US3693736A - Cutter insert for rock bits - Google Patents

Abstract

A carbide cutter insert for a rock bit body is strengthened against breakage and its removal and replacement are facilitated by encasing the insert in a protective jacket of material substantially softer than the carbide. The composite element is then firmly pressed and/or bonded in an orifice in the cutting face of the bit body. The element can be readily removed simply by cutting away the softer jacket by a suitable machine tool operation without damaging the body bore.

Description

United States Patent Gardner [45] Sept. 26, 1972 154] CUTTER INSERT FOR ROCK BITS 3,618,683 11/1971 Hughes 175/410 [72] Inventor: Jimmy D. Gardner, HOUSIOH, Tex. FOREIGN PATENTS OR APPLICATIONS [731 Assign: Missim' Manmcmring Cmnpany, 70,945 10/1942 Norway ..175/410 203,122 8/1956 Australia ..175/410 [22] Filed: Sept, 4, 1969 683,018 1 1/1952 Great Britain ..175/410 [21] Appl' 855208 Primary Examiner-James A. Leppink Attorney-Bertram H. Mann, Frank B. Pugsley, James [52] U.S. Cl ..175/410 Ulmer. Delmar Sroufe n Larry l m n [51] Int. Cl ..E21c13/0l [58] Field of Search 175/410, 413; 299/92 [57] ABSTRACT A carbide cutter insert for a rock bit body is [56] References cued strengthened against breakage and its removal and UNITED STATES PATENTS replacement are facilitated by encasing the insert in a protective jacket of material substantially softer than 2,842,342 7/1958 B "175/410 the carbide. The composite element is then firmly 3,268,259 8/1966 Snipe ..175/410 pressed and/Or bonded i an fi in the cutting f 3,342,531 9/1967 Krekeler ..175/410 of the bit body The element can be readily removed 3,342,532 9/1967 Krekeler ..175/410 simply by Cutting away the Softer jacket by a suitable 3,357,507 12/1967 Steuvart ..175/410 machine tool operation without damaging the body 3,388,757 6/1968 Flttmger ..175/410 bore. 3,397,012 8/1968 Krekeler ..299/92 1,522,593 1/1925 Pickin ..175/413 3 Claims, 17 Drawing Figures PATENIEMzrzs I972 SHEET 1 BF 3 INVENTOR.

ATTORNEY CUTTER INSERT FOR ROCK'BITS I BACKGROUND OF THE INVENTION Many rock bits, both of the solid and rotary type, are

provided with hardened cutter inserts, usually of tungare secured in place by silver soldering so that they may be replaced. However, the large difference in thermal expansion betweenthe carbide inserts and the steel body causes cooling cracks, .and the poor surface wettability of the carbide by the solder often results in poor bond coverage percentage. On the other hand,'if the carbides'are securedin place by press fitting, they cannot be removed. In that case, the entire bit is thrown away when the inserts have become'dull or broken. These inserts are quite brittle. and their exposed parts fracturable by glancing blowsplacing the material under tension. This condition is aggravated by the fact that the mounting orifices in the bit body usually. are slightly bell-mouthed due to the methods of formation.

Accordingly, an object of the present invention is to providemeans for firmly mounting carbide cutterinserts in rock bit bodies while facilitating removal of .the

inserts to facilitate their replacement and thus avoid the necessity of scrapping the entirebit body whenthe inserts become dull.

Another object is to provide means for strengthening such carbide inserts.

Still another object is to provide a novel method of constructing a carbide insert composite.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which illustrate'a the -invention,

FIG. 1 is a partial transverse longitudinal. section through a solid-type rock bit embodying one form of the invention.

FIG. 2 is an enlarged longitudinal section through one of the cutter insert composites.

'FIG. 3 is an end view of the structure in FIG. 2.

FIG. 4 is an enlarged view of a detail of FIG. I and showing the composite seated in an orifice in the bit body.

FIG. 5 is a viewsimilar to FIG. 4 but showing prior practice in somewhat exaggerated form.

7 FIG. 6 is a partial forward end view of a rock bit as in FIG. 1, but showing a slight modification.

FIG. 7 is a detail section taken substantially on line 7-7 of FIG. 6.

FIGS. 8 and 9 are longitudinal sections showing two different forms of armored carbide composites in an initial assembly stage.

FIG. 10 is an end view of the structure in FIG. 8.

FIG. 1 l is a view of the structure in FIG. 8 after being driven into a matching orifice in the bit body.

FIG. 12 shows a driving tool being applied to a further modified cutter composite.

FIG. 13 is a perspective view of a further modified cutter composite.

FIG. 14 is a perspective view of a composite along the lines of that in FIG. 13 but showing a different form of carbide cutter element.

FIG. 15 is a longitudinal section through an armored carbide element in a preliminary stage of manufacture and illustrating a method of making the carbide inserts.

FIG. 16 is a detail cross section illustrating still another form of cutter insert composite.

FIG. 17 is a section taken on line 17-17 of FIG. 16.

