Injection/compression molding method, a die for injection/compression molding and an injection/compression molding machine

• US 5,340,528 A
• Filed: 02/16/1993
• Issued: 08/23/1994
• Est. Priority Date: 02/21/1992
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kondo, Hiroshi, Sasaki, Nobuyuki, Kiso, Hiroyuki, Machida, Tetsuo
• Primary Examiner(s): VARGOT, MATHIEU D
• Application Number:
  US08/018,305
• Time in Patent Office: 553 Days
• Field of Search: 264/40.5, 264/328.1, 264/328.7, 264/334, 425/129.2, 425/139, 425/554, 425/555, 425/556
• US Class Current: 264/328.7
• CPC Class Codes: B29C 2045/5685 for eliminating internal voids in the moulding material
• CPC Class Codes: B29C 2045/575 preventing backflow of moulding material to the injection means during after-pressure
• CPC Class Codes: B29C 45/40 Removing or ejecting moulded articles
• CPC Class Codes: B29C 45/572 using movable mould wall or runner parts

Abstract

An injection molding die includes a fixed half die and a movable half die which has a core surface and which is provided with ejector pins. The ejector pins are held with their extremities retracted from the core surface to form recesses corresponding to compression allowances. The ejector pins are advanced toward the cavity to compress the compression allowances after a molten resin has been injected into the injection molding die in a manner which fills the cavity and the recesses. The compression with the ejector pins renders the pressure distribution int he cavity uniform, so that a molding can be formed with a high degree of accuracy and so that the injection molding cycle time can be reduced.

Claims

1. An injection molding die comprising:

a fixed half die;

a movable half die having a core surface for forming a surface of a molding to be formed, said movable half die being joined to the fixed half die to form a cavity in the injection molding die;

ejector pins axially movably supported on the movable half die; and

a compressing mechanism which holds some of the ejector pins respectively at positions where the extremities of said some of the ejector pins are retracted from the core surface of the movable half die to form recesses corresponding to compression allowances int he core surface, said compressing mechanism advancing the ejector pins toward the cavity after a molten resin has been injected into the injection molding die and fills the cavity and the recesses,

wherein said some of said ejector pins are fixed to a first ejector plate, ad the rest of the ejector pins are fixed to a second ejector plate, and wherein said compressing mechanism controls the first ejector plate to compress the resin in the recesses corresponding to the compression allowances with said some of sad ejector pins and subsequently both ejector plates to advance the ejector pins thereon to eject the molding from said cavity.

2. An injection molding die according to claim 1, wherein respective ejector pins are different in diameter and/or length from other said ejector pins.

3. An injection/compression molding machine comprising:

a fixed platen fixedly holding a fixed half die of an injection molding die;

a movable platen fixedly holding a movable half die of the injection molding die, said movable half die having a core surface for forming a surface of a molding to be formed, said movable half die being joined to the fixed half die to form a cavity in the injection molding die; and

a compressing mechanism with ejector pins which is provided on the movable platen, which holds some of the ejector pins respectively at positions where the extremities of said some of the ejector pins are retracted from the core surface of the movable half die to form recesses corresponding to compression allowances in the core surface, ad which advances the ejector pins toward the cavity after a molten resin has been injected into the injection molding die to fill up the cavity and the recesses,

wherein said some of said ejector pins are fixed to a first ejector plate, the rest of said ejector pins are fixed to a second ejector plate, and wherein said compressing mechanism controls the first ejector plate to compress the resin in the recesses corresponding to the compression allowances with said some of said ejector pins and subsequently both ejector plates to advance the ejector pins thereon to eject the molding from the cavity.

4. An injection/compression molding machine according to claim 3, wherein respective ejector pins are different in diameter and/or length from other of said ejector pins.

5. An injection/compression molding method comprising the steps of:

forming a cavity in an injection molding die using a fixed half die and a movable half die, said movable half die having a core surface for forming a surface of a molding to be formed, ejector pins, and a plurality of recesses corresponding to compression allowances in the core surface, said movable half die being joined to the fixed half die to form said cavity in the injection molding die;

fixing some of said ejector pins to a first ejector plate;

fixing the rest of the ejector pins to a second ejector plate;

sealing the cavity to prevent molten resin form flowing out of said cavity by pressing said movable half die against said fixed half die;

injecting a molten resin into said cavity while it is maintained sealed to fill the cavity and said plurality of recesses; and

using a compression mechanism to advance said first ejector plate and said some of said ejector pins toward said cavity to compress the resin in said plurality of recesses corresponding to the compression allowances int he core surface and subsequently advance both ejector plates with the ejector pins thereon to eject the molding form the cavity.