Title:
DRILLING TOOL
Document Type and Number:
Japanese Patent JP2713266
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To enlarge a diameter in case drilling and positively contract the diameter regardless of the property of the natural ground.
SOLUTION: A device 2 coaxially inserted in a casing pipe 30 is provided with a plurality of blocks 5 arranged in such a way that side end faces 5a, 5b are opposed and that circular arc parts 5c nearly form a circle of almost the same diameter as the device 2 as a whole. This block 5 can be enlarged in diameter by autorotation around the axis of the block. A tip face 30a of the casing pipe 30 is provided with a protrusion 1 at least in one place so as to come in contact with the outer peripheral surface 5d of the diameter-enlarged block 5 at the time of rotating the device 2 in a reverse direction to a drilling rotating direction and to autorotate the block 5 around its axis until its rotating locus becomes the inner diameter or less of the casing pipe 30.
Inventors:
Takeshi Hayashi
Akihiro Saburi
Kazuyoshi Yoshida
Akihiro Saburi
Kazuyoshi Yoshida
Application Number:
JP23309795A
Publication Date:
February 16, 1998
Filing Date:
September 11, 1995
Export Citation:
Assignee:
Mitsubishi Materials Corporation
International Classes:
E21B10/32; E21B7/28; E21B7/30; E21B10/40; (IPC1-7): E21B10/32; E21B7/28; E21B7/30
Attorney, Agent or Firm:
Masatake Shiga (2 outside)