EP3464749A1

EP3464749A1 - Lost formwork cladding to reinforcement connector and method of using same

Info

Publication number: EP3464749A1
Application number: EP17801837.0A
Authority: EP
Inventors: Geoff Wyett
Original assignee: Ozm Australia Pty Ltd
Current assignee: Ozm Australia Pty Ltd
Priority date: 2016-05-25
Filing date: 2017-05-24
Publication date: 2019-04-10
Also published as: SG11201810118YA; US20190203485A1; WO2017201577A1; AU2017268708A1

Abstract

A connector for securing reinforcing rod elements to an adjacent spaced formwork panel, the connector including: a compression resistant spacer element having a first end and a second end defining a depth there between; one or more securing flanges extending from said first end for securing the connector to a formwork panel, and reinforcing rod retention means extending from said second end.

Description

Lost formwork cladding to reinforcement connector and method of using same Field of the invention

[0001 ] The present invention relates to means for connecting reinforcing elements to formwork cladding panels for what are often termed "lost formwork" concrete filled construction systems, where the cladding defining the outside surfaces of the formwork remains part of the final structure after concrete is poured into the formwork and cured.

[0002] The invention has been developed primarily for use in offsite prefabrication of structural forms such as steel reinforced concrete columns and the like, and will be described herein with reference to this preferred use. However, it will be appreciated by those skilled in the art that the invention is also suited for use in constructing lost formwork structures for steel reinforced structural forms that are fabricated on site. Some embodiments of the invention are particularly suited to on site fabrication where there may be limited access to some external surfaces.

Background to the invention

[0003] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

[0004] Lost formwork methods of construction are widely used in the building industry for forming structural load bearing walls and columns and the like. Such systems typically include a number of panels that define the external surfaces of the form, with an arrangement of steel reinforcing elements disposed within the form. In most cases the reinforcing elements are supported or tied together into a three dimensional cage type arrangement. This cage of reinforcing elements is ideally disposed a predetermined distance from the external panels, to ensure adequate and even concrete coverage of the steel reinforcement after the concrete has been poured into the form.

[0005] One of the biggest challenges in structures of this kind is ensuring that the formwork panels are supported to resist the hydrostatic pressures applied by the wet concrete during the pour and prior to the concrete curing, while at the same time ensuring that the reinforcing elements remain in their designed location. This is particularly relevant in tall structures like walls and columns where the head of flowable concrete creates significant pressure against the cladding.

[0006] While external bracing may be used in some applications, this is dependent on the nature of the structure to which the form is to be secured and reliance on external bracing doesn't help facilitate offsite prefabrication.

[0007] Most commonly in wall and column structures, removable tensile tie elements in the form of long bolts (generally known as "Z-bars") are used that extend through conduit that passes through the reinforcing and opposing cladding panels and are secured by external fasteners against the external surfaces of the formwork cladding panels. Where needed, internal spacers are disposed between the reinforcing elements and the panels to position the reinforcement and panels in their designed locations, which are secured in place by the tensile forces applied by the tie elements. This method is time consuming and results in a number of holes in the finished concrete structure which need to be patched and finished.

[0008] An improvement was proposed by the applicant in WO2016/061627 which describes, in one embodiment, the use of tensile ties in the form of high strength flexible strapping, which results in a lighter structure and an outer surface that is much easier to finish, as the strapping is easily covered over with further cladding or simply cut and removed. It also readily facilitates off-site prefabrication of forms pre-loaded with correctly positioned reinforcement. However, there is still a need to provide openings in the formwork cladding panels to receive the tensile ties and once again forming the holes and securing the ties is still relatively labour intensive.

[0009] There are also wall structures that obviate the requirement for drilling through holes and inserting tie elements, by providing rigid internal web elements of metal or cladding material that extend between opposing formwork cladding panels. However, these rigid web elements take up a lot of internal space and often section the void internally, thereby reducing the space available for the reinforcing and limiting the design to structures of certain shapes and sizes and load bearing capacities. These rigid web elements can also inhibit the concrete flow and access to the reinforcement during the concrete pour.

[0010] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. Summary of the invention

[001 1 ] According to a first aspect of the invention there is provided a connector for securing reinforcing rod elements to an adjacent spaced formwork panel, the connector including: a compression resistant spacer element having a first end and a second end defining a spacer depth there between; one or more securing flanges extending from said first end for securing the connector to a formwork panel, and reinforcing rod retention means extending from said second end.

[0012] Preferably, the connector is generally longitudinal, extending in a longitudinal direction generally transverse to the spacer depth. In one preferred form, the compression resistant spacer is in the form of a spacer web.

