WO2016066804A1

WO2016066804A1 - Fluid treatment element, method of manufacturing it and fluid treatment device

Info

Publication number: WO2016066804A1
Application number: PCT/EP2015/075257
Authority: WO
Inventors: André Köhler
Original assignee: Brita Gmbh
Priority date: 2014-10-31
Filing date: 2015-10-30
Publication date: 2016-05-06

Abstract

A fluid treatment element is fluid-pervious and includes at least a fluid-pervious porous body (2) of thermally bonded material. The body (2) has at least a first major surface, of which at least a section is planar, and an axis (7) perpendicular to the plane of the first major surface. The first major surface forms the surface closest to an axial end of the fluid treatment element of a surfaces of porous bodies of thermally bonded material included in the fluid treatment element. The body (2) has a thickness corresponding to a maximum axial dimension of the body (2). A width of at least the first major surface of the body (2), corresponding to a maximum distance from a point on a circumferential edge of the first major surface to an opposite point on the circumferential edge, is larger than the thickness of the body (2). The body (2) has a lateral surface (8), closed on itself around the axis (7) and adjoining the first major surface at a circumferential edge thereof. At least a section of the lateral surface (8) extending from the first major surface tapers in axial direction.

Description

FLUID TREATMENT ELEM ENT, METHOD OF MANUFACTURING IT AND FLUID TREATMENT DEVICE

The invention relates to a fluid treatment element,

fluid-pervious and including at least a fluid-pervious porous body of thermally bonded material,

the body having at least a first major surface, of which at least a sec- tion is planar, and an axis perpendicular to the plane of the first major surface,

wherein the first major surface forms the surface closest to an axial end of the fluid treatment element of all surfaces of porous bodies of thermally bonded material included in the fluid treatment element,

wherein the body has a thickness corresponding to a maximum axial dimension of the body,

wherein a width of at least the first major surface of the body, corresponding to a maximum distance from a point on a circumferential edge of the first major surface to an opposite point on the circumferential edge, is larger than the thickness of the body, and

wherein the body has a lateral surface, closed on itself around the axis and adjoining the first major surface at a circumferential edge thereof.

The invention also relates to a method of manufacturing a fluid-pervious porous body of such a fluid treatment element.

The invention also relates to a fluid treatment device, including a replaceable fluid treatment element.

A water filter bottle marketed by the applicant under the name "Fill & Go" includes a replaceable filter disc integrated into the lid . The filter disc is made of thermally bonded activated carbon. Its major surfaces are covered by non- woven material. In use, the disc is pressed into a holder, which is then placed into the lid from below. The disc is clamped between seals that contact the major surfaces of the disc to prevent a bypass of water. A disc of this type is available by calendaring or moulding, whereby a mix of binder and activated carbon is placed at an elevated temperature high enough to make the binder tacky but not completely liquid. A relatively low pressing force is exerted in axial direction to ensure good contact between the compo- nents of the mix and adequate transfer of heat. A problem may arise from the fact that the binder remains slightly elastic. The thickness of the resulting porous element is not exactly equal to the distance between the pressing surfaces due to this elasticity. It is therefore difficult to obtain discs of a consistent thickness. Furthermore, it is difficult to make the surface exactly pla- nar, primarily because it is difficult to avoid wrinkles in the non-woven material. Also, process variations, e.g. in the rate of cooling upon thermal bonding of the material of the discs, may give rise to variations in the dimensions of the discs. These factors make it difficult to obtain a good seal when sealing elements of a holder for the disc are pressed against the opposing major sur- faces. The pressing force will differ, depending on the actual thickness of the disc concerned and on where the sealing elements are pressed against the surface(s). This is compounded by the fact that the sealing elements are generally annular, to ensure that all the liquid flows through the disc from the upstream major surface to the opposite, downstream major surface. The sealing elements will each extend in a circle close to the edge of a major surface, so that planarity is important. In any event, some of the surface area at the edges that is not enclosed by a sealing element is "wasted", in that no liquid passes through it.

It is an object of the invention to provide a fluid treatment element, method of manufacturing it and fluid treatment device of the types defined above in the opening paragraphs that allow for relatively effective sealing in use, when the fluid treatment element is held in axial direction in a seat provided for it in the fluid treatment device.

This object is achieved according to a first aspect by the fluid treatment ele- ment according to the invention, which is characterised in that at least a section of the lateral surface extending from the first major surface tapers in axial direction. The fluid treatment element is fluid-pervious, so that it has no impervious housing with inlet and outlet apertures. Instead, it is configured for placement in a direct sealing arrangement in a seat of a fluid treatment device, with the seat provided in a part separating an upstream section of the device from a downstream section of the device. The sealing arrangement ensures that fluid is forced to flow through the fluid treatment element from the upstream to the downstream section of the device. The fluid treatment element includes at least a fluid-pervious porous body of thermally bonded material. The thermally bonded material may be particulate material. It may comprise essentially only binder or a mix of binder and particles of material active in the treatment of fluid contacting this active material . The use of thermally bonded material has the effect that the porous element is less vulnerable to abrasion and need not be completely encased in material such as a mesh or non-woven providing for relatively fine mechanical filtering. The lateral surface in par- ticular may be left exposed . Even if covered with such material, there is less danger of particles blocking the material prematurely, because they are bound by the binder included in the body of thermally bonded material.

The body made of thermally bonded material will generally be self-supporting and retain its shape relatively well. It will therefore generally define the shape of the fluid treatment element. At least one, generally both, of an exposed first major surface and an exposed lateral surface of the fluid treatment element conform in shape to the first major surface and the lateral surface of the body respectively. Any layers covering the body can be supported by the body, rather than being rigid enough to be self-supporting if separated from the body. The first major surface forms the surface closest to an axial end of the fluid treatment element of all surfaces of porous bodies of thermally bonded material included in the fluid treatment element. Thus, with the body having at least a first essentially planar major surface, the fluid treatment element will also have a first essentially planar major surface either correspond- ing to or being parallel to and overlying the first major surface. In use, fluid flows through the body in axial direction. Because the width (e.g. the diameter in case of a first major surface having a circular perimeter) of the first major surface of the body is larger than the thickness of the body, the resistance to flow is relatively low. This is of use in gravity-driven fluid treatment devices or devices in which a user has to suck a potable liquid through the fluid treatment element to treat it.

