Abstract:
A nozzle assembly usable with an upright vacuum cleaner, comprising: a nozzle assembly body; a drum brush unit disposed in the nozzle assembly body, the drum brush unit having a drum brush disposed to move dirt or dust adhered to a surface to be cleaned while coming in rotational contact therewith; a subsidiary brush unit disposed in front of the drum brush unit, and the subsidiary brush unit having a subsidiary brush to preliminarily move the dust or dirt adhered to the surface to be cleaned before the drum brush moves the dirt or dust adhered to the surface to be cleaned; and a locking unit disposed to the drum brush unit to selectively fix the subsidiary brush unit to the drum brush unit, wherein the subsidiary brush unit is rotatably connected to the drum brush unit to selectively maintain a contact state or a non-contact state to the surface to be cleaned, and, when the subsidiary brush unit maintains the contact state to the surface to be cleaned, the locking unit fixes the subsidiary brush unit to the drum brush unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional Application of U.S. patent application Ser. No. 11/900,024, filed on Sep. 7, 2007, and claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Nos. 60/850,736, 60/850,895, 60/875,898, and 60/919,253, filed Oct. 11, 2006, Oct. 11, 2006, Dec. 20, 2006, and Mar. 21, 2007, respectively, in the United States Patent and Trademark Office, and claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application Nos. 10-2006-0128520, 10-2006-0128522, 10-2007-0015589, 10-2007-0044275, filed on Dec. 15, 2006, Dec. 15, 2006, Feb. 14, 2007, and May 7, 2007, respectively, in the Korean Intellectual Property Office, the entire contents of all of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to a vacuum cleaner. More particularly, the present disclosure relates to a nozzle assembly of a vacuum cleaner, which comes in contact with a surface to be cleaned to draw in dust or dirt with air from the surface to be cleaned. 
     2. Description of the Related Art 
     In general, a vacuum cleaner is provided with a nozzle assembly capable of drawing in dust or dirt from a surface to be cleaned. Such a nozzle assembly draws in the dirt or the dust from the surface to be cleaned by a suction force generated form a suction motor mounted in a cleaner body in a state where it comes in contact with the surface to be cleaned. 
     However, among such conventional nozzle assemblies, a nozzle assembly, which is applied to an upright vacuum cleaner, has a drum brush unit to brush away the dust or dirt stained to the surface to be cleaned, more particularly, a carpet. The nozzle assembly including the drum brush unit is disclosed in Japanese patent publication No. 4132529, German patent publication DE 19602406, and Korean patent publication No. 10-2004-0075569. The disclosed nozzle assembly has a drum brush rotatably joined to a cleaner body, so that it strikes dust or dirt of a surface to be cleaned in an dust inlet thereof to brush away the dust or dirt from the surface to be cleaned. The drum brush is rotated by a motor mounted in the nozzle assembly or by a kinetic energy of drawn-in air. A brush member or blade projected from an outer circumferential surface of the drum brush strikes the surface to be cleaned in a tangential direction while coming in rotation contact therewith. When the drum brush strikes a portion of the surface to be cleaned, which is stained with the dust or dirt, the dust or dirt is scattered while separating from the portion of the surface to be cleaned, and is drawn into the nozzle assembly. 
     However, dirt, such as hair, fur or the like, which is firmly stuck to the surface to be cleaned, particularly, a surface of carpet, is not separated therefrom well only by the drum brush. Although the drum brush strikes or scrapes against the surface to be cleaned while rotating, scraping strength thereof is too weak to separate the dirt from the surface to be cleaned. If spidery dirt, such as the hair, the fur or the like, is wound on cilia or fibers of the carpet, it is not easily separated from the carpet. In this case, there is an inconvenience in that to clean the carpet, a user should take the spidery dirt off one by one from the carpet, or clean the carpet again by using a cleaning outfit, such as a comb or the like. 
     SUMMARY 
     An aspect of the present disclosure is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide a nozzle assembly of a vacuum cleaner capable of cleaning hair or fur of a pet as well as dust or dirt, which is firmly stuck to a surface to be cleaned. 
     Another aspect of the present disclosure is to provide a nozzle assembly of a vacuum cleaner having a subsidiary brush capable of selectively coming in contact or non-contact with a surface to be cleaned according to whether there is a need to use it. 
     Further another aspect of the present disclosure is to provide a nozzle assembly of a vacuum cleaner having a subsidiary brush, which is convenient to use, maintain and repair. 
     Still another aspect of the present disclosure is to provide a nozzle assembly of a vacuum cleaner having a subsidiary brush capable of coming in contact with a surface to be cleaned well even though the surface to be cleaned is crooked or irregular. 
     In accordance with an aspect of the present disclosure, a nozzle assembly of a vacuum cleaner includes a nozzle assembly body; a drum brush unit disposed in the nozzle assembly body, and having a drum brush disposed to brush away dirt or dust adhered to a surface to be cleaned while coming in rotation contact therewith; and a subsidiary brush unit disposed to the nozzle assembly body or the drum brush unit, and having a subsidiary brush to preliminarily brush away the dust or dirt adhered to the surface to be cleaned. With the subsidiary brush unit disposed to the nozzle assembly body or the drum brush unit to preliminarily brush away the dust or dirt, the nozzle assembly can efficiently clean the dirt, particularly, hair or the like, from the surface to be cleaned, particularly, a carpet. 
     Here, preferably, but not necessarily, the subsidiary brush unit is rotatably connected to the nozzle assembly body or the drum brush unit to selectively maintain a contact state or a non-contact state to the surface to be cleaned. Accordingly, when a floor, a carpet or a quilt is cleaned, the subsidiary brush unit can be selectively used. 
     According to an exemplary embodiment of the present disclosure, the subsidiary brush unit may be disposed to the nozzle assembly body and may include a subsidiary brush member to selectively maintain the contact state or the non-contact state to the surface to be cleaned, at least one bracket member having one side connected to the nozzle assembly body, and at least one link member to connect the bracket member and the subsidiary brush member. Here, the link member may be rotatably connected to the bracket member and the subsidiary brush member. 
     The subsidiary brush unit may further include at least one guide member to connect the subsidiary brush member and the bracket member. The bracket member may have at least one guide groove formed therein, and one end of the guide member may be inserted into and moved in the guide groove to change a position of the subsidiary brush member. 
     Also, the subsidiary brush unit may further include at least one rotation-prevention part to restrict a rotation of the link member. Here, the rotation-prevention part may be configured to include a hook to restrain the link member from rotating in a direction toward the surface to be cleaned, and a stopper to restrain the link member from rotating in an opposite direction to the direction toward the surface to be cleaned, which are disposed on the bracket member. 
     The subsidiary brush member may include a subsidiary brush casing rotatably connected with the link member, and a subsidiary brush joined to the subsidiary brush casing to selectively maintain the contact state or the non-contact state to the surface to be cleaned. Here, the subsidiary brush may be detachably joined to the subsidiary brush casing, and may include a plurality of protrusions projected from a surface thereof facing the surface to be cleaned. 
     In accordance with another aspect of the present disclosure, a nozzle assembly of a vacuum cleaner includes left and right bracket parts projected forward from both sides of the front face of the drum brush unit, and the subsidiary brush unit may be connected to the left and the right bracket parts. 
     In an exemplary embodiment of the present disclosure, the subsidiary brush unit may be configured to include a frame member rotatably connected to the drum brush unit, an upper casing to wrap an upper part of the frame member, a lower casing connected with the upper casing to wrap a lower part of the frame member, and a subsidiary brush member detachably connected to an undersurface of the lower casing. The upper and the lower casings may be configured, so that they are movable up and down and rotatable. 
