FIELD OF THE INVENTION 
     The present invention relates to a drinking water feeding apparatus having a sterilizing function in an automatic vendor, a beverage dispenser, a water cooler, an ice maker or a home water purifier. The invention also relates to a chlorine generator to be used in the drinking water feeding apparatus. 
     BACKGROUND OF THE INVENTION 
     Service water fed to a drinking water feeding apparatus typically may have a chlorine smell or a muddiness and a rust from the piping. If a beverage (e.g. soft drink or coffee) is dispensed using service water as provided, its intrinsic taste or flavor may be unacceptable. In order to satisfy the water quality standards based on the service water regulations, a filter is frequently used. Such filters must have a filtering function, a dechlorinating function and the ability to remove perceived muddiness. Most filters are troubled by bacterial contamination. Carbon type filters are frequently used for drinking water. They have excellent filtering, dechlorinating and muddiness-removing abilities, but the filtering material (carbon) deactivates the active chlorine contained in the service water, so that the filter loses its sterilizing and fungistatic abilities against the bacteria or the like which migrate into the service water. 
     Under circumstances in which no service water facilities are available, the service water is stored in a tank (cassette tank). In this system, however, it is difficult to keep either the cassette tank itself or the reserved water of the cassette tank which is in contact with the atmosphere in a sanitary state. Furthermore, the filtering material typically has to be replaced when the quantity of the water which has been filtered exceeds a predetermined maximum value. During filter replacement, aerobacteria can migrate into the filter. 
     Thus, there arises a problem that the inside and the downstream of the filter become hotbeds for the growth of various bacteria. When bacteria are present in concentrations of 15 MPN/100 ml in the service water, for example, they can propagate to concentrations of up to 3.9×10 3  cfu/ml after being left for one day at the ambient temperature of 30° C., in a filter container of 1 L containing 390 ml activated charcoal, with an 80 ml collecting pipe and 340 ml water in a filter cartridge. 
     For this reason, methods have been devised to attempt to control the number of bacteria in the filter, in which carbon and a fibrous filter are combined to retain active chlorine. Thus, an effective quantity of active chlorine is fed to the downstream of the filter, providing a sterilizing effect. About one third of the total chlorine ion concentration present in typical feed water would be effective for removing bacteria, but the method is not expected to be sufficiently effective for locations where the chlorine concentration contained in the service water is low or for the service water in which most of the active chlorine is effectively deactivated. 
     In order to avoid drinking water contamination by the bacteria, a drinking water feeding apparatus is disclosed in Unexamined Published Japanese Patent Application No. 9-1149. This reference discloses a closed-type drinking water feeding apparatus which is constructed to isolate the drinking water pipelines from the atmosphere, thereby preventing possible contamination by aerobacteria. Also inherent in Unexamined Published Japanese Published Japanese Patent Application No. 9-1149, is the difficulty that while air can be removed upstream of the chlorine generator, it cannot be removed from the passage downstream of the chlorine generator. Moreover, as drinking water is electrolyzed in the chlorine generator, oxygen or other gases are generated at the positive electrode, and hydrogen gas is generated at the negative electrode. The generation of these gases leads to a reduction in the electrolysis efficiency of the chlorine generator, such that a desired chlorine concentration necessary for sterilization cannot be achieved. This apparatus generates active chlorine by causing electrodes to contact drinking water as it is fed through a filter and by electrolyzing the drinking water so that the drinking water is sterilized by active chlorine. In order to maintain levels of active chlorine sufficient for sterilization purposes, it was found necessary to elongate the electrode surfaces in the flow stream or, alternatively, to reduce the flow speed of the drinking water through the apparatus. There are several drawbacks to this approach however. An elongation of the electrodes inevitably enlarges the apparatus because the elongated electrodes cannot be accommodated in the limited space of a standard beverage dispenser. Furthermore, reducing the feed rate of the service water unduly limits the dispensing rate of the drinking water. 
     Another way to generate active chlorine in effective sterilizing concentrations without changing the size of the electrodes or reducing the water flow speed, is to increase the electric current to be applied. In this case, however, as the current density rises, electrode consumption accelerates. In an attempt to minimize consumption of electrodes, therefore, the current value has to be suppressed and the problem arises that a predetermined uniform chlorine concentration value (e. g., 0.2 ppm) cannot be achieved for the drinking water for all the geographic areas having different water qualities. Specifically, the desired chlorine concentration depends mainly on the two parameters: the quality (especially, conductivity and chlorine ion concentration) of water to be electrolyzed; and an “ON” time period. If the electrodes cannot be enlarged and if the “ON” time period (that is, the time period for the drinking water to pass the length of the electrode surface) cannot be lengthened, the predetermined chlorine concentration may not be attained for all potential water qualities. 
     Unexamined Published Japanese Patent Application No. 59-150950 discloses a filter in which electrodes for the electrolysis are packaged to give the sterilizing effect. This filter kills bacteria adsorbed by the activated charcoal or suppresses their propagation by providing a chlorine generator to feed the activated charcoal with active chlorine generated by service water electrolysis. As a result, the active chlorine concentration can be reduced by the activated charcoal after the sterilization to provide sterilized water having minimal chlorine smell. 
     In this arrangement however, the active chlorine generated by the chlorine generator mounted therein only affects bacteria absorbed by the activated charcoal without being fed downstream. When the drinking water feed is interrupted and the drinking water resides downstream, then bacteria can propagate. 
     Unexamined Published Japanese Patent Application No. 60-283391 and Japanese Patent No. 2564943 disclose drinking water feeding devices. In these references, drinking water such as the service water introduced from the water source and containing chlorine ions is electrolyzed to produce active chlorine having a sterilizing activity so that electrolyzed water may be fed as the drinking water. The drinking water feeding devices thus disclosed electrolyze service water to generate active chlorine and this service water is reserved in a cistern vented to the atmosphere, or in a water reservoir. However, the cistern vented to the atmosphere or the water reservoir is easily contaminated by aerobacteria. When the cistern is equipped with electrolyzing electrodes, on the other hand, the drinking water is fed intermittently, the feeding being determined by the water level, which is detected by a water level sensor. The chlorine concentration changes with the fluctuation of the quantity of water within the range of the difference between the highest water level and the lowest water level so that a constant concentration of active chlorine cannot be stably generated. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides a drinking water feeding apparatus which can ensure a chlorine concentration necessary for sterilizing drinking water of various qualities with a simple construction. 
     In another aspect, the invention provides a drinking water feeding apparatus which can feed, even for long intervals between feeding of the drinking water, drinking water uncontaminated by bacteria. 
     In yet another aspect, the invention provides a filter having a chlorine generator packaged therein. This filter facilitates the reduction in size of a drinking water feeding apparatus, an icemaker or a home water purifier when packaged therein. 
     In a further aspect, the invention provides a drinking water feeding apparatus and a chlorine generator, which enables high electrolysis efficiency, by releasing any gases produced by electrolysis such as hydrogen and oxygen gas generated during electrolysis. 
     As used in the claims and specification, the term “active chlorine” refers to chlorine-containing molecules which have toxic activity against microorganisms, particularly bacteria, and refers specifically to those chlorine-containing molecules which are produced through electrolysis of chlorine-ion containing aqueous solutions. Such molecules include Cl 2 , hypochlorous and hydrochloric acids, and species produced therefrom in aqueous solution. 
     As used in the claims and specification, the terms “service water” or “civil water” refers to water as supplied by municipal and other sources, commonly known as “tap water.” The term “feed water” refers to filtered service water. The term “sales water” refers to electrolyzed feed water. The term “drinking water” is synonymous with “sales water.” 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods and examples are illustrative only, and not intended to be limiting. 
     Other features and advantages of the invention will be apparent from the following detailed description, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a beverage dispenser as a drinking water feeding apparatus. 
     FIG.  2 ( a ) is a side view of a chlorine generator. 
     FIG.  2 ( b ) is a section taken along a portion A-A of FIG.  2 ( a ). 
     FIG. 3 is a control block diagram of the beverage dispenser. 
     FIG. 4 is a timing chart illustrating the “ON” actions of the chlorine generator of a beverage dispenser. 
     FIG.  5 ( a ) is a plot of the aging of the quantities of active chlorine contained in the sales water. 
     FIG.  5 ( b ) is a plot of the relationship between the active chlorine generating efficiency of the sales water and the water temperature. 
     FIG. 6 is a beverage dispenser as a drinking water feeding apparatus. 
     FIG.  7 ( a ) is a side view of a chlorine generator. 
     FIG.  7 ( b )is a cross-section taken along a portion A-A of FIG.  7 ( a ). 
     FIG. 8 is a control block diagram of the beverage dispenser. 
     FIG. 9 is a beverage dispenser as a drinking water feeding apparatus. 
     FIG.  10 ( a ) is a longitudinal section of an electrode packaged filter. 
     FIG.  10 ( b ) is a cross section of electrode packaged filter. 
     FIG. 11 plots the relative bacterial concentration and the chlorine concentrations for individual servings from beverage dispensers having electrolysis cells with different volumes, and for a beverage dispenser with no electrolysis cell in operation. 
     FIG. 12 is a graph showing the extent of bacterial death in three water samples with different chlorine concentrations. 
     FIG.  13 ( a ) is a side view of a chlorine generator. 
     FIG.  13 ( b ) is an overhead view of the chlorine generator shown in FIG.  13 ( a ). 
     FIG.  13 ( c ) is a cross-section taken along a portion A—A of FIG.  13 ( a ). 
    
