Abstract:
A folding sling chair is provided in which members of the chair frame incorporate internally mounted hinges, preferably invisible hinges. When an invisible hinge is in a neutral or stop position, only a seam or dividing line is visible; the internally mounted hinge structure is invisible. In operation, the hinge structure of the invisible hinge is less likely to interfere with a pliable fabric sling than in conventional designs. For example, the side rails of a seat of a folding sling chair may fold at invisible hinges mounted internally within the side rails, which can be angled to create an adjustable backrest. Various other applications of the present invention include angled and adjustable foot rests, head rests, chaise lounge arrangements, folding task chairs, etc.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to sling chairs, and more particularly to folding sling chairs. 
   2. Background 
   Informal, occasional use furniture has become quite popular. Manufacturers are increasingly called upon to offer comfortable, practical, and stylish products. Frequently, consumers desire this furniture to be capable of being stored during inclement weather or when out of season. Accordingly, there is a significant and growing market for occasional use furniture having hinges or pivots so that it can be folded and stored. 
   A hinge or pivot is a device that connects two members and permits some sort of rotation or pivot between the members. Hinges have long been useful in the construction of a wide variety of furniture, most commonly for mounting access covers such as desk tops or cabinet doors, or for foldable extensions, such as the leaves of tables. Hinges or pivots have also been used in chairs where a portion of the chair structure may fold or rotate. Folding chairs are useful in that when they are no longer needed, the chair may be folded into a smaller volume and stored. 
   A sling chair is a type of chair in which all or a portion of the chair&#39;s seat or backrest, known in the field as the “sling,” is sustained in suspension. A subset of sling chairs include folding chairs that have slings made of a pliable material such as a woven fabric or mesh of natural or manmade material forming the back and/or seat that is suspended by a portion of the chair frame. Because of the use of a suspended sling, folding sling chairs may be light weight and easy to store. Further, sling chairs do not require cushions as the sling is generally sufficiently pliable for sitting comfort. Thus, the fabric sling provides comfortable surfaces that are easily cleaned and cool in hotter weather. 
   The sling panel or panels fastened to the chair frame in order to suspend it in place and bear the weight of the sitting individual. One typical way of fastening is a stitched or woven loop forming a sleeve or channel along opposing edges of the sling into which frame members may be inserted so that the sling may be suspended. Alternatively, dowels may be inserted into the sleeve after the sleeve has been inserted into a slotted keyway within a seat member. The dowel typically has a diameter greater than keyway width, thereby restraining the sling. In either case, the sling may be suspended or supported by the frame to serve as a seat, backrest, or both, and may be under tension, depending on the application. 
   For a folding sling chair, the design of the seat and back must accommodate or be adaptable to the change in chair frame geometry when the chair is folded. If not, the sling may interfere with the folding process, be creased or otherwise damaged when folded. In some conventional examples, the sling may have to be removed from the frame for folding, adding complexity and the requirement to store the sling separately from the frame. A folding backrest is a common example where this issue can arise. 
   Accordingly, folding sling chairs have fallen into several rough categories. One category of conventional folding sling chairs involves a side X-frame that scissors longitudinally about a transverse axis, an example of which may be seen in  FIG. 2 . When folded or pivoted about hinge  38 , the frame members  32  operate as a scissor, such that upper portions of frame members  32  (acting as backrest and seat support) are brought together on top, while lower portions of frame members  32  (acting as the legs) are brought together below. When unfolded, the lower portions of frame members  32  spread out for stability. Cross members  34  often do not fold in this design, and this design typically lacks side rails about the seat or back. Therefore, this design of folding sling chairs suspends the sling panel from a lower front cross member and an elevated rear cross member. When this sling chair  30  is unfolded and set up, the sling  36  hangs in a dipping effect between the cross members  34 , thereby forming a catenary that permits casual seating. The elevated rear cross member creates a form of backrest. This type of folding sling chair is often used on beaches or around pools. Although this simple design uses a single piece of fabric that need not be removed for folding, it has several drawbacks. The dipping design of sling  36  is necessary for stability during seating, but it elevates the front and can pressure the popliteal area of the leg. In addition, scissor chair  30  can be uncomfortable because the weight of the individual is focused largely on the seat area. As a design limitation, the cross members  34  must be sufficiently strong to carry the entire weight of the individual. Some efforts to address these problems have involved adding members to frame members  32  or extending frame members  32  to accomplish new support functions. Other efforts add fabric pieces to provide support to sling  36  to distribute the weight, with a significant loss of simplicity in frame design and sometimes loss of the simplicity of a single piece design for sling  36 . 
