AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant(s): ONESTEEL REINFORCING PTY LTD Invention Title: BAR CHAIRS The following statement is a full description of this invention, including the best method for performing it known to me/us:
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BAR CHAIRS The present invention relates to bar chairs and bar chair modules that comprise at least two bar chairs s that are coupled together. Bar chairs are used in the construction of reinforced concrete structures, such as slabs or beams, to support steel reinforcing within structures at a desired 10 height or heights above or below top or bottom surfaces of the structures. Reinforcing can take the form of individual bars or mesh made from longitudinal and transverse bars welded 15 together at intersections of the bars. Hereinafter, reinforcing is described as being in the form of a "mat" of reinforcing. A mat can be made up of one or more layers of reinforcing. 20 In use, bar chairs are positioned on a formwork or on a sub-base of the structure in selected positions and reinforcing is then positioned on the bar chairs and is supported by the bar chairs. The positions of known 25 bar chairs and reinforcing is illustrated diagrammatically, by way of example, in Figures l[a] and l[b]. Figure l[a] illustrates a situation in which a 30 single mat 3 of reinforcing positioned on a plurality of bar chairs 7 is required. Figure 1[b] illustrates a situation in which two mats 3, 5 of reinforcing are on a plurality of different sized bar chairs 7, 9 required. 35 Two or more mats of reinforcing may be required for concrete structures that are between -200 and 2000 mm thick. 2203440_1 (GHMatters) -2 As is shown in Figure 1[b], where the structures are less than - 500 mm thick and two mats 3,5 of reinforcing are required, conventional bar chairs 7 of a s selected size can be used to support reinforcing at one height and different-sized, in this case larger, conventional bar chairs 9 can be used to support reinforcing at the other height. Both types of conventional bar chairs can be placed on the formwork (not 10 shown) or on the sub-base - as shown in the Figure. This same process of using different-sized bar chairs for supporting reinforcing at different heights, with the bar chairs being placed on the formwork or on the is sub-base, can be repeated to create more than two mats of reinforcing. However, when concrete structures exceed - 500 mm thickness, conventional bar chairs that are positioned on 20 the formwork or on the sub-base can no longer be used. Typically, the process of using bar chairs on the formwork or on the sub-base of such structures leads to over crowding of the bar chairs and/or to the use of bar chairs that are relatively small but are not of sufficient height 25 and/or strength to support the reinforcing properly. Known alternative bar chairs to these conventional bar chairs 7, 9 are shown in Figure 2. 30 The known bar chair 11 shown in Figure 2[a] is manufactured from bar that may vary in diameter from between 10 and 20 mm. The known bar chairs 13, 15 shown in Figures 2[b] and 2[c] are manufactured by bending mesh into the shapes shown in the Figures. 35 The known bar chair shown in Figure 2[a] is an example of a widely used type of bar chair. The bar chair 2293440_1 (GHMatters) -3 is manufactured by first forming a "U" shape as shown in Figures 3[a] and 5[a]. This first shape may be manufactured automatically on bar processing equipment. In a second step, carried out manually, one leg 17 (Figure s 3[b]) and then the other leg 19 (Figure 3[c]) are bent outwardly in oppositely facing directions to create a bar chair of an appropriate height "H" with oppositely extending feet of length "L" that can support the bar chair - Figures 2[a], 3[c], 4 and 4[a]. 10 In use, a plurality of the bar chair 11 shown in Figures 2[a], 3[c], 4 and 4[a] is positioned to sit on an existing mat 23 of reinforcing (or on a sub-base of the structure - not shown) as illustrated in Figures 4 and is 4[a], with the oppositely extending feet of the bar chairs resting on and tied to the reinforcing. In the case of Figure 4, parallel pairs of bars 25 are then positioned on and tied to the bar chairs 11 and form a layer of reinforcing. In the case of Figure 4[a], "dummy" bars 27 20 are then positioned on and tied to the bar chairs 11 and a layer of reinforcing (not shown) is then placed on the "dummy" bars. In practice, it is found that the bar chair 11 25 shown in Figures 2[a], 3[c], 4 and 4[a] tends to be unstable when placed on a layer of reinforcing and, typically, one or more of the horizontal legs must be tied to the reinforcing as shown in Figures 4 and 4[a]. 30 In addition to the above-mentioned stability issue, manufacturing the bar chair 11 shown in Figures 2[a], 3[c], 4 and 4[a] by the method shown in Figure 3 potentially places an operator of a manual bender at risk of crush injury to his/her hands or fingers. 