Abstract:
A folding chair utilizes a gear train to control a folding motion and to achieve a compact closed form. While holding a handle integrated into a backrest, the weight of the chair allows it to open and unfold automatically into an open position. The folding chair locks in place in the open position. To refold the chair, a button is depressed to release the lock and the seat is pulled toward the backrest. The gear train refolds the front and rear legs. In the compact folded position, the lightweight chair can be carried with one hand in a relaxed position, similar to an attache case. The handle is contoured so that it is possible for an adult to carry two chairs back to back in each hand.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 60/938,877, filed on May 18, 2007, which is incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to folding chairs and in particular to a chair that folds compactly in a controlled fashion. 
   2. Description of the Related Art 
   Chairs presently used in business environments for occasional use are available in several types of configurations. These configurations are chiefly known by the nature of how the chairs are efficiently stored when not in use. 
   In the past, one type of chair (type 1) could fold by having the front and rear legs compress together along with the seat. The back is formed as part of the front legs that extend upward. An example of this type of design is illustrated by a chair disclosed in U.S. Pat. No. 6,871,906 B2 to Haney. This type of chair is stored when folded in an upright position and stacked horizontally next to one another. Trollies exist to contain a number of this type of folding chair together and transport them to the place where needed. 
   Another occasional chair configuration (type 2) stacks vertically for storage. Each chair is designed such that the legs can fit over the seat so the chairs can stack over each other. Multiple stacks can be transported on trollies for set-up. An example of this type of chair is disclosed in U.S. Pat. No. 6,109,696 to Newhouse. The stacks vary in height and verticality depending on the design. Since Type 2 chairs do not compress they are often made to higher quality standards, are heavier in weight, and are used in a wider range of contract environments. 
   Type 1 and Type 2 chairs represent the majority of contract market occasional seating configurations. There are numerous designs available within each category. More recently, an alternate configuration (Type 3) was created in which the chairs have wheels and nest together horizontally for storage. This approach is commonly used in retail shopping carts typically found at grocery stores, etc. It is represented by the Dance chair by KI. These chairs are stored by wheeling them together in compact rows. 
   SUMMARY OF THE INVENTION 
   The chairs of Type 1, 2, and 3 can satisfy a wide range of business needs, but in certain environments, an appropriate solution is lacking. The folding chair invention disclosed herein was created to satisfy the need for an occasional chair to be used on an outdoor deck or terrace for business meetings and entertaining clients for coffee or drinks. 
   For this use, a lightweight chair that could be easily carried by each participant from an indoor office to the outside deck is desired. It also could be conveniently stored within the office and not in a central storage location, so that it can be readily used when desired. For client entertainment needs the chair preferably is special and comfortable and not left out in the elements. 
   Type 1 chairs are somewhat heavy and cumbersome to carry, especially with one hand. They are not typically used in a contract office setting and are not manufactured to contract quality standards. They are commonly used in training or conference settings and can be quite uncomfortable. 
   Type 2 and 3 chairs are comfortable, but rather heavy, and not conveniently stored and carried from an office to a deck, especially if it is up a short flight of stairs, or separated by door rails. 
   Other low cost plastic chairs are available and used and left outdoors, but they are not contract quality, must be cleaned often, and typically degrade in the elements. Better quality café and patio chairs cannot be left outside without security, as they are frequently stolen. 
   From the foregoing, it will be appreciated that there is a need for a lightweight, easily transported and stored, high-quality folding chair, suitable for business client entertainment. 
   The aforementioned needs are satisfied by various features, aspects and advantages of the present folding chair design. In some embodiments, the chair comprises sets of folding members (e.g., subassemblies) connected to the seat, which are attached to the seat, that control the position of the subassemblies. In some embodiments, the gearboxes each contain a gear train that attaches to the front leg, rear leg and back subassemblies. Thus, pivot motion of any of the back, front legs, or rear legs will effect the positions of the other subassemblies. 
   This interconnection of the front legs, rear legs, and back relative to the seat provides a convenient means of quickly folding and unfolding the chair for occasional use. The gear trains coordinate the relative positions of the subassemblies such that positive open and closed positions can be achieved without excess exertion of force on the subassembly members. By holding the closed chair with one hand on the integrated back handle, the weight of the leg subassemblies will allow them to automatically unfold in a coordinated fashion to the open position. To refold the chair, the second hand grasps the front end of the seat and pivots it up to the back. The front and rear leg subassemblies can automatically refold in a coordinated fashion during this motion as controlled by the gear trains. 
   The gear boxes can be rigidly constructed to maintain gear train alignments and to withstand seating forces and operation forces. The gear boxes are connected to each other by a gear brace, which in turn is attached to the underside of the seat in some embodiments. Thus, the pivot mechanics of the folding chair are separate from the seat and allow alternate embodiments of seat design and construction. Also, the attachment of the subassemblies to the gear boxes completes the rigidity of each subassembly and allows for weight reduction in the legs and back support members. 
   To control a stop point in the open (i.e., use) position the gear boxes can feature abutments in the front housings that stop motion of the rear leg and back subassemblies. This method offers direct contact with the back and leg posts. In some embodiments, the abutments are replaced with internal structural features built-in to the gear housings and the mating gear elements. This approach provides a more aesthetically pleasing configuration but may result in a heavier construction technique. 
   To achieve structural stability in the open (use) position the front of the seat can be attached to the front leg subassembly by the angle stop subassembly. This acts as a brace to maintain the seat in the desired angled position for use. The angle stop can be a structural member connected at a lower end by two pivot points to the front leg posts. The upper end can have two pins that ride in slots created by the seat and the pivot cover subassembly. The pins allow the angle stop to pivot in place during unfolding and refolding of the chair. When unfolded, the angle stop acts as a brace and forms part of the chair lock. During refolding, the angle stop maintains consistent motion of the leg subassemblies. 
   The pivot cover subassembly attaches to the underside of the seat and contains and provides slots for angle stop pins. The main structural element is the u-shaped pivot bar, which is used to secure the chair in a locked position. The pivot bar is suspended within the cover and is secured to it with two axis pins that allow it to pivot. The front end has an extended protuberance that serves as a button. The back end has two recessed pockets which are fitted with two compression springs nested in the cover. These springs maintain the pivot bar in a neutral (locked) position. Above the spring pockets on the pivot bar are two angled surfaces that interface with the pins from the angle stop subassembly and prevent pin motion unless the button is depressed. 
   In some embodiments, the back, front and rear leg assemblies can be constructed in a similar fashion for efficiency in manufacture and final assembly. The back can be attached to extruded aluminum posts, which are in turn attached to a cast or molded common joint. The joint can be contoured to mate with the gear hubs in a socket fitting for structural integrity. The fastener can be used merely to secure the subassembly to the gearboxes. 
