NZ743448B2 - Debris filter - Google Patents

Abstract

downpipe filter comprising: a housing configured to connect to a downpipe, and a screen removably mounted within the housing, configured to filter debris from water flowing in the downpipe, wherein the screen including a plurality of spaced elements having a wave pattern or undulation for reducing trapped debris. This addresses problems which existing debris filters may suffer from, including ineffective filtering. trapped debris. This addresses problems which existing debris filters may suffer from, including ineffective filtering.

Description

DEBRIS FILTER FIELD This invention relates to a debris filter, a method of retrofitting a debris filter, and a method of manufacturing a debris filter.

BACKGROUND As water flows from spouting/gutters into downpipes, it may bring debris (such as tree leaves, sticks, dirt, etc) with it. Debris can build up and cause blockage or contamination of water drains or water storage tanks.

Debris filters may be used with rainwater systems to direct debris out of the flow of water. Existing debris filters may suffer from ineffective filtering, being difficult/expensive to manufacture, being difficult to clean/maintain or requiring regular maintenance, excessive water loss, and/or being difficult to retrofit to existing downpipes.

SUMMARY The present invention may provide an improved debris filter, method of retrofitting a debris filter and/or method of manufacturing a debris filter, or to at least provide the public with a useful choice.

In general terms in a first aspect, there is provided a downpipe filter comprising a housing configured to connect to a downpipe, and a screen removably mounted within the housing, configured to filter debris from water flowing in the downpipe, wherein the screen including a plurality of spaced elements having a wave pattern or undulation for reducing trapped debris.

It is acknowledged that the terms “comprise”, “comprises” and “comprising” may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, these terms are intended to have an inclusive meaning – i.e. they will be taken to mean an inclusion of the listed components which the use directly references, and possibly also of other non-specified components or elements.

Reference to any prior art in this specification does not constitute an admission that such prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention.

Figure 1 is a perspective view of a rainwater system 100; Figure 2A is a perspective view of a debris filter 200; Figure 2B is a front view of the debris filter of Figure 2A; Figure 2C is a side view of the debris filter of Figure 2A; Figure 2D is a back view of the debris filter of Figure 2A; Figure 2E is a top view of the debris filter of Figure 2A; Figure 2F is a bottom view of the debris filter of Figure 2A; Figure 2G is a cross section through J—J of Figure 2B; Figure 2H is a front view of the debris filter of Figure 2A unassembled with the screen omitted; Figure 2I is a cross section through K—K of Figure 2H; Figure 2J is a cross sectional view of the debris filter of Figure 2A assembled with the screen omitted.

Figure 3A is a perspective view of a screen; Figure 3B is a front view of the screen of Figure 3A; Figure 3C is a back view of the screen of Figure 3A; Figure 4 is a cross section of a row of filter elements; Figure 5A is a bottom view of a screen of a filter according to one embodiment; Figure 5B is a cross section of the screen of Figure 5A through E—E; Figure 5C is an enlargement of Detail G of Figure 5B; Figure 5D is an enlarged view of a filter element; Figures 6A-C are filter elements shown at varying degrees of tilt relative to the screen plane; and Figure 7 is a cross sectional view of a mould according to one embodiment.

DETAILED DESCRIPTION Figure 1 is a rainwater system 100. The system 100 includes spouting 102 which directs water into downpipes 104. Downpipes 104 lead into debris filters 106 with screens 108, which filter the water to stop leaves and other debris from entering water or water collection components, such as water filters 110 or water tanks 112.

Figure 2A is a perspective view of a debris filter 200. The debris filter 200 has an inlet 202, which connects to an upper portion of a downpipe, and an outlet 204 which connects to a lower portion of the downpipe (not shown). The debris filter 200 includes a housing 206 which houses a screen 208. The debris filter 200 may be retrofitted to an existing downpipe, or it may be installed with a new downpipe. The terms downpipe and pipe are used interchangeably in the context of this specification.

Figures 2B, 2C and 2D are front, side and back views respectively of the debris filter 200 of Figure 2A, showing the housing 206 including a top portion 210 and a bottom portion 212. The screen 208 is flush with the top of the bottom portion 212 of the housing 206.

