| 摘要 |
<p>In a door frame (1) consisting of a core (2) of rigid non-metallic material and a metal covering (3), e.g. of extruded aluminium, the new feature is that the core (2) consists of medium-hard compacted wood-fibre material, e.g. of the quality 'MDF' ('Medium Density Fibreboard'). In this manner, an improved fire protection is achieved compared to what is achieved with a door frame, in which the core consists of e.g. pinewood, at the same time as the tendency of the frame to warp has practically disappeared.</p> |
