WO2014006127A1

WO2014006127A1 - Method and device for forming a fluid treatment system

Info

Publication number: WO2014006127A1
Application number: PCT/EP2013/064109
Authority: WO
Inventors: Hilmar Walde; Thomas Nagel; Peter Weidner; Berthold Conradt
Original assignee: Brita Professional Gmbh & Co. Kg
Priority date: 2012-07-05
Filing date: 2013-07-04
Publication date: 2014-01-09

Abstract

A fluid treatment system includes a first unit (36;62). The first unit includes an inlet (39;65) for untreated fluid and a branch point between the inlet (39;65) and at least one first fluid path and at least one second fluid path. Each first path includes at least one fluid treatment (45) part for treating fluid led through the first fluid path. Each second fluid path bypasses at least one of the fluid treatment parts (45). The at least one second fluid path is arranged, in use, to conduct a blending fraction of the fluid received through the inlet (39;65). The first unit includes a mixing location (16;46), where the first and second fluid paths join, at least one device (4) for setting the blending fraction and a first element (42) for forming a link between at least one movable valve element (41) of the device (4) for setting the blending fraction and an actuator (5) for adjusting a position of the movable valve element (41). A device for forming a component of the fluid treatment system includes the actuator (5) and a second unit (37;70), configured for attachment to a housing part (63) of the first unit (36;62) and supporting at least a second element (49;72) for forming the link between the movable valve element (41) and the actuator (5), the second element (49;72) configured for coupling to the first element (42).

Description

Method and device for forming a fluid treatment system

The invention relates to a device for forming a compo^¬ nent of a fluid treatment system, the fluid treatment system including :

a first unit including:

an inlet for untreated fluid;

a branch point between the inlet and at least one first fluid path and at least one second fluid path;

each first path including at least one fluid treatment part for treating fluid led through the first fluid path,

each second fluid path bypassing at least one of the fluid treatment parts, wherein the at least one second fluid path is arranged, in use, to conduct a blending fraction of the fluid received through the inlet;

a mixing location, where the first and second fluid paths join;

at least one device for setting the blending fraction; and

a first element for forming a link between at least one movable valve element of the device for setting the blending fraction and an actuator for adjusting a position of the movable valve element.

The invention also relates to a method of assembling a fluid treatment system, including:

providing a first unit including:

a housing part;

an inlet for untreated fluid;

a branch point between the inlet and at least one first fluid path and at least one second fluid path of the fluid treatment system, each first path including at least one fluid treatment part for treating fluid led through the first fluid path,

each second fluid path bypassing at least one of the fluid treatment parts, wherein the at least one second fluid path is arranged, in use, to conduct a blending fraction of the fluid received through the inlet,

wherein the fluid treatment system further includes a mixing location, where the first and second fluid paths join;

at least one device for setting the blending fraction; and

a first element for forming a link between at least one movable valve element of the device for setting the blending fraction and an actuator for adjusting a position of the movable valve element;

providing the actuator; and

linking the at least one movable valve element to the actuator .

The invention also relates to a kit of parts for use in assembling a fluid treatment system, the kit of parts including at least:

a first unit including:

a housing;

an inlet for untreated fluid;

a branch point between the inlet and at least one first fluid path and at least one second fluid path of the fluid treatment system,

each second fluid path bypassing at least one of the fluid treatment parts, wherein the at least one second fluid path is arranged, in use, to conduct a blending fraction of the fluid received through the inlet, wherein the fluid treatment system, when assembled, further includes a mixing location, where the first and second fluid paths join;

at least one device for setting the blending fraction; and

US 2011/0132818 Al discloses a control unit for a sof^¬ tening device, wherein the control unit comprises:

a primary inlet for untreated water;

a primary outlet for blended water;

a sensor for determining the water hardness of the un- treated water or the blended water;

a secondary outlet which is supplied with untreated wa^¬ ter from the primary inlet;

a secondary inlet which is supplied to the primary out^¬ let;

a bypass line which is guided parallel to the secondary outlet and the secondary inlet;

a blender which can be automatically adjusted for mix^¬ ing a blended water flow from a first partial flow of the secondary inlet and a second partial flow of the bypass line; and

an electronic control means, wherein the control means is designed to readjust the adjustment position of the blender according to the determined water hardness in such a fashion that the water hardness in the blended water flow is adjusted to a predetermined desired value. The control unit is designed in the form of an external control unit for the softening device. The control unit has a control unit housing, the outer side of which is provided with the primary inlet, the primary outlet, the secondary outlet and the secondary inlet. The control unit housing contains the sensor, the bypass line, the blender and the electronic control means.

A problem of the known control unit is that it is a dedicated product, intended as a substitute for existing filter heads without electronic control means, which are adjusted by hand using a tool (generally an Allen key) when they are first installed. Manufacturers of such filter heads who wish to offer both filter heads with electronically controlled blending ratios and filter heads with a feature for manually adjusting the blending ratio have to manufacture and stock both types. Users wishing to upgrade from a filter head with a feature for manual^¬ ly adjusting the blending ratio to a filter head offering automatic setting of the blending ratio have to throw away their old filter head.

It is an object of the invention to provide a device, method of assembling a fluid treatment system and kit of parts of the type defined above that allow manufacturers to provide both fluid treatment systems with manual blending fraction ad- justment and systems with automatic blending fraction

adjustments, as well as an upgrade from the former to the latter relatively efficiently.

This object is achieved according to a first aspect by the device according to the invention, which is characterised in that the device includes the actuator and a second unit, config^¬ ured for attachment to a housing part of the first unit and supporting at least a second element for forming the link be^¬ tween the movable valve element and the actuator, the second element configured for coupling to the first element.

The first unit is the base unit for both a fluid treat^¬ ment system with manually adjustable blending fraction and a fluid treatment system with an automatic adjustment feature. In the version with manual adjustment, a tool or a knob configured in the same manner as the second element for coupling to the first element is used to adjust the blending fraction. The first unit can correspond substantially to filter heads that are currently in common use, in which case the housing part of the first unit encases the device for setting the blending fraction substantially completely and the inlet and an outlet are provid^¬ ed at the ends of conduit sections passing through walls of the housing part. Because the first unit includes the device for setting the blending fraction, the inlet and the outlet, with associated connectors, the parts common to the fluid treatment system with manual blending fraction adjustment and the fluid treatment system with automatic blending fraction adjustment need be manufactured in only one version. Whether the first unit is used to assemble a fluid treatment system with manual blending fraction adjustment or one with an automatic adjustment feature can be decided at a relatively late point in time. Be^¬ cause the device includes a second unit, configured for

attachment to a housing part of the first unit, assembling the fluid treatment system with automatic blending fraction adjust- ment involves the relatively simple act of attaching the first and second unit to one another. The second unit supports at least a second element for forming the link between the movable valve element and the actuator. Thus, the second element is at least indirectly attached to a frame or housing of the second unit such as to be movable when driven by the actuator. Because the second element is configured for coupling to the first ele^¬ ment, attachment of the second unit to the housing part of the first unit can complete the link between the valve element and the actuator. The simple assembly method also makes the device suitable for upgrading an installed fluid treatment system with manual blending fraction adjustment to an automatic version in the field. Very few, if any, of the components of the manual system need be discarded or returned. The actuator converts en- ergy, in particular electrical energy, into motion, and is thus a relatively expensive component. It need not be included in the first unit, so that the first unit can remain relatively in^¬ expensive .

In an embodiment, the second unit includes the actua^¬ tor .

An effect is that the number of separate parts is re^¬ duced, because there is no need to provide a separate unit housing the actuator and a flexible linkage between the actuator and the second element in the second unit. Instead, the actua^¬ tor is mounted to one of a frame and a housing part of the second unit so as to be supported by it. The second element may be supported by the second unit only via the actuator, so that separate bearings or guides for the second element can be dis- pensed with.

