CROSS REFERENCE TO A PROVISIONAL APPLICATION 
     This patent application claims priority on Provisional Application Ser. No. 60/362,026, filed on Mar. 5, 2002, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to sewn articles and sewing operations and, more particularly, to sewn attachment of different pieces of material by gussets. 
     In the sewn construction of padded articles, such as mattresses and furniture cushions, a padded layer or layers may be enclosed in upholstery and attached by a gusset to an accompanying pad or spring unit. For example, in a pillow-top style mattress, a pillow-top is attached to a panel by a gusset, which in one form is a folded band of material sewn along a fold line to the panel, and then sewn to a flange (which is subsequently stapled to the mattress) along the first edge opposite the fold and sewn to the pillow-top along the second edge opposite the fold, thereby attaching the pad to the mattress. At corners of the panel to which the gusset is sewn, the gusset is mitered at a seam to allow the gusset to turn the ninety degree corner of the mattress. The mitering of the gusset at the corners requires at least one miter cut to be made in the gusset at each right angle corner of the adjoining panel. Each of the mitered corner cuts must be precisely measured and individually sewn so that the gusset forms a closed structure between the mattress and the pillow-top. In a manual assembly process, the gusset is separately constructed by sewing together each leg of the gusset at the mitered corners to form a gusset frame which matches the mattress panel. The gusset is then sewn to the edges of the panel of the mattress by a tape edge. Thereafter, the pillow-top is attached to the other free edge of the gusset by a second tape edge. If the miter cuts at the corners of the gusset are not made at the correct angles, the gusset corner will not have a smooth contour or appearance. Also, in articles where the gusset remains visible, the multiple seams in the gusset are unsightly and vulnerable to separation. Constructing a gusset this way is a tedious manual production process which adds significantly to the cost of producing pillow-top mattresses and similar sewn articles. 
     Therefore, there is a need for a mattress having a continuously cornered gussets. There is also a need for a system for producing mattresses having continuously cornered gussets. There is also a need for a system that combines the process for sewing the flange and the gusset to the panel, or for a system the eliminates the need for a flange. 
     SUMMARY OF THE INVENTION 
     The disadvantages of the prior art are overcome by the present invention which, in one aspect, is an apparatus for attaching a gusset to a panel that includes a gusset folder that receives and folds a gusset material to form the gusset for attachment to the panel. The panel is received on and supported for sewing by a sewing table. A sewing machine is positioned relative to the sewing table so as to be able to sew the gusset to the panel. A gusset guide guides the gusset fed to the sewing machine toward a selected edge of the panel so that the gusset is held in substantial alignment with the edge of the panel. An edge detector detects when a next edge of the panel is approaching the sewing machine. A turning mechanism is positioned along the sewing table and is moveable into engagement with the panel. The turning mechanism turns the panel relative to the sewing machine when the edge detector detects the next edge of the panel is approaching the sewing machine. 
     In another aspect, the invention is a method of sewing a gusset to a panel, in which the gusset is sewn to the panel along a first substantially linear path with a sewing machine. A corner of the panel is detected. The panel is turned when the corner of the panel approaches the sewing machine so that the gusset follows a curved path adjacent the corner of the panel. The gusset is sewn to the panel along a second substantially linear path, angularly divergent from the from the first substantially linear path, after the gusset has been sewn around the corner of the panel. 
     In another aspect, the invention is an apparatus for sewing a gusset and a flange to a panel. The apparatus includes a first reel holding a gusset material and a second reel holding a flange material. A folding device folds the gusset material from the first reel along a substantially linear path. A first sewing machine receives the gusset material from the folding device and the flange material from the second reel and sews the gusset material to the flange material, thereby forming a gusset-flange. A second sewing machine receives the gusset-flange from the first sewing machine and sews the gusset-flange to the panel. 
     In another aspect, the invention is a gusset for attachment to a panel that has at least one first corner. The gusset includes a strip of gusset material having a first edge and a second edge. The strip of gusset material is folded substantially along a centerline and the first edge of the gusset material is sewn to the first panel. The gusset defines at least one pleat that causes the gusset material to change direction. The pleat is placed adjacent to the first corner. 
     In another aspect, the invention is a mattress having a first panel over one side of a mattress inner-spring. The mattress includes a gusset attached substantially about a perimeter of the first panel. The gusset is made of an elongated piece of material folded along a length dimension. The gusset is attached to the first panel proximate to a fold in the gusset material. A first edge of the gusset opposite the fold is attached to a perimeter of the first panel. A second edge of the gusset is adapted for attachment to a second panel. The gusset includes at least one corner that has at least one pleat forming a ruffled gusset corner. 
     In another aspect, the invention is an outer layer for attaching a pillow-top to a mattress that includes a panel having at least one outer end. A gusset includes a strip of gusset material that has a first edge and an opposite second edge and that has been folded substantially in half along a fold line so the first edge is substantially adjacent the second edge. The gusset is sewn to panel along a line adjacent the fold line and near the outer end of the panel so that the outer end extends beyond the first edge and so that the second edge has sufficient distance to provide an attachment surface on the panel to enable attaching the outer layer to the mattress. 
