Percussion device and rock drilling machine
A percussion device ( 5 ) for a rock drilling machine ( 1 ) including a percussive piston ( 6; 15 ) which is reciprocally movable inside a cylinder and an impact receiving element ( 7;16 ) with an impact surface (A;A′), against which the percussive piston is arranged to perform strikes in an impact direction for transferring of percussive energy through Shockwaves to a percussive tool. The percussion device is distinguished by the impact receiving element ( 7; 16 ) including a Shockwave modifying portion ( 9; 17 ) which extends in a direction opposite to the impact direction as seen from a plane (P; P′) through the impact surface (A; A′). The invention also concerns a rock drilling machine and a rock drilling rig.
1. Percussion device for a rock drilling machine including a percussive piston which is reciprocally movable inside a cylinder and an impact receiving element with an impact surface (A;A′), against which the percussive piston is arranged to perform strikes in an impact direction towards a percussive tool for transferring percussive energy through shockwaves to said a percussive tool, wherein the impact receiving element includes a shockwave modifying portion which extends in a direction opposite to the impact direction as seen from a plane (P;P′) through the impact surface (A;A′), said shockwave modifying portion being formed integrally with said impact receiving element, said impact receiving surface being provided at the forward end of said shockwave modifying portion, and a damping piston arranged to engage the rear end of said shockwave modifying portion, wherein the shockwave modifying portion has a length, as seen from said plane, which is essentially the same as the length of the percussive piston.
2. Percussion device according to claim 1 , wherein all portions of the shockwave modifying portion along the length thereof have a cross sectional area which is essentially half of the cross sectional area of the percussive piston.
3. Percussion device according to claim 2 , wherein the shockwave modifying portion has an essentially circular cross section.
4. Percussion device according to claim 2 , wherein the percussive piston has an essentially circular cross section.
5. Percussion device according to claim 1 , wherein the shockwave modifying portion has an essentially circular cross section.
6. Percussion device according to claim 1 , wherein the percussive piston is tubular and surrounds the shockwave modifying portion.
7. Percussion device according to claim 1 , wherein the percussive piston has an essentially circular cross section.
8. Percussion device according to claim 1 , including means for providing bearing support for the shockwave modifying portion in a distal region, as seen from said plane.
9. Percussion device according to claim 1 , including means for providing bearing support of the impact receiving element in a position forwardly in the impact direction as seen from said plane.
10. Percussion device according to claim 1 , wherein said damping piston provides means for exerting an axial damping force against said rear end of the shockwave modifying portion.
11. Percussion device according to claim 1 , wherein the impact receiving element is an intermediate block, positioned between a drill tool adaptor and the percussive piston.
12. Percussion device according to claim 1 , wherein the impact receiving element is a took shank, in particular a drill shank.
13. Percussion device according to claim 1 , including means for driving the percussive piston with pressure fluid.
14. Rock drilling machine including a percussion device according to claim 1 .
15. Rock rig including a rock drilling machine according to claim 14 .
16. Percussion device for a rock drilling machine including a percussive piston which is reciprocally movable inside a cylinder and an impact receiving element with an impact surface (A;A′), against which the percussive piston is arranged to perform strikes in an impact direction towards a percussive tool for transferring percussive energy through shockwaves to said a percussive tool, wherein the impact receiving element includes a shockwave modifying portion which extends in a direction opposite to the impact direction as seen from a plane (P;P′) through the impact surface (A;A′), said shockwave modifying portion being formed integrally with said impact receiving element, wherein the shockwave modifying portion has a length, as seen from said plane, which is essentially the same as the length of the percussive piston, wherein the percussive piston has an essentially circular cross section, and wherein the shockwave modifying portion is tubular and surrounds the percussive piston.
17. Percussion device according to claim 16 , including a damping piston arranged to engage the rear end of the percussive piston.