Patent Publication Number: US-2012024021-A1

Title: Washing machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Korean Patent Application No. 2010-0073968, filed on Jul. 30, 2010, and No. 2010-0091569, filed on Sep. 17, 2010, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a washing machine having a water supply unit provided with a branch pipe allowing a portion of water supplied to a tub to be utilized for purposes other than washing. 
     2. Description of the Related Art 
     In general, a washing machine is an apparatus which includes a drum to receive laundry, for example, such as clothes, and a motor to drive the drum, and performs a series of washing, rinsing and spin-drying cycles using rotation of the drum. 
     The washing machine is provided with a door glass on the front surface thereof such that the inside of the washing machine can be viewed. During the washing or rinsing cycle, detergents used in washing or contaminants separated from the laundry may stick to the door glass. These detergents or contaminants not only provide a bad impression to a user but also contact the laundry and thus re-contaminate the laundry while the laundry is taken out of the drum after completing washing of the laundry. 
     The washing machine receives water required to perform washing or rinsing of the laundry from an external water supply source. For this purpose, the washing machine is provided with water supply hoses connected to the external water supply source. 
     During operation of the washing machine, water containing the detergents or contaminants may flow backward to the water supply hoses. The backflow of water is introduced into the external water supply source and is then contaminates the external water supply source, thereby causing environmental problems. 
     SUMMARY 
     Therefore, it is an aspect to provide a washing machine having a water supply unit provided with a branch pipe. 
     Additional aspects of the invention will be set forth in part in the description which follows and will be apparent from the description, or may be learned by practice of the invention. 
     In accordance with one aspect, a washing machine includes a main body, a tub provided within the main body, a water supply hose connected to a water supply source to supply water to the tub, a water supply unit including channels defined by at least one inlet and at least one outlet and at least one structure discriminated from the channels, at least one of the at least one inlet and the at least one outlet being connected to the water supply hose, and a branch pipe provided on the water supply unit to allow a portion of water introduced into the water supply unit to branch off and be discharged to the outside of the water supply unit. 
     The water supply unit may be a detergent supply device provided to supply detergents to the tub. 
     The detergent supply device may include at least one inlet pipe protruded from the at least one inlet so as to be connected to the water supply hose, and the branch pipe may branch off from the at least one inlet pipe. 
     The at least one inlet may include a first inlet into which water is introduced during a main washing cycle and a second inlet into which water is introduced during a preliminary washing cycle, the at least one inlet pipe may include a first inlet pipe protruded from the first inlet and a second inlet pipe protruded from the second inlet, and the branch pipe may be fixed to the second inlet pipe so as to communicate with the second inlet pipe. 
     The branch pipe may be extended downwards. 
     A cross-sectional area of the branch pipe may be smaller than a cross-sectional area of the at least one inlet pipe from which the branch pipe branches off. 
     A length of the second inlet pipe may be greater than a length of the first inlet pipe. 
     The water supply unit may be a backflow prevention device provided to prevent wash water from flowing backward and being introduced into the water supply source. 
     The backflow prevention device may include a case provided with the at least one inlet and the at least one outlet and a backflow blocking unit disposed within the case to block a backflow of water into the at least one inlet, and the at least one inlet may be connected to the water supply hose and the at least one outlet may be a plurality of outlets provided so as to discharge water in different directions. 
     The case may include a nozzle part provided with the at least one inlet and a connector part provided with the at least one outlet. 
     The nozzle part and the connector part may be coupled with each other by screw connection. 
     The backflow blocking unit may include a moving member moving within the case according to a water flow so as to selectively open and close the at least one inlet. 
     The backflow blocking unit may further include a separation member disposed around the at least one outlet so as to separate the moving member from the at least one outlet. 
     The backflow blocking unit may further include an inclined surface part formed on the inner wall of the case so as to guide the moving member to the at least one inlet. 
     The moving member may be a spherical ball having a designated diameter, and the diameter of the ball may be greater than a diameter of the at least one inlet. 
     The moving member may be closely adhered to the at least one inlet due to water pressure and close the at least one inlet when water flows backward in the direction of the at least one inlet. 
     The case may include an outlet pipe connected to one of the plurality of outlets and protruded to the outside of the case, and at least one of the plurality of outlets may be formed on the side wall of the outlet pipe. 
     The branch pipe may communicate with the at least one of the plurality of outlets formed on the side wall of the outlet pipe and be protruded to the outside of the outlet pipe. 
     The washing machine may further include a door to open and close the main body and a door washing hose to guide water to the rear surface of the door, and the branch pipe may be connected to the door washing hose. 