   In a similar fashion, the front and rear leg stringers can be attached to extruded aluminum posts that are attached to joints. The joints in turn can attach to the respective gear hubs with socket fittings secured with fasteners. 
   The back, front and rear leg stringers can be one-piece structural pieces that may be injection molded with gas assist. They can be fastened to the joints and extruded posts with rivets. The seat can be made in a similar process. In another embodiment, the back, front and rear stringers can be made using the blow molding process and can be fastened to the joints and extruded posts with threaded fasteners. This approach allows customer part upgrade and/or replacement. Both embodiments provide a high level of structural integrity and a lightweight chair. 
   The front leg stringer can be contoured at a sloping angle to allow backward foot motion. The upper edge can serve as a foot rest. In some embodiments, it also projects to the rear of the front posts to nest between the rear stringer in the folded position. The rear leg stringer preferably has two slots molded-in for security cable pass-through during event set up. 
   The seat and back surfaces can be contoured for comfortable sitting. The seat preferably is contoured and angled to allow water runoff if it is left out in the rain. Back contours can provide support for lumbar and thoracic regions. The back preferably has a built-in handle that is sized and sloped so the folded chair can be comfortably carried by a child in one hand or two chairs can be carried back-to-back by an adult. 
   In yet another embodiment, the back, front and rear leg posts are constructed of wood and can be attached to modified joints, back and leg stringers. In this design, the stringers can be cast aluminum for greater bottom weight. This added weight may be partially offset with back and seat designs that are made of perforated lightweight composites. This approach can be used in windy outdoor conditions to help prevent tip-over of the lightweight chair. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings. 
       FIG. 1  is a side perspective view of one embodiment of a folding chair that is arranged and configured in accordance with certain features, aspects and advantages of the present invention. 
       FIG. 2  is a front perspective view of the folding chair of  FIG. 1 . 
       FIG. 3  is a rear perspective view of the folding chair of  FIG. 1 . 
       FIG. 3A  is a rear perspective view of another embodiment of a folding chair that is arranged and configured in accordance with certain features, aspects and advantages of the present invention. 
       FIG. 4  is a perspective view of the folding chair of  FIG. 1  in a collapsed position. 
       FIG. 5  is an exploded view of the main subassemblies of the folding chair of  FIG. 1 . 
       FIG. 6  is an exploded view of a right gearbox subassembly shown in  FIG. 5 . 
       FIG. 6A  is an exploded view of a left gearbox subassembly shown in  FIG. 5 . 
       FIGS. 6B and 6C  are exploded views of another configuration of a gearbox subassembly such as that shown in  FIG. 3A . 
       FIG. 7  is a bottom view of seat details from  FIG. 5  with the left gearbox subassembly attached. 
       FIG. 8  is a bottom view of the seat of  FIG. 5  with the remaining subassemblies of an angle stop, a pivot cover and the right gearbox attached, along with a gear brace. 
       FIG. 8A  is a bottom view of another configuration of a seat, gear brace, angle stop, pivot cover and gearbox subassembly such as that shown in  FIG. 3A . 
       FIG. 9  is an exploded view of the angle stop subassembly of  FIG. 5 . 
       FIG. 9A  is an exploded view of another configuration of an angle stop subassembly such as that shown in  FIG. 3A . 
       FIG. 10  is an exploded view of the pivot cover subassembly of  FIG. 5 . 
       FIG. 10A  is an exploded view of another configuration of a pivot cover subassembly such as that shown in  FIG. 3A . 
       FIG. 11  is a detailed side view of a preferred embodiment of the folding chair of  FIGS. 1-3  illustrating the angular relationships of the front leg, rear leg, and back subassemblies with the seat. 
       FIGS. 12 ,  12 A are centerline section views of an assembled preferred embodiment of the folding chair of  FIGS. 1-3  illustrating locked and unlocked positions of the pivot bar within the pivot cover subassembly. 
       FIG. 12B  is a section view of an assembled embodiment of a folding chair such as that shown in  FIG. 3A  illustrating a locked position of a pivot latch within a pivot cover subassembly. 
       FIG. 13  is an exploded view of the front leg subassembly of  FIG. 5 . 
       FIG. 14  is an exploded view of the rear leg subassembly of  FIG. 5 . 
       FIG. 15  is an exploded view of the back subassembly of  FIG. 5 . 
       FIG. 16  is a view of a person holding three chairs. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference will now be made to the drawings wherein like numerals refer to like parts throughout.  FIGS. 1-5  illustrate an embodiment of an open folding chair assembly  100  that is arranged and configured in accordance with certain features, aspects and advantages of the present invention. In some embodiments, the open folding chair assembly  100  comprises a seat  132  to which is attached a right gearbox subassembly  145 S in a manner described below. The right gearbox subassembly  145 S preferably is on the right side of the folding chair as defined by a user while sitting in the folding chair  100 . In  FIG. 2 , a left gearbox subassembly  168 S also is shown attached to the seat  132  on the left side in a manner similar to the right gearbox subassembly  145 S. The gearbox subassemblies  145 S,  168 S control the folding motion of the chair  100  during opening and closing and are described in more detail below. 
   In the illustrated configuration, a front leg subassembly  101 S is fastened to the right gearbox subassembly  145 S with a joint  106 R, and to the left gearbox subassembly  168 S with a joint  106 L. Two pins  107 R,  108 R preferably attach a post  103 R, which can be extruded in some configurations, to the right joint  106 R. Two additional pins  107 L,  108 L preferably attach a post  103 L, which also can be extruded, to the left joint  106 L. Other configurations also can be used. 
   The free ends of the posts  103 R,  103 L can be joined with a front stringer  102 , which can be molded and can have mating integral shafts. Other configurations are possible. The right shaft preferably is secured to the right post  103 R with pins  104 R,  105 R. The left shaft preferably is secured to the left post  103 L with pins  104 L,  105 L. The stringer  102 , which can have integral shafts, preferably provides a generally rigid substantially 90 degree connection with the posts  103 R,  103 L such that the front leg subassembly  101 S is stable and is less likely to rock from side to side under load. Other configurations can be used. 
