| 摘要 |
<p>A fixed surround (1) and trap door (2) are each made in one piece from medium and/or high density wood fibres and a bonding agent, compressed at high temperature and at least 40 mm thick, with the surround forming a stepped frame (3) round an opening. T The fixed surround (1) and trap door (2) are each made in one piece from medium and/or high density wood fibres and a bonding agent, compressed at high temperature and at least 40 mm thick, with the surround forming a stepped frame (3) round an opening. The surround has a flat surface (3A) to receive the trap door, which has a matching stepped outer surface (4), and there is a seal (5), preferably both sound resistant and intumescent, between the flat horizontal surfaces (3A, 4A) of the surround and trap door. Both surround and door can have a polymer coating, preferably 0.4 mm thick, and the door has locking catches that are accessible from the outside e.g. by a square key.</p> |
