Patent Publication Number: US-9408485-B2

Title: Bed pillow

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 14/221,345, filed Mar. 21, 2014, hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This relates to bed pillows. 
     SUMMARY 
     A bed pillow is made of elastic foam material. The pillow&#39;s top surface extends along both a longitudinal direction and a lateral direction that are mutually perpendicular, follows a top undulating pattern in the longitudinal direction, and is uniform in the lateral direction. The pillow&#39;s bottom surface is opposite the top surface, follows a bottom undulating pattern in the longitudinal direction, and is uniform in the lateral direction. The pillow&#39;s front surface and a rear surface extend from the top surface to the bottom surface, and are uniform in the lateral direction. The pillow has two laterally-opposite parallel planar side surfaces that extend from the top surface to the bottom surface and extend from the front surface to the rear surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an example mattress. 
         FIG. 2  is an exploded view of the mattress. 
         FIG. 3  is a perspective view of a core of the mattress. 
         FIG. 4  is an expanded view of a top surface of a lower section of the core. 
         FIG. 5  is an expanded view of a top surface of an upper section of the core. 
         FIG. 6  is a schematic sectional view of the mattress, taken at line  6 - 6  of  FIG. 1 , illustrating airflow paths in the mattress. 
         FIG. 7  is a section view of the mattress, taken at line  8 - 8  in  FIG. 1 . 
         FIG. 8  is a sectional view, similar to  FIG. 8 , showing a second example mattress having two cores like the core shown in the  FIGS. 1-8 . 
         FIG. 9  is a perspective view of a pillow assembly that is well suited for use with the mattress. 
         FIG. 10  is a side view of the pillow assembly. 
         FIG. 11  is a perspective exploded view of the pillow assembly. 
         FIG. 12  is an exploded side view of the pillow assembly. 
         FIGS. 13-15  are side views of other pillow assemblies that can be assembled from the pillows shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  respectively show an assembled view and exploded view of an example bed mattress  1 , which might typically overlie a bed frame, box sprint or other flat surface (e.g., floor). The mattress  1  includes a foam core  10  comprising an softer upper core section  11  and a firmer lower core section  12 , encased in a flexible encasement  13 , and topped by a flexible topper pad  14 . 
     Referring to  FIG. 3 , the softer and firmer core sections  11 ,  12  are made of Elio-cell foam, which is an open-cell breathable polyurethane foam. The softer core section  11  overlies the firmer section  12 , with reference to the core&#39;s orientation shown in  FIGS. 1-2 . The softer upper core section  11  has six peripheral surfaces: a top surface  11 T, a bottom surface  11 B, a front end surface  11 F, a rear end surface  11 R and two opposite side surfaces  11 S. Similarly, the firmer lower core section  12  has six peripheral surfaces: a top surface  12 T, a bottom surface  12 B, a front end surface  12 F, a rear end surface  12 R and two opposite side surfaces  12 S. All of the core&#39;s peripheral surfaces are planar, except for the softer core section&#39;s bottom surface  11 B and the firmer core section&#39;s top surface  12 T. 
     In the following description of mattress components, a “longitudinal” direction (arrow “A” in  FIG. 3 ) extends from the front surface  11 F to the rear surface  11 R and is parallel with the side surfaces  11 S. A “lateral” direction (arrow “B” in  FIG. 1 ) extends from one side surface  11 S to the other side surface  11 S and is parallel with the front surface  11 F and the rear surface  11 R. 
     As shown in  FIG. 3 , the softer upper section&#39;s bottom surface  11 B and firmer lower section&#39;s top surface  12 T share a common nonuniformly undulating pattern P. These surfaces  11 B,  12 T are mating surfaces that matingly contact each other (are adjoined) along their entire lengths and widths to define an interface that embodies the common pattern P. The mating contact may be non-adhering and removable, by surface  11 B simply resting on surface  12 T. Or the mating contact may be adhering contact, such as by adhesive or melting. The softer core section&#39;s front, rear and side surfaces  11 F,  11 R,  11 S are respectively coextensive with the firmer core section&#39;s front, rear and side surfaces  12 F,  12 R,  12 S, so that each peripheral surface—front, rear and side  10 F,  10 R,  10 S—of the core  10  is flat (planar) from top  10 T to bottom  10 B and from front  10 F to rear  10 R. 
     The interface pattern P is undulating in the longitudinal direction A. The pattern P is uniform in the lateral direction B, such that that an intersection of the interface P with a vertical laterally-extending plane at any longitudinal location yields a straight horizontal line. 
     The undulating pattern P has three types of features: plateaus P 1 , P 2 , P 3 ; hills H 1 , H 2 ; and valleys V 1 , V 2 . The locations of these core features in this example can be defined by the following approximate X,Y coordinates, in centimeters, with respect to a coordinate origin (0,0) located at the rearmost point of the interface. The core&#39;s top surface  11 T is uniformly 9 cm above the origin. The core&#39;s bottom surface  12 B is uniformly 13 cm below the origin. P 1  (first plateau) extends from (0,0) to (32,0). H 1  (first hill) extends from (32,0) to (64,0) and peaks at (47,3). V 1  (first valley) extends from (64,0) to (88,0) and is deepest at (76,−3). P 2  extends from (88,0) to (107,0). H 2  extends from (107,0) to (135,0) and peaks at (123,2). V 2  extends from (135,0) to (168,0) and is deepest at (152,−3). P 3  extends from (168,0) to (200,0). 
