Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
2000-08-30
2004-10-05
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C156S140000, C425S034200, C425S384000, C425S395000
Reexamination Certificate
active
06800236
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a molding method for an endless crawler which is mounted and used on a construction vehicle or a high-speed snowfield vehicle such as an RV or the like.
2. Background Art
In recent years, the number of cases has risen in which ordinary driving wheels on a leisure RV vehicle are removed and a crawler driver formed of a plurality of sprockets and rotation wheels is mounted in order for the vehicle to be used as a snowfield vehicle or the like. A crawler structured of an endless rubber belt and the like is mounted on the crawler driver. However, the need to accommodate a trend in higher traveling speed has been a prime concern attendant with mounting a crawler on an RV vehicle. Further, accommodating the crawler to a higher traveling speed has been a pressing concern not only with ordinary snowfield vehicles and the like but with construction vehicles on which rubber crawlers which reduce noise and vibration have come to be mounted.
Generally, a crawler mounted on the crawler driver is molded and vulcanized according to such methods as those illustrated in
FIGS. 9A and 10C
.
FIGS. 9A
to
9
C illustrate a basic production method. A crawler
70
illustrated in
FIG. 9A
, which is formed of a belt-shaped rubber and the like in which reinforcing cords (not illustrated) are embedded, is nipped by an upper mold
74
and a lower mold
72
, as illustrated in FIG.
9
B. The upper and lower molds are further nipped by an outer heating plate
76
and an inner heating plate
78
to vulcanize the crawler
70
by heating. Thereafter, as illustrated in
FIG. 9C
, staggered end portions
70
A and
70
B of the crawler
70
are overlapped with each other, and then both end portions are vulcanized and joined by a lower mold
80
and an upper mold
82
and by an outer heating plate
84
and an inner heating plate
86
to obtain an endless crawler product.
FIGS. 10A
to
10
C illustrate a production method known as feed vulcanization which is used when vulcanizing a comparatively lengthy crawler. A crawler
70
illustrated in
FIG. 10A
, which is formed of a lengthy belt-shaped rubber and the like in which reinforcing cords (not illustrated) are embedded, is nipped by a lower mold
80
and an upper mold
82
, as illustrated in FIG.
10
B. The lower mold
80
and the upper mold
82
are of a relatively short predetermined length, and are further nipped by an outer heating plate
84
and an inner heating plate
86
which vulcanize a predetermined length portion of the crawler
70
by heating. This is sequentially repeated so that the entire length of the crawler
70
is vulcanized. Thereafter, as illustrated in
FIG. 10C
, staggered end portions
70
A and
70
B of the crawler
70
are overlapped with each other, and then both end portions are vulcanized and joined by the lower mold
80
and the upper mold
82
and by the outer heating plate
84
and the inner heating plate
86
to obtain an endless crawler product.
PROBLEMS TO BE SOLVED BY THE INVENTION
However, the production process for crawlers molded in accordance with such conventional vulcanization methods requires an excessive amount of time because the molding of the crawlers is conducted in advance in separate processes before entering the vulcanization process.
The vulcanization method illustrated in
FIG. 9
requires not only a setting site with a large amount of space because the mold and the heating plate become longer and larger, but also requires a joining-vulcanization process just for the ends.
The vulcanization method illustrated in
FIGS. 10A
to
10
C requires that vulcanization be repeated from a few times to as many as ten times for each predetermined length even though the mold and the heating plate are compacted. In addition, this method requires an excessive amount of time for vulcanization and, similar to the vulcanization method illustrated in
FIGS. 9A
to
9
C, a joining-vulcanization process just for the ends.
Moreover, in these production methods which use vulcanization, it is impossible to endow the endless ring-shaped crawler belt with uniform properties at every point on the circumference of the crawler, since both longitudinal end portions of the belt-shaped crawler must be vulcanized and joined. Further, the process of connecting respective, paired end portions of reinforcement cords which are plurally provided in a row in the lengthwise direction of the crawler and embedded therein is burdensome. With regard to reinforcement strength, there has also been the fear that the continuity might be severed, not to mention the impossibility of embedding spiral reinforcement cords that could make a circumferentially uniform reinforcement strength possible.
Conventional production methods which employ vulcanization have thus been unable to accommodate the rotation of the crawler at a high speed accompanying a higher vehicle speed.
SUMMARY OF THE INVENTION
Therefore, the present applicants proposed a crawler molding method (see JP-A No. 9-76369) and a crawler molding device and a molding method thereof (Japanese Patent Application No. 9-355208) so as to solve the problems described above in conventional molding and vulcanization methods. The crawler molding device and molding method thereof disclosed in Japanese Patent Application No. 9-355208 relate to an inner mold and release of the inner mold. In the seamless crawler molding method disclosed in JP-A No. 9-76369, the number of production steps is few, endowing the crawler with a circumferentially uniform strength property is made possible, and the embedding of spiral reinforcement cords in the rubber crawler and the like which can accommodate high-speed traveling is made possible.
An object of the present invention is to mold a seamless crawler which improves upon the proposed crawler molding device and molding method mentioned above, and in which the number of production steps is few, embedding of spiral reinforcement cords and a circumferentially uniform strength property are made possible, which can further accommodate high-speed traveling, which enables a uniform, reliable outer mold pressure, and in which a seamless crawler can be molded only by adding or removing a portion of the mold, even for crawlers whose circumferential lengths are different.
Means for Solving the Problems
The invention provides a crawler molding method, in which structural components of a crawler are placed between an outer mold and an inner mold to form an endless shape and vulcanized to integrally mold a crawler, comprising: disposing the structural components of the crawler on an outer peripheral surface of an inner mold, which inner mold is dividable in the axial direction of the crawler; and thereafter radially contracting and pressurizing toward the inner mold by a radially contracting means a diameter of a circle defined by a plurality of outer molds which are divided and disposed along the outer peripheral surface of the inner mold, whereby the structural components of the crawler are integrally vulcanized.
The invention provides a crawler molding space which is formed by an outer peripheral surface of the inner mold and an inner peripheral surface defined by the plurality of outer molds is circular from a side view.
The invention provides the inner mold is structured by two semi-circular inner molds and by a plurality of square inner molds which are disposed between the semi-circular inner molds and which allow the outer peripheral surfaces thereof to be continued; and the outer mold is structured by a plurality of circular arc-shaped outer molds to form a crawler molding space between the outer molds and the semi-circular inner molds, the crawler molding space being semi-circular from a side view, and by a plurality of square outer molds to form a linear crawler molding space between the outer molds and the square inner molds.
The invention provides a length of the square outer molds is determined by a crawler pitch such as an interval between driving sprocket holes of the crawler or the embedded metals,
Kumano Yoichi
Kurata Tomoyuki
Bridgestone Corporation
Oliff & Berridg,e PLC
Vargot Mathieu D.
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