CA1102717A

CA1102717A - Composite tubing product and method of making same

Info

Publication number: CA1102717A
Application number: CA323,958A
Authority: CA
Inventors: Eugene D. Bonnes
Original assignee: Eaton Corp
Current assignee: Eaton Corp
Priority date: 1978-03-27
Filing date: 1979-03-22
Publication date: 1981-06-09
Also published as: BE875040A; JPS54154482A; ZA791258B; AU4536979A

Abstract

Abstract of The Disclosure An elongate deformable tube for use in the conveyance of fluids and/or fluid transmission signals under pressure having a hose therethrough enclosed by a composite annular wall comprising a seamless or welded and drawn inner tubular shaped layer made from a metallic material and an outer tubular shaped layer made from a polymeric material. The walls of bot? the inner and outer layers are substantially uniform in radial thickness around their circumferences and the outer polymeric layer is preferably formed about the inner layer by means of an extrusion process. The inner and outer layers are preferably bonded together by means of an extruded polymeric adhesive interposed therebetween and the outer diameter of the outer layer is sized, during the process of making the tube, such that the tube can be attached, without dimensional alteration, to fittings standardly used to couple equivalently dimensioned tubes having a singular polymeric or metallic wall.

Description

This invention relates generally to a deformable tube for use in the conveyance of fluids and/or ~luid transmission signals under pressure and more particularly to a deformable tube suitable for such use having a composite wall comprising an inner seamless or welded and drawn metallic layer and an outer polymeric layer disposed about the inner layer wherein the walls of both the inner and the outer layer are substantially uniform in radial thickness around their circumferences and the outer diameter is sized, during the process of making the tube, such that the tube can be attached, without dimensional altera-tion, to conventional fittings, standardly used to couple tubing having an e~uivalently dimensioned singular wall of polymeric or metallic material.

BACKGROUND OF THE INVENTION
Tubing heretofore used in the conveyance of fluids and/or fluid transmission signals under pressure has in the main been of the type wherein the wall of the tube is made singularly from either a polymeric or a metallic material and the outer diameter of the tube has been sized such that, depe~dent upon 2Q whether the tube is made from a metallic or polymeric material, it can be attached to conventional fittings generally peculiar to each. To a lesser extent, tubes having an extremely thin inner metallic layer formed by longitudinally folding metallic tapes into a tubular shape and extruding a polymeric material thereabout have also been used for such purposes. Tubes having a longitudin-ally folded metallic inner layer can be found for example, in U.S. Patents 3,233,036 or 3,806,358 and are also presently made , .
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and sold by the assignee of the present invention under the trade name "Dekabon". Tubes having an inner lay~r formed by the folding of metallic tapes have the disadvantage of having an inner exposed seam which can lessen their thermal resistance and mechanical handling capabilities and which may also provide a point of attack in applications requiring the conveyance of corrosive fluids. The mechanical handling capabilities of tubes having an inner layer formed by the longitudinal folding of a metallic tape are necessarily limited, particularly in smaller tube sizes, due to the fact that metal tapes are generally required to be relatively thin in order to fold them longitudinally into a tubular shape at attractive production rates. Generally, tubular shapes formed by the longitudinal folding of metallic tapes are made in such a manner as to provide an overlap between their oppositely facing longitudinally extending edges for the purpose of mechanically interlocking or otherwise adhesively affixing the folded tape into a closed tubular configuration. As a result of this practice, the radial thickness of the folded metal tape is necessarily larger in the region of the overlap than elsewhere about the cir-cumference of the tube. Non-uniformity in radial thickness of metallic tubular shaped forms can, and often does, lead to greater tendency for fluid leakage under pressure in the region of fitting attachment. Tubes made in accordance with the present invention do not possess the aforesaid disadvantages in that they comprise a tubular shaped seamless or welded and drawn inner layer of metal-lic material having a substantially uniform radial wall thickness around its circumference; an outer tubular shaped layer of poly-meric material of substantially uniform radial wall thickness - . :
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Z7~17 around its circumference disposed in encompassing relationship about the inner layer; and an outer tube diameter sized during the process of making the tube such that the tube can be attached, without dimensional alteration, to fittings standardly used in the industry. The term "seamless or welded and drawn", as herein used, shall not mean metallic tubing which has been formed by the longitudinal folding or spiral wrapping of metallic tapes having abutting or overlaping edges which are mechanically interlocked or adhesively adhered together so as to result in a discontinuous or interrupted wall in the form of a seam and which is further characterized as not having a substantially uniform radial wall thickness around its circumference. The term "seam-l~ss or welded and drawn", as herein used, means tubing that has been formed by extrusion, drawing, or welding and drawing, and the like, such that the tube wall is integrally sealed and of substantially uniform radial wall thickness around its circum-ference.
The coating of metallic tubes and pipes with polymeric materials has long been recognized as a method of providing pro-tect~on from corrosive environments~ U.S. Patent 2,447,420 discloses, for example, the coating o~ rigid electrical conduit with a polymeric material and U.S. Patent 2,724,660 discloses an immersion process of applying a protective jacketing to flexible metal tubes while in a shaped configuration. In U.S. Patent 3,815,640, a synthetic resin coated pipe is disclosed that has annular projections at regular intervals for use as a supporting pole in agricultural applications and U.S. Patent 3,502, 492 discloses the method of electrostatically coating metal s~bstrates , : --, . .

