Patent Publication Number: US-7216936-B2

Title: Cushion construction for seating unit

Description:
CROSS REFERENCES TO RELATED APPLICATION 
     This application is a continuation of patent application Ser. No. 10/136,599, filed May 1, 2002, entitled METHOD OF MANUFACTURING CUSHION CONSTRUCTION FOR SEATING UNIT (now U.S. Pat. No. 6,880,215), which is a divisional of commonly assigned, co-invented application Ser. No. 09/294,665, filed Apr. 19, 1999, entitled CUSHION CONSTRUCTION FOR FURNITURE (now U.S. Pat. No. 6,425,637). 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to methods of manufacturing cushion constructions for seating, where the cushion has improved cushioning properties. 
     Chairs having upholstery covered cushions on their seat and backs are known. The cushions provide a cushioning effect that conforms at least somewhat to a seated user&#39;s body to provide increased comfort. A common cushion in chairs is a polyurethane open-celled foam cushion that is pre-formed to an initial shape. For example, U.S. Pat. No. 4,718,153, to Armitage et al., issued Jan. 12, 1998, entitled Cushion Manufacturing Process, discloses one such cushion manufacturing process utilizing a polyurethane foam. A problem is that the polyurethane will degrade over time, leading to breakdown of the polyurethane foam that generates dust and a degradation of cushioning properties. The dust and breakdown potentially adds to environment dust in the building where the chair is located. Also, the breakdown and loss of material results in changes to the cushioning support provided by the cushion. Polyurethane foam cushions also suffer from other disadvantages. Polyurethane foam is not recyclable, leading to increased landfill costs when scrap is generated. Further, the polyurethane foam typically has a pinched-off edge or weld line of higher density material running around its perimeter. The higher density material can cause quality problems, both in terms of poor appearance due to its roughness, stiffness, and protruding nature, and also in terms of an unattractive bumpy feel when a person sits on or feels the fabric covering the higher density material. Still another problem is caused when a seated user sweats against a polyurethane foam cushion, because the polyurethane foam cushions are sometimes not able to wick away the sweat (or at least not fast enough), depending on the foam and the volume of sweat. 
     Accordingly, an improved cushion construction for furniture is desired that solves the aforementioned problems and has the aforementioned advantages. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention includes a seating unit having a base and a seat support supported by the base. A back upright is operably supported on the base for movement between an upright position and a reclined position. A back construction includes a back support attached to the back upright. A cushion is supported by a surface on one of the back support and the seat support, the cushion having opposing side edges. An edge stabilizer extends along the opposing side edges and is attached to the side edges to control a position of the side edges relative to the one back and seat support. 
     These and other features, objects, and advantages of the present invention will become apparent to a person of ordinary skill upon reading the following description and claims together with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  are front and rear perspective views of a chair embodying the present invention; 
         FIG. 3  is an exploded front perspective view of the back construction shown in  FIG. 1 ; 
         FIG. 4  is a vertical cross-sectional view taken through a center of the back construction shown in  FIG. 1 ; 
         FIGS. 5 and 6  are enlarged views of the circled areas V and VI in  FIG. 4 ; 
         FIG. 7  is an exploded perspective view of the stiffened cushion subassembly shown in  FIG. 3 ; 
         FIG. 8  is a perspective view of the cover assembly shown in  FIG. 3 ; 
         FIG. 9  is a rear view of the cushion assembly shown in  FIG. 3 , including the stiffened cushion subassembly and the cover assembly; 
         FIG. 10  is a front perspective view, partially broken away, showing the back construction of  FIG. 3 ; 
         FIG. 11  is a rear view of a modified cushion assembly similar to that shown in  FIG. 9 , but with edge stiffener legs extending downwardly along side edges of the cushion pad; 
         FIG. 12  is a side view of the modified cushion assembly shown in  FIG. 11 ; 
         FIG. 13  is a flow diagram showing a method of assembly; and 
         FIG. 14  is a force versus deflection curve comparing the novel cushion of non-woven PET fibers to a conventional polyurethane foam cushion. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     A chair  20  ( FIGS. 1 and 2 ) embodying the present invention includes a base  21 , a back upright or arch-shaped back frame  22 , a seat  23 , and a back construction  24 . The base  21  includes a control housing  25  with fixed side support structures  26  extending laterally and upwardly from the control housing  25 . The back upright  22  is movable between an upright position and a reclined position. The back construction  24  ( FIG. 3 ) includes a back support shell  27  (also referred to as a “back support”) attached to the back upright  22  ( FIG. 4 ), and further includes a cushion assembly  28  ( FIG. 3 ) attached to the back support shell  27  with quick-attach hooking top connection  29  and a “zip-lock” type bottom connection  30 . The cushion assembly  28  includes a cover assembly  31  ( FIG. 8 ) having an upholstery front panel  32  and a rear panel  33  forming a sock that can be inverted and “pulled” upwardly onto a cushion  35  and cushion stiffener  34  as the cover assembly  31  is inverted. The rear panel  33  includes a first sheet/fabric section  36  having a one-directional stretch in a vertical direction, and further includes a lower second fabric section  37  having a high-stretch property. The second section  37  hangs downwardly from the front panel  32  and has a strip of stiff material  38  sewn along its lower edge to form the stiffened edge flange  39  noted below, which stiffened edge flange  39  forms part of the bottom connection  30 . The stretchable second section  37 , in combination with the other structure of top and bottom connections  29  and  30 , allow for quick assembly, yet provide for a tensioned cover assembly  31  on the back construction  24  that tends to remain flat and unwrinkled, even with considerable flexure of the back construction  24  in the lumbar region of the back construction  24 . 
