Abstract:
A seating cushion for use as a seat bottom, back, headrest, arm or the like in a seating product. The seating cushion comprises an outer enclosure formed of a relatively durable and inert polymer and a resilient inner pad fitted within the enclosure. The outer enclosure is preformed of a three dimensional unitary polymeric wall configured to receive the inner pad so as to cover the top, sides and at least a portion of the bottom of the pad. The preformed enclosure may be used in place of conventional upholstery in most seating products. The wall of the enclosure is generally thicker than conventional upholstery material so as to provide durability and structure, but is sufficiently thin and flexible to enable the user to feel the comfort of the pad disposed within the enclosure. The enclosure is preferably formed of polyurethane molded in a two-sided mold to provide a three dimensional enclosure of controlled thickness.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally directed to seating products, and is more particularly directed to a seating cushion comprised of a preformed polymeric three-dimensional enclosure configured to receive a resilient inner pad so as to cover the top, sides and at least a portion of the bottom of the pad. The seating cushion is particularly well suited for industrial and vehicular seating products. 
     2. Description of Related Art 
     Seating products such as chairs, stools and benches are commonly subjected to heavy wear and often times nearly continuous use, particularly in industrial or vehicular settings. In these and other environments, users may spill food, beverages, chemicals or other damaging materials onto the seating product. In such environments, seating products made from conventional upholstery materials must be repaired or replaced frequently, which can be quite expensive. Thus, there is a need for durable seating products that can withstand heavy use and spilled materials. In addition, in many industries, such as the pharmaceutical and microelectronics industries, there is a need for seating products that are not only durable, but are comprised of relatively inert materials suitable for use in a clean room environment. Unfortunately, because of the need for durable and/or inert seating products, comfort is often a secondary consideration in designing and purchasing these seating products. 
     Attempts to construct durable seating products suitable for clean room and other industrial use include providing solid molded polyurethane seat bottoms and backs. The solid polyurethane is highly durable and resists wear and spillage. In addition, the solid polyurethane is relatively inert and does not release particles that can contaminate a clean room environment. Although such seats are suitable for use in vehicles and clean rooms, the polyurethane is hard and uncomfortable. This can be a particular problem insofar as persons who work in clean rooms and other industrial settings are often required to remain seated for prolonged periods of time. Thus, use of solid polyurethane seating products can lead to unhappy workers, poor job performance and expenses related to health problems (e.g., back problems). 
     Other attempts to construct durable seating products have focused on vehicular seating products, such as seats or benches used in buses. U.S. Pat. No. 5,609,395 to Burch discloses bus seat modules comprised of an elastomeric skin bonded to a polyurethane foam interior and a plywood base. The bus seat modules are formed by coating the interior surface of a mold with a spray elastomer, inserting the plywood base into the mold and injecting urethane foam therebetween. The foam bonds to the skin and the plywood to form a unitary piece. Although the elastomeric skin may be durable, the method for spraying the elastomer into the mold expels harmful chemicals into the air and is difficult to control, resulting in wasted elastomer, overspray that requires clean-up, and inconsistencies in the thickness of the sprayed skin. Further, it is extremely difficult to position the spray gun to coat sharp angles or overhanging portions of the mold, and joining separately formed pieces of skin is generally unsatisfactory because overspray at the parting line makes joinder of the pieces difficult. Thus, the shape of the skin that may be produced utilizing spray elastomer is somewhat limited to shapes without overlapping walls or sharp angles. 
     Therefore, it is an object of the present invention to provide a durable seat cushion that can be utilized in heavy use environments, where the cushion is subjected to almost continuous usage, such as in industrial settings or for commercial vehicles. 
     It is a further object of the present invention to provide a durable seat cushion that can be easily cleaned and can withstand chemical spills. 
     It is another object of the present invention to provide a such a seat cushion that is as durable as conventional industrial seats, but is much more comfortable. 
     It is yet another object of the present invention to provide such a seat cushion that is suitable for use in clean rooms. 
     It is another object of the present invention to provide such a seat cushion that can be constructed accurately with predetermined characteristics. 
     It is another object of the present invention to provide such a seat cushion that can be constructed economically without significant waste. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a durable and relatively inert seating cushion comprising a preformed outer enclosure configured to cover and receive a resilient inner pad. The preformed enclosure is preferably three-dimensional and may be used in place of conventional upholstery in most seating products. The enclosure comprises a unitary polymeric wall that terminates in a lower peripheral edge to define an opening through which the pad can be inserted. Preferably, the wall comprises a substantially horizontal top wall, a peripheral side wall and a substantially horizontal bottom lip adjacent the lower peripheral edge. The bottom lip will cover a portion of the bottom surface of the pad contained within the enclosure. 
