Patent GB-797420-A (GB)
Title: Improvements in and relating to automatic programme control systems
Inventor: DOWNING BRIAN THOMAS
IPC: G05B19/14
Filed: 1955-02-02
Abstract: 797,420. Switching systems. ENGLISH ELECTRIC CO., Ltd. Jan. 27, 1956 [Feb. 2, 1955], No. 25377/57. Divided out of 797,419. Class 38 (4). [Also in Group XXXVIII] In order to conserve recording tape in an automatic programme control system wherein the magnitude of a quantity. is controlled as a function of time in response to a record of successive values spaced on a recording tape according to their respective desired durations, the tape is moved at a slow speed between readings of the recorded values, which are read relatively quickly. The control information is derived from a record of digitally-coded numerical data wherein a recorded item comprises at least two closely-adjacent parts which are read in turn as the record is passed through a reading unit, and means are provided for passing said record through the reading unit at a steady rate so that each successive item of recorded information is read after a time interval proportional to its position on the record. The invention also comprises means for adjusting the controlled quantity in accordance with each successive reading, means for retaining the quantity at an adjusted value until the next reading and means for accelerating the movement of the record between the reading of each part of a recorded item. 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 punched in the tape and means are provided for quickly stepping on the tape between adjacent rows of each such value, whereby an economical slow movement of the tape may be used to record long time intervals between successive recorded values without delaying the reading of a complete recorded value. The tape 10 is normally stepped regularly by motor 11 receiving pulses from a timer 12. The four hole positions a, b, c and d in row 1 of a recorded item such as A or B represent 1, 2, 4 and 8 units in the desired temperature; row 2 correspondingly represents tens, and row 3 hundreds. Thus the temperature recorded at A is 597‹ and at B is 325‹. A reading system 13 causes relays (not 'shown) connected to respective terminals 16 to 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 a 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 motor 11 and 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.