E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
E21B 10/38 (2006.01) E21B 10/56 (2006.01)
Patent
CA 2098581
The present invention relates to a drill bit (10) for rock drilling, pref- erably a down-the-hole drill bit, said drill bit (10) including a head (11) and a shaft (12), said head (11) defining a cutting face (14) that carries a num- ber of hard material button inserts (l5) having end portions extending out- wardly of said cutting face (14), means (16, 17) for transporting flushing medium from the free end (13) of the shaft (12) to the cutting face (14) of the head (11), said means for transporting flushing medium including a central passage (16) extending from the free end (13) of the shaft (12) and terminating in the head (11) short of the cutting face (14) and at least one branch passage (17) emanating from the central passage (16) and emerging in the cutting face (14). In the filed of down-the-hole drill bits big volumes of flushing medium, normally compressed air, are used since the flushing medium is also activating the down-the-hole hammer. Those big volumes provide erosion of the cutting face since the flushing medium has a very high speed when passing the front face of the drill bit. Said erosion creates problems when so much material, usually steel, of the cutting face has been eroded away that the button inserts are lost before they are worn out. The idea of the present invention is to decrease the velocity of the flushing me- dium before reaching the cutting face (14) of the drill bit (10). This is done by increasing the cross-sectional area of the branch passage (17) along a certain length (L) of said branch passage (17).
Asberg Bengt
Hedlund Jan-Gunnar
Gowling Lafleur Henderson Llp
Sandvik Ab
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