Abstract:
A topper for selectively changing the firmness of a bed includes first and second sheets of foam which are bonded together at a flexible interface. The firmness of the first and second sheets differ, so that by putting one sheet face up on the bed one level of firmness is achieved, and by reversing the topper and putting the other sheet face up another level of firmness is achieved.

Description:
TECHNICAL FIELD 
     The present invention pertains generally to beds, and more particularly to a topper which is placed on top of a bed to change the firmness of the bed in accordance with the preference of a user. 
     BACKGROUND OF THE INVENTION 
     With the high cost of mattresses, more and more people were attempting to find a good foam mattress topper to add comfort to their existing mattress and thereby obviate the need for a new mattress. The thickness of the topper is usually between one and four inches. Over four inches would be too high to fit an existing bed, and less than one inch would not be provide enough material to provide the needed comfort needed. Toppers are typically fabricated from several variations of latex, polyurethane, and memory foams of differing indentation load deflection (ILD) and weight. 
     Patent Application U.S. 2003/0097715 illustrates a selectively contoured single unibody foam piece for use as a layer in a cushioned load bearing structure has a first zone with a first surface topography having distinct support properties from a second zone with a second surface topography. The zones of differing topography are formed in the surface of a single, unibody piece of foam by applicable foam cutting techniques. Patterned removal of foam material from a single piece creates zones with different density, ILD or other load bearing properties with different support and feel characteristics. A single unibody component in a responsive flexible support structure has distinct zones with distinct support characteristics, the zones corresponding in location with the anticipated loads and loading patterns of a flexible support device in use. 
     U.S. Pat. Re. 32,734 discloses a cushion or mattress assembly having first and second resilient support surfaces of varying firmness each secured to a center piece stiffener board. The stiffener board is formed from a plurality of hinged sections allowing flexure of the stiffener board in one direction only, as well as allowing the entire assembly to be folded or rolled up for storage. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a topper for a bed. A topper is also commonly called a foam overlay, a foam topper, and a foam mattress. The topper consists of two sheets of foam which are bonded together. The firmness of the sheets is different, so that one sheet is firmer than the other sheet. The topper is placed on top of a mattress to make the mattress more comfortable, and are reversible to provide more firmness or softness as desired without having to buy a new mattress or change to a different mattress topper. The present invention provides users with a way to make their mattress feel more comfortable with a mattress topper which has either (1) a layered feel of softness over a more supportive firm layer, or (2) a layered feel of firmness over a less supportive soft layer. This allows the user to choose a different feel if there preferences change or if another person sleeps on their mattress and has a different firmness preference. 
     However, for a mattress topper to be reversible and still have the comfort of using both layers for support, a bonding process must be used that will still allow the user to feel through both layers to the mattress below. This gives the user the benefit of the mattress below for support, with comfort of the two layered design of the topper. It also retains the ability to be reversible in feel, as the user can choose which level of softness he or she desires directly placed under their body. To retain this flexibility, but still maintain a one piece design, a very soft and flexible glue or heating process is needed to bond the two layer topper together. 
     While one layer toppers that are made out of various densities of foam were created to add comfort to an existing mattress and to allow for different softness preferences, a two layer topper with reversibility enhances comfort by going from a softer (lower ILD) and/or different density on one side, to a more firm higher ILD or densitiy on the opposite side. In a preferred embodiment of the present invention one memory foam layer that is a 10 ILD 4 lb., that is placed over a 20 ILD 5 lb. density memory foam layer. This gives a feeling of immediate softness, or a little more firmness, but either way allows the user to get cushioning over the existing mattress without loosing the support of their overall mattress. The mattress topper must be at least one inch thick and no more than four inches thick, as any less would not be enough to change the mattress feel below, and any more would be too much material and change the efficiency of the mattress support below the topper. Also, another advantage to using no more than four inches is the ease of portability from one mattress to another for purposes of travel. This is also made easier because it is made of pure foam, so it can be compressed to a very small size for traveling. 
     In accordance with a preferred embodiment of the invention, a topper for a bed comprises:
         a first sheet of foam, the first sheet having a first firmness;   a second sheet of foam, the second sheet having a second firmness different from the first firmness;   the first sheet and the second sheet bonded together in stacked aligned relationship; and,   so that the topper may be (1) placed on top of the bed with the first sheet facing upward to present a first firmness to a user, or (2) placed on top of the bed with the second sheet facing upward to present a second firmness to a user.       

