Abstract:
A seating unit includes a base, a seat, a back, and a control operably supporting the seat and the back on the base for movement between upright and recline positions. The control includes a spring providing a biasing supporting force to the back during recline, and further includes a booster mechanism capable of increasing the supporting force, and still further includes a selector device for activating and deactivating the booster mechanism. The selector device is easily moveable with a low effort that is separated from and independent from any friction generated by internal components of the booster mechanism. In a narrower aspect, the control is powered, such as by an electrical or electromechanical device from a remote location. A back stop is attached to the selector device, for movement between a disengaged position, a partial-recline position, and a recline-prevented position.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is related to an application Serial No. ______, filed on even date herewith, entitled SEATING WITH COMFORT SURFACE, and also to an application Serial No. ______, filed on even date herewith, entitled CONTROL MECHANISM FOR SEATING UNIT, the entire contents of both of which are incorporated herein by reference.  
         BACKGROUND  
         [0002]    The present invention relates to a seating unit having an adjustable back tension function and an adjustable back stop function.  
           [0003]    Comfort, simplicity, and adjustability continue to be highly-demanded features in seating. Specifically, it is desirable to provide a control that is easy to operate, simple to manufacture and assemble, relatively low cost and relatively few components, and that has a modern thin sleek appearance. It is further desirable that the structure complement the ability to provide weight-activated support upon recline so that heavier seated users feel secure upon recline even without adjustment.  
           [0004]    In particular in regard to adjustability, it is desirable to provide adjusters that are easier to adjust and more intuitive to operate. For example, many chairs having a reclineable back also have an adjustable spring for varying the back support provided upon recline. However, many adjusters work against the spring to compress the spring during adjustment. This takes considerable effort, even if a mechanical advantage is provided, since the springs are substantial and there is significant energy input required to compress the spring. Even adjustments that decompress the spring require effort to overcome frictional forces that prevent unexpected decompression. Further, seated users constantly find themselves searching among several different controls trying to find the correct control for the adjustment that they desire. Still further, once the proper control is selected, the user still has to figure out which way to adjust the control to achieve the desired effect. It is desirable to find a single control mechanism that provides a logical and intuitive arrangement of back adjustments, where increasingly supportive adjustments cause an increasing level of back support, even though the increasing support is provided by different mechanisms.  
           [0005]    In addition to the above, it is desirable to provide a chair that is optimally designed to use recyclable parts, and that uses components that can be easily separated for recycling and/or repair. Expanded thermoset foam products are usually classified as not recyclable, and further are generally considered to be unfriendly to the environment as compared to steel, remeltable thermoplastic, recyclable materials, and more natural materials. Eliminating thermoset foam would be a significant step toward making a chair 100% recyclable. However, the comfort and cost advantage must be maintained for competitive reasons.  
           [0006]    Accordingly, an apparatus solving the aforementioned problems and having the aforementioned advantages is desired.  
         SUMMARY OF THE PRESENT INVENTION  
         [0007]    In one aspect of the present invention, a seating unit includes a base, a seat, a back, and a control operably supporting the seat and the back on the base for movement between upright and recline positions. The control includes a first mechanism providing a biasing supporting force to the back during recline, and further includes a booster spring mechanism capable of increasing the supporting force, and still further includes an on/off selector device for selectively activating and deactivating the booster spring mechanism.  
           [0008]    In another aspect of the present invention, a seating unit includes a base, a seat, a back, and a control operably supporting the seat and back on the base for movement between upright and recline positions. The control includes a link pivoted to the seat at one end and pivoted to the base at another end. The control also includes a first mechanism adapted to provide a biasing supporting force during recline and further includes a booster spring mechanism operably attached to the link. The booster mechanism comprises a torsion spring and a stop selectively engageable with the torsion spring to activate the torsion spring to boost and increase the supporting force provided to a seated user during recline.  
           [0009]    In another aspect of the present invention, a control adapted to adjustably support a movable structural component on a base of a seating unit includes a pivot pin adapted to be rotatably supported on one of the base and the structural component. The pivot pin is rotatably coupled to the other of the base and the structural component for coordinated rotation therewith during recline. A torsion spring has an inner ring keyed to the pivot pin, an outer second ring having a protrusion extending from the outer second ring, and a resilient spring portion operably interconnecting the inner and outer rings. A booster stop is operably coupled to the one of the structural component and the base, the booster stop being movable between a disengaged position where the protrusion misses and passes by the booster stop when the pivot pin is rotated as the structural component is moved, and an engaged position where the protrusion engages the booster stop and prevents the outer second ring on the torsion spring from rotating. By this arrangement, the booster stop activates the torsion spring to provide a bias when the structural component is moved, whereby the torsion spring can be selectively engaged and disengaged to adjust a biasing force on the structural component.  
           [0010]    In another aspect of the present invention, a seating unit includes a base, a seat, and a back. A control supports the back on the base for movement between upright and reclined positions, the control including a plurality of mechanisms including first and second energy mechanisms for biasing the back toward the upright position, and a back stop mechanism for limiting movement of the back to a position short of the reclined position. A selector device is operably connected to said plurality of mechanisms for selectively activating said plurality of mechanisms.  
           [0011]    In still another aspect of the present invention, a seating unit having a base, a seat, and a back adapted to pivot between upright and reclined positions, an energy mechanism for biasing the back toward the upright position, a tension adjustment mechanism for adjusting the force biasing the back toward the upright position, and a back stop mechanism for limiting the range of motion of the back to a position short of the reclined position. An improvement includes a single actuator operably attached to both the tension adjustment mechanism and the back stop mechanism for operating said mechanisms.  
           [0012]    In another aspect of the present invention, a seating unit having a base, a back, and an underseat control operably coupled to and supporting the back for movement between upright and reclined positions. The control includes a housing, an energy adjustment mechanism and a back stop mechanism. An improvement includes an actuator movable to a first operative position for selectively engaging the energy adjustment mechanism, and movable to a second operative position for selectively engaging the back stop mechanism.  
           [0013]    These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0014]    [0014]FIG. 1 is a perspective view of a seating unit embodying the present invention, the seating unit including transverse wires in a back and seat forming a comfortable support surface;  
         [0015]    [0015]FIG. 2 is a schematic cross-sectional view showing the position of the transverse wires in the seat and back of FIG. 1, the wire support members being shown in solid lines without a seated user, the wire support members being shown in phantom lines with a seated user in an upright position;  
         [0016]    [0016]FIG. 2A is a view similar to FIG. 2, but showing the chair with seated user in the upright position in phantom lines and in a reclined position in dashed lines;  
         [0017]    [0017]FIG. 2B is a schematic view similar to FIG. 2A, but with the change in shape of the seat being overlaid to eliminate confusion caused by a translation/rotational (up and forward) movement of the seat during recline;  
         [0018]    [0018]FIGS. 3-4 are plan and side views of the seat of FIG. 1;  
         [0019]    [0019]FIGS. 5-6 are plan and side views of the seat frame of FIG. 3;  
         [0020]    [0020]FIG. 7 is a partially exploded perspective view of a corner section of the seat in FIG. 3;  
         [0021]    [0021]FIGS. 8-10 are side, top, and end views of a bearing shoe used to slidably support an end of one of the wires shown in FIG. 7;  
         [0022]    [0022]FIGS. 11-12 are plan views of two different wires used in the seat shown in FIG. 3;  
         [0023]    [0023]FIGS. 13-14 are side and plan views of a cover for side sections of the seat frame shown in FIG. 5-6;  
         [0024]    [0024]FIGS. 15-16 are front and rear perspective views of the back shown in FIG. 1;  
         [0025]    [0025]FIG. 17 is a side view of the back shown in FIG. 15;  
         [0026]    [0026]FIG. 18 is a side view of the underseat control shown in FIG. 1;  
         [0027]    [0027]FIGS. 19-20 are cross-sectional views similar to FIG. 18, but showing cross-sectioned components, FIG. 19 being taken along line XIX in FIG. 33 and showing the booster mechanism disengaged, and FIG. 20 showing the booster mechanism engaged;  
         [0028]    [0028]FIGS. 21-23 are cross-sectional views similar to FIG. 18, but showing cross-sectioned components, FIG. 21 being taken along line XXI in FIG. 33 and showing the backstop mechanism disengaged, and FIG. 22 showing the backstop mechanism engaged to a first level for partial back recline, and FIG. 23 showing the backstop mechanism engaged to a second level for no back recline;  
         [0029]    [0029]FIG. 24 is a graph showing different lines of back support force versus deflection, depending upon whether the booster is disengaged or engaged, and whether the backstop is engaged for partial recline or to prevent any recline;  
         [0030]    [0030]FIG. 25 is a graph showing different strength booster mechanisms on a chair where they provide selectively increasing amounts of energy as each successive one is engaged;  
         [0031]    [0031]FIG. 26 is an exploded perspective view showing an underseat-located manual control for the booster and backstop mechanism;  
         [0032]    [0032]FIGS. 26A and 27A are similar to FIGS. 26 and 27, but showing alternative embodiments;  
         [0033]    [0033]FIG. 27 is a cross-sectional view taken along the line XXVII in FIG. 33;  
         [0034]    [0034]FIG. 28 is an exploded perspective view of the manual control of FIG. 26;  
         [0035]    [0035]FIGS. 29-30 are cross-sectional views of the hand control of FIG. 28, FIG. 29 being fully assembled, FIG. 30 being exploded apart;  
         [0036]    [0036]FIG. 31 is an enlarged fragmentary view of the clutch and its engagement with the exterior housing, showing the clutch in a locking position;  
         [0037]    [0037]FIGS. 31A and 31B are enlarged fragmentary views of a portion of FIG. 31, FIG. 31A showing a locked position and FIG. 31B showing a released position;  
         [0038]    [0038]FIGS. 32-33 are front and rear partial perspective views of the base and control of FIG. 18;  
         [0039]    [0039]FIGS. 34-35 are front and plan fragmentary views of the control shown in FIG. 33;  
         [0040]    [0040]FIG. 36 is an exploded perspective view of FIG. 33;  
         [0041]    [0041]FIG. 37 is an enlargement of the energy boost mechanism shown in FIG. 36; and  
         [0042]    [0042]FIGS. 38-39 are cross sections taken along the line XXXIX in FIG. 33, and are side views of the control, seat and back, FIG. 38 being in an upright position and FIG. 39 being a recline position, FIGS. 38-39 being similar to FIG. 18, but being simplified to show operation of the pivot link during recline.  
         [0043]    [0043]FIGS. 40-42 are front perspective, rear perspective, and side views of a modified form of the present inventive chair;  
         [0044]    [0044]FIG. 43 is a perspective view of the underseat control for the chair in FIG. 40;  
         [0045]    [0045]FIG. 44-46 are a top perspective, a second top perspective, and a bottom perspective exploded view of a portion of the underseat control and related base components of FIG. 43;  
         [0046]    [0046]FIG. 47-49 are exploded perspective views of the underseat control of FIG. 43, FIGS. 48 and 49 showing a hand control for adjusting the booster and back stop mechanism shown in FIG. 45;  
         [0047]    [0047]FIG. 50-51 are perspective and fragmentary perspective views of the seat shown in FIG. 40;  
         [0048]    [0048]FIG. 52 is a cross section showing flexing of the wire support member for the wire support members shown in FIG. 50, and FIG. 52A is a similar view showing an alternative mounting structure;  
         [0049]    [0049]FIGS. 53-54 are exploded perspective views of the back shown in FIG. 40;  
         [0050]    [0050]FIGS. 55-57 are perspective views of the lumbar devices and their effect on the wire support sections;  
         [0051]    [0051]FIG. 58 is a schematic showing the lumber device of FIG. 57;  
         [0052]    [0052]FIG. 59 is a perspective view of the chair of FIG. 40 with the lumber device of FIG. 55 in a disabled storage position;  
         [0053]    [0053]FIG. 60 is an exploded perspective view of the headrest assembly on the chair of FIG. 40;  
         [0054]    [0054]FIGS. 61-62 are an exploded perspective and exploded cross section of the headrest assembly of FIG. 60;  
         [0055]    [0055]FIG. 63 is an exploded perspective view of the seat frame and wire support members of FIG. 50, including the depth adjustment latch and release handle;  
         [0056]    [0056]FIG. 64 is an enlarged top perspective view similar to FIG. 51, but which focuses on a front corner of the seat subassembly of FIG. 50;  
         [0057]    [0057]FIGS. 65 and 66 are cross sectional views taken perpendicularly through the latching area of FIG. 64, FIG. 65 showing a latched position and FIG. 66 showing an unlatched position of the latching member;  
         [0058]    [0058]FIGS. 67-69 are fragmentary views of the back frame of FIG. 53 and side frame members of FIG. 45; FIGS. 67 and 68 showing assembly of upright members together, FIG. 69 showing the full assembly; and  
         [0059]    [0059]FIGS. 70 and 71 are cross sectional views showing an attachment configuration for attaching a cushion assembly to the back frame of FIG. 53. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0060]    A chair  20  (FIG. 1) embodying the present invention includes a base  21 , a seat  22 , and a back  23 , with the seat  22  and back  23  being operably supported on the base  21  by an underseat control mechanism  24  for synchronous movement upon recline of the back  23 . Upon recline, the control mechanism  24  moves and lifts the seat  22  upwardly and forwardly, such that the back  23  (and the seated user) is automatically provided with a weight-activated back-supporting force upon recline. Advantageously, heavier-weight seated users receive greater back-supporting force, thus eliminating (or at least reducing) the need for them to adjust a tension device for back support when reclining in the chair. The seat  22  (and also the back  23 ) includes a highly comfortable support surface formed by a locally-compliant support structure (hereafter called “a comfort surface”) that adjusts to the changing shape and ergonomic support needs of the seated user, both when in an upright position and a reclined position. Specifically, the comfort surface changes shape in a manner that retains the seated user comfortably in the chair during recline, yet that provides an optimal localized ergonomic support to the changing shape of the seated user as the user&#39;s pelvis rotate during recline. In addition, the chair  20  avoids placing an uncomfortable lifting force under the seated user&#39;s knees and thighs, by well-distributing such forces at the knees and/or by flexing partially out of the way in the knee area. Further, comfort surfaces of the seat  22  and back  23  create a changing bucket shape (FIGS. 2A and 2B) that “grips” a seated user and also actively distributes stress around localized areas, such that the seated user feels comfortably retained in the seat  22 , and does not feel as if they will slide down the angled/reclined back and forward off the seat during recline, as described below.  
         [0061]    The illustrated control mechanism  24  also has several advantages and inventive aspects. The control mechanism  24  includes a “booster” mechanism  25  (FIG. 19) that can be engaged (with low effort) to provide an even greater back support upon recline, if the seated user desires the additional support upon recline. Advantageously, the control mechanism  24  has a thin profile and is very cost-effective to manufacture and assemble, such that it can be well integrated into chair designs having a thin, side profile. The combination of the comfort surface on the back  22  and seat  23  (FIG. 1) with the control mechanism  24  provides a surprising and unexpected result in the form of a very comfortable and supportive “ride” in all positions of the chair, including upright and recline positions. The comfortable “ride” is at least partially due to the fact that, while the seat that lifts upon recline to provide a weight-activated back support force, with the seat  22  and back  23  surfaces dynamically changing shape to relieve pressure behind the seated user&#39;s knees. Also, the comfort surfaces of the seat  22  and back  23  also create a changing bucket (see FIGS. 2A and 2B) to support the pelvis as it “rolls” and changes shape during recline, which counteracts the gravitational forces causing the seated user&#39;s body to want to slide down the reclined/angled surface of the back  23  and slide forward off the seat  22 . Also, the booster mechanism  25  on the control mechanism  24  is very easy to engage or disengage, (almost like a switch that flips on or oft) making it more likely to be used. Also, this allows the booster mechanism  25  to be operated by automatic panel and/or remote devices, including electronic, mechanical, and other ways. Advantageously, all major components of the chair  20 , including the control mechanism  24 , are separable and recyclable, thus facilitating repair, and promoting components and processes that are friendly to the environment, while maintaining low cost, efficient assembly, relatively few complex parts, and other competitive advantages.  
         [0062]    The seat  22  (FIGS. 3-4) includes a molded perimeter frame  30  made of nylon or the like. The illustrated frame  30  is semi-rigid, but is able to flex and twist a limited amount so that the frame  30  gives and moves with a seated user who is reaching and stretching for items while doing work tasks. The frame  30  includes a U-shaped rear with horizontal side sections  31  connected by a transverse rear section  32 , and further includes a U-shaped front  33  that connects a front of the side sections  31 . It is contemplated that the perimeter frame  30  can be a single-piece molding, or a multi-piece assembly. The illustrated frame  30  defines a continuous loop, but it is contemplated that the frame could also be U-shaped with an open front, for example. The U-shaped front  33  includes side sections  34  that connect to an end of the side sections  31  and extend downward and rearward, and further includes a transverse section  35  that connects the side sections  34 . The U-shaped front  33  forms a “U” when viewed from a front, and angles downward and rearward, such that it leaves an upwardly open area in a front of the perimeter frame  30  at a location corresponding to the underside of a seated user&#39;s knees. This allows the perimeter frame  30  to avoid putting pressure on the bottom of a seated user&#39;s knees upon recline, even though the seat  22  is raised, as described below.  
         [0063]    The side sections  31  include a series of notches  36  (six such notches are illustrated) at about 3 to 7 inches rearward of a front end of the side sections  31 , or more preferably 4 to 6 inches. The notches  36  create a flex point, which causes a front section  37  of the side sections  31  to flex downwardly when pressure is placed on the front end of the side sections  31 . For example, front section  37  will flex when the front of the seat  22  is lifted against the knees of a seated user and the user is lifted, which occurs during recline of back  23 .  
         [0064]    A pair of tracks  38  are attached to the bottoms of the side sections  31  rearward of the notches  36 . The pair of tracks  38  are adapted to slidably engage a seat support structure for providing a depth-adjustable feature on the chair  20 . Nonetheless, it is noted that the present inventive concepts can be used on chairs not having a depth-adjustment feature.  
         [0065]    The side sections  31  of perimeter frame  30  (FIG. 5) each include longitudinally-extending recesses  40 , respectively, in their top surfaces for receiving steel rods  42  (FIGS. 3 and 12). The side rods  42  resiliently support and stiffen the side sections  31 , particularly in the area of notches  36 . As illustrated (in FIGS. 3-4), the recesses  40  are primarily located rearward of the notches  36 , but also include a front portion that extends forward past the notches  36  to provide added resilient support for side sections  31  at the notches  36 . It is noted that the rods  42  can be different shapes or sizes, or multiple rods can be used. Also, different materials can be used in the rods  42 , if desired, such as plastic or composite materials. However, the illustrated rods  42  are linear and made of a “hard-drawn spring steel” for optimal strength, low weight, long life, and competitive cost. Further, they are mechanically attached into position in their front and rear. It is contemplated that the rods  42  could also be insert-molded, snapped in, or otherwise secured in place.  
         [0066]    The comfort surface of the seat  22  (FIG. 3) (and of the back) are formed by individual support members  45  with parallel long sections  51  and U-shaped ends  52  that slidably engage pockets  50  in the side sections  31 . There are thirteen pockets  50  illustrated, but it is contemplated that more or less could be included depending on the chair design and functional requirements of the design. Further, the multiple pockets  50  could be replaced with continuous long channels formed longitudinally along the side sections  31 , if desired. Each pocket  50  includes inwardly facing pairs of apertures  51 ′ (FIG. 5) with an “up” protrusion  51 ′ formed between the apertures  51 ′. The ends  52  of the front eight support members  45  are positioned in and directly slidably engage the front eight pockets  50  for limited inward and outward movement, while the ends  52  of the rear five support members  45  are carried by bearings  53  in the rear five pockets  50 , as discussed below. The inboard surface of the pockets  50  (i.e. the “up” protrusion  51 ′ formed between the apertures  51 ′) forms a stop for limiting inward sliding movement of the ends  52  of the support member  45 , By doing this, it limits the downward flexing of the long sections  51  with a “sling”-type action when a person sits on the comfort surface of the seat  22 . Notably, this results in a “soft” stopping action when a seated user reaches a maximum flexure of the long sections  51 . Part of the reason for the “soft” stopping action is the inward flexure of the side sections  31  as the ends  52  bottom out in the pockets  50 , but also part of the “soft” stopping action is due to the independent action of the individual support members  45  and due to the paired arrangement of the long sections  51  on the support members  45 . By this arrangement, a seated user remains comfortable and does not feel a sharp and sudden stop that is uncomfortable, even though the seat  22  is held to a maximum depression.  
         [0067]    Support members  45  (FIG. 7) are hard-drawn spring steel rods (FIG. 11) having a circular cross section. The rods (i.e. support members  45 ) are bent into a rectangular loop shape with relatively sharply bent corners, and include parallel/linear long sections  51  and flat/short end sections  52 . The illustrated end sections  52  have relatively sharply bent corners, such that they form relatively square U-shaped configurations. Also, one of the illustrated end sections  52  has opposing ends of the wire that abut, but that are unattached. It is contemplated that the abutting ends in the one end section  52  could be welded together if needed, but this has not been found necessary in the present chair  20 , particularly where bearings  53  are used, as discussed below. It is also contemplated that individual linear rods could be used instead of the support member  45  being a rectangular loop shape with parallel long sections  51 , if desired. In such event, the ends  52  could be hook-shaped or L-shaped so that they engage the “up” protrusion in the pockets  50  for limited inwardly movement when a person sits on the seat  22 . However, the interconnection of adjacent pairs of long sections  51  by end sections  52  can provide an additional stability and “coordinated” cooperative movement in the pairs that is believed to have beneficial effects. In particular, the rear five support members  45  with bearings  53  undergo considerable movement and flexure as a seated user reclines and/or moves around in the chair  20 , such that bearings  53  with coupled wire sections  51  have been found to be desirable with those five support members  45 .  
         [0068]    As noted above, the rearmost five support members  45  (FIG. 7) include bearing shoes  53  (also called “bearings” herein) (FIGS. 8-10) that are attached to the end sections  52 . The bearing shoes  53  are made of acetal polymer and are shaped to operably fit into the pockets  50  for oscillating (inward and outward) sliding movement in a transverse direction as a seated user moves around in the chair  20  and as the long sections  51  of the support member  45  flex. The bearing shoes  53  include a U-shaped channel  54  shaped to mateably receive the U-shaped end sections  52 . The bearing shoes  53  can include a friction tab at locations  55  for snap-attachment to the U-shaped ends  52 , if desired, though a friction tab is not required per se when a top cap is provided that captures the bearing shoes  53  in the pockets  50 . Notably, the bearing shoes  53  retain together the end sections  52  having the wire ends that touch each other even where the abutting ends of the wire are not attached directly together by welding.  
         [0069]    Right and left top caps  57  (FIGS. 13-14) are screw-attached, heat-staked, or otherwise attached to the side sections  31 . The top caps  57  (FIG. 7) include a body  58  shaped to cover the pockets  50  and operably hold the bearing shoes  53  in place. A rear of the body  58  extends laterally and potentially includes a slot  59  to better cover a rearmost one of the pockets  50  while still allowing the rearmost wire section  51  to freely flex (FIG. 7). It is contemplated that the side sections  31  and top caps  57  will both be made of nylon, and the bearing shoes  53  made of acetal, because these materials have a very low coefficient of friction when engaged with each other. Further, the apertures  51 ′ (FIG. 7) are oversized to be larger than a diameter of the long sections  51  of the rod support members  45 , such that there is no drag during flexure of the support members  45  and concurrent movement of the bearing shoes  53  in the pockets  50 .  
         [0070]    The illustrated seat  22  (FIG. 1) is covered with a fabric  60 , and potentially includes a top thin foam or non-woven PET fiber cushion under the fabric  60  on both the seat  22  and the back  23 . However, it is contemplated that the seat  22  and/or back  23  may not require a foam cushion because, based on testing, the present seat  22  is so comfortable that a cushion is not necessary. Further, the space between the wire sections  51  allows the construction to breathe, so that a seated user does not become sweaty while resting on the present chair  20 , which can also be a competitive advantage. A thin topper cushion or webbing could also be used under the fabric for aesthetics, if desired.  
         [0071]    The present arrangement of seat  22  offers several advantages. Assembly is easy, and it is difficult to incorrectly assemble the seat. By the present arrangement, each different pair of wire sections can be flexed different amounts, and further, each long section  51  in a given support member can be flexed more or less (and can be flexed in a different direction) than the other long section  51  in the pair. The pockets  50  engage the bearing shoes  53  and limit their movement, such that they in turn limit flexure of the wire long sections  51  to a maximum amount so that the support surface cannot flex “too far”. Based on testing, the maximum limit of flexure provided by the pockets  54  is a soft limit, such that a seated user does not feel an abrupt stop or “bump” as the maximum flexure is achieved. It is noted that the present wire long sections  51 / 52  are all the same diameter and shape, but they could be different diameters, stiffnesses, or shapes. The individual wire long sections  51  travel to support a seated user&#39;s body along discrete and independent lines of support, with the wire long sections  51  moving in and out to meet the body and support the user. Specifically, as a seated user reclines, the wires move and flex to create a shifting new “support pocket” for the seated user. FIG. 2 shows the comfort surface  60  of the seat  22  as being relatively flat (i.e. position P 1 , see solid lines) when there is no seated user resting on the seat  22 . (I.e. The wire long sections  51  of the support members  45  of the seat  22  are located in a generally horizontal common plane.) When a seated user sits in the chair  20  in an upright position, the comfort surface  60  flexes to a new shape (i.e. position P 2 , see phantom lines), which includes an “upright position” support pocket  63  formed by (and which receives and supports) the protruding bone structure, muscle, and tissue of a seated user&#39;s hips. As the seated user reclines the back  23  toward a fully reclined position (FIG. 2A), the comfort surface  60  flexes to a new shape (i.e. position P 3 , see dashed lines), which includes a newly formed “recline position” support pocket  65  formed by (and which receives and supports) the protruding portion, muscle, and tissue of a seated user&#39;s hips. Notably, the support pocket  65  formed in the seat  22  while in the recline position (FIG. 2B) is located rearward of the support pocket  63  formed in the seat  22  when in the recline position (see FIG. 2B, where a shape of the seat in the upright and reclined positions is overlaid to better show the shape change). This is caused by a rolling motion of the hips during recline. The long sections  51  of rod support members  45  are independent and provide a localized freedom and dynamic of movement able to comfortably accommodate the rolling activity of the hips of a seated user in a novel and unobvious way not previously seen in task chairs.  
         [0072]    The back  23  (FIG. 2) also undergoes a shape change, as shown by the comfort surface  66  in the unstressed position P 1  (unstressed, no seated user), the flexed comfort surface  66  in the upright stressed position P 2  (“upright position” with seated user), and the flexed reclined comfort surface  66  in the reclined stressed position P 3  (“recline position” with seated user) (FIG. 2A).  
         [0073]    The pairs of long wire sections  51  act in a coordinated distributed dynamic fashion (primarily in a vertical direction) that provides an optimal comfort surface. This is a result of the constrained/limited movement of the bearing shoes  53  on adjacent pairs of the long sections  51  of the rod support members  45  and also is a result of the fabric  60  as it stretches across and covers the long sections  51 . Nonetheless, it is noted that an extremely comfortable support can be achieved even without the fabric  60 , because the long sections  51  flex in a manner that does not pinch or bind the seated user as the shape of the support pocket for their body changes.  
         [0074]    It is noted that the long sections  51  in the seat  22  flex and move to provide support primarily vertically, but that some of the long sections  51  may have a horizontal or angled component of movement and/or may provide a horizontal or angled component of force to a seated user. In particular, the long sections  51  located at a front of the “recline” support pocket  65  (see wires  51 A) tend to engage any depression in the flesh of a seated user at a front of the seated user&#39;s protruding hip area (i.e. behind the seated user&#39;s thighs and in front of the seated user&#39;s “main” hip area) which tends to securely hold the seated user in the seat  22 . This occurs regardless of the location of the depression in the flesh of a particular seated user, due to the plurality of independently flexible long sections  51  in the seat  22 . This added holding power appears to be important in preventing seated users from feeling like they will slide down an angled back (such as during recline) and forward and off the seat. The present inventors believe that this benefit, though subtle, is a very important and significant advantage of the chair  20 . Notably, even with a fabric cover, there may be a horizontal component of force provided by the long sections  51 , limited only by the movement of the long section  51  under the fabric, the stretchability of the fabric, the movement of bearing shoes  53 , and the forces generated by the rolling action of the seated user&#39;s hips.  
         [0075]    The operation of the seat  22  is illustrated in FIGS. 2-2B. FIG. 2 shows flexure of a center of the long sections  51  of the support member  45  between the unstressed state (i.e. no seated user, see solid lines P 1 ), and a stressed state (i.e. with a seated user, see phantom lines P 2 ) (both in an upright position of the chair  20 ). FIG. 2A shows the chair  20  with a seated user in the chair  20  in the upright position (solid lines) and a reclined position (dashed lines). FIG. 2B is a schematic view intended to show the change of shape in the comfort surface of the seat  22  between the upright position (see solid lines P 2 ) and the reclined position (see dashed lines P 3 ). In FIG. 2B, the seat  22  is compared as if it did not move forward upon recline, to better show the change in shape of the “pocket” in the seat  22  where the seated user&#39;s hips are located. Nonetheless, it is noted that the seat  22  does move forward during recline in the present chair  20 .  
         [0076]    The FIG. 7 shows some of the support members  45  with long sections  51  unstressed (i.e. that are located in an outboard position in their respective pocket  50 ), and shows some of the rod support members  45  with wires  51  flexed (i.e. see the bearing shoes  53  at location “B” that are located in an inboard position in their respective pocket  50 ). FIG. 7 also shows some of the bearing shoes  53  exploded out of the pockets  50  and pre-attached to ends of the rod support members  45  (see location “C”). The bearing shoes  53  are ready to drop downward into the pockets  50 , which illustrates a first assembly technique. FIG. 7 also shows one of the bearing shoes  53  positioned in a pocket  50 , with the associated rod support member  45  being positioned above it and ready to be moved downward into engagement with the recess in the bearing shoe  53  (see location “D”), which illustrates a second assembly method.  
         [0077]    The back  23  (FIGS. 15-17) is similar to the seat  22 . Thus, a detailed description of the back  23  is not required for an understanding by a person skilled in this art, since it would be quite redundant. Nonetheless, a description follows that is sufficient for an understanding of the present invention as used on backs, in view of the discussion regarding seat  22  above.  
         [0078]    Briefly, the back  23  (FIGS. 15-17) includes a back perimeter frame  70  composed of L-shaped side frame members  71 . Top and bottom transverse frame members  72  and  73  are attached to the side frame members  71  to form a semi-rigid perimeter. The frame  70  can be one-piece or multi-piece. An additional transverse frame member  72 A (FIG. 1) can also be added, if needed for strength and stability. The side frame members  71  include forwardly-extended lower sections  74  extending below the bottom transverse frame member  73 . The lower sections  74  are pivoted to a seat support  122  of the control mechanism  24 , at location  75 , and are pivoted to a flexible arm part of the control mechanism  24  at location  141 , as described below.  
