Uncoated woven fabric and method of manufacturing same

A woven fabric is wove using warps (6) and wefts (7) having coated threads (6a) and (7a), respectively, every other thread, with the remaining threads being uncoated threads (6b), (6c). The coated threads (6a), (7a) are melted by a heat setting treatment, thereby fusing the coated threads (6a) in the warps (6) to the wefts (7) and the coated threads (7a) in the wefts (7) to the warps (6). The woven fabric becomes an uncoated woven fabric on which a thin coating film has not been formed. Accordingly, the uncoated woven fabric has a predetermined amount of air permeability. The threads will not become frayed or tattered and the amount of air permeability will not change even when the uncoated woven fabric is cut.

BACKGROUND OF THE INVENTION 
This invention relates to an uncoated woven fabric, which comprises a woven 
fabric, ideal for use in an air bag for vehicles or the like, as well as a 
method of manufacturing the uncoated woven fabric. 
An air bag device provided on a stationary portion of the vehicle body of 
an automobile in front of a seat of the automobile has an air bag inflated 
instantaneously by the pressure of a reaction gas emitted by an inflator 
secured to the steering wheel or dashboard, thereby protecting a seated 
passenger from injury caused by a vehicular collision. Thus, the air bag 
device performs a very important function. 
The shape of the air bag in such an air bag device differs depending upon 
the location at which the air bag is mounted. For example, as shown in 
FIG. 6, an air bag 1 for the driver's seat comprises a substantially 
circular bag body having a disk-shaped base fabric 1a attached to a fixed 
portion of the vehicle body, such as the steering wheel, and a circular 
base fabric 1b facing the driver. The base fabrics 1a, 1b are superimposed 
and sewn together at A along their circumferential edges and turned over. 
The air bag 1 has an opening 2 provided in the base fabric 1a, which is 
secured to the vehicle body, into which the inflator (not shown) that 
generates the reaction gas is inserted. The air bag 1 is further provided 
with vent holes 3 from which the reaction gas is discharged after the 
driver is impacted against the air bag 1. 
As shown in FIG. 7, a passenger air bag 4 is provided in the instrument 
panel and has a complicated shape owing to the fact that the space between 
the assistant driver's seat and the instrument panel is large. The 
passenger air bag 4 includes a front panel 4a, a rear panel 4b and a pair 
of side panels 4c, 4d. The edges of these panels are overlapped and sewn 
together and turned over to form the air bag 4. 
In general, the driver and passenger air bags 1, 4 both consist of a 
synthetic resin such as polyimide resin and are formed from a suitable 
number of base fabrics in which a thin coating film 5 (shown only on the 
driver's air bag 1 in FIG. 6) of chloroprene rubber or silicone rubber is 
provided on the inner surface. By providing the thin coating film on the 
inner surface of the base fabric, the base fabric is protected from the 
high temperature and high pressure of the reaction gas jetted from the 
inflator when the air bag is inflated. 
In order to lighten the air bag device and make it more compact, there has 
recently been greater demand for an air bag base fabric that can lighten 
the air bag and reduce the volume of the package. Since progress has been 
made in lowering the temperature of the reaction gas by virtue of an 
improvement in the performance of the inflator and the development of 
aspirator-type air bag devices, air bags which use a fabric on which a 
thin coating film is not formed (such a fabric shall also be referred to 
as an "uncoated fabric" hereinafter) have become the focus of interest. 
Since the uncoated fabric does not have a thin coating film such as 
chloroprene rubber or silicone rubber formed thereon, the thickness of the 
base fabric is reduced by an amount equivalent to the thickness of the 
thin coating film, and therefore the air bag is reduced in both weight and 
package volume. 
