Rock drill

Abstract

A rock drill wherein a piston is the only moving hammer part and such piston is movable without independent valve means or the like.

What is claimed is:  .[.1. In a rock drill, the combination comprising: an elongated body member having a chamber extending longitudinally therein; a hammer piston reciprocable within said chamber for percussively actuating a striking bar upon movement of said piston from a first portion of said chamber to a second portion of said chamber; first passageway means in said body member adapted to be connected to a fluid pressure source; second passageway means in said hammer piston in constant open communication with said first passageway means during at least a major portion of the reciprocable travel of said piston; third passageway means in said body member openly communicating between said second passageway means and a piston impact portion of said chamber only when said piston is moving through said first portion of said chamber; and fourth passageway means in said body member openly communicating between said second passageway means and a piston retracting portion of said chamber only when 
     
        said piston is moving through said second portion of said chamber..]. 2. A rock drill as specified in claim .[.1.]. .Iadd.11 .Iaddend.wherein chamber exhaust means in said body member openly communicate between the exterior of said body member and said piston impact chamber portion at least when said piston is moving through said second portion of said chamber; and when said piston is moving through said first portion of said chamber said 
     
     
        last mentioned open communication is discontinued by said piston. 3. A rock drill as specified in claim .[.1.]. .Iadd.11 .Iaddend.wherein chamber exhaust means in said body member openly communicate between the exterior of said body member and said piston retract chamber portion at least when said piston is moving through said first portion of said chamber; and when said piston is moving through said second portion of said chamber said 
     
     
        last mentioned open communication is discontinued by said piston. 4. A rock drill as specified in claim 2 wherein said chamber exhaust means additionally communicate between the exterior of said body member and said piston retract portion at least when said piston is moving through said first portion of said chamber and when said piston is moving through said second portion of said chamber said last mentioned open communication is 
     
     
        discontinued by said piston. 5. A rock drill as specified in claim .[.1.]. .Iadd.11 .Iaddend.comprising: rotation means in said body member for rotating said striking bar during percussive actuation; and thrust bearing means disposed intermediate a stationary portion of said body member and a rotatable portion of said rotation means for the rotatable carrying of 
     
     
        said rotatable portion within said body member. 6. A rock drill as specified in claim .[.1.]. .Iadd.11 .Iaddend.wherein said second passageway means is in constant communication with said first passageway means during the entire reciprocable travel of said piston.  .[.7. A rock drill as specified in claim 1 wherein said hammer piston comprises a head portion and a reduced diameter stem portion; said head portion being of a diameter substantially equal to the diameter of said first and second portion of said chamber; and said second passageway means being in said 
     
     
        stem portion..]. 8. A rock drill as specified in claim .[.1.]. .Iadd.11 .Iaddend.wherein a portion of said hammer piston blocks communication of said piston impact and retracting portions of said chamber with said fluid pressure source when said piston is moving through a central portion of said chamber between said second and said first portions of said chamber. 
     
     
         . A rock drill as specified in claim 8 .[.wherein said hammer piston comprises a head portion and a reduced diameter stem portion;.]. .Iadd.with .Iaddend.said head portion being of a diameter substantially equal to the diameter of said first and second portions of said chamber. 
     
     
        .[.and said second passageway means being in said stem portion.]. 10. A rock drill as specified in claim 9 wherein chamber exhaust means in said body member openly communicate between the exterior of said body member and said piston impact portion at least when said piston is moving through said second portion of said chamber and openly communicate between the exterior of said body member and said piston retract portion at least when said piston is moving through said first portion of said chamber; and when said piston is moving through said first and second portions of said chamber discontinuing, by said piston, said open communication of said impact and retract portions respectively. .Iadd. 11. In a rock drill, the combination comprising: an elongated body member having a chamber extending longitudinally therein; a hammer piston having a head portion and a reduced diameter stem portion; said piston being reciprocable within said chamber for percussively actuating a striking bar by engagement of said stem portion with said striking bar upon movement of said piston from a first portion of said chamber to a second portion of said chamber; first passageway means in said body member adapted to be connected to a fluid pressure source; second passageway means in said stem portion in constant open communication with said first passageway means during at least a major portion of the reciprocable travel of said piston; third passageway means in said body member openly communicating between said second passageway means and a piston impact portion of said chamber only when said piston is moving through said first portion of said chamber; and fourth passageway means in said body member openly communicating with said second passageway means and a piston retracting portion of said chamber only when said piston is moving through said second portion of said chamber. .Iaddend..Iadd. 12. A rock drill as specified in claim 11 wherein said second passageway means is cyclically indexable with respect to adjacent portions of said third and fourth passageway means. .Iaddend..Iadd. 13. A rock drill as specified in claim 12 wherein said body member includes a bore therein coaxially aligned with said chamber and said stem portion is slidably received within said bore. .Iaddend..Iadd. 14. A rock drill as specified in claim 13 wherein such indexing occurs within said bore. .Iaddend.