Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Safety net, preferably for securing an embankment
The invention relates to a safety net, preferably for securing an embankment.
With a known safety net according to publication EP-B-0 979 329 the latter is
in the
form of diagonal netting with rhomboid-shaped meshes and a three-dimensional
mattress-type structure which is woven from individual wires bent in the form
of
coils and made of high-strength steel. The wires have a high degree of tensile
strength, and so, even in the stretched out state, the netting retains a three-
dimensional mattress-shaped structure, and when covering the surface of the
earth
can act as a holder or stablilisation for layers of vegetation. The wire
netting can be
folded up and only requires a small amount of space for storage or
transportation.
The object forming the basis of the present invention is to improve a safety
net of
the type specified at the start, and to reduce the risk of it breaking.
This object is achieved according to the invention by a safety net which is
formed
by diagonal netting produced from wires and a three-dimensional mattress-like
structure, characterised in that the diagonal netting is woven from wire
strands, wire
bundles or wire ropes which comprise at least two wires, wire ropes and/or
wire
strands make of steel.
Further preferred embodiments of the safety net according to the invention are
de-
scribed further herein.
Since according to the invention the safety net is woven from individual wire
strands, wire ropes or wire bundles bent in the form of coils, and which corn-
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prise one, two or more wires (or wire strands) advantageously made of high-
strength steel, a high-strength safety net is provided that with normal loads
allows hardly any deformation and which gets by without any mesh fixing
elements (for example cross-type clamps). Since the wire strand is made up
of 2 or more wires, the tear resistance of the cross-over points is increased
significantly in comparison to the cross-over points of netting with just one
wire.
The diagonal netting according to the invention made of wire strands, wire
ropes or wire bundles can be produced practically "infinitely" in rolls, at
least
partially high-strength peripheral knots in the form of loops formed on the
ends of wire strands, wire ropes or wire bundles advantageously also being
provided on the long sides of the rolls.
In the following the invention is described in more detail by means of the
drawings. These show as follows:
Fig. 1 a perspective view of an apparatus for producing wire bundles bent in
the form of coils,
Fig. 2 a top view of a partially illustrated safety net according to the inven-
tion, and
Fig. 3 a side view of a partially illustrated safety net.
The diagrammatically illustrated bending apparatus 10 according to Fig.1
serves to produce wire bundles 30, wire strands or wire ropes bent in the form
of coils which are then woven together to form a safety net.
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This bending apparatus 10, of which not all details are shown, has a cylindri-
cal housing 12 which has an approximately horizontally continuous opening
on the front side of which there is a guide device 15 for the wire bundle 30
wound, for example, from three wires. This guide device 15 is positioned ad-
justably on a holder 21 on which the mandrel 25 is mounted quasi rotatably,
and about which the wire bundle 30 is then respectively bent by approx. 1800
.
The mandrel 25 is fastened in a chuck 22 rotatably mounted in mounting
brackets 23, 24, the chuck 22 being driven via a pulley 22' by a toothed belt
27, and the latter being driven by a rotary drive on the lower side of the
holder 21.
A bending arm 18 is mounted pivotably in the housing 12 and has a bearing
surface 19 on the front side of the bending arm 18 a specific distance away
from the mandrel 25. The bending arm 18 is guided by the ring 11 contained
within the housing 12 and by additional curved guides 17 in which a connect-
ing member 14 engages on the bending arm. During the bending process the
bending arm is guided around the mandrel 25, a curved shape 17' of the
guides 17 enabling the bending arm 18, after a movement about approx. 180 ,
to be removed from the mandrel 25, and so the wire bundle 30 is not bent any
further. The bending arm 18 is consequently pivoted further until it lies with
its bearing surface 19 beneath the mandrel again and bends the wire bundle
pushed forward by this specific length in its longitudinal direction about
these 180 . Therefore, the bending arm 18 can be pivoted further continu-
ously respectively about 360 without pausing.
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While bending with this bending apparatus 10, in a first step the wire bundle
30 is delivered at a defined angle of elevation c to the mandrel 25 and bent
into this defined length around this mandrel 25 about approximately 1800, as
illustrated by this already bent part 30a of the wire bundle 30. This bending
is
repeated until a selectable length of the coil-shaped wire bundle produced in
this way is achieved.
These wire bundles bent in the form of coils are then woven together until the
wire netting of the desired size has been produced, as shown in Fig. 2.
Fig. 2 and Fig. 3 show a partially illustrated safety net for securing a
surface
layer of earth, such as for example for securing an embankment or for secur-
ing a rock face by the side of a road or similar, which is in the form, for ex-
ample, of a sqare diagonal netting 20 with quadrangular or polygonal meshes
17. The diagonal netting 20 is woven from a number of wire bundles 30 bent
in the form of coils. As illustrated, the wire bundles 30 are respectively com-
prised of three wires 31, 32, 33, preferably made of a high-strength steel,
looped together.
This can be at least two wires twisted together to form a wire strand, two or
more wires bundled to form a wire bundle, as mentioned above, wire strands
twisted to form a wire rope, or a combination of these elements.
