Hammering and rotatable drill bit

#This application is a National Stage application of International Application No. PCT/FI2015/000002, filed Jan. 20, 2015, which claims priority to Finnish Application No. 20140015, filed Jan. 20, 2014, which are incorporated by reference herein in their entireties.

#Field

#Object of the invention is a hammering and rotatable drill bit belonging to a drilling device and meant for ground and rock drilling through a hollow shaft of which bit flushing air is directed to the drilling surface to the front of the drill bit and further from it towards the outer edge of the drill bit.

#In the following the invention is described more detailed by referring to the accompanying drawing in which

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

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

#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.

#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.

#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.