GB1114938A - Microwave-heating ovens - Google Patents

Abstract

1,114,938. Microwave ovens; R.F. couplings. HIRST (MICROWAVE HEATING) Ltd. 16 Sept., 1966 [1 Oct., 1965], No. 41771/65. Heading H5H. [Also in Divisions E2, F2, F4 and H2] A microwave-heating oven comprises an electrically conductive shell having a stationary section 14 and a movable section 26, biased away from stationary section 14 but movable into engagement therewith to form a heating cavity, a microwave-transmissive support 23 for the material to be heated, a microwave-energy source connected to the cavity, an electromagnet 38 arranged to hold movable section 26 in engagement with stationary section 14, and a supply circuit for electromagnet 38 including a timer 49 to interrupt the supply of power through the circuit after a predetermined interval, and at least one switch 46 normally preventing the supply of power through the circuit but being held to permit the supply by movable section 26 when the latter is in engagement with stationary section 14. Section 26 is mounted on rods 31 slidable in nylon gearings 32 and biased upwardly by springs 33 and having a bar 34 between them carrying a spring-loaded soft iron bar 36 engageable by electromagnet 38 to hold section 26 down when it has been depressed and the electromagnet energized. Section 26 has a microwave sealing ring 29. The microwave supply is through waveguides 12 and 13 with a probe 19 and disc 21 for matching purposes. Bar 34 carries a resilient pad 35 to damp the impact when section 26 rises. When main switch 40 is closed the supply is completed via leads 42 to the magnetron heater circuit, then after a warming-up interval timer 43 closes contact 44 preparing the circuit so that when microswitch 46 is closed by rod 31 by depressing section 26, push-button 47 may be closed energizing relay coil 50 through timer 49, closing contact 56 energizing through contacts 53, 54 (closed when section 26 is in the lower position) transformer 55, silicon-controlled rectifier 57, electromagnet 38 and the supply 58 to the magnetron anode. After a predetermined interval timer 49 de-energizes relay 50 de-energizing the electromagnet and magnetron anode.