Abstract:
A seating assembly comprising a seat structure including a seat member having an undersurface and a seat edge, a mounting bracket mounted to the undersurface of the seat member, a base including a central hub and a plurality of leg members, the mounting bracket mounted to the base and spaced above the central hub, a first vertical axis passing through the central hub, a base tube mounted to and extending upward along the first vertical axis from the central hub, a mounting collar mounted to the base tube for rotation about the first vertical axis, the mounting collar positioned proximate the mounting bracket and located at least in part located between the mounting bracket and the central hub, a support arm having first and second ends, the first end mounted to the mounting collar for rotation therewith about the vertical axis, the support arm extending radially outward from the mounting collar along the undersurface of the seat member and upward to the second end and a tablet member mounted to the second end.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/793,784 filed on Jul. 8, 2015, which is a continuation of U.S. patent application Ser. No. 14/179,888 filed on Feb. 13, 2014, which is a continuation of U.S. patent application Ser. No. 14/104,473 filed on Dec. 12, 2013, which is a continuation of U.S. Pat. No. 8,696,056 filed on Jan. 10, 2011, and issued on Apr. 15, 2014, which claims priority to U.S. Provisional Patent Application Ser. No. 61/300,298 filed on Feb. 1, 2010, each of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a movable seating unit including an optional tablet assembly. More particularly, the present invention relates to a seating unit having a seat structure freely rotatable on a base, and optionally a tablet assembly. The tablet assembly includes a tablet which rotates on the end of a support arm and the support arm which rotates around the center shaft of the seating unit. The present invention also relates to a seating unit having a stable, mobile base with storage capability. 
     The need for learning is a fundamental rule of business, and a critical element of success. In an information age, effective, technology-driven learning is required not only in school, but also on the job. In part, effective learning depends on an environment which promotes interaction and collaboration with other students or coworkers and accommodates the use of multimedia technology. As new interactive technologies and multimedia training programs emerge, the use of seating designed to support the necessary amount of collaboration and self-direction is important. 
     Traditional classrooms, lecture halls, auditoriums, and meeting rooms often provide comfortable seating which allows students and employees to concentrate and take notes. However, traditional seating options are not sufficiently flexible to adapt to a variety of seating arrangements which foster interactions required for group learning. Typically, traditional seating options also do not provide storage and easy access to personal belongings. Whether it is a backpack, computer, briefcase or purse, in a dynamic learning environment, persons want their belongings to accompany them and be readily accessible. Seating must also provide a range of postural choices and accommodate persons of different sizes. Optionally, seating which promotes interaction and collaboration must also provide a worksurface that can be positioned in a variety of ways and is large enough for electronic devices such as a laptop computer. 
     At the same time, seating must be economical. In today&#39;s economy, both schools and companies must work within a limited budget. Thus, a low cost seating unit which provides comfort, convenience, durability and flexibility in learning and collaborating environments is desired. 
     BRIEF SUMMARY OF THE INVENTION 
     In one embodiment of the present invention, a seating unit includes a tablet assembly including a support arm attached at one end to the seating structure. A second end of the support arm includes a projection and is attached to a pivot assembly. The pivot assembly includes a tablet mount having a connecting portion, a bushing having a rib and an adjacent cutout, and an inner tube. The bushing is inserted into the support arm second end such that the projection protrudes through the cutout. The bottom of the inner tube is inserted into the bushing and the top of the inner tube is inserted into the connecting portion. 
     In another embodiment of the present invention, a seating unit includes a seat structure, a base and a tablet assembly mounted between the seat structure and the base. The seat structure includes a mounting bracket having a female connector. The tablet assembly includes a support arm having a mounting collar on one end. The base includes a base support and a base mounting assembly having a cup attached to the base support, a base tube having a first end inserted into the cup, and a second end extending through the mounting collar and mateably engaging the female connector. 
     In yet another embodiment of the present invention, a seating unit includes a seat structure, a pedestal base, and a tablet assembly mounted between the seat structure and the base. The seat structure includes a mounting bracket having a female connector. The pedestal base includes a gas cylinder having a top actuator button and a base mounting assembly. The base mounting assembly includes a receiver having a top male connector, a bottom internal taper, and an internal button extender. The tablet assembly includes a support arm having a mounting collar on one end of the support arm. The gas cylinder is inserted into the bottom internal taper such that the button extender abuts the top actuator button, and the top male connector extends through the mounting collar and mateably engages the female connector. 
