Air bag and method for making the air bag

An air bag is made by bonding a pair of sheets to each other by heat-sealing with a releasing layer corresponding to a pattern of a number of cellular air chambers sandwiched therebetween. A check valve for air infusion, which is used for filling air in the air bag, is mounted in one of the air chambers. When air is infused into a space between either of a pair of sheets and the releasing layer through an air infusion port of the check valve, the releasing layer and the corresponding sheet are peeled from each other by the air pressure. As a result, the air chambers are formed between the two layers.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to an air bag used for many 
applications such as a buffer, thermal insulation, a balloon, a cushion 
and also relates to a sheet, and its production method, and particularly 
relates to a simple air bag which is composed of resinous laminated film 
and has a multitude of air-chamber cells, and the production method 
thereof. 
2. Description of the Related Art 
Conventionally, air bags of the type described above, to be used as a 
buffer and the like, are manufactured by heat-sealing two heat-sealable 
sheets lapped one over the other. In its manufacturing process the 
heat-sealing is generally performed by a press mold formed of a heating 
rod. However, the conventional method has such problems such as: (1) 
because this air bags of the type include a large number of air chamber 
cells, the heating rod to be used is required to be formed in a complex 
shape, and such a complex shape cannot be minutely formed, and (2) due to 
the batch processing, the work inevitably has to be done intermittently, 
leading to poor production efficiency. 
SUMMARY OF THE INVENTION 
Accordingly, an essential object of the present invention is to solve the 
problems of the conventional art, i.e. to provide an air bag which can be 
easily and efficiently produced with easy formation of air chamber cells 
having sophisticated and fine patterns, and a method for manufacturing 
such an air bag. 
Another object of the present invention is to provide the above air bag 
having a suitable air infusion valve. 
In order to accomplish these and other objects, an air bag according to the 
present invention is formed by bonding together a first sheet and a second 
sheet sandwiching between them a releasing layer having a pattern 
corresponding to a desired air chamber pattern. 
In the above construction, when air is introduced under pressure into a 
space between the first sheet and the releasing layer, due to the weak 
adhesive force therebetween, peeling occurs at the interface between them 
by the pneumatic pressure, and an air chamber is formed between the two 
layers. In other words, by supplying air into the gap between the two 
layers, the air bag having the air chamber formed corresponding to the 
above pattern is made. 
In the above construction, it is preferable to construct the air bag in 
such a way that at least one of the first and second sheets includes a 
picture pattern print layer or a vacuum metallizing deposition layer. By 
this construction, the an bag having an excellent design and thermal 
insulation effects is made. 
The above air bag may have a single air chamber, but generally, the air 
chamber comprises a large number of cellular air chambers communicating 
with one another. Also, the air bag is generally provided with an air 
infusion valve communicating with the above air chamber. 
One of preferable valves used as the air infusion valve is a film valve. In 
using a film valve of this type, an opening communicating with the above 
air chamber is formed between the two sheets at a predetermined position 
of a peripheral part of the air bag, and the film valve is inserted into 
the opening. As a preferred embodiment, the film valve comprises a pair of 
films mutually bonded on both sides, and outer ends of the two films are 
respectively bonded to the first and second sheets at a peripheral part of 
the opening, while their inner ends are respectively kept released from 
the first and second sheets. 
According to another preferred embodiment, the film valve is made up of a 
valve body comprising a pair of front and back films and a valve member 
formed by bending itself in a V-shape. On the other hand, between the two 
sheets, at a predetermined position of a peripheral part of the above air 
bag, an opening communicating with the above air chamber is formed. The 
valve member, with a bent portion thereof facing a side of an air infusion 
port of the valve, is held between the pair of films of the valve body, 
and both sides of the valve member are bonded to the two films of the 
valve body. Further, each tongue piece formed at the tip side of each of 
the two films is bonded to the surfaces of the first and second sheets at 
the opening of the air bag. In this case, it is preferable that a 
heat-sealable layer to which each tongue piece of the pair of front and 
back films of the film value is bonded is provided on each surface of the 
first and second sheets. With this arrangement, by a simple operation of 
fitting each tongue piece of the film valve to each of the surfaces of the 
first and second sheets and heating it the outside, the film valve can be 
fitted to the air bag body airtightly. 
