AU2023226694A1

AU2023226694A1 - Rebate formwork system for slip form casting

Info

Publication number: AU2023226694A1
Application number: AU2023226694A
Authority: AU
Inventors: Robert Urquhart Connell; Alexander Charles Knott
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2013-09-19
Filing date: 2023-09-06
Publication date: 2023-09-21
Also published as: AU2021203845A1; AU2013231067A1; AU2019201933A1; AU2013231067B2; AU2019201933B2

Abstract

C:\Interwo n\NRPortbl\DCC\EJL\1859725 I.doc-6/09/2023 ABSTRACT A formwork system for forming a rebate in the face of a core produced by slip form casting, the system comprising a rebate form comprising a rear part defining a hollow 5 interior and a forward part applicable to the rear part to close the hollow interior from the front, reinforcing bar couplers extending rearwardly from the rear part and engaged to the rear part by a threaded fastener passing into the coupler from the interior of the rear part, and a sealing strip extending along a rear face of the rear part and engaged by forward ends of the couplers to provide a seal against ingress of concrete slurry between the rear part 10 and the interior of the coupler.

Description

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REBATE FORMWORK SYSTEM FOR SLIP FORM CASTING

The disclosure of the complete specification of Australian Patent Application Nos. 2013231067, 2019201933, 2021203845 as originally filed are incorporated herein by reference.

The present invention relates to a rebate formwork system for use in slip form casting central cores of high rise buildings.

As is well known in the construction industry, the central core of a high rise building is conventionally constructed by a slip form casting process by which successive stages of the core are formed, typically with each stage corresponding to one storey of the building. The central core forms the principal structure of the building from which the individual floors are cantilever mounted. It typically acts as the structure for containing lifts, fire escape stairs, and service ducts.

When each storey is cast, it is conventional to form along the outer side of the core a rebate into which will be cast the inner end of a floor slab at that level. The rebate is defined by a form of appropriate cross-section and which acts in conjunction with the main formwork. Accommodation has to be made for reinforcement which needs to extend from the core at the level of the rebate in order to subsequently tie into the reinforcement for the cast floor slab.

One system in current use provides reinforcement which is cast into the core, but because of the presence of the main formwork and rebate form during casting, the part of the reinforcement which is to project from the core needs to be bent to lie along the interior of the rebate form. For this purpose, the rebate form is of hollow or box-like construction so as to receive the bent lengths of reinforcement. The subsequent actions of straightening the reinforcement after casting and to set the reinforcement in the correct configuration for use, are quite time-consuming. In addition the initial bending and subsequent straightening can lead to reduced ductility of the reinforcement which is undesirable and difficulties are sometimes encountered in ensuring that the ductility remains within prescribed limits. On

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occasions, workers may re-bend a straightened reinforcement to move it away while other activities take place and then to straighten the reinforcement a further time and this can result in shearing of the reinforcement or at least it can lead to substantial weakness.

The present invention in its preferred embodiment relates to a rebate formwork system using reinforcing bar couplers which avoids the difficulties discussed previously and which can be produced economically with facility for easy customisation to suit a range of different reinforcing bar spacing.

According to one aspect of the invention, there is provided a formwork system for forming a rebate in the face of a core produced by slip form casting, the system comprising a rebate form comprising a rear part defining a hollow interior and a forward part applicable to the rear part to close the hollow interior from the front, the rear part being adapted to carry reinforcing bar couplers extending rearwardly therefrom and clamped thereto by a threaded fastener within the interior of the rear part, wherein the interior of the rear part includes seats for receiving and locating the threaded fasteners.

According to another aspect of the invention, there is provided a formwork system for forming a rebate in the face of a core produced by slip form casting, the system comprising a rebate form comprising a rear part defining a hollow interior and a forward part applicable to the rear part to close the hollow interior from the front, the rear part being adapted to carry reinforcing bar couplers extending rearwardly therefrom and clamped thereto by a threaded fastener within the interior of the rear part, wherein the rear part includes transverse walls spaced along the length of the rear part whereby to permit the rebate form to be shortened by cutting in the zone of one of the transverse walls whereby that transverse wall then forms an end wall of the shortened form.

