TIRES WITH MULTI-LAYER INSERT

Description

FIELD OF INVENTION

[0001] This application relates to the reduction of noises generated by tires as they contact the road. More particularly, the present application relates to devices inserted within tires to reduce such noise, wherein the noise reducing devices move within the tire.BACKGROUND

[0002] Known tire noise dampers are placed within the tire and permanently affixed to a tire innerliner. The dampers may include foam or fibers. The dampers reduce noise within the tire, and thus reduce noise emitted from the tire.

[0003] According to its abstract, EP 1 795 377 A2 describes a pneumatic tire and noise damper assembly that comprises a pneumatic tire, a noise damper being attached to an inner surface of the tire and extending in the circumferential direction of the tire, and a protective cover being detachably attached to the tire and protecting the noise damper from ultraviolet rays and water.

[0004] According to its abstract, DE 10 2011 053686 A1 describes a tire that has two side walls formed with treads, and two tire beads for fastening the tire on a rim. A carcass is extended between the tire beads. A belt is provided between the tread and the carcass. An air-impermeable inner layer is formed on a side of the carcass towards a tire inner side and extended between the tire beads along the carcass. A vibration damper is arranged within a circumference of the tire on a radial inner side of the inner layer, for damping vibration along the circumference, where the radial inner side is opposite to the tire inner side.

[0005] According to its title and abstract, DE 10 2009 024454 A1 describes a pneumatic tire that has a running-surface section and sidewall sections connecting to it on both sides and bordering a hollow space / cavity with an element for damping down noise. The element for damping down noise fits on a support with fastening sections protruding on its underside towards the inner wall of the running-surface section. The fastening sections fasten on the inner wall so that the underside of the element for damping down noise or of the support has a clearance from the inner wall of the running-surface section.SUMMARY OF THE INVENTION

[0006] Aspects of the present invention are defined by the appended independent claims. Preferred embodiments of the present invention are defined by the appended dependent claims.

[0007] In one embodiment, a tire and noise damper assembly includes a tire having a first annular bead, a second annular bead, and a body ply extending between the first annular bead and the second annular bead. The tire further includes an innerliner, disposed radially under the body ply and extending axially across a portion of the body ply. The tire also has an annular belt package, disposed radially upward of the body ply and extending axially across a portion of the body ply. The tire further has a circumferential tread disposed radially upward of the annular belt package and extending axially across a portion of the body ply. The tire also includes a first sidewall extending between the first annular bead and a first shoulder and a second sidewall extending between the second annular bead and a second shoulder. The first shoulder is associated with the circumferential tread, and the second shoulder is associated with the circumferential tread. The assembly also includes a noise damper made of an open cell foam and having a continuous circumferential upper tier and an interposed circumferential lower tier including blocks and voids. The interposed circumferential lower tier has a radial height that is 1.5-14.0% of a section height and an axial width that is 20-80% of a tread width. The continuous circumferential upper tier has a radial height that is 1.5-14.0% of the section height and an axial width that is 20-80% of a tread width. The blocks span 20-40% of the continuous circumferential upper tier's inner circumference and the voids span 60-80% of the continuous circumferential upper tier's inner circumference. Each of the blocks has an axial width that is 80-120% of the axial width of the continuous upper tier.

[0008] In another embodiment, a noise damper includes an open cell foam having a circumferential first tier and an interposed circumferential second tier including blocks and voids. The first tier has a radial height that is 3.0-8.0% of a section height and a first axial width. The second tier has a radial height that is 3.0-12.0% of a section height and a second axial width. The blocks span 10-30% of the second tier's inner circumference and the voids span 70-90% of the second tier's inner circumference.

[0009] In yet another embodiment, a noise damper is made of an open cell foam. The noise damper includes a circumferential upper tier and a lower tier having a plurality of blocks spaced apart in a circumferential direction. The upper tier has a radial height that is 3.0-14.0% of a section height and an axial width that is 20-70% of a tread width. The lower tier has a radial height that is 3.0-14.0% of a section height and an axial width that is 20-70% of a tread width. Each of the plurality of blocks includes a leading edge including a polymer with a Rockwell hardness of up to 100 HRR.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the accompanying drawings, structures are illustrated that, together with the detailed description provided below, describe exemplary embodiments of the claimed invention. Like elements are identified with the same reference numerals. It should be understood that elements shown as a single component may be replaced with multiple components, and elements shown as multiple components may be replaced with a single component. The drawings are not to scale and the proportion of certain elements may be exaggerated for the purpose of illustration. Figure 1 is a cross-section of one embodiment of a noise reduction system including an exemplary tire with one embodiment of a noise damper; Figure 2 is a cross-section of an alternative embodiment of a noise reduction system including the exemplary tire with an alternative placement of the noise damper; Figure 3A is a perspective view of the noise damper; Figure 3B is a side view of the noise damper; Figure 4 is a side view of an alternative embodiment of a noise damper; Figure 5 is a side view of another alternative embodiment of a noise damper; Figure 6 is a side view of yet another alternative embodiment of a noise damper; Figure 7 is a side view of still another alternative embodiment of a noise damper; and Figure 8 is a side view of yet another alternative embodiment of a noise damper. DETAILED DESCRIPTION

[0011] The following includes definitions of selected terms employed herein. The definitions include various examples and / or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions.

