Abstract:
A pivoting joint for use in a task chair or the like provides an adjustable elastomeric coupling that permits multi-axis rocking of the seat pan with a restoring force that provides controlled stability.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application 60/889,844, filed Feb. 14, 2007, the disclosure of which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     BACKGROUND OF THE INVENTION 
     The present invention relates to chairs and other seating devices and in particular to a seat that promotes healthy active sitting. 
     Many people, particularly in industrialized countries, sit for much of the time that they are awake. Although inactive sitting requires less physical effort than standing or walking, it can put excessive stress on the lumbar area of the spine. Prolonged inactive sitting also decreases muscle tone in the back, fluid movement in and around the spine, and blood circulation. Research studies indicate that small movements throughout the day can benefit metabolism, circulation, digestion, and even healing. 
     One innovative seating alternative proposed to promote this desirable movement is a “seating ball”, an inflated ball having a diameter approximating a standard height of a chair seat upon which the user sits. The seating ball is fundamentally unstable and therefore can be difficult to control, presenting some risk that the user may fall. Because the balls tend to roll around on the floor, they can be difficult to keep clean. While seating balls can be found in business settings, they lack professional and functional appeal. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a seat that promotes small movements by the seated user through a seat pan that may flex in multiple directions from a horizontal position as supported by an elastomeric joint. The elastomeric joint provides controlled stability (unlike a seating ball) to better balance the user while still promoting small movements. This type of movement promotes circulation, facilitates nourishment and preservation of the intervertebral discs of the lower spine, improves core muscle stability, and relieves the effects of static strain on the body (especially the back). Human intervertebral discs have no direct blood supply. The continuous osmotic fluid exchange that maintains the nutrition, health and integrity of the discs to act as efficient load transfer devices and shock absorbers depends on movement of this type. 
     Specifically then, the present invention provides an ergonomic seat having a seat pan for receiving and supporting a seated user, and a base sitting against the floor and providing an elevated mounting point. An elastomeric joint connects the elevated mounting point to the seat pan allowing a flexing of a plane of the seat pan from a neutral position, substantially parallel to the floor, to a flex angle where the seat pan is tipped from the neutral position. The elastomeric joint provides increasing resistance to increased flex angle as the flex angle increases and an adjustment mechanism provides for control of a functional relationship between flex angle and resistance to increased flex angle. 
     It is thus an object of the invention to provide a seat with improved mobility in the seat pan while preserving stability to the seated user. 
     The elastomeric joint may include at least one elastomeric washer sandwiched between rigid plates, a lower of which is attached to the base and an upper of which is attached to the seat pan. 
     It is thus another object of the invention to provide an extremely simple and reliable mechanism that does not require high force metal springs or metal-to-metal contact that can result in undesirable noise under constant joint movement. 
     The elastomeric joint may include one or more spacers between the elastomeric washer and at least one of the rigid plates whereby flexing of the plane of the seat pan from the neutral position changes a pressure contact area between the elastomeric washer and at least one of the rigid plates as a function of flex angle. 
     It is thus another object of the invention to permit precise tailoring of the functional relationship between flex angle and return force by changing not only the amount of compression but the area of interface with the elastomeric washer. 
     The spacers may also be elastomeric washers. 
     It is thus an object of the invention to permit further tailoring of the return force through the introduction of different elastomeric materials. 
     The elastomeric joint may include an adjustable clamp for controlling a pre-compression (or pre-loading) of the elastomeric washer in the neutral position. 
     It is thus an object of the invention to allow adjustment of the return force, for example, for users of different weights. 
     The flex angle may extend over 360° around a normal to the neutral plane of the seat pan. 
     It is thus an object of the invention to provide greater freedom of movement to the seated user than is obtained in a standard rocking-type chair. 
     The functional relationship between flex angle and resistance to flex angle may be increasingly increasing as one moves from the neutral position. 
     It is thus an object of the invention to provide a functional relationship between flex angle and return force that can counteract the torque exerted on the seat pan by the seated user whose effects also increase with angle. 
     The functional relationship between flex angle and resistance to flex angle may substantially offset increasing torque on the seat pan as a function of flex angle caused by the weight of an average seated user. 
     It is thus an object of the invention to provide a high mobility seat pan that is fundamentally stable. 
     The base may include a standard telescopic column providing swivel rotation and adjustable height of the seat pan. The base may also include standard caster wheels or glides. 
     It is thus an object of the invention to provide a mechanism that can be incorporated into standard adjustable-height seating such as office chairs and stools. 
     The elastomeric joint may include at least one washer providing a sliding interface between the elastomeric washer and one of the rigid plates to allow relative rotation between the elastomeric washer and the rigid plate. 
     It is thus an object of the invention to provide a rotating interface between the washer and the plates for simple implementation of a clamp by a central carriage bolt or the like. 
     The seat may further include a sensor array detecting flex angle and communicating it as electrical signals. 
     It is thus an object of the invention to provide a seat that may monitor activity by the user. 
     The seat may further include an electronic computer operating a stored program to receive the electrical signals indicating flex angle and to provide an interactive visual display to a seated user encouraging the seated user to maneuver the seat pan to different flex angles. 
     It is thus an object of the invention to provide a seat not only with improved mode ability but that may be used to implement an active therapeutic regimen with the user. 
     These particular features and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a seat having a seat pan and a base as may be used with the present invention and further showing a control handle having two degrees of movement for adjusting seat height and for adjusting compression force characteristics of an elastomeric joint; 
         FIG. 2  is an exploded view of the elastomeric joint of  FIG. 1  connecting the seat and base of the stool, the elastomeric joint providing one or more elastomeric washers as may be held between rigid plates; 
         FIG. 3  is a cross-section taken along lines  3 - 3  of  FIG. 1  showing the joint of  FIG. 2  assembled and attached to the seat of  FIG. 1 ; 
         FIG. 4  is a simplified representation of the joint of  FIG. 3  with three different amounts of flex angle showing a force curve that is increasingly increasing as one moves from a neutral position; 
         FIG. 5  is a simplified perspective view of a clamp mechanism for pre-compressing the elastomeric joint of  FIG. 3  in which the handle is used to measurably increase or decrease the pre-loading on the washer(s) changing a force offset of the force curve; 
         FIG. 6  is a simplified schematic of a sensor array positioned on the seat of  FIG. 1  to communicate movements of the user to a computer, the latter which may be programmed to provide a diagnostic or therapeutic routine; and 
         FIGS. 7   a  and  7   b  are front elevational views of embodiments of the seat of  FIG. 1  providing armrests and a backrest that move with the seat pan (in  FIG. 7   a ) or to remain stationary during movement of the seat pan (in  FIG. 7   b ). 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a seat  10  suitable for use with the present invention may provide a seat pan  12  having an upper surface  14  for supporting a seated user. The seat pan  12  may be supported on a base  16 , for example, a standard office chair pedestal base having multiple legs  18  and caster wheels  20 . 
     A control lever  22  may extend horizontally outward from beneath the seat pan  12  to provide for control of the seat  10  through a horizontal actuation  24  or a vertical actuation  26 . The vertical actuation  26  controls a standard air spring incorporated into the base  16  according to methods known in the art. The base  16  provides an elevated mounting point at the top of the stanchion  28  (not visible in  FIG. 1 ) which may connect the base  16  to the seat pan  12  through an elastomeric joint  30  that will now be described. 
     Referring now to  FIGS. 2 and 3 , the top end of the stanchion  28  may be received by a support block  32  providing the elevated mounting point and receiving the control lever  22 . The support block  32  includes a mechanism for providing control of an air spring and changing the height of stanchion  28  according to standard techniques. The air spring and stanchion  28  permit swiveling rotation around a vertical axis. 
     The support block  32  provides a substantially horizontal upper face that may support a first rigid plate  34  which may, for example, be constructed of a disk of metal such as aluminum or steel. The first rigid plate  34  is held to the upper face of the support block  32  by bolts  36  passing through the support block  32  to be received by corresponding threaded holes  38  in the rigid plate  34 . Bolts  36  are of a length that does not interfere with components on top of plate  34 . 
     The rigid plate  34  includes a center hole  40  having a square perimeter that may engage with a corresponding square shank  42  extending from the head  44  of a carriage bolt  46 . The engagement of the square shank  42  and the rigid plate  34  is such as to prevent relative rotation between the two. The carriage bolt  46  may pass upward through the hole  40  so that the threaded portion  48  of the carriage bolt  46  extends upward from the support block  32  to rotate about a vertical axis therewith. Swiveling stanchion  28  allows rotation of support block  32  without rotating the whole base  16 . 
     On top of rigid plate  34  may be placed two slide washers  50  being substantially of equal diameter with rigid plate  34  and having central holes for receiving the threaded portion  48  of the carriage bolt  46 . These slide washers  50  may be constructed of a self-lubricating or low friction material such as ultrahigh molecular weight plastic, polyethylene, Teflon or the like. 
     On top of slide washers  50  is fit an elastomeric washer  52  being of equal diameter to slide washers  50  and rigid plate  34  but being substantially thicker than slide washers  50  and being in the preferred embodiment between ½″ and 1½ inches. A material having a durometer-Shore A of 63 and a tear strength of 135 pounds per inch may be used. The elastomeric washer  52  also has a center aperture held and stabilized by the threaded portion  48  of the carriage bolt  46 . 
     A lower washer  56  and upper washer  58  may rest on top of the elastomeric washer  52  with the lower washer  56  having a diameter equal to or smaller than elastomeric washer  52  and upper washer  58  having a diameter equal to or smaller than lower washer  56 . These washers may preferably also be elastomeric material and may be of the same or different material as washer  52 . Within the scope of this invention, it would be apparent to someone skilled in the art that different quantities, sizes, shapes and materials of washers could be used to achieve desired effects. 
     On top of upper washer  58  is placed a second rigid plate  60  serving with rigid plate  34  to sandwich elastomeric washer  52  (and washers  50 ,  56  and  58 ) therebetween. Rigid plate  60  has peripheral holes  62  that may receive screws  66  passing upward through the rigid plate  60  to affix it to the underside of the seat pan  12 . 
     A square spacer  68  may be positioned above a central hole in the rigid plate  60  receiving passage of the threaded portion  48  of the carriage bolt  46  therethrough. Square spacer  68  may be made of elastomeric material. On top of the square spacer  68  may be positioned a square nut  70  of similar dimensions engaging the threaded portion  48  of the carriage bolt  46 . Square spacer  68  prevents rigid nut  70  from incurring direct force against rigid plate  60 . As will be understood, tightening of the nut  70  will compress the elastomeric washers  52 ,  56  and  58  between rigid plates  34  and  60  together and hold the seat pan  12  to the stanchion  28 . The seat top (including seat pan  12 , square nut  70 , square spacer  68  and rigid plate  60 ) can be quickly attached or removed as one unit. This permits ready interchange of the seat top and easy access to reconfigure elastomeric washers  52 ,  56  and  58 . Therefore, the seat top and the elastomeric joint can be readily optimized for many different applications. 
     Referring now to  FIG. 3 , the seat pan  12  may include an upper foam layer  72  supported by a rigid layer  74 , the latter for example being plywood or composite wood or the like. A square bore  76  cut in the underside of the rigid layer  74  receives the square spacer  68  and square nut  70  and holds them to allow axial motion but to prevent lateral motion. When adjusting  24  pre-compression of the elastomeric joint  30  with control lever  22 , the square bore  76  prevents square spacer  68  and square nut  70  from rotating when receiving the threaded portion  48  of carriage bolt  46 . A thin layer of flexible retaining material (not shown) may be fastened to the top surface of rigid layer  74  directly above square bore  76  to prevent a non-engaged square nut  70  from migrating upward into the foam layer  72 . 
     The aperture of the rigid plate  60  may be sized to be larger than the diameter of the threaded portion  48  of the carriage bolt  46  so that the positioning of the rigid plate  60  to the rigid layer  74  prevents contact between rigid plate  60  and the threaded portion  48  of the carriage bolt  46 , the latter as held by the square spacer  68  away from contact with the rigid plate  60 . This spacing is such as to prevent rubbing of the metallic rigid plate  60  against the threaded portion  48  of carriage bolt  46  during angular motion of the seat pan  12 . 
     Referring now to  FIG. 4 , when the seat  10  is unoccupied the rigid plate  60  (and thus the seat pan  12 ) is generally in a horizontal position having a vertical surface normal. This normal position will be termed the neutral position  80 . 
     Flexure to a first flex angle  81  deviating from the neutral position  80  will experience a generally linear return force  82   a  as a function of flex angle  81  caused by the effective linear spring constant of compression of the washers  58 ,  56  and  52  against the rigid plate  60  over a first contact area  84  that is approximately constant because of a spacing of the plate  60  from the washers  56  and  52  by washer  58 . 
     As the flex angle increases to flex angle  81 ′ past a first angle limit  86 , in any of 360° about neutral position  80 , the rigid plate  60  contacts the second washer  56  increasing the effective surface of contact area  84 ′ between the rigid plate  60  and the washers  58 ,  56  and  52  causing an upward angling in the return force curve  82  as indicated by return force segment  82   b.    
     When the flex angle  81 ″ exceeds a second threshold  90 , the rigid plate  60  contacts all three of the washers  58 ,  56  and  52 , increasing the contact area  84 ″ and providing yet a steeper return force segment  82   c  caused by that increased contact area. 
     Generally the seated user will exert a user torque  92  on the elastomeric joint  30  that will also increase with flex angle  81 . The direction of this user torque  92  is opposite that provided by the joint  30 , and thus the combined effect of the return force curve  82  and the torque exerted by the user by the user&#39;s off-center weight can be balanced to provide a stable flexure  94  or a slightly unstable flexure  96 , the latter promoting a small amount of motion inducing instability. 
