Patent Document

TECHNICAL FIELD 
     The subject invention relates to hose construction. More specifically, the subject invention relates to a method for constructing a hose assembly having an inner fluorocarbon polymer liner and reinforcing layer thereabout. 
     BRIEF DESCRIPTION OF THE RELATED ART 
     Hose assemblies for conveying fuel and other corrosive materials are well known in the art. Such assemblies are exposed to a variety of fuel mixtures, fuel additives, and caustic materials in addition to being exposed to extreme temperatures. Thus, such hose assemblies must be resistant to chemical, environmental, and physical degradation as a result of chemical exposure, environmental exposure to heat, and physical degradation resulting from bending and repeated movement or forces applied to the assembly. 
     Polymeric fluorocarbon materials such as polytetrafluoroethylene possess the requisite chemical and temperature resistant properties for most fuel hose applications. Unfortunately, polymeric fluorocarbon materials exhibit relatively poor tensile and hoop strengths. As a consequence, such fluorocarbon materials are prone to kinking. Such kinking remains permanent and provides a continual resistance to the fluid flow through the hose assembly. Moreover, as a result of a fluorinated material&#39;s low tensile strength, attachment or securing of coupling members to the hose assembly is substantially compromised. 
     Various approaches have been described for offering additional strength to a polymeric fluorocarbon liner. One approach involves braiding fibers about the inner fluorocarbon liner. The braided fibers offer additional strength to the fluorocarbon liner resulting in a hose assembly that resists kinking. Examples of such approaches are disclosed in U.S. Pat. No. 5,124,878 issued Jun. 23, 1992, U.S. Pat. No. 5,142,782, issued Sep. 1, 1992, and U.S. Pat. No. 5,192,476 issued Mar 9, 1993, all assigned to the assignee of the subject invention. 
     The hose assembly described in the &#39;878 patent includes an inner fluorocarbon polymeric liner, a braided reinforcing layer disposed about the exterior of the inner liner, and is characterized by including an organic polymeric material dispersed in the reinforcing layer which connects the reinforcing layer to the inner liner thereby providing a hose assembly which is stronger and more kink resistant. 
     Both the &#39;782 and &#39;476 patents disclose methods for producing a hose assembly of the type shown in the &#39;878 patent. The &#39;782 patent discloses a method of making a lightweight hose assembly including the steps of extruding an inner liner, applying a braided reinforcing material having gaps extending therethrough about the inner liner. The inner liner and the braided layer are then passed through a reservoir containing a solution of a fluorocarbon polymer. After the solvent is removed, the fluorocarbon polymer coating is dispersed throughout the braided layer and bonds the braided layer to the inner fluorocarbon liner. 
     The &#39;476 patent discloses a method of forming a hose assembly in which an inner liner of a fluorocarbon material is extruded and then passed through a reservoir containing a dispersion including a fluorocarbon polymer material. A reinforcing layer is then braided about the exterior of the inner liner to form a braided layer having the dispersion thereabout such that the dispersion penetrates the interstitial spaces of the braided layer. Subsequently, the assembly is heated to remove the solvent and the braided reinforcing layer is then bonded to the fluorocarbon polymer inner liner. 
     The methods disclosed in the &#39;782 and &#39;476 patents yield a highly desirable and excellent performing hose assembly, however, the steps of applying the fluorocarbon polymer dispersion to the inner liner can allow some of the fluorocarbon polymer dispersion to enter the interior of the hose where it may cause problems when the hose assembly is used in a desired application. Additionally, the hose assemblies discussed above preferably utilize non-melt extrudable fluorocarbon polymers for the inner liner. These non-melt extrudable fluorocarbon polymer materials typically possess a higher permeation rate than do melt extrudable fluorocarbon polymer materials. That is, the ability of volatile fluids or gases to escape through the wall of the inner liner is greater with non-melt extrudable fluorocarbon based hose assemblies. Additionally, non-melt extrudable fluorocarbon materials are not as easily adapted to recycling or reuse of the material as are melt-extrudable fluorocarbon materials. 
