US2297363A - Cutting bit - Google Patents

Description

Sept. 29, 1942.

H. M. MORROW' CUTTING BI T Filed Oct. 3, 1940 fia. 4

fia 5 INVENTOR. Maw A4. Mo/mow Patented Sept. 29, 1942 CUTTING BIVT Harry M. Morrow, Canton, Ohio, assignor to The Bowdil Company Application October 3, 1940, Serial No. 359,508 A 6 Claims. (01. 262-33) My invention relates in general to cutting bits and more particularly to bits for cutting coal or other substances.

In the mining of coal or other substances, a cleft is cut in the lower level of the vein by means of a cutter bar around which revolves a power driven endless chain carrying a plurality of staggeredly arranged cutting bits constituting the subject matter of this invention. The shelf formed by the cleft is subsequently broken off by means of explosives or other suitable methods. When cutting the cleft, in the interest of economy and the saving of power, it is highly desirable that the cutting bits be not only strong and durable but also eificient in operation andv free from drag.

An object of my invention is the provision of a cutting bit which requires a minimum amount of power tooperate.

Another object of my invention is the provision of a cutting bit which produces very little drag.

Another object of my invention is the provision of a cutting bit which has a greater cutting clearance as the bit wears away.

Another object of my invention is to make the cutting clearance of the bit increase in substantial proportion to the amount that the cutting points of the bit wear away.

Another object ofmy invention is to make my bit have relatively narrow cutting faces for a substantial. distance to give longer wear.

Another object of my invention is the provision of a cutting bit which is durable and adapted to cut through hard substances.

Another object of my invention is the provision of a longitudinal double-ended bit having the shape of a minor segment of a double-concave disc.

Other objects andv a fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure 1 shows a front elevational View of my new and improved cutting bit;

Figure 2 shows a side elevational View of my new and improved cutting bit as shown in Figure 1;

Figure 3 shows a cross-sectional View of my bit, taken along the line 3-3 of Figure 2;

Figure 4 shows a cross-sectional view of my bit, taken along the line 4-4 of Figure 2;

Figure 5 shows a cross-sectional view of my bit, taken along the line 55 of Figure 2;

Figure 6 shows a front elevational view of a modified form of my cutting bit;

Figure 7 shows a side elevational view of the bit in Figure 6;

Figure 8 shows a front elevational view of a further modified form of my bit; and

Figure 9 shows a side elevational view of the bit shown in Figure 8.

With reference to Figures 1 to 5, inclusive, my improved cutting bit is solid and may be made of steel, shaped by forging or in any other suitable fashion. In front elevation, the cutting face .ll] of my bit is substantially diamond-shaped and has a relatively wide central portion, II and two relatively narrow opposite edge portions l2 and I3. The contour of the side edges l4, l5, l6 and ll of the front cutting face I!) between the relatively wide central portion l0 and the relatively narrow opposite edge portions l2 and I3 are depressed, arcuate, or concaved, and form cutting points l8 and I9 at opposite ends of the bit.

The side clearance faces 20 and 2| of my bit are substantially identical and are shaped like the segment of a circle. The side clearance faces 20 and 2| converge toward the rear edges thereof and meet in a relatively sharp juncture 22 which curves in a general longitudinal direction between the opposite cutting points I8 and I9, see Figures 2, 3, 4 and 5. The side clearance faces between the relatively wide central portion and the relatively narrow opposite edge portions [2 and I3 are depressed, arcuate, or concaved to produce a greater cutting clearance as the cutting points wear away. The shape of my bit constitutes a. minor segment of a double-concave disc. That is to say, the shape of my bit in Figures 1 to 5, inclusive, is substantially the same as that which would be produced if a disc having double-concave marginal edge surfaces were cut upon acord of the circumference, the

arcuate juncture 22 being equivalent to the arc of t'he circumference of the disc and the front face l0' being equivalent to the plane produced by the cutting action.

