GB835150A - Double-throw locks for doors - Google Patents

Abstract

835,150. Key locks. COOPER, H., and LLEWELLYN, L. July 23, 1958 [July 31, 1957], No. 24220/57. Class 44 In a door lock of the double throw type in which a key operated dead bolt 11 is shot out to the full extent in two throws by two complete turns of the same key in one direction, two complete turns of said key in the opposite direction being required to withdraw the bolt fully, the dead bolt is provided or formed with an abutment which when the bolt is in its mid position having been moved thereto from either extreme position by a single turn of the key in the appropriate direction, co-operates with the key to prevent withdrawal of the key from the lock. As shown,. the abutment is the horizontal part of an L-shaped member 16 which is formed or provided on the bolt tail 12; the part is of such length that its free end is clear of the keyhole when the bolt is in one extreme position and it is formed with a clearance notch 18 for the key bit which notch registers with the keyhole when the bolt is in its other extreme position. When the bolt is in the mid position' shown a central lever step or notch '17 in the key bit engages the abutment to. prevent the key being withdrawn.