GB2240994A

GB2240994A - Webbing for safety belt

Info

Publication number: GB2240994A
Application number: GB9103076A
Authority: GB
Inventors: Tsuneo Chikaraishi
Original assignee: Takata Corp
Current assignee: Takata Corp
Priority date: 1990-02-14
Filing date: 1991-02-13
Publication date: 1991-08-21
Also published as: FR2658087B1; JP2892417B2; DE4104516A1; GB9103076D0; CA2036356A1; JPH03241033A; FR2658087A1; KR910021318A

Abstract

A webbing for a safety belt comprising polyester warps and wefts is characterized in that the wefts exhibit an elongation of at least 30% at breakage. Accordingly, the wefts stretch a large amount and with comparative ease when the warps are tensioned or pulled, and therefore leakage of the wefts and warps is reduced. The belting may be a twill weave with knitted selvedge.

Description

:;->:2,4 0 53 D.4 WEBBING FOR SAFETY BELT This invention relates to

webbing for a safety belt such as a seat belt used in a vehicle such as an automobile or a protective belt for workers performing activities at great heights.

A seat belt installed at a seat in an automobile functions to restrain the passenger in the event of an emergency such as a collision, thereby protecting the passenger against injury caused by striking the body of the vehicle. A protective belt for a worker functions to protect the worker against falls by preventing him from falling from a high place, as when work is being carried out on the upper floors of a building or the like.

The webbing for safety belts such as these seat belts or protective belts is subjected to impact force and therefore is required to have sufficient strength.

However, the following problems arise when it is attempted to form such webbing having the required strength:

When it is attempted to form webbing having, say, a width of about 50 mm and a strength of no less than 3000 kgf from a woven fabric comprising a 2/2 twill weave, the total denier number of warps exceeds a value of about 420,000, meaning that the amount of thread used is very large. As a consequence, the manufacturing cost for weaving is high. Moreover, strength utilization rate declines when the number of warps is increased. The reason for this is deemed to be as follows, in which reference is made to Pigs. 3(a) and (b): Since the amount of warps 2 used is large, the warps 2 are woven so as to be crimped when webbing 1 is not tensioned, as illustrated in Fig. 3(a). Wefts 3 under such a condition assume a straightened state. However, when the webbing 1 is tensioned or pulled, as shown in Fig. 3(b), the warps 2 become straightened and therefore the wefts 3 are tensioned while being crimped. Consequently, first one of the wefts 3 may break or sc thus causing an imbalance in the tensile force ever, borne by the warp at this location and by a warp at another location. As a result, the warp 2 snaps, thereby causing a loss in strength.

If the number of warps 2 is simply increased in order to raise thestrength of the webbing 1, strength increases linearly up to a warp number of about 420,000 denier, as shown in Fig. 4, but the rise in the strength curve flattens for a warp number greater than this figure. Accordingly, strength cannot be raised effectively merely by increasing the quantity of thread.

On the other hand, when it is attempted to form the webbing 1 by a woven fabric of patterned textile, the strength of the webbing declines in comparison with a webbing not consisting of patterned textile. The reason j i for this is construed to be as follows: When the webbing is formed of a varied twill weave which is in the form of a skip twill weave at point A, as shown in Fig. 5, tensioning the webbing in the longitudinal (warp) direction causes the g portions where the warps 2 are emerging to sink and causes the Cl portions where the warps 2 are sunken to rise. With regard to the frame indicated by the bold line above point A, the wefts 3 emerge at opposite sides owing to the warps 2a, 2b, and therefore these wefts 3 are crimped more at point A than at any other portions. Consequently, first the wefts 3 snap and then the warps 2, as a result of which strength declines, just as set forth above.

An object of the present invention is to provide a safety belt webbing in which strength can be improved while decreasing the amount of thread used.

In order to attain the foregoing object, the present invention provides a safety belt webbing characterized in that elongation at breakage of the wefts is greater than 30%.

in the safety belt webbing of the present invention constructed as described above, elongation at breakage of the wef ts is set to a large value. Accordingly, the wefts stretch a large amount and with comparative ease when the warps are tensioned or pulled, and therefore the wefts almost never break. The result is that the warps also almost never sever. The end result is a 1 1 webbing of increased strength.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction, combinations of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

Fig. 1 is a diagram of a woven-structure and illustrates the woven structure of an embodiment of a webbing for a safety belt according to the present invention; Fig. 2 illustrates another embodiment of the present invention, in which (a) is a diagram of the woven structure of the embodiment and (b) is a partially enlarged view of this embodiment; Fig. 3 illustrates the behavior of threads in a conventional webbing when the webbing is tensioned, in which (a) is a diagram showing the state of the webbing when untensioned and (b) is a diagram showing the state of the webbing when tensioned; Fig. 4 is a diagram showing the relationship between the number of threads and strength of a webbing; and Fig. 5 is a diagram useful in describing the strength of a patterned textile.