In an embodiment, the second unit includes a control device for controlling the actuator.

An effect is that the first unit can be provided with a relatively simple control unit or none at all. Thus, the ver- sion of the fluid treatment system with a manually adjustable blending fraction feature can be simpler and cheaper. Where the second unit also includes the actuator, it is sufficient to pro^¬ vide only the second unit with a power supply, e.g. a battery.

In an embodiment, the second unit includes a housing part, configured for attachment to the housing part of the first unit and at least partially surrounding at least one of the ac^¬ tuator and a control device for controlling the actuator.

An effect is that the components of the fluid treatment system that require a power supply are shielded from outside in- fluences, at least when the housing part of the second unit is attached to the housing part of the first unit. In a variant of this embodiment, the second element ex^¬ tends through an aperture defined by at least one wall of the housing part of the second unit.

The aperture may be in a plane of a wall of the housing part, so that the housing part can form an essentially closed housing with a protruding part of the second element. When at^¬ tached to the housing part of the first unit, the protruding second element can protrude into the confines of the first unit to engage the first element. Alternatively or additionally, the aperture can be defined by edges of a side wall or side walls that surround the interior of the second unit. When the second unit is attached to the housing part of the first unit, the edg^¬ es abut the housing part of the first unit so as to complete a housing essentially completely surrounding the interior of the second unit. Part of the second element protrudes into an inte^¬ rior of the first unit to engage the first element.

In an embodiment, the second element is journalled so as to be rotatable about a body axis thereof.

This allows the second unit to be relatively compact, because it need not accommodate a wide range of movement of the second element. The actuator can be a rotary electric motor, such as a servomotor or a stepper motor, and optionally include a torque-converting gear unit. The first element can also be arranged for rotary movement about a body axis. A further ef- feet is that it is easier to construct one or both of the first and second elements so as to protrude from a housing and to en^¬ sure that the housing is essentially closed.

In a variant, the second unit is configured for attach^¬ ment to the housing part of the first unit by at least a

movement in a direction essentially parallel to the body axis of the second element.

An effect is to have only a small part of the first or second element protrude from the housing part of one of the first and second unit. This part is inserted into the confines of the other of the first and second unit merely by attaching the second unit to the housing part of the first unit. The parts that journal the second element can be fully contained within the confines of the second unit.

In an embodiment, the second element is provided with a feature shaped to engage a co-operating part of the first ele^¬ ment to establish a mechanical coupling.

An effect is that the position of the valve element can be controlled relatively accurately, because there is less risk of relative movement between the first and second element. This type of coupling is also generally more reliable than, for in^¬ stance, a magnetic coupling.

In an embodiment, the device further includes at least one electrical connector for receiving a signal representative of a parameter of the fluid.

Thus, the device can include the control unit, even though the fluid is not conducted through the second unit. A separate sensor unit can be provided to determine the signal representative of a parameter of the fluid. The connector may be situated at the end of a lead passing through or from a hous^¬ ing part of the second unit or it may comprise a socket provided in a wall of the housing part of the second unit. In case the first unit includes the sensor unit, then the connector of the second unit may be arranged to mate with a connector of the first unit on attachment of the second unit to the housing part of the first unit, e.g. because it is fixed to a housing part of the second unit at an appropriate outwardly facing position.

In an embodiment, for use in a fluid treatment system in which the fluid treatment part bypassed by the second fluid path is configured to remove to at least a certain extent at least some types of components in fluid led through the fluid treatment part, the device includes a data processing unit con- figured to determine a measure of a concentration of components removable from fluid by the fluid treatment part in at least one of the untreated fluid and fluid downstream of the mixing loca^¬ tion, wherein the device is configured to receive at least one signal carrying measurement values representative of respective values of a parameter of the fluid depending partly on the con^¬ centration of components removable by the fluid treatment part, at least a first of the measurement values being a value ob^¬ tained from a first measurement made downstream of the mixing location, and wherein the data processing unit is configured to determine an output value representative of the measure as a function of at least a difference between the first measurement value and a second measurement value, the second measurement value being obtained from one of a measurement downstream of the mixing location at a different value of the blending fraction than the first and a measurement carried out on untreated fluid.

The term component is used herein to denote components dissolved or suspended in the fluid. It may in particular re^¬ late to certain ion species of a definable proportion of certain ion species such as those of salts contributing to temporary hardness, for example.

The second unit is configured to execute a method using measured values of a parameter depending only partly on the concentration of components removable by the fluid treatment part but also on the concentration of other components. An example of such a parameter is the electrical conductivity of a liquid, which depends on the total concentration of dissolved ions, not just on those of salts contributing to hardness or temporary hardness. The ratio between the concentration of components of interest and that of those not of interest in the untreated flu^¬ id is generally not known or even constant. By taking a

difference between a first and second measurement value at dif^¬ ferent ratios of treated and untreated fluid, it is possible to separate out the contribution by components not removable by the fluid treatment part. It will be appreciated that the simplest way of doing this would be subtract a measurement value obtained in a measurement carried out on fully treated fluid from a meas- urement value obtained in a measurement carried out on fully untreated fluid. However, the mixing location will generally be within the first unit or within a replaceable cartridge connect^¬ ed to the first unit. A measurement value from a measurement made on fully treated fluid would have to be made within the first unit or within a cartridge connectable to the first unit. Instead, this embodiment of the device is arranged to execute a method in which a measurement on fully treated fluid is not re^¬ quired. It is suitable for obtaining a measure of the

concentration of components removable by the fluid treatment part using only measurement values obtainable in measurements carried out upstream or downstream of the first unit. As a con^¬ sequence, this embodiment does not require an adaptation

involving the addition of a sensor to the first unit or to a cartridge connectable thereto.

In a variant, the device is configured to obtain the first and second measurement values by causing the actuator to adjust the blending fraction.

This variant is suitable for use with only one sensor arranged downstream of the mixing location. The measurement values can be obtained from the same sensor (at successive points in time) . The measurements are carried out on at least partially treated fluid. Typically, the fluid treatment part will remove components that also impact on the operation of the sensor. By using a sensor arranged to carry out measurements on at least partially treated fluid, the lifetime of the sensor can be increased. Because the measurement values all derive from the same sensor, the problem of sensor drift becomes less acute. The output value is determined as a function of the difference between two measurement values. Where a single sensor is used and the time between measurements is relatively short compared to the timescale on which sensor drift manifests itself, system^¬ atic errors due to sensor drift are thus eliminated. Were use to be made of measurement values from two sensors, then differ^¬ ent and independently varying systematic errors due to sensor drift would affect the output value. Such an error would be all the more likely to occur where one sensor is permanently exposed to untreated fluid and the other is not. The only remedy would be frequent re-calibrations the need for which is thus reduced or eliminated in this embodiment.

In an embodiment of the device, for use in a fluid treatment system in which the fluid treatment part bypassed by the second fluid path is configured to remove to at least a cer- tain extent at least some types of components in fluid led through the fluid treatment part, the device includes a control unit configured to obtain a measure of the concentration of com^¬ ponents removable from fluid by the fluid treatment part in at least one of the untreated fluid and fluid downstream of the mixing location, and to control the actuator in dependence on at least the obtained measure.

This embodiment is suitable for providing a system ar^¬ ranged to provide fluid with a concentration of components removable by the fluid treatment part that can have any desired value within a range. This is in spite of the fact that the fluid treatment part is generally configured to remove the com^¬ ponents to a fixed and constant extent.

