GB2124922A - Filter for effluent screening - Google Patents

Abstract

Solids are removed from effluent in tank 2 by an endless, inclined, moving belt in the form of a flexible elastomeric backing strip from which project rows of wire teeth, which catch the solids and lift them to where they are removed by a rotary brush 14 and spray pipes 15,16. Solids brushed from the belt are fed from receiver 11 into rotary sieve 12. The teeth are bent halfway along their length, and the belt may have areas without teeth (Figure 2 not shown). <IMAGE>

Description

SPECIFICATION Improvements in filter screens for effluent screening This invention relates to filter screens for effluent screening of the kind in which movable endless belt is disposed at such an attitude relative to the horizontal that projections on the outer face of the delivery run of the belt are adapted to separate solid material from effluent and elevate same from a sump at the lower end of the belt to a receiving station adjacent to and disposed below the upper discharge end of the belt.

In known filter screens of the kind set forth the belt comprises a grid consisting of rows of longitudinally extending links of which the links in each row are pivotally connected at opposite ends to adjacent ends of the links in adjacent rows, and each link incorporates an integral hook portion defining the projection. Rods may be passed through adjacent openings in the hook portions in a common row to assist the removal of the solids from the sump. Filter screens of this kind are relatively expensive to produce and maintain, and it is a time consuming operation to replace any of the links which may fail in service, particularly when the links are constructed from a plastics material.

According to our invention in a filter screen of the kind set forth the belt comprises an endless flexible backing strip, and rows of discrete teeth are carried by the strip project and from the outer face of the strip.

In operation solid material is separated by the teeth in a comb-like manner, and the material is elevated particularly by the uppermost edges of the rows on the delivery run.

The length of the teeth, and the spacing between adjacent rows, are chosen in accordance with the type of effluent with which the screen is to be used.

For example, the length of the teeth and the spacing between the rows may be greater if the screen is to be used with effluent from slaughter houses, than will be required when sewage is to be treated.

In one construction the teeth are arranged in parallel rows across the width of the belt to define an array, and longitudinally extending gaps of substantial lengths are provided in the array by the omission of teeth over discrete areas. The gaps are spaced across the width of the belt in parallel rows and the gaps constituting one such row are displaced transversely with respect to the gaps constituting the two adjacent rows of gaps. Preferably the gaps are all arranged at substantially constant pitch.

Preferably the teeth are manufactured from metal, suitably stainless steel wire, and the backing strip is manufactured from any suitable synthetic plastics or other natural or synthetic elastomeric material.

The belt acts to divide the sump into separate supply and return compartments, the effluent to be treated being conveyed to the supply compartment from which the delivery run of the belt extends, and the return run of the belt passing through the other compartment, whereby to rinse the belt before entry into the return compartment.

Two embodiments of our invention are illustrated in the accompanying drawings in which: Figure 1 is a side elevation of a filter screen; Figure 2 is a part section of the belt of the screen of Figure 1; Figure 3 is a side elevation of another construction of filter screen with a part of the wall of the sump omitted for clarity; Figure 4 is a plan of the filter screen of Figure 3; Figure 5 is an end elevation; and Figure 6 is a section through the tail drum.

The filter screen illustrated in Figure 1 of the drawings includes two spaced members 1 of channel outline with are supported at their lower ends in a sump 2 for effluent. The members 1 extend from the sump 2 at an angle which is inclined with respect to the vertical and are supported at intermediate points in their lengths on a framework 3 which is upstanding from ground surrounding the rim of the sump 2.

An upper driven head drum 5, and a lower tail drum 6, of a diameter smaller than that of the drum 5, are both journalled for rotation between the members 1.

An endless belt 4 consisting of a flexible backing strip 7 of synthetic plastics or synthetic or natural elastomeric material is trained around the head and tail drums 5 and 6, and is tensioned by a snubbing roll 8 which engages with the return run of the belt at a position spaced below the drum 5, but is located above the framework 3. The delivery run of the belt is supported at a number of spaced intermediate positions by supports 9 which extend between the members 1.

The roller 5 is driven by a variable speed gear reducing motor.

The backing strip 7 carries a number of axially spaced rows of discrete teeth 10 which project from the outer face of the strip and are arranged to separate solid material from the sump 2 and discharge same into a receiving box 11 at a receiving station below the upper drum 6 on the return run side of the belt. The teeth 10 may be arranged in strips with the adjacent teeth and adjacent rows of teeth being relatively close to each other but with the strips of teeth themselves spaced from adjacent strips of teeth to facilitate the elevation of solid material from the sump.

A typical strip of teeth is shown in Figure 2 of the drawings from which it will be observed that regions of teeth are omitted from local regions 12, and these are spaced transversely across the width of the belt, to facilitate the passage of water through the spaces between the teeth 10. The regions 12 and adjacent rows are also disposed transversely with respect to each other.

The teeth 10 themselves may be of any suitable profile. Preferably however, they are of angled outline, being cranked approximately half-way along their length, so that a first portion projects substantially radially from the backing strip 5, and a second portion is disposed at a suitable angle to facilitate separation of the solid material.

