WO2025071983A1

WO2025071983A1 - Foam mattress core with integrally formed side rails

Info

Publication number: WO2025071983A1
Application number: PCT/US2024/047040
Authority: WO
Inventors: Douglas W. Anderson; Steven D. Hawkins
Original assignee: ER Carpenter Co
Current assignee: ER Carpenter Co
Priority date: 2023-09-28
Filing date: 2024-09-17
Publication date: 2025-04-03
Anticipated expiration: 2026-03-28

Abstract

A foam mattress utilizes an integrally formed core that includes both a convoluted central section and side rails. The central section includes foam pillars that simulate coil springs. The integrally formed core is formed using a convolution machine. To ensure that the top surfaces of the side rails are flat and parallel to the bottom surface, one of the rollers of the convolution machine is provided with frusto-conical end sections.

Description

FOAM MATTRESS CORE WITH INTEGRALLY FORMED SIDE RAILS CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. provisional application Serial No. 63/586,094 filed September 28, 2023, the disclosure of which is hereby incorporated in its entirety by reference herein. TECHNICAL FIELD The present disclosure relates to a foam mattress. More particularly, the disclosure relates to a foam mattress having a core with a convoluted portion and integrally formed side rails. BACKGROUND Mattress design is a significant factor in sleep quality. A variety of different mattress structures are in use. In coil-type mattresses, metal springs support weight of the occupant while deflecting to conform to the occupant’s body shape. A layer between the springs and the occupant distributes the forces. Foam-type mattresses rely on the resilient properties of the foam material to support weight and conform to the occupant to a desired degree. Different degrees of stiffness may be desirable in different regions. For example, it may be desirable to have the sides be stiffer to better support a person sitting on the edge of a bed. In addition to material selection, mattress designers may include various patterns of bumps and recesses to customize the properties of a foam mattress. The desired pattern of bumps and recesses may be formed using a convolution machine. A convolution machine includes two counter-rotating rollers having cooperating projections and recesses. A block of foam is passed between the counter-rotating rollers. The rollers compress the foam block to varying degrees in different areas and deflect some areas toward one of the rollers. A cutting blade located between the two rollers cuts the foam while it is in the compressed and deflected state. When the foam exits the machine and returns to its uncompressed density, the two pieces have varying thicknesses. In areas that were deflected toward the top roller, the top piece is thicker and the bottom piece is thinner. Conversely, in areas that were deflected toward the bottom roller, the top piece is thinner and the bottom piece is thicker. The two pieces are complimentary, with the thicknesses adding up to the thicknesses of the initial block of foam. U.S. Patent 7,174,613 discloses use of a convolution machine to fabricate a foam core for a mattress. The convolution machine is used to create voids in the foam core into which coil springs or foam with different material properties is inserted. The cutting blade is positioned close to the top roller such that some portions of the foam are not cut and those portions of the bottom piece have the same thickness as the original block of foam. Instead of a contiguous top piece, a number of discrete pieces are removed from the top of the block of foam. In some embodiments, the outer three inches of the block of foam are not cut, resulting in a foam core with an integral head and foot rail that are the same thickness as the original block of foam. In some applications, these uncut portions may be unsuitable as side rails. U.S. Patent Application Publication 2011/0145966 discloses a reversible foam mattress. The mattress is formed using a convolution machine that is narrower than the width of the original block of foam, leaving uncut side rails on either side of the convoluted portion. Both the top surface and the bottom surface of the core have convolutions, although the convolutions are different sizes. The side rails have flat top and bottom surfaces which may be substantially flush with the peak height of the convolutions on each side. SUMMARY A mattress includes an integrally formed foam core and a foam top piece. The integrally formed foam core has a flat bottom, a convoluted central region, and two side regions. The convoluted central region has an array of pillars extending away from the flat bottom. The two side regions each extend between an edge and the central region. A thickness is substantially equal throughout the side regions. The side region may have a width of at least 3 inches. The side regions may extend no farther from the flat bottom than the pillars. The pillars may extend farther from the flat bottom than the side regions. The foam top piece extends over the integrally formed core across the side regions and the central region. A foot rail may extend between first ends of the side regions. A head rail may extend between second ends of the side regions. The convoluted central region may include a torso region between a head region and a foot region. The foot region is adjacent to the foot rail. The head region is adjacent to the head rail. A height of the pillars may be less in the torso region than in the head region and in the foot region. A single-piece foam mattress core includes a convoluted central region and a first side rail and may have a second side rail. The convoluted central region has an array of pillars that extend away from a flat bottom surface. The first side rail, which is on a first side of the central region, has a flat first top surface inclined no more than 5 degrees relative to the bottom surface. The first side rail is integrally formed with the central region. The pillars extend farther from the bottom surface than the first top surface extends from the bottom surface. The second side may be a second side of the central region opposite the first side and may have a second flat top surface inclined no more than 5 degrees relative to the bottom surface. The first and second side rails may each have a width of at least 3 inches. The first and second flat top surfaces may be inclined no more than 2 degrees relative to the bottom surface. The convoluted central region may include a torso region between a head region and a foot region, wherein a height of the pillars is less in the torso region than in the head region and in the foot region. A method of making a single-piece foam mattress core includes passing a block of foam two rollers and cutting the block of foam as it emerges from the rollers to separate the block into a foam mattress core and a scrap piece. The rollers are supported to rotate in opposite directions about parallel axes. Each roller has a convolution section defining projections or recesses. One of the rollers has a first frusto-conical end section. A larger diameter end of the first frusto-conical end section may be adjacent to the convolution section. An angle of a conical surface of the first frusto-conical end section relative to a centerline may be between 1 degree and 3 degrees. The roller having the first frusto-conical end section may also have a second frusto- conical end section on an opposite side of the convolution section from the first frusto-conical end section. The foam mattress core has a flat bottom surface. A portion of the foam mattress core that passed between the convolution sections of the rollers has a convoluted top surface. A portion of the foam mattress core that passed by the first end-section has a flat top surface substantially parallel to the flat bottom surface. The scrap piece may have a width equal to a width of the foam mattress core. The projections or recesses may be arranged such that the convoluted top surface of the foam mattress core has an array of pillars. The pillars may extend farther from the bottom surface than the flat top surface. The method may further include changing a distance between the rollers to change a height of the pillars. The distance between the rollers may be increased and then decreased while passing the block of foam between the rollers. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a top view of a foam mattress having a convoluted core region with foam pillars that similar coil springs. FIG. 2 is a partial exploded view of the mattress of FIG. 1. FIG. 3 is a cross-sectional view of the integrated core of the mattress of FIG. 1. FIG. 4 is a cross-sectional view of a convolution machine suitable for fabricating the integrated core of FIG. 3. FIG. 5 is a pictorial view of the rollers of the convolution machine of FIG. 4. FIG. 6 is a partial side view of the rollers of the convolution machine of FIG. 4. DETAILED DESCRIPTION As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. Figure 1 is a top view of a foam mattress. The foam mattress has a core region 12, a side rail region 14, a head rail region 16, and a foot rail region 18. In the core region, an array of foam pillars 20 simulate coil springs. As shown in the partial exploded view of Figure 2, the mattress 10 is formed from an integrated core piece 22, a foot rail 24, a head rail (not shown), and a top piece 26. The integrated core piece includes both the array of pillars 20 and side rail 28. The foot rail, head rail, and top piece may be separate pieces or may be integrally formed with one another. Figure 3 is a partial cross section of the integrated core piece 22. The integrated core piece 22 has a flat bottom surface 30. The side rails 28 have a flat top surface 32 which is substantially parallel to the bottom surface and offset by a distance A. More particularly, surface 32 should be inclined by no more than 5 degrees relative to surface 30 and preferably no more than 2 degrees. In an exemplary embodiment, dimension A is slightly less than 6 inches. The top surface of the side rails has a width B which, in the exemplary embodiment is approximately 4 inches. The peaks of the pillars extend a distance C from the bottom surface. To avoid an appearance of sagging, it is important for the pillars to extend at least as high, and preferably slightly higher, than the side rails. A base of the pillars is a distance D from the flat bottom surface. In the exemplary embodiment, D is approximately 2.75 inches. The pillars are frusto-conical with flat, circular top surfaces having a diameter of E, which in the exemplary embodiment is approximately 2.75 inches. The inventors have discovered that the methods described in the prior art do not produce acceptable side rails for the integrated core piece 22 as illustrated in Figure 3. If the cutting blade is adjusted such that no material is removed at the side rails, then the side rail height A will be at least equal to the height C of the pillars. The inventors have discovered that using convolution rollers narrower than the original foam block produced side rails in which the top surface 32 is not substantially parallel to the flat bottom surface 30. In particular, a ridge is formed in the side rail with inclined portions on either side of the ridge. The inventors have developed a modified convolution process for producing the integrated core piece 22 of Figure 3. The tooling for this process is illustrated in Figures 4-6. Figure 4 is a side view of a convolution machine 40. A block of foam 42 is pushed along a feed table 44 between two counter-rotating rollers 46 and 48. A pattern of projections and recesses on the two rollers compress the foam and translate the foam vertically to different extents in different areas. As the foam emerges from the rollers, it is cut by a cutting blade 52. The cutting blade may be a band saw blade, an oscillating blade, a heated wire, or other mechanism that cuts foam. The blade cuts the block of foam into two pieces - integrated core piece 22 and a single scrap piece. The two pieces have complimentary thicknesses which add to the thickness of the foam block 42. Each of the two pieces have the same width (defined as parallel to the axis of the rollers) and the same length (defined as perpendicular to the axis of the rollers) as the foam block. The scrap piece has a top surface that is contiguous and uninterrupted because the cutting blade does not extend outside of the foam block during the process. Figure 5 is a pictorial view of the rollers. Tapered end pieces 54 and 56 are appended to the end of one of the rollers. The tapered end pieces are frusto-conical. A diameter of the tapered end piece adjacent to the roller is greater than a diameter of the tapered end piece on the outside. As shown in Figure 6, the conical surfaces are inclined at an angle α with respect to the centerline. The inventors have discovered that α should be approximately 2 degrees to achieve a side rail as depicted in Figure 3. Use of a tapered roller to produce a constant-height side rail was a surprising, unexpected result. An axial length of each of the tapered end pieces is at least equal to the dimension B. The inventors have further discovered that, by moving bottom roller 48 vertically with respect to roller 46 and blade 52, dimension D in Fig. 3 can be adjusted without appreciably changing dimensions A, B, C, and E. Increasing dimension D makes the pillars 20 shorter which makes the mattress firmer. This permits fabrication of mattresses with different degrees of firmness without changing the tooling. Furthermore, adjusting the separataion between the rollers while foam block 42 is being drawn through the machine produces a mattress core with different firmness regions. More particularly, a mattress core is produced with a central firmer region to support a user’s torso and softer, more compliant regions for the user’s head and feet. Specifically, the rollers are moved apart from one another when the block of foam is approximately one third of the way through and then moved back to the original distance when the block of foam is approximately two thirds of the way through. While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.

