Patent Publication Number: US-2023157497-A1

Title: Nozzle for cleaner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 17/375,513, filed on Jul. 14, 2021, which is a continuation of U.S. application Ser. No. 16/399,013, filed on Apr. 30, 2019 (now U.S. Pat. No. 11,096,536 issued on Aug. 24, 2021), which claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2018-0050059, filed in the Republic of Korea on Apr. 30, 2018, Korean Patent Application No. 10-2018-0050085, filed in the Republic of Korea on Apr. 30, 2018, and Korean Patent Application No. 10-2018-0094341, filed in the Republic of Korea on Aug. 13, 2018, the disclosures of all of which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     The present specification relates to a nozzle for a cleaner. 
     The cleaner is a device which suctions or wipes dust or foreign matter in a region to be cleaned to perform a cleaning. 
     Such a cleaner can be classified into a manual cleaner for performing cleaning while a user directly moves the cleaner and an automatic cleaner for performing cleaning while traveling itself. 
     The manual cleaner can be classified into a canister-type cleaner, an upright-type cleaner, a handy-type cleaner, and a stick-type cleaner, according to the type of the cleaner. 
     These cleaners can clean a floor using nozzles. In general, nozzles can be used so as to suction air and dust. According to the type of the nozzle, the nozzle may be attached with a mop to clean the floor with the mop. 
     Korean Patent Registration No. 10-0405244, which is a related art 1, discloses a suction port assembly for a vacuum cleaner. 
     The suction port assembly of the related art 1 includes a suction port main body provided with a suction port. 
     The suction port main body includes a first suction path in the front, a second suction path in the rear, and a guide path formed between the first suction path and the second suction path. 
     A mop is rotatably installed on the lower end of the suction port main body, and a rotation driving unit for driving the mop is provided in the suction port main body. 
     The rotation driving unit includes one rotation motor and gears for transmitting the power of one rotation motor to a plurality of rotating bodies to which mops are attached. 
     Meanwhile, according to the related art 1, since a pair of rotating bodies disposed on both sides of the rotation driving unit is rotated using one rotating motor, if the rotating motor fails or malfunctions, there is a problem that all of the pair of rotating bodies cannot be rotated. 
     In addition, so as to rotate the pair of rotating bodies using one rotation motor, since the rotation motor is positioned at the center of the suction port main body, it is necessary to design a suction path for preventing interference with the rotation motor, and thus there are disadvantages that the length of the suction path is lengthened and the structure for forming a suction path is complicated. 
     In addition, since the related art 1 does not have a structure for supplying water to a mop, in a case where cleaning is desired to be performed using a mop with water, there is a disadvantage that a user has to directly supply water to a mop. 
     In addition, in a case of the related art 1, since the rotation motor is positioned at the central portion of the suction port main body, it is difficult to form the suction path in the central portion of the suction port main body and if the suction path is formed in the central portion of the suction port main body, there is a disadvantage that the height of the suction port main body is increased. 
     In a case where the height of the suction port main body is increased, there are disadvantages that the suction port main body does not easily enter under the furniture or narrow space and thereby the cleanable area is reduced, and the size of the suction port main body is enlarged as a whole, and thus there is a disadvantage that it inconveniences the user during operation. 
     For example, in a case where the user intends to straighten the suction port main body but the suction port main body is moved eccentrically, there is a disadvantage that the amount of eccentricity is further increased due to the weight of the suction port main body and thus it is difficult for the user to overcome the eccentricity and move the suction port main body back to the original straight path. 
     On the other hand, Korean Patent Laid-Open Publication No. 10-2017-0028765, which is the related art 2, discloses a cleaner. 
     The cleaner disclosed in the related art 2 includes a cleaner main body in which a mop is rotatably installed on a lower portion thereof, a water bottle which is mounted to a handle which is connected to the cleaner main body, a water spray nozzle which is installed so as to spray water to the front of the cleaner main body, and a water supply unit for supplying the water in the water tank to the water spray nozzle. 
     In a case of the related art 2, since the water spray nozzle is sprayed forward from a front surface of the cleaner main body, there is a possibility that the sprayed water may wet other nearby structures, instead of a mop. 
     When the water spray nozzle is disposed at the center of the cleaner main body, while the mop is arranged in the lateral direction, there is a problem that the mop cannot sufficiently absorb the water sprayed forward from the cleaner main body. 
     In addition, in a case of the related art 2, since there is no flow path for suctioning air, there is a disadvantage that only the floor can be wiped, and foreign matters present on the floor have to be manually cleaned again by the user. 
     SUMMARY OF THE INVENTION 
     The present embodiment provides a nozzle for a cleaner which can suction foreign matters on the floor while making the overall size of the nozzle small and slim. The nozzle can clean the floor by rotating a mop and supply water to the mop. 
     The present embodiment provides a nozzle for a cleaner in which the length of an air flow path for air to flow is prevented from being increased, thereby reducing the flow path loss, even when a structure capable of wiping the floor using the mop is applied. 
     The present embodiment provides a nozzle for a cleaner in which the weight of a plurality of driving devices is uniformly distributed to the left and right. 
     This embodiment provides a nozzle for a cleaner in which the driving unit cover is configured to cover the driving device, constituting the driving motor and the power transmission unit, thereby simplifying the structure of the driving unit cover and preventing the volume of the driving unit cover from becoming large. 
     The present embodiment provides a nozzle for a cleaner in which directional change is facilitated in a process of cleaning using a nozzle. 
     A nozzle for a cleaner according to an aspect includes a nozzle housing including a suction flow path through which air, containing dust, flows; a first rotation cleaning unit and a second rotation cleaning unit which are disposed on a lower side of the nozzle housing and spaced apart from each other in the lateral direction, each of the first and second rotation cleaning unit including a rotation plate to which a mop can be attached; a first driving device disposed in the nozzle housing and having a first driving motor configured to drive the first rotation cleaning unit; a second driving device disposed in the nozzle housing and having a second driving motor configured to drive the second rotation cleaning unit; and a water tank mounted on the nozzle housing and configured to store water to be supplied to the mop. 
     The nozzle housing may include a plurality of driving unit covers having a protruding shape disposed so as to surround each of the driving devices. 
     At least one of the driving unit covers may include a first protruding surface and a second protruding surface positioned higher than the first protruding surface and formed with a curvature different from that of the first protruding surface. 
     A center of the at least one of the driving unit covers and a center of the second protruding surface are eccentric. 
     An axis of each of the driving motors may be disposed at a position offset from a center of the second protruding surface. 
     The second protruding surface may be disposed so as to overlap with at least a portion of the driving motor in the vertical direction. 
     An axis of each of the driving motors may extend in a horizontal direction. 
     The axis of each of the driving motors may extend in the front and rear direction. 
     The left and right length of the second protruding surface may be longer than the front and rear length. 
     A length direction of the second protruding surface may intersect an extending direction of an axis of the driving motor. 
     A center of the driving unit cover may be positioned on the second protruding surface, and a rotation center of the rotation plate may overlap with the second protruding surface in the vertical direction. 
     The suction flow path may include a centerline in the front and rear direction, and a centerline in the front and rear direction may be positioned between each of the driving unit cover. 
     A center of the driving unit cover may be positioned between a centerline of the front and rear direction and a center of the second protruding surface. 
     An axis of the driving motor may be positioned between the centerline in the front and rear direction and the center of the driving unit cover. 
     A rotation center of each of the rotation plates may be eccentric with the center of each of the driving unit covers. 
     The center of the driving unit cover may be positioned between the centerline of the front and rear direction and the rotation center of the rotation plate. 
     The axis of the driving motor may be positioned between the centerline in the front and rear direction and the rotation center of the rotation plate. 
     A center of the second protruding surface and a rotation center of the rotation plate may be eccentric. 
     A central axis which bisects the front and rear length of the nozzle housing and the second protruding surface may vertically overlap. 
     The center of the second protruding surface may be positioned farther from the front end of the nozzle housing than the central axis. 
     The rotation center of the rotation plate may be positioned farther from the front end of the nozzle housing than the central axis. 
     The center of the driving unit cover may be positioned farther from the front end of the nozzle housing than the central axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating a nozzle for a cleaner according to an embodiment of the present invention. 
         FIG.  2    is a perspective view illustrating a nozzle for a cleaner according to an embodiment of the present invention. 
         FIG.  3    is a bottom view illustrating a nozzle for a cleaner according to an embodiment of the present invention. 
         FIG.  4    is a perspective view illustrating the nozzle for the cleaner of  FIG.  1    viewed from the rear side. 
         FIG.  5    is a sectional view taken along line A-A of  FIG.  1   . 
         FIG.  6    is an exploded perspective view illustrating a nozzle according to an embodiment of the present invention. 
         FIG.  7    is another exploded perspective view illustrating a nozzle according to an embodiment of the present invention. 
         FIG.  8    is a perspective view illustrating a water tank according to an embodiment of the present invention. 
         FIG.  9    is another perspective view illustrating a water tank according to an embodiment of the present invention. 
         FIG.  10    is a sectional view taken along line B-B in  FIG.  8   . 
         FIG.  11    is a sectional view taken along the line C-C of  FIG.  8   . 
         FIG.  12    is a sectional view taken along line D-D in  FIG.  8   . 
         FIG.  13    is a sectional view taken along line E-E of  FIG.  8   . 
         FIG.  14    is a perspective view illustrating a nozzle cover according to an embodiment of the present invention as viewed from above. 
         FIG.  15    is a perspective view illustrating a nozzle cover according to an embodiment of the present invention as viewed from below. 
         FIG.  16    is a perspective view illustrating a state where the operating unit, the first coupling unit, and the supporting body are separated from each other in the nozzle cover. 
         FIG.  17    is a sectional view taken along line F-F of  FIG.  14   . 
         FIG.  18    is a sectional view taken along the line G-G in  FIG.  16    in a state where the first coupling unit is coupled with the nozzle cover. 
         FIG.  19    is a sectional view illustrating a state where the first coupling unit and the second coupling unit are released by pressing the operation unit. 
         FIG.  20    is a view illustrating a state where a valve operating unit and a sealer are separated from each other in a nozzle cover according to an embodiment of the present invention. 
         FIG.  21    is a view illustrating a state where a flow path forming portion is coupled to a nozzle base according to an embodiment of the present invention. 
         FIG.  22    is a view illustrating a nozzle base according to an embodiment of the present invention as viewed from below. 
         FIG.  23    is a view illustrating a plurality of switches provided on a control board according to an embodiment of the present invention. 
         FIG.  24    is a view illustrating the first and second driving devices according to one embodiment of the present invention as viewed from below. 
         FIG.  25    is a view illustrating the first and second driving devices according to the embodiment of the present invention as viewed from above. 
         FIG.  26    is a view illustrating a structure for preventing rotation of the motor housing and the driving motor. 
         FIG.  27    is a view illustrating a state where a power transmission unit is coupled to a driving motor according to an embodiment of the present invention. 
         FIG.  28    is a view illustrating a state where a power transmitting unit is coupled to a driving motor according to another embodiment of the present invention. 
         FIG.  29    is a view illustrating a relationship between a rotating direction of a rotation plate and an extending direction of an axis of the driving motor according to an embodiment of the present invention; 
         FIG.  30    is a plan view illustrating a state where a driving device is installed on a nozzle base according to an embodiment of the present invention. 
         FIG.  31    is a front view illustrating a state where a driving device is installed on a nozzle base according to an embodiment of the present invention. 
         FIG.  32    is a view illustrating a structure of a driving unit cover of a nozzle cover and a disposition relationship between a rotation center of a rotation plate and a driving motor according to an embodiment of the present invention. 
         FIG.  33    is a view illustrating a rotation plate according to an embodiment of the present invention as viewed from above. 
         FIG.  34    is a view illustrating a rotation plate according to an embodiment of the present invention as viewed from below. 
         FIG.  35    is a view illustrating a water supply flow path for supplying water of a water tank to the rotation cleaning unit according to an embodiment of the present invention. 
         FIG.  36    is a view illustrating a valve in a water tank according to an embodiment of the present invention. 
         FIG.  37    is a view illustrating a state where the valve opens the discharge port in a state where the water tank is mounted on the nozzle housing. 
         FIG.  38    is a view illustrating a disposition of a rotation plate and a spray nozzle according to an embodiment of the present invention. 
         FIG.  39    is a view illustrating a disposition of a water discharge port of a spray nozzle in a nozzle main body according to an embodiment of the present invention. 
         FIG.  40    is a conceptual diagram illustrating a process of supplying water to a rotation cleaning unit in a water tank according to an embodiment of the present invention. 
         FIG.  41    is a perspective view illustrating the nozzle for the cleaner from which a connection tube is separated according to an embodiment of the present invention as viewed from the rear side. 
         FIG.  42    is a sectional view illustrating area ‘A’ in  FIG.  41   . 
         FIG.  43    is a perspective view illustrating the gasket of  FIG.  42   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG.  1    and  FIG.  2    are perspective views illustrating a nozzle for a cleaner according to an embodiment of the present invention,  FIG.  3    is a bottom view illustrating a nozzle for a cleaner according to an embodiment of the present invention,  FIG.  4    is a perspective view illustrating the nozzle for the cleaner of  FIG.  1    viewed from the rear side, and  FIG.  5    is a sectional view taken along line A-A of  FIG.  1   . 
     Referring to  FIG.  1    to  FIG.  5   , a nozzle  1  of a cleaner (hereinafter referred to as “nozzle”) according to an embodiment of the present invention includes a nozzle main body  10 , and a connection tube  50  which is connected to the nozzle main body  10  so as to be capable of moving. 
     The nozzle  1  of the present embodiment can be used, for example, in a state of being connected to a handy type cleaner or connected to a canister type cleaner. 
     In other words, the nozzle  1  may be detachably connected to a cleaner or an extension tube of a cleaner. Accordingly, the user can clean the floor using the nozzle  1  as the nozzle is connected to the cleaner or the extension tube of the cleaner. At this time, the cleaner to which the nozzle  1  is connected can separate the dust in the air by a multi-cyclone method. 
     The nozzle  1  itself has a battery to supply power to the power consumption unit therein, or can be operated by receiving power from the cleaner. 
     Since the cleaner to which the nozzle  1  is connected includes a suction motor, a suction force generated by the suction motor applies to the nozzle  1  to be capable of suctioning foreign matter and air on the floor at the nozzle  1 . Accordingly, in the present embodiment, the nozzle  1  can perform a function of suctioning foreign matter and air on the bottom surface and guiding the foreign matter and air to the cleaner. 
     Although not limited thereto, the connection tube  50  is connected to the rear central portion of the nozzle main body  10  to guide the suctioned air to the cleaner. 
     In the present embodiment, a portion of the nozzle  1  to which the connection tube  50  is connected is the rear side of the nozzle  1  and a portion of the opposite side of the connection tube  50  is the front side of the nozzle  1 . 
     Alternatively, with respect to  FIG.  3   , an upper portion is a front side of the nozzle  1  and a lower portion thereof is a rear portion of the nozzle  1 . 
     The nozzle  1  may further include rotation cleaning units  40  and  41  rotatably disposed below the nozzle main body  10 . 
