IMPROVED DOWNHOLE APPARATUS

摘要

The invention relates to apparatus for use in wellbores and particularly, bu t not exclusively, to circulating subs used during downhole drilling operation s. The apparatus (2) comprising a control groove (38) and a pin (not shown) received within the control groove (38) for determining whether or not a longitudinal movement of a piston (26) in a given direction relative to the apparatus body (4) will move the apparatus between open and closed configurations. The apparatus further comprises a control member (52) locate d between and movable relative to the body (4) and the piston (26). The contro l groove (38) 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 (48, 50) are also provided for constraining movement of the piston (26) relative to the body (4) to longitudinal movement only. The invention provides apparatus whi ch has improved reliability in moving between open and closed configurations.