Abstract:
A connecting structure and method for affixing an open end of a tube composed from thermoplastic resin material(s) to a tube connecting portion of a quick connector having a cylindrical geometry and at least one annular stopper on the cylindrical outer circumference thereof with said tube connecting portion being adapted to be press fitted into said open end of said resin tube. The connecting structure comprises; an annular band composed of elastomeric rubber which surrounds the open end of said resin tube adjacent the location of attachment to said quick connector having a length at least about equal to the diameter of the cylindrical outer circumference of the quick connector and a diameter such that a tightening force is applied to the resin tube upon press fitting said tube connecting portion into the open end of said resin tube to prevent disengagement therefrom. The connecting structure forms an integrated assembly with the tube connecting portion of the quick connector.

Description:
TECHNICAL FIELD  
       [0001]    The present invention relates to a connecting structure for connecting a thermoplastic tube to fluid tube connector, an integrated assembly and method for connecting a resin tube to a fluid tube connector to provide piping for transmitting fluids in an automobile, home water heating systems, or for general industrial purposes. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Automotive fuel tubes, for example, use a rubber hose which is flexible and can be freely bent for connection to a quick connector without relative displacement. Nonetheless a rubber hose is too heavy and is not manageable for this application. It would be preferable to use a resin tube and to connect the resin tube to another tubular body utilizing a quick connector as the coupling joint for fluid delivery therethrough. A quick connector has a tube connecting portion with a cylindrical outer circumference at one end and a retainer means on the other end. The tube connecting portion has an annular stopper adapted for connection to one end of the hose.  
           [0003]    A thick resin tube by itself is not suitable to form a simple connecting structure for use with a quick connector since the only force fitting the resin tube to the tube connecting portion of a quick connector is the stress from the thick resin tube pushing against the tube connecting portion of the quick connector. This stress is not strong enough to hold the resin tube against the force working to pull it out of the tube connecting portion during fluid delivery.  
           [0004]    In the plumbing of radiators or water heating systems, a typical resin tube will require a large diameter to permit the flow of a high pressure fluid or a high temperature fluid. This will promote or generate creep at the resin tube&#39;s connecting end which cancels the tightening force at the connecting end causing the resin tube to fall off easily. Further tightening of the resin tube at the end of the tube connecting portion does not help the resin tube and/or the tube connecting portion to resist the internal high pressure. A tube composed of resin material is therefore not currently desirable for use in the plumbing of radiator and/or heating systems.  
           [0005]    In addition to the plumbing in heating systems, tubes extending from an engine or boiler room which for example, branch into a heater core at the front or rear end utilize a multi-way joint. A resin tube would also provides an unreliable connection for use with a quick connector in these applications as well.  
           [0006]    A known technology for connecting a resin tube to a quick connector is taught in Unexamined Japanese Patent Publication No. 2001-343092 in which the quick connector is bonded to the edge of a resin tube by over injection. To strongly bond a quick connector to a resin tube, the quick connector and resin tube should be made of the same material. Moreover, a resin tube is composed typically of multiple layers with its edge exposing each of the layers. As a result, the over all edge of the resin tube does not bond well to the connector, causing the connector to break or crack at the edge of the resin tube. For example, a resin tube, which is constructed with an outer layer made of heat resistant Nylon 12(PA 12) and an inner layer made of water resistant polypropylene (PP), polyolefin, or fluororesin, has a drawback in that the inner layer does not completely bond to a connector made of Nylon 12(PG 12GF) containing glass fiber. Therefore, many configurations of this type do not provide a reliable connecting structure for a resin tube.  
           [0007]    Another known technology for enhancing the engaging force between a resin tube and a quick connector is taught in Unexamined Japanese Patent Publication No. H04-248095 wherein a male screw portion is formed around the outer circumference of a tube connecting portion of a quick connector for insertion into a connecting end of a resin tube over which is fitted a sealing ring ( e.g. o-ring); screwing the o-ring into the male screw portion and tightening the tube connecting portion.  
           [0008]    Alternately, there is another known technology in which a rubber protector is coated on the outer circumference of a resin tube and the tube connecting portion of a quick connector is press fitted into the resin tube as taught in Unexamined Japanese Patent Publication No. H 11-280958. This configuration will also enhance the engaging force that prevents the resin tube from disintegration and enhances sealing between a resin tube and a connector.  
         PROBLEMS WITH THE PRIOR ART SOLUTIONS  
         [0009]    The configuration in which a male screw portion is formed on the outer circumference of a tube connecting portion in combination with the use of an o-ring requires the tube connecting portion of the quick connector to be thin causing the resin tube connecting structure to have poor reliability. The configuration using a rubber protector coating involves coating the entire resin tube for the purpose of enhancing the heat resistance and fire resistance of the resin tube. This may adversely affect the light weight merit of the resin tube, particularly for a resin tube of large diameter and increases the cost of manufacturing the resin tube.  
           [0010]    The present invention provides a connecting structure for connecting a light weight resin tube to a quick connector with excellent disintegration resistance and consistent sealing performance, and can be manufactured cost effectively. The present invention also provides a method of connecting a light weight resin tube to a quick connector in a cost effective manner.  
         SUMMARY OF THE INVENTION  
         [0011]    One embodiment of the present invention is a connecting structure for affixing an open end of a thermoplastic tubular body (resin tube) to a tube connecting portion of a quick connector having a cylindrical geometry and at least one annular stopper on the cylindrical outer circumference thereof with said tube connecting portion adapted to be press fitted into the open end of said resin tube; said connecting structure comprising: an annular band composed of elastomeric rubber surrounding the open end of the resin tube adjacent the location of attachment to said quick connector, with the annular rubber band having a length equal to about at least the diameter of said cylindrical outer circumference and a diameter such that a tightening force is applied to said resin tube upon press fitting said tube connecting portion into the open end of said resin tube to prevent disengagement therefrom and with said annular rubber band being formed of at least a plurality of elastomeric rubber layers.  
