Description

The present invention relates to a filter cartridge, particularly a filter cartridge for use in gravity operated water filtration devices, a water filter device comprising a filter cartridge and an inlet funnel with a seat for the filter cartridge, a method for manufacturing a filter cartridge.

Filtration devices of the above-referenced kind particularly are being used as wa ter filters for everyday use in households, which is why they are also called table water filters. They are primarily used for clearing tap water of unwanted sub stances. Among these substances are chloride and hardness builders such as calcium and magnesia, but also lead, which finds its way into tap water through the use of lead pipes, especially in older houses.

In case of gravity-operated table water filters besides the pouring of tap water into the water filter, no work is necessary for filtering the water. The water simply flows downwards through a filter cartridge and into a receptacle for the filtered water due to the gravitational force. The filter cartridge is accordingly also gravity-oper ated.

One type of filter cartridges for such filtration devices is known for example from EP 1 748830 B. The filter cartridge comprises a housing consisting of a body portion with at least one water outlet and a head portion with at least one water inlet and at least one air outlet, the head portion being arranged on top of the body portion. Both components of the housing are made of a thermoplastics, in partic ular polypropylene. The housing is filled with water treatment media. The treat ment media usually comprises ion exchange resin and/or active coal, but other components may be used as treatment media as well. Inside the filter cartridge there is a mesh that prohibits the treatment media from exiting the openings (wa ter inlets and air outlets) that are located in the head portion of the filter cartridge.

Another type of filter cartridge is known from EP 3392201 A1 , for example. This type of filter cartridges comprises a housing consisting of three separate compo nents, namely a head portion with at least one water inlet and at least one air outlet, a circumferential side wall portion and a filter element including a flat po rous filter body and a rim. The head portion being arranged on top of the circum ferential side wall portion which is closed at the bottom by the filter element. The head portion and the circumferential side wall portion are made of a thermoplas tics, in particular polypropylene. The porous filter body extends over almost the entire bottom surface of the filter cartridge providing the filter cartridge with a large water outlet. The porous filter body is a sintered filter material containing active coal, which is known to extract certain substances from water including chlorine. The active coal has a particulate form whereby the active coal particles are fixed by the use of a thermoplastic binder such as polyethylene. This sintered filter ma terial can be produced in the form of a flat material having two opposite plane surfaces from which small disc shaped filter bodies can be cut or, as described in the EP 3 392 201 A1, it can be directly formed as a disc. Such filter bodies are also referred to as coal discs.

Water flowing through such coal disc is filtered by the active coal contained therein. The porous filter body can further contain other particulate filter material such as particles of an ion exchange or chelating resin. The interior of the filter cartridge can likewise be filled with a particulate water treatment media such as ion exchange resin and/or active coal, but other components may be used as treatment media as well. Also, inside the filter cartridge there is a mesh that pro hibits the treatment media from exiting the openings (water inlets and air outlets) that are located in the head portion of the filter cartridge. Because the filter ele ment fulfills two functions, the closing of the filter cartridge and filtering the water, the cartridge can be built relatively compact. On the other hand, mounting the porous filter body on the rim and then welding the rim to the circumferential side wall requires more production steps.

Thermoplastic materials are commonly used for the housings of the filter car tridges as they are food-safe, easy to process and sufficiently deformable in order to establish a fluid tight sealing with the seat of the inlet funnel.

It is an object of the invention to provide an alternative filter cartridge that com bines a compact design with an improved choice of material without affecting the functionality of the cartridge.

This object is achieved by a filter cartridge according to claim 1 and a water filtra tion device according to claim 10.

The filter cartridge comprises a cup-shaped housing with an open top and a cover closing the open top of the housing, the housing comprising a bottom wall and a circumferential wall integrally formed with the bottom wall. The bottom wall and a circumferential wall comprise active coal and a binder.

The filter cartridge is preferably a gravity-operated filter cartridge. Terms like top, bottom, above, below, upper, lower, upwards, downwards etc. refer to the filter cartridge or its parts when the filter cartridge is in an operational orientation, e.g. when it is plugged into a seat of an inlet funnel of a filtration device.

