Boring or penetrating the earth – Bit or bit element – Specific or diverse material
Reexamination Certificate
2002-06-25
2003-12-02
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
Bit or bit element
Specific or diverse material
C076S108200
Reexamination Certificate
active
06655481
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to earth-boring drill bits and methods of fabricating such bits and the components thereof. Particularly, the present invention relates to the controlled deposition and affixation of layers of one or more material employed as a matrix material of the bit or bit component, which is also referred to as “layered manufacturing”. More particularly, the present invention relates to methods of fabricating a substantially hollow shell of a component of a drill bit, such as a bit crown or other article of manufacture, comprising disposing the substantially hollow shell adjacent a cavity of a mold, disposing a material within the substantially hollow shell and within the cavity of the mold, and infiltrating the shell.
2. Background of Related Art
Earth-boring drill bits that include fixed cutting elements on the face thereof, which are commonly termed “rotary drag bits” or simply “drag bits,” typically include a bit body formed of steel or fabricated from an infiltrated matrix of a hard, particulate material, such as tungsten carbide. Particulate-based bit bodies are typically infiltrated with infiltrants, or binder materials, such as copper alloys. The bit body of a drag bit is typically secured to a steel shank. The steel shank typically includes a conventional American Petroleum Institute (API) threaded pin connection by which the drill bit may be secured to the drive shaft of a downhole motor or a drill collar at the distal end of a drill string.
Conventionally, steel bodied bits have been machined from round stock to a desired shape, with topographical features and internal watercourses for delivering drilling fluid to the bit face. Hard-facing may then be applied to the bit face and other critical areas of the surface of the bit, and cutting elements secured to the face of the bit. A shank may be machined and threaded on the drill bit.
In the conventional manufacture of a particulate-based drill bit, a mold, including inserts therefor, is milled or machined to define the exterior surface features of the drill bit. Typically, after a first milling of a block of mold material, such as graphite, to define a mold cavity that will subsequently define larger topographical features of the drill bit, a secondary milling is required to define cutter pockets and side supports therefor on the face of the drill bit. Additional hand milling or clay work may also be required to create or refine topographical features of the drill bit.
Once the mold has been milled or otherwise machined, a preformed bit blank of steel or other suitable material may be disposed within the mold cavity to internally reinforce the bit body matrix upon fabrication of the bit body. Inserts, such as preforms that define internal fluid courses, pockets for cutting elements, ridges, lands, nozzle displacements, junk slots, or other topographical features of the bit body, are also inserted into the cavity of the mold. The preforms must be individually designed and fabricated, and even minor changes in a drill bit design may necessitate the use of new and different preforms. The preforms must be placed at precise locations within the mold to ensure the proper placement of cutting elements, nozzles, junk slots, etc.
A quantity of particulate-based material may then be disposed within the cavity of the mold to define a bit body matrix. The bit body matrix is then infiltrated with a molten metal infiltrant to form a solid bit body after solidification of the metal infiltrant and to secure the preformed bit blank to the bit body.
The bit body may then be assembled with other drill bit components. For example, a threaded shank is then welded or otherwise secured to the blank and cutting elements (typically diamond, and most often a synthetic polycrystalline diamond compact or PDC) are secured within the cutting element pockets, such as by brazing, adhesive bonding, or mechanical affixation. Alternatively, the cutting elements may be bonded to the face of the bit body during furnacing and infiltration thereof if thermally stable PDC's, commonly termed “TSP's,” are employed.
Accordingly, the process of fabricating a particulate-based drill bit is a somewhat timely, costly, and complex process that requires the labor-intensive production of an intermediate product (the mold) before the end product (the bit body) can be cast.
In some cases, the mold fabrication process has been made faster and less costly through the use of rubber displacements, which duplicate, in fine detail, the topography of an entire bit profile and face. These displacements are used to cast a ceramic bit mold having an appropriate interior configuration, from which a bit may be cast. Typically, however, such rubber displacements may only be employed in the fabrication of “standard” bits, which are fixed in design as to the size, number, and placement of cutting elements and as to the size, number, and placement of nozzles. Thus, rubber displacements are only cost effective for fabricating high-volume drill bits, of which there are relatively few. With frequent advances and changes in bit design, preferences of individual customers for whom bits are fabricated, and the general decline in the number of wells being drilled in recent years, high-volume standard bits have become almost nonexistent.
Layered-manufacturing processes, such as those disclosed in U.S. Pat. No. 5,433,280 (hereinafter “the '280 patent”), issued to Smith on Jul. 18, 1995, and in U.S. Pat. No. 5,544,550 (hereinafter “the '550 patent”), issued to Smith on Aug. 13, 1996, both of which are assigned to the assignee of the present invention and incorporated herein in their entireties by this reference for all purposes, were originally intended to reduce the cost and time required to fabricate particulate-based bit bodies.
The '280 and '550 patents disclose a method of fabricating a bit body, drill bit component, or other article of manufacture in a series of sequentially superimposed layers or slices. As disclosed, a drill bit is designed as a three-dimensional “solid” model using a computer-aided design (CAD) program, which allows the designer to size, configure and place all internal and external features of the bit, such as (by way of example) internal fluid passages and bit blank voids, and the rakes and locations of external cutting element pockets, as well as the height, thickness, profile and orientation of lands and ridges on the bit face, and the orientation, depth and profile of waterways on the bit face and junk slots on the bit gage. The CAD program then provides a “.STL” file (i.e., a file which represents the surface of the bit body), which may later be transformed into a solid model and numerically “sliced” into a large number of thin, planar layers by known processes employing known computer programs.
After the mathematical slicing or layering is performed, a horizontal platen is provided on which a granular or particulate material such as a tungsten carbide coated with a laser-reactive bonding agent, such as a polymer, a resin, and/or a low melting point metal such as Wood's metal or a lead alloy, or tungsten carbide intermixed with such a laser-reactive bonding agent is deposited in a thin, uniform layer. A finely focused laser, a focused light source such as from an incandescent or discharge type of lamp, or other energy beam, programmed to follow the configuration of the exposed section or layer of the bit body, is directed on the powder layer to melt the bonding agent and bond the metal particles together in the areas of the layer represented as solid portions of the bit in the model. Another layer of powder is then substantially uniformly deposited over the first, now-bonded layer, after which the metal particles of the second layer are bonded simultaneously to each other and to the first, or previously fabricated, layer by the laser. The process continues until all layers or slices of the bit, as represented by the solid model, have been deposited and bon
Butcher Trent N.
Findley Sidney L.
Tibbits Gordon A.
Baker Hughes Incorporated
Mammen Nathan
Pezzuto Robert E.
TraskBritt
LandOfFree
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