Note: Descriptions are shown in the official language in which they were submitted.
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"Improvements in or relating to form~ork -ties"
This invention relates to formwork ties for use
in the casting of concrete. Such ties are used to
support the formwork in place and to restrain wet
concrete loads on the formwork caused by hydrostatic
pressure in the wet concrete or the dead load of the
concrete, or a combination of both.
Many systems of formwork ties are known in the
prior art. A conventional system, which is still used,
comprises a tensile tie rod having, for wall construction,
a spacer, or cone, threadedly connected or welded to each
end. The spacers or cones abut the inner surfaces of
the formwork members and hold them in the desired spaced
apart relationship to define the wall thickness.
Retaining bolts or threaded rods with plane washers and
nuts or clamps are then screwed into the cones from
outside the formwork members to restrain the members
from outward movement under the concrete loads mentioned
above. After the concrete has been poured and has set
the bolts are removed, the formwork is removed, and, i~
threadedly connected to the tie rod, the cones may also
be extracted rom the concrete.
This conventional system has a number of inherent
disadvantages in operation, a main one of which is the
difficulty of effecting registry of the retaining bolts
and cones at the stage of erection of the formwork. Access
to the inner faces of the ~formwork is required. This
problem was resol~ed by a further prior art system,
sometimes known as the "she bolt"system. This involved
a tie rod threaded at both ends as before but to each
end is threadedly connect~d a she bolt. Su~h bolts
comprise a tapered shank portion adjacent the tie rod,
the remainder or part of the remainder of the shank bein~
threaded, for example with an Acme or like threadl and
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68~6
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having a squared outer end or other provision at the
larger end of the tapered shank portion for fitting a
spanner to rotate the she bolt relative ko the tie rod.
In use, the she bolts are connected at each end to
the tie rod and the assembly is then inserted, from one
side only be it noted, through registering apertures in
the formwork members. Clamps are then applied over the
protruding threaded ends of the she bolts and abuttingly
engaged with the outex faces of the formwork members or
waling if provided. The clamps may be formed with an
internal thread to engage the she bolts, or may include
a nut held captive but rotatable thereon. To dismantle
the formwork after use, the clamps are removed and the
she bol~s removed from the tie rod using a spanner or
wrench on the squared ends or backs of tapered shanks
thereof. The tie rod may be lost in the concrete.
Nhile providing significant advantages over the
conventional system in terms of ease of use, the she
bolt system still has inherent difficulties in terms of
efficiency of operation. The problem lies in the
necessity for the components to ~e suitably sized for the
thickness of the wall and o the formwork. Tie lengths
and she bolts must be fabricated in accordance with the
wall thickness and shutter make-up respectively.
Manufacturers therefore hold stocks of she bolts to
"standard" lengths in incremements and will also supply
to specified lengths. Ties must be manufactured to
specified lengths and to avoid delays some manufacturers
hold stocks of ties for some common wall thicknesses.
From the contractor's point of view an assessment of
requirement has to be made quite early. Often assessments
have to be made purely from tender drawings and prior to
completion of contract drawings and prior to establishing
construction sequence. On large Civil Engineering works
which require a very great number of ties of many different
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lengths early assessment of ties can lead to wrong
lengths or wrong numbers being ordered. ChangeS of
programme often mean rush oxders or delays. The
problem is worse on overseas contracts where supplies
have to be shipped out and cases of last minute
airfreighting are not uncommon. Some Civil Engineering
works such as jetty construction require a varie~y of
long she bolts the length of which cannot be assessed
until the falsework schemes have been finalised.
It is therefore an object of this invention to
provide an improved formwork tie system wherein the
above-mentioned disadvantages are overcome.
Viewed from one aspect the invention provides a
formwork tie comprising a tie rod threadedly engaged
with the smaller end of an elongate tapered member with
whose other end is threadedly engaged a connecting rod
adapted to threadedly receive a formwork clamp, means
being provided for securing the connecting rod and
tapered member against relative rotation, the tie rod
~0 and connectiny rod being threaded along their lengths and
being provided with lonyitudinally extending engagement
means ~hereby the rods may be lockingly gripped ~or
manual rotationa ~s will hcrcinafter bc dcscribcd, the
lonyitudinal enga~e~ent means ~ay also ser~e for the
locking connection to the rod of other components of
the system.
