Patent Publication Number: US-2005127668-A1

Title: Gas impermeable tube joint and method of forming same

Description:
BACKGROUND  
      This invention relates to the joining of tubes to other components in fluid systems. More specifically, this invention relates to gas impermeable tube joints and methods for forming gas impermeable tube joints in fluid systems.  
      In general, fluid systems serve to contain a fluid (e.g., a liquid, vapor, gas) as it is transported from one location to another. Fluid systems typically include a number of components interconnected by one or more tubes, which transport the fluid between the components. The components and tubes are connected together by joints, which allow the fluid to flow between the components and tubes while preventing leakage of the fluid from the system.  
      For certain fluid systems, it is important to prevent the infiltration or escape of the fluid in its gaseous state. One such fluid system, for example, is a fuel fill system in a motor vehicle, through which fuel is delivered to a storage tank. The escape of fuel vapor from fuel fill systems can be hazardous to the environment, and as a result, the U.S. Environmental Protection Agency prescribes limits to the amount of fuel vapor that may escape from the filler pipe. Another example of such a fluid system, is a radiant heating system found in homes and businesses. Often times hoses in a radiant heating system supply water or other heating fluid to heat exchangers located in floors, ceilings, roofs, and concrete or asphalt slabs. The hoses may be embedded in the surfaces to be heated. A significant problem with such hoses is that they are subject to gas infiltration and exfiltration. Oxygen is particularly troublesome because it is able to penetrate all known plastic films, at least to some small degree. Once oxygen has gained entry to such a heating system, it deteriorates the hoses and corrodes the pumping system. These are only a few examples of systems requiring gas impermeable tube joints and there are myriad fluid systems for which the prevention of the infiltration or escape of gas is critical to operation.  
      One way to reduce the infiltration or escape of gas in a fluid system is through the use of tubes having metallic barrier layers. For example, U.S. Pat. No. 6,074,717 to Little et al., describes a flexible hose that has an aluminum barrier layer for preventing ingestion of oxygen and other gasses. The aluminum barrier layer is securely bonded between two adhesion tubes which are vulcanized in place against the aluminum. The resulting tube is flexible and substantially gas impermeable. While such tubing is sufficiently gas impermeable to prevent the permeation of gas along the tube, the joints between tubes and components remain an area where the infiltration or escape of gas can occur.  
      Typically, the joints in such fluid systems are formed by sliding the tube over a projection on the component, and securing the tube in-place by way of a barb formed on the projection and/or a mechanical fastener (e.g., a hose clamp). Problematically, this method may allow for the permeation of gas through the joint connection. If the tube has a metallic layer, the permeation may be worse because of the relative inflexibility of the tube material and the resulting inability of the tube to form a tight fit with the projection.  
      Thus, there is a need for gas impermeable tube joints and methods for forming gas impermeable tube joints in fluid systems.  
     BRIEF SUMMARY OF THE INVENTION  
      The above-described and other drawbacks and deficiencies of the prior art are overcome or alleviated by a method of forming a gas impermeable joint in a fluid system. The method includes: providing a tube having a metallic barrier layer disposed between an inner plastic layer and an outer plastic layer; forcing at least one of the inner plastic layer and the outer plastic layer into contact with a plastic surface of a component; and welding the at least one of the inner plastic layer and the outer plastic layer with the plastic surface to form the gas impermeable joint. The welding may include: spin welding, hot plate welding, vibration welding, and ultrasonic welding.  
      In one embodiment, the component includes a recess disposed therein, the recess being dimensioned to receive an end of the tube, and the plastic surface of the component being formed within the recess to contact at least one of the inner plastic layer and the outer plastic layer. In another embodiment, the component includes a cylindrical protrusion, the plastic surface being formed on either the outer circumference or the inner circumference of the cylindrical protrusion.  
