CHAIR HAVING OPEN SHOULDER BACKREST

Abstract

An ergonomically improved chair in which the user's thoracic region is supported by a narrow and generally flat or moderately convex thoracic cushion in the midrest region of the chairback. The design omits or greatly minimizes support for the user's scapulae and other areas of the back outside the thoracic region, excepting lumbar and cervical support features in some embodiments. The design differs from the prior art at least in that the thoracic cushion is narrow and configured not to complement that user's spinal curvature. By appropriate selection and design, a chair incorporating the invention may comprise a fabric covering portions of the chairback without significantly affecting functionality. Other embodiments include a chairback comprising regions having differing levels of firmness and/or differing cushion height at appropriate regions to promote concentrated support of the user's thoracic region.

Claims

1. A chair for a human user, said user having scapulae and further having lumbar and thoracic and cervical regions of the user's spine, said chair comprising: a seat platform; a back support frame having a proximal end attached to the seat platform and a distal end extending above the proximal end; a lumbar cushion having a front for supporting the lumbar region; a midrest attached to the back support frame for supporting the thoracic region, said midrest separate and spaced apart from the lumbar cushion, said midrest situated between the lumbar cushion and the distal end, said midrest comprising a thoracic cushion having a width, the thoracic cushion further having a generally vertical length and a front; wherein the thoracic cushion is less than five inches wide along at least two thirds of its length; and said chair comprises no elements that engage the user's scapulae.

2. The chair of claim 1 further comprising: a neckrest cushion having a front for supporting the cervical region, wherein the neckrest cushion front and the lumbar cushion front generally define a first plane and the thoracic cushion front is behind the first plane.

3. The chair of claim 1 wherein the front of the thoracic cushion does not bend or curve to complement a dorsal spinal curvature of the user.

4. The chair of claim 1 wherein the thoracic cushion is less than four inches wide along at least two thirds of its length.

5. The chair of claim 1 wherein the back support frame is rigid.

6. The chair of claim 5 wherein the midrest is permanently secured to the back support frame, and wherein said midrest comprises a generally flat and vertically oriented thoracic cushion having a front that does not bend or curve to complement a dorsal spinal curvature of the user, said thoracic cushion being less than four inches wide along at least two thirds of its length.

7. A chair for a human user having scapulae and further having lumbar and thoracic spinal regions, said chair comprising: a seat platform; a back support frame having a proximal end and a distal end extending above the proximal end, the proximal end attached to the seat platform; a lumbar cushion having a lateral width and a front for engaging the lumbar region; a midrest attached to the back support frame between the lumbar cushion and the distal end for supporting the thoracic region, said midrest separate and spaced apart from the lumbar cushion, said midrest comprising a vertically oriented, substantially elongated thoracic cushion having a width and a generally vertical length and a front and an effective initial load deflection (ILD) firmness; one or more interstitial areas laterally proximate to the thoracic cushion; a chairback fabric attached to a fabric frame, the fabric frame configured to allow the fabric to hold an intended shape, the chairback fabric and fabric frame attached to the back support frame, the chairback fabric extending across at least one interstitial area wherein the chairback fabric covering the interstitial area that is laterally proximate to the thoracic cushion has an interstitial effective initial load deflection (ILD) firmness; wherein the thoracic cushion is less than five inches wide along at least two thirds of its length; and wherein the thoracic cushion effective initial load deflection (ILD) firmness is substantially higher than the interstitial effective initial load deflection (ILD) firmness such that the midrest primarily supports the seated user's thoracic spinal region and only minimally engages with the seated user's scapulae.

8. The chair of claim 7 wherein the chairback fabric is in direct contact with the thoracic cushion and with the lumbar cushion, the chairback fabric extending across at least the width of the thoracic cushion and the width of the lumbar cushion.

9. The chair of claim 7 further comprising a seat cushion on top of the seat platform, and wherein the fabric frame extends below the seat cushion.

10. The chair of claim 7 wherein the chairback fabric is in front of at least one cushion selected from the group consisting of: thoracic cushion and lumbar cushion.

