GB2068649A

GB2068649A - System for fastening the end cover of an electric motor

Info

Publication number: GB2068649A
Application number: GB8039301A
Authority: GB
Original assignee: Societe de Paris et du Rhone SA
Current assignee: Societe de Paris et du Rhone SA
Priority date: 1979-12-12
Filing date: 1980-12-08
Publication date: 1981-08-12
Also published as: FR2471688A1; DE3045255C2; FR2471688B1; DE3045255A1; GB2068649B; ES263223Y; ES263223U

Abstract

Each of the tie rods 7, for connecting the end cover 8 to the yoke 9 of an electric motor 2 has at least one fastening element 11 in the form of a V provided with hooks 12, 13 whose oblique edges 12a, 13a cooperate with the oblique face 15a of a depression 15 in the end portion 8b of the end cover 8. The end cover is not deformed during fastening. A couple is produced which tends to move the tie rods towards the periphery of the yoke. <IMAGE>

Description

SPECIFICATION Improved system for fastening the end cover of an electric motor The present invention relates to improvements made to systems for fastening an end cover of an electric motor to the yoke, particularly in a starter motor for an engine. The invention is concerned with electric motors having tie rods disposed outside the yoke for the purpose of joining at least one of the end covers to the yoke.

In electric motors of the type in question the end covers are in the form of castings provided with the same number of external lugs as there are tie rods.

The cost price of these end covers is high because they require precision machining.

Other end covers are known which are made by stamping sheet metal blanks, so that their cost price is low. They may be fastened by means of tabs or bands fixed at one end to the motor support, while the other end is provided with a hook cooperating with the said end cover. A fastening system of this kind is described for example in French Patent No.

71/21979. It will be noted that the fastening means disclosed by this patent provide practically no adjustment of the tension of the tabs or bands, so that play may exist in the connection. Furthermore, if it were possible to tension the tabs or bands sufficiently for good joining of the end cover to the motor yoke, the forces applied to the end cover would be liable to deform it, thus impairing good alignment of the rotor shaft bearings, since one of the latter is supported by the end cover.

The improvements forming the subject of the present invention seek to obviate these disadvantages and to provide for the connection of the end cover of an electric motor to the yoke to be achieved in an effective and economical manner, applicable either in the case of a stamped end cover or in the case of a moulded end cover of simple shape.

According to the present invention in one of its aspects each of the tie rods has associated therewith means for fastening the end cover which are adapted to cooperate with the end cover in such a manner as to avoid any deformation of the end cover and to give rise to a couple tending to move the said tie rod towards the periphery of the yoke.

In another aspect each tie rod has an associated fastening element having an oblique edge forming a hook which cooperates with the similarly sloping edge of a depression formed in the end portion of the cover.

The accompanying drawing, which is given by way of example, will permit better understanding of the invention, the characteristics which it possesses, and the advantages that it can provide.

Figure 1 is an external view on a small scale of an electric starter, to whose motor the improvements according to the invention are applied; Figure 2 is a side view thereof in the direction of the arrow F in Figure 1; Figure 3 is a longitudinal section of the fastening according to the invention; Figure 4 is an exploded view in perspective of a hook constructed according to the invention and of part of a stamped end cover with which the hook cooperates; Figure 5 is a section along the line V-V in Figure 3; Figure 6 is a partial view in the direction of the arrow F in Figure 1, but relates to a modified form of the hook; and Figure 7 is a section thereof along the line VII-VII in Figure 6.

In Figure 1 is shown an electric starter comprising a casing 1 with which are associated an electric motor 2, a switch unit 3, and a nose 4. The nose 4 supports a bearing 4a for a shaft 5, along which moves a drive pinion assembly including a pinion 6 adapted to cooperate with the flywheel ring gear of the engine to be started.

The electric motor 2 is held against a collar 1 a of the casing 1 by means of three tie rods 7 intended to join an end cover 8 to the yoke 9 of the said electric motor. The end cover 8 is advantageously in the form of a stamping made from a flat sheet metal blank; at its centre it carries a bearing 8a for the shaft 10 of the rotor of the electric motor.

Each tie rod 7 is screwed by one of its ends into the collar la, while its opposite end is provided with a head 7a adapted to act on a fastening element 11 constructed in accordance with the invention (Figure 3).

Each of the elements 11 is constructed as shown in Figure 4 in the form of a metal sheet folded into a V having a rounded base, in such a manner that the corresponding tie rod 7 is situated as close as possible to the periphery of the yoke 9. At one end of each element its branches are each extended by a hook 12 and 13 respectively, whose operative edges 12a, 13a are oblique and merge into a step 12b, 13b formed on the top edge of the branches of the V, the point where they merge being rounded. It will be noted that the end of each element where the hooks are provided is slightly set back so as to form two beaks 12c, 13c adapted to retain and centre a washer 14 disposed under the head 7a.

