Abstract:
Seating for a telescoping row system or the like is mounted to a beam pivotally secured to a base anchored to the platform and riser. The beam is raised arcuately into a use position by a pneumatic bellows and is mechanically locked in the upright position to permit deenergization of the bellows. Reinflation of the bellows disengages the lock and the assembly collapses slowly against the controlled deflation of the bellows. 
     The seat is positionable on the beam initially without fasteners to facilitate installation. In similar fashion, armrests are secured to the beam separate from the seat and adjustable along the beam to permit overall width variations.

Description:
This is a continuation of application Ser. No. 765,710, filed Aug. 14, 1985 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to telescoping seating systems of the type which include a plurality of rows. Each row consists of a riser and platform structure, the rows being mounted on a movable structure so that they are adapted to move between an extended position for use during which the rows are stepped or tiered and a retracted or storage position during which the rows are generally vertically aligned. Seating of this type is often referred to as temporary seating since it is movable into a use position and removed to permit other activity at the seat location. 
     The present invention relates specifically to the type of telescopic seating system wherein the seats themselves are integrally anchored to the rows and are capable of being automatically folded between a use position and storage position wherein the rows can be retracted with the seats collapsed to permit the vertical alignment described. 
     Seating systems of the type described are principally utilized in roofed stadia, auditoriums, convention centers and the like wherein significant aspects of concern relate to economic, functional and aesthetic considerations. Cost of procurement, installation and maintenance over the service life are significant concerns. The ability to maintain same in a clean, tidy, attractive condition while deterring or prohibiting vandalism, unintended or prankster manipulation is equally important. The prior art teaches various proposals that attempt to respond to the needs of current industry demands but nonetheless do not accomplish same for varied reasons. Systems which require manual manipulation in one form or another to permit the seat to collapse are not sufficiently tamper-proof to prevent pranksters from undertaking the referenced manipulation. Others propose mechanisms which are either relatively complicated and thereby impractical over the normal service life or provide disadvantages through their arrangements in that they are easily rendered unsightly by the ingress or egress of natural elements or items disposed of by the user such as concessionaire items including dropping of food items and the like. Others yet do not provide the comfort desired or minimization of profile in the seat in its collapsed state to maximize the telescoped effect. In many situations, the desirability of chair seating versus bleacher seating is recognized, but the provision of a back interferes with the closing of the rows or the amount of time required in setting up or knocking down the seating system requires too much effort and labor intensity. 
     Prior art systems known to Applicant which are purported to be automatic all require the platform to engage and/or otherwise power the folding and erection of the seats. This requires increased strength and power of the system itself to actuate not only the telescoping, but the seat actuation. Finally, the ability to retrofit an in place seating system with more current state of the art seats has been heretofore complicated by the degree of modification required to the system in order to accommodate the desired seats. Thus, there is a broad based need for an improved seating assembly specifically adapted for a telescoped system. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, in its preferred form, a beam is pivotally mounted to a base structure by one or more supports, the base being anchored to at least one of the riser or platform. A pneumatic bellows interacts with the pivotally mounted support whereby the beam can be raised to an elevated generally parallel position vis-a-vis the platform but relatively adjacent the riser or rotated forwardly upon deflation of the bellows to a position generally adjacent the platform. 
     In a preferred aspect of the invention, the beam is tubular and mounted so that in its raised position, one edge of the beam defines the uppermost position with two upper surfaces falling away at a roughly forty-five degree angle to inhibit the collection of dirt and food items or the like on the beam. In another preferred aspect of the invention, the seat includes a pair of spaced vertically extending side supports, the lower ends of which are configurated to form a saddle relationship with the beam. The seat back and bottom are pivotally anchored to the side supports, the overall center of gravity of the seat being such that the seat assembly can be placed on the beam in a freestanding manner to facilitate desired spacing during installation. A novel strap means is provided to secure the seat assembly in place. In a more refined aspect of the invention, the seat back and bottom pivot about spaced axes and the cross-sectional configuration of the seat back and bottom are matched to provide an extremely low profile when the seat is pivoted up into nesting engagement and still permit the installation of cushioning means if desired. The pivotal movement at the back and bottom are later connected to lock the back in position when the seat is occupied and facilitate collapsing when the bottom is urged up. 
     In yet another preferred aspect of the invention, armrests are provided independent of the seat assembly with vertically depending supports likewise configurated at their lower end to form a saddle engagement with the beam, the center of gravity of the armrest also permitting freestanding placement during installation. Similar clamping means are provided to permanently join the armrest to the beam. The separate mounting of the armrest permits overall width adjustment of the seat on a linear basis. 