According to yet another aspect of the invention, there is provided a formwork system for forming a rebate in the face of a core produced by slip form casting, the system comprising a rebate form comprising a rear part defining a hollow interior and a forward part applicable to the rear part to close the hollow interior from the front, reinforcing bar

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couplers extending rearwardly from the rear part and engaged to the rear part by a threaded fastener passing into the coupler from the interior of the rear part, and a sealing strip extending along a rear face of the rear part and engaged by forward ends of the couplers to provide a seal against ingress of concrete slurry between the rear part and the interior of the coupler.

The reinforcing bar couplers may be open at each end with a coarse internal thread opening onto both ends or open at its outer end only with a coarse internal thread opening onto that end only whereby it is in the form of a footed ferrule or insert.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a perspective view from the front of an assembled rebate form with engaged reinforcing bar couplers according to a preferred embodiment of the invention; Figure 2 is an exploded view of the rebate form shown in Figure 1; Figure 3 is a view showing a rear part of the rebate form prior to punching of apertures therein at a required spacing between adjacent couplers; Figure 4 is a view showing the interior of a forward part or lid which seals to the rear part of the form; and Figure 5 is a view showing the assembled form from the rear prior to punching of the apertures.

With initial reference to Figures 1 to 4, the preferred embodiment of the invention includes a box 2 for forming the rebate and carrying couplers 4 for reinforcing bar. The box 2 comprises a rear part 6 having a base wall 8 with upper and lower walls 10, 12 which form the basic profile of the rebate and opposed end walls 14 whereby the rear part is itself of box-like form. A lid 16 which forms the front side of the rebate box is applied to the rear part to seal the interior of the rebate box against ingress of concrete slurry during casting. The base wall of the rear part of the box is formed with apertures 20 for passage of threaded fasteners 22 by which the couplers 4 are clamped to the external surface of the base wall 8 prior to casting. The rear box part 6 and lid 16 are preferably of moulded

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plastic.

The couplers 4 have an internal coarse thread into which, after casting and removal of the box 2, reinforcing rod can be screwed into the exposed outer end of the coupler within the rebate thus formed. In the specific form shown, the coupler 4 is in the form of a footed ferrule or insert closed at its inner end, but it may alternatively be open at both ends with the coarse internal thread extending its entire length so that it can be screwed at its inner end onto reinforcing rod prior to casting. Couplers of both types just described are widely available and do not have to be especially configured for use in this particular application.

The threaded fasteners 22 by which the couplers 4 are clamped to the rear box part 6 comprise a large diameter relatively thin head and a short threaded shank with a coarse thread which corresponds to that within the coupler. Fasteners of that basic form are currently produced as so-called nailing plates with a circular head of 2-3 times the diameter of the shank. Nailing plates are widely available and were originally designed for nailing onto formwork for positioning of couplers of the type just mentioned. Although the nailing function is not required in this application, nevertheless we have determined that existing nailing plates are particularly suitable for this application not only because they are widely available and inexpensive to produce (they are moulded from plastic) but also they provide other advantages as will be described. The head of the fastener includes an internal hex drive by which its threaded shank can be driven into the interior of the coupler during assembly of the system and subsequently removed after casting. Although existing available nailing plates could be used as the fasteners 22 without modification, it is preferred to adopt a modified form which provides an additional sealing function as will be described below.

Sealing of the forward faces of the couplers 4 against the outer surface of the rear face of the base wall 8 in the clamped assembled condition of the couplers to the box in order to prevent seepage of concrete slurry into the interior of the couplers is achieved by an elastomeric sealing strip 26 applied to the rear of the base wall 8 (see Figure 5). The strip 26 can either be applied adhesively to the outer side of the base wall after moulding (the

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strip 26 having an adhesive backing for that purpose) or could be incorporated within the base wall during moulding. The sealing strip is formed with apertures which align with those in the base wall as shown in Figure 2, although for the reasons now to be discussed these apertures will normally be punched into the strip post-application.

