Boring or penetrating the earth – Bit or bit element – Impact or percussion type
Reexamination Certificate
1998-12-31
2001-01-23
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Impact or percussion type
C175S427000, C299S11200T
Reexamination Certificate
active
06176332
ABSTRACT:
BACKGROUND OF THE INVENTION
The expansion of an underground mine (e.g. a coal mine) requires digging a tunnel which initially has an unsupported roof. To stabilize and support the roof a roof bolt must be inserted into the roof to provide support. The operator must first drill holes in the roof through the use of a rotatable cutting bit or roof drill bit. A roof bolt is then inserted into each one of the holes.
A common roof drill bit design uses a cutting insert that has been brazed into a slot at the axially forward end of the roof drill bit body. U.S. Pat. No. 5,400,861 to Sheirer discloses various roof drill bits. U.S. Pat. No. 4,603,751 Erickson also discloses various roof drill bits. Applicants hereby incorporate U.S. Pat. No. 4,603,751 and U.S. Pat. No. 5,400,861 by reference herein. In addition, the following catalogs published by Kennametal Inc. of Latrobe, Pa. (U.S.A.), which are hereby incorporated by reference herein, disclose roof drill bits: “Kennametal Mining Products”, Catalog A96-55(15)H6 (September 1996) [36 pages in length], and “Kennametal Mining Products” Catalog B92-75R(3)M5 (1992) [36 pages in length]. Furthermore, U.S. patent application Ser. No. 09/108,181 filed on Jul. 1, 1998, now U.S. Pat. No. 6,044,920 by Massa and Siddle and U.S. patent application Ser. No. 08/893,059 filed on Jul. 15, 1997, now U.S. Pat. No. 6,109,377 by Massa and Siddle disclose roof drill bits and cutting inserts for roof drill bits. These two patent applications (U.S. Pat. Nos. 6,109,377 and 6,044,920) are hereby incorporated by reference herein.
While the above roof drill bits and the cutting inserts for such roof drill bits have provided satisfactory performance characteristics, there remains room for improvement of the overall performance, as well as room for improvement of certain features of the roof drill bits and the cutting inserts therefor. In this regard, applicants believe that it would be desirable to provide for an improved rotatable cutting bit (e.g., roof drill bit), as well as the cutting insert for the rotatable cutting bit, that presents a cutting insert which has cutting edges with increased strength over earlier cutting inserts.
SUMMARY OF THE INVENTION
In one form thereof, the invention is a rotatable cutting bit for penetrating an earth formation. The rotatable cutting bit comprises an elongate bit body having a forward end and a rearward end. The bit body further defines a peripheral surface. The bit body has a first cutting insert affixed thereto at the axially forward end thereof. The first cutting insert has a first leading cutting edge and a first side clearance cutting edge. The first cutting insert is attached to the bit body so that the first side clearance cutting edge radially extends past the peripheral surface of the bit body so as to engage the earth formation. At least a portion of the first leading cutting edge is arcuate.
In another form thereof, the invention is a rotatable cutting bit for penetrating an earth formation wherein the rotatable cutting bit comprises an elongate bit body which has a forward end and a rearward end and the bit body defines a peripheral surface. The bit body also has a first cutting insert attached to the bit body at the axially forward end thereof wherein the first cutting insert presents a top surface and a leading surface wherein the top surface intersects the leading surface to form a first leading cutting edge. The first cutting unset further presents a first side clearance cutting edge. The first cutting insert is attached to the bit body so that the first side clearance cutting edge radially extends past the peripheral surface of the bit body so as to engage the earth formation. The leading surface has a radially inward surface portion and a radially outward surface portion wherein the radially inward surface portion is distinct from the radially outward surface portion. The first leading cutting edge has a radially inward portion defined by the intersection of the top surface and the radially inward surface portion of the leading surface and a radially outward portion defined by the intersection of the top surface and the radially outward surface portion of the leading surface. The radially inward portion is disposed at an angle with respect to the radially outward portion.
In still another form thereof, the invention is a cutting insert for use in a rotatable cutting bit for the penetration of an earth formation wherein the cutting insert is disposed in a seat in the cutting bit with a peripheral surface. The cutting insert comprises a cutting insert body that has a top surface, a bevelled surface, and a leading surface. The leading surface and the top surface intersect so as to form a leading cutting edge at the intersection thereof. The bevelled surface and the leading surface intersect so as to form a side clearance cutting edge at the intersection thereof. The leading cutting edge has at least a portion thereof being arcuate.
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Massa Ted R.
Siddle David R.
Bagnell David
Dougherty Jennifer R.
Kennametal Inc.
Prizzi John J.
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