11. The chair of claim 7 wherein the chairback fabric is behind at least one cushion selected from the group consisting of: thoracic cushion and lumbar cushion.

12. The chair of claim 7 further comprising a neckrest cushion having a front for engaging a cervical region of the user's spine, wherein the neckrest cushion front and the lumbar cushion front generally define a first plane, and wherein the thoracic cushion front is behind the first plane.

13. The chair of claim 7 wherein the thoracic cushion effective initial load deflection (ILD) firmness is above 28 and the interstitial area effective initial load deflection (ILD) firmness is below 24.

14. A chair for a human user having scapulae and a thoracic spinal region, said chair comprising: a seat platform; a back support frame having a proximal end and a distal end extending above the proximal end, the proximal end attached to the seat platform; a chairback attached to the back support frame between the proximal end and the distal end, said chairback comprising a cushion having at least two cushion regions, the regions comprising a vertically oriented thoracic cushion region centrally situated in the chairback, the thoracic cushion region having an elevation and a front; and a scapular cushion region laterally abutting and extending from both sides of the thoracic cushion region, the scapular cushion region also having an elevation; wherein the thoracic cushion region is less than five inches wide along at least two thirds of its length; and wherein the thoracic cushion region's elevation is substantially greater than the proximately adjacent scapular cushion region elevation thereby creating a ridge, such that the chairback primarily supports the seated user's thoracic spinal region and only minimally engages with the seated user's scapulae.

15. The chair of claim 14 wherein the user has a lumbar region and wherein the chairback further comprises a lumbar cushion region, said lumbar cushion region situated approximately normal to the seated user's lumbar region and below the scapular cushion region, said lumbar cushion region having a front and having an elevation that is substantially greater than the proximately adjacent thoracic cushion region.

16. The chair of claim 15 wherein the human user has a cervical spinal region, and wherein the chair further comprises a neckrest cushion having a front for engaging the cervical spinal region; and wherein the neckrest cushion front and the lumbar cushion region front generally define a first plane, and wherein the thoracic cushion region front is behind the first plane.

17. A chair for a human user having scapulae and a thoracic spinal region, said chair comprising: a seat platform; a back support frame having a proximal end and a distal end extending above the proximal end, the proximal end attached to the seat platform; a chairback attached to the back support frame between the proximal end and the distal end, said chairback comprising a cushion body having a vertically oriented thoracic cushion region laterally centered in the chairback, the thoracic cushion region having an effective initial load deflection (ILD) firmness; and a scapular cushion region laterally abutting and extending from both sides of the thoracic cushion region, the scapular cushion region generally normal to the seated user's scapulae, the scapular cushion region having an effective initial load deflection (ILD) firmness; wherein the thoracic cushion region is less than five inches wide along at least two thirds of its length; and wherein the thoracic cushion region's effective initial load deflection (ILD) firmness is substantially greater than the proximately adjacent scapular cushion region cushion effective initial load deflection (ILD) firmness, such that the chairback primarily supports the seated user's thoracic spinal region and only minimally engages with the seated user's scapulae.

18. The chair of claim 17 wherein the human user has a cervical spinal region and a lumbar region, and wherein the chair further comprises a neckrest cushion having a front for engaging the cervical spinal region; the chairback further comprising a lumbar cushion region having a front; wherein the neckrest cushion front and the lumbar cushion front generally define a first plane, and wherein the thoracic cushion front is behind the first plane.

19. The chair of claim 17 wherein the thoracic cushion region has a thoracic cushion region elevation and the scapular cushion has a scapular cushion region elevation, and wherein the thoracic cushion region's elevation is substantially greater than the proximately adjacent scapular cushion region.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009] These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein:

[0010] FIG. 1 is a front view of a first chair embodiment

[0011] FIG. 2 is a side view the first chair embodiment

[0012] FIG. 3 is a perspective view of the first chair embodiment

[0013] FIG. 4 is a front view of a second chair embodiment

[0014] FIG. 5 is a side view of a second embodiment

[0015] FIG. 6 is a side view of a user shown seated in the first chair embodiment

[0016] FIG. 7 is an enlarged view of a portion of the chair back in the first embodiment