     In accordance with an aspect of the invention:
         the first sheet fabricated from 10 ILD 4 lb memory foam; and,   the second sheet fabricated from 20 ILD 5 lb memory foam.       

     In accordance with another aspect of the invention:
         the first sheet and the second sheet are bonded together so that a flexible interface is created between the first sheet and the second sheet.       

     Other aspects of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a topper for a bed in accordance with the present invention; 
         FIG. 2  is a side elevation view of the topper; 
         FIG. 3  is an end elevation view of the topper; 
         FIG. 4  is a bottom plan view of the topper; 
         FIG. 5  is a perspective view of the topper; 
         FIG. 6  is an exploded perspective view showing the two foam sheets that form the topper; 
         FIG. 7  is a side elevation view of the topper placed upon a bed with a first sheet facing upward; 
         FIG. 8  is a side elevation view of the topper placed upon a bed with the second sheet facing upward; and, 
         FIG. 9  is an enlarged fragmented cross sectional view of a load being applied to the topper. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIGS. 1–5 , there are illustrated top plan, side elevation, end elevation, bottom plan, and perspective views respectively of a topper for a bed in accordance with the present invention, generally designated as  20 . Topper  20  comprises a separate overlay which is typically placed on top of the mattress of a bed (refer to  FIGS. 7 and 8 ). 
     Topper  20  includes a first sheet  22  of foam having a first firmness, and a second sheet  24  of foam having a second firmness different from the first firmness. That is, one side of topper  20  is firmer than the other side. First sheet  22  and second sheet  24  are bonded together in stacked aligned relationship. As used herein stacked aligned relationship means that one sheet is placed on top of the other sheet with the edges of the sheets aligned (as one would stack two sheets of plywood). Bonded together means that the two sheets are directly connected so that they effectively act as one thicker sheet. The bonding may be effected by a flexible adhesive or by a heating process. It is important that a ridged layer not exist between the two sheets, but rather that the interface (joint) between the sheets is flexible. Referring also to  FIGS. 7 and 8 , topper  20  may be (1) placed on top of the bed with the first sheet facing upward to present a first firmness to a user ( FIG. 7 ), or (2) placed on top of the bed with the second sheet facing upward to present a second firmness to a user ( FIG. 8 ). In a preferred embodiment of the invention, first sheet  22  is fabricated from 10 ILD 4 lb memory foam, and second sheet  24  is fabricated from 20 ILD 5 lb memory foam. This combination has been found particularly useful in that first sheet  22  provides a soft feel which rapidly conforms to a user&#39;s body, while second sheet  24  provides a firm feel which more slowly conforms to a user&#39;s body. Additionally the memory foam results in a softer feel in that once the foam is deformed, it tends to maintain the deformed state and does not “push back” at the user. 
     In a preferred embodiment of the invention, the thickness of topper  20  is between one inch and four inches. Also in the shown embodiment, first sheet  22  and second sheet  24  are of substantially equal in thickness. However embodiments having unequal thicknesses are also possible (for example 75% thickness first sheet  22 , and 25% thickness second sheet  24 ). 
       FIG. 6  is an exploded perspective view showing the two foam sheets that form topper  20 . First sheet  22  is aligned with second sheet  24  and then the two sheet are bonded together. 
       FIG. 7  is a side elevation view of topper  20  placed upon a bed  500  with a first sheet  22  facing upward. In the shown embodiment, bed  500  comprises a conventional mattress  502  and box spring  504 . However, it may be appreciated that topper  20  could also be utilized on other bed configurations, such as just mattress  502 , just box spring  504 , or even a hard surface such as a floor or the ground. 
       FIG. 8  is a side elevation view of topper  20  placed upon bed  500  with second sheet  24  facing upward. 
       FIG. 9  is an enlarged fragmented cross sectional view of a load being applied to topper  20 . First sheet  22  and second sheet  24  are bonded together so that a flexible interface  26  is created between first sheet  22  and second sheet  24 . Topper  20  is placed on top of bed  500  with first sheet  22  facing upward. When a downward load  600  (such as from the body of a user) is applied to first sheet  22 , both first sheet  22  and second sheet  24  locally compress (only compress in the immediate vicinity of the load) in response to the applied load  600 . Similarly, when topper  20  is reversed, both second sheet  24  and first sheet  22  will similarly locally compress when load  600  is applied. 
     In terms of use, a method for changing the firmness of a bed, comprises:
         (a) providing a bed  500 ;   (b) providing a topper  20  for bed  500 , topper  20  including:
           a first sheet  22  of foam, first sheet  22  having a first firmness;   a second sheet  24  of foam, second sheet  24  having a second firmness different from the first firmness;   first sheet  22  and second sheet  24  bonded together in stacked aligned relationship;   
           (c) a user selecting one of the first firmness and the second firmness; and,   (d) the user placing topper  20  on top of bed  500  so that the sheet corresponding to the selected firmness faces upward.       

