Hard metal plate for rock drill and rock drill

1. A rock drill comprising: a hard metal plate inserted into a seat formed at one end of a drill shaft, said drill shaft having a radial dimension defining a first side and a second side of the drill shaft and an axial direction, and said hard metal plate comprising a substantially rectangular base shape having two opposed long sides extending in the axial direction of the drill shaft which are at least partially covered by the seat, two opposed, substantially axial free short sides, a radial bottom side facing towards the seat and a roof-shaped cutting face facing away from the seat, wherein both short sides are formed by an axial section having a purely axial direction component and a conical section inclined towards the axial direction, so that at the short side, the substantially rectangular plate tapers towards the bottom side wherein the hard metal plate protrudes radially beyond both the first side and the second side of the drill shaft such that a portion of the long sides are exposed beyond both the first side and the second side of the drill shaft.

2. The rock drill of claim 1 , wherein the conical section is inclined with respect to the axial direction by less than 10°.

3. The rock drill of claim 1 , wherein the conical section forms more than half of the short sides.

4. The rock drill of claim 1 , wherein the axial section opens axially linearly into the cutting face and forms less than half of the short sides.

5. The rock drill of claim 1 , wherein the conical section and the axial section are separated from one another by a transition edge.

6. The rock drill of claim 1 , wherein the conical section extends linearly in the axial direction from the axial section towards the bottom side.

7. The rock drill of claim 1 further comprising a concave groove extending linearly in the axial direction formed on at least one long side.

8. The rock drill of claim 7 , wherein the groove extends away from the cutting face and opens along a linear profile into the bottom side.

9. The rock drill of claim 7 , wherein the groove diminishes radially in the axial direction in the conical section.

10. The rock drill of claim 7 , wherein the groove lies at a transition to the adjacent short side.

11. The rock drill of claim 1 , wherein the cutting face comprises two long cutting edges which meet in a tip region and each of the two long cutting edges comprise an edge section close to the tip region and an edge section remote from the tip region, wherein both the edge section close to the tip region and an edge section remote from the tip region are inclined towards a radial direction perpendicular to the axial direction, wherein the edge section close to the tip region is more strongly inclined than the edge section remote from the tip region and a transition region between the edge section close to the tip region and the edge section remote from the tip region is continuously concavely curved.

12. The rock drill of claim 11 , wherein the edge section remote from the tip region is inclined with respect to the radial direction by about 5° to 20°.

13. The rock drill of claim 11 , wherein the edge section close to the tip region is inclined with respect to the radial direction by about 25° to 35°.

14. The rock drill of claim 11 , wherein the linear edge section remote from the tip region is at least five times longer than the linear edge section close to the tip region.

15. The rock drill of claim 11 , wherein the cutting face comprises two short cutting edges which extend substantially linearly from the long sides into the tip region with the same inclination towards the radial direction.

16. The rock drill of claim 15 , wherein the short cutting edges are inclined with respect to the radial direction by about 25° to 35°.

17. The rock drill of claim 1 , wherein the cutting face comprises two long cutting edges extending linearly radially outwards from a common tip region, which open in a linear course in the respective short side, and are inclined to a flat radial extension of the long sides at an angle greater than 1° and less than 10°.

18. The rock drill of claim 1 , wherein the two short sides are formed by a substantially flat side section remote from the bottom side and a stepped side section close to the bottom side, said stepped side section in the conical section comprising at least two steps.

19. The rock drill of claim 18 , wherein the stepped side section comprises a radial jump surface and an axial pedestal surface.

20. The rock drill of claim 19 , wherein the pedestal surface is at least twice as large as the jump surface.

21. The rock drill of claim 19 , wherein the pedestal surface is inclined between 1° and 20° with respect to the axial direction.

22. The rock drill of claim 1 , wherein the conical section is inclined with respect to the axial direction by about 6°.

23. The rock drill of claim 11 , wherein the edge section remote from the tip region is inclined with respect to the radial direction by about 12° to 13.

24. The rock drill of claim 11 , wherein the edge section close to the tip region is inclined with respect to the radial direction by about 29°.

25. The rock drill of claim 15 , wherein the short cutting edges are inclined with respect to the radial direction by about 31° to 32°.

26. The rock drill of claim 1 , wherein the cutting face comprises two long cutting edges extending linearly radially outwards from a common tip region, which open in a linear course in the respective short side, and are inclined to a flat radial extension of the long sides at an angle of about 5° to 6°.