Patent Publication Number: US-8528290-B2

Title: Flooring article

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a National Stage Patent Application of PCT International Patent Application No. PCT/KR2010/001560 (filed on Mar. 12, 2010) under 35 U.S.C. §371, which claims priority to Korean Patent Application No. 10-2009-0027225 (filed on Mar. 31, 2009), which are all hereby incorporated by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to floorboard, and more particularly, to a flooring panel assembly having mechanical coupling elements, which is mounted to the floors of buildings, etc. 
     2. Description of the Related Art 
     In general, flooring panels are used to decorate the floors of buildings. Although flooring panels made of synthetic resins have conventionally been used, flooring panels made of wood are increasingly used in recent years to provide a more aesthetically pleasing appearance and excellent functions. 
     There is known a wood flooring panel, which is configured in such a manner that a fastening structure is provided at a long or short side of the flooring panel to ensure that opposite sides of neighboring flooring panels are assembled with each other, in order to assure easy assembly between flooring panels and consequently, enhanced construction efficiency. 
       FIG. 1  is a view illustrating an assembly relationship between two flooring panels of a conventional floorboard. 
     Specifically, as illustrated in  FIG. 1 , in the case of the conventional floorboard, a first flooring panel  1  and a second flooring panel  2  are assembled with each other as a tongue part  20  of the second flooring panel  2  is coupled with a recessed part  10  of the first flooring panel  1 . To this end, the tongue part  20  is first horizontally introduced into the recessed part  10  and then, is pivotally rotated downward by a predetermined angle about a pivot point A. 
     More particularly, the tongue part  20  is introduced into the recessed part  10  in a substantially horizontal direction until a tip protruding portion  21  of the tongue part  20  is fitted into a recess  11  of the recessed part  10  and at this time, the tongue part  20  comes into contact with the recessed part  10  at the pivot point A. 
     The tongue part  20  includes a retaining portion  22 , which protrudes downward by a predetermined length. Also, when the tongue part  20  is introduced into the recessed part  10 , an upper lip  15  of the recessed part  10  and a front surface portion  25  of the tongue part  20  come into contact with each other at a point. This contact point is the pivot point A. 
     If the tongue part  20  is rotated along an arc B designated by a dotted line in  FIG. 1  about the pivot point A, the retaining portion  22  of the tongue part  20  is fitted into and seated in a retaining recess  13  of the recessed part  10  to ensure coupling between the tongue part  20  and the recessed part  10 . 
     That is, the tongue part  20  is coupled with the recessed part  10  as it is pivotally rotated along the arc B about the pivot point A. 
     However, in the above described coupling manner, to prevent an inner wall  12   a  of a raised portion  12  provided at an end of the recessed part  10  from hindering rotation of an outer wall  22   a  of the retaining portion  22  when the outer wall  22   a  of the retaining portion  22  is pivotally rotated and inserted into the retaining recess  13  along the arc B, the inner wall  12   a  of the protrusion  12  must be configured such that an angle C between the inner wall  12   a  and a horizontal plane has a gentle gradient. 
     In other words, if the angle C has a steep gradient, the outer wall  22   a  of the retaining portion  22  may fail to pass the inner wall  12   a  of the raised portion  12 , thus making coupling of the tongue part  20  difficult and also, it is necessary to apply sufficient external force to interference-fit the retaining portion  22  of the tongue part  20  to the raised portion  12  of the recessed part  10  when the tongue part  20  is coupled with the recessed part  10 , which causes damage to the flooring panels and makes it difficult to assemble the flooring panels. 
     However, the gentle gradient angle C of the protrusion  12  problematically provides weak coupling force in a horizontal direction even if the tongue part  20  is coupled with the recessed part  10 . 
     In the case where the above described coupling structure is applied to a modern heating system using a heating element (e.g., an electric film or an electric panel) in a simplified construction manner, moreover, a constituent material of a floorboard (conventionally, plywood, Particle Board (PB), Medium Density Fiberboard (MDF), High Density Fiberboard (HDF), etc.) may be severely contracted or expanded due to rapid temperature increase generated when the heating system installed beneath the floorboard is turned on, thereby causing expansion of the recessed part  10 , and especially, causing the raised portion  12  to be severely deformed to a state designated by reference numeral  12 - 1  as illustrated in  FIG. 1 . This may cause the outer wall  22   a  of the retaining portion  22  to be separated from the inner wall  12   a  of the raised portion  12 , resulting in an unwanted separation of two flooring panels. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a floorboard in which neighboring flooring panels are assembled with each other using a new assembly method completely different from a conventional flooring panel assembly method, the floorboard providing simplified assembly of flooring panels without damage because it is unnecessary to apply external force to assemble the flooring panels and resulting in enhanced coupling force in a horizontal direction after assembly of the flooring panels. 