           [0012]    The annular rubber band should preferably be arranged with one end thereof positioned adjacent the open end of the resin tube into which the tube connecting portion is press fitted to form an exposed free end of resin tube. Moreover, it is preferred for the annular rubber band to be of a length such that the opposite end thereof extends longitudinally beyond the end of the tube connecting portion upon being press fitted into said resin tube.  
           [0013]    The annular rubber band may be made of a vulcanized rubber or may be injection molded or extrusion molded utilizing a thermoplastic elastomer with good heat resistance and may be formed by slicing a section from a cylindrical tubular body of such composition. The annular rubber band does not contact the fluid inside the pipe. Further, the annular rubber band is fitted over the resin tube and configured to tighten around the open end of the resin tube when the tube connecting portion of a quick connector is inserted therein thereby preventing the resin tube from disintegration. The annular rubber band may have an inner diameter which is equal to or nearly equal to the outer diameter of the resin tube before the tube connecting portion of the quick connector is press fitted therein and should preferably be longer in length than the outer diameter of the connecting portion of the quick connector by about 2.0 mm or more. The annular rubber band thus tightens the resin tube when the tube connecting portion is inserted therein and increases the engaging force between the resin tube and the tube connecting portion. The stress or pressing force of the annular rubber band does not decrease at a high temperature and/or high pressure even though a fluid at high temperature flows through the resin tube and the tightening force does not mitigate at the connecting end of the resin tube. The connecting structure is adaptable to a resin tube having an inner diameter in a wide range of between 6.0-40 mm and a thickness of 0.5-4.0 mm.  
           [0014]    Another embodiment of the present invention is an integrated assembly comprising: a fluid tube connector having a tube connecting portion of cylindrical geometry and an annular stopper on the cylindrical outer circumference thereof; a thermoplastic resin tube, having an open end through which the tube connecting portion of said fluid tube connector is press fitted to form a tight coupling; and an annular rubber band fitted to the outer circumference of the open end of said resin tube, said annular rubber band having a length equal to at least the diameter of said cylindrical outer circumference and a diameter such that a tightening force is applied to said resin tube adjacent at the open end into which said tube connecting portion has been press fitting to prevent disengagement therefrom.  
           [0015]    To further ensure adequate tightening and accurate sealing of the connecting structure, the outer circumference of the annular rubber band may be further tightened by a clamping means. It is also desirable for the annular rubber band to include a reinforcing layer made of reinforcing threads or a canvas cloth to maintain a good tightening force on the tube connecting portion of the quick connector.  
           [0016]    Yet another embodiment of the present invention is a method for connecting an open end of a resin tube to one end of a tube connecting portion of a quick connector having a cylindrical geometry and an annular stopper on the cylindrical outer circumference thereof, comprising the steps of: inserting the tube connecting portion into the open end of said resin tube to form a tight coupling; and placing an annular rubber band over said resin tube at said open end thereof for tightening said coupling with said annular rubber band having a length equal to at least the diameter of the cylindrical outer circumference and a diameter such that a tightening force is applied to the resin tube at the press fitted end to prevent disengagement.  
           [0017]    The present invention also provides a method of connecting a resin tube to a tube connecting portion of a quick connector having an annular stopper on the cylindrical outer circumference thereof such that one end of the resin tube tightly engages the tube connecting portion comprising the steps of: fitting an annular rubber band on an open end of the resin tube representing the connecting end of said rein tube; enlarging the open end with the annular band fitted thereon; heat softening the connecting end of the resin tube and press fitting the tube connecting portion of the quick connector into the connecting end of the resin tube. The connecting end of the resin tube may have an inner diameter which is about equal to or smaller than the outer diameter of the tube connecting portion before enlargement. The tube connecting portion should preferably be press fitted into the connecting end of the resin tube while the open end thereof is being enlarged. Enlargement of the open end of the resin tube will also enlarge the annular rubber band at the end thereof adjacent the connecting end of the resin tube. Thereafter upon releasing the force applied to enlarge the open end of the resin tube the annular rubber band may shrink. Preferably, the tube connecting portion is quickly press fitted into the connecting end of the resin tube as soon as the force enlarging the open end of the resin tube is released. However, when the force applied to enlarge the open end of the resin tube is released during press fitting the shrinking rate at the open end may be too fast to correctly press fit the tube connecting portion into the resin tube. For this reason it is desirable that the annular rubber band be positioned with one end thereof slightly displaced from the open end of the resin tube to leave a short portion of resin tube exposed, i.e. to form an exposed free end of resin tube relatively small in length. Moreover, it is also preferred that the annular rubber band be of a length such that the end thereof opposite the open end of the resin tube extend longitudinally beyond the end of the tube connecting portion after being press fitted into said resin tube.  
           [0018]    Moreover, it is also desirable for the open end of the resin tube to be enlarged such that the inner diameter thereof becomes 5%-20% larger than the outer diameter of the tube connecting portion before or during press fitting to prevent any entrapment of the annular stopper within the resin tube.  
