GB2343385A

GB2343385A - Filter apparatus with tapering filter screen walls

Info

Publication number: GB2343385A
Application number: GB9824140A
Authority: GB
Inventors: John Martin Sill
Original assignee: Wedge Wire Screens Ltd
Current assignee: Wedge Wire Screens Ltd
Priority date: 1998-11-04
Filing date: 1998-11-04
Publication date: 2000-05-10
Anticipated expiration: 2018-11-04
Also published as: GB2343385B; GB9824140D0

Abstract

Filtering apparatus 18, for screening sewage or food waste, has tapering filter screen walls 20. The apparatus is preferably mounted in a vertical axis, with the filter screen walls diverging from the top end of the apparatus to the bottom end. Material to be filtered is fed onto the top of the apparatus, so that the liquid matter passes through the filter screen walls into the interior, while solid screenings are retained on the tapering filter screen surface. Preferably the filter screen is a frustro-conical drum, with concave walls (fig 2), which may be made out of wedge wire. The apparatus may be provided with a vibrating mechanism 38 in order to remove the screenings, or may be rotatable. In order to ensure an even distribution of material from the inlet, a distribution cone 24 may be provided, or alternatively there may be a collection area (52, fig 3) with overflow weir (50, fig 3). The solid screenings may slide down the outer surface to a collective funnel 36, while the liquid phase can be reused or disposed.

Description

Improvements Relating to Screening Apparatus This invention relates to screening apparatus, and is for use in the screening of fluent materials which in the interest of simplicity can be described as having a solid material phase and a liquid material phase, which have to be separated. Such screening apparatus is well-known in connection with the screening of sewage.

Conventionally, screening apparatus comprises a large circular screening drum having screening panels or meshes thereon, and the fluent material is applied to the drum screening surface either from the inside or from the outside, so that the liquid phase is separated from the solid phase by means of the screens.

These drums are arranged with their axes horizontal and are usually are rotatable, and the solid material, the screenings, typically will be scraped from the drum screen whilst the liquid phase which has separated from the screenings is led away for possible reuse or for disposal as waste.

Rotation of the drum is required in order that the drum will present a large surface treatment area, but of course the inclusion of a rotary mechanism increases the complexity of the apparatus, the space it occupies and also the expense.

The present invention seeks to provide a screening apparatus which will provide a large amount of screening area to be accommodated within a relatively small space whilst the apparatus still provides a high through put of the material to be screened.

In accordance with the present invention the apparatus comprises a screen assembly of tapering form and the apparatus is adapted to be arranged so that in use the tapering is divergent in a downwards direction.

By this means, the material can be fed onto the top of the screen and it will shed down the tapering screen so that the liquid passes through the screen into the interior thereof, whilst the screenings are retained on the tapering screen surface.

It can be seen that such a construction enables the apparatus to be accommodated in a relatively small space, and furthermore it is not necessary that the screen should be rotated as all of the screen surface is effective by the pouring of the material onto the screen at the top end.

It may be desirable, although not necessary, to have the screen capable of being vibrated in order to dislodge screenings from the screen surface so that they can be collected, and to allow fresh material to be charged onto the screen surface.

The screen is preferably a wedge wire screen, but it could be of alternate construction.

The wedge wires may extend longitudinally and/or circumferentially as required, and in a preferred case the screen is of a conical configuration and is in fact frusto-conical with a solid distribution cone being provided at the top end of the screen. The solid distribution cone may be of larger cone angle than the screen, and there may be a feed inlet pipe for the incoming material in order to distribute the material evenly over the distribution cone which in turn causes the material to flow evenly down over the outer surface of the screening cone. In another embodiment the screen may have side walls which are concave in shape to suit particular requirements. In a yet further embodiment the supply to the screen is from an overflow weir assembly rather than via a distribution cone.

The screening apparatus preferably has an outer casing in which the screen assembly is contained, and appropriate liquid and solid discharge ducts may also be provided.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings; wherein Figure 1 shows in sectional elevation screening apparatus according to one embodiment of the invention; Figure 2 illustrates screening apparatus with a drum with concave side walls; and Figure 3 illustrates apparatus with an overflow weir supply means.

Referring to Figure 1 the apparatus comprises an outer casing 10 having a top 12 and support legs 14 by which the apparatus is supported upright. On a platform 16 inside the casing 10 is supported the screening assembly 18 which comprises a frustoconical screening drum 20 arranged with its axis vertical, and its larger diameter lowermost. On top of the screening assembly 20 is a distribution cone 24 which fits into a distribution funnel 26 at the end of a feed inlet pipe 28.