     For example, a pair of rotation cleaning units  40  and  41  may be arranged in the lateral direction. The pair of rotation cleaning units  40  and  41  can be independently rotated. For example, the nozzle  1  may include a first rotation cleaning unit  40  and a second rotation cleaning unit  41 . 
     Each of the rotation cleaning units  40  and  41  may include mops  402  and  404 . The mops  402  and  404  may be formed in a disc shape, for example. The mops  402  and  404  may include a first mop  402  and a second mop  404 . 
     The nozzle main body  10  may include a nozzle housing  100  forming an outer shape. The nozzle housing  100  may include suction flow paths  112  and  114  for suctioning air. 
     The suction flow paths  112  and  114  include a first flow path  112  extending in the lateral direction in the nozzle housing  100  and a second flow path  114  communicating with the first flow path  112  and extending in the front and rear direction. 
     The first flow path  112  may be formed at a front end portion of the lower surface of the nozzle housing  100 , as an example. 
     The second flow path  114  may extend rearward from the first flow path  112 . For example, the second flow path  114  may extend rearward from the central portion of the first flow path  112  toward the connection tube  50 . 
     Accordingly, a centerline A 2  of the first flow path  112  can extend in the lateral horizontal direction. A centerline A 2  of the second flow path  114  can extend in the front and rear direction and can intersect the centerline A 2  of the first flow path  112 . However, the centerline A 2  of the second flow path  114  is not horizontal but may be inclined in the front and rear direction. 
     In this embodiment, the centerline A 2  of the second flow path  114  may be referred to as centerline of the suction flow path in the front-rear direction. 
     The centerline A 2  of the second flow path  114  may be positioned at a position where the nozzle main body  10  is bisected right and left, as an example. 
     A portion of the mops  402  and  404  is protruded to the outside of the nozzle  1  in a state where the rotation cleaning units  40  and  41  are connected to the lower side of the nozzle main body  10  and thus the rotation cleaning units  40  and  41  can clean not only a floor positioned directly below the nozzle but also the floor positioned outside the nozzle  1 . 
     For example, the mops  402  and  404  may protrude not only to both sides of the nozzle  1  but also to the rear of the nozzle  1 . 
     The rotation cleaning units  40  and  41  may be positioned on the rear side of the first flow path  112  from below the nozzle main body  10 , for example. 
     Therefore, when the nozzle  1  is advanced and cleaned, the floor can be cleaned by the mops  402 ,  404  after foreign substances and air on the floor are suctioned by the first flow path  112 . 
     In the present embodiment, the first rotation center C 1  of the first rotation cleaning unit  40  (for example, rotation center of rotation plate  420 ) and the second rotation center C 2  of the second rotation cleaning unit  41  (for example, rotation center of rotation plate  440 ) are disposed in a state of being spaced apart from each other in the lateral direction. 
     The centerline A 2  of the second flow path  114  may be positioned in a region between the first rotation center C 1  and the second rotation center C 2 . 
     The central axis Y bisecting the front and rear length L 1  of the nozzle main body  10  (except for extension portion) can be positioned forward of the rotation centers C 1  and C 2  of the respective rotation cleaning units  40  and  41 . 
     The rotation centers C 1  and C 2  of the respective rotation cleaning units  40  and  41  may be positioned farther from the front end portion of the nozzle main body  10  than the central axis Y bisecting the front and rear length L 1  of the nozzle main body  10 . This is to prevent the rotation cleaning units  40 ,  41  from blocking the first flow path  112 . 
     Accordingly, the front and rear horizontal distance L 3  between the central axis Y and the rotation centers C 1  and C 2  of the respective rotation cleaners  40  and  41  may be set to a value greater than zero. 
     In addition, the distance L 2  between the rotation centers C 1  and C 2  of the rotation cleaning units  40  and  41  may be formed to be larger than the diameter of each of the mops  402  and  404 . This is to prevent the mops  402  and  404  from interfering with each other during the rotation and to prevent the area which can be cleaned by the interfered portion from being reduced. 
     The diameters of the mops  402  and  404  are preferably 0.6 times or more than half the width of the nozzle main body  10 , although not limited thereto. In this case, the cleaning area of the floor facing the nozzle main body  10  by the mops  402  and  404  is increased, and the area for cleaning the floor not facing the nozzle main body  10  is also increased. In addition, the cleaning area by the mops  402  and  404  can be secured even with a small amount of movement when the nozzle  1  is used for cleaning. 
     In addition, the mops  402 ,  404  may be provided with sewing lines  405 . The sewing lines  405  may be positioned in a state of being spaced apart inwardly in the center direction at the edge portions of the mops  402  and  404 . The mops  402  and  404  may be formed by combining a plurality of fiber materials, and the fiber materials may be joined by the sewing lines  405 . 
     At this time, the diameters of the rotation plates  420  and  440 , which will be described later, may be larger than the distance to a portion of the sewing lines  405  relative to the centers of the mops  402  and  404 . The diameters of the rotation plates  420  and  440  may be smaller than the outer diameters of the mops  402  and  404 . 
     In this case, the rotation plates  420  and  440  can support a portion of the mops  402  and  404  positioned outside the sewing lines  405 , thereby reducing the distance between the mops  402  and  404 , and it is possible to prevent mutual friction between the mops  402  and  404  or vertical overlapping between the mops  402  and  404  due to the deformation of the mops  402  and  404  by pressing the edge portions. 
     The nozzle housing  100  may include a nozzle base  110  and a nozzle cover  130  coupled to the upper side of the nozzle base  110 . 
     The nozzle base  110  may form the first flow path  112 . The nozzle housing  100  may further include a flow path forming portion  150  forming the second flow path  114  together with the nozzle base  110 . 
     The flow path forming portion  150  may be coupled to the upper central portion of the nozzle base  110  and the end portion of the flow path forming portion  150  may be connected to the connection tube  50 . 
     Accordingly, since the second flow path  114  can extend substantially in a straight line shape in the front and rear direction by the disposition of the flow path forming portion  150 , the length of the second flow path  114  can be minimized, and thus the flow path loss in the nozzle  1  can be minimized. 
     The front portion of the flow path forming portion  150  may cover the upper side of the first flow path  112 . The flow path forming portion  150  may be disposed to be inclined upward from the front end portion toward the rear side. 
     Therefore, the height of the front portion of the flow path forming portion  150  may be lower than that of the rear portion of the flow path forming portion  150 . 
     According to the present embodiment, since the height of the front portion of the flow path forming portion  150  is low, there is an advantage that the height of the front portion of the entire height of the nozzle  1  can be reduced. The lower the height of the nozzle  1 , the more likely it is that the nozzle  1  can be drawn into a narrow space on the lower side of furniture or a chair to be cleaned. 
     The nozzle base  110  may include an extension portion  129  for supporting the connection tube  50 . The extension portion  129  may extend rearward from the rear end of the nozzle base  110 . 
     The connection tube  50  may include a first connection tube  510  connected to an end of the flow path forming portion  150 , a second connection tube  520  rotatably connected to the first connection tube  510 , and a guide tube  530  for communicating the first connection tube  510  with the second connection tube  520 . 
     The first connection tube  510  may be seated on the extension portion  129  and the second connection tube  520  may be connected to an extension tube or hose of the cleaner. 
     A plurality of rollers for smooth movement of the nozzle  1  may be provided on the lower side of the nozzle base  110 . 
     For example, the first roller  124  and the second roller  126  may be positioned behind the first flow path  112  on the nozzle base  110 . The first roller  124  and the second roller  126  may be spaced apart from each other in the lateral direction. 
     According to the present embodiment, the first roller  124  and the second roller  126  are disposed behind the first flow path  112  so that the first flow path  112  can be positioned as close as possible to the front end portion of the nozzle base  110  and thus the area which can be cleaned by using the nozzle  1  can be increased. 
     As the distance from the front end portion of the nozzle base  110  to the first flow path  112  increases, the area in which the suction force does not apply in front of the first flow path  112  during the cleaning process increases, and thus the area where the cleaning is not performed is increased. 
     On the other hand, according to the present embodiment, the distance from the front end portion of the nozzle base  110  to the first flow path  112  can be minimized, and thus the cleanable area can be increased. 
     In addition, by disposing the first roller  124  and the second roller  126  behind the first flow path  112 , the length of the first flow path  112  in the lateral direction can be maximized. 
     In other words, the distance between both end portions of the first flow path  112  and both end portions of the nozzle base  110  can be minimized. 
     In the present embodiment, the first roller  124  may be positioned in a space between the first flow path  112  and the first mop  402 . The second roller  126  may be positioned in a space between the first flow path  112  and the second mop  404 . 
     The first roller  124  and the second roller  126  may be rotatably connected to a shaft  125 , respectively. The shaft  125  may be fixed to the lower side of the nozzle base  110  in a state of being disposed so as to extend in the lateral direction. 
     The distance between the shaft  125  and the front end portion of the nozzle base  110  is longer than the distance between the front end portion of the nozzle base  110  and each of the mops  402  and  404  (or a rotation plate described later). 
     At least a portion of each of the rotation cleaning units  40  and  41  (mop and/or rotation plate) can be positioned between the shaft  125  of the first roller  124  and the shaft  125  of the second roller  126 . 
     According to this disposition, the rotation cleaning units  40  and  41  can be positioned as close as possible to the first flow path  112 , and the area to be cleaned by the rotation cleaning units  40  and  41  of the floor on which the nozzle  1  is positioned can be increased, and thus the floor cleaning performance can be improved. 
     The plurality of rollers are not limited, but the nozzle  1  can be supported at three points. In other words, the plurality of rollers may further include a third roller  129   a  provided on the extension portion  129  of the nozzle base  110 . 
     The third roller  129   a  may be positioned behind the mops  402 ,  404  to prevent interference with the mops  402 ,  404 . 
     In a state where the mops  402  and  404  are placed on the floor, the mops  402  and  404  are pressed against the floor and are in close contact with the floor, so that the friction force between the mops  402  and  404  and the bottom surface  404  is increased. In the present embodiment, since the plurality of rollers are coupled to the lower side of the nozzle base  110 , the mobility of the nozzle  1  can be improved by the plurality of rollers. 
     Meanwhile, the nozzle main body  10  may further include a water tank  200  to supply water to the mops  402  and  404 . 
     The water tank  200  may be detachably connected to the nozzle housing  100 . The water in the water tank  200  can be supplied to each of the mops  402  and  404  in a state where the water tank  200  is mounted on the nozzle housing  100 . 
     The water tank  200  can form an outer appearance of the nozzle  1  in a state of being mounted on the nozzle housing  100 . 
     The entire upper side wall of the water tank  200  substantially forms an outer appearance of an upper surface of the nozzle  1 . Therefore, the user can easily recognize that the water tank  200  is mounted or the water tank  200  is separated from the nozzle housing  100 . 
     The nozzle main body  10  may further include an operating unit  300  that operates to separate the water tank  200  in a state where the water tank  200  is mounted on the nozzle housing  100 . 
     The operating unit  300  may be provided in the nozzle housing  100  as an example. The nozzle housing  100  may be provided with a first coupling unit  310  for coupling with the water tank  200  and the water tank  200  may be provided with a second coupling unit  254  for coupling with the first coupling unit  310 . 
     The operating unit  300  may be disposed so as to be capable of vertically moving in the nozzle housing  100 . The first coupling unit  310  can be moved under the operation force of the operating unit  300  at the lower side of the operating unit  300 . 
     For example, the first coupling unit  310  may move in the front and rear direction. For this purpose, the operating unit  300  and the first coupling unit  310  may include inclined surfaces contacting each other. 
     When the operating unit  300  is lowered by the inclined surfaces, the first coupling unit  310  can move horizontally (for example, movement in the front and rear direction). 
     The first coupling unit  310  includes a hook  312  for engaging with the second coupling unit  254  and the second coupling unit  254  includes a groove  256  for inserting the hook  312 . 
     The first coupling unit  310  may be resiliently supported by the second elastic member  314  so as to maintain a state where the first coupling unit  310  is coupled to the second coupling unit  254 . 
     Therefore, when the hook  312  is in a state of being inserted into the groove  256  by the second elastic member  314  and the operating unit  300  is pressed downward, the hook  312  is separated from the groove  256 . The water tank  200  can be separated from the nozzle housing  100  in a state where the hook  312  is removed from the groove  256 . 
     The nozzle  1  may further include a support body  320  for lifting the second coupling unit  254  of the water tank  200  in a state where the hook  312  is withdrawn from the groove  256 . The operation of the support body  320  to raise the second coupling unit  254  will be described later with reference to the drawings. 
     In the present embodiment, the operating unit  300  may be positioned directly above the second flow path  114 , for example. For example, the operating unit  300  may be disposed to overlap the centerline A 2  of the second flow path  114  in the vertical direction. 
     Accordingly, since the operating unit  300  is positioned at the central portion of the nozzle  1 , there is an advantage that the user can easily recognize the operating unit  300  and operate the operating unit  300 . 
     Meanwhile, the nozzle main body  10  may further include an adjusting unit  180  for adjusting the amount of water discharged from the water tank  200 . For example, the adjusting unit  180  may be positioned on the rear side of the nozzle housing  100 . 
     The adjusting unit  180  can be operated by a user and the adjusting unit  180  can prevent the water from being discharged from the water tank  200  or the water from being discharged. 
     Alternatively, the amount of water discharged from the water tank  200  can be adjusted by the adjusting unit  180 . For example, when the adjusting unit  180  is operated, water is discharged from the water tank  200  by a first amount per unit time, or water is discharged by a second amount greater than the first amount per unit time. 
     The adjusting unit  180  may be pivotally mounted to the nozzle housing  100  in a lateral direction or may be pivoted in a vertical direction. 
     For example, in a state where the adjusting unit  180  is in the neutral position as shown in  FIG.  4   , the amount of water discharged is 0, and when the left side of the adjusting unit  180  is pushed to pivot the adjusting unit  180  to the left, water may be discharged from the water tank  200  by a first amount per unit time. 
     When the adjustment unit  180  is pushed to the right by pushing the right side of the adjustment unit  180 , the second amount of water may be discharged from the water tank  200  per unit time. The configuration for detecting the operation of the adjusting unit  180  will be described later with reference to the drawings. 
       FIG.  6    and  FIG.  7    are exploded perspective views of a nozzle according to an embodiment of the present invention, and  FIG.  8    and  FIG.  9    are perspective views of a water tank according to an embodiment of the present invention. 
     Referring to  FIG.  3    and  FIG.  6    to  FIG.  9   , the nozzle main body  10  may further include a plurality of driving devices  170  and  171  for individually driving the respective rotation cleaning units  40  and  41 . 
     The plurality of driving devices  170  and  171  may include a first driving device  170  for driving the first rotation cleaning unit  40  and a second driving device  171  for driving the second rotation cleaning unit  41 . 
     Since each of the driving devices  170  and  171  operates individually, even if some of the driving devices  170  and  171  fail, there is an advantage that some of the rotation cleaning devices can be rotated by another driving device. 
