Plastic and nonmetallic article shaping or treating: processes – With step of cleaning – polishing – or preconditioning...
Patent
1989-01-26
1994-01-25
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
With step of cleaning, polishing, or preconditioning...
264 401, 2643281, 425225, B29C 4517, B29C 4524
Patent
active
052813746
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to an automatic purging method for an injection molding machine which is applicable when replacement of the material to be injected with another material or replacement of the material to be injected with one having a different color is made, and particularly to an effective automatic purging method for an injection molding machine having a nozzle valve in the nozzle unit thereof.
BACKGROUND ART OF THE INVENTION
In case replacement of the material to be injected with one of a different kind is made while the injection molding machine is in operation, the existing material remaining in a screw cylinder in the molding machine must be purged completely. It is publicly known that this purging is made automatically and a variety of means for effecting such purging have been proposed and carried out effectively. In particular, as for the purging means, it has been recognized effective to apply a high pressure to a resin (material for injection molding) remaining in the screw cylinder, and there are many technical means for automatic purging based on this principle.
For example, the techniques described in publications of Japanese Laid-Open Patent Applications Nos. SHO-57-57926, SHO-58-158228, SHO-59-87136, SHO-59-87137 and SHO-60-175617 require application of additional pressure into a screw cylinder.
However, the prior art examples disclosed in these publications have several points desired to be improved from the viewpoint of mechanism and operation thereof.
Stating in brief, the techniques described in the Japanese Laid-Open Patent Applications Nos. SHO-57-57926, SHO-58-158228 and SHO-59-87136 require troublesome operation of attaching a resin replacing block or a purging container when an automatic purging is made. Further, in the techniques described in Japanese Laid-open Patent Application No. SHO-59-87137, there is a problem in that an arbitrary material among different kinds of materials cannot be injected into the mold because molds having different draft angles and adapted to set different thicknesses of final products need to be used depending on the material to be subjected to injection molding. Further, the techniques described in the Japanese Laid-Open Patent Application No. SHO-60-175617 require provision of a separate material supply means for increasing the material supply pressure with the result that the apparatus per se becomes complicated and increases in the equipment cost and in the number of manufacturing processes are unavoidable.
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 automatic purging method for an injection molding machine which is capable of injecting an arbitrary material among different kinds of materials into a mold without having to provide a resin replacing block or a purging container and a separate material supply means for increasing the material supply pressure, and which has a nozzle valve in the nozzle unit thereof.
Another object of the present invention is to provide an automatic purging method for an injection molding machine having a nozzle valve in the nozzle unit thereof which is capable of effecting automatic purging smoothly and speedily by operating the nozzle valve so that it may behave according to a predetermined program.
To achieve the above-mentioned objects, according to a first aspect of the present invention, there is provided an automatic purging method for an injection molding machine having a nozzle valve adapted to control the flow of the molten resin in the nozzle unit thereof, characterized in that it includes the steps of supplying a fresh material from a hopper accommodating the material into a screw cylinder, rotating a screw with the nozzle valve closed for a predetermined period of time or until the screw has been moved back over a preset stroke so as to plasticize the resin, and then purging the molten resin with the nozzle valve kept at a predetermined degree of opening.
Further
REFERENCES:
patent: 4808355 (1989-02-01), Kamiyama et al.
Funabashi Tetsuji
Inaba Nobuaki
Kaminishi Masashi
Matsuda Kazuo
Tanaka Nobukazu
Heitbrink Jill L.
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
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