     The present description of chair  20  is believed to be sufficient for an understanding of the present combination. Nonetheless, it is noted that a more detailed description of the chair  20  can be found in U.S. Pat. No. 5,871,258, issued Feb. 16, 1999, entitled Chair with Novel Seat Construction, and also in U.S. Pat. No. 5,975,634, issued Nov. 2, 1999, entitled Chair Including Novel Back Construction, the entire contents of both of which are incorporated herein in their entirety by reference. It is to be understood that a scope of the present invention includes using the present attachment and construction methods in combination with different office chairs, but also in many other chairs and seating units where upholstery covering is desired, such as in couches, lounge seating, mass transit seating, automotive or bus seating, and stadium seating, or also in other upholstery-covered furniture, such as padded desking furniture and the like, and also in non-furniture situations where upholstery or sheeting must be attached to a flexible or bendable component in a wrinkle-free manner. 
     The back support shell  27  ( FIG. 4 ) comprises a sheet of polypropylene material or similar engineering-type stiff structural material, and includes relatively stiff thoracic and pelvic sections  41  and  42  connected by a flexible lumbar section  43 . The back support shell  27  is relatively stiff in a plane defined by the sheet, but is flexible in the lumbar section  43  in a direction perpendicular to the sheet. The thoracic and pelvic sections  41  and  42  are attached to the back frame  22  at top and bottom pivot locations  44  and  45 , and the lumbar section  43  protrudes forwardly from the thoracic and pelvic sections  41  and  42 . A belt bracket  46  extends parallel a lower edge of the pelvic section  42 , and includes forwardly extending side flanges  47  each having a hole defining the bottom pivot location  45 . The belt bracket  46  is encapsulated in an enlarged section  48  that extends along the lower edge of the pelvic section  42 , and forms a horizontal recess  49  defined between a longer rear lip  50  and a shorter front lip  51 . Slots  52  extend horizontally across a center area of the lumbar section  44  to form horizontal bands  54 , but terminate short of the edges of the lumbar section  44  to define vertical side edge bands  55  ( FIG. 3 ). The horizontal and vertical bands  54  and  55  are semi-flexible and designed to be sufficient in size and strength to provide the support desired. Due to the locations of top and bottom pivot locations  44  and  45  and also due to the shape and characteristics of the sections  41 – 43  and belt bracket  46 , the back support shell  27  flexes significantly in the lumbar area, but rotates along a predetermined path a substantial amount around the bottom pivot location  45  and to a lesser extent around the top pivot location  44 . This results is significant wrinkling of the upholstery material, unless the back construction  24  is constructed to compensate and make up for this high flexure, and the high compressing and stretching of the surfaces (i.e., the upholstery) in the lumbar section  43 . 
     The thoracic section  41  ( FIG. 6 ) includes a ridge  57  along its upper edge and a series of hooks  58  spaced below the ridge  57  that project forwardly and then upwardly. A pair of apertures  59  is spaced below the hooks  58 . The apertures  59  are positioned to receive screws  60  ( FIG. 4 ) that extend rearwardly through the apertures  59  into threaded engagement with bosses  61  near a top of the arch-shaped back frame  22 . The apertures  59  are recessed to create a rearwardly deformed pocket to receive a head of the screws  60  as desired. A pair of alignment stops  62 ′ is located in the recesses on a front of the back support shell  27  adjacent apertures  59  to assist in assembly, as described below. 
