Abstract:
A folding chair includes collapsible rungs in a backrest and seat permitting folding in two directions. Stability is further enhanced by the upholstery which further forces the top rung of the chair downward and the center rung rearward, making the chair rigid in the open position. Siderails and back supports slide freely along the chair&#39;s rear legs creating a folding mechanism that folds the seat upwards while also pulling the rear leg upwards in the same direction resulting in greater stability without increasing the height of the folded package.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a folding chair, and more specifically to a portable folding chair designed to fold in two directions for easier transport and compact storage. 
     BACKGROUND INFORMATION 
     Folding chairs can be found in a wide variety of outdoor recreational settings. From beach resorts to suburban backyards, people enjoy the portability and ease of storage of these chairs. 
     Known to the art are chairs that fold in two directions, often referred to as a quad chair, i.e., the seat folds in towards the backrests and the sides fold in towards each other. However, prior art chairs that fold in two directions achieve their compactness by eliminating rungs from the backrest and seat frames, with the primary support for a user being provided by the upholstery. This decreases the level of seat and back support, sacrificing comfort and stability. 
     Also known to the art are folding chairs that employ longer rear legs which extend rearward past the backrest. This design provides greater stability to the unfolded chair. However, prior art folding mechanisms fold the seat upward and push the rear leg downwards in the opposite direction. The result is a taller, less compact package when the chair is folded. 
     Thus there exists a need in the art for a chair that folds in two directions into a compact package that also provides enhanced seat and back support. There is also a need in the art for a chair that provides the stability offered by a rear leg that extends past the back of the chair and that also folds into a shorter package. 
     SUMMARY OF THE INVENTION 
     A folding chair, according to an exemplary embodiment of the present invention, makes use of collapsible rungs in a backrest and seat, permitting the chair to fold compactly in two directions while providing better back and seat support than is found in the prior art. The stability of the present invention is further enhanced by the chair&#39;s upholstery which, when mounted, further forces the top rung of the chair downward and the center rung rearward, making the chair very rigid in the open position, especially when being used. Moreover, the siderails and back supports slide freely along the chair&#39;s rear legs, creating a folding mechanism that folds the seat upward while also pulling the rear leg upward in the same direction. Thus the rear legs extend past the back of the chair for greater stability in the unfolded state without increasing the height of the chair in its folded state, resulting in a very compact package. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a front view of a folding chair in its unfolded state according to an exemplary embodiment of the present invention. 
     FIG. 2 illustrates a side view of a folding chair in its unfolded state according to an exemplary embodiment of the present invention. 
     FIG. 3 illustrates a close up view of a releasably lockable hinge joint according to an exemplary embodiment of the present invention. 
     FIG. 4 illustrates a folding chair with upholstery attached according to an exemplary embodiment of the present invention. 
     FIG. 5 illustrates a folding chair in its folded state according to an exemplary embodiment of the present invention. 
     FIG. 6 illustrates a tendon joint according to an exemplary embodiment of the present invention. 
     FIG. 7 illustrates a lap joint according to an exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Various aspects of the present invention will be described, and for purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Furthermore, well known features have been omitted or simplified in order to prevent obscuring the present invention. 
     According to an exemplary embodiment of the present invention, FIGS. 1 and 2 depict a folding chair  100  in its unfolded state. Top rung  130  and center rung  170  are each made up of, for example, three separate segments  130   a-c  and  170   a-c , respectively, pivotally connected to one another with releasably lockable hinge joints  300 . A releasably lockable hinge joint  300  may be a tendon joint, depicted in FIG. 6, or a lap joint, depicted in FIG. 7, or any standard or suitable joint known to the art that functions as a releasably lockable hinge joint  300 , indicated for example in the dotted box. Referring to FIGS. 6 and  7 , a lap joint differs from a tendon joint in the type of hinge used. The hinge on a lap joint has, for example, two fingers  710   a  and  720   a  that are pivotally interconnected. The hinge on a tendon joint has, for example, four fingers  610   a-b  and  620   a-b  which pivotally interconnect by overlapping each other such that, for example, finger  610   b  fits between fingers  620   a  and  620   b , and finger  620   b  fits between fingers  610   a  and  610   b.    
     Each end of rung segments  130   a-c  and  170   a-c , which may be composed of, for example, injection molded plastic or cast aluminum, are, for example, pivotally connected with releasably lockable hinge joints  300 . End segments  130   a  and  130   c  and  170   a  and  170   c  are also pivotally connected by way of releasably lockable hinge joints  300  to tube caps  120 , which may be composed of, for example, injection molded plastic or cast aluminum. An exemplary releasably lockable hinge joint is depicted in FIG.  3 . Segments  130   a-c  and  170   a-c  are preferably curved as shown in FIG. 1, but may also be straight. 