      The thickness of the inner plastic layer and the outer plastic layer before welding is preferably greater than about 0.6 millimeters, and more preferably greater than about 1 millimeter. The thickness of the inner plastic layer and the outer plastic layer before welding may be between about 0.6 millimeters and 1.5 millimeters, and more preferably between about 1 millimeter and 1.2 millimeters.  
      The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings wherein like elements are numbered alike, and in which:  
       FIG. 1  is a partial cross-sectional view of a portion of a fluid system including a gas impermeable tube joint in accordance with an embodiment of the present invention;  
       FIG. 2  is a perspective view of a tube having a metallic barrier layer;  
       FIG. 3  is a partial cross-sectional view of an end of the tube separated from the component before welding;  
       FIG. 4  is a partial cross-sectional view of an end of the tube forced onto the component before welding;  
       FIG. 5  is a flow chart depicting a method of forming the gas impermeable joint;  
       FIG. 6  is a flow chart depicting an alternative method of forming the gas impermeable joint;  
       FIG. 7  is a cross-sectional view of the end of the tube separated from the component showing various dimensions of the tube and the component;  
       FIG. 8  is a partial cross-sectional view of an end of the tube forced onto the component before welding in accordance with a first embodiment of the invention;  
       FIG. 9  is a partial cross-sectional view of an end of the tube forced onto the component before welding in accordance with a second embodiment of the invention;  
       FIG. 10  is a partial cross-sectional view of an end of the tube forced onto the component before welding in accordance with a third embodiment of the invention;  
       FIG. 11  is a partial cross-sectional view of an end of the tube forced onto the component before welding in accordance with a fourth embodiment of the invention;  
       FIG. 12  is a cross-sectional view of a first alternative arrangement of the tube and component before welding;  
       FIG. 13  is a cross-sectional view of a second alternative arrangement of the tube and component before welding;  
       FIG. 14  is a cross-sectional view of a third alternative arrangement of the tube and component before welding;  
       FIG. 15  is a cross-sectional view of a fourth alternative arrangement of the tube and component before welding;  
       FIG. 16  is a cross-sectional view of a fifth alternative arrangement of the tube and component before welding; and  
       FIG. 17  is a cross-sectional view of a sixth alternative arrangement of the tube and component before welding. 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is a partial cross-sectional view of a portion of a fluid system  10  including a gas impermeable tube joint  12 . The fluid system  10  includes a tube  14  having an end coupled to a component  16  via the joint  12 , which allows fluid to be communicated between the tube  14  and the component  16  as indicated by arrow  17 . The component  16  may be any component in the fluid system  10  such as, for example a pump, funnel, tank, heat exchanger, valve, tube-to-tube coupling, flange, quick disconnect coupling, filter, and the like. For example, component  16  may be a funnel used within a fuel fill system in a motor vehicle, as described in commonly owned U.S. patent application Ser. No. ______ to Swane (Attorney Docket No. 02-13), filed concurrently herewith and entitled “Fuel Fill System”, which is incorporated by reference herein in its entirety. The component  16  may also be another tube. It will be appreciated that the fluid system  10  may include any number of joints  12  connecting tubes  14  to components  16 .  
      Referring to  FIGS. 1 and 2 , the tube  14  is formed by a metallic barrier layer  18  disposed between an inner plastic layer  20  and an outer plastic layer  22 . The metallic barrier layer  18  extends along the entire length of the tube  14 . The joint  12  is formed by welding at least one of the inner plastic layer  20  and the outer plastic layer  22  to a plastic surface formed on the component  16 . As will be discussed in further detail hereinafter, the weld may be performed using spin welding, hot plate welding, vibration welding, ultrasonic welding, and the like. Advantageously, because the weld is formed with the outer and/or inner plastic layers  20 ,  22  of the tube  14 , the metallic barrier layer  18  extends substantially to the component  16 , thus improving the gas impermeability of the joint  12  between the tube  14  and the component  16 . The joint  12  is also lightweight and corrosion resistant.  
