Abstract:
A pad changer capable of automatically replacing a pad used to wipe out dust on a floor, a cleaner and a cleaner system having the pad changer are provided. The pad changer to replace a pad mounted to a cleaner includes a replacement unit. The replacement unit includes a separation cartridge to separate the pad from the cleaner and receive the separated pad therein, and a mounting cartridge to receive a pad therein and mount the pad to the cleaner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to, and claims the priority benefit of, Korean Patent Application No. 10-2013-0167184, filed on Dec. 30, 2013 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a pad changer by which pads are changed, and a cleaner and the cleaner system having the same. 
     2. Description of the Related Art 
     A robot cleaner is a self-motive appliance utilizing an automatic travel function to clean a room or the like by vacuuming foreign materials, such as dust, from a floor of a room without user intervention. The robot cleaner detects a distance to an obstacle, such as furniture, office supplies, walls or the like, present in a zone to be cleaned using a distance sensor, and changes traveling directions by selectively driving a left-wheel motor and a right-wheel motor to perform cleaning of the zone to be cleaned. 
     Besides robot cleaners capable of vacuuming foreign materials, such as dust, from a floor, robot cleaners capable of wiping floors have been developed recently. A conventional robot cleaner may be structured such that a pad may be removably attached to a bottom surface thereof using Velcro or the like. When a pad needs to be replaced because of contamination, a user turns a robot cleaner over, or stands a robot cleaner up, to remove the contaminated pad and attach a new pad. 
     SUMMARY 
     It is an aspect to provide a pad changer capable of automatically replacing a pad used to wipe dust on a floor, a cleaner and a cleaner system having the pad changer. 
     Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     In accordance with an aspect of an exemplary embodiment, a pad changer to replace a pad mounted to a cleaner is provided. The pad changer includes a replacement unit including a separation cartridge to separate the pad from the cleaner and receive the separated pad therein and a mounting cartridge to receive a pad therein and mount the pad to the cleaner. 
     The separation cartridge may include a pad separation device configured to move up and down in the separation cartridge and separate the pad from the cleaner. 
     The mounting cartridge may include a mounting plate on which the pad is seated and which is configured to move up and down in the mounting cartridge. 
     The pad changer may include a case. The replacement unit may include a base configured to rotate with respect to the case, on which the separation cartridge and the mounting cartridge are seated. 
     The case may be formed with an opening at a portion thereof, through which the separation cartridge and the mounting cartridge are inserted into the case. 
     The separation cartridge may be seated on a separation holder to be inserted into the case, and the mounting cartridge may be seated on a mounting holder to be inserted into the case. 
     The opening of the case may be provided with a guide protrusion at an inner side surface thereof, and the separation cartridge or the mounting cartridge may be formed with a guide recess which extends in a forward and backward direction and into which the guide protrusion is inserted. 
     The pad changer may include a plate unit on which the cleaner is seated and which is configured to move between the front of the case and a portion of the case corresponding to a position of the replacement unit. 
     The plate unit may include a frame, a first plate, a second plate and a third plate. The first plate, the second plate and the third plate may be connected to the frame. 
     The frame may be provided with fixing protrusions to support the cleaner. 
     The case may be provided with a rack gear, and the plate unit may be provided with a pinion gear tooth-engaged with the rack gear. 
     The pad changer may include a connection unit which is connected to the third plate and is formed with a guide slot into which a rotating shaft of the pinion gear is inserted. 
     The guide slot may be formed in a gradual curve. 
     In accordance with an aspect of an exemplary embodiment, a cleaner system is provided including a cleaner having a pad assembly and a pad changer to replace a pad mounted to the pad assembly. The pad assembly includes a pad unit and a locking member to which the pad unit is coupled, and the pad changer includes a replacement unit including a separation cartridge to separate the pad unit from the locking member and receive the separated pad unit therein and a mounting cartridge to receive a pad unit therein and mount the pad unit to the locking member. 
     The pad unit may include a pad and a pad mounting part. The pad may be removably mounted to a bottom surface of the pad mounting part. The pad mounting part may be provided with locking protrusions which have locking parts formed at tops thereof. 
     The pad assembly may include locking member accommodation parts to accommodate the locking member therein, and the locking member may have free ends, by which the locking member is elastically deformed. 
     The locking member and the locking member accommodation parts may be formed with locking holes through which the locking protrusions are inserted, and the locking holes of the locking member accommodation parts may partially interfere with the locking member. 
     The separation cartridge may include a separation device configured to move up and down in the separation cartridge, and the separation device may push the locking member upward to release interference of the locking protrusions with the locking member. 
     The mounting cartridge may include a mounting plate on which the pad unit is seated and which is configured to move up and down in the mounting cartridge, and the mounting plate may move upward so that the locking protrusions of the pad unit interfere with the locking member, thereby mounting the pad unit to the locking member. 
     The pad changer may include a plate unit to support the cleaner above the replacement unit. 
     The cleaner may be provided with guide protruding parts at side surfaces thereof, and the plate unit may be provided with fixing protrusions to support the guide protruding parts of the cleaner. 
