| 摘要 |
A device for stretching reinforcement strands 11, 52 in concrete constructions comprises a cylinder 16, 62 and a cooperating piston 17, 57 and the device is provided with members 22, 67 designed to enable the cylinder to be filled with pressure gas produced by the burning of gun powder 23, 68, or similar means. The device can be arranged so that either the piston or the cylinder is movable and the choice of size and composition of the gun powder batch enables the device to be used both for an introductory stretching, often carried out in several stages, and for a final pressure shock. The device is provided with members for defining the stroke length of the piston and can be formed with an accumulator 15, in which combustion takes place, the device being provided with members 32, 33 for, according to requirement, making the gunpowder gas act upon the piston. <IMAGE> |
