| 摘要 |
PURPOSE:To obtain a mold, in which crack is hard to develop even in repeated use and consequently which has long service life by a structure wherein a first split mold has a notched part for cutting off at least the tips of tooth space forming parts at the terminal part of each tooth form, which terminates in other end face of a tooth form core art and at which the width of tooth face decreases gradually. CONSTITUTION:A first split mold 1 consists of a tooth form core part 11, in which tooth forms with twisting angle are formed on the inner peripheral surface, and the end surface part 12 of the tooth form core part 11. At the terminal part, at which the tooth space forming parts 14 on the inner peripheral surface of the tooth form core part 11 terminates in the parting face of the mold 1, an annular notched part 13 is formed round the inner peripheral surface. The first split mold 1 and a second split mold 2 are clamped together so as to pour molten resin or the like into a cavity formed by the clamping of the molds. Because no sharp edge emerges owing to the notched part, the abutting of the sharp edge parts against the second split mold at the clamping of the molds is prevented from occurring. Accordingly, the cracks due to the fatigue of metal by the mold clamping stress in repeated use is prevented from developing and consequently the service life of the mold is strikingly lengthened. |
