Patent Publication Number: US-6220664-B1

Title: Base structure for chair seat

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a base structure for a chair seat that allows rapid adjustment in the inclination angle of the backrest relative to the chair seat as well as rapid adjustment of distance between the backrest and the chair seat. 
     2. Description of the Related Art 
     A chair is often provided with an adjusting device for adjusting the inclination angle of the backrest relative to the seat, yet the adjustment is limited. Namely, the backrest can only be adjusted to two or three different inclined positions relative to the seat. In addition, the distance between the seat and the backrest is also not adjustable. The present invention is intended to provide an improved base structure for a chair seat that mitigates and/or obviates the above problems. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide an improved base structure for a chair seat that allows rapid adjustment in the inclination angle of the backrest relative to the chair seat as well as rapid adjustment of distance between the backrest and the chair seat. 
     In accordance with a first aspect of the invention, a base structure for a chair seat comprises: 
     a base adapted to be mounted to an underside of the chair seat, the base including two lateral walls, the lateral walls including aligned vertical slots, a first pin being slidably extended through the aligned vertical slots, one of the lateral walls including a vertical retaining means consisting of a plurality of vertical retaining positions, the other of the lateral walls including a guiding slot in alignment with the retaining means; 
     a swivel seat including a first end pivotally mounted between the lateral walls of the base by a second pin and a second end, the swivel seat being adapted to connect with an end of a backrest to pivot therewith; 
     an elastic member pivotally mounted to the swivel seat, the elastic member including a first end engaging the second pin and a second end engaging the first pin; and 
     an adjusting rod having a first operative end and a second end extended through the second end of the swivel seat and the lateral walls of the base, the second end of the adjusting rod being releasably engaged with one of the vertical retaining positions, thereby allowing adjustment of an inclination angle of the backrest relative to the seat. 
     The vertical retaining positions of the vertical retaining means are formed by a plurality of consecutively connected holes. 
     The swivel seat includes a horizontal retaining means consisting of a plurality of horizontal retaining positions, and the end of the backrest is connected to the swivel seat by a fastener, wherein the fastener is releasably engaged with one of the horizontal retaining positions, thereby allowing adjustment of horizontal position of the backrest relative to the seat. The horizontal retaining positions of the horizontal retaining means are formed by a plurality of consecutively connected holes. The fastener includes an enlarged head with a diameter greater than that of the holes of the horizontal retaining means, the fastener further including a shank extended from the enlarged head and having a diameter smaller than that of the holes of the horizontal retaining means. The fastener further includes a distal threaded end, and further includes a nut with a screw hole for engaging with the distal threaded end of the fastener, thereby preventing disengagement of the fastener. 
     In accordance with a second aspect of the invention, a base structure for a chair seat comprises: 
     a base adapted to be mounted to an underside of the chair seat, the base including two lateral walls, the lateral walls including aligned first vertical slots, a first pin being slidably extended through the aligned first vertical slots, one of the lateral walls including a vertical retaining means consisting of a plurality of vertical retaining positions, the other of the lateral walls including a guiding slot in alignment with the retaining means; 
     a swivel seat including a first end pivotally mounted between the lateral walls of the base by a second pin and a second end, the swivel seat further including a second vertical slot through which the first pin is slidably extended, the swivel seat being adapted to connect with an end of a backrest to pivot therewith, the swivel seat including a horizontal retaining means consisting of a plurality of horizontal retaining positions, the end of the backrest being connected to the swivel seat by a fastener, the fastener being releasably engaged with one of the horizontal retaining positions, thereby allowing adjustment of the horizontal position of the backrest relative to the seat; 
     an elastic member including a coil portion pivotally mounted in the swivel seat by a third pin, the elastic member including a first end engaging the second pin and a second engaging the first pin; and 
     an adjusting rod having a first operative end and a second end extended through the second end of the swivel seat and the lateral walls of the base, the second end of the adjusting rod being releasably engaged with one of the vertical retaining positions, thereby allowing adjustment of an inclination angle of the backrest relative to the seat. 
     In accordance with a third aspect of the invention, a base structure for a chair seat comprises: 
     a base adapted to be mounted to an underside of the chair seat; and 
     a swivel seat connected to the base, the swivel seat including a horizontal retaining means consisting of a plurality of horizontal retaining positions, an end of the backrest being connected to the swivel seat by a fastener, the fastener being releasably engaged with one of the horizontal retaining positions, thereby allowing adjustment of horizontal position of the backrest relative to the seat. 
    
