Patent Publication Number: US-2021169297-A1

Title: Cleaner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. application Ser. No. 16/056,971, filed Aug. 7, 2018, which claims the priority benefit of Korean Patent Application No. 10-2017-0099757, filed on Aug. 7, 2017 in the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a cleaner that performs a wiping operation on a cleaning surface 
     2. Background 
     Cleaners are devices used for removing foreign substances, such as dust and the like, from the floor. A vacuum cleaner may suction foreign substances from the floor. Another type of cleaner may perform a wiping operation to remove foreign substances from the floor or other cleaning surface. A robot cleaner (also referred to as an autonomous cleaner) is a device that may perform cleaning while autonomously travelling. 
     Korean Patent No. 10-1654014 (registered on Aug. 30, 2016) describes a robot cleaner capable of travelling and cleaning using rag surfaces of spinning rotation members. The robot cleaner in this reference has a first rotation member and a second rotation member, to which a pair of rag surfaces are fixed. The rag surfaces are tilted downward and outward with respect to a vertical axis. The robot cleaner in this reference travels by rotation of the first rotation member and the second rotation member, while only a portion of the rag surfaces, which are fixed to the first rotation member and the second rotation member, contacts the floor due to the tilt. 
     The above reference is incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG. 1  is a perspective view of a cleaner according to an embodiment of the present disclosure; 
         FIG. 2  is a perspective view of the cleaner illustrated in  FIG. 1 , as seen from a different angle; 
         FIG. 3  is an exploded perspective view of a body and a mop module illustrated in  FIG. 1 ; 
         FIG. 4  is an exploded perspective view of the body and the mop module illustrated in  FIG. 1 , as seen from a different angle; 
         FIG. 5  is an elevation view of the cleaner illustrated in  FIG. 1 , as seen from the front side; 
         FIG. 6  is an elevation view of the cleaner illustrated in  FIG. 1 , as seen from the rear side; 
         FIG. 7  is an elevation view of the cleaner illustrated in  FIG. 1 , as seen from the lateral side (left side); 
         FIG. 8  is an elevation view of the cleaner illustrated in  FIG. 1 , as seen from the bottom side; 
         FIG. 9  is an elevation view of the cleaner of  FIG. 1 , as seen from the top side; 
         FIG. 10  is a cross-sectional view of the cleaner of  FIG. 8 , vertically taken along line S 1 -S 1 ′ of  FIG. 8 ; 
         FIG. 11  is a cross-sectional view of the cleaner of  FIG. 8 , vertically taken along line S 2 -S 2 ′ of  FIG. 8 ; 
         FIG. 12  is a cross-sectional view of the cleaner of  FIG. 8 , vertically taken along line S 3 -S 3 ′ of  FIG. 8 ; 
         FIG. 13  is a cross-sectional view of the cleaner of  FIG. 8 , vertically taken along line S 4 -S 4 ′ of  FIG. 8 ; 
         FIG. 14  is a perspective view of the cleaner of  FIG. 1  from which a case  31  is removed; 
         FIG. 15  is an elevation view of the cleaner illustrated in  FIG. 14 , as seen from the top side; 
         FIG. 16  is a perspective view of the cleaner of  FIG. 14  from which a water tank  81  is removed; 
         FIG. 17  is a perspective view of the cleaner of  FIG. 16 , as seen from the top; 
         FIG. 18  is a partially enlarged perspective view of a body of  FIG. 4 ; 
         FIG. 19  is a bottom side elevation view of a module mounting portion of the body illustrated in  FIG. 18 ; 
         FIG. 20  is a top side elevation view of the mop module illustrated in  FIG. 4 ; 
         FIG. 21  is an exploded perspective view illustrating a connective relationship between a master joint of the body of  FIG. 4  and a slave joint of the mop module of  FIG. 20 ; 
         FIG. 22  is a partially cross-sectional view of the cleaner of  FIG. 20 , vertically taken along line S 5 -S 5 ′ of  FIG. 20 ; 
         FIG. 23  is an exploded perspective view of the mop module illustrated in  FIG. 20 ; and 
         FIG. 24  is an exploded perspective view of the mop module illustrated in  FIG. 23 , as seen from a different angle. 
     
    
    
     DETAILED DESCRIPTION 
     Throughout the descriptions set forth herein, expressions indicating directions, such as front (F) and rear (R), left (Le) and right (Ri), and up (U) and down (D), are defined as indicated in the drawings, and are used only to clearly explain the application to help better understand the application. Each direction may be defined differently according to a reference point. 
     Terms such as “first,” “second,” and “third” used herein to describe various elements, are used only to distinguish one element from the other to avoid confusion, and do not imply a sequence, importance or a master-slave relationship between these elements. For example, an embodiment may be implemented in which only the second element is included without the first element. A “rag” as used herein may refer to a mop pad or other component that is moved to wipe a cleaning surface and may be made of various materials, such as fabric, paper, and the like. The rag materials may be washable when dirty for reuse or may be disposable after use to be replaced by another rag or other cleaning material. 
     The principles described in present disclosure may be applied to a manual cleaner which travels by a user&#39;s manual control or to a robot cleaner which travels autonomously. Hereinafter, these principles will be described with respect to a robot cleaner. However, it should be appreciated that principles described in present disclosure may also be applied to a manually controlled cleaner. 
     As illustrated in  FIGS. 1 to 17 , a cleaner (also referred to as a robot cleaner or an autonomous cleaner)  1  according to an embodiment of the present disclosure may include a body  30  having a controller (Co). The cleaner  1  may include a mop module (or mop head)  40  which contacts a floor (surface to be cleaned) to wipe or otherwise clean the floor. The cleaner  1  may include a collection module (or cleaning head)  50  which removes and collects foreign substances from the floor. 
     The mop module  40  may support a portion (e.g., a rear portion) of the body  30 . The collection module  50  may support another portion (e.g., a front portion) of the body  30 . Thus, the body  30  may be supported on a floor or other cleaning surface by the mop module  40  and the collection module  50 . The body  30  forms an outer appearance of the cleaner  1 . The body  30  may connect the mop module  40  and the collection module  50 . 
     The mop module  40  may be coupled to a lower surface of the body  30 . The mop module  40  may include at least one rag part (or rag surface)  411  which wipes the floor while rotating. The mop module  40  may include at least one spin mop  41  which contacts the floor while rotating clockwise or counterclockwise when viewed from the top. The mop module  40  may include a pair of spin mops  41   a  and  41   b . The pair of spin mops  41   a  and  41   b  wipes the floor while rotating clockwise or counterclockwise. The pair of spin mops  41   a  and  41   b  may include a left spin mop  41   a  and a right spin mop  41   b . In one embodiment, the spin mops  41  may be configured to rotate about rotation axes Osa and Osb which extend substantially vertically (e.g., Substantially in an up-and-down direction). 
     The mop module  40  may be positioned below the body  30  and rearward of the collection module  50  (e.g., such that the mop module  40  wipes a region of a floor surface after the collection module  50  removes foreign substances from that region of the floor surface). 
     Each of the left spin mop  41   a  and the right spin mop  41   b  may include a rag part  411 , a rotary plate  412 , and a spin shaft  414 . Each of the left spin mop  41   a  and the right spin mop  41   b  may include a water accommodation portion (or water accommodation cavity)  413 . Each of the left spin mop  41   a  and the right spin mop  41   b  may include a slave joint  415 . Descriptions of the rag part  411 , the rotary plate  412 , the spin shaft  414 , the water accommodation portion  413 , and the slave joint  415 , which will be described later, may be understood as descriptions of elements included in each of the left spin mop  41   a  and the right spin mop  41   b.    
     The collection module  50  may be is positioned at a position forward and spaced apart from the mop module  40 . The collection module  50  contacts the floor at a position spaced apart from and forward of the mop module  40 . The collection module  50  collects foreign substances from the floor. The collection module  50  is positioned in front of the mop module  40 . The collection module  50  collects foreign substances from the floor at a position forward of the mop module  40 . 
     The collection module  50  may contact the floor. The collection module  50  is positioned below the body  30 . The collection module  50  contacts the floor at a position forward of the mop module  40 . In the embodiment, the collection module  50  may include an auxiliary wheel  58  which contacts the floor. 
     The collection module  50  may include at least one collection unit (or collection bin)  53  which forms a collection space  53   s  to store the collected foreign substances. The collection unit  53  may include a pair of collection units  53   a  and  53   b  that are left-right symmetric with respect to a central vertical plane Po. Further, the collection module  50  may include at least one sweeping unit (or roller)  51  which contacts the floor while rotating to suction or otherwise collect the foreign substances from the floor into the collection space  53   s.    
     In the embodiment, the collection module  50  may include the collection unit  53  and the sweeping unit  51 . The sweeping unit  51  rotates about a rotation axis Of which extends in a horizontal direction (e.g., parallel to a floor surface being cleaned). The rotation axis Of of the sweeping unit  51  may be an axis that extends in a left-and-right direction relative to the cleaner  1 . The sweeping unit  51  is positioned forward of the collection unit  53 . The pair of sweeping units  51  may be positioned forward of the pair of collection units  53 . A blade  511  of the sweeping unit  51  sweeps the floor to collect relatively large foreign substances into the collection unit  53  when the sweeping unit  51  rotates. 
     In another example, the collection module  50  may wipe the floor while sliding on the floor as the body  30  travels. In yet another example, the collection module  50  may wipe the floor while rotating. In still another example, the collection module  50  may be capable of vacuum cleaning that suctions contaminants. Hereinafter, descriptions will be made based on the embodiments, but a specific embodiment of cleaning of the collection module  50  may be modified. 
     The cleaner  1  may include the body  30  which is movable by at least one rotation action of the mop module  40  and the collection module  50  without a separate driving wheel. The body  30  may travel solely due to the rotation of the mop module  40 . In the cleaner  1 , the body  30  may be movable by the rotation of the pair of spin mops  41   a  and  41   b  without a separate driving wheel. 
     The cleaner  1  may include a mop driving unit (or mop driving motor)  60  which provides a driving force to the mop module  40 . Torque provided by the mop driving unit  60  is transmitted to the spin mop  41 . 
     The cleaner  1  may include a collection driving unit (or collection driving motor)  70  which provides a driving force to the collection module  50  to rotate the sweeping unit  51 . Torque provided by the collection driving unit  70  is transmitted to the sweeping unit  51 . 
     The cleaner  1  may include a water supply module (or water supply)  80  which supplies water for wiping. The water supply module  80  may supply water necessary for the mop module  40  or the collection module  50 . In the embodiment, the water supply module  80  supplies water to the mop module  40 . The water supply module  80  supplies water to the pair of spin mops  41   a  and  41   b.    
     The water supply module  80  may include a water tank  81  which stores water to be supplied to the mop module  40  or the collection module  50 . In one embodiment, the water tank  81  stores water to be supplied to the mop module  40 . The mop module  40  may perform wet-type wiping by wetting the rag surface  411  with water from the water supply module  80  to clean the floor surface and the move the cleaner  1 . 
     The cleaner  1  may include a battery Bt to provide power. The battery Bt may provide power for rotation of the mop module  40 . For example, the battery Bt may drive the mop driving unit  60 . Additionally or alternatively, the battery Bt may provide power for rotation of the collection module  50 . For example, the battery Bt may drive the collection driving unit  70 . 
     The body  30  and the mop module  40  may be detachably connected with each other. A state where the body  30  and the mop module  40  are connected may be referred to as a “connected state,” and a state where the body  30  and the mop module  40  are separated from each other may be referred to as a “separated state”. The cleaner  1  may include a detaching module (or mop release mechanism)  90  (see  FIG. 16 ) which detachably engages the mop module  40  to the body  30 . In the separated state, the detaching module  90  may release the mop module  40  from the body  30 . The detaching module  90  enables the mop module  40  and the body  30  to be detachably connected with each other. In the connected state, the detaching module  90  may enable the mop module  40  to be engaged with the body  30 . In one example, the detaching module  90  may be positioned across the gap between the water tank  81  and the battery Bt. 
     Referring to  FIGS. 1 to 9 , the cleaner  1  may include a case  31  which forms an outer appearance of the body  30 . In one example, the case  31  forms a three-dimensional curved surface which is upwardly convex. The cleaner  1  may include a base  32  which forms a bottom surface of the body  30 . The base  32  may form a bottom surface, a front surface, a rear surface, a left surface, and a right surface, of the body  30 . The mop module  40  may be connected to the base  32 . The collection module  50  may also be connected to the base  32 . The controller Co and the battery Bt are positioned in an inner space formed by the case  31  and the base  32 . Further, the mop driving unit  60  may be positioned in the body  30 . The water supply module  80  may also be positioned in the body  30 . The detaching module  90  is also positioned in the body  30 . 
