U.S. patent application number 11/537954 was filed with the patent office on 2008-03-13 for device for connecting bars end-to-end.
This patent application is currently assigned to DEXTRA ASIA Co., Ltd.. Invention is credited to Jean-Jacques BRAUN.
Application Number | 20080060291 11/537954 |
Document ID | / |
Family ID | 37714521 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080060291 |
Kind Code |
A1 |
BRAUN; Jean-Jacques |
March 13, 2008 |
DEVICE FOR CONNECTING BARS END-TO-END
Abstract
A device for connecting bars end-to-end includes a hollow body
having an internal cavity with at least one bar insertion opening
and a longitudinal axis extending through the at least one
insertion opening, and a plurality of radially adjustable clamping
elements. The device further includes at least one locking element
movably arranged inside the hollow body. The internal cavity of the
hollow body has at least one slope inclined relative to the
longitudinal axis of the hollow body. The at least one locking
element has an inclined face that matches the profile of the at
least one slope and a gripping face with at least one
protrusion.
Inventors: |
BRAUN; Jean-Jacques;
(Bangkok, TH) |
Correspondence
Address: |
EGBERT LAW OFFICES
412 MAIN STREET, 7TH FLOOR
HOUSTON
TX
77002
US
|
Assignee: |
DEXTRA ASIA Co., Ltd.
Bangkok
TH
|
Family ID: |
37714521 |
Appl. No.: |
11/537954 |
Filed: |
October 2, 2006 |
Current U.S.
Class: |
52/223.2 |
Current CPC
Class: |
E04C 5/165 20130101 |
Class at
Publication: |
52/223.2 |
International
Class: |
E04H 5/00 20060101
E04H005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 8, 2006 |
EP |
06018815.3 |
Claims
1. A device for connecting bars end-to-end, said device comprising:
a hollow body having an internal cavity with at least one bar
insertion opening and a longitudinal axis extending through said at
least one insertion opening, said internal cavity having at least
one slope inclined relative to a longitudinal axis of said hollow
body; a plurality of radially-adjustable clamping elements mounted
on said hollow body; and at least one locking element movably
arranged inside said hollow body, said at least one locking element
having an inclined face matching said at least one slope of said
internal cavity and a gripping face having at least one
protrusion.
2. The device according to claim 1, wherein said internal cavity of
said hollow body has at least two slopes inclined relative to the
longitudinal axis of said hollow body, said at least two slopes
being inclined in opposite directions.
3. The device according to claim 1, wherein said gripping face is
generally parallel to the longitudinal axis of said hollow
body.
4. The device according to claim 1, wherein said internal cavity of
said hollow body has a cross-section area increasing from a minimum
at one end of said internal cavity to a maximum at a middle of said
internal cavity and decreasing from said maximum at said middle of
said internal cavity to a minimum at an opposite end of said
internal cavity.
5. The device according to claim 1, wherein said internal cavity of
said hollow body has a cross-section area decreasing from a maximum
at one end of said internal cavity to a minimum at a middle of said
internal cavity and increasing from said minimum at said middle of
said internal cavity to a maximum at an opposite end of said
internal cavity.
6. The device according to claim 1, wherein said
radially-adjustable clamping elements have a designated
preferential location of failure.
7. The device according to claim 1, further comprising: stop means
provided in said internal cavity of said hollow body.
8. The device according to claim 2, wherein said at least one
locking element has a radial thicknesses to accommodate bars of
different sizes.
9. The device according to claim 1, further comprising: pushing
means for pushing said at least one locking element from outside of
said hollow body.
10. The device according to claim 1, wherein said at least one
locking element having an end chamfered in order to reduce maximum
height thereof.
11. The device according to claim 1, wherein said hollow body has
at least one external face being comprised of ribs or grooves.
12. The device according to claim 1, further comprising: a
corrosion-protection substance poured or injected inside said
hollow body.
13. The device according to claim 1, further comprising: a binding
substance poured or injected inside said hollow body.
