AU657809B2 - A grating - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: Actual Inventor: Address for Service: Invention Title: Details of Associated Provisional Application No: PHILIP GRAHAM BREENE Philip Graham Breene TREVOR DREDGE ASSOCIATES Patent Trade Mark Attorneys 13th Floor, 379 Queen Street BRISBANE, QLD, 4000 (GPO Box 1339, BRISBANE, 4001) "A Grating" Australian Patent Application No.

PK9520 filed 15 November, 1991.

The following statement is a full description of this invention, including the best method of performing it known to me: 2 THIS INVENTION relates to a grating and in particular but not limited to a roadway drainage grating suitable for use in conjunction with, and adjacent to, a roadway kerb or raised median for collection of water flowing along the roadway.

The applicant's Australian Patent No. 471,361 teaches a roadway drainage grating having a plurality of spaced water flow through slots which in use extend in the direction of water flow across the grating and in most cases, this is also the direction of traffic flow along the roadway. The grating is of a "drop in" type in that it .0 drops in to the frame and is removed completely to open and 44 4give access to the gully pit. This type of grating has high hydraulic efficiency but is unsafe because thin bicycle tyres can pass through the slots, thus this form of 0 grating potentiates injury to cyclists. Other forms of a roadway drainage grating include a plurality of slots which in use are set transverse to the direction of flow. These drainage gratings are safer than the grating of Patent No.

471,361 but have low hydraulic efficiency because of turbulence, water tends to skip across the grating.

Another problem with the aforementioned gratings of a drop in type is that because they are usually employed over a gully pit, from time to time, access to the gully pit is required and such gratings do not provide ease of access to the gully pit.

It is an object of the present invention to alleviate at least to some degree the aforementioned problems

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3 associated with the prior art.

In one aspect therefore, the present invention resides in a drainage pit comprising a grating set above the pit in a surface having means inducing a flow of water in a predetermined direction across the grating, the grating having a plurality of apertures defining a grid-pattern, the apertures having water flow through passages including grating wall portions, some of said grating wall portions, in use, being set across the direction of water flow, said wall portions set across the direction of water flow having So underflow means to promote a curved flow of water through the grating adjacent the wall portion.

The underflow means is typically a passive part of the grating on which water impinges so that due to generally continued downstream flow, the underflow means causes a greater proportion of water to flow through the grating than would otherwise be the case should the underflow means be omitted. Advantageously, the underflow means comprises an undersurface extending cross-stream and receding in the downstream direction so that water impinging on the undersurface is deflected through the grating in a curved fashion and continues to travel downstream and thereby reduces turbulence. In a most advantageous form, the grating employs an upstanding step means adjacent the underflow means, the underflow means generally underlying the step means so that water flowing over the grating is interrupted by the step means to reduce the tendency of water to "skip" across the grating. Advantageously, the 4 underflow means are arranged so that the grating has universal operation independent of the direction of water flow over the grating.

The grating typically comprises a plurality of longitudinally and transversely extending frame members, the transversely extending frame members having the underflow means defined by said members being generally truncated having a smaller edge below a larger edge.

Typically, the larger edge of the transversely extending frame members form the upstanding step means by projecting above the longitudinally extending frame members.

The transversely extending frame members can be any shape that provides the underflow means but is typically generally triangular in transverse section thereby providing underflow means in opposite directions.

In order that the present invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:- :Figure 1 is a plan view illustrating a grating according to a preferred embodiment of the present invention; Figure 2 is a section drawn to enlarged scale taken through 2-2 of Figure 1; Figure 3 is a plan view of a grating support frame suitable for use with the grating of Figure 1; Figures 4 and 5 are respective longitudinal and transverse sectional views illustrating a grating assembly according to the present invention, the grating assembly is shown in situ and employing the grating of Figure 1 and the grating support frame of Figure 3; and Figure 6 is an end view of the grating of Figure 1.

