US 5,472,334 AGranted

Injection molding die for injection-molding base boards

AssigneeSeikoh Giken Co., Ltd.

InventorMitsuo Takahashi

Life of this patent

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Abstract

To produce base boards each usable for an information recording medium such as a photoelectromagnetic disc or the like by employing an injection molding process, an injection molding die of the type comprising a die half on the stationary side and a die half on the movable side includes a cylindrical supporting member on the stationary side, a die assembly on the stationary side arranged in the cylindrical supporting member, a cylindrical supporting member on the movable side, a die assembly on the movable side arranged in the cylindrical supporting member, a cylindrical guide member located between both the cylindrical members, a first driving unit for displacing the die half on the movable side, and a second driving unit for actuating an ejector sleeve. Each injection-molding operation is achieved by way of the steps of filling a cylindrical die cavity with a pressurized molten resin, forming a center hole through a molded product of base board, holding the die cavity in the fully closed state, and then re-compressing the molded produce of base board by actuating the first driving unit. While the step of re-compressing is executed, the molded product of base board is squeezed against the die cavity and the outer peripheral surface of a cut sleeve by a high inner pressure of the molten resin with the result that a final molded product of base board has a high density and exhibits a smooth surface on the center hole formed through the molded product of base board.

An injection molding die for injection-molding base boards in a cylindrical die cavity, comprising:

(A) a movable side, including:
(1) a first platen;
(2) a first base plate;
(3) a first cylindrical supporting member integrally secured to the first base plate;
and
(4) a first die assembly arranged in the first cylindrical supporting member and being operatively connected to the first base plate, including:
(a) a first die half fixedly secured to the first platen;
(b) an ejector sleeve;
(c) a cut sleeve;
(d) an ejector pin, said ejector pin, the ejector sleeve and cut sleeve being positioned within the first die half in a coaxial arrangement;
(e) a floating member slidably positioned around the first die half to define an outer peripheral surface of the cylindrical die cavity;
and
(f) a movable plate;
(B) a stationary side, including:
(1) a second platen;
(2) a second base plate;
(3) a second cylindrical supporting member integrally secured to the second base plate;
and
(4) a second die assembly arranged in the second cylindrical supporting member and fixedly secured to the second base plate, including:
(a) a second die half fixedly secured to the second platen, the first and second die halves defining a cylindrical die cavity therebetween;
(b) a nozzle bush;
and
(c) a flange bush for supporting a stamper plate, said nozzle bush and flange bush being positioned within the second die half in a coaxial arrangement;
(C) first spring means for biasing the floating member toward the second die half;
(D) second spring means for biasing the ejector pin away from the second die half;
(E) third spring means for biasing the cut sleeve away from the second die half;
(F) cylindrical guide member means located between the first and second cylindrical supporting members for aligning the first die assembly with the second die assembly, said guide member means defining a minimum gap between the first and second die assemblies;
(G) first driving means for moving the cut sleeve, the ejector pin, and the movable plate, said movable plate displacing the first die half and ejector sleeve;
and
(H) second driving means for actuating the ejector sleeve so as to remove a finished molded base board away from the cylindrical die cavity;
whereby the cylindrical die cavity is filled with pressurized molten resin fed through the nozzle bush to produce a primarily molded base board, the cut sleeve is actuated by said first driving means to form a center hole through the primarily molded base board, the cylindrical die cavity is held in a fully closed state, and the first driving means is additionally activated to recompress the primarily molded product by a distance corresponding to a quantity of recompression to produce a secondarily molded base board, respectively.

28 more elements

Facts

Application

08/128,666Filed 30 Sep 1993

Priority

JP 5-08795223 Mar 1993

Granted

5 Dec 1995

Term ends

Not estimatedThe source records don’t support an estimate.

Classification10 codes

B29C 45/38
Component parts, details or accessories; Auxiliary operations: cutting-off equipment for sprues or ingates
B29C 45/263
Moulds: with mould wall parts provided with fine grooves or impressions, e.g. for record discs
B29C 45/561
Using mould parts movable during or after injection, e.g. injection-compression moulding: injection-compression moulding
G11B 7/263
Apparatus or processes specially adapted for the manufacture of record carriers: preparing and using a stamper, e.g. pressing or injection molding…

Abstract

Claims11