A fastening system and method for securing an anchor plate

Abstract

A fastening system for securing an anchor plate 1 to a rebar cage, 4, 5, 6, 7, prior to a pour of concrete in which the anchor plate is to be embedded. The fastening system 8 comprises two support bars 9a, 9b, each having associated therewith a hook 11 to extend over and hook behind a first horizontally extending rebar 4 and a bracket 17, 14 arranged to slide vertically on a respective support bar 9a, 9b and to be fixed in a desired position on a fastening system 8 arranged to secure at least one shear stud 3b of the respective support bar 9a, 9b, each bracket 17, 14 comprising a clamp 19 arranged to clamp to a shear stud 3a, 3c of the anchor plate 1 to the support bars 9a, 9b.

Description

The present invention relates both to a fastening system and to a method for securing an anchor plate in position on a reinforcing bar (rebar) cage, prior to the pouring of concrete in which the anchor plate is to be embedded. Anchor plates can be embedded in a poured concrete structure so that the anchor plates may subsequently provide anchor points in the finished concrete structure for brackets or other fixings to be secured to, either by welding or by other means. These then enable structural items to be anchored to the concrete structure, such as steelwork, which may form part of a roof or floor structure, for example. An anchor plate normally comprises a rectangular steel plate having a front face which remains exposed in the finished structure, while the remainder of the steel plate, and shear studs extending from the steel plate, extend into the concrete structure to anchor the steel plate in place. It is necessary to secure each anchor plate, of which there may be many, to a rebar cage with a relatively high degree of positional accuracy before the shuttering is erected and the concrete poured. The positional accuracy is necessary to ensure that a front face of the anchor plate is positioned so that it will closely abut the shuttering, to avoid the anchor plate becoming totally embedded below the surface of the poured concrete (if spaced too far from the shuttering) or to avoid the anchor plate obstructing the correct positioning of the shuttering, requiring repositioning of the anchor plate which may be very time consuming process which may significantly disrupt the construction process. It is also important that the anchor plate is at the correct height and lateral position in the concrete structure and that it has a correct orientation, so that the front face of the anchor plate is in the same plane as the surface of the concrete structure. At present, the common method for securing anchor plates to a rebar cage requires that an ancillary rebar structure be first mounted to the structural rebars of the rebar cage, to provide an ancillary structure appropriately positioned to support an anchor plate. This is a time consuming process, with the ancillary structure being joined to the main rebar cage by being wired to it in the normal manner. An anchor plate will then normally be craned into place, to be secured to the ancillary rebar structure. In order to assist in the correct positioning of an anchor plate on the ancillary structure, temporary wooden blocks are normally first wired to the rebar structure, so that when the anchor plate is craned into position it may rest on the temporary wooden blocks in the correct position. Each anchor plate normally has at least four shear studs extending back from respective corners of the face plate, in order to anchor the anchor plate in the finished concrete structure. However, larger anchor plates may have very many shear studs. The shear studs are themselves normally wired or clamped to the ancillary rebar structure, which is again a time consuming process, particularly as the anchor plates are often mounted high on a rebar cage. Then, once the anchor plate is wired or clamped to the ancillary rebar structure, the temporary wooden blocks are removed before the shuttering is erected and the concrete poured. In the above process an anchor plate to be be displaced when the wooden blocks are removed, which may result in the process having to be recommenced for it is difficult to finely adjust the position of an anchor plate which has become misaligned. In addition to the above, a further problem which may be encountered is that occasionally an anchor plate may be displaced by concrete striking the anchor plate as the concrete is poured. This can then result in a defect in the finished structure, which can be both costly and time consuming to rectify. It is an object of the present invention to provide an improved fastening system for securing an anchor plate to a rebar cage and to provide an improved method for fastening an anchor plate to a rebar cage. According to a first aspect of the present invention there is provided a fastening system arranged to secure an anchor plate to a rebar cage prior to a pour of concrete or other settable material in which the anchor plate is to be embedded, the fastening system comprising two support bars, each support bar having associated therewith: a first hook arranged to, in use, extend over and hook behind a first horizontally extending rebar of the rebar cage, to permit the support bar to be suspended vertically from the first rebar by the first hook; and a first bracket arranged to slide vertically on the support bar and to be fixed in a desired position on the support bar, the first bracket comprising a clamp arranged to, in use, clamp to a shear stud of an anchor plate. A fastening