Patent GB-725042-A (GB)
Title: Method and apparatus for low power tensioned winding of concrete articles
IPC: E04G21/12
Filed: 1953-05-21
Abstract: 725,042. Winding reinforcements. CROM, J. M. May 21, 1953 [May 21, 1952], No. 14265/53. Class 20 (4). The reinforcing wires of concrete articles, such as a concrete pipe 21, Fig. 1, are prestressed as they are continuously applied to the article, the pipe 21 and a tapering drum 22 for paying out the wire being mounted on a common splined shaft 23 rotatable by a motor 24. The diameter of the drum 22 is chosen to be less than that of the pipe 21 so that the amount of reinforcing wire 20 paid out by the drum 22 as the shaft 23 is rotated. is less than the amount taken up by the pipe 21, the wire 20 being stressed accordingly. The wire 20, wound several times round the drum 22 and provided with an initial back tension to prevent the wire slipping round the drum 22, passes over wheels 26, 27, and is secured at one end of the pipe, the wheel 27 being advanced along a lead screw 28 as the pipe 21 is rotated. The degree of stress in the wire 20 increases or decreases, as the difference between the diameters of the drum 22 and the pipe 21 is made larger, or smaller. In practice it becomes difficult to select the correct size of drum for the desired stress and to overcome this a drum 22 of smaller diameter than is necessary to properly stress the wire, is selected, a torque regulating device in the form of a clutch, or brake, being incorporated in the drum to relieve the overstress and maintain the tension of the wire constant. A mechanical dry friction clutch is preferably used and, in order to prevent chattering, the clutch is arranged to slip several r.p.m. under the normal operating conditions to bring it into the range of dynamic friction. In a modification the pipe to be wound is mounted on rubber rollers, the weight of the pipe on the rollers developing sufficient friction for the pipe to be turned by the rollers against the pull of tensioned wire. The reinforcing wire is paid out to the pipe from a drum mounted on a trolley which moves on tracks at the side of the pipe and is advanced by a threaded shaft, the latter, and one of the rubber rollers, being connected for driving purposes to a splined shaft which drives the drum. To wind a pipe in a vertical position the pipe is mounted on a turntable which is chain driven by a motor, the reinforcing wire being paid out from a drum and passed between a pair of guide rollers which are progressively moved down the pipe as the wire is wound from top to bottom, on to the pipe. To wind a reinforcement wire round a large tank a chain 70, Fig. 10, placed in frictional engagement round the wall 72 of the tank, is arranged to mesh with a sprocket 73 driven by a motor, not shown, and located on a shaft 78 on a truck frame 74 movable on wheels 75, 76 round the tank wall 72. A drum 80, containing a brake assembly is mounted on the shaft 78, the reinforcing wire 84 being supplied by a roll 82. Since the drive sprocket 73 has a greater diameter than that of the drum 80 the rate of forward movement of the truck 74 will exceed the rate at which the wire 84 is paid out. Multiple wire stressing, e.g. for a road bed, is carried out by a car 90, Fig. 11, provided with flanged wheels which run on rails 92. A series of wire rolls 95, mounted on the frame 93 of the car, supply wires to drums 104, having a brake assembly mounted therein, drive sprockets 99 mounted on the ends of a shaft 97, which carries the drums 104, meshing with chains 100 for moving the car along the track. One end of each chain 100 is deadended at a point ahead of the car 90, the other end being connected to a tractor, winch, or other suitable device. Here again the drive sprockets 99 have a diameter which exceeds that of the drums 104 so that the wires are tensioned.