Down-the-hole hammer drill assembly

Abstract

The invention provides a down-the-hole drill assembly ( 21 ) comprising an assembly of a bit ( 9 ) and co-operating chuck ( 19 ) including a bit ( 9 ) mounting with an external sleeve ( 4 ) surrounding the bit ( 9 ) mounting, the sleeve ( 4 ) during operation of the drill being clamped between the chuck ( 19 ) and the bit head ( 9 ). The sleeve ( 4 ) provides a shield against ingress of debris into the bit and chuck assembly, and provides control of exhaust from the assembly. The sleeve ( 4 ) further provides control of a pin ( 107 ) releasably engaging the bit ( 9 ) to the chuck ( 19 ).

1 . A down-the-hole drill assembly comprising an assembly of a bit and co-operating chuck including a bit mounting with an external sleeve surrounding the bit mounting, the sleeve during operation of the drill being clamped between the chuck and the bit head. 
     
     
         2 . The down-the-hole drill assembly as claimed in claim I in which the sleeve forms a shield against ingress of debris into the bit and chuck assembly. 
     
     
         3 . The down-the-hole drill assembly as claimed in  claim 1  in which the assembly includes a lower chamber for operating fluid and the sleeve controls an exhaust outlet from the lower chamber. 
     
     
         4 . A The down-the-hole drill assembly as claimed in  claim 1  in which the sleeve is internally splined to engage complementary splines on the bit and chuck. 
     
     
         5 . The down-the-hole drill assembly as claimed in  claim 4  in which the bit splines are axially shorter than the chuck splines. 
     
     
         6 . The down-the-hole drill assembly as claimed in  claim 5  in which the splines in the sleeve are of substantially equal length to the combined length of the splines on the bit and the chuck. 
     
     
         7 . The down-the-hole drill assembly as claimed in  claim 1  in which the sleeve provides control for exhaust from the assembly through the wall of the chuck for reverse circulation through pick up holes and a bore in the bit. 
     
     
         8 . The down-the-hole drill assembly as claimed in  claim 1  in which the sleeve provides control of a pin releasably engaging the bit to the chuck. 
     
     
         9 . The down-the-hole drill assembly as claimed in  claim 8  in which the assembly comprises a stepped drill bit engageable with its narrow end within a drill chuck and having a transverse retaining pin engaged through the chuck and a slot in the bit with a sleeve slidably mounted on the chuck to be operatively held on the chuck against the step on the bit. 
     
     
         10 . The down-the-hole drill assembly as claimed in  claim 8  in which the chuck is stepped to enable the sleeve to slide on a reduced diameter end of the chuck to be clamped between the chuck or the end of a wear sleeve and the bit head. 
     
     
         11 . The down-the-hole drill assembly as claimed in  claim 1  comprising a drill bit having a shank engageable in the end of a chuck adapted to be retained in the end of a casing for the drill, the shank and chuck provided with alignable longitudinally extending transverse slots and means to releasably retain a pin on which the shank can be reciprocated. 
     
     
         12 . The down-the-hole drill assembly as claimed in  claim 11  in which the pin is flat and has a shaped head at each end. 
     
     
         13 . The down-the-hole drill assembly as claimed in  claim 11  in which the chuck and drill shank have a series of mating splines. 
     
     
         14 . The down-the-hole drill assembly as claimed in  claim 11  in which the bit has a head adapted to seat on the drill chuck. 
     
     
         15 . A The down-the-hole drill assembly as claimed in  claim 14  in which the chuck is securable in the end of a drill string wear sleeve. 
     
     
         16 . The down-the-hole drill assembly as claimed in  claim 12  in which the heads on the pin are offset on the ends of the pin.