[0013] Desirably, the reinforcing rod retention means includes a spring formed portion adapted with some form of shoulder formation to secure to a reinforcing rod element by a resilient deformation from a closed rest configuration, through an opened receiving

configuration, back to a closed rest configuration at which the rod is retained by the shoulder formation.

[0014] Preferably, the connector has a generally T shaped cross sectional configuration, with two flange portions extending in opposite directions from the first end of the spacer element or web in a direction generally transverse to the spacer element..

[0015] In a first embodiment, the spacer web and flanges are defined by two opposing L shaped arms positioned back to back to define the T shaped cross section which are interconnected by the rod receiving means.

[0016] In one such an arrangement the reinforcing rod engagement means preferably comprises an incomplete loop or tube of sprung material configured such that in the rest position it seats closely around the reinforcing rod with the intersection of the web and loop defining a shoulder to thereby secure the rod a fixed distance from the securing flanges equal to the height of the spacer element or web. In a second embodiment, the spacer web is a single planar element and the reinforcing rod engagement means is an incomplete sprung loop or tube open at a location distal from the point of connection of the spacer web. [0017] In some forms the securing flanges may include openings to receive fasteners to assist in securing the flanges to a formwork panel. The flanges may also or alternatively include surface markings, indentations or other formations that may assist in securing the flanges with an adhesive.

[0018] In a third embodiment, rather than have the connection means in the form of an incomplete tube formation with continuous shoulder formations that run the length of the connector, L shaped formations defining the spacer web and associated flanges, are spaced apart the width of the reinforcing rod with a channel portion adapted to receive the reinforcing rod, and a series of longitudinally aligned and spaced inwardly directed protrusions are provided in the spacer portion of each L shaped formation to form the shoulder by which the reinforcing rod is retained.

[0019] In a fourth and preferred embodiment, the connector is configured for clamping connection to a formwork panel, thereby obviating the need to use adhesives or conventional fasteners such as screws and the like.

[0020] In this fourth embodiment, the connector for securing reinforcing rod elements to an adjacent spaced formwork panel includes a first inner part having two opposing L shaped formations defining the spacer web and associated respective flanges for connection to an inner surface of a formwork panel, the L shaped formations being interconnected at an end remote from the flanges so they are spaced apart to define reinforcing rod receiving means remote from the flanges, the spacer portion of each L shaped formation including first retention means operable to retain the reinforcing rod within the rod receiving means and second retention means for cooperation between, and a second outer part in the form of a clamping and locking element to be inserted between the opposed spacer portions from an outer surface of the formwork panel to clamp the formwork panel there between.

[0021 ] The shape of the reinforcing rod receiving means may be arcuate to conform closely to an adjacent portion of the circular periphery of the reinforcing rod, or may include flat regions to reduce the tendency of the connector rotating on the reinforcing rod.

[0022] In this fourth embodiment, one or more apertures need to be provided within the formwork panel for insertion of the clamping and locking element into the first part of the connector. [0023] In one preferred form, the outer clamping and locking element has a similar overall shape to the first inner part of the connector in that it includes two opposing and interconnected L shaped formations. However, the outer clamping element has a shorter outer width along the direction of the spacer web, and a shorter length along the direction of the spacer webso that in use it nests within the first inner part of the connector.

[0024] In a preferred form, the second retention means for cooperation between the first inner part of the connector and the second outer part in the form of a clamping and locking element, is in the form of protrusions formed on one of said inner or outer parts that engage with depressions or apertures formed on the adjacent surfaces of the other of said parts.

[0025] In one form the second retention means takes the form of flaps or barbs formed on an outer surface of one or more of the parallel portions of the L shaped formations, configured to resiliently deform and engage corresponding depressions or apertures formed in the internal surfaces of the parallel portions of the L shaped formations on the first part as the flanges of the two parts are bought towards each other. The first and second parts are configured such that in the locked position with the second retention means engaged, the space between the flanges of each part corresponds to the thickness of the formwork panel so that it is clamped there between.

[0026] The first retention means for securing the reinforcing rod at the desired location remote from the flanges of the first part can take any suitable means including the series of inwardly directed protrusions as used in the third embodiment. Alternatively, the depth of the second part outer connector in the direction of the parallel portions of the L shaped formations can be configured to sit against the reinforcing rod thereby holding it captive in the desired position.

[0027] However, in a preferred form when the connector is made of a deformable material such as metal, the first retention means is provided in the form of bendable tabs formed in the parallel portions of the L shaped formations of the first part of the connector which can be bent inwardly into the gap between the parallel portions to retain the clip on the reinforcing rod in the desired location. In another variation a split pin type arrangement may be used to the same effect. [0028] In another preferred form, particularly suited for where the connector is made of a plastics material, the first retention means may comprise resiliently deformable rod engaging arms, pivotally connected with the L shaped formations, which move outwardly as the connector is pushed over the reinforcing rod, and which spring back into position to engage and retain the rod.