system in accordance with a first aspect of the present invention, in providing two support bars each with an associated hook, enables each support to be quickly and easily mounted to a rebar cage by simply hanging the support bar on a first horizontally extending rebar of the rebar cage. Furthermore, each support bar having an associated first bracket arrange to slide vertically on the support bar permits the position of the bracket to be vertically adjusted on the support bar to correctly receive a shear stud of an anchor plate. This avoids the need to have an ancillary rebar structure correctly positioned and the problems associated with such structures if it is desired to subsequently reposition or adjust the position of an anchor plate suspended therefrom. It also makes it far quicker and easier to suspend an anchor plate in position prior to making fine adjustments to finalise the position of the anchor plate, before shuttering is erected. This avoids the need to temporarily support the anchor plate on temporary wooden blocks and thus the need to perform the separate process of subsequently removing the temporary wooden blocks, which itself could result in movement of the anchor plate away from the correct position. The fastening system described above enables the position of the anchor plate to be set in all three axes and to subsequently be adjusted in all the axes. As mentioned, the height of the anchor plate could be adjusted by adjusting the position of the brackets on the support bars, but in addition the clamp of the bracket can be released or tightened to permit an anchor plate to be positioned further forwards or backwards relative to the intended front face of the poured structure in which it is embedded. These are the two main adjustments that are normally required, with the longitudinal position of the anchor plate unlikely to change. However, this can also be adjusted by repositioning of the support bars on the horizontally extending rebar by which they are supported. Preferably, each support bar has further associated with it a second hook arranged to, in use, extend under and hook behind a second horizontally extending rebar, the first and second hooks arranged to be held in position on the support bar so that in use they may clamp the support bar to the first and second horizontally extending rebars of a rebar cage. This arrangement permits each support bar to be securely anchored to the rebar cage, by the opposed hooks positioned at either end of each support bar. Preferably, each support bar has further associated with it a second bracket arranged to slide vertically on the support bar and to be fixed in a desired position on the support bar, the second bracket also comprising a clamp arranged to, in use, clamp to a shear stud of an anchor plate. The provision of two brackets on each support bar enables both an upper and lower shear stud of an anchor plate to be fastened by the fastening system, with the ability to slide each bracket vertically on the support bar enabling the first and second brackets to be correctly positioned relative to each other to accommodate the vertical spacing between the respective shear studs. It also enables the brackets to not only support the anchor plate but to also control the pitch of the anchor plate. The brackets and hooks may be retained on their respective support bars by any appropriate means, but it is preferable that the support bars are each threaded bars and it is further preferable that each hook is slidable on its respective support bar and has a nut associated with it, which nut is threaded on to the support bar to retain the hook towards an end of the support bar and to permit the vertical position of the hook on the support bar to be adjusted by rotation of the nut. The above arrangement permits the vertical positioning of each support bar (and thus the vertical positioning of an anchor plate mounted by brackets to the support bars) to be adjusted by rotating the respective nuts, permitting very fine adjustments to the vertical position of an anchor plate to be made by using the nuts and winding the support bars up or down as appropriate, without the need to separately support the anchor plate during this process. This may permit an anchor plate to be attached to brackets attached to the support bars of the fastening system prior to the fastening system and anchor plate being craned into position and hooked onto the rebar cage. This thus permits anchor plates to be quickly installed on the rebar cage, with any necessary vertical adjustment of the position of the anchor plates subsequently performed by rotating the nuts to cause the support bars to be raised or lowered, during which process the entire weight of the anchor plate and fastening system is borne by the rebar cage permitting the crane or other mechanical means by which the anchor plate is initially lifted into place to quickly move on to its next task. Where each support bar has a hook at each end, the two associated nuts may be simultaneously or incrementally tightened and slackened, to permit the support bar to be raised or lowered relative to the rebar cage to which it is clamped by the two hooks. Where the support bar is threaded, each bracket is preferably slidable on the selective threaded support bar with each bracket having a first nut associated with it, which nut is threaded on the support bar such that in use the position of the bracket may be adjusted vertically on the support bar by rotation of the first nut. This permits brackets to be positioned correctly relative to each other