BACKGROUND

The present invention relates to the field of tubing manufacture and in particular to the field of automotive fuel and vapor transmission tubes.

Presently manufactured fuel lines for automobiles are usually thick walled tubes made of nylon 11 or 12. The wall thickness is approximately forty-thousandths of an inch, however only one- to two-thousandths are actually necessary to contain the fuel. The remainder of the thickness is necessary to protect the inner thickness and support it.

In order to properly route the fuel line, turns and bends must be thermally preformed into the thick tube. Thus formed, the tube is often difficult to "fish" through the vehicle from the fuel tank to the carburetor or fuel pump during assembly in the vehicle.

In the same manner, vapor tubes for recycling the fuel vapors in an automobile pollution control device must be resistant to the fuel as well. The tubing used must be made of a resistant material which, as with fuel lines, must be fished through the vehicle for assembly.

In many applications plastic tubing cannot prudently be used because of the work environment. -Plastic tubing in the area of a welding operation is subject to rupture by weld splatter which may melt the tube wall. This occurrence could have disastrous effects if the tube is carrying a flamable substance such as fuel.

There are flexible hose assemblies for fuel lines shown in the prior art. U.S. Patent No. 2,787,289 to Press discloses such a flexible line. The line discl-θββd *n this patent is made up of an extruded polytetrafluoroethylene tube which is surrounded by one or more layers of reinforcing wire braid of stainless steel and covered by a

flexible tubular cover which is made of asbestos impregnated with a substantially oil proof material. This type of line although flexible, is also resilient and therefor does not maintain the shape it is bent into. This is undesirable in many automotive applications as at least some type of semi-rigidity or shape holding is necessary to hold the line in the proper position.

In U.S. Patent 4,327,248 to Campbell, there is disclosed a shielded electrical cable. The shield is made of a flexible metal tape with a coating of a copolymer of ethylene with a monomer having a reactive carboxyl group bonded to at least one of its sides. An adhesive is used to bond the coating to a flexible or semi-rigid non-olefinic polymeric material.

SUMMARY OF THE INVENTION

The tubing of the invention includes a plastic/metal composite wall formed around a nylon fuel or vapor tube component. When the composite wall of the invention is used, there is a plastic casing or jacket surrounding a thin metallic layer such as aluminum which in turn surrounds a thin petroleum resistant liner giving it a bendable quality without buckling. The metallic layer offers sufficient strength to dominate over the resiliency of the plastic layer when the tubing is bent to a desired configuration. The tube thus has a formability characteristic and maintains the configuration it is formed into. The presence of the plastic/metal covering over the actual conduit inner tube offers sufficient mechanical protection to safely allow a much smaller wall thickness of the inner liner. The inner liner is normally made of an expensive substance and therefor reducing the wall thickness results in significant savings.

A tightly formed plastic/metal covering also offers an encapsulation effect over the outside of the inner tube which minimizes kinking. Optionally the inner tube may be supplied with longitudinal ribs to further reinforce the tube against kinks. These features enhance the mechanical characteristics of the inner tube as, for example, by providing enhanced burst strength.

The metal layer also provides several significant characteristics to the tube assembly. First, the metal layer provides protection against tube rupture caused by torch sparks or weld splatter commonly encountered in muffler or body repair shops. The layer offers a metal barrier to the spark or splatter while providing a tremendous heat sink, through its heat capacity and good thermal conductivity, to dissipate the heat. Second, because all plastics have some degree of moisture permeability, the metallic layer provides a significantly reduced moisture vapor transmission rate as compared to a 100% plastic tube. Third, the metal layer also overcomes resiliency of the outer covering to permit bending into self-sustaining contour or shape.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 is a partially cut-away perspective view of the fuel or vapor tube of the invention.

Fig. 2 is a cross-sectional view of an embodiment of the invention having internal ribs.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The fuel or vapor tube includes an inner liner 1 made of a fuel resistant material, such as but not limited to nylon 12, and is approximately four to twenty mils thick. The liner 1 is cylindrical in shape. Longitudinally wrapped

about the longitudinal axis of the liner is an aluminum strip 2 which forms a longitudinally extending lap joint 4. The aluminum strip 2 is approximately twelve mils thick. Encasing the strip 2 is a plastic casing 5. The strip is coated on both sides with an adhesive 3 which bonds to the plastic casing. More particularly, the adhesive is made from a copolymer of ethylene and a monomer having a reactive carboxyl group such as acrylic acid or an acrylic acid ester. An example of such a coated aluminum strip is currently manufactured under the "Zetabon" trademark by Dow Chemical Company. It is understood that the layer 2 may be made of any sufficiently bendable metal which has the characteristic of staying in bent shape, however, aluminum is preferred. Alternatively, the aluminum strip may be coated with adhesive 3 on one side only which would provide sufficient adhesion between the laps of the joint 4. A two-sided coating is preferred, however, as it creates an adhesive to adhesive bond in the lap joint 4.

The casing is extruded onto the aluminum strip 2 after the strip is wrapped around the liner. It is made of a plastic, such as polyethylene, chlorinated polyethylene if flame retardation is desired, or other plastics.

As shown in Fig. 2, the liner 1 may be provided with longitudinally extending ribs 6 for enhancing the rigidity and anti-buckling of the liner 1. The ribs ^' 6 may extend longitudinally parallel to the axis of the liner or they may follow a helical path along the inner surface of the liner. Although four ribs are shown, a greater or lesser number of ribs may be used depending on the characteristics desired in the liner.

The tube is formed by continuously wrapping the adhesive coated aluminum strip around the extruded l*ner. The liner may be supplied from rolls or extruded as part of the manufacturing procedure. The aluminum strip has two longitudinal margins which overlap to form a longitudinally

extending lap joint. The plastic casing is then extruded around the aluminum tube which has the liner already disposed within it. The heat of the extrusion process causes the plastic to bond to the adhesive and the adhesive in the lap joint to bond producing a securely attached aluminum tube and plastic jacket with a nylon liner disposed therein.

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