At least a section of the first major surface, e.g. at least a section extending to the circumferential edge, is planar. The element is relatively easy to manufacture if the entire first major surface is essentially planar. The planar first major surface or planar first major surface section, which also defines the axial end surface of the fluid treatment element as a whole, allows for an axial pressing force to be exerted in a holder for the fluid treatment element, e.g. at three or more points on the surface in the plane. It can thus be ensured that the axis of the fluid treatment element is essentially aligned with an axis of the seat.

The body has a lateral surface, closed on itself around the axis and adjoining the first major surface at a circumferential edge thereof, of which at least a section extending from the first major surface tapers in axial direction. The taper is provided in the direction from the major surface, so that the major surface will be the upper surface when the fluid treatment element is dropped into a seat with a side wall conforming in shape. The lateral surface may be shaped as the lateral surface or surface sections of a truncated cone or pyra- mid. The lateral surface may comprise contiguous sections that are at an angle to each other to define ribs of the porous body. In fact, more complicated polyhedral shapes are possible. The porous body may have a cross-section (with the cross-sectional plane perpendicular to the axis) that is star-shaped, for instance. There will be relatively little variation in the shape and dimension of the lateral surface, because any pressing force exerted during thermal bonding will generally be in axial direction. Thus, even though the thickness of the element may vary, the fluid treatment element, which has a shape conforming essentially to that of the body, will protrude from the seat in which it is placed to an extent that varies relatively little between different fluid treatment elements. It is thus possible to provide for a part holding the fluid treatment el- ement in the seat and contacting the fluid treatment element at an end corresponding to the end at which the first major surface is provided . For a fixed position of such a part relative to the seat, the pressing force will be relatively consistent across a range of fluid treatment elements, even if the thicknesses of the fluid treatment elements included in them varies to quite some extent.

Moreover, sealing in the fluid treatment device will be against the lateral surface of the fluid treatment element. This lateral surface may be left uncovered, because the fluid flow is in axial direction, and not through the lateral surface. It can have a well-defined shape, conforming closely to the sealing surface of the seat of the fluid treatment device into which the fluid treatment element is placed, in use. The tapered seat surface sealing against the tapered lateral surface may be made large enough (in axial direction) to allow the edge of the major surface adjoining the tapered lateral surface to be covered . The entire major surface is thus available for fluid to enter without it taking a shortcut through the lateral surface.

It is observed that DE 10 2007 037 766 Al discloses a single-use filter cartridge for household water treatment. The filter cartridge consists of a three- dimensional, preferably cylindrical arrangement with a multi-layer build-up. It consists of two porous outer shells, a non-woven upper part and a non-woven lower part. A cavity in the upper non-woven part is filled with a tablet made of activated carbon and having a corresponding geometry. A cavity between a membrane foil and the non-woven lower part is filled with a mineral tablet. The respective layers - non-woven upper part, membrane, non-woven lower part - are provided in their edge regions with flush sealing surfaces in overlaid arrangement. The tablets are not made of thermally bonded material . When the cartridge is in the seat, the upper tablet, which is circle-cylindrical, determines how far the cartridge protrudes from the seat provided for the cartridge.

It is further observed that JP 2003-245564 A discloses a chip filter including an approximately cylindrical porous sintered body. A method for manufacturing the chip filter includes a step for softening and deforming a peripheral wall surface thereof by heating a punching blade when the approximately cylindrical porous sintered body is punched from a porous sintered body for punching. It is preferable that the porous sintered body is a product made of resin. Ultra-high molecular weight polyethylene is the preferable material . The form of the sintered porous body should just be approximately cylindrical in shape and the peripheral wall surface may be a truncated cone. The filter is for insertion inside the inner circular wall of a tip body having a tapered shape (the shape of a pipette). The thickness of the porous sintered body is relatively large compared to its maximum diameter. This gives it a relatively large peripheral surface, which guides it within the pipette, so that the axis of the porous sintered body is aligned with that of the pipette. If the thickness were to be reduced, the porous body would be likely to adopt a skewed position, resulting in leaks.

In an embodiment of the fluid treatment element according to the invention, the lateral surface of the body tapers over an extent corresponding to the thickness of the body.

This ensures that it is the tapering surface of the body, or the exposed surface of a layer overlying it and conforming in shape, that contacts a sealing part of the seat for receiving the fluid treatment element. The tapering section of the lateral surface of the body may be at an angle relative to the axis of at least 5°, especially an angle of at least 10°, e.g. 15°.

This angle is sufficient to ensure that the fluid treatment element is properly supported in the seat for receiving it.

In an embodiment, the tapering section of the lateral surface of the body is at an angle relative to the axis of at most 30°, especially an angle of at most 20°. This allows the fluid treatment element to be manufactured without too much difficulty. The angle also allows the fluid treatment element to sink into the seat sufficiently.

The width may be at least ten times the thickness, to yield an essentially pla- nar body and fluid treatment element. It has a relatively low resistance to flow directed through the plane of the first major surface.

In an embodiment, the lateral surface of the body is an exposed surface forming a lateral surface of the fluid treatment element.

If the lateral surface of the body were to be covered with a layer of material, e.g. a layer of sheet material, then the tapering shape might be defined less precisely. Moreover, if such material were to be fluid-pervious, there would be a risk of leaks due to fluid flowing into and within such a layer.

In an embodiment, a region of the body at the lateral surface of the body has a lower porosity than a remainder of the body. This avoids short-cuts through the body. The fluid is forced to flow in essentially axial direction over a distance essentially equal to the thickness of the body. With reference to a body axis of the body parallel to or aligned with the axis, the radially outermost region of the body is denser than a radially innermost region. In an embodiment, the lateral surface of the body is an essentially closed surface.

