Abstract:
A mattress includes reduced-firmness materials along a central region thereof in order to mitigate the occurrence of a central ridge following repeated use of the mattress as a sleeping surface. An associated box spring may also, or instead, present a central region with reduced firmness. An adjustable member may be employed to controllably compensate for the development of a central ridge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 10/671,903, filed Sep. 26, 2003, U.S. Pat. No. 7,748,066, the entire contents of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to mattresses with center ridge compensation. 
         [0004]    2. Description of the Related Art 
         [0005]    A mattress center ridge is characterized by two disadvantages of conventional mattress. 
         [0006]    First, elevation of the surface along the center ridge is greater than the elevation of surrounding areas. Materials in a two-person mattress, such as a queen or king size mattress, become compressed in the areas of the surface where people sleep. By comparison, materials along the center of the mattress remain uncompacted, and over time present an elevated surface. The center ridge is also caused, or worsened, by the manner in which people enter and exit beds. As users sit on the edges of the mattress and roll into the mattress from the sides, materials within the mattress core are continuously urged toward the mattress&#39;s center. As a result, the center of the mattress may eventually have a greater density of material than the edges. 
         [0007]    Second, firmness at the center of the mattress may be greater than firmness across the conventional sleeping areas. This results in part from the phenomena discussed above. It is also caused by fatigue in the mattress core over repeated used. Further, box springs for large mattresses may be provided in two sections. This design may presents a rigid upper surface to the mattress along a center line where two box springs meet. 
         [0008]    There remains a need for a mattress design that prevents or mitigates the development of a center ridge. 
       SUMMARY 
       [0009]    A mattress includes reduced-firmness materials along a central region thereof in order to mitigate the occurrence of a central ridge following repeated use of the mattress as a sleeping surface. An associated box spring may also, or instead, present a central region with reduced firmness. An adjustable member may be employed to controllably compensate for the development of a central ridge. 
         [0010]    In one aspect, the invention is a mattress including a head end, a foot end, a first side and a second side; and a center region traversing the mattress from the head end to the foot end, the center region including one or more materials that mitigate the emergence of a center ridge over repeated uses of the mattress. 
         [0011]    The center region may be separated by an approximately equal distance from the first side and the second side. The mattress may be a queen size mattress or a king size mattress. The center region of the mattress may have a width of between about six inches and about twelve inches. The center region may have a firmness reduced by about ten percent to about thirty percent relative to other regions of the mattress. The mattress may include a quilted material over a sleeping surface thereof, the quilted material having a firmness in the center region reduced by about ten percent to about thirty percent relative to other regions of the mattress. The mattress may include an upholstery material over a sleeping surface thereof, the upholstery material having a firmness in the center region reduced by about ten percent to about thirty percent relative to other regions of the mattress. The mattress may include a core that has a firmness in the center region reduced by about ten percent to about thirty percent relative to other regions of the mattress. The core may include a plurality of open coil springs, a plurality of pocket springs, and/or foam, which may be viscoelastic foam. 
         [0012]    In another aspect, a box spring according to the invention may be configured for use with another box spring to support a mattress, the box spring including a head end, a foot end, an outer side configured to support an edge of a mattress above the box spring, and an inner side configured to abut a second box spring beneath a center region of the mattress, the inner side having a firmness reduced by about ten percent to about thirty percent relative to the outer side. 
         [0013]    The box spring may be used with a second box spring wherein the box spring and the second box spring may be placed side by side to present a support surface to a mattress, the support surface having a center region along the inner side of the box spring and an inner side of the second box spring with a firmness reduced by about ten percent to about thirty percent relative to the outer side of the box spring and an outer side of the second box spring. The box spring may include a core including one or more open coil springs and/or one or more pocket coil springs. 
         [0014]    In another aspect, a mattress according to the invention may include a head end, a foot end, a first side and a second side, and a center region traversing the mattress from the head end to the foot end, the center region including one or more materials having a firmness reduced by about ten percent to about thirty percent relative to other regions of the mattress. The center region may be separated by an equal distance from the first side and the second side. 
         [0015]    In another aspect, a mattress according to the invention may include a head end, a foot end, a first side and a second side, a center region separated from the first side and the second side and traversing the mattress from the head end to the foot end, and a compensation means for reducing a firmness of the center region by about ten percent to about thirty percent relative to other regions of the mattress. 
         [0016]    In another aspect, there is disclosed a method for manufacturing a mattress including constructing a first region and a second region of one or more materials having a first firmness, the first region and the second region being configured to provide a sleeping surface to one or more users of the mattress, and constructing a center region between the first region and the second region, the center region being constructed of one or more materials that together have a second firmness less than the first firmness. The second firmness may be reduced by about ten percent to about thirty percent relative to the first firmness. 
