Patent GB-867663-A (GB)
Title: Improvements in or relating to electrical locks
Inventor: LANCE THOMAS MARMADUKE CONSTAB
IPC: G07C9/00
Filed: 1957-03-13
Abstract: 867,663. Burglar and like alarms. BUSH & RANK CINTEL Ltd. March 13, 1958 [March 13, 1957], No. 8276/57. Class 118. [Also in Groups XXV and XL (b)] An electrical lock comprises a plurality of detector devices arranged to respond to the presence in predetermined positions in a key receptacle of material having predetermined characteristics by predetermined electric responses which are applied to switching means arranged to respond to only one predetermined set of responses from said detector devices by completing a first electrical circuit. The lock comprises a U-shaped ferromagnetic yoke 5 which is excited by a coil 6 connected to an alternating current supply. Upon one limb of the yoke 5 are fixed a number of ferromagnetic cores 7 each carrying a coil 8, the ends of the cores being spaced from the other limb of the yoke to provide the key receptacle in which a device 9 can be inserted. Each coil 8 is connected to the coil of a relay such as 10g through a circuit comprising a rectifier 11 and a condenser 12 and the relay will only operate if a low reluctance path is provided for the flux through the coil 8. The key device 9 consists of a matrix member 1 which is provided with a number of apertures 2. In some of the apertures are inserted discs 3 formed of material having a high permeability in the axial direction, such as iron powder bonded with a minimum of resin. The other apertures are filled with discs which are not of high permeability but otherwise are as similar as possible to the other discs; the matrix member 1 and the discs are covered with an opaque sheath 4. When the key device is inserted into the receptacle the high permeability discs reduce the reluctance of the magnetic circuits through the corresponding coils 8 and the relays associated with such coils are operated to complete a circuit which opens an enclosure, for example, with which the lock is associated. When the key device is inserted into the key receptacle its end encounters a feeler 13 which operates a make-or-break contact set 14 to remove a short circuit between terminals 15 which are connected to an alarm circuit of known type; the short circuit preventing the operation of the alarm circuit. Instead, one contact set of each of the relays is connected in series between the terminals 15 and the alarm circuit is only short-circuited when the correct key device is inserted in the receptacle to operate the correct combination of relays. Any incorrect key will cause the wrong relays to operate and the short circuit across the alarm circuit will not be completed; the operating circuit will also remain open in such a case. The contact set 16 operated by the feeler 13 keeps the operating circuit open until a key device is inserted in the receptacle. In another embodiment some of the cores 7 are provided with sets of coils so arranged that the coupling between the coils is varied by the presence of the discs 3 in the key device; this variation in coupling is arranged to cause a circuit associated with the coils to commence or alternatively to cease oscillation, the change operating the relay. With this construction, instead of using ferromagnetic discs in the matrix member conductive discs can be used. In another embodiment one wall of the key receptacle contains a radio-active isotope, radiation from which normally energizes a number of semi-conductor detector devices in the opposite wall. When the key device is inserted into the receptacle some of these detector devices are shielded by lead discs in the matrix member and the reduction in radiation changes the output of the corresponding semi-conductor detector devices, the change operating the relays. The detector devices and discs can be arranged in a twodimensional array, and different types of detector devices can be used together.