Mining Tool And Support Block Therefor

Abstract

A mining tool of the pick type which is symmetrical about a longitudinal axis and which has a shank which is circular in cross section that is rotatably received in a correspondingly shaped bore in a support block. The bore in the support block has a forwardly facing shoulder intermediate the ends and the shank of the bit has a rearwardly facing shoulder engaging the forwardly facing shoulder in the bore. The forward face of the support block is flat and perpendicular to the axis of the bore therein and the bit comprises a radial flange which is spaced from the forward end of the block when the bit and block are new but which, upon one or the other of the shoulders on the bit shank and block becoming worn, will engage the front of the block and take at least part of the axial load imposed on the bit.

Description

The present invention relates to mining tools and is particularly concerned with pick type bits and support blocks in which the pick type bits are rotatably supported.

Bits and support blocks of the general nature referred to are known and are illustrated, for example, in U.S. Pat. Nos. 3,499,685, 3,519,309 and 3,650,565. In each case, the bits and support blocks have interengaging tapered shoulders thereon for absorbing thrusts imposed on the bit during working operations. In many cases, the provision of the tapered shoulders are adequate for supporting the bit throughout its working life and wear on the shoulders is not particularly pronounced.

In its simplest form, the pick and block combination has the tapered load bearing shoulder disposed at the mouth of the bore extending into the block and this has proved to be quite satisfactory for supporting the smaller sized bits. In one of the patents referred to above, the tapered shoulder is disposed about midway in the length of the bore in the block and the shank on the tool is formed to two diameters with a rearwardly facing shoulder at the juncture thereof which engages the shoulder in the block.

This arrangement has been provided for the purpose of permitting a sleeve to be interposed between a small type pick and the block to distribute wear between the pick and sleeve and block while at the same time permitting the sleeve to be withdrawn from the block and replaced by a heavy duty bit having a substantially larger shank than a bit that is receivable in the sleeve.

Such heavy duty picks can operate under loads that would break or bend the small bits and are, thus, employed when hard formations are to be reduced by the mining tool.

As a natural consequence of a formation being hard, fine abrasive particles will be developed which can get into the bore in the block around the shank of the bit and promote wear of the bit shank and of the block. Some of this wear naturally occurs on the shoulders in the block and on the bit but, inasmuch as the bit rotates in the block, there is also wear on the periphery of the bit shank and on the sides of the bore in the block. Such wear has led to the bits becoming loose in the blocks and has led to premature failure of the bits and the wearing out of the blocks before their normally useful term of life had expired.

With the foregoing in mind, the present invention has as a primary objective the provision of a bit and block combination in which the bit and block are provided with additional opposed interengageable areas which will come into engagement upon any appreciable wear taking place on the conventional tapered shoulders provided on the bit and block.

A further object is the provision of a bit construction in which access of fine abrasive material into the bore in the block is inhibited and wherein the operation of the bit is stabilized and made more secure.

These and other objects and advantages of the present invention will become more apparent upon reference to the following detailed specification taken in connection with the accompanying drawings in which:

FIG. 1 is a side view showing a bit according to the present invention mounted in a support block with the bit partially in cross section and the block in full cross section.

FIG. 2 is a fragmentary view similar to FIG. 1 but showing a different arrangement for holding the bit in the bore in the block.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, a mining tool support block is provided having a bore extending therethrough from the front end on an axis perpendicular to the front end and with a larger forward part and a smaller rearward part with a forwardly facing tapered shoulder at the juncture of the parts of the bore.

A mining bit having a shank which is circular in cross section iw provided with a shank which is circular in cross section and receivable in the bore in the block with the shank having a rearwardly portion of smaller diameter and a forward portion and a rearwardly facing shoulder at the juncture of said portions; the shoulder on the bit shank engaging the shoulder in the bore. The bit projects forwardly from the front end of the block and has a circular forward portion which tapers inwardly to a point disposed on the longitudinal axis of the bit and which point is advantageously provided by an element of hard wear resistant material such as a cemented hard metallic carbide which is mounted in the forward portion of the bit.

Immediately forwardly of the front face of the block the bit is provided with a rearwardly facing radial shoulder, formed by an annular flange on the bit. The rearwardly facing shoulder is normally spaced at least a slight distance forwardly from the front end of the block but will engage the block when any sensible amount of wear occurs on one or both of the shoulders in the bore of the block and on the shank of the bit.

