AU659539B2

AU659539B2 - Filter cartridge

Info

Publication number: AU659539B2
Application number: AU35226/93A
Authority: AU
Inventors: Francis Robert Bannigan
Original assignee: Kambrook Distributing Pty Ltd
Current assignee: Kambrook Distributing Pty Ltd
Priority date: 1992-03-17
Filing date: 1993-03-16
Publication date: 1995-05-18
Anticipated expiration: 2013-03-16
Also published as: AU3522693A

Description

9539

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT A..N 00 0S8 Ineto Tile FITE CATRDG 44 t The following statement is a full description of this in~vention, including the best method of performing it known to I I I- I L m- 2 o

TITLE

Filter Cartridge FIELD OF THE INVENTION This invention relates to a filter cartridge for use in water filters.

o°e* BACKGROUND OF THE INVENTION The treatment of tap water has led to a recent 0 demand for the use of water filtration devices to improve the drinking qualities of tap water. There are a number of water filtration devices currently available that operate on a gravity fed system whereby a filter cartridge O placed in the flow of water that is fed from the top of a suitable container. Other filters use a pump to force unfiltered water to flow through a filter cartridge. In the gravity fed devices the water flows through the filtar cartridge to percolate beneath the cartridge in filtered form. The cartridge is usually a sealed cylindrical unit with a polypropylene mesh filter across the top and the bottom. The cylindrical unit contains a blend of P- 3 granulated activated carbon and beads of ion exchange resin. The polypropylene mesh filters ensure that the granulated carbon and ion exchange resin do not escape from the unit. Most filters have end portions that allow entry and exit of water respectively. The filter is designed so that a litre of water takes approximately seven minutes to permeate through the filter to ensure completion of the filtration process. In some cases, the filter cartridge is subjected to gamma radiation to further purify the assembly. It is usuelly recommended that the filter cartridge be replaced every thirty days or every one hundred litres of filtered water.

The filter cartridge has to be designed so that it is a simple exercise to remove and replace a used filter cartridge. It is also important that the design of the filter cartridge is such that its production costs are kept to a minimum. For successful operation of filter cartridges, it is important that the water permeates slowly through all the filter medium. It is also important that the filter medium does not escape from the cartridge. The filters that are placed above and below the filter medium are required to control the flow of water whilst ensuring S* full exposure to the filter medium. One problem with existing filter cartridges is the entrapment of air within the cartridge assembly. The fact that the exeunt water apertures are small to ensure a slow controlled release of 0 filtered water tends to cause the generation of air pockets -within the cartridge. Thus, when a new cartridge is fitted to a filter unit, the cartridge has first to be conditioned to shake out any air bubbles that are entrapped within the cartridge and to collect any residual dust from the filter medium. With existing cartridges there is a necessity to shake and jiggle the cartridge immersed in water before it attached to the unit. It can take four to five minutes j 1.

-4 to remove all the air bubbles. If the air bubbles are not totally removed, the efficiency of the cartridge is substantially reduced and there is a tendency for the cartridge to float in the water.

It is these problems that have brought about the present invention.

SUMMARY OF THE INVENTION According to the present invention there is provided a filter cartridge comprising a cartridge body having a top and a botto' adapted to allow a controlled flow of liquid through the cartridge body, a pair of filter screens extending across the body adjacent the top and bottom respectively to define a space therebetween arranged to contain a filter medium, characterised in that the S s 15 filter screen adjacent the top of the cartridge body is of conical shape and of fluted cross-section.

sp Preferably, both filter screens are of conical shape and of fluted cross-section, and the filter screens are inverted whereby the tips of the cones point towards 00° 20 the bottom of the cartridge body.

The upper filter screen may have at least one o 0* .0 o° narrow aperture to allow upward escape of air.

S: In a preferred embodiment, the upper filter screen has a peripheral rim that has a plurality of equally spaced narrow apertures positioned therein to allow upward escape of air, the apertures being positioned outside the 0 conical portion of the filter screen.

Preferably, apertures are provided in or adjacent the top and bottom of the cartridge, the apertures facilitating throughflow of liquid and escape of air and means is provided to control the flow of liquid from the apertures on or adjacent the bottom of the cartridge body.

DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawingu in which: NT O? 0i Lu I Figure 1 is an exploded perspective view of a water filter cartridge, Figure 2 is a plan view of the filter cartridge, Figure 3 is a side elevational view of the cartridge, and Figure 4 is a cross-sectional view of the cartridge shown in Figure 3.

DESCRIPTION OF EMBODIMENTS As shown in Figure 1, the water filter cartridge essentially comprises a slightly tapered cylindrical cartridge body 10 having a closed base 11 and a cover member 12. A pair of conical filter screens 14 and 15 are spaced r-spectively across the top and bottom of the filter body, and a filter medium 20 is located between the filter screens 14 and 15. The filter medium is in the form of granules of activated carbon resin and beads of ion exchange resin.