     In accordance with another aspect, a washing machine includes a main body, a tub provided within the main body, a water supply hose connected to a water supply source to supply water to the tub, and a backflow prevention device mounted on the water supply hose to prevent wash water in the tub from flowing backward and being introduced into the water supply source, wherein the backflow prevention device includes a backflow prevention part provided with an inlet and an outlet, an inlet channel communicating with the inlet, outlet channels communicating with the outlet, and a backflow blocking unit disposed in the backflow prevention part to prevent water from flowing backward into the inlet channel, and the outlet channels include a first outlet channel and a second outlet channel formed separately from the first outlet channel. 
     The second outlet channel may branch off from the first outlet channel. 
     The second outlet channel may directly communicate with the backflow prevention part. 
     In accordance with another aspect, a washing machine includes a main body, a tub provided within the main body, a water supply hose connected to a water supply source to supply water to the tub, and a detergent supply device connected to the water supply hose to supply detergents to the tub, wherein the detergent supply device includes a housing, inlet pipes protruded to the outside of the housing so as to be connected to the water supply hose, and a branch pipe branching off from at least one of the inlet pipes. 
     In accordance with another aspect, a washing machine includes a main body provided with an inlet through which laundry is put into the main body, a tub formed within the main body and provided with an opening corresponding to the inlet, a door to open and close the inlet, a gasket to shield a space between the inlet and the opening, a water supply hose connected to a water supply source to supply water to the tub, a door washing hose connected to a wash water spray hole formed on the gasket, and a backflow prevention device mounted on the water supply hose to prevent wash water from flowing backward along the water supply hose and being introduced into the water supply source, wherein the backflow prevention device includes a case, an inlet pipe and an outlet pipe communicating with the inside of the case and protruded to the outside of the case, a backflow blocking unit disposed at the inside of the case, and a branch pipe forming a channel separately from the outlet pipe, and the branch pipe is connected to the door washing hose. 
     In accordance with another aspect, a detergent supply device includes a housing, a detergent container provided within the housing so as to receive detergents, inlet pipes protruded to the outside of the housing so as to supply water to the detergent container, and a branch pipe fixed to at least one of the inlet pipes so as to allow a portion of water introduced into the inlet pipe to branch off. 
     In accordance with a further aspect, a backflow prevention device includes a case including a nozzle part provided with an inlet and a connector part provided with an outlet, a backflow blocking unit disposed within the case to prevent water within the case from flowing backward and being introduced into the inlet, and a branch hole forming a channel separately from the outlet, wherein the nozzle part and the connector part are coupled with each other by screw connection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a cross-sectional view illustrating a main configuration of a washing machine in accordance with one embodiment; 
         FIG. 2  is an exploded perspective view of a detergent supply device of the washing machine in accordance with the embodiment; 
         FIG. 3A  is a plan view illustrating water supply channels of the detergent supply device shown in  FIG. 2 ; 
         FIG. 3B  is a cross-sectional view illustrating an inlet pipe and a branch pipe of the detergent supply device shown in  FIG. 2 ; 
         FIG. 4A  is a cross-sectional view illustrating a main configuration of a washing machine in accordance with another embodiment; 
         FIG. 4B  is a view illustrating connection between a backflow prevention device and a detergent supply device of the washing machine in accordance with the embodiment; 
         FIG. 5  is an exploded perspective view of the backflow prevention device in accordance with the embodiment; 
         FIG. 6A  is a cross-sectional view of the backflow prevention device in accordance with the embodiment; 
         FIG. 6B  is a cross-sectional view of a backflow prevention device in accordance with a further embodiment; and 
         FIGS. 7A and 7B  are views illustrating operation of a backflow prevention device in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
       FIG. 1  is a cross-sectional view illustrating a main configuration of a washing machine in accordance with one embodiment. 
     As shown in  FIG. 1 , a washing machine  1  in accordance with this embodiment includes a main body  10  forming the external appearance of the washing machine  1 , a tub  20  disposed within the main body  10 , a drum  30  rotatably disposed within the tub  20 , and a motor  40  to drive the drum  30 . 
     An inlet  14  through which laundry is put into the drum  30  is formed through the front surface portion of the main body  10 , and is opened and closed by a door  12  installed on the front surface portion of the main body  10 . Further, a door glass  13  made of a transparent material is mounted along the inner circumferential surface of the door  12  such that a user may view the interior of the drum  30  with the naked eye. 
     An opening  21  is formed on the front surface portion of the tub  20  at a position corresponding to the inlet  14  of the main body  10 . In order to shield a space between the inlet  14  of the main body  10  and the opening  21  of the tub  20 , a gasket  11  connecting the inlet  14  and the opening  21  is installed. The gasket  11  is fixed to the main body  10  and the tub  20 , respectively. The gasket  11  may be made of an elastic material so as to cope with vibration of the tub  20 . 