    
     DETAILED DESCRIPTION 
     Particular embodiments of a drinking water feeding apparatus of the invention are described in detail below, with reference to the accompanying drawings. 
     FIG. 1 shows a beverage dispenser according to a first embodiment of the invention for vending beverages such as colas or juices. This beverage dispenser includes, beginning at the water inlet labeled “in”: intake pipe  1  connected to service water faucet  1 B attached to service water pipe  1 A; intake valve  1 C provided in intake pipe  1 ; water filter  2  connected to intake pipe  1  for filtering the service water to prepare filtered water (“feed water”); the chlorine generator  4  connected to water filter  2  via two pipelines, namely pipeline  3  and pipeline  5 , as can be seen in FIG. 1; feed water electromagnetic valve  6  connected to chlorine generator  4  via feed pipeline  5 ; feed pump  8  connected to chlorine generator  4  and not directly to feed water electromagnetic valve  6 ; a temperature modification tube, such as cooling coil  10 , connected to feed pump  8  via feed pipeline  9  for modifying the temperature of the sales water; a temperature modified reservoir, such as cooled water cell  10 B, for reserving temperature modified water  10 A which modifies the temperature of the sales water through cooling coil  10 ; flow regulator  12  connected to cooling coil  10  via feed pipeline  11  for controlling the sales water flow rate; electromagnetic valve  14  connected to flow regulator  12  via feed pipeline  13 ; valve  17  connected to electromagnetic valve  14  via feed pipeline  15  for dispensing the sales water into cup  16 ; and drip tray  38  into which cooled water  10 A having over-flown from cooled water cell  10 B, is discharged via overflow water pipeline  10 C. Into valve  17  can be introduced syrup from syrup feed pipeline  49  leading from syrup reservoir  50 , and carbonated water from carbonated water pipeline  51   a,  leading from carbonator  52   a,  which are mixed in valve  17  so that the mixture can be dispensed as a carbonated beverage into cup  16 . Suitable methods for providing acceptable qualities of syrup and carbonated water, including the methods described herein, can be employed. In this embodiment, sales water is used as a diluent for diluting the syrup and carbonated water. 
     Water filter  2  in this embodiment includes an activated charcoal filter having an activated charcoal filled layer as a filter member, and intake pipe  1  is provided with check valve  2 A for preventing the back flow of the filtered water. 
     Feed pipelines  3 ,  5 ,  7 ,  9 ,  11 ,  13  and  15  are formed of material that facilitates the sterilization and provides simple and cost-effective installation and maintenance. Exemplary of such material is polyethylene, although one of skill in the art will readily be able to substitute other suitable materials. Cooling coil  10  is formed of a material having excellent heat transferring properties; such materials can be for example stainless steel, although a number of substitute materials are available. In particular embodiments, feed pipelines  3 ,  5 ,  7 ,  9 ,  11 ,  13  and  15  have an internal diameter of 4 mm, and cooling coil  10  has an internal diameter of 5.5 mm. The invention is in no way limited by specific dimensions of such parts. As indicated above, cooling coil  10  may serve equally well as a heating coil, with attendant modifications to components involved in temperature modification or stabilization, should sales water be desired at temperatures above ambient. 
     Chlorine generator  4  has a structure for reserving the feed water temporarily, and includes degassing pipe  4 A for discharging any gases produced by electrolysis such as hydrogen and oxygen gas. Chlorine generator  4  also includes a gas release valve, for example electromagnetic degassing valve  4 B, disposed in a gas conduit, such as degassing pipe  4 A, so that the steam- or vapor-containing gases produced upon electrolysis are discharged via degassing pipe  4 A into cooled water  10 A whenever degassing valve  4 B is opened. The gas-liquid mixture to be released together with the electrolyzed gas from chlorine generator  4  may be discharged not only into cooled water cell  10 B, such as at a point below the surface of the cooled water, but also into a liquid in a waste liquid bucket or into drip tray  38 . 
     Table 1: according to the description, the chlorine generator has the reference numeral  4 , wherein the electrolysis cell has the reference numeral  40 . As table 1, 2 nd  to 4 th  lines, also refer to the electrolysis cell, reference numeral  4  should be corrected to read reference numeral  40 . 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Volume of Beverage Dispenser Sections (FIG. 1) 
               
             
          
           
               
                   
                   
                 actual section of beverage 
                 Volume of 
               
               
                   
                 Section of dispenser 
                 dispenser 
                 Section (cc) 
               
               
                   
                   
               
             
          
           
               
                   
                 feed pipeline 5 
                 end of valve 6 to start of cell 
                 15 
               
               
                   
                   
                 4 
               
               
                   
                 electrolysis cell 4 
                 entire cell 
                 152 
               
               
                   
                 feed pipeline 7 
                 end of cell 4 to start of pump 
                 15 
               
               
                   
                   
                 8 
               
               
                   
                 feed pipeline 9 
                 end of pump 8 to start of coil 
                 33 
               
               
                   
                   
                 10 
               
               
                   
                 cooling coil 10 
                 entire coil 
                 362 
               
               
                   
                 feed pipeline 11 
                 end to coil 10 to start of 
                 8 
               
               
                   
                   
                 regulator 12 
               
               
                   
                 feed pipeline 13 
                 end of regulator 12 to start of 
                 8 
               
               
                   
                   
                 valve 14 
               
               
                   
                 feed pipeline 15 
                 end of valve 14 to valve 17 
                 4 
               
               
                   
                 total 
                   
                 597 
               
               
                   
                   
               
             
          
         
       
     
     FIG.  2 ( a ) shows chlorine generator  4  which can be used in a particular embodiments of the invention. Chlorine generator  4  includes: an electrolysis cell  40  equipped therein with electrolyzing electrodes  40 A and  40 B which are electrically connected with constant current unit  47  as a power source; cover members  41 A and  41 B for isolating electrolysis cell  40  from the atmosphere by sealing its end portions; bolts  43  fitted through cover members  41 A and  41 B; and nuts  42  screwed on bolts  43  for fixing cover members  41 A and  41 B on the two ends of electrolysis cell  40 ; degassing pipe  4 A for discharging gases produced by electrolysis such as hydrogen and oxygen gas; and electromagnetic degassing valve disposed in the degassing pipe  4 A (shown as  4 B in FIG.  1 ), so that vapor is discharged via degassing pipe  4 A as the degassing valve is opened. This degassing valve is exemplified by a ball-type check valve which is opened when the pressure in electrolysis cell  40  is greater than the weight of the ball. In preferred embodiments of the invention, a degassing valve is operated by a timer is used, as described below. 
     As described before, feed pipelines  5  and  7  have an internal diameter of 4 mm. Thus, a cross-sectional area of feed pipelines  5  and  7  is 12.56 mm 2 . On the other hand, electrolysis cell  40  has an internal diameter of 40 mm in this preferred embodiment. Thus, the cross-sectional area of electrolysis cell  40  is 1256 mm 2 . 
     For instance, when the untreated water is supplied via feed pipeline  5  to electrolysis cell  40  at a flow velocity of 3.78 m/sec, and the purified water is supplied from electrolysis cell  40  to feed pipeline  7  at the same flow velocity, a flow velocity of water to be electrolyzed in electrolysis cell  40  is 0.0378 in/sec in accordance with the below calculation based on a ratio of the cross-sectional areas. 
     
