Boring or penetrating the earth – Bit or bit element – Specific or diverse material
Reexamination Certificate
1998-09-18
2001-11-13
Neuder, William (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Specific or diverse material
C175S432000, C408S145000
Reexamination Certificate
active
06315066
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
This disclosure is directed to an insert which is an advance over well known tungsten carbide inserts used here before. The insert of the present disclosure utilizes a tungsten carbide (or WC) body. This adherent body is made from a shaped and molded mass of tungsten carbide particles which are held together by a cobalt based metal alloy binder. The cobalt based alloy is distributed throughout the body. It adheres to and forms a bond with the tungsten carbide particles distributed evenly throughout the body. This enables the construction and fabrication of a solid, rugged, long life wear part. It can take substantial impact and is able to resist wear readily. The shock impact is handled well by this device. One well known problem of tungsten carbide inserts however is that they wear on the face which makes contact with moving parts. More importantly, such faces have been protected in the past by the incorporation of a wear layer. One technique has been the incorporation of a cap which has been polycrystalline diamond compact (or PDC) material. This unitary body has been adhesively joined typically by a braze layer or other techniques. That has met with real success. There are however some limitations to the use of that two component system. There is the serious tendency of shearing at the interface. This interface is normally the braze area. The interface is susceptible to one set of shear forces which are formed across that interface region merely by the fabrication of the product. Fabrication involves construction of the insert using the cast tungsten carbide body with an integrally formed or later attached cap after separate manufacture. In all instances, there are difficulties arising from the stress in the braze bond plane.
SUMMARY OF THE INVENTION
The present disclosure is directed to an insert which is made of tungsten carbide and which is reinforced with thermally stable diamond (TSP) and in some cases dispersed diamond grit particles also. In this instance, the TSP is fabricated in the form of a cylinder which is placed in the insert body. The cylinder is located at an angle with respect to the common stresses applied to the insert body. By doing this, the finished structure is supported and structurally reinforced by the TSP insert. A TSP component formed as a cylinder is especially beneficial because it is easily gripped by the surrounding body. The TSP reinforced insert construction then has better distribution of stresses. That is, stresses which originate at the time of fabrication do not become so severe that they create problems. Stresses which are encountered in the dynamics of use do not pose a problem. Finally, stresses which derive from impact are handled more readily to prevent shattering the TSP. The TSP provides the composite structure in the insert which is able to provide reinforcement, longer life and better resistance to both shock loading and steady state stresses. In this aspect the insert of the present disclosure is especially beneficial in that the structure substantially grips the TSP fully around and holds it in place. The TSP component when held in this fashion provides much longer life to the composite insert made by the present process. The TSP shape will be discussed in detail later.
Consider now the situation which arises after this insert has been used for a long while. The insert use normally entails wearing from one end. The wear applied to the insert grinds away the exposed end. As it is abraded, it is ground and polished time and time again. Eventually, wearing away the WC body exposes the TSP. The TSP is also worn away and exposed. Eventually, the internal TSP will form an exposed island at the end face where wear occurs. This continues indefinitely. Even while this gradual wear occurs, there is no particular problem arising from this accumulated wear because the accumulation of wear does not prompt the device to shatter or break in an unintended fashion. Moreover there is little likelihood of TSP separation.
In one aspect of the present disclosure a drawing die is disclosed. The drawing die is especially beneficial for converting bar stock into drawn wire. The metal is forced through the die and is deformed. The bulk of the wear of the die made with an insert of TSP within a surrounding WC body is handled readily by this improved drawing die. The common risk to this sort of drawing die is that the diamond insert, of a multitude of shapes, tends to pull free from the surrounding WC body. It is somewhat like unnesting a stack of cups or cones. The force applied to the die cutter of diamond material typically initiates that kind of failure mode. It will operate successfully for a while and then the die cutter diamond component will either pull free or break into a few large pieces on release of the grip by the surrounding strong or re-reinforced body. In all instances, that poses a serious problem of catastrophic failure.
The present disclosure sets forth a diamond drawing mechanism which is able to endure that kind of wear and tear without that kind of catastrophic failure. While it not only lasts longer, it lasts longer with greater durability and less likelihood of failure in that mode. The diamond insert that is on the interior of the drawing die is gripped and held by the surrounding WC body so that release does not accidentally occur. The common failure mode in this instance is defeated.
The insert for the present disclosure of a drawing die is made of TSP which is surrounded in a WC body. A suitable drilled hole of appropriate diameter is formed. The hole is drilled through the die typically along the center line axis. The hole however passes through the TSP which is surrounded by the WC body. The TSP has the form of an elongate cylinder. The hole through the cylinder is at right angles so that the cylinder is gripped by the surrounding body.
After long use of the drawing die, the accumulated wear and tear on this construction eventually enlarges the gauge of the hole but it is less likely to cause a complete failure of the die.
Finally the present disclosure sets out a construction of an insert where two or more of the TSP cylinders are placed in the insert body. This provides separate wear pads when they finally erode, thereby exposing the TSP at two different locations. Last of all, the TSP cylinder is protected by scattering a few separate diamonds in the near vicinity of it. These cause redistribution of stress patterns in the WC support body which makes up the bulk of the insert.
REFERENCES:
patent: 5199832 (1993-04-01), Meskin et al.
patent: 5205684 (1993-04-01), Meskin et al.
patent: 5217081 (1993-06-01), Waldenstrom et al.
patent: 5524719 (1996-06-01), Dennis
Munsch Hardt Kopf & Harr P.C.
Neuder William
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