Abstract:
An inflatable seat belt apparatus is formed of an inflatable portion which is usually maintained in a band shape and has an envelope part inflated and deployed in a spindle shape by introducing a gas generated by a gas generating device, the gas generating device acting in case of exceeding a predetermined threshold, a webbing having the inflatable portion extending over at least a range directly contacting with an occupant, a tongue fixed to an end of the inflatable portion and having a gas inlet from the gas generating device inside thereof and a buckle which detachably engages the tongue. The envelope part is made of a knitted fabric expanded in the weft direction in a range of contacting the chest of the occupant when the envelope part is inflated. The inflatable seat belt apparatus includes an inflation restricting device for restricting the expansion in the weft direction besides the range.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an inflatable seat belt apparatus, more particularly to an inflatable seat belt, wherein a webbing of a seat belt apparatus to restrain an occupant has an inflatable portion formed in an envelope shape which is usually maintained in a band shape and is inflated, in an accident, in a predetermined shape with gas spouted  from a gas generating means. 
     Presently, a seat belt apparatus is necessary for a vehicle or the like as an apparatus for securing  to secure an occupant&#39;s body , which . Such apparatus restrains the occupant from sudden movement by a deceleration and an impact in a crash. 
     Such a seat belt apparatus comprises  may comprise a webbing such as a woven belt made of a fabric which has approximately a 50 mm width and is formed according to Japanese Industrial Standard, to . The seat belt apparatus may have a retractor (hereinafter referred to as an ELR: Emergency Locking Retractor), a buckle, a tongue, an anchor and so on. 
     The ELR winds the webbing by a winding force of a spring and locks the webbing from withdrawing only at a crash so as to restrain the occupant. The buckle is mounted on a suitable position near a floor so that the webbing fits the occupant&#39;s body well. 
     Conventionally, the seat belt apparatus locks the webbing from withdrawing by the function of the ELR at a crash to restrain the occupant from a forward movement. 
     For improvement in the efficiency of restraining the occupant, each of U.S. Pat. Nos. 3,841,645  3,841,654, 3,865,398, and 3,866,940 discloses a seat belt apparatus in which the webbing has a portion formed in an envelope shape and is folded like a bellows. The portion is provided with a weak adhesive so as to usually maintain in  in a band shape, or the folded portion is held in the  a band shape by fastening means such as a fastener, so that in a crash, the portion formed in the envelope shape is inflated and deployed by a spouted  gas from a gas generator connected to the webbing. 
     According to the seat belt apparatus having the  an inflatable portion formed in an envelope shape (hereinafter, it is called as  “an inflatable seat belt apparatus”), force applied to the occupant can be distributed over the  a range wider than the conventional webbing so as to decrease the stress applied to the occupant and a higher safety efficiency can be provided. 
     The inflatable seat belt apparatus is effective even for a rear seat. For mounting an air bag apparatus for an occupant on the rear seat, the air bag apparatus is generally mounted on the rear side of the back portion of the front seat. It is necessary that the front seat structure has a high rigidity for suitably operating the air bag apparatus for the rear seat to efficiently restrain and secure the occupant. However, it is difficult to provide the reclining mechanism having a movable portion to the front seat if the air bag apparatus is mounted on the rear side of the back portion of the front seat. Therefore, the inflatable seat belt apparatus is effective for the rear seat because the inflatable seat belt apparatus can be independently mounted on the rear seat and has no restriction such as the above mentioned air bag apparatus. 
     In such an inflatable seat belt apparatus, wherein the envelope shaped portion is folded to form a band shaped belt having a predetermined width as mentioned above, the folded envelope shaped portion is piled up to be thickened. Therefore, the belt is hard to fit the occupant&#39;s body during wearing and hard to pass smoothly through a slip guide of a pillar anchor. Accordingly, there is a fear of decreasing the belt wearing rate because the occupant feels an incongruity during wearing. 
     Further, the folded portions are glued together and therefore, the inflatable portion is hard to deploy smoothly even when the spouted  gas is introduced into the envelope shaped portion during the  deployment. 
     Therefore, the applicant has already proposed anDisclosed in commonly- owned Japanese patent applications are  inflatable seat belt apparatus which can overcome these problems (Japanese Patent Application No.  210353/1992, publication no. 6 -   144138 , published May  24 ,  1994 ; and Japanese Patent Application  No.  210355/1992, publication no. 6 -   56001 , published Mar.  1 ,  1994   ). 
     These applications disclose inventions that  in which the envelope shaped portion is structure by  comprises a knitted fabric member, i.e. a woven textile member having wefts which expands enough. 
     According to these inventions, the seat belt apparatus is maintained in a relatively thin band shape and can inflate and develop the envelope shaped portion reliably and promptly at  in an emergency. 
