Patent Publication Number: US-7908895-B2

Title: Laundry treatment apparatus and control method thereof

Description:
This application claims the benefit of Korean Patent Application No. 10-2005-0069991 filed on Jul. 30, 2005, Korean Patent Application No. 10-2005-0069992 filed on Jul. 30, 2005 and Korean Patent Application No. 10-2005-0069993 filed on Jul. 30, 2005, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, in general, to a laundry treatment apparatus and a control method thereof, and more particularly, to a laundry treatment apparatus and a control method thereof, in which steam flowing backward to a water supply channel of a tub is removed by the water of a condensing pool disposed in the water supply channel of the tub through condensing. 
     2. Description of the Conventional Art 
     In general, a laundry treatment apparatus is an apparatus for washing or drying fabrics by rotating the drum with them being contained in the drum. The laundry treatment apparatus may be classified into a washing machine that removes pollutants stained on clothes, bedclothes, etc. (hereinafter, referred to as “fabrics”) by employing water, a detergent, a mechanical action, and so on and a combined dry and washing machine that dries wet fabrics. 
     In the conventional laundry treatment apparatus, water mixed with a detergent or water not mixed with a detergent is supplied into a tub via an inlet bellows connecting an outlet of a detergent holder and a water supply port of the tub. As the drum within the tub is rotated, fabrics contained in the drum are washed and rinsed. 
     Recently, in order to increase the washing ability of fabrics, there is a tendency that high-temperature washing is performed using water heated by a heater installed within the tub or steam generated from an additional steam-generating device is supplied directly into the drum. 
     In the conventional laundry treatment apparatus, however, steam within the tub may be drained into the detergent holder via the water supply port of the tub and the inlet bellows, leading to a polluted detergent holder and peripheral portions thereof. There is another problem in that a dewy phenomenon occurs due to steam drained outside the laundry treatment apparatus. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a laundry treatment apparatus that can prevent the pollution of a detergent holder, which may occur when steam flows backward, by preventing steam within a tub from flowing backward into a water supply port of the tub. 
     Another object of the present invention is to provide a method of controlling a laundry treatment apparatus, in which external drainage of steam can be minimized by periodically filling a steam reverse flow-preventing unit with water in preparation for when the water within the steam reverse flow-preventing unit is overflowed. 
     Further another object of the present invention is to provide a method of controlling a laundry treatment apparatus, in which it can prevent steam from flowing backward during a dry cycle. 
     To achieve the above objects, a laundry treatment apparatus according to an aspect of the present invention includes a condensing pool disposed within a water supply port formed in a tub. A water supply passage is formed between the condensing pool and the water supply port. The laundry treatment apparatus further includes a cap that guides water, which is supplied to the water supply port, to the condensing pool, and stops steam flowing backward through the water supply passage so that the steam is introduced into the condensing pool. 
     The condensing pool has an opened top surface so that the supplied water can be overflowed to the water supply passage. 
     The condensing pool has a circumferential portion isolated from an inner wall of the water supply port in order for a water supply passage to be formed between the circumferential portion and the inner wall of the water supply port. 
     The laundry treatment apparatus further includes at least one rib connecting a circumferential portion of the condensing pool and an inner wall of the water supply port between the circumferential portion of the condensing pool and the inner wall of the water supply port. 
     The condensing pool has a bottom surface formed on the same concentric cycle as the tub. 
     The cap includes a shielding unit disposed on an upper side of the water supply passage, for stopping the rise of the steam, and a hollow water supply unit integrally formed with the shielding unit such that the hollow water supply unit is projected toward the inside of the condensing pool. 
     The shielding unit has an outer diameter fit into an inner wall of the water supply port so that the shielding unit can be inserted into the water supply port and is mounted therein. 
     The water supply unit has a tapered diameter. 
     The water supply unit has a bottom end lower than a top surface of the condensing pool. 
     The water supply unit has a bottom end having a height isolated from a bottom surface of the condensing pool. 
     The laundry treatment apparatus further includes a dry device coupled to the tub, for drying a fabric within a drum. 
     To achieve the above objects, a method of controlling a laundry treatment apparatus according to an aspect of the present invention includes the step of, at the time of hot-water washing of a set temperature or higher, of the laundry treatment apparatus, supplying water to a steam reverse flow-preventing unit disposed on a water supply channel of the laundry treatment apparatus. 
     The method further includes a water temperature sensing step of sensing a water temperature within a tub, a comparison step of comparing the sensed water temperature with the set temperature, and a condensing water supply step of, if the sensed water temperature is higher than the set temperature, supplying the water to the steam reverse flow-preventing unit disposed on the water supply channel of the laundry treatment apparatus. 