     The cleaner  1  may include a module housing (or mop module hosing)  42  which forms an outer appearance of the mop module  40 . The module housing  42  is positioned below the body  30 . The cleaner  1  may include a module cabinet (or collection module housing)  52  which forms an outer appearance of the collection module  50 . The module cabinet  52  is positioned below the body  30 . The module housing  42  and the module cabinet  52  are positioned spaced apart from each other in a forward and backward direction. 
     The cleaner  1  may include the auxiliary wheel  58  which is positioned at a position spaced apart from the mop module  40  in a forward and backward direction. The auxiliary wheel  58  may prevent the cleaner  1  from overturning forward and rearward. The auxiliary wheel  58  may position the sweeping unit  51  a given distance from, thereby positioned the sweeping unit  51  to perform sweeping efficiently. 
     The cleaner  1  may include a battery insertion unit (or battery insertion cover)  39  that is used by a user to replace the battery Bt. The battery insertion unit  39  may be positioned on the bottom surface of the body  30 . 
     A cleaner  1  may include a sensing module (or sensors) which detect external conditions. The sensing module may include at least one of the following: a bumper (not shown) which senses contact with an external obstacle; an obstacle sensor  21  which senses an external obstacle spaced apart from the cleaner; and a cliff sensor  23  which senses the presence of a cliff on a traveling surface (floor). The sensing module may include an image sensor  25  which captures or otherwise senses external images. The sensing module may include a gyroscopic (gyro) sensor which senses an actual rotation angle of the cleaner  1 . The sensing module may include an encoder (not shown) which recognizes an actual traveling path of a robot cleaner  1 . The auxiliary wheel  58  may be coupled to the encoder. For example, the encoder may detect the actual traveling path of the robot cleaner  1  based on a quantity of rotations of the auxiliary wheel  58 . 
     The cleaner  1  may travel autonomously. The robot cleaner  1  may travel autonomously based on sensor data collected by the sensing module. For example, the cleaner  1  may autonomously learn a traveling area. The cleaner  1  may recognize a current position in the traveling area. By using the sensing information of the sensing module, the robot cleaner  1  may learn the traveling area and recognize the current position. 
     The cleaner  1  may include a bumper (not shown) which senses when the collection module  50  contacts an external object. The bumper may include a surface which is exposed to the outside of the cleaner  1 . When the external object comes into contact with the bumper, the bumper may be pressed such that a bumper switch (not shown) positioned inside the cleaner  1  is pressed. The bumper switch is pressed when the collection module  50  is pressed rearward based on contacting the obstacle. 
     The cleaner  1  may include the obstacle sensor  21  which senses a forward obstacle. A plurality of obstacle sensors  21   a ,  21   b ,  21   c ,  21   d , and  21   e  may be provided. The obstacle sensor  21  may include the obstacle sensors  21   a ,  21   b , and  21   c  which sense an obstacle forward of the cleaner  1 . The obstacle sensor  21  may include the obstacle sensors  21   d  and  21   e  which senses an obstacle on the left side and the right side of the cleaner  1 . The obstacle sensor  21  may be positioned in the body  30 . The obstacle sensor  21  may emit ultrasonic waves and detect reflections of these ultrasonic waves from an obstacle. For example, when the robot cleaner  1  performs cleaning while traveling straight near a left (right) wall, and senses a forward obstacle, the robot cleaner  1  makes a curved movement to rotate 180 degrees, and travels straight while cleaning to avoid the wall and obstacle. In this case, the robot cleaner  1  may perform cleaning while travelling in zigzags with a cleaning trajectory partially overlapping. 
     The cleaner  1  may include a cliff sensor  23  which senses the presence of a cliff on the floor. A plurality of cliff sensors  23   a  and  23   b  may be provided. The cliff sensors  23   a  and  23   b  may be provided below the collection module  50  to sense the presence of a cliff. A cliff sensor (not shown) may also be provided rearward of the mop module  50  to sense the presence of a cliff. The cliff sensors  23   a  and  23   b  may sense the presence of a cliff forward of the mop module  40 . 
     The cleaner  1  may include the image sensor  25  which captures external images of a region around the cleaner  1 . The image sensor  25  may be positioned in the body  30 . The image sensor  25  may capture an image upward from the body  30 . 
     The cleaner  1  may include a power switch  29  to switch on and off power supply. The cleaner  1  may include an input unit (or user interface) (not shown) to receive input related to various instructions from a user. The cleaner  1  may include a communication module or antenna (not shown) to communicate with an external device. 
     The cleaner  1  may include a communication module (or communication interface) (not shown) to connect to a network. According to a communication protocol, the communication module may be implemented by using wireless communication techniques such as IEEE 802.11 WLAN, IEEE 802.15 WPAN, UWB, Wi-Fi, Zigbee, Z-wave, Blue-Tooth, and the like. For example, the communication module may include an Ultra-Wideband (UWB) sensor and the like to recognize the current indoor location of the cleaner  1 . 
     The cleaner  1  may include an Inertial Measurement Unit (IMU) (not shown). Based on the information of the IMU, the cleaner  1  may stabilize a traveling motion. 
     The cleaner  1  may include a manipulation unit (or release button)  953  to separate the body  30  and the mop module  40 . The manipulation unit  953  may be exposed to the outside of the cleaner  1 . Once the manipulation unit  953  is pressed, the mop module  40  may be released from the body  30 . 
     The cleaner  1  may include the controller Co which controls autonomous traveling. The controller Co may control traveling of the cleaner  1  by receiving input of a sensing signal of the sensing module. The controller Co may process a sensing signal of the obstacle sensor  21 . The controller Co may process a sensing signal of the cliff sensor  23 . The controller Co may process a sensing signal of the bumper. The controller Co may process a sensing signal of the image sensor  25 . The controller Co may process a sensing signal of the UWB sensor and the IMU. The controller Co may process a signal of the input unit or a signal input through the communication module. The controller Co may include a printed circuit board (PCB) included in the body  30  (see  FIGS. 14 to 17 ). 
     The controller Co may also control the water supply module  80  to selectively supply water to the mop module  40 . The controller Co may control a pump  85  to adjust the amount of water to be supplied to the mop module  40 . By the control of the pump  85 , the amount of water supplied to the mop module  40  per hour may be changed. In another example, the controller Co may control an opening and closing of a valve (not shown), which will be described later, so as to change whether water is supplied. 
     The controller Co may learn a traveling area by using images sensed by the image sensor  25  and may recognize a current position of the cleaner  1 . The controller Co may perform mapping of the traveling area by using the images. The controller Co may recognize the current location on a map mapped by using the images. The images captured by the image sensor  25  may be used to generate a map of the traveling area and to sense the current location in the traveling area. For example, the controller Co may generate a map of the traveling area by using a boundary between the ceiling and a side surface in the upper side images captured by the image sensor  25 . Further, the controller Co may sense the current location in the traveling area based on feature points of the images. 
     The controller Co may control the robot cleaner  1  to return to a charging stand after traveling. For example, the robot cleaner  1  may return to the charging stand by sensing an infrared (IR) signal transmitted from the charging stand. The controller Co may control the robot cleaner  1  to return to the charging stand based on the signal transmitted from the charging stand and sensed. The charging stand may include a signal transmitter (not shown) which transmits a return signal. The return signal may be an ultrasonic signal, an infrared signal, or UWB signal, but is not limited thereto. 
     In another example, the controller Co may recognize the current location of the robot cleaner  1  on the map and may control the robot cleaner  1  to return to the charging stand. The controller Co may recognize a location corresponding to the charging stand and the current location, and based on the recognized locations, the robot cleaner  1  may return to the charging stand. 
     The controller Co may control the cleaner  1  based on information input from a user terminal (e.g., smartphone, computer, etc.) that is separate from the cleaner  1 . The cleaner  1  may receive the input information through the communication module. The controller Co may control a traveling pattern (e.g., traveling in zigzags or traveling to clean a certain area intensively) of the cleaner  1 . Based on the input information, the controller Co may control activation of specific functions (e.g., finding a lost article, repelling insects, etc.). Based on the input information, the controller Co may set a cleaning start point of the cleaner  1  to be a specific point (cleaning reservation function). 
     The body  30  may include a first portion (or front section)  30   a  positioned above the mop module  40 , and a second portion (or rear section)  30   b  positioned above the collection module  50  (see  FIG. 7 ). The first portion  30   a  and the second portion  30   b  may be integrally formed. The body  30  may include the case  31 , which forms an outer appearance, and the base  32 . 
     Referring to  FIGS. 1 to 12 , the collection module  50  contacts the floor forward of the mop module  40 . The collection module  50  moves according to movement of the body  30 . The collection module  50  sweeps up or otherwise collect foreign substances from the floor. The collection module  50  may move forward to collect foreign substances from the floor into the collection space  53   s . The collection module  50  may be left-right symmetric. 
     The collection module  50  may include at least one sweeping unit  51  which sweeps the floor. In one example, the collection module  50  may include a pair of sweeping units  51   a  and  51   b . The collection module  50  may include at least one collection unit  53  which stores foreign substances collected from the floor. In one example, the collection module  50  may include a pair of collection units  53   a  and  53   b . The collection module  50  may include a module cabinet (or collection module housing)  52  in which the sweeping unit  51  and the collection unit  53  are positioned. The module cabinet  52  may be connected to the body  30 . A lower surface of the collection module  50  may include the auxiliary wheel  58  which rolls while contacting the floor to reduce friction and to space the collection module  50  from the floor. The auxiliary wheel  58  may be positioned below the module cabinet  52 . 
     As illustrated in  FIG. 12 , the sweeping unit  51  rotates about the rotation axis Of that extends horizontally. The rotation axis Of may be extended in a direction parallel to an arrangement direction of the left spin mop  41   a  and the right spin mop  41   b . The rotation axis Of may extend horizontally. The rotation axis Of of the left sweeping unit  51   a  and the rotation axis Of of the right sweeping unit  51   b  may be substantially identical to each other. As illustrated in  FIG. 12 , when viewed from the right side, a clockwise rotation direction of the sweeping unit  51  may be defined as a third forward (or circumferential) direction w 3 . The sweeping unit  51  may sweep up the foreign substances from the floor into the collection space  53   s  while rotating in the third forward direction w 3 . 
     The pair of sweeping units  51   a  and  51   b  may be left-right symmetric. The pair of sweeping units  51   a  and  51   b  may be left-right symmetric with respect to the central vertical plane Po. The central vertical plane Po is defined as a virtual plane which passes through the center of the pair of the spin mops  41   a  and  41   b  which are left-right symmetric, and which is perpendicular to a left-and-right direction (see  FIGS. 15 and 17 ). The left sweeping unit  51   a  and the right sweeping unit  51   b  are left-right symmetric. Hereinafter, descriptions of each element of the sweeping unit  51  may be understood as description of each of the pair of sweeping units  51   a  and  51   b.    
     The sweeping unit  51  may include a blade  511  which directly contacts the floor. The blade  511  is fixed to an outer circumference surface of the rotation member  512 . The blade  511  may protrude from the circumference surface of the rotation member  512  in a direction further away from the rotation axis Of. 
     In one embodiment, the blade  511  is of a plate or wiper type, but the blade  511  may be formed to have a plurality of brushes which are densely positioned. The blade  511  is may extend substantially in a left-and-right direction, and may extend in a spiral shape along the circumference of the rotation axis Of. The spiral extending direction of the blade  511  of the left sweeping unit  51  and the spiral extending direction of the blade  511  of the right sweeping unit  1  may be opposite to each other. A plurality of blades  511  may be provided. In one embodiment, six blades  511   a ,  511   b ,  511   c ,  511   d ,  511   e , and  511   f  are spaced from each other at predetermined intervals along the circumference of the rotation member  512 . 
     The collection module  50  may include a rotation member  512  which is rotatable. The rotation member  512  supports the blade  511 . The blade  511  is fixed to an outer circumferential surface of the rotation member  512 . The rotation member  512  is formed longitudinally in an extending direction of the rotation axis Of. The rotation member  512  has a cavity  512   s  formed at the inner side thereof. The rotation member  512  receives a driving force of the collection driving unit  70 , and rotates along with the blade  511 . The rotation member  512  rotates about the rotation axis Of. 