14. A method of connecting bars end-to-end, said method comprising:
inserting bars into a device comprised of a hollow body having an
internal cavity with at least one bar insertion opening and a
longitudinal axis extending through said at least one insertion
opening, said internal cavity having at least one slope inclined
relative to a longitudinal axis of said hollow body; a plurality of
radially-adjustable clamping elements mounted on said hollow body;
at least one locking element movably arranged inside said hollow
body, said at least one locking element having an inclined face
matching said at least one slope of said internal cavity and a
gripping face having at least one protrusion; and stop means
provided in said internal cavity of said hollow body, said bars
being inserted until contacting said stop means; and tightening
said radially-adjustable clamping elements until ends of said bars
are forced against said gripping face, said radially-adjustable
clamping elements being locked into a surface material of said
bars, said at least one locking element being further forced
against said bars when said bars are subjected to a tensile load.
Description
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT
[0003] Not applicable.
REFERENCE TO AN APPENDIX SUBMITTED ON COMPACT DISC
[0004] Not applicable.
BACKGROUND OF THE INVENTION
[0005] 1. Field of the Invention
[0006] The present invention relates to a device for connecting two
bars in an end-to-end relationship. The device has a particular
application in coupling the ends of reinforcing bars used in
structural concrete.
[0007] 2. Description of Related Art
[0008] Including Information Disclosed Under 37 CFR 1.97 and 37 CFR
1.98.
[0009] In the art of joining two bars end-to-end in order to extend
their continuity, it is known to use a tubular sleeve that receives
the end portion of each bar, the sleeve having radially-oriented
elements that are forced into the material of the bars in order to
lock them. According to one device as disclosed in U.S. Pat. No.
5,046,878 issued to Young on Sep. 10, 1991, the radially oriented
elements are provided as screws and racks that are arranged
longitudinally along the sleeve.
[0010] The prior art systems have drawbacks. First of all, the
pneumatic and electric tools that are commonly available on the
market are of limited capacity, which means that it is not possible
to increase the size or strength of the screws beyond a certain
limit. The connection of larger or stronger bars is therefore not
possible. Secondly, the effort generated by torquing the screws
serves to press the racks into the sleeve as much as to press them
into the bars. Less than half of the tightening effort is thus
available to actually clamp the bars. Finally, its performance
under a tensile load is very difficult to maintain and to control.
Indeed, the effectiveness of the fitting of the sleeve onto the bar
end wholly depends on the torque applied on the screws, which is
the torque at which the screw heads shear off.
[0011] These screws have their neck reduced so that the shearing
occurs outside their threaded area. The precision of this diameter
reduction, as well as the radius at the bottom of the reduction,
are difficult to achieve. The stress riser at the reduction may
vary from 1 to 4, depending on the radius at the bottom of the
reduction, which on top of being difficult to produce accurately,
is also difficult to measure and control. This variation in stress
riser affects directly the torque at which the screws shear off,
and consequently the performance of the system.
[0012] Moreover, the screws are calculated to shear off under a
purely torsion effort. In practice however, it cannot be guaranteed
that the pneumatic or electric wrench or screwdriver is perfectly
aligned on the axis of the screw. Because this tool is manually
held, a certain angle between its axis and that of the screw is
unavoidable. Such an angle adds a flexural effort to the torsion
effect, thereby reducing the torque necessary to shear off the
screws, and hence reducing the system performance.
[0013] Also known are prior art devices disclosed in U.S. Pat. No.
5,909,980 and U.S. Pat. No. 6,202,282 that work essentially in the
same way as the previously referenced device. These prior art
systems replace the gripping effect of the racks by the friction
effect of the bar against the internal surface of the sleeve.
Because friction is not as efficient as gripping in transmitting
effort, it compensates by using a longer length and a larger number
of screws. Being so closely related to the other prior art cited,
these other prior art systems do not bring any particular
additional benefit, while still suffering from the same
disadvantage and the additional drawback of bulkiness.
[0014] Also known is a device as disclosed in U.S. Patent
Publication No. 2004/0238558 that also works essentially in the
same way as the previously cited prior art systems. This particular
prior art system provides two rows of screws and uses an internal
thread rather than racks to produce the gripping effect inside the
sleeve. Being so closely related to the other prior art cited, this
prior art system does not bring any additional benefits, while
still suffering from the same disadvantages and the additional
drawback that the angle between the two rows of screws requires
extra free space for installation.