     The condensing water supply step is repeated at predetermined time intervals. 
     The condensing water supply step includes opening a water supply valve disposed in the water supply channel for a set time. 
     The set time is set in proportion to the capacity of a condensing pool of the steam reverse flow-preventing unit. 
     The water is supplied periodically. 
     To achieve the above objects, a method of controlling a laundry treatment apparatus according to another aspect of the present invention includes the step of, at the time of a dry cycle of the laundry treatment apparatus, supplying water to a steam reverse flow-preventing unit disposed on a water supply channel of the laundry treatment apparatus. 
     The method further includes a fabric-amount sensing step of sensing an amount of fabrics at the time of the dry cycle, and a condensing water supply step of operating a dry device, while rotating a drum, so that a fabric is dried after the fabric-amount sensing step and supplying the water to the steam reverse flow-preventing unit installed in the water supply channel. 
     The condensing water supply step opens a water supply valve disposed in the water supply channel for a set time while the drum is rotated in a one-way direction for the first time. 
     In the laundry treatment apparatus constructed above according to the present invention, steam flowing backward from the inside of the tub to the water supply port of the tub is brought into contact into with water contained in the condensing pool formed in the water supply port of the tub and is condensed. Accordingly, the present invention is advantageous in that it can prevent the pollution of the detergent holder or peripheral portions thereof, which may occur when steam flows backward into the detergent holder or peripheral portions thereof via the water supply port of the tub. 
     In the method of controlling the laundry treatment apparatus constructed above according to the present invention, if a water temperature within the tub is higher than a set temperature at which steam is generated within the tub, water is supplied to the steam reverse flow-preventing unit installed on the water supply channel. The water supplied to the steam reverse flow-preventing unit precludes the reverse flow of the steam. Therefore, the present invention is advantageous in that it can minimize the reverse flow of steam and can prevent the contamination of the detergent holder, and the like. 
     In the method of controlling the laundry treatment apparatus constructed above according to the present invention, if a dry cycle begins, water for condensing steam is supplied to the steam reverse flow-preventing unit installed on the water supply channel. Therefore, the present invention is advantageous in that it can prevent the reverse flow of steam, which has occurred during the dry cycle, although the water of the steam reverse flow-preventing unit is overflowed during a dehydration cycle anterior to the dry cycle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a laundry treatment apparatus having an opened top surface according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of the laundry treatment apparatus according to an embodiment of the present invention; 
         FIG. 3  is an exploded perspective of the steam reverse flow-preventing unit of the laundry treatment apparatus according to the present invention; 
         FIG. 4  is an enlarged cross-sectional view when water is feed to a water supply channel in the laundry treatment apparatus according to an embodiment of the present invention; 
         FIG. 5  is an enlarged cross-sectional view when steam is reverse flowed to the water supply channel in the laundry treatment apparatus according to an embodiment of the present invention; 
         FIG. 6  is a control block diagram illustrating a method of controlling the laundry treatment apparatus according to an embodiment of the present invention; 
         FIG. 7  is a flowchart illustrating a method of controlling the laundry treatment apparatus according to an embodiment of the present invention; 
         FIG. 8  is a partially cutaway sectional view of a laundry treatment apparatus according to another embodiment of the present invention; 
         FIG. 9  is a partially exploded perspective view of the laundry treatment apparatus according to another embodiment of the present invention; 
         FIG. 10  is a cross-sectional view of the laundry treatment apparatus according to another embodiment of the present invention; and 
         FIG. 11  is a flowchart illustrating a method of controlling the laundry treatment apparatus according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described in detail in connection with specific embodiments with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of a laundry treatment apparatus having an opened top surface according to an embodiment of the present invention, and  FIG. 2  is a cross-sectional view of the laundry treatment apparatus according to an embodiment of the present invention. 
     Referring to  FIGS. 1 and 2 , the laundry treatment apparatus includes a cabinet  2 , a tub  10  supported within the cabinet  2  in a shock-absorbing manner, for containing water W, a drum  20  rotatably disposed within the tub  10 , for containing fabric m, driving means  25  for rotating the drum  20  so that the fabric m is washed, rinsed, and dehydrated, a water supply device  30  for supplying the water W to the tub  10 , and a discharge device  40  for forcibly discharging polluted water W within the tub  10  or water dehydrated from the fabric m outside the cabinet  2 . 
     The cabinet  2  includes a base  3 , a cabinet main body  4  disposed on the base  3 , a cabinet cover  6  disposed at the front of the cabinet main body  4  and having a fabric inlet hole  5  through which the fabric m can go in and out, and a top cover  7  disposed on a top surface of the cabinet main body  4 . 
