Abstract:
A top board structure capable of easily and simply assembling and welding a reinforcing frame to a top board body, providing a sufficient strength with a reduced weight, and reducing abnormal noise that might occur when an impact is applied. A reinforcing frame formed by assembling lateral reinforcing member directed in a lateral direction with a longitudinal reinforcing member directed in a longitudinal direction is fixed to the lower surface of a base board in a top board body formed at the peripheral edge thereof in a box shape opened downward by a downward piece, a rear surface cover in a box shape opened upward by an upward piece is formed at the peripheral edge of a cover base board, and the rear surface cover is fixed to the top board body with the upward piece of the rear surface cover kept fitted/inserted into gaps formed between the inside surface of the erect piece portion of the downward piece in the top board body and the outside portion of the reinforcing frame or the inside partition wall of the reinforcing member constituting the reinforcing frame.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §371 National Phase conversion of PCT/JP2007/066454, filed Aug. 24, 2007, which claims benefit of Japanese Application No. 2006-229791, filed Aug. 25, 2006. The PCT International Application was published in the Japanese language. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to the top board structure of office furniture such as a table and a desk used in an office. 
     The top board of a table or a desk is made of wood or a wooden base on which a decoration plate such as melamine resin is applied. To keep sufficient strength, it is necessary to thicken the base. Flexibility in design is not good and its appearance becomes poor. The top board also becomes heavier. It is necessary to strengthen the support structure for the top board. 
     JP2003-174935A discloses that the top board of a table is made of resin on which Aluminum is applied, but is not preferable in view of environmental aspects such as wastes and recycling. 
     The top board of a table is made of sheet metal. But if impact is given, abnormal noise is likely to occur. In order to keep sufficient strength, it is necessary to increase thickness of the sheet metal. The top board becomes heavier as well as wooden base. 
     JP2005-137714A discloses that the top board of the furniture is made of steel sheet metal and reinforced with a core made of the same material thereby reducing its weight, preventing abnormal noise and providing advantages in environmental aspects such as wastes and recycling. 
     However, in the top board in JP2005-137714A, the core comprises a honeycomb structure. It is very difficult to join an upper plate on a lower plate. Its manufacturing is complicated to increase cost. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing disadvantages, it is an object of the invention to provide the top board structure of office furniture in which a reinforcing frame can be assembled and welded more easily, the top board structure providing less weight but sufficient strength, abnormal noise being reduced even if impact is given. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the first embodiment of the top board structure according to the present invention, seen from below. 
         FIG. 2  is a vertical sectional view taken along the line II-II in  FIG. 1 . 
         FIG. 3  is a vertical sectional view taken along the line III-III in  FIG. 1 . 
         FIG. 4  is an exploded perspective view showing a reinforcing frame and a bottom cover upside down. 
         FIG. 5  is a perspective view showing the second embodiment of the top board structure according to the present invention, seen from below. 
         FIG. 6  is a vertical sectional view taken along the line VI-VI in  FIG. 5 . 
         FIG. 7  is an exploded perspective view showing how to mount the reinforcing frame and bottom cover to the top board in  FIG. 5  upside down. 
         FIG. 8  is an exploded perspective view of the reinforcing frame. 
         FIG. 9  is an exploded perspective view showing how to assemble a reinforcing frame to a top board in the third embodiment upside down. 
         FIG. 10  is a vertical sectional view showing how to assemble the reinforcing frame to a top board. 
         FIG. 11  is an exploded perspective view of a reinforcing frame in the fourth embodiment. 
         FIG. 12  is an exploded perspective view of a reinforcing frame in the fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  is an enlarged perspective view of the first embodiment of a top board according to the present invention, seen from below;  FIG. 2  is a vertical sectional view taken along the line II-II in  FIG. 1 ;  FIG. 3  is a verticals sectional view taken along the line and  FIG. 4  is an exploded perspective view showing how to mount a reinforcing frame and a bottom cover to the top board upside down. 