     The collection module  50  may include a first axis portion (or first axial end)  514  positioned at one end of the rotation member  512 . The collection module  50  may include a second axis portion (or second axial end)  515  positioned at the other end of the rotation member  512 . The first axis portion  514  and the second axis portion  515  are positioned at both ends in the extending direction of the rotation axis Of of the collection module  50 . 
     The first axis portion  514  and the second axis portion  515  are positioned at opposing ends of the rotation member  512 . For example, the first axis portion  514  may be positioned on a right end portion of the rotation member  512  of the left sweeping unit  51 , and the second axis portion  515  may be positioned on a left end portion thereof. The first axis portion  514  is positioned on the left end portion of the rotation member  512  of the left sweeping unit  51 , and the second axis portion  515  is positioned on the right end portion thereof. 
     One end of the rotation member  512  may be recessed inward, and the first axis portion  514  may be positioned at the recessed portion on the one end of the rotation member  512 . The other end of the rotation member  512  may be recessed inward, and the second axis portion  515  may be positioned at the recessed portion on the other end of the rotation member  512 . 
     The first axis portion  514  may connect the one end of the rotation member  512  and the collection driving unit  70 . The first axis portion  514  may be recessed in a direction of the rotation axis Of. An end portion of the sweeping shaft  74  may be fixed in a groove of the first axis portion  514 . When the sweeping shaft  74  rotates, the first axis portion  514  rotates integrally with the sweeping shaft  74 , and the sweeping unit  51  rotates. 
     The second axis portion  515  may connect the other end of the rotation member  512  and the module cabinet  52 . The second axis portion  515  may protrude in a direction of the rotation axis Of. The protrusion of the second axis portion  515  is inserted into a groove formed on the module cabinet  52 . 
     The module cabinet  52  forms an outer appearance of the collection module  50 . The module cabinet  52  may be left-right symmetric. The module cabinet  52  forms a top surface which is connected to a portion of the body  30 . The module cabinet  52  may also include a bottom surface which is formed to face the floor (surface to be cleaned) and to include an opening through which the blades  511  extend. The module cabinet  52  forms a distal end of a foremost portion of the cleaner  1 . In the case where the module cabinet  52  collides with an external object, the cleaner  1  may sense the shock. 
     The module cabinet  52  may have a sweeping unit arrangement groove (or sweeping unit receiving groove)  52   g  formed by the bottom surface and is recessed upward so that the sweeping unit  51  may be positioned therein. The bottom portion of a front end of the sweeping unit arrangement groove  52   g  may be opened forward. 
     The module cabinet  52  may further have a collection unit arrangement groove (or collection unit receiving groove)  52   h  formed by the bottom surface and is recessed upward so that the collection unit  53  may be positioned therein. The collection unit arrangement groove  52   h  is positioned rearward of the sweeping unit arrangement groove  52   g . The collection unit arrangement groove  52   h  and the sweeping unit arrangement groove  52   g  may be connected in a forward and backward direction. 
     The collection unit  53  may define a collection space  53   s  which receives and stores foreign substances drawn up by the blade  511 . The collection space  53   s  is positioned rearward of the sweeping unit  51 . The pair of collection units  53   a  and  53   b  may each include respective collection space  53   s.    
     The pair of collection units  53   a  and  53   b  may be left-right symmetric. The pair of collection units  53   a  and  53   b  are left-right symmetric with respect to the central vertical plane Po. The left collection unit  53   a  and the right collection unit  53   b  may be left-right symmetric. Hereinafter, descriptions of each element of the collection unit  53  may be understood as descriptions of each of the pair of collection units  53   a  and  53   b.    
     As illustrated in  FIGS. 8, 12, and 13 , the left side and the right side of the collection space  53   s  may be blocked by a wall of the module cabinet  52 . The rear side, the top side, and the bottom side of the collection space  53   s  may be blocked by walls of the module cabinet  52 . The collection unit  53  may include a bottom surface  532  which forms the bottom side of the collection space  53   s . The collection unit  53  may include a top surface  534  which forms the top side of the collection space  53   s.    
     The collection space  53   s  is opened forward (e.g., on a front surface facing the sweeping unit  51 . The collection unit  53  has an open portion which is formed at the front, and communicates with the collection space  53   s . Foreign substances pushed by the sweeping unit  51  from the front side to the rear side are introduced into the collection space  53   s  through the open portion of the collection unit  53 . 
     The collection unit  53  may include an edge portion (or edge wall)  531  which forms edges extended in a left-and-right direction at the lower front end of the collection unit  53 . The edge portion  531  is positioned at the lower front end of the collection space  53   s . The edge portion  531  is fixed to a front end of the bottom surface  532 . The top surface of the edge portion  531  has an inclined portion, which is inclined rearward such that the height becomes higher toward the rear side thereof. The front end of the edge portion  531  is positioned adjacent to a rotation trajectory of the blade  511 , such that the edge portion  531  guides the foreign substances smoothly into the collection space  53   s.    
     The collection unit  53  may include a top edge portion (or top edge surface)  539  which forms edges extended in a left-and-right direction at the upper front end of the collection unit  53 . The top edge portion  539  is positioned at the upper front end of the collection space  53   s . The top edge portion  539  is fixed to a front end of the top surface  534 . The bottom surface of the top edge portion  539  has an inclined portion, of which height becomes higher toward the rear side thereof. The front end of the top edge portion  539  is positioned adjacent to a rotation trajectory of the blade  511 , thereby helping foreign substances, which are scattered rearward and upward of the blade, to be introduced into the collection space  53   s.    
     The collection unit  53  may include a set connection unit (or collection unit connection wall)  535  which couples a pair of collection units  53 . A portion of the set connection unit  535  may be positioned between the pair of collection units  53 . The set connection unit  535  is positioned below the collection unit  53 . The set connection unit  535  is exposed downward of the module cabinet  52 . 
     The collection unit  53  may be detachable from the module cabinet  52 . The collection unit  53  may include a collection unit releasing button  537 , so that when the collection unit releasing button  537  is pressed, the collection unit  53  is released from the module cabinet  52 . A pair of collection unit releasing buttons  537  may be positioned to be left-right symmetric. The pair of collection units  53  are connected by the set connection unit  535 , such that the pair of collection units  53  may be connected to or detached from the module cabinet  52  at the same time when the collection unit releasing button  537  is pressed. 
     The auxiliary wheel  58  may be positioned at the bottom surface of the module cabinet  52 . The auxiliary wheel  58  rolls to enable the module cabinet  52  to smoothly move back and forth on the floor surface. As illustrated in  FIG. 7 , the auxiliary wheel  58  may be provided so that the floor H and the bottom surface of the module cabinet  52  are spaced apart from each other in a distance range in which the pair of sweeping units  51  may still extend adjacent to or contact the flat floor H. 
     At least one auxiliary wheel  58  is left-right symmetric with respect to the central vertical plane Po. A plurality of auxiliary wheels  58   a ,  58   b , and  58   m  may be provided. The plurality of auxiliary wheels  58   a ,  58   b , and  58   m  may be left-right symmetric. The pair of auxiliary wheels  58   a  and  58   b , each of which is positioned on the left side and the right side, may be provided. The left auxiliary wheel  58   a  is positioned on the left side of the left sweeping unit  51   a . The right auxiliary wheel  58   b  is positioned on the right side of the right sweeping unit  51   b . The pair of auxiliary wheels  58   a  and  58   b  are left-right symmetric. 
     Further, a central auxiliary wheel  58   m  may be provided. The central auxiliary wheel  58   m  is positioned between the pair of collection units  53 . The central auxiliary wheel  58   m  is spaced apart from the pair of auxiliary wheels  58   a  and  58   b  in a forward and backward direction. The central auxiliary wheel  58   m  may be positioned on the central vertical plane Po. 
     As illustrated in  FIG. 13 , the collection driving unit  70  may be a motor that provides a driving force to rotate the sweeping unit  51 . The collection driving unit  70  may provide torque to both of the pair of sweeping units  51 , or the collection driving unit  70  may provide torque to one of the sweeping units  51 , and rotation of that sweeping units  51  may drive another sweeping unit  51 . For example, the collection driving unit  70  may provide a driving force to rotate the rotation member  512 . 
     The collection driving unit  70  is positioned at or within the collection module  50 . The collection driving unit  70  is left-right symmetric with respect to the central vertical plane Po. For example, the collection driving unit  70  may be positioned on the central vertical plane Po. 
     Although not illustrated in the drawings, the collection driving unit  70  may be configured to transmit torque, obtained by a rotation of the auxiliary wheel  58  without a motor, to the sweeping unit  51  in another embodiment. For example, the collection driving unit  70  may include a gear that is rotated through the rotation of the auxiliary wheel  58  to transmit torque to the sweeping unit  51 . In an embodiment illustrated in the drawings, the collection driving unit  70  may include a motor  71  to transmit torque to the sweeping unit  51 , and descriptions below will be made based on this embodiment. 
     The collection driving unit  70  may include a sweeping motor  71  having a motor rotation axis  71   s  positioned on the central vertical plane Po. For example, the sweeping motor  71  may include a shaft positioned on the central vertical plane Po. The motor rotation axis  71   s  is extended in a direction perpendicular to a left-and-right direction. In one embodiment, the motor rotation axis  71   s  is extended diagonally forward and upward. 
     The sweeping motor  71  may be positioned at a gap between the pair of collection units  53 , or may be positioned at a gap between the pair of sweeping units  51 . The pair of collection units  53  and the pair of sweeping units  51  form their respective gaps therebetween, so that the collection driving unit  70  may be positioned on the central vertical plane Po and may be left-right symmetric. 
     The collection driving unit  70  may include a driving force transmission unit (or driving force transmission assembly)  72  to transmit torque of the motor rotation axis  71   s  to the sweeping shaft  74 . The driving force transmission unit  72  may include a gear and/or a belt, and may include a gear shaft which is a rotation axis of the gear. 
     The driving force transmission unit  72  may include a worm gear  721  which rotates while being fixed to a motor rotation axis  71   s . The driving force transmission unit  72  may include at least one gear  722  which rotates by being engaged with the worm gear  721  by rotation of the worm gear  721 . Any one of the at least one gear  722  is fixed to the sweeping shaft  74  to rotate along with the sweeping shaft  74 . In one embodiment, the worm gear  721  rotates along with the motor rotation axis  71   s , and thus the gear  722  and the sweeping shaft  74  rotate integrally with each other, and the pair of sweeping units  51 , which are fixed to both ends of the sweeping shaft  74 , rotates along with the gear  722  and the sweeping shaft  74 . 
     The driving force transmission unit  72  may include the sweeping shaft  74 , both ends of which are connected to the pair of sweeping units  51  respectively. The sweeping shaft  74  is extended in a left-and-right direction. The sweeping shaft  74  is positioned on the rotation axis Of. The sweeping shaft  74  is positioned between the pair of sweeping units  51 . 
     As illustrated in  FIGS. 13 to 17 , the water supply module  80  may selectively supply water to the mop module  40 . In the drawings, water W filled in the water tank  81  and a water flow WF are illustrated. The water supply module  80  supplies water to the mop module  40  due to the water flow WF. For example, the water supply module  80  may supply water to the module water supply unit  44 . 
     The water supply module  80  may include the water tank  81  that may include a cavity to store water. The water tank  81  is positioned in the body  30 . The water tank  81  may be positioned at the rear side of the body  30  to counter the weight of the collection module  50 . The water tank  81  and the battery Bt may be provided with a vertical gap formed therebetween. 
     The water tank  81  may be drawn out of the body  30  from the outside. The water tank  81  may slide rearward of the body  30 . While the water tank  81  is mounted in the body  30 , a water tank catching portion  84  may be provided, which catches the water tank  81  to the body  30 . 
     The water supply module  80  may include a water tank opening and closing part  82  to open and close the water tank  81 . The water tank opening and closing part  82  is positioned on the top surface of the water tank  81 . When the water tank  81  is drawn out of the body  30 , the water tank opening and closing part  82  may be opened to fill water in the water tank  81 . 
     The water supply module  80  may include a water level display unit (or window)  83  which displays a water level within the water tank  81 . The water level display unit  83  may be positioned on an external cover of the water tank  81 . The water level display unit  83  may be displayed at a rear surface of the water tank  81 . The water level display unit  83  may be made of a transparent material, so that a user may directly view the water level inside the water tank  81 . 
     The water supply module  80  may include a pump  85  which applies pressure to move the water W in the water tank  81  to the mop module  40 . The pump  85  is positioned in the body  30 . The pump  85  may be positioned on the central vertical plane Po. 
