GB2295778A

GB2295778A - Self-cleaning gravity filter

Info

Publication number: GB2295778A
Application number: GB9525202A
Authority: GB
Inventors: Peter Walker
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-12-07
Filing date: 1995-12-07
Publication date: 1996-06-12
Anticipated expiration: 2015-12-07
Also published as: GB9525202D0; GB2295778B

Abstract

A self-cleaning gravity filter comprises a generally rectangular housing and a screen generally horizontally disposed in the housing. An inlet is provided into the housing through which liquid to be screened can be introduced into the housing so as to pass onto the upper side of the screen and an outlet is provided from the base of the housing through which screened liquid can be discharged. An array of spray nozzles is mounted on a frame located below the screen. Suspension arms support the frame from the housing in the manner of a pendulum so that the frame can be swung backward and forward below the screen. A drive motor swings the frame in its backward and forward motion through an arc which is selected so that the spray nozzles spray at substantially the entire undersurface of the screen. <IMAGE>

Description

SELF-CLEANING GRAVITY FILTER THIS invention relates to a self-cleaning gravity filter, particularly, although not exclusively, to a filter of the type adapted to filter particles in the 30 to 200m size range.

Filtering particles in the aforementioned particle size range is known to be an economically difficult area within which to operate. Where it is desired to filter out smaller particles typically a sand or like medium filter is used.

Larger particles ale usually filtered out with the aid of screens. However, particles in the 30 to 2001lm size range tend to clog small gauge screens, and also are not efficiently screened in sand type filters.

Where screen type filters are used to filter out particles in the 30 to 200pm range they have, in the past, been cleaned by high pressure sprays which are located below the screen and spray upwardly to continuously unblock the screen apertures. One known prior art arrangement comprises a circular screen below which an upwardly directed array of sprays is rotated to unblock the screen apertures. This arrangement is considered to be less than entirely satisfactory, particularly due to the complexity and cost of constructing a round screen and screen housing, and the difficulty of achieving a regular spray configuration over the entire surface of the screen.

According to the invention there is provided a self-cleaning gravity filter comprising, a generally rectangular housing, a screen generally horizontally disposed in the housing, an inlet into the housing through which liquid to be screened can be introduced into the housing so as to pass onto the upper side of the screen, an outlet from the housing through which screened liquid can discharge, an array of spray nozzles mounted on a frame located below the screen, suspension means supporting the frame from the housing in the manner of a pendulum so that the frame can be swung back and forward below the screen, and drive means for swinging the frame in its back and forward motion through an arc which is selected so that the spray nozzles are adapted to direct sprays at substantially the entire undersurface of the screen.

Further there is provided for the suspension means to comprise a plurality of suspension arms which are each generally vertically orientated, the upper ends of the arms being pivotally connected to the housing and the lower ends being connected to the frame. The drive means may comprise a motor and cam assembly, the cam assembly being linked to the frame through a connecting rod adapted to transmit a reciprocal motion to the frame. The motor may be adapted to reciprocate the frame at a speed of between 20 and 40 cycles per minute.

The frame may comprise a series of parallel tubes to which the spray nozzles are connected, the tubes being adapted to convey spray liquid to the spray nozzles. Optionally each of the tubes is connected to a main carrier pipe by a flexible hose, the carrier pipe being connected to a spray pump. The screen may have a discharge end to which screened particles are discharged.

The discharge end may lead to a trap, sump, basket, or other collection arrangement for collecting screened particles. A baffle arrangement is preferably associated with the inlet to ensure that liquid passing onto the screen flows evenly and relatively non-turbulently.

An embodiment of the invention is described in detail in the following passages of the specification which refer to the accompanying drawings.

The drawings, however, are merely illustrative of how the invention might be put into effect so that the specific form and arrangement of the various features shown is not to be understood as limiting on the invention.