With respect to the above valve the infusion of air, it is also possible to 
use one, having a configuration frequently adopted for a tire for 
swimming, which comprises an air infusion port communicating with the 
above air chamber and projecting outside from the air chamber, and a plug 
for opening and closing the air infusion port. 
As an air infusion system, there may be adopted a system where, at a 
predetermined position of a peripheral part of the air bag, an air 
infusion port is formed between the first and second sheets. The air 
chamber and the air infusion port are communicated by a narrow, meandering 
air infusion passage filled with viscous liquid. 
Further, as another valve for air infusion, there may be adopted a 
button-type valve which is provided by thrusting through the pair of 
sheets at a location of a cellular air chamber of the above air chamber. 
This button-type valve, which is a check valve having an air infusion port 
is constructed such that air infused from the air infusion port is infused 
into the above cellular air chamber of the air chamber. A pair of upper 
and lower flanges of the valve positioned outside the above sheets are 
airtightly bonded to the surfaces of the above sheets. 
According to a preferred embodiment of the above button-type valve, it 
comprises a valve body having a flanged bottom wall and a cylindrical leg 
which penetrates the sheets. A flange-type cap fitted to at least one end 
of the leg and has the air infusion port. A disk-shaped elastic valve 
member is sandwiched between the cap and a valve seat at a top of the leg 
of the valve body. The leg of the valve body has an axial groove on top of 
the valve seat, and the air infused from the air infusion port of the cap 
is led to the cellular air chamber through the groove when the elastic 
valve member is pushed down the groove by the air. 
According to another preferred embodiment of the above button-type valve, 
it comprises a valve body having a flanged bottom wall with an air 
infusion port and a cylindrical leg which penetrates the sheets, a 
flange-type cap fitted to at least one end of the leg and having an air 
infusion port, a seat member housed in the leg, and a disk-shaped elastic 
valve members sandwiched between the cap and a valve seat at an upper top 
of the seat member and between the bottom wall and a valve seat at a lower 
top of the seat member. The seat member has notched air passages at the 
upper and lower tops thereof, so that the air infused from the air 
infusion port of the cap or from the air infusion port of the bottom wall 
of the valve body is led to the cellular air chamber through the groove 
when each elastic valve member is pushed down each air passage by the air. 
Further, according to the present invention, there is provided a production 
method suitable for producing the air bag with the above construction. 
That is, the production method comprises the steps of printing a releasing 
layer having a pattern corresponding to a desired air chamber pattern on 
an inner surface of either a first sheet or a second sheet, and bonding 
the first and second sheets to each other with the releasing layer being 
sandwiched therebetween. 
By adopting the above method, the releasing layer having the pattern 
corresponding to the desired air chamber pattern can be continuously, 
freely, and easily formed, so that the production efficiency can be 
greatly improved. 
In the above production method, the second sheet is preferably bonded to 
the first sheet by a heat fusion extrusion laminate method. According to 
this method, no special bonding step is necessary, and only by laminating 
the second sheet by the heat fusion extrusion laminate method, the second 
sheet is automatically and continuously bonded to the first sheet in the 
whole region where no releasing layer exists. 
As another preferred embodiment of the above production method, there is a 
method for forming heat-sealing bonding layers on the inner surfaces of 
the above first and second sheets, respectively, and bonding the first and 
second sheets to each other by heating under pressure at the above bonding 
step. According to the method, the first and second sheets are led through 
a pair of heating rolls, thereby making it possible to bond the two sheets 
to each other continuously.

DETAILED DESCRIPTION OF THE INVENTION 
A first embodiment will be explained with reference to FIGS. 1 to 6. 