     Water supply hoses  60  to supply wash water to the tub  20  are installed above the tub  20 . One end of each of the water supply hoses  60  is connected to an external water supply source (not shown) and the other end of each of the water supply hoses  60  is connected to a detergent supply device  100 . Here, the other end of each of the water supply hoses  60  may be connected directly to the detergent supply device  100 . 
     The detergent supply device  100  is connected to the tub  20  through a connection hose  64 . Water supplied through the water supply hoses  60  is supplied to the detergent supply device  100  and is mixed with detergents in the detergent supply device  100 . Then, water containing the detergents is supplied to the inside of the tub  20 . 
     A drain pump  70  and a drain pipe  72  to discharge the water in the tub  20  to the outside of the main body  10  are installed under the tub  20 . 
     The drum  30  includes a cylindrical member  31 , a front plate  32  disposed at the front part of the cylindrical member  31 , and a rear plate  33  disposed at the rear part of the cylindrical member  31 . An opening  32   a  through which the laundry is put into the drum  30  is formed on the front plate  32 , and a drive shaft  42  to transmit drive force of the motor  40  is connected to the rear plate  33 . 
     A bearing housing  50  is installed on the rear wall of the tub  20  so as to rotatably support the drive shaft  42 . The bearing housing  50  is made of an aluminum alloy and is inserted into the rear wall of the tub  20  when the tub  20  is formed through injection molding. Bearings  52  are installed between the bearing housing  50  and the drive shaft  42  so as to efficiently rotate the drive shaft  42 . 
     The drive shaft  42  is disposed between the drum  30  and the motor  40 . One end of the drive shaft  42  is connected to the rear plate  33  of the drum  30 , and the other end of the drive shaft  42  is extended to the outside of the rear wall of the tub  20 . When the motor  40  drives the drive shaft  42 , the drum  30  connected to the drive shaft  42  is rotated around the drive shaft  42 . 
     A plurality of through holes  34  to circulate wash water is formed through the circumferential surface of the drum  30 , and a plurality of lifters  35  to tumble laundry during rotation of the drum  30  is installed on the inner circumferential surface of the drum  30 . 
     During the washing and rinsing cycles, the motor  40  rotates the drum  30  at a low velocity in regular and reverse directions. As the laundry in the drum  30  is repeatedly tumbled due to rotation of the drum  30 , contaminants are removed from the laundry. 
     During the spin-drying cycle, the motor  40  rotates the drum at a high velocity in one direction, thereby removing water from the laundry using centrifugal force applied to the laundry. 
     A device which allows water supplied from the external water supply source (not shown) to pass through the inside of the device and includes at least one structure except for internal channels may be defined as a water supply unit. That is, the water supply unit is provided with an inlet and an outlet and includes internal channels and structures discriminated from the channels, and at least one of the inlet and the outlet is connected to the water supply hose  60 . For example, since the detergent supply device  100  is provided with inlets  129  and an outlet  131  and includes internal channels along which water flows and structures discriminated from the channels, for example, such as a siphon device  147 , a detergent container  140 , and guide rails  132 , and the inlets  129  of the detergent supply device  100  are connected to the water supply hoses  60 , the detergent supply device  100  may be referred to as a water supply unit. On the other hand, since a Y-shaped connector or a T-shaped connector mounted on the water supply hoses  60  includes no structure discriminated from internal channels in addition to internal walls forming the internal channels, such a connector may not be referred to as a water supply unit. In addition to the detergent supply device  100 , a steam generator (not shown), a backflow prevention device (not shown), and water supply valves  62  may be referred to as water supply units. 
     Detergents or contaminants removed from the laundry may stick to the door glass  13  during the washing and rinsing cycles. When the laundry is taken out of the drum  30  after washing of the laundry, the laundry comes into contact with the door glass  13  and thus may be re-contaminated with the detergents or the contaminants. 
     Therefore, the washing machine  1  includes a door washing hose  61  to guide water from the water supply source (not shown) to the door glass  13  so as to wash the door glass  13 . A spray hole  11   a  to spray water toward the door glass  13  is formed on the gasket  11 , and the door washing hose  61  is connected to the spray hole  11   a . The door washing hose  61  may branch off from the water supply hose  60  or be connected to the external water supply source (not shown) separately from the water supply hoses  60 . 
     In order to allow the door washing hose  61  to branch off from the water supply hose  60  or to connect the door washing hose  61  to the external water supply source (not shown) separately from the water supply hoses  60 , a separate component is required. Particularly, if a separate branch component, for example, such as the Y-shaped connector or the T-shaped connector, is mounted on the water supply hose  60  and then the door washing hose  61  is connected to the separate branch component, production costs may be increased and water leakage at a connection portion between the components may occur. 