     The wall of the enclosure is relatively thick, which adds durability and structure to the seating cushion. However, the enclosure wall is sufficiently thin and of a density that allows the user to feel the characteristics of the pad contained within the enclosure. In a preferred embodiment, the enclosure is comprised of a unitary wall of polyurethane having a thickness of at least 0.030 inch, and a density ranging between 0.5 and 1.2 grams/cubic centimeter. 
     The enclosure is preferably formed by casting or injection molding using a two-sided mold. The two-sided mold allows the wall of the enclosure to be formed in a predetermined thickness, which thickness may vary at predetermined locations along the enclosure wall. In addition, a two-sided mold allows the enclosure to be formed with an overlapping bottom lip at the lower portion of the wall. After molding, a pad with the desired characteristics is inserted into the enclosure through the opening to form a cushion for use as a seat bottom, seat back, arm rest or headrest of a seating product. 
     A seating cushion formed using the preformed enclosure of the present invention is both highly comfortable and highly durable. Because the enclosure is formed separately from the pad, the characteristics of the enclosure can be varied independently of the pad without compromising the comfort of the seating cushion. Further, because the pad is not bonded to the enclosure, if the pad becomes compressed or otherwise unsuitable for use, or if the enclosure is somehow damaged, the pad and/or enclosure can be replaced without need to purchase an entire new seat. 
     In a preferred embodiment, the enclosure is formed in a two-sided mold, which allows the enclosure to be constructed with a consistent, repeatable and predetermined pattern of wall thickness. The two-sided mold also allows various shapes of enclosures, including enclosures having an overlapping lip. Also, because the enclosure is preformed into the desired three-dimensional shape, there are few of the wrinkles that result from utilizing a flat sheet of upholstery material to cover a pad. Although a cushion for a seat bottom is generally described herein and depicted in the figures, it should be understood that the seating cushion of the present invention may also be used to form back cushions, arm cushions, headrests and the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of one embodiment of the preformed enclosure of the present invention. 
     FIG. 2 is a cross-sectional view of the preformed enclosure of the present invention with a pad inserted therein taken along line  2 — 2  of FIG. 3, with the drawstring shown extending therefrom for clarity. 
     FIG. 3 is a bottom view of the preformed enclosure of FIG. 1 with a pad inserted therein. 
     FIG. 4 is an exploded view of the preformed enclosure FIG. 1 associated with a pad, a base and a pedestal. 
     FIG. 5 is a cross-sectional view of a two-sided mold that may be used to form the preformed enclosure of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Turning to FIG. 1, a preformed outer enclosure consistent with the present invention is generally designated by the numeral  10 . Enclosure  10  comprises a unitary polymeric wall  12  configured to receive and cover a pad  14  therein, as shown in FIGS. 2 and 3. Enclosure  10  does not completely enclose pad  14 . Instead, wall  12  of enclosure  10  terminates in a lower peripheral edge  16  that defines a lower opening  18  through which pad  14  may be inserted. The lower portion of wall  12  adjacent peripheral edge  16  forms a substantially horizontal lip  20 . As best shown in FIG. 3, lip  20  covers a portion of the bottom surface  22  of pad  14  when pad  14  is installed within enclosure  10 . 
     Wall  12  of enclosure  10  is generally thicker than conventional upholstery material, which adds durability and structure to the seating cushion. However, wall  12  is sufficiently thin and flexible that the user is able to feel pad  14  disposed within enclosure  10 . Preferably, the thickness of wall  12  is between 0.030 and 0.250 inches, and most preferably wall  12  is between 0.060 and 0.100 inches thick. Wall  12  may be of uniform thickness or may be designed with a thickness that varies over different portions of enclosure  10 . 
     The desired flexibility of enclosure  10  is obtained by forming enclosure  10  from a relatively flexible and durable material. Preferably, enclosure  10  is formed from a material having a density between 0.5 grams/cc and 1.3 grams/cc, more preferably between 0.7 grams/cc and 1.1 grams/cc and most preferably 0.80 grams/cc. Enclosure  10  formed from such material is durable, yet sufficiently soft and flexible to provide comfort to the user and to allow the user to feel pad  14  disposed therein. Preferably enclosure  10  is comprised of a polymeric composition and is more preferably formed from polyurethane. Elastameric or integral-skin polyurethane compositions consistent with the present invention are produced by Bayer Corporation under the mark BAYFLEX, and by DOW CHEMICAL COMPANY under the mark VORALAST. 