       
         0.0378 m/sec=3.78 m/sec×(12.56 mm 2 /1256 mm 2 ) 
       
     
     The flow velocity of the water is negligible to provide substantially stationary water in electrolysis cell  40 , while the untreated water and the purified water flow through feed pipelines  5  and  7  to ensure a practical dispensing rate of the drinking water without any elongation of electrolysis electrodes and any increase of electrolyzing current. 
     Even with the provision of the described degassing mechanism, about 80% or more of the evolved gas flows downstream from the container of the chlorine generator  4 . In order to reduce the gas outflow, it can be desirable to introduce a separating filter in a gas purge region so that the gas phase and the liquid phase may be separated to more effectively discharge the gas. A flow changing member can be provided in the vicinity of the connecting portion between feed pipeline  7  on the discharge side of chlorine generator  4  and electrolyzing cell  40   b  for example, by forming chlorine generator  4  into a bulging shape. Alternately, by staggering feed pipeline  5  extending into chlorine generator  4  and the feed pipeline  7  extending from the chlorine generator  4 , turbulence can be established in the water flow in the electrolysis cell. Specifically, the structure is desirably constructed so that the gases generated by the electrolysis are not directly introduced into feed pipeline  7  extending from chlorine generator  4  at a lower pressure. Moreover, there may be a baffle or similar element provided in the container for altering the liquid flow as desired to minimize the introduction of gas into the sales water. 
     The chlorine generator thus far described can maintain a predetermined chlorine concentration reliably by releasing the gases produced by electrolysis such as hydrogen and oxygen gas. The chlorine generator acts as an effective sterilizing member when packaged in the drinking water feeding apparatus such as the automatic vendor, beverage dispenser, water cooler, ice maker or home water purifier. 
     In particular embodiments of the invention, electrolysis cell  40  has an external diameter dl of 43 mm, a height h of 130 mm and an internal diameter d 2  of 40 mm, and of 152 cc. The invention is not limited by specific dimensions of such parts. In an alternate embodiment, electrolysis cell  40  and cover member  41 A or  41 B may be integrated with each other. The cover member with joint  41   a  for feed pipeline  5  and joint  41   b  for degassing pipe  4 A. Cover member  41 B is equipped with joint  41   c  for feed pipeline  7 . 
     FIG.  2 ( b ) is a cross-section of a portion A—A of FIG.  2 ( a ). Electrolysis cell  40  is equipped with paired electrodes  40 A and  40 B which are made of suitable electrode material (for example, titanium coated with an alloy of platinum). Electrode  40 A acts as a positive pole and electrode  40 B acts as a negative pole. Electrodes  40 A and  40 B are preferably operated by periodically alternating them as positive and negative poles so that their complete depletion may be postponed. In particular embodiments, electrodes  40 A and  40 B are formed to have width w of 36 mm and to be separated by electrode gap g of 3 mm and are disposed in electrolysis cell  40  that they contact the reserved water of the electrolysis cell  40  at their front and rear faces. That is, they may be immersed in the reserved water. In this case, electrodes  40 A and  40 B have a submerged length of about 120 mm. However, the invention is in no way limited by specific dimensions of such parts. 
     In a preferred embodiment, the feed water is introduced into electrolysis cell  40  at the start of the sales water vending operation and is reserved therein for subsequent electrolysis. The beverage dispenser according to this embodiment of the invention is characterized in that it provides an electrode “ON” time period necessary for establishing an effective chlorine concentration. As a result, the time period for energizing electrodes  40 A and  40 B can be arbitrarily set according to the water qualities of any particular region. Further, the electrodes can be activated to provide an effective chlorine concentration at times other than upon vending. In contrast, a beverage dispenser which electrolyzes the feed water only at the start of the sales water vending operation will only perform electrolysis during the vending operation. This method of operation is inferior because it cannot maintain the chlorine concentration which may be required for some water qualities. 
     The duration of the “ON” time period is determined by the quality of the water location is ascertained by measuring the chlorine concentration (C m ) by performing electrolysis for an arbitrary time period (T m ) at the time of installation of the beverage dispenser. The optimum “ON” time period (T s ) to be set is deduced from the following equation expressing a relationship between the measured chlorine concentration (C m ) and a desired chlorine concentration (C s ): 
     