[0017] FIG. 8 is a front view of a third embodiment

[0018] FIG. 9 is a front view of a fourth embodiment

[0019] FIG. 10 is a front view of a fifth embodiment

[0020] FIG. 11 is a side view essentially common to embodiments 3, 4 and 5

[0021] FIG. 12A is a top view of the first embodiment

[0022] FIG. 12B is a top view of the third embodiment

[0023] FIG. 12C is a top view of the fourth embodiment

[0024] FIG. 12D is a top view of the fifth embodiment

[0025] FIG. 13 is a front view of a sixth embodiment showing a chair having cushion regions

[0026] FIG. 14 is a front view of a seventh embodiment showing a chairback having cushion regions

[0027] FIG. 15 is a front view of an eighth embodiment

[0028] FIG. 16 is a perspective view of a ninth embodiment in rest position

[0029] FIG. 17 is a perspective view of the ninth embodiment in deflected position

[0030] FIG. 18 is a side view of the ninth embodiment in rest position

[0031] FIG. 19 is a top view of the ninth embodiment in rest position

[0032] FIG. 20A is a perspective view of an exemplar neckrest and adjustment means

[0033] FIG. 20B is a side view of a second exemplar neckrest and adjustment means

[0034] FIG. 21A is a front view of a rectangular thoracic cushion with rounded corners

[0035] FIG. 21B is a front view of an oblong thoracic cushion

[0036] FIG. 21C is a front view of a diamond-shaped thoracic cushion

[0037] FIG. 21D is a front view of a thoracic cushion having a vertical ventral depression

[0038] FIG. 21E is an end view of the thoracic cushion having a vertical ventral depression

DETAILED DESCRIPTION OF THE INVENTION

[0039] Referring to the figures, wherein like numerals indicate like or corresponding parts throughout the several views, FIG. 1 and FIG. 2 are front and side views, respectively, of a first embodiment of a chair 10. Chair 10 is comprised of a base 12 having a plurality of legs 14 and casters 16 attached to each leg, the wheels or casters adapted to roll upon a floor. The plurality of legs 16 are attached to a vertical support column 18. In one embodiment, support column 18 may be vertically adjusted, such as by telescopic extension.

[0040] Support column 18 supports a seat platform 20 rotatably attached to support column 18. Seat platform 20 comprises a topside portion 22. In a preferred embodiment, topside portion 22 comprises a seat cushion 24, though a cushion is not required. If a seat cushion 24 is utilized, it sits on cushion support 26 (shown in FIG. 2). Seat platform 20 may also comprise attachment points for armrests 30, a mechanism to adjust seat platform height (not shown), and a tilt mechanism 28 to control the longitudinal (front-to-back) angle of topside portion 22 of the seat platform. Seat platform 20 may also comprise a mechanism to control recline angle and/or recline resistance of back support frame 40 relative to the seat platform, as well as various other adjustments such as for controlling the rotation and swivel of seat platform 20, adjustments for user weight, arm rest mechanisms, and lumbar adjustments.

[0041] Attached to seat platform 20 is a back support frame 40 comprising a lower back support frame 44 at the end that is proximal to seat platform 20, and an upper back support frame 46 terminating at the distal end of back support frame 40. The lower back support frame 44 may attach to seat platform 20 at any number of attachment points 42. Back support frame may be of any configuration. In a first embodiment best shown in FIGS. 1 and 2, back support frame 40 may comprise two laterally-spaced proximal lower frame members 45 that each attach to the underside portion of seat platform 20, the laterally-spaced proximal lower frame members being laterally sider at the proximal end than the distal end. As best shown in FIGS. 1 and 3, the proximal lower frame members 45 may extend back and up, laterally merging into one upper back support frame member 46 at the distal end of back support frame 40, forming an “arrow” shape when viewed from the front. Back support frame 40 may be comprised of metal, plastic, carbon fiber, or a combination thereof. It may be a unitary (unibody) or a plurality of elements welded, screwed, bolted, or otherwise attached together.

