APPARATUS FOR ANCHORING A VOIDED FLAT SLAB FORMING MODULE TO A FORMWORK USING A REBAR FRAME

Technical Field of the Invention

The present invention relates to an apparatus for anchoring a voided flat slab forming module to a formwork structure, to an assembly comprising the apparatus and the formwork structure, to a method of anchoring a voided flat slab forming module to a formwork structure and to a kit of parts that comprise the apparatus for anchoring a voided flat slab forming module to a formwork structure.

Background to the Invention

The formation of void spaces in concrete floor structures is desirable since such voids can be arranged to have functionality in a number of different advantageous ways.

EP2800844 discloses a voided flat slab forming module which comprises framework that encloses one or more inflatable tubular members. In use, the void forming tubular members are inflated on site in pre-determined positions and in-situ concrete is poured over the modules to form the void flat slab once the concrete has hardened. However, an inevitability of such systems is that as the concrete is poured over the module it becomes buoyant and starts to move within the wet concrete. Accordingly, there is an increased risk that the inflated tubular members will move from their pre-determined positions resulting in misaligned voids in the hardened concrete floor structure.

In light of the above it is an object of embodiments of the present invention to prevent or at least control flotation lifting of the voided flat slab forming modules in wet concrete. It is another object of embodiments of the present invention to prevent or at least minimise lateral movement of the voided flat slab forming modules in wet concrete.

It is a further object of embodiments of the present invention to provide an efficient and cost-effective route to preventing or at least controlling the vertical or lateral movement of the voided flat slab forming modules in wet concrete.

Summary of the Invention

According to a first aspect of the invention there is provided an apparatus configured to anchor a voided flat slab forming module to a formwork structure.

It has been found that the apparatus is very suitable for preventing floatation lifting and lateral movement of the module until the concrete hardens to form a concrete floor structure. As such, the apparatus according to the first aspect of the invention enables improvements in alignment to be obtained between voids of adjacent modules. Moreover, the apparatus can be installed easily and quickly in the formwork structure which saves on labour costs and reduces the overall time it takes to produce concrete floors with accessible void spaces. Further, once the apparatus has served its initial purpose of anchoring the module to the formwork structure during the wet concrete stage, the apparatus may be re-employed to serve as a ready-made grid of anchor points for hanging underfloor services, e.g. lighting, HVAC ducts, false ceilings, sprinkler systems, cable trays, service pipes and folding/sliding partitions. The apparatus may also be re-employed to serve as a ready-made grid of anchor points for securing the top of internal fixed position, prefabricated partition wall panels.

The voided flat slab forming module may comprise framework enclosing a series of expandable tubular members. The expandable tubular members may be provided side-by-side and may be expandable to an extent limited by the framework. When the tubular members are expanded they adopt a configuration in which they have a flattened top and/or bottom. With this arrangement it is possible to provide a concrete floor structure which causes a void to be created within the flooring which is accessible through an aperture. The aperture may be closed off when required or as desired by insertion of a closure in the form of a plug.

The apparatus may comprise a head portion. In particular, the head portion may comprise an upper blade member and a lower blade member which are configured to rotate between substantially aligned and non-aligned configurations. Each blade member may comprise an inclined upper edge.

Each blade member may be elastically deformable. This means that as the module is lowered onto the formwork structure, the framework contacts the blade members causing them to adopt a substantially aligned configuration. Once the framework is moved to a position beyond the head portion, the blade members spring back into a substantially non-aligned configuration which traps the framework between the head portion and the formwork structure.

The upper blade member may comprise a cap. The cap may be formed from a brightly coloured material or may be coated with a brightly material. Preferably, the colour of the cap differs from the colour of the formwork structure and/or from other components of the apparatus. This helps an operative to correctly locate the module on the formwork structure. The cap may be formed integrally with the upper blade member. The underside of the cap may be configured to rotationally capture the lower blade member. The lower blade member may comprise an elastically distorting feature that is bent when the blades are forced towards an alignment configuration by the module installation. Once the modules’ reinforcement bars have passed beneath the blades, the distorted feature springs-back and returns the blades to a perpendicular-on position configuration. In some embodiments the head portion may be adapted to receive a service hanger rod. In particular, the service hanger rod may be secured to the apparatus by a corresponding fastener located in the head portion. The fastener may be made from steel which is preferable since it ensures that the service hanging rod is safely maintained in the event of a fire. The steel fastener may have a sherardized finish. The steel fastener may have an embossed outer surface to bond to the concrete.