      The inner and outer plastic layers  20 ,  22  of the tube  14  may be formed from any thermoplastic material. For example, the inner and outer plastic layers  20 ,  22  may be formed from polyethylene, polypropylene, acetals, nylons, fluoropolymers, rubbers, and combinations, composites, or multiple layers of any of the foregoing. The metallic layer  18  may be formed from any metal in sufficient quantity to prevent permeation of gas into or out of the system  10 . Preferably, the metallic layer  14  is formed from a malleable metal such as aluminum, steel, tin, copper, brass, or combinations or alloys formed from one or more of the foregoing.  
      One example of a tube  14  that may be used with the present invention is described in U.S. Pat. No. 6,074,717, which is incorporated by reference herein in its entirety. The &#39;717 patent describes a tube wherein the inner plastic layer  20  is formed by a first tube, the metallic barrier  18  is formed by an aluminum foil bonded exteriorly about the first tube, and the outer plastic layer  22  is formed by a second tube bonded exteriorly about the aluminum foil. The aluminum foil may be between about 0.0005 and 0.030 inches thick. The first tube and the second tube (i.e., inner and outer plastic layers  20 ,  22 ) each comprise about 20 percent by weight of ethylene propylene diene polymethylene (EPDM) rubber and from about 2 to 9 percent by weight of polybutadiene-maleic anhydride adduct resin. The formulation preferably includes about 2-8 percent by weight of active peroxide as a curing agent. The peroxide cure is performed in any conventional manner at a temperature of about 325° F., and provides a strong bond between the aluminum metallic barrier layer  18  and the inner and outer layers  20 ,  22 . Suitable conventional black and non-black filler ingredients, and paraffinic or naphthenic plasticizers may be added to the mixture as desired. In addition, one or more reinforcement layers (not shown) may be added to the outer surface of the outer plastic layer  22 . The reinforcement layer may be fabricated from, for example, rayon, polyester, polyvinyl acetate, wire, aramid, or any other suitable material. The reinforcement layer may also include a cover selected from any of numerous thermosetting elastomeric compounds such as natural rubber, styrene butadiene, polychloroprene, acrylonitrile butadiene, chlorosulfonated monomer, or chlorinated polyehtelene. Where the outer plastic layer  22  is used to form the weld, a portion of the reinforcement layer will be removed to expose the outer plastic layer  22  for welding.  
      Referring to  FIG. 3 , the tube  14  and component  16  are shown separated, before welding. In the embodiment shown, the component  16  includes a generally cylindrical inner protrusion  26  and a coaxial, generally cylindrical outer protrusion  28 . An annular recess  30  is formed between an outer surface  32  of the inner protrusion  26  and an inner surface  34  of the outer protrusion  28 . The annular recess  30  is dimensioned to receive an end of the tube  14 , as shown in  FIG. 4 . The inner and outer surfaces  32 ,  34  may be angled relative to each other such that the end of the tube  14  becomes wedged within the recess  30  when forced therein. A relief cut  36  may be provided at the inlet end of the annular recess  30  to ease insertion of the end of the tube  14  into the recess  30 .  
      The component  16  may be molded from a plastic material such that one or more of the surfaces  32 ,  34  form the one or more plastic surfaces to which the tube is welded. Alternatively, the plastic surfaces  32  and/or  34  may be formed by inserts secured to the component  16 .  