     An additional example of strengthening an inner fluorocarbon liner with an outer liner while also increasing flexibility is shown in U.S. Pat. No. 3,023,787 to Phillips et al. The Phillips et al. patent discloses a convoluted hose assembly having a fluorocarbon inner liner constructed of many layers of helically wrapped Teflon® tape. Convoluted hoses are typically employed because they provide flexibility to a fluorocarbon hose assembly, however, convoluted hose assemblies have inherent weaknesses. A reinforcing strip consisting of reinforcing fibers coated with a plastic material is wrapped about the inner layer to provide additional strength to the assembly due to the inherent weakness of wrapped convoluted core construction. In its final assembly, a metal braid is applied to the outside of the hose assembly to impart greater strength. 
     Hose assemblies of the type described in the Phillips et al. patent have several inherent drawbacks. First, because the inner liner is formed by helically wrapping layers of a fluorocarbon tape, it requires a greater amount of fluorocarbon material to be utilized in order to construct the inner liner which adds to both the cost of constructing the hose assembly and to the labor intensity of constructing the hose assembly. Other drawbacks associated with hoses of the type disclosed in the Phillips et al. patent includes failure of seams created by helically wrapping layers of Teflon® tape. These failures occur due to inherent weaknesses in bonding the seams created by the overlapping layers of tape which, under internal pressures and prolonged movement are prone to leakage or to bursting. In addition, the seams create undulations within the inner liner which cause disruption in the flow of liquids therein which could give rise to increased electrical charge buildup within the hose. 
     Therefore, it would be desirable to have a method for constructing a fluorocarbon hose assembly which eliminates the necessity for liquid fluorocarbon polymer dispersions in order to bond reinforcing layers to a fluorocarbon liner. 
     Further, it would be desirable to have a hose assembly which includes a polymeric fluorocarbon inner liner which is resistant to kinking while additionally possessing greatly increased bending properties while maintaining the overall integrity of the hose assembly. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     In accordance with the present invention, there is provided a method for constructing a hose assembly. The method includes the steps of disposing a reinforcing layer having interstitial spaces extending therethrough about a tubular inner liner and dispersing the tubular inner lines into the interstitial spaces and bonding the reinforcing layer to the inner liner. 
     Additionally, accordingly to the present invention, there is provided a hose assembly including an extruded, smooth bore tubular inner liner including a melt extrudable polymeric fluorocarbon material having an external surface and a reinforcing layer having gaps extending therethrough disposed about the external surface. The external surface of the inner liner is dispersed into the reinforcing layer and bonds the reinforcing layer to the external surface of the inner liner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
     FIG. 1 is a perspective view of the preferred embodiment of the present invention; 
     FIG. 2 is an enlarged sectional view of the hose assembly; 
     FIG. 3 is a perspective view of an alternative embodiment of the present invention; 
     FIG. 4 is a perspective view of the extrusion of the inner liner of the method of the preferred embodiment of the present invention; 
     FIG. 5 is a perspective view of the hose assembly having a hose attached thereto; and 
     FIG. 6 is a perspective view of the hose assembly with the administration of both heating and cooling elements to ensure adhesion of the braid layer. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A hose assembly made in accordance with the present invention is generally shown at  10  in FIG.  1 . The assembly  10  includes a tubular inner liner  12  and a reinforcing layer  14  disposed about the inner liner  12 . A coupling means  20  adapted to engage the ends of the hose assembly  10  may be included. 
     The tubular inner layer  12 , as best shown in FIGS. 1 and 2, includes a melt extrudable polymeric fluorocarbon material resistant to both chemical and heat degradation, thus allowing a variety of fluids, particularly automotive fuels and fuel additives, e.g., detergents, alcohols, etc., to pass through the inner liner  12  without corroding or degrading the inner liner  12 . The inner liner  12  is preferably extruded using well known melt or paste extrusion techniques and has a wall thickness between 0.001 and 0.120 inches. The walls of the inner liner  12  define an inner surface  15  and an interior passageway  22  of the inner liner  12 . Although the inner liner  12  may be made of any number of polymeric fluorocarbon materials, the inner liner  12  is preferably made from a melt extrudable fluorocarbon polymeric material including perfluorinated ethylene-propylene (FEP), copolymer of tetrafluoroethylene and hexafluoropropylene sold under the trademark TEFLON® FEP by DuPont, perfluoroalkoxy fluorocarbon resins (PFA), the copolymer of tetrafluoroethylene-perfluorovinyl ether sold under the trademark TEFLON® PFA by DuPont, or the copolymer of ethylene tetrafluoroethylene (ETFE) sold under the trademark TEFZEL by DuPont. In addition to the aforementioned polymeric fluorocarbon materials, any other melt extrudable fluorocarbon polymeric materials known to those skilled in the art can be used. Aside from the manufacturing benefits detailed herein, utilizing melt extrudable materials allows for any scrap melt extrudable material to be remelted and thereby recycled within the manufacturing facility. Another benefit of utilizing a melt extrudable inner liner  12  is that it lowers the permeation rate of gas and/or liquids through the hose assembly  10 . Paste extrudable fluoroplastic such as PTFE, during sintering process, may have voids which in turn may have higher permeation. 