In an embodiment, the second unit is configured for at^¬ tachment to a housing part of a first unit including a

mechanical interface for replaceably attaching a fluid treatment cartridge including the fluid treatment part, the device in^¬ cludes a device for obtaining data identifying at least a type of the cartridge, and the device is configured to adapt at least one of a method of determining a measure of a concentration of components removable from fluid by the fluid treatment part and a method of controlling the actuator in dependence on the identified type.

This embodiment is able to cope with fluid treatment cartridges with different types of fluid treatment parts. In particular, it can take account of the degree to which the fluid treatment part removes certain components from the fluid, for example. It can also execute algorithms conditional upon deter- mining that the fluid treatment cartridge is of a suitable type for that algorithm.

In a variant of this embodiment, the device for obtain^¬ ing data identifying at least a type of the cartridge comprises a device for contactless reading of information from a token at- tached to the cartridge.

This embodiment takes account of the fact that the first unit is generally situated in between the cartridge and the second unit. The device for obtaining data can thus, for example be arranged to obtain the data through wireless communi- cation with the token, which may be an RFID token, for example. It can therefore be located within a housing of the second unit.

In an embodiment, the second unit includes a human- machine interface.

In general, the first unit will be in the shape of a filter head for attachment of a filter cartridge. Typically, an end of the first element or a knob or similar device enabling a user to manipulate the first element will be provided on the top side of the first unit. Pipes will run from the sides and the cartridge will be attached to the side or underside. The top of the first unit is thus generally the most easily accessible po^¬ sition at which to attach the second unit. With the second unit on top, providing the human-machine interface on the second unit, in particular on a housing part of the second unit, makes for a relatively ergonomic arrangement. Because the second unit includes the human-machine interface, any display device on the first unit for use when the first unit is part of a fluid treat^¬ ment system with manually adjustable blending ratio may be covered by the second unit or removed before attachment of the second unit. The human-machine interface will generally include at least one of a display device and at least one device for providing user input, such as hard or soft keys. Because they are provided on the second unit, all controls necessary to im- plement the fluid treatment system with automatic blending fraction adjustment need be provided only on a device that is exclusively used in that version of the fluid treatment system.

In a variant, the second unit includes an output device for providing a signal representative of a state of at least one of the fluid treatment parts in a form perceptible to a user.

The state may be a state of exhaustion of a fluid treatment me^¬ dium in the fluid treatment part, e.g. in the form of an

indication of a fraction of initial capacity used up or remaining. In a particular variant, it may be configured to provide the signal conditional upon determining that fluid is being pro^¬ vided from the fluid treatment system to a device downstream of the mixing location. This particular variant saves energy, in that is provides a signal only in situations in which a user is likely to be around to observe the signal.

According to another aspect, the method of assembling a fluid treatment system according to the invention is characterised in that the step of linking the at least one movable valve element to the actuator includes attaching to the housing part of the first unit a second unit supporting at least a second el- ement for forming the link between the movable valve element and the actuator and coupling the second element to the first ele^¬ ment . This method can be part of a manufacturing method or it can be carried out in order to upgrade a fluid treatment system with a manual blending ratio feature to one with an automatic adjustment feature.

In an embodiment, at least a further housing part at^¬ tached to the housing part of the first unit is removed from the first unit prior to attaching the second unit to the housing part of the first unit.

This embodiment is typically part of a method of up- grading an already deployed fluid treatment system with a manual blending fraction adjustment feature. The further housing part can be a cover or a complete housing, e.g. containing at least one of a battery compartment and a human-machine interface. An effect of this embodiment is that the fluid treatment system with automatic blending fraction adjustment can be more compact, since the second unit need not be placed piggy-back on a com^¬ plete unit of a fluid treatment system with manual blending fraction adjustment. Any parts exclusive to the fluid treatment system with manual blending fraction adjustment can be attached to the further housing part, so that removal of the further housing part also removes those parts that would become redun^¬ dant on the upgrade. A further effect is that the first unit can have one set of mechanical connector elements (e.g. screw- threads) for attaching either the further housing part or the second unit. The second unit need therefore not be provided with clamps, straps or the like in order to attach it to the housing part of the first unit.

In an embodiment, the second unit is a second unit as included in a device according to the invention.

According to another aspect, the kit of parts according to the invention further includes a device according to the invention . In an embodiment, ends of the first element and second element configured for coupling to each other include a socket and a keyed part fitting the socket.

An effect is that the manually adjustable version of the fluid treatment system can be provided with the first ele^¬ ment without any further parts permanently attached to the end configured for coupling to the second element. A tool, e.g. an Allen key, configured to engage this end of the first element is suitable for manually adjusting the blending fraction. When the second unit is attached to the housing part of the first unit in a generally linear motion, the co-operating ends of the first and second elements engage in the process. To facilitate this, one or both of the first and second elements may be journalled to their respective units by flexible bearings or bearings flex- ibly attached to the unit concerned. This allows larger

tolerance ranges.

In an embodiment, the first unit is provided with a me^¬ chanical interface for replaceably attaching a fluid treatment cartridge including the fluid treatment part.

An effect is to enable the use of a weakly acidic cati^¬ on exchanger or any other fluid treatment medium forming the fluid treatment part that cannot easily be regenerated at the point of use.

In a variant, the first unit is provided with: a first outlet for connection to a first inlet of the fluid treatment cartridge to form the first fluid path;

a second outlet for connection to a second inlet of the fluid treatment cartridge to form the second fluid path; and

at least one inlet for connection to an outlet of the fluid treatment cartridge to enable the first unit to receive at least one of the fluid led along the first fluid path and the fluid led along the second fluid path. As a consequence, both the first and the second fluid path extend through the cartridge, so that the flows of fluid along both paths can be subjected to treatment. This is useful when one or more components of the fluid need to be removed es- sentially completely and one or more components only partially. The latter (e.g. temporary hardness in water) are removed by the fluid treatment part through which the first fluid path passes. The former (e.g. chlorine) are removed by a fluid treatment part (e.g. activated carbon) arranged in both paths. Supplements may be added to both fractions as well.

In a variant, at least one of the first and second units includes a device for obtaining input data identifying a type of fluid treatment cartridge, in particular a device for contactless reading of information from a token attached to the fluid treatment cartridge.

This embodiment allows the blending fraction to be ad^¬ justed in dependence on the type of fluid treatment part

contained in the cartridge. The first and second units are thus suitable for use with cartridges of different types. For exam- pie, in the field of water treatment, the cartridge can be one including a fluid treatment part configured to treat water with only a high level of temporary hardness or it can be one includ^¬ ing a fluid treatment part configured to treat water with a high level of gypsum (calcium sulphate dihydrate) . In the latter case, only an unreliable measure of temporary hardness could be obtained by measuring a change of value of a parameter dependent partly on the concentration of calcium ions in the water due to treatment by the fluid treatment part. Thus, no such measure would be obtained. Instead, the blending fraction could be set to a default value. In other words, control of the temporary hardness based on a measurement of a change of value of a param^¬ eter dependent partly on the concentration of calcium ions would be suspended. An embodiment of the kit of parts further includes at least a third unit, the third unit including:

an inlet for connection to at least one of a fluid con^¬ duit and an outlet of the first unit;

an outlet for connection to at least one of a fluid conduit and an inlet of the first unit;

a fluid path between the inlet and the outlet; at least one sensor for measuring a value of a parame^¬ ter of fluid led through the fluid path; and

an interface for providing measurement values to the device including the second unit.

The parameter can characterise a chemical property (e.g. concentration of certain or all ion species) and/or a physical property (e.g. temperature, conductivity, rate of flow) . The third unit can be used to enable continuous and/or completely automatic adjustment of the blending ratio without the need to re-configure the first unit to provide sensors.

