Patent Publication Number: US-6209753-B1

Title: Water dispenser for upright stand type water bottles

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a water dispenser, and more particularly to a water dispenser for upright stand type water bottles which allows an easy installation of the water bottle. In addition, users may selectively purchase one from among those for cool water, hot water, or for both use. 
     2. Description of the Related Art 
     Recently, as the public&#39;s awareness of the impurities in the public water supply increases, bottled drinking water is widely used in offices and homes throughout the world. As a result, water dispensers which can rapidly heat or chill the water have been introduced to allow people to drink hot and cool water. 
     These conventional water dispensers are designed such that water bottles are inverted and placing them onto the top of the dispensers in such a manner that the open end of the water bottle contacts the top of the dispenser. Thus, the water contained in the water bottle falls down as users want. 
     However, since the bottle filled with water is too heavy to lift up to the top of the dispenser, many individuals, especially senior citizens are reluctant to make use of such a conventional type of water dispenser. In addition, since the water bottle must be placed on top of the cabinet with the bottle&#39;s open end down, it is inevitable that water will occasionally spill onto the dispenser and floor, which creates further inconvenience and risk of injury. This conventional design also does not provide any means for preventing the open end of the dispenser from being contaminated. 
     To overcome such a problem, there has been proposed a water dispenser in which a water bottle is installed in a lower portion of the main body of the dispenser. Thus, the water in the bottle is pumped to the reservoir which is provided at the upper portion of the dispenser. 
     Referring to FIG. 1, a dispenser  100  has faucets  102 ,  103  which are provided at the upper portion of a front face of a main body  101  thereof. A tray  104  is provided under faucets  102 ,  103 , and a cabinet  105  and a door  107  are provided in the lower portion of dispenser  100 . 
     A groove  106  for guiding the water bottle is formed at the bottom surface of cabinet  105 , and door  107  has a plurality of elongated holes  108  for checking the water bottle in cabinet  105 . Magnets  109 ,  109 ′ for closing door  107  are provided respectively at a predetermined portion of door  107  and at the corresponding portion of main body  101 . An operation switch  110  which is operated according to door  107  in order to control a suction tube carrying device which will be described later is provided at main body  101 . 
     As shown in FIGS. 2A and 2B, if a pulley  112  is driven by a motor, a suction tube  111  is wound around or off pulley  112 , to thereby elevate or descend suction tube  111 . 
     Suction tube  111  consists of a buffer unit  111   a  for preventing pulley  112  from being twisted to a pump, and a winding unit  111   b  connected to buffer unit  111   a  and which is wound around pulley  112  in accordance with the rotation of pulley  112 . A guiding groove  112 ′ for allowing a smooth winding of suction tube  111  is formed along the periphery of pulley  112 . In addition, pulley  112  has a perforation  112 ″ for connecting buffer unit  111   a  and winding unit  111   b  so as to allow a smooth operation of winding unit  111   b . To prevent any damage onto suction tube  111 , buffer unit  111   a  is connected to winding unit  111   b  via tube  111   c  made up of a plastic or an aluminum having a high stiffness. 
     Reference numeral  113  denotes a band fastener for fixing suction tube  111  onto the front surface of pulley  112 . 
     Operation of the water dispenser will be explained with reference to FIGS. 1,  3 A, and  3 B. 
     The water contained in a bottle  140  in cabinet  105  is pumped into a cool water reservoir  116  via suction tube  111  and a conduit  115 . Subsequently, the water pumped into reservoir  116  flows into a hot water reservoir  118  via conduit  117 . The water in reservoirs  116  and  118  is chilled or heated by a cooling element  119  or by a die-casting heater  120 . 
     To minimize the transmittance of the heat from hot water reservoir  118  to cool water reservoir  116 , a connector  117 ′ provided at the upper portion of cool water reservoir  116  is made up of a metal, for example, a brass. In addition, a connector  117 ″ provided at the upper portion of hot water reservoir  118  is made up of a plastic, and conduit  117  for connecting both connectors  117 ′ and  117 ″ is made up of a silicon rubber. 
     Float sensors  121 ,  122  for sensing the amount of water are provided inside of reservoirs  116 ,  118  so as to control the operation of a pump  114 . If reservoirs  116 ,  118  are filled with water, a sensor signal is transmitted from float sensors  121 ,  122  to a control unit(not shown) so as to stop the operation of pump  114 . If reservoirs  116 ,  118  are not filled with water, pump  114  is driven so as to pump the water from water bottle  140 . 