'DESCRIPTION'OF THE PREFERRED EMBODIMENTS FIG. 1 shows a more-or-less conventional, solid type anvil-bit combination including a shank portion 20 forming part of the anvil of a percussion type drill motor, and a bit body portion 21 having a forward cutter face, generally designated 22. As best shown in FIG. 6,

srthe bodyis provided with wings 23, 24, and 25 terminating in peripheral chamfers 26 and inner chamfers and various known types of bit bodies, either solid or rotary, maybe utilized in connection with the invention ,as hereafter described.

FIGS.'2, 3, and 4 illustrate in substantial enlargement one of the composite cutter inserts, say, one of the peripheral inserts 28. At the center of the insert there is :provided a generally cylindrical tungsten carbide cutter element 39 having a suitably shaped in this instance,

composite-then press fitted within orifice 43. However,

itv may befound desirable to sweat sleeve 41 into element 39,,that is, by heating and cooling of the sleeve,

- and also sleeve 41 may besilver soldered in orifice 43 withoutthe formation of thermal expansion cracks previously mentioned. In any case, the bottoms of sleeve 41 and carbide element 39 should be firmly seated against the bottom of orifice 43. It willbe observed, that sleeve 41 projects somewhat beyond the mouth of orifice 43 and along the exposed part of car- -bide button element 39, thus, providing reinforcement for the button. In addition, the carbide element will be held by the-sleeve firmly in compression so as to be thereby further strengthened. Preferably, the sleeve should be made of steel having a high yield point and high ductility to accommodate and withstand the high compressive forces.

FIG. 3 shows a small radial longitudinal groove 44 formed in, the outer surface of cylindrical sleeve 41. This serves two purposes. In the first instance, it provides a relief vent for air trapped in orifice 43 during the pressing of the composite element into position therein. Furthermore, the slot facilitates release of the carbide buttonelement in that sleeve 41, of steel or other drillable material softer than the carbide button 39, which is substantially notmachinable may be cut away by a trepanning or other machine tool operation to release the button. The machining need out only to the bottom of groove 44, as suggested by dot-dash line 45, so the hole wall will not be affected leaving a split sleeve extending around the hole when the remainder of sleeve 41 is cut away. This remainder split sleeve can be readily collapsed and removed without damage to bore 43.

FIG. 5 illustrates prior practice in which a substantial part of carbide button element 39a is exposed outwardly of the bell mouth 43b of orifice 43a in bit body 210. The peripheral cutter elements 28 and others at the gauge surface of the bit body'are especially subject to glancing blows which heretofore have caused breakage of these carbides with resultant deterioration of the bit cutting capacity. Sleeve 41 of FIG. 2 does not present'a bell mouth because his initially longer than shown and is cut off after the pressing operation. This does not reduce the effective cutting life of the carbide, since the material of the sleeve, being softer than the carbide, wears away first so as to continuously expose additional carbide until the element is fully worn out.

FIGS. 6 and 7 illustrate a modified cutter insert assembly and means for locking the same in position in a bit body. In thisinstance, the carbide element 39b is mounted in the forward, cup-like orifice 46 of a conveniently cylindrical rod 47 of steel or like material somewhat softer than the carbide. The rod is seated in a long orifice 48 extending vertically into the cutter body through the forward cutter face 22a thereof. A bore 49 transversely intersecting orifice 47 receives a locking pin 50 which alsoseats in a recess 51 in rod 47 abreast of bore 49. Only one of the locking pins is shown in FIG. 6 cooperating with a pair of the carbide. composites but eachof the composites may be similarly locked in position in the bit body. Pin 50 can be removed and reinserted as through opposing wing chamfers 26 and 27. A passage 52 opening into the bottom of orifice 48 may accommodate a pressured fluid, as gun grease, for forcing rod 47 out of orifice 48.

FIGS. 8, 9, l0, and 11 illustrate another means for anchoring the carbide element firmly in the bit body. In FIG. 8-, sleeve 41b, initially, has a generally cylindrical inner'surface 57 and'a conical outer surface 53 tapering upwardly and outwardly from the smaller inner or bottom end 54. Carbide element 390 is tapered oppositely-to sleeve outer surface 53, that is, upwardly and inwardly from its larger base portion 55, which fairly snugly fits within base portion 54 of the sleeve jacket, to its smaller outer or forward extremity 40a. When this assembly is driven into an orifice in the body which is approximately of the diameter of the base portion 54 of sleeve 41b, the sleeve is distorted or swaged, as illustrated in FIG. 11, to cause sleeve inner surface 52 to heavily encase carbide outer surface 56, thus locking both the sleeve and the carbide firmly in position in the bit body. In order to facilitate this action, sleeve 41b may be radially split as shown in FIG. 10. However, if inclines 53 and 56 are not too great, such splitting of the sleeve may not be necessary and the sleeve may be swaged into the distorted form shown in FIG. 11' upon the application of suitable pressure thereto. I v

The form in FIG. 9 is similar to that in FIG. 8 except for the provision of a bottom web 58 in jacket 41c with outwardly tapered outer surface 580. Carbide element 390 is the same as in the previous form, and the method of firmly anchoring the carbide and sleeve into the body orifice is the same.

