Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Patent
1995-11-07
1998-06-30
Czaja, Donald E.
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
264101, 264102, 264571, 425389, 4254051, 4254052, B28B 706
Patent
active
057729468
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a press-forming apparatus for press-forming a preform, such as ceramic green sheet, a prepreg comprising reforcing fibers impregnated with thermoplastic resin or the like, and so on, and to a method of press-forming such a preform.
BACKGROUND ART
In the past, a multilayer capacitor was known as an example of ceramic laminate. The multilayer capacitor has a plurality of layers of internal electrodes formed in the ceramic unit and external electrodes electrically connected to the internal electrodes and disposed on the opposite ends of the capacitor.
In the conventionally known method of making such multilayer capacitor, a plurality of rectangular electrodes are formed on a ceramic green sheet. A plurality of such green sheets each having a plurality of electrodes are stacked one upon another and, thereafter, are pressed by a mechanical press to bond the green sheets together. The press-bonding is carried out such that the stacked green sheets are placed in a lower mold member of a metallic mold and then pressed by an upper mold member so that the green sheets are formed or moulded into a caramic unit free of any gap between the sheets. After the press-bonding, the ceramic unit is cut into a columnar chip which is then subjected to a burning. Thereafter, the external electrodes are formed on the opposite sides of the thus burned chip.
The press-bonding method carried out by the mechanical press has a problem that, because each sheet has different thicknesses in a portion formed with internal electrodes and in other portions free of the electrodes, the other portion of the sheet cannot be pressed to a desired density and thus is liable to cause a delamination.
Especially, the difference in density attained by the press-bonding is greater and becomes highly influential as the number of stacked green sheets is increased. Thus, there has been a problem that the production of multilayer capacitors is liable to make defective products due to insufficient or poor press-bonding with a resultant low production yield.
In addition, the press-bonding by the mechanical press causes strain in the metallic mold during pressing, so that the application of force varies with the operative positions of the upper and lower mold members to generate uneven pressing force which is one of the causes of the delamination.
Moreover, when the press-bonding is carried out by the mechanical press, the chip after the burning has a substantially completely columnar shape. Thus, the external electrodes formed on the columnar chip project or bulge therefrom a distance equal to the thickness of each external electrodes, with a resultant problem that the mountability of the chip onto a substrate is lowered.
The present invention was made under the circumstances explained above.
In other words, the present invention has an object to provide apparatus and method which solve the problems pointed out above and are effective to uniformly press a preform such as, for example, a stack of ceramic green sheets to produce, at an improved yield, a press-formed product such as a ceramic laminate which is free of delamination and damage.
Another object of the present invention is to provide a press-forming apparatus which is free from mechanical trouble and which is operative to produce laminated products speedily and cyclically.
A further object of the present invention is to provide a press-forming apparatus in which, when a projecting portion of a lid member is to be fitted into or removed from a cavity in a pressure container, the projecting portion of the lid member can be fitted into and removed from the cavity easily, smoothly and without any trouble.
A still further object of the present invention is to provide a press-forming apparatus in which, when a projecting portion of a lid member is to be fitted into or removed from a cavity in a pressure container, the projecting portion of the lid member can be fitted into and removed from the cavity easily, smoothly and without any trouble, and in whic
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Imai Kouichi
Kagawa Teruo
Kaminaga Kenzo
Matsuno Hisao
Nishioka Akira
Czaja Donald E.
Nikkiso Company Limited
Vincent Sean
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