Abstract:
A chair including a novel seat construction which includes in the illustrated embodiment a single sheet of fabric having a front support portion of relatively high resistance to resilient deformation and a rear support portion of relatively low resistance to resilient deformation. The differential deformation of the two regions locates an occupant&#39;s ischial tuberosity behind the forward support portion which thereby resists forward movement of the sitter from the chair to thus retain the sitter back in its correct position.

Description:
TECHNICAL FIELD 
     Chair designs have been continually refined in order to insure that the occupant is seated with the correct posture to minimize and hopefully eliminate back pain. While the perfect chair has yet to be invented substantial strides have been made and continue to be made. 
     BACKGROUND ART 
     Various attempts have been made to design a chair that will insure correct posture and one such chair has been invented by the subject inventor as disclosed in U.S. Pat. No. 4,889,387. The chair in question while very satisfactory is somewhat complex and sufficiently costly that it does not lend itself to being used in a chair that is priced sufficiently low to reach a mass market and thus provide the desired benefit to a very large number of consumers. In essence there has long been a need to provide a relatively low cost chair that will maintain a sitter in the desired correct posture while resisting forward movement of the sitter from the seat. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided a novel chair construction that is capable of having all the desired movements including seat height and tilt adjustment, synchronized back and seat angle adjustment and incorporates a novel seat construction that will provide the desired posture support. The seat is composed of a single sheet of fabric or mesh material having a front portion that is more resistant to deformation than its rear portion. The front portion is composed of high resilient elastic fibers that is tighter in construction than the rear softer portion that comprises less resilient elastic fibers. The sheet of fabric or mesh having the desired dual density resilience is formed of separate sections of fiber that are woven or sealed together to form a single fabric. Prior to installation in the seat frame the fabric is prestretched and while in its stretched condition is inserted into recesses in the seat frame and maintained in the stretched condition by suitable locking inserts. 
     The novel aspects of the applicant&#39;s invention will be apparent from the drawings and attached description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a chair incorporating applicant&#39;s invention; 
     FIG. 2 is a front view of the chair; 
     FIG. 3 is a view showing the fabric construction of the portion circled in FIG. 2; 
     FIG. 4 is a view showing the framing construction of the seat and back portion; 
     FIG. 5 is a view of the undersection of the chair; 
     FIG. 6 is a view taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is a view taken along  7 — 7  of FIG. 5; 
     FIG. 8 is a perspective view of the aluninum extrusion; and 
     FIG. 9 is a perspective view of the longitudinally extending T-shaped member for retaining the fabric in position under tension. 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring first to FIG. 1 there is illustrated a perspective view of a chair  10  incorporating applicant&#39;s invention. The illustrated chair is merely representative of a chair that would employ applicant&#39;s novel seat construction. While various adjustment features will be disclosed and referred to these features are common to chairs of this type and are not essential to applicant&#39;s invention. They are described and illustrated so that one may have a complete understanding of the operation and construction of a chair and the environment in which applicant&#39;s invention is used. 
     Essentially, the chair  10  of FIG. 1 includes a seat assembly  12  which is an inclined or inclinable seat, a back section  14  and a back support  16  for the back section  14 . There is provided an adjustable connection  17  for the back section  14  and support  16  relative to the seat assembly  12 . The seat support structure  18  supports the seat assembly  12 , back section  14  and back support  16  relative to the seat column  21  that is located in a tubular support  22 . The tubular support  22  is affixed to a leg assembly  23  that is supported on wheels  24 . 
     It is to be noted that the seat support structure also includes a tension adjustment  20  for the seat back section  14  and back support  16 , a height adjustment mechanism  25  and a seat tilting mechanism  26 . 
     The back section  14  is made up of a back frame  30 , in which is disposed, a back fabric  28  that is suitably secured in place under tension to support the sitters back. The back section  14  is connected to the back support  16  by connectors  31  as shown in FIG.  5 . 
     Turning now to the applicants novel seat construction reference is specifically made to FIGS. 2 and 3 which illustrates the seat fabric in place and its construction and FIGS. 6 and 7 which show the details of how the seat fabric  32  is secured in place relative to the seat frame  42 . The seat fabric  32  is a single unitary sheet made of two sections of woven material secured together by weaving, heat sealing or other suitable methods. The seat fabric  32  consists of a front seat fabric section  34  and a rear seat fabric section  36  that is normally about 15% to 20% softer than the front seat fabric section. The difference in the weaving construction of the seat fabric can be seen in FIG. 3 in which the front seat fabric section  34  contains more resilient mesh than that rear seat fabric section  36  that consists of less resilient mesh. The resiliency can be changed by changing the diameter of the elastomeric fibers or by changing the number of fibers or by any other method that will effect resilience. 
     In a preferred embodiment the seat fabric is made of polyester elastomeric fibers in which the front section  34  is made of a dual tension high resilient mesh and the rear section  36  is made of a less resilient mesh. The front section is made more elastic and has less tendency to stretch and thus is more resistant. It is essential to note that the formed single piece of material  32  is fixed in place in the front seat frame  42  after being prestretched from its normally unstretched condition. This method of assembly will be described in more detail in connection with FIGS. 6 and 7. 
     Turning again to the seat construction it is seen from FIG. 4 that the frame  42  is an aluminum extrusion that is generally U-shaped to which the fabric is tightly secured and this U-shaped extrusion is enclosed by an end piece  43 . To provide additional support for the seat frame  42  are support bars  44 ,  46 . 
     In FIG. 4 there is also illustrated the synchronized back and seat angle adjustment  48 . During this adjustment the back moves approximately twice that of the seat. 
     FIG. 5 illustrates in some detail the underseat construction of the chair including in addition to the aforementioned seat and back adjustments the support structure  50  for supporting the back assembly relative to the main underseat frame construction. It is also noted that the chair of FIG. 5 includes an adjustable arm support  52 . 
     In FIG. 6 and 7 are illustrated the details of the adjustable arm support  52  and most importantly the assemblage of the seat fabric  32  that is held under tension in the U-shaped front seat frame  42 . As shown in FIG. 7 the overlapped portions of the fabric are secured together by threads  53 . 
     The U-shaped frame section  42  is an aluminum extrusion (see FIG. 8) that is suitably secured to and supported by the seat frame members  44 ,  46 . The extrusion  42  includes a longitudinally extending recess  56  in which the seat fabric is secured after it has been prestretched the desired amount which by way of example only may be 12% more than its unstretched length. The novel machine used for stretching includes a series of clamps that hold the fabric and then stretches the fabric to the desired length so that the excapsulated beading  58  can be fed into the recess  56  before the T-section  60  is positioned above and beside the mesh encapsulated beading. With the bead  58  located in the recess  56  a longitudinally extending T-shaped member  60  (see FIG. 9) is located in the recess  56  to secure the bead  60  and thus the fabric  32  in its extended stressed condition to form applicants novel seat which will support and occupant in the correct posture position while resisting forward movement of the sitter from the seat. This is accomplished by forming the seat fabric with a front portion  34  that is more resistant to deformation than the rear portion  36 , which contains less fibers and is thus less resistant to deformation. 
     It remains to note that the arm rest  54  includes arm support openings  62  which provides for selective positioning of the arms relative to the seat. After the arm is properly positioned a fastener  64  is employed to secure the arm rest in place. 
     It is intended to cover by the appended claims all features, which come within the true spirit and scope of the invention.