Note: Descriptions are shown in the official language in which they were submitted.
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FLEXIBLE BRAIDED GARDEN HOSE
Field of the invention
[0001] The present invention generally relates to the technical
field of the flexible hoses, and particularly concerns a reinforced
flexible braided garden hose and its manufacturing process.
Background of the invention
[0002] It is known that flexible garden hoses, i.e. those hoses
which are designed for irrigation purposes, include one or more inner
layers, one or more reinforcing layers and one or more outer layers.
[0003] The inner and outer layers are usually made of an
extruded polymer thermoplastic material, such as PVC, while the
reinforcing layers are made of polyester yarns.
[0004] Generally speaking, two kinds of reinforcing layers are
known for garden hoses, the knitted one and the braided one. As
known, these two different kinds of reinforcing layers give to the hose
unique properties.
[0005] In fact, while the knitted hoses have high quality and
great flexibility and resistance to deflections, the braided hoses are
preferable for cost-effectiveness and resistance to internal pressure.
[0006] A braided reinforcing layer usually consist of a first
plurality of textile yarns superimposed to a second plurality of textile
yarns.
[0007] In order to form the reinforcing layer, a braiding machine
is used which has two consecutive counter-rotating braiding units.
During the braiding process, the first braiding unit winds the first
plurality of textile yarns around the bearing layer in a spiral-like
manner with a predetermined first inclination with respect to the axis of
the hose, while the subsequent braiding unit winds the second plurality
of textile yarns onto the first plurality with an inclination which is
opposite to the first inclination.
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[0008] One of the problem of the known flexible hoses is the so-
called "swelling" under internal pressure. This is mainly due to the
nature of the materials used both for the inner and outer layers and for
the reinforcing layers. The swelling of the hose unavoidably negatively
affects also the burst pressure.
[0009] Although in general the braided hose is less subject to
this problem with respect to the knitted hose, for certain applications it
is desirable to minimize as much as possible or even completely
overcome the swelling problem, as well as to improve the burst
pressure.
[0010] To date, the known solutions to this problem are
unacceptably expensive for the market of braided hoses.
[0011 ] In fact, hoses are known having one or more reinforcing
layers fully consisting of high tenacity fibers, such as Kevlar , carbon
fibers and the like. From EP-A-0074747 is known an example of these
hoses.
[0012] As it is apparent, although these solutions can completely
obviate to the swelling problem, they are designed for applications
different from the irrigation. In fact, the reinforcing layers are netted on
the bearing layer, in such a manner to completely cover it. As a result,
these solutions are unacceptably expensive for the market of the
braided garden hose.
[0013] An other alternative solution to this problem is to
superimpose to the first braided layer at least one second reinforcing
polyester layer. From FR-A-2762376 is known an example of these
hoses.
[0014] This solution cannot completely obviate to the swelling
problem, because of the nature of the materials used. Moreover, it
again increases the production costs of the hose. As it is apparent, a
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high production cost means also a high environmental impact of the
hose.
[0015] Another solution to the problem of the swelling known in
the art of hose manufacturing is to increase the thickness of the outer
PVC layer, in such a manner that it cooperate with the reinforcing
layer to contrast the internal pressure.
[0016] This solution also cannot completely obviate to the
swelling problem, because of the nature of the materials used, and
again involves unacceptably high production costs and environmental
impact. Moreover, as it is apparent, a thick outer layer reduces the
flexibility and the so-called "malleability" of the hose.
Summary of the invention
[0017] Main object of the present invention is, therefore, to
provide a braided garden hose, as well as a manufacturing process
thereof, that minimizes or even completely eliminates the problem of
swelling under pressure in an economical and simple manner.
[0018] An other object of the present invention is to provide a
braided garden hose having an improved burst pressure.
[0019] Another object of the present invention is to provide a
cost-effective braided garden hose.
[0020] A further object of the present invention is to provide a
braided garden hose that has the lowest possible environmental
impact.
[0021] Another object of the present invention is to provide a
process for manufacturing a braided garden hose in a simple and
economical manner.
[0022] These objects, as well as others that will be more
apparent hereinafter, are fulfilled by a flexible hose which comprises
one or more inner first layers made of a first thermoplastic polymer
material, preferably plasticized PVC; one or more reinforcing braided
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layers and one or more outer second layers made of a second
thermoplastic polymer material, preferably plasticized PVC.
[0023] The first polymer material may have a Shore A hardness
higher than the hardness of the second polymer material.
[0024] in particular, the Shore A hardness of the first polymer
material may be of 40 to 95, and preferably of 70 to 80, while the
Shore A hardness of the second polymer material may be of 40 to 95,
and preferably of 60 to 70.
[0025] As used herein, the term "braided layer" or derivatives
thereof is intended as a layer formed by a first plurality of textile yarns
superimposed to a second plurality of textile yarns.