     In another embodiment of the present invention, a seating unit includes a seat structure and a base. The base includes a top support and a bottom pan. The top support includes three or more curved legs which extend from a central hub. The pan is attached to the top support and includes twice as many casters as the top support has legs. Both the legs and casters are positioned equidistantly around a periphery of the pan, but the positioning of the legs is offset from the casters. In particular, the distance between a leg and an adjacent caster is approximately equal to 70/4x)−W/2, where D is the diameter of the pan, x is the number of legs, and W is the width of the leg. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other items and advantages of the present invention will be appreciated more fully from the following figures, where like reference characters designate like features in which: 
         FIG. 1  is a perspective view of a seating unit in a first embodiment, the seating unit including a tripod base and a tablet assembly; 
         FIG. 2  is a perspective view of a seating unit in a second embodiment, the seating unit including a tripod base and no tablet assembly; 
         FIG. 3  is a right side view of the seating unit of  FIG. 1 ; 
         FIG. 4  is a right side view of the seating unit of  FIG. 2 ; 
         FIG. 5  is a front view of the seating unit of  FIG. 1 ; 
         FIG. 6  is a top view of the seating unit of  FIG. 1 ; 
         FIG. 7  is a perspective view of a seating unit in a third embodiment, the seating unit including a pedestal base and a tablet assembly; 
         FIG. 8  is a perspective view of a seating unit in a fourth embodiment, the seating unit including a pedestal base and no tablet assembly; 
         FIG. 9  is a right side view of the seating unit of  FIG. 7 ; 
         FIG. 10  is a right side view of the seating unit of  FIG. 8 ; 
         FIG. 11  is an exploded top perspective view of the seating unit of  FIG. 1 ; 
         FIG. 12  is an exploded bottom perspective view of the seating unit of FIG. 
         FIG. 13  is an exploded view of a base to seat mounting assembly of the seating unit of  FIG. 1 ; 
         FIG. 14  is an exploded cross-sectional view of the base to seat mounting assembly of  FIG. 13 ; 
         FIG. 15  is a cross-sectional view of the base to seat mounting assembly of 
         FIG. 16  is a bottom perspective view of a pivot assembly of the seating units of  FIGS. 1 and 7 ; 
         FIG. 17  is an exploded bottom perspective view of the pivot assembly of  FIG. 16 ; 
         FIG. 17  A is an enlarged fragmentary view of a connecting portion of a tablet mount of the pivot assembly of  FIG. 17 ; 
         FIG. 18  is an exploded cross-sectional view of the tablet assembly of  FIGS. 1 and 7 ; 
         FIG. 19  is a cross-sectional view of the tablet assembly of  FIGS. 1 and 7 ; 
         FIG. 20A  is a top view of the seating unit of  FIG. 1  where the tablet assembly including a pivot assembly and a mounting assembly is in a right side, fully outward position; 
         FIG. 20B  is a cross-sectional view of the pivot assembly of  FIG. 20A , showing pivot assembly stops corresponding to the right side, fully outward position; 
         FIG. 20C  is a cross-sectional view of the tablet mounting assembly of  FIG. 20A  and a seating mounting rib, showing tablet mounting assembly stops corresponding to the right side, fully outward position; 
         FIG. 21A  is a top view of the seating unit of  FIG. 1  where the tablet assembly including a pivot assembly is in a right side, partially inward position; 
         FIG. 21B  is a cross-sectional view of the pivot assembly of  FIG. 21A , showing pivot assembly stops corresponding to the right side, partially inward position; 
         FIG. 22A  is a top view of the seating unit of  FIG. 1  where the tablet assembly including a pivot assembly and a mounting assembly is in a right side, fully inward position; 
         FIG. 22B  is a cross-sectional view of the pivot assembly of  FIG. 22A , showing pivot assembly stops corresponding to the right side, fully inward position; 
         FIG. 23A  is a top view of the seating unit of  FIG. 1  where the tablet assembly including a pivot assembly and a mounting assembly is in a front, outward position; 
         FIG. 23B  is a cross-sectional view of the pivot assembly of  FIG. 23A , showing pivot assembly stops corresponding to the front, outward position; 
         FIG. 23C  is a cross-sectional view of the tablet mounting assembly and a seating mounting rib of  FIG. 23A , showing tablet mounting assembly stops corresponding to the front, outward position; 