     The first driving device  170  and the second driving device  171  may be spaced apart from each other in the lateral direction in the nozzle main body  10 . 
     The driving devices  170  and  171  may be positioned behind the first flow path  112 . 
     For example, at least a portion of the second flow path  114  may be positioned between the first driving device  170  and the second driving device  171 . At this time, the first driving device  170  and the second driving device  171  may be disposed symmetrically with respect to the centerline A 2  of the second flow path  114 . 
     Therefore, even if the plurality of driving devices  170  and  171  are provided, the second flow path  114  is not affected, and thus the length of the second flow path  114  can be minimized. 
     According to the present embodiment, since the first driving device  170  and the second driving device  171  are disposed on both sides of the second flow pathway  114 , the weight of the nozzle  1  can be uniformly distributed to the left and right so that it is possible to prevent the center of gravity of the nozzle  1  from being biased toward any one side of the nozzle  1 . 
     The plurality of driving devices  170  and  171  may be disposed in the nozzle main body  10 . For example, the plurality of driving devices  170  and  171  may be seated on the upper side of the nozzle base  110  and covered with the nozzle cover  130 . In other words, the plurality of driving devices  170  and  171  may be positioned between the nozzle base  110  and the nozzle cover  130 . 
     Each of the rotation cleaning units  40  and  41  may further include rotation plates  420  and  440  which are rotated by receiving power from each of the driving devices  170  and  171 . 
     The rotation plates  420  and  440  may include a first rotation plate  420  which is connected to the first driving device  170  and to which the first mop  402  is attached and a second rotation plate  420  which is connected to the second driving device  171  and a second rotation plate  440  to which the second mop  404  is attached. 
     The rotation plates  420  and  440  may be formed in a disc shape, and the mops  402  and  404  may be attached to the bottom surfaces of the rotation plates  420  and  440 . 
     The rotation plates  420  and  440  may be connected to each of the driving devices  170  and  171  on the lower side of the nozzle base  110 . In other words, the rotation plates  420  and  440  may be connected to the driving devices  170  and  171  at the outside of the nozzle housing  100 . 
     &lt;Water Tank&gt; 
       FIG.  10    is a sectional view taken along line B-B in  FIG.  8   ,  FIG.  11    is a sectional view taken along the line C-C of  FIG.  8   ,  FIG.  12    is a sectional view taken along line D-D in  FIG.  8   , and  FIG.  13    is a sectional view taken along line E-E of  FIG.  8   . 
     Referring to  FIG.  8    to  FIG.  13   , the water tank  200  may be mounted on the upper side of the nozzle housing  100 . For example, the water tank  200  may be seated on the nozzle cover  130 . The upper side wall of the water tank  200  can form a portion of an outer appearance of the upper surface of the nozzle main body  10  in a state where the water tank  200  is seated on the upper side of the nozzle cover  130 . For example, the water tank  200  may protrude upward from the nozzle cover  130 . 
     The water tank  200  may include a first body  210 , and a second body  250  coupled to the first body  210  and defining a chamber in which water is stored together with the first body  210 . The second body  250  may be coupled to the upper side of the first body  210 . 
     The second body  250  may substantially protrude upward from the nozzle cover  130  to form an outer appearance of an upper surface of the nozzle  1 . Though not limited thereto, the entire upper surface wall of the second body  250  may form an outer appearance of the upper surface of the nozzle  1 . 
     The chamber may include a first chamber  222  positioned above the first driving device  170 , a second chamber  224  positioned above the second driving device  171 , and a connection chamber  226  communicating the first chamber  222  with the second chamber  224 . 
     The first body  210  may define a bottom wall and a side wall of the chamber, and the second body  250  may define an upper wall of the chamber. Of course, a portion of the second body  250  may also define an upper wall of the chamber. 
     In the present embodiment, the volume of the connection chamber  226  may be formed to be smaller than the volumes of the first chamber  222  and the second chamber  24  so that the amount of water to be stored is increased while minimizing the height of the nozzle  1  by the water tank  200 . 
     The water tank  200  may be formed so that the front height is low and the rear height is high. The upper surface of the water tank  200  may be inclined upward or rounded from the front side to the back side. 
     For example, the connection chamber  226  may connect the first chamber  222  and the second chamber  224  disposed on both sides in the front portion of the water tank  200 . In other words, the connection chamber  226  may be positioned in the front portion of the water tank  200 . 
     The water tank  200  may include a first bottom wall  213   a.  For example, the first body  210  may include the first bottom wall  213   a.    
     The first bottom wall  213   a  is a wall which is positioned at the lowest position in the water tank  200 . 
     The first bottom wall  213   a  is a horizontal wall and can be seated on the bottom wall  131   a  of the nozzle cover  130  described later. 
     The first bottom wall  213   a  may be a bottom wall positioned at the foremost end portion of the water tank  200 . 
     The first bottom wall  213   a  may include a first wall portion  214   a  extending to be long in the left and right direction and a pair of second wall portions  214   b  extending in the front and rear direction at both ends of the first wall portion  214   a.  The left and right lengths of the first wall portion  214   a  may be substantially the same as the left and right lengths of the first body  210 . 
     The width of each of the second wall portions  214   b  in the lateral direction is formed to be larger than the width of the first wall portion  214   a  in the front and rear direction. 
     At this time, the lateral width of the second wall portion  214   b  is the largest in the portion adjacent to the first wall portion  214   a  and may be reduced in the portion far away from the first wall portion  214   a.    
     A discharge port  216  for discharging water from the water tank  200  may be formed in any one of the pair of the second wall portions  214   b.    
     Alternatively, the discharge port  216  may be formed at a boundary between one of the pair of second wall portions  214   b  and the first wall portion  214   a.    
     The discharge port  216  may be opened or closed by a valve  230 . The valve  230  may be disposed in the water tank  200 . The valve  230  can be operated by an external force, and the valve  230  keeps the discharge port  216  closed unless an external force is applied thereto. 
     Therefore, water can be prevented from being discharged from the water tank  200  through the discharge port  216  in a state where the water tank  200  is separated from the nozzle main body  10 . 
     In this embodiment, the water tank  200  may include a single discharge port  216 . The reason why the water tank  200  is provided with the single discharge port  216  is to reduce the number of components that can cause water leakage. 
     In other words, in the nozzle  1 , there is a component (control board, driving motor, or the like) that operates upon receiving power, and such a component must be completely cut off from contact with water. So as to block the contact between the component and the water, leakage in the portion through which water is discharged from the water tank  200  is basically minimized. 
     As the number of the discharge ports  216  in the water tank  200  is increased since a structure for preventing water leakage is additionally required, the structure is complicated, and even if there is a structure for preventing water leakage, there is a possibility that water leakage cannot be completely prevented. 
     Also, as the number of the discharge ports  216  in the water tank  200  is increased, the number of the valves  230  for opening and closing the discharge port  216  is also increased. This means that not only the number of components is increased but also the volume of the chamber for water storage in the water tank  200  is reduced by the valve  230 . 
     Since the height of the rear side of the water tank  200  is higher than that of the front side of the water tank  200 , so as to smoothly discharge water in the water tank  200 , the discharge port  216  is formed on the first bottom wall  213   a  which is positioned at the lowest position of the first body  210 . 
     The first body  210  may further include a second bottom wall  213   b  positioned at a different height from the first bottom wall  213   a.    
     The second bottom wall  213   b  is a wall positioned behind the first bottom wall  213   a  and positioned higher than the first bottom wall  213   a.  In other words, the first bottom wall  213   a  and the second bottom wall  213   b  have a height difference of H 2 . 
     The second bottom wall  213   b  may be a horizontal wall or a curved wall that is rounded upward. 
     The second bottom wall  213   b  may be positioned directly above the driving device  170  and  171 . The second bottom wall  213   b  is positioned higher than the first bottom wall  213   a  so that the second bottom wall  213   b  does not interfere with the driving devices  170  and  171 . 
     In addition, since the second bottom wall  213   b  is positioned higher than the first bottom wall  213   a  and there is a water level difference between the second bottom wall  213   b  and the first bottom wall  213   a,  the water on a side of the second bottom wall  213   b  can smoothly flow toward a side of the first bottom wall  213   a.    
     In this embodiment, a portion or all of the second bottom wall  213   b  has the highest height among the bottom walls. 
     The second bottom wall  213   b  may be formed to have a larger left and right width than a front and rear width. 
     The first body  210  may further include a third bottom wall  213   c  positioned at a different height from the first bottom wall  213   a  and the second bottom wall  213   b.    
     The third bottom wall  213   c  is positioned higher than the first bottom wall  213   a  and is positioned lower than the second bottom wall  213   b.    
     Therefore, the heights of the third bottom wall  213   c  and the first bottom wall  213   a  are different by H 1  smaller than H 2 . 
     The third bottom wall  213   c  may be positioned behind the second bottom wall  213   a.    
     A portion of the third bottom wall  213   c  is positioned at the rearmost end of the first body  210 . 
     In this embodiment, as the third bottom wall  213   c  is positioned lower than the second bottom wall  213   b,  the water storage capacity in the water tank  200  can be increased without interference with the surrounding structure. 
     The first body  210  may further include a fourth bottom wall  213   d  extending downward from an edge of the second bottom wall  213   b  so as to be inclined. The fourth bottom wall  213   d  may surround the second bottom wall  213   b.    
     The fourth bottom wall  213   d  may, for example, extend downwardly while being rounded. 
     The first body  210  may further include a fifth bottom wall  213   e  which extends so as to be inclined downwardly from the periphery of the fourth bottom wall  213   d.    
     In other words, the height decreases from the second bottom wall  213   b  toward the fourth bottom wall  213   d  and the fifth bottom wall  213   e.    
     The fifth bottom wall  213   e  may connect the fourth bottom wall  213   d  and the third bottom wall  213   c.    
     In addition, the fifth bottom wall  213   e  may connect the fourth bottom wall  213   d  and the first bottom wall  213   a.    
     A portion of the bottom walls of the first body  210  can form receiving spaces  232  and  233  having a recessed shape by the second bottom wall  213   b,  the fourth bottom wall  213   d,  and the fifth bottom wall  213   e.  The driving devices  170  and  171  may be positioned in the receiving spaces  232  and  233 . 
     Accordingly, a portion of the bottom wall of the first body  210  may surround the periphery of each of the driving devices. 
     The first body  210  may further include a sixth bottom wall  213   f  which is positioned on the rear side of each of the second wall portions  214   b  and positioned higher than each of the second wall portions  214   b.  The sixth bottom wall  213   f  may be positioned lower than the third bottom wall  213   c.    
     The third bottom wall  213   c  may be connected to the sixth bottom wall  213   f  by a connection wall  215   g.    
     Therefore, even if the third bottom wall  213   c  is positioned on the rear side of the second bottom wall  213   b  while being lower than the second bottom wall  213   b,  the water on the second bottom wall  213   b  can flow to the sixth bottom wall  213   f  by the connection wall  215   g.  The water of the sixth bottom wall  213   f  can flow to the first bottom wall  213   a.    
     The first wall portion  214   a  of the first bottom wall  213   a  and the second body  250  may define a connection flow path  226 . 
     Since the first bottom wall  213   a  positioned at the lowest position forms the connection flow path  226  as described above, water in the first chamber  222  and the second chamber  224  can uniformly flow to the discharge port  216 . 
     The first body  210  may further include a first sidewall  215   a  extending upward from the first wall portion  214   a  of the first bottom wall  213   a.  The first side wall  215   a  may be the front wall of the first body  210 . 
     The first side wall  215   a  may extend vertically upward from the front end of the first wall portion  214   a.    
     The first body  210  may further include a second side wall  215   b  extending upward from the second wall portions  214   b  of the first bottom wall  213   a.    
     In other words, the pair of second sidewalls  215   b  extends rearward from both sides of the first sidewall  215   a,  and the height of the second sidewall  215   b  increases as the distance from the first sidewall  215   a  increases. 
     The pair of second side walls  215   b  may include a left side wall and a right side wall. At this time, the left side wall may form the first chamber  222 , and the right side wall may form the second chamber  224 . 
     An inlet for introducing water into one or more of the pair of second sidewalls  215   b  may be formed. 
       FIG.  6    illustrates a state where an inlet is formed in each of the pair of second sidewalls  215   b.    
     For example, the left side wall may have a first inlet  211  for introducing water into the first chamber  222  and the right side wall may have a second inlet  212  for introducing water into the second chamber  224 . 
     At this time, each of the second sidewalls  215   b  may include a recessed portion  215   e  recessed inward, and the recessed portion  215   e  may be provided with each of the inlets  211  and  212 . 
     The first inlet  211  may be covered by a first inlet cover  240  and the second inlet  212  may be covered by a second inlet cover  242 . 
     For example, each of the inlet covers  240  and  242  may be formed of a rubber material. 
     The inlet covers  240  and  242  can cover the inlets  211  and  212  in a state of being received in the recessed portion  215   e.  At this time, the sizes of the inlet covers  240 ,  242  are formed to be smaller than the size of the recessed portion  215   e.    
     Therefore, a portion of the recessed portion  215   e  is covered by the inlet covers  240 ,  242 , the other portion thereof is not covered by the inlet covers  240 ,  242 , and thus a space  215   f  in which a user&#39;s finger can be inserted can be formed. 
     Accordingly, after inserting the finger into the space  215   f,  the inlet covers  240 ,  242  may be pulled so that the inlet covers  240 ,  242  open the inlets  211 ,  212 . 
     According to the present embodiment, the water tank  200  is provided with each of the inlets  211  and  212  on both sides of the water tank  200 , so that it is possible to easily introduce water into the water tank  200  by opening any one of the two inlets. 
     The inlet covers  240 ,  242  may be positioned between the space  215   f  and the first sidewall  215   a  such that the size of the space  215   f  is secured. 
     The first body  210  may further include a third side wall  215   c  extending upward from a rear end of the third bottom wall  213   c.    
     In addition, the first body  210  may further include a front and rear extending wall  215   d  which extends forward from an end portion of the third side wall  215   c  and is connected to a third bottom wall  213   c,  a fourth bottom wall  213   d,  and a fifth bottom wall  213   e.    
     In the first body  210 , the pair of front and rear extending walls  215   d  is disposed and spaced apart from each other in the lateral direction. 
     A pair of front and rear extending walls  215   d  is disposed to face each other. When the water tank  200  is seated on the nozzle housing  100 , the connection tube  50  can be positioned between the pair of front and rear extending walls  215   d.    
     The pair of front and rear extending walls  215   d  is positioned higher than the first bottom wall  213   a.    
     In this embodiment, the chamber is formed by the first body  210  and the second body  250 , and the second bottom wall  213   b  and the second body  250  are separated from each other to receive water, and the second bottom wall  213   b  and the second body  250  have the difference in height of H 3 . 
     The first bottom wall  213   a  and the second body  250  have the difference in height of H 4 . At this time, H 4  is larger than H 3 . According to this structure, there is an advantage that the water storage capacity can be increased while reducing the height (or total thickness) of the water tank  200 . 
