Patent Publication Number: US-8113586-B2

Title: Apparatus for adjusting the seat back angle

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for adjusting the seat back angle, and more particularly to an apparatus that ensures a fixed inclination of the seat back and permits a resilient swing of the seat back. Moreover, the tightness thereof is adjustable. 
     2. Description of the Related Art 
     The conventional office chair is ergonomically designed to achieve an optimal sitting comfort. It would be better if the angle of the seat back is adjustable. As shown in  FIG. 1 , a conventional office chair  10  includes primarily a seat portion  11  that is supported by a support base  12 . A seat back  13  is positioned at the rear side thereof. When the operator is tired, he can lean against the seat back for taking a rest. However, an L-shaped bar  14  is interposed between the seat back  13  and the seat portion  11 . Therefore, the position of the seat back  13  stays unchanged, and an inclination for an optimal sitting comfort is not obtained when the operator leans against the seat back for taking a rest. 
       FIG. 2  illustrates another conventional office chair  20  whose structure is the same to the structure in  FIG. 1  except the shape. As shown in  FIGS. 3A and 3B , the office chair  30  has the function of adjusting the angle of the seat back. A retainer  34  is interposed between a seat portion  31  and the support portion  32 . In other words, the retainer  34  is pivotally attached by pivoted bolts  321  to the top  323  of the support portion  32 . Moreover, a spring  322  is positioned at the front end thereof for providing a resilient force when the retainer  34  is inclined backwards. The above-mentioned structure permits a backward inclination of the seat back  33 . However, the seat back  33  and the seat portion  31  create an L-shaped backward inclination. It is not suitable for the operator who wants to lean his back backwards and does not want to raise the seat portion. The retainer  34  has to bear the whole weight when the seat portion is swiveled. Therefore, the entire structure becomes so heavy that the flexibility of the office chair is lost. Besides, the seat portion  31  that is inclined backward will easily lose the center of gravity. Therefore, the operator has to take care of inclination when sitting on the chair. Otherwise, the entire chair can tip over backwards. 
     As shown in  FIG. 4 , an office chair  40  disclosed in U.S. Pat. No. 6,149,236 includes an inclination-adjustment pneumatic spring  43  between a rear support  41  and a seat support  42  for providing a cushioning resilience for the rear support  41 . The above-mentioned pneumatic adjustment structure will be practical when it is upright and used for adjusting the height of the seat support  42  on the shaft portion  44 . However, the resilience and the flexibility to change with the to-and-fro swing of the operator&#39;s body are not optimal when it is applied to the rear support  41 . Therefore, it requires further improvements. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an apparatus for adjusting the seat back angle that combines the locking and unlocking function into one body. When in locked position, the seat back is positioned at a preset inclination angle as required. When in unlocked position, the seat back is resiliently supported. Moreover, the operators may adjust the swing resilience of the seat back  200  according to their own needs for obtaining a greatest sitting comfort. 
     Another object of the invention is to provide an apparatus for adjusting the seat back angle that is mechanically made without employing pneumatic or electronic elements, thereby permitting a convenient operation and ensuring a long service life. 
     In order to achieve the above-mentioned objects, an apparatus for adjusting the seat back angle in accordance with the invention includes: 
     a) a rotating sleeve having an opening at the front end thereof such that a cavity is created, a threaded hole being positioned in axial direction at the center of the bottom of the cavity; 
     b) an L-shaped connection body having a threaded rod at the lateral side thereof, the threaded rod being screwed into the threaded hole of the rotating sleeve, the threaded rod of the connection body having a through hole extended in axial direction, the L-shaped connection body having a first pivoted portion at the longitudinal side thereof, a longitudinal hole extending to the through hole being formed in the connection portion between the longitudinal side of the connection body and the threaded rod; 
     c) a large spring having a tail portion fitting into the cavity of the rotating sleeve; 
     d) a shift shaft having a second pivoted portion at the front end thereof, the second pivoted portion having a pivotal hole, a first stem having a smaller external diameter being positioned at the internal side of the second pivoted portion, a second stem having a still smaller diameter being disposed at the internal side of the first stem and fitting into the through hole of the threaded rod, an end stop having an external diameter greater than the through hole being formed at a connection area between the first stem and the second stem, the tail of the shift shaft passing through the large spring and the through hole first whereupon a positioning element at the end of the shift shaft is employed to fix the shift shaft within the connection body in such a manner that the shift shaft is axially movable and the large spring is confined between the second pivoted portion and the cavity, the second stem being provided with a plurality of pin holes corresponding to the longitudinal hole of the connection body; and 