   In a similar manner, a rear leg subassembly  110 S can be fastened to the right gearbox subassembly  145 S with a joint  115 R, and to the left gearbox subassembly  168 S with a right joint  115 L. Two pins  116 R,  117 R attach a right post  112 R, which can be extruded, to the right joint  115 R. Two additional pins  116 L,  117 L attach a left post  112 L, which also can be extruded, to the left joint  115 L. The free ends of the posts  112 R,  112 L preferably are joined with a rear stringer  111 , which can be molded and which can have mating integral shafts. The right shaft can be secured to the right post  112 R with pins  113 R,  114 R. The left shaft preferably can be secured to the left post  112 L with pins  113 L,  114 L. The stringer  111 , which can have integral shafts, preferably provides a generally rigid substantially 90 degree connection with the posts  112 R,  112 L such that the rear leg subassembly  110 S can be stable and is less likely to rock from side to side under load. 
   Also, in a similar manner, a back subassembly  137 S is fastened to the right gearbox subassembly  145 S with a right joint  142 R, and to the left gearbox subassembly  168 S with a left joint  142 L. Two pins  143 R,  144 R can be used to attach a post  139 R, which can be extruded, to the right joint  142 R. Two additional pins  143 L,  144 L can be used to attach a post  139 L, which can be extruded, to the left joint  142 L. The free ends of the posts  139 R,  139 L preferably are joined with a backrest  138 , which can be molded and which can have mating integral shafts. The right shaft can be secured to the post  139 R with pins  140 R,  141 R. The left shaft can be secured to the post  139 L with pins  140 L,  141 L. The backrest  138  preferably provides a generally rigid substantially 90-degree connection with the posts  139 R,  139 L to reduce the likelihood that it will sway from side to side under pressure. 
   An angle stop subassembly  118 S is shown beneath the seat  132  in  FIG. 1 . The angle stop subassembly  118 S preferably fits between the right post  103 R and the left post  103 L of the front leg subassembly  101 S. The angle stop subassembly  118 S preferably pivots in a coordinated fashion with both the front leg subassembly  101 S and a pivot cover subassembly  122 S. In the open locked position, the angle stop subassembly  118 S forms a triangular brace with the seat  132  and the front leg subassembly  101 S to rigidly support the seat  132  in a desired position. The angle stop subassembly  118 S also increases lateral stability in the front leg subassembly  101 S. The construction and connection details for the angle stop subassembly  118 S and the pivot cover subassembly  122 S are described further below. 
   A crossbrace  133  preferably connects the right gearbox subassembly  145 S to the left gearbox subassembly  168 S. In some embodiments, the crossbrace  133  also connects to the seat  132 . The crossbrace  133  can have any suitable configuration and can be an extruded tube in some embodiments. The crossbrace  133  helps to stabilize the upper ends of the front leg subassembly  101 S, the upper ends of the rear leg subassembly  110 S, and the lower ends of the back subassembly  137 S. In some embodiments where the seat  132  does not connect to the gearbox subassemblies  145 S,  168 S, the crossbrace can connect the seat  132  to the gearbox subassemblies  145 S,  168 S. 
     FIG. 3A  shows the folding chair assembly  100  which is slightly modified such that it is arranged and configured in accordance with certain features, aspects and advantages of some embodiments of the present invention. In the illustrated configuration, a seat back  354 , a front leg stringer  348  and a rear leg stringer  349  each can be one-wall structural pieces that are injection molded with ribs for additional strength where needed or desired. While all three are shown in this configuration, any one of these members can be formed as shown in either  FIG. 3A  or  FIG. 3 , for example. In addition, the illustrated angle stop subassembly  350 S shown in  FIG. 3A  preferably uses injection molded plastic with structural ribs, such as within the angle stop  389 . Moreover, as will be described further below, the angle stop  389  and the angle stop subassembly  350 S can be slightly reconfigured when compared to the angle stop subassembly  118 S introduced above and shown in  FIG. 1 . 
   A seat  353  in the construction illustrated in  FIG. 3A  preferably has a one-wall construction and can be mated with an enclosed version of a pivot cover subassembly  352 S, and a crossbrace  379 , which is described further below. Connected to the crossbrace  379  are a left gearbox subassembly  351 S and a right gearbox subassembly  378 S. The illustrated left gearbox subassembly  351 S shows internal gear stops and construction details for the gearbox subassembly  315 S are described below. 
   As discussed above, the chair assembly  100  can be folded for storage and carrying.  FIG. 4  illustrates the chair assembly  100  in a folded configuration. As illustrated, the seat  132  folds into a space defined generally between the left and right posts  139 L,  139 R. In addition, a portion of the back  138  in the illustrated configuration overlies a portion of the seat  132 . The front stringer  102  preferably lies along a portion of the back  138  when in the folded configuration. In addition, the front posts  103 R,  103 L preferably fold to a location inside of the rear posts  112 R,  112 L. Moreover, when folded, the illustrated rear posts  112 R,  112 L lie alongside the seat back posts  139 R,  139 L. Preferably, the front posts  103 R,  103 L are positioned between at least a portion of the rear stringer  111  and at least a portion of the seat back  138 . 
   Thus, the illustrated folded chair assembly  100  generally defines two layers: a first layer generally comprising the seat  132 , the seat posts  139 R,  139 L and the seat back  138 ; and a second layer generally comprising the front posts  103 R,  103 L, the rear posts  112 R,  112 L the front stringer  102  and the rear stringer  111 . The two layers can be connected by the gearbox subassemblies  145 S,  168 S. 
   Now turning to  FIG. 6 , details of the right gearbox subassembly  145 S are illustrated. The illustrated gearbox subassembly  145 S comprises three gear and axle combinations contained within three housings. A front housing  146  preferably connects to a middle housing  147  with four screws. Other mounting arrangements also can be used. Two alignment pins  251 ,  252  on a rear surface of the front housing  146  mate with corresponding holes in the middle housing  147 . 
   A bulkhead  246  preferably protrudes from the front housing  146  and has an upper control surface  248  that is used to limit the travel of the backrest subassembly  137 S, and specifically the joint  142 R. A lower control surface  247  can be used to limit the travel of the rear leg subassembly  110 S, and specifically the joint  115 L. A 1.5R gear/axle  150  and a ComboR gear/axle  149  mesh and preferably are contained between the front housing  146  and the middle housing  147 . The illustrated 1.5R gear/axle  150  has a protruding front axle hub  262  on the front side and a smaller protruding rear axle hub  265  at the rear. The front axle hub  262  fits into a bearing surface  249  of the front housing  146 . The rear axle hub  265  fits into a bearing surface  266  of the middle housing  147 . 
   In a similar manner, the ComboR gear/axle  149  has a protruding front axle hub  256  on the front side and a larger protruding rear axle hub  257  at the rear. The axle hub  256  fits into a bearing surface  250  of the front housing  146 . The axle hub  257  fits into a bearing surface  267  of the middle housing  147 . Gear teeth  260  of the 1.5R gear/axle  150  and gear teeth  259  of the ComboR gear/axle  149  preferably mesh with a 1:1 ratio. 
