| 摘要 |
A single foil is biaxially stretched on a frame for movement relative thereto by being secured intermittently to a single rubbing strip over a guide ledge. The rubbing strip is stretchable and movable lengthwise of the associated frame side. Torsional forces arising because of the one-sided loading of the frame by the stretched foil are taken up by the frame which is made with a torsionally rigid cross-section. The single foil can be clamped without creasing and in a manner which ensures freedom from creasing notwithstanding differences in the heat expansion of the foil and frame. |