Figure 1 shows a side view of a gravity filter according to the invention; Figure 2 shows a plan view of the filter shown in Figure 1; Figure 3 shows an end view of the filter shown in Figures 1 and 2; Figure 4 shows a detail of the connection arrangement between the drive motor and the spray frame; and Figure 5 shows a detail of the drive connection to the suspension rods.

As shown in the drawings, a gravity filter 10 comprises a housing 12 which, as will be clear from Figure 2, is of generally rectangular configuration in plan view and has an inlet 14 and an open base 16 which defines an outlet from the housing. The outlet will generally be a sump (not shown) from which filtered liquid will be pumped. The housing 12 has side walls 18 and end walls 20 and 22. A screen 24 is mounted within the housing and is generally horizontally orientated, as shown, so as to divide the interior of the housing into an upper part and a lower part. A series of baffles 26 are associated with the inlet side of the housing so that liquid entering the housing from the inlet 14 is forced to follow a sinusoidal path as depicted by arrow 28.This ensures that liquid entering onto the screen 24 is flowing relatively evenly and in a non-turbulent manner as it passes onto the upper side of the screen 24. Liquid to be screened will then pass through the screen 24 in the direction of arrows 30 so that the screened liquid then passes out through outlet 16. Screened particles, of course, are deposited on the upper surface of the screen 24.

To prevent the apertures in the screen 24 from clogging, a series of sprays 32, as seen in Figure 3, are directed at the under surface of the screen 24.

These sprays 32 emit from spray nozzles 34 which are mounted on a spray frame 36 which is suspended below the screen 24.

The frame 36 is suspended below the screen 24 by four suspension rods 38 which are connected to the corners of the frame 36. The suspension rods 38 are pivotally connected at the upper ends 40 to the side wall 18 of the housing 12 and at their lower ends 42 to the frame 36. The frame 36 is thus able to pivot backwards and forwards in a lengthwise direction of the housing below the screen 24 due to the pivotal connections at the upper and lower ends of the suspension rods 38.

A drive motor 44 is used to reciprocate the frame 36. The drive motor 44 is connected to a cam-type flywheel 46 to which a connecting rod 48 is connected. The opposite end of the connecting rod 48 is connected to a crank arm 50 which, in turn, is mounted to a cross-beam 52 which spans across the width of the housing 12. As shown in Figure 5, the ends of the cross-bar 52 are connected by a bracket 54 to the upper ends 40 of a pair of suspension arms 38. Thus, as the motor 44 rotates the flywheel 46 will rotate causing the connecting arm 48 to cause a reciprocating motion on the crank arm 50. This, in turn, will be transmitted via the cross beam 52 to the suspension arms 38 which, in turn, will cause the frame 36 to reciprocate backwards and forwards.It will be noted that even though the frame 36 is reciprocating backwards and forwards it is maintained in a horizontal orientation and thus the spray nozzles 34 will remain perpendicular to the plane of the screen 24. It is envisaged that the total movement of the frame 36 between its limits of travel will be approximately 320mm. Whilst the frame is reciprocating it will, to a small extent, move closer to the screen as it nears the end of its arc of travel. That change in distance between the nozzles and the underside of the screen will not, it is envisaged, effect to any great extent the efficacy of the sprays in clearing the screen.

The frame 36 is comprised, in an embodiment shown, of 6 parallel tubes 50 which are connected together by side bars 53 which ensure that the frame 36 is maintained in a relatively rigid condition. The individual tubes 50 are connected via flexible hoses 54 to a central carrier pipe 56 which, in turn, is connected to a high pressure pump (not shown) adapted to supply liquid under pressure to the nozzles 34. It is envisaged that the spray liquid will be under pressure of approximately 700kPa and each spray nozzle will emit spray liquid at a rate of approximately 0.35m3/hr. The screen size will, of course, depend on the flow rate of liquid to be screened and the capacity of the filter depends on various considerations such as, for example, the screen apertures, the quality of the liquid being screened, and like considerations.

It is envisaged that the filter will filter between 100 and 300m3 of water per hour.