~2~7~7 with epoxy resin and polyvinyl chloride powder. Such art, however, does not teach or suggest tubing of the type made in accordance with the present invention in that it is devoted to the coating, with polymeric materials, of standardly recognized metal tube wall thicknesses resulting in over-sized tube outer diameter in relationship to what is normally a fixed standardized inner diameter, or vice versa, and generally requires dimensional alteration such as, for example, skiving away of the polymeric material in order to make fluid-tight seals when attached to conventional fittings.
Tubes made in accordance with the present invention provide a means of transferring fluid and/or fluid transmission signals under pressure from one location to another with the corrosion resistance and integrity of a seamless or welded and drawn metallic inner liner and the protective benefit of an outer polymeric coating while maintaining a standardized outer diameter such that the tube can be attached, without dimensional altera-tion, to fittings standardly used to couple equivalently dimen-sioned tubes having a singular polymeric or metallic wall.

SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved elongate deformable tube for use in the conveyance of fluids and/-or fluid transmission signals under pressure. It is a further object of this invention to provide an elongate deformable tube of substantially uniform radial wall thickness around its circum-ference having a composite wall comprising a seamless or welded and drawn metallic inner layer encompassed by a polymeric outer layer having an outer diameter sized during the process of making . ~
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il~, 27~7 the tube such that the tube can ~e attached to conventional fittings without dimensional alteration. It is a more specific object of this invention to provide a deformable tube, and the method of making a tube, for use in the conveyance of fluids and/or fluid transmission signals under pressure having a seamless or welded and drawn metallic inner layer of substantially uniform radial wall thickness about its circumference; an extruded poly-meric outer layer of substantially uniform radial wall thickness around its circumference disposed about and coextensive with the inner layer; a dimensionally standardlzed outer diameter that is sized during the process of making the tube such that the tube can be attached to conventional fittings, without dimensional alterations; and the inner and outer layer are bonded together by means of an extruded polymeric adhesive interposed therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS
Other objects will become apparent from the following description with reference to the accompanying drawing in which:
Figure 1 is a partially cut-away perspective view of an embodiment of the invention wherein the outer polymeric layer Z0 has been cut back for the purpose of showing the dimensional relationships involved;
Figure 2 is a cross-sectional view A-A of the embodi-ment of Figure 1: and Figure 3 is a cross-sectional view of another embodi-ment of the inYentiQn wherein the outer polymeric layer is bonded to the inner metallic layer by means of an adhesive interposed between the two layers.