     A door  8  for opening and closing the fabric inlet hole  5  is rotatably disposed in the cabinet cover  6 . 
     A control panel  9  for inputting washing/rinse/dehydration, high-temperature/steam washing, and/or so on is disposed on one side of the cabinet  2 . 
     A detergent holder inlet  9   a  for containing a detergent holder  36  is formed in the control panel  9 . 
     A water supply port (not shown) to which the water supply device  30  is connected on the upper side of the tub  10  is projected from the tub  10 . 
     A discharge port (not shown) to which the discharge device  40  is connected on the lower side of the tub  10  is projected from the tub  10 . 
     The tub  10  has a tub-opening unit  11  formed on the rear side of the fabric inlet hole  5 . 
     To the tub-opening unit  11  is coupled a gasket  12  for preventing the water W or the fabric m from flowing between the tub-opening unit  11  and the fabric inlet hole  5 . 
     The tub  10  is resiliently supported to the cabinet  2  by means of a spring  13  or a damper  14 . 
     A heater  15  for heating the water W supplied to the tub  10  in order to wash the fabric m at high temperature is disposed in the tub  10 . 
     The heater  15  heats the water W to any one of 40° C., 50° C., 60° C., 70° C., and 90° C. if high-temperature/steam washing is input through the control panel  9 . 
     The drum  20  includes a fabric inlet hole  21  through which fabrics enter the drum  20 , which is disposed at the rear of the fabric inlet hole  5  of the cabinet cover  6 . 
     In the drum  20  is formed a through-hole  22  through which the water W can go in and out. 
     In the drum  20  is disposed a lifter  23  for drawing the fabric m upwardly when the drum  20  is rotated and then dropping the fabric m. 
     The driving means  25  is a motor mounted on the rear surface of the tub  20 . The driving means includes a drive shaft  26  coupled to the back of the drum  20  via the through-hole formed on the rear side of the tub  10 . 
     The water supply device  30  includes water supply valves  32   a ,  32   b , and  32   c  coupled to external hoses  31   a  and  31   b , for controlling the water supplied to the external hoses  31   a  and  31   b , water supply hoses  33   a ,  33   b , and  33   c  for guiding the water that has passed the water supply valves  32   a ,  32   b , and  32   c , a detergent supply unit  34  having formed a detergent reception unit and a water supply passage therein so that the water guided to the water supply hoses  33   a ,  33   b , and  33   c  can be mixed with a detergent while passing, and a water supply bellows tube  38  for guiding the water that has passed the detergent supply unit  34  to the water supply port of the tub  10 . 
     The water supply valves  32   a ,  32   b , and  32   c  include a plurality of cold-water supply valves  32   a  and  32   b , one hot-water supply valve  32   c , and so on. 
     The water supply hoses  33   a ,  33   b , and  33   c  include a plurality of cold-water supply hoses  33   a  and  33   b  for guiding the water that has passed the cold-water supply valves  32   a  and  32   b  to the detergent supply unit  34 , and a hot-water supply hose  33   c  for guiding the water that has passed the hot-water supply valve  32   c  to the detergent supply unit  34 . 
     The detergent supply unit  34  includes a detergent holder housing  35  to which the water supply bellows  38  is coupled, the detergent holder  36  detachably disposed in the detergent holder housing  35 , and a dispenser cover  37  disposed on a top surface of the detergent holder housing  35 , for supplying water to the detergent holder  36 . The dispenser cover  37  is coupled to the plurality of water supply hoses  33   a ,  33   b , and  33   c.    
     In the detergent holder  36  are formed detergent reception units  36   a  and  36   b  for containing a detergent. 
     The discharge device  40  includes a drainage bellows  41  coupled to the discharge port of the tub  10 , for guiding the water within the tub  10 , a drainage pump  42  for pumping the water guided to the drainage bellows  41 , and a drainage hose  43  for guiding the water pumped from the drainage pump  42  outside the cabinet  2 . 
     Meanwhile, the laundry treatment apparatus further includes a steam reverse flow-preventing unit for preventing steam within the tub  10  from flowing backward to the detergent holder  36  via the water supply port of the tub  10 , the water supply bellows rube  38 , and so on. 
     The steam reverse flow-preventing unit is a kind of a condenser for condensing reverse-flown steam onto the water W and removing the steam. The steam reverse flow-preventing unit may be disposed within at least one of the tub  10 , the water supply port of the tub  10 , the water supply bellows the  38 , and the detergent holder  36 . 