FIGS. 1 and 2 are a whole plan view and a partially enlarged view of an air 
bag, respectively, according to this embodiment, and FIGS. 3 to 5 show 
sections of essential parts of the air bag shown in FIGS. 1 and 2, 
respectively. Further, FIG. 6 shows lamination steps in order for making 
the air bag. 
As shown in FIG. 3, the air bag has a construction made by laminating, in 
order, a first base film 2, an anchor coat layer 6, a first bonding layer 
4 made preferably of polyethylene resin, a releasing layer 8, a second 
bonding layer 10 made preferably of polyethylene resin, an anchor coat 
layer 6, and a second base film 12. Now, regarding the releasing layer 8 
as a border, the part of the whole layers above the border is named a 
first sheet S1 and the part of the whole layers below the border is named 
a second sheet S2. Accordingly, this air bag is made by bonding the first 
sheet S1 and the second sheet S2 with the releasing layer 8 sandwiched 
therebetween. In FIGS. 1 and 2, a reference numeral 18 shows the air 
chamber provided in the air bag. The above releasing layer 8, having a 
pattern conforming to any desired air chamber pattern, is laminated on the 
first bonding layer 4. As shown in the figure, this air chamber 18 is 
composed of a plurality of longitudinal cells which are connected to each 
other, and in conformity with the pattern, the releasing layer 8 is formed 
continuously between the first and second bonding layers 4 and 10. On the 
other hand, in FIGS. 1 and 2, numerals 15 and 16, respectively, show an 
air infusion passage provided for sending air into the abovementioned air 
bag 18 and an infusion port thereof. A numeral 14 shows a film valve 
provided in the infusion port 16, i.e. a kind of a check valve formed by 
laminating a plurality of films. As shown in FIG. 4, the film valve 14 
according to this embodiment is composed of a pair of films 14a and 14b, 
and both sides of the films 14a and 14b are bonded to each other, while 
two ends thereof, i.e. the outer end, and the inner end are left open. The 
outer end parts of both films are, respectively, bonded to the first 
bonding layer 4, after removal of the releasing layer 8, and the second 
bonding layer 10, at the location of the air infusion port. On the other 
hand, the other ends of the film 14a and 14b, i.e. the inner end parts, 
are left open without being bonded to each other. However, the inner ends 
are mutually in tight contact so that the film valve 14 is constructed to 
function as a check valve that allows air to be sent only in one 
direction, from the infusion port 16 of the air infusion passage 15. In 
other words, in FIG. 4, when air is sent in, the two ends of the films 14a 
and 14b are readily opened to make air flow possible, but because the two 
films 14a and 14b come into tight contact with each, other air leakage is 
prevented. In FIGS. 1 and 2, the hatched portions show the portions where 
the first bonding layer 4 and the second bonding layer 10 are bonded to 
each other without the releasing layer 8 between them. 
When air is forced through the film valve 14 under pressure, the air is 
guided into the air infusion passage 15. And, as shown in FIG. 3, as the 
releasing layer 8 and the second bonding layer 10 are weakly bonded to 
each other, they are readily peeled from each other at their interface by 
the pneumatic pressure, and the air chamber 18 formed between the two 
layers 8 and 10 is filled up with air, as shown in FIG. 5. By continuing 
to force air in under pressure, the peeling of the two layers 8 and 10 
spreads over the whole air bag. 
Next, the method for producing a air bag having the abovementioned 
constitution is explained in accordance with FIG. 6. 
First, as shown in FIG. 6 (I), on the first base film 2 having a film 
thickness of, for example, 7-25 .mu.m, an anchor coat layer 6 is formed by 
extruding a lamination of polyethylene, and then a polyethylene resin 
layer, i.e. the first bonding layer 4, is formed on the anchor coat layer 
in a thickness of, for example, 15-50 .mu.m. 