     In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a floorboard including a tongue part protruding from one side of a first flooring panel and a recessed part provided at one side of a second flooring panel for insertion and assembly of the tongue part, wherein the tongue part includes a tongue protrusion having a predetermined length, a tongue bottom portion extending from the tongue protrusion to define the bottom of the tongue part, and a raised retaining portion protruding downward from the tongue bottom portion, wherein the recessed part includes an upper lip defining the ceiling of the recessed part, the tongue protrusion being caught by the upper lip as the tongue part is inserted into and rotated in the recessed part, a lower lip defining a bottom portion of the recessed part, a raised portion protruding upward from an end of the lower lip, and a guide wall defining an inner wall of the recessed part, the guide wall having the same contour as an arc drawn by an end of the tongue protrusion as the tongue part is introduced into a space between the upper lip and the lower lip and is pivotally rotated about a contact point with respect to the raised portion, and wherein a space is defined by the guide wall and lower lip such that an upper corner of the tongue part is located below the upper lip and the raised retaining portion is located inside the raised portion when the tongue part is inserted into the recessed part. 
     In accordance with another aspect of the present invention, there is provided a floorboard including a tongue part protruding from one side of a first flooring panel and a recessed part provided at one side of a second flooring panel for insertion and assembly of the tongue part, wherein the recessed part includes an upper lip defining the ceiling of the recessed part, a lower lip defining a bottom portion of the recessed part, and a raised portion protruding upward from an end of the lower lip, wherein the tongue part includes a tongue protrusion configured to be caught by the upper lip as the tongue part is inserted into and is pivotally rotated upward in the recessed part, a tongue bottom portion extending from the tongue protrusion to define the bottom of the tongue part, and a raised retaining portion protruding downward from the tongue bottom portion, and wherein, when the tongue part is inserted into and is pivotally rotated in the recessed part, the raised retaining portion comes into contact with an inner wall of the raised portion to slide downward along the inner wall of the raised portion and an end of the tongue protrusion is pivotally rotated upward toward a lower end of the upper lip such that the tongue protrusion is caught by the upper lip to ensure that the tongue part is assembled with the recessed part. 
     In accordance with a further aspect of the present invention, there is provided a floorboard including a tongue part protruding from one side of a first flooring panel and a recessed part provided at one side of a second flooring panel for insertion and assembly of the recessed part, wherein the recessed part includes an upper lip defining the ceiling of the recessed part, a lower lip defining a bottom portion of the recessed part, and a raised portion protruding upward from an end of the lower lip, wherein the tongue part includes a tongue protrusion configured to be caught by the upper lip as the tongue part is inserted into and is pivotally rotated upward in the recessed part, a tongue bottom portion extending from the tongue protrusion to define the bottom of the tongue part, and a raised retaining portion protruding downward from the tongue bottom portion, and wherein the recessed part further includes a space in which the tongue protrusion is located below the upper lip, the raised retaining portion is located inside the raised portion, and the tongue bottom portion comes into contact with or is located close to the bottom portion of the recessed part when the tongue part is inserted into the recessed part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side sectional view illustrating an assembly relationship between two flooring panels of a conventional floorboard; 
         FIG. 2  is a perspective view illustrating one flooring panel of a floorboard according to an embodiment of the present invention; 
         FIG. 3  is a side sectional view illustrating a recessed part and a tongue part provided in the floorboard according to one embodiment of the present invention in more detail; 
         FIG. 4  is a side sectional view explaining a difference between the conventional floorboard and the floorboard according to the embodiment illustrated in  FIG. 3 ; 
         FIGS. 5 to 8  are side sectional views illustrating a stepwise coupling sequence of the tongue part and the recessed part provided in the floorboard according to the embodiment illustrated in  FIG. 3 ; 
         FIGS. 9 and 10  are side sectional views explaining a coupling mechanism of the tongue part and the recessed part provided in the floorboard according to the embodiment illustrated in  FIG. 3 ; 
         FIG. 11  is a side sectional view illustrating a tongue part and a recessed part provided in the floorboard according to another embodiment of the present invention; 
         FIG. 12  is a side sectional view illustrating a tongue part and a recessed part provided in the floorboard according to a further embodiment of the present invention; and 
         FIG. 13  is a side sectional view illustrating a stepwise coupling sequence of the tongue part and the recessed part provided in the floorboard according to the embodiment illustrated in  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, exemplary embodiments of the floorboard according to the present invention will be described in more detail with reference to the accompanying drawings. 