     In yet a further aspect of the invention, a unique locking means is provided whereby when the beam and seat assemblies attached thereto are raised by inflation of the bellows, a latch is cammed into position over a lock pin to absolutely lock the seat assembly into its use position in a tamper-proof manner. The latch means secures and holds the seat assembly in its upright position such that the bellows can be depressurized. Upon repressurization of the bellows, a pawl means engages the latch means to disengage same from the lock pin whereby the beam and seat assembly are urged by the gravitational weight thereof to the collapsed storage position, the seat assembly and beam rotating slowly against the bellows as it deflates. 
     In yet other aspects of the invention, one bellows means actuates a plurality of interconnected seat assemblies and one portable pneumatic source operates a bank of bellows. 
     In accordance with the invention, a single operator and pneumatic source is all that is required to run a relatively large system unless the magnitude of the total number of collapsible seats is such that multiple compressed air sources would be preferred. In any event, a single operator is all that is required to raise, lower, retract and/or extend the telescoped seating assembly of the present invention. 
     Significant savings can be realized by the present invention in that the operation of the telescope function (whether automatic or manual) is completely separate from the seat mechanism. The present invention provides a compact, simplistic facile arrangement synergistically incorporating multiple concepts to provide a system with an extremely long service life which operates in a way to prevent involuntary or undesired manipulation. The linear separation of each seat assembly can be simply arranged by adjusting the armrest width whereby a single width seat assembly can be utilized over a given desired range. The installation of the system permits quick and easy centering of each seat and armrest prior to final fastening in a manner that does not require unnecessary labor. The overall profile and appearance of the seats provides an extremely aesthetically attractive system projecting an exposed surface area which will not collect or attract dirt or other items. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the preferred seating assembly in its erected use position with one armrest pivoted up; 
     FIG. 2 is a fragmentary side elevation view of one aspect of the seating assembly of the invention; 
     FIG. 3 is a fragmentary perspective view of a single seat assembly in its raised use position with the body support rotated upwardly; 
     FIG. 4 is a fragmentary perspective view of the seat assembly in its collapsed position; 
     FIG. 5 is a cross-sectional view of the armrest attachment to the beam taken along line V--V of FIG. 3; 
     FIG. 6 is a side view of the bellows and latching means of the invention; 
     FIG. 7 is a front elevational view thereof partially fragmentized; 
     FIG. 8 is a side elevation of the latch plate of the invention; 
     FIG. 9 is a side elevation of the pawl of the invention; 
     FIG. 10 is a side elevation of the lifting plate of the invention; and 
     FIG. 11 is a fragmentary side elevation of the seat. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A portion of a seating system 10 is depicted in FIG. 1 designed to include three laterally adjacent seat assemblies 12, only one of which is shown in FIG. 1, the other two being identical in configuration and mounted to beam 14 on each side of the seat assembly shown. 
     The seat assemblies 12 and beam 14 are pivotally supported by a base 16 preferably secured to a platform 18 and associated riser 20 (FIG. 4) which are part of a conventional telescoping system well known to the art. 
     Beam 14 is tubular in configuration and mounted to base 16 by a pair of tubular support arms 22 rotatably secured to base 16 by support plates 24a, 24b and 26a, 26b by a pin 28. Plates 24a, 24b, 26a, 26b are welded to a base mounting plate 30 which is in turn anchored to platform 18 by bolts 19 secured through a platform portion 32 of the base as depicted in FIGS. 4, 6 and 7. A reinforcement plate 15 is welded to the riser portion 34 of mounting plate 30 which in turn is anchored to riser 20 by bolts 19a. In the preferred embodiment wherein three seat assemblies 12 are mounted to beam 14, additional outrigger support arms 22 (FIGS. 1 and 3), are provided to lend lateral stability to the movement of beam 14 as described hereinafter along with the seat assemblies mounted thereon. 
     Additional paired mounting plates 24 (FIG. 3) are also provided in the same manner described herein with respect to spaced plates 24a, 24b; 26a, 26b and associated pins 28. Beam 14 is mounted on support arms 22 on the bias such that its uppermost edge 36a forms the top of beam 14 in its raised position (FIGS. 1-3), the upper surface thereof being comprised of sides 38a, 38b as illustrated in FIG. 6. Conversely when the seat is collapsed into its storage position, beam 14 is rotated into close proximity to or in contact with platform 18 as shown in FIG. 4 and edge 36b now becomes the top of beam 14 with sides 38a, 38b forming the upper surfaces, again. In either position, the collection of dirt or the like on beam 14 will be inhibited and rather fall onto platform 18 for easy cleaning. 
