| 摘要 |
A fireproof trap door particularly for an attic, consists of a metal casing, open top and bottom, enclosing the fireproof material (8), and closed on the underside by a sheet metal tray (5), half being shown in the drawing. This door, when closed, fits inside a metal frame which is S shaped in section. The upper edges of the tray are folded back, inwards, at a sharp angle (10) to penetrate into the top surface of the fireproof material, retaining it. The sharp edge of this folded back portion also embeds into a layer of fireproof material (12) under the top flange of the S section. The horizontal bottom flange of the S section supports a further layer (4) of fireproof material, insulating the surrounding ceiling from the frame. |
