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Title:
COMMUTATOR FOR ELECTRIC MOTORS AND APPARATUS FOR AUTOMATIC WELDING OF NON NOBLE METAL CURRENT INPUT LEGS TO SEGMENTS OF THE SLIP RING OF A COMMUTATOR
Document Type and Number:
WIPO Patent Application WO/1993/026065
Kind Code:
A1
Abstract:
The commutator according to the invention contains a slip ring made of noble metal, wherein the segments of said slip ring are provided with current input legs. The current input legs (2) are made of non noble metal or alloy and are fixed to the segments of the slip ring (1) by welding. The apparatus for automatic welding of non noble metal current input legs to segments of the slip ring of a commutator consists of: a welding unit (A), a holding unit (B) and a feeding unit (C); said welding unit (A) comprising a fixed horizontal electrode (6) and a movable vertical electrode (7), a cutter block (10) and a wire feed drum (8) for feeding wire (9) to the horizontal electrode (6); said holding unit (B) comprising a slide (12) movable in parallel and perpendicular directions with respect to the horizontal electrode (6), said slide carryinig a rotatable collet (13) being provided with an ejector (14) and a retractor (15), for holding and ejecting the slip rings (1) and said feeding unit (C) comprising a jigging feeder (16) with guide rails (17), an expansion mandrel (18) arranged on a delivery unit at the end of said guide rails (17) and provided with a brake (24) and a throwout shoulder (21), a rotating mandrel (25) opposite to and coaxial with said expansion mandrel (18) and an adjusting means having a positioning finger (32) and a plate spring (31).

Inventors:
Kardos
Lajos, Nagy
Bélßné, Rudasi
Kßroly
Application Number:
PCT/HU1992/000023
Publication Date:
December 23, 1993
Filing Date:
June 10, 1992
Export Citation:
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Assignee:
Kardos
Lajos, Nagy
Bélßné, Rudasi
Kßroly
International Classes:
H01R39/32; (IPC1-7): H01R39/32; H02K15/00
Foreign References:
US0842829A
DE2143708A1
US3421212A
US4764700A
EP0119172A2
DE2723893A1
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Claims:
C L A I M S
1. Commutator having a slip ring made of noble metal, wherein the segments of said slip ring are provided with current input legs characterized in that the current input legs 2 are made of non noble metal or alloy and are fixed to the segments of the slip ring (1) by welding.
2. The commutator according to claim l, characterized in that current input legs (2) are made of wire (9) .
3. The commutator according to claim 1, characterized in that current input legs (2) are made of plates.
4. A commutator as claimed in any of claims 1 to 3, characterized in that the current input legs (2) are fixed to the segments of the slip ring (1) by spot welding (3) .
5. An apparatus for automatic welding of non noble metal current input legs to segments of the slip ring of a commutator, characterized in that it has a welding unit (A) , a holding unit (B) and a feeding unit (C) , said welding unit (A) comprising a fixed horizontal electrode (6) and a movable vertical electrode (7) , a cutter block (10) and a wire feed drum (8) for feeding wire (9) to the horizontal electrode (6) ; said holding unit (B) comprising a slide (12) movable in parallel and perpendicular directions with respect to the horizontal electrode (6) , said slide carrying a rotatable collet (13) being provided with an ejector (14) and a retractor (15),for holding and ejecting the slip rings (1) and said feeding unit (C) comprising a jigging feeder (16) with guide rails (17) , an expansion mandrel (18) arranged on a delivery unit at the end of said guide rails (17) and provided with a brake (24) and a throwout shoulder (21) , a rotating mandrel (25) opposite to and coaxial with said expansion mandrel (18) and an adjusting means having a positioning finger (32) and a plate spring (31) .
Description:
COMMUTATOR FOR ELECTRIC MOTORS AND APPARATUS FOR AUTOMATIC WELDING OF NON NOBLE METAL CURRENT INPUT LEGS TO SEGMENTS OF THE SLIP RING OF A COMMUTATOR

This invention relates to a commutator for electric motors, having a slip ring made of noble metal, wherein the segments of said slip ring are provided with current input legs. Furthermore the invention relates to an apparatus for automatic welding of non noble metal current input legs to segments of the slip ring of a commutator.

Commutation of small rotating machines is generally carried out by mechanical or electronic units. Actually, mechanic units are mainly used as they are considerably cheaper than the electronic ones. Mechanic slip rings ensure that the parts of the windings are connected with the stationary brushes being in the same region of the magnetic field. The segments of the slip ring of a commutator are connected to wire coils by resistive connection via current input legs. These current input legs are generally produced from the material of the slip ring itself.

The slip rings of the commutators can be produced of noble or non noble metals. Generally, the noble metals are of superior parameters, but they are rather expensive. The main advantage of the slip rings made of noble metals is the good corrosion resistance and, due to this, a rather good electric and thermal conductivity, stable contact resistance and a low friction coefficient.