[0029] In one form, the longitudinal length of the second clamping and locking part of the connector of the fourth embodiment relative to a reinforcing rod to which it is to be connected, is approximately equal to the longitudinal length of the first part of the connector which remains internal of the formwork panel. In such an embodiment, a slot needs to be provided in the formwork panel through which the second part can be inserted from outside the formwork panel. However, in other embodiments, multiple shorter length second clamping elements could be inserted into one longer first part of the connector, in which case multiple spaced smaller apertures would suffice.

[0030] In preferred forms of the fourth embodiment, the formwork panels comprise two or more layers of material. In this manner, a first stage formwork and reinforcement cage assembly can be produced using the two part connectors, with the flanges of the second clamping and locking elements sitting flush on the external surface of the first layer of formwork panels. The assembly can then be finished by securing a further outer layer of formwork panel over the first stage assembly. This results in a clean surface requiring minimum finishing. Furthermore, the material cost for the laminated panel structure using two thinner layers is usually less expensive that using a thicker panel of equivalent strength.

[0031 ] In some forms, the connectors are made from sheet metal. One preferred form according to the second embodiment is made from 0.8 - 1 .00mm sheet steel with a longitudinal length of 100mm to 150mm. The depth of the spacer web depends on each application, but typical examples used in column forms, for example, are 50mm. The reinforcing rod engagement means is similarly tailored to the reinforcing rods to be used, which in most cases has a nominal diameter of 8-12mm.

[0032] In one preferred form according to the fourth aspect of the invention, the inner and outer parts of the connectors are made from sheet steel of around 0.8mm with a longitudinal length of around 100mm. The width of the panel engaging flanges are each around 20mm. The gap between the internal surfaces of the parallel portions of the L shaped formations of the first inner part is sized to receive a reinforcing rod of the targeted size, and the gap between the outer surfaces of the parallel portions of the L shaped formations of the outer clamping part is sized for a clearance fit with the first part with the exception of the second retention means which will extend into that gap. In the preferred form, the second retention means is in the form of outwardly extending flaps on the second outer part hinged at a location toward a distal end of the part, which resiliently deform inwardly during insertion and return outwardly to form a barb that engages with corresponding apertures in the parallel portions of the L shaped formations of the inner part, thereby locking the two parts together.

[0033] The reference to reinforcing rods used herein includes reference to any reinforcement bar element and includes tie elements commonly referred to as ligatures.

[0034] In applications where the reinforcing rod elements are prefabricated into a cage structure prior to assembly with the formwork panels, it is desirable to produce a range of connectors based around the nominal offset required, which include connectors that are slightly bigger and slightly smaller than that offset, to allow for manufacturing tolerances in the cage. In a preferred application where the cage comprises parallel spaced longitudinal reinforcing rods tied by ligatures that circumscribe some or all of the longitudinal rods, the connectors are secured to the ligatures.

[0035] According to a second aspect of the invention there is provided a method of constructing a reinforcement and formwork panel assembly comprising the steps of: securing the reinforcing rod retention means provided on the second end of one or more connectors according to the first aspect of the invention to a reinforcing rod or rods; and securing the flanges of the first end of each connector to an adjacent formwork panel.

[0036] For methods using single piece connectors according to the first three embodiments of the invention, the flanges of the first end of each connector are secured to an inside surface of an adjacent formwork panel using fasteners such as screws, or adhesive, or a combination of both.

[0037] For methods using the two part connectors according to the fourth embodiment of the invention, the first inner part of the connector is secured to a reinforcing rod via the first retention means, a formwork panel with suitably formed through apertures is aligned with the inner connector and reinforcing rod assembly and the second clamping and locking outer part of the connector is inserted from the outside surface of the formwork panel and secured to the inner part of the connector using the second retention means.

[0038] Preferably the method is applied to constructing a prefabricated reinforcement and formwork assembly for a longitudinally extending structural element, the assembly including: a prefabricated longitudinally extending reinforcement cage; an open ended formwork tube extending around said longitudinally extending cage, said formwork tube including a plurality of panels disposed around the reinforcement cage , wherein the panels are secured with the reinforcement cage using a plurality of connectors according to the first aspect of the invention.

[0039] In one particularly preferred form, the method includes the step of selecting connectors of varying depth as needed to accommodate variations in offset due to

manufacturing tolerances arising during prefabrication of the reinforcement cage.

