Note: Descriptions are shown in the official language in which they were submitted.
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A SET OF REINFORCING BARS FOR PRODUCTS MADE OF REINFORCED
CONCRETE, A METHOD AND AN INSTALLATION FOR MANUFACTURING IT
The invention relates to a set of reinforcing bars for
products made of reinforced concrete and to a method and an
installation for manufacturing said set.
For reinforcing concrete slabs, a known technique consists
in using a "welded mesh" constituted by two layers of steel
bars or wires, with the two layers being superposed in two
perpendicular directions and being assembled together by spots
of welding.
Reinfo~cement of this type is suitable for products made
of reinforced concrete in which the mechanical forces that need
taking up extend in two perpendicular directions, i.e. for
products which are two-directional.
In contrast, reinforcement of this type suffers from the
drawback of being ill-suited to products made of concrete in
which the mechanical forces to be taken up extend in a sinyle
direction (unidirectional forces) or else in which the forces
in one direction are already taken up by other reinforcing
bars. This applies in particular to products made of
prestressed concrete which include prestressing bars or wires
that already take up forces in one direction. In these special
cases, it appears that one of the two layers of reinforcing
~5 bars in the welded mesh serves only to hold the other sheet at
a given spacing. As a result, two layers of reinforcing bars
is excessive for ensuring that the reinforced concrete products
have adequate strength.
Another drawback of a conventional welded mesh lies in the
fact that it is very bulky during transport, handling, and
storage. This drawback applies both when the welded mesh is in
the form of panels and when the welded mesh is in the form of a
roll. When in the form of a roll, the stiffness and the
thickness of the longitudinal reinforcing bars make it
impossible to optimize volume or to optimize installation.
Further, conventional welded meshes are generally
prefabricated in a factory by means of installations that are
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particularly bulky, and the meshes are generally of
predetermined sizes, thereby preventing the user from
optimizing the quantity of steel used, and also requiring
cutting operations to be performed during installation which
implies a great deal of manipulation, since it is generally
necessary to use a plurality of panels in a single application.
This gives rise to losses both of material and of labor time.
Finally, another drawback of conventional welded meshes is
that they often suffer from planeness defects, and as a result,
given the stiffness of the steel bars constituting such
reinforcement, it is often necessary to fix such a
reinforcement sheet many times in order to hold it in a plane.
An object of the invention is to provide a set of
reinforcing bars suitable for mitigating the above-mentioned
drawbacks.
Another object of the invention is to provide a set of
reinforcing bars capable of being used in general in the same
way as the distribution reinforcing bars of a conventional
reinforced concrete structure.
It is also an object of the invention to provide a set of
reinforcing bars intended more particularly for reinforced
concrete products in which the mechanical forces that are to be
taken up extend in a single direction or else in which the
mechanical forces in one direction are already taken up by
other reinforcing bars.
A particular object of the invention is to provide such a
set of reinforcing bars which is most particularly intended for
use in prestressed concrete products.
Another ob~ect of the invention is to provide such a set
of reinforcing bars which is not bulky during transport,
handling, and storage, which is easily cut up during
installation, and which does not suffer from planeness defects.
The present invention provides a set of reinforcing bars
for products made of reinfor oe d concrete the set comprising a
multiplicity of spaced-apart rigid transverse reinforcing bars
together with at least two flexible longitudinal connecting
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elements connected to the transverse bars to hold them spaced
apart at selected intervals.
In a preferred embodiment of the invention, the transverse
reinforcing bars are generally rectiline æ steel bars held
p æ allel to one another by the flexible elements.
Once spread out, this set of reinforcing bars then takes
up the form of a sheet made up of said steel bars and of said
flexible connecting elements which are connected to the bars at
each intersection. The width of the sheet is then defined by
the length to which the steel bars are cut, whereas its length
may be adapted to the needs of the application, since it is
merely necessarv to cut the flexible elements to the desired
length. The inter-bar spacing or interval may be constant or
variable as a function of the mechanical forces to be taken up.
The set of reinforcing bars of the invention thus offers
various significant advantages over conventional welded meshes.
In the particular case where the transverse bars are
rectilinear bars, the set may be packaged in a form of a roll.
This roll facilitates transport since, for a given quantity of
useful reinforcing bars, it occupies less volume than a welded
mesh. The flexible elements occupy less volume than the steel
elements they replace, and they are lighter. They also make it
possible to wind the sheet onto a small diameter drum. Such
packaging consequently facilitates storage and handling on the
site of use.
