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Title:
WATER PURIFICATION DEVICE WITH OVERMOLDED VALVE MEMBER
Document Type and Number:
WIPO Patent Application WO/2011/110173
Kind Code:
A1
Abstract:
Water purification device (1) with overmolded valve member A portable point-of-use water purification device with a housing (2) containing a water purification medium and a water in let (3) for intake of contaminated water and a water outlet (4, 6). The water outlet (4, 6) comprises a stop valve (5, 7) having an inner chamber with an inlet port and/or an outlet port and a valve member arranged in the inner chamber movable between a state for water passing through the stop valve and a second state for water blocking. The valve member has a support which on at least part of its outer side is overmolded by an elastic polymer seal softer than the support, wherein the seal is sealing against the inlet port or the outlet port in the second state.

Inventors:
PEDERSEN MICHAEL STANLEY (CH)
MADIER DE CHAMPVERMEIL JEAN-LUC (FR)
GOUIN SEBASTIEN (CH)
BOTTEMA ROELIE (NL)
FRAUCHIGER DANIEL (CH)
VESTERGAARD FRANDSEN MIKKEL (CH)
Application Number:
PCT/DK2010/050055
Publication Date:
September 15, 2011
Filing Date:
March 08, 2010
Export Citation:
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Assignee:
VESTERGAARD SA (CH)
PEDERSEN MICHAEL STANLEY (CH)
MADIER DE CHAMPVERMEIL JEAN-LUC (FR)
GOUIN SEBASTIEN (CH)
BOTTEMA ROELIE (NL)
FRAUCHIGER DANIEL (CH)
VESTERGAARD FRANDSEN MIKKEL (CH)
International Classes:
F16K5/04; C02F1/00; F16K1/12; F16K35/02
Domestic Patent References:
WO2008110172A22008-09-18
WO2004057226A12004-07-08
WO2007076375A22007-07-05
WO2008110172A22008-09-18
WO2008110166A12008-09-18
WO2009019592A22009-02-12
WO2008025358A12008-03-06
WO2008067816A22008-06-12
WO2008067817A22008-06-12
Foreign References:
US20020017497A12002-02-14
US20040112562A12004-06-17
GB2017265A1979-10-03
FR2495730A11982-06-11
US20090229671A12009-09-17
FR87687E1966-09-23
CA2199061A11998-09-04
US6237440B12001-05-29
US20060208213A12006-09-21
Attorney, Agent or Firm:
PATRADE A/S (Aarhus C, DK)
Download PDF:
Claims:
CLAIMS

1. A portable point-of-use water purification device (1) with a housing (2) containing a water purification medium, the housing (2) having a water inlet (3) for intake of contaminated water and a water outlet (4, 6) wherein the water outlet (4, 6) comprises a stop valve (5, 7) having an inner chamber (27) with an inlet port (29) or an outlet port (12) or both and a valve member (13, 25) arranged in the inner chamber (27) movable between a first state, in which water can pass through the stop valve, and a second state blocking for water through the stop valve, characterised in that the valve member (13, 25) has a support (14, 36) that on at least part of its outer side is overmolded by an elastic polymer seal (18, 28) softer than the support (14, 25), wherein the seal (18,28) is sealing against the inlet port (29) or the outlet port or both in the second state.

A device according to claim 1, wherein the elastic polymer seal (18, 28) is made of a thermoplastic elastomer or thermoplastic vulcanizate with a compression set value of between 10% and 50% at 70°C according to ISO 815.

A device according to claim 2, wherein the compression set value of between 10%> and 21% at 70°C according to ISO 815.

4. A device according to any preceding claim, wherein the hardness of the soft material in terms of Shore A is 55-85.

A device according to any preceding claim, wherein the valve member (13, 25) has a channel (15, 38) through the valve member (13, 25) for releasing water from the inlet port (29) or for releasing water to the outlet port (12) in the first state.

