Abstract:
A stiffening system for the perimeter edges of a foam core mattress comprising a coil spring (or other spring-based) structure disposed along one or more perimeter edges (e.g., one or both side edges, the foot, the head, or a combinations thereof including the foot and both side edges) of a mattress having a foam sleeping area. The perimeter spring structure is rectangular or square in cross-section and provides sufficient stiffness for comfortable seating on the edges of the mattress and is joined to the foam core by planar fabric elements that span the joint between them and are attached to both. The sleep area provides the softness and other salutary effects of a foam sleeping surface while the stiffer spring perimeter element provides the rigidity need for comfortable seating and wear resistance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/805,097, filed May 21, 2007, now U.S. Pat. No. 7,574,763, which is a continuation of U.S. patent application Ser. No. 10/914,939, filed Aug. 9, 2004, now U.S. Pat. No. 7,219,381, which is a continuation of U.S. patent application Ser. No. 10/102,276, filed Mar. 20, 2002, now U.S. Pat. No. 6,772,463, the entire contents of each of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to bedding products (including but not limited to mattresses) and in particular to edge support systems used to stiffen the perimeter of a bedding product. 
     2. Description of the Related Art 
     A traditional bedding or seating product has an inner spring core comprising a plurality of identically configured coil springs arranged in linear columns and rows. If such a spring core is used in a bedding product, the spring core is covered with a mattress pad or covering materials and an upholstered covering surrounds and encases the spring core and mattress pad. Sometimes, an additional padding layer, known as a “topper” is attached to the top sleeping surface. The topper may also be attached to the bottom sleeping surface as well, so that the mattress can be flipped. 
     Traditional bedding or seating products typically have one degree of firmness throughout because all of the springs of the spring core are identical. 
     Alternatively, bedding and seating systems may have a resilient foam core. This foam core may be surrounded by perimeter bolsters, located around the edges of the sleeping surface, i.e., at the head, foot, or sides of the mattress as those terms are known in the art. Foam core mattresses may also include toppers, in addition to mattress pads and covers. 
     Also known in the art are bedding or seating products that have increased firmness about their perimeter edge portions, primarily to prevent collapse of the side edges of the bedding or seating product when a person sits on the side edges. The well-known border wires found in almost all mattresses and seating products are one such device. These edge reinforcements also prevent loss of resiliency of the perimeter edge of the bedding or seating product as a result of persons repeated getting on and off the product or by sitting or leaning on one edge of the bedding or seating product. 
     Most of these edge supports enhances the firmness by locating firmness enhancing materials or devices between the upper and lower border wires of the product. This limits the effectiveness of the edge support and subjects the border wires to excessive bending forces. 
     What is needed is an edge support for a bedding or seating product which enhances the firmness of the edge of the product while preventing the border wire from being repeatedly flexed and possibly permanently bent due to a user sitting on the edge of the bedding or seating product. 
     SUMMARY 
     A stiffening system for the perimeter edges of a foam core mattress comprising a coil spring (or other spring-based) structure disposed along one or more perimeter edges (e.g., one or both side edges, the foot, the head, or a combinations thereof including the foot and both side edges) of a mattress having a foam sleeping area. The perimeter spring-based structure is rectangular or square in cross-section and provides sufficient stiffness for comfortable seating on the edges of the mattress, while the sleep area defined within the perimeter spring structure provides the softness and other salutary effects of a foam sleeping surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure may be better understood and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. 
         FIG. 1  is an isometric view of a bedding product according to one embodiment of the invention. 
         FIG. 2  is a cross-section view at AA of  FIG. 1 . 
         FIG. 3  is an alternate embodiment of the invention, shown in cross-section view at AA. 
         FIGS. 4A ,  4 B, and  4 C are plan views of a bedding product according to several alternate embodiments of the invention. 
     
    
    
     The use of the same reference symbols in different drawings indicates similar or identical items. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates, in an isometric view, a bedding product generally and in particular a mattress  10  manufactured according to one embodiment of this invention. Mattress  10  consists of a top sleeping surface  12 , a bottom sleeping surface  14 , a head  15 , a foot  16 , and two side edges  17 . Top sleeping surface  12  and bottom sleeping surface  14  may include within them, or have attached to them, a topper (not shown). The topper may contain one of more layers of fabric, batting, ticking, foam, and/or coiled springs. When present, the foam layer(s) of the topper may include latex and/or synthetic foam, including but not limited to polyurethane foam. 
     Although omitted for clarity, the topper may be either permanently or removably attached to sleeping surface  12  and  14 . Examples of permanently attached topper, seen in the art, are those that are sewn or bonded onto the mattress cover or those that are encased within a sealed pocket in the mattress cover, yet disposed on the surface of the mattress. Removable toppers are typically attached with a temporary fastener, such as a zipper or hook-and-loop fastener in one or more locations. Either attachment method may be used, or no topper may be supplied. 
     Mattress  10  also includes foam core  20  and perimeter element  25 . Foam core  20  is, in some embodiments, a single, monolithic block of a single type of resilient foam selected from foams having a range of densities (themselves well-known in the art) for supporting one or more occupants during sleep. In one embodiment, foam core  20  is made of any industry-standard natural and/or synthetic foams, such as (but not limited to) latex, polyurethane, or other foam products commonly known and used in the bedding and seating arts having a density of 1.9 and a 22 ILD (also known as “192 foam”). Although a specific foam composition is described, those skilled in the art will realize that foam compositions other than one having this specific density and ILD can be used. For example, foams of various types, densities, and ILDs may be desirable in order to provide a range of comfort parameters to the buyer. 