         [0079]    Similar to the seat  22 , the back side frame members  71  include pockets  77  (see seat frame pockets  50 ), covers  77 ′ covering the pockets  77  (only a left cover  77 ′ is shown), and support members  78  (similar to seat support members  45 ) are provided as hard-drawn spring steel wires with long sections  79  (similar to seat long sections  51 ). Several of the support members  78  have ends that are operably supported by bearing shoes  80  (similar to bearing shoes  53 ). Notably, the illustrated back support members  78  come in two different lengths because the back  23  has a smaller top width and a larger bottom width. (See FIG. 15 and notice the change in position of the pockets  77  at a middle area on the side frame members  71 .) The top half of the side frame members  71  includes a plurality of U-shaped pockets  81  for receiving a wire  79  without a bearing shoe  80 . A top edge of the top frame member  72  is U-shaped and bent rearwardly for increased neck support and comfort to a seated user. Wire strips  83  extend from the top corners of the back frame  70  to a center point located between a seated user&#39;s shoulders, and then extend downward into connection to a center of the bottom transverse member  73 . When tensioned, the wire strips  83  cause the comfort surface of the back (i.e. support members  78 ) to take on an initial concave shape (sometimes referred to as a “PRINGLES potato chip shape”). This concave shape increases the comfort by providing a more friendly “pocket” in the back  23  for a seated user to nest into when they initially sit in the chair  20 .  
         [0080]    An adjustable lumbar support  85  (FIGS. 15-17) is provided on the back that includes a pair of bodies  86  slidably connected to an inboard rib  87  on each of the side frame members  71 . The bodies  86  may (or may not) be connected by a cross member. The bodies  86  are located behind the wires  79  adjacent the side frame members  71  and the wires  79 . Handles  88  extend from a rear of the bodies  86  for grasping by a seated user reaching behind the back  23 . The bodies  86  each include a flange  90  that engages a section of the wires  79  as the wire extends in an inboard direction out of the pockets  77 . By adjusting the bodies  86  vertically, the flanges  90  move behind different wires  79 , causing a different level of support (since an effective length of the supported wires are shortened). Alternatively, the flange  90  can physically engage and bend the wires  79  when vertically adjusted, if desired. FIG. 17 also shows a maximum of rearward flexure of the wires  79 , as shown by the line  95 .  
         [0081]    The present control mechanism  24  (FIG. 18) includes a stationary base support  121  forming a part of the base  21 . The seat  22  includes a seat support  122 , and the back  23  includes a back support  123 . The seat and back supports  122  and  123  are operably attached to the base support  121  as follows. The base support  121  includes an upwardly-facing recess  115  covered in part by plate  115 A. The recess  115  forms a first pocket  116  for receiving the booster mechanism  25 . The recess  115  also forms a tapered second pocket  117  that extends vertically down through the base support  121  for receiving the tapered top section  118  of a height adjustable post  21 A. The illustrated base  21  (FIG. 1) includes a hub at a bottom of the post  21 A, radially extending side sections extending from the hub, and castors at ends of the side sections for supporting the chair  20 . A lockable pneumatic spring is incorporated into the post  21 A for providing counterbalancing support during height adjustment. The post  21 A (FIG. 18) includes a vertically-actuated release button  21 B positioned at a top of the base support  121 . In this location, the release button  21 B can be actuated by a handle (not shown) operably attached to a top or side of the base support  121 , with the handle being pivotally or rotationally movable to selectively cause the handle to depressingly engage the release button  21 B and release the pneumatic spring for height adjustment of the chair. Though one particular base is illustrated, it is specifically contemplated that a variety of different chair bases can be used in combination with the present chair  20 .  
         [0082]    The seat support  122  (FIG. 36) is operably supported on the base support  121  by a front leaf spring  123 ′ and by a pivot mechanism  124  spaced rearward of the leaf spring  123 ′. Specifically, the front leaf spring  123 ′ includes a center portion  125  supported on and attached to an angled front surface  126  (oriented at about 45°) of the base support  121  by threaded fasteners, and includes arms  127  having barrel-shaped or spherically-shaped bearings  128  on each end that slidably and rotatably fit into cylindrical recesses  129  in side members  130  of the seat support  122 . The bearings  128  are barrel-shaped instead of cylindrically-shaped, so that the bearings  128  permit some non-axial rotation and axial sliding as the arms  127  flex, thus helping to reduce high stress areas and accommodating a wider range of movement during recline. However, it is contemplated that different bearing arrangements are possible that will still meet the needs of the present inventive concepts.  
         [0083]    The side members  130  are rigidly interconnected by a cross beam  131  (FIG. 36). The pivot mechanism  124  includes one (or more) pivoted arms  132  that are pivotally supported at one end on the base support  121  by a pivot pin  133 , and pivotally connected to a center of the cross beam  131  at its other end  134  by pivot pin  134 ″ and pin bearings  134 ′. Pin bearings  134 ′ are attached to cross piece  131 , such as by screws. The pivot pin  133  is keyed to the arm  132 , so that the pivot pin  133  rotates upon movement of the seat (i.e. upon recline). Thus, the direction and orientation of movement of the seat support  122  (and seat  22 ) is directed by the linear movement of the bearing ends  128  as the arms  127  of leaf spring  123 ′ flex (which is at a 45° angle forward and upward, see R 1  in FIG. 38), and by the arcuate movement of the pivoted arm  132  on the pivot mechanism  124  as the pivot arm  132  rotates (which starts at a 45° angle and ends up near a 10° angle as the back  23  approaches a full recline position, see R 2  in FIG. 38). The distance of travel of the front of the seat  22  is preferably anywhere from about ½ to 2 inches, or more preferably is about 1 inch upward and 1 inch forward, but it can be made to be more or less, if desired. Also, the vertical component of the distance of travel of the rear of the seat is anywhere from about ½ to 1 inch, but it also can be made to be more or less as desired. Notably, the vertical component of seat movement is the component that most directly affects the potential energy stored during recline in the chair  20 . Restated, the greater the vertical component of the seat (i.e. the amount of vertical lift) during recline, the more weight-activated support will be received by the seated user during recline.  
         [0084]    The back-supporting upright  123  (FIG. 36) includes side sections  135  pivoted to the side members  130  of the seat support  122  at pivot location  75 , which is about halfway between the location of pivot  129  and the pivot  134 . The illustrated pivot location  75  is about equal in height of the bearings  128  (see FIG. 19), although it could be located higher or lower, as desired, for a particular chair design. A rear leaf spring  137  (FIG. 36) includes a center portion  138  attached to a forwardly angled surface  139  on a rear of the base support  121 , and includes arms  140  with barrel-shaped or spherically-shaped bearings  141  that pivotally and slidably engage a cylindrical recess  142  in the side sections  135  of the back upright  123 . The rear surface  139  is oriented at about a 30° forward angle relative to vertical, which is an angle opposite to the rearward angle of the front surface  126 . As a result, as the side sections  135  of the rear spring  137  are flexed during recline, the rear bearings  141  are forced to move forward and downward in a direction perpendicular to the rear angled surface  139  (see directions R 3  and R 4 , FIG. 38). Thus, the pivot  75  drives the seat  22  forward along lines R 1  and R 2  upon recline, and in turn a reclining movement of the back  23  causes the seat support  122  to move forward and upward. As noted above, the movement of the seat support  122  is controlled in the front area by the flexure of the ends of the front spring  123 , which moves the bearings  128  in a linear direction at a 45° angle (up and forward in direction “R 1 ”), and is controlled in the rear area by the pivoting of the pivoted arm  132 , which is arcuate (up and forward along path “R 2 ”). The pivot arm  132  is at about a 45° angle when in the upright rest position (FIGS. 19 and 38), and is at about a 10° angle when in the full recline position (FIG. 39), and moves arcuately between the two extreme positions upon recline. The movement of the seat support  122  causes the pivot location  136  (FIG. 38) to move forwardly along a curvilinear path. As a result, the back upright  123  rotates primarily rearward and downward upon recline (see line R 3 ), but also the lower side section  74  moves forward with a coordinated synchronous movement with the seat  22 , as shown by arrows R 1 -R 2  (for the seat  22 ) and R 3 -R 5  (for the back  23 ) (FIG. 38).  
         [0085]    Specifically, during recline, a rear of the seat support  122  initially starts out its movement by lifting as fast as a front of the seat support  122 . Upon further recline, the rear of the seat support  122  raises at a continuously slower rate (as arm  132  approaches the 10° angle) while the front of the seat support  122  continues to raise at a same rate. The back  23  (i.e. back upright  123 ) moves angularly down and forward upon recline. Thus, the seat support  122  moves synchronously with the back upright  123 , but with a complex motion. As will be understood by a person skilled in the art of chair design, a wide variety of motions are possible by changing the angles and lengths of different components.  
         [0086]    The booster mechanism  25  (FIG. 19) includes a torsion spring  150  mounted on the pivot pin  133  to seat support  121 . The torsion spring  150  includes an inner ring  151  (FIG. 37) keyed to the pivot pin  133 , a resilient rubber ring  152 , and an outer ring  153  with an arm  154  extending radially outwardly. A stop member  155  is pivoted to the base support  121  by a pivot pin  155 ′ (and is keyed to pivot pin  155 ′) and includes a stop surface  156  that can be moved to selectively engage or disengage the arm  154 . When the stop member  155  is moved to disengage the stop surface  156  from the arm  154  (FIG. 19), the torsion spring  150  freewheels, and does not add any bias to the control  120  upon recline. However, when the stop member  155  is moved to engage the stop surface  156  with the arm  154  (FIG. 20), the outer ring  153  is prevented from movement upon recline. This causes the torsion spring  150  to be stressed and tensioned upon recline, since the pivot pin  133  does rotate upon recline, such that the torsion spring  150  “boosts” the amount of energy stored upon recline, . . . thus adding to the amount of support received by a seated user upon recline. It is contemplated that the torsion spring  150  will be made to add about 15% to 20% of the biasing force upon recline, with the rest of the biasing force being supplied by the bending of the leaf springs  123  and  137  and by the energy stored by lifting the seat support and the seated user upon recline. However, the percentage of force can, of course, be changed by design to meet particular functional and aesthetic requirements of particular chair designs.  