A purification device according to any preceding claim, wherein the valve member (13, 25) is connected to a manually operated safety member (33) that prevents direct manual access to the valve member, the safety member being arranged transla- tional between a first and a second safety position, the safety member having acti- vation means (34) that are activated only in the second safety position, in which the activation means (34) of the safety member (33) lock to the valve member (13, 25) for movement of the valve member by the safety member.

A device according to any one of the claims 1-6, wherein the valve member (13, 25) has a sleeve (14) arranged in the inner chamber rotational between a first orientation for water passing through the stop valve and a second orientation for blocking water flow through the stop valve, the sleeve (14) having a channel (15) inside the sleeve for release of water from the inlet port or to the outlet port (12) or both through the channel (15) in the first orientation, wherein the sleeve (14) is covered at least partly on its outer side by an elastic polymer seal (18) softer than the sleeve and for elastic sealing against the inlet port or the outlet port (12) or both. 8. A purification device according to claim 7, wherein the sleeve (14) is tubular with at least one opening (16, 17) lateral to the tubular sleeve.

A purification device according to claim 8, wherein the seal (18) has an outwardly protruding lip (22) around the lateral opening (16,17), the lip sealingly surrounding the inlet port or outlet port (12) or both in the first position.

10. A purification device according to claim 9, wherein the seal (18) extends along the tubular sleeve (14) and has a first end part (20, 20') and a second end part (19, 19') and a waist (21) between the end parts, the waist having a narrower cross section than the end parts, wherein the lip (22) protrudes outwardly from the waist (21).

A device according to any one of the claims 1-6, wherein at least part of the elastic polymer seal is compressed by 10%-25% when the valve member is inside the inner chamber.

12. A device according to any one of the claims 1-6, wherein the valve member is a piston (25) arranged in the inner chamber (27) translational along its longitudinal axis between a first position for water passing through the stop valve (7) and a second position for blocking water flow, the piston having the softer seal (28) overmolded at an end (36) in order to elastically seal against the inlet port (29) or outlet port or both in the second position.

13. A device according to claim 12, wherein the seal (28) is covering a central part of the end (36), and the piston has a channel (38) extending longitudinally through the piston, the channel connecting to the inlet port (29) in a first position of the piston for water release from the inlet port, wherein an opening (30) is provided in the piston (25) for flow-communication between the channel (38) and the inlet port when the valve member is in the first position.

14. A device according to claim 13, wherein the opening (30) is provided in the side of the piston (25) or at the first end of the piston excentric outside the seal (28).

15. A device according to claim 13 or 14, wherein the piston (25) is translated by a screw mechanism with a threading (32a, 32b) slidably connecting a turnable ring (26) with the piston (25) such that turning of the ring (26) moves the piston (25) along the threading (32b) parallel with the longitudinal axis of the piston (25).

16. A device according to claim 15, wherein the ring (26) is surrounded by a manually operated safety member (33) that covers the ring to prevent direct manual access to the ring and which has first gripping means (34) for cooperating with second gripping means (35) of the ring (26) for rotation of the ring when the safety mem- ber is manually rotated, wherein the safety member is translatable between a first safety position and a second safety position, and wherein the gripping means (34, 35) only cooperate in the second safety position of the safety member.

17. A device according to claim 15, wherein the ring (26) is surrounded by a manually operated safety member that covers the ring to prevent direct manual access to the ring and which has gripping means for gripping the ring for rotation of the ring when the safety member is manually rotated, wherein the safety member is loosely fitted around the ring and is compressible, and wherein the gripping means only grip the ring in the case of manual compression of the safety member.

Description:
Water purification device with overmolded valve member

Field of the Invention

The present invention relates to a stop valves in portable point-of-use water purification devices. The purification device has a housing containing a water purification medium and a water inlet for intake of contaminated water and a water outlet. The water outlet comprises a stop valve with a valve member arranged in the inner chamber movable between a first state for water passing through the stop valve and a second state for water blocking.