Claims

WHAT IS CLAIMED IS: 1. A mattress comprising: an integrally formed foam core having a flat bottom, a convoluted central region having an array of pillars extending away from the flat bottom, and two side regions each extending between an edge and the central region, wherein a thickness is substantially equal throughout the side regions; and a foam top piece extending over the integrally formed core across the side regions and the central region.

2. The mattress of claim 1 further comprising: a foot rail extending between first ends of the side regions; and a head rail extending between second ends of the side regions.

3. The mattress of claim 2 wherein: the convoluted central region comprises a torso region between a head region and a foot region; the foot region is adjacent to the foot rail; the head region is adjacent to the head rail; and a height of the pillars is less in the torso region than in the head region and in the foot region.

4. The mattress of claim 1 wherein the side region has a width of at least 3 inches.

5. The mattress of claim 1 wherein the side regions extends no farther from the flat bottom than the pillars.

6. The mattress of claim 1 wherein the pillars extend farther from the flat bottom than the side regions.

7. A single-piece foam mattress core comprising: a convoluted central region having an array of pillars that extend away from a flat bottom surface; and a first side rail on a first side of the central region, the first side rail having a flat first top surface inclined no more than 5 degrees relative to the bottom surface; wherein the first side rail is integrally formed with the central region; and the pillars extend farther from the bottom surface than the first top surface extends from the bottom surface.

8. The single-piece foam mattress core of claim 7 further comprising: a second side rail on a second side of the central region opposite the first side, the second side rail having a second flat top surface inclined no more than 5 degrees relative to the bottom surface; wherein the second side rail is integrally formed with the central region; and the pillars extend farther from the bottom surface than the second flat top surface.

9. The single-piece foam mattress core of claim 8 wherein the first side rail and the second side rail each have a width of at least 3 inches.

10. The single-piece foam mattress core of claim 8 wherein: The first and second flat top surfaces are inclined no more than 2 degrees relative to the bottom surface.

11. The single-piece foam mattress core of claim 8 wherein the convoluted central region comprises a torso region between a head region and a foot region, wherein a height of the pillars is less in the torso region than in the head region and in the foot region.

12. A method of making a single-piece foam mattress core, the method comprising: providing two rollers, the rollers supported to rotate in opposite directions about parallel axes, each roller having a convolution section defining projections or recesses, and at least one of the rollers having a first frusto-conical end section; passing a block of foam between the rollers; and cutting the block as it emerges from the rollers to separate the block into a foam mattress core and a scrap piece; wherein the foam mattress core has a flat bottom surface; a portion of the foam mattress core that passed between the convolution sections of the rollers has a convoluted top surface; and a portion of the foam mattress core that passed by the first end-section has a flat top surface substantially parallel to the flat bottom surface.

13. The method of claim 12 wherein the scrap piece has a width equal to a width of the foam mattress core.

14. The method of claim 12 wherein the projections or recesses are arranged such that the convoluted top surface of the foam mattress core has an array of pillars.

15. The method of claim 14 wherein the pillars extend farther from the bottom surface than the flat top surface.

16. The method of claim 14 further comprising changing a distance between the rollers to change a height of the pillars.

17. The method of claim 14 further comprising, while passing the block of foam between the rollers, increasing a distance between the rollers and then decreasing the distance.

18. The method of claim 12 wherein a larger diameter end of the first frusto- conical end section is adjacent to the convolution section.

19. The method of claim 12 wherein an angle of a conical surface of the first frusto-conical end section relative to a centerline is between 1 degree and 3 degrees.

20. The method of claim 12 wherein the at least one roller having the first frusto-conical end section also has a second frusto-conical end section on an opposite side of the convolution section from the first frusto-conical end section.