     The frame member may include a frame body, at least one frame key projected downward from a lower end of the frame body, a frame axis projected from both sides of the frame body, and uneven parts disposed on both ends of the frame axis, respectively. 
     The left and the right bracket parts may include elongated holes formed in a horizontal direction therein, respectively. In this case, the nozzle assembly may further include first elastic members inserted in the elongated holes, respectively, and cam members engaged with the uneven parts of the frame member, respectively. 
     At least one key may be projected from inner walls of the elongated holes, respectively and at least one key groove may be formed on the cam members, respectively. In this manner, the cam members may be configured to move in the horizontal direction with respect to a rotating movement of the frame member. At least one boss may be formed in the lower casing so as to accommodate the frame key of the frame member therein, and a second elastic member may be disposed in the boss. 
     In accordance with further another aspect of the present disclosure, a nozzle assembly of a vacuum cleaner includes a locking unit disposed to the drum brush unit to selectively fix the subsidiary brush unit thereon. Accordingly, with the locking unit, the subsidiary brush unit can be rotated from a use position to a non-use position when it is temporarily not used, and fixed to the use position when it is used. 
     Also, the drum brush unit may include a drum brush, and a drum brush casing to wrap the drum brush, and the subsidiary brush unit may be configured to join with or separate from the drum brush casing. 
     The locking unit may include a hook member to lock to the subsidiary brush unit, and a spring to press the hook member in a upward direction, the subsidiary brush unit may include a subsidiary brush casing, a panel joined to a lower end of the subsidiary brush casing, and a subsidiary brush joined to a lower end of the panel, and the subsidiary brush casing may be selectively locked to the hook member of the locking unit. 
     In addition, the panel may be configured to be elastically movable up and down and to be rotatable. For this, the panel may include a plurality of bosses formed on a upper surface thereof, each of the bosses having a spring disposed therein, and supporting axes formed on both ends thereof and rotatably supported in elongated holes formed in the subsidiary brush casing. The subsidiary brush may include a plurality of protrusions projected from an undersurface thereof. 
     Also, the drum brush casing may have at least one bracket disposed thereon, the subsidiary brush casing may have at least one cover arm rotatably joined to the bracket, and the bracket may be configured to mount on or separate from the drum brush casing. 
     Also, the drum brush casing may have at least one sliding rail disposed thereon, and the bracket may have at least one sliding groove joined with the sliding rail. 
     In accordance with still another aspect of the present disclosure, the subsidiary brush unit is configured, so that the panel is disposed to be movable back and forth and in a horizontal direction with respect to the subsidiary brush casing. For this, the subsidiary brush unit may include at least one hinge bracket disposed between the panel and the subsidiary casing to hingedly fix the panel to the subsidiary brush casing and thus to move the panel in the horizontal direction to the subsidiary brush casing. The hinge bracket may include a body fixed to a fixing boss formed on a undersurface of the subsidiary brush casing, and a link member having at least one link hingedly fixed to the body and the panel by hinge screws. In this manner, preferably, but not necessarily, each of the hinge screws includes a raised portion rotatably supported in one of hinge holes formed in both ends of the link, and a screw portion screwed to the panel or body. 
     The subsidiary brush may include a picker attached to an undersurface of the panel and formed of a wool, cloth, or fabric with shag. In this manner, preferably, but not necessarily, the picker is formed, so that a shag portion thereof has a texture inclined in one direction, for example, a direction toward the drum brush unit. In this case, to exactly set the texture of the shag in fabrication, a first positioning part may be disposed between the panel and the picker to position the picker to panel, and a second positioning part may be disposed between the subsidiary brush casing and the panel to position the panel to the subsidiary brush casing. Preferably, but not necessarily, the first positioning part includes a projection formed on a side of the undersurface of the panel, and a projection-accommodating groove formed in the picker to accommodate the projection, and the second positioning part includes at least two ribs formed on a undersurface of the subsidiary brush casing, the two ribs being apart from the center of the subsidiary brush casing in different distances, and at least two rib-accommodating spaces formed on an upper surface of the panel to correspond to the ribs and to accommodate the ribs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features, and advantages of certain exemplary embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view exemplifying a nozzle assembly of a vacuum cleaner according to a first exemplary embodiment of the present disclosure; 
         FIG. 2  is a perspective view diagonally exemplifying an undersurface of the nozzle assembly of  FIG. 1 ; 
         FIG. 3  is a perspective view exemplifying only a subsidiary brush unit of the nozzle assembly of  FIG. 1 ; 
         FIG. 4  is a view exemplifying another example of projections of a subsidiary brush of the subsidiary brush unit of  FIG. 1 ; 
         FIG. 5  is a view exemplifying still another example of the projections of the subsidiary brush of the subsidiary brush unit of  FIG. 1 ; 
         FIG. 6  is a cross-sectional view exemplifying a hook of a rotation-prevention part of the subsidiary brush unit of  FIG. 1 ; 
         FIG. 7  is a cross-sectional view exemplifying another example of the hook of  FIG. 6 ; 
         FIG. 8  is a view exemplifying only a subsidiary brush member, a right bracket member, and a right link of the subsidiary brush unit of the nozzle assembly of  FIG. 1  when a subsidiary brush member of the subsidiary brush unit is folded, the subsidiary brush member being schematically illustrated, so that a guide member and a second hinge axis is shown; 
         FIG. 9  is a side elevation view exemplifying the nozzle assembly of  FIG. 1  when the subsidiary brush member is folded; 
         FIG. 10  is a view exemplifying only the subsidiary brush member, the right bracket member, and the right link of the subsidiary brush unit of the nozzle assembly of  FIG. 1  when the subsidiary brush member is unfolded; 
         FIG. 11  is a side elevation view exemplifying the nozzle assembly of  FIG. 1  when the subsidiary brush member is unfolded; 
         FIG. 12  is a perspective view exemplifying a nozzle assembly of a vacuum cleaner according to a second exemplary embodiment of the present disclosure; 
         FIG. 13  is a perspective view exemplifying the nozzle assembly illustrated in  FIG. 12  from which an upper casing of a subsidiary brush unit are removed; 
         FIG. 14  is a side elevation view exemplifying a cleaning state, that is, an use state, of the subsidiary brush unit of the nozzle assembly illustrated in  FIG. 12  where it comes in contact with a surface to be cleaned; 
         FIG. 15  is a schematic cross-sectional view exemplifying an operation of left and right bracket parts of the nozzle assembly when the subsidiary brush unit of the nozzle assembly is positioned in the state illustrated in  FIG. 14 ; 
         FIG. 16  is a schematic cross-sectional view exemplifying the left and the right bracket parts when the subsidiary brush unit is rotated at an angle of approximately 45° from the use state illustrated in  FIG. 14 ; 
         FIG. 17  is a side elevation view exemplifying a non-cleaning state, that is, a non-use state of the subsidiary brush unit of the nozzle assembly illustrated in  FIG. 12  where it is rotated to form an angle of approximately 90° to the surface to be cleaned; 
         FIG. 18  is a schematic cross-sectional view exemplifying an operation of the left and the right bracket parts of the nozzle assembly when the subsidiary brush unit of the nozzle assembly is positioned in the state illustrated in  FIG. 17 . 
