BIT ASSEMBLY
A bit assembly in a drilling apparatus working by hammering and for rotating said assembly comprising of a pilot bit (1) drilling the central part of the hole and a ring bit (2), fitted in connection with said pilot bit(1) and furnished with cylindrical inner surface drilling the outer surface of said hole, and further, between the pilot bit (1) and ring bit (2) a blocking arrangement of mutual rotation and axial movement, whereby opening of said blocking arrangement makes it possible to pull the pilot bit (5) off the hole, while ring bit (2) remains in the hole, and the bit assembly comprises a casing tube and its extension (6) and an interlocking system, which is through a ring-shaped device (8) from the extension (6) of the casing tube adapted to transfer pulling force from the pilot or ring bit to the casing tube extension (6) and said interlocking system can be opened in order to continue drilling with the ring and pilot bits (1, 2) when the casing tube remains in its place. That the ring like device (8) comprises parts directed to the inside, by means of which said device is permissively fitted to rotate into the traverse groove (10) on the outer surface of either the pilot or ring bit so that its motion is limited or blocked, in both axial directions.
The invention relates to a bit assembly in a drilling apparatus said apparatus working by hammering and/or rotating said assembly comprising of a pilot bit, drilling the central part of the hole and a ring bit fitted in connection with the said pilot bit and furnished with cylindrical inner surface drilling the outer surface of said hole, and further, between the pilot bit and the ring bit a blocking arrangement of mutual rotation and axial movement, whereby opening of said blocking arrangement makes it possible to pull the pilot bit off the hole, while the ring bit remains in the hole, and the bit assembly comprises a casing tube and its extension, and an interlocking system which is through a ring-shaped device from the extension of the casing tube adapted to transfer pulling force from the pilot or ring bit to the casing tube extension, and said interlocking system can be opened in order to continue drilling with the ring and pilot bits, when the casing tube remains in its place.
Previously known from publications WO2004/057148 is a drilling apparatus like the above presented comprising a pilot bit and a ring bit. However, with this solution it is not possible to continue drilling so that the protecting tube would be left in the drilled hole at wanted point.
From publication WO96/718798 it is known a drilling apparatus the casing tube and ring bit of which can be left in a drilled hole in the place wanted and drilling continued merely by the pilot bit, in other words by the middle bit. In this solution the diameter of the hole lessens essentially, when drilling is continued with the pilot bit only. In drilling made for anchorage the anchor bolt or cable sticks to this by continued drilling, this made smaller hole of its. The joint surface of anchorage is in this case formed smaller than which would be possible if the hole diameter would remain constant until the end of hole.
From publication EP 1144797 it is known a casing shoe most suitably fixed in the front edge of the casing tube by welding, which shoe is fixed around the ring bit by shrinking so that they can roll in regard to each other, but locked in axial direction. In the outer surface of the ring bit there must be a groove into which a ring like elevation part of the inner surface of the casing shoe is placed. A groove of this kind requires that the ring mantle of said ring bit of its wall thickness is enough for the groove.
From publication FI 98649 it is known a protecting tube release system, which has a ring that pulls the casing tube and can like bayonet-locking be locked on the outer surface of the pilot or the ring bit. On its inner surface the ring has grooves, and respectively there are elevation parts on the outer surface of the bit in order to produce mutual locking. In this solution the making of elevation parts on the cylindrical bit surface will be difficult. For instance, even on the pilot bit surface often formed flushing grooves are in this solution not utilized. In connection with the casing tube the tube extension is not used, but a cantilever ring, whereby the other axial direction remains unlocked. This results in difficulty, because if the casing tube is left too early in the hole the “finding” of it along again by means of the bits does not work, since the ring that pulls the casing tube cannot with the bit be returned into locking when it inside the casing tube escapes the bit.
In order to eliminate the disadvantages contained in the above presented solutions, and also to improve the technical effect of these solutions, a new bit assembly is developed, characteristic of which is that a ring like device comprises parts directed to the inside, by means of which said device is permissively fitted to rotate into the traverse groove on the outer surface of either the pilot or ring bit so that its motion is limited or blocked in both axial directions.