The invention represents a radical departure from
.. . .
the previously known systems since the provision of che
tapered member and securing means as aforesaid enables
the tie rod and connecting rod to be cut on site to
the desired lengths from standard lengths of rod stock,
threaded and provided with said enyagement means
continuously along their lengths. In its assembled state,
the tie functions in substantially exactly the same
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manner as the previously known she bolt tie, but is not
subject to the inefficiencies mentioned above.
The combination of tapered member and connecting
rod effectively forms a she bolt, and this may be sized
on site as required. The connecting rod to form the she
bolt may be cut on site to the desired length from the
standard stock. This avoids the problem of having to
plan and order she bolts of suita~le lengths well in
advance, and imparts flexibïlity to the system so that
any last minute changes in or corrections to the
building specification do not involve the urgent supply
of further she ~olts. The same is true of the tie rods.
Thus in accordance with the invention the operational
difficulties involved with the she bolt with regard to
length requirements of both she bolts and ties
are completely overcome.
Viewed from another aspect the invention provides
a method of making a formwork tie comprising cutting
a connecting rod from a length of rod stock, such stock
being continuously threaded and formed with longitudinally
extending engagement means whereby the rod may be
lockingly gripped for manual rotation, threadedly
engaginq the connecting rod with the larger cnd of an
elongate tapered member, pxoviding means for securi~ng
the connecting rod and tapered member against relative
rotation thus effectively forming a she bolt, repeating
the process to provide a further she-bolt, cutting a tie
rod from the or a further length of sa;d stock,
threadedly engaging the tie rod with the smaller ends of
the tapered member of the she bolts and providing form-
work clamps to be threadedly enaaged on the connecting
rods of the she bolts.
Viewed from yet a further aspect the invention
provides a system of fabricating formwork ties comprising
cutting tie rods and connecting rods from a length of
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rod stock, such stock being continuously threaded and
formed with longitudinally extending engagement means
whereby the rod may be lockingly gripped for manual
rotation, and interconnecting the tie rods and connecting
rods by threaded engagement with respective ends of a
tapered member, providing means at the larger end of the
tapered member for securing it against rotation relative
to the connecting rod, and threadedly engaging formwork
clamps with respective connecting rods.
The longitudinally extending engagement means may
comprise one or more flat sides formed on the rod stock
suitably sized for the operational purpose of their design.
Two opposed flat sides would preferably be provided to
enable the rods to be rotated by means of a spanner~or
like wrench. In a preferred embodiment however one or
more, preferably two longitudinal slots are formed in the
rods. Where two slots are provided, these may be
diametrically opposed. A suitable tool will then be
provided with a key or keys for engagement in the slot~s)
to be able to rotate the rod. In both cases, i.e.
flats or slots, it should be noted that the rods may be
drivingly engaged by the appropriate rotating tool at
any point along their length. Furthermore a flat or slot
as aforesaid affords a convenient location ~or stamping
on the rod information regarding its tensile strength,
safe working load etc. This may be advisable for
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recognition purposes when different types of stock are
used as the purpose requires.
As mentioned above, the rotational fixing of the
connecting rod to the tapered member effectively creates
a she bolt. Once therefore the clamp has ~een removed
after setting of the concrete, a suitable tool may be
engaged with the exposed end o~ the connecting rod and
the rod rotated so as to disengage the tapered me~ber
from the tie rod. The said securing means may take any
one of a number of forms. Where the rods have one or
more longitudinal slots, the securing means can
comprise a key engaging in a said slot and in a locating
groove formed in the tapered member. Such a key may be
held in its locating slot by a locknut engaged with the
rod. The slots may be of any cross section, but
semi-circular is presently preferred. This enables
the keys to be substantially cylindrical, which is
easy to manufacture, and easy to insert in their receiving
bores. The keys may be arranged to protrude from their
bores so that their ends may be engaged for removal~
A particularly convenient way of arranging this ~s to
provide an annular groove at the end of the key for
engagement by the edge of a tool, or a fingernail.
