GB912588A - Improvements in or relating to hydraulic pre-stressing means for reinforced concrete - Google Patents

Abstract

912,588. Strainers. PAUL, O., PAUL B., and PAUL, E., [trading PAUL & SOHNE MASCHINENFABRIK MAX.]. Feb. 9, 1961 [Feb. 9, 1960], No. 4797/61. Class 45. A hydraulic press for tensioning a reinforcing rod 3, in a concrete structure comprises, a double acting piston 42 of an anchoring device 4 which when actuated in one direction serves to force wedges 41 into a seating to anchor the rod 3 to the concrete structure, a tensioning device 5 actuated by a piston 51 and rod gripping device 6 attached to the tensioning device between the tensioning device and the anchoring device 4, the gripping device 6 including a head 61 carrying jaws 63 in a conical seating for actuation by a piston 64, the arrangement being such that over at least the initial part of the tensioning stroke, movement of the piston 42 in the other direction causes it to bear upon the jaws 63 and thereby supplement the action of the tensioning device 5. The press may be adapted to tension several rods simultaneously. The hydraulic operating system Fig. 4 (not shown) includes three remotely electrically controlled valves, opening of two of which effect tensioning movement of the tensioning device and alternate opening of the other of which effects anchoring of the tensioning rod to the concrete structure, release of the rod gripping device 6, and return of the tensioning device 5 into position in readiness for a further tensioning stroke on the same rod if necessary. The hydraulic stem also includes appropriate pressure control valves, non return valves and excess pressure valves.