     FIG. 1 (a) shows an example of the   an inflatable seat belt apparatus, wherein one portion of a shoulder belt is structured by  comprised of a cylindrical knitted fabric member. And  In this example, a rubber tube formed in an envelope shape is inserted into the cylindrical knitted fabric member. 
     In this figure, numeral  51  designates a tongue. The tongue  51  has a gas inlet  53  for introducing gas into the rubber tube in a belt  52 inside thereof . The gas inlet  53  is coupled to a gas outlet of gas generating means, i.e. gas generator (not shown), connected inside a buckle  54  when the tongue  51  is engaged with the buckle  54  for fixing a belt end  52 a to the vehicle body. 
     FIG. 1 (b) shows an example of a state where a predetermined gas pressure is applied to the belt portion of the inflatable seat belt apparatus structured as stated above. 
     As shown in this figure, the rubber tube is inflated by the gas pressure in the tube. And a whole  The shape of the rubber tube is defined by the envelope shaped knitted fabric member wrapping  covering the tube and is inflated in a spindle shape. Because the area of the belt portion touching the chest and the like of the occupant is increased, an impact applied to the occupant is softened and the apparatus can protect the occupant efficiently. 
     Because the inflatable portion formed in an envelope shape is radially increased, the length of the belt in a longitudinal direction is shortened by ΔL. Therefore, the inflatable seat belt apparatus has a function  functions as a pre-tensioner so that the occupant is more effectively retained  restrained. 
     However, the following problems become apparent from various tests using a model and a real vehicle for the inflatable seat belt apparatus as mentioned above. The tests are executed by using a full-sized dummy. 
     As shown in FIG. 2, the knitted fabric structural portion of the shoulder belt  52  is effectively inflated and deployed in a crash. 
     When the belt tries to restrain the dummy D from movement, the gas in the tube escapes to a space  52 b between the buckle near the floor and the waist of the dummy D and to a space  52 c between a pillar anchor  55  and the shoulder of the dummy D, so that the shoulder belt  52  is inflated in a gourd shape. In this state, the shoulder belt  52  can not be inflated over an enough area at the important place for catching the chest of the dummy D. This spoils the merit of using an inflatable structure for the shoulder belt. 
     Because the tube is inflated in the whole extent of the longitudinal direction thereof, the inflation volume becomes large and then the gas pressure in the tube is hard to be increased  increase . In addition, because the tube can not be inflated enough in the radial direction thereof, the length of the belt in the longitudinal direction is not shorted  shortened enough. Therefore, the above mentioned function as a pre-tensioner does not work effectively. 
     Furthermore, the above mentioned inflatable seat belt apparatus has various inconveniences. In the inflatable seat belt apparatus, the envelope shaped portion of the shoulder belt is also wound in an ELR mounted in the under portion in the pillar. The belt portion formed of the knitted fabric is slightly thicker than the belt portion formed of the fabric textile. Therefore, the ELR should be exchanged for a special ELR which can accommodate the thick belt formed of a knitted fabric. 
     A slip guide is mounted to the pillar anchor to change the direction of the belt withdrawn form  from the ELR. The slip guide has a guide opening for the belt. The width of the guide opening is narrow for preventing the belt from twisting and turning over. Therefore, it is hard to allow the thick belt to smoothly pass therethrough. 
     On the other hand, in case that  when the belt is formed to have  has a short width, the occupant feels the belt is undependable. The belt must maintain its stiffness and its  a form which give dependence  imparts a feeling of dependability to the occupant when the occupant uses the belt. 
     ItA suitable design should be considered toalso prevent the surface of the knitted fabric from abrasion. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to overcome the above mentioned problems of the prior art and to provide an inflatable seat belt apparatus maintaining  that maintains a proper inflation shape and an internal pressure therein when the apparatus restrains the occupant from movement during deployment. 
     Furthermore, the  it is an object of the invention to provide an inflatable seat belt apparatus which fits an occupant&#39;s body well and has enough durability even if the apparatus is used repeatedly. 
     For accomplishing the above mentioned object  objects, a first invention provides an inflatable seat belt apparatus comprising an inflatable portion which is usually maintained in a band shape and has an envelope part inflated and deployed in a spindle shape by introducing a gas generated by gas generating means, the gas generating means actuating in case of exceeding a predetermined threshold, a webbing having the inflatable portion extending over at least a range directly contacting with an occupant, a tongue fixed to an end of the inflatable portion and having a gas inlet for receiving the gas from the gas generating means, and a buckle detachably engaging the tongue, wherein the envelope part is made of a knitted fabric, and the knitted fabric is expandable in the weft direction in a range of contacting the chest and around the chest of the occupant when the envelope part is inflated, while the inflatable seat belt apparatus includes inflation restricting means for restricting the expansion in the weft direction besides the range. Therefore, the inflatable seat belt apparatus can restrain the occupant form  from movement with a wide contacting area around the chest of the occupant. Further, the pressure in the inflatable portion can be increased because the volume of the inflation is minimized and the webbing is shortened certainly  reliably in the longitudinal direction. Therefore, the function as a pre-tensioner is effectively provided to restrict the occupant more effectively. 