[0042] Chair 10 may also comprise armrests 30. Armrests 30 may attach to the underside or topside 22 portions of seat platform 20, or to lower back support frame 44. The armrests may be adjustable in the vertical, lateral (side to side) and longitudinal directions. Armrests 30 may also pivot around one or more lateral or longitudinal axes, or retract into a portion of the chair, e.g. the underside of seat platform 20.

[0043] Chair 10 may also comprise a lower backrest 50 and a lumbar cushion 52, attached to the back support frame 40. Lower backrest 50 is placed near the proximal end of back support frame 40 to engage with a seated user's lumbar region. Lower backrest 50 is preferably vertically adjustable, and may also be adjustable longitudinally, i.e. normal (perpendicular) to the user's back. The adjustment means may be manual or electric, and comprise complementary rails 43 as shown in FIG. 3, or one or more rods inserted into back support frame 40, into either lower back support frame 44 or into upper back support frame 46. Other adjustment means such as threaded screw(s), gears, cam mechanisms, telescopic tubes, inflatable bladders, or other lumbar adjustment mechanisms known to those skilled in the art may be used either singularly or in combination.

[0044] A second embodiment of chair 10 is shown in FIGS. 4 and 5. Unlike the first embodiment shown in FIGS. 1 through 3, the lower back support frame is comprised of one structural element (though not necessarily comprised of only one material) attached to the underside of seat platform 20. In a preferred embodiment, the topside portion 22 of the seat platform 20, typically comprising a seat cushion 24, is slightly tilted longitudinally forward at a seat angle 32. In a preferred embodiment, seat angle is between approximately 2-4 degrees.

[0045] Chair 10 may also comprise a neckrest 60 and optionally a neckrest cushion 62 having a front and attached to the distal end of back support frame 40. Like lower backrest 50, neckrest 60 is preferably vertically adjustable, and may also be adjustable longitudinally, i.e. normal (perpendicular) to the user's neck. In a preferred embodiment, neckrest 60 may be structurally secured to upper back support frame 46 by means of a single rod or a plurality of frictionally secured rods as shown in FIG. 20A, or by a complementary rail system as shown in FIG. 20B, or any means of adjustment similar to those described above for adjusting lower backrest 50. In other embodiments, neckrest 60 or neckrest cushion 62 may be combined with another section of chair back cushion (e.g., an extension of a thoracic cushion 48 or thoracic cushion region 78) or may be a separate element attached to the upper portion of midrest 47 by sewing, straps, Velcro, buttons, zipper, etc. (not shown).

[0046] FIG. 6 profiles a user sitting in the first chair embodiment. The user's spine is comprised of vertebrae including a cervical region 34 with seven cervical vertebrae (conventionally numbered top-to-bottom C1-C7), a thoracic region 36 with twelve thoracic vertebrae (T1-T12), and a lumbar region 38 with five lumbar vertebrae (L1-L5).

[0047] Returning to FIG. 1, a midrest 47 is situated between lower backrest 50 and neckrest 60 to support the user's thoracic region 36. Midrest 47 may be separate and spaced apart from lower backrest 50 and separate and spaced apart from neckrest 60. Midrest 47 preferably comprises a forward-facing and centrally situated thoracic cushion 48 placed to normally engage the user's thoracic region 36. Thoracic cushion 48 has a vertical length but its length preferably does not extend above or below thoracic region 36 of a given user. For the embodiment shown in FIG. 6, thoracic cushion 48 engages the seated user's back from about vertebrae T3 through T12 and does not significantly engage with the seated user's back below vertebrae T12.

[0048] FIGS. 1, 2 and 3 are, respectively front, side and perspective views of a first chair embodiment. As understood from the front views of the chair embodiments in FIGS. 1 and 4, a user sitting normally in chair 10 feels no pressure/support on the user's scapulae (shoulder blades) because chair 10 has no structure to engage with that region of the user's back. There is likewise an absence of cushioning or supportive structure in the interstitial area between thoracic cushion 48 and lower backrest cushion 52. Consequently, the user's back is supported by the narrow thoracic cushion 48 engaging the thoracic region 36 of the user's spine and by lower backrest cushion 52 engaging lumbar region 38.

[0049] In a preferred embodiment the length of thoracic cushion 48 is significantly longer than its width. In a more preferred embodiment, the width of thoracic cushion 48 is less than five inches along its length. In another preferred embodiment, the width of the upper two-thirds of thoracic cushion 48 is less than four inches and the width of the lower third no more than than six inches. Thoracic cushion 48 preferably has a thickness (in the longitudinal dimension) less than two inches or even less than one inch. Thoracic cushion 48 is characterized by a cushion firmness, which may be measured by Indentation Load Deflection (ILD). As is known to those skilled in the art, a plush cushion has a range of about 16.5 ILD to 22.5 ILD, a soft cushion has a range of about 22.5 ILD to 26.5 ILD, a medium cushion has a range of about 26.5 ILD to 30.5 ILD, a firm cushion has a range of about 30.5 ILD to 34.5 ILD, a very firm cushion has a range of about 34.5 to 38.5 ILD, and an extremely firm cushion may have an ILD as high as 50 ILD. In one embodiment, thoracic cushion 48 is at least medium firmness corresponding to an effective ILD above about 26.5. Lumbar cushion 52 and neckrest cushion 62 preferably also have at least medium firmness. For purposes of the specification and the claims “effective ILD” means the human-perceived firmness of a chair element, such as a chair cushion or chair fabric region, that relates most closely with the firmness of a molded urethane foam sample as measured by industry standard ASTM D3574-17.

[0050] The front face of thoracic cushion 48 may be generally rectangular as shown in FIG. 4, or have a slightly broader base as shown in FIG. 1, or have any other shape such as examples shown in FIGS. 21A-21E. In a preferred embodiment the front face of thoracic cushion 48 has a generally straight or slightly convex profile as shown in FIG. 7. I.e., the anterior face of thoracic cushion 48 is generally straight or slightly convex as viewed from the side; thoracic cushion 48 has no significant concave curvature to complement the natural dorsal curve of the user's thoracic region 36. Thoracic cushion 48 may be vertically adjustable to accommodate users having different heights or spinal lengths, and may also be longitudinally adjustable, using any adjustment means described above or known to skilled artisans.

[0051] In another embodiment, thoracic cushion 48 may comprise a ventral depression through its middle, running vertically along some or all of the length of thoracic cushion 48, to center and cradle the thoracic region 36 of the user's spine, that embodiment illustrated in FIGS. 21D and 21E showing the front view and end view respectively of a cradle-shaped thoracic cushion 48. As shown in FIGS. 21D and 21E, the depression in this embodiment laterally centers the user's spine on thoracic cushion 48. Like other embodiments described herein, in this embodiment the side profile of thoracic cushion 48 is generally straight with the anterior front optionally being slightly convex. The front of thoracic cushion 48 does not bend or curve to attempt to complement the dorsal curvature of the user's thoracic region 36.

[0052] FIG. 7 shows a side view of a preferred embodiment of the chair back. The front face of neckrest cushion 62 and the front face of lumbar cushion 52 generally define a first plane 66. The front face of thoracic cushion 48 is significantly behind the first plane 66. For embodiments in which thoracic cushion 48 is generally flat and generally defines a second plane 68, as shown in FIG. 7, first plane 66 is located in front of the second plane 68.

[0053] FIGS. 8 through 11 illustrate related embodiments in which the chairback comprises a fabric 70 in addition to a thoracic cushion 48 and lumbar cushion 52. Adding fabric 70 may mimic familiar shapes relating to traditional chair designs thereby increasing aesthetic appeal for some users, or be preferred for other reasons unrelated to seating comfort, such as user privacy. Fabric 70 which may be a mesh, leather, or any other textile-like material. A fabric frame 74, which may be comprised of metal, plastic, carbon fiber, or other materials known to those knowledgeable in the art, helps fabric 70 hold its intended shape. Fabric frame 74 may also comprise a reinforced perimeter of fabric 70, such as a rolled and sewn perimeter edge, or an edge that has been treated by heat or chemicals to reinforce or stiffen the material in a desired shape. Fabric 70 may be made in a variety of shapes such as generally deltoid (FIG. 8), trapezoidal (FIG. 9), rectangular (FIG. 10), or oval, pear-shaped, circular, etc.

