US1908161A - Coal-cutting chisel with hard metal cutting edge - Google Patents

Description

Patented May 9, 1933 UNITED STATES PATENT-OFFICE ADOLF MEUTSCH, OF ESSEN, GERMANY, ASSIGNOR T0 GEWERKSCHAIT WALLRAM,

' OF ESSEN, GERMANY COAL-CUTTING CHISEL WITH HARD METAL CUTTING EDGE Application filed august 20, 1930; Serial No. 476,473, and in Gerniany May 6, 1930.

The present invention relates to picks for coal-cutting machines provided with inserted hard metal cutting-edges to keep sharp longer, and particularly to picks employed in coaLcutting machines of the bar and chain type. In view of the extraordinary stresses to which picks for coal-cutting machines are subjected by impact and breaking effects due to inequalities in the structure of the material to be cut, and especially to pipes or funnels of iron pyrites embedded therein, it was ting chisel with inserted hard metal cuttingranged in a bore of the pick.

edge by inserting the latter in the chisel member so that itis supported relative to both the cutting pressure and the tilting moments produced thereby. The efliciency of the new coal-cutting pick is increased further by providing-means for keeping the pick always in proper cutting position.

Several embodiments of the new invention are illustrated in the accompanying drawing, in which: 7

Figure 1 is a side-view of a pick for a coalcutting machine of the bar type, in which the hard metal piece is received by a milled groove.

Figure 2 is a front-view thereof.

Figure 3 is a top-view thereof.

Figures 4a and 4b disclose a section on the line IV-IV, of Fig. 1, seen from above, with two different forms of cross-section of the hard metal piece. I

Figure 5 is .a side-view, partly in section, of a pick for a coal-cutting machine of the bar type, in which the hard metal piece is ar- Figure 6 is a front-view thereof. Figure 7 is a side-view of a plck for a coal cutting machine of the chain type and Figure 8 is a top-view thereof.

In the modification shown in Fig. 1 the coal-cutting chisel is flattened on both sides of its front end 1 and provided with a continuous milled groove 2 inclined towards the longitudinal direction of the pick and adapted to receive the hard metal piece 3 so that the front upper' end thereof remains free to serve as cutting-edge, the free front surface-4 of the hard metal piece being kept consideraby smaller than the upper surface 5 in order to provide a suifciently broad cut ting surface 5 in connection with a suflicient support by the front portion of the chisel. "lhecomponents of cutting pressure are fully supported and, furthermore, the t lting moments acting approximately in the direction of the arrow andendangering the connection of the hard metal piece with the chisel are safely taken up by the overla ping chisel portion. The cross-section of t e slot "2 may be rectangular (Fig. 4a) ,thoughit is preferred to give it the form shown in Fig.

4b where it is broader in the centre than on the sides so as to protect the hard metal piece against any lateral stresses also. Par-' ticularly preferred is the rounded or circularform of cross-section, which avoids sharp corners favouring the formation of cracks owing to continuous strain and permits convenient production of the slot as a bore.

Owing to the considerably increased stressing of the coal-cutting pick due to the use of hard metal as cutting-edge, special and ample provisionmust be made for preventing the coal-cutting pick inserted in the band by means of an ordinary conical bolt 7 from moving. In the modification according to Fig. 1 the cross-cutting pick is thus provided with an eccentric projection 8 which fits into a corresponding clearance 9 in the bar 6. As the eccentricity of the projection is directed downwardly, the moment'of resistance of the pick relative to the 'bendingstresses of-the cutting pressureis simultaneously increased v to a considerable extent.