Next, as shown in FIG. 6 (II), on the first bonding layer 4, the releasing 
layer 8 having a continuous pattern corresponding to the above mentioned 
desired pattern of the air chamber is formed by gravure printing or 
flexographic printing, or the like. 
Next, as shown in FIG. 6 (III), on the whole surface of the first bonding 
layer 4 on which the above releasing layer 8 is formed, a second bonding 
layer 10 made of a material of the same kind as that of the first bonding 
layer 4, i.e. a polyethylene resin, is formed in a thickness of, for 
example, 15-50 .mu.m. The second base film 12, of 7-25 .mu.m, made of the 
same kind of material as that of the first base film 2, is provided with 
the anchor coat layer 6 and laminated on the second bonding layer 10. 
Next, as shown in FIGS. 1 and 2, at a predetermined position on the 
periphery of the air bag body, the second bonding layer 10 and the 
releasing layer 8 are peeled from each other at a part of the interface in 
which they are weakly bonded to each other in order to make an opening. 
Next, the film valves 14a, 14b are inserted into the opening between the 
two layers 10 and 8, and, in order to make it possible to achieve sealing 
between one of the film valves 14a and the first bonding layer 4, a part 
of the releasing layer 8 is either peeled off forcibly by applying an 
adhesive tape to the releasing layer under pressure or removed by it off 
with a solvent. The outer ends of the film valves 14a and 14b are bonded 
to the first bonding layer 4 and the second bonding layer 10, 
respectively, as shown in the figure, by which the desired air bag is 
formed. 
By performing the operation of filling air into the air bag from the air 
infusion port 16 as above, an air bag filled with air is made. When the 
air bag is cut by a predetermined unit length while being subjected to 
heat sealing, a large number of air bags are obtainable after a single air 
filling operation. 
Formation of the releasing layer 8 is suitably performed, as described 
above, by gravure printing or flexographic printing. When the pattern is 
fine, gravure printing which excels in precision printing is preferred. 
Using the gravure printing, the size of the width of the air chamber, and 
the size of the space between the adjacent air chambers, can be reduced to 
a minimum of 0.5 mm. 
Further, the releasing layer 8 may be colored. The colored layer has 
advantages, such as the design property of the air bag being improved and 
facilitating confirmation of the configuration of the pattern in printing. 
As materials for forming the abovementioned films, sheets and layers 2, 4, 
6, 8, 10 and 12, the followings are desirable. As materials for forming 
the first and second base films 2 and 12, for example, polyester, 
stretched nylon, unstretched nylon, polyester or stretched nylon coated 
with polyvinylidene chloride, or, polyester or stretched nylon or 
stretched polypropylene or the like provided with aluminum vacuum 
metallizing deposition is preferably used. Suitable examples of materials 
for the first and second bonding layers 4 and 10 are low density 
polyethylene, linear low density polyethylene, ethylene-vinyl acetate 
copolymer, surlyn, ethylene-methacrylic acid copolymer, unstretched 
polypropylene, etc. As for materials for the anchor coat layer 6, for 
example, urethane resin, titanium resin, imine resin, isocyanate resin, or 
the like is preferably used. As materials for the releasing layer 8, for 
example, any varnish formed of a single composition of polyamide resin, 
cellulose resin, urethane resin, cyclic rubber resin, chlorinated 
polypropylene resin or the like, or, any varnish formed by mixing more 
than two types of varnishes each of which is formed of the abovementioned 
single composition is preferably used. This releasing layer 8 can be 
pigmented to any desired color by mixing pigment into any one of the 
abovementioned varnishes. Suitable examples of materials for the film 
valve are soft films formed of polyethylene, ethylene-vinyl acetate 
copolymer. 
Next, a second embodiment will be explained with reference to FIGS. 7 to 
10. 
FIGS. 7 to 9 show, respectively, the sections of the essential parts 
similar to those shown in FIGS. 3 to 5, and FIG. 10 shows lamination steps 
in order for making the air bag of the present invention. 
