Boring or penetrating the earth – Bit or bit element – Impact or percussion type
Patent
1996-10-25
1998-01-06
Schoeppel, Roger J.
Boring or penetrating the earth
Bit or bit element
Impact or percussion type
175431, 175432, E21B 1040
Patent
active
057044384
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a rotary borer of the kind comprising a body having mounting means for mounting it on a drill steel, and carrying one or more cutting tips of a hard, abrasion resistant material, which tips are arranged to cut into rock or rock-like substrate in use.
It relates further to a method of releasing such a tip from such a body.
The Applicant believes that this invention will find application particularly in the field of borers for use in coal mining operations. For purposes of this specification, that application will predominantly be borne in mind, but the invention is not limited to that application. In coal mining, a coal seam is mined by means of continuous miners leaving a void between a hanging wall and a foot wall. To prevent the hanging wall from collapsing, deep holes are bored into the hanging wall and roof bolts are anchored in the holes to allow support structure to be suspended from the roof bolts. The Applicant believes that a borer in accordance with this invention can advantageously be used in the drilling of such deep holes.
SUMMARY OF THE INVENTION
In accordance with a first aspect of this invention, there is provided a rotary borer including a body which is generally round having a rotation axis, a front and a rear, the body comprising drill steel mounting means for releasably mounting the borer on a drill steel to be rotated in a predetermined rotary direction about the rotation axis in use, and tip mounting means including an anvil formation defining a forwardly extending anvil surface and an opposing retaining formation defining a forwardly extending retaining surface, the anvil surface and retaining surface being forwardly diverging to form between them a correspondingly forwardly extending slot which slot tapers rearwardly at an angle smaller than about 5.degree.; and a tip of hard, abrasion-resistant material having a front, a rear and sides tapering toward the rear at an angle which is complemental to the angle of the slot, the tip being operatively received in the slot such that pressure on the tip during boring, in a longitudinal direction opposite to the direction in which boring advances, wedges the tip into the slot to cause frictional retention of the tip in the slot, wherein the anvil surface, relative to the predetermined direction of rotation in use, is arranged to trail the tip, the anvil surface having a non-planar seat to seat the tip which has a complemental seat formation, the anvil surface extending forwardly to a position at most a small distance short of the forward extremity of the tip to support the tip along a major portion of its length, the retaining formation terminating longitudinally short of the forward extremity of the anvil surface and well short of the forward extremity of the tip to leave a relatively long portion of the tip toward its front exposed.
The taper angle may be between about 1.degree. and about 3.degree., preferably about 2.degree..
In a preferred embodiment, said tip mounting means may be first tip mounting means disposed generally radially toward one side of the rotary axis and in which said tip may be a first tip, the borer including second tip mounting means circumferentially spaced from the first tip mounting means and a second tip similarly received in the second tip mounting means. The borer may be symmetrical about the rotation axis. The first and second tip mounting means may be identical and the first and second tips may be identical. The first and second tips may be radially aligned.
In one embodiment, the tips may have peaks or forward extremities toward their radially inner ends. If desired, the first and second tips may be integral to form a composite tip. This embodiment may be particularly useful in so called "dry drilling" application, i.e. when drilling is effected without water as a lubricant or flushing medium.
In another embodiment, the first tip may have a peak or forward extremity toward a radially inner end and the second tip may have a peak or forward extremity to
REFERENCES:
patent: 4026372 (1977-05-01), Hampson
patent: 5172775 (1992-12-01), Sheirer et al.
patent: 5184689 (1993-02-01), Sheirer et al.
patent: 5220967 (1993-06-01), Monyak
Holtshausen Richard G.
Kloppers Stephanus F.
Wright Noel G.
Kennametal Inc.
Kennametal South Africa (Proprietary) Limited
Prizzi John J.
Schoeppel Roger J.
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