         [0087]    In operation, when the booster mechanism  25  is “off” (FIG. 19), the arm  154  moves freely as a seated user reclines in the chair. Thus, during recline as the seat rises and lifts the seated user, the flexible arms  127  and  140  of leaf springs  123 ′ and  137  flex and store energy. This results in the seated user receiving a first level of back support upon recline. When additional support is needed (i.e. the equivalent of increased spring tension for back support in a traditional chair), the booster mechanism  25  is engaged by rotating stop  155  (FIG. 20). This prevents the arm  154  from moving, yet pivot pin  133  is forced to rotate by the arm  132 . Therefore, during recline, the rubber ring  152  of the torsion spring  150  is stretched, causing additional support to the seated user upon recline. In other words, the support provided to the back  23  during recline is “boosted” by engagement of the booster mechanism  25 .  
         [0088]    It is contemplated that several separate torsion springs  150  can be added to the axle of pivot  154 ′, and that they can be sequentially engaged (such as by having their respective stops  155  engage at slightly different angles). This would result in increasing back support, as additional ones of the torsion springs were engaged. (See FIG. 25.) In another alternative, it is contemplated that a single long rubber ring  152  could be used and anchored to the pivot pin  133  at a single location, and that several different outer rings  153  and arms  154  (positioned side-by-side on a common axle) could be used. As additional arms were engaged, the torsional force of the torsion spring would increase at a faster rate during recline. It is also conceived that the stop  155  could have steps, much like the stop  205  (FIG. 21), such that the “booster” torsion spring  150  engages and becomes active at different angular points in time during recline. There are also several other arrangements and variations that a person of ordinary skill will understand and be able to make from the present disclosure. These additional concepts are intended to be covered by the present application.  
         [0089]    A stop pin  290  (FIG. 37) is provided on the arm  132 , and an abutment  291  is provided on the outer ring  153  of torsion spring  150 . The engagement of the components  290  and  291 , and also the engagement of the arm  132  with the base support  121  results in a positive location of the back  23  in the upright position. The rubber ring  152  can be pre-tensioned by engagement of the pin  290  and abutment  291 . Thus, when the stop member  156  is engaged, this preload in rubber ring  152  must be overcome prior to initiation of recline of the back  23 . This results in the elevated pre-tension (see FIG. 24) whenever the stop member  155  is engaged (see FIG. 20). In an alternative construction, a stop pin  290 ′ is located on the arm  132  and positioned to abut a surface on the chair control base support  121  as a way of setting the upright position of the back  23 .  
         [0090]    A backstop  205  (FIG. 21) is formed on the stop member  155 . The backstop  205  is keyed directly to the pivot pin  155 ′ so that it moves with the pivot pin  155 ′. There is no torsion spring element on the illustrated backstop  205 . The arm  132  includes a lever  202  with an abutment surface  203 . A backstop  205  is pivoted to pivot pin  155 ′ at a location adjacent to the booster stop member  155 . The backstop  205  includes a first abutment surface  206  and a second abutment surface  207 .  
         [0091]    A manual control mechanism  220  (FIG. 26) includes a selector device  227  mounted to base support  121  under the seat-supporting structure  122 . The selector device  227  is operably connected to pivot pin  155 ′ as noted below for moving the booster stop  155  and backstop  205 . The backstop  205  does not engage the abutment surface  203  of lever  202  when the manual control mechanism  220  for booster mechanism  25  and backstop  205  is in a “home” disengaged position (FIGS. 19 and 21). The stop member  155  of booster mechanism  25  engages and activates the torsion spring  150  when the selector device  227  is moved to a first adjusted position (FIG. 20). In the first position, the abutment surface  203  is not yet engaged (FIG. 20). However, when the control  220  is moved to a second adjusted position (FIG. 22), the backstop abutment surface  206  engages the abutment surface  203  of the lever  202 , and the back  23  is limited to only ⅓ of its full angular recline. (The backstop  205  can of course have additional intermediate steps if desired.) When the selector device  227  is to a third adjusted position (FIG. 23), the backstop abutment surface  207  engages the abutment surface  203  of the lever  202 , and the back  23  is limited to zero recline. The effect of these multiple positions of selector device  227  are illustrated by the lines labeled  211 - 214 , respectively, on the graph of FIG. 24.  
         [0092]    The combination of the booster mechanism  25  and the backstop  205  results in a unique adjustable control mechanism, as illustrated in FIG. 24. Literally, the device combines two functions in a totally new way—that being a single device that selectively provides (on a single member) a backstop function (i.e. the backstop mechanism  202 / 205 ) and also a back tension adjustment function (i.e. the booster mechanism  150 / 155 ).  
         [0093]    It is contemplated that the pivot pin  155 ′ can be extended to have an end located at an edge of the seat  22  under or integrated into the seat support  122 . In such case, the end of the pivot pin  155 ′ would include a handle for grasping and rotating the pivot pin  155 ′. However, the selector device  227  of the manual control mechanism  220  (FIGS. 26-27) can be positioned anywhere on the chair  20 .  
         [0094]    A manual control mechanism  220  (FIG. 26) includes a Bowden cable  251  having a sleeve  221  with a first end  221 ′ attached to the base support  121 , and an internal telescoping cable  222  (FIG. 27) movable within the sleeve  221 . A wheel section  223  is keyed or otherwise attached to the pivot pin  155 ′ of the back booster and backstop mechanism, and an end  224  of the cable  222  is attached tangentially to a perimeter of the wheel section  223 . (Alternatively, if the diameter of the pivot pin  155 ′ is sufficiently large, the cable end  224  can be connected tangentially directly to the pivot pin  155 ′.) Optionally, a spring  225  can be used to bias the wheel section  223  in direction  225 ′, pulling the cable in the first direction  225 . However, spring  225  is not required where the cable  222  is sufficient in strength to telescopingly push as well as pull. The cable sleeve  221  includes a second end attached to the seat support  122 , such as on the end of a fixed rod support  226  extending from the seat support  122 . A selector device  227  is attached near an end of the rod support  226  for operating the cable  222  to select different back supporting/stopping conditions.  
         [0095]    The selector device  227  (FIG. 28) operates very much like a gearshift found on a bicycle handle bar for shifting gears on the bicycle. The selector device  227  is also not unlike the lumbar force-adjusting device shown in U.S. Pat. No. 6,179,384 (minus the gears  56  and  56 ′). It is noted that a patent entitled “FORCE ADJUSTING DEVICE”, issued Jan. 30, 2001, U.S. Pat. No. 6,179,384, discloses a clutch device of interest, and the entire contents of U.S. Pat. No. 6,179,384 are incorporated herein by reference in its entirety for the purpose of disclosing and teaching the basic details of a sprag clutch and its operation.  
         [0096]    The illustrated selector device  227  (FIGS. 28-30) includes a housing  228  fixed to the rod support  226  with an inner ring section  229  attached to the rod, and an annular cover  230  rising from the ring and forming a laterally-open cavity  231  around the ring  229 . Detent recesses  237  are formed around an inside of the cover  230 . A one-piece plastic molded rotatable clutch member  233  including a hub  242  is positioned in the cavity  231  and includes a first section  234  attached to the cable end  221 ″. The rotatable clutch member  233  further includes a clutch portion  235  integrally formed with hub  242 . A handle  236  is rotatably mounted on an end of the support  226  and includes protrusions  238  that engage the clutch  235  to control engagement with the detent recesses  237  as follows.  
         [0097]    The clutch portion  235  (FIG. 28) includes one or more side sections  240  (preferably at least two side sections  240 , and most preferably a circumferentially symmetrical and uniform number of side sections, such as the illustrated six side sections) having a resilient first section  241  that extends at an angle from the hub  242  to an elbow  243  that is in contact with the detent recesses  237 , and a second section  244  that extends in a reverse direction from the end of the first section  241  to a free end  245  located between the hub  242  and the detent recesses  237 . Each free end  245  includes a hole  248 . The handle  236  includes a clutch-adjacent section  246  that supports the protrusions  238  at a location where the protrusions  238  each engage the hole  248  in the associated free end  245  of every side section  240 . Due to the angle of the first sections  241  (FIG. 31A, see arrow  280 ) relative to the inner surface of the housing that defines detents  237 , the first sections  241  interlockingly engage the detent recesses  237  against the bias of the spring  225  as communicated by the tension in cable  222  (see arrow  281 ), preventing movement of the clutch  235  when it is biased in direction  249  (FIG. 31) by the hub  242 . Thus, when handle  236  is released, the clutch  235  again locks up against the force  281  of spring  225  (FIG. 27) as communicated by cable  222  to the clutch  235 . However, when the handle  236  is grasped and moved in the rotational direction  283  (FIG. 31A) relative to housing  228 , the handle protrusions  238  pull the second section  244  to thus pull the first and second sections  241  and  244  so that the rotatable member  230  (and the clutch  231 ) rotates. When the handle  236  is moved in a rotational direction  282  (FIG. 31A), the handle protrusions  238  push the second section(s)  244  at a low angle relative to the detent recesses  237 , such that the second sections  244  (and first sections  241 ) slip out of and over the detent recesses  237  (FIG. 31B), allowing the rotatable member  230  (and clutch  231 ) to adjustingly move in direction  281 . Thus, the present arrangement allows adjustment in either direction, but interlocks and prevents unwanted adjustment in a particular direction against a spring biasing force.  
         [0098]    It is noted that actuation of the booster mechanism  25  and the backstop  205  is particularly easily accomplished, since the actuation action does not require overcoming the strength of a spring nor of overcoming any friction force caused by the spring  150 . Further, the actuation action does not require movement that results in storage of energy (i.e. does not require compressing or tensioning a spring). Thus, a simple battery-operated DC electric motor or switch-controlled solenoid would work to operate the booster mechanism  25  and/or the backstop  205 . FIG. 26 illustrates a housing  300  supporting a battery pack and electric rotary motivator (such as a DC motor), and includes an end-mounted switch. FIG. 27A illustrates a linear motivator  301  operably connected to cable  222 , and also illustrates a rotary motivator  302  connected to axle  155 ′. Since the movement of the booster mechanism  25  and the backstop  205  requires only a very small amount of energy with minimal frictional drag, it can be accomplished without a need for a large energy source. Thus, a small battery-operated device would work well for a long time before needing recharge of its battery.  
         [0099]    The illustrated control mechanism  24  above has front and rear leaf springs used as flexible weight bearing members to support a seat and back for a modified synchronous movement, and has a pivoted link/arm that assists in directing movement of a rear of the seat. However, the present arrangement can also include stiff arms that are pivoted to the base support  121 , or can include any of the support structures shown in application Ser. No. 10/241,955, filed on Sep. 12, 2002, entitled “SEATING UNIT WITH MOTION CONTROL”, the entire contents of which are incorporated herein in their entirety. Also, a “booster” mechanism  25  provides added biasing support upon recline when a stop is engaged. However, it is contemplated that a continuously adjustable biasing device such as a threaded member for adjusting a spring tension or cam could be used instead of the booster mechanism  25 .  
         [0100]    Since the seat support  122  raises upon recline, potential energy is stored upon recline. Thus, a heavier seated user receives greater support upon recline than a lightweight seated user. Also, as a seated user moves from the recline position toward the upright position, this energy is recovered and hence assists in moving to the upright position. This provides a weight-activated movement seat, where the seat lifts upon recline and thus acts as a weight-activated motion control. (I.e. The greater the weight of the seated user, the greater the biasing support for supporting the user upon recline.) It is noted that a variety of different structures can provide a weight-activated control, and still be within a scope of the present invention.  
       Modification  
       [0101]    A modified chair or seating unit  20 B (FIGS. 40-42) includes changes and improvements from that of chair  20 . In order to minimize redundant discussion and facilitate comparison, similar and identical components and features of the chair  20 B to the chair  20  will be identified using many of the same identification numbers, but with the addition of the letter “B”.  
         [0102]    The chair  20 B (FIG. 40) includes a base  21 B, a seat  22 B, and a back  23 B, with the seat  22 B and back  23 B being operably supported on the base  21 B by an underseat control mechanism  24 B for synchronous movement upon recline of the back  23 B. As with chair  20 , upon recline of chair  20 B, the control mechanism  24 B moves and lifts the seat  22 B upwardly and forwardly, such that the back  23 B (and the seated user) is automatically provided with a weight-activated back-supporting force upon recline. The seat  22 B (and also the back  23 B) includes a highly comfortable support surface formed by a locally-compliant support structure (hereafter called “a comfort surface”) that adjusts to the changing shape and ergonomic support needs of the seated user, both when in an upright position and a reclined position. Specifically, the comfort surface changes shape in a manner that retains the seated user comfortably in the chair during recline, yet that provides an optimal localized ergonomic support to the changing shape of the seated user as the user&#39;s pelvis bones rotate during recline. In addition, the chair  20 B avoids placing an uncomfortable lifting force under the seated user&#39;s knees and thighs, by well-distributing such forces at the knees and/or by flexing partially out of the way in the knee area. Further, comfort surfaces of the seat  22 B and back  23 B create a changing bucket shape (similar to that shown in FIGS. 2A and 2B) that “grips” a seated user and also actively distributes stress around localized areas, such that the seated user feels comfortably retained in the seat  22   b , and does not feel as if they will slide down the angled/reclined back and forward off the seat during recline, as described below.  
         [0103]    The chair control mechanism  24 B (FIG. 43) includes a booster/back stop selector device  227 B with a handle  300  rotatable about a first axis  301  for selectively moving the backstop and booster mechanisms (see FIGS. 19-23) (components  156  and  205 ) between the multiple positions illustrated in FIGS. 19, 20,  22 , and  23 . The control mechanism  24 B further includes a second control device  302  with a radially-extending lever handle  303  rotatable about a rod  304  forming a second axis  304 . The second axis extends parallel to but is spaced from the first axis  301 . The handle  303  is made to be positioned adjacent the handle  300 , and includes a projection that engages the handle  300  to form a stop surface to limit back rotation of the handle  303 . On an inner end of the rod  304  (FIG. 48) is a radially extending finger  305 . The base  21 B (FIG. 45) includes a releasable self-locking pneumatic spring  307  having two fixed tabs  308  for engaging a sheath on a cable sleeve, and a side-activatable lever  309  that operably engages an internal release button in the spring  307 . A side-activatable pneumatic spring such as pneumatic spring  307  is commercially available in commerce and need not be described in detail in this application. (See Cho U.S. Pat. No. 6,276,756.) A cable assembly (FIG. 48) includes a cable  310  connected at one end  311  to the finger  305  and at another end  312  (FIG. 45) to the lever  309 . The cable assembly further includes a sleeve  313  (FIG. 48) that is connected to the base support  121 B near the handle  303 , and that extends to and is connected to the tabs  308  (FIG. 45) on the pneumatic spring  307 .  
         [0104]    As shown in FIGS. 44-46, the base support  121 B is inverted from the base support  121 . Specifically, the base support  121 B (FIG. 46) includes a similar cavity and internal surfaces and structure for supporting the levers, stops, and booster mechanisms within the base support  121 B, similar to base support  121 . However, the front portion  116 B of the cavity in base support  121 B opens downwardly, and the cover  115 B engages a bottom of the base support  121 B. An upright arm  315  (FIG. 45) is attached to the stop member  155 B and extends up through a top aperture  155 B′ in the base support  121 B. An end  316 ′ of a cable  316  is connected to the arm  315  and extends to a tangential connection on the booster/back stop selector device  227 B (FIG. 48), such that when the handle  300  is rotated, the cable  316  is pulled (and/or pushed) . . . and hence the stop member  155 B is moved to a selected position. (See FIGS. 19, 20,  22  and  23 ).  
         [0105]    The laterally-extending arms  127 B of the front spring  123 B′ (FIG. 47) include a tab  320  that non-removably snap-attaches into a spherical bearing  321 . The seat support  122 B (FIG. 45) includes a pair of side frame members  322  and a transverse cross piece  323  rigidly connecting the opposing side frame members  322 . Each side frame member  322  includes a bore  324 , which, if desired, includes a bearing sleeve  325 . The spherical bearings  321  on the ends of leaf springs  123 B′ each rotatably and telescopingly slidingly engage the sleeve  325 /bore  324  to accommodate non-linear movement of the spherical bearing  321  during recline of the back  23 B. Hole  75 B (FIG. 47) receives a pivot pin that rotatably connects the respective side sections  135 B of the back supporting upright  123 B to the seat support  122 B. A flange  327  forms a slot  328  along a top of the side frame members  322 .  
         [0106]    Each seat  22 B (FIG. 43) includes a bracket  480  that forms a mounting socket  481  on seat side frame members  322  for receiving and fixedly supporting an “L-shaped” armrest support structure  482  (FIG. 42) and T-shaped armrest  483 .  
         [0107]    The seat  22 B is depth adjustable, and includes a pair of seat carriers  330  (FIG. 45) attached to each side for sliding depth adjustment. Specifically, the seat carriers  330  each include a body  331  (FIG. 65) adapted to slidably engage a top of the side frame members  322  of the seat support  122 B, and further include a lateral flange  332  that fits into and slidably engages the slot  328  for providing fore/aft depth adjustment of the seat  22 B. The seat  22 B is captured on the seat support  122 B because flanges  332  on the right side and left side seat carriers  330  face in opposite directions. A series of notches  333  in the top inboard side of the seat carriers  330  are engaged by a latch  334  mounted on the seat carriers  330 , the latch  334  being movable downward into an engaged position to engage a selected notch  333  for holding the seat  22 B at a selected depth position. The latch  334  is movable upward to disengage the notches  333 , thus permitting horizontal depth adjustment of the seat  22 B. It is contemplated that the latch  334  can be a variety of different constructions, such as a blade mounted for vertical movement on the seat  22 B, or a bent wire rod that when rotated has end sections that move into and out of engagement with the notches  333 . It is contemplated that other latching and adjustment arrangements can also be constructed.  
         [0108]    In the illustrated chair design, the latch  334  is two-sided (FIG. 63) and is adapted to engage both sides of the seat  22 B to prevent racking and unwanted angular twisting and rotation in the horizontal plane of the seat  22 B. In other words, it is preferable that both seat carriers  330  be fixed to their respective side frame members  322  when latched to provide a stable seat arrangement that does not torque and twist in an undesirable unbalanced manner when a seated user is attempting to recline.  
         [0109]    The illustrated latch  334  (FIG. 63) is actuated by a U-shaped bent wire actuator  334 ′ which includes a transverse handle section  470  forming a handle graspable under the seat front section  388 , and includes a pair of legs  471  and  472 . Each leg  471  (and  472 ) (FIG. 64) fits into a space between sidewall  365  and side section  359  (and between sidewall  366  and side section  359 ) of seat  22 B. An annular groove  473  (FIG. 64) fits mateably into a notch  474  in a rib  475  between walls  365  and  366  to form a pivot for leg  471  (and  472 ). The latch  334  is pivoted on an axle  476 , and includes a latching end  477  shaped to move into and out of engagement with notches  333 , and includes a second end  478  operably connected to a rear tip  479  of leg  471  in direction “D”. When handle section  470  is moved up, side legs  471  and  472  pivot at rib  475 , such that leg tip  479  moves down. When leg tip  479  moves down, latching member  334  pivots about pivot  476  to lift latching end  477  out of notches  333 . A depth of seat  22 B can then be adjusted. One or more resilient springs  480  (FIG. 63) located between transverse handle section  470  and seat front section  388  bias section  470  downwardly, causing latching tip  479  to again engage a selected notch  333  when handle section  470  is released.  
         [0110]    As noted above, the chair control mechanism  24 B (FIG. 43) includes a booster/back stop selector device  227 B with a handle  300  rotatable about a first axis  301  for selectively moving the backstop and booster mechanisms (see FIGS. 19-23) (components  156  and  205 ) between the multiple positions illustrated in FIGS. 19, 20,  22 , and  23 . More particularly, a tubular support  340  (FIG. 48) is attached to the outboard side of the right side frame member  322 . A bearing sleeve  341  is positioned in the tubular support  340  along with a coiled compression spring  342 , a crown-shaped detent ring  343  with pointed axial tips  344 , and the handle  300 . A rod  345  extends from the handle  300  through the components  343 ,  342 , and  340  to an inside of the side frame member  322 . The handle  300  includes teeth-like projections  346  (FIG. 49) that engage the axial tips  344  of the detent ring  343 , and the detent ring  343  is biased axially in an outboard direction so that the tips  344  continuously engage the projections  346 . Further, the detent ring  343  is keyed to the tubular support  340  so that the detent ring  343  cannot rotate, but is able to telescope axially. The tips  344  and projections  346  include angled surfaces so that upon rotation of the handle  300 , the detent ring  343  will move axially inward against the bias of spring  342 , and then snap back outwardly as the tips  344  fit between adjacent projections  346 , thus permitting rotation of the handle  300  in directions  347 . This arrangement causes the handle  300  to move with a detented rotation. The illustrated arrangement includes four projections  346  on the handle  300 , and sixteen tips on the detent ring  343 , but it is contemplated that more or less of each can be used. It is contemplated that the handle  300  can include markings  349  to identify its function, and that any of the handle shapes commonly used in the chair art can be incorporated into the illustrated design.  
