Abstract:
Chairs, seating systems, chair sub-assemblies and sub-systems, and associated methods of assembly and use. Aspects relate to chairs and methods of assembling chairs including chair controls of a relatively compact and effective design with desirable synchronous raising and tilting motions. Aspects also relate to tilt lock assemblies for achieving secure and effective tilt securement. Additional aspects relate to forward and rearward adjustment, or extension and retraction, of a seating assembly of the chair.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Provisional Application No. 61/981,071, filed Apr. 17, 2014, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Seating functionality, such as office and residential seating, is enhanced by chair motion including the chair seat lifting as the chair back reclines. Various controller designs for chair motion, including weight-activated motion and synchrotilt motion, for example, have been proposed. Various examples of controller designs are described in U.S. Publication 2013/0313883 by Machael et al., published Nov. 28, 2013, and entitled “Chair with Pivot Function and Method of Making”; U.S. Pat. No. 8,613,482 by Yong-Xing Ni, published Dec. 24, 2013 and entitled “Chair Chassis”; and European Publication EP 2 409 602 A by Yong-Xing Ni, published Jan. 25, 2012 and entitled “Rolling Axis Adjusted Tilt Chair Mechanism.” 
     SUMMARY 
     Some aspects of the instant disclosure relate to chairs, seating systems, chair sub-assemblies and sub-systems, and associated methods of assembly and use. Some aspects relate to chairs and methods of assembling chairs including chair controls of a relatively compact and effective design with desirable synchronous raising and tilting motions. The instant disclosure also relates, in part, to tilt lock assemblies for achieving secure and effective tilt securement. Additional aspects relate to forward and rearward adjustment, or extension and retraction, of a seating assembly of the chair. While various aspects are shown and described in the instant disclosure by way of example, the claims are intended to given their full breadth, including aspects not expressly discussed, but made apparent by the instant disclosure. 
     Some aspects of the instant disclosure relate to a chair control cartridge including a seat support, a link arm, and a control body. In some embodiments, the seat support includes a first rider and a second rider. The link arm includes an arm body and a pivot link, the arm body having a first end and a second end. The second end of the arm body is pivotably coupled to the pivot link and the pivot link is pivotably coupled to the seat support. The control body has a first slot and a second slot, each of the first and second slots extending upwardly and rearwardly. The first slot receives the first rider of the seat support and the second slot receives the second rider of the seat support. Upon pivoting the arm body relative to the control body the riders of the seat support traverse the first and second slots of the control body, respectively, to raise and lower the seat support. The pivot link is pivotably coupled to the first rider and an intermediate location on the arm body is pivotably coupled to the control body toward a rear location on the control body. 
     In other embodiments, the control body additionally or alternatively includes one or more riders and the seat support has one or more slots for receiving the one or more riders. In different terms, the complementary slot(s) and rider(s) previously describes are located as desired on either the seat support or the control body to accomplish raising and lower of the seat support of the control cartridge. In some embodiments, each of the first and second slots is located in the seat support, the first and second slots extending upwardly and rearwardly. The first slot receives the first rider of the control body and the second slot receives the second rider of the control body. If desired, the first slot is located in the control body and the first rider is located on the seat support and the second slot is located in the seat support and the second rider is located on the control body (or vice versa). Upon pivoting of the body of the link arm relative to the control body, the riders traverse the slots, respectively to raise and lower the seat support. In still other embodiments, three, four, or more riders and complementary slots are implemented. 
     In some embodiments, one or more of the riders include a hub and a slider that is rotatably secured to the hub such that the particular rider is rotatably secured to the control body or seat support. In some embodiments, one or more of the riders includes a slider that is non-rotatably, or fixedly secured to the control body or seat support. 
     In some embodiments, the body of the link arm extends rearwardly relative to the control body to provide a back support attachment location. For example, a back mount is optionally secured to the arm body and the back mount is secured to the back assembly. 
     In some embodiments, the first slot extends in a first direction and the second slot extends in a second direction, the first direction being angularly offset from the second direction. In some embodiments, the first and second slots extend in substantially parallel directions. 
