequently inserting it within the stator spaces for 5 winding it around the coils.

Referring to figure 3, shown therein is a section of the completed stator, in which the end 7 of the band 5, has been locked after having been passed around the coil over the corresponding section and having insulated the part of the winding within the space which faces the opening thereof, against the projection 8 provided on the corresponding edge at the other end of the insulating layer.

The structural features of the article will be apparent to an expert in the art; after the pack of plates has been produced in an entirely conventional manner, it is introduced into a suitable mould which is in turn mounted in a machine for moulding plastics material. After the moulding operation, the article is as shown in figure 1. 20 It will be noted that the internal surface of all the spaces is protected and thus insulated by the layer 4 which thus performs the function of providing insulation which was previously performed by the individual strips, completely and in a fast and economical manner and using known technology.

In addition figure 1 also shows the multiplicity of the tongue portions which are moulded together with the layer 4 and which for all purposes replace the binding produced with different material and involving a manual and labourious operation.

6

Claims (6)

1. An electric motor comprising a stator and a rotor, said stator being formed by a pack of ferromagnetic plates which are superposed and clamped together and having passing therethrough a multiplicity of spaces for containing the coils, said spaces having their surface protected by an insulating element, wherein said insulating element is formed by a continuous layer of plastics material which is injected and moulded on the surface of said spaces.

2. An electric motor according to claim 1 wherein extending from the outside edges of said insulating layer are bands which are made of the same material, of dimensions such that they can be passed around the coil and can be locked with their end to the opposite outside edge of said insulating layer.

3. An electric motor according to claim 2 wherein said bands are not made in one piece with the insulating layer but are produced separately and are subsequently inserted into the spaces in the stator, wound around the coils and locked at their two ends.

4. An electric motor according to claim 2 or claim 3 wherein said bands are passed around the coil and are locked by glueing, welding, riveting or the like to the opposite outside edges of said insulating layer.

5. An electric motor according to claim 3 wherein said bands are inserted into the opening of the respective space but outside the corresponding coil in such a way as to complete the insulation of said coil over the surface portion corresponding to the section in the space.

t A 7

6. An electric motor constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.