   A second category of conventional folding sling chairs has a sling seat and backrest where portions of the sling that might interfere with operation of the hinge are omitted. An example of this type is chair  40  shown as a lawn chair in  FIG. 3A . This approach enables a variety of frame designs, but increases the complexity of the sling or fabric panel design. A difference of this approach over sling chair  30  is that sling  46  may be suspended by frame members  42  in addition to cross members  44 . Without the need for a catenary, sling  46  may be drawn more tightly across the frame for a more even distribution of weight. In many cases, as shown, sling  46  includes cutouts  47  in the vicinity of hinges  48  to avoid fabric wear on the sling or entanglement with hinges  48 . In addition, exposed hinges  48  produce a cluttered, utilitarian element that detracts from the architectural appearance of the chair. In other cases, as shown in  FIG. 3B , chair  40  may use multiple pieces of fabric (e.g., sling  46  split into sling fabric panels  461  and  462 ). Dividing sling  46  into multiple pieces means that gap  43  may be provided at the pivoting axis for hinge  48 , so that sling  46  does not interfere with hinge  48  or the folding action. In general, the greater the number of hinges  48  (i.e., pivoting or folding portions), the greater the number of pieces of sling  46 . For both of these designs, the structure of hinge  48  can complicate or block the mounting of the sling  46 . In addition, a primary drawback of these designs is the greater complexity and inconvenience of multiple fabric pieces (e.g., sling fabric panels  461  and  462  in  FIG. 3B ), cutouts (e.g., cutout  47  in  FIG. 3A ), or open fabric gaps (e.g., gap  43  in  FIG. 3B ) located near hinges or pivot lines. This complexity can pose problems for assembly, convenience of use, or inter-operability of the fabric pieces. 
   The exposed hinge structure can have other drawbacks. Depending on the design, an individual or their garments may be pinched by a hinge when it is pivoted. This problem can also arise in the case of folding a sling chair with X-shaped scissor hinges. With a scissor hinge, the longitudinal frame members do not lie in the same plane. As the adjacent but pivoting members scissor, they can easily trap and pull loose garments or cloth into the space between the members. Aside from problems during operation, an exposed hinge butt can also scratch individuals or protrude into the sitting space. Further, the use of exposed hinges in higher end products can be unsightly and impair the integrity of an aesthetic design. 
   Accordingly, there is a need for folding sling chairs that offer simplicity and safety in fabric sling and hinge design in order to reduce fabric wear of the sling, user discomfort, risk of pinching injury, and the expense of construction. The simple scissor arrangement does not provide effective side support nor fully addresses the problem of hinge interference. More complicated approaches solve some problems, but introduce difficulties in manufacture and expense. Therefore, the conventional categories of design do not offer a folding sling chair having single piece of fully supported sling that is free from the problems of exposed hinges. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is a folding sling chair frame in which the disadvantages of conventional designs are minimized by use of hinges mounted internally within chair frame members. This novel approach avoids the complications that are presented by the hinge structure of prior folding chairs. In particular, the present invention is capable of having a pliable sling that is a single piece of fabric mounted onto side rails without special adaptation or cutout of the fabric. Further, the internal mounting of the hinge produces a more uniform surface for the frame of the chair. 
   Briefly, the present invention overcomes the limitations of past approaches to folding chairs, and folding sling chairs in particular, by using hinges that do not alter the exterior structural profile of the chair frame. The present invention is a folding sling chair in which the chair frame incorporates internally mounted hinges, preferably “invisible” hinges. For example, a form of invisible hinge is disclosed in U.S. Pat. No. 1,687,271 to J. Soss, which is incorporated by reference. Invisible hinges have been internally mounted in doors and access covers for desks or cabinets. However, they have not been used in foldable sling chairs as claimed in the present invention. When such an invisible hinge is in a neutral or stop position, only a seam or dividing line is visible; the internally mounted hinge structure is invisible. 
   The particular configuration of a sling chair can vary, depending on the overall design and application of the embodiment. For example, the side rails of a folding chair may fold at invisible hinges mounted internally within the side rails, which can create an adjustable backrest. In one embodiment, the side rails of a chair may be fashioned to support a fabric panel sling or seating member as described in U.S. Pat. Nos. 6,293,624 and 6,585,323 to Gaylord et al., which are hereby incorporated by reference. In such an embodiment, the side rails may include a keyhole slot extending along the side rail, as disclosed in the referenced patents, except where the invisible hinge is mounted. The fabric panel sling or seating member may be retained within the slots using fabric loops and dowels or rods for inserting into the loops for each side rail. Cross members span and space apart the side rails to suspend the sling and draw it tight. Variations in this structural design could provide an angled and adjustable back or footrest, head rest, chaise lounge arrangements, folding task chairs, etc., as will be apparent for those skilled in the art. Further, other attachment technologies and frame configurations known in the field will also work. 
