Patent GB-589478-A (GB)
Title: Improvements in electro magnetically operated timing mechanisms
IPC: H04M19/02
Filed: 1945-03-27
Abstract: 589,478. Changing frequency of pulses. BURNS, D. O., and KELK, W. H. H. March 27, 1945, No. 7776. [Class 38 (ii)] In electromagnetic timing mechanism such as is used for the release.of bombs, pulses at a frequency selected from one of a number of frequencies at which they may be generated, are applied to a series of channels, one pulse per channel in succession, and certain of the channels are selected to afford output pulses at predetermined time intervals or frequency. The mechanism described comprises two cross. connected relays 15, 18 for generating the pulses ; condensers C1, C2, C3 and a selector switch 19 connected in the circuit of a further winding of relay 18 to allow variation of the pulse frequency at will ; a uniselector switch with a hold-in bank of contacts 11, and a timing bank of contacts 12 some or all of which may be chosen by selector switches 16, 17, to determine the periods at which pulses are produced in an output circuit by the closing of contact 26b of the relay 26 ; and a counter mechanism embodying a ratchet 21 and pawl 22 released by a magnet coil 20. In operation the three ganged switches 16, 17, 19 are set to any one of twelve positions whereby the frequency of the initial impulses and the operative channels are selected, and the ratchet wheel 21 is rotated against a spring by a number of teeth equal to the total number of output impulses needed, which latter operation closes contacts 23, 24. Switch 27 is then closed in the downward position, and press-button 28 depressed, when warning lamp 29 lights, holding relay 25 closes contacts 25a, and relay 18 closes contacts 18a, 18b. The latter contacts energize relay 26 to close contacts 26b and produce an impulse in the output circuit, while contacts 18a energize relay and uniselector coil 15 to open the normally closed contacts 15a, whereby relay 18 is again de-energized and contacts 18a, 18b open at a speed determined by condenser C, with either or neither of condensers C2, C3 in the subsidiary winding circuit. Coil 15 is again deenergized to cause uniselector contacts 13, 14 to move to the next contacts of the banks 11, 12 and since all but the starting Mold-in contacts are connected to the supply the uniselector switch steps completely round to the starting contact again, as pulses are generated by the relays 15, 18, but only those pulses energize relay 26 which are generated at the times when moving contact 14 engages a fixed contact of the timing- bank 12 which is connected by selector switches 16, 17 to the supply. Each energization of relay 26 not only produces an output pulse by closing contact 26b, but by closing 'contacts 26a and energizing magnet coil 20 allows ratchet wheel 21 to slip back one tooth. When wheel 21 is back to zero the number of pulses produced is equal to the original setting, and contacts 23, 24 open so that although the selector steps round to the starting contacts, the supply to contact 14 is broken and no further output pulses can be produced. For some settings of the counter mechanism the uniselector switch may rotate through more than one revolution, while other contacts of the hold-in bank 11 may be isolated as stop-start contacts, if desired. Single impulses may be produced in the output circuit by depressing switch 28 when switch 27 is in the upper position.. Specification 579,659 is referred to.