   The ComboR gear/axle  149  has additional gear teeth  258  extending beyond the rear axle hub  257  and beyond the middle housing  147 . These teeth  258  have a 1:1.5 ratio with the gear teeth  259  of the ComboR gear/axle  149 . Protruding beyond the gear teeth  258  is a smaller axle hub  258   a  that fits into a bearing surface  274  of a rear housing  148 . The rear housing  148  attaches to the middle housing  147  with four screws in the illustrated configuration. Two alignment pins  278 ,  279  on a front surface of the rear housing  148  mate with corresponding holes in the middle housing  147 . 
   The third gear/axle, identified as 2.0R gear/axle  151  has a protruding front axle hub  270  on a front side and a larger protruding rear axle hub  271  at the rear. The front axle hub  270  fits into the bearing surface  266  of the middle housing  147 , but preferably has a separation space between its front hub  270  and the rear hub  265  of the 1.5R gear/axle  150 . This separation space allows the two hubs  270 ,  265  to turn independently while sharing the same bearing surface  266 . In other words, the two hubs  270 ,  265  preferably are axially spaced apart while being within the same region defined by the bearing surface  266 . 
   The 2.0R gear/axle  151  has gear teeth  269  that mesh with the gear teeth  258  of ComboR gear/axle  149  with a 2:1 ratio. 
   The combination of ratios contained within the gearbox subassembly  145 S allow the connecting subassemblies to move in a controlled coordination. 
   Extending beyond the rear surface of the rear housing  148  are two controlled mounting cylinders  275 ,  276  which are used to secure the gearbox subassembly  145 S to the seat  132  using two screws, for example. The mounting cylinders  275 ,  276  preferably fit securely within molded pockets in the seat and are described further below. Also, extending beyond the rear surface in the illustrated configuration is a protrusion  277  that has a contour that fits securely within the crossbrace  133  and that is secured within the crossbrace  133  with a single fastener in the illustrated configuration. 
   External moving attachments to the gearbox subassembly  145 S are the front leg subassembly  101 S, the rear leg subassembly  110 S and the backrest subassembly  137 S. Common to each subassembly in the illustrated configuration and used for mating is the joint, referred to as the joint  106 R, the joint  115 R, and the joint  142 R in the respective subassemblies. By using a component with a generally common construction, manufacturing costs and procedures can be simplified. The joint  106 R mates with the protruding rear hub  271  of 2.0R gear/axle  151 . The rear hub  271  can be aligned with the cutoff surface  272  of the hub  271  and, in the illustrated configuration, the socket fit can be secured with a central fastener and a metal threaded insert  273 . Preferably, the threads are self-locking. Other constructions may use a lock washer and other secure fastener attachments, for example. 
   The joint  115 R mates with the protruding hub  262  of 1.5R gear/axle  150 . The hub  262  can be aligned with a cutoff surface  263  of the hub  262  and, in the illustrated configuration, the socket fit can be secured with a central fastener and a metal threaded insert  264 . 
   In a similar manner, the joint  142 R mates with the protruding hub  253  of ComboR gear/axle  149 . The hub  253  can be aligned with a cutoff surface  255  of the hub  253  and, in the illustrated configuration, the socket fit can be secured with a central fastener and a metal threaded insert  254 . 
   For assembly efficiency, it may be desirable for the joints  106 L,  115 R, and  142 R to be attached to the gearbox subassembly  145 S prior to attachment to their respective leg and back subassemblies. In such a configuration, the joints  106 R,  115 R, and  142 R could be considered part of the gearbox subassembly  145 S. 
   On each part within the right gearbox subassembly  145 S, an identifying letter mark “R” can be molded or machined. The letter mark is used to distinguish the parts from those of left gearbox subassembly  168 S, which do not have the letter marks. The letter marks are illustrated on their respective parts for items such as  256 ,  268 ,  280 ,  281 , and  282 . 
   Preferably, the gear/axles and the housings of gearbox subassembly  145 S are made of die cast aluminum with bearing surfaces made of Delrin. Other materials can be used. The bearing surfaces may be integral or may be made as separate sleeves that fit over the hubs. 
   In some configurations, the gears can be made as reinforced injection molded plastic parts with integral bearing properties. 
   In some configurations, the gear teeth and the housings can be made of stamped steel and the gearbox subassembly  145 S can be securely assembled with rivets. In such configurations, the gearbox will have a reduced width and can be somewhat tamperproof in that it cannot be readily disassembled and reassembled. 
   From the forgoing it can be appreciated that the gearbox subassembly  145 S and the connecting subassemblies utilize a common joint assembly technique requiring minimal specialized tools as an advantage for product assembly. The use of controlled mating surfaces (e.g., the cutoff surface  272 , the cutoff surface  263  and the cutoff surface  255 ) between parts also advantageously reduces the amount of fasteners needed and contributes to the lateral structural integrity of the assembled chair during load. 
     FIG. 6A  illustrates details of the left gearbox subassembly  168 S. Gearbox subassembly  168 S is a mirror of gearbox subassembly  145 S. All parts are unique and readily distinguished from those of gearbox subassembly  145 S as they are not marked with the identifying “R”. Mates and assembly steps are as in  FIG. 6  and the previous discussion. Moreover, the reference numerals will remain the same for the left and right unless otherwise indicated or apparent. 
   With reference to  FIGS. 6B and 6C , other constructions of the left gearbox subassembly  351 S are illustrated. The operation and construction approach of the configurations shown in  FIGS. 6B and 6C  are similar to left gearbox subassembly  168 S described above. However, the left gearbox subassembly  168 S comprises an internal gear stop control surface. The internal control surfaces replace the external bulkhead  246  shown  FIG. 6A , or can be used together with the external bulkhead  246 . 
     FIG. 6B  illustrates three housings containing three gear/axles. A front housing  355  is shown without an external bulkhead. A Combo gear/axle  359  and a 1.5 gear/axle  356  have sufficient gear teeth for engagement within the about 104° of travel desired, but the remainder of the gear/axle bodies are configured to control and limit rotation. In other words, the remainder of the gear/axle body can be toothless. In a similar manner, a 2.0 gear/axle  364  has sufficient teeth for engagement with the Combo gear/axle  359  while the remainder of the body can be configured to control and limit rotation. A control surface  365  on the 2.0 gear/axle can contact a control surface  368  on a rear housing  367  to prevent further rotation of the front leg assembly  101 S while opening the chair  100  and so serves as a stop or an internal bulkhead. 