in order to receive respective shear studs of an anchor plate. More preferably, however, each bracket has a second nut associated with it which is threaded on the support bar, with the bracket slidable on the support bar between the first and second nuts, wherein, in use, the second nut may be rotated to lock the bracket in a vertical position on the support bar against the first nut. This ability to lock each bracket in place stiffens the resultant fastening system making it less likely that the position of the anchor plate will be disturbed during a pour. Preferably, all the components of the fastening system may be preassembled and then retained on the two support bars during the entire process of securing an anchor plate to a rebar cage. This may be particularly desirable as it enables the complete fastening system as a whole to be installed on a rebar cage with, in the case of threaded support bars, it only then being necessary to then adjust the nuts on the support bars to correctly vertically position the support bars and the anchor plate. The position and pitch of the front face of an anchor plate, relative to the intended front face of the structure, can then also be adjusted by releasing the clamps of the brackets to permit respective shear studs to slide forwards or backwards in the clamps, while being supported by the clamps. Each bracket may be shaped to define a channel portion for receiving a shear stud, permitting each shear stud to be correctly received in a respective bracket. The weight of some anchor plates may make it desirable to spread the load of the anchor plate across more than one rebar of the rebar cage. Here it may be desirable that each support bar has further associated with it a third hook arranged to, in use, extend over and hook behind a third horizontally extending rebar, so that the weight of an anchor plate may be supported on two horizontally extending rebars of a rebar cage. Advantageously, all the hooks are identical to each other and / or all the brackets are identical to each other significantly reducing the number of component types used in the fastening system. The ability to make fine adjustments to the position of the anchor plate, once assembled on the rebar cage, offers the advantage of also permitting anchor plates to be preassembled on preassembled rebar cages. These can then be craned into place with the preassembled rebar cage, avoiding the need to individually lift each anchor plate into position on the rebar cage. This greatly increases the speed at which anchor plates may be installed on a rebar cage, for it is far easier and safer to install them on a rebar cage lying horizontally prior to the rebar cage being stood upright and craned into position. It also permits the whole assembly to be manufactured off site in an appropriate facility. This is only possible due to the ability to subsequently make fine adjustment to the position of each anchor plate on the erected rebar cage, which adjustments will almost inevitable be required, partly due to distortion of the preassembled rebar cage during lifting. According to a second aspect of the present invention there is provided a bracket for use in a fastening system as described above, the bracket comprising: a main body having a passage extending therethrough to enable the bracket to slide along a support bar; a channel in the main body for receiving a shear stud of an anchor plate; and a clamp bar for clamping the shear stud to the main body of the bracket. According to a third aspect of the present invention there is provided a method for fastening an anchor plate to a rebar cage, the method comprising, in no particular order, the steps of: clamping two shear studs of an anchor plate to respective ones of two brackets at desired positions along the studs, which positions will determine the position of the anchor plate in an X-direction relative to the rebar cage, hooking a hook associated with a support bar for the two brackets on a first horizontally extending rebar of the rebar cage; hooking a second hook associated with the support bar under a second vertically extending rebar of the rebar cage; adjusting the position of the two brackets on the support bar in dependence on the spacing between the two shear studs; adjusting the position of the two hooks to both secure the support bar to the rebar cage and to adjust the position of the brackets and the anchor plate vertically in a Z-direction, perpendicular to the X-direction, and preferably the method comprises using a threaded support bar, wherein the steps of adjusting the position of the hooks and adjusting the position of the brackets is performed by rotating nuts on the threaded support bar to control the position of the hook and brackets on the support bar. Such a method has the advantages described above. One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying figures, of which: Figure 1 is a perspective view of an anchor plate supported on horizontal rebars of a rebar cage by a fastening system in accordance with a first aspect of the present invention; Figure 1A shows to an enlarged scale the inset A of Figure 1; Figure 1B shows to an enlarged scale the inset B of Figure 1; Figure 2 is a front elevation of the components shown in Figure 1; Figure 3 is a underneath view of the components shown in Figures 1 and 2; Figure 4 is a side elevation of the components shown in Figures 1 to 3; Figure 4A shows to enlarged scale the inset C of Figure 4; Figure 5 is a perspective view of a hook of the fastening system shown in Figures 1 to 4A; Figure 6 is a perspective view