Note: Descriptions are shown in the official language in which they were submitted.
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Bac~ground of the Invention
Field of the Invention
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This invention relates to flexible hydraulic hose,
and more particularly to hydraulic hose which can withstand ~;
high pressure, maintain flexibility, and which can be -
assembled to couplings designed for other hoses.
Description of the Prior Art
Flexible hoses made of elastomeric or flexible
plastic materials require reinforcement by material such as
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10~ braided, helically wound, or knitted rayon, Dacro~, stainless
steel wire, or the like when the hoses are to be used for
conveying fluids under high pressure, such as hydraulic
pressures over 1,000 psi. For small diameter hoses, such as
hoses having an inner diameter of 1/4", one layer of
reinforcement material may be sufficient to give the hose
a burst strength of up to 6,000 psi, depending upon the extent
of coverage provided by the reinforcement, and the reinforcement
material used. For larger diameter hoses, such as hoses
having an inner diameter larger than 1/4", more than one
layer of reinforcement material is usually required to
provide a high burst strength.
When two or more layers of reinforcement material
are used, several problems arise. If the reinforcement
material is steel wire applied at a conventional braid angle
o~ approximately 54, the burst strength of the hose is high,
however, there is little expansion or elongation of the
reinforcement material, and upon application of internal
fluid pressure to the hose, the first reinforcement layer
does not stretch a sufficient amount to transfer a substantial
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3 1078308
part o~ the load to the second reinforcement layer. In
addition, the rigidity of the steel wire and the resultant
resistance to elongation and expansion of the hose under
hydraulic shock pressures results in the hose failing to
cushion or dilssipate such shock pressures, which may have
adverse effects on the other parts of the hydraulic system.
In contrast, if a fibrous non-metallic material
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E such as Nylon 6/6, Dacro~, rayon, or the like is used as
the reinforcement material, the expansion or elongation
of the reinforcement material is higher, and when hydraulic
shock pressures occurr the reinforcement material yields
to a greater extent that steel wire and the insides of the
hose may increase in volume to the extent that sluggish
or spongy reaction of other components in the hydraulic
system will occur.
An additional disadvantage of steel wire reinforce-
ment is that the hose is stiff and relatively infleXible.
When a conventional fibrous non-metallic reinforcement
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material such as ~ylon 6/6, Dacron~ rayon, or the like is used,
the hose is more flexible but may be subject to excessive
elongation or expansion.
The aforementioned problems were overcome in
co-pending canadian patent application No. 224,898 filed on
April 17, 1975 in the name of Parker-Hannifin Corporation by
the use of two layers of a braided fibrous aromatic nylon
yarn that is available from the E.I. duPOnt de Ne~mours Company
under the trade mark Kevlar and which was formerly designated
by duPont as Fiber B ~ylon. These two layers of Kevlar replace
the other reinforcement layers used in the prior art. The use
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of two layers of Kevlar results in a relatively flexible hose
having a very high burst strength and which can dissipate
shock pressures without causing system sluggishness or spon-
giness. The disadvantage of such a hose construction is that
it is relatively expensive due to the high cost of the Kevlar
material. However, because of the high strength of Kevlar, a
single layer of Kevlar reinforcement material may provide suf-
ficient strength for some applications that would otherwise
require two layers of some other non-metallic reinforcement
material. The use of a single layer of Kevlar in such an
application minimizes the cost problem associated with this
material, but results in a hose with a smaller total wall
thickness than hoses using two layers of other reinforcement
material. Thus, a hose using a single layer of Kevlar would
require a different set of couplings than those used by hoses
of another construction. In addition, the smaller wall thick-
ness results in the hose having less resistance to kinking.
-S-ummary of the;Invention
The present invention provides a solution to the
aforementioned problems of hose strength, flexibility, dissi-
pation of shock pressures, hydraulic system sluggishness, cost,
utilization of existing couplings and kinking. This is accom-
plished by providing a hose with a synthetic polymeric core
tube, a first layer of Kevlar reinforcement material about
the core tube, a second layer of some other less expensive
fibrous reinforcement material over the Kevlar reinforcement
material, and a sheath of synthetic polymeric material over
the less expensive reinforcement material.
According to the present invention, there is provi-
ded a high burst strength flexible composite reinforced hose
for conveying fluids under pressure comprising a synthetic
polymeric core tube, a first layer o fibrous reinforcing ~-
material disposed adjacent the core tube having synthetic
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10783()8
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filaments having a tenacity at room temperature of from 15 to
about 25 grams per denier, and another layer of reinforcing
material over the first layer and formed of composite fibers
having a tenacity at room temperature less than that of said
first layer.
