AU671734B2 - Bar chairs - Google Patents

Description

<I Regulatia. 3.2

AUSTRALIA

Patents Act 1952 COMPLETE SPECIFICATION FOR A STANDARD PATENT

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C Name of Applicant: Modflx Australia Pty. Ltd.

Actual Inventor(s): ANDREW EMDEN O'LOUGHLIN C S C. C Address for Service: Invention Title: DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

Bar Chairs 7#4

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(4 C C C. C .4 5* Details of Associated Provisional Application(s): No(s): PL9011/93 26 May, 1993 The following statement is a full description of this invention, including the best method of performing it known to us: -1-

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-2- BAR CHAIRS The present invention relates to bar chairs for supporting reinforcing bars or mesh for concrete, and is particularly ~rocerned with bar chairs for use in concrete slabs.

Concrete floor slabs at ground level are poured on a water impermeable membrane, usually a plastic sheet, to provide a water seal between the slab and the ground on which it is supported. There is a tendency today to the use of thicker concrete slabs than has been the case in the past. Since there is a requirement for the reinforcing to be at a constant predetermined depth from the surface of the slab, to this tendency calls for taller bar chairs which can withstand the forces applied to them, particularly the weight of the supported reinforcing as well as of people and 0 to items on the reinforcing before the concrete is poured.

Eisting taller bar chairs, for example above 100 mmn, are commonly formed from wire and comprise two inverted substantially U-shaped wire components too oriented at right angles to each other and secured together so as to form a substantially pyramid shaped wire frame having four legs with an upper recess for too.~ locating the reinforcing bar. A disadvantage of such bar chairs is that the legs tend 25 to spread when weight is applied to the bar chair before concrete is poured, so that the reinforcing may not be supported at the correct height. Furtb,-ntore, the relatively small feet of such wire bar chairs often pierce the water impermeable membrane, particularly if the legs are caused to spread, allowing access for moisture to the concrete and especially to the wire bar chairs. Over a period of time the stvel from which these bar chairs are formed is subject to rusting and may eventually I completely deteriorate allowing access for moisture to the reinforcement itself. A separate base plate may be supplied for use with these wire bar chairs to alleviate 94O526,pAoper~dabchaIr~spe,2 -3these problems, but this increases costs and is cumbersome to use so separate bases tend not to be used in practice.

Plastics bar chairs have also been produced in an effort to overcome the problem of rusting and are often specified for concrete structures in coastal regions.

These bar chairs commonly comprise an annular base plate and a hollow turret defining one or more upper recesses to locate the reinforcing. The base plate reduces the problem of the bar chairs piercing the water impermeable membrane, but the hollow turret presents the disadvantage that it is difficult to fill as the concrete is poured and can cause a weak line in the concrete. These bar chairs are also expensive to manufacture in a relatively tall configuration and generally are not made over a height of about 100 mm. Their configuration requires the manufacture of a complex high cost mould. Furthermore, the configuration generally is not compatible with using one mould which can be readily modified for different height bar chairs.

Some of the disadvantages of the aforementioned plastics bar chairs have been alleviated by the use of a hollow or tubular support leg as opposed to a turret but such modified bar chairs have still required complex and therefore expen~sive moulds to be injection moulded. Furthermore, such bar chairs also tend to' cause weakness in the concrete since they are difficult to fill as the concrete is pioured.

Similar disadvantages also apply to multiple-legged plastics bar chairs of the type proposed in AU-A-59001 /86 which, if injection moulded ia~ plastics, would 25 require a mould that is not only complex but also not appropriate for moulding such bar chairs of different height.[ A less complex mould would be required to injection mould the single leggedj bar chair proposed in AU-S-92837, and also briefly described in AU-A-59001 /86, since a two-part mould could be used but this proposed design would not enable the same mould to be readily modified to vary, the height of the bar chair. With an integral base to provide stability to this bar chair and to alleviate tearing of the water 94O526,p:Aoper~dab,chaIrspe, 3 -11 i" I i- ,-gp J PA\OPER\ H\6369.94.18 28/6/96 -4impermeable membrane, this bar chair can only be injection moulded in a two-part mould with all of the bar chair except the base moulded in one of the parts. This limits the chair height practically and economically to about 60 mm. It is also not possible to have an extended seat for the bar. The seat must be defined only by the upper end of the leg to allow the bar chair to be ejected from the mould. The problems of a separate base have been discussed herein in relation to wire bar chairs.