Although it is possible for the rebate box to be produced in a range of different lengths and with different ranges of coupler spacings and such an arrangement is within the scope of the present invention, nevertheless in our particularly preferred embodiment the box is specifically designed for customisation so that a single moulding can be adapted during manufacture to provide boxes of different length with different coupler spacings to suit the customer's needs. This will now be described in detail.

It will be seen from Figure 3 that a series of circular or part-circular seats 30 are formed along the length of the rear box part 6. Each seat opens onto the base wall 8 and is of a diameter corresponding to that of the circular head of the fastener 22 and is in a position where a coupler 4 can be placed according to the requirements of the customer. Although for a given length of box and which is itself variable as will be described below, it is likely in most cases that a coupler 4 will be located at each end of the box, and the variable factor according to customer requirements is likely to be the spacing between the end couplers and the intermediate couplers, in other words the coupler-to-coupler spacing. The intermediate seats between the two end seats will accommodate a range of different coupler-to-coupler spacings. After moulding of the rear box part of the box and application of the sealing strip 26, selected seats can then be punched to provide the apertures for passage of the threaded shanks of the fasteners in the positions where the customer requires the couplers. Figure 2 shows the rear box part with five punched seals for the five couplers shown in that figure and also in Figure 1. This is a straightforward operation and allows customisation to a range of different customer requirements from a single moulding. While punching can take place in all the required seats post-moulding, as it is envisaged that the seat at each end will always be required for use, apertures can be formed in those seats as part of the moulding process.

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The peripheral edge of the head of currently available nail plates is tapered and the peripheral wall of each seat is correspondingly tapered. The interaction between the tapered edge of the head and seat acts to centre the fastener within the seat for accurate placement of the corresponding coupler. Although as previously mentioned existing nail plates could be used without modification as the fasteners 22, it is preferred to modify these by the incorporation of an annular rib on the undersurface of the head to engage against the surface of the base wall 8 to seal against ingress of concrete slurry to the interior of the coupler should the box not be properly sealed by the lid. Such a rib is readily incorporated during the moulding of the fastener.

In addition to the single moulding being capable of customisation to different coupler-to coupler spacings, it can also be customised to a range of different lengths. It will be seen from Figure 3 that a series of intermediate transverse walls 34 are formed along the length of the rear box part. Although these walls assisting rigidifying the box, their principal effect is to provide a series of points which the single moulding can be cut to provide a reduced length component with the intermediate wall remaining at the cut end then constituting the end wall at that cut end. By way of example, for a single moulding which provides an uncut box length of 900mm, by cutting at the second or third transverse walls from the left hand end, cut lengths of say, 600 and 750mm can be achieved. It is particularly preferred that the intermediate walls 34 are not symmetrically spaced along the length of the box. In the configuration as shown with three intermediate walls 34, the left hand wall is spaced from the left end by a greater distance than the right hand intermediate wall is spaced from the right hand end, and the third intermediate wall within the central zone is offset from the geometric centre so that it is spaced closer to the right hand end than the left hand end. This asymmetry of the intermediate walls allows a further range of cut lengths to be achieved from the same mould. In that case measuring from the right hand end and cutting at the "central" intermediate wall or left hand intermediate wall cut lengths of, say, 550 and 700mm can be achieved. Although it is to be understood that these different cut lengths are given by way of representative examples only, nevertheless they do correspond to the range of cut lengths likely to be required in practice.