     e) a locking device mounted on the longitudinal hole of the L-shaped connection body, an insertion pin at the front end of the locking device fitting in the longitudinal hole and being extended into a prearranged pin hole of the second stem such that the shift shaft is locked in an unmovable state, the locking device further having a control lever; 
     wherein, when the insertion pin is removed with the control lever, the shift shaft is unlocked in an axially movable state, and wherein the compression state of the large spring is adjustable by a to-and-fro rotation of the rotating sleeve on the threaded rod, thereby achieving a practical control of the telescopic tightness of the shift shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accomplishment of this and other objects of the invention will become apparent from the following descriptions and its accompanying figures of which: 
         FIG. 1  is a perspective view of a conventional office chair; 
         FIG. 2  is a perspective view of another conventional office chair; 
         FIG. 3A  is a side view of a conventional angle-adjustable office chair; 
         FIG. 3B  is a perspective view of partial components in  FIG. 3A ; 
         FIG. 4  is a schematic drawing of the structure according to U.S. Pat. No. 6,149,236; 
         FIG. 5  is an exploded perspective view of an apparatus for adjusting the seat back angle in accordance with the invention; 
         FIG. 6  is an assembly perspective view of an apparatus for adjusting the seat back angle in accordance with the invention; 
         FIG. 7  is a cutaway view of an apparatus for adjusting the seat back angle in accordance with the invention in a locked position; 
         FIG. 8  is an enlarged view of the partial structure in  FIG. 7 ; 
         FIG. 9  is a cutaway view of an apparatus for adjusting the seat back angle in accordance with the invention in an unlocked position wherein the large spring has a greater telescopic length L 1 ; 
         FIG. 10  is a cutaway view of an apparatus for adjusting the seat back angle in accordance with the invention in an unlocked position wherein the large spring has a shorter telescopic length L 2 ; and 
         FIG. 11  is an application view of the apparatus for adjusting the seat back angle in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First of all, referring to  FIGS. 5 through 8 , an apparatus in accordance with the invention includes a rotating sleeve  50 , an L-shaped connection body  60 , a shift shaft  70 , a large spring  80 , and a locking device  90 . 
     The rotating sleeve  50  includes an opening at the front end thereof such that a cavity  51  is created. A threaded hole  52  is positioned in axial position at the center of the bottom of the cavity  51 . 
     The L-shaped connection body  60  includes a threaded rod  61  at the lateral side thereof. The threaded rod  61  is screwed into the threaded hole  52  of the rotating sleeve  50 . The threaded rod  61  of the connection body  60  has a through hole  62  extended in axial direction. Moreover, the L-shaped connection body  60  includes a first pivoted portion  63  at the longitudinal side thereof. The first pivoted portion  63  has a pivotal hole  64 . A longitudinal hole  65  extending to the through hole  62  is formed in the connection portion between the longitudinal side of the L-shaped connection body  60  and the threaded rod  61 . 
     The large spring  80  has a tail portion fitting into the cavity  51  of the rotating sleeve  50 . 
     The shift shaft  70  includes a second pivoted portion  71  at the front end thereof. The second pivoted portion  71  has a pivotal hole  711 . A first stem  72  having a smaller external diameter is positioned at the internal side of the second pivoted portion  71 . A second stem  73  having a still smaller diameter is disposed at the internal side of the first stem  72  and fits into the through hole  62  of the threaded rod  61 . An end stop  721  having an external diameter greater than the through hole  62  is formed at a connection area between the first stem  72  and the second stem  73 . The tail of the shift shaft  70  passes through the large spring  80  and the through hole  62  first. Thereafter, a positioning element  75  at the end of the shift shaft  70  is employed to fix the shift shaft  70  within the L-shaped connection body  60  in such a manner that the shift shaft  70  is axially movable and the large spring  80  is confined between the second pivoted portion  71  and the cavity  51 . Moreover, the second stem  73  is provided with a plurality of pin holes  76  corresponding to the longitudinal hole  65  of the L-shaped connection body  60 . 
     The locking device  90  is mounted on the longitudinal hole  65  of the L-shaped connection body  60 . An insertion pin  951  at the front end of the locking device  90  fits in the longitudinal hole  65  and is extended into a prearranged pin hole  76  of the second stem  73  such that the shift shaft  70  is locked in an unmovable state. The locking device  90  includes a control lever  98 . When the insertion pin  951  is removed with the control lever  98 , the shift shaft  70  is unlocked in an axially movable state. Moreover, the compression state of the large spring  80  is adjustable by a to-and-fro rotation of the rotating sleeve  50  on the threaded rod  61 . In this way, a practical control of the telescopic degree of the shift shaft  70  is achieved. 
