Patent GB-805401-A (GB)
Title: Clothes dryer
IPC: D06F34/30
Filed: 1956-03-06
Abstract: 805,401. Clothes driers. LOVELL MANUFACTURING CO. March 6, 1956 [March 11, 1955], No. 6975/56. Class 34(2) A tumbler drier in which the drying period is controlled by a timer motor has hand-operated means so that the drying period may be automatically repeated a number of times. The drier shown comprises a perforated clothes drum 2, Fig. 1, mounted for rotation within a cabinet 1. In operation, a fan 12, Fig. 2, draws air diagonally across the drum from a slot 14 to a drum 10 and discharges it in a hot moist state to atmosphere through a lint trap 16. An electric heater 18 mounted within a reflector 19 adjacent the slot 14 heats the air. In a control circuit a knob 39, Fig. 3, is timed to give up to five extra automatically repeated drying periods. In use it is turned to the desired position and a thermostat 29 in the exhaust air outlet is adjusted at 31 to operate at the desired exhaust temperature. Rotation of the knob 39 turns cams 34, 38, 25, the first. two closing, respectively, contacts 33 in series with a fan and drum motor 32 and contacts 37 in series with a time motor 35 which drives a shaft 40 through a slipclutch 34a. During cam rotation, a projection 24a, one of five, equi-spaced around the cam 25, contacts the upper end of a switch operating rod 23 and depresses it so connecting the heater 18 to a power source 20. The rod is held depressed by an over-centre spring 28 and although the motor 32 operates and clothes are dried the timer motor circuit is interrupted at 36. After a time determined by the temperature rise of the exhaust air, the thermostat through a bellows 30, moves the rod upwards causing simultaneous breaking of the heater circuit and closing of the timer circuit. The cams 25, 34, 38 are then driven anti-clockwise until the projection 24a again contacts the rod and depresses it so once again closing the heater circuit whilst opening that of the timer. The interval between closing and opening the timer circuit-about five minutes-depends upon the time motor speed and the distance between the projections on the cam 25. During this time the heater is " off " and the exhaust air temperature drops thus allowing the thermostat bellows to retract leaving subsequent space for depression of the rod 23. With the heater " on " and the timer " off " a further drying period ensues until the thermostat once again causes the rod 23 to move upwards and break and make the heater and timer circuits respectively. The timer motor then runs for a period until the cams 34, 38 cause the circuits of both motors to be broken through breaking respective contacts 33, 37 and the drier is thus shut down. If the knob 39 had been turned such that the projection 24a has been set slightly to the right of the top end of rod 23 then the control would have automatically programmed the dryer through five successive cycles in each of which a cool-down period, during which the fan continued to circulate air with the heater off, followed the point at which the pre-set thermostat actuating temperature was reached by the hot exhaust air. A thermostat 22 is provided in the heater circuit to safeguard against belt breakage or normal air flow interference. In the drier control system of Fig. 4, a knob 57 is turned to set the additional drying time desired after the clothes are damp dried. This setting rotates cams 52, 55 such that contacts 57A, 56 are closed and the motor 32 is thus started. A start-button 60 is then pushed and rods 59, 59a are moved axially such that heater contacts 54 are closed whilst timer motor contacts 44, 45 are opened. Both rods 59, 59a have over-centre springs. When the exhaust air temperature has risen to the pre-set operating temperature of the thermostat 49 expansion of bellows 48 depresses the rod 59 to close the timer contacts 44, 45. The timer motor then rotates the cam 53 causing a portion 58 thereof to depress the rod 59a to open the heater circuit, the time between the closing of the contacts 44, 45 and depression of the rod 59a depending upon the setting of the knob 57. This time may be between five and thirty minutes. After switching off the heater the timer allows the drum and fan to rotate until cams 52, 55 operate so that the contacts 57A, 56 may open and thus shut down the drier. Fig. 7 shows another control diagram in which the operator selects the added drying time as in Fig. 4. The drier is started by turning a knob 68 to set a cam 67 to a position equivalent to a desired added drying time. This closes switches 69, 70 to actuate the heater and the drum motor 32. The timer 35 does not start until the exhaust air temperature causes an adjustable normally open thermostat 71 to close when the timer circuit comprises a normally closed thermostat 72 and the switch 70. The timer then runs for the time set by the cam 67 unless in the meantime the thermostat 72-set at a higher air exhaust temperature value than 71-opens. If this happens the timer and heater circuits are interrupted and the drum and fan continue to operate until the air temperature falls to allow 72 to re-close whereupon the timer and heater are once against switched on. When the time set by cam 67 has almost elapsed a cam 66 allows the heater switch to open and closes a switch 73 to keep the timer running. This runs for a cool-down period controlled by the cam 67 at the end of which the switch 70 opens to switch off both drum and timer motors.