     Support arms 22 are cut at their upper free end 23 (FIG. 6) in a configuration matching the cross-sectional configuration of beam 14 so that they act as saddles which fit over and seat on the beam in a positive manner. The support arms and beam are permanently joined by a weld, the weld material not being shown in the drawings. 
     Beam 14 by reason of the pivotal rotation of arms 22 about the axis of pins 28 can be positioned in a raised position wherein the beam is parallel to both the platform 18 and riser 20 spaced from platform 18 but generally adjacent to and in close proximity to riser 20 as depicted in FIG. 3 and in a lowered position as depicted in FIG. 6 wherein beam 14 is still parallel to both platform 18 and riser 20 but generally adjacent to or in contact with platform 18 being spaced from riser 20 approximately the length of support arms 22. The beam thus rotates through about an eighty degree arc as illustrated in FIG. 6. 
     A latch rod 40a is rotatably mounted through each of adjacently paired support plates 24a, 24b (FIG. 3) and its adjacent outrigger plates 24 of the type shown in FIG. 3 and a second latch rod 40b is identically mounted on the opposite side through plates 26a, 26b and its adjacent outrigger plates 24. 
     A latch 42 (FIGS. 4 and 8) is rigidly secured to rods 40a, 40b between each set of support plates and rotatable therewith. Latches 42 are generally elongated comprising a slot 44 at the free end (FIGS. 4, 6) and an actuating pin 46 projecting from each side thereof forwardly of but in close proximity to rods 40a and 40b.  Slot 44 has reversed curvature portions 44a, 44b which facilitate latching and unlatching in a manner to be described. Preferably, rods 40a, 40b are spring biased by a torsion spring (not shown) to urge latch 42 into its downwardmost position whereby stop surface 48a abuts the reinforcement plate 15 of base plate 30 as shown in FIGS. 4 and 6, the upwardmost position being defined when stop surface 48b abuts plate 15. 
     Turning to FIGS. 4, 6 and 7, base 16 includes a bellows 54 anchored at its lower surface to the base mounting plate 30. Bellows 54 has a plate 55 (FIG. 7) integral with its lower surface having a surface area approximating the lower surface area of the bellows in its inflated position. The bellows deforms slightly over plate 55 directly onto the base portion 32 of mounting plate 30 in its deflated position. An upper plate 58 identical to plate 55 is likewise provided integral with the bellows. The upper surface of bellows 54 is anchored to a channel-shaped lifting beam or bar 56. An intermediary plate 62 is positioned between beam 56 having an enlarged surface area compared to plate 58 approximating to some extent the upper surface area of the bellows when deflated as shown in FIG. 4. This provides support to bellows 54 during deflation and prohibits abusive distortion. The upper plate 58, intermediary plate 62 and lower plate 55 are anchored by fasteners 60 as shown in FIG. 7. The entire base assembly 16 is anchored to platform 18 by fasteners 19, the only opening required through the platform beneath the bellows being one to permit an appropriate air pressure line 66 to access bellows 54, line 66 extending to an access location in the system (not shown) to permit attachment of the air supply source. Typically, line 66 would be in series with other bellows such that a bank of bellows and associated seats are actuated simultaneously by a single operation using a portable air pump. 
     Turning to FIG. 4, support arms 22 as mentioned previously are tubular in configuration having an outer free end configuration matching beam 14 to permit facile welded attachment thereto. If one views the seat depicted in FIG. 4 in the direction of &#34;A&#34;, support arms 22 have mirrored configurations with respect to the one immediately to the left of bellows 54 and the one on the right side. In each case, there is a rearward access opening 50 which exposes a lock pin 52 secured between the outer sidewall 25a and inner sidewall 25b extending beyond the outer surface of inner sidewall 25b, the latter extension accommodating interaction with a lifting plate 70. A pawl 72 is pivotally anchored within the opening 50 of support arms 22 to a pin 84 (FIG. 6) protruding inwardly through sidewall 25b from a lifting plate 70 through an arcuate slot 86 in sidewall 25b of arm 22. Pawl 72 is generally &#34;V&#34; shaped, one arm 73 having opposed cam surfaces 74, 76, the other arm 75 having a cam surface 77. Pawl 72 is biased by its weight such that cam surface 76 is urged into contact with pin 52 when the seat assembly is in its collapsed position. 