         FIG. 24A  is a top view of the seating unit of  FIG. 1  where the tablet assembly including a pivot assembly and a mounting assembly is in a front, partially inward position; 
         FIG. 24B  is a cross-sectional view of the pivot assembly of  FIG. 24A , showing pivot assembly stops corresponding to the front, partially inward position; 
         FIG. 25A  is a top view of the seating unit of  FIG. 1  where the tablet assembly including a pivot assembly and a mounting assembly is in a front, fully inward position; 
         FIG. 25B  is a cross-sectional view of the pivot assembly of  FIG. 25A , showing pivot assembly stops corresponding to the front, fully inward position; 
         FIG. 26  is a bottom perspective view of a seating structure and tablet mounting assembly of  FIGS. 1 and 7 ; 
         FIG. 27  is an exploded view of a pedestal base and base to seat mounting assembly of the seating unit of  FIG. 7 ; 
         FIG. 28  is an exploded view of the base to seat mounting assembly and seat structure of the seating unit of  FIG. 7 ; 
         FIG. 29  is an exploded cross-sectional view of the base to seat mounting assembly of the seating unit of  FIG. 28 ; 
         FIG. 30  is a cross-sectional view of the base to seat mounting assembly of the seating unit of  FIG. 7 ; 
         FIG. 31  is a perspective view of a base of the seating unit of  FIGS. 1-6 ; 
         FIG. 32  is an exploded perspective view of the base of  FIG. 31 ; 
         FIG. 33  is a top view of the base of  FIG. 31 ; and 
         FIG. 34  is a bottom view of the base of  FIG. 31 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     For purposes of description herein, the terms “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices illustrated in the attached drawings, and described below are simply exemplary embodiments of the invented concepts. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting. 
     The present seating unit  10  includes a seat structure  12  and a base  14  ( FIGS. 2, 4, 8 and 10 ). The seat structure  12  and base  14  are connected by a base to seat mounting assembly. The base to seat mounting assembly includes a base mounting assembly and a seat mounting bracket, both discussed in detail below. Optionally, the seating unit  10  may include a tablet assembly  16  ( FIGS. 1, 3, 5-7 and 9 ). Referring to  FIGS. 11-15 , the tablet assembly  16  includes a tablet mounting assembly  18 , a support arm  20  attached to the mounting assembly at a first end  22 , a pivot assembly  24  engaging the support arm at a second end  26 , and a tablet  28  attached to the pivot assembly. The mounting assembly  18  attaches to the seating unit  10  between and in-line with the seat structure  12  and base  14 . Referring to  FIGS. 13-15 and 27-30 , the mounting assembly  18  includes a mounting collar  30  attached to the support arm first end  22 , a bushing  32  or  32   a  press fit into a bottom  34  of the mounting collar, and a pivot cover  36  nested over a top  38  of the mounting collar and the support arm  20 . The pivot cover  36  preferably is constructed of plastic material and includes a channel  40 , a mousehole-shaped opening  42  and stop surfaces  44  and  46 . The pivot cover  36  conceals stops and prevents pinch points when the stops engage. The mousehole-shaped opening  42  ensures that stop surfaces  44  and  46  contact the pivot cover  36  instead of the first end  22  of the support arm  20 . Where the pivot cover  36  includes plastic, the mouse hole-shaped opening  42  replaces noisy metal-to-metal contact with a quieter metal-to-plastic contact condition. 
     The tablet assembly  16  may turn freely on the base  14  through 360 degrees of rotation. However, rotation of the support arm  20  is constrained relative to the seat structure  12  to prevent the tablet  28  from contacting the seat structure. The support arm  20  can rotate approximately 110 degrees relative to the seat structure  12 . Specifically, movement of the support arm  20  relative to the seat structure  12  is restricted by stop surfaces  44  and  46  contacting stops on the seat structure. Rotation of the tablet assembly  16  relative to the seat structure  12  is illustrated in  FIGS. 20C and 23C . Contact and friction between the tablet assembly  16  and the seat structure  12  are designed such that if a seated user swivels the seat structure relative to the base  14 , but does not touch the tablet assembly  16 , the tablet  28  will remain stationary relative to the base, until a stop is reached, at which point the tablet assembly will begin moving along with the seat structure. The stops prevent contact between the tablet assembly and the seat structure which may damage both over time. 
