Patent GB-729632-A (GB)
Title: Improvements in or relating to time control apparatus
IPC: G05B19/02
Filed: 1950-02-27
Abstract: 729,632. Timed control of electric circuits. LINDARS, H. Feb. 23, 1951 [Feb. 27, 1950], No. 4961/50. Class 118 (2). A timing device for controlling one or more events in an industrial process or the like comprises a constant speed reversible driving mechanism which after initiation runs in one direction until reversed by a preset control arrangement whereon it returns to its initial position. A reversible synchronous motor 1 shown schematically in the Figures as a forward rotor F and a reverse rotor R carries on its shaft a pair of contact discs 2 and 3, the disc 2 constituting an annular conductive periphery 4 having a short insulating segment 5 at one point whilst the disc 3 has an annular insulating periphery 6 interrupted at the corresponding point by a short conductive segment 7. In the initial position shown in Fig. 1 a brush 8 rests on the segment 5 and an angularly adjustable brush 9 co-operates with the disc 3; brushes 12 and 13 form a permanent connection between the portions 4 and 7 and one side N of the supply mains. The other supply line L is connected through relay contacts to the forward rotor F. A timing cycle is initiated by push-button switch 20 which completes a circuit to rotor F and the motor runs in the forward direction causing brush 8 to make connection across the switch 20 which may then be released. The motor thus runs until segment 7 contacts brush 9 and relay 15 is energized, thereby changing over the line L connection to the reverse rotor R and holding itself by the contacts 21. The motor now runs in the reverse direction until segment 5 lies under brush 8 which breaks the circuit to both the motor and relay and initial conditions are restored. A third disc 23 may be provided on the motor shaft for control of an external event by means of brushes 24, 25, or if the half-cycle period is to be utilized additional contacts 22 on the relay 15 may be provided. The embodiment of Fig. 2 extends the principle of Fig. 1 by the addition of a uniselector and two relays arranged so that the forward and reverse movements of the motor continue automatically for a predetermined number of cycles. The synchronous motor 1 is connected to A.C. mains via relay contacts A1 and B1 and carries on its shaft a disc 3 having a small conductive segment 7 co-operating with two brushes 9a and 9b, the former being angularly adjustable around the periphery of the disc and the latter being fixed at a " zero " position. A D.C. supply has its negative pole earthed and the positive is fed into the circuit as indicated in the Figure. Operation of push-button P connects the D.C. supply to the uniselector operating coil S via the zero contact of level SL2 and wipers 26 and 27 are stepped to the first contacts of their respective levels. Relay B is thus energized and contacts B1 cause the motor 1 to run forward until segment 7 reaches brush 9a when relay A is energized to reverse the motor 1 by change-over contacts A1. At the same time contacts A2 energize coil S and the uniselector steps to its second contacts, thus holding the relay A operated over level SL1. When segment 7 arrives back at brush 9b relay B is energized and contacts B2 step the uniselector so that level SL1 releases relay A and holds relay B. This returns motor 1 to forward running and the previous cycle is repeated. The motor thus automatically continues to oscillate segment 7 back and forth between brushes 9b and 9a for as many cycles as there are pairs of contacts on level SL2 strapped to relay contacts A2 and B2. On the final return of segment 7 to brush 9b the wiper 27 steps on to the remaining contacts of level SL2 which are all connected to the D.C. supply such that the uniselector homes to the zero position. Relay B is operated until the forward rotation of the motor 1 just moves segment 7 away from brush 9b when all supplies are disconnected and the device is in its original condition ready for further initiation by push button P. External events may be controlled by means of a further disc 23 on the motor shaft as shown, or by contacts of a further level of the uniselector. The embodiment of Fig. 3 (not shown), is a development of that of Fig. 2, wherein the uniselector has a third level SL3 which selects one of three timing brushes 9a, 9c or 9d so that the overall timing operation may comprise cycles of different duration. A relay C is also added so that brushes 9a, 9c and 9d may be left out of circuit, allowing segment 7 to make a full revolution and return to brush 9b where it operates relay C to step the uniselector. Thus the total time of operation may be built up of various numbers of cycles of four different durations. The embodiment of Fig. 4 (not shown), utilizes sequentially energized relays in place of a uniselector. Several events may be controlled by a corresponding number of timing units, each comprising a motor 1, disc 3 and brushes as desired and Fig. 5 (not shown), illustrates a system of co-ordination using only one relay and one uniselector. The uniselector has a fifth level in which all contacts, except the zero position, are strapped to the D.C. supply and a switch T is provided so that on operation of this switch T the selector homes from any position. The different timing units may have different drive speeds so that a very wide range of times is possible without prolific apparatus. This embodiment may employ a constructional arrangement of four timing discs 3 connected by different gear ratios to a common shaft driven by one motor which is described with respect to Fig. 6 (not shown). A manuallyoperable knob is provided for each adjustable brush 9a. The electromagnetic relays may be replaced or controlled by gas-discharge tubes or hard valves. The synchronous motors may be replaced by clockwork or other constant speed motors, or, if great accuracy of timing is not essential, by induction motors. Cam projections or other mechanical trip devices may be used instead of the segments 5, 7 on discs 2, 3 respectively.