     In some embodiments, the pivot link rotates in a first rotational direction upon rotation of the arm body in a second rotational direction that is opposite to the first rotational direction. 
     In some embodiments, the first and second riders travel in substantially linear paths in the first and second slots, respectively. 
     In some embodiments, the seat support includes a front end and a rear end, where the front end of the seat support is raised and lowered at greater rate than the rear end of the seat support such that the seat support is tilted rearwardly upon raising the seat support. 
     Some aspects of the instant disclosure relate to a seating system, chair assembly, or chair according to one or more of the described embodiments. In some embodiments, the chair includes a control assembly including one or more chair control cartridges according to one or more of the described embodiments. In some embodiments, the chair includes a base assembly operatively coupled to the control assembly for maintaining the chair assembly relative to a floor surface, a seat assembly operatively coupled to the control assembly, and a back assembly operatively coupled to the control assembly. 
     In some embodiments, the slots of the control cartridge(s) extend at an inclined, non-zero angle relative to the floor surface on which the base assembly is configured to maintain the chair. In some embodiments, the control assembly includes the first chair control cartridge and a second control cartridge according to one or more of the previously described control cartridges. The first control cartridge is optionally positioned toward a first side of the seat and the second control cartridge is optionally positioned toward a second side of the seat, the first and second control cartridges being coupled to the seat assembly and the back assembly. 
     Some aspects of the instant disclosure relate to a method of making or assembling the seating system, chair assembly, or chair according to one or more of the embodiments previously described. In some embodiments, the method includes assembling the chair control assembly, operatively coupling the chair control assembly to the base assembly, operatively coupling the seat assembly to the control assembly, and operatively coupling a back assembly to the chair control assembly. 
     While multiple embodiments are specifically disclosed, other embodiments falling within the scope of the claims will be apparent from the instant disclosure, which shows and describes illustrative embodiments of the invention. In different terms, the drawings and embodiments specifically shown and described are to be regarded as illustrative in nature and not restrictive with regard to the scope of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a chair from an isometric view, according to some embodiments. 
         FIG. 2  shows the chair with a seat assembly of the chair removed, according to some embodiments. 
         FIG. 3  shows the control assembly of the chair from an isometric view, according to some embodiments. 
         FIG. 4  shows the control assembly of the chair in a disassembled state, according to some embodiments. 
         FIG. 5  shows a first chair control cartridge of the control assembly in a disassembled state, according to some embodiments. 
         FIG. 6  shows a seat support of the chair from a first side view and  FIG. 7  shows the seat support from an opposite, second side view, according to some embodiments. 
         FIG. 8  shows the seat support from a bottom view, according to some embodiments. 
         FIG. 9  shows a link arm of the chair control cartridge from a top view, according to some embodiments. 
         FIG. 10  shows the link arm of the chair control cartridge from a side view, according to some embodiments. 
         FIG. 11  shows the link arm of the chair control cartridge in a disassembled state, according to some embodiments. 
         FIG. 12  shows the chair control cartridge from a side view in a first, lowered state and with some portions partially see-through to assist in understanding, according to some embodiments. 
         FIG. 13  shows the chair control cartridge from a side view in a second, raised state and with some portions partially see-through to assist in understanding, according to some embodiments. 
         FIGS. 14 to 16  show the link arm and a control body of the chair control cartridge in various states of actuation and with some portions partially see-through to assist in understanding, according to some embodiments. 
         FIG. 17  shows a control assembly of the chair in the first lowered state from an isometric view, according to some embodiments. 
         FIG. 18  shows the control assembly of the chair in the first lowered state from a side view, according to some embodiments. 
         FIG. 19  shows the control assembly of the chair in the second, raised state from an isometric view, according to some embodiments. 
         FIG. 20  shows the control assembly of the chair in the second, raised state from a side view, according to some embodiments. 
         FIGS. 21 and 22  are isometric views of a portion of the chair showing the chair control assembly, according to some embodiments. 