There is no need to provide users with a test kit for determin^¬ ing fluid parameters that then have to be entered by the user in order to provide them to the control unit. When a fluid treat^¬ ment system with a manual blending fraction adjustment feature is upgraded to provide it with an automatic adjustment feature, one of the pipe connected to the inlet and the pipe connected to the outlet is disconnected, and the third unit is connected to that pipe and to the disconnected inlet or outlet, as the case may be .

In an embodiment, the third unit further includes a temperature sensor, and is configured to adapt values obtained from the at least one sensor in dependence on temperature, in particular in dependence on a deviation of the temperature from a reference temperature.

Many parameters of a fluid, in particular those depend^¬ ent on the concentration of e.g. ions in the fluid, depend also on a temperature-dependent activity coefficient. This dependen^¬ cy is known. In one variant, a data processor comprised in the third unit uses the known dependency to adjust measured values of the parameter to the value it would have under standard or reference conditions. In another variant, the sensor for meas^¬ uring the parameter of the fluid is combined with a temperature- dependent electrical circuit component, e.g. a temperature- dependent resistor. An analogue signal already adjusted for temperature is processed further, e.g. digitised, in the third or second unit. Both variants simplify algorithms to be carried out by a control unit or data processing device in the second unit. Moreover, it is not necessary to provide a temperature signal to the second unit. Compared to having a temperature sensor in the second unit, the adjustment is more accurate, be- cause the temperature measured is more closely representative of the temperature of the fluid when the value of the parameter was obtained .

In an embodiment, the at least one sensor includes a sensor for measuring electrical conductivity of the fluid.

The conductivity sensor may be part of an ion-selective sensor. However, in an embodiment, the sensor is not ion- selective, but a method involving a variation in the blending fraction and measurements of the electrical conductivity is used to determine a measure of the hardness or temporary hardness of a liquid.

In an embodiment, the fluid treatment part is a liquid treatment part. It may in particular comprise a weakly acidic ion exchange medium through which liquid is led, in use.

In a particular variant, the fluid treatment part is a liquid treatment part comprising an ion exchange medium that is at least initially in the hydrogen form. This results in a rel^¬ atively strong signal from the at least one sensor, because cations are removed from the liquid in exchange for hydrogen ions, which react to form water and carbon dioxide, so removing cations from the liquid. The result is a marked change in e.g. electrical conductivity. In the alternative, there would still be a change, due to differing activity levels of the cations re- moved and those released in exchange, but this change would be smaller. The ion exchange medium in the hydrogen form may be the only type of cation exchange medium for treating the liquid, such that liquid at the mixing location has been exposed in part to cation exchange medium only in the hydrogen form and in part to no cation exchange medium or no ion exchange medium at all.

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

Fig. 1 is a schematic diagram of functional parts of a fluid treatment system with automatic blending fraction adjust- ment;

Fig. 2 is a flow chart of a method of determining a measure of the temporary hardness of water using a system as il^¬ lustrated in Fig. 1 ;

Fig. 3 is a flow chart of another method of determining a measure of the temporary hardness of water using a system as illustrated in Fig. 1 ;

Fig. 4 is a schematic diagram of an implementation of a system of the type illustrated in Fig. 1 in which a replaceable fluid treatment cartridge is used;

Fig. 5 is a perspective view of a fluid treatment appa^¬ ratus with manual blending fraction adjustment prior to being upgraded to one with automatic blending fraction adjustment;

Fig. 6 is a perspective view of a first stage in the process of upgrading the apparatus of Fig. 5;

Fig. 7 is a perspective view of a second stage in the process of upgrading the apparatus of Fig. 5 and 6;

Fig. 8 is a perspective view of a third stage in the process of upgrading the apparatus of Figs. 5-7; and Fig. 9 is a perspective view of the apparatus of

Figs. 5-8 in the upgraded state.

In the following, the example of a liquid treatment system, specifically a system for softening water will be used. The apparatus is equally suitable for treating other types of liquid, and the methods discussed below for determining a meas^¬ ure of hardness can also be used to determine the concentration of components removable by a liquid treatment part of a liquid treatment device for treating such other liquids.

The liquid treatment system that is the focus of the present description includes a first unit and a separate second unit that is attachable to a housing part of the first unit. However, the functionality of the system will be explained with reference only to the component parts of the overall system, without limitation to a particular division of these parts between separate units.

These component parts of the system are illustrated by way of example in Fig. 1, which shows a water treatment appa^¬ ratus including an inlet 1 for receiving untreated water and an outlet 2 for providing water with a desired level of temporary hardness. The inlet 1 is connectable to a supply of untreated water, in particular the mains water supply. The outlet 2 is connectable to an appliance such as a steam cooker, dish washer or a device for preparing beverages (e.g. a coffee maker) . The fluid treatment apparatus includes a fluid treatment device 3 configured to remove temporary hardness to at least a certain extent from the water led through it. In the following, it will be assumed for simplicity that the fluid treatment device 3 is effective to remove essentially all temporary hardness. Tempo- rary hardness, also known as carbonate hardness, is caused by the presence of dissolved carbonate minerals (essentially calci^¬ um and magnesium carbonate) . It is distinguished from permanent hardness, to which other minerals such as calcium chloride also contribute .

In an alternative embodiment, the fluid treatment de^¬ vice 3 is effective to remove not just the temporary hardness, but all hardness from the water led through it, and the fluid treatment apparatus is configured to supply water with a desired level of total hardness. This is merely a question of using a fluid treatment device 3 with a different filter medium. Re^¬ turning to the example of temporary hardness, the fluid

treatment device 3 can comprise a filter medium including a weakly acidic ion exchanger that is at least initially in the hydrogen form, for example.

There is thus a first fluid path running from the in^¬ let 1 through the fluid treatment device 3 to the outlet. There is also a second fluid path from the inlet 1 to the outlet 2. This second fluid path bypasses the fluid treatment device 3. In the illustrated embodiment, the water passing through the second fluid path is not treated at all, to simplify the discus^¬ sion.

A variable ratio flow divider 4 is arranged at a branch point where the first and second fluid paths go their separate ways. The flow divider 4 is adjustable by a motor 5 controlled by a control device 6 provided with an interface 7 to the motor 5. In this way, an adjustable fraction of the water pass- ing through the inlet 1, which fraction is referred to herein as a blending fraction x, is led through the second fluid path.

The first and second fluid paths join at a mixing location 16, so that the water treated by the fluid treatment device 3 and that left untreated can mix. In the illustrated embodiment, the control device 6 is programmed to relate positions of the motor 5 to values of the blending fraction x and vice versa.

The control device 6 includes a data processing unit 8 and memory 9. It is provided with an interface 10, e.g. a user interface, for receiving input relating to a target value of the temporary hardness of the water at the outlet 2. The input may be a value or information representative of the type of applica^¬ tion the water is to be used in. In an embodiment, such input can be communicated from another device through the interface 10. The control device 6 is configured to determine the temporary hardness of the water at the inlet and to set the blending fraction x to the appropriate value by adjusting the settings of the motor 5 and flow divider 4. In this way, a par- ticular target value of the temporary hardness can be achieved even though the fluid treatment device 3 is able to remove the temporary hardness from water led through it to only a fixed extent, generally 100 %.

In the illustrated embodiment, the control device 6 in- eludes an interface 11 to a flow meter 12 configured to measure the volumetric flow through the fluid treatment apparatus.