     Therefore, the washing machine  1  includes the detergent supply device  100  provided with a branch pipe  150  to supply water to the door washing hose  61 . 
       FIG. 2  is an exploded perspective view of the detergent supply device of the washing machine in accordance with the embodiment,  FIG. 3A  is a plan view illustrating water supply channels of the detergent supply device shown in  FIG. 2 , and  FIG. 3B  is a cross-sectional view illustrating an inlet pipe and a branch pipe of the detergent supply device shown in  FIG. 2 . 
     As shown in  FIGS. 2 to 3B , the detergent supply device  100  includes a housing  101 , the front surface of which is opened, and a detergent container  140  detachably connected to the front surface of the housing  101 . The detergent container  140  includes detergent storage parts  143 ,  144 ,  145  and  146  formed so as to be divided from one another by a front surface  141   a , a rear surface  141   d , side walls  141   b  and  141   c  of a tray  141 , and diaphragms  142   a ,  142   b  and  142   c.    
     The housing  101  includes an upper housing part  120 , a lower housing part  130 , and a cover  110  to cover the upper portion of the upper housing part  120 . First, second, third and fourth water supply parts  123 ,  124 ,  125  and  126  divided from one another by a plurality of diaphragms, are provided within a rectangular side wall  122  on the front surface of the upper housing part  120 . The first, second, third and fourth water supply parts  123 ,  124 ,  125  and  126 , are provided with inlets  129   a ,  129   b ,  129   c  and  129   d  respectively connected to water supply valves  62   a ,  62   b ,  62   c  and  62   d  and the water supply hoses  60 . 
     A plurality of through holes  128  to supply water, introduced into the respective water supply parts  123 ,  124 ,  125  and  126  through the inlets  129   a ,  129   b ,  129   c  and  129   d , to the inside of the detergent container  140 , are provided on the bottom of the upper housing part  120 . The through holes  128  are properly distributed along channels  123   b ,  124   b ,  125   b  and  126   d  formed in the respective water supply parts  123 ,  124 ,  125  and  126 . 
     The lower housing part  130  is provided with an outlet  131  connected to the connection hose  64  shown in  FIG. 1  so as to supply water having passed through the through holes  128  of the upper housing part  120  to the tub  20  shown in  FIG. 1 . The outlet  131  is sloped downwards at the rear portion thereof such that the water easily flows to the outlet  131 . Guide rails  132  are provided on both side surfaces of the lower housing part  130  such that the detergent container  140  may be slidably connected to the lower housing part  130  along the guide rails  132 . 
     The detergent container  140  includes the tray  141 , the upper surface portion of which is opened, and the tray  141  is divided into a main washing detergent storage part  143 , a bleaching detergent storage part  145 , and a rinsing detergent storage part  146  by the front surface  141   a , the rear surface  141   d , the side walls  141   b  and  141   c , and the diaphragms  142   a ,  142   b  and  142   c . Further, a preliminary washing detergent storage part  144  used during a preliminary washing cycle may be selectively installed. 
     The rear portion of the main washing detergent storage part  143  is opened such that supplied water is discharged to the outlet  131  via the first water supply part  123  and the through holes  128 . A siphon device  147  to discharge supplied water to the outlet  131  is formed on the bottom of each of the bleaching detergent storage part  145  and the rinsing detergent storage part  146 . The bottoms of the main washing detergent storage part  143 , the preliminary washing detergent storage part  144 , the bleaching detergent storage part  145 , and the rinsing detergent storage part  146  are sloped downwards at the rear portions thereof. 
     Water supplied from the external water supply source through the water supply valves  62  and the water supply hoses  60  is supplied to the inside of the detergent supply device  100  through the respective inlets  129   a ,  129   b ,  129   c , and  129   d.    
     As the water supplied to the inside of the detergent supply device  100  passes through the first, second, third, and fourth water supply parts  123 ,  124 ,  125  and  126  and the detergent storage parts  143 ,  144 ,  145 , and  146  according to the washing, rinsing, and spin-drying cycles, the water is mixed with detergents and is then supplied to the tub  20  shown in  FIG. 1  through the outlet  131  and the connection hose  64 . 
     During the preliminary washing cycle, water supplied through the water supply valve  62   b  is introduced into the through holes  128  disposed in the second water supply part  124 . The water is mixed with a detergent stored in the preliminary washing detergent storage part  144  and is then supplied to the tub  20 . 