That is to say that the surface is essentially impervious to at least liquid. The surface may be obtainable by bringing binder at the lateral surface into a flowable state and distributing it over the surface to close any pores that are open to the lateral surface. The body can for example be punched out of a porous layer of thermally bonded material with a heated tool or it can be formed in a cavity of a mould having a side wall at an elevated temperature. In an embodiment, the thermal ly bonded material consists essentially of particulate material .

This provides smoother su rfaces, since there are no protruding fibre ends. Also, there is no risk of unbound fibre ends breaking off and being fl ushed out. Particulate material is amenable to forming porous material, the particles being point-bonded only.

In an embodiment, the thermal ly bonded material incl udes a mix of at least a binder and at least one material for the treatment of fl uid in a diffusive process, e.g . a material for the treatment of fl uid by sorption. Sorption for the present pu rposes includes adsorption, absorption and ion exchange. The active material may treat the flu id by elution of a su bstance into the fl uid as an alternative to treatment by sorption. In yet another embodiment, both types of material are present. The binder may be a thermoplastic polymer material, especially ultra-high density polyethylene. Such binders and the way in which they are processed are described, for example, in StrauB, S, "Gesinterte Kunststoff-Formteile fiir die Fest-/Fl iissig-Filtration", Technische Mitteilungen 05, (2), July 1992, pp. 100- 104.

In an embodiment of the flu id treatment element, the lateral surface of the body extends to a circumferential edge of a second major su rface, wherein, at least at the circu mferential edge, the second major su rface faces essentially in an opposite axial direction to the direction in which the first major surface faces.

The edge of the second major su rface, which is also an edge of the lateral surface, is thus relatively well-defined . In this embod iment, it is ensured that the lateral surface contacts a surface of a seal ing part of the seat for receiving the fl uid treatment element in the fl uid treatment device.

In an embodiment, the second major su rface is an essential ly u ninterrupted planar su rface. The second major surface is thus essentially planar over its entire extent.

This embodiment is relatively easy to manufacture. In particular, the body can be cut (e.g . punched, sawed or cut by means of a laser) from a sheet or plate of thermally bonded material obtainable by compacting and heating the mate- rial in a relatively simply shaped press. Moreover, such a sheet or plate can be covered on one or both sides by a sheet of fluid-pervious sheet material before the fluid treatment element is separated from it. This embodiment is particularly easy to manufacture, because pieces of the sheet material cut to shape need not be aligned before bonding them to the body, nor placed care- fully in a mould in which the fluid treatment element is formed. The fluid treatment element, in particular the body, of this embodiment has essentially the shape of a frustum, e.g. a frusto-conical shape or the shape of a square or triangular frustum.

In an embodiment, at least a surface of the body on an opposite side to the first major surface seen in axial direction is covered by at least one layer of fluid-pervious sheet material .

This surface corresponds to the second major surface in the embodiment described previously. The layer of fluid-pervious sheet material allows the thermally bonded material to be bonded relatively loosely, since the sheet material retains any unbound particles. There is no need to provide the body with a surface region of decreased average pore size to provide this retaining effect. In this embodiment, the covered surface would be the downstream surface, so that the first major surface is the upstream surface through which fluid enters the body. In such an embodiment, the pressure difference across the fluid treatment element also helps press the fluid treatment element into the seat of the fluid treatment device. The sheet material may be woven or non-woven textile material. Fibres of the material may be made of plastic, e.g. polypropylene or polyethylene.

In an embodiment, at least the first major surface is covered by at least one layer of fluid-pervious sheet material. The sheet material may be of the type described above. Where both su rfaces are covered by at least one layer of fl uid-pervious sheet material, the opposite exposed surfaces formed by the sheet material on the su rfaces of the body may have a different appearance. This hel ps a user place the fluid treatment element in a seat of a flu id treatment device with the right side up.

The same effect can be achieved more easily if the first major surface is left exposed . This can be done, since it wil l be the upstream major su rface. The tapered lateral su rface makes it impossible to place the flu id treatment element the wrong way u p into a seat that conforms in shape to the flu id treat- ment element. Moreover, cost savings are achieved if only the surface of the body on an opposite side to the first major surface seen in axial direction is covered by at least one layer of flu id-pervious sheet material .

According to another aspect, the method of manufactu ring a flu id-pervious porous body of a fl uid treatment element according to the invention includes : forming a porous, fl uid-pervious planar structure including at least a layer of thermally bonded material ; and

cutting at least the body of the flu id treatment element from the planar structu re,

wherein cutting the body from the planar structu re includes moving a cutting tool part in an axial direction relative to the planar structu re, and

wherein the cutting tool part includes a cutting edge defining an edge of an orifice del imited by an inner tool surface extending from the cutting edge, and

wherein at least a section of the inner tool surface is angled with re- spect to the axis of movement, such that a size of the orifice decreases in axial d irection away from the cutting edge.

This is a relatively efficient way of providing a porous body of a flu id treatment element with a tapering lateral surface. In particular, many such flu id treatment elements can be cut from a sing le planar structure, which is rela- tively easy to produce. Furthermore, the cutting process resu lts in a relatively accurately shaped lateral surface, even if the planar structu re is formed by calendaring and/or applying webs of sheet material to the porous planar structure, and even if the thermally bonded material is still at an elevated temperature with respect to ambient temperature when the porous body is separated from the layered structure. The cutting tool also ensures consistency, even if the process conditions during thermal bonding vary between production runs.

The method may comprise manufacturing a fluid treatment element according to the invention.

In an embodiment of the method, the angled section of the inner tool surface has an axial extent equal to at least the thickness of the body of the fluid treatment element.

This ensures that the lateral surface is completely tapered.

In an embodiment of the method, the angled section of the inner tool surface has a sufficient extent and is moved through the planar structure to compress an outer region of the planar structure entering the orifice. Thus, the cutting edge is advanced to emerge from an opposite surface of the planar structure to the one through which it entered, and then advanced to such an extent that the radially outer region is compressed, i.e. densified. When the fluid treatment element is placed in a seat of a fluid treatment device, short-cuts through the body are prevented to at least some measure. Most of the fluid is forced to pass through the body over a distance corresponding to the thickness thereof.

