GB2109168A - Coil retainer - Google Patents

Abstract

A coil retainer (10) comprises a plurality of coil formers (12) and a strap (14) along which the coil formers (12) are attached, the coil formers (12) having a configuration for receiving respective ones of a plurality of stator winding sections between flanges (18) and the strap (14), the strap (14) being flexible between the coil formers (12) such that the coil retainer (10) is capable of being wrapped around a pole stack to position the winding sections at the desired positions around the pole stack with the strap (14) encompassing and shielding the winding. The unitary arrangement of the present invention enables automated winding of the stator winding sections, automatic positioning of the coil retainer (10) around a pole stack and automatic insertion of the complete unit into the housing of a motor or generator. <IMAGE>

Description

SPECIFICATION Coil retainer The present invention relates to coil retainers and more particularly to improvements in such articles.

A coil retainer is known in accordance with German Patent No. 2107312 which provides a coil retainer comprising a coil former which receives a stator winding. This known coil retainer is of a bobbin shape with one end of the bobbin formed so as to accept a pole piece and the other end of the bobbin being provided with extensions which extend over the wound stator winding and contact the opposite end of the bobbin, adjacent the ends of the pole piece. Recesses are formed in the bobbin at the position where the extensions contact the pole piece end of the bobbin. These recesses provide an isolated region in which lead wires may be connected to the stator winding. The extensions act as covers for these recesses. The pole piece extends longitudinally through the bobbin so as to contact the yoke stack when the coil retainer is assembled to form part of an asynchronous motor.

The known coil retainer serves as an insulattor for the wound coils thus eliminating the wrapping papers normally employed and hence reducing the labour and time which is normally involved in wrapping the coils and the lead wires. The shape of the coil retainer sheilds the statorwinding which reduces the possibility of the winding being broken during handling and thus reduces the number of components which have to be scrapped. However, when assembling a motor using the known coil retainers, the coils have to be positioned on the stator and then the unit assembled into the motor or yoke stack. It is also necessary to electrically connect the statorwindings and this is usually achieved by soldering together respective ends of the stator windings before the assembly is inserted into the motor stack.

It is the object of the present invention to retain the advantageous effects of the known coil retainer whilst mitigating the disadvantages of the known coil retainer and thereby providing an improved coil retainer.

According to the present invention there is provided a coil retainer comprising a plurality of coil formers each operative to receive a respective one of a plurality of series connected stator winding sections, the coil formers being arranged at predetermined intervals along a flexible strap capable of being wrapped around a unitary pole stack to position the winding sections at the desired positions around the pole stack while surrounding and shielding the windings.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which; Figure 1 shows a partly sectioned side elevation of a coil retainer, Figure 2 shows a plan view of the coil retainer shown in Figure 1, Figure 3 shows a partial view on an enlargedscale of a section taken on the line B-B of Figure 2, Figure 4 shows an underneath view of a cover which cooperates with that portion of the coil retainer shown in Figure 3, Figure 5 shows a side elevation of a section taken on the line C-C in Figure 4, and Figure 6 shows a side elevation of the coil retainer in the position adopted prior to insertion into an electric machine.