Referring to the drawings and initially to Figures 1 and 2, there is illustrated a grating 10 suitable for use adjacent to a kerb or raised median of a roadway to intercept water flowing along the roadway in the direction of arrow 11 (or in the opposite direction), the grating has a plurality of apertures 12 defined by longitudinal frame members 13 and transverse frame members 14 which define a grid-pattern of apertures, the apertures define water flow through passages having wall portions which in this case include underflow means in the form of undersurfaces which recede in the downstream direction according to flow across the grating. Water flowing above the grating will continue to travel in the downstream direction and follow a generally curved path adjacent the undersurfaces Each of the transverse members 14 also project above the frame members 13 to form upstanding steps 16 which intercept flow of water along the longitudinal members 13.

Turbulence is reduced and the tendency of water to "skip" across the top of the grating is reduced. Hydraulic efficiency of the grating is improved. As can be seen in Figure 2, each transverse grating member is of modified triangular section in which the apices are truncated to form the steps 16. The surfaces 15 may be made flat or 6 concave in shape as indicated in phantom to facilitate easy removal of a pattern from a mould to simplify manufacture by casting.

In Figure 2:t width of a member 14 s width of opening between members 14 w width of lower truncation dl depth of step 16 on the sides of members 14 d2 depth of members 14 below the step 16 The preferred relations between these measurements are as follows:dl lies between 2mm and o (dl d2) lies between 0.5 and 2.0 times t; and s lies between 1.0 and 6.0 times t.

In an example generally effective for a kerbside I o grating, the dimensions are:t 0o O dl 00 2 d2 o 20 w 6mm s It will be seen from the preferred ratios of t and s that the ratio of the open area of the grating to its total area may range from 0.16 to 0.50.

While the direction of flow is normally at 90 degrees to transverse grating members 14, it may be at an angle as low as 30 degrees to these members.

This grating 10 fits in the frame 23 shown in Figure 7 3, the grating being supported on end rebates 17 and an optional seating 18 to lie flush with the road or gutter surface (see Figures 4 and The frame includes a frame edge 19 which extends round three sides of the frame, the fourth being a relatively thin bar 20. Extensions 21 on the level of rebate 17 are provided to support bar 22 (see Figure 1) during insertion of the grating and prevent the grating from dropping through the frame 23 as it is slid endwise into position.

The grating 10 may be hinged within the frame using concealed hinge means by way of a recess 24 in support bars 22, which match respective stubs 25 cast in a corresponding position on the frame 23. The stubs would not be employed where the grating simply slides into position. The hinge means would permit the roadway edge 26 of the grating to be raised and rotated up and towards the kerb 27 while pivoting on the stubs Figure 5 shows a grating 10 in its frame 23 adjacent a kerb 27 and feeding to a gully pit 28 adjacent a gutter.

20 The grating 10 and frame 23 combination, are sloped towards kerb 27 to conform with the slope of the gutter. Bar 20 of the frame is spaced from the projecting kerb face 30 to Sgive a kerb inlet 29 not appreciably impeded by the thin bar 20. Bar 20 is beneath the projecting face 30 of the kerb inlet 29 and so cannot be subjected to traffic loads.

The overall hydraulic efficiency of the grating as described is increased by at least two factors:- Once the restricted area of opening at the surface has i 0 00 o0 0 00 0 000 0 0 0 00 00 0 00 00 0 00 0 C 0t00 000 o 0 0 0 0 00 00000 0 0 been passed by the flow, the water enters a wider area for free fall into pit 28.

The receding undersurfaces of members 14 which face the flow cause the flow to be deflected into the pit using the energy of the flowing water to improve the capture of water into the pit.

The small height of the steps given by vertical section having measurement dl in proportion to measurement d2 minimises the tendency of the flow to dam up against the 10 members 14 and so minimises the tendency of flow to skip from bar to bar across the grating.

It will be apparent that in certain circumstances only some instead of all of the transverse bars need to have the aforedescribed underflow means and not all need be of modified triangular section but many other mechanically equivalent arrangements will be apparent to those skilled in the art.

