Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-03-06
2003-05-27
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S451000, C152S556000, C152S563000
Reexamination Certificate
active
06568446
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire for a bicycle. A bicycle pneumatic tire comprises on respective left and right sides thereof a bead, each of which has a bead core. A carcass, preferably, a carcass having diagonally oriented cords, is disposed such that each respective end of the carcass is wound about one of the bead cores. The carcass is comprised of at least one cord ply (which is preferably folded and arranged such that multiple cord layers are produced). A “cord ply” is a rubber layer or sheet reinforced by reinforcements such as cables or cords and these cables or cords are arranged within the cord ply such that substantially all of them in a cord layer extend parallel to one another. The bicycle tire of the present invention comprises, in addition to the afore-described constituent elements, sidewalls which extend along the exterior of the carcass in a wear protecting manner within the axial edges of the tread of the tire.
The bicycle tire of the present invention is particularly adapted for fitment as a bicycle tire for so-called “mountain bikes”, otherwise known as off road capable bicycles. With such mountain bicycle tires, in addition to low weight, minimal ground surface pressure, and decreased rolling resistance, a relatively high wear resistance is desirable such that, during cycling through thorny bushes or underbrush or the like, the chances of a tire failure are reduced to the greatest possible extent.
In the historical development of the fabrication of carcasses for pneumatic tires, the deployment of a full weave type of carcass stands as the starting development. Tires of such construction—which engendered relatively low production costs as a result of the reduced number of plies—beneficially revealed, as a function of their own relatively low weight, a more than adequate carcass structure for withstanding the effects of the interior air overpressure. However, the durability of such carcasses was relatively modest.
After several years, tire designers recognized that the intersection locations of a full weave carcass—in other words, the locations where one cord (either a warp or weft cord) overlapped an orthogonally oriented respectively opposite weft or warp cord—led to wear or chafing through of cords. This recognition led to a turning away from full weave carcasses in tire construction and the development of a functional separation: each former full weave carcass construction was replaced with a pair of layers which comprised one respective layer with reinforcements having right side increasing reinforcement strength and the other respective layer with reinforcements having left side increasing reinforcement strength. With regard to the rubber layer or sheet having the therein embedded, parallel extending reinforcements, the term “cord ply” is used while the term “cord” or “tire cord” is used to refer to the yet to be covered in rubber arrangement of the cords.
The above noted approach avoided the creation of cord intersection locations at which reinforcement cords crossed one another without the presence of rubber therebetween. The preferred configuration of diagonal cord carcasses fabricated in this manner should therefore comprise at least two cord layers, whereby, in one of the cord layers, all reinforcement cords increase in one given direction and, in the contiguous cord layer, all reinforcement cords increase in the direction opposite to the one given direction.
As viewed from the perspective of slip movement associated with tire delamination in tractive settings and the hysteresis of the tread material, a portion of the rolling resistance of a tire occurs in its sidewall due to the periodic compression, expansion, and bending of the sidewall rubber during the travel of the tire. The technical development of premium tires thus evolved toward ever decreasing amounts of rubber in the sidewalls and this effect can be particularly noted in the “skinwall” tire models which have come into use in racing activities. In these types of tires, the only rubber to be found in the sidewalls is the rubber added during the calendaring of the cord weave with the rubber mixtures.
The rubber covering of the carcass cords at the sidewall periphery above the thickest location of cords is only a few microns or micrometers thick. As a result of this thinness, the carcass cords are visible through the sidewall, whereby the carcass appears naked or as a “skin”.
Such tires permit the achievement of a reduced weight and a relatively low rolling resistance in comparison to “gum-wall” tires in which the carcass in the sidewall region is covered on its respective axial outer side with an additional rubber layer which contains, without fail, carbon black.
Another measure to reduce rolling resistance of tires of the upper quality tire segment includes the use of reinforcements having ever increasing elongation resistance properties, thus permitting the use of thinner reinforcements and, correspondingly, a thinner application of the rubber layer in which these reinforcements are calendared or embedded. A substantial reduction in rolling resistance can be achieved in particular with mountain bike tires subjected as they are to discontinuous travel paths. The customers of such tires are willing to pay for the increased cord density per tire necessitated by the thinning of the cords.
Unfortunately, the problem consequently occurs that the carcass reinforcements are increasingly susceptible to wear in correspondence with their decreasing thickness.
The susceptibility of the cord reinforcements in such tires to wear can, to be sure, be compensated for by the provision of a thick rubber layer (gum-wall) but this tends to defeat the advantages of such tires as the amount of rubber in the sidewall is increased by this compensation approach and, as a result, the rolling resistance is increased.
SUMMARY OF THE INVENTION
One object of the present invention is to fabricate a sidewall configuration for a bicycle tire, in particular, a mountain bicycle tire and, especially, “skinwall” type embodiments of such tires, such that the bicycle tire substantially approaches the reduced weight and minimized rolling resistance of the conventionally known skinwall tire while at the same time substantially approaching the high wear resistance of a rubber walled tire.
In connection with the individually enumerated aspects, the objects of the present invention are accomplished by:
providing a textile sheet structure (
1
.
9
), which is especially preferably a ply, as wear protection in the sidewall region on the outside of the carcass,
the textile sheet structure having cords (
1
.
91
) extending in two cord directions oriented substantially perpendicular to one another,
whereby both of the cord directions are diagonal—in other words, at an angle of 30 to 70 degrees with respect to the circumferential direction, and
whereby the textile sheet structure is not wound about the bead cores (
1
.
2
).
The orientation of the cords diagonally not only saves weight but, additionally, the respective cords in a left hand textile strip for wear protection on the left sidewall and the respective cords in a right hand textile strip for wear protection on the right sidewall which comprise the wear protection textile sheet structures are scarcely extended or elongated by virtue of full inflation of the cured tire.
Preferably, the extension or elongation of the two lamellar textile sheet structures by virtue of the inner tire pressure are substantially completely precluded. This is achievable if the green uncured tire is inflated after the disposition thereon of the two textile sheet structures but before linking or vulcanization (which transform the initially plastic uncured rubber into elastic rubber); this procedure leads to small plastic displacements of the cords of the wear protection textile sheet structures relatively along the thus inflated carcass cords that, on the cured tire, the cords of the wear protection textile sheet structure are only first put in tension upon r
Becker R W
Continental Aktiengesellschaft
Fischer Justin
Maki Steven D.
R W Becker & Associates
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