Patent GB-449469-A (GB)
Title: Improvements in or relating to regulating means for cookers
IPC: F24C7/08
Filed: 1934-11-23
Abstract: 449,469. Time switches. MOWER, G. A., 147, Queen Victoria Street, London. Nov. 23, 1934, No. 33747. [Class 38 (v)] [See also Groups VI, XXIX, and XXXVIII] In a control for a thermostatically - controlled electrically - heated oven, a pointer 44 on being set by the user winds up and sets a clockwork timing mechanism 43 (not shown), so that at the expiry of a period determined by the setting the timing mechanism will trip a spring-actuated mechanism which operates a visible or audible alarm, the setting of the pointer simultaneously winding up the alarm mechanism which when tripped also cuts off or cuts down the supply of heat to the oven. As shown, the heating circuit comprises a main heating element 11, Fig. 5, and a heat-maintaining element 12 each controlled by a switch 13, 14, these switches being opened successively by a thermostat to keep the temperature down at the desired level. A main switch 15 operable both by hand and by the timing mechanism breaks the current through the heating elements. When the oven has reached the required temperature the main heating element 11. is cut out by switch 13 and a signal lamp 16 in shunt therewith is illuminated to indicate that the oven is readv for use. One of the contacts 25, Fig. 3, of the switch 15 is carried by a pivoted lever 32 and the other contact 24 is urged to engaged position by a spring 30, both being coated on their contact faces with silver. The lever 32 is urged by a spring 34, Fig. 1, to disengaged position and has at its other end a follower 56 engaging a cam 50 in the alarm mechanism. A key 23 is first turned upwardly by hand and has a lug 40 which thereupon engages lever 32 and closes contacts 24, 25. When the lamp 16 carried by a socket 65 has illuminated to show the oven is ready, the food is placed therein and the timing mechanism 43 set for the desired period by setting pointer 44 in relation to a dial (not shown), the pointer 44 being fixed to the arbor 45 which winds the clock spring of the mechanism to the desired extent. A pinion 47 on arbor 45 meshes with a pinion 48 on a spindle 49 associated with the spring-actuated alarm mechanism adapted to be tripped by the mechanism 43 when the pointer 44 returns to zero position. Circular cams 50, 51 secured together by a rivet 52, Fig. 4, are mounted on spindle 49 on which they and the pinion 48 are a moderately tight frictional fit. A pin 54 on pinion 48 engages in a groove 53 in cam 50 in which its travel is limited by a stop 55. The cam 50 has a notch into which follower 56 can drop when in neutral position to open contacts 24, 25. The cam 51 engages peripherally a stud 57 on key 23 and has a notch 58 in which stud 57 engages when the key is in the "off" position, the cam being then at zero position. As the timing mechanism operates the pin 54 is rotated in a clockwise direction in groove 53 but cams 50, 51 remain in their original setting. A spring 59 mounted on spindle 49 operates, when the timing mechanism 43 is tripped by return of pointer 44 to zero position, to rotate spindle 49 and bring cams 50, 51 back to zero position, on which current to the oven is cut off and the signal lamp 16 extinguished, key 23 returning to the "off" position. Provision may bo included to keep the food in the oven hot without cooking it further, as by a circuit which leaves a small heating element in operation. In a modification, alarm mechanism may operate an audible alarm instead of or as well as extinguishing the signal lamp 16. The Provisional Specification describes the use of timing devices which either givo a visible or an audible alarm or cut down or cut off the supply of heat after expiry of a predetermined time.