The illustrated coil retainer 10 is suitable for a two pole electric motor. As best seen from Figure 1, the coil retainer 10 comprises two coil formers 12 joined by a flexible strap 14 which also projects beyond the coil formers 12. That portion of Figure 1 lying to the left of the line A-A in Figure 1 is shown in section taken on the central longitudinal axis of the coil retainer 10. The coil foromers 12 project perpendicu larly from the strap 14 and the sides of the coil formers 12 which lie across the strap are of arcuate form such that the distance between these sides, for each coil former, increases with increasing distance above the strap 14. The arcuate sides 16 are terminated at their upper extreme by respective flanges 18 which project horizontally from the coil formers 12 and longitudinally with respect to the strap 14.Offset from the respective point of contact between the arcuate sides 16 and the flange 18 and further from the central vertical, but inset from the edge of the flange 18, the sides of the coil former extends horizontally towards the central vertical of the coil former to a position which is vertically above the point of contact between the respective side 16 and the flange 18. Between these points the upper surface of the coil former comprises the arc of a circle which reaches a depth greater than that of the flanges 18 from the horizontal top of the coil former 12. On either side of the coil former 12 and along that part of the surface of the coil former joining the flanges 18, there is provided a flange 22 which extends laterally with respect to the strap 14.A flange 24 which has a lateral extent the same as or slightly less than the flanges 22 is provided as part of the strap 14 at the point of emergence of the coil former 12. The flange 24 has a slightly greater longitudinal extent than the base of the former 12 but terminates before the longitudinal position of the point of contact of the respective side 16 and flange 18. The centre of each coil former 12 is a hollow 26 and the sides 28 of the hollow 26 follow the curve of the side 16 so as to define a wall between the respective sides 16 and 28. Above the base of the flange 18 the sides 28 of the hollow 26 follow the curve of the curved portion of the upper surface of the coil former 12 and at a short distance therefrom so as to terminate approximately centrally of the horizontal portion of the upper surface of the coil former 12.As can best be seen from Figure 2, which is a plan view of the coil retainer, the hollow 26 is laterally more extensive to the right of the central vertical of the coil former 12 than to the left of the central vertical. This difference in lateral extent of the hollow 26 can ensure the correct orientation of an insert which is inserted into the hollow 26.

The two flanges 18 which are closest to the respective ends of the strap 14 are each provided with a central cutout portion 30 which extends through the thickness oftheflange 18. A pair of cutout portions 32 are provided in the sides of the strap 14 adjacent the ends of the strap 14. The pair of cutout portions 32 divides each end of the strap 14 into a tab portion 34, which is the extreme end of the strap 14, and a cover portion 36 which extends between the pair of cutouts 32 and the base of the coil former 12.The strap 14 and in particularthe cover portions 36 are flexible and the dimensions of the cover portion 36, cutout portions 32 and tab 34 are such that upon bending the cover portions 36, the cutout portions 32 cooperate with the flange 18 and cutout portion 30 thereof such that the tab 34 may be retained against the side 20 which is adjacent the cutout portion 30. A ridge 38 extends across the strap 14 adjacent the cutout portions 32 and extending perpendicularly from the underside of the respective cover portion 36. The ridge 38 aids in the operation of attaching the tab 34 above flange 18.

A wiring house 40 is provided on the strap 14 and is positioned centrally with respect to the coil formers 12. The wiring housing 40 comprises two elongate bars, one at either longitudinal extreme of the housing 40, which extend across the strap 14. A side wall 44 extends along each longitudinal edge of the strap 14 between the bars 42. The side walls 44 are positioned centrally with respect to the wiring housing 40 and are less longitudinally extensive than the longitudinal spacing of the bars 42. Both the bars 42 and the walls 44 extend perpendicularly from the upper surface of the strap 14, but the walls 44 are approximately twice the height of the bars 42. Two pairs of ribs parallel to the side walls 44 are located symmetrically with respect to the longitudinal axis of the coil retainer 10 and between the walls 44.The ribs consist of an outer pair of ribs 46 which are adjacent a respective one of the walls 44 and an inner pair of ribs 48 which are positioned closer to the longitudinal axis of the coil retainer 10 and which are longitudinally more extensive than the outer ribs 46 and slightly less extensive than the walls 44. The bars 42 are provided with recesses 43 which extend across the width of the bars 42 and down to the upper surface of the strap 14. The bars 42 with their recesses 43, the walls 44, outer ribs 46 and inner ribs 48 provide a means whereby the lead wires to the stator windings (not shown) may be held rigid with respect to the coil retainer and so as to be anchored against forces tending to separate the lead wires from the coil retainer 10, without relying upon or placing a significant strain upon the connections between the lead wires and the stator windings.