   Additional control surfaces can be used for each gear/axle to provide a positive limit that corresponds to a stop position and to spread any load forces when the chair is being used. A control surface  361  of the Combo gear/axle  359  contacts a control surface  369  of the rear housing  367 . A control surface  357  of the 1.5 gear/axle and a control surface  360  of the Combo gear/axle  359  contacts control surfaces positioned inside of the front housing  355  that are illustrated in  FIG. 6C . 
   Secondary control surfaces also can be used when closing the chair assembly  100 . A control surface  366  of the 2.0 gear/axle can contact a control surface  370  of the rear housing  367 . Additional secondary control surfaces also are illustrated in  FIG. 6C . 
   All gears/axles and housings preferably are made of diecast aluminum with bearing surfaces made of Delrin. The illustrated middle housing  362  is shown with cored sections  363  to reduce material and lighten weight. The gear/axles and other housings can be similarly cored as desired. 
   Now turning to  FIG. 6C , the left gearbox subassembly  351 S is illustrated from a reverse view to better illustrate some of the remaining control surfaces. The control surface  357  of the 1.5 gear/axle  356  can contact a control surface  375  of the front housing  355  to limit travel of the rear leg subassembly  110 S during opening. The control surface  360  of the Combo gear/axle  359  can contact a control surface  377  of the front housing  355  to limit travel of the back subassembly  137 S during opening. 
   Another secondary control surface  358  of the 1.5 gear/axle  356  contacts a control surface  374  of the front housing  355  to limit travel when closing the chair assembly  100 . A control surface  360 A also contacts a control surface  376  of the front housing  355  during this operation. 
   The illustrated rear housing  367  is shown with a slightly reconfigured shaft  371 . The illustrated shaft  371  comprises two attachment holes  372 ,  373  for connection to the crossbrace  379 , which can connect with the seat  353 . 
   In some embodiments, the control surfaces and the secondary control surfaces of the front housing  355  and the rear housing  367  can be located on the middle housing  362  or can have a portion formed on the middle housing  362  with the remainder formed on the front and rear housings  355 ,  367 . Moreover, in some configurations, the control surfaces and the secondary control surfaces can be formed on an insert that is received between the front and middle housings and the middle and rear housings. Any other suitable combinations also can be used. If the control surfaces and the secondary control surfaces are formed on the middle housing  362 , the middle housing  362  increases in width to accommodate the control surfaces  368 ,  369 ,  375 ,  377  and the secondary control surfaces  370 ,  374 , and  376 . It also reduces structural requirements on the front housing  355  and rear housing  367  that would allow alternate process and material selections for the housings. 
   With reference to  FIG. 7 , the left gearbox subassembly  168 S is illustrated in position relative to a bottom surface of the seat  132 . The two mounting cylinders  275 ,  276  nest into a recessed pocket  315  molded into the seat  132  and can be secured by screws at mounting holes  275   a ,  276   a . The recessed pocket  315  preferably extends across the width of the seat  132 , allowing clearance room for the crossbrace  133 , and then expands out to define a mounting position for the right gearbox subassembly  145 S. In some configurations, the recessed pocket adds structural rigidity to the gearbox subassemblies because the gearbox subassemblies are mounted directly to the seat  132 . 
     FIG. 8  illustrates the bottom of the seat  132  with the gearbox subassembly  168 S, the gearbox subassembly  145 S, the pivot cover subassembly  122 S, and the angle stop subassembly  118 S in position and attached. The crossbrace  133  fits within the recess pocket  315  and is connected to the left gearbox subassembly  168 S and the right gearbox subassembly  145 S with one screw at either end. Other configurations are possible. In the illustrated configuration, when the crossbrace  133  is used, the crossbrace  133  preferably first is attached to the gearbox subassemblies  168 S,  145 S and then the completed unit can be secured to the seat  132  bottom. Other assembly techniques also can be used. 
   The angle stop subassembly  118 S can be held between the seat  132  and the pivot cover subassembly  122 S with two pins, as described below. In such a configuration, the pivot cover subassembly  122 S is attached to the seat  132  bottom with, for example, six screws. In some configurations, the pivot cover subassembly  122 S as well as the gearbox subassemblies  145 S,  168 S can be secured to the seat  132  bottom with rivets or tamperproof fasteners to hinder disassembly. Other configurations also are possible. 
     FIG. 8A  is a bottom exploded view of another configuration of a seat  353  and the pivot cover subassembly  352 S, the angle stop subassembly  350 S, the gearbox subassembly  351 S, and the gearbox subassembly  378 S from  FIG. 3A . The crossbrace  379  can be connected with two fasteners  380 ,  381 , for example, to the right gearbox subassembly  378 S, and with two fasteners  382 ,  383 , for example, to the left gearbox subassembly  351 S. The crossbrace  379 , with the attached gearbox subassemblies  351 S,  378 S, is then attached with two additional fasteners  384 ,  385 , for example, which connect to two respective bosses  386 ,  387  on the underside of the seat  353 . The bosses  386 ,  387  can have a curved upper surface to mate with a curvature of the crossbrace  379  such that the components have a snug fit. 
   The angle stop subassembly  350 S can be fitted to the pivot cover subassembly  352 S, which can be connected to the bottom of the seat  353  at four bosses  388 . Connection details are described further below. 
     FIG. 9  is an exploded view of the angle stop subassembly  118 S that illustrates four pins  120 L,  120 R,  121 L,  121 R that can be fitted to the molded angle part  119 . The angle part  119  can be sized to fit between the posts of the front leg subassembly  101 S. The pins  120 L,  120 R can fit into respective post holes  109 L,  109 R, which allows the angle stop subassembly  118 S to pivot relative to the seat  132  and the front leg subassembly  101 S during opening and closing of the chair  100 . 
   The top portion of the angle part  119  can have a narrow construction such that the top portion of the angle part  119  can fit between the sides of the pivot cover subassembly  122 S during closure of the chair  100 . A transition ramp  316  and a radius  317  can be sized to provide strength to the angle part  119  so as to support the seat  132  while the chair  100  is open and to for generally avoid interference with the pivot cover subassembly  122 S during closure. Pins  121 L,  121 R preferably fit between the pivot cover subassembly  122 S and the seat bottom control surfaces described below. The assembly approach takes advantage of the molded seat  132  details to eliminate a control surface part used in conjunction with the pins  121 L,  121 R. 
