| 摘要 |
The core is of multi-part construction. By axial sliding of at least one of its parts (224) relative to the others, the cross sectional area of the core is reduced. Preferred features: The core includes a blunt pyramidal inner component (224). External surfaces of the four outer sections (226, 228, 230, 232) form the core casing. Outer components and inner component are locked together by guides, especially of dovetailed cross section, which allow them to slide relatively, in mutual contact. Opposite outer components are symmetrical. Adjacent sides of outer components are slanted in the axial direction. During axial sliding, first and second outer components move inwardly or outwardly, relative to the third and fourth outer components. To remove the core from a molding, first the inner section is withdrawn axially, moving the outer sections inwardly on the guides. On further withdrawal, first and second outer sections can be removed together, simultaneously moving third and fourth outer sections inwardly, on the guides. Thus the entire core is withdrawn axially without contacting the channel walls. |