Background of the Invention

Manually activated stop valves are known where a single operation with a quarter turn of a handle shifts the valve between an open and a closed state. Such a valve is disclosed and explained with reference to earlier patent publications in US patent application No. 2006/208213 by Turnau et al. Common for such valves is an inserted polymer sleeves for sealing against leakage and in order to have a low friction. In this Turnau disclosure, the problem is raised and solved that valves of this type only are operated seldom resulting in material deposit in the valve, making it increasingly difficult to open or close. It is proposed to increase the strength of the connection between the handle and the polymer sleeve in order to prevent breakage. The sleeve is elastomeric and not rigid in order to facilitate expansion under fluid pressure for better sealing. A low friction thermoplastic elastomer (TPE) material of the type Santoprene™ is proposed for the sleeve.

A different type of valve is disclosed in International patent application WO2007/076375. The disclosed valve is used for a soft drink dispenser, where a plunger is pressed against a spring load in order to remove the plunger end from a dispenser opening. Instead of using traditional o-rings for the sealing between the plunger and the opening, the end of the plunger is surrounded by a ring of overmolded thermoplastic elastomer, for example of the type having the commercial name Santoprene TPV 271-55. In the field of point-of-use water purification devices, for example as disclosed in International patent application WO2008/110172 by Vestergaard Frandsen, shut-off valves of a likewise kind are employed as well. However, for such kind of filters when used for emergency cases and for use in regions, where drinking water is scarcely available, a totally different problem concerns the valves, as will be explained in the following. Due to the use of such filters in regions with poor infrastructure, the filter has to be long lasting. For example, the water purification devices marketed by the company Vestergaard Frandsen under the name of LifeStraw® are designed to last for a time span of years. The LifeStraw® filter for family use is designed to purify at least 18,000 litres of contaminated water. This implies that the valves are operated many times during the lifespan of the device, typically more than 1000 times. As such filters are not repaired, the valves must be ensured to be tight also after at least 1000 times of operation in tropically hot conditions. This problem for the valves needs a solution.

Object of the Invention

It is the object of the invention to provide a portable point-of-use water purification device with a stop valve that is operable at least 1000 times without leakage.

Description of the Invention

This purpose is achieved with a portable point-of-use water purification device according to the following. The purification device has a housing containing a water purification medium and a water inlet for intake of contaminated water and a water outlet. The water outlet is a clean water outlet for outlet of water after purification. Alternatively, the water outlet is flush water outlet in case that the filter has a flush mechanism for cleaning of a microporous filter in the housing. The water outlet comprises a stop valve having an inner chamber with an inlet port or an outlet port or both and a valve member arranged in the inner chamber movable between a first state for water passing through the stop valve and a second state for water blocking. The valve member has a support which on at least part of its outer side is overmolded by an elastic polymer seal softer than the support, wherein the seal is sealing against the inlet port or the outlet port or port or both in the second state.

The valve of this type has a high degree of sealing, because the supporting sleeve underneath the softer elastic polymer assures that the softer elastic polymer changes shape only to a degree that is just necessary to get a good sealing. Relative to the aforementioned disclosure US2006/208213 by Turnau et al, it does not need a high fluid pressure in order to seal satisfactory. Also, as has turned out, the overmolded supporting sleeve can maintain continuously complete tightness of the water for more than 1000 and even up to 50,000 movements.

The term "softer than the support" means that is more easily compressible. For example, it has a lower Shore hardness value.

Preferably, the valve member is made of a polymer or at least is made mainly of a poly- mer, for example by comprising metal parts, which, however, do not dominate the weight. Preferably, the support is entirely made of polymer. A preferred polymer is a thermoplastic polymer, for example a polyolefm. A preferred polyolefm is polypropylene. However, also other materials are suitable including Acrylonitrile Styrene Acrylate (ASA), Acrylnitrile-Butadiene- Styrene polymer (ABS), PolyCarbonate (PC), PolyAm- ide, PolyVinylChloride (PVC), or PolyButylene Terephtalate (PBT). Preferred are PP, ABS and PBT. Mixtures of polymers or copolymers are also possible. For example a blend of PC and ABS is one preferred option.