Since the control device 6 controls the settings determining the blending fraction x, it can convert the total accumulated volu^¬ metric flow through the fluid treatment apparatus into a value representative of the volume of water that has passed through the fluid treatment device 3. Since it also determines the tem^¬ porary hardness of water at the inlet 1, it is able to determine a measure of the total amount of temporary hardness-inducing components to which the fluid treatment device 3 has been ex- posed over a certain period (generally commencing at first use) . In this way, it can signal when the fluid treatment device has become exhausted and is to be replaced or regenerated. This signal is provided through the interface 10 or a separate inter^¬ face (not shown) . Where the interface 10 is a user interface, the signal is provided in a form perceptible by a user, e.g. by way of a visible and/or audible indication of the remaining lifetime of the fluid treatment device and/or of the percentage of initial capacity that has been used up. Where the interface 10 is a data communication link to an external appli^¬ ance, the same information is communicated in the form of a data signal for processing and/or output by the external appliance. Optionally, the signal is only provided upon determining that fluid is being provided from the fluid treatment apparatus.

The control device 6 is also provided with an inter^¬ face 13 to a sensor device 14 including an electrical

conductivity sensor 15 arranged to measure the electrical con^¬ ductivity of the water downstream of the mixing location 16.

The electrical conductivity of water is dependent on the concen^¬ tration of dissolved ions of all species, not just those

contributing to hardness or that fraction of those species con^¬ tributing to hardness that contributes to the temporary

hardness. Thus, for example, the water can contain dissolved calcium chloride, of which the calcium ions do not contribute to temporary hardness, but do contribute to permanent hardness.

Moreover, certain ion species do not contribute to hardness at all, but their concentration partly determines the electrical conductivity of the water. The control device 6, specifically the data processing unit 8, is programmed to determine the tem^¬ porary hardness of the untreated water using measurement values obtained from the sensor device 14.

In the illustrated embodiment, the sensor device 14 in^¬ cludes a temperature sensor 17 and a data processor 18 for converting electrical conductivity values from the conductivity sensor 15 into values that would have been obtained if the tem^¬ perature had been at a certain reference value, e.g. 25°C.

These corrected values are provided as output to the control de^¬ vice 6. This takes account of the fact that the electrical conductivity for a given concentration varies with the tempera^¬ ture of the water. The temperature signal need not be provided to the control device 6, saving on connectors and leads and re^¬ ducing the potential for failures. The electrical conductivity of the water at the loca^¬ tion of the sensor device 14, i.e. downstream of the mixing location 16 is dependent on the electrical conductivity of the untreated water, the blending fraction and the electrical con- ductivity of the water at an exit point 19 directly downstream of the fluid treatment device 3, but upstream of the mixing lo^¬ cation 16. Let the electrical conductivity of the untreated water be So and the electrical conductivity at the exit point 19 be Si . The difference As = so^~Si is due to the removal of the temporary hardness, i.e. representative of a change in the elec^¬ trical conductivity due to treatment by the fluid treatment device 3. This value is to be obtained and converted into a measure of temporary hardness. The electrical conductivity of the water at the location of the sensor device 14 is given by the following equation:

s(x) = x^■ s₀ + (l - x)^■ S_j = (s₀ - S_j ) · x +S_j= As^■x + s₁ . ( 1 )

A method of determining the temporary hardness of the untreated water and a method of determining the temporary hard^¬ ness of the treated water will now be described with reference to Fig. 2.

In a first step 20, the control device 6 sets the blending fraction x to a reference value xi by causing the motor 5 to adjust the variable ratio flow divider 4. In partic^¬ ular, the reference value xi is set to zero, corresponding to a completely closed second fluid path.

The associated value of the electrical conductivi^¬ ty s (xi) , which value is already corrected for any deviations from a reference temperature, is then obtained (step 21) . This value is stored in memory 9. The control device then returns to normal operation (step 22) . It also sets a timer (step 23) to enable it to repeat the first step 20 at an appropriate later point in time. The blending fraction is then set (step 24) to an appropriate second value x₂, different from the reference value xi . This value ₂ can be a default value determined by the target value of the temporary hardness and the latest available value for the temporary hardness of the untreated water (or a default value in case the control device 6 is being used for the very first time) . The control device 6 then again obtains (step 25) from the sensor device 14 a measurement value representative of the electrical conductivity, corrected for deviations from a reference temperature. This step 25 is executed after a delay that is long enough to ensure that the sensor device 14 measures the electrical conductivity at the new value X2 of the blending fraction .

In case the control device is configured to determine a measure of the temporary hardness H of the untreated water it proceeds as follows:

_H_s(x₂)-s(x_l) ^ ₍₂₎ (x₂-x_l)-F '

where F is a conversion factor. The conversion factor F is a constant in one embodiment. It can be equal to approximately 30 μΞ/' Η, where dH stands for deutsche Harte.

Where the reference value of the blending fraction xi is zero, the determination is simplified:

_{H =} s(x₂)-s(_Xl) _{^ (3)} x₂-F

In embodiments in which the temporary hardness H^* of the blended water is determined in this step 26, the calculation becomes :

f_f. _¾·( )- )) ₍₄₎

(x₂-x_l)-F

Where the reference value of the blending fraction xi is zero, the determination is simplified further: Thus, where the value s (xi) of the electrical conduc^¬ tivity is a value obtained from a measurement downstream of the mixing location 16 at a reference value xi of the blending frac- tion of exactly zero, it is sufficient to determine the

difference between the further value s (x_∑) of the electrical con^¬ ductivity and the value s (xi) obtained at the reference value xi of the blending fraction. Knowledge of the exact value of the blending fraction is not required.

With knowledge of the temporary hardness H of the un^¬ treated water or the temporary hardness H^* of the water

downstream of the mixing location 16, the control device 6 pro^¬ ceeds (step 27) to adjust the blending fraction x to a new value Χ3 in accordance with a target value, if required. The target value is a value appropriate to the type of appliance connected to the outlet 2.

At a later point in time, the steps 25-27 of determin^¬ ing the conductivity, calculating the temporary hardness and adjusting the blending fraction x if required are repeated.

However, the value s (xi) of the electrical conductivity at the reference value xi that is used in the calculations remains the same one as used in the previous iteration. In particular, the blending fraction is not re-set to zero first. In one embodi^¬ ment, these steps 25-27 are repeated at pre-set intervals. The interval can be in the order of hours, a day or even more. In^¬ stead of using pre-set time intervals, the passing of a pre^¬ determined volume of water through the system or a change in conductivity exceeding a pre-set level can trigger a repeat of these steps 25-27.

Returning to the illustrated example, once more than a pre-determined interval of time ti has elapsed since the timer was set (step 23) , the control device 6 proceeds to obtain a new reference value of the electrical conductivity s (x) by returning to the first step 20, in which the blending fraction x is set to a reference value, in particular zero. Instead of using a pre^¬ determined interval of time ti, it is also conceivable to return to the first step 20 after a pre-determined number of iterations of the steps 25-27 using the same value s (x ) of the electrical conductivity at the reference value xi of the blending fraction. In yet another embodiment, re-use of the same reference val^¬ ues (xi) of the electrical conductivity ceases once a determined output value deviates from a preceding value by more than a cer^¬ tain amount. It is noted that, if the same value s (xi) is used for too long, changes in electrical conductivity due to varia^¬ tions in the concentration of other components than hardness- inducing components could lead to errors in the determined meas- ure of temporary hardness.

In an embodiment, this repeat execution of the first step 20 is preceded by an output signal, for example provided via the user interface 10, so that any appliance connected to the outlet 2 can be disconnected first. In another embodiment, a flow diverter (not shown) is connected to the outlet 2, con^¬ trolled by the control device 6 and connected to both the water- consuming appliance and a drain, so that the control device 6 can cause the untreated water that flows out of the outlet 2 when the blending fraction x is set to zero to be discharged down the drain. Alternatively, it is possible to use a fluid treatment device containing a buffering agent. This ensures that appliances connected to the outlet 2 do not receive water with a very low pH when the blending fraction x is set to zero. However, where a buffering agent is used, a different value for the conversion factor F may need to be used, because the change in electrical conductivity due to the fluid treatment will gen^¬ erally be smaller (ions are released into the fluid) . Alternatively, a correction factor may be applied to the meas^¬ ured values of the electrical conductivity.

