This application claims priority to South African provisional patent application number 2015/08575 filed on 20 November 2015, which is incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to a microfiltration assembly and a method of manufacturing a microfiltration filter and assembly.

BACKGROUND TO THE INVENTION

Filtration involves removing particulate matter from water by forcing water through a porous media. This porous media can be natural, in the case of sand, gravel, and clay or it can me a membrane wall made of various materials. Microfiltration can be used for removal of particulate and macromolecules from raw water to produce potable water. It is a type of physical filtration process where a contaminated fluid is passed through a special pre-sized membrane to separate microorganisms and suspended particles from process liquid. Many microfiltration assemblies and filters are known and an example of such a unit is disclosed in the South African patent application number 2009/07042 entitled "Reverse Flow Microfiltration". It discloses a microfiltration unit, which includes two co-planar flexible woven fibre filtration sheets peripherally connected to define at least one internal collection chamber and a fluid outlet extending from inside the collection chamber to an outside thereof. It further discloses a microfiltration assembly, which includes at least one microfiltration unit and a fluid extraction manifold, the manifold being in fluid flow communication with the fluid outlets of the microfiltration units.

The invention of this application provides for a microfiltration filter, an assembly containing such a filter and a method of manufacturing it. The disclosures of this invention are useful in the treatment of water for providing safe drinking water.

The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.

In the remainder of this specification the word "tube" or "tubular" should be construed broadly so as not to be limited to a structure that has a circular cross-section, but shall include any elongate structure that accommodates confined flow along a substantially longitudinal direction of the structure within a transversely enclose body.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a method of manufacturing a microfiltration filter, the method comprising the steps of:

providing an elongate, tubular collection chamber having two substantially parallel planar sides manufactured from woven fibre filtration material and having opposing long edges and opposing open edges;

positioning an elongate collection manifold between the sides at least partway along and at or near a long edge of the collection chamber;

providing a fluid outlet in at least one of the sides, the fluid outlet being in fluid communication with an interior of the collection manifold;

sealing open long and short edges of the collection chamber to form a liquid impervious seal ; and

folding the collection chamber across the long edges to create a filter with multiple adjacent layers of the elongate, tubular collection chamber.

Further features of the invention provide for the step of providing the elongate, tubular collection chamber to include folding a sheet of woven fibre filtration material onto itself, thereby providing an elongate double sheet of filtration material, forming the two substantially parallel planar sides with aligned edges, the double sheet having open and blind long edges and two short opposing open edges; and for the step of folding the collection chamber to include rolling it into a coil or, alternative, folding it into a zig-zag pattern.

Still further features of the invention provide for the method to include the steps of: positioning a spacer between the parallel sides prior to sealing the edges; and securing a substantially rigid end cover to one or both long edges of the folded collection chamber, the end cover defining apertures through which operatively outer surfaces of the collection chamber are accessible. The spacer may be foraminous and may include an antimicrobial agent. Yet further features of the invention provide for the step of sealing open long and short edges of the collection chamber to include securing aligned edges together with overlook stitches and applying a liquid impervious sealing agent over the stitched edges.

The invention further provides a microfiltration filter comprising:

an elongate, tubular collection chamber having two substantially parallel planar sides manufactured from a woven fibre filtration material and having opposing long edges and opposing short edges;

an elongate collection manifold between the sides and positioned at least partway along and at or near a long edge of the collection chamber; and

a fluid outlet in at least one of the sides, the fluid outlet being in fluid communication with an interior of the collection manifold, wherein open long and short edges of the collection chamber are sealed to form a liquid impervious seal and the collection chamber is folded across the long edges to create a filter with multiple adjacent layers of the elongate, tubular collection chamber.

Further features provide for the elongate, tubular collection chamber to comprise a sheet of flexible woven fibre filtration material folded onto itself to provide and elongate double sheet of filtration material forming the two substantially parallel planar sides with aligned edges, the double sheet having open and blind long edges and two short, opposing open edges; for the collection chamber to be rolled into a coil or, alternative, folded into a zig-zag pattern; for the filter to include a spacer between the folded parallel sides; and for the filter to include one or two substantially rigid end covers secured to one or both long edges of the folded collection chamber, the end covers defining apertures through which operatively outer surfaces of the collection chamber are accessible.