Advantageously, the elastic polymer seal is made of a thermoplastic elastomer (TPE) or a thermoplastic vulcanizate (TPV). Advantageously, the TPE or TPV should not be too soft, although it is supported by the harder support. A soft elastomer is a good sealing, but it also has to be made sure that the sealing lasts for long time and survives many opening. This has led to the experimental finding that the best results are achieved with a special range of hardness values. Especially, the hardness of the overmolded seal is advantageously 55-85, or rather 60-80, in terms of Shore A values.

It has also been found that certain compression set values are advantageous, for example 10%-50% or 10%-30%, at 70°C according to ISO 815. Surprisingly good results have been achieved with a compression set value of 10%-21% at 70°C according to ISO 815. Especially, when combined with the above hardness parameters for the elastomer or vulcanizate, experiments show continuous tightness even after 50,000 turns of a rotational valve member in a stop valve.

In a concrete embodiment, the valve member has a channel through the valve member for releasing water from the inlet port or through an outlet port in the first state.

Preferably, the valve member has a sleeve arranged in the inner chamber rotational be- tween a first orientation for water passing through the stop valve and a second orientation for blocking of water through the stop valve. For example, there is provided a channel inside the sleeve for release of water from the inlet port through the channel in this first orientation. Alternatively, there is provided a channel inside the sleeve for release of water through the channel and to the outlet port in this first orientation. If the valve has an inlet port as well as an outlet port, the channel may be arranged to connect the inlet port with the outlet port in the first orientation and disconnecting the inlet port from the outlet port in the second orientation.

Advantageously, the sleeve is covered at least partly on its outer side by an elastic polymer seal softer than the sleeve and for elastic sealing against the inlet port or the outlet port or both. Typically, the stop valve will be operated by a rotation of quarter turn of half turn.

In an embodiment, the sleeve is tubular. For example, the sleeve has an opening lateral to the tubular sleeve, that is, in the side of the tubular sleeve. The opening may be one in a number of openings. Optionally, the seal has an outwardly protruding lip, for example around the lateral opening. Preferably, the lip sealingly surrounds the inlet port or outlet port in the first position. For example, the seal extends along the tubular sleeve and has a first end part and a second end part and a waist between the end parts, the waist being narrower than the cross section of the end parts. Preferably, the lip protrudes outwardly from the waist. Good sealing has been achieved when the seal in the inner chamber of the stop valve is slightly compressed. In practice, good results have been achieved, if the seal, or at least part of it, is compressed by 10%-25% when the valve member is inside the inner chamber. For example, the compressed part is predominantly the lips of the seal or the end parts or both.

Alternatively, the valve member is arranged in the inner chamber translational between a first position for water passing through the stop valve and a second position for blocking water flow. For example, the valve member is a piston that is translated along its longitudinal axis. As preferred option, such a piston has the softer seal provided at its end in order to elastically seal against the inlet port in the second position or, optionally, against an outlet port if such an outlet port exist or against both.

In a further example, the piston has a first end and the seal is overmolded at the first end covering a central part of the first end.

Preferably, the stop valve member is free from a spring, because a spring load is not necessary in contrast to the above mentioned disclosure of WO2007/076375. Instead, a good mechanical solution has been found in the piston having a channel through the piston connecting to the inlet port for water release from the inlet port in a first position of the piston and blocking the inlet port in the second position of the piston. Alternatively, the piston has a channel through the piston connecting to the outlet port for water release from the channel and to the outlet port in a first position of the piston and blocking the outlet port in the second position of the piston.

