GB2315684A - A self-cleaning filter system - Google Patents

Abstract

A self-cleaning filter system for filtering solids from a fluid flow comprises a filter screen 4 located between inlet channel 1a and outlet channel 2. The cleaning means comprises an actuating means, paddle wheel 7, powered by the flow of fluid to the outlet channel. The actuating means is either pivotally linked 8-12 directly to the screen or to a scraping member to facilitate cleaning.

Description

A FILTER SYSTEM The present invention relates to a filter system for filtering fluids from a liquid (such as water). Particularly, but not exclusively, the invention relates to a filter system for installation in an overflow facility of a sewerage system.

It is conventional to provide a sewerage system with an overflow facility to channel off some flow to a natural watercourse in the event of the system becoming overloaded. Such facilities are generally referred to as combined sewer overflows. It would clearly be unacceptable to allow raw sewage to flow into a natural watercourse and thus combined sewer overflows must be fitted with a filter system to remove at least larger elements of waste from the sewage.

Combined sewer overflows essentially comprise an open section of sewerage conduit lying below a simple weir from which sewage may overflow to an overflow channel when the conduit is overloaded. For instance, the open section of conduit could lie at the bottom of an exicavation with the overflow channel opening into the excavation such that its wall forms the weir.

Typical filter systems employed in such facilities comprise a perforated filter screen installed between the open section of sewerage conduit and the overflow channel. While such filter systems may be advantageously simple, they suffer a disadvantage in that they can become clogged with debris which may prevent efficient operation of the filter and overflow facility.

It is an object of the present invention to obviate or mitigate the above disadvantage.

According to the present invention there is provided a filter system for filtering solids from a fluid flowing between an inlet channel and an outlet channel, comprising a filter screen located between the inlet channel and the outlet channel, and means for clearing the filter screen of solid debris, wherein said clearing means comprises actuating means powered by the flow of fluid to the outlet channel such that the filter screen is continuously cleared of debris as fluid flows to the outlet channel.

The present invention thus provides a filter system suitable for installation at a combined sewer overflow and which overcomes the problem mentioned above by providing means for continuously clearing the screen (particularly its upstream surface) of debris whenever fluid is flowing therethrough. The clearing means may comprise a clearing member mounted for movement across the upstream surface of the screen or may be provided by movement of the screen itself.

In a preferred embodiment of the invention the filter screen is mounted for reciprocating movement within the overflowing fluid, and said actuating means operates to continuously reciprocate the screen as fluid flows to the outlet channel, whereby the reciprocation of the screen within the fluid provides the means for clearing the screen.

The reciprocation of the screen will effectively pump fluid through the screen and in each alternate stroke of the screen the pumping action will be opposite the direction of flow of fluid from the inlet channel to the outlet channel which will tend to clear debris from apertures on the upstream surface of the screen.

The filter screen may for example be mounted for pivotable movement about an axis, said reciprocating motion being a pivoting motion about said axis.

The actuating means preferably comprises a paddle wheel located such that it is rotated by fluid flowing from the inlet channel to the outlet channel.

For instance, the filter screen and paddle wheel may be positioned upstream and downstream respectively of a weir such that fluid flowing from the inlet channel passes through the filter screen before flowing over the weir and paddle wheel.

A linkage provided between the paddle wheel and the filter screen to convert rotational motion of the paddle wheel to the required reciprocating motion may preferably comprise a pivotably mounted arm one end of which is connected to the filter screen and the other end of which co-operates with the paddle wheel in such a way that rotation of the paddle wheel causes the arm to rock about its pivot thereby imparting reciprocal motion to the filter screen.

Forms of conventional reciprocating or oscillating linkage which might be employed between the paddle wheel and filter screen will be apparent to the skilled engineer.

As mentioned above, rather than reciprocating the screen itself (or possibly in addition thereto), a clearing member may be provided for scraping debris from the surface of the filter screen. For instance, the clearing means may comprises a clearing member mounted for reciprocating movement across a surface of the filter screen. The clearing member may, for example, be pivotably supported such that said reciprocating movement is a pivotal movement (in which case the screen may preferably be arcuate).

Here again the actuating means preferably comprises a paddle wheel and a suitable linkage provided to convert rotational motion of the paddle wheel to the required reciprocating motion of the clearing member.

According to a second aspect of the present invention there is provided a filter system for filtering solids from a fluid flowing between an inlet channel and an outlet channel, comprising a filter screen located between the inlet channel and the outlet channel, wherein the filter screen is mounted for reciprocating movement within the fluid flowing between the inlet channel and the outlet channel and actuating means are provided for reciprocating the screen as fluid flows to the outlet channel, whereby reciprocation of the screen within the fluid provides the means for clearing the screen.

