Patent GB-689107-A (GB)
Title: Improvements in or relating to the measurement of the rotation of shafts or like rotary members
IPC: G01P3/56
Filed: 1950-04-26
Abstract: 689,107. Direction, extent and speed of revolution indicating. SOC D'ELECTRONIQUE ET D'AUTOMATISME. April 26, 1950 [April 27, 1949], No. 10290/50. Class 40 (i) [Also in Groups XIX, XXXVI, XL(b) and XL(c)] To measure the direction, extent and speed of rotation of a rotor, two sets a, b Fig. 4 of recurrent pulses are developed, the direction of rotation determining which set lags in phase, the extent of rotation (angle) governing the number of pulses generated, and the speed of rotation determining the frequency of recurrence of each set; the signals of one set, e.g. a Fig. 4 are converted e.g. by squaring c and differentiation d, into alternate positive and negative pulses d Fig. 4 occurring at twice the recurrence frequency, and the pulses dare gated by the pulses b so that for one direction of rotation the positive pulses f are allowed to pass, and for the other direction of rotation the negative pulses g are allowed to pass, the sign of the pulses allowed to pass being indicated to indicate direction of rotation, the number being counted to indicate extent of rotation, and recurrence being indicated to indicate speed of rotation. Instead of indicating, voltages may be developed for controlling apparatus. ' As shown, a shaft 1 Fig. 1 carries a cylinder 4 having alternate opaque and transparent divisions, so that as the shaft rotates, pulses are developed in photo-cells 2, 3. The pulses may be developed by electrostatic or electromagnetic pick-offs in place of the photo-electric cells. The cells or pick-offs may rotate absolutely as well as relatively to shaft 1. The pulses developed in cell 2 (a Fig. 4), lag or lead the pulses developed in cell 3 (b Fig. 4). The pulses a Fig. 4 are squared b to produce pulses c' Fig. 4, differentiated to produce pulses d' Fig. 4 and applied to a gating circuit 16 fed with square-pulses c' Fig. 4 developed from pulses b. The relative phase of pulses a, b, determines whether the positive pulses of d are cut off so that the emergent train is as at e Fig. 4, or whether the negative pulses are cut out to produce the emergent train e<SP>1</SP> Fig. 4. The emergent train is applied to binary counters 20, 31, one being responsive to positive pulses and the other responsive to negative pulses. The outputs of each unit of the counters is taken to indicators 21, 23 and feeds a line 25 in which are developed signals for controlling apparatus. The total number of pulses is shown on integrators 22, 33 in conjunction with re-cyling indicators 23, 34. Devices 35, 36 may be employed to change the sign from one counter to ensure that the control signals are always of the same sign. A coded control signal may be developed by applying a pulse from generator 28 Fig. 1A, to a delay line 30 from which taps are taken to an output line 27 via relays 26 actuated by the units of the counter 20; the pulse from 28 may also be applied to 18 to block the input to the counter during the production of the code pulses. As shown. in Fig. 6, the rotations of two independent shafts are arranged to produce control signals, either to control one by the other or for mutual control. Each shaft produces two sets of pulses as in Fig. 1, and the positive pulses from each shaft are fed over 18, 18' to a counter 43, while the negative pulses are fed over 19, 19' to counter 44. The counters 43, 44 are of the type described in Specification 679,390, [Group XIX], and are such that a positive or negative output is given corresponding to whether one input is greater or lesser than the other input; to avoid the actuation of the counter when the pulses from 18, 18' (or 19, 19<SP>1</SP>) coincide, anti-coincidence circuits 49, 50 are interpolated. Coding may be obtained by each counter 43, 44 feeding two delay lines as in Fig. 1A, one delay line dealing with, a positive output, and the other dealing with a negative output, Fig. 7 (not shown). As shown in Fig. 8, the output from the counter 60 associated with one shaft provides the pulse for application to the delay lines 62, 63 associated with the counter 61 which is fed with the pulses from a second shaft.