[0026] The yarns of the first and second plurality are not knitted,
netted nor otherwise connected each other.
[0027] The yarns of the first and second plurality do not
completely cover the bearing layer on which they are wound.
[0028] In particular, each yarn of the first and second plurality
has a predetermined pitch, i.e. the distance between two points of the
same yarn taken along an axis parallel to the axis of the hose, and a
predetermined distance from the preceding and subsequent yarn of
the same plurality.
[0029] The first plurality and/or the second plurality of yarns of
at least one of the braided layers of the hose comprises one or more
first yarns consisting of fibers having an elongation at break of less
than 5%,. and preferably less than 3%, at ambient temperature as
measured according to DIN EN ISO 2062 and one or more second
yarns consisting of polyester fibers.
[0030] Thanks to these features, the one or more first yarns
having low tensile elongation, which are spiral-like wound around the
hose for the entire length thereof, act as "barrier" against the pressure
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internal to the hose, in such a manner to minimize or even completely
overcome the problem of swelling.
[0031] At the same time, the fact that the braided reinforcing
layer comprise both low tensile elongation and polyester fibers results
in an important cost-effectiveness of the hose, which also means a low
environmental impact.
[0032] In fact, as it is apparent, the hose according to the
invention is very economical if compared with the netted hoses of the
prior art, such as the above cited EP-A-0074747.
[0033] Moreover, the hose according to the invention is easier to
manufacture, and therefore more economical, with respect to the
double layered hoses of the prior art such as FR-A-2762376, because
only one layer is to be manufactured instead of two. As a result, less
energy is to be spent for manufacturing the hose of the invention with
respect to the hoses of the prior art.
[0034] Further, the hose of the present invention may have
thinner outer layers with respect to the prior art solutions, because its
braided layer need not to cooperate with the outer layer to contrast the
swelling.
[0035] Advantageously, the first yarns having low tensile
elongation, which may pertain to the first and/or the second plurality of
textile yarn of the braided layers, may also have high tenacity.
[0036] In particular, the first yarns may have a tenacity of at
least 1500 mN/tex at ambient temperature as measured according to
DIN EN ISO 2062, preferably of at least 2000 mN/tex and more
preferably of at least 2500 mN/tex.
[0037] Suitably, the first yarns may be chosen among the group
consisting of aramid fibers, particularly Kevlar , Nomex or Twaron ,
high modulus polyethylene fibers, poly-ether-ether-ketone fibers,
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metallic fibers, carbon fibers, basalt fibers, Rayon fibers or hybrid
fibers obtainable by coupling two or more thereof.
[0038] In a further aspect, the present invention relates to a
process for manufacturing the above braided garden hose, which
comprises the steps of: a) extruding a first thermoplastic polymer
material for manufacturing at least one inner first layer; b) braiding
externally to said at least one inner first layer at least one reinforcing
layer for manufacturing a semi-finished hose and c) extruding
externally to the semi-finished hose a second thermoplastic polymer
material for manufacturing at least one outer second layer.
[0039] The braiding step b) comprises a first step b') of
deposition externally to the at least one inner first layer of the second
plurality of textile yarns and a second step b") of deposition onto the
second plurality of the first plurality of textile yarns to form the
reinforcing layer.
[0040] Suitably, the above process may further comprise a step
d) of heating the semi-finished hose after the second deposition step
b") for heat shrinking the polyester yarns.
[0041] This is particularly advantageous if the first plurality of
the braided layer fully consist of polyester fibers, while the second
plurality comprise both low elongation and polyester fibers. In this
case, the polyester fibers of the first plurality heat shrink over the low
tensile elongation fibers of the second plurality, in such a manner to
stabilize it onto the bearing layer.
[0042] In fact, the polyester fiber is a high-heat shrinkable fiber,
while the low elongation fibers are generally not or very few heat
shrinkable.
[0043] Therefore, thanks to the heating step, the low elongation
fibers perfectly adhere to the bearing layer, thus improving the
mechanical properties and the performances of the hose.
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[0044] Advantageous embodiment of the invention are defined in
accordance with the dependent claims.
Brief description of the drawings
[0045] Further features and advantages of the invention will
become more apparent from the detailed description of a few
preferred, non exclusive embodiments of the invention, presented by
way of illustrating and non-limiting examples in connection with the
accompanying drawings in which:
[0046] the FIGS. I and 2 are schematic views of a first and
second embodiment of the hose according to the invention;
[0047] the FIGS. 3 and 4 are schematic views of a third and
fourth embodiment of the hose according to the invention;
[0048] the FIGS. 5 and 6 are schematic views of a fifth and sixth
embodiment of the hose according to the invention;
[0049] the FIG. 7 is a schematic view of a production line of the
hose according to the invention.