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The lid 16 which is applied to the rear box part 6 to prevent ingress of slurry to the interior of the box during casting, has on its interior surface a peripheral channel 38 which engages over a projecting peripheral edge of the top, bottom and end walls of the rear box part 6, and ribs defining transverse channels 40 which engage over the outer edges of the intermediate transverse walls 34. This inter-engagement provides an effective sealing function between the lid and rear part of the box when the lid is correctly applied. It will be noted from Figures 2 and 3 that whereas the rear box part 6 has three intermediate transverse walls 34, the lid 16 has three pairs of channels 40 for engagement with these walls. The reason for this is that due to the asymmetric placement of the intermediate walls 34 a lid with only a single corresponding set of transverse channels could only be properly fitted in a single orientation and there is a risk that an operator on a construction site might attempt to fit the lid when in the incorrect orientation resulting in the lid being incorrectly fitted. By providing the pairs of intermediate fitting channels 40, one or other of the channels of each pair will engage with the intermediate transverse walls 34 in each of the two possible orientations 180 displaced in which the lid could be applied. It will be understood that when the rear box part is cut to a required length, the lid will also be cut to that length and the transverse channel at the cut end will engage with the intermediate wall which now forms the end wall at that cut end.

The embodiments have been described by way of example only and modifications are possible within the scope of the invention. By way of example, while it is preferred to use threaded fasteners of a form the same as or similar to nailing plates as discussed, the fasteners could alternatively be in the form of bolts, preferably of moulded plastic, with an integral or separate washer. While the use of the sealing strip applied to the rear face of the box is particularly preferred for its convenience, nevertheless separate sealing washers could alternatively be used.

Claims

C:\Interwo n\NRPortbl\DCC\EJL\1859725 1-.doc-6/09/2023 -8 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A formwork system for forming a rebate in the face of a core produced by slip form casting, the system comprising a rebate form comprising a rear part defining a hollow interior and a forward part applicable to the rear part to close the hollow interior from the front, the rear part being adapted to carry reinforcing bar couplers extending rearwardly therefrom and clamped thereto by a threaded fastener within the interior of the rear part, wherein the interior of the rear part includes seats for receiving and locating the threaded fasteners.

2. A system according to claim 1, wherein the interior of the rear part is formed with a series of adjacent said seats along the length of the wall with selected ones of said seats being apertured for communication with the interior of the coupler whereby the box can be adapted to be used with couplers at different spacings.

3. A system according to claim 1 or claim 2, wherein the rear part includes transverse walls spaced along the length of the rear part whereby to permit the rebate form to be shortened by cutting in the zone of one of the transverse walls whereby that transverse wall then forms an end wall of the shortened form.

4. A formwork system for forming a rebate in the face of a core produced by slip form casting, the system comprising a rebate form comprising a rear part defining a hollow interior and a forward part applicable to the rear part to close the hollow interior from the front, the rear part being adapted to carry reinforcing bar couplers extending rearwardly therefrom and clamped thereto by a threaded fastener within the interior of the rear part, wherein the rear part includes transverse walls spaced along the length of the rear part whereby to permit the rebate form to be shortened by cutting in the zone of one of the transverse walls whereby that transverse wall then forms an end wall of the shortened form.

5. A system according to claim 3 or claim 4, wherein the transverse walls are

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asymmetrically positioned along the length of the box.

6. A system according to any one of claims 3 to 5, wherein an inner surface of the forward part includes sealing means for sealing engagement with an outer peripheral edge of top, bottom, and end walls of the rear part of the form and with the transverse walls, whereby the forward part when cut correspondingly to that of the rear part will form a seal with the end walls of the shortened rear part.

7. A system according to any one of claims 1 to 6, wherein the fasteners comprise a threaded shank extending from a head having an external diameter substantially larger than that of the threaded shank, the head having an internal drive for driving the threaded shank into the associated coupler prior to casting and for withdrawing the threaded shank from the coupler following casting.

8. A system according to claim 7, wherein the underside of the head which lies adjacent an inner surface of the rear part includes at least one annular rib for sealing engagement with the inner surface to provide a seal against possible ingress of concrete slurry into the interior of the associated coupler.

9. A system according to claim 7 or claim 8 when dependant on claim 1, wherein the head is of circular external periphery with a peripheral edge which tapers from the outer surface of the head to the inner surface, and the seats have peripheral walls inclined to match the taper at the peripheral edge of the head of the fasteners.

