| 摘要 |
An attic inlet has a square tube to communicate between an attic and a room through a substrate, and a lid to permit airflow through the inlet when open, and prevent it when closed. The lid is moved by an upper pull bar and lower connecting bars attached to the lid. Upper pull bar and lower connecting bars are attached by clevis pins to yoke arms pivoting about parallel axles. Movement of the upper pull bar rotates the yoke arms, and so lowers the connecting bars and the attached lid. Springs urge pull bar and lid into closed default position, while a cord is used to displace pull bar and lid into open position. The lid is attached by tabs on the connecting bars passing through the lid, and lid locking bars engaging apertures in the tabs. |