         FIG. 23  is a side view of a portion of the chair showing the control assembly and the back assembly of the chair, according to some embodiments. 
         FIG. 24  shows the chair control assembly from an isometric view, according to some embodiments. 
         FIG. 25  is a top view of a portion of the chair control assembly, according to some embodiments. 
         FIGS. 26 and 27  are top views of a portion of the chair control assembly with portions removed for understanding, according to some embodiments. 
         FIG. 28  shows the seat assembly of the chair from an isometric view, according to some embodiments. 
         FIG. 29  shows the seat assembly of the chair from an isometric view according to a second point of view, according to some embodiments. 
         FIGS. 30 and 31  are side views of a seat assembly of the chair, according to some embodiments. 
         FIG. 32  is an isometric view of a portion of the chair, according to some embodiments. 
         FIG. 33  shows the chair from a side view with the seat assembly in a fully retracted state, according to some embodiments. 
         FIG. 34  shows the chair from a side view with the seat assembly in an fully extended state, according to some embodiments. 
     
    
    
     While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a chair  10  from an isometric view, according to some embodiments.  FIG. 2  shows the chair with a seat assembly of the chair removed, according to some embodiments. As shown, the chair  10  includes a back assembly  12 , a base assembly  14 , a seat assembly  16 , and a control assembly  18 . The back assembly  12  includes an upper portion  20  and a lower portion  22 , the lower portion  22  being adapted to be secured to the control assembly  18 . As shown, the base assembly  14  includes a lower portion  30  configured to rest on a surface, such as a floor (not shown), to support he chair  10  in use, as well as an upper portion  32  configured to be secured to the control assembly  18 . As shown, the lower portion  30  is configured as a pedestal and the upper portion  32  as a cylinder, although a variety of base assembly configurations are contemplated. 
     As described in greater detail, the control assembly  18  is configured to transition the seating assembly from a lowered position to a raised position as the back assembly  12  transitions between an upright state, or upright position to a reclined state, or reclined position. In particular, in some embodiments the chair  10  is configured such that when the back assembly  12  is in a first upright state the control assembly  18  is in a first lowered state and when the back assembly  12  is in a reclined state the control assembly is in a second raised state. In some embodiments, the control assembly  18  is configured to raise a front portion of the seat assembly  16  more quickly and/or to a greater extent than a rear portion of the seat assembly  16  such that raised position includes the seat assembly  16  being tilted and moved upwardly and rearwardly. 
       FIG. 3  shows the control assembly  18  of the chair  10  from an isometric view and  FIG. 4  shows the control assembly  18  in a disassembled state, according to some embodiments. As shown in  FIGS. 3 and 4 , the control assembly  18  includes a hub  40 , a first cartridge  42 , a second cartridge  44 , a back mount  46 , a torsion assembly  48 , a tilt lock assembly  50 , and a height lever  52 . In general terms, the control assembly  18  is coupled to the back assembly  12 , the base assembly  16 , and the seat assembly  18 . The control assembly  18  also includes covers  56 . As shown and according to some embodiments, the control assembly  18  is generally a central component that interconnects the back assembly  12 , the base assembly  16 , and the seat assembly  18 . 
     As shown in  FIG. 4 , the hub  40  includes a central opening  60 , defines a front  62 , a back  64 , a first side  66 , and a second side  68  and includes a variety of mounting features for securing various components of the control assembly  18  with fasteners such as bolts. As with all the various components of the chair  10 , the hub  40  is formed of desired materials, such as polymeric or metallic materials for example. 
       FIG. 5  shows the first cartridge  42  in a disassembled state, according to some embodiments. As shown, the first cartridge  42  includes a seat support  70 , a link arm  72 , and a control body  74 . The second cartridge  44  is optionally similar to the first cartridge, e.g., with a support  70 A of the second cartridge  44  being a mirror image of the first cartridge  42  as shown in  FIG. 4 . Thus, various features of the second cartridge  44  are not separately described, instead being described collectively with reference to the first cartridge  46 . When specifically referenced, features of the second cartridge  44  and are designated by similar reference numbers to the first cartridge followed by an “A” when specifically referenced. Although similar cartridges  42 ,  44  are shown and described, it should be understood that differing cartridges are also contemplated. 