     A pair of saw-tooth ridges  63  ( FIG. 3 ) extends along a front face of the vertical bands  55  at a location near to but spaced inwardly from outer edges of the bands  55 . A lumbar adjustment device  65  is positioned between the cushion assembly  28  and the back support shell  27 . The lumbar adjustment device  65  includes a carrier  66 , a lumbar support member  67  with vertical leaf-spring-like fingers  68  supported on the carrier  66 , and a pair of side handles  69 . The side handles  69  telescopingly engage mating structures  70  on ends of the carrier  66 , and further include a channel for slidably engaging the saw-tooth ridges  63 . A detent on the handles  69  engages the saw-tooth ridges  63  to hold the lumbar adjustment device in a selected vertical position. 
     The cushion assembly  28  includes a back cushion  35  ( FIG. 3 ) formed of non-woven PET fibers, as described below. The back cushion  35  provides an excellent initial support and feel to a seated user when he/she initially leans against the cushion assembly  28 , even without use of a topper sheet commonly used in the seating industry. The cushion stiffener  34  comprises a stiff polypropylene panel. The cushion  35  includes a rear surface shaped to mateably receive the cushion stiffener  34 . An upper edge  74  ( FIG. 7 ) on a rear surface of the cushion  35  is wrapped over the upper edge  74  and onto a rear surface of the cushion stiffener  34 . The cushion stiffener  34  is adhered to the cushion  35  if needed to maintain the stability of the assembly desired. The cushion stiffener  34  includes a series of spaced-apart apertures  75  that correspond to the hooks  58  ( FIG. 3 ). A horizontal down flange  76  ( FIG. 7 ) extends along a lower edge of the cushion stiffener  34 , which flange  76  is deformed inwardly toward the cushion  35  at least a thickness of the material of rear panel  33 , so that the rear panel  33  does not protrude outwardly when attached to the flange  76 , as described below. The cushion  35  has a recess  76 ′ that mateably engages the flange  76 . 
     As noted above, the cover assembly  31  ( FIG. 8 ) includes a front panel  32  and a rear panel  33 . The front panel  32  includes sections of upholstery material sewn together to form the front and sides of a covering for the cushion  35 . The rear panel  33  includes the first fabric section  36 , which comprises a material that stretches horizontally only about five percent (5%), but that stretches vertically about forty percent (40%). The one-directional stretch material is available in commerce, such as from Milliken Company, Spartanburg, S.C. This first fabric section  36  is sized to extend from the mid-level horizontal flange  76  on the cushion stiffener  34  downwardly to a bottom of the cushion  35 . The second section  37  is a high-stretch material having a stretchability of about one hundred percent (100%). This second section  37  is about two inches high and extends across a bottom of the rear panel  33  of the cover assembly  31 . A strip of stiffener material  78 , such as polypropylene, is about ¼-inch wide in a vertical direction and is placed along a lower edge of the second section  37 . The lower edge is folded over the strip  78  and sewn to the lower edge. This forms a stiffened edge flange  79  horizontally across the second section  37  that is optimally suited to be pressed or “zipped” into and frictionally retained in the horizontal recess  49  with a zip-lock like motion (see  FIG. 5 ). Notably, the stiffened edge flange  79  is rectangular in shape and is rolled forwardly 180 degrees before it is inserted into the recess  49  ( FIG. 5 ). This results in a surprisingly positive and secure bottom connection arrangement and one that can be quickly made by an assembler. The top rear edge of the front panel  32  ( FIG. 6 ) is folded and sewn to form a tunnel  79 ′, and a drawstring  80  is located in the tunnel. The front and rear panels  32  and  33  are sewn together to form an upwardly open sock. The panels  32  and  33  are initially sewn in an inverted position, and the cushion  35  is inserted into the sock as the sock in inverted. This also hides the seam lines where the panel  32  and first and second fabric sections  36  and  37  are sewn together. 