         [0017]    In another aspect, a mattress according to the principles of the invention may include a head end, a foot end, a first side and a second side; and a center region traversing the mattress from the head end to the foot end, the center region including one or more adjustable members controllable to adjust the center region in response to an emerging center ridge 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    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: 
           [0019]      FIG. 1  shows a cutaway perspective view of a mattress with center ridge compensation; and 
           [0020]      FIG. 2  shows a pair of box springs with center ridge compensation. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Described herein is a mattress having a center ridge compensation system that mitigates the development of a center ridge over repeated uses of the mattress. However, it will be appreciated that the principles of the system described herein may be adapted to a wide range of applications where a cushioned surface is subjected to repetitive stresses over less than all of the surface. For example, the principles of this disclosure may be applied to automotive seats or couches where a user typically sits in certain locations. The systems described herein may also be used in padded outdoor furniture or on any other surface where a compensation system can advantageously mitigate the development of an undesired ridge over repeated uses. 
         [0022]      FIG. 1  shows a cutaway perspective view of a mattress with center ridge compensation. The mattress  100  may include a center region  102  and one or more side regions  104 , each abutting a side  106  of the mattress, a head end  108 , and a foot end  110 . The mattress  100  may include one or more quilting layers  112 , one or more upholstery layers  114 , a core  116  including, for example, a plurality of springs  118  to support a sleeper using the mattress, and one or more adjustable members  120 . 
         [0023]    The mattress  100  may be, for example, a queen size mattress or a king size mattress, or any other mattress of conventional or unconventional dimensions. Typically, the mattress  100  will be of a size for more than one concurrent user. As will be described in greater detail below, the mattress  100  may be of any general construction, and may employ, for example, a foam core, an open spring core, or a pocket spring core to provide a suitable sleeping surface. The mattress may be designed for use in two orientations, in which case both an upper and lower surface of the mattress will include a ridge compensation system as described herein, or the mattress may be a no-flip mattress that is designed for use in one or two orientations with a single upper surface. In this latter case, ridge compensation is only required for the single upper surface. 
         [0024]    The center region  102  extends from the head end  108  to the foot end  110  of the mattress  100 , and may be separated from the sides  106  by side regions  104 . It is generally expected that users of the mattress will sleep in the side regions  104  and not in the center region  102 . In certain embodiments, the center region  102  may not extend fully to the head end  108  and the foot end  110 . The center region  102  may be of any suitable width, such as two inches to twelve inches, or any other width according to the size of the mattress  100  and the regions where sleepers are expected to repose. It will also be appreciated that the center region  102 , while depicted as parallel to the sides  106 , may vary in width along the length of the mattress  100 , and may be, for example, wider near the head end  108  and the foot end  110 , or narrower at the ends  108 ,  110  and wider between the ends  108 ,  110 . The shape may be varied according to considerations of cost, materials, or expected regions of use of the mattress  100 . It will also be appreciated that the center region  102  may be asymmetric in profile (either in width along the sleeping surface or in thickness and firmness of center ridge compensating materials), depending on the number of orientations for which the mattress  100  is intended to be used. 
         [0025]    The one or more quilting layers  112  may include any suitable or conventional mattress quilting materials, and may be quilted in any manner to provide a desired texture or appearance to an exterior surface of the mattress  100 . The one or more quilting layers  112  may have increased firmness in the center region  102  that mitigates the development of a center ridge between the side regions  104 . This increased firmness may be achieved, for example, by the use of additional quilting layers in the center region  102 , or the use of reinforcing materials such as plastic sheets or fibers within or between the one or more quilting layers  112 , or any other suitable material or materials for increasing firmness. The relative firmness in the center region  102  and the side regions  104  may be measured using Indentation Deflection Force (“IDF”) or any other suitable, objective scale used in the mattress making or cushioning arts. In one embodiment, the firmness of the one or more quilting layers  112  is ten percent to thirty percent firmer in the center region  102  than in the abutting side regions  104 . The transition from the relatively firm center region  102  to the relatively less firm side regions  104  may be smooth or abrupt, according to the desired feel of the mattress and the materials used to enhance the firmness of the one or more quilting layers  112 . 
         [0026]    The one or more upholstery layers  114  may include, for example, padding, batting, waterproof or water absorbent materials, or any other suitable layers for use with the mattress  100  that may be employed for comfort, longevity, or specific functional features desired for the mattress  100 . The one or more upholstery layers  114  may have increased firmness in the center region  102  that mitigates the development of a center ridge between the side regions  104 . This increased firmness may be achieved, for example, by the use of additional upholstery layers in the center region  102 , or the use of reinforcing materials such as plastic sheets or fibers within or between the one or more upholstery layers  114 , or any other suitable material or materials for increasing firmness. The relative firmness in the center region  102  and the side regions  104  may be measured using Indentation Deflection Force (“IDF”) or any other suitable, objective scale used in the mattress making or cushioning arts. In one embodiment, the firmness of the one or more upholstery layers  114  is ten percent to thirty percent firmer in the center region  102  than in the abutting side regions  104 . The transition from the relatively firm center region  102  to the relatively less firm side regions  104  may be smooth or abrupt, according to the desired feel of the mattress and the materials used to enhance the firmness of the one or more upholstery layers  112 . 
