Patent GB-1063974-A (GB)
Title: Key operated lock
IPC: E05B27/00
Filed: 1965-09-07
Abstract: 1,063,974. Locks. L. J. HILL. Sept. 7, 1965 No. 38160/65. Heading E2A. A key operated lock comprises a body 12 having a cylindrical bore 14 therethrough and having apertures 16 communicating with the bore and extending radially outwardly from the bore into the body, an elongated plug 18 extending axially in the bore and mounted in the bore for rotation about the axis thereof, the plug having a longitudinally extending key slot 48 therein for receiving a key 50, a changekey passageway 54 extending in substantially the same direction as the cylindrical bore and adapted for receiving a change-key 108 therein, tumblers 56 carried by the plug and movable radially in the cylindrical bore, each tumbler registering with a respective one of said apertures in the body in one rotational position of the plug relative to the body and adapted to engage the milled edge of the key 50 when inserted in the key slot, each tumbler including a plunger 58 positioned for radial movement in the plug, key-following extensible means 64 adjustably attached to the plunger for varying the dimension of the tumbler as measured in a radial direction relative to the cylindrical bore and latch means 74 releasably and adjustably securing the extensible means to the plunger to prevent relative movement therebetween, the latch means extending into the change-key passageway for cooperation with the change key when inserted into the passageway to release said extensible means from the plunger whereby the extensible means can move relative to the plunger to change the dimension of the tumbler, and a driver member 32 movably disposed in each of said apertures in the body, adapted to coact with a corresponding said tumbler to hold the plug against rotational movement in the bore when the plug is in the one rotational position relative to the body and when the key 50 is removed from the key slot 48. As shown each plunger is a hollow cylindrical member having one end closed, the extensible means having a portion slidingly disposed in the cylindrical portion of the plunger, its lower end being engageable with the milled edge on the main key. The portion which slidingly engages the plunger has a plurality of flanges 66 and the end portion of the latch means engages between pairs of flanges under the urge of a spring 76. The change-key passageway is normally substantially closed by the free end portion of a plate 96 Fig. 5A which is pivotally mounted near its other end in a recess 100 in the plug 18 and in the locking position of the plug this lever is prevented from movement by the abutment of its free end portion against the wall of the bore 14. The body is however provided with a recess 106 extending from the bore 14 and if the plug is rotated through a small angle the free end portion 102 of the plate 96 comes opposite the recess to allow the change key to be inserted into the passageway by movement of the plate 96 into the recess. Hence to change the plunger lengths for the use of a different key the original key is first inserted into the main keyway so that the tops of the plungers are aligned with the periphery of the plug; this allows the plug to be rotated until a pair of index marks, one on the plug and the other on the body, are aligned. In this position of the plug and end portion 102 of the plate 96 is adjacent the recess 106 and the change-key can then be inserted into the change key passageway. The insertion causes the change-key to bear on each of the latch means 74 to release the extensible means 66. The original key is then removed and the new key inserted into the keyway 48 this moving the extensible means 64 relative to the plungers to the desired extents after which the change-key is removed which allows the latch means to re-engage; the plug can then be turned back to the locking position and the new key removed. A retaining member is provided in a slot in the plug which extends between the key slot 48 and the change-key passageway 54; the retaining means has an end portion which projects into the change-key passageway and an end portion which projects into the key slot 48. The purpose of the retaining member is to prevent the change-key being removed when there is no key in the key slot 48 since this would immobilise the lock by permitting the latch means to hold the extensible means in their positions of maximum extension from the plungers and release would not be possible. The insertion of the key 50 into the keyway 48 moves the retaining member to a position such that the change-key can be inserted into the change-key passageway and when the key 50 is subsequently withdrawn the end portion 90 of the retaining member then moves under the bias of a spring 92 into a notch in the change-key to prevent its removal. In a modification the lock is adapted for the use of a master key by providing the key slot 48 with two portions one to receive the normal key 50 and the other to receive the master key, the normal key portion extending through the plug as previously so that the key 50 engages the extensible means 64 and the master key portion extending longitudinally through the plug so that the master key can engage lugs one on each tumbler and extending downwardly adjacent the extensible means 64; hence the provision of the master key slot portion and the lugs does not interfere with the provision for changing the main key.