A different embodiment of a method of determining a measure of temporary hardness is illustrated in Fig. 3. It in- volves obtaining a value approximating the derivative of the electrical conductivity (corrected for deviations from a refer^¬ ence temperature) with respect to the blending fraction so as to determine the change in electrical conductivity caused by the treatment effected by the fluid treatment device 3.

It is assumed in the following that the blending frac^¬ tion x is at a certain value XQ. At first use of the system this value xo can be a default value or a value dependent on a target value for the temporary hardness at the outlet 2 and a default value representative of a common level of temporary hardness.

In a first step 28, the control device 6 causes the mo^¬ tor 5 and flow divider 4 to adjust such that the blending fraction is changed to a first value xi, e.g. χι= χο+Δχ/2. In a next step 29, a measurement value s(xi) is obtained from the sen^¬ sor device 14, the value pertaining to a measurement carried out with the blending fraction at the first value. Next (step 30), the control device 6 causes the motor 5 and flow divider 4 to adjust such that the blending fraction is changed to a second value X2, e.g. x_∑= χο^_Δχ/2. Then (step 31), a second measurement value s (χ_∑) is obtained from the sensor device 14, the value per- taining to a measurement carried out with the blending fraction at the second value x_∑.

The control device can now determine (step 32) a dif^¬ ference value s{x2)-s{xi) and (step 33) divide this value by the blending fraction differential Ax to obtain an approximation of the derivative of the conductivity s (x) of the mix of treated and untreated water with respect to the blending fraction x, which, it will be recalled, approximates the difference in con^¬ ductivity caused by the temporary hardness that is removable by the fluid treatment device 3. It then obtains the value of a conversion factor F (step 34) and converts (step 35) the output of the preceding step 33 into a value of the temporary hardness. For example, the conversion can be carried out by dividing the result of the division step 33 by a constant conversion fac^¬ tor F = 30 μΞ/' Η, where dH stands for deutsche Harte .

The change in blending fraction Ax can be quite small, of the order of 0.2 or smaller, e.g. 0.1. As a consequence, any appliance connected to the outlet 2 can remain connected whilst the method of Fig. 3 is carried out. It can be repeated rela^¬ tively often, but intervals of the order of one or more days generally suffice to capture variations in the temporary hard^¬ ness supplied to the inlet 1.

A schematic diagram of a water treatment apparatus in- eluding separate first, second and third units 36,37,38 is shown in Fig. 4. The apparatus has the same component parts as that of Fig. 1 and functions in essentially the same way, but it is characterised by a particular division of the component parts over the three units 36,37,38.

The first unit 36 includes an inlet connector 39 for connecting a supply of untreated fluid. It further includes a variable-ratio flow divider 40 including at least one valve and a valve element 41. A suitable example of the variable-ratio flow divider 40 is illustrated in WO 2009/101188 Al, hereby in- corporated by reference. This publication describes a blending valve with an inlet channel and at least two outlet channels, and with an element for setting flow cross-sections. The set^¬ ting element is provided with a respective setting means between the inlet channel and each outlet channel for setting a respec- tive flow cross-section. The setting means are coupled to each other in such a way that the sum of the flow cross-sections re^¬ mains constant during adjustment of the setting element. The setting element is to be regarded as a movable valve element, being rotatable within a valve body in which the inlet channel and the two outlet channels are provided. It is essentially part of two valves, each for throttling the flow to one of the outlet channels.

As illustrated schematically in Fig. 4, the valve ele^¬ ment 41 comprises or is connected to a first element 42 for forming a mechanical link to the valve element 41. Part of the first element 42 protrudes from the valve body or is at least externally accessible.

The first unit 36 is provided with a mechanical inter^¬ face for attaching a replaceable fluid treatment cartridge 43. The variable-ratio flow divider 40 constitutes a branch point from which a first fluid path leads through an outlet of the first unit 36, through a first inlet of the replaceable fluid treatment cartridge 43, down a fall tube 44 into a first bed 45 of liquid treatment medium. The liquid treatment medium may be in granular form, for example. In the example used herein, the first bed 45 comprises a liquid treatment medium arranged to re^¬ move temporary hardness from the water. In this example, it comprises a weakly acidic ion exchange resin (and no other type of ion exchange resin) . The ion exchange resin is predominantly in the hydrogen form, at least on first use.

A second fluid path leads from the branch point consti^¬ tuted by the variable-ratio flow divider 40 through a second outlet of the first unit 36, through a second inlet of the car^¬ tridge 43 directly into a second bed 46 of liquid treatment medium, bypassing the first bed 45. The second bed 46 includes a medium arranged to remove different components of the water. Optionally, it may be arranged to remove temporary hardness to a different, lesser extent than the medium in the first bed 45. The second bed 46 includes activated carbon as a liquid treat^¬ ment medium in one embodiment. The water led through the first fluid path flows through the first bed 45 into the second bed 46, where it mixes with the water that has bypassed the first bed 45. The mixing location is thus within the liquid treatment cartridge 43. The proportion of water flowing into the first unit 36 through the inlet connector 39 that bypasses the first bed 45 constitutes the blending fraction x. The settings of the variable-ratio flow divider 40 determine the size of the blending fraction x. They can be adjusted by rotating the first element 42 about a body axis of the first element 42.

Once mixed, the water leaves the cartridge 43 through an outlet that is connected in a fluid-tight manner to an inlet of the first unit 36. A flow meter 47 in the first unit 36 rec^¬ ords the volumetric flow or flow rate. The water then leaves the first unit 36 through an outlet connector 48 of the first unit 36.

The first unit 36 corresponds essentially to certain types of filter heads for use with replaceable filter cartridges and provided with a facility for manually adjusting the blending fraction.

The second unit 37 is configured for attachment to a housing part of the first unit 36. It supports a second ele^¬ ment 49, which, in the illustrated embodiment, completes a mechanical link between the valve element 41 of the variable- ratio flow divider and a motor 50. The motor 50 is also mounted in the first unit 36 so as to be supported by a frame or housing part of the first unit 36. Generally, the motor 50 will support the second element 49. In this way, the second element 49 is journalled so as to be rotatable about a body axis thereof. At an end facing away from the motor 50 one of a socket and key for engaging the socket is provided. An end of the first element 42 co-operating with this end of the second element 49 is provided with the other of the socket and key for engaging the socket. When the second unit 37 is attached to the first unit 36, the key engages the socket to complete the mechanical link, such that rotational movement of the motor 50 is transferred to the first element 42 such as to adjust the settings of the variable- ratio flow divider 40.

The motor 50 operates under the control of a data pro^¬ cessing unit 51 having access to memory 52 and configured to carry out a method of controlling the temporary hardness involving a method of determining a measure of temporary hardness as illustrated in Fig. 2 or Fig. 3. The data processing unit 51 and memory 52 thus function as a control device for controlling the motor 50.

The data processing unit 51 receives a signal repre^¬ sentative of the electrical conductivity of the water downstream of the mixing location in the cartridge 43 from the third unit 38 via an interface 53 of the second unit 37 that includes an electrical connector for receiving the signal. The third unit 38 includes an inlet connector 54 for coupling to the out^¬ let connector 48 of the first unit 36 in a fluid-tight manner. It further includes an outlet connector 55 for coupling to a conduit for supplying the water treated by the fluid treatment apparatus to an appliance (not shown) . The third unit 38 is provided with an electrical conductivity sensor, temperature sensor and data processor (not shown in Fig. 4) as described above in relation to the sensor device 14 of Fig. 1. It is thus arranged to provide the second unit 37 with measurement values representing values of the electrical conductivity of the water passing through the third unit 38, corrected to take account of deviations from a reference temperature.

