Patent GB-1277950-A (GB)
Title: Microwave heating apparatus
Inventor: KEE DAVID MONTGOMERY
IPC: H05B6/78
Filed: 1970-06-22
Abstract: 1277950 Microwave heating MICROWAVE MERCHANDISERS Ltd 22 June 1970 [2 Sept 1969] 43398/69 Heading H5M A microwave oven comprises a resonant cavity 2 with aligned inlet and outlet ports closable by doors 5, 6 when an article to be heated is conveyed by belt 4 into the cavity and means to prevent energization of the source of microwave energy if either door is not fully closed. In operation klystron 41 is switched on and allowed to reach its operating temperature before the cooking time is selected on a control box 51. The article to be cooked is placed on the belt 4 in a plastics container between a photo-cell 52 and its illuminating lamp (not shown). Interruption of the light beam energizes motor 16 which drives the belt 4 via belt 18 anticlockwise to convey the article into the cavity 2. As the article passes a photo-cell 53 it interrupts the light beam from its illuminating lamp (not shown) causing the motor 16 to be de-energized after a suitable delay subsequently energizing a door operating motor 26 which closes doors 5, 6. Complete closure of the doors 5, 6 actuates four microswitches, two per door, only two 9 and 10 being shown, so that photo-cell 53a may actuate klystron 41 for the pre-selected cooking time. At the end of this time, klystron 41 is deactivated, the belt 4 moves the article out of cavity 2 on to a delivery panel 20, and the belt is stopped by the article interrupting the illuminating beam of a lamp (not shown) for photo-cell 54. The belt 4 is tensioned by a tensioning device 23, 24. A fan motor 44 drives a blower 43 which draws cooling air over the motor switching assembly 45, through transformer housing 46 and along ducts 47, 48 to the cathode of klystron 41. The air then passes up the launch tube 42 coupling the klystron 41 to the cavity, into the cavity 2, and out of the cavity through perforations in doors 5, 6. The cavity 2 is lined with a polypropylene shell (not shown) through which belt 4 passes, in contact with the floor. A mode stirrer is provided in the cavity and an adjustable cover is provided in one end of the launch tube 42 for tuning (Figs. 3 and 4, not shown). As shown, each door e.g. 6, is pivoted to a lever 82 pivoted at 83 to a plate 80 pivoted at 81. A spring (not shown) keeps the door vertical in its movement and a spring 84 links lever 82 and plate 80. A Bowden cable 33, actuated by motor 26 via a lever 31, opens and closes the door. The closing movement is a compound movement the door first following the path B until it reaches conveyer belt 4 and then moving inwardly with continued anticlockwise movement of plate 80 until it firmly engages the cavity wall. In Fig. 7 (not shown) the door is raised by pulley cords sliding on inclined guides under spring action. A fixed reflector beneath the belt 4 co-operates with a channel member carried on the lower outer edge of the door to form a quarter-wave leakage preventing stub. In Fig. 8 (not shown), the lower edge of each door is castellated and co-operates with corresponding apertures in the belt. The belt may be provided with transverse pleats spaced by a distance slightly less than the length of the oven.