     The lifting plate 70 has a generally triangular configuration (FIG. 10) and is pivotally mounted to the base assembly about one corner in the same manner as support arms 22 by pins 28. Lifting beam 56 has a pair of downwardly depending side plates 78 (FIG. 7) welded thereto forms a lift frame. A pin 80 is mounted through openings of side plates 78 and anchored to lifting plate 70 about a second corner such that when bellows 54 is inflated or deflated to raise or lower same, lifting plate 70 is likewise lifted and pivoted about the axis of pin 28. A plastic washer 82 is positioned intermediate plates 78 and lifting plate 70 to facilitate relative movement therebetween. As noted earlier, a pin 84 projects from plate 70 through arcuate slot 86 (FIG. 4) in the inner wall 25b of arm 22 to which pawl 72 is rotatably mounted. Lifting plate 70 also includes a cam drive surface or pusher 79 at the third corner which engages lock pin 52 when the seat assembly is collapsed. The pawl 72 is preferably mounted intermediate latch 42 and lifting plate 70, sidewall 25b of arm 22 being intermediate pawl 72 and lifting plate 70. 
     Turning now to FIGS. 4 and 6-10, it will become apparent how the mounting beam 14 and seat assemblies attached thereto are raised, locked, released and lowered. Assuming that the beam 14 is oriented as shown in FIG. 4, bellows 54 being deflated, a source of pressurized air (not shown) is supplied through line 66 to inflate bellows 54. As the bellows are inflated, lifting beam 56 moves vertically up. Due to the pin engagement of its side plates 78 with lifting plate 70, plate 70 is simultaneously lifted and pivoted about the axis of pin 28. As this occurs, arms 22 are rotated upwardly by the direct driving engagement between drive surface 79 and lock pins 52. As the arms pivot upward, lock pin 52 will engage latch 42 in the general vicinity of slot 44 pivoting same upwardly until pin 52 is securely biased against the inwardly radiused slot surface 44b. Further movement slides lock pin 52 up to its upper limit position securely engaged within slot 44 of latch 42 as depicted in FIG. 6. The upward movement of lifting plate 70 during this initial inflation of bellows 54 is limited by the contact of pin 84 within slot 86 prior to stop surface 48b engaging reinforcement plate 15. During the course of this rotation from the position shown in FIG. 4, as the drive cam 79 moves lock pin 52, pawl 72 is concurrently rotated because of its interconnection to lifting plate 70 by pin 84. However, as it is rotated in the counterclockwise direction from the viewpoint of FIG. 6, the stop surface 77 engages pin 52 because of the configuration of pawl 72. Since arm 75 and stop surface 77 are prohibited from further counterclockwise rotation other than concurrent movement with lifting plate 70, the pawl arm 73 slides ever so smoothly within the spacing between latch pin 46 and lock pin 52. This spacing diminishes and rotates relatively as the arms 22 are raised. The spacing is such that the cam surface 74 will not engage latch pin 46 during the erection of the seat assembly. The final position of pawl 72 in the raised position is depicted in FIG. 6. 
     Once latch plate 42 has locked firmly over lock pin 52, the beam 14 and seats mounted thereto are completely locked into their raised upright position. At this juncture, the seating system could be used without fear of manipulation or collapse. There is no meaningful access to release latch 42. At this stage, the source of pressurized air to bellows 54 is preferably removed and the bellows will collapse slowly by its own weight allowing lifting plate 70 to rotate in a clockwise direction with the concurrent clockwise rotation of pawl 72 completely disengaged from lock pin 52. This movement is permitted by the arcuate slot 86 in support arm 22. As a result of this rotation, and the bias of pawl 72, the cam surface 74 will fall into place beneath latch pin 46. 
     The downward rotation of pawl 72 and lifting plate 70 is limited by pin 84 engaging the end 85 of slot 86. This stop preferably occurs at a position wherein bellows 54 is slightly bulged from its normal deflated position to keep an element of tension on the system so that the beam and seat assemblies will not and cannot rock or be moved. In this way there will not be any looseness or rattling during use which could occur if the system were relaxed. 