     The second invention provides an inflatable seat belt apparatus comprising an inflatable portion having an envelope part formed over a range of connecting  contact with an occupant and usually maintained in a band shape, the envelope part being inflated and deployed in a rough spindle shape by introducing a gas generated by gas generating means thereinto in case of exceeding a predetermined threshold, a webbing having one end fixed to the inflatable portion and the other end accommodated in winding means by winding, a tongue fixed to a distal end of the inflatable portion and having a gas inlet for receiving the gas from the gas generating means, and a buckle detachably engaging the tongue, wherein the envelope part is made of a knitted fabric, and the knitted fabric is expandable in the weft direction in a range of contacting the chest and around the chest of the occupant when the envelope part is inflated, while the inflatable seat belt apparatus includes inflation restricting means for restricting the expansion in the weft direction besides the range. 
     Therefore, the inflatable portion can become thinner so that the inflatable seat belt apparatus becomes useful. As well as  with the first invention, the inflatable seat belt apparatus can restrain the occupant from movement with a wide contacting area around the chest of the occupant. Further, the pressure in the inflatable portion can be increased because the volume of the inflation is minimized and the webbing is shortened certainly  reliably in the longitudinal direction. Therefore, the function as a pre-tensioner is effectively provided to restrict the occupant more effectively. 
     In the above inventions, preferably, the inflation restricting means comprises a cylindrical cloth cover having a connecting portion extending in the longitudinal direction thereof, the cylindrical cloth cover being formed to cover the envelope part. The connecting portion comprises a first part corresponding to the chest and  of the occupant and a second part, the first part being broken away by a pressure in the envelope part during the inflation and deployment, and the second part being maintained without break  breaking even even during the inflation and deployment. Therefore, the inflation shape and inflation volume of the inflatable portion during the inflation and deployment thereof can be easily controlled. In addition, the envelope part is effectively protected during wearing and so on and the durability of the belt portion constructing the inflatable structural portion is improved. 
     Preferably, the connecting portion is formed by a seaming  a seam. 
     Furthermore, preferably, the envelope part is formed by a tubular knitted textile. 
     In the first invention, preferably, the webbing has an end fixed to the tongue with the inflatable portion and the other end accommodated in a winding means by winding , the inflatable portion extending over at least a range directly contacting with  an occupant to wrap the webbing as a core thereof . 
     In the above mentioned inventions, preferably the inflatable portion has a tubular inflatable member inserted thereto, the tubular inflatable member being inflatable by introducing a gas. 
     Preferably, the inflation restricting means has an inflation restricting part disposed on the surface of the tubular inflatable member, so that an inflation of the envelope part is restricted by restricting an inflation shape of the tubular inflatable member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 (a), and  1  (b) are explanatory views showing an example of inflation shapes of a conventional inflatable seat belt apparatus having an inflatable member structured by a knitted fabric; 
     FIG. 2 is a perspective view simply showing a result of tests using a dummy, wherein the inflatable seat belt apparatus as shown in FIG. 1 is inflated and deployed; 
     FIG. 3 is a simplified perspective view showing an embodiment of an inflatable seat belt apparatus according to a first invention; 
     FIG. 4 is a perspective partial view magnifying and exemplifying the inside of the inflatable portion when an occupant usually  wears the inflatable seat belt apparatus shown in FIG. 3; 
     FIG. 5 is a perspective partial view exemplifying the inside of the inflatable structural portion when the inflatable seat belt apparatus shown in FIG. 4 is inflated and deployed; 
     FIG. 6 is a longitudinal sectional view showing a structure of a slip guide side of the inflatable portion taken along a line VI-VI in FIG. 4; 
     FIGS. 7 (a)- 7  (c) are explanatory drawings showing a state of sewing of a cover of the inflatable portion and a state of the inflatable portion restricting the inflation shape by the cover; 
     FIG. 8 is a perspective view simply  showing a result of tests using a dummy, wherein the inflatable seat belt apparatus of the present invention is inflated and deployed; 
     FIGS. 9 (a)- 9  (c) are perspective views showing an altered example of a member for restricting an inflation shape of the inflatable portion; 
     FIG. 10 is a plain stitch pattern showing an altered example of a knitted fabric structure; 
     FIG. 11 is a perspective view showing a fitting structure between a tongue and the end of the inflatable portion; 
     FIG. 12 is a longitudinal sectional view showing a section of the fitting structural taken along a line XII—XII in FIG. 11; 
     FIG. 13 is a cross sectional view showing a simplified structure of an engaged portion of a buckle; 
     FIG. 14 is a vertical sectional view showing a releasing operation of the tongue by a press button of the buckle; 
     FIG. 15 is an end view showing a front face of the buckle; 
     FIG. 16 is a partial longitudinal sectional view showing a structure of a slip guide side of the inflatable portion according to the second invention; and 
     FIGS. 17 (a)- 17  (c) are perspective views showing altered examples of members for restricting an inflation form of the inflatable portion according to the second invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of an inflatable seat belt apparatus according to the present invention is now described referring to the attached drawings. 