A simple design of bar chair comprising a base and a single leg is proposed in AU-B- 1 87130/82. However, this bar chair is proposed to be extruded in two parts, namely the base and the leg plus integral reinforcing bar seat, which must be fitted together before use.

Other bar chairs have been proposed for use with reinforcing for tilt slabs and pre-cast concrete in which the reinforced concrete product, once cast and set, is moved into the desired location. Since the underside of the cast product is often visible once the product has 15 been moved into the desired location it is not acceptable for a bar chair used under these 4 circumstances to have a fixed base.

It is an object of the present invention to provide a bar chair having an integral base in which at least some of the disadvantages of the described prior art are alleviated.

According to the present invention, there is provided a bar chair for supporting reinforcing for concrete, comprising: a single upstanding leg; an integral seat at an upper end of the leg for supporting part of a reinforcing bar or mesh which extends from one side to an opposite side of the bar chair; and an integral base at a lower end of the leg, wherein said bar chair is injection moulded in a mould having two parts which define, respectively, said one side and said opposite side of the bar chair and which meet when the mould is closed at a join line on the bar chair between the one side and the opposite side. It

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will be appreciated that the join line may not be visible in the finished bar chair.

k n 'r .lt P:\OPERPIH\66369-94.180 28/6/96 By the present invention the bar chair can be readily injection moulded in a simple two-part mould. Since the two parts of the mould define respective sides, usually respective halves, of the bar chair, the mould cavity in each part has a depth which is not controlled by the height of the bar chair and each part of the mould can be relatively small compared to the height of the chair. This is of major advantage in that it substantially reduces the cost of the mould and therefore of the mouldings made therefrom, particularly for bar chairs over about mm high and most especially for 100 mm+ bar chairs. It also makes it easier to manufacture thinner wall sections in the mould than for example with the design of AU-S- 92837, allowing faster production times and lower manufacturing costs as well as lower packing and freight costs. The present invention also allows for the provision of a seat in a single leg bar chair which has a greater cross-section than the upper end of the leg. This can spread the load of the reinforcing, giving greater strength to the bar chair, and increase the stability of the bar chair. Furthermore, such a mould can be readily modified to form a bar chair of increased height by providing inserts (which are fixed during injection moulding) for each of said mould parts which together define an extended length of the leg, preferably of a substantially constant cross-section portion of the body. The integral base provides stability to the bar chair, particularly to taller bar chairs.

The single leg is most preferably of substantially constant cross-section along a major part of its length, the cross-section optionally increasing at a support portion which merges :a:nf: with the base. Preferably, the leg is solid but it may have, for example, a hollow core formed by a simple removable pin insert in the mould or material-saving openings therethrough. The leg advantageously has a ribbed cross-section so as to maximise the strength of the bar chair with the minimum amount of material. Most preferably the ribbed cross-section does not include a central core. The ribbed cross-section may be, for example, cross-shaped or substantially H-shaped.

The leg advantageously has a section which does not reduce from either said one side or said opposite side to the join line so that it can be formed without removable mould inserts, a sarI to the ba c pl *t P:\OPER\PHH\66369.94. 180 -28/6/96 -6- The seat may comprise a groove of, for example, substantially U- or V-shape, or it may snap engage over the bar to positively locate it. The seat may readily have a greater length than the corresponding dimension of the upper end of the leg from said one side to the opposite side, which may be important in providing adequate stability to taller bar chairs, especially over 150 min and even 200 mm or more, while at the same time maintaining a minimum body cross-section relative to the required strength. The bar chair may also readily include hooks or other features by which the reinforcing bar may be tied down on the seat.

A seat comprising a simple groove may have a section which does not reduce from either said one side or said opposite side to the joint line so that it can be formed without removable mould inserts. Preferably the groove extends linearly from said one side to the opposite side.

