Patent GB-972811-A (GB)
Title: Improved lock release device
Inventor: LEE JOHN GWYN WILLIAM
IPC: G07C9/00
Filed: 1959-11-04
Abstract: 972,811. Locks; fastenings operable from a distance. DE HAVILLAND AIRCRAFT CO. Ltd. Oct. 21, 1960 [Nov. 4, 1959], No. 37357/59. Heading E2A. A lock release system comprises a source of coded radiation pulses 10, a detector of radiation pulses 42 and a comparator operable to compare output signals of the detector with a pre-set sequence of signals and to operate a lock release 100 upon completion of a correct sequence of radiation pulses. The source of coded radiation pulses comprises a casing containing a battery operated lamp 12 which sends light through a stop and shutter 14 to fall on the edge of a rotatable chopper disc 16. The chopper disc 16 is rotatable in steps by a manually operable escapement drive 32. The edge of the chopper disc is divided into a series of forty stations and at alternate stations 17, 19, 21 &c. termed dwell stations the material of the disc is cut away to a predetermined extent. Between the dwell stations are stations 18, 20, 22, 24, 26 &c. termed pulse stations at which the material of the disc is either not cut away (stations 24, 26) or is cut away to an extent twice that of the dwell stations (stations 18, 20, 22) thus at the dwell stations the light passes through a predetermined area and at the pulse stations either no light passes or the light passes through twice the area of the dwell stations. Light from the disc passes through a filter 30 which allows only radiations within a predetermined range of wavelength to pass. Instead of the disc being cut away radially slidable shutters may be used at the pulse stations. The remaining apparatus of the system is intended for mounting within a safe. In the wall of the safe is a disguised window 40 through which radiations from the source 10 can pass, these radiations falling on a detector 42. This detector comprises an optical filter 44 which is set at an angle of 45 degrees and which passes only radiations within the predetermined range of wavelength; these fall on a radiation sensitive cell 46; other radiations are deflected to a second radiation sensitive cell 48. The arrangement is such that when white light falls on the filter 44 the voltage input to an amplifier 56 is at a reference level, a signal voltage is applied to the amplifier from the cell 46 when the detector is illuminated with radiations of the predetermined range of wavelengths. The amplifier 56 amplifies and then differentiates the signal. A positive pulse followed by a negative pulse is produced where the radiation rises from an intermediate value at a dwell station 17, 19, 21 &c. to a maximum value at a pulse station 12, 18, 20 &c. and a negative pulse followed by a positive pulse is produced where the radiation falls from the intermediate level to the reference level at a pulse station 24, 26 &c. The pulses from the amplifier 56 are passed to a gating circuit 60 in which the second of each pair of incoming pulses is eliminated and the first of each pair of incoming pulses is directed to one or other of two output channels 62, 64, positive pulses going to channel 62 and negative pulses after reversal to channel 64. Channels 62 and 64 lead to a distributer circuit 66 which is controlled by signals received from an index pick-off disc 68. The output of the distributer circuit consists of three channels 70, 72, 74. Channels 70 and 74 lead to an escapement release circuit 76 which upon receipt of a pulse operates an escapement 78 to permit a step rotation of a shaft 80 which carries an index disc 86 having twenty code stations 88 which in conjunction with the index pick-off 68 produce pulses to operate the distributer circuit 66. Channel 72 leads to a reset release circuit 82 which upon receipt of a pulse operates a reset device 84 which overrides the escapement 78 and returns the shaft 80 to initial position. The twenty code stations on the index disc 86 each consist of a magnetized portion, this is either close to the periphery of the disc or spaced therefrom. When the magnetized portion is close to the periphery a negative pulse is produced by the movement of the disc past the pick-off 68; when it is spaced from the periphery a positive pulse is produced by the movement of the disc. In use the source 10 is presented to the window 40, the lamp 12 is switched on and the power for the electrical parts of the detector release device and for driving the shaft 80 is made available by a contact switch. The escapement drive 32 is manually operated so that the disc 16 moves from station to station; when signals caused by movement of the disc 11 and signals caused by movement of the index disc 86 agree a signal is fed by either channel 72 or channel 74 to the escapement release circuit 76 and the disc 86 is stepped to the next station. When the signals do not agree a signal is fed over channel 72 to the reset release circuit 82 and the index disc is returned to its initial position and if desired an alarm can be sounded. When the disc 86 has been rotated through 20 stations the lock release 100 is operated to release the safe lock. The reset device 84 is clock driven to override and prevent operation of the escapement 78 during predetermined periods of time for example at night and week-ends.