     FIG. 3 is a simplified perspective view showing a whole structure of the inflatable seat belt apparatus  1 . This figure illustrates for clarifying  relationships among respective components of the inflatable seat belt apparatus applied to the right side front seat. 
     In this figure, numeral  2  designates a shoulder belt. The shoulder belt  2  has an end  2 a to which a tongue  3  is fixed. The shoulder belt  2  is engaged and fixed to a buckle  4  mounted on a predetermined position of the floor between the right and left front seats via the tongue  3 . The shoulder belt has the other end  2 b downwardly guided through a slip guide  5  of a pillar anchor (not shown) mounted on a pillar P. The pillar anchor is adjustable in upper and lower directions. The shoulder belt is thus hung from the slip guide  5  to be wound up in an ELR  6  arranged near the floor. 
     A loop belt  7  has an end  7 a fixed to an anchor plate  8  fixed to a mouthpiece of the tongue  3  and has the other end  7 b wound in the ELR  9  mounted on the floor at the door side beyond the seat cushion. 
     The description will now be made as regard to detailsDetails of the structures of the shoulder belt, peripheral components of the tongue, and the buckle, respectively will now be described. 
     The shoulder belt  2  comprises the end  2 b wound and accommodated in the ELR  6 , the other end  2 a connected to the tongue  3 , and a piece of webbing  10  as a through member as shown in FIG.  3 . In this embodiment, for the webbing  10 , a band shaped belt having a 50 mm width and a 1.6 mm thickness which is tightly woven by twilling, plain weaving or the like by using polyester finished yarn is employed . The webbing  10  is equivalent to one of a conventional seat belt apparatus. The webbing  10  has a section between an abdominal region and a right shoulder region which directly touches the body of an occupant wherein the section has a portion covered by a cylindrical cover  20  made of a cloth and formed to have a slight thickness. 
     In the inside of the portion having the slight thickness, several kinds of envelope shaped members are accommodated overlappingly. 
     In FIG. 4, numeral  10 a shows the webbing  10  positioned within the cover  20 . Because of the difference of the functions  in function, this portion of the belt is called an inner belt  21 , the portion of the belt which is exposed outside and is wound into the ELR is called the webbing  10 , and these portions are designated by the different numerals  10  and  21 , respectively. 
     The inner belt  21  is inserted in a flat condition into a tube  22 , formed of a thin film and made of silicone rubber as shown in FIG.  4 . The tube  22  made of silicone rubber is cylindrical and has an end  22 a sealingly fixed to a predetermined position of the inner belt  21  as shown in FIG.  6 . Therefore, the tube  22  is inflated in a long and slender cylindrical shape as a gas is introduced into the tube  22 . 
     This tube  22  is accommodated in a cylindrical knitted textile member  23  of flat type which is knitted in a size slightly larger than the tube  22 . In this embodiment, the knitted textile member  23  is constituted by a tubular knitted textile using a polyester finished yarn (1500 denier). The knitted textile member  23  of the tubular knitted textile has a characteristic by which it does not expand in the longitudinal direction of the belt (wrap  that is in the warp direction of the knitted fabric) and is easily expandable in a direction (  weft direction of the knitted fabric )  so that the circumference of the cylindrical shape is increased. 
     The cloth cover  20  as described above is arranged to wholly  completely cover the knitted textile member  23  of a cylindrical shape, and the knitted textile member  23  and the cover  20  are firmly sewn together with the inner belt  21  as shown in FIG.  6 . 
     Preferably, a material for the cover  20  does not show a crease and is soft in touching  to the touch because the cover  20  is a portion directly touched with the hand of the occupant and directly contacts with the clothe  clothing of the occupant. In this embodiment, a tricot knit fabric knitted by warp knitting with a polyester finished yarn is employed for the cover  20 . 
     The thick portion has the inflatable tube  22  with the inner belt  21  as a core, and the end is connected to the gas generator via the tongue  3  so as to be inflated and deployed by the gas introduced in a very short period of time at a crash. Therefore, the inflatable seat belt apparatus can efficiently restrain the occupant from movement. In this specification, reference is made to an “inflatable portion” will be denoted  instead of a whole set of  the entire  inflatable member hereinafter . 