     When the user opens door  107  in order to change the water bottle, switch  110  is operated so as to rotate pulley  112  by a motor  123 . Thus, suction tube  111  elevates winding onto pulley  112 . 
     When the elevation of suction tube  111  completes, the empty water bottle is replaced by a new water bottle, and door  107  is closed, to thereby press switch  110 . Then, suction tube  111  descends towards the inside of the newly replaced water bottle. 
     At this time, armatures  126 ,  127  fixed at pulley  112  are in contact with micro-switches  124 ,  125  at the upper end portion of a pulley fixation bracket  128 . Thus, micro-switches  124 ,  125  are operated so as to detect whether suction tube  111  has completed an elevation or a descending. Motor  123  is controlled by a control signal which is output from a control unit according to the operation of micro-switches  124  and  125 . 
     Reference numeral  129  denotes a sealing cap for preventing water bottle  140  from being contaminated, and reference numeral  130  denotes an intake block. 
     However, such a conventional water dispenser has problems as explained below. 
     First, it is difficult to replace water bottles because the cabinet for accommodating water bottles has a limited space. 
     In addition, a cool water reservoir, a hot water reservoir, and a means for chilling or heating the water have to be provided to the water dispenser, and a device for elevating or descending an suction tube is required, which increases a manufacturing cost. A person who intends to use only either hot or cool water has to purchase such a conventional dual-use water dispenser. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a water dispenser for upright stand type water bottles in which water bottles can be easily replaced. 
     It is another object of the present invention to allow users to selectively purchase a water dispenser for cool water, hot water, or for dual use. 
     It is still another object of the present invention to provide a water dispenser for upright stand type water bottles with various design applied thereto. 
     To achieve the above objects and other advantages, there is provided a water dispenser for upright stand type water bottles including: a post; a base plate which rests on the ground and supports an end portion of the post; a water tank assembly having a housing, a cover for opening or closing the housing, a water tank installed in the housing, and a unit for chilling or heating the water in the water tank, and which is installed to be attachable or detachable onto or from a holder coupled to another end portion of the post; a faucet for controlling a flow of the heated or chilled water from the water tank assembly; a suction tube one end portion of which is inserted into a water bottle so as to provide a path for supplying the water in the bottle to the water tank assembly; a pump assembly which is connected to the suction tube so as to pump the water from the water bottle; and a control means for controlling the operation of the pump assembly. 
     According to the present invention, the water tank assembly includes those for exclusive use of cool water having a unit for chilling the water in the water tank, and those for exclusive use of hot water having a unit for heating the water in the water tank. Users may choose either the water tank assembly for exclusive use of cool, hot, cool/hot, cool/cool or hot/hot water. 
     Preferably, the water tank assembly further includes a cooling fan for discharging the heat generated from the inside of the housing. The housing further includes a vent for discharging the heat. 
     The water tank assembly further includes a water level sensing circuit having two electrodes for sensing the water level in the water tank. The water level sensing circuit inverses the polarity of the electrodes every predetermined period so as to remove ions contained in the water attached to the electrodes. 
     Preferably, the water level sensing circuit includes a control unit for outputting a polarity changing signal every predetermined period, a polarity changing unit for inversing the voltage of each electrode according to the polarity changing signal output from the control unit, a water level sensor unit having a water level sensor consisting of two electrodes and which senses a voltage level of either of the two electrodes so as to sense whether the electrode contacts the water, and a logical operation unit for outputting a water level signal according to the result of the sensing of the water level sensor unit and the polarity changing signal of the control unit. 
     The control unit includes a counter for counting predetermined periods and outputting a reset signal according to the result of the counting, and a polarity changing signal generating unit for generating a polarity changing signal according to the reset signal output from the counter. 
     The polarity changing unit includes a first inverter for firstly inverting the voltage of the polarity changing signal output from the control unit and providing the same to one of electrodes of the water level sensor, and a second inverter for secondly inverting the voltage of the polarity changing signal which is inversed by the first inverter and providing the same to another electrode. 
     The water level sensor unit includes a third inverter for inverting the voltage of one of the electrodes of the water level sensor, and outputting the inverted voltage to the logical operation unit. 
