Patent GB-933321-A (GB)
Title: Improvements in instruction systems
IPC: G09B7/08
Filed: 1959-12-23
Abstract: 933,321. Control of A.C. motors. U.S. INDUSTRIES Inc. Dec. 23, 1959 [Oct. 16, 1959], No. 43707/59. Class 38 (3). [Also in Groups XV and XX] In a self-teaching apparatus, items of information comprising a logical sequence in a course of study are randomly positioned on a strip movable in either direction by a reversible motor to select and display a given item in accordance with a digital selection operation that is indicated on the presently-studied item. As shown in Figs. 1 and 2 the items of information are recorded on separate randomly chosen film frames back-projected on a hooded screen 13. A given frame on the film 22 corresponds to a given setting of the buttons on keyboard 70, the selected number being visually registered at 150, 151, 152, for example, by means of Nixe bulbs. On selection of a further frame, the previously depressed buttons are restored to their normal position. Each one of each vertical row of buttons opens a switch on depression, each switch being connected to a corresponding fixed conducting segment (0, 1 . . . 9) of the three limit-switches 36, 37, 38 all the switches in one row forming a conducting chain when all are closed (see Fig. 3). Conducting arms 48-51, 49-52, 50-53 are driven via 10: 1 reduction gearing in decimal cascade from shaft 28 of an A.C. motor 26 so that the arms rotate respectively at speeds corresponding to units, tens and hundreds. The circuit through the fixed segments and rings 45, 46, 47 of the switches is supplied from a D.C. source 64 and is maintained as the switch arms sweep the segments until that segment associated with a depressed button is reached whereupon a relay coil 96 or 97 (depending upon the direction of rotation of the motor as explained below) becomes de-energized thus causing a circuit to be established via switches 123, 124 of a clutch coil 122 and a braking coil 129 to the positive pole of D.C. source 64, to stop the motor 26. The cycle of operations, once a digital selection has been made, is commenced by momentarily depressing the control button (" viewing button ") 71 to energize the self-holding relay 84 through switch 91, whereby the negative pole of the D.C. source 64 is connected to one end of relay 84, the other end being connected to the positive pole via the switching systems 55, 56, switches 98, 99 and diodes 81, 83. The change of setting of the highest order switching system 56 will cause current to flow either via lead 78 and diode 80 through switch 98, or via lead 79 and diode 82 through switch 99, to produce the required sense of rotation in the motor 26. As one or other of switches 98 or 99 becomes conducting, the opposite one of the pair of relays 96, 97 will be energized and either switch 101 or 102 will be closed thus reversing the connections between armature 100 and field coil 103 of the motor 26. Such reversal is prevented from being effected by any but the highest order switching system by means of diodes 106, 108 which allow energization of relay 107 (control relay) to isolate switching system 55 (and all others) at switches 110, 111. When no more current flows through system 56 (i.e. when arm 52 has arrived at its destination), switches 110, 111 are closed. The timer 130 measures the cumulative elapsed time since the machine was set into operation, and at each command the printer 131 records both the time and the frame number corresponding to the digital command.