AU2009201399A1 - Ferrule chair - Google Patents

Description

FERRULE CHAIR This invention relates to ferrule chairs. The invention has particular application to ferrule chairs for supporting fixing ferrules of the type used in the construction of concrete tilt-slab panels and the invention will be described with particular reference to such use. However, it is to be understood that the invention may have application to supporting ferrules and the like in concrete slabs generally and perhaps in slabs and panels formed of settable materials other than concrete. Present practice for manufacturing concrete slabs for tilt slab construction involves mounting the fixing ferrules in chairs (or supports) and securing them to a layer of reinforcing mesh within the formwork or moulds in which the panels are formed before pouring the concrete or by holding them in position by wooden dowels driven through both the ferrules and the chairs into the previously formed slab below while it is still green. In many cases, the chairs are not secured in the correct location which results in the ferrules being in the wrong location when the concrete sets. The problem is particularly distressing when ferrules are in the wrong location relative to each other rather than to the edge of the slab which can cause the end plate of the -2 beam or joist to be secured in a tilted attitude relative to the wall and of course the beam or joist is correspondingly tilted. Often, ferrules in the wrong location can be accommodated by enlarging the holes in the end plates or by making new holes. However, that is a time consuming and costly task which can result in a building not being of the desired quality. Further, where wooden dowels are used to temporarily secure the ferrules and their chairs, they are often difficult to remove and consequently are sometimes left in the tilt slab. Where they are removed, the holes they leave have to be patched. Consequently, some builders prefer not to use dowels but rather rely on securing the chairs to the reinforcing mesh only which is normally done with wire ties. Commonly, fixing ferrules are circular or hexagonal in cross section and have a threaded axial bore opening at one end (the proximal end) and terminating in a blind end towards the other end (the distal end) with a lateral (or cross) bore extending from one side to the other between the blind end and the distal end. Some fixing ferrules have a cross or star shaped foot extending laterally from the distal end designed to help the ferrule stand upright when placed on a formwork surface and to inhibit pull-out or turning in the concrete. However, fixing -3 ferrules need not have the particular features mentioned and could be made in other configurations if desired. Typically, fixing ferrules are set in various locations in tilt-slab panels for the purpose of connecting braces, plates, brackets or the like thereto. The locations selected depend on the particular purpose of the ferrule. Typically, some ferrules are located such that the threaded bore opens to one side of the panel while some may have it opening to the other side. Some may open to the top or bottom edges of the panel and some may open to the side edges. The position and spacing of ferrules in some cases is very important or even critical while in others some variations can be easily accommodated. One relatively critical case is where two or more ferrules are to be located for the purpose of bolting a pre-punched plate thereto with the punched holes at a pre-selected spacing. Typically, the spacing will be 100mm and the plate will be punched with 22mm holes for 19mm bolts thus not allowing much room for error in placement of the ferrules. Such plates will typically be arranged to bolt to an adjacent panel also to hold the two panels together and that panel also will be subject to the same small tolerances. Various types of chairs are used to locate ferrules within the formwork or moulds in which tilt-slab panels are manufactured depending on the desired location. The basic chair used to locate -4 ferrules opening to the underside face or the upperside face of the panel (as seen during construction in a horizontal mould) has a tubular centre portion with four equi-angular spaced arms extending radially outwards therefrom and four legs depending from the arms so as to support the centre portion at a predetermined height above the formwork on which it is to be placed. Four radial webs extend upwards from the arms to provide lateral support for the ferrule. Suitably the angular spaces between the webs allow a reinforcing bar to be passed through the lateral bore in the ferrule and to be suitably encompassed in concrete when the slab is poured. In use, where the proximal end of the ferrule is required to open to the underside face of the slab, the ferrule is placed upright in the tubular centre portion and simply rests on the upper face of the underside formwork (or underside slab if a previous one has been poured) and the reinforcing bar is passed through the lateral bore, the ferrule chair not being required to hold the chair at a predetermined height. On the other hand, where the proximal end of the ferrule is required to open to the upper face of the slab, the reinforcing bar rests on the centre portion of the chair thus preventing the ferrule from falling through the tubular portion to the underside formwork. Suitably, the chair is selected according to leg length such that the ferrule is held at the -5 right height whereby the proximal end is co-planar with the upper face of the slab. Some basic chairs have a tubular centre portion with two pairs of opposite quadrants providing different heights on which the reinforcing bar can rest so that one chair can suit two different thickness slabs. The presently known ferrule chairs of the type previously described do not lend themselves to easy use for setting ferrules at common spacing to suit common punched plates and can easily move if not tied down well or suitably dowelled in the desired position. Further, such known ferrule chairs allow the ferrules supported thereby to rise up in the chair when the concrete is being vibrated so that they do not open to the underside face.and are completely encapsulated in concrete in one case or stand proud of the upper face of the slab in the other case. Another problem is that the known ferrule chairs do not hold the ferrules vertical which results in later difficulties in fitting and tightening holding bolts therein. The present invention is aimed at ameliorating one or more of the aforementioned problems or at least to provde a ferrule chair which is efficient in use. With the foregoing in view, the invention resides broadly in a ferrule chair including: -6 a ferrule holding portion adapted to hold a ferrule against undesired lateral movement; a plurality of legs operatively connected to said ferrule securing portion; coupling means operatively connected to said ferrule holding portion and adapted to engage with complementary coupling means on an adjacent like chair so as to couple the ferrule chair to the like ferrule chair to prevent relative lateral movement therebetween. Preferably, said coupling means are arranged such that two or more chairs can be coupled together such that the spacing between the respective ferrule holding portions results in the respective ferrules held thereby to be spaced apart by a common technical specified distance, for example, 100mm, 125mm or 150mm. In another aspect, the invention resides broadly in the combination of two ferrule chairs, each ferrule chair including a ferrule holding portion adapted to hold a ferrule against undesired lateral movement, a plurality of legs operatively connected to said ferrule holding portion and coupling means operatively connected to said ferrule holding portion and adapted to engage with complementary coupling means on the other chair so as couple said ferrule chairs together to prevent relative lateral movement therebetween.