     In addition to the embodiment described above, this invention may be accomplished by the following embodiments having modified components of the inflatable structural portion. 
     For the tube  22 , a rubber material which has high elasticity even against a rapid inflation and has heat-resistance because the high temperature gas is filled in the inside of the tube  22  is suitable for using  use. The material having rubber-like elasticity may be used for the tube  22 . The material may be, for example, various kinds of thermoplastic elastomer, urethane rubber, fluorocarbon rubber, blended rubber or the like. 
     The knitted textile member  23  is the  a seamless tubular knitted textile of wefts having no seam for  forming a cylindrical shape in the above mentioned embodiment. The stitch may be plain stitch, rib stitch, pearl stitch, interlock stitch or the like. In this case, the elongation of the knitted textile member  23  in the weft direction is changeable by converting  altering the density of knitted loops into  in the wrap  warp direction. 
     The knitted fabric of a flat type is made by plain weave. In this case, it is possible that two sheets of the knitted fabrics in a long and slender shape are overlapped and the ends of the knitted fabrics are sewn together to make a cylindrical form, and that both ends of one sheet of the knitted fabric are sewn together to make a circular form. 
     A cloth employed for the cover  20  may be a plain weave fabric using a nylon yarn or polyester yarn. 
     Besides the materials as described above, other material such as a resin film, an artificial leather or the like is considered to be employed for the cover if the material satisfies the conditions of the  feel, the  stiffness, the  persistence and so on. 
     FIG. 5 is a perspective partial section view for understanding  illustrating the inside of the inflatable portion shown in FIG. 4 when the inflatable seat belt apparatus is inflated and deployed. 
     As the tube  22  is inflated by the introduced gas, the knitted textile member  23  constituted by the tubular knitted textile is elongated in the radial direction to be inflated in a cylindrical shape. When the predetermined inner pressure is applied, a portion of the thread sewing together the cloths of the cover  20  is torn. A seam  20 a of the cover is then opened like a mouth, and the tube  22  covered by the knitted textile member  23  is inflated in a spindle shape to be forced out from the opening of the seam  20 a. 
     While, becauseBecause a seam  20 b of the cover  20  is sewn firmly at a predetermined range on the pillar anchor side of the inflatable portion  25  and at a predetermined range on the tongue side, the inflation of the tube  22  is limited by a cover portion  20 c of the cover  20 , so that the cover portion  20 c is inflated only in a long and slender cylindrical form. The diameter of the cylindrical form is approximately 3.6 cm in this embodiment. 
     The length in the longitudinal direction of the belt is shortened because the inflatable portion  25  is inflated in a spindle shape. At this point, because the knitted textile member  23  of the inflatable portion  25  receives a tensile force in the longitudinal direction of the belt, the inner belt  21  does not receive the tensile force so that the inner belt  21  is loose. 
     FIG. 6 is a sectional view showing the structure of an end of the inflatable portion  25  and the webbing  10  (the webbing  10  is called the inner belt  21 in case thatwhere it is located inside the inflatable portion  25  as mentioned above) near a slip guide side. 
     As the structure is not now be  described again, the end of the knitted textile member  23  is integrally glued to the end  20 d of the cover  20  by the adhesive and is firmly sewn to the webbing  10 . The end  22 a of the silicone rubber tube  22 made of silicone rubber  is glued to the inner belt  21  within the knitted textile member  23  inside of the sewing part. 
     A cylindrical bag filter  26  is accommodated in the tube  22  to collect cinders such as carbon powder spouted  produced with the high temperature reaction gas. 
     The bag filter  26  is made of a cloth which is closely woven to be able to collect the high temperature fine cinders and to be able to pass the gas freely. Since the high temperature cinders are adhered to the inner surface of the filter, the material for the filter is preferably a cloth having heat resistance. 
     The description will now be made as regard to aA method for controlling a shape of the inflatable portion  25  fully inflated and the inflatable volume will now be described. 
     FIG. 7 (a) is a plan view showing the cloth cover  20  used in this embodiment. The cloth cover  20  is made by seaming together the ends of tricot knit fabric having a predetermined size to be a slender cylindrical shape. In this embodiment, a margin for seaming of the inflatable portion  25  is approximately 800 mm in whole length and has a range (A) of approximately 300 mm in length at the tongue side, a range (B) at the middle and a range (c) of approximately 200 mm in length at a slip guide side. The margin is seamed by a fine thread (60 denier) along the whole length once. 
     Further, the range (A) and the range (c)  (C) are seamed by a heavy thread (630 denier) twice. The seam pitch by the heavy thread is closer than the seam pitch by the fine thread. That is, the seamed portion  20 a of the range (B) is seamed only by the fine thread. At this stage, the fine thread is so strong that the thread is not broken as the occupant pulls the seam during wearing. 