     The liner  12  is extruded to provide an inner liner  12  which has a smooth bore, free of undulations and seams which can cause turbulence of fluid flow within the inner liner  12 . Turbulence can cause build-up of electrical charge within the hose assembly which is undesirable in the situation where potentially flammable fluids are being transported therethrough. Extruding the inner liner  12  creates an inner liner  12  which as no seams and undulations and is, therefore, the preferred method for forming the inner liner  12 . 
     By melt extrudable fluorocarbon polymeric material, it is meant that the material, at suitable conditions such as raised temperature, can be caused to melt or flow such that the fluorocarbon material flows about the reinforcing layer  14  and substantially encapsulates the reinforcing layer  14  whereupon cooling of the fluorocarbon material, the inner liner  12  and the reinforcing layer  14  are bond to one and other forming an integral hose assembly. 
     The assembly  10  includes the reinforcing layer  14  having gaps extending therethrough. Generally, the reinforcing layer  14  is constructed of a braided or woven material. Because the inner liner  12  is made of a melt extrudable material, it allows for the use of monofilament braid material for the reinforcing layer  14  which is significantly less expensive than multifilament braid material. The layer  14  can comprise any non-metallic material disposed in interleaving fashion or wrapped tightly about the inner liner  12 . The material that the layer  14  is constructed of is generally a braid or weave of interlocking fibers which create gaps or interstitial spaces which facilitate the connection of layer  14  to the inner liner  12 . Preferably, the material used for the layer  14  is glass fiber such as fiberglass. Glass fibers provide the necessary strength needed to reinforce the inner liner  12  and are heat resistant which is important for use in high temperature environments. The layer  14  adds tensile strength to the hose assembly  10 , and the layer  14  imparts increased hoop strength to the hose assembly  10 . 
     In a preferred embodiment, the glass fibers are tightly woven such that the gaps and spaces between the adjacent fibers are minimized. 
     The glass fibers are preferably woven at a neutral braid angle. This angle is preferred since there is no movement of the hose under internal pressure in either the longitudinally or diametrically. It is preferred that the braid angle is as close to the neutral angle as possible. However, variations in materials, selection of reinforcing fiber material, and the machines used to apply the braid in part some variation. 
     The reinforcing layer  14  is preferably applied about the exterior of the inner liner  12  by utilizing a braiding machine well known in the art. The machine includes a plurality of spools which carry the fiber material. The fibers are fed through the machine to a braiding area. In the braiding area, the fibers are braided or wound about the inner liner  12  to form the braided reinforcing layer  14 . Alternatively, the braided reinforcing layer  14  also can be constructed in a pre-made, sock-like fashion and then can be applied about the exterior of the inner liner  12 . 
     Due to the chemical inertness and general lubricious nature of polymeric fluorocarbon materials, relative movement between inner and outer concentric polymeric fluorocarbon liners is often encountered in prior art hose assemblies. This relative movement leads to weakness in the final hose assembly. The present hose assembly  10  is modified to eliminate such relative movement between the inner liner  12  and the layer  14 . 
     The hose assembly  10  is constructed such that the melt extrudable fluorocarbon material which forms the inner liner  12  also bonds the reinforcing layer  14  to the inner liner  12  to form an integral assembly and thereby eliminate relative movement between the inner liner and the reinforcing layer  14 . 
