GB2063947A

GB2063947A - Webbing

Info

Publication number: GB2063947A
Application number: GB8035864A
Authority: GB
Original assignee: Akzo NV
Current assignee: Akzo NV
Priority date: 1979-11-09
Filing date: 1980-11-07
Publication date: 1981-06-10
Also published as: FR2469278A1; JPS5683634A; DE2945222A1; BR8007069A; SE8007828L; IT8050092A0; BE886065A; IT1149211B

Abstract

Webbing, particularly for use in car seat belts which comprises filament yarns (2) having a tensile strength of at least 65 cN/tex and consisting of a plurality of individual filaments. The yarns are in the form of flat bands of parallel threads and are sheathed by a plastics material which is abrasion-resistant, heat-resistant and light-resistant. <IMAGE>

Description

SPECIFICATION Webbing The present invention relates to webbing, preferably for car seat belts, composed of high strength filament yarns which consist of a plurality of individual filaments.

Conventional car seat belts are woven from high strength textile filament yarns, in particular from polyamide or polyester yarns. They usually have from 50 to 200 (continuous) individual capillaries per filament yarn. The starting material supplied by the man-made fibre producer to the webbing weaver generally has a maximum strength of 80 cN/tex, strength values of from about 65 to 75 cN/tex being predominant. These original tensile strengths of yarn are not completely available in the woven belt. Depending on the weft density and the polymer used, the woven webbing has only a tensile strength which is reduced by 10 to 30%. The cross-overs and interlacing of the yarn thus cause a reduction in the tensile strength to about 50 to 70 cN/tex.

Moreover, only about 70 to 90% of the original tensile strength of the yarn is utilised in a new car seat belt.

Due to the mechanical stress (abrasion, kinking) the action of light (decomposition of the polymer) and the action of heat and moisture, a conventional car seat belt suffers a loss of strength of about 35% on average within about 5 years. After 10 years, the average service life of a car, the loss of strength in a conventional car seat belt is about 70%.

Starting with a minimum tensile strength of about 1,500 daN, prescribed by the legislators, and also taking into consideration the fact that the industry operates by taking into account a safety factor with minimum tear strengths of about 2,500 to 3,000 daN, it can be estimated that a car seat belt would have to be exchanged after about 5 years in order to satisfy the legal requirements.

An object of the present invention is primarily to propose webbings for car seat belts which, throughout the service life of a car, always have a tensile strength higher than the prescribed standard and can thus fulfil their proposed functions completely.

In order to achieve this object, conventional car seat belts could be provided with a much higher initial tear strength so that they still have a sufficiently high level of strength after 10 years even with the normal reduction in tear strength.

However, the webbing would have to be much larger (i.e. in thickness, in width) for this purpose and this would result, among other things, in reduced flexibility and would necessitate much greater retractors (automatic belt-winding device).

Accordingly, an object of the invention is, in particular, to provide webbing which still has adequate tensile strength after 10 years and is at the same time equal to or smaller than conventional webbing in size, with sufficient flexibility and transverse strength.

The solution to this problem is based on the notion that, when using sufficiently high strength filament yarns in the actual production of belts, all strength-reducing factors, in particular cross-overs and interlacing of yarn, are to be avoided. In addition, the filament yarns should be protected by a covering, in particular from mechanical, thermal and/or light-induced damage during subsequent use of the webbing.

Moreover, webbing which it is possible to produce with much smaller width tolerances than with conventional woven webbing is to be provided. This permits more precise guidance of the webbing in the retractor so that the belts no longer jam so readily as they are wound in and out and abrasion damage to the edges of the belt as it is wound in and out is substantially avoided.

According to the present invention there is provided webbing comprising high strength filament yarns consisting of a plurality of individual filaments and having a tensile strength of at least 65 cN/tex, the yarns are in the form of a flat band of parallel threads and are sheathed by a sufficiently abrasion-resistant, heat-resistant and light-resistant plastics material which keeps the harmful radiation of the light away from the filament yarns.

The filament yarns should initially have a sufficiently high level of strength to be able to remain in or below the conventional webbing dimensions. To avoid reducing this high level of strength in the starting material due to the abovementioned disadvantages of the conventional art of belt weaving, any cross-overs and interlacing of threads, conventional in weaving, knitting or in the production of non-woven fabrics, are avoided according to the invention. For this purpose, the filament yarns are wound in the form of a "flat band of parallel threads". The term "band of parallel threads" means that the filament yarns, whether they lie in straight lines, in a meandering configuration or in any other way, are arranged parallel to each other and thus without crossovers.This band of parallel threads should be "flat", unlike the warp threads (also arranged in parallel) of conventional webbing which form an upward and downward line extending physically over the entire thickness of the belt. According to the invention, each filament yarn should lie in an imaginary plane parallel to the surface of the belt.

