IE42814B1 - Improvements relating to the reinforcement of resilient articles - Google Patents

Description

This invention relates to the reinforcement of articles made of resilient material such as rubber or plastics, e.g. tyres, conveyor belts, transmission belts and high pressure hoses.

Xt is known to reinforce such articles with strands consisting of a number of wires, or with cords consisting of a number of such strands. Various methods of producing such strands and cords exist: the wires may be unreeled from stationary or rotating bobbins and stranded together, or the wires may be bunched together by means of a rotating head and then coiled as a strand or cord onto a drum.

A disadvantage of such strands or cords is that the wires cross each other at close intervals, making point contacts. Such point contacts are disadvantageous when considering a reinforced manufactured product such as a tyre, since the product may be subjected to many loads varying in magnitude and direction during normal use. This will cause the wires to chafe on one another or undergo so-called frettihg which may result in the wires breaking at less than their theoretical tensile strength. In addition, the torsional stresses present in the wire as a result of stranding increase the initial stresses to which the wires are subjected. These factors combined result in a so-called cabling loss which equals the difference between the theoretical and the actual tensile strength. Moreover, the cost bf reinforcement may be high due to the production steps required to form the strands or cables. -ΒΙΕ has been proposed to reinforce articles not with strands, but with groups of unstranded wires positioned next to each other. Thus, in Patent Specification No. 39596 there is disclosed and claimed a plain weave fabric for reinforcing a resilient material, wherein the warp of the fabric consists of unstranded steel wires held together in groups by the weft of the fabric.

An advantage of employing groups of unstranded wires rather than strands is that the wires of each group make a line contact with one another instead of crossing each other to make point contacts. It will be appreciated though that there may still be a small number of point contacts where wires are displaced and cross each other. In addition, torsional stresses in the wires which would be caused by stranding or cabling are eliminated. The result is more effective and reliable reinforcement.

We have found that the properties of an article reinforced in this manner can be further improved by arranging for the wires to have undulations along their length, for example by crimping the wires. Thus, according to one aspect of the invention, there is provided an article of resilient material reinforced by having embedded therein a plurality of elongate, generally parallel, spaced reinforcing members, each member comprising a group of substantially unstranded wires laid next to each other, at least some of said wires being formed with a set so as to have undulations along their length.

By providing such undulations in the wires, it has been found that the adhesion between the wires and the resilient material is considerably improved, whilst the previous advantages are substantially retained. Moreover, the wires have improved tensile and compression stress - 4 characteristics than straight wires. Particularly when subject to violent axial compression stresses, for example of the type which may be encountered in the casings of tyres, straight wires may become separated and dislocated,· so that the wires lose contact with adjacent wires. Undulated wires on the other hand are able to absorb such stresses. Moreover it is possible to alter the characteristics of the wires by changing the form of the undulations i.e. their shape, amplitude, or spacing.

The article may be reinforced by means of a fabric, and thus according to another aspect of the invention there is provided a method of reinforcing a resilient material which comprises embedding in said material a woven fabric wherein the warp of the fabric consists of substantially unstranded wires held together in spaced groups by the weft of the fabric, at least some of said wires being formed with a set so as to have undulations along their length.

Suitable reinforcing fabrics are disclosed and claimed in Patent Specification No. 42813.

Alternatively, the wires may be directly introduced into the article whilst it is being manufactured, and thus according to a further aspect of the invention there is provided a method of manufacturing a reinforced article of resilient material, including the step of passing directly into said article whilst being formed, a plurality of gener ally parallel spaced groups of substantially unstranded wires laid next to each other, at least some of said wires being formed with a set so as to have undulations along their length.

The invention also extends to means for carrying out the above described method, and thus according to a particular aspect of the invention there is provided apparatus - 5 for manufacturing a reinforced article of resilient material, comprising means for forming resilient material into an article, means for feeding into said article whilst being formed, generally parallel, spaced groups of substantially unstranded wires laid next to each other, and means for crimping at least some of said wires before entering said article so as to have undulations along their length.

