AU620283B1 - Drainage grating - Google Patents

Description

t m t i i 620283 COMPLETE SPECIFICATION FOR A STANDARD PATENT

AUSTRALIA

Patents Act 1990 Name of Applicant(s): Actual Inventor(s): Address for Service: DAVID ALBERT WEIGALL DAVID ALBERT WEIGALL CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, Qld. 4000, Australia.

4 4P a ot

I

'a I i .4 Invention Title: DRAINAGE GRATING Details of Associated Provisional Applications: Nos. PK 1059 The following statement is a full description of this invention, including the best method of performing it known to me: i~L U_ me appiicanits) or me appllcatons) listea in te declaration unOer Anrcie ou ui r I or L entitled to rely on the application(s) listed in he declaration under Article 8 of the PCT.

(Continued over) a 2 i THIS INVENTION relates to drainage devices and is particularly concerned with gratings for draining subsurface water and for permitting air circulation below ground level.

Many forms of subsurface drainage devices are available for draining water from water laden ground. These range from the common general purpose "Agricultural" or "AG" pipe which is a slotted corrugated plastic pipe varying in diameter from about 25 mm to about 150 mm, to more elaborate structures such as exemplified by the multilayer drainage matting of Australian Patent Specification AU 68,533/87. All these drainage devices however have one disadvantage or another. In the case of "AG" pipe, it is not usually suitable o for placement close to ground surfaces which are subject to

O.

heavy traffic since in this environment it is liable to i~5 collapse and to loose the majority of it's effectiveness.

o P Furthermore, when it is used in an appropriate location, it must always be used along with aggregate which necessitates excavating a relatively large trench to ensure that the pipe Sis sufficiently covered with the aggregate so that clogging of Q the pipe with ground soil is prevented. While these problems

S

have been overcome by more recently developed drainage systems 0 4 such as the aforementioned matting, this has been at a substantial cost which, in many cases, potential customers are a.

unable or unwilling to bear.

It is therefore an object of the present invention to provide an alternative form of subsurface drainage which can withstand heavy traffic, does not require massive excavations for use, and which is economical to produce.

i 3 According to the present invention, there is provided a drainaye grating comprising two sheets of plastics material spaced from one another by a plurality of load bearing ribs arranged in rows, said grating including a multiplicity of openings in each of the sheets wherein the openings in one sheet are substantially aligned with the openings in the adjacent spaced sheet and wherein the area of the openings in each sheet is less than 40% of the total surface area of each sheet.

The drainage grating may be manufactured by injection moulding or by extrusion in the form of a single sheet which can be mated with another substantially identical I sheet or which can be folded in two and fitted together by 4Ii I heat welding or press-fitting. Injection moulding is preferred as it permits a particularly strong integral LI r O structure to be formed which can withstand loads which are substantially greater than can be withstood by conventional "AG" pipe. Furthermore, the fact that the product can be produced in a substantially one-step operation means a very t I *2G' economical product results which is very competitive compared with the previously mentioned multilayer drainage.

The ribs are suitably solid or, preferably, hollow projections which are formed integrally with one or both S sheets. The ribs are preferably formed in both sheets such that approximately one-half project in rows from one sheet and the remainder project in rows from the other sheet. Most preferably, the ribs in any one row comprise alternate projections from each of the sheets.

9 i- 4 The location where the ribs projecting from any one sheet meet the other of the sheets can be such as to enable press-fitting or welding of those ribs to the other of the sheets to ensure 4 rigid structure is produced. Rigidity of structure can also be achieved by an edgewise integral connection between the sheets, along one pair of opposite edges.

As defined above, the area of the openings in each sheet is less than 40% of the total surface area of each sheet. This is not only to ensure that the drainage grating has sufficient structural integrity (the greater part of which is provided by the ribs) but also to ensure that large pieces 0 l oo of ground material do not pass into the grating and cause blockages. Most preferably the area of the openings is less than 25% of the total surface area of each sheet.

The shape of the openings is generally chosen to a nG maximise the flow of water into the grating and to this end will generally be circular or rectangular, most preferably square. Typical dimensions will be in the range of 5 mm X mm to 20 mm X 20 mm.

The overall structure of the grating will be such as a' to provide uninterrupted channels for water to flow through in one of the two directions at right angles to one another. The a a channel of predominant water flow will be the one which is placed to coincide with the direction of water removal and it may be desirable to have the base on which the grating is placed, graded downwardly in such a direction. This is not, however, essential as water will still tend to find its way out from a horizontally placed grating.

Preferably, the grating is formed in modules which interconnect edgewise with one another. This may be achieved my forming o,pposite edges with complementary profiles and connecting the modules with clips through the openings located adjacent to those edges. Suitable size modules measure approximately 300 mm X 550 mm.

The grating may include a filter fabric of known type as a membranous cover extending over one or both of the componentry sheets. The purpose of such a filter fabric is to prevent the aggregate, soil or other ground material from clogging the openings or the channels in the grating which would impede the natural flow of water.

The grating may be manufactured from a wide range of 4* 1"f plastics materials; the major criteria being that the plastics 0 00 S material is capable of being moulded and is capable of forming a rigid self-supporting structure. Preferred plastics materials are high density polypropylene, polyethylene and 0 polyvinylchloride.

The gracing thus produced is very economical and can o0 6 withstand heavy traffic at low subterranean locations. It can 00 a oe 0 also be used in much smaller sized excavations than conventional "AG" pipe.

