Replaceable Cutter Using Internal Ductile Metal Receptacles

FIG. 1 is a side cross-sectional view of a cutter and a metal receptacle disposed in a matrix bit according to the invention.

FIG. 2 is a front elevational view of the metal receptacle and cutter of FIG. 1 shown in isolation without the remaining portions of the bit.

FIG. 3 is a perspective view of the metal receptacle shown in FIG. 1 and 2.

FIG. 4 is a side cross-sectional view of the metal receptacle of FIG. 1 shown in combination with an insert as utilized during the manufacturing process.

FIG. 5 is a cross-sectional front view of a plurality of cutters as described in connection with FIGS. 1-4 as would appear on the crown of the bit.

FIG. 6 is a front elevational view of an alternative embodiment of two cutters shown in isolation of the surrounding bit material.

FIG. 7 is a side elevational view of the cutter shown in FIG. 6.

The invention may be better understood by now turning to the following detailed description.

A replaceable stud cutter for use in matrix drag bit is provided by furnacing a ductile metallic receptacle within the body of the drag bit as it is fabricated. The metal receptacle is characterized by having a receiving cavity defined therein and by preferably including various mechanisms such as grooves or flares which facilitate retention of the metallic receptacle within the matrix body. The lowermost portion of the receptacle within the matrix body may also shaped or tapered to allow dense packing of the receptacle adjacent to other receptacles along a given radial line on the bit face. A replaceable cutter is brazed, adhesively bonded and/or mechanically locked within the receiving cavity defined in the metal receptacle. When the replaceable cutter becomes worn through normal use, the mechanical locking elements can be drilled out, the brazing melted or adhesive dissolved to allow insertion of a new replacement cutter without causing any damage or alteration either to the receptacle, matrix body or bit face.

FIG. 1 is side sectional view of a replaceable cutter together with an internal ductile metal receptacle shown in place within a matrix drag bit. A ductile metal receptacle, generally denoted by reference numeral 10, is molded in place within a matrix bit, generally denoted by reference numeral 12. Bit 12 is formed by conventional powdered matrix metal techniques. A replaceable cutter, generally denoted by reference numeral 14, is fixed or secured within receptacle 10 and bears on a portion positioned for exposure to the rock formation, a cutting element generally denoted by reference numeral 16. In the illustrated embodiment, replaceable cutter 14 is a metallic plug having an exposed diamond table 18 on a forwardly disposed face 20. Diamond table 18 is bonded by conventional means to a backing slug 22 which in turn is mechanically and/or metallurgically bonded into the body of cutter 14. In the preferred embodiment the rear portion of cutter 14 is provided with a generally conical shape which is disposed into a corresponding conically shaped cavity 24 defined in metal receptacle 10. Of course it will be understood by those of ordinary skill in the art that other cutter/cavity configurations are possible. For example, a cylindrical, triangular, or hexagonal cutter might be mated into a like-shaped cavity, or into one of a different shape to provide additional channels for braze or adhesive material, or mechanical locking means.

In the illustrated embodiment as shown in FIG. 1, metal receptacle 10is completely embedded beneath the bit face of bit 12 during the fabrication process of the bit face and is disposed so that when replaceable cutter 16 is fixed within conical cavity 24, diamond table 18 is properly disposed adjacent to a waterway 26 above the bit face. However, the placement of metal receptacle 10 relative to various features or element included within the design of the bit 12 is largely irrelevant to the invention as long as metal receptacle 10 is in some manner securely fixed or attached to bit 12.

Full embedment is illustrated, since this not only provides nearly integral and faultless retention of metal receptacle 10 within bit 12, but also serves to provide a high degree of impact resistance to receptacle 10. Retention of metal receptacle 10 is facilitated by the definition of one or more horizontal grooves 28 defined in root 30 of receptacle 10 which are filled in by the metallic matrix during molding.

In an alternative embodiment, as best illustrated in the front elevation view of FIG. 2, root 30 of receptacle 10 may also be provided with a bilateral flare 32 which serves to positively lock receptacle 10 within the body of bit 12.

It is also contemplated that a combination of grooves with flares may be employed, or that knurled or packed surfaces or multiple, smaller flares may be utilized as retention means.