[0040] While the connectors of the invention, and methods of constructing reinforcement and formwork using them has significant advantages in enabling fast an accurate assembly of prefabricated reinforced formwork assemblies without the need for expensive tools or jigs for retaining the structure during slow adhesive curing processes, it will be appreciated that the connectors can be used in any application on or off site where reinforcing rods or cages need to be secured to formwork.

Brief description of the drawings

[0041 ] Preferred embodiments of the invention will now be described, by way of example only, with reference to the following drawings in which:

[0042] Figure 1 is a perspective view of an incomplete column form structure using a first embodiment connector according to the invention;

[0043] Figure 2 is a plan view taken on section line 2-2 of Figure 1 ;

[0044] Figure 3 is sectional view taken on line 3-3 of Figure 2;

[0045] Figure 4 is an enlarged sectional view of the first embodiment connector taken on line 4-4 of Figure 3; [0046] Figure 5 is an enlarged sectional view of a second embodiment connector;

[0047] Figure 6 is a series of three enlarged sectional views of the first embodiment connector shown in Figures 1 to 4 illustrating a method of attachment to a reinforcing rod;

[0048] Figure 7 is a perspective sectional part view of a third embodiment connector;

[0049] Figure 8 is a perspective view of a first inside part of a fourth embodiment connector according to the invention positioned over a reinforcing rod with a tool for setting locking tabs to secure the part to the reinforcing rod;

[0050] Figure 9 is a perspective view of the first inner part of the fourth embodiment of Figure 8 with reinforcing rod, including the second outer part of the connector ready for insertion with a formwork panel there between;

[0051 ] Figure 10 is a perspective view of the first inner part and second outer parts of the connector shown in Figure 9 in the locked position clamped about the formwork panel;

[0052] Figure 1 1 is a transverse sectional view taken on line 1 1 -1 1 of Figure 10; and

[0053] Figure 12 is a series of perspective views of a fifth embodiment connector form designed to be made from moulded polymeric materials

Description of preferred embodiments

[0054] Referring to Figures 1 to 4 there is shown a first embodiment connector 1 used in the construction of a formwork and reinforcement assembly 2 for a longitudinal structural element such as a column. The assembly 2 is illustrated part way through assembly to more clearly depict the connectors and the way in which they work.

[0055] The assembly 2 includes a prefabricated reinforcement cage 3 comprising a plurality of parallel spaced longitudinally extending reinforcement rods 4, secured in a three dimensional cage configuration by means of longitudinally spaced circumferentially extending external and internal ligatures 5 and 6 respectively. These ligatures are usually made from the same or similar material as the longitudinal reinforcing rods. The ligatures 5 and 6 are secured to the longitudinal reinforcing rods 4 by any suitable means including wire ties, but most often by localised welding. The assembly also includes a plurality of bounding formwork panels such as panels 7 and 8 shown in Figures 1 and 3.

[0056] Details of first preferred form of the connector 1 are shown more clearly in the sectional view depicted in Figure 4. As can be seen, the connector 1 includes a compression resistant spacer element, which in this particular embodiment is in the form of a web 9. The web has a first end 10 from which extend securing flanges 1 1 and 12 which facilitate connection of the connector to the adjacent formwork panels as shown. The flanges are preferably configured for connection to the formwork panels by adhesive and may include surface treatment or other formations to assist in achieving a strong bond. However, the flanges may also include one or more through apertures 13 to enable the use of fasteners, either as an alternative or supplemental fixing means, or to hold the assembly while the adhesive is curing.

[0057] At the second end 14 of the web 9 there is provided a reinforcing rod engagement means shown generally at 15. In this particular embodiment the engagement means is in the form of an incomplete loop or tube 16 which is configured such that it closely circumscribes the reinforcing rod or ligature to which it is to be secured.

[0058] In this particular form the tube 16 is formed from a spring material such as sheet steel, with the web 9 being defined by the two parallel coextending arms 17 and 18 of L shaped formations 19 and 20 that extend from the open top region of the tube 16. The portions of the L shaped formations 19 and 20 remote from the tube 16 define the flanges 1 1 and 12. The configuration of the tube and the connection of the tube 16 to the arms 17 and 18 are formed to be sufficiently sharp an angle to define a shoulder 21 to ensure that the reinforcing rod 5, which in the form illustrated in the previous figures is a ligature, is rigidly secured and maintained a fixed distance from the flanges 1 1 and 12.