       FIG. 6  shows the seat support  70  from a first side view and  FIG. 7  shows the seat support  70  from an opposite, second side view, according to some embodiments.  FIG. 8  shows, the seat support  70  from a bottom view, according to some embodiments. As shown, the seat support  70  includes a first flange  76 , a second flange  78  spaced from the first flange  76 , and a seat mount  80 . The first flange  76  includes a front rider  81  and a back rider  82  and has a pivot aperture  83 . The second flange  78  includes a front rider  85  and a back rider  86  and has a pivot aperture  87 . The front riders  81 ,  85  are generally positioned opposite one another at a forward position on the seat support  70  and the back riders  82 ,  86  are positioned at a rearward position on the seat support  70 . The first and second flanges  76 ,  78  define a gap  88 , also described as a channel, for receiving the link arm  72  ( FIG. 5 ). As shown, the seat mount  80  includes a plurality of notches  89 , or recesses, that assist in providing a seat adjustment feature, as subsequently described in greater detail. 
     As shown, the pivot apertures  83 ,  87  are coaxial with the front riders  81 ,  85 , although the pivot apertures can also be located elsewhere. Additionally, as shown, the front and/or back riders  81 ,  85 ,  82 ,  86  are formed as monolithic projections with square transverse cross-sections with rounded corners. In some embodiments, one or more of the riders  81 ,  82 ,  85 ,  86  is formed as a two part component including a post having a round transverse cross-section and a sleeve having a square transverse cross-section with rounded corners, the sleeve being rotatably or non-rotatably received over the post. 
       FIG. 9  is a top view of the link arm  72  and  FIG. 10  is a side view of the link arm  72 , according to some embodiments. As shown, the link arm  72  includes a body  90  and a pivot link  92 . The body  90  has a first end  94  and a second end  96  and an intermediate pivot pin  98  located at an intermediate position between the first and second ends  94 ,  96 . The body  90  also includes a locking recess  99  formed into the top of the body  90  toward the second end  96 . As shown, the pivot link  92  includes a first end  100  that is pivotably connected to the second end  96  of the body  90 . The pivot link  92  also includes a second end  102  having an aperture  104  for pivotably connecting the pivot link  92  to the seat support  70 . As shown, the link arm  72  includes a link pivot pin  106  for pivotably securing the pivot link  92  to the body  90 . 
       FIG. 11  shows the link arm  72  in a disassembled state. As shown, the link arm  72  includes a plurality of plate members  110 , or laminate members, secured together with the link arm  72  centrally interposed between the plate members  110  and pivotably connected thereto by the front pivot pin  106 . 
     Returning to  FIG. 5 , the control body  74  of the first cartridge  42  includes a first wall  120 , or side portion, and a second wall  122 , or side portion. As shown, the first wall  120  includes a first, rear channel  124 , or slot and a second, front channel  126 , or slot. The rear channel  124  extends in a first direction D 124  and the front channel  126  extends in a second direction D 126 . The first wall  120  also includes a pivot recess  128 , or hub for receiving the intermediate pivot pin  98  of the link arm  72 . As shown, the first wall  120  also includes mating features for aligning and/or securing the first wall  120  to the second wall  122 . The first wall  120  also has a locking aperture  129  to facilitate a tilt locking feature, as subsequently described. 
     The second wall  122  is shown including a first, rear channel  130 , or slot corresponding to the rear channel  124  of the first wall  120  and a second, front channel  132 , or slot corresponding to the front channel  126  of the first wall  120 . The rear channel  130  extends in a first direction D 130  (parallel to and laterally offset from first direction D 124 ) and the front channel  132  extends in a second direction D 132  (parallel to and laterally offset from second direction D 126 ). The second wall  122  also includes a pivot recess  138 , or receiver that corresponds to the pivot recess  128  for receiving the intermediate pivot pin  98  of the link arm  72 . The second wall  122  includes complementary mating features for aligning and/or securing the first wall  120  to the second wall  122 . The second wall  120  also has a locking aperture  139  to facilitate a tilt locking feature, as subsequently described. 
