| 摘要 |
The plastic sheet in at least two edges is so formed that the edges can be retained by devices in corresponding frames so that it is stretched between these frames. The sheet is tight and has at least one edge strip (8). The devices (13) in at least one frame ar displaceable inwards and outwards from the panel outer edge. They hold the sheet tensioned by elastically pressing the sheet strip (8) against the frame bottom. The devices comprise a stiff strip (15) or several successively arranged stiff strips, the free edge(s) (16) of which can engage against the plastic sheet strip. This strip or strips can be at different distance(s) from the bottom of the frame along the frame length. |