35 Furthermore, the method of manufacture is expensive and slow and the irregular 3-dimensional shape 229340.1 (GHMAtters) -4 of the finished product is difficult to pack, store and transport, further adding to the cost of the bar chair. The above description of the prior art is not to 5 be taken as a description of the common general knowledge in Australia or elsewhere. The present invention provides a bar chair for supporting reinforcing in a reinforced concrete structure, io which bar chair comprises an assembly of (a) two base members that can be positioned horizontally on an underlying support such as a sub-base of the structure or a layer of reinforcing that is already in position on the structure and (b) an upright member that can be coupled to 15 the base members to extend upwardly from the base members when the base members are on the underlying support and define a support for a new layer of reinforcing spaced above the structure, wherein the upright member includes a "U" shaped section with two parallel legs and an 20 interconnecting web, wherein each base member comprises a bar and a socket coupled to the bar, and wherein each socket can receive one of the legs of the "U"shaped section to thereby couple the members together to form the assembly. 25 The socket may be formed as a separate component that can be removably coupled to the bar. For example, the socket may have a first opening for receiving the upright member and a second transverse opening for 30 receiving the bar and allowing the socket to be slid along the bar to a selected location on the bar. The construction of the bar and the socket as separate components has advantages in terms of manufacture and allowing a range of different forms of the base member to 35 be assembled on a site to suit particular conditions on the site. 2293440_2 (GHMatters) -5 The "fit" of the leg or legs of the "U" of the upright member in the socket of the base member may be a tight fit or one that allows relative rotation of the components to facilitate adjustment of the shape of the s bar chair to avoid obstructions. The present invention also provides a reinforced concrete structure that comprises reinforcing supported on one or more of the bar chair of the above-described bar 10 chair or bar chair module. The present invention is described further by way of example with reference to the accompanying drawings, of which: 15 Figures 1 to 4 show a series of known bar chairs, as described above; Figures 5 to 9 show one embodiment of a bar chair 20 in accordance with the present invention; Figures 10 and 11 show another embodiment of a bar chair in accordance with the present invention; 25 Figure 12 shows the versatility of the two bar chairs shown in Figures 5 to 11; and Figure 13 shows 4 different embodiments of base members that can be used in embodiments of a bar chair in 30 accordance with the present invention. The bar chair of the present invention is an assembly of two basic components, namely a base member 31 and an upright member 33, each of which is straight 35 forward to manufacture, can be packed and transported flat, and can be conveniently assembled on site to form a bar chair. Two embodiments of the bar chair are shown in 2293440.) (GIIMers) -6 Figures 5-11. In the embodiment shown in Figures 5-9, the upright member 33 is a "U" shaped member and the base 5 member 31 (referred to hereinafter as a "$"-shaped based member) is a short length of bar 35 with a centrally located socket 37 extending outwardly from the bar and capable of receiving an end of one of the legs of the "U" shaped upright member 33. As viewed in Figures 5-9, the 10 "S"-shaped base member 31 has a shape of an inverted "T". A first step in manufacturing the Figures 5-9 bar chair includes manufacturing the "U" shaped member 33 shown in Figure 5[b] as previously described, typically on is automatic equipment. As illustrated in Figure 5, the legs "Hl" of the "U" shaped upright member - see Figure 5[b] can be made shorter than the combined length of the members "H" and "L" of the legs of the conventional "U" shaped member - see Figure 5[a]. 20 A second step in manufacturing the Figures 5-9 bar chair includes manufacturing two "0" shaped base members 31. 25 With reference to Figure 6, each "0" shaped base member 31 is manufactured from a short length of bar 35 of a suitable diameter and a short length of tubing 37 that defines a socket. The bar could be flat, rectangular, round, square etc and the tubing could be square, round, 30 rectangular etc and can vary in length from 20-100 mm, but is more preferably 50 mm in length. As can best be seen in Figure 6, the "P" shaped base member 33 is manufactured by welding the tubing 35 centrally to the bar 35 and at 900 to the bar to form a socket that extends transversely to the bar. 2293440.2 (GHMatlrs) -7 Alternatively, the socket 37 could be in the form of a short length of tubing that has aligned transverse openings in the wall of the tubing 37 so that the tubing can be slid onto the bar 35 and positioned as required s along the length of the bar 35, with the main opening in the tubing 37 extending perpendicular to the axis of the bar 35. In this context, it is relevant to note that there will be situations in which it is not necessary that the socket 37 be positioned centrally of the bar 35. 