     Assembly of the first cartridge  42  includes receiving the link arm  72  in the gap  88  formed between the first and second flanges  76 ,  78  of the seat support  70 . The front pivot pin  140  is received through the pivot apertures  83 ,  87  that extend through the front riders  81 ,  85 . The first and second walls  120 ,  122  are positioned opposite one another about the link arm  72 , as well as the flanges  80 ,  82  of the seat support  70 . Upon assembly, the intermediate pivot pin  98  is received in the pivot recesses  128 ,  138  and the front riders  81 ,  85  are slidably and/or rotatably received in the front channels  126 ,  132  and the rear riders  82 ,  86  are slidably and/or rotatably received in the rear channels  124 ,  130 . The link arm  72  is thereby pivotably secured to the control body  74  at an intermediate position on the link arm body  90  and the link arm pivot link  92  is pivotably secured to the seat support  70 . 
       FIG. 12  is side view of the first cartridge  42  with the first cartridge in a lowered state and  FIG. 13  is a side view of the first cartridge  42  in a raised state, according to some embodiments. For ease of understanding, portions of the first wall  120  of the control body  74  and the seat support  70  are shown partially see through in  FIGS. 12 and 13 , such that the position and movement of the various components in operation, including the seat support  70  and the link arm  72  is more visible. 
     As indicated in  FIG. 13 , the body  90  of the link arm  72  is rotated in a first direction R 1  about a first pivot P 1  which causes the pivot link  92  to rotate in a second direction R 2  that is opposite to the first direction R 1  about a second pivot P 2 . This rotation causes the front riders  81 ,  85  and the rear riders  82 ,  86  of the seat support  70  to move upwardly and rearwardly in the front channels  126 ,  132  and the rear channels  124 ,  130 , respectively, of the control body  74 . As shown, the motion of the riders in the channels causes the seat mount  80  of the seat support  70  to move from a first lowed support position S 1  to a second raised support position S 2 . As indicated, the front of the seat mount  80  is raised to a relatively greater extent than the rear of the seat mount  80 . In different terms, there is both a tilting motion, with the front of the seat support being tilted at an angle “A” and an upward and rearward motion of the seat mount  80  upon rotation of the body  90  of the link arm  72  in the first direction R 1 . 
     In some embodiments, the raising and tilting action is adjusted by selecting the directions of the front channels D 126 , D 132  and the rear channels D 124 , D 130  and the relative angular offsets of those channels. In some embodiments, the rear sets of channels  124 ,  130  extend in parallel direction to the front set of channels  126 ,  132  such that only a raising and lowering motion (e.g., in an upward and rearward direction) is accomplished. In other embodiments, and as shown, the directions D 126 , D 132  in which both the front channels extend is angularly offset from the direction D 124 , D 130  in which both the rear channels extend to accomplish the described tilting action. In particular, and as shown, the front channels rise at a relatively steeper angle than the rear channels to accomplish rearward tilting, although the opposition angular offset (a relatively shallower front angle) can also be employed to achieve a forward tilting action. 
     In some embodiments, the chair  10  is configured such that when the chair is supported on a horizontal surface, the front channels  126 ,  132  extend along directions D 126 , D 132  at an angle of about 37 degrees relative to horizontal, or from about 20 degrees to about 60 degrees, for example, although a variety of angles are contemplated, and the rear channels  124 ,  130  extend along directions D 124 ,  130  at an angle of about 25 degrees relative to horizontal, or from about 10 degrees to about 40 degrees, for example, although a variety of angles are contemplated. In some embodiments, the front channels  126 ,  132  are angularly offset from the rear channels  124 ,  130  by an absolute angle of about 12 degrees (in the counterclockwise direction as shown in  FIG. 13 ), or from about 0 degrees to about 25 degrees, for example, although a variety of angles are contemplated. 
