Patent GB-746141-A (GB)
Title: Improved lock controlled alarm switch for preventing unauthorised use of motor vehicles
IPC: B60R25/00
Filed: 1954-04-07
Abstract: 746,141. Latches controlled from a distance. POLUDNIAK, W. B. April 7, 1954, No. 10270/54. Addition to 705,632, [Group XXXVIII]. Class 44. [Also in Groups XXVII, XXXI, XXXVII and XXXVIII] In a vehicle theft alarm, similar to that described in the parent Specification, and in which a combination lock, when released, allows a bridging member 2 to move and thereby open or close an ancillary ignition-circuit switch, but, otherwise, prevents movement of the bridging member, and in which the bridging member, when the ancillary ignition-circuit switch is open, closes a second switch to complete a portion of an alarm circuit including a further switch which is closed to sound an alarm (e.g. the vehicle's horn) when an attempt is made to operate the bonnet release mechanism, the bridging member 2 is linked by a cable 40 with a mechanical locking device serving to lock the bonnet 47 when the second switch is closed. The combination lock comprises two rotatable discs 12, 13, each having a cut-away portion at one position on its periphery, so that, when they are set appropriately by the knobs 16, 17, the collar 14 mounted on a shaft attached to a knob 6 may freely pass the discs. With the device as shown in the Figure, the ignition circuit, comprising the coil 59, contacts 10 and 11, main switch 63 and battery 36, is broken, the bridging member 2, which when the knob 6 is depressea completes the circuit between the contacts 10 and 11, completing the circuit between contacts 8 and 9. The contacts 8 and 9 form part of an alarm circuit comprising contacts 31, 31a, the horn 35 and battery 36. On an attempt being made to open the bonnet by pulling the bonnet release cable 37, the alarm circuit is completed through a conducting member 39 making contact with the contacts 31, 31a and the alarm is sounded. Further contacts 32, 32a, &c. are provided to protect other portions of the vehicle. Furthermore when the knob 6 is withdrawn to render the alarm circuit sensitive, the cable 40 lifts the plunger 41 to the position shown, thus causing the locking pin 45 to be extended and thus preventing the bonnet release cable 37 from being moved sufficiently to allow the bonnet to be released. When the knob 6 is depressed, the rounded head of the pin 45 is accommodated within the indentation 43 of the plunger 41 whereby free motion of the cable 37 becomes possible. In addition, with the knob 6 in its elevated position, a conducting disc 48 bears against a contact 49 which is connected through a lead 50 to one of the distributer contacts 51, and consequently earths the distributer. Further protection is afforded by the fact that lead 50 passes for the greater portion of its length through a sheath 53 and is held under tension within the sheath by an enlarged portion 58 of the lead and a compression spring 56. In the event of the sheath 53 and lead 50 being cut, the spring 56 drives a conducting collar 55 downwards to bear against the housing 54 and maintain the earthing of the distributer. The discs 12 and 13 are also included in an alarm circuit, connection being made thereto by spring-loaded contacts 21, 22. Depression of the knob 6, when it is in its elevated position, causes the collar 14 to make contact with the discs 12 and 13 unless the combination has been correctly set. In order to prevent sounding the alarm when slight accidental pressure is applied to the knob 6, the collar 14 is divided by an insulating portion, so that a direct connection between the discs 12 and 13 cannot be made through it. If, however, greater pressure is applied, a further spring-loaded conducting member 29 is depressed, thereby making contact between the discs and causing the alarm to be sounded. Should an attempt be made to remove the device as a whole from its mounting on the dashboard, a conducting disc 61, which is connected to a lead 62 and the contact 31a is forced against the earthed metal tube 60, thus completing the alarm circuit. An attempt to cut through the tube 60 will likewise cause the alarm to sound due to the cutting tool making contact between the tube and the lead 62.