     The pad changer may include a case to receive the replacement unit therein, and the plate unit may be configured to move between the front of the case and a portion of the case corresponding to a position of the replacement unit. 
     In accordance with an aspect of the present invention, a cleaner is provided including a pad assembly which includes a pad unit and a locking member to which the pad unit is coupled. The pad unit includes a pad and a pad mounting part to which the pad is removably mounted. The pad mounting part is provided with locking protrusions which have locking parts formed at tops thereof. 
     The pad assembly may include locking member accommodation parts to accommodate the locking member therein, and the locking member may have free ends, by which the locking member is elastically deformed. 
     The locking member and the locking member accommodation parts may be formed with locking holes through which the locking protrusions are inserted, and the locking holes of the locking member accommodation parts may partially interfere with the locking member. 
     As is apparent from the above description, since a contaminated pad may be automatically replaced by a new pad, pad replacement becomes convenient and cleaning efficiency is enhanced due to the newly attached pad cleaning a floor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a view illustrating a robot cleaner system according to an exemplary embodiment; 
         FIG. 2  is a view illustrating a robot cleaner according to an exemplary embodiment with a cover removed therefrom; 
         FIG. 3  is an exploded perspective view illustrating a pad assembly of the robot cleaner according to an exemplary embodiment; 
         FIG. 4  is a view illustrating a part of the pad assembly of the robot cleaner according to an exemplary embodiment; 
         FIGS. 5 and 6  are views illustrating a pad changer according to an exemplary embodiment; 
         FIG. 7  is an exploded perspective view illustrating a guide part of the pad changer according to an exemplary embodiment; 
         FIGS. 8A and 8B  are views illustrating a state in which a plate unit of the pad changer according to an exemplary embodiment slides; 
         FIG. 9  is a sectional view illustrating a part of the plate unit of the pad changer according to an exemplary embodiment; 
         FIGS. 10A through 10E  are views illustrating a state in which the robot cleaner according to an exemplary embodiment is seated on the pad changer; 
         FIG. 11  is an exploded perspective view illustrating the pad changer according to an exemplary embodiment with the plate unit removed therefrom; 
         FIG. 12  is a view illustrating the pad changer according to an exemplary embodiment with a cover of a replacement unit removed therefrom; 
         FIG. 13  is an exploded perspective view illustrating a separation cartridge according to an exemplary embodiment; 
         FIG. 14  is an exploded perspective view illustrating a mounting cartridge according to an exemplary embodiment; 
         FIG. 15  is a sectional view of the separation cartridge according to an exemplary embodiment; 
         FIG. 16  is a sectional view of the mounting cartridge according to an exemplary embodiment; 
         FIG. 17  is a view illustrating a locking release state of the pad assembly according to an exemplary embodiment; 
         FIG. 18  is a view illustrating a driving unit to rotate the replacement unit according to an exemplary embodiment; and 
         FIG. 19  is a view illustrating a robot cleaner system according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
       FIG. 1  is a view illustrating a robot cleaner system according to an exemplary embodiment. 
     Referring to  FIG. 1 , a robot cleaner system according to an exemplary embodiment comprises a robot cleaner  1  and a pad changer  5 . The robot cleaner  1  includes a pad assembly  2 . A cover  10  is provided at a top surface of the robot cleaner  1 . A bumper  11  may be provided at a side surface of the robot cleaner  1 . The cover  10  may be provided with a water tank accommodation part  100 . A water tank  101  to supply water to the pad assembly  2  may be accommodated in the water tank accommodation part  100 . The water tank  101  and the pad assembly  2  may be connected by a tube (not illustrated). The pad assembly  2  may be configured to wet clean a floor using water supplied from the water tank  101 . The water supply from the water tank  101  to the pad assembly  2  may be mechanically and/or electronically controlled. When the robot cleaner moves to the pad changer  5  for pad replacement, the water supply may be interrupted. 
     The pad assembly  2  may include a first pad assembly  2   a , a second pad assembly  2   b , a third pad assembly  2   c  and a fourth pad assembly  2   d . The first pad assembly  2   a , the second pad assembly  2   b , the third pad assembly  2   c  and the fourth pad assembly  2   d  are configured to scrub a floor by rotating by a driving source. 
     A pad to scrub a floor may be provided at a bottom surface of the pad assembly  2 . In other words, a pad to scrub a floor may be attached to a bottom surface of each of the first pad assembly  2   a , the second pad assembly  2   b , the third pad assembly  2   c  and the fourth pad assembly  2   d.    
     A contaminated pad may be replaced by a new pad by the pad changer  5 . After the robot cleaner  1  travels on a floor and scrubs a floor for a predetermined time, the robot cleaner  1  may move to the pad changer  5 . The pad changer  5  replaces the contaminated pad with a new pad. The robot cleaner  1  with the new pad exits from the pad changer  5  and scrubs a floor again. 