1 1 i i i Ebnbodiments of the present invention will now be described with reference to the drawings.

A webbing 1 shown in Fig. 1 is formed by weaving warps 2 of 1500 D (denier) at 290 threads and wefts 3 of 500 D at 16.75 threads per 25 mm. The woven structure is a patterned weave comprising a combination of a skip twill weave And a varied-warp rib weave. In this case, the elongation at breakage of the wefts 3 is set at 33.8%.

Three of the webbings 1 of this embodiment were fabricated and actually subjected to a strength test. The results were measured strengths of 3460 kg, 3500 kg and 3480 kg, respectively.

In order to compare these strengths obtained according to this embodiment with the strength of a webbing using wefts 3 having an elongation of 24. 92% at breakage, three of the webbings 1 using the same wefts and woven into the structure shown in Fig. 1 were fabricated and subjected to a strength test (this latter webbing shall be referred to as a "test webbing"). The results of this test were measured strengths of 3260 kg, 3260 kg and 3280 kg, respectively.

Comparing the results of these tests demonstrates that the strength of the webbing in this embodiment is raised by about 200 kg in comparison with the test webbing. The reason for this is that the elongation at breakage of the wefts 3 in the webbing of the embodiment 1 is set to have a large value, as a result of which the wefts 3 stretch by a large amount and comparatively easily when the warps 2 are tensioned. Consequently, even though the wefts 3 undergo crimping,'the latter is absorbed by the stretching thereof and therefore the wefts 3 sustain almost no breakage. As a result, the warps 2 also do not break. The end result is a stronger webbing 1. Since the webbing of this embodiment exhibits improved strength, the quality of the webbing is also improved.

Viewed from a different standpoint, the results of the tests show that the strength of the webbing 1 can be raised even if the quantity of warps 2 is reduced. Accordingly, the amount of thread used can be reduced and so can the manufacturing cost of the webbing.

Fig. 2 illustrates another embodiment of the present invention, in which (a) is a diagram showing the woven structure of the embodiment and (b) in a partially enlarged view showing the selvage of thewebbing according to this embodiment. Portions in this embodiment identical with those of the embodiment shown in Fig. 1 are designated by like reference characters and need not be described again.

As shown in (b) of Fig. 2, the edge of the selvage of the webbing is formed by a weft 3, an binding thread 4 and an auxiliary binding 5. By way of example, in this case polyester threads having derniers of 1500 D, 500 D and 250 D are used as the warp 2, weft 1 i 4 1 3 and binding thread 4, and the selvage is woven in a 2/2 warp rib weave to the woven structure shown in Fig. 2(a), namely to a single, double- faced twill main body the woven texture of which is 2/2 herringbone twill. As in the first embodiment described above, the warp 3 and binding thread 4 are set to have a comparatively high elongation at breakage.

In accordance with this embodiment, the weft 3 is prevented from breaking, and so also is the binding thread 4, when the warp 2 is tensioned. Accordingly, the strength of the webbing 1 in this embodiment also is improved.

In accordance with the present invention, as is evident from the forgoing description, elongation at breakage of the wefts in the webbing is set to a large value. Consequently, the wefts almost never break, and hence neither do the warps. The end result is a webbing of increased strength and improved quality.

In addition, by raising the strength of the webbing, the amount of thread used can be reduced and so can the manufacturing cost of the webbing.

As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, i,t is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

1 1 8 -

Claims

CLAIMS:

I. Webbing for a safety belt formed by a woven fabric comprising warps and wefts, the wefts having an elongation at breakage of at least 30%.
2. Webbing as claimed in claim 1 and substantially as herein described.
3. Webbing substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawings.
4. A belt or harness incorporating webbing as claimed in any preceding claim.
5. The features as herein disclosed, or their equivalent, in any novel patentable selection.

Published 1991 at The Patent Office. State House. 66171 High Holborn. London WC1R47P. Further copies may be obtained frorn Sales Branch. Unit
6. Nine Mile Point Cwmfelinrach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent,