Patent Publication Number: US-7717515-B2

Title: Chair having an automatically adjusting resistance to tilting

Description:
I. CROSS-REFERENCE TO RELATED APPLICATION 
     This application incorporates the contents of the provisional application Ser. No. 60/745,434, filed Apr. 24, 2006, by reference in its entirety. 
     II. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not Applicable. 
     III. BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention generally relates to a device for supporting an occupant in a seated position, and in one preferred embodiment, to a chair of the reclining back type. In a further preferred embodiment, the present invention relates to a chair having a resistance to tilting that automatically adjusts in proportion to the weight of the user and the tilt angle. 
     B. Description of the Related Art 
     Reclining type chairs commonly used in offices typically provide for the back support to recline alone, for the seat and back support to recline as a unit, or for the back support to recline in a coordinated proportion with the seat. If the back support alone pivots, it generally creates a problem known as “shirttail pull.” This problem is particularly acute if the pivot of the chair back support is not coordinated with the natural body action of the occupant. This problem can also be accentuated by the tendency of the hips of the occupant to slide forward as the back support tilts rearwardly. 
     In chairs where both the seat and back recline as a unit, in the reclined position there is a tendency to lift the legs of the occupant from the floor, which creates an undue pressure by the forward edge of the seat against the underside of the legs of the occupant immediately above the knee. To overcome this problem, the pivot point of the reclining action may be moved forward sufficiently to permit the occupant&#39;s feet to remain on the floor. One undesirable effect of this arrangement is that the body angle between the occupant&#39;s torso and his legs is unchanged, and as a result, the occupant&#39;s eye level drops undesirably when the chair is reclined. 
     In any reclining chair, it is desirable that the recline pivot point be at the center of the body or where the occupant&#39;s back normally pivots (i.e., an axis through the user&#39;s hip joints). However, the pivot point of a reclining chair is normally displaced from the ideal pivot point. It is also desirable to have a chair wherein the angle between the occupant&#39;s torso and his legs opens up to relieve internal congestive body pressures. It is further desirable to provide a chair wherein the user&#39;s feet remain on the floor and the recline action parallels the natural body action closely enough to avoid the common shirttail pull problem. 
     Therefore, it is also desirable to provide a chair of simple, economical construction that lends itself to high production manufacturing and fabrication procedures, and yet of clean, pleasing appearance emphasizing the isolated and separate appearance of the seat and back support with respect to the supporting frame and base. 
     U.S. Pat. No. 4,429,917 to Diffrient allegedly reports a chair with a four bar non-parallel linkage mechanism to obviate many of these problems. Likewise, U.S. Pat. No. 4,943,114 to Piretti allegedly reports a chair with a compact backrest linkage mechanism that enables the chair back support and seat to recline. U.S. Pat. No. 5,251,958 to Roericht et al. allegedly reports a chair with a synchronous adjusting device that uses the weight of the user to provide a restoring force to return the chair back support to an upright position after a user has reclined in the chair. U.S. Pat. No. 5,486,035 to Koepke, et al., asserts, without providing any showing, that “[i]n such constructions, the difficulty of reclining the chair, i.e., generating the reclining force, increases the further the chair is reclined, and it is common to employ adjusting apparatus for increasing or decreasing the reclining tension of a chair, such adjusting apparatus changing the tension of a spring, or otherwise modifying the reclining mechanism” (col. 1, 11. 29-34). 
     Moreover, while it is believed that some reclining chairs heretofore available have had a means to adjust their resistance to reclining, such adjustments have been less than ideal, very cumbersome or not practicable to an occupant. Instead, rather than confront the processes necessary to adjust their chairs to fit the needs of their particular body build, most occupants of chairs use them without making any adjustments. Consequently, any ergonomic advantages that might be delivered by the properly tuned chair are not achieved. Thus, there remains a need for a chair that is adjustable to the needs of the individual chair occupant without requiring any substantial effort on the occupant&#39;s part to effect the adjustments—in other words, a substantially self-adjusting ergonomic chair. 
     IV. BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, the present invention provides a chair comprising: a) a base; b) a frame mounted on the base; c) a seat pivotally mounted to a distal end of the frame; d) a back pivot member pivotally mounted to a proximate end of the frame, the back pivot member having a back support extension and a seat lift extension, wherein the seat lift extension lifts a proximate end of the seat when the back pivot member rotates in a rearward direction; and e) a back support mounted to the back support extension of the back pivot member. 