     First, a basic configuration of the floorboard according to the embodiment of the present invention will be schematically described with reference to  FIG. 2 . 
     Preferably, the floorboard according to the present invention is basically made of wood, plywood, MDF, HDF, PB, PVC, and mixtures thereof. 
     Here, MDF is an abbreviation for Medium Density Fiberboard, HDF is an abbreviation for High Density Fiberboard, PB is an abbreviation for Particle Board, and PVC is an abbreviation for Poly Vinyl Chloride. 
     The floorboard according to the present invention is constructed by assembling a plurality of flooring panels with one another. Each flooring panel has long sides and short sides, each of which is provided with an assembly structure. 
     As such, any one flooring panel may be assembled with another flooring panel through connection at the short sides and may be assembled with a further flooring panel through connection at the long sides, to construct the entire floorboard. 
     Of course, assembly structures are not essentially provided respectively at all the long sides and the short sides of the flooring panel. For example, assembly structures may be provided only at the short sides or at the long sides of a flooring panel. 
     Referring to  FIG. 2  illustrating a flooring panel according to one embodiment, the flooring panel F is provided at one side thereof with a first assembly structure F 1  and at the other side thereof with a second assembly structure F 2 . 
     The first assembly structure F 1  of the flooring panel F is coupled with a second assembly structure (not shown) of another flooring panel. The second assembly structure F 2  of the flooring panel F is coupled with a first assembly structure (not shown) of a further flooring panel. 
     The first assembly structure F 1  includes a recessed part  100  and the second assembly structure F 2  includes a tongue part  200 . The recessed part  100  includes a predetermined space and a coupling structure for insertion and assembly of a tongue part (not shown) of another flooring panel. The tongue part  200  includes a protruding structure to be inserted into the space of a recessed part (not shown) of a further flooring panel. 
     More detailed configurations of the recessed part  100  and the tongue part  200  will be described later. 
     The floorboard according to the embodiment of the present invention may further include a decorative layer provided at an upper end U or a lower end L of each flooring panel F to provide the floorboard with an aesthetically pleasing appearance, and a protective layer to protect the decorative layer or the flooring panel F. 
     Alternatively, the decorative layer and the protective layer may be provided at both the upper end U and the lower end L of the flooring panel F. 
     Next, the configuration and assembly sequence of the floorboard according to one embodiment of the present invention will be described in more detail with reference to  FIGS. 3 to 8 . 
     The floorboard according to the present invention includes the recessed part  100  and the tongue part  200 .  FIG. 3  illustrates the recessed part  100  provided in a first flooring panel  1  and the tongue part  200  provided in a second flooring panel  2 . 
     As illustrated in  FIG. 3 , the recessed part  100  may include an upper lip  110 , a lower lip  120 , a space  130 , and a raised portion  140 . 
     The upper lip  110  protrudes from a lateral edge of an upper end  101  of the first flooring panel  1  by a predetermined length, thereby defining a ceiling portion  111  of the recessed part  100 . 
     The lower lip  120  protrudes from a lateral edge of a lower end  102  of the first flooring panel  1  by a greater length than the upper lip  110 , thereby defining a bottom portion  131  of the recessed part  100 . 
     The upper lip  110  and the lower lip  120  are spaced apart from each other by a predetermined distance. The space  130  is a space defined between the upper lip  110  and the lower lip  120  for insertion and assembly of the tongue part  200 . 
     The raised portion  140  protrudes upward from an end of the lower lip  120 . When the tongue part  200  is inserted into the space  130 , the raised portion  140  provides horizontal coupling force with respect to the tongue part  200 . 