The seat may incorporate second locating means for locating a second reinforcing bar, for example at right angles to the reinforcing bar which extends from said one side to said *:opposite side of the bar chair. The second locating means may comprise respective grooves in the opposed sides of the aforementioned groove of the seat which may be readily defined 4 by a removable pin insert in the mould.

The base of the bar chair is prfrbysubstantially fltbut covninl has a small 4 it taper, preferably a linear taper in its upper surface, to facilitate ejection from the mould, and/or a bevelled edge, By preferably giving the base a cross-section which does not reduce from either sai one side or said opposite side to the join line, the need for removable inserts in the mould to define thp, base is avoided.

Various embodiments of a bar chair in accordance with the invention will S: k1 -7now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a top perspective view of a first embodiment of the bar chair; Figure 2 is an elevational view of the bar chair of Figure 1 from the opposite side and showing a modification; Figure 3 is an elevational view of the bar chair of Figure 1 taken at right angles to Figure 2; Figure 4 is a view similar to Figure 3 but showing further modifications; Figure 5 is a top perspective view of a second embodiment of the bar chair; and Figure 6 is a schematic plan view of one part of a simple two part mould for injection moulding a modified version of the bar chair of Figure 1.

As shown in Figures 1 to 3 of the accompanying drawings, a bir chair 1 is integrally injection moulded with a single solid leg 2, a seat 4 at the upper end of the leg 2 for supporting a reinforcing bar (not shown) which extends from one side 3 of the bar chair to the opposite side 5, and a solid base 6 at the lower end of the leg 2.

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The leg 2 has a ribbed cross-section 8 defining a cros without a central enlarged core. This shape reduces the amount of plastics material in the bar chair while providing strength as well as bend resistance. The cross-section of the leg is substantially constant along its length, except at a support portion 10 in which the ribbed cross-section 8 extends like a foot associated with each rib to adjacent the $CIl 25 periphery of the base 6. However the thickness and shape of the leg 2 may be varied depending on the strength required. The leg 2 may be of any suitable length, Susually so that a reinforcing bar is supported at a height in the range of about S* mm upwards, for example to 200 mm or higher. The substantially constant crosssection of the leg enables the saire mould to be readily used to mould different i height bar chairs by providin, appropriate length mould inserts, as described hereinafter with reference to Figure 6, and also allows for a reduced amount of plastics material being used in the bar chair provided the minimum strength 940526,p:\opcr\dab,chairspe,7 i" t -8requirements are met.

The seat 4 is substantially U-shaped defining a plain groove which extends linearly from the one side 3 to the opposite side 5. The seat 4 is provided with enlarged top edge portions 7 for increased strength. It will be appreciated that any suitable type of seat which extends from the one side to the opposite side of the bar chair may be used, including one having resilient arms which snap engage over the reinforcing bar. Furthermore, the length of the seat may be selected as desired to provide the required stability. Preferably, as shown, the seat is of the same length as the ribs 11 which extend from the one side 3 to the other side The bar chair may conveniently include hooks 13 (shown only in Figure 2) for ties to locate the reinforcing in the seat. 1 The base 6 is solid of circular cross-section and has a substantially greater area than the substantially constant cross-sectional area of the leg 2 to spread the Sload applied to the bar chair and reduce the likelihood of the bar chair tearing an impermeable membrane onto which the concrete is poured, as well as to give the bar S 2 chair stability. The base is also substantially flat on its bottom surfa 1, but its top surface tapers very slightly (not visible in the drawings) to the periphery to facilitate ejection from the mould. The base may have a bevelled or rounded (for example with a radius of 1 mm) bottom edge of the periphery (also not shown).

By making the base 6 substantially flat, the leg 2 solid and the seat 4 with a 25 plain groove extending i only one direction, it will be appreciated that the section of the bar chair does not reduce either from the one side 3 to the opposed ribs 12 :of the leg 2 or from the opposite side 5 to the opposed ribs 12. This allows the bar 1 *chair to be injection m,)ulded in a simple two-part mould which two parts close on a plane including the opposed ribs 12 which defines the join line. The taper in the base 6 extends from its centre towards the periphery in all directions to facilitate ejection of the bar chair from the mould. The ribs 11 of the leg may have a similar taper. The aforementioned hooks must, if provided, be designed to allow this j 940526,pA\oper\dab,char,sp,8 L k -9injection moulding and ejection, and may be defined as shown as projections 13 extending from the opposed ribs 12 in the plane of those bs or as straight projections extending from the seat or leg in the opening and closing direction of the mould parts.

