Plastic article or earthenware shaping or treating: apparatus – Female mold and means to shape parison directly by internal... – Including means to prepare parison
Reexamination Certificate
2002-05-21
2004-09-28
Davis, Robert B. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and means to shape parison directly by internal...
Including means to prepare parison
C264S539000, C425S532000, C425S533000
Reexamination Certificate
active
06796785
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a hollow article made of a thermoplastic resin and having both end portions whose wall thickness changes multidirectionally with extremely high accuracy, such as tri-port type CV-joint boots for automobiles.
(ii) Description of the Related Art
Conventionally, as illustrated in
FIG. 7
for example, a hollow article
8
such as a CV-joint boot for an automobile is known. In the CV-joint boot
8
, one end portion (the upper end portion in
FIG. 7
)
40
has been formed by injection molding and all other portions have been formed by blow molding. As an apparatus for manufacturing such a hollow article
8
, an apparatus illustrated in
FIG. 6
is known (Japanese Patent No. 2556647).
The apparatus illustrated in
FIG. 6
is a parison manufacturing apparatus for blow-molding bellows (hollow article)
8
, in which the bellows is blow-molded with its cross-sectional profile being changed into a wave shape through the whole length of a parison
18
, as illustrated in FIG.
6
. Since the circular parison
18
is never flatly compressed, the plastic is extended evenly throughout the whole periphery. This prior art is very superior for molding such bellows
8
. In the bellows molded with this apparatus, since its one end portion (the upper end portion in
FIG. 6
)
40
is injection-molded with a neck mold, the thickness of that portion can be changed multidirectionally on the circumference with high accuracy. In the portion other than the one end portion
40
, however, its thickness cannot but be uniform throughout the circumference because it is blow-molded. As a result, the apparatus can provide only such a general automobile CV-joint boot (bellows)
8
as illustrated in FIG.
7
. This point is a problem of the prior art, which the present invention is to solve in particular. More specifically, some tri-port type CV-joint boots, for example, may require not only a high dimensional accuracy at the one end portion
40
(the wall thickness must be changed multidirectionally with high accuracy) but also a high dimensional accuracy at the other end portion (the lower end portion in
FIG. 6
)
41
(the inner circumference must be formed unevenly in height and the outer circumference must be formed into an accurate circle), that is, they may require an accurate shape at either of both end portions of the bellows, whose wall thickness is changed multidirectionally. The above-described prior art, however, has a problem that it can not meet this requirement. Further, in case of a conventional automobile CV-joint boot (
FIG. 7
) made with a manufacturing apparatus of this kind, the molded portion from the distal end of a nozzle mouthpiece
2
to the other end
41
of the CV-joint boot is an unnecessary portion, and such an unnecessary portion is very large. This brings about a problem that a great deal of waste is generated. On the other hand, Japanese Patent Application Laid-open No. 10-272679 discloses a method in which, upon injection-blow molding, the mold for the final product shape portion (portion corresponding to the other end portion
41
in the above-described prior art) is not changed for injection molding and for blow molding and it is successively molded, and thereby no flash is generated and the dimensional accuracy is kept. By this technique, only the other end portion as the final product shape portion
41
meets the above-described object, but the one end portion (portion corresponding to the one end portion
40
in the above-described prior art) is blow-molded by changing an injection mold and a blow mold with each other. Therefore, even by this technique, a configuration in which the wall thickness at both ends is changed multidirectionally with high accuracy can not be formed. So, as a result of repeating earnest studies and examinations, by improving the manufacturing apparatus of the above-described prior art (Japanese Patent No. 2556647), the present applicant has succeeded in newly developing a hollow article made of a thermoplastic resin and having both end portions whose wall thickness changes multidirectionally with extremely high accuracy, a manufacturing method of the hollow article, and a manufacturing apparatus for the hollow article.
SUMMARY OF THE INVENTION
The present invention has been developed in view of such problems of the prior art, and its object is to provide a hollow article made of a thermoplastic resin and having both end portions whose wall thickness changes multidirectionally with extremely high accuracy.
Technical measures made by the present invention to solve the above problems are as follows. A hollow article made of a thermoplastic resin is formed by bringing a cavity of a drawing unit into contact with an outlet gap of an annular orifice nozzle made up of a nozzle core constituted so as to be upwardly and downwardly movable, and a nozzle mouthpiece concentrically surrounding said core to form said outlet gap having a variable gap width for upward extruding the thermoplastic resin between it and said core; injecting the thermoplastic resin into said cavity through said outlet gap to form one end portion having a configuration in which a wall thickness changes multidirectionally with extremely high accuracy; drawing and forming a tubular parison while moving said drawing unit apart from said annular orifice; blow-molding the tubular parison after replacing an uppermost portion of said nozzle mouthpiece constituting said outlet gap with a blow mold to form a hollow article body; injection-molding the other end portion of a hollow article having a configuration in which a wall thickness changes multidirectionally with extremely high accuracy, through a cavity having a desired shape of said nozzle mouthpiece at a lower portion; and laterally moving said blow mold and said nozzle mouthpiece upon taking out a product to open them. A typical example of the hollow article is a tri-port type CV-joint boot for an automobile.
A manufacturing apparatus for the hollow article is as follows.
The apparatus comprises an annular orifice nozzle made up of a nozzle core constituted so as to be upwardly and downwardly movable, and a nozzle mouthpiece concentrically surrounding said core to form an outlet gap having a variable gap width for upward extruding a thermoplastic resin between it and said core; a drawing unit having a cavity of a desired shape downward opened for forming one end portion of a hollow article, said drawing unit being moved apart from said annular orifice nozzle to draw and form a tubular parison after injecting the thermoplastic resin into said cavity on said outlet gap of said annular orifice nozzle; and a blow mold for blow-molding said tubular parison to form a hollow article body of a desired shape, wherein said nozzle mouthpiece is multi-divided vertically and laterally, each divided part is disposed so as to be able to reciprocate laterally, an uppermost portion of said nozzle mouthpiece divided is constituted so as to be replaceable with said blow mold upon blow molding, and a lower portion of said nozzle mouthpiece has a desired cavity and said blow mold and said nozzle mouthpiece can be moved laterally upon taking out a product after forming the other end portion of the hollow article into a desired shape to open them. The above nozzle mouthpiece is divided into at least a portion for forming the outlet gap, and a portion for injection-molding the other end portion of the hollow article having a configuration in which a wall thickness changes multidirectionally with extremely high accuracy.
The nozzle mouthpiece multi-divided vertically and laterally can have an individual independent temperature conditioning system to set the thermoplastic resin in the nozzle mouthpiece at a proper temperature any time.
A manufacturing method of the above hollow article comprises the steps of bringing a cavity of a drawing unit into contact with an outlet gap of an annular orifice nozzle made up of a nozzle core constituted so as to be upwardly and downwardly mov
Kawamoto Taro
Sueoka Kazuhiko
Takada Yasuji
Davis Robert B.
Fukoku Co., Ltd.
Jacobson & Holman PLLC
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