       
         “ON” Time Period ( T   s )=( T   m )×( C   s )/( C   m )  Eq. 1 
       
     
     If for example, electrodes  40 A and  40 B are energized with a constant current (e.g., 800 mA), and electrolysis is performed for a T m  of 5 seconds, and the chlorine concentration (Cm) obtained for that time period is 0.5 ppm, it follows that an “ON” time period of 7 seconds will be necessary to give a chlorine concentration of 0.7 ppm, and that an “ON” time period of 5 seconds is necessary for a chlorine concentration of 0.5 ppm. This current value 800 mA is arbitrarily selected according to the size of the electrodes, as determined by the design of the chlorine generator, and may take a different value taking into account the consumption of the electrodes. One of skill in the art will readily be able to determine appropriate current and electrolysis time values for the achievement of these goals. 
     When a current of 800 mA is fed for the size of the electrodes  40 A and  40 B as given in FIG. 2, the current density reaches a value of about 1.85 A/cm 2 . If the current density exceeds 2.00 A/cm 2 , however, the electrodes are found to be heavily eroded. 
     FIG. 3 shows a control block of the beverage dispenser according to a first embodiment of the invention. This control block includes: power circuit  18  for applying a DC voltage to electrodes  40 A and  40 B; timer  19  for setting the ON/OFF time of power circuit  18  and metering the time period from the feed water end; feed water signal generator  20  for generating a feed water signal when vending switch unit  20 A is operated to input feed water command P 1 ; malfunction detector  21  for generating an “ON” stop signal in case of a disaster such as earthquake or a malfunction such as a water failure; “ON” time register  22  for metering the “ON” time period to store an accumulation time; and control unit  23  for controlling power circuit  18 , feed water electromagnetic valve  6 , feed pump  8 , degassing valve  4 B, electromagnetic valve  14  and intake valve IC. 
     FIG. 4 is a timing chart illustrating “ON” operations of chlorine generator  4 , and the operations of the drinking water feeding apparatus of the invention will be described with reference to the timing chart. When the feed water signal based on the feed water command P 1  is input at an instant to from feed water signal generator  20  to control unit  23 , intake valve IC, feed water electromagnetic valve  6  and electromagnetic valve  14  are turned on, and feed pump  8  is driven so that the service water is fed to water filter  2  from intake pipe  1  connected to service water faucet  1 B and is filtered by filter  2 . In a particular embodiment of the invention, the feed time period of the service water is 5 seconds, and the quantity of feed is 150 cc. The filtered feed water is fed via feed pipeline  3  by the service water pressure and is reserved in chlorine generator  4 . On the other hand, according to particular embodiments of the invention, power circuit  18  energizes electrodes  40 A and  40 B for 7 seconds when it receives a drive signal S 1  from control unit  23 . 
     When the current of 800 mA is fed to electrodes  40 A and  40 B under the condition of a current density of 1.85 A/dm 2 , for example, sales water containing an active chlorine concentration of 0.7 ppm is generated by energizing the electric current for 7 seconds for the service water of a region having a chlorine ion concentration of 25 ppm and a conductivity of 250 (Ω·cm) −1  or for 4 seconds for the service water of a region having a chlorine ion concentration of 45 ppm and a conductivity of 300 (Ω·cm) −1 . Many regions have water falling within a chlorine ion concentration of 5 to 50 ppm and a conductivity of 50 to 500 (Ω·cm) −1 . Since a predetermined quantity of water is thus reserved in electrolysis cell  40 , the electrolysis can be prolonged, if necessary, even after lapse of the 5 seconds vending time period, so that a constant chlorine concentration can be achieved by performing the electrolysis determined by the water qualities of a wide variety of regions without enlarging the electrodes. 
     By energizing electrodes  40 A and  40 B in chlorine generator  4 , chloride ions Cl −  are released from positive electrode  40 A immersed in the service water, so that active chlorine Cl 2  is generated and dissolved in the service water to generate sales water containing active chlorine at a concentration of 0.7 ppm. Since the solubility of chlorine in 100 g of water (10° C.) is 0.9972 g, active chlorine can be largely dissolved in the sales water so that the sales water has a sterilizing activity. 
     Besides active chlorine, oxygen gas is also generated at positive electrode  40 A, and hydrogen gas is generated at negative electrode  40 B. Most of these gases produced by electrolysis are reserved in chlorine generator  4  which also contains a minute quantity of steam. After several electrolyses the quantity of residual gas increases. The resulting gas pressure depresses the liquid surface in electrolysis cell  40 . Then, the contact area between electrodes  40 A and  40 B and the reserved water decreases. The current density subsequently rises to over 2.00 A/cm2, and the burden on the electrodes is increased. 
     To counteract this effect, the beverage dispenser according to this embodiment is able to record and store a total accumulation of the “ON” time periods of electrodes  40 A and  40 B in “ON” time register  22 . Also, a gas release control aspect of control unit  23  controls degassing valve  4 B, causing it to open when the time accumulation of“ON” time periods reaches a predetermined value. When the accumulated “ON” time period reaches a predetermined value, for example 150 seconds, control unit  23  outputs degassing signal P n . By opening degassing valve  4 B on the basis of the input of the degassing signal, control unit  23  discharges the gas produced by electrolysis into cooled water cell  10 B via degassing pipe  4 A. The accumulated time period of “ON” time register  22  is desirably set that the gases produced by electrolysis are released when the water level in electrolysis cell  40  is lowered by increased gas pressure by about 5 mm as the electrolysis proceeds. If the water level drop in electrolysis cell  40  is about 5 mm, the current density of the particular electrode arrangement described herein is about 1.93 A/dm 2  at the highest and will not exceed the upper limit of 2.00 A/dm 2  so that electrodes  40 A and  40 B are not excessively consumed. One of skill in the art will be able to adjust the predetermined maximum time between degassing signals on the basis of a particular electrode configuration, and chlorine generator configuration. After venting, control unit  23  shuts degassing valve  4 B, and clears the accumulated time period from “ON” time register  22 . 
     Degassing valve  4 B may be additionally opened by control unit  23  for 5 to 10 seconds once a day, independently of the accumulated “ON” time period. A timer associated with control unit  23  can record the accumulated time since the valve was last opened and send a signal to the degassing valve when this accumulated time reaches a predetermined maximum value. Even if aerobacteria migrate into the electrolysis cell, they are subjected to a sterilizing or fungistatic treatment with the active chlorine in the closed container. 
     The chlorine-containing sales water is fed via feed pipeline  7 , feed pump  8  and feed pipeline  9  to cooling coil  10  so that it is cooled while passing through cooling coil  10 . The sales water thus cooled through cooling coil  10  is dispensed from valve  17  into cup  6  via feed pipeline  11 , flow regulator  12 , feed pipeline  13 , electromagnetic valve  14  and feed pipeline  15 . As mentioned above, sales water can also be provided at temperatures above ambient, by adapting the cooling coil, cooled water cell and other relevant parts of the dispensing apparatus, to handle warmed sales water. 
     Timer  19  starts its timing action from feed water shut off time t 1 ′ of the sales water. Referring again to FIG. 4, in response to a new feed water command P 2  at timing instant t 2 , timer  19  stops its timing action to reset the timing data. In response to this feed water command, control unit  23  outputs drive signal S 2  to power circuit  18  so that electrodes  40 A and  40 B are energized for 7 seconds to electrolyze the feed water. On the other hand, timer  19  outputs a time-up signal to control unit  23  at an instant t n  if no feed water signal has been produced for a predetermined maximum dormancy time period (e.g., 4 hours), counted from feed water ending instant t 2 ′. In response to the time-up signal from the timer  19 , the control unit  23  outputs drive signal S n  to power circuit  18  so that electrodes  40 A and  40 B are energized for 7 seconds to electrolyze the feed water. 
     The beverage dispenser provides for the opening of electromagnetic degassing valve  4 B on the basis of the accumulated value stored in “ON” time register  22 . However, electromagnetic degassing valve  4 B may be replaced by a ball type check valve which is opened when the pressure in electrolysis cell  40  exceeds the weight of the ball. Thus, the gas-liquid mixture, discharged together with the gases produced by electrolysis from chlorine generator  4 , can be properly treated while preventing a rise in internal pressure of chlorine generator  4 . As a result, the water in chlorine generator  4  can be kept at a constant level even without any water level sensor. Therefore, the deterioration of the electrolyzing efficiency, which might otherwise be caused by the gases produced by electrolysis is inhibited. 
     Since beverage dispenser is sealed from the atmosphere in all its feed pipelines including chlorine generator  4 , there is a danger that it may expand and explode if the gases produced by electrolysis are not timely released from degassing valve  4 B. For safety reasons, therefore, the feed pipe line system is preferably equipped with a safety valve or the like which has a diaphragm or a breakable member for releasing gases when the residual gases produced by electrolysis reach some maximum allowable pressure. It is considered desirable that the gas release valve be activated to the extent needed to maintain a slightly positive gas pressure within the air-shielded container, so that foreign agents, including microorganisms, are not introduced upon opening the container. The beverage dispenser thus far described is equipped with a degassing mechanism in the electrolysis cell  40  of the chlorine generator. The degassing mechanism is not limited to this description, but can be equipped with a degassing electromagnetic valve or ball type check valve in the feed pipeline downstream of the chlorine generator. 
     In order to effectively retain active chlorine generated by the chlorine generator, the valve for vending the sales water and the connecting pipeline to the chlorine generator are preferably adapted to contain at least one sales water feed. In such an arrangement, the sales water, containing active chlorine generated by electrolysis, resides in the connecting pipeline. When the interval between vending operations is lengthy, thereby lengthening intervals between electrolyses, contamination sets in only upstream, near the water source so that the sales water having a relatively high chlorine concentration, and remaining uncontaminated, can be fed in a subsequent vending operation. Considering that active chlorine contained in the sales water is more readily solubilized and stabilized at lower water temperature, a cooling coil is preferably disposed in that connecting pipeline for cooling the sales water. 
     According to the beverage dispenser thus far described, feed water is fed to the chlorine generator  4  in a quantity according to the quantity (about 150 cc) of the vended sales water. This quantity of feed water is reserved in chlorine generator  4  each time the sales water is fed to the cup on the basis of the feed water command. As a result, feed water in a regular quantity of one cup is electrolyzed in the chlorine generator  4 . In a preferred embodiment, electrodes  40 A and  40 B of chlorine generator  4  are energized simultaneously with the start of sales water vending. Specifically, electrodes  40 A and  40 B can be energized in response to the water feed command, and feed pump  8  may be driven one second later to vend the sales water. 
     Some beverage dispensers are provided with buttons for selecting individual cup sizes such as small (150 cc), medium (200 cc) and large (300 cc) so that the quantity of beverage to be vended can be selected by operating any of the select buttons. In preferred embodiments of a beverage dispenser according to the invention, cup size selection buttons are mounted in vending switch unit  20 A so that control unit  23  controls the sales of the beverage according to the selected cup size and changes the “ON” time period according to the sales when it receives the feed water command P 1  indicating the cup size from vending switch unit  20 A. When the aforementioned “ON” time period of 7 seconds is that for the vending time of the S size, for example, control unit  23  calculates the “ON” time periods of the vending time of the other sizes to control the energization of electrodes on the basis of the “ON” time period of the small size if the sales of medium or large size is selected. In preferred embodiments, the volume of water contained within the chlorine generator is approximately the same as the largest of volumes anticipated as being dispensed in a beverage dispenser. 