The bar chair may be moulded in any suitable plastics material, such as, for example acrylonitrile-butadiene-styrene (ABS) graft terpolymers, polypropylene, polycarbonate and alloys thereof. It will be appreciated that additives such as fillers, binders etc. may be incorporated in the plastics material. ABS and polycarbonate are preferred since they give greater support strength, allowing thinner sections and faster production times, and higher softening temperatures.

Referring to Figure 4, the bar chair 21 is identical to the bar chair 1 except in specific respects and the same or similar parts will be given the same reference 15 numeral followed by a prime. For convenience, only the features of the bar chair 21 which differ from the corresponding features of bar chair 1 will be described.

S. The bar chair 21 is illustrated with the preferred tie-down hooks 13' (one only shown) respectively located on the opposed ribs 12' as described with reference to Figure 2 in regard to the bar chair 1.

In the bar chair 21 the ribs 11' and 12' merge into the support portion through a gradually curved junction 23 which greatly increases the strength of the bar chair as compared to the right-angle junction illustrated in the bar chair 1.

In the bar chair 21 the cross-sectional length of the ribs 11' hafi been extended 4 so that it is substantially the same as that of the ribs 12', in order to increase the rigidity of the bar chair 21. This allows a corresponding increase in the length of the seat 4' and correspondingly increased stability. However, it is not necessary to increase the enlarged top edge portions 7' in order to provide this increased stability and the opposed ends 25 of the seat 4' taper from the base of the seat to the top-end portions 7'.

S94Os20526,p\opr\dabfspe,9 I i Each of the variations described with reference to the bar chair 21 may be used independently or with any or all of the others in the bar chair 1.

Referring now to Figure 5, a bar chair 31 is integrally injection moulded with a single. solid leg 33, a seat 35 at the upper end of the leg 33 for supporting a reinforcing bar (not shown) which extends from one side 37 of the bar chair to the opposite side 39, and a solid base 41 at the lower end of the leg 33.

The leg 33 has a ribbed cross-section, roughly in the shape of an H, defined by a &,paced pair of ribs 43 extending from the one side 37 to the opposite side 39 of the bar chair which are each bisected by a single rib or web 45 extending at right angles to and beyond the ribs 43. This shape increases the amount of plastics material compared to the bar chair 1 but provides substantially improved strength as well as bend resistance. The cross-section of the leg 33 is substantially constant along its length, except at a support portion 47 in which each of the rihs 43 and has a foot 49 extending to adjacent the periphery of the base 41. Each foot 49 Voo% merges wiith its associated rib at a smoothly curved junction 51. The thickness and too shape of the leg 33 may be varied depending on the strenpth required. The leg 33 too. may be of any suitable length, usually so that a reinforcing bar is support:!d at a height in the range of about 20 mm upwards, for example to 200 mm or higher, depending upon the thickness of the concrete. 7be substantially constant crosssection of the leg enables the same mould to be readily used to mould different to height bar chairs by providing appropriate length mou!d inserts, as generally 0*66 0 described hereinafter with reference to Figure 6.

too, 0 6 0 7le seat 35 is substantially V-shaped with a rounded bottom 53 defining a I t plain groove 54 which extends from the one side 37 to the opposite side 39 between the spaced pair of ribs 43 to support a reinforcing bar therein. The sides and bottom 53 of the groove 54 extend linearly from the one side 37 to the opposite side 39 in order to facilitate moulding from said opposed sides, The bottom 53 of the seat is shorter than the top portion 55 at each side, so that the ends 57 taper upwardly and outwardly to adjacent the top ends of the ribs 43.