     The first body  210  may include a first slot  218  for preventing interference with the operating unit  300  and the coupling units  310  and  254 . The first slot  218  may be formed such that the center rear end portion of the first body  210  is recessed forward. At this time, the pair of front and rear extending walls  215   d  may form a portion of the first slot  218 . 
     In addition, the second body  250  may include a second slot  252  for preventing interference with the operating unit  300 . The second slot  252  may be formed such that the center rear end portion of the second body  230  is depressed forward. 
     The second body  250  may further include a slot cover  253  covering a portion of the first slot  218  of the first body  210  in a state of being coupled to the first body  210 . In other words, the front and rear length of the second slot  252  is shorter than the front and rear length of the first slot  218 . 
     The second coupling unit  254  may extend downward from the slot cover  253 . Accordingly, the second coupling unit  254  may be positioned within the space formed by the first slot  218 . 
     Accordingly, when the overall shape of the water tank  200  is viewed, the length of the water tank  200  in the lateral direction is longer than that of the water tank  200  in the front and rear direction. The front and rear lengths of the central portion of the water tank  200  where the slots  218  and  252  are positioned are shorter than the front and rear lengths of both sides. 
     The water tank  200  has a symmetrical shape with respect to the slots  218  and  252 . 
     The water tank  200  may further include coupling ribs  235  and  236  for coupling with the nozzle cover  130  before the second coupling unit  254  of the water tank  200  is coupled with the first coupling unit  310 . 
     The coupling ribs  235  and  236  also perform a role which guides the coupling position of the water tank  200  in the nozzle cover  130  before the second coupling unit  254  of the water tank  200  is coupled with the first coupling unit  310 . For example, a plurality of coupling ribs  235  and  236  protrude from the first body  110  and may be disposed so as to be spaced apart in the left and rear horizontal direction. 
     Though not limited, the plurality of coupling ribs  235  and  236  may protrude forward from the first sidewall  215   a  of the first body  210  and may be spaced apart from each other in the lateral direction. 
     Each of the driving devices  170  and  171  is provided in the nozzle main body  10  so that a portion of the nozzle main body  10  protrudes upward at both sides of the second flow path  114  by each of the driving devices  170  and  171 . 
     According to the present embodiment, the portion protruding from the nozzle body  10  is positioned in the pair of receiving spaces  232  and  233  of the water tank  200 . The pair of receiving spaces  232  and  233  may be divided into right and left by the first slot  218 . 
     &lt;Nozzle Cover&gt; 
       FIG.  14    is a perspective view illustrating a nozzle cover according to an embodiment of the present invention as viewed from above, and  FIG.  15    is a perspective view illustrating a nozzle cover according to an embodiment of the present invention as viewed from below. 
     Referring to  FIG.  6   ,  FIG.  14   , and  FIG.  15   , the nozzle cover  130  may include a bottom wall  131   a  and a peripheral wall  131   b  extending upward at the edge of the bottom wall  131   a.    
     The nozzle cover  130  may include driving unit covers  132  and  134  that cover the upper side of each of the driving units  170  and  171 . 
     Each of the driving unit covers  132  and  134  is a portion which protrudes upward from the bottom wall  131   a  of the nozzle cover  130 . The driving unit covers  132  and  134  may be separated from the peripheral wall  131   b.  Therefore, a space may be formed between the driving unit covers  132  and  134  and the peripheral wall  131   b,  and the water tank  200  may be positioned in the space. 
     Accordingly, the increase in the height of the nozzle  1  by the water tank  200  can be prevented in a state where the water tank  200  is seated on the nozzle cover  130  while the storage capacity of the water tank  200  can be increased. 
     Each of the driving unit covers  132  and  134  is a portion which protrudes upward from the nozzle cover  130 . Each of the driving unit covers  132  and  134  can surround the upper side of the driving devices  170  and  171  without interfering with each of the driving devices  170  and  171  installed in the nozzle base  110 . In other words, the driving unit covers  132  and  134  are spaced apart from each other in the lateral direction in the nozzle cover  130 . 
     When the water tank  200  is seated on the nozzle cover  130 , each of the driving unit covers  132  and  134  is received in each of the receiving spaces  232  and  233  of the water tank  200 , and thus interference between the components is prevented. 
     In addition, in the water tank  200 , the first chamber  222  and the second chamber  224  may be disposed so as to surround the periphery of each of the respective driving unit covers  132  and  134 . 
     Thus, according to the present embodiment, the volumes of the first chamber  222  and the second chamber  224  can be increased. 
     The first body  210  of the water tank  200  may be seated at a lower portion of the nozzle cover  130  than the driving unit covers  132  and  134 . 
     At least a portion of the bottom wall of the water tank  200  may be positioned lower than the axis of the driving motor (see A 3  and A 4  in  FIG.  21   ) so that the height increase by the water tank  200  is minimized, as will be described later. 
     For example, the first bottom wall  213   a  of the water tank  200  may be positioned lower than the axis of the driving motor (A 3  and A 4 ), which will be described later. 
     The nozzle cover  130  may further include a flow path cover  136  covering the flow path forming portion  150 . The flow path cover  136  may be positioned between the driving unit covers  132  and  134  and may be disposed at a position corresponding to the first slot  218  of the water tank  200 . 
     The nozzle cover  136  may also protrude upward from the bottom wall  131   a  of the nozzle cover  130 . 
     In the present embodiment, so as to increase the water storage capacity of the water tank  200 , a portion of the water tank  200  may be positioned on both sides of the flow path cover  136 . Therefore, the water storage capacity of the water tank  200  can be increased while preventing the water tank  200  from interfering with the second flow path  114 . 
     In addition, so as to prevent the water tank  200  from colliding with structures around the nozzle  1  during the movement of the nozzle  1 , the entire water tank  200  can be disposed to overlap with the nozzle housing  100  in the vertical direction. In other words, the water tank  200  may not protrude in the lateral and the front and rear directions of the nozzle housing  100 . 
     The first bottom wall  213   a  of the water tank  200  may be seated on the bottom wall  131   a  of the nozzle cover  130 . In this state, the slot cover  253  of the water tank  200  may be positioned directly above the flow path cover  136 . The slot cover  253  may be in contact with the flow path cover  136  or may be spaced apart from the flow path cover  136 . 
     When the water tank  200  is mounted on the nozzle cover  130 , the slot cover  253  is positioned in front of the operating unit  300 . 
     When the water tank  200  is seated on the nozzle cover  130 , the first body  210  may be surrounded by the peripheral wall  131   b  of the nozzle cover  130 . Accordingly, when the water tank  200  is seated on the nozzle cover  130 , the inlet cover on both sides of the water tank  200  is covered by the peripheral wall  131   b  of the nozzle cover  130  and is not exposed to the outside. 
     The nozzle cover  130  may further include rib insertion holes  141  and  142  into which the coupling ribs  235  and  236  provided in the water tank  200  are inserted. The rib insertion holes  141  and  142  may be spaced apart from the nozzle cover  130  in the lateral horizontal direction. 
     Accordingly, the center or rear portion of the water tank  200  is moved downward in a state where the coupling ribs  235  and  236  are inserted into the rib insertion holes  141  and  142 , and thus the second coupling unit  254  may be coupled to the first coupling unit  310 . 
     The nozzle cover  130  may be provided with a valve operating unit  144  for operating the valve  230  in the water tank  200 . The valve operating unit  144  may be coupled to the nozzle cover  130 . 
     The water discharged from the water tank  200  can flow through the valve operating unit  144 . 
     The valve operating unit  144  may be coupled to the lower side of the nozzle cover  130 , and a portion of the valve operating unit  144  may protrude upward through the nozzle cover  130 . 
     The valve operating unit  144  protruding upward is introduced in the water tank  200  through the discharge port  216  of the water tank  200  when the water tank  200  is seated on the nozzle cover  130 . In other words, the valve operating unit  144  may be disposed at a position facing the discharge port  216  of the water tank  200 . 
     The valve operating unit  144  will be described later with reference to the drawings. 
     The nozzle cover  130  may be provided with a sealer  143  for preventing water discharged from the water tank  200  from leaking from the vicinity of the valve operating unit  144 . The sealer  143  may be formed of rubber material, for example, and may be coupled to the nozzle cover  130  from above the nozzle cover  130 . 
     The nozzle cover  130  may be provided with a water pump  270  for controlling water discharge from the water tank  200 . The water pump  270  may be connected to a pump motor  280 . 
     A pump installation rib  146  for installing the water pump  270  may be provided on the lower side of the nozzle cover  130 . The water pump  270  and the pump motor  280  are installed in the nozzle cover  130  so that the pump motor  280  is prevented from contacting the water even if the water drops into the nozzle base  110 . 
     The water pump  270  is a pump that operates so as to communicate the inlet and the outlet by expanding or contracting the valve body therein while being operated, and the pump can be realized by a well-known structure, and thus a detailed description thereof will be omitted. 
     The valve body in the water pump  270  can be driven by the pump motor  280 . Therefore, according to the present embodiment, water in the water tank  200  can be continuously and stably supplied to the rotation cleaning units  40  and  41  while the pump motor  280  is operating. 
     The operation of the pump motor  280  can be adjusted by operating the above-described adjusting unit  180 . For example, the adjusting unit  180  may select the on/off state of the pump motor  280 . 
     Alternatively, the output (or rotational speed) of the pump motor  280  may be adjusted by the adjusting unit  180 . 
     The nozzle cover  130  may further include at least one fastening boss  148  to be coupled with the nozzle base  110 . 
     In addition, the nozzle cover  130  may be provided with a spray nozzle  149  for spraying water to the rotation cleaning units  40  and  41  to be described later. For example, a pair of spray nozzles  149  may be installed on the nozzle cover  130  in a state where the spray nozzles  149  are spaced apart from each other in the lateral direction. 
     The nozzle cover  130  may be provided with a nozzle installation boss  149   c  for mounting the spray nozzle  149 . For example, the spray nozzle  149  may be fastened to the nozzle installation boss  149   c  by a screw. 
     The spray nozzle  149  may include a connection unit  149   a  for connecting a branch tube to be described later. 
     &lt;Description of Structure and Operation of Operating Unit, First Coupling Unit, and Supporting Body&gt; 
       FIG.  16    is a perspective view illustrating a state where the operating unit, the first coupling unit, and the supporting body are separated from each other in the nozzle cover, and  FIG.  17    is a sectional view taken along line F-F of  FIG.  14   . 
       FIG.  18    is a sectional view taken along the line G-G in  FIG.  17    in a state where the first coupling unit is coupled with the nozzle cover, and  FIG.  19    is a sectional view illustrating a state where the first coupling unit and the second coupling unit are released by pressing the operation unit. 
     Referring to  FIG.  16    to  FIG.  19   , the operating unit  300  may be supported by the flow path cover  136 . The flow path cover  136  may include an operating unit receiving portion  137  having a recessed shape for supporting and receiving the operating unit  300 . 
     On both sides of the operating unit  300 , a coupling hook  302  for coupling the operating unit  300  to the flow path cover  136  may be provided. 
     The operating unit  300  can be received in the operating unit receiving portion  137  from above the operating unit receiving portion  137 . 
     The bottom wall of the operating unit receiving portion  137  is provided with a slot  137   b  penetrating in the vertical direction and the coupling hook  302  penetrates the slot  137   b  to be hooked on the lower surface of the bottom wall of the operating unit receiving portion  137 . 
     When the coupling hook  302  is hooked on the bottom wall of the operating unit receiving portion  137 , the operating unit  300  can be prevented from being displaced upward of the flow path cover  136 . 
     The operating unit  300  may be elastically supported by the first elastic member  306 . A plurality of first elastic members  306  can support the operating unit  300  so that the operating unit  300  is not moved to one side when the operating unit  300  is operated. 
     The plurality of first elastic members  306  may be disposed to be spaced apart from each other in the lateral direction, although not limited thereto. 
     The operating unit  300  may include a first coupling protruding portion  304  for coupling each of the first elastic members  306 . The first coupling protruding portion  304  may protrude downward from a lower surface of the operating unit  300 . The protruding length of the first coupling protruding portion  304  may be shorter than the protruding length of the coupling hook  302 . 
     The first elastic member  306  may be, for example, a coil spring, and the upper side of the first elastic member  306  may be received in the first coupling protruding portion  304 . For this, the first coupling protruding portion  304  may be a cylindrical rib that forms a space therein. 
     The bottom wall of the operating unit receiving portion  137  may include a second coupling protruding portion  137   a  to which the first elastic member  306  is coupled. 
     The second coupling protruding portion  137   a  may protrude upward from the bottom wall of the operating unit receiving portion  137 . In a state where the first elastic member  306  is wrapped around the second coupling protruding portion  137   a,  the first elastic member  306  can be seated on the bottom wall of the operating unit receiving portion  137 . In other words, the second coupling protruding portion  137   a  may be received in the space formed by the first elastic member  306 . 
     The outer diameter of the second coupling protruding portion  137   a  may be smaller than the inner diameter of the first coupling protruding portion  304 . Therefore, the second coupling protruding portion  137   a  and the first coupling protruding portion  324  can be prevented from colliding with each other during the descent of the operating unit  300 . 
     The first coupling unit  310  is positioned on the slot  137   b  of the operating unit receiving portion  137  and both side end portions thereof can be coupled with the bottom wall of the operating unit receiving portion  137 . 
     The first coupling unit  310  may include a hook  312  and may include coupling rails  316  on both sides of which the bottom wall of the operating unit receiving portion  137  is coupled. 
     A portion of the coupling rail  316  can be seated on the upper surface of the bottom wall of the operating unit receiving portion  137  and another portion of the coupling rail  316  can contact the lower surface of the bottom portion of the receiving portion  137 . 
     Therefore, the first coupling unit  310  can be stably moved in the horizontal direction in a state of being coupled to the bottom wall of the operation unit receiving portion  137  by the coupling rail  316 . 
     As described above, the first coupling unit  310  may be elastically supported by the second elastic member  314  and the second elastic member  314  may elastically support the first coupling unit  310  on the opposite side of the hook  312 . 
     The flow path cover  136  may further include a coupling unit receiving portion  136   a  in which the second coupling unit  254  is received. The coupling unit receiving portion  136   a  may be positioned in front of the operation unit receiving portion  137 . 
     The flow path cover  136  may further include a body receiving portion  138  positioned below the coupling unit receiving portion  136   a  and receiving the supporting body  320 . 
     Accordingly, the second coupling unit  254  may be positioned directly above the supporting body  320  in a state where the second coupling unit  254  is received in the coupling unit receiving portion  136   a.    
     The supporting body  320  may include a pair of coupling hooks  322  for coupling to the body receiving portion  138 . The body receiving portion  138  may be provided with a hook coupling slot  138   a  to which the coupling hooks  322  are coupled. 
     The supporting body  320  can be moved vertically in a state where the coupling hook  322  of the supporting body  320  is coupled to the hook coupling slot  138   a.  Therefore, the hook coupling slot  138   a  may extend in the vertical direction. 
     The supporting body  320  may be resiliently supported by the third elastic member  324 . 
     In a state in which the coupling of the first coupling unit  310  and the second coupling unit  254  is released, the third elastic member  324  supporting the supporting body  320  may provide an elastic force for moving the second coupling unit  254  upward to the second coupling unit. 