In an embodiment, the cutting tool part has an outer tool surface extending away from the cutting edge, the inner and outer tool surfaces forming opposite surfaces of a cutting blade. The cutting tool part is thus configured like a die cutter or cookie cutter. The body of the fluid treatment element is separated cleanly from the planar structure. In a variant of this embodiment, the outer tool surface includes at least a section, seen in axial direction, at a smaller angle with respect to the axis than a corresponding section of the inner tool surface.

To provide adequate separation, at least one of the inner and outer tool sur- faces must be at an angle. In this variant, the inner tool surface is at an angle, whereas the outer tool surface can be more or less parallel to the axis of movement (the stroke direction) of the cutting tool part. As a result, fluid treatment elements, or at least the porous bodies thereof, can be cut at a smaller mutual spacing from the planar structure. More of the planar structure is used to produce fluid treatment elements. Material is not pushed radially outwards with respect to a central axis of the orifice, which would require a higher spacing to be used in order to generate porous bodies with generally flat major surfaces and a relatively uniform porosity that decreases only close to the lateral surface of each porous body. The angle smaller than the angle of the corresponding section of the inner tool surface may be smaller than 5°, e.g. about 0°, at every axial position within the section.

It is noted that the section of the outer tool surface may be contiguous to a facet angled with respect to the axis and extending up to the cutting edge. This leads to a sharper cutting edge. Where the outer tool surface is provided with a facet at an angle with respect to the axis and extending essentially to the cutting edge, the axial extent of the angled section of the inner tool surface is a multiple of the axial extent of the facet, for example a multiple of at least ten, more generally at least a hundred. Such a facet functions to provide a sharp cutting edge but has too small an axial extent to compress the planar structure to any appreciable degree when the cutting edge is advanced into the planar structure. This is useful, because multiple porous bodies can thus be cut from a single planar structure at a smaller spacing, leading to less waste. In an embodiment, the cutting edge extends in a round, e.g. circular shape. This embodiment results in a porous body of a fluid treatment element of which the first major surface has a round, e.g. circular shape. In particular when the shape is essentially circular, the fluid treatment element can be rota- tionally invariant, facilitating its placement in a seat of a fluid treatment de- vice.

In an embodiment of the method, at least part of the cutting tool part is heated.

This embodiment is suitable for providing the porous body of the fluid treatment element with a lateral surface that is essentially impervious to at least liquid. Binder at the lateral surface is brought into a flowable state and distributed over the surface to close pores open to the lateral surface.

A similar effect is achievable with an embodiment in which at least the body of the fluid treatment element is cut from the planar structure whilst the latter is at a temperature above ambient temperature. This embodiment is also relatively fast. However, the layer of thermally bonded material is likely to be more elastic at elevated temperatures. The method is thus of extra benefit, in that the variation in thickness will be higher than if the planar structure were to be allowed first to cool down to ambient temperature. In an embodiment, an ejector is provided within the orifice and the ejector is used to move the body of the fluid treatment element out of the cutting tool part.

In one variant, the ejector is an elastic structure, which is compressed as the cutting tool part advances into the planar structure and ejects at least the po- rous body of the fluid treatment element from the orifice by relaxing after the part of the fluid treatment element in the orifice has been separated from the remainder of the planar structure. In another embodiment, the ejector includes a support device movable within the orifice, wherein at least one of the cutting tool part and the support device is driven by an actuator to move it relative to the other.

An embodiment of the method includes applying at least one layer of fluid- pervious sheet material to at least one surface of the layer of thermally bond- ed material prior to cutting the fluid treatment element from the planar structure.

In this embodiment, shaped pieces of sheet material need not be aligned exactly with the first major surface or an opposite surface of the porous body of the fluid treatment element in order to bond them to it. In an embodiment, at least the bodies of multiple fluid treatment elements are cut from the planar structure in parallel .

In this embodiment, the cutting tool part is one in an array, e.g. a row, of similar cutting tool parts, advanced together into the planar structure.

The method may include manufacturing additional fluid-pervious porous bod- ies, wherein at least two of the fluid-pervious porous bodies have different shapes, seen in cross-section with the cross-sectional plane perpendicular to the axis.

This allows one to provide fluid treatment elements for different uses that cannot be mixed up. Thus, the fluid-pervious porous bodies with different shapes may differ in terms of at least one of material composition and bulk properties (e.g . pore size distribution, average or mean pore size, porosity), thickness and flow resistance.

According to another aspect, the fluid treatment device according to the invention includes a replaceable fluid treatment element according to the invention and a seat for the fluid treatment element, wherein the seat is included in a barrier for separating an upstream part from a downstream part of the fluid treatment device,

wherein the seat includes an aperture closable by the replaceable fluid treatment element and surrounded by a sealing part arranged to contact a lat- eral surface of the replaceable fluid treatment element.

The fluid treatment device may include multiple fluid treatment elements and multiple seats. The latter may be provided in the same barrier, so that parallel treatment is achieved . The thicknesses of fluid treatment elements, particular the porous bodies thereof, can be within a relatively wide tolerance range without the extent to which the fluid treatment elements protrude from the cartridge seat varying wildly.

An embodiment of the fluid treatment device further includes a device for contacting an exposed planar surface of the fluid treatment element that is one of a surface corresponding to and a surface parallel to and overlying the first ma- jor surface of the replaceable fluid treatment element to limit axial movement of the fluid treatment element out of the seat.

This helps prevent the fluid treatment element from adopting a skewed position in the seat.

In a variant, the contacting device is arranged to contact the exposed major surface at multiple, e.g. three, discrete contact areas.

The contact areas can be relatively small, since three points of contact define the position of the plane of the exposed major surface. There is thus more surface area available for fluid to enter.

In an embodiment, the sealing part includes a part made of a material more elastic than that of an adjacent part of the barrier. Thus, small misalignments of the fluid treatment element can be compensated for. Also, a relatively large area of contact between the lateral surface, or a surface of a layer overlying it, and the sealing part can be provided.