     In case of using a thinner cloth for the cover  20 , another cover  20 A is preferably covered over the range (A) besides the cover  20  as shown in FIGS. 7 (a) and  7  (b) to restrict the cloth of a cover portion  20 e of the cover  20  near the tongue  3  from breaking when the gas is introduced into the tube  22  rapidly. 
     FIG. 7 (c) is an explanatory drawing showing an example of a state that the inflatable portion  25  covered by the cover  20  shown in the same FIG. 7 (a) is inflated and deployed by the spouted gas. 
     First, an impact sensor senses a rapid deceleration over a predetermined threshold at a crash or the like and then outputs an operational signal to the gas generator. Thus, the gas generator generates the gas rapidly. The gas is then spouted to be  introduced into the inflatable portion  25  through the gas inlet of the tongue  3 . The inflatable portion  25  is rapidly inflated in a long and slender cylindrical shape as a whole. When the gas pressure in the tube  22  is increased to the predetermined gas pressure, the seam  20 a of the above mentioned cover  20  is broken to extrude the tubular knitted textile at the range (B) in a spindle shape. As a result of this, the inflatable portion is formed in a shape as shown in FIG. 7 (c) as a whole. 
     Therefore, the inflation volume of the inflatable portion  25  can be restricted about ⅓ of the inflatable portion without the cover  20  as shown in FIG. 1 which is the same size of the inflatable portion  25 . The gas pressure in the inflatable portion  25  is increased since the amount of the gas generated from the gas generator is the same, so that the above mentioned function as a pre-tensioner is exactly provided. 
     FIG. 8 is a simplified perspective view showing a result of tests using a full-sized dummy D which is for testing the inflation and deployment of the inflatable seat belt apparatus according to the present invention. 
     According to the inflatable seat belt apparatus covered by the cover  20  shown in FIG.  7 (a), the inflatable portion  25  is inflated around a chest of the dummy D as the center thereof. At this stage, at either side of the chest of the dummy D, the apparatus can provide the  a wide area touching the dummy D which is wider by 1.6 times than a seat belt apparatus having a normal webbing  10 . Therefore, the inflatable seat belt apparatus can protect the occupant securely and softly. 
     It should be understood that the seam portion and range for breaking of the cover  20  can be set freely by changing the margin portion for seaming of the cover. 
     As apparent from FIG. 8, the inflatable portion  25  is inflated in the slender cylindrical shape at  across the chest, so that the inflatable seat belt apparatus can restrain a portion between the clavicle and the shoulder and a portion between the waist and the hip of the occupant softly as compared with the normal webbing. 
     The inflatable range of the inflatable portion  25  can be controlled by adjusting the strength for seaming the cover. Thus, the suitable inflation shape and the reduction of the inflatable volume are accomplished. 
     Though the description is made as  in regard to the seaming by the thread for joining the cover in the above description, an adhesive strength can be changed by changing the adhesive surface if the joint is provided by adhesion, or a joint strength is controlled by a mechanical joining member and thereby the same effect can be provided. 
     The description will now be made as regard to alteredModified examples for restricting the inflatable range of the inflatable portion  25  instead of the cover  20 referringwill now be described in reference to FIGS. 9 (a)- 9  (c) and FIG.  10 . 
     FIG. 9 (a) shows the knitted textile member  23  constituted by a tubular knitted textile. The knitted textile member  23  has a stitched portion which are  is hardened by impregnated  impregnation of a resin so as not to expand even if the tube  22  inserted inside thereof is inflated. 
     A resin coating  23 c indicating  with a weak tackiness is provided onto  on the knitted textile member  23  so that the stitches of the knitted textile member  23  can not be expanded when the belt is pulled during normal wearing. As the tube  22  is inflated by the introduced gas and then the gas pressure is applied, the adhesive of the resin coating impregnated into the stitches is broken so that the inflatable portion is inflated promptly. Since the  both side portions  23 a having strong resin coatings are not deformed and remain as they are even when the tube is inflated, only the gas path portion is inflated in a slender cylindrical shape. Also in this altered example, an inflation shape similar to the state shown in FIG. 8 is accomplished. 
     Further, according to the altered example, the inflatable range can be controlled by the knitted fabric per se and the cover  20  can be omitted since the stitches do not expand during normal wearing because of the weak resin coating. 
     FIG. 9 (b) shows an altered example in which the inserted inner belt  21  and the end of the tube  22  made of silicone rubber are welded or glued together to form a gas path  22 G and the tube  22  is inserted into the knitted textile member  23  constituted by a tubular knitted textile so as to construct the inflatable portion  25 . Also in this altered example, an inflation shape similar to the state shown in FIG. 8 is accomplished because an inflation shape of the heat sealed or glued side portion  22 b of the tube  22  is restricted. 