     The space  130  is defined by the ceiling portion  111  of the upper lip  110 , the bottom portion  131  of the lower lip  120 , and a guide wall  132 . 
     The guide wall  132  serves as an inner wall of the recessed part  10 , more particularly, an inner wall of the space  130 . A more detailed configuration of the guide wall  132  will be described later. 
     The upper lip  110  includes the ceiling portion  111  and a guide portion  112 . The ceiling portion  111  preferably provides a substantially horizontal surface and the guide portion  112  preferably provides an inclined surface protruding outward from the ceiling portion  111 . 
     The guide portion  112  serves to guide the tongue part  200  when the tongue part  200  is introduced into the space  130 . This will be described later in detail. 
     As illustrated in  FIG. 3 , the tongue part  2 Q 0  may include a tongue protrusion  210 , a raised retaining portion  220 , and an accommodating portion  230 . 
     The tongue protrusion  210  is configured to be caught by the ceiling portion  111  of the upper lip  110  as the tongue part  200  is inserted into the recessed part  100  and is pivotally rotated upward. 
     The tongue protrusion  210  includes a hook portion  211  corresponding to the ceiling portion  111  of the upper lip  110  of the recessed part  100 , an extension portion  212  extending upward from the hook portion  211  and corresponding to the guide portion  112  when the hook portion  211  is caught by the ceiling portion  111 , and a tongue bottom portion  213  extending downward from the hook portion  211  to define a bottom portion of the tongue protrusion  210 . 
     The raised retaining portion  220  protrudes downward from the tongue bottom portion  213 . When the tongue part  200  is inserted into the recessed part  100 , the raised retaining portion  220  is caught by the raised portion  140  of the recessed part  100 , thereby serving to provide horizontal coupling force of the floorboard in cooperation with the raised portion  140 . 
     The accommodating portion  230  is configured to accommodate the raised portion  140  of the recessed part  100  when the tongue part  200  is inserted into the recessed part  100 . 
     In the floorboard according to the embodiment illustrated in  FIG. 3 , horizontal coupling force of the floorboard is provided by the raised portion  140  and the raised retaining portion  220 . More particularly, horizontal coupling force of the floorboard is provided as an inner wall  142  of the raised portion  140  comes into contact with an outer wall  223  of the raised retaining portion  220 . 
     Preferably, an angle θ 1  between the inner wall  142  of the raised portion  140  and a horizontal plane is substantially in a range of 80°≦θ 1 ≦100°, and an angle θ 2  between a lower end  221  and the outer wall  223  of the raised retaining portion  220  is substantially in a range of 80°≦θ 2 ≦100° 
     More preferably, the angle θ 1  between the inner wall  142  of the raised portion  140  and a horizontal plane is substantially 90°, which can enhance coupling force between the recessed part  100  and the tongue part  200 . 
     That is, the inner wall  142  of the raised portion  140  is oriented in a substantially vertical direction, and the outer wall  223  of the raised retaining portion  220  is oriented in a substantially vertical direction, which can provide extremely strong coupling force in a horizontal direction. 
     In addition, preferably, a height of the raised portion  140 , i.e. a length {circle around (e)} from an upper end  141  of the raised portion  140  to the lower end  102  of the first flooring panel  1  is substantially equal to a length {circle around (f)} from a ceiling portion  231  of the accommodating portion  230  to a lower end  202  of the second flooring panel  2 . 
     The raised retaining portion  220  protrudes downward from the ceiling portion  231  of the accommodating portion  230 . 
     As such, a vertical length from a lower end  221  of the raised retaining portion  220  of the tongue part  200  to the lower end  202  of the second flooring panel  2  must always be less than a length of an outer wall  143  of the raised portion  140  of the recessed part  100 . Therefore, when the tongue part  200  is horizontally introduced into the recessed part  100 , an inner wall  222  of the raised retaining portion  220  of the tongue part  200  is caught by the outer wall  143  of the raised portion  140 , which prevents the tongue part  200  from being introduced into the recessed part  100 . 
     In addition, as illustrated in  FIG. 3 , an angle θ 3  between the upper end  141  and the outer wall  143  of the raised portion  140  is preferably substantially in a range of 80°≦θ 3 ≦100°, in other words, is preferably substantially at a right angle. Therefore, horizontally coupling the tongue part  200  with the recessed part  100  is impossible. 