     During the main washing cycle, water supplied through the water supply valves  62   a  and  62   c  is introduced into the through holes  128  disposed in the first water supply part  123 . The water is mixed with a detergent stored in the main washing detergent storage part  143  and is then supplied to the tub  20 . 
     The rinsing cycle is repeated twice. During the first rinsing cycle, water supplied through the water supply valve  62   d  is mixed with a bleaching agent via the third water supply part  125  and the bleaching detergent storage part  145  and is then supplied to the tub  20 . During the second rinsing cycle, water supplied through the water supply valves  62   a  and  62   d  is mixed with a fabric softener via the fourth water supply part  126  and the rinsing detergent storage part  146  and is then supplied to the tub  20 . 
     The detergent supply device  100  is provided with first, second, third, and fourth inlet pipes  127   a ,  127   b ,  127   c , and  127   d  protruded outward so as to connect the respective inlets  129   a ,  129   b ,  129   c , and  129   d  to the water supply hoses  60 . 
     Since the branch pipe  150  is connected to the door washing hose  61 , water introduced into the door washing hose  61  through the branch pipe  150  may contain no detergent such that water containing no detergent is introduced into the branch pipe  150 . Therefore, the branch pipe  150  may branch off from at least one of the first, second, third, and fourth inlet pipes  127   a ,  127   b ,  127   c , and  127   d.    
     A branch hole  151  is formed on the side wall of the at least one of the first, second, third, and fourth inlet pipes  127   a ,  127   b ,  127   c  and  127   d , and the branch pipe  150  is extended to the outside of the at least one of the first, second, third, and fourth inlet pipes  127   a ,  127   b ,  127   c , and  127   d  so as to communicate with the branch hole  151 . The branch pipe  150  may be fixed to the outside of the at least one of the first, second, third, and fourth inlet pipes  127   a ,  127   b ,  127   c , and  127   d  so as to be extended downwards. This is carried out in consideration of an assembly process between the door washing hose  61  and the branch pipe  150  and overall space utility. 
     A portion of water supplied to the first, second, third, or fourth inlet pipe  127   a ,  127   b ,  127   c , and  127   d  through each of the water supply hoses  60  branches off into the branch pipe  150  and is then introduced into the door washing hose  61 , and the remaining portion of the water is supplied to the tub  20  shown in  FIG. 1  via the detergent supply device  100 . Since washing or rinsing of laundry requires a greater amount of water than that of water required during washing of the door glass  13 , an amount of water supplied to the tub  20  may be greater than an amount of water introduced into the door washing hose  61 . Therefore, a cross-sectional area of the branch pipe  150  may be smaller than a cross-sectional area of the inlet pipes  127   a ,  127   b ,  127   c , and  127   d.    
     The branch pipe  150  may be connected to the second inlet pipe  127   b  such that a portion of water introduced through a second water supply hose  60   b  branches off. Therefore, a portion of water introduced into the second inlet pipe  127   b  during the preliminary washing cycle may be supplied to the door washing hose  61  through the branch pipe  51 . Since the preliminary washing cycle is carried out prior to the main washing cycle and less water is introduced into the second inlet pipe  127   b  than into the first inlet pipe  127   a  throughout the overall process from the washing cycle to the spin-drying cycle, the branch pipe  150  branches off from the second inlet pipe  127   b , thereby allowing water to be more effectively used. Further, the second water supply valve  62   b  is opened so that water is introduced into the door washing hose  61  prior to completion of the spin-drying cycle. Here, a length of the second inlet pipe  127   b  is longer than that of the first, third, and fourth inlet pipes  127   a ,  127   c , and  127   d  so that the branch pipe  150  may be fixed to the side wall of the second inlet pipe  127   b.    
       FIG. 4A  is a cross-sectional view illustrating a main configuration of a washing machine in accordance with another embodiment and  FIG. 4B  is a view illustrating connection between a backflow prevention device and a detergent supply device of the washing machine in accordance with the embodiment. 
     As shown in  FIGS. 4A and 4B , a washing machine  2  in accordance with this embodiment includes a main body  10 , a tub  20 , water supply hoses  60 , water supply valves  62 , a detergent supply device  100 , and a door washing hose  61 . Such components in this embodiment are substantially the same as or similar to those in the embodiment shown in  FIG. 1 , and a detailed description thereof will thus be omitted because it is considered to be unnecessary. 
     Water containing detergents or contaminants may flow backward along the water supply hoses  60  and be introduced into a water supply source (not shown). In order to prevent such a backflow, the washing machine  2  includes a backflow prevention device  200  mounted on the water supply hose  60 . 
