Abstract:
A water purification apparatus comprising at least: (a) one or more water purification components to provide a purified water stream, preferably having a conductivity of less than 1 μS/cm; and (b) a stepper motor ( 35 ) to control the dispense of the purified water stream ( 28 ) from the water purification apparatus. Stepper motors can provide very fine and accurate control of the dispense of the purified water stream from the water purification apparatus, which control is unaffected by the flow or flow rate of the purified water stream.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates a water purification apparatus and method, particularly, but not exclusively for laboratory water. 
       BACKGROUND 
       [0002]    Water purification apparatus for use in laboratories and healthcare facilities are well known. Generally they involve the reduction and/or removal of contaminants and impurities to low levels. They typically contain a variety of technologies that remove particles, colloids, ionic species and organic substances and/or molecules. 
         [0003]    Water purification apparatus generally allow manual variation by a user of the volume of water to be dispensed, such as from drops to litres, and/or the speed (i.e. flow rate) of water dispense, again from drop-wise to a number of litres per minute. 
         [0004]    However, as well as manual dispensing based on a user physically operating a tap and manually gauging the volume of water being dispensed, frequently water purification apparatus provide for ‘automatic dispensing’, such as on a time basis or measured basis; optionally following a pre-programmed or pre-stored dispense profile as discussed in our WO2007/015048A1. 
         [0005]    In order to accommodate such a range of dispensing options, the control of the water dispense outlet of water purification apparatus is often ‘electronic’, to automate this activity. Typically, a simple on/off solenoid-controlled valve is used. However, solenoids are limited in that the internal flow rate of the water dispense apparatus, and hence the flow rate of the dispense of the purified water stream, is conventionally set at a single and high value, and this does not allow for the easy dispense of slow or small volumes, particularly into smaller water collecting vessels such as beakers and flasks. 
         [0006]    U.S. Pat. No. 5,925,240 describes a water treatment system having dosing control for providing treated water that can be accurately dispensed. In one embodiment, its controller converts an input signal to a motor control signal that causes the motor to operate at a speed which drives the pump and causes the flow of water at the outlet valve to correspond to the desired flow rate. In another embodiment of U.S. Pat. No. 5,925,240, the controller controls the outflow cross-section of a valve and causes the flow of water at the valve to correspond to the desired flow rate. However, both such embodiments involve increasing costs for additional solenoids and additional hydraulic complexity. 
         [0007]    In order to overcome such limitations, but retain a good degree of dispense control, voltage or frequency dependent solenoids can be used, whereby adjustment of the coil, voltage or frequency adjusts the position of the armature, enabling some flow adjustment through such solenoid-controlled valves. However, such solenoids are still limited at very low and/or very accurate (such as drop wise) flows that can be desired or required when very precise volumes are to be dispensed. This is because on initial lifting of the valve diaphragm to start a dispense, the change in pressure on the valve diaphragm affects the delicate electronically-floating armature, leading to its incorrect positioning and therefore incorrect flow control. 
         [0008]    A further disadvantage of solenoids is that in energising the activation coil of a solenoid over a long period, (such as during drop wise dispense for very accurate volume dispense), the heated coil causes undesirable localised heating of the passing purified water stream to occur, affecting the properties of the purified water stream. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the present invention to provide a water purification apparatus and method which provide greater control of the dispense of the purified water. 
         [0010]    Thus, according to one aspect of the present invention, there is provided a water purification apparatus comprising at least: 
         [0000]    (a) one or more water purification components to provide a purified water stream, preferably having a conductivity of less than 1 μS/cm;
 
(b) a stepper motor to control the dispense of the purified water stream from the water purification apparatus.
 
         [0011]    Stepper motors are generally brushless synchronous electric motors that can divide a full rotation of an armature into a number of discrete steps, usually a large number of small steps. This can then provide very fine and accurate control of the dispense of the purified water stream from the water purification apparatus, which control is unaffected by the flow or flow rate of the purified water stream. 
         [0012]    A stepper motor can rotate its armature to a number of rotational positions corresponding to the number of phases of the motor. Consequently a stepper motor with a large number of phases has the ability to position its armature into a large number of positions with a correspondingly small difference or change. As such positions are known and can be indexed, they provide very fine control of the water dispense operation. 
         [0013]    Furthermore, once the armature has been positioned into a desired position for a particular dispense, the stepper motor will hold the armature in position, preventing any disruptive influence to occur to the dispense without the use of additional power or the generation of heat. 