[0059] In use, the connectors are secured to the selected reinforcing rods as shown in Figure 6. This is done by first opening up the open top region of the tube 16 by pulling apart the flanges 1 1 and 12, thereby moving the connector from a closed rest position to an opened reinforcing rod receiving configuration in which the rod can be seated within the tube. When the flanges are then released, the sprung device returns to the closed rest position and captures and retains the reinforcing rod. The connector is then rotated to the correct position for securing to an adjacent formwork panel such as panel 7 shown in Figures 1 to 4. In this way no separate fasteners are needed which helps to speed up assembly. When constructing a column form of the kind shown in Figures 1 and 3, this is usually done one side at a time and as noted above fasteners may be used in addition to adhesive to hold the assembly while the adhesive is working. As each additional panel is secured to the internal reinforcement, the panels can also be secured to each other at the intersecting edges, with the final aim of achieving a tube which is sealed along the edges to retain concrete during the concrete pour.

[0060] It will also be noted in Figure 2, that the cage has been constructed with the internal ligatures 6 longitudinally offset from the external ligatures 5 to provide adequate access for assembling the connectors 1 as shown. In other embodiments the connectors may be attached directly to the longitudinally extending reinforcing rods 4.

[0061 ] While in an ideal world, the reinforcement cage will be accurately constructed, such that the distance of the reinforcing rods or ligatures from the adjacent external formwork panel is constant, the nature of metal working techniques, particularly those involving welding, usually result in some form of variation from target. Accordingly, the invention recommends that connectors be manufactured to a range around a target offset depth. Most usually this will include connectors fixed at the nominal depth or offset, as well as connectors slightly longer and slightly shorter according to expected manufacturing variations. This will enable a rigid and secure connection of the panels to the reinforcing along the full length. This is important as the integrity of the final structure will rely on a reasonable level of consistency of connection throughout the assembly. However, the strength of the final assembly can be enhanced by use of additional fasteners such as tensile ties or bolts that extend through or around the assembly as required.

[0062] Referring next to Figure 5 there is shown a second alternative embodiment of the connector 1 ' and where relevant like numerals will be used to denote corresponding features.

[0063] In this second embodiment, the spacer element or web 9 and flanges 1 1 and 12, are formed as a single T sectioned element, rather than two separate L formations as in the first embodiment. The second end 14 of the web 9 is rigidly connected to the tube 16, which in this case is open at the bottom 24 rather than on the top. In this embodiment, the resilient deformation of the tube to receive the reinforcing rod 5 is achieved by making the two curved elements 22 and 23 of the tube sufficiently flexible to enable a snap fit over the reinforcing rod 5. The rest of the connector structure may be rigid. [0084] A further alternative and preferred embodiment is shown as a sectioned part view in Figure 7. This embodiment is a variation of the embodiment shown in Figures 4 and 6. Rather than having the connection means in the form of an incomplete tube formation, with continuous shoulder formations 21 that run the length of the connector, the L shaped formations 19 and 20 are spaced apart the width of the reinforcing rod 5, and a series of spaced indentations 25 are formed at intervals along the length. These are provided at a location from the base so as to form discrete internal protrusions 26 which combine along the length to provide a shoulder 21 by which the reinforcing rod is retained. The advantage of this arrangement is that less overall deformation of the connector is required to connect it to the reinforcing rods. This makes it easier to assemble and enables use of cheaper materials as the entire structure does not need to be resilient to the same degree. While the illustrated form utilises small discrete indentations 25 with large gaps, other arrangements such as a continuous indentation or longer discrete indentations with small gaps may also work.

[0065] The connectors may be made from sheet metal. One preferred form according to the first embodiment as described in Figures 4 and 6 is made from 1 .2-2.00mm sheet steel with a longitudinal length of 150mm to 250mm. The depth of the spacer web depends on each application, but typical examples used in column forms, for example, are 50mm. The reinforcing rod engagement means is similarly tailored to the reinforcing rods to be used, which in most cases has a nominal diameter of 8-12mm.

[0066] A fourth embodiment connector is shown in Figures 8 to 1 1 , and again like reference numerals will be used to denote features common to the other embodiments. This preferred connector is formed in two parts which push fit together to form a clamping connection to a formwork panel, thereby obviating the need to use adhesives or conventional fasteners such as screws and the like.

[0067] In this fourth embodiment, the connector for securing reinforcing rod elements to an adjacent spaced formwork panel 7 includes a first inner part 30 for connection to an inner surface of a formwork panel, which is similar to the third embodiment connector 1 shown in Figure 7. This first inner part also has two opposing L shaped formations 19 and 20 defining the spacer web and associated respective flanges 1 1 and 12 for connection to an inner surface 31 of a formwork panel 7. The L shaped formations 19 and 20 are interconnected by an arcuate web 32 at an end remote from the flanges 1 1 and 12 so they are spaced apart to define a reinforcing rod 5 receiving location 33 remote from the flanges. [0068] The parallel spacer portions or arms 17 and 18 of each L shaped formation include first retention means shown generally at 34 operable to retain the reinforcing rod 5 within the rod receiving location 33, and second retention means for cooperation between a second outer part 35, which secures to an outer surface of a formwork panel, in the form of a clamping and locking element to be inserted between the opposed spacer portions 17 and 18 from an outer surface 36 of the formwork panel 7 to clamp the formwork panel there between.

