GB1316973A - Lock unit - Google Patents

Abstract

1316973 Locks MINNESOTA MINING & MFG CO 15 June 1970 [16 June 1969] 28946/ 70 Heading E2A A lock unit comprises a pin tumbler lock mechanism having a rotatable member 12 movable from a first to a second position, said lock mechanism having a driver 19, 20 associated with each of the pin tumblers 14, a number of the drivers less than all of the drivers having a shape affording limited rotation of the rotatable member from the first position to the second position, a cam 36 joined to and rotatable with said rotatable member, said cam having at least one peripheral lobes, a cam follower engaging the cam and movable by the lobe or one of the lobes when the rotatable member moves from the first position; and a circuit -including a switch 45 activatable by movement of the cam follower, a time delay device actuatable by the switch and a signal device actuated by the time delay device after a predetermined time interval the circuit being made inoperative by deactivation of the switch within the time interval. The unit is intended to produce an audible or visible signal if too long a time is taken in rotating the rotatable member 12 from the first position to the second position in which a dead bolt (not shown) operated by the rotatable member is in releasing condition which could occur if an attempt is made to pick the lock unit. The cam has two lobes as shown so that rotation of the cam in either direction causes the switch to be operated. The drivers 19 is of cylindrical shape and the other drivers 20 are of dumbbell shape to permit some movement of the rotatable member 12 whether or not all the drivers 20 are raised by their pin tumblers 14 to the parting surfaces between the rotatable member 12 and a bore 11 in a housing 10. The driver 19 normally maintains the rotatable member in the locking position; the driver 19 is the rearmost driver as shown although it could be the front driver since one or other of these is the driver which would normally be picked first in an attempt to pick the lock; once this has been raised the dumbbell shaped drivers then permit the limited rotation of the rotatable member a few degrees from the locking position both to the right and to the left and make it difficult to pick the remaining tumblers. The extent of rotation is also enough to cause one or other of the lobes to move the cam follower to operate the switch and thus cause the signal device, which as shown is a horn, to sound provided the attempt to pick the lock mechanism is maintained for more than the interval provided by the delay circuit. Normal operation of the lock mechanism only causes momentary operation of the switch 45.