     In some embodiments, the body  90  of the link arm  72  is secured to the lower portion  22  of the back assembly  12  with the back mount  46  and the seat assembly  18  is secured to the seat mount  80  of the seat support  70 . The second control cartridge  44  is similarly secured to the back assembly  12  and the seat assembly  18  such that rearward tiling, or reclining, of the back assembly  12  causes the control assembly  18  to transition from the lowered state ( FIG. 17 ) to the raised state ( FIG. 19 ), thereby resulting in raising the seat assembly in an upward and rearward direction and also tilting of the seat assembly  18  in a rearward, or counterclockwise direction (from a right side view). 
       FIGS. 14 to 16  show progressive movement of the first control cartridge  42  from the lowered state ( FIG. 14 ) to the fully raised state ( FIG. 16 ). 
       FIG. 17  shows the back mount assembled to the rear portions of the link arms  72 ,  72 A. As shown, the back mount  46  is configured to extend between the cartridges and includes recesses  137  (see also  FIG. 22 ) for receiving a portion of the torsion assembly  48 . 
       FIGS. 17 and 18  show the control assembly  18  in an assembled state, with the control assembly  18  in the lowered state.  FIGS. 19 and 20  show the control assembly  18  in an assembled state with the control assembly  18  in the raised state. As shown, the back mount  46  of the control assembly  18  is secured to the second ends of the bodies  90 ,  90 A of the link arms  72 ,  72 A. The first and second cartridges  42 ,  44  are maintained by the hub  40  on opposite sides of the hub  40 . The tilt lock assembly  50  is positioned between the cartridges  42 ,  44  and is also maintained by the hub  40 . The torsion assembly  48  is positioned rearward of the tilt lock assembly  50 . The torsion assembly  48  facilitates return of the chair back assembly  12  to the upright position, return of the control assembly  18  to the lowered state, and also provides a desired resistance to tilting of the chair back assembly  12 , according to some embodiments. 
       FIGS. 21 and 22  are enlarged views showing the torsion assembly  48  in greater detail. As shown, the torsion assembly  48  includes torsion spring(s)  150 , and an adjustment plate  152  secured to the hub  40 . Although shown unsecured in  FIGS. 3, 17, 21 and 22 , first ends  156  of the torsion springs  150  are received under the adjustment plate  152  and an associated fastener  158 , such as a bolt, is tightened or loosened to increase or decrease the spring tension, as shown more clearly in the side view of  FIG. 23 . Second ends  158  of the torsion springs  150  are received below the back mount  46  to provide the desired force/resistance against the back mount  46  and/or the back assembly  12 . 
     The tilt lock assembly  50  is shown in greater detail in  FIGS. 24 to 27 , according to some embodiments. As shown in the various figures, the tilt lock assembly  50  includes first and second tilt lock bars  170 ,  172 , first and second lock gears  174 ,  176 , tilt lock lever  178 , and tilt lock spring  180 . In  FIGS. 26 and 27 , the tilt lock lever  178  is not shown so the various components and locking operation are visible. 
     As shown, the tilt lock lever  178  is rotatably coupled to the hub  40 , as are the lock gears  174 ,  176 . The lock gears  174 ,  176  are intermeshed and in turn are coupled to the tilt lock bars  170 ,  172  such that rotation of the gears results in extension or retraction of the tilt lock bars  170 ,  172 . The tilt lock lever  178  is engaged with the tilt lock spring  180 , which in turn is coupled to the first lock gear  174 . In use, the tilt lock lever is rotated in a first direction, engaging the tilt lock spring  180 , which in turn causes the first gear  174  to rotate. As the first and second gears  174 ,  176  are intermeshed, such that rotation of the first gear  174  results in rotation of the second gear  176 . Rotation of the first gear  174  results in extension of the first tilt lock bar  170  through the lock aperture  129 A, the locking recess  99 A, and the lock aperture  139 A of the second cartridge  44 , thereby locking the link arm  72 A to the control body  74 A with the first tilt lock bar  170 . In this manner, the second cartridge is locked in the lowered state. The first cartridge  42  is similarly (and simultaneously) locked by the second tilt lock bar  172  as it is extended by the second gear  176 . This operation locks the control assembly  18 , which is secured to the chair back assembly  12 , thereby locking the chair  10  against tilting of the chair back assembly  12 . Upon rotation of the tilt lock lever  178  in the opposite direction, the tilt lock bars  170 ,  172  are released from the cartridges  42 ,  44 , allowing the chair  10  to take on a reclined state. 
