AU627759B2 - Slabs for false floors - Google Patents

Description

62 'Ia 59 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-1962 COMPLETE SPECIFICATION (Original) FOR OFFICE USE: Class Int. Class

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Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art:

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I '4 Name of Applicant: *Address of Applicant: Actual Inventor(s): Address for Service: 1 Little Collins Stre 3-Hunter-Street

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:loou ytrra,um-la- Frorc\in Austa-l-i-an-Cap.i-ta.l-Ter-r-ito ry-2600- Austra--ia- WILLIAM JOHN MATTHEWS DAVIES COLLISON, Patent Attorneys, et, Melbourne V 3000, Australia ca$~tDI-ir~~tue 31yg.ell.

WL--IAM-,OHN-MATT W-S- -I .Ho PTh L'M rEo /jt~ -i 0: Complete Specification for the iniention entitled: "SLABS FOR FALSE FLOORS" The following statement is a full description of this invention, including the best method of performing it known to me 1 i ~I(IIPII 4 c~ 4', la TECHNICAL FIELD This invention concerns slabs used to create false floors. False floors, in this specification, are floors which are supported above a true floor or above a roof on pedestals. Among the purposes for which a false floor may be constructed are: a) to provide a trafficable surface over a roof 4. or over a floor requiring protection; a 10 b) to provide a space in which heat insulation 9* or sound attenuation members can be located;' S* and 4.

c) to provide a cavity for electrical wiring or other services.

15 BACKGROUND ART o. At present, false floors are constructed of rectangular slabs or tiles which are supported on packing blocks or column supports set under the four corners of each slab or tile. Typically, these slabs or tiles are pre-cast reinforced concrete members or s. are pressed steel members filled with concrete or particle board. Unless the floor or roof above which S the false floor is located is planar and the column supports are of uniform height, the slabs or tiles are not supported on all four supports simultaneously. Planar floors and uniform column supports, however, are rare and either the slabs or

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2 tiles rock about the pivot provided by two of the supports, or each slab has to be supported on adjustable jacks at each corner or has to be carefully packed to ensure that it is supported evenly on all four supports. Rocking slabs produce an unsatisfactory false floor. Careful jacking or packing at each support, however, adds considerably to the cost of the installation of the false floor.

DISCLOSURE OF THE PRESENT INVENTION It is an object of the present invention to overcome the disadvantages of the existing construction of false floors and provide a slab or tile construction which can be securely mounted on support columns which do not have their top surfaces in precisely the same plane, without the need for special jacking or packing of the slab or tile.

This objective is achieved, according to the present invention, by the provision of a rigid tile adapted for use in the construction of a false floor, comprising a quadrilateral slab of concrete, characterised in that the slab of concrete has a line of weakness located along a 20 diagonal of the quadrilateral shape, said line of weakness f i, being such that non-resilient flexure of the tile about the line of weakness, together with cracking along the line of weakness, occurs when the tile is supported on four pedestals, each having a top surface, which are located one at each corner of the tile; the top surfaces of the pedestals are not co-planar; t and a normal lod is applied to the tile.

a normal load is applied to the tile.

•i 1 3 When such a slab is unevenly supported at its four corners, the application of pressure to the slab causes the slab to yield and crack along the line of weakness, so that the slab becomes, effectively, two triangular slabs, joined along the line of weakness, with each triangular slab being supported at its three corners.

The line of weakness in the slab or tile may be formed by the provision of a groove extending along a diagonal of the slab, or by any other suitable construction.

Preferably, for ease of construction of false floors over substantial areas, the quadrilateral shape will be a parallelogram. The most useful shapes are the rectangle, square and rhombus.

A panel formed as a plurality of slabs, each constructed in accordance with the present invention, is a useful realisation of the present invention.

These and other features of the present invention will become more apparent from the following description of embodiments of the present invention, in which reference 20 will be made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of one embodiument of a floor tile constructed in accordance with the present invention.

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4 Figure 2 is a sectional view at II-II Of the floor tile of Figure 1.

Figure 3 shows, using a schematic sectional view at III-III of the slab of Figure 1, the mounting of the slab of Figure 1 on a planar floor, using support columns of equal height.

Figures 4 and 5 are similar drawings to Figure 3, illustrating the way in which the slab of Figure 1 yields when the floor above which it is mounted is not planar and/or the support columns are not of equal height.

Figure 6 is a perspective sketch of another embodiment of the present invention.

Figure 7 is a. view (similar to that of Figure 2) of the tile of Figure 6.

Figure 8 is a perspective sketch of a different tile 15 construction conceived by the present inventor.

