| 摘要 |
PURPOSE:To stabilize tube elements, located at the opposite side of a tank, more surely and permit the maintenance of an uniform pitch at all times, by a method wherein a connecting section, having recesses and protrusions alternately along the peripheral rim of a forming plate, is provided on the forming plate at the opposite side of the tank while the ends of the neighboring tube elements are abutted against the connecting section at the opposite side of the tank. CONSTITUTION:Tube elements are abutted against a connecting section 15 at the opposite side of a tank. The other end of a forming plate 3 is bent toward the side of fins 2 and a multitude of recesses 16 and protrusions 17 are formed alternately along the peripheral rim of the plate 3 to form the connecting section 15. The arrangement of the recesses 16 and protrusions 17 are formed asymmetrically in the upstream side and the downstream side so that the position of the recesses 16 before conversion is positioned at the protrusions 17 after conversion by converting the upstream side of the forming plate to the downstream side of the same. According to this constitution, the opposing connecting sections 15 are abutted against each other at a part where the recesses 18 are changed into the protrusions 17 and the recesses 16 of one connecting section 15 are engaged with the protrusions 17 of the connecting section 15 under a condition that the pawls 17a of the protrusions 17 are superposed on the recesses 16 of the connecting section 15.
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