     These features of the interface pattern P are located with respect to parts of a body of an adult person lying on the mattress  1  with his/her head adjacent the front surface. P 1  is configured to be under a person&#39;s feet. H 1  is configured to be under the person&#39;s leg calves. V 1  is configured to be under the person&#39;s thigh. P 2  is configured to be under the person&#39;s buttocks. H 2  is configured to be under the person&#39;s back. V 2  configured to be under the person&#39;s shoulders. P 3  is configured to be under the person&#39;s head. The undulatory interface pattern, combined with the difference in firmness between the softer and firmer core sections, helps keep the spine and legs of a person, while lying on back, side or stomach, straighter than if the interface pattern P was planar. The undulating pattern P also augments the interface adhesive&#39;s function of reducing longitudinal movement of the softer core section  11  relative to the firmer core section  12 . 
     The firmer core section&#39;s top surface  12 T is interrupted by three groups  21 ,  22 ,  23  of laterally-extending internal grooves  20 . In this example, the first group  21  is located below where the person&#39;s leg calves would be. The second group  22  is located below where the person&#39;s pelvis would be. The third group  23  is located below where the person&#39;s shoulders would be. The first group  21  extends only along plateau P 1  and hill H 1  (mentioned above). The second group  22  extends only along plateau P 2 . The third group  23  extends only along valley V 2 . 
     In this example, the internal grooves  20  are alike. Each groove  20  extends laterally from one side surface  12 S of the firmer section  12  to the opposite side surface  12 S. A first group-spacing distance GS 1  between the first and second groups  21 ,  22 , and a second group-spacing distance GS 2  between the second and third groups  22 ,  23  are each at least five times the groove-spacing distance GS between neighboring internal grooves  20  within each group  21 ,  22 . 
     In this example, the first, second and third groups  21 ,  22 ,  23  respectively have seven, four and seven internal grooves  20 . GS is about 2 cm, GS 1  is about 35 cm, and GS 2  is about 31 cm. The first group  21  is spaced about 31 cm from the rear surface  10 R, and the third group  23  is spaced about 35 cm from the front surface  10 F. 
       FIG. 4  is an expanded view of one of the internal grooves  20 . Each internal groove  20  has a rectangular cross-section, with planar side surfaces  20 S that are about 1.5 cm deep (measured from the firmer core section&#39;s top surface  12 T). Each internal groove  20  further has a planar base surface  20 B that is 2 cm wide and parallel with the firmer core section&#39;s top surface  12 T in the vicinity of the groove  20 . 
     As shown in  FIG. 3 , the groove-spacing distance GS, which is the spacing between adjacent grooves  20  within each group is about 3 cm. In this example, the firmer lower core section  12  has at least ten grooves  20 , and each groove  20  is at least 0.6 cm deep and at least 1.3 cm wide, and has a ratio of depth to width in the range 0.25-0.75. Unlike the firmer core section&#39;s top surface  11 T, the groove&#39;s base surface  20 B does not adjoin or support the softer core section  11  but is instead spaced vertically away from the top core section  11 . 
     The areas of the mattress  1  that are directly over the internal groove groups  21 ,  22 ,  23  will feel less firm to a person lying on the mattress  1 , and will deflect more under the person&#39;s weight, than areas of the mattress  1  that are not directly over the groove groups  21 ,  22 ,  23 . This helps the user&#39;s legs, calves, pelvis and shoulders sink more deeply into the mattress  1  than other parts of the person&#39;s body. The combination of the firmness difference between the softer and firmer core sections  11 ,  12 , the undulating interface pattern P, and the groove configuration are together designed to help keep the person&#39;s spine and legs straight. 
     Between each adjacent pair of internal grooves  20  is an internal upward projection  26  of the foam material of the lower core section  12 . Each projection  26  extends laterally from one side  12 S of the lower core section  12  to the opposite side  12 S. Each projection  26  is bounded longitudinally by neighboring grooves  20  and is bounded from above by, and adjoins, the upper core section&#39;s bottom surface  11 B. The projections  26  laterally reinforce the lower core section&#39;s top surface  12 T, which tends to keep to the profile of core  10  in the lateral direction more uniform than its profile in the longitudinal direction. When the core&#39;s top surface  11 T deflects downward under the weight of a person, the projections  26  reduce the downward bow in the lateral direction but not in the longitudinal direction. 
     The top surface  11 T of the core  10  in this example is interrupted by three groups of laterally-extending external upper grooves  30 . The upper grooves  30  are alike in size and shape. Each upper groove  30  extends laterally from one side surface  11 S of the core  10  to the opposite side surface  11 S. The first upper group  31  is located under where the person&#39;s feet would be, and is longitudinally centered approximately directly above the rearmost one of the internal grooves  20 . The second upper group  32  is located under where the person&#39;s pelvis would be, and is longitudinally approximately centered directly above the longitudinal center of the second internal groove group  22 . The third upper group  33  is located under where the person&#39;s head would be, and is longitudinally approximately centered directly above the frontmost one of the internal grooves  20 . 
