GB2549959A

GB2549959A - Automatic screen cleaning apparatus

Info

Publication number: GB2549959A
Application number: GB1607711.7A
Authority: GB
Inventors: Munn Samuel
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-05-03
Filing date: 2016-05-03
Publication date: 2017-11-08
Anticipated expiration: 2036-05-03
Also published as: GB201607711D0; GB2549959B

Abstract

An automatic screen cleaning apparatus that cleans itself by flushing the attached debris back through the inlet screen 25 as part of its operating cycle. It comprises a body having an upper tank 20 for receiving a liquid, the upper tank having a fluid inlet 24 comprising a perforated screen; a lower tank 22 in fluid communication with the upper tank; a valve 26 located between the upper and lower tank; a float member 32 located in the upper tank; a screen seal member 30 adapted to seal the fluid inlet; and a resiliently biased actuator 33 in engagement with the float, the valve and the screen seal member and moveable between a first configuration in which the valve is closed and the fluid inlet is open and a second configuration in which the valve is open and the fluid inlet is sealed by the screen seal member, the movement between the two configurations being in dependence upon the position of the float within the upper tank. Later embodiments relate to a method of cleaning a screen using the apparatus and a sewage pumping station comprising the apparatus.

Description

AUTOMATIC SCREEN CLEANING APPARATUS

The present invention relates to an automatic screen-cleaning apparatus. In particular, the present invention relates to an automatic screen cleaning apparatus for use as part of a sewage pumping station or the like.

Background to the invention

Sewage pumping stations are conventionally underground structures that foul water or sewage is discharged into. There are various types of sewage stations, but in some systems the sewage station is typically a wet well i.e. where the pumping station houses one or more submersible pumps which pump the sewage onwards to its next destination. In other types of station there may be a separate dry well, adjacent to the wet well, which houses the pumps. Alternatively, on some pumping stations the pumps may be housed above ground near the wet well.

In storm conditions or other extreme circumstances which would be sufficient to flood the pumping station with sewage in volumes which exceed the intended capacity of the sewage pumping station, many pumping stations have consent to discharge sewage in a controlled manner into a nearby river or stream. Such consent is issued by the Environmental Agency in an effort to avoid a breach of raw sewage at ground level where the pumping station is situated. In the event of such an extreme situation arising, sewage is discharged from the pumping station via an ‘outfall’ pipe into a nearby river or stream.

The most common causes of flooding of pumping stations include heavy rainfall, electrical power failure, for example caused by power-cuts, mechanical breakdown of pumps, and downstream blockage of the sewage transit pipe system.

Generally, the Consent to Discharge notice will have certain conditions attached. One such condition is that the outfall in the pumping stations are required to filter (generic name is screen) the sewage to prevent larger particles of sewage solids or rag being discharged. Rag is the generic name for any non-organic material that is present in the sewage liquid and includes materials such as toilet tissue, old dish cloths and other fabric materials, and other items that may be found floating on the top of the sewage surface.

If the screen becomes blocked, the flowrate through the screen is obviously restricted hence less filtered sewage is discharged and thus, if more sewage is entering the pumping station than is able to be discharged through the blocked or partially blocked screen, the sewage level at the pumping station rises and overflows (unscreened through a failsafe weir incorporated in the current static screen) thus discharging. In this case the rag and solids still end up being discharged into the water course which is an undesirable event.

One prior art solution that attempts to address this problem involves a high pressure jet arrangement located so as to spray the residue or rag off the screen in a cleaning action, thereby keeping the screen in an unblocked state. Such systems may be automated when used in combination with a sonar device, but have expensive installation and operating costs. For most pumping stations the cost of automated screen cleaning is not economical, and so the screen is cleaned manually using a rake or a mobile pressure washer when an operator visits the site. The manual cleaning is normally triggered after a storm event, but this operation is often missed and the screen remains at least partially blocked. WO-2008/104773 (Samatrix Limited) discloses an automatic screen cleaning apparatus comprising a housing provided with a liquid inlet, a liquid outlet and a screen member. A rake member is received within the housing and has one or more protrusions. Each protrusion extends into a respective aperture of the screen member. A resilient member is arranged so as to apply a first force to a first surface of the rake member. A float member is adapted to apply a second opposing force to the rake member so that the rake member is moveable relative to the screen member in dependence upon variations in the volume (i.e. the level) of liquid received within the housing. The changes in the position of the rake and the speed with which the rake moves up and down is dependent on the variations in the volume of liquid. As a result, the rake moves relatively slowly and can become jammed when brought into contact with debris which is stubbornly adhered to the screen member.

