GB2045120A

GB2045120A - Method for the manufacture of a pole shoe for electrical machines

Info

Publication number: GB2045120A
Application number: GB8007479A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1979-03-09
Filing date: 1980-03-05
Publication date: 1980-10-29
Also published as: FR2451125A1; JPS55125058A; ES489316A1; GB2045120B; FR2451125B1; IT8020451A0; DE2909214A1; IT1130940B; DE2909214C2

Abstract

The present specification discloses a method for the manufacture of a pole shoe for electrical machines by the non-cutting shaping of a rolled- section blank. In known non-cutting methods the blank is fully subjected, during each shaping stage, to the forming forces simultaneously both in the region of the pole shoe core and in the region of the pole horns. The method of the present invention is performed by means of a progressive tool (1, 2,) (8, Figure 1, not shown) in two shaping stages, or in a device comprising two upsetting dies (24, 26). In the first shaping stage the core region (12) of the pole shoe is fully formed, and, in the second shaping stage, the pole horns (18, Figures 3,6, not shown) are fully formed by pressing. According to this method the forming of the core region (12) and the forming of the pole horns (18) are performed by separate applications of force, whereby the forming forces may be substantially reduced. <IMAGE>

Description

SPECIFICATION Method for the manufacture of a pole shoe for electrical machines The present invention relates to a method for the manufacture of a pole shoe for electrical machines.

In particular the present invention relates to a method utilising the non-cutting shaping of a rolledsection blank. Methods are already known according to which the blank is formed into a pole shoe by non-cutting means in one or more shaping stages. A disadvantage ofthe known methods, however, is that during each shaping stage the blank is fully subjected in the press tool to the forming forces simultaneously both in the region of the core and of the pole horns. Consequently, such methods require the use of very substantial forming forces, which result in the application to the tool of stresses of such a magnitude that, because of variations in the weights of workpieces, they may be difficult to control, and which disadvantageously reduce the life of the shaping dies.

According to the present invention there is provided a method for the manufacture of a pole shoe for electrical machines by the non-cutting shaping of a rolled-section blank, comprising a first shaping stage, wherein a core region of the pole shoe receives its final shape and, without intermediate heat treatment, a second shaping stage wherein pole horns are formed by pressing on the pole shoe, during which latter process the core region is relieved of pressure.

In contrast to known methods, the method according to the present invention has the advantage that the force for shaping the core and the force for shaping the horns are separately applied. Consequently, it is possible to reduce substantially the forming forces required to form the core region and the pole horns of the pole shoe, and thereby to prolong substantially the life of the forming tools, and, in particular, it is possible to employ smaller power generating equipment.

It is particularly advantageous that forming may be performed either in a progressive press die in two shaping stages (the first stage for the core region and the second stage for the pole horn) or in a tool comprising independently-movable split dies.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a simplified cross-section view of a progresive tool for the first shaping stage of the present invention, with an inserted blank for a pole shoe which is to be formed; Figure 2 shows the progressive tool of Figure 1 for the first shaping stage, with a fully-formed core region of the pole shoe; Figure 3 shows a simplified cross-sectional view of a progressive tool for the second shaping stage of the present invention, with fully-formed pole-shoe horns; Figure 4 shows a simplified cross-sectional view of a device comprising a split shaping die for use in the present invention, with inserted blank for the pole shoe which is to be formed;; Figure 5 shows the position of the shaping dies of the device of Figure 4, at the end of the first shaping stage, together with the fully-formed core region of the pole shoe; and Figure 6 shows the position of the shaping dies of the device of Figure 4, at the end of the second shaping stage, with fully-formed pole-shoe horns.

