Metal tools and implements – making – Blank or process
Reexamination Certificate
1999-04-12
2001-08-07
Rachuba, M. (Department: 3724)
Metal tools and implements, making
Blank or process
C228S124100, C228S122100, C083S651000
Reexamination Certificate
active
06269714
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a cutter knife to be mounted on a thermoplastic resin pelletizer for pelletizing thermoplastic resin. The invention also relates to a production method of said cutter knife.
BACKGROUND OF THE INVENTION
For the sake of convenience of transportation, reducing costs of later processing and other reasons, thermoplastic resin is normally produced and distributed in the form of pellets, which are small, approximately rice-grain sized particles. These pellets are produced industrially by means of a kneading pelletizing (extrusion) machine incorporated in a chemical apparatus. Examples of types of a pelletizing device used in such a pelletizer include a hot cut type and a underwater cut type. There are also various blades used for this purpose; a typical example of fixed blades is a die plate, while there is a cutter knife
1
shown in
FIG. 8
as an example of movable blades. Nowadays, because of their superior abrasion resistance and resin cutting capability, ceramic alloys are most widely used as a material of cutter knife
1
.
However, ceramic alloys used as a material of such a cutter knife present various problems; not only are they expensive and hard to acquire but also prone to being chipped or broken because they have lower resistance to a transverse load, in other words are more fragile, compared with steel which is the most typical blade material. Although ceramic alloys require a thorough countermeasure to solve the above problems, it cannot be said that a sufficiently effective countermeasure exists at present. Furthermore, a ceramic alloy is difficult to process by using machine, which means that processing a ceramic alloy is costly. Therefore, using a ceramic alloy, which is itself an expensive material, to produce cutter knives substantially increases their costs.
A prior art method of producing a ceramic alloy cutter knife uses a process of sintering powdered ceramic alloy directly to two large base metal bodies by using a special container and then subjecting the contents to a hot isostatic pressing (HIP) process. The bodies are removed from the container and separated from each other. Each body is then cut along its longitudinal axis which is directly in the middle of the ceramic alloy material. Each half is then cut again into individual pieces or blanks, which are in turn cut again and formed into individual cutter knives. In addition, the process requires that the ceramic alloy be ground into a knife edge. The powdered ceramic alloy HIP process is complicated and presents various technological difficulties, for example, the air must be removed from the container prior to sintering which naturally results in the discharge of some of the powdered material. The entire production method is expensive and does not alleviate any problems associated with fragility of the ceramic alloy blade or that of avoiding unnecessary processing. In addition, powdered ceramic alloy material is less available and must be specially procured from a powder manufacturer. In short, the prior art method does not address the problems associated with producing a ceramic alloy cutter knife in terms of expense, the delicate nature of the material, availability of ceramic alloy material and the reduction of processing of the blade.
SUMMARY OF INVENTION
In order to solve the above problems presented by conventional cutter knives, an object of the invention is to provide a cutter knife for a thermoplastic resin pelletizer and its production method by using a ceramic alloy as a material for said cutter knife, wherein said cutter knife can easily be produced with reduced costs and without danger of breakage in spite of using a ceramic alloy as a material. A feature of the invention is a cutter knife to be mounted on a thermoplastic resin pelletizer for pelletizing thermoplastic resin, wherein the main body and the knife edge of the cutter knife are integrally formed, the main body formed out of steel and the knife edge formed out of ceramic alloy. According to the second feature of the invention, a groove is formed in a corner of a rectangular steel body in such a manner as to extend in the longitudinal direction of the steel body which has an appropriate thickness, a ceramic alloy plate is inserted into the groove and bonded thereto by means of diffusion bonding, and the material is then cut into a specified shape. According to the third feature of the invention, a steel block is shaped as to have a step when viewed from the side and, after having a ceramic alloy plate bonded to the upper surface of the lower step thereof by means of diffusion bonding, is diagonally cut at specified intervals, and then, each cut piece is cut into a specified shape. A fourth feature of the invention is the use of a functionally gradient material between the bonding surfaces of the ceramic alloy plate and the steel body prior to the diffusion bonding which acts as a binder during the diffusion bonding process to improve the strength, defacement resistance and chipping resistance of the cutter knife and in particular, the ceramic alloy blade.
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Kakoh Kiki Co., Ltd.
Oldham & Oldham Co. L.P.A.
Rachuba M.
LandOfFree
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