10. A system according to any one of claims 1 to 9, further comprising a sealing strip extending along a rear face of the rear part and engaged by forward ends of the couplers to provide a seal against ingress of concrete slurry between the rear part and the interior of the coupler.

11. A formwork system for forming a rebate in the face of a core produced by slip form casting, the system comprising a rebate form comprising a rear part defining a hollow

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interior and a forward part applicable to the rear part to close the hollow interior from the front, reinforcing bar couplers extending rearwardly from the rear part and engaged to the rear part by a threaded fastener passing into the coupler from the interior of the rear part, and a sealing strip extending along a rear face of the rear part and engaged by forward ends of the couplers to provide a seal against ingress of concrete slurry between the rear part and the interior of the coupler.

12. A system according to claim 11, wherein the sealing strip is of an elastomeric material.

13. A formwork system according to claim 11 or claim 12, wherein the sealing strip is adhesively attached to the rear face of the rear part.

14. A system according to any one of claims 11 to 13, wherein the fasteners comprise a threaded shank extending from a head having an external diameter substantially larger than that of the threaded shank, the head having an internal drive for driving the threaded shank into the associated coupler prior to casting and for withdrawing the threaded shank from the coupler following casting.

15. A system according to claim 14, wherein the underside of the head which lies adjacent an inner surface of the rear part includes at least one annular rib for sealing engagement with the inner surface to provide a seal against possible ingress of concrete slurry into the interior of the associated coupler.

16. A system according to claim 14 or claim 15, wherein the interior of the rear part is formed with a series of adjacent seats along the length of the wall for receiving and locating the heads of the fasteners with selected ones of said seats being apertured to receive the stem of a fastener whereby the box can be adapted for use with couplers at different spacings.

17. A formwork system according to any one of claims 11 to 13, wherein the fasteners

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comprise a threaded shank for engagement into the interior of the coupler, and a head lying adjacent a base wall of the rear part, the base wall being apertured for passage of the threaded shank of the fasteners and the sealing strip being correspondingly apertured.

18. A system according to any one of claims 11 to 17, wherein the rear part includes transverse walls spaced along the length of the rear part whereby to permit the rebate form to be shortened by cutting in the zone of one of the transverse walls whereby that transverse wall then forms an end wall of the shortened form, with the forward part being correspondingly cut.

19. A system according to claim 18, wherein the transverse walls are asymmetrically positioned along the length of the box.

20. A system according to any one of claims 11 to 19, wherein an inner surface of the forward part includes sealing means for sealing engagement with an outer peripheral edge of top, bottom and end walls of the rear part of the form.

21. A system according to claim 20, wherein the sealing means comprises channels into which the peripheral edges of the walls engage.

22. A system according to claim 19, having pairs of channels for sealing engagement with the outer peripheral edges of the transverse walls whereby to permit the lid to be applied in either one of two orientations 180° displaced despite the asymmetry in the positioning of the transverse walls.

23. A system according to any one of claims 1 to 22, wherein the couplers are open at each end with a coarse internal thread for engagement of reinforcing bar into each end, or are open at their outer ends only with a coarse internal thread for engagement of reinforcing bar into that end.

24. A rebate form for use in a system according to any one of the preceding claims

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comprising a rear part and forward part as defined in any one of the preceding claims.

25. A method of adapting a formwork system according to any one of claims 1 to 23 to meet the requirements of a customer, comprising providing a rebate form according to any one of the preceding claims wherein the rear part is of moulded plastic construction and is moulded without apertures for at least some of the threaded fasteners, and apertures are subsequently formed through the wall of the rear part for the shanks of the threaded fasteners at a required spacing between adjacent fasteners.

26. A method according to claim 25, using a rebate form as defined in any one of claims 3, 4 or 18, wherein the rear part is cut to a required length in the zone of one of said transverse walls whereby that transverse wall then forms an end wall of the cut box.