Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-01-25
2002-10-15
Silbaugh, Ian H. (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S212000, C156S244170, C156S244180, C264S479000, C264S480000, C264S486000, C264S487000, C264S148000, C264S149000, C264S171140, C264S210200, C264S291000, C264S296000, C425S17480R, C425S383000, C425S394000
Reexamination Certificate
active
06464814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for molding an end of a long resin molded article, and particularly to an end molding method in which a front surface of an end portion of a long resin molded article such as a side molding for an automobile, or the like, formed into a general sectional shape by extrusion molding is heated so as to be softened and further pressed into a predetermined shape such as an inclination shape toward a rear surface, or the like.
2. Description of the Related Art
A conventional example of this type method for molding an end of a long resin molded article is a technique shown in FIGS.
15
and
16
(
a
) to
16
(
c
).
FIG. 15
is an explanatory view showing a heating step in a conventional method for molding an end of a long resin molded article. FIGS.
16
(
a
) to
16
(
c
) are explanatory views showing a pressing step in the conventional method for molding an end of a long resin molded article. FIG.
16
(
a
) shows a state in which a long resin is disposed in press molds; FIG.
16
(
b
) shows a state in which the end portion of the long resin is pressed by the press molds; and FIG.
16
(
c
) shows a state in which rebounding occurs in an end portion of a long resin molded article obtained by pressing the long resin after evaluation of heat resistance.
This technique is provided to obtain a desired long resin molded article, for example, a finished product such as a side molding for an automobile, or the like, by a molding method in which an end portion of a long resin is heated so as to be softened and further pressed into a predetermined shape, that is, by a so-called hot press method. As shown in
FIG. 15
, in this technique, an end portion
2
(a left end portion in
FIG. 15
) of a long resin
1
obtained by extrusion-molding a resin such as polyvinyl chloride (PVC), polyolefins such as polypropylene (PP), polyethylene or the like, thermoplastic elastomer (TPO), vinyl acetate or the like and then cutting the end portion of the long resin obliquely at a predetermined position is concentratedly heated so as to be softened between electrodes
11
and
12
of a high frequency induction heating machine. Then, as shown in FIGS.
16
(
a
) to
16
(
c
), the end portion
2
of the long resin
1
which is softened by heating is pressed to form a predetermined sectional shape in which the end portion
2
is inclined from the front surface side to the rear surface side (from the upper side to the lower side in FIGS.
16
(
a
) to
16
(
c
)), so that a long resin molded article having a predetermined end shape can be obtained. Hereupon, the front surface serves as a design surface which is exposed outside, and the rear surface serves as an attachment surface which is attached to other parts such as an automobile door.
To perform such hot press molding, there are conventionally used press molds composed of an upper mold
15
having a press surface
15
a
corresponding to a design surface of the long resin molded article, and a lower mold
16
having a press surface
16
a
corresponding to the rear surface of the long resin molded article. After the steps of extrusion molding a resin, cutting the resin into a predetermined length and heating the end portion of the cut resin, the heated end-portion
2
of the long resin
1
is pressed while being held between the press surfaces
15
a
and
16
a
of the upper and lower molds
15
and
16
respectively to there by obtain a predetermined end shape as described above. Incidentally, escape cavities
15
b
and
16
b
are formed in the upper and lower molds
15
and
16
respectively so as to serve as portions for making a surplus resin R escape after hot pressing the end portion
2
of the long resin
1
, so that the surplus resin R is reserved in the escape cavities so that such surplus resin R never exerts influence on the quality of external appearance of the final product.
Because the conventional method for molding an end of a long resin molded article is configured as described above, residual stress is generated in the inside of the end portion
2
with the plastic deformation of the end portion
2
of the long resin
1
by hot pressing. For example, as shown in FIG.
16
(
c
), there is the possibility that disadvantages such as rebounding of the end portion
2
A in a direction (upward in the drawing) reverse to the pressing direction, or the like, may occur after evaluation of heat resistance of the long resin molded article
1
A.
Furthermore, conventionally, an insert of a metal such as aluminum, or the like, may be longitudinally embedded in the inside of the long resin molded article such as a side molding, or the like, for the purpose of increasing stiffness, or the like. When the end portion
6
(the right end portion in the drawing) of the long resin
5
having such an insert
7
embedded therein is to be molded into a predetermined shape by a hot press method as shown in
FIGS. 17
(
a
) and
17
(
b
), the end portion
6
is first concentratedly heated by a high frequency induction heating machine as shown in FIG.
15
. In this case, as shown in FIG.
17
(
b
) , there is, however, the possibility that the end portion
6
of the long resin
5
is melted and contracted by high frequency induction heating so that the insert
7
may be exposed from an end surface of the long resin
5
by heating. In this case, sparks may be generated between the electrodes
11
,
12
of the high frequency induction heating machine and the insert
7
by high frequency induction heating, so that there is the possibility that pressing operation after that may be made difficult because the high frequency induction heating machine may stop before the temperature of the end portion
6
of the long resin
5
reaches a press-enabled point.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for molding an end of a long resin molded article, in which disadvantages such as rebounding of an end portion, or the like, are prevented in evaluation of heat resistance, or the like, after molding.
It is another object of the present invention to provide a method for molding an end of a long resin molded article, in which a heating operation can be performed smoothly even in the case where an end portion of a long resin having an insert embedded therein is heated by high frequency induction heating.
The inventors of the present invention have made studies to find the reasons of the rebounding as shown in FIG.
16
(
c
), and it the following facts were found:
(i) In the hot pressing step as shown in FIGS.
16
(
a
) and
16
(
b
), the end portion of the long resin molded article becomes inclined from the front surface to the rear surface. At this time, the resin of the front surface side is stretched largely by plastic deformation. On the other hand, the resin of the rear surface side is stretched very slightly. During the processing step, the resin of the front surface is plastically deformed to a greater degree than the resin of the rear surface. This difference in plastic deformation results in a residual stress F in the inside of the end portion as shown in FIG.
18
. Thus generated residual stress is remained also after the hot pressing, and the residual stress is released by the gradual cooling after the evaluation of heat resistance as shown in FIG.
18
. This stress release generates rebounding of the end portion.
(ii) Thermal shrinkage of resin in the thick portion of the end portion (area A in
FIG. 18
) is larger than that in the thin portion of the end portion (area B in FIG.
18
), so that residual stress F shown in
FIG. 18
is generated as similar to the above (i). It should be noted that if only at least one of the above factors (i) and (ii) is solved, it becomes possible to achieve the objects of the present invention. Although the rebounding of the end portion is based on the combination of the above (i) and (ii), if one of (i) and (ii) is solved, almost all of the other is also removed.
In a first aspect of the invention, a method is
Goto Shinichi
Ito Tatsuo
Iwasaki Hiroshi
Mukai Hiroshi
Nakatani Masahiro
Poe Michael I.
Silbaugh Ian H.
Toyoda Gosei Co,., Ltd.
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