     These and other aspects of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the following drawings. As would be obvious to one skilled in the art, many variations and modifications of the invention may be effected without departing from the spirit and scope of the novel concepts of the disclosure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a mattress constructed according to an illustrative embodiment of the invention. 
     FIG. 2 is a top plan view of a portion of a ruffled gusset according to an illustrative embodiment of the invention. 
     FIG. 3 is a top plan view of a gusset manufacturing machine according to an illustrative embodiment of the invention. 
     FIG. 4 is an elevational view of the gusset manufacturing machine shown in FIG. 3, as viewed from lines  4 — 4 . 
     FIG. 5A is a top plan view of a portion of the gusset manufacturing machine shown in FIG. 4, as viewed from line  5 — 5 , while in the process of sewing a gusset to a strait edge of a panel. 
     FIG. 5B is a top plan view of a portion of a gusset manufacturing machine shown in FIG. 4, as viewed from line  5 — 5 , while in the process of sewing a gusset to a corner of a panel. 
     FIG. 6 is a top perspective view of a sewing table employing several aspects of the invention. 
     FIG. 7 is an exploded top perspective view of an air table employed in one embodiment of the invention. 
     FIG. 8 is a top perspective view of a mechanism for rotating a panel about a corner, according to one aspect of the invention. 
     FIG. 9 is a top perspective view of a ruffler, according to one aspect of the invention. 
     FIG. 10 is a side cross-sectional view of an air table employing directional air jets, according to one aspect of the invention. 
     FIG. 11 is a side elevational view of an apparatus for sewing both a gusset and a flange to a panel, according to one aspect of the invention. 
     FIG. 12 is a top plan view of a panel with a recessed gusset, according to one aspect of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” 
     As shown in FIG. 1, a pillow-top mattress  100 , according to one illustrative embodiment of the invention, includes a main mattress body  102  and a pillow-top portion  108  attached to the mattress body  102  with a gusset  110 . The gusset  110  is folded in half along a centerline  116  and sewn to a panel  106  along a stitch line  120  so as to have a first edge  112  and a second edge  114 . A strip of flange material  122  is sewn to the periphery of the panel  106 , along stitch line  120 . The flange is also attached to the first edge  112  by stitches  127 . The flange material  122  extends from the outermost edge of the panel  106  and is stapled to a spring unit  125  of the mattress body  102 . A strip of fabric tape  126  is sewn to the first edge  112 , along stitch line  128 , and the side wall  124  along stitch line  128 , thereby securing the gusset  110  to the mattress body  102 . 
     The second edge of the gusset is aligned with the outermost edge of the pillow-top  108  and a strip of fabric tape  132  is sewn around the junction of the gusset  110  and the pillow-top  108  along a stitch line  134 , thereby securing the panel  106  (and thus the mattress body  102 ) to the pillow-top. 
     As shown in FIG. 2, as the gusset  110  is being sewn to the panel  106 , when a corner  204  of the panel  106  nears the point of sewing, a plurality of ruffles  216  are stitched into the gusset  110  so that the gusset  110  is a continuous piece of gusset material. This eliminates the need for mitering the gusset material. 
     A gusset sewing system  300  is shown in FIG.  3 . The sewing system  300  includes an air table  310 , a sewing machine  320 , a supply reel  312  for the gusset material  314 , a folding device  316 , a ruffler  318  (also referred to as a pleat generator) and a turning device  330  for turning the panel  106  as the corner  214  approaches the sewing machine  320 . The air table  310  includes a plurality of openings  340  through which air is forced to provide an air cushion between the table  310  and the panel  106 , thereby facilitating movement of the panel  106 . 
     As shown in FIG. 4, the turning device  330  includes a frame  422  that supports a first pneumatic actuator  424  and a second pneumatic actuator  428 . The frame  422  is affixed to a support  434  that is coupled to the table  310 . A cornering actuator  432  is coupled to the frame  422  so as to be able to rotate the frame  422  between a first position and a second position. The first pneumatic actuator  424  is capable of raising and lowering a first arm  426  and the second pneumatic actuator  428  is capable of raising and lowering a second arm  430 . The first arm  428  and the second arm  430  work in concert to engage and turn the panel  106  at the corners of the panel. 
     A conveyor  412  moves the panel  106  along a linear path when the corners are not being sewn. A guide wheel  450  keeps the panel  106  running along a substantially straight line during sewing. The guide wheel  450  is controlled by an optical sensor (not shown) that directs the edge of the panel  106  to a predetermined point when the edge of the panel  106  deviates from the predetermined point. 
     The sewing machine  320  includes a needle  442  and a sewing foot  444  for holding the gusset material  314  against the panel  106 . The ruffler  318  includes a plunger assembly  446  and a ruffler foot  440 . The plunger assembly  446  is capable of driving the ruffler foot  440  back and forth to push ruffles (also referred to as pleats) into the gusset material  314 . The plunger assembly  446 , in one embodiment, includes a pneumatic piston that is controlled so as to push the gusset material  314  into a ruffle when the needle  442  is in an “up” position and to retract the ruffler foot  440  when the needle is in a down position. 
