Patent Publication Number: US-10321763-B2

Title: Chair

Description:
BACKGROUND 
     The present invention relates to a chair and, in particular but not exclusively, to a chair of the kind used in an office environment. 
     Over recent years, office working practices have evolved. ‘Knowledge-based’ workers are no longer based at the same desk each day and the workplace is becoming more focused on collaboration in order to drive innovation across multi-disciplinary platforms. Offices are evolving to become a place where workers ‘touch-down’ for shorter periods of time, and where ‘hot-desking’ is becoming the norm in a range of businesses. Whereas once every employee had their own desk and their own chair, businesses are now under pressure to gain greater efficiencies by increasing the ratio of people to desks, therefore eliminating the need for banks of desks that may previously have been only partially filled at any given time. 
     From a seating perspective, the traditional ‘eight-hour’ (i.e. full working day), fully-ergonomic, manually adjusted task chair is no longer required in every case. However, providing a smaller number of desks and chairs, for use by a variety of different people at different times may be problematic. Physical characteristics such as height, weight, build, posture etc. vary from person to person. A chair that would be comfortable for a tall person of heavy build may not be suitable for a shorter, leaner person. Typically, office chairs are manually adjustable such that a person can vary the chair settings to a set-up that is comfortable for them. This may involve manually adjusting the height of the seat above the ground, or the inclination of the backrest. However, if a chair is being used by a number of different people in a ‘hot desk’ environment, each person will either need to adjust the chair each time they use it after someone else, or they will endure using a chair that has been used by someone else, even though their settings may be inappropriate leading to discomfort and potential injury. 
     U.S. Pat. No. 4,429,917 by Diffrient discloses a tilting-type chair including a base, a seat, and a back. The back of the U.S. Pat. No. 4,429,917 chair is fixedly connected to a frame of the chair and cannot swivel relative to the frame. In U.S. Pat. No. 4,429,917, a mechanism effects that the seat and the back both tilt in a ratio of about 1 to 3, to prevent that only the back tilts or that the seat and back tilt as a unit. 
     WO 00/67615 by Bujaryn describes a chair comprising a seat pan and an armrest support pivotably attached to a mounting assembly comprising a lower and an upper rail. The potential maximum rearward tilt of the seat pan is limited by the tilt of the mounting assembly, and if the mounting assembly is not fully titled, the seat pan cannot achieve its maximum rearward tilt. 
     The subject of U.S. 2007/0222265 A1 by Machael is an adjustable reclining chair in which a force applied onto a back-upright of a chair is re-directed by the back-upright to lift the seat assembly. The seat assembly cannot pivot independently. 
     The present invention has been devised with the foregoing in mind. 
     SUMMARY 
     According to the present invention there is provided a chair. The chair provides a combination of independent pivoting movements which work together to adapt to a user whilst still allowing the complete chair to move into and out of a reclined position. 
     Advantageously, embodiments of the chair of the present invention caters for the new way of working discussed above, by offering more comfort and support than a meeting chair whilst still being dynamic. Embodiments of the invention allow the body to move like it does in a task chair, but without the plethora of manual adjustments traditionally found on a task chair. 
     In an embodiment, the chair comprises a backrest, a seat, a supporting structure for supporting the backrest and/or the seat and a base support, wherein the supporting structure, the seat and the backrest are each pivotably mounted to permit the supporting structure, the seat and the backrest to each tilt over a predetermined range, to allow the chair to move into and out of a reclined position. The seat is free to pivot over its predetermined range relative to the supporting structure independently of any tilt of the supporting structure. In an embodiment, the backrest is free to pivot over its predetermined range relative to the supporting structure independently of any tilt of the supporting structure. Preferably the supporting structure is pivotably mounted with respect to the base support, the seat is pivotably mounted with respect to the supporting structure and the backrest is pivotably mounted with respect to the supporting structure. 
     In an embodiment, the chair further comprises a seat tilt mechanism that permits the seat to pivot about a pivot point and with respect to the base support such that the seat is tiltable between a first limit in a first direction and a second limit in a second and opposite direction, the first limit and the second limit defining the predetermined range of the seat. The seat tilt mechanism may comprise a component for regulating or dampening the motion and return of the seat during tilting. Preferably, the component is or comprises a pre-tensioned or resiliently deformable component that is deformable when the seat is tilted in one or each direction. The component may be or comprise a spring steel member, a spring, an elastomeric member, or a hydraulic dampener. The first and second limits may be defined by stop positions on the supporting structure. In an embodiment, the seat is tiltable from a neutral position at substantially 0° to the first limit of approximately +5° and to the second limit of approximately −5°. 
     In an embodiment, the chair further comprises a backrest tilt mechanism that permits the backrest to pivot about a pivot point with respect to the supporting structure such that the backrest is tiltable between a first limit in a first direction and a second limit in a second and opposite direction, the first limit and the second limit defining the predetermined range of the backrest. Preferably, the backrest tilt mechanism comprises a component for regulating or dampening the motion and return of the backrest during tilting. The component may be or comprise a pre-tensioned or resiliently deformable component that is deformable when the backrest is tilted in one or each direction. Preferably, the component is or comprises a spring steel member, a spring, an elastomeric member, or a hydraulic dampener. The first and second limits may be defined by stop positions on the supporting structure. The backrest may be tiltable from a neutral position to the first limit of approximately −12°. 
     In another embodiment, the chair further comprises a tilt mechanism that permits the supporting structure to pivot about a pivot point with respect to the base support such that the supporting structure is tiltable between a first limit in a first direction and a second limit in a second and opposite direction, the first limit and the second limit defining the predetermined range of the supporting structure. The tilt mechanism may comprise a component for regulating or dampening the motion and return of the backrest during tilting. The component may be or comprise a pre-tensioned or resiliently deformable component that is deformable when the backrest is tilted in one or each direction. The component may be or comprise a spring steel member, a spring, an elastomeric member, or a hydraulic dampener. The component may be one or more compression springs. The first and second limits may be defined by one or more buffers provided within the tilt mechanism. The supporting structure may be tiltable from a neutral position (approximately 0°) to the first limit of approximately −9°. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described with reference to the following drawings, in which: 
         FIG. 1  is a rear perspective view of a chair according to an embodiment of the present invention; 
         FIG. 2 a    is side view of the chair of  FIG. 1 ; 
         FIG. 2 b    is a side view of the chair of  FIG. 1 , illustrating the range of movement of the backrest, seat and cradle; 
         FIGS. 3 a , 3 b  and 3 c    are side, front and top views respectively, showing the pivot points for providing the movement ranges illustrates in  FIG. 2   b;    
         FIG. 4  illustrates the cradle movement; 
         FIGS. 5 a  and 5 b    illustrate the seat movement; 
         FIG. 6  illustrates the backrest movement; 
         FIG. 7 a    is a transparent cross sectional perspective view through the cradle housing and cradle tilt block; 
         FIG. 7 b    is an open perspective view of the interior of the cradle tilt block; 
         FIG. 7 c    is a transparent perspective view showing the interior of the cradle tilt block; 
         FIG. 7 d    is a cross sectional side view through the cradle tilt block at a 0° starting position; 
         FIG. 7 e    is a cross sectional side view through the cradle tilt block at a −9° end position; 
         FIG. 7 f    is an underneath view of the chair; 
         FIG. 8 a    is a front perspective view of the backrest frame/cradle connection; 
         FIG. 8 b    is an open front perspective view of the interior of the backrest frame showing part of the backrest tilt mechanism; 
         FIG. 8 c    is a transparent front perspective view through the backrest frame showing the backrest tilt mechanism; 
         FIG. 8 d    is a cross sectional side view through the backrest frame at a 0° starting position; 
         FIG. 8 e    is a cross sectional side view through the backrest frame at a −12° end position; 
         FIG. 8 f    is an open front view through the backrest at the 0° starting position of  FIG. 8   d;    
         FIG. 9 a    is a perspective view of the seat frame/cradle connection; 
         FIG. 9 b    is a transparent perspective view of the seat frame/cradle connection; 
         FIG. 9 c    is an inner side view of the seat frame/cradle connection at a 0° starting position; 
         FIG. 9 d    is an inner side view of the seat frame/cradle connection at a 5° stop position; 
         FIG. 9 e    is an inner side view of the seat frame/cradle connection at a −5° stop position; 
         FIG. 9 f    is a top view of the seat frame/cradle connection at the 0° starting position; 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2   a  show a chair  10  according to an embodiment of the present invention. The chair  10  has a base  12  comprising a plurality of legs  14 . In the embodiment shown there are five legs provided equally spaced around the centre of the base. The legs  14  extend radially away from a central sleeve  16  that surrounds and is coupled to an inner sleeve or receptacle  18 . The other end of each leg  14  comprises a castor  20 . The inner sleeve (gas lift)  18  is configured to receive a first end of vertical member or shaft  22 , the other (second) end of which is coupled to a seat assembly  24 , which will be discussed in greater detail below. The shaft  22  may be rotatably mounted within the sleeve  18  so as to permit rotating/swivelling movement between the seat assembly  24  and the base  12 . The central shaft  22  is connected to the outer sleeve  18  via a bearing ring and is prevented from being pulled out of the top by a locking washer on the underside thereof. The gas lift  18  is connected to the base  12  via a morse taper of 1°. 
     The second end of the shaft  22  is received within a support  26  that forms a base for the seat assembly  24 . The support  26  also houses a ‘tilt mechanism’ that enables a pivoting or rocking movement of the seat assembly  24  with respect to the shaft  22  and base  12 . To the support  26  is attached a supporting structure or cradle  28 . Two cradle base arms  30  are coupled to the base support  26 , on opposite sides thereof. Each cradle arm  30  extends laterally outwardly with respect thereto, in opposing directions (in the x direction of  FIG. 1 ), and then transitions into a more upright portion  32  (that extends in the y direction, and at an angle in the y-z plane), before returning substantially in the y direction) to form an armrest  34 . 
     The seat assembly  24  further comprises a seat  36  comprising a frame  38  and seat pad  40 . The seat assembly  36  is attachable to the cradle  28  at fixing locations  42 . The height of the seat  36  is adjusted manually via a small ‘seat height pull’ lever ( 19  as shown in  FIG. 7 c   ) under the cradle  28 . The range of adjustment is, in an example, substantially 120 mm taking the seat height from substantially 400 to 520 mm from the floor. It will be appreciated that other seat heights are possible. 
     The seat assembly  24  also comprises a backrest  44 , which itself also comprises a frame  46  and a pad  48 . Each of the ends of the cradle arms  34  is connectable to the backrest at fixing locations  50 . 
       FIG. 2 b    illustrates the movement combinations that are possible in the embodiment described above. 
     In a neutral (or starting) position, e.g. before a person sits on the chair  10 , the cradle  28  is in position ‘A’, the seat  36  is in position ‘C’ and the backrest is in position ‘F’. As can be seen in  FIGS. 3 a  to 3 c   , the cradle  28  is pivoted with respect to the shaft  22  and base  12  at pivot point ‘I’, the seat  36  is pivoted with respect to the cradle  28  at pivot points J and the backrest  44  is pivoted with respect to the cradle  28  at pivot points ‘K’. In the embodiment shown, and with reference to  FIGS. 2 b  and 3 a  to 3 c   , the cradle  28  can rotate about pivot point ‘I’ from the natural position ‘A’ to the reclined position ‘B’. The seat  36  can rotate about pivot point J from neutral position ‘C’ to the reclined position ‘E’ in one direction and to the inclined position ‘D’ in the other. The backrest  44  can rotate about pivot point ‘K’ from the neutral position ‘F’, through position ‘G’ to position ‘H’.  FIG. 4  shows the rotation of the cradle  28  in direction ‘i’.  FIG. 5 a    shows the backward rotation (reclining) of the seat  36  in direction ‘j 1 ’ and  FIG. 5 b    shows the forward rotation (inclining) of the seat  36  in direction ‘j 2 ’.  FIG. 6  shows the rotation of the backrest  44  in direction ‘k’. 
     It is evident from a comparison of  FIGS. 4 to 6  that the seat  36  and the backrest  44  are each decoupled, i.e., pivotable in a decoupled manner. By “decoupled”, it is meant that the seat  36  is pivotable independently of the tilt of the cradle  28 . Likewise, the backrest  44  is pivotable independently of the tilt of the cradle  28 . Further, the seat  36  is pivotable independently of the backrest  44 . 
     It is evident from  FIGS. 2 a , 2 b   , and  4  to  6  that the axis of the seat  36 , pivot joint J, and the axis of the backrest  44 , pivot joint K, translate together in response to a tilt of the cradle  28 , because the pivot joint J and the pivot joint K are each in a fixed relationship with the cradle  28  via the upright portions  32  and the armrests  34 . 
     However,  FIGS. 2 a , 2 b   , and  4  to  6  show that regardless of the tilt of the cradle  28 , the seat  36  retains its full range of movement (tilt about joint J). Regardless of the tilt of cradle  28 , the backrest  44  retains its full range of movement (tilt about joint K). The full range of movement may be referred to as “full-range tilt” for brevity. This also means that there is no fixed angular relationship between the seat  36  and the backrest  44 . For instance, the backrest  44  may be inclined fully back, to a position ‘H’ (or ‘G’, or ‘F’), and the seat  36  may, independently of the backrest, swivel at any angle, e.g. between positions ‘D’ and ‘E’. Likewise, the seat  36  may be inclined at any one of positions ‘C’, ‘D’, or ‘E’, and the backrest  44  is free to swivel independently of the tilt of seat  36 . 
     Referring now to  FIGS. 7 a  to 7 e   , the mechanism for rotation of the cradle  28  about pivot point ‘I’ will now be described. (It is to be noted that part of the cradle arm  30  shown in  FIGS. 7 a  and 7 c    is depicted transparently, to aid understanding of the components provided therein.) 
     Each cradle base arm  30  terminates in an end portion  52 . Each end portion  52  is configured with a hollow portion or recess  54 . When placed adjacent to each other, the recesses  54  in the ends  52  of the cradle arms  30  define a larger recess that is sized to receive the support block  26 . Since the ends  52  of the cradle arms  30  meet without any discontinuity therebetween, this gives the impression that the lower part of the cradle  28  is continuous, e.g. as can be seen in  FIGS. 3 b  and 3 c   . The support block  26  is secured to the cradle  28  using a bearing block  27  on each side (see  FIG. 7 f   ). An aperture  56  extends through the support block  26 , for receiving the shaft  22  as previously described. The cradle  28  and support block  26  are preferably formed of cast aluminium. 
     Reducing discontinuities reduces the risk of body parts, e.g. fingers, becoming entrapped. As the ends  52  of the cradle arms  30  are received without discontinuity in the support block  26 , this improves the safety of the mechanism. 
     The support block  26  comprises two apertures  58 , in each of which is provided an annular bearing  60 . An axle  62  (e.g. formed of steel) is located within the apertures  58  and is rotatable therein. Each end of the axle  62  is located within one of the end portions  52  of the cradle arm  30  so as to couple the cradle arms  30  to the support block  26  and permit relative movement therebetween. The cradle  30  can thus pivot with respect to the support block  26  which is fixed relative to the shaft  22  and base  12 . The pivoting motion is dampened or regulated by two coiled steel springs  64 . Bearings  66  are provided at each end of the springs  64  to help constrain the motion of the spring and reduce friction between the springs  64  and the support block  26 . Four rubber buffers  70 ,  72  are provided on the upper surface of the support block  26 , to act as movement limiters or stops. A first pair of buffers  70  is provided along a first edge  74  of the support block  26  and a second pair of buffers  72  are provided along a second edge  76  of the support block  26 . 
     The pivoting motion enables the cradle to move between a first position as shown in  FIG. 7 d    and a second position as shown in  FIG. 7 e   .  FIG. 7 d    represents the cradle in a “neutral” position at substantially 0° with respect to the horizontal. In this position, the spring  64  is in an uncompressed, or primarily uncompressed state. The spring  64  thus urges the cradle end  52  away from the support block on one side of the support block (in the vicinity of the second edge  76 ) and the cradle end  52  is spaced from the stops  72 . Due to the coupling via pivot  58 ,  62 , this in turn forces the cradle housing end  52  on the opposite side of the support block  26  (in the vicinity of the first edge  74 ) into contact with the stops  70  of the support block  26 . No further movement is possible and so a state of equilibrium is present. 
     When a user sits on the chair  10 , the action of sitting down can cause the cradle  28  to tilt backwards at the pivot point  62 , into the position depicted in  FIG. 7 d   . This causes compression of the spring  64  and, at the maximum permitted limit, forces the cradle end  52  into contact with the stops  72 . The opposite cradle end  52  is, consequentially, urged away from the stops  70 . If a user were to then alight from the chair, the compression would be released from the spring  64  to urge the cradle  30  back towards the neutral position. In an embodiment, the movement from the neutral position to the position of  FIG. 7 e    wherein contact with the stops  72  is achieved provides a cradle  28  tilt of approximately −9°. It will be appreciated that the chair  10  can be configured to provide for tilting at other angles, e.g. up to approximately −12° or more and e.g. approximately −11.5°, −11°, −10.5°, −10°, −9.5°, −8.5°, −8°, −7.5°, −7°, −6.5° and −6° or less. The chair  10  may also be configured such that tilting in the opposite direction (i.e. greater than 0°) is possible, to e.g. approximately 0.5°, 1°, 1.5°, 2° etc. A ‘gas height release’  78  can be activated by the manual adjustment mentioned above and with reference to  FIG. 7 c   . A cable  77  connects the seat height pull  19  to the gas height release  78 , which activates a button  79  on the top of the inner column  22  to pneumatically adjust the height of the seat  36 . 
     Referring now to  FIGS. 8 a  to 8 f   , the mechanism by which rotation of the backrest  44  about pivot point ‘J’ will now be described. (It is to be noted that part of the backrest frame  46  shown in  FIGS. 8 c  to 8 f    is depicted transparently, to aid understanding of the components provided therein.) 
       FIG. 8 a    is an external view showing the portion of the backrest frame  46  where it is coupled to the armrest portion  34  of the cradle  28 . The remaining  FIGS. 8 b  to 8 f    show the interior of the portion of the backrest frame  44 . An annular bearing  80  is secured within an aperture  82  of the armrest  34 . Within the central aperture of the bearing  82  a connector  84  is provided that is fixed with respect to the armrest  34 . The connector  84  may be secured within the armrest  34  with a grub screw (not visible in the Figures). The connector  84  is preferably formed of sintered steel. A first stop  86  is provided that can be brought into contact with a first end  84   a  of the connector  84 . A second stop  88  is provided that can be brought into contact with a second end  84   b  of the connector  84 . Movement between the stops  86  and  88  is achieved through pivoting of the backrest frame  44  with respect to the connector  84  and the armrest  34 . The stops  86 ,  88  may be formed of glass filled nylon. 
     A resiliently biased component  90  is also provided with the backrest frame  44 , e.g. in the form of a spring steel bar. A first end  92  thereof is received in and supported by a recess  94  in the connector  84  (as can be seen in  FIG. 8 c   ). The recess  94  acts as a stop or movement limiter. Movement of the opposite end  96  is limited by a stop  98 . 
       FIG. 8 d    illustrates the backrest  44  at a neutral starting position. Although the backrest  44  is itself provided at a small angle with respect to the vertical in the neutral position, for reference this position is considered to be substantially 0°. Here, the spring steel bar  90  is in a substantially undeformed state when the chair  10  is not in use. When a user sits down in the chair  10 , they will naturally lean back into the chair, and urge the backrest  44  backwards. The backrest  44  pivots about pivot point J, pushing the upper part of the backrest  44  backwards, away from the vertical. This causes the spring steel bar  90  to deform. The first end  92  thereof is fixed within the recess  94 , but the second, free end  96  is urged towards the stop  98 . Once full contact has been made, no further movement is possible.  FIG. 8 e    depicts the position in which the backrest  44  is fully reclined. In a preferred embodiment this represents a declination of approximately −12° with respect to the vertical. It will be appreciated that the stop  98  may be provided at a different position within the backrest frame  44  to provide a different maximum movement limit. The range of movement may e.g. be up to approximately −15° or more, or e.g. −14.5°, −14°, −13.5°, −13°, −12.5°, −11.5°, −11°, −10.5°, 10°, −9.5° or −9° or less. The chair  10  may also be configured such that tilting in the opposite direction (i.e. greater than 0°) is possible, to e.g. approximately 0.5°, 1°, 1.5°, 2° etc. 
     Referring now to  FIGS. 9 a  to 9 f   , the mechanism by which rotation of the seat  36  about pivot point ‘K’ will now be described. (It is to be noted that part of the seat frame  38  shown in  FIGS. 9 b  to 9 f    is depicted transparently, to aid understanding of the components provided therein.) 
       FIG. 9 a    is an external view showing the portion of the seat frame  36  where it is coupled to the upright portion  32  of the cradle  28 . The remaining  FIGS. 9 b  to 9 f    show the interior of the portion of the seat frame  36 . A connector  100  couples the seat frame  38  to the cradle  28 . As is visible in  FIG. 9 f   , the connector  100  comprises a shaft  102  receivable within a bearing  104  provided within an aperture  106  of the cradle  28 . A cap  108  helps to secure, via fastenings  110 , the connector  100  in place and provide a continuous/flush surface within the seat frame  36 . 
     The connector  100  further comprises a housing  112 . A resiliently biased component such as a spring steel bar  116  is passed through and is supported by the housing  112  approximately half way along its length. A first end of the spring steel bar  116  is received and fixed within a recess  120  provided within the seat frame  44 . A second and opposite end of the spring steel bar  116  is received and fixed within a recess  122  provided within the seat frame  44 . As such, a first portion  118  of the spring steel bar  116  is located on one side of the housing  112 , and a second portion  118 ′ of the spring steel bar  116  is located on the other side thereof. The bearing  104  is configured with first and second bearing surfaces  124 ,  126 . The seat frame  44  comprises first and second stop surfaces  128 ,  130  respectively configured to abut the first and second bearing surfaces at first and second movement limits as will now be described. 
       FIG. 9 c    shows the seat at a neutral (0°) starting position where both portions of the spring steel bar  118 ,  118 ′ are substantially undeformed.  FIG. 9 d    illustrates the seat frame  38  rotated in a first direction with respect to pivot point K. Here, the first stop surface  128  of the seat frame  38  contacts the first bearing surface  124  to prevent or at least limit further movement in the positive direction.  FIG. 9 e    illustrates the seat frame  38  rotated by in a second direction with respect to pivot point K. Here, the second stop surface  130  of the seat frame  38  contacts the second bearing surface  126  to prevent or at least limit further movement in the negative direction. In each case, the spring steel bar  116  is caused to deform, as can be seen from the displacement of the spring steel bar portions  118 ,  118 ′ visible in  FIGS. 9 d  and 9 e    away from their neutral positions, which provides a dampening effect. 
     In a preferred embodiment, the bearing  14  and seat frame  38  are configured such that the stops  128 ,  130  provide a rotation with respect to pivot point K of approximately 5° in each direction with respect to the horizontal. It will be appreciated that the bearing surfaces  124 ,  126  and the stop surfaces  128 ,  130  may be configured (e.g. by altering the angle, position, size thereof) to provide a different maximum movement limit. The range of movement may e.g. be up to approximately ±8° or more, or e.g. ±7.5°, ±7°, ±6.5°, ±6°, ±5.5°, ±4.5°, ±4°, or ±3° or less. The chair  10  may also be configured such that tilting in one direction only is permitted. 
