Bit assembly for a down-the-hole hammer drill

Abstract

The invention provides for a down-the-hole drill bit assembly comprising a drill bit having a screw-thread at its anvil end, external splines on the drill shank and co-operating splines within a drill casing as well as a co-operating screw thread carried by a component within the casing. The assembly is arranged to have engagement of the splines with the screw threads disengaged for driving the drill and to have the screw threads engaged and splines disengaged to permit removal of the bit from the assembly.

1 . A down-the-hole drill bit assembly comprising a drill bit having a screw-thread at its anvil end and splines and cooperating splines and a cooperating screw thread carried by a component within the casing, the assembly being arranged to have engagement of the splines with the screw threads disengaged for driving the drill and the screw threads engaged and splines disengaged to permit removal of the bit from the assembly. 
     
     
         2 . A drill bit assembly as claimed in  claim 1 , in which the screw thread and splines are on the drill bit shank. 
     
     
         3 . A drill bit assembly as claimed in  claim 1 , in which the screw thread is within a bore in the anvil end of the drill bit shank. 
     
     
         4 . A drill bit assembly as claimed in  claim 1 , in which splines are an integral part of the casing. 
     
     
         5 . A drill bit assembly as claimed in  claim 1 , in which the splines are an integral part of a chuck member secured in the casing. 
     
     
         6 . A drill bit assembly as claimed in  claim 1 , in which the cooperating threads are inside a chuck. 
     
     
         7 . A drill bit assembly as claimed in  claim 3 , in which the cooperating threads are on a fixed, rotary or axially movable control member. 
     
     
         8 . A chuck for a drill bit assembly as claimed in  claim 1 , comprising at its operatively upper end a bush at the lower end of which is an internal thread, internal splines extending below the thread having an internal diameter greater than the internal diameter of the thread, the external surface of the chuck providing a seat for a wear sleeve and operatively above the seat an external screw thread adapted to engage an internal screw thread in a wear sleeve. 
     
     
         9 . A drill bit assembly having a drill head adapted to operatively engage in the bottom of a drill chuck, external splines set back from the drill head and adapted to engage internal splines in the chuck having an internal screw thread with an internal diameter less than that of the external splines on the bit and the end of a drill shank having an external screw thread along part thereof adjacent its bit anvil to engage and pass through a complementary screw thread in the drill bit chuck. 
     
     
         10 . A drill bit assembly as claimed in  claim 9 , in which the bottoms of the internal splines in the chuck and external splines on the bit each are shaped as one turn of a helical cam with a pitch equal to that of a screw thread in the chuck to provide for rotation of the bit with the chuck. 
     
     
         11 . A drill bit assembly as claimed in  claim 1 , in which the bit has a screw thread extending from the anvil and which is engageable with complementary screw thread on a bit mounting such that the engagement of the screw threads provides for the bit to be moved into and out of limited sliding engagement with the mounting by the passage of screw threads one though the other. 
     
     
         12 . A drill bit assembly as claimed in  claim 11 , in which the bit and bit mounting carry mating splines engaged when the screw threads have passed one through the other. 
     
     
         13 . A drill bit assembly as claimed in  claim 12 , in which the mounting is a chuck or a control rod in which assembly the screw threads will be externally on the rod and within a bore provided in the anvil end of the bit. 
     
     
         14 . A drill bit assembly as claimed in  claim 1 , which the bit has a series of splines along its shank and a screw thread within an axial bore extending from the anvil end of the shank, a series of internal splines extending from the end of the assembly wear-sleeve to cooperate with the splines on the bit shank and a rod in the assembly with a screw thread engageable with the screw thread in the shank and means for sliding the rod relative to the bit to engage and disengage the splines. 
     
     
         15 . A drill bit assembly as claimed in  claim 14 , in which the rod to be a distributor control rod extending from the backhead of the assembly, for the drill assembly to be a cluster drill including assemblies above defined wherein the rods are individually or collectively movable and rotatable. 
     
     
         16 . A drill bit assembly as claimed in  claim 15 , in which the screw threads are disengageable to permit the bit to be moved around the rod to index its position in the assembly and engaged to release the bit from the assembly. 
     
     
         17 . A down-the-hole drill bit assembly comprising a casing supporting in its operative end a resilient split retainer ring and a drill bit shank carrying splines around its anvil end for sliding engagement in co-operative splines in the casing to open the split ring for passage of the bit shank splines into and out of the casing. 
     
     
         18 . A down-the-hole drill bit assembly as claimed in  claim 17 , in which the ends of the splines on the bit shank and the upper and lower edges of the inner surface of the split ring are tapered. 
     
     
         19 . A down-the-hole drill bit assembly as claimed in  claim 17 , in which the operative end of the casing is provided by a chuck. 
     
     
         20 . A down-the-hole bit assembly as claimed in  claim 17 , in which is included a slideable control rod with a free end engageable with free end of the bit anvil to move the bit shank through the retainer ring.