Earth boring apparatus
Large hole boring equipment is used for boring a large diameter blind pilot hole. Then such equipment is removed from the hole and a room is blasted at the closed or blind end of the hole. Then the large hole cutterhead is replaced by a reamer and the equipment is inserted back into the hole. The reamer is an adjustable diameter type and its diameter is increased once it is within such room. A wrench carried by a drive head of a drilling machine is used to rotate a small diameter shaft which extends downwardly through the drill string to a lead screw which is a part of the reamer. Rotation of the lead screw causes axial travel of a lead nut. As the lead nut travels it moves a plurality of links which in turn swing a plurality of cutter carrying arms outwardly from the axis of rotation. Once the desired fly diameter of the reamer is achieved, the wrench is removed from the drive head, then the small diameter shaft is locked against additional rotation, and the drive head is drivingly attached to the upper end of the drill string so that it can be used for rotating the drill string and the reamer attached thereto.
- Assignee:
- Robbins Co
- Patent Number(s):
- US 4270618
- OSTI ID:
- 6148998
- Resource Relation:
- Patent File Date: Filed date 20 Apr 1979
- Country of Publication:
- United States
- Language:
- English
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