Plastic and nonmetallic article shaping or treating: processes – Orienting or aligning solid particles in fluent matrix material
Reexamination Certificate
2000-11-28
2004-02-10
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Orienting or aligning solid particles in fluent matrix material
C264S148000, C264S152000, C264S210600, C264S248000
Reexamination Certificate
active
06689297
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a magnetic rubber ring, and more particularly to a method of manufacturing a magnetic rubber ring wherein the magnetic rubber ring thus obtained can provide high magnetic forces that are polarized regularly and distributed evenly around its circumference when it is subsequently placed in a magnetic field and then becomes magnetized.
2. Prior Art
A conventional method for manufacturing a magnetic rubber ring of the type referred to above is known, in which an unvulcanized rubber that contains a mixture of an adequate quantity of rubber material and magnetic powders is flattened into a flat rubber sheet by a roll sheeting process. The flat rubber sheet is cut into a square rubber band of a given length having opposite ends cut like slits, and the square rubber band is formed into a rubber band ring by temporarily joining the opposite ends of the square rubber band together. Finally, the rubber band ring is placed in a metal mold where it is compression molded into a finished magnetic rubber ring.
Another conventional method for manufacturing a magnetic rubber ring of the type referred to above is also known. This method, which is more widely used, is designed to provide improved workability and moldability. Specifically, this method consists of using an extruding machine to extrude an unvulcanized rubber containing rubber material and magnetic powders into a rubber band of a given length and having a nearly round cross section, forming a rubber band ring by temporarily joining opposite ends of the rubber band together, and placing the rubber band ring in a metal mold where it is compression molded into a finished magnetic rubber ring.
According to the first mentioned method in which unvulcanized rubber containing an adequate quantity of rubber material and magnetic powders is flattened into a flat rubber sheet by a roll sheeting process, the unvulcanized rubber containing an adequate quantity of rubber material and magnetic powders may inevitably become harder since it originally contains magnetic powders. This is not desirable because a kneading or mixing process for components such as rubber material and magnetic powders can only take place with extreme difficulty. This also applies to the roll sheeting process, where the unvulcanized rubber containing the adequate quantity of rubber material and magnetic powders is flattened into the flat rubber sheet, as well as a process of cutting the flat rubber sheet into a square rubber band of a given length having opposite ends cut like slits. These processes involve much labor and time.
The magnetic powders, such as ferrites, that are contained in the square rubber band normally have poles aligned in an orderly regular fashion, and in one particular direction before it is formed into a rubber band ring. If the square rubber band is twisted inadvertently at or near a middle point thereof when its opposite ends are temporarily joined together to form a rubber band ring, the magnetic powders contained in the rubber band ring would have poles disturbed in a disorderly fashion and oriented irregularly in a circumferential direction of the rubber band ring. Therefore, extreme care is required to ensure that such twisting does not occur at or near the middle point of the square rubber band when the square rubber band is formed into the rubber band ring by temporarily joining the opposite ends of the square rubber band together. This process is not recommended because it must proceed under laborious working conditions as described.
According to the above method, as described above, the magnetic rubber ring may be obtained by cutting the magnetic rubber sheet into the square rubber band having opposite ends cut like slits, forming the square rubber band into the rubber band ring by temporarily joining the opposite ends of the square rubber band together, and placing the rubber band ring into the metal mold where it is compression molded into a finished magnetic rubber ring. This method has a major disadvantage, however, in that when the finished magnetic rubber ring is placed in a magnetic field and is then magnetized, magnetic forces that are produced by the magnetic rubber ring may have poles disturbed in a disorderly fashion and oriented irregularly in a circumferential direction. As a consequence, it is practically difficult to provide a magnetic rubber ring that produces uniform and powerful magnetic forces all over a circumferential direction, when it the ring is placed in a magnetic field and then becomes magnetized.
Thus, it is desirable to provide a method that may provide a magnetic rubber ring that produces uniform and powerful magnetic forces anywhere in a circumferential direction when the ring is placed in a magnetic field and then becomes magnetized.
It may be appreciated from the foregoing description that there are two factors that may potentially cause disturbed magnetic forces in a circumferential direction when a magnetic rubber ring is placed in a magnetic field and then becomes magnetized.
The first factor is that magnetic powders, such as ferrites, that are originally contained in a rubber sheet obtained by a roll sheeting process may have poles that are not oriented regularly.
The second factor is that when a square rubber band is formed into a rubber band ring by temporarily joining opposite ends thereof together, a joint is obtained by simply overlapping slit-like cut faces of opposite ends in a direction in which the ends are compressed, and ferrites contained in a molded rubber band ring may therefore have their pole orientation disturbed at a joint of the opposite ends when the ring is molded, which may cause poles of the ferrites to be oriented irregularly.
As a consequence, it is practically difficult to produce a magnetic rubber ring that provides uniform and powerful magnetic forces all over a circumferential direction of a magnetic rubber ring without disturbing magnetic orientation at a joint of the ring, when the ring is placed in a magnetic field and then becomes magnetized.
Therefore, it is desirable to provide a method that provides a magnetic rubber ring that produces uniform and powerful magnetic forces anywhere in a circumferential direction of the ring when the ring is placed in a magnetic field.
In order to solve the problems described above, a second-mentioned process for manufacturing a magnetic rubber ring is proposed, in which a mixture containing rubber material and magnetic powders, such as ferrites, are extruded into a rubber band by using an extruding machine. This allows ferrites to be aligned in a direction of extrusion.
Even when the above-described extruding machine is used, however, this method has the same problem as does the preceding method. Specifically, when a rubber band obtained by extrusion is formed into a rubber band ring, a joint of the rubber band is obtained by simply overlapping cut faces of opposite ends of the rubber band in a direction in which the rubber band is compressed. This is similar to the rubber band that is obtained by performing the roll sheeting process, and then is cut into a strip of a rubber band having opposite ends cut like slits. Thus, ferrites that are initially aligned and oriented regularly at a time of extrusion molding may be disturbed at a joint of the rubber band when the rubber band ring is formed. When a magnetic rubber ring thus formed is placed in a magnetic field and then becomes magnetized, ferrites contained in the magnetic rubber ring may produce magnetic forces whose orientation is disturbed at a joint of the ring. Thus, uniform magnetic forces in a circumferential direction of a magnetized rubber ring cannot be produced.
SUMMARY OF THE INVENTION
In light of the problems of the prior art methods as described above, it is an object of the present invention to provide a method of manufacturing a magnetic rubber ring that can produce uniform and powerful magnetic forces anywhere in a circumferential direction of the ring when i
Horichi Tsukasa
Mizuta Hideo
Yamaguchi Yoshihiko
Eashoo Mark
Uchiyama Manufacturing Corp.
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