0 940526,pAopOAdabdmIr.spe,10 projects linearly laterally outwardly to the extent of the respective rib 45. The curved flanges 59 are supported centrally at the' )adest, lowest point by the ribs and define concavolinear support surfaces f a reaforcing bar extending at right angles to a reinforcing bar received in the groove 54. Since the concavity of the curved flanges 59 is not as great as the depth of the groove 54, a reinforcing bar received in the groove 54 can comfortably sit beneath a second reinforcing bar received by the concave support surfaces. Accordingly she bar chair can be located Sat the intersections of reinforcing msh.

The bar chair 31 may incorporate tie-down hooks (not shown) on the ribs similar to the tie-down hooks 13 described with reference to Figure 2. The hooks would preferably be disposed below the level of the bottom 53 of the groove 54.

S The base 41 is solid and of cruciform cross-section and has a substantially greater area than the cross-sectional area of the support portion 47 of the leg 33 to spread the load applied to the bar chair and reduce the lkelihood of the bar chair tearing an impermeable membrane onto which the concrete is poured, as well as to give the bar chair stability. The base is also substantially flat on its bottom surface, but its top surface tapers very slightly (iot visible in the drawing) to the periphery to facilitate ejection from the mould. The base may have a bevelled or rounded (for example with a radius of 1 mm) bottom edge of the periphery (also not shown).

!eThe cruciform shape of the base 41 covers a larger area thaa the overall cross-sections of the support portion 47 of the leg 33 by extending between the ribs 43, and slightly outwardly of them, and projecting ia the one direction and the opposite direction from the ribs 45. The shape of the base 41 is such as to give adeqtaate load-bearing abilty nd stability while reducing the volume of plastics used.

However it will be readily appreciated that other slapes of substantially flat, base may be used, including the circular base described with reference to Figures 1 to 4.

By making the base 41 subantially flat, the leg 33 solid and the groove 54 914526P9\AOPr\dbleh*spe.11 0 f -12linear it will be appreciated that these sections of the bar chair do not reduce either from the one side 37 to the opposed ribs 45 of the leg or from the opposite side 39 to the opposed ribs 45. This allows the bar chair to be injection moulded in a twopart mould which close on a plane including the opposed ribs 45 to define the join line. Although the seat 35 has a section that does reduce from both the one side 37 and die opposite side 39 towards the opposed ribs 45, and therefore towards the join line, by virtue of the concavolinear support surfaces defined by the flanges 59, these flanges can be readily defined in the mould by a simple removable pin, for example as described with reference to Figure 6, since they are linear in the lateral direction.

The bar chair 31 may be moulded from the same materials as the bar chair 1, and features of the bar chair 31 may be incorporated in the bar chair 1.

Referring now to Figure 6 there is shown one part of a two-part mould for 4 15 injection moulding a bar chair which, for convenience, is shown highly schematically as having a combination of the leg 2 and base 6 of the bar chair 1 of Figure 1 and the seat 35 of the bar chair 31 of Figure 5. The mould part 61 thus has a mould cavity 63 which defines the one side of the bar chair,, including shallow recesses each of which defines one-half of the thickness of the respective rib 12, a parallel central deeper recess 67 which defines the respective rib 11, a recess 69 at right angles to and at one end of the recess 67 which has a semi-circular bottom surface and defines one-half of the base 6 of the bar chair, and a curved recess 71 at the other end of the recess 67 which defines the seat 35. As noted already, Figure 6 depicts the shape of the mould cavity highly schematically.

A mirror image mould part (not shown) will be superposed over the mould part 61 to fully define the mould cavity before thermoplastic material is injected into the cavity. After the moulding has cooled sufficiently that its shape is set, the mould parts are separated and the moulding is ejected. However, it will be appreciated that because the bar chair includes the seat 35 which has the curved flanges 59, the moulding cannot be ejected directly. In order to facilitate the ejection, the top curved surface of the flanges 59 are defined by a removable pin 73 which is slidably 9402,pA opr \dab,chalr,sp, 12 il i P:\OPER\FH\ 6369-94.180. 2816196 13but closely received in a corresponding passage 75. The pin 73, which is preferably of circular cross-section, is located in the passage 75 prior to the thermoplastic material being injected and is removed before or after the mould parts are separated so that once they are separated the moulding can be ejected directly.

