GB797419A - Improvements in and relating to automatic programme control systems - Google Patents

Abstract

797,419. Switching systems. ENGLISH ELECTRIC CO., Ltd. Jan. 27, 1956 [Feb. 2, 1955], No. 3052/55. Class 38 (4). [Also in Group XXXVIII] An automatic programme control system by which a quantity is controlled as a function of time in response to control information derived from a record of coded data comprises a sequence of rows of holes in a strip material, the rows running transverse to the length of the strip, and each one or group of such rows which represents a value of a controlled quantity being recorded on the strip between two similarly-recorded representations of the programmed time duration of an adjacent-recorded value of the controlled quantity. Means are provided to move a punched tape for reading the recordings of a desired value of the quantity and the time duration for which it is required and then to stop the tape for the said time interval, whereafter it is stepped on for reading the next value of the quantity. The embodiment described uses standard five-hole teleprinter tape to control the temperature of an electric furnace and each recorded temperature value comprises three rows of holes in the binary-coded decimal system followed by a further three rows of holes representing its programmed duration. The tape is automatically stepped on between adjacent rows of holes until the sixth row is reached when the next step is delayed for the required time interval. The tape 10 is moved by a drive unit 11 (pulsed as described below) and a reading system 13 controls five circuits corresponding to holes in positions a, b, c, d and e on the tape 10. The five circuits from system 13 are distributed as shown diagrammatically by a rotary switch 17 (pulsed in synchronism with drive unit 11). The holes in positions a, b, c and d are used to record the desired temperature and its time duration, and a hole in the fifth position, e, provides the automatic stepping-on signal. Row 1 of item A represents 1, 2, 4 and 8 units in the recorded temperature, row 2 correspondingly represents tens, and row 3 hundreds. Therefore, as shown, the temperature recorded at A is 597 ‹, and at C it is 599 ‹. As the system 13 reads one row of a temperature recording, relays (not shown) connected to respective terminals 16 operate or not according to whether there is a corresponding hole in the tape or not. These relays, when operated, close respective switches 15 to put resistors 14 into a control circuit. Each resistor 14 has a conductance proportional to the partial temperature represented. After reading row 1 of a recorded temperature the tape must be quickly stepped on to row 2 and switch 17 moved to the next set of terminals 16. This is controlled by the fifth hole position e on the tape, a pulse from the reading of a hole in this position being delayed slightly in system 13 and then fed to a terminal 18 from whence it causes both the drive unit 11 and the switch 17 to step on once. Thus the required temperature value is quickly stored on selected resistors 14 as their total conductance. These resistors are connected in parallel with the arm 23 of a bridge network having a resistance thermometer 22 in the opposite arm. Unbalance is detected by means 20 which controls the heating of furnace 21. After thus storing the required temperature value the tape is stepped on and the time duration (as recorded at B, or D) is similarly stored in unit 12 by connections from switch 17 to terminals 32, terminals 34 carrying the step-on pulses. The time interval may be recorded other than in the decimal system. For example, a maximum interval of 64 hours, yet allowing adjustments of one minute, may be catered for by making the first row of four holes represent up to 15 periods of 4 hours, the second row periods of 15 minutes, and the third row periods of one minute. A timer 38 is arranged to provide pulses at the rate of six per day, four per hour, or one per minute under selective control of unit 12. Each pulse fed to unit 12 reduces by one period the quantity stored therein. Thus at the beginning of a time interval the timer 38 supplies pulses every four hours, and when the stored number of four-hour periods has been reduced to zero the unit 12 adjusts the setting of timer 38 to supply a pulse every fifteen minutes. When the stored number of fifteen minute periods has been reduced to zero the timer 38 is adjusted by unit 12 to give one-minute pulses. When these have finally balanced the stored quantity the unit 12 delivers a pulse to drive unit 11 to cause a new temperature to be read by the system. Specification 797,420 is referred to.