     Although not illustrated herein, the water supply module may include a valve, in which when the valve is opened, the water in the water tank may be moved to the mop module by the gravity of water without the pump in another embodiment. Although not illustrated herein, the water supply module may include a water-permeable lid in another embodiment. The water-permeable lid is positioned in the supply pipe, such that water passes through the water-permeable lid, while reducing a moving speed of water. 
     Hereinafter, description will be made based on an embodiment including the pump  85 , but is not limited thereto. While the water tank  81  is mounted in the body  30 , the water supply module  80  may include a water tank connection portion (or connection pipe)  89  which connects the water tank  81  and the supply pipe  86 . The water W in the water tank  81  is introduced into the supply pipe  86  through the water tank connection portion  89 . 
     The water supply module  80  may include the supply pipe  86  which guides movement of the water W from the water tank  81  to the mop module  40 . The supply pipe  86  guides movement of the water W by connecting the water tank  81  and the water supply connection portion (or water supply connection channel)  87 . 
     The supply pipe  86  may include: a first supply pipe  861  which guides movement of the water W from the water tank  81  to the pump  85 ; and a second supply pipe  862  which guides movement of the water W from the pump  85  to the mop module  40 . One end of the first supply pipe  861  is connected to the water tank connection portion  89 , and the other end thereof is connected to the pump  85 . One end of the second supply pipe  862  is connected to the pump  85  and the other end thereof is connected to the water supply connection portion  87 . 
     The second supply pipe  862  may include a common pipe (not shown) which guides movement of relatively upstream water. After passing through the common pipe, water diverges via three direct links (not shown) in a left-and-right direction. The three direct links form a T-shape flow path. 
     The second supply pipe  862  may include a first diverging pipe  862   a  which guides movement of the water W to the water supply connection portion  87  of the left module mounting portion  36 ; and a second diverging pipe  862   b  which guides movement of the water W to the water supply connection portion  87  of the right module mounting portion  36 . One end of the first diverging pipe  862   a  is connected to the three direct links, and the other end thereof is connected to the water supply connection portion  87  on the left side. One end of the second diverging pipe  862   b  is connected to the three direct links, and the other end thereof is connected to the water supply connection portion  87  on the right side. Water introduced into the water supply connection portion  87  on the left side is supplied to the left spin mop  41   a , and water introduced into the water supply connection portion  87  on the right side is supplied to the right spin mop  41   b.    
     The water supply module  80  may include the water supply connection portion  87  which guides water in the water tank  81  to the mop module  40 . Through the water supply connection portion  87 , the water W is moved from the body  30  to the mop module  40 . The water supply connection portion  87  is positioned below the body  30 . The water supply connection portion  87  is positioned at the module mounting portion  36 . The water supply connection portion  87  is positioned on the bottom surface of the module mounting portion  36 . The water supply connection portion  87  is positioned on a bottom surface portion  361  of the module mounting portion  36 . A pair of water supply connection portions  87 , corresponding to the pair of spin mops  41   a  and  41   b , are provided. The pair of water supply connection portions  87  are left-right symmetric. 
     The water supply connection portion  87  protrudes from the module mounting portion  36 . The water supply connection portion  87  protrudes downward from the module mounting portion  36 . The water supply connection portion  87  is engaged with the water supply corresponding portion  441 , which will be described later, of the mop module  40 . The water supply connection portion  87  forms a hole which vertically penetrates, and the water moves from the body  30  to the mop module  40  through the hole of the water supply connection portion  87 . The water passes through the water supply connection portion  87  and the water supply corresponding portion  441  to move from the body  30  to the mop module  40 . 
     As illustrated in  FIGS. 16, 17, and 22 , the water flow WF will be described as follows. The pump  85  operates to induce movement of the water W. The water W in the water tank  81  passes through the supply pipe  86  to be introduced into the water supply connection portion  87 . The water W in the water tank  81  moves by sequentially passing through the first supply pipe  861  and the second supply pipe  862 . The water W in the water tank  81  sequentially passes through the supply pipe  86  and the water supply connection portion  87  to be introduced into the water supply corresponding portion  441  of the mop module  40 . The water introduced into the water supply corresponding portion  441  passes through a water supply delivery portion (or water supply delivery channel)  443  and a water supply guiding portion (water supply guiding channel)  445  to be introduced into a water accommodation portion  413 . The water introduced into the water accommodation portion  413  passes through a water supply hole  412   a  to be introduced into a central portion of the rag part  411 . The water introduced into the central portion of the rag part  411  moves to the edges of the rag part  411  by a centrifugal force generated by rotation of the rag part  411 . 
     As illustrated in  FIGS. 4, 10, 12, and 14 to 17 , the cleaner  1  may include a mop driving unit  60  which provides a driving force to rotate the spin mop  41 . The mop driving unit  60  provides torque to the pair of spin mops  41   a  and  41   b . The mop driving unit  60  may be left-right symmetric. For example, the mop driving unit  60  may left-right symmetric with respect to the central vertical plane Po. 
     The mop driving unit  60  is positioned in the body  30 . The torque of the mop driving unit  60  is transmitted to the spin mop  41  of the mop module  40 . While the body  30  and the mop module  40  are connected, the torque of the mop driving unit  60  is transmitted to the pair of spin mops  41   a  and  41   b . When the body  30  and the mop module  40  are separated, the torque of the mop driving unit  60  may not be transmitted to the spin mop  41 . 
     The mop module  40  may include a left mop driving unit  60  which provides a driving force to rotate the left spin mop  41   a ; and a right mop driving unit  60  which provides a driving force to rotate the right spin mop  41   b . The pair of mop driving units  60  are left-right symmetric with respect to the central vertical plane Po. Hereinafter, descriptions of elements of one of the mop driving unit  60  may be understood as also describing the elements of another one of the mop driving units  60 . 
     The mop driving unit  60  may include a mop motor  61  which provides torque. The left mop driving unit  60  may include a left mop motor  61   a  and the right mop driving unit  60  may include a right mop motor  61   b . A rotation axis of the mop motor  61  may be vertically extended. 
     The mop driving unit  60  may also include a driving force transmission unit (or mop transmission)  62  which transmits the torque of the mop motor  61  to a master joint  65 . The driving force transmission unit  62  may include a gear and/or a belt, and may include a gear shaft which is a rotation axis of the gear. 
     The driving force transmission unit  62  may include at least one transmission gear  621 . The at least one transmission gear  621  may include a first gear  621   a , a second gear  621   b , and a third gear  621   c . The first gear  621   a  rotates while being fixed to a rotation axis of the mop motor  61 . The first gear  621   a  is a worm gear. The second gear  621   b  rotates while being engaged with the first gear  621   a . The second gear  621   b  is a spur gear. The third gear  621   c  rotates while being engaged with the second gear  621   b . The third gear  621   c  is a worm gear. 
     The driving force transmission unit  62  may include a shaft gear  622  fixed to the master shaft  624 . The shaft gear  622  rotates while being engaged with at least any one transmission gear  621 . In one embodiment, the shaft gear  622  rotates while being engaged with the third gear  621   c . The shaft gear  622  may rotate integrally with the master shaft  624 . 
     The master shaft  624  rotates about a rotation axis which may be vertically extended. The shaft gear  622  is fixed to an upper end of the master shaft  624 . The master joint  65  is fixed to a lower end of the master shaft  624 . The master shaft  624  is rotatably supported by the body  30  through a bearing Bb. 
     In this connected state, the master joint  65  is engaged with the slave joint  415 . In the connected state, when the master joint  65  rotates, the slave joint  415  rotates along with the master joint  65 . The master joint  65  is exposed downward of the body  30 . The master joint  65  is exposed downward of the module mounting portion  36 . A pair of master joints  65 , which correspond to the pair of spin mops  41   a  and  41   b , may be provided. The pair of master joints  65  is engaged with a corresponding pair of slave joints  415 . For example, the master joints  65  may contact and the slave joints  415  when rotating due to friction between the master joints  65  and the slave joints  415 . In another example, a lower end surface of the master joint  65  may include a shape (e.g., a protrusion or cavity) that mates with a corresponding shape of an upper end surface of the slave joint  415  to couple the master joint  65  and the slave joint  415 . 
     As illustrated in  FIGS. 1 to 4, 6 to 8, and 18 to 24 , each configuration of the mop module  40 , and the relationship between the mop module  40  and the body  30  will be described as follows. The mop module  40  performs wet-type wiping by using water in the water tank  81 . The pair of spin mops  41   a  and  41   b  performs wiping by rotating while contacting the floor. The pair of spin mops  41   a  and  41   b  may be connected with each other to form a set. When the connected state is changed to the separated state, the pair of spin mops  41   a  and  41   b , which is connected by the mop module  40 , may be detached from the body  30 . Further, when the separated state is changed to the connected state, the spin mops  41   a  and  41   b , which is connected by the mop module  40 , may be integrally connected to the body  30 . 
     As illustrated in  FIGS. 3, 4, and 18 to 20 , the mop module  40  may be detachably connected to the body  30 . The mop module  40  is connected below the body  30 . The body  30  is connected above mop module  40 . The body  30  may include the module mounting portion (also referred to as a mop housing mounting region or module mounting region)  36 , and the mop module  40  may include a body mounting portion (or body mounting region)  43 . The body mounting portion  43  may be detachably connected to the module mounting portion  36 . 
     The module mounting portion  36  is provided below the body  30 . The body mounting portion  43  is provided above the mop module  40 . The module mounting portion  36  is positioned at a bottom surface of the base  32 . The body mounting portion  43  is positioned at a top surface of the module housing  42 . 
     Any one of the module mounting portion  36  and the body mounting portion  43  vertically protrudes, and the other one thereof is vertically recessed to be engaged with the any one. In one embodiment shown in the drawings, the body mounting portion  43  protrudes upward from the mop module  40 . The body mounting portion  43  is recessed upward from the body  30  to be engaged with the body mounting portion  43 . 
     When viewed from the top, the shape of the body mounting portion  43  may be asymmetric in a forward and backward direction. In this manner, the mop module  40  and the body  30  may be connected to each other in a predetermined direction, since if the mop module  40  is reversely connected to the body  30 , the body mounting portion  43  is not shaped to engage the module mounting portion  36 . 
     When viewed from the top, the shape of the body mounting portion  43  may be formed to be elongated in the forward and backward direction further away from the central vertical plane Po. When viewed from the top, the body mounting portion  43  has an inclined shape with a portion relatively far from the central vertical plane Po being adjacent to the front. 
     The mop module  40  may include a pair of body mounting portions  43   a  and  43   b  which are spaced apart from each other. The pair of body mounting portions  43   a  and  43   b  correspond to the pair of spin mops  41   a  and  41   b . The pair of body mounting portions  43   a  and  43   b  correspond to the pair of module mounting portions  36   a  and  36   b.    
     The body  30  may include the pair of module mounting portions  36   a  and  36   b  which are spaced apart from each other. The pair of module mounting portions  36   a  and  36   b  correspond to the pair of body mounting portions  43   a  and  43   b . The pair of body mounting portions  43   a  and  43   b  protrudes upward of the mop module  40 . The pair of module mounting portions  36   a  and  36   b  are recessed upward to be engaged with the pair of body mounting portions  43   a  and  43   b.    
     The pair of body mounting portions  43   a  and  43   b  are horizontally spaced apart from each other. The pair of module mounting portions  36   a  and  36   b  are horizontally spaced apart from each other. The pair of body mounting portions  43   a  and  43   b  are left-right symmetric with respect to the central vertical plane Po. The pair of module mounting portions  36   a  and  36   b  are left-right symmetric with respect to the central vertical plane Po. Hereinafter, descriptions of the body mounting portions  43  may be understood are applicable to each of the pair of body mounting portions  43   a  and  43   b , and descriptions of the module mounting portion  36  may be understood as being applicable of each of the pair of module mounting portions  36   a  and  36   b.    
     The module mounting portion  36  may include a bottom surface portion  361  which forms a bottom surface of the module mounting portion  36 . In the connected state, the bottom surface portion  361  may be positioned adjacent to or contact the top surface portion  431  of the body mounting portion  43 . The bottom surface portion  361  faces downward. The bottom surface portion  361  may be formed to be horizontal. The bottom surface portion  361  is positioned above a periphery corresponding portion (or periphery surface)  363 . 