     Embodiments of the present invention advantageously create a fully dynamic chair  10 , which tilts, turns and fully supports an anthropometrically broad range of users, but which is more intuitive, eliminating the need for manual adjustment by the user. A chair  10  according to embodiments of the present invention would lend itself to the modern workplace, where people can be sat in several different places and on several different chairs each day, by taking away the time-consuming requirement to ‘set-up’ the chair to suit a particular user, therefore making the need for training redundant, which can be currently a costly part of each employer&#39;s duty-of-care. Advantageously embodiments of the invention provide a combination of features that provides for seat, back and tilting movement without the need for manual adjustment. 
     An embodiment of a chair  10  according to the present invention has undergone an ergonomics assessment. The seat height was adjusted so that all the users were able to sit on the chair with their feet flat on the floor (no undue pressure at the back of knees). The ergonomics assessment consisted of 10 people (4 females and 6 males) with varying stature from 5th to 95th centile UK population sitting on the chair which was part of a rig. Subjects sat on a pressure map on the seat pad  40  and backrest  44  and their pressure profiles were recorded. 
     As the backrest  44  comprises a mesh back  48  without a lumbar device, in order to determine how well the mesh deforms whilst still providing good lumbar support automatically for different sizes of people, the spines of the test subjects were traced when they were standing, when they are sitting on a box in a relaxed (semi-slouched) posture and when leaning back on the mesh backrest  48 . The working assumption was that if the mesh back  48  gives a good support and automatically adjusts to the user&#39;s back, the tracing of their spines when seated in the chair  10  should be more like the shape of standing posture, not like the sitting slouched posture. 
     In addition users were questioned about the overall feel and comfort of the chair, and their likes and dislikes about the chair. Users were asked about levels of discomfort experienced at different parts of their body. Discomfort assessment is used as physiologically people have discomfort (pain) sensors not comfort sensors. 
     Preliminary measurements of the chair  10  in the rig gave the following approximate dimensions:
         Seat pad depth: 450 mm   Seat pad width: 495 mm   Backrest width: 485 mm   Seat pad angle: approximately −5° to +5°   Angle of backrest relative to vertical: −9°       

     Dimensionally most of the test subjects were happy with the dimensions of the chair  10 , and it was possible to obtain a correct seat height for each user by adjusting the seat height. It was found that the seat depth was appropriate to cover the range of users of different heights and stature and any significant departure therefrom could potentially be to the detriment of some users. 
     Analysis of the pressure mapping of the backrest  44  and the spinal tracing showed that the mesh back  48  sufficiently deforms and adapts the back of the user and provides adequate support around the lumbar area. Responses of the users supported this, in a way that they all felt a good lumbar support. In most instances, spinal tracing showed the lumbar protrusion of the curve, but there was no evidence of slouching from any of the users. Pressure mapping of the users&#39; backs also showed the support around the lumbar. 
     Pressure distribution of the seat pad  40  was generally good—only a couple of traces showed high pressure points and only one user felt some awareness of firmness under their pelvis. 
     Users found the resistance of backrest to pivot was about right—no user found it to be too strong or too weak. 
     In conclusion, the concept of a pivoting backrest  44  and pivoting seat pad  36  is beneficial to a user in terms of encouraging dynamic sitting. Having only a pivoting backrest is not sufficient. A pivoting seat pad  36  additionally allows a user to automatically open up the angle between their thighs and torso. This not only improves the user&#39;s breathing, and hence the blood supply to the brain (keeping them alert and more productive), but also helps them to exercise their core muscles which can help towards avoiding back pain and discomfort. 
     The independent full-range tilt of the seat  36  and backrest  44  relative to the cradle  28  permits the chair to compensate for micro-movements of a person sitting in it. For instance, a person may sit upright at a desk and momentarily stretch their feet. The seat  36 , being independently swivelable, is able to swivel forward in response to the more inclined angle of the upper thighs and continue to support the upper thighs without the seat&#39;s forward edge pressing into the underside of the thighs. Upon bending the legs back to an upright sitting position, the tilt of seat  36  follows the angle of the upper thighs and returns to a more horizontal attitude. The responsiveness and range of the seat  36  is independent of the tilt of the cradle  28  or the backrest  44 . This provides a continuously responsive, adaptive chair configuration that by some test persons has been described as “fluidic”, without requiring a user to manually adjust a seat or backrest.