GB1458592A - Pipe extraction apparauts - Google Patents

Abstract

1458592 Pipe extraction apparatus BRITISH GAS CORP 18 April 1975 [19 April 1974] 17171/74 Heading F2P [Also in Division E1] Apparatus for extracting buried pipes from surrounding material comprises a plurality of gripping devices connected at intervals along a rod, or alternatively a rope or cable, such that the rod can be freely threaded into the pipe and by exerting a force on the rod in one direction the gripping devices can be operated to grip the inner surface of the pipe to enable the pipe to be extracted, while force exerted on the rod in the opposite sense causes the gripping devices to disengage so that the apparatus may be removed from, or repositioned within, the pipe. In a preferred embodiment each gripping device comprises a support member 1 formed with diametrically opposed inclined ramps 2 supporting toothed gripping pieces 3 slidably connected thereto by mutually engaging grooves and tongues formed respectively on the gripping pieces 3 and ramps 2. A resilient plastics actuating means 8 is slidably supported on a cylindrical section 7 of the support member 1 and incorporates external annular ribs 10 and flexible members 11 which abut the gripping pieces 3 such that, when a force is applied to the support member 1, through rod sections 14 interconnecting the gripping devices, in the direction of arrow A in Fig. 2 the ribs 10 slide freely on the inner surface of the pipe and the gripping pieces 3 are in a non-gripping position as in Fig. 2. When, however, a force is exerted on the rod in the direction of arrow B in Fig. 3 the ribs 10 frictionally engage the inner wall of the pipe and the support member 1 moves in the direction of the force having the net effect that the gripping pieces 3 slide along the ramp 2 and grip the pipe wall as in Fig. 3. After extraction a subsequent force on the rod in the direction of arrow A will restore the apparatus to the state shown in Fig. 2 whence it may be repositioned or removed from the pipe.