         FIG. 19  is a perspective view exemplifying a nozzle assembly of a vacuum cleaner according to a third exemplary embodiment of the present disclosure; 
         FIG. 20  is a perspective view of the nozzle assembly taken along line XX-XX of  FIG. 19 ; 
         FIG. 21  is a cross-sectional view of the nozzle assembly taken along line XXI-XXI of  FIG. 19 ; 
         FIG. 22  is a perspective view of the nozzle assembly of  FIG. 19  in which a subsidiary brush unit is rotated and positioned over a drum brush casing (a non-use state); 
         FIG. 23  is a perspective view of the nozzle assembly of  FIG. 19  in which the subsidiary brush unit is separated and disassembled from the drum brush unit; 
         FIG. 24  is a perspective view exemplifying a nozzle assembly of a vacuum cleaner according to a fourth exemplary embodiment of the present disclosure; 
         FIG. 25  is a perspective view of the nozzle assembly of  FIG. 24  in which a subsidiary brush unit is rotated and positioned over a drum brush casing (a non-use state); 
         FIGS. 26A, 26B and 26C  are partial cross-sectional views exemplifying an operation of the nozzle assembly of  FIG. 24 ; 
         FIG. 27  is a perspective view exemplifying a undersurface of the nozzle assembly of  FIG. 24 ; 
         FIG. 28  is a perspective view exemplifying a undersurface of a subsidiary brush casing of the subsidiary brush unit of the nozzle assembly illustrated in  FIG. 27 ; 
         FIG. 29  is a perspective view exemplifying an upper surface of a subsidiary brush of the subsidiary brush unit of the nozzle assembly illustrated in  FIG. 27 ; 
         FIG. 30  is a partial cross-sectional view exemplifying a picker attached on a undersurface of the subsidiary brush illustrated in  FIG. 29 ; 
         FIG. 31  is a perspective view exemplifying a hinge bracket, which hingedly connects the subsidiary brush of  FIG. 27  to the subsidiary brush casing; 
         FIG. 32  is a perspective view of the hinge bracket illustrated in  FIG. 31 ; and 
         FIG. 33  is a perspective view exemplifying a hinge screw, which hingedly fixes a link member of the hinge bracket illustrated in  FIG. 32 . 
     
    
    
     Throughout the drawings, the same reference numerals will be understood to refer to the same elements, features, and structures. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a nozzle assembly of a vacuum cleaner according to exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawing figures. 
     First Embodiment 
     Referring to  FIGS. 1 through 3 , there is illustrated a nozzle assembly  1  according to a first exemplary embodiment of the present disclosure. The nozzle assembly  1  includes a nozzle assembly body  2 , a drum brush unit  5  and a subsidiary brush unit  10 . 
     The nozzle assembly body  2  includes a body casing  3 . The body casing  3  has an air passage (not illustrated), which is connected to a dust inlet  7  (see  FIG. 2 ) formed in the drum brush unit  5 . Accordingly, when a vacuum motor (not illustrated) mounted in a cleaner body (not illustrated) generates a suction force, dust or dirt along with air is drawn in through the dust inlet  7 , and flows into the cleaner body in the rear of the nozzle assembly body  2  via the air passage of the nozzle assembly body  2 . In addition, a turbine, which is rotated by the drawn-in air, or a driving motor (not illustrated), which drives a drum brush  28 , can be disposed in the body casing  3 . To easily move the nozzle assembly  1 , a pair of wheels  4  is installed in the rear of the body casing  3 . A lever  8  for tilting the cleaner body connected to a rear side of the nozzle assembly  1  is disposed on the body casing in the vicinity of one of the pair of wheels  4 . In  FIG. 1 , a reference numeral  9  is a height adjusting knob. Since constructions of the lever and the height adjusting knob  9  are the same as those of the conventional ones, detailed descriptions thereof will be omitted. 
     The drum brush unit  5  includes a drum brush casing  26 , and a drum brush  28 . 
     The drum brush casing  26  may be integrally formed with or separately from the body casing  3 , and has the drum brush  28  disposed therein. The dust inlet  7  is formed in an undersurface of the drum brush casing  26  to draw in the dust or dirt and the air. To prevent a patch of quilt or cloth among the air laden with the dust or dirt drawn in through the dust inlet  7  from flowing into the cleaner body, a plurality of ribs  6  are formed to cross the dust inlet  7 . 
     The drum brush  28  strikes the surface to be cleaned in a tangential direction while coming in rotation contact with the surface to be cleaned and thus brushes away the dust or dirt adhered to the surface to be cleaned. For this, the drum brush  28  is rotatably disposed inside of the dust inlet  7  of the body casing  3 . The drum brush  28  may be connected to the turbine or the driving motor of the body casing  3  as described above and rotated thereby. 
     The subsidiary brush unit  10  is installed in front of the body casing  3 , so that it preliminary brushes away the dust or dirt adhered to the surface to be cleaned in front of the drum brush  28 . Preferably, but not necessarily, the subsidiary brush unit  10  is installed to pivotable in a certain angle to the body casing  3 . 
     Referring to  FIG. 3 , the subsidiary brush unit  10  includes a subsidiary brush member  11 , left and right bracket members  13  and  14 , and left and right links  15  and  16 . 
     The subsidiary brush member  11  scrapes against the surface to be cleaned, particularly, a carpet or the like, to separate the dust or dirt, particularly, hair or fur of a pet tangled thereto, and includes a subsidiary brush casing  11   a  and a subsidiary brush  30 . 
     The subsidiary brush casing  11   a  is formed to have an approximately rectangular cross section. The subsidiary brush casing  11   a  at an upper side thereof has a handle  12  (see  FIG. 1 ) installed to allow a user to apply a force to the subsidiary brush member  11  and thus to fold and unfold it. The subsidiary brush casing  11   a  can be formed in various shapes or materials according to the object of the use. The subsidiary brush casing  11   a  at both sides thereof has a pair of guide members  25  (see  FIG. 8 , only a right guide member illustrated), such as guide rollers. The pair of guide members  25  is inserted into left and right guide grooves  23  (only a right guide groove illustrated) formed on inner side surfaces  13   b  and  14   b  of the left and the right bracket member  13  and  14 , respectively, so that they guide folding and unfolding movements of the subsidiary brush member  11 . 
     The subsidiary brush  30  is joined to an undersurface of the subsidiary brush casing  11   a , and has a plurality of projections  30   a  formed on an undersurface thereof, so that it can scrape against the carpet or the like to separate the hair or fur tangled thereto. Each of the plurality of projections  30   a  is formed in a rectangular parallelepiped shape, and projected toward the surface to be cleaned from the subsidiary brush  30 . Alternatively, instead of the rectangular parallelepiped shape, each of the plurality of the projections can be formed in a cylinder shape  30   b  as illustrated in  FIG. 4 , or a sphere shape  30   c , which is configured, so that an end tip coming in contact with the surface to be cleaned is supported on a cylinder projected from the subsidiary brush  30  and rounded to have a diameter larger than that of the cylinder, as illustrated in  FIG. 5 . Also, in the exemplary embodiment of the present disclosure, the subsidiary brush  30  and the projections  30   a  are formed of a rubber having elasticity. The subsidiary brush  30  is detachably joined to the undersurface of the subsidiary brush casing  11   a . Accordingly, in maintenance, since only the subsidiary brush  30  stained with the dust or dirt after use can be separated from the subsidiary brush casing  11   a  and cleaned, it is easy to maintain and repair the subsidiary brush  30 . 
