Boring or penetrating the earth – Bit or bit element – Impact or percussion type
Reexamination Certificate
2002-10-03
2004-11-16
Dang, Hoang (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Impact or percussion type
C175S427000
Reexamination Certificate
active
06817429
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention pertains to drill bits. More specifically, the present invention is directed to drill bit blades adapted to be received in a drill body, the drill bit blades and drill body being keyed or indexed to facilitate centering.
2. Description of the Related Art
It is well known that drill bits adapted to bore through rock for the installation of roof bolts or to drill and blast to allow material to be removed in mines and the like have a carbide blade mounted or brazed in a transverse slot at the distal end of a drill body such as an elongate hollow tubular body or the like. One drill body used in association with a conventional dust collection system has access ports positioned near the blade, and the ports communicate with the inner bore of the body. Another embodiment used in association with a conventional auger system, for example, defines a post for mounting. Such blades are adapted to drill holes having a diameter of one inch and larger into the strata in the roof of a mine or the like. A vacuum is drawn through the hollow drill body to draw cuttings removed by the blade through the ports, through the hollow shaft of the drill bit, and to a collection location remote from the drilling. Alternately, a water flushing system may be used in which pressurized water is forced through the drill body, and out through the ports to flush the cuttings out the mouth of the hole. Also, an auger system can be used to remove the cuttings or material.
To withstand the wear incurred as such drill bits bore through the strata or rock, the blades of such drill bits are typically made of tungsten carbide and have a hardness in the range of 89.0 to 91.0 on the Ra hardness scale. A relatively small increase in the hardness of the tungsten carbide of the blade will substantially extend the useful life of a drill bit and enable the drill bit to bore or drill through substantially more rock before it becomes unusably dull. For example, a first drill blade which is harder than a second blade by a hardness rating of 0.5 on the Ra hardness scale may be capable of drilling through 50 percent or more rock or strata such as salt, gypsum, etc., when compared to the second drill blade.
On the other hand, harder carbide blades are more brittle than softer tungsten carbide blades and tend to fracture as a result of the stresses upon the blade. It has been found that tungsten carbide blades typically fracture along the central longitudinal axis of the blade as a result of the thrust forces applied during the drilling.
A drill blade attached to a drill bit and used to bore a cylindrical hole is subjected to a number of forces. At the center of the drill blade, the thrust forces arising from the drill being forced into the hole are maximized. At the outer edges of the blade, strong shear forces are developed as the blade removes stone to extend the hole. The cutting edges of drill blades generally wear most noticeably at the outer ends rather than at their centers because the blade surface footage and the sheer forces are greater at the ends of the blade than at the center. To wit, speed is measured as the ratio of distance to time. The time to complete one rotation of the blade is the same at any distance from the center. The distance traveled through one rotation is measured by the circumference at the particular radius, which is measured by &pgr;r
2
. Because one factor of the circumference is the square of the radius, the speed of the blade at any point increases exponentially from the center (zero) to the outer limit. If the blade is not centered on the body of the drill bit, it will be subjected to uneven forces causing stress and breakage of the blade.
Various drill bit blades have been provided for various uses. Typical of the art are those devices disclosed in the following U.S. Patents:
U.S. Pat. No.
Inventor(s)
Issue Date
4,342,368
D. Denman
Aug. 3, 1982
4,489,796
J. Sanchez et al.
Dec. 25, 1984
4,550,791
E. Isakov
Nov. 5, 1985
4,787,464
R. W. Ojanen
Nov. 29, 1988
5,184,689
D. C. Sheirer et al.
Feb. 9, 1993
5,269,387
L. S. Nance
Dec. 14, 1993
5,287,937
P. A. Sollami et al.
Feb. 22, 1994
5,297,643
R. H. Montgomery, Jr. et al.
Mar. 29, 1994
5,311,959
W. F. Adams
May 17, 1994
5,375,672
K. Peay et al.
Dec. 27, 1994
5,429,199
D. C. Sheirer et al.
Jul. 4, 1995
5,458,210
P. Sollami
Oct. 17, 1995
5,628,376
W. Kleine
May 13, 1997
5,630,478
T. O. Schimke
May 20, 1997
5,735,648
W. Kleine
Apr. 7, 1998
5,829,540
K. Reay et al.
Nov. 3, 1998
5,996,715
K. Reay et al.
Dec. 7, 1999
6,026,918
L. A. Briese
Feb. 22, 2000
6,044,919
L. A. Briese
Apr. 4, 2000
6,145,606
P. W. Haga
Nov. 14, 2000
6,260,637
A. Hausmann et al.
Jul. 17, 2001
6,260,638
T. R. Massa et al.
Jul. 17, 2001
6,267,542
A. Salmon
Jul. 31, 2001
Des. 340,248
W. J. Brady
Oct. 12, 1993
Des. 351,174
W. J. Brady
Oct. 4, 1994
Des. 424,579
W. J. Brady
May 9, 2000
Des. 430,578
W. J. Brady
Sep. 5, 2000
Of these patents, the '638 patent issued to Massa et al., discloses several embodiments of cutting inserts. One in particular, illustrated in FIGS. 20A and 20B therein, includes a bottom surface defining a saw tooth shaped notch. The notch as a generally vertical surface, perpendicular to the bottom surface, and an inclined surface. A portion of the bit body including the slot has a bottom surface defining a saw tooth shaped projection. The projection has a surface which is generally perpendicular to the bottom surface of the slot and an inclined surface. The configurations of the cutting insert notch and the bit body projection are complementary, thereby serving a means for fixing the position of the cutting insert relative to the bit body. Other similar embodiments are disclosed by Massa et al., as well. However, Massa et al., do not disclose a cutting bit that extends across the entire diameter of the bit body and therefore are not concerned with centering the cutting insert.
Sheerer et al., in the '689 patent, disclose an insert for use in a rotary drill bit define two opposing portions, each having a leading face. The first and second portions of the insert are offset from the center such that the cutting edge on the first portion is linearly aligned with the cutting edge on the second portion, the cutting edges meeting at the center of the cutting insert. The drill bit body must define a slot having a configuration to complement the offset configuration of the insert. If the slot in the drill bit body is closely toleranced, then the insert will be centered.
In the '478 patent, Schimke discloses a masonry drill having an elongated axial body with at least one discharge groove and a transverse slot located at one end with a hardened drill bit insert brazed within the slot. The hardened insert has projections extending outward from flat planar surfaces which hold the insert in proper orientation within the axial drill body so that it may be brazed into place subsequent to insertion into the drill body. More specifically, the cylindrical drill body defines a transverse slot having smooth channel side walls. The drill bit insert defines at least one rib member on either side thereof, the rib members being fabricated from hardened carbide material. The drill bit insert is pressed into slot using a press with force sufficient enough to insert the carbide insert fully into the slot and allow the rib members to engage the side walls. As the drill bit insert is pressed into the drill body slot, the rib members score the side walls when properly inserted. Scoring of the side wall faces ensures the snug fit of the drill bit insert into the slot so that the insert may be subsequently properly affixed thereto by thorough brazing. However, Schimke does not address centering of the drill bit insert.
Sollami et al., in their '937 patent, disclose a drill bit and blade. The blade defines a vertical rib positioned axially along the centerline of at least one side of t
Dang Hoang
Pitts & Brittian P.C.
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