     In a state where the first coupling unit  310  is coupled with the second coupling unit  254 , the second coupling unit  254  presses the supporting body  320  and the third elastic member  324  is contracted to accumulate elastic force. 
     In this state, so as to separate the water tank  200 , when the operating unit  300  is pressed downward, the downward movement force of the operating unit  300  is transmitted to the first coupling unit  310  so that the first coupling unit  310  is moved in the horizontal direction. 
     At this time, the first coupling unit  310  is moved in a direction away from the second coupling unit  254  so that the hook  312  of the first coupling unit  310  is missed from the groove  256  of the second coupling unit  254  and thus the coupling of the first coupling unit  310  and the second coupling unit  254  is released. 
     The force pressing the third elastic member  324  is removed and the elastic restoring force of the third elastic member  324  is transmitted to the supporting body  320  so that the support body  320  lifts the second coupling unit  254  placed on the supporting body  320 . 
     Then, the portion of the second coupling unit  254  in the water tank  200  is lifted above the nozzle cover  130 . Therefore, there is a gap between the water tank  200  and the nozzle cover  130 , so that the user can easily grasp the water tank  200 . 
     When the force for pressing the operating unit  300  is removed in a state where the second coupling unit  254  is lifted to a predetermined height, the first coupling unit  310  is returned to the original position thereof by the second elastic member  314 . 
     The hook of the first coupling unit  310  protrudes into the coupling unit receiving portion  136   a  and is positioned on the upper side of the supporting body  320 . The lower end of the second coupling unit  254  is positioned on the hook  312  of the first coupling unit  310 . 
       FIG.  20    is a view illustrating a state where a valve operating unit and a sealer are separated from each other in a nozzle cover according to an embodiment of the present invention. 
     Referring to  FIG.  20   , the nozzle cover  130  may include a water passage opening  145  formed at a position corresponding to the discharge port  216  of the water tank  200 . 
     A sealer  143  is coupled to the bottom wall  131   a  at an upper side of the bottom wall  131   a  of the nozzle cover  130  and the valve operating unit  144  is coupled to the bottom wall  131   a  at a lower side of the bottom wall  131   a.    
     The sealer  143  may include a hole  143   a  formed at a position corresponding to the water passage opening  145 . The water can pass through the water passage opening  145  after passing through the hole  143   a.    
     The sealer  143  may further include a coupling protrusion  143   b  formed around the hole  143   a  and coupled to the bottom wall  131   a  of the nozzle cover  130 . The bottom wall  131   a  of the nozzle cover  130  may have a protrusion hole  145   a  for coupling with the coupling protrusion  143   b.    
     A guide protrusion  144   b  for guiding the coupling position of the valve operating unit  144  may be provided around the valve operating unit  144 . A pair of guide ribs  145   b  and  145   c  spaced apart from each other in the horizontal direction may be provided on the bottom surface of the bottom wall  131   a  of the nozzle cover  130  so that the guide protrusion  144   b  may be positioned. 
     An absorption member  147  capable of absorbing water discharged from the water tank  200  may be coupled to the valve operating unit  144 . When water is discharged from the water tank  200 , the absorption member  147  primarily absorbs water and when the amount of water discharged from the water tank  200  increases, the water absorbed by the absorption member  147  can be supplied to the mops  402  and  404  through the water supply flow path, as will be described later. 
     The absorption member  147  may be formed in a cylindrical shape, for example, and may include a pressing portion hole  147   a  through which the pressing portion  144   a,  which will be described later, penetrates. 
     The valve operating unit  144  may be coupled to the nozzle cover  130  in a state where the absorbing member  147  is coupled to the valve operating unit  144 . 
     The valve operating unit  144  may be coupled to the nozzle cover  130  by a fusion bonding method or may be coupled to the nozzle cover  130  by an adhesive, although not limited thereto. 
     The absorption member  147  may also act to filter foreign matters contained in the water discharged from the water tank  200 . 
     &lt;Nozzle Base&gt; 
       FIG.  21    is a view illustrating a state where a flow path forming portion is coupled to a nozzle base according to an embodiment of the present invention, and  FIG.  22    is a view illustrating a nozzle base according to an embodiment of the present invention as viewed from below. 
     Referring to  FIG.  6   ,  FIG.  21   , and  FIG.  22   , the nozzle base  110  may include a pair of shaft through-holes  116  and  118  through which a transmission shaft (to be described later) that is connected to each of the rotation plates  420  and  440  in each of the driving devices  170  and  171  passes. 
     The nozzle base  110  is provided with a seating groove  116   a  for seating a sleeve (see  174  in  FIG.  24   ) provided in each of the driving devices  170  and  171 , and the shaft through-holes  116  and  118  may be formed in the seating groove  116   a.    
     The seating groove  116   a  may be formed in a circular shape, as an example and may be recessed downward from the nozzle base  110 . The shaft through-holes  116  and  118  may be formed in the bottom of the seating groove  116   a.    
     In the process of moving the nozzle  1  or the operation of the driving devices  170  and  171  as the sleeves (see  174  in  FIG.  24   ) provided in the driving devices  170  and  171  are seated in the seating groove  116   a,  the horizontal movement of the driving devices  170  and  171  can be restricted. 
     A protruding sleeve  111   b  protruding downward is provided on a lower surface of the nozzle base  110  at a position corresponding to the seating groove  116   a.  The protruding sleeve  111   b  is a portion which is formed as the lower surface of the nozzle base  110  protrudes downward substantially as the seating groove  116   a  is recessed downward. 
     Each of the shaft through-holes  116  and  118  may be disposed on both sides of the flow path forming portion  150  in a state where the flow path forming portion  150  is coupled to the nozzle base  110 . 
     The nozzle base  110  may be provided with a board installation portion  120  for installing a control board  115  (or first board) for controlling each of the driving devices  170  and  171 . For example, the board installation portion  120  may be formed as a hook shape extending upward from the nozzle base  110 . 
     The hooks of the board installation portion  120  are hooked on the upper surface of the control board  115  to restrict upward movement of the control board  115 . 
     The control board  115  may be installed in a horizontal state. The control board  115  may be installed so as to be spaced apart from the bottom of the nozzle base  110 . 
     Therefore, even if water falls to the bottom of the nozzle base  110 , water can be prevented from contacting the control board  115 . 
     The nozzle base  110  may be provided with a support protrusion  120   a  for supporting the control board  115  away from the bottom. 
     The board installation portion  120  may be positioned at one side of the flow path forming portion  150  in the nozzle base  110 , although not limited thereto. For example, the control board  115  may be disposed at a position adjacent to the adjusting unit  180 . 
     Therefore, a switch (to be described later) installed on the control board  115  can sense the operation of the adjusting unit  180 . 
     In the present embodiment, the control board  115  may be positioned on the opposite side of the valve operating unit  144  with respect to the second flow path  114 . Therefore, even if leakage occurs in the valve operating unit  144 , water can be prevented from flowing to a side of the control board  115 . 
     The nozzle base  110  may further include supporting ribs  122  for supporting the lower sides of each of the driving devices  170  and  171  and fastening bosses  117  and  117   a  for fastening each of the driving devices  170  and  171 . 
     The supporting ribs  122  protrude from the nozzle base  110  and are bent at least once to separate each of the driving devices  170  and  171  from the bottom of the nozzle base  110 . Alternatively, a plurality of spaced apart supporting ribs  122  may protrude from the nozzle base  110  to separate each of the driving devices  170  and  171  from the bottom of the nozzle base  110 . 
     Even if water falls to the bottom of the nozzle base  110 , the driving devices  170  and  171  are spaced apart from the bottom of the nozzle base  110  by the supporting ribs  122  so that it is possible to minimize the flow of water to the side of the driving device  170 ,  171 . 
     In addition, since the sleeves (see  174  in  FIG.  24   ) of the driving devices  170  and  171  are seated in the seating grooves  116   a,  even if water falls to the bottom of the nozzle base  110 , it can prevent water from being drawn into the driving devices  170 ,  171  by the sleeve (see  174  in  FIG.  24   ). 
     In addition, the nozzle base  110  may further include a nozzle hole  119  through which each of the spray nozzles  149  passes. 
     A portion of the spray nozzle  149  coupled to the nozzle cover  130  may pass through the nozzle hole  119  when the nozzle cover  130  is coupled to the nozzle base  110 . 
     In addition, the nozzle base  110  may further include an avoidance hole  121   a  for preventing interference with the structures of each of the driving devices  170  and  171 , and a fastening boss  121  for fastening the flow path forming portion  150 . 
     At this time, a fastening member passing through the flow path forming portion  150  can be fastened to a fastening boss  121  after passing through a portion of the driving devices  170  and  171 . 
     A portion of each of the driving devices  170  and  171  may be positioned in the avoidance hole  121   a  so that the supporting rib  122  may be positioned at the periphery of the avoidance hole  121   a  so as to minimize the flow of water to the avoidance hole  121   a.    
     For example, the supporting rib  122  may be positioned in the avoidance hole  121   a  in the formed region. 
     A plate receiving portion  111  which is recessed upward can be provided on the lower surface of the nozzle base  110  so that the first flow path  112  is as close as possible to the floor on which the nozzle  1  is placed in a state where the rotation cleaning units  40  and  41  are coupled to the lower side of the nozzle base  110 . 
     The increase in the height of the nozzle  1  can be minimized in a state where the rotation cleaning units  40  and  41  are coupled by the plate receiving portion  111 . 
     The rotation cleaning units  40  and  41  may be coupled with the driving devices  170  and  171  in a state where the rotation cleaning units  40  and  41  are positioned in the plate receiving portion  111 . 
     The nozzle base  110  may be provided with a bottom rib  111   a  disposed to surround the shaft through holes  116  and  118 . The bottom rib  111   a  may protrude downward from the lower surface of the plate receiving portion  111  and may be formed in a circular ring shape, as an example. 
     The shaft through holes  116  and  118 , the nozzle holes  119 , and an avoidance holes  121   a  can be positioned in the region formed by the bottom rib  111   a.    
     &lt;Installation Position of a Plurality of Switches&gt; 
       FIG.  23    is a view illustrating a plurality of switches provided on a control board according to an embodiment of the present invention. 
     Referring to  FIG.  4    and  FIG.  23   , the nozzle base  110  is provided with a control board  115  as described above. A plurality of switches  128   a  and  128   b  may be provided on the upper surface of the control board  115  to sense the operation of the adjusting unit  180 . 
     The plurality of switches  128   a  and  128   b  may be installed in a state of being spaced apart in the lateral direction. 
     The plurality of switches  128   a  and  128   b  may include a first switch  128   a  for sensing a first position of the adjusting unit  180  and a second switch  128   b  for sensing a second position of the adjusting unit  180 . 
     For example, when the adjusting unit  180  is pivoted to the left and moves to the first position, the adjusting unit  180  presses the contact of the first switch  128   a  to turn on the first switch  128   a.  In this case, the pump motor  280  operates as a first output, and water can be discharged by the first amount per unit time in the water tank  200 . 
     When the adjusting unit  180  pivots to the right and moves to the second position, the adjusting unit  180  presses the contact of the second switch  128   b  so that the second switch  128   b  is turned on. 
     In this case, the pump motor  280  operates as a second output, which is larger than the first output, so that the water can be discharged by the second amount per unit time in the water tank  200 . 
     The pump motor  280  may be controlled by a controller installed on the control board  115 . The controller can control the duty of the pump motor  280 . 
     For example, the controller may control the pump motor  280  to be off for M seconds after N seconds of on. The pump motor  280  may be repeatedly turned on and off for discharging water from the water tank  200 . 
     At this time, the off time may be varied in a state where the on time of the pump motor  280  is maintained by the operation of the controller  180  so that the amount of water discharged from the water tank  200  may vary. 
     For example, so as to increase the water discharge amount in the water tank  200 , the controller can control so as to turn on the pump motor  280  for N seconds and then turn off the pump motor  280  for P seconds smaller than M. In either case, the off time of the pump motor  280  may be controlled to be longer than the on time thereof. 
     When the adjusting unit  180  is positioned at a neutral position between the first position and the second position, the adjusting unit  180  does not press the contacts of the first switch  128   a  and the second switch  128   b,  and the pump motor  280  is stopped. 
     &lt;Driving Device&gt; 
       FIG.  24    is a view illustrating the first and second driving devices according to one embodiment of the present invention as viewed from below,  FIG.  25    is a view illustrating the first and second driving devices according to the embodiment of the present invention as viewed from above,  FIG.  26    is a view illustrating a structure for preventing rotation of the motor housing and the driving motor, and  FIG.  27    is a view illustrating a state where a power transmission unit is coupled to a driving motor according to an embodiment of the present invention. 
     Referring to  FIG.  23    to  FIG.  27   , the first driving device  170  and the second driving device  171  may be formed and disposed symmetrically in the lateral direction. 
     The first driving device  170  may include a first driving motor  182  and the second driving device  171  may include a second driving motor  184 . 
     A motor PCB  350  (or second board) for driving each of the driving motors may be connected to the driving motors  182  and  184 . The motor PCB  350  may be connected to the control board  115  to receive a control signal. The motor PCB  350  may be connected to the driving motors  182  and  184  in a standing state and may be spaced apart from the nozzle base  110 . 
     The controller can sense the current of each of the driving motors  182  and  184 . Since the frictional force between the mop  402  and the floor acts as a load on the driving motors  182  and  184  in a state where the nozzle  1  is placed on the floor, the current of the driving motors  182  and  184  may be equal to or greater than the first reference value. 
     Meanwhile, when the nozzle  1  is lifted from the floor since there is no frictional force between the mops  402  and  404  and the floor, the current of each of the driving motors  182  and  184  may be less than the first reference value. 
     Accordingly, when the current of each of the driving motors  182  and  184  sensed is less than the first reference value and the time sensed as being less than the first reference value is equal to or longer than the reference time, the controller can stop the operation of the pump motor  280 . Alternatively, the controller may stop the operation of the pump motor  280  when the current of each of the driving motors  182  and  184  sensed is less than the first reference value. 
     In addition, when the current of each of the driving motors  182  and  184  sensed is less than the first reference value and the time sensed as being less than the first reference value is equal to or longer than the reference time, the controller can stop the operation of each of the driving motors  182  and  184 . Alternatively, the controller may stop the operation of each of the driving motors  182  and  184  if the current of each of the driving motors  182  and  184  sensed is less than the first reference value. 
     The controller can simultaneously or sequentially operate the pump motor  280  and each of the driving motors  182  and  184  when the currents of the driving motors  184  and  184  sensed become equal to or greater than the first reference value. 
     A terminal for supplying power to the nozzle  1  of the present embodiment may be positioned in the connection tube  50 . 
     The nozzle  1  may include the rotation cleaning units  40  and  41  and driving devices  170  and  171  and a pump motor  280  for driving the rotation cleaning units  40  and  41 , as described above. Therefore, only when the power is supplied to the connection tube  50 , the driving devices  170  and  171  and the pump motor  280  operate to rotate the rotation cleaning units  40  and  41  to clean the floor, and water may be supplied from the water tank  200  to the rotation cleaning units  40  and  41 . 
