Patent Abstract:
A chair having a swingable chair back with a top pivot includes a frame having laterally spaced first and second uprights. A back having upper and lower ends is attached to the frame. Also attached to the frame adjacent the lower end of the back is a seat. A pivot assembly couples the first and second uprights to the back and permits pivoting of the back about a substantially horizontal pivot axis. The pivot axis projects laterally of the back and is positioned in the vicinity of the upper end of the back. A biasing device cooperates with the back and normally urges the lower portion of the back forwardly away from a rearward position.

Full Description:
RELATIONSHIP TO OTHER APPLICATION 
     This application claims priority from provisional Application Ser. No. 60/287,320, filed Apr. 30, 2001 and entitled CHAIR. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a chair of the type used in offices and the like, and in particular to an improved chair back having limited vertical swinging movement about an axis disposed adjacent the upper edge of the back. 
     BACKGROUND OF THE INVENTION 
     Chairs of the type used in offices and the like are often utilized for permitting a seated occupant to carry out work-intensive tasks adjacent a desk or worksurface, including keyboarding and other tasks which require the person to sit generally upright or even lean forwardly so as to partially overlie a worksurface. When used in this manner, the back of the chair generally loses contact with the occupant&#39;s back, and thus provides no supportive engagement therewith. 
     It is an object of this invention to provide an improved office-type chair wherein the back of the chair has limited vertical swinging movement generally about the upper portion thereof so that when a person using the chair leans forwardly, the back of the chair will be urged forwardly, as by a spring, through at least a limited extent and hence the lower portion of the chair back, such as in the lumbar region, will continue to maintain supportive engagement with at least the lower back of the chair occupant. 
     SUMMARY OF THE INVENTION 
     This invention is directed to a new and useful chair including a frame having laterally spaced first and second rigid uprights. A back is attached to the frame and includes upper and lower ends. Also attached to the frame adjacent to the lower end of the back is a seat. A pivot assembly couples the first and second uprights to the back for permitting pivoting of the back about a substantially horizontal pivot axis that projects laterally of the back and is positioned in the vicinity of the upper end of the back. The pivot assembly includes a spring arrangement that exerts a force on the back a substantial distance below the pivot axis for biasing the back toward a forward position. 
     Other objects and purposes of the invention will be apparent to persons familiar with constructions of this type upon reading the following specification and inspecting the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a chair according to the present invention shown positioned adjacent a conventional desk. 
     FIG. 2 is a side view of the chair shown in FIG.  1 . 
     FIG. 3 is a further perspective view taken generally from the rear of the chair shown in FIG.  1 . 
     FIG. 4 is a perspective view which illustrates solely the back frame for the chair back of this invention and its connection to the rear inner shell of the chair back. 
     FIG. 5 is a back elevational view of the construction illustrated in FIG.  4 . 
     FIG. 6 is a side elevational view of the arrangement shown in FIGS. 4 and 5. 
     FIG. 7 is a side elevational view showing in cross sectional view the chair arm and its connection to the upright associated with the back frame, and specifically showing in solid lines the chair arm in both its uppermost and lowermost height adjusted positions. 
     FIG. 8 is a top view of the arrangement shown in FIG.  7  and showing both positions of the chair arm in solid lines. 
     FIG. 9 is a rear elevational view of the arrangement shown in FIGS. 7-8 and again showing both elevational positions of the chair arm in solid lines. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1-3, there is illustrated a chair  10  according to the present invention. This chair includes a conventional base  11  having legs  12  and a central height-adjustable pedestal  13  projecting upwardly therefrom. The pedestal at its upper end connects to the underside of a generally horizontally enlarged seat arrangement  14 . The seat arrangement  14 , as is generally conventional, includes a generally rigid structural inner shell  15  having a cushion thereover  16 , with the cushion and shell being generally enclosed by a surrounding covering such as a fabric or vinyl covering. 
     A back frame structure  21  joins to the underside of the seat structure  14  and projects upwardly for supportive engagement with a back arrangement  22  which projects upwardly from the seat arrangement  14  in the vicinity of the rear edge thereof. This back arrangement  22 , in the illustrated embodiment of the invention, has chair arms  61  associated therewith, which chair arms are cantilevered forwardly from the back frame arrangement  21  and are mounted for height adjustment with respect thereto. 