BRIEF SUMMARY OF THE INVENTION
[0015] Compared to many of the existing systems to connect two bars
end-to-end, such as threading or forging the bar ends, the device
of the present invention presents the advantage of not needing any
preparation of the bar end. This means that it is not necessary to
either transport the bars to a workshop where their ends can be
prepared, or transport to the location of the bars the machinery
needed to prepare their ends. This system was indeed developed with
the aim of enabling a site assembly, with only a pneumatic or
electric wrench needed to torque the screws. A site assembly is a
great benefit in some industries such as the construction or the
oil industry. It is also a great benefit in large countries where
transport of bars is an issue, due to long distances.
[0016] It is an object of the present invention to provide a device
for connecting bars in an end-to-end relationship that upholds the
benefit of site assembly, in addition to new benefits in terms of
increased reliability, improved safety to the structure, and better
tensile and load bearing performance.
[0017] The present invention also reduces bulkiness compared to the
prior art systems. The improved size of the device improves safety
for the installer and the individuals working around the device at
the work or construction site.
[0018] The present invention is a device for connecting bars
end-to-end comprising a hollow casing or body whose internal cavity
presents slopes, or surfaces that are at a certain angle relative
to the axis of the bars to be connected.
[0019] According to the present invention, the device further
comprises at least one locking element movably arranged inside the
hollow body. The internal cavity of the body comprises at least one
slope, that is inclined relative to the longitudinal axis of the
body. The locking element also has an inclined face that matches
the profile of at least one slope of the internal cavity and a
gripping face with at least one protrusion. With this structure,
the device according to the present invention achieves a
self-locking effect in which the clamping and gripping force of the
device increases with increased loading of the bars to be
connected. As a result, the device according to the invention
achieves a higher load bearing performance on an improved safety
and reliability level. Moreover, thanks to a reduced bulkiness of
the device, improved safety is provided to the installer and the
people working around the device on an industrial or construction
site.
[0020] In the preferred embodiment, the hollow body has at least
two insertion openings and its internal cavity has at least two
slopes. The slopes are inclined relative to the longitudinal axis
of the hollow body, these inclinations being in opposite
directions. As a result, a plurality of bars can be reliably
connected in a self-locking manner. If part of the device is to be
welded to a steel structure, it can be adapted to receive one bar
only. Then, the hollow body has only one insertion opening, and its
internal cavity has only one slope.
[0021] The shape of the slopes and inclined faces is not
particularly limited in the present invention, as long as
cooperating slopes and inclined faces match each other.
[0022] The slopes may be flat or curved.
[0023] In order to achieve an optimum gripping force and an easy
and reliable operation of the device, it is preferred that the
gripping surface is generally parallel to the longitudinal axis of
the hollow body. The material of the gripping surface is chosen and
its teeth are shaped to suitably bite into the material of the bars
to be connected.
[0024] According to a further development of the present invention,
the cross-sectional area of the internal cavity of the hollow body
is not regular but rather increases from a minimum at the extremity
towards a maximum at the middle and then decreases back to a
minimum at the other extremity. Alternatively, the cross-sectional
area of the internal cavity may also decrease from a maximum at the
extremity towards a minimum at the middle and then increase back to
a maximum at the other extremity. This allows an easy manufacture
and a stable construction of a hollow body having slopes in its
internal cavity.
[0025] The shape and type of the radially-adjustable clamping
elements are not specifically restricted in the present invention.
In many cases, these will be screws which may have pointed or flat
ends, depending on the material of the bars to be connected. They
may have standard necks or neck reductions designed to shear under
a certain torque.
[0026] There may be provided one or more rows of screws.
[0027] In order to achieve a proper and easy positioning of the
bars/bar ends to be connected, it is preferred that stop means are
provided in the internal cavity of the body.
[0028] In order to increase the variability of the device, the
locking elements are of different radial thickness in order to
accommodate bars of different sizes.
[0029] The locking elements may in the present invention act as
"passive" locking elements which develop a "self-locking effect"
only after an increase load has been brought on the bars to be
connected. However, in order to reduce possible slip or
deformation, the device according to the present invention further
comprises a pushing means for pushing the locking elements from
outside of the hollow body. In this way, the locking elements may
be prestressed and/or it can be avoided during fastening the
radially-adjustable clamping elements that the at least one locking
element(s) slides away.