     In an alternative embodiment, foam core  20  may comprise one or more horizontal layers of multiple types of foams arranged in a sandwich arrangement. This sandwich of different foams, laminated together, may be substituted for a homogeneous foam block of a single density and/or ILD. Accordingly, the invention is not limited to any particular type of foam density or ILD or even to a homogenous density/ILD throughout foam core  20 . 
     In a further embodiment, foam core  20  may comprise one or more vertical regions of different foam compositions (including vertical regions having multiple horizontal layers), where the different foams are arranged to provide different amounts of support (also referred to as “firmness” in the art) in different regions of the sleeping surface. 
     Perimeter element  25  is an array of coil springs  32  of substantially the same height as foam core  20  is thick, as shown in  FIG. 2 .  FIG. 2  is a cross-section view at AA of  FIG. 1  and illustrates the relative placement of perimeter element  25  abutting side edges  17 . The term “perimeter element” is used herein to denote the entire perimeter spring array, whether it abuts one or more than one edge of foam core  20 . Accordingly, while  FIG. 1  shows a perimeter element  25  that abuts three edges of foam core  20  (to with, foot  16  and two sides  17 ), the definition of the term “perimeter element,” and the invention in general, are not limited to the configurations illustrated herein. 
     Springs  32  are of a conventional helical or semi-helical type known and used in the art today. Springs  32  may also be encased in a fabric pocket, either individually, in groups, or pocketed in strings joined by fabric, all of which are well-known in the bedding art. 
     Note also that the mattress drawn in  FIG. 1  is not drawn to scale: the perimeter element  25  is generally about two to six inches wide (measured from the sleeping surface outward to the ultimate edge of the mattress), while the overall mattress dimensions typically fall into the ranges commonly found in the trade and referred to, for example, as Twin, Full, King, Queen, Double, etc. 
     Returning to  FIG. 2 , border wires  40  of a type and construction well-known in the art are placed at the outer vertices of perimeter element  25 . Alternatively, to supply even more stiffness at the mattress edges, an additional set of border wires  40  may be placed at the inner vertices  35  of perimeter element  25  (see  FIG. 3 ). All of these border wires  40  may be used as attachment points for securing springs  32  within perimeter element  25 , as with the clips or metal “hog ring” attachment devices currently known and used in the bedding art today. 
     Although hog ring or clip attachment means are described, those skilled in the art will realize that attachment devices other than hog rings, such as plastic snap fasteners, locking cable ties, wire twists, lacing, or cord can be used. Accordingly, the invention is not limited to any particular type of attachment means for securing coils  32  to border wires  40 . 
     In some embodiments, border wires  40  may also be omitted, along with the hog ring/clip attachment means in order to reduce cost and/or manufacturing complexity. 
     Perimeter element  25  and foam core  20  are attached one to the other by planar elements  50 . Each planar element  50  is a textile material, including but not limited to a tape or webbing or open-weave material, non-woven fibers, or a coated fabric capable of heat lamination (fusion, i.e., a “fusible fabric”) to and with both foam core  20  and perimeter  25 . Alternatively, planar elements  50  may be attached by means of gluing, stitching, quilting, riveting, or welding, or by other attachment means currently known or afterwards discovered for attaching fabric-like, planar materials to both foam and metallic elements (i.e., the perimeter element&#39;s array of springs), whether or not the perimeter element consists of fabric-pocketed coils and whether or not the perimeter element is encased in a covering. 
     In one embodiment, planar elements  50  consist of strips of Weblon® or Duon® brand ticking. Duon is a polyethylene or polypropylene fiber (an olefin, generally) manufactured by Phillips Fiber Corp. 
     Planar elements  50 , which may consist of a single piece of material cut or otherwise formed to span all foam core/perimeter element interfaces or multiple strips of material that abut or overlap when they intersect, is typically about three to six inches wide, though the exact width is not critical. ( FIG. 1 , by way of example and not limitation, shows planar elements  50  as three strips of material overlapping at two intersections.) Planar elements  50  are placed on the sleeping surface of mattress  10  substantially as shown in  FIG. 2 , roughly centered on the joint formed by the abutting components and overlapping portions of both foam core  20  and perimeter element  25  prior to attachment to both. Alternatively, planar element(s)  50  may be first attached to foam core  20  before the core is brought into abutment with perimeter element  25 , in order to aid handling and manufacturing. Such an arrangement creates a foam core with a “flange” of planar element material around it. 
     Alternate Embodiments 
       FIG. 3  is an alternate embodiment of mattress  10 , shown in a cross-section view at AA (referring to  FIG. 1 ), illustrating an alternate embodiment having two sets of border wires  40 . 
     In some embodiments, planar elements  50  may be omitted entirely. In these embodiments, a perimeter element  25  consisting of pocketed coils may be glued directly to foam core  20 . 
       FIG. 4A  illustrates, in plan view, a further alternate embodiment of the invention, in which perimeter elements  25  extend around all four sides of foam core  20 . Such an embodiment is useful, for example, in bedding products for use without a headboard or footboard or when it is desirable to be able to flip the mattress from head to foot to extend the lifetime of the sleeping surfaces. Other embodiments, in which perimeter element  25  is placed on only one or only two sides or on the head or foot alone, are equally within the scope and spirit of this invention and are shown in  FIGS. 4B and 4C . 
     The order in which the steps of the present method are performed is purely illustrative in nature. In fact, the steps can be performed in any order or in parallel, unless otherwise indicated by the present disclosure. 
     In particular, as an aid to manufacturing, the planar elements may be first attached to the foam core to form a soft “flange” prior to placing the perimeter elements in abutment with the foam core (or vice-versa). Once abutting, the “flange” (unattached) portion of the planar element can be laminated or otherwise bonded to the perimeter element. 
     While particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspect and, therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit of this invention.