     If the steam reverse flow-preventing unit is disposed within the tub  10 , there is a high possibility that it may collide against the drum  20 . If the steam reverse flow-preventing unit is disposed within the water supply bellows tube  38 , it is difficult to install the steam reverse flow-preventing unit and also to preserve the water W. If the steam reverse flow-preventing unit is disposed within the detergent holder  36 , the structure of the detergent holder  36  becomes complicated and the detergent holder  36  becomes bulky. Therefore, it is most preferred that the steam reverse flow-preventing unit is disposed within the water supply port of the tub  10 . 
       FIG. 3  is an exploded perspective of the steam reverse flow-preventing unit of the laundry treatment apparatus according to the present invention,  FIG. 4  is an enlarged cross-sectional view when water is fed to a water supply channel in the laundry treatment apparatus according to an embodiment of the present invention, and  FIG. 5  is an enlarged cross-sectional view when steam is reverse flowed to the water supply channel in the laundry treatment apparatus according to an embodiment of the present invention. 
     Referring to  FIGS. 3 to 5 , a steam reverse flow-preventing unit  50  includes a condensing pool  52  disposed within a water supply port  18  of the tub  10  so that a water supply passage  51  is formed between the condensing pool  52  and the water supply port  18 , and a cap  60  that guides the water W supplied to the water supply port  18  to the condensing pool  52  and stopping steam W′ flowing backward through the water supply passage  51  so that the steam is introduced into the condensing pool  52 . 
     A top surface  53  of the condensing pool  52  is opened so that the supplied water W can overflow a circumferential portion  54 . 
     The circumferential portion  54  of the condensing pool  52  is isolated from an inner wall  19  of the water supply port  18  in order for the water supply passage  51  to be formed between the circumferential portion  54  and the inner wall  19 . 
     That is, the water supply channel of the water W has a zigzag shape in which a ∪-shaped passage and a ∩-shaped passage are continuous. 
     At least one rib  55  for connecting the circumferential portion  54  of the condensing pool  52  and the inner wall  19  of the water supply port  18  is formed between the circumferential portion  54  of the condensing pool  52  and the inner wall  19  of the water supply port  18 . 
     The rib  55  extends up and down lengthily and has a thin thickness. 
     A plurality of the ribs  55 , which are isolated from each other, may be formed in the circumferential direction of the water supply port  18 . 
     If a portion of the condensing pool  52  is projected downwardly from the inner wall of the tub  10 , there is a high possibility that it may collide against the drum  20 . Accordingly, it is preferred that the condensing pool  52  is formed as large as possible in consideration of rapid supply of water. It is also preferred that a bottom surface  56  of the condensing pool  52  is formed on the same concentric cycle O as the tub  10 . 
     The condensing pool  52  and the rib  55  are integrally formed with the water supply port  18  at the time of injection molding of the tub  10 . 
     The cap  60  is located on the upper side of the water supply passage  51 . The cap  60  includes a shielding unit  62  that prevents the steam W′ from rising upwardly from the water supply passage  51 , and a hollow water supply unit  64  integrally formed with the shielding unit  62  and projecting toward the inside of the condensing pool  52 . 
     The shielding unit  62  has an outer diameter D fit into the inner well  19  of the water supply port  18  so that it can be inserted into the water supply port  18  and seated therein. 
     The water supply unit  64  has a tapered diameter. 
     The water supply unit  64  has a bottom end  65  lower than the top surface  53  of the condensing pool  52 , but has a height H isolated from the bottom surface  56  of the condensing pool  52 . 
     The operation of the laundry treatment apparatus constructed above according to an embodiment of the present invention will be described below. 
     At the time of a water supply process for washing or a water supply process for rinse, the water W that has passed the detergent holder  36  is supplied to the water supply port  18  of the tub  10  via the water supply bellows  38 . The water W is then stopped by the top surface of the shielding unit  62  of the cap  60  and does not drop to the water supply passage  51 , but is guided to the top surface of the shielding unit  62  and then drops to the water supply unit  64  of the cap  60 . 
     The water W dropped to the water supply unit  64  is supplied to the condensing pool  52 . If the water W within the condensing pool  52  is full to the brim of the condensing pool  52 , it is overflowed to the water supply passage  51  between the circumferential portion  54  of the condensing pool  52  and the inner wall  19  of the water supply port  18  of the tub  10 . Thereafter, the water W drops to the tub  10  through the water supply passage  51  and is contained within the tub  10 . 
     Meanwhile, in the laundry treatment apparatus, at the time of high-temperature/steam washing carried out subsequently to the above-mentioned water supply, a portion of the steam W′ within the tub  10  may rise and be introduced into the water supply port  18  of the tub  10 . Therefore, the steam W′ rises along the water supply passage  51 . 