     FIG. 9A  is an exploded view of another configuration of the angle stop subassembly  350 S. This illustrated angle stop  389  can be an injection molded plastic part that has ribs for additional strength and that has cored-out areas  402  to reduce mass.  FIG. 9A  also illustrates two rods  390 ,  391  that are connected to the angle stop  389 , which can be molded. The rod  390  slides into one end boss  397 , is substantially centered within the angle stop  389  and is secured by two fasteners  398 ,  399 . The fastener  398  preferably screws into a threaded hole  400  and the fastener  399  preferably screws into a threaded hole  401 . Both fasteners  398 ,  399  can apply pressure to the rod  390  to secure the rod  390  in position. In some embodiments, the fasteners  398 ,  399  may pass through non-threaded holes in the angle stop  389  and can screw into threaded holes formed in the rod  390 . The rod  390  may also be marked with an incised groove or have a protrusion near one end to establish a positive center position within the angle stop  389 . In a similar manner, the rod  391  can slides into one end boss  392 , can be centered within the angle stop  389 , and can be secured by two fasteners  393 ,  394 . 
     FIG. 10  is an exploded view of the pivot cover subassembly  122 S. In the illustrated configuration, a cover  123  connects directly with the bottom of the seat  132  using six fasteners, for example. In some embodiments, the pivot cover  123  can have a control enclosure part that would provide guidance for the pins  121 L,  121 R of the angle stop subassembly  118 S. In some embodiments, the components of the pivot cover subassembly  122 S are substantially fully enclosed such that flexible mesh seats also can be used. 
   A pivot arm  124  preferably connects to the cover  123  with pins  126 L,  126 R, for example. The pin  126 L fits into a bearing surface hole  318 , passes through a boss hole  322 L on the pivot arm  124  and fits into a bearing surface hole  319  on the left wall of the cover  123 . In a similar manner, the pin  126 R fits a bearing surface hole  320 , passes through a boss hole  322 R on the pivot arm  124  and fits into a bearing surface hole  321  on the right wall of the cover  123 . The pivot arm  124  maintains a rest position under pressure supplied by two compression springs  125 L,  125 R. A spring  125 L is contained by a ring wall  324 L in the pivot cover  123  and by a cylindrical cup  323 L in the pivot arm  124 . In a similar manner, a spring  125 R can be contained by a ring wall  324 R in the pivot cover  123  and by a cylindrical cup  323 R in the pivot arm  124 . 
   In the rest position, a central handle  224 , which can be molded as part of the pivot arm  124 , passes through an opening  223  in the pivot cover  123 . The rest position of the pivot arm  124  can be changed by pressing on the central handle  224 . This causes the pivot arm  124  to change angular position relative to the seat  132  and, in particular, to change the angular position of ramp surfaces  227 L,  227 R. The purpose of changing the rest position of the pivot arm  124  is to unlock the chair  100  for folding. 
   The ramp surfaces  227 L,  227 R control and lock the position of the pins  121 L,  121 R of the angle stop subassembly  118 S as described below. It can be appreciated that the molded central handle  224  offers a single point of user contact to disengage the two ramp surfaces and free the pins  121 L,  121 R, compress the angle stop subassembly  118 S, and allow the chair to fold compactly in an orderly manner controlled by the gear box subassemblies  145 S,  168 S. In some embodiments, the molded pivot arm  124  and the pin arrangement can be constructed as a sheet metal part with riveted pivot joints. Other configurations also are possible 
     FIG. 10A  is an exploded view of another pivot cover subassembly  352 S. As discussed above, the illustrated pivot cover subassembly  352 S has a control enclosure part  404  that provides guidance for the pins  121 L,  121 R of the angle stop subassembly  118 S, or the corresponding ends of the rod  390  of the other illustrated angle stop subassembly  350 S. The control enclosure part  404  connects to a cover  403  at six boss  406  locations, for example. In some embodiments, the control enclosure part  404  can connect to the seat  353  at four holes  409 . Other configurations also are possible. 
   In the illustrated configuration, between the cover  403  and the control enclosure part  404 , a pivot bar  405  is mounted with two pins  126 L,  126 R. Springs  125 L,  125 R also can be fitted as described above. The pivot bar  405  preferably has two upward extensions  407 L,  407 R that mate with corresponding downward extensions of the control enclosure part  404 . The downward extensions are part of cantilevered beams  408 L,  408 R, which can be molded as part of control enclosure part  404 . Other configurations also are possible. 
   These cantilevered beams  408  are used to trap the pins and the rods of the respective angle stop subassemblies  118 S,  350 S in order to lock the chair  100  in the closed position. Locking the chair into the closed position reduces the likelihood of the chair unfolding while the chair is being carried, for example. The central handle  224 , which can be molded as part of the pivot bar  405 , can be depressed to unlock the chair when it is in a closed position. Details of this operation are illustrated and described below. 
   Cantilever springs  418 L,  418 R can be molded into the upper surface of the control enclosure part  404  and can apply downward pressure to the pins and rods of the respective angle stop subassemblies  118 S,  350 S. The cantilever springs  418 L,  418 R are used in conjunction with extended track pockets  421 L,  421 R to reduce the likelihood of inadvertent chair closure while the chair  100  is in use. Details are described and illustrated below. 
   A surround wall  422  can be used to reduce the likelihood of inadvertent pressing of the central handle  224  while the chair is in use. While sitting in the chair  100 , people may attempt to grasp a front edge of the seat and pull it forward or push it rearward. The surround wall  422  reduces the likelihood of inadvertent pressing of the central handle  224  in this situation. 
   As illustrated, the assembly sequence would have the control enclosure part  404  mounted first to the bottom of the seat  132  using the four mounting holes  409 , for example. The angle stop subassembly  350 S would be laid in position next, and the cover  403  with the pre-assembled pivot bar  405  and the attached pins  126 L,  126 R and springs  125 L,  125 R, would be attached at the six boss  406  locations, for example. 
   In some embodiments, four clearance holes are added in the cover  403  and the clearance holes generally align with the four attachment holes  409  of the control enclosure part  404 . The clearance hole addition would allow driver access to the four fasteners of holes  409  and so enable seat replacement without disassembly of the pivot cover subassembly  352 S. 
   In addition, the size of the central handle  224  on the pivot bar  405  can be reduced so that the central handle  224  can be contained within the cover  403  at all times. The opening  223  would be reduced in size so that only a small diameter tool could be inserted into the opening  223  to push the reduced-size central handle  224  to release the rod  390 . The tool diameter would be sized to reduce the likelihood of finger access and to reduce the likelihood of inadvertent operation. 