     The pivot assembly  24  connects the tablet  28  to the support arm  20  and allows the tablet to rotate horizontally on the second end  26  of the support arm. Referring to  FIGS. 16-19 , the pivot assembly  24  includes a tablet mount  48  secured to a bottom  50  of the tablet  28 , a bushing  52  press fit into the second end  26  of the support arm  20 , and an inner tube  54 . The tablet mount  48  includes a connecting portion  56  having a central passage  58  and a depression  60 . The depression  60  includes edges  62  and  64  which form stops. The bushing  52  includes a central throughbore  66 , and a top annular flange  68 . A top surface  70  of the annular flange  68  includes a rib  72  with bent ends  74  and  76  which form stop surfaces which restrict the relative motion of the tablet  28  on the support arm  20 . Typically, rib  72  is made of a plastic material, so bent ends  74  and  76  replace hard, noisy metal-to-metal contact with a quieter metal-toplastic contact condition. The top flange  68  also includes a cutout  78  positioned parallel to the rib  72 . The second end  26  of the support arm  20  includes a projection  80  corresponding to the cutout  78 . The shapes of the rib  72 , cutout  78  and projection  80  correspond to each other and may be linear, angled or arcuate. However, in a preferred embodiment, the shapes of the rib  72 , cutout  78  and projection  80  are arcuate. 
     To assemble the pivot assembly  24 , the bushing  52  is press fit into the second end  26  of the support arm  20  with the projection  80  passing through the cutout  78  such that the rib  72  and projection are adjacent to each other. A lower end  82  of the inner tube  54  is inserted and secured in the bushing throughbore  66 , and an upper end  84  of the inner tube  54  is inserted and secured in the tablet mount passage  58 . When the inner tube  54  is inserted into the passage  58  of the tablet mount connecting portion  56 , the top surface  70  of the annular flange  68  abuts a bottom  86  of the connecting portion and the rib  72  and projection  80  reside in the depression  60 . When assembled, the bottom  86  of the connecting portion  56  and the annular flange  68  work together to conceal the stops where edge  64  contacts bent end  76  and edge  62  contacts bent end  74 , thereby preventing pinch points. 
     Rotation of the tablet  28  relative to the support arm  20  is illustrated in  FIGS. 20A  and B through  25 A and B. Horizontal rotation of the tablet  28  is restricted to prevent the tablet  28  from contacting the seat structure  12 , to allow a user to comfortably sit on and exit from the chair, and to ensure adequate stability of the seating unit  10 . Regarding stability, horizontal outward rotation of the tablet  28  is restricted to prevent tipping of the chair. When the tablet  28  is rotated outward and an object is placed on the tablet, the weight of the object, W obj , produces a moment, M obj , that can tip the seating unit  10  over if the center of the tablet extends beyond the base of the seating unit. The value of moment M obj  is equal to the weight of the object, W obj , multiplied by the shortest horizontal distance, L obj , between the center of the weight, W obj , and the axis of rotation, where the axis of rotation is a line drawn through the centerlines of two casters  162  nearest to the object. For the seating unit  10  to be stable, M obj  must be less than or equal to a counterbalancing moment, M su , formed by the weight of the seating unit, W su , multiplied by the shortest horizontal distance L su  from the seating unit&#39;s center of mass to the axis of rotation. This is expressed mathematically as M obj ≦M su  or (W obj *L obj ) S (W su *L su ). In a preferred embodiment, maximum outward rotation of the tablet  28  relative to the support arm  20  is restricted to an angle where the tablet  28  does not tip when an object weighing up to 25 pounds is placed onto the center of the tablet (Le., W obj ≦25 pounds). Specifically, maximum outward rotation of the tablet  28  is restricted to approximately 60 degrees by bent end  74  contacting edge  62  ( FIGS. 20A, 20B, 23A, 23B ) to prevent the seating unit  10  from tipping. Also, in a preferred embodiment, maximum inward rotation of the tablet  28  relative to the support arm  20  is restricted to approximately 60 degrees by bent edge  76  contacting edge  64  ( FIGS. 22A, 22B, 25A, 25B  to prevent the tablet from contacting the seat structure  12 . 
