Apparatus for dwelling in injection molding

• US 6,017,210 A
• Filed: 09/26/1996
• Issued: 01/25/2000
• Est. Priority Date: 09/27/1995
• Status: Expired due to Fees

• Current Assignee: Nissei Plastic Industrial Co., Ltd.
• Original Assignee: Nissei Plastic Industrial Co., Ltd.
• Inventors: Takizawa, Kiyoto, Takayama, Kazutoshi
• Primary Examiner(s): HEITBRINK, JILL LYNNE
• Application Number:
  US08/720,289
• Time in Patent Office: 1,216 Days
• Field of Search: 264/328.1, 264/328.8, 264/328.19, 425/555, 425/557, 425/558, 425/559, 425/560, 425/561, 425/562, 425/567
• US Class Current: 425/557
• CPC Class Codes: B29C 45/57 Exerting after-pressure on the moulding material B29C45/174 takes precedence

Abstract

To avoid generation of air bubbles and silver which otherwise may be caused due to forced retraction of a dwelling plunger after a dwelling cycle is completed. A dwelling cycle is performed at the same time of metering by using an injection machine 1 and a dwelling machine 2. The injection machine 1 comprises an injection screw 11 mounted in a heating cylinder 12. The dwelling machine 2 comprises a dwelling plunger 21 slidably mounted therein and faced to a resin passage 14. An advancing motion of the dwelling plunger 14 is limited to the side surface of the resin passage while a backward movement of the dwelling plunger is limited to a position at which a desired volume of a resin trap 26 is formed for the resin to be packed in the passage between the head of the plunger and the resin passage 14. The dwelling plunger 21 is allowed to be in a free state during an injection cycle or the metering. The dwelling plunger 21 is retracted by means of a pressure of the resin to be injected or a pressure of a metered resin to from the resin trap 26. The resin in the resin trap 26 is forced into the resin passage 14 as the dwelling plunger 21 moves forward when the injection cycle is completed and the valve 16 is closed to block the resin passage 14. This provides the dwelling.

Claims

1. An injection machine provided with a dwelling machine, said injection machine comprising:

a heating cylinder;

an injection screw rotatably and slidably mounted in the heating cylinder;

a screw driving device and rotating device located behind the heating cylinder;

a head member having opposed sides attached at one opposed side to an end of the heating cylinder; and

a nozzle member projected from the head member at another of said opposed sides;

said dwelling machine comprising;

a dwelling cylinder attached to said head member at the same side as the heating cylinder;

a dwelling plunger slidably mounted in the dwelling cylinder; and

driving means for the dwelling plunger provided behind the dwelling cylinder;

wherein said head member further comprises;

a resin passage therewithin having at least one corner and extending from a portion where the heating cylinder is attached, through a portion where the dwelling cylinder is attached, to a portion where the nozzle member is attached, said resin passage providing fluid communication between said heating cylinder and said nozzle member;

a valve along said resin passage between the portion where the heating cylinder is attached and the portion where the dwelling cylinder is attached;

a resin trap proximate to and in fluid communication with said resin passage which has a predetermined volume for a resin to be packed, said resin trap located at one of said at least one corners and defined by said dwelling cylinder and the position of said dwelling plunger; and

wherein

said predetermined volume is evacuated into said resin passage upon movement of said dwelling plunger.