Patent ID: 6425449
Filing Date: 2002-07-30
Classification: E21B

Abstract:
A drilling head assembly having an axially extending central axis and being axially movable in a drill string having an inner peripheral surface to a position adjacent to the bit end of the drill string to latchingly engage a drill string latch seat and being retractable through the drill string in a direction outwardly of the bit end, comprising an axially elongated latch body having an enlarged diametric portion providing a latch body shoulder, a fluid bypass channel that includes an axially extending bore, a first port opening radially outwardly axially outwardly of the enlarged diametric portion and opening to the bore and a second port opening radially outwardly axially inwardly of the enlarged diametric portion and opening to the bore axially inwardly of the first port opening to the bore, annular resilient fluid seal means mounted to the latch body axially intermediate the radially outwardly opening of the first port and the radially outwardly opening of the second port, the maximum outer diameter of the annular seal means being greater than the maximum outer diameter of the enlarged diametric portion, a latch assembly mounted to the latch body for movement between a latch seated position and a latch retracted position, spring means acting between the latch body and the latch assembly for constantly resiliently urging the latch assembly toward its latch seated position, retractor means mounted to the latch body for limited axial movement relative to the latch body between an inner latch seated position and a retracted axial outer position to retract the latch body, said retractor means extending axially outwardly of the enlarged diametric position and including an overshot coupling device, and valving mechanism for controlling fluid flow through the bypass channel.