A plurality of locat:ing grooves may be provided, two being
1 1668~
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preferable. The disposition of said two grooves at a
radial separation will afford four relative radial
locking posïtions for a two diametrically opposed slot
rod. Depending on the configuration and the number and
relative orientation of grooves in the tapered member
and slots in the stock rod one or more securing lugs may
be used.
The system may also be supplïed with coupling
members comprising a rod or tube with an internal thread
at each end adapted to receive a length of said stock
in threaded engagement. Theoretically, the provision of
one such coupling member per standard length of stock
will result in no waste of the stock through cutting.
The coupling members may also be provided at one or
both ends with relative rotation securing means as
discussed hereinbefore. Thus they may be used to
interconnect parts of a connecting rod as well as those
of a tie rod.
Any number of she bolts of any desired lengths may
be fabricated as described above and if necessary longer
than the standard stock rod described above by coupling
whole or parts of such rod stock with said coupling
members. She bolts fabricated as described above may be
retained for use in those lengths fabricated or if
desired taken apart so that their constituent parts may
be used for such or other configurations. Two such she
bolts fabricated as above may be attached at each end
of a formwork tie by threadedly engaging their elongated
tapered ends at each end of such tie, where such tie
may be any length of stock rod as used for the
fabrication of she bolts and where such a length of tie
as required may be one single lenyth or fabricated out
of two or more lengths of stock rods used for she bolts
and coupled together with coupling members as described
above and where parts or the whole of these tles may be
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1 lB6866
rod from dismantled she bolts. Two she bolts connected
with a formwork tie at their elongate tapered ends and
with threadedly engaged clamps at the other ends may
constitute the entire formwork tie system.
The versatility of the system and its constituent
components so far described as a formwork tie system
is very great and it is envisaged that the constituent
parts may ~e utilised singly or collectively in a
variety of configurations to cover the great majority
of requirements to be encountered.
A distinct advantage which clearly demonstrates the
versatility of the system is the adaptation of the system
with the same components as described above to its use
as a cone spacer formwork tie system with the advantages
of the cone spacer system over the she bolt formwork
tie system. The advantage of the she bolt formwork tie
system over the cone spacer formwork tie system in that
it offers the facili~y to assemble the formwork tie to
the formwork by offering the completely assembled parts
of the tie assembly including one of the external clamps
from one side only through registering apertures in
the formwork is inherent of the disadvantage of the she
bolt system in that it does not space or hold firmly
apart at a specific distance apart the formwork at the
position of the tie. It often becomes a criterion
of the formwork design that the formwork ties must act
as spacers in which e~ent preference is given to the cone
spacer system and it is quite common for both systems
to be employed on the same site. It oftens becomes
necessary to employ both systems on the same formwork
shutter.
It should be noted therefore that with reference
to the components so far ~escribed and th method of
assembly and use of the components so far descri~ed,
if the formwork tie is envisaged as assembled in the
~ormwork with the exception that the lugs and locknuts
holding the tapered members captive against rotation
to the connecting rods are excluded and the registering
holes in the formwork are larger than the rods but
smaller than the larger ends of the tapered members
which abut the internal faces of the formwork the
system effectively becomes a cone spacer system.
The tapered members which when locked to a length
of stock rod become the tapered ends of she bolts may
be used as the cone spacers in a cone spacer tie system
configuration. Therefore the system proposed according
to the invention is designed in such a manner as to
offer the user a choice for its use as either a she bolt
or a cone spacer formwork tie system at will and without
any additions or modifications to the minimum essential
standard components for its use as a she bolt system.
In other words , the system proposed is designed in such
a manner that it may be looked upon as a cone spacer
formwork tie system which may be converted easily and at
will to a she bolt formwork tie system purely by locking
the tapered member to the connecting rod with the means
provided.
It may be noted that this dual identity of the
system is enhanced by the concept of stock rod supply
and use to an extent that decision as to the mode of
application of the system and sizing of the components
may be left as late as the time at which formwork
erection is actually in progress.