[0054] When designed and built appropriately, adding chairback fabric 70 to chair 10 does not significantly reduce the aforementioned functionality of concentrating upper back support to the user's thoracic region 36. Chair fabric 70 may cover thoracic cushion 48 and lumbar cushion 52 as well as interstitial areas 72. As shown in FIGS. 8-11, interstitial areas 72 correspond to regions of the chairback that are not longitudinally adjacent to thoracic cushion 48, to lumbar cushion 52, or to neckrest cushion 62. The chairback at interstitial areas 72 has substantially less firmness than these supportive cushions, thereby providing little or no support to a user's back normal to interstitial areas 72. In one embodiment, thoracic cushion 48 and lumbar cushion 52 have limited deflection capacity because of 1) relatively shallow cushion depth and 2) firmness corresponding to an effective ILD above about 28. In contrast, chair fabric 70 over the interstitial areas 72 has 1) substantially greater deflection capacity and 2) are substantially less firm, and in a preferred embodiment a softness corresponding to an effective ILD below about 24. Consequently, a user sitting in any of the embodiments shown in FIGS. 8 through 11 does not experience significant pressure or support on areas normal to interstitial areas 72, including on the user's scapulae (shoulder blades) or on the user's back between lumbar cushion 52 and thoracic cushion 48. Moreover, as best shown in FIG. 11, some fabrics such as certain meshes, are subjected to varying tension after being stretched over and around cushions and fabric frame 48. Chair fabric 70, under uneven fabric tension, tends to cling closely to the front surface of thoracic cushion 48 and lumbar cushion 52, but tends to contract and subside rearward in interstitial areas 72, thereby further reducing the firmness and decreasing any support fabric 70 provide to the user's back normal to interstitial areas 72.

[0055] Chairback fabric 70 may unitarily cover the lateral expanse of midrest 47, or cover the entire chairback including neckrest 62, or only partially cover the chairback. Chairback fabric 70 and chairback frame 74 may extend below lumbar cushion 52 as shown in FIG. 8, or be attached to and/or cover seat cushion 24 (not shown), or extend below seat cushion 24 as shown in FIG. 9. Chairback fabric may cover the front of both thoracic cushion 48 and lumbar cushion 52 as shown in FIGS. 8, 10 and 11. In another embodiment shown in FIG. 9, chair fabric 70, is placed so as to frontally expose thoracic cushion 48 and lumbar cushion 52. Such exposure can be accomplished in many ways such as by bordering chair fabric 70 around the perimeter of the cushions, or placing fabric 70 behind the cushions. In another embodiment (not shown) chair fabric 70 may cover one cushion but not the other. In another embodiment, chairback fabric 70 may be comprised of a plurality of pieces of fabric, and/or a plurality of fabric types.

[0056] FIG. 15 shows another embodiment of a chairback comprising a thoracic cushion 48 and chair fabric 70 covering interstitial areas 72. In this embodiment, interstitial areas 72 include regions normal to a user's scapulae, but the chairback comprises an upper transverse element immediately above the user's scapulae that can provide some structural support. This embodiment functions similarly to the earlier embodiments having a generally open shoulder design, while possibly being more aesthetically pleasing to some users.

[0057] The same functional effect can be achieved by structuring a chairback with a single back cushion body having a plurality of regions, with firmer and/or more elevated support in some regions and softer and/or lower elevation of support in others. It is known to fabricate a cushion or mattress characterized by a plurality of regions having different levels of firmness or height elevation. As shown in FIG. 13, chairback 77 may be attached to back support frame 40 between the frame's proximal end and the distal end. Chairback 77 may comprise a cushion having a plurality of regions. Thoracic cushion region 78 is vertically oriented in the lateral center of chairback 77, located above lumbar cushion 82. The location of thoracic cushion region 78 corresponds generally to the location of above described thoracic cushion 48. Thoracic cushion region 78 is vertically longer than wide. Scapular cushion region 80 is situated on either lateral side of thoracic cushion region 78 and above lumbar cushion region 82. Lumbar cushion region 82 is below and normal to the seated user's lumbar region 38.

