Abstract The piston (2) of a hydraulically operated percussion implement moves jointly with a juxtaposed distributor (3) in a cylinder bore to strike a tool (16) seated in the lower end of that bore. The admission of high-pressure oil to a space (11) adjacent a rear face of the piston is jointly controlled by the distributor and by a valve (20) inserted between that space and an inlet port. The distributor has an enlarged head (3a) which overlies a fluid cushion in an annular recess (10) communicating with an expansion chamber (9) in the piston, this chamber being defined by an axial bore (6) and a stationary plunger (7) entering same. One or more pushers (12) under oil pressure bear upon the distributor to depress it, in the wake of the piston, after the latter has begun its descent and causes the application of high pressure to a space (11a) above the distributor. The descent of the piston enlarges the expansion chamber (9) which thereby draws part of the oil from the annular recess (10) to reduce the resistance to the downward movement of the distributor.
A percussion implement comprising an elongated body provided with a bore having an open front end for receiving a tool, a piston slidable in said bore, a distributor slidable in said bore adjacent a rear face of said piston remote from said front end, a hydraulic circuit in said body including a high-pressure branch and a low-pressure branch, control means including said distributor for connecting a fluid space adjacent said rear face alternately to said high-pressure and low-pressure branches, said low-pressure branch forming an annular recess around said distributor occupied by an incompressible fluid and forwardly of an enlarged head thereof for cushioning a forward movement of said distributor, pusher means in said body bearing in a forward direction upon said distributor under pressure from said highpressure branch, and suction means on said piston operative upon incipient forward movement thereof for drawing fluid from said recess to accelerate a corresponding movement by said distributor, said suction means including a stationary plunger in said body projecting axially into a blind bore of said piston and defining therewith a chamber expanding upon forward movement of the piston.
Claim 2
Dependent Claim
185 words
A percussion implement comprising an elongated body provided with a bore having an open front end for receiving a tool, a piston slidable in said bore, a distributor slidable in said bore adjacent a rear face of said piston remote from said front end, a hydraulic circuit in said body including a high-pressure branch and a low-pressure branch, control means including said distributor for connecting a fluid space adjacent said rear face alternately to said high-pressure and low-pressure branches, said low-pressure branch forming an annular recess around said distributor occupied by an incompressible fluid and forwardly of an enlarged head thereof for cushioning a forward movement of said distributor, pusher means in said body bearing in a forward direction upon said distributor under pressure from said highpressure branch, and suction means on said piston operative upon incipient forward movement thereof for drawing fluid from said recess to accelerate a corresponding movement by said distributor, said suction means including a stationary plunger in said body projecting axially into a blind bore of said piston and defining therewith a chamber expanding upon forward movement of the piston.
Claim 3
Dependent Claim
34 words
A percussion implement as defined in claim 1 wherein said hydraulic circuit includes an annular extension of said fluid space adjacent a rear surface of said head, said pusher means passing through said extension.
Claim 4
Dependent Claim
58 words
A percussion implement as defined in claim 2 wherein said extension is cut off from said fluid space in a retracted position of said distributor and wherein said hydraulic circuit includes piston-controlled switching means for alternately connecting said extension with said low-pressure branch and said high-pressure branch in a withdrawn piston position and an advanced piston position, respectively.