     The module mounting portion  36  may include a periphery corresponding portion  363  positioned along the circumference of the bottom surface portion  361 . In the connected state, the periphery corresponding portion  363  contacts a periphery portion (or periphery surface)  433  of the body mounting portion  43 . The periphery corresponding portion  363  may be an inclined surface that extends from a bottom surface of the base  32  and to the bottom surface portion  361 . The periphery corresponding portion  363  has an inclined portion, of which height becomes higher from the bottom surface of the base  32  toward the bottom surface portion  361 . The periphery corresponding portion  363  is positioned to surround the bottom surface portion  361 . 
     The pair of module mounting portions  36  may include a pair of catching surfaces  363   a  which are inserted into a space between the pair of body mounting portions  43 . In the periphery corresponding portion  363  of any one module mounting portion  36 , the catching surface  363   a  may be positioned at a region close to the other adjacent module mounting portion  36 . The catching surface  363   a  is positioned at a region relatively close to the central vertical plane Po in the periphery corresponding portion  363 . The catching surface  363   a  forms a portion of the periphery corresponding portion  363 . 
     The module mounting portion  36  forms a joint hole  364  which exposes at least a portion of the master joint  65 . The joint hole  364  is formed at the bottom surface portion  361 . The master joint  65  may be positioned by passing through the joint hole  364 . 
     Catching portions (or catching extensions)  915  and  365  which protrude from a surface of any one of the module mounting portion  36  and the body mounting portion  43  may be provided. Catching corresponding portions (or catching cavities)  435  and  436  which are recessed on a surface of the other one of the module mounting portion  36  and the body mounting portion  43  to be engaged with the catching portions  915  and  365  in the connected state, may be provided. 
     Catching portion  915  which are protruded from a surface of any one of the module mounting portion  36  and the body mounting portion  43  is provided. Catching corresponding portions  435  which are recessed on a surface of the other one of the module mounting portion  36  and the body mounting portion  43  to be engaged with the catching portions  915  in the connected state, are provided. 
     Catching portions  365  which are protruded from a surface of any one of the module mounting portion  36  and the body mounting portion  43  is provided. Catching corresponding portions  436  which are recessed on a surface of the other one of the module mounting portion  36  and the body mounting portion  43  to be engaged with the catching portions  365  in the connected state, are provided. In one embodiment, the catching portions  915  and  365  are provided on a surface of the module mounting portion  36 , and the catching corresponding portions  435  and  436  are provided on a surface of the body mounting portion  43 . 
     The catching portions  915  and  365  may be formed in a hook shape. The catching portions  915  and  365  may be positioned at the periphery corresponding portion  363 . The bottom surface of a protruding end portion of the catching portions  915  and  365  is inclined in a manner that gets closer to the top toward an end thereof. The plurality of catching portions  915  and  365  may be provided on one body mounting portion  43 . 
     The catching portions  915  and  365  may include a first catching portion  915  which is elastically movable in a protruding direction. The first catching portion  915  is pressed when the body mounting portion  43  is connected with the module mounting portion  36 , but protrudes by a restoring force in the connected state, to be inserted into a first catching corresponding portion  435  of the body mounting portion  43 . The first catching portion  915  protrudes by passing through a hole formed on the catching surface  363   a.    
     The catching portions  915  and  365  may include a second catching portion  365  which is fixedly positioned. The second catching portion  365  may protrude from the periphery corresponding portion  363 . The second catching portion  365  is fixed to the periphery corresponding portion  363 . In the connected state, the second catching portion  365  is inserted into the second catching corresponding portion  436  of the body mounting portion  43 . 
     The body mounting portion  43  may include a top surface portion  431  which forms a top surface. In the connected state, the top surface portion  431  contacts the bottom surface portion  361  of the module mounting portion  36 . The top surface portion  431  faces upward. The top surface portion  431  may be formed to be horizontal. The top surface portion  431  is positioned above a periphery portion  433 . 
     The body mounting portion  43  may include the periphery portion  433  positioned along the circumference of the top surface portion  431 . The periphery portion  433  contacts the periphery corresponding portion  363  of the module mounting portion  36  in the connected state. The periphery portion  433  forms an inclined surface which extends the top surface of the module housing  42  and the top surface portion  431 . The periphery portion  433  has an inclination of which height becomes higher from the top surface of the module housing  42  to the top surface portion  431 . The periphery portion  433  is positioned to surround the top surface portion  431 . 
     The body mounting portion  43  may include a catching corresponding surface  433   a  which contacts the catching surface  363   a  in the connected state. The pair of body mounting portions  43  may include a pair of catching corresponding surfaces  433   a . The pair of catching corresponding surfaces  433   a  faces each other obliquely in a symmetrical manner. The pair of catching corresponding surfaces  433   a  is positioned in the middle of the pair of body mounting portions  43 . 
     In the periphery portion  433  of any one body mounting portion  43 , the catching corresponding surface  433   a  is positioned at a region close to the other adjacent body mounting portion  43 . The catching corresponding surface  433   a  is positioned at a region relatively close to the central vertical plane Po in the periphery portion  433 . The catching corresponding surface  433   a  forms a portion of the periphery portion  433 . 
     The body mounting portion  43  forms a driving hole  434  which exposes at least a portion of the slave joint  415 . The driving hole  434  is formed at the top surface portion  431 . In the connected state, the master joint  65  is inserted into the driving hole  434  to be connected with the slave joint  415 . 
     The catching corresponding portions (or catching recesses)  435  and  436  may be holes or grooves formed on the surface of the body mounting portion  43 . The catching corresponding portions  435  and  436  may be positioned at the periphery portion  433 . A plurality of catching corresponding portions  435  and  436 , which correspond to the plurality of catching portions  915  and  365 , may be provided. 
     The catching corresponding portions  435  and  436  include a first catching corresponding portion  435 , on which a first catching portion  915  is caught. The first catching corresponding portion  435  is formed on the catching corresponding surface  433   a . The catching corresponding portions  435  and  436  include a second catching corresponding portion  436 , on which a second catching portion  365  is caught. The second catching corresponding portion  436  is formed on the periphery portion  433 . 
     The mop module  40  may include at least one spin mop  41 . The at least one spin mop  41  may include a pair of spin mops  41 . The pair of spin mops  41  are left-right symmetric with respect to a virtual, central vertical plane. The left spin mop  41   a  and the right spin mop  41   b  are left-right symmetric. 
       FIG. 8  illustrates a point where a spin rotation axis Osa of the left spin mop  41   a  intersects a bottom surface of the left spin mop  41   a , and a point where a spin rotation axis Osb of the right spin mop  41   b  intersects a bottom surface of the right spin mop  41   b . When viewed from the bottom, a clockwise direction of rotation of the left spin mop  41   a  is defined as a first forward direction w 1   f , and a counterclockwise direction thereof is defined as a first reverse direction w 1   r . When viewed from the bottom, a counterclockwise direction of rotation of the right spin mop  41   b  is defined as a second forward direction w 2   f , and a clockwise direction thereof is defined as a second reverse direction w 2   r . Further, when viewed from the bottom, an acute angle formed between an inclination direction of the bottom surface of the left spin mop  40   a  and a left-and-right direction axis, and an acute angle formed between an inclination direction of the bottom surface of the right spin mop  40   b  and a left-and-right direction axis, are defined as inclination direction angles Ag 1   a  and Ag 1   b  respectively. The inclination direction angle Ag 1   a  of the left spin mop  41   a  may be substantially identical to the inclination direction angle Ag 1   b  of the right spin mop  40   b . Further, as illustrated in  FIG. 6 , an angle formed between a virtual horizontal surface H and a bottom surface I of the left spin mop  40   a , and an angle formed between a virtual horizontal surface H and a bottom surface I of the right spin mop  40   b  are defined as inclination angles Ag 2   a  and Ag 2   b  respectively. 
     As illustrated in  FIG. 8 , when the left spin mop  41   a  rotates, a point Pla, to which the largest frictional force is applied from the floor on the bottom surface of the left spin mop  41   a  is positioned on the left side of the center of rotation Osa of the left spin mop  41   a . Greater load may be transmitted to the ground surface at the point Pla than any other point on the bottom surface of the left spin mop  41   a , thereby generating the largest frictional force at the point Pla. In the embodiment, the point Pla is positioned on the left front side of the center of rotation Osa; but in another embodiment, the point Pla may be positioned exactly on the left side or on the left rear side of the center of rotation Osa. 
     As illustrated in  FIG. 8 , when the right spin mop  41   b  rotates, a point Plb, to which the largest frictional force is applied from the floor on the bottom surface of the right spin mop  41   b , is positioned on the right side of the center of rotation Osb of the right spin mop  41   b . Greater load may be transmitted to the ground surface at the point Plb than any other point on the bottom surface of the right spin mop  41   b , thereby generating the largest frictional force at the point Plb. In the embodiment, the point Plb is positioned on the right front side of the center of rotation Osb; but in another embodiment, the point Plb may be positioned exactly on the right side or on the right rear side of the center of rotation Osb. 
     Each of the bottom surface of the left spin mop  41   a  and the bottom surface of the right spin mop  41   b  may be inclined. An inclination angle Ag 2   a  of the left spin mop  41   a  and an inclination angle Ag 2   b  of the right spin mop  41   b  each form an acute angle. The inclination angles Ag 2   a  and Ag 2   b  are formed at the points Pla and Plb where the largest frictional force is applied, and may be set to be small enough for the entire bottom surface of the rag part  411  to touch the floor by rotation of the left spin mop  41   a  and the right spin mop  41   b.    
     The bottom surface of the left spin mop  41   a  has an overall downward inclination formed in the left direction. The bottom surface of the right spin mop  41   b  has an overall downward inclination in the right direction. As illustrated in  FIG. 6 , the bottom surface of the left spin mop  41   a  has the lowest point Pla formed on the left side. The bottom surface of the left spin mop  41   a  has the highest point Pha formed on the right side. The bottom surface of right spin mop  41   b  has the lowest point Plb formed on the right side. The bottom surface of the right spin mop  41   b  has the highest point Phb formed on the left side. 
     In certain embodiments, the inclination direction angles Ag 1   a  and Ag 1   b  may also be set at 0 degrees. Further, certain embodiments, when viewed from the bottom, the inclination direction of the bottom surface of the left spin mop  120   a  may form the inclination direction angle Ag 1   a  in a clockwise direction with respect to a left-and-right direction axis. The inclination direction of the bottom surface of the right spin mop  120   b  may form the inclination direction angle Ag 1   b  in a counterclockwise direction with respect to a left-and-right direction axis. In the embodiment, when viewed from the bottom, an inclination direction of the bottom surface of the left spin mop  120   a  forms the inclination direction angle Ag 1   a  in a counterclockwise direction with respect to a left-and-right direction axis, and an inclination direction of the bottom surface of the right spin mop  120   b  forms the inclination direction angle Ag 1   b  in the clockwise direction with respect to a left-and-right direction axis. 
     The cleaner  1  may move by a frictional force with the ground surface that is generated by the mop module  40 . The mop module  40  may generate a ‘forward movement frictional force’ to move the body  30  forward, or may generate a ‘rearward movement frictional force’ to move the body rearward. The mop module  40  may generate a ‘leftward moment frictional force’ to turn the body  30  to the left, or may generate a ‘rightward moment frictional force’ to turn the body  30  to the right. The mop module  40  may generate a frictional force by combining any one of the forward movement frictional force and the rearward movement frictional force, and any one of leftward moment frictional force and the rightward moment frictional force. 
     In order to generate the forward movement frictional force, the mop module  40  may rotate the left spin mop  41   a  in a first forward direction w 1   f  at a predetermined rpm R 1 , and rotate the right spin mop  41   b  in a second forward direction w 2   f  at the predetermined rpm R 1 . In order to generate the rearward movement frictional force, the mop module  40  may rotate the left spin mop  41   a  in a first reverse direction w 1   r  at a predetermined rpm R 2 , and rotate the right spin mop  41   b  in a second reverse direction w 2   r  at the predetermined rpm R 2 . 
     In order to generate the rightward moment frictional force, the mop module  40  may rotate the left spin mop  41   a  in the first forward direction w 1   f  at a predetermined rpm R 3 ; and i) may rotate the right spin mop  41   b  in the second reverse direction w 2   r , ii) may halt the right spin mop  41   b  without rotation, or iii) may rotate the right spin mop  41   b  in the second forward direction w 2   f  at an rpm R 4 , which is smaller than the rpm R 3 . 
