Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-02-19
2004-07-06
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S130700, C156S131000, C156S132000, C156S135000
Reexamination Certificate
active
06758929
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of manufacturing a pneumatic tire which can efficiently manufacture a tire having an improved bead portion structure.
2. Description of Related Art
In the conventional pneumatic tires such as heavy duty tire or the like, at least one carcass ply is toroidally extended from a tread portion through a sidewall portion to a bead portion, and wound around a ring-shaped bead core embedded in the bead portion from an inside of the tire toward an outside thereof in a radial direction so as to make a turnup height sufficiently high for preventing pull-out of a ply cord during the running of the tire under loading, and a turnup portion is embedded and fixed in a rubber portion.
In
FIG. 8
a
is schematically shown a cross-sectional view of a bead portion in the above conventional tire, wherein a carcass ply
52
is wound around a bead core
51
from an inside of the tire toward an outside thereof in a widthwise direction and a radially outer end of a turnup portion
53
of the carcass ply is positioned outward from an outer end of a wire chafer
54
, which is turned around the bead core along an outer surface of the carcass ply, in a radial direction of the tire.
In such a conventional bead portion structure, however, a difference in rigidity is created between an inside and an outside bordering the outer end position of the turnup portion
53
of the carcass ply
52
in the radial direction of the tire, so that stress is concentrated in the outer end of the turnup portion
53
and a neighborhood thereof by repetitive distortion deformation ranging from a bead portion to a sidewall portion and circumferentially shearing deformation during the running of the tire under loading. As a result, it is apt to easily create separation of such an outer end from rubber, which results in the occurrence of bead portion crack cr as shown in
FIG. 8
b.
In order to solve such a problem in the conventional bead portion structure, it is useful that the turnup portion
53
of the carcass ply
52
is wound along a peripheral face of a ring-shaped bead core
51
instead of highly winding up around the bead core
51
outward in the radial direction to substantially or completely eliminate projection of the turnup portion
53
outward from the bead core
51
in the radial direction as shown in FIG.
9
. In this case, it has been confirmed that the reduction of a tire weight can be realized in addition to a high improvement of a durability of the bead portion.
In the bead portion structure as shown in
FIG. 9
, however, the turnup portion
53
is wound along the outer peripheral face of the bead core
51
, so that a stiffener
55
to be disposed at an outer peripheral side of the bead core
51
can not be previously attached to the bead core
51
in a shaping operation of the tire and hence a subsequent step of attaching only the stiffener
55
is separately required. For this end, the shaping time becomes longer and the shaping efficiency lowers to not less than 20% as compared with such a conventional structure that the stiffener
55
may be previously attached to the bead core
51
as shown in FIG.
8
.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to solve the above problem of the conventional technique and to provide a method of manufacturing a pneumatic tire wherein it is possible to prevent the lowering of the tire shaping efficiency by previously attaching the stiffener to the bead core prior to the tire shaping even in the bead portion structure shown in FIG.
9
and also it is possible to handle the stiffener and the bead core as a single part even in steps of arrangement, setup and so on prior to the tire shaping operation.
Even in the bead portion structure as shown in
FIG. 9
, there are considered some points that a region of the bead core
51
not covered with the turnup portion
53
is existent in a full peripheral face at a cross section of the bead core
51
, and it is possible to sandwich a part of the stiffener
55
between the bead core
51
and the turnup portion
53
wound therearound, and the stiffener previously attached to the bead core can be handled as a one-piece body unless the stiffener is not separated from the bead core even if the stiffener is provided with a notch or the stiffener is partly ripped off from the bead core, and it is possible to arrange the stiffener on a given position by turning the stiffener from a fall-down posture based on the notch, partial ripping or the like to a stand-up posture under the winding of an end portion of the carcass ply around the bead core, and so on. The invention is made by noticing these points.
According to the invention, there is the provision of a method of manufacturing a pneumatic tire, characterized in that when an end portion of a carcass ply is wound around a ring-shaped bead core and a stiffener is arranged on an outer peripheral side of a turnup portion of the carcass ply to shape a green tire, a carcass material is previously folded at both axially end portions in a direction opposite to each other and shaped into a cylinder to form a carcass band, and a pair of bead cores each attached with a stiffener are set to insides of both resulting hook-shaped wrap portions of the carcass band at a fall-down posture of the stiffener, and thereafter the stiffener of the fall-down posture is stood up on an outer peripheral side of the wrap portion, and a belt and a tread are piled on an outer peripheral side of the carcass band.
According to the invention, the bead core previously attached with the stiffener is set at a given position of the carcass band, whereby the stiffener can be placed without a separate and independent step of arranging the stiffener alone. And also, the stiffener can be arranged on and attached to the outer peripheral side of the wrap portion of the carcass band with given shape and dimensional accuracy by standing up the stiffener previously rendered into a fall-down posture after the setting of the bead core. Therefore, the separate step of attaching only the stiffener alone is useless and hence the shaping efficiency of the tire can be advantageously improved.
Further, the bead core previously attached and integrally united with the stiffener is handled as a single part, so that their handling can be more facilitated in the steps of arrangement, setup and so on prior to the tire shaping operation.
In this case, the setting of the bead core to the inside of the wrap portion of the carcass band can be naturally conducted by a hand work of a worker. However, in order to automate such a setting work, it is favorable that each of the bead cores attached with the stiffener is previously supported a bead setter and moved to a given position in an axial direction between the wrap portions and thereafter the wrap portion is subjected to an elastically enlarging deformation by moving the bead setter, for example, in the axial direction and subsequently the bead setter is retracted outward in a radial direction at that position to set the bead core attached with the stiffener of the fall-down posture into an inside of an elastically returned wrap portion.
In this case, the bead setter itself adsorbing and supporting the bead core through a magnetic action or under a negative pressure can set the bead core to a given position under a state of elastically enlarging and deforming the wrap portion of the carcass band and hence a special means for conducting only the enlarging deformation is useless, so that the structure of the tire shaping apparatus becomes simple and a cycle time for actuating the above special means is useless and it can be attempted to more improve the shaping efficiency.
In the method according to the invention, when the stiffener previously attached to the bead core is fallen down at a position corresponding to a notch formed in the stiffener, there is a merit that the stiffener can be surely and smoothly fallen down at a given position without causing an extra deformation in the stiffene
Bridgestone Corporation
Knable Geoffrey L.
Sughrue & Mion, PLLC
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