     The tablet  28  is illustrated in  FIG. 18  and includes a tray base  88  attached to the tablet mount  48  and a skin  90  attached to the tray base. The tray base  88  is typically constructed of a strong structural material such as glass-filled nylon. The skin  90  can be molded from a wide variety of materials, such as acrylonitrile butadiene styrene (A8S) or other plastic materials. Optionally, an insert  92  may be molded into the skin  90 . Suitable inserts  92  may be constructed of a high pressure laminate (HPL) or thermoplastic polyurethane (TPU). To prevent rattling and to dampen sound resonating through the tray base  88 , an intermediate layer  94  may be positioned between the tray base and skin  90 . Typically, the intermediate layer  94  includes a nonwoven sheet. A thin layer of soft cellular foam or damping foil may also be used as the intermediate layer. 
     The seat structure  12  rotates freely on the base  14  through 360 degrees of rotation and includes a backrest  96 , a seat  98 , armrests  100  and a seat mounting bracket  102  ( FIGS. 12, 13, 26 and 28 ). Typically, the backrest, seat and armrests are formed as a one-piece shell. Alternatively, the backrest, seat and armrests may be separate. The backrest and seat may also include upholstery. The armrests  100  extend upwardly and outwardly from a lower portion  104  of the backrest  96  to form a valley  106  between the armrest and the backrest. A backpack, purse, bag, or other article having a strap can be hung on an armrest  100  by placing the strap into the valley  106  and around the armrest. The article supported by the armrest is available for easy access by a seated user. 
     Referring to  FIGS. 13 and 28 , an underside  108  of the seat  98  includes multiple protrusions  110  molded into and integral with the seat. The protrusions  110  include an over-molded boss insert  112  having a central aperture  114 . Although the seat  98  may include any number of protrusions  110 , preferably, there are four protrusions. Attached to protrusions  110  is the mounting bracket  102  for connecting the seat structure  12  to the base  14  and optionally to a tablet assembly  16 . The mounting bracket  102  can be any shape, but preferably the bracket is X-shaped and includes an aperture  116  near an end  118  of each leg  120  of the X. The mounting bracket  102  can be attached to the seat  98  by passing a fastener  122  through the aperture  116  in the leg  120  and into a corresponding aperture  114  in a protrusion  110 . Alternatively, the mounting bracket  102  may be attached to the seat  98  using an adhesive or rivets. The mounting bracket  102  also includes a central female connector  124  and an annular rib  126  surrounding the female connector. As illustrated in  FIGS. 12, 13 and 26 , the height of the annular rib  126  is not uniform, but rather includes a first portion  128  having a greater height than a second portion  130 . The first and second portions  128 ,  130  are connected by angled portions  132  and  134 . Angled portions  132 ,  134  form stop surfaces which restrict movement of the tablet assembly  16  relative to the seat structure  12 . In particular, movement of the support arm  20  toward the rear of the seat structure  12  is restricted by stop surface  44  contacting angled portion  132 . Likewise, movement of the support arm  20  toward the front of the seating structure  12  is restricted by stop surface  46  contacting angled portion  134 . (See  FIGS. 20C and 23C ). Referring to  FIGS. 9, 10 and 27-30 , for a seating unit  10  including a pedestal base, the mounting bracket  102  may also include a lever  136 . The lever  136  is used to activate an actuator button  138  of a vertically adjustable gas cylinder  140 . 
     The base  14  includes a base support  142  and a base mounting assembly  144  ( FIG. 11 ). As illustrated in  FIGS. 1-6, 11, 12 and 31-34 , the base support  142  may have three or more legs  146 . In an alternative embodiment, the base support may include a pedestal with radially extending legs  148 , such as a five-star pedestal ( FIGS. 7-10 and 27-30 ). 