Figure 2E is a top view of the debris filter 200 of Figure 2A. The top portion 210 of the housing 206 includes an upper downpipe extension 214, which joins an upper part of the downpipe (not shown). The upper downpipe extension 214 has a circular cross section (though other suitable cross sections may be used), through which an upper surface of the screen 208 is visible. The cross section geometry and size of the upper downpipe extension 214 is configured to seal around the outside of the downpipe.

Figure 2F is a bottom view of the debris filter 200 of Figure 2A. The bottom portion 212 of the housing 206 includes a lower downpipe extension 216, which joins a lower part of the downpipe (not shown). The lower downpipe extension 216 has a circular cross section, through which a lower surface of the screen 208 is visible. The cross section geometry and size of the lower downpipe extension 216 is configured to seal around the outside of the downpipe, and to overlap the inside of the pipe.

The lower body may include a drip edge 310. The drip edge 310 may stop debris and/or water from tracking down the front of the housing and subsequently the downpipe below. The drip edge 310 may extend between 2mm to 10mm. The drip edge 310 includes a downward facing edge, configured to cause water to drip down from the edge rather than track along the front of the housing. The drip edge is laterally spaced from the downpipe.

Figure 2G is a cross section through J—J of Figure 2B. The top portion 210 of the housing 206 includes a twin wall 218, consisting of an inner wall 218a and an outer wall 218b. The inner wall 218a ensures water does not splash outward and is directed to the top of the screen 208. In particular, the inner wall 218a may be configured to deflect water/debris to an upper part of the screen, to increase the working surface of the filter screen and reduce water loss. The inner wall 218a acts as an extension of the downpipe down to the screen, and has an offset angle cut 220. The angle of the cut 220 may match the angle at which the filter 200 is mounted. The end of the downpipe is distanced from the surface of the filter 200. Fins 226 may also be included at each side of the diverter housing. The fins 226 are configured to direct water and/or debris toward the centre of the screen 208.

Figure 2H is a front view of the debris filter of Figure 2A unassembled with the screen omitted. Figure 2I is a cross section through K—K of Figure 2H. The bottom 212 portion of the housing includes a projection 222 configured to slot into corresponding a corresponding recess 224 in the top 210 portion of the housing, to form a rigid joint. This ensures the product and downpipe appear and perform as one body, and that the screen is retained within the body. A relief space may be added to allow the projection 222 to locate easier in the recess 224. When the projection 222 and the recess 224 are joined, the joint still remains rigid. Figure 2J is a cross sectional view of the debris filter of Figure 2A assembled with the screen omitted, showing how a relief 230 may be included to aid installation.

The top 210 and bottom 212 portions of the housing may releasably connect in any suitable manner, including but not limited to: push fit, snap/clip fit, twist-lock, using fasteners or adhesive. In other embodiments the top 210 and bottom 212 portions may be integrally formed. The upper downpipe extension 214 may have a diameter slightly greater than that of the downpipe, which is encapsulated in the upper downpipe extension 214, allowing it to slide up and down relative to the pipe. This allows separation of the top portion 210 and bottom portion 212 in situ, making it easier to access and remove the screen whilst the filter 200 is still connected to the downpipe. The lower downpipe extension 212 is connected to a downpipe by push fit, via a tapered socket. Adhesive may be used to secure the downpipe and lower downpipe extension 212. A socket lap 228 may stop water tracking out at the joint.

Retrofitting the filter 200 to an existing downpipe includes the following steps: 1. Cutting and removing a section of downpipe of a length between 265mm to 300mm. The section of downpipe that is cut and removed does not have to be cut at any specific angle/and or height in relation to the ground, because the inner wall 218 of the top portion 210 of the housing acts as an extension of the downpipe and is already formed with an offset angle cut 220. This reduces the chance of installation errors. 2. Fitting the top portion 210 of the housing over the top part of the downpipe. 3. Lifting the top portion 210 up to create clearance for the bottom portion 212. 4. Fitting the bottom portion 212 of the housing over the bottom part of the downpipe, connecting the lower downpipe extension 216 to the bottom part of the downpipe.

. Fitting the screen 208 into the bottom portion 212. The screen 208 should sit flush with the top of the bottom portion 212. Once the top portion 210 is lowered into place, the screen 208 is attached. 6. Lowering the top portion 210 of the housing and connecting the top portion 210 of the housing to the bottom portion 212 of the housing 206.

The debris filter may include a periodic means of ejecting capturing matter (not shown). Debris will periodically exit fall from the front of the screen to the ground below. It may take multiple rain events for debris to work its way down the screen.