An opening is provided in the piston for flow-communication between the channel and the inlet port or outlet port when the valve member is in the first position. A centrally overmolded tip of the piston co-operates well with the following optional embodiment, wherein the first end of the piston is provided with an opening to the channel, the opening being located excentric relatively to the centric seal. Alternatively or in addition, an opening is provided at the side of the piston. In a practical embodiment, the piston is translated by a screw mechanism with a threading slidably connecting a turnable ring with the piston such that turning of the ring moves the piston along a threading parallel with the longitudinal axis of the piston.

The purification medium comprises preferably a microporous membrane, for example a bundle of microporous fibres. The term microporous is used for the case of microfiltra- tion as well as nanofiltration. Such microporous fibres in connection with portable water purification devices are well known, for example as described in International patent applications WO2008/110166, WO2008/110172 or WO2009/019592. Alternatively or in addition, the purification medium may contain chemical steps and/or absorbing resins, for example as disclosed in International patent applications WO2008/025358, WO2008/067816, or WO2008/067817. In the case, where microporous filters are applied, for example hollow fibres, the influent side of the filter will accumulate microorganisms and particles. In order to prolong the lifetime of the membranes, these microorganisms and particles are typically flushed out by involving back flushing and forward flushing along the influent membrane surface. This is explained in more detail in International patent applications WO2008/110166, WO2008/110172 or WO2009/019592. For the reason of backflush, the water purification device has a flush outlet.

Although, for the water purification device in the above description, the different valve types have been explained for use with the clean water outlet, the valves may alterna- tively or in addition also be used for this flush outlet.

In order to prevent children from opening the clean water outlet or, especially, a flush water outlet due to the severe contamination of the flush water, it is an advantage if a portable point-of-use water purification device is provided with a safety mechanism configured for preventing opening of the stop valve in connection with the flush water outlet or the clean water outlet or both before the safety mechanism is activated. Advantageously, the safety mechanism has to be activated manually, for example by press- ing, pushing, turning or rather a combination of these in order for the stop valve to be able to open.

Such a safety mechanism can be employed in the water purification device as described above, but is also in general useful for other point-of-use water purification devices having a housing containing a water purification medium and a water inlet for intake of contaminated water and a water outlet. The water outlet is a clean water outlet for outlet of water after purification. Alternatively, the water outlet is flush water outlet in case that the filter has a flush mechanism for cleaning of a microporous filter in the housing. The water outlet may comprise a stop valve having an inner chamber with an inlet port or an outlet port or both and a valve member arranged in the inner chamber movable between a first state for water passing through the stop valve and a second state for water blocking. Optionally, the valve member has a support which on at least part of its outer side is overmolded by an elastic polymer seal softer than the support, wherein the seal is sealing against the inlet port or the outlet port or both in the second state.

For example, the valve member is connected to a manually operated safety member that prevents direct manual access to the valve member, typically, by covering it.

For example, the safety member is arranged translational between a first and a second safety position, wherein only in the second safety position, the safety member locks to the valve member for movement of the valve member by the safety member. In case of a rotational sleeve, the valve member may have an extension reaching out of the inner chamber of the stop valve. The extension should not be directly accessible for manual operation unless the safety member is activated to lock to the extension. For example, the safety member may be a ring that has to be pushes axially in order to lock to the extension.

In case of a translational piston, an example of a safety mechanism includes the following. In this case, a ring is arranged for axial translation of the piston when the ring is rotated around its axis due to a screw mechanism with a threading slidably connecting the rotational ring with the piston, and the ring is surrounded by a manually operated safety member that covers the ring to prevent direct manual access to the ring. The safety member has first gripping means and the ring second gripping means for cooperation such that the safety member - when activated - locks to the ring for rotation of the ring when the safety member is manually rotated.

For example, the safety member is translatable between a first safety position and a second safety position, and the gripping means only cooperate in the second safety position of the safety member.