The clamping members may be of convenient design.
Thus the clamping member may be prodived with a fixed
threaded bore for engaging the connecting rod such that
rotation of the whole member is required for tightening
or removal, Equally, clamping members of the kind
incorporating a rotatable but captive nut may be
employed, where ro~ation of the maln body of the clamp
1 ~686~
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is not required. As a particularly preferred feature
of the invention however I have dev~sed a novel clamping
member whereby a plurality of functions of known clamps
are incorporated in a single unit.
Viewed from yet a further aspect therefore, the
inventïon provides a formwork clamp comprising a main
clamp body having a part-spherical socket formed therein,
a rod engaging member comprising an at lea~t part-
spherical body captively received in t~e socket for
universal movement therein r said member including a
threaded bore for threadedly receiving a rod therein,
engagement means whereby the member may be lockingly
gripped for manual rotation, and first locking means
whereby the member may be fastened to the rod, said
clamp body including second locking means adapted to
prevent axial rotation of the member but permit
pivoting thereof about a transverse axis.
The engagement means may most conveniently
comprise a nut portion integral with or fixed to said
member. The first locking means may comprise a
transversely disposed screw adapted to engage a 1at or
longitudinal slot formed in the rod. The second
locking means may comprise a further transver~ely
disposed screw engaged in the clamp body and adapted to
engage in an at least part-aircumferential groove
formed in the part-spherical body and lying in the
plane of the axis of the threaded bore.
Such a clamp thus incorporates a plurality of
selectable functions. With the second locking means
engaged, the clamp performs substantially as a ~ixed
clamp wherein the entire clamp boay is rotated to
effect tightening. Release of the second locking means
enab~es the rod engaging member to be rotated relative
to the clamp body for example by a spanner or other
wrench to achieve a greater tightening force. Engagement
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of the first locking means with the rod enables the
clamp to ~e used as the rigid abutment of a formwork
jack.
The ball and socket embodiment in the clamp design
allows the axis of the rod to take up a position other
than perpendicular to the plane of the face of the clamp
and depending on the allowable deviation from the
perpendicular governed by design parameters would
partly or wholly eliminate the use of simple or
compound wedge members as frequently used between the
clamp face and the member on which this face abuts.
In order that the invention may be readily
understood, certain embodiments thereo will now be
described by way of example with reference to the
accompanying drawings wherein:-
Fig. 1 is a part-sectional elevation of a formwork
tie according to the invention;
Fig. 2 is a sectional view of erected~formwork
using formwork ties according to the invention; and
20Fig. 3 is a side view of a clamp in accordance
with the invention.
The tapered member 1 comprises a steel rod having
a threaded bore 2 extending throughout its length,
although separate blind threaded bores at its respective
ends could be provided instead if desired. At the
larger end a pair of diametrically opposed radial
grooves 3 of semi-circular cross section are machined
in the member. These may be machined out of the
threaded bore, or may be formed by first drilling
opposed blind bores in the larger end of the tapered
member 1 before machining out the central bore.
The rod stock shown as 4 combines with the
tapered member 1 to form a she bolt. This stock will
be supplied to the site in standard lengths in an
appropriate quantity and then cut to size as required
1 ~ 686~
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by the formwork dimensions. The rod 4 i~ a skeel
rod formed with an external rolled thread. Such rolling
of the thread is expected to be the most economical
way of producing the stock~ but an Acme or similar
or other thread could instead be used if desired.
The rod 4 is also formed with a pair of diametrically
opposed longitudinal slots 5 again of semi circular
cross section, and of substantially the same radius
as that of the grooves 3.
To form a she bolt th~tapered member 1 is
threadedly en~aged with a length of ~onnecting rod 4 to a
sufficient depth, and the slots 5 and grooves 3 are
aligned. A key 6 is inserted in each bore so formed,
and it will be seen that the length of the keys is such
that their endsprotrude from the receiving bores when
pushed fully home. This is to facilitate removal
of the keys when dismounting, whereby the edge of a
tool may be engaged in an annular groove 7 formed at
the ends of the keys to draw the keys out~
The she bolt assembly is completed by a lock nut
3 which is screwed up to engage the larger end of the
tapered member, the nut being provided with a cavity
9 to receive the protruding ends o~ the keys 6.