Figure 9 is a sectional view of the tile of Figure 8, taken at the diagonal of the slab which is transverse to the adjacent sides of the two triangular tiles which form the composite tile of Figure 8.

20 Figures 10 and 11 illustrate panels which have been constructed as an assemblage of rectangular and rhomboid tiles, respectively, having the features of the present invention.

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Figure 12 shows how three rhombus-shaped tiles, each having a construction similar to the tile shown in Figures 8 and 9, may be interconnected to form a hexagonal panel for a false floor.

Figures 13 and 14 are sectional views, partly schematic, in the direction X-X of Figure 10, showing alternative constructions of the panel of Figure L 4 C 444 4 *i 4 Vi 4* 4, i C 44 *r 4 4 4' 4 .i' pi 0 o 1 6- DETAILED DESCRIPTIONS OF ILLUSTRATED EMBODIMENTS The floor slab 10 shown in Figures 1 and 2 is substantially square (a square being one example of a rectangle,. which is a particular form of parallelogram, which is a preferred form of the quadrilateral shape of the present invention). It has a groove or slot 11 formed along one diagonal, which creates a line of weakness in the slab along this diagonal.

1~ Typically, the slab 10 will be of pre-cast, reinforced concrete, and wi!.l be a square having sides of 500mm or 600mm and a thickness in the range *from 20 to 40mm. In such slabs the reinforcing mesh- 12 (see Figure 2) will normally be positioned about 2 or 3mm from the bottom surface of the slab and the groove 11 will extend from the upper surface of the slab to about imm above the top of the reinforcing material 12. These dimensions are not limiting.

e• .•.4The groove 11 may be created by including a strip of particle board or similar material in the mould for 0. the slab when the concrete is poured into the mould.

94 With this approach, strength for the slab may be provided by a strong membrane attached (for example, by gluing) to the top of this particle board strip, instead of by reinforcement in the concrete. The particle board remains in the groove or slot 11.

A convenient way of forming an open groove 11 is to stretch a tape, having a thickness of imm, across the mould for the slab after the reinforcing mesh has iiii I

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7 been positioned and before the concrete is poured.

After the slab has been cast with the tape in this position, the tape can be removed, t'us creating groove 11.

Another technique for forming the groove or slot 11 is to provide an extending thin flange or knife edge on the lower surface of the press that is used to compact the concrete in the mould for the slab (most slabs will be formed using a pressure compaction process). When the compaction of the slab is o effected, the projecting flange or knife edge creates .the groove or slot 11 in the slab.

a cP Other techniques may be used to form the slot or 4 groove 11.

The slab 10 shown in Figures 1 and 2 has two preferred, but optional, features. These are the sit chamfer 13 on the slab at each end of the groove or slot 11, and the provision of one or more small holes o '14 in the side walls.

4 44 The chamfer at the corner of the slab is preferred to reduce the possibility of a weakness to abrasion at see* the acute angle formed by an edge of the slab and the a contiguous inside face of the groove 11. When all 4@4444 the slabs have a chamfer 13 on the corners at the ends of the slot or groove 11, and the slabs are assembled such that the slots or grooves 11 of four adjoining slabs come to a single point, a square hole is formed at that point. (If the chamfer is not at

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8 right angles to the direction of slot 11, the hole at this point will have a non-square, polygon shape.) This hole can be filled with a plug of resilient Smaterial (such as PVC, rubber or neoprene).

Preferably, the plug used for this purpose has a cross-section which matches the shape of the hole, and has a slight taper so that it has to be tamped into position (to assist in securing the assembled slabs in their required locations). If the plug is longer than the thickness of the slab, the top of the plug can be cut off flush with the top of the La assembled slabs. If the plug contains metal wires or is otherwise manufactured so that it conducts electricity, it can be used to remove unwanted static electricity from a carpet or other floor covering laid on top of the false floor formed by the assembled slabs. For this purpose, the plugs will have to contact earthed conductors on the top of the supporting columns for the assembled false floor.

The holes 14 in, the sides of the slabs are provided to enable small resilient plugs, inserted into the holes, to form connections between the adjacent faces of assembled tiles (which also assists in securing the assembled slabs in their required positions).

shown in Figure 3, when a floor 16 is planar and the support columns 15 for the slabs of a false floor are of uniform height, the slabs 10 will be supported evenly at their four corners, in the same manner as a conventional floor slab would be supported. However, as shown in Figures 4 and 5, when the tops of the 1 -9supporting columns 15 do not all lie in the same plane, the pressure is applied to the top of a tile 10, it will deform until all its four corners are supported on the columns Because the tile 10 is rigidly constructed, this deformation requires the tile to crack along its diagonal line of weakness, as shown at reference 17 in Figures 4 and With such deformation or yielding of the tile, the width of the slot 11 will either increase (as shown in Figure 4) or decrease (see Figure Thus, for most practical purposes, the slot or groove 11 should be at least 1 mm in width.