In a case where an uncoated woven fabric is used, there are occasions where 
the threads of the uncoated woven fabric become frayed or tattered when 
the fabric is subjected to cutting. In general, when such an uncoated 
woven fabric is subjected to a heat-resistance aging test in which it is 
maintained at a temperature of 80.degree..about.120.degree. C. for 
600.about.1000 hrs, the threads becomes ball shaped owing to contraction 
of the threads and locations are produced where the spaces between threads 
widen and other locations where the spaces become small. As a result, 
there are instances where there is a change in properties, such as a 
change in the amount of air permeability of the base fabric. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an uncoated woven fabric, 
as well as a method of manufacturing the same, in which the threads will 
not become frayed or tattered when the fabric is cut, and in which there 
will be no change in such properties as amount of air permeability after 
cutting. 
According to the present invention, the foregoing object is attained by 
providing an uncoated woven fabric consisting of a woven fabric woven from 
warps and wefts and not having a thin coating film formed thereon, 
characterized in that a predetermined number of threads of at least one of 
the warps and wefts comprise coated threads coated with a coating 
material, and the coated threads are fixed to the threads of the other of 
the warps and wefts. 
A method of manufacturing the above-mentioned uncoated woven fabric 
according to the present invention is characterized by using a 
predetermined number of coated threads as the threads of at least one of 
the warps and wefts, forming a woven fabric by weaving the coated threaded 
and uncoated threads, and fusing the coated threads to the threads of the 
other of the warps and wefts by performing a heat setting treatment in 
which the woven fabric is held at a predetermined temperature for a 
predetermined period of time. 
In the uncoated woven fabric and method of manufacturing the same according 
to the present invention described above, a predetermined number of 
threads of at least one of the warps and wefts comprise coated threads 
coated with a coating material, and the coated threads are fixed to the 
threads of the other of the warps and wefts. As a result, the threads will 
not become frayed or tattered even when the uncoated woven fabric is cut 
to prescribed dimensions. In addition, owing to the coated threads, the 
spaces between the mutually adjacent threads in the threads of the other 
of the warps and wefts are prevented from widening or narrowing when a 
heat-resistance aging test is performed. As a result, the amount of air 
permeability does not change but remains at a substantially constant 
value. 
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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the present invention will now be described with reference 
to the drawings. 
FIG. 1 is a partially enlarged plan view showing an embodiment of an 
uncoated woven fabric according to the present invention. 
As shown in FIG. 1, an uncoated woven fabric C is woven from warps 6 and 
wefts 7 in the same manner as in the prior art. In accordance with this 
embodiment, every other thread of the warps 6 is coated to provide 
alternating coated threads 6a, and every other thread of the wefts 7 is 
coated to provide alternating coated threads 7a. The coating material for 
coating the coated threads 6a, 7a may be any which will fuse the threads 
together when a base fabric is heat-set, as will be described later. An 
example of such a material is a thermoplastic resin. 
The woven fabric using the coated threads 6a, 7a as every other one of the 
warps 6 and wefts 7, respectively, is subjected to a heat setting 
treatment at a predetermined temperature for a predetermined period of 
time. In general, the heat setting treatment involves maintaining the 
woven fabric at a temperature of 190.degree. C. for about 40 sec after the 
fabric has been washed. By virtue of this treatment, the coated threads 
6a, 7a are melted so that the coated threads 6a in the warps 6 are fused 
to the wefts 7, namely to the coated threads 7a and uncoated threads 7b in 
the wefts 7 while the coated threads 7a in the wefts 7 are fused to the 
warps 6, namely to the coated threads 6a and uncoated threads 6b in the 
warps 6. The woven fabric thus formed serves as an uncoated woven fabric, 
namely a woven fabric on which a coating film has not been formed. 
Accordingly, the uncoated woven fabric has a prescribed amount of air 
permeability. 