     As stated above, the inner liner  12  is constructed of a material, which, when heated to a desired temperature, 500° F.-750° F., the external surface  16  of the inner liner  12  melts and flows into the gaps or interstitial spaces of the reinforcing layer  14  and about the fibers which comprise the braided material to form a mechanical bond which integrally forms the reinforcing layer  14  to the inner liner  12 . That is, heat is applied to the external surface  16  of the inner liner  12  by a mechanism such as a forced air heating unit. 
     The material comprising the inner liner  12  is heated such that substantially only the external surface  16  becomes fluid enough to flow into and about the reinforcing layer  14 . Heating of the external surface  16  is controlled in a manner which does not allow the inner surface  15  of the inner liner  12  nor substantially all of the wall thickness of the inner liner  12  to become heated enough to become fluid, melt, or deformed. 
     In order to further control the bonding of the layer  14  to the inner liner  12 , the interior passageway  22  of the inner liner  12  can be pressurized and/or cooled to prevent the interior passageway  22  and inner surface  15  of the inner liner  12  from becoming deformed or imprinted with the braid pattern of the layer  14 . By maintaining a positive pressure in the interior passageway  22  of the inner liner  12  during the heating of the external surface  16 , uniformity of the inner liner  12  can be controlled and/or maintained. The internal pressure is preferably in the range of 1-100 psi. 
     Bonding of the layer  14  to the inner liner  12  can also be enhanced by cooling the interior  22  of the inner liner  12  while applying heat thereto. The interior  22  of the inner liner  12  can be cooled by, for example, passing a fluid, or gas having a temperature lower than the melting temperature of the particular melt extrudable fluorocarbon material, through the interior  22  of the inner liner  12 . The cooling fluid can be a gas, a liquid or any other fluid or combination of fluids suitable for this purpose. For example, the fluid can be air or water. 
     Generally, the fluid is chosen such that it is compatible with the desired melt extrudable fluorocarbon material and such that it will not cause problems if residual cooling fluid is left in the hose assembly  10 . The temperature range for the cooling fluid can range from −40° F.-200° F. using fluids such as nitrogen, helium, etc. 
     The coolant can also be applied under pressure, as described above, to accomplish simultaneous heating of the exterior  16  of the liner  12 , and cooling of the interior  22  of the inner liner  12 . An example, air or water maintained at a temperature less than the melting temperature of the melt extrudable polymer can be pressurized to a pressure (eg. 50 ps.) sufficient to maintain the integrity and dimension of the inner liner  12  while simultaneously preventing the flow or melting of the inner surface  15  of the inner liner  12 . 
     The hose assembly  10  is then subsequently sintered at a suitable temperature (approximately 700° F.) to cure the fluorocarbon polymer material dispersed throughout the layer  14 . The sintering operation fuses the fluorocarbon polymer material of the inner liner  12  to both the layer  14  and the inner liner  12 . 
     The bond between the layer  14  and the inner liner  12  prevents slippage, i.e., relative longitudinal or rotational movement between the inner liner  12  and the layer  14 . That is, the material melted from the inner liner  12 , disperses throughout the layer  14  and mechanically bonds the layer  14  to the inner liner  12  thereby providing strength to the inner liner  12  upon bending of the hose assembly  10 . Thus, by using a melt extrudable polymeric fluorocarbon inner liner  12  which is dispersed throughout the layer  14 , a hose assembly  10  is produced which results in the hoop strength of the inner liner  12  being increased such that the inner liner  12  can be bent without kinking. Further, bonding together the inner liner  12  and the layer  14  allows the hose assembly  10  to operate at higher working pressures and, therefore, to accommodate fluids transported under greater pressures. 
     An optional metallic braided outer liner or painted layer  18 , as best shown in FIGS. 1 and 2, can be disposed about the layer  14 . The metallic braided layer  18  includes a metallic material for increasing the strength and flexibility of the hose assembly  10 . More specifically, the metallic outer layer  18  allows the inner liner  12  to be bent to smaller radii without kinking. The outer metallic layer  18  provides strength to the inner liner  12  upon bending. This is commonly referred to as hoop strength. Thus, by disposing the outer metallic layer  18  about the layer  14  and the inner liner  12 , the hoop strength of the inner liner  12  is increased, thus improving the bend radius of the hose assembly  10 . Improvement in the bend radius allows the hose assembly  10  to be manipulated or placed into configurations which would impinge or kink the inner liners of prior art hose assemblies. That is, the metallic outer layer  18  allows for a reduction in the static bend radius of the hose assembly  10  thereby allowing the hose assembly  10  to be utilized in a greater number of applications. Additionally, the metallic outer layer  18  adds to the burst strength of the hose assembly. The metal outer layer  18  allows the hose assembly  10  to be used in applications where the hose assembly  10  is operated at much higher operating pressures without bursting of the hose assembly  10 . Further, the metallic outer layer  18  provides for more positive affixation of couplings or end fittings  20  to the hose assembly  10  as shown in FIG.  1 . The metallic outer layer  18  additionally increases the tensile strength that the hose assembly  10  sufficiently to fixedly connect the coupling member  20  (FIG. 1) to the hose assembly  10 . 