There is therefore a need for an improved efficient automated screen cleaning with improved cleaning ability of the screen member.

Summary of the Invention

The present invention seeks to address the problems of the prior art.

Accordingly, the present invention provides an automatic screen cleaning apparatus comprising a body having an upper tank for receiving a liquid, the upper tank having a fluid inlet comprising a perforated screen; a lower tank in fluid communication with the upper tank; a valve located between the upper and lower tank; a float member located in the upper tank; a screen seal member adapted to seal the fluid inlet; and a resiliently biased actuator in engagement with the float, the valve and the screen seal member and moveable between a first configuration in which the valve is closed and the fluid inlet is open and a second configuration in which the valve is open and the fluid inlet is sealed by the screen seal member, the movement between the two configurations being in dependence upon the position of the float within the upper tank.

The use of a float to move the resiliently based actuator between the first and second configurations allows the respective opening and closing of the valve and fluid inlet to correspond to level of fluid present in the upper tank.

In one embodiment, the lower tank is provided with an outlet adapted for engagement with an outfall pipe. However, it is to be appreciated that any other suitable drainage system may be provided as an alternative.

In a further embodiment, the resiliently biased actuator comprises an over-centre linkage, such as an over-centre spring or similar arrangement known to the skilled person and suitable for purpose.

The over-centre linkage may comprise a rocker arm, a rocker arm extension pivotally engaged with the rocker arm, and a resilient biasing means having a first end engaged with the rocker arm and a second end engaged with the rocker arm extension.

In a further embodiment, the valve is a butterfly valve.

The automatic screen cleaning apparatus may further comprise a butterfly actuator having a first end in fixed engagement with the butterfly valve and a second end in rotational engagement with the rocker arm.

In a further embodiment, the float is in pivotal engagement with the rocker arm extension.

The automatic screen cleaning apparatus may further comprise a float arm with a first end in fixed engagement with the float and a second opposing end in engagement with the rocker arm extension.

In a further embodiment, the screen seal member is in fixed engagement with the rocker arm and movable relative to the fluid inlet in dependence upon the position of the actuator.

In a further embodiment, the fluid inlet further comprises a collar located around the perforated screen. The collar defines a volume therein which can be filled with liquid when the upper tank fluid inlet is open and liquid is passing through into the upper tank.

In the second configuration, the screen seal member may be adapted to form a seal with the screen. The screen seal moves in an arc through the collar towards the screen, forcefully displacing water back through the screen and forming a seal with the screen to prevent liquid ingress into the upper tank. A further aspect of the present invention provides a method of automatically cleaning a screen, the method comprising the steps of: a. providing an automatic screen cleaning apparatus according to any preceding claim; and b. receiving liquid into the upper tank through the fluid inlet so as to vary the volume of liquid received within the housing.

In one embodiment, the method further comprises receiving sufficient liquid into the upper tank to raise the float from a first lowered position to a second fully raised position, thereby moving the actuator from the first configuration to the second configuration such that the screen seal member is moved rapidly into sealed communication with the fluid inlet, wherein liquid is forced back through the perforated screen in a direction away from the upper chamber.

The method may further comprise the step of engaging the drainage outlet of the lower tank with an outfall pipe to remove water received into the lower tank from the upper tank. A further aspect of the present invention provides a sewage pumping station comprising an automatic screen cleaning apparatus according to any preceding aspect.