As a result of this arrangement of the filament yarns, each filament yarn in the belt has its original high tensile strength, which should be at least 65 cN/tex. These strength values are achieved, fqr example, in conventional high strength filament yarns composed of polyethylene terephthalate or of polyamide 6,6 or polyamide 6.

Particularly progressive results are achieved if filament yarn having a tensile strength of at least 100 cN/tex are used, as this permits a clear reduction in the thickness of the belt (with the same belt width). Carbon threads, or threads of aromatic polyamides (aramides), for example, have tensile strengths of this order of magnitude (about 1 20 or 1 80 cN/tex). Filament yarns with tensile strengths of at least 1 50 cN/tex are particularly preferred.

If, as already mentioned, it is possible at the same time to use conventional polymers such as polyesters or linear polyamides, preference is given to the aromatic polyamides, not only due to their extremely high tensile strength. As these aramides have a very low breaking elongation, webbing produced from them can be processed into safety belt systems provided with shock absorbers which guarantee a maximum or irreversible work absorption in the event of straining. In this case, in particular, webbing is preferred in which the filament yarns exist in a rectilinearly stretch form. However, if a belt having a specific material elongation, like the conventional belts, is preferred, the filament yarns can be present in undulating form in the webbing so that sufficient elasticity in the longitudinal direction is provided by the elongation of the plastics covering.Webbing of this type also have the advantage that permanently rectilinearly stretched filament yarns are a sign of the unserviceability of the belt due to excessive strain.

In order to prevent the parallel filament yarns from affecting each other during use of the belt and to protect each filament yarn effectively from harmful influences, in particular of a strengthreducing type, webbing in which each filament yarn is completely sheathed by a plastics material is preferred. This can also be a different plastics material from that forming the sheath of the entire band of threads.

Suitable materials for the sheath include any sufficiently abrasion-resistant, heat-resistant and light-resistant plastics material such as, for example, polyvinylchloride, polyurethanes, polyamides or polyester elastomers, providing that they are capable of keeping the harmful light radiation away from the filament yarns.

To prevent the light radiation which is harmful to the filament yarns from penetrating through the plastics covering, additives such as absorbers, stabilisers or reflectors can be added to the plastics material. The light-transmitting capacity can also be influenced within certain limits by means of the thickness of the covering layer.

The sheath can be produced, for example, by extrusion. In this case, a band of parallel threads running in a plane is passed through a slot into an extrusion nozzle of an extruder and is sheathed continuously with the plastics material melted in the extruder.

It is also possible to surround the filament yarns by lamination with films. In this case, the flat band of parallel threads is coated with two plastics films on glazing rollers. The upper side and under side can be applied in one or more operations. The melt roller coating method, in which the film to be laminated is produced immediately prior to the lamination process is a special example of this method.

The band of parallel threads can also be covered by brush-coating. In this case, the plastics coating is applied directly or indirectly in dissolved or pasty form using a doctor blade and is then dried, cured or gelled in a heating duct. It is also possible to combine indirect and direct application for the upper side and lower side.

The band of threads can also be coated by an immersion process. In this case, the band of threads is passed through a bath of the dissolved or pasty plastics material. It entrains a certain proportion of the plastics material, which is then dried, cured or gelled in a heating chamber. This process can be repeated several times or combined with a blade coating process in order to achieve the desired thickness of covering.

It is also possible initially to sheath the individual filament yarns and then to arrange them in a parallel layer and bond them together by the action of heat. The sheath can be produced during the thread production process by spinning threads of bi-component (core-sheath) structure, the sheath component of which has a lower melting point.

Plastics materials which can be cross-linked by radiation can also be used, the curing, drying or gelling of which is effected by a cross-linking reaction, for example, by ultra-violet or P rays.

Finally, it is also possible to combine the previously mentioned technologies. The filament yarns can also be pretreated before being sheathed, for example with a preparation for improving the adhesion between the yarns and the plastics material.

The filament yarns can be arranged in such a way that they are equidistant from each other.

However, they are preferably arranged in groups, and plastics cross-pieces having widths of a few mm, for example, from about 1 mm to about 8 mm can be provided between the individual groups. These cross-pieces can also contain cavities to lighten the weight and/or to influence the transverse rigidity of the webbing.

The webbing according to the invention can be produced in conventional or belt widths. However, it is also possible to produce, in the first instance, a band of parallel threads which is, for example, 2 metres wide and is sheathed with plastics material with plastics cross-pieces arranged at the distance of the conventional belt width and to cut the web into webbing of a conventional width along these cross-pieces.