     The logical operation unit includes an exclusive OR element which performs an exclusive OR on the sensor signal output from the water level sensor unit and the polarity changing signal output from the control unit and outputs the sensor signal according to the result of the operation of the exclusive OR. 
     The base plate is provided with a switching means for controlling the power supplied to the pump and the control means, and has a groove or recess for accommodating water bottles. 
     The holder has a main body thereof at which a receptacle to be coupled with one end of the post is formed, and a protruded shaft which is extended from the main body of the holder at a predetermined angle and has at an end portion thereof a projection. The housing of the water tank assembly has a groove into which the projection of the protruded shaft is inserted. 
     As an embodiment, two protruded shafts are diverged from the main body of the holder, and the water tank assemblies for an exclusive use of cool water and for an exclusive use of hot water, respectively, are coupled to the two protruded shafts. 
     Preferably, when the projection formed at the end portion of the main body of the holder is inserted into the groove formed at the water tank assembly, the projection can be fixed to the housing using a locking means such as a screw. 
     In addition, a water catching tray one end portion of which is connected to the post and which projects from the post by a predetermined length can be further provided under the water tank assembly. Also, a cup holder one end portion of which is connected to the post and which projects from the post by a predetermined length can be further provided under the water tank assembly. The cup holder is a ring so that a cup can be held under the faucet by inserting it into the ring. 
     The pump assembly has a pump for pumping the water from the water bottle, and a pump case for accommodating the pump and which is fixed to the post. The pump case has a clip for holding the suction tube. 
     The suction tube of the present invention includes a first hose which is made up of a soft substance and has one end thereof connected to an intake port of the pump, a second hose which is made up of a hard substance and has one end thereof connected to the first hose and another end thereof provided with an absorption member to be inserted into the water bottle, and a third hose for connecting an outlet port of the pump and the water tank. Preferably, the second hose has a sealing cap which is made up of a soft substance and substantially seals the opening of the water bottle. The sealing cap has an air vent for an airflow between the interior and exterior of the water bottle. In addition, the sealing cap may have inside thereof a filtering member for filtering the air flowing into the water bottle via the air vent. As an embodiment, the second hose consists of two hoses which are interconnected by a connecting hose made up of a silicon. 
     The second hose has at an end thereof a check valve for preventing the water in the suction tube from flowing back. The check valve includes a hollow cylinder having at the bottom surface thereof a valve seat onto which a ball is loaded, an orifice, and a cap provided at the upper surface of the cylinder so as to restrict the movement of the ball. 
     As an embodiment, the water contained in the water tank is cooled using a thermoelectric cooling element. 
     Preferably, the water tank may have an air vent for an airflow between the interior and exterior of the water tank, and a filtering member for filtering the air flowed into the water tank via the air vent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above object and other advantages of the present invention will become more apparent by describing in detail the preferred embodiments thereof with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view showing a conventional water dispenser; 
     FIG. 2A is a perspective view showing an elevating or descending device of a conventional water dispenser, and FIG. 2B is a section view showing the elevating or descending device shown in FIG. 2A; 
     FIG. 3A is a front section view showing a conventional water dispenser, and FIG. 3B is a side section view showing the conventional water dispenser; 
     FIG. 4 is a front view showing a water dispenser for an upright stand type water bottle according to the present invention; 
     FIG. 5 is a section view showing a water dispenser for an upright stand type water bottle according to the present invention; 
     FIG. 6 illustrates a water level sensing circuit adopted to the water dispenser according to the present invention; 
     FIG. 7A illustrates a voltage level at a low-level water, and FIG. 7B illustrates a voltage level at a full-level water; 
     FIG. 8 is a section view showing a suction tube according to the present invention; 
     FIG. 9A is a section view showing a check valve according to the present invention, and FIG. 9B is a perspective view showing a cap according to the present invention; 
     FIG. 10 is a plan view showing a holder according to a first embodiment of the present invention; and 
     FIG. 11 illustrates the suction tube according to a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those having skill in the art. 
     As shown in FIGS. 4 and 5, a base plate  10  has a water bottle loading portion  11  which is formed as a recess so that an water bottle  65  can be loaded standing upright, and a post supporting portion  12  is formed at the rear of water bottle loading portion  11 . 
     Post  20  has one end thereof fixed by post supporting portion  12 , an intermediate portion thereof provided with a pump assembly  30  for pumping the water from water bottle  65 , and another end thereof provided with a water tank assembly  50  which is attachable and detachable by a holder member  40 . 
