Soil drill bit assembly or boring rig

Abstract

A drill bit assembly includes a drill bit, suited to be fixed to a distal end of a drill string; a casing shoe, for being mounted at the distal end of a casing column; and a ring bit, supported in its rotation by the casing shoe. The drill bot and the ring bot mutually axially slide inside one another, so that the drill bit is configured to take on a cooperating condition and an independent condition. In the cooperating condition, the ring bit surrounds the drill bit and is rotationally integral with the drill bit. The ring bit is operated in rotation, when the drill bit is rotated. In the independent condition, the drill bit axially exceeds the ring bit and the ring bit is rotationally independent of the drill bit. The drill bit is capable of rotating independently of the ring bit.

1 . Drill bit assembly or boring rig to drill soil comprising:
 a drill bit, for being fixed to a distal end of a drill string;   a casing shoe, for being mounted at a distal end of a casing column; and   a ring bit, supported in rotation by said casing shoe;   said drill bit and said ring bit are mutually axially slidable inside one another, so that said drill bit is configured to take on:
 a cooperating operating condition, in which said ring bit surrounds said drill bit and is integral in rotation to said drill bit said ring bit being operated in rotation, when said drill bit is rotated; and 
 at least one independent operating condition, in which said drill bit and said ring bit are axially offset and mutually independent in their rotation. 
   
     
     
         2 . The assembly according to  claim 1 , wherein, in said at least one independent operating condition, said drill bit axially exceeds said ring bit and is rotatable independently of said ring bit. 
     
     
         3 . The assembly according to  claim 1 , wherein, in said at least one independent operating condition, said ring bit axially exceeds said drill bit and is rotatable independently of said drill bit. 
     
     
         4 . The assembly according to  claim 1 , said drill bit and said ring bit having, respectively, a radially inner portion and a radially outer portion, which are complementary to one another and cooperate with one another to create a mutual sliding movement in an axial direction and a mutually integral movement in rotation, when said radially inner portion and said radially outer portion are in said cooperating operating condition. 
     
     
         5 . The assembly according to  claim 4 , wherein said radially inner portion and said radially outer portion are uncoupled from one another, when said drill bit is in said at least one independent operating condition. 
     
     
         6 . The assembly according to  claim 4 , wherein said radially inner portion of said ring bit has at least one between a recess and a projection, for mechanically cooperating with at least one complementary projection or recess of said radially outer portion of said drill bit. 
     
     
         7 . The assembly according to  claim 6 , wherein said radially inner portion of said ring bit has a plurality of said recesses or projections and said radially outer portion of said drill bit has a plurality of said projections. 
     
     
         8 . The assembly according to  claim 7 , wherein said recess and said projections are equally spaced apart from one another. 
     
     
         9 . The assembly according to  claim 1 , further comprising a rotary unit, for generating a torque, and a drill string, on which distal end is fixed said drill bit and which is capable of transmitting said torque to said drill bit. 
     
     
         10 . The assembly according to  claim 1 , further comprising a casing column, on which distal end is supported in rotation said ring bit. 
     
     
         11 . The assembly according to  claim 10  further comprising a vibrating unit, for imparting vibrations in an axial direction to said casing column. 
     
     
         12 . The assembly according to  claim 11 , wherein said vibrating unit is located close to a proximal end of said casing column. 
     
     
         13 . The drill bit assembly according to  claim 11 , wherein said vibrating unit is located close to the distal end of said casing column. 
     
     
         14 . The assembly according to  claim 11 , wherein a frequency of vibration of said vibrating unit ranges from 80 Hz to 200 Hz. 
     
     
         15 . The assembly according to  claim 10 , further comprising a rotary unit, for generating and transmitting a torque to said casing column. 
     
     
         16 . The assembly according to  claim 11 , wherein a frequency of vibration of said vibrating unit ranges from 120 Hz to 150 Hz,