           [0019]    If the tube connecting portion of the quick connector is first press fitted into the connecting end of the resin tube, a flow of high temperature fluid into the resin tube and quick connector, this will heat soften the connecting end of the resin tube. The high temperature fluid may be any fluid that flows under normal conditions. The softened connecting end of the resin tube will cause the resin tube to conform to the outer circumference of the tube connecting portion under the tightening force of the rubber band over a period of time, i.e. gradually.  
           [0020]    To facilitate press fitting the tube connecting portion should have guiding tapered surface at the longitudinal end thereof. The guiding portion may have an outer diameter which is about equal to or somewhat larger than the inner diameter of the open connecting end of the resin tube. As a result, enlargement of the connecting end of the resin tube begins upon entry of the tapered surface. A large differential elasticity is thus generated on the resin tube at the border defined by the longitudinal end of the tube connecting portion. Any longitudinal vibration or displacement of the resin tube relative to the tube connecting portion causes shifting of the tube connecting portion to centralize stress. Abrasion may also result thereby wearing out the resin tube and the tube connecting portion. For this reason the longitudinal tip of the rubber band should be spaced apart from the longitudinal end of the tube connecting portion to prevent the tip of the tube connecting portion from being displaced upon entry into the resin tube. It is effective that the longitudinal tip of the rubber band be designed to contact or push the enlarged connecting end of the resin tube.  
           [0021]    The connecting structure of the resin tube, integrated assembly and the method of the present invention find their applications in piping for automotive fuels, radiators, heating systems or air conditioning systems. They can also be applied to piping of home water heating systems or a personal hygiene water injection system. For these applications the fluid tube connector (e.g. connector housing or multi-way joint) be made of fluororesin including PA 6, PA 66, poly(phenylenesulfide) (PPS), aromatic Nylon, poly(vinylidenfluoride), and the like, or glass fiber reinforced resin including denatured poly(phenylene ether) (denatured PPE) and acrylonitrile-butadiene-styrene (ABS). Alternatively, the fluid tube connector can be made of metallic materials such as stainless steel, aluminum alloy, or copper as well. The resin tube may be compressed of a single layer member of PA, polyolefin, polyester, liquid polymer, or fluororesin such as PVDF, perfluoroalkoxyalkane (PFA), poly (ethylenetetrafluoride) (ETFE) and the like. Alternately, the resin tube may be a member having multiple layers each made of the above materials.  
           [0022]    The connecting structure for the resin tube, integrated assembly and the method of connecting a resin tube to a fluid tube connector further find their applications in piping for fuel cell cooling, pure water supply, air conditioning, and hydrogen supply. It is desirable that a fluid tube connector for these applications be made of a material whose impurities barely dissolve into water such as stainless, aluminum alloy, PPS, polyethersulfone (PES), polysulfone (PSU), PVDF, polycycloolefin, denatured PPE, or polyetherethylketone (PEEK) and the like. The resin tube may also be a single layer of a material whose impurities barely dissolve into water. Examples of such materials include polyolefin, PPS, polycycloolefin, denatured PPE, PEEK or fluororesin such as PVDF, PFA, ETFE, and the like. Alternately, the resin tube may have a layered structure comprising: an inner layer of any of the above materials; an outer layer of PA or polyolefin; and a middle layer of ethylene-vinyl alcohol copolymer (EVOH).  
           [0023]    A rubber o-ring may be arranged inside the fluid tube connctor of the quick connector. Any material may be appropriate for the o-ring. Nonetheless, desirable materials for use in gasoline piping are those that have low gasoline permeability including fluorinated rubber (FKM), which has a very low gasoline permeability, a copolymer of vinilydenefluoride, perfluoromethylvinylether, tetrafluoroethylene, and olefin bromide e.g. Viton GLT or GFLT: Viton, GLT, and GFLT, perfluoroelastomer, e.g. Kalrez: or fluorosilicone rubber (FVMQ). Effective materials for use in water systems are those that are waterproof and have a low extraction property. An example of such material is ethylene-propylene-diene monomer (EPDM) rubber. As for piping a hydrogen supply, the use of an o-ring made of butyl rubber (IIR) is desirable for its hydrogen barrier performance and low permeability. In this case, two EPDM o-rings should be attached to both longitudinal ends of IIPR o-rings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is a perspective view of the quick connector in the integrated assembly of the present invention.  
         [0025]    [0025]FIG. 2 is a cross section of the quick connector of FIG. 1.  
         [0026]    [0026]FIG. 3 is an enlarged diagram illustrating the tube connecting portion of the quick connector of FIG. 1.  
         [0027]    [0027]FIG. 4 is a perspective view of the retainer in the quick connector of FIG. 1.  
         [0028]    [0028]FIG. 5 is a cross section illustrating the tube body connected to the quick connector.  
         [0029]    [0029]FIG. 6 is a diagram illustrating how a resin tube is connected to the tube connecting portion of the quick connector.  
         [0030]    [0030]FIG. 7 is a diagram illustrating a first embodiment (Structure  1 ) of the resin tube integrated assembly according to the present invention.  
         [0031]    [0031]FIG. 8 is a diagram illustrating a second embodiment (Structure  2 ) of the resin tube integrated assembly according to the present invention.  
         [0032]    [0032]FIG. 9 is a diagram illustrating a third embodiment (Structure  3 ) of the resin tube integrated assembly according to the present invention.  
         [0033]    [0033]FIG. 10 is a diagram illustrating a fourth embodiment (Structure  4 ) of the resin tube integrated assembly according to the present invention.  
         [0034]    [0034]FIG. 11 is a diagram illustrating a fifth embodiment (Structure  5 ) of the resin tube integrated assembly according to the present invention.  
         [0035]    [0035]FIG. 12 is a perspective view of a T-connector for connecting a plurality of resin tubes according to another embodiment of the present invention.  