     The pad changer  5  includes a plate unit  6 , a case  7  and a replacement unit  8 . The replacement unit  8  may be received in the case  7 . The plate unit  6  may be connected to the case  7  by a connection unit  9 . The plate unit  6  may be positioned on the case  7 . If there is a need to replace a contaminated pad, the plate unit  6 , for example, may slide to the front of the case  7 . The robot cleaner  1  may be seated on the plate unit  6 . The plate unit  6  may slide, for example, to the top of the case  7 . A bottom surface of the robot cleaner  1  may be positioned on the replacement unit  8 . The replacement unit  8  separates a contaminated pad from the bottom surface of the robot cleaner  1  and replaces the same with a new pad. 
       FIG. 2  is a view illustrating the robot cleaner according to the exemplary embodiment with the cover removed therefrom. 
     Referring to  FIG. 2 , the robot cleaner  1  may include a pad assembly  2  to wipe a floor, and a base  12  provided with bumpers  11  and driving sources. The pad assembly  2  may include a first pad assembly  2   a , a second pad assembly  2   b , a third pad assembly  2   c  and a fourth pad assembly  2   d.    
     Sensors  110  may be provided at a portion of the bumper  11 . The sensors  110  may be configured to interact with sensors  640  provided at the pad changer  5  so that the robot cleaner  1  is seated on the plate unit  6  of the pad changer  5 . 
     Guide protruding parts  111  may be provided at the other portion of the bumpers  11 . A recess (not illustrated) may be formed at a bottom surface of each guide protruding part  111 . The guide protruding parts  111  may be supported by fixing protrusions  600  provided at the pad changer  5 . In a case in which a recess is formed at the bottom surface of each guide protruding part  111 , each fixing protrusion  600  may be inserted into the recess. Accordingly, the robot cleaner  1  may be fixedly seated on the plate unit  6  of the pad changer  5 . 
     Since the first pad assembly  2   a , the second pad assembly  2   b , the third pad assembly  2   c  and the fourth pad assembly  2   d  are similar and the driving units to drive the first through fourth pad assemblies are similar, only the first pad assembly  2   a  is explained hereinafter. 
     The robot cleaner  1  may include a first motor  120 , a second motor  121  and a third motor  122  that are the driving sources. The first motor  120  and the second motor  121  may be provided at the base  12 . The third motor  122  may be mounted to the first pad assembly  2   a . The first pad assembly  2   a  rotates and scrubs a floor by the third motor  122 . 
     A first shaft  123  may be connected to the first motor  120 . The first shaft  123  may rotate by the first motor  120 . A first wire W 1  may be connected to the first shaft  123 . If the first shaft  123  rotates clockwise or counterclockwise by the first motor  120 , the first wire W 1  may be wound on the first shaft  123 . One end portion or the other end portion of the first wire W 1  may be fixed to the first pad assembly  2   a . If the first wire W 1  is wound on the first shaft  123  by rotation of the first shaft  123 , the first pad assembly  2   a  may tilt by the first wire W 1 . For example, if the first wire W 1  is wound on the first shaft  123  by rotation of the first shaft  123 , the first pad assembly  2   a  may tilt about an x-axis by the first wire W 1 . If the first pad assembly  2   a  tilts, when the first pad assembly  2   a  rotates about a z-axis by the third motor  122 , non-uniform frictional force may be generated between the bottom surface of the first pad assembly  2   a  and a floor. 
     A second shaft  124  may be connected to the second motor  121 . The second shaft  124  may rotate by the second motor  121 . A second wire W 2  may be connected to the second shaft  124 . If the second shaft  124  rotates clockwise or counterclockwise by the second motor  121 , the second wire W 2  may be wound on the second shaft  124 . One end portion or the other end portion of the second wire W 2  may be fixed to the first pad assembly  2   a . If the second wire W 2  is wound on the second shaft  124  by rotation of the second shaft  124 , the first pad assembly  2   a  may tilt by the second wire W 2 . For example, if the second wire W 2  is wound on the second shaft  124  by rotation of the second shaft  124 , the first pad assembly  2   a  may tilt about a y-axis by the second wire W 2 . If the first pad assembly  2   a  tilts, when the first pad assembly  2   a  rotates about the z-axis by the third motor  122 , non-uniform frictional force may be generated between the bottom surface of the first pad assembly  2   a  and a floor. 
     The first pad assembly  2   a  may scrub a floor by tilting by the first motor  120  or the second motor  121  and rotating clockwise or counterclockwise by the third motor  122 . The second pad assembly  2   b , the third pad assembly  2   c  and the fourth pad assembly  2   d , similar to the first pad assembly  2   a , may also scrub a floor by tilting about the x-axis and the y-axis by the first motor or the second motor and rotating clockwise or counterclockwise by the third motor. The robot cleaner  1  may travel in a specific direction by non-uniform frictional force between the pad assembly  2  and a floor. 
     The robot cleaner  1  may travel in a direction in which the frictional force between the bottom surface of the pad assembly  2  and a floor is large. A traveling speed of the robot cleaner  1  may be changed by a rotational speed of the third motor  122 . 
       FIG. 3  is an exploded perspective view illustrating the pad assembly of the robot cleaner according to an exemplary embodiment, and  FIG. 4  is a view illustrating a part of the pad assembly of the robot cleaner according to an exemplary embodiment. 
