Protective safety device including an electric switch controlled by a guard for electrically driven machinery

摘要

731,714. Machinery safety devices. HUNTLEY & PALMERS, Ltd. Dec. 4, 1953 [Dec. 5, 1952], No. 30883/52. Class 80 (4). [Also in Group XXXVII] An electric switch 1 controlling machinery protected by a wire guard 2 ensures that the motor driving the machinery is disconnected from the supply except when the guard is in position, and comprises a pair of contactcarrying blades 14, 15 mounted on an insulating block 7 within a non-magnetic casing 3, the contacts 25, 26 co-operating with fixed contacts 12, 13 on a conducting arm 9 also mounted on the block. The free ends of the blades 14, 15 are connected by an insulating sleeve 20 and the blades are biased so that the contacts 12, 25 engage and contacts 13, 26 disengage. A bolt 23, in the sleeve 20 carries a permanent magnet 24 and the guard 2 carries a permanent magnet 32 so that when the guard is placed in position the magnet 24 is attracted and contacts 12, 25 are opened and contacts 13, 26 closed. In a modification, the magnets are arranged with their like poles opposite so that the magnet 24 is repelled. Further, either of the magnets may be replaced by an armature and part of the guard may constitute an armature.