     In another embodiment, the present invention provides a chair wherein the frame comprises at least one rear pivot extension. 
     In one embodiment, the present invention provides a chair wherein the back pivot member further comprises at least one retaining plate, wherein the rear pivot extension is pivotally mounted to the back pivot member by the retaining plate, which brackets an outer edge of the rear pivot extension such that the retaining plate slides along the outer edge of the rear pivot extension as the back pivot member rotates in a rearward direction. 
     In yet another embodiment, the present invention provides a chair wherein the back pivot member further comprises a slider bracket mounted to the back pivot member underneath the seat lift extension, wherein the rear pivot extension comprises a transverse slot in a rearward direction, such that the rear pivot extension pivotally mounts to the back pivot by the slider bracket positioned within the slot and slides within the transverse slot as the back pivot member rotates in a rearward direction. 
     In yet another embodiment, the present invention provides a chair wherein the back pivot member further comprises a rod, and wherein rear pivot extension has a through-hole, the rear pivot extension pivotally mounted to the back pivot member by the rod positioned through the through-hole. 
     In still other embodiments, the present invention provides a chair wherein the rod has a through-bore, and wherein the back pivot member further comprises a washer with diameter greater than the through-hole, the washer positioned outward from the through-hole of the rear pivot extension, a long bolt, and a slot, such that the long bolt may be inserted through the washer, the through-hole of the rear pivot extension, the through-bore of the rod, and engaged with the slot of the back pivot member to pivotally secure the back pivot member to the rear pivot extension of the frame. 
     In other embodiments, the present invention provides a chair wherein the frame further comprises two rear pivot extensions having coaxial through holes. 
     In some embodiments, the present invention provides a chair wherein the back pivot member further comprises a rod, the rear pivot extensions pivotally mounted to the back pivot member by the rod positioned through the coaxial through-holes of the rear pivot extensions. 
     In some embodiments, the present invention provides a chair wherein the seat comprises a pivot clevis mounted to an underside of the seat. 
     In still other embodiments, the present invention provides a chair wherein the frame further comprises at least one front pivot extension. 
     In some embodiments, the present invention provides a chair further comprising two front links, wherein the front pivot extension pivotally mounts to the seat by a first pin connecting the two front links to the pivot clevis and by a second pin connecting the two front links to the front pivot extension. 
     In yet other embodiments, the present invention provides a chair wherein the frame further comprises two front pivot extensions. 
     In some embodiments, the present invention provides a chair wherein the front pivot extensions pivotally mount to the seat by a pin connecting the pivot clevis to the front pivot extensions. 
     In some embodiments, the present invention provides a chair wherein the seat comprises a glide plate mounted to the underneath of the seat such that the seat lift extension lifts a proximate end of the seat by engaging the glider plate when the back pivot member rotates in a rearward direction. 
     In yet other embodiments, the present invention provides a chair wherein the seat lift extension is a glider cam. 
     In some embodiments, the present invention provides a chair wherein the seat lift extension slidably mounts to a railing mounted to an underside of the seat such that seat lift extension slides toward the proximate end of the seat when the back pivot member rotates in a rearward direction. 
     In yet other embodiments, the present invention provides a chair wherein the seat lift extension includes a carriage containing ball bearings, the carriage slidably mounted to the railing located on the underside of the seat. 
     In yet other embodiments, the present invention provides a chair wherein at least one spring engages the seat and the frame. 
     To the accomplishment of the foregoing and related ends, the present invention comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed. 
    
    
     
       V. BRIEF DESCRIPTION OF THE DRAWINGS 
       In consideration of the following detailed description of various embodiments, the invention may be more completely understood in connection with the following drawings. 
         FIG. 1  is a side view of one embodiment of the present invention. 
         FIG. 2(   a ) is a perspective view of one embodiment of a back pivot member of the present invention. 
         FIG. 2(   b ) is a perspective view of one embodiment of a frame of the present invention. 
         FIG. 2(   c ) is a perspective view of one embodiment of a seat of the present invention. 
         FIG. 2(   d ) is a perspective view of an alternate embodiment of a back pivot member of the present invention. 
         FIG. 2(   e ) is a top view of an embodiment of a back pivot member pivotally mounted to a frame of the present invention. 
         FIG. 3  is a side view of an embodiment of the present invention. 
         FIG. 4  is a perspective view of another embodiment of the present invention. 
         FIG. 5(   a ) is a top view of an embodiment of a back pivot member pivotally mounted to a frame of the present invention. 
         FIG. 5(   b ) is an exploded view of an embodiment of a back pivot member pivotally mounted to a frame of the present invention. 
         FIG. 6  is a side view of an embodiment of the present invention. 
         FIG. 7(   a ) is a perspective view of an embodiment of a frame of the present invention. 
         FIG. 7(   b ) is a perspective view of an embodiment of a seat of the present invention. 
         FIG. 8(   a ) is a perspective view of an embodiment of a back pivot member pivotally mounted to a frame of the present invention. 
         FIG. 8(   b ) is a side view of an embodiment of the present invention. 
         FIG. 9(   a ) is a perspective view of another embodiment of a back pivot member pivotally mounted to a frame of the present invention. 
         FIG. 9(   b ) is a side view of another embodiment of the present invention. 
     
    
    
     Although the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     VI. DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS 
     The present invention relates generally to a chair having an automatically adjusting resistance to tilt. As used herein, the term “back support” means any back rest or structure to support the back located on a chair. The term “seat” means any seating cushion, surface or structure to support the weight of an occupant of a chair. 
     Referring to the embodiment shown in  FIGS. 1-3 , a chair featuring a reclining back support comprises base  110 , seat  111 , back pivot member  121 , frame  113 , and back support  112 . Base  110  includes vertical post  120 , which projects upward from the center of base  110 . Base  110  further includes a plurality of legs, a plurality of legs accommodating casters, or any other base known in the art. Vertical post  120  is preferably cylindrical in shape, and may be hollow or solid. Base  110  rests on the floor to support the chair mounted on the distal end of vertical post  120 . 
     Referring still to the embodiment shown in  FIGS. 1-3 , the rearward portion of seat  111  is supported by glide plate  124 , a flat plate connected to the underside of seat  111  to provide a contact surface for seat lift extension  123  of back pivot member  121 . Pivoting clevis  118  extends from the forward portion of seat  111  and pivotally mounts to frame  113  with pin  19  to form a horizontal pivot point for seat  111 . 
     Back pivot member  121  has a back support extension  122  and a seat lift extension  123 , and pivotally mounts to frame  113  with back pivot rod  125  to form a horizontal pivot point for back support  112 . Seat lift extension  123  extends upward from back pivot member  121  such that its distal end is in contact with glide plate  124 . Back support extension  122  extends rearward from back pivot member  121  to receive back support  112  for attachment thereto. 
     Frame  113  preferably comprises a rectangular frame supporting two pairs of frame extensions. Front pivot extensions  114 ,  115  are separated by a distance great enough to receive pivoting clevis  118 , and pin  119  inserts into bores through front pivot extensions  114 ,  115  to pivotally mount seat  111  to frame  113 . Rear pivot extensions  116 ,  117  are separated by a distance great enough to receive back pivot member  121 , and back pivot rod  125  inserts into through-holes through rear pivot extensions  116 ,  117  to pivotally mount back pivot member  121  to frame  113 . As shown in  FIG. 2(   a ), back pivot rod  125  may be an integral part of back pivot member  121 , or as shown in  FIG. 2(   d ), back pivot rod  125  may be a separate component inserted through back pivot member  121  and frame  113  to pivotally mount back pivot member  121  to frame  113 . Also as shown in  FIG. 2(   d ), optional flanges  126 ,  127  on back pivot rod  125  may retain back pivot rod  125  within back pivot member  121  and rear pivot extensions  116 ,  117 . 
     Referring now to the embodiment shown in  FIG. 3 , spring  128  may be connected between frame  113  and seat  111 . Spring  128  can be used to adjust the amount of force required to recline back support  112 . In a similar manner, spring  128  can be used to restore back support  112  to its resting position when the chair is unoccupied. 
     In operation, an occupant of the chair sitting on seat  111  reclines by exerting a rearward force on back support  112 . This rearward force causes back support  112  to move in a rearward direction, which, in turn, causes back pivot member  121  to rotate about back pivot rod  125 . The rotation causes seat lift extension  123  to move in an upward direction, which exerts an upward force on glide plate  124 . Seat  111  then rotates about pin  119  and the rearward portion of seat  111  moves substantially in the vertical direction to incline seat  111 . It is preferred that the inclining of seat  111  to counteract the reclining of back support  112  raises seat  111  between about 0.2 and 2 inches from a substantially horizontal resting position. It is further preferred that the inclining of seat  111  raises seat  111  between about 0.4 and 1 inch from a substantially horizontal resting position. In a particularly useful embodiment, the inclining of seat  111  raises the forward portion of seat  111  about 0.6 inches, and raises the rearward portion of seat  111  about 0.8 inches. 