     In order to generate the leftward moment frictional force, the mop module  40  may rotate the right spin mop  41   b  in the second forward direction w 2   f  at a predetermined rpm R 5 ; and i) may rotate the left spin mop  41   a  in the first reverse direction w 1   r , ii) may halt the left spin mop  41   a  without rotation, or iii) may rotate the left spin mop  41   a  in the first forward direction w 1   f  at an rpm R 6  which is smaller than the rpm R 5 . 
     As illustrated in  FIGS. 10 and 22 to 24 , the mop module  40  may include the pair of spin mops  41   a  and  41   b  which are left-right symmetric with respect to the central vertical plane Po. Hereinafter, descriptions of elements of the spin mop  41  may be understood as being applicable to each of the pair of spin mops  41   a  and  41   b.    
     The spin mop  41  may include a rotary plate  412  which rotates below the body  30 . The rotary plate  412  may be formed to be a circular plate member. The rag part  411  is fixed at the bottom surface of the rotary plate  412 . The rotary plate  412  rotates the rag part  411 . A spin shaft  414  is fixed to a central portion of the rotary plate  412 . 
     The rotary plate  412  may include a rag fixing portion (not shown) which fixes the rag part  411 . The rag fixing portion may detachably fix the rag part  411 . The rag fixing portion may be a Velcro and the like which is positioned at the bottom of the rotary plate  412 . The rag fixing portion may be a hook and the like which is positioned on the edge of the rotary plate  412 . 
     A water supply hole  412   a  is formed, which vertically penetrates the rotary plate  412 . The water supply hole  412   a  connects a water supply space Sw and the bottom side of the rotary plate  412 . Water in the water supply space Sw moves to the bottom side of the rotary plate  412  through the water supply hole  412   a . The water in the water supply space Sw moves to the rag part  411  through the water supply hole  412   a . The water supply hole  412   a  is positioned at the central portion of the rotary plate  412 . The water supply hole  412   a  is positioned at a position where it is possible to avoid the spin shaft  414 . 
     The rotary plate  412  may be provided with a plurality of water supply holes  412   a . A connection portion  412   b  is positioned between any two adjacent ones of the plurality of water supply holes  412   a . The connection portion  412   b  connects a portion in a centrifugal direction XO and a portion in a counter-centrifugal direction XI. Here, the centrifugal direction XO is a direction further away from the spin shaft  414 , and the counter-centrifugal direction XI is a direction closer to the spin shaft  414 . 
     A plurality of water supply holes  412   a  may be spaced apart from each other along the circumference of the spin shaft  414 . A plurality of water supply holes  412   a  may be spaced apart from each other at predetermined intervals. A plurality of connection portions  412   b  may be spaced apart from each other along the circumference of the spin shaft  414 . The water supply hole  412   a  is positioned between the plurality of connection portions  412   b.    
     The rotary plate  412  may include an inclination portion  412   d  positioned at a bottom end of the spin shaft  414 . The water in the water supply space Sw flows by gravity along the inclination portion  412   d . The inclination portion  412   d  is formed along the bottom end of the spin shaft  414 . The inclination portion  412   d  forms a downward inclination in the counter-centrifugal direction XI. The inclination portion  412   d  may form a bottom surface of the water supply hole  412   a.    
     The spin mop  41  may include the rag part (or rage surface)  411  which is connected to the bottom side of the rotary plate  412  to contact the floor. The rag part  411  may be fixedly coupled to the rotary plate  412 , or may be detachably connected. The rag part  411  may be fixed to the rotary plate  412  in a detachable manner by using a Velcro, a hook, or the like. The rag part  411  may include only a rag, or may include a rag and a spacer (not shown). The rag is a portion that directly contacts the floor for wiping. The spacer may be interposed between the rotary plate  412  and the rag to adjust the position of the rag. The spacer may be detachably fixed to the rotary plate  412 , and the rag may be detachably fixed to the spacer. The rag  121   a  may also be detachably fixed to the rotary plate  412  directly without the spacer. 
     The spin mop  41  may include the spin shaft  414  which rotates the rotary plate  412 . The spin shaft  414  is fixed to the rotary plate  412  to transmit torque of the mop driving unit  610  to the rotary plate  412 . The spin shaft  414  is connected to the top side of the rotary plate  412 . The spin shaft  414  is positioned at the center of an upper portion of the rotary plate  412 . The spin shaft  414  is fixed to the center of rotation Osa and Osb of the rotary plate  412 . The spin shaft  414  may include a joint fixing portion (or joint fixing end)  414   a  which fixes the slave joint  415 . The joint fixing portion  414   a  is positioned at a top end of the spin shaft  414 . 
     The spin shaft  414  is extended vertically with respect to the rotary plate  412 . A left spin shaft  414  is positioned perpendicular to the bottom surface of the left spin mop  41   a . A right spin shaft  414  is positioned perpendicular to the bottom surface of the right spin mop  41   b . In one embodiment, the bottom surface of the spin mop  41  is inclined with respect to a horizontal plane, and the spin shaft  414  is inclined with respect to a vertical axis. The spin shaft  414  is inclined in such a manner that the top end thereof is inclined to one side with respect to the bottom end thereof. 
     The angle of inclination of the spin shaft  414  with respect to the vertical axis may be changed according to rotation of the tilting frame  47  about the tilting shaft  48 . The spin shaft  414  is rotatably connected to the tilting frame  47  to be integrally inclined with the tilting frame  47 . When the tilting frame  47  is inclined, the spin shaft  414 , the rotary plate  412 , the water accommodation portion  413 , the slave joint  415 , and the rag part  411  are inclined integrally with the tilting frame  47 . 
     The mop module  40  may include the water accommodation portion (or water accommodation recess)  413  which may be positioned above the rotary plate  412  to accommodate water. The water accommodation portion  413  forms a water supply space Sw which stores water. The water accommodation portion  413  surrounds the spin shaft  414 , but is spaced apart therefrom to form the water supply space Sw. The water accommodation portion  413  enables water, supplied to the top side of the rotary plate  412 , to be collected in the water supply space Sw before the water passes through the water supply hole  412   a . The water supply space Sw is positioned at a top central portion of the rotary plate  412 . The water supply space Sw has a cylinder volume. The top portion of the water supply space Sw is open, so that water is introduced into the water supply space Sw through the open top portion. 
     The water accommodation portion  413  protrudes upward from the rotary plate  412 . The water accommodation portion  413  is extended along the circumference of the spin shaft  414 . The water accommodation portion  413  may be a ring type rib. The water supply hole  412   a  is positioned on an inner bottom surface of the water accommodation portion  413 . The water accommodation portion  413  is spaced apart from the spin shaft  414 . The bottom end of the water accommodation portion  413  is fixed to the rotary plate  412 . The top end of the water accommodation portion  413  has a free, open end. 
     As illustrated in  FIGS. 10 and 18 to 23 , the connection between the master joint  65  and the slave joint  415  will be described as follows. The mop driving unit  60  may include the master joint  65  which rotates by the mop motor  61 . The spin mop  41  may include the slave joint  415  which rotates by being engaged with the master joint  65  in the connected state. The master joint  65  is exposed to the outside of the body  30 . At least a portion of the slave joint  415  is exposed to the outside of the mop module  40 . 
     As illustrated by dotted lines a in  FIGS. 3 and 4 , the master joint  65  and the slave joint  415  are separated from each other in the separated state; and in the connected state, the master joint  65  and the slave joint  415  are engaged with each other. Any one of the master joint  65  and the slave joint  415  may include a plurality of driving protrusions  65   a  which are positioned in a circumferential direction with respect to a rotation axis of the any one; and the other one thereof may include a plurality of driving grooves  415   h  which are positioned in a circumferential direction with respect to a rotation axis of the other one. 
     The plurality of driving protrusions  65   a  are spaced apart from each other at predetermined intervals. The plurality of driving grooves  415   h  are spaced apart from each other at predetermined intervals. In the connected state, the driving protrusion  65   a  is inserted into the driving groove  415   h . In the separated state, the driving protrusion  65   a  is separated from the driving groove  415 . 
     In one embodiment, the number of the plurality of driving grooves  415   h  is greater than the number of the plurality of driving protrusions  65   a . The number of the plurality of driving protrusions  65   a  may be n, and the number of the plurality of driving grooves  415   h  may be n*m (value obtained by multiplying n and m), where “n” is a natural number equal to or greater than 2, and “m” is a natural number equal to or greater than 2. In the embodiment, four driving protrusions  65   a   1 ,  65   a   2 ,  65   a   3 , and  65   a   4 , which are spaced apart from each other at predetermined intervals, are provided; and eight driving grooves  415   h   1 ,  415   h   2 ,  415   h   3 ,  415   h   4 ,  415   h   5 ,  415   h   6 ,  415   h   7 , and  415   h   8 , which are spaced apart from each other at predetermined intervals, are provided. 
     Any one of the master joint  65  and the slave joint  415  may include the plurality of driving protrusions  65   a  which are spaced apart from each other in a circumferential direction with respect to a rotation axis of the any one thereof. And, the other one of the master joint  65  and the slave joint  415  may include a plurality of opposing protrusions  415   a  which are spaced apart from each other in a circumferential direction with respect to a rotation axis of the other one thereof. The plurality of opposing protrusions  415   a  protrude in a direction the any one of the master joint  65  and the slave joint  415 . 
     The plurality of opposing protrusions  415   a  are spaced apart from each other at predetermined intervals. In the connected state, any one driving protrusion  65   a  is positioned between two adjacent opposing protrusions  415   a . In the separated state, the driving protrusion  65   a  is separated from a space between two adjacent opposing protrusions  415   a . In the connected state, at least one opposing protrusion  415   a  is positioned between two adjacent driving protrusions  65   a . In the embodiment, in the connected state, two opposing protrusions  415   a  are positioned between two adjacent driving protrusions  65   a.    
     A protruding end of the opposing protrusion  415   a  may be formed to be rounded. For example, the protruding end of the opposing protrusion  415   a  may be formed to be rounded in an arrangement direction of the plurality of opposing protrusions  415   a . The protruding end of the opposing protrusions  415   a  has a corner portion which is rounded toward adjacent opposing protrusions  415   a  with respect to a central axis of the protruding direction. In this manner, when the separated state is changed to the connected state, the driving protrusion  65   a  may smoothly move along the rounded protruding end of the opposing protrusion  415   a  to be inserted into the driving groove  415   h.    
     The number of the plurality of opposing protrusions  415   a  may be greater than the number of the plurality of driving protrusions  65   a . The number of the plurality of driving protrusions  65   a  may be n, and the number of the plurality of opposing protrusions  415   a  may be n*m (value obtained by multiplying n and m), where “n” is a natural number equal to or greater than 2, and “m” is a natural number equal to or greater than 2. In the embodiment, four driving protrusions  65   a   1 ,  65   a   2 ,  65   a   3 , and  65   a   4 , which are spaced apart from each other at predetermined intervals, are provided; and eight opposing protrusions  415   a , which are spaced apart from each other at predetermined intervals, are provided. 
     In the embodiment, the master joint  65  may include the driving protrusion  65   a , and the slave joint  415  forms the driving groove  415   h . In the embodiment, the slave joint  415  may include the opposing protrusion  415   a . Hereinafter, description will be made based on the embodiment. 
     The master joint  65  is fixed to a bottom end of the master shaft  624 . The master joint  65  may include a driving protrusion axis  65   b  which is fixed to the mater shaft  624 . The driving protrusion axis  65   b  may be formed in a cylindrical shape. The driving protrusion  65   a  protrudes from the driving protrusion axis  65   b . The driving protrusion  65   a  protrudes in a direction further away from a rotation axis of the master joint  65 . The driving protrusions  65   a  are spaced apart from each other in a circumferential direction of the driving protrusion axis  65   b . The driving protrusion  65   a  may have a circular cross-section, and may protrude in a direction further away from the master joint  65 . 
     The slave joint  415  is fixed to the top end of the spin shaft  414 . The slave joint  415  may include a slave shaft portion  415   b  which is fixed to the spin shaft  414 . The slave shaft portion  415   b  may be formed in a cylindrical shape. The driving groove  415   h  is formed at a front portion of a circumference of the slave shaft portion  415   b . The driving groove  415   h  is vertically recessed. A plurality of driving grooves  415   h  are spaced apart from each other along the circumference of the slave shaft portion  415   h . The slave joint  415  may include an opposing protrusion  415   a  which protrude from the slave shaft portion  415   b . The opposing protrusion  415   a  protrudes from the slave shaft portion  415   b  toward the master joint  65  in a vertical direction. 