     Post  20  is a hollow shaft that includes inside thereof a power supply circuit and a hose  61 ′, which will be described later. 
     Pump assembly  30  includes a pump case  31  to be fixed onto post  20 , and a pump  32  installed into pump case  31 . Preferably, pump case  31  consists of injections  31   a  and  31   b . In addition, a clip  33  for holding suction tube  60  when it is not used is provided at the side surface of pump case  31 . 
     Water tank assembly  50  consists of a housing  51 , a cover  51 ′ for closing or opening housing  51 , a water tank  52  installed inside of housing  51 , units for heating or chilling the water in water tank  52 , and a cooling fan  54  for discharging the heat generated from the inside of the housing  51  during the operation of the unit  53 ,  53 ′,  53 ″ for chilling the water. 
     The water tank assembly of the present invention may vary according to the use of the water dispenser. If a user intends to use a water dispenser exclusively for a hot water or a cool water, a water tank assembly in which a housing has inside thereof a cooling or a heating unit can be used. 
     Water tank assembly  50  further includes a water level sensing circuit having two electrodes E 1  and E 2  for sensing the water level in water tank  52 . The water level sensing circuit is constructed to remove ions in the water which are attached to electrodes E 1  and E 2  by inversing the polarity of electrodes E 1  and E 2  every predetermined period. 
     As shown in FIG. 6, a water level sensing circuit  55  includes a control unit  55   a  for periodically generating a polarity changing signal for changing the polarity to be supplied to the water level sensor, a polarity changing unit  55   b  for inverting the voltage of electrodes E 1  and E 2  according to the polarity changing signal output from control unit  55   a , a water level sensor unit  55   c  provided with a water level sensor having electrodes E 1  and E 2  and which senses whether electrodes E 1  and E 2  contact the water by sensing the voltage level of one of the electrodes, and a logical operation unit  55   d  for outputting a water level signal according to the result of the sensing of water level sensor unit  55   c  and the polarity changing signal of control unit  55   a.    
     Control unit  55   a  further includes a counter  55   a′  for counting a predetermined polarity changing period, and a polarity changing signal generating unit  55   a″  for outputting a polarity changing signal according to the result of the counting of counter  55   a′ . Here, counter  55   a′  may be structured to set a time that corresponds to a predetermined polarity changing period, and count down the time corresponding to such a period. When the countdown reaches zero, counter  55   a′  outputs a reset signal to polarity changing signal generating unit  55   a″  so as to invert the voltage level of the polarity changing signal. 
     Polarity changing unit  55   b  consists of a pair of inverters  55   b′  and  55   b″  which are connected in serial. Bifurcation point N 1  between an output terminal of inverter  55   b′  and an input terminal of inverter  55   b″  is connected to first electrode E 1  of the water level sensor in water level sensor unit  55   c  via a bias resistance R 1 . An output terminal of inverter  55   b″  is connected to second electrode E 2  of the water level sensor in water level sensing unit  55   c  via a bias resistance R 2 , and is simultaneously connected to an input terminal of inverter  55   c′  in water level sensor unit  55   c.    
     In addition, an output terminal of inverter  55   c′  of water level sensor unit  55   c  is connected to an input terminal of an exclusive OR element  55   d′  of logical operation unit  55   d.    
     Exclusive OR element  55   d′  of logical operation unit  55   d  simultaneously receives the polarity changing signal output from polarity changing signal generating unit  55   a″  and the signal output from inverter  55   c′  of water level sensor unit  55   c , performs a logical operation on the same, and outputs a water level sensor signal. 
     Now, an operation of the water level sensing circuit will be explained with reference to FIGS. 5 through 7. 
     When a user sets a polarity changing signal output time, which then is set to counter  55   a′.    
     Subsequently, counter  55   a′  counts down the time, and outputs a reset signal to polarity changing signal generating unit  55   a″  when the counting reaches zero. 
     Polarity changing signal generating unit  55   a″  inverts the voltage level (i.e., a polarity) which is output according to the reset signal output from counter  55   a′.    
     As shown in FIGS. 7A and 7B, an output of inverter  55   b′  is inverted to logic LOW, if a first polarity changing signal is assumed as logic HIGH. Therefore, first electrode E 1  of the water level sensor unit  55   c  becomes logic LOW. Since the output of inverter  55   b  is inverted to logic HIGH, second electrode E 2  of the water level sensor unit  55   c  becomes logic HIGH. 
