The invention relates to a bit assembly for a hammering and rotating drill, in which assembly the drill body is arranged to drill essentially the middle portion of the hole and in the drill body mounted one or more hammering bit is arranged to drill the outer circle of the hole and the mentioned outer circle of the hole drilling bits are arranged to drill a drilling surface, which locates further behind in the drilling direction than for the drill body meant drilling surface and that the mentioned bits ate further mounted in a drill body formed counter cavities, the axial directions of which have either the same direction as the drilling direction has or deviate outwards from it.
Earlier is known from patent publication FI-95618 a drilling apparatus in which the outer circle of the hole drilling ring bit drills the outer circle so that a casing tube can be pulled into the hole in connection with the drilling. When the drilling apparatus is pulled out from the hole so that the casing tube remains in the hole, the ring bit also has to remain in the hole bottom.
Also from patent publication FI-85302 is known a drilling apparatus for drilling large holes in which apparatus in the centre locating bit drills the hole centre portion and separate on the outer circle of the drilling apparatus placed bits drill the outer circle of the hole. The outer circle drilling bits need in this case rotating and hammering devices of their own. The drilling apparatus can be applied for drilling of horizontal holes when it is meant finally to penetrate through the ground into free space.
It is abundantly known with a casing tube drilling eccentric drills where drilling is carried out by a rotating bit which is mounted eccentric in relation to centre axis of the casing tube, and by means of which it is possible to drill a larger hole than the diameter of the casing tube. When drilling is stopped the eccentricity of the bit in relation to the centre axis of the casing tube is changed so that the bit can be pulled out from the hole and the casing tube is left in the hole.
The disadvantage for these known solutions is that in these drilling apparatuses in which the ring bit is left in the hole, there is in every hole always loosen relative expensive bit. When used an eccentric bit the bit will be lifted up from the hole, but the bit will wear very quickly because the drilling surface in the bit is remarkable smaller than the drilling surface of the hole, that's why the worn bits have to be often changed. In certain drilling apparatuses where the drilling bits can be pulled against each other thus allowing the bit assembly to be lifted up in spite of the casing tube, the mechanism by means of which the bits are pulled against each other has to be complicated, it is difficult to change the bits and they can be very easily damaged.
By means of the bit assembly according to the invention in the business area existing problem can be unexpectedly solved, and characteristics for the bit assembly according to the invention is that in the counter cavities mounted bits can at least a part of their way out of the counter cavities be transported out in the direction which deviates from the axial direction of the counter cavity in order to make the outer diameter of the drilling unit smaller.
The advantage for the bit assembly according to the invention is that the large hole drilling, diameter 300-1000 mm, is possible by means of the hammering devices, when thanks to many separate in the drilling body mounted and only the outer circle of the hole drilling bits the total drilling surface area becomes smaller than the front surface area of the drilled hole. The bit assembly doesn't need so effective and inconvenient heavy hammer device, than with corresponding drills whose bit is hammering against whole drilling surface.
The separate outer circle drilling bits can also easily be changed. Further the outer circle drilling bits can be according to the invention mounted in the drill body in such a way that when the bit assembly is pulled out from the hole, the bits are moving inwards at the casing tube edge and are thus allowing the pulling of the whole bit assembly out and that the casing tube remains in the hole. In the solution no expensive is remaining in the hole and drilling becomes advantageous.
In the following the invention is more closely described by referring to the enclosed drawings, where
a shows a section view of the bit mounting in a drill body.
The bit 2 can be mounted in the drill body 1 by using as a help a separate bushing 5 which is placed into a hole drilled in the drill body 1. It is easier to machine in this kind of bushing 5 the needed counter cavities 7 as for example in the drill body 1. In
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Number | Date | Country | Kind |
---|---|---|---|
20022043 | Nov 2002 | FI | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FI03/00876 | 11/18/2003 | WO | 5/17/2005 |