The upper filter screen 14 as shown in Figures 1 and 4 comprises an annular peripheral rim 9 with a downwardly projecting frusto-conical web 8. A spun polypropylene mesh in a fluted or corrugated configuration 3 is formed into a conical enclosure 7 which is bonded to interior of the web 8. As shown in Figure 1, the peripheral rim has four equally spaced arcuate slots 4 formed therein. The slots 4 allow upwards escape of air from the underside of the screen. The fluted configuration of the filter screen increases the effective crosssectional area of the screen without causing an undesired increase in the length or downward projection of the conical screen. The polypropylene mesh allows controlled through flow of water whilst preventing escape of the filter medium. The upward inclination of the flutes 3 also provides an escape route for entrapped air away from the flow of water through the filter screen.

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1- -I 6 3As shown with particular reference to Figures 1, 3 and 4, the cartridge body 10 is provided with a pair of diametrically opposed upwardly extending indents 25, 26 adjacent the closed base 11. Each indents 25 or 26 terminates in an arcuate slot 27 or 28 positioned between the surface of the indents 25 or 26 and the inner surface of the outer wall 29 of the cartridge body 10. The inner surface of each indent 25 or 26 is also provided with a small slit 30 which is positioned adjacent a larger rectangular cut-out 31. Both the slits 30 and cut-outs 31 communicate with the interior of the cartridge body The lower filter screen 15, like the upper screen 14, comprises an annular plastics peripheral rim 35 which supports a spun polypropylene filter member 40 pre-formed in a fluted configuration to be bonded or otherwise secured to a downwardly projecting frusto-conical web 36. The a€.

annular rim 35 is also provided with a pair of a diametrically opposed downwardly extending flanges 41 and 42. As shown in Figures 3 and 4, the flanges 41 and 42 are arranged to extend through the slots 27, 28 positioned between the indents 25, 26 and the outer wall 29 of the cartridge. The location of one of the flanges 41 is shown a in greater detail in Figure 3. The filter screen is secured within the cartridge body so that the annular rim 35 and therefore the filter screen as a whole can rotate a.a ointernally of the cartridge body. This rotation causes the flanges 41 and 42 to rotate through a small angle across the gap defined by the indents 25, 26. In one position, the flanges project over the larger rectangular cut-outs 31 allowing a very slow rate of water escape through the slits and in the other position, the flanges cover the slits but expose the larger rectangular cut-outs 31 thereby substantially increasing the rate of flow. Thus, the combination of the lower filter screen 15 and the indents i ^I lr i 7 in the base of the filter cartridge provides a very simple means of adjusting the flow rate of the filter. In this manner, the filter cartridge can be used in either gravity fed filters or pump filters by selection of the desired flow rate.

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*r S 00 00 041 As shown in Figures 1 and 4, the lower filter screen 15 sits near the base of the filter cartridge with the pointed end 40A of the conical filter 40 extending towards the base 11 of the cartridge. This arrangement allows air that may be trapped between the upper rim 35 of the filter and the base of the cartridge to escape via the apertures 30, 31 that are formed in the wall of the cartridge. It should be noted that the apertures in the wall of the cartridge are at the highest point that the air 15 can reach in the base of the cartridge. Thus, air trapped in the base of the cartridge has a simple and effective means of escape which substantially speeds up the conditioning process of the cartridge.

As shown in Figure 4, the filter medium 20 sits in the core of the cartridge body filling the cone 40 of the lower filter screen 15. The upper filter screen 14 is positioned so that the tip of the cone is just above the upper level of the filter medium 20. The positioning of the filter screens 14 and 15 allows for expansion of the filter medium when wet.

The upper end of the cartridge 10 is provided with a flared lip 50 that has two annular shoulders 51, 52, the inner shoulder 51 supports the underside of the rim 9 of upper filter screen 14 whilst the outer and upper shoulder 52 is arranged to support the inner edge 53 of the cover member 12 that is sonically welded to the periphery of the cartridge. The cover member 12 is dome shaped and has a plurality of elongate apertures 61 provided equally spaced around its periphery as shown with particular

I

k aference to Figure 2. An upwardly standing arcuate boss 62 is provided centrally in the top of the cover and the boss 62 has an elongate slot 63 with a cross cut 64 into which the stem 65 of a removable handle b'6 is a snap fit.

The removable handle 66 comprises a circular gripping portion 66A with a downwardly projecting stem 65 that terminates in a neck portion 68 and a tapered tip 69. The tapered tip 69 can extend through the cross cut 64 in the top of the cover and the neck portion 68 then locates against the slot 63. The slot 63 also serves as an aperture that facilitates escape of air with the cartridge.

