US2904374A - Well drilling tool - Google Patents

Description

E. G. BOICE WELL DRILLING TOOL Sept. 15, 1959 2 Sheets-Sheet 1 Filed April 4, 1955 INVENTOR.

4'. s g UM 'gjE'PrmwL E/V/f? 6150/01? Filed April 4, 1955 p 15, 1959 E. G. BOICE 2,904,374

. WELL DRILLING TOOL 2 Sheets-Sheet 2 f V l? 61190/05 9 I INVENTOR.

dl k bl M 4.1% f, t I, uw-i-nl 'B, R- PWLL z? TTOR/VE VJ United States Patent WELL DRILLING TOOL Elvin G. Boice, Houston, Tex., assignor to Reed Roller Bit Company, Houston, Tex., a corporation of Texas Application April 4, 1955, Serial No. 499,087

1 Claim. (Cl. 3088.2)

This invention relates generally to deep well drilling equipment and particularly to drill bits.

The invention will be found particularly useful in cone bits. The conventional cone bit includes a bit head having a recess in the bottom thereof with shafts projecting downwardly and inwardly, approximately toward the longitudinal axis of the head. There are usually two or three of these shafts and on each shaft is rotatably mounted a substantially conical roller cutter. The bearing assembly includes roller bearings between the shaft and the base end of the cutter to take the radial load at the base portion of the cutter, ball bearings between the shaft and the middle portion of the cutter to take the axial thrust, and the shaft has a reduced end fitting in a bore in the point portion of the cutter to take the radial load at the point portion of the cutter. The reduced end of the shaft is relatively small, but during drilling operations it is subjected to great loads and wearing action. When the reduced end of the shaft becomes worn, the axis of rotation of the cutter ceases to be coincident with the axis of the shaft, and this causes an acceleration of bearing wear, and consequent premature failure of the bearing assembly. This has for many years presented a serious problem, and various constructions have been suggested for its solution.

One of the specific objects of the present invention is to provide a new and improved cone bit having a shaft with a reduced end and a bearing element which will efiiciently resist wearing action and strongly support the cone.

Other objects will hereinafter appear.

The preferred embodiment of the invention is illustrated by the accompanying drawings wherein:

Fig. 1 is a sectional elevation of a two-cone bit embodying the invention.

Fig. 2 is a sectional view of the end portion of the cutter shaft on the line 22 of Fig. 1.

Fig. 3 is a view of the end portion of the cutter shaft taken on the line 33 of Fig. 1.

Fig. 4 is a fragmentary view of the end portion of the shaft taken on the line 44 of Fig. 1.

Fig. 5 is a detail view of the bearing element.

Fig. 6 is an enlarged sectional fragmentary view illustrating the curvature of the bearing element and the curvature of the reduced end of the shaft.

Referring to Fig. 1 of the drawings, the bit head is indicated at 1 and is provided with the usual threaded shank 2 whereby it is connected to the drill stem (not shown), and suitable drilling fluid passageways 1a in order that mud-laden drilling fluid may be circulated in the usual manner. The bit head 1 may be made in two sections in the conventional manner.

The head has a cutter recess in the bottom thereof, and on the head are cutter shafts projecting downwardly and inwardly in the recess approximately toward the longitudinal axis of the head. The drawings illustrate two such shafts. It will be understood that three shafts may be provided. Two-cone bits and three-cone bits are in common use and are well known to those skilled in the art. The shafts are indicated by the numeral 3 and the cutters on the shafts by the numerals 4 and 5. Roller bearings 6 are interposed between the shaft 3 and the base end of the cone cutter 4, and ball bearings 7 are interposed between the shaft 3 and the middle portion of the cutter 4. The ball bearings may be inserted into the raceways through the bore 8 and retained in place in the usual manner.

The end of the shaft 3 is reduced and is indicated at 30. The cutter 4 is provided with a bore 40 to receive the reduced end 30 of the shaft 3. The reduced end 30 has a longitudinal groove in its lower trailing portion. The bottom of this groove is indicated at 31 and the side walls at 32 (Figs. 2, 3, 4 and 6) and this groove communicates with a socket 3a in the shoulder formed by the reduction of the end 30. Fig. 5 illustrates a sintered tungsten carbide bearing element 9 which is placed in the groove 31, 32 and the socket 3a.

The side walls 32 of the groove are initially made substantially parallel so that the bearing element 9 may be slipped into the groove and socket 3a. After the bearing element is in place, the extremities of the walls 32 are moved into engagement with the flattened portions of the bearing element 9. The bearing element is thereby retained in the groove. The inner portions of the walls 32 are curved, as indicated at 32a, and merge with the curved wall of the socket 3a in the shoulder formed by the reduction of the end 30. The end of the bearing element 9 is rounded to fit the same. The base 31 of the groove is flat to conform with the flat bottom of the bearing element 9.

