Abstract:
A chair includes a seat mounted on a seat base, a backrest disposed rearwardly of the seat base, a footrest disposed frontwardly of the seat base, and a linkage unit interconnecting the footrest and the seat. The linkage unit includes a plurality pair of crank arms provided with at least one arm spacer therebetween as such the crank arms thereof do not clamp a user&#39;s finger when the crank arms are folded.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a chair, more particularly to a chair with an extendible footrest. 
     2. Description of the Related Art 
     A conventional chair includes a seat base, a seat disposed above the seat base, a footrest disposed frontwardly of the seat, a backrest disposed rearwardly of and pivoted to a rear end of the seat, and a linkage unit interconnecting the footrest and the seat. The linkage unit includes at least two pairs of pivotally connected crank arms which are movable between extended and retracted positions relative to the seat. 
     One disadvantage of the aforementioned conventional chair resides in that the crank arms of the linkage unit may accidentally clamp a user&#39;s finger when the crank arms are disposed at the retracted position. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of this invention is to provide a chair having a linkage unit that interconnects a seat and a footrest and that has a plurality. of crank arms provided with an arm spacer therebetween such that the crank arms will not clamp the user&#39;s finger when the crank arms are disposed at a retracted position. 
     Accordingly, a chair of the present invention includes: a seat base; a seat mounted on the seat base, extending in longitudinal direction, and having left and right sides, front and rear ends, and a bottom; a backrest disposed rearwardly of and connected to the seat; a footrest disposed frontwardly of the seat; and a linkage mounting unit including left and right brackets fixed to the bottom of the seat and extending in the longitudinal direction. Each of the left and right brackets has opposite front and rear ends. A shaft is mounted rotatably on the rear ends of the brackets, and extends in a transverse direction relative to the longitudinal direction. An operating lever is secured to the shaft for turning the shaft. The chair further includes a linkage unit and an arm spacer. The linkage unit interconnects the seat and the footrest, and includes a pair of crank mechanisms disposed at the left and right sides of the seat, respectively. Each of the crank mechanisms includes a first crank arm having a rear end pivoted to the front end of a respective one of the brackets  21  and a front end opposite to the rear end thereof, a second crank arm having a front end pivoted to the footrest and a rear end pivoted to the front end of the first crank arm, a third crank arm fixed to and extending transversely from the shaft and having a pivot end distal from the shaft, and a fourth crank arm having opposite front and rear ends respectively pivoted to the footrest and the pivot end of the third crank arm such that rotation of the shaft via actuation of the operating lever results in turning of the third crank arm via the shaft, thereby permitting extension and retraction of the linkage unit relative to the seat between folding and extended positions. The first and second crank arms are spaced apart from and are generally parallel to the third and fourth crank arms. The arm spacer has a fixed end fixed to one of the first and fourth crank arms, and a pivot end that extends from the fixed end and that is pivoted to the other one of the first and fourth crank arms so that the first crank arm and the second crank arm cooperatively define a first gap in the longitudinal direction therebetween, and that the third crank arm and the fourth crank arm cooperatively define a second gap in the longitudinal direction therebetween when the linkage unit is positioned at the folding position, thereby preventing clamping of a user&#39;s finger when the linkage unit is moved from the extended position to the folding position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of this invention will become more apparent in the following detailed description of the preferred embodiment of this invention, with reference to the accompanying drawing, in which: 
     FIG. 1 is a schematic side view of a preferred embodiment of a chair according to the present invention, illustrating a linkage unit at a retracted position relative to a seat; 
     FIG. 2 is a schematic side view of the preferred embodiment, illustrating the linkage unit at an extended position relative to the seat; 
     FIG. 3 is a fragmentary and enlarged side view of the preferred embodiment shown in FIG. 1; 
     FIG. 4 is a fragmentary and enlarged bottom view of the preferred embodiment, illustrating how first and fourth crank arms employed therein are spaced apart from each other; 
     FIG. 5 is a schematic side view of the preferred embodiment, illustrating the state of a backrest relative to the seat prior to adjustment; and 
     FIG. 6 is a schematic side view of the preferred embodiment, illustrating the state of the backrest relative to the seat after an inclination adjustment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 to  3 , the preferred embodiment of a chair according to the present invention is shown to include a seat base  10 , a slidable seat  11 , a backrest  12 , a footrest  13 , a linkage mounting unit, a linkage unit  2 , and an arm spacer  235 . 
     As illustrated, the seat  11  is mounted on the seat base  10 , extends in a longitudinal direction, and has left and right sides, front and rear ends  110 ,  111 , and a bottom. 
     The backrest  12  is disposed rearwardly of the seat  11 , and has a lower end connected pivotally to the rear end  111  of the seat  11  about a horizontal pivot  109 . 
     The footrest  13  is disposed frontwardly of the seat  11 . 
     The linkage mounting unit includes left and right brackets  21  fixed to the bottom of the seat  11 , and extending in the longitudinal direction. Each of the brackets  21  has opposite front and rear ends  211 ,  212 . A shaft  22  is mounted rotatably on the rear ends  212  of the brackets  21 , and extends in a transverse direction relative to the longitudinal direction. An operating lever  291  is secured to the shaft  22  for turning the shaft  22 . 