     The bottom surface of the lower core section  12  in this example is also interrupted by three “lower” groups  41 ,  42 ,  43  of laterally-extending lower external grooves  40 , identical in number, size, shape and longitudinal positioning as the upper external grooves  30 . 
     All of the external grooves  30 ,  40  are alike. They are described as follows with reference to one of the upper external grooves  30  shown in  FIG. 5 . Each external groove  30  has planar side surfaces  30 S that are vertical (i.e., perpendicular to the top surface  11 T) and a circular base surface  30 B. Each external groove  30  is about 1.3 cm deep and about 0.3 cm wide, yielding a depth-to-width ratio of about 4.0, and its circular base surface follows a 0.4 cm radius. The external grooves  30  are longitudinally spaced apart on approximately 3 cm centers, leaving about 5.6 cm between neighboring grooves  30 . The ratio of groove on-center spacing to groove depth is about 5. The external grooves ( 30  when the softer core section  11  is on top, and  40  when the firmer core section  12  is on top) provide a softer, more cushiony, feel to the person&#39;s body, especially at the pressure points of the feet, pelvis and head, by enabling the core section&#39;s external surface to conform to a person&#39;s body curves better than if the grooves were absent. 
     Each adjacent pair of external upper grooves  30  defines an external upper projection  36  of foam material of the upper core section  11 . Similarly, each adjacent pair of external lower grooves  40  defines an external lower projection  46  of the foam material of the lower core section  12 . Each external projection  36 ,  46  extend laterally from one side  10 S of the core  10  to the opposite side  10 S of the core  10 . The projections  36 ,  46  reinforce the core  10  in the lateral direction and not in the longitudinal direction. 
     As shown in  FIGS. 3-5 , the core  10  has an array of vertical air channels  50 . In this example, the channels  50  are alike. Each channel  50  extends vertically from the core&#39;s bottom surface  12 B to the core&#39;s top surface  11 T. Each channel  50  is cylindrical, with a diameter of approximately 0.6 cm, and extends straight through both sections  11 ,  12  of the core  10 . The channels  50  can be made by boring the core  10  after the core&#39;s softer and firmer sections  11 ,  12  are adhered together. The channels  50  are arranged in an array (matrix), with rows perpendicular to columns, and with the rows and the columns both evenly spaced apart by a same distance, which in this case is about 2.8 cm. The array is angled at 45 degrees to both the longitudinal direction and the lateral direction. Therefore, the channels  50  are spaced apart by approximately 4 cm with reference to the lateral direction and with reference to the longitudinal direction. The number of channels  50  is preferably at least thirty. 
       FIG. 6  illustrates possible airflow paths  51  through the grooves  30 ,  40  and channels  50 . As shown, air can flow both left and right through the horizontal grooves  30 ,  40  and both upward and downward through the vertical channels  50 . Most of the vertical channels  50  terminate at the core&#39;s top and bottom surfaces  11 T,  12 B. Some vertical channels  50  terminate in the external grooves  30 ,  40 , in that some extend downward from one of the external upper grooves  30  to the bottom  12 B and upward from one of the lower grooves  40 . Some vertical channels  50  are intercepted by the internal grooves  20 . This provides many possible airflow paths  51 , which ultimately extend through the porous panels ( 13 T,  13 B,  13 F,  13 R and  13 S) of the encasement  13 . Which airflow paths are active and which directions air flows through the active paths can depend on how the mattress is compressed and released with body movements. The airflow  51  can be caused by bellows action or peristaltic pump action due to moving body compression of the grooves  30 ,  40  and channels  50 . The airflow  51  can also be caused by air temperature differentials between different zones of the core  10 . 
     As shown in  FIG. 2 , in this example, the encasement  13  encases the core  10  in that it covers all six sides (top, bottom, front, rear and two sides) of the core  10 . The encasement  13  has six flexible panels: a top panel  13 T, a bottom panel  13 B, and four peripheral panels comprising a front panel  13 F, a rear panel  13 R and two side panels  13 S. The peripheral panels are adjoined (e.g., stitched) along their top edges to the top panel  13 T and along their bottom edges to the bottom panel  13 B. The top panel  13 T is softer (less firm, less stiff) than the bottom panel  13 B. 
     A zipper  60  (portrayed as two separated zipper halves in  FIG. 2 ) is vertically centered between the upper and lower panels  13 U,  13 L. The zipper  60  extends horizontally around the entire periphery of the encasement  13 , except for a living hinge section  62  of the front panel  13 F. The living hinge  62  is located between opposite ends of the zipper, which are spaced laterally apart by a spacing distance in the range 8-16 cm. The encasement  13  includes an upper section  13 U located above the zipper  62  and a lower section  13 L located below the zipper  62 . As shown in  FIG. 2  a user may unzip the zipper  60  and lift the encasement&#39;s upper section  13 U from its lower section  13 L about the living hinge  62 , to insert the core  10  into the encasement  13  or remove the core  10  from the encasement  13 . 