     In  FIG. 1 , a top board  1  comprises a top board body  2  on which a computer is placed; a reinforcing frame  3 ; and a bottom cover  4  made of the same material such as sheet metal. 
     In  FIGS. 2 and 3 , the top board body  2  comprises a base  5  the upper surface  5   a  of which is used for working; and a downward portion  6  which extends downward from the outer periphery of the base  5 . At the front edge  2   a  of the top board body  2 , the downward portion  6  is tilted rearward. 
     In  FIG. 4 , the reinforcing frame  3  comprises a longitudinal reinforcement  7  extending along the periphery in a right and left direction; and a lateral reinforcement  8  extending in a forward and backward direction. In the frame  3 , three longitudinal intermediate reinforcements  9 A, 9 B, 9 C are disposed. 
     The reinforcements  7 , 8 , 9 A, 9 B, 9 C are fixed on the lower surface  5   b  of the base  5  of the top board body  2  by spot welding to form the reinforcing frame  3 . 
     In  FIGS. 2 and 3 , there is a gap “a” between the the outer side  3   a  of the reinforcing frame  3  and the inner side of a standing portion  6   a  of the downward portion  6  except parts along the front edge  2   a  of the top board body  2 . The gap “a” is slightly wider than the thickness of the upward portion  11 . 
     Furthermore, in  FIG. 2 , there is a gap “b” between the inner side of the standing portion  6   a  of the downward portion  6  of the top board body  2  and an inner partition wall  7   a  of the longitudinal reinforcement  7  forming the front edge of the reinforcing frame  3 . The upward portion  11  of the bottom cover  4  is disposed in the gap “b”. A flange  6   b  extends between the downward portion  6  and the standing portion  6   a.    
     The gap “b” may be slightly wider than the thickness of the upward portion  11  of the bottom cover  4  as well as the gap “a”. 
     The bottom cover  4  is formed like a box having an upper opening with a cover base  10  and the upward portion  11  standing upward from the periphery of the cover base  10 . 
     In  FIGS. 2 and 3 , the upward portion  11  is disposed in the gaps “a” and “b” and mounted to the top board body  2 . 
     In order to assemble the top board  1  in the first embodiment of the present invention, the reinforcing frame  3  is fixed on the lower surface of the top board body  2  by spot welding in  FIG. 4 . Then, the upward portion  11  of the bottom cover  4  is put in the gap “a” between the top board body  2  and the reinforcing frame  3 , and the bottom cover  4  is fixed to the reinforcing frame  3  by spot welding. 
     In this embodiment, the reinforcing frame  3  is fixed to the lower surface  5   b  of the base  5  of the box-like top board body  2  having a lower opening, and the bottom cover  4  is fixed to the top board body  2  while the upward portion  11  of the bottom cover  11  is disposed in the gaps “a” and “b” thereby facilitating assembling and welding of the bottom cover  4  to the top board body  2 . 
     The reinforcing frame  3  is fixed to the lower surface  5   b  of the base  5  of the top board body  2  thereby making the base  5  of the top board body  2  thinner, reducing the total weight and providing sufficient strength as the top board  1 . 
     Even if impact is given, the reinforcements  7 , 8  of the reinforcing frame  3  will absorb vibration thereby reducing abnormal noise. The top board body  2 , the reinforcing frame  3  and the bottom cover  4  are made of the same material which is preferable in view of environmental aspects such as wastes and recycling. 
     Furthermore, the reinforcing frame  3  is covered with the bottom cover  4  mounted to the lower surface of the top board body  2 , so that the reinforcing frame  3  is stored within the top board  1  in good appearance. 
       FIG. 5  is a partially enlarged perspective view of the second embodiment of a top board according to the present invention seen from below;  FIG. 6  is an enlarged sectional view taken and seen along the line VI-VI in  FIG. 5 ;  FIG. 7  is an exploded perspective view of a reinforcing frame and a bottom cover mounted to the top board in  FIG. 5  upside down; and  FIG. 8  is an exploded perspective view of the reinforcing frame. 
