Patent GB-955795-A (GB)
Title: Heating control
Inventor: FERNELL WILLIAM RONALD
IPC: G05B19/12
Filed: 1959-11-02
Abstract: 955,795. Timing apparatus for controlling cooking in ovens. UNILEVER Ltd. Oct. 25, 1960 [Nov. 2, 1959], No. 37172/59. Heading A4D. [Also in Divisions A2 and H3] Packets of prepared, e.g. frozen, food are heated, e.g. in a microwave oven, to an extent determined either by the shape of the packet, or by electrical conducting means in or on the packet, or, preferably, by a hole or holes drilled in a projecting flange on the food packet. A sensing means F, Fig. 2 for detecting a pre-selected arrangement of holes 4 to 10 in a flange on a food packet 1, comprises a plurality of pivoted actuating arms 44 connected to microswitches the arms having ends 45 which engage in the flange holes. The flange fits into a groove 41 in a wall 42 of the sensing means housing as the packet 1 slides between guides 14 into a three-sided locating tray 12 fixed to the surface 11 of a trolley. The flange is then severed from the packet by both movable and fixed knives 55, 56 of a guillotine, and the trolley transports the packet into the oven 22 through an open door 25, transporting it out again when the pre-determined heating time has elapsed. The flared end 47 of a lever 46 then pushes the arms 44 out of the flange holes and the flange is ejected. A block 58 carrying a point 59 punctures the packet before it enters the oven to allow escape of steam. A gear wheel 35 driven by an electric motor M, Fig. 4, rotates a wheel 34 on a shaft 30, a pair of endless belts 28 passing over pulleys 29 mounted on the shafts 30, 31 each endless belt carrying an arm 37 supporting a cross bar 38 which engages a flap 39 to move the trolley into the oven and a flap 40 to move it out, the trolley running on rollers 17, 18 on fixed rods 19, 20 at either side. Rotation of the gear wheel 35, Fig. 1, turns a shaft 36 carrying a series of cams including a cam 51 which works the lever operating the arms 44, a cam wheel 63 operating the blade 56, a cam 69 actuating the flange ejecting arm 65 and a cam 71, Fig. 4, operating the electric motor contacts. The sensing circuit comprises microswitches S 1 , and S 2  to S 7  which are actuated by the arms 44. A further microswitch S 8  serves to cut out the motor when the trolley has passed into the oven and is operated by being engaged by the lower part of the frame 16 as the trolley conveys the food packet into the oven. When microswitches S 1  and any of S 2  to S 7  are closed (Fig. 4) the corresponding relay(s) A to F is energized and the corresponding three contacts of the same letter are closed and a lamp or lamps L 2  to L 7  lighted. By this means the heating time of the oven is preset, contacts G 2 , G 3  controlling the power supply to the microwave oven. The heating control circuit comprises a rectifier Q and neon-filled stabilizing tubes T 1 , T 2  supplying stabilized D.C. to the rest of the network. The operation of microswitches S B  closes I 1  and opens I 2 , momentarily energizing a relay G and charging a capacitor U 1 , contacts G 1  closing to hold on the relay G. At the same time G 2 , G 3 , G 4  are closed and G 5  opened and mercury contacts G 6  momentarily closed. Relay G remains energized via contacts G 1  and H 3 , and closing G 4  charges a capacitor U 2  in a pre-determined time through a timing circuit A 3  to F 3  whichever is the contact (or contacts) closed. As U 2  charges the voltage on the priming electrode V of a cold cathode trigger tube T 3  increases and ultimately the tube fires energizing a relay H to close contacts H 1  and H 2  and open H 3  and thereby allowing H 2  to discharge, locking on the relay H, quenching the tube T 3  and also de-energizing the relay G so opening G 1 -G 4 , closing G 5  and also momentarily closing G 6 . A capacitor U 3  holds on relay H whilst it discharges via H 1 , H 2  to safeguard against the tube T 3  refiring. In the motor circuit at the bottom of Fig. 4 a motor M is in series with a relay P, which operates contacts P 1 , and the cam actuated contacts W. To commence a cycle of operations a starter button Z is pressed. If contacts W are open M is energized through Z 1 , Z 2 , P, Z 3 , Z 4  and immediately cam 71 closes contacts W and since P is now energized contacts P 1  close and P is held on. Z is now released and the motor only stops when either contacts G 5  or W are opened. If, when Z is pressed, contacts W are closed, M is energized through P and W and contacts P 1  close to hold on P.