Patent attributes
The invention relates to apparatus for use in wellbores and particularly, but not exclusively, to circulating subs used during downhole drilling operations. The apparatus includes a control groove and a pin received within the control groove for determining whether or not a longitudinal movement of a piston in a given direction relative to the apparatus body will move the apparatus between open and closed configurations. The apparatus further includes a control member located between and movable relative to the body and the piston. The control groove is defined in one of the piston and control member, and the pin is provided on the other of the piston and control member. Means are also provided for constraining movement of the piston relative to the body to longitudinal movement only. The invention thus provides an apparatus which has improved reliability in moving between open and closed configurations.