The bearing element 9 fits the groove, preferably with a clearance of two or three thousandths of an inch between the element and the side walls 32 of the groove. After the bearing element 9 has been inserted in the groove and socket, the extremities of theside walls 32 are then preferably so moved toward the flattened por tions 90 of the bearing element as to gently embrace and retain the bearing element in the groove.

Referring to Fig. 6, the radius of the arcuate outer surface of the bearing element 9 is slightly less than the radius of the outer surface of the reduced end 30. The arcuate surface of the bearing element 9 is in bearing contact with the wall of the bore 40 of the cutter, and no sharp edges of the bearing element are in such bearing contact. The reduced end 30 of the shaft and the bearing element 9 have a running fit in the bore 40 of the cutter 4, the clearance between the two being, for eX- ample, about ten one-thousandths of an inch.

It will be observed that this invention permits the use of a relatively large bearing element of sintered tungsten carbide. In the preferred embodiment shown, the thickness of this bearing element is approximately one-fourth the diameter of the reduced end 30 of the shaft, and the width of the bearing element is approximately one-half the diameter of the reduced end 30 of the shaft. At the same time, a substantial amount of the steel body of the reduced end 30 of the shaft is undisturbed and therefore remains to provide a substantial and strong support for the bearing element 9.

As stated above, the bearing element 9 is made of sintered tungsten carbide. The preferred sintered tungsten carbide contains approximately twenty percent cobalt, by weight. The shaft 3 and its reduced end 30 are made of steel, preferably the heat-treated alloy steel commonly employed in rock bit shafts. The reduced end 30 is preferably not carburized so that it will be tough but not brittle. The cutter 4 may be made of the usual heattreated alloy steel of the type commonly used in rock bit cutters, and the bore 40, as well as the interior and exterior of the cutter 4, may be carburized.

The sintered tungsten carbide bearing element 9 cooperates with the steel wall of the bore 40 of the cutter 4 to reduce friction. Both the bearing element 9 and the reduced end 30 may be of large dimensions so that the steel of the reduced end 30 will strongly support the sintered tungsten carbide bearing elementT9 and the hearing element will not crack under heat and strain in operations. Manufacture may be accomplishedat a relatively low cost.

When the bit 1 is lowered to the .bottom of the hole and rotated (by the drill stern, not shown) in a clockwise direction, looking down, the cutters revolve on their respective shafts and drill the formation. The bearing element 9 functions most efliciently inbits drilling hard rock formations if it is disposed on thelower trailing portion of the reduced end 30. Thus, in Figs. 2, 3 and 6, it will be seen that the bearing element 9 is not centrally disposed in the bottom of the reduced end 30, but instead is disposed at an angle of approximately 10 degrees to the left, which is the trailing side of the reduced end 30, since the shaft travels in a circular direction to the right.

The invention is not limited to the preferred embodiment and use herein disclosed. Other embodiments and uses will be apparent to those skilled in the art from the above description, and within the scope of the following claim.

I claim:

A drill bit having a head, said head having a roller cutter recess in its lower end; a steel shaft on said head and extending downwardly and inwardly in said recess approximately toward the longitudinal axis of said head,

and having a reduced end; a substantially conical steel roller cutter rotatable on said shaft with its base end outermost, and having a bore to receive said reduced end of said shaft; roller bearings between said shaft and the base portion of said cutter; ball bearings between said shaft and the middle portion of said cutter; said reduced end of said shaft having a-longitudinal groove in its lower trailing portion, the shoulder formed by the reduction of said end having a-socket communicating with said groove; and a sintered tungsten carbide bearing element fitting in said groove and socket and having an arcuate outer surface in bearing contact with the wall of said bore of said cutter, said bearing element having a thickness approximately equal to one-fourth the diameter of said reduced end, and a width approximately equal to one-half the diameter of said reduced end, the radius of said arcuate outer surface of said bearing element being slightly less than the radius of said reduced end.

References Cited in the file of this patent UNITED STATES PATENTS 1,721,416 Schroter July 16, 1929 2,030,442 Garfield et al Feb. 11, 1936 2,086,681 Scott July 13, 1937 2,086,682 Scott July 13, 1937 2,104,819 Schlumpf et a1 Jan. 11, 1938 2,444,724 Brown July 6, 1948 2,513,634- Francis July 4, 1950 2,644,671 Ingram July 7, 1953

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