     If the water in water tank  52  is at a low-level (i.e., if the water in water tank  52  does not reach the water level sensor), first and second electrodes E 1  and E 2  are opened, and the output of inverter  55   c′  becomes logic LOW. Logic signal LOW output from water level sensor unit  55   c  is supplied to logical operation unit  55   d . Subsequently, logical operation unit  55   d  performs an exclusive OR on the polarity changing signal at logic HIGH and the water level sensor signal at logic LOW, and outputs a water level signal at logic HIGH. The output of water level signal at logic HIGH indicates that the water in water tank  52  is at a low-level. Thus, pump  32  is driven so as to pump the water from water bottle  65 . 
     If the water in water tank  52  is at a full-level (i.e., if the water in water tank  52  reaches the water level sensor), the voltage of second electrode E 2  flows toward first electrode E 1  via the water. Thus, the voltage of second electrode E 2  becomes logic LOW, and an output of inverter  55   c′  becomes logic HIGH. As a result, logic signal HIGH output from water level sensor unit  55   c  is supplied to logical operation unit  55   d . Subsequently, logical operation unit  55   d  performs an exclusive OR on the polarity changing signal at logic HIGH and the water level sensor signal at logic HIGH, and outputs a water level signal at logic LOW. Therefore, if a water level signal at logic LOW is output, the water in water tank  52  is at a full-level, which stops the operation of pump  32 . As a result, the water in water bottle  65  stops flowing toward water tank  52 . 
     Meanwhile, counter  55   a′  outputs a reset signal to polarity changing signal generating unit  55   a″  when it reaches zero. Accordingly, polarity changing signal generating unit  55   a″  outputs the polarity changing signal which is inverted to logic LOW. When a polarity changing signal is at logic LOW, an output of inverter  55   b′  is inverted to logic HIGH, and first electrode E 1  of the water level sensor becomes logic HIGH. In addition, an output of inverter  55   b″  is inverted to logic LOW, second electrode of the water level sensor becomes logic LOW. 
     At this time, if the water in water tank  52  is at a low-level, first and second electrodes E 1  and E 2  are opened, and the output of inverter  55   c′  becomes logic HIGH. Logic signal HIGH output from water level sensor unit  55   c  is supplied to logical operation unit  55   d . Subsequently, logical operation unit  55   d  performs an exclusive OR on the polarity changing signal at logic LOW and the water level sensor signal at logic HIGH, and outputs a water level signal at logic HIGH. The output of water level signal at logic HIGH indicates that the water in water tank  52  is at a low-level. Thus, pump  32  is driven so as to pump the water from water bottle  65 . 
     If the water in water tank  52  is at a full-level, the voltage of first electrode E 1  flows toward second electrode E 2  via the water. Thus, the voltage of second electrode E 2  becomes logic HIGH, and an output of inverter  55   c′  becomes logic LOW. As a result, logic LOW signal output from water level sensor unit  55   c  is supplied to logical operation unit  55   d . Subsequently, logical operation unit  55   d  performs an exclusive OR on the polarity changing signal at logic LOW and the water level sensor signal at logic LOW, and outputs a water level signal at logic LOW. The output of a water level signal at logic LOW indicates that the water in water tank  52  is at a full-level, which stops the operation of pump  32 . As a result, the water in water bottle  65  stops flowing toward water tank  52 . 
     It can be seen from the above description that the signal to be finally output is determined by the result of the sensing of the water level sensor even when the voltage level of the polarity changing signal changes. 
     A power applying direction between first and second electrodes E 1  and E 2  is changed according to the change of the voltage level of the polarity changing signal. Thus, ions in the water which are attached to electrodes E 1  and E 2  as the water dispenser becomes old can be removed. That is, since the power applying direction between first and second electrodes E 1  and E 2  is periodically changed, ions at electrodes E 1  and E 2  of the water level sensor are detached when the polarity changes. As a result, a stabled water level sensing operation can be performed. 
     The above-described embodiment shows sensing of water level within one water tank. However, the water level sensing circuit having the above-described structure can be also applied when the water tank assemblies for an exclusive use of hot and for an exclusive use of cool water are employed. 