In some embodiments the head portion may comprise a stiffening rib while in other embodiment the stiffening rib may be absent from the head portion.

The apparatus may comprise a shank adapted to receive the head portion. The shank and the head portion may be respectively shaped to form a push fit connection. The shank may comprise a cover. The shank length sets the thickness of fire protection concrete cover to the modules pair of parallel reinforcing bars. The length of the shank can be varied depending on the application and extent of fire protection that is desired.

The apparatus may comprise a bearer for protecting the formwork surface. The bearer may comprise a wheel member that it configured to slide over the shank. The bottom of the shank may be flared which serves to retain the wheel member on the shank. When the concrete is poured the module may relocate to the entrapped position. The bearing wheel returns to its default state in-line with the top of the shank flare and self-conceals in wet concrete. Thus, the bearer will not be visibly obtrusive from the slab soffit.

The apparatus may comprise a removable fixing for securing the apparatus to the formwork. The removable fixing may be deformable between an engaged configuration in which an upper end of the removable fixing engages an inner wall of the shank and a release configuration that enables the removable fixing to be removed from the shank. When in its release configuration the removable fixing may be simply pull-out removed through a hole formed in the formwork structure. When free, it spring unfolds and simply falls free which then enables it to be reused. Removing the removable fixings from the apparatus releases the formwork structure from the soffit of the cured slab.

The removable fixing may be configured to receive an extraction tool for removing the removable fixing from the shank.

According to a second aspect of the invention there is provided an assembly comprising a formwork structure and the apparatus according to the first aspect of the invention. The assembly according to the second aspect of the invention comprises the apparatus according to the first aspect of the invention and may, as appropriate, contain any or all features described in relation to the first aspect of the invention.

The formwork structure may comprise a pattern of holes for receiving the apparatus. In particular, the formwork structure may be a formwork table or deck. The formwork structure may comprise a grid of holes for receiving the apparatus. The grid of holes preferably matches the regular spacing of the voids in the slab forming modules, in both orthogonal directions. The holes may be drilled or otherwise formed in formwork structure. One or more of the holes may be covered by tape. The tape is preferably one which can be penetrated by the apparatus as it is pushed into formwork structure.

The voided flat slab forming module may be anchored to the formwork structure by the apparatus.

According to a third aspect of the invention there is provided a method of anchoring a voided flat slab forming module to a formwork structure, the method comprising the step of installing the apparatus according to the first aspect of the invention in a plurality of pre-determined positions in the formwork structure for anchoring the module.

The third aspect of the invention may include any or all features described in relation to the apparatus according to the first aspect of the invention and/or the assembly according to the second aspect of the invention.

The module may comprise a framework for enclosing a series of expandable tubular members and the module may be anchored to the formwork structure by positioning at least part of the framework between a head portion of the apparatus and the formwork. In particular, the base of the framework may comprise one or more pairs of parallel reinforcing bars and the apparatus may be arranged so that each pair of reinforcing bars is positioned between the head portion and the formwork structure. In some embodiments of the invention the module may be secured to the formwork structure by sliding the module framework over the head portion of the apparatus. Lowering the reinforcing bars of the framework over the head portion causes the blade members to rotate into a substantially aligned configuration which allows the reinforcing bars to be lowered to a position below the head portion. Once the reinforcing bars have moved beyond the head portion, the blade members spring back to their substantially unaligned“resting” configuration to trap and secure the reinforcing bars between the head portion and the formwork structure. In another embodiment the method may comprise the steps of providing the module on the formwork structure, removing a bearer for protecting the formwork structure from the module framework according to the first aspect of the invention, if present, and then installing the apparatus in the pre-determined positions to retain at least part of the framework between the head portion of the apparatus and the formwork structure. In particular, the shank of the apparatus may be passed between the pair of parallel reinforcing bars and pushed into the holes in the formwork structure. This “post-fit” method may be followed if the module has already been lowered onto the formwork structure.

According to a fourth aspect of the invention there is provided a kit of parts comprising the apparatus according to the first aspect of the invention and an extraction tool for removing a removable fixing from the apparatus. The kit according to the fourth aspect of the invention may include any or all of the features described in relation to the first, second and third aspects of the invention.