     Therefore, when the nozzle  1  of the present embodiment is connected to the cleaner used by the existing user, the floor can be cleaned using the nozzle  1 , so that the nozzle  1  can be used with an additional accessory of the existing cleaner. 
     The motor PCB  350  may include a plurality of resistors  352  and  354  for improving Electro Magnetic Interference (EMI) performance of the driving motor. 
     For example, a pair of resistors  352  and  354  may be provided in the motor PCB  350 . 
     One resistor of the pair of resistors  352  and  354  may be connected to the (+) terminal of the driving motor and the other resistor may be connected to the (−) terminal of the driving motor. Such a pair of resistors  352  and  354  can reduce the fluctuation of the output of the driving motor. 
     The pair of resistors  352  and  354  may be spaced laterally from the motor PCB  350 , for example. 
     Each of the driving devices  170  and  171  may further include a motor housing. The driving motors  182  and  184  and a power transmission unit for transmitting power can be received in the motor housing. 
     The motor housing may include, for example, a first housing  172 , and a second housing  173  coupled to the upper side of the first housing  172 . 
     The axis of each of the driving motors  182  and  184  may substantially extend in the horizontal direction in a state where each of the driving motors  182  and  184  is installed in the motor housing. 
     If the driving devices are installed in the motor housing so that the axis of each of the driving motors  182  and  184  extends in the horizontal direction, the driving devices  170  and  171  can be compact. In other words, the heights of the driving devices  170  and  171  can be reduced. 
     The first housing  172  may have a shaft hole  175  through which the transmission shaft  190  for coupling with the rotation plates  420  and  440  of the power transmission unit passes. For example, a portion of the transmission shaft  190  may protrude downward through the lower side of the motor housing. 
     The horizontal section of the transmission shaft  190  may be formed in a non-circular shape such that relative rotation of the transmission shaft  190  is prevented in a state where the transmission shaft  190  is coupled with the rotation plates  420  and  440 . 
     A sleeve  174  may be provided around the shaft hole  175  in the first housing  172 . The sleeve  174  may protrude from the lower surfaces of the first housing  172 . 
     The sleeve  174  may be formed in a ring shape, for example. Therefore, the sleeve  174  can be seated in the seating groove  116   a  in a circular shape. 
     The driving motors  182  and  184  may be seated on the first housing  172  and fixed to the first housing  172  by the motor fixing unit  183  in this state. 
     The driving motors  182  and  184  may be formed in an approximately cylindrical shape and the driving motors  182  and  184  may be seated in the first housing  172  in a state where the axes of the driving motors  182  and  184  are substantially horizontal (in a state where driving motors  182  and  184  are lying down). 
     The motor fixing unit  183  may be formed in an approximately semicircular shape in cross section and may cover the upper portion of the driving motors  182  and  184  seated on the first housing  172 . The motor fixing unit  183  may be fixed to the first housing  172  by a fastening member such as a screw, as an example. 
     The second housing  173  may include a motor cover  173   a  covering a portion of the driving motors  182  and  184 . 
     The motor cover  173   a  may be rounded so as to surround the motor fixing unit  183  from the outside of the motor fixing unit  183 , for example. 
     For example, the motor cover  173   a  may be formed in a round shape such that a portion of the second housing  173  protrudes upward. 
     Rotation preventing ribs  173   c  and  173   d  are formed on the surface facing the motor fixing unit  183  from the motor cover  173   a  so as to prevent relative rotation between the motor cover  173   a  and the motor fixing unit  183  during the operation of the driving motors  182  and  184 , and a rib receiving slot  183   a  in which the rotation preventing ribs  173   c  and  173   d  are received can be formed in the motor fixing unit  183 . 
     Though not limited, the widths of the rotation preventing ribs  173   c  and  173   d  and the width of the rib receiving slot  183   a  may be the same. 
     Alternatively, a plurality of rotation preventing ribs  173   c  and  173   d  may be spaced apart from the motor cover  173   a  in the circumferential direction of the driving motors  182  and  184 , and a plurality of rotation preventing ribs  173   c  and  173   d  can be received in the rib receiving slot  183   a.    
     At this time, the maximum width of the plurality of rotation preventing ribs  173   c  and  173   d  in the circumferential direction of the driving motors  182  and  184  may be equal to or slightly smaller than the width of the rib receiving slot  183   a.    
     The power transmission unit may include a driving gear  185  connected to the shaft of each of the driving motors  182  and  184  and a plurality of transmission gears  186 ,  187 ,  188 , and  189  for transmitting the rotational force of the driving gear  185 . 
     The axis of each of the driving motors  182  and  184  (see A 3  and A 4  in  FIG.  20   ) substantially extends in the horizontal direction while the centerlines of the rotation plates  420  and  440  extend in the vertical direction. Therefore, the driving gear  185  may be a spiral bevel gear, for example. 
     The plurality of transmission gears  186 ,  187 ,  188 , and  189  may include a first transmission gear  186  that engages with the driving gear  185 . The first transmission gear  186  may have a rotation center extending in a vertical direction. 
     The first transmission gear  186  may include a spiral bevel gear so that the first transmission gear  186  can engage with the driving gear  185 . 
     The first transmission gear  186  may further include a helical gear disposed at a lower side of the spiral bevel gear as a second gear. 
     The plurality of transmission gears  186 ,  187 ,  188  and  189  may further include a second transmission gear  187  engaged with the first transmission gear  186 . 
     The second transmission gear  187  may be a two-stage helical gear. In other words, the second transmission gear  187  includes two helical gears arranged vertically, and the upper helical gear can be connected to the helical gear of the first transmission gear  186 . 
     The second transmission gear  187  may be a two-stage helical gear. In other words, the second transmission gear  187  includes two helical gears arranged vertically, and the upper helical gear can be connected to the helical gear of the first transmission gear  186 . 
     The plurality of transmission gears  186 ,  187 ,  188  and  189  may further include a third transmission gear  188  engaged with the second transmission gear  187 . 
     The third transmission gear  188  may also be a two-stage helical gear. In other words, the third transmission gear  188  includes two helical gears arranged vertically, and the upper helical gear may be connected to the lower helical gear of the second transmission gear  187 . 
     The plurality of transmission gears  186 ,  187 ,  188  and  189  may further include a fourth transmission gear  189  engaged with the lower helical gear of the third transmission gear  188 . The fourth transmission gear  189  may be a helical gear. 
     The transmission shaft  190  may be coupled to the fourth transmission gear  189 . In other words, the fourth transmission gear  189  is an output end of the power transmitting portion. The transmission shaft  190  may be coupled to penetrate the fourth transmission gear  189 . The transmission shaft  190  may be rotated together with the fourth transmission gear  189 . 
     Accordingly, an upper bearing  191  is coupled to the upper end of the transmission shaft  190  passing through the fourth transmission gear  189  and a lower bearing  191   a  is coupled to the transmission shaft  190  at the lower side of the fourth transmission gear  189 . 
       FIG.  28    is a view illustrating a state where a power transmitting unit is coupled to a driving motor according to another embodiment of the present invention. 
     The present embodiment is the same as the previous embodiment in other portions but differs in the configuration of the power transmitting portion. Therefore, only the characteristic parts of the present embodiment will be described below. 
     Referring to  FIG.  28   , the power transmitting unit of the present embodiment may include a driving gear  610  connected to the shafts of the driving motors  182  and  184 . 
     The driving gear  610  may be a worm gear. The rotational shaft of the driving gear  610  may extend in the horizontal direction. Since the driving gear  610  is rotated together with the rotating shaft of the driving gear  610 , a bearing  640  may be connected to the driving gear  610  for smooth rotation. 
     The first housing  600  may include a motor support portion  602  for supporting the driving motors  182  and  184  and a bearing support portion  604  for supporting the bearings  640 . 
     The power transmission unit may further include a plurality of transmission gears  620 ,  624  and  628  for transmitting the rotational force of the driving gear  610  to the rotation plates  420  and  440 . 
     The plurality of transmission gears  620 ,  624  and  628  may include a first transmission gear  620  engaged with the driving gear  610 . The first transmission gear  620  may include an upper worm gear to engage with the driving gear  610 . 
     Since the driving gear  610  and the second transmission gear  620  mesh with each other in the form of a worm gear, there is an advantage that noise is reduced by friction in a process in which the rotational force of the driving gear  610  is transmitted to the second transmission gear  620 . 
     The first transmission gear  620  may include a helical gear disposed at the lower side of the upper worm gear as a second gear. 
     The first transmission gear  620  may be rotatably connected to a first shaft  622  extending in the vertical direction. The first shaft  622  may be fixed to the first housing  600 . 
     Accordingly, the first transmission gear  620  can be rotated with respect to the fixed first shaft  622 . According to the present embodiment, since the first transmission gear  620  is configured to rotate with respect to the first shaft  622 , there is an advantage that a bearing is unnecessary. 
     The plurality of transmission gears  620 ,  624 , and  628  may further include a second transmission gear  624  engaged with the first transmission gear  620 . The second transmission gear  624  is, for example, a helical gear. 
     The second transmission gear  624  may be rotatably connected to a second shaft  626  extending in the vertical direction. The second shaft  626  may be fixed to the first housing  600 . 
     Accordingly, the second transmission gear  624  can be rotated with respect to the fixed second shaft  626 . According to the present embodiment, since the second transmission gear  624  is configured to rotate with respect to the second shaft  626 , there is an advantage that no bearing is required. 
     The plurality of transmission gears  620 ,  624 , and  628  may further include a third transmission gear  628  engaged with the second transmission gear  624 . The third transmission gear  628  is, for example, a helical gear. 
     The third transmission gear  628  may be connected to a transmission shaft  630  connected to the rotation plates  420  and  440 . The transmission shaft  630  may be connected to the third transmission gear  628  and rotated together with the third transmission gear  628 . 
     A bearing  632  may be coupled to the transmission shaft  630  for smooth rotation of the transmission shaft  630 . 
     &lt;Disposition of Driving Device in Nozzle Base&gt; 
       FIG.  29    is a view illustrating a relationship between a rotating direction of a rotation plate and an extending direction of an axis of the driving motor according to an embodiment of the present invention, and  FIG.  30    is a plan view illustrating a state where a driving device is installed on a nozzle base according to an embodiment of the present invention, and  FIG.  31    is a front view illustrating a state where a driving device is installed on a nozzle base according to an embodiment of the present invention. 
     Particularly,  FIG.  30    illustrates a state where the second housing of the motor housing is removed. 
     Referring to  FIG.  29    to  FIG.  31   , the first rotation plate  420  and the second rotation plate  440  arranged in the nozzle  1  in the lateral direction may be rotated in opposite directions to each other. 
     For example, a portion closest to the centerline A 2  of the second flow path  114  in each of the rotation plates  420  and  440  may be rotated away from the first flow path  112  toward a side of the first flow path  112 . 
     The axes A 3  and A 4  of the driving motors  182  and  184  may be disposed substantially parallel to the tangents of the rotation plates  420  and  440 . 
     In the present embodiment, the term “substantially parallel” means that the angle formed between the two lines is within 5 degrees even if they are not parallel. 
     When considering the vibration due to the driving force generated in each of the driving motors  182  and  184  and the vibration due to friction with the floor generated by the rotation of the rotation cleaning units  40  and  41 , the driving motors  182  and  184  may be disposed to be symmetrical with respect to the centerline A 2  of the second flow path  114 . 
     Each of the driving motors  182  and  184  may be disposed so as to be vertically overlapped with the rotation plates  420  and  440 . 
     At least a portion of each of the driving motors  182  and  184  may be positioned in a region between the rotation centers C 1  and C 2  of the rotation plates  420  and  440  and the outer peripheral surfaces of the rotation plates  420  and  440 . For example, all of the driving motors  182  and  184  may be disposed so as to overlap with the rotation plates  420  and  440  in the vertical direction. 
     Preferably, each of the driving motors  182  and  184  may be positioned as close as possible to the centerline A 2  of the second flow path  114  from the nozzle  1  such that the vibration balance is maximized in the entire nozzle  1 . 
     For example, as illustrated in  FIG.  30   , the axes A 3  and A 4  of the driving motors  182  and  184  may be disposed to extend in the front and rear direction. At this time, the axes A 3  and A 4  of the driving motors  182  and  184  may be substantially parallel to the centerline A 2  of the second flow path  114 . 
     The driving motors  182  and  184  may include a front end portion  182   a  and a rear end portion  182   b  spaced apart from each other in the extending direction of the axes A 3  and A 4 . 
     The front end portion  182   a  may be positioned closer to the first flow path  112  than the rear end portion  182   b.    
     The rotation center of the fourth transmission gear  189  (which is substantially rotation center of rotation cleaning unit) may be positioned in a region corresponding to a region between the front end portion  182   a  and the rear end portion  182   b.    
     At least a portion of the fourth transmission gear  189  may be disposed so as to overlap with the driving motors  182  and  184  in the vertical direction. 
     The driving motors  182  and  184  include a connection surface for connecting between the front end portion  182   a  and the rear end portion  182   b  and an outermost line  182   c  of the connection surface can overlap with the fourth transmission gear  189  in the vertical direction. 
     The axes A 3  and A 4  of each of the driving motors  182  and  184  may be positioned higher than the locus of rotation of the transmission gears. 
     By this disposition of the driving devices  170  and  171 , the weight of each of the driving devices  170  and  171  can be evenly distributed to the right and left of the nozzle  1 . 
     In addition, as the axis A 3  of the first driving motor  182  and the axis A 4  of the second driving motor  184  extend in the front and rear direction, by each of the driving motors  182  and  184 , the height of the nozzle  1  can be prevented from being increased. 
     The imaginary line A 5  connecting the axis A 3  of the first driving motor  182  and the axis A 4  of the second driving motor  184  passes through the second flow path  114 . This is because each of the driving motors  182  and  184  is positioned close to the rear side of the nozzle  1  so that the increase in the height of the nozzle  1  by the driving motors  182  and  184  can be prevented. 
     In addition, in a state where the driving gears  185  and  185  are connected to the shaft of each of the driving motors  182  and  184 , so that the increase in the height of the nozzle  1  is minimized by each of the driving devices  170  and  171 , the driving gear  185  may be positioned between the driving motors  182  and  184  and the first flow path  112 . 
     In this case, since the driving motors  182  and  184  having the longest vertical length of the driving devices  170  and  171  are positioned as close as possible to the rear side in the nozzle main body  10 , the increase in height of a side of the front end portion of the nozzle  1  can be minimized. 
     Since the driving devices  170  and  171  are positioned close to the rear side of the nozzle  1  and the water tank  200  is positioned above the driving devices  170  and  171 , the center of gravity of the nozzle  1  may be pulled toward the rear side of the nozzle  1  due to the weight of the water in the water tank  200  and the driving devices  170  and  171 . 
     Accordingly, in the present embodiment, the connection chamber (see  226  of  FIG.  6   ) of the water tank  200  is positioned between the first flow path  112  and the driving devices  170  and  171  with respect to the front and rear directions of the nozzle  1 . 
