WO2014026024A1

WO2014026024A1 - Rebate formwork system for slip form casting

Info

Publication number: WO2014026024A1
Application number: PCT/US2013/054178
Authority: WO
Inventors: Robert Urquhart Connell; Alexander Charles KNOTT; Andrew Saul BARRACLOUGH
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2012-08-08
Filing date: 2013-08-08
Publication date: 2014-02-13
Anticipated expiration: 2015-02-08
Also published as: AU2012211412A1; AU2012211412B2

Description

REBATE FORMWORK SYSTEM FOR SLIP FORM CASTING

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a rebate formwork system for use in slip form casting central cores of high rise buildings.

2. Description of the Prior Art

[0002] 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.

[0003] 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.

[0004] 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 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.

SUMMARY OF THE INVENTION

[0005] The present invention in its preferred embodiment relates to a rebate formwork system using reinforcing bar couplers installed in a manner which provides significant ease in use.

[0006] According to the present 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 couplers each having an outer end portion projecting into the interior of the form, each coupler being engaged with the rear part of the form by a clamping nut engageable with an externally threaded surface at the outer end portion of the coupler, and means for closing open outer ends of the couplers within the hollow interior of the form and being removable after casting to expose the open ends.

[0007] In one preferred embodiment, the means for closing the outer ends of the couplers comprises a strip of adhesive tape which is applied across the open outer ends of the couplers within the form. In another preferred embodiment, the means for closing the outer ends of the couplers comprises a removable end wall of each of the clamping nuts.

[0008] Preferably each coupler has a flange or shoulder at or adjacent the rear end of the external thread to provide an abutment surface which lies externally of the rear part of the form and against which a wall of the rear part of the form is clamped by application of the nut. [0009] The present invention also provides a coupler for use in the system defined above, wherein the coupler is internally-threaded and open at at least its outer end for threaded engagement with reinforcement, the coupler at its outer end portion being externally threaded for receipt of the clamping nut and having an externally-projecting flange or shoulder at or adjacent the inner end of the external thread to provide the abutment surface.

[00010] These couplers also have utility in other aspects of concrete construction.

[00011] The present invention also provides a rebate form for use in the system defined above, the form comprising a rear part which provides a hollow interior and a forward part applicable to the rear part to close the hollow interior from the front, the rear part being formed with apertures through which the threaded forward end portions of the couplers can extend to lie within the interior of the form.

BRIEF DESCRIPTION OF THE DRAWINGS

[00012] Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

[00013] Figure 1 is an exploded perspective view of a rebate formwork system in accordance with an embodiment of the invention and having reinforcing bar couplers open at their outer and inner ends for engagement with reinforcement;

[00014] Figure 2 is a section showing the rebate form coupled to reinforcement within a central core in preparation for casting;

[00015] Figure 3 is an enlarged detail of Figure 2 to show the clamped mounting of the outer end portion of a coupler within the rebate form;

[00016] Figure 4 is an exploded perspective view showing the rebate form used in conjunction with couplers in the form of internally-threaded footed ferrules; [00017] Figure 5 shows the rebate form of Figure 4 in its assembled state;

[00018] Figure 6 is a perspective view showing an alternative form of nut for clamping the end portion of the coupler within the rebate form; and

[00019] Figure 7 is a cross section corresponding to Figure 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[00020] With reference to Figures 1 to 3, the preferred embodiment of the invention provides a box for forming the rebate and carrying couplers for reinforcing bar. The box itself is similar to that currently used with bend-out bars and comprises a rear part 2 of channel form and a forward part 4 also of channel form which fits within the rear part and acts as a closure or cap during casting. The base wall of the rear part of the box is formed with apertures 5 to receive the outer ends of couplers 6 for reinforcement. In the particular embodiment shown, the couplers 6 are of the type having an internal coarse thread (see Figure 3) opening onto both ends whereby the inner end of the coupler can be screwed onto reinforcing rod of appropriate type within the central core prior to casting as shown in Figure 2 and, after casting reinforcing rod can be screwed into the exposed outer end of the coupler within the rebate formed during casting by the box. However, the coupler may alternatively be in the form of an internally-threaded ferrule open at its outer end and closed at its inner end. This is shown in Figures 4 and 5 in which the ferrule, designated 8, is of the type having an enlarged foot portion for anchorage within the core following casting. The ferrules 8 may also be tied into the reinforcement of the core in a conventional manner.

