GB1234622A - - Google Patents

Abstract

1,234,622. Microwave heating. VARIAN ASSOCIATES. 26 April, 1968 [28 April, 1967], No. 19992/68. Heading H5H. A microwave heating apparatus comprising a plurality of parallel,preferably open-ended,waveguides 11 coupled together by apertures 13 in the walls near the end of the waveguides to provide a serpentine path for microwave energy wherein all of the waveguides have aligned horizontal slots 12 in their side walls to receive a workpiece, is characterized by conductive members 24, 26 which are positioned between the respective coupling apertures 13 and the open ends 22, 23 of each waveguide 11 to provide a short-circuit path for the electric field component of the microwave energy and thereby minimize reflections at the coupling holes and prevent leakage from the ends if open. The microwave apparatus is made in two identical sections, e.g. an upper section comprising a set 34 of half waveguides and a lower section comprising a set 36 of half waveguides. As shown, the conductive member 24 comprises a pair of longitudinal extending parallel strips 37, 38 and the member 26 a similar pair of strips 39, 40. These strips are secured by nuts and bolts 64, 66 to bridge the side walls of the waveguides and extend the length of the apparatus. The position of the strips relative to the length of each waveguide is adjustable, the bolts 66 being adjustable in slots 113, 114. To allow for variations in dielectric strength of material as it is heated in passing from one end of the apparatus to the other, the pairs of strips 37, 38 and 39, 40 converge slightly. Alternatively, the waveguides could have individual short circuiting conductive members 24, 26. Each set 34, 36 of waveguide halves is mounted on two U- shaped channels 49, 57. Energy may be injected anywhere into the waveguide but as shown a magnetron 14 is coupled by means of an H-plane T-junction 18 to one end of the outer waveguide. A similar T-junction 18<SP>1</SP> terminated in a dissipative water load 21 is provided at the opposite end to prevent reflections. Plenums 29, 32 on opposite sides of the apparatus are provided so that drying air may be passed by means of a series of pumps 31 through the waveguides and out via exit ports 33. The apparatus is used to dry continuous flowing paper sheets.