Note: Descriptions are shown in the official language in which they were submitted.
2i40~~6
The invention relates to a mechanical connection for
reinforcing bars. It relates to a mechanical connection for
reinforcing bars, a sleeve with a hollow body and a device for
placing this mechanical connection. The invention also relates
to a process for fixing the mechanical connection for
reinforcing bars.
It is used inter alia in building construction using concrete,
such as buildings in a town or harbour or road structures.
It is known in these fields to use mechanical connections to
connect reinforcing bars in order to ensure the continuous
transmission of tensile stress.
The mechanical connection according to the invention may be
used on site in order to connect components having been
subjected to industrial treatment in the workshop to other
reinforcing bars available on site.
These bars used on site may have a rectilinear end or may be
curved and the bar is provided in the known manner on its outer
surface with ribs or ridges, the dimensions of which are
relatively irregular, but are of course in proportion with the
diameter of the bar. All of these elements are designed to
give the connection a certain strength and, depending on the
structure used, the bars may have a large diameter and large
ribs or a small diameter and smaller ribs.
These ribs are generally disposed on the outer surface of the
bar, e.g. in a helicoid, the pitch of which depends both on the
diameter of the bar used and on the desired strength.
In some cases, it will sometimes be necessary to connect
reinforcing bars embedded in a mass of old concrete to new
reinforcing bars in order to extend or modify a structure.
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In many cases, the reinforcing bars available on the existing
site have not been designed with a mechanical connection such
as a thread in order to facilitate connection or, on the other
hand, have a thread which has been damaged by corrosion or sea
water.
In many cases, the ends of bars embedded in concrete to be
connected are not designed with a sufficient mechanical
connection. The ends of untreated reinforcing bars are devoid
of threading and it is therefore not possible to connect two
reinforcing bars end to end in a simple manner.
Sometimes, the absence of threading on the end of a bar is due
not to the construction of the bar, but to the fact that it is
impossible to use this thread as it is corroded.
The absence of threading may also be the result of an accident
on site, e.g. if a previously threaded bar were unfortunately
to be sawn off.
Any mechanical treatment of the ends of the bars must be
carried out in a specialised workshop. This operation creates
a break in the reinforcement production line and entails
considerable handling. This break of load is very expensive
and often entails the transportation of hundreds of tonnes of
steel from the site of the mechanical treatment to the works
site and/or assembly point.
The aim of this invention is to integrate the mounting of the
bush into the production circuit without having to treat the
end of the bar prior to the assembly of the reinforcements.
It may also be necessary on site to connect a row of vertical
bars to a concrete slab, such as a floor produced industrially
in the workshop having a row of horizontal bars at the outlet
240196
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of the concrete. These bars can be rectilinear or curved, but
it is their ends to be connected on site to vertical
reinforcing bars that constitute the vertical concrete
elements.
There is sometimes also a high concentration of steel on site
when the bars of the floor and the vertical bars are very close
together and it is sometimes difficult to gain easy access
thereto with large tools.
It is known nowadays to connect bars of this kind by means of a
tubular sleeve crimped by a press. To this end, it is
necessary to use bulky outer jaws as the system using an
encompassing jaw operating by external pressure has to be
powerful. This bulkiness is a disadvantage when the steel and
reinforcing bar concentration is high as rapid intervention on
site is no longer possible if the two bars are too close
together.
The pressing elements and the environment of the tools are
heavy and bulky and therefore sufficient space is required
between the axes of the reinforcing bars for crimping, fifteen
centimetres being required between the axes in practice.
The daily output of the operator on site is very modest and
four to eight connections per hour must be reckoned on in the
case of equipment of considerable weight, e.g. approximately
one hundred and sixty kilograms.
It should also be noted that when the jaws are operated by
external pressure in order to crimp the two bars end to end, it
is not possible to check and test whether the operation has
been effected correctly and it is therefore necessary to rely
on the operator.