     On the other hand, some beverage dispensers are provided with a consecutive vending button for executing continuous sales of the sales beverage while that button is continuously operated. In this case, control unit  23  controls the continuous or interrupted energization of the electrodes with a current of 800 mA while the continuous vending button is depressed. In the continuous sales made of operation, the “ON” time period is not fixed but selected for maintaining a predetermined chlorine concentration by operating the electrodes continuously or interruptedly during the consecutive operation of the vending button on the basis of the fact that the “ON” time period for vending the small size is 7 seconds. 
     Chlorine generator  4  container is preferably made of a material which would minimize any changes in chlorine concentration of the sales water residing in the feed pipelines. Suitable construction materials are either a polyethylene tube or a resin of a fluorine containing resin, i.e., a resin material having fewer hydroxyl or hydrogen groups which are made less reactive with active chlorine, or a resin material not containing either group. As a result, the self-decomposition of active chlorine in the sales water can be suppressed, inhibiting the reduction in chlorine concentration, and improving the taste and flavor of the water, and products made with it. Further, the propagation of various bacteria can be minimized, keeping the feed pipelines sanitary for extended periods. 
     It is observed that the loss of active chlorine in aqueous solutions is slowed by the cooling action of the cooling coil. Moreover, it is preferable to adjust the “ON” time period by detecting the temperature of the feed water by means of a sensor or the like. 
     FIG.  5 ( a ) plots the concentration of active chlorine in sales water versus time at water temperatures of 25° C. and 1° C. At 25° C., the concentration of active chlorine is drastically reduced with time, whereas at 1° C., the loss of active chlorine is less. 
     FIG.  5 ( b ) plots the relationship between the active chlorine generating efficiency and the water temperature of feed water in chlorine generator  4 . The active chlorine generating efficiency becomes higher for lower water temperature so that the deactivation of the active chlorine is less for lower water temperature. This means that the “ON” time period can be shortened if the water temperature is sufficiently low. 
     FIG. 6 shows a beverage dispenser serving as a drinking water feeding apparatus according to a second embodiment of the invention. This beverage dispenser includes: cooled water cell  45  for reserving cooled water  45 A; chlorine generator  4  immersed in cooled water  45 A; service water temperature detecting sensor  46  for detecting the water temperature of the service water or the feed water fed to chlorine generator  4 ; and cooled water temperature detecting sensor  45 B for detecting the water temperature of cooled water  45 A. Cooled water  45 A is cooled to a predetermined temperature by a cooler. If warmed water is instead desired, The remaining construction is identical to that of the beverage dispenser of the first embodiment shown in FIG.  1 . 
     FIG.  7 ( a ) shows chlorine generator  4  according to a second embodiment of the invention. Electrodes  40 A and  40 B are electrically connected to constant current source  47  as a power source in which electrode  40 A has a positive polarity and electrode  40 B has a negative polarity, although regular polarity reversal is anticipated for best usage of the electrode material. The electrolysis cell is equipped with service water temperature detecting sensor  46  for outputting a detection signal according to the water temperature of the service water to the service water temperature detecting unit. On the other hand, cooled water temperature detecting sensor  45 B shown schematically in FIG. 8 outputs a detection signal according to the water temperature of the cooled water to the cooled water temperature detecting unit. The remaining construction is identical to that shown in FIG.  2 ( a ). 
     FIG.  7 ( b ) is a cross-section taken across A—A of FIG.  7 ( a ). Electrolysis cell  40  is equipped therein with paired electrodes  40 A and  40 B which are made of an alloy of titanium coated with platinum. These electrodes  40 A and  40 B are formed to have width w of 36 mm and spacing g of 3 mm and to contact the reserved water of electrolysis cell  40  on their front and back faces. That is, the electrodes  40 A and  40 B are immersed in the reserved water of electrolysis cell  40 . Electrodes  40 A and  40 B are best operated by changing their positive and negative polarities at a predetermined “ON” time interval. Further, service water temperature detecting sensor  46  is arranged so as not to physically interfere with electrodes  40 A and  40 B. 
     FIG. 8 shows a control block of the beverage dispenser according to the second embodiment of the invention. This control block includes service water temperature detecting unit  24  for detecting the water temperature of the service water on the basis of the detection signal output from service water temperature detecting sensor  46 . The control block also includes cooled water temperature detecting unit  25  for detecting the water temperature of the cooled water in the cooled water cell (or tank) on the basis of the detection signal outputted from cooled water temperature detecting sensor  45 B. Control unit  23  includes a temperature difference-based control for providing an electrolysis signal based upon the difference between temperatures of the service water and cooled water in the cooled water tank, as reported by temperature detecting units  24  and  25 . The result of such control is that water in the electrolysis cell will be electrolysed for a time which is dependent on this temperature difference, and in some preferred embodiments, is inversely dependent. The constructions and functions of the remaining components of the power circuit  18 , timer  19 , feed water signal generator  20 , malfunction detector  21 , “ON” time register  22  and control unit  23  are identical to those of the first embodiment shown in the control block diagram of FIG.  3 . 
     Control unit  23  controls the electrolysis on the basis of the temperature difference between the temperature of the service water, as input from service water temperature detecting unit  24 , and the temperature of the cooled water, as input from cooled water temperature detecting unit  25 . The following specific description is based on the aforementioned small cup size (150 cc). The control is made such that the “ON” time period can be shorter than 7 seconds as the temperature difference increases, and can be longer than 7 seconds as the temperature difference decreases. This makes it possible to retain a constant chlorine concentration. 
     When chlorine generator  4  is cooled or when the sales beverage is cooled by the cooling coil or the like, chlorine-generating efficiency is improved so that deactivation of chlorine is suppressed by keeping the chlorine-containing sales water at a low temperature. Fluctuations in chlorine concentration are suppressed by controlling the electrolysis in chlorine generator  4  on the basis of the temperature difference between the service water and the cooled water. As a result, the sterilizing force of the sales water is maintained for an extended period. 
     On the other hand, the construction for feeding the syrups, to be mixed with the sales water from a Bag In Box (BIB) may be modified so that chlorine generator  4  is provided in the portion accommodating the BIB so that the chlorine generator is cooled together with the BIB. 
     FIG. 9 shows a beverage dispenser as the drinking water feeding apparatus according to a third embodiment of the invention. This beverage dispenser includes: pressure pump  26  for pressurizing and feeding the service water as the feed water to be fed from the civil water service pipe  1 A; water cell  28  reserving cooled water  27 ; and cooling unit  29  for cooling cooled water  27  in water cell  28 . 
     Cooling unit  29  includes: compressor  29 B for compressing a coolant; condenser  29 C for condensing the coolant; a condenser fan motor for providing a cooling air flow to condenser  29 C; and evaporation pipe  29 A made of copper for evaporating the coolant, which is condensed by condenser  29 C, to cool the surroundings at the time of evaporation. The coolant can be any of a number of useful refrigeration coolants known and used by those of skill in the art. As mentioned herein, cooling unit  29  could be replaced by any number of heating units, should sales water be desirably provided at temperatures above ambient. 
     Water cell  28  includes: a carbonator (not-shown) for generating carbonated water by mixing the sales water and carbon dioxide; agitation motor  30  for agitating cooled water  27  by agitation propeller  30 A; circulation pump  31  attached to agitation motor  30 ; coil unit  32  having a carbonated water coil for passing the carbonated water, and a sales water coil for passing the sales water; evaporation pipe  29 A constructing cooling unit  29 ; IBC (Ice Bank Control) sensor  33  for outputting an ice detection signal on the basis of the change in the resistance by any ice produced between a pair of conductors on evaporation pipe  29 A, and cell temperature sensor  34  for detecting the temperature of cooled water  27  in water cell  28 . Circulation pump  31  and the entrance of cooled water pipeline  35 A of cooler  35  are connected through cooled water pipe  36 A, and cooled water pipe  36 B returning to water cell  28  is connected to the exit of cooled water pipeline  35 A of cooler  35 . Bag-in-Box  37 A in cold reserving cell  37  is kept cold by pumping cooled water  27  of water cell  28  via cold water pipe  36 A to cold reserving cell  37  by the action of circulation pump  31 , circulating it in cooled water pipeline  35 A of cooler  35 . Chlorine generator  4  is accommodated together with substantially the entire length of the feed pipelines from intake pipe  1  to feed pipeline  15 , as connected to valve  17 , in cold reserving cell  37 . 
     In the beverage dispenser thus far described, substantially the entire length of the feed pipelines from intake pipe  1  to feed pipeline  15 , as connected to valve  17 , is cooled by cold reserving cell  5 . As a result, the electrolyzing efficiency of the feed water by chlorine generator  4  is improved, while the deactivation of the active chlorine contained in the sales water is suppressed throughout the entire length of the feed pipelines in cold reserving cell  5 . This makes it possible to keep the chlorine concentration in the feed pipelines at 0.2 ppm or higher, even when the sales water fed downstream of chlorine generator  4  resides for a long time in the feed pipelines to valve  17 . It is also possible to sterilize the sales water while inhibiting the contamination of the inner walls of the feed pipelines with the bacteria or the propagation of the bacteria absorbed. Moreover, the active chlorine can be efficiently generated by prolonging the operational cycle of chlorine generator  4  when no feed water command is input for a long time. 
     In place of the aforementioned cold reserving cell, on the other hand, the construction may be made such that substantially the entire length of the feed pipelines is immersed in cooled water  27  to be reserved in water cell  28  and such that cooled water  27  is cooled by cooler  25 . With this modification, it is possible to omit cooled water cell  10 B for immersing cooling coil  10  therein. 
     To provide beverages according to consumer tastes, it is also possible to provide a source of flavoring, connected by piping to a mixer adapted to mix sales water from the water purifier apparatus, so that flavoring can be mixed with purified water in any desired ratio. A nozzle suitable for dispensing beverage into a cup or other container to be received by the consumer can also be present. As described above, carbon dioxide can also be provided for beverages desirably carbonated, preferably immediately before or upon dispensing. 
     The foregoing embodiment has been described with a beverage dispenser as the drinking water feeding apparatus. The chlorine generator can be employed not only in the beverage dispenser but also in a water cooler, ice maker, automatic vendor or home water purifier having a water circuit for feeding the drinking water. The water source should not be limited to the service water but may be exemplified by drinking water which is reserved in a cassette tank and contains chlorine ions. 
     At the rear stage of chlorine generator  4 , however, 0.7 ppm of active chlorine is retained. Depending upon the kind of bacteria, it is important to maintain an effective contact period between the active chlorine and bacteria. A sterilizing effect can be expected even against bacteria having high chlorine resistance by reserving a predetermined quantity of chlorine in the electrolysis cell  40  and by retaining it at the rear stage. In the sales water, as reserved in electrolysis cell  40  for a sales standby time, the active chlorine becomes deactive with time at a water temperature of 25° C. (see FIG. 5 a ), so that the active chlorine having the sterilizing action disappears. In order to suppress the propagation of bacteria in the feed pipelines, therefore, 0.7 ppm of active chlorine can be generated by energizing electrodes  40 A and  40 B for one hour each. 