Afirst method of manufacture for a pole shoe by cold forming is performed by means of a progressive press tool whose first stage is shown in an initial position in Figure 1. The embodiment includes an upsetting plate 1, the shape of whose surface corresponds to that of the concave inner face of the pole shoe in order to match the rotor of an electrical machine. An upsetting die 2 of the progressive tool is movable in a known manner (not shown) in a direction towards the upsetting plate 1. The upsetting die 2 has a recess 3 which forms the mating shape of the core region of the pole shoe which is to be formed. The recess 3 has a concave base 4 corresponding to the internal diameter of the housing of the electrical machine in which the pole shoe is to be arranged.Laterally adjacent to the recess 3 there is a concave bevelled surface 5, whose shape is the same as that of the rear face of the pole-shoe horns which are to be formed on the pole shoe. The bevelled surface 5 changes to a planar end face 6 of the upsetting die 2, which planarface extends perpendicularly to the longitudinal axis of the upsetting die 2. The upsetting die 2 has a central bore 7, which receives a longitudinally movable ejector 8. In its initial position shown in Figure 1 the ejector 8 projects outwardly of the upsetting die 2. It retains a blank 9, which is to be formed into a pole shoe 10, in its central position on the upsetting plate 1, to which the blank 9 is applied in a known manner (not shown). The end face 11 of the ejector 8 may be of tapered construction in order to retain the blank 9 more securely.

In the first shaping stage (Figure 2) the upsetting die 2 is moved in a direction towards the upsetting plate 1. The core region 12 of the pole shoe 10 is thereby fully formed on the blank 9 by the recess 3 of the upsetting die 2. The excess material 13 of the blank 9 is thereby laterally displaced between the end face 11 and the upsetting plate 1 along the bevelled surfaces 5. The ejector 8 moves only such a distance relative to the upsetting die 2 that the alignment of its end face 11 with respect to the base 4 of the recess 5 is such that a central countersink is formed in the rearface of the pole shoe.

For the second shaping stage (Figure 3) an upsetting die 14 is provided with a recess 15 which is deeper than the recess 3 in the upsetting die 2.

Consequently, during the upsetting process in the second shaping stage, the base 16 of the recess 15 does not abut the already fully-formed core region 12 of the pole shoe 10 which is to be formed. The forming forces which act upon the upsetting die 14 move the upsetting die 14 in a direction towards an upsetting plate 17, whose shape is the same as that of the upsetting plate 1, the final desired shape for the pole horns being formed from the material laterally displaced in the first shaping stage.

An ejection 20 which is movably arranged in central bore 19 and which extends into the recess 15, maintains the pole shoe 10, which is to be formed, pressed against the upsetting plate 17, and thereby prevents the pole shoe 10, which is to be formed, from reaching the base 16 of the recess 15 of the upsetting die 14, whereby, notwithstanding a bevelled surface 21 corresponding to the required shape for the pole horns 18 and delimiting the recess 15 in the end face 22 of the upsetting die 14, the pole horns 18 may be broken off by bending or sheared off at the rim of the core region 12.

Following retraction of the upsetting die 14to its initial position, the pole shoe 10 thus formed in the two above described shaping stages is ejected from the upsetting die 14, 15,21 by the ejector 20.

The forming of the blank 9 into the pole shoe 10 is effected without intermediate heat treatment between the two shaping stages, and with reduced upsetting forces, since only one region (first the core region and then the pole horn) of the pole shoe 10 which is to be formed is subjected to the forming pressures and given its final shape at each respective shaping stage.

A second method for the manufacture of a pole shoe by cold forming is performed with a device comprising a two-part upsetting die. Figure 4 shows a drive in its initial position. It has an upsetting plate 23, whose shape again corresponds to that of the inner face of the pole shoe 10, which is curved to match the rotor of an electrical machine. A first upsetting die 24 has the shape of the periphery of the core region 12 of the pole shoe 10 which is to be formed. Its end face 25 is correspondingly concave in form. The first upsetting die 24 is guided in a second upsetting die 26, which projects beyond the end face 25 of the first upsetting die 24.On its end face 27, extending outwardly from the inner rim of the upsetting die 26, there are formed two lateral bevelled surfaces 28, whose shape corresponds to the convex rear face of the pole horns 18 of the pole shoe 10 which is to be formed. Through the first upsetting die 24 there extends an ejector 29, which is guided in a central bore 30 of the first upsetting die 24. In its initial position shown in Figure 4the end face 31 of the ejector 29 still projects beyond the end face 27 of the second upsetting die 26 in a direction towards the upsetting plate 23, and retains the blank 9, which is inserted and centrally located by known means (not shown) upon the upsetting plate 23. The end face 31 may again be of tapered construction.