       FIG. 5  is a flow chart depicting a method  50  of forming the gas impermeable joint  12  of  FIG. 1 . Referring to  FIGS. 1-5 , the method  50  can be described. With the tube  14  separated from the component  16 , as shown in  FIG. 3 , the tube  14  is secured in a fixture  38  with the end of the tube  14  facing the component  16  (block  52  of method  50 ). The fixture  38  may be a chuck disposed on the outside of the tube  14 , a chuck disposed inside the tube  14 , or a combination of both. Preferably, the inner and outer protrusions  26 ,  28  of the component  16  are sufficiently rigid such that they need not be held by a chuck. However, where the component is a tube or where the inner and outer protrusions  26 ,  28  are not rigid, the inner and outer protrusions  26 ,  28  may also be secured by a separate chuck. Next, the tube  14  is forced onto the component  16  such that at least one of the inner plastic layer  20  and the outer plastic layer  22  come into contact with a plastic surface  32  and/or  34  of the article  16  (block  54 ). In the embodiment shown, the outer plastic layer  22  contacts the inner plastic surface  34  and the inner plastic layer  20  contacts the outer plastic surface  32 . The inner and/or outer plastic layers  20 ,  22  are then moved relative to the plastic surface(s)  32 ,  34  to create frictional heat (block  56 ). The relative motion may be created by spinning, vibration, ultrasound, or any other convenient method which results in melting of the inner and/or outer plastic layers  20 ,  22  and the plastic surface(s)  32 ,  34 . After the layers  20 ,  22  and surfaces  32 ,  34  have melted, the relative motion is stopped and the tube  14  and component  16  are held stationary to allow the melted plastics to bond and form a weld (block  58 ). The joined tube  14  and component  16  are then removed from the fixture  38  (block  60 ).  
       FIG. 6  is a flow chart depicting an alternative method  70  of forming the gas impermeable joint  12 . Unlike the method  50  of  FIG. 5 , which uses a frictional method of generating heat, the method  70  of  FIG. 6  uses an external source of heat to melt the plastic. In the method  70  of  FIG. 6 , an external source of heat (e.g., a hot plate) is applied to the one or more plastic surface  32  and/or  34  on the article  16  and to the inner and/or outer plastic layers  20 ,  22  to melt each of these surfaces (block  72  of method  70 ). The external source of heat is then removed (block  74 ) and the melted inner and/or outer layers  20 ,  22  are forced against the melted plastic surface(s)  32 ,  34  of the component  16 . The component  16  and tube  14  are held stationary to allow the melted plastics to bond and form a weld (block  78 ), after which the tube  14  and component  16  are removed from the fixture  38  (block  80 ). The method  70  of  FIG. 6  may be used instead of the method  50  of  FIG. 5 , for example, where the plastic material used in the inner and/or outer plastic layers  20 ,  22  has a substantially different melting temperature than that of the plastic surfaces  32 ,  34  on the article  16 . The method  50  of  FIG. 5  requires that the melting temperature of the materials used in the inner and/or outer plastic layers  20 ,  22  and the plastic surfaces  32 ,  34  have a melting temperature that is sufficiently the same (e.g., within 20° F.) so that all of the materials forming the weld are melted by the friction welding process.  
       FIG. 7  is a cross-sectional view of the end of the tube  14  separated from the component  16  showing various dimensions of the tube  14  and the component  16 . The outside diameter (O.D.) and inside diameter (I.D.) of the tube  14  are selected based on the particular application of the tube  14  and component  16 . It has been determined that to provide sufficient material to form a weld, the inner and outer plastic layers  20 ,  22  forming the weld preferably each have a thickness “t” greater than about 0.6 millimeters (about 0.024 inches), and more preferably greater than about 1 millimeter (about 0.039 inches). The maximum thickness “t” of the one or more plastic layers  20 ,  22  forming the weld is determined based on the requirements of the system  10  (e.g., pressure requirements, temperature requirements, and the like). However, as a practical limit to provide for the flexibility of tube  14 , each plastic layer  20  and/or  22  forming the weld may have a thickness “t” less than about 3 millimeters (about 0.12 inches).  
      The recess  30  has a depth “d”, which is the effective depth of the weld. As a result, the depth “d” of the recess may be used to control the strength of the joint  12  ( FIG. 1 ) as needed to meet system  10  requirements.  
