Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Consolidation of powder prior to sintering
Reexamination Certificate
2001-08-31
2002-03-12
Jenkins, Daniel J. (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Consolidation of powder prior to sintering
C425S078000
Reexamination Certificate
active
06355210
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a powder-compacting method and apparatus suited for a process in which powder (hereinafter simply called powder, which includes granulated powder containing a binder) is compacted in a manufacturing line, such as ceramics, powder metallurgy, a magnetic material in the field of electric materials, a ferrite magnet, and a rare earth magnet. More particularly, it relates to a powder-compacting technique and apparatus in which the apparatus includes a mechanism designed to sequentially apply a sufficient pressure for the powder compacting to each part of a pressurized area, while the technique includes step compression for reducing a total pressurizing force.
2. Description of the Related Art
It has heretofore been believed that powder compacting usually requires a total pressurizing force in which a sufficient pressure to obtain a target compacting density is applied to the entire compact or an area (an area of a die opening) in a direction in which the pressure is projected.
A mold for use in the powder compacting includes a die and upper-lower punches when a compact does not includes a hole in a direction in which pressure is applied. The mold is filled with powder, which is then pressurized by the upper-lower punches. The total pressurizing force is applied to an area of the powder at which the punches contact the powder.
A compact positioned in the middle of the mold after pressurization is knocked out and then thrown out of the mold by means of the lower punch. In the process of such an operation, the compact is held in frictional contact with an inner wall surface of the die under elevated pressure. As a result, a high level of discharging pressure is required during knockout. In metallic powder, there occur defects during a series of the above processes, such as scuffing adhesion between the inner wall of the die and the punches, cracks, and chip-off. In addition, other general compacts such as oxides tend to chip off, crack, and laminated-crack because of internal distortion.
In order to eliminate such defects, the die is made of an ultra-hardened alloy having good abrasion resistance to the powder, or otherwise a special film having a reduced degree of surface adhesion is applied to the die. In addition, a mold for the die must be fabricated with a high degree of precision.
It is assumed that a basic patent on the above powder compacting was initially filed in Europe nearly at the year of 1910. (See “History and Development of Powder Metallurgy” by Kimura Hisashi, issued by Agune Gijyutu Center.)
A powder compacting process under magnetic field conditions in the field of magnets is described in, e.g., “Magnetic Materials for New Era” issued by Mitokako Kakoh Gijyutu Kyoukai, second edition, 1983, and “COBALT 53”, December 1971, by R. E. Johnson, A. I. M., and C. J. Fellows, on pages 191-196. In addition, the same powder compacting process has recently been filed for patent, as seen from published Japanese Patent Application Laid-Open No.3-40861.
However, similarly to the above-mentioned typical powder compacting, the prior art as given above pressurizes the die at a pressurized opening area thereof, and thus requires a similar total pressurizing force.
In an overall process for manufacturing a product in each field, a compacting process is believed to require the most important key technology that determines manufacturing cost of the product as well as a quality level of the product. The present invention provides a new key technology-based technique and apparatus to related wide fields.
The prior art powder compacting as described above has shortcomings of high energy to be supplied to an apparatus, high costs, and a large-scaled apparatus with a consequential increase in space to be occupied by such an apparatus, because a large-sized powder compact, an elongated powder compact, a plurality of powder compacts are produced by a large-scaled compacting apparatus having an increased overall pressurizing force.
In view of the above, an object of the present invention is to provide an improved powder-compacting method and apparatus designed to require a reduced level of a pressurizing force for powder compacting, thereby allowing powder to be compacted by means of a smaller-scaled compacting apparatus instead of a larger-scaled compacting apparatus.
SUMMARY OF THE INVENTION
A powder-compacting method according to the present invention comprises the steps of: filling powder to be pressurized into a molding container; and, individually pressing a plurality of pressurizing members in sequence toward the powder, the pressurizing members being aligned on a pressurized surface of the powder through an elastic plate.
According to the present invention, step compaction makes it possible to reduce a total pressurizing force required for conventional techniques, and thus allows a smaller-scaled compacting apparatus to compact the powder. As a result, a low cost apparatus is achievable.
A powder-compacting apparatus according to an aspect of the present invention comprises a molding container having a plurality of pressurizing members disposed on a bottom of the container, and further having an elastic plate disposed on the pressurizing members as a bottom surface, wherein the plurality of pressurizing members are sequentially driven to pressurize powder via the elastic plate for compacting.
A powder-compacting apparatus according to another aspect of the present invention comprises: a molding container having a bottom, the container having a powder-filled opening formed at an upper portion thereof and a wedge-inserted hole defined through a sidewall of the container; a plurality of pressurizing members aligned on a bottom plate of the molding container; an elastic plate disposed on the plurality of pressurizing members for providing a bottom surface of the powder when the powder is filled into the molding container through the powder-filled opening; a lid body for closing the powder-filled opening; and, a wedge inserted into the molding container through the wedge-inserted hole, the wedge being pushed along the bottom plate into between an inner surface of the bottom plate and the pressurizing members, thereby permitting the plurality of pressurizing members to sequentially pressurize the powder via the elastic plate for compacting.
In a powder-compacting apparatus as previously defined, at least the lid body and compacting surfaces of the pressurizing members contiguous with the elastic plate are curvilinear in shape in order to allow the compact to be formed into one of a pillar shape, substantially semi-pillar shape, substantially semi-cylindrical shape, partially cylindrical shape.
The above structure provides compacts having a wide variety of shapes.
In a powder-compacting apparatus as previously defined, the wedge includes a slanted surface for raising the pressurizing members and a planar surface continuously extending from the slanted surface for retaining the pressurizing members at a position where the pressurizing members are raised.
The above structure allows the powder to remain pressurized for a certain time. This feature prevents the occurrence of cracks in the compact.
In a powder-compacting apparatus as previously defined, the molding container has an inner peripheral surface tapered at the powder-filled opening so as to expand outward.
The above structure permits a knockout position at which the compact is discharged to be positioned adjacent to an opening of the container at the top of the die. In addition, the draft-tapered upper opening reduces a draft pressure and internal compact distortion. Such a reduction in internal compact distortion contributes toward reductions in compact chip-off, cracks, and laminated cracks, eliminates an inconvenience of scuffing on a die, which otherwise would occur in metallic powder. Moreover, the reduced internal compact distortion is believed to contribute toward reductions in quantity of binders and lubricating agents, which are required for
Hirabayashi Yasuyuki
Jenkins Daniel J.
Stevens Davis Miller & Mosher LLP
LandOfFree
Powder-compacting method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Powder-compacting method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Powder-compacting method and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2869830