A circular recess 50 is provided in the centre of the wiring housing 40 and the recess 50 is partially formed by cutout portions on the inner sides of the inner ribs 48. As can be seen from Figure 3, the recess 50 extends down to the upper surface of the strap 14. The ribs 46 and 48 have a height equal to approximately half of the height of the side walls 44.

The inner surfaces of the side walls 44 are provided with a respective recess 52 which extend for approximately half of the thickness of the wall 44 and to a depth equal to the upper surfaces of the ribs 46 and 48. The relative heights of the ribs 46 and 48 and the recesses 50 and 52 are provided in order to locate and retain a cover 54 which shields the wires and connections which are, in operation, located within the wiring housing 40. The cover 54 is shown in Figures 4 and 5. The cover 54 comprises a flat plate having a central boss 56 extending from one of its surfaces. The boss 56 is inserted into the recess 50 of the winding housing 40 and the plate of the cover 54 engages the upper surfaces of the ribs 46 and 48 and also the horizontal surfaces of the recesses 52 in the side walls 44.The side walls of the boss 56 are slightly inclined so as to aid insertion into the recess 50 and the sides of the recesses 52 are slightly inclined in order to provide a retaining force acting on the cover 54, additional to the retaining force provided by the engagement of the boss 56 with the sides of the recess 50 defined by the inner ribs 48.

Ridges 58 are provided on the under side of the strap 14 adjacent either end of the side walls 44 and extending across the width of the strap 14. A reinforcing member 60 which abuts the outermost side wall of the ridge 58 and which extends along the strap 14 with its upper surface inclined so as to meet the strap 14 beneath the respective bar 42, is provided for each of the ridges 58. The 58 are provided to facilitate the correct positioning of the coil formers 12 prior to insertion of the coil retainer 10 into a motor stack.

The coil retainer 10 is a one piece plastics moulding and the thickness of the strap 14 and choice of plastics material is such that the strap 14 is flexible.

The stator winding is provided by winding a coil on one of the coil formers 12 between the flanges 18 and the strap 14 and encircling the side walls 16 of the coil former 12. When one coil has been wound, the coil wire is inserted into one of the recesses 43 in the bar 42 adjacent the coil former 12. The wire is passed across the winding housing 40 and out through a recess 43 in the opposite bar 42 and as can be seen from Figure 2 the wire may pass through the central recesses 43 in the bars 42 and between the inner ribs 48, the boss 56 on the cover 54 does not extend to the bottom of the recess 50 and thus the wire does not prevent the cover 54 from seating properly. The final coil of the stator winding is then wound onto the other coil former 12 in the same fashion as the first coil was wound onto the first coil former 12.The coils of the stator winding are thus wound from a continuous wire and the need to connect the coils of the stator winding is negated.

This produces a saving in labour since the previously known coil retainers necessitated the soldering together of the respective ends of the coils. The coil retainer of the present invention also reduces the risk of breakage of the wire of the coils during their assembly onto the coil retainer and their interconnection. The mould for producing the illustrated coil retainer and in particular the wiring housing section of the coil retainer is simpler than the mould required to produce the known coil retainers in which connections to the coils are held in formations on the vertical sides of the coil retainer.

The lead wires are connected to the respective ends of the coils of the stator winding and these connections are housed within the wiring housing 40. The lead wires enter the wiring housing by the gap between the bars 42 and one of the side walls 44 and are gripped between a respective combination of an outer rib 46 and an inner rib 48. The lead wires are passed around the end of the respective outer rib 46 and are further gripped between the outer rib 46 and the respective side wall 44. The connection to the respective coil extends from between the outer rib 46 and side wall 44 through one of the recesses 43 in one of the bars 42 to the coil wound on the coil former 12. The lead wires are thus securely gripped and present an enhanced resistance to any forces tending to stress the connection of the lead wire to the coil wire.The cover 54 is then positioned on the winding housing 40 and the connections are thus shielded.