Still further features provide for open long and short edges of the collection chamber to be sealed by securing aligned edges together with overlook stitches and applying a liquid impervious sealing agent over the stitched edges.

Yet further features provide for the spacer to include an antimicrobial agent; for the filter to include a stiffening support for supporting the folded collection chamber in an operatively vertical orientation; for the flexible woven fibre filtration material to be manufactured from polyester; and for the sheet of flexible woven fibre filtration material to be selected from the group including: GELVANOR BFP0068 standard flat sheet; GELVANOR BFP0068 tubular flat sheet; GELVANOR BFP0642 Heatset (F04); and GELVANOR BMP7523 Scour/Heatset.

A yet further feature provides for the spacer to be foraminous, preferable a mesh manufactured from a resiliently flexible material.

The invention still further provides a microfiltration assembly comprising:

a liquid receptacle having an open, operatively upper end;

a microfiltration filter as described above secured inside the receptacle; and

a permeate outlet in an operatively lower region of the receptacle, wherein the permeate outlet is in fluid communication with the fluid outlet of the microfiltration filter and sealed off from the interior of the receptacle.

Further features provide for the microfiltration assembly to include a course secondary filter including a mesh held within a collar which is securable over the open end of the receptacle; a lid; a tap secured within a permeate outlet line; a run-off tube secured in the tap nozzle; and a pedestal within which the assembly may be seated during use, thereby increasing the gravitational drop of water being filtered through the assembly.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 is an elongate woven fibre material sheet used in a method according to embodiments of the invention;

Figure 2 is an illustration of a folded woven fibre material sheet of Figure 1 ;

Figure 3 is an illustration of the folded woven fibre material sheet of Figures 1 and 2 with a permeate collection manifold positioned therein;

Figure 4 is an illustration of the sealed folded elongate woven fibre material of Figure 2 including a permeate discharge nozzle secured in a side thereof; Figure 5 is an illustration of a sealed microfiltration filter of the invention rolled into a spiral configuration;

Figure 6 is an illustration of the sealed microfiltration filter of Figure 5 with a substantially rigid end cover secured to the sealed long edge of the folded collection chamber;

Figure 7 is an illustration of a microfiltration assembly according to embodiments of the invention;

Figure 8 is an illustration of on opened microfiltration assembly of Figure 7;

Figure 9 is an illustration of a secondary, rough particulate filter of a reservoir used in an assembly according to an embodiment of the invention;

Figure 10 is an illustration of the inside of a microfiltration assembly showing a cleaning brush being introduced to the filter during a cleaning process;

Figure 1 1 is an illustration of the inside of a microfiltration assembly showing a cleaning brush partially inserted through an aperture in an end cover of the filter during a cleaning process;

Figure 12 is an illustration of the inside of a microfiltration assembly showing a cleaning brush entirely inserted through an aperture in an end cover of the filter during a cleaning process;

Figure 13 is an illustration showing an alternative configuration of the filter unit of the invention; and

Figure 14 is an illustration showing a further alternative configuration of the filter unit of the invention.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS An embodiment of the invention provides a method of manufacturing a microfiltration filter. The method is described in what follows with reference to Figures 1 to 5. In broad outline the method comprises folding a sheet of woven fibre filtration material onto itself, thereby providing an elongate double sheet of filtration material having two substantially parallel planar sides with aligned edges. The folded double sheet has open and blind long edges and two short opposing open edges. The method includes positioning an elongate collection manifold between the sides at least partway along and at or near the blind edge, providing a fluid outlet in at least one of the sides wherein the fluid outlet is in fluid communication with an interior of the collection manifold. The method further includes sealing the open long edge and short edges of the double sheet to form a liquid impervious seal and a tubular, elongate collection chamber between the sides, and folding the elongate collection chamber across the long edges to create a filter with multiple adjacent layers of the tubular, elongate collection chamber.

