| 摘要 |
913,181. Making prestressed panels; stretch forming. FROMSON, H. A. May 9, 1961 [May 10, 1960], No. 16837/61. Classes 83 (2) and 83 (4). A method of making a structure composed of a panel 10 extending between frame members 11 comprises fixing the frame members 11 in relationship to each other, providing the panel 10 with inflatable portions 13 between the side edges which are secured to the frame and then inflating the panel until it is placed in tension between the side edges whilst maintaining the fixed distance between the frame members to form a prestressed reinforced panel. In a modification, a sheet metal panel 21 comprises unbonded internal surfaces 22, an arched centre portion 23 and flanges 24 which are clamped between strips 25, 26 and attached by means of bolts 29 and nuts 30 to a former 28 having a raised centre portion 31 of wood, plaster or other suitable material. The panel is inflated to produce the tubular forms 32 and the resulting contraction of the panel draws it tightly on to the former, preventing further expansion of the panel at the contacting points and causing the surfaces to be expanded non-uniformly along their length. Alternatively, the tube portions of the panel may be initially fully inflated for their whole length and the panel drawn down on to the former by clamping strips causing the expanded portions to collapse and produce the required form and prestressing. Specification 816,979 is referred to. |
