US3493268A - Cutter bit - Google Patents

Description

Feb. 3, 1970 A. B. BOWER, JR 3,493,268

' CUTTER BIT Filed June 16, 1965 INVENTOR. ARNOLD B. BOWER,JR

BY WWW/M A T TORNEV United States Patent C) 3,493,268 CUTTER BIT Arnold B. Bower, Jr., St. Clair Shores, Mich., assignor to General Electric Company, a corporation of New York Filed June 16, 1965, Ser. No. 464,370 Int. Cl. E21c 13/00 U.S. Cl. 29986 2 Claims ABSTRACT OF THE DISCLOSURE A cutter bit having a generally cylindrical shank and a cutter tip mounted centrally at both axial extremities of the shank. The center portion of the cutter bit contains a radially projecting shoulder encircling the shank, providing seating surfaces for the bit on both sides thereof, so that the bit may be reversibly held in a block. Circumferential recesses between the shoulder and both cutter tips are adapted to receive holding means to retain the bit in a block.

Cutter bit This invention relates to a cutter bit, and more specifically to a cutter bit of the type used in mining machines.

Cutter bits of the type having a generally cylindrical shank and a cutter tip mounted at a central axial extrimity of the shank are known and have been used to advantage in mining machines. Such cutter bits possess the advantage, as contrasted with rectangular bits in which the cutting tip is mounted radially offset from the central axis, of having the cutting forces operate through a larger cross section of both the bit body and the block in which it is mounted.

The principal object of the present invention is to provide a cutter bit, of the type having a generally cylindrical shank and a centrally located cutting tip, with cutting tips at both ends thereof so that the bit is reversible, thereby having approximately twice the life of previous cutter bits of this type but nevertheless retaining its advantages. Other objects will appear from the description of the invention which follows.

The reversible cutter bit of the present invention comprises a generally cylindrical shank having cutting tips at its axial opposite ends and a raised or projecting collar at its approximate axial midpoint. The collar provides dual seating or bearing surfaces for the cutter bit when it is positioned in a block in which it is held. The shank contains two circumferential recesses, one between each of the cutting tips and the central collar to receive a holding means for retaining the bit in a block.

The invention will be more clearly understood from the following description taken in connection with the accompanying drawing in which FIGURE 1 is an elevational view, partially in section, of a block of the type used in the mining of coal with the bit of the invention mounted for operation therein;

FIGURE 2 is a side elevational view of the cutter bit shown in FIG. 1; and

FIGURE 3 is a fragmentary side elevational view showing an alternate tip design.

In the drawing, FIG. 1 shows a block 1 having a cylindrical bore 2 in which is mounted a reversible cutter bit 3 of the invention. The bit 3 may form a relatively loose fit in the bore 2 for easy insertion and removal of the bit and for rotation of the bit in the block during operation. The forward end of bore 2 is flared to provide a seating or bearing surface 4 for the corresponding bearing surface 5' (FIG. 2) of the bit. The cutter bit 3 is held in block 1 by means of a retention pin 6 fitting a hole 7 through the block. A plurality of blocks of the type shown in FIG. 1 may be attached to a mining machine in conventional fashinon, as by welding or other suitable means.

As can be most clearly seen in FIG. 2, the cutter bit comprises a generally cylindrical shank 8 having identical cutting tips 9 and 9' of cemented tungsten carbide at axially opposite ends thereof. Shank 8 is conically tapered at 10 and 10' toward cutting tips 9 and 9' respectively at both ends of the shank. The central portion of the shank contains a raised rim or collar 11 projecting annularly around the axial center of the cutter bit. The collar 11 is tapered radially on both sides thereof to provide annular seating surfaces 5 and 5' for the bit When the bit is held in the block. As can be seen in FIG. 1, when cutting tip 9 is in operational position projecting from the block, the seating surface 5' most remote from tip 9 is utilized for seating the cutter bit in the block and, of course, seating surface 5 is used when the position of the cutter bit in the block is reversed to place cutting tip 9" in operational position. A continuous curved circumferential recess 12 and 12' between the collar 11 and each tip 9 and 9' respectively is adapted to receive a holding pin to prevent removal of the bit from the block (as shown in FIG. 1).

The cutting tips may assume a variety of shapes. The exposed portion of the tips may be conical and terminate in a point or they may even be cylindrical and terminate in a fiat cutting surface. The drawing illustrates two such shapes. As can be seen in FIGS. 1 and 2, the exposed portions of tips 9 and 9' are tetrahedral and contain a plurality of surfaces 13 and 13' which terminate in a sharp cutting point 14 and 14' and which together form a generally tetrahedral shaped cutting tip at both ends of the shank. The base 15 and 15' of the tips 9 and 9, which are brazed to the bit by conventional brazing techniques, are of cylindrical shape.

FIG. 3 illustrates an alternate tip shape in which the projecting portion of tip 16 is of hemispheroidal shape. The tip is otherwise the same as tips 9 and 9 of FIGS. 1 and 2.

As will be noted from the drawing, the cutter bit is symmetrical .about a plane radially bisecting the shank, i.e., a plane passing perpendicular to the axis of the bit through the center of collar 11 in FIG. .2. Such symmetry is of course necessary if the cutter bit is to be truly reversible in the block in which it is mounted to present two cutting tips in substantially identical operating position. As will also be noted from the drawing, the design of the bit is such that it is also symmetrical about a plane passing through the central axis of the bit. Such design is desirable to permit rotation of the bit in the block during cutting, or to permit utilization of the bit regardless of its particular position of rotation around its central axis when inserted in the block.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A reversible cutter bit comprising a generally cylindrical shank having cutting tips at central axially opposite ends thereof, said shank being conically tapered at said opposite ends toward said cutting tips,

the central portion of said shank containing a radially projecting collar encircling the shank, said coller being tapered radially on both sides thereof to provide annular seating surfaces for the bit on both sides thereof when the bit is held in a block,

said shank containing a continuous circumferential recess along a cylindrical portion thereof between said collar and the conically tapered portions of said shank to receive a holding pin adapted to retain said bit rotatably in a block,

said bit being symmetrical about both its central axis and a plane radially bisecting the shank, the shank being in the shape of a right cylinder except for the conically tapered opposite ends thereof, the tapered radially projecting collar and the circumferential recess.

2. A bit member comprising: a body symmetrical about a central longitudinal axis and having an enlarged diameter region in about the middle of the length thereof with tapered shoulders on opposite sides, the body on each side of said region being smaller in diameter than said region and including a cylindrical region operable to serve as a supporting shank for the bit member, the body on each end terminating in a point, an element harder than said body carried by said body at each said point, a support block having a bore for receiving the shank of the bit member, and means for retaining such shank in said bore against axial movement therein while permitting free rotation of said body on said axis.

References Cited UNITED STATES PATENTS Krekeler 299-92 Krekeler 299-92 Holmes 175-383 Simmons 299-93 Ellis et al. 175-383 Cummingham 175-410 Krekeler 299-92 Snipe 299-91 US. Cl. X.R.

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