[0030] According to a further development of the present invention,
at least one internal phase of the body comprises ribs or grooves.
This will improve the bond and anchoring of the device when used in
concrete or the like.
[0031] Further, in order to increase the durability of the device
according to the present invention, a corrosion-protection or
binding substance is poured or injected inside the body.
[0032] According to a further aspect, the present invention
provides a method of connecting bars end-to-end using the device as
described above. Further details on the method of connecting bar
ends according to the present invention will be apparent from the
following detailed description.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0033] FIG. 1 shows a perspective view of a device for connecting
bar ends according to a first embodiment of the present
invention.
[0034] FIG. 2 shows a cross-sectional view of the embodiment shown
in FIG. 1.
[0035] FIG. 3 shows a cross-sectional view of a variant of the
first embodiment where a corrosion-protection or binding substance
has been injected inside the body.
[0036] FIG. 4 shows a perspective view of a device for connecting
bar ends according to a second embodiment of the present
invention.
[0037] FIG. 5 shows a perspective view of a device for connecting
bar ends according to a third embodiment of the present
invention.
[0038] FIG. 6 shows a cross-sectional view of the device for
connecting bar ends according to a further embodiment of the
present invention.
[0039] FIG. 7a to 7f show perspective views of various locking
elements.
[0040] FIG. 8 shows a cross-sectional view of a device for
connecting bars end-to-end according to a fourth embodiment of the
present invention adapted to connect bars of different
diameters.
[0041] FIG. 9 shows a cross-sectional view of a device for
connecting bars end-to-end according to a fifth embodiment of the
present invention provided with a pushing means.
[0042] FIG. 10 shows a cross-sectional view of a device for
connecting bars end-to-end according to a sixth embodiment of the
present invention, also provided with a pushing means.
[0043] FIG. 11 shows a cross-sectional view of a device for
connecting bars end-to-end according to a seventh embodiment of the
present invention adapted to receive mainly compressive forces.
[0044] FIG. 12 shows a cross-sectional view of a device for
connecting bars end-to-end according to a seventh embodiment of the
present invention adapted to receive both tensile and compressive
forces.
DETAILED DESCRIPTION OF THE INVENTION
[0045] Preferred embodiments of the invention are discussed in the
following with reference to the enclosed drawings.
[0046] A device 1 for connecting the ends 2' of a bar according to
a first embodiment of the present invention is schematically shown
in a perspective view in FIG. 1 as well as in a cross-sectional
view in FIG. 2. The device is adapted for connecting rebars and the
like end-to-end as they are used in construction, for instance, in
reinforced concrete structures. The device 1 comprises a hollow
body 10 having an internal cavity 12 which, in the present
embodiment, comprises two insertion openings 14 through which a
longitudinal axis extends. The direction of extension of the
longitudinal axis coincides with the direction of extension of the
bars 2 to be connected (FIG. 2).
[0047] Furthermore, the device 1 comprises a plurality of clamping
screws 16 which are fitted into threaded holes formed in the hollow
body 10. The screws may have a reduced neck so as to produce a
defined failure. As can be seen in FIG. 2, the screws 16 are
adapted to press on the bars 2 inserted into the hollow body
10.
[0048] Further, the device 1 comprises two locking elements 18
which are movably arranged inside the internal cavity 12 of the
hollow body 10. Specifically, the internal cavity 12 of the body 10
comprises two slopes 12' which are inclined relative to the
longitudinal axis of the body 10, and the locking elements 18 each
comprise a inclined face 18' which matches the profile of the
corresponding slope 12' and is in contact therewith. In addition,
each locking element 18 has a gripping face 18'' having a plurality
of rack teeth. The gripping face 18'' is adapted to grip and fix
the respective bar 2 together with the screws 16. Therefore, it is
preferred that the gripping faces 18'' are generally parallel to
the longitudinal axis of the bars 2 and body 10.
[0049] As can be seen in FIG. 2, the device 1 further comprises
stop means 20, for example in the form of stop or separation walls.
As shown in FIG. 6, this stop or separation wall 20 may also fully
separate the internal cavity 12 in two parts.
[0050] For applications where the connection needs to grip or bond
with an external surrounding material, for example in concrete
construction, ribs or grooves 24 may be provided on the external
surface of the body 10.