      The width “w” of the recess, as well as the outside diameter of the inner protrusion  26  and the inside diameter of the outer protrusion  28 , may be selected in relation to the dimensions of the tube  14  to determine which of the surfaces  32 ,  34  and layers  20 ,  22  form the weld. For example, these various dimensions may be selected such that the inner plastic layer  20  contacts the outer surface  32  of the inner protrusion  26 , and the outer plastic layer  22  contacts the inner surface  34  of the outer protrusion  28 , as shown in  FIG. 8 . As a result, both the inner and outer plastic layers  20 ,  22  will form the weld with the component  16 . In one example of this embodiment, the depth “d” of the recess may be about four times the total thickness “T” of the tube, with the width “w” of the recess being about 0.01 inch less than the total thickness “T”. Preferably, the surfaces  32  and  34  are angled relative to each other to provide an included angle of about 1° to about 3°. Where the surfaces  32  and  34  are angled, the width “w” represents the minimum width of the channel.  
       FIG. 9  depicts an embodiment where the weld is formed only between the outer plastic layer  22  and the inner surface  34  of the outer protrusion  28 . In this embodiment, the inner protrusion  26  provides internal support to the tube  14 , but is not welded to the tube  14 . It is contemplated that the component  16  may be formed without the inner protrusion  26 , such that the recess  30  is formed only by the inner surface  34 .  
       FIG. 10  depicts an embodiment where the weld is only formed between the inner plastic layer  20  and the outer surface  32  of the inner protrusion  26 . In this embodiment, the outer protrusion  28  provides external support to the tube  14 , but is not welded to the tube  14 . It is contemplated that the component  16  may be formed without the outer protrusion  28 , such that the recess  30  is formed only by the outer surface  32 .  
       FIG. 11  depicts another embodiment where the weld is formed as a butt weld between the tube  14  and the component  16 . In this embodiment, the plastic surface is formed on a face  80  of the component  16 , and the weld is formed between both the inner and outer layers  20 ,  22  and the face  80 .  
       FIGS. 12-17  depict various arrangements of the tube  14  and component  16  that may be used in forming the joint  12  of the present invention. These arrangements have been found to be especially well suited for use where the tube  14  and component  16  are joined by spin welding.  FIGS. 12-17  depict the tube  14  and component  16  just before welding, when the tube  14  is forced against the component  16 . In each of  FIGS. 12-14 , the weld is formed on the inner and outer layers  20  and  22  of the tube  14 . Unlike the straight-walled tube  14  used in the embodiment described with reference to  FIGS. 7 and 8 , the end of the tube  14  used in the arrangements of  FIGS. 12-14  is shaped to have an included angle “F” between the contact surface “C” of the inner layer  20  and the contact surface “D” of the outer layer  22 . The included angle “F” is preferably between about 20° to about 40°, and more preferably between about 25° to 30°. The arrangements of  FIGS. 12-14  are also shown to include various shoulders  82  disposed on the tube  14 .  
      In  FIGS. 12-14 , the total thickness of the tube  14  is indicated at “T”, and the welded surface is indicated by the sum of the contact surface on the inner layer  20 , indicated at “C”, and the contact surface on the outer layer  22 , indicated at “D”. Preferably, the welded surface (C+D) is equal to about 1.5×T to about 3.5×T, and more preferably between about 1×T to  2 ×T. As discussed above, the welded surface may be increased or decreased depending on the required strength of the weld, among other variables. The depth of the weld, as indicated at “A”, is preferably between about 0.3×T to about 10.0×T, and more preferably between about 0.5×T to about 0.8×T.  
      Each of the arrangements in  FIGS. 12-14  includes a shoulder  82  protruding radially outward around the circumference of the outer plastic layer  22  of the tube  14 . With the tube  14  and component  16  forced together prior to welding, the shoulder  82  is preferably separated from the outer protrusion  28  by a distance “E”, which is preferably equal to the depth of the weld “A” plus about 0.01 inch. The shoulder  82  prevents the tube  14  from extending within the component  16  substantially beyond the depth of the weld, “A”.  
