Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to hydraulic hose
and more particularly to an improved hose constructed of
synthetic materials.
It has been proposed before to provide a hydraulic
hose having an extruded synthetic polymeric core tube, fibrous
material disposed about the core tube to reinforce it against
bursting under the pressure of fluids conveyed by the hose
and an extruded polymeric sheath to protect the fibrous ma-
terial from abrasion. For example, such hoses are disclosed
in the Matthews Paten~ U.S. 3,604,461 and in the Atwell Patent
i U~S. 3,654,967. The fibrous reinforcing material may be braided
synthetic filaments or, as disclosed by Matthews and Atwell,
the ibrous reinforcing material may be layers of synthetic
filaments helically wound about ~he core tube. The helically
wound reinforcement is always used in pairs of overlapping ~`
` oppositely wound layers to resist both radial and axial elon-
gation of the hose under pressure. The helically wound rein-
forcement~ or so-called "lapped construction" has the advantage ;~
over braided layers that it can be applied at faster production
rates and, because there is no interweaving of fibers as in
braiding, it permits greater efficiency in the use of the fiber
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and increased fatigue life. ~owever, in order to obtain optimum
performance, each layer, i.e., each layer of helically wound
fibers must be bonded to the adjacent layer.
Both ~atthews and Atwell recognize that the adjacent
layers must be bonded together. Matthews bonds the layers
together by flowing a heated bonding agent such as Adiprene
L-100, a polyurethane prepolymer, over the surface layer of
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reinforcing material wound about a core tube, passes the
coated product through a wiper to spread the bonding agent
over the surface and then winds a second layer of filaments
over the bonding material.
Atwell, on the other hand, bonds the adjacent layers - -
together by applying a solvent such as resorcinol to the
surface of one layer and winding a second layer over the `
`~ solvent-wet surface. The assembly must then be passed through ; ~ ;
a hot water bath to remove the solvent.
If the bond is made by an adhesive or bonding mechanism ;~
~;i which is weak or flexible the burst strength of the hose is `~
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~`~ low. But if the bond is strong or very stiff, the hose burst
strength is much higher. With no bond at all the burst is very
low showing very poor efficiency in fiber use. In fact, with-
out any bonding on a hose with a single lap (2 layers) of
~r~ helically wound reinforcement, the burst strength is not as
~:: ! good as it would be if braided reinforcing material were used. `~
~i The method of bonding usediby Atwell is to dissolve a `~
; portion of the fibers in each layer and bond these dissolved
fibers to each other. This has the disadvantage that it is `;
necessary to replace that portion of the fiber lost by dis- ;
solution to compensate for loss in burst strength. ~ ! .
The Matthews type of bond has the advantage over the
Atwell bond that no fibers are destroyed and also the bond
is resilient and elastomeric. With the Atwell bo~d, the
fibers themselves carry the load and do not have the resilience
to withstand overload without breaking which weakens the bond
~, interface and deleteriously afects the hose performance. i
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With the resilient bond mechanism of Matthews, the
bonding materials tend to soak in and saturate the fiber
layers and eliminate the desired mobility of fibers in the
reinforcing layer. The Matthews construction inherently
gives a very stiff hose. Any attempts to increase flexibility
by making the adhesive more flexible also weakens the bond
; and lowers hose performance. Therefore, the Matthews hose
can be stiff with high performance or flexible with low
performance, but never both.
It has also been proposed to coat layers of braided
insulation with a rubber solution such as, for example in
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U.S. Patent No. 3,750,712. ~oreover, hoses having helically
~;`, wound layers of wire with a rubber intermediate ply have
-1 been disclosed in U.S. Patents No's. 3,506,040; 2,033,559;
.....
l 3,481,368; 3,866,633; 2,237,490 and 2,047,770. In addition,
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a hose having wound tape reinforcing is disclosed in U.S. `
Patent No. 1,940,868. Also, a pipe having at least three
oppositely wound layers of reinforcing threads bonded by
I wetting the threads with a bonding substance or by applying
a liquid bonding material to surface of the wound threads
is disclosed in U.S. Patent 3,107,698. However, none of
the heretofore available hoses have a reinforcing structure
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for the core tube which is both flexible and sufficiently
strong to provide a high burst strength. ;~
It is an object of this inven$ion to prc)vide a hose
i ~ having a synthetic polymeric core tube and reinforcement for
r; the core tube which is flexible and effectively supports the
~ core tube against bursting under high fluid pressures.