The air bag according to this embodiment has the same basic constitution as 
that of the air bag of the first embodiment mentioned above, but the first 
bonding layer 4 is omitted, and the releasing layer 8 is directly 
laminated on the first base film 2. The position to mount the film valve 
14 is changed, thereby making the peeling position between layers 
different from that of the first embodiment. In other words, as shown in 
FIG. 7, this air bag has a construction formed by laminating a first base 
film 2, a releasing layer 8, an anchor coat layer 6, a second bonding 
layer 10, an anchor coating layer 6, and a second base film 12, in this 
order. Consequently, according to this embodiment, regarding the releasing 
layer 8 as a border, the part above it constitutes a first sheet S1, and 
the part below it a second sheet S2. 
On the other hand, with respect to the position to mount the film valve 14, 
as shown in FIG. 8, an end part of each film 14a. 14b is bonded to the 
first base film 2 and the releasing layer 8, respectively. Alternatively, 
a part of the releasing layer 8 may be removed so as to have one end of 
the one film valve 14b directly bonded to the anchor coat layer 6. 
When air is forced in, under pressure, through the air infusion port 16 
having a film valve 14, the film valve 14 is opened and air is introduced 
into an air infusion passage 15. And, by the pneumatic pressure thereof, 
the first base film 2 and the releasing layer 8, which are weakly bonded 
to each other as shown in FIG. 7, are peeled from each other at their 
interface, thus forming an air chamber 18 between the two layers 2 and 8 
as shown in FIG. 9. By continuing to force air in under pressure, the 
peeling of the two layers 2 and 8 spreads over the whole air bag. 
Next, the method for producing the air bag having the above construction is 
described according to FIGS. 10. 
First, as shown in FIGS. (I) and (II), the releasing layer 8 is formed on 
the first base film 2 by gravure printing, flexographic printing or the 
like. 
Next, as shown in FIG. 10 (III), after the anchor coat layer 6 is coated on 
the whole surface of the first base film 2 on which the releasing layer 8 
is formed, the second bonding layer 10, made of the same kind of material 
as that of the first bonding layer, is formed on the anchor coat layer 6 
by extruding polyethylene. And, simultaneously, on the second polyethylene 
resin layer 10, the second base film 12 having the anchor coat layer 6 is 
laminated. 
Next, in a predetermined position of a peripheral part of the air bag body 
according to this embodiment, the film valves 14a and 14b are inserted 
into the opening between the first base film 2 and the releasing layer 8. 
Then the outer ends of the films 14a and 14b are bonded to the first base 
film 2 and the releasing layer 8, respectively, as shown in FIG. 8. By 
this step, the air bag is formed. 
Next, this laminated body is filled with air in the same manner as in the 
first embodiment. If necessary, the body is cut while being heat-sealed in 
order to make a large number of air bags. The material and size of each 
layer constituting the air bag according to this second embodiment is the 
same as the material and size of each layer constituting the air bag 
according to the first embodiment. 
As an example of modification of the abovementioned method, it is also 
possible to prepare, in advance, both the first and second sheets S.sub.1 
and S.sub.2, whose bonding layers 4 and 10 are formed of a heat-sealable 
material (thermoplastic resin), by employing a heat fusion extrusion 
laminate method, and then to put the first and second sheets together 
under pressure with a pair of heating rollers. 
FIGS. 7A and 7B show, respectively, a modifications of lamination 
structures of the sheets S1 and S2. FIG. 7A is characterized in that a 
picture pattern layer 100 is printed on the surface of the base film 2 of 
the first sheet S1, and that a vacuum metallizing deposition layer 200 is 
laminated between the base film layer 2 and the anchor coat layer 6. 
Preferably the picture pattern layer 100 and the vacuum metallizing 
deposition layer 200 are formed on the outer and inner surfaces of the 
base film 2, respectively, in advance. 
