초록 ▼

A mold assembly has a fixed mold incorporating a base with a movable member supported thereon so as to be movable relative thereto and which is closed against a movable mold by a spring. A protrusion on the base passing through the movable member, and a recess on the movable mold engage to form a ca

A mold assembly has a fixed mold incorporating a base with a movable member supported thereon so as to be movable relative thereto and which is closed against a movable mold by a spring. A protrusion on the base passing through the movable member, and a recess on the movable mold engage to form a cavity. A runner and a gate are formed between the movable member and movable mold. Resin is filled into the cavity with the mold lightly closed and the movable member and movable mold closed, but with the movable member and base apart. During filing, the movable member and base open under resin pressure which is held constant inside the cavity. The movable member and base are then closed and when the gate closes with engagement of the protruding and recess portions, a constant amount of resin remains in the mold cavity, which is then compressed.

대표청구항 ▼

[ What is claimed is:] [1.] A method of injection molding using:a mold assembly incorporating a first mold member and a second mold member which open and close relative to each other and which form a mold cavity therebetween when closed, said first mold member having:a base member;a movable member s

[ What is claimed is:] [1.] A method of injection molding using:a mold assembly incorporating a first mold member and a second mold member which open and close relative to each other and which form a mold cavity therebetween when closed, said first mold member having:a base member;a movable member supported on said base member so as to be movable relative thereto in the open and close direction of said first mold member and said second mold member, and said movable member closes against said second mold member; biasing means for biasing said movable member relative to said base member towards said second mold member; and a protruding portion provided integral with said base member, said second mold member having a recess portion for removably engaging with the protruding portion on said first mold member, the construction being such that said mold cavity is formed by the recess portion and the protruding portion, and a material passage is formed between said movable member and said second mold member so that a gate to said mold cavity is formed therefrom, said gate being closed by said protruding portion engaging in said recess portion;a material supply apparatus for supplying mold material in a moldable condition to said material passage in said mold assembly; anda mold clamping device with adjustable clamping force for opening and closing said first mold member and said second mold member of said mold assembly,said method comprising the steps of:closing said first mold member and said second mold member with a light mold clamping force, and closing said movable member against said second mold member, but leaving said movable member and said base member in an open condition, then supplying mold material from said material supply device to said material passage of said mold assembly to fill said mold cavity;at the same time, adjusting the pressure of the mold material inside said mold cavity so as to make the density of the mold material even by the displacement of said movable member and said second mold member relative to said base member, as a result of an equilibrium between the pressure of the mold material inside said mold assembly, and the mold clamping force; andstopping supply of mold material from said material supply device, and increasing the mold clamping force to close the base member and the movable member towards each other, and during this operation, allowing some of the mold material on the mold cavity side to return to said material supply device side, and after a constant amount of mold material remains in said mold cavity at the point in time of closing said gate, closing said base member and said movable member against each other, thereby compressing the mold material inside said mold cavity.