Stock material or miscellaneous articles – Circular sheet or circular blank – Aperture containing
Reexamination Certificate
2001-10-24
2003-08-05
Lechert, Jr., Stephen J. (Department: 1732)
Stock material or miscellaneous articles
Circular sheet or circular blank
Aperture containing
C428S131000, C428S137000, C428S220000, C428S692100, C264S118000, C264S153000, C264S232000, C156S307100, C156S307700, C156S308200, C324S200000, C324S207220
Reexamination Certificate
active
06602571
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic encoder and a method for manufacturing such a magnetic encoder, wherein the magnetic encoder may be used in conjunction with a sensor on a semiconductor chip that is placed opposite the magnetic encoder, and is capable of producing codes as represented by a sequence of pulses that are generated by magnetic forces. More particularly, the present invention relates to a magnetic encoder that includes a supplemental or reinforcing ring member and a ring-like magnetic rubber member, wherein the magnetic rubber member is obtained by vulcanizing a raw rubber in its unvulcanized state, and magnetizing the rubber so that the rubber member has S poles and N poles alternately around its circumference. The magnetized rubber member is firmly combined with the supplemental ring member and is uniformly magnetized in its circumferential direction, and accordingly, the magnetic encoder can provide strong magnetic forces. Furthermore, the present invention provides a method for manufacturing such a magnetic encoder.
2. Description of the Prior Art
Conventional magnetic encoders that include a rubber material possessing magnetism have been manufactured by a number of methods, some examples of which are described below.
According to one method, a proper quantity of magnetic ferrite powder is added to a raw rubber material in its unvulcanized state (which may also be referred to as “an unvulcanized raw rubber material”), and the powder and rubber material are mixed together. Then, a resulting mixture is formed into a rubber sheet in an unvulcanized state by performing a sheet rolling process. The unvulcanized raw rubber sheet is then cut into slit-like square strips. Each of the square strips is then joined annularly at opposite ends thereof so that a ring-like rubber blank is formed. The ring-like rubber blank thus obtained is then placed in a cavity in a metal mold, where the rubber blank is compressed, while applying heat thereto, so that the rubber blank is formed into a rubber member having a round circumference. Finally, the rubber member is magnetized so that S poles and N poles appear alternately around its circumference.
According to another method, an unvulcanized raw rubber material that contains a magnetic ferrite powder is extruded into elongated strips by using an extruding machine. Then, each of the strips is temporarily joined annularly at opposite ends thereof so that a ring-like rubber blank is formed. The ring-like rubber blank thus obtained is then placed in a cavity in a metal mold, where the rubber blank is compressed, while applying heat thereto, so that the rubber blank is formed into a rubber member having a round circumference. Finally, the rubber member is magnetized so that S poles and N poles appear alternately around its circumference. This method is widely used since it is expected to enhance moldability and workability.
According to still another method, a raw rubber material that contains a magnetic ferrite powder is rolled into elongated sheets by using a roll machine. A rubber blank having an annular shape is stamped out from each of the sheets by using a shearing machine. The rubber blank having the annular shape is then magnetized so that S poles and N poles appear alternately around its circumference. Finally, the rubber member thus obtained is attached to a supplemental or reinforcing ring by virtue of an adhesive.
The conventional methods that have been mentioned above have respective problems, which will be described below.
In the first method mentioned above, at an initial stage where the magnetic powder, such as ferrite, is added to and mixed with the raw rubber material, it is not considered that the magnetic powder should be aligned regularly in a particular orientation when the rubber material is magnetized. Accordingly, when the rubber material containing such magnetic ferrite powder is magnetized, magnetic forces are produced that are not aligned regularly in a circumferential direction. It is therefore impossible to obtain a magnetic encoder that provides powerful and uniform magnetic forces in the circumferential direction when the encoder becomes magnetized.
In the second method mentioned above, although that part of the magnetic powder, such as ferrite, that exists in a middle portion of the strip may be aligned regularly in a particular orientation, remaining parts of the magnetic powder that exist at joined ends tend to be aligned irregularly in a circumferential direction. Therefore, it is also impossible to obtain a magnetic encoder that provides powerful and uniform magnetic forces in the circumferential direction when the encoder becomes magnetized.
In the third method mentioned above, a rubber ring member that has S poles and N poles alternately around its circumference is attached to a supplemental or reinforcing ring member by virtue of adhesive, after the rubber ring member is magnetized. It is therefore difficult to firmly join the rubber ring member and the supplemental or reinforcing ring member into a single unit.
SUMMARY OF THE INVENTION
In light of the problems of the prior art methods described above, it is therefore one object of the present invention to provide a magnetic encoder that includes a rubber ring member having S poles and N poles alternately arranged in a circumferential direction, and a supplemental or reinforcing ring member, wherein the rubber ring member and the supplemental or reinforcing ring member are firmly joined into a single unit, such that the magnetic encoder provides powerful and uniform magnetic forces in the circumferential direction when the encoder is magnetized.
Another object of the present invention is to provide a method for manufacturing such a magnetic encoder.
According to the method of the present invention, and the magnetic encoder of the present invention obtained by the method, the magnetic encoder may be used with a sensor on a semiconductor sensor chip that is placed opposite the magnetic encoder, and may produce codes as represented by a sequence of pulses generated by magnetic forces. The method, as well as the magnetic encoder obtained by the method, will be described below in some detail by referring to accompanying drawings.
In the method for manufacturing the magnetic encoder in accordance with the present invention, an unvulcanized raw rubber material is first provided, to which material a magnetic ferrite powder is added, and the rubber material and ferrite powder are mixed together. A resulting mixture of the unvulcanized raw rubber material and magnetic ferrite powder is passed through a rolling or extruding machine that forms the mixture into a sheet blank
1
that contains the magnetic ferrite powder aligned regularly in a particular orientation, as shown in FIG.
1
. Altematively, a sheet blank
1
can be produced by extruding the mixture using an extruding machine, then by passing an output of the extruding machine through a rolling machine so as to form the sheet blank
1
. In this case, the sheet blank
1
that has been extruded and then passed through the rolling machine may also contain magnetic ferrite powder aligned regularly in a particular orientation.
Next, the sheet blank
1
in either case is stamped across a planar direction. This results in a ring-like sheet blank or annular blank
11
as shown in FIG.
2
.
The ring-like sheet blank
11
, along with a supplemental or reinforcing ring
4
, is placed on a metal mold, specifically between lower and upper halves
2
,
12
of the metal mold as shown in FIG.
3
. Then, the metal mold is operated to compress the ring-like sheet blank
11
and supplemental ring
4
in an axial or vertical direction while applying heat thereto. This compression provides a vulcanizing action that forms a ring-like rubber member
6
which is a composite annular member including the ring-like sheet blank
11
and supplemental ring
4
, which are joined together by the vulcanizing action.
The ring-like rubber member
6
thus obtained may the
Lechert Jr. Stephen J.
Uchiyama Manufacturing Corp.
Wenderoth , Lind & Ponack, L.L.P.
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