Patent Publication Number: US-6709060-B1

Title: Chair backrest

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a chair backrest. In particular, the present invention relates to a chair-backrest with improved stability, improved sitting comfort, and improved safety. 
     2. Description of the Related Art 
     FIGS. 5 and 6 of the drawings illustrate a conventional chair including a backrest  1 ′, a seat  2 ′, a chassis  3 ′, a leg assembly  4 ′, and a connecting plate  5 ′.  2 he backrest  1 ′ includes an engaging portion  11 ′ with fixing holes  12 ′ on a lower central portion thereof for connection with the connecting plate  5 ′. The chassis  3 ′ is fixed to a central portion of an underside of the scat  2 ′ and includes a lower end for connection with the leg assembly  4 ′ and an engaging portion  31 ′ with fixing holes  32 ′ for connection with the connecting plate  5 ′. The connecting plate  5 ′ is a substantially L-shaped plate including two plate sections having fixing holes  51 ′ and  52 ′ through which screws are extended for connecting the backrest  1 ′ and the seat  2 ′ in a perpendicular manner. 
     The backrest  1 ′ is supported by the connecting plate  5 ′ when the user is lying down. However, the supporting point provided by the connecting plate  5 ′ is only at the lower central portion of the backrest  1 ′ such that the forces exerted on the two sides of the backrest  1 ′ are not uniform when center of gravity of the user&#39;s back shifts as a result of movement of the user. As a result, the connecting plate  5 ′ could not provide a stable support when the user&#39;s back is not lying flat in the backrest  1 ′. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a chair backrest with improved stability, improved sitting comfort, and improved safety. 
     A chair in accordance with the present invention includes a seat, a chassis fixed to an underside of the scat, a leg assembly attached to an underside of the chassis, a backrest, and a support frame. A plurality of engaging posts are formed on a peripheral portion of a rear side of the backrest, each engaging post having a groove, each engaging post further including a transverse fixing hole. The support frame extends along the peripheral portion of the rear side of the backrest A connecting beam includes a first end fixed to a lower portion of the support frame and a second end fixed to the chassis. 
     A plurality of connecting blocks are provided fixing the support frame to the rear side of the backrest. Each connecting block includes a sleeve portion through which the support frame extends. Each connecting block further includes an insertion portion engaged in the groove of the respective engaging post. The sleeve portion of each connecting block includes a slit allowing expansion of the sleeve portion when the support frame is extending through said connecting block. A fastener is extended through the transverse fixing hole in the respective engaging post into the insertion portion of the respective connecting block. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view, partly exploded, of a chair in accordance with the present invention. 
     FIG. 2 is a perspective view of the chair in accordance with the present invention. 
     FIG. 3 is a side view, partly sectioned, of the chair in accordance with the present invention. 
     FIG. 4 is a top view, partly sectioned, of the chair in accordance with the present invention. 
     FIG. 5 is a perspective view, partly exploded, of a conventional chair. 
     FIG. 6 is a perspective view of the conventional chair. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, a chair in accordance with the present invention generally comprises a backrest  1 , a seat  2 , a chassis  3 , a leg assembly  4 , a support frame  5 , and a plurality of connecting blocks  6 . The backrest  1  includes a plurality of engaging posts  11  on a rear side thereof, each engaging post  11  having a groove  12  in a central portion thereof into which an insertion portion  62  of a respective connecting block  6  is inserted. A spacing member  13  is mounted in the groove  12  of the respective engaging post  11 , and a transverse fixing hole  14  extends in a transverse direction of the respective engaging post  11 . Preferably, the engaging posts  11  are provided on a peripheral portion of the rear side of the backrest  1 . 
     The support frame  5  is mounted to the peripheral portion of the rear side of the backrest  1 . In this embodiment, the support frame  5  is a substantially inverted U-shaped member having two substantially L-shaped limbs. A connecting beam  51  is fixed by, e.g., soldering to a lower portion of the support frame  5 . The connecting beam  51  includes an engaging portion  52  (in the form of an extension plate extending from a central portion of the connecting beam  51  in this embodiment) for connection with a rear end of he chassis  3 . The support frame  5  further includes a fixing hole  53  in each of two sides thereof. 
     Each connecting block  6  includes a sleeve portion  61  in an end thereof and an insertion portion  62  on the other end thereof. In this embodiment, the sleeve portion  61  is a substantially C-shaped member with a gap or slit  612  defined between two adjacent ends of the C-shaped member. The C-shaped member has a longitudinal through-hole  611  through which the support frame  5  extends. The insertion portion  62  includes two insertion plates  620  respectively projecting radially outward from the two ends of the C-shaped member and having aligned holes  621 . The insertion portion  62  is inserted into the groove  12  of the respective engaging post  11 , and a fastener  140  (e.g., a self-tapping screw) is extended through the fixing hole  14  of the respective engaging post  11 , the holes  621  of the insertion plates  620 , and a hole  130  in the respective spacing member  13 , best shown in FIG.  3 . It is noted that the insertion plates  620  are located on two sides of the spacing member  13 . Each connecting block  6  on the two sides of the backrest  1  includes a transverse hole  63 . After connection with the support frame  5 , a respective fastener  630  is extended through the respective transverse hole  63  and the respective fixing hole  53  of the support frame  5 . 
     Referring to FIGS. 1 through 4, in assembly, the slit  612  of the respective connecting block  6  allows expansion of the respective connecting block  6  so as to be mounted around the support frame  5 . Further, the insertion portion  62  of the respective connecting block  6  is engaged with the respective engaging post  11 . Thus, the support frame  5  would not be loosened, as the upper end and the sides of the support frame  5  are engaged with the connecting blocks  6 . The lower portion of the support frame  5  is fixed to the chassis  3  via the connecting beam  51 . Thus, the lying force exerted by the user to the backrest  1  is supported by the loop-like support frame  5 . The support stability and safety are both improved. 
     It is noted that engaging posts or protrusions (not shown) can be directly formed on the rear side of the support frame  5  for engaging with the engaging posts  11 . In this case, the engaging blocks  6  can be omitted. 
     Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.