Note: Descriptions are shown in the official language in which they were submitted.
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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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
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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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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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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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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
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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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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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