Thebits are removably mounted in the lugs of the endless power driven chain which revolves around the cutter bar. When one of the cutting points of the bits wears away the bits are reversed, giving a double cutting life to the bits. The cutting points may be treated or hardened by any suitable means such as, for example, by depositing a hardened metal thereon. The bits areheld in the chain lugs at a slight forward angle as shown in Figure 2.

, The provision of the varying cutting clearance is progressively shown in Figures 3, 4 and 5. In

the region near the cutting points shown by Figure 3, the clearance is rather small. At the cutting points of the bit, the drag does not have an opportunity to manifest itself since the horizontal distance of the side walls across the bit in the rear of the cutting faces is small, and for this reason the cutting clearance in the region of the cutting points may be rather small without producing any substantial increase in the drag of the bits in the cutting operation. By making only a very small clearance in the region of the cutting points, the cross-sectional area of the cutting points may be kept at a maximum, thereby giving additional strength to the cutting points which are subjected to a great deal. of strain during the cutting operation. As the cutting points wear away, the horizontal distance of the side clearance faces 20 and 2| of the bit in rear of the cutting face increases, and for this reason an additional side clearance face drag would tend to be produced. In order to reduce this drag of the side clearance faces because of the additional cutting side wall depth of the bit, I provide for making the side clearance faces 20 and 2| of the bit depressed, arcuate or concaved, so that a greater clearance is produced as the cutting points of the bits wear away. The cutting clearance is indicated by the reference character 23 and the increase in cutting clearance is illustrated by the increased lateral space upon opposite sides of the cross-sectional views of Figures 4 and 5 over Figure 3, taken at different horizontal cutting sections through the bits. Therefore, with my improved cutting bit the drag is kept at a low minimum, regardless of the amount of wear that might occur upon the bits. Another result growing out of the depressed, arcuate, or concaved side clearance faces 20 and 2! of my cutting bit is the fact that the cutting faces remain relatively narrow for a considerable distance and do not begin to broaden until the side clearance faces 20 and 2| approach the central body portion ll of the bit. Moreover, the clearance is proportionately distributed throughout the entire life of the bit, so that the drag is always maintained at a low minimum value.

In Figures 6 and '7, I show a modified arrangement of my improved bit, in that the portion 24 of the side clearance faces in the region of the relatively wide central portion is substantially flat to give lateral support to the bits in the chain lugs. The shape of my modified bit in Figures 6 and '7 is substantially the same as that which would be produced if a disc having double-concave marginal edge surfaces and a central fiat portion were out upon a cord of the circumference of the disc intersecting a small part of the fiat portion to make the fiat area 24.

In Figures 8 and 9, I show a further modified arrangement of my improved bit in that the portion 25 of the side clearance faces in the region of the relatively wide central portion is substantially convex in both a general longitudinal direction and a transverse direction to give lateral support to the bits in the chain lugs. The shape of my modified bit in Figures 8 and 9 is substantially the same as that which would be produced if a disc having double-concave marginal edge surfaces and a central convex portion were out upon a cord of the circumference-of the disc intersecting a small part of the convex portion to make the convex area 25.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. A longitudinal double-ended bit comprising a solid piece of metal having a longitudinal front cutting face and side clearance faces, said front cutting face having a relatively wide central portion and relatively narrow opposite edge cutting portions, the contour of the side edges of the front cutting face between the said relatively wide central portion and the said relatively narrow opposite edge cutting portions being concaved and forming cutting points at opposite ends thereof, the contour of the front edges of the side clearance faces meeting with the side edges of the front cutting face and being substantially straight in side elevation and the contour of the rear edges of the side clearance faces meeting in a relatively narrow juncture, said juncture in side elevation being curved in a general longitudinal direction between the opposite cutting points, each of said side clearance faces beginning at a central place near the front edge thereof and substantially mid-way of the cutting points converging toward the narrow juncture in a radial direction, each of said side clearance faces being also concaved in said radial direction and producing a greater cutting clearance as the cutting points wear away.