The amplitude of the undulations may be perpendicular to the general direction in which the groups are spaoed from one another, or may lie in such direction. Thus, in the case of a fabric or a reinforced sheet the undulations could lie in the general plane of the fabric or sheet, or perpendicular thereto.

The wires are typically of steel, and may be coated with brass if desired. For use in reinforcing for example tyres, their diameters are typically in the range of 0.1 mm to 0.5 mm, preferably 0.15 mm to 0.3 mm.

For ease of manufacture and to provide uniformity in properties in a reinforced article, preferably each wire is 20 provided with undulations, or at least eaoh wire in a particular group. Moreover, the undulations are advantageously periodic, for example, being sinusoidal or following a triangular wave-form, to provide uniformity in properties along the length of the wires, the period being preferably 25 the same for all the wires to provide uniformity in properties across the article. Sinusoidal undulations are particularly advantageous since the tensile strength of the wires is greater than for undulations having sharp bends, such as those following a triangular wave-form.

The phase of the undulations may be the same for all the wires, or simply the same for all the wires in a particular group in which case the phase may differ between 43814 - 6 adjacent groups of wires, the difference being preferably regular, for example 180 degrees between any two adjacent groups of wire?. Such differences in phase further improve adhesion with the resilient material.

It will be appreciated that, to provide uniformity of properties across a reinforced article, the simplest method is to have constant period undulations as hereinabove t mentioned, and constant phase, or at least a very simple phase relationship between adjacent wires and/or groups.

However, acceptable results may be obtained if there is a suitable periodic variation across the article of the period and/or phase of the undulations.

Ih the use of a reinforcing fabric in a method in accordance with the invention, the weft may be made of a suitable synthetic material such as nylon or polyester.

The fabric may be formed as a strip with the weft comprising a single filament, or a yarn, passing from side to side of the strip. It should be noted that the weft need not perform any load-bearing function, and may be substantially more flexible than the warp wires. A further advantage of the invention as applied to a fabric is that the undulations may serve to restrict movement of the weft longitudinally of the warp wires.

The undulations may be formed in the wires by any suitable means which will deform the wires beyond their elastic limit so as to leave a set. Thus the means could comprise a pair of gear rollers between which is passed a fabric as shown in Patent Specification No. 39596 in the direction of the warp wires, or groups of wires from bobbins. If the phase of the undulations is to vary between adjacent groups, each roller may suitably comprise a plurality of individual gear wheels each arranged to - 7 contact a single group, the teeth of which are circumferentially displaced with respect to one another. Thus if the phase variation is to be 180 degrees between adjacent groups of wires, the circumferential displacement between adjacent gear wheels will be one tooth-wide.

Three embodiments of the present invention will now be described by way of example:In Figure 1 there is shown a portion of a strip of plain weave reinforcing fabric 1 for reinforcing a resilient article in a method in accordance with the invention, near the edge thereof. The warp of the fabric comprises a plurality of groups 2 of unstranded steel wires. Each group is provided with undulations in a direction generally perpendicular to the general plane of the fabric.

These undulations are periodic, the wires following a generally triangular wave-form so as to have peaks 3 and troughs 4. The period and phase are the same for all the wires, so that all the peaks 3 are aligned, as are the troughs 4.

The weft comprises a yarn or a single filament 5 of nylon or polyester, passing from side to side of the fabric strip.

In Figure 2, there is shown a portion of a fabric similar to that of Figure 1. However, in this embodiment there is a 180 degrees phase difference between the undulations of adjacent groups of wires, so that the peaks 3 of one group are aligned with the troughs 4 of an adjacent group.

Whilst in the above-described embodiments the wires of each group have been shown as lying adjacent one another in a direction parallel to the general plane of the fabric, it will be appreciated that it would be possible to have - 8 additional wires superimposed in a direction perpendicular to the general plane of the fabric.