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7~7 DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 1 in which tube ~ of the in-vention has bore 5 therethrough enclosed by an annular composite wall comprising a seamless or welded and drawn tubular shaped inner layer 2 coextensively about which is disposed outer poly-meric layer 3. Outer layer 3 is cut back in Figure 1 to show more clearly the dimensional relationship between inner layer 2 and outer layer 3. The annular walls of inner layer 2 and outer layer 3 are substantially uniform in radial thickness around their circumferences. Outer diameter "y" of outer layer 3 and tube l is sized to conform to tubing outer diameters standardly established as whole fractional ~alues increasing by equal in-crements of 1/16 inch such as, for example, 1/4"; 5/16"; 3/8"
and so on up through 1 inch outside diameter and increasing by 1/8" increments from l inch to about 2 inch outside diameter (and including any present decimal or metric equivalents thereof).
For the purposes of this invention, deformable tubing is tubing that is generally included within the outer diameter size range of 1~16 inchthrough 2 inch outer diameter and is distinguished 2Q from rigid tubing or pipe in that it can be deformed by bending or shaping with relative ease. Experience has shown that the more popular sizes of such tubiny are wherein the outer diameter "y" is 1~4"; 3~8'l or 1/2". Inner diameter "x" shown in Figure l has been standardized to a lesser intent for polymeric tubing in contrast to metallic tubing and is gener~lly dependent upon the strength characteristics desired of the tube and whether the tube i5 s;ngularly made from either a metallic or polymeric material.
Generally, inner diameter "x" may be a whole fractional number or .

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E`Z7 5L7 it may be a decimal or metric value equivalent thereto. For illustrative purposes, a standard metal tube may have an outer diameter "y" of about 1/4" and an inner diameter "x" of about .190" whereas a polymeric tube used for similar purposes may have an outer diameter "y" of about 1/~" and an inner diameter "x"
of about .170". Generally, as illustrated by the comparative example, polymeric tubing is designed with a heavier wall and consequently a smaller inner diameter "x" in order to provide increased strength for use in applications normally handled by metal tubing. As a consequence of this practice and because of differences in resilience between metallic and polymeric materials, conventional fittings have evolved that are peculiar to each other. Likewise, certain fittings are available that w;ll suitably attach to a standardly sized tube whether it be made from a metallic or a polymeric material. It is to be under-- stood that dimensions referred to herein lie nominally within the range of tolerance established by the manufacturer thereof or as otherwise established in the trade. The radial thickness of poly-meric outer layer 3 is shown as "tp" in Figure 1 and the radial thickness "tm" of inner layer 2 shown in Figure 1 can be sized so as to provide the approximate minimum radial wall thickness "tm"
required to provide suitable handling and strength characteristics desired by the end user. The ability to tailor the radial wall thickness of inner metallic layer 2 while maintaining a standard-ized outer diameter, as hereinbefore described, provides a means of minimizing the cost and use o valuable metals and yet provides the end user with handling and strength characteristics tailored for hisneeds~

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Figure 2 shows cross section A-A of Figure 1 wherein tube 1 of the invention has bore 5 enclosed by an annular composite wall comprising an inner seamless or welded and drawn metallic layer 2 enclosed by outer polymeric layer 3. As in Figure 1, the annular walls of inner layer 2 and outer layer 3 are suhstantially uniform in radial thickness around their circumferences. Also shown in Figure 2, is standardized outer diameter "y" of outer layer 3 and tube 1; inner diameter "x" of inner layer 3 and tube l; radial wall thickness "t " of outer layer 3; and radial wall thickness "tm" of inner layer 2 which has been sized so as to minimize the amount of metal used in tube 1 while providing suit-able handling and strength characteristics required for its in-tended application. Although inner layer 2 of Fi~ure 1 (as for all embodiments of the invention) may be made from any suitable metallic material, it is preferred that inner layer 2 be made from an alloy of either copper or aluminum~ Inner tubular metal-lic layer 2 may be made, for example, by any suitable process which provides a seamless or welded and drawn metallic tube having a relatively smooth bore thereth~o~gh and having a substantially uniform radial wall thickness around its circumference. Outer layer 3 of Figure 2, as with all embodiments of the invention, may be made from any suitable polymeric material which provides the corrosion resistance, weatherability and other characteristics desired. Although polymeric outer layer 3 may be applied over the outer surface of inner layer 2 by processes such as, for example, dipping, spraying, powder fusion, and the like, it is preferred that outer polymeric layer 3 be extruded about th~ outer surface of inner layer 2 in such a manner that outer layer 3 fits snugly _ g _ ..
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.. ' ' ' about inner layer 2 with its inner surface (excepting in the event an adhesive is disposed intermediate the two layers) directly in contact with the outer surface of inner layer 2. Although, a variety of thermoplastically processihle polymeric materials may be selected for outer layer 3 such as, for example, rubber, nylon, thermoplastic rubber, polyurethane, and the li~e, it is preferred that outer layer 3 be extruded from either a thermoplastically processible polyvinyl chloride or a high density polyethylene . composition since they appear to provide a broad range of charac-teristics desirable for many end-user applications. It is also to be understood that polymeric materials used to make outer layer 3 o~ tube l o~ the invention may be cross-linked to improve certain properties prior to, during, or subsequent to the process of applying them about inner layer 2. Such cross-linking may be accomplished by either conventional chemical means such as, for example, heat curing of polymeric compdsitions containing suitable amounts of a cross-linking agent, such as a peroxide, or they may . be of the type that can be cross-linked by suitable exposure to irradia*ion such as, for example, high energy electrons. In cases