   In another embodiment, the side rails may be tubular and the seating member may be a sling or fabric panel having sleeves that are adapted to receive portions of the side rails or parallel members. Because the invisible hinge presents no surface structure, such a sleeve may be readily drawn over large lengths of the tubular side rails, enabling the sling to be fashioned of a single piece. Similarly, embodiments having fasteners along the side rail margins of the sling may be used where the sling is folded over the side rails, including the area where the invisible hinge is mounted, and then fastened, optionally to a mating fastener on the sling. Such fasteners may be hook and loop, buttons, zippers, etc. In such embodiments, the sling need not be so tightly fitting onto the rails as to contract into the gap presented by the butting portions of the side rails when the hinge is opened. However, as the obverse side retracts when an invisible hinge pivot is closed, then the stress on the reverse side will be lessened. Even if there were any bunching or pinching of sling fabric, it would occur on the reverse side. 
   In some cases, an invisible hinge may be used to provide other folding features to the structure of chairs. For example, an invisible hinge may be used to pivotally mount a moveable arm rest. Such a folding arm rest member may be hinged near the back of the chair for improved clearance when the arm rest is folded out of the way. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an example of an embodiment of the invention; 
       FIG. 2  is a scissor frame sling chair of the prior art; 
       FIG. 3A  is an example of a sling chair of the prior art having cutouts in the sling fabric near hinges; 
       FIG. 3B  is an example of a sling chair of the prior art having a sling with multiple fabric pieces; 
       FIG. 4A  shows an invisible hinge in the closed position; 
       FIG. 4B  shows an invisible hinge opened to a 90 degree angle, as seen from the reverse side; 
       FIG. 4C  shows an invisible hinge opened to a 180 degree angle; 
       FIG. 5  shows the components for installation of an invisible hinge; 
       FIG. 6  shows a folding sling chair of the present invention with an adjustable back folded at an acute angle; and 
       FIG. 7  shows a folding sling chair of the present invention with an adjustable back completely folded at a 180 degree angle. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating general principles of embodiments of the invention. 
   As introduced above, the present invention is a folding sling chair in which the chair frame members incorporate internally mounted hinges, preferably invisible hinges. Invisible hinges may be mounted within the cross section of tubular members to add features over conventional folding sling chair frames. 
   With reference to the drawings, an example of the present invention is shown in  FIG. 1 . Folding sling chair  20  in this example is a simple chaise lounge embodiment. Two left side rails  21  and  23  are tubular members supporting the left side of sling  25 , such as a pliable fabric panel. The mounting of sling  25  for this embodiment is somewhat similar to that disclosed in &#39;624 and &#39;323 to Gaylord et al. However, a wide variety of mounting arrangements will work with the present invention, as will be apparent to those of ordinary skill in the art. Notably, left invisible hinge  26 L is closed and therefore is visible only as a seam between the two left side rails  21  and  23 . However, it may be appreciated from this perspective that rear left side rail  23  may pivot with respect to front left side rail  21 . Similarly, two right side rails  22  and  24  support the right side of sling  25 , and rear right side rail  24  may pivot with respect to front right side rail  22 . Together, side rails  21 – 24 , when assembled with transverse members  29 , form a supporting seating zone for an individual to sit or recline. In this way, the fabric of sling back area  25 B (i.e., a seat back) may pivot with respect to fabric of sling front area  25 F (i.e., a seat.) Support may be provided from approximately 360 degrees around the seating zone, or from merely a desired portion thereof. 