The screen may be removed and replaced with an unperforated screen, to completely block off the downpipe. This may be done to facilitate cleaning of the gutter, for example to prevent cleaning chemicals entering the water system or water tanks.

In some embodiments a secondary screen may be added to the inside of the bottom portion of the housing for even higher water filtration. A fine mesh screen may sit in the lower part of 212 directly above the lower downpipe extension 216. The fine mesh screen captures fine matter that has passed through the primary screen apertures. To access the fine mesh screen, the main screen may be removed. The fine mesh screen may be manually removed and cleaned.

The debris filter 200 and/or the screen 208 may include vanes/flow diverters to divert the flow of water onto the screen in a suitable manner to facilitate debris diversion.

The filter may be cleaned by dislodging any blocked apertures using high pressure water. Flexibility in the material used may facilitate cleaning. The filter shape is configured such that the narrowest opening is at the top and widens out laterally to allow debris to fall through.

Figures 3A to 3C show one embodiment of a screen 208 of a filter. The screen 208 includes a frame 302 and a series of filter elements 304. As water passes through the screen 208 debris is filtered out from the water by the filter elements 304.

As visible in Figure 3C, the screen includes a reinforcing rib 328. This increases the rigidity of the screen and facilitates manufacture by injection moulding (discussed in more detail below). The rib has a thickness of between 1mm to 4mm. The thickness of the rib may be between 20-100% of total screen thickness.

Other embodiments may include a plurality of ribs. Although ribs will aid in the injection moulding manufacturing process, they are not necessary. Various levels of rigidity may be achieved through use of different materials. The bottom part of the screen may include a tab 306. The tab 306 may facilitate removal of the screen. The perimeter 308 of the screen may include a chamfered edge to direct any water into the screen, to avoid water tracking down the edge/to the side of the screen.

In one embodiment, the screen is configured to produce the Coanda effect. The Coanda effect is the tendency of a moving stream of fluid (e.g. water) in contact with a surface to follow the curvature of the surface rather than continue traveling in a straight line. A Coanda-effect screen used for filtration includes tilted profile wire bar screens, which siphon water flowing over the top through the bars without impacting on flow performance and with minimal clogging compared to other types of filters. The tilted profile wires of the Coanda Screen slice off thin layers of water, allowing debris to pass over the screen and water to fall through the screen.

Coanda screens may use filter elements which are tilted with respect to the screen plane to create the Coanda effect. Coanda screens with tilted filter elements may be difficult to manufacture from plastic, in particular by injection moulding.

Figure 4 is a cross section of a row of filter elements 404 of a screen 400. Filter elements generally form elongate horizontal rows along the length of a screen. The following geometrical parameters of the screen 400 are variable: • Angle a, the inclination of the longitudinal axis 402 of the screen 400 from horizontal (in use) • The maximum width w of filter elements 404 (taken from the axis of the screen plane) • The maximum height h of filter elements 404 (taken from the axis perpendicular to the screen plane).

• The maximum distance d between filter elements 404 (taken from the axis of the screen plane) • The angle b between the screen plane 402 and a top surface 408 of filter elements 404 • The profile of the top surface 408 of the filter element 404 (in Figure 4 it is a flat surface, though as will be discussed in more detail below, it may be chamfered, or have another suitable type of profile) • The cross sectional shape of the filter elements 404 (for example, may be wedges, triangles or rectangles) Figure 5A a bottom view of a screen 500 of a debris filter according to one embodiment. Figure 5B is a cross section of the screen 500 of Figure 5A through E—E. Figure 5C is an enlargement of Detail G of Figure 5B at a scale of 3:1. The screen uses the Coanda effect, in that filter elements 504 of the screen allow debris to pass over the screen and water to fall between each element.

In an example embodiment, the filter elements 504 are not tilted with respect to the plane of the screen.

The filter elements 504 of the screen 500 are oriented 90 degrees relative to the plane of the screen. In other words, the filter elements 502 are not tilted, and are perpendicular to the screen plane. For explanatory purposes, Figures 6A to 6C show enlarged filter elements with varying degrees of tilt. 6A shows a filter element 604 with an orientation (angle c) of < 90 degrees (measuring from the side of the screen that is configured to be elevated in use). Figure 6B shows a filter element 404 with an orientation (angle c) of 90 degrees. Figure 6C shows a filter element 604 with an orientation (angle c) greater than 90 degrees.

