Patent GB-731536-A (GB)
Title: Improvements in or relating to counting devices and to measuring apparatus incorporating such devices
IPC: H03K23/82
Filed: 1952-03-04
Abstract: 731,536. Counting-apparatus. BRANSON, L. C., and KAPELLA, Ltd. March 2, 1953 [March 4, 1952], No. 5640/52. Class 106 (1). [Also in Group XL (b)] A reversible counter for counting cyclical changes in a reversible and cyclically variable parameter comprises two detectors responsive to first and second parameters displaced in phase with respect to one another. The invention is applied to measuring apparatus such as a linear-dimension gauge used in jig-boring apparatus. A diffraction grating has a number of slots T3, Fig. 10, spaced an odd number of quarter wavelengths from a number of slots T4 so that movement of the grating energizes photo-cells S, S alternately a number of times corresponding to the amount of movement. A gauge attached to a jig-boring apparatus includes an overload device U10 and a dashpot U8, Fig. 11, carryirig a movable mirror U5 forming part of an interferometer. Light passes from a source U to mirror U3, movable mirror U5, through U3 to photo-cells S, S1 and from U, through U3 to fixed mirror U4, back to U3 and so to the photo-cells. That part of mirror U5 co-operating with photo-cell S1 is stepped above the other part by an odd number of # wavelengths. Alternatively a delay plate of appropriate thickness and refractive index may be inserted in one of the beams. Counting-circuit. The output of photo-cell S is applied to the grid A2 of the first valve of a detector A comprising a Schmitt trigger circuit, Fig. 1, the potential on the grid A2 and anode A3 during successive cycles being shown in Fig. 2. Operation of the first valve cuts off the second valve, so that potential on the anode A6 of the second valve is the opposite of that on A3. The square wave-forms produced at A3, A6 are converted to pulses of alternate sign by differentiating networks before passing to grids B2, B5 of two triodes constituting a gate device B. The output of the second photo-cell Sl is similarly applied to a second detector comprising a trigger circuit C which applies a square waveform to a gate control triode D, whose cathode is connected to the cathodes B1, B4 of gate device B (see line C3, D2, D1, B1, B4 in Fig. 2) so that the gate device B can control the pulses, from the first detector A according to the state of the second detector C at the time of said pulses. The passage of current through gate control triode D raises the potential of cathodes B1, B4 so preventing passage of current through either valve of gate device B. A negative pulse appears at the anodes of B only when the first oscillating voltage crosses from negative to positive with the second voltage lagging behind or in reversal when the first voltage crosses from positive to negative with the second voltage leading. First stage. The negative pulses from B pass to the first binary counting stage E which comprises a trigger pair to produce square waveforms of opposite sense on anodes E3, E6. These square wave-forms are converted to pulses on grids F2, F5 of second gate device F, which has its cathodes connected separately to the cathodes Jl, J4 of gate control device J. A trigger-action delay device H is fed through a delay network from detector A so that the anode outputs H3, H6 of H consist of square waveforms of opposite sign lagging behind the outputs of A (A3, A6). By this means negative pulses on anodes F3, F6 appear half as often as those at the anodes of the first gate device B. Second and subsequent stages. Second gate device F controls the carry-over from the first counting stage to the second binary counting stage G and similar equipment effects carry-over to subsequent stages. Indication of count. The count can be indicated by a series of neon tubes E13, G7 ... energized from the anode output of the first valve of the corresponding stage so that the neon tube glows when the valve is cut off to indicate 1 and goes out when the valve conducts to indicate O. Counting on. decimal scale. Use is made of a valve, Fig. 4, having a disc-shaped anode K1 with ten cathodes and twenty guide electrodes. Nine cathodes are connected to a common terminal K3 and the tenth or zero cathode to a separate terminal K5. The guide electrodes are arranged in two interspaced groups of tens connected to terminals K8, K9. By applying negative pulses in succession to K8, K9 or K9, K8 the discharge is transferred from one cathode to the next in a clockwise or counter-clockwise direction, respectively. In Fig. 3, the anodes B3, B6 are not connected as in Fig. 1. As long as the originating voltages are proceeding in the forward direction, all the negative pulses appear at anode B6, while if the process is reversed they appear at anode B3. The anode B6 is connected through a potential divider and rectifier to terminal K9 of the gas-discharge counting device K and through the junction of a resistance and capacitor and rectifier to terminal K8, while B3 is similarly connected to K8 and K9 in the reverse sense. For forward counting the pulse on K9 is effective before that on K8, while for reverse counting the opposite condition occurs. When the discharge reached the zero cathode K4 the voltage rises sharply and then falls sharply as the discharge passes to the next cathode. Cathode K4 is connected to the grid of a phase-splitter M to produce equal and opposite square wave-forms which are transformed by networks into pulses applied to the grids of the second gate device N, the cathodes of which are controlled by gate control device J in the same manner as in the first arrangement. N controls the second stage counting device O, which operates in the same manner as K in respect of the tens digit. Electromagnetic relay system. For counting at a lower speed electromagnetic relays may be used. The parameters control relays P, P5, energization of P operating P7 slowly and release of P restoring P7 slowly so that in a forward count Q and Q4 energize, the latter lifting its pawl R3 from counter wheel R while Q acts on pawl R2 to advance the wheel more than half a step at which time Q4 releases so that pawl R3 completes the movement. Release of Q allows pawl R2 to ride over the tooth of R to snap into its new position. Reverse counting takes place under the control of Q2 and Q5.