     The polymeric composition used to form enclosure  10  may additionally include various additives to alter the characteristics of enclosure  10  for certain intended environments. For example, antifungal, antibacteiral or antimicrobial agents may be included in the polymeric composition. Alternatively, enclosure  10  can be constructed to conduct electricity, and when combined with a suitable seat base, can form a seating product that dissipates static electricity for use in a microelectronics clean room or similar environment. 
     Returning to FIG. 1, wall  12  of enclosure  10  is preferably three-dimensional having a substantially horizontal top wall  24 , a peripheral curved side wall  26  and lower horizontal lip  20 . The dimensions of top wall  24  and side wall  26  will depend on the type of seating cushion desired, as can be readily calculated by one of ordinary skill in the art. In some instances, top wall  24  will flow directly into lip  20  with no side wall  26  therebetween. Lip  20  must be sufficiently wide to cover a portion of bottom surface  22  of pad  14 , yet sufficiently narrow to allow pad  14  to fit through opening  18 . Preferably the width of lip  20  ranges between 0.5 and 8 inches, more preferably between 1.5 and 2.5 inches. 
     In the embodiment depicted in FIG. 4, the exterior surface of top wall  24  is provided with raised sections  28 . Raised sections  28  provide traction to prevent the user from sliding on top wall  24  of enclosure  10 . In addition, raised sections  28  define passageways that allow air to flow between the seating surface of the user and the top wall  24  of enclosure  10 , thereby helping to prevent the user from becoming hot and sweating. Raised sections  28  may be of any suitable height and shape to help prevent slipping and/or provide air flow. 
     In a preferred embodiment best shown in FIGS. 2 and 3, a casing  30  containing a drawstring  32  is provided around opening  18 . Preferably casing  30  is formed separately from enclosure  10  and is affixed to the exterior surface of lip  20  by any suitable fastener, preferably by stitching. Alternatively, casing  30  may be formed integrally with wall  12 , for example by folding over peripheral edge  16  of wall  12  and securing it in place. When tightened and tied, drawstring  32  holds enclosure  10  snugly against pad  14  and secures pad  14  in place within enclosure  10 . Because enclosure  10  is preformed to enclose pad  14 , tightening drawstring  32  will produce only minor wrinkling in lip  20  of enclosure  10 . Although casing  30  and drawstring  32  are shown in the figures, it should be understood that pad  14  may be held in place within enclosure  10  using any suitable means known in the art. 
     Pad  14  may be any resilient pad or cushion known in the art, preferably a preformed foam pad, and most preferably a preformed polyurethane foam pad. The characteristics of pad  14  will depend in part on the environment in which pad  14  will be used, as will be apparent to one in the art. For example, pad  14  may be formed with a contoured bottom surface  22 , as shown in FIG. 3, to conform to the upper surface of base  34 , depicted in FIG.  4 . Because pad  14  is formed independently of enclosure  10 , the characteristics of cushion  14  may be varied without compromising the durability or other characteristics of enclosure  10 . Pad  14  may be removed from the enclosure and replaced without need to replace the enclosure. 
     Turning to FIG. 4, in a preferred embodiment a seating cushion comprising enclosure  10  and pad  14  further comprises a base  34  mounted on a pedestal  36 . Enclosure  10  forms the exterior of the seating surface of the seating cushion. An upper edge  38  of base  34  is positioned within enclosure  10  adjacent to and overlapping a portion of lip  20  and closing opening  18 . When tightened, drawstring  32 , disposed within casing  30 , holds base  34  in position relative to pad  14  and enclosure  10 . Base  34  and pedestal  36  may be any standard seating components known in the art, and may be comprised of any suitable material known in the art such as metal, wood or plastic. 
     Base  34  may be attached to enclosure  10  and/or pad  14  by any fastening means known in the art. Preferably base  34  is removably attached to enclosure  10  to allow pad  14  to be removed from enclosure  10  without destroying enclosure  10 . Base  34  may be removably attached to enclosure  10  using casing  30  and drawstring  32 , using staples, or using any suitable removable fastening device. Additionally, base  34  may be removably attached to enclosure  10  utilizing a more permanent fastening means, such as glue. In such embodiment, base  34  and pad  14  may be removed by cutting base  34  from enclosure  10 , while leaving a portion of lip  20  at the lower end of wall  12 . Pad  14  may then be removed and a new pad inserted. Base  34  may then be re-attached to enclosure  10  utilizing the remaining portion of lip  20 . 