     As is apparent from the above description, the horizontal pivot point for the reclining of back support  112  is not the chair occupant&#39;s hip joint. Consequently, the reclining of the back support  112  circumscribes an arc that is displaced from the arc based on the chair occupant&#39;s hip joint. However, the concurrent action of the reclining mechanism described herein of raising the rearward portion of seat  111  produces a net positioning of the occupant of the chair that is substantially the same as the positioning which would have been achieved if the center of the arc circumscribed by the reclining of back support  112  recline were coextensive with the arc based upon the chair occupant&#39;s hip joint. 
     Referring now to alternative embodiments of frame  113  and seat  111  shown in  FIGS. 7(   a ) and  7 ( b ), frame  313  comprises instead one front pivot extension  314  having a through bore  315 . Front pivot extension  314  preferably has a width great enough to accommodate pivoting clevis  318  of seat  111 . Pin  319  inserts through bore  315  of front pivot extension  314  to mount frame  313  to front links  329 ,  330 . Pin  331  inserts through pivoting clevis  318  of seat  111  to mount front links  329 ,  330  to pivoting clevis  318 . Pins  319 ,  331  may be capable of rotating or may be fixed in place. If pins  319 ,  331  are fixed, links  329 ,  330  would rotate about the pins  319 ,  331 . Back pivot member  121  may pivotally mount to frame  313  in any manner herein described or known in the art. Likewise, back support  112  may mount to back pivot member  121  and base  110  may mount to frame  313  in any manner herein described or known in the art. 
     Referring now to the embodiment shown in  FIGS. 4-6 , a chair featuring a reclining back support comprises base  110 , seat  111 , back pivot member  221 , frame  213 , and back support  112 . Base  110  and vertical post  120 , operate as described herein with respect to other embodiments, and as is known in the art. 
     Referring still to the embodiment shown in  FIGS. 4-6 , the rearward portion of seat  111  is supported by glide plate  224 , a flat plate connected to the underside of seat  111  which contacts glider cam  223  of back pivot member  221 . Pivoting clevis  118  extends from the forward portion of seat  111  and pivotally mounts to frame  213  with pin  119  to form a horizontal pivot point for seat  111 . 
     Back pivot member  221  includes back pivot rod  225 , back support extension  222  and glider cam  223 , and pivotally mounts to frame  213  with integral back pivot rod  225  to form a horizontal pivot point for back support  112 . Glider cam  223  extends upward as back pivot member  221  pivots about back pivot rod  225  such that glider cam  223  contacts glide plate  224 . Back support extension  222  extends rearward from back pivot member  221  to receive back support  112  for attachment thereto. Back pivot rod  225  may include a through-bore in order to facilitate pivotally securing back pivot member  221  to frame  213 . 
     Frame  213  preferably comprises a rectangular frame supporting rear pivot extension  216 , which may incorporate an integral through-hole, and front pivot extensions  214 ,  215 . Front pivot extensions  214 ,  215  are separated by a distance great enough to receive pivoting clevis  218 , and pin  219  inserts through front pivot extensions  214 ,  215  to pivotally mount seat  111  to frame  213 . Rear pivot extension  216  receives back pivot rod  225  to pivotally mount back pivot member  221  to frame  213 . Washer  226  secures back pivot rod  225  within rear pivot extension  216 . Washer  226  may be a plate having a circumference greater than the through-hole of rear pivot extension  216 , and washer  226  may be secured to a threaded slot (not shown) in back pivot member  221  by long bolt  227 . 
     In operation, an occupant of the chair sitting on seat  111  reclines by exerting a rearward force on back support  112 . This rearward force causes back support  112  to move in a rearward direction, which, in turn, causes back pivot member  221  to rotate about back pivot rod  225 . The rotation causes glider cam  223  to move in an upward direction, which exerts an upward force on glide plate  124 . Seat  111  then rotates about pin  119  and the rearward portion of seat  111  moves substantially in the vertical direction to incline seat  111 . It is preferred that the inclining of seat  111  to counteract the reclining of back support  112  raises seat  111  between about 0.2 and 2 inches from a substantially horizontal resting position. It is further preferred that the inclining of seat  111  raises seat  111  between about 0.4 and 1 inch from a substantially horizontal resting position. In a particularly useful embodiment, the inclining of seat  111  raises the forward portion of seat  111  about 0.6 inches, and raises the rearward portion of seat  111  about 0.8 inches. 