Detailed description of some preferred embodiments of the invention
[0050] With reference to the above cited drawings, a flexible
garden hose 1 is described which comprises an inner first layer 2
made of a first thermoplastic polymer material, e.g. plasticized PVC, a
reinforcing braided layer 3 and an outer second layer 4, made of a
second thermoplastic polymer material, e.g. plasticized PVC.
[0051] The hose I may comprise other polymer layers, both
internally and externally to the inner and outer layers 2 and 4, as well
as other reinforcing layers. However, preferably, the hose I will
comprise only one braided layer 3.
[0052] The braided layer 3, which consists of a first plurality 5 of
textile yarns superimposed to a second plurality 6 of textile yarns, may
comprise both yarns consisting of polyester fibers and one or more
yarns consisting of a fiber having a tensile elongation of less than 5%,
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preferably less than 3%, at ambient temperature as measured
according to DIN EN ISO 2062 and a tenacity of at least 1500 mN/tex
at ambient temperature as measured according to DIN EN ISO 2062,
preferably of at least 2000 mN/tex and more preferably of at least 2500
mN/tex.
[0053] The latter fibers may be, as a non limiting example,
Kevlar or Carbon fibers having a linear density of 1100 or 2200 dtex.
In fact, the Kevlar fiber has a tenacity of 2000 - 2500 mN/tex and an
elongation at break of 2 - 4%, while the carbon fiber has a tenacity of
1500 - 2000 mN/tex and an elongation at break of 1 - 3%.
[0054] By way of comparison, the polyester fibers having a
linear density of 550 or 1100 dtex have an elongation at break of about
- 15% and a tenacity of about 800 mN/tex.
[0055] In the FIGS. I to 6 several embodiments of the invention
are shown, which differ each other in the configuration of the braided
reinforcing layer 3. In these drawings, the Kevlar or Carbon fibers
have been outlined in solid black, while the polyester fibers are in
white. In each drawing, the working direction by which the hose moves
along the production line is indicated by V.
[0056] The FIG. I shows a first embodiment of the hose
according to the invention, in which the yarns of the first plurality 5 of
the braided layer 3 consist only of polyester fibers, while in the second
plurality 6 one first yarn 7 consists of a Kevlar or Carbon fiber and
the remaining second yarns 8 consist of polyester fibers.
[0057] The FIG. 2 shows a second embodiment of the hose
according to the invention, in which the first plurality 5 of the braided
layer 3 consists only of polyester fibers, while in the second plurality 6
two first yarns 7, 7' consist of Kevlar or Carbon fibers and the
remaining second yarns 8 consist of polyester fibers.
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[0058] The FIG. 3 shows a third embodiment of the hose
according to the invention, in which the second plurality 6 of the
braided layer 3 consists only of polyester fibers, while in the first
plurality 5 one first yarn 7 consists of a Kevlar or Carbon fiber and
the remaining second yarns 8 consist of polyester fibers.
[0059] The FIG. 4 shows a fourth embodiment of the hose
according to the invention, in which the second plurality 6 of the
braided layer 3 consists only of polyester fibers, while in the first
plurality 5 two first yarns 7, 7' consist of Kevlar or Carbon fibers and
the remaining second yarns 8 consist of polyester fibers.
[0060] The FIG. 5 shows a fifth embodiment of the hose
according to the invention, in which the first plurality 5 of the braided
layer 3 comprises one first yarn 7 consisting of a Kevlar or Carbon
fiber and the remaining second yarns 8 consisting of polyester fibers,
while the second plurality 6 comprises third yarns 9 consisting of
polyester fibers and one fourth yarn 10 consisting of a Kevlar or
Carbon fiber.
[0061] The FIG. 6 shows a sixth embodiment of the hose
according to the invention, in which the first plurality 5 of the braided
layer 3 comprises two first yarns 7, 7' consisting of Kevlar or Carbon
fibers and the remaining second yarns 8 consisting of polyester fibers,
while the second plurality 6 comprises third yarns 9 consisting of
polyester fibers and two fourth yarns 10, 10' consisting of Kevlar or
Carbon fibers.
[0062] Anyway, it is understood that the number of polyester
and Kevlar or Carbon fibers may vary in the first and/or the second
plurality of the braided layer 3 according to needs, without departing
from the scope or spirit of the invention.
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[0063] The hose of the invention may be manufactured by the
production line 20 shown in FIG. 7. In this drawing, the direction in
which the hose advances trough the production line is indicated by V.
[0064] In the first extruder 21 a first thermoplastic polymer
material, e.g. plasticized PVC, is extruded for manufacturing the inner
first layer 2.