         [0014]    The water purification apparatus may comprise one or more valves for the dispense of the purified water stream. The motor may be coupled to one or more of such valves in such a manner that enables the motor to control the position of at least one of the valves, optionally each valve that directly affects the flow rate of the dispense. This allows the stepper motor to directly control the dispense of the purified water stream by controlling the position of the valve(s). 
         [0015]    The motor may be operable to position a valve between at least a first open position and at least a second closed position, wherein in the first open position, the purified water stream is free to flow through the valve at a first flow rate, and in the second closed position, the purified water stream is prevented from flowing through the valve. 
         [0016]    Preferably, the motor is operable to position a valve between at least a plurality of open positions as well as a closed position, wherein each open position allows purified water to flow through the valve at a different flow rate. Such flow rates can correspond to ‘drop-wise’, such as 20 ml/min, up to 1 l/min, 2 l/min, 5 l/min or more. 
         [0017]    The motor may be further arranged to prevent displacement of one or more valves when positioned into a desired position. 
         [0018]    The motor may be coupled to a valve via at least one of a cam mechanism or a gearing mechanism. The use of at least a gearing mechanism enables the motor to impart even finer control of the dispense of the purified water stream from the water purification apparatus by the use of the gearing ratio in a manner known in the art. 
         [0019]    Thus, the present invention allows an electric motor, optionally with a servo controller and an integral production gearbox, to convert the rotational energy of the motor into a precise linear movement. The degree of movement can be controlled by adjusting the electrical conditions. 
         [0020]    The motor may be controlled using any suitable controller, being directly or indirectly operable by a user, generally being an input device. Typically, the motor will be activated and/or controlled via a manual input device such as a button or rotational control, which converts the user&#39;s hand operation into suitable electrical signals which then electronically operate the motor, and any associated dispense valve. Because the motor can control a drive shaft very precisely, typically through a reduction gearbox, any valve is held very firmly, so that the changes in pressure which occur when dispense begins, such as the valve beginning to open, does not affect the controllability of the dispense, unlike the situation on the variable solenoid where the armature is floating and not held rigidly. 
         [0021]    The variations in possible relationships between a user&#39;s hand operation and suitable electrical signals are known in the art, and can include varying the timing, speed, degree and/or amount of the control of the motor in relation to a user&#39;s hand movement or operation via one or more pre-programmed operations or algorithms or other relationships into the proportional electrical signals to operate the control of the water dispense. 
         [0022]    For example, the degree of a user&#39;s hand operation may provide a non-linear and/or dampened control to create a suitable electrical signal to proportionally control the motor by the required amount. 
         [0023]    The advantages of the present invention include the use of relatively low cost electronic motors/servos, the possibility of extremely precise operation, even at very low flow rates, and no heat build up by the use of such a motor, avoiding any unintended heat transfer to the purified water stream being dispensed. 
         [0024]    Where the water purification apparatus includes a pump, control of the motor may additionally be coupled with control of the pump, such as the pump speed. In this way, precise and fully adjustable dispense flow rates over the whole range of the water purification apparatus&#39; operational flow rates can be achieved. 
         [0025]    The stepper motor can include a threaded or otherwise helically-grooved axle. The shape and diameter of such an axle, and/or its throw and/or pitch, may be directly or indirectly proportional to the fineness of control that may be achieved. 
         [0026]    The water purification apparatus of the present invention may comprise any number of water purification components, as well as other devices, parts, lines, etc, including but not limited to one or more of the following: pumps, meters, oxidisers, sensors, de-ionisers, valves, drains, controllers, taps, reservoirs, recirculation loops, filters and membranes. One or more of such components may be integral with the water purification apparatus, such as a pump, and one or more of such components may be separable from the water purification apparatus, such as an ion-exchange cartridge. 
         [0027]    Water purification apparatus are known in the art, and are generally intended to provide purified water, preferably as a purified water stream, having a conductivity of less than 1 μS/cm, preferably less than 0.1 μS/cm, more preferably less than 0.067 μS/cm, at 25° C. This can be equated to the purified water stream having a resistivity of at least 1 MΩ-cm, preferably at least 10 MΩ-cm, more preferably at least 15 MΩ-cm. Additionally, purity specifications can be made for organic species to content levels of less than 500 ppb of total organic carbon (TOC), preferably less than 50 ppb; bacteria to levels less than 100 colony forming units (cfu) per millilitre, preferably less than 1 cfu/ml; and for dissolved oxygen and/or particles. 