[0069] In this fourth embodiment, one or more apertures need to be provided within the formwork panel for insertion of the clamping and locking element into the first part of the connector such as the elongate slot 37 shown in Figures 9 and 10.

[0070] In the preferred form illustrated in Figures 9 to 1 1 , the outer clamping and locking element 35 has a similar overall shape to the first inner part 30 of the connector, in that it includes two opposing and interconnected L shaped formations 17' and 18'. However, the outer clamping element 35 has a narrower outer width 38 transverse to the direction of the spacer web, and a shorter depth along the direction of the spacer web, so that in use it nests within the first inner part of the connector as shown in Figures 10 and 1 1 .

[0071 ] In a preferred form as illustrated, the second retention means for cooperation between the first inner part 30 of the connector and the second outer part in the form of a clamping and locking element 35, is in the form of protrusions formed on one of said inner or outer parts such as outwardly hinged flaps 39 on the outer part 35 which form resiliently deformable barbs, that engage with depressions or apertures formed on the adjacent surfaces of the other of said parts, such as the corresponding holes 40 provided in the inner part 30.

[0072] The first and second parts 30 and 35 are configured such that in the locked position with the second retention means engaged as shown in Figures 10 and 1 1 , the space between the flanges of each part corresponds to the thickness of the formwork panel so that it is clamped there between.

[0073] The first retention means for securing the reinforcing rod at the desired location remote from the flanges of the first part can take any suitable means including the series of inwardly directed protrusions as used in the third embodiment. Alternatively, the depth of the second part outer connector in the direction of the parallel portions of the L shaped formations can be configured to sit against the reinforcing rod thereby holding it captive in the desired position.

[0074] However, in the preferred form shown in the drawings, the first retention means is provided in the form of tabs 41 formed in one of the parallel arms 17 and 18 of the L shaped formations of the first part of the connector, which can be bent inwardly across the gap between the parallel portions into a locking aperture 42 on the opposing arm, to retain the inner connector part 30 on the reinforcing rod 7 in the desired location. In another variation a split pin type arrangement may be used to the same effect. However, the advantage of the illustrated form is that there are no separate components to be lost and the locked in tabs 41 provide a secure and strong connection.

[0075] In the form illustrated in Figures 8 to 1 1 , the longitudinal length of the second clamping and locking part 35 of the connector relative to a longitudinal axis of the reinforcing rod 5 to which it is to be connected, is approximately equal to the longitudinal length of the first part of the connector 30 which remains internal of the formwork panel. In such an embodiment, a slot 37 of matching length needs to be provided in the formwork panel through which the second part can be inserted from outside the formwork pane 7I. However, in other

embodiments, multiple shorter length second clamping elements could be inserted into one longer first part of the connector, in which case multiple spaced smaller apertures would suffice.

[0076] Turning next to Figure 12 there is shown a fifth embodiment connector according to the invention specifically designed to be made from mouldable polymeric materials and where possible like reference numerals will again be used to denote corresponding features.

[0077] As can be seen, this embodiment is very similar to the two part connector of the fourth embodiment 8 to 1 1 . The primary differences relate to the first and second retention means. In this regard the bendable tab 41 of the first retentions means of the fourth

embodiment, is replaced by a series of resiliently deformable rod engaging arms 45, pivotally connected with the L shaped formations at hinge points 46, which move outwardly as the inner connector 30 is pushed over and onto the reinforcing rod, and which spring back into position to engage and retain the rod by means of rod engaging formations 47. This eliminates the need for any special tools or secondary operations to connect the inner part 30 to the reinforcing rods. The same result could be achieved by a similar variation to the first embodiment and so is not dependent on material selection. Another useful but optional variation includes providing one or more at least partially flat surface formations at or instead of arcuate formations 32 to reduce any tendency for the inner connector to rotate about the reinforcing rod.

[0078] The second retention means, which secures the inner clamping part 30 to the outer clamping part 35, is very similar to the fourth embodiment, in that the clamping portion includes resilient barb formations 48 that engage with retaining edges 49 of corresponding apertures 50 formed on the inner part 30.

[0079] Another difference resides in the form of the spacer portion of the L shaped elements, which instead of being generally planar, as in the previous embodiments, has longitudinally spaced openings corresponding to apertures 50 so as to define a plurality of U - shaped supports 51 which connect via a common connecting portion 52 to the flanges 1 1 and 12 as shown. Each of the U-shaped supports may include reinforcing ribs 53 to increase stiffness and reduce the overall amount of plastics material needed.