     When it is desired to collapse the system once more, bellows 54 is once more pressurized causing cam surface 74 of pawl 72 to lift latch 42 out of locking engagement with lock pin 52. During this movement, the drive cam 79 of lifting plate 70 will remain spaced from and out of contact with lock pin 52 since pawl 72 can move relative plate 70 by reason of pin 84 in arcuate slot 86. The movement of latch 42 will not be large in magnitude as it is limited by the abutment of stop surface 48b coming into contact with reinforcement plate 15. The movement will be sufficient however to allow disengagement of lock pin 52 from slot 44 of latch 42. Once latch plate 42 is rotated upwardly relative lock pin 52, the weight of beam 14 and seats mounted thereon will cause the beam, support arm and seats mounted thereon to be biased toward rotation in a clockwise direction with respect to FIG. 6. This is assured by the overall center of gravity of the seats and the cant of support arms 22 reflected in FIG. 6 wherein they are approximately twelve degrees off the vertical. The assembly will abruptly shift at this point until lock pin 52 rotates into contact with cam drive surface 79 of lifting plate 70. Ideally, this rotation will not exceed a ten degree fall. At this juncture, the entire seating assembly is free to collapse but for the pressurization of bellows 54. If this pressurization source is removed along with an appropriate bleed down opening, the weight of the entire structure will deflate bellows 54 in a smooth steady manner such that the seating assembly settles slowly into the position depicted in FIG. 4. At this point, the system can be telescoped into a storage position by conventional means. 
     Particular reference is directed to the unique configuration of slot 44 in assisting the operation of latch 42 both in the locking and unlocking phase. If this surface were straight, the lock pin 52 would have to be driven into the slot past the center point to assure positive locking. Likewise, to disengage latch 42, the movement of latch 42 during unlocking by reason of the force generated from pawl 72 on pin 46 would require some movement of the system at large to permit release below the center point of slot 44 to permit disengagement. The reverse curvature solves this since as the lock pin 52 is initially driven into the recessed area defined by surface 44b, removal of the driving force from that point on would still result in complete latching because of the bias of latch 42 and the fact that further movement of latch 42 into the downward locking position results in an internal cam outward by surface 44a. Likewise, when pin 46 drives latch 42 upwardly, the reverse curvature eliminates the need to exert any additional raising force on the system itself. The location and operation of pin 84 in slot 86 by limiting the deflation of bellows 54 during use keeps the system tight thereby avoiding swag or undesired movement of the seats during use. 
     Turning once more to FIG. 3, it is noted that two separate latch rods 40a, 40b are provided rather than a single bar through the entire base assembly. A single rod could be utilized, but installation is facilitated by using two since it only requires the rod be aligned with two openings, namely, the inner support plates 24a, 24b and its associated outrigger, the second rod 40b requiring alignment only with plates 26a, 26b and its associated outrigger 24. 
     As presently conceived, a bank of seven seats are actuated by a single bellows and base. Three seats are mounted to the beam depicted in FIG. 1, only the center seat being shown. Two double seat modules referred to as dummy units are preferably mounted at each end of the three seat unit, each dummy unit having its own spaced support, support arms, beam, latch and latch rod in the manner previously described. By interconnecting the beams and rods, the outer dummy units are equally actuated with the pneumatically operated inner unit. The rods 40 and beams 14 can be joined in a conventional way by an angle iron fastened to the beams and a tube and roll pin connection of the rods (not shown). 
     Turning now to FIG. 11, the individual seat 12 encompasses a back support 100 pivotally secured to tubular depending support legs 102 (FIGS. 3 and 4), the latter attaching directly to beam 14. A body support or bottom 104 is pivotally secured to support arms 102 by a pivot plate 106 which hinges directly into and through a slot in legs 102 (FIG. 3). The axis &#34;B&#34; of rotation of back support 100 is spaced from the axis &#34;C&#34; of rotation of body support 104. Body support seat element 104 may be spring biased into a raised position or can be manually rotated into a raised position as well. Armrests 110 (FIG. 2) are mounted to beam 14 independent of seat 12. One advantage of this is to permit no armrests if desired, or, alternatively, depending on the space demand within the installation itself, a single width seat can provide multiple width spacings by simply adjusting the armrest spacing as desired. In normal seating widths, a single seat having a width of eighteen inches can in effect be used to provide seat width variance from eighteen to twenty inches by merely adjusting the armrests. A second seat of twenty inches in width permits normal flexibility for a seat ranging from twenty to twenty-three inches in width by armrest adjustment. 