     FIG. 9 (c) shows an altered example in which a reinforcing thread  22 c is wound spirally around the end of the tube made of silicone rubber to restrict the inflation shape of the wound portion. In this altered example, a polyester finished yarn is employed as the reinforcing thread  22 c and is wound around the periphery of the tube  22  with a predetermined pitch and fixed to the surface of the tube by an adhesive or the like. Therefore, the periphery of the tube  22  is not enlarged even when the gas is introduced thereto. 
     At this stage, the inflation shape of the tube  22  can be freely controlled by changing the winding pitch of the reinforcing thread  22 c. 
     Further, the reinforcing thread may not only be wound around the surface of the tube  22  already manufactured but also buried in the tube  22  to be incorporated with the tube  22  as a core during manufacturing. 
     FIG. 10 shows an example that  in which the inflation shape of the inflatable portion  25  is controlled by changing the stitch of the tubular knitted textile as another altered example . 
     FIG. 10 shows an example of a plain stitched knit pattern. In such a knitting structure, the warps  warp threads  23 e are inserted besides the wefts  weft threads at the same intervals as the courses (c) of weft knitted loop  23 d or proper intervals relative to the courses (c) so that the inflation shape in the weft direction is controlled. That is, an expanding amount in the lateral direction of the knitted fabric member  23  is freely controlled by changing the number, pitch, size or type of the warp threads  23 e inserted . 
     It should be understood that the above mentioned method can be applied to another tubular knitted textile such as rib stitch and pearl stitch. 
     The description will now be made as regard to the detailDetails of the fitting structure between the inflatable portion  25  according to the present invention and tongue  3  having the gas inlet referring  will now be described in reference to FIG.  11  and FIG.  12 . 
     FIG. 11 is a perspective view showing a connecting portion between the tongue  3  and the inflatable portion  25 . In FIGS. 11 and 12, the end  25 a of the inflatable portion  25  is fixed to cover an end fitting  31  made of metal which has a flat square section. Furthermore, the end  25 a is fixed firmly by a caulking fitting  32  so as to cover the periphery thereof, so that the inflatable portion  25  is not easily broken away from the end fitting  31 . 
     The end fitting  31  has a tongue pipe  33  secured to the distal end thereof. The tongue pipe  33  is inserted and engaged to the buckle body of the buckle  4  (not shown). The tongue pipe  33  has a gas path  34  formed inside thereof. The gas from gas generating means (not shown) is introduced into the inflatable portion  25  through the gas path  34  and the inside of the end fitting  31 . 
     The tongue  3  is integrally structured by a combination of the end fitting  31 , the caulking fitting  32 , and the tongue pipe  33  in this embodiment. 
     The tongue pipe  33  has a lap belt anchor plate  8  fixed to the bottom part thereof to secure an end  7 a of a lap belt  7  as a normal webbing. 
     FIG. 12 is a longitudinal sectional view showing a fitting structure for the members of the inflatable portion  25  and the tongue  3 . 
     As shown in FIG. 12, the inner belt  21 , the bag filter  26 , the rube  22 , the knitted textile member  23  and the cover  20 , of the inflatable portion  25  are overlapped to the peripheral portion of the end fitting  31  coated by a rubber coating  31 a to tightly touch with  each other. The caulking fitting  32  having an inside coated by a rubber coating  32 a is fixed to the peripheral portion of the inflatable portion. (In FIG. 12, the caulking fitting  32  is separated.). 
     Since the inflatable portion  25  is structured as described above, the inflatable portion  25  is sealingly maintained at the end  25 a thereof and a break off or a breakage of the end fitting  31  is not possible even if the reaction gas having high pressure is rapidly introduced into the inflatable portion  25 . 
     FIGS. 13-15 are explanatory views showing an embodiment of the buckle. The buckle  4  supports fixedly the tongue pipe  33  and has the gas generating means disposed inside thereof to introduce the spouted gas form the gas generating means through the gas path  34  in the tongue pipe  33  to the inflatable portion  25 . 
     The “coupling” between the buckle  4  and tongue  3  is achieved by engaging an annular groove  33 b disposed on the peripheral surface of a distal end of the tongue pipe  33 , to metal balls  47  inserted in respective tapered coupling holes  44 a   44 b formed on the buckle  4 , in which each of the metal balls  47  has a portion projecting from the inner surface of the coupling hole  44 a. 
     In FIG. 13, numeral  41  designates a housing in which a portion of a flange plate  42  is fixed. The buckle  4  is secured to the flange plate  42  which is fixed to the floor of the vehicle (not shown). In the housing  41 , a gas generator  43  as the gas generating means is fixed to the flange plate  42 . The gas generator  43  is firmly connected to a buckle body  44  acting also as a gas passing pipe. 
