GB606058A - - Google Patents

Abstract

606,058. Bore-hole apparatus. DEHN, S. G. (Grant Oil Tool Co.). Jan. 9, 1946, No. 819. [Class 85] A well tool of the expansible cutter-type him a hollow tubular body 11, having formed in the wall a number of slots 20 in which cutters 21 slide radially, each having wedge surfaces 26 and 27 formed on the inner face. These surfaces abut wedge surfaces of plungers, both capable of axial movement relative to each other. The plunger 29 slides along a wash pipe 31 welded to the plunger 28, water-tight connections being formed between the wash pipe and the plunger 29 and between the plungers 28, 29 and the casing. A spring formed of two elements 38a and 38b normally keeps the cutters in the retracted position during lowering and raising of the tool whilst they are expanded by fluid pressure acting on the outer ends of the plungers. The pressure is built up, due to a constriction 18 in the flow passage between the bore of the body and a pilot cutter 19. In one modification the portions of the spring are normally in the expanded position. Another modification is that the passage is reduced by a holed bush so that the restriction of flow and subsequent increase in fluid pressure is independent of the tool at the end of the body 11.