     The left and the right bracket members  13  and  14  are fixed to both sides of the front of the body casing  3 , and supports the subsidiary brush member  11  to pivot in a certain angle about the nozzle assembly body  2 . Constructions of the left and the right bracket members  13  and  14  are the same. Referring to  FIGS. 2 and 3 , the left and the right bracket members  13  and  14  are connected to the left and the right fronts of the body casing  3 , respectively, so that they are symmetrically disposed to each other while interposing the subsidiary brush member  11  therebetween. Thus, since the left and the right bracket members  13  and  14  have the same construction, only the right bracket member  14  will be explained in detail below. 
     In the inner side surface  14   b  of the right bracket member  14  is formed the right guide groove  23 , which guides the pivot movement of the subsidiary brush member  11 . The guide member  25  installed on the subsidiary brush casing  11   a  is inserted in the right guide groove  23 . When the guide member  25  is positioned to a top  23   a  of the right guide groove  23 , the subsidiary brush member  11  is comes to a folded state, that is, a state where it is approximately perpendicular to the surface to be cleaned (see  FIG. 8 ). When the guide member  25  is positioned to a bottom  23   b  of the right guide groove  23 , the subsidiary brush member  11  is comes to an unfolded state, that is, a state where it is parallel to the surface to be cleaned (see  FIG. 10 ) 
     Also, on the right bracket member  14  is installed a rotation-prevention part to restrict a pivot movement of the right link  16 . The rotation-prevention part includes a stopper  14   a  and a hook  21 . 
     The stopper  14   a  restricts an angle where the right link  16  is pivoted upward, and is projected in a predetermined distance from the inner side surface  14   b  of the right bracket member  14 , so that the right link  16  is not exposed to the outside. 
     The hook  21  restrains the right link  16  from pivoting downward, and is formed on the inner side surface  14   b  of the right bracket member  14 , so that the right link  16  can climb up and cross over the hook  21  when the user applies the force to the subsidiary brush member  11 . As illustrated in  FIG. 6 , the hook  21  is formed in such a manner that a portion of the right bracket member  14  is cut and partially projected from the right bracket member  14 . If the user grasps the handle  12  formed on the subsidiary brush casing  11   a  and then raises it up, the right link  16  is rotated in a clockwise direction as illustrated in an arrow B in  FIG. 8  while coming in contact with the inner side surface  14   b  of the right bracket member  14 . When the right link  16  is rotated to some extent, it pushes down the hook  21  while climbing up an inclined portion  21   a  of the hook  21 , as illustrated in  FIG. 6 . As a result, as illustrated in a dotted line in  FIG. 6 , the portion of the right bracket member  14  to which the hook  21  is formed is bent, so that the right link  16  crosses over the hook  21 . After that, the right link  16  is blocked by the stopper  14   a  to stop moving, and the bent portion of the right bracket member  14  is returned to an original position by its own elastic force. 
       FIG. 7  illustrates another example of the hook. The hook  121  is inserted into and movably disposed in a penetrated hole  115  formed in the right bracket member  14 , and is connected with a supporting projection  114   c  formed in the right bracket member  14  by a spring  124 . That is, the spring  124  at one side thereof is supported around and fixed to the supporting projection  114   c , and at the other side thereof is fixed to the hook  121 . Accordingly, the spring  121  elastically urges the hook  121  in a direction where it is exposed out of the penetrated hole  115  formed in the right bracket member  14 . Thus, if the right link member  16  climbs up and crosses over the hook  121 , the hook  121  retreats into the right bracket member  14 , so that the spring  124  is compressed. After that, when the right link  16  passes by the hook  121 , the hook  121  is returned to an original position by an elastic force of the spring  124 . 
     Referring to  FIGS. 3 and 10 , an elastic member  22  is installed on a first hinge axis  19 , which connects the right link  16  with the right bracket member  14  (see  FIG. 10 ). The elastic member  22  presses the right link  16  in a counterclockwise direction (see an arrow A in  FIG. 10 ). Accordingly, if the right link  16  is positioned between the stopper  14   a  and the hook  21 , the right link  16  are to rotate in the counterclockwise direction by the elastic member  22 , but cannot be rotated in a reverse direction (a direction of the arrow A in  FIG. 10 ) only by its own weight because it is hanged on a vertical portion  21   b  of the hook  21 . Here, as the elastic member  22 , a coil spring, a torsion spring, or the like may be used. 
     The left and the right links  15  and  16 , which connect the subsidiary brush member  11  and the left and the right bracket members  13  and  14 , respectively, are installed, so that both ends thereof are hinged to the subsidiary brush member  11  and the left and the right bracket members  13  and  14 , respectively. That is, the right link  16  at one end thereof is rotatably assembled to the first hinge axis  19  installed on a lower end of the right bracket member  14  toward the nozzle assembly body  2 , and at the other end thereof is rotatably assembled to the second hinge axis  20  installed in the vicinity of the guide member  25  (see  FIG. 8 ). Also, the right link  16  is formed, so that when the user pushes down the handle  12  with her or his hand or foot, it can climbs up and cross over the hooks  21 . The left link  15  has the same construction as that of the right link  16 . 
     Hereinafter, an operation of the nozzle assembly  1  according to the first exemplary embodiment of the present disclosure constructed as described above will now be described in detail with reference to  FIGS. 3, and 8 through 11 . 
     If the user wants to clean a carpet, she or he pushes down the handle  12  (see  FIG. 1 ) installed on the subsidiary brush member  11  with her or his hand or foot. Then, the left and the right links  15  and  16  are rotated in a counterclockwise direction (see the arrow A) about the first hinge axis  19 , as illustrated in  FIG. 10 . In this manner, with a pressing force of the user to the handle  12 , the left and the right links  15  and  16  cross over the vertical portions  21   b  of the hooks  21  and move. As the left and the right links  15  and  16  are rotated downward as described above, the subsidiary brush member  11  is unfolded, as illustrated in  FIGS. 10 and 11 . Thus, after the left and the right links  15  and  16  cross over the hooks  21 , they are rotated in the counterclockwise direction by their own weights and an elastic force of the elastic member  22  pressing them, even though the user does not additionally apply a force to the handle. At the same time, when the guide members  25  installed on both sides of the subsidiary brush member  11  are moved down along the left and the right guide grooves  23  formed on the left and the right bracket members  13  and  14  and then positioned to the bottoms  23   b  of the left and the right guide grooves  23 , the subsidiary brush member  11  comes to a completely unfolded state as illustrated in  FIGS. 10 and 11 . That is, the subsidiary brush member  11  comes to a state where it is approximately parallel to the surface to be cleaned, that is, the carpet, by the left and the right link members  15  and  16  and the left and the right guide grooves  23  guiding the guide members  25 . Also, since the elastic member  22  presses the left and the right links  15  and  16 , the subsidiary brush member  11  is maintained in a state where it press the carpet in a certain force, and a friction force between a bottom of the subsidiary brush member  11  and the carpet is uniformly maintained. 
     In this state, if the user moves the nozzle assembly  1 , the subsidiary brush  30  mounted below the subsidiary brush casing  11   a  scrapes against the carpet while contacting the carpet in a certain pressure, and thus separates a dust or dirt, such as hair, fur of a pet, or the like, tangled to the carpet therefrom. Then, the separated dust or dirt is drawn into the cleaner body through the dust inlet  7  of the body casing  3 . 
