Background of the Invention

The present invention relates to electromotors in general, and more particularly to an electromotor with a laminated stator in which a stator ring has inwardly protruding pole pieces. The pole pieces have a substantially T-shaped cross section with a shaft or foot portion projecting from the stator ring and a head portion projecting from both sides of the shaft portion and having its surface facing the rotor curved to form a cylindrical surface having a radius slightly greater than the outer radius of the rotor with which it cooperates, and being slightly spaced therefrom. Relevant stator coils are mounted on the shaft portions of the pole pieces in such a manner that they fill the space behind the rear sides of the projecting parts of the head portion.

The easier way of shaping the pole pieces is to stamp them out, together with the remaining portions of the stator laminations, from the plate material used for manufacturing of the laminated stator, such that the pole pieces will appear as inwardly projecting, integrated parts of the stator ring. This, however, incurs -the essential drawback residing in that the stator coils will be mounted by being heeled over the broader head portions of the pole pieces and then narrowed about the shaft portions. However, it has been difficult to mount the coils on the pole pieces in such a way and even more difficult to change them when necessary.

It has long ago been suggested and practiced to provide the pole pieces as separate units from the stator ring and to mount the coils with a narrow shape about the shaft portions, which was easier because they were placed on the shaft portions of the poles from the narrow ends thereof, that is without being heeled over the head portions, and the coil carrying pole pieces were then mounted on the inside of the stator ring and fixed thereto in any suitable manner. The connection of the pole pieces to the stator ring could even be easily releasable, whereby it was possible to replace a burnt coil with a new one in a relatively simple manner.

However, there are considerable problems connected with the production and particularly securing of the separately made laminated pole pieces to the stator ring. Ideally the single lamination for the pole pieces should be formed in connection with the stamping out of each single stator lamination, by cutting off the inwardly projecting pole portions from the ring area along their base connection with the inner side of the stator ring, i.e. along or rather across the roots of their shaft portions. However, with this technique it is difficult to achieve an accurate and non-problematic mounting of the assembled, rod-like pole pieces on the interior side of the likewise assembled stator ring. It has been proposed to fasten the pole pieces by means of bolts introduced from the outside thereof. However, such fastening would require accurately drilled radial holes in the assembled lamination material and cutting threads in the holes of the pole pieces, which would amount to a quite difficult working. Moreover, it may have

quite serious consequences for the entire motor if the spanner bolts of just a single pole piece would get loose, e.g. in case of a less qualified mounting or repair.

Furthermore, fastening of the above-described nature would also require the provision of radial passages through the stator ring or cylinder, which is undesired as this would facilitate penetration of moisture into the rotor area.

In order to avoid these problems it has already been proposed to shape the pole pieces and the single laminations thereof with protruding, narrow foot portions fitting into a corresponding recess in the inner wall of the stator ring, a corresponding recess being formed in each single stator lamination, to thereby ensure a very accurate positioning of the pole pieces, and, at the same time, achieve a safer fastening of the pole pieces using locking means that are active at the radial or lateral sides of the foot portions of the pole pieces, respectively. Such loαr-ing means can be formed by locking rods inserted through axially extending holes or opposed half holes formed in the adjacent side faces.

Howe- er, even this soxution is problematic because it is hardly possible to form both the foot portions and the corresponding recesses in one operation or by stamping from one common lamination pl~te in such a manner that the parts can later be easily joined to each other. The foot portions should be just slightly narrower than the recesses, and for this to be possible the pole piece laminations, in practice, should be stamped out from plate or lamination members other than those, from which the stator ring laminations are

stamped out, this incurring a heavy excess consumption of lamination plate material.

Summary of the invention

_I t is an object of the present invention to provide an improved electric motor.

The present invention provides for a solution which allows separate pole pieces to be prepared by a pure follow die operation on the lamination members which are stamped out for forming the stator ring and preferably also the body of the rotor, and which also enables an easy and effective fastening of the pole pieces to the stator ring. According to the invention the different pole parts of each single lamination member are shaped in three different manners; partly (for more than one pole piece part) by a clean cutting at the root, i.e. by cutting along the inner contour of the stator ring, partly (for at least one pole piece part) by cutting along this contour over only a part of the width of the root, while cutting at the remaining part of the width of the root into the stator ring portion so that a local bulge in the form of an ear-shaped portion provided with a hole will occur on the root line of the pole portion, this ear-shaped portion leaving a complementary recess in the inner contour of the stator ring, and partly (again for at least one pole piece) by a clean cutting of the pole piece along the root line. In the latter case, with the addition of a separate stamping out of an adjacent portion of the inner area of the stator ring portion, there is formed a notch or depression of a shape

and size apt for receiving the projecting ear-shaped portion on the pole piece part mentioned above. For the same reason this notch or depression should be worked out to be of a size slightly larger than the ear-shaped portion and thus also slightly larger than the recess left by the shaping of the ear-shaped portion.