   Base assembly  28  supports folding sling chair  20  and, for this embodiment, comprises four curvilinear tubes that depend downwardly at the ends. As shown, base assembly  28  directly supports a fixed portion of sling  25  through fixed (i.e., front) side rails  21  and  22  and indirectly supports a pivoting portion of sling  25  through invisible hinges  26 L and  26 R. Transverse members  29  are disposed between, attach to, and structurally maintain left side rails  21  and  23  in a fixed and opposing orientation from right side rails  22  and  24 . Of course, transverse members  29  may be configured as disclosed in &#39;624 and &#39;323 to Gaylord et al., or alternatively as a simple tubular piece in which the hollow of the piece mounts onto or receives a protruding lug, fastener, etc. (not shown), as known in the art. As noted above, transverse members  29  may support sling  25  or simply fill a structural function in maintaining side rails  21 – 24  in opposing disposition. In some embodiments, the structural function of one of transverse members  29  may be integrated into a portion of base assembly  28 ; those skilled in the art will see that base assembly  28  may be designed to integrate transverse structure that separates and maintains side rails  21  and  22  in a fixed and opposing orientation. In that case, only one discrete transverse member  29  in the form shown in  FIG. 1  would be present, located on the pivoting portion of sling  25 , or fabric of sling back area  25 B. Accordingly, transverse member  29  should expressly be construed to encompass such hybrid function for base assembly  28  in those cases where base assembly  28  provides transverse, separating structure maintaining side rails  21  and  22  in a fixed and opposing orientation. In addition to the example of curvilinear tubes shown in  FIG. 1 , those in the field will recognize that a wide variety of other designs (not shown) for base assembly  28  are available, including by way of example four or more simple and discrete legs depending from non-pivoting front side rails  21  and  22 , a single pedestal, telescoping members, skid like members, one or more wheeled supports, etc. In addition, a variety of backrest support  281  (not shown) known in the art may be used to support the fabric backrest portion of sling  25 B as it is pivoted or adjusted about invisible hinges  26 . 
   For purpose of contrast,  FIGS. 2 ,  3 A, and  3 B, which were discussed above, show examples of conventional folding sling chairs. 
     FIGS. 4A through 4C  show from the reverse, or rear perspective, the operation of invisible hinge  26  at different angles of pivot.  FIG. 4A  depicts a closed or 0-degree angle of pivot, and only a seam of invisible hinge  26  is visible, none of hinge structure  27  is visible.  FIG. 4B  depicts a 90-degree angle of pivot, where a portion of hinge structure  27  is visible.  FIG. 4C  depicts the full or 180-degree angle of pivot, so that hinge structure  27  is fully extended and most is visible.  FIG. 5  shows an embodiment of the components of hinge structure  27 , where fasteners  271  attach hinge mechanism  272  to connecting tube  273 , which is then mated into a cross section of side rails  21 – 24 , connecting and interposed between the respective rails, or other frame member depending on the desired folding portion. 
   For the present invention, frame members are preferably tubular, such as side rails  21 – 24 , at the point of invisible hinge  26  so that invisible hinge  26  may mate with or be recessed into the tubular structure. Of course, apart from portions of the frame members at the point of invisible hinge  26 , the frame members may be of a wide variety of cross sections or shapes, or even solid, as is known in the art. That is, the frame member cross section need not be solely circular, elliptical, or consistently tubular. The cross section profile may vary over the length of the frame member or side rails  21 – 24 . Preferably, however, the cross section of the frame member will provide sufficient area at the vicinity of invisible hinge  26  to enable internal mounting, as with a tube. Thus, tubular for the members of the present invention means having sufficient internal volume to permit the internal mounting of invisible hinge  26 . Preferably, but not necessarily, the frame members may be somewhat hollow for lighter weight. 
   Pivoting two frame members about an invisible hinge  26  initially opens the hinge to the reverse side. In some cases, the frame and hinge may be oriented so that one frame member may be rotated or folded fully onto the other member, at which point the hinge structure is exposed or visible to the obverse side. An invisible hinge  26  is clearly advantageous from an aesthetic perspective. The tubular frame exterior may take a wide variety of design forms in which the hinge structure is not an issue; the hinge is only visible when the frame member is folded into a storage position. In addition, the design of invisible hinge  26  provides a track or groove in blank  274  of the hinge that defines the relative motion of the frame members during pivoting. Unlike conventional hinges, this track may be adapted to the shape of the frame members, and to minimize situations in which a fabric piece or occupant might be pinched. Those skilled in the art will readily see how invisible hinge  26  may be adapted for use with other tubular frame members, such as an arm rest member (not shown) hinged for folding out of the way. 
     FIG. 6  depicts folding sling chair  20  where invisible hinges  26  have been pivoted to an acute degree angle.  FIG. 7  shows folding sling chair  20  where invisible hinges  26  have been pivoted fully forward, revealing backrest support  281 . 
   As noted above, those skilled in the art will recognize that such a folding sling chair may take a variety of configurations, depending on the application. While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.