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Another object of the invention is to provide a hose having
a synthetic polymeric core tube and oppositely helically ;
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wound reinforcing strands of fibers with an improved bond ~
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between layers of the strands. A further object of the
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invention i5 to provide a hose having oppositely helically
wound layers of s~rands of synthetic fiber bonded together
with a bonding material which does not modify or destroy
the surface of the strands and provides a flexible and
strong reinforcing structure for the core tuba.
Other objects will become apparent from the follow-
ing description with reference to the accompanying drawing
wherein
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; Figure 1 is a fragmentary side elevation illustrating ~
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an embodiment of the invention;
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;i Figure 2 is a cross-section taken along the line 2-2
i~ of Figure l; and
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`1 Figure 3 is a diagrammatic illustration of a method
of ma!king the hose provided by the invention.
The foregoing objects and others are accomplished
-~ 20 in accordance with this invention, generally speaking, by
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providing a hydraulic hose having an extruded synthetic
;
; polymeric core tube, a first layer or half-lap of helically ;
wound strands of fibroùs material wound in one direction di-
rectly against the core tube and mechanically bonded thereto, a
second layer of oppositely helically wound strands about the
first layer, an extruded layer of flexible elastomeric material
` I disposed between the two layers mechanically bonding the layers
together and preferably an extruded synthetic polymeric sheath
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about the r~inforcing layers. The hose may have one,
two or more pairs of half-laps of helicallY wound strands
of fibrous material bonded together with an intermediate
polymeric layer.
.: The novel hydraulic hose may be made by extruding
:~ a synthetic polymer to form a core tube of indeterminate
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; length, softening the surface of the core tube with a solvent
, therefor, helically winding a layer of strands of fibrous ~.
~:~ material to form a layer on the core tube while the surface ~: :
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; 10 is still soft at a tension whereby the skrands becomes only ; -
partially embedded in the surface, extrud.ing a synthetic . .:
~ polymer over the first layer to form a flexible layer of
f~ polymer and winding in a direction opposite from that of the
j. fi.rst layer a second layer of strands of fibrous material
, over the polymer layer while it is still soft at a.tension
~ ~ whereby the strands becomes only partially embedded therein
i~ J to form a mechanical bond between the two layers. Additional
. bonded layers may be provided and a sheath may be formed over ;;~
~¦ the surface of reinforcing layers by extruding a polymer ..
. 20 thereover. .:
:1 It has been found that the extruded layer of polymer
~: between the two layers forms a bond at the fiber layer .lnter-
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. face with a minimum number of fibers of the strands being
restrained so that the fibrous reinforcing material is re-
silient and does not appreciably stiffen the tube. At the
~: same time, however, the lapped helically wound reinforcing
material provides greater resistance to bursting of the core :~
tube than would a braid containing a similar number of fibers. `~
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Since the extruded layer of polymer is a continuous coherent ~-~
layer of material the mechanical bonding of the two layers `
together does not aepend upon adhesion of the elastomeric
layer to the fibers.
The core tube may be extruded from any suitable
synthetic polymer such as, for example, an elastomeric poly~
urethane, nylon, a segmented thermoplastic copolyester
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~: elastomer, polyvinyl chloride or the like. The segmented ~
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thermoplastic copolyester elastomer may be the one disclosed
in U.S. Patent 3,766,146 or "Hytrel" sold by E.I. duPont de
Nemours and Company. Suitable polyurethanes are disclosed .
in the Matthews Patent U.S. 3,722,550 and suitable nylon is
~ ~, disclosed in the Brumbach Patent U.S. 3,062,241.
!`, ~ Any suitable fibrous material or mixtures thereof may
;~ be used to form the reinforcing layers. For example, an
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aromatic polyamide such as "Kevlar" sold by E.I. duPont de
-, Nemours and Company may be used. A poly(alkyleneterephthalate)
ester, nylon or the like may be used. Suitable materials are
disclosedj for example, in the aforesaid patents. i`
~; 20 Any suitable synthetic polym~r or blend thereof may be ~ ;
~l extruded over one layer to provide an intermediate bonding
;~ layer. The polymer may be, for example, a segmented thermo-
' plastic copolyester elastomer such as "Hytrel", nylon, poly-
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urethane or other thermoplastic polyester or blend thereof.