       FIG. 13  discloses a method including forming a sock-like cover assembly  31  in a step  90  from the panels  32  and  33  and second fabric section  37 . Step  90  further includes sewing a strip  78  to a bottom of second fabric section  37  and attaching a drawstring  80  in a tunnel  79 ′. A second step  91  includes attaching cushion stiffener  34  to the cushion  35 . The cover assembly  31  is positioned adjacent the cushion  35  and inverted onto an end of the cushion  35  opposite the cushion stiffener  34  in a step  92 . This results in the high-stretch second fabric section  37  being positioned at a lower edge of the cover assembly  31  remote from the cushion stiffener  34 . The cover assembly  31  is then adjusted on the cushion  35  and cushion stiffener  34  to eliminate wrinkles and to properly position the seam lines. This may include tensioning the drawstring  80 , as shown in step  93 . Specifically, in the illustrated embodiment, the drawstring  80  is tensioned to draw a top of the cover assembly  31  downwardly onto the cushion stiffener  34 . This also tensions the front panel  32 . The tensioned drawstring  80  helps hold the cover assembly  31  in position during the steps of inserting staples  82  and  83 , and during a step of setting any adhesive in the assembly. The front panel  32  is then staple-attached along its upper edge to the cushion stiffener  34  by staples  82  ( FIG. 9 ) that extend through the wrapped-over top edge of the front panel  32  into the cushion stiffener  34 . The upper edge  33 ′ of the rear panel  33  is overlapped onto the down flange  76  and is stapled with staples  83  that extend through the upper edge into the down flange  76 . Where desired, heat-activated adhesive is applied to a front surface of the cushion  35 , and the adhesive is activated by steam or heat to adhere the front panel  32  to the cushion  35 . This assembly results in cushion assembly  28 . 
     The back support shell  27  of the back construction  24  ( FIG. 13 ) is attached in a step  94  to the back frame  22  by screws at the top connection  44  and by pivot studs at the bottom connection  45 . A lumbar force adjusting device  95  ( FIG. 1 ) is attached to the back frame  22  to bias the flange  47  of belt bracket  46 , such that the lumbar section  43  of the back support shell  27  naturally is biased to a forwardly concave shape. 
     The cushion assembly  28  is assembled onto the back support shell  27  in a step  96  ( FIG. 13 ) to form the back construction  24  by abutting stops  62 ′ on the cushion stiffener  34  against the stops  62 ′ on the back support shell  27 , and by extending the hooks  58  on the thoracic section  41  of the back support shell  27  into the apertures  75  of the cushion stiffener  34 . Then, the back cushion  35  including the cushion stiffener  34  is moved downwardly to frictionally engage the hooks  58 . Thereafter, the stiffened edge flange  39  at the bottom of the rear panel  33  is stretched, rolled 180 degrees, and tucked upwardly into the downwardly facing horizontal recess  49  on the back support shell  27  (in a step  97 ). The stiffened edge flange  39  is tucked into position from one side to another with a “zip-lock” type motion. After it is fully inserted, the side edges of the high-stretch second section  37  are pulled back, and a staple is extended through the stiffened edge flange  39  into each end of the rear lip  50  in a step  98 . The high-stretch second section  37  is then pulled laterally out to a wrinkle-free condition where it hides these end-located staples. Notably, the high-stretch second section  37  is a dark or black color and is located behind the seat  23  below the back construction  24  in the shadow of the back construction  24 , such that the bottom connection  30  including the enlarged section  48  of the back support shell  27  is not easily visible to a person standing in or around the chair  20 . 
     In the embodiment of  FIGS. 11 and 12 , a modified cushion stiffener  34 A is provided that includes an upper portion like the stiffener  34 , but further includes perimeter bands  34 B that extend down side edges and along a bottom of the cushion  35  to stiffen the edges completely around the cushion  35 . Cushion stiffener  34 A is desirable where the fabric panels  32  or  33  are so strong as to overpower the cushion edges causing wrinkling. 
     As noted above, the cushion  35  is made from a recycled non-woven PET fibrous mat supplied by Sackner Co., Grand Rapids, Mich. The PET mat is molded to form a novel cushion that is substituted for the polyurethane cushion and the topper cushion often used in prior art. Non-woven polyester or PET is a polyester with a phenylene group in a chain. The stiffness of this chain is what allows the thermoplastic to perform surprisingly and unexpectedly well as a cushioning fiber, as discussed below. 
     When PET completely burns, it turns into carbon dioxide and water and does not emit any poisonous gases. Food products can be packaged in this material without any worry, and containers can be burned without the need for extraordinary emission control measures. This is not true for polyurethane, which will emit dangerous byproducts when burned. Use of PET material is also environmentally friendly. A major source of the PET material for cushion  35  comes from re-ground pop bottles. Recycling of PET pop bottles into headliner cores, insulation, and door panels has apparently been previously done. However, its use as a complete cushion for a chair seat or chair back has not been done to my, the inventor&#39;s, knowledge. 