Alternatively, or in addition, the safety member is loosely fitted around the ring with an inner cross section larger than the outer cross section of the ring, and the safety member is compressible such that the gripping means only cooperate in the case of manual compression of the safety member. In the latter case, the gripping means are pressed towards the ring for gripping the ring for rotation.

A possible practical embodiment for the overmolding process implies a production of the support, typically by molding the support in a thermoplastic polymer, after which the seal is overmolded on top of at least part of the surface of the support.

As an example, the portable point-of-use water purification device may be used with gravity feeding of contaminated water from a contaminated water tank with a tube of between 0.5 m and 2 meter from the water tank to the purification device, yielding a pressure of between 0.05 and 0.2 bars, typically 0.1 bar. An example if of such a device is disclosed in International patent application WO2008/110166.

The term "between" for limits of any mentioned interval, optionally, also includes end- points of the intervals. The term "a" or "an" for an aspect, for example "an opening", does not restrict the term to only imply one aspect, for example "one opening". It means "at least one" and implies a plurality as well, such as 2, 3, 4, or more. A reasonable number occurs from the context.

Description of the Drawing FIG. 1 illustrates a water purification device,

FIG. 2 illustrates a rotational valve, a) in overview and b) with a demounted valve member,

FIG. 3 illustrates a piston valve a) in cross section and b) with a demounted valve member

FIG. 4 illustrates shows a photo of a piston valve for the clean water outlet,

FIG. 5 illustrates a piston valve with a safety member in a) a deactivated state and b) an activated state

Detailed Description of the Invention

FIG. 1 illustrates a water purification device 1. The device 1 has a housing 2 inside which there is provided a water purification medium in the form of a microporous membrane, preferably a hollow fibre microporous filter. Alternatively, the housing 2 may contain purification steps including resins and chemical purification. Such purification media are described in various publications, for example as mentioned above.

A typical size of the housing is 20-40 cm in length and 3-7 cm in width. The water purification device is useful for the commercial product LifeStraw®.

The housing 2 has a contaminated water inlet 3 for intake of contaminated water and a clean water outlet 4 with a valve 5 for outlet of water after purification. The valve comprises a handle 9 as part of a valve member. Turning of the handle 9 causes the valve 5 to open or close. The housing also has a flush water outlet 6 with a valve 7 in connection with a flush mechanism for cleaning of the microporous filter inside the housing 2.

In order to activate the flushing, there is provided a balloon 8 connected to the filtrate side of the microporous filter inside the housing and, thus, filled with clean water. In order to backflush, the balloon 8 is compressed 2 simultaneously with the valve 5 of the clean water outlet 4 being closed. Water is then pressed backwards through the micro- porous membranes and loosens particles and microbes from the inflow side of the membrane. These microbes and particles are then removed from the housing by forward flushing water from the contaminated water inlet 3 along the membrane surface and out and out of the flush water outlet 6 by opening the flush valve 7. The background and function is explained in more detail in the International patent applications WO2008/110166, WO2008/110172 or WO2009/019592 According to FIG. 1, the clean water outlet 5 comprises a stop valve which is explained in greater detail with reference to FIG. 2a.

FIG. 2a shows in detail that the stop valve 5 has an inner chamber 10 with an outlet port 12 and a valve member 13 arranged in the inner chamber 10 rotational between a first state for water passing through the stop valve 5 and a second state for water blocking. Typically, this is a quarter turn valve or half turn valve activated by a handle 9. The water passes from the inner volume 11 of the hosing into a channel 15 and through outlet port 12 and outlet opening 16 into the clean water outlet 4. As illustrated in more detail in connection with FIG. 2b, the valve member 13 has a supporting tubular sleeve 14 with a channel 15 between two lateral openings 16, 17 for flow through these two openings 16, 17 from the inlet port 11 and/or to the outlet port 12. At part of the outer surface of the sleeve 14 is overmolded by an elastic polymer seal 18 softer than the sleeve 14. The seal 18 extends along the tubular sleeve 14 and has a first end part 19 and a second end part 20 and a waist 21 between the end parts 19, 20, the waist having a narrower cross section than the end parts, which comprise ring-formed thickenings 19', 20'. The seal 18 has lips 22 around the lateral openings 16, 17. The lips 22 protrude outwardly from the waist 21 in order to seal around the inlet port 11 and/or outlet port 12.