         [0036]    [0036]FIG. 13 is a plan view illustrating the T-connector.  
         [0037]    [0037]FIG. 14 is a cross section illustrating a resin tube connecting structure of yet another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]    [0038]FIG. 1 is a perspective view of a quick connector adapted to be connected to a resin tube in accordance with the present invention. FIG. 2 is a cross section thereof. FIG. 3 is an enlarged diagram illustrating the tube connecting portion of the quick connector of FIG. 1. FIG. 4 is a perspective view of a retainer adapted to be connected to one end of the quick connector on the side opposite the tube connecting portion.  
         [0039]    Quick connector  1  finds its use in connecting gasoline piping for automobiles and has a cylindrical connector housing  3  with an annular retainer  5  at one end thereof and a tube connecting portion  7  (hereafter “tube connector”) at the opposite end. Connector housing  3 , being made of reinforced Nylon 12(PA12GF30) containing 30 weight % glass fiber, is integrally formed with the tube connector  7  at the longitudinal end (hereinafter referred to as the “first end”) of the housing  3  and a cylindrical retainer holder  9  at the other longitudinal end (hereinafter referred to as the “second end”). Connector housing  3  has a through hole  11  that originates at the first end (tip) and reaches the second (back) end.  
         [0040]    Three annular stoppers are formed on cylindrical outer circumference  13  of tube connector  7 . Each of the stoppers projects outwardly by the same height. As is illustrated in FIG. 3, the outer surface of stopper  15  has a tapered surface  17 , a level cylindrical surface  19 , and a radial plane  21  transversely intersecting the level surface  19 . The tapered surface  17  widens from the first end of cylindrical outer circumference  13  of tube connecting portion  7  toward the second end thereof. Cylindrical surface  19 , which is a short extension from the second end of tapered surface  17  and radial plane  21 , which extends or widens from the second end of cylindrical surface  19  to cylindrical outer surface  13  in a radial direction. Tapered surface  17  provides a guiding tapered surface  25  having a taper edge  23  which continuously widens from the first end toward the second end of tube connecting portion  7  at a constant angle along the tapered surface. The outer diameter of the first end of guiding tapered surface  25  is larger than that of cylindrical outer circumference  13  of tube connecting portion  7 . One annular stopper  27  is located at a longitudinal mid point between annular stopper  15  and annular stopper  29 . The annular stopper  27  and annular stopper  29  each have a tapered surface  31  and a radial surface  33  with the radial surface  33  of each receding abruptly to transversely intersect the cylindrical outer circumference  13  in a radial direction respectively.  
         [0041]    As illustrated in FIG. 1, cylindrical bushing  35  is fitted into the first end of the inner circumference of tube connecting portion  7 . The second end  37  (tip) thereof projects from the first end of tube connection portion  7 . The outer circumference of the first end  37  of cylindrical bushing  35  somewhat extends guiding tapered surface  25  of tube connecting portion  7  toward the first end (outer end) without interruption. The outer diameter of the first end is somewhat smaller than the second end of guiding tapered surface  25  thereof.  
         [0042]    As illustrated in FIG. 2, annular projection  39  is formed on the inner circumference of tube connecting portion  7 . Between annular projection  37  and cylindrical bushing  35  are fitted, for example, a pair of O-rings made of FKM (hereinafter referred to as “FKM O-ring”) with collar  41  therebetween. Another type, FVMQ O-ring  45  is fitted to the second end of annular projection  39  on the inner circumference of tube connecting portion  7 ; annular resin bushing  47  is fitted to the first end of the inner circumference of retainer holder  9 , which is continuously formed on tube connecting portion  7  to prevent FVMQ O-ring  45  from sliding toward the second end.  
         [0043]    Cylindrical retainer holder  9  having a diameter larger than the diameter of tube connecting portion  7  has engagement windows  49 ,  49  of the same structure arranged symmetrically in a radial direction.  
         [0044]    PA retainer  5  is fitted into retainer holder  9 . Retainer  5  has a “C” shaped body (cross section)  55  at points on the second end that are symmetrical in a radial direction, providing a space between circumferential edges  53  and  53  that allow relatively large deformation therein. A pair of arms  57 ,  57  are integrally formed with the second end of body  55  in such a manner that arms  57 ,  57  extend from the points corresponding to hooks  51 ,  51  toward the second end (outer end in the axial direction) at an angle in a radial direction. Operating edge  59 , projecting outward in a radial direction, is provided at the second end of each arm  57 . Engagement slits  63 ,  63  extend circumferentially in a facing manner at the first end (tip)  61  of body  55 : retainer  5  constructed in the above manner has hook  51  to be inserted into engagement window  49  of retainer holder  9  to be locked therein; operating edge  59  is fitted to concavity  65  formed at the second end of retainer holder  9  to be locked therein as well. Hook  51  is then pushed from the second end opening  67  into retainer holder  9  to be further locked therein.  
         [0045]    [0045]FIG. 5 is a cross section illustrating the connection of a tube body  69  into quick connector  1  through the retainer holder  9  at one end of the quick connector.  
         [0046]    The tube body  69  is inserted into the opening  67  of retainer holder  9 , and more specifically from the operating end  59  and locked into retainer  5 . The tube body  69  which may be made of a metallic material has an insertion edge  73  and an annular hook  71  at the first end of the outer circumference thereof. Annular hook  71  is pushed into quick connector  1  or connector housing  3  until it is snapped into slits  63 ,  63  of retainer  5 , where the linkage between tube body  69  and quick connector is sealed by rubber o-rings  43 ,  45 .  