     When the water in the water bottle  65  is pumped by driving pump  32 , if the water level signal is not inverted to logic LOW even when a predetermined time period elapses after pump  32  is driven, it is determined that the water in water bottle  65  is all consumed. Subsequently, an alarm is given to the user and pump  32  stops its operation. 
     Water tank  52  has at an upper surface thereof a connection unit  52 ′ to which an end of suction tube  61 ′ is connected, an air hole (not shown) for an airflow between the interior and exterior of water tank  52 , and a filtering member  52 ″ for filtering the air flowed into via the air vent. 
     Housing  51  has at the front surface thereof a faucet  56  for controlling a flow of the heated or chilled water from water tank  52 , and has at the front, rear, left and right surfaces thereof a vent  57  for discharging the heat which is generated when the water is chilled, to the outside of housing  51  via cooling fan  54 . 
     Preferably, a thermoelectric cooling element or a semiconductor element which can perform a cooling operation with less occupation is used as a cooling unit, considering that water tank  52  is accommodated into housing  51 . Preferably, a band heater which wraps around the water tank or a seize heater is used as a heating unit. 
     In addition, a semiconductor element  53  which is formed by a junction of P-type and N-type semiconductors has a cold block  53 ′ which is combined thereonto as a heat absorption member for effectively transmitting a cool temperature generated by operating semiconductor element  53  to water tank  52 . Semiconductor element  53  further has a radiation member  53 ″ which is combined therebelow for discharging a hot temperature generated by operating semiconductor element  53 . 
     Preferably, as is not shown, a thermal insulation material is installed between housing  51  and water tank  52 . 
     Holder member  40  for installing water tank assembly  50  to be attachable or detachable consists of a body  41  having a groove into which one end portion of post  20  is inserted, and a protruded shaft  42  which is extended from body  41  at a predetermined angle and has at an end portion thereof a projection  42 ′. Housing  51  has a groove  51 ″ into which projection  42 ′ of protruded shaft  42  is to be inserted. 
     Preferably, to firmly fix water tank assembly  50  to holder member  40 , projection  42 ′ of protruded shaft  42  is inserted into groove  51 ″ of water tank housing  51 , and projection  42 ′ is firmly fixed to water tank housing  51  by using a screw (not shown). 
     FIG. 10 illustrates a holder member according to another embodiment of the present invention. Here, body  41  provided with a groove into which a post is to be inserted has two shafts  42  which are protruded at a predetermined angle. Thus, water tank assemblies for exclusive use of hot and cool water, respectively, can be used simultaneously. 
     A tray  70  for catching the water falling from faucet  56  and which projects from post  20  by a predetermined length is installed above pump assembly  30 . A switching unit  80  for controlling the power supplied to pump  32  and a control unit for controlling pump  32  is installed at the rear of base plate  10 . Also, a cup holder (not shown) one end portion of which is connected to the post and which projects from the post by a predetermined length can be further provided under the water tank assembly. The cup holder is formed into a ring shape so that a cup can be held inserting into the ring. 
     Meanwhile, as shown in FIG. 8, suction tube  60  which is connected to pump  32  so as to intake the water from water bottle  65  consists of a first hose  61  which is made up of a soft substance and has one end thereof connected to an intake part of the pump, a second hose  62  which is made up of a hard substance and has one end thereof connected to first hose  61  and another end thereof provided with a suction block  63  to be inserted into the water bottle, and a third hose  61 ′ of FIG. 5 for connecting an outlet part of pump  32  and water tank  52 . Second hose  62  is provided with a cap  64  for sealing the opening of water bottle  65  and which is made up of a soft polyvinyl chloride (PVC) or a silicon and installed to be slidable along second hose  62 . Cap  64  has an air vent for an airflow between the interior and exterior of water bottle  65 , and a filtering member  67  for filtering the air flowed into water bottle  65  via the air vent. Filtering member  67  is made up of a non-woven fabric or a zeolite. 
     Cap  64  is installed to be slidable to allow free use of suction tube  60  because water bottles manufactured by different manufacturers vary in height. 
     In addition, a check valve  66  for preventing the water contained in suction tube  60  from flowing back is provided at one end of second hose  62  which also has suction block  63 . As shown in FIGS. 9A and 9B, check valve  66  consists of a hollow cylinder  66   b  having at the bottom surface thereof a valve seat  66   d  onto which a ball  66   a  is loaded, an orifice, and a cap  66   c  provided at the upper surface of cylinder  66   b  so as to restrict the movement of the ball. 