     Selection of the dimensions and materials of washers  58 ,  56 , and  52  can precisely control the shape of this flexure  94  or  96 . It will be understood, that a similar effect to that provided by washers  56  and  58  may be had by shaping the upper surface of washer  52 , for example, to provide a convex surface. Generally the composition of the  58 ,  56 , and  52  need not be homogenous and/or their shapes may be varied from disks to provide for anisotropic restoring forces providing different degrees of support for different directions of tilting of the seat pan  12 . 
     Referring now to  FIG. 5 , rotation of the support block  32  with respect to the nut  70  held in the seat pan (not shown) by movement of the control lever  22  in a horizontal actuation  24  can cause rotation of the carriage bolt  46  with respect to the nut  70 . This in turn clamps elastomeric washers  58 ,  56  and  52  between rigid plate  60  and rigid plate  34  (shown in  FIG. 2 ) increasing the pre-compression and shifting the return force curve  82  upward to return force curve  82 ′. This adjustment mechanism may be guided by a graduated shroud  100  surrounding the joint  30  having marked intervals  102  that may be aligned with the control lever  22  to provide repeatable and quantifiable adjustment. Similarly, a mechanical or electronic encoder may quantify actuation  24  of control lever  22 . This adjustment, by shifting the return force curve  82  upward to return force curve  82 ′, can compensate for steeper force curves of user torque  92  caused by users of higher weight. Alternatively, the lever  22  may be provided with a torque control or indicator (in the manner of a conventional torque wrench) to control the degree of compression of elastomeric joint  30  while also providing a quantitative adjustment mechanism. 
     Referring now to  FIG. 6 , the present invention provides multiple degrees of freedom  104  in flex angles  81  about the neutral position  80  allowing improved accommodation of the user&#39;s natural desire to move while seated. The particular flex angles  81  both in amount of angulation and direction of angulation may be detected by sensors  106 , for example, mounted beneath the seat pan  12  and, in the simplest case, being switches that are compressed with flex angles  81  in different directions to a threshold amount. Alternatively the sensors may be accelerometers or solid-state gyroscopes attached to the seat pan  12 . The sensors  106  may provide electrical signals to harness  108  communicated to a computer  110  either by direct-wired connection or wireless link  112  as depicted. A foot pedal unit  114  may also be provided and connected to the harness  108  so that together the sensors  106  and foot pedal unit  114  emulate the standard joystick or two-button mouse control familiar to computer users. For example, this may provide a hands-free alternative for handicap accessibility to computers. For another example, in an office environment, the seat pan may provide for general improved seating quality while also being enlisted periodically to promote exercise by the user. 
     The seat  10  may thus be enlisted in controlling a cursor  118  on a computer screen  119  with the seat standing in for a normal cursor control device. Alternatively or in addition the computer  110  may be programmed to provide an exercise routine, for example, generating a moving object that must be tracked with crosshairs  116  controlled by the user by tilting the seat  10  and activating the sensors  106 . 
     For example, as part of a therapeutic computer program, performance results may be stored in data files and patterns of weakness may be used diagnostically to analyze balance and core muscle stability disorders. Therapeutic “games” may then target prescribed exercise movement patterns to address specific problems. Scores may then be charted from stored data files to observe and quantify patient progress over time. 
     It will be understood that many new and existing computer games may be used with this invention for entertainment or therapeutic purposes. 
     Referring now to  FIG. 7   a , the seat  10  may be provided with armrests  120  having supports  122  attached between the armrests  120  and the lower surface of the seat pan  12 . Likewise the seat  10  may be provided with a seatback  124  or lumbar support having a support  126  attached between the seatback  124  and the lower surface of the seat pan  12 . In this embodiment, the seatback  124  and armrests  120  will move in angulation in multiple directions with corresponding movement of the seat pan  12 . In this way, the seatback  124  and armrests  120  permit natural movement while providing continuous support. 
     Referring to  FIG. 7   b , in an alternative embodiment, a lower end of the support  126  of the seatback  124  may be attached to the stanchion  28  as may be the lower end of the supports  122  of the armrests  120 . In this configuration, the seatback  124  and armrests  120  will remain stationary during movement of the seat pan  12 . 
     In both the embodiments of  FIGS. 7   a  and  7   b , the seatback  124  and armrests  120  are free to rotate about a vertical axis with the seat pan  12  in the manner of a standard task chair and may elevate with the seat pan  12  for height adjustment. The height of the armrests  120  and seatback  124  may be adjusted by conventional mechanisms (not shown). 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.