Patent GB-1218674-A (GB)
Title: Improvements in or relating to the prestressing of concrete structures
Inventor: DYKMANS MAXIMILLIAAN J
IPC: B28B21/64
Filed: 1969-03-27
Abstract: 1,218,674. Coiling helices; tensioning. M. J. DYKMANS. 27 March, 1969 [2 April, 1968; 3 April, 1968], No. 16147/69. Heading B3E. [Also in Divisions F2 and G3]  Apparatus for laying wire under controlled tension in the pre-stressing of concrete structures such as reservoirs, nuclear reactor housings, pipes and pressure vessels comprises a carriage, means whereby the carriage can be driven along a surface whilst receiving the wire from a supply and feeding means on the carriage for releasing the wire to the surface and wherein means are provided for sensing a condition and for varying the relation between the linear rate of feed of the wire and the rate at which the carriage is driven along the surface. In an embodiment the apparatus comprises a stationary chain C encircling the wall W of a concrete structure T the chain being used to propel a wheeled carriage 7 around the wall. The chain passes over guide sprockets 2, 3 a spring- loaded tensioning sprocket 4 a drive sprocket 22 driven by an hydraulic motor 30 and a sprocket wheel 20 on a shaft 20A. The wire S extends from a supply reel (not shown) to and around a drum 21 and then to the wall W. The wire is spring-urged against the drum by a device 6. The drum has a sprocket wheel 21B connected to a sprocket wheel 42 by a chain 41. The wire S is tensioned and stretched as a result of the lineal speed of the carriage 7 being greater than the rate at which the wire is laid on the wall. The hydraulic motor 30 which drives the carriage also drives the drum through a differential gearing 82 and a torque transducer 100 (Fig. 2) which actuates a servo system 93 controlling a motor 92 which rotates the ring gear 89 of the differential gearing to vary the rotational speed of the carriage drive sprockets and the drum. Instead of using the torque transducer 100 to maintain the wire tension at a constant value the servo system 93 may be actuated by a potentiometer 50 having a movable roller 51 engaging the wire between fixed rollers 52, 53. In another embodiment the drum sprocket wheel is coupled to an hydraulic motor 61 acting as a pump (Fig. 3) and another hydraulic motor 60 is coupled to the drive of the carriage. A torque transducer 72 actuates a serve system 74 which energizes a pump 70 which delivers fluid to motor 60. The motor 61 acting as a pump supplies fluid to motor 60 to tend to increase its speed and this acts as a brake, the extent of which is determined by the torque transducer. A further embodiment comprises a variable gear transmission incorporating a differential speed motor and hand wheel for controlling the relative speeds of the drum and chain sprocket wheel. Inanother embodiment the stress sensed in the: torque transducer 100 or potentiometer 50 controls the fluid pressureactuating the rams in a segmental expanding drum which maintains a constant tension in the wire. The wire gripping drum may also be of conical form. Also thecarriage driving chain C may be dispensed with and the carriage driven by the wire itself. In a further embodiment the wire is clamped between jaws 135, 136 (Fig. 6) actuated by a bell-crank lever 161 hydraulically operated by the potentiometer 50, to control the wire tension. The carriage 7 is supported for vertical adjustment in a movable framework comprising two trussed end sections 201, 203 (Fig. 7) and an open centre section 202 within which the carriage may move vertically on cables 210 (Fig. 8). In another embodiment (Fig. 11) the speed of the wire corresponds to the speed of metering wheels 330 and the speed of the carriage by the wheel 333 which travels round the tank. The wheel 333 is geared to one side of a differential system 362 and the wheel 330 to the other side via an electrical switch coupling 372. The ring gear of the differential system is geared to a manuallyoperated variable speed drive device 386 which, is also geared to the drive shaft 358 from the wheel 333.- The coupling 372 indicates by lamps any fluctuation of the difference in' speed between the shafts 371 and 373 and the operator can then restore the conditions by adjustment of the device 386. The differential speed control means 338D may be adjusted automatically using a servo system. 440 to adjust the speed of the wire drum 338 in relation to the speed of travel of the carriage 310 around the tank and the wire feed out. The servo system may control the speed of a motor driving the ring gear of the differential gearing thus controlling the relative speeds of sprocket wheels 322 and 338E: