FIELD OF THE INVENTION
The present invention relates to the field of rebar used in concrete construction
site, and more particularly, the invention relates to a process of joining of rebar
ends without turning of the rebar ends, or welding.
BACKGROUND OF THE INVENTION
Rebars are generally manufactured in 8-15 metres length or other convenient
length for transportation. Those rebars are joined end-to-end at construction site
to make up a longer continuous rebar having mechanical property equivalent to
a single continuous rebar. The joining of the rebars can be done in three routes,
for example, welding, pouring of molten metal and mechanical coupling.
The welding method is generally used for steel bars with diameter higher than
16mm. Welding is usually done by using an electric arc wherein the joining
quality depend on weld-ability of the particular steel grade, welding condition
and axial alignment of the welded rebars. The welded joint is made by different
ways for example, butt joint of two rebar ends; bend and overlap of the two
rebar ends and then welding; add additional hollow piece of tube and place two
rebar ends within it and weld their end tube with rebar individually. Rebars are
generally produced by thermo mechanical treatment (TMT) to achieve unique
microstructure throughout its cross section, ferrite-perlite phase form at the core

and comparatively hard temper martensite is obtained at surface. This
microstructural combination results in high strength without sacrificing the
ductility. However, if the two rebars are joined by welding, the microstructure
changes which adversely affects its mechanical properties.
Another technique to join steel rebars directly in an end-to-end relation is
pouring of molten metal between the rebar ends and a sleeve which is
essentially placed outside the rebar ends. This method is applied to effectively
transfer high tension-compression loads which arise from load borne by concrete
structure made with rebars. In this technique, a steel sleeve with slightly higher
diameter than that of the rebar is symmetrically placed outside the rebar ends,
then molten metal is poured into a space between the rebar and sleeve. After
cooling of the molten metal, the bond becomes strong and permanent. Fire
hazard is always present whenever molten metal is being used. Apart from fire
hazard, the process is cumbersome and joined section becomes weaker
especially for high strength rebar.
Four types of mechanical coupling are present, which are (i) a sleeve pipe clod
swaged on the two rebars ends, (ii) internally threaded, (iii) jaw assembly with
interior teeth and (iv) steel sleeve with two converging sides.
Type (i): Description: A deformable soft hollow sleeve pipe having adequate
thickness with inner diameter equal to the rebars outer diameter is first

positioned outside the two rebars ends. Smooth inner surface of the sleeve pipe
being deformed by the application of sufficient clamping force and the created
impressions on the inner surface of the sleeve pipe to interlock with the ribs of
the rebars outer surface. For clamping, sets of rings are welded with the outer
surface of the sleeve pipe, and bolts are passed through the rings, and by
tightening the nuts-bolts sufficient clamping force have been created.
Limitation: Load carrying capacity of the created impressions on the inner
surface of the soft sleeve pipe is low, in that case large sleeve pipe is required
which is leading to higher cost and difficult for handling and placing. If, instead
of a soft sleeve pipe, a hard sleeve pipe being used then the ribs of the rebar get
deformed and impression on the inner surface of the sleeve pipe becomes very
small. Welding of a ring on the outer surfaces of sleeve pipe is cumbersome and
costly. Application of high torque is required to tighten the nuts and bolts to
generate high clamping force for creating impressions on the inner surface of the
soft sleeve pipe. Application of high torque at construction site restricts its use.
Type (ii): Description : Rebar ends are threaded on outer surface and sleeve is
internally threaded. By the threading action, the sleeve is placed in such a
manner that the sleeve covers equal distance of both rebar ends. In this type of
coupler, the thread and sleeve carry rebar's load in the joint.