An embodiment of the invention illustrated in Figures 7 to 13 provides a microfiltration assembly. The microfiltration assembly comprises a liquid receptacle, having an open operatively upper end, a microfiltration filter as described above secured inside the receptacle, and a permeate outlet, located in an operatively lower region of the receptacle. The permeate outlet is in fluid communication with the fluid outlet of the microfiltration filter and sealed off from the interior of the receptacle.

A microfiltration filter and a method of manufacturing the microfiltration filter is shown with reference to Figures 1 to 6. As shown in Figures 1 and 2, an elongate sheet of flexible woven fibre filtration material (100) is folded upon itself over one of its long edges (102), until opposing long edges align as shown in Figure 2, thereby defining two substantially parallel filtration sheets (202, 204) forming filtration sides. Once so folded, the material (100) forms a double sheet of filtration material having open (208) and blind (210) long edges and two short opposing open edges (212).

A spacer (206) including an antimicrobial agent and manufactured from a resiliently flexible mesh is interposed between the sides (202, 204) as shown in Figure 2. A permeate collection manifold (302) as shown in Figure 3 is positioned between the sides (202, 204) at or near the blind edge (210) and extending substantially the entire length of the edge (210). The manifold (302) includes a plurality of apertures (304) providing access into the manifold and through which liquid may pass and collect and flow inside the manifold. The manifold (302) has an outlet (306) which is secured and sealed around the periphery of a fluid outlet in a side of the filtration material, so as to be in fluid communication with the interior of the manifold. As shown in more detail in Figure 4, a permeate discharge nozzle (402) is secured in the fluid outlet (306) for discharge of fluid from within the manifold (302). The aligned edges of the open long and short edges of the sides (202, 204) are then secured together by means of an overlooking stitch, after which they are covered with a liquid impermeable sealing agent such as a waterproof glue (404) as shown in more detail in Figure 4. Once so sealed, the folded, sealed sheet forms an elongate, tubular collection chamber between the sides with the collection manifold (302) positioned at the blind edge (210) providing fluid communication between the collection chamber, through the apertures (304) in the manifold (302) and out the discharge nozzle (402) in the side. As shown in Figure 5, the entire unit is then rolled or folded into a spiral (502) which, when placed on the blind, then operatively lower, edge (210), provides the sealed, long edge (208) at its top and the discharge nozzle (402) at the bottom. A stiffening support may be provided for supporting the tubular, elongate collection chamber in an operatively vertical orientation. In use, the microfiltration filter is at least partially submerged in a feed suspension which is to be filtered. Permeate or clean liquid then moved through the side sheets, leaving the contaminants in the feed suspension. The flow of liquid is from the outside of the sheets into the interior space between the sheets, referred to above as the tubular collection chamber. The mesh or spacer between the two sheets is a grid and biases the two filtration sheets apart, thereby permitting or facilitating the flow of liquid between the sides, through the collection chamber towards and into the collection manifold through the apertures therein. The clean water then collects in the permeate collection manifold from where it can be discharged via the permeate discharge nozzle. The flow of liquid through the filtration sheets into the tubular collection chamber may be facilitated by applying positive pressure to the feed suspension or negative pressure to the interior of the collection chamber or at the discharge nozzle. However, the filter according to this embodiment of the invention may be particularly suited for use in gravity fed, low-cost filtration assemblies in which a water reservoir including the filter is slightly elevated from ground level. The spirally configured filter unit can be unrolled to clean and rolled back again for subsequent use.