The term “circumferential” is particularly to be understood relating to an axis of the filter cartridge parallel to the gravitational direction. Hence, if an element is “circumferential”, the element preferably extends along a closed path around said axis. The axis is preferably located in the center of the filter cartridge. The bottom wall and the circumferential wall of the housing further may option ally comprise additives or, for example, other particulate filter material than ac tive coal such as particles of an ion exchange or chelating material or the like.

Ion exchange resin and active coal are among the most commonly used water treatment media types. Each type of water treatment media can serve different purposes. Ion exchange resin is used to reduce the hardness of the water by fil tering out the hardness builders like calcium and magnesia. Active coal on the other hand is used to clear water of substances that have a negative impact on the water taste such as chloride and substances that are harmful to the health of the consumer such as lead.

Like the known filter discs the cup shaped body is made of particulate active coal and a binder. However, by forming the entire cup-shaped body of the filter car tridge from the same material and closing it by a cover only two components have to be assembled. The invention therefore reduces the number of production steps and the number of different materials being used.

The water filtration device comprises such a filter cartridge and an inlet funnel with a seat for the filter cartridge. The seat of the inlet funnel is adapted to the filter cartridge design in that it provides an inner circumferential sealing surface adapted to accommodate an outer circumferential surface of the circumferential wall of the filter cartridge in a form fitting manner.

Known filter cartridges commonly comprise a flexible sealing rim being integrally formed with and extending horizontally from the cartridge housing. The filter car tridge when being plugged into the seat of the inlet funnel creates a seal between the seat and the sealing rim of the filter cartridge.

According to the invention the inner circumferential sealing surface of the seat particularly is adapted in shape and designed to be sufficiently elastic to compensate for higher form tolerances of the filter cartridge housing while ensur ing that a seal is created between the filter cartridge and the inlet funnel.

The only water inlet and air outlet of the filter cartridge is defined by the cover and optionally by at least a top portion of the circumferential wall extending above the seat when the filter cartridge is placed in the inlet funnel. The only water outlet of the cartridge is defined by the bottom wall and optionally by at least a portion of the circumferential wall extending below the seat when the filter cartridge is placed in the inlet funnel.

According to a preferred embodiment of the invention the binder is a plastic-free carbonized material and more preferably the binder is made of a sugar-based material.

As the invention allows for a reduced number of different materials it is particularly suitable to for taking environmental aspects into account, particularly for reducing the need for plastics and even for avoiding any plastics.

The sugar-based binder may be processed in the form of molasses, i.e. basically a highly viscous treacle of sugar and water, which is mixed with the active coal to produce a mouldable mass from which the cup shaped housing can be formed. Alternatively, the sugar-based binder may be processed in the form of a dry sugar which is mixed with the active coal to produce a dry granulate or powder mixture from which the cup shaped housing can be formed.

Sugar in the sense of the invention is not limted to sugar from saccharose, i.e. household sugar. In general, sugar includes sugars obtained from any kind of saccharides and mixtiures thereof. If the sugar-based binder is processed in the form of a dry sugar, preferably, low-melting sugar such as for example fructose is of particular relevance. Preferably, the cover is made of a plastic-free fabric in order to further improve the environmental sustainability.

Known filter cartridge housings comprise a cover or head portion made of ther moplastic materials and only the water inlet and the air outlet are additionally cov ered by a separate mesh, a permeable foil, a non-woven fabric and/or a grid lo cated inside the housing for prohibiting the water treatment media from exiting the inner volume of the filter cartridge. The cover according to the invention is entirely made of a plastic-free fabric providing an inlet opening and air outlet extending over almost the entire open top of the housing. It can be made in the form of a mesh, a woven fabric and, most preferably a non-woven fabric. It is manufactured separately from the housing and fixed to the same after the production of the housing is finished and its inner volume is filled with water treatment media, in particular ion exchange particles and loose active coal particles. Fixing the cover to the housing can be accomplished, for example, by gluing, beading, clamping with a clamping element, particularly a clamping ring, or a combination of these measures.

Plastic-free fabric can for example be made of fibers from the Abaca plant (Musa textilis) which is a species of banana.

While the so formed cover prohibits granular water treatment media from exiting the inner volume of the cup-shaped housing through open top of the housing, i.e. through the water inlet and air outlet, the material of the housing itself fulfills the same function, i. e prohibiting granular water treatment media from exiting the inner volume through the water outlet.

