AU722694B2 - Improvements in key joints for slabs - Google Patents

Description

i P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 *.o

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "IMPROVEMENTS IN KEY JOINTS FOR SLABS" The following statement is a full description of this invention, including the best method of performing it known to us: 2 THIS INVENTION relates to improvements in key joints for slabs.

Because concrete undergoes thermal expansion and contraction, it is necessary to provide expansion joints or breaks in concrete slabs, footpaths and the like to at least minimise unwanted cracking in the concrete.

For example, it is common practice to provide expansion joints or break lines every 1.0 to 1.5 metres along footpaths.

Many different key joint systems have been disclosed 10 where a joint plate is supported by a plurality of spaced stakes. It is necessary that vertical adjustment is possible between the joint plate and the stakes so that the height of the plate can be selectively adjusted.

Examples of adjustable connection between the plate and the stakes is disclosed in US 4411404 and US 4455104 (ALBERT P.

WEISBACH); AU-B-36515/89 (604612) (PAUL F. CONNOLLY et al) and AU-B-28152/92 (666883) (DANIEL C. UNDERWOOD). In the US Patents of WEISBACH, the top end of each stake is flattened and has a plurality of closely spaced, vertically arranged serrations formed on one side to releasably engage the hem of a downturned flange on the joint plate, the edge of the hem serving as a locking pawl for cooperating with the serrations. In AU-B-36515/89, wedges are engaged between a central portion of the plate and respective stakes to releasably lock the plate to the stakes. In AU-B-28152/92 (UNDERWOOD), the stakes pass through pairs of aligned, elongate apertures in the plate and are rotatable through 90' so that formations on the sides of the stakes releasably engage sides of the apertures to secure the plates to the stakes.

It is an object of the present invention to provide alternative means for releasably securing the stakes to the key joint plate.

It is a preferred object of the present invention to provide such means which allow easy adjustment of the plate to the stakes when the key joint assembly is being set up which will prevent accidental or unwanted adjustment of the plate relative to the stakes.

It is a further preferred object of the present invention to provide stakes which can be adapted to suit a wide range of V applications, eg., where a slab is to be poured on an existing slab.

15 Other preferred objects of the present invention will become apparent from the following description.

Throughout the specification, the term "a keyed joint plate assembly for concrete of the type hereinbefore described" shall include: S.o.

20 "a joint plate having substantially co-planar, vertical top Oil6 and bottom sections interconnected to a rearwardly-spaced central section by rearwardly-convergent upper and lower inclined sections, a plurality of pairs of holes spaced along the plate, the holes from each

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pair being provided respectively in the upper and lower inclined sections in substantially vertical alignment to each other, and a substantially horizontal top edge; and a plurality of stakes to support the plates substantially vertically, each stake passing through a respective pair of the vertically aligned holes." Such definition is based on Claim 1 of parent Patent No. 604612.

In a first aspect, the present invention resides in a keyed joint plate assembly for concrete as hereinbefore defined wherein: the central section has at least one inwardly (or forwardly) directed protuberance or deformation; and each stake has a plurality of substantially circumferential flanges; so arranged that: oeoe each protuberance or deformation on the central section is releasably engageable between a respective pair of the flanges on the stake to releasably lock the plate to the stake.

The central section may be parallel to the top and bottom section and may be substantially planar or inwardly curved and the protuberances may extend substantially at right angles to the axis of 20 the stake or be provided as a plurality of concentric circles or ellipses, one or more chevrons or like formations.

To enable the invention to be fully understood, preferred embodiments will now be described with reference to the accompanying drawings in which: FIGS. 1 and 2 are respective rear and front perspective views of a keyed joint assembly of a first embodiment; FIG. 3 is a sectional end view of the joint plate of the first embodiment; FIGS. 4 and 5 are respective rear and front perspective views of a keyed joint assembly of the second embodiment; FIG. 6 is a sectional end view of the keyed joint of the second embodiment; .0 FIGS. 7 and 8 are respective rear and front perspective views of a keyed joint assembly of a third embodiment; and FIG. 9 is a sectional end view of the joint plate of the 15 *z -I 9*S,* 9~ 4-

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third embodiment.

Referring to FIGS. 1 to 3, the joint plate 10 has respective, substantially co-planar, vertical top and bottom sections 11 and 12 interconnected to an inwardly curved central section 13 by rearwardly convergent upper and lower inclined sections 14, Aligned holes 16, 17 are formed in the inclined portions 14, 15 to receive a stake 20, the upper hole 16 having a resilient finger 18 adapted to urge the stake 20 towards the central section 13. A plurality of concentric, inwardly-directed protuberances 19 are provided in the central section 13 and are adapted to engage between respective peripheral flanges 21 on the stake 20 as the stake is inserted through the holes 16, 17. (The finger 18 also engages the flanges 21 to limit the upward withdrawal of the stake 20 from the plate In the second embodiment of FIGS. 4 to 6, the central portion 113 of the keyed joint plate 110 is substantially planar, but has an inwardly-directed protuberance 19 (substantially at right angles to the axis of the stake 20) to be releasably engaged between adjacent pairs of flanges 121 on the stake 120.

In the third embodiment of FIGS. 7 to 8, a pair of the inwardly-directed formations 219 are provided in the central section 13 to engage respective pairs of the circumferential flanges 221 on the stake 220.

Preferably, the joint plates are roll-formed from metal strip, with safety edges top and bottom and may have reinforcing ribs in the top handle bottom sections. Alternatively, joint plates may be, eg., extruded from suitable plastics material.

The stakes may be formed from steel rod, eg., with digging points at their lower end or may be moulded from suitable plastics material.

It will be readily apparent to the skilled addressee that the joint plates may have a range of profiles and/ that the circumferential flanges on the stakes may be provided with screwthread like formations.

*99* 9 9 99 9 9 9 99 9 9 I N I 3U Ct C-ft Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

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Claims (4)

1. A keyed joint plate assembly as hereinbefore described wherein: the central section has at least one inwardly (or forwardly) directed protuberance or deformation; and each stake has a plurality of substantially circumferential flanges, so arranged that: each protuberance or deformation on the central section is releasably engageable between a respective pair of the flanges on the stake to releasably lock the plate to the stake.

2. An assembly as claimed in Claim 1 wherein: the central section is parallel to the top and bottom sections and is substantially planar or inwardly curved; and the protuberances extend substantially at right angles to 15 the axis of the stake, or are provided as a plurality of concentric l circles or ellipses, one or more chevrons or like formations.

3. A keyed joint plate assembly for concrete substantially 'as hereinbefore described with reference to FIGS. 1 to 3; or FIGS.

4 to 6; or FIGS. 7 to 9 of the accompanying drawings. l O• 20 DATED this fifth day of June 2000. 2:e: PAUL FRANCIS CONNOLLY and ALMA IRENE CONNOLLY By their Patent Attorneys S FISHER ADAMS KELLY U L.