Drawback of the noble metal slip rings further to the costs is the rather low resistance to mechanical and electric corrosion. This resistance can be improved only within limits due to the special technology of producing the slip rings. The corrosion and abrasion resistance can namely be improved by a

rather high degree cold working, which, however, makes conventional production rather difficult. To bent a ring from a havily cold worked plate is not easy: the plate is rather rigid and has an affinity to cracking as well. That is a serious problem, the more so because the plate should be bent into different directions during production of the slip ring. The current input legs should be bent along a rather short radius and perpendicularly to the rolling direction and so cracking is a serious danger.

A heat treatment can also be applied for the same purpose. For such heat treatments, however, only noble metal alloys can be applied, which have a good conductivity, but at the same time the structure contains segregations at the borders of the silver crystals, after the heat treatment following the cold working. The segregations, however, deteriorate the conductivity as well as the contact resistance.

An object of the present invention is therefore to provide a commutator made of noble metal being, however, without the above drawbacks, i.e. it can be produced simply and cheaply and enables safe operation.

A further object of the present invention is an apparatus for automatic welding of non noble metal current input legs to segments of the slip ring of a commutator.

The apparatus according to the invention has a welding unit A, a holding unit B and a feeding unit C.

Welding unit A comprises a horizontal electrode and a movable vertical electrode, a cutter block and a wire feed drum for feeding wire to the horizontal electrode.

The holding unit comprises a slide movable in parallel and perpendicular directions with respect to the horizontal

electrode, said slide carrying a rotatable collet provided with an ejector and a retractor for holding and ejecting the slip rings.

The feed unit comprises a jigging feeder with guide rails, an expension mandrel arranged on a delivery unit at the end of said guide rails and provided with a brake and a throwout shoulder, a rotating mandrel opposite to and coaxial with said expansion mandrel and an adjusting means having a positioning finger and a plate spring.

The invention is based on the recognition that it is reasonable to produce slip rings of noble metal, but not the current input wires. In view of the operation, there is no need of making the current input legs of noble metal and they are generally made of it only because the slip rings itselfs are of noble metal and the current input legs are made of the same piece.

If the current input legs of a slip ring made of noble metal are not made of noble metal, then the amount of noble metal for producing a slip ring can be considerably reduced, and at the same time a slip ring formed without current input legs has a superior quality: it has a good corrosion resistance, stable contact resistance, a good electric and thermal conductivity as well as a low friction coefficient. It can be produced by strong cold working because no bending of current input legs is needed. In this way, a rather high hardness can be achieved without the danger of difficult forming.

Accordingly, the commutator according to the invention contains a slip ring made of noble metal and current input legs made of non noble metal. Due to this feature the commutator is cheap, has a superior quality and enables safe operation.

The apparatus according to the invention enables a quick, cheap and reliable automatic production of commutators, more over slip rings for commutators.

The present invention will become more apperent from the following detailed description of preferred embodiments of the invention when read in conjunction with the accompanying drawings. In the dwawings

Fig. 1 is an embodiment of a commutator according to the invention, Fig. 2 is a slip ring according to an other embodiment of the present invention, Fig. 3 is a shematic illustration of the apparatus according to the invention in side view, Fig. 4 is a top view of the apparatus in Fig. 3, Fig. 5 is the feed unit in section,

Fig. 6 is part of the holding unit together with a part of the feeding unit during operation,

Fig. 7 is the holding unit together with the welding unit in section and Fig. 8 is the holding unit and the welding unit together with the cutter block, when cutting and forming one of the current input legs.

The collector made of noble metal shown in Fig. 1 contains a slip ring 1 and input legs 2. The input legs 2 are fixed to the slip ring 1 by spot welding 3. Both the slip ring 1 and the input legs 2 are embedded in a plastic body 4.

Input legs 2 are made of copper wire provided with a covering layer of tin.

The other embodiment of the commutator according to the invention is shown in Fig. 2. All the input legs 2 are cut out of a single plate and are held by a ring 5 which is connected to the slip ring 1 by spot welding 3. These input legs 2 and

the slip ring 1 are also embedded in a plastic body which, however, isn't shown in Fig. 2.

It is to be noted that the segments of slip ring 1 are not shown in Figs. 1 and 2, because these segments are produced by milling out grooves in the finished collector.

It is noted that welding of the current input legs can be any appropriate welding i.e. laser beam welding, though the examples show spot welding.

The apparatus according to the invention for producing slip rings with input legs is shown shematically in Figs. 3 and 4. The main units of the apparatus are marked with dash lines. Welding unit A, holding unit B and feeding unit C can be seen more in details in Figs. 5 to 8.