     The risen steam W′ is stopped by the shielding unit  62  of the cap  60 , no longer rises, and is thus directed toward the condensing pool  52 . Accordingly, at the time of the water supply, the raised steam W′ is brought in contact with the water W left without being overflowed from the condensing pool  52  and is condensed. The water W left in the condensing pool  52  and condensed water in which the steam W′ is condensed are mixed and remain in the condensing pool  52 . 
     Meanwhile, the water level of the condensing pool  52  is raised by the condensed water. A part of the mixed solution of the water and the condensed water is overflowed to the water supply passage  51  during the water supply process for washing or the water supply process for rinse and drops to the tub  10 . 
     In other words, the steam W′ is not flown backward to the upper side of the water supply port  18  of the tub  10 . 
       FIG. 6  is a control block diagram of the laundry treatment apparatus according to the present invention. 
     The laundry treatment apparatus of the present invention further includes a temperature sensor  16  that senses a temperature of the water W, and a control unit  70  that controls the water supply valves  32   a  and  32   b  according to the input of the control panel  9  or a temperature value of the water W, which is sensed by the temperature sensor  16 . 
     The control unit  70  controls the water supply valves  32   a  and  32   b  to periodically supply condensing water to the steam reverse flow-preventing unit  50  in preparation for when the water W is overflowed within the steam reverse flow-preventing unit  50  due to vibration of the tub  10 , and so on at the time of hot-water washing of a set temperature or higher (for example, 50° C. or more). 
     The hot-water washing may be typical hot-water washing in which washing is performed by hot water supplied through the hot-water valve  32   c , high-temperature washing in which washing is performed by hot water within the tub  10 , which is heated by the heater  15 , or steam washing in which washing is carried out by high-temperature steam, which is generated from a steam generating device (not shown) provided separately from the water supply device  30  and is sprayed into the drum via the hoses, nozzles, and the like. 
     Hereinafter, it is assumed that high-temperature washing employing the heater  15  is the hot-water washing for the convenience of description. 
     Furthermore, the control unit  70  may control the water supply valves  32   a  and  32   b  to periodically supply condensing water to the steam reverse flow-preventing unit  50  regardless of whether steam exists within the tub  10  at the time of the input of the above-mentioned hot-water washing, and also control the water supply valves  32   a  and  32   b  to periodically supply condensing water to the steam reverse flow-preventing unit  50  only when steam is generated within the tub  10 . In the present embodiment, it is assumed that condensing water is periodically supplied only when steam is generated within the tub  10 . 
     The control unit  70  can turn on/off both the water supply valves  32   a  and  32   b  periodically. Hereinafter, it is assumed that the control unit  70  turns on/off only the water supply valve  32   a  at a predetermined cycle. 
       FIG. 7  is a flowchart illustrating a method of controlling the laundry treatment apparatus according to an embodiment of the present invention. 
     In the method of controlling the laundry treatment apparatus according to the present embodiment, at the time of the hot-water washing in which the heater  15  heats the water W within the tub  10 , the temperature sensor  16  senses a temperature of the water W supplied to the tub  10  and transmits a sensed temperature to the control unit  70 . 
     The control unit  70  compares the temperature sensed by the temperature sensor  16  with a set temperature in step S 1 . 
     The set temperature is an approximate temperature of the water at which steam is generated within the tub  10 . Hereinafter, it is assumed that the set temperature is 50° C. 
     If it is determined that the sensed temperature of the water W is higher than 50° C., the control unit  70  determines that the steam W′ has been generated within the tub  10 . Accordingly, the control unit  70  periodically turns on/off the water supply valve  32   a  at predetermine intervals in order to fill the steam-generating device (more particularly, the condensing pool  52 ) with water in step S 2 . 
     The turn-on/off of the water supply valve  32   a  at predetermined time intervals and an operation accordingly will be described in more detail below. 
     The control unit  70  turns on the water supply valve  32   a  for a set time (for example, 5 seconds) at predetermined time (for example, 10 minutes) intervals and then turns off the water supply valve  32   a.    
     The predetermined time may be set in proportion to the degree in which water is overflowed from the condensing pool  52  due to vibration of the tub  10 , etc. It is preferred that when the overflow of water is frequent (for example, the vibration of the tub is great), the predetermined time is set short and when the overflow of water is not frequent (for example, the vibration of the tub is small), the predetermined time is set long. 
     It is preferred that the predetermined time is set in proportion to the number of vibration of the tub  10  or the number of rotation of the drum  20 . 
     Furthermore, the set time may be set in proportion to the capacity of the condensing pool  52 . When the capacity of the condensing pool  52  is small, the set time is set so that a small amount of water is supplied. When the capacity of the condensing pool  52  is great, the set time is set so that a great amount of water is supplied. 