A receiving box 11 leads into a rotary sieve 12 which is mounted on the framework 3 and has a reservoir 13 from which the residue of sieved water is removed to an appropriate place. Depending on the effluent being treated, the sieved water may be removed to a clean water supply, a closed circuit water system orto a main drain.

in order to clean the belt and ensure the removal of the solid material into the box 11 a rotary brush 14 of wire or nylon bristle is engageable with the outer face of the belt as it leaves the drum 6. We also provide water spray pipes 15 and 16 above and between the points of contact of the brush 14 with the belt 4 and a drip chute 17 to direct such water, and water carried by the belt 4 from the effluent, back into the sump 2.

Our screen is relatively simple in construction and easy to install. The belt, which is hard wearing, is relatively inexpensive and can be replaced simply and speedily. Further, sections of the belt can readily be replaced by using belt fasteners.

In practice the snubbing roll 8 may be omitted to prevent the teeth being forced back through the backing strip 7. In such a modified construction the belt may be tensioned, as necessary, by arranging for the spacing between the drums 5 and 6 to be adjustable.

Our invention can be used with all presently known effluents in order to remove solid materials.

In the filter screen of Figure 3 to 6 the framework 3 is mounted on spaced parallel skids 20 which also support the sump 2 which is in the form of a tank.

The screen is thus readily transportable to an appropriate work station.

The sump 2 has a transverse baffle 21 at its forward end and the lower end of the baffle 21 is spaced from the base of the sump 2 to permit the passage therebetween of effluent to be treated. The height of the baffle is adjustable to adjust the spacing between its lower end, and the base of the tank, in accordance with the type of effluent being treated.

The head and tail drum 5 and 6 are substantially equal in diameter and the tail drum 5 is carried by an axle 22 which is journalled for rotation at opposite ends in bearings 23 and 24 mounted in the members 1 and accessible through the side plates of the tank 2.

The head drum 5 is longitudinally adjustable to adjust the tension of the belt 4 by means of an hydraulic belt tensioner 25. This enables us to omit a snubbing roll. The supports 9 comprise idler rollers of which opposite ends of stub axles 26 are rotatably received in journals 27 which are upstanding from the members 1.

An electric drive motor 28 mounted on the framework 3 drives the head drum 5 and the rotary brush 14 through an endless belt 29.

A removable skip 30 may be placed beneath the sieve 12to receive solid material discharged from it.

An inlet 31 provided in the forward end of the tank 2 has an down pipe 32 through which effluent is discharged close to the lower end of a receiving chamber defined between the forward end of the the tank 2 and the baffle 21. An outlet 33 for water is provided in the opposite, rear end, of the tank 2 at a height below that of the inlet 31. Finally an overflow 34 is provided in the forward end of the tank 2, above the level of the inlet 31 to cater for any excess water.

In the constructions described above, and in particular the construction of Figure 1, difficulty may be experienced in retrieving the tail drum 6 and withdrawing it from between the members 1 when it is necessary to remove the drum 6for maintenance, either of the drum itself, or of the belt 4. In a modification the bearings in which the axle is journalled are received in a pair of short, addition, beams, and these beams are provided with dead eyes with which a hoist or other support mechanism is adapted to co-operate.

The construction and operation of the filter screen of Figures 3 to 6 is otherwise the same as that of Figures 1 and 2 and corresponding reference numerals have been applied to corresponding parts.

Claims (12)

1. A filter screen of the kind set forth in which the belt comprises an endless flexible backing strip, and rows of discrete teeth carried by the strip project from the outer face of the strip.

2. A screen as claimed in Claim 1, in which teeth are arranged in strips.

3. A screen as claimed in Claim 2, in which adjacent rows of teeth are relatively close to each other but with the strips of teeth themselves spaced from adjacent strips of teeth to facilitate the elevation of solid material from the sump.

4. A screen as claimed in any preceding claim, in which the teeth are arranged in parallel rows across the width of the belt to define an array, and longitudinally extending gaps of substantial lengths are provided in the array by the omission of teeth over discrete areas.

5. A screen as claimed in Claim 4, in which the gaps are spaced across the width of the belt in parallel rows and the gaps constituting one such row are displaced transversely with respect to the gaps constituting the two adjacent rows of gaps.

6. A screen as claimed in Claim 5, in which the gaps are all arranged at substantially constant pitch.

7. A screen as claimed in any preceding claim in which the teeth are manufactured from metal, and the backing strip is manufactured from a synthetic plastics or other natural or synthetic elastomeric material.

8. A screen as claimed in any preceding claim in which the teeth are of angled outline, being cranked substantially half-way along their length to define a first portion which projects substantially radially from the backing strip, and a second portion disposed at an angle with respect to the first to facilitate separation of the solid material.

9. A screen as claimed in any preceding claim in which the belt is trained around head and tail drums, and the delivery arm of the belt is supported by a plurality of intermediate supports, a transverse rotary brush being provided for removing solid material from the return run of the belt as it leaves the head drum.

10. A screen as claimed in Claim 9, in which water sprays are provided above and between the points of contact of the brush with the belt.

11. A rotary screen substantially as described herein with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

12. A rotary screen substantially as described herein with reference to and as illustrated in Figures 3 to 6 of the accompanying drawings.