Furthermore, installing the set of reinforcing bars is
simplified since it suffices merely to unroll the sheets of
reinforcing bars, with the flexible elements exerting no
resistance against unrolling. After the set of reinforcing
bars has been unrolled, the flexibility of the connection
elements enables the reinforcing bars to settle in a plane
under gravity, thereby reducing or eliminating the need for
fixings. Considerable labor savings are obtained.
Further, the shape of the sheet (length, width, pitch
between transverse reinforcing bars) may be accurately matched
to the site of use and to the desired mechanical strength.
This makes it possible to optimize the quantity of steel used
and to reduce wastage.
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Another advantage of the invention lies in the fact that
the longitudinal flexible elements are cheaper than the steel
bars they replace.
Finally, the set of reinforcing bars of the invention may
be manufactured using equipment that is simpler than that which
is required for manufacturing a conventional welded mesh.
The set of reinforcing bars of the invention may also be
made having non-rectilinear elements, such that when the set is
unwound it is not in the form of a flat sheet. In this case,
instead of being packaged as a roll, the set may be packaged in
a concertina-like structure, where the longitudinal reinforcing
bars are moved close together.
The flexible elements used for making the set of re-
inforcing bars of the invention may be made from wires, strings,
adhesive tapes, metal strips, plastic strips, or the like.
In a preferred embodiment of the invention, each flexible
element is made from at least one strip of plastic material, in
particular of polypropylene. Advantageously, each flexible
element comprises two strips which are superposed and locally
welded to each other on either side of each reinforcing bar.
For example, one of the strips may be continuous while the
other may be continuous or in discontinuous short lengths.
In another aspect, the invention provides a method of
manufacturing the above-specified set of reinforcing bars, the
method comprising the following operations:
paying out equal lengths of flexible elements from a
flexible element feed to obtain said lengths in a mutually
parallel disposition at a connection station;
bringing the reinforcing bars one-by-one transversely to
the flexible element at the connection station;
connecting one reinforcing bar to the flexible elements;
advancing the flexible elements by one step, thereby
entraining the reinforcing bar previously connected thereto;
and
repeating the above operations with other reinforcing
bars.
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Naturally, the connection method depends on the nature of
the flexible elements used and may include, in particular,
knotting, gluing, welding either ultrasonically or by means of
a hot iron, stapling, etc.
In the preferred implementation of the invention where
each flexible element is made from at least one strip of
plastic material, the connection method may make use of welding
either ultrasonically or by means of a hot iron.
In the particular case where each flexible element is made
of two strips of plastic material, namely a bottom strip paid
out from a first mechanism and a top strip paid out from
another mechanism, the two strips are welded together locally
on either side of each reinforcing bar to be fixed.
Such welding is preferably performed by ultrasonic means
provided in the connection station.
After a reinforcing bar has been connected, e.g. by
welding, the sheet of bars is caused to advance by one step by
paying out the flexible elements, and the size of the step may
be adjustable. Subsequently, the manufactured sheet may simply
be wound up on a drum.
In another aspect, the invention provides an installation
for manufacturing the above-specified set of reinforcing bars.
Essentially, the installation comprises:
a connection station;
feed means for supplying each length of flexible element
and for providing them in a mutually parallel disposition to
the connection station;
a reinforcing bar dispenser suitable for delivering
reinforcing bars one by one transversely to the flexible
elements at the connection station; and
advance means for causing the flexible elements to adva~ce
by one step, thereby entraining the reinforcing bar that has
been previously been connected to the connection elements.
According to another characteristic of the invention, the
connection station is provided with a connection head
corresponding to each flexible element for the purpose of
connecting it to the reinforcing bar.
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When each flexible element is made from at least one strip
of plastic material, in particular polypropylene, each
connection head is provided with welding means, e.g. ultrasonic
welding means.
In a preferred embodiment of the invention, in which each
flexible element is made from two strips of plastic material,
the feed means for each flexible element comprise two paying
out mechanisms, respectively suitable for receiving a top reel
and a bottom reel of strip. This makes it possible to
superpose the two strips prior to welding, with each
reinforcing bar that is to be connected then lying between the
two strips. Welding is then preformed on either side of the
bar over a limited length of strip.