     Since the backflow prevention device  200  is provided with an inlet and an outlet and includes internal channels along which water flows and a structure discriminated from the channels, such as a moving member  242  (with reference to  FIG. 5 ), and the inlet of the backflow prevention device  200  is connected to the water supply hose  60 , the backflow prevention device  200  corresponds to a water supply unit. Therefore, the backflow prevention device  200  includes a branched structure connected to the door washing hose  61 . 
     The backflow prevention device  200  may be mounted on at least one of first, second, third, and fourth water supply hoses  60   a ,  60   b ,  60   c , and  60   d . For example, if the backflow prevention device  200  is mounted on the fourth water supply hose  60   d , the backflow prevention device  200  prevents a bleaching agent or a fabric rinse used in rinsing of laundry from flowing backward along the fourth water supply hose  60   d  and being introducing into the water supply source. Although the backflow prevention device  200  is mounted on any one of the water supply hoses  60   a ,  60   b ,  60   c , and  60   d , the backflow prevention device  200  may prevent contamination of the water supply source. However, since the main washing cycle is generally carried out while the washing machine  2  is used, the backflow prevention device  200  may be mounted on the first water supply hose  60   a.    
     A portion of water introduced into the backflow prevention device  200  branches off within the backflow prevention device  200  and is introduced into the door washing hose  61 . The water introduced into the door washing hose  61  is guided to the door glass  31  and is used to wash the door glass  31 . 
     Supply of water to the water supply hose  60  on which the backflow prevention device  200  is mounted may be carried out before the spin-drying cycle or during the spin-drying cycle. Hereinafter, the backflow prevention device  200  mounted on the first water supply hose  60   a  will be described. 
     The first water supply valve  62   a  may be opened so as to supply water to the first water supply hose  60   a . A portion of the water supplied to the first water supply hose  60   a  is branched off within the backflow prevention device  200  and is supplied to the detergent supply device  100 , and the remaining portion of the water is guided to the door glass  13  through the door washing hose  61 . The water supplied to the detergent supply device  100  is supplied to the tub  20  through the connection hose  64 , and the water guided to the door glass  13  is used to wash the door glass  13 . Here, an amount of the water branched off into the door washing hose  61  may be about 40% of the total amount of water supplied to the backflow prevention device  200 . 
     A control unit (not shown) opens the first water supply valve  62   a  so as to supply water to the first water supply hose  60   a  at least five minutes before the spin-drying cycle is terminated. A time for which water supply is carried out is about 10 seconds, and an amount of water supplied to the first water supply hose  60   a  for this time may be about 1 liter (1 l). 1 l of water is divided within the backflow prevention device  200  so that 600 ml of water is supplied to the tub  20  through the detergent supply device  100  and 400 ml of water is guided to the door glass  13  through the door washing hose  61  and used to wash the door glass  13 . Here, the water supplied to the tub  20  is discharged to the outside through the spin-drying cycle. 
       FIG. 5  is an exploded perspective view of the backflow prevention device in accordance with the embodiment and  FIG. 6A  is a cross-sectional view of the backflow prevention device in accordance with the embodiment. 
     As shown in  FIGS. 5 and 6A , the backflow prevention device  200  includes a case  210  provided with an inlet  261  and an outlet  262  and a backflow blocking unit  240  disposed within the case  210 . 
     The case  210  forms the external appearance of the backflow prevention device  200 , and a backflow prevention part  260  communicating with the inlet  261  and the outlet  262  is provided within the case  210 . The backflow blocking unit  240  is disposed in the backflow prevention part  260 . 
     The case  210  includes a nozzle part  220  on which the inlet  261  is formed, and a connector part  230  on which the outlet  262  is formed. The backflow prevention part  260  is defined by the inner walls of the nozzle part  220  and the connector part  230 . The nozzle part  220  and the connector part  230  are coupled through screw connection, thus forming the case  210 . In order to achieve screw connection, screw threads  222  and  234  having a corresponding shape may be formed on the nozzle part  220  and the connector part  230 . 
     In order to prevent water leakage at a connection area between the nozzle part  220  and the connection part  230 , a sealing member  250  may be disposed between the nozzle part  220  and the connector part  230 . The sealing member  250  may be a ring-shaped packing made of an elastic material, for example, such as rubber. 
     The inlet  261  is formed at one side of the nozzle part  220 . The inlet  261  has a circular cross-section. The inlet  261  communicates with the water supply hose  60 , and water in the water supply hose  60  is introduced into the backflow prevention part  260  through the inlet  261 . 
     The nozzle part  220  includes an inlet pipe  221  communicating with the inlet  261  and provided with one end fixed to the nozzle part  220  and the other end protruded to a designated length to the outside of the nozzle part  220 . The inlet pipe  221  may be formed integrally with the nozzle part  220 , or be formed separately and is then connected to the nozzle part  220 . 
