Patent GB-1108885-A (GB)
Title: Improvements relating to domestic ovens
IPC: F24C14/02
Filed: 1965-07-15
Abstract: 1,108,885. Door fastenings. GENERAL ELECTRIC CO. 15 July, 1965 [4 Aug., 1964], No. 30058/65. Heading E2A. A domestic oven has means for heating the oven to a temperature sufficiently high for a heat cleaning operation to take place to remove food. soil lodged on the inner surface of the walls of the oven, control means for controlling the heat cleaning means, a bolt 35 movable to bolt an access door 15 of the oven in a closed position, or locking arrangement 38 for automatically locking the bolt in its bolting position so that the door cannot be opened during heat cleaning, and an electro-responsive device 54 arranged to de-activate the locking arrangement upon receipt of a signal from the control means that a heat cleaning operation is completed to permit movement of the bolt to its releasing position and the door to be opened. In the construction shown the oven is electrically heated and is provided with a lower baking element 16, an upper broiling element 17 and a perimeter heater element 18 that is wrapped around the oven liner; for the heat cleaning operation all three elements are used. The door bolt is manually operated by handle lever 31 which extends through an elongated slot in the front wall of the cabinet in a position parallel to the top edge of the oven door 15; the handle lever 31 is pivotally supported about a vertical axis 32 from a stationary mounting bracket 33 and the handle lever is swingable through an angle -of about 60. The lever 31 operates the bolt 35 which is pivoted by a pin and-slot lost-motion connection (not shown). Movement of the lever swings the bolt 35 into and out of engagement with a slot in the inner surface of the oven door the bolt having a hook portion which enters the slot. The locking arrangement 38 is located at the rear of the oven liner and locks the bolt in both the releasing and the bolting positions. The locking arrangement 38 comprises a lever 44 which is pivotally connected at one end 45 to a vertical side flange of a support bracket 42 which extends from the bolt 35 to the locking arrangement 38; the opposite end of the lever 44 is connected by a member 48 to a plunger 53 of a solenoid 54 which constitutes the electro-responsive device, a spring surrounds the member 48 and engages the lever 44 at one end and a fixed bracket 47 at the other with the member 48 passing through the bracket. The solenoid overcomes the lifting force of the spring to move the lever 44 out of locking position. To lock the bolt 35 the lever 44 is provided with a pin 60 and this co-operates with either of two detents 56, 57 which are provided in a movable rod 39 which at one end is connected to the handle lever 31 by means of a pivot pin 40. When the pin 60 is biased by the spring 48 into the detent 56 the handle lever and hence the bolt is retained in the bolting position and when the pin is in the detent 57 the handle lever and bolt are in the releasing position. There are also two switches 63 and 65 associated with the locking arrangement 38. To start the heat cleaning operation a control switch 68 is set to a "clean" position and this energises the solenoid 54 through contacts 87. The solenoid then releases the pin 60 from the detent 57 so that the handle lever 31 can be swung to the bolting position and this movement. via the rod 39, closes the switch 63 and as soon as a "clean" switch 102 is manually actuated a motor of a sequence timer is actuated. During the first ten minutes of the operation of the sequence timer the solenoid 54 remains energised and the heating elements remain de-energised so that during this period the door can be opened, in which case the switch 63 stops the timer motor. At the end of the ten minutes wait, the solenoid 54 is de-energised by the movement of the arm of a timer switch 76 and the switch 76 also energises a relay Rl via contacts 65 which are closed by the de-energisation of the solenoid. The relay Rl connects the perimeter heater element 18 in parallel with the baking and broiling elements 16 and 17. At the same time as the switch 76 is operated, a timer switch 78 is also operated and this applies power to a transformer 70 and thus energises an oven temperature responder 69 which via a relay R2 switches on all the elements 16, 17 and 18. Contacts of the relay R1 put a resistance 72 in parallel with a variable resistance temperature sensor 71 to change its range to that required for the heat cleaning operation so that the heat cleaning temperature is controlled by the oven temperature responder at the required level. A bimetallic switch 103 in the circuit of the relay R1 opens if the temperature exceeds a desired level for any reason. At the end of a ninety minute cleaning period the sequence timer initiates a twenty minute cooling period by moving the arm of switch 76 so that it does not make with either of its contacts 103 or 104. This de-energises the relay R1 which in turn de-energises the perimeter heater element 18; it also disconnects the resistor 72 so setting the oven temperature responder back to its normal cooking temperature range. The temperature responder 69 via relay R2 then cuts off power from the heater elements 16 and 17. At the end of the cooling period the timer motor opens the "clean" switch 102 which stops the motor and simultaneously moves the switch 78 to open position and closes the arm of switch 76 to contact 103 to energise the solenoid 54 so that the door can be opened. The switch 78 cuts power to the oven responder 69 which then releases the relay R2 if it has been energised in the cooling period which cuts power to the elements 16 and 17. Various indicator lamps are provided in the circuit to indicate the operational sequence.