         [0047]    Tube connecting portion  7  of quick connector  1  is 32 mm long with an inner diameter of  29  mm (inner diameter of cylindrical bush  35  and annular hook  39 ): the largest diameter of annular stoppers  15 ,  27 ,  29  is set to 39 mm. The first end  37  of cylindrical bushing  35  extending tube connecting portion  7  toward the first end is 3.0 mm long.  
         [0048]    [0048]FIG. 6 is a diagram illustrating how a resin tube is connected to the connecting portion  7  of the quick connector  1 . FIG. 7 is a diagram illustrating the resin tube integrated assembly of the present invention.  
         [0049]    Resin tube  75  to be connected to tube connecting portion  7  of quick connector  1  is given an outer diameter of 34.5 mm and a thickness of 1.4 mm, and is constructed with a 0.5 mm thick denatured ETFE inner layer and a 0.9 mm PA outer layer containing plastic by 5 weight %, thereby providing a stacked layered structure.  
         [0050]    To connect a resin tube  75  to the connecting portion  7  of the quick connector  1 , a band of vulcanized rubber (hereafter “rubber band”)  79  is fitted to the outer circumference at one end  77  of the resin tube  75  in advance (hereafter “connecting end”) of resin tube  75 . The inner diameter of the connecting end  77  of resin tube  75  is smaller than the outer diameter of cylindrical circumference  13  of tube connecting portion  7  and is also somewhat smaller than the outer diameter of cylindrical bushing  35  at the first end. The rubber band  79  has a plural layered structure comprising: a 2.0 mm thick weather, i.e., humidity, resistant EPDM inner layer  81 ; a 2.0 mm EPDM outer layer  83 ; and a reinforcing layer  85  of PA  66  threads blade-knitted between inner layer  81  and outer layer  83  so that a band is formed which is somewhat longer than the tube connecting portion  7  and will project from the first end  37  of cylindrical bushing  35 . The rubber band  79  has a length larger than the diameter of the tube connecting portion at the outer circumference  13  of between 1 to 1.2 times the tube diameter. For the example shown the band length is between 38 mm and 46 mm and has a diameter of 34.5 mm, and a thickness of 4.8 mm. The rubber band  79  is meshed with the outer circumference about the connecting end  77  of resin tube  75  such that the second end thereof (back end in the shaft direction) is positioned at the connecting end  77  to leave the resin tube  75  with a short exposed free end  87  of e.g. 5 mm in length. Reinforcing layer  85  may be made of canvas cloth.  
         [0051]    The connecting end  77  of resin tube  75  is fitted with the rubber band  79  before the connecting end  77  is enlarged. The connecting end  77  is enlarged by pushing a tapered surface of a flared push plug  89  against the inner surface of connecting end  77  at the opening end thereof such that its inner diameter becomes 5-20% larger than the outer diameter of cylindrical outer circumference  13  of tube connecting portion  7 . The open end at the connecting end  77  is enlarged to the extent that it looks like a funnel, where enlargement begins at the first end rather than the second end of rubber band  79 : enlargement of the open end at the connecting end  77  results in enlargement of the second (back) end of the rubber band  79  adjacent the free end  87  of resin tube  75 . The flare punch plug  89  inserted into connecting end  77  and then withdrawn so that the tube connecting portion  7  of the of quick connector  1  can be immediately pushed into the connecting end  77  of the resin tube  75 . In this way, the open end at the connecting end  77  quickly shrinks and is pressed against the outer circumference of the tube connecting portion  7  with the assistance of the rubber band  79 . The connecting end  77  of resin tube  75  is thus pushed against the outer circumference of tube connecting portion  7 . Note that the flared punch plug  89  may be molded for use as a heating member such that it can heat the opening in the connecting end  77  of resin tube  75  to make it soft.  
         [0052]    As illustrated in FIG. 7, the first end (tip in the shaft direction) of the rubber band  79  extends to the edge adjacent the first end of cylindrical bushing  35  of the tube connecting portion  7 . When the tube connecting portion  7  is press fitted into the resin tube  75  the resin tube  75  may vibrates or may slide with respect to the quick connector  1 . This is minimized by leaving a distance between the rubber band  79  and the first end  37  of tube connecting portion  7  in a range of between 5.0-15.0 mm (e.g. 10 mm).  
         [0053]    An annular channel  91  may be provided on the annularstopper  15  at the first end of tube connecting portion  7  and a FVMQ O-ring  93  may be fitted to annular channel  91  to seal the linkage between the stopper  15  and the resin tube  75  as illustrated in FIG. 8. Alternately, an FKMQ O-ring  93  may be used for the tube. FIG. 8 is a diagram illustrating a second embodiment for connecting quick connector  1  to resin tube  75  utilizing o-ring  93 .  
         [0054]    In place of rubber band  79 , a rubber band  95  may be used having a single EPDM layer of hardness 7 Mohs which is 40 mm long with an inner diameter of 34.5 mm and a thickness of 5.0 mm. The rubber band  95  is fitted to the outer circumference of the connecting end  77  of resin tube  75  in the same manner as was rubber band  79 . FIG. 9 is a diagram illustrating a third embodiment in which the quick connector  1  has the O-ring  93  placed around tube connecting portion  7  before being connected to resin tube  75  with rubber band  95 . Alternately, the quick connector may be used without O-ring  93 .  