Limitation: The threading of the rebar ends are done by heating and
compressing the rebar ends to increase their diameter including thread cutting
on rebar ends. This operation alters the mechanical properties of the rebar end.
Moreover the process of threading is cumbersome and time consuming.
Type (iii): Description: The outsides of the rebar ends are bite by jaw assembly
with interior teeth. In both axial ends, tapered locking collar constrict the jaw
assembly.
Limitation: However to assemble the total jaw assembly, the coupler requires a
special assembling machine, and the assembly process is highly energy
consuming. In addition, to generate sufficient resistance between internal thread
of jaw assembly and the rebar a large coupler length is needed.
Type (iv): Description: A steel sleeve with two converging side and few screws
are required for such type of mechanical coupling. The sleeve is positioned in
such a way that rebars ends make almost equal distance from the sleeve ends. A
series of cone-pointed screws are then tighten along the sleeve length in such a
way that the screws ends indent the surface of the rebar.
Limitation: This coupling method can be successfully applied in soft material like
epoxy-coated or galvanized etc. But for steel rebar with higher diameter, a large
sleeve length and a large number of screws are required, for leading to higher
cost.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a mechanical flange coupler
for end-to-end connection of the reinforcement bars to produce long continuous
reinforcement bars, which eliminates the disadvantages of prior art.
Another object of the invention is to propose a mechanical flange coupler for
end-to-end connection of reinforcement bars to produce long continuous
reinforcement bars, which maintains high mechanical properties of the long
continuous reinforcement bars after connection.
A further objection of the invention is to propose a mechanical flange coupler for
end-to-end connection of reinforcement bars to produce long continuous
reinforcement bars, which eliminates the prior art requirements of heating of the
rebar ends including cutting threads in the rebar ends prior to joining through a
sleeve.
SUMMARY OF THE INVENTION
According to this invention a flange coupler is provided for quick end-to-end
connection of rebars at construction site. The coupler is comprises of two
separable elongated components. Each elongated component has a hollow semi-
cylindrical member and two continuous longitudinal flanges at the splitting edges

of the hollow semi-cylindrical member. Rebar ends are generally feed into the
hollow inner cylinder between the two elongated components and bolting is done
between the flanges of the two elongated components. The imprint i.e.
deformation (female) of inner surfaces of semi-cylinders of two elongated
components and the ribs (male) of the rebars, the outer surfaces are interlocked
to carry load.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: Schematic 3D view of flange coupler joint according to the invention.
Figure 2: Top view of the second elongated component (D) of the flange coupler
of Figure 1.
Figure 3: Side view of the second elongated component (D) of the flange coupler
of Figure 1.
Figure 4: Top view of the first elongated component (C) of the flange coupler of
Figure 1.

DETAIL DESCRIPTION OF THE INVENTION
On the drawings, the alphabets indicate the elements; in figure 1 two rebars A
and B are connected by a flange coupler which have three elements, wherein C
is the first elongated component, D is the second elongated component and E
are the bolts. Each elongated component (C,D) has one each hollow semi-
cylindrical member F and flange G. The rebars (A, B) have ribs H at the surface.
The first and second elongated component C and D can be generally fabricated
from a strong metallic material such as steel. C and D can be fabricated by
various processing routes such as forging or rolling. The number of bolts (E)
required for clamping the first and second elongated components (C,D) depends
upon the diameter of the rebars (A, B).
The top view of the second elongated component (D) is shown in figure 2.
Deformation (imprint) (J) is clearly shown in inner surfaces of the semi-
cylinders ( F). The cross sectional view of the imprint (J) is also shown clearly in
figure 2. Circular bolt holes (I) are present in the flange (G) of the second
elongated component (E) can be fitted through the holes (I) for clamping the
two elongated components (C, D). The side view of the second elongated
component (D) is shown in figure 3, which shows the semi-cylindrical member
(F), flange (G) and bolt holes (I).