It will be appreciated that the reinforcing material 12 used in pre-cast concrete slabs of this type has to be chosen with reference to the thickness of the slab, (b) the location of the reinforcing material within the slab or tile, and the load capacity of the slab or tile. The selection of the type and location of the reinforcing material is an engineering exercise which persons of skill in this art can readily perform.

If, as a consequence of the chosen reinforcement material, 6i the slab or tile becomes too stiff to flex and crack as 2 shown in Figures 4 and 5, the reinforcing material will ."have to be weakened immediately below the diagonal slot or "groove 11 in the slab or tile. This can be effected, when a wire mesh is used for reinforcing, by cutting through (or partially cutting through) at least some of the mesh wires SI. that lie directly underneath the slot or groove 11.

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When using a reinforcing mesh 12 in the slabs or tiles of the present invention, it has been found to be advantageous to locate the mesh approximately 2 mm clear of the underside of the slab or tile. If the tensional reinforcement could be located closer to the underside of the slab, then either the tension forces that oppose the flexing of the slab are increased, or a smaller gauge of reinforcing material may be used to provide a slab with the same torsional strength. To locate a torsional reinforcement at the bottom of the slab, a reinforcing mesh with lugs on its uppermost side, able to be bonded into the r r concrete of the slab, is preferred. Alternatively, a l .mesh formed from flat wires which are twisted into 15 the vertical plane between each cross-wire (thus increasing the area that is bonded to the concrete) may be used. Such special types of reinforcement mesh, however, add to the cost of production of the slab or tile, and the additional cost of fabricating such special reinforcement mesh can be counterbalanced by ensuring that a conventional mesh is located at the correct height in the concrete.

The reinforcement of the slab or tile may be achieved by using a mesh or other structure fabricated from a 25 polycarbonate or other strong plastics material, instead of the conventional steel mesh.

An alternative slab construction to that described above is illustrated in Figures 6 and 7. In this embodiment of the present invention, the slab or 60 is formed as a concrete block 61 which is 'i ii N' -11bonded to the top of a tray 63 which forms the base of the slab or tile. The tray may be a steel tray, or it may be formed from a polycarbonate material or from another strong plastics material. The tray 63 may be deformed or have lugs proJecting upwardly from it to key into the concrete block 61. In this embodiment of the present invention, the diagonal line of weakness of the slab or tile 60 can be created by providing the groove or slot 62 in the cast material. Additionally, or alternatively, the tray 63 can be weakened along the line of a diagonal, or the tray 63 can be formed as two triangular metal dishes, bonded together by fabric (for example, reinforcing mesh) in the concrete block 61 (the groove or slot 62 may then become an optional feature, depending on the strength of the slab and the use to which it is to be put).

TVe weakening of the tray along a diagonal may be achieved b7 cutting into the tray along the line of the diagonal, by forming a series of incisions in the tray along the line of the diagonal, by forming a series of holes along the line of the diagonal, or by deforming the tray to create an a ;upwardly-extending ridge along the line of the diagonal.

S"Another way of constructing a slab in accordance with the present invention is to construct a shell of a plastics t material in the required shape of the slab, and l 25 subsequently to inject lightweight concrete or other into the shell. The line of weakness in the slab can be formed c in the plastic shell in the same way as the line of S' weakness may be created in the tray 53 of the embodiment of Figure 6.

V RAQ I I 12 Instead of using a plastics material, the shell may be constructed by spot weldi"zy an upper and a lower steel tray, to form the shape of the tile.

Yet another way of constructing a tile in accordance with the present invention is to cast a slab of lightweight concrete, then to mould a shell of a strong plastics material around all or part of the cast concrete. Again, the diagonal line of weakness can be created, in the moulded plastic coat, by any one of the techniques that may be used to weaken the tray 63 of the embodiment illustrated in Figure 6.

The slab or tile shown in Figures 8 and 9 comprises a pair of right-angled triangular slabs or tiles 80 joined along their adjacent hypotenuses by a hinge or flexible joint 81.

The joint 81 may be of any flexible material including metal and may conveniently be incorporated into the slab or tile during the simultaneous casting of the blocks The joint 81 may be replaced by a suitable hinge construction.