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The devices and dies used are very heavy in order to allow for
the reaction of the stress applied to the tools. The
considerable force applied to the die means that a heavy and
bulky outer frame must be used as the stress has to be
transmitted to the frame. Pressures of up to two hundred
tonnes are used and it is not easy to work rapidly and
efficiently with complete reliability on all of the crimp
connections.
The known devices crimping perpendicularly to the bars in
successive passes act in a random manner as they do not know
exactly how the bar will be urged into a hollow or into a rib.
Sleeves of considerable length, of approximately 200 to 250 mm
must therefore be used and it is impossible to ensure that all
of the crimp connections are produced under good conditions.
The crimping result thus depends on the pressure applied by the
operator.
The known devices using perpendicular crimping with a movable
jaw and a fixed die also result in almost obligatory offset of
the two bars to be connected as the two bars are no longer
aligned in view of the asymmetry and irregularity of the
reinforcing bars used.
The aim of this invention is to propose a mechanical connection
for reinforcing bars which mitigates the aforementioned
disadvantages and allows for the connection of a reinforcing
bar the end of which has no connecting means such as a thread.
This absence of threading may be as a result of corrosion or
quite simply as a result of the fact that no mechanical
connection was provided at the time of construction. It may
also be the case that this mechanical connection was cut off by
accident on site.
Another aim of the mechanical connection for reinforcing bars
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according to the invention is to allow for rapid operation on
site and therefore with lightweight, handy tools.
Another aim of the mechanical connection for reinforcing bars
according to the invention is to make it possible to work with
reinforcing bars in a high concentration, i.e. which are very
close together, simply as a result of the small dimensions of
the tool.
Another aim of the mechanical connection for reinforcing bars
according to the invention is to allow for testing by applying
stress, e.g. equal to 90 % of the elastic limit, thereto after
connection.
Another aim of the device for placing a mechanical connection
according to the invention is to allow for the production of
tested connections so that all of the connections produced are
completely reliable from the point of view of the quality of
the crimping of the bush to the end of the bar.
Another advantage of the mechanical connection for reinforcing
bars according to the invention is the fact that, by checking
the quality of the crimp connection, it is therefore possible
to reduce considerably the length of the sleeve itself and of
course to arrive at a very low cost price for the mechanical
connections in a structure as the quantity of metal used is
considerably reduced.
Another aim of this invention is to allow for rapid operation
on site in order to connect an element produced industrially
with projecting reinforcing bars to other reinforcing bars
available on site.
E.g. all of the horizontal slabs can be prepared industrially
at the same time and then connected to vertical bars all
adjusted to the same height, e.g. by means of prior trimming of
the ends of the bars.
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Another advantage of the device according to the invention is
that it is very handy and simple to use on site.
The device is provided with the possibility of testing the work
just carried out in order to prove that the connection is
functional, this of course being very advantageous as it was
not hitherto possible to check the quality of the connection
produced using crimping by means of jaws.
Another aim of the device according to the invention is to
allow for a considerable increase in the quantity of
connections produced, which can go up to four hundred a day
instead of forty nowadays. The device can be installed in a
stationary manner in order to industrialise the preparation of
the bars.
According to this invention, the mechanical connection for
reinforcing bars, used inter alia in the construction of
concrete elements on site, intended to be fitted to a
rectilinear or curved end, the bar having ribs on its outer
surface, is characterised in that it comprises:
- a bush with a hollow cylindrical body into which the end of
the bar not having a connecting element is introduced,
- a thread at the end of the bush,
- the hollow body and the thread being coaxial so that two bars
disposed end to end can be connected,
- the outer material of the bush having been subjected to
deformation by the formation of linear or helical
indentations,
- the material of the ribs of the bar penetrating into the
hollow body of the bush,
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_, _
in order to connect the bar and the bush.