         [0027]    The core  116  may be of any conventional or unconventional construction suitable for use in a sitting, sleeping, or reclining surface such as the mattress  100 . Although coils  118  are depicted in the core  116  of  FIG. 1 , it will be appreciated that any material or materials may be used in the core  116 , including open coils, pocket coils, a monolithic or composite foam (such as viscoelastic foam), fluids or gasses in one or more bladders, and so forth, or any combination of these. The core  116  may have increased firmness in the center region  102  that mitigates the development of a center ridge between the side regions  104 . This increased firmness may be achieved, for example, by the use of additional springs, stiffer springs, springs that are smaller and more densely packed, firmer materials (for, e.g., foam or air bladders), and so forth. The relative firmness in the center region  102  and the side regions  104  may be measured using Indentation Deflection Force (“IDF”) or any other suitable, objective scale used in the mattress making or cushioning arts. In one embodiment, the firmness of the core  116  is ten percent to thirty percent firmer in the center region  102  than in the abutting side regions  104 . The transition from the relatively firm center region  102  to the relatively less firm side regions  104  may be smooth or abrupt, according to the desired feel of the mattress and the materials or techniques used to enhance the firmness of the core  116 . 
         [0028]    One or more adjustable members  120  may be provided to adjust firmness within the center region  102  or to compensate for the development of a ridge within the center region  102  as the mattress ages. The one or more adjustable members  120  may include, for example, one or more air bladders, pneumatic cylinders, or other adjustable members  120  within the center region  102  that controllably stiffen or elevate this region of the mattress, or controllably reduce the stiffness to remove an emerging center ridge. Any other type of adjustable member suitable for use within a mattress may be suitably employed, such as hydraulically adjustable devices or adjustable springs. The one or more adjustable members  120  may be placed along the center region  102  within the core  116 , the quilting layers  112 , and/or the upholstery layers  114 . Although not depicted in  FIG. 1 , it will be appreciated that the adjustable members  120  may also, or instead, be placed along the side regions  104  so that the side regions  104  may be stiffened or raised in response to an emerging center ridge. 
         [0029]      FIG. 2  shows a pair of box springs with center ridge compensation. The box springs  200  may be of a conventional box spring construction, and each box spring  200  may include an assembly of wire springs  202 , a padded upper surface  204 , a head end  205 , a foot end  206 , ticking (not shown), a dust cover  208 , an inner side  210  and an outer side  212 . 
         [0030]    The box springs  200  may be of a size to be supported on a bed frame (not shown) that raises the box springs  200  to a desired level above the floor. The assembly of wire springs  202  may instead be any non-resilient or semi-resilient structure attached to a rigid frame (not shown) located at a bottom of the box spring  200 . The padded upper surface  204  may optionally be included on a top surface of the box spring  200 . The ticking  206  may encase the entire box spring  200 , and may be sewn together around a periphery of the box spring  200  and/or stapled or otherwise attached to a border of the box spring  200  or the rigid frame. The dust cover  208  may be fashioned of light plastic film or a like material and applied to the underside of the rigid bottom frame to prevent accumulation of dust and other particles or debris within the box spring  200 . 
         [0031]    The inner side  210  of each box spring  200  is intended to abut an inner side  210  of another box spring  200  so that, in tandem, the box springs  200  present a surface to support a correspondingly sized mattress. The outer side  212  of each box spring  200  may be aligned below an outer edge of the mattress  100  of  FIG. 1 . The inner side  210  may be firmer than the outer side  220  so that ridge compensation is provided. This may be accomplished, for example, by providing stiffer guide wires or other materials along the inner side  210 , or adding additional springs or supports along the inner side  210 . These or other techniques may be readily adapted to provide a firmer inner side  210  for the box springs  200 . 
         [0032]    While box springs  200  may be manufactured in pairs so that each individual, rigid box spring  200  may be readily moved through doors or other openings, it is also possible to have a single box spring  200 . Any of the reinforcement techniques used above may be adapted to such a box spring to provide increased firmness in an area corresponding to the center region of a mattress. 
         [0033]    More generally, other constructions than the single or dual box springs noted above may be employed to provide a foundation for the mattress  100  of  FIG. 1 , and may be constructed to provide increased firmness in an area corresponding to the center region  102  of the mattress  100 . 
         [0034]    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 the scope of the invention, and therefore, the following claims are to be interpreted in the broadest sense allowable by law.