     As shown schematically in  FIG. 7 , each panel  13 T,  13 B,  13 F,  13 R,  13 S of the example encasement  13  includes four layers that are stitched together both along their peripheries and also along meandering paths (not shown) that are spaced away from the peripheries. 
     The encasement&#39;s top panel  13 T has the following four layers: 
     The first (lowest and closest to the core) layer  61  of the top panel  13 T is a carbon fabric, comprising a 48% polypropylene, 46% polyester, 5.5% polyamid and 0.5%/carbon fabric. The carbon enhances electrical conductivity. The electrical conductivity of this layer  61  provides EMF shielding. It also provides electrical grounding when connected to a grounding terminal. 
     The second layer  62  of the top panel  13 T is an open cell memory foam. It is a memory foam in that is viscoelastic (low-resilience). It releases pressure points on the body and does not restrict or constrict blood circulation. Its open cell structure enables fresh air to enter the mattress, and does not retain moisture, which reduces bacteria, mold and odors. 
     The third layer  63  of the top panel  13 T is a flame barrier. It may comprise a blend of 90% viscose fire retardant yarn and 10% polyester. 
     The fourth (outer) layer  64  of the top panel  13 T is a CLIMA 3-D AIR CHAMBER fresh air system. It is a flexible pad comprising an upper sheet, a lower sheet and microfibers. Each microfiber projects vertically upward from the lower sheet to the upper sheet to space the upper sheet from the lower sheet. The fibers have a density of tens of thousands of fibers per square inch. The fibers create tiny air chambers which allow the mattress to regulate body temperature, keeping the mattress and the person&#39;s body cooler in summer and warmer in winter. The fibers also relieve pressure points on the body. 
     The bottom panel  13 B of the encasement  13  has the following four layers: 
     The first (closest to the core) layer  71  of the bottom panel  13 B is the carbon fabric described above. It enhances electrical conductivity and reduces EMF. 
     The second layer  72  of the bottom panel  13 B is a 100% polyurethane foam 6.5 mm thick. 
     The third layer  73  of the bottom panel  13 B is the flame barrier described above. 
     The fourth layer  74  of the bottom panel  13 B is a forial cover fabric. It has a fire retardant treatment. It also has silver fibers that enhance electrical conductivity and inhibit bacteria growth and odors. The electrical conductivity of this layer  74  provides EMF shielding. It also provides electrical grounding when connected to a grounding terminal. 
     The peripheral panels  13 F,  13 R,  13 S share the same three layers. They are described as follows with reference to the side panels  13 S shown in  FIG. 7 : 
     The first (closest to the core) layer  81  of the side panel  13 S is the carbon fabric described above. 
     The second layer  82  of the side panel  13 S is the flame barrier described above. 
     The third layer  83  of the side panel  13 S is a forial cover fabric, like the forial cover fabric described above. It has a fire retardant treatment. It also has silver fibers that enhance electrical conductivity and inhibit bacteria growth and odors. 
     Each panel  13 T,  13 B,  13 F,  13 R and  13 S of the encasement  13  includes an electrically conductive layer and is thus itself electrically conductive. This reduces static electricity and static shocks, and also shields the person (lying on the mattress) from electromagnetic fields (EMF) generated within the home (e.g., by electrical wiring and electronic devices within the home) and EMF generated outside the home (e.g., radio signals). 
     As shown in  FIG. 1 , the mattress topper  14  has the same peripheral size and shape as the encasement  13 . The topper  14  is configured to be placed on the encasement  13  to provide extra comfort, electrical conductivity, and bacterial inhibition. It also reduces pressure points on the core  10  and encasement  13  to increase their service life. 
     With reference to  FIG. 7 , the topper  14  has the following four layers: 
     The first (lowest, closest to the encasement) topper layer  91  is a blend of 51% polypropylene and 42% polyester, interwoven with 4.5% Lurex silver fibers and 2.5% polyester silver fibers. The silver fibers enhance electrical conductivity and inhibit bacterial growth, creating a 99.9% bacterial free environment. This layer  91  provides EMF shielding. It also provides electrical grounding when connected to a grounding terminal. 
     The second topper layer  92  is an open cell polyurethane foam pad. It is a “memory” foam in that it is viscoelastic (low-resilience). It has silver ions that inhibit bacteria growth (yielding 99.9% bacteria free environment) and odors, which would otherwise be enhanced to the person&#39;s warm sweat. It also releases body pressure points and enables improved blood circulation. Its open cell arrangement allows fresh air to enter the mattress. This layer  92  also does not retain moisture, which further reduces the occurrence of bacteria, mold and odors. 
     The third topper layer  93  is a flame barrier like the flame barrier described above. 
     The fourth (top) topper layer  94  is a forial cover fabric described above. 
