Bit assembly

Abstract

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.

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.