According to another characteristic of the installation of
the invention, each of its paying out mechanisms is associated
with a brake controlled by a pivoting lever provided with a
deflector pulley around which the strip travels, such that the
brake is released whenever traction is exerted on the strip,
while the brake engages whenever the traction ceases.
Advantageously, the installation includes four pairs of
paying out mechanisms, thereby enabling four flexible elements
to be fixed, with each flexible element comprising two
superposed strips.
The advance means of the installation of the invention
advantageously comprise horizontal translation clamps each
suitable for grasping one of the flexible elements downstream
from the connection station in order to advance the set bars
through one step.
Advantageously, the installation includes a fixed abutment
and an adjustable abutment associated with each clamp in order
to enable the size of the step between two successive
transverse reinforcing bars to be adjusted at will.
When the installation is used for manufacturing a set of
reinforcing bars made up from rectilinear transverse bars, the
installation further includes a pick-up drum onto which the
sheet manufactured in this way is wound.
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Embodiments of the invention are described by way of
example with reference to the accompanying drawings, in which:
Figure 1 is a plan view of a set of reinforcing bars of
the invention;
Figure 2 is a diagrammatic side view of an lnstallation of
the invention;
Figure 3 is a diagrammatic fragmentary section view
showing the connection between a transverse reinforcing bar and
a flexible element constituted by two superposed strlps of
plastic material;
Figure 4 is a fragmentary side view of the installation
shown in Figure 2;
Figures 5A to 5D show different successive stages in the
operation of the installation of Figure 4;
Figure 6 shows a strip paying out mechanism forming a part
of the installation of Figure 2;
Figure 7 shows a detail of the installation of Figure 2;
Figure 8 is a diagram showing a set of reinforcing bars of
the invention in which the bars are not rectilinear; and
Figure 9 is a diagram showing another set of reinforcing
bars of the invention in which the transverse bars are not
rectilinear, but follow a closed outline.
Reference is made initially to Figure 1 which shows a set
of reinforcing bars of the invention given an overall reference
10. This set comprises a multiplicity of spaced-apart rigid
transverse reinforcing bars 12 which, in the example shown, are
same length steel bars disposed parallel to one another. The
assembly 10 also includes longitudinal flexible elements 14
which are four in number in the example shown. Each bar 12 is
thus connected to four flexible elements 14 by four nodes 16.
By way of example, each of the bars 12 is a steel bar
having a diameter of 4 or 5 millimeters and a length of 2.40
meters. The interval (or pitch) i between successive bars 12
may be adjustable in 50 millimeter steps over a range of 100
millimeters to 450 millimeters, for example.
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In the example, the flexible elements 14 extend parallel
to each other, with the distance _ between two successive
elements 14 being equal to 60 centimeters.
In the example shown, ~ach flexible element is made up of
two 10 millimeter wide strips of plastic material which are
welded together locally as explained below.
Reference is now made to Figure 2 which is a diagram
showing an installation for manufacturing a set of reinforcing
bars of the invention. This installation comprises a
connection station 18 comprising a fixed stand 20 forming a
horizontal table 22 having four connection heads 24 co-
operating therewith and intended to connect each reinforcing
bar 12 with the flexible elements 14. In the example, each
flexible element 14 (only one of which can be seen in Figure 2)
is constituted by an assembly of two strips, namely a top strip
14A and a bottom strip 14B, with these two strips being taken
respectively from a top roll 26A and a bottom roll 26B carried
respectively by a top paying out mechanism 28A and a bottom
paying out mechanism 28B. The installation thus has four top
paying out mechanisms 28A and four bottom paying out mechanisms
28B.
The installation also includes a dispenser 30 comprising a
moving stand 32 provided with wheels 34 and possessing a
sloping table 36, thereby forming a magazine which is intended
to present the transverse bars 12. These bars are subsequently
taken one by one into the space delimited between the four
pairs of strips 14A, 14B immediately upstream from the connec-
tion heads 24 in the strip displacement direction (arrow F).
In the example, the strips 14A and 14B are made of plastic
material, in particular polypropylene, and the four heads 24
are welding heads for welding together the four pairs of strips
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on either side of each transverse bar, as described below with
reference to Figure 3.
However, the general principle of the installation shown
in Figure 2 is applicable to other types of flexible el } nts,
and the connection heads 14 are not necessarily welding heads.