According to another preferred embodiment the cup-shaped housing is at least partially filled with an anorganic ion exchange material and most preferably comprises one or more zeolites. This aspect further takes environmental issues into account.

Zeolites are the aluminosilicate {AIO% ^~ and SiO% ^~ ) members of microporous solids called "molecular sieves". They mainly consist of Si, Al, 0, and metals including Ti, Sn, Zn, and others. They have a porous structure that can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+ and others. These positive ions can readily be exchanged for others in a contact solution. Both naturally oc curring and artificially produced zeolites are considered for the purpose of the invention. Commonly known mineral zeolites that can be taken into consideration are for example analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite.

Preferably the circumferential wall exhibits an outer circumferential surface having a smaller horizontal cross section next the bottom wall than next to the open top.

This measure on the one hand provides a draft angle simplifying the demoulding process. Additionally it adds to improve the seal between the seat of the inlet funnel and the circumferential wall in that the conical form additionally compen sates for higher form tolerances of the filter cartridge housing.

This requirement can be fulfilled by different geometries. The circumferential wall of the housing can for example widen continuously from the bottom to the top. It can alternatively have a circumferential wall being divided top down into a circum ferential top portion, a circumferential transitional portion and a circumferential bottom portion, wherein mainly the transitional portion provides a transition from the smaller horizontal cross-section to the larger horizontal cross-section of the housing. In the latter case the seat of the inlet funnel has to be provided with a sealing seat having an inner circumferential sealing surface adapted to accom modate the outer circumferential surface of the transitional portion of the circumferential wall in a form fitting manner. Hence, any one of these geometries provides for an improved seal created between the outer circumferential surface of the housing wall and the seat.

According to another aspect the circumferential wall is thicker next to the open top than next to the bottom wall.

This has two advantages. Firstly, the thicker wall at the top increases the strength of the cup shaped body of the filter cartridge housing. Thus the cartridge does not tend to deform in an uncontrolled manner even if it is pushed too hard into the seat of the inlet funnel. Secondly a larger wall thickness next to the open top locally increases the flow resistance of the wall material next to the top thereby preventing the water to bypass the water treatment media located in the inner volume of the filter cartridge.

The above object is also achieved by a method for manufacturing a filter cartridge according to claim 11.

The method comprises the steps mixing active coal particles with a sugar-based binder (and optionally with additives or other particulate filter material than active coal), forming a cup shaped body from the mixture, carbonising the cup-shaped body to form a cup-shaped housing, filling the cup-shaped housing with water treatment media, in particular with ion-exchange material, and closing the filled cup-shaped body with a cover.

The method includes different alternative ways to obtain the cup shaped body from the mixture. According to a first alternative, the step of mixing includes mixing the active coal particles with a sugar-based binder to a mouldable mass. The binder in this case preferably is composed of molasses, i.e. basically a highly viscous treacle of sugar and water. The cup shaped body accordingly is formed from said mouldable mass. The viscosity of the moldable material is to be adjusted during the mixing step and optionally by a pre-drying step depending on the de mands of the forming step. Forming the cup shaped body, for example, can be accomplished by known methods such as dye molding, extruding, deep-drawing, thermoforming, additive manufacturing (3D-printing) or the like. In an optional step the cup shaped body may be dryed after forming and before it is carbonized in order to obtain a sufficiently firm intermediate product.

According to a second alternative, the step of mixing includes mixing the active coal particles with a dry sugar-based material to a dry granulate or powder mix ture. The cup shaped body accordingly is formed from said dry granulate or pow der mixture. This forming step includes injection moulding wherein the binder is melted under the action of heat during injection moulding. The forming step ac cording to another alternative includes sintering, wherein the dry granulate or powder mixture is introduced into a mould and then sintered in a furnace.

Both the drying and sintering steps help to ensure that the cup-shaped body dur ing and particularly after the forming step achieves sufficient structural stability to be able to be passed on to the following processing steps. During the carbonizing step the sugar, after drying/sintering still being soluble in water, looses is solubil ity, the measure being essential to obtain a sufficiently water-resistant material for the intended purpose of use.

According to the method the bottom wall and a circumferential wall of the housing preferably will be intergrally formed from same the material.