         [0028]    Such water purification apparatus generally only provide up to 1000 litres of purified water per hour, such as up to 5 l/min. 
         [0029]    Such water purification apparatus are generally ‘stand alone’ units, generally only requiring connection to nearby water and electricity supplies to be operable. Thus, they are generally independent and/or moveable units operating in or at a specific location such as a laboratory. Preferably, at least the majority of the purification actions or processes occur within a housing. They are intended to provide a purified water stream only, such stream not being in combination with any other substance or compound. 
         [0030]    In general, a water purification apparatus includes a pump, an inlet, one or more de-ionisers, optionally one or more oxidisers, and a water outlet (for dispense of the purified water stream). 
         [0031]    One common oxidiser involves the use of ultraviolet light, and the ultraviolet treatment of water for decomposing organic compounds or substances in water is well known in the art. Apparatus and instruments for providing suitable ultraviolet light are well known in the art, and typically involve emitting ultraviolet light at one or more specific wavelengths in an area or space through which the water passes. The or each oxidiser can be provided as a distinct component, typically a separable component such as a replaceable cartridge, having an ultraviolet emitter therein around which the water stream passes from an inlet to an outlet. The purification of water in the present invention may involve one or more oxidisers, being in series, parallel or both. 
         [0032]    Ionic species in the feedwater (and created by any oxidiser(s)) are generally removed from the water stream to provide purified water by the use of one or more de-ionisers. Many types and forms of de-ioniser are known in the art, and include, but are not limited to, one or more of the following; (electro)deionisation apparatus or units, reverse osmosis (RO) units or apparatus, membranes, filters, ion exchange resins and zeolites. The action and operation of de-ionisers is well known in the art, and they are not further described in detail herein. 
         [0033]    The water purification apparatus may comprise a plurality of ion-exchangers, including one or more “pre-treatment” ion exchangers upstream of any oxidiser, as well as one or more ion-exchangers downstream of any oxidiser. 
         [0034]    The dispense of at least a portion of the purified water from the water purification apparatus can be provided through any form or type of outlet or outlets, optionally being co-ordinated or separate. 
         [0035]    The water purification apparatus may have a dispense mode or other such form of operation, and a recirculation mode. Preferably, the or each point of dispense of the purified water involves at least one valve and motor, more preferably operable between a dispense position and a recirculating position. One or more valves may also provide control over the volume and/or rate of flow of the purified water at the dispense. 
         [0036]    The movement of water through a water purification apparatus is generally provided by the use of one of more pumps known in the art. The nature and operation of a pump is not further discussed in detail herein. 
         [0037]    The present invention encompasses all combinations of various embodiments or aspects of the invention described herein. It is understood that any and all embodiments of the present invention may be taken in conjunction with any other embodiment to describe additional embodiments of the present invention. Furthermore, any components of an embodiment may be combined with any and all other components from any of the embodiments to describe additional embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: 
           [0039]      FIG. 1  is a diagrammatic perspective view of the water purification apparatus according to one embodiment of the present invention; and 
           [0040]      FIG. 2  is a diagrammatic part cross-sectional part perspective view of a water dispense arrangement from the water purification apparatus of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0041]    Referring to the drawings,  FIG. 1  shows a water purification apparatus  10 . The water purification apparatus  10  comprises one or more water purification components such as those described hereinabove. Such components may be integral and/or separable from a housing (not shown). 
         [0042]    Separable components include ion-exchange cartridges and UV cartridges known in the art, but the present invention is not limited by the number, nature or location of the water purification components. The operations of water purification components are well known to those skilled in the art, and are generally intended to reduce and/or remove contaminants and impurities in water provided from a water input, so as to provide a purified water stream from at least one water dispense outlet. 
         [0043]    Water purification components can include physical, magnetic, electrical and/or light-based components in any arrangement or line-up known in the art. 
         [0044]    The water purification apparatus  10  is typically intended to be located on or near a work bench, optionally supported thereby or self-supporting. A water purification apparatus may include one or more water inlets, generally from a single source such as a tap or other potable water supply, to provide a purified water stream to one or more water dispense outlets or points. 
         [0045]      FIG. 1  shows a water purification apparatus  10  with a single water dispense outlet  12  integral with the water purification apparatus  10 , by way of example only. Water dispense points can be movable relative to the main parts of the water purification apparatus  10 , such as to any housing, and/or they can be located in remote locations such as through water supply piping or conduits such as a ring main to one or more remote locations, such as a separate room, workbench or laboratory. 