[0051] The connection is achieved by inserting the ends 2' of bars
2 until they hit the wall 20. The screws 16 are then tightened
either until a given torque, or until their heads shear off,
thereby forcing the ends 2' of bars 2 against the gripping face
18'' of the locking elements 18, and locking themselves into the
surface material of the bars 2.
[0052] The bars 2 are then put in use and sustain a tensile load.
This tensile load tends to pull both bars apart, along with the
locking elements 18 thanks to the gripping achieved on their
gripping faces 18''. When the locking elements 18 move apart by
sliding over the slopes 12', they force their grip 18'' further
into the material of the bars 2. Thus, the resistance of the device
increases with the load applied on the bars.
[0053] FIG. 3 relates to a second embodiment for applications where
it is necessary to fill up the cavity 12 with a
corrosion-protection or binding substance, end caps 26 may be
provided to close the spaces at each extremity of the connection,
and a hole 28 may be provided in the body 10, through which the
substance may be poured or injected.
[0054] FIGS. 4 and 5 show that the external shape of the hollow
body 10 may be widely varied within the present invention. Further,
the device 1 may comprise one row or also plural rows of screws 16,
as shown in FIG. 5.
[0055] Also the shape of the locking elements 18 is not
specifically limited in the present invention. Various examples of
suitable locking elements 18 are shown in FIGS. 7A to 7G. For
instance, the inclined face 18' may be flat or curved just like the
gripping face 18''. Of course, further designs are possible.
[0056] FIG. 8 shows an embodiment which is adapted to connecting
bars 2 having different diameters. For this purpose, the locking
elements 18 have a different radial thickness. Specifically, in
FIG. 8, the locking element 18 on the left hand side is adapted to
grip a bar 2 having a smaller diameter and, therefore, itself has a
smaller radial thickness than the locking element 18 on the right
hand side.
[0057] FIGS. 9 and 10 show a sixth and seventh embodiment,
respectively, with additional pushing means 22 for pushing the
locking elements 18 against the ends 2' of bars 2 prior to the
tightening of screws 16. This feature is illustrated in FIG. 9 with
a cam 23 that is rotated around its axis. In FIG. 10 the pushing
means 22 comprises a central screw 25 that pushes on the rear faces
of the locking elements 18.
[0058] FIG. 11 schematically shows an eighth embodiment of the
present invention for cases where the connection must withstand not
tensile, but mainly compression efforts. In this embodiment, the
slopes 12' are diverging towards the insertion openings 14.
[0059] Under a compression effort, the locking elements 18 are
moving towards the center of the body, thereby securing the
clamping of the bars 2.
[0060] FIG. 12 schematically shows an ninth embodiment of the
present invention for the cases where the connection must withstand
alternate cyclic tensile and compression efforts. In this
embodiment, a total of four locking elements 18a, 18b are provided,
namely two locking elements 18a, 18b per bar 2. Further, the
locking elements 18a, 18b of each bar have their respective slopes
18' inclined in opposite directions. Thus, under a tensile effort,
the locking elements 18a are moving towards the extremities of the
body, thereby securing the clamping of the bars. Under a
compression effort, the locking elements 18b are moving towards the
center of the body, thereby securing the clamping of the bars.
[0061] The connection of the bars 2 is achieved by inserting the
device lover the end 2' of a first bar 2, said bar end 2 being
received by the cavity 12 between the locking element 18 and the
screws 16. A second bar 2 is then inserted into the other side of
the device 1. The device can now be oriented in the radial
direction deemed most suitable either for access purpose or for
space optimization. The pushing means 22 may then be used to reduce
the clearance between the bars 2 and the device 1. The screws 16
are finally torqued so that they press the bar 2 against the
locking elements 18 and themselves penetrate into the surface of
the bars 2.
[0062] When the bars 2 are pulled by application of a tensile load,
the initial resistance comes from the gripping effect between the
screws 16 and the locking elements 18. As the load increases, the
locking elements 18 move along the slopes 12' of the body 10, and
further lock the bar ends 2' inside the cavity, thereby greatly
improving the tensile performance: the stronger the pull on the
bars, the stronger the lock.
* * * * *