     Referring to  FIGS. 31 and 32 , in one embodiment, the seating unit  10  includes a base  14  having a tripod base support  150 . The tripod base support  150  includes a top  152  attached to a bottom pan  154 . The pan  154  can be used to store a backpack, purse, bag, or other article. The top  152  includes three curved legs  146  extending from a central hub  156  and attached to a bottom ring  158 . A seated user can also use the pan  154  or bottom ring  158  as a footrest. Preferably, the bottom ring  158  is attached to legs  146  to minimize cost and maximize structural integrity of base  150 . However, in an alternative embodiment, the bottom ring  158  may be attached to the bottom pan  154 . The bottom ring  158  includes a plurality of pintle mounts  160  for mounting casters  162  or glides. In a preferred embodiment, the legs  146  and pintle mounts  160  are positioned equidistantly around the bottom ring  158  (see  FIGS. 33 and 34 ). Flanking the pintle mounts  160  are fastening bosses  164 . The bottom pan  154  can be any shape, but preferably is circular. The pan  154  typically includes a series of holes  166 . The series of holes  166  permits air flow through the pan  154  and allows liquids from stored articles or shoes which may accumulate to drain. Typically, the series of holes  166  is arranged in a circular pattern of small holes, however, any other pattern or hole size can be used. The bottom pan  154  also includes a plurality of apertures  168  located equidistantly adjacent a periphery  170  of the pan. The plurality of apertures  168  includes a central opening with a smaller hole on each side of the central opening. The position of the apertures  168  corresponds to the position of the pintle mounts  160  and fastening bosses  164 . To assemble the base  14  including a tripod base support  150 , the top  152  is positioned over the bottom pan  154  with the pintle mounts  160  extending through the central hole of apertures  168 . Fasteners  172  pass through the two smaller holes of apertures  168  and engage the fastening bosses  164  to secure the pan to the top  152 . Optionally, the top  152  and bottom pan  154  may include clips (not shown) positioned between pintle mounts  160  and casters  162 , respectively. The top clips are releasably engaged to the bottom clips. The clips help maintain contact between the top  152  and bottom pan  152  and prevent gaps between them. Casters  162  or glides are inserted into the pintle mounts  160 . As the seating unit  10  moves around, articles stored on the pan  154  remain with the seating unit and are available for access by a seated user. 
     Typically, the tripod base support  150  includes six pintle mounts  160  and casters  162 , although more pintle mounts and casters can be used. As noted above, in a preferred embodiment, the pintle mounts  160  and legs  146  are positioned equidistantly around the bottom ring  158  of the top  152 . When the tripod base support  150  includes six pintle mounts  160 , each pintle mount is positioned approximately 60 degrees from adjacent mounts and each leg  146  is positioned approximately 120 degrees from adjacent legs. To maximize stability of the seating unit  10  and minimize deflection of the base pan  154 , the pintle mounts  160  and casters  162  are offset from the legs  146 . It has been discovered that when at least some of the pintle mounts  160  and casters  162  line up with the legs  146 , the structural integrity of the base  150  and the stability of the seating unit  10  is compromised. Specifically, where the pintle mounts  160  and casters  162  are in-line with the legs  146 , a user sitting on the seating unit  10  applies a load which is transferred to the casters below the legs. However, almost no load is transferred to the remaining casters. An uneven load distribution can cause pintles and casters to break. Also, the in-line configuration may also compromise the stability of the seating unit and create potential safety issues for a seated user. For example, if a user turns the seating unit  10  such that one of the legs  146  faces straight forward and an open section faces backward, and then leans back, the user can rock with the seating unit pivoting on the two rear legs. The rear portions of the pan  154  and bottom ring  158  flex excessively and the front casters  162  lift off the ground, causing the seated user to tip backwards. Offset casters  162  and legs  146  address both of these issues by distributing loads and stresses evenly among all casters and reducing the ability of a user to flex the pan  154  and bottom ring  158  when leaning backwards. This is true whether the pintle mounts  160  and casters  162  are positioned equidistantly around the bottom ring  158  or not. However, it has been discovered that preferably the number of casters  162  is 2x, where x is the number of legs  146 , and the distance between a midpoint  174  of where the leg attaches to the bottom ring  158  (Le., half the width, W, of the bottom of the leg) and adjacent casters is TTD/4x, where D is the diameter of the pan  154 . In other words, the distance from an edge of a leg  146  to the nearest adjacent caster is TTD/4x−W/2. 
     The base mounting assembly  144  components vary depending on the type of base support. The base mounting assembly  144  for a tripod base support  150  is illustrated in  FIGS. 13-15 . In this embodiment, the base mounting assembly  144  includes a cup  176  with a flange  178  at a top end  180 , a bushing  182  press fit into the cup, and a base tube  184 . The cup  176  is inserted into the central hub  156  and the flange  178  is secured to the base top  152 . A bottom end  186  of the base tube  184  is inserted through the bushing  182  and into the cup  176 . The bushing  182  and bottom end  186  of the base tube  184  are secured to a bottom  188  of the cup  176  with a fastener and a series of washers and thrust bearings  190 . Typically, the fastener is a mechanical fastener such as a shoulder bolt. 
