Patent GB-884586-A (GB)
Title: An electrical system for generating trains of control pulses
IPC: G05B19/4103
Filed: 1958-03-18
Abstract: 884,586. Electric selective signalling systems. GENERAL DYNAMICS CORPORATION. March 18, 1958 [Aug. 7, 1957], No. 8634/58. Class 40(1). [Also in Group XIX] The apparatus described is a modification of two embodiments that are described in Specification 825,772, which is referred to, for producing simultaneously trains of pulses so related in frequency that when each pulse corresponds to an equal increment of length the pulse trains can be used in a machine tool control system for causing motion of a tool along a desired path, the modification being that a different form of accumulating and dividing device (see Group XIX) is described. In a first embodiment, Fig. 1, described in Specification 825,772 two pulse trains, an X and a Y, are produced for controlling straight line motion between two points (x 1 , y 1 ) and (x 2 , y 2 ). The pulse trains appear on leads labelled " + " or " - " depending upon the direction of motion required. To produce these pulse trains the numbers #X# X 2  - x 1  and #Y # y 2  - y 1  are entered by an input device and registered, and a constant frequency pulse generator then applies pulses to two counters 42, 46. The first of these counters 42 is arranged to be reset by a coincidence detector every time the count reached is the same as the registered number AX, and the resetting pulse is also applied to a Y output channel lead, via either a "+" gate of a "-" gate, and to a #Y channel counter which thus counts the pulses sent to the Y output channel. Hence if the pulse generator has a frequency f then the Y channel receives pulses at a frequency f/ #X. Similarly the X channel receives pulses at a frequency f/ #Y, and since the ratio of the frequency of the pulses on the Y channel to that of those on the X channel is f/ #X ¸ f/ #Y = #Y/ #X, it follows that these pulse trains, if each pulse represents an equal increment of length, can control a straight line motion between the given points. When the total number of pulses produced on the Y channel equals #Y, this being detected by coincidence detector 34, and taking a time #Y ¸ f/ #X = #X. #Y, the pulse generator is stopped. In the same time, of course, the X channel will have received #X pulses. In the modified form of this embodiment the counter 42 and the coincidence detector 32 are replaced by an accumulator 252, Fig. 4, which by means of scale factor selectors (see Group XIX) can be set, in effect, to have a capacity which is the product of two numbers one from each of the groups 1, 10, 100, 1,000, 10,000, 100,000 and 2, 5, 10, so that the accumulator effectively divides by this number since when its capacity is exceeded it produces an output (carry) and commences accumulating again from zero. In operation the number #Y is entered into accumulator 252 once every ten clock pulses via a " bus selector." Thus if the clock pulse frequency is f and if the accumulator is set to have a capacity A then pulses are applied to the Y output channel at a frequency f #Y/10A. In a similar manner the frequency of the X pulses is f #X /10A and the ratio of these two frequencies is #Y/ #X as before. Also, as before, when the Y channel has received #Y pulses, which occurs in a time #Y ¸ f #Y/10A = 10A/f the clock pulses are stopped. In this modification A has to be chosen larger than the larger of #X and #Y and if A is chosen just larger than the larger of #X and #Y then the higher frequency of the X and Y output pulse trains should not be lower than about f/25 whereas in the unmodified embodiment the output frequencies were f/ #X and f/ #Y the higher of which could be considerably less than f/25. Thus the modification causes the output pulses to be produced quicker. The embodiment in Specification 825,772 for describing an arc of a circle is similarly modified (Fig. 5, not shown) and it is also shown (Fig. 6, not shown) for straight line motion how the scaling factor selectors can be controlled by #X and #Y instead of being controlled manually.