GB903311A - Improvements in pipe jacks - Google Patents

Abstract

903,311. Hydraulic jacks. PASS & CO. Ltd., E. Dec. 28, 1960 [Sept. 29, 1959], No. 32955/59. Class 78 (3). To extract a service pipe from the ground its free end is clamped between jaws 34, 35, Fig. 1, in a cross-head 28, with the length of pipe passing through a slot in a back-plate 2 whereupon the crosshead is moved away from the backplate 2 by two hydraulic rams. As described, the rams 10, Fig. 4, are housed within tubes 1 to which plates 2, 3 are clamped by bolts 4. The heads 16 of the rams abut a W-shaped member 26 having locating plugs 29 therein. A spring 17 returns the two portions 11, 12 of the ram to the position shown in Fig. 4. The crosshead may be arranged to abut nuts 18 at the rear of the rams in which case the tubes 1 could be slotted to allow movement of the crosshead or alternatively dispensed with and small diameter tubes provided round the bolts 4. In a further embodiment hydraulic cylinders 50, 51, Fig. 6, are spaced apart by plates 54, 55 and 56. Rams 52, 53 move a crosshead 57 which carries a gripping device 59 on a boss 58. The jaws are closed by a spring-loaded member 67 mounted in a nut 65. The rams are of different diameters and a valve 70 of the type described in Specification 622,045 is provided, by means of which fluid can be admitted to either or both rams through passages within the plates 54, 56. To return the rams to the position shown, fluid is applied to the smaller diameter cylinder only. The rams in the first embodiment may be of different diameters and fluid may be supplied to either or both.