[0012] "Axial" and "axially" refer to a direction that is parallel to the axis of rotation of a tire.

[0013] "Circumferential" and "circumferentially" refer to a direction extending along the perimeter of the surface of the tread perpendicular to the axial direction.

[0014] "Radial" and "radially" refer to a direction perpendicular to the axis of rotation of a tire.

[0015] "Sidewall" as used herein, refers to that portion of the tire between the tread and the bead.

[0016] "Tread" as used herein, refers to that portion of the tire that comes into contact with the road or ground under normal inflation and normal load.

[0017] "Tread depth" refers to the distance between a top surface of the tread and the bottom of a major tread groove.

[0018] "Tread width" refers to the width of the ground contact area of a tread which contacts with the road surface during the rotation of the tire under normal inflation and load.

[0019] While similar terms used in the following descriptions describe common tire components, it is understood that because the terms carry slightly different connotations, one of ordinary skill in the art would not consider any one of the following terms to be purely interchangeable with another term used to describe a common tire component.

[0020] Directions are stated herein with reference to the axis of rotation of the tire. The terms "upward" and "upwardly" refer to a general direction towards the tread of the tire, whereas "downward" and "downwardly" refer to the general direction towards the axis of rotation of the tire. Thus, when relative directional terms such as "upper" and "lower" or "top" and "bottom" are used in connection with an element, the "upper" or "top" element is spaced closer to the tread than the "lower" or "bottom" element. Additionally, when relative directional terms such as "above" or "below" are used in connection with an element, an element that is "above" another element is closer to the tread than the other element.

[0021] Furthermore, to the extent the term "under" is used in the specification or claims, it is intended to mean not only "directly under" but also "indirectly under" where intermediary tire layers or components are disposed between two identified components or layers.

[0022] The terms "inward" and "inwardly" refer to a general direction towards the equatorial plane of the tire, whereas "outward" and "outwardly" refer to a general direction away from the equatorial plane of the tire and towards the sidewall of the tire. Thus, when relative directional terms such as "inner" and "outer" are used in connection with an element, the "inner" element is spaced closer to the equatorial plane of the tire than the "outer" element.

[0023] Figure 1 is a cross-section of one embodiment of a noise-reduction system 100 for a vehicle wheel assembly. The system 100 includes a tire 105 mounted on a wheel 110. The tire 105 has a section height SH, measured from a heel to a radially outermost portion of the tire. The tire 105 also has a section width SW and a tread width TW. In the illustrated embodiment, the tire 105 is a passenger tire, but it should be understood that the tire may be a high performance tire, light-truck, or truck-and-bus-radial tire. In other embodiments, the tire may be an agricultural tire or off the road tire.

[0024] The tire 105 includes a circumferential tread 115 in a crown region of the tire. In the illustrated embodiment, the tread 115 includes a plurality of circumferential grooves 120. While four grooves 120 are shown, it should be understood that any number of grooves may be employed. The tread 115 may further include ribs, blocks, lugs, lateral grooves, sipes, or any other tread elements. The crown region of the tire 105 further includes a pair of belts 125. In alternative embodiments (not shown), any number of belts or cap plies may be employed.

[0025] In the illustrated embodiment, the tire 105 further includes a first bead portion 130a and a second bead portion 130b. The bead portions 130a,b include a first bead 135a and a second bead 135b, which are shown schematically in Figure 1. The bead portions 130a,b may also include one or more bead fillers (not shown) and other known components such as abrasions, chafers, and reinforcements.

[0026] A first sidewall 140a extends between the tread 115 and the first bead portion 130a. Similarly, a second sidewall 140b extends between the tread 115 and the second bead portion 130b. The sidewalls 140a,b may include any number of reinforcements (not shown). A carcass ply 145 extends from the first bead portion 130a, through the first and second sidewalls 140a and the crown portion, to the second bead portion 130b. In alternative embodiments (not shown), any number of carcass plies may be employed.

[0027] With continued reference to Figure 1, a noise damper 150 including a first tier 150a and a second tier 150b is disposed in a cavity formed by the tire 105 and wheel 110. The first tier 150a is an upper tier that is adhered to the tire 105 with an adhesive. The second tier 150b is a lower tier that is adhered to the first tier 150a with an adhesive. The adhesive may be in the form of adhesive tape, or it may be bead glue or other liquid adhesive. In the illustrated embodiment each of the tiers 150a,b has a rectangular cross-section. However, it should be understood that the noise dampers may have any geometric shape.

[0028] In one embodiment, the damper 150 forms a continuous loop about the tire. In an alternative embodiment, the damper 150 includes a series of dampers placed about the tire. In such an embodiment, the series of dampers may be spaced apart from each other, or in contact with each other.

