Fluid operable hammer

In a fluid operable impactor assembly wherein a hammer piston is axially movably carried within an elongated bore and is reciprocable therewithin by means including fluid means for supplying hydraulic fluid into a portion of said bore to alternately displace and be displaced by said piston and exhaust fluid receiving means for receiving hydraulic fluid exhausted from said impactor assembly, the improvement comprising:

• said exhaust fluid receiving means including a variable volume exhaust chamber maintained in intermittent fluid communication with said portion of said bore and having a minimum volume and a maximum volume wherein the differential volume between said minimum and said maximum volumes is substantially no less than the displacement of said piston within said portion of said bore.

In an impacting assembly in which a hammer piston is reciprocably movable through alternate work strokes and return strokes within an elongated bore of a body member with the return strokes being effected by hydraulic fluid which is selectively supplied to a variable volume return chamber formed in the bore in conjunction with one axial end of the hammer piston and the work strokes being effected by a drive system operable to accelerate the hammer piston in an axial direction to decrease the volume of the variable volume chamber, and wherein a valve means includes a movable valve member which is selectively movable to a first position to permit the supplying of hydraulic fluid to the variable volume chamber to effect a return stroke and subsequently to a second position to permit an exhaust fluid receiving chamber in the body member to receive hydraulic fluid from the variable volume chamber thereby permitting the drive system to effect a work stroke, the improvement comprising:

• integral means carried by said valve member and movable therewith to discharge hydraulic fluid from said exhaust fluid receiving chamber during movement of said valve member from said second to said first position.