| 摘要 |
A one-piece, unitary, molded resin wall sleeve precursor has two cup-shaped end sections of external diameter D1 each having a hollow transition section of enlarged diameter that connects the end section to a sleeve of internal diameter D1; one transition section has an outer diameter D2 and the other has an inner diameter just slightly larger than D2. D2 is appreciably larger than D1. A wall sleeve assembly of extended length is derived from two of these precursor members by cutting off the end sections; the precursor members can then be joined with a strong, inexpensive, welded joint to afford a long wall sleeve of consistent internal diameter.
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