The layer should be sufficiently thick to provide for the
surfaces of the fibers of both laps to be partially embedded
~3 therein and form a mechanical bond. For best results, the
i layer will usually be from about 0.003 inch to 0.10 inch
thick~
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~ The protective sheath may be formed by extruding
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any suitable synthetic polymer over the surface of the
fibrous reinforcing material. Examples of suitable polymers
are nylon, segmented thermoplastic copolyester elastomer
and polyurethane.
Best results have been obtained so far with hoses
in which the bonding material used between the layers of
reinforcing material is a segmented thermoplastic copolyester
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elastomer. Such a polyester having a hardness of Shore 90A
~ 10 is preferred because it produces a bond haviny the best peel
,` strength but other polyesters of this type having a hardness
o~ Shore 55D and 63D have been used to advantage. In fact,
a hose in which the intermediate layer of elastomer has a
~ ' hardness of Shore 63D has given the best overall hose per- ~
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formance.
Referring now to the drawingl one embodiment of the
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hydraulic hose provided by the invention is illustrated in
Figures 1 and 2. This hose has a core tube 10 formed by ~ `
;; extruding "Hytrel" having a hardness of Shore 55D and
i~ 20 extruding a skin lOa of elastomeric polyurethane over the
external surface~of core tube 10. Strands of Kevlar
aromatic polyamide fibers having a 1500 denier, a tenacity
of about 20 and an elongation of about 4% are wound at
~; a lay of about 52 with the axis of the core tube directly
over core tube 10. The core tube 10 has been wet with
t solvent for the polyurethane to soften it before the -~
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strands are wound thereabout so that the strands become
~;i partially embedded in the surface lOa of core tube 10
and the first layer is mechaniGally bonded thereto. A
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second layer of strands 13 wound in a direction opposite
from the winding of layer 11 is disposed about layer
ll with an intermediate layer of extruded "Hytrel"
about 0.003 inch thick which mechanically bonds the
two layers ll and 13 together. A sheath 14 is extruded
over layer 13. A suitable adhesive may be included
between layer 13 and the sheath. The sheath may be
"~ytrel" or a polyurethane elastomer.
As illustrated in Figure 3 of the drawing, the
hose of Figure 1 is formed by first extruding the core
tube lO, wetting the core tube sur~ace with a suitable
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solvent or plasticizer which will suften the surface ~-
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thereof and winding strands of fibrous material about the
core tube to form a first layer ll. A polymer layer 12 is
then extruded over layer ll and while this polymer layer
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, is still soft a second layer 13 of fibrous material is
` wound under a tension which will cause the strands to
~ become partially embedded in layer 12 to form a mech^anical
'-l bond. A sheath is then 0xtruded over layer 13. The polymer
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l 20 of the sheath may be ~ured by irradiation with electrons,
; if desired.
Suitable solvents for softening the surface of
core tube lO and for adhesively bonding the reinforcing
material to the sheath are disclosed, for example, in
U.S. Patents 3,726,321 and 3,332,447. Alternately, a hot
melt adhesive or a solvent free adhesive of the type disclosed
in U.S. Patent 3,1I6,760 may be used.
i~ It has been found that the hose illustrated in Figure
l will perform at unusually high temperatures. A hose
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having the structure described above with xespect ~o
Figure 1, for example, had a burst strength of 20,500
p.s.i. at room temperature and 15,500 p.5.i. at 200F.
A hose made in accordance with the disclosure in U.S.
Patent 3,604,461 to the same dimensions as those used in
the hose of the invention, on the other hand, had a burst
strength of 22,000 p.sJi. at room temperature but only
14,000 p.s.i. at 200~F. This is an indication that the
novel elastomeric layer between layers of reinforcing
strands does not permit the fibers to displace at high
temperatures so the hose loses less of its burst strength.
It is to be understood that core tube 10 may be
;, extruded from any suitable polymer, other than "Hytrel."
- For example, it may be a nylon core tube which is not
bonded to the reinforcing material or it may be a nylon
tube 10 having an elastomeric polyurethane skin lOa bonded
to the reinforcing material. Moreover, a hot melt adhesive
may be used to bond the core tube to the reinforcing material.
An advantage of the hose of this invention is that
~; 20 it can be made with a conventional extruder and avoids the
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necessity of making critical adhesive formulations and of
accurate control of the processing to ensure proper curing
of the adhesive to produce the desired properties.
Although the invention has been described in detail
for the purpose o illustration, it is to be understood that
such detail 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 except
as it may be limited by the claims.
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