     Ball  66   a  is raised and contacts a bottom surface of cap  66   c  when the pump is driven, and drops onto valve seat  66   d  when the pump is not driven. 
     Any contamination which may be caused by a flowback of the water contained in suction tube  60  when water bottle  65  is replaced when pump  32  stops can be prevented by installing check valve  66  at one end of second hose  62 . 
     FIG. 11 is a fragmentary view showing a suction tube  60 ′ of another embodiment of the present invention, wherein second hose  62 ′ consists of two hoses  62   a′  and  62   b′  which are interconnected by a connection hose  62   c′  made up of a silicon. A cap  64 ′ is fixed to hose  62   a′ . Thus, when cap  64 ′ is fixed to the opening of water bottle  65  at the state where suction tube  60 ′ is inserted into water bottle  65 , second hose  62 ′ is bent at connection hose  62   c′ . In such a manner, suction tube  60 ′ of the present invention can be used for any type of water bottle. 
     The water dispenser of the present invention operates as follows. 
     First, the water bottle is positioned upright adjacent the post  20  preferably, the water bottle is placed on water bottle loading portion  11  of base plate  10 . Then, suction tube  60  which is fixed by clip  33  of pump case  31  is inserted into the water bottle, and cap  64  of suction tube  60  is fixed to the opening of the water bottle. 
     Subsequently, pump  32  is driven so as to pump the water from the water bottle, and the pumped water is supplied to water tank  52  via suction tube  60 . Here, the water pumped into water tank  52  is chilled by a cooling unit if water tank assembly  50  is for an exclusive use of cool water, and is heated by a heating unit if water assembly  50  is for an exclusive use of hot water. If water tank assembly  50  is for both use, the water pumped into two water tanks assemblies  52  used for hot and cold water, respectively, is chilled and heated. 
     As the chilled or heated water is consumed, and if it is sensed that the water in water tank  52  is at a low-level, the water in water bottle  65  is pumped into water tank  52  by driving pump  32 . If it is not sensed that the water in water tank  52  does not reach the full-level even when a predetermined time period elapses after the driving of pump  32 , an alarm sounds and the driving of pump  32  stops. At this time, users are allowed to replace the empty water bottle with the new one at the state where suction tube  60  is fixed by clip  33  of pump case  31 . 
     In regard to the replacement of water bottles, the conventional system provides a restricted space for water bottle replacement, because the water bottle loading portion is within the main body of the water dispenser. However, in the present invention, water bottles may placed on the water bottle loading portion of the base plate or to any appropriate place adjacent the post, which allows a convenient replacement of water bottles. 
     In the conventional system, the water in suction tube  60  flows back when a pump stops its operation. However, the present invention eliminates such a flowback by installing the check valve into suction tube  60 . 
     In addition, since the power applying direction between first and second electrodes E 1  and E 2  of the water level sensor unit is periodically changed, ions at electrodes E 1  and E 2  of the water level sensor unit are detached when the polarity changes. As a result, a stable water level sensing operation can be performed. 
     Furthermore, if a user intends to use the water tank assembly as an exclusive use for hot or cold water, he may open cover  51 ′ of housing  51 , detach suction tube  61 ′ from connection unit  52 ′ of water tank  52 , and separates holder member  40  and water tank assembly  50  by disassembling the screw which is fixing projection  42 ′ into groove  51 ″. Then, the user can easily replace the water tank assembly in the reverse order. 
     As described above, the present invention has benefits which can be explained as follows. First, the space for an replacement of water bottles is not restricted, which allows an easy replacement of water bottles. In addition, users may selectively purchase one from among those for cold water, hot water, or for both use. 
     Moreover, users may use both cold and hot water by separately purchasing the water tank assembly and/or the holder member, which enhances a practical use and an economical efficiency. 
     Furthermore, the water dispenser of the present invention has an improved appearance, and the water flowback in the suction tube which is likely to occur when the water bottle is replaced can be prevented. The air which flows into the water bottle and the water tank passes through the filtering member, which prevents the water from being contaminated by the polluted air. 
     This invention has been described above with reference to the aforementioned embodiments. It is evident, however, that many alternative modifications and variations will be apparent to those having skill in the art in light of the foregoing description. Accordingly, the present invention embraces all such alternative modifications and variations as fall within the spirit and scope of the appended claims.