[0058] Demarcating the boundaries between thoracic cushion region 78, scapular cushion region 80, and lumbar cushion region 82 may be accomplished by fabricating chairback 77 with these regions having differing firmness levels. Preferably the firmness of thoracic cushion region 78 is substantially higher than the firmness of scapular cushion regions 80. For example, thoracic cushion region 78 may be firm and have an effective ILD above about 28, and scapular cushion region 80 may be soft and have an effective ILD below about 24. In another embodiment, demarcation may be accomplished by fabricating chairback 77 with the regions having varying cushion height/elevation. In the embodiment shown in FIG. 14, thoracic cushion region 78 has a significantly higher anterior elevation than scapular cushion region 80 (elevation of the cushion regions being measured relative to a chairback plane such as second plane 68 illustrated in FIG. 7) effectively forming a narrow “ridge” normal to the user's thoracic region 36. In a preferred embodiment, elevated thoracic cushion region 78 is generally flat or slightly convex. In another embodiment, thoracic cushion region 78 may comprise a central depression running within the elevated ridge to cradle the user's spine, as illustrated in FIGS. 21D (front view) and 21E (end view).

[0059] In other embodiments, chairback 77 may comprise a cushion whereby the regions are demarcated by a combination of varying cushion firmness and varying elevation. The functional outcome of thoracic cushion region 78 being firmer and/or higher than nearby scapular cushion region 80 is that chairback 77 primarily supports the seated user's thoracic spinal region 36 and only minimally engages with the seated user's scapulae. The thoracic cushion region's anterior elevation may be higher and/or firmer than the proximately adjacent scapular cushion region thereby creating a ridge, such that the upper portions of chairback 77 primarily support the seated user's thoracic spinal region and only minimally engages with the seated user's scapulae. Similarly, lumbar cushion region 82 may comprise a cushion having a higher anterior elevation and/or degree of firmness than both thoracic cushion region 78 and scapular cushion region 80. Lumbar cushion region 82 may comprise a cushion being more firm than nearby areas. As in all other embodiments described above, the thoracic cushion region 78 and lumbar cushion region 82 may be vertically or longitudinally adjustable using means described above and known to those skilled in the art.

[0060] Another embodiment of the invention is shown in FIGS. 16-19. FIG. 16 shows a perspective view of a chair midrest 47 at rest position, and FIG. 17 shows the same chair in a deflected position. Midrest 47 comprises a central element 84 which may be generally flat and having a relatively narrow width and a front/anterior face, attached to and extending upward from seat platform 20. Central element 84 has a first means for resisting deflection of central element 84. The chairback further comprises two side elements 86 on either side and laterally adjacent to central element 84, similarly extending upward from seat platform 20, the side elements 86 also optionally being generally flat and each wider than central element 84 and each having a front/anterior face, and each side element 86 having a second means for resisting deflection of side elements 86. FIGS. 16 and 17 show an embodiment where side elements 86 deflect away from the user's body by increasing the recline angle about a spring-like attachment to resist deflection, or a pivot mechanism with spring or torsion resistance. It is understood that deflection could be via a rearward translational motion with appropriate translational linkage, or some combination of spring, torsion control, translation, or pivot mechanisms.

[0061] In the embodiment shown, the first means of resisting rearward deflection for central element 84 is substantially stronger/higher than the second means of resisting rearward deflection for side elements 86. As shown in FIG. 18, the face of central element 84 is positioned forward of the face of side elements 86. Thus when a user sits and applies pressure to the chairback, most or substantially all of the user's back is supported by central element 84 applying pressure to the user's thoracic region because side elements 86 deflect more easily than central element 84, thus little support/pressure is experienced by the user at the scapulae. This multi-element chairback embodiment may optionally comprise a neckrest 60 and neckrest cushion 62, and may further comprise an integrated or separate lower backrest support 50 or lumbar cushion 52.

[0062] The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Furthermore, particular features of one embodiment can replace corresponding features in another embodiment or can supplement other embodiments unless otherwise indicated by the drawings or this specification.