     FIG. 13 shows a state of coupling the tongue pipe  33  to the coupling hole  44 a. As shown in the figure, when the tongue pipe  33  is coupled to the coupling hole  44 a of the buckle body  44 , a tongue pipe releasing ring  45  is pressed against a biasing force of the spring  46  by the tongue pipe distal end  33 a in a direction of the arrow A. 
     While, theThe tapered holes  44 b are formed on a peripheral surface of the buckle body  44  at predetermined intervals. The metal ball  Each of the metal balls  47  is inserted with allowance for moving from the peripheral surface side of the buckle body  44  to each of the tapered holes  44 b so that the one portion of the  each metal ball  47  projects from the inner surface of the coupling hole  44 a. When the tongue pipe  33  is coupled to the coupling hole  44 a, each of the metal balls  47  is pressed from the peripheral surface side of the buckle body by releasing operation ring  49  biased by a spring  48  in a direction of the arrow B. Therefore, one portion of the  each metal ball  47  projects into the annular groove  33 b disposed on the peripheral surface of the tongue pipe  33  to engage the annular groove  33 b of the tongue pipe  33 , so that the tongue pipe  33  is coupled and fixed inside of the coupling hole  44 a. 
     While, releaseRelease of the tongue pipe  33  is accomplished by pressing a press button  50  disposed on the housing in a direction of the arrow C as shown in FIG.  14 . 
     The press button  50  is an operational button of a non-circular type and has a pressing face  50 a directed toward an upper front position of the housing as shown in FIG.  15 . Therefore, the occupant can operate the button  50  by one action. 
     The description will now be briefly made in regard to aA mechanism offor releasing the tongue  3  from the buckle  4 will now be described in brief. 
     As the press button  50  is pressed in the direction of the arrow C as shown in FIG. 14, a protuberance portion  49 a of the release operational ring  49  is pressed by an operational arm  50 b mounted on the press button  50  in the direction of the arrow C so that the release operational ring  49  slide against a biasing farce  force of the spring  48  in the direction of the arrow C to release the pressure of the metal ball  balls  47  from the release operational ring  49 . Therefore, the metal ball  balls  47 becomesbecome free so as to release the press fixing of the metal ballballs relative to the tubularannular groove  33 b of the tongue pipe  33 . As a result, the tongue pipe releasing ring  45  in the buckle body  44  is biased by a spring  46  in a direction of the arrow D to press out the tongue pipe  33  from the inside of the buckle body  44  and then the tongue  3  is released from the buckle  4 . 
     An embodiment of the second invention is now described referring to FIGS. 16 and 17. 
     FIG. 16 is a sectional view showing a sewing portion of the inflatable portion  25  near the slip guide side corresponding to FIG. 6 of the first embodiment. 
     The end of the tubular knitted textile shown in FIG. 16 is integrally glued to the end  20 d of the cover  20  as in FIG.  6  and is firmly sewed to the predetermined position of the webbing  10 . The end of the tube  22  made of silicone rubber is heat-sealed or glued to the inner belt  21  (it is also  called the inner belt  21 ;  because it is located inside the inflatable portion  25  as in the first invention.).  The inner belt  21  is cut at a portion corresponding to the end  22 a where the tube  22  made of silicone rubber is fixed. In the tube  22 , only the cylindrical bag filter  26  for performing the same function as the bag filter as described in the first invention is accommodated. 
     In the inflatable seat belt apparatus structured in the manner according to the second invention, the inflatable portion  25  is operable as “webbing” at a weak crash which does not causes  cause the gas generating means to work. That is, the inflatable portion  25  is expanded little in the longitudinal direction due to the characteristics of the knitted textile member  23  used therein so that the inflatable portion  25  receives a tensile force of the belt as well as a normal webbing and can restrain the occupant reliably. 
     The inflatable portion  25  is inflated in the proper shape at a crash as in the first invention so as to restrain the occupant for the wider area of the inflatable portion  25 . 
     Furthermore, the inflatable portion  25 , otherwise structured as mentioned above, hasmay have no inner belt  21 , so that the tube  22  made of silicone rubber may be modified as shown in FIGS. 17 (a)-(c). 
     FIG. 17 (a) shows an altered example in which the tube  22  is restricted by heat sealing or gluing except the gas path  22 G. 
     FIG. 17 (b) shows an altered example in which the diameter near the gas inlet is reduced to approximately the same as the diameter of the gas path  22 G, and the reinforcing thread  22 c is then wound around the periphery of the tube  22 . 
     FIG. 17 (c) shows an altered example in which the diameter near the gas inlet is reduced to approximately the same as the diameter of the gas path  22 G, and the thickness of this portion is increased so as not to inflate during the gas introduction.