CYLINDER LOCKS

A cylinder lock includes two barrels (23, 37), a first (23) carrying tumblers (30) that abut internal shoulders (36) of the lock casing (2) to obstruct clockwise rotation only, and the second (37) carrying a single tumbler (43) which obstructs only counter-clockwise rotation by abutment with a shoulder (48) of a rear-end casing-cover (8). A key (5) inserted through a keyhole-defining assembly (11, 16, 21) withdraws the first-barrel tumblers (30) during initial clockwise turning from the insertion position, and the second-barrel tumbler (43) during initial counter-clockwise turning. Lost-motion coupling between the barrels (23, 37), provided by lug-in-slot (38, 39) interengagement, enables clockwise turning of the second barrel (37) with the key (5) relative to the first barrel (23) during withdrawal of the first-barrel tumblers (30), and corresponding counter-clockwise turning of the first barrel (23) relative to the second (37) during withdrawal of the second-barrel tumbler (43). Lug-in-slot coupling (22, 24) between the keyhole-defining assembly (11, 16, 21) and the first barrel (23) similarly allows initial slip for clockwise key-turning. A coiled spring (42) opposes resiliently turning of both barrels (23, 37) in both directions.