     For this reason, in order to introduce and assemble the tongue part  200  into the recessed part  100 , it is necessary to pivotally rotate the tongue part  200  upward such that the tongue part  200  is obliquely inserted into the space  130  of the recessed part  100 . 
     In this case, a distance between the upper lip  110  and the raised portion  140  of the recessed part  100  must be sufficient to allow the oblique introduction of the tongue part  200 , but an excessive distance therebetween is undesirable. 
     For example, the distance between the upper lip  110  and the raised portion  140  of the recessed part  100  and the height of the raised portion  140  are preferably determined in consideration of a relationship with regard to the tongue part  200 . This will be described below with reference to  FIG. 4 . 
     As illustrated in  FIG. 4 , to insert the tongue part  200  into the recessed part  100 , the second flooring panel  2  is pivotally rotated upward such that the tongue part  200  is inserted into the space  130 . This serves to prevent the inner wall  222  of the raised retaining portion  220  from being caught by the outer wall  143  of the raised portion  140 . 
     When the tongue part  200  is inserted into the recessed part  100 , as illustrated in  FIG. 4 , an end of the upper lip  110  of the recessed part  100  (more particularly, an end of the guide portion  112  as illustrated in  FIG. 3 ) and an upper corner E (see  FIG. 5 ) of the tongue part  200  (more particularly, a corner where the upper end  201  and the extension portion  212  as illustrated in  FIG. 3  meet each other) come into contact with each other at a point, and this contact point is a pivot point P. If the tongue part  200  is pivotally rotated downward about the pivot point P, the raised retaining portion  220  of the tongue part  200  is caught by the raised portion  140  of the recessed part  100 . 
     More specifically, if the tongue part  200  is pivotally rotated downward about the pivot point P, an arc C illustrated in  FIG. 4  is drawn. 
     In this case, the arc C is drawn by rotation of a corner R (see  FIG. 6 ) where the lower end  221  and the outer wall  223  of the raised retaining portion  220  of the tongue part  200  meet each other. 
     The floorboard according to the embodiment of the present invention has a feature in that the recessed part  100  and the tongue part  200  are configured such that the arc C passes through the upper end  141  of the raised portion  140 . 
     In other words, the upper lip  110 , the lower lip  120  and the raised portion  140  are preferably configured such that the arc C drawn by the corner R of the raised retaining portion  220  of the tongue part  200  passes through the upper end  141  of the raised portion  140  when the tongue part  200  is pivotally rotated about the pivot point P along the arc C as illustrated in  FIG. 4 . 
     With the above described configuration, however, it is impossible to couple the tongue part  200  with the recessed part  100  by pivotally rotating the tongue part  200  about the pivot point P as illustrated in  FIG. 4 . 
     The floorboard according to the present invention has a feature of allowing the tongue part  200  and the recessed part  100  to be coupled with each other in a manner different from the above described assembly manner, despite of the above described configuration that makes assembly of the tongue part  200  and the recessed part  100  difficult. 
     Hereinafter, an assembly sequence of the recessed part  100  and the tongue part  200  of the floorboard according to the embodiment will be described with reference to  FIGS. 3 and 5  to  8 . 
     As illustrated in  FIGS. 5 and 6 , to couple the tongue part  200  and the recessed part  100  of the floorboard with each other according to the embodiment of the present invention, in a state in which the tongue part  200  is pivotally rotated upward so as to be obliquely oriented, it is necessary to move the upper corner E of the tongue part  200  downward along the guide portion  112  of the upper lip  110  and simultaneously, to completely introduce the tongue protrusion  210  and the raised retaining portion  220  into the space  130   
     In this case, the tongue bottom portion  213  of the tongue protrusion  210  may come into contact with the bottom portion  131  of the recessed part  100 , or may be located close to the bottom portion  131 . 
     More specifically, once the tongue part  200  is completely introduced into the space  130  of the recessed part  100 , the upper corner E of the tongue part  200  is located below the ceiling portion  111  of the upper lip  100  and the raised retaining portion  220  is located inside the inner wall  142  of the raised portion  140  (see  FIG. 6 ). 