-7 In yet another aspect, the' invention resides broadly in a ferrule chair including: a ferrule holding portion adapted to hold a ferrule against undesired lateral movement.; a plurality of legs operatively connected to said ferrule holding portion; one or more bar securing means operatively connected to said legs, said one or more bar securing means being movable from an inactive position in which they do not secure a bar extending through the lateral bore of a ferrule being supported by said chair to an active position in which they are adapted to engage with such a bar so as to secure the bar to the chair. In still yet another aspect, the invention resides broadly in a ferrule chair including: a ferrule holding portion adapted to hold a ferrule against undesired lateral movement; a plurality of legs operatively connected to said ferrule holding portion; and hold down means operatively connected to said legs, said hold down means being adapted to engage with one or more wires of a sheet of reinforcing mesh placed thereon to hold down the chair against upward movement.

-8 Terms such as vertical, horizontal, upper, lower, side, top, bottom etc are used herein to refer to the normal position in which a slab is poured or a wall or formwork panel is erected for the purpose of describing the invention and is not intended to limit the invention to use in any particular orientation unless clearly indicated otherwise. In order that the invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein: Fig. 1 is a pictorial representation a ferrule chair according to the invention from the front; Fig. 2 is a pictorial representation of the ferrule chair of Fig. 1 from one side; Fig. 3 is a pictorial representation of the ferrule chair of Fig. 1 from above; Fig. 4 is pictorial representation of the ferrule chair of Fig. 1 from below; Fig. 5 is a pictorial representation a two of the ferrule chairs of Fig.1 coupled together from one side; and Fig. 6 is a pictorial representation of the ferrule chairs as coupled together in Fig. 5a from above.