Welding unit A contains a fixed horizontal electrode 6 and a movable vertical electrode 7. Horizontal electrode 6 is provided with a wire drum feed 8 for providing wire 9 to produce the input legs for the slip rings.

A welding unit A also contains a cutter block 10 for cutting and bending out the wire sections welded to the slip rings.

Holding unit B consists of a slide 12 guided on table 11. Slide 12 can be moved on table 11 parallel with and perpendicular to the axis of horizontal electrode 6. A collet 13 is arranged on slide 12 for holding slip rings 1. For this purpose, collet 13 is provided with a retractor 15 and an ejector 14. In this way, slip rings 1 can be brought to the right position on horizontal electrode 6 for spot welding.

Feeding unit C contains a jigging feeder 16 and guide rails 17 connected to the jigging feeder 16. At the lower end of the guide rails 17, there is an expansion mandrel 18 for taking

out slip rings 1 from the guide rails 7. Expansion mandrel 18 can be moved along its geometrical axis and further to this can be tilted around an external axis by delivery unit 19. Delivery unit 19 is further provided with a pneumatic cylinder unit 20 for moving expansion mandrel 18 along its geometrical axis.

Expansion mandrel 18 has a throwout shoulder 21 which is supported by a coil spring 22. A brake 24 is provided for fixing expansion mandrel 18 in appropriate position.

At the end of the expansion mandrel 18, there is a slot 24 in order to ensure a spring force to hold slip rings around it.

On the other side of the guide rails 17, there is a rotating mandrel 25 coaxial with expansion mandrel 18. Rotating mandrel 25 is connected to an electric motor via clutch 26. The electric motor is not shown in Fig. 5.

Rotating mandrel 25 is hold rotatable by bracket 27 and is provided with a head 28 urged to the expansion mandrel 18 by spring 29. The head of rotating mandrel 25 is provided with a face toothing 30 for rotating the slip ring 1 held by the expansion mandrel 18. Slip ring 1 is rotating until plate spring 31 urges finger 32 into the slot of slip ring 1 and then brake 24 holds it in this position during the delivery into the holding unit.

Expansion mandrel 18 is retracted from rotating mandrel 25 by pneumatic cylinder unit 20 and then it can be tilted by lever 33 of the delivery unit 19.

The apparatus according to the invention works as follows.

Cold pressed slip rings 1 are charged into the jigging feeder 16 and the end of the wire 9 on the drum feed 8 is drawn to

the horizontal electrode 6 via guide ring 35, as shown in Fig. 7.

The slip rings 1 are moving on the guide rails 17 into a position shown in Fig. 5 and there expansion mandrel 18 penetrates into the lowest slip ring 1 until throwout shoulder 21 reaches the ring. Due to further feeding of the expansion mandrel 18, the face of the slip ring 1 abuts on the face toothing 30 of the rotating mandrel 25. Then electric motor turns mandrel 25 via clutch 26 until finger 32 springs in the slot of the slip ring 1. The clutch 26 begins to slip and, thereafter, electric motor stops. Then slip ring 1 fixed in that position by brake 24 is delivered to the holding unit B.

Slide 12 is fed to a position coaxial with the tilted position of expansion mandrel 18 and then the mandrel 18 moves forward to set slip ring 1 in the collet 13. When retractor 15 makes the collet 13 to fix the slip ring 1, expansion mandrel 18 is retreated and moved to the starting position.

Collet 13 is moved then into a position coaxial with horizontal electrode 6. Slide 12 moves then forward and puts slip ring 1 over horizontal electrode 6 and wire 9.

Vertical electrode 7 is then lowered and spot welding is produced as shown in Fig. 7.

After the spot welding has been completed, slide 12 moves again backwards and pulls slip ring 1 out from horizontal electrode 6. At the same time slip ring 1 pulls wire 9 further from wire drum 8.

In this position the jaws 10a and 10b of cutter block 10 will be closed and, accordingly, wire 9 is cut and bent out at the same time as shown in Fig. 8.

The next step is to rotate collet 13 in 120° and setting it again on horizontal electrode 6. Spot welding, cutting and bending is again carried out and then the slip ring 1 is turned again into a third position to produce the third current input leg 2.

When the slip ring 1 is provided with all the three input legs 2, slide 12 is fed to a throwout position. Here, retractor 15 opens collet 13 and ejector 14 throws the ready slip ring 1 into a container and the cycle starts again with taking the next slip ring 1 from the guide rails 17 by expansion mandrel 18.

The collectors shown as examples and the apparatus explained above do not restrict, of course, the scope of the invention and both the collectors and the apparatus can be carreid out in many other forms within the scope claimed in the attached set of claims. Anyway, the feeding movements can be provided by pneumatic units in cooperation with electropneumatic control valves. A programmed electronic unit may be applied for controlling the whole system.