         [0111]    A lever  351  (FIG. 48) extends from an inner end of the rod  345 , and is operably connected to one end  353  of the cable  316 . Recall that the other end  316 ′ (FIG. 45) of the cable  316  is connected to the arm  315  of the stop member  155 B of the booster and back stop engaging member  155 B.  
         [0112]    The seat  22 B (FIG. 50) includes a seat frame  357  comprising an upper frame component  358  and right and left seat lower frame components  359  and  360  attached to right and left sides of the upper frame component  358 . The lower frame components  359  and  360  are attached directly to the top of the seat carriers  330  mentioned earlier (FIG. 45), or can be integrally formed to incorporate the features of the illustrated carriers  330 . The support members  45 B (FIG. 50) comprise single wires with down-hooks formed at each end, as described below.  
         [0113]    The lower frame components  359  and  360  (FIG. 50) are mirror images of each other, and accordingly only the lower frame component  359  will be described. The lower frame component  359  is a plastic molded component having a bottom wall  362 , front and rear end walls  363  and  364 , and three longitudinal walls  365 - 367 . The outer wall  365  formed an aesthetic and structural outer surface. The intermediate wall  366  includes a plurality of apertures bosses  368  for receiving screws (not shown) to attach the upper and lower frame components  358  and  359 / 360  together. The inner wall  367  includes a plurality of vertically open slots  369  that extend from its top surface to about halfway down into its height, and further includes parallel walls  370  and  371  that extend from wall  367  to wall  366  on each side of the slots  369 . A recess or pocket  50 B is formed between each of the parallel walls  370  and  371  for receiving the end sections  52 B, as described below. The inboard side of the intermediate wall  366  forms a first stop surface  372  (FIG. 52), and the outboard side of the inner wall  367  forms a second stop surface  373  with an angled ramp surface  374  extending inwardly and downwardly away from the second stop surface  373 .  
         [0114]    Each support member  45 B (FIG. 50) comprises a single wire of the same type wire as support member  45  described above. Each support member  45 B has a long section  51 B and has L-shaped down-formed end sections  52 B forming hooks. The long section  51 B is linear and extends generally horizontally through a bottom of the slots  369  when in an installed position without a user setting on the seat  22 B. The end sections  52 B are linear and extend downwardly into the pockets  50 B. When in an installed position without a user setting on the seat  22 B (see solid lines in FIG. 52), the end sections  52 B abut the outer (first) stop surface  372 , causing the wire long section  51 B to have a slight downward bow in its middle area at location  374 ′. This provides a pretension and pre-form in the wire support member  45 B. When a user sets on the seat  22 B (see dashed lines in FIG. 52), the long section  51 B bends until the end sections  52 B engage the inboard (second) stop surface  373 . This limits further bowing or bending of the long section  51 B. Further, the angled ramp surface  374  provides additional support to the end portions of the long section  51 B, inboard from the end sections  52 B, such that the effective length of the long section  51 B is reduced. This results in the support member  45 B having a preset maximum bend that is limited by the inner stop surface  373  (i.e. a sling type effect), and further is limited by a shorter effective length of the long wire section  51 B (which feels stiffer). Both of these circumstances cause a soft bottoming out as the wire support member  45 B deflects to a maximum bend. At the same time, the wire support member  45 B can bend at any location, more than only at their center point, such that the seated user receives a particularly comfortable and ergonomic support.  
         [0115]    The seat  22 B also includes a cushion assembly  375  (FIG. 40) comprising a cushion and an upholstery or cloth covering. It is contemplated that the supports  45 B are so flexible and comfortable that the cushion can be eliminated. Alternatively, a cushion assembly  375  can be used that is preferably anywhere from {fraction (1/4)} inch to 1 inch in thickness. The upholstery covering can be any material, but preferably should allow some (though not too much) elastic stretch and give to accommodate the shape changes permitted by the individual movement of the support members  45 B.  
         [0116]    Where the cushion assembly  375  is sufficiently elastic and resilient, the cushion assembly  375  can include front and rear hook-like formations that permit it to be hook-attached to a front and a rear of the seat support structure (i.e. frame  30 B). (See the discussion of FIGS. 70-71 below.)  
         [0117]    It is contemplated that, instead of the support members  45 B comprising a single long wire with bent ends, that the support members  45 B can be made to include long resilient wires or stiff members, supported at their ends by hinges to the side frame components, with the axis of rotation of the hinges extending forwardly and being at or slightly below the long resilient wires. For example, FIG. 52A discloses seat having a modified lower frame component  359  made to include a strap  380  supported by a downwardly offset living hinge  381  at a bottom of where the second (inner) stop surface  373  would be. The strap  380  has a groove shaped to receive a straight length of wire  382 . When there is no seated user, the wire  382  extends horizontally, and the living hinge  381  moves to allow the inner wall  367 ′ to move to a normal raised position. When a person sits on the seat, the living hinge  381  flexes, causing the wall  367 ′ to tip inward and downward. (See dashed lines.) This results in an action and movement similar to that noted above in regard to seat  22 B.  
         [0118]    The seat upper frame component  358  (FIG. 50) includes a perimeter frame portion with side sections  385  and  386 , rear section  387  and under-the-knee “waterfall” front section  388  defining a large opening  389  across which the support members  45 B extend. The side sections  385  and  386  screw-attach to the lower side frame components  359  and  360 , and both stiffen the side frame components  359  and  360  and also capture the end sections  52 B in the pockets  50 B. The rear section  387  forms a stiff rear area of the seat  22 B. The front section  388  extends forwardly 3 to 6 inches, and forms a front “waterfall” front surface that comfortably supports the thigh area of seated users of the chair  20 B. Multiple slots  390  and/or stiffening ribs provide an optimal stiffness so that the front section  388  will resiliently flex but provide adequate support and a good feel in both the upright and reclined positions of the chair  20 B.  
         [0119]    Fore-aft leaf springs and transverse leaf springs can be added to optimize anyone of the sections  385 - 388 . In particular, it is contemplated that fore/aft springs will be added to help support the transition area at ends of the front section  388  near a front of the side sections  385 - 386 .  
         [0120]    The illustrated reinforced-plastic springs  490  (FIG. 63) are pultruded flat leaf-springs made to flex without taking a permanent set. They fit snugly into a recess in the upper frame component  358 , and are held thereagainst by the lower frame components  359 . It is contemplated that they will have a flat horizontal cross-sectional shape, and that they will extend forward of the front end of the side sections  359 , but other configurations and arrangements are possible, while still accomplishing the same function.  
         [0121]    The structure of back  23 B (FIGS. 53-54) is not dissimilar to the structure of the seat  22 B. Hence a detailed repetitious description is not required. Nonetheless, it is noted that the back  23 B includes a back perimeter frame  70 B with upright side sections  400 ,  401 , top transverse section  402  and bottom transverse section  403  defining a large open area  404 . A bottom of the side sections  400  and  401  extend forwardly to form forwardly-extending side leg sections  135 B, and are pivotally connected to the seat side sections at pivot  75 B. The upright side sections  400  and  401  include a bottom wall  405  (FIG. 53), end walls  406  and  407 , and inner and outer walls  408  and  410 . Half-depth slots  411  (FIG. 54) are formed in inner wall  408 , and parallel walls  412  and  413  extend between the inner and outer walls  408  and  410  on each side of each slot  411 . A pocket  77 B is formed on the bottom wall  405  between the parallel walls  409 - 410 . Bosses  409  are formed between the inner and outer walls  408  and  410 , and are supported by a short intermediate wall  409  that extends between adjacent ones of the parallel walls  412  and  413  (at locations not interfering with the recesses or pockets  77 B). Support members  78 B (similar to support members  50 B in the seat  22 B) are positioned on the back  23 B, and each include a long wire section  414  that extend into the slots  411 , and L-shaped bent end sections  415  that extend down into the pockets  77 B. The movement of end sections  415  within the pockets  77 B is similar to that described above in regard to the seat  22 B. In the rest position, the end sections  415  abut outer surfaces  417  of the pockets  77 B, thus holding the wires in a partially bent condition. When a seated user rests in the chair and leans on the back, the long wire sections  414  flex, until the end sections  415  move abuttingly into the inboard stop surface  418 , thus limiting any further flex of the wire support members  78 B. Front covers  420  and  421  (FIG. 53) are attached to a front of the back upright side sections  400  and  401 . The covers  420  and  421  both stiffen the side sections  400  and  401 , and also hold the end sections  415  within the pockets  77 B.  
         [0122]    A cushion assembly  375 ′ (FIG. 40) similar to that described above in regard to the seat  22 B is attached to the back frame  70 B. It can be attached in different manners. It is contemplated that one optimum method is to stretch and hook attach the cushion assembly to the top and bottom transverse frame sections  402  and  403 . It is contemplated that a person skilled in the art will be able to use and adapt the attachment structure shown in FIGS. 70-71 to the top and bottom of the back  23 B for attaching the back cushion assembly  375 ′, and to the front and rear of the seat  22 B for attaching the seat cushion assembly  375 . Thus, a detailed description of each is not required.  
         [0123]    As shown in FIG. 71, the bottom frame section  403  of the back frame  400  includes a pair of ridges  528  and  529  that define a downwardly-facing rectangularly-shaped pocket or channel  530  that extends continuously across a width of the back frame  400 . A detent channel  531  (or ridge if desired) is formed parallel the channel  530  along an outside front surface of the bottom frame section  403 . The cushion assembly  375 ′ includes a U-shaped extruded plastic attachment clip  532 , including a flat leg  533 , a barbed leg  534 , and a resilient section  535  connecting the legs  533  and  534 . The legs  533  and  534  are spaced apart to receive and matably engage the forward ridge  529 . A detent protrusion  536  is biased into engagement with the detent channel  531  by the resilient section  535 .  