     Meanwhile, in the laundry treatment apparatus of the present invention, when the water supply valve  32   a  is turned on, the water of the external hose  31   a  is supplied to the water supply hose  33   a  via the water supply valve  32   a . Thereafter, the water sequentially passes the detergent supply unit  34  and the water supply bellows  38  and is then guided to the water supply port  18  of the tub  10 . 
     The water guided to the water supply port  18  of the tub  10  is guided to the top surface of the shielding unit  62  of the cap  60  and is dropped to the water supply unit  64  of the cap  60 . The water then fills the condensing pool  52 . 
     A portion of the steam W′ generated from the inside of the tub  10  rises along the water supply passage  50  and is then stopped by the shielding unit  62  of the cap  60 . The risen steam W′ is brought in contact with the water W filled in the condensing pool  52  and is condensed accordingly, so that the steam does not flow backward to the upper side of the water supply port  18  of the tub  10 . 
     On the other hand, if the sensed temperature is less than the set temperature in step S 1 , the control unit  70  determines that steam has not been generated within the tub  10  or an amount of steam generated is very small. Accordingly, the control unit  70  does not repeat the turn-on/off the water supply valve  32   a  in step S 3 . 
       FIG. 8  is a partially cutaway sectional view of a laundry treatment apparatus according to another embodiment of the present invention,  FIG. 9  is a partially exploded perspective view of the laundry treatment apparatus according to another embodiment of the present invention, and  FIG. 10  is a cross-sectional view of the laundry treatment apparatus according to another embodiment of the present invention. 
     The laundry treatment apparatus according to the present embodiment includes a dry device  70  for drying a fabric m within a drum  20 , as shown in  FIGS. 8 to 10 . The laundry treatment apparatus of the present embodiment has the same or similar construction and function as those of the laundry treatment apparatus according to an embodiment of the present invention except for the dry device  70 . Therefore, the laundry treatment apparatus of the present embodiment will use the same reference numerals as those of the laundry treatment apparatus according to an embodiment of the present invention and will not be described in detail for simplicity. 
     The dry device  70  includes a dry duct  73  having built a heater  71  and a circulation fan  72  therein, for supplying hot wind to the inside of the drum  20 , a condensing duct  74  through which air within the tub  10  passes, and a coolant feeder  75  for supplying a condensing coolant to the inside of the condensing duct  74 . 
     The condensing duct  74  has one end coupled to the tub  10 . 
     The dry duct  73  has one end coupled to the other end of the condensing duct  74  and the other end coupled directly to the gasket  12  or the tub  10 . 
     The coolant feeder  75  includes a water supply nozzle  76  formed on one side of the condensing duct  74 , for causing the coolant to flow into the condensing duct  74  so that moisture in the air passing through the condensing duct  74  is condensed, a coolant hose  77  that guides the coolant to the water supply nozzle  76 , and a coolant valve  79  that stops the coolant supplied to the coolant hose  77 . 
     Meanwhile, the laundry treatment apparatus of the present embodiment includes the same steam reverse flow-preventing unit as that according to an embodiment of the present invention in the water supply port  18  of the tub  10 . 
       FIG. 11  is a flowchart illustrating a method of controlling the laundry treatment apparatus according to another embodiment of the present invention. 
     The method of controlling the laundry treatment apparatus according to the present embodiment can be applied to not only a case where a dry cycle is performed after a washing cycle, a rinse cycle, and a dehydration cycle are preformed, but also a case where only the dry cycle is performed. An example in which the dry cycle is performed after the washing cycle, the rinse cycle, and the dehydration cycle are implemented will be described below. 
     In the method of controlling the laundry treatment apparatus according to the present embodiment, at the time of the dehydration cycle anterior to the dry cycle, water is supplied to the steam reverse flow-preventing unit  50  at the time of the dry cycle in preparation for when the water of the steam reverse flow-preventing unit  50  (more particularly, the condensing pool  52 ) is overflowed. 
     Furthermore, in the laundry treatment apparatus, the water W is supplied to the steam reverse flow-preventing unit  50  after an amount of fabrics is sensed because the water supplied while sensing the amount of the fabrics, which is performed at the initial stage of the dry cycle, can be overflowed. 
     That is, the laundry treatment apparatus first senses the amount of the fabrics if the dry cycle has been input in steps S 11  and S 12 . 
     At this time, the amount of the fabrics can be sensed using a time, which is taken for the drum  36  to rotate once from the start-up of the motor  15 . If the motor  15  reaches a set RPM after the start-up, the motor is kept to a constant velocity for a set time and is then turned off. It is possible to sense the amount of the fabrics by adding a value in which an average value of a pulse width modulation (PWM) duty value from when the motor starts up to when the motor is kept to the constant velocity and a PWM duty value obtained by measuring a marginal rotary angle since the motor  30  is turned off is multiplied by a proportional constant, and a value in which a rotary angle by marginal force is multiplied by a proportional constant. 