         [0046]      FIG. 1  shows an incoming water stream  14 , available from a water source or the like, which passes through a pump  16 . From the pump  16 , the water stream passes through one or more water purification components.  FIG. 1  shows, by way of example only, two water purification components  22   a ,  22   b , which could comprise an oxidiser such as an ultraviolet light emitter, followed by an ion-exchanger, adapted to remove the ionic species in the feed water as well as those created by the oxidiser; and so to purify the water stream. 
         [0047]    The so-formed purified water stream  24  passes through a first tee-piece  26  to be provided as a purified water stream  28 , available to the dispense outlet  12  via a dispense valve assembly  20  in a conduit  50 . 
         [0048]      FIG. 1  also shows a recirculation loop  30  extending from the first tee-piece  26  through a one way valve  32  to a second tee piece  18 . Recirculation loops are well known in the art, and commonly provide maintenance of the purity of the purified water stream  24  during periods of non-dispense from the water purification apparatus  10  operating continuously or intermittently. 
         [0049]      FIG. 2  shows a cross-sectional view of the final portion of  FIG. 1 , wherein the purified water stream  28  is able to pass to the dispense outlet  12 , whether for direct dispense as a point of use or for subsequent passage to one or more separate water dispense points, through conduit  50  by the operation of a dispense valve  34  as part of the dispense valve assembly  20 . The dispense valve  34  can be positioned between a number of distinct or indexed open positions, and a closed position. In the open positions, the purified water stream  28  can pass to the dispense outlet  12  at different flow rates. In the closed position, the flow of the purified water stream  28  is restricted by the dispense valve  34  against a valve housing  56  such that the water is prevented from passing to the dispense outlet  12 . 
         [0050]    The dispense valve  34  comprises an axle  42  attached to a restrictor element  46  moveable within the conduit  50 . A plurality of evenly spaced recesses  52  such as a screw thread is defined along the surface of the axle  42 . The axle is held in one or more fixed and correspondingly threaded axle-holders (not shown). 
         [0051]    As shown in  FIG. 2 , part of the restrictor element  46  is located within the conduit  50 , to define a flow channel  51  thereinbetween. The axle  42  is able to undergo linear movement along the axle-holder(s) to selectively locate a desired portion of the restrictor element  46  within the conduit  50 . The size of the flow channel  51  is dependant on the portion of the restrictor element  46  located within the conduit  50 . The size of the flow channel  51  may be reduced by moving the axle  42  linearly downwards to locate a greater portion of the restrictor element  46  within the conduit  50  against the valve housing  56 . When the axle  42  is moved fully downwards, the restrictor element  46  fully meets with the valve housing  56  and fills the conduit  50 ; in this state the dispense valve  34  is in a fully closed position. 
         [0052]    Conversely, moving the axle  42  linearly upwards will remove part or all of the restrictor element  46  from the conduit  50 , thereby increasing the size of the flow channel  51 . When the axle  42  is moved fully upwards, optionally such the restrictor element  46  is fully outwith the conduit  50 , the dispense valve  34  is in a fully open position. Consequently, the position of the dispense valve  34  is controlled by linear movement of the axle  42 . As the greater the size of the flow channel  51  the larger volume of water that can flow within the conduit  50 , the rate of flow of the purified water  28  to dispense outlet  12  may be controlled by means of the linear movement of the axle  42 . 
         [0053]    The linear position of the axle  42  can be controlled by a stepper motor  35  shown in  FIG. 2 , generally having a number of electromagnets  36  arranged around a threaded rotor  37  on the axle  42 . 
         [0054]    Operation of the stepper motor  35  provides rotational movement of the rotor  37  and so the axle  42 . The stepper motor  35  may be operated to effect clockwise or anti-clockwise rotation of the rotor  37  and axle  42 . 
         [0055]    A user may operate the stepper motor  35  by means of an input device  54  such as a rotating button, keypad, touch sensitive pad, etc operable by a user. The input device  54  provides, upon activation by a user, direct or indirect electrical signals to the electromagnets  36  on the armature of the stepper motor  35  to effect operation of the stepper motor  35 . The activation and/or operation of the input device  54  may be relayed to the stepper motor  35  in a direct and/or proportional and/or variable and/or delayed relationship. For example, the degree of rotation of a rotational input device may be amplified or dampened before operating the stepper motor  35 . 