In the first shaping stage (Figure 5) the upsetting dies 24 and 26 are together moved in a direction towards the upsetting plate 23. The core region 12 is thereby fully formed on the blank 9. The core region 12 is thereby fully formed on the blank 9. The core region receives its shape from the end face 25 of the first upsetting die 24 and the second upsetting die 26 which projects beyond the end face 25 and surrounds the core region 12. The excess material 13 of the blank 9 is thereby laterally displaced between the upsetting plate 23 and the bevelled surfaces 28 of the second upsetting die 26. The ejector 29 is moved only a distance such that its end face 31 is in alignment with the end face 25 of the first upsetting die 24, and that it projects slightly in order to form a central countersink in the rear face of the pole shoe.

In the second shaping stage (Figure 6) the second upsetting die 26 is moved closer to the upsetting plate 23. The pole horns 18 are thereby fully formed by the bevelled surfaces 28. During the second shaping stage the first upsetting die 24 is raised clear of the core region 12 of the pole shoe 10 which is to beformed and is relieved of forming forces. Again, no heat treatment of the blank 9 is necessary between the two shaping stages.

The pole shoe 10 produced in the two described shaping stages is pushed out of the upsetting dies 24, 26 by the ejector 29 after retraction of the two upsetting dies 24 and 26 to the initial position shown in Figure 4.

Whereas, in the first shaping stage, the forming forces act substantially upon the upsetting die 24 which fully forms the core region 12, in the second shaping stage they act only upon the upsetting die 26 which fully forms the pole horns 18. The forming forces required during the process are consequently less substantial than in the case of the known methods, because of the separate application of forces for the core region 12 and the pole horns 18 of the pole shoe 10, which are fully formed in respective separate stages. The blank 9 is a simple rolled-section workpiece cut from rectangular-, square-or round-section material.

Claims

1. A method for the manufacture of a pole shoe for electrical machines by the non-cutting shaping of a rolled-section blank, comprising a first shaping stage wherein a core region of the pole shoe receives its final shape and without intermediate heat treatment, a second shaping stage wherein pole horns are formed by pressing on the pole shoe during which iatter process the core region is relieved of pressure.

2. A method as claimed in claim 1, in which in the first shaping stage, the core region of the pole shoe receives, in a progressive tool, its final shape from an upsetting die having a recess corresponding to the shape of the core region upon an upsetting movement of the upsetting die in a direction towards an upsetting plate, whereby the excess material is displaced between the end face of the rim of the die, which surrounds the core region and the upsetting plate, which excess material, in the second shaping stage, is pressed by the rim of a second upsetting die to the final shape of the pole horns the recess in the upsetting die for receiving the core region of the pole shoe being deeper than the depth of the core region of the pole shoe.

3. A method as claimed in claim 1, in which the core region of the pole shoe receives its final shape from a first upsetting die, which, in the first shaping stage, moves in the compression direction towards the upsetting plate, during which process the excess material is displaced between the end face of a second upsetting die which laterally surrounds the core region of the pole shoe and the upsetting plate, which excess material, in the second shaping stage, is pressed by the second upsetting die, which moves, relative to the first upsetting die in a direction towards the upsetting plate, into the final shape of the pole horns.

4. A method as claimed in claim 3, in which the first upsetting die no longer exerts compressive forces upon the core region of the pole shoe during the second shaping stage.

5. A method as claimed in claim 3, in which in the second shaping stage, the first upsetting die is raised slightly clear of the core region of the pole shoe.

6. A method as claimed in claim 2 or 3, in which an ejector extends longitudinally movably through the upsetting die for forming the core region and, during the first shaping stage, by its pressure holds the blank in abutment with the upsetting plate and is moved in a direction towards the upsetting plate in order to remove the pole shoe from the retracted upsetting die.

7. A method for the manufacture of a pole shoe for electrical machines by the non-cutting shaping of a rolled-section blank, substantially as hereinbefore described with reference to Figures 1 to 3, or Figures 4 to 6 of the accompanying drawings.