The fabrics of Figures 1 and 2 are identical to those described and illustrated in Patent Specification No.

Referring now to Figure 3, there is shown apparatus for manufacturing a reinforced article in accordance with the invention, by directly passing wires into the article whilst being formed. A plurality of bobbins 11, forming a creel, are rotatably mounted. These bobbins contain unstranded groups of parallel steel wires 12. The steel wires 12 have a diameter ranging from 0.1 mm to 0.5 mm, preferably ranging from 0.15 mm to 0.3 mm. Each group is passed through an opening 13 in guide plate 4. It is possible to use bobbins on which only one wire is wound, and in this case, the wires of several bobbins, for instance 2 to 7 or even more, are guided through a single opening 13 of the guide plate 14'to form a group.

The groups of. steel wires 12 are guided through a pair of gear rollers 15 to crimp the groups. The resultant undulations are periodic, the wires following a generally triangular wave-form so as to have peaks and troughs. It is clear, that by changing the characteristics of the gear rollers 15, it is possible to change the amplitude and the period of the wave-form and to give the groups of wires any desired wave-form depending on the desired elongation, compression and tensile strength characteristics of these groups of wires. Preferably, the groups of wires are given a sinusoidal wave-form because in this case the decrease of the tensile strength characteristics has the smallest value.

When the crimped groups of wires leave the gear rollers 15, they can be directly incorporated or embedded in the usual manner in a rubber or plastics article such - 9 as a ply 16 whilst being formed by means of an extruding or calendering machine 18. However, it is also possible to place between the gear rollers 15 and the extruding machine a set of flat rollers 17 to reorient the wires of the groups so that they are turned over by an angle of 90 degrees, whereby the wave-forms are not perpendicular but parallel to the upper and lower planes of the ply to be formed. In this way, it is possible to form very thin sheets or plies 16.

Although as above described the process is carried out in a continuous manner, it is also possible to start with bobbins on which groups of already crimped parallel wires are wound, so that the gear rollers 15 can be omitted at the forming stage. Particularly in this case, it may be worthwhile to spirally wrap around the groups of crimped parallel wires a filament with a small diameter, for instance 0.15 mm, with a large pitch to keep the crimped parallel wires together in the same group. This can also be obtained by spraying a settable agglutinant on the crimped parallel wires so that they keep together in groups.

Also, while the invention has been described particularly with reference to groups of completely unstranded crimped wires because in this way no point contacts are made, it will be understood that it would be possible to strand the bundle of wires with a very large pitch, such as a pitch of 40 mm or more, so that wires twisted in this manner or with such a large pitch can be considered to be substantially parallel to one another, and unstranded.

Claims (38)

1. An article of resilient material reinforced by having embedded therein a plurality of elongate generally parallel, spaced reinforcing members, each member comprising a group of substantially unstranded wires laid next to each other, at least some of said wires being formed with a set so as to have undulations along their length.

2. An article as claimed in Claim l F wherein the amplitude of the undulations is perpendicular to the general direction in which the groups are spaced from one another.

3. An article as claimed in Claim 1, wherein the amplitude of the undulations is in the general direction in which the groups are spaced from one another.

4. An article as claimed in any preceding Claim, wherein each wire in any one group is provided with the said undulations.

5. An article as claimed in Claim 4, wherein each group consists of wires provided with the said undulations.

6. An article as claimed in any preceding Claim,wherein the undulations are periodic.

7. An article as claimed in Claim 6, wherein the period is the same for all the undulated wires.

8. An article as claimed in Claims 4 and 7, wherein the phase of the undulations is constant within any one group.

9. An article as claimed in Claims 5 and 8, wherein the phase of the undulations is the same for each group.

10. An article as claimed in Claims 5and 8 , wherein the phase of the undulations differs between adjacent groups.

11. An article as claimed in Claim 10, wherein the phase difference between any two adjacent groups is 180 degrees.

12. An article as wherin the undulations

13. An article as wherin the undulations claimed in any of Claims 6 to 11, follow a triangular wave-form. claimed in any of claims 6 to 11, are sinusoidal.

