GB935474A - Improvements in or relating to key controlled switching devices - Google Patents

Abstract

935,474. Magnetic switches. STANDARD TELEPHONES & CABLES Ltd. March 18, 1960 [March 21, 1959 ; March 26, 1959], No. 9666/60. Class 38 (5). [Also in Group XXXIX] On depressing a key of a keyboard switching device at least one permanent magnet is moved relative to an adjacent reed switch to close the reed switch. Strips X1, X2, X3, X4, Y1, Y2, Y3, Fig. 1, preferably of non-magnetic material are fastened to a base-plate 1 by springs 2, 4 and are held in a position of equilibrium by permanent magnets 3, 5 which are fixed to side walls to attract the ends of springs 2, 4. The strips (except for strip X1) carry permanent magnets 6 for actuation of reed switches a, b . . . i (a not shown) each comprising two magnetic reed contacts in a sealed protective envelope. Each key is arranged at the intersection of two strips and, when depressed, engages profiles in the two strips at the intersection and displaces such strips longitudinally against the action of springs 2, 4 to bring at least one magnet 6 into proximity with an associated reed switch a, b . . . &c. to operate such reed switch. Alternative arrangements.-Rods X, Y, Fig. 2, are used as coupling elements and one of each is rotated on depressing a key, projections 13, 14 on the key engaging projections 11, 12 on the rods. At one end of each rod is a permanent magnet 16 which, on depressing an appropriate key, is rotated from a short-circuit position in a shunt 17 to a position, adjacent flux-deflecting members 15, in which it operates a reed switch a. A spiral spring (not shown) provides the return motion. In a third arrangement a housing 29, Figs. 4, 5, carries a support 32 on which are mounted four reed switches 25, one above the other. Pivotally mounted arms 23 have extensions which carry permanent magnets 24 for actuation of the switches 25, the arms being moved by movement of keys 21. Springs 26 restore the arms 23 and springs 36 restore the keys 21. Movement of any key 21 also provides operation of a common reed switch 25<SP>1</SP> by movement of permanent magnet 241 through slide 27, Fig. 6. Slots 34 in the slide 27 prevent intercoupling of the arms 23 and consequent movement of all magnets 24 when only one key is depressed. Reed switch 25<SP>1</SP> is normally closed, and is released when any key is operated but, by mounting magnet 24<SP>1</SP> higher up, the reverse condition could be obtained. Reed switches 25 may be made to close at the end of travel of the arms 23 but, with a larger travel, they may be made to close momentarily during the key depression and to be released while the key is fully depressed.