     Referring to  FIG. 15 , to assemble the seating unit  10  including a base  14  having a tripod base support  150  and a tablet assembly  16 , a top end  192  of the base tube  184  is inserted through the tablet mounting assembly  18  and mateably engages the female connector  124  of the seat mounting bracket  102 . In this configuration, a bottom portion  194  of the tablet mounting assembly  18  resides in the base cup  176 , and the annular rib  126  of the seat mounting bracket  102  resides in the channel  40  of the tablet mounting assembly pivot cover  36 . 
     Referring to  FIGS. 7-10 , in an alternative embodiment, the seating unit  10  includes a base  14  having a pedestal base support  196 . One example of a suitable pedestal base support is a five-star pedestal base support having a vertically adjustable gas cylinder  140  and radially extending legs  148 . Typically, the gas cylinder  140  is tapered and includes a top activated actuator button  138 . The base mounting assembly  144  for a pedestal base support  196  including a tapered gas cylinder  140  is illustrated in  FIGS. 27-30 . In this embodiment, the base mounting assembly  144  includes a receiver  198  having a top  200  and a bottom  202 , and a button extender  206 . The receiver  198  is generally cylindrical and includes a tapered male connector  208  at the top  200 . The receiver  198  also includes an internal taper  210  and an outer flange  212  at the bottom  202 . The tapered gas cylinder  140  is accepted into the internal taper  210  and the button extender  206  is inserted into the male connector  208 . 
     Referring to  FIG. 30 , to assemble the seating unit  10  including a pedestal base support  196  and a tablet assembly  16 , receiver  198  of the base mounting assembly is inserted into the bushing  32   a  of the tablet assembly  16  such that the bottom  34  of the mounting collar is supported by the receiver flange  212  and bushing, and the receiver extends through the pivot cover  36 . In this configuration, the male connector  208  including the button extender  206  of the receiver  198  extends past the top of the bushing  32   a  and mateably engages the seat mounting bracket  102  female connector  124 , and the annular rib  126  of the seat mounting bracket resides in the channel  40  of the tablet mounting assembly pivot cover  36 . The button extender  206  abuts the lever  136 . To vertically adjust the height of the seating unit  10 , a user engages the lever  136  which depresses the button extender  206 . In turn, the button extender  206  depresses the gas cylinder actuator button  138  to provide vertical adjustment of the seating unit. Advantageously, the height of the tablet assembly is adjustable in tandem with the seat structure  12  when the gas cylinder  140  is activated. 
     For a seating unit  10  having either a tripod base support  150  or pedestal base support  196 , the pivot assembly  24  and base mounting assembly  144  advantageously cooperate to allow a seated user to pull the tablet  28  closer, or push it farther away, maintaining the front edge of the tablet perpendicular to the centerline of the seat, with minimal side-to-side displacement of the tablet. This cooperation between the pivot assembly  24  and base mounting assembly  144  allows users of various sizes to comfortably use the tablet  28 . 
     As illustrated in  FIGS. 2, 4, 8 and 10 , the seating unit  10  may be assembled without a tablet assembly  16 . In particular, to assemble the seating unit  10  including a base  14  having a tripod base support  150 , the base tube  184  is inserted into the seat mounting bracket  102 , with the top end  192  mateably engaging the female connector  124 . Similarly, to assemble the seating unit  10  including a base  14  having a pedestal base support  196 , the receiver  198  is inserted into the seat mounting bracket  102 , with the male connector  208  including the button extender  206  mateably engaging the female connector  124 . A seating unit  10  not including a tablet assembly  16  may also include an aesthetic cover positioned between the base mounting assembly  144  and seat mounting bracket  102 . Alternatively, a seating unit  10  without a tablet assembly  16  may be constructed by omitting the receiver  198 , the button extender  206  and any aesthetic covers. The tapered top of the gas cylinder  140  would mateably engage the female connector  124  of the mounting bracket  102 , and the lever  136  would directly activate top activator button  138 . 
     The seating unit  10  is easy to ship in a ready-to-assemble form with the seat structure  12 , base  14  and optional tablet assembly  16  separate. This saves space and reduces packaging costs, while minimizing final assembly labor and complexity. Final assembly of the seating unit  10  is accomplished by optionally placing the tablet assembly  16  onto the base  14  and then placing the seat structure  12  onto the base and applying downward pressure. The final assembly processes disclosed above require no tools or small parts or hardware items which can be lost.