The advantage of the invention is that the casing tube, which during drilling is pulled into the hole can be left in the hole in the place wanted, for instance on hitting the rock, without pulling the drilling apparatus occasionally from the hole. When the pilot and also ring bits continue drilling without the casing tube therewith the diameter of the drilled hole remains unchanged. The ring bit which is often to be left in a finished hole, can for its part be made material saving, since the pulling system that pulls the casing tube into the hole comes in this solution around the pilot bit. When the casing tube is pulled by means of the pilot bit and not the ring bit the hammering surfaces between pilot and ring bits can be remarkably smaller in regard to former solutions, whereby the wall thickness of the pilot bit in its cylindrical portion can also be made smaller. On the other hand, the hammering faces between the ring like device according to the invention and the casing tube extension are easily made bigger, which extends the durability of the pilot bit. The ring like device can advantageously be locked on the pilot bit outer surface so that by locking at least apart of the flushing grooves or of the ring bit grooves on the pilot bit outer surface are utilized. This is possible, since according to the invention, the ring like device comprises on its inner surface elevating parts directed to the inside.
In the following the invention is closer disclosed with reference to the enclosed drawing. where
The
In the figures there are presented the pulling arrangement of the casing tube from the pilot bit 1 by means of the ring like device 8 to the extension 6 of the casing tube. Said pulling can also be arranged by means of the said ring like device 8 from the outer surface of the ring bit 2 correspondingly to the extension 6 of the casing tube.
Claims
1. A bit assembly in a drilling apparatus working by hammering and/or rotating said assembly comprising of a pilot bit (1) drilling the central part of the hole and a ring bit (2), fitted in connection with said pilot bit (1) and furnished with cylindrical inner surface drilling the outer surface of said hole, and further, between the pilot bit (1) and ring bit (2) a blocking arrangement of mutual rotation and axial movement, whereby opening of said blocking arrangement makes it possible to pull the pilot bit (5) off the hole, while ring bit (2) remains in the hole, and the bit assembly comprises a casing tube and its extension (6) and an interlocking system, which is through a ring-shaped device (8) from the extension (6) of the casing tube adapted to transfer pulling force from the pilot or ring bit to the casing tube extension (6) and said interlocking system can be opened in order to continue drilling with the ring and pilot bits (1, 2) when the casing tube remains in its place, characterized in that the ring like device (8) comprises parts directed to the inside, by means of which said device is permissively fitted to rotate into the traverse groove (10) on the outer surface of either the pilot or ring bit so that its motion is limited or blocked in both axial directions.
2. A bit assembly according to claim 1 characterized in that the ring like device (8) is in axial direction locked in the extension (6) of the casing tube as fitted in the ring like groove (11) that belongs to the inner surface of extension (6) so that it can rotate in said extension.
3. A bit assembly according to claim 1 characterized in that the extension (6) of the casing tube furnished with a ring like groove (11) is shrunk around the ring like device (8).
4. A bit assembly according to claim 1 characterized in that the pilot bit (1) or the ring bit (2) can by means of mutual rotation be opened off the ring like device (8) into position
- where it can be threaded through said device.
5. A bit assembly according to claim 1 characterized in that the ring like device (8) is in a way like bayonet coupling fixed in the traverse and ending grooves (10) in the outer surface of the pilot bit (1).
6. A bit assembly according to claim 1 characterized in that the longitudinal flushing groove (12) on the surface of the pilot bit (1) is deeper than the longitudinal interlocking grooves (17) and traverse grooves (10) on the pilot bit surface.
Type: Application
Filed: Jul 10, 2008
Publication Date: Aug 12, 2010
Inventors: Mikko Mattila (Tampere), Pekka Salmi (Sahalahti)
Application Number: 12/668,323
International Classification: E21B 10/62 (20060101); E21B 10/26 (20060101); E21B 10/40 (20060101);