Other features illustrated in the drawings include the generally tapered form of the longitudinal and transverse 20 members 13 and 14 which serves to assist in removing the cast grating from a mould. Likewise, in the illustrated embodiment as shown in Figure 4 and also in Figure 6, the longitudinal frame members 13 are tapered adjacent their respective opposed ends so that they are strengthened in the middle but the quantity of cast material employed is minimised by this feature.

The illustration of Figure 6 is an end view of the grating of Figure 1 showing that portion of the grating p- 9 remote from the kerb and as can be seen, the two central transverse frame members include support extensions 31 and 32 which seat on the rebate 18 of the frame illustrated in Figure 3 to provide additional support to the grating.

Whilst the above has been given by way of illustrative example of the present invention, many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set forth in the appended claims.

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Claims (9)

1. A drainage pit comprising a grating set above a pit in a surface having mear,: inducing a flow of water in a predetermined direction across the grating, the grating having a plurality of apertures defining a grid-pattern, the apertures having water flow through passages including grating wall portions, some of said grating wall portions, in use, being set across the direction of water flow, said wall portions set across the direction of water flow having underflow means to promote a curved flow of water through the grating adjacent the wall porti 4

2. A drainage pit according to claim 1 wherein the underflow means comprises an undersurface extending cross- stream and receding in the downstream direction so that water impinging on the undersurface is deflected through the grating in a curved fashion and continues to travel downstream and thereby reduces turbulence.

3. A drainage pit according to claim 1 or claim 2 wherein the grating employs an upstanding step means, extending cross-stream and profecting into the flow of water adjacent the underflow means, the underflow means generally underlying the step means so that water flowing over the grating is interrupted by the step means to reduce the tendency of water to "skip" across the grating.

4. A drainage pit according to any one of the preceding claims wherein the grating comprises a plurality of longitudinally and transversely extending frame members, the transversely extending frame members having the Sunderflow means defined by said members being generally M 11 truncated giving a smaller edge and a larger edge and having the smaller edge below the larger edge.

A drainage pit according to claim 4 wherein the larger edge of the transversely extending frame members form the upstanding step means by projecting above the longitudinally extending frame members.

6. A drainage pit according to any one of the preceding claims wherein the transversely extending frame members are generally triangular in transverse section thereby providing underflow means effective in opposite directions.

7. A drainage pit substantially as described with reference to Figure 2 of the drawings wherein:- t width of a member 14 s width of opening between members 14 w width of lower truncation dl depth of step 16 on the sides of members 14 d2 depth of members 14 below the step 16 The preferred relations between these measurements are as follows and where:- dl lies between 2mm and (dl d2) lies between 0.5 and 2.0 times t; and s lies between 1.0 and 6.0 times t.

8. A drainage pit according to any one of the preceding claims wherein the ratio of the open area of the grating to its total area ranges from 0.16 to 0.50.

9. A drainage pit substantially as described with reference to the accompanying drawings. A drainage pit employing a grating according to any i 12 one of the preceding claims, a frame supporting the grating and a concealed hinge holding the grating and frame together. DATED this 16th day of November, 1992. PHILIP GRAHAM BREENE By his Patent Attorneys TREVOR DREDGE ASSOCIATES 00 o0- u f 0 000 0 0 0000 0 '0 ABSTRACT A grating 10 suitable for use adjacent to a kerb or raised median of a roadway to intercept water flowing along the roadway in the direction of arrow 11 (or in the opposite direction), the grating has a plurality of apertures 12 defined by longitudinal frame members 13 and transverse frame members 14 which define a grid-pattern of apertures, the apertures define water flow through passages having wall portions which in this case include underflow means in the form of undersurfaces 15 which recede in the downstream direction according to flow across the grating. Water flowing above the grating will continue to travel in the downstream direction and follow a generally curved path adjacent the undersurfaces ei a 0 0