     In the present embodiment, the rotation centers C 1  and C 2  of the rotation plates  420  and  440  coincide with the rotation center of the transmission shaft  190 . 
     The axes A 3  and A 4  of the driving motors  182  and  184  can be positioned in the region between the rotation centers C 1  and C 2  of the rotation plates  420  and  440 . 
     In addition, the driving motors  182  and  184  may be positioned in a region between the rotation centers C 1  and C 2  of the rotation plates  420  and  440 . 
     In addition, each of the driving motors  182  and  184  may be disposed so as to overlap with the imaginary line connecting the first rotation center C 1  and the second rotation center C 2  in the vertical direction. 
     &lt;Driving Unit Cover of Nozzle Cover, and Disposition Relationship Between Rotation Center of Rotation Plate and Motor&gt; 
       FIG.  32    is a view illustrating a structure of a driving unit cover of a nozzle cover and a disposition relationship between a rotation center of a rotation plate and a driving motor according to an embodiment of the present invention. 
     Referring to  FIG.  14    and  FIG.  32   , a pair of the driving unit covers  132  and  134  of the nozzle cover  130  is disposed to be symmetrical in the lateral direction and have a convex shape upward. 
     Each of the driving unit covers  132  and  134  may include a first protruding surface  135   a  extending upward from the bottom wall  130   a  of the nozzle cover  130  and a second protruding surface  135   b  positioned higher than the first protruding surface  135   a  and having a different curvature from the first protruding surface  135   a.    
     The first protruding surface  135   a  and the second protruding surface  135   b  may be directly connected or may be connected by a third protruding surface  135   c.    
     At this time, the third protruding surface  135   c  is formed to have a curvature different from that of each of the first protruding surface  135   a  and the second protruding surface  135   b.  The third protruding surface  135   c  is positioned higher than the first protruding surface  135   a  and lower than the second protruding surface  135   b.    
     In the present embodiment, the second protruding surface  135   b  may overlap with the second bottom wall  213   b  of the water tank  200  in the vertical direction. In addition, the second protruding surface  135   b  may be formed in a shape corresponding to the second bottom wall  213   b  of the water tank  200 . 
     The second protruding surface  135   b  may be the surface that is positioned at the highest position in the driving unit covers  132  and  134 . 
     The second protruding surface  135   b  may be formed to have a longer left and right length (width) than a front and rear length (width), for example. In the present embodiment, the length direction of the second protruding surface  135   b  is long in the lateral direction. 
     The length direction of the second protruding surface  135   b  intersects with the extending direction of the axes A 3  and A 4  of the driving motors  182  and  184 . 
     The center C 3  of the driving unit covers  132  and  134  (for example, center of curvature) may be positioned on the second protruding surface  135   b.    
     The center C 4  of the second protruding surface  135   b  is eccentric with the center C 3  of the driving unit cover  132 . 
     For example, the center C 4  of the second protruding surface  135   b  is eccentric in a direction away from the centerline A 2  of the second flow path  114  at the center C 3  of the driving unit cover  132 . 
     Therefore, the centers C 3  of the driving unit covers  132 ,  134  are positioned between the center C 4  of the second protruding surface  135   b  and the centerline A 2  of the second flow path  114 . 
     In addition, the rotation centers C 1  and C 2  of the rotation plates  420  and  440  may be positioned so as to overlap with the second protruding surface  135   b  in the vertical direction. 
     The rotation centers C 1  and C 2  of the rotation plates  420  and  440  are eccentric with the centers C 3  of the driving unit covers  132  and  134 . 
     For example, the rotation centers C 1  and C 2  of the rotation plates  420  and  440  may be eccentric in a direction away from the centerline A 2  of the second flow path  114  at the centers C 3  of the driving unit covers  132  and  134 . 
     Accordingly, the centers C 3  of the driving unit covers  132  and  134  are positioned between the rotation centers C 1  and C 2  of the rotation plates  420  and  440  and the centerline A 2  of the second flow path  114 . 
     At this time, the rotation centers C 1  and C 2  of the rotation plates  420  and  440  are aligned with the center C 4  of the second protruding surface  135   b  or are spaced apart from the center C 4  of the second protruding surface  135   b  in the front and rear direction. 
     The centers C 3  of the driving unit covers  132  and  134  may be positioned between the axes A 3  and A 4  of the driving motors  182  and  184  and the center C 4  of the second protruding surface  135   b.    
     The centers C 3  of the driving unit covers  132  and  134  can be positioned between the axes A 3  and A 4  of the driving motors  182  and  184  and the rotation centers C 1  and C 2  of the rotation plates  420  and  440 . 
     The central axis Y bisecting the length of the nozzle cover  130  (or nozzle main body or nozzle housing) in the front and rear direction may be disposed to overlap with the second protruding surface  135   b  in the vertical direction. 
     The central axis Y bisecting the length of the nozzle cover  130  in the front and rear direction may be positioned closer to the front end of the nozzle cover  130  than the center C 4  of the second protruding surface  135   b.    
     &lt;Rotation Plate&gt; 
       FIG.  33    is a view illustrating a rotation plate according to an embodiment of the present invention as viewed from above, and  FIG.  34    is a view illustrating a rotation plate according to an embodiment of the present invention as viewed from below. 
     Referring to  FIG.  33    and  FIG.  34   , each of the rotation plates  420  and  440  may be formed in a disc shape so as to prevent mutual interference during the rotation process. 
     Each of the rotation plates  420  and  440  includes an outer body  420   a  in the form of a circular ring, an inner body  420   b  positioned in a central region of the outer body  420   a  and spaced apart from the inner peripheral surface of the outer body  420   a,  and a plurality of connection ribs  425  connecting the outer circumferential surface of the inner body  420   b  and the inner circumferential surface of the outer body  420   a.    
     The height of the inner body  420   b  may be lower than the height of the outer body  420   a . The upper surface of the inner body  420   b  may be positioned lower than the upper surface  420   c  of the outer body  420   a.    
     A shaft coupling unit  421  for coupling the transmission shaft  190  may be provided at a central portion of each of the rotation plates  420  and  440 . 
     For example, the shaft coupling unit  421  may be provided at the central portion of the inner body  420   b.  The shaft coupling unit  421  may protrude upward from the upper surface of the inner body  420   b  and the upper surface may be positioned higher than the upper surface  420   c  of the outer body  420   a.    
     For example, the transmission shaft  190  may be inserted into the shaft coupling unit  421 . For this purpose, a shaft receiving groove  422  for inserting the transmission shaft  190  may be formed in the shaft coupling unit  421 . 
     A fastening member may be drawn into the shaft coupling unit  421  from below the rotation plates  420  and  440  and be fastened to the transmission shaft  190  in a state where the transmission shaft  190  is coupled to the shaft coupling unit  421 . 
     The rotation plates  420  and  440  may include a plurality of water passage holes  424  disposed outwardly of the shaft coupling unit  421  in the radial direction. 
     In the present embodiment, since the rotation plates  420  and  440  are rotated in a state where the mops  402  and  404  are attached to the lower sides of the rotation plates  420  and  440 , so as to smoothly supply water to the mops  402  and  404  through the rotation plates  420  and  440 , the plurality of water passage holes  424  may be spaced circumferentially around the shaft coupling unit  421 . 
     The plurality of water passage holes  424  may be defined by a plurality of connection ribs  425 . At this time, each of the connection ribs  425  may be positioned lower than the upper surface  420   c  of the rotation plates  420  and  440 . In other words, each of the connection ribs  425  may be positioned lower than the upper surface  420   c  of the outer body  420   a.    
     Both sides of the connection ribs  425  may include inclined surfaces that are inclined downward so that the water can flow smoothly into the adjacent water through holes  424  in a case where the water falls into the connection ribs  425 . The inclined surface may be planar or rounded. 
     Therefore, the width of the connection rib  425  is increased from the upper side to the lower side with respect to the vertical section of the connection rib  425 . 
     A portion of the connection rib  425  connected to the inner circumferential surface of the outer body  420   a  and a portion of the connection rib  425  connected to the outer circumferential surface of the inner body  420   b  are rounded in the horizontal direction and have the maximum width of the entire length (length of rotation plate in radial direction). 
     The inner body  420   b  is provided with a groove portion  421   a  for providing a space for positioning the protruding sleeve  111   b  of the nozzle base  110 . The protruding sleeve  111   b  may be seated in the groove portion  421   a.  Alternatively, the lower surface of the protruding sleeve  111   b  is spaced apart from the bottom of the groove portion  421   a  but is lower than the upper surface of the inner body  420   b.    
     The protruding sleeve  111   b  surrounds the shaft coupling unit  421 . Therefore, the water dropped onto the rotation plates  420  and  440  can be prevented from flowing toward a side of the shaft coupling unit  421  by the protruding sleeve  111   b.    
     Since the rotation plates  420  and  440  rotate, centrifugal force acts on the rotation plates  420  and  440 . It is necessary to prevent the water sprayed to the rotation plates  420  and  440  from flowing radially outward in a state where the water cannot pass through the water passage holes  424  in the rotation plates  420  and  440  due to the centrifugal force. 
     Therefore, a water blocking rib  426  may be formed on the upper surface of the rotation plates  420  and  440  radially outside of the water passage hole  424 . 
     For example, the water blocking ribs  426  may protrude upward from the upper surface  420   c  of the outer body  420   a.  The water blocking ribs  426  may be formed continuously in the circumferential direction. 
     The plurality of water passage holes  424  may be positioned in the inner region of the water blocking ribs  426 . The water blocking ribs  426  may be formed in the form of a circular ring, for example. 
     The center of the water blocking ribs  426  may coincide with the center of the bottom rib  111   a  formed in the nozzle base  110 . 
     The diameter of the bottom rib  111   a  of the nozzle base  110  may be larger than the diameter of the water blocking ribs  426  (see  FIG.  39   ). Therefore, since the two ribs are arranged sequentially outward in the radial direction, the water blocking effect can be improved. 
     An installation groove  428  may be formed on the lower surface  420   d  of the rotation plates  420  and  440  to provide attachment means (see  428   a  of  FIG.  38   ) for attaching the mops  402  and  404 . For example, the installation groove  428  may be formed on a lower surface of the outer body  420   a.    
     The attachment means (see  428   a  of  FIG.  38   ) can be, for example, a hook-and-look fastener such as Velcro®. 
     A plurality of installation grooves  428  may be spaced apart in the circumferential direction with respect to the rotation centers C 1  and C 2  of the rotation plates  420  and  440 . Therefore, a plurality of attachment means (see  428   a  of  FIG.  38   ) may be provided on the lower surface  420   b  of the rotation plates  420  and  440 . 
     In the present embodiment, the installation groove  428  may be disposed radially outward of the water passage hole  424  with respect to the rotation centers C 1  and C 2  of the rotation plates  420  and  440 . 
     For example, the water passage hole  424  and the installation groove  428  may be sequentially arranged radially outward from the rotation centers C 1  and C 2  of the rotation plates  420  and  440 . 
     The plurality of installation grooves  428  may be formed in an arc shape, for example, and the length of the arcs of the plurality of installation grooves  428  may be formed to be larger than a distance between two adjacent installation grooves. 
     A through hole among a plurality of water through holes may be positioned in an area between two adjacent installation grooves. 
     The lower surface  420   d  of the rotation plates  420  and  440  may be provided with a contact rib  430  which contacts the mop  402  or  404  in a state where the mop  402  or  404  is attached to the attachment means. 
     The contact ribs  430  may protrude downward from a lower surface  420   b  of the rotation plates  420  and  440 . For example, the contact rib  430  may protrude downward from a lower surface of the outer body  420   a.    
     The contact ribs  430  are disposed radially outward of the water passage holes  424  and may be formed continuously in the circumferential direction. For example, the contact rib  430  may be formed in a circular ring shape. 
     Since the mops  402  and  404  can be deformed by themselves, for example, as a fiber material, gaps can exist between the mops  402  and  404  and the lower surfaces  420   d  of the rotation plates  420  and  440  in a state where the mops  402  and  404  are attached to the rotation plates  420  and  440  by the attaching means. 
     When the gap existing between the mops  402  and  404  and the lower surfaces  420   d  of the rotation plates  420  and  440  is large, there is a fear that water is not absorbed to the mops  402  and  404  in a state of passing through the water passage hole  424  and flows to the outside through the gap between the lower surfaces  420   d  of the rotation plates  420  and  440  and the upper surface of the mops  402  and  404 . 
     However, according to the present embodiment, when the mops  402  and  404  are coupled to the rotation plates  420  and  440 , the contact ribs  430  can be brought into contact with the mops  402  and  404 . When the nozzle  1  is placed on the floor, the contact ribs  430  press the mops  402 ,  404  by the load of the nozzle  1 . 
     Accordingly, the contact ribs  430  prevent the formation of the gap between the lower surfaces  420   d  of the rotation plates  420  and  440  and the upper surfaces of the mops  402  and  404  and thus water passing through the water passage holes  424  can be smoothly supplied to the mops  402  and  404 . 
     &lt;Water Supply Flow Path&gt; 
       FIG.  35    is a view illustrating a water supply flow path for supplying water of a water tank to the rotation cleaning unit according to an embodiment of the present invention,  FIG.  36    is a view illustrating a valve in a water tank according to an embodiment of the present invention, and  FIG.  37    is a view illustrating a state where the valve opens the discharge port in a state where the water tank is mounted on the nozzle housing. 
       FIG.  38    is a view illustrating a disposition of a rotation plate and a spray nozzle according to an embodiment of the present invention and  FIG.  39    is a view illustrating a disposition of a water discharge port of a spray nozzle in a nozzle main body according to an embodiment of the present invention. 
       FIG.  40    is a conceptual diagram illustrating a process of supplying water to a rotation cleaning unit in a water tank according to an embodiment of the present invention. 
     Referring to  FIG.  35    to  FIG.  40   , the water supply flow path of the present embodiment includes a first supply tube  282  connected to the valve operating unit  144 , a water pump  270  connected to the first supply tube  282 , and a second supply tube  284  connected to the water pump  270 . 
     The water pump  270  may include a first connection port  272  to which the first supply tube  282  is connected and a second connection port  274  to which the second supply tube  284  is connected. On the basis of the water pump  270 , the first connection port  272  is an inlet, and the second connection port  274  is a discharge port. 
     In addition, the water supply flow path may further include a connector  285  to which the second supply tube  284  is connected. 
     The connector  285  may be formed such that the first connection unit  285   a,  the second connection unit  285   b,  and the third connection unit  285   c  are arranged in a T-shape. The second connection tube  284  may be connected to the first connection unit  28   a.    
     The water supply flow path may further include a first branch tube  286  connected to the second connection unit  285   b  and a second branch tube  287  connected to the third connection unit  285   c.    
     Accordingly, the water flowing through the first branch tube  286  may be supplied to the first rotation cleaning unit  40  and may be supplied to the second rotation cleaning unit  41  flowing through the second branch tube  287 . 
     The connector  285  may be positioned at the central portion of the nozzle main body  10  such that each of the branch tubes  286  and  287  has the same length. 