The coil retainer 10 can now be positioned ready for insertion into a motor stack. The coil retainer of the present invention enables the positioning of the coils of the stator windings relative to each other and insertion of the coil retainer into the motor stack to be carried out automatically. With the known coil retainers, two coil retainers had to be positioned relative to each other, the coils interconnected and the assembly inserted into the motor stack. The present invention enables this operation to be carried out automatically and thus represents a significant advantage in the ease and speed of assembling complete motor units. A unitary magnetic pole piece having diametrically opposed external projections would normally be employed.One of the projections is inserted into a hollow 26 of one of the coil formers 12 and the curved surface 23 of the coil former 12 engages a section of the pole piece. The projection of the pole piece inserted into the hollow 26 of the coil former 12 extends through the hollow 26 such that the end of the projection is approximately coplanar with the external face of the flange 24 in order that contact with the motor pack can be provided. The ridges 38 and 58 are engaged by the assembly machine and the flexible strap 14 and covers 36 are urged into the positions shown in Figure 6. The tabs 34 engage the flange 18 and the surface 20 of the respective coil former 12 and the cover 36 thus shields one side of the coil wound onto the coil former 12.On bending the flexible strap 14, the surfaces 23 of the coil formers 12 are brought into face to face relationship and consequently the other projection of the pole piece is inserted into the hollow 26 of the other coil former 12. On bending the flexible strap 14 so that the coil formers 12 face each other, the flanges 18 adjacent the winding housing 40 are forced into the gaps between the ends of the side walls 44 and the bars 42, the corresponding surfaces 20 of the coil formers 12 are thus brought into contact with the top of the cover 54. The flanges 18, gripped between the side walls 44 and the bars 42 do not contact the flexible strap 14 so as to leave an aperture through which the lead wires protrude.

When wrapped into the position illustrated in Figure 6, the coil retainer 10 can then be slid into the motor stack.

The illustrated embodiment comprises two coil formers, but the present invention can be applied to coil retainers having more than two coil formers, for example, so as to produce a coil retainer suitable for a four pole motor having four coils. In such a case, a winding housing as described may be provided between two of the coil formers and a simplified housing provided for retaining the wire spaning the gap between the coils.

Claims (9)

1. A coil retainer comprising a plurality of coil formers and a strap along which the coil formers are attached, the coil formers having a configuration for receiving respective ones of a plurality of stator winding sections, the strap being flexible between the coil formers such that the coil retainer is capable of being wrapped around a pole stack to position the winding sections at the desired positions around the pole stack with the straps encompassing and shielding the winding.

2. A coil retainer as claimed in claim 1,wherein the coil retainer is moulded as a unitary construction.

3. A coil retainer as claimed in claim 2, wherein the unitary construction is moulded from an electrically insulating plastics material.

4. A coil retainer as claimed in any preceding claim wherein a wiring housing is provided on the strap between two coil formers, the housing accommodating and protecting the electrical connection between the respective stator winding sections.

5. A coil retainer as claimed in claim 4, wherein the coil formers adjacent the wiring housing are providing with flanges which engage and are retained by the wiring housing when the coil retainer is wrapped into position around a pole stack.

6. A coil retainer as claimed in any preceding claim wherein the strap is provided with formations enabling the coil retainer to be mechanically gripped and mechanically wrapped into position.

7. A method of assembling an electric motor or generator comprising the steps of providing a plurality of stator winding sections on respective coil formers of a unitary coil retainer, mechanically gripping the coil retainer and mechanically wrapping the retainer around a pole stack and thereby positioning the winding sections at the desired positions around the pole stack, and mechanically inserting the coil retainer and pole stack into the motor or generator housing.

8. A coil retainer substantially as herein before described with reference to and as illustrated in the accompanying drawings.

9. A method of assembling an electric motor or generator substantially as herein before described with reference to the accompanying drawings.