Patent GB-662437-A (GB)
Title: Improvements in or relating to control apparatus for drying appliances
IPC: D06F34/08
Filed: 1948-06-29
Abstract: 662,437. Automatic circuit breakers; thermal switches. BOBERTSHAW-FULTON CONTROLS CO. June 29, 1948. No. 17466/48. Class 38 (v). [Also in Groups XI and XIII] In control apparatus for clothes dryers (see Group XIII), the switching mechanism 26 for the electric motor 16 comprises a housing 24 with a main switching means in the form of a switch lever 140 pivoted at one end on a bracket 142 and carrying at its free end a contact 144 biased into engagement with a fixed contact 146 by a coil spring 148. Lever 140 is restrained against movement under the bias of spring 148 by portion 156 of a lever 154 pivoted intermediate its ends on the bracket 142. The opposite end of lever 154 is engaged between the ends of stems 116, 126 for transmitting motion from a push button 88 to a gas fuel valve 50 and an aperture 158 in the lever receives one end 161 of a pivoted latch 162 which is biased counter-clockwise by a spring 164 so that when lever 154 is moved clockwise a step 166 on the latch engages the lever to prevent counter-clockwise movement. This latching operation may be prevented by operation of a slidable pin 168 held in engagement with the element 162 by the arm 110 of a bell crank lever 100, the pin 168 being biased away from the latching element by a spring 170. Another arm of the lever 106 is engaged between armature stem 84 and re-set stem 92 the armature 82 being held by electromagnet 83 operated by thermocouple 76 in the pilot flame so that if there is no flame, armature 82 is released, lever arm 110 rises, lifts pin 168 which releases the latch allowing the lever 154 to open the switch under the biasing action of springs 120, 160. Auxiliary switching is provided for co-operation with terminal bar 150 and includes a switch lever 174 having a contact 176 adapted to engage contact .178- on the bar 150, the lever being arranged for snap action. A conventional lever and spring device has an operating lever 180 and an overcentre spring 182 having one end hooked around a bearing portion on the lever 174 and its other end hooked on to lever 180. The lever 174 has a pair of legs 184, the terminal end of each having a knife-edge portion for co-operation with a knife edge bearing 186 in bracket 188 and similarly the end of lever 180 has a knife edge for co-operation with bearing 190 in a bracket 192. The lower end of the lever 180 extends beyond stem 116 and is apertured to provide clearance therefor, this depending end of the lever extending adjacent an inclined portion 163 formed on the latching element 162 adapted to engage upon sufficient clockwise movement of the lever 180. This lever 180 is engaged by a stud 193 carried by the expanding- capsule, temperature-responsive, device 22 and is moved by the expansion and contraction of the element to close and open the switch, the operating temperature being adjusted by rotation of a dial 194 on a threaded stem 196 which moves the stud 193 axially into and out of engagement with the lever 180. In order to prevent the closing of contacts 144, 146 unless the dial 194 of the thermostat is moved from. the "off" position to a desired temperature setting, the dial carries a cam element 216 having a shoulder 218 and a bar 220, extends through the housing into engagement with switch lever 140 and carries a wedge-shaped element 222. Co-operating with element 222 is a slidable pin 224, one end of which engages one end of. pivoted member 226 having its other end engaging a collar 172 on the pin 168, so that in the "off" position the shoulder 218 acting on bar 220 prevents closing of contacts 144, 146 and also prevents rotation of latching member 162 through pin 168.