Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TWO PART CONNECTOR FOR
CONCRETE REINFORCING_~ARS
The invention relates to the joining of a pair of concrete
reinforcing bars or rods or the like, in end-to-end
relation. In particular the inven~ion concerns the joining
of the bars in end-to-end relation by means of a two part
connector in such a way that the tensile strength of the
joint is not less than that of the bars or otherwise
satisfies the requirements of a building code or regulation.
One way of joining together two concrete reinforcing bars
is by forming a male thread on both bars and a female
thread on an i~ntermediate coupler and threading the bars
together `in the coupler. Unfortunately the threading
reduces the tensile strength of the bar and the cutting of
the threads is an extra time consuming and inconvenient
step.
It is known to join the bars together by means of swaged
sleeves and an intermediate member or stud. These
techniques are effective but they do require extra steps
and involve the use of an extra element; in some cases it
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is important to ensure that the stud is provided with left
and right hand threads.
It is one okject of the invention to provide a means and a
method to join two concrete reinforcing bars in end-to-end
relation without threading the bars, and which will form a
joint having the required properties, e.g~ a tensile
strength not less than that of the bars themselves and
which involves the use of a two part connector without an
intermediate member.
It is another object of this invention to provide a
connector and a method of joining reinforcing bars which is
quick to assemble on site, is of substantially uniform
externaL diameter, requires no mechanical torquing and which
can be performed to the predetermined quality at low over-
lS all:cost by unskilled operators~
According to one aspe t of the inventio:n there is provided
a method of making a connection between two concrete
reinforcing bars, which are arranged in end-to-end relation,
the method comprising connecting the bars by means of a
2Q connector comprising only two connector portions, each
having threads by which the connector portions may be
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engaged together, each portion comprising a sleeve which
has a through bore and which is engaged to the respective
bar by the step of locating a portion o~ the hollow sleeve
about the bar and then swaging that portion to the
respective contained bar.
The steps of the method may be performed in any sequence;
the threaded parts may be interengaged b~efore both sleeves
are swaged on to the bars.
Most preferably the threads are parallel and/or inclined to
the major axis of the sleeve, say by about 10 degrees. The
threads may be of any suitable shape: threads of V section
may be used; in some instances ! e.g. for joining bars of
relatively larger diameter, it is preferred to use square
threads with sloping faces such as ACME threads. Also the
lead of the
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threads may be greater than the pitch. The lead of
the thread may be double, triple or higher; generally
a double lead pitch ;s preferred.
It is important to form the two part connector,
especially the male part, of a material which can both
be swaged and threaded without any decrease of
strength. Steel is preferred. It will be appreciated
that in forming the male sleeve threaded part to be
received in the female sleeve threaded socket one
wishes to avoid an increase in the overall diameter of
the sleeve assembly. This may involve a reduction in
the cross-sectional area of the part of the male
sleeve to be threaded. We have found that by reducing
the external diameter of the precursor of the sleeve
. while holding the other dimensions one can have a
threaded male part for a two part connector without
losing strength. It is an advantage that the external
diameter of the assembled connection is substantiallv
uniform.
According to another aspect of the invention there is
providea a connection of two concrete reinforcing bars
arranged in end-to-end relation, a first sleeve being
swaged to one bar and projecting towards t'ne second
bar, the sIeeve having a bore with a t:hreaded portion,
a second sleeve swaged to the second t)ar ana
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projecting towards the first, the second sleeve having an
externally threaded end portion, the externally threaded
portion of the second sleeve being hollow and being
received in the threaded portion of the first sleeve
directly and without the interposition between the sleeves
of any third connecting element.
According to another aspect of ~he invention there is
provided a two part connector adapted and dimensioned for
use in joining together two concrete reinforcing bars, the
connector consisting exclusively of two sleeves, each
sleeve having one unthreaded end portion for swagin~ onto
a bar and another end portion for interengagement with the
other sleeve r one of the sleeve engagement parts having a
male locating nose, the other sleeve having a female socket
for reception of the male extension, the interengaging
parts being hollow and threaded~
Preferably t~le concrete reinforcing bars range from about
10 mm to 57 mm in diameter. The bars may be of any type
and have any rib deformation and are available under a
2Q variety of names.