     Referring to  FIGS. 3 and 4 , the pad assembly  2  of the robot cleaner  1  includes a locking member  23  and a pad  25  that is configured to contact a floor. A structure of the first pad assembly  2   a  is explained. The structure of the second pad assembly  2   b , the third pad assembly  2   c  and the fourth pad assembly  2   d  is similar to that of the first pad assembly  2   a.    
     The locking member  23  may be accommodated in locking member accommodation parts  21  and  22 . The locking member accommodation parts  21  and  22  may include a first locking member accommodation part  21  and a second locking member accommodation part  22 . The locking member  23  may be accommodated in a space defined by the first locking member accommodation part  21  and the second locking member accommodation part  22 . The first locking member accommodation part  21  and the second locking member accommodation part  22  may be coupled to each other, for example, by hooks. 
     The locking member  23  may be formed with locking holes  235 ,  236 ,  237  and  238  through which locking protrusions  241 ,  242 ,  243  and  244  formed at a pad mounting part  24  (that will be described later) are inserted. The locking protrusions  241 ,  242 ,  243  and  244  inserted through the locking holes  235 ,  236 ,  237  and  238  may interact with the locking member  23  around the locking holes  235 ,  236 ,  237  and  238 . The locking holes  235 ,  236 ,  237  and  238  may be provided plural in number. For example, the locking holes  235 ,  236 ,  237  and  238  may include a first locking hole  235 , a second locking hole  236 , a third locking hole  237  and a fourth locking hole  238  that are spaced apart from each other with a predetermined interval therebetween. 
     The locking member accommodation parts  21  and  22  may be formed with holes corresponding to the first locking hole  235 , the second locking hole  236 , the third locking hole  237  and the fourth locking hole  238 . The locking member  23  may be positioned such that a part of the holes  221 ,  222 ,  223  and  224  formed at the second locking member accommodation part  22  interferes with the locking member  23  formed with the locking holes  235 ,  236 ,  237  and  238 . Accordingly, the locking protrusions  241 ,  242 ,  243  and  244  passing through the holes  221 ,  222 ,  223  and  224  formed at the second locking member accommodation part  22  may push the locking member  23  to the side. 
     A part of the locking member  23  may be cut off so that the locking member  23  has free ends. The free ends of the locking member  23  may be fixed to a portion of the locking member accommodation parts  21  and  22 . For example, the free ends of the locking member  23  may be formed with holes, and protrusions provided at the second locking member accommodation part  22  are inserted through the holes of the free ends, thereby fixing the free ends of the locking member  23  to the locking member accommodation parts  21  and  22 . 
     Due to the free ends  231 ,  232 ,  233  and  234 , the locking member  23  may have elasticity in a direction parallel to one surface of the locking member  23 . Therefore, when the locking protrusions  241 ,  242 ,  243  and  244  are inserted through the locking holes  235 ,  236 ,  237  and  238 , the locking member  23  may be pushed to one side by the locking protrusions  241 ,  242 ,  243  and  244 . After the locking protrusions  241 ,  242 ,  243  and  244  pass through the locking holes  235 ,  236 ,  237  and  238 , the locking member  23  moves to the other side by elastic force and thus returns to the original position. When the locking member  23  returns to the original position, the locking member  23  may interact with the locking protrusions  241 ,  242 ,  243  and  244 . Accordingly, the pad mounting part  24  is mounted to the bottom surface of the locking member accommodation parts  21  and  22  by the locking member  23 . 
     The free ends  231 ,  232 ,  233  and  234  may be provided plural in number. For example, in a case wherein the locking holes  235 ,  236 ,  237  and  238  include a first locking hole  235 , a second locking hole  236 , a third locking hole  237  and a fourth locking hole  238  that are spaced apart from each other with a predetermined interval therebetween, the free ends  231 ,  232 ,  233  and  234  may include a first free end  231 , a second free end  232 , a third free end  233  and a fourth free end  234 . The first locking hole  235  may be formed near the first free end  231 . The second locking hole  236  may be formed near the second free end  232 . The third locking hole  237  may be formed near the third free end  233 . The fourth locking hole  238  may be formed near the fourth free end  234 . 
     The pad mounting part  24  may be mounted to the bottom surface of the locking member accommodation parts  21  and  22 . The pad mounting pad  24  may be provided with the locking protrusions  241 ,  242 ,  243  and  244  on one surface thereof. Each of the locking protrusions  241 ,  242 ,  243  and  244  may have a locking part that extends to the side from the top of each protrusion. While passing through the locking holes  221 ,  222 ,  223  and  224  of the second locking member accommodation part  22 , the locking protrusions  241 ,  242 ,  243  and  244  may push the locking member  23  accommodated in the locking member accommodation parts  21  and  22  to one side. After the locking parts of the locking protrusions  241 ,  242 ,  243  and  244  pass through the locking member  23 , the locking member  23  returns to the original position. If the locking member  23  returns to the original position, the locking parts interfere with the locking member  23 . Accordingly, the pad mounting part  24  is mounted to the bottom surface of the second locking member accommodation part  22 . 