     Thus, the space  130  of the recessed part  100  must have a sufficient size to allow the tongue protrusion  210  of the tongue part  200  to be located below the upper lip  110  and the raised retaining portion  220  to be located inside the inner wall  142  of the raised portion  140  as described above. 
     In this case, as illustrated in  FIG. 3 , a width {circle around (a)} of the bottom portion  131  of the recessed part  100  is preferably substantially equal to or greater than a length {circle around (b)} from an end S of the tongue protrusion  210  of the tongue part  200  to the corner R where the lower end  221  and the outer wall  223  of the raised retaining portion  220  meet each other. 
     In addition, as illustrated in  FIG. 6 , once the tongue part  200  is completely introduced into the recessed part  100 , preferably, the end S of the tongue protrusion  210  comes into contact with or is located close to the guide wall  132  of the recessed part  100 , and the corner R of the raised retaining portion  220  comes into contact with or is located close to the inner wall  142  of the raised portion  140 . 
     Then, referring to  FIG. 7 , after the tongue part  200  is completely inserted into the space  130  of the recessed part  100  as illustrated in  FIGS. 5 and 6 , the tongue part  200  is pivotally rotated such that the tongue protrusion  210  is moved upward. 
     In this case, the end S of the tongue protrusion  210  is moved upward along the guide wall  132  and the outer corner R of the raised retaining portion  220  is moved downward along the inner wall  142  of the raised portion  140 . 
     In other words, the guide wall  132  of the recessed part  100  guides movement of the end S of the tongue protrusion  210  of the tongue part  200 , and the inner wall  142  of the raised portion  140  guides movement of the raised retaining portion  200 . A more detailed guiding mechanism will be described later with reference to  FIGS. 9 and 10 . 
     In addition, the upper corner E of the tongue part  200  is preferably moved upward along the guide portion  112  of the upper lip  110 . 
     Then, if the hook portion  211  of the tongue protrusion  210  comes into contact with the ceiling portion  111  of the upper lip  110  via the above described rotation, as illustrated in  FIG. 8 , the tongue part  200  is completely coupled with the recessed part  100 . 
     After completion of the coupling between the tongue part  200  and the recessed part  100 , as illustrated in  FIG. 8 , a space having a predetermined volume is defined by the bottom portion  131  and the guide wall  132  of the recessed part  100  and the tongue bottom portion  213  of the tongue part  200 . 
     Also, after completion of the coupling between the tongue part  200  and the recessed part  100 , as illustrated in  FIG. 8 , the raised portion  140  is accommodated in the accommodating portion  230 . In this case, the upper end  141  of the raised portion  140  preferably comes into contact with the ceiling portion  231  of the accommodating portion  230 . 
     This configuration can be realized when the length {circle around (e)} from the upper end  141  of the raised portion  140  to the lower end  102  of the first flooring panel  1  is substantially equal to the length {circle around (f)} from the ceiling portion  231  of the accommodating portion  230  to the lower end  202  of the second flooring panel  2 . 
     Also, a width {circle around (c)} of the raised portion  140  is preferably less than a width {circle around (d)} of the accommodating portion  230 . Specifically, after completion of the coupling between the tongue part  200  and the recessed part  100 , as illustrated in  FIG. 8 , the raised portion  140  is preferably accommodated in the accommodating portion  230  with a slight gap therebetween. 
     In the meantime, as illustrated in  FIG. 3 , a length {circle around (w)} of the guide wall  132  is preferably greater than a vertical length from the hook portion  211  of the tongue protrusion  210  to the lower end  221  of the raised retaining portion  220 . 
     Here, with regard to the bottom portion  131  of the recessed part  100 , a part thereof near the guide wall  132  preferably has a different height from that of a part thereof near the raised portion  140 . 
     Specifically, the bottom portion  131  of the recessed part  100  is preferably gradually reduced in height from the inner wall  142  of the raised portion  140  to the guide wall  132 . 
     That is, as illustrated in  FIG. 3 , the height of the bottom portion  131  near the guide wall  132  is less than the height of the bottom portion  131  near the raised portion  140 . 
