| abstract |
A metal plate (40) for use in producing a flat tube comprising a pair of flat walls opposed to each other, two side walls interconnecting opposite side edges of the two flat walls, and a plurality of reinforcing walls interconnecting the flat walls, extending longitudinally of the tube and spaced apart from one another by a predetermined distance, nthe metal plate (40) comprising two flat wall forming portions (12;13) connected together by a joint portion (11), a plurality of reinforcing wall forming portions (14;15) upwardly projecting from each of the wall forming portions (12;13) integrally therewith, and a side wall forming portion (16;17) formed at each of opposite side edges of the plate and upwardly projecting therefrom integrally therewith, the joint portion (11) having a larger thickness than the flat wall forming portions (12;13). |