Modular chair seat structure
BACKGROUND OF THE INVENTION 
     1. Related Application 
     The chair seat structure of this disclosure is particularly applicable to structures shown in commonly assigned, co-pending U.S. patent application Ser. No. 494,568 filed May 13, 1983, and entitled Modular Furniture System. 
     2. Field of Invention 
     This invention relates to a plurality of separate components assembled to form a substantially non-warpable, dimensionally adjustable chair seat. 
     3. Description of Prior Art 
     Prior art chair seats which the present invention replaces have been comprised of one sheet of laminated wood. The laminated wood is formed into the desired configuration using heat and pressure. 
     Disadvantages of this prior art construction are that such seats are expensive to form; they are susceptible of warpage and, consequently, frequently unusable; they are difficult to mount to the supporting frame; and they are not adjustable. For example, if a formed chair seat is out of tolerance it must often be scrapped. Such scrappage imposes a severe cost penalty due to the investment the manufacturer has made in the purchase of the laminate, the forming of the laminate and, frequently, transporting the formed seat to the point of assembly. Also, such formed chair seats take up a good deal of space for transport and storage. 
     SUMMARY OF THE INVENTION 
     A chair seat is formed of three planar members or boards having substantially equal dimensions. As the boards have the same dimensions, they are interchangeable and may be placed in any of three positions in the chair seat. 
     The boards, which are preferably formed of a material such as pressed wood, are not subject to warpage when exposed to ambient changes in humidity and temperature. 
     Molded or extruded plastic members serve to connect the boards to each other and adapt the formed chair seat for attachment to a supportive base or frame member. The plastic connective members have engagement slots appropriately sized to receive edge portions of the boards. The boards are maintained engaged with the slots by appropriate means such as mechanical fasteners or adhesives. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a prior art chair seat formed of laminated wood; 
     FIG. 2 is an elevation view of the prior art chair seat shown in FIG. 1; 
     FIG. 3 is a perspective exploded view of the chair seat of this invention in which the components are shown relative to each other prior to assembly; 
     FIG. 4 is a partial top view showing the adjustable relationship of the edge of a board member to a slot in a connective member; 
     FIG. 5 is a sectional view of FIG. 4 as indicated by the section line 5--5; 
     FIG. 6 is a side elevation view of the assembled components of a chair seat of this invention; 
     FIG. 7 is a side elevation view of the assembled components of a chair seat of this invention placed on a representative forming fixture; 
     FIG. 8 is a perspective view of a prior art support frame for a chair seat; 
     FIG. 9 is a perspective view of a preferred support frame to be used with this invention; and 
     FIG. 10 is a side elevation view of the chair seat of this invention installed onto the preferred support frame of FIG. 9. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows, in perspective, a typical prior art chair seat consisting of a sheet of a laminated wood which has been formed from a substantially planar sheet into the configuration shown. FIG. 2 is a side elevation view of the prior art chair seat 2. These seat structures are formed using heat and pressure to mold the laminate to a desired form, such as that shown, in which the integral one-piece seat has a substantially planar back portion 3, a curved portion 4, a substantially planar back support portion 5, a center curved portion 6, a substantially planar seat support portion 7 and a forward curved portion 8. 
     While these prior art seat structures perform well in assembled chairs, they are susceptible to warpage from ambiant humidity prior to installation on a chair base, and they are cumbersome and expensive to ship and store. Moreover, if not made to close tolerances, they will not fit properly on the frame at the time of assembly of a chair since they are not adjustable. 
     FIG. 3 is a perspective view showing the components of a chair seat 10 of this invention which overcomes the disadvantages of the one piece molded prior art chair shown in FIGS. 1 and 2. 
     Chair seat 10 is comprised of three substantially planar members 11 which are substantially identical in size and shape and, consequently, interchangeable with each other. 
     Any member 11 can interchangeably serve as a back portion 12, the back support portion 13 or the seat support portion 14. 