     In  FIG. 5 , the top board  12  in this embodiment comprises a top board body  13 , a reinforcing frame  14  and a bottom cover  15 . 
     In  FIGS. 6 and 7 , the top board body  13  has a downward portion  17  extending downward from the periphery of a base  16 . The lower end of the downward portion  17  is bent inward like L to form a standing portion  17   a , so that the top board body  13  is formed like a box having a lower opening. 
     The reinforcing frame  14  comprises a plurality of lateral reinforcements  18  extending in a forward and rearward direction; and a plurality of longitudinal reinforcements  19  extending in a right and left direction crossed to the lateral reinforcements  18 . 
     The lateral reinforcement  18  comprises a vertical portion  18   a  and a pair of horizontal portions  18   b , 18   c  extending oppositely from the upper and lower ends of the vertical portion  18   a . The lateral reinforcement  18  is made of extruded material having a Z-like cross-section. 
     As well as the lateral reinforcement  18 , the longitudinal reinforcements  19  comprises a vertical portion  19   a  and a pair of horizontal portions  19   b , 19   c  extending oppositely from the upper and lower ends of the vertical portion  19   a . The longitudinal reinforcement  19  is made of extruded material having a Z-like cross-section. 
     In  FIGS. 6 and 7 , the bottom cover  15  has an upward portion  21  extending from the periphery of a cover base  20  and is formed like a box having an upper opening. 
     The cover base  20  has a plurality of welding holes  22  through which a welding gun (not shown) can be put at positions corresponding to the lateral and longitudinal reinforcements  18 , 19  arranged like a lattice. 
     In order that the lateral reinforcements  18  are disposed with the longitudinal reinforcements  19  like a lattice in the reinforcing frame  14 , in  FIG. 8 , there is formed a first V-like notch  23  having a first slit  23   a  extending from the upper end of the vertical portion  18   a  including the horizontal portion  18   b.    
     Meanwhile, there is formed a second V-like notch  24  having a second slit  24   a  extending from the lower end of the vertical portion  19   a  including the lower horizontal portion  19   c . A third notch  25  joined to the second notch  24  is formed so that the upper horizontal portion  18   b  of the lateral reinforcement  18  can be put in the third notch  25 . 
     Into the first notch  23  of the lateral reinforcement  18 , the second notch  24  of the longitudinal reinforcement  19  is put through the third notch  25  from above. The first slit  23   a  engages with the second slit  24   a  to allow the lateral reinforcement  18  to engage with the longitudinal reinforcement  19  like a lattice. 
     A fourth notch  26  of the lower horizontal portion  18   c  of the lateral reinforcement  18  is fitted with the second notch  24  of the longitudinal reinforcement  19 . 
     The upper horizontal portion  19   b  of the longitudinal reinforcement  19  has a fifth notch  27  which fits with the first notch  23  of the lateral reinforcement  18 . The engagement allows the upper and lower horizontal portions  18   b , 18   c  of the lateral reinforcement  18  to become coplanar with the upper and lower horizontal portions  19   b , 19   c  of the longitudinal reinforcement  19 . 
     In  FIG. 6 , between an outer side  14   a  of the reinforcement frame  14  and the inner side of the standing portion  17   a  of the downward portion  17  extending from the periphery of the base  16  of the top board body  13 , there is formed a gap “a” slightly wider than a thickness of the upward portion  21  of the bottom cover  21 . The bottom cover  15  is fixed to the top board body  13  while the upward portion  21  of the bottom cover  15  is disposed in the gap “a”. 
     To assemble the top board  12 , in  FIG. 7 , on the lower surface of the inverted top board body  13 , a plurality of lateral reinforcements  18  is disposed at regular spacings and connected to a plurality of longitudinal reinforcements  19  like a lattice. 
     The gap “a” is formed between the inner side of the standing portion  17  of the top board body  13  and the outer side  14   a  of the reinforcing frame  14  to be slightly wider than the thickness of the upward portion  21  of the bottom cover  15 . 