     The beverage dispenser thus far described is characterized in that the chlorine generator for reserving the feed water to be electrolyzed is disposed downstream of the filter, and in that the electrolysis electrodes are immersed in the feed water or the reserved water. These characteristics provide a high sterilizing effect and do not enlarge the size of the electrode thereby allowing a reduction in the size of the apparatus. This size reduction is further promoted by mounting the electrolyzing electrodes in the filter allowing reduction of the connecting pipelines. 
     FIG.  10 ( a )is a longitudinal section of electrode packaged filter  38 . This filter includes: primary reservoir portion  38 A formed in the lower portion of a cylindrical body ;for accommodating filter member  38 B; secondary reservoir portion  38 C formed over filter member  38 B; tertiary reservoir portion  38 E partitioned from secondary reservoir portion  38 C through a partition portion  38 D; passage  38 F formed in partition portion  38 D and having an internal diameter corresponding to that of the feed water pipeline; and electrodes  38 G and  38 G (later-described) arranged at a predetermined spacing on the side walls of tertiary reservoir portion  38 E and adapted to be immersed in the filtered water or the feed water. By energizing electrodes  38 G and  38 G′ disposed downstream of filter member  38 B, chlorine in the feed water, deactivated by the filter, is activated to a predetermined chlorine concentration. 
     For the purposes of describing the following embodiment, the filtered water having passed through the filter member  38 B will be deemed as the feed water, and the filtered water at and downstream of tertiary reservoir portion  38 E will be deemed as the sales water. 
     In a particular embodiment, electrodes  38 G and  38 G′ are formed to have a width w of 36 mm, a length l of 120 mm and a spacing of 3 mm (not-shown) and are positioned to be always immersed in the feed water reserved in tertiary reservoir portion  38 E. To this tertiary reservoir portion  38 E, there is connected degassing pipe  4 A for discharging gases generated by feed water electrolysis. The invention is not, however, limited in any way to these dimensions, and one of skill in the art can readily design suitable electrodes which are of different dimensions. 
     Secondary reservoir portion  38 C shown in FIG.  10 ( a ) is a water collecting pipe, which contacts directly with filter member  38 B so that the chlorine activated in the electrolysis cell may possibly contact filter member  38 B and may be deactivated again. Therefore, passage  38 F is formed to restrict the flow rate of the generated active chlorine to penetrate from the tertiary reservoir portion  38 E into secondary reservoir portion  38 C thereby to inhibit active chlorine from contacting the filter member and becoming inactive and has a flow resistance similar to that of the ordinary filter. On the other hand, this system aims at preventing the re-activated chlorine from flowing backward and from being deactivated by the reaction with filter member  38 B, and can be replaced by a check valve. In an ordinary place having a low vacuum, although not shown, the chlorine generated by electrolysis cell  38 E is disposed in secondary reservoir portion  38 C, more specifically, the electrode-packaged filter can be constructed by setting chlorine generator  38 G while considering the chlorine to be absorbed by filter member  38 B. 
     In FIG.  10 ( a ), input and output feed pipelines have internal diameters sufficiently smaller than an internal diameter of tertiary reservoir portion  38 E, so that substantially stationary water is electrolyzed therein, while untreated water is supplied via input feed pipeline to filter member  38 B, and purified water is supplied from tertiary reservoir portion  38 E to output feed pipeline. 
     FIG.  10 ( b ) is a cross-section of electrode packaged filter  38 , taken along a portion A—A of FIG.  10 ( a ). Paired electrodes  38 G and  38 G′ are inserted into tertiary reservoir portion  38 E through the side wall of the cylindrical body. 
     A beverage dispenser serving as a drinking water feeding apparatus for diluted water or carbonated water can be equipped with the aforementioned electrode-packaged filter in feed pipelines. The packaging filter member  38 B can have activated carbon for filtering the service water into feed water and a pair of electrodes for electrolyzing the filtered feed water. According to such a beverage dispenser, electrodes  38 G are disposed downstream of filter member  38 B to electrolyze the sales water just filtered, so that the feed pipeline portion between the filter and the chlorine generator, where the bacteria propagate, can be omitted to prevent inhibit propagation of the bacteria. By omitting the feed pipeline, it is possible to minimize the portion where the bacteria to be sterilized will propagate, realizing a small size. 
     Even if the number of live bacteria is increased by the various bacteria adsorbed by the filter member  38 B of electrode-packaged filter  38 , on the other hand, paired electrodes  38 G arranged in the tertiary reservoir portion are energized to electrolyze the reserved feed water thereby generating active chlorine, so that the sales water to be fed to feed pipeline  5  can be fed with number of live bacteria, i.e., reduced by the sterilizing force of the active chlorine to the level of the number of live bacteria in the service water fed from intake pipe  1 . 
     In some preferred embodiments of the invention, the filter member and the reservoir for electrolysis are disposed in one container such that the filter member is arranged on the feed side whereas the reservoir is arranged on the discharge side. As a result, at least two joint portions can be reduced to one part, and the construction of the feed pipelines is simplified. Further, since the electrodes are always wholly immersed in the feed water, the electrolysis efficiency can be kept constant to reduce the electrode consumption. Moreover, since the feed water corresponding to one sale of the sales water to be vended (e.g. to the cup) is reserved for the electrolysis, the reservoir portion can be shaped to the accommodation space without being elongated. 
     The invention has been described for the case in which an electrode-packaged filter according to the invention is used in a beverage dispenser, but the electrode-packaged filter can also be disposed in a water cooler, an ice maker or an automatic vendor or a home water purifier having a water circuit for feeding the drinking water therein. 
     In some preferred embodiments of the invention, the reserved drinking water is electrolyzed so that the drinking water contaminated in the filter can be reliably sterilized and fed downstream. As compared with the method of electrolyzing drinking water as it flows, the drinking water containing the active chlorine sufficient for the sterilization can be fed without lengthening the electrodes or reducing the flow speed of the drinking water. 
     In some preferred embodiments of the invention, the filter member is disposed on the feed side of the air-shielded container, and the paired electrode for the electrolysis is disposed on the discharge side of the container, so that active chlorine sufficient for, sterilization can be fed downstream. Unlike the arrangement in which the filter member and the electrolysis cell are separately arranged in different containers, moreover, drinking water containing no active chlorine will not reside in the pipeline between the container of the filter member and the electrolysis cell and the sterilizing ability will be improved. 
     In some preferred embodiments of the invention, electrolysis is performed in an air-shielded electrolysis cell so that no aerobacteria migrate. Since the water reserved in the electrolysis cell is electrolysis, on the other hand, the chlorine concentration of the drinking water can be easily maintained at a constant value which is independent of the water quality. 
     Since the cooling coil is arranged downstream of the air-shielded electrolysis cell, according to the second drinking water feeding apparatus of the invention, it is possible to prevent the reduction of the chlorine concentration of the drinking water emanating from the electrolysis cell. The effect is further improved if the electrolysis cell is also cooled. 
     Since at least one feed of the drinking water electrolyzed in the chlorine generator is reserved downstream of the chlorine generator, according to the third drinking water feeding apparatus of the invention, it is possible to feed the drinking water which is not contaminated by bacteria even for a long interval between feed. 
     In some preferred embodiments of the invention, the chlorine generator is equipped with a release unit for releasing gases generated by electrolyzing the drinking water such as hydrogen and oxygen gas, so that a drop of the electrolyzed water level can be prevented and a corresponding increase in the electrode current density can be prevented, thereby reducing necessary consumption of the electrodes. The release unit includes a gas release valve and associated control of the valve. Further, electrolyzed drinking water is fed by energizing the electrodes at the time of feeding the drinking water on the basis of the feed water pressure from the water source, so that drinking water having a predetermined chlorine concentration can be stably fed. 
     In some preferred embodiments of the invention, reserved drinking water in the electrolysis cell down stream of the filter is electrolyzed so that the contaminated drinking water in the filter can be reliably sterilized and fed downstream. As compared with the method of electrolyzing the flowing drinking water, the drinking water containing chlorine sufficient for the sterilization can be fed without lengthening the electrodes or reducing the flow speed of the drinking water. 
     In some preferred embodiments of the invention, a filter member is disposed on the feed side of the air-shielded container, and the paired electrode for the electrolysis is disposed on the discharge side of the container, so that chlorine sufficient for the sterilization can be fed downstream. Unlike the arrangement in which the filter member and the electrolysis cell are separately arranged in different containers, the drinking water containing no active chlorine will not reside in the pipeline between the container of the filter member and the electrolysis cell so that the sterilizing ability is improved. 
     In some preferred embodiments of the invention, there is provided an apparatus in which the sales water can be reserved in the electrolysis cell. During the sales standby time, when the bacteria propagate to the greatest extent in the pipelines, sales water is reserved in the electrolysis cell so that the number of live bacteria can be minimized. Even for bacteria having an especially high resistance, the number of live bacteria decreases to an order of about 10 2  cfu/ml, (see FIG.  12 ), when the elapsed contact time is 30 minutes or more, so that the bacteria in the pipelines can be suppressed in number. Moreover, at the next feed, sales water having less bacterial contamination will be delivered. 
     FIG.  13 ( a ) to ( c ) show an electrode-packaged filter in a further preferred embodiment. The electrode-packaged filter comprises housing  53 , filter member  56  such as carbon contained in housing  53  to be formed with a recessed portion serving as electrolysis cell  55 , and a pair of electrodes  54 A and  54 B extended inside electrolysis cell  55  and supported to be connected to a power source (not shown) by a top wall of housing  53 , wherein feed pipelines (not shown) are connected to input  51  and output  52  provided on the top wall of housing  53 . Filter member  53  has a height H (for example, 125 mm) and an outer diameter D 1  (for example, 83 mm), electrolysis cell  55  has an internal diameter D 2  (for example, 30 mm) and a height h (for example, 110 mm), and electrodes  54 A and  54 B having a length L (for example, 100 mm) are arranged to have a gap g (for example, 3 mm) therebetween. On the other hand, input  51  and output  52  have internal diameters d 1  (for example, 7 mm) and d 2  (for example, 7 mm) which are sufficiently smaller than the internal diameter D 2  of electrolysis cell  55 , so that substantially stationary water is contained in electrolysis cell  55 , while untreated water is supplied via input  51  to filter member  56 , and purified water is supplied from electrolysis cell  55  via output  52  to a dispensing end (not shown). In this preferred embodiment, active chlorine generated by energizing electrodes  54 A and  54 B is penetrated into filter member  56 , so that bacterial concentration is kept to be approximately the level C 2  inside filter member  56 , and will never be above the level C 3 . 
     The invention will be further illustrated in the following examples, which do not limit the scope of the invention as defined by the claims. 
     EXAMPLES 
     Example 1 
     Performance of a Beverage Dispenser 
     Table 2 shows changes in the residual chlorine concentrations of individual portions of sales water dispensed from the beverage dispenser shown in FIG.  1 . 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Residual Chlorine Concentrations 
               
