Patent GB-277787-A (GB)
Title: Improvements in or relating to the control of electric circuits
IPC: H01H36/00
Filed: 1926-08-13
Abstract: 277,787. General Electric Co., Ltd., and Myers, G. R, Aug. 13, 1926. Electromagnetic switches; interrupters; bases; electric-motor actuation. - Relates to means for controlling a circuit comprising a plurality of magnetically-controlled switches, at least one permanently or constantly energized magnet, and a device for varying the force exerted by the magnet on the switches so that they are actuated in a desired sequence. The invention consists in enclosing the contacts of the switches in separate envelopes evacuated or containing inert gas. Fig. 1 shows the contact-making device comprising a highly-evacuated or gas-filled envelope containing two soft iron strips 4, 5 having feet 6, 7. A molybdenum spring 10 on the strip 4 carries a movable armature 12 recessed at 13 to receive a tungsten contact 14 which co-operates with a similar fixed contact 15. Nickel wires 19, 20 are connected to strip 5 by conductor 21 whilst wires are similarly connected to strip 4 by conductor 18. If now a magnet be brouht up to the feet 6, 7, flux will be set up in the strips and the armature will be moved to make (or break) circuit. Fig. 3 shows how a series of such switches can be operated in sequence by one magnet. The gear-box 24, which may contain lubricant, supports a continuouslydriven shaft 27 carrying a brass disc 34 on which is adjustably mounted at least one U-shaped permanent magnet 35. Supported on a table 38 are aluminium rings 40, 41 formed with a series of holes to receive the switches which are secured by springs 44. Soft iron rings 43 are bolted to each ring over each hole and arranged to be adjacent the first 6, 7 so that when the magnet is rotated, the twelve switches are operated in sequence. Fig. 5 shows a form in which one magnet is provided for each switch, the continuously-driven spindle 46 in this case rotating a cam 50 comprising two similar plates 72, 73 normally fastened together but adjustable to vary the cam surface. The switches are assembled in brass tubes 55 circularly arranged on a guide plate 54 supported by means of pillars on a table 51. This table carries eight blocks 62 formed with grooves to receive the ends of supports 64 on which are adjustably mounted the permanent magnets 69. Rollers 71 on the supports 64 engage the cam'50 so that, as the latter rotates, the magnets are moved in turn away from the switches to actuate them in one direction, the return movement acting under gravity actuating them in the reverse direction. The magnets are guided during this movement by slots 65 in the guide plate 54. This plate supports an ebonite ring 57 backed by a copper ring 58 carrying eight pairs of insulated terminals 59 and eight terminals 61 connected to the ring 58. One lead of each switch is connected to a terminal 61 and the other to one of a pair of contacts 59. The cam or magnet may if desired be rotated from point to point in its path by distant control apparatus and the vacuum switches may be evacuated as described in Specification 277,158. In an alternative form, the magnet poles and switch feet are separated and adapted to be bridged by soft iron blocks.