Furthermore, provision is made also for preventing as much as possible the development of torsional stresses during cutting by disposing the edge 5 of the hard metal piece on a plane extending within or below the axis 10 of the bolt 7. To return the coal-cutting pick if moved out of its correct turning position by extraordinary strain,'the flattened of another drawback of the known kinds of of tools, which hasto do with frequent damaging of the hard metal piece or of the front portions of the chisel when the. coal-cutting pick is knocked into the bar 6. Since the cutting portions are lowered, it is possible to protide the pick with a broad striking surface 11' which excludes any possibility of damaging the cutting parts when driving in the chisel. In the modification shown in Figs. 5 and 6 the simplified production of the coal cutting .pick is emphasized, the front chisel portion 13, which has the form of'a bilaterally fiattened truncated cone projecting from the collar '12, being provided with a. prismatic or cylindrical bore 14 wherein the prismatic or cylindrical hard metal piece 3 is soldered. 'The hard metal piece is thus inserted 1n the pick in such a way that, with the exception of one end surface, it is surrounded on all sldes by the chisel to which it can be soldered everywhere so that the connection cannot be severed even by any transverse stresses. The conical shape of the chisel portion 13 permits convenient removal of the chisel metal during I regrindingof the edge 15, as the chisel cone :can be handled like the wood of a lead pencil.

As the slope of the chisel cone corresponds approximately to the inclination of the hard metal piece 3, the height of the supporting chisel portion being in front never vanes 1n spite of regrinding. This modification may bolt.

be provided also with an eccentric projection 8 (Fig. 1), and in a corresponding construc tion of the front chisel portion the cuttingedge may be disposed, as in Fig. 1, on a plane extending along or below the axis 10 of the The collar 12 serves further for facilitating the attachment and removal of the pick. The front face 16 of the collar 12 is kept broad enough to permit a pipe to be put thereon during driving in. The transition from the surface 16 to the chisel portion is hollowed out considerably to prevent the formation of cracks which would surely develop, owing to high continuous strains, if the transition were sharp-cornered. I

The modification according to Figs. 7 and 8 relating to coal-cutting pick of prismatic cross-section for a coal-cutting machine of t e chain, type discloses 'an attachment of t eha'rd metal bouy 3"sifnilar to the modification according to Fig. 1, and the form of cross-section in particular maybe chosenac- I cording to Fig. 4b.

Picksas described cannot be utilized up to the limit of efiiciency of their hard metal cutting edges, since the great stresses which the insertions will withstand, owing to the peculiar described arrangement, exceed the strength of the chisel itself. Particularly the chisel metal taking up the components of cutting pressure is exposed to such' great unit pressure as to be forced away when cutting pressure is at its highest. Furthermore, in the portion of the pick projecting from the bar or chain in the coal-cutting ma chine excessive bending strains are produced by the blows during the cutting operation, and the grinding effect due to 'the cross-feed of the pick acts destructively on the lateral surfaces of the latter so that the bearing strength of the pick head is reduced quickly. 'As to the form of invention shown in Fig. 1, under increased strain the pick portion 17 positioned under thehard metal portion will be forced away, thepickbreak off within the zone indicated by the line18,:or the. side surfaces ground off rapidly.

These drawbacks are eliminated by hardening the surface layer of the pick metal sup 1 6' porting the hard metal insertion and of the pick portion chiefly exposed to bending and grinding so that the' surface pressure available for supporting the hard metal insertion is sufliciently large and, on the other hand, sufficient toughness of the pick relative to impacts and ample resistance to insured.

It was hitherto impossible to provide a hardened body portion for picks, since .oxidation processes and quenching, in view of the high hardening temperatures, had a crushing or generally" damaging effect upon the hard metal portion. However, the damaging effects of high hardening temperatures are eliminated by the described universal embedding of the hard metal insertion and by the hardening and production processesdescribed below, and a useful hardened coal cutting pick with hard metal insertion is produced possessingsuperior efficiency compared with unhardened ones.