     In the embodiment, the opposing protrusion  415   a  protrudes upward. The opposing protrusion  415   a  forms the protruding end upward. The opposing protrusion  415   a  forms a rounded protruding end. When the separated state is changed to the connected state, and a surface of the driving protrusion  65   a  contacts the rounded end of the opposing protrusion  415   a , the driving protrusion  65   a  naturally slides to be inserted into the driving groove  415   h . The opposing protrusion  415   a  is positioned forward of the slave shaft portion  415   b . The plurality of opposing protrusions  415   a  and the plurality of driving grooves  415   h  are alternately positioned along the circumference of the slave shaft portion  415   b.    
     In the connected state, when the suspension units  47 ,  48 , and  49 , which will be described later, are freely movable within a predetermined range, the driving protrusion  65   a  and the driving groove  415   h  are movable but are engaged with each other to transmit torque. Specifically, a vertical depth of the driving groove  415   h  is formed to be greater than a vertical width of the driving protrusion  65   a , such that even when the driving protrusion  65   a  freely moves in the driving groove  415   h  within the predetermined range, the torque of the master joint  65  may be transmitted to the slave joint  415 . 
     A module housing  42  connects the pair of spin mops  41   a  and  41   b . The pair of spin mops  41   a  and  41   b  are integrally detached from, and integrally connected to, the body  30  by the module housing  42 . The body mounting portion  43  is positioned above the module housing  42 . The spin mop  41  may be rotatably supported by the module housing  42 . The spin mop  41  may be positioned by passing through the module housing  42 . 
     The module housing  42  may include a top cover  421  which forms a top portion of the module housing  42 , and a bottom cover  423  which forms a bottom portion. The top cover  421  and the bottom cover  423  are connected with each other. The top cover  421  and the bottom cover  423  form an inner space to partially accommodate the spin mop  41 . 
     The suspension units  47 ,  48 , and  49  may be positioned at the module housing  42 . The suspension units  47 ,  48 , and  49  may be positioned in the inner space formed by the top cover  421  and the bottom cover  423 . The suspension units  47 ,  48 , and  49  support the spin shaft  414  in a manner that enables the spin shaft  414  to be vertically movable within a predetermined range. According to the present disclosure, the suspension units  47 ,  48 , and  49  may include a tilting frame  47 , a tilting shaft  48 , and an elastic member  49 . 
     The module housing  42  may include a limit, which limits a rotation range of the tilting frame  47 . The limit may include a bottom limit  427 , which limits a range of downward rotation of the tilting frame  47 . The bottom limit  427  may be positioned in the module housing  42 . The bottom limit  427  is provided to contact a bottom limit contacting portion  477  when the tilting frame  47  rotates as downward as possible. When the cleaner  1  is normally positioned on an external horizontal plane, the bottom limit contacting portion  477  is spaced apart from the bottom limit  427 . With no power being provided to push upward from a bottom surface of the spin mop  41 , the tilting frame  47  rotates to a maximum angle, the bottom limit contacting portion  477  contacts the bottom limit  427 , and the inclination angles Ag 2   a  and Ag 2   b  becomes the largest. 
     The limit may include a top limit (not shown), which limits a range of upward rotation of the tilting frame  47 . In the embodiment, as the master joint  65  and the slave joint  415  are attached to each other, the range of upward rotation of the tilting frame  47  may be limited. When the cleaner  1  is normally positioned on an external horizontal plane, the master joint  65  and the slave joint  415  are attached to each other to the maximum, and the inclination angles Ag 2   a  and Ag 2   b  becomes the smallest. 
     The module housing  42  may include a second supporting portion  425  which fixes an end portion of the elastic member  49 . When the tilting frame  47  rotates, the elastic member  49  is elastically deformed or elastically restored by a first supporting portion  475 , which is fixed to the tilting frame  47 , and a second supporting portion  425  which is fixed to the module housing  42 . 
     The module housing  42  may include a tilting shaft supporting portion  426  which supports the tilting shaft  48 . The tilting shaft supporting portion  426  supports both ends of the tilting shaft  48 . 
     As illustrated in  FIGS. 22 to 24 , the mop module  40  may include a module water supply unit  44  which guides water, introduced from the water supply connection portion, into the spin mop  41 . The module water supply portion (or module water supply channel)  44  guides water from upward to downward. A pair of module water supply portions  44 , which correspond to the pair of spin mops  41   a  and  41   b , may be provided. The water W in the water tank  81  is supplied to the spin mop  41  through the module water supply portion  44 . The water W in the water tank  81  is introduced into the module water supply portion  44  through the water supply connection portion  87 . 
     The module water supply portion  44  may include a water supply corresponding portion (or a water supply corresponding channel)  441  to receive water from the water supply module  80 . The water supply corresponding portion  441  is connected with the water supply connection portion  87 . The water supply corresponding portion  441  forms a groove into which the water supply connection portion  87  is inserted. The water supply corresponding portion  441  is positioned in the body mounting portion  43 . The water supply corresponding portion  441  is positioned at the top surface portion  431  of the body mounting portion  43 . The water supply corresponding portion  441  is formed by a downwardly recessed surface of the body mounting portion  43 . 
     In the connected state, the water supply corresponding portion  441  is formed at a position corresponding to the water supply connection portion  87 . In the connected state, the water supply connection portion  87  is connected with the water supply corresponding portion  441  by being engaged with each other. In the connected state, the water supply connection portion  87  is inserted from below into the water supply corresponding portion  441 . In the separated state, the water supply connection portion  87  and the water supply corresponding portion are separated from each other (see dotted line b in  FIGS. 3 and 4 ). 
     The module water supply portion  44  may include a water supply delivery portion  443  which guides water, introduced into the water supply corresponding portion  441 , into the water supply guiding portion  445 . The water supply delivery portion  443  may be positioned in the module housing  42 . The water supply delivery portion  443  may protrude downward on an inner top surface of the top cover  421 . The water supply delivery portion  443  may be positioned below the water supply corresponding portion  441 . The water supply delivery portion  443  may be provided to flow water downward. The water supply corresponding portion  441  and the water supply delivery portion  443  may form a hole which vertically penetrates, and water flows downward through the hole. 
     The module water supply portion  44  may include the water supply guiding portion  445  which guides water, introduced into the water supply corresponding portion  441 , to the spin mop  41 . The water, introduced into the water supply corresponding portion  441 , is introduced into the water supply guiding portion  445  through the water supply delivery portion  443 . 
     The water supply guiding portion  445  is positioned at the tilting frame  47 . The water supply guiding portion  445  is fixed to the frame base  471 . The water is introduced through the water supply corresponding portion  441  and the water supply delivery portion  443  into a space formed by the water supply guiding portion  445 . The water supply guiding portion  445  may minimize dispersion of water, thereby inducing all drops of water to be introduced into the water accommodation portion  413 . 
     The water supply guiding portion  445  may include an introduction portion  445   a  forming a space which is recessed downward from above. The introduction portion  445   a  may accommodate a bottom end of the water supply delivery portion  443 . The introduction portion  445   a  may form a space having an open top portion. After passing through the water supply delivery portion  443 , the water is introduced through the open top portion of the space of the introduction portion  445   a . The space of the introduction portion  445   a  has one side which is connected with a flow passage having a flow passage portion  445   b  formed at one side. 
     The water supply guiding portion  445  may include the flow passage portion  445   b  which connects the introduction portion  445   a  and an discharge portion  445   c . One end of the flow passage portion  445   b  is connected with the introduction portion  445   a , and the other end of the flow passage portion  445   b  is connected with the discharge portion  445   c . The space formed by the flow passage portion  445   b  is a flow passage of water. The space of the flow passage portion  445   b  communicates with the space of the introduction portion  445   a . The flow passage portion  445   b  may be formed of a channel type having an open top portion. The flow passage portion  445   b  may have an inclined portion, of which height is lowered from the introduction portion  445   a  to the discharge portion  445   c.    
     The water supply guiding portion  445  may include the discharge portion  445   c  which discharges water into the water supply space Sw of the water accommodation portion  413 . A bottom end of the discharge portion  445   c  may be positioned in the water supply space Sw. The discharge portion  445   c  forms a hole which connects an inner space of the module housing  42  and an upper space of the rotary plate  412 . The hole of the discharge portion  445   c  vertically connects the two spaces. The discharge portion  445   c  forms a hole which vertically penetrates the tilting frame  47 . The space of the flow passage portion  445   b  communicates with the hole of the discharge portion  445   c . A bottom end of the discharge portion  445   c  may be positioned inside the water supply space Sw of the water accommodation portion  413 . 
     The tilting frame is connected with the module housing  42  through the tilting shaft  48 . The tilting frame  47  rotatably supports the spin shaft  414 . The tilting frame  47  is provided to be rotatable about tilting rotation axes Ota and Otb within a predetermined range. The tilting rotation axes Ota and Otb are extended in a direction transverse to the rotation axes Osa and Osb of the spin shaft  414 . The tilting shaft  48  is positioned on the tilting rotation axes Ota and Otb. The left tilting frame  47  is provided to be rotatable about the tilting rotation axis Ota within a predetermined range. The right tilting frame  47  is provided to be rotatable about the tilting rotation axis Otb within a predetermined range. 
     The tilting frame  47  is provided to be inclined with respect to the mop module  40  within a predetermined angle range. Inclination angles Ag 2   a  and Ag 2   b  of the tilting frame  47  may be changed according to floor states. The tilting frame  47  may perform a function of suspension (supporting weight while reducing vertical vibration) of the spin mop  47 . 
     The tilting frame  47  may include a frame base  471  which forms a bottom surface. The spin shaft  414  is positioned to vertically penetrate the frame base  471 . The frame base  471  may be formed in a plate shape which has a thickness in a vertical direction. The tilting shaft  48  connects the module housing  42  and the frame base  471  in a rotatable manner. 
     A bearing Ba may be provided between a rotation axis supporting portion  473  and the spin shaft  414 . The bearing Ba may include a first bearing B 1 , which is positioned at the bottom, and a second bearing B 2  which is positioned at the top. 
     A bottom end of the rotation axis supporting portion  473  is inserted into the water supply space Sw of the water accommodation portion  413 . An inner circumferential surface of the rotation axis supporting portion  473  supports the spin shaft  414 . 
     The tilting frame  47  may include a first supporting portion  475  which supports one end of the elastic member  49 . The other end of the elastic member  49  is supported by a second supporting portion  425  positioned in the module housing  42 . When the tilting frame  47  is inclined with respect to the tiling shaft  48 , a position of the first supporting portion  475  is changed, and the length of the elastic member  49  is changed. 
     The first supporting portion  475  is fixed to the tilting frame  47 . The first supporting portion  475  is positioned at the left side of the left tilting frame  47 . The first supporting portion  475  is positioned at the right side of the right tilting frame  47 . The second supporting portion  425  is positioned at a left region of the left spin mop  41   a . The second supporting portion  425  is positioned at a right region of the right spin mop  41   b.    
     The first supporting portion  475  is fixed to the tilting frame  47 . The first supporting portion  475  is inclined along with the tilting frame  47  when the tilting frame  47  is inclined. In the case where the inclination angles Ag 2   a  and Ag 2   b  are the smallest, the distance between the first supporting portion  475  and the second supporting portion  425  is the shortest. In the case where the inclination angles Ag 2   a  and Ag 2   b  are the largest, the distance between the first supporting portion  475  and the second supporting portion  425  is the longest. When the inclination angles Ag 2   a  and Ag 2   b  are the shortest, the elastic member  49  is elastically deformed and provides a restoring force. 
     The tilting frame  47  may include a bottom limit contacting portion  477  which is provided to contact the bottom limit  427 . The bottom surface of the bottom limit contacting portion  477  may contact the top surface of the bottom limit  427 . 
     The tilting shaft  48  is positioned in the module housing  42 . The tilting shaft  48  is a rotation axis of the tilting frame  47 . The tilting shaft  48  may be extended in a direction perpendicular to an inclination direction of the spin mop  41 . The tilting shaft  48  may be extended in a horizontal direction. In the embodiment, the tilting shaft  48  is extended from a forward and backward direction to a direction inclined at an acute angle. 
     The elastic member  49  applies an elastic force to the tilting frame  47 . The elastic member  49  applies the elastic force to the tilting frame  47  so that the inclination angles Ag 2   a  and Ag 2   b  of the bottom surface of the spin mop  41  may increase. 
