Pilot Drilling Control Limited

Malcolm Adrian Abbott

George Swietlik

Within a longitudinally-extending main housing having a longitudinally-extending duct, an indexing mechanism comprises a mandrel within the duct and capable of longitudinal movement relative to the main housing; a cam sleeve rotatable with respect to the mandrel but constrained in terms of longitudinal movement with respect to the mandrel, the cam sleeve having an external surface provided with a groove in the form of a closed loop; a cam follower resiliently urged into the groove of the cam sleeve; a main spring tending to urge the mandrel in a first direction along the duct; and a fluid abutment face, on which, in use, fluid under pressure can act to tend to urge the mandrel in a second direction opposite to the first direction; the groove having ramps and associated steps thereby restricting relative movement of the cam follower with respect to the groove, to one direction progressively around the closed loop; the groove having a plurality of rest positions at which the cam follower can rest, depending on which of the force of the main restoring means and the force of the fluid pressure dominates the other.

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Halesworth, United Kingdom

Malcolm Adrian Abbott