     The arm portion 112 of armrest 110 is pivotally secured to its support tube 114 by a recessed hinge 113. With reference to FIGS. 2-4, the armrest support leg 114 has its lower free end 116 cut angularly to match the configuration of beam 14 forming a saddle-like configuration. With arm 112 rotated up (FIG. 2), the center of gravity of armrest 110 is such that it can be placed on beam 14 during installation without attaching same. This greatly facilitates proper spacing prior to final installation. 
     To secure armrest 110 to beam 14, a rear strap 116 is welded to the rear surface of support leg 114 and shaped to match the contour of beam 14. At the lower edge 36c a vertical tab 118 with an aperture therein is provided. A mating strap 120 is provided with a configuration to fit around the opposite side of beam 14 and a slot 122 is provided in the front face 124 of leg 114 for insertion of a hook 126 formed on the upper end of strap 120. Two different forms of hook 126 are shown in FIGS. 2 and 5. The lower end 128 forms a tab similar to tab 118 with an aligned aperture to permit insertion of a mechanical fastener. The two straps 116 and 120 completely encapsulate beam 14 and permanently secure the armrest assembly to the beam. Quick and easy adjustment can be made however by loosening the fastener 130 or it can be removed entirely with ease. 
     FIG. 2 illustrates the movement of arm 112 about pin 150 which is biased by spring 152 into either the up or down position indexed by roller 154 against the internal walls of support 114. 
     Each seat 12 is also mounted to beam 14 in a manner similar to the armrest assembly. With the body support seat 104 folded up and generally aligned with back support 100, the entire seat can be positioned on beam 14 in that legs 114 are likewise configurated at their bottom end to form a saddle-like configuration to fit over beam 14. With the body support seat raised, the center of gravity of the seat is such that it can rest on beam 14 in freestanding fashion. Welded rear straps and hook mounted forward straps are provided identical to that described with respect to armrest 110. This provides accurate and easy installation, adjustment and/or removal in the manner described. 
     Turning to FIG. 11, both the back support 100 and body support 104 are pivotally attached to supports 102 about spaced axes &#34;B&#34; and &#34;C&#34; and interactive such that when body support 104 is pulled down or someone sits on it, the back 100 is biased to and locked in its most upright position. Upon raising support 104, the linkage rotates the back 100 into a juxtaposed alignment creating a relatively thin or low cross-sectional profile enhanced by the configuration of the seat support 104 and seat back 100. This close juxtaposition is also enhanced by the fact that the axes of rotation of support 104 and back 100 are displaced. 
     Seat bottom 104 includes a pivot plate 106 anchored therein and extending into support 102 being pivotally mounted therein by pin 132. A leaf spring 134 biases the seat up as shown in phantom position &#34;E&#34; by interacting on plate 106 as shown. A rubber stop 136 engages stop 138 to position support 104 in its use position when the support 104 is rotated by a force sufficient to overcome spring 134 such as a person using the seat. 
     Back support 100 also has a pivot plate 140 anchored therein and extending out of the support 100 into tube 102 and pivotally anchored about pin 142. A leaf spring 144 biases the back into its use position defined by rubber bumper 146 on plate 140. When body support 104 is positioned in its use position as depicted in FIG. 2, plate 120 includes a portion 123 which engages bumper 136 preventing rotation of back support 100. Once support 104 rotates up, back 100 is free to move to the phantom position E. As the seat rotates, the weight of both back 100 and bottom 104 will overcome springs 134 and 144 and fold together. The displacement of the axes &#34;B&#34; and &#34;C&#34; of pins 142 and 132 permit a very close essentially parallel juxtaposition as shown in FIG. 4. 
     The configuration of back 100 is characterized by recess portions 160 and 162 (FIG. 1) which are contoured to provide not only comfort to the user, but to overlap in the collapsed state with the contour of bottom 104 so that the cross-sectional width of the profile of the folded units is minimized. Indeed, it has been found that whether the seat portions are comprised of wood or plastic, the overall cross-sectional width can be reduced to five inches and one-half and yet permit up to three inches of cushioning material to be attached thereto without causing an increase in the cross-sectional profile during the collapsed position. Finally, a metallic or plastic cover (not shown) is provided to fit over base 16 cooperating with the configuration of the support plate 30 to prevent accidental or unwarranted ingress. 
     Having thus disclosed in detail a preferred embodiment of the invention, persons skilled in the art will be able to modify certain of the structure which has been illustrated and to substitute equivalent elements for those disclosed while continuing to practice the principle of the invention; and it is, therefore, intended that all such modifications and substitutions be covered as they are embraced within the spirit and scope of the appended claims.