     In the top board body  13  to which the reinforcing frame  14  is mounted, the bottom cover  15  is put upside down and the upward portion  21  of the bottom cover  21  is inserted in the gap “a”, so that the bottom cover  15  is mounted. 
     Through the welding hole  22  of the bottom cover  15 , the welding gun (not shown) is put, and at least one of the lateral and longitudinal reinforcements  18 , 19  is fixed to the lower surface of the base  16  by spot welding. And the bottom cover  15  is fixed to the reinforcing frame  14  by spot welding or plug welding or with screws. 
     Thus, the lower opening of the top board body  13  is closed with the bottom cover  15 , so that the reinforcing frame  14  is hidden by the bottom cover  15 . 
     In the embodiment, in the reinforcing frame  14 , a plurality of reinforcements  18  is crossed with a plurality of reinforcements  19  like a lattice thereby improving strength of the top board  12  and reducing a vibrating surface. Thus, abnormal noises are reduced. 
     In the reinforcing frame  14 , the notches  23 , 26  and  24 , 25 , 27  respectively formed in the lateral and longitudinal reinforcements  18 , 19  are engaged with each other and the slit  23   a  is engaged with the slit  24   a  thereby improving strength of the top board  12  further and certainly assembling the lateral and longitudinal reinforcements  18  and  19  with simple structure. 
       FIG. 9  is an exploded perspective view showing assembling of a reinforcing frame to the top board and a bottom cover upside down, and  FIG. 10  is an enlarged vertical sectional view showing mounting of a reinforcing frame to the top board and the bottom cover. 
     In  FIG. 9 , the reinforcing frame  30  fixed on the lower surface  29  of the top board  28  comprises a plurality of lateral reinforcements  31  extending in a forward and rearward direction and a plurality of longitudinal reinforcements  32  directed in a right and left direction, arranged to each other like a lattice. 
     The reinforcements  31 , 32  comprise lower horizontal portions  31   a , 32   a , vertical portions  31   b , 32   b  extending upward from the lower horizontal portions  31   a , 32   a  respectively; and upper horizontal portions  31   c , 32   c  extending outward from the vertical portions  31   a , 32   a  respectively, and has the same shape of a V-like cross section. 
     The longitudinal reinforcement  32  is divided into a plurality of divided reinforcements  32 ′ which are disposed between the adjacent lateral reinforcements  31  and  31 . 
     Cutaway portions  33 , 33  are formed respectively at each end of the upper horizontal portions  32   c , 32   c  of each of the divided reinforcements  32 ′. 
     In  FIG. 10 , the upper horizontal portions  31   c , 31   c  are engaged in the cutaway portions  33 , 33  of the lateral reinforcement  31 , so that the lower horizontal portions  31   a , 32   a  of the reinforcements  31 , 32  are coplanar with each other. 
     Between the inner side of a standing portion  35   a  of a downward portion  35  extending from the periphery of a base  34  of the top board body  29  and the outer sides of the lateral and longitudinal reinforcements  31 , 32  of the reinforcing frame  30 , there is formed a gap “a” slightly wider than a thickness of an upward portion  38  extending from the periphery of a cover base  37  of a bottom cover  36 . In the gap “a”, the upward portion  38  of the bottom cover  36  is put. 
     For assembling of the top board  28 , the lateral reinforcements  31  and the longitudinal reinforcements  32  of the reinforcing frame  30  are fixed on the lower surface of the top board body  29  by spot welding. 
     Then, into the gap “a”, the upward portion  38  of the bottom cover  36  is put. The bottom cover  36  is mounted on the lower surface of the top board body  29  to allow the reinforcing frame  30  to be covered and fixed to the reinforcing frame  30  by spot welding or plug welding or with screws. 
     In this embodiment, the longitudinal reinforcement  32  is divided into a plurality of parts which are disposed between the adjacent lateral reinforcements  31  and  31 . The lateral and longitudinal reinforcements  31 , 32  are fixed on the lower surface of the base  34  of the top board body  29 . The bottom cover  36  is mounted under the top board body  29  and fixed to the reinforcements  31 , 32 . 