     The method further including:
         (e) a second user selecting the other of the first firmness and the second firmness; and,   (f) the second user placing topper  20  of top of bed  500  so that the sheet corresponding to the selected firmness faces upward.       

     The method further including:
         in (b), first sheet  22  fabricated from 10 ILD 4 lb memory foam; and,   in (b), second sheet  24  fabricated from 20 ILD 5 lb memory foam.       

     The method further including:
         in (d), the user placing topper  20  on top of bed  500  with first sheet  22  facing upward; and,   the user applying a downward load to first sheet  22  wherein both first sheet  22  and second sheet  24  compress in response to the applied load.       

     The method further including:
         in (d), the user placing topper  20  on top of bed  500  with second sheet  24  facing upward; and,   the user applying a downward load to second sheet  24  wherein both second sheet  24  and first sheet  22  compress in response to the applied load.       

     The method further including:
         the first firmness being less firm than the second firmness;   wherein when topper  20  is placed on top of bed  500  so that first sheet  22  faces upward, topper  20  provides a feeling to a user of softness over a supportive lower layer; and,   when topper  20  is placed on top of bed  500  so that second sheet  24  faces upward, topper  20  provides a feeling to a user of firmness over a yielding lower layer.       

     Another useful feature of topper  20  is the convenience in which it may be transported. This feature is beneficial to a user who must sleep in a foreign bed  500  (such as at a motel). Since topper  20  can be easily rolled up and transported, the user can take topper  20  to the foreign bed  500 , and thereby provide a desired bed firmness. In terms of use, a method for providing a desired bed firmness to a user who must sleep in a foreign bed  500  comprises:
         (a) providing a foreign bed  500 ;   (b) providing a topper  20  for bed  500 , topper  20  including:
           a first sheet  22  of foam, first sheet  22  having a first firmness;   a second sheet  24  of foam, second sheet  24  having a second firmness different from the first firmness;   first sheet  22  and second sheet  24  bonded together in stacked aligned relationship;   
           (c) a user transporting topper to foreign bed  500 ;   (d) the user selecting one of the first firmness and the second firmness; and,   (d) the user placing topper  20  on top of bed  500  so that the sheet corresponding to the selected firmness faces upward.       

     The preferred embodiments of the invention described herein are exemplary and numerous modifications, variations, and rearrangements can be readily envisioned to achieve an equivalent result, all of which are intended to be embraced within the scope of the appended claims.