CUTTING ELEMENT HAVING A SELF SHARPENING TIP

Abstract

A cutting element including a shank portion and a conical cutting portion. The conical cutting portion has a narrow end and a broad end connected to the shank portion. The conical cutting portion narrow end has an insert receiving recess, and an insert is secured in the insert receiving recess. The insert has an outer layer made of tungsten carbide, and an inner core made of a material with a greater hardness than the outer layer.

Description

BACKGROUND OF THE INVENTION

This invention relates to cutting elements or bit members or picks and is particularly concerned with such elements having a pointed end that makes contact with the material to be cut. Such cutting elements are typically called a rotary cone bit of the pick type.

A cutting element or pick or bit member according to the present invention is a member somewhat like the cutting bit in a machine tool and having a metal body with a hard region or a hard insert therein at the place where the bit member engages the work. Such bit members are well known in many industries, such as in the mining industry and usually comprise a steel body, such as forged steel, with a cemented tungsten carbide tip or insert secured thereto as by brazing. The tip usually ends with a small radius and thus is easy to penetrate into the material being cut. As the carbide wears, the tip rounds off or dulls slowing penetration into the material to be cut.

Some bit members have been made with one or more layers of polycrystalline diamond or a diamond and carbide mixture, coating the exposed part of the bit tip. However, the diamond coating is brittle and flakes off except under the easiest cutting conditions.

SUMMARY OF THE INVENTION

One of the principal objects of the invention is to provide an improved cutting element that maintains its hard tip longer than with current cutting elements, and which tends to remain pointed or sharp as the cutting element wears.

The cutting element of the invention has a bit tip with a diamond (or other material harder than the grade of carbide making up the rest of the bit tip) core on the cylindrical axis of the bit tip. The tougher carbide on the outside will protect the brittle diamond from impact. The diamond exposed at the tip will protect the carbide from excessive wear. As the diamond and carbide wear together, they should provide a self sharpening action.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a bit holding apparatus.

FIG. 2 is a partial cross-sectional view of the bit shown in FIG. 1, with a hardened insert at the end of the bit according to the present invention.

FIG. 3 is a cross sectional view of an alternate embodiment of the insert at the end of the bit shown in FIG. 2.

Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of “consisting of” and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. Further, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upward” and “downward”, etc., are words of convenience in reference to the drawings and are not to be construed as limiting terms.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein the showings are for purposes of illustrating the present preferred embodiments of the invention only and not for purposes of limiting same, the Figures show a mining machine cutting drum (not shown) which supports a cutting bit 12 by means of a bit holder 18.

As is well known in the art, the cutting drum (not shown) is supported by a mining machine (not shown) for rotation while being vertically moveable and while the mining machine advances forward. As is also well known, the cutting drum (not shown) typically includes a plurality of cutting bits 12 arranged thereon; however, the present description will now be directed to a single cutting bit 12 and the structure of a single present bit holder 18.

The bit holder 18 may be attached directly or indirectly to the drum 10. For example, the bit holder may be welded or clamped to the drum 10 or may be secured to a mounting block attached to the drum 10. As described hereinafter, the bit holder 18 receives and retains a sleeve 50 which rotatably receives the bit 12.

The cutting element or bit 12 includes a central cylindrical shank portion 24 and having an enlarged conical cutting portion or nose 26 attached thereto such that a shoulder area 28 is formed there between. The cutting bit has a central axis shown at 29 with a hard cutting tip 30 on one end of the cutting bit 12. The cutting bit 12 includes on its other end a recessed notch 32 and terminates in an end shoulder 34 such that a retaining ring (not shown) may be received within the notch 32 to prevent the axial removal of the cutting bit 12 from a sleeve 50. In other embodiments (not shown), the shoulder area 28 can be omitted.