     In addition, a first pad  81  is interposed between the large spring  80  and the bottom of the cavity  51  of the rotating sleeve  50 . A second pad  82  is interposed between the large spring  80  and the internal side of the second pivoted portion  71  of the shift shaft  70 . 
     According to the embodiment, the positioning element  75  at the tail of the shift shaft  70  is a radially installed retaining clip engaged in a groove  74  at the tail of the shift shaft  70 . 
     According to an applicable embodiment, the locking device  90  includes a housing  91 , a middle spring  94 , a telescopic locking element  95 , and a connection element  96 . 
     The housing  91  is hollow and has a connection hole  911  at the end portion thereof. Two positioning pieces  92  are extended from the bottom of the right and left sides of the housing  91 . Moreover, the positioning pieces  92  are provided with through holes  93  in the lateral direction. In alignment to the longitudinal hole  65 , the locking device  90  is mounted by the positioning pieces  92  on the L-shaped connection body  60  and fixed by screws  67  screwed through the through holes  93  into threaded holes  66  of the L-shaped connection body  60 . 
     The middle spring  94  is positioned within the housing  91 . 
     The telescopic locking element  95  includes an insertion pin  951  at the bottom thereof, a hollow plug  952  secured to the insertion pin  951 , a stem  953  disposed within the hollow plug  952 , a small spring  954  mounted on the stem  953 , and two locking elements  955  fixing the small spring within the hollow plug  952  in place. 
     The connection element  96  is secured in the connection hole  911  of the housing  91 . The connection element  96  is connected with a cable line  97 , in which a pullable guide wire  971  is positioned. The front end of the guide wire  971  passes through the housing  91  and is secured to the stem  953 . The free end of the guide wire  971  is attached to a control lever  98  disposed on a chair. The guide wire  971  is controlled by the control lever  98  to impart an axial motion to the telescopic locking element  95 . 
     Based on the above-mentioned structure, the operation and the effect of the invention are described more hereinafter. 
     1. As shown in  FIG. 7 , the apparatus  100  in accordance with the invention is brought in a locked position. In other words, the insertion pin  951  of the locking device  90  is vertically inserted into one of the pin holes  76  of the shift shaft  70  such that a fixed length between the second pivoted portion  71  of the shift shaft  70  and the first pivoted portion  63  of the L-shaped connection body  60  is created. Referring now to  FIG. 11 , the seat back  200  is inclined at a certain angle when the pivoted portions  63 ,  71  are pivotally mounted on the seat portion  300  and the seat back  200 , respectively. 
     2. As shown in  FIG. 9 , the apparatus  100  in accordance with the invention is brought in an unlocked position. In other words, the guide wire  971  is pulled by the control lever  98  of the locking device  90  such that the telescopic locking element  95  is moved upwards. In this way, the insertion pin  951  is removed from the pin hole  76  such that a variable length between the second pivoted portion  71  of the shift shaft  70  and the first pivoted portion  63  of the L-shaped connection body  60  is created. Referring now to  FIG. 11 , the first pivoted portion  63  pivoted at the rear side of the seat portion  300  is made unmovable while the shift shaft  70  is axially movable within the through hole  62  of the L-shaped connection body  60  such that the seat back  200  articulated on the second pivoted portion  71  may change its inclination angle with the to-and-fro swing of the operator&#39;s body at any time, thereby creating a cushioning resilience. The degree of the cushioning resilience is adjustable by the rotating sleeve  50 . As shown in  FIG. 9 , the rotating sleeve  50  is disposed at the leftmost side of the threaded rod  61 . At that time, the large spring  80  have a greatest telescopic length L 1  and the shift shaft  70  has a looser resilience that is suitable for the operators with less weight. The shiftable distance of the shift shaft  70  is the distance D between the end stop  721  of the first stem  72  and an external face  611  of the threaded rod  61 . The end stop may prevent the seat back from a too large inclination. 
     3. As shown in  FIG. 7 , the rotating sleeve  50  may be rotated in such a way that the rotating sleeve  50  is moved outward toward the external side of the threaded rod  61  when the operator has a greater weight. In this way, the large spring  80  is compressed to have a shorter telescopic length L 2 . At that time, the shift shaft  70  has a tighter resilience that is suitable for the operators with greater weight. As a result, the operators may adjust the resilience of the seat back  200  according to their own needs for obtaining a greatest sitting comfort. 
     Therefore, the apparatus for adjusting the seat back angle in accordance with the invention combines the structure having the adjustable positioning effect and the structure having the not-adjustable positioning effect into one body, thereby ensuring a convenient use. Thus, the apparatus for adjusting the seat back angle in accordance with the invention is a practical adjuster. 
     Many changes and modifications in the above-described embodiments of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.