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The four pairs of strips 14A and 14B æ e displaced
stepwise in the direction of arrow F, while a transverse bar 12
is brought onto the table 22 beneath the welding heads 24 by
means which are described below. These heads 24 are then
displaced vertically downwards in order to connect together the
four pairs of strips which then imprison the corresponding bar
12. A sheet is thus obtained suitable for being wound onto a
pick-up drum 36 (Figure 2).
As shown in Figure 3, the top strip 14A is wound around
the bar 12 and is welded locally to the bottom strip 14B over
two weld zones 38 and 40 disposed on either side of the bar 12.
For example, these two zones 38 and 40 may each extend over a
length Q of about 10 mm. Thus, for strips that are 10 mm wide,
two weld zones are obtained, each of which occupies a s~uare
having a side of 10 mm.
Reference is now made to Figure 4. The table 36 has a
curved sloping top extending from an upstream end 42 to a
downstream end 44, with the downstream end 44 being lower than
the upstream end 42. A guide 46 is placed above the table 36
and is provided with a bottom surface 48 which is curved in
shape and which faces a portion of the table 36. Together the
table 36 and the guide 46 thus define a magazine suitable for
receiving a plurality of transverse bars 12 disposed side-by-
side. A horizontal bar 50 is placed at the upstream end of the
guide 46 in order to prevent two overlapping reinforcing bars
12 going past it. The table 36 and the guide 46 thus form a
magazine in which the reinforcing bars 12 are stored side-by-
side, parallel to each other and to the horizontal. The bottom
end of this magazine adjacent to its end 44 is practically
tangential to the vertical. Four extractor slides 52 are
provided beneath the magazine formed in this way and are driven
synchronously in horizontal translation. The slides 52 are
provided with respective notches 54 which, when the slides are
in a rear position (Figure 4), receive one of the reinforcing
bars 12. The slides are displaceable synchronously and they
are suitable for taking one bar 12 into the horizontal space 56
delimited between a top plate 58 and a bottom plate 60, said
space 56 terminating in a retractable abutment 62.
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The operation of the portion of the installation shown in
Figure 4 is now described with reference to Figures 5A to 5D.
During their advance motion, as shown by the arrow in Figure
5A, the slides 52 convey one bar 12, while simultaneously
closing the magazine constituted by the table 36 and the guide
46. During this displacement, the bar 12 is guided between the
plates 58 and 60.
The bar 12 is then brought into contact with the
retractable abutment 62 (Figure SB) and is held against the
abutment 62 and each of the slides 52 in position for
connection with the strips 14A and 14B. The welding heads 24
are then displaced synchronously vertically downwards (Figure
5B) in order to connect together the four pairs of strips 14A &
14B around the bar 12.
When this operation is over, the welding heads 24 are
displaced vertically upwards and the slides are displaced
horizontally rearwards (Figure 5C) in order to return to their
initial position (Figure 5D) ready to receive a new reinforcing
bar 12 so as to begin the same cycle over again.
Reference is now made to Figure 6. Each of the paying out
mechanisms, e.g. the mechanism 28A for receiving the roll 26A
comprises two side plates fixed to a cylindrical hub 64 which
is coaxial with the axis 66 of the paying out mechanism. Each
mechanism, e.g. 26A, is associated with a brake 68 constituted
by a lever 70 having one end 72 mounted to pivot about an axis
74 and having its other end 76 carrying a freely rotating
deflector pulley 78 over which the strip 14A passes, with the
strip then passing over a pulley 80 mounted to rotate about a
fixed axis 82. The lever 72 includes a curved intermediate
portion 84 suitable for rubbing against the hub 64 to brake
rotation of the paying out mechanism. When the pulley 78 and
the lever 70 are in the low position shown in Figure 6, the
brake-forming curved portion 84 of the lever bears against the
hub 64 and rotation of the roll of strip is braked.
When traction is exerted on the strip 14A, the strip
raises the pulley 78 and thus the lever 70, thereby releasing
the brake and allowing the roll to rotate freely.
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When a desired length of strip has been paid out, the
pulley 78 and the lever 70 moves back down so that the roll of
strip is braked again, with the tension of the strip being
substantially the same after each paying out operation.
In the example shown, the installation includes four
paying out mechanisms 28A and four paying out mechanisms 28B.
The bottom four strips 14B reach the welding station by passing
beneath the table 36 (Figure 2) and thus beneath the bar to be
fixed, while the four top strips 14A come over the bar 12 to be
fixed. The strips are guided and positioned by means of eight
pulleys 80.