2~ where outer layer 3 is disposed thermoplastically about inner layer 2, the cross-linking is necessarily accomplished subsequent to such p~ocess~
Figure 3 shows an embodiment of the invention where tube 1 . h.as bore 5 therethroug~ enclosed by an annular composite wall com-prising ad~esive layer 4 disposed between and bonding together inner metallic layer 2 and outer polymeric layer 3. As in all ~ em~odiments of the invention, the walls of inner layer 2 and outer layer 3 aPe substantially uni~orm in radial thickness around their ., : .
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27~7 circumferences. Although it is not required that outer layer 3 be bonded to inner layer 2, it is preferred that they be bonded in order to provide improved handling characteristics; minimize relative slippage between the layers; and to improve the ability to retain fittings under variable and fluctuating internal and/or environmental temperature conditions. Adhesive layer 4 may be formed from a suitably selected adhesive that is separately ap-plied during the process of making tube 1 of the invention such as, for example, by dipping, spraying, hot melt extrusion, and the like, or it may be formed by melt fusing the inner surface of inner layer 2 such as, for example, by suitably controlling the extrusion temperatures during the process of applying thermo-plastically processible polymers as outer layer 3 about inner layer 2. Whether with the use of separately applied adhesives or by melt fusion or by combinations of both, it is to be understood that the outer surface of inner layer 2 may also be altered in such a manner as desirable to enhance its ability to bond to adhesive layer 4 or directly to the inner surface of outer layer 2, as hereinbefore described, such as, for example, by suitable 2Q etching and/~or priming the outer surface of inner layer 2.
In making tubing in accordance with certain bonded embodi- -ments of the invention, it has been found that by preheating the inner metallic layer, the bond between the inner metallic layer and outer polymeric layer can be greatly enhanced. More particu-larly, a method of making a preferred embodiment of the invention is where an elongate seamless or welded and drawn metal tube, having an annular wall of substantially uniform radial thickness around its circum~erence with a bore therethrough, is moved .

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through a heater having suitable heat capacity to bring the tube to a desired temperature and wherein the tube, if irregular in shape, may be straightened before or after the heating step by means of a straightening device such as, for example, a device using oppositely opposed spaced-apart rollers. A suitable thick-ness of polymeric adhesive is then deposited (preferably by ex-trusion) coextensively about the outer surface of the still heated metallic tube and the adhesively coated tube, while still heated, is then moved through an extrusion device where a heated outer layer of polymeric material is extruded coextensively about the - heated adhesi~ely coated metal tube. The outer polymeric layer is extruded in such a manner as to provide an annular wall thereof which is substantially uniform in radial thickness around its circumference and which is of sufficient thickness that, upon cooling to ambient temperature, its outer diameter is sized such that the tube can be attached, without dimensional alteration, to ; fittin~s standardly used to couple equivalently dimensional tubes having a singular polymeric or metallic wall. The still heated tube ~now having a bore therethrough enclosed by a composite wall comprising a heated inner metallic layer, an intermediate heated polymeric adhesive layer dlsposed about the inner layer and en-closed by an outer heated extruded layer of heated polymeric material) is then sufficiently cooled by suitable means (such as a water bath~ so that the outer polymeric layer becomes effective-ly bonded to the inner metallic layer and the tube can be handled and packaged.
~ lthou~h the invention has been described in detail for the purpose of illustrationt it is to be understood that such de-- . . , , . ~
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tail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An elongate deformable tube for use in the conveyance of fluids and/or fluid transmission signals under pressure having a bore therethrough enclosed by a composite annular wall comprising a seamless or welded and drawn inner layer made from a metallic material and an outer layer made from a polymeric material dis-posed in encompassing relationship about the inner layer, said inner and outer layers having annular shaped walls of substantial-ly uniform radial thickness around their circumferences, and said outer layer having its outer diameter sized during the pro-cess of making the tube such that the tube can be attached, with-out dimensional alteration, to fittings standardly used to couple equivalently dimensioned tubes having a singular polymeric metal-lic wall.

