Abstract: A portion of a drill assembly operated by a supply of compressed fluid comprises a backhead, a cylinder portion, a hollow elongate wear sleeve and a piston. The backhead has a proximal end connectable to the supply, an axial bore and an open distal end having an integrated cylinder portion defined therein. The backhead has passages extending between the axial bore and the outer surface of the backhead. The cylinder portion is aligned with and in selective fluid communication with the backhead. The hollow elongate wear sleeve surrounds the cylinder portion and is connected to the backhead. The piston is housed by the wear sleeve and has a proximal end shaped to fit within the cylinder portion. The piston is slideably movable along the wear sleeve and the cylinder portion in response to compressed fluid conveyed through the backhead. When the drill assembly is in a drop open position, the proximal end of the piston is radially spaced apart from a nearest surrounding surface.

Abstract: In representative embodiments, a backhead for a drill assembly comprises an elongate member having a proximal end connectible to a source of pressurized fluid, a side wall defining an axial bore and an open distal end. A portion of the bore extending proximally from the distal end has an inner surface defining a cylinder portion shaped to receive an axially movable piston. The axial bore also comprises a check valve receiving area shaped to receive a check valve and to separate, during normal operation when a check valve is received in the check valve receiving area, an inlet area extending proximally to the proximal end from the cylinder portion extending distally to the distal end. Various improvements in retaining the distributor and increasing flow efficiency are described.

Abstract: In representative embodiments, a backhead for a drill assembly comprises an elongate member having a proximal end connectible to a source of pressurized fluid, a side wall defining an axial bore and an open distal end. A portion of the bore extending proximally from the distal end has an inner surface defining a cylinder portion shaped to receive an axially movable piston. The axial bore also comprises a check valve receiving area shaped to receive a check valve and to separate, during normal operation when a check valve is received in the check valve receiving area, an inlet area extending proximally to the proximal end from the cylinder portion extending distally to the distal end. Various improvements in retaining the distributor and increasing flow efficiency are described.

Abstract: A portion of a drilling tool having a drill bit driven in a rotating motion and in an axial percussion motion comprises a keyed connection between the drill bit and a driver sub that receives the drill bit. The keyed connection comprises a transverse member coupling the drill bit to a driver sub having a bore within which the drill bit is received. The driver sub has a pair of opposed openings and the bit has an axial slot. The openings and the slot are dimensioned to receive the transverse member. The keyed connection transmits force to the drill bit to drive the drill bit during operation and removably secures it in the driver sub.

Abstract: In representative embodiments, a backhead for a drill assembly comprises an elongate member having a proximal end connectible to a source of pressurized fluid, a side wall defining an axial bore and an open distal end. A portion of the bore extending proximally from the distal end has an inner surface defining a cylinder portion shaped to receive an axially movable piston. The axial bore also comprises a check valve receiving area shaped to receive a check valve and to separate, during normal operation when a check valve is received in the check valve receiving area, an inlet area extending proximally to the proximal end from the cylinder portion extending distally to the distal end. Various improvements in retaining the distributor and increasing flow efficiency are described.