In an embodiment, the aperture is delimited by a tapering surface.

This also helps ensure that a relatively large area of contact between the lateral surface, or a surface of a layer overlying it, and the sealing part can be provided .

According to another aspect, a set of fluid treatment devices according to the invention includes at least two devices with seats having different shapes, seen in cross-section with the cross-sectional plane perpendicular to the axis. They are each provided with fluid treatment elements of which at least the fluid-pervious porous bodies have corresponding different respective shapes, seen in cross-section with the cross-sectional plane perpendicular to the axis.

These fluid-pervious porous bodies with different shapes may differ in terms of at least one of material composition and bulk properties (e.g. pore size distribution, average or mean pore size, porosity), thickness and flow resistance.

The invention will be explained in further detail with reference to the accompanying drawings, in which :

Fig . 1 is a diagram of an apparatus for manufacturing fluid treatment elements;

Fig. 2 is a schematic side view of a fluid treatment element obtainable using the apparatus;

Fig. 3 is a cross-section of a cutting tool part for producing the fluid treatment element; is a diagram showing in cross-section part of a tool for obtaining multiple fluid treatment elements in parallel; Fig. 5 is a diagram showing in cross-section part of a tool for obtaining multiple fluid treatment elements in parallel that is a variant of the tool of

Fig . 5;

Fig. 6 is a diagram showing in cross-section the fluid treatment element in a seat of a fluid treatment device; and

Fig. 7 is a diagram showing a fluid treatment device in the form of a filter bottle, arranged to receive a fluid treatment element as shown in

Figs. 2 and 6.

In the following, the example of fluid treatment elements 1 (Fig . 2) and devic- es for treating a liquid will be used. The liquid may be drinking water, for example.

The fluid treatment element 1 is fluid-pervious and includes at least a fluid- pervious porous body 2 of thermally bonded material. The porous body 2 is self-supporting and essentially defines the shape of the fluid treatment ele- ment 1.

The porous body 2 is covered on opposite major surfaces by respective layers 3,4 of fluid-pervious sheet material. A first, larger, major surface of the porous body is covered by a first layer 3 exposing a first major surface 5 of the fluid treatment element 1. A second, smaller, major surface of the porous body 2 is covered by a second layer 4 exposing a second major surface 6 of the fluid treatment element 1. The sheet material is a piece of woven or non- woven textile, e.g . a mesh or fleece, for example a non-woven made of point- bonded polypropylene or polyethylene fibres.

The first and second major surfaces 5,6 conform to the underlying major sur- faces of the porous body 2, in that they have essentially the same extent and shape. A body axis 7 of the porous body 2 extends essentially perpendicularly to the first major surface of the porous body and thus to the first major surface 5 of the fluid treatment element 1. A lateral surface 8 of the porous body 2 extends from a circumferential edge of the first major surface of the porous body 2 to a circumferential edge of the second major surface of the porous body 2 over a shortest possible distance. Where the porous body 2 has the shape of a polygonal frustum, the lateral surface 8 for present purposes is the ensemble of all faces joining a section of the circumferential edge of the first major surface to a section of the circumferential edge of the second major surface.

The lateral surface 8 tapers in axial direction. The angle of taper with respect to the body axis 7 is at least 5°, e.g. at least 10°. About 15° is an appropriate value.

The lateral surface 8 is exposed, such that it also essentially forms a lateral surface of the fluid treatment element 1 as a whole. This is because the first and second layers 3,4 have a thickness at least an order of magnitude smaller than the thickness of the porous body 2. The thickness of the porous body 2 corresponds to a maximum axial dimension of the porous body 2. In the illustrated embodiment, the porous body 2 has essentially parallel opposite first and second major surfaces. It thus has an essentially uniform thickness and the shape of a frustum. The thickness is generally at least 4 mm. The thickness may be less than 40 mm, e.g. less than 20 mm.

The width of the porous body 2 at the first major surface thereof is larger than a thickness of the porous body 2, e.g. by a factor of at least two. The width corresponds to the maximum distance from a point on the circumferential edge of the first major surface to an opposite point on the circumferential edge, i.e. the diameter in case of a circular edge. The opposite point is where a line drawn through the point perpendicularly to the edge cuts through the edge again.

In the illustrated embodiment, the porous body 2 is formed from a single layer of thermally bonded material . Alternative embodiments may comprise multiple porous layers differing in at least one of composition, porosity, pore size and/or distribution of any one of these parameters.

The porous body 2 of the example has a substantially uniformly distributed porosity and pore size, except in a region near the lateral surface 8, where the porosity and pore size are lower. In the majority of the porous body 2, the porosity has a value larger than 20 %, in particular larger than 30 %, more particularly larger than 40 %. It may have a value smaller than 80 %, in particular smaller than 70 %, more particularly smaller than 60 %. Typically, the average pore size in the majority of the porous body 2 will be larger than 2 Li m, in particular larger than 5 urn. This average pore size will be smaller than 100 urn, in particular smaller than 70 ii m , more particularly smaller than 50 .urn.

In the examples discussed herein, the porous body 2 is made of thermally bonded particulate material . The material includes both a binder and an ac- tive material, in particular a sorbent. Examples include activated carbon, heavy metal sorbents, ion exchange materials, chelating agents and the like. In other embodiments, the material includes a component that leaches into the liquid as the liquid passes through the porous body 2.