The filament yarns can exist in the form of interlaced or interwoven individual filaments, Le.

in the form of a bundle having an approximately circular cross-section. In order to achieve optimum properties of strength, the filaments yarns should preferably be untwisted and exist in ribbon form, i.e. the cross-section of the bundle should have the shape of a flat ellipse.

The plastics material forming the covering can have a textured surface. Interesting surface configurations, for example, for aesthetic purposes, can be achieved by stamping patterns or grains on the plastics material to match the other interior fittings of the car.

The plastics material forming the covering is preferably coloured, the colour also being adapted to the colour of the internal fittings in the car.

The webbing can be pattern by using a plastics material which is at least partially transparent, in such a way that the filament yarns or groups of filament yarns are coloured in different ways during spinning. Thus, for example, it is possible to alternate groups of black and white filament yarn.

It is also possible to make technically effective modifications in the surface. Thus, webbing is preferred in which the plastics sheath has longitudinal grooves on both flat sides of the webbing which are profiled in such a way that the longitudinal grooves on the underside can be joined together integrally with the longitudinal grooves on the upper side. In particular, the longitudinal grooves on the underside and the longitudinal grooves on the upper side should be profiled to correspond to a key and slot connection. Webbings having profiles surfaces of this type do not slip as quickly as conventional webbings as they are wound and unwound in the retractor.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 to 8 each show a cross-section through a preferred embodiment of the present invention.

Figure 1 shows a detail of a webbing in which filament yarns 2 are embedded in a plastics material 1 and exist in a rectilinearly stretched form.

Figure 2 shows a detail of a webbing in which filament yarns 3 are encased in plastics material 1 and exist in undulating form.

Figure 3 shows a cross-section through a webbing in which twisted filament yarns 4 are embedded equidistant from each other in the plastics material 1.

Figure 4 shows a cross-section through a webbing in which twisted filament yarns 5 are embedded in groups 6 in the plastics material 1.

Figure 5 shows a cross-section through a webbing 5 consisting of a flat band of parallel threads which are embedded in plastics material 1 and comprise untwisted filament yarns 7 existing in ribbon form.

Figure 6 shows a cross-section through a webbing in which groups 8 of untreated white filament yarns 9 and groups 10 of black spundyed filament yarns 11 are embedded alternately in the plastics material 1.

Figure 7 shows a cross-section through a webbing whose upper side 12 is provided with slot-shaped longitudinal grooves 13 and whose underside 14 is provided with key-shaped longitudinal grooves 15.

Figure 8 shows a cross-section through a webbing which is produced by laminating a flat band of parallel threads 16 on both sides with two films 17, 18 which have longitudinal grooves 21 , 22 on their outward facing surfaces 19,20.

Claims

1. Webbing comprising high strength filament yarns consisting of a plurality of individual filaments and having a tensile strength of at least 65 cN/tex, the yarns being disposed in the form of a flat band of parallel yarns and are sheathed by a sufficiently abrasion-resistant, heat-resistant and light-resistant plastics material which keeps the harmful radiation of the light away from the filament yarns.

2. Webbing according to Claim 1, wherein the filament yarns have a tensile strength of at least 100 cN/tex.

3. Webbing according to Claim 1 or 2, wherein the filament yarns have a tensile strength of at least 1 50 cN/tex.

4. Webbing according to any one of Claims 1 to 3, wherein the filament yarns are composed of an aromatic polyamide.

5. Webbing according to any one of Claims 1 to 4, wherein the filament yarns exist in a rectilinearly stretched form.

6. Webbing according to any one of Claims 1 to 5, wherein each filament yarn is completely surrounded by a plastics material.

7. Webbing according to any one of Claims 1 to 6, wherein the filament yarns are arranged in groups and plastics cross-pieces are provided between the individual groups.

8. Webbing according to any one of Claims 1 to 7, wherein the filament yarns are untwisted and exist in the form of ribbons.

9. Webbing according to any one of Claims 1 to 8, wherein the plastics material forming the covering has a textured surface.

10. Webbing according to any one of Claims 1 to 9, wherein the plastics material forming the covering is coloured.

11. Webbing according to any one of Claims 1 to 10, wherein the filament yarns or groups of filament yarns are spun-dyed differently.

12. Webbing according to any one of Claims 1 to 11, wherein the plastics sheath has, on the two flat sides of the webbing, longitudinal grooves which are profiled in such a way that the longitudinal grooves on the underside can be positively joined together with the longitudinal grooves on the upper-side.

13. Webbing according to Claim 12, wherein the longitudinal grooves on the underside and upper side of the webbing are profiled respectively to correspond to a key and slot connection.

14. Webbing substantially as herein described with reference to and as illustrated in any one of the figures of the accompanying drawings.

15. Webbing according to any preceding claim adapted for use in a car seat belt.

16. A car seat belt comprising webbing as claimed in any preceding claim.