     The laundry treatment apparatus decides a subsequent dry time, etc. based on the sensed amount of the fabrics and controls the motor  15 , the heater  41 , the circulation fan  42 , and the coolant valve  48  to begin the dry cycle in step S 13 . 
     The laundry treatment apparatus opens the water supply valve  32   a  for a set time (for example, 20 to 30 seconds) so that the water can be supplied to the condensing pool  52  when the motor  15  rotates the drum  36  in a one-way direction (for example, at the time of the first left rotation of alternating left and right rotations) for the first time after the amount of the fabrics is sensed (step S 12 ) in steps S 14  and S 15 . 
     The laundry treatment apparatus does not open the water supply valve  32   a  until the motor  15  rotates the drum  36  in a one-way direction for the first time and waits in steps S 14  and S 16 . 
     The set time may be set in proportion to the capacity of the condensing pool  52 . When the capacity of the condensing pool  52  is small, the set time is set so that a small amount of the water W is supplied. When the capacity of the condensing pool  52  is great, the set time is set so that a relatively great amount of the water W is supplied. 
     The opening of the water supply valve  32   a  may be performed after the dry process is performed for a long time or may be performed at the initial stage of the dry process as described above. It is preferred that the opening of the water supply valve  32   a  is performed when the drum  20  is rotated in a one-way direction for the first time, as described above, in order to efficiently preclude steam generated at the early stage of the dry process. 
     In the laundry treatment apparatus of the present embodiment, when the water supply valve  32   a  is turned on, the water W of the external hose  31   a  is supplied to the water supply hose  33   a  via the water supply valve  32   a . The water W is then guided to the inside of the water supply port  18  of the tub  10  sequentially through the dispenser  37 , the detergent holder  36 , the detergent holder housing  35 , and the water supply bellows  38 . 
     The water W guided to the water supply port  18  of the tub  10  is guided to the top surface of the shielding unit  62  of the cap  60  and is dropped to the water supply unit  64  of the cap  60 . The water W fills the condensing pool  52 . 
     Meanwhile, in the laundry treatment apparatus, the steam W′ is generated within the tub  10  by controlling the heater  71  and the circulation fan  72 . A portion of the steam W′ rises along the water supply passage  51 . 
     The risen steam W′ is stopped by the shielding unit  62  of the cap  60 . The risen steam W′ is then brought in contact with the water W filled in the condensing pool  52  and is condensed accordingly, so that the steam W′ does not flow backward to the upper side of the water supply port  18  of the tub  10 . 
     In the laundry treatment apparatus, dry according to an amount of fabrics is performed with the reverse flow of the steam W′ being stopped as described above. If the dry process is completed, a cold-wind dry process in which only the motor  25  and the circulation fan  42  are controlled is performed and the whole dry process is finished in step S 17 . 
     Meanwhile, the present invention is not limited to the above-mentioned embodiments, but may be applied to hot-water washing in which washing is performed by hot water supplied through the hot-water valve  32   c  and steam washing in which washing is carried out by high-temperature steam, which is generated from a steam generating device, while spraying the steam toward the inside of the drum through the hoses, nozzles, and the like. The present invention may also be applied to a case where the steam reverse flow-preventing unit  50  is disposed within the water supply bellows  38  or the detergent holder  36 . It will be evident to those having ordinary skill in the art that the present invention can be implemented in various ways within the scope of the present invention. 
     The laundry treatment apparatus constructed above according to an embodiment of the present invention has the following advantages. 
     In accordance with the laundry treatment apparatus according to the present invention, steam flowing backward from the inside of the tub to the water supply port of the tub is brought into contact into with water contained in the condensing pool formed in the water supply port of the tub and is condensed. Therefore, the present invention is advantageous in that it can prevent the pollution of the detergent holder or peripheral portions thereof, which may occur when steam flows backward into the detergent holder or peripheral portions thereof via the water supply port of the tub. 
     Furthermore, in the laundry treatment apparatus of the present invention, the condensing pool is formed within the water supply port of the tub. Therefore, the present invention is advantageous in that the structure is simple compared with when the condensing pool is formed in the tub, the water supply bellows or the detergent holder and damage to the water supply bellows, the detergent holder or the like due to high-temperature steam can be prevented. 
     Furthermore, in the laundry treatment apparatus of the present invention, the cap mounted in the water supply port of the tub guides water supplied to the water supply passage of the tub to the condensing pool and also guides steam flowing backward through the water supply passage to the condensing pool. Accordingly, the water supply channel of the water is identical to the reverse flow passage of the steam. Therefore, the present invention is advantageous in that an additional water supply channel for containing water in the condensing pool is unnecessary and the structure is simple. 