             
          
           
               
                   
                 H 0   
                 H 1   
                 H 2   
                 H 3   
                 H 4   
               
               
                   
                   
               
             
          
           
               
                   
                 initial value 
                 0.42 
                 0.42 
                 0.40 
                 0.42 
                 0.44 
               
               
                   
                 1 st  cup 
                 0.42 
                 0.24 
                 0.29 
                 0.25 
                 0.07 
               
               
                   
                 2 nd  cup 
                 0.43 
                 0.31 
                 0.32 
                 0.30 
                 0.21 
               
               
                   
                 3 rd  cup 
                 0.42 
                 0.27 
                 0.28 
                 0.27 
                 0.12 
               
               
                   
                 4 th  cup 
                 0.43 
                 0.25 
                 0.17 
                 0.24 
                 0.06 
               
               
                   
                 5 th  cup 
                 0.38 
                 0.05 
                 0.02 
                 0.07 
                 0.02 
               
               
                   
                 6 th  cup 
                 0.31 
                 0.02 
                 0.02 
                 0.03 
                 0.02 
               
               
                   
                   
               
             
          
         
       
     
     Twenty cups of sales water were vended for: a single cup feed volume of 150 cc, an electrode “ON” time period of 7 seconds at the feed water time, a current value of 800 mA, at a feed water interval of 4 cups/minute, a vending flow rate of 30 cc/second, an electrode current density of 2 A/dm 2  or smaller. With the initial value of the residual chlorine concentration of the sales water as sampled at the 20 th  cup, electrodes  40 A and  40 B of chlorine generator  4  were left deenergized from the preceding feed water action. After this, the residual chlorine concentrations of the next 6 cups of sales water, as sampled without energizing the electrodes, were metered at the respective times of H 0  (just after the sampling), H 1 , H 2 , H 3  and H 4  hours later. The time H 4  is set being assumed the end of consecutive holidays (e.g., 67 hours). The residual chlorine concentrations were metered by calorimetry according to the DPD method. For the initial value or the sales water after the 20th cup had been vended, the residual chlorine concentration of about 0.4 ppm was metered just after sampling, and the aging was low even after time H 4 . 
     As to the 6 cups of drinking water sampled after the preceding vending operation: the 1 st  cup is the sales water which has resided in the piping from valve  17  to the exit portion of cooling coil  10 ; the 2 nd  and 3 rd  cups are the sales water which has resided in cooling coil  10 ; the 4 th  cup is the sales water which has resided in the piping from the entrance portion of cooling coil  10  to feed pump  8 ; the 5 th  cup is the sales water which has resided in the piping from feed pump  8  to chlorine generator  4  (including some residual water in the container); and the 6 th  cup is the sales water which has resided in chlorine generator  4 . According to this beverage dispenser, therefore, the electrolyzed sales water is retained in the connecting pipelines from the rear stage of the chlorine generator to the feed valve so that the sales water, uncontaminated by bacteria, can be fed in the next vending operation even for a long interval between feeds. 
     The 2 nd  and 3 rd  cups of sales water have a low rate of residual chlorine concentration loss due to cooling. These cups keep an active chlorine concentration having a predetermined value (ca. 0.2 ppm) at the exit of valve  17 , even 67 hours later. Thus, the residual water in the cooling coil retains its chlorine concentration even after 67 hours. 
     Table 3 tabulates the chlorine concentrations of the individual portions, as based on the chlorine generation by the electrolytic action of chlorine generator  4  at instant t n . 
     
       
         
               
             
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Chlorine Concentrations of Individual Portions 
               
             
          
           
               
                   
                 Chlorine concentration (ppm) 
               
               
                   
                   
               
             
          
           
               
                   
                 1 st  cup 
                 0.24 
               
               
                   
                 2 nd  cup 
                 0.31 
               
               
                   
                 3 rd  cup 
                 0.27 
               
               
                   
                 4 th  cup 
                 0.26 
               
               
                   
                 5 th  cup 
                 0.27 
               
               
                   
                 6 th  cup 
                 0.32 
               
               
                   
                   
               
             
          
         
       