     In the case where the length {circle around (w)} of the guide wall  132  is greater than the vertical length from the hook portion  211  to the lower end  221  and the height of the bottom portion  131  near the guide wall  132  is less than that of the remaining bottom portion, as illustrated in  FIG. 6 , as the tongue part  200  is inserted into the space  130  of the recessed part  100 , the tongue protrusion  210  can be located below the upper lip  110  and the raised retaining portion  220  can be located inside the inner wall  142  of the raised portion  140 , which ensures that the tongue part  200  can be completely deeply inserted into the recessed part  100 . 
     Next, a mechanism by which the tongue part  200  is inserted into and rotated in the recessed part  100  will be described in detail with reference to  FIGS. 9 and 10 . 
       FIG. 9  is a view illustrating a stepwise sequence of pivotally rotating the tongue protrusion  210  upward in a state in which the tongue part  200  is inserted into the recessed part  100 . As illustrated in  FIG. 9 , when the tongue part  200  is pivotally rotated in the recessed part  100 , the end S of the tongue protrusion  210  is moved upward along the guide wall  132  and the outer corner R of the raised retaining portion  220  is moved downward along the inner wall  142  of the raised portion  140 . 
       FIG. 10  illustrates several points on a movement path of the end S of the tongue protrusion  210  and several points on a movement path of the outer corner R of the raised retaining portion  220 . 
     In  FIG. 10 , P 1 , P 2 , . . . P n  represent the points on the movement path of the outer corner R of the raised retaining portion  220  of the tongue part  200 , and Q 1 , Q 2 , . . . Q n1 , Q n2 , Q n3 , Q n4  represent the points on the movement path of the end S of the tongue protrusion  210  of the tongue part  200 . 
     Here, P 1  corresponds to Q 1 , P 2  corresponds to Q 2 , and P n  corresponds to Q n1 , Q n2 , Q n3 , Q n4 . 
     Specifically, if the outer corner R of the raised retaining portion  220  is located at the point P 1  via rotation of the tongue part  200 , the end S of the tongue protrusion  210  is located at the point Q 1 . Then, if the outer corner R of the raised retaining portion  220  is located at the point P 2 , the end S of the tongue protrusion  210  is located at the point Q 2 . 
     Thereafter, if the outer corner R of the raised retaining portion  220  is located at the point P n , the end S of the tongue protrusion  210  is pivotally rotated about the point P n  along the points Q n1 , Q n2 , Q n3 , Q n4  until the hook portion  211  is caught by the ceiling portion  111 . In this way, coupling between the tongue part  200  and the recessed part  100  is completed. 
     When the tongue part  200  is introduced into the space  130  of the recessed part  100  and is initially rotated, the tongue part  200  is rotated about an intersection point of a line connecting the points P 1  and Q 1  to each other and a line connecting the points P 1  and Q 1  to each other, which allows the end S of the tongue protrusion  210  to slide along the guide wall  132  and the outer corner R of the raised retaining portion  220  to slide along the inner wall  142  of the raised portion  140 . 
     Then, after the outer corner R of the raised retaining portion  220  reaches the point P n , the point P n  is fixed as a rotation center point and the end S of the tongue protrusion  210  is moved along the guide wall  132  to draw an arc passing through the points Q n1 , Q n2 , Q n3 , Q n4 . 
     Thus, the guide wall  132  preferably has a shape conforming to the arc as illustrated in  FIG. 10  and in other words, has substantially the same contour as the arc drawn by the end S of the tongue protrusion  210 . 
     Next, another embodiment of the floorboard according to the present invention will be described with reference to  FIG. 11 . 
     The floorboard illustrated in  FIG. 11  is basically identical to the floorboard illustrated in  FIG. 3 , but has a difference with regard to a configuration of the upper lip  110  of the recessed part  100 . 
     As illustrated in  FIG. 11 , the upper lip  110  of the recessed part  100  preferably further includes a bevel portion  113  inclined in a direction opposite to the guide portion  112 . 
     When the recessed part  100  is provided with the bevel portion  113 , the bevel portion  113  defines a substantially “V”-shaped groove along with the extension portion  212  of the tongue part  200  when the tongue part  200  is completely coupled with the recessed part  100 , which can provide the constructed floorboard with a more aesthetically pleasing appearance. 
     Other configurations of the floorboard according to the present embodiment except for the bevel portion  113  are identical to those as illustrated in  FIG. 3  and thus, a detailed description thereof will be omitted herein. 