It follows that the first unit 36 need not be provided with an electrical conductivity sensor. The second unit 37 need not be provided with any parts that could come into contact with water. Furthermore, the second unit 37 need not be provided with a temperature signal or a temperature sensor, since the temperature correction is carried out in the third unit 38.

The data processing unit 51 is able to receive data representative of the volume of water flowing and/or the volu- metric rate of flow through the first unit 36 from the flow meter 12 via interfaces 56,57 of the first and second

units 36,37, respectively. The physical parts of these inter^¬ faces 56,57 are arranged to mate upon attachment of the second unit 37 to a housing part of the first unit 36. Because the da- ta processing unit 51 also controls the settings of the motor 50 and flow divider 40 and repeatedly calculates the temporary hardness of the untreated water, it is able to calculate the load presented by the volume of water that has passed through the first filter bed 45. It is therefore able to determine when the cartridge 43 is to be replaced.

The data processing unit 51 is arranged to receive in^¬ formation representative of a target value of the temporary hardness or information enabling it to determine the target val^¬ ue of the temporary hardness through an interface 58, which may include either or both of a user interface and an interface for exchanging data with an appliance.

The cartridge 43 can be one of several different types. It is provided with a machine-readable token 59, e.g. a bar code, RFID tag or similar device. The second unit 37 is provid- ed with a device 60 for at least obtaining information from the token 59. Because the first unit 36 is positioned between the cartridge 43 and the second unit 37 and the second unit is pro^¬ vided with the device 60 for reading data from the token 59, the device 60 is suitably a device for the contactless, more partic- ularly wireless, reading of information from the token 59.

The reader device 60 is arranged to provide a signal to the data processing unit 51. Thus, the data processing unit 51 is arranged to obtain input data identifying at least a type of the cartridge 43, type information being among the information stored in the token 59.

Using the data obtained from the token 59, the data processing unit 51 is able to carry out one of the methods of Figs. 2 and 3, modified in dependence on the identified type of the cartridge 43. In particular, the temporary hardness of the untreated or treated water is determined as a function of at least one value associated with the type of the cartridge 43, there being a different value associated with each of several possible types in the memory 52. In particular, the extent to which the medium in the first bed 45 is arranged to remove tem^¬ porary hardness and/or the extent to which certain ion species not associated with temporary hardness are removed by the medium in the first bed 45 can be stored in association with each type of cartridge 43. Thus, the data processing unit 51 would use a different factor F in equations (2) -(5) (corresponding to step 26 in the method of Fig. 2 and step 35 in the method of Fig. 3) . It may also suspend execution of the methods of

Fig. 2 or 3 upon determining that the cartridge 43 is of an un- suitable type.

In another embodiment, a value representative of the extent to which the medium in the first bed 45 removes temporary hardness is associated with each of several different types of cartridge 43 in the memory 52. Let this value be ε, a value less than 100 % (e.g. ε = 0.9). Equations (2)-(5) would be re-written by dividing by ε, and the conversion steps 26,35 in the methods of Fig. 2 and 3 adapted accordingly.

In another embodiment, characteristics of the water are inferred from the electrical conductivity measurements and/or the calculated values of the temporary hardness. These charac^¬ teristics are compared to the type identification of the

cartridge. If the cartridge is unsuitable for the characteris^¬ tics of the water, an appropriate output signal is provided. An actual implementation of a fluid treatment apparatus as shown schematically in Fig. 4 is illustrated in Figs. 5-9. These show the process of adapting an existing water treatment apparatus to provide it with an automatic blending fraction ad- justment feature.

A replaceable filter cartridge 61 is shown attached to a filter head 62 that corresponds functionally to the first unit 36. The filter head 62 includes a housing including a base part 63 and a cover part 64. It further includes an inlet fit- ting 65 for mating with a coupler 66 at the end of a conduit for carrying a supply of untreated water. An outlet fitting 67 is provided for mating with a coupler 68 at the end of a conduit for delivering a mix of softened and unsoftened water to an ap^¬ pliance (not shown) .

A mechanical coupling element 69 (see also Fig. 7) in^¬ cludes a hexagonal socket for insertion of an Allen key. At least the socket is accessible through an aperture in the cover part 64 of the housing of the filter head 62. The coupling element 69 is linked to an element (not shown) corresponding to the first element 42 for establishing a link to a valve element of a variable-ratio flow divider (not shown) arranged in the filter head 62. Thus, in the state shown in Fig. 7, the water treat^¬ ment apparatus is provided with a facility for manually

adjusting the blending fraction using an Allen key or similar tool.

To upgrade the apparatus with an automatic adjustment facility, the cover part 64 of the housing of the filter head 62 is removed (cf . Fig. 6) . The outlet fitting 67 is disconnected from the coupler 68 at the end of the conduit leading to a wa- ter-consuming appliance. Then (cf. Fig. 7), the coupling element 69 is removed.

A module 70 corresponding functionally to the second unit 37 shown in Fig. 4 comprises a housing part 71 of which side walls define an aperture. An axle 72 corresponding to the second element 49 (Fig. 4) protrudes from the aperture. It is provided with one of a socket and key for engaging the other of a socket key provided at an exposed end of a first element (not shown) in the filter head 62. The axle 72 is mounted to the module 70 so as to be rotatable about a body axis that is essen^¬ tially parallel to a direction in which the module 70 is moved when attached to the filter head 62. The module housing part 71 is configured to fit to the base part 63 of the housing of the filter head 62 so as to complete a housing enveloping the parts contained therein (essentially corresponding to the components parts of the first and second units 36,37 as described with ref^¬ erence to Fig. 4) . The axle 72 is aligned with the element it is arranged to engage through the act of aligning the module housing part 71 with the base part 63 of the housing of the fil^¬ ter head 62.

A sensor unit 73 corresponding to the third unit 38 as described with reference to Fig. 4 is provided with a coupler 74 for mating with the outlet fitting 67 of the filter head 62. It is further provided with an outlet fitting 75 for mating with the coupler 68 at the end of the conduit leading to a water- consuming appliance. An electrical connector 76 at the end of a lead 77 is configured for insertion into a socket (not shown) of the module 70 to provide it with the signal representative of electrical conductivity values (corrected to take account of temperature deviations, as explained) .

Fig. 9 shows the apparatus in the final assembled state. A further lead 78 is provided for exchanging data with an appliance (not shown) . A power supply 79 for providing elec- trical power to the module 70 is also connected. Thus,

automatic measurement of the temporary hardness using a single electrical conductivity sensor and automatic adjustment of the blending fraction to achieve a target value of the temporary hardness are made possible.

The invention is not limited to the embodiments de^¬ scribed above, which may be varied within the scope of the accompanying claims. For instance, instead of a key and socket at the ends of the first and second elements 42,49, gears ar^¬ ranged to mesh when the second unit 37 is attached to a housing part of the first unit 36 may be used to establish a link. The module 70 attached to the filter head 62 may be battery-powered in an alternative embodiment.