     The pad  25  to clean a floor may be mounted to the pad mounting part  24 . The pad  25  may be made of a fabric material. The pad  25  may be fixed to the pad mounting part  24  using, for example, Velcro. A coupling structure of the pad  25  and the pad mounting part  24  may be referred to as a pad unit. 
     The locking member accommodation parts  21  and  22 , the locking member  23 , the pad mounting part  24  and the pad  25  may be formed with holes  210 ,  220 ,  230 ,  240  and  250 , respectively, that communicate with each other. Water contained in the water tank  101  may be supplied to the pad  25  through the holes  210 ,  220 ,  230 ,  240  and  250 . The locking member  23  may be positioned such that the holes  210 ,  220 ,  240  and  250  of the locking member accommodation parts  21  and  22 , the pad mounting part  24  and the pad  25  communicate with a part of the hole  230  of the locking member  23 . In other words, the locking member  23  may be positioned such that a region of the locking member  23  around the hole  230  interferes with a part of the holes  210 ,  220 ,  240  and  250  of the locking member accommodation parts  21  and  22 , the pad mounting part  24  and the pad  25 . 
       FIGS. 5 and 6  are views illustrating the pad changer according to the exemplary embodiment,  FIG. 7  is an exploded perspective view illustrating a guide part of the pad changer according to the exemplary embodiment,  FIGS. 8A and 8B  are views illustrating a state in which the plate unit of the pad changer slides, and  FIG. 9  is a sectional view illustrating a part of the plate unit of the pad changer according to the exemplary embodiment. 
     Referring to  FIGS. 5 through 8B , the pad changer  5  includes the plate unit  6 , the case  7  and the replacement unit  8 . The plate unit  6  may be positioned, for example, on the case  7  or in front of the case  7 . The replacement unit  8  may be received in the case  7 . When there is a need to replace a contaminated pad of the robot cleaner  1 , the plate unit  6  may move, for example, slide to the front of the case  7 . 
     The plate unit  6  may include a frame, a first plate  61 , a second plate  62  and a third plate  63 . The frame may include side frames  60  provided at left and right sides of the plate unit  6 , and a rear frame  64  provided at a rear portion of the plate unit  6 . The frame may be connected to the first plate  61  or may be provided integrally with the first plate  61 . The first plate  61  may be positioned in front of the side frames  60 . The first plate  61  is an area that the robot cleaner  1  first approaches. In order for the robot cleaner  1  to easily enter the plate unit  6 , the first plate  61  may be slanted such that the height of the first plate  61  from a floor increases rearward. 
     The second plate  62  may connect the first plate  61  and the third plate  63 . The second plate  62  may be pivotably connected to the first plate  61  and the third plate  63 . For example, one portion of the second plate  62  may be hinged to the first plate  61 , and the other portion of the second plate  62  may be hinged to the third plate  63 . 
     When the frame and the first plate  61  are positioned on the case  7 , the second plate  62  may be positioned such that one surface of the second plate  62  opposes a front surface of the case  7 . The second plate  62  may form a predetermined angle with the first plate  61  and the third plate  63 . When the frame and the first plate  61  slide to the front of the case  7 , the second plate  62  may rotate about a hinge shaft and thus, may lie in the same plane as the third plate  63 . 
     The third plate  63  may be positioned under the case  7  or in front of the case  7 . When the frame and the first plate  61  are positioned on the case  7 , the third plate  63  may be positioned under the case  7 . When the frame and the first plate  61  slide and are positioned in front of the case  7 , the third plate  63  may also slide together with the frame and the first plate  61  and may be positioned in front of the case  7 . Wheels  630  may be provided at the bottom surface of the third plate  63 . The third plate  63  may easily slide, for example, by virtue of the wheels  630 . 
     The frame and the third plate  63  may be connected by the connection unit  9 . The connection unit  9  may be connected to the side frames  60  or the rear frame  64 . An exemplary structure wherein the connection unit  9  is connected to the rear frame  64  is explained. 
     Rack gears  94  may be provided at the side surfaces of the case  7 . The frame may be provided with pinion gears  92  configured to move along the rack gears  94 . A shaft  91  and a motor  93  may be connected to each of the pinion gears  92 . The pinion gear  92  may move forward or backward along the rack gear  94  by the motor  93 . The shaft  91  connected to the pinion gear  92  may move forward or backward with the pinion gear  92 . 
     The connection unit  9  may be formed with a guide slot  90  into which the shaft  91  is inserted. The guide slot  90  may be formed to have a predetermined curvature. The guide slot  90  may extend from a front lower portion of the connection unit  9  to a rear upper portion of the connection unit  9 . If the pinion gear  92  moves forward or rearward along the rack gear  94 , an inner surface of the guide slot  90  interferes with the shaft  91  and thus the connection unit  9  may move forward or rearward with the shaft  91 . If the connection unit  9  moves forward or rearward, the plate unit  6  connected to the connection unit  9  may move forward or rearward with the connection unit  9 . 
     A front portion of the rack gear  94  provided at the case  7  may have a shape corresponding to the shape of the guide slot  90 . Accordingly, the shaft  91  connected to the pinion gear  92  may move to the end of the guide slot  90  that is positioned at a front lower portion of the connection unit  9 . As a result, the plate unit  6  may be seated on a floor. 