     The elastic member  49  is provided to stretch (or extend) when the tilting frame  47  rotates downward, and to shrink when the tilting frame  47  rotates upward. The elastic member  49  enables the tilting frame  47  to act in a shock-absorbing (elastic) manner. The elastic member  49  applies a moment force to the tilting frame  47  in a manner that increases the inclination angles Ag 2   a  and Ag 2   b.    
     As illustrated in  FIGS. 15 and 17 , the center of mass Mw of the water tank lies on the central vertical plane Po. The center of mass Mw of the water tank  81  is positioned behind the points Pla and Plb on which the largest frictional force acts. The center of mass of a battery Mb lies on the central vertical plane Po. The center of mass Mb of the battery Bt is positioned behind the points Pla and Plb on which the largest frictional force acts. 
     Further, the center of mass Mp of a pump lies on the central vertical plane Po. The center of mass Mp of the pump is positioned between the pair of spin mops  41   a  and  41   b . The center of mass Mc of the detachable module  90  lies on the central vertical plane Po. The center of mass Mc of the detachable module  90  is positioned behind the center of mass Mp of the pump. 
     The center of mass Mr of the mop module  40  lies on the central vertical plane Po. The pair of spin mops  41   a  and  41   b  are left-right symmetric. The center of mass of the pair of spin mops  41   a  and  41   b  lie on the central vertical plane Po. 
     The center of mass Mn of the mop driving unit  60  lies on the central vertical plane Po. The pair of mop driving units  60  are left-right symmetric. The center of mass Mn of the mop driving unit  60  is positioned between the pair of spin mops  41   a  and  41   b.    
     The center of mass Mf of the collection module  50  lies on the central vertical plane Po. The collection module  50  may be left-right symmetric. The center of mass of the pair of sweeping units  51  may lie on the central vertical plane Po. The pair of sweeping units  51  may be left-right symmetric. The pair of collection units  53  may be left-right symmetric. The center of mass of the pair of sweeping units  51  may lie on the central vertical plane Po. 
     The center of mass Mm of the collection driving unit  70  lies on the central vertical plane Po. The collection driving unit  70  may be left-right symmetric with respect to the central vertical plane Po. 
     A first aspect of the present application increases a frictional force between a rag and a floor surface so that a cleaner may wipe and travel effectively. A second aspect of the present application improves stability in leftward and rightward and forward and backward traveling of a robot cleaner in comparison to other robot cleaners that are typically supported at two points by a pair of rags provided on the left side and the right side, thereby reducing the stability of these robot cleaners in forward and backward traveling. 
     A third aspect of the present application relates to providing consistent friction against a floor surface by the spinning mops in comparison to another robot cleaner which travels by a pair of rotating rag surfaces provided on the left side and the right side, such that a frictional force generated by the pair of rotating rag surfaces frequently changes and the robot cleaner has difficulty moving straight. When the robot cleaner has difficulties moving straight, the cleaner may by pass an area to be cleaned, such as a surface near a wall, where the robot cleaner is required to move straight. 
     If the robot cleaner is supported by more than two supporting points, load is distributed to the plurality of supporting points. In this case, however, there is a problem in that a frictional force generated by the action of some of the plurality of supporting points is reduced due to load distribution, which reduces traveling performance of the robot cleaner. Thus, a fourth aspect of the present application improves traveling performance while securing stability. 
     A fifth aspect the present application reduces occurrences of eccentric movement (for example, a case where the robot cleaner performs curved traveling, which is different from a controlled command signal), which occurs unexpectedly as the center of gravity is leaned to one side when the robot cleaner travels by a pair of rags on the left side and the right side. 
     A sixth aspect of the present application solves a problem that when the robot cleaner performs wiping, relatively large foreign substances are difficult to be attached to a rag surface and may remain on the floor even after the wiping. A seventh aspect of the present application provides a cleaner which may perform both wet-type and dry-type wiping, thereby enabling the cleaner to perform clean and efficient wiping. 
     In order to achieve the above aspects of the present application, a cleaner may include a mop module having a pair of spin mops that contacts a floor while rotating clockwise or counterclockwise when viewed from a top and is left-right symmetric with a virtual central vertical plane. Further, the cleaner may include a collection module that collects foreign substances from the floor at a position spaced apart from the mop module in a forward and backward direction. The collection module may include at least one collection unit that forms a collection space which stores the collected foreign substances. The at least one collection unit is left-right symmetric with respect to the central vertical plane. In addition, the cleaner may include a body which is disposed to connect the mop module and the collection module. The collection module further may include at least one sweeping unit which contacts the floor while rotating to suck the foreign substances from the floor into the collection space. And, the at least one sweeping unit is left-right symmetric with respect to the central vertical plane. The cleaner further may include a collection driving unit which provides torque to the pair of sweeping units. And, the collection driving unit is left-right symmetric with respect to the central vertical plane. 
     The collection module may include: a module cabinet which forms a bottom surface facing the floor; and at least one auxiliary wheel is configured to make the floor and the bottom surface of the module cabinet spaced apart from each other in a range where the at least one sweeping unit contacts the floor. 
     The at least one auxiliary wheel may be left-right symmetric with respect to the central vertical plane. The at least one sweeping unit may include a left sweeping unit and a right sweeping unit which are left-right symmetric with respect to the central vertical plane. 
     The collection driving unit may include: a sweeping motor having a motor rotation axis disposed on the central vertical plane; a sweeping shaft, both ends of which are connected to the left sweeping unit and the right sweeping unit respectively, and which is extended in a left-and-right direction; and a driving force transmission unit which transmits torque of a motor rotation axis to the sweeping shaft. 
     The driving force transmission unit may include: a worm gear which rotates while being fixed to the motor rotation axis; and at least one gear which rotates by being engaged with the worm gear by rotation of the worm gear. One of the at least one gear may be fixed to the sweeping shaft to rotate along with the sweeping shaft. 
     The collection module may be disposed in front of the mop module. The at least one sweeping unit may be disposed in front of the pair of collection units. The at least one collection unit may have an open portion at the front. And, The open portion communicates with the collection space. 
     The cleaner may further include: a water tank which stores water to be supplied to the mop module; and a battery which provides power. A center of gravity of the water tank and a center of gravity of the battery may be configured to be disposed on the central vertical plane. The cleaner may further include a pump which performs pumping to move water in the water tank to the mop module. A center of gravity of the pump may be configured to be disposed on the central vertical plane. 
     The cleaner may further include a mop driving unit or motor which provides torque to the pair of spin mops, and is left-right symmetric with respect to the central vertical plane. The collection module may be disposed in front of the mop module. A point, to which the largest frictional force is applied from the floor on a bottom surface of a left spin mop of the pair of spin mops, may be configured to be disposed on a left side of a center of rotation of the left spin mop, and a point, to which the largest frictional force is applied from the floor on a bottom surface of a right spin mop of the pair of spin mops, may be configured to be disposed on a right side of a center of rotation of the right spin mop. The center of gravity of the water tank and the center of gravity of the battery may be configured to be disposed rearward of the points of the left spin mop and the right spin mop, on which the largest frictional force is applied. 
     The water tank and the battery may be disposed with a vertical gap formed therebetween. The cleaner may be disposed across the gap between the water tank and the battery; and may further include a detaching assembly which operates to enable the mop module and the body to be detachably connected with each other. In the cleaner, the body may configured to move by rotation of the pair of spin mops without a separate driving wheel. 
     The cleaner may further include: an image sensor which senses external images; and a controller which learns a traveling area by using the images, and controls to recognize a current position of the cleaner. The cleaner may further include a sensing module, which may include at least one of a bumper, which senses contact with an external obstacle, an obstacle sensor, which senses an external obstacle spaced apart from the cleaner, and a cliff sensor which senses presence of a cliff on a traveling surface. The cleaner may further include a controller which controls traveling of the cleaner by receiving input of a sensing signal of the sensing module. 
     In accordance with an aspect of the present application, there is provided a cleaner including: a mop module which may include a pair of spin mops that contacts a floor while rotating clockwise or counterclockwise when viewed from a top; a collection module which contacts the floor at a position spaced apart from the mop module in a forward and backward direction, and collects foreign substances from the floor; and a body which is supported by the mop module and the collection module. 
     In accordance with an aspect of the present application, there is provided a cleaner including a mop module which may include a pair of spin mops that contacts a floor while rotating clockwise or counterclockwise when viewed from a top and is left-right symmetric with a virtual central vertical plane. Further, the cleaner may include a collection module that collects foreign substances from the floor at a position spaced apart from the mop module in a forward and backward direction. The collection module may include at least one collection unit that forms a collection space which stores the collected foreign substances. The at least one collection unit is left-right symmetric with respect to the central vertical plane. In addition, the cleaner may include a body which is disposed to connect the mop module and the collection module. In addition, the cleaner may include a water tank configured to store water to be supplied to the mop module, wherein a center of gravity of the water tank is configured to be disposed on the central vertical plane. And, the cleaner may include a battery configured to provide power, wherein a center of gravity of the battery is configured to be disposed on the central vertical plane. 
     As described above, the cleaner may perform wiping while collecting relatively large foreign substances. Further, as the cleaner is supported by the mop module, wiping efficiency may be increased. In addition, by securing stability in the leftward and rightward movement of the cleaner using a pair of spin mops provided on the left side and the right side, with the collection module, which is spaced apart from the mop module in a forward and backward direction, contacting the floor using an auxiliary wheel, stability in the forward and backward movement of the cleaner may be increased. Specifically, with respect to a supporting point of the mop module, the collection module prevents the cleaner from overturning forward, and a rag surface of the mop module prevents the cleaner from overturning rearward. 
     Further, the collection module provides a frictional force for leftward and rightward vibration, thereby enabling the cleaner to move straight by the frictional force of the rag surface while traveling. Moreover, in one configuration, while securing stability in forward and backward movement and leftward and rightward movement of the cleaner, load may be distributed by applying a relatively large load on the mop module which is a supporting point for traveling. Specifically, by providing the center of gravity of the water tank and/or the center of gravity of the battery relatively at the rear side, a ratio of the load applied to the mop module to the load applied to the collection module may be increased. Further, by applying the largest frictional force to a left front side of the bottom surface of the left spin mop and to a right front side of the bottom surface of the right spin mop, a ratio of the weight of the rear side to the weight of the front side is increased with respect to a virtual axis connecting two points Pla and plb on which the largest frictional force acts. In this case, with respect to the entire load of the cleaner, a ratio of the load applied to the mop module to the load applied to the collection module is increased, thereby increasing efficiency of wiping and traveling according to rotation of the mop module. 
     The auxiliary wheel is provided to enable the floor and the bottom surface of the module cabinet to be spaced apart from each other in a range where the pair of sweeping units may contact the floor, a frictional force between the collection module and the floor may be reduced while the cleaner travels, the cleaner may be prevented from overturning forward and backward, and the sweeping unit may sweep the floor at a predetermined height. 
     Further, the pair of collection units, which collect foreign substances, are left-right symmetric with respect to the virtual central vertical plane, which is a reference plane based on which the pair of spin mops are left-right symmetric, such that accurate traveling control may be provided by the pair of left and right spin mops, and unexpected eccentric movement may be prevented. In addition, with respect to the central vertical plane, the pair of sweeping units, the at least one auxiliary wheel, the mop driving units and/or the collection driving units are left-right symmetric, thereby enabling accurate traveling control. 
     Moreover, the center of gravity of the water tank, the battery and/or the pump is disposed on the central vertical plane, thereby enabling accurate traveling control. Further, the collection driving part, which includes a motor rotation axis disposed on the central vertical plane, is provided in a manner that enables the collection driving part to be left-right symmetric with respect to the central vertical plane. The pair of collection units and the pair of sweeping units each have a gap therebetween, such that the collection driving part may be disposed on the central vertical plane, and may be left-right symmetric. The collection module is disposed in front of the mop module, and the pair of sweeping units is disposed in front of the pair of collection units. In this manner, after foreign substances are first swept up from the floor at the front side, wiping is performed following the swept floor, thereby enabling efficient cleaning. 
     It will be understood that when an element or layer is referred to as being “on” another element or layer, the element or layer can be directly on another element or layer or intervening elements or layers. In contrast, when an element is referred to as being “directly on” another element or layer, there are no intervening elements or layers present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section could be termed a second element, component, region, layer or section without departing from the teachings of the present application. 
     Spatially relative terms, such as “lower”, “upper” and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “lower” relative to other elements or features would then be oriented “upper” relative the other elements or features. Thus, the exemplary term “lower” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments of the disclosure are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the disclosure. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the disclosure should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.