     The back arrangement  22  includes an inner structural back member or shell  23  typically constructed of wood or rigid plastic, and this inner shell is appropriately covered on a front side thereof with a cushion  24  such as of plastic foam, and the inner shell and foam cushion are appropriately enclosed within an outer covering of fabric, vinyl or the like. The rear of the back arrangement is typically closed by a rear cover or shell  27  which overlies the inner structural shell and is secured thereto. The general construction of the back arrangement  22 , like the seat arrangement, is conventional. 
     The back frame arrangement  21  as illustrated in FIGS. 4-6 includes a pair of generally upright frame members  31  which are substantially identical except for being mirror images of one another so as to be disposed adjacent the right and left sides of the chair back. Each upright frame member  31  includes a main elongate center part  32  which extends generally vertical and which at a lower end joins to a curved portion  33  which projects forwardly so as to terminate at a lower free end part  34 . The lower free end parts  34  of the upright frame members  31  are rigidly joined by a cross strap or plate  35 , the latter in turn being fixedly secured to the underside of the structural shell  15  associated with the seat arrangement  14 . The upright frame members  31 , at the upper ends thereof, are also provided with curved portions  36  which form an upper leg which projects toward and terminates in a free end  37  disposed adjacent the rear surface  28  of the inner back shell  23  in the vicinity of the upper edge  45  thereof. 
     The pair of sidewardly-spaced upright frame members  31 , at their upper ends, are rigidly joined by a top cross rod or bar  38  which has the free ends thereof non-rotatably and fixedly joined to the upper free end parts  37  of the side frame members  31 . This cross bar  38 , extending inwardly from the free ends thereof, has generally aligned and substantially horizontally extending rod portions  41  which project inwardly from the side frame members toward the center of the back shell. These horizontal rod members  41  are bent through about 90° angles and joined to a generally U-shaped center rod portion  42 . This center rod portion  42  includes side legs  43  which project generally vertically downwardly adjacent the rear surface of the back shell  23 , and these side legs  43  join through generally right angle bends to a bottom cross rod  44  which extends generally horizontally. The cross bar  38  and its rigid securement between the upper ends of the spaced side frame members  31 , and the bottom strap  35  and its rigid securement between the lower ends of the side frame members  31 , thus define a rigid frame assembly which is of a generally closed endless configuration, and provides a connection to support the back arrangement  22  from the seat arrangement  14  as described hereinafter. 
     To connect the back arrangement  15  to the frame arrangement, the back shell  23  fixedly mounts thereon, in the vicinity of the upper corners thereof, a pair of sidewardly spaced journals or bearings  46  which are fixed to and project outwardly from the rear surface  28  of the back shell  23 . This pair of spaced journals  46  define aligned openings  47  therein in which are snugly but rotatably accommodated the horizontal rod parts  41  of the cross bar  38 . This connection of the horizontal rod parts within the journals secured to the back shell thus couples the back shell  23 , and hence the back arrangement  22 , to the frame assembly  21  while permitting relative pivoting of the back arrangement  22  about the longitudinally extending horizontal axis  48  defined by the horizontal rod parts  44 . 
     To control and limit the amount of pivoting movement of the back arrangement  22  relative to the back frame assembly  21  about the pivot axis, the back assembly  22  has a restraining member  51  fixedly secured to and projecting rearwardly from the rear surface of the back shell  23  at an elevation which is spaced downwardly a substantial distance below the horizontal pivot axis  48 . This restraining member  51  in the illustrated arrangement is formed generally as a horizontally elongate strap which is fixedly secured to the back shell  23 , and the strap has a pair of control parts  52  in sidewardly spaced relationship therealong. These control parts  52  are formed generally as U-shaped parts, or yokes, and effectively extend around and provide control over the vertical rod portions  43 . More specifically, each of the control yokes  52  has generally parallel side legs  53  which are spaced apart so as to permit the side rods  43  to move lengthwise of the control yoke until restricted by the closed end  54  of the yoke which is spaced from the rear surface  28  of the seat shell  23  and functions as a stop. These control yokes  51  thus permit the back shell  23  to pivot about the horizontal pivot axis  48  through a limited extent as permitted by the vertical rods  43  abutting the ends of the yokes  52  as a forward limit position, and by the shell  23  swinging rearwardly into a rearwardmost position in which it effectively abuts the U-shaped center rod part  42 . The forward and rearward positions are diagrammatically indicated in FIG.  6 . 
