Cylinder lock mechanisms

#This invention relates to cylinder lock mechanisms.

#Such lock mechanisms are very widely used, but are not in general notable for a high degree of security against picking or other means of obtaining unauthorized operation of the mechanism.

#Various forms of cylinder lock mechanism providing a higher degree of security have been evolved, but these in general have entailed increased dimensions and/or substantially increased complexity and difficulty of assembly. One relatively simple but highly effective form of high security cylinder lock mechanism is of the type described in British Patent Specification No. 1,227,731. In this mechanism a plug is freely rotatable within a cylinder, and a locking element is coaxial with but normally disengaged from the plug. A rocker element is pivotally mounted on the plug for rocking movement between a position out of engagement with the locking element and a position engaging the locking element, which latter position it can however only assume when a portion of the rocker element enters slots in a group of tumbler elements axially moveable in the plug by means of a key so as to bring the slots into alignment to receive the rocker element portion. Since the plug is freely rotatable in the cylinder, it is impossible for a lock picker to `feel` the appropriate positions of the tumbler elements.

#Other features of the invention will be apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings, in which

#FIG. 1 shows an axial section of a lock mechanism, on the line I--I in FIG. 9,

#FIG. 2 is a front end view of a housing of the mechanism,

#Referring to FIGS. 1-11 of the drawings, the lock mechanism comprises a hollow cylindrical housing 2, having at its front end an opening 4 which is shaped to match the profile of a collar 8 on a key 10 (see FIG. 11) and thus to admit the key only when the latter is correctly oriented. A relieved portion 12 of the opening permits rotation of the key when fully inserted.

#An abutment 6 in the internal bore of the housing serves to locate the various remaining portions of the mechanism, which are assembled into the housing from the rear. The first part so inserted is a shield plate 14, which may be of metal selected, hardened or toughened so as to provide a desired degree of resistance to drilling or other attempts to disrupt the mechanism from the front. It is formed with a keyway 16, and a lug 18 which serves to maintain the keyway in register with bores 20 in a front plug 22 which receives the pins 24 of the key 10, by engaging the front entrance to a recess 26 in the plug 22. The bores 20 are formed with interconnected counterbores 28 to receive pin tumblers in the form of bobbins 30, each formed with a circumferential groove 32 and a number of spaced shallower circumferential grooves (not shown). The location of the groove 32 differs on different bobbins, and the resulting numerous possible different combinations provide the differs for the lock mechanism, as will be further discussed below. A further bore 34, rectangular in cross section, provides in conjunction with the plate 14, a socket for the heel 102 of a tapering rocker lever 36.

#An actuating member in the form of a wafer 38 is placed over the lever 36 so that the narrow end of the latter passes through a window 40 in the wafer, and the latter enters a rebate 42 in the rear end of the front plug 22. Lugs 44 on the rear end of the front plug locate a rear plug 46, which has a rectangular bore 48 aligned the bore 34, and blind interconnected bores 50, which together with the counterbores 28 accommodate the bobbins 30 and also springs 52 urging the bobbins 30 toward the bores 20 so that reduced diameter portions 54 of these bobbins enter and obturate the bores 20 by reason of having a shape complementary thereto. The springs are located by reduced diameter portions 56 on the rear of the bobbins.