20 In the slab or tile illustrated in Figure 8, there is a S" chamfer 83 at each corner of the slabs 80 which are at the end of joint 81, and a syas of holes 84 I in the side walls of the blocks 80. Th chamfer 83 and i* *i

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Sthe holes chamfer 13 Figure 1.

features is In the illus have been c I been square 1 earlier in shapes, inc slabs or til 13 84 perform the same functions as the and holes 14 of the slab or tile 10 of Thus no further explanation of these required.

strated embodiments onsidered so far, or substantially this .specification, cluding a rhombus, es.

of the invention that the slab or tile has square. As recited other quadrilateral may be used for the $i $t It t C 1 C -9 Ci i 1, Some (or all) of the slabs or tiles used in a false floor may be provided with a small, covered opening," through which conduits and wiring may pass to the sub-floor space, and through which there is an access ,5 to the cavity formed beneath the false floor.

A modification of the present invention is the production of a composite panel comprising an assemblage of slabs or tiles which are constructed in accordance with the present invention. Two examples 20 of this modification are illustrated in, respectively, Figures 10 and 11.

'Figure 10 consists of a panel for use in the construction of a false floor which comprises nine square slabs. Typically, the panel is a square of side length 500mm or 600mm, and contains nine square slabs, each having a side dimension of about 200mm 4IIE '.44 4 444e 14 and a diagonal line of weakness 101. The line of weakness may be established by any suitable technique described above.

In the illustrated embodiment of Figure 10, at the corner of each rectangular slab portion, there is provided a leg 102 (see Figures 13 and 14)o The legs may be moulded with the slab or attached to it later. In an alternative arrangement (not illustrated), each rectangular section is provided with a single leg or support column at one of its corners, and solid dowel bonding is used to connect the corners of the triangle remote from the leg-carrying corner to the corresponding corners of the adjacent triangle. A layer of floor covering material (for example, carpet, as shown at 106 in Figure 14) may be bonded to the top of individual slabs of the panel to act as a binding membrane for the slabs and to provide a flexible bonding between adjacent triangular sections. An edge strip 105 is usually provided around the side of each composite panel.

Similar considerations apply to the panel illustrated on Figure 11, which is an assemblage of twelve rhomboidal slabs.

Figure 12 shows how three rhomboidal slabs, constructed S in accordance with the arrangement shown in Figures 8 and 9, each with each triangular portion 120 connected :i! U t *t 7.1-,'4 i 1 I r i I 1 15 to its adjacent triangular portions by hinges 121, and with supports 122 at each corner of a triangular portion 120, form a composite hexagonal panel.

The advantage of hexagonal panels is that when they used to construct a false floor, portions of the floor can be removed to provide access to the sub-floor and the buttressing (that is, the lateral thrust) of the remaining panels ensures that these panels do not move sideways to close or reduce the opening to the sub-floor. This "closing" phenomenum is often experienced with conventional false floor constructions, and is known as "creep" in computer floors. It will be appreciated that "creep" makes itdifficult to replace floor panels, and can endanger the stability of a false floor.

With panels of the type shown in Figures 10, 11 and 12, having a side length in the range from 150mm (in the case of a hexagonal panel) to 600mm (square or rectangular panels), it is possible to reduce the 20 thickness of each triangular component of the panel to about 6mm. If the legs 102 and 122 givre a sub-floor clearance of about 12mm, an overall height for the false floor is about 18mm. This arrangement 4. is particularly suitable for us- in buildings where the floor to ceiling height is about 2.4 metres.

A convenient method of constructing panels of the type illustrated in Figures 10, 11 and 12 is to mould the panels in one piece, using a rigid plastics material (or a metal). The edges adjoining each I i i I 16 rigid triangular portion are formed as thin strips of material by any suitable pressing technique. The thickness of each of these thin strips is such that it will flex and yet remain integrated with the triangular portions it connects.

INDUSTRIAL APPLICATION OF THE INVENTION The major applications of the present invention have 4 been mentioned already in the first paragraph of this specification. It may be noted that, when buildings :1 10 are constructed, the extent to which a floor may depart from being flat is recognised throughout the world by the standards laid down by each country. In Australia, for example, the standards laid down in" 4 AS 1480-1982 and AS 1509-1974 result in a requirement that a concrete floor in an office block must be flat to within 25 mm in a distance of 7.3 metres when 4t r the formwork is removed from the floor.

4 Subsequently, some creep deflection of the cast floor is likely. Observations of office buildings in general use have shown that a departure from flatness of 50mm in 7.3 metres is acceptable to tenants of the office buildings. A square slab of side 500mm, constructed as shown in Figure 1, with a diagonal groove 11 of width imm, is able to provide a stable C• f25 false floor above such a cast concrete floor.