[00021] With particular reference to Figure 3, the couplers 6, 8 used in the preferred embodiments of the invention differ from equivalent couplers in current use in that the outer end portion of the coupler is formed with an external thread 10 and with a flange or shoulder 12 forming an abutment surface at or adjacent the base of the thread. A large diameter washer 14 is fitted over the outer end to lie against the flange or shoulder 12 and when the outer end of the coupler is located within the box by passage through the aperture 5 it is secured in position by the application of a flanged nut 16 onto the external thread 10 so that the outer end of the coupler is firmly fixed to the rear part of the box by clamping of the base wall between the flange of the nut and the rear washer as is clearly shown in Figure 3. The box is formed from relatively thin gauge metal and in order to ensure firm anchorage of the outer end of the coupler within the box, the rear washer and the flange on the nut are of relatively large diameter to ensure adequate distribution of the clamping load and in the embodiment shown their diameters are approximately equivalent to the internal width of the box. The flanged nut is preferably of moulded plastic which will provide adequate clamping load to retain the coupler during casting and to retain the rear part of the box following casting.

[00022] Although application of the forward part or cap 4 of the box does shield the interior of the box to a substantial extent against ingress of slurry during casting nevertheless minor amounts of slurry can enter for example through the open ends of the box where adjacent boxes abut and in order to prevent ingress of slurry into the interior of the couplers within the box a strip of adhesive tape 18 is applied across the open ends of the row of couplers within the box. While this is one preferred method as it provides a simple means for temporarily closing the outer ends of the couplers and is removable from the entire row in a single action, there are alternatives as will now be described.

[00023] In the modified arrangement shown in Figures 6 and 7 the flanged nut 16 is formed with an integral end wall 20 which spans and thereby encloses the open end of the coupler 6, 8. The end wall 20 is of circular shape, in other words disc-shaped, and is integrally coupled to the remainder of the nut by a thin-walled annular web 22 defining a weakened zone. The end wall 20 also includes an integral ring-pull or other tab 24 whereby after casting, the end wall 20 can be removed to expose the interior of the coupler by pulling the tab 24 which will cause the end wall to separate from the remainder of the nut by tearing around the thin-walled web 22. Advantageously, the interior face of the separable end wall 20 includes an inwardly-projecting annular lip 26 which engages against an interior chamfer at the outer end of the coupler to provide a secondary seal against possible ingress of slurry into the interior of the coupler. In this regard particularly in the case of couplers of the type shown in Figure 3, it is likely that the entire coupler including the external thread will be of cast construction. The casting process will inevitably leave an external flash on the casting and which will extend along the length of the thread at opposite sides. That flashing must be removed from the thread and will result in flats being formed along the thread on opposite sides whereby the thread will be interrupted rather than continuous; accordingly there is in principle a risk, albeit a relatively low risk that some slurry could pass into the interior of the coupler by passage between the flanged nut and the base wall of the box and along the interrupted zones of the thread and this is avoided by the presence of the secondary seal provided by the annular lip 26. In an alternative to use of the pull tab 24, the central part of the end wall bounded by the sealing lip 26 is connected to the remainder of the end wall by an annular zone of weakness whereby the central part can be pushed into the interior of the coupler to expose the interior after casting.

[00024] In yet a further alternative, the outer ends of the couplers could be closed by removable plastic plugs which seal into their outer ends.

