Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Reexamination Certificate
1998-03-12
2001-01-30
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
C425S552000, C425S563000, C425S564000
Reexamination Certificate
active
06179604
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an injection molding method, an injection mold and a valve gate device including a movable pin (valve pin) for opening and closing a gate.
2. Description of the Related Art
In a known injection mold of this type, a cavity is formed between a stationary mold plate and a movable mold plate, and a valve body with a resin-conveying path communicates with the cavity through a gate within the stationary mold plate. In addition, a movable pin is movable in an axial direction thereof in the resin-conveying path of the valve body, with one end of the movable pin used for opening and closing the gate.
SUMMARY OF THE INVENTION
In the conventional injection mold, in order to supply a larger amount of resin into the cavity or to supply the resin into the cavity with a greater speed, the diameter of-the gate is increased. However, when the diameter of the gate is increased and an attempt is made to close the large-diameter gate with the movable pin, the resin offers a large resistance to the movable pin, which prevents the gate from being easily closed.
It is therefore an object of the present invention to provide an injection molding method, an injection mold and a valve gate device, wherein the movable pin moves easily, without excess force being exerted thereto, so that it properly opens and closes the gate.
According to an aspect of the invention, the above and other objects are carried out by an injection molding method for producing a molded product by supplying resin into a cavity formed between a pair of mold plates, through a gate, wherein after supplying the resin into the cavity with one end of a supporting pin facing the center portion of the gate, the gate is closed by a cylindrical movable pin disposed around the supporting pin in order to form the molded product in the cavity.
Closing the gate with a cylindrical movable pin causes excess resin to easily return towards the resin-conveying path through the outer edge portion at one end of the supporting pin. Therefore, even a large-diameter gate can be reliably closed by the movable pin which moves easily due to reduced resin resistance on the movable pin.
According to another aspect of the invention, the injection mold having a cavity between a pair of mold plates in order to supply resin into the cavity through a gate, wherein one end of a supporting pin is disposed at the center portion of the gate and a cylindrical movable pin for opening and closing the gate is provided around the supporting pin so as to be movable along an axial line of the movable pin. Opening and closing the gate by a movable pin supported and guided by the supporting pin allows the movement of the movable pin to be stabilized and reduces the resin resistance on the movable pin, allowing the movable pin to move easily.
According to yet another aspect of the invention, the valve gate device uses an injection mold having a cavity between a pair of mold plates in order to supply resin into the cavity through the gate, the valve gate device comprising a valve body having a resin-conveying path which communicates with the cavity through the gate, a supporting pin having one end facing the center portion of the gate. A cylindrical movable pin for opening and closing the gate is provided around the supporting pin so as to be movable along an axial line of the movable pin. Opening and closing the gate with a cylindrical movable pin supported and guided by the supporting pin reduces the resin resistance on the movable pin, making it easier to open and close the gate.
According to yet another aspect of the invention, the valve gate device further comprises biasing means which bias the supporting pin towards the one end side. When the pin (core pin) opposing the supporting pin is placed at the movable mold side, the biasing means allows both pins to easily and closely abut against each other.
According to yet another aspect of the invention, the valve gate device comprises cooling means provided at the supporting pin for cooling the supporting pin. Cooling the supporting pin by a cooling means reliably prevents overheating of the supporting pin.
REFERENCES:
patent: 4521179 (1985-06-01), Gellert
patent: 4826641 (1989-05-01), Takeda et al.
patent: 4882117 (1989-11-01), Takeda et al.
patent: 5882693 (1999-03-01), Silkowski et al.
patent: 2-243314 (1990-09-01), None
patent: 10-15995 (1998-01-01), None
patent: 91/18727 (1991-12-01), None
Heitbrink Tim
Mitsubishi Materials Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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