     
     According to these data, even when chlorine generator  4  is operated while the sales water resides, two cups of sales water are left in the piping between chlorine generator  4  and cooling coil  10 , so that the chlorine concentration of the sales water of cooling coil  10  is hardly influenced. 
     Example 2 
     Bacterial Concentrations in a Beverage Dispenser 
     Generally, some bacteria have a high resistance, and others do not. The highly resistive bacteria are capable of surviving in the presence of chlorine in the service water, enterococcua, or the like. On the other hand, the bacteria having a low resistance are colibacillus groups, as called the “pollution index bacteria”. In the bacteria highly resistive to the active chlorine, the extra-bacterial protein acts as a barrier against active chlorine, which has to break the extra-bacterial protein before it penetrates into the bacteria, so that active chlorine takes a considerable time to penetrate. 
     FIG. 11 plots the bacterial concentration and the chlorine concentrations for the sales (expressed as cup number) when the beverage dispenser makes consecutive sales under conditions where bacteria of a high chlorine resistance propagate in the filter. A range, indicated by the letter a in FIG. 11, indicates the bacterial concentration and the chlorine concentrations, as contained in the sales beverage initially dispensed when the beverage is consecutively vended. The initial cups of sales beverage contain residue in the pipeline including the filter and the downstream chlorine generator. The range after range a indicates the bacterial concentration and the chlorine concentrations of the sales beverage, as contained in the sales beverage dispensed subsequently to the initial cups when the beverage is consecutively vended. The sales beverage for these cups has been reserved in the cartridge of the filter. In the beverage for later cups, the water in the cartridge is vended, and the bacteria on the filtering material are carried away by the feed water so that the bacterial concentration is gradually reduced at every sale. 
     Conditions labeled as f in FIG. 11 show the bacterial concentration at sales when the chlorine generator is not used. It is found that the beverage dispenser with no electrolysis has large bacterial concentrations at individual sales and that the sales beverage contained in the filter obviously has the highest bacterial concentration. 
     Conditions c of FIG. 11 report the chlorine concentrations in sales when consecutive sales were made by the beverage dispenser using a chlorine generator equipped with the electrolysis cell having a capacity of 150 cc. In initial sales, the residual product was present in the pipelines including the filter and the downstream chlorine generator so that the chlorine concentration was lowered by the aging change in the pipelines. At and after the initial sales, on the other hand, 340 ml of water in the cartridge of the filter was introduced into the electrolyzing cell for electrolysis. Here, the quantity of chlorine exhibits a transient state after the initial sales and before the sales of subsequent cups. This is because the active chlorine is deactivated by the reaction with highly resistant bacteria. 
     Conditions e of FIG. 11 report the bacterial concentration for sales when consecutive sales were made by the beverage dispenser using a chlorine generator equipped with an electrolysis cell having a capacity of 150 cc. In this case, the capacity of 150 cc of the electrolysis cell means that 150 cc of sales water containing a predetermined chlorine concentration is reserved in the electrolysis cell so that it is mixed with the feed water in the electrolysis cell. As a result, the feed water, flowing at a rate of 30 cc per second into the electrolysis cell, flows out as sales water at a rate of 30 cc per second while being mixed with 150 cc of water which has been reserved in the electrolysis cell and has a predetermined chlorine concentration. As a result, the feed water can maintain an effective period of contact time with the active chlorine against the bacteria. 
     Under conditions e of FIG. 11, therefore, the sales beverage contains a high chlorine concentration in the pipelines downstream of the chlorine generator for the initial cups so that a sufficient period of contact time between the active chlorine and the bacteria is maintained to keep a low bacterial concentration. For the cups after initial sales, however, 340 ml of sales water in the cartridge of the filter is fed to the electrolysis cell. As a result, the chlorine concentration cannot be maintained at the value of 0.2 ppm which is necessary for killing the highly resistive bacteria. Thus, the concentration of bacteria rises to a peak. At and after the initial sales, as illustrated by conditions c of FIG. 11, 0.25 ppm or more of active chlorine is generated by the chlorine generator so that it can suppress the bacterial concentration. As a result, the bacterial concentration is less than that observed under conditions f with no electrolysis. 
     From the description thus far made, propagation of resistive bacteria is compared during consecutive sales between a beverage dispenser having a chlorine generator equipped with an electrolysis cell of the capacity of 150 cc and the beverage dispenser having no chlorine generator. It is found that a beverage dispenser having a chlorine generator exhibits a greater sterilizing effect, but that sales water reserved in the filter makes insufficient contact with the chlorine, and that the chlorine concentration cannot be maintained at a concentration of 0.2 ppm necessary for killing the highly resistant bacteria so that the beverage dispenser has no sterilizing effect even with a chlorine generator. 
     When a chlorine generator having a 150 cc electrolysis cell is used, the beverage dispenser has no sterilizing effect on the sales water reserved in the filter. This is because the electrolysis cell has such a small capacity that the chlorine is insufficient to sterilize the water reserved in the filter when the filter water of the flows into the chlorine generator. By enlarging the electrolysis cell to increase the reserve capacity, therefore, the time period of contact between the active chlorine and the bacteria can be lengthened to enable effective sterilization of the sales water reserved in the filter. 
     Conditions b of FIG. 11 report the chlorine concentrations in the individual consecutive sales from the beverage dispenser which uses a chlorine generator equipped with an electrolysis cell having a capacity of 1,000 cc. 
     On the other hand, conditions d report the bacterial concentration in individual sales of this example. It is found that the initial cups of sales water are in the pipelines at and downstream of chlorine generator  4  and contain a high chlorine concentration and that the sales water has a higher sterilizing ability than that of conditions f without the electrolysis, so that the bacterial concentration is two orders of magnitude lower. For the subsequent cups, on the other hand, when 340 ml of water in the cartridge of the filter is fed to the electrolysis cell, it is mixed with 1,000 cc of water reserved in the electrolysis cell having a predetermined chlorine concentration. As compared with the case in which the electrolysis cell has a 150 cc capacity, the time contact between the active chlorine and the bacteria increases, so that the bacterial concentration is effectively suppressed without exhibiting any peak. For the later sales, moreover, the bacterial concentration can be effectively suppressed at all times low levels. 
     FIG. 12 is a graph plotting the extent of bacterial death. The bacteria were of a highly resistant strain living in the service water and sampled from the faucet, and were cultured in 15 MPN/100 ml in the filter so that the initial bacteria were extracted in about 105 cfu/ml. The graph of FIG. 12 plots the relationship between the highly resistant bacteria and the kill time period for three samples of water having chlorine concentrations of 0.9 ppm, 1.5 ppm and 3.0 ppm generated in the chlorine generator. The water sample size was 200 cc. These results indicate that to kill highly resistant bacteria, contact time is generally more important than chlorine concentration. 
     As described herein before, feed water flowing at a rate of 30 cc per second into the electrolysis cell is mixed with 1,000 cc of the reserved water having a predetermined chlorine concentration so that it flows out as sales water at a rate of 30 cc per second. As a result, the mixing ratio increases more than that of the capacity of 150 cc so that the contact time of chlorine with bacteria can be maintained to suppress the bacterial concentration effectively at all times. 
     Thus, the time period for the bacteria to die can not be maintained by the direct sterilizing or fungistatic treatment of the filter. If chlorine is prevented from acting directly on the filtering material of the filter, on the other hand, the lifetime of the filter can be made longer than that of the case in which chlorine does act directly. This effect is further improved not only by reserving sales water in the electrolysis cell but also by selecting a filter such as a UV filter having different sterilizing mechanisms; an MF filter having a pore size of about 0.5 microns so as to cause the filtering material to absorb bacteria having a size of 1 micron or more and to prevent the bacteria from flowing downstream of the filter; or a carbon block type filter. Moreover, this method may be combined with a variety of sterilizing methods such: a method of establishing conditions, in which the bacteria do not propagate well, by keeping the temperature of the feed water or the reserved water in the filter at 10° C. or lower; a method of heating the feed water to a temperature of 63° C. or higher, at which the bacteria are apt to die; a method of using ozone in the pipelines; or a method of sterilizing the bacteria by the electron mobility reaction in a low potential range (at 0.74 V). 
     On the other hand, low resistance bacteria such as colibacillus will almost certainly die under the conditions of pH 7.0, 20 to 25° C., 0.055 ppm chlorine and 1 minute of contact time. When electrodes  40 A and  40 B are fed with a constant electric current of 800 mA with a current density of 2 A/dm 2  or less, for example, a constant chlorine concentration can be obtained. Under these conditions, 90% of the water quality falls within a chlorine ion concentration of 5 to 50 ppm and a conductivity of 50 to 500 (Ω·cm) −1 . As a result, the chlorine concentration, as produced by chlorine generator  4 , is higher than 0.2 ppm, and is capable of killing pollution-indexing bacteria such as colibacillus, and water downstream of chlorine generator  4  has sterilizing action sufficient for both the vending time and the standby time. 
     In the beverage dispenser thus far described, electrodes  40 A and  40 B of chlorine generator  4  are energized simultaneously with the feed water start of the sales water. In response to the feed water command, however, electrodes  40 A and  40 B may be energized, and feed pump  8  may be driven after 1 second to vend the sales water. 
     According to the beverage dispenser thus far described, even if the bacteria absorbed by the filter member are discharged to the reservoir, electrolysis is performed on a predetermined quantity of reserved feed water so that chlorine can be generated in a sufficient sterilizing quantity. When the electrolysis electrodes are not provided on the side walls of the reservoir, the electrolysis electrodes are always wholly immersed in the feed water even if the water level changes, so that the electrolysis efficiency can be kept constant while the electrode consumption of the can be minimized. Since a feed water quantity corresponding to one sale of sales water is reserved for electrolysis, on the other hand, the shape of the reservoir is not elongated but can match the accommodation space. Since one sale of feed water is reserved for electrolysis, on the other hand, sales water can be fed at an ordinary vending rate so that the quick service is achieved. Moreover, the chlorine concentration can be controlled properly and simply. Further, the water level is always kept at a predetermined level without providing any water level sensor so that the electrolysis efficiency can be kept at a predetermined level. If the feed water according to one sale is reserved so that it may be electrolyzed each time the sales water is vended, on the other hand, the water line is filled up with the sales water having the predetermined chlorine concentration so that the bacteria will not propagate even the sales water resides. 
     Other Embodiments 
     It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.
A water purification apparatus and methods for the purification of water are provided. The invention features an atmospherically-isolated, but ventable, reservoir electrolysis cell with control features for selecting an electrolysis duration depending on temperature, time since last electrolysis, or time since last gas venting. The device and associated method can easily take a wide range of input water qualities into account for the production of an effective amount of sterilizing water.