The pole portions are also provided with holes located near the sides of their shaft portions, such that the stamped off pole piece parts can be assembled together to form the laminated pole pieces. The laminated pole pieces are held together by means of anchoring rods inserted through said holes; the anchoring is effected by axially pressing together tl pole piece parts in the pack and carrying out a welding along the side areas of the pack, to which the anchoring rods extend in close proximity. The pole piece parts are packed in series or blocks such that between relatively long blocks of evenly cut off pole piece parts there are interposed shorter blocks of the pole parts which were stamped out with the ear-shaped portions. These ear-shared portions in the assembled condition of the stator pole piece are spaced-apart projecting block portions on the root surface of the pole piece.

The stamped out stator laminations are likewise assembled into block sections, which will not be different from each other since all stator laminations are similar to each other. However, adjacent block sections are angularly turned relative to each other about the stator axis in such manner that along each mounting area of a pole piece alternating block sections will be positioned, of which some sections will respectively have non-recessed inner side

portions and others will have inner side portions provided with larger and smaller recesses. In the assembled stator ring or pack these recesses will form marked depressions in the inside of the ring, and the arrangement may be such that 5 these depressions be located in accordance with the protruding ear-shaped block portions on the pole pieces so as to receive these block portions upon the insertion of the pole pieces at the respective mounting areas of the inner side of the stator ring.

10 As mentioned above, the ear-shaped portions are provided with holes, which in the assembled condition of the pole piece laminations will provide axial passages to receive a holding rod therethrough. The ear-shaped block portions are spaced from each other and when the pole pieces

15 are introduced into the assembled stator ring it is possible to secure the inserted pole pieces in the stator ring merely by introducing with more or less pressure a holding rod axially through the alternating hole passages extending through the ear-shaped block portions of the pole pieces and

20. the holes provided in the intermediate block portions of the stator ring, respectively.

Hereby the pole pieces, with premounted stator coils introduced over the narrow root ends thereof, will be connected to the inner side of the stator ring in a very

25 easy and advantageous manner, as there will be no need for any radial penetration of the stator ring. The connection will be easy to release merely by pulling out the axial holding rod, and it will be easy to repair a given motor by interchanging a burnt stator coil.

It is to be noted that it has been already known in the relevant field to effect a modular turning of the stamped out laminations, namely for achieving compensation for thickness variations of the laminations, i.e. the machine equipment required for such turning already exists, and in connection with the invention it should only be ensured that the turning is effected in blocks or packs, without any turning between the single lamination members in the same block. The invention is directed to a motor, preferably a

DC motor, which is made up in accordance with the new pr ⁱ nciples here disclosed. In this connection it will even b a possibility that the pole pieces be provided separately, as solid bodies, the projecting ear-shaped blocks of which may be mounted and secured in the depressions provided in the inner side of the laminated motor ring.

The aforementioned objects, features and advantages of the invention will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawings, which form an integral part thereof.

Brief Description of the Drawings

Fig. 1 is a plan view of a stator and rotor lamination member for use in a motor according to the present invention;

Fig. 2 is a plan view of a stamped out stator lamination for forming a stator pack;

Fig. 3 is a perspective view of stator lamination blocks which are to be assembled to form the stator of the motor;

Fig. 4 is a perspective view with a portion cut away, illustrating the assembled stator;

Fig. 5 is a perspective view of a row of pole blocks for forming a pole piece of the motor; Fig. 6 is a perspective view of the assembled pole piece; and

Fig. 7 is a plan view of the assembled stator.

Detailed Description of the Invention

To manufacture a stator and a rotor of the motor according to the invention use is made of lamination members as shown in Fig. 1. The stamping lines are shown by drawn lines. The main parts of the motor are an outer, closed stator ring 2, pole pieces 4 inwardly projecting from the inner surfaces of the stator ring and a central rotor part 6 having slot openings at an outer periphery thereof for receiving rotor coils. At its corners, between the pole pieces 4, the stator ring 2 has inwardly protruding, so- called turning poles 8, which are, however, not part of the present invention and therefore will not be described further.