of a main body of a bracket of the fastening system illustrated in Figure 1; and Figure 7 is a perspective view of a clamp bar of a bracket of the fastening system of Figure 1. Referring now to Figures 1 to 4A, here there is shown an anchor plate, indicated generally as 1, having a face plate 2 from which four shear studs 3a to 3d extend to enable the anchor plate 1 to be anchored in a body of concrete, once poured. A rebar cage of the structure to be poured comprises multiple pairs of rebars, four pairs of which, 4 to 7, can be seen in Figures 1,2 and 4. The anchor plate 1 is connected to a first pair of horizontal rebars 4 and a second pair of horizontal rebars 6 by means of a fastening system indicated generally as 8. The fastening system 8 comprises a first threaded support bar 9a and a second threaded bar 9b, each with a set of equivalent components. These comprise, for each threaded support bar 9a and 9b, a top hook 11 which extends over and hooks behind the upper rebar pair 4 and a bottom hook 12 which extends under and hooks behind a lower rebar pair 6. As can be more clearly seen in the inset B of Figure 1, shown to an enlarged scale in Figure 1B, each upper hook 11 has an associated nut 13 threaded on the threaded support bar 9a, 9b holding the hook 13 captive on the threaded support bar 9a, 9b. Each lower hook 12 has corresponding nut 13 (not shown) to urge the lower hooks 12 upwards so as to clamp the respective threaded support bars 9a and 9b to the rebar cage. Each of the top hooks 11 and 12 are identical and such a hook 11 is shown to an enlarged scale in Figure 5. The hook 11 is pressed from steel plate and, although not shown, the gaps in the edges may are welded to strengthen the hook 11. The anchor plate 1 is attached to the two threaded support bars 9a and 9b, and thus to the rebar cage, by means of four brackets 14 to 17, one of which can is shown to an enlarged scale in Figure 1A. As can been seen from Figure 1A, each bracket 14 to 17 has two nuts 13 associated with it, each threaded onto a respective threaded support bar 9a or 9b. As can also be seen from Figure 1A, the bracket 15 comprises a main body 18, shown in greater detail in Figure 6, and a clamp bar 19, shown in detail in Figure 7, each formed from a pressed steel plate and welded at the joins, although in Figures 6 and 7 the welds are again not shown. With reference to Figure 6, the main body 18 of the bracket 15 is shaped so as to form a passage 20 through which a threaded support bar 9a or 9b may extend, so that the bracket 15, as shown in Figure 1A, may slide up and down on the threaded support bar 9b, with the position of the bracket being determined by the two associated nuts 13, which permit the position of the bracket 15 to be adjusted and locked. Returning to Figure 6, the main body 18 of the bracket has a channel 21 formed in it which, as seen in Figure 1 A, receives the shear stud 3a which is then clamped in position by clamp bar 19 and fastenings 22 and 23. Slacking the fastenings 22 and 23 permits the shear stud 3c to slide through the bracket 15 permitting the face plate 2 of the anchor plate 1 to be correctly positioned. In use an anchor plate 1 may be fastened to rebars, or rebar pairs 4 to 7, of a rebar cage by means of the fastening system 8, by taking threaded support bars 9a and 9b, with pairs of hooks 11 and 12 and brackets 14 to 17 preassembled on the threaded bars 9a and 9b, held in approximate desired positions by nuts 13, and temporarily clamping the four brackets 14 to 17 to respective ones of the shear studs 3a to 3d. The resultant assembly may then be positioned on the rebar cage by inserting the shear studs 3a and 3d between the rebars, or rebar pairs 5 to 7, and hooking the top hooks 11 onto an upper rebar pair 4 and positioning the lower hooks 12 below a lower rebar pair 6, before adjusting associated nuts 13 to cause the pairs of hooks 11 and 12 to clamp the two threaded support bars 8 and 9 to the rebar cage. The nuts 13 associated with the hooks 11 and 12 can then be adjusted to move respective threaded support bars 9a and 9b up and down, to vertically position the anchor plate 1. The clamp bars 19 can then be slackened to permit the face plate 2 to be correctly positioned so that it will abut the shuttering, when erected, with the clamp bars 19 being subsequently tightened to lock the anchor plate 1 in place. In this manner, the assembly comprising both the anchor plate 1 and the fastening system 8 may be hoisted into place and simply hooked by hooks 11 on to the rebar cage with subsequent adjustments made once in position, greatly simplifying the installation process. The above process may also permit anchor plates to be assembled on a preassembled rebar cage prior to installation of that rebar cage. 5 All references to “vertical” and “lateral” in this specification are in relation to the positioning of an anchor plate on a rebar cage when the rebar cage is in position prior to the pouring of concrete. Where the rebar cage is preassembled and the fastening are applied when the rebar cage has an orientation different to its intended orientation during the pouring of concrete, then all references to vertical 10 and lateral are made relative to when the preassembled rebar cage is erected prior to the pouring of concrete and the description and claims of this specification are to be interpreted accordingly. The present invention has been described above by way of example only 15 and it will be apparent to the skilled person that modifications may be made which may fall within the scope of the following claims.

