GB609580A - Improvements in and relating to locks and keys - Google Patents

Abstract

609,580. Locks. WOLLASTON, H. J. BUCHANAN-. March 18, 1946, No. 8280. [Class 44] The lock described in Specification 510,179 is provided with a modified form of key guide enabling it to be used as a mortice lock, and modifications are made to the tumblers and tumbler housings to prevent picking. The key guide comprises a part A, Figs. 2 and 5, mounted on the lock, and a part B, Figs. 1, 2 and 3, adapted to be inserted in a hole cut through the door and then secured to the part A. The part B consists of a metal block 1, with curved ramps 1a and a central slot 1b, and two other blocks 2 having lower curved faces corresponding to the ramps 1a, the blocks being assembled between end plates 1c so that the curved surfaces form narrow guide ways for the strip metal key. The part A comprises two metal plates 4, assembled closely parallel by means of distance pieces 5 at each side so as to leave a central channel for the key. At one lower corner of each plate 4 a part is cut out, and a vertical slit is made in the other plate to enable the opposed corner part 7 to be pressed out as shown in Fig. 5. A flap 8 is bent outwardly from the centre part of each plate 4. Four small plates 6 are fitted at the side edges of the assembly. The upper part of the assembly A is inserted into slots cut in the lower part of the lock, and secured therein. A hole, as indicated at C, Fig. 2, is made through the door below the mortice and the part B inserted; the lock, with the part A attached, is then inserted into the mortice so that the lower edge of part A slides into the slot 1b in the part B. The flaps 7 at the lower corners of part A are then turned outwardly by a tool, securing the parts against relative movement. The guide enables the strip metal key to be inserted into the lock from either side of the door. In order to prevent picking by using a metal strip or false key to push the tumblers up one by one while applying force to the bolt or handle to hold up the upper tumblers by friction, a notch 9, Fig. 6, of the form shown is formed in the rear or right-hand wall of the upper tumbler space in the bolt, the upper end of the notch being just above the top of the upper tumbler 11 when in the locked position. Application of force to the bolt will cant the upper tumblers slightly, and the end tumbler will be prevented, by engagement in the notch, from being raised by a false key. A notch 10, of similar but inverted shape, may be provided in the upper tumbler at the other end. Similar notches may be formed in each upper tumbler of the lock, if the total lengths of each pair of tumblers is increased from one end to the other of the set.