Radial tire forming device

Details Radial tire forming device Radial tire forming device

2002-05-23

2004-11-09

Knable, Geoffrey L. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Surface bonding means and/or assembly means therefor

Tire body building type

C156S132000, C156S398000, C156S401000

Reexamination Certificate

active

06814122

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an apparatus for forming a radial tire mounted on a passenger car or the like.
BACKGROUND ART
Methods forming a radial tire are broadly divided into two methods.
A first method is a method in which when an inner liner and a ply which constitute a carcass layer serving as a back cloth are assembled into a carcass band, the outer peripheral length thereof is larger than the outer peripheral length of a bead core, and the bead core is installed by decreasing the diameters (usually, referred to as ply down) of a bead core region and a bead core outside portion. A second method is a method in which the outer peripheral length of a carcass band, which is same as described above, is smaller than the inner peripheral length of the bead core, and the bead core is installed by increasing the diameter (usually, referred to as bead lock) of the bead core region.
The present invention relates to an improvement in the latter second method.
Further, the second tire forming method is classified into three methods (method A, method B
1
, and method B
2
). Of these three methods, method A is a method in which “after the bead core is installed on the carcass band, a portion between the bead cores are swelled into a toroidal shape, and then the carcass band (including a sidewall) in the outside end portion of both of the bead cores is folded and pressed so that the bead core is wrapped in the aforementioned toroidal carcass band”, and a ring-shaped belt-tread structure, which is assembled in advance to the toroidal outer peripheral portion, is assembled, by which a green tire for radial tire is completed. This method is a forming method in which “the carcass band including the sidewall is folded”.
Method B is a method in which “after the bead core is installed on the carcass band, a portion between the bead cores is slightly expanded into a cylindrical shape, and then the carcass band in the outside end portion of both of the bead cores is folded and pressed so that the bead core is wrapped in the aforementioned cylindrical carcass band”, and a ring-shaped belt tread structure, which is assembled in advance, is assembled to the outer peripheral portion swelled into a toroidal shape, by which a green tire for radial tire is completed. Of method B, method B
1
is a tire forming method in which the carcass band including the sidewall is folded, and method B
2
is a tire forming method in which the carcass band not including the sidewall is folded and subsequently the sidewall is affixed.
In all of the above-described three methods, a tire construction called a tread over sidewall, in which the end portion of tread is provided so as to cover the outside of the end portion of sidewall, is used to improve the productivity.
In the case of such a construction, if the position in which the sidewall end is affixed is inexact relative to the end position of belt layer, the durability and quality of tire is seriously affected.
In the conventional forming machine of method A,
(I) A rubber bag called a bladder is used for folding, and careful attention is paid to the performance and quality control of bladder and the operation control of equipment for the above-described reasons. However, great swelling occurs from a portion near the bead diameter of tire to a position near the outside diameter of tire, and the dimensions inevitably change with use. Therefore, it is difficult to make the degree of swell of right and left bladders uniform and to stabilize the slip of bladder surface.
(II) Further, taking notice of the behavior near the end of pressing of the member end portion (explanation is given in a portion at the left of the equator line of toroidal tire), there is a problem in that a member on the bladder having a curvature that is convex toward the right flies to the toroidal carcass having a curvature that is convex toward the left while rolling on the curvature while sliding on the bladder by means of the shrinkage force of member, by which the affixing position is made unstable.
Contrarily, in method B
1
, a single bladder is used for folding, and the amount of swell in the radial direction is regulated by the action of a rollover ring, so that the amount of swell is remarkably small. Therefore, the profile after the bladder has swelled is stable. Further, because of the folding action in which transfer is effected in the state in which the member is held between the bladder and the ring inside cylinder face, the profile is stable as compared with method A.
Contrarily, in method B
2
, after the folding work, the end portion of sidewall can be affixed with a projected bright line representing the affixing position to be controlled being the reference, the sidewall end portion on the tire equator line side has a high accuracy as compared with method B
1
.
The bladder used for folding is classified into a single bladder type and a dual bladder type. The single bladder type is a type in which one bladder is used on one side of a forming drum. The dual bladder type is a type in which two bladders are used. For the single bladder type, in order to assist the folding action of the swelled bladder, a ring-shaped body called a “push can” or a “rollover ring” is indispensable.
For the folding in method B
2
, any of a rollover type using the single bladder, a push can type using the single bladder, and a dual bladder type can be used. The type to be used is determined by the length of folding and the construction and arrangement of forming equipment.
For the purpose of the improvement in high-speed durability, a tire having a two-layer construction of plies constituting the carcass has been needed.
As the two-layer construction, the following types have been considered. (Herein, a ply bonded to an inner liner layer in the cross section of a completed tire is called a first ply.)
(a) A type in which the two-layer construction is formed by laminating a ply with the same width as that of the first ply on the first ply so as to be slightly shifted in the axial direction of a forming former. In this case, the position of ply end folded while wrapping the bead core is almost the same as that of the tire of one-layer construction, and lies close to the bead core of sidewall.
(b) A type in which the two-layer construction is formed by laminating a ply with a width slightly narrower than that of the first ply on the first ply. In this case, the position of ply end is similar to that in item (a).
(c) A type in which the overall two-layer construction is formed by one ply by increasing the width of the first ply and by lapping the folded plies on each other at the tire equator position.
(d) A type in which the overall two-layer construction is formed by making the width of the first ply equal or approximately equal to the width of tire of one-layer construction and by adding a second ply extending to both end portions of the folded first ply.
(e) A type in which the substantial two-layer construction is formed by one ply by increasing the width of the first ply and by positioning the end portion of the folded ply slightly on the tire equator position side of the end portion of the belt layer.
(f) A type in which the two-layer construction is formed by making the width of the first ply equal or approximately equal to the width of tire of one-layer construction, by adding the second ply to the end portion of the first ply, and by positioning the end portion of the second ply slightly on the tire equator position side of the end portion of the belt layer.
When a tire of two-layer construction of each of these types is to be produced, in method A,
The two-layer construction of items (a) and (b) can be formed.
The two-layer construction of item (c) cannot be formed because of a too large length of folding.
The two-layer construction of item (d) can be formed if the construction is such that the folded first ply is lapped on the second ply, but cannot be formed if the construction is such that the second ply is lapped over the folded first ply.
The two-layer construction of items

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