GB305610A - Improvements in apparatus for enlarging the bores of rock drills and the like - Google Patents

Abstract

305,610. St. Stephens, R. de H., and Climax Rock-Drill & Engineering Works, Ltd. Nov. 8, 1927. Percussive drills.-In apparatus for enlarging the bores of hollow drill steels &c. of the kind comprising a feed plunger working in a cylinder and moved towards the drill whilst the bore is being enlarged by a punch and away therefrom when the punch is being withdrawn the feed plunger has two hammer pistons mounted therein, one for driving the punch and the other for withdrawing it according to the direction of movement of the plunger. The! hollow plunger a mounted in the end plates b of the casing b<1> is divided by a central partition e into two cylinders f, g in which the hammer pistons h, k are fitted. The front anvil l carrying the punch m and the rear anvil n are mounted in end covers o secured together by bolts p. Movement of the valve c in one direction admits air or other pressure fluid into the casing moving the plunger a to the left. At the same time air passes through a passage q in the plunger and through a passage r in the hammer piston h to the rear of the latter moving it forward to drive the punch m into the bore of the drill steel; at the end of its forward movement the air behind the hammer piston h exhausts through the port u and passage q<1> and more live air passes through the passage q and annular groove v and second passage r to the front of the hammer piston h to effect its rearward stroke. Tha advance of the plunger a and reciprocation of the hammer piston h is continued until the enlargement of the drill steel bore is completed, whereupon the valve c is reversed admitting air to the passage w to move the plunger a backwards, air also passing through passage q<2> and passages s in the hammer piston k for reciprocating the latter so as to strike the rear anvil n as the punch is withdrawn.