Patent GB-678909-A (GB)
Title: Improvements in or relating to rotary electric control switches
IPC: H01H25/06
Filed: 1951-05-31
Abstract: 678,909. Press-button retractive switches; regulating switches; mechanical switches, without quick-action. HOMANN, W., (trading as HOMANN-WERKE W. HOMANN). May 31, 1951. [Oct. 1, 1948 ; Sept. 5, 1949] No. 12810/51. Class 38 (v). A rotary switch for controlling heating resistances is connected in series with a snap-acting main switch operated by longitudinal movement of the spindle operating the rotary switch, the main switch being opened before and closed after operation of the rotary switch. The latter is shown as of the usual four-position type and comprises a drum 44 carrying contact segments 48 ... 50 cooperating with fixed contacts 1, 2, P<SP>3</SP>, L, mounted in one half 33 of a twopart housing 33, 34. The spindle 40 has a flat portion 74 co-operating with a similarly-shaped hole in the drum and is forced outwards by a spring 75. The main switch comprises fixed contacts 53, 54, the former of which is connected to contact 2. The contact P<SP>3</SP> is connected by a bridge 52 to a terminal P<SP>1</SP>, the supply being connected to terminal P<SP>1</SP> and to a terminal P<SP>2</SP> connected to contact 54. Movable contacts 46, 47 are carried by a conducting cup 45 connected by two wire toggles 68, 69 to a sleeve 67 slidable on the spindle, which also carries a slotted disc 76 co-operating with projections 81, 82 on the cover 39. The slots 77 ... 79 in disc 76 are deeper radially than a fourth slot 80 and projection 81 is farther than projection 82 from the axis of spindle 40 so that while the projection 81 can enter any of slots 77 ... 80, projection 82 can only enter slots 77 ... 79. In the "off" position, the projection 82 is opposite the slot 80 and engages the disc 76 to hold it in an intermediate position in which the contacts 46, 47 are open, but projection 81 is in slot 78, so that the rotary switch can only be rotated to an "on" position after depression of the spindle to the position shown to disengage 78, 81. After rotation of the drum 44, the spindle is released and returned by spring 75 and the projections 81, 82 enter two of the slots to allow the main switch to close and prevent further rotation of the control switch without first depressing the spindle. The contacts 46, 47 are moved rapidly when the toggle 68, 69 is moved over-centre by movement of sleeve 67. In the closing movement, the cup 45 acts as a damper to prevent contact chatter and, in opening, forces air from above the cup into the space below it so as to cause an air blast across the contacts. Permanent magnets 112, 113 or magnet coils are provided to assist in arc extinction when breaking direct currents. In a modification, Fig. 13, the main switch disc 83 is slidable on the spindle 63 and is connected thereto by a tension spring 85, and to the housing 58 by spring toggles 88, so that on movement of the spindle to the left, the spring 85 is stressed until it eventually overpowers the toggle and moves the disc to the left to separate contacts 84, 89. This movement of the spindle also frees a key 91 from slots in a fixed disc 95, thereby allowing rotation of the control switch drum 90, the switch 84, 89 being held open when the key 91 is not opposite a slot in disc 95. In a further modification, Fig. 15, the toggle comprises two telescopic links 101, 102 urged apart by a compression spring 104, the link 101 engaging a groove 103 in spindle 63, and the link 102 carrying a roller contact 105 movable over a curved track, comprising conducting and insulating portions 107 and 99 respectively.