     The topper  14 , like the encasement  13 , includes electrically conductive layers and is thus itself electrically conductive. This reduces static electricity and static shocks, and also shields the person (lying on the mattress) from electromagnetic fields (EMF) generated within the home (e.g., by electrical wiring and electronic devices within the home) and EMF generated outside the home (e.g., radio signals). 
     The encasement  13  and the topper  14  can each be electrically grounded as follows. Metal grounding terminals  100 , in this example electrical connector buttons, are attached (e.g., riveted) to the encasement  13  and to the topper  14 . The mattress  1  may be supplied with at least one electrical grounding wire cable  110  (cord) ( FIG. 1 ). In this example, the grounding cable  110  has a clip terminal  111  at one end that can connected to (e.g., snapped onto) any one of the grounding buttons  100 . The cable  110  has a ground terminal  112  at its opposite end that can be connected (attached) to an electrical ground (grounded metal, grounding source) to ground the encasement  13  and/or topper  14 . The ground terminal  112  might be, for example, an adapter plug with a prong that can be plugged into a ground terminal of a wall socket, which can be used with a wall socket of any voltage (e.g., 110 VAC, 220 VAC). The ground terminal  112  might include an alligator clip to be connected to any grounding source. An example grounding source is a metal water pipe. Another example grounding source is a metal rod that may be sold to the user along with mattress, for the user to embed into the earth him/herself. The cable  110 , when connected to the buttons  100  of the encasement  13  and/or the topper  14 , grounds the encasement  13  and the topper  14  and the person lying on them. The grounding reduces static electricity and static shocks, and also improves the EMF shielding. 
     When the mattress user plans to travel and stay overnight at a location away from home, he/she may roll up the topper  14  and cable  110  and take them along on the trip. The person may lie the topper  14  over a mattress where the person is lodging, and use the cable  110  to ground the topper  14 . The topper  14  will then provide the benefits of bacteria inhibition, extra comfort, EMF shielding and electrical grounding to the person while away from home. Those same benefits are provided to a person lying on the encasement  13  without the topper  14  present. The topper  14  and cable  110  may be purchased even without the mattress, and laid on any surface (e.g., a standard mattress) to obtain the advantages that the topper  14  provides. 
     As shown in  FIG. 2 , the topper  14  is configured to be removably attached to the encasement by zipper halves  120 ,  121 . One zipper half  120  extends about the entire periphery of the topper  14 . A mating zipper half  121  extends about the entire periphery of the encasement&#39;s top panel  13 T, for attaching (zipping) the topper  14  to the encasement&#39;s top panel  13 T if desired. Another mating zipper half is  122  extends about the entire periphery of the encasement&#39;s bottom panel  13 B, for attaching (zipping) the topper  14  to the encasement&#39;s bottom panel  13 B in case the user inverts (flips upside down) the encasement  13  and sleeps on the bottom panel  13 B. 
     The mattress  1  can provide four user-selectable levels of firmness when lying on the mattress  1 . This is enabled by three factors: (1) The encasement&#39;s top panel  13 T is softer than its bottom panel  13 B. (2) The difference in firmness between the softer and firmer core sections  11 ,  12  is more pronounced than the difference in firmness between softer and firmer encasement panels  13 T,  13 B. (3) The zipper  90  enables the core  10  to be easily removed from the encasement  13  and inverted and reinserted. Extra soft level is achieved by having the softer core section  11  and the softer encasement panel  13 T on top. Medium soft is achieved by having the softer core section  11  and the firmer encasement panel  13 B on top. Medium firm is achieved by having the firmer core section  12  and the softer encasement panel  13 T on top. Extra firm is achieved by having the firmer core section  12  and the firmer encasement panel  13 B on top. 
       FIG. 8  shows a second example mattress  13 ′ that is best suited for king and queen size. This mattress  13 ′ includes two cores  10 , each like the core  10  described above, lying side by side within a single encasement  13  like the encasement described above. One person can lie above one core  10  and another person can lie above the other core  10 . Each core  10  can be inverted (in the manner a described above) independent of the orientation of the other core  10  and independent of the orientation of the encasement  13 . This provides independently-adjustable comfort zones for the two people laying on the mattress  13 ′. For example, in  FIG. 8 , one core  10  has its softer section  11  on top, and the other core  10  has its firmer section  12  on top. Since three components—the encasement  13  and the two cores  10 —has two orientations (upright and inverted), this second mattress  13 ′ provides eight firmness configurations. 
     Referring to  FIG. 3 , the firmness felt by the user depends on which core section  11 ,  12  is on top. Therefore, the core  10  may include indications that indicate (distinguish) to a user which core section is the firmer section  12  and which is the softer section  11 . In  FIG. 3 , the indication includes a marking  131 , such as text imprinted on the core&#39;s foam itself or imprinted on labels adhered to the core&#39;s foam, stating “FIRMER SECTION” or “SOFTER SECTION”. The indication may also include a difference in color between the softer section  11  and the firmer section  12 , with the user being informed which color corresponds to which core section. 
