Stock material or miscellaneous articles – Structurally defined web or sheet – Edge feature
Patent
1990-05-01
1992-03-24
Bell, James J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Edge feature
156174, 156250, 1563041, 264175, 428294, B32B 2302
Patent
active
050987682
DESCRIPTION:
BRIEF SUMMARY
This invention relates to flexible reinforced polymeric material and in particular, although not exclusively, to flexible reinforced polymeric material for use as a rubberised ply fabric reinforcement for a flexible elastomeric article such as a pneumatic tire.
Conventionally the reinforcement of at least a part of a pneumatic tire, whether of the radial or cross-ply type, is formed from a sheet-like reinforcing ply of rubberised fabric. The ply is constructed from a woven cord fabric comprising relatively strong parallel warp cords maintained spaced apart and in parallel relationship with the aid of relatively light weft elements. The fabric is dipped to coat it with a bonding agent and then passed between the bowls of a calender at which rubber is applied over and forced between the cords to effect rubberisation of the fabric.
In constructing a pneumatic tire it is often required that the warp cords shall extend obliquely or at a right angle relative to the direction of the length of a strip of the rubberised fabric. Accordingly the intially produced rubberised fabric is cut on the bias or at 90 degrees into sections of equal length, the sections then being arranged with the original side edges of one section overlying the original side edge of a second section and the other sections being successively overlapped at their respective edges to form a strip of rubberised fabric in which the aforementioned warp cords extend obliquely or at a right angle relative to the direction of the length of the strip so formed.
The strip is wrapped around a tire building former and cut to length at a position which results in a small overlapped joint when the cut end is pressed against the former.
Although the aforedescribed method of forming part of a tire reinforcement from bias cut fabric is used extensively and is long established it suffers a number of disadvantages which themselves are also well known and understood.
Most notably the aforedescribed method undesirably results in adjacent sections of the initially produced fabric being joined by lap joints of a joint thickness therefore double that of the fabric. These lap joints will occur at random positions in the resulting tire and therefore inhibit the provision of a uniform reinforcement construction. Apart from important technical considerations this lack of uniformity undesirably mars the visual appearance of the finished tire.
Additional to the problem of overlapping, the presence of the weft elements, necessary to assist in locating the warp cords only during calendering, entails certain disadvantages as well as the cost aspect associated with the need for a weaving operation. For example, during the shaping process, in which the components applied around a tire building former are expanded to a generally toroidal shape, the spacing of the warp cords can be disturbed by the presence of the weft elements. This is a particular problem especially in the manufacture of pneumatic tires of the radial type.
Even during the calendering and pre-calendering operations, when the weft elements are needed to assist in locating warp cords relative to one another, the weft elements do not eliminate difficulties. Prior to entering the calender the unrubberised woven fabric is fed over spreader rolls which are intended to maintain a constant pitch of the cords across the width by creating tension in the weft elements. In practice the warp cords are found to bunch together at the edges of the strip and this results in undesirable non-uniformity of cord spacing especially in the regions of the respective joints between the sections forming a length of the bias cut fabric. Particularly in the case of a radial ply type pneumatic tire in which the length of a piece of rubberised ply fabric wound around the tire building former approximately equals the width of the fabric in the calender this bunching undesireably results in an area of bunched cords at one circumferential position.
Accordingly although providing some assistance with location of the warp cords when passing throug
REFERENCES:
patent: 1608102 (1926-11-01), Jury
Holroyd Eric
Perkins David J. B.
Bell James J.
Bridgestone/Firestone Inc.
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