Figure 5D is an enlarged view of a filter element 504 according to one embodiment. The filter element is perpendicular to the plane 502 of the screen. The top surface 508 is inclined relative to the plane of the screen, with the leading edge (the uppermost edge of the filter element in use) of the filter element higher than the trailing edge of the filter element relative to the screen plane. An angle b between the screen plane and a top surface 508 of the filter elements 504 provides a height change of between 0.2mm to 1.0mm between the leading edge and the trailing edge (relative to the plane of the screen). The leading edge corner of the filter element includes a chamfer 526. The term chamfer is to be interpreted broadly to include any cut-out from the leading edge corner, including a rounded cut edge (as shown in Figure 5D) as well as a straight cut/cuts. Taking a leading edge height of 1mm, the chamfer may have an approximate radius of up to 1mm (though it may not be a true radius).

With reference to the parameters defined in Figure 4, the applicants have found that other suitable parameters for the screen 500 are as follows: • A degree of tilt (angle a) of the screen plane relative to horizontal is 58 degrees from horizontal (+5, -10 degrees). The tilt (angle a) of the screen plane relative to horizontal may be varied to optimise debris filtering according to the direction of the flow of water, volume of flowing water, volume of debris and/or other factors. A steeper tilt (angle a) improves debris ejection but increases the chance of water loss. A flatter tilt (angle a) increases the chance of debris staying on the screen.

• A width w of filter elements of between 1.8mm to 3.8mm. A larger width w of filter elements reduces the total permeable area of the screen, resulting in reduced flow capacity which may result in water splashing as it hits the screen.

• A height h of filter elements of between 4mm to 10mm • A distance d between filter elements of 0.8mm. The distance d may be configured to optimally filter a particular size or type of debris. The distance d may range between 0.2mm to 1.5mm to filter out gutter debris such as twigs, dead insects, and different types or combinations of leaves.

Increasing the distance d between filter elements allows for water to pass through easier but it also allows more debris to pass through, and for larger matter to become caught between the openings. Smaller distances d provide higher levels of filtration, however flow capacity is reduced.

It will be appreciated that this is specific to the types of debris commonly found in downpipes from domestic roofs. The parameters will therefore depend on the application.

As shown in Figures 3A to 3C, the filter elements of the screen may form a wave pattern or undulations configured to reduce trapped debris.

In the embodiment of Figure 3B, the undulations are at a maximum height at the centre 330 of the screen, dip downwards to low-points on either side out from the centre at 332 and then return to a level just below the maximum-point, at the edges 334 of the screen 208. The undulations are symmetrical about the centre 330 of the screen. The raised edges of the undulations at the edges 334 of the screen draw water away from the edges of the screen. The gradients in the undulations are sloped to maximise the working area of the screen (amount of the screen which filters and allows water to pass) and avoid overloading the low points 332 of the filter elements.

The filter elements may form patterns other than undulations. For example, filter elements may form sinusoids, polynomials, zig-zags, u-shapes, or any other suitable pattern configured to reduce trapped debris.

In domestic rainwater installations, a suitable screen area may be between 200mm by 120mm, with a thickness of 10mm. Screen area and thickness may vary according to the application.

The shape of the screen may be varied in accordance with where it is to be mounted. In the shown embodiments, the screen has a substantially rectangular shape with rounded edges. In other embodiments it may be circular, ovular, rectangular, or any other suitable shape.

In the shown embodiments, the screen has a flat surface plane. In other embodiments the screen may have a curved surface profile.

The screen may be manufactured from a polymer (e.g. nylon, ABS, PC, PP, PMMA or PVC), or any other suitable material. There may be an ultra violet stabiliser incorporated within the polymer material from which the debris filter is formed. This provides the ultra violet light resistance required for weatherability.

The polymer may include other additives such as anti mould or anti bacterial agents.

The production of a debris filter screen by means of a polymer is desirable as the per unit cost may be cheaper than metal fabrication methods. The screen may be injection moulded. The process of injection moulding the screen may include the steps of: 1. Forming a mould which includes a mould cavity. Figure 7 is an example of a suitable mould 700 including a first mould half 704 and a second mould half 706, together producing a mould cavity 702. 2. Injecting a molten thermoplastic polymer into the cavity. The polymer provides sufficient heat and plasticity to flow in the cavity to fill the cavity, including around the projections. The projections in the mould cavity may include rounded portions exposed to the flow of plasticised polymers, encouraging flow without voids. 3. Allowing the polymer to set 4. Removing the screen from cavity Although the debris filter has been described with reference to a downpipe filter, it may be used in any other application in which debris filtration from a fluid is required. Examples include surface channel drainage, spouting/gutters and rainheads.