     The outer metallic layer  18  can be made of any suitable metal material. In the preferred embodiment of the hose assembly  10 , the outer layer  18  is made from stainless steel. The metallic outer layer  18  is preferably braided in place over the reinforcing layer  14 . The metallic braided outer layer  18  is preferably applied about the exterior of the reinforcing layer  14  by utilizing a braiding machine well known in the art. The machine includes a plurality of spools which carry appropriately sized stainless steel wire material. The stainless steel wire is fed through the machine to a braiding area. In the braiding area, the wires are braided or wound about the exterior of the reinforcing layer  14 . Alternatively, the metallic braided layer  18  also may be constructed in its entirety in a sock-like fashion and then applied about the exterior of the reinforcing layer  14 . Unlike the layer  14 , the metallic braided outer layer  18  is not bonded to any of the underlying structure. That is, the braided metallic outer layer  18  is not affixed to the underlying hose assembly. The braided layer  18  can be applied utilizing a braiding machine which is commonly known as a maypole braider or may be applied using a rotary braider which is commonly known in the art. Each machine applies the braid differently, however, achieve the same results, that is, a Z over Z, construction. 
     As fluid flows through the inner liner  12 , electrical charges can build up throughout the length of the inner liner  12 . In order to prevent these electrical charges from accumulating, the inner liner  12  can include an integral longitudinal conductor  20  co-extensive with the length of the inner liner  12  for conducting an electrical charge along the length of the inner liner  12 . The integral conductor  24  includes a conductive strip  24  of carbon black, as shown in FIGS. 1 and 2. The integral conductor can also be interspersed throughout the inner liner  12  by intermixing carbon black  26  throughout the polymeric fluorocarbon material either while the inner liner  12  is extruded or prior to the extrusion of the inner liner  12  as shown in the Figures. 
     The hose assembly  10  can further include a coupling  20  as shown in FIG.  1 . The coupling is adapted to engage the ends of the hose assembly  10  for interconnecting the hose assembly  10  to a flow of fluid, e.g., fuel flow to and from a fuel tank (not shown). Couplings suitable for use with the hose assembly  10  of the present invention are well known in the art. Typically, the couplings  20  are adapted to engage the ends of the hose assembly  10 . Typically, the couplings are adapted by way of barbs which engage the inner surface  15  of the inner liner  12 . 
     The coupling  20  can also include an engaging portion (not shown) extending longitudinally from the insert portion for engaging a fitting (not shown). The engaging portion can comprise a male threaded member  28  or female threaded member (not shown). The engaging portion can comprise any configuration that will cooperate with the member to which it is connected with. For example, the engaging portion can comprise a socket to receive a mating ball joint (not shown). 
     Alternatively, the coupling  20  can be molded, such as by injection molding, to the hose assembly (not shown). The melt extrudable material allows for plastic fittings to be molded directly onto the hose assembly  10  thereby eliminating crimping, and its associated disadvantages, as the preferred method of affixing fittings to the hose assembly  10 . This makes it possible to eliminate the separate operations of hose manufacturing, fitting manufacturing, and fitting attachment to the hose by allowing the fitting to be directly formed (molded), affixed, and sealed to the hose assembly. 
     Additionally, the coupling  20  can be any other well known type of the coupling known to those skilled in the art. 
     Throughout this application various publications are referenced by citation or number. Full citations for the publication are listed below. The disclosure of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains. 
     The invention has been described in an illustrative manner, and it is to be understood the terminology used is intended to be in the nature of description rather than of limitation. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.

Technology Category: b