The actuating means may take a variety of forms and need not be powered by a flow of fluid to the outlet channel as in the above embodiments of the first aspect of the present invention. For instance, the activated means may comprise an electric (or alternatively powered) motor. The motor may be activated by an operator, or may, for example, be actuated in response to sensors detecting the flow of fluid to the outlet channel. Such sensors could take a variety of forms including, for example, mechanical float sensors or electronic sensors.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic side elevation of a sewage overflow facility incorporating a filter system in accordance with a first embodiment of the present invention; Fig. 2 is a plan view from above of Fig. 1; and Fig. 3 is schematic side elevation of a filter system in accordance with a second embodiment of the present invention.

Referring to Figs. 1 and 2, the illustrated filter system forms part of a sewerage overflow facility known as a combined sewer overflow. The overflow facility essentially comprises an open section la of a sewerage conduit 1 through which sewage can flow to an overflow channel 2 in the event that the conduit 1 becomes overloaded. The overflow channel 2 extends laterally from the conduit 1, an edge 3 of which is raised to form a weir between the conduit 1 and the overflow channel 2.

The filter system comprises a rectangular filter screen 4 which is positioned in the open section la of the conduit 1 and pivotably mounted to the edge 3 by way of hinges 5 which support the filter screen 4 along one of its longer edges. The opposing long edge of the filter screen 4 is provided with an upstanding arcuate sealing lip 6. Similar sealing lips (not shown) are provided along each of the shorter edges of the filter screen 4. The mounting of the filter screen 4 is such that it can pivot about the hinges 5 within the open section of conduit la, as illustrated by the dotted lines in Fig. 1. However, the sealing lips provided on the filter screen 4 remain in contact with respective edges of the open section of conduit la to maintain a seal therebetween.

A pair of paddle wheels 7 are located within the overflow channel 2 and are mounted for rotation on a common shaft 8 which extends parallel to the open section of conduit la below the level of the edge 3. The positioning of the paddle wheels 7 is such that they will be rotated by fluid flowing into the overflow channel 2.

The filter screen 4 is linked to the paddle wheels 7 by two cranked rocker arms 9 which are pivotably mounted about respective pivots 10. One end of each rocker arm 9 is connected to the lip 6 of the filter screen 4 by way of a short connecting member 11. The opposite end of each arm is forked and embraces a respective cam 12 which is eccentrically mounted to the shaft 8. The arrangement is such that rotation of the paddle wheels 7 causes the rocker arms 9 to rock about their pivots 10 and thereby impart a reciprocating motion to the filter screen 4 which pivots up and down about the hinges 5.

In operation, in the event that the sewage conduit 1 becomes overloaded, sewage will flow up through the open section la, through the filter screen 4, and over the edge 3 to the overflow channel 2. Larger solid elements of sewage will be prevented from flowing to the overflow channel 2 by the filter screen 4. The fluid flowing to the overflow channel 2 drives the paddle wheels 7 which, by way of the rocker arms 9, cause the filter screen 4 to pivot about the hinges 5 in the manner described above. It will thus be seen that so long as fluid is flowing to the overflow channel 2 and over the paddle wheels 7, the filter screen 4 will be pivoted up and down about the hinges 5. On each upward stroke of the filter screen 4 fluid will be effectively pumped through the screen 4 from its downstream side to its upstream side (i.e. against the direction of the overall flow of fluid to the overflow channel 2). This pumping action will clear debris from the filter screen 4 which may otherwise tend to block the apertures on its upstream surface. This cleaning action will continue as long as sufficient fluid is flowing to the overflow channel 2 to rotate the paddle wheels 7.

It will thus be seen that the present invention provides a mechanism for keeping the filter screen substantially clear of debris, which mechanism comes into operation when, and only when, fluid is actually overflowing to the overflow channel 2.

It will be appreciated that many modifications could be made to the filter system and overflow facility described above, and by way of example an alternative embodiment of the present invention is schematically illustrated in Fig. 3. In this embodiment of the invention, a single paddle wheel 13 is located within an overflow channel 14 arranged to one side of a sewersgr conduit 15 through which sewage flows in a direction indicated by arrow A. An open section 15a extends laterally from the conduit 15, a wall 16 of which forms a weir which separates the open section l5a from the paddle wheel 13 and overflow channel 14.

A rectangular filter screen 17 is pivotably mounted within the open section of conduit 15a by means of hinges 18 located along one of its longer edges.

The opposing long edge of the filter screen 17 is linked to the paddle wheel 13 by way of a rocker arm 19 and connecting link 20. The rocker arm 19 is mounted to a pivot 21 intermediate its ends, one of which is connected to the link 20. The opposite end of the rocker arm 19 is provided with a slot 19a which receives a pin 22 provided at the circumference of a drive wheel 23 mounted to the axis of the paddle wheel 13. The arrangement is essentially an oscillating crank mechanism by way of which rotational motion of the paddle wheel 13 causes the rocker arm 19 to rock about its pivot 21 and impart reciprocating motion to the filter screen 17 by way of link 20. As the filter screen 17 pivots up and down its free edge remains in sealing contact with an arcuate sealing surface 24 of the conduit 15.

