Metal deforming – By deflecting successively-presented portions of work during... – To form helical coil or tube
Reexamination Certificate
1999-11-15
2001-10-30
Larson, Lowell A. (Department: 3725)
Metal deforming
By deflecting successively-presented portions of work during...
To form helical coil or tube
C072S142000
Reexamination Certificate
active
06308549
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method of manufacturing a stator core of a vehicle ac generator and, particularly, a spirally wound stator core of a magnetic steel strip.
2. Description of the Related Art
JP-A-1-164247 disclosed a pair of forming rollers for pressing a magnetic strip in an inclining, thereby thinning the magnetic strips toward one side thereof, thereby forming a spirally piled core.
JP-B2-38-7402 discloses an apparatus for manufacturing a stator core comprising a pair of tapering rollers providing a wedge-shaped space therebetween. A magnetic steel strip is inserted in the space to press-form a spirally piled core.
Because the magnetic steel strip is moved by means of a friction force of the steel strip with the forming roller in any one of the above disclosed apparatuses, it is difficult to prevent the steel strip from slipping on the forming rollers. This occasionally varies thickness of the steel strip and, therefore, the radius of the spiral.
U.S. Pat. No. 4,116,033 or its corresponding Japanese Patent JP-B2-59-36503 discloses an apparatus having a rotatable disk with a plurality of pins fixed thereto, which engage with slots of a magnetic strip to form the strip into a spirally piled core.
Because the number of pins are fixed according to the number of the core slots, it is necessary to change the rotatable disk if a stator core has different number of the core slots.
SUMMARY OF THE INVENTION
A main object of the invention is to provide an improved apparatus and a method for manufacturing spirally wound cores, in which a magnetic steel strip is smoothly moved.
Another object of the invention is to provide an improved apparatus and a method for manufacturing high-precision stator cores.
According to a preferred embodiment of the invention, an apparatus for forming a spirally wound stator core from a strip of magnetic material includes a pair of rollers for pressing one side of the strip to gradually reduce the thickness and a stopper for restricting a distance between the rollers. Preferably, one of the rollers is provided with a sprocket which engages a part of inner cuts of the strip. A guide for restriction movement of the strip in the thickness direction can be also effective to wind the strip.
According to another embodiment of the invention, an apparatus for forming a spirally wound stator core includes a pair of forming rollers having a wedge-shaped gap therebetween, a roller-drive motor connected to one of the forming rollers for continuously inserting a strip of magnetic material into the wedge-shaped gap to bend the strip into a spiral with one side of the strip being radially inside, a winding drum, a drum-drive motor, and a roller presser. A control unit can be provided so that the controlled pressure is changed automatically according to a memorized relationship between the running speed of the strip or the rotation speed of the pair of forming rollers and the pressure applied to the strip.
According to another aspect of the invention, a method for forming a stator core from a strip of magnetic material includes the following steps: a step of pressing the strip at one side thereof to gradually reduce thickness, a step of engaging a sprocket with a part of inner cuts of the strip to move the strip, and a step of winding the strip spirally.
According to another aspect of the invention, a method for forming a spirally wound stator core includes the following steps: continuously inserting a strip of magnetic material into a wedge-shaped gap formed between a pair of forming rollers, pressing one of the forming rollers to reduce the wedge-shaped gap at a controlled pressure, thereby bending the strip into a spiral with one side of the strip being radially inside, positioning a strip-winding drum close to the one side with its axis being perpendicular to the pair of forming rollers, and rotating the strip-winding drum to wind the strip that is bent into a spiral. The controlled pressure is changed according to the running speed of the strip. It can be represented by the rotation speed of one of the pair of forming rollers and the strip-winding drum.
REFERENCES:
patent: 2437500 (1948-03-01), Bruegger
patent: 2812794 (1957-11-01), Chapman
patent: 2815790 (1957-12-01), Mayrath
patent: 2845555 (1958-07-01), Carpenter et al.
patent: 4116033 (1978-09-01), Iwaki et al.
patent: 4445353 (1984-05-01), Taleff et al.
patent: 38-7402 (1960-08-01), None
patent: 62-173955 (1987-07-01), None
patent: 1-164247 (1989-06-01), None
patent: 1-210126 (1989-08-01), None
Asano Masahiro
Fujimoto Toshihiko
Maeda Kazutaka
Matsumoto Katsumi
Nagasaka Katsumi
Denso Corporation
Larson Lowell A.
Pillsbury & Winthrop LLP
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