14. An article as claimed in any preceding Claim, wherein the wires of each group lie side by side in a direction parallel to the general direction in which the groups are spaced from one another. 5 15. A method of manufacturing a reinforced article of resilient material as claimed in any one of Claims 1-14, including the step of passing directly into said article whilst being formed, a plurality of generally parallel spaced groups of substantially unstranded wires laid next 10 to each other, at least some of said wires being formed with a set so as to have undulations along their length. 16. Apparatus for manufacturing a reinforced article of resilient material as claimed in any one of Claims 1-14, comprising means for forming resilient material into an

15. Article, means for feeding into said article whilst being formed generally parallel, spaced groups of substantially unstranded wires laid next to each other, and means for crimping at least some of said wires before entering said article so as to have undulations along their length. 20 17. An apparatus as claimed in Claim 16, including means for crimping said wires in a direction perpendicular to the general direction in which the groups are spaced from one another, and means for rotating said wires through a right angle so that the amplitude of the undulations is in the 25 general direction in which the groups are spaced from one another.

16. 18. A method of reinforcing a resilient material which comprises embedding in said material a woven fabric, wherein the warp of the fabric consists of substantially unstranded 30 wires held together In spaced groups by the weft of the fabric, at least some of said wires being formed with a set so as to have undulations along their length.

17. 19. A method as claimed in Claim 18, the fabric being plain weave. 35

18. 20. A method as claimed in Claim 18 or 19 wherein the fabric is in the form of a strip and the weft is constituted by a single filament passing from side to side of the strip.

19. 21. A method as claimed in. Claim 18 or 19 wherein the fabric is in the form of a strip and the weft is constituted by a yarn passing from side to side of the strip.

20. 22. A method as claimed in any of Claims 18 to 21 wherein the weft is made from a synthetic material.

21. 23. A method as claimed in Claim 22, wherein the weft is nylon or polyester.

22. 24. A method as claimed in any one of Claims 18 to 23, wherein the amplitude of the undulations is perpendicular to the general direction in which the groups are spaced from one another.

23. 25. A method as claimed in any one of Claims 18 to 23, wherein the amplitude of the undulations is in the general direction in which the groups are spaced from one another.

24. 26. A method as claimed in any one of Claims 18 to 25, wherein each wire in any one group is provided with the said undulations.

25. 27. A method as claimed in anyone of Claims 18'to 26) wherein each group consists of wires provided with the said undulations

26. 28. A method as claimed in anyone of Claims 18-to 27,wherein the undulations are periodic.

27. 29. A method as claimed in Claim 28, wherein the period is the same for all the undulated wires.

28. 30. A method as claimed in Claims 26and 30, wherein the phase of the undulations is constant within any one group.

29. 31. A method as claimed in Claims 27 and 30, wherein the phase of the undulations is the same for each group.

30. 32. A method as claimed in Claims 27 and 30, wherein the phase of the undulations differs between adjacent groups.

31. 33. A method as claimed in Claim 32, wherein the phase difference, between any two adjacent groups is 180 degrees.

32. 34. A method as claimed in any of Claims 28 to 33, wherein the undulations follow a triangular wave-form. - 13

33. 35. A method as claimed in any of Claims 28 to 33, wherein the undulations are sinusoidal.

34. 36. A method as claimed in any preceding Claim, wherein the· wires of each group lie side by side in a direction parallel to 5 the general direction in which the groups are spaced from one another.

35. 37. A reinforced article of resilient material, substantially as hereinbefore described with reference to the accompanying drawings. IO

36. 38. A method of reinforcing a resilient material which comprises embedding in said material a woven fabric, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

37. 39. A method of manufacturing a reinforced article of 15 resilient material substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

38. 40. Apparatus for manufacturing a reinforced article of resilient material, substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.