The handle 66 is designed to be a removable snap fit so that the handle is only attached to the cartridge when Oo necessary. It has been found that in certain containers 15 designed to take the cartridge, people with large hands 0o °0 have difficulty in locating the cartridge without the aid 9 of the handle.

oo oe The filter cartridge described above is manufactured in moulded plastics. The number of components o° 20 has been kept to a minimum and the design of each component 0 0 reflects simplicity in tooling. The filter cartridges are sold as a sealed unit containing the filter medium. The oS units are subjected to gamma radiation to kill any residual o0oo 060 bacteria. Users of the filters are encouraged to replace the filter cartridges every thirty days or every 100 litres .00. of use. Thus, it is important to keep the cost of the replacement cartridges to a minimum. The design of cartridge described above reflects these needs.

The adjustability of the flow rate allows the cartridge to be used both in gravity fed and pump operated filter mechanisms. The design of the upper and lower filter screens in association with the positioning of exeunt air apertures in the cartridge and upper filter screen provides enhanced conditioning and allows the 9 cartridge to be conditioned much more quickly than conventional cartridges. The cartridge can now be conditioned in four or five seconds which means that the likelihood of the cartridge being used with entrapped air is remote which improves the overall efficiency of the assembly.

It is understood that the invention in its broadest aspects embraces a variety of modifications. In one option, the handle could be moulded integrally with the cover member which could be a snap fit onto the end of the cartridge body. The adjustability of flow rate, provided in the preferred embodiment by rotation of the lower filter screen could also be provided by a clip-on restrictor in the form of a disc having small discharge apertures that clips onto the base of the cartridge body. The cartridge body base could carry larger discharge apertures that could be covered by the removable restrictor.

1 ta o 'i

Claims

4. 0 010* 044,46 O 0 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A filter cartridge comprising a cartridge body having a top and a bottom adapted to allow a controlled flow of liquid therethrough, a pair of filter screens extending across the body adjacent the top and bottom respectively to define a space therebetween arranged to contain a filter medium, characterised in that the filter screen adjacent the top of the cartridge body is of conical shape and of fluted cross-section. 2. The filter cartridge according to Claim 1 wherein both filter screens are of conical shape and of fluted cross-section. 3. The filter cartridge according to Claim 2 wherein the filter screens are inverted whereby the tips of the cones point towards the bottom of the cartridge body. 4. The filter cartridge according to any one of the preceding claims wherein the upper filter screen is provided with at least one narr~ow aperture to allow upward escape of air.
5. The filter cartridge according to Claim 4 wherein the upper filter screen has a peripheral rim that has a plurality of equally spaced narrow apertures positioned therein to allow upward escape of air, the apertures being positioned outside the conical portion of the filter screen.
6. The filter cartridge according to any one of the preceding claims wherein apertures are provided in or- adjacent the top and bottom of the cartridge, the apertures facilitating throughf low of liquid and escape of air.
7. The filter cartridge according to Claim 6 wherein means is provided to control the flow of liquid from the apertures on or adjacent the bottom of the cartridge body.
8. The filter cartridge according to Claim 7 wherein the means comprises a displaceable flap that can be moved 11 to alter the cross sectional area of the discharge apertures.
9. The filter cartridge according to Claim 8 wherein the discharge apertures are positioned in the wall of the cartridge body adjacent the bottom, the discharge apertures being positioned at a height above the bottom that corresponds to the highest point of the filter screen adjacent the bottom of the cartridge body. The filter cartridge according to Claim 9 wherein the flap is formed integrally with the filter screen adjacent the bottom of the cartridge body, the flap being located to extend across an indentation in the side wall of the cartridge body whereby circumferential displacement of the flap causes the filter screen to rotate within the cartridge body, the flap being adapted to cover at least one discharge aperture formed in the indentation in the r side wall of the cartridge body. S11. The filter cartridge according to any one of the preceding claims wherein the top includes an upwardly extending removable handle. o° 1
12. The filter cartridge according to any one of the preceding claims wherein the top comprises a cover member 1o' that is sonically welded onto the top of the cartridge body, the cover member having therein a plurality of apertures to allow throughflow of liquid and escape of air. at
13. A filter cartridge substantially as described herein with reference to and as illustrated in the accompanying drawings. DATED this 16th day of March, 1993. KAMBROOK DISTRIBUTING PTY. LTD. By Its Patent Attorneys GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia i ABSTRACT A filter cartridge comprising a cartridge body having a top and a bottom adapted to allow a controlled flow of liquid therethrough, a pair of filter screens excending across the body adjacent the top and bottom respectively to define a space therebetween arranged to contain a filter medium, characterised in that the filter screen adjacent the top of the cartridge body is of conical shape and of fluted cross-section. 4, i l i t I a a 6«94 MN it S_