Hpm Corporation

Koehring Company

Thomas G Bishop

William T Flickinger

An injection molding machine which is capable of injecting both thermoplastic compounds and glass loaded thermosetting polyester compounds, wherein the machine is capable of rapid conversion from its thermoplastic configuration to its thermosetting configuration, and vice versa. The machine comprises an elongated charge forming barrel having a rearward thermoplastic feed opening, which is customarily supplied by pelletized thermoplastic material from a vertical feed hopper, and a thermosetting material feed opening extending into the barrel at a position forwardly of the thermoplastics feed opening. When processing thermoplastics materials, a conventional, fully flighted plasticizing screw is installed in the barrel so that the pelletized material is conveyed forwardly from the rear feed opening, and plasticized for subsequent injection. During thermoplastics processing, the thermosetting feed opening is plugged. To convert the machine to process the aforementioned thermosetting materials, the second feed opening is unplugged, and the plasticizing screw is exchanged for a deeper flighted conveying screw having flights extending from the forward end thereof to just behind the unplugged, second opening. A stuffer unit is then attached to the unplugged feed opening and dough-like glass loaded thermosetting material is forced through the second opening into the barrel by means of a reciprocating plunger, or the like. The thermosetting material is conveyed forwardly and mixed slightly as the screw rotates.

Combination thermoplastic and glass loaded thermosetting injection

Both a method and apparatus are disclosed for controlling a cyclically operated injection molding machine such that uniform, high quality molded articles are repeatedly produced from plasticized synthetic resinous material. The method and apparatus include integration of a sensed injection pressure with respect to time from the beginning of an injection stroke until plasticized material in a mold reaches a predetermined pressure. The integration defines a work index which is compared with a preset allowable range. If the work index lies outside the preset range, an adjustment is made to the back pressure acting on the plasticizing screw during the plasticizing portion of the subsequent molding cycle. The apparatus is permitted to make a predetermined number of adjustments in the back pressure after which a suitable indication is made that the molding apparatus is out of control itself. Other viscosity-affecting parameters may be controlled including injection screw rotary speed and injection screw velocity, and barrel temperature of the plasticizing apparatus. A mold cavity pressure sensor indicates that the cavity is full, and thereupon stops the integration and may also reduce the injection pressure to a lower value, sufficient to supply additional material to compensate for shrinking due to cooling, yet not high enough to introduce strains, or cause flashing.

Injection molding process control

A molding system for producing articles of mottled appearance includes a plasticizing unit having an inner bore which communicates with a mold cavity. A feed screw is mounted within the bore and is connected to fluid-actuated motors for rotary and translational movement within the bore. A spreader device is positioned in a heated part of the bore ahead of the feed screw. The screw is rotated to feed and soften molding materials of diverse coloration and is subsequently translated to push the materials through the spreader device such that final plasticization occurs. A bridging conduit is provided between the rotary and translational motors to divert a controlled amount of fluid from the latter to the former during a pushing operation, to rotate the screw forwardly at a controlled rate or to hold pressure on the screw to prevent backward rotation or to limit the amount of backward rotation.

Mottled appearance injection molding methods

An injection mold includes a stationary platen carrying a pair of stationary die sections, a movable platen carrying a pair of movable die sections, and a pair of floating die sections disposed between the movable and stationary die sections. The respective floating and stationary die sections are mutually configured to define a pair of die cavities which are arranged for alternate communication with an injector unit. The floating die sections are selectively connectable to their associated movable and stationary die sections to expose one of the die cavities for article ejection, while maintaining the other die cavity closed for continuing a curing stage.

Injection-mold clamping unit having alternately ejecting die assemblies

A screw for injection molding of synthetic resinous material having a tendency to abrade and score the injection molding apparatus is provided along a substantial length of the feed section with a substantially undercut screw flight. An average particle of synthetic resinous feed stock material may pass between the undercut screw flights and a cooperating barrel without squashing. The undercut screw flights are effective to provide a controlled feed pressure for the particulate material entering the downstream portion of the screw.

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Mount Gilead, OH, United States of America

Thomas G Bishop