Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Consolidation of powder prior to sintering
Reexamination Certificate
1999-12-27
2001-10-09
Jenkins, Daniel J. (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Consolidation of powder prior to sintering
C425S003000, C425S078000
Reexamination Certificate
active
06299832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for supplying a rare earth metal-based alloy powder to a cavity in a mold, for example, in order to subject the rare earth metal-based alloy powder to a pressing for producing a rare earth metal-based magnet, and to an apparatus suitable for use in such process. More particularly, the present invention relates to a powder supplying process which is capable of uniformly supplying and filling, into a cavity, even an alloy powder which is poor in flowability and difficult to be filled in a cavity and moreover, is inflammable and difficult to handle, as is the above-described rare earth metal-based alloy powder, without production of agglomerates and bridges and without occurrence of inflammation.
2. Description of the Related Art
To supply a powder poor in flowability from a feeder box into a cavity in a mold, a supplying apparatus is conventionally used, which is designed so that a feeder box having an opening in its bottom is moved to above a cavity defined in a mold, whereby a rare earth metal-based alloy powder is supplied from the feeder box into the cavity. There are such conventionally known powder supplying apparatus in which a rotary blade rotated in the feeder box is used as described in Japanese Patent Application Laid-open No.59-40560; a spherical member rotated in the bottom of the feeder box, as described in Japanese Patent Application Laid-open No.10-58198; or a rotary blade rotated spirally within the feeder box is used, as described in Japanese Utility Model Application Laid-open No.63-110521.
In the above prior art systems, however, the height of the feeder box is increased, and the stroke of a punch is prolonged. Therefore, the time taken for one run of the pressing is prolonged, resulting in a reduced productivity. A powder poor in flowability such as a rare earth metal-based alloy powder cannot be filled uniformly into the cavity, if a uniform urging force is not provided. Particularly, a rare earth metal-based alloy powder produced by a strip casting process and having an excellent magnetic characteristic is extremely poor in flowability and difficult to be filled uniformly into the cavity, because it has a small average particle size and a narrow and sharp distribution of particle sizes. Further, when a lubricant such as a fatty ester for enhancing the orientation is added, the alloy powder has an increased viscosity, and hence, is more difficult to be filled uniformly into the cavity.
In addition, in the apparatus having the above-described arrangement, there is a possibility that the rare earth metal-based alloy powder is exposed to the atmosphere to become inflamed, because each of the die surface and the bottom of the feeder box is formed of a metal, and the alloy powder is sometimes caught between them.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a powder supply process and apparatus for supplying an alloy powder from a feeder box having an opening in its bottom into a cavity defined in a mold by moving the feeder box to above the cavity, wherein even a powder difficult to handle such as a rare earth metal-based alloy powder can be supplied from the feeder box into the cavity under a uniform pressure, as compared with the conventional agitation means, without a fear of inflammation.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an apparatus for supplying a rare earth metal-based alloy powder from a feeder box having an opening in its bottom surface into a cavity by moving the feeder box to above the cavity, the apparatus comprising a bar-shaped member which is moved horizontally and in parallel in the bottom of the feeder box.
With the above feature, the powder in the feeder box is supplied into the cavity, while reciprocally moving the bar-shaped member in the horizontal direction in the bottom of the feeder box. Therefore, the powder in the feeder box can be supplied into the cavity under a uniform pressure sequentially in an order of from a powder portion present in the vicinity of the bottom to a portion present in the top of the box, and filled with a uniform density without production of agglomerates and bridges.
According to a second aspect and feature of the present invention, in addition to the first feature, a plurality of the bar-shaped members are provided horizontally at distances.
With the above feature, the plurality of the bar-shaped members are provided horizontally at distances and therefore, the alloy powder can be filled more efficiently into the cavity.
According to a third aspect and feature of the present invention, in addition to the second feature, the distance between the bar-shaped members is generally equal to a distance between cavities arranged in a plurality of rows in a direction of arrangement of the bar-shaped members.
With the third feature, the uniform supplying and filling of the powder into each of the cavities disposed in the plurality of rows can be achieved by each of the bar-shaped members. Even if the finally stopping position for the bar-shaped member after the parallel movement thereof has been failed to be established at a point offset from the opening surface of the cavity, each of the bar-shaped members is stopped at the same position relative to each of the cavities and hence, the supplying and filling of the powder can be carried out, so that a variability in amount of alloy powder filled in the cavities is not produced for each of the cavities.
According to a fourth aspect and feature of the present invention, in addition to the first feature, the bar-shaped member is of an arcuate shape in section.
With the fourth feature, the section of the bar-shaped member is of the arcuate shape, but may be of any of polygonal shapes such as triangular, quadrilateral and pentagonal shapes and the like. However, if the section of at least lower half of the bar-shaped member for guiding the alloy powder is of an arc-shape of a circle or an ellipse, the alloy powder coming into contact with the bar-shaped member with the horizontal movement of the bar-shaped member is guided into the cavity, while being moved downwards along a peripheral surface of the bar-shaped member, whereby the supplying and filling of the powder into the cavity can be achieved under an extremely uniform pressure.
According to a fifth aspect and feature of the present invention, in addition to the fourth feature, the bar-shaped member has a diameter in a range of 0.3 to 7 mm.
With the above feature, the diameter of the bar-shaped member is in the range of 0.3 to 7 mm. However, if the diameter of the bar-shaped member is smaller than 0.3 mm, the urging force is insufficient. On the other hand, if the diameter exceeds 7 mm, the pressure applied to the alloy powder during horizontal movement of the bar-shaped member is too high and produces agglomerates in the alloy powder.
According to a sixth aspect and feature of the present invention, in addition to the first feature, the bar-shaped member is disposed, so that the distance between its lower end and a die surface at a peripheral edge of the opening in the cavity is from 0.2 to 5 mm.
With the above feature, the lower end of the bar-shaped member is spaced at a distance of 0.2 to 5 mm apart from the die surface at the peripheral edge of the opening in the cavity. This is because if the distance is smaller than 0.2 mm, the alloy powder is pressed between the die surface at the edge of the opening in the cavity and the bar-shaped member and produces agglomerates in the alloy powder. On the other hand, if the distance exceeds 5 mm, an effect for urging the alloy powder into the cavity under a uniform pressure is not obtained.
According to a seventh aspect and feature of the present invention, an addition to the first feature, another bar-shaped member is also provided at a location above the bar-shaped member provided in the first feature, so that it is moved horizontally and in parallel in th
Kohara Seiichi
Nakamura Akira
Okumura Shuhei
Armstrong Westerman Hattori McLeland & Naughton LLP
Jenkins Daniel J.
Sumitomo Special Metals Co. Ltd.
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