Change-key locks.

摘要

In a change-key lock there are two packs of levers 5A,5B meshing with respective packs of rotary tumblers 10A,10B. The bolt 1/2 carries two stumps 3A,3B which can be withdrawn into notches 13A,13B in the rotors 10A,10B when the latter are aligned by a double-bitted key lifting the levers 5A,5B. The pivot pins 11A,11B for the rotors are carried by a shiftable plate 12, normally locked by a lever 27. To reprogramme the lock the existing correct key is first used to align the rotor notches 13A,13B with the stumps 3A,3B; an auxiliary "change" key inserted to keyhole 31 then lifts the lever 27 and shifts the plate 12 to carry the rotors out of engagement with the levers and pass the rotor notches over the bolt stumps; the existing correct key is replaced by the new key which sets the levers to correspondingly new positions; and the "change" key is turned back to re-engage the rotors with the levers in their new positions. In another embodiment designed especially for safe deposit lockers the bolt is split into two portions 50/51 and 52 controlled by separate sets of tumblers 53C and 53A/53B requiring the use of two different keys, tumbler set 53C being reprogrammable independently of tumbler sets 53A/53B.