The picture pattern layer 100 and the vacuum metallizing deposition layer 
200 may be provided on the second sheet, as shown in FIG. 7B, in entirely 
the same manner as in the case of the first sheet. Further, on the 
surfaces of the sheets S1 and S2, i.e. on each of the picture pattern 
layers 100, a heat sealable bonding layer 300 may be formed. In this case, 
as the base films 2 and 12 are, respectively, sandwiched between the heat 
sealable bonding layers 300 and the first and second bonding layers 4 and 
10, even if it undergoes any crease or bend, the occurrence of pinholes in 
each base film 2 and 12 can be effectively prevented. 
As described above, by forming a picture pattern layer 100, a design 
decoration effect can be improved. Also, by forming a vacuum metallizing 
deposition layer 200, a heat insulation effect can be provided. The 
product is, accordingly, most suitable for use for cushion sheets and the 
like. 
FIGS. 11 to 21 show modified embodiments of the valve or the air infusion 
passage used for the air bags according to the first and second 
embodiments and the abovementioned modified embodiments. 
In FIG. 11, a reference numeral 24 shows a conventional type of valve used 
for a tire for swimming and the like. As shown in the figure, the valve 24 
has a cylindrical valve body 24c, a valve seat 24b provided on the inner 
surface of the valve body 24c, a check valve 24a which is rotatably 
provided on the inner surface of the valve body 24c and which is designed 
to work with the valve seat 24b, and a plug 24d which can be fitted in the 
inner surface of the air infusion port 16 of the valve body 24c. 
This valve can be used instead of the film valves 14a and 14b, according to 
the first and second embodiments and the abovementioned modified 
embodiments, by mounting at the same location as the film valves 14a and 
14b. 
On the other hand, in FIG. 12, numerals 16' and 15', respectively, show an 
air infusion port and air infusion passage. As shown in the figure, by 
forming the air infusion passage 15' in a longitudinal meandering form, 
the passage is provided with the function of a check valve so that the air 
filled in the air chamber 18 through the air infusion passage 15' from the 
air infusion port 16' does not flow reversely. It is to be noted that in 
this modification that the reverse flow of air, as mentioned above, after 
the infusion of air, can be more effectively prevented by filling a 
viscous liquid material such as silicon in the air infusion passage 15' in 
advance, before the infusion of air. 
FIGS. 13 to 16 show another air infusion valve. This is a button-shaped 
valve 25, which is not of the type to be mounted by opening the periphery 
of the air bag body as in the foregoing embodiment, but of the type to be 
directly mounted in one of the desired air chambers 18 of an air bag body 
A. In this embodiment, a special shaped air chamber 18a, i.e. an air 
infusion chamber 18a, is formed on a corner of a body A. This air chamber 
has a circular shape in planar view, and is communicated with other air 
chambers 18 through an air infusion passage 15. In FIG. 13, a reference 
numeral 18b shows an opening to be provided at a central part of the air 
chamber 18a to mount the valve 25. 
FIG. 15 shows an enlarged section of the valve part shown in FIG. 14. 
Further, FIG. 16 shows a disassembled state of the button-shaped valve 25. 
This valve 25, generally, comprises a flange-like cap 25a and a valve body 
25b, which are mutually engaged, and a rubber-made, disk-like, elastic 
valve member 25e. The valve body 25b comprises a bottom wall 25g having a 
flange 25f around its periphery and a cylindrical leg 25h standing 
thereon. At the top of the cylindrical leg 25h is formed a flange 25j. The 
cylindrical leg 25h is vertically split into two parts by a groove 25i so 
as to form two divisional legs 25h-1 and 25h-2. This groove 25i 
constitutes an air path. The top face of the cylindrical leg 25 
constitutes a valve seat 25k for the valve member 25e. 
On the other hand, the cap 25a has a recess 25s for receiving the top part 
of the valve body 25b, and an air infusion port 25d passing through a 
central part thereof. 
Now, the valve 25 is mounted to the air bag body A in the following manner. 