Evaluations have shown that the invention is advantageous
because skilled operators are not required on site. There
is no need to thread the
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bars, nor for an inspection, or extra protection of
the threads: the only job done on site is rotation of
one bar with respect to the other.
In order that the invention may be we].l understood it
will now be described by way of example with reference
to the accompanying diagrammatic drawings in which
Figure 1 shows a system for joining two concrete
relnforcing bars Bl and B2 together;
Figure 2 is a .sectional elevation of another two
bars to be joined: and
Figure 3 is a sectional elevation of the formed
joint:of Figure 2.
The bars~Bl and B2 of Figure 1 are to be joined by
means of two sleeves 51 and S2. The sleeve Sl has a
bore 1 wlth an unthreaded portion SlA which has been
swaged on to the bar Bl and a threaded portion SlB,
which has a screw thread 2 at one end, the rlght, as
seen ln Figure 1. The sleeve S2 has a portion S2A
with an unthreaded bore 3 and the left hand end
portion S2B has an internal thread 4, shaped and
dimensioned to complement the:thread 2 of the sleeve
Sl. The sleeve S2 is swaged onto the bar B2 and the
thread 4 is then threaded into the threaded bore 2 of
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the sleeve Sl. The assembled connection of the
sleeves is of substantially uniform external diameter
which is an advantage.
In the embodiment of Figures 2 and 3, two lengths of
concrete reinforcing bars Bl, B2 are to be joined by
couplers S3, S4. One coupler S3, the male, comprises
a length of steel, originally having a straight sidea
end portion S3A, which as shown, has been swaged on to
the bar Bl, a threaded portion S3B, and a nose 7, the
portions transist by an integral neck 5. The threaded
portion S3B comprises threads 6 which have a multi-
lead, le. a double lead, so that rotation of a nut
thereon moves two threads per full rotation. The nose
7 serves for location and alignment into coupler S4.
,,
The coupler S4 has an originally straight sided end
portion S4A, and a socket end portion S4B which is
internally threaded to receive the threaded portion
S3B of the male coupler S3. The threads 8 of the
socket S4B mate with tnose 6 of the male coupler.
The mouth of the socket S4B has an internal chamfer to
initially guide the nose of the male into the socket.
In use, one of the couplers S4, S4 is swaged to a bar
Bl, B2. For example, the male coupler S3 may be
swaged to the bar Bl in a Eabrication shop. The
female coupler is tnen swaged to the bar B2 and
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brought to the male coupler or vica versa, and by a
few rotations the female is threaded on to the male so
joining the bars together. (If the bar B2 is too long
to rotate, the coup]ers may be joined ana then the bar
B2 may be swaged to the coupler S4). The joint formed
meets the appropriate building code requirements. The
joint is fast to assemble. It is easy for an operator
to see that the couplers are properly joined, since no
full threads will be left exposed. The bars may range
from U.S. size no. 4 (12 mm) to U.S. size no. 18 (57
mm).
The invention is further illustrated by the following
example. Two concrete reinforcing bars of diameter
specified in the Table below were joined by
appropriately dimensioned connectors according to
Figure 2 above. The sleeves were swaged on to the
bars and the splice was completed by threaaing the
connector parts together to a hand tight connection
and then unthreading the connection one half turn to
~simulate the situation where such unthreading may be
necessary for example to join misaligned bars. The
joint was then continuously tensioned under a load
until the joint failed. The tensile strength was
determined by dividing the maximum load by the nominal
reinforcing bar area. These results show that the
joint had a tensile strength exceeaing tne 125% oE the
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specified bar yield strength of 517 Newtonsimm2 and so
the connector would conform for example to the
mecnanical splice requirement of the American Concrete
Institute standard ACI 318 The tensile strength of
the joint is in Newtons/mm and the bar yield strength
is Newtons/m ~n ~
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