|
(11) | EP 0 561 538 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||
| (54) | Flexible sheets for use in the construction of cavity floors |
| (57) A flexible sheet (1) for use as a support in the construction of a cavity floor has
a plurality of legs (2) therein. Each leg (2) has a plurality of sections, comprising
a bottom section (3), one or more intermediate sections (4, 5, 6) and a top section
(7) each of which is polygonal in horizontal cross-section and has planar lateral
faces (8-16). The lateral faces (8) of the bottom section (3) of the leg (2) flare
upwardly at an angle of less than 60° to the horizontal, and the lateral faces (9-16)
of each of the remaining sections (4-7) flare upwardly in such a manner that the angle
between the lateral faces (9-16) and the horizontal decreases progressively from the
section (4) adjacent the bottom section to the top section (7) of the leg (2). |
[0001] This invention relates to flexible sheets for use in the construction of cavity floors. Although the sheets may be made of another material such as a metal, the invention is particularly concerned with flexible sheets of moulded thermoplastics material, and it is in the context of such sheets that the invention will be described.
[0002] It is common practice in the construction of so-called "cavity floors" to use a flexible sheet of a material such as a thermoplastics which is placed on a lower floor and which supports an upper floor. The flexible sheet has hollow legs moulded therein and when the floor is laid a concrete-forming composition is poured on to the flexible sheet, filling up the hollow legs and forming the upper floor layer on top of the sheet so as to produce a cavity floor.
[0003] It has now been found that a flexible sheet having legs of a particular shape and configuration offers certain advantages in the production of the sheet and its use in cavity floor construction.
[0004] According to the invention there is provided a flexible sheet for use as a support in the construction of a cavity floor, the sheet having a plurality of uniformly spaced legs therein, wherein each leg comprises a plurality of sections, comprising a bottom section, one or more intermediate sections and a top section, each of which is polygonal in horizontal cross-section and has planar lateral faces, the lateral faces of the bottom section of the leg flare upwardly at an angle of less than 60° to the horizontal, and the lateral faces of each of the remaining sections flare upwardly in such a manner that the angle between the lateral faces and the horizontal decreases progressively from the section adjacent the bottom section to the top section of the leg.
[0005] Although sheets having leg sections with other polygonal horizontal cross-sections may be used in a preferred embodiment of the flexible sheet of the invention the horizontal cross-section of the bottom section of the leg is a regular octagon, and the other sections have an irregular octagonal horizontal cross-section and lateral faces consisting of two pairs of opposite identical major faces of the same width and two pairs of opposite identical minor faces of the same width. Such a configuration produces a stronger floor compared with a similar leg design in which all the sections of the leg have a regular octagonal horizontal cross-section because the space between adjacent legs in the region of the top section of the legs is reduced, thus reducing in size zones of potential weakness.
[0006] The lateral faces of the bottom section of the leg preferably flare upwardly at an angle of 45° to the horizontal and the height of the bottom section is preferably less than about 5 mm in order to prevent electrical or other cables which pass through the cavity from being trapped by the legs.
[0007] The height of each of the other sections of the leg will vary depending on the overall height of the cavity which it is desired to construct but in each case it is preferred that the height of the bottom section and the height of the section adjacent to the bottom section together are the same as the height of each of the other sections.
[0008] In order to facilitate the passage of cables through the cavity it is preferred that irrespective of the overall height of the legs and the height of the cavity it is desired to construct the spacing of the legs in the sheet is the same.
[0009] As mentioned above the material from which the sheet is formed may be another material such as a metal but the material is preferably a thermoplastics material such as polyvinyl chloride, polyethylene, polypropylene or polystyrene. Polyvinyl chloride is the preferred thermoplastics material.
[0010] The flexible sheet of the invention has the following advantages:-
(1) The chamfer at the base of the legs facilitates moulding of the legs into the sheet by vacuum forming. When the legs are vacuum formed in a sheet the flat portion at the base of the leg has the same thickness as the original thickness of the unformed sheet while the lateral surfaces of the leg are thinner than the original thickness of the sheet. The shape and configuration of the legs of the sheet of the invention produce legs whose lateral surfaces have a smaller reduction in thickness compared to designs in present commercial use.
(2) The shape and configuration of the legs enable sheets to be readily stacked one on top of another so that the sheets can be transported in large numbers in a flat condition and without distortion. The sheets can readily be pulled apart because there is no vacuum suction effect between the stacked sheets and they remain flat even in cold climatic conditions. Furthermore because the sheets can be transported flat and they do not become distorted, they can be placed next to each other in use and joined simply by overlapping adjacent edges and fixing the overlapped edges together by means such as an adhesive. Certain existing moulded sheets are transported in the form of a roll, and on unrolling the sheets are distorted, they tend not to lie flat, particularly in cold climatic conditions, and they have to be designed with a special flexible jointing piece at the edge to enable adjacent sheets to be joined together.
(3) When filled with concrete the sheets of the invention are strong and stable. Existing sheets tend to be weak towards the bottom of the legs and can break in use. The legs in the sheets of the invention also contain relatively more concrete and this provides higher floor strength and reduced sound transmission. Since the sheets remain flat no problems arise due to the concrete floor being too thin in certain areas as can happen when using existing unrolled moulded sheets, and levelling pins which are used to control the thickness and eveness of the concrete floor can be placed on top of the sheet rather than on the base of the legs.
(4) The planar lateral sections of the legs are advantageous over curved lateral sections because the resulting cavity floor transmits sound less readily.
(5) The shape and configuration of the legs enables thermoplastics sheet of lower thickness to be used for producing the moulded sheet compared with sheet thicknesses which are normally used.
[0011] The invention is illustrated by way of example in the accompanying drawings in which
Figure 1 is a bottom plan view of part of a flexible sheet of thermoplastics material having a plurality of legs moulded therein according to the invention
Figure 2 is a side elevation of one of the legs of the flexible sheet of Figure 1 and
Figure 3 is a schematic representation of legs of a range of overall heights.
[0012] Referring to Figures 1 and 2 a flexible sheet 1 of thermoplastic material for use as a support in the construction of a cavity floor has a plurality of uniformly spaced legs 2 moulded therein.
[0013] Each of the legs 2 comprises five sections 3, 4, 5, 6, 7 each of octagonal horizontal cross-section. The bottom section 3 has a regular octagonal horizontal cross-section and lateral faces 8 which flare upwardly at an angle of 45°to the horizontal. The other sections 4, 5, 6, 7 have irregular octagonal horizontal cross-sections and two pairs of opposite identical major lateral faces 9, 10, 11, 12 of the same width and two pairs of opposite identical minor lateral faces 13, 14, 15, and 16 of the same width.
[0014] The lateral faces 9-16 of sections 4, 5, 6, 7 flare upwardly in such a manner that the angle between lateral faces 9-16 and the horizontal decreases progressively from section 4 through sections 5 and 6 to section 7.
[0015] In use a number of the flexible sheets are placed on a lower floor and joined together and concrete forming material is poured over the sheets so that it fills the hollow legs and forms a layer on top of the sheets, thus producing, on setting of the concrete, an upper floor separated from the lower floor by a uniform array of cavities.
[0016] Figure 3 shows the shape and configuration of the leg of flexible sheets according to the invention for producing a range of cavity heights from 50 to 130 mm. For each of the legs the height (h) of each of the sections and the length (s5) of the bottom sections are the same. The length (s1, s2, s3, s4) of the other sections varies depending on the overall height of the leg and the height of the cavity to be produced. The height (h) and the lengths (s1 to s5) for the range of legs in the drawing are shown in the table below.