         [0056]    In this way, rotational movement of the rotor  37  will effect linear movement of the axle  42  via the threading with fixed the axle holder(s). 
         [0057]    To increase the rate of flow of the purified water stream  28  passing to the water dispense outlet  12 , the stepper motor  35  is operated to affect the relevant rotation of the axle  42 , and so also cause the axle  42  to undergo an upward linear movement. As the axle  42  moves upwards a portion of the restrictor element  46  will be removed from the conduit  50  to increase the size of the flow channel  51 , thereby permitting a larger volume of purified water  28  to flow through dispense outlet  12 . Once the desired flow is achieved at the dispense outlet  12  the stepper motor  35  could be stopped manually by the user, or stopped by a pre-determined or pre-programmed limit. 
         [0058]    Conversely, to decrease the rate of flow of purified water stream  28  to pass to the water dispense outlet  12 , the stepper motor  35  is operated to cause the axle  42  to undergo a downward linear movement. As the axle  42  moves downwards a larger portion of the restrictor element  46  will be positioned into the conduit  50  to decrease the size of the flow channel  51 , thereby permitting a smaller volume of purified water  28  to flow to the dispense outlet  12 . Once the desired flow is achieved at the dispense outlet  12  the stepper motor  35  is stopped by the user and/or stopped by a pre-determined or pre-programmed limit. 
         [0059]    One advantage of use of the stepping motor  35  is that the number of phases of the stepper motor  35  is directly proportional to the number of discrete or distinct rotational positions of the rotor  37 . Consequently, the number of phases of the stepper motor relates to the number of positions at which the axle  42  may be located by the stepper motor  35  and any associated gear assembly (not shown). Using a stepper motor  35  with a significant number of phases will therefore permit very fine and accurate control of the flow of purified water stream  28  passing through the conduit  50  to the dispense outlet  12 . 
         [0060]    Furthermore, the arrangement and operation of the stepper motor  35  and dispense valve  34  are such that water pressure acting upon the restricting element  46  (such as caused by the pressure of the pump  16  in the water purification apparatus  10 ), either in general, and/or as the purified water stream  28  flows through the conduit  50 , does not move or otherwise displace the restrictor element  46 . Thus, the accuracy of the passage of the purified water stream  28  through the passage  51  can be very accurately maintained by the present invention. 
         [0061]    The stepper motor may be arranged to ensure that the position of the dispense valve  34  is maintained during use. Once the dispense valve  34  has been located at a desired position, the axle  42  can be held in its current position by friction. 
         [0062]    The input device  54  may be in the form of, for example, a potentiometer, a keypad, one or more push buttons, an angle encoder and the like. The input device  54  permits a user to easily provide an electrical signal to the stepper motor  35  such that the stepper motor  35  is operated to position the dispense valve  34  into a desired position. The input device  54  may allow a user to enter a desired fluid dispensing rate (e.g. 1 litre/min or 0.1 ml/sec), which can be calibrated to provide a corresponding electrical signal to the stepper motor  35  so that the dispensing valve  34  is moved to a position wherein the desired dispersion rate at the dispense outlet  12  is achieved. An angle encoder may be used to achieve such an effect. 
         [0063]    In this way, either the user or a controller involved in the automatic dispense, is able to relate the input information of the user, such as the degree of rotation of an angle encoder, with the dispense valve  34  to a very accurate degree. 
         [0064]    In a first alternative arrangement, the input instruction of the user is not directly proportional to movement of the dispense valve  34 . For example, the water purification apparatus  10  may allow any initial significant input by the user, such as large angular movement to be varied, such as delayed and/or dampened, in proportion to the movement of the dispense valve  34 . Thus, accidental over-input or movement by a user does not immediately relate to over-movement of the dispense valve  34  and thus possible ruin of the dispense operation. 
         [0065]    One or more variations of the movement of the dispense valve  34  in relation to the input by the user can be provided so as to vary the dispense operation and/or profile depending either upon the known or expected dispense input being provided, and/or to avoid unexpected input. The use of one or more controllers in a water purification apparatus is known to those skilled in the art, and the operation of such controller(s) to affect a variation between input signal and movement of the dispense valve  34 , is well known to those skilled in the art. 
         [0066]    It will be appreciated that although specific embodiments of the invention have been described herein for the purposes of illustration, various modifications may be made without deviating from the spirit of the scope of the invention.