| 摘要 |
IMPROVEMENTS IN OR RELATING TO ROLL-UP AND OTHER RETRACTABLE DOORS, SHUTTERS, BLINDS AND THE LIKE Door re-inforcements are automatically positioned and removed by the door's closing and opening movements, respectively. A roll-up, sliding or retractable door is strengthened in its closed position by an arrangement of bars held in position by brackets on the door frame. The door, by its opening movement, progressively and sequentially catches and removes the bars to a location wherein they will not obstruct the doorway thereby opened. Conversely, the bars are progressively and sequentially replaced by the door's closing movement.
|