Firstly, a moderate size opening 18b is made through the central part of 
the air infusion chamber 18a. Next, the top of the leg 25h of the valve 
body 25b is projected upward through the opening 18b from underneath. 
Subsequently, the valve member 25e is placed on the valve seat 25k of the 
leg 25h, and the cap 25a is put thereon. At this time, the flange 25j at 
the top of the leg 25h is airtightly engaged with the recess 25s of the 
cap 25a, and simultaneously, a circumference of the valve member 25e is 
strongly held between the valve seat 25k and the inner surface of the 
recess of the cap 25a. In other words, the communication between the 
opening 25d of the cap 25a and the chamber beneath the valve member 25e is 
shut off. Between the bottom face of the cap 25a and the surface of the 
first sheet S1 of the air bag A, and between the top face of the flange 
25f and the surface of the second sheet S2, adhesive 25c, i.e. ring-like 
adhesive tapes, are placed to bond airtightly. 
In the air bag furnished with the button-shaped valve 25 having the above 
construction, when air is supplied under pressure from the air infusion 
port 25d, a portion facing the groove 25i of the valve member 25e is 
extended inside and bent as shown by an alternate dot and dash line in 
FIG. 15. At this moment, the air sent under pressure leaks toward the 
groove 25i as shown by an arrow, and the air goes into the air chamber 
formed between the sheets S1 and S2, i.e. the air infusion chamber 18a. 
The infused air is sent to many other air chambers through the air 
infusion passage 15. 
If a heat-sealable layer is formed on each surface of the sheets S1 and S2 
with advance in the button-shaped valve 25 of the above construction, the 
adhesive tape 25c is unnecessary, and the valve 25 can be easily mounted 
on the air bag body A. 
The above button-shaped valve has the advantage of making any difficult 
work such as peeling off a part of the releasing layer unnecessary, unlike 
the foregoing embodiment. 
According to the above construction, the air infusion port is provided only 
in a single spot (25d). However, in a case of providing two air infusion 
ports, the valve may be formed into a vertically symmetric structure. That 
is, it may be so designed that, in place of the flanged bottom wall, a 
flanged leg top part is formed, and both the top and the bottom parts are 
covered with caps. Alternatively, a modification as shown in FIGS. 17 and 
18 may be adopted. 
The basic structure of the button-shaped valve according to this 
modification is the same as that shown in FIGS. 15 and 16, and the parts 
having the same functions as those of FIGS. 15 and 16 are shown by the 
same reference numerals. This modification is characterized by two air 
infusion ports being provided on the upper and lower portions thereof. In 
this case, one air infusion port is provided in the cap 25a as described 
in the above embodiment, and the other air infusion port 25m is provided 
at a center of a bottom wall 25g of a valve body 25b. Between a pair of 
split legs 25h-1 and 25h-2, a seat member 25n is provided, and on the 
upper and lower parts of the member 25n, a pair of valve members 25e are 
provided. 
The shape of the seat member 25n is shown well in FIG. 18. As shown in the 
drawing, the seat member 25n is cylindrical, and its upper and lower end 
portions, respectively, have a pair of notched air passages 25q facing in 
diametrical directions. And, the upper and lower air passages are 
differentiated in phase by 90 degrees. These passages 25q have the same 
function as the groove 25i of the foregoing embodiment. As shown in FIG. 
17, in the state that the cap 25a is fitted on top of the leg 25h of the 
valve body 25b, the upper valve member 25e is strongly held between the 
upper face of the seat member 25n and the inner face of the recess 25s of 
the cap 25a, while the lower valve member 25e is strongly held between the 
lower face of the seat member 25n and the inner face of the bottom wall 
25g, by which the chamber within the leg 25 is kept airtight with each 
valve member 25e forming a border. 