In order to make it possible to harden the pick provided with a hard metal insertion, the swaged blank, as indicated by the hatched grinding are lines Figs. 1, 3 and 4, is overdimensioned in its front portion so as to universally enclose-v the hard metal piece after the clearance 2 has been milled or drilled while its upper end is disposed somewhat below the opening 19 of the clearance 2. The hard metal piece may be provided with its final working surfaces already at the time when it is intro-- duced from above, and when the copper solder is poured in, the hollow space 20 formed in this manner is filled with copper solder to such an extent that the hard metal piece is on within a surface layer measuring some millimetres, the superfluous portions in front of the chisel and of the solder are removed until the chisel has the form indicated by the full lines, and the cutting edge and perhaps the side surfaces of the hard metal piece are exposed.

What is claimed is 1. In a coal cutting pick with hard metalcutting edge a recessed front pick portion, a staff-like hard metal piece inserted in said front pick portion and fastened to it by soldering, and metal parts of said front pick portion completely overhangin the foremost boundary surface of the har metal piece adapted to support the tilting forces produced by the cutting pressure.

for protecting the said hard metal 2. Ina coal-cutting pick with hard metal .cutting edge, a recessed front pick portion, and a staff-like hard metal piece inserted in the said front pick portion and fastened to it by soldering, the recess being inclined towards the longitudinal direction of the pick and adapted to receive the said hard metal piece so as to leave a cutting edge free on the front upper end thereof.

3. In a coal-cutting pick'with hard metal cutting edge, a recessed front pick portion, and a staff-like hard metal piece inserted in the said front pick portion and fastened to .it by soldering, the recess being inclined towards the longitudinal direction of the pick and adapted to receive the said hard metal iece so as to leave a cutting edge'free on the iiiont upper end thereof and being wider in cross-section in the center than on the sides piece against lateral stresses.

4. In a.- c'oal-cuttin pick with hard metal cutting edge, a pick ont portion, a boring in the said front portion Inclined towards the lon 'tudinal direction of the ick, and a cylindrical staff-like hard meta piece inserted in the boring and fastened to the pick by soldering, the said hard metal piece being covered on all sides by the pick metal with the exception of the upper front end surface.

h, 5. In a coal-cutting pick, a hard metal piece, and a front pick portion having a re-.

cess;for receiving the said hard metal piece, the recess being inclined towards the axis of the body of the pick and the supporting portion of the pick extending correspondingly parallel therewith and maintaining approxi mately the same height during regrinding of tion havin the she e of a truncated cone, and a hat metal p1ece inserted in the said pick, the truncated cone shape of the, said pick facilitatin removal of the pick metal during regrin 'ng while maintaining the universal support of the hard metal p1ece.

. 7. In a coal-cutting machine, a pick, a bar for inserting the ick therein, a bolt for hold ing the pick, an a cutting ed e on the said pick disposed on a lane extending below the axis of the said be t to prevent the development of torsional moments.

8. In a coal-cutting machine, a ick, a bolt thereon, and the flattened sides 0 the front portion of the said pick located below the axis of the bolt being almost parallel and downwardly extended to push back, in cooperation with the cutting groove in the coal, the ick into correct turning position if displace I by extraordinary strains. I

9. In a coal-cutting machine, a pick and a collarattached to the pick, the collar having an annular front driving face extending through a flute into the front pick portion.

10. A. coal-cutting pick comprising a hard metal insertion connected to the ick metal by soldering and su'rface-hardene pick portlons, the said pick portions supporting the hard metal insertion and being exposed to bending and grinding stresses to insure ample unit pressure for sup orting the said hard metal insertion, sufiiclent toughness of the pick relative to impact stresses, and ample resistance to grinding stresses.

11. In a coal cutting machine a pick, a bar for inserting the pick therein, a bolt for holding the pick, a projection on the bolt in the form of a cylindrical disc having a greater diameter than the bolt and 'the axis of which is disposed below the axis of the bolt,

"and a cylindrical recess in the bar fitting over the said projection.

The foregoing s ification signed at C0-' logne, Germany this lst day of August 1930.

ADOLF MEUTSCH.

' let 6. In a coal-cutting pic a front pick por-

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