GB1212309A - Hydraulic jack for tensioning rods or wires in pre-stressed concrete structures - Google Patents

Abstract

1,212,309. Rod &c. tensioning devices. MAX PAUL & SOEHNE. 2 April, 1969 [28 May, 1968; 16 Aug., 1968], No. 17187/69. Heading F2G. An hydraulic jack for tensioning rods or wires in pre-tensioned concrete structures includes a device V having jaws 5 for anchoring a rod 2 in prestressed condition on an abutment surface or member 1, a device K having clamping jaws 21 for gripping the end of the rod, and a tensioning device for tensioning the rod by means of the clamping device, at least the anchoring and tensioning devices being actuated by hydraulic pistons 15, 28 slidable in cylinder chambers 29, 30, and wherein an anchoring piston 15 and pressure tube or piston-rod 16 is provided at least one part of which encircles the clamping device and is connected to an anchoring thrust body 17 removably arranged between the clamping device and anchoring jaws. As shown, the jaws 5 are displaceable by an anchoring ring 3 to engage with the rod 2, the jaws being acted upon by the thrust body 17 which is operated by the pressure tube 16 slidable in the jack housing 18 and integral with the piston 15. The latter is guided in a partition 11 connected to a cylinder 13 in which is slidable the tensioning piston 18. The clamping jaws 21, in a ring 23, are actuated by a piston 40 connected by piston-rod 27a with the piston 28; the piston 15 and return piston 27 operate in a common cylinder chamber 29. Changing of the jaws 21 is effected by unscrewing a nut 10 and drawing off the housing 18 so that the ring 23 may be screwed off the piston 27. In modifications (a) a compression spring disposed in a chamber in the piston 27 acts on the jaws 21, (b) a separate cylinder chamber is provided for an external anchoring piston 15 and the piston-rod 27a has a tubular extension projecting through the rear cover of the cylinder 13 and which is provided with a scale to indicate the amount of extension applied to a tensioned rod; the rod engages the cover by a key to prevent rotation of the clamping device, (c) an anchoring cylinder is formed at the forward end of the housing tube 9, and (d) the tensioning piston 28<SP>11</SP>, Fig. 7, is connected by an extension 67 to a piston base 68 provided with sets of spring biased clamping jaws 21, the jaws 5 being operated by hydraulic or spring-loaded pistons 71 and the anchoring piston 1511 being biased by a return spring 69 or by the use of an air chamber 70.