As shown in Figure 7, the bar 12 and the four strips 14A
and the four strips 14B are thus all positioned in the
connection station. The four welding heads 24 are then
displaced synchronously vertically downwards in order to weld
together the four pairs of strips. To do this, the bottom
portion of each welding head is provided with a die 86 having
the same shape as the bar so that each welding head straddles
the bar and welds together the two strips on either side
thereof, as shown above in Figure 3.
Advantageously, the welding heads are of the ultrasonic
type so as to cause localized melting of the material from
which the strips are made where the strips contact each other.
This melting is followed by a period of time during which the
welding head is kept pressed in position after the ultrasonic
feed has been switched off, thereby causing the four pairs of
strips to be welded together.
As shown in F'igure 7, the installation also includes step-
wise advance means comprising four horizontally displaceable
clamps 88. Each clamp comprises a top jaw 88A and a bottom jaw
88B, and each is suitable for grasping one of the strips 14
downstream from the connection station in order to cause the
set of bars to advance by one step in the direction of arrow F.
The respective pairs of jaws of the clamp are brought together
so as to clamp on the corresponding strip, after which the
clamps are displaced synchronously and horizontally to the left
in Figure 7 over a distance corresponding to the desired pitch.
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Clamp displacement motion is limited by a fixed abutment 90
close to the welding heads and by an adjustable abutment at the
other end of their stroke. This adjustable abutment serves to
adjust the pitch between successive bars.
From the beginning of the welding operation, the clamp 88
comes close to the welding head and their respective jaws are
actuated to clamp onto the strips and hold them firmly in
position once the welding operation has been terminated.
When the welding operation has been terminated, the
welding heads are raised, the abutment 62 (Figure 4) is
retracted, and the clamps 88 advance to the left in Figure 7
pulling the manufactured sheet of reinforcing bars with them
and paying out one step length of the strip.
From the beginning the following welding operation, the
clamps 88 open and return to a position adjacent to the welding
heads.
At the outlet from the installation, the sheet formed in
this way passes firstly over a deflection roller 94 and then
over another deflection roller 96 prior to being wound onto a
take-up drum 36 which is suitable for being rotated by means of
a transmission 98 and a motor 100. The roller 96 is guided in
vertical translation with two sensors (not shown) detecting the
top and bottom positions of this roller. When the roller 96 is
in its bottom position, the drive motor 100 for the drum 36
starts up, thereby causing the sheet to be wound onto the drum
until the roller 96 reaches its top position.
While the sheet is being wound around the drum 36, the
drum is caused to reciprocate along its axis in order to avoid
superposing the strips.
Reference is now made to Figure 8 which shows a set of
reinforcing bars of the invention comprising non-rectilinear
rigid transverse bars 112 interconnected by three flexible
strips 14. This set may be packaged in a configuration which
has been folded concertina-like.
Reference is now made to Figure 9 which shows another set
of reinforcing bars of the invention, this set comprising non-
rectilinear transverse reinforcing bars 212. In this example,
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these bars are folded to form a generally rectangular closed
outline, with the bars being interconnected by three flexible
elements 14. As in the Figure 9 case, the set of bars may be
packaged in a configuration which is folded concertina-like.
A set of bars of the invention is particularly suitable
for manufacturing products made of prestressed concrete,
particularly slabs of prestressed concrete which include
prestressing bars or wires disposed parallel to one another.
In such a case the sheet of bars of the invention is merely
unwound so that the rigid transverse bars extend
perpendicularly to the prestressing wires.
However this set of reinforcing bars may also be used in
more general manner as load-spreading or distribution bars in
conventional prestressed concrete work.
Thus, the set of reinforcing bars of the invention may be
used to replace bars for a welded mesh for reinforcing a floor
slab of conventional reinforced concrete, which slab may be
cast in situ or on shuttering.
It may also be used to form "capping reinforcing bars"
(positive moment reinforcing bars) on a support, in particular
a preslab, or as bars positioned in a compression table
(unidirectional force). It can also be used for bars that
overlie prefabricated parts, in particular preslabs, over
joints.
The set of reinforcing bars of the invention is also
usable to constitute transverse load-spreading reinforcement in
a concrete compression table made up of floors, girders, or
floor filler, and as "capping pieces" on supports.
The invention can be varied in numerous ways. For
example, instead of being precut to the desired length, the
bars constituting the transverse reinforcing bars could be
taken from a reel of steel wire, individual bars being
straightened out and cut off by the installation.
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