EP0736623B1 - Woven webbing for an occupant restraint system - Google Patents

Description

The invention relates to a woven webbing for a vehicle occupant restraint system according to the preamble of claim 1.

In particularly serious accidents, the restraining forces of the Belt strap become so large that there is injury to the vehicle occupant is coming. For this reason, vehicle occupant restraint systems increasingly with force limiting devices provided where it is constructively exceeded predetermined tensile load in the webbing to a Length increase of the force limiting device under energy conversion comes, causing stress peaks in the restraint system can be reduced.

Such force limiting devices can, for example be formed by stretching devices that are attached to an end fitting of the belt or on its belt retractor could be. By exceeding a predetermined Tensile stress occurring plastic deformation, which leads to a Increasing the length of the stretching device can result in belt force to be limited to a structurally predetermined dimension. The disadvantage of such force limiting devices is that additional construction effort necessary for them, in addition to that Added risk of incorrect assembly.

A force limit can also be achieved using tear elements be formed on the belt in the manner of a belt loop and when a given tensile load is exceeded successively release an additional length of belt, whereby also limit the tensile load to one predetermined dimension is possible. But there is one Force limitation characteristic of unsatisfactory reproducibility.

US 4,228,829 A shows a woven webbing in which shorter warp threads with high extensibility and a few longer warp threads with low extensibility are arranged parallel to one another. Due to the stretchability of the shorter warp threads, the webbing can stretch under a certain load until the longer warp threads are tensioned.

The object of the invention is to limit the force with simple To realize means on the belt itself, whose Force limiting characteristic can be influenced constructively and is good is reproducible.

This object is achieved by means of a woven webbing with the features according to the characterizing part of claim 1. Such one Webbing avoids any additional construction work for a force limiting device, because when a controlled tensile load a controlled increase in length of the webbing by stretching the shorter warp threads is achievable, whereby the tensile load acting in the webbing to be limited to a structurally predetermined dimension can. Another advantage of the webbing according to the invention is that by appropriate selection of the aspect ratios of the warp threads and their dimensioning the characteristic from tensile load to stretching the webbing in a wide range Range is freely adjustable.

In the preferred embodiment of the invention, that the longer warp threads with long warp threads uniform length are formed, starting from the difference in length corresponding between the short and the long warp threads first stretch value of the webbing on the holder who are involved in this acting tensile load. By using warp threads with only two different ones Lengths result in an advantageous compromise between cheaper production on the one hand and sufficient Possibility of varying the characteristic from tensile load via Elongation of the webbing on the other hand.

Further advantageous embodiments of the invention result itself from the subclaims.

• Fig. 1 eine schematische Teilansicht eines erfindungsgemäßen Gurtbandes;
• Fig. 2 eine schematische Ansicht der Kettfäden des Gurtbandes von Fig. 1 zusammen mit zwei Schußfäden; und
• Fig. 3 einen möglichen Verlauf der Kurve von Zugbelastung F über Dehnung δ des Gurtbandes von Fig. 1.

The preferred embodiment of the invention is described below with reference to the accompanying drawings. In this show:

• Figure 1 is a schematic partial view of a webbing according to the invention.
• Fig. 2 is a schematic view of the warp threads of the webbing of Fig. 1 together with two weft threads; and
• 3 shows a possible course of the curve of tensile load F over elongation δ of the belt strap from FIG. 1.

The preferred embodiment is shown schematically in FIGS of a webbing 1 according to the invention. It consists of interwoven weft threads 5 and warp threads running in the longitudinal direction of the webbing 7. As can be seen in particular in FIG. 2, the Half of the warp threads 7 have a greater length than the remaining ones Warp threads. The warp threads 7 thus comprise short ones Warp threads 10 and long warp threads 20. As also in particular seen in Fig. 2 are the short and the long Warp threads 10, 20 arranged alternately. To be particularly advantageous has proven to be when the long warps are 20 um about 20% longer per unit length of the webbing 1 than the short warp threads 10. The force limitation of the invention Webbing 1 takes place in the event of a vehicle accident in the following way (see also FIG. 3): In one normal use of the webbing 1 is in this acting tensile load only from the short warp threads 10 added. There is essentially no stretch of the webbing 1. Only after reaching a first one Limit force in the case of that shown in Fig. 3 Curve is approximately 3 kN, there is a noticeable Elongation of the webbing 1. Since the weft threads 5 and the warp threads 7 consist of polyethylene, takes place upon reaching this first limit force a considerable stretching of the webbing 1 up to a first elongation value of approximately 20%, this stretching of the webbing 1 at substantially constant tension of the webbing 1 takes place. Until This first stretch value is reached in the webbing 1 acting tensile load still exclusively from the short warp threads 10 added.

From this first stretch of the webbing 1, which corresponds to the difference in length between the short warp threads 10 and the long warp threads 20, the long warp threads 20 are also involved in absorbing the tensile load F acting in the webbing 1, which limits the stretching of the short ones Warp threads 10 leads. As a result, the curve of tensile load F over elongation δ is changed such that an increase in the elongation δ is also associated with an increase in the tensile load F. This ensures that the webbing 1 still has sufficient strength even after the first elongation value has been reached, if it has to absorb an even higher tensile load. For the use of the webbing 1 according to the invention as a force limiting device in a vehicle occupant restraint system, the structural parameters of the webbing 1 are selected such that the first limit force at which the webbing 1 stretches up to the first elongation value corresponds to the force, from the exceeding of which an injury occurs of the vehicle occupant must be feared and from which the force limiting function should start.

Claims (3)

1. A woven belt webbing for a vehicle occupant restraint system, consisting of interwoven weft and warp threads, the warp threads (7) possessing lengths differing for a given length unit of the belt webbing, that is to say in the form of short warp threads (10) and longer warp threads (20), which short warp threads (10) bear the tensile load acting in the belt webbing (1) up to a first elongation value of the belt webbing (1) without loading of the longer warp threads, and which longer warp threads (20) as from this elongation value of the belt webbing (1) take part in withstanding the tensile load acting in the belt webbing (1) in a manner dependent on the ratio of the length thereof to the length of the short warp threads (10), characterized in that the short and the longer warp threads (10, 20) consist of polyethylene and that the proportion of the short warp threads (10) in all warp threads (7) is approximately equal to that of the longer warp threads (20), the short and the longer warp threads (10, 20) being arranged alternatingly.
2. The belt webbing as claimed in claim 1, characterized in that for a given length unit of the belt webbing (1) the long warp threads (20) are approximately 20 % longer than the short warp threads (10).
3. Belt webbing as claimed in any of the preceding claims, characterized in that the weft threads consist of polyethylene.

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