Claims

1. A fastening system arranged to secure an anchor plate to a rebar cage prior to a pour of concrete or other settable material, in which the anchor plate is to be embedded, the fastening system comprising two support bars, each support bar having associated therewith:a first hook arranged to, in use, extend over and hook behind a first horizontally extending rebar, to permit the support bar to be suspended vertically from the first rebar by the first hook; anda first bracket arranged to slide vertically on the support bar and to be fixed in a desired position on the support bar, the first bracket comprising a clamp arranged to, in use, clamp to a shear stud of an anchor plate.

2. A fastening system as claimed in Claim 1, wherein each support bar has further associated with it a second hook arranged to, in use, extend under and hook behind a second horizontally extending rebar, the first and second hooks arranged to be held in position on the support bar so that in use they may clamp the support bar to the first and second horizontally extending rebars of a rebar cage.

3. A fastening system as claimed in Claim 1 or 2, wherein each support bar has further associated with it a second bracket arranged to slide vertically on the support bar and to be fixed in a desired position on the support bar, the second bracket comprising a clamp arranged to, in use, clamp to a shear stud of an anchor plate.

4. A fastening system as claimed in any preceding claim, wherein each support bar is a threaded bar.

5. A fastening system as claimed in Claim 4, wherein the, or each, hook is slidable on the support bar and has a nut associated with it which is threaded ontothe support bar to retain the hook towards an end of the support bar and permit the position of the hook to be adjusted by rotation of the nut.

6. A fastening system as claimed in Claim 4 or 5, wherein the, or each, bracket is slidable on a respective threaded support bar and each bracket has a first nut associated with it which is threaded on the support bar such that, in use, the position of the bracket may be adjusted vertically on the support bar by rotation of one first nut.

7. A fastening system as claimed in Claim 6, wherein each bracket has a second nut associated with it which is threaded on the support bar, with the bracket slidable on the support bar between the first and second nuts, wherein, in use, the second nut may be rotated to lock the bracket in a vertical position on the support bar against the first nut.

8. A fastening system as claimed in any preceding claim, wherein all components of the fastening system may preassembled and then retained on the two support bars during the entire process of securing an anchor plate to a rebar cage.

9. A fastening system as claimed in any preceding claim, wherein each bracket is shaped to define a channel portion for receiving a shear stud.

10. A fastening system as claimed in any preceding claim, wherein each bracket comprises a main body and a clamp plate arranged to clamp a shear stud to the main body of the bracket.

11. A fastening system as claimed in any preceding claim, wherein each support bar has further associated with it a third hook arranged to, in use, extend over and hook behind a third horizontally extending rebar so that the weight of an anchor plate may be supported on two horizontally extending rebars of a rebar cage.

12. A fastening system as claimed in any preceding claim, wherein all hooks are identical to each other.

13. A fastening system as claimed in any preceding claim, wherein all brackets are identical to each other.

14. A bracket for use in a fastening system as claimed in any preceding claim, the bracket comprising: a main body having a passage extending therethrough to enable the bracket to slide along a support bar and a channel for receiving a shear stud of an anchor plate; and a clamp bar for clamping the shear stud to the main body of the bracket.

15. A method for fastening an anchor plate to a rebar cage, the method comprising each of the steps of:clamping two shear studs of an anchor plate to respective ones of two brackets at desired positions along the studs, which positions will determine the position of the anchor plate in an X-direction relative to the rebar cage, hooking a hook associated with a support bar for the two brackets on a first horizontally extending rebar of the rebar cage;hooking a second hook associated with the support bar under a second vertically extending rebar of the rebar cage;adjusting the position of the two brackets on the support bar in dependence on the spacing between the two shear studs;adjusting the position of the two hooks to both secure the support bar to the rebar cage and to adjust the position of the brackets and the anchor plate vertically in a Z-direction, perpendicular to the X-direction.

16. A method as claimed in Claim 15, comprising using a threaded support bar, wherein the steps of adjusting the position of the hooks and adjusting the position of the brackets is performed by rotating nuts on the threaded support bar to control the position of the hook and brackets on the support bar.

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