The woven fabric in which the coated threads 6a in the warps 6 are fused to 
the wefts 7 and the coated thread 7a in the wefts 7 are fused to the warps 
6 is cut to appropriate dimensions in accordance with the purpose of use, 
thereby forming a base fabric. In this case, the fact that the threads are 
fused together assures that they will not fray or become tattered when the 
woven fabric is cut. When a heat-resistance aging test is conducted, the 
filaments are prevented from becoming ball shaped, thereby preventing the 
gaps between the threads from increasing or decreasing in size. As a 
result, there is almost no change in the amount of air permeability. 
Accordingly, when the uncoated woven fabric C is used to form the 
aforementioned air bag, such as the driver's air bag 1 shown in FIG. 6, 
the base fabric 1a secured to the vehicle body is formed by an uncoated 
woven fabric having a comparatively large amount of air permeability, and 
the basic fabric 1b facing the driver is formed by an uncoated woven 
fabric having a comparatively small amount of air permeability or by a 
fabric on which a thin coating film has been formed. As a result of such a 
construction, the amount of air permeability can be adjusted to a desired 
value. As a consequence, the reaction gas within the air bag after the bag 
has been impacted by the driver can vent in appropriate fashion. 
Accordingly, it is unnecessary to provide vent holes 3 with which the 
conventional air bag is furnished. This makes it possible to reduce the 
number of manufacturing steps. 
In the air bag 4 for the passenger shown in FIG. 7, the side panels 4c, 4d 
may be formed by an uncoated woven fabric having a comparatively large 
amount of air permeability, and the front panel 4b and rear panel 4a may 
be formed by an uncoated woven fabric having a comparatively small amount 
of air permeability, whereby the reaction gas within the air bag after the 
bag has been impacted by the driver can vent in appropriate fashion. 
FIGS. 2 through 5 are partially enlarged plan views showing other 
embodiments of the uncoated woven fabric according to the present 
invention. Elements identical with those of the foregoing embodiment are 
designated by like reference characters and need not be described again in 
detail. 
In the embodiment shown in FIG. 2, every third thread of the warps 6 is the 
coated thread 6a, and every third thread of the wefts 7 is the coated 
thread 7a. In the embodiment shown in FIG. 3, every fourth thread of the 
warps 6 is the coated thread 6a, and every fourth thread of the wefts 7 is 
the coated thread 7a. In the embodiment shown in FIG. 4, every third 
thread of the warps 6 is the coated thread 6a, and every fourth thread of 
the wefts 7 is the coated thread 7a. In the embodiment shown in FIG. 5, 
every other thread of the warps 6 is the coated thread 6a, and every third 
thread of the wefts 7 is the coated thread 7a. In each of these 
embodiments, actions and effects identical with those of the first 
embodiment are obtained. Which particular embodiment of the uncoated woven 
fabric is employed may be selected appropriately depending upon the 
purpose of use. It should be noted that the present invention is not 
limited to the foregoing embodiments since the coated threads 6a, 7a may 
be arranged at suitable intervals besides those mentioned above. 
Thus, in accordance with the present invention, as described above, the 
threads can be prevented from becoming frayed or tattered when the 
uncoated woven fabric is cut. In addition, a change in the properties of 
the uncoated woven fabric, such as a change in the amount of air 
permeability, caused by external conditions is prevented, and therefore 
such properties as the amount of air permeability can be held 
substantially constant. Accordingly, by employing the uncoated woven 
fabric of the present invention as the base fabric of a vehicular air bag, 
for example, an air bag exhibiting a desired amount of air permeability 
can be manufactured in simple fashion. As a result, there are cases in 
which the vent holes that are provided in the conventional air bag on 
which the thin coating film is formed can be eliminated. Moreover, the 
base fabric of the air bag can be reduced in thickness by an amount 
equivalent to the coating film, thereby making it possible to achieve a 
greater reduction in weight and to reduce the package volume of the air 
bag. 
As many apparently widely different embodiments of the present invention 
can be made without departing from the spirit and scope thereof, it is to 
be understood that the invention is not limited to the specific 
embodiments thereof except as defined in the appended claims.