         [0055]    Alternately, the outer circumference of rubber band  79  or rubber band  95  may be tightened by a clamping means. FIG. 10 is a diagram illustrating an embodiment utilizing a clamping means, specifically the screw type metallic band  97  having a screw at a longitudinal mid point where stopper  27  is provided on the outer circumference of the rubber band  79 . FIG. 11 employs a screw type metallic band  97  which enhances tightening the mid point where stopper  27  is provided on the outer circumference of rubber band  79 . The screw type metallic band  97  may be used with or without an o-ring  93 . Alternately, a spring type band may be used for the clamping means. Typically, a clamping means is fitted, for example, to resin tube  75  prior to press fitting such that it is tightened after tube connecting portion  7  is press fitted into connecting end portion  77  of resin tube  75  at the connecting end.  
         [0056]    Next, the function of the annular stopper(s) used in the embodiments 1-5 will be described.  
         [0057]    Connector  1  of Comparative Structure  1  was tested without the rubber band  79  tightly fitted therein, and quick connector  1  of Comparative Structure  2  was tested with o-ring  93  fitted to resin tube  75  without a rubber band tightened. The initial pressure resistance and the load required for resin tube  75  to come off were measured. In addition, resin tube  75  was heated at 100° C. for 480 hours and its pressure resistance after aging (hereinafter referred to as the “post aging pressure resistance”) by heat was measured. The results are illustrated in Tables 1 and 2.  
         [0058]    The quick connector [ 1 ] was connected to resin tube [ 75 ], in a pressurizing apparatus for test purposes and water was then pumped through the quick connector [ 1 ] and resin tube [ 75 ]. The water pressure was increased at 7 MPa/min. until the resin tube [ 75 ] burst, when the water pressure was confirmed. The confirmed pressure was determined to be the initial pressure resistance. The destruction mode of resin tube [ 75 ] was also visually inspected. Further, the load required for causing disintegration was measured utilizing a strograph V-10B manufactured by Toyoseiki wherein the quick connector [ 1 ] was fixed thereto and the resin tube [ 75 ] was pulled at 500 mm/min. until it came off. The load at which resin tube  75  came off was determined to be the load that caused disintegration thereof. The post aging pressure resistance for resin tube [ 75 ] was measured in the same manner as the initial pressure resistance was measured.  
                                                                 TABLE 1                                   Example 1   Example 2   Example 3   Example 4   Example 5                                    Initial pressure resistance   1.3   1.5   2.3   1.4   2.2       (MPa)   Disintegration   Disintegration   Breakage   Disintegration   Breakage       Resin tube destruction mode       Load causing disintegration   1.5   1.6   2.5   1.7   2.4       (kN)       Post aging pressure resistance   1.5   1.6   2.5 1.6   2.6       (MPa)   Disintegration   Disintegration   Breakage   Disintegration   Breakage       Resin tube destruction mode                  
 
         [0059]    [0059]                                         TABLE 2                                   Comparative   Comparative           Example 1   Example 2                                    Initial pressure resistance (MPa)   0.7   1.0       Resin tube destruction mode   Disintegration   Disintegration       Load causing disintegration (kN)   0.6   1.1       Post aging pressure resistance (MPa)   0.4   0.8       Resin tube destruction mode   Disintegration   Disintegration                    
         [0060]    The integrated structures (hereinafter referred to as “Examples”) 1-5 provided good sealing performance for the quick connector  1  and resin tube  75  in all categories, specifically, the initial pressure resistance, the load required for causing disintegration, and the post aging pressure resistance. In the Comparative Structures (hereinafter referred to as the “Comparative Examples”) 1 and 2, the post aging pressure resistance is lower than the initial pressure resistance. However, in Examples 1-5, the post aging pressure resistance is higher than the initial pressure resistance. It is inferred that in the integrated structures of Comparative Examples 1 and 2, the tightening stress mitigates at connecting end portion  77  of tube connecting portion  7  of resin tube  75 ; in the integrated structures of Examples 1-5, the connecting end  77  of the resin tube  75  was softened by heating so that it conforms to the peaks and valleys of tube connecting portion with the assistance of tightening of connecting end  77  utilizing the rubber band  79 . Examples 1, 2, 4, and 5 demonstrated nearly identical performance in all categories, specifically, initial pressure resistance, load required for causing disintegration, and post aging pressure resistance. Rubber bands  79  and  95 , having good pressure resistance, thus, provide excellent sealing performance even though a highly gasoline or fluid resistant but expensive O-ring  93  is not provided to tube connecting portion  7  of quick connector  1 . Elimination of O-ring  93  provides advantages including (1) reduction in manufacturing cost of a quick connector; (2) elimination of the enlargement step for connecting end portion  77  of resin tube  75 , which is required for preventing o-ring  93  from damage during press fitting; and (3) elimination of a thin portion at the connecting end of connecting end portion  77  thereof, which makes O-ring  93  susceptible to breakage. In addition, even if O-ring  93  is used in Examples 1, 2, 4, and 5, and is damaged, these structures prevent resin tube  75  from fluid leakage by taking advantage of the complete coverage of O-ring  93  by resin tube  75 .  
         [0061]    [0061]FIG. 12 is a perspective view of a T-connector [ 97 ] adopted for the integrated structure of another embodiment of the present invention. FIG. 13 is a plan view of the T-connector [ 97 ].  
         [0062]    T-connector  97  finds applications in automotive heating systems for example. Being made of reinforced Nylon 66 (PA 66 GF 30 ) containing 30 weight % glass fiber, T-connector  97  is integrally formed with: a cylindrical first tube connecting portion  99  (tube connecting portion) at the first end; a cylindrical second tube connecting portion  101  (tube connecting portion) at the second end; a joint  103  provided between first tube connecting portion  99  and second tube connecting portion; and a cylindrical third tube connecting portion  105  (tube connecting portion) connected to joint  103  in such a manner that third tube connecting portion  105  is perpendicular to the plane that is parallel to the shaft direction of first tube connecting portion  99  and second tube connecting portion  101 . Through holes  107 ,  109 , and  111  of each first tube connecting portion  99 , second tube connecting portion  101 , and third tube connecting portion  105  merge into joint  103 .  