10 The position of the tubing 37 along the length of the bar 35 is not critical. However, a position near the centre is preferred. The bar should be long enough to span between the bars in a layer of reinforcing on which 15 the bar chair sits plus approximately 100 mm overhang. A bar of 400 mm would be suitable for most applications. The "P" shaped base member 33 could be manufactured from injection moulded plastic, cast metals, 20 pressed metal or other suitable materials, such that the tubing 37 is integral to the bar and does not have to be joined to the bar in a separate operation. Alternatively, tubing 37 manufactured from injection moulded plastic, cast metals, pressed metal or other suitable materials 25 could be clipped onto a suitable bar made from any of the materials mentioned. On site, the "D" shaped base member 31 is placed on a sub-base of a structure to be constructed or on the 30 first, second or third etc., layers of reinforcing and, if required, is tied in position to hold the tubing of the member in a vertical position, as shown in Figure 7. One leg of the "U" shaped upright member is then inserted into the tubing as shown in Figure 8. A second "P" shaped 35 member 31 is then placed under the second leg of the "U" shaped member to complete assembling the bar chair with the bar chair being thereby supported on the layer of 22934402 (GHMAtters) -8 reinforcing. This is illustrated in Figure 9. The above sequence of placement steps is not critical and, by way of example, the components of the bar 5 chair could be assembled together completely before placing the bar chair on the sub-base of a structure to be constructed or on the first, second or third etc., layers of reinforcing. 10 Figures 10 and 11 illustrate another, although not the only possible other, embodiment of the bar chair of the present invention. The bar chair of this embodiment includes (a) a different shaped upright member 41 to the "U" shaped upright member 33 of the Figures 5-9 15 embodiment of the bar chair described above and (b) a single "p" shaped base member. Specifically, the "U" upright member 41 of the bar chair shown in Figures 10 and 11 includes a "U" shaped 20 section 43 and an arm part 45 that extends outwardly from one end of one leg of the "U" shaped section parallel to the web of the "U" shaped section. The length "H2" of one leg may be different to the length "Hl" of the other leg to take into account the bend radius forming this leg and 25 the difference in height resulting from not using a second "$" shaped member to support the leg "H2". In use, on site the "U" shaped upright member is positioned in a similar manner to that shown in Figure 8 30 but without the need for the second "" shaped base member, as illustrated in Figure 9. The use of this shape is illustrated in Figure 11. With reference to Figure 12, both embodiments of 35 the bar chairs of the present invention are formed so that the legs of the "U" shaped upright members that extend into the sockets of the base members are free to rotate 2293440_2 (GHMatters) -9 within the sockets. Being able to rotate the "P" shaped base member allows the assembly to be positioned on site in irregular arrangements to avoid obstructions 47 - as shown in Figure 12. 5 When assembled prior to placing a bar chair on reinforcing, the legs of the "U" shaped upright members 33, 41 of both embodiments of the present invention could be secured in the sockets of the base members to prevent 10 the assembly falling apart. By way of example, the sockets could have an indent, and integral clip or a weld bead etc., that allows the "U" shaped upright members 33, 41 to be inserted and held with sufficient force to prevent the parts separating and preferably allow the legs is of the "U" shaped members 33, 41 to rotate in the sockets. This would allow the bar chairs to be assembled at a manufacturing site and packed flat for storage and transport to the site. On site the assemblies shown in Figures 9 and 11 would be created by simply rotating the 20 "$" shaped base members through 90*. Being manufactured as separate components that can be assembled off-site or on-site as described above allows the bar chair of the first aspect of the present 25 invention to be manufactured more safely and improves production efficiency. The elimination of the bending process to form the legs "L" is also a major advantage. The bar chair also has the advantage of being able to utilise scrap reinforcing to manufacture the "@" shaped 30 base member 33, 41. The value of the steel manufactured component that utilises scrap is approximately 4 times the value of the scrap value of the component. The financial benefit of utilising scrap is quite significant. The design of the bar chair also improves the handling, 35 storage and freight of the bar chair. Other embodiments of the base member are shown in 2293440_2 (GHMattes) -10 Figure 13. Each of these alternatives, which are not the only possible alternatives, is the same conceptually as the "0" shaped base member 33, 41 shown in Figures 5-11. Each of these alternatives is essentially a two 5 dimensional member that is an assembly of (a) bars that form particular shapes as shown in the Figure and (b) a plurality of sockets extending from the bars. A plate support (not shown) is a further 10 alternative, although this is less preferred as it would have limitations in application. Some of these do not allow a pre-assembled bar chair to be packed as a flat pack. 15 Many modifications may be made to the embodiments of the present invention described above without departing from the spirit and scope of the invention. By way of example, whilst the embodiment of the 20 bar chair in accordance with the present invention includes sockets, the present invention is not so limited and extends to any suitable member to couple together the two components of the bar chairs. 22934402 (GHMatters)