GB821075A - Improvements in and relating to screw jacks - Google Patents

Abstract

821,075. Tensioning wires. SPEEDACC CO. Ltd. Jan. 15, 1958 [Feb. 6, 1957], No. 4113/57. Class 45. [Also in Group X] A wire tensioning screw jack having a wire grip has means for indicating the wire tension ; the means being actuated by the deformation of a part of the jack subjected to the tension applied to the wire. The jack comprises a ram 3 engaged by a nut 2 rotatably mounted on the jack body 4. The grip comprises jaws 11 sliding within inclined bores in a member 10 carried by a rod 5, the jaws being biassed to the closed position by a spring 12. The rod 5 is the part subjected to the tension applied to the wire, and carries at the upper end a casing 8 containing the tension indicator 9 which is connected by means of a rod 7 to the lower end of the rod 5. Before tensioning a reinforcement wire 14, extending through concrete 21, a thrust plate 15, a gripper sleeve 17, a pressure tube 18 and a disc 19 are arranged about the wire. The jack carrying an axially movable heavy ring 13 is then positioned above the wire with the wire engaged between the jaws 11. The nut is rotated to raise the ram which engages the casing 8 to lift rod 5 to cause the jaws to grip the wire which is then tensioned by further rotation of the nut. The pressure exerted by the jack and tube on the gripper sleeve during tensioning of this wire causes the gripper sleeve to grip the wire. When the required wire tension is reached the nut rotation is stopped and the disc 19 is struck by the ring 13 to thrust the gripper sleeve into further gripping engagement with the wire. The rotation of the nut is reversed to free the jaws, the jack, pressure tube and disc are removed from the wire, the free end of the wire is cutoff, and the end of the wire is burred over the upper end of the sleeve.