[0065] In the subsequent braiding machine 22 the reinforcing
layer 3 is braided onto the inner layer 2. In particular, the braiding
machine 22 comprises a first braiding unit 23 for winding the first
plurality of textile yarns 5 around the bearing layer 2 and a subsequent
second braiding unit 23' for winding the second plurality of textile
yarns 6 onto the first plurality 5. As a result, a semi-finished hose is
manufactured comprising the inner layer 2 and the braided layer 3.
[0066] In the second extruder 24 a second thermoplastic
polymer material, e.g. plasticized PVC, is extruded to cover the semi-
finished hose by the outer layer 4.
[0067] According to the exemplary embodiments shown in the
FIGS. 1 to 6, each braiding unit 23, 23' comprises six yarn reels, in
such a manner that both first and second plurality 5 and 6 consist of
six yarns.
[0068] In particular, the first embodiment of FIG. I may be
manufactured by a braiding machine 22 having the first braiding unit
23 comprising a single reel of the first yarn 7 consisting of a Kevlar
or Carbon fiber and the remaining five reels of second yarns 8
consisting of polyester fibers, while the second braiding unit 23'
comprises six reels of polyester yarns.
[0069] The second embodiment of FIG. 2 may be manufactured
by a braiding machine 22 having the first braiding unit 23 comprising
two reel of the first yarns 7, 7' consisting of a Kevlar or Carbon fibers
and the remaining four reels of second yarns 8 consisting of polyester
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fibers, while the second braiding unit 23' comprises six reels of
polyester yarns.
[0070] The third embodiment of FIG. 3 may be manufactured by
a braiding machine 22 having the first braiding unit 23 comprising six
reels of polyester yarns, while the second braiding unit 23' comprises
a single reel of the first yarn 7 consisting of a Kevlar or Carbon fiber
and the remaining five reels of second yarns 8 consisting of polyester
fibers.
[0071] The fourth embodiment of FIG. 4 may be manufactured
by a braiding machine 22 having the first braiding unit 23 comprising
six reels of polyester yarns, while the second braiding unit 23'
comprises two reels of the first yarns 7, 7' consisting of a Kevlar or
Carbon fibers and the remaining four reels of second yarns 8
consisting of polyester fibers.
[0072] The fifth embodiment of FIG. 5 may be manufactured by
a braiding machine 22 having both the first and second braiding units
23, 23' which comprise a single reel of Kevlar or Carbon fiber and
the remaining five reels of polyester fibers. In particular, the first
braiding unit 23 comprises a single reel of the fourth yarn 10
consisting of a- Kevlar or Carbon fiber and the remaining five reels of
third yarns 9 consisting of polyester fibers, while the second braiding
unit 23' comprises a single reel of the first yarn 7 consisting of a
Kevlar or Carbon fiber and the remaining five reels of second yarns 8
consisting of polyester fibers.
[0073] The sixth embodiment of FIG. 6 may be manufactured by
a braiding machine 22 having both the first and second braiding units
23, 23' which comprise two reels of Kevlar or Carbon fiber and the
remaining four reels of polyester fibers. In particular, the first braiding
unit 23 comprises two reels of the fourth yarns 10, 10' consisting of
Kevlar or Carbon fibers and the remaining four reels of third yarns 9
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consisting of polyester fibers, while the second braiding unit 23'
comprises two reels of the first yarns 7, 7' consisting of a Kevlar or
Carbon fibers and the remaining four reels of second yarns 8
consisting of polyester fibers.
[0074] Advantageously, the semi-finished hose may be heated
in a suitable heating device 25, e.g. an oven, interposed between the
braiding machine 22 and the second extruder 24, in order to heat
shrunk the polyester fibers.
[0075] Thanks to this feature, the layers comprising polyester
fibers heat shrink over the layers below. This is particularly
advantageous in case of the embodiment of the invention shown in the
FIGS. 1 and 2, because the first plurality of polyester fibers heat shrink
over the second plurality comprising the Carbon or Kevlar fiber, i.e. a
not-heat shrinkable material, in such a manner to stabilizing thereof on
the inner layer 2.
[0076] By way of comparison, while the polyester fibers at 180
C heat-shrink by about 10 - 15% as measured according to DIN
53866, the Kevlar O or Carbon fibers at 400 C only heat-shrink by 0,1
-2 %.
[0077] The temperature of the heating device 25 may be
comprised between 160 and 200 C, preferably close to 180 C.
[0078] Suitably, cooling tanks 26, 27 may be provided
downstream the first and second extruders 21, 24 for cooling the
extruded layers. Further, hauling-off machines 28, 29 and 30 may be
provided along the line 20.
[0079] The hose of this invention is susceptible of a number of
changes and variants. All the components thereof may be replaced by
other technically equivalent compounds without departure from the
spirit or scope of the invention. The present embodiment, therefore,
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are to be considered in all respects as illustrative and not restrictive of
the invention.
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