Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1995-04-26
1996-10-22
Thurlow, Jeffery R.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 405, 264 407, 264167, 26417719, 425140, 425145, 425149, 425162, 425172, B29C 4792
Patent
active
055673686
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an extrusion molding method for manufacturing a molded article of which the cross-sectional configuration is longitudinally modified, more particularly for manufacturing a good molded article which has no dimensional error, no variation in quality and the like.
BACKGROUND ART
To manufacture an elongated rubber product, an extrusion molding method has been used. The extrusion molding method is a molding method in which a molding material such as rubber, PP (polypropyrene) and PVC (polyvinyl chloride) is molded into a desired configuration by extruding the molding material from an extrusion nozzle (die) having an opening corresponding to the configuration of a molded article under pressure while kneading and plasticizing the molding material with a screw.
When the article has a uniform cross-sectional configuration, the molding material may be continuously extruded from an invariant die having a definitely configured opening. However, in manufacturing the extrusion molded article of which the cross-sectional configuration is longitudinally modified, the configuration and the area of the die opening must be changed to conform to the cross-sectional configuration of the molded article.
An example of such an extrusion molded article is a weather strip for an automobile body shown in FIG. 9(A), FIG. 9(B), FIG. 9(C) and FIG. 10.
As shown in FIG. 9(A), the weather strip 50 is mounted along a circumferential edge of a windshield 42 of the automobile body 40. The weather strip 50 includes side sections 52 extending along both sides of the windshield 42 and an upper section 54 extending along an upper edge of the windshield 42 and is integrally molded by extrusion molding, as shown in FIG. 10.
As shown in a sectional view of FIG. 9(B), the side section 52 has a cross-sectional configuration centrally provided with a partition wall 52a to prevent flowing of rainwater toward side surfaces of the automobile body 40. On the other hand, as shown in FIG. 9(C), the upper section 54 does not include such a partition wall and has a cross-sectional configuration smaller than that of the side section 52. Therefore, in extrusion molding of the weather strip 50, the cross-sectional configuration must be changed during a single molding process (1 cycle) for one piece of the molded article, as shown in FIG. 10.
To this end, as shown in FIG. 11, a movable die 208 is provided on a die 204 of an extrusion molding machine 201, which may change the configuration of a die opening 210. The movable die 208, although not illustrated in detail in FIG. 11, is constituted of two movable die halves which are movable in a direction crossing at right angles relative to each other. One of the movable die halves, when positioned, defines the top-to-bottom dimension in FIGS. 9(B) and 9(C). The other of the movable die halves, when positioned, defines the configuration of the right-to-left constricted portion in FIGS. 9(B) and 9(C).
The construction of the extrusion molding machine including such two movable die halves is identical with that described in previous patent applications, for example, Japanese Laid-Open Patent Publication No. 4-356216.
The position of the movable die 208 is moved by a control mechanism (not shown) in synchronous with an extruding operation of an extrusion screw S so that the configuration of the die opening 210 is changed between the cross-sectional configuration 52 in FIG. 9(B) and the cross-sectional configuration 54 in FIG. 9(C).
Thus, as shown in FIG. 10, the weather strip 50 is formed in which the cross-sectional configuration thereof is modified for a desired length.
Now, in manufacturing an extrusion molded article such as the weather strip 50 of which the cross-sectional configuration is modified, it is important to constantly form the molded article which has no variation in quality and which has a desired dimension of cross-sectional configuration at each section thereof. For this purpose, the molding material has to be controlled to be stably extruded in prop
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Ando Yukimasa
Kishino Katsutomi
Thurlow Jeffery R.
Tokai Kogyo Kabushiki Kaisha
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