     FIG. 11  is a side view of the chair  100  showing some of the angular relationships of the seat  132  relative to the back subassembly  137 S, the front leg subassembly  101 S, and the rear leg subassembly  110 S. While certain angles are shown, the angles can differ somewhat from those shown depending upon the application. In the fully opened and locked position shown, the illustrated seat  132  tilts rearward about 3° relative to a horizontal plane that is generally parallel to the ground. This orientation sets up reference planes  325 ,  326 , which are generally parallel to the generally flat bottom of the seat  132 . The angular relationships can be measured from the reference planes  325 ,  326 . 
   The rear leg assembly  110 S is about 104° from the reference plane  325  as measured from the centerline of post  112 L. The back assembly  137 S is about 104° from the reference plane  326  as measured from the centerline of post  139 L. When folded in the closed position, the rear leg subassembly  110 S will pivot at the joint  115 L in line with the reference plane  325  until it comes to a stop substantially coincident with the reference plane  325 . In a similar manner, the back subassembly will pivot at the joint  142 L in line with the reference plane  326  until it comes to a stop substantially coincident with the reference plane  326 . In the closed position, the back subassembly post  139 L and the rear leg subassembly post  112 L will be generally parallel to each other and separated by a small clearance distance. 
   The front leg subassembly  101 S is about 52° from the reference plane  325  as measured from the centerline of post  103 L. When folded in the closed position, the front leg subassembly  101 S will pivot at the joint  106 L in line with the reference plane  325  until it comes to a stop substantially coincident with the reference plane  325 . The angular travel of about 52° of the front leg subassembly is half of about 104° of the rear leg subassembly and similarly half of about 104° of the back subassembly. 
   It can be appreciated that the stance of the chair  100  in the fully opened locked position is at least partially determined by the angular relationships described above. The coordinated motion of the front leg subassembly  101 S, the rear leg subassembly  110 S, and the back subassembly  137 S as controlled by the left gear box subassembly  168 S and the right gearbox subassembly  145 S is limited and can be determined by the angular relationships described above. Further, the gear ratios within the gearbox subassemblies  137 S,  168 S are at least partially determined by the angular relationships as described above, and in turn effect the stance of the chair  100 . 
   Also, the back angle of about 104°, the seat angle of about 3°, the seat height, the back contour, and the seat contour can be determined by ergonomic considerations of the user. Alteration of one or more of the angular relationships and back  138  and seat  132  contours will affect the comfort of the chair  100  for the user. 
     FIG. 12  and  FIG. 12A  are centerline section views of a portion of the folding chair  100 .  FIG. 12  illustrates the locked position of the pivot arm  124 , while  FIG. 12A  illustrates the unlocked position of the pivot arm  124 . In  FIG. 12  the pivot arm  124  is shown mounted on the pin  126 R, which is fitted into the pivot cover  123  that is installed onto the seat  132 . The pivot arm  124  is in the rest position and held in place by the compression spring  125 R. In this position, a rear surface  226  of the pivot arm  124  preferably substantially blocks forward travel of the pin  121 R of the angle stop subassembly  118 S. Since the pin  121 R in this position also is less likely to move in any of the rearward, upward, and downward directions, it is effectively locked in place, and the chair  100  is locked in the open position. 
   In  FIG. 12A , the central handle  224  has been depressed to unlock the chair  100 . The central handle travels up through the opening  223  in the pivot cover  123 . At the same time, rearward of the pivot pin  126 R, the ramp surface  227  travels down so that it is substantially coincident with the bearing wall  228  of the pivot cover  123 . In this position, the pin  121 R is free to travel forward, and the chair  100  is unlocked and can be folded. The pin  121 R travels between two generally parallel planar surfaces  228 ,  329  of the pivot cover  123  and of the seat  132 , respectively. In some embodiments, the upper surface  314  may be created as part of an enclosing part which is attached to the pivot cover  123  and becomes part of the pivot cover subassembly  122 S. 
   To open and lock the chair  100 , the coordinated unfolding of the front leg subassembly  101 S, the rear leg subassembly  110 S and the back subassembly  137 S cause the angle stop subassembly  118 S to also move and the pin  121 R to travel rearward. As the pin  121 R travels rearward, it engages the ramp angle surface  227 R of the pivot arm  124  causing the ramp angle surface  227 R to pivot downward. As the ramp angle surface  227 R pivots downward, it encounters increasing resistance due to the increased pressure created by the compression spring  125 R. When the downward movement reaches a point where the ramp angle is generally coincident with the bearing surface  228 , the pin  121 R can pass further until it is stopped by a seat wall  327 . At this point, the pin has passed the rear surface  226  of the pivot arm  124 , and the pivot arm  124  now travels upward due to the compression spring  125 R pressure, effectively locking the pin  121 R and the chair  100  in the open position. 
   The central handle  224  fits within the opening  223  in the pivot cover  123  and has minimal clearance in the rest position. When depressed, the central handle  224  travels upward in an arc and so the front surface  225  is contoured in a concentric arc to reduce the likelihood of interference with the leading edge of the opening  223 . 
     FIG. 12B  is a section view of the pivot cover subassembly  352 S attached to the seat  353  with the angle stop subassembly  350 S and the folding chair  100  in the folded locked position. When the chair is in a folded closed position, the rod  390  attached to the angle part  389  of the angle stop subassembly  350 S is trapped in position by the downward extension of the cantilever beam  408 R, a rear rib surface  412  of the cantilever beam  408 R, an upper control surface  414  of the control enclosure part  404 , and a lower control surface  413  of the pivot cover  403 . In this position, the chair  100  is effectively locked. To open the chair  100 , the central handle  224  is pressed, which causes the upward extension  407 R of the pivot bar  405  to move upward and cause the corresponding cantilever beam  408 R to bend upward. When the rib  412  of the cantilever beam  408 R moves up far enough, the rod  390  is free to move rearward and the chair can be opened. 
   A contact surface  410  between the pivot bar extension  407 R and the downward extension of the cantilever arm  408 R can be adjusted to control the amount of pressure needed to free the rod  390  and thus the effort needed to open the chair. In addition, the geometry of a junction  411  of the cantilever beam  408 R to the control enclosure part  404  can be adjusted to control the relative stiffness of the arm and the effort needed to deflect it. In another embodiment, the cantilever beam  408 R, which can be molded in, can be replaced with one or more separate attached parts that have a spring behavior to accomplish the locking function. 
   During opening of the chair  100 , the freed rod  390  of the angle stop subassembly  350 S travels rearward between upper control surfaces  414  of the control enclosure part  404  and lower control surface  413  of the cover  403  until it once again becomes trapped by the geometry at the rear as shown in  FIG. 12 . This action effectively locks the chair in the open position as described previously. 
