| 摘要 |
PURPOSE:To make it hard to develop internal stress and especially make it possible to shrink just after the outsert molding of a long rack gear or the like by a method wherein the rack gear to transform a rotary motion into a linear motion is molded integrally with a thin metal sheet so as to be allowed to shrink in a longitudinal direction. CONSTITUTION:A thin metal sheet 10 has one positioning hole 11 and a plurality of elongated holes 12-19, one corner of each of which is square and the other corner is curved [a square cornered hole has a mark (a) at the end of the hole numeral and a curved cornered hole has a mark (b)]. As an outsert molded item, a rack gear 20 is constituted in such a manner that the elongated holes 12a-19a are not molded since the struts of a mold are formed in said holes. On the other hand, the elongated holes 12b-19b are molded so as to act as anti-rotation catches. Accordingly, the rack gear 20 constituted in a mold extends as far as to the end face 10a of the thin metal sheet, resulting in allowing to shrink to a gear form through the shrinkage after molding. In other words, the sizes of the struts of the mold are formed larger in the order of 19a>12a and, after the shrinkage, 12a-19a are left in the form of the holes, which have nearly the same size with one another. Consequently, internal stress is hard to be applied to the rack gear through shrinkage. |