     The back arrangement  22  is normally maintained in its forwardmost position by the urging of a spring arrangement  56  which, in the illustrated embodiment, comprises two coil-type torsion springs  57  which surround the horizontal center rod part  44  and have one leg  58  thereof anchored to the rod, with the other leg  59  of each torsion type coil spring being in abutting engagement with the rear surface of the back shell  23 . The legs  59  of the torsion springs which project inwardly for contact with the back shell  23  are, in the preferred embodiment, joined together to define a generally U-shaped configuration which bears against the rear surface of the seat shell at a location disposed in the vicinity of the horizontal rod part  44  and hence vertically approximately at the middle of the back shell. The contact of the spring against the seat shell is thus spaced a substantial distance downwardly from the pivot axis  48  and hence, acting through the long lever arm defined between the pivot axis and the spring, urges the seat shell  23  forwardly into the forward position as limited by the vertical rods  43  contacting the stop parts  54  defined at the ends of the control yokes  52 . 
     When the chair of this invention is not occupied, the spring  56  will normally urge the back arrangement  22  forwardly (counter-clockwise in FIG. 6) about axis  48  into the forwardmost position for the back. When the chair is occupied, however, and the occupant leans against the back in the normal manner, the force imposed on the back  22  by the occupant will overcome the spring force and the back will swing back (clockwise) into its rearwardmost position wherein the back shell  23  abuts the U-shaped rod part  42  and thus defines a generally solid or rigid back assembly. 
     However, if the occupant leans forwardly and relieves the force against the back  22 , such as when carrying out an intensive task on a table, such as a keyboarding function, then the back of the occupant will partially move away from the back and relieve the load on the back. At the same time, however, the spring  56  acting against the back shell  23  causes the lower portion of the back  22  to pivot forwardly about the top hinge axis  48 , and thus the lower portion of the back  22  will be disposed so as to continue to maintain supportive engagement with at least the lower portion of the occupant&#39;s back, particularly in the lumbar area. 
     Since the torsion springs  57  and their reaction against the rear surface of the back shell  23  occurs at a point which is spaced downwardly a substantial distance below the hinge axis  48 , the springs  57  acting through the large lever arm created by this spacing thus results in creation of a significant mechanical advantage so that a rather significant moment can be applied to the back  22  about the pivot axis  48 , even though the individual torsion springs themselves are small, and thus a significant force urging the lower portion of the back  22  forwardly can be achieved so as to continue to maintain partial supportive contact with the lower region of the occupant&#39;s back. 
     At the same time, however, the overall mechanism including the cross bar  38  as well as the restraining member  51  and springs  57  is small and compact, and can be easily enclosed in a small space defined between the inner structural back shell  23  and the outer rear cover  27 . The uprights  31 , however, and specifically the elongate upright parts  32  are positioned exteriorly of the back arrangement 22 and connect thereto only adjacent the upper corners thereof. 
     Considering now the construction and operation of the height-adjusting chair arms  61  as associated with the chair of this invention, each height-adjusting chair arm  61  includes an elongate support sleeve  63  which is fixed to and encircles the vertically extending portion  32  of the respective side frame member  31  over a significant extent of the length thereof. This tubular support member  63  has an opening therethrough for snugly receiving therein the elongate straight portion  32  of the side frame member  31 , and the tubular support member  63  is formed in two halves which enable it to be snugly clamped around the side frame member and then secured thereto by screws or similar fasteners which extend through the two halves of the support member as well as the side frame member. 
     The tubular support member  63  has an exterior configuration which is preferably polygonal and is defined by a plurality of flat sides, which exterior polygonal configuration in the preferred embodiment is generally rectangular and more specifically square. 
     The exterior front side wall  64  of the support tube  63  has a toothed or racklike configuration formed thereon throughout the vertical extent thereof, whereby adjacent teeth  65  are vertically separated by a notch or recess  66  which extends transversely (i.e. generally horizontally) with the upper side of this notch merging smoothly into a ramplike surface which slopes outwardly and upwardly to define the tooth. 
     The opposite or rear flat wall  67  of the support tube  63  is generally flat but has a series of transversely (i.e. horizontally) extending notches or recesses  68  formed therein. The series of notches  68  are disposed in vertically spaced relationship along the support tube, with the vertical spacing between adjacent notches  68  generally corresponding to the vertical spacing between adjacent recesses  66  associated with the front wall of the support tube  63 . 