     As described above regarding  FIG. 3 , the undulating interface pattern P of the interface  11 B provides different firmnesses at longitudinally-different locations along the top surface  11 T. Since the lower core section  12  is firmer than the upper core section  22 , firmness at any location along the core  10  is a positive function of thickness of the lower core section  12  at that location. So, for example, the core  10  is firmer over the hills H 1 , H 2  than over the valleys V 1 , V 2 . Since the core&#39;s interface pattern P is not longitudinally symmetric, neither is the core&#39;s firmness pattern P. Therefore, a user lying in a forward orientation with his/her head adjacent the core&#39;s front end  10 F would experience a different feel than a user lying in a reverse orientation with his/her head adjacent the rear end  10 R. For example, in the forward orientation, the user&#39;s shoulders are over a valley (V 2 ), which provides extra softness that lets the shoulders sink lower into the core  10  than the rest of the body, which helps keep the user&#39;s spine straight. In contrast, if the user lies in the reverse orientation, his/her shoulders will be over a hill (H 1 ) which provides extra firmness that resists the shoulders sinking into the core  10 . 
     Accordingly, the feel of the mattress  10  depends on the person&#39;s longitudinal orientation relative to the core  10 . Therefore, the core  10  may include an indication  132  that differentiates (distinguishes), for the user, the core&#39;s front  11 F from its rear  11 R. The indication might include markings  132  on the core  10 , such as text on a label stating “HEAD HERE”, “FEET HERE”, “FRONT END” or “REAR END”. The indication might also include highlighting of the path P of the interface. This highlighting may be achieved by the upper core section  11  having a different color than the firmer core section  12  (as described above), so that the boundary between the two colors follows the interface. The user may also recognize from the pattern of the color boundary which end is front and which is rear. Also, since the user realizes that firmness at any location is a positive function of the height of the color boundary (with reference to the firmer core  12  section being on the bottom), the color boundary serves as a graph of the core&#39;s firmness versus longitudinal location. The graph reveals the core&#39;s firmness pattern, so the user can make an informed decision as to what location (of the mattress) and what longitudinal orientation he/she should lie or sit in. 
     The inventors have found that, counter-intuitively, the preferred lying orientation (based on comfort) among people who have tried out this mattress, tends to depend on which of the core sections is on top. Specifically, people prefer the forward orientation (head at core&#39;s front end  10 F) when the softer core section  11  is on top, and prefer the reverse orientation (head at core&#39;s rear end  10 R) when firmer core section  12  is on top. Therefore, the core  10  may include markings, such as imprinted on the core foam or on labels, that indicate which user orientation is recommended for which orientation. For example, a first marking  141  at the soft section&#39;s front end  11 F might state “HEAD HERE”, and a second marking  142  just below the first marking at the firm section&#39;s front end  12 F stating “FEET HERE” upside down relative to the first marking Conversely, a third marking  143  at the soft section&#39;s rear end  11 F might state “FEET HERE”, and a fourth marking  144  just below the third marking might state “HEAD HERE” upside down relative to the third marking. 
     The above description regarding the mattress of  FIGS. 1-8 , and the following description regarding an accompanying pillow assembly of  FIGS. 9-11 , include prefaces with directional terms of “front” and “rear”, “upper” and “lower” and “top” and “bottom”. These designations are made only with reference to how the components may be oriented in the figures, and can be equivalently replaced with “first” and “second”. This is exemplified by the fact that, as explained above, the components can be used in inverted orientations in which the “lower” or “bottom” component is above the “upper” or “top” component. 
       FIGS. 9-12  show an example pillow assembly  200  that is well suited for use with the mattress of  FIGS. 1-8 .  FIGS. 9 and 10  are respectively a perspective assembled view and a side assembled view of the pillow assembly  200 .  FIGS. 11 and 12  are respectively an exploded perspective view and an exploded side view of the pillow assembly  200 . As shown in  FIGS. 9-12 , the pillow assembly  200  includes first and second main pillows  201 ,  201 ′ and first and second auxiliary pillows  202 ,  202 ′ that are stacked together. 
     The main pillows  201 ,  201 ′ are alike, and the auxiliary pillows  202 ,  202 ′ are alike. All four pillows are made of Eliocell open cell polyurethane foam. The foam of the main pillow  201  may be of the same firmness as the foam of the auxiliary pillow  202 . It may alternatively be more firm than the foam of the auxiliary pillow  202 . It may alternatively be less firm than the foam of the auxiliary pillow  202 . 
     The following description of the pillow assembly  200  is made with reference to a longitudinal direction (arrow “A”) and a lateral direction (arrow “B”). The longitudinal direction A is the direction along which a user would typically lie when resting his/her head on the pillow assembly. 
     Referring to  FIG. 10 , the main pillows  201 ,  201 ′ in this example are identical (same size and shape), and described as follows with reference to the first main pillow  201 . The main pillow  201  is generally wedge shaped, in that it has a taller front end surface  201 F and a longitudinally opposite shorter rear surface  201 R. It also has a top end surface  201 T and a bottom end surface  201 B. It also has two laterally opposite planar parallel planar side surfaces  201 S. In this example, the main pillow  201  is about 32 cm wide in the longitudinal direction, about 17 cm tall at its highest point, and about 66 cm long in the lateral direction. 
