Patent GB-1284393-A (GB)
Title: Improvements in or relating to vehicle anti-theft devices and warning means incorporating such devices
Inventor: SMITH PETER JOHN
IPC: B60R25/021
Filed: 1968-06-25
Abstract: 1284393 Anti-theft devices WILMOTBREEDEN Ltd 6 Sept 1969 [25 June 1968 11 Oct 1968 30 Jan 1969 13 May 1969] 30283/68; 48278/68 5268/69 and 24389/69 Heading B7J [Also in Division E2] A key-operated vehicle anti-theft device has a housing 1 containing a mechanism operable when the device is fitted in a vehicle to disable the vehicle, and a tumbler lock structure 6 including a plug 8 containing the lock tumblers and rotatable by an inserted key to operate said mechanism, a pair of electrical contacts 24, 25; 52, 53 or 73, 76 being disposed in the housing to be placed in electrical communication as a result of insertion of the key and without the key being turned. In a first form of the device, Fig. 2, the housing is a die-cast body 1 which is split into two parts so that it can be mounted on and around a vehicle steering column by means of clamp bolts 3 which have heads which shear off when the bolts are tightened. The disabling mechanism includes a bolt 4 which is slidable radially of the column in use, the bolt being moved by a slide 5. The lock structure 6 includes a cylinder 7 slidably but non-rotatably mounted in one side of the body 1 and which contains the plug 8 which is rotatably coupled to a non- circular stem 9 of the disabling mechanism which passes through the slide 5; the stem also provides a drive-shaft for a switch mechanism 10; it controls the slide 5 by means of a cam section, the slide being biased by a spring (not shown) into engagement with the cam section and towards the locking position. The plug has four positions, i.e. an off position in which the steering is locked, an auxiliary position in which the vehicle auxiliary circuits are energized, an ignition position and a start position; the lock structure has to be depressed inwardly in order to turn it to the locking position and is spring- loaded to return it from the start position to the ignition position. The body 1 mounts a spring- loaded pawl 13 and the plug carries a coupling member 15 attached to its inner end which includes a radial projection 14 which engages the pawl 13. The pawl 13 and projection 14 have inclined end surfaces and when the plug cylinder is rotated by the key from the lock position to the auxiliary position these engage and the pawl is depressed against the bias of its spring 16 to allow the movement without depressing the lock structure; to move the plug to the lock position the lock structure must be depressed against the bias of the spring 16 so that the projection clears the pawl 13. In the outer end portion of the plug 8 there is a radial slot 21 which breaks into a key slot 22 in the plug and in the slot is a plunger 23 which is retained therein by an end cap 19 for the plug. The plunger has a chamfered nose 23a which projects into the key slot 22 so that it is engaged by the key as the key is inserted and is moved outwardly by the key along the slot 21 for operation of the pair of contacts 24 and 25. The contact 24 is in the form of a spring strip which is wrapped around the plug 8 and an end portion of which is disposed in a peripheral groove 26 in the plug. The radial slot 21 opens into the groove 26 so that the outer end of the plunger 23 engages the end portion of the contact 24 to move it into engagement with the contact 25 as the key is inserted. The contact 25 is mounted in a peripheral recess 29 in an insulating sleeve 17 which is secured to the outer end portion of the plug, the recess having an arcuate aperture through which the contact 24 can engage the contact 25. The angular extent of the aperture 30 governs the range of lock positions in which the contacts are in engagement and thus the range in which a warning circuit which includes the contacts is operative. The contact 25 is connected to an external electrical terminal 33 mounted on the body 1 via a spring blade 38 which projects through an aperture 39 in the body 1 for engagement with the contact 25. The contact 24 being connected to the plug is effectively connected to the vehicle earth. In a second embodiment, Fig. 8, the bolt 4 is operated as before by a slide 5 and a stem 9 with a cam section and the spring loaded pawl 13 and projection 14 are again provided; in place of the contacts 24 and 25 and the sleeve 17, however, a disc-like insulation plate 50 is provided which surrounds and turns with the stem 9 and is held against the cam section of the stem by a return spring of the lock structure 6; the plate 50 carries an external conducting ring segment 52 which extends an angle slightly greater than the angle of movement between the lock and auxiliary positions; contact with the segment 52 is made by a wiper contact 53 which is slidable in an insulating mounting block 54 which projects at the side of the body 1 and is mounted in a stepped bore in the body; at its outer end the block has an external terminal 55. The stem 9 has a blind bore in which a contact assembly is slidable against the return spring 58. The assembly includes a rod 59 which makes electrical contact with the plug 8 and which is engaged by the tip of the key when the latter is inserted to displace the assembly axially of the lock structure into the stem 9 against the spring 58; the assembly also includes an insulating sleeve 60 which is mounted on the rod 59 and slides freely in the stem 9 and a contact provided by a brass plunger 62 is slidably mounted in the plate 50 and urged by a spring 63 towards the sleeve 60; thus when the assembly 57 is depressed inwards, the plunger 62 registers with an elongated aperture in the sleeve through which it contacts the brass rod 59 to complete, in use, an electrical circuit. In a third embodiment, Fig. 9, the bolt 4 is operated by a cam section of the stem 9 via the slide 5 as previously described although in this embodiment the lock plug has five positions in that a garage position is interposed between the auxiliary position and the ignition position; the construction makes it necessary to depress the lock structure axially in the auxiliary position before the plug can be moved to the lock position, a pawl and projection (not shown) being provided to prevent movement to the lock position before the axial depression; in addition there is a raised pad (not shown) in the body 1 which is engaged by the cam section to block rotation of the latter if an attempt is made to turn the stem line to the lock position with a lock structure and stem depressed before the auxiliary position is reached. Of the two contacts the fixed contact 73 is mounted centrally in an insulating end closure plate 74 of the housing of the switch and the movable contact 76 is mounted in line with the lock structure axis and is slidable in a stepped bore of the stem 9, the step providing an abutment for return spring 77 which urges the contact 76 away from the fixed contact 73 to a normally open position; the contact 76 is in the form of a telescopic assembly comprising two telescopic parts 78 and 79 and a spring 18; the part 78 is of hollow shell-like form and remote from the contact 73 and the part 79 has its end portion disposed in the part 78, the spring 80 being trapped between the two parts; when the key is inserted into the plug its tip engages the part 78 and moves it axially in the bore of the stem 9 against the pressure of the spring 77. The part 79 is moved into contact with the fixed contact 73 by the spring 80; the telescopic assembly allows the axial depression of the lock structure necessary to enable the plug to be moved by the key to the lock position.