     Each of the planar members 11, such as the member 11 used as the seat support portion 14, has a first side 15, a second side 16, a first connective end 17, a second connective end 18, a first surface, such as the upper surface 19 of planar member 11 used as seat support surface 14 and a lower surface 20. The members 11 are preferably manufactured or formed of a suitable material, such as fiber board, pressed wood, particle board, or the like, which is not susceptible to warpage due to ambient atmospheric conditions such as high or fluctuating humidity. A fiber board 3/4 inch in thickness has adequate strength for most applications. 
     The planar members 11 used in positions 12 and 13 are connected together by a first connective member 21 having a first planar member connective end receiving slot 22 and a second planar member connective end receiving slot 23. A connective portion or bight 24 connects slot 22 and slot 23 and maintains the slots in a substantially parallel, laterally spaced relationship substantially as shown. 
     A second connective member 25 is used to connect together the planar members 11 used in the positions 13 and 14. Connective member 25 has a first planar member connective end receiving slot 26 and a second planar member connective end receiving slot 27. Slots 26 and 27 are connected together by a connective portion 28. Connective portion 28 maintains slots 26 and 27 in the laterally spaced, substantially parallel relationship shown. A plurality of openings, such as openings 29 and 30, are provided in connective portion 28 to receive appropriate attachment means, such as mechanical fasteners. 
     A third connective member 31, having a planar member connective end receiving slot 32, is provided to connect the planar member 11 occupying seat support position 14 to a chair base or frame. Connective member 31 is provided with a channel 33 which extends substantially parallel to connective slot 32. Channel 33 is provided with a plurality of openings, such as openings 34 and 35, adapted for receiving appropriate attachment means, such as mechanical fasteners. At a lower terminal end 35 of member 31 a rigidifying spacer flange 37 is provided. 
     A curved connective portion 38 connects slot 32 to channel 33 and maintains them in a substantially parallel laterally spaced relationship. Similarly, a connective portion 39 connects channel 33 and flange 37 together and maintains them in a substantially parallel, laterally spaced relationship. 
     Each of the connective members 21, 25, and 31 are preferably formed of a returningly deformable substantially rigid material having a limited degree of flexibility and the ability to return to its original shape after it has undergone slight flexing or deformation. For example, connective members formed of extruded polyvinylchloride (PVC) and having a average wall thickness of about 0.156 inch serve well. Such connective members are substantially rigid and, as previously indicated, they have good &#34;memory&#34; properties in that they tend to return to their original shape after being distorted. 
     FIG. 4 shows a connective end of a planar member 11, such as end 17 of the member 11 in position 14, inserted into a slot of a connective member, such as slot 27 of connective member 25. In this figure, the end 17 of the planar member has been shown as skewed or not square with the sides 15 and 16 of the planar member. However, due to the fact that the slot is preferably 1/2 inch to 1 inch in depth, the board can be adjusted to have sides 16 and 15 be aligned with sides 40 and 41, respectively, of the connective member by skewing the end 17 in slot 27 substantially as shown. Thus, each of the members 11 can be adjusted for length or angle with respect to a connective member 21, 25, or 31 to obtain during assembly a chair seat with predetermined specifications to make each chair seat compatible with the base or frame on which it is to be installed. 
     FIG. 5 is a sectional view of FIG. 4 as indicated by the section line 5--5 and shows the typical relationship between a connective end 17 of a member 11, such as that occupying position 14, and a connective member receiving slot, such as slot 27 of connective member 25. Typical of each of the slots 22, 23, 26, and 32 of the connective members, slot 27 has a first wall 50, a second wall 51 parallel to and laterally spaced from the first wall and a connective wall 52 which maintains the walls 50 and 51 in the substantially parallel, laterally spaced relationship shown. Slot 27 has an open side through which a connective end portion 17 of a planar member 11 is received. Affixing means, such as a plurality of mechanical fasteners, such as staple 53, or a suitable adhesive, are preferably used to maintain the connective members in a desired fixed relationship with the connective slot. 
     FIG. 6 is a side elevation view of the desired configuration of a typical chair seat structure 10 of this invention in which each of the three planar members 11 is dimensioned correctly and consequently each planar member 11 fully engages a connective slot 22, 23, 26, 27, and 32. 