By one or more initial stamping operations the rotor lamination part 6 as well as the interconnecting lamination portions between the stator and the rotor parts are stamped out, and respective holes 10 are stamped out in the stator ring 2 in the proximity to the pole pieces 4 marked A and B. The pole pieces A and B are stamped out along the marked dash-and-dot-lines a, which extend in continuation of the inner contour of the stator ring 2. The same applies to the pole piece designated at D, while the pole piece designated at C is stamped out along a line which generally follows the inner contour of the stator ring but has a local bulging-out portion 12 at the middle of a root portion of the pole piece C. Hereby a depressic 14 will be produced at the inner side of the stator ring 2, along with an outwardly projecting ear-shaped portion 16 formed on the pole piece C. A hole 18 is stamped out in the ear portion

16.

Upon stamping out the pole piece D along the contour line a, a depression 20 is stamped out from the , inner edge of the stator ring 2. The shape of depression 20 corresponds to that of the ear-shaped portion 16 of the pole piece C, though being slightly larger than that portion. In the following description the reference numeral 20 will be used to identify the depression produced by _, the stamping operation here rmsidered.

The finished stator lamination is shown in Fig. 2.

Typically the laminations are fully symmetrical and are assembled together into a stator pack while being turned by one pole pitch for each new lamination, but here the laminations are not fully symmetrical. They are assembled

together without being mutually turned, into small packs 22, as shown in Fig. 3. The small packs 22 in turn, are turned by one pole pitch when they are consecutively assembled together to form a complete stator ring pack or block. In the conventional electric motors, the purpose of turning the laminations was to compensate for obliquities which could occur as a result of certain non-uniformities or variations in the plate thickness across the plate or lamination members. However, it should be appreciated that this problem will be solved quite as well also when the laminations are assembled with a non-changed orientation of the laminations in the small packs 22, provided that these pre-aεsembled small packs are turned when being laid or assembled together. Packs 22 when assembled together, form a stator ring block 25 as shown in Fig. 4. Packs 22 are successively turned by 90° as shown in Fig. 3, and the recesses 14 and 20 will form depressions designated 24 and 26, respectively, in otherwise smooth inner side portions of the stator ring _ packs 22. With the arrangement shown in Figs. 3 and 4 the depressions 24 and 26 will be positioned pairwise, in mutual extension and in regularly angularly displaced positions on the respective four inner side portions of the stator ring 25. On each of the inner side portions the double depressions 24, 26 will be located with an even spacing, namely with a spacing corresponding to the width of two lamination packs or sub-assemblies 22 or to the double length of the depression in each pack, of which each single depression 24, 26 constitutes one half.

The stamped out pole piece laminations are correspondingly assembled together so as to form pole blocks or sub-assemblies 28, 30 as shown in Fig. 5. The blocks 28 consist of the respective pole piece laminations A, B and D while the blocks 30 consist of the pole piece laminations C respectively, whereby each block 30 has a protruding profile portion or protrusion 32 formed by the ear-shaped portions

16 of pole piece laminations C. It will be understood that it is possible to assemble these blocks together in such a manner that they will form a unitary pole piece assembly or block 34 as shown in Fig. 6, in which block the spaced-apart protrusions 32 are located so as to mate respective depressions 24, 26 in the respective inner side portions of the stator ring. An easy reception of the protrusions 32 in the depressions 26 will be ensured in that the latter, due to the stamping of recesses 20 as described above, are slightly larger than the recesses 14 that were left by the stamped out ear portions 16.

Positioning depressions 24 and 26 so that they mutually extend one another will provide a sufficient space for an untroubled introduction of the protrusions 32, which can be slightly axially displaced within the so-formed double-depression 24, 26, which will permit each protrusion

32 to enter partly into the depression 24, where, due to the pointed shape of the protrusion 32, would be a sufficient space for the initial insertion of the protrusion. In practice, the mounting of the pole block 34 into an accurate position in the stator ring may be effected by such a loose insertion of the protrusions 32, whereafter the pole block is forced to slide in the axial direction to cause a lateral

engagement between the protrusions 32 and the walls of the _d epressions 26; then the final mounting can be effected as described below.

