Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to cause relative movement between mold and charger
Patent
1988-06-29
1990-02-20
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to cause relative movement between mold and charger
425589, 425590, B29C 4568
Patent
active
049022202
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of the Invention
The present invention relates to a vertical injection molding machine having an upper die and a lower die which define a die cavity therebetween when brought together by a relative vertical movement between them.
2. Description of Background and Relevant Materials
In general, an injection molding machine has a die closing device for closing a pair of dies, and an injection unit. Since the injection of molten resin into the die cavity is effected by the injection unit, the die closing device and the injection unit are mounted on a frame in a predetermined relationship to each other.
In the use of such an injection molding machine, it is often required to conduct a trial operation of the injection unit. Such a trial injection is necessary, for example, when the dies on the die closing device have been changed for the production of a different article or when the kind of the resin material is changed. After the trial injection, the operator inspects the nozzle of the injection unit for the purpose of confirmation of safe injection of the resin from the injection unit. In the conventional injection molding machine of the type described, however, this inspection takes a considerably long time and requires laborious work, because of difficulty in obtaining a large clearance between the injection unit and the die closing device, due to the fixed positional relationship between the injection unit and the die closing device.
In the operation of an injection molding machine, a molten resin is injected into the die cavity between the pair of dies, after the die cavity is closed by the die closing device which usually includes a die closing cylinder. If the resin solidifies while the die cavity is closed, i.e., with the dies clamped by the die closing device, a pressure gradient is caused in the molten resin with the result that the molded article exhibits a shrink mark or deformation. In order to overcome this problem, a method known as "compression injection molding method" has been used in which, after the dies are closed by a main cylinder, a compression forming cylinder is operated to slightly open the dies and, thereafter, the molten resin is injected and the cylinders are closed again.
Two types of compression injection molding method have been known: a method known as "micro-molding method" and a method known as "Rollinks" method. In the micro-molding method, the force produced by the injection pressure is born by the die closing force, as in the case of ordinary injection molding method. This method, therefore, suffers from a disadvantage in that the die closing force cannot be utilized in the compression which requires a large compression force. Another problem is that, since the compression forming cylinder is installed within the dies, the size of the hydraulic cylinder is limited so that only a small compression force is available. On the other hand, in the Rollinks method, the volume in the cavity is increased by the internal pressure of the cavity and then compression is effected by making use of the die closing force. This method suffers from a problem in that the thickness size of the article unfavorably fluctuates.
Furthermore, these known methods involve a common disadvantage in that, since the compression forming cylinder is combined with the dies, it is necessary to prepare the compression forming cylinder for each of a plurality of die sets for different articles to be formed. This undesirably raises the installation cost and inevitably increases the size of the die set. A large storage space is required for storing a lot of die sets each of which has a large size.
Under these circumstances, the present invention is aimed at providing, as its first object, a vertical injection molding machine which remarkably facilitates the maintenance and inspection thereof.
A second object of the present invention is to provide a vertical injection molding machine which has, in addition to the features mentioned above, an advantage in that a compression forming cylinder d
REFERENCES:
patent: 2484777 (1949-10-01), Ziska
patent: 3162900 (1964-12-01), Huelskamp
Japanese Patent Abstract, vol. 10, No. 114 (M-473) (2171), Apr. 26, 1987, AIDA ENGINEERING.
Aida Engineering Ltd.
Heitbrink Timothy W.
Woo Jay H.
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