The binder is a material that binds other particles when subjected to heat or radiation of another form. In the examples to be discussed herein, the binder is a thermoplastic binder, for example an ultra-high-molecular-weight polyethylene or high-density polyethylene. The melting point (as determined using differential scanning calorimetry) of the binder is at least 120° C, e.g. in the range of 120-150° C and it is thermally stable to at least 250° C, preferably at least, 300° C. The particle size of the binder may be of the order of

10-1000 Li m, for example. The particles of binder material may have an average diameter larger than that of the particles of active material. Thus, they increase the pore size without reducing the available surface area of the active material. The apparatus for manufacturing fluid treatment elements (Fig . 1) includes a main endless belt 9 on support drums 10, 11, of which at least one is driven by a motor (not shown). A device 12 for depositing a layer comprising particulate material including at least the binder particles and the particles of active ma- terial onto a lower web 13 of the fluid-pervious sheet material supported by the main endless belt 9 is provided. The second layer 4 of sheet material is formed from the lower web 13. The particles are deposited in dry form in the example, to save energy, but they may be sprayed on in an alternative embodiment. The lower web 13 is unwound from a reel 14. A doctor blade 15 sets the thickness of the layer. A device 16 for applying heat to an upper surface of the layer of particulate material applies heat in a contactless manner. This enables the application of an upper web 17 of fluid- pervious sheet material from a further reel 18. The first layer 3 of fluid- pervious sheet material is made from the upper web 17. The application of heat by the device 16 allows the upper web 17 to be applied to the layer of particulate material in such a manner that the exposed surface of the upper web 17, and thus the first major surface 5, is relatively smooth and free of wrinkles.

The layered structure resulting upon application of the upper web 17 is then heated in a double-belt press 19. The heated surfaces in contact with the layered structure can have a temperature of the order of 50° C above the melting point of the thermoplastic binder, for example. The double-belt press 19 is primarily used to improve the transfer of heat to the layered structure. The pressure applied by the double-belt press 19 is therefore minimal, e.g. below 5000 Pa.

A cutting device 20 cuts plates 21 from the layered structure before it can cool down to ambient temperature. Each plate 21 in turn is then transferred to a cutting apparatus 22 for cutting fluid treatment elements 1 from the plate 21. In an alternative embodiment, the cutting device 20 is omitted. Instead, ar- rays, e.g. rows, of fluid treatment elements 1 are cut from the layered structure as it emerges from the double-belt press 19. Thus, in such an embodi- ment, multiple fluid treatment elements are cut out in parallel . The cutting apparatus 22 would in this case move in synchrony with the layered structure emerging from the double-belt press 19 to cut a set of fluid treatment elements 1. After separating a set, it would then return to its original position, before again being moved in synchrony with the layered structure to separate the next set from the layered structure.

A cutting tool part 23 (Fig. 3) for cutting out a single fluid treatment element 1 from the plate 21 is provided with a cutting edge 24 defining an edge of an orifice. The cutting edge 24 is closed on itself around a central axis 25 of the orifice. The central orifice axis 25 is essentially aligned with the axis of movement of the cutting tool part 23. It is also aligned with the axis 7

(Fig . 2) of the fluid treatment element 1 formed using the cutting tool part 23.

In the illustrated embodiment, the cutting edge 24 is round, in particular circular, in shape. The cutting tool part 23 has an outer tool surface including an angled facet 26 for providing a sharp cutting edge 24 and an outer tool surface section 27 that is essentially parallel to the orifice axis 25. The facet 26 is at an angle β with respect to the central orifice axis 25. The angle β has a value higher than about 5°. An upper limit to the angle β is about 30°. A value within a range of 10-20° has been found to be quite suitable. The orifice is delimited by an inner tool surface comprising, in this example, an angled section 28 extending in axial direction from the cutting edge 24 to an opposite edge 29. An adjoining straight inner tool surface section 30 extends in axial direction to an aperture 31 at an axial end of the cutting tool part 23. In an alternative embodiment, the straight inner tool surface sec- tion 30 is dispensed with or provided with an extremely small axial extent compared with the angled section 28.

The angled section 28 is at an angle a with respect to the orifice axis 25. The angle a has a value higher than about 5°. An upper limit to the angle a is about 30°. A value within the range of 10-20° has been found to be quite suitable, with 15° providing sufficient functionality whilst keeping the rates of abrasion of the angled section 28 and dulling of the cutting edge 24 within acceptable bounds. This angle a corresponds essentially to the angle of the lateral surface 8 of the porous body 2 with respect to the body axis 7. It should not be too high, in order to ensure that the first major surface 5 stays essentially planar.

In an embodiment, heating coils (not shown) are provided to heat the cutting tool part 23 so that heat is transferred through the inner tool surface. The binder is then spread over the lateral surface 8 of the fluid treatment element 1 (Fig . 2), resulting in an essentially closed lateral surface 8 In use, with the plate 21 still at an elevated temperature relative to ambient temperature, the cutting tool part 23 is advanced into the plate 21 over a sufficient distance for the cutting edge 24 to emerge on the other side thereof. The plate 21 is supported by a support structure (not shown) with a prominent support surface having essentially the shape and dimensions of the first major surface 5 of the fluid treatment element 1.

It is observed that the angled inner tool surface section 28 extends axially over a distance equal to at least the thickness of the fluid treatment element 1. In an embodiment, the angled section 28 extends axially over an appreciably larger distance. The cutting tool part 23 can thus be advanced through and out of the plate 21 over a sufficient distance to compress a region of the porous body 2 at the lateral surface 8. The compression has the effect of reducing the porosity in this region. In particular where the cutting tool part 23 is heated, a shearing effect serves to distribute binder at the lateral surface so as to close many or all of the pores otherwise open to the surface. This further helps make the fluid treatment element 1 less pervious to liquid at the lateral surface 8.

After the fluid treatment element 1 has been separated from the plate 21, the cutting tool part 23 is lifted to allow the remainder of the plate 21 to be removed. Then, the fluid treatment element 1 is ejected from the orifice. An ejector device (not shown) may be inserted through the aperture 31, for example.

A simple alternative cutting apparatus includes a cutting tool 32 (Fig . 4) for cutting multiple fluid treatment elements 1 from the plate 21 in parallel with relatively little waste.

A first cutting tool part 33 is arranged about a first central axis 34. The first cutting tool part 33 includes a first cutting edge 35 having a quadrilateral shape. An adjacent second cutting tool part 36 is arranged about a second central axis 37 and is provided with a second cutting edge 38 with a similar shape to the first cutting edge 35. The first and second cutting edges 35,38 have a section 39 in common.

