Patent ID: 7268323

Claim:
A heat treatment apparatus comprising: at least a heat treatment chamber having an inlet and an outlet for a sheet in external wall portions at its two opposite ends; a gas inlet part for letting gas, which is a thermal medium, into the heat treatment chamber; a gas outlet part for discharging the gas out of the heat treatment chamber; and carrying means for running the sheet along a linear route connecting the sheet inlet and outlet within the heat treatment chamber, wherein said gas inlet part has nozzle boxes which blow out gas in a slit shape in a direction substantially orthogonal to the running direction of said sheet, whose lengthwise direction is arranged to be substantially orthogonal to the running direction of said sheet, and whose lengthwise size is greater than the width of the sheet, said nozzle boxes blow out gas having a uniformity of gas velocity fluctuating no more than ±25% in the lengthwise direction of the nozzles, said heat treatment chamber has blocking members which are extended between the external walls at the two ends of the heat treatment chamber and block the gaps between the side wall portions of the heat treatment chamber and the side walls of the nozzle boxes, and flow-rectifying lattices whose rate of aperture area is 70% or more, whose aperture pitch P is from 5 to 50 mm and whose height Z satisfies the condition of P≦Z≦10×P are installed within said nozzle boxes.