     The turning device  330 , as shown in FIGS. 5A and 5B, can include a transverse arm  434  extending from second arm  430 . The transverse arm  430  helps to prevent the panel  106  from becoming bunched-up during a turn. Straight sewing is shown in FIG. 5A, whereas the turning operation is shown if FIG.  5 B. Essentially, the turning device  330  causes the arms  426 ,  430  and  434  to engage the panel  106  and the frame  422  is rotated in the direction of arrow A as the corner ruffling is sewn into the panel  106 . 
     As shown in FIG. 6, the gusset sewing system can include a gusset-cutting knife  610  that can extend outwardly from the sewing machine  320  at the termination of the gusset sewing process. The knife  610  can include a pneumatically-driven blade that cuts the gusset material. To allow an operator to gain access to the sewing machine  320  while the knife  610  is in the retracted position, a trap door  612  is included in the table  310 . The trap door  612  may be driven by a pneumatic piston and controlled so that the trap door  612  is in the “up” position during the automatic part of the sewing process and when the knife  610  is in the extended cutting position. The trap door  612  is driven to the down position when the operator is needed to control the sewing machine  320  at the termination of the sewing process, after the gusset has been cut by the knife  610 . 
     A plurality of controllable directional air jets  630  are included in the air table  310  to provide directional jets of air when the panel is being moved so as to prevent bunching up of the panel. The directional jets of air are aimed toward the direction of intended movement, which can include along the normal linear path taken by the panel and along the turning direction of the panel while the corners are being ruffled. Air flow to the directional air jets  630  can be controlled to provide more or less force on the panel, depending on the needs of the panel. For example, heavier panel materials would require more force, as would more porous panel materials. Also, as a panel becomes heavier as a result of gusset material being sewn thereto, the airflow may be increased. Air flow control may be accomplished either by controlling the speed of the blowers that provide the air supply for the air table and the directional air jets or by opening or shutting louvers at the intake to the blowers. 
     An accumulator  620  may be included to ensure that sufficient gusset material is available to complete an entire panel. At the start of the sewing process, a clamp  626  holds the gusset material in a fixed position as the accumulator  620  pays out from the reel  312  onto a plurality of rollers  622  (two rows of which expand away from each other) a length of gusset material required for a given panel. An optical sensor  624  detects whether the gusset material covers all of the rollers  622  (the last one of which may be covered with a reflective material). If the last roller is not covered with gusset material, then the operator is notified through an alarm. If insufficient gusset material exists for a panel, the operator can determine, by counting the number of rollers that are interleaved with the gusset material, the operator can determine if there is sufficient gusset material to edge a smaller-sized panel (e.g., a twin-size mattress panel, rather than a full-size panel). 
     An exploded view of a section  700  of an air table is shown in FIG.  7 . The section  700  includes a surface portion  710  that defines a plurality of openings  712  passing there through. The surface portion  710  is sealed to a manifold  720  that includes at least one passage  714  to an air supply (not shown), which could comprise one of many types of blowers generally available. A baffle  716  is disposed above the passage  714  to prevent local high concentrations of air flow through the surface portion  710 . 
     The turning mechanism  330  is shown in greater detail in FIG.  8  and the ruffler  318  is shown in greater detail in FIG. 9. A detail of a directional air jet  630  and the air table  310  is shown in FIG.  10 . The directional air jet  630  is supplied by an air supply  1112  and controlled remotely by a solenoid  1110 . 
     In one embodiment, as shown in FIG. 11, the gusset material  1120  and the flange material  1130  may be sewn to the panel  106  in a single operation. To do this, the system requires a first sewing machine  1150  for sewing the flange material  1130  to the gusset material  1120  and a second sewing machine  1140  for sewing the combined gusset/flange to the panel  106 . 
     In one embodiment of a panel/gusset combination, as shown in FIG. 12, the gusset  1210  may be sewn to the panel  1200  so as to leave a predetermined width of panel  1200  extending away from the gusset  1210 . In this embodiment, the extra panel material eliminates the need for a flange, as the periphery of the panel  1200  is attached directly to the side wall of the mattress body. 
     The above described embodiments are given as illustrative examples only. It will be readily appreciated that many deviations may be made from the specific embodiments disclosed in this specification without departing from the invention. Accordingly, the scope of the invention is to be determined by the claims below rather than being limited to the specifically described embodiments above.
An apparatus for attaching a gusset to a panel includes a gusset folder that receives and folds a gusset material to form the gusset. The panel is supported by a sewing table. A sewing machine is positioned relative to the sewing table so as to be able to sew the gusset to the panel. A gusset guides the gusset toward a selected edge of the panel so that the gusset is held in substantial alignment with the edge of the panel. An edge detector detects when a next edge of the panel is approaching the sewing machine. A turning mechanism is positioned along the sewing table and is moveable into engagement with the panel. The turning mechanism turns the panel relative to the sewing machine when the edge detector detects the next edge of the panel is approaching the sewing machine.