     The reinforcements  31 , 32  comprise the lower horizontal portions  31   a , 32   a , the vertical portions  31   b , 32   b  extending upward from the lower horizontal portions  31   a , 32   a , and upper horizontal portions  31   c , 32   c  extending horizontally from the vertical portions  31   b , 32   b  to have a U-like cross section. The lower surfaces of the lower horizontal portions  31   a , 32   a  of the reinforcements  31 , 32  are coplanar with each other to allow the reinforcing frame  30  to be mounted to the top board body  29  firmly. 
       FIG. 11  is an exploded perspective view showing a reinforcing frame in the fourth embodiment of the present invention. 
     In  FIG. 11 , the reinforcing frame  39  has the same cross section as those of the lateral and longitudinal reinforcements  18 , 19  in the second embodiment. In the middle of the lower horizontal portion  40   a  of a lateral reinforcement  40 , there is formed a cutaway portion  42  that engages with the lower horizontal portion  41   a  of a longitudinal reinforcement  41 . 
     In the middle of the longitudinal reinforcement  41 , there is formed an L-sectioned cutaway portion  43  extending from the lower horizontal portion  41   a  to the upper horizontal portion  41   c  through the vertical portion  41   b.    
     The cutaway portion  43  is engaged with the upper horizontal portion  40   a  of the lateral reinforcement  40  though the vertical portion  40   c.    
     The upper horizontal portion  41   c  of the longitudinal reinforcement  41  contacts the upper horizontal portion  40   b  of the lateral reinforcement  30  to allow the reinforcements  40  to be connected with the reinforcements  41  like a lattice. 
     The upper horizontal portion  41   a  of the longitudinal reinforcement  41  is engaged with the cutaway portion  42  of the upper horizontal portion  40   a  of the lateral reinforcement  40 , so that the lower surfaces of the upper horizontal portions  40   a , 41   a  of the reinforcements  40 , 41  are allowed to become coplanar with each other. 
       FIG. 12  is an exploded perspective view of a reinforcing frame in the fifth embodiment of the present invention. 
     In  FIG. 12 , a lateral reinforcement  45  of the reinforcing frame  44  comprises an upper horizontal portion  45   a ; horizontal portions  45   b , 45   b  extending downward from the upper horizontal portion  45   a , and lower horizontal portions  45   c , 45   c  extending horizontally from the vertical portions  45   b , 45   b  to form an inverted U-like cross section. 
     A longitudinal reinforcement  46  comprises a lower horizontal portion  46   a ; vertical portions  46   b , 46   b  extending upward from the lower horizontal portion  46   a ; and upper horizontal portions  46   c , 46   c  extending outward from the upper ends of the vertical portions  46   b , 46   b  to form an inverted U-like cross section. 
     In the middle of the lower horizontal portions  45   c , 45   c  of the lateral reinforcement  45 , there is formed a U-sectioned cutaway portion  48  extending from the lower horizontal portion  46   a  to the upper horizontal portion  46   c , 46   c  through the vertical portions  46   b , 46   b.    
     The cutaway portion  48  is allowed to engage with the upper horizontal portion  45   a  of the lateral reinforcement  45  through the vertical portions  45   b , 45   b.    
     The upper horizontal portions  46   c , 46   c  of the longitudinal reinforcement  46  is allowed to contact the upper horizontal portion  45   a  of the lateral reinforcement  45  to enable the reinforcements  45  and  46  to be connected like a lattice. 
     The lower horizontal portion  46   a  of the longitudinal reinforcement  46  is engaged with the cutaway portions  47 , 47  formed in the lower horizontal portions  45   c , 45   c  of the lateral reinforcement  45 , so that the lower horizontal portion  45   c  of the reinforcement  45  is allowed to become coplanar with the lower horizontal portion  46   a  of the reinforcement  46 .