     The upright back frame members  31  are disposed substantially totally exteriorly of the back arrangement  22 , and the elongate vertical uprights  32  associated with the back frame members  31  are disposed so that they are positioned closely adjacent but spaced slightly rearwardly and slightly outwardly from opposite sides of the back arrangement  22 . Each of the elongate vertical upright portions  32  of the back frame elements  31 , specifically those portions having the support tubes  63  secured therearound, support thereon one of the cantilevered arm assemblies  61 . 
     Each cantilevered arm assembly  61  includes a generally horizontally elongate arm member  71  which is mounted on and projects forwardly from the respective support tube  63 , with this arm member in turn having a top cap member  72  fixedly mounted thereon, which top cap member typically incorporates some type of resilient cushioning material enclosed within an appropriate exterior cover, such as is conventional, so that further description thereof is believed unnecessary. 
     The arm member  71  at the rearward end thereof is provided with a sleeve part  73  which has an opening  74  extending vertically therethrough, the cross section of which is noncircular and is sized so as to nonrotatably but vertically axially accommodate therein the respective support tube  63 , as illustrated in FIG.  8 . 
     The sleeve part  73  defines thereon, on the front side of the interior opening  74  adjacent the lower end thereof, a transversely extending rib  75  which projects rearwardly into the interior of the sleeve part and is sized so as to engage a selective one of the recesses  66  defined between the teeth  65  on the front or rack-bearing side of the support tube  63 . 
     The rear side of the opening  74 , in the vicinity of the upper end thereof, has a further rib  76  which extends transversely and projects outwardly in a forward direction so as to terminate in a generally flat outer end. This latter projection  76  is adapted to bear against the rear surface  67  of the support tube  63  in the flat regions between the notches  68 . This rear projection  76  is also disposed vertically upwardly a substantial distance above the front projection  75 , as illustrated by FIG.  7 . 
     The support hub  73  on the arm member  71  also has a small platelike spring  77  which is mounted interiorly thereof and has a cantilevered portion which terminates in a free end part  78  adapted to resiliently engage one of the latching notches  68  formed on the rear wall of the support tube  63 . This spring  77  has the upper end thereof secured over the rear support rib  76  associated with the support hub so that the spring is fixed to and hence carried with the support hub  73 . The spring  77  as it projects downwardly is cantilevered so as to be resiliently urged forwardly for engagement with the rear wall  67  of the support tube  63 . 
     With the height-adjusting arm arrangement of the present invention, the individual arms can each be vertically adjusted in height from an uppermost position as illustrated in FIGS. 7-9 to the lowermost position illustrated therein. This height adjustment range is preferably between about seven inches, with the arm when at the upper limit as illustrated in FIGS. 7-9 typically being at the uppermost height which is conventionally provided for arms associated with office type chairs. Conversely, however, when the arm is in the lowermost position illustrated in FIGS. 7-9, the arm is now disposed so that it is positioned closely adjacent the outer side edges of the seat arrangement  14 , and elevationally is positioned closely adjacent or just slightly above the upper surface of the seat arrangement, whereby in this latter position the arms are at an elevation whereby they are compactly stored directly adjacent the seat arrangement, and thus the chair in its entirety, except for the back arrangement, can be readily stored in a position under even low tabletops or worksurfaces. Further, even when the chair is occupied, the arms can be disposed in this lowermost position whereby they do not interfere with the occupant&#39;s movements if the occupant prefers to have the sides of the chair seat free of obstructions. 
     The operation of the height-adjusting arms is extremely simple since, if the occupant when sitting in the chair grips the arm  71  adjacent the rear end thereof and lifts upwardly, this causes the arm to rock about the bearing rib  76 , thereby causing the locking rib  75  to be withdrawn from engagement with the rack. The operator can then move the arm vertically, either upwardly or downwardly, since the spring  77  will merely function like a releasable detent and effectively “click” upwardly or downwardly along the support tube  63  and hence define the various locking positions. When the arm reaches the desired elevational position, the operator then allows the arm to tilt back downwardly causing the locking rib  75  to engage the respective recess  66  associated with the rack, thereby relocking the arm in the selected position, substantially in the manner illustrated by FIG.  7 . In this locking position, the weight of the arm tending to swing it downwardly (counter-clockwise in FIG. 7) thus effectively maintains the support hub  73  of the arm in locked engagement with the support tube  63 . No additional complex locking mechanisms are required, and in addition no separate levers or trigger mechanisms are required so as to release the arm for height adjustment purposes. 
     Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.

Technology Classification (CPC): 0