         [0124]    The cushion assembly  375 ′ further includes a sheet of upholstery material  540  connected to the flat leg  533  by a strip of elastic sheet material  541 . (Alternatively, the elastic sheet material  541  can be eliminated, and the upholstery material  540  attached directly to the flat leg  533 , if testing shows that the added elastic stretch from the sheet material  541  is not required.) Specifically, one edge of the elastic sheet material  541  is sewn to the flat leg  533  of clip  532  by stitching  542 , and an opposite edge is sewn to the upholstery material  540  by stitching  543 . The strip  541  extends completely across a width of the back frame  400 . Different methods are known for attaching and sewing the upholstery material  540  to the strip  541 , and of for attaching and sewing the strip  541  to the flat leg  533 , such that only a single simple seam is illustrated. It is contemplated that in a preferred form, in addition to the sheet material  541 , a foam layer  544  and stable backing sheet  545  will be attached to the cushion assembly  375 ′, although this is not required.  
         [0125]    To attach the cushion assembly  375 ′ to the back frame  400 , the flat leg  533  of the extruded clip  532  of the cushion assembly  375 ′ is pressed into the channel  530  of the bottom frame section  403  of the back frame  400 , with the opposing leg  534  frictionally engaging an outer front surface of the bottom frame section  403 . The combined thickness of the elastic sheet material  541  and the flat leg  533  captured within the channel  530 , along with the detent protrusion  535  engaging the detent channel  531 , form a strong secure connection that retains and holds the cushion assembly  375 ′ to the back frame  400 . It is noted that the sheets  540  and  541  overlay onto the barbed leg  534  when the cushion assembly  375 ′ is fully installed onto the back frame  400  (see the arrow  548  in FIG. 71, and see the assembly of FIG. 70). Since the barbed leg  534  has a thickened cross section, a tension in the sheets  540  and  541  further biases the detent protrusion  535  into engagement with the detent channel  531 . Also, the thickened section of the barbed leg  534  can help hide the stitching, by providing a space to receive the stitched area and to receive the multiple thicknesses of pleats in the stitched area.  
         [0126]    A rail  424  (FIG. 55) is formed on a front of an inwardly-directed flange  425  on the side sections  400  and  401 . The rail  424  extends vertically about half to two-thirds of a length of the side sections  400  and  401 , and includes a top termination or end  426  that forms a access port for engaging the rail  424 . Different accessories can be mounted on the rail  424 . For example, a lumbar device  427  and a headrest support  428  (FIG. 40) are illustrated.  
         [0127]    The illustrated lumbar device  427  (FIG. 55) includes a plastic body  430  that extends around flange  425 , a pair of hook-shaped retainer fingers  431  that slidably engage the rail  424 , and a handle  432  that extends from body  430  opposite the retainer  431 . A pair of detent bumps or recesses  433  are formed on the body  430  adjacent the retainer fingers  431 , and are adapted to detentingly engage successive wire support members  78 B as the lumbar device  427  is moved up and down. Interestingly, the lumbar device  427  can be adjusted downwardly to a non-use storage position (see FIG. 59), where the lumber device  427  is so low that it is effectively disabled since it is no longer effective to provide lumbar support to a seated user. As the lumbar device  427  is moved upwardly, the area of body  430  adjacent the detent bumps  433  supports the long wire sections  414  at locations inboard of the inner wall  408 . (See FIG. 56.) Thus the effective bendable length of the long wire sections  414  is foreshortened, as illustrated by FIGS. 56-57. Thus, the added lumbar support comes from less flexing of the long wire sections  414 , and does not come from a forced shape change to the lumbar support area on the back  23 B (although it could also be designed to create a shape change in the lumbar, if desired). This “flat” adjustment is believed to have good ergonomic benefits, since a seated user receives the added lumbar support that they desire, yet their back and upper torso are not forced to take on a different body shape.  
         [0128]    Another important discovery is the independent action of the right and left lumbar devices  427 . By adjusting the right and lumber devices  427  to a same height, a maximum lumbar support force can be achieved in a particular area (i.e. two wire long support sections  414  are supported). By adjusting the right and left lumbar devices  427  to different heights, the lumbar support area is effectively enlarged (i.e. four wire long support sections  414  are supported). Further, where one lumbar device  427  is adjusted high and the other is adjusted relatively low but still in an effective lumbar supporting area, the lumber devices  427  provide an exceptionally wide range of non-uniform adjustability, i.e. more to the right in one area and more to the left in another area. It is also conceived that different lumbar devices  427  can be provided, such that a user can select the lumbar support that they desire by choosing an appropriate lumber device  427 .  
         [0129]    Even if a single one of the illustrated lumbar devices  427  is used (e.g. if the other side lumbar support device  427  is parked in the disabled position), the seated user does not feel an unbalanced lumber support from the back  23 B. However, it is conceived that the present lumbar device  427  can be designed to appreciably shift the lumbar support to one side (i.e. the long wire section  414  is supported only on one side, such that more lumber support is provided on one side of the chair and less support on the other side). This initially may seem to be undesirable since the lumbar support is unbalanced. However, testing has shown that some seated users want and even prefer an unbalanced lumbar support. This may be particularly true for users having a curved spine, where non-uniform support has beneficial health effects. Also, users may want different lumbar support at different times as they sit and/or recline sideways in unsymmetrical positions, and as they turn and shift to different unbalanced positions in their chairs.  
         [0130]    The illustrated back frame  70 B (FIG. 67) has a unique construction that facilitates assembly. The bottom  500  of side sections  400  and  401  are hollow and each define an arcuate cavity  501 . Side leg sections  135 B include an arcuately-shaped body  502  configured to telescopingly slide into cavity  501 . Once telescoped together, holes  503  and  504  on the bottoms  500  and side leg sections  135 B align. Pivot pins are extended through holes  503  and  504  to form pivot  75 B, and both secure the components (bottoms  500  and side leg sections  503  and  504 ) together, but also act as pivots for the back frame  70 B on the seat  22 B.  
         [0131]    The side frame members  322  of the seat  22 B include a pair of arcuate recesses  510  (FIGS. 48 and 67) that extend partially circumferentially around the hole  75 B. The recesses  510  and holes  75 B form a bow-tie-shaped feature. An inboard side of the side leg sections  135 B include a pair of opposing protrusions  511  (FIG. 67) that fit into recesses  510 . The protrusions  511  engage opposing ends of the recess  510  as the back frame  70 B (i.e. back  23 B) is rotated around pivot pins  505  between upright and fully-reclined positions, thus acting as a stop to set a maximum recline position of the back  23 B.  
         [0132]    A headrest  440  (FIG. 60) can be added to the chair  20 B. The headrest  440  includes a headrest support  441  and a vertically and angularly adjustable headrest assembly  442 . The headrest support  441  includes a center tube  443  and right and left arms  444  and  445  that extend to side sections  400  and  401  of the back frame  70 B. The center tube  443  is positioned rearward of the transverse upper frame section  402  and includes a tab  443 ′ configured to securely engage and be attached to the top frame section  402  of the back frame  70 B. Alternatively, it is contemplated that the tube  443  can be positioned under and in-line with an opening in the rearwardly flared top frame member  402  of the back  238 . The arms  444  and  445  each have an end  447  configured to engage the accessory rail  424  for stability. The headrest assembly  442  includes a cushioned C-shaped head-engaging support  441 . A pair of mounts  449  are attached to a rear of a stiff sheet  448  under the C-shaped support  441 . An upright support  450  includes a vertical leg  451  that extends slidably through the opening in the center tube  443 . Detents can be provided in the upright support  450  and tube  443  to retain the headrest in a selected position.  
         [0133]    A top of the upright support  450  includes a transverse T-shaped hand  452  (FIG. 61) that extends between the mounts  449 . The hand  452  (FIG. 61) includes a hollow tube member  453  with longitudinal serrations  454  around its inner surface. A bar  455  extends between and is fixed to the mounts  449 . The bar  455  includes a pair of longitudinal channels  456 , and a pair of detent rods  457  are positioned in the channels  456 . Springs  458  are positioned in transverse holes in the bar  455 , and bias the detent rods  457  outwardly into engagement with the serrations  454 . By this arrangement, the headrest assembly  442  can be angularly adjusted on the headrest support  441 . The C-shaped headrest support structure  448  has a forward surface that, in cross section, is spiral in shape and is non-symmetrical about the bar  455 . Due to the shape of the C-shaped headrest support structure  448 , the effective area for supporting a seated user&#39;s head moves forward as the headrest support structure  448  is angularly rotatingly adjusted.  
         [0134]    The seat supports (FIG. 50), back supports  78 B (FIG. 53), seat frame  30 B (FIGS. 45 and 50), back frame  70 B (FIGS. 53 and 69), springs  123 B′ and  137 B and control mechanism  24  (FIG. 45) form a compliant chair assembly that results in a soft stop as the back  23 B reaches a full upright position, and results in a soft stop as the back  23 B reaches a full recline position. This avoidance of a hard “clunk” or jerky stop, in combination with the fluidity and smoothness of the ride during recline is noticeable, and results in a surprising and unexpected level of support and comfort to a seated user.  
         [0135]    It has been discovered that during recline of the chair  20 B (FIG. 40) (and similarly chair  20  of FIG. 1), the structure of the link  132 B and the arms  127 B and the back frame upright  123 B permit some compliant motion of the back  23 B even when the back stop member  205 B is engaged. Specifically, with the illustrated components, when the back  23 B “bottoms out” against the back stop during recline, the support arms  127 B and related components in the present chair control provide a compliancy internal to the control not previously seen in prior chair controls. Specifically, the arms  127 B and related components allow the back  23 B to give and comply a limited but noticeable amount. Thus, at the point of engaging the back stop, an increased back support force is provided to a seated user . . . but the feel of a rigid “brick wall” stop is avoided. Instead, the compliant support arms  127 B and back frame upright  123 B flex permitting the back  23 B to move along a limited changed path to provide a compliant “soft stop”. The forces on the back  23 B along this limited changed path can be controlled by varying a strength and massiveness of the various structural elements of the chair, as will be understood by a person skilled in the art of manufacturing chairs and seating units.  
         [0136]    It is noted that the present appearance and design of the illustrated chairs and individual components of the chairs, (such as the armrest, headrest, wires visible on a rear of the back, “gull wing” shape of the underseat control spring, and other items) are considered by the present inventors to be novel, ornamental, and non-obvious to a person of ordinary skill in this art, and hence are believed to be patentable.  
         [0137]    Although an office chair is illustrated, it is specifically contemplated that the present inventive concepts are useful in other seating units other than office chairs. It is also contemplated that the present inventive concepts are useful in non-chair furniture and other applications where movement of a first structure relative to a second structure is desired, particularly where simultaneous coordinated or synchronized movement is desired and/or where a bias force is desired or adjustable stop is desired.  
         [0138]    It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.