| 摘要 |
<p>A one-piece, unitary, molded resin wall sleeve precursor has two cup-shaped end sections (11,21) of external diameter D1 each having a hollow transition section (15,25) of enlarged diameter that connects the end section to a sleeve (31,32) 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 (11,21); the precursor members can then be joined with a strong, inexpensive, welded joint to afford a long wall sleeve of consistent internal diameter. <IMAGE></p> |
