Nissei Plastic Industrial Co., Ltd.

Hidemi Aoki

Yasuhiko Takeuchi

Kazuo Anzai

Haruo Okada

Kunio Yuhara

An improved method of manufacturing a multilayer molding having a core and a surface layer by means of a double nozzle structure can eliminate a damaging phenomenon of producing a mixture of a resin material for forming the core remaining in and out of the aperture of the inner nozzle of the double nozzle structure and a resin material for forming the surface layer in the initial stages of molding operation by effectively driving back the remaining resin into the inner nozzle. A double nozzle structure that can suitably be used with such a method includes a shut-off pin arranged in the inner nozzle disposed at the center of the outer nozzle. The resin material for forming the core is driven out simultaneously with the resin material for forming the surface layer coming from the outer nozzle. The operation of resin injection from the inner nozzle is terminated at an arbitrarily selected moment during the operation of injecting the resin material for the surface layer of the outer nozzle. Then, the inside of the inner nozzle is brought into a no-load condition while the shut-off pin is held to its open position. Thereafter, the remaining resin material for the core found in and out of the aperture of the inner nozzle is driven back into the inner nozzle by the pressure of the resin injected from the outer nozzle. Finally, the inner nozzle is closed by the shut-off pin and the injecting operation of the outer nozzle is terminated.

Method of manufacturing a multilayer molding

A method of injection molding whereby a polyethylene terephthalate (PET) without being predried or with having an irregular-shape is fed by a feed screw from a material feeder to an injection cylinder and plasticated by an injection screw. The rotational torque of the injection screw is detected in correspondence with the revolution speed of the feed screw during material feed, and a flection point of the rotational torque is determined. The feed screw is operated at a revolution speed within a range around the flection point of the rotational torque to provide a stable feed rate of the PET and to avoid difficulty in rotating the injection screw.

Method of injection molding polyethylene terephthalate

A method of injection molding polyethylene terephthalate without being predried or with having an irregular-shape wherein a vent type injection machine is employed and the vent is forcedly performed by vacuum suction within a range of a specified degree of vacuum, i.e. 50 to 150 torr (equal to 6666.1.about.19998.3 Pa.) and/or at the same time the material is forcedly fed by a feed screw having a specifically set revolution speed. According to the present invention, it is possible to provide an injection molding method in which an PET without being predried or with having an irregular-shape can be molded.

A motor driven type die tightening apparatus for an injection molding machine includes a plurality of tie bars horizontally bridged between a pair of stationary die boards mounted on a platform of the injection molding machine, and a movable die board is displaceably arranged between the stationary die boards with the tie bars inserted therethrough. A part of each of the tie bars inserted through the movable die board is designed in the form of a ball screw shaft adapted to be threadably engaged with a ball nut member. As an electric motor installed on one of the stationary die boards is rotationally driven to rotate the ball nut members, the movable die board is slidably displaced toward or away from one of the stationary die boards. A rotary sleeve having a number of balls arranged on the inner peripheral surface thereof is received in a stationary case firmly fitted into the movable die board, and a rotational shaft designed in the form of a ball spline shaft is inserted through the movable die board so as to enable the movable die board to be displaced in the axial direction by engagement of the balls with a plurality of splines formed along the spline shaft. The ball nut members, the rotary sleeve, the rotational shaft and the electric motor are operatively connected to each other via rotational power transmission members each extending around these components. The rotational power transmitting member is usually designed in the form of a geared endless belt.

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Hanishina-gun, Japan

Hidemi Aoki