Patent GB-597561-A (GB)
Title: Improvements in the control of periodically reversible and unidirectional machines such as washing machines, rotary drying machines, dry cleaning machines, dyeing machines, or the like
IPC: D06F37/30
Filed: 1945-08-23
Abstract: 597,561. Control of motors. BRAITHWAITE & SON ENGINEERS, Ltd., I., and WALKER, T. B. Aug. 23, 1945, No. 21566. [Class 38(iii)] [Also in Group XXXVI] Travelling between pre-determined limits. - The direction of rotation of an electrically driven washing machine or similar periodically reversible laundry machine is determined by a pair of thermionic valves in the armature circuit of the driving motor, and a switch reverses the motor automatically, after the machine has made a pre-determined number of revolutions in either direction by energising one valve and de-energising the other by grid control. The layshaft B driven by the rotary cylinder of the machine carries cams B1-B4, any one of which can be brought under the lever D by axially moving the layshaft by the knob B5, Fig. 1. This shaft is located by the ball catch b1. Another cam J, which can be rotated by handwheel J1, may also act on lever D2. The shaft F, which is oscillated by the quadrant E1 when lever D or D2 is rocked by one of the cams or by the spring D1, carries a fork T1 which actuates the snap-action tilting mercury switches S5 and S6 and also carries the control drum G. The insulating drum G carries contact strips G1-G2 and K1-K2 and resistances R1-R2, which are engaged by stationary brushes P1-P4. Alternatively the strips and resistances may be arcs mounted on a stationary or oscillating plate. In Fig. 4 the brushes are replaced by stationary flexible swashplates W1 and W2 each having a point on its circumference pressed against a stationary arcuate contact strip by one of the spring-pressed balls X carried by but insulated from the levers X1 and X2 mounted on shaft F. The armature of the D.C. motor M driving the machine is supplied in one direction or the other through one or other of the gas-filled triodes V1 and V2, Fig. 2. The grid potentials are provided by transformer windings S1 and S2 through phase shifting circuits made up of resistors R1 and R3 and condensers C1 and C3 and of resistors R2 and R4 and condensers C2 and C4 respectively. With the motor M supplied by triode V2 and driving the machine and one of the cams in one direction, the oscillation of shaft F causes relative movement of brush P4 over resistance R2, thereby varying the phase of the potential of the grid 5 and increasing the output voltage of the triode V2 to accelerate the motor. When all the resistance R2 is out of circuit the brush travels on the strip K2. The motor rotates until further movement of shaft F opens switch S6 and closes switch S5; the grid 5 makes the triode V2 non-conducting and the motor M stops, but the triode V1, controlled by grid 4 and brush P1 engaging resistance R1 now supplies and accelerates the motor in the reverse direction, and so on. Other phase shifting circuits, including inductance, may be used; variable inductances having magnetic core members on levers moved by the cams B1-B4 may take the place of the control drum G. The different cams are shaped to give different speed variations, one being shaped to keep the motor rotating very slowly for a substantial part of the cycle. One cam may be shaped to cause the motor to turn continuously in one direction at varying speeds without operating switches S5 and S6. The cycle of operations goes on repeatedly until the motor is stopped by turning handwheel J1. According to the Provisional Specification this handwheel may also be used for inching.