The first cutting edge 35 defines an edge of a first orifice, delimited by a first inner tool surface extending from the first cutting edge 35. The first inner tool surface includes an angled first inner tool surface section 40 that is an- gled with respect to the first cutting tool part axis 34, so that the size of the first orifice decreases away from the first cutting edge 35. The angled first inner tool surface section 40 adjoins a straight first inner tool surface section 41. An elastic ejection device 42, e.g. a piece of foam, is arranged within the first orifice. The elastic ejection device 42 is arranged to be compressed sufficiently to provide an ejection force on the return stroke, which causes a fluid treatment element 1 cut from the plate 21 and still present in the first orifice to be ejected.

The axial extent of the angled first inner tool surface section 40 is greater than the thickness of the porous body 2. Indeed, the straight first inner tool surface section 41 may be omitted in an alternative embodiment. The axial extent of the angled first inner tool surface section 40 is large enough and the cutting tool 32 is advanced sufficient far through the plate 21 to compress a region of the porous body 2 at the lateral surface 8. The angled first inner tool surface section 40 has an angle with respect to the first cutting tool part axis 34 within the ranges indicated above for the angle a of the angled section 28 of the cutting tool part 23 of Fig . 3.

The ang led first inner tool su rface section 40 del imiting the first orifice is provided on an opposite side of a divid ing wall section 43 to an angled second inner tool surface section 44 del imiting an orifice in a second cutting tool part 36. The second cutting tool part 36 is arranged about a central axis 37. The angled second inner tool su rface section 44 has an axial extent corresponding essentially to that of the first angled inner tool surface section 40. It angle with respect to the central axis 37 is the same as that of the angled first inner tool su rface section 40.

The cutting tool 32 may include a heating device for transferring heat through at least the angled tool surface sections 40,44. In this embodiment, the binder is spread over the lateral surface 8 in a flowable state, resulting in an essential ly closed lateral surface. A support plate (not shown) may be used to support the plate 21 when the cutting tool 32 is advanced through it. In addition, a clamping apparatus (not shown) may be used to hold the plate 21 against the su pport plate. The su pport plate may be provided with grooves having a complementary shape to that of the cutting edges 35,38, so as not to blu nt them when the cutting tool 32 emerges on the other side of the plate 21.

The q uadrilaterally shaped cutting edges 35,38 resu lt in fl uid treatment elements 1 having the shape of a quadrilateral, generally square, frustu m. Any other shape resu lting in a regular tiling may be used for the cutting edges 35,38. In a variant 32' (Fig . 5) of the cutting tool 32, the elastic ejection device 42 in the first cutting tool part 33 is replaced by an ejection pin 45, arranged within the orifice of the first cutting tool part 33'. The ejection pin 45 is movable with respect to the first cutting tool part 33' to eject the fl uid treatment element 1 after it has been cut from the layered structu re. A fluid treatment device for receiving the fluid treatment element 1 includes a holder (Fig. 6). The holder includes a seat provided in a first barrier 46 for separating an upstream from a downstream region of the fluid treatment device. The seat includes a seat aperture 47 closable by the fluid treatment el- ement 1. The shape of the seat aperture 47 corresponds to that of the fluid treatment element 1, in particular the first and second major surfaces 5,6. In the illustrated embodiment, it is defined by a sealing element 48 made of elastic material, which is distinct from the remainder of the first barrier 46. The sealing element 48 has a tapered inner surface 49 delimiting the aperture, which is provided in the sealing element 48. The angle of taper with respect to an axis 50 of the seat perpendicular to the plane of the aperture corresponds essentially to the angle of taper of the lateral surface with respect to the body axis 7 (Fig. 2).

A second barrier 51 includes a through-going channel 52 and supports three pins 53, of which only one is shown. The pins 53 extend essentially in axial direction. The respective free ends are arranged to contact the first major surface 5, when the first and second barriers 46,51 are positioned at their operational locations. A chamber is then defined between the first and second barriers 46,51. The pins 53 hold the fluid treatment element 1 in the seat with its body axis 7 aligned with the seat axis 50.

The chamber is established, when the first barrier 46 is releasably connected to the second barrier 51 via a threaded connection. Threads 54,55 define the position of the first barrier 46 relative to the second barrier 51. In alternative embodiment, stops may perform this function. This well-determined position of the first barrier 46 relative to the second barrier 51, together with the lengths of the pins 53 defines the position of the first major surface 5 relative to the seat. The tapering lateral surface 8 and the conical seat surface allow for a relatively well-defined sealing force to be exerted. The intended position of the first barrier 46 relative to the second barrier 51 can be reached, even in the face of varying thicknesses of the porous body 2. To replace the fluid treatment element 1 when the active material included in the porous body 2 has become exhausted, the first barrier 46 is unscrewed to provide access to the fluid treatment element 1, which can then be replaced. The first barrier 46 is then screwed back in place. As an example of a suitable fluid treatment device, a filter bottle 56 (Fig . 7) is provided at its open top with a removable closure 57 including a holding device of the type described above. The second barrier 46 is integrated into a body of the closure. The first barrier 46 is accessible at an underside of the closure. The closure 57 can be removed from the filter bottle 56 to fill it with liquid to be treated, e.g . drinking water. The channel 52 in the second barrier 51 extends to a mouthpiece 58. In use, liquid is sucked through the fluid treatment element 1. Thus, the concentration of contaminants such as chlorine or heavy metals is reduced.

The invention is not limited to the embodiments described above, which may be varied within the scope of the accompanying claims. For instance, the plate 21 may be reheated upon being cut from the layered structure by the cutting device 20 before fluid treatment elements are cut from it. Instead of applying the lower and upper webs 13, 17 in the manner described, sheets of the material may be applied to the plate 21 prior to the cutting of fluid treat- ment elements 1 from it.

The fluid may be a liquid, so that the fluid treatment element is a liquid treatment element, the porous body is liquid-pervious, and any covering sheet material is liquid-pervious.

The holder as described above with reference to Fig . 6 may be provided in a gravity-driven liquid treatment device of the jug-type, for example, in which liquid to be treated flows from a reservoir of liquid to be treated through one or more fluid treatment elements in respective seats in a barrier separating the reservoir from a vessel for collecting the treated liquid . The pins 53 or a similar contacting device need not depend from a barrier but may be support- ed by some other structure arranged at a pre-determined position relative to the barrier in which the seat for the fluid treatment element is provided.