     To form a seating cushion comprising enclosure  10 , a polymeric composition, preferably polyurethane, is first molded into the desired preformed shape. Any desired additives should be added to the polymeric composition prior to molding. Enclosure  10  is preferably molded in a two-sided mold by injection molding or casting. The two-sided mold defines the shape and thickness of enclosure  10  in a manner that can not be achieved in spray or rotational molding. 
     Turning to FIG. 5, the two-sided mold utilized to form the enclosure in a preferred embodiment is generally shown by the number  40 . Mold  40  comprises a concave base  42  that defines the shape of the exterior surface of top wall  24  and upper portion of side wall  26 . The two-sided mold further comprises a concave lid  44  that defines the shape of the exterior surface of the lower portion of side wall  26  and lip  20 . Mold lid  44  is designed to be lowered onto mold base  42 , such that the lower edge  46  of lid  44  rests on the upper edge  48  of base  42  and a seal can be formed around the periphery of the edges of lid  44  and base  42 . When lid  44  is in place on base  42 , the interior surfaces of lid  44  and base  42  define the exterior surface of enclosure  10 . 
     A generally egg-shaped interior form  50  extending from lid  44  defines the shape of the interior surface of enclosure  10 . Lid  44  and interior form  50  are designed such that when lid  44  is lowered onto base  42 , there is a space between the lower surface of form  50  and the interior surface of base  42  and a space between the upper surface of form  50  and lid  44 . Thus, when lid  44  and form  50  are lowered into place on base  42 , the concave base  42  and lid  44  define the exterior of enclosure  10 , and egg-shaped form  50  defines the interior of enclosure  10 , such that the space between the interior form  50  and the exterior base  42  and lid  44  corresponds to the desired shape of enclosure  10 . Opening  18  is formed where interior form  50  extends from lid  44 . 
     To mold enclosure  10 , the polymeric composition is poured into base  42 . As lid  44  is lowered, the polymeric composition is displaced by interior form  50  to fill the space between the interior form  50  and the exterior base  42  and lid  44 . As previously described, prior to pouring the polymeric composition into the mold, a foaming agent may be added to the polymeric composition to cause the polymeric composition to expand to assure that all spaces between the interior form  50  and the exterior base  42  and lid  44  are filled with polymeric composition. Any foaming agent known in the art is suitable for this purpose. 
     By utilizing a two-sided mold, enclosure  10  can be formed accurately in a consistent and repeatable predetermined thickness with angles and overhanging sections, such as lip  20 . Two-sided molds may be constructed to produce various shapes of enclosures. For example, the two-sided mold may be constructed such that the thickness of enclosure  10  varies in an accurate and predetermined pattern. Further, the base  42  may be provided with cavities  52  to form raised sections  28  on the exterior surface of top wall  24 . If overhanging sections are not required, the two-sided mold may be comprised of only a concave base  42  and a complimentary convex lid, with no interior form. In addition, use of a two-sided mold minimizes waste and does not produce harmful airborne chemicals that are produced by spray molding polyurethane. 
     When the polymeric composition has cured, mold lid  44  is raised, and enclosure  10  is removed from the interior form  50  of the mold. A preformed pad  14  is placed within enclosure  10 . Preferably, casing  30  containing drawstring  32  is fastened in place on the exterior surface of lip  20  of wall  12  around opening  18 . Pad  14  is secured in place within enclosure  10 , and opening  18  of enclosure  10  is closed. Preferably, pad  14  is secured in place and opening  18  is closed by inserting upper edge  38  of base  34  into opening  18  to close opening  18 , tightening drawstring  32  to pull enclosure  10  snugly around pad  14 , and tying drawstring  32  to hold base  34  and pad  14  in place relative to each other and enclosure  10 . 
     From the foregoing it will be seen that this invention is one well adapted to attain all ends and objectives herein-above set forth, together with the other advantages which are obvious and which are inherent to the structure. 
     Since many possible embodiments may be made of the invention without departing from the scope thereof, is to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative, and not in a limiting sense. 
     While specific embodiments have been shown and discussed, various modifications may of course be made, and the invention is not limited to the specific forms or arrangement of parts described herein, except insofar as such limitations are included in the following claims. Further, it will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.