Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-12-18
2001-08-07
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S130700, C156S133000, C156S135000, C156S136000
Reexamination Certificate
active
06270606
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire heightened in bead durability and reduced in weight, and its manufacturing method.
FIELD OF THE INVENTION
In various pneumatic tires for passenger car or heavy duty vehicle, generally, both ends of the carcass are fixed by turning up around the bead core. The turned up height of the carcass is usually set higher than the rim flange height in order to fix securely by preventing the carcass from blowing through against the internal inflating pressure or load weight.
When the pneumatic tire contacts the ground, however, it is deformed, as shown in
FIG. 20
, so that the portion
100
of the bead above the rim flange
104
is tilted axially outwardly, and therefore the stress of bending and compressing acts repeatedly in the turned up portion
102
of the carcass ply
101
, and this stress is concentrated on the outer end of the turned up portion
102
. At the outer end of the turned up portion
102
, since the carcass cord is interrupted as cutting section, its adhesion with the surrounding rubber is inferior, and together with the stress concentration, looseness between the cord and rubber occurs early at the outer end of the turned up portion
102
. And it may initiate progress into separation of carcass
101
, and the bead damage is likely to occur. In particular, such bead damage tends to occur in the tire of radial structure heightened in the degree of deformation of the bead to the contrary due to increase of rigidity of the tread, or the tire for heavy load vehicle heavy in the load weight and large in the deformation of the tire itself.
To avoid such damage, hitherto, the rubber quantity of the bead apex rubber was increased to heighten the cushioning performance or extend the time to reach looseness, or cord reinforcing layers were provided around the bead core
103
, inside and outside of the turned up portion
102
to increase the rigidity of the bead
100
to decrease the amount of deformation itself, among other measures.
Such measures were, however, insufficient in the damage preventive effect especially in the tire for heavy load, and further due to increase of volume of the bead, the tire weight was increased and the fuel economy was spoiled.
As a result of intensive studies in the light of such background, the present inventor discovered that the bead durability can be substantially increased, thereby contributing to reduction of weight, by using a endless carcass cord ply having a carcass cord arranged zigzag by folding in U-form sequentially at both ends of the ply, and forming bead cores by spirally winding a bead cord substantially continuous to the carcass cord. To form the pneumatic tire of such structure, still more, a novel manufacturing method of tire is also needed.
SUMMARY OF THE INVENTION
It is hence a first object of the invention to present a pneumatic tire and its manufacturing method capable of enhancing the adhesion of cord and rubber at both ends of a carcass ply, decreasing and dispersing the stress acting on both ends of the ply, substantially increasing the bead durability, and contributing to reduction of weight.
It is a second object to present a pneumatic tire and its manufacturing method capable of enhancing the strength of a bead core particularly, employing a low modulus cord in a carcass ply and an upper bead core portion.
It is a third object to present a pneumatic tire and its manufacturing method having a turned-up structure of carcass ply capable of further enhancing the improving effect of bead durability while promoting the weight reduction of tire. According to one aspect of the present invention, a pneumatic tire comprises a carcass extending from a tread through side-walls to a bead core in each of two bead parts and having at least one endless carcass cord ply,
said endless carcass cord ply provided with a multiplicity of folding points arranged in the tire's circumferential direction at both outer ends of the endless carcass cord ply, and formed by at least one carcass cord extending zigzag in the tire's circumferential direction while being folded around the respective folding points of the both outer ends alternately to right and left, and
said bead core having an upper bead core portion disposed radially outside said endless carcass cord ply in the bead part and formed by an upper bead cord being substantially continuous to said carcass cord and spirally wound in one or more stages in the tire's circumferential direction.
The endless carcass cord ply is preferable to have a parallel cord arrangement in a ply main portion straddling between the bead cores.
The bead core may have a lower bead core portion formed by a lower bead cord being either substantially continuous to or discontinuous to said carcass cord and spirally wound in the tire's circumferential direction.
The outer end of the endless carcass cord ply may be terminated inside of the bead core or substantially terminated on a radially inner surface of the bead core, or projected from the bead core in the tire axial direction so as to form a project portion. The project portion may be turned up radially outwardly and terminated on an axially outer surface of the bead core or a bead apex rubber. Or the project portion may be turned up radially outwardly and extend between the bead core and the bead apex rubber, and terminated between the bead core and the bead apex rubber or on an axially inner surface of the bead apex rubber.
In the second invention, a manufacturing method of pneumatic tire comprising
an inner liner mounting step of rolling an inner liner rubber sheet on an outer circumference of a principal tire former in a cylindrical form and expandable in a toroidal form;
a carcass ply forming step of forming a tubular ply base body for carcass ply by turning, in the circumferential direction, a carcass cord on the outer circumference of the inner liner rubber sheet while folding alternately to right and left at both sides of the principal tire former;
a bead forming step of forming a bead core by spirally winding a bead cord substantially continuous to the carcass cord in a small width in one or more stages at both sides of the ply base body;
a junction step of mutually joining the tire forming member containing a bead apex rubber to the ply base body provided with the bead core; and
an inflation step of inflating the principal tire former to obtain a raw cover tire.
In the carcass ply forming step, it is preferable to arrange the carcass cord substantially parallel in a ply main portion extending between the bead cores.
The inflation step may include a side-wall forming step of jointing side-wall rubbers by inflation of side formers provided at both sides of the principal tire former.
When the bead core have a lower bead core portion and an upper bead core portion, the lower bead core portion may be formed by spirally winding a lower bead cord continuous or not continuous to the carcass cord prior to the carcass ply forming step.
The bead forming step may form the bead core such that the side end of the ply base body is aligned with the axially outside surface of the bead core, or aligned withheld inward from the axially outside surface of the bead core, or projected from the axially outside surface of the bead core.
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patent: 4830781 (1989-05-01), Oswald
patent: 5039372 (1991-08-01), Deal
patent: 5344514 (1994-09-01), Siegenthaler
patent: 5394920 (1995-03-01), Siegenthaler
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patent: 58-105806 (1983-06-01), None
Birch & Stewart Kolasch & Birch, LLP
Knable Geoffrey L.
Sumitomo Rubber Industries Ltd.
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