GB1269418A - Tamper-proof axial tumbler lock - Google Patents

Abstract

1,269,418. Barrel locks. CHICAGO LOCK CO. 30 July, 1969 [5 Aug., 1968], No. 38285/ 69. Heading E2A. An axial tumbler barrel lock is protected against picking by dividing the rotatable barrel into two parts 16, 18, the tumbler pins being also divided into parts 36, 40 separated by a ball 42, such that any picking attempt has the effect of moving the pins into the position shown in Fig. 9 or 10 allowing ineffective rotation of the front barrel 18, while the part 16 which is coupled to the bolt 27 is held against rotation by pin part 38 or 40 engaging in fixed barrel part 14. This fixed barrel is secured housing 12 by a pin 20. When the correct key 100 is used, the balls 40 of all seven tumblers, lie on the interface between barrel parts 16 and 18 to provide a drive between them, the rearward tumbler parts 38, 40 meeting at the interface with the fixed feather 108 engaging in slot 74. A notch 80 65 in the shank lock face 62 ensures correct placing of the key which is guided on a pilot post 68 mounted in the front barrel by a tail 70. The key carries an internal guide feather 108 engaging in slot 74. A notch accommodates a spring-loaded limit pin projecting forwardly from the middle barrel 16 to limit the relative rotation of these two barrels and to urge the outer barrel into a forward position, Figs. 8 and 13. The key 100 has shoulders 106 for depressing the tumblers to the correct amount. A feather 110 enters a key 65 for correct alignment. When the key is inserted it pushes the front plug-part into contact with the middle one and thereafter the tumblers will be pushed back to the correct extent, Fig. 11. The key torque is transmitted through the pilot post 68 to the front barrel part. If a picking tool is inserted, it will push back the front plug part 18 as above, but this time the tumbler pins will be driven back so as to engage with the fixed barrel part to prevent rotation (Fig. 12, not shown). Eventually an intermediate situation, Fig. 9 or 10, is arrived at which frees the front cylinder but locks the intermediate one.