Brief Description of the Drawings

An embodiment of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a screen cleaning apparatus in accordance with an embodiment of the present invention in a first position with an open fluid inlet and a closed valve;

Figure 2 is a side view of the apparatus of figure 1 in the first position;

Figure 3 is a view from above of the apparatus of figure 1 in the first position;

Figure 4 is a rear view of the apparatus of figure 1;

Figure 5 is a perspective view of the apparatus of figure 1 part way between the first position and a second position with a closed fluid inlet and an open valve;

Figure 6 is a front view of the apparatus of figure 1 part way between the first and second positions;

Figure 7 is a side view of the apparatus of figure 1 part way between the first and second positions;

Figure 8 is a view from above of the apparatus of figure 1 part way between the first and second positions;

Figure 9 is a perspective view of the apparatus of figure 1 in the second position; Figure 10 is a front view of the apparatus of figure 1 in the second position;

Figure 11 is a side view of the apparatus of figure 1 in the second position; and Figure 12 is a view from above of the apparatus of figure 1 in the second position.

Detailed Description of the Invention

An embodiment of the present invention will now be described with reference to all of figures 1 to 12, in which common features are indicated using common figure references.

Automatic screen cleaning apparatus 10 comprises a body having an upper tank 20 and a lower tank 22, each tank being adapted to receive a liquid therein. Upper tank 20 is provided with a fluid inlet 24 in the form of a screen 25 having one or more perforations through which liquid can pass. Lower tank 22 is in fluid communication with upper tank 20 with a butterfly valve 26 located at fluid opening 21 between the first and second tanks 20, 22 to control fluid flow from the first tank 20 into the second tank 22. Lower tank 22 is further provided with a drainage outlet 28 through which liquid received in lower tank 22 can exit tank 22 into a drainage system (not shown). Such a drainage system may comprise a drainage pipe to transport the liquid away from apparatus 10 or may comprise a soak-away structure to dissipate the drainage fluid in a conventional manner.

Apparatus 10 is further provided with a screen seal 30 located in upper tank 10 and dimensioned to seal fluid inlet 24 when brought into sealed engagement with screen 25, thus preventing ingress of fluid into upper tank 10. Screen seal guide 31 is provided around screen 25 into which screen seal 30 fits when moving into sealed engagement with screen 25. Screen seal guide 31 is dimensioned to form a cylindrical collar around screen 25. Although in the present embodiment, the screen seal guide 31 is cylindrical in shape, it is to be appreciated that the screen seal guide 31 may be any suitable shape provided that it corresponds to the shape of the seal 30. For example, the screen seal guide 31 may comprise a rectangular collar around screen 25, where the seal 30 is rectangular in shape.

Further, a float member 32 is located in upper tank 20. Float member 32 may comprise any suitable non-porous robust material such as, but not restricted to, stainless steel or polypropylene or any similar non-rusting material known to the skilled person. The float member 32 must have a volume to weight ration that enables the float to have an acceptable (and ideally maximum) buoyancy upthrust to activate the seal mechanism to close. However, the float member 32 must also have sufficient weight that it is operable to activate the search mechanism to close, on its descent. Typically, the Plimsoll Line of float member 32 is approximately 50% when allowed to float freely in water. However, it is important that the volume of float member 32 is related to the volume of the upper tank 20 so that a fixed volume of fluid is exhausted into the lower tank 22 on each operating cycle of the apparatus. These feature requirements will become apparent from the description of the apparatus structure and mechanism of operation and herein described.

Apparatus 10 is further provided with a resiliently biased actuator in the form of a spring 33. Spring 33 is engaged at a first end with a first end of an elongate rocker arm 34. The first end of elongate rocker arm 34 is also in fixed engagement with screen seal 30. The opposing end of rocker arm 34 is pivotable about a pivot point 36. A first end of a rocker arm extension 38 is pivotally engaged with rocker arm 34 and is pivotable about pivot point 36. The opposing end of rocker arm extension 38 is in pivotable engagement with float arm 40 about pivot point 42. Float arm 40 is engaged with float member 32 and any movement of float member 32 causes consequential movement of float arm 40, rocker arm extension 38, rocker arm 34 and screen seal 30. Similarly, any movement of rocker arm 34 causes consequently movement of rocker arm extension 38, float arm 40 and float member 32.