-9 The ferrule chair 10 illustrated in Fig. 1 is die moulded of a plastics material, in this case, a polyolefin, and includes a full annular ring 11 comprising two opposed pairs of quarter ring segments 12,13 and 14,15 with the segments being separated by radially extending arms 16, 17, 18 and 19 from which depend legs 21, 22, 23 and 24 respectively. Opposed pairs of webs 26, 28 and 27, 29 extend upwards from the four arms respectively and are adapted to engage the cylindrical face of a ferrule supported therebetween at 90 degree angular spacing around the vertical axis of the ferrule and to hold the ferrule firmly. Engagement with the ferrule is by way of a thin flexible fin 26a to 29a which extend along the inner edges of the webs respectively. Suitably, the quarter ring segments are arranged to support thereon a piece of 12mm reinforcing bar when passed through the lateral bore of a cylindrical ferrule of hexagonal or circular cross section when held by the webs. In this embodiment, the ring segments are the same in height so that a bar will be at the same height above the formwork on which the chair is placed irrespective of which pair of ring segments on which it is placed. However, in other embodiments, one pair of segments has its upper face at a height above the other pair thus providing a choice of bar height within the slab to be constructed.

- 10 Downwardly directed spigot or pin portions 31 and 32 extend from legs 21 and 22 respectively and are adapted to engage in the hollows 23b and 24b )which form complementary sockets)of a like chair so as to couple two chairs together in the manner shown in Figs. 5 and 6. The spigot portions can be broken off the legs if desired to allow a clearer space around the legs. Loop portions 33 and 35 extend radially outwards from the ring quadrants 13 and 15 respectively and are connected thereto by a living hinge portion integrally moulded therewith to allow the loop portions to pivot through 90 degrees from the horizontal position shown in Fig. 3 to a vertical position (not shown) whereupon a piece of 12mm reinforcing bar can be passed therethrough and rest on the upper circular faces of the ring quadrants 13 and 15. Suitably, a ferrule may be placed in the required position between the fins 26a to 29a such that the lateral bore therethrough aligns with the passage defined by the loops so that a piece of reinforcing bar can be passed through the loops and the ferrule to secure the ferrule to the chair. Advantageously, the loops act to prevent the ferrule lifting out of the chair or even rising in the chair which can otherwise happen during vibrating of the wet concrete in a mould. If the loops are not required to hold the bar they can simply remain in the non-active horizontal position.

-11 Post portions 41 to 44 stand up from the arms 16 to 19 respectively to define spaces 51 to 54 between the posts and the outer edges of the webs 26 to 29 which are adapted to receive therein the wires of a sheet of steel reinforcing fabric such as that commonly known as F82 or F92 fabric. Advantageously, the bar chairs can be fitted under such fabric with a wire locating in adjacent spaces and resting on the upper face of the relevant arms such that the steel fabric thereby holds the chair down hard against the underlying formwork. The foregoing description has been given by way of illustrative example of the invention and many modifications in variations which will be apparent to persons skilled in the art may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (4)

1. A ferrule chair including: a ferrule holding portion adapted to hold a ferrule against undesired lateral movement; a plurality of legs operatively connected to said ferrule securing portion; coupling means operatively connected to said ferrule holding portion and adapted to engage with complementary coupling means on an adjacent like chair so as to couple the ferrule chair to the like ferrule chair to prevent relative lateral movement therebetween.

2. In combination, two ferrule chairs, each ferrule chair including a ferrule holding portion adapted to hold a ferrule against undesired lateral movement, a plurality of legs operatively connected to said ferrule holding portion and coupling means operatively connected to said ferrule holding portion and adapted to engage with complementary coupling means on the other chair so as couple said ferrule chairs together to prevent relative lateral movement therebetween.

3. A ferrule chair including: a ferrule holding portion adapted to hold a ferrule against undesired lateral movement; - 13 a plurality of legs operatively connected to said ferrule holding portion; one or more bar securing means operatively connected to said legs, said one or more bar securing means being movable from an inactive position in which they do not secure a bar extending through the lateral bore of a ferrule being supported by said chair to an active position in which they are adapted to engage with such a bar so as to secure the bar to the chair.

4. A ferrule chair including: a ferrule holding portion adapted to hold a ferrule against undesired lateral movement; a plurality of legs operatively connected to said ferrule holding portion; and hold down means operatively connected to said legs, said hold down means being adapted to engage with one or more wires of a sheet of reinforcing mesh placed thereon to hold down the chair against upward movement.