While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the Applicant’s general inventive concept.

Claims (27)

1. A downpipe filter comprising a housing configured to connect to a downpipe, and a screen removably mounted within the housing, configured to filter debris from water flowing in the downpipe, wherein the screen including a plurality of spaced elements having a wave pattern or undulation for reducing trapped debris.

2. A downpipe filter as claimed in claim 1 wherein the screen is configured to create the Coanda effect as water falls on the screen in use.

3. A downpipe filter as claimed in any of the preceding claims wherein the screen is manufactured from a polymer.

4. A downpipe filter as claimed in any of the preceding claims wherein the screen is injection moulded.

5. A downpipe filter as claimed in any of the preceding claims wherein the wave pattern or undulation has a high point at the centre of the screen.

6. A downpipe filter as claimed in any of the preceding claims wherein the wave pattern or undulation is symmetrical about the centre of the screen.

7. A downpipe filter as claimed in any of the preceding claims wherein the wave pattern or undulation has high points at or near edges of the screen.

8. A downpipe filter as claimed in any of the preceding claims wherein the wave pattern or undulation is configured to draw water away from edges of the screen.

9. A downpipe filter as claimed in any of the preceding claims wherein the wave pattern or undulation gradients are sloped to optimise the working area of the screen.

10. A downpipe filter as claimed in any of the preceding claims wherein the plurality of elements have a substantially triangular cross section.

11. A downpipe filter as claimed in any of the preceding claims wherein top surfaces of the plurality of elements are inclined relative to the plane of the screen.

12. A downpipe filter as claimed in claim 11 wherein the top surfaces of the plurality of elements are inclined to provide a height change of between 0.2mm to 1.0mm of the top surfaces relative to the plane of the screen.

13. A downpipe filter as claimed in any of the preceding claims wherein the plurality of elements are substantially perpendicular to the plane of the screen.

14. A downpipe filter as claimed in any of the preceding claims wherein the plurality of elements include chamfers.

15. A downpipe filter as claimed in claim 14 wherein the chamfers are on leading edge corners of the plurality of elements.

16. A downpipe filter as claimed in claim 14 or claim 15 wherein the chamfers are rounded.

17. A downpipe filter as claimed in any one of the preceding claims wherein the housing includes a drip edge.

18. A downpipe filter as claimed in any of the preceding claims wherein in use, the screen is mounted within the housing at between 48 degrees to 63 degrees from horizontal.

19. A downpipe filter as claimed in any of the preceding claims wherein the spacing of the plurality of elements is between 0.2mm to 1.5mm.

20. A downpipe filter as claimed in any of the preceding claims wherein the plurality of elements have a width of between 1.8mm to 3.8mm.

21. A downpipe filter as claimed in any of the preceding claims wherein the plurality of elements have a height of between 4mm to 10mm.

22. A downpipe filter as claimed in any of the preceding claims including a second fine mesh screen.

23. A downpipe filter as claimed in any one of the preceding claims wherein the housing includes an inner wall configured to deflect water to an upper part of the screen.

24. A screen for a downpipe filter configured to filter debris from water flowing in the downpipe, the screen including: a plurality of elements having a wave pattern or undulation for reducing trapped debris; wherein the plurality of elements are substantially perpendicular to the screen plane; and wherein top surfaces of the plurality of elements are chamfered and inclined relative to the screen plane.

25. A guttering system including: a. a downpipe; and b. a downpipe filter as claimed in any one of claims 1 to 23, wherein the downpipe filter is located to filter debris from water flowing in the downpipe.

26. A method of manufacturing the screen of claim 24 comprising: providing a mould for the screen; injecting thermoplastic polymer into the mould; and removing the screen from the mould.

27. A method of retrofitting the downpipe filter of any one of claims 1 to 23 to a downpipe comprising providing a downpipe filter in at least two pieces; connecting a first filter piece to a first downpipe section; connecting a second filter piece to a second downpipe section; and connecting the first filter piece to the second filter piece.