       FIGS. 10A through 10E  are views illustrating a state in which the robot cleaner according to the exemplary embodiment is seated on the pad changer. 
     Referring to  FIGS. 10A through 10E , if replacement of the pad  25  of the robot cleaner  1  is not necessary, the frame of the pad changer  5  may be positioned on the case  7 . The pinion gear  92  and the shaft  91  may be positioned at a rear portion of the rack gear  94 . Such a state may be referred to as an initial position of the plate unit  6 . 
     If there is a need to replace a contaminated pad of the robot cleaner  1 , as illustrated in  FIG. 10B , the plate unit  6  of the pad changer  5  may slide and may be positioned in front of the case  7 . If the pinion gear  92  moves forward along the rack gear  94  while rotating by the motor  93 , the connection unit  9  moves forward by the shaft  91 . The plate unit  6  connected to the connection unit  9  also moves forward together. The shaft  91  moves along the guide slot  90  formed at the connection unit  9 , by which the plate unit  6  is seated on a floor. The second plate  62  may rotate about the hinge shaft and may lie in the same plane as the third plate  63 . 
     If the plate unit  6  of the pad changer  5  is positioned in front of the case  7 , the robot cleaner  1  may move to the plate unit  6  and may be seated on the third plate  63 . The robot cleaner  1  may easily move to the top surface of the plate unit  6  via the slanted first plate  61 . 
     If the robot cleaner  1  is seated on the top surface of the third plate  63 , the pinion gear  92  may rotate by the motor  93  and may move to a rear upper portion of the guide slot  90  along the shape of the guide slot  90 . The first plate  61  may move to the rear upper portion of the guide slot  90  together with the pinion gear  92  and the shaft  91 . The third plate  63  is kept seated on a floor and the second plate  62  rotates about the hinge shaft and forms a predetermined angle with the first plate  61  and the third plate  63 . The fixing protrusions  600  provided at the side frames  60  are coupled to the guide protruding parts  111  provided at the side surfaces of the robot cleaner  1 , thereby lifting the robot cleaner  1  from the third plate  63 . 
     If the pinion gear  92  moves rearward along the rack gear  94 , the shaft  91  may also move rearward. The shaft  91  may move rearward while pushing the inner surface of the rear upper portion of the guide slot  90  formed at the connection unit  9 . The connection unit  9  may move rearward by the shaft  91 . The plate unit  6  may move rearward together with the connection unit  9 . The robot cleaner  1  seated on the plate unit  6  may also move rearward and may reach the top surface of the replacement unit  8  received in the case  7 . 
     If the robot cleaner  1  is positioned on the replacement unit  8 , the contaminated pad  25  provided at the bottom surface of the robot cleaner  1  may be replaced with a new pad by the replacement unit  8 . After replacement is finished, the pinion gear  92  may move along the rack gear  94  so that the plate unit  6  is seated on a floor. The robot cleaner  1  may escape from the plate unit  6  to clean a floor. After the robot cleaner  1  exits from the plate unit  6 , the pinion gear  92  moves along the rack gear  94  so that the plate unit  6  returns to the initial position. 
       FIG. 11  is an exploded perspective view illustrating the pad changer according to the exemplary embodiment with the plate unit removed therefrom. 
     Referring to  FIG. 11 , the replacement unit  8  may be received in the case  7 . The replacement unit  8  may include a separation cartridge  83  and a mounting cartridge  84 . 
     The replacement unit  8  may include a base  80  that has a circular shape. The separation cartridge  83  and the mounting cartridge  84  may be received in the base  80 . The separation cartridge  83  may be formed with a pad unit receiving part  830  in which the pad unit to which a contaminated pad is mounted is received. The mounting cartridge  84  may be formed with a pad unit receiving part  840  in which the pad unit to which a new pad is mounted is received. 
     A cover  81  may be disposed on the replacement unit  8 . A part of the cover  81  positioned on the separation cartridge  83  and the mounting cartridge  84  may be opened. The cover  81  may rotate with the case  80 . 
     The case  7  may be formed with openings  70  and  71  at a side surface thereof, through which the separation cartridge  83  and the mounting cartridge  84  are inserted. The separation cartridge  83  and the mounting cartridge  84  inserted through the openings  70  and  71  may be seated on the circle-shaped base  80 . If the separation cartridge  83  and the mounting cartridge  84  are totally inserted, a front outer surface of the separation cartridge  83  and a front outer surface of the mounting cartridge  84  may lie in the same plane as an outer surface of the base  80 , or may be positioned in the rear of the outer surface of the base  80 . If the base  80  rotates, the separation cartridge  83  and the mounting cartridge  84  may rotate with the base  80 . 
     The separation cartridge  83  may be seated on a separation holder  85 . The separation holder  85  and the separation cartridge  83  may be inserted into the case  7  through the opening  70 . If the separation cartridge  83  and the separation holder  85  are inserted together into the case  7 , the separation cartridge  83  may be seated on the base  80 . 