     In case that a cleaning operation of the carpet is completed or there is no need to use the subsidiary brush member  11 , the subsidiary brush member  11  is maintained in a folded state. If the user wants to fold the subsidiary brush member  11 , she or he pushes up the handle (see  FIG. 1 ) with her or his hand or foot. Then, the left and the right link members  15  and  16  are moved in a clockwise direction as illustrated in an arrow B in  FIG. 8  about the first hinge axis  19 , and the guide members  25  are moved in the clockwise direction along the left and the right guide grooves  23 . As a result, the subsidiary brush member  11  begins to fold. When the left and the right links  15  and  16  are continuously moved in the clockwise direction to cross over the hooks  21 , the subsidiary brush member  11  comes to a completely folded state. That is, after the left and the right links  15  and  16  climb up and cross over the hooks  21 , the subsidiary brush member  11  comes to a state where it is approximately perpendicular to the surface to be cleaned, that is, the carpet, and the guide members  25  are positioned to the tops  23   a  of the left and the right guide grooves  23 . Under this state, the nozzle assembly  1  according to the first exemplary embodiment of the present disclosure removes the dust or dirt by using only the drum brush  28  like the general nozzle assembly. 
     Second Embodiment 
       FIG. 12  is a perspective view exemplifying a nozzle assembly  1 ′ of a vacuum cleaner according to a second exemplary embodiment of the present disclosure, and  FIG. 13  is a perspective view exemplifying the nozzle assembly  1 ′ illustrated in  FIG. 12  from which an upper casing  132  of a subsidiary brush unit  110  are removed and in which left and right bracket parts  180  are partially cut away, so that a lower casing  140  and a frame member  150  are shown in detail. 
     Referring to  FIGS. 12 and 13 , the nozzle assembly  1 ′ according to the second exemplary embodiment of the present disclosure includes a nozzle assembly body  2 , a drum brush unit  5 , left and right bracket parts  80 , cam members  170 , first elastic members  172 , and a subsidiary brush unit  110 . Here, since constructions of the nozzle assembly body  2  and the drum brush unit  5  are the same as those of the nozzle assembly  1  of the first embodiment, detailed descriptions thereof will be omitted. 
     The left and right bracket parts  180  are projected forward in front of both sides of the drum brush casing  26 , respectively, and supports the subsidiary brush unit  110 . The left and right bracket parts  180  are integrally formed with the drum brush casing  26 . However, alternatively, the left and right bracket parts  180  can be separately formed from the drum brush casing  26 . Referring to  FIGS. 13 and 15 , elongated holes  182  in which both ends of a frame axis  154  of the subsidiary brush unit  110  are inserted, respectively, are formed in the left and right brackets parts  180 , respectively. The elongated holes  182  are elongatedly formed in an up-and-down direction, and a first elastic member  172  and a cam member  170  are installed in each of the elongated holes  182 . The first elastic members  172  are fixed to ends of inner walls of the elongated holes  182  to press the cam members  170 , respectively. Referring to  FIG. 15 , upper and lower guide grooves  187  and  189  are formed in intervals of 180° in each of the inner walls of the elongated holes  182 . In the upper and lower guide grooves  187  and  189  are mounted an upper key  185  and an upper coil spring  197 , and a lower key  186  and a lower coil spring  199 , respectively. The upper and the lower coil spring  197  and  199  press the upper and the lower keys  185  and  186  into the corresponding elongated hole  182 . Accordingly, when the cam members  170  are moved upward, the upper keys  185  are further inserted into the upper guide grooves  187  by the cam members  170  to compress the upper coil springs  197 , and the lower keys  186  are further protruded out of the lower guide grooves  189  by pressing forces of the lower coil springs  199 . To the contrary, when the cam members  170  are moved downward, the upper keys  185  are further protruded out of the upper guide grooves  187  by their own eights and pressing forces of the upper coil springs  197 , and the lower keys  186  are further inserted into the lower guide grooves  189  by pressing forces of the cam members  170  to compress the lower coil springs  199 . 
     Referring to  FIGS. 13 and 15 , each of the cam members  170  is formed in a cylindrical shape, one side of which is flat and the other side of which has furrows P 1 , threads P 2 , and inclined portions S connecting the furrows P 1  and the threads P 2  formed in a circumferential direction thereof like one side of each of uneven parts  158  of the frame axis  154 . The one side of the cam member  170  comes in contact with the corresponding first elastic member  172 , and the other side of the cam member  170  engages with the corresponding uneven part  158  of the frame axis  154 . Two key grooves  174  are formed in a longitudinal direction in intervals of 180° on an outer circumferential surface of each of the cam members  170 , so that the upper and the lower keys  185  and  186  are inserted therein, respectively. Accordingly, even though the uneven parts  158  are rotated, the keys  185  and  186  and the key grooves  174  are engaged with each other to restrain rotations of the cam members  170 . As a result, the cam members  170  are not rotated, but moved in a horizontal direction as the inclined portions S of the cam members  170  and the uneven parts  158  are slid to each other. 
     The drum brush  28  is disposed in the vicinity of the dust inlet  7  in the drum brush casing  26  (see  FIG. 12 ). Accordingly, when the drum brush  28  is rotated, a blade or a brush member, which is formed on an outer circumferential surface of the drum brush  28 , scrapes against a surface to be cleaned. 
     Referring to  FIG. 12 , the subsidiary brush unit  110  is installed to connect with the left and right bracket parts  180 . That is, the subsidiary brush unit  110  is rotatably and detachably mounted to the drum brush casing  26  in front thereof, so that it preliminarily brushes away dust or dirt from the surface to be cleaned in front of the drum brush  28 . Referring to  FIGS. 12 and 13 , the subsidiary brush unit  110  includes an upper casing  132 , a lower casing  140 , a frame member  150 , a subsidiary brush  190 , and second elastic members  144 . 
     The upper casing  132  and the lower casing  140  are joined with each other while interposing the frame member  150  therebetween to wrap the frame axis  154  of the frame member  150 . Accordingly, the upper casing  132  and the lower casing  140  are rotated and moved along with the frame axis  154  (see  FIGS. 13 and 15 ). Referring to  FIG. 12 , a handle  112  is disposed in front of an upper surface of the upper casing  132 . Referring to  FIG. 13 , three bosses  142  are formed in the lower casing  140 , and the second elastic members  144  are mounted in the bosses  142 . 
     Referring to  FIGS. 13 and 15 , the frame member  150  includes a frame body  152 , frame keys  151 , a frame axis  154 , and uneven parts  158 . As illustrated in  FIG. 13 , the frame body  152  forms a middle portion of the frame member  150  to which the frame axis  154  and the frame keys  151  are integrally connected. The frame keys  151  are configured, so that three frame keys are formed in a cylindrical shape and projected downward from an undersurface of the frame body  152 . The frame keys  151  are inserted into the bosses  142  of the lower casing  140 , so that they compresses the second elastic members  144  mounted in the bosses  142 . Accordingly, weights of the frame member  150  and the upper casing  132  are elastically transmitted to the lower casing  140 , and thus the subsidiary brush  190  disposed on an undersurface of the lower casing  140  scrapes off the dust or dirt adhered to the surface to be cleaned while pressing the surface to be cleaned in a certain pressure. The frame axis  154  is projected from both sides of the frame body  152 , and the uneven parts  158  are formed on both ends of the frame axis  154 , respectively. The uneven parts  158  are inserted into the elongated holes  182  of the left and right bracket parts  180 , so that they can rotate while engaging with the cam members  170  and move in the elongated holes  182 , respectively. 
     The subsidiary brush  190  is formed of a rubber material, and detachably mounted on the undersurface of the lower casing  140 . Referring to  FIG. 13 , the subsidiary brush  190  is made up of a plurality of projections  193 . 