Typical materials for the sleeve are thermoplastic polymers, preferably polyolefins, for example polypropylene. The overmoulded polymer is preferably a thermoplastic elas- tomer.

The flush valve 7 as illustrated in FIG. 1 has a valve member with a handle 9, where the valve member when open connects an inlet port and an outlet port in a vertical line. In this case, the lateral opening 16, 17 of the valve member connecting the inlet port with an outlet port for drainage.

As an alternative to the stop valve with the rotational valve member, the flush water outlet valve 7 or the valve 5 for the clean water outlet 4 or both may be provided with a piston valve as illustrated in greater detail in FIG. 3 a, where a line drawing is shown for details and a hatched drawing for ease of understanding. The hatched drawing shows the valve rotated 90 degrees along the vertical axis. FIG. 3a illustrates that at the lower end 24 of the housing 2, there is provided a flush water exit with a valve member in the form of a piston 25, which is shown in a side view drawing in FIG. 3b. With reference to FIG. 3a, the piston is arranged in the inner chamber 27 translational between a first position for water passing through the stop valve and a second position for water blocking. Shown in FIG. 3a is the second posi- tion, where the piston 25 with its end 36 that is overmolded by a soft seal 28 rests seal- ingly against the inlet port 29.

The piston 25 is provided with a channel 38 through which water is released when the valve 7 is opened by lowering the piston by which the seal 28 is removed from the inlet port 29 and water flows from the inlet port 29 around the seal 28 and through an opening 30 into the channel 38 for final release downwards out of the channel 38. The valve piston 25 is provided with ribs 39 on its outer side for attachment of a tube.

The piston 25 is translated by a screw mechanism with a threading 32a, 32b slidably connecting a turnable ring 26 with the piston 25 such that turning of the ring 26 moves the piston along the threading 32b parallel with the longitudinal axis of the piston 25.

FIG. 4 is a drawing of a piston valve for the clean water outlet 4' illustrating the over- molded seal 28. The channel openings 30 are in the side of the piston 25, which is of a slightly different kind relatively to the drawing of FIG. 3. The rotational ring 26 has barbs 40 which during mounting snap behind circular rib 41. The final mount is illustrated in FIG. 3a. As illustrated in FIG. 5, the stop valve of FIG. 3 may be provided with a safety mechanism. In this case, the ring 26 is surrounded by a manually operated safety member 33 that covers the ring 26 to prevent direct manual access to the ring 26. The safety member 33 has first gripping means 34 for cooperation with corresponding second gripping 35 means by the ring 26. The safety member 33 is translatable between a first safety position, as illustrated in FIG. 4a, and an activated second safety position, as illustrated in FIG. 4b. The gripping means 34, 35 between the safety member and the ring only cooperate in the second, upper safety position of the safety member 34. Rotation of the ring 26 is achieved only when the safety member 33 is manually rotated in the activated, second safety position. In the shown orientation of the water purification device according to FIG. 1, the safety member will be in the lower position, normally, due to gravity.

The gripping means as shown in FIG. 5 are only illustrative for the principle and can be provided in different forms. For example, relatively to the orientation in FIG. 5, the gripping means can be provided as downwards directed teeth on the ring 26 and cooperate with corresponding teeth directed upwards from the safety member 33.

As an alternative or in addition to the translational function of the safety member, it may be configured for squeezing in order to make gripping means of the ring and the safety member cooperate.