[00025] The rebate form is intended to be supplied to customers in an assembled state with the couplers clamped to the box at their outer ends which are closed by the removable tape or other easily removable closure. The rebate form is supplied in standard lengths, perhaps several different standard lengths, and while the embodiments illustrated have four couplers clamped to the box it will be understood that there could be more than or less than four according to requirements.

[00026] In the setting up of the overall formwork for casting, the caps of the boxes of the rebate forms are attached to the main formwork such as by nailing so that when the main formwork is removed following casting, the caps of the rebate boxes will be pulled off to expose the outer ends of the couplers within the boxes and thus within the rebate formed by the boxes. Removal of the tape or other temporary closures will expose the open outer ends of the couplers in preparation for the next stage of construction. [00027] Although the couplers described herein with external thread and associated flange or shoulder have significant utility as a part of the described rebate formwork system, they also have utility in other applications such as to provide a tight screwed connection to a void former or formwork other than rebate formwork, to provide an external thread for a nut to attach other steel connectors, to provide engagement of a connector externally swaged onto the thread and, in the particular case of couplers of the type shown in Figures 1 to 3, a coupling for converting the coarse thread used for receiving reinforcing bar into a metric or other thread. The nuts of the form shown in Figures 6 and 7 may also have utility with the couplers in these other applications.

[00028] The embodiments have been described by way of example only and modifications are possible within the scope of the invention.

Claims

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, reinforcing bar couplers each having an outer end portion projecting into the interior of the form, each coupler being engaged with the rear part of the form by a clamping nut engageable with an externally threaded surface at the outer end portion of the coupler, and means for closing open outer ends of the couplers within the hollow interior of the form and being removable after casting to expose the open ends.

2. A system according to claim 1 , wherein the means for closing the outer ends of the couplers comprises adhesive tape which is removable after casting.

3. A system according to claim 2, wherein the outer ends of the couplers lie within a row within the hollow interior of the form and the outer ends of the couplings are closed by a strip of adhesive tape applied across the ends of the row.

4. A system according to claim 1 , wherein the means for closing the outer ends of the couplers comprises a removable end wall of each of the clamping nuts.

5. A system according to claim 4, wherein the removable end wall is of disc shape and is integrally coupled to the remainder of the nut by an annular zone of weakness, the end wall having an integral pull which can be grasped to remove the end wall at the zone of weakness.

6. A system according to any one of claims 1 to 5, wherein each coupler has a flange or shoulder at or adjacent the rear end of the external thread to provide an abutment surface which lies externally of the rear part of the form and against which a wall of the rear part of the form is clamped by application of the nut.

7. A system according to claim 5, wherein the nut has an integral external flange engageable against an inner surface of the wall and a washer is mounted on the outer end portion of the coupling externally of the rear part of the form to lie between the external surface of the wall and the abutment surface of the coupler.

8. A system according to any one of the preceding claims, wherein the coupler is internally-threaded and open at each end for threaded engagement with reinforcement.

9. A system according to any one of claims 1 to 7, wherein the coupler is in the form of an internally-threaded ferrule closed at its inner end and open at its outer end for threaded engagement with reinforcement.

10. A coupler for use in a system according to claim 1, wherein the coupler is internally-threaded and open at at least its outer end for threaded engagement with reinforcement, the coupler at its outer end portion being externally threaded for receipt of the clamping nut and having an externally-projecting flange or shoulder at or adjacent the inner end of the external thread to provide an abutment surface whereby the coupler can be clamped to the rear part of the form by a clamping action between the nut and the abutment surface.

11. A coupler according to claim 10, wherein the coupler is open at its outer and inner ends for threaded engagement with reinforcement.

12. A coupler according to claim 10, wherein the coupler is the form of an internally-threaded ferrule configured for threaded engagement with reinforcement at its outer end and closed at its inner end.

13. A rebate form for use in a system according to any one of claims 1 to 7, the form comprising a rear part which provides a hollow interior and a forward part applicable to the rear part to close the hollow interior from the front, the rear part being formed with apertures through which the threaded forward end portions of the couplers can extend to lie within the interior of the form.