Patent GB-770920-A (GB)
Title: Methods and apparatus for measuring angular movement
IPC: H03M1/00
Filed: 1954-11-19
Abstract: 770,920. Electric selective signalling. INTERNATIONAL BUSINESS MACHINES CORPORATION. Nov. 19, 1954 [Nov. 24, 1953], No. 33543/54. Class 40 (1). [Also in Group XL (b)] Apparatus for translating increments of angular motion to digital form, such as by measuring the angular displacement of a shaft rotating less than 360 degrees from a zero position, comprises a scanning device for generating pulses in a movable pick-up element coupled to the shaft, and in a stationary pick-up element positioned to have a predetermined angular relation to the movable pick-up element with said shaft at the zero position, a signal generating component for controlling the scanning device and applying signals through a gate circuit closing and opening in response to the pulses, to a counter, and a circuit for selectively reading out the information of the counter. The number of signals received by the counter represents the angular movement of the shaft from a zero position. As shown, the shaft 10 carries a pointer 11 and an arm 13 which is provided with a " stop " pick-up coil 14. The coil 14 is connected to the primary winding 16 of a transformer 17, the winding 16 also being attached to the shaft 10 and co-operating with a fixed secondary winding 18 of the transformer, which is connected to a " stop " amplifier 21. A flywheel 24 is driven by a synchronous motor 26 and carries bar magnets 22, 23, which as they pass the coil 14 induce a sharp pulse therein. Power at the correct frequency for the motor 26 is provided from an oscillator 32 via a scaledown counter 30 and amplifier 28. Further pick-up coils 33, 37, 40 are positioned adjacent the flywheel 24 and produce sequential pulses which are passed to a " start " amplifier 36, a " reset " amplifier 39, and a " transfer to relays " amplifier 42, respectively. In operation the " start " pulse from the coil 33 is applied via amplifier 36 and the open gate 53 to turn on the counter gate trigger 46 to open the counter gate 48, whereby signals are fed from the oscillator 32 to the result counter 50. The counter 50 accumulates signals until the coil 14 generates a " stop " pulse which is fed via amplifier 21 and the open gate 44 to turn off the counter gate trigger 46 to close the counter gate 48, a pulse from trigger 46 being applied to a count to ten counter 56. The coil 40 produces a pulse which through amplifier 42 attempts to turn the transfer to relays trigger 75 off, but this trigger is already in the off position. Similarly a pulse from coil 37 is applied through amplifier 39 to a reset trigger 61 and a control trigger 69 but these triggers also are in the off position. The action described is repeated ten times and each time a pulse is applied to the count to ten counter 56. At the tenth pulse the counter 56 moves to zero and generates a pulse which turns a start and stop gate trigger 60 on, the reset trigger 61 on, and initiates the operation of relay clearing circuits 62 to de-energize any relays 84 energized in a previous cycle. Shifting of the trigger 60 closes gates 53 and 44. The reset pulse then turns the reset trigger 61 off which generates a pulse to turn the transfer to relays trigger 75 on. In the eleventh revolution of flywheel 24 the pulse from coil 40 turns the trigger 75 off, which generates a pulse to turn control trigger 69 on and to energize transfer to relays circuit 81 whereby the information in counter 50 is read out and transferred via circuit 81 to energize appropriate relays 84. Relays 84 control individual lamps 86 to display in digital form the position of shaft 10. To record the information on a card a punch button 79 is operated to connect trigger 75 to the punch control circuits 71 and the pulse generated as trigger 75 is turned off initiates operation of the circuits 71, the punch 88 operating in accordance with the energized relays 84. A bias voltage is applied from the circuit 71 to the control trigger 69 to keep the trigger on for the duration of the punching operation. During the eleventh revolution, or after the punching operation, the pulse from the coil 37 then turns the control trigger 69 off which generates a pulse to turn the trigger 60 off and thus open gates 53 and 44, the shifting of trigger 60 also energizing the result counter reset circuits 66 to reset the counter 50 to a predetermined number below zero determined by the position of the coil 33 in relation to the true zero position of the shaft 10. The coil 33 is displaced from the true zero position to avoid the simultaneous generation of start and stop pulses in instances when the shaft 10 has not been rotated. Ten readings are applied to the counter 50 before the information is read to the relays 84 and by shifting the decimal point one place to the left an averaging of the results is obtained. The rotating magnets and coils for generating the control pulses may be replaced by optical systems utilizing photo-cells (see Group XL (b)).