The bit holder 18 has a body portion 38 and a base portion 40. The base portion 40 attaches directly to the cutting drum (not shown) or indirectly by means of a mounting block (not shown). The body portion 38, which is integral to the base portion 40, includes an aperture 42 for receiving a coaxial sleeve 50. The aperture 42 defines an inner surface 42a. The body portion 38 includes a contact face 44 which is shown as perpendicular to the longitudinal axis 46, which is the same as the central axis 29 of the aperture 42, but which may also be formed as a cone whose surface is at an angle with respect to the longitudinal axis 46 of the aperture 42.

The sleeve 50 has an elongated body member 52 and a collar 54, the collar 54 having an inside surface 56 and an outside surface 58. The inside surface 56 of the collar 54 abuts the contact face 44. The collar 54 is shown as having an inside surface 56 which is perpendicular to the longitudinal axis 46 of the aperture 42; however, the inside surface can be conical having a conical surface at an angle with respect to the longitudinal axis 46 corresponding to the angle of the contact face 44. The outside surface 58 of the collar 54 has a beveled surface 60 and a flat surface 62. The body member 52 of the sleeve 50 defines an outer surface 52a.

The body member 52 of the sleeve 50 has a bore 64 which is coaxial with the bit axis 29. The bit 12 is rotatably received by the bore 64. The shank 24 of the bit 12 is slightly smaller than the bore 64. The shank 24 is retained in the bore 64 by the retaining ring and the shank may rotate about the central axis 29 in order to avoid uneven wearing of the tip 30 of the cutting bit 12. The shoulder area 28 of the bit 12 abuts the flat surface 62 to position the bit 12 axially in the bore 64 and transmit cutting forces.

More particularly, as shown in FIG. 2, the conical cutting portion 26 has a narrow end 70 and a broad end 74 connected to the shank portion 24. The conical cutting portion narrow end 70 has an insert receiving recess 78, and the hard cutting tip or insert 30 is secured in the insert receiving recess 78, such as by brazing. The insert 78 has an outer layer 82 made of tungsten carbide, and an inner core 86 on the cylindrical axis 29 (see FIG. 1) of the conical cutting portion 26. The inner core 86 is made of a material with a greater hardness than the outer layer 82. Preferably, the insert 30 has a cylindrical portion with the outer end 90 of the insert 30 having a small radius so that the outer end 90 forms a point for aiding in cutting material.

In the preferred embodiment, the inner core 86 is made of diamond, but in less preferred embodiments, a hardened form of tungsten carbide can be used. The diamond core 86 is a solid diamond, not a coated structure. Further, in the preferred embodiment, the inner core 86 is exposed at the outer end 90. The inner core 86 is made from a sheet of material, but in other embodiments (not shown), the inner core 86 may be cylindrical, or any other shape. Further, in an alternate embodiment, as shown in FIG. 3, the insert 94 can include a second layer or core 96 with a hardness between that of the outer layer 82 and the inner core 86, or even more layers or cores. In order to obtain the advantage of maintaining the small radius at the insert outer end 90, each more inner layer in the insert 30, going from the outside of the insert 94 to the inside, should be harder than the preceding more outer layer.

Various other features and advantages of the invention will be apparent from the following claims.

Claims

1. A cutting element including

a shank portion, a conical cutting portion, the conical cutting portion having a narrow end and a broad end connected to the shank portion, said conical cutting portion narrow end having an insert receiving recess, and an insert secured in said insert receiving recess, said insert having an outer layer made of tungsten carbide, and an inner core made of a material with a greater hardness than the outer layer.

2. A cutting element in accordance with claim 1 wherein said inner core is made of diamond.

3. A cutting element in accordance with claim 1 wherein said insert forms a point at the end of the conical cutting portion, and said inner core is exposed at said point.

4. A cutting element in accordance with claim 1 wherein said broad end is wider than said shank portion, forming a shoulder between the conical cutting portion and the shank portion.

5. A cutting element in accordance with claim 1 wherein said conical portion has a cylindrical axis, and said insert is on the cylindrical axis of said conical portion.