     Next, a further embodiment of the floorboard according to the present invention will be described with reference to  FIGS. 12 and 13 . 
     The floorboard according to the embodiment illustrated in  FIGS. 12 and 13  is basically identical to the floorboard of the embodiment illustrated in  FIG. 3 , except for a configuration of the raised portion  140  of the recessed part  100  and the raised retaining portion  220  of the tongue part  200 . Thus, the following description centers only on a difference therebetween and other configurations of the floorboard according to the present embodiment will not be described hereinafter because they are identical to those of the embodiment illustrated in  FIG. 3 . 
     As illustrated in  FIG. 12 , the raised portion  140  of the recessed part  100  includes stepped portions  144  and  145 , which define a substantially step shaped portion between the inner wall  142  and the upper end  141  of the raised portion  140 . To correspond to the stepped portions  144  and  145 , the raised retaining portion  220  of the tongue part  200  includes stepped portions  224  and  225 , which define a substantially step shaped portion between the outer wall  223  and the lower end  221  of the raised retaining portion  220 . 
     The stepped portions of the recessed part  100  include a stepped bottom portion  144  and a stepped sidewall portion  145 , and the stepped portions of the tongue part  200  include a stepped bottom portion  224  and a stepped sidewall portion  225 . 
     An assembly sequence of the floorboard according to the embodiment illustrated in  FIG. 12  is identical to that illustrated in  FIG. 13 . 
       FIG. 13(   a ) illustrates a state in which the tongue part  200  of one flooring panel, which is pivotally rotated upward so as to be obliquely oriented, is introduced into the recessed part  100  of another flooring panel such that the tongue protrusion  210  is inserted toward the bottom portion  131  of the recessed part  100 .  FIG. 13(   b ) illustrates a state in which the tongue part  200  is completely inserted into the space  130  of the recessed part  100  (i.e. the upper corner E of the tongue part  200  is located below the upper lip  110 , the tongue protrusion  210  is located at a lower position of the guide wall  132 , and the raised retaining portion  220  is completely located inside the raised portion  140 ). 
       FIG. 13(   c ) illustrates a process of rotating the tongue part  200  within the space  130  of the recessed part  100  such that the tongue protrusion  210  is moved upward.  FIG. 13(   d ) illustrates a state in which the tongue part  200  is completely coupled with the recessed part  100 . 
     The basic assembly mechanism, i.e. the assembly sequence of the present embodiment is identical to the assembly mechanism of the floorboard according to the embodiment illustrated in  FIGS. 5 to 8 . The present embodiment has a feature in that, with provision of the stepped portions  224  and  225  of the raised retaining portion  220  and the stepped portions  144  and  145  of the raised portion  140 , corners R 1  and R 2  of the raised retaining portion  220  are adapted to slide on the corresponding inner wall  142  and stepped sidewall portion  145  respectively. 
     In the present embodiment, the end S of the tongue protrusion  210  moves in the same arc as that in the embodiment illustrated in  FIGS. 5 to 8 . 
     When tongue part  200  is pivotally rotated in the recessed part  100 , the end S of the tongue protrusion  210  slides upward along the guide wall  132  as the corner R 1  slides downward along the inner wall  142 . After the corner R 2  comes into contact with the stepped sidewall portion  145 , the corner R 2  slides downward along the stepped sidewall portion  145 . 
     Once the tongue part  200  is completely coupled with the recessed part  100 , preferably, the inner wall  142  of the raised portion  140  comes into contact with the stepped sidewall portion  225  of the raised retaining portion  220 , the stepped bottom portion  144  of the raised portion  140  comes into contact with the stepped bottom portion  224  of the raised retaining portion  220 , the stepped sidewall portion  145  of the raised portion  140  comes into contact with the outer wall  223  of the raised retaining portion  220 , and the upper end  141  of the raised portion  140  comes into contact with the ceiling portion  231  of the accommodating portion  230 . 
     As is apparent from the above description, the present invention provides a floorboard in which neighboring flooring panels are assembled with each other using a new assembly method completely different from a conventional flooring panel assembly method. The floorboard according to the present invention has the effects of providing simplified assembly of flooring panels without damage because it is unnecessary to apply external force to assemble the flooring panels and of achieving enhanced coupling force in a horizontal direction after assembly of the flooring panels. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.