     Furthermore, in the laundry treatment apparatus of the present invention, the top surface of the condensing pool is opened, and the circumferential portion is isolated from the inner wall of the water supply port. Accordingly, the water supply channel of the water has a zigzag shape in which the ∪-shaped passage and the ∩-shaped passage are continuous. Therefore, the present invention is advantageous in that it can supply water to the tub easily while leaving a predetermined amount of water in the condensing pool. 
     Furthermore, in the laundry treatment apparatus of the present invention, at least one rib is formed between the circumferential portion of the condensing pool and the inner wall of the water supply port. Therefore, the present invention is advantageous in that the condensing pool can be integrally formed within the water supply port and the water supply channel of water overflowing from the condensing pool can be secured. 
     Furthermore, in the laundry treatment apparatus of the present invention, the bottom surface of the condensing pool is formed on the same concentric cycle as the tub. Therefore, not only the collision of the condensing pool and the drum can be prevented, but also an internal capacity of the condensing pool can be maximized. Accordingly, the present invention is advantageous in that it can prevent the reverse flow of a portion of steam, which may occur when an amount of water within the condensing pool is small. 
     Furthermore, the laundry treatment apparatus of the present invention includes the shielding unit having the cap disposed on the upper side of the water supply passage, for preventing the rise of steam, and the hollow water supply unit integrally formed with the shielding unit and projecting toward the inside of the condensing pool. Therefore, the present invention is advantageous in that it can supply water and can also preclude steam using a simple structure. 
     Furthermore, in the laundry treatment apparatus of the present invention, the shielding unit has an outer diameter fit into the inner wall of the water supply port. Therefore, the present invention is advantageous in that it can prevent steam from leaking between the cap and the water supply port. 
     Furthermore, in the laundry treatment apparatus of the present invention, the water supply unit has a tapered diameter and the space between the water supply unit and the outer wall unit of the condensing pool is sufficiently wide. Therefore, the present invention is advantageous in that water can be overflowed widely over the whole top surface of the condensing pool and the supply of water is convenient. 
     Furthermore, in the laundry treatment apparatus of the present invention, the bottom end of the water supply unit is formed lower than the top surface of the condensing pool. Therefore, the present invention is advantageous in that steam is not brought in contact with water and can be prevented from flowing backward through the bottom end of the water supply unit. 
     Furthermore, in the laundry treatment apparatus of the present invention, the bottom end of the water supply unit is isolated from the bottom surface of the condensing pool, and the bottom end of the water supply unit is not stopped by the bottom surface of the condensing pool accordingly. Therefore, the present invention is advantageous in that water can be supplied easily and rapidly. 
     Furthermore, in the method of controlling the laundry treatment apparatus according to the present invention, if a water temperature within the tub is higher than a set temperature at which steam is generated within the tub, water is supplied to the steam reverse flow-preventing unit installed on the water supply channel. The water supplied to the steam reverse flow-preventing unit precludes the reverse flow of the steam. Therefore, the present invention is advantageous in that it can minimize the reverse flow of steam and can prevent the contamination of the detergent holder, and the like. 
     Furthermore, in the method of controlling the laundry treatment apparatus according to the present invention, the supply of water to the steam reverse flow-preventing unit is repeated at predetermined time intervals. Therefore, although the water supplied to the steam reverse flow-preventing unit is overflowed because of vibration, etc., new water can be supplied continuously. Accordingly, the present invention is advantageous in that it can preclude the reverse flow of steam consistently at the time of hot-water washing. 
     Furthermore, in the method of controlling the laundry treatment apparatus according to the present invention, the water supply valve is opened for a set time, which is proportional to the capacity of the condensing pool of the steam reverse flow-preventing unit. Therefore, the present invention is advantageous in that it can prevent the excess or shortage of water supplied to the condensing pool. 
     Furthermore, in the method of controlling the laundry treatment apparatus according to the present invention, if the dry cycle is input, water for condensing steam is supplied to the steam reverse flow-preventing unit installed on the water supply channel. Therefore, the present invention is advantageous in that it can prevent the reverse flow of steam, which has occurred during the dry cycle, although the water of the steam reverse flow-preventing unit is overflowed during the dehydration cycle anterior to the dry cycle. 
     Furthermore, in the method of controlling the laundry treatment apparatus according to the present invention, since water supplied while sensing an amount of fabrics can be overflowed, the water is supplied to the steam reverse flow-preventing unit after the sensing of the amount of fabrics. Therefore, the present invention is advantageous in that it can minimize an amount of water supplied and the number of water supplied. 
     While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.