List of reference numerals

1 - fluid treatment element

2 - porous body

3 - 1^st layer

4 - 2^nd layer

5 - 1^st major surface

6 - 2^nd major surface

7 - body axis

8 - lateral surface

9 - main endless belt

10 - 1^st support drum

11 - 2^nd support drum

12 - device for depositing particulate material

13 - lower web

14 - reel for lower web

15 - doctor blade

16 - device for applying heat

17 - upper web

18 - reel for upper web

19 - double-belt press

20 - cutting device

21 - plate

22 - cutting apparatus

23 - cutting tool part

24 - cutting edge

25 - orifice axis

26 - facet

27 - outer tool surface section

28 - angled inner tool surface section

29 - edge of angled section

30 - straight inner tool surface section

31 - cutting tool part aperture 32 cutting tool

33 1^st cutting tool part

34 axis of 1^st cutting tool part

35 1^st cutting edge

36 2^nd cutting tool part

37 axis of 2^nd cutting tool part

38 2^nd cutting edge

39 common cutting edge section

40 angled 1^st inner tool surface section

41 straight 1^st inner tool surface section

42 elastic ejection device

43 dividing wall section

44 angled 2^nd inner tool surface section

45 ejection pin

46 1^st barrier

47 seat aperture

48 sealing element

49 inner surface of sealing element

50 seat axis

51 2^nd barrier

52 through-going channel

53 pin

54 thread on 1^st barrier

55 thread on 2^nd barrier

56 filter bottle

57 closure

58 mouthpiece

Claims

Fluid treatment element,

fluid-pervious and including at least a fluid-pervious porous body (2) of thermally bonded material,

the body (2) having at least a first major surface, of which at least a section is planar, and an axis (7) perpendicular to the plane of the first major surface,

wherein the first major surface forms the surface closest to an axial end of the fluid treatment element of all surfaces of porous bodies of thermally bonded material included in the fluid treatment element, wherein the body (2) has a thickness corresponding to a maximum axial dimension of the body (2),

wherein a width of at least the first major surface of the body (2), corresponding to a maximum distance from a point on a circumferential edge of the first major surface to an opposite point on the circumferential edge, is larger than the thickness of the body (2), and wherein the body (2) has a lateral surface (8), closed on itself around the axis (7) and adjoining the first major surface at a circumferential edge thereof, characterised in that

at least a section of the lateral surface (8) extending from the first major surface tapers in axial direction.

Fluid treatment element according to claim 1,

wherein the lateral surface (8) tapers over an extent corresponding to the thickness of the body (2).

Fluid treatment element according to claim 1 or 2,

wherein the tapering section of the lateral surface (8) is at an angle relative to the axis (7) of at least 5°, especially an angle of at least 10°, e.g. 15°.

Fluid treatment element according to any one of the preceding claims, wherein the tapering section of the lateral surface (8) is at an angle relative to the axis (7) of at most 30°, especially an angle of at most 20°.

Fluid treatment element according to any one of the preceding claims, wherein the lateral surface (8) extends to a circumferential edge of a second major surface, wherein, at least at the circumferential edge, the second major surface faces essentially in an opposite axial direction to the direction in which the first major surface faces.

Fluid treatment element according to claim 5,

wherein the second major surface is an essentially uninterrupted planar surface.

Fluid treatment element according to any one of the preceding claims, wherein at least a surface of the body (2) on an opposite side to the first major surface seen in axial direction is covered by at least one layer (4) of fluid-pervious sheet material.

Method of manufacturing a fluid-pervious porous body of a fluid treatment element ( 1) according to any one of the preceding claims, including :

forming a porous, fluid-pervious planar structure including at least a layer of thermally bonded material; and

cutting at least the body (2) of the fluid treatment element ( 1) from the planar structure,

wherein cutting the body (2) from the planar structure includes moving a cutting tool part (23;33,36;33',36') in an axial direction relative to the planar structure, and

wherein the cutting tool part (23;33,36;33',36' includes a cutting edge (24; 35,38;35',38') defining an edge of an orifice delimited by an inner tool surface extending from the cutting

edge (24;35,38; 35',38'), and wherein at least a section (28;40,44;40',44') of the inner tool surface is angled with respect to the axis of movement, such that a size of the orifice decreases in axial direction away from the cutting edge (24;35,38;35',38').

Method according to claim 8,

wherein the angled section (28;40,44;40',44') of the inner tool surface has an axial extent equal to at least the thickness of the body (2) of the fluid treatment element (1).

10. Method according to claim 8 or 9,

wherein the angled section (28;40,44;40',44') of the inner tool surface has a sufficient extent and is moved through the planar structure to compress an outer region of the planar structure entering the orifice.

11. Fluid treatment device, including a replaceable fluid treatment element (1) according to any one of claims 1-7 and a seat for the fluid treatment element ( 1),

wherein the seat is included in a barrier (46) for separating an upstream part from a downstream part of the fluid treatment device, wherein the seat includes an aperture (47) closable by the replaceable fluid treatment element ( 1) and surrounded by a sealing part (48) arranged to contact a lateral surface (8) of the replaceable fluid treatment element ( 1).

Fluid treatment device according to claim 11,

further including a device (53) for contacting an exposed planar surface (5) of the fluid treatment element ( 1) that is one of a surface corresponding to and a surface parallel to and overlying the first major surface of the replaceable fluid treatment element ( 1) to limit axial movement of the fluid treatment element ( 1) out of the seat. Fluid treatment device according to claim 12,

wherein the contacting device (53) is arranged to contact the exposed major surface (5) at multiple, e.g. three, discrete contact areas.

Fluid treatment device according to any one of claims 11-13,

wherein the sealing part (48) includes a part made of a material more elastic than that of an adjacent part of the barrier (46).

Fluid treatment device according to any one of claims 11-14,

wherein the aperture (47) is delimited by a tapering

surface (49).