         [0063]    Cylindrical outer circumference  113  of first tube connecting portion  99 , cylindrical outer circumference  115  of second tube connecting portion  101 , and cylindrical outer circumference  117  of third tube connecting portion  105  each have two annular stoppers in the shaft direction putting a space therebetween, wherein the two stoppers stick out by the same or about the same height.  
         [0064]    Stopper  119 , provided at the first (front) end of cylindrical outer circumference  113  on first tube connecting portion  99 , has an outer surface defined by a tapered surface  121  widening from the first end to the second (back) end of cylindrical outer surface  113  of first tube connecting portion  99 ; a cylindrical surface  123 , which is a cylindrical short extension from the second end of tapered surface  121 ; and a radial surface, which is an extension toward first tube connecting portion  99  in a radial direction. Tapered surface  121  provides a guiding tapered surface  127  utilizing taper edge  129  which continuously widens from the first end toward the second end of first tube connecting portion  99  at a constant angle. The outer diameter of the first end (tip) of guiding tapered surface  129  is smaller than that of cylindrical outer circumference  113  of first tube connecting portion  99 . Stopper  131 , provided at the second end, has an outer surface defined by a tapered surface  133  widening from the cylindrical outer surface  113  toward the second end in a tapered manner; cylindrical surface  135 , which is a cylindrical short extension from the second end of tapered surface  133 ; and a radial surface  137 , which is an extension from the second end of cylindrical surface  135  toward cylindrical outer circumference  113 . Stopper  139 , provided at the second end of cylindrical outer circumference  101  of second tube connecting portion  101 , has an outer surface defined by a tapered surface  141  widening from the second end of cylindrical outer circumference  115  of second tube connecting portion  101  to the first (back) end; a cylindrical surface  143 , which is a cylindrical short extension from the first end of tapered surface  141 ; and a radial surface  145 , which is an extension from the first end of cylindrical surface  143  to cylindrical outer circumference  115  in a radial direction. Tapered surface  141  provides a guiding tapered surface  149  utilizing taper edge  147  which continuously widens from the second end of second tube connecting portion  101  at a constant angle. The outer diameter of the first end (tip) of guiding tapered surface  149  is smaller than that of cylindrical outer circumference  115  of second tube connecting portion  101 . Stopper  151  at the second end has an outer surface defined by a tapered surface  153  continuously widening from cylindrical outer circumference  115  toward the first end in a tapered manner; a cylindrical surface  155 , which is a cylindrical short extension from the first end of tapered surface  153 ; and a radial surface  157 , which is an extension from the first end of cylindrical surface  155  to cylindrical outer circumference  115  in a radius direction. Stopper  159 , provided at the tip of cylindrical outer circumference  117  of third tube connecting portion  105 , has an outer surface defined by a tapered surface  161  continuously widening from the tip of cylindrical outer surface  117  of third tube connecting portion  105  to the back end; a cylindrical surface  163 , which is a cylindrical short extension from the back end of tapered surface  161 ; and a radial surface  165 , which is an extension from the back end of cylindrical surface  163  to cylindrical outer circumference  117  in a radial direction. Tapered surface  161  provides a guiding tapered surface  169  utilizing taper edge  167  which continuously widens from the tip of third tube connecting portion  105  toward the back end thereof at a constant angle. The outer diameter at the tip of guiding tapered surface  169  is smaller than that of cylindrical outer circumference  117  of third tube connecting portion  105 . Stopper  171 , provided at the back of cylindrical outer circumference  117  on third tube connecting portion  105 , has an outer surface defined by a tapered surface  173  widening from cylindrical outer circumference  117  toward the back end in a tapered manner; a cylindrical surface  175 , which is a cylindrical short extension from the back end of tapered surface  173 ; and a radial surface  177 , which is an extension from the back end of cylindrical surface  175  to cylindrical outer circumference  117  in a radial direction.  
         [0065]    [0065]FIG. 14 is a diagram illustrating the connection structure of the resin tube of another embodiment of the present invention.  
         [0066]    Each of first tube connection portion  99  and second tube connection portion  101  of T-connector  97  is 30 mm long and has an inner diameter of 15 mm. Annular stoppers  119 ,  131 ,  139 , and  151  have a maximum diameter of 21 mm. Third tube connecting portion  105  is 30 mm long and has an inner diameter of 11 mm. Annular stoppers  159 ,  171  have a maximum diameter of 17 mm. Each of first tube connecting portion  99 , second tube connecting portion  101 , and third tube connecting portion  105  is connected to a resin tube. Resin tube  179  to be connected to first tube connecting portion  99  and second tube connecting portion  101  has an outer diameter of 18 mm and a thickness of 1.5 mm, and has a stacked layer structure comprising: a 0.7 mm thick polypropylene (PP) inner layer; a 0.7 mm thick PA  12  outer layer containing 5 weight % plastic; and a 0.1 mm thick acid denatured PP middle layer. Resin tube  181  to be connected to third tube connecting portion  105  has an outer diameter of  14 . 4  mm and a thickness of 1.2 mm, and has a stacked layer structure comprising: a 0.5 mm thick PP inner layer; a 0.6 mm thick PA 12 outer layer containing 5 weight % plastic; and a 0.1 mm thick acid denatured PP middle layer.  
