Valveless pneumatic hammer

Abstract

A valveless pneumatic hammer comprising a backhead assembly at one end of a hollow casing and a bit assembly at the other end of the casing, a rod extending into the casing and having a passage out to atmosphere at the other end of the assembly, a chamber divider in the backhead end of the casing having a control rod projecting into the casing, a piston having a large bore in one end and a smaller bore end and the larger bore end being adapted to cooperate with the chamber divider end for the sealing of the larger bore, the piston reciprocating between a first position with the smaller bore end against the bit assembly, and a second position with the piston displaced towards the backhead assembly, a first chamber with the piston in the first position, a second chamber with the piston in the second position, first and second fluid supply paths through the backhead assembly, between chamber divider walls and the casing wall, first and second fluid exhaust paths from the first and second chambers, respectively out into atmosphere, and a second fluid exhaust from the second chamber out to atmosphere, wherein the hammer is characterized by the chamber divider and the backhead assembly being integral and at least one passage formed between the casing wall and the piston, in the first piston position, in the first fluid supply path includes a concentric, annular recess in the middle region of the casing wall and the outer surface of the piston includes a first fluid passage from the backhead end thereof to a position adjacent the middle region thereof and a second fluid passage from a position adjacent the middle region thereof, remote from the first fluid passage, to the bit end thereof.