Prior to the aforedescribed initial assembling of the stator ring 25 and the pole piece block 34 these parts are stabilized so as to form rigid, axially compressed bodies. The pole piece blocks 28 and 30 can be held together by means of welding wires 40 shown in Fig. 5, which wires are inserted into through passages 36 formed by holes 36' (Fig. 1) in the shaft portions of the pole piece laminations, whereafter the entire pole piece block 34 is pressed together axially and welded at weld seams 42 (shown in Fig. 6) , laid along the respective lateral portions, such that the laminations will be secured to the welding wires 40 and to each other in a conventional manner known per se. A similar technique may be used for the stator ring body 25, using, for example, stamped out passages 44 (Fig. 7) provided at the corners of the stator laminations which are here of square shape as shown. Alternatively, stay bolts 46 cooperating with suitable spanner means at the opposite ends of the stator ring can be provided, for example, along the outer corners of the stator ring body.

Upon assembling of the pole piece blocks 34, suitable stator coils 48 (Fig. 7) are placed onto the shaft portions of the pole pieces, and thereafter the thus- assembled pole pieces are attached to the inner side of the stator ring as described above.

Hereafter the pole piece blocks 34 are fastened to the stator ring body by introducing anchoring rods 50, one for each pole piece (Fig. 7), through the passages in the

stator ring formed by the holes 10 in the stator laminations 2. Each lamination is provided with only two such holes, but the recesses 14 and 20 make it possible to insert rods 50 which pass through the holes 10 in those lamination packs 22 which have holes 10 located in alignment with these recesses. The anchoring rods 50 will pass freely through recesses 14, 24, while in recesses 20, 26 they will pass through holes 18 formed in protrusions 32 which are inserted into these recesses. Thereby the pole piece blocks 34 will be anchored to the stator ring at each of the protrusions 32.

As indicated in Fig. 7, which shows the pole piece blocks 34 in their mounted positions, holes 18 are positioned slightly closer to the base surface of the lamination packs 30 than holes 10 relative to the inner side of the stator ring 25. If the anchoring rods 50 used for insertion into the passages formed by the holes 10 are pointed at their leading end, then it is possible to achieve a desirable, very strong tightening of the pole pieces against the stator ring. However, it will still be practicable to effect the removal of the anchoring rods 50 from the stator ring 25, such that one or more pole pieces may later be dismounted for exchange of the associated stator coils 48, should such a repair become necessary. Thus, a rigid and yet a reasonably easily releasable fastening of the pole pieces is achieved by the simple measure of introducing anchoring rods 50 into the holes 10.

Depressions 26 will be almost totally filled by protrusions 32, while depressions 24 will remain open

between the inner side of the stator ring and the base portions of the adjacent pole lamination packs 28. This results in an undesired air space in the magnetically conductive system, but it has been found that this disadvantage is of such minor significance that it is entirely overshadowed by the advantages connected with the present invention.

If desired it is possible to arrange for more than just a single ear-shaped portion 16 of the pole lamination, whereby, with the corresponding use of more holes 10 and anchoring rods 50 for each pole piece block 34, a still more rigid and stabilized tightening of the pole pieces against the stator ring will be achievable.

It will be readily understood that the invention is not limited to the embodiment shown, because there may be fewer or more poles than the four shown, e.g. more poles on a circular stator ring.

It should be noted that it is possible to make use of inverted engagement systems, i.e. where the protrusions 32 are provided on the inner side of the stator ring, while complementary depressions 24, 26 would be formed on the base portion of the pole pieces. What is to be ensured is that except holes 10 and 18 in the two parts there is sufficient material to provide for a safe holding connection by means of the anchoring rods, and it is not of any principal importance whether the holes are located inside or outside the base contour of the hole pieces. The holes may even be located in the contour line, i.e. line a (Fig. 3), crossing the hole 10, with only the hole 18 being located correspondingly. The straight cuttings at the poles A and B

can be changed so as to have e.g. a lat outward bulging such that they will project sufficiently outside the holes for securing the holding effect. The ear-shaped portion 16 on pole piece lamination C may protrude a lesser amount. Also the shape of the base of the pole lamination shall be taken into account at the pole laminations D and C.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure, which modifications do not constitute departures from the spirit and scope of the invention.

The principle of the invention may, optionally in certain cases, be utilized even for the manufacturing of laminated rotors with coils.