| 摘要 |
A riser sleeve comprises a sleeve body (1) and a lost pattern fit into the sleeve body to pass through a side wall thereof. The lost pattern (3) is shaped to enable casting, integrally with the riser cast by the sleeve body, of a projecting portion (8) capable of receiving a wedge blade of an openable wedge blade type riser breaker. Even a top riser (6) can therefore be broken off the main casting (7) at a neck portion (9) by an opening force applied to the wedge blades of the riser breaker, without use of a special jig. <IMAGE> |