     FIGS. 3,  6 , and  7  depict respectively closer views of a releasably lockable hinge joint  300 , a tendon joint  600 , and a lap joint  700  according to an exemplary embodiment of the present invention. Segment  310 ,  610 ,  710  which may be a tube cap  120  or another rung segment (e.g.,  130   b-c  or  170   b-c ) , moves with respect to segment  320 ,  620 ,  720  which may also be a tube cap  120  or another rung segment (e.g.,  130   a-b  or  170   a-b ), about an axis of rotation  330 ,  630 ,  730 . Rotation of segment  310 ,  610 ,  710  with respect to segment  320 ,  620 ,  720  is stopped, for example, when segment  310 ,  610 ,  710  comes into contact with position block  340 ,  640 ,  740 , which is, for example, a surface of a slot or notch cut into the ends of segments  310 ,  320 ,  610 ,  620 ,  710 ,  720  at the portion where each of the segments interconnect. For example, the slot or notch is shaped to limit the range of rotation to only one direction and to halt the rotation when a segment  310 ,  320 ,  610 ,  620 ,  710 ,  720  comes into contact with a side of the slotted or notched portion which serves as a position block  340 ,  640 ,  740 . Thus position block  340 ,  640 ,  740  of releasably lockable hinge joint  300 ,  600 ,  700  limits the range of rotation of each of the segments  310 ,  320 ,  610 ,  620 ,  710 ,  720  of top rung  130  or center rung  170  with respect to one another, halting the rotation at a predetermined critical angle. The critical angle is set, for example, as a function of the dimensions of position block  340 ,  640 ,  740 . Different critical angles may be employed to modify the shape of top rung  130  and center rung  170 , for example, to make the rungs  130  and  170  more curved, less curved, or straight, thus varying the overall width of the chair  100 . 
     When chair  100  is in its unfolded state, for example as shown in FIG. 1, an upward force applied to top rung  130 , such as by a person pulling upward on center rung segment  130   b  of the rung  130 , causes the rung segments  130   a-c  of top rung  130  to pivot or rotate with respect to one another. As a result, rung segments  130   a  and  130   c  will depend downwards from center rung segment  130   b . Similarly, a user pulling upward or forward on center rung segment  170   b  would cause rung segments  170   a  and  170   c  to depend downward from rung segment  170   b.    
     By contrast, when a downward force is applied to top rung  130  or a rearward force is applied to rung  170 , the movement of the rung segments  130   a-c  or  170   a-c  is stopped by the action of position blocks  340  of releasably lockable hinge joint  300 . 
     Thus, for example, in the unfolded state, top rung  130  will remain rigid in response to a force applied to the rung in a downward direction, and will bend in response to a force applied in the upward direction. Similarly, center rung  170  will remain rigid in response to a force applied to rung  170  in a rearward direction, but will collapse in response to a force applied in the forward direction. According to an embodiment of the present invention, movement of rungs  130  and  170  in the upward direction to fold the chair cause movement of the seat portion toward the back portion as well as movement of the arm portions of the chair towards each other. 
     A backrest according to an exemplary embodiment of the present invention is made up of, for example, two back supports  140 , which may be composed of, for example, aluminum tubing. The top ends of back supports  140  are, for example, rigidly connected to a tube cap  120  which is in turn pivotally connected to the ends of a top rung  130  by way of a releasably lockable hinge joint  300 . A seat frame is made up of, for example, two side rails  230 , which may be composed of, for example, aluminum tubing. The forward ends of side rails  230  are rigidly connected to tube caps  120  which are in turn pivotally connected to the ends of a center rung  170  (e.g.  170   a ,  170   c ) by way of a releasably lockable hinge joint  300 . 
     Referring to FIGS. 1 and 2, bottom ends of back supports  140  and rear ends of side rails  230  are, for example, each pivotally connected to a slide pivot  190 . A slide pivot  190 , which may be composed of, for example, injection molded plastic or cast aluminum, is disposed around each rear leg  220  such that rear legs  220  pass through slide pivots  190 . Similarly, a pivot  180 , which may be composed of, for example, injection molded plastic or cast aluminum, disposed around each rear leg  220 , such that rear legs  220  also may pass through pivots  180 . 
