Patent GB-766126-A (GB)
Title: Change key locks
IPC: E05B29/00
Filed: 1954-04-05
Abstract: 766,126. Change key locks; barrel locks. KENNEDY, E. N. March 11, 1955 [April 5, 1954], No. 9872/54. Class 44. A change key lock comprises a fixed part and a movable part, one of which carries sliding tumblers adapted to be lifted by the correct key from a position in which they prevent movement of the movable part to a position in which they permit such movement, the effective length of at least one tumbler formed of two parts in frictional engagement being adjustable in either the lifting or the lowering direction so that the lock can be altered to operate with keys of different patterns. In the arrangement according to Figs. 1, 2, 5 and 11 as applied to a cylinder lock 10, 11, controlling a night latch 16, each tumbler comprises a shank 20, Fig. 5, and a lifting member 21 made of spring steel bent to form a tubular part 22 and wing portions 23 and 24. The part 22 frictionally grips the shank 20. A key-way 25 and a hole 26 for a neutralizing member 27 extend through the cylinder 10. The lock barrel 11 is formed with a line of holes 28 diametrically opposite to a groove 29 and between the holes and grooves is formed a recess 30 having a cam surface 31. A guard plate 32, Fig. 2, is fastened to the barrel 10 and is provided with an aperture 33 having a quadrant-shaped edge 34 terminating in notches 35 and 36 which register with the bottom of the key-way 25 when the lock is in the locked and unlocked condition respectively. A slot 37 in the guard plate registers with the hole 26 when the lock is in the unlocked condition. A key 38 is provided with a notch in its lower edge which registers with the quadrant 34 whenever the key is positioned intermediate the locked and unlocked positions to prevent withdrawal of the key. In the locked position, insertion of the correct key lifts the tumbler shanks 20 clear of holes 28 and groove 29 to permit rotation of the cylinder 10. If it is desired to adjust the lock to suit a different key, the lock is held in the position shown in Fig. 7, the key 38 is withdrawn, and the neutralizing member 27, Fig. 11, inserted into hole 26. During this operation the lifting members 21 are forced to the right-hand end of the shanks 20. The member 27 is then withdrawn, a new key 38 is then inserted, all the tumblers are removed towards the left and a knob 15 of the latch is released and the lock cylinder is returned to the locked position, the ends of shanks 20 contacting the surface 31 and being forced back thereby into the cylinder and through the parts 22 of the lifting members 21. In a modification, additional holes or grooves may be provided opposite both ends of the shanks 20 and into which the latter can enter when the lock is in the unlocked condition and the original key is withdrawn. One such hole or groove may be beyond the keep end of the recess 30 which may subtend a smaller angle than that shown. Alternatively, the recess may be of the form shown, but such that the angle between locked and unlocked positions is greater than 90 degrees. An additional notch is provided in the quadrant of the guard plate corresponding to the additional position permitting withdrawal of the original key. In another modification, the holes 28 may be of unequal length to prevent picking. In a further modification, the lock may be constructed for operation by a key having its operating profile on one edge only, the key being provided on its opposite edge with a ramp formation, which, as the key is withdrawn, in the unlocked condition, forces the lifting members to their lowest position on the shanks. Insertion of a new key lifts the tumblers without affecting the lifting members, the final position of which is effected by turning the key back to locked position. In the arrangement according to Figs. 18 and 19, the neutralizing member is dispensed with. Each tumbler comprises a shank 49 having a rectangular slot 50 and mounts a lifting member 51 having a slot 52, which is of substantially the same depth as keys 53 and 53A. Insertion of the key 53 lifts all tumblers to permit rotation of the cylinder to unlock the lock. If key 53 is then withdrawn and key 53A inserted, the lifting members are moved to the position corresponding to that key and the cylinder can be returned to the looked position. In all arrangements, the tumblers may be spring-loaded. In alternative arrangements, a spring or springs housed in the lock may be provided for setting the lifting members to the maximum effective tumbler length and for pressing them against the key. Also, the construction may be such that only the lifting members come into contact with the lock or key during locking or unlocking.