fig1 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 fig2 . fig2 is a cross - section view at aa of fig1 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 fig1 shows a perimeter element 25 that abuts three edges of foam core 20 ( to wit , 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 fig1 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 fig2 , 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 fig3 ). 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 . ( fig1 , 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 fig2 , 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 . fig3 is an alternate embodiment of mattress 10 , shown in a cross - section view at aa ( referring to fig1 ), 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 . fig4 a 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 fig4 b 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 .
a stiffening system for the perimeter edges of a foam core mattress comprising a coil spring structure disposed along one or more perimeter 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 .