Boring or penetrating the earth – Tool removable or insertable through or around driving or... – Laterally shiftable cutter element movable through shaft
Patent
1995-07-07
1997-09-02
Tsay, Frank
Boring or penetrating the earth
Tool removable or insertable through or around driving or...
Laterally shiftable cutter element movable through shaft
175273, E21B 1064
Patent
active
056621825
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a system for in situ replacement of cutting means for a ground drill, and in particular, though not exclusively, to a system for the in situ replacement of drill bits and/or reamers of core sampling drills.
BACKGROUND OF THE INVENTION
In ground drilling it is customary to detachably fix a drill bit to a lower end of a drill string of a ground drill and rotate the drill string to effect drilling of a hole in the ground by the drill bit. A reamer is usually connected between the lower end of the drill string and the drill bit to ream the circumferential wall of a hole being drilled. The drill string is formed by screwing individual drill rods together. Drill rods usually come in fixed lengths of 1.5, 3 or 6 meters. As the drill progresses into the ground additional drill rods are screwed into the upper end drill string.
During drilling it will be necessary to replace the drill bit and reamer either as a result of dulling of the drill bit or due to variations in the sub strata. Although the drill bit must be replaced more often (usually at least six times more often) than the reamer.
In order to replace a drill bit or reamer the entire drill string must be pulled out of the ground rod by rod, the drill bit replaced, and the drill string reassembled, rod by rod as it is relowered into the ground to continue drilling. The need to fully withdraw, disassemble and reassemble the drill string when changing the drill bit/reamer is a slow and costly exercise, with the cost increasing as hole depth increases and the drill string becomes longer.
Several attempts have previously been made to overcome this problem at least insofar as drill bits are concerned by use of retractable drill bits which releasably engage the lower end of the drill string and can be disengaged and retracted through the drill string for changing while the drill string remains in situ, thereby avoiding the need to withdraw the drill string from the hole. However, these attempts have not proven to be commercially successful for various reasons including: being extremely complicated in design or application thereby resulting in a large number of failure modes and/or being to costly to manufacture or maintain in an operational state; being prone to fouling due to drilling fluid and contaminants burring or jamming segments of the drill bit; misalignment of drill bit segments upon engagement with the drill string; reduction in diameter of the core sample due to fixing of the drill bit to an inner tube of the drill string; reduction in penetration rate; and breaking of individual segments of the drill bit.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system for in situ replacement of drill bits and/or reamers of a ground drill which attempts to overcome at least one of the above-described deficiencies in the prior art.
According to the present invention there is provided a system for in situ replacement of cutting means of a ground drill where the cutting means is composed of a plurality of segments, said system comprising: drill, said tubular member provided with seating means formed circumferentially about an inner wall of said tubular member for seating said segments in a cutting position in which said segments can contact the ground; for transporting said segments to and from said member, said tool being switchable between an installation mode in which segments are loaded onto said tool for installation in said member and a retrieval mode in which said tool is devoid of segments for retrieval of segments previously installed in said member; being moveable by said tool between an installation position in which said insert locates said segments in said seating means and retains said segments in said cutting position between said insert and said member and, a retrieval position in which said insert is retracted to release said segments from between said insert and said member, said insert dimensioned to allow said tool to extend therethrough, and said insert and t
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PCT/SU89/00123; Feb. 1990; Grigorievich.
Egan Matthew Vance
McLeod Gavin Thomas
Down Hole Technologies Pty Ltd.
Tsay Frank
LandOfFree
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