         [0067]    When resin tube  179  is connected to first tube connection portion  99  and second tube connecting portion  101  of T-connector  97 , vulcanized rubber band  185  is fitted to the outer circumference of connecting end  183  of resin tube  179  in advance. The inner diameter of connecting end  183  of resin tube  179  is smaller than the outer diameter of cylindrical outer circumferences  113 ,  115  of first tube connecting portion  99  and second tube connecting portion  101 , and somewhat smaller than the outer diameter of first tube connecting portion  99  and second tube connecting portion  101 , or that of the tip of guiding tapered surface  129 ,  149 . Rubber band  185  has a stacked structure comprising: a 1.5 mm thick weather sic, humidity resistant EPDM inner layer  187 ; a 1.5 mm thick EPDM outer layer  189 ; and a 1.5 mm inner layer  187 ; and a 1.5 mm reinforcing layer  191  of blade-knitted PA 66 threads being sandwiched between inner layer  187  and outer layer  189  to make a band 40 mm long (somewhat longer than first tube connecting portion  99  and second tube connecting portion  101  ) having an inner diameter of 18 mm, and a thickness of 3.6 mm. Rubber band  185  is further fitted to the connecting end  183  of resin tube  179  such that the back end thereof is positioned somewhat before the open end of connecting end  183 . For this reason, open end portion  193  of connecting end  183  of resin tube  179  is exposed by 5.0 mm, for example. In the same manner, resin tube  181  is connected to third tube connecting portion  105  of T-connector  97 ; vulcanized rubber band  197  is fitted to the outer circumference of connecting end  195  of resin tube  181  in advance. The inner diameter at connecting end  195  of resin tube  181  is smaller than the outer diameter of cylindrical outer circumference  117  of third tube connecting portion  105  and somewhat smaller than the outer diameter of third tube connecting portion  105  or the outer diameter of the tip of guiding tapered surface  169 . Rubber band  197  has a stacked structure comprising: a 1.5 mm thick weather sic, humidity resistant EPDM inner layer  199 ; a 1.5 mm thick EPDM outer layer  201 ; and a 1.5 mm inner layer  199 ; and a 1.5 mm reinforcing layer  203  of blade-knitted PA 66 threads being sandwiched between inner layer  199  and outer layer  201  to make a band 40 mm long (somewhat longer than third tube connecting portion  103  ) having an inner diameter of 15 mm and a thickness of 3.6 mm. Rubber band  197  is further fitted to connecting end  195  of the outer circumference of resin tube  181  such that the back end is positioned somewhat before the open end of connecting end  195 . For this reason, open end portion  205  at connecting end  195  of resin tube  181  is exposed by 5.0 mm, for example. The reinforcing layer  203  may be made of a canvas cloth.  
         [0068]    Resin tubes  179 ,  181  are connected to first tube connecting portion  99 , second tube connecting portion  101 , and third tube connecting portion  105  at the outer circumference being locked therein in the same manner as quick connector  1  and resin tube  77 . The longitudinal tip of rubber band  185 ,  197  are extended to a point somewhat before or outside the tip of first tube connecting portion  99 , second tube connecting portion  101 , and third tube connecting portion  105  to touch the outer circumference of resin tube  179 ,  181  whose diameter is enlarged before the tip thereof. The space between the first end (tip) of rubber band  185  and the first end of first tube connecting portion  99 , and the first end of second tube connecting portion  101  is within a range of 5.0 mm-15 mm (e.g. 10 mm). The space between the tip of rubber band  197  and the tip of third tube connecting portion  105  is also within a range of 5.0 mm-15 mm (e.g. 10 mm). In place of rubber band  185 ,  197 , another EPDM single layer (hardness 70 Hs) rubber band of 40 mm long having an inner diameter of 18 mm and a thickness of 4.0 mm with excellent weather [sic, humidity] resistance may be used. Alternately, a rubber band of 40 mm long having an inner diameter of 18 mm and a thickness of 4.0 mm may be used.  
         [0069]    Rubber band  185 ,  197  may be tightened at the outer circumference utilizing a clamp means such as a spring type metallic band or a screw type metallic band.  
         [0070]    The outer circumferences of resin tubes  179 ,  181  are pressed against peaks and valleys of first tube connecting portion  99 , second tube connection portion  101 , and third tube connection portion  105  at the point of use, causing conformation to the structure of this embodiment. T-connector tube  97  and resin tube  179 ,  181  are thus sealed very well. The resin tube connecting structure of finds applications in water system piping as well.  
       ADVANTAGEOUS EFFECTS OF THE INVENTION  
       [0071]    As described above, the connecting structure or method for a resin tube of the present invention provides a thin and light weight resin tube with excellent disintegration resistance and sealing performance in a cost effective manner, which is suited to high temperature and high pressure fluid applications.  
       REFERENCE SYMBOLS  
       [0072]    [0072] 1  quick connector  
         [0073]    [0073] 7 ,  99 , 101 ,  105  tube connecting portion  
         [0074]    [0074] 13 ,  113 ,  115 ,  117  cylindrical outer circumference  
         [0075]    [0075] 15 , 27 , 29 , 119 , 131 , 139 ,  151 , 159 , 171  stopper  
         [0076]    [0076] 75 ,  179 ,  181  resin tube (thermoplastic resin tube)  
         [0077]    [0077] 77 ,  183 ,  195  connecting end  
         [0078]    [0078] 79 ,  95 ,  185 ,  197  rubber band (rubber resilient band)  
         [0079]    [0079] 97  T-connector