The extraction tool may comprise a rod with moving and fixed ring parts configured to deform the removable fixings to an extent that enables them to be removed from a shank of the apparatus as the rod is pushed into the apparatus via holes formed in the formwork structure and then pulled out. In some embodiments the kit may comprise one or more further removable fixings.

According to a fifth aspect of the invention there is provided a tool for extracting a removable fixing from the apparatus according to the first aspect of the invention, the extraction tool comprising a rod and a ring member. The tool according to the fifth aspect of the invention may include any or all of the features described in relation to the first, second, third and fourth aspects of the invention.

In some embodiments the extraction tool may comprise two or more ring members. The ring member may be fixed and/or moving ring members configured to remove the removable fixing. In one embodiment, the tool may comprise one fixed ring member and one moving ring member.

Detailed Description of the Invention

In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 shows a perspective view of a voided flat slab forming module with several anchor apparatus shown in-line;

Figure 2 shows a plan view of a formwork structure;

Figure 3 shows a view of an apparatus for anchoring the module shown in Figure

1 to the formwork structure shown in Figure 2;

Figure 4 shows a cross-sectional view of the apparatus shown in Figure 3 anchored to the formwork structure; Figure 4A shows a front view of the apparatus shown in Figure 3 anchored to the formwork structure.

Figure 5 shows an exploded view of a head portion of the apparatus shown in

Figures 3, 4 and 4A; Figure 6 shows a plan view of the head portion;

Figure 7 shows a view on the unfolded default shape of a removable fixing for anchoring the apparatus shown in Figures 3, 4 and 4A to the formwork structure shown in Figure 2.

Figure 8 shows a cross-sectional view of the removable fixing shown in Figure 7 with clipping-in barbs in a retracted un-sprung position as if being installed.

Figure 1 shows a perspective view of side-by-side voided flat slab forming modules 10 anchored to a soffit formwork deck 20 by the apparatus 30 shown in Figures 3 and 4. Each module 10 comprises an expandable tubular member 11 held between upper and lower mesh framework elements 12, 13. The tubular members 11 are held in position by restraint members 14 which fix the tubular members 11 in position.

As best shown in Figure 2 the formwork deck 20 comprises a plurality of drilled holes 21 which are adapted to receive the apparatus 30. The holes 21, which are provided in the form of a grid, are arranged to match the regular spacing of the tubular members 11 in the voided flat slab forming modules 10 in both orthogonal directions. Figure 2 also shows that each line of holes 21 is covered by a tape 22 so that any unused holes 21, i.e. holes 21 which do not receive the anchoring apparatus 30 are blanked off. Figures 3, 4 and 4 A show detailed views of the apparatus 30 for anchoring the modules 10 to the formwork deck 20. The apparatus 30 comprises a head portion 40, a shank 50 and a removable fixing 60.

The head portion 40, which is best shown in Figure 5, comprises an upper blade member 41 and a lower blade member 42 which are configured to be rotatable with respect to one another. Each blade member 41, 42 is formed from a resiliently stiff but bendable and mouldable thermoplastic material such as Polycarbonate or Nylon. The blade members 41, 42 comprise a central cavity 43 (Figure 6) which is adapted to receive a service hanger rod (not shown). In this embodiment the service hanger rod is threaded and the head portion 40 comprises a threaded fastener 44 for securing the service hanger rod to the head portion 40 of the apparatus 30. The threaded fastener 44 is made from mild steel and is located in a slot 45 formed in each of the blade members 41, 42. The lower blade member 42 and the upper end of the shank 50 comprise reciprocating push-fit connection details 46, 51 for securing the head portion 40 to the upper end of the shank51. The head portion 40 also comprises a safety cap 47. The safety cap 47 is formed from a brightly coloured plastic material and is an integral feature of the upper blade member 41. The colour of the safety cap 47 differs from the colour of the formwork deck 20 and the other components of the apparatus 30 so as to increase its visibility in use. The shank 50 comprises a substantially tubular hollow body and a cover 52. The upper end of the shank 50 is configured to receive the push-fit connection detail 46 of the lower blade member 42 and the removable fixing 60 which is discussed in more detail below. The lower end of the shank 50 is slightly flared meaning the diameter of the opening at the base of the shank 50 is greater than the opening at the top of the shank 50. Accordingly, the shank 50 is able to accommodate the removable fixing 60 in use, so as to secure the apparatus 30 to the formwork deck 20, and to receive a tool 70 for extracting the removable fixing 60 once the concrete floor structure has been formed. The flared end of the shank 50 also serves to retain a bearer 53, in the form of a wheel member, on the shank 50 which in use protects the formwork deck 20 surface from damage and impact indentations as the module 10 is lowered onto the formwork deck 20.