According to DIN standard 2078 the wires preferably have a nominal strength
of between 1000 and 2300 N/mm2, for example a strength of 1770 N/mm2.
However, spring steel wires according to DIN standard 17223 could also be
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used. The wire thickness is dependent upon the required tensile strength, and
can be, for example, 2.5 -- 4.5 mm.
These wires 22 are generally galvanised, provided with a coating of
zinc/aluminium alloys and/or a synthetic covering or made of a chrome alloy
in order to achieve the required corrosion resistance. For this purpose, for
example, a galvanised coating with a surface weight of between 125 and 275
g/m2 is preferably provided.
At the side ends of the netting 20 the wire bundles 30 are connected to one
another flexibly in pairs by loops 30', these loops 30' being formed by the
wire bundles 30 themselves bent away on the ends. After they have been bent
into loops, the wire bundles 30 are additionally provided with preferably a
number of windings 32 wound around their own circumference and which,
due to the tensile stress to which these loops are subjected in the used state
guarantee sufficient security against opening of the latter.
When using the diagonal netting 20 to secure an embankment, said netting is
held on the ground at a defined tension by claw-shaped fastening elements
(not detailed) sunk into the ground. Preferably, a respective wire or rope is
looped into a peripheral wire rope, peripheral wire strand or peripheral wire
bundle, bent in the form of coils, located at the upper and lower end of the
netting 20, and this is on its part stretched over the ground or similar by
the
fastening elements.
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The individual wire bundles 30 bent in the form of coils have an angle of ele-
vation E and a length L between two bends which determine the shape and
size of the meshes 37 of the diagonal netting 20. An angle of approximately
90 is advantageously chosen for the angle of elevation E. The individual
meshes 37 respectively form an approximately square rhomboid, the mesh
width being for example 390 x 400 mm. The advantage of this is that the net-
ting 20 does not stretch a great deal when it is laid over a surface layer of
the
earth and is pretensioned in its longitudinal extension by the ropes at the
ends. Despite the advantageously small amount of stretching of the safety net
the effect of the multi-wired structure of the strand is above-average
flexibil-
ity/adaptability to the surface of the ground.
In particular when securing an embankment to a slope, two of these wire net-
tings 20 could also be positioned one over the other in order to achieve even
greater security. Advantageously, the upper wire netting, which is not shown,
is provided with a larger mesh width than the lower one.
In the woven state the individual wire bundles 30 are held together flexibly,
the result of which is that the diagonal netting 20 can be drawn together,
folded up or rolled up like a mat. Consequently, only a small amount of space
is required for the storage and transportation of such nettings.
In the side view of the partially illustrated netting 20 according to Fig.3 it
is
illustrated that the latter has a three-dimensional, mattress-like structure
which in turn is made possible by the use of high-strength steel wires. For
this purpose, the individual wire bundles 30 respectively wound from three
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wires 31, 32, 33 are bent in the form of coils and then woven together so that
the netting 20 produced from these forms an approximately rectangular out-
line, as viewed as a cross-section.
This elongate rectangle has a thickness 20' of a number of wire bundle thick-
nesses. Therefore, even in the pre-tensioned state this wire netting 20 is
three-diemensional in form. The effect of this is on the one hand an increased
springiness property of the netting because the wire bundles can be stretched
with increasing tension in their longitudinal extension and provide this net-
ting with increased elasticity. On the other hand, by means of this three-
dimensional form, when covering an earth surface, for example an embank-
ment, support or stabilisation of the layers of vegetation caught up in this
net-
ting or of sprayed on coverings is achieved.
Since, according to the invention, the safety netting is woven from individual
wire strands, wire ropes or wire bundles bent in the form of coils, which have
two or more wires, preferably made of high-strength steel, twisted together to
form a wire strand or combined to form a wire bundle, or are formed from
two or more wire strands made of high-strength steel, twisted to form a wire
rope, a high-strength safety net is produced which allows hardly any deforma-
tion when subjected to loads.
The diagonal netting according to the invention formed from wire strands,
wire ropes or wire bundles can be produced practically "infinitely" in rolls,
high-strength peripheral knots also advantageously being provided in the
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form of loops formed on the ends of the wire strands, wire rope or wire bun-
dles on the long sides of the rolls.
Basically however, the safety nets can also be produced from wire strands,
wire bundles, spiral ropes with thinner or thicker wires which are not, or are
only partially, produced from high-strength steel.
With this type of safety net system optimal securing of a slope can be
achieved. With the form of the nets according to the invention large shearing
forces, which arise due to loosened stones or boulders in the embankment,
can also be absorbed without any problem.
Due to the special netting parameters, in addition to applications in the
field
of natural dangers, it can also be used for architectural, structural
engineering
and safety-relevant applications. For example, these nets can also be used for
separating functions, facade and roof elements, break-in and break-out pro-
tection, passageway blocks, maritime protection applications, shatter protec-
tion, etc..