The radial shoulder at the front end of the block inhibits the entrance of grit into the bore of the block and, furthermore, once it engages or comes quite close to the front end of the block, stabilizes the bit in the block by inhibiting tilting of the bit in the block. Once the radial shoulder on the bit engages the front end of the block, it stabilizes the bit to the fullest extent possible while also sharing in the axial load imposed on the bit during working operations and even more completely sealing the bore in the block against the ingress of fine abrasive material.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings somewhat more in detail, in FIG. 1, the support block, indicated at 10, has a bore generally indicated at 12 extending therethrough from front face 14 to rearward face 16 of the block and the axis of which is perpendicular to front face 14. The bore has a smaller rear part 18 and a larger front part 20 and an inclined shoulder 22 at the juncture of said parts and disposed about midway along the length of bore 12.

A pick type bit is adapted for being rotatably mounted in support block 10 and includes a shank generally indicated at 30 having a smaller rearward portion 32 and a larger forward portion 34 and a shoulder 36 connecting portions 32 and 34 and inclined so as to be complementary to shoulder 22 in the bore.

Smaller diameter portion 32 of the shank may extend out of the bore beyond the rear face 16 of the block and having snap ring 38 mounted in a groove 40 provided in the shank so as to retain the shank in the block while permitting free rotation of the shank in the block.

Outwardly from forward face 14 of the block the bit has a forward working portion 42 tapering inwardly to a pointed end 44 and which pointed end is advantageously provided by an insert 46 formed of cemented hard metal carbide, tungsten carbide, for example. Point 44, it will be noted, is on the axis of the bit and the bit is circular at each point therealong and symmetrical about the aforementioned axis.

Immediately forwardly of front face 14 of block 10 the bit has a flange or larger diameter portion 48 which provides a rearwardly facing shoulder radial 50 which is parallel to the plane of front face 14 of the block. When the bit and shank are new, radial shoulder 50 is spaced at least a slight distance forwardly from the front face 14 of block 10 but will engage face 14 when one or the other, or both of the shoulders on the bit shank and in the bore in the block wear down.

At all times, flange 48 tends to inhibit the entrance of abrasive grit into the bore in block 10 and, when shoulder 50 engages front end face 14 of the block, shoulder 50 shares the axial load on the bit and inhibits tilting of the bit in the block, thus, reducing wear on the periphery of the bit shank and on the axial portions of the bore in the block. Further, when shoulder 50 engages face 14, the bore in the block is substantially sealed against the ingress of abrasive grit.

FIG. 2 shows a modification in which the bit, generally designated at 60, is held in the block, designated generally at 62, by a resilient annular spring clip 64 mounted in a groove 66 formed in the shank of the bit and resiliently contractable in the groove to permit the bit to be inserted in the bore in the block and then radially expansible when the bit is positioned in the block so as to engage the annular undercut 68 formed in the bore in the block.

The resilient clip 62 forms a connecting arrangement which will hold the bit in the block while permitting free rotation thereof and, furthermore, permits the bit to be pressed into the block and either pried or driven therefrom quite readily.

Claims

What is claimed is:

1. In a mining tool; a bit symmetrical about a longitudinal axis and having a cylindrical shank portion at the rear end with the rearward part of the shank portion substantially smaller in diameter than the forward part thereof and with an inclined rearwardly facing annular shoulder at the juncture of said parts, said bit having a cylindrical working portion at the front end of about the same diameter as the forward part of said shank and terminating in a point at the forward end with the point on said longitudinal axis of the tool, the rear end of said working portion being integrally joined to the forward end of said forward part of said shank portion, and a radially outwardly projecting annular flange at the juncture of said working portion with said shank portion forming a rearwardly facing radial shoulder in a plane substantially perpendicular to the longitudinal axis of the tool.

2. A mining tool according to claim 1 in which the said rearward part of said shank portion includes means for detachably and rotatably retaining said bit in a support block.

3. A mining tool according to claim 1 in which the said rearward and forward parts of said shank portion are about equal in length.

4. A mining tool according to claim 1 in which the length of said forward working portion is about equal to the length of said shank portion.

5. A mining tool according to claim 1 including in combination therewith a support block having a shouldered bore adapted rotatably to receive said shank portion of said bit, the shoulder in said bore facing forwardly and being inclined at the same angle as the inclined shoulder on said shank portion and engaging the inclined shoulder on said shank portion, said block having a forward face with at least the portion surrounding said bore disposed in a plane perpendicular to the axis of said bore, said portion of said forward face of said block being positioned immediately rearwardly of said radial shoulder on said bit so as to be engageable with said radial shoulder in the event of wear of said inclined shoulders.