Electropneumatic hammer

Claim 1

An electropneumatic hammer arranged to impart a rotary and impacting action on a tool, comprising a housing, cylinder positioned within said housing forming an axially elongated bore having a forward end and a rearward end, a tool carrier mounted on and in communication with and extending forwardly from the forward end of the bore in said cylinder and arranged to hold a tool therein in an operating position, a striking piston mounted within and axially displaceable through the forward end of said cylinder into said tool carrier for imparting an impacting action to a tool positioned in the operating position in said tool carrier forwardly of the forward end of the bore in said cylinder, a driving piston positioned within and axially displaceable within the bore in said cylinder at the rearward end thereof, said driving piston being spaced rearwardly from said striking piston for forming an air cushion therebetween for transmitting the reciprocating action of the driving piston to said striking piston, means for reciprocating said driving piston within said cylinder so that through the medium of the air cushion therebetween said striking piston moves forwardly and rearwardly and in its forward motion strikes the tool in said tool carrier, the forward movement of said striking piston through the forward end of said bore into said tool carrier is limited by the tool positioned within the operating position in said tool carrier, openings in said cylinder communicating with the bore therethrough are located in said cylinder so that during impacting action said striking piston is restrained by the tool in said tool carrier from moving forwardly into the bore to the extent that the air cushion is exhausted through the openings in said cylinder whereby the air cushion is maintained between said striking piston and driving piston and, when the tool is not in the operating position within said tool carrier, said striking piston can move forwardly through the forward end of the bore in said cylinder into said tool carrier to the extent that the air cushion is opened to the opening in said cylinder and is no longer maintained between said striking piston and driving piston, wherein the improvement comprises means located within said tool carrier in the path of movement of said striking piston for securing said striking piston against axial movement when the opening in said cylinder communicates with the space between said striking piston and said driving piston for releasing the air cushion therebetween and for releasing said striking piston when a tool is inserted into the operating position within said tool carrier, said means being arranged to engage said striking piston frictionally and to hold it in position spaced forwardly of said driving piston so that the opening in said cylinder communicates with the space between said striking piston and driving piston, said striking piston having an axially extendIng section displaceable through the forward end of said bore in said cylinder into said tool carrier when a tool is not in the operating position in said tool carrier, said means comprises a ring located in said tool carrier contiguous to the forward end of the bore in said cylinder so that when a tool is in the operating position in said tool carrier the leading end of said axially extending section of said striking piston can pass through said ring in contact free relation for imparting an impacting action against the tool located within said tool carrier, said axially extending section of said striking piston has a cylindrically-shaped part spaced rearwardly from its leading end and said cylindrically-shaped part has a diameter greater than the diameter at the leading end of said striking piston, the interior surface of said tool carrier is shaped to provide an annular shoulder immediately forward of said ring and arranged to contact the rearward end of the tool and to define its operating position, said ring is a split ring formed of metal and is radially expandable, in the unexpanded state said split ring has an inside diameter less than the diameter of the cylindrically-shaped part of said axially extending section of said striking piston so that the inside diameter surface of said ring frictionally engages the cylindrically-shaped part of said axially extending section of said striking piston rearwardly from its leading end for securing said striking piston against axial movement, said tool carrier has a recess in its end contiguous to the forward end of said bore in said cylinder for receiving said ring, the surface of said recess extending in the axial direction has a frusto-conical configuration with the frusto-conical surfaces diverging in the direction toward said cylinder, the outer surface of said ring has a frusto-conical configuration and is arranged to correspond to and to seat in closely fitting engagement against the frusto-conical surface in said recess, the end of said striking piston extending axially forward from the cylindrically-shaped part of said axially extending section thereof and which extends into said tool carrier is beveled forwardly from said cylindrically-shaped part to the leading end of said striking piston which contacts said tool carrier with said beveled surfaces arranged in converging relationship toward the end of said striking piston which impacts against the tool, and the end portion of the inner surface of said ring closer to said cylinder is correspondingly beveled to permit said striking piston to extend into contact with a tool in the operating position in said tool carrier without frictional contact between the cylindrically-shaped part of said axially extending section of said striking piston and said ring during normal operating conditions.