     The water supply hose  60  is made of an elastic material, for example, such as rubber, and is connected to the inlet pipe  221  such that the water supply hose  60  surrounds a part of one end of the inlet pipe  221 . Here, a clamp  63  to fix the water supply hose  60  to the inlet pipe  221  may be mounted. 
     An inlet channel  270  is defined by the inlet  261  and the inlet pipe  221 . Water supplied through the water supply hose  60  is introduced into the backflow prevention part  260  via the inlet channel  270 . The water introduced into the backflow prevention part  260  is discharged to the outside through the outlet  262 . 
     The outlet  262  is formed at one side of the connector part  230 . The connector part  230  includes an outlet pipe  231  communicating with the outlet  262  and provided with one end fixed to the connector part  262  and the other end protruded to a designated length to the outside of the connector part  230 . The outlet pipe  262  may be formed integrally with the connector part  230 , or be formed separately and is then connected to the connector part  230 . 
     An outlet channel  280  is defined by the outlet  262  and the outlet pipe  231 . The water introduced into the backflow prevention part  260  is discharged to the outside through the outlet channel  280 . 
     The outlet  262  is divided into a first outlet  263  and a second outlet  264 . The water introduced into the backflow prevention part  260  is branched off by the first outlet  263  and the second outlet  264  and is then discharged to the outside. Water discharged through the first outlet  263  is supplied to the tub  20  through the water supply hose  60 . Here, the second outlet  264  is a branch outlet. 
     The outlet pipe  231  is divided into a first outlet pipe  232  communicating with the first outlet  263  and protruded to a designated length to the outside of the connector part  230 , and a second outlet pipe  233  communicating with the second outlet pipe  264  and protruded to a designated length to the outside of the connector part  230 . A first outlet channel  281  is defined by the first outlet  262  and the first outlet pipe  232 , and a second outlet channel  282  is defined by the second outlet  264  and the second outlet pipe  233 . Such a channel branched structure of the backflow prevention device  200  reduces production costs, as compared with mounting of a separate branch component on the water supply hose  60 , and eliminates additional water leakage points generated due to mounting of the separate branch component. Here, the second outlet pipe  233  is a branch pipe. 
     Amounts of water flowing along the first outlet channel  281  and the second outlet channel  282  are determined by cross-sectional areas of the first outlet  263  and the second outlet  264 . Therefore, the cross-sectional areas of the first outlet  263  and the second outlet  264  are adjusted according to usage purposes of the respective channels  281  and  282 . 
     The first outlet channel  281  is connected to the water supply hose  60 . Therefore, water supplied to the water supply hose  60  may sequentially pass through the inlet channel  270 , the backflow prevention part  260  and the first outlet channel  281 , and then be supplied to the tub  20 . 
     The water supply hose  60  is connected to the first outlet pipe  232  such that the water supply hose  60  surrounds a part of one end of the first outlet pipe  232 . In order to fix the water supply hose  60  to the first outlet pipe  232 , the clamp  63  is provided. 
     The second outlet  264  is formed on the side wall of the first outlet pipe  232 , and the second outlet pipe  233  is fixed to the side wall of the first outlet pipe  232  and protruded to the outside of the connector part  230 . Therefore, a portion of water passing through the first outlet pipe  232  branches off into the second outlet  264  and is introduced into the second outlet pipe  233 . 
     The second outlet pipe  233  is connected to the door washing hose  61 . Therefore, water supplied to the water supply hose  60  may sequentially pass through the inlet channel  270 , the backflow prevention part  260  and the second outlet channel  282 , and then be guided to the door glass  13 . 
     The door washing hose  61  is connected to the second outlet pipe  233  such that the door washing hose  61  surrounds a part of one end of the second outlet pipe  233 . In order to fix the door washing hose  61  to the second outlet pipe  233 , a clamp  61   a  is provided. 
     The backflow blocking unit  240  is disposed within the backflow prevention part  260  and prevents water introduced into the backflow prevention part  260  from flowing backward and being introduced into the inlet channel  270 . The backflow blocking unit  240  includes a moving member  242  movably disposed in the backflow prevention part  260 . 
     The moving member  242  moves within the backflow prevention part  260  due to a flow of water within the backflow prevention part  260 , thereby selectively opening and closing the inlet  261 . When water is introduced into the inlet  261  through the inlet channel  270 , the moving member  242  moves in the direction of the outlet  262  and thus opens the inlet  261 . On the other hand, when water is introduced into the outlet  262  through the outlet channel  280 , the moving member  242  moves in the direction of the inlet  261  and thus closes the inlet  261 . 