[0080] In preferred forms of the fourth embodiment and fifth embodiments, the finished formwork panels comprise two or more layers of material. In this manner, a first stage formwork and reinforcement cage assembly can be produced using the two part connectors, with the flanges of the second clamping and locking elements sitting flush on the external surface of the first layer of formwork panels as shown in Figures 10 and 1 1 . The assembly can then be finished by securing a further outer layer of formwork panels (not shown) over the first stage assembly. This results in a clean surface requiring minimum finishing. Furthermore, the material cost for the laminated panel structure using two thinner layers is usually less expensive that using a thicker panel of equivalent strength.

[0081 ] In one preferred form according to the fourth aspect of the invention, the inner and outer parts of the connectors are made from sheet steel of around 0.8mm with a longitudinal length of around 100mm. The width of each of the panel engaging flanges is around 20mm. The gap between the internal surfaces of the parallel portions of the L shaped formations of the first inner part is sized to receive a reinforcing rod of the targeted size, and the gap between the outer surfaces of the parallel portions of the L shaped formations of the outer clamping part is sized for a clearance fit with the first part with the exception of the second retention means which will extend into that gap. Commonly used reinforcing rods have a nominal diameter of 8- 12mm. [0082] In preferred form according to the fifth embodiment, the inner and outer parts of the connectors are made from moulded plastic. Suitable polymeric materials include polypropylene and nylon, but other plastics materials can be used. Preferably the material will be suitable for injection moulding, have a tensile yield strength of at least 75Mpa, a flexural strength of at least 75Mpa and a suitable impact toughness. In a preferred form, the connectors are injection moulded from polypropylene, have a length of about 100mm, and flange widths around 20mm.

[0083] In applications where the reinforcing rod elements are prefabricated into a cage structure prior to assembly with the formwork panels, it may be desirable to produce a range of connectors based around the nominal offset required, which include connectors that are slightly bigger and slightly smaller than that offset, to allow for manufacturing tolerances in the cage. In a preferred application where the cage comprises parallel spaced longitudinal reinforcing rods tied by ligatures that circumscribe some or all of the longitudinal rods, the connectors are secured to the ligatures.

[0084] The invention also provides a method of constructing a reinforcement and formwork panel assembly including the steps of: securing the reinforcing rod retention means provided on the second end of one or more connectors according to the invention to a reinforcing rod or rods; and securing the flanges of the first end of each connector to an adjacent formwork panel.

[0085] For methods using single piece connectors according to the first three embodiments of the invention illustrated in Figures 1 to 7, the flanges of the first end of each connector are secured to an inside surface of an adjacent formwork panel using fasteners such as screws, or adhesive, or a combination of both.

[0086] For methods using the two part connectors according to the fourth embodiment of the invention as illustrated in Figures 8 to 1 1 , the first inner part of the connector is secured to a reinforcing rod via the first retention means. This involves using a suitable tool, such as the tool 45 shown in Figure 8, to bend the tabs 41 across the gap above the reinforcing rod 5 and into the close fitting locking aperture 42. A formwork panel 7 with suitably formed through apertures 37 is then aligned with the inner connector 30 and reinforcing rod 5 assembly, and the second clamping and locking outer part 35 of the connector is inserted from the outside surface 36 of the formwork panel. As the outer part 35 is pushed in, the hinged flaps or barbs 39 deform inwardly against the adjacent inner surfaces of the inner connector 30, until they align with the inner connector locking apertures 40. At this point the barbs resiliently deform outwardly again and thereby secure the outer locking part to the inner part of the connector. The method of using the fifth embodiment illustrated in Figure 12 is even more simple in that a simple push fit connection is required to connect to the reinforcing rod and to the outer connector. This simple push fit connection used in both the fourth and fifth embodiments is fast, strong and

inexpensive to both make and install.

[0087] The size and number of connectors required for any given application will vary according to the structure. In the assembly illustrated in Figure 1 , which is for forming columns for use in high rise construction, the ligatures are typically spaced at 250mm centres, meaning the connectors are similarly spaced longitudinally. A typical connector of the first or second embodiments will have flange widths of around 30mm either side of the web 9. The connector may be made of sheet steel in a thickness of around 1 .2 - 2.0 mm. Typical connectors of the fourth embodiment push fit clamping connectors are described above.

[0088] The spacing peripherally will depend on the structure shape and expected loading. The aim is to ensure sufficient connectors to withstand the loads applied during assembly and most importantly during the post assembly concrete pour.

[0089] For this particular application, one form of connectors according to the third embodiment has indentations that are around 10mm long and 0.5mm deep and are spaced every 50 to 75 mm.