The device for using the mechanical connection on a reinforcing
bar, the end of which does not have a connecting element,
intended to connect two bars end to end is characterised in
that it comprises:
- a double-acting jack body,
- a tapped or threaded extension tube fitting on to the thread
on the end of the bush and fixed to the body of the jack,
- a hollow piston of the jack being displaced between the body
and the extension tube,
- a tool provided with balls or rings disposed at the end of
the piston capable of being displaced vertically and/or in
rotation in order to effect deformation of the outer material
of the bush and to force the ribs of the reinforcing bar to
penetrate into the interior of the bush in order to produce
the connection and to crimp the bush to the end of the bar.
The process for fixing a mechanical connection for reinforcing
bars, used inter alia on site, using the connection according
to the invention, is characterised in that it consists in:
- covering the end of a reinforcing bar not having a
connecting element by means of a bush,
- pressing the bush over the end of the bar by the vertical
and/or circular displacement of a tool,
- selecting a material for the bush which is more malleable
than the material of the bar so that the ribs of the bar
penetrate into the interior of the hollow body of the bush,
2140196
_8_
- transmitting the stresses induced by the tool back to the
bar.
This invention will be more readily understood from the
following description given purely by way of a non-limiting
example. It is accompanied by the attached drawings which form
an integral part thereof and in which:
Figure 1 shows the mechanical connection for reinforcing bars
according to the invention used on a vertical bar and
on a curved horizontal bar;
Figure 2 is a view of the device according to the invention
for effecting the mechanical connection of a
reinforcing bar to a bar the end of which does not
have a connecting element;
Figure 3 is a sectional view of the bush showing the shape
obtained after deformation, and
Figure 4 shows a variant of the tool which, instead of being
provided with offset rings as shown in Figure 2, is
provided with balls.
Referring to Figure 1, it shows a mechanical connection for a
reinforcing bar designated in general by the reference numeral
( 1 ) . This reinforcing bar known to the person ski lled in the
art is used widely nowadays on site in order to reinforce
constructions. The reinforcing bar (2) is to be connected to
another reinforcing bar (3) disposed coaxially and end to end
in relation to the bar (2). The connection (1) thus ensures
the continuous transmission of the tensile stress between the
bar (2) and the bar (3).
Figure 1 shows one single bar (3), but it could form part, e.g.
of a horizontal floor (4) comprising a multitude of bars
disposed in a substantially parallel manner. Each bar (3) can
2~~~~~6
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extend from the floor (4) in a rectilinear manner or, on the
contrary, can have a curved end (5) as shown in Figure 1.
The mechanical connection for reinforcing bars according to the
invention may also be used in other devices adapted to certain
buildings with male/male or female/female sleeves.
The structure moreover comprises a vertical part into which a
row of bars (2) disposed in parallel is integrated. The end
(6) of the bar (3) therefore has to be connected to the end (7)
of the bar (2). It should be noted that this end (7) of the
reinforcing bar does not have a connecting element, i.e. it has
no thread or tap as it would then be simple for the person
skilled in the art to produce a mechanical connection.
It has been seen that the absence of threading may be due to
the design or may be as a result of corrosion or unfortunate
sawing on site.
Once the mechanical connection (1) according to the invention
has been made integral with the end (7) of the bar by the
process according to the invention, it may be connected to the
bar (3), e.g. by screwing. The system used is of the "union"
type (3 parts), where no bar can be turned.
Referring to Figure 2, it shows the reinforcing bar (2) with
its end (7) not having a connecting element, inter alia a
thread. This reinforcing bar of appropriate diameter is
provided on its outer surface with ribs (10) disposed, e.g. in
a circular or helical manner. These ribs can be irregular, but
facilitate support of the bars in the concrete in the known
manner when they are subjected to high stresses. These ribs
have different width and height dimensions adapted to the
diameter of the bar.
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In view of the method of construction, the diameter of the bar
is not very regular and these ribs are not distributed in a
very precise manner over the outer surface of the bar.
The mechanical connection for reinforcing bars according to the
invention comprises a bush (11) with a hollow cylindrical body
into which the end (7) of the bar is introduced via the orifice
(12).
In one embodiment, the bush (11) has a cylindrical shape over a
large part of its height, but also has a chamfered part ( 13 ) .