In the modified embodiment with the above construction, when air is sent in 
under pressure from the upper air infusion port 25d, in the same manner as 
in the foregoing embodiment, the valve member 25e is partially bent so as 
to drop into the passage 25q. As a result, after the pressurized, fed air 
is guided into the groove between the split legs 25h-1 and 25h-2, the air 
is led to the air chamber 18a between the first and second sheets S1 and 
S2 of the air bag body A. On the other hand, in the case where air is 
forced from the lower air infusion port 25m, the valve works in a similar 
way as above. In this case, the air which is introduced into the leg 25h 
is first led between the inner circumferential surface of the leg 25h and 
the outer circumferential surface of the sheet member 25n, and then led 
into the groove 25i. 
Further, a modification of a film valve 26 is shown in FIGS. 19 to 21. This 
film valve, showing an improvement of the one shown in FIGS. 1 and 2, is 
made so that the film valve 26 is mounted externally to the air bag body. 
In the embodiment of FIGS. 1 and 2, as explained above, it is necessary to 
peel off a part of the releasing layer 8 in bonding the film valve 14 to 
the sheets S1 and S2. The work is, however, fairly troublesome. The 
modification as shown in FIGS. 19 to 21 eliminates this problem. 
The film valve 26 comprises a bag-like valve body 26a and a valve member 
26b housed in it. The valve body 26a is formed of a pair of front and back 
films 26c and 26d. As shown in FIG. 21, these front and back films 26c and 
26d are made up of a laminate comprising a base film 26e, an anchor coat 
layer 26f, and a heat-sealing bonding layer 26g. On the other hand, the 
valve member 26b is formed by bending a sheet of film in a V-shape and 
bonding its two sides mutually. As shown in the drawing, the valve member 
26b, being so disposed that its bent part is directed to the side of an 
air infusion port 26k of the valve body, is sandwiched between the two 
sheets of films 26c and 26d, and the two sides thereof are bonded to the 
films 26c and 26d. Further, at the central part, the upper piece 26h of 
the valve member 26b is bonded to the front film 26c, and the lower piece 
26i of the valve member 26b to the back film 26d. Their bonding spots are 
shown by shading in the drawing. Each tip of the front and back films 26c 
and 26d extends in front of the tip of both pieces 26h and 26i of the 
valve member so as to constitute tongue pieces 26j that are separate from 
each other. In the valve with this constitution, when air is sent under 
pressure from the air infusion port 26k having a construction made by the 
outer ends of the two sheets of the front and back films 26c and 26d, the 
air passes through a space between the upper piece 26h of the valve member 
26b and the front film 26c and also passes through a space between the 
lower piece 26i of the valve member 26b and the back film 26d, and the air 
is sent forward. On other hand, with respect to the air flow in the 
reverse direction, because the tip sides of the upper and lower pieces 26h 
and 26i of the valve member 26b are respectively brought into close 
contact with the front and back films 26c and 26d, any flow of air in the 
reverse direction is prevented. 
The film valve with the abovementioned construction is externally mounted 
on one of the air chambers 18b at the periphery of the air bag A. In other 
words, this valve is fitted to the sheets S1 and S2 by heat-sealing a pair 
of tongues 26j to the surfaces of the sheets S1 and S2. Accordingly, the 
releasing layer 8 in the periphery of the air chamber 18b need not be 
peeled off, but is left unpeeled as shown in FIG. 21. In this case, as a 
part of the air chamber is composed of the releasing layer, even if heat 
is applied in fitting the film valve to it, the upper and lower sheets S1 
and S2 are not mutually bonded. 
According to the air bag having the film valve with the above construction, 
the pressurized air passed through the space between the front film 26c of 
the valve 26 and the upper piece 26h of the valve member 26b and passed 
through the space between the back film 26d and the lower piece 26i is 
introduced into the air chamber 18b of the air bag body A. 
In the above construction, the surfaces of the front and back films 26c and 
26d of the film valve are formed out of the heat sealing bonding layers. 
However, instead of this, even if the air bag body A of FIG. 7B, in which 
the surfaces of the air bag body A itself have heat sealable bonding 
layers, is used, the film valve can be easily mounted on the air bag body 
A by heat-sealing.