Brief Descripti~n of the Drawings
Figure 1 illustrates a side elevation, partly broken
away in successive structural layers, of a hose made .........
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E
.. . ............. .. ... ~ ~ . . .
. . .. . ...... . .. ~ ..... .
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in accordance with the present invention.
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Description of the Preferred Embodiment
.
A hose constructed in accordance with this
invention is illustrated in figure 1. This figure illustrates
a hose 10 having a core tube 12 of synthetic polymeric
material, a first layer of reinforcement material 14 comprising
composite fibers, a second layer of reinforcement material
16 of composite fibers, and an outer sheath 18 of synthetic
polymeric material. The material utilized to form the
core tube 12 and the outer sheath 18 may be selected from
any of the well-known synthetic polymers used in the hose :
industry to produce reinforced hoses, such as Nylon 6/66,
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Nylon 11, Hytre~, polyurethane, or the like. The
selection of the particular material used for the core
tube and sheath will depend upon the end use and the properties
desired of the hose. The material selected for the sheath
18 may be the same or different from the material chosen
for the core tube 12.
The first reinforcing layer 14 is composed of Kevlar
material which has a modulus of elasticity of between 400
and 500 grams per denier at room temperature and at least
300 grams per denier at 300F. Its tenacity is between
15 and 25 grams per denier at room temperature, and over
10 grams per denier at 260F. At room temperature, Kevlar
has an elongation at break of about 4%. The density of the
yarn is between 1.40 and 1.50 and the tensile strength is
about 405,000 psi.
The second reinforcing layer 16 is composed of
synthetic filaments having a tenacity lower than that of
30 E Kevlar, such as Nylon 6/6, rayon, or Dacron~C, whlch is
6- ~1~783()~3
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either a polyethylene terephthalate ester or a polyalkylene
terephthalate ester. These materials have a tenacity of
about 7 to 11 grams per denier.
:
Both the first and second reinforcing layers may
be either braided or helically wound. In the case of a ~-;helically wound reinforcement, one strand is helically wound
; on the core tube in one direction and another strand is
helically wound over the first strand in the opposite
direction and the two strands together comprise one layer
of reinforcement material. The first reinforcing layer
may or may not be bonded to the core tube and the second
reinforsing layer may or may not be bonded to the first
reinforcing layer and/or the sheath. However, in the
preferred embodiment of the invention, there is no bon~
between the first and second reinforcing layers, but there
is a bond between the second layer and the sheath. Any
suitable method may be used for bonding the various layers
together such as epoxy adhesives, polyurethane adhesives,
or solvents.
The Kevlar yarn imparts greater radial and axial
dimensional stability to the hose when subjected to fluid
pressure than hoses having reinforcement layers of Nylon 6/6, -
Dacron, rayon and other non-metallic fibrous materials
heretofore used because it has a substantially higher modulus
and a lower elastic elongation value than those other materials.
The lower elastic elongation, however, still permits
sufficient expansion of the first reinforcement layer to
allow some sharing of the load by the second reinforcement
layer, but the expansion is less than that of Nylon 6/6, Dacron,
rayon, or the like so that hydraulic system sluggishness or
sponginess is minimi~ed.
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On the other hand, because the elastic elongation
of Kevlar i5 substantially greater than that of steel wire,
the expansion in volume under fluid pressure of the hose -
having a Kevlar reinforcement layer is greater than that
of a hose having a steel wire reinforcement layer. Thus, `~-
a hose using Kevlar as the reinforcement material cushions
or dissipates hydraulic shocks to a greater degree than a
hose with steel reinforcement.
Although the second reinforcing layer, which is
of material other than Kevlar, shares part of the load, it
also functions as a filler to increase the wall thickness
of the hose so that the hose can be assembled to standard
co~plings. (Use of a second layer of Xevlar to increase the
wall tllickness so that the hose can be assembled to standard
couplings is not economical because, as previously mentioned,
Kevlar is more expensive than ~ylon 6/6, Dacron, rayon, or the
like.) In addition, the second reinforcing layer prevents
crushing of the Kevlar layer when the coupling is attached
since it is not as brittle as Kevlar. Also, by reinforcing
the hose structure, the second layer also minimizes hose
kinking. It should be noted that the hose can be constructed
with or without an outer sheath. When constructed without
an outer sheath, the hose is very flexible since the material
used for the second reinforcing layer is more flexible than
that used for the outer sheath.
Variations of the present invention will be apparent
to those having ordinary skill in the art and the invention -~
is limited only by the spirit and scope of the following claims.