The screens are preferably formed of a stainless steel screen material mounted on a removable galvanised steel frame. A support screen may be located below the fine mesh screen material.

Some form of collection arrangement for collecting screened particles will be located adjacent the end 22 of the filter. This collection arrangement may comprise a basket, sump, tank or other arrangement for collecting and disposing of the screened particles. Generally the screened particles will pass over the end 22 of the housing in the direction of arrow 58 into the collection arrangement. If necessary, from time to time, the screened particles can be hosed off the screen 24 using a manually held high pressure hose. During normal operation the liquid entering on to the screen 24 will tend to push the previously screened particles towards the end 22.

Optionally a set of automotive sprays (not shown) may direct clearing liquid at the upper surface of the screen to move screened particles towards the end 22.

It is preferred that the frame 36 is easily removable from the housing. Thus, there will be a simple nut and bolt type connection arrangement between the frame 36 and the suspension rods 38. Where maintenance to the frame 36 or to the hoses 54 is required it will be a simple matter to lift out the frame 36 and do the necessary maintenance with a minimum interruption of the screening operation. Likewise, the screen 24 will be removable simply by lifting it out of the housing 12. It will not be necessary to have space around the outside of the housing for maintenance since all moving parts, fixtures and fittings will be accessible from vertically above the housing.

This is considered to be a distinctive advantage over prior art arrangements where considerable space is required to one or other side of the screen.

Various alterations may be made to the above described embodiment without departing from the scope of the invention. For example, the installation can be larger or smaller than that described herein which will then necessitate a different array of spray nozzles. Smaller arrangements may, for example, have say two or four tubes 50 rather than the six tube arrangement depicted in the drawings. Likewise, different arrangements for collecting the screened particles can be utilised particularly when the screened particles themselves have value.

Claims

1. A self-cleaning gravity filter comprising, a generally rectangular housing, a screen generally horizontally disposed in the housing, an inlet into the housing through which liquid to be screened can be introduced into the housing so as to pass onto the upper side of the screen, an outlet from the housing through which screened liquid can be discharged, an array of spray nozzles mounted on a frame located below the screen, suspension means supporting the frame from the housing in the manner of a pendulum so that the frame can be swung backward and forward below the screen, and drive means for swinging the frame in its backward and forward motion through an arc which is selected so that the spray nozzles are adapted to spray at substantially the entire undersurface of the screen.

2. A self-cleaning gravity filter according to claim 1, wherein the suspension means comprises a plurality of suspension arms which are each generally vertically orientated, the upper ends of the arms being pivotally connected to the housing and the lower ends of the arms being pivotally connected to the frame.

3. A self-cleaning gravity filter according to either claim 1 or 2, wherein the drive means comprises a motor and cam assembly, the cam assembly being linked to the frame through a connecting rod adapted to transmit a reciprocal motion to the frame.

4. A self-cleaning gravity filter according to claim 3, wherein the motor is adapted to reciprocate the frame at a speed of between 20 and 40 cycles per minute.

5. A self-cleaning gravity filter according to any one of the preceding claims, wherein the frame comprises a series of parallel tubes to which spray nozzles are connected, the tubes being adapted to convey spray liquid to the spray nozzles.

6. A self-cleaning gravity filter according to claim 5, wherein each of the tubes is connected to a main carrier pipe by a flexible hose, the carrier pipe being connected to a spray pump.

7. A self-cleaning gravity filter according to any one of the preceding claims, wherein the screen has a discharge end to which screened particles are discharged.

8. A self-cleaning gravity filter according to claim 7, wherein the discharge end leads to a trap, sump, basket, or other collection arrangement for collecting screened particles.

9. A self-cleaning gravity filter, wherein a baffle arrangement is associated with the inlet to ensure that liquid passing onto the screen flows evenly and relatively non-turbulently onto the screen.

10. A self-cleaning gravity filter substantially as herein described with reference to the illustrated embodiment.