Above the chamfer ( 13 ) , the end of the bush ( 11 ) has a thread
(8) also shown in Figure 1.
The mechanical connections for reinforcing bars are therefore
formed by the cylindrical bush (11) fitting on to the
unthreaded end (7) of the bar (2) and comprising a thread (8).
It should be noted that the bar (2) and the thread (8) are
disposed coaxially along the axis (14) so that the bars (2 and
3) can be connected end to end.
It should be noted that the bars must be very well aligned and
coaxial, as, if the edges are no longer aligned, this may
result in offset stresses creating a moment having an adverse
effect on the tension of the bars and on the "permanent
elongation" tests or sliding test.
According to the invention, as a result of the axial crimping
effected by the threaded rod and the tapping of the sleeve to
be crimped and as a result of the annular shape of the tool,
the process according to the invention results more reliably in
centring of the two bars irrespective of the shape of the
reinforcing bar.
The various elements of the mechanical connection are of course
z~~.~~~6
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made of metal, but it may be advantageous to select a material
for the bush (11) which is more malleable than the material
constituting the reinforcing bar (2) so that the ribs (l0)
penetrate into the interior of the bush (11) when pressure is
applied to the outer surface of this bush. This penetration
may be effected, e.g. at the end (7) of the bar, thereby
pressing the bush over the end of the bar. This can be
achieved, e.g. by vertical and/or circular displacement of a
tool designated in general by the reference numeral (15).
The material of the ribs of the reinforcing bar penetrates into
the inner zone of the bush opposite the bar in order to connect
the bar and the bush.
The device (15) for placing the mechanical connection (1) is
shown in Figure 2.
This device is provided with a threaded extension tube (16)
comprising at one of its ends a thread (17) and a tap (30)
which is screwed on to the thread (8) of the connection (1).
The thread (17) of the extension tube is fixed in the end (18)
of the body of the preferably double-acting hollow jack used.
The body (19) of this jack defines together with the extension
tube (16) a zone (20) in which a hollow piston (21) can be
displaced. The end (22) of this piston is made integral with a
tool (23) which may have different appropriate shapes, e.g.
circular, provided with offset rings or with balls. In some
cases, these devices may be adjustable in accordance with the
diameter of the bar to be connected. The crimp connection may
be adjusted by altering the number of balls and possibly
creating a circular movement in order to effect crimping in a
helical line.
In order to improve the surface contacts and to obtain a better
214011 q6
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connection, it may be advantageous to use a heating system
allowing for an increase in temperature to 500 to 750°0 for
five to ten seconds. A high-frequency self-induction system is
suitable to ensure the localised heating of components of small
dimensions. Rapid heating and an increase in temperature can
be achieved in a few seconds with small low-frequency
lightweight equipment.
The cooling of the metal after connection has an important
advantage as the thermal stress of the contraction accentuates
crimping and therefore results in good adhesion and a
completely integral connection between the bar and the sleeve.
The heating, inter alia by self-induction, results in much
lower crimping forces and allows for the use of smaller tools.
It should therefore be noted that a bar diameter of 40 requires
sixty tonnes of pressure with four balls and a bar diameter of
40 requires fifteen tonnes of heat pressure for a circular tool
(23).
As a result of having controlled the connection in this manner
by integrally connecting the bar and the coupler in a reliable
manner, it is thus possible to considerably reduce the length
of the coupler compared to the couplers used, e.g. with
crimping perpendicular to the bars.
Figure 4 shows a detail of this tool (23) provided with balls.
Balls produce deformations (27) on the outer part of the bush
(11). Longitudinal and/or circular crimping is effected during
the vertical descent of the tool, engaging with the outer
surface of the bush, thereby resulting in controlled
penetration and possible adjustment by means of the balls.
This adjustment is obtained, e.g. by means of the screws shown
in diagrammatic form at (28).
