Importance

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Abstract

A tunnel oven contains a plurality of transversely extending radiant heating elements 17, 18 arranged at intervals along the length of the oven 1, the oven 1 being provided with conveyor band 10 for transporting material to be heated through the oven radiant heating elements 17, 18 supplying thermal energy, a sensing tube 31, 32 which extends within the oven 1 over a part of the length of the oven 1 that contains at least two radiant heating elements 17 or 18 that are spaced from each other along the length of the oven 1, the sensing tube 31 or 32 being arranged to absorb radiation from the said at least two heating elements 17 or 18 with pump 34 for causing a liquid to flow through the sensing tube 31 or 32 at a controlled rate with thermocouple junctions 35, 36 for producing a signal that provides a measure of the temperature increase of the liquid resulting from its passage through the sensing tube 31, 32 within the oven, and control means 29, 30 and with processor 29 and valve controller 30 arranged to control the rate of emission of radiant heat by a radiant heating element or elements 17, 18 in accordance with the signal.

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First Claim