LIST OF REFERENCE NUMERALS

1 - inlet

2 - outlet

3 - fluid treatment device

4 - flow divider

5 - motor

6 - control device

7 - interface to motor

8 - data processing unit

9 - memory

10 - interface

11 - interface to flow meter

12 - flow meter

13 - interface to sensor device

14 - sensor device

15 - conductivity sensor

16 - mixing location

17 - temperature sensor

18 - data processor

19 - exit point

20 - step (set blending fraction to reference value)

21 - step (determine conductivity)

22 - step (return to normal operation)

23 - step (set timer)

24 - step (set blending fraction)

25 - step (determine conductivity)

26 - step (calculate temporary hardness)

27 - step (adjust blending fraction)

28 - step (set 1^st blending fraction)

29 - step (obtain first conductivity value)

30 - step (set 2^nd blending fraction)

31 - step (obtain 2^nd conductivity value) - step (determine difference value)

- step (divide by blending fraction differential) - step (determine conversion factor)

- step (convert to temporary hardness)

- 1^st unit

- 2^nd unit

- 3^rd unit

- inlet connector

- flow divider

- valve element

- 1^st element

- fluid treatment cartridge

- fall tube

- 1^st bed

- 2^nd bed

- flow meter

- outlet connector

- 2^nd element

- motor

- data processing unit

- memory

- interface to sensor device

- inlet connector of 3^rd unit

- outlet connector of 3^rd unit

- interface to flow meter of 1^st unit

- interface to flow meter of 2^nd unit

- interface for providing input data

- machine-readable token

- device for reading information from token

- filter cartridge

- filter head

- base part of filter head housing

- cover part of filter head housing - inlet fitting

- coupler for mating with inlet connector - outlet fitting

- coupler for mating with outlet connector - coupling element

- module

- housing part of module

- axle

- sensor unit

- coupler of sensor unit

- outlet fitting of sensor unit

- electrical connector

- lead

- further lead

- power supply

Claims

1. Device for forming a component of a fluid treat^¬ ment system, the fluid treatment system including:

a first unit (36; 62) including:

an inlet (39; 65) for untreated fluid;

a branch point between the inlet (39; 65) and at least one first fluid path and at least one second fluid path;

each first path including at least one fluid treat^¬ ment (45) part for treating fluid led through the first fluid path,

each second fluid path bypassing at least one of the fluid treatment parts (45) , wherein the at least one second flu^¬ id path is arranged, in use, to conduct a blending fraction of the fluid received through the inlet (39; 65);

a mixing location (16;46), where the first and second fluid paths join;

at least one device (4) for setting the blending frac^¬ tion; and

a first element (42) for forming a link between at least one movable valve element (41) of the device (4) for set- ting the blending fraction and an actuator (5) for adjusting a position of the movable valve element (41), characterised in that

the device includes the actuator (5) and a second unit (37;70), configured for attachment to a housing part (63) of the first unit (36; 62) and supporting at least a second ele^¬ ment (49; 72) for forming the link between the movable valve element (41) and the actuator (5), the second element (49;72) configured for coupling to the first element (42) .

2. Device according to claim 1,

wherein the second unit (37; 70) includes the actuator (5) .

3. Device according to any one of the preceding claims ,

wherein the second unit (37; 70) includes a housing part (71), configured for attachment to the housing part (63) of the first unit (36; 62) and at least partially surrounding at least one of the actuator (5) and a control device (51) for con^¬ trolling the actuator (5) .

4. Device according to claim 3,

wherein the second element (49; 72) extends through an aperture defined by at least one wall of the housing part (71) of the second unit (37;70) .

5. Device according to any one of the preceding claims ,

wherein the second element (49; 72) is journalled so as to be rotatable about a body axis thereof.

6. Device according to claim 5,

wherein the second unit (37; 70) is configured for at^¬ tachment to the housing part (63) of the first unit (36; 62) by at least a movement in a direction essentially parallel to the body axis of the second element (49; 72) .

7. Device according to any one of the preceding claims ,

for use in a fluid treatment system in which the fluid treatment part (45) bypassed by the second fluid path is config- ured to remove to at least a certain extent at least some types of components in fluid led through the fluid treatment

part (45),

wherein the device includes a control unit (51) config^¬ ured to obtain a measure of the concentration of components removable from fluid by the fluid treatment part (45) in at least one of the untreated fluid and fluid downstream of the mixing location (16;46), and to control the actuator (5) in dependence on at least the obtained measure.

8. Method of assembling a fluid treatment system, in^¬ cluding :

providing a first unit (36; 62) including:

a housing part (63);

an inlet (39; 65) for untreated fluid;

a branch point between the inlet (39; 65) and at least one first fluid path and at least one second fluid path of the fluid treatment system,

each first path including at least one fluid treatment part (45) for treating fluid led through the first fluid path, each second fluid path bypassing at least one of the fluid treatment parts (45) , wherein the at least one second flu- id path is arranged, in use, to conduct a blending fraction of the fluid received through the inlet (39; 65),

wherein the fluid treatment system further includes a mixing location (16;46), where the first and second fluid paths j oin;

at least one device (4) for setting the blending frac^¬ tion; and

a first element (42) for forming a link between at least one movable valve element (41) of the device (4) for set^¬ ting the blending fraction and an actuator (5) for adjusting a position of the movable valve element (41);

providing the actuator (5) ; and

linking the at least one movable valve element (41) to the actuator (5) , characterised in that

the step of linking the at least one movable valve ele- ment (41) to the actuator (5) includes attaching to the housing part (63) of the first unit (36; 62) a second unit (37;70) sup^¬ porting at least a second element (49; 72) for forming the link between the movable valve element (41) and the actuator (5) and coupling the second element (49; 72) to the first element (42) .

9. Method according to claim 8,

wherein the second unit (37; 70) is a second

unit (37;70) as defined in any one of claims 1-7.

10. Kit of parts for use in assembling a fluid treat^¬ ment system, the kit of parts including at least:

a first unit (36; 62) including:

a housing ( 63 ) ;

an inlet (39; 65) for untreated fluid;

each first path including at least one fluid treatment part (45) for treating fluid led through the first fluid path, each second fluid path bypassing at least one of the fluid treatment parts (45) , wherein the at least one second flu^¬ id path is arranged, in use, to conduct a blending fraction of the fluid received through the inlet (39; 65),

wherein the fluid treatment system, when assembled, further includes a mixing location (16;46), where the first and second fluid paths join;

at least one device (4) for setting the blending frac^¬ tion; and

a first element (42) for forming a link between at least one movable valve element (41) of the device (4) for set^¬ ting the blending fraction and an actuator (5) for adjusting a position of the movable valve element (41),

wherein the kit of parts further includes a

device (37; 70) according to any one of claims 1-7.

11. Kit of parts according to claim 10,

wherein ends of the first element (42) and second ele^¬ ment (49; 72) configured for coupling to each other include a socket and a keyed part fitting the socket.

12. Kit of parts according to claim 10 or 11, wherein the first unit (36; 62) is provided with a me^¬ chanical interface for replaceably attaching a fluid treatment cartridge (43; 61) including the fluid treatment part (45).

13. Kit of parts according to claim 12,

wherein the first unit (36; 62) is provided with:

a first outlet for connection to a first inlet of the fluid treatment cartridge (43; 61) to form the first fluid path;

a second outlet for connection to a second inlet of the fluid treatment cartridge (43; 61) to form the second fluid path; and

at least one inlet for connection to an outlet of the fluid treatment cartridge (43; 61) to enable the first

unit (36; 62) to receive at least one of the fluid led along the first fluid path and the fluid led along the second fluid path.

14. Kit of parts according to any one of claims 10-13, further including at least a third unit (38;73), the third unit (38;73) including:

an inlet (54;74) for connection to at least one of a fluid conduit and an outlet (48; 67) of the first unit (36; 62);

an outlet (55; 75) for connection to at least one of a fluid conduit and an inlet of the first unit (36) ;

a fluid path between the inlet (54; 74) and the outlet (55; 75) ;

at least one sensor for measuring a value of a parame- ter of fluid led through the fluid path; and

an interface for providing measurement values to the device including the second unit (37; 70) .

15. Kit of parts according to claim 14,

wherein the at least one sensor includes a sensor for measuring electrical conductivity of the fluid.