     By coupling the tilt lock lever  178  to the first gear  174  with the lock spring  180 , a safety feature is optionally incorporated to help prevent inadvertent unlocking of the chair. In other words, if the chair back assembly  12  is being pushed rearwardly, an inadvertent pressure on the tilt lock lever  178  will be less likely to unlock the chair  10 . Also, enhanced lock activation is also incorporated as the spring action provides a resilient force that helps the tilt lock bars  170 ,  172  locate and pass through the locking features in the cartridges  42 ,  44 . Similarly, the tilt lock spring  180  acts as a clutch mechanism to allow a user to activate the lever  178  at any time during recline, where the tilt lock lever  178  remains in a locking position (e.g., by a detent or retaining means), and upon taking a sufficiently upright state (or non-reclined state), the tilt lock bars  170 ,  172  are activated to lock the chair  10  in the upright state. 
       FIG. 28  shows the seat assembly  16  from a top-down oriented perspective view and  FIG. 29  shows the seat assembly  16  from a bottom-up oriented perspective view. As shown, the seat assembly  16  includes an adjustable mount  200  on the bottom of the seat assembly  16 , the adjustable mount including two opposing guide channels  202 ,  204  and a latch assembly  206  that mate with the seat supports  70 ,  70 A ( FIG. 17 ) of the first and second cartridges  42 ,  44 . 
       FIGS. 30 and 31  are side views of the seat assembly  16 . As shown, the latch assembly  206  includes a front handle  208 , an intermediate portion  210  that is pivotably coupled to a lower portion of seat assembly  16 , and a rear clamp  212  that is configured to engage into the notches  89  of the seat support  70  (and  70 A). As shown in  FIG. 31 , upon depression of the front handle  208 , the rear clamp  212  is actuated downwardly. 
       FIG. 32  is an enlarged view of a portion of the chair  10 , showing the seat assembly  16  and the control assembly  18 . As shown, the guide channels  202 ,  204  are slidably received over the seat supports  70 ,  70 A such that the seat assembly  16  is able to be slide forward (and backward) upon disengagement of the rear clamp  212  from the notches  89  of the seat support  70  and notches  89 A of the seat support  70 A. 
     As indicated previously, a method of assembling the chair  10  includes coupling the base assembly  14  to the control assembly  18 . As shown in  FIG. 32 , the upper portion  32  of the base assembly  14  is configured as a cylinder that is received into the central opening  60  of the hub  40  and secured thereto. The seat assembly  16  is slidably secured to the control assembly  18  as previously described. The lower portion  22  ( FIG. 23 ) of the back assembly  12  is secured to the back mount  46 . 
       FIG. 33  indicates a syncrotilt action of the chair  10 , according to some embodiments. As shown, as the chair back assembly  12  transitions from a first, upright position T 1  to a second, relatively tilted position T 2 , the seat assembly  16  transitions from a first lowered position S 1  to a second raised position S 2 . As previously described, and as indicated in  FIG. 33 , the second raised position S 2  of the seat assembly  16  includes the seat assembly  16  being moved upwardly and rearwardly relative to the first position S 1 , as well as tilted rearwardly relative to the first position S 1 . 
       FIG. 34  illustrates the chair  10  with the seat assembly  16  in a fully extended position E 1  relative to the fully retracted position E 2 , where the chair  10  is shown in the retracted potion in  FIG. 33 . As previously indicated, upon depression of the front handle  208  of the latch assembly  206 , the rear clamp  212  is actuated to facilitate adjustment, or sliding of the seat assembly  16  on the control assembly  18 . 
     Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.