In one embodiment of the invention, as shown in Figure 56 the spiral configuration of the tubular collection chamber may be maintained by means of a substantially rigid end cover (602) secured to the sealed long edge (208) of the folded collection chamber. The end cover (602) can be moulded from a resilient or hard plastic material and may define a plurality of apertures or slots (604) through which operatively outer surfaces of the tubular, elongate collection chamber may be accessible. The cleaning functionality provided by the end cover is described in more detail further below. It will also be apparent that the end cover may serve to keep the adjacent sections of the filter spaced apart so that the feed suspension may be exposed to as much surface area of the filter as possible. A gravity-fed microfiltration assembly (700) according to another aspect of the invention is shown in Figures 7 to 12. The assembly (700) as shown from the outside in Figure 7, includes a water reservoir or container (702) with a spiral microfiltration filter as described above secured therein in an upright configuration in which the sealed long edge is positioned at the top and the blind long edge with the collection manifold positioned therein is positioned at the bottom of the reservoir (702). The permeate discharge nozzle of the microfiltration filter protrudes outside the reservoir and a tap (704) with a permeate feed-off tube (706) is connected to the permeate discharge nozzle in the outlet line. The entire assembly (700) has a secondary, large particulate filter cover (708) (as shown in more detail in Figures 8 and 9), which includes a mesh (710) secured within a rim (712) which is securable over an open end of the reservoir (702). The assembly (700) further includes a lid (714) and is elevated off the ground within a three-legged pedestal (716) within which the assembly may be seated during use. It will be appreciated that the pedestal increases the gravitational drop of the water being filtered through the assembly, while placing the reservoir at a convenient height so that a container for filtered water may be placed below the assembly with the feed-off tube (706) placed through an opening in the container.

In use, feed suspension is poured through the large particulate filter cover into the reservoir. The large particulate filter cover removes the larger particles from the suspension. The feed suspension then permeates through the side membranes of the coiled filter and clean water collects inside the collection chamber, moves between the side walls to the collection manifold where it collects and can be discharged through the tap and permeate feed-off tube. It should be noted that the permeate nozzle and tap should be completely sealed off from the interior of the reservoir to prevent feed suspension coming into contact with the filtered water and again contaminating it.

As shown in more detail in Figures 10 to 12, a cleaning mechanism of the microfiltration filter unit in this embodiment includes a brush (1002) which is used to mechanically clean the external surfaces of the spirally configured filter unit (1004) by extending the brush head through the apertures in the end cover, between external surfaces of the coiled filter and brushing the surfaces with an up-and-down motion. Suitable organic or chemical agents may be used to facilitate cleaning of the filter surfaces. The brush may also include antimicrobials. The flexible woven fibre filtration material used in the manufacture of the filter may be manufactured from polyester. In specific embodiments of the invention it is foreseen that the sheet of flexible woven fibre filtration material may be manufactured from a material selected from: GELVANOR BFP0068 standard flat sheet; GELVANOR BFP0068 tubular flat sheet; GELVANOR BFP0642 Heatset (F04); and GELVANOR BMP7523 Scour/Heatset.

The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiment of the invention is intended to be illustrative, but not limiting, of the scope of the invention and numerous changes and modification may be made to the embodiments described without departing from the scope of the invention.

It is, for example, foreseen that the planar, tubular collection chamber may be folded in a number of different ways including but not limited to a spiral configuration, a pleated configuration, a zig-zag configuration, or any suitable configuration that ultimately has a large surface area per unit volume as shown in Figures 13 and 14.

Likewise, a microfiltration assembly may be made using any suitable reservoir and the microfiltration filter may be folded to accommodate the shape of such a reservoir. For example, the filter may be mounted within a waterproof bag which may be carried or hung on a tree or placed against a wall instead of on a stand. The waterproof bag according to this example adds portability to the product. Further, the reservoir may be replaced with a standard commercially available round plastic tube, which may be more readily available or robust. It is also foreseeable that alternative techniques may be used to seal the open long and short edges of the folded woven fibre filtration material. It is also anticipated that instead of using a single sheet of woven fibre filtration material that is folded onto itself to form the tubular, elongate collection chamber, two equally sized, elongate sheets of the woven fibre filtration material may be used. It will be appreciated that the use of two sheets of filtration material will necessitate the sheets to be secured together and sealed along all four edges.

The construction method of a microfiltration filter as described above holds numerous advantages over other known techniques, in particular it includes fewer seals and is of a simpler construction that other known methods.

Throughout the specification and claims, unless the contents requires otherwise, the word 'comprise' or variations such as 'comprises' or 'comprising' will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.