It will be appreciated by civil engineers that the present invention is particularly suited for the construction of false floors over curved shapes such as domes, or over the surface formed by the intersection of inclined plahes.

i I i 17 When used to provide a protective surface or a sound-isolating surface, the joints between the assembled slabs will usually be fillsd with a jointing strip, mastic material, putty or the like.

A floor covering (such as carpet) may be laid on top of a false floor formed by an assembly of the slabs of the present invention. The floor covering may be bonded to the false floor by adhesive, or by using mechanical clips (such as plastic plugs).

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Claims (21)

1. 2. A tile as defined in claim i, in which said quadrilateral is a parallelogram, and said line of weakness is formed by a slot or groove formed in said S"concrete.
2. 3. A tile as defined in claim 2, in which reinforcing means is included in said concrete.
3. 4. A tile as defined in claim 3, in which said slot or i '[groove extends from the top surface of the tile to ~about 1 mm above said reinforcing means, and said reinforcing means comprises a mesh which is located above the base of the tile at a distance therefrom in t the range from 2 mm to 3 mm. Lhi 19 A tile as defined in claim 3, in which said reinforcing means is located at the base of the tile.
4. 6. A tile as defined in claim 5, in which the reinforcing means comprises a reinforcing mesh with upwardly projecting lugs.
5. 7. A tile as defined in claim 5, in which said reinforcing means comprises a reinforcing mesh formed from flat wire, said flat wire being twisted between cross-wries to increase the surface area of the mesh in a plane perpendicular to the plane of the mesh.
6. 8. A tile as defined in any one of claims 3 to 7, in which said reinforcing means is weakened along said diagonal line of weakness.
7. 9. A tile as defined in any one of claims 2 to 8, further S" characterised in that said tile has a chamfer at the corners thereof which are located at the end of the diagonal line of weakness.
8. 10. A tile as defined in claim 1, further characterised in that said quadrilateral is a parallelogram and said concrete is cast upon a metal tray.
9. 11. A tile as defined in claim 10, in which said line of weakness is formed by a slot or groove formed in said concrete. N tr 4g \a
10. 12. A tile as defined in claim 10 or claim 11, in which said metal tray is provided with a structural weakness along said line of weakness.
11. 13. A tile as defined in claim 12, in which the structural weakness in said metal tray comprises an incision, or a line of holes, or a ridged region of said metal tray.
12. 14. A tile as defined in claim 1, in which said quadrilateral is a parallelogram, and said concrete is cast upon a pair of triangular metal trays, each of said triangular metal trays having a side adjacent to and parallel to a corresponding side of the other metal tray, whereby said diagonal line of weakness is formed at the region between the adjacent sides of said triangular metal trays. i .fc 15. A tile as defined in claim 14, having a slot or groove S, formed in the concrete along said diagonal line of weakness.
13. 16. A tile as defined in claim 14 or claim 15, including zeinforcing means extending across said diagonal line of weakness.
14. 17. A tile as defined in any one of claims 2 to 16, in which said parallelogram is a rectangle, a square or a rhombus. H T -x S- 21-
15. 18. A tile as defined in any one of claims 2 to 17, including at least one hole formed in each side wall of the tile, for receiving a flexible plug.
16. 19. A tile as defined in claim 1, in which the concrete is located within a shell of a plastics material, and the line of weakness is created in said shell. A tile as defined in any preceding claim, including a respective leg at each corner of the tile, each leg extending below the tile and being attached to or formed integrally with the tile.
17. 21. A false floor formed by an assemblage of tiles as dfined in any one of claims 1 to 19, said assemblage of tiles being mounted on support columns or the like assemblage. I 22. A false floor formed by an assemblage of tiles as defined in claim
18. 23. A panel for a false floor, comprising a plurality of interconnected slabs or tiles, as defined in any one .of claims 1 to t 4
19. 24. A panel as defined in claim 23, said panel having a hexagonal shape. t ro 25. A false floor formed by an assemblage of panels as S defined in claim 23 or claim 24. Il C -22
20. 26. A tile for use in the construction of a false floor, substantially as hereinbefore described with reference to Figures 1, 2, 3, 4, 5, 6 and 7 of the accompanying drawings.
21. 27. A panel as defined in claim 23, substantially as hereinbefore described with reference to Figures 11, 13 eid 14 of the accompanying drawings. DATED this twenty-ninth day of June 1992 LIFHOLT PTY LIMITED By its Patent Attorneys DAVIES COLLISON CAVE I r:7 3t i I *T 7«*