     As can be seen from FIG. 1, each pivot  180  is, for example, pivotally connected to one end of a crossrail  110 , which may be composed of, for example, aluminum tubing, and slides freely along a respective upper portion of rear leg  220 . Pivotally connected to the other end of each crossrail  110  is the bottom portion of a slide pivot  190 . Slide pivot  190  slides freely along the lower portion of rear legs  220 . Crossrails  110  also may be pivotally connected to one another at their approximate centers. Thus, pivots  180 , slide pivots  190  and crossrails  110  form a scissors-like structure that opens and closes by sliding along the rear legs  220  of chair  100 . It will be apparent to one skilled in the art, that this scissors-like structure, which slides along rear legs  220 , provides support by which chair  100  maintains its unfolded state, and provides the mechanism by which the sides of chair  100  fold inwards. 
     Front legs  210  and rear legs  220  may be composed of, for example, aluminum tubing. The top ends of rear legs  220  and the top ends of front legs  210  are, for example, pivotally connected to a forward portion of arm rests  150  such that each front leg  210  shares a common vertex and a common pivoting connector with a rear leg  220 . The rear portion of arm rests  150  are pivotally connected, for example, to the center portion of back supports  140 . Front legs  210  are pivotally connected, for example, to side rails  230  at the approximate front portion of side rails  230 . 
     Referring to FIG. 4, according to an exemplary embodiment of the present invention, upholstery  410 , which may be composed of, for example, nylon or polyester, is fastened to top rung  130 , for example, at  415  and  420 , and is also fastened to center rung  170  at  425  and  430 . FIG. 4 also depicts use of gripping elements  131 ,  171  for gripping the center rungs  130   b ,  170   b . Upholstery  410  is further connected to back supports  140 , for example using loops at  435 ,  440 ,  445 , and  450 , and to side rails  230  using loops at  455  and  460 . Other conventional fastening means to connect the upholstery to the frame may be used. The weight of a person sitting in chair  100  further applies a downward tension to upper rung  130  at loops  415  and  420 , while simultaneously applying a rearward tension to center rung  170  at loops  425  and  430 . These tension forces add to the stability of chair  100 , making the chair  100  very rigid in the operi position when being used. 
     As illustrated in FIG. 5, according to an exemplary embodiment of the present invention, folding chair  100  folds in one direction by lifting center rung  170  up towards top rung  130  until side rails  230  are substantially parallel and closely spaced to back supports  140 . This folding action raises arm rests  150  to a position substantially parallel to and closely spaced to side rails  230  and back supports  140 , while pulling rear legs  220  upward through slide pivots  190 . As rear legs  220  slide upward through slide pivots  190  and pivots  180 , front legs  210  pivot towards rear legs  220  such that legs  210  and  220  are substantially parallel and closely spaced to one another. FIG. 5 illustrates a folding chair in the folded state. 
     Lifting center rung  170  up towards top rung  130  simultaneously releases any tension applied by the upholstery to upper rung  130  and center rung  170 . This allows rungs  130  and  170  to fold, the right and left segments (e.g.  170   a ,  170   c ,  130   a , and  130   c ) of the rungs bending towards each other until the segments are substantially parallel to one another and substantially perpendicular to the center segments. 
     As rungs  130  and  170  fold, rear legs  220  move inwards towards each other, causing the top end of each crossrail  110  to slide upward along rear leg  220  via pivot  180 , and the bottom end of each crossrail  110  to slide downwards along rear legs  220  via the attachment to slide pivot  190 . Since crossrails  110  also may be pivotally connected at their approximate center, crossrails  110  pivot with respect to one another until each crossrail  110  is substantially parallel to the other, and substantially vertical with respect to the ground. 
     Referring to FIG. 5, the sides of chair  100  fold in towards each other, creating a very compact folded state, in which side rails  230 , back supports  140 , rear legs  220 , front legs  210 , crossrails  110 , and armrests  160  are all substantially parallel and closely spaced to one another. FIG. 5 depicts the folded state of chair  100 . 
     It has been shown that folding chair  100 , by making use of collapsible rungs  130  and  170 , folds compactly in two directions while providing better back and seat support than is found in the prior art. The stability of chair  100  is enhanced by upholstery  410 , which forces top rung  130  downward and center rung  170  rearward, making chair  100  very rigid in the open position, especially when being used. Moreover, by allowing the seat frame and backrest frame to slide along the rear leg via slide pivot  190  and pivot  180 , the rear leg can be extended past the back for greater stability without sacrificing compactness.