Because the mould part 61 and the opposite mould part define respective longitudinal halves of the mould cavity, the maximum depth of the recesses in the mould parts the recesses 65, 67, 69 and 71 in mould part 61) is not excessive, even for tall bar chairs, and the mould parts are readily able to be modified mould essentially the same bar chair but with different heights. The relatively shallow mould cavities in ech mould part enables substantial cost savings to be made as well as facilitating thinner wall sections in the moulding since the t mould cavity is more readily worked on. By way of example the mould part 61 is shown E' f having two removable inserts, each of which may increase the height of the bar chair by, for Sexample, 10 or 20 mm over a bar chair defined by the mould part 61 without the inserts 77.

15 The inserts are shown as being selectively fixed in place by nut and bolt assemblies 79, and ft t it will be appreciated that the opposite mould part must have the identical inserts. The inserts are conveniently arranged to define a constant cross-section part of the leg of the bar chair S" *so that the order in which they are fitted is of no concern.

Those skilled in the art will appreciate that the invention described herein is C C susceptible to variations and modifications other than those specifically described. It is to be it I understood that the invention includes all such variations and modifications which fall within its spirit and scope, Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be i;.

understood to imply the inclusion (f a stated integer or group of integers but not the exclusion of any other integer or group of integers.

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Claims (1)

14- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A bar chair for supporting reinforcing for concrete, comprising: sins\e as4ge upstanding leg; an integral seat at an upper end of the leg for supporting part of a reinforcing bar or mesh which extends from one side to an opposite side of the bar chair; and an integral base at a lower end of the leg, wherein said bar chair is injection moulded in a mould having two parts which define, respectively, said one side and said opposite side of the bar chair and which meet when the mould is closed at a join line on the bar chair between the one side and the opposite side. 2. A bar chair according to claim 1 wherein the leg is of substantially constant cross- section along a major part of its length. 9 S. 15 3. A bar chair according to claim 1 or claim 2 wherein the leg has a cross-section which does not reduce from either said one side or said opposite side to the join line. 4. A bar chair according to any one of claims 1 to 3 wherein the leg is ribbed. 5. A bar chair according to any one of the preceding claims wherein the base has a cross- section which does not reduce from either said one side or said opposite side to the join line. 0 6. A bar chair according to claim 5 wherein the base is substantially flat. 7. A bar chair according to any one of the preceding claims wherein the seat comprises a groove of U- or V-shape. 8. A bar chair according to claim 7 wherein the groove extends linearly from said one side to the opposite side. 0 -x -I. p:\OPER\PEH\66369-94.180 28/6/916 15 9. A bar chair according to any one of the preceding claims wherein the seat has a section which does not reduce from either said one side or said opposite side to the join line. A bar chair according to any one of claims 1 to 7 wherein the seat incorporates second locating means for locating a second reinforcing bar. 11. A bar chair according to claim 10 wherein the second locating means is adapted to locate the second reinforcing bar at right angles to the first-mentioned reinforcing bar. 12. A bar chair substantially as herein described with reference to the accompanying drawings. 15 DATED this 28th day of June, 1996. MODFIX AUSTRALIA PTY. LTD. By its Patent Attorneys DAVIES COLLISON CAVE 1 4~ I SS S S 41 S Sits 54 it 4( 4 4 4 .1 4 4~ 44 4 4. S S 4 4 45,5 4 4 4 *14* 4* ii 4. 4. 4 5 44 1 *,54 *4 4 4 SS 4 t4 S. I (4 i~ S ~2 16 ABSTRACr A bar chair for reinforcing in concrete comprises an upstanding body an integral seat at a top end of the body and an integral base at a lower end of the body. The bar chair is injection moulded in a mould having two parts which define, respectively, one side and an opposite side of the bar chair so that the depth of the mould cavity in each mould part need not increase with increasing height of the bar chair. '4 4. 4 4 4 4* 9 4 4 4 4 4. 5444 I 4-45 44 .t 4 444 .5.4 4 4 44 4 1 4444 .4 C 54 14 9405264popr\dab,chiulspe,16