    
     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 of a chair seat base structure in accordance with the present invention; 
     FIG. 2 is an exploded perspective view of the chair seat base structure in accordance with the present invention; 
     FIG. 3 is a rear view of the chair seat base structure in accordance with the present invention; 
     FIG. 4 is a view similar to FIG. 3, illustrating a first step for adjustment in the inclination angle of the backrest; 
     FIG. 5 is a partially sectioned side view of the chair seat base structure in accordance with the present invention; 
     FIG. 6 is a side view of the chair seat base structure in accordance with the present invention, illustrating adjustment in the inclination angle of the backrest; 
     FIG. 7 is a left side view of the chair seat base structure in accordance with the present invention; 
     FIG. 7 a  is an enlarged view of a circle in FIG. 7; and 
     FIG. 8 is a side view of the chair seat base structure in accordance with the present invention, illustrating adjustment in the position of the backrest. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, a chair seat base structure in accordance with the present invention generally includes a substantially U-shape base  10  mounted to an underside of a chair seat (FIG. 5, not labeled) and having two lateral walls  18  extended from a top wall  19 , thereby defining a compartment  17  therebetween. The lateral walls  18  include aligned first holes  11  and aligned second holes  12 . The lateral walls  18  further including aligned vertical slots  13  and  14 . In addition, one of the lateral walls  18  includes a retaining section  15  in the form of a retaining slot  151  consisting of a plurality of consecutively connected retaining holes. 
     The other lateral wall  18  includes an adjusting section  16  in the form of a guiding slot  161 . 
     The base structure further includes a substantially U-shape swivel seat  20  received in the compartment  17  of the base  10 . The swivel seat  20  includes two lateral walls  26  that have aligned pivotal holes  21 , aligned slots  22 , and aligned holes  23 . A bottom wall of the swivel seat  20  includes a retaining slot  24  consisting of a plurality of consecutively connected retaining holes  241 . 
     A fastener  25  includes an enlarged conic head  251 , a shank  252  extended from the enlarged head  251 , and a distal threaded end  254 . The shank  252  is connected to a connecting end of a backrest  80  (FIG. 5) to move therewith. The shank  252  has a diameter smaller than the inner diameter of each retaining hole  241 . The enlarged head  251  has a diameter that is greater than the inner diameter of each retaining hole  241 . In addition, the enlarged head  251  includes a notched section  253  for releasably engaging with an associated retaining hole  241  to thereby retain the backrest  80  in a desired horizontal position relative to the seat  90  (FIG.  5 ). A nut  255  with a screw hole  2551  is engaged with the distal threaded end  254  of the fastener  25  to prevent disengagement of the fastener  25 . 
     An elastic member  30  is mounted in the swivel seat  20  and includes a coil portion  31  with a longitudinal hole (not labeled) that aligns with the holes  21  of the swivel seat  20 . A pin  50  is extended through the holes  12  of the base  10 , the holes  21  of the swivel seat  20 , and the longitudinal hole of the coil portion  31  and then retained in place by a C-clip  51 . The elastic member  30  further includes a first end with a hook  32  and a second end  33 . The hook  32  of the elastic member  30  is engaged with a pin  40  that is extended through the aligned holes  11  of the base  10  and retained in place by a C-clip  41 . The second end  33  of the elastic member  30  bears against a pin  60  that is extended through aligned slots  13  and  14  of the base  10  and the aligned slots  22  of the swivel seat  20  and retained in place by a C-clip  63 . Washers  61  and  62  are provided to outer surfaces of the lateral walls  18  of the base  10 , respectively. An adjusting rod  70  is extended through the aligned holes  23  of the swivel seat  20  and the guiding slot  161  as well as the retaining slot  151 . An end of the adjusting rod  70  is provided with an operative handle  71  for manual operation. The other end of the adjusting rod  70  is retained in one of the retaining holes of the retaining slot  151  and thus cannot be moved in the vertical direction. 
     FIG. 3 is a rear view of the base structure of the present invention. When adjustment of inclination angle of the backrest  80  relative to the seat is required, the adjusting rod  70  is pulled outward such that the other end of the adjusting rod  70  disengages from the retaining slot  151 , as shown in FIG.  4 . Then, the adjusting rod  70  is pushed downward and thus exerts a downward force to cause the swivel seat  20  to pivot about the pin  50 . Provision of the slots  13 ,  14 , and  22  (preferably arcuate slots) allows such pivotal movement of the swivel seat  20  relative to the pin  50 . As illustrated in FIG. 5, the hook  32  of the elastic member  30  is engaged with the pin  40  and the second end  33  of the elastic member  30  bears against the pin  60 . The swivel seat  20  together with the backrest  80  is pivotable relative to the seat  90 , best shown in FIG.  6 . When the backrest  80  is adjusted to a desired inclination angle relative to the seat  90 , the other end of the adjusting rod  70  is moved back to engage with a new retaining hole of the retaining slot  151 , as shown in FIGS. 7 and 7 a . Thus, the backrest  80  can be rapidly adjusted to the desired inclination angle relative to the seat 
     Referring to FIG. 8, when adjustment of the horizontal position of the backrest  80  relative to the seat  90  is required, the fastener  25  is moved upward such that the notched section  253  disengages from the associated retaining hole  241 . Next, the fastener  25  together with the backrest  80  are moved horizontally relative to the swivel seat  20  until the backrest  80  and the seat  90  have a desired distance therebetween. Then, the fastener  25  is released and thus falls such that the notched section  253  of the enlarged head  251  engages with a new retaining hole  241 . 
     According to the above description, it is appreciated that the chair seat base structure in accordance with the present invention allows rapid adjustment in the inclination angle of the backrest relative to the chair seat as well as rapid adjustment of distance between the backrest and the chair seat. 
     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 spirit and scope of the invention as hiereinafer claimed.