     The separation cartridge  83  may be formed with guide recesses  831  at a side surface thereof, and the separation holder  85  may be formed with guide recesses  850  at a side surface thereof. The guide recesses  831  and  850  are extended in a forward and backward direction. A front portion of each guide recess  850  may be bent upward. The case  7  may be provided with guide protrusions  72  at an inner side surface thereof, that are inserted into the guide recesses  831  and  850 . By insertion of the guide protrusions  72  into the guide recesses  831  and  850 , the separation holder  85  and the separation cartridge  83  may be securely introduced into the case  7 . Since the separation holder  85  is held by the guide protrusions  72 , when the separation cartridge  83  seated on the base  80  rotates with the base  80 , the separation holder  85  may be prevented from rotating. 
     The mounting cartridge  84  may be seated on a mounting holder  86 . The mounting holder  86  and the mounting cartridge  84  may be inserted into the case  7  through the opening  71 . If the mounting cartridge  84  and the mounting holder  86  are inserted together into the case  7 , the mounting cartridge  84  may be seated on the base  80 . 
     The mounting cartridge  84  and the mounting holder  86  may be formed with guide recesses (not illustrated) at side surfaces thereof. The guide recesses may be extended in a forward and backward direction. A front portion of the guide recess may be bent upward. The case  7  may be provided with guide protrusions  72 P at an inner side surface thereof, which are inserted into the guide recesses. By insertion of the guide protrusions  72 P into the guide recesses, the mounting holder  86  and the mounting cartridge  84  may be securely introduced into the case  7 . Since the mounting holder  86  is held by the guide protrusions  72 P, when the mounting cartridge  84  seated on the base  80  rotates with the base  80 , the mounting holder  86  may be prevented from rotating. 
       FIG. 12  is a view illustrating the pad changer according to the exemplary embodiment with the cover of the replacement unit removed therefrom,  FIG. 13  is an exploded perspective view illustrating the separation cartridge,  FIG. 14  is an exploded perspective view illustrating the mounting cartridge,  FIG. 15  is a sectional view of the separation cartridge,  FIG. 16  is a sectional view of the mounting cartridge, and  FIG. 17  is a view illustrating a locking release state of the pad assembly according to the exemplary embodiment. 
     Referring to  FIGS. 12 through 17 , a rotation part  833  provided with threads on an outer surface thereof may be disposed at a lower portion of the separation cartridge  83 . The rotation part  833  may be disposed in the pad unit receiving part  830  of the separation cartridge  83 . The rotation part  833  may be arranged to extend upward from the bottom of the separation cartridge  83 . 
     A separation device  832  may be coupled to the rotation part  833 . The separation device  832  may be provided with threads on an inner surface thereof, which correspond to the threads on the outer surface of the rotation part  833 . When the rotation part  833  rotates, as illustrated in  FIG. 13 , since the separation device  832  is prevented from rotating, the separation device  832  may move up and down in a longitudinal direction of the rotation part  833 . 
     A gear part  834  may be connected to the rotation part  833 . A part of the separation cartridge  83  may be cut off so that the gear part  834  is connected to a motor  87  to receive driving force from the motor  87 . The gear part  834  may be connected to a gear coupled to the motor  87 . The gear part  834  may rotate by receiving driving force from the motor  87  provided in the case  7 . The rotation part  833  may rotate by the gear part  834 . If the rotation part  833  rotates, the separation device  832  may move up and down. 
     If the robot cleaner  1  is placed on the replacement unit  8  and the separation device  832  moves upward, the pad unit having the contaminated pad may be separated. The separation device  832  may apply a pressure to the holes  210 ,  220 ,  230 ,  240  and  250  of the pad assembly. The separation device  832  moving upward may push the locking member  23  interfering with the holes  210 ,  220 ,  230 ,  240  and  250  to the side. The locking member  23  may be pushed to the side and may move upward by a predetermined distance. Accordingly, the locking state between the locking member  23  and the locking protrusions  241 ,  242 ,  243  and  244  formed at the pad mounting part  24  may be released. By the release of the locking state by the locking member  23 , the pad mounting part  24  may be separated from the first pad assembly  2   a . Accordingly, the pad unit having the contaminated pad may be separated from the first pad assembly  2   a . The separated pad unit may be received in the pad unit receiving part  830  formed at the separation cartridge  83 . 
     A rotation part  843  provided with threads on an outer surface thereof may be disposed at a lower portion of the mounting cartridge  84 . The rotation part  843  may be disposed in the pad unit receiving part  840  of the mounting cartridge  84 . The rotation part  843  may be arranged to extend upward from the bottom of the mounting cartridge  84 . 
     A mounting plate  842  may be mounted to the rotation part  843 . The mounting plate  842  may be formed with a mounting hole  842 P, and the rotation part  843  may be inserted through the mounting hole  842 P. The mounting hole  842 P may be provided with threads on an inner surface thereof, which correspond to the threads on the outer surface of the rotation part  843 . 