The she bolt thus assembled may now be used in
the conventional way, it being noted that a urther
length of the same rod stock is cut to provide the tie
rod 10, which will be lost in the cured concrete.
The formwork consisting of panels 11, walings 12 and
soldiers 13 is erected in the usual way and support~d
by an array of she bolt/tie rod assemblies with clamps
14 threadedly engaged over the ends of the exposed rods
to abut the soliders 13.
At this stage a further and substantially
advantageous feature of the invention comes into play.
The locknuts which are abutting the larger ends of the
tapered members 1 can be unscrewed to abut the inner
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~ 1668~
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faces of ~he soldiers 13 by the intermediary of spllt
washers2~laterally engaged over the she bolts assembly,
and thus provide a spacing funct;on in the manner o~
known cone spacers.
Disassembly of the formwork is simple. Once the
clamps 14 are removed the exposed rod is engag~d by a
tool (not shown) which has operative parts which engage
in the longitudinal slots 5. The engagement of iool
and rod may be anywhere along its length and permits
the rod to be manually rotated to withdraw the
tapered member from the concrete, since it is locked
onto the rod by the keys 6.
The she bolt may now be used again, or may be
disassembled for storage. Used rods may be connected
together to form a desired new length by means of
comlecting members lS which are provided with internal
grooves for locking in the same way as the tapered
members. The fact that tie rods and she bolts do not
have to be ordered in advance and to the correct si~e
makes the system extremely flexible, and the hitherto
encountered problems regarding supply or parts is
overcome simply but effectively.
A novel clamp which may be used with the formwork
tie already described, or may indeed be used with
e ting she bolts or connecting rods, is shown in
"~Fig.4.) It comprises a cast main clamp body 16 formed
h~~a part-spherical socket 17. In this socket is
captively received for universal swivelling a rod
engaging member 18 comprising a substantially spherical
body having an integral nut portion 19 formed therewith.
Threadedly received in the member 18 (the threaded
engagement may only be with nut portion 19) is a
grooved threaded rod 21 as described previously. A
radially disposed grub screw 20 is engaged in the
nut portion 19, the inner end of whlch i5 arranged to be
received in the groove 22 to lock member 18 to the rod.
31 ~6~6~
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A second grub screw 23 is threaded into the clamp
body 16/ whose inner end is adapted to be received
in a peripheral groove 24 formed in the spheric~ body.
It will thus be seen that with neither grub screw
engaged, the clamp body can pivot in all directions
with respect to the rod 21. With grub screw 20 engaged
the clamp body is fixed in position on the rod and so
may be used as the fixed abutment of a formwork jack,
able to pivot in all directions to attain the desired
orientation. Its ability to pivot is restricted by
engagement of the grub screw 23 in the groove 24 which
restricts the pivoting to a single plane and prevents
axial rotation of the body 18.
It will be appreciated that the novel system
proposed according to the invention radically
simplifies the planning as to hardware required in
concxete construction. The adoption of uni~orm rod
stock for both tie rods and she bolt assemblies
imparts a hitherto unavailable flexibility t~ the system.
Furthermore, the adoption of the multi-function clamp
described lowers still further the number o~ basic
parts required whereby any desired formwork may be
erected and supported.
It will further be appreciated that th~ supply
to a construction site of means ~or putting the
invention into effect will at the same time provide
materials for other functions, and the versatility of
the material is such that it may be used on site for
such other functions only. This is due ~o the fact
that in particular the stock rod may be used for other
purposes, for example as concrete reinforcement, or it
can be cut up and used to make general purpose or
special bolts. In the former example the use of the
stock rod as reinforcement in view of its continuous
thread~will lend itself particularly well in applications
where end to end coupling of the reinforcement is
38~6
required using said couplers and lock nuts and keys
if necessary and will provide adequate bond strength
with the surrounding concrete. The longitudinal
flats or slots will in this case provide an engagement
with the cured cvncrete which will be of substantial
torsional resistanceO