As best shown in Figure 3, the apparatus comprises a removable fixing 60 for anchoring the apparatus 30 to the formwork deck 20. The removable fixing 60 is made from a stiff mouldable plastic (Figure 7). The removable fixing 60 comprises and upper end which engages the inner walls of the shank 50 and a lower end which engages the underside of the formwork deck 20 in use. In this embodiment the lower end of the removable fixing comprises four fin members 61 for engaging the formwork deck 20 while the upper end comprises four barb members 62 for engaging the inner walls of the shank 50. It will be appreciated that the removable fixing 60 could comprise fewer or more fin and barb members 61, 62. The fin members 61 and the barb members 62 are both elastically deformable, meaning the barb members 62 can be pushed into and pulled out of the shank 50, and the fin members 61 can be pushed into and through the holes in the formwork deck, without becoming damaged.

To anchor the flat slab forming module 10 to the formwork deck 20, the apparatus 30 is assembled by rolling the removable fixing 60 into a cylinder and then inserting the upper end of the removable fixing 60 into the shank 50 which causes the barb members 62 to engage the inner walls of the shank 50. Figure 4A shows the barb members 62 in a locked positioned within the shank. Then, the lower blade member 42 comprising the push-fit connection detail 46 is pushed into the corresponding push-fit connection detail 51 in the upper end of the shank 50 to secure the head portion 40 to the shank 50. Once the apparatus 30 has been assembled, the apparatus is inserted into pre-determined holes 21 in the formwork deck 20. As the removable fixing 60 enters the formwork deck holes 21, the fins 61 are forced into a retracted configuration until they spring back upon exiting the hole 21 to engage the underside of the formwork deck 20. With the apparatus 30 installed and secured to the formwork deck 20, the module 10 is then lowered into position. As best shown in Figure 6, the module 10 is lowered so that a pair of parallel reinforcing bars 15 engages the upper and lower blade members 41, 42 causing them to elastically deform and to adopt a substantially aligned configuration. Once the reinforcing bars 15 have moved to a position in which they no longer contact the blade members 41, 42, the blade members 41, 42 spring back into their substantially non-aligned configuration to trap the reinforcing bars 15 between the head portion 40 and the formwork deck 20. Having secured the module 10 to the formwork deck 20, concrete is then poured over the module 10. Under normal circumstances the module 10 would become buoyant in the wet concrete thereby increasing risk of the voids formed by the tubular members becoming misaligned in the hardened concrete floor structure. However, the apparatus 30 prevents the module 10 from floating out of position and therefore the issue of misaligned voids is avoided. The bearing wheel 53 is shown dashed in Fig 4a. The dashed line represents the bearer 53 forced down on the surface of the formwork 20 by the weight of the module 10. As the concrete is poured the module 10 floats up to be arrested by the head portion 40. The spokes of the bearer (53) then spring the wheel back to its original position so that it becomes fully embedded and hidden in the concrete, leaving no aesthetically obtrusive trace of the bearer 53 from the slab soffit.

Once the concrete has hardened and the voided concrete floor structure has been produced, an operative can extract the removable fixings 60 so that they can be re-used to anchor another apparatus 30 to another formwork deck 20. Extraction of the removable fixing 60 involves the use of an extraction tool 70 (Figure 4). The extraction tool 70 comprises a rod 71 and two ring members 72, 73 which are adapted to pass through the hole 21 in the formwork deck 20 and into the lower flared end of the shank 50. As the rod 71 is pushed into the lower end of the shank the ring members 72, 73 contact the barb members 62 causing them to deform into a release position (Figure 4), which allows the removable fixings 60 to be pulled out together the extraction tool 70 as it is removed from the shank 50 and from the formwork deck 20.

In another example of the invention the apparatus 30 is post-fitted to the formwork deck 20. In this case, the bearer 53 is removed from the apparatus 30 prior to its installation into the formwork deck 20. Removal of the bearer 53 enables the apparatus 30 to be lowered through the pair of parallel reinforcing bars 15 to an extent that enables the fins 61 of the removable fixing 60 to engage with the underside of the formwork deck 20.

The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.