US2276983A - Electric current transmission mechanism - Google Patents

Description

Marci! I7, 1942. Y J JONAS 2,276,983

ELECTRIC CURRENT TRANSMISSION MECHANISM Filed 001?. 4, 1940 Patented Mar. 17, 1942 ELECTRIC CURRENT TRANSMISSION MECHANISM Julius Jonas, Zurich, Switzerland, assignor to Aktiengesellschaft Brown,

Boveri & Cie.,

Baden, Switzerland, a joint-stock company Application October 4, 1940, Serial No. 359,787 In Switzerland September 30, 1939 1?. Claims.

When electric currents have to be transmitted from a rotating to a stationary conductor it is usual to use a slip-ring which is connected to the rotating conductor and a brush or set of brushes to which the stationary conductor is connected. There is then generally a considerable amount of friction between slip-ring and brushes, depending upon the speed of rotation, the condition of the surfaces in contact with each other, and the materials used for the slip-ring and brushes, this friction being converted into heat and causing the slip-ring and brushes to wear. This mechanically produced heat adds itself to the heat produced by the current and reduces the electrical loading capacity of the current collector.

These and other disadvantages of the prior arrangement are overcome according to the present invention by the current being transmitted from the movable to the stationary element by means of a planet gear made of electrically conductive material whereby all sliding contacts are avoided and exclusively rolling contacts are used.

In the practical constructional forms of the invention, of which a number are illustrated in the accompanying drawing, the current collecting elements preferably consist of transmission members, such as bands or ropes, hereinafter generically called belts, which roll over discs. In the planet gear according to the invention which is provided with such transmission members, the movable and the stationary conductors are in the form of coaxial cylindrical discs each of which is connected by means of an electrically conductive endless transmission member with an electrically conductive rotating wheel, these wheels being free to rotate in bearings which are located on at least one carrier which is arranged to swivel freely about an axis which is coaxial with that of the discs.

In the accompanying drawing:

Fig. 1 shows a side elevation and Fig. 2 a front view in perspective of the current transmitting device; Fig. 3 shows a perspective front view of a modified form of the invention; Fig. 4 another modified form of the invention in lateral ele vation;

Fig. 5 shows how the invention is applied to current collection in a high current unipolar machine.

In Figs. 1-4 a is the driving shaft from which the current is to be collected. A swivel arm 0 is located at b coaxially with the driving shaft and supports at its outer end the intermediate shaft e. An electrically conductive disc 1 is fixed on the shaft a, this disc being connected with the The speed of the swivel arm 0 has a. simple relationship to the speed of the driving shaft a. and also depends upon the diameter of the discs h, i, m. If the speeds are indicated by the letter 11 and the disc diameters by the letter D, the indices referring to the reference letters in the drawing, the following relationship is obtained:

1 a hX m 1 i DIX D.-

The minus sign applying to the case when both belts g and k are open as shown in Fig. 2 or if both belts are crossed, whilst thesplus sign refers to such arrangements Where only one of the belts is crossed, for instance it as shown in Fig. 3. A negative value for the above equation means that the motion is in the reverse direction to that of the shaft a. When the belts are open the current cannot be transmitted if the relationship between the discdiameters is because then nc= All other relationships give, however, finite values for 720. For the constructional examples shown in Figs. l-3 it is assumed that for crossed belts.

With the arrangement illustrated in Fig. 4, Dh Di so that now the current collection in unipolar machines has been the source of high losses and has presented a problem which has so far found no satisfactory solution. This can, however, be remedied by the invention and Fig. shows a diagrammatic arrangement for collecting the current in a unipolar machine, the electrical transmitting elements on the right side of the figure being omitted for the sake of clearness.

In Fig. 5 the armature q is supported in the bearing end shields r and rotates inside the yoke 0 to which the exciting Coils p are fixed. Two broad slip-rings s are provided between which the current is induced. The current is transmitted by means of electrically conductive belts u passing through insulated slots t to the two discs 1;. At this point the current collecting mechanism according to the invention is applied, the various elements of this mechanism having the same reference letters as in Figs. 1-3. The swivel arm 0 with the intermediate shaft e and the discs 72 and z' are duplicated in order to provide a balanced system; as a result of this the first disc 1 and the last disc m have to be made twice as wide as the intermediate discs h and i. The current is transmitted through the belt u and the discs 12 to the shaft 11 which is supported in insulated bearings. A stationary conductor w is connected to the last disc m which is fixed to and insulated from the casing r. The complete current collecting mechanism is entirely enclosed but adequate ventilation openings are provided, for instance as shown at a, so that the rotating conductive bands g, k can carry heavy loads. If natural air cooling should prove to be inadequate it is always possible to provide artificial cooling by means of a gas or liquid.