Preferred embodiments of the invention will now be described with reference to the accompanying drawing, in which:- 'igure i is a partially cut-away elevational view of a grating according to the aspect of the invention; 6 Figure 2 is a cross-sectional view of the grating of Figure 1, Figure 3 is a partial plan view of a second embodiment of the invention; Figure 4 is a cross-section of Figure 3; and Figure 5 is a partial top perspective view of the Figure 3 embodiment.

Referring firstly to Figures 1 and 2, there is illustrated a moulded polyethylene grating comprising a first sheet 10 and a second sheet 11 separated by a plurality of rows of ribs 12. The sheets form integral rigid structures and the ribs are designed to prevent collapse of the sheets under loading by the passage of traffic thereover when the grating is in situ. Naturally, the degree of rigidity and strength of the grating will be adapted to the type of traffic S which is expected to pass over the grating since it would be uneconomical to utilize a grating designed, for instance, to withstand 10 tonne trucks when only foot traffic is contemplated. Consequently, the particular density of plastics material and the thickness and design of the ribs and sheets will vary from application to application.

The ribs 12 are in the form of rectangular perpendicular walls which extend from the inner planar faces of the sheets 10, 11. The ribs are equidistantly separated from one another so as to form a uniform pattern throughout the grating.

Rows of rectangular-shaped openings 13 in first sheet 10 are formed co-linearly with the rows of ribs 12 and L u- L__i 4L~ 1 7 align with similar dimensioned openings in the second sheet 11. The alignment of the openings in both sheets is such as to form a passage between adjacent ribs in each row.

The number of openings account for approximately of the surface area of each sheet and are more than adequate to allow for the rapid passage of large volumes of surrounding ground-water therethrough into the grating. Once in the grating, the water is immediately dispersed along one of the passages 14 or 15, depending upon the location of the outlet, in a smooth laminar flow pattern.

The grating depicted has excellent load-bearing capacity in view of the large number of ribs which are capable *oo of transmitting loads from one sheet to the other and can

S'

l therefore be used in locations where normal "AG" pipe would be T 1 prone to collapse. The sheet-like structure also means that it can be laid to immediately take off the ground water in a particular region, rather than small locations in that region as in the case of "AG" pipe, and has significant economic advantages over currently available drainage mats.

Referring now to the second embodiment illustrated in Figures 3, 4 and 5, the grating comprises a first sheet and a second sheet 21 separated by a plurality of rows of hollow ribs 22 which alternatively extend from one sheet and S, then the other. The ribs are columnar in shape and are pressfitted to the opposite sheet at locations 23. Such pressfitting may be accompanied by heat sealing if necessary.

Openings 24 in aligned array extend through the sheets.

-I

i~.t The grating may be connected to an adjacent similarly configured grating by interlocking end 25 with a complementary configuration on the other grating. Surclips, not illustrated, may be utilized to this end.

Passageways for disposal of water in a smooth laminar flow pattern are formed similarly to the previous embodiment.

The grating also has excellent load bearing capacity and exhibits substantial benefits over existing products.

Whilst the above has been given by way of illustrative example of the invention, many modifications and variations may be made thereto by persons skilled in the art 6"a o without departing from the broad scope and ambit of the °8 invention as herein set forth in the following claims.

660 9. 0 4t 4 a t a a r i

S

Claims (11)

1. A drainage grating comprising two sheets of plastics material spaced from one another by a plurality of load bearing ribs arranged in rows, said grating including a multiplicity of openings in each of the sheets wherein the openings in one sheet are substantially aligned with the openings in the adjacent spaced sheet and wherein the area of the openings in each sheet is less than 40% of the total surface area of each sheet.

2. A drainage grating as claimed in claim 1, wherein f, the ribs are hollow projections formed integrally with one or both sheets.

3. A drainage grating as claimed in claim 2, wherein approximately one-half of the ribs are formed integrally with one sheet and the remainder are formed integrally with the other sheet.

4 o 4. A drainage grating as claimed in claim 3, wherein the ribs arranged in any one row comprise alternate I% projections from each of the sheets.

A drainage grating as claimed in claim 4, wherein the ribs formed integrally with one sheet are either press- fitted or heat welded to the other sheet.

6. A drainage grating as claimed in any one o- the preceding claims, wherein the openings are rectangular in shape.

7. A drainage grating as claimed in any one of the preceding claims, wherein the area of the openings in each sheet is less than 25% of the total surface area of each sheet.

8. A drainage grating as claimed in any one of the preceding claims, wherein the two sheets are integrally connected along one pair of opposite edges.

9. A drainage grating as claimed in any one of the preceding claims, which is formed in modules which interconnect edgewise with one another.

A drainage grating as claimed in any one of claims 1 S 8, which is formed in a continuous length.

11. A drainage grating as substantially as herein described with reference to the accompanying drawings. DATED this 2nd day of July 1991 DAVID ALBERT WEIGALL By his Patent Attorneys CULLEN CO. 4 000 o 4 4 4( '4 i1 4 td ABSTRACT A drainage grating for subsurface water. It comprises two perforated sheets of plastics material (10, 11) separated by a plurality of load bearing ribs The openings (13) through which the water passes into the grating have a surface area which is less than 40% of the total area of each sheet. The grating may be produced by injection moulding or extrusion in two sections which are pressed together. Sto I geo 41 9 0 9 It