     The top surface  201 T of the main pillow  201  follows a longitudinally undulating first pattern P 1  that is very pronounced and nonuniform and not longitudinally symmetrical. The bottom surface  201 B follows a longitudinally undulating second pattern P 2  that is less pronounced than the first pattern P 1 . Both the top and bottom surfaces  201 T,  201 B undulate only in the longitudinal direction A, and are uniform in the lateral direction B. The front and rear surfaces  201 F,  201 R are convex and are uniform in the lateral direction B. The two side surfaces  201 S are flat, vertical and parallel. 
     The first pattern P 1  is common to both main pillows&#39; top surfaces  201 T. The first pattern P 1  includes a longitudinal series of projections  210 . Each projection includes a neck  211  and a bulbous head  212  that is wider (laterally) than the neck  211 . The pattern P 1  is configured for the top surfaces  201 T,  201 T′ to interleavingly mate (dovetail) with each other if, and only if, one of them is vertically inverted (upside down) and longitudinally flipped so that the front end  201 F′ of one overlies the rear end  201 R of the other. In this mating configuration, each bulbous head  212  of each main pillow  201 ,  201 ′ fits perfectly between two necks  212  of the other pillow, to provide the dovetail arrangement. This dovetailing capability is counterintuitive in view of the apparently wildly random (haphazard) path that the pattern P 1  follows. 
     The tops of the projections  210  define a smooth curve  214  that is concave  215  along half of the main pillow  201  and convex  216  along another half of the pillow  201 . This provides a user with an option for his/her head to rest in the concave section  215  and the convex section  216 . 
     The second pattern P 2 , which is common to the main pillows&#39; bottom surfaces  201 B,  201 B′, is configured for the bottom surfaces  201 B,  201 B′ to interleavingly mate (dovetail) with each other when one of them is vertically inverted, whether or not it is flipped longitudinally. 
     The second pattern P 2  is longitudinally uniform in that it is substantially a sine-wave shaped, with a repeating wave motif. The repeating motif has a uniform amplitude and period, and is centered on a longitudinal straight line  217 . 
     The auxiliary pillows  202 ,  202 ′ are the same, and described as follows with reference to the first auxiliary pillow  202  shown in  FIG. 11 . The auxiliary pillow  202  is generally wedge shaped, in that it has a taller front end surface  202 F and a longitudinally opposite shorter rear end surface  202 R. It also has a top end surface  202 T and a bottom end surface  202 B. It also has two laterally opposite planar parallel planar side surfaces  202 S. The auxiliary pillow  202  is about 32 cm wide, about 4 cm tall at its highest point, and about 66 cm long in the lateral direction. 
     The auxiliary pillow&#39;s top surface  202 T follows the second pattern P 2  of the main pillow&#39;s bottom surface  201 B. Therefore, the auxiliary pillows&#39; top surface  202 T,  202 T′ can interleavingly mate (dovetail) with each other when one of them is vertically inverted, whether or not it is flipped longitudinally. Also, therefore, each auxiliary pillow&#39;s top surfaces  202 T can interleavingly dovetail with any one of the main pillows&#39; bottom surface  202 B when one of them is vertically inverted, whether or not the other is flipped longitudinally. 
     The auxiliary pillow&#39;s bottom surface  202 B follows a longitudinally undulating third pattern P 3 . The third pattern P 3  is less pronounced than the first pattern P 1 . The third pattern P 3  is longitudinally uniform in that it is substantially a flat-topped sine-wave, with a repeating trapezoidal motif. The repeating motif has a uniform amplitude and period, and is centered on a straight longitudinal line  218 . The third pattern P 3  is configured for the auxiliary pillows&#39; bottom surfaces  202 B,  202 B′ to interleavingly dovetail with each other when one of them is vertically inverted, whether or not the other is flipped longitudinally. 
     Since the shapes of both the main pillow  201  and the auxiliary pillow  202  are laterally uniform with flat parallel vertical sides  201 S, both pillows  201 ,  202  can be formed by extrusion and cut to any desired length. 
     The shapes of the pillows  201 ,  201 ′,  202 ,  202 ′ enable a user to assemble a wide variety of pillow assemblies (pillow combinations, composite pillows), with different heights and with different slopes of the resulting top surface  220  and with different textures (either P 1 , P 2  or P 3 ) of the resulting top surface  220 . 
     For each pillow assembly (combination of the pillows  201 ,  202 ) yielding a sloped resulting top surface  220 , the user may rest his/her head in a forward orientation with the top surface sloping downward away from the user&#39;s neck and in an reverse orientation in which the resulting top surface slopes downward toward the user&#39;s neck. Also, each pillow assembly&#39;s top surface  220  may have any of three different possible patterns (P 1 , P 2  or P 3 ). So the user may choose between three possible patterns to lay his/her head on. Besides resting each pillow assembly being used to rest the user&#39;s head, it may be used to resting anything else. For example, a pillow assembly may be used as a foot rest, with feet extending in the lateral direction. 
