Patent GB-791788-A (GB)
Title: Improvements in or relating to control systems for clothes drying apparatus
IPC: D06F34/08
Filed: 1956-03-12
Abstract: 791,788. Clothes drier. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. March 12. 1956 [March 22, 1955], No. 7607-56. Class 34(2) A tumbler clothes drier having a motordriven perforated basket 16, Figs. 1, 2, for the clothes and a fan 33 for blowing hot air through the drum is provided with a time switch 41 setting the period of operation of the fan motor 29 and an electric air heater 37, and a thermostatically-operated switch 42, Fig. 3, for over-riding the time switch and shutting off: the heater and motor when a predetermined temperature is reached in the drier. The timing switch comprises a shaft 48 carrying a cam 51 and a disc 78 having a finger 81 which abuts a stop 82. The shaft 48 is splined to a shaft 47 driven by a slow-speed (e.g. 1 revolution in one or two hours), electric motor 46, the shaft 48 being manually movable axially to disengage the finger 81 from stop 82 and being manually rotatable by a knob 54. The drying sequence is as follows, the clothes are placed in the perforated basket 16 and the door 26 of the drier is closed which action closes a switch 43 in the motor circuit. The knob 54 is then moved axially to the right so that the finger clears the stop and is then turned to the selected "on" position. The axial movement actuates a pivoted lever 76 and wire 74 to close the thermostatically-operated switch 42 comprising a snap-acting bimetal element 67 carrying a member 68 which in the closed position bridges the contacts 71, 72 and 73. The rotative movement closes the cam-operated switches 52 and 53 as the cam follower 63 rides upwardly from the lower surface 64 to the surface 66. The closing of the switch 52 completes a circuit for the motor 29 through conductor L1, contacts 71, 72, door switch 43, running winding 85 of the motor and the neutral conductor N. The starting winding 86 is energized through a circuit including the fixed contact 89 and the movable switch blade 88 of the centrifugal switch. Thus the motor 29 is operated to drive the basket 16 and the blower 33. The centrifugal switch 87 now moves the blade 88 into engagement with the contact 91 thus completing a circuit through conductor C, contacts 71, 73, the coil 93 of the heater relay, contact 91 and blade 88 to the neutral conductor. This causes the relay contacts 92 to close completing a circuit through onductor L2, switch 53, contacts 92, thermostat 95, heater 37 to conductor L2. Thus heated air is. delivered to the tumbling clothes through a conduit 38 the temperature of the heated air being determined by a thermostat 95. A circuit for the time motor can be traced through conductors C2. C3 to the neutral conductor. The drying cycle is ended by the operation of the timer 41, a short time before the end of the cycle switch 53 is opened so that the heater is turned off and the motor circulates unheated air through the drying chamber before the switch 52 is opened and the drying completed. If the clothes are completely dried before the set time, the temperature inside the chamber increases to that at which the switch 42 is set so that it snaps the contacts 71, 72 and 73 thus breaking the heater and motor circuits. The motor continues to operate because of a shunt circuit provided through a thermostat 94 in conduit 38, until the thermostat is cooled when it Opens and the circuit is broken.