     Hereinafter, an operation of the nozzle assembly  1 ′ according to the second exemplary embodiment of the present disclosure constructed as described above will now be explained with reference to  FIGS. 14 through 18 . 
       FIGS. 14 and 15  illustrate a use state of the subsidiary brush unit  110  where it comes in contact with the surface to be cleaned. When the subsidiary brush  190  of the subsidiary brush unit  110  comes in close contact with the surface to be cleaned to clean the surface to be cleaned, as illustrated in  FIG. 14 , it scrapes against the surface to be cleaned while pressing the surface to be cleaned in a certain pressure by weights of the frame member  150  and the upper casing  132  disposed above the subsidiary brush  190 . Dust or dirt, such as hair or the like, adhered to the surface to be cleaned are preliminarily scraped off by the subsidiary brush unit  110  in front of the drum brush  28  (see  FIG. 12 ), again scattered by the drum brush  28  mounted in the drum brush casing  26 , and then drawn in through the dust inlet  7 . In this manner, the frame axis  154  and the cam members  170  inserted into the elongated holes  182  are inclined to bottom surface  183  of the inner walls of the elongated holes  182 . In addition, the upper keys  851  mounted in the upper guide grooves  187  are protruded out thereof by the upper coil springs  197 , and the lower keys  186  are further inserted inside of the lower guide grooves  189  due to weights of the cam members  170  to compress the lower coil spring  199 . Also, the first elastic members  172  are relaxed, and the uneven parts  158  and the cam members  170  are secured to each other in a state where the furrows P 1  and the threads P 2  thereof are engaged with each other. Since the cam members  170  cannot be rotated, the frame axis  154  is not rotated as so far as an external force is not applied thereto. Accordingly, the subsidiary brush unit  110  is not rotated, but maintained in the state where it comes in contact with the surface to be cleaned. Here, a length L represents a diameter o the elongated holes  182 . 
     If a user grasps the handle  112  of the upper casing  132  and then rotates the subsidiary brush unit  110  by an angle of 45° in a direction of arrow C in  FIG. 14 , the frame axis  154  and the uneven parts  158  are rotated in the same direction. However, since the upper and the lower keys  185  and  186  restrains the cam members  170  from being rotated, the inclined portions S of the cam members  170  and the uneven parts  158  are slid to each other, and thus the furrows P 1  and the threads P 2  thereof are in contact with each other, as illustrated in  FIG. 16 . As a result, the cam members  170  moves by a height of the threads P 2  of the uneven parts  158  in a direction of arrow A′ in  FIG. 16  while compressing the first elastic members  172 . Since the upper casing  132  and the frame member  150  pressing the lower casing  140  also incline in an angle of approximately 45°, the frame member  150  is lifted a little in the elongated holes  182  by pressing forces of the second elastic members  144  mounted in the bosses  142  (see  FIG. 13 ), which presses the frame keys  151 . The cam members  170 , which are engaged with the frame member  150 , are also lifted in the same height. 
     If the subsidiary brush unit  110  is further rotated to reach a vertical state, as illustrated in  FIG. 17 , the cam members  170  are moved in a direction of arrow B′ by the first elastic members  172 , and thus the cam members  170  and the uneven parts  158  are secured to each other in the elongated holes  182 , as illustrated in  FIG. 18 . Since the furrows P 1  of the cam members  170  and the threads P 2  of the uneven parts  158  are engaged with each other and the cam members  170  are not rotated by the upper and the lower keys  185  and  186 , the uneven parts  158 , which are engaged with the cam members  170 , are also not rotated as so far as an external force is not applied thereto. As the subsidiary brush unit  110  almost reaches the vertical state, the weights applied to the lower casing  140  by the upper casing  132  and the frame member  150  are removed. As a result, the cam members  170  and the uneven parts  158  come in close contact with top surfaces  181  of the inner walls of the elongated holes  182  by the first elastic members  144  mounted in the bosses  142  of the lower casing  140 . 
     Third Embodiment 
       FIGS. 19 through 23  are views exemplifying a nozzle assembly  1 ″ of a vacuum cleaner according to a third exemplary embodiment of the present disclosure. 
     Referring to  FIG. 19 , the nozzle assembly  1 ″ of the third exemplary embodiment includes a nozzle assembly body  2 , a drum brush unit  5 , left and right brackets  240 , a locking unit  260 , and a subsidiary brush unit  210 . Here, since constructions of the nozzle assembly body  2  and the drum brush unit  5  are the same as those of the nozzle assemblies  1  and  1 ′ of the first and the second exemplary embodiments, detailed description thereof will be omitted. 
     The drum brush casing  26  has two sliding rails  226  (see  FIG. 23 ) disposed on both sides in front thereof, and a mounting space  221  (see  FIG. 20 ) disposed in the middle in front thereof. In the sliding rails  226  are mounted the left and right brackets  240 , respectively, and in the mounting space  221  is installed a locking member  260 . As illustrated in  FIG. 21 , the sliding rails  226  are inserted into sliding grooves  244  of the left and right brackets  240 , so that they are connected with the left and right brackets  240 . That is, when the sliding rails  226  are inserted into the sliding grooves  244  of the left and right brackets  240  and moved in a longitudinal direction of the sliding rails  226 , the left and right brackets  240  are mounted on the drum brush casing  26 . Under this state, when the sliding rails  226  are moved in a direction opposite to the mounting direction, the left and right brackets  240  are separated from the drum brush casing  26 . Accordingly, it is easy to mount the left and right brackets  240  on the drum brush casing  26  or separate the left and right brackets  240  from the drum brush casing  26 . Alternatively, after the left and right brackets  240  is mounted on the drum brush casing  26  though the sliding rails  226  and the sliding grooves  244 , they can be fixed to the drum brush casing  26  with screws (not illustrated) or hook members (not illustrated). In this case, if a fastening by the screws or a locking by the hook members is released, the left and right brackets  240  can be removed from the drum brush casing  26 , thereby allowing the subsidiary unit  210  to repair or replace. 
     Referring to  FIGS. 21 and 23 , each of the left and right brackets  240  is provided with a mounting groove  241 , a sliding groove  244  and a spring  242 . As described above, the left and right brackets  240  are mounted on the drum brush casing  26 , and two cover arms  278  of the subsidiary brush casing  232  are coupled to the left and right brackets  240 , respectively. The mounting groove  241  is formed in a longitudinal direction from one side of each of the left and right brackets  240 . In the mounting groove  241  is disposed the spring  242 . Also, in the mounting groove  241  is inserted and disposed a cover axis  284  of the subsidiary brush casing  232 . 
     The sliding groove  244  is formed in a longitudinal direction on upper and lower sides of each of the left and right brackets  240 , and the sliding rail  226  is inserted in the sliding groove  244 . The spring  242  is installed in the mounting groove  241  of each bracket  240  into which the cover axis  284  of the subsidiary brush casing  232  is inserted. That is, the spring  242  at one side thereof is fixed to each bracket  240  and at the other side thereof is fixed to the cover arm  278 . The spring  242  elastically urges the subsidiary brush casing  232  in an upward direction, that is, in a direction of rotating it to an upper end of the drum brush casing  26 , as illustrated in  FIG. 22 . 