Finally the object is also achieved by making use of sugar-based material as a binder for a cup-shaped housing in the manufacturing of a filter cartridge. As men tioned above, sugar-based material includes sugar from saccharose or sugar from any other kind of saccharides and mixtures thereof, wherein, depending on the particular way of processing, low-melting sugar such as for example fructose may be of particular interest.

The invention will be described in detail with reference to the examples shown in the drawings, in which the following is shown:

Figure 1 a first embodiment of a water filtration device according to the inven tion in vertical sectional view;

Figure 2 a second embodiment of a water filtration device according to the invention in vertical sectional view and

Figure 3 a third embodiment of a water filtration device according to the in vention in vertical sectional view.

Figure 1 shows a water filtration device 10 comprising an inlet funnel 12 with a seat 14 and with a gravity-operated filter cartridge 20 being inserted into the seat 14. The seat 14 of the inlet funnel 12 has an inner circumferential sealing surface 16.

The filter cartridge 20 comprises a housing 22 with an open top 24 and a cover 26 covering the open top 24. The housing 22 comprises a bottom wall 28 and a circumferential wall 30. The circumferential wall 30 exhibits an outer circumferen tial surface 32 having a smaller horizontal cross-section next to the bottom wall 28 than next to the open top 24. The outer circumferential surface 32 constantly widens from bottom to top. The circumferential wall 30 also is thicker next to the open top 24 than next to the bottom wall 28.

Inside the housing 22 of the filter cartridge 20 an inner volume 34 is provided in which water treatment media 36 is located. The inner circumferential sealing surface 16 of the seat 14 is conical with a larger horizontal cross-section at its upper end than at its lower end. It is particularly adapted to accommodate the outer circumferential surface 32 of the cir-cumfer- ential wall 30 of the filter cartridge housing 22 in a form fitting manner thereby forming a seal therebetween.

The filtration device 10 is gravity-operated. Besides the pouring of tap water into the water filter, no work is necessary for filtering the water. The water simply flows predominantly downwards into direction of gravity indicated by arrow 11 through the filter cartridge and after filtration is collected in a receptacle 40 for the filtered water. The receptacle 40 is also called pitcher. In a top section thereof it accom modates the inlet funnel 12.

According to this embodiment the cover 26 and a top portion 42 of the circumfer ential wall 30 being positioned above the seat 14 when the filter cartridge 20 is placed in the inlet funnel 12 defines the water inlet which is permeable for unfil tered water. The water entering the inner volume 34 of the housing 22 comes in contact with the water treatment media 36 and leaves the inner volume through the water outlet after a defined duration of treatment.

The bottom wall 28 and a bottom portion 44 of the circumferential wall 30 is posi tioned below the seat 14 when the filter cartridge 20 is placed in the inlet funnel 12. The bottom wall 28 and the bottom portion 44 of the circumferential wall 30 thus define the water outlet of the cartridge 20 from which filtered water enters into the receptacle 40. The duration of treatment is adjusted by the length of the filter cartridge 20 extending below the seat 14 and further by the wall thicknesses of the bottom wall 28 and the bottom portion 44 of the circumferential wall 30. An advantage of the top portion 42 of the circumferential wall 30 extending above the seat 14 of the inlet funnel 12 is that the filter cartridge 20 for insertion and removal can be easily grasped without the need for an additional handle.

The second embodiment according to figure 2 differs from the first embodiment in that the filter cartridge 20 is less high so that no portion of the circumferential wall 30 extends above and below the seat 14. Accordingly only the cover 26 de fines the water inlet and the bottom wall 28 defines the water outlet of the car tridge. The reduced overall height aims at a more compact housing and thus also material savings.

The third embodiment according to figure 3 differs from the first embodiment in that the filter cartridge 20 has a circumferential wall 30 being divided top down into a top portion 42, a transitional portion 46 and a bottom portion 44, wherein mainly the transitional portion 46 provides a transition from the smaller horizontal cross-section at the bottom to the larger horizontal cross-section at the top of the housing 22. Only the outer circumferential surface of the transitional portion 46 contributes to the sealing in that the seat 14 of the inlet funnel 12 has an inner circumferential sealing surface 16 adapted to accommodate the outer circumfer ential surface of the transitional portion 46 in a form fitting manner.

After use the filter cartridge can be disposed of, incinerated or composted without hesitation. Although the active coal and the zeolites themselves are not com postable they are nonhazardous to the environment.