CA1166866A - Formwork ties - Google Patents

Abstract

ABSTRACT

"Improvements in or relating to formwork ties"

A system is disclosed of making up formwork ties on site from standard components which are supplied, The components comprise length of stock rod, continuously threaded and provided with two diametrically opposed longitudinal slots (5) by means of which the rod may be lockingly engaged for manual rotation. A length of rod (4) threadedly engaged with a tapered member (11 forms a she bolt, the two parts being prevented from relative rotation by keys (6) inserted in the bores formed by the registering slots (5) and internal grooves (3) formed in the tapered member (1). A locknut (8) provided with a cavity (9) maintains the keys (6) in their bores. A connecting member (15) enables ties of any length to be made up from a number of shorter lengths of stock rod. The rod itself may serve other on site purposes such as reinforcement for concrete.

Description

6 ~;

"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 . ~

68~6 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 ~ :~66~

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 1~66~6 ~ 4 --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 8 6 ~

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 1 ~6~6~

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~

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 'i 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~
_ 10--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 68~
- 11 ~

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~

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 .

~ 1668~

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~

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

Claims (15)

1. A formwork tie comprising:
(1) an elongate tapered member having threadedly receiving means at each end, (2) a tie rod threadedly engaged with said receiving means at the smaller end of said tapered member, (3) a connecting rod threadedly engaged with said receiving means at the other end of said tapered member, (4) means for securing the connecting rod and tapered member against relative rotation, (5) said tie rod and said connecting rod being threaded along their lengths and being provided with longitudinally extending engagement means whereby the rods may be lockingly gripped for manual rotation.

2. A formwork tie as set forth in claim 1 wherein said longitudinally extending engagement means comprises at least one flat side formed on the rods.

3. A formwork tie as set forth in claim 1 wherein said longitudinally extending engagement means comprises at least one longitudinal slot formed in the rods.

4. A formwork tie as set forth in claim 3 wherein two diametrically opposed said slots are formed in the rods.

5. A formwork tie as set forth in claim 3 wherein (1) the receiving means at said other end of the tapered member is formed with at least one internal longitudinal groove registrable with said slot and including:
(2) a key for insertion into the bore formed by the mating groove and slot to lock the connecting rod and tapered member against relative rotation.

6. A formwork tie as set forth in claim 5 wherein:

(1) the slot and groove are substantially semicircular in cross section, (2) the key is in the form of a round pin, and (3) the end of the key protrudes from the tapered member to permit engagement thereof for withdrawal.

7. A formwork tie as set forth in claim 1 including a coupler member for connecting one of said rods to a further rod, said coupler member having opposed ends, each end being formed with an internal thread adapted to receive a said rod in threaded and coupled connection.

8. A method of making a formwork tie comprising:
(1) cutting a connecting rod from a length of rod stock which is continuously threaded and formed with longitudinally extending engagement means whereby the rod may be lockingly gripped for manual rotation, (2) threadedly engaging the connecting rod with the larger end of an elongate tapered member, (3) securing the connecting rod and tapered member against relative rotation to form a she bolt, (4) repeating steps (1), (2) and (3) to form a further she bolt, (5) cutting a tie rod from a length of said rod stock, (6) threadedly engaging the tie rod with the smaller ends of the tapered members of the she bolts, and (7) threadedly engaging formwork clamps on the connecting rods of the she bolts.

9. A method as set forth in claim 8 in which the longitudinally extending engagement means comprises at least one longitudinal slot in said rod stock and the tapered member is formed with at least one groove in its threaded part receiving said connecting rod, including (l) aligning said slot and groove to form a bore, and (2) inserting a key into said bore to lock the connecting rod and tapered member against relative rotation.

10. A method as set forth in claim 9 including threadedly engaging a locknut with the connecting rod to maintain said key in said bore.

11. A method as set forth in claim 10 including rotating the locknut to disengage it from the tapered member and withdrawing it along the connecting rod to spacingly engage formwork.

12. A system of fabricating formwork ties comprising (1) cutting tie rods and connecting rods 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, (2) 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 (3) threadedly engaging formwork clamps with respective connecting rods.

13. A system as set forth in claim 12 wherein (l) said longitudinally extending engagement means comprises two diametrically opposed slots formed in the rods, (2) the tapered member is formed with two diametrically opposed longitudinal grooves adapted to register with said slots to form bores, and (3) a key is inserted in each bore to secure the connecting rod against rotation relative to the tapered member.

14. A system according to claim 12 including inter-connecting said connecting rods or tie rods with lengths of similar rod by means of a coupler member consisting of a threaded sleeve.

15. A system according to claim 13 wherein a locknut is threadedly engaged with the connecting rod to maintain the keys in said bores during assembly, the locknut being withdrawn from the tapered member when the formwork is erected to engage the formwork in a spacing manner.