     Since the cross-section of the inlet  261  is circular, the moving member  242  may be a spherical ball having a designated diameter so as to be closely adhered to the inlet  261 . The diameter of the ball is at least greater than the diameter of the inlet  261 . 
     The backflow blocking unit  240  includes an inclined surface part  241  inclined toward the inlet  261  so as to guide the moving member  242  to the inlet  261  when water introduced into the backflow prevention part  260  moves from the outlet  262  to the inlet  261 . 
     One end of the inclined surface part  241  is separated from the outlet  262  by a designated distance and the other end of the inclined surface part  241  is located on the frame of the inlet  261 . Further, the inclined surface part  241  may be formed on at least one of the inner wall of the nozzle part  220  and the inner wall of the connector part  230 . 
     While the inlet  261  is selectively opened and closed, the outlet  262  needs to maintain an opened state at all times. Since the moving member  242  moves in the flow direction of water within the backflow prevention part  260 , the moving member  242  may close the outlet  262  when the water flows from the inlet  261  to the outlet  262 . Therefore, in order to prevent the moving member  242  from closing the outlet  262 , the backflow blocking unit  240  includes a separation member  243  to separate the moving member  242  from the outlet  262  by a designated distance so as to prevent the moving member  242  from closing the outlet  262 . 
     The separation member  243  is disposed around the outlet  262  and protruded to the inside of the backflow prevention part  260  by a designated distance. Therefore, the moving member  242  may not approach the outlet  262  by the designated distance or less due to the separation member  243 . The separation member  243  may be fixed to one of the nozzle part  220  and the connector part  230 . The separation member  243  has the shape of a protruded rib. 
       FIG. 6B  is a cross-sectional view of a backflow prevention device in accordance with a further embodiment. 
     As shown in  FIG. 6B , a first outlet  263  and a second outlet  264  directly communicate with a backflow prevention part  260  and a second outlet pipe  233  is formed separately from a first outlet pipe  232 . The first outlet pipe  232  and the second outlet pipe  233  are fixed to a connector part  230  by a designated distance between the first outlet pipe  232  and the second outlet pipe  233 . Here, a plurality of separation members  243  is provided around the first outlet pipe  232  and the second outlet pipe  233 , respectively. 
       FIGS. 7A and 7B  are views illustrating operation of a backflow prevention device in accordance with one embodiment. 
     As shown in  FIG. 7A , when water is introduced into the backflow prevention part  260  through the inlet channel  270 , the moving member  242  moves to the outlet  262  due to a water flow. Since the separation member  243  is disposed around the outlet  262 , the moving member  242  does not close the outlet  262 . Therefore, the water introduced into the backflow prevention part  260  is discharged to the outside through the outlet channel  280  regardless of movement of the moving member  242 . Here, the water is branched off into the first outlet channel  281  and the second outlet channel  282 . Water introduced into the first outlet channel  281  is supplied to the tub  20 , and water introduced into the second outlet channel  282  is guided to the door glass  13  shown in  FIG. 1  and used to wash the door glass  13 . 
     As shown in  FIG. 7B , water may flow backward through the outlet  262  and be introduced into the backflow prevention part  260 . The moving member  242  together with water flowing toward the inlet  261  moves to the inlet  261 . The moving member  242  moves along the inclined surface part  242  and closes the inlet  261  and thus water within the backflow prevention part  260  does not flowing toward the inlet channel  270 . 
     When the moving member  242  closes the inlet  261 , a pressure difference between the inlet channel  270  and the backflow prevention part  260  occurs. Therefore, force in the direction of the inlet channel  270  is applied to the moving member  242  due to such a pressure difference, and the moving member  242  maintains the state of being closely adhered to the inlet  261  by the force. 
     When the water introduced into the backflow prevention part  260  is discharged to the outside through the outlet  262 , the force applied to the moving member  242  is eliminated, and thus the moving member  242  opens the inlet  261 . 
     As is apparent from the above description, a washing machine in accordance with one embodiment allows a branch pipe provided on a water supply unit, for example, such as a detergent supply device or a backflow prevention device, to guide water to a door glass, thereby maintaining the door glass in a clean state. Further, the washing machine does not use a separate branched structure, thereby reducing the number of necessary parts and thus reducing production costs. Moreover, the washing machine reduces the number of the necessary parts and thus simplifies an assembly process, and reduces the number of water leakage points between the parts and thus has improved durability. 
     Further, the washing machine prevents a backflow of water along a water supply hose, thereby preventing water containing detergents or contaminants from flowing backward into an external water supply source during operation of the washing machine. Therefore, environmental problems, for example, such as contamination of the water supply source due to the backflow, may be solved. 
     Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.