Hammering and rotatable drill bit

Abstract

A hammering and rotatable drill bit, which is meant for ground and rock drilling includes a hollow shaft having a hole that is adjusted to direct flushing air onto the drilling surface to the front of the drill bit and further from there towards the outer edge of the drill bit. the drill bit includes a drilling part which protrudes from the surface of the drill bit, functions as a drill point and drills the mid-area of the hole to be created wherein the mentioned part is adjusted to prevent the flushing flow from flowing directly through the mentioned hole located inside the shaft onto the drilling surface. The mentioned part is arranged to allow the outlet of the flushing flow in a sideways direction to the grooves belonging to the drilling surface, which grooves lead to the edge of the drill bit, and is arranged to allow the outlet also partly to the front of the drill bit to the drilling surface by adjusting the groove, which leads to the edge of the drill bit, to start from the mentioned part from such a distance (d) from the center line (L) of the drill bit which distance (d) is less than the radius (R) of the hole.

Claims

1. A hammering and rotatable drilling device for ground and rock drilling, said drilling device comprising: a drill bit defining a drilling surface at a front portion thereof and an outer edge, said drilling surface including a plurality of grooves, and; a hollow shaft, said shaft connected to said drill bit and having a hole defining a radius which is adjusted to direct a flushing flow onto the drilling surface at the front of the drill bit and further from there towards the outer edge of the drill bit; and wherein the drill bit comprises a drilling part which protrudes from the front portion of the drill bit, functions as a drill point and drills a mid-area of a drilled hole to be created wherein the drilling part is adjusted to prevent the flushing flow from flowing directly through the hole located inside the shaft onto the drilling surface, wherein the drilling part is arranged to allow a portion of the flushing flow to exit the hole in the shaft in a sideways direction to the grooves belonging to the drilling surface which grooves lead to the outer edge of the drill bit and is also arranged to allow a portion of the flushing flow to exit the hole in the shaft in a forward direction towards the front portion of the drill bit to the drilling surface by adjusting the grooves, which lead to the outer edge of the drill bit, to start from the drilling part from a distance from a centre line of the drill bit, and wherein said distance is less than the radius of the hole in the shaft.

2. The drilling device according to claim 1, wherein the grooves are adjusted to such depth adjacent the drilling part such that the grooves extend deeper in the drill bit than a level defining a bottom of the hole.

3. The drilling device according to claim 1, wherein each of said grooves includes a starting point, and wherein the distance of the starting point from the centre line of the hole is (0.7-0.99)R when R is the radius of the hole.

4. The drilling device according to claim 1, wherein each of said grooves includes a starting wall defining a starting point, and wherein the starting wall is directed in a drilling direction.

5. The drilling device according to claim 1, wherein the hole which is located inside the drill bit extends to a level which is beyond a level defining a bottom of one of said grooves near a starting point of said one of said grooves.

6. The drilling device according to claim 1, wherein said drill bit further includes a plurality of ducts extending from said hole towards said outer edge, and wherein part of the flushing flow is directed to turn backwards along the ducts that are formed inside the drill bit.

7. The drilling device according to claim 1, wherein the drilling part has a drilling diameter of 25-60% of a drilling diameter of the drill bit.

8. The drilling device according to claim 1, wherein the drilling part includes a planar directing surface.

9. The drilling device according to claim 1, wherein the grooves are at least partly curvilinear.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the invention is described more detailed by referring to the accompanying drawing in which

(2) FIG. 1 shows a drill bit according to the invention as a side and section view.

(3) FIG. 2 shows the drill bit of the FIG. 3 directly from the front.

(4) FIG. 3 shows a drill bit according to the invention diagonally seen.

(5) FIG. 4 shows the directing part as an enlargement.

DETAILED DESCRIPTION

(6) In the FIG. 1 the drill bit 1 and the shaft 2 belonging to it are shown as a section view. The flushing flow is directed through a hole 3 which is directed through the drill bit 1 and the centre line L of the shaft towards the front surface of the drill bit 1. The hole 3 however ends at a planar directing part 5 before the mentioned surface and the flushing flow is turned to the side with the help of such a solution in which it is possible for the flushing flow to move in a sideways direction towards the outer edge of the drill bit 1 along grooves 6 which are formed to be curvilinear. These grooves 6 also transfer the drilling waste to the outer edge of the drill bit 1 and further from there backwards along an outlet duct 7 and further along the drilled hole onto the ground surface.

(7) The hole 3 ends in the drill bit 1 at the level s in such a way that the grooves 6 start from the side of the hole 3 in this case in three different directions. The grooves 6 are still split immediately at their starting part to be two separate grooves 6. The grooves 6 are arranged in relation to the hole 3 in such a way that the grooves 6 start from the centre line L of the drill bit 1 at the distance d which is less than the radius R of the hole 3. The starting point of the grooves 6 is located at the distance d from the centre line L and this distance d is less than the radius R of the hole 3. This results in a fact that the flushing flow can partly turn also diagonally towards the drilling surface when one of its parts, most advantageously exactly the largest part, turns in a sideways direction and proceeds along the grooves 6 in a sideways direction.

(8) At the same time the grooves 6 start from the part 5 which is formed in the centre of the drill bit 1 and drills the mid-area of the hole in which case the grooves 6 are deeper regarding this part than outside the mentioned part 5. Due to the part 5 the hole 3 can be extended inside the drill bit 1 at least to the same level where the front surface of the drill bit 1 is outside the part 5. The part 5 also functions as the directing part of the drilling by drilling the top part of the hole. Due to the part 5 the drilling surface of the drill bit 1 can be made to endure drilling hammerings despite the weakening caused by the hole 3 which weakening in this case will be nearly eliminated. The diameter D of the part 5 is most advantageously 25-60% of the diameter of the drill bit 1.

(9) In one implementation way in order to reduce the flushing flow to be directed onto the drilling surface inside the drill bit 1, part of the flushing flow is turned to be a return flow with the help of ducts 4 already before the hole 3 ends.

(10) FIG. 2 shows the drill bit from the front and FIG. 3 diagonally as a side view. It can be seen in the figures that the starting points of the grooves 6 start from inside a cylindrical part. It can be seen in the FIG. 2 that the length of the radius of the hole 3 is slightly longer than the distance from the centre line L of the hole 3 to the starting point of the grooves 6.

(11) In the FIG. 4 the starting point of the groove 6 is shown more accurately in which starting point the groove 6 has a starting wall 9 which is directed in the drilling direction. The bottom of the groove 6 is at the level h and the bottom of the hole 3 is at the level s. The distance d of the starting wall 9, in other words the starting point of the groove 6 from the centre line L of the hole 3 is most advantageously 0.7-0.99R in which case R is the radius of the hole 3