The butterfly valve 26 also is pivotally connected to the rocker arm 24 via valve extension arm 27 and is engaged with rocker arm 34 at engagement point 25 such that movement of the rocker arm 24 results in corresponding movement of extension arm 27 and subsequent movement of the butterfly valve 26.

Figures 1 to 4 show the automatic screen cleaning apparatus 10 in a first position with an open fluid inlet 24 and a closed valve 26. This is the default position for the screen cleaning apparatus when not in use and the external water level will be below the level of the open fluid inlet 24. As the water external water level rises, for example, during a flood situation, the water surface level will rise until the external water level reaches the level of the open fluid inlet 24, at which point the water will enter upper tank 20 through open water inlet 24. This ingress of water will result in a rising water level within upper tank 20, thereby raising the level of float member 32.

As discussed above, and as can be seen in figures 5 to 8, movement of float member 32 has a consequential movement of float arm 40 and rocker arm extension 39. However rocker arm 34 and thus screen seal 30 cannot rotate anti clockwise (or open any further) as it is restrained by the valve linkage or a stop. Thus, a rising float member 32 will cause the float arm 40 to rise and the rocker arm extension 38 to pivot about pivot point 36, thus exerting force on spring 33 and forcing spring 33 to extend in a direction away from rocker arm 34. As the water continues to enter upper tank 20 through open water inlet 24, float member 32 will continue to rise to its top position where spring 33 is fully extended to its designed maximum, moving the rocker arm extension 38 to just beyond its fulcrum point. At this stage, the spring 33 decompresses under natural spring bias to return to its state of rest, thereby releasing its energy and forcefully pushing screen seal 30 into sealed engagement with fluid inlet 24 at high velocity so as to force any trapped water in screen seal guide 31 out of the upper tank 20 via fluid inlet 24 through the perforations in screen 25. This forceful ejection of water from upper tank 10 through the perforations in screen 25 results in any material that had previously been adjacent screen 25 due to water ingress into upper tank 20 being blown off the surface of screen 25 and back into the external water.

At the same time as closing fluid inlet 24 by pushing screen seal 30 into sealed engagement with fluid inlet 24, the movement of rocker arm 34 results in corresponding movement of valve extension arm 27 about engagement point 35 such that valve extension arm 27 is lowered thereby moving butterfly valve 26 into the open position. Water can then flow from upper tank 20 to lower tank 22 via fluid opening 21. Fluid opening 21 and corresponding valve 26 have a very large opening area to allow the maximum rate of discharge of fluid from the upper tank 20 to the lower tank 22. The lower tank 22 has a volume related to the total volume discharged from upper tank 20 during the discharge stage of the apparatus operation cycle such that the drainage of fluid does not throttle or restrict the descent of the float member 32. The lower tank volume is designed for fluid storage whilst the fluid drains out of lower tank 22 via drainage outlet 28 into drainage system (not shown). This second position arrangement is shown in figures 9 to 12. This design allows the maximum average flowrate to pass through the screen 10 even though the seal 30 is closed as part of the screen 10 operating cycle.

The egress of water from the upper tank 20 into lower tank 22 coupled with the closed fluid inlet 24 preventing further water entering upper tank 20 results in the lowering of the water level in upper tank.

As the water level in upper tank 20 lowers, float member 32 is lowered, thereby moving float arm 40 and rocker arm extension 39 downwards, the seal cannot rotate clockwise as it is restrained by the screen face 25, so pivoting rocker arm extension 39 about pivot point 36 with rocker arm 34, extending spring 33 in a direction away from rocker arm 34. As the water level continues to recede in upper tank 20, float member 32 will continue to lower with spring 33 continuing to be expanded against its bias until spring 33 is fully extended again to its designed maximum. As rocker arm extension 38 is moved to just beyond its fulcrum point, spring 33 decompresses under natural spring bias to return to its state of rest, thereby releasing its energy and forcefully returning the screen seal 30 to its original open position relative to fluid inlet 24.

