AU602108B2 - Forming keyed joints in concrete - Google Patents

Description

I

9 60210ca -i This (Act (.*clt~inc; t:: 8 ;ttni'rcdn-."' s I'ii.^ COMMONWEALTH OF AUSTRALIA Patents Act 1952 Name of Applicant Address of Applicant Actual Inventor Address for Service R.F.A. AUSTRALIA PTY LTD 39 Weyba Street, Nudgee, Queensland, 4014, Australia SYDNEY CHARLES REEVES GRANT ADAMS COMPANY, Patent Trade Mark Attorneys, 333 Adelaide Street, BRISBANE. QUEENSLAND. 4000

AUSTRALIA.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: "FORMING KEYED JOINTS IN CONCRETE" The following statement is a full description of the invention including the best method of performing it known to us.

THIS INVENTION relates to forming keyed joints in concrete.

In the construction of a concrete floor, for example, it is usual to form contraction joints at appropriate intervals. This may be done in a number of ways, one widely accepted method being by the use of key joint formers. Such a former may be a strip of sheet metal with a longitudinal deformation so that the strip, viewed .:rom one side, has a fairly substantial .longitudinal concavity or groove and, viewed from the opposite side, a corresponding longitudinal convexity or tongue. A series of such strips are accurately located and levelled before the concrete for the floor is poured and consequently, at each joint, the adjacent concrete sections, separated only by the former, interfit with tongue and groove interengagement, to prevent vertical displacement of the one relative to the next.

To assist in the fixing of these formers, each may have a bottom flange extending in the same direction as the longitudinal deformation, to form a supporting Sfoot, and if the floor is to be poured in successive sections the former may be held in place by stakes driven adjacent to its other side. However, if the floor is to be laid over a waterproof membrane, staking is of course undesirable and a good deal of difficulty is encountered in accurately locating and supporting the former.

The present invention has been devised with ,the general object of providing means whereby key joints in concrete floors or the like may be quickly, easily and accurately formed.

With this and other objects in view, the invention resides broadly in means for forming a key joint in a concrete floor or the like including a key joint former strip having a longitudinal median deformation forming a concavity or groove viewed from 2 1 one side and a convexity or tongue viewed from the other side, apertures thrcu.gh the former strip to accept c' ;e-fitting dowels or tie bars; and support means for supporting the dowels substantially horizontally above the base on which concrete is to be formed to hold the former strip upright with its top substantially horizontal. Other features of the invention will become apparent from the following description.

In order that a preferred embodiment of the invention may be readily understood and carried into practical effect, reference is now made to the accompanying drawings, wherein:- FIG. 1 is a perspective view of part of a key joint former supported in place prior to the pouring of a concrete floor or the like, and .1 FIG. 2 is a cross-sectional view of part of the poured floor or the like with a key joint formed between adjacent floor sections.

The former 10 shown in the drawings is rollformed or otherwise shaped from any suitable material such as galvanized sheet steel strip so that it has a longitudinal median deformation 11 to produce a groove or concavity viewed from one side and a corresponding convexity or tongue viewed from the other.

The normally upper edge of the strip is doubled-over at 12 to form a reinforced upper edge, and its normally lower edge portion is bent to form a narrow i foot flange 13 which is concave, viewed from below, its I width being no greater than that of the deformation 11.

S, 30 At intervals, holes 14 (one only of which is shown) are formed through the former, in the example illustrated about midway between its top and bottom, and thus through the longitudinal deformation 11. Each of these holes will accommodite closely a round-section metal dowel or tie bar 3 I-utl--sl e*-~icrur_ The floor is to be formed of concrete laid over a membrane 16 which overlies a compacted and levelled bed of sand 17. Dowels 15 are closely inserted through selected ones of the holes 14 and each, to one side only of the former 10, is greased or coated with any suitable known type of bond-breaker.

Each of the dowels 15 is supported, near to its ends, by a pair of chairs 18 of any suitable type and, in the example illustrated, of one of many types developed for supporting concrete reinforcing rods or mesh. Although, in the drawings, the chairs 18 resting on the membrane 16 support the dowel 15 so that the former 10 is held with its foot 13 also resting on the membrane, the chairs may in some cases so support the former that its foot 13 is clear of the membrane, or, if a f'.Ioor of lesser than usual depth is to be poured, the membrane beneath the former foot and the chairs (if they are not of reduced height) may be depressed into the sand bed 17 so that the foot 13 of the former is located below the general level of the membrane. The supported dowels 15 not only ensure that the top 12 of the former is horizontal, but also, because of their close fit through the holes 14, prevent the former from tilting to any significant extent.

The former will in most cases have, as shown in FIG. 2, an extruded channelled strip 19 of extruded resilient plastics material fitted on its doubled-over top edge. This strip is of such cross-sectional configuration that it may be snapped onto the top edge of the former, resisting removal therefrom; and both flanges of the channel are formed with outwardly extending keys Concrete, as indicated at 21, is poured onto the prepared base and about the arrangement of the supported formers 10, and is screeded off to the level of the plastic strips 19. The concrete will not adhere to the bond breaker on one half of each dowel, which therefore, upon any contraction of the concrete, will be slidable in the concrete, supplementing the effect of the key joint.

Except in the case of long joints, it will usually be sufficient to use two supported dowels to hold the former in its correct location, the former, because of its cross-sectional configuration, being Squite rigid and resistant to bending either horizontally or vertically.

The invention, though of simple character, will be found to be very effective in achieving the objects for which it has been devised. Modifications of constructional detail and design, which will be readily apparent to persons skilled in the art, are considered to lie within the scope and ambit of the invention hereinafter claimed.

Claims (5)

1. Means for forming a key joint in a concrete floor or the like including: a key joint former strip having a longitudinal median deformation forming a~ ea or groove viewed from one side and a convexity or tongue viewed from the other side, apertures through the former strip to accept close-fitting dowels or tie bars, and support means for supporting the dowels substantially horizontally above the base on which the concrete is to be formed to hold the former strip upright with its top substantially horizontal.

2. Means for forming a key joint according to Claim 1 wherein: the bottom part of the strip is bent to one side to form a foot flange of no greater width than that of the longitudinal median deformation of the strip.

3. Means for forming a key joint according to either of the preceding claims wherein: the top of the former strip is doubled-over, and an extruded inverted channel is engaged on the doubled-over top of the former strip.

4. Means for forming a key joint according to Claim 3 wherein: the extruded inverted channel is formed with key flanges projecting from the lower parts of its sides.

5. Means for forming a key joint in a concrete floor or the like substantially as herein described with reference to the accompanying drawings. DATED this second day of August 1988. R.F.A. AUSTRALIA PTY LTD By their Patent Attorneys, GRANT ADAMS COMPANY.