     The linkage unit  2  interconnects the seat  11  and the footrest  13 , and includes a pair of crank mechanisms  23  disposed at the left and right sides of the seat  11 , respectively. Each of the crank mechanisms  23  includes a first crank arm  231 , a second crank arm  232 , a third crank arm  233 , and a fourth crank arm  234 . The first crank arm  231  has a rear end  271  pivoted to the front end  211  of a respective one of the brackets  21 , and a front end  273  opposite to the rear end  271 . The second crank arm  232  has a front end pivoted to the footrest  13  and a rear end  281  pivoted to the front end  273  of the first crank arm  231 . The third crank arm  233  is fixed to and extends transversely from the shaft  22 , and has a pivot end distal from the shaft  22 . The fourth crank arm  234  has opposite front and rear ends  264 ,  261  respectively pivoted to the footrest  13  and the pivot end of the third crank arm  233 . As such, rotation of the shaft  22  via actuation of the operating lever  291  results in turning of the third crank arm  233  via the shaft  22 , thereby permitting extension and retraction of the linkage unit  2  relative to the seat  11  between folding and extended positions, as best shown in FIGS. 1 and 2, respectively. At the folding and extended positions, the first and second crank arms  231 ,  232  are spaced apart from and are generally parallel to the third and fourth crank arms  233 ,  234 . 
     The arm spacer  235  has a fixed end  235 F (see FIG. 4) fixed to the fourth crank arm  234  and a pivot end  235 P that extends from the fixed end  235 F and that is pivoted to the first crank arm  231  such that the first crank arm  231  and the second crank arm  232  cooperatively define a first gap  25  in the longitudinal direction therebetween, and that the third crank arm  233  and the fourth crank arm  234  cooperatively define a second gap  24  in the longitudinal direction therebetween when the linkage unit  2  is positioned at the folding position, as best shown in FIG. 3, thereby preventing clamping of a user&#39;s finger when the linkage unit  2  is moved from the extended position of FIG. 2 to the folding position of FIGS. 1 and 3. 
     Referring to FIG. 4, the first crank arm  231  has an intermediate straight portion  272 . The front and rear ends  273 ,  271  of the first crank arm  231  are bent relative to the intermediate straight portion  272 . The second crank arm  232  has an intermediate straight portion  282 . The rear end  281  of the second crank arm  232  is bent relative to the intermediate straight portion  282  so as to define the first gap  25  between the intermediate straight portions  272 ,  282  of the first and second crank arms  231 ,  232  when the linkage unit  2  is positioned at the folding position. The fourth crank arm  234  has a front straight portion  263 . The rear end  261  of the fourth crank arm  234  is L-shaped and bent relative to the front straight portion  263  so as to define the second gap  24  between the front straight portion  263  of the fourth crank arm  234  and the third crank arm  233  when the linkage unit  2  is positioned at the folding position. 
     Referring to FIGS. 5 and 6, the seat base  10  includes a circular foundation  101  disposed on a floor surface, an upright post  102  rotatably mounted on the foundation  101 , and a seat mounting unit  104  fixed onto the post  102  for co-rotation therewith relative to the foundation  101 . The seat mounting unit  104  includes left and right tubular frame parts  103  fixed onto the post  102  via two fixing elements  108 , and left and right L-shaped frame parts  105 . Each of the L-shaped frame parts  105  includes a horizontal portion  106  that is secured to a respective one of the tubular frame parts  103 , and a vertical portion  107  that extends from the horizontal portion  106  and that is pivoted to the backrest  12  above the horizontal pivot  109 . The invention further includes an angle adjusting unit  3  which includes a transverse rod  34 , left and right L-shaped slide rods  33 , and a fastener knob  35 . The transverse rod  34  is fixed to the left and right tubular frame parts  103 , extends in the transverse direction, and is formed with two slide holes. The left and right L-shaped slide rods  33  are secured to the bottom of the seat  11 . Each of the left and right L-shaped slide rods  33  has a short rod section  331  that is secured to the bottom of the seat  11  and that is disposed rearwardly of the transverse rod  34 , and a long rod section  332  that extends frontwardly and upwardly from the short rod section  331  through a respective one of the slide holes in the transverse. rod  34 . As such, pivotal action of the backrest  12  relative to the seat  11  results in frontward and rearward movement of the slide rods  33  together with the seat  11  relative to the transverse rod  34 . The fastener knob  35  is mounted threadedly on the transverse rod  34 , and is movable between a locking position, in which the fastener knob  35  moves toward and abuts against a respective one of the slide rods  33 , thereby immobilizing the seat  11  relative to the seat base  10 , and an unlocking position, in which the fastener knob  35  moves away and disengages from the respective one of the slide rods  33 , thereby permitting synchronous movement of the backrest  12  and the seat  11  relative to the seat base  10 . 
     With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that the invention be limited only as indicated in the appended claims.