The end portion 8b of the cover 8 is provided with a number of depressions 15 corresponding to the number of tie rods 7. Each depression has at least one oblique wall 15a situated parallel to the periphery of the said end portion 8b, the inclination of this oblique wall being identical to that of the edges 12a, 13a of the hooks 12, 13. Thus, when the hook is in position as shown in Figure 3, the tightening of the tie rod applies the inclined edges 12a, 13a of the hook against the corresponding face 1 5a of the depression 15, so that this tightening causes the yoke 9 to be supported in a socket 1 b in the collar 1 a, and then effects the axial connection of the end cover on the opposite end of the yoke 9, in a socket 9a in the latter.Because of the inclination of the hooks and of the corresponding face of the depressions, this tightening also gives rise to a couple which tends to bring the tie rods 7 back against the yoke, that is to say to cause the steps 1 2b, 13b of the hooks to bear against the periphery of the skirt 8c of the end cover and also to cause the zones 11 a and 11 b of the arms of the element 11, at the opposite end to the hooks 12, 13 to lie on the cover in line with the socket 9a in the yoke.

It will be noted that the zones of action of the hooks lie in a transverse plane closely adjacent to the cylindrical surface of the above mentioned skirt 8c, so that all deformation of the end cover, including the bending of its end portion which could bring about the displacement of the bearing 8a, is avoided.

It will be observed (Figure 5) that the two faces 15b, 15e of each depression 15 which lead to the ends of the face 15a are at a distance from one another substantially equal to the distance between the end portions of the hooks 12,13 of the element 11,so that the tightening of each tie rod cannot give rise to any movement of the hooks away from one another, since they come to bear against the faces 15b, 15e in question, whereby excessive deformation of the hooks is avoided.

As shown in Figure 6, each depression 15 could be in the form of a simple narrow hollow 16 having a rounded cross-sectional shape, while the hooks 12, 13 of each element 11 would have a complementary shape. The depressions 15 and the hollows 16 could obviously be made in the form of a continuous annular groove, but in that case the advantage mentioned above, namely that the hooks are safeguarded against any transverse movement apart, would be lost.

It is obvious that the junction between the inclined edge 12a, 13a of each hook and the corresponding step 12b must be so disposed that it does not come to bear against the periphery of the end portion 8b of the cover 8. For this purpose provision is made for its radius to be smaller than, or at most equal to, that of the complementary shape of the said end portion 8b.

It should moreover be understood that the description given above has been given only by way of example and that it does not in any way limit the scope of the invention, which would not be exceeded if the details of construction described were replaced by any other equivalent details. In particular, another element 11 could be provided for that end of each tie rod which cooperates with the collar 1 a, this element being retained by a nut, while the said collar would also be provided with depressions similar to the depressions 15 or 16. Similarly, the cover 8 could be made of moulded material.

It will be appreciated too that the end element on an electric motor may take a variety of forms, all of which are embraced by the term "cover" used herein.

Claims

1. A system for fastening an end cover of an electric motor to the yoke, of the kind comprising tie rods disposed outside the yoke, characterised in that with each tie rod there are associated means for fastening the end cover which are adapted to cooperate with the end cover in such a manner as to avoid any deformation of the end cover and to give rise to a couple tending to move the said tie rod towards the periphery of the yoke.

2. A system for fastening an end cover of an electric motor to the yoke of the kind comprising tie rods disposed outside the yoke, characterised in that with each tie rod there is associated a fastening element having an oblique edge forming a hook which cooperates with the similarly sloping edge of a depression formed in the end portion of the cover.

3. Afastening system according to Claim 2, wherein the end cover has a peripheral skirt, and the sloping edge of the depression is located very clost to the skirt.

4. Afastening system according to Claim 2 or Claim 3, wherein each element is in the form of a sheet metal element folded into a V having a rounded base, each arm of the V forming an end hook.

5. Afastening system according to Claim 4, wherein each arm has a beak adapted to centre a washer.

6. A fastening system according to Claim 4 or Claim 5, wherein the arms of each V-shaped element are provided with a step which comes to bear against the yoke when the tie rods are tightened.

7. A fastening system according to any one of Claims 2 to 6, wherein the end cover has a peripheral skirt which fits into a seating on the yoke and each element is of sufficient length to ensure that under the action of the tie rods it can be supported, at the opposite end of its arm to the hook forming end, at a position in line with the said seating on the yoke.

8. Afastening system according to any one of Claims 2 to 7, wherein the end cover has a number of depressions equal to the number of tie rods.

9. Afastening system according to any one of Claims 2 to 7, wherein the end cover has a single annular depression with which all the hooks cooperate.

10. Afastening system according to Claim 8, wherein the side edges of each depression are so arranged as to form a stop for the two hooks of the corresponding element.

11. A system according to any preceding Claim, wherein each tie rod is provided with a second fastening element cooperating with a second end bracket or the like.

12. A system for fastening an end cover of an electric motor to the yoke substantially as shown in the accompanying drawings and described herein with reference thereto.