     A gear part  844  may be connected to the rotation part  843 . A part of the mounting cartridge  84  may be cut off so that the gear part  844  is connected to a motor  88  to receive driving force from the motor  88 . The gear part  844  may be connected to a gear coupled to the motor  88 . The gear part  844  may rotate by receiving driving force from the motor  88  provided in the case  7 . The rotation part  843  may rotate by the gear part  844 . If the rotation part  843  rotates, the mounting plate  842  may move up and down along the rotation part  843  by a rotation prevention member  841  illustrated in  FIG. 14 . 
     A new pad unit may be seated on the mounting plate  842 . If the mounting plate  842  moves upward, the new pad unit may be mounted to a position of the first pad assembly  2   a  from which the contaminated pad unit is separated. If the mounting plate  842  moves upward, the locking protrusions  241 ,  242 ,  243  and  244  formed at the pad mounting part  24  may be inserted through the holes  221 ,  222 ,  223  and  224  formed at the second locking member accommodation part  22  and may push the locking member  23  interfering with the holes  221 ,  222 ,  223  and  224  to the side. If the mounting plate  842  moves upward further and the locking protrusions  241 ,  242 ,  243  and  244  pass through the locking member  23 , the locking parts extending to the side from the tops of the locking protrusions  241 ,  242 ,  243  and  244  interfere with the locking member  23  and thus the pad mounting part  24  may be mounted to the bottom surface of the locking member accommodation parts  21  and  22 . Accordingly, the new pad unit may be mounted to the first pad assembly  2   a.    
       FIG. 18  is a view illustrating a driving unit to rotate the replacement unit according to an exemplary embodiment. 
     Referring to  FIG. 18 , the base  80  may rotate by a motor  89  provided in the case  7 . A gear part  800  may be protrudingly provided at the bottom surface of the base  80 . The gear part  800  may be formed integrally with the base  80  or may be fixed to the bottom surface of the base  80  so as to rotate with the base  80 . The gear part  800  may be formed with a hole  801 . The case  7  may be provided with a fixing part  73  at an inner surface thereof which is inserted into the hole  801 . By insertion of the fixing part  73  into the hole  801 , the position of the base  80  in the case  7  may be fixed. 
     The motor  89  provided in the case  7  may be configured to drive the base  80 . The motor  89  and the gear part  800  provided at the bottom surface of the base  80  may be connected by plural gears  890 . If the motor  89  is driven, the plural gears  890  rotate and the gear part  800  tooth-engaged with at least one of the plural gears  890  may also rotate. Accordingly, the base  80  having the gear part  800  may rotate clockwise or counterclockwise about the fixing part  73 . 
     If the robot cleaner  1  is placed on the replacement unit  8  and the contaminated pad unit is separated by the separation cartridge  83 , the base  80  may rotate clockwise or counterclockwise by the motor  89 . If the first pad assembly  2   a  from which the contaminated pad unit is separated is placed on the mounting cartridge  84 , operation of the motor  89  may be stopped and thus rotation of the base  80  may be stopped. A new pad unit received in the mounting cartridge  84  may be mounted to the bottom surface of the first pad assembly  2   a . Accordingly, the contaminated pad unit may be removed, and a new pad unit may be mounted to the first pad assembly  2   a.    
     By rotation of the base  80  clockwise or counterclockwise, pad units, for example, all of the contaminated pad units mounted to the pad assembly  2  provided at the robot cleaner  1  may be replaced with new pad units. 
       FIG. 19  is a view illustrating a robot cleaner system according to an exemplary embodiment. 
     Referring to  FIG. 19 , a robot cleaner system according to an exemplary embodiment may include a robot cleaner  1 P, a case  7 P, a replacement unit  8 P, a pad unit receiving part  830 P, a separation device  832 P, and a mounting plate  842 P. An exemplary structure and operation of the robot cleaner  1 P and the replacement unit  8 P are similar to that of the robot cleaner  1  and the replacement unit  8  according to an exemplary embodiment described above. However, the robot cleaner system according to this embodiment does not include the plate unit  6  and the connection unit  9  of the robot cleaner system according to the previous embodiment. Therefore, if there is a need to replace a contaminated pad of the robot cleaner  1 P, a user may manually place the robot cleaner  1 P on the replacement unit  8 P. If the robot cleaner  1 P is placed on the replacement unit  8 P, the contaminated pad unit of the robot cleaner  1 P may be separated by the replacement unit  8 P and a new pad unit may be mounted to the robot cleaner  1 P. 
     As described above, since a contaminated pad mounted to the robot cleaner may be automatically replaced with a new pad, problems generated when a user manually removes a contaminated pad, for example, drop of contaminants on a floor or adherence of contaminants to a user&#39;s hand, may be prevented. An accident of dropping the robot cleaner by mistake when a user manually removes a contaminated pad may be prevented. Since a user can collect the pad units piled in the separation cartridge  83  all at once and separate the pads from the pad mounting parts to wash or discard the pads, convenience in use may be enhanced. In addition, in a case wherein the robot cleaner system is controlled to automatically replace contaminated pads with new pads at a regular time interval, a floor may be cleaned by clean pads and accordingly, cleaning efficiency may be enhanced. 
     Although a few embodiments have been illustrated and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of that is defined in the claims and their equivalents.