2. A longitudinal double-ended bit comprising a solid piece of metal having a longitudinal front cutting face and side clearance faces, said front cutting face having a relatively wide central portion and relatively narrow opposite edge cutting portions, the contour of the side edges of the front cutting face between the said relatively wide central portion and the said relatively narrow opposite edge cutting portions being concaved and forming cutting points at opposite ends thereof, the contour of the front edges of the side clearance faces meeting with the side edges of the front cutting face and being substantially straight in side elevation and the contour of the rear edges of the side clearance faces meeting in a relatively narrow juncture, said juncture in side elevation being curved in a general longitudinal direction between the opposite cutting points, each of said side clearance faces beginning at a central place near the front edge thereof and substantially mid-way of the cutting points converging toward the narrow juncture in a radial direction, each of said side clearance faces being also concaved in said radial direction and producing a greater cutting clearance as the cutting points wear away, the curvature of the said juncture in a general longitudinal direction being substantially an arc of a circle.

3. A longitudinal double-ended bit comprising a solid piece of metal having a longitudinal front cutting face and side clearance faces, said front cutting face being substantially diamond-shaped and having a relatively wide central portion and relatively narrow opposite edge cutting portions, the contour of the side edges of the front cutting face between the said relatively wide central portion and the said relatively narrow opposite edge cutting portions being concaved and forming cutting points at opposite ends thereof, the contour of the front edges of the side clearance faces meeting with the side edges of the front cutting face and being substantially straight in side elevation and the contour of the rear edges of the side clearance faces meeting in a relatively narrow juncture, said juncture in side elevation being curved in a general longitudinal direction between the opposite cutting points, each of said side clearance faces beginning at a central place near the front edge thereof and substantially mid-way of the cutting points converging toward the narrow juncture in a radial direction, each of said side clearance faces being also concaved in said radial direction and producing a greater cutting clearance as the cutting points wear away.

4. A longitudinal double-ended bit comprising a solid piece of metal having a longitudinal front cutting face and side clearance faces, said front cutting face having a relatively wide central portion and relatively narrow opposite edge cutting portions. the contour of the side edges of the front cutting face between the said relatively Wide central portion and the said relatively narrow opposite edge cutting portions being concaved and forming cutting points at opposite ends thereof, the contour of the front edges of the side clearance faces meeting with the side edges of the front cutting face and being substantially straight in side elevation and the com tour of the rear edges of the side clearance faces meeting in a relatively narrow juncture, said juncture in side elevation being curved in a general longitudinal direction between the opposite cutting points, each of said side clearance faces beginning at a central place near the front edge thereof and substantially mid-way of the cutting points converging toward the narrow juncture in a radial direction, each of said side clearance faces being also concaved in said radial direction and producing a greater cutting clearance as the cutting points wear away, the curvature of the said juncture in a general longitudinal direction being substantially an arc of a' circle, said relatively wide central portion being substantially flat.

5. A longitudinal double-ended bit comprising a solid piece of metal having a longitudinal front cutting face and side clearance faces, said front cutting face having a relatively wide central portion and relatively narrow opposite edge cutting portions, the contour of the side edges of the front cutting face between the said relatively wide central portion and the said relatively narrow opposite edge cutting portions being concaved and forming cutting points at opposite ends thereof, the contour of the front edges of the side clearance faces meeting with the side edges of the front cutting fa'ce and being substantially straight in side elevation and the contour of the rear edges of the side clearance faces meeting in a relatively narrow juncture, said juncture in side elevation being curved in a general longitudinal direction between the opposite cutting points, each of said side clearance faces beginning at a central place near the front edge thereof and substantially mid-way of the cutting points converging toward the narrow juncture in a radial direction, each of said side clearance faces being also concaved in said radial direction and producing a greater cutting clearance as the cutting points wear away, the curvature of the said juncture in a general longi-- tudinal direction being substantially an arc of a circle, the portion of each of said side clearance faces in the region at the said central place being convex in said radial direction and gradually meeting in a compound curve with the concaved surface of each of said side clearance faces.

6. A longitudinal double-ended bit comprising a solid piece of metal having a. longitudinal front cutting face and concave side clearance faces, the shape of said bit being a minor segment of a disc having concave opposite walls intermediate its center and longitudinal edge.

HARRY M. MORROW.

Images