     Referring to  FIGS. 19 and 20 , the locking unit  260  is disposed in the mounting space  221  of the subsidiary brush casing  232 , and includes a hook member  262  and a spring  264 . To move in upward and downward directions, the hook member  262  has an outwardly projected protrusion, that is, a button  266 , at an upper part thereof and a retaining part  263  at a lower part thereof. The retaining part  263  is engaged with a locking part  282  of the subsidiary brush casing  232 . The spring  264  is disposed in a lower part of the mounting space  221 , and urges the hook member  262  in an upward direction. 
     Referring to  FIGS. 19 through 21 , the subsidiary brush unit  210  includes a subsidiary brush casing  232 , a panel  274 , and a subsidiary brush  276 . 
     The subsidiary brush casing  232  has two cover arm  278  inclinedly projected upward from both sides of an upper surface thereof, and the cover arms  278  have cover axes  284  (seen  FIG. 23 ) integrally formed with and horizontally projected from one end thereof. The cover arms  278  are elastically urged in the upward direction by the springs  242  installed in the left and right brackets  240 , respectively. Referring to  FIGS. 20 and 21 , the subsidiary brush casing  232  has a plurality of keys  290  projected downward from an undersurface thereof. 
     Referring to  FIGS. 19 through 21 , the panel  274  is joined to a lower end of the subsidiary brush casing  232 , so that it is elastically movable up and down and rotatable. The panel  274  at an upper surface thereof has a plurality of bosses  292 , each of in that a spring  294  is installed. The plurality of keys  290  of the subsidiary brush casing  232  is inserted in the bosses  292 , and is urged in an upward direction by the springs  294  in the bosses  292 , respectively. Also, as illustrated in  FIG. 19 , panel axes  286  of the panel  274  are inserted in elongated holes  280  in both side surfaces of the subsidiary brush casing  232 , so that the panel  274  can be rotated with respect to the subsidiary brush casing  232 . Accordingly, even though a surface to be cleaned is crooked or irregular, the panel  274  presses the surface to be cleaned in a certain pressure while being elastically moved up and down and rotated. In the middle of the upper surface of the subsidiary brush casing  232  is formed the locking part  282 . The locking part  282  is locked to the retaining part  263  of the hook member  262 . 
     Referring to  FIGS. 20 and 21 , the subsidiary brush  276  is formed of a rubber material to have elasticity, and has a plurality of protrusions  288  projected downward from an undersurface thereof. Each of the protrusions  288  may be configured to have various shapes, such as a cylinder, an oval with a rounded tip, etc. The protrusions  288  scrapes against hair or fur of a pet adhered to the surface to be cleaned to separate it therefrom and thus to fly it in all directions. The subsidiary brush  276  is fixed to an undersurface of the panel  274 , but since the panel  274  is configured to be movable up and down and rotatable with respect the subsidiary brush casing  232 , the subsidiary brush  276  can be movable up and down and rotatable with respect the subsidiary brush casing  232 . 
     Hereinafter, an operation of the nozzle assembly  1 ″ of the vacuum cleaner according to the third embodiment of the present disclosure will be explained in detailed with reference to  FIGS. 19 through 23 . 
     If a user wants to use the subsidiary brush unit  210  to clean a portion of a quilt or carpet to that the dirt, such as the hair or the fur of the pet, is adhered, she or he pushes down the subsidiary brush unit  210  against an elastic force of the springs  242  with her or his hand or foot to allow the subsidiary brush unit  210  to come in contact with the surface to be cleaned, as illustrated in  FIG. 19 , the locking part  282  of the subsidiary brush casing  232  is locked to the retaining part  263  of the hook member  262 . As a result, the subsidiary brush unit  210  is fixed in a use position to the drum brush unit  5  by the locking unit  260 . In this manner, the user moves the nozzle assembly  1 ″ onward, so that the protrusions  288  of the subsidiary brush  276  comes in contact with the surface to be cleaned, that is, the carpet, to scrape against the dirt, such as the hair or the fur, tangled to the carpet and thus to preliminarily separate the dirt therefrom, and the drum brush  28  strikes the carpet again to fly the dirt in all directions and thus to draw in it through the dirt inlet  7 . Since the bosses  292  of the panel  274  and the keys  290  of the subsidiary brush casing  232  are elastically coupled with each other and the panel axes  286  are movably and rotatably connected in the elongated holes  280  of the subsidiary brush casing  232 , the panel  274  scrapes against the carpet while elastically moving up and down and rotating with respect to subsidiary casing  232  and thus coming in well contact with the carpet. 
     If the user does not temporarily want to use the subsidiary brush unit  210 , she or he pushes the button  266  of the hook member  262  in a downward direction, and thus releases the locking connection between the locking part  282  of the subsidiary brush casing  232  and the retaining part  263  of the hook member  262 . The subsidiary brush unit  210  separated from the drum brush unit  5  is moved to an upper part of the drum brush casing  26  by a pressing force of the springs  242  installed in the left and right brackets  240 , as illustrated in  FIG. 22  (non-use position). If the user does not push again the subsidiary brush unit  210  in the downward direction, the subsidiary brush unit  210  is maintained in the non-use position illustrated in  FIG. 22  by the pressing force of the springs  242  installed in the left and right brackets  240 . 
     If the subsidiary brush unit  210  is not to be used for a long time, or is to be maintained or repaired, the user moves the left and right brackets  240  in a horizontal direction to the sliding rails  266  to disassemble the subsidiary brush unit  210  from the drum brush unit  5 . The separated subsidiary brush unit  210  is separately kept, and only the drum brush  28  is used in cleaning. To assemble the subsidiary brush unit  210  to the drum brush casing  26  again, the user inserts the sliding rails  226  into the sliding grooves  244  of the left and right brackets  240  and then moves the subsidiary brush unit  210  in a direction reverse to the disassembling direction. 
     Fourth Embodiment 
       FIGS. 24 through 33  shows a nozzle assembly  1 ′ of a vacuum cleaner according to a fourth embodiment of the present disclosure. 
     Referring to  FIG. 24 , the nozzle assembly  1 ′ of the fourth embodiment includes a nozzle assembly body  2 , a drum brush unit  5 , left and right brackets  240 , a locking unit  260 , and a subsidiary brush unit  310 . Since a construction of the nozzle assembly  1 ′ of the fourth embodiment except the subsidiary brush unit  310  is the same as that of the nozzle assembly  1 ″ of the third embodiment, a detailed description thereof will be omitted. 
     Referring to  FIGS. 24 and 25 , the subsidiary brush unit  310  includes a subsidiary brush casing  372 , a panel  374 , and a subsidiary brush  376 . 
     The subsidiary brush casing  372  has two cover arm  278  inclinedly projected upward from both sides of an upper surface thereof, and rotatably installed in the left and right bracket  240 . The cover arms  278  are elastically urged in an upward direction by springs installed in the left and right brackets  240 , respectively. Also, as illustrated in  FIG. 28 , the subsidiary brush casing  372  has two fixing bosses  373  formed on both sides of an undersurface thereof to fix first and second hinge brackets  380  (one shown in  FIGS. 26A through 26C and 31 ) to be described later. 
