Stock material or miscellaneous articles – All metal or with adjacent metals – Macroscopically anomalous interface between layers
Reexamination Certificate
1999-04-30
2001-03-27
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Macroscopically anomalous interface between layers
C428S614000, C428S627000, C030S345000, C030S348000, C030S350000, C030S351000, C228S165000, C228S170000, C228S190000
Reexamination Certificate
active
06207294
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a self-sharpening cutting tool. More specifically, it relates to a laminated cutting tool or knife blade which has improved laminate strength and continues to stay sharp as it is used.
BACKGROUND OF THE INVENTION
Knives, blades and cutting edge tools have traditionally been made of an essentially uniform material which is typically hardened for cutting purposes. The hardening usually occurs through known heat tempering.
Historically, blacksmiths forged axes by folding softer iron around an iron mold and hammer welding a steel insert between the two iron sides so the steel formed the actual cutting edge. This gave a superior cutting edge and conserved the most expensive steel. Other blades such as samurai blades use methods of incorporating a soft and hard alloy to gain the benefits of both. An example of a knife blade construction utilizing an outer layer of a soft material and an inner layer of a hard material is found in U.S. Pat. No. 3,681,846. In this patent an outer layer of steel or aluminum encases an inner layer of a relatively hard material such as tungsten carbide. Another patent disclosing a laminated knife blade is shown in U.S. Pat. No. 5,256,496. In this patent a titanium-high carbon steel laminate is made with an outer layer of titanium encasing an inner steel blade.
One of the major problems with laminating hard alloy metals is securing the metals together. Delamination of the metals at the interface between the dissimilar metals often results when the laminated cutting tool is put to use. This delamination results in an inferior product and could also result in a safety hazard.
There is a need for a cutting tool which successfully employs a laminated structure.
There is a need for a cutting tool which can be easily laminated without fear of delamination.
There is a need for a cutting tool which sharpens itself constantly via the processes of normal use and wear.
Finally, there is a need for a method which can successfully adhere multiple alloys together to form a self-sharpening tool.
SUMMARY OF THE INVENTION
The present invention comprises a laminated cutting tool so constructed as to be perpetually self-sharpening through the processes of normal wear and use. Two different manufacturing processes, both novel, are presented to achieve this goal, both resulting in the extensive welding or bonding of metal to metal and particularly like metal to like metal, to achieve a tool sufficiently strong to withstand the fatigue of heavy use and potential loss of tool strength resulting from corrosive processes between unlike metal laminations.
In the simplest form of the first process, the present invention utilizes a hard inner metal, surrounded on both sides by a softer metal. The harder inner layer is preferably a perforated layer, which allows for the junction of the two softer layers together through the perforations. The sandwich layers of metal are explosively welded together. This results in a much stronger cutting tool.
In the simplest form of the second process, no preformed hard, perforated, central layer is utilized; rather the hard central layer is formed by drilling or etching pits or cutting or stamping slots in the lower lamination, which are then filled with extremely hard particles, e.g., tungsten carbide, ceramic dusts, or diamond or mixtures of such compositions. For example, tungsten carbide grit may be mixed with ceramic dust or mineral crystals. In addition, other materials, with characteristics other than hardness, could also be included to improve tool function in desired applications. The upper lamination is then explosion welded onto the lower; the pits retaining their hard particles in place, against the force of the explosion generated plasma jet. This results in the very strong bonding of metal to metal, alternating with regions of integral incorporation of the hard particles into a central layer, which forms the working edge.
The preferred cutting tool is made with layers of like metals. However, dissimilar metals may alternatively be used. Most importantly, however, in either case, the small hard particles (or the hard layer) wear(s) more slowly than the surrounding softer metal. Therefore they (it) will constantly present a sharp edge on the tool to the work and the sharp edge will be continually sharpened as the blade wears. The cutting tool in accordance with the present invention can be constructed and used with multiple laminations, such as a cutting tool with three, four, or five layers of metal.
The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of the preferred embodiments of the invention as illustrated in the accompanying drawings.
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“Explosive Welding Engineering and Design Basics” flyer from High Energy Metals, Inc. (Mar. 12, 1998).
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Merchant & Gould P,C,
Wahl John R.
Zimmerman John J.
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