At the same time as opening fluid inlet 24, the rocker arm 34 is returned to its original position, thereby lifting valve extension arm 27 and returning butterfly valve 26 to its original closed position, thereby closing fluid opening 21 and preventing water in upper tank 20 flowing into lower tank 22.

This flushing process cleans the screen face 25 of adhered debris each time and is repeated as a cycle until such time as the external water level outside of apparatus 10 falls below the level of fluid inlet 24. When this occurs, the cycle will continue until sufficient water has flowed out of upper tank 20 into lower tank 22 to lower the float and the consequential closing of butterfly valve 26 and the resultant closing of fluid opening 21.

The system will then remain in position (with clear openings in the screen face 25) until such time as the external water level rises above to the level of fluid inlet and water can, once again, flow into upper tank 20 through fluid inlet 24.

Although aspects of the invention have been described with reference to the embodiment shown in the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment shown and that various changes and modifications may be effected without further inventive skill and effort.

Claims

CLAIMS:

1. An automatic screen cleaning apparatus comprising a body having an upper tank for receiving a liquid, the upper tank having a fluid inlet comprising a perforated screen; a lower tank in fluid communication with the upper tank, the lower tank being further provided with a drainage outlet; a valve located between the upper and lower tank; a float member located in the upper tank; a screen seal member adapted to seal the fluid inlet; and a resiliently biased actuator in engagement with the float, the valve and the screen seal member and moveable between a first configuration in which the valve is closed and the fluid inlet is open and a second configuration in which the valve is open and the fluid inlet is sealed by the screen seal member, the movement between the two configurations being in dependence upon the position of the float within the upper tank.

2. An automatic screen cleaning apparatus according to claim 1, wherein the lower tank is provided with an outlet adapted for engagement with an outfall pipe.

3. An automatic screen cleaning apparatus according to claim 1 or claim 2, wherein the resiliently biased actuator comprises an over-centre linkage.

4. An automatic screen cleaning apparatus according to claim 3, wherein the over-centre linkage comprises a rocker arm, a rocker arm extension pivotally engaged with the rocker arm, and a resilient biasing means having a first end engaged with the rocker arm and a second end engaged with the rocker arm extension.

5. An automatic screen cleaning apparatus according to any preceding claim, wherein the valve is a butterfly valve.

6. An automatic screen cleaning apparatus according to claim 5, further comprising a butterfly actuator having a first end in fixed engagement with the butterfly valve and a second end in rotational engagement with the rocker arm.

7. An automatic screen cleaning apparatus according to any preceding claim, wherein the float is in pivotal engagement with the rocker arm extension.

8. An automatic screen cleaning apparatus according to claim 7, further comprising a float arm with a first end in fixed engagement with the float and a second opposing end in engagement with the rocker arm extension.

9. An automatic screen cleaning apparatus according any preceding claim, wherein the screen seal member is in fixed engagement with the rocker arm and movable relative to the fluid inlet in dependence upon the position of the actuator.

10. An automatic screen cleaning apparatus according to any preceding claim, wherein the fluid inlet further comprises a collar located around the perforated screen.

11. An automatic screen cleaning apparatus according to claim 10, wherein in the second configuration, the screen seal member is adapted to form a seal with the screen.

12. A method of automatically cleaning a screen, the method comprising the steps of: a. providing an automatic screen cleaning apparatus according to any preceding claim; and b. receiving liquid into the upper tank through the fluid inlet so as to vary the volume of liquid received within the housing.

13. A method according to claim 12, further comprising receiving sufficient liquid into the upper tank to raise the float from a first lowered position to a second fully raised position, thereby moving the actuator from the first configuration to the second configuration such that the screen seal member is moved rapidly into sealed communication with the fluid inlet, wherein liquid is forced back through the perforated screen in a direction away from the upper chamber.

14. A method according to claim 13, further comprising the step of engaging the drainage outlet of the lower tank with an outfall pipe to remove water received into the lower tank from the upper tank.

15. A sewage pumping station comprising an automatic screen cleaning apparatus as claimed in any one of claims 1 to 14.