GB2277459A

GB2277459A - Screen grid for overflow tanks

Info

Publication number: GB2277459A
Application number: GB9408349A
Authority: GB
Inventors: Werner Nill
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-30
Filing date: 1994-04-27
Publication date: 1994-11-02
Anticipated expiration: 2014-04-27
Also published as: ATA81594A; GB2277459B; DE4414094A1; FR2704448A1; AT400251B; DE9406759U1; GB9408349D0

Description

2277459 SCREEN GRID ARRANGEMENT FOR OVERFLOW TANKS The subject-matter of

the present invention is a screen grid arrangement for overflow tanks, flood relief installations and the like, having a grid comprising parallel strip-shaped rods disposed at a mutual distance apart and attached by their ends to a framework, and having a comb, movable along the grid rods, and whose teeth are intended to engage in the interspaces between the rods.

In the case of heavy rainfall, the waste water arriving at a sewage plant can no longer be directly fed as a whole to the treatment process, because the capacity of sewage plants is not designed to accommodate the maximum possible inflow. For this reason, sewage treatment plants are preceded by rain overflow tanks into which the incoming water is first diverted on such occasions. As long as the incoming amount of water can be absorbed by the treatment plant, no water flows to a main outfall or directly to a standing body of water. If the incoming amount of water exceeds the capacity of the treatment plant, the proportion which exceeds this capacity is diverted into the rain overflow tank. In order, however, to enable the coarsest impurities, particularly the floating ones, to be held back, the water is passed through screens or grids. In this respect, it is possible to move water through such screens or grids from the bottom upwards, in order to wash back the retained impurities after the rainfall and the like pass them to the treatment plant. A verticallydisposed grid can also fulfil this purpose, instead of a horizontal grid or screen. Such grids are conventionally disposed on an overflow rim separating the rain overflow tank from the feed to the main outfall.

- 2 Previously, substantially the same grids were used for the horizontal constructions, i.e. the stripshaped grid rods come to lie in a horizontal position. Experience has now shown that such rods, contrary to horizontal ly- lying grids, become fouled very rapidly and therefore require to be cleaned more frequently.

The purpose of the present invention is now to provide a grid arrangement for vertical ly-upright grids whose rods have a restricted tendency to fouling, and which are easy to clean.

According to the present invention there is provided a grid arrangement for rain overflow tanks, floodwater relief installations or the like, having a grid comprising parallel strip-shaped rods disposed at a mutual distance apart and attached by their ends to a framework, and having a comb, movable along the grid rods, and whose teeth are intended to engage in the interspaces between the rods, in which the side surfaces of the rods forming the interspaces are oriented at an angle inclined to the horizontal, and in which the edges of the rods which are situated lower are disposed on the inflow side.

By means of oblique positioning of the wide side of the strip-shaped grid rods it is possible to successfully prevent deposition of impurities on the upwardly-oriented side surfaces of the rods, even with a low throughput and velocity. In addition, the surfaces of the rods are freed of impurities lying on the rods when there is a drop in the inflow, i.e, when the excess water is reduced, by means of water already cleaned by the grids and flowing back. The profiles disposed on the inflow side and reducing the cross-sectional aperture between the individual rods retain impurities which could 1 - 3 j am between the rods. However, impurities which have entered between the profiles and have remained stuck there are simply removed by the teeth of a cleaning comb.

The present invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a cross-section through a rain overflow tank with a flood relief pipe lying adjacent thereto; Fig. 2 is an enlarged view of the cross-section through the grid, with a comb disposed on the outf low side; Fig. 3 is an enlarged view of the cross-section through the grid, with the comb disposed on the inf low side; Fig. 4 is a diagrammatic view of a grid with curved grid rods; Fig. 5 is a cross-section through an individual grid rod with a thickened profile disposed asymmetrically, and Fig. 6 is a diagrammatic view of a cross-section through a grid with adjustable grid rods (cleaning comb not shown).

In the floodwater relief installation 1 shown diagrammatically and in cross-section in Fig. 1, a relief or rain overflow tank 3 is visible on the left-hand side, and a relief channel 4 on the right-hand side. The relief channel 5, which is on a higher level than the overflow tank 3, is separated from the overflow tank 3 by an overf low wall 7 with an overf low rim 9. Mounted on the overf low rim 9 is a vertical ly-upright grid 11 with horizontally-disposed strip- shaped grid rods, e.g. metal or plastics profiles 13. The rods 13 are connected by their ends to the vertical portions of a framework 15 and lie at an inclined angle a to the horizontal, in such a way that the edges 17 situated lower come to rest on the inlet side, i.e. on the side of the relief tank 3. Profiles 19 may be attached to the edges 17, said profiles 19 having a rounded cross-section, which reduce the through passage aperture between adjacent rods 13, i. e. the space a. Consequently impurities which could still penetrate between the adjacent rods 13, are already retained by the preceding profiles 19. Jamming of large impurities between the rods 13 is in this way successfully prevented. The profiles 13 may be welded to the edges 17 of the rods 13. It is also possible to provide the rods 13 at the outset with a bead- shaped rim (profile 19), while they are being rolled or drawn.