Similar sealing surfaces may be provided at the other edges of the filter screen 17.

It will thus be seen that the embodiment of figure 3 operates in much the same way as the embodiment of figures 1 and 2. That is, as the conduit 15 becomes overloaded fluid passes through the screen 17, over the weir edge 16 and onto the paddle wheel 13. The rotation of the paddle wheel 13 then causes the filter screen 17 to pivot up and down as described above. The resulting pumping action tends to keep the upstream surface of the filter screen 17 clear from debris in the manner described above in relation to the embodiment of figures 1 and 2.

It will be appreciated that many modifications could be made to the filter systems described above. For instance, alternative mechanisms may be employed to convert rotational motion of the paddle wheels to the required reciprocating motion of the filter screen. For instance other conventional oscillating crank mechanisms or slider-crank mechanisms might be used.

Alternatively, the paddle wheels might be replaced by other actuating means powered by flow of fluid to the overflow channel.

As a further alternative, actuating means which is not directly powered by flow of fluid to the overflow channel might be used. For instance, some form of motor (e.g. electric) may be used to reciprocate a filter screen in the manner mentioned above.

It will be further appreciated that exact details of the design and arrangement of components may depend upon the application to which the filter system is to be put. The invention is not limited to application in sewerage overflow facilities.

It will also be understood that whilst in the above described embodiments of the invention the reciprocating motion of the filter screens is a pivotable motion, this need not necessarily be the case. Alternative mountings could be provided for the filter screen so that it could, for instance, be raised and lowered in a simple up and down motion.

Furthermore, the filter screen could be fixed in position and a separate cleaning member could be provided which is mounted for reciprocating motion such that it scrapes across the surface of the filter screen to clean debris therefrom. For example, the filter screen could be arcuate and a pivotably mounted clearing member could be linked to a paddle wheel to derive the necessary reciprocating motion from the flow of fluid to the overflow channel in the same general manner as is described above.

Other possible modifications of the above described filter systems will be apparent to the skilled person.

Claims (12)

1. A filter system for filtering solids from a fluid flowing between an inlet channel and an outlet channel, comprising a filter screen located between the inlet channel and the outlet channel, and means for clearing the filter screen of solid debris, wherein said clearing means comprises actuating means powered by the flow of fluid to the outlet channel such that the filter screen is continuously cleared of debris as fluid flows to the outlet channel.

2. A filter system according to claim 1, wherein the actuating means comprises a paddle wheel located such that it is rotated by fluid flowing from the inlet channel to the outlet channel.

3. A filter system according to claim 2, wherein the filter screen and paddle wheel are positioned upstream and downstream respectively of a weir such that fluid flowing from the inlet channel passes through the filter screen before flowing over the weir and paddle wheel.

4 A filter system according to any preceding claim, wherein the filter screen is mounted for reciprocating movement within the overflowing fluid, and said actuating means operates to continuously reciprocate the screen as fluid flows to the overflow channel, whereby the reciprocation of the screen within the fluid provides the means for clearing the screen.

5. A filter system according to claim 4, wherein the filter screen is mounted for pivotable movement about an axis, said reciprocating motion being a pivoting motion about said axis.

6. A filter system according to claim 4 or claim 5, wherein a linkage is provided between the paddle wheel and the filter screen, the linkage comprising a pivotably mounted arm one end of which is connected to the filter screen and the other end of which co-operates with the paddle wheel in such a way that rotation of the paddle wheel causes the arm to rock about its pivot and thereby impart reciprocal motion to the filter screen.

7. A filter system according to any one of claims 1 to 3, wherein the clearing means comprises a clearing member mounted for reciprocating movement across a surface of the filter screen to thereby clear debris from the filter screen.

8. A filter system according to claim 9, wherein the clearing member is pivotably supported such that said reciprocating movement is a pivotal movement.

9. A filter system for filtering solids from a fluid flowing between an inlet channel and an outlet channel, comprising a filter screen located between the inlet channel and the outlet channel, wherein the filter screen is mounted for reciprocating movement within the fluid flowing between the inlet channel and the outlet channel and actuating means are provided for reciprocating the screen as fluid flows to the outlet channel, whereby reciprocation of the screen within the fluid provides the means for clearing the screen.

10. A waste fluid system overflow facility including a filter system according to any preceding claim, wherein said inlet channel is an open portion of waste fluid conduit and said outlet channel is an overflow channel for channelling away fluid overflowing from the open portion of conduit.

11. A filter system substantially as hereinbefore described with reference to the accompanying drawings.

12. A waste fluid system overflow facility substantially as hereinbefore described with reference to the accompanying drawings.