The lower side of the screening drum 20 is closed by a deflection plate 30 which leads to a liquids discharge funnel 32 which eventually discharges to a pipe 34.

Under the platform 16 is a collection funnel 36 for collecting separated solids or screenings.

The screening assembly is mounted on the platform 16 by means of a vibration mounting 38 by which the drum 20 can be vibrated for dislodging screenings from the outer surface thereof. Rotation of the screen assembly can be provided if selected but the same can operate efficiently when rotated or stationery.

The operation of the apparatus will be understood from the above, but to summarise, the material to be screened is fed into inlet pipe 28, and then is distributed over the distribution cone 24. It pours evenly and regularly over the outer surface of the screening drum 20, and as a result the liquids content flows into the inside of the drum 20 as shown by arrows 40 whilst the screenings collect on the outer surface of the screen 20 as shown by reference 42. The screenings fall into the collection funnel 36 as indicated by arrow 44, whilst the liquid phase of the screened material is collected in the funnel 32 and eventually is discharged through the pipe 34.

Should it be necessary, the assembly 18 is vibrated by the vibrating mechanism 38 to dislodge screenings 42 from the outer surface of the screen to cause them to fall into the funnel 36.

The vibratory arrangement is an optional extra, as the device can be utilised without any vibration mechanism.

Instead of using the distribution cone 24 at the top of the screen, an overflow weir 50 may be adopted as shown in Figure 3, wherein the material flows into a collection area 52 from pipe 54 and then overflows over the weir 50 to run down and be separated by the walls of the screening assembly. Thus in any of the embodiments there is even distribution of the material to be screened over the conical drum 20.

The solid matter of screenings may build up and eventually slide down the outer surface of the screen under its own weight to the collective funnel 36. The screenings can be disposed of in conventional manner. The liquid phase can be reused or disposed of as waste.

As shown in Figure 2 the side walls of the drum 20 can be concave shaped 29 to improve the operation of the apparatus in certain instances.

The apparatus according to the invention enables a large amount of screening area to be accommodated within a small confined space and provides a high throughput of feed material. Also, the solid screenings and filtered liquid can be contained within a small confined area within the unit.

Although a conical screen is preferred, it could be of other tapering configuration.

Claims

CLAIMS 1. Screening apparatus comprising a screen assembly with tapering walls and said apparatus adapted to be arranged so that in use the tapering is divergent in a downwards direction.

2. Screening apparatus according to claim 1 wherein the screen assembly is mounted in a substantially vertical axis with screen walls diverging from the axis from the top end of the screen assembly to the bottom end.
2. Screening apparatus according to claim 2 wherein material to be screened is fed onto the top of the screen assembly and sheds down the tapering screen walls so that the liquid passes through the screen into the interior thereof whilst the screened material is retained on the tapering screen walls surface.
3. Screening apparatus according to claim 1 wherein the screen assembly is vibrated in order to dislodge screenings from the screen walls surface to be collected.
4. A screening apparatus according to any preceding claims wherein the screen walls are manufactured from wedge wire material.
5. Screening apparatus according to claim 4 wherein the wedge wire extends longitudinally and/or circumferentially of the screen walls.
6. Screening apparatus according to claim 1 wherein the screen assembly walls are provided in a conical configuration.
7. Screening apparatus according to claim 6 wherein the screen assembly walls are provided in a frusto-conical configuration with a distribution cone provided at the top end of the screen.
8. Screening apparatus according to claim 7 wherein the solid distribution cone is of a larger cone angle than the screen assembly walls.
9. Screening apparatus according to claim 7 wherein there is provided a feed inlet pipe for the incoming material to be screened in order to distribute the material evenly over the distribution cone which in turn causes the material to flow evenly down over the outer surface of the screen assembly walls.
10. Screening apparatus according to claim 1 wherein the screen assembly has side walls which are concave in shape to suit particular screening requirements.
11. Screening apparatus according to any of claims 1-8 and 10 wherein an inlet feed arrangement is provided so that the material to be screened flows onto the assembly over an overflow weir.
12. Screening apparatus according to any of the preceding claims wherein the screening apparatus includes an outer casing in which the screen assembly is contained and appropriate liquid and solid discharge ducts are provided in the outer casing for the screened materials.
13. Screening apparatus as hereinbefore described with reference to the accompanying drawings.