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The crimping by means of balls can be helical if an inclined,
semi-peripheral groove is formed on the exterior of the ring of
the tool, a fixed point forcing it to rotate when pressure is
applied, the tool ,being fixed to a thrust ball bearing, the
angle of the groove being determined as a function of the pitch
or pitches of the helix and in relation to the spacing of the
bolts of the reinforcing bar.
The aim of this is to considerably increase the length of the
indentation and to penetrate well into the hollow spaces in the
reinforcing bar, while recreating the adhesive action of the
reinforcing bar on the mechanical components.
The outer material of the bush undergoes deformation by the
formation of linear or helical indentations.
When the piston descends in the direction of the arrow F, the
end of the tool (23) is displaced vertically by a distance D.
The base (24) of the tool (23) comes into contact with a pinned
element (25). This element is itself placed on a pinned plate
(26) with an interposed neoprene washer.
The tool (23) is first applied to the plane (13) and then over
the entire outer periphery of the bush (11) by means of a
considerable pressure imparted by the piston. It is by means
of this pressure and the simultaneous deformation of the
periphery of the bush, as shown in Figure 3, that the end (7)
of the reinforcing bar is connected to the bush. The tool
produces ridges (27) in a sufficient quantity on the outer part
of the bush, preferably distributed regularly over the entire
periphery. The number of ridges is of course a function of the
diameter of the bar to be connected.
During its vertical and/or circular displacement over the
distance D, the tool presses the ridges over the outer
~i4U1~6
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periphery of the bush and, by means of pressure, also causes
the penetration of the ribs (10) of the reinforcing bar at its
end (7). This penetration is of course made possible by the
selection of the material constituting the bush (11), which is
more malleable than the material of the bar at (7).
In this manner, the bush can be connected to the end of the
reinforcing bar and crimped. The material of the ribs of the
bar at its end (7) are housed in the inner part of the bush in
order to produce this connection.
Referring to Figure 2, it will be seen that the device (15) is
operated by the piston (21) when oil is delivered under
pressure. The bush (1) integral with the extension tube (16)
is fixed to the body of the jack (8). This results in a
reaction on the hollow piston which descends by the distance D
and effects crimping. The patterns (10) on the outer surface
of the bar penetrate into the material in the inner zone of the
bush which is more malleable.
At the end of operation, the face (24) of the tool bears
against the pinned element and testing is effected at the
predetermined value, e.g. 99 % of the elastic limit of the
reinforcing bar. This test is considered as good if no sliding
recorded by a drop in oil pressure read off the manometer of
the jack is observed during the tensile stress applied.
If crimping has not been effected under good conditions, the
connection will come apart during the test and it is preferable
for this to happen at this time to prevent subsequent problems
on site. It either has to be redone or replaced.
It will be seen that the device for placing the mechanical
connection described is very compact and acts vertically on the
bar. It can therefore be used in a simple manner in zones
2 ~ av g5
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where there is limited space available or where there is a high
concentration of reinforcing bars.
It should be noted that the stresses induced by the tool (23)
are transmitted back to the bush (1) and the bar (3). Use is
made of the reaction of the component. The stress induced by
the jack is transmitted back to the component. This stress
contained in the component is not dispersed and it is not
necessary to have a large press frame in order to dampen it.
The stress dispersed by the jack is transmitted back and taken
up wholly by the component. It is the inertia of the
components that completely tolerates the stress of the jack,
something which was not possible with the former devices as the
component did not play this reactive role during crimping. The
bush and the end of the bar play a reactive role during
operation and it is possible to work in the open air without a
lot of equipment and without a support.
The value of the distance D over which crimping is effected of
course depends on the density of the ribs and the protuberances
on the bar, and on the diameter of the bar and the mode of
operation, i.e. cold, hot, longitudinal or helical.
This invention may also be used for products other than
reinforcing bars, e.g. plain~bars for crimping, the end
preferably being "marked" in advance by a mechanical means or
by the compression of an indentation.
For the final test, there is the pinned supporting device for
bars projecting from the concrete, and for the test on plain
bars, the system for locking to the bar is of the self-closing
jaw type found in tractive machines.