2. The tube of claim 1 wherein the inner and outer layers are bonded together by means of a polymeric adhesive interposed therebetween during the process of making the tube.

3. The tube of claim 2 wherein the adhesive is interposed by means of extrusion.

4. The tube of claim 1 wherein the outer polymeric layer is disposed in encompassing relationship about the inner layer by means of extrusion.

5. The tube of claim 1 wherein the polymeric material of the outer layer is a polyethylene composition.

6. The tube of claim 1 wherein the polymeric material of the outer layer is a polyvinyl chloride composition.

7. The tube of claim 1 wherein the metallic material of the inner layer is an alloy of copper.

8. The tube of claim 1 wherein the metallic material of the inner layer is an alloy of aluminum.

9. The tube of claim 1 wherein the polymeric material of the outer layer is a cross-linked polymeric material.

10. The tube of claim 9 wherein the cross-linked polymeric material is a high energy electron cross-linked material.

11. An elongate deformable tube for use in the conveyance of fluids and/or fluid transmission signals under pressure having a bore therethrough enclosed by a composite annular wall comprising a seamless or welded and drawn inner layer made from a metallic material and an outer layer disposed in encompassing relationship about the inner layer made from an extruded polymeric material, an extruded polymeric adhesive interposed between the inner and outer layers bonding them together, said inner and outer layers having annular shaped walls of substantially uniform radial thick-ness around their circumferences, and said outer layer having its outer diameter sized during the process of making the tube such that the tube can be attached, without dimensional alteration, to fittings standardly used to couple equivalently dimensioned tubes having a singular polymeric or metallic wall.

12. In a method of making an elongate deformable tube for use in the conveyance of fluids and/or fluid transmission signals under pressure having a bore therethrough enclosed by a composite annu-lar wall comprising a seamless or welded and drawn inner layer made from a metallic material and an outer layer made from an ex-truded polymeric material disposed in encompassing relationship about and bonded to the inner layer by means of a polymeric ad-hesive interposed therebetween, said inner and outer layers having annular shaped walls of substantially uniform radial thickness around their circumferences, and said outer layer having its outer diameter sized during the process of making the tube such that the tube can be attached, without dimensional alteration, to fittings standardly used to couple equivalently dimensional tubes having a singular polymeric or metallic wall, the method including the steps of:
a. Heating the inner metallic layer to a temperature suitable for effecting the bond desired;
b. Extruding a suitable thickness of the polymeric adhesive in encompassing relationship about the still heated inner layer;
c. Extruding the polymeric outer layer in encompassing relationship about the still heated adhesively coated inner layer in an amount such that, upon cooling the tube to ambient tempera-ture, the outer diameter of the outer layer is sized such that the tube can be attached, without dimensional alteration, to fittings standardly used to couple equivalently dimensioned tubes having a singular polymeric or metallic wall; and d. Cooling the tube so as to effectively bond the inner and outer layers together and permit handling and packaging of the tube.

13. The method of claim 12 including the step of straighten-ing the metallic inner layer prior or subsequent to the heating process of Step a.

14. The method of claim 12 including the step of cross-linking the polymeric outer layer by means of high energy elec-trons subsequent to the cooling process of Step d.