[0090] While the embodiments of connectors illustrated are generally longitudinal, this is not essential and could be proportionally shorter or longer or of different peripheral shape, so long as the rod engagement means securely attaches to the reinforcing elements, the spacer element operates to space and retain the rod element from the formwork panel, and the flanges have sufficient area to securely attach to the panel if using adhesive, or enable securing to the panel by another means such as the clamping action of the fourth embodiment.

[0091 ] Further, the use of the connectors of the invention is not limited to making prefabricated column forms of the kind described herein. For example, they may also be used in constructing lost formwork on-site.

[0092] Connectors according to the first three embodiments of the invention will be particularly useful where there may be limited access to some external surfaces. [0093] Accordingly, while the invention has been described with reference to particular examples, it will be appreciated that it may be embodied in many other forms.

Claims

1 . A connector for securing reinforcing rod elements to an adjacent spaced formwork panel, the connector including:

a compression resistant spacer element having a first end and a second end defining a depth there between;

one or more securing flanges extending from said first end for securing the connector to a formwork panel, and

reinforcing rod retention means extending from said second end.

2. A connector according to claim 1 wherein the connector is generally longitudinal, extending in a longitudinal direction generally transverse to the spacer depth.

3. A connector according to claim 1 or claim 2 wherein the reinforcing rod retention means is movable from or through a rod receiving position to a rod retaining position.

4. A connector according to any one of the preceding claims having a generally T shaped cross sectional configuration, with two flange portions extending in opposite directions from the first end of the spacer element in a direction generally transverse to the spacer element.

5. A connector according to claim 4 wherein the spacer element and flanges are defined by two opposing L shaped arms positioned back to back to define the T shaped cross section which are interconnected by a rod receiving portion.

6. A connector according to any one of the preceding claims wherein the reinforcing rod retention means includes a spring formed portion adapted with a shoulder formation to secure to a reinforcing rod element by a resilient deformation from a closed rest configuration, through an opened rod receiving configuration, back to a closed rest configuration at which the rod is retained by the shoulder formation.

7. A connector according to any one of the preceding claims wherein the connector includes flange portions with formations to assist in receiving fasteners and/or adhesive for securing the connector to the formwork panel.

8. A two part connector including an inner connector according to any one of claims 1 to 7 configured whereby in use the securing flanges abut an inner surface of an adjacent formwork panel, in combination with a separate flanged locking element that is insertable through an aperture in the formwork panel to engage the inner connector and clamp the formwork panel between the flanges of the inner connector and the flanges of the locking element.

9. A two part connector according to claim 8 wherein a barbed push fit connection is provided between the inner connector and the locking element.

10. A two part connector according to claim 8 or claim 9 wherein the reinforcing rod retention means includes a region to locate the reinforcing rod and tabs or arms on a portion of the spacer element that are deformable to prevent the reinforcing rod exiting said region.

1 1 . A two part connector according to any one of claims 8 to 10 wherein the inner connector and outer connector have approximately the same longitudinal length.

12. A connector or two part connector according to any one of the preceding claims wherein each element or elements are made from sheet metal material.

13. A connector or two part connector according to any one of claims 1 to 1 1 wherein each element or elements are made from a moulded polymeric material.

14. A connector or two part connector according to any one of the preceding claims wherein the rod retaining means on the connector or inner connector include resiliently deformable arms which deflect out of the way as the rod is inserted and automatically return to a locking position after the rod is fully located.

15. A method of constructing a reinforcement and formwork panel assembly comprising the steps of:

securing the reinforcing rod engagement means provided on the second end of one or more connectors according to claims 1 to 7 to a reinforcing rod or rods; and

securing the flanges of the first end of each connector to an adjacent formwork panel.

16. A method according to claim 15 applied to constructing a prefabricated reinforcement and formwork assembly for a longitudinally extending structural element, the assembly including:

a prefabricated longitudinally extending reinforcement cage; and

an open ended formwork tube extending around said longitudinally extending cage, said formwork tube including a plurality of panels disposed around the reinforcement cage , wherein the panels are secured with the reinforcement cage using a plurality of connectors according to claims 1 to 7.

17. A method according to claim 15 applied to constructing a prefabricated reinforcement and formwork assembly for a longitudinally extending structural element, the assembly including:

a prefabricated longitudinally extending reinforcement cage; and

an open ended formwork tube extending around said longitudinally extending cage, said formwork tube including a plurality of panels disposed around the reinforcement cage , wherein the panels are secured with the reinforcement cage using a plurality of two part connectors according to claims 8 to 1 1 .

18. A method according to claim 17 further including the step of applying a further outer layer of formwork panel to the assembly.