The tension in the transmission belts is produced automatically as a result of the electrodynamic forces, because the currents at the points where the belts leave the discs are opposed to each and therefore repel each other. Special tensioning devices can, however, also be provided.

If doubling the rotating discs h, i is not sufiicient to balance the system, then either a large number of narrow bands or ropes g, k can be provided alternately on each side, or instead of having two diametrically opposed arms 0, three or more such arms 0 can be used, these being equally spaced and equipped with the corresponding number of discs h, 2'. When there are more than two intermediate shafts e it is expedent to replace the arms by a disc wheel. If the equilibrium is disturbed by the unequal masses of the discs h and 2' and their unequal distance from their hearing points, this can be eliminated by supplying additional balance weights to the system.

In order to obtain an even current distribution in the slip-rings s of the unipolar machine, each slip-ring can be provided with several, preferably two current collecting devices,which are arranged opposite to each other. For instance next to the transmission belt u which emerges in an upward direction and enloses the lower half of the slipring s, a second transmission belt can be located which encloses the upper half of the slip ring and extends downwards through the machine casing. If the bands are replaced by transmission ropes it is expedient to let these run in grooves in the discs whereby these ropes are arranged to pass alternately upwards and downwards through the casing.

The electrically conductive bands and ropes are made of a highly flexible, good conducting metal which is free from corrosion, such as phosphor bronze or copper braid with a small percentage of beryllium.

It will be evident to those skilled in the art that many variations may be made in the details of the structure and that the invention is capable of other embodiments besides these illustrated; therefore it is not intended that the patent be limited except as necessitated by the prior art and indicated by the claims.

I claim:

1. Apparatus for conducting electrical current comprising a current source, a rotating electrically conductive cylindrical member electrically connected to said current source, a stationary electrically conductive cylindrical member coaxial with said rotating member, a rigid member pivoted about the common axis of said rotating and stationary members, a plurality of rotatable electrically conductive cylindrical members carried by said rigid member on an axis spaced apart from but parallel to said common axis, said last named rotatable members being electrically and mechanically connected to rotate together, a flexible electrically conductive belt conmeeting the first named rotating member with one of said last named rotatable members, a flexible electrically conductive belt connecting said stationary member with another of said rotatable members, and a stationary contact member electrically connected to said stationary member.

2. Apparatus as defined in claim 1 in which the current source is a rotating electrically conductive ring and is connected to said rotating member through an electrically conductive belt.

3. Apparatus as defined in claim 1 in which the current source is a rotating electrically conductive ring, and in which said rotating member is carried on and electrically connected with a rotating electrically conductive shaft, an electrically conductive disc carried by and rotating with said shaft and electrically connected therewith, and an electrically conductive belt connecting said current source and said disc.

4. Apparatus as defined in claim 1 in which the rotatable members are carried on a common shaft supported by said rigid member.

5. Apparatus as defined in claim 1 in which the rotatable members are carried on a shaft which is supported between said rotatable members by said rigid member.

6. Apparatus as defined in claim 1 in which said rotatable members are carried on a shaft supported outside said rotatable members by said rigid member.

'7. Apparatus as defined in claim 1 in which said rotatable members together constitute a unitary cylinder carried on a shaft supported out side said rotatable members by said rigid member.

8. Apparatus as defined in claim 1 comprising a plurality of rigid members pivoted about the common axis of the rotating and stationary members, each of said rigid members carrying a plurality of rotatable members on axes par allel to but equally spaced from said first named axis; one rotatable member carried by each rigid member being connected to said rotating member by an electrically conductive belt and another of said rotatable members carried by each of said rigid members being connected to said stationary member by an electrically conductive belt.

9. Apparatus as defined in claim 1 in which the rotating member is carried by a rotating shaft which passes through the stationary them-- her.

10. Apparatus as defined in claim 1 in which the rotating member is carried on a rotating shaft and in which said rigid member is pivoted about said shaft.

11. Apparatus as defined in claim 1 in which said rigid member is pivoted about a shaft which

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