      The shoulder  82  may be of various shapes. For example, the shoulder  82  and the outer protrusion  28  may include opposing recesses  84  formed therein, as shown in  FIGS. 12 and 13 , for receiving excess material formed during the weld.  FIG. 14  depicts an arrangement where the outer protrusion  28  includes a lip  86  extending outside the opposing shoulder  82  for aiding in the alignment of the tube  14  and component  16 . As shown in  FIGS. 12-14 , the shoulder  82  and outer protrusion  28  may be supported by ribs  88 .  
       FIGS. 15-17  depict arrangements where the weld is formed along only one of the inner and outer layers  20  and  22  of a straight-walled tube  14 . While  FIGS. 15-17  depict the weld as being formed on the outer layer  22 , it will be appreciated that the weld may alternatively be formed on the inner layer  20 .  FIG. 15  depicts an arrangement where the outer layer  20  is configured with a first shoulder  90  recessed from a distal end of the tube  14  by a distance equal to the thickness “T” of the tube  14 . The distal end of the tube  14  is preferably separated from the end of the recess by a distance equal to the thickness “T” of the tube  14 , and is preferably offset from the outer protrusion  28  by an offset distance “G” of about 0.002 inches. The distal end of the tube  14  aids in the alignment of the tube  14  and component  16  during the welding process. The depth of the weld, as indicated at “B”, is the distance between the first shoulder  90  and a shoulder  82  formed on the outer layer  22  of the tube  14 . The depth of the weld “B” may be between about 1×T to about 2×T, and more preferably about 1.5 T, and may be increased or decreased depending on the required strength of the weld. The interference between the tube  14  and the component  16 , indicated at “i”, may be between about 0.005 inches to about 0.025 inches, and preferably between about 0.01 inches to about 0.02 inches. The shoulder  82  may be supported by ribs  88 .  
       FIG. 16  depicts an arrangement where the outer protrusion  28  is configured with a first shoulder  92  disposed at a distance from the bottom surface of the channel  30  to establish the depth of the weld “B”. The depth of the weld “B” may be between about 1×T to about 2×T, and more preferably about 1.5 T, and may be increased or decreased depending on the required strength of the weld. The first shoulder  92  is preferably offset from a distal end of the outer protrusion  28  by a distance equal to the thickness “T” of the tube  14 , thus allowing the outer protrusion  28  to aid in the alignment of the tube  14  and component  16  during the welding process. The interference between the tube  14  and the component  16 , indicated at “i”, may be between about 0.005 inches to about 0.025 inches, and preferably between about 0.01 inches to about 0.02 inches. The inner protrusion  26  is offset from the inner layer of the tube.  
       FIG. 17  depicts an arrangement wherein the inner surface  34  of the outer protrusion  28  is angled by about 20 degrees relative to the outer layer  22 . The angled inner surface  34  of the outer protrusion  28  has a height that establishes the depth of the weld “B”. The depth of the weld “B” may be between about 1×T to about 2×T, and more preferably about 1.5×T, and may be increased or decreased depending on the required strength of the weld. The angled inner surface  34  is preferably offset from the distal end of the outer protrusion  28  by a distance “L”, which may be between about 0.020 inches to about 0.040 inches, thus allowing the distal end of the outer protrusion  28  to aid in the alignment of the tube  14  and component  16  during the welding process.  
      The present invention uses the metallic barrier layer  18  of a tube  14  to improve the gas impermeability of the joint  12  between the tube  14  and a component  16 . Advantageously, because the weld is formed with the outer and/or inner plastic layers  20 ,  22  of the tube  14 , the metallic barrier layer  18  extends substantially to the component  16 , thus improving the gas impermeability of the joint  12  between the tube  14  and the component  16 . The joint  12  is also lightweight and corrosion resistant.  
      A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.