Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1990-01-05
1991-10-22
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 405, 2643287, 425145, 425147, 425150, B29C 4570, B29C 4577
Patent
active
050593641
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to an injection-compression molding machine for molding a plastic resin and a method of molding by using the molding machine.
BACKGROUND TECHNIQUE OF THE INVENTION
The conventional method of molding by using a compression molding machine as disclosed, for example, in the specifications and drawings of Japanese Laid-open Specification Nos. SHO 60-21225 and SHO 60-110419 of Japanese Patent Applications, respectively, is conducted by charging a plastic resin material to be molded into a heated mold, actuating the molding machine thereby pressuring the material at a low pressure to fill the mold with the resultant molten resin, and then opening the upper and lower molds once slightly to vent the gaseous matter present in the material, pressurizing the material again at a high pressure, continuing the pressurizing and the heating until the material has been cured, and then opening the mold and taking out the molded article. Whilst, in the method of injection and compression molding, when a molten resin material is injected into a mold, the injection flow rate and the injecting speed of the molten resin are controlled by the moving speed and the pressing force of a screw.
In the above-mentioned conventional compression molding method, however, since the resin to be molded is subjected in turn to a low pressure and a high pressure, the number of the processes is increased, and also since after the mold is filled with the resin it is subjected to a predetermined pressure, there is a tendency of molded articles undergoing shrink marks or warping.
Further, in the method of molding by using the injection-compression molding machine, a molten resin is injected into a mold in such a manner that the moving speed and the pressure of the screw is varied with the shape of the mold used and that of an article to be molded. In this case, since the flow speed of the molten resin will change in compliance with the shape of the mold and that of an article to be molded, the mold can not be filled uniformly with the molten resin with the result that the molded articles tend to have defects such as haze weld lines, flow marks and entrap gases.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned circumstances, and has for its object to provide an injection-compression molding machine and a method of molding by using the molding machine wherein the injecting speed and the injection flow-rate of a molten resin by the injection unit can be varied in compliance with the filling speed (or spreading speed) of the molten-resin within the mold and/or the injecting speed of the molten resin can be varied in compliance with the filling speed so that, when the molten resin injected by the injection unit into the mold may fill the latter so as to spread therein as it is compressed in the mold by a mold compression unit, the mold can be filled uniformly with the molten resin.
To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided an injection-compression molding machine having a compression unit for clamping a mold and an injection unit for injecting a molten resin into the mold, the molding machine comprising a means for detecting the stroke of the compression unit; a means for detecting the injecting speed of the injection unit; an input means for setting the stroke of the compression unit; an input means for setting the injecting speed of the injection unit; a stroke signal generator means for converting the detected stroke of the compression unit into a stroke signal corresponding to a value present by the stroke setting input means; a means for generating an injecting speed signal for the injection unit in response to the stroke signal; and an injection unit driving means adapted to be actuated in response to the injecting speed signal.
To achieve the above-mentioned object, according to a second aspect of the present invention, there is provided an injection-compression molding mach
REFERENCES:
patent: 3787159 (1974-01-01), Bielfeldt
patent: 4855095 (1989-08-01), Sato
Fujimoto Satoshi
Higuchi Makoto
Mimura Kazuhiro
Okubo Hideaki
Sato Kan'ichi
Heitbrink Jill L.
Kabushiki Kaisha Komatsu Seisakusha
Kananen Ronald P.
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