     In each pillow combination, the undulations of mating surfaces (of either P 1 , P 2  or P 3 ) keep mating pillows from sliding longitudinally, and the dovetailing resists lateral sliding of each pillow over the other. This is especially true for the P 1  pattern, in which each projection  210  of one main pillow  201  has a bulbous section  212  that is locked in place between adjacent necks  211 ′ of the other main pillow  201 ′. Also, with any of the resulting combinations, the undulations (P 1 , P 2 , P 3 ) provide air circulation under the user&#39;s head, or any body part resting on them. 
     In each pillow combination, the side surfaces  201 S,  201 S′,  202 S,  202 S′ of the two or more pillows are coextensive, so as to form one planar side surface on one side of the composite pillow and another planar side surface at the laterally opposite side of the composite pillow. Also, as shown in  FIG. 10 , the auxiliary pillow&#39;s front surface  202 F is coextensive with the main pillow&#39;s rear surface  201 R to form a smoothly rounded convex composite surface, and the auxiliary pillow&#39;s rear surface  202 R is coextensive with the main pillow&#39;s front surface  201 F to form a smoothly rounded convex composite surface. Similarly, as shown by the top auxiliary pillow of  FIG. 14 , the auxiliary pillow&#39;s front surface  202 F is coextensive with the main pillow&#39;s front surface  201 F to form a smoothly rounded convex composite surface, and the auxiliary pillow&#39;s rear surface  202 R is coextensive with the main pillow&#39;s rear surface  201 R to form a smoothly rounded convex composite surface. 
     Some example pillow combinations (assemblies) are as follows. 
       FIG. 10  shows a first four-piece composite pillow  200 , in which the taller end  202 F,  202 F′ of each auxiliary pillow  202 ,  202 ′ is adjacent the shorter end  201 R,  201 R′ of the adjoining main pillow  201 ,  201 ′. This arrangement yields a horizontal (non-sloping) top surface  220 . This is well suited as a foot rest. 
       FIG. 13  shows a two-piece composite pillow comprising the main pillow  201  and the auxiliary pillow  202 , with the taller end of one overlying the shorter end of the other. This composite pillow  250  may be oriented in either of two longitudinally opposite orientation, so that the user&#39;s head can lie on the lower concave section  215  or on the higher convex section  216  section. And this composite pillow  250  may be oriented in either of two vertically opposite orientations. 
     Alternatively, the user&#39;s head may lie on only the main pillow  201  ( FIG. 12 ). The main pillow  201  may be oriented in either of two vertical orientations (i.e., upright orientation  201  in  FIG. 12  or inverted orientation  201 ′ in  FIG. 12 ) and either of two longitudinal orientations (e.g., with the user&#39;s neck adjacent the front end  201 F or adjacent the rear surface  201 R). 
     Alternatively, the user&#39;s head may lie on only the auxiliary pillow  202  ( FIG. 12 ). The auxiliary pillow  202  may be oriented in either of two vertical orientations (i.e., upright orientation  202  in  FIG. 12  or inverted orientation  202 ′ in  FIG. 12 ) and either of two longitudinal orientations (e.g., with the user&#39;s neck adjacent the front end  202 F or adjacent the rear surface  202 R). 
       FIG. 14  shows a second four-piece composite pillow  300 , which differs from the first four-piece composite pillow  200  in that the top auxiliary pillow  202 ′ is flipped longitudinally so that its shorter end  202 R′ is adjacent the shorter end  201 R of the main pillow  201 ′ below it. This arrangement yields a sloping top surface  220 . 
       FIG. 15  shows a twelve-piece composite pillow  400  in which three four-piece composite pillows  200 , like that of  FIG. 10 , are stacked together. In this configuration, interleaving of the third pattern P 3  of the different composite pillows  200  keeps the composite pillows  200  from slipping apart. 
     In another composite, two or more auxiliary pillows  202  ( FIG. 12 ) may be stacked together, alternating auxiliary pillows  202  vertically inverted so as to render P 2  patterns dovetailed together and P 3  patterns dovetailed together. 
     In fact, the user may assemble a composite pillow from any combination of main pillows  201 , any combination of auxiliary pillows  202 , and any combination of both main and auxiliary pillows  201 ,  202 , as long as P 1  patterns dovetail together, P 2  patterns dovetail together, and P 3  patterns dovetail together. When dovetailing one P 1  surface with another, the two P 1  surfaces have be to longitudinally aligned for the dovetailing to succeed. In contrast, when dovetailing one P 2  surface with another, or dovetailing one P 3  surface with another, the surfaces do not must be longitudinally aligned since the P 2  and P 3  patterns are longitudinally uniform along their lengths. This is illustrated in  FIG. 15 , in which one P 3  surface straddles two P 3  surfaces that are below it and is significantly longitudinally offset from the P 3  surface of each one below it. 
     The components and procedures described above provide examples of elements recited in the claims. They also provide examples of how a person of ordinary skill in the art can make and use the claimed invention. They are described here to provide enablement and best mode without imposing limitations that are not recited in the claims. In some instances in the above description, a term is followed by a substantially equivalent term enclosed in parentheses.