On the inlet (Fig. 3) or on the outlet side (Fig. 2), a travelling comb 21 may be disposed, whose teeth 23 are attached on a vertical beam 24, and engage in the interspaces between adjacent rods 13. The width b of the teeth is slightly less than the spacing between the profiles 19, so that jamming of the teeth 23 in the rods 13 cannot occur during horizontal displacement of the comb 21. The teeth 23 may be pivotably attached to the comb 21. The development of a pivotal attachment of the teeth 23 on the comb 21 is not the subject-matter of this invention. A possible development is disclosed for example in DE-GM 9206114.1.

The comb 21 may be suspended in a travelling manner on one or a plurality of support rollers 25, and guided in a rail 27 on the framework 15 of the grid 11. As an alternative to rollers 25, the comb 21 may be 1 1 - 5 longitudinally movably guided at bottom and/or the top by means of sliding guides (not illustrated) on the framework 15.

As an alternative to grid rods 13 produced as flat profiles, curved grid rods may be used, according to the view in Fig. 4. These enable outflow of water on both sides as soon as the throughflow of water stops. Both longitudinal edges of these curved grid rods may lie at the same level or at dif f erent levels, so that, f or example, the water rising between the rods flows through the grid, as shown in Fig. 1. The teeth 23 of comb 21 have a corresponding curvature, ensuring perfect cleaning of the interspaces between the individual grid rods 13.

Profiles 19 may also be attached to the curved grid rods 13, preventing the penetration of impurities. The drive system for the comb 21, in the form of a linear drive with compressed air, oil or electricity may be located within a duct 12 formed on the grid 11.

The prof iles 19 need not only, as shown in Figs. 2 and 3, be attached or integrally f ormed on one of the edges of the grid rods 13, but, as Fig. 5 shows, may lie asymmetrically and project only over the underside. In a particularly advantageous development of the invention, the profiles 19 are a part of the grid rods 13, i.e. the profiled shape of the profiles 19 is produced by a rolling, edging or drawing process. In a further development of the invention, the grid rods 13 may be pivotably attached to the framework 15 of the grid 11. In order to securely hold the grid rods 13 in the selected angular position, and in order to alter this angular position, the edges of the grid rods 13 facing away from the pivotal axis are articulated to an adjustment means 29, e.g. a rod or a strip. The adjustment means 29 may be vertically displaced by a manual or automatic drive means 31. By means of the vertical displacement of the adjustment means, all the grid rods 13 of the grid 11 are pivoted synchronously.

In order to increase the throughflow passage of the grid 11 with a constant hydraulic level, the framework 15 of the grid 11 may be inclined to the vertical (not illustrated).

In order that, if there is an unexpectedly large occurrence of impurities which can no longer be removed by the comb 21, no damage occurs to the grid 11, the framework 15 of the grid 11 may be articulated to the overflow wall 7. This enables the grid 11 to be tilted, thus reducing the overflow height.

- 7

Claims

A grid arrangement for rain overflow tanks, floodwater relief installations or the like, having a grid comprising parallel strip-shaped rods disposed at a mutual distance apart and attached by their ends to a framework, and having a comb, movable along the grid rods, and whose teeth are intended to engage in the interspaces between the rods, in which the side surfaces of the rods forming the interspaces are oriented at an angle inclined to the horizontal, and in which the edges of the rods which are situated lower are disposed on the inflow side.
2. A grid arrangement as claimed in claim 1, in which the rods comprise flat iron components having a rectangular cross-section, or sheet metal strips having a cross-section in the form of a segment of a circle.
3. A grid arrangement as claimed in claim 2, in which profiles are attached to the inlet-side edges of the rods, said profiles having a substantially rounded cross-section and restricting the clear crosssection between the rods.
4. A grid arrangement as claimed in claim 3, in which the profiles are designed to form part of the rods and are manufactured by a rolling or drawing process, or in which the profiles comprise a rolled rim on the edge of a rod.
5. A grid arrangement as claimed in claim 2, 3 or 4, in which the teeth are attached at the same angle inclined to the horizontal on the comb as the rods, and in which the teeth are designed to project through the rods and the profiles.
6. A grid arrangement as claimed in any preceding claim in which the rods are pivotably articulated on the framework, whose inclination with respect to the horizontal is adjustable and displaceable by an adjustment means.
7. A grid arrangement as claimed in any preceding claim in which the grid is pivotal about a horizontal axis when overload occurs.
8. A grid arrangement as claimed in any preceding claim in which the drive system for the comb is located within a duct disposed on the upper edge of the grid.
A grid arrangement as claimed in claim 4, in which the profiles project only over the surface of the underside of the rods.
10. A grid arrangement for rain overflow tanks, floodwater relief installation or the like, substantially as hereinbefore described with reference to the accompanying drawings.

A 1