Top view of the first elongated component (C) is shown in figure 4. The only
difference between the first and second elongated component (C, D) is in the
bolt holes (I, K) wherein the bolt holes (I) are circular for the second elongated
component (D), wherein the bolt holes (K) are elongated ellipse for the first
elongated component (C). Rebars A and B have two continuous longitudinal ribs
and transverse ribs are placed in-between the longitudinal one. Therefore two
sides of a longitudinal rib contain two arrays of transverse ribs and they might
or might not meet not meet at the same point on a longitudinal rib.
The variation in the position of two arrays of transverse ribs can be taken care
by the elongated elliptical bolt holes (K) which are placed at the first elongated
component (C).
The flange coupler for connecting the rebars (A, B) at construction site has the
following advantages:
(i) fabrication cost is low;
(ii) easy to install and disassembly at site;
(iii) time required for installation is minimum;
(iv) Provides a very strong bond between rebars;
(v) no welding and machining operation required during fabrication;
(vi) no welding is required at the construction site.

The invented rebar coupler can be easily installed. Two rebar ends A and B are
placed in concentric and axially aligned position. The second elongated
component (D) is placed in such a way that its deformation (imprint) (J) and the
rabars ribs (H) are interlocked each other, and the coupler is at the middle of
two rebar ends (A, B). The first elongated component (C) is placed above the
second elongated component (D) and the two rebar ends (A, B) lie in-between
the first and second elongated components (C, D). During placing the first
elongated component (C) it should be done in such a manner that the
deformation (imprint) (J) and rebars ribs (H) should be interlocked with each
other. Accordingly, a horizontal movement of the first elongated component (C)
might be necessary which eliminates positioning the first and second elongated
components in complete alignment. Even then the two elongated components
(CD) can be bolted as the bolt hole (K) of the first elongated component (C) is
elliptical. The major axis of which is bigger than the diameter of the bolt hold (K)
of the first elongated component (C). It is also to be noted that in order to match
with the ribs (H) of the rebar (A, B) to the female deformation (imprint) on the
elongated component inner surface, the two rebar ends (A, B) might have to be
put at same suitable distance. That means with the coupler setup, two ends of
the rebars (A, B) might not touch each other. Bolts (E) are placed through the
bolt holes (I, K) of the first and second elongated component (C, D). Bolts (E)
are tightened by the nuts to properly clamp the two elongated components
(C, D) to the rebar ends (A, B).

WE CLAIM:
1. A mechanical flange coupler for connecting rebars, the coupler
comprising:
a first elongated component (C) having at least two elongated elliptical
bolt holes (K) and deformation (J) on the inner side;
a second elongated component (D) having at least two circular bolt holes
(I) and deformations (J) on the inner side, wherein ribs (H) on the outer
surface of the connecting rebars (A, B) embed into the deformations (J) of
the inner sides of the first elongated component (C) and the second
elongated component (D) of the coupler, wherein the first elongated component and the second elongated component of the coupler are
clamped along the longitudinal axis.
2. The coupler as claimed in claim 1, wherein the first elongated component
(C) and the second elongated component (D) are metallic.
3. The coupler as claimed in claim 1, wherein the first elongated component
and the second elongated component are fabricated by a route selected
from the group consisting of rolling, forging and casting.

4. The coupler as claimed in claim 1, wherein the first elongated component
and the second elongated component are semi-cylindrical in shape with
flanges (G) extending outwardly along the horizontal axis.
5. The coupler as claimed in claim 1, wherein clamping means comprises
nuts and bolts (E).

ABSTRACT

The invention relates to a mechanical flange coupler for end-to-end connection
of reinforcing bars is made of two elongated components (C, D). Each elongated
component has a half cylindrical shell and two longitudinal flanges (G) which are
attached to the half cylindrical shell edges along its axial direction. Each
elongated components have deformation (J) on its inner surface to match with
rebar outer surfaces ribs (H). The elongated components inner surface
deformation (imprint) interlock with ribs (H) of the rebar's outer surfaces to hold
the rebar ends (A, B) together. To secure the firm joint between the two rebar
ends (A, B), the longitudinal flanges (G) of the elongated components (C, D) are
bolted together.