     As illustrated in  FIGS. 26A through 26C , the panel  374  is configured to be movable back and forth and in a horizontal direction with respect to the subsidiary brush casing  372 . For this, first and second hinge brackets  380  are disposed between both side ends of the panel  374  and the subsidiary brush casing  372  to hingedly fix the panel  374  to the subsidiary brush casing  372 . Referring to  FIGS. 31 and 32 , each of the first and second hinge brackets  380  is formed of a body  381  and a link member  385 . The body  381  at the middle thereof has a penetrated hole  384  into which a screw  383  is inserted. The screw  383  is fixed to the corresponding fixing boss  373  of the subsidiary brush casing  372 . In addition, the body  381  has two screw holes (not illustrated) formed in a direction perpendicular to the penetrated hole  384  at both sides of the penetrated hole  384 . In the screw holes are fixed screw portions  388   b  of hinge screws  388  to be described later, respectively. The link member  385  is formed of two link  386 , each of which has two hinge holes  387  formed at both ends thereof and hinged by two hinge screws  388 . As illustrated in  FIG. 33 , each of the hinge screws  388  has a raised portion  388   a  rotatably supported in one of the hinge holes  387  of the link  386 , and a screw portion  388   b  screwed to one of screw holes  375  (see  FIG. 29 ) of the panel  374  or one of the screw holes of the body  381 . As illustrated in  FIG. 29 , the screw holes  375  of the panel  374  are formed at both ends of the panel  374 . Accordingly, as illustrated  FIGS. 26A through 26C , when the nozzle assembly body  2  of the nozzle assembly  1 ′″ is moved back and forth by a user, each of the links  386  of the link member  385  of the first and the second hinge brackets  380  at both ends thereof is pivoted to the body  381  and the panel  374 , and thus the panel  374  and the subsidiary brush  376  fixed thereto can be moved back and forth and in the horizontal direction. 
     The subsidiary brush  376  is made up of a picker  377  adhered on an undersurface of the panel  374 . The picker  377  may be formed of a wool, cloth, or fabric with shag. As illustrated in  FIG. 30 , the picker  377  is preferably formed, so that a shag portion  378  thereof has a texture inclined in one direction, for example, a direction toward the drum brush unit  5  to scrape off dust or dirt toward the drum brush unit  5  when the nozzle assembly body  2  of the nozzle assembly  1 ′ is pulled in a direction arrow A″ as illustrated in  FIG. 26A . 
     In this case, to exactly set the texture of the shag portion  378  in fabrication, a first positioning part  390  is disposed between the panel  374  and the picker  377  to position the picker  377  to panel  374  (see  FIG. 27 ), and a second positioning part  395  is disposed between the subsidiary brush casing  372  and the panel  374  to position the panel  374  to the subsidiary brush casing  372  (see  FIGS. 28 and 29 ). As illustrated in  FIG. 27 , the first positioning part  390  is preferably formed of a projection  392  and a projection-accommodating groove  391 . The projection  392  is formed on a side of the undersurface of the panel  374 , and the projection-accommodating groove  391  is formed in the picker  377  to accommodate the projection  392 . As illustrated in  FIGS. 28 and 29 , the second positioning part  395  is preferably formed of two ribs  396  and two rib-accommodating spaces  397 . The two ribs  396  are formed on a undersurface of the subsidiary brush casing  372 , so that they are apart from the center of the subsidiary brush casing  372  in different distances, and the two rib-accommodating spaces  397  are formed on an upper surface of the panel  374  to correspond to the ribs  396  and to accommodate the ribs  396 . 
     Accordingly, in fabrication, if while the projection  392  of the panel  374  is aligned with and inserted into the protrusion-accommodating grooves  391 , the picker  377  is attached to the undersurface of the panel  374  and while the ribs  396  of the subsidiary brush casing  372  are aligned with and inserted into the rib-accommodating spaces  397 , the panel  374  is attached to the subsidiary brush casing  372 , the picker  377 , the panel  374  and the subsidiary brush casing  372  are assembled, so that the shag portion  378  of the picker  377  has the texture inclined the direction toward the drum brush unit  5 . 
     An operation of the nozzle assembly  1 ′ of the vacuum cleaner according to the fourth embodiment constructed as described above is the same as that of the nozzle assembly  1 ″ of the third embodiment explained with reference to  FIGS. 19 through 23 , except that when the nozzle assembly body  2  of the nozzle assembly  1 ′ is pulled in the direction of arrow A″ as illustrated in  FIG. 26A , the picker  377  scrapes against the dust or dirt to move and scatter it toward the drum brush unit  5  (that is, the direction of arrow A″), and when the nozzle assembly body  2  of the nozzle assembly  1 ′ is pushed in a direction of arrow B″ as illustrated in  FIG. 26C , the picker  377  does not push the dust or dirt out of the nozzle assembly body  2  (that is, the direction of arrow B″). Accordingly, the operation of the nozzle assembly  1 ′ of the fourth embodiment will not be explained. 
     As apparent from the foregoing description, according to the exemplary embodiments of the present disclosure, the nozzle assembly of the vacuum cleaner has the subsidiary brush unit disposed in front of the drum brush unit. Accordingly, the subsidiary brush unit preliminarily scrapes off the dust or dirt, particularly, the hair or the fur of the pet, which is not separate from the surface to be cleaned well, and the drum brush unit secondly brushes away and scatters the scraped dust or dirt to be drawn into the nozzle assembly, thereby improving cleaning efficiency for the dust or dirt, such as the hair or the fur of the pet. 
     Further, the nozzle assembly of the vacuum cleaner according to the exemplary embodiments of the present disclosure is configured, so that the subsidiary brush unit is pivotably disposed to the nozzle assembly body or the drum brush unit, thereby allowing the subsidiary brush to selectively come in contact or non-contact with the surface to be cleaned, such as the carpet or the like, according to whether there is need to use it. Accordingly, the nozzle assembly according to the exemplary embodiments of the present disclosure can extend a lifespan of the subsidiary brush. In addition, alternatively, the subsidiary brush unit can be rotated in the non-use position and then maintained in the rotated state only by pushing the button, thereby allowing the nozzle assembly to easily use. 
     Furthermore, the nozzle assembly of the vacuum cleaner according to the exemplary embodiments of the present disclosure is configured, so that the subsidiary brush unit can be assembled with or disassembled from the drum brush casing by engaging the brackets with or separating from the sliding rails. Accordingly, it is easy to mount and dismount the subsidiary brush unit on or from the drum brush casing. 
     Moreover, the nozzle assembly of the vacuum cleaner according to the exemplary embodiments of the present disclosure is configured, so that the subsidiary brush is elastically movable up and down and rotatable, or movable in the horizontal direction to the subsidiary brush casing. Accordingly, when the subsidiary brush is in the use state where it comes in contact with the surface to be cleaned, it always scrapes against the surface to be cleaned in the state, which presses the surface to be cleaned in the certain pressure, thereby allowing the subsidiary brush to always scrape against the surface to be cleaned in a proper contact area even though the surface to be cleaned is crooked or irregular and thus improving the cleaning efficiency for the dirt, such as the hair or the fur of the pet. 
     Also, if the subsidiary brush is formed of the picker having the texture inclined in one direction, that is, the direction toward the drum brush unit, it does not push out the dust or dirt when the nozzle assembly is pushed in the front direction, thereby preventing the dust or dirt from scattering and going into user&#39;s respiratory organs in cleaning. 
     In addition, if the subsidiary brush casing and the panel have the ribs and the rib-accommodating spaces, respectively, and the panel and the picker have the projection and the projection-accommodating groove, respectively, the subsidiary brush casing and the panel can be easily be assembled with the panel and the picker, respectively. 
     Although representative exemplary embodiments of the present disclosure have been shown and described in order to exemplify the principle of the present disclosure, the present disclosure is not limited to the specific embodiments. It will be understood that various modifications and changes can be made by one skilled in the art without departing from the spirit and scope of the disclosure as defined by the appended claims. Therefore, it shall be considered that such modifications, changes and equivalents thereof are all included within the scope of the present disclosure.