     FIG. 7 shows the chair seat 10 of FIG. 6 placed on a representative forming fixture 56. Forming fixture 56 provides locating surfaces 57, 58, 59, and 60 for locating planar members 11 and surfaces 61, 62, 63, 64, 65, 66, and 67 for locating connective members 21, 25, and 31 in their proper position with respect to each other. 
     Upon placement of chair seat 10 on fixture 56 the components are properly aligned and may be affixed to each other by use of appropriate affixing means, such as gluing or adhering members 11 to connective members 21, 25, and 31 or by mechanical fasteners, such as staples or brads, as shown in FIG. 5 to form a substantially rigid, dimensionally stable chair seat. 
     Forming or assembly fixture 56 has upwardly extending locating surfaces whereby the chair seat assembly of FIG. 6 can be either assembled on the fixture or pre-assembled and moved vertically down into the fixture to accurately locate each of the components with respect to each other. The components are then fixedly engaged to each other by adhesives or mechanical fasteners and the resulting assembly is removed from the fixture by vertical upward movement as a rigidly affixed chair seat structure. Attached to the structure, as shown in FIG. 10, is padding, such as foam rubber pads 110 and 111. 
     FIG. 8 shows in a perspective view a prior art chair base or frame 70 on which the one-piece chair seats shown in FIGS. 1 and 2 were generally installed and FIG. 9 shows a modified prior art chair frame 70&#39; on which the prior art chair seats were frequently installed. The frame 70&#39; of FIG. 9 is the frame on which the modular chair seats of this invention are preferably installed. 
     Chair frame 70 is made from a formed tubular member 71 and a first and second side brace 72 and 73 respectively. Lowermost portions 74 and 75 of member 71 serve to rest on a support surface, such as a floor. Upper connective members 76 and 77 provide supportive attachments for the chair seat and braces 72 and 73 provide upper surfaces 78 and 79, respectively, to supportively engage portion 6 of the prior art seats. These frames combined with the one-piece laminated chair seat tend to make the chair assembly susceptible to teetering when placed on an uneven surface. 
     Frame 70&#39; shown in FIG. 9 has the central or connective portions of lowermost portions 74&#39; and 75&#39; of member 71&#39; removed. This construction forms a strong frame capable of slight flexing or adjustment to conform to surface abnormalties present on a support surface on which the frame is placed. 
     FIG. 10 shows a side elevation view of a chair seat structure 10 of this invention installed on to a support frame 70&#39; to form a chair assembly. 
     As shown, the members 11 are maintained in the connective member receiving slots by a plurality of mechanical fasteners, such as staples 53. 
     As shown, planar member 11 in position 12, serving as the back member, has at its lower portion 80 a plurality of attachment means, such as nut 81 to which a fastener means, such as threaded member 82, is engaged through an opening 83 in portion 77&#39; of frame 70&#39;. 
     Additionally, an attachment means, such as threaded nut and bolt assembly 84, is used to affix portion 28 of connective member 25 to a portion of the upper surface of each side brace as shown at 70&#39; of side brace 73&#39;. 
     At the front of the chair assembly, a lower portion 90 of slot 32 of connective member 31 rests upon and is supported by an upper surface of cross member 76&#39; and a plurality of attachment means, such as nut and bolt assembly 91, in which the nut 92 is accommodated within channel 33, are used to rigidly engage connective member 31 to frame 70&#39;. 
     Channel 33 and flange 37 serve as strength enhancing members and also as stand-offs to maintain connective member 31 properly located with respect to frame 70&#39;. 
     The structure shown in FIG. 10 forms a strong, durable chair seat structure which is susceptible to neither warpage nor teetering. A support member 100 is provided between the members 11 at positions 12 and 13 to increase the central rigidity between these two members. Support member or board 100 is also shown in dashed lines in FIG. 3 to clarify its position. 
     The structure and method disclosed above can also be used to form a wedge-shaped chair seat such as those used at corners in modular furniture systems. In these applications, the three planar members and the three connective members would be of different sizes and widths, respectively, to accomodate the unique geometry required for these special application chair seats, but the basic construction would be the same with respect to the connections and constructions of the planar members and the connective members.