Segmental tire curing mould

2017-07-18 15:11:12

57 ABSTRACT A segmental mould mechanism for curing a pneumatic tire is described and includes two opposed sidewall moulding sections, a plurality of radially movable tread moulding segments mounted between said sections and means for effecting radially inward and outward movement of the tread moulding segments upon movement of the sidewall mould sections towards and away from one another. The mechanism includes a unique floating segment mounting arrangement whereby sliding contact between the segments and the bearing surface on which they are mounted'for radially inward and outward movement is minimized. More specifically, the segment mounting arrangement is adapted to permit limited axial movement of the segments away from the bearing surface on which they are mounted under the influence of resilient biasing means interspaced between the adjacent surfaces of the segments and the bearing surface thereby preventing direct contact between these surfaces until the segments are pressed towards the bearing surface with sufficient force to overcome the force of the resilient biasing means. Ina preferred 7 form, the segment mounting is also adapted to permit limited pivotalmize binding or jamming of the segments during their inward and outward radial movement.

17 Claims, 5 Drawing Figures PATENTED APR 2 3 I974 SHEET 1 OF 3 1 SEGMENTAL TIRE CURING MOULD This invention relates to a mould mechanism for curing and moulding a tire under heat and pressure and, more particularly, to a mould mechanism of the segmental type which is particularly adapted for moulding and curing radial tires.

BACKGROUND OF THE INVENTION Varioustypes of moulding and .curing presses are known in the art and may conveniently be categorized into two groups, namely those presses utilizing a twopart mould having opposed annular mould halves suitable for shaping and curing passenger size cross-ply tires and those presses utilizing segmental moulds having opposed annular mould sections together with radially movable tread moulding segments generally used for curing radial-ply tires and giant cross-ply tires.

-The segmental type of mould has been developed forseveral reasons, an important one being that, in the curing of radial-ply tires, it is generally not practicable to further expand the tire radiallyafter its location in the mould. A radial-ply tire generally includes two or more circumferential, substantially inextensible belts or breaker layers above the carcass pliesand, due to the,

ineittensibility of such breaker layers, it has been necessary in the building of the tire to expand the carcass radially outwardly into contact with the breaker layers and tread rubber so that the green tire assumes a partially shaped configuration before its insertion in the mould; it is thus generally impractical to expand suchpartially shaped green tire radially outwardly when it is located in the mould and, in any event, the stiffened tread region of a radial-ply tire, when cured, would not release readily from a two-part mould during axial separation of the mould halves; the tendency being to tear rubber during such mould separation and to cause damage to the. mould elements.

In the known mechanisms provided for effecting movement of the tread moulding segments radially inwardly and outwardly the moulding segments generally are slidably mounted on a bearing or support surface and have guide means, such as tongue and groove configurations, to ensure that the segments are maintained in true radial and axial alignment at all times. As a result, such mounting arrangements are characterized by very close tolerances between relatively moving adjacent surfaces of the segments, the bearing surface and the guide means. This, in turn, results in a number of problems. Firstly, the very close tolerances required add greatly to the manufacturing costs of such segmental mould mechanisms. Secondly, friction between the adjacent sliding surfaces of the mould segments and the mounting mechanism necessitates that these surfaces be formed of hard, wear resistant material. This also increases the manufacturing costs of the moulds and, even with the use of wear-resistant surfaces and careful lubrication, wear does occur over a period of time under the severe conditions of commercial tire curing operations. I r