     A major advantage of the PET cushion material are that it is 15 to 20 percent lighter than polyurethane foam, yet it provides a high value and high value per unit cost. Further, the PET cushion material provides improved comfort to a seated user including a very uniform force versus deflection curve (see  FIG. 14 ) with a surprisingly constant slope over a major portion of its compression. The more conventional polyurethane foam has a much less constant rate of compression. Often a topper cushion (e.g., about a ¼-inch thick cushion) is placed on a main cushion (e.g., about a 1-inch thick cushion) to “smooth out” the initial compression of the main cushion. However, this adds considerable expense. The non-woven fibrous cushion  35  does not need any such topper cushion. Further, the PET cushion material provides more breathability including the ability to wick away a seated user&#39;s sweat, provides excellent fatigue resistance and long life with little or no generation of dust after extended time in service, provides a capability of easy and low-cost recycling, and has no carcinogens or VOC&#39;s in its manufacture. Further, my initial research indicates that replacing molded foam with an equivalent piece of PET cushion results in a break-even or a decrease in costs. 
     Thermal comfort studies done by or for Steelcase, the assignee of the present invention, indicate a 50 percent higher/greater moisture permeability index in the supplied PET cushion than molded urethane foam cushions. This is believed to be due to the more open internal (fibrous) structure of the PET material. Higher index numbers equate to more desirable comfort. Also, the evaporative resistance of the PET cushion is less than half that of the molded foam cushion. The lower evaporative resistance correlates to improved comfort also in that the moisture given off by the body is absorbed and dispersed through the PET cushion much faster than through the molded urethane cushion. 
     Testing of the PET and molded urethane foam, using tests known to persons skilled in making chairs, indicates a lower initial load deflection characteristic of the PET cushions over the more traditional urethane foams, but a higher support factor, better ball rebound, better tensile strength and elongation, and a more linear cushioning rate. Tests suggest the feel to be more “residential” verses “industrial” (see  FIG. 14 ). 
     Advantageously, the non-woven PET cushion can be formed into a three-dimensional shape to conform properly to a particular chair geometry. Leaving the material in a flat shape and attaching it to the chair can result in a “kinking” of the PET material in some highly contoured chair designs, which may telegraph a crease or wrinkle into the face fabric of these chairs. 
     My proposed system works as follows. For the seat  23  of chair  20 , batting of material is optimally produced to a known raw mat density and thickness, such as about 2.3 to 2.6 lb./ft 3 , with a thickness of about 2 inches (unformed) or about 2.3 to 3.5 lb./ft 3  density (or more preferably between about 3.1 to 3.5 lb./ft 3 ) with a thickness of about 1½ inches (formed). A similar density of about 2.3 to 2.6 lb./ft 3  is used for back cushion  35 , but the thickness is different. For example, in cushion  35  the thickness is about 1 inch (unformed) or about 2.3 to 5.2 lb./ft 3  density (or more preferably between about 4.6 to 5.2 lb./ft 3 ) with a thickness of about ½ inch (formed). The material is cut to a predetermined size with a die cut, laser cut, or any other efficient means of trim. This pre-form is then loaded into a three-dimensional aluminum tool cavity of the desired shape. The cavity and lid are both pre-drilled to allow steam to pass through the tool halves. The material is then introduced to about a 30 second (plus or minus 5 to 10 seconds) steam heating cycle of about 250 degrees Fahrenheit that breaks the temporary thermal adhesive bond, and a 10 second (plus or minus 5 seconds) cooling cycle of ambient air that allows the material to rebond in the desired three-dimensional shape. The memory of the material is thus changed to the new shape and the part is removed from the tool. Since no edge trimming is required, edges can be produced round, and since the edges are not trimmed, edges do not have a hard edge or look non-uniform. Less handling and sensitive trimming also result in reduced costs of manufacture. Also, there is no scrap in terms of flashing or trimmings from the forming process, and any scrap, if generated, can be recycled. 
     The compressibility and shape of the cushion is also more uniform, since a uniformly produced batting of material, cut to a controlled size, was loaded into the tool and no materials were discarded in the forming process. Feature lines, depressions, and the like can be molded or pressed into the cushion material. Characteristically, no flash lines or parting lines are formed, such that the marginal material around a perimeter of the part feels the same as (and has the same density and compressibility as) the main part of the cushion. 
     In the foregoing description, it will be readily appreciated by persons skilled in the art that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims by their language expressly state otherwise.