   When weight is then applied to the seat  353 , the cantilever springs  418 L,  418 R bend upward from pressure of the rod  390  until the rod  390  rests against an upper pocket surface  419  of the track pockets  421 L,  421 R. In this position, vertical walls  420 L,  420 R block the forward motion of the rod  390  so that, even if the central handle  224  is depressed, the chair  100  is less likely to fold inadvertently. 
   As the person gets up and weight is removed from the seat  353 , the cantilever springs  418 L,  418 R apply downward pressure to the rod  390  to return it to the track generally defined by the control surfaces  413 ,  414 . When the cantilever springs  418 L,  418 R are compressed by the rod  390 , the maximum opening position of the chair is decreased slightly. To compensate, the angular travel of the rear leg, front leg and back subassemblies may be increased slightly to substantially maintain the desired stance of the chair  100 . 
   When the rod  390  of angle stop assembly  350 S or pin  121 R of the angle stop assembly  118 S is released again as in  FIG. 12A  during closure of the chair  100 , the rod  390  is free to travel forward. When moving forward, the rod  390  encounters a ramp  415  of the cantilever beam  408 R that causes the beam  408 R to bend upward. The beam  408 R can bend upward until it contacts an underside surface  417  of the seat. But just prior to this maximum deflection, the rod  390  passes forward of the lower edge of the rib surface  412 . The arm  408 R will then snap downward trapping the rod  390 , effectively locking the chair  100  again in the closed folded position. 
     FIG. 13  is an exploded view showing the construction technique employed in the front leg subassembly  101 S described earlier. Additional detail shown here is the front stringer  102  connection to the left post  103 L utilizing an integral shaft  328 , which can be molded. In a similar manner, the joint  106 L has a mating shaft  330 L, which can be molded. In this embodiment, both shafts have an elliptical cross section that fits into a mating elliptical section of the extruded post  103 L. 
   The front stringer  102  preferably has a curved back profile  335  for greater front foot clearance. A top curve height  336  preferably drops down in the center to allow foot and shoe heels to be pulled back during seating. The curved back profile  335  is reinforced at the rear with a rail extension  337  molded into the illustrated front stringer  102 . The shaft  328  has a stop ridge  329  that correctly orients the post  103 L as it slides onto the shaft  328 . In a similar manner, the joint  106 L preferably has a stop ridge  331  that correctly orients the post  103 L as it slides onto the shaft  330 L. 
   The joint  106 L preferably has a recessed surface  334 L that has a curved edge in clearance with the mating surface of the left gear box subassembly  168 S. A further recess socket  332 L fits over the mating shaft of 2.0L gear/axle  150 . The opposite side of recess socket  332 L has another recess  333 L used for a washer and connecting bolt. This recess is more clearly depicted on that joint  106 R as the recess  333 R. 
   As described earlier, the joint  106 L and the front stringer  102  are connected to the extruded post  103 L with rivets or fasteners, for example. In some embodiments, the integral shaft  330 L of the joint  106 L and the integral shaft  328  of the front stringer  102  may be constructed with a tighter fit and employ a snap detail that would securely position within a respective slot within the extruded post  103 L. Such a construction might be appropriate if the joint  106 L were to become part of the gearbox subassembly  168 S for assembly efficiency, for example. In a similar fashion, the snap detail attachment method could be employed in rear leg subassembly and back subassembly described below. 
     FIG. 14  illustrates an exploded view of the rear leg subassembly  110 S. The assembly technique and details are similar to those used in the front leg subassembly  101 S. The rear stringer  111  curves back from the rear edge of the posts  112 R,  112 L to reduce the likelihood of interference in the closed state with the front leg subassembly  101 S stringer  102 . The rear stringer  111  can be reinforced with a rail extension  340 , which can be molded near the upper edge at the rear. The illustrated rail extension  340  comprises two pass-through slots  341 ,  342  that are used with a security cable to string together multiple chairs in larger gatherings. 
     FIG. 15  illustrates an exploded view of the back subassembly  137 S. The assembly technique and details are similar to those used in the front leg subassembly  101 S and the rear leg subassembly  110 S. The back  138  preferably comprises a handle  345  integrally molded with a hand clearance slot  346 . The handle  345  can comprise a carved back contour profile  347  that forms a half circle section. When two folded chairs are placed back to back the handle profiles are adjacent and form a complete circle section that can be carried as a single handle. This enables two folded chairs to be carried in one hand. 
   In some embodiments, the shaft  343  of the back  138  can comprise a single hole that mates with the hole  141 R of the right post  139 R and that accepts a pin connector. The shaft  343  cross-section can be contoured for a snug fit with the right post  139 R, the stop ridge  344  can establish position, and the pin can be used to retain position. In some embodiments, the shaft  343  has a clearance fit with the right post  139 R and two pins or rivets are used, for example. One pin can mate with the hole  141 R to retain position, while the second pin can mate with the hole  140 R to reduce the likelihood of off centerline orientation. In such an embodiment, the stop ridge  344  would not be available to establish position. 
     FIG. 16  illustrates a detail and a section view of a 50 percentile (approximately 68.8″ tall) U.S. male carrying two folded chairs  100  in his right hand and one folded chair  100  in his left hand. In some preferred embodiments, the integral handle  345  of the backrest  138  is contoured as described above such that when two chairs are carried back-to-back the carved back contour profile forms a circle section that is carried as a single handle. Carrying two chairs in one hand is suitable for adults of average height (50 percentile) and grip size. In an alternate embodiment, the contour profile  347  of the integral handle  345  is adjusted to fit smaller grip sizes. 
   It can be appreciated that the overall length of the folded chair  100  in the folded position can be compact such that it is possible for a child of 9 years of age (approximately 53″ tall) to carry the chair in one hand with the arm fully extended in the downward relaxed position. In chairs of length exceeding 23″ the child would have to raise the arm to avoid dragging the chair and fatigue sets in quickly. 
   The overall chair  100  width can be determined primarily by the gearbox housings  145 S,  168 S, and also by the front and rear stringers  102 ,  111 . In some embodiments, the width can be reduced by decreasing the gear diameters (but not the gear ratios) of the geartrains and the enclosing housings. The front leg, rear leg and back subassembly components can then be reduced in width. Also, in some embodiments, the front and rear stringers  102 ,  111  are made flat and so the effective overall chair width is driven only by the gear housings. Such configurations can be especially desirable to minimize arm flare-out when carrying two chairs in one hand. 
   Although certain features, aspects and advantages of the present invention have been disclosed in the context of certain preferred embodiments, examples and variations, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while a number of variations of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is specifically contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed invention. Moreover, some variations that have been described with respect to one embodiment and not another embodiment can be used with such other embodiments. Many other variations also have been described herein and cross-application is intended where physically possible. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.