FIG. 12 showsa cup-likesteel jacket 60 receiving cylindrical carbide button 61 being driven into a snugly fitting orifice 62in the bit body 63 by means'of a tubular punch 64. If desired,the punch may have a solid centralpart, as suggested at 65, for insuring proper driving of carbide element 61.

FIGS. 13 and 14 illustrate cutter insert composites including jacket parts of modified'polyhedral shapes of the carbide'cutters shown, for instance, in Bassinger US. Pat. No. 2,976,944. In FIG. 13 there is shown a jacket body 66 having a wedgeor roof-shaped cutter face 67 terminatingin an edge 68. In the Bassinger patent, as in other prior art devices, member 66, 67 is itself formed of hardened carbide cutter material, and edge 68 is the cutting edge. However, in the present instance member 66, 67 is of steel or other softer 'machinable material which may be readily secured in the body metal of the bit as by silver soldering. Projecting into the apex of roof part 67 are a plurality of carbide cutter insert buttons 69 which are pressfitted into orifices 70 in body 66, 67. Additional carbide inserts are shown at 71 and 72.

In FIG. 14 the body 66a, 67a is provided with a slot 78 depending from the apex in which is firmly seated a plate-like carbide cutter element 73. In both of the latter forms, the carbide cutter element can be removed by cutting away of the body part 66, 67 or 66a, 67a by suitable machining operation which may be effected without damaging the bit body itself.

FIG. 15 illustrates a method of manufacturing the carbide composite inserts. An elongated sleeve 75 of steel or other sufficiently rugged yet drillable material is provided with a filler 76 of tungsten carbide conveniently inpowdered form and then solidified as with the use of heat and pressure. Alternatively, the jacket sleeve may be silver soldered or sweated on a solid carbide core. The long carbide composite is then cut into longitudinal sections commensurate with the desired length of the composite insert. In addition to a convenient manufacturing method, this form insures complete encasement of the carbide filler, an advantage over conventional practice in which the carbide insert frequently is pressed .in a bell-mouthed orifice which, therefore, fails to support and protect the full length of the insert within the orifice.

FIGS. 16 and 17 illustrate a form of insert composite in which the internal carbide element 75 is star-shaped and snugly fits within a similarly shaped orifice in drillable jacket 76. The carbide can be removed by trepanning around the star points. Alternatively, the composite 75, 76,the latter being cup-shaped, may be removed by providing a'plug 77 of material as lead of greater thermal expansion coefficient than bit body 78 or jacket 76 inan extension of bore 79 in the body, inwardly of the composite insert. When it is desired to remove the insert, the bit body is heated sufficiently to cause the lead plug to push the insert slightly outwardly of its orifice. The insert then can be grasped by a gripping tool and withdrawn from the bore. Various noncircular carbide shapes may be utilized for the purpose, for instance, of increasing the contact surface area between the carbide and jacket and thus, the bonding or frictional efficiency.

It is contemplated that the drillable sleeve or other jacket be merely of adequate size to mount a carbide insert or several of them, as, for instance, in FIG. 13, and that this jacket will then be suitably secured within the bit body either by a press fit or by brazing or silver soldering technique. The armoring jacket maintains the carbide insert under firm compressive forces so as to support and protect the element against chipping or breakage. The preferred form utilizes a cylindrical jacket, as in FIG. 4, for instance, which is best adapted for removal by a trepan or crown saw operation. Such saw may be guided by the carbide, particularly if the carbide is cylindrical, and may remove at least the outer portion of the sleeve so that the entire sleeve jacket and carbide may be withdrawn. The exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim:

1. A rock bit comprising body structure having a cutting face, a hardened, substantially non-machinable cutter element extending into and seated in said body structure and projecting beyond said face, and a protective jacket interposed between and firmly anchoring said element in said structure, said'jacket being of machinable metal, being substantially non-yieldable radially, and being annular so as to be removable from said structure by an annular milling cutter without damaging said structure.

2. A rock bit as described in claim 1 further including a bore in said body structure in which said jacket snugly fits and in which said jacket is provided with a generally radial, longitudinal slot in its outer surface to facilitate removal of said jacket by a trepanning operation without damaging the surface of said bore.

3. A rock bit as described in claim 1 in which said jacket and said cutter element have oppositely tapering, generally conical outer walls and said jacket is radially split to facilitate the collapse of said jacket and anchoring of said composite in said body structure bore.

Claims (3)

1. A rock bit comprising body structure having a cutting face, a hardened, substantially non-machinable cutter element extending into and seated in said body structure and projecting beyond said face, and a protective jacket interposed between and firmly anchoring said element in said structure, said jacket being of machinable metal, being substantially nOn-yieldable radially, and being annular so as to be removable from said structure by an annular milling cutter without damaging said structure.

2. A rock bit as described in claim 1 further including a bore in said body structure in which said jacket snugly fits and in which said jacket is provided with a generally radial, longitudinal slot in its outer surface to facilitate removal of said jacket by a trepanning operation without damaging the surface of said bore.

3. A rock bit as described in claim 1 in which said jacket and said cutter element have oppositely tapering, generally conical outer walls and said jacket is radially split to facilitate the collapse of said jacket and anchoring of said composite in said body structure bore.

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