     For example, the connector  285  may be positioned below the flow path cover  136  and above the flow path forming portion  150 . In other words, the connector  285  may be positioned directly above the second flow path  114 . Thus, substantially the same amount of water can be dispensed from the connector  285  to each of the branch tubes  286  and  287 . 
     In the present embodiment, the water pump  270  may be positioned at one point on the water supply flow path. 
     At this time, the water pump  270  may be positioned between the valve operating unit  144  and the first connection unit  285   a  of the connector  285  so that water can be discharged from the water tank  200  using a minimum number of the water pumps  270 . 
     In the present embodiment, the water pump  270  may be installed in the nozzle cover  130  in a state where the water pump  270  is positioned close to the portion where the valve operating unit  144  is installed. 
     As an example, the valve operating unit  144  and the water pump  270  may be provided on one side of both sides of the nozzle main body  10  with respect to the centerline A 2  of the second flow path  114 . 
     Therefore, the length of the first supply tube  282  can be reduced, and accordingly, the length of the water supply flow path can be reduced. 
     Each of the branch tubes  286  and  287  may be connected to the spray nozzle  149 . The spray nozzle  149  can also form the water supply flow path of the present invention. 
     The spray nozzle  149  may include a connection unit  149   a  to be connected to each of the branch tubes  286  and  287  as described above. 
     The spray nozzle  149  may further include a water discharge port  149   b.  The water discharge port  149   b  extends downward through the nozzle hole  119 . In other words, the water discharge port  149   b  may be disposed on the outside of the nozzle housing  100 . 
     When the water discharge port  149   b  is positioned outside the nozzle housing  100 , water sprayed through the water discharge port  149   b  can be prevented from being drawn into the nozzle housing  100 . 
     At this time, so as to prevent the water discharge port  149   b  exposed to the outside of the nozzle housing  100  from being damaged, groove  119   a  recessed upward is formed in the bottom of the nozzle base  110 . The water discharge port  149   b  may be positioned in the groove  119   a  in a state of passing through the nozzle hole  119 . In other words, the nozzle hole  119  may be formed in the groove  119   a.    
     The water discharge port  149   b  may be disposed to face the rotation plates  420  and  440  in the groove  119   a.  The lower surface of the water discharge port  149   b  may be positioned at the same height as the lower surface of the nozzle base  110  or may be positioned higher. The lower surface of the water discharge port  149   b  may be positioned higher than the upper surface  420   c  of the outer body  420   a.    
     The water sprayed from the water discharge port  149   b  can pass through the water passage hole  424  of the rotation plates  420  and  440 . 
     The minimum radius of the water passage hole  424  at the center of the rotation plates  420  and  440  is R 2  and the maximum radius of the water passage hole  424  at the center of the rotation plates  420  and  440  is R 3 . 
     The radius from the center of the rotation plates  420  and  440  to the center of the water discharge port  149   b  is R 4 . At this time, R 4  is larger than R 2  and smaller than R 3 . 
     D 1 , which is a difference between R 3  and R 2 , is larger than the diameter of the water discharge port  149   b.    
     In addition, D 1 , which is a difference between R 3  and R 2 , is formed to be smaller than a minimum width W 1  of the water passage hole  424 . 
     When the outer diameters of the rotation plates  420  and  440  are R 1 , the R 3  may be larger than half of R 1 . 
     A line perpendicularly connecting the first rotation center C 1  and the centerline A 2  of the first flow path  112  may be referred to as a first connection line A 6 , and a line perpendicularly connecting the second rotation center C 2  and an axis A 2  of the first flow path  112  may be referred to as a second connecting line A 7 . 
     At this time, the first connection line A 6  and the second connection line A 7  may be positioned in a region between a pair of water discharge port  149   b  for supplying water to each of the rotation cleaning units  40  and  41 . 
     In other words, the horizontal distance D 3  from the water discharge port  149   b  to the centerline A 2  of the second flow path  114  is longer than the horizontal distance D 2  to the rotation center C 1  and C 2  of each of the rotation plates  420  and  440  and centerline A 2  of the second flow path  114 . 
     This is because the second flow path  114  extends in the front and rear direction at the central portion of the nozzle  1  so that water is prevented from being suctioned into the nozzle  1  through the second flow path  114  during the rotation of the rotating plates  420 . 
     The horizontal distance between water discharge port  149   b  and the centerline A 2  of the first flow path  112  is shorter than the horizontal distance between each of the rotation centers C 1  and C 2  and the centerline A 2  of the first flow path  112 . 
     The water discharge port  149   b  is positioned opposite to the axes A 3  and A 4  of the driving motors  182  and  184  with respect to the connection lines A 6  and A 7 . 
     Meanwhile, the valve  230  may include a movable unit  234 , an opening and closing unit  238 , and a fixing unit  232 . 
     The fixing unit  232  may be fixed to a fixing rib  217  protruding upward from the first body  210  of the water tank  200 . 
     The fixing unit  232  may have an opening  232   a  through which the movable unit  234  passes. 
     The fixing unit  232  restricts the movable unit  234  from moving upward at a predetermined height from the fixing unit  232  in a state where the fixing unit  232  is coupled with the fixing rib  217 . 
     The movable unit  234  can be moved in the vertical direction in a state where a portion of the movable unit  234  passes through the opening  232   a.  In a state where the movable unit  234  is moved upward, water can pass through the opening  232   a.    
     The movable unit  234  may include a first extension portion  234   a  extending downward and coupled with the opening and closing unit  238  and a second extension portion  234   b  extending upwardly and passing through the opening  232   a.    
     The movable unit  234  may be elastically supported by an elastic member  236 . One end of the elastic member  236 , as a coil spring, for example, may be supported by the fixed portion  232  and the other end may be supported by the movable unit  234 . 
     The elastic member  236  provides a force to the movable unit  234  to move the movable unit  234  downward. 
     The opening/closing unit  238  can selectively open the discharge port  216  by moving the movable unit  234  up and down. 
     At least a portion of the opening/closing unit  238  may have a diameter larger than the diameter of the discharge port  216  so that the opening/closing unit  238  may block the discharge port  216 . 
     The opening/closing unit  238  may be formed of, for example, a rubber material so that the leakage of water is prevented in a state where the opening/closing unit  238  blocks the discharge port  216 . 
     The elastic force of the elastic member  236  is applied to the movable unit  234  so that a state where the opening and closing unit  238  blocks the discharge port  216  can be maintained unless an external force is applied to the movable unit  234 . 
     The movable unit  234  can be moved by the valve operating unit  144  in the process of mounting the water tank  200  to the nozzle main body  10 . 
     The valve operating unit  144  is coupled to the nozzle cover  130  from below the nozzle cover  130  as described above. 
     The valve operating unit  144  may include a pressing portion  144   a  passing through the water passage opening  145 . The pressing portion  144   a  may protrude upward from the bottom of the nozzle cover  130  in a state of passing through the water passage opening  145  of the nozzle cover  130 . 
     The valve operating unit  144  may form a water supply flow path together with the bottom of the nozzle cover  130 . A connection tube  144   c  for connecting the first supply tube  282  may be provided at one side of the valve operating unit  144 . 
     The diameter of the water passage opening  145  may be larger than the outer diameter of the pressing portion  144   a  so that water flows smoothly in a state where the pressing portion  144   a  passes through the water passage opening  145 . 
     When the water tank  200  is mounted on the nozzle main body  10 , the pressing portion  144   a  is drawn into the discharge port  216  of the water tank  200 . The pressing portion  144   a  presses the movable unit  234  in a process in which the pressing portion  144   a  is being drawn into the discharge port  216  of the water tank  200 . 
     The movable unit  234  is lifted and the opening and closing unit  238  coupled to the movable unit  234  moves upward together with the movable unit  234  to be separated from the discharge port  216  to open the discharge port  216 . 
     The water in the water tank  200  is discharged through the discharge port  216  and absorbed into the absorption member  147  in the valve operating unit  144  through the water passage opening  145 . The water absorbed by the absorption member  147  is supplied to the first supply tube  282  connected to the connection tube  144   c.    
     The water supplied to the first supply tube  282  flows into the second supply tube  284  after being drawn into the water pump  270 . The water flowing into the second supply tube  284  flows to the first branch tube  286  and the second branch tube  287  by the connector  285 . The water flowing into each of the branch tubes  286  and  287  is sprayed from the spray nozzle  149  toward the rotation cleaning units  40  and  41 . 
     The water sprayed from the spray nozzle  149  is supplied to the mops  402  and  404  after passing through the water passage holes  424  of the rotation plates  420  and  440 . The mops  402  and  404  are rotated while absorbing the supplied water to wipe the floor. 
     In the present embodiment, since the water discharged from the water tank  200  passes through the first supply tube  282  after passing through the absorption member  147  and the absorption member  147  absorbs the pressure generated by the pumping force of the water pump  270 , it prevents the water from suddenly flowing into the connector  285 . 
     In this case, the water pressure is concentrated on one of the first branch tube  286  and the second branch tube  287 , and concentration of water into a branch tube can be prevented. 
       FIG.  41    is a perspective view illustrating the nozzle for the cleaner from which a connection tube is separated according to an embodiment of the present invention as viewed from the rear side,  FIG.  42    is a sectional view illustrating area ‘A’ in  FIG.  41   , and  FIG.  43    is a perspective view illustrating the gasket of  FIG.  42   . 
     Referring to  FIG.  41    to  FIG.  43   , at least one air hole  219  for introducing outside air may be formed in the water tank  200 . Hereinafter, as an example, one air hole  219  is formed in the water tank  200 , but a plurality of the air holes  219  may be provided. 
     The air holes  219  may be formed on one side of the water tank  200 . For example, the air holes  219  may be formed in any one of a pair of the front and rear extending walls  215   b  facing each other in the water tank  200 . 
     Although the pair of the front and rear extending walls  215   b  is spaced apart from each other to define a space and the connection tube  50  is positioned in the space, a portion of the front and rear extending walls  215   b  formed with the air holes  219  is spaced apart so that the air can be smoothly supplied to the air holes  219 . 
     In detail, the gasket  290  may be press-fitted into the air hole  219 . 
     The gasket  290  can guide the outside air into the interior space of the water tank  200 . 
     The gasket  290  may be referred to as a check valve in that the outside air flows into the water tank  200  while the water in the water tank  200  is interrupted so as not to be discharged to the outside. 
     The gasket  290  may be formed of a material deformed in shape by an external force. For example, the gasket  290  may be formed of polyethylene material but is not limited thereto. 
     The gasket  290  may include a cylindrical body  293 , for example. 
     An end portion of one side of the body  293  may be received inside the water tank  200  through the air hole  219 . The other end portion of the body  293  may be exposed to the outside of the water tank  200 . 
     At least one sealing protrusion  294  and  295  may be formed on the outside of the body  293 . The outer diameter of the sealing protrusions  294  and  295  may be larger than the inner diameter of the air hole  219 . When the sealing protrusions  294  and  295  are formed as described above, leakage between the body  293  and the air holes  219  can be prevented. 
     In a case where a plurality of the sealing protrusions  294  and  295  are formed, a portion of the sealing protrusions  294  and  295  may be positioned inside the water tank  200 . 
     A flange  292  having an outer diameter larger than that of the body  293  and the sealing protrusions  294  and  295  may be formed at the other end portion of the body  293 . The flange  292  has a larger diameter than the air hole  219 . The entirety of the gasket  290  is prevented from entering the inside of the water tank  200  by the flange  292 . 
     In addition, the gasket  290  may be formed with an air flow path  291  through which air flows in the central portion thereof and a slit  297  may be formed at the other end portion thereof. At this time, the other end portion of the gasket  290  may contact water in the water tank  200 . 
     In addition, so that the slit  297  formed at the other end portion of the gasket  290  is blocked by the pressure of water, the gasket  290  is formed such that the sectional area of the gasket  290  decreases from one point to the other end portion, and thus inclined surfaces  296  can be formed on the outer side. 
     In detail, the inclined surfaces  296  may be formed on both sides of the slit  297 . 
     According to an embodiment, the water pressure is applied to the inclined surface  296  formed at the other end portion of the gasket  290  and thus the other end portion of the gasket  290  inwardly shrinks, and in this process, the slit  297  is blocked in a state where the inner pressure of the water tank  200  is not lowered (a state where water is not discharged). 
     Therefore, water in the water tank  200  is prevented from leaking to the outside through the slit  297 . 
     In addition, the slit  297  is blocked by the water pressure of the water tank  200  so that the air is not supplied to the inner portion of the water tank  200  through the slit  297  in a state where no external force is applied to the gasket  290 . 
     Meanwhile, outside air can be supplied to the water tank  200  through the gasket  290  in a state where the internal pressure of the water tank  200  is lowered (a state where water is discharged). 
     Specifically, when the pump motor  280  operates, the water in the water tank  200  is discharged through the discharge port  216  by the water pump  270 . The internal pressure of the water tank  200  is instantaneously lowered. 
     While the pressure applied to the inclined surface  296  of the gasket  290  is also lowered, the other end portion of the gasket  290  is restored to an original state thereof, and the slit  297  can be opened. 
     As described above, when the slit  297  is opened, the outside air can be supplied to the water tank  200  through the slit  297 . 
     In a state where the slit  297  is opened, the surface tension of the water around the slit  297  and the force with which the external air flows are greater than the water pressure in the water tank  200 , and water is not discharged to the outside of the water tank  200  through the slit  297 . 
     According to the present embodiment, water in the water tank  200  can be prevented from being discharged to the outside through the gasket  290  when the water pump  270  is not operated. 
     In addition, in a state where the water pump  270  is operated, since air can be introduced into the water tank  200  through the slits  297  of the gasket  290 , the water in the water tank  200  can be stably supplied to the mops  402  and  404 . 
     According to the proposed embodiment, since foreign matters on the floor can be suctioned, the floor can be wiped by rotating the mop, and water can be supplied to the mop, there is an advantage that cleaning performance is improved. 
     In addition, according to the present embodiment, even when a structure capable of wiping the floor using the mop is applied, since the driving devices are disposed on both sides of the flow path extending in the front and rear direction, the length of the air flow path is prevented from increasing, and thus flow path loss can be reduced. 
     In addition, according to the present embodiment, since each of the driving devices is disposed symmetrically on both left and right sides with respect to the front and rear centerlines of the suction flow path, there is an advantage that the weight of the plurality of driving devices is uniformly distributed to the left and right. 
     In addition, according to the present embodiment, since each of the driving motors is disposed so as to overlap with each of the rotation plates in the vertical direction and is positioned in the area between the rotation center and the outer peripheral surface of each of the rotation plates, the power transmission path for transmitting the power of the driving motor to the rotating plate is reduced and the vibration generated in the power transmission process is reduced. 
     In addition, according to the present embodiment, since each of the driving devices is positioned as close as possible to the front and rear centerline of the suction flow path, there is an advantage that the nozzle can be rotated by applying less force when the direction of the nozzle is changed in the process of cleaning using the nozzle. 
     In addition, according to the present embodiment, since the driving unit cover covers the driving device, constituting the driving motor and the power transmission unit, the structure of the driving unit cover can be simplified and the volume of the driving unit cover can be prevented from becoming large.