Cutter 16 is secured within cavity 24 within ductile metal receptacle 10 by brazing, adhesive bonding, mechanical locking or any other means now known or later devised. In most applications the degree of the bonding strength between cutter 16 and receptacle 10 may be somewhat relaxed inasmuch as most of the stress placed upon replaceable cutter 16 is compressive. In the illustrated embodiment, cutter 16 is mechanically locked into place into cavity 24 by means of a locking pin 34 as illustrated in side view in FIG. 1, which is disposed partly in a longitudinal groove running along at least a part of the outside conical surface of the lower portion of cutter 16 and partly in a corresponding and mating longitudinal groove 38 defined within cavity 24 in receptacle 10. Locking pin 34 thus serves to prevent rotational movement of cutter 16 within receptacle 10. Transversely oriented locking pins or key fingers may also be employed to orient cutter 16 and to aid in its retention within receptacle 10. Affixation may be further secured by brazing and by annular retention grooves 36 defined into the lower portion of the conical surface of cutter 16 to provide annular locking ribs from the brazing material. Whether mechanical locked in cavity 24 by pins or the like metallurgically bonded by brazing or the like, or adhesively bonded, cutter 16 is replaceable within bit 12 in the field.

The lower portion of cutter 16 does not bottom out against the bottom of cavity 24 but allows a space 25 to be defined therebetween which facilitates the brazing or bonding of cutter 16 within cavity 24.

The detailed aspects of the shapes of receptacle 10 are better illustrated in the perspective view of FIG. 3 wherein receptacle 10 is shown in isolation of bit 12 and cutter 16, clearly depicting a longitudinal groove 38 defined within cavity 24.

Turn now to FIG. 4 wherein the fabrication of the invention is described. Metal receptacle 10 is placed in a conventional manner within a graphite mold 40 shown in fragmentary cross-sectional view in FIG. 4. A pressed graphite insert 42 which may also be appropriately made of ceramic, dental plaster or other filler material, is disposed into cavity 24 on the one hand and appropriately placed on or in mold 40 on the other. Mold 40 is then filled with matrix powder 43 in a conventional manner and furnaced. The shape of insert 42 is appropriately machined or formed not only to prevent matrix powder from entering cavity 24, but to accommodate and define the outwardly extending envelope of replaceable cutter 16 with respect to adjacent metal matrix portions of the bit face. Thus it can be readily understood that a large variety of cutter shapes can be accommodated without redesign of ductile metal receptacle 10.

The structure and manufacture of a single cutter and receptacle combination now having been described and illustrated, consider the combination of such cutters and receptacles in an assembly as shown in FIGS. 5-7. FIG. 5 illustrates three such cutters shown in front cross-sectional view on the crown of a bit 12. The tapered shape of the lower portion of metal receptacle 10 allows their compact grouping on crown 44 without interference or contact between adjacent receptacles. This clearly allows not only high density of cutters, but also placement on highly curved bit portions.

An alternative embodiment of the invention is illustrated in front elevational view in FIG. 6 and in side elevational view in FIG. 7. FIGS. 6 and 7 illustrate a combination of two receptacles 10 and 46 in a side-by-side interlocking or at least interleaved relative position. Receptacle 10 has a shape as described in connection with FIGS. 1-4 while receptacle 46 is shaped with an alternative geometry which allows its linking with receptacle 10. In the illustrated embodiment, receptacle 46 has a bent or slanted lower portion 48 which allows the root of receptacle 46 to be placed immediately behind root 30 of receptacle 10 without interference while allowing the cutters of each of the receptacles to lie on a common radius of the bit face. Thus, FIGS. 6 and 7 illustrate that it is entirely included within the scope of the invention that alternative and/or complementary geometries of the receptacles could be employed to acquire even greater cutter densities and placements at even greater bit face curvatures than possible with the design and arrangement shown in Figure 5.

Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. For example, receptacles capable of accomodating a plurality of cutters may be employed, or a receptacle utilizing a plurality of roots might be utilized to receive and retain a large diamond compact cutter of the type recently developed for use in bits. Therefore, it is expressly understood that the illustrated preferred embodiments have been set forth only for the purposes of example and should not be taken as limiting the invention which is defined in the following claims.