Positive latch core barrel apparatus

Abstract

The drilling apparatus includes a wire line core barrel inner tube assembly movable to a drill string bit end to have its landing ring seat on the drill string landing shoulder and its latches latchingly retain the assembly adjacent the bit end. The assembly includes a fluid bypass channel in a latch body, fluid retention mechanism movable in the latch body to a fluid restriction position to maintain a head of fluid in the drill string even when drilling into a fractured earth formation and an axial outer-open position, a retractor for retaining the latches fully retracted as the assembly moves inward and after the latch body seats on the shoulder, retain the retention mechanism to provide a higher pressure signal than in the restriction position until both latches are in their latch seated position, and thence moves to retain them in their seated position until the retractor is moved outwardly and an overshot coupling device axially movable relative to the retractor and the latch body to through the retractor, move the retention mechanism toward its open position prior to retracting the latch body outwardly of the landing shoulder. The assembly also includes a hollow spindle bearing subassembly fluidly connecting a core receiving tube to the bypass channel to permit more rapid descent of the assembly in the drill string and a valve ball to prevent inward fluid flow through the subassembly.