     As is apparent from the above description, the horizontal pivot point for the reclining of back support  112  is not the chair occupant&#39;s hip joint. Consequently, the reclining of the back support  112  circumscribes an arc that is displaced from the arc based on the chair occupant&#39;s hip joint. However, the concurrent action of the reclining mechanism described herein of raising seat  111  produces a net positioning of the occupant of the chair that is substantially the same as the positioning which would have been achieved if the center of the arc circumscribed by the reclining of back support  112  recline were coextensive with the arc based on the chair occupant&#39;s hip joint. 
     Referring now to an alternative embodiment shown in  FIGS. 8(   a ) and  8 ( b ), back pivot member  421  includes back support extension  422 , one or more retaining plates  424 , and seat lift extension  423 . Retaining plate  424  may be an “L” shaped bracket, any type of bracket known in the art could be used, attached to back pivot member  421  and positioned to slide along the inside wall of rear pivot extension  416  such that back pivot member  421  pivotally mounts to frame  413  to form a horizontal pivot point for back support  112 . Seat lift extension  423  extends upward as back pivot member  421  pivots about frame  413  such that seat lift extension  423  contacts glide plate  124 . Back support extension  422  extends rearward from back pivot member  421  to receive back support  112  for attachment thereto. 
     Referring still to  FIGS. 8(   a ) and  8 ( b ), frame  413  preferably comprises a rectangular frame supporting rear pivot extension  416 , which is an integral through-hole, and pivotally mounts to seat  111  in any manner described herein or known in the art. Rear pivot extension  416  receives retaining plate  424  to pivotally mount back pivot member  421  to frame  413 . 
     Alternatively, as shown in the embodiment in  FIGS. 9(   a ) and  9 ( b ), back pivot member  421  may have a central slot  440  through which slider post  441  extends into the cavity defined by rear pivot extension  416 . Slot  440  runs longitudinally along the centerline of rear seat extension  416 , in the direction of the rotation of back pivot member  421 . Sliding bracket  442  is mounted onto slider post  441 . Sliding bracket  442  is positioned within the cavity defined by rear seat extension  416  such that the rear wall of frame  413  is interposed between back pivot member  421  and sliding bracket  442 , and sliding bracket  441  may slide within slot  440  to pivotally mount back pivot member  421  to frame  413 . 
     In operation, an occupant of the chair sitting on seat  111  reclines by exerting a rearward force on back support  112 . This rearward force causes back support  112  to move in a rearward direction, which, in turn, causes back pivot member  421  to rotate about rear seat extension  416 . The rotation causes seat lift extension  423  to move in an upward direction, which exerts an upward force on glide plate  124 . Seat  111  then rotates about pin  119  and the rearward portion of seat  111  moves substantially in the vertical direction to incline seat  111 . It is preferred that the inclining of seat  111  to counteract the reclining of back support  112  raises seat  111  between about 0.2 and 2 inches from a substantially horizontal resting position. It is further preferred that the inclining of seat  111  raises seat  111  between about 0.4 and 1 inch from a substantially horizontal resting position. In a particularly useful embodiment, the inclining of seat  111  raises the forward portion of seat  111  about 0.6 inches, and raises the rearward portion of seat  111  about 0.8 inches. 
     In yet another alternative embodiment (not shown), seat lift extension  423  may be slidably connected to the underside of seat  111 . The slidable connection could be accomplished by using a rail and a ball bearing connection or any means known in the art. The rearward force would cause back support  112  to move in a rearward direction, which, in turn, would cause back pivot member  421  to rotate about rear seat extension  416  of frame  413 . The rotation would cause seat lift extension  423  to slide rearward, which exerts an upward force on seat  111 . As seat lift extension  423  slides rearward, seat  111  then rotates about pin  119  and the rearward portion of seat  111  moves substantially in the vertical direction to incline seat  111 . As would be readily envisioned by one of skill in the art, the various mechanisms described herein are particularly useful in combination for providing functional and attractive chairs. All combinations of the multiple mechanisms described herein are therefore encompassed by the present invention. 
     Preferentially, unless otherwise indicated, the various components of the present invention are constructed generally out of a strong, lightweight material, such as aluminum. Various different materials could also be used, such as other metals or plastics. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teaching presented in the foregoing descriptions and the associated drawings. For instance, as is well known in the art, base  110  may be mounted on vertical post  120  via a piston, such as a conventional gas cylinder and connected operating lever for raising or lowering the height of the chair. It is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.