[0029] In one embodiment, the noise damper 150 is a foam body constructed of compressible and elastic open cell foam material. Exemplary foam materials include, without limitation, polyurethane, polyester, polyether, melamine fiberglass, and rock wool. In an alternative embodiment, the noise damper is made of fibers or fibrous materials. In one embodiment, the first tier 150a and the second tier 150b are constructed of the same material. In an alternative embodiment, the first tier 150a and the second tier 150b are constructed of different materials. For example, the first tier 150a may be made of polyurethane while the second tier 150b is made of melamine.

[0030] In either embodiment, the noise damper 150 has a sound absorption coefficient between 0.4 and 1.2. In an alternative embodiment, the noise damper 150 has a sound absorption coefficient of less than 0.4. In one particular embodiment, the noise damper 150 has a sound absorption coefficient of between 0.05 and 0.15, which is known to be an effective sound absorption coefficient of noise at a frequency of about 250 Hz. The damper 150 is also configured to reduce noise having a frequency between 180-220 Hz. In another particular embodiment, the noise damper 150 has a sound absorption coefficient between 0.7 and 1.2.

[0031] The first tier 150a has a radial height that is 1.5-14.0% of the section height SH and an axial width that is 20-80% of the tread width TW. In another embodiment, the first tier 150a has a radial height that is 3.0-14.0% of the section height SH and an axial width that is 20-70% of the tread width TW. In one particular embodiment, the first tier 150a has a radial height that is 3.0-8.0% of the section height SH.

[0032] The second tier 150b likewise has a radial height that is 1.5-14.0% of the section height SH and an axial width that is 20-80% of the tread width TW. In another embodiment, the second tier 150b has a radial height that is 3.0-14.0% of the section height SH and an axial width that is 20-70% of the tread width TW. In one particular embodiment, the second tier 150b has a radial height that is 6.0-10.0% of the section height SH. In another particular embodiment, the second tier 150b has a radial height that is 3.0-12.0% of the section height SH and an axial width that is 20-70% of the tread width TW. In another particular embodiment, the second tier 150b has a height of 1.5-3.0 cm.

[0033] Figure 2 is a cross-section of an alternative embodiment of a noise reduction system 200 including the exemplary tire 105 with the noise damper 150 placed in an alternative location. The tire 105 is the same as the tire 105 discussed above with respect to Figure 1.

[0034] The damper 150 is substantially the same as that described above with respect to Figure 1, except for the differences in location and orientation discussed below. The noise damper 150 includes a first tier 150a and a second tier 150b. The first tier 150a is a lower tier that is adhered to the wheel 110 with an adhesive. The second tier 150b is an upper tier that is adhered to the first tier 150a with an adhesive. In the illustrated embodiment each of the tiers 150a,b has a rectangular cross-section. However, it should be understood that the noise dampers may have any geometric shape.

[0035] The damper 150 may be constructed of the same material and have the same dimensions as discussed above with respect to Figure 1.

[0036] Figure 3A is a perspective view of a portion of one embodiment of the noise damper 150. The noise damper 150 includes the first tier 150a and the second tier 150b. The first tier 150a can be adhered to a crown region of a tire, in the manner shown in Figure 1, or it can be adhered to a wheel of a tire as shown in Figure 2. Different adhesives may be employed, depending on whether the damper is adhered to a tire or to a wheel.

[0037] The second tier 150b is a lower tier when the first tier 150a is adhered to a crown region of the tire, as shown in Figure 1. The second tier 150b is an upper tier when the first tier 150a is adhere to a wheel. The second tier 150b includes a plurality of spaced apart blocks. In one embodiment, the blocks are adhered to the first tier 150a by an adhesive. In an alternative embodiment, the blocks are formed by cutting or otherwise removing material from the noise damper 150 to form the blocks. In another alternative embodiment, the blocks are formed on top of the first tier 150a by an additive manufacturing process.

[0038] In the illustrated embodiment, the blocks are rectangular cuboids. That is, each block is a polyhedron bounded by six quadrilateral faces. Each block has substantially the same axial width as the axial width of the first tier 150a. In alternative embodiments, the axial width of each block is 80-120% of the axial width of the first tier 150a.

[0039] In one embodiment, each block has the same width. In an alternative embodiment, the widths of the blocks vary. In one such embodiment, the widths of the block may be selected to balance the weight of the tire.

[0040] The blocks are separated by voids, such that the blocks span 20-40% of the length of the first tier 150a and the voids span 60-80% of the length of the first tier 150a. Thus, when the damper 150 is connected to the crown region of the tire, the blocks span 20-40% of the inner circumference of the first tier 150a. When the damper 150 forms a continuous loop connected to the wheel, the blocks span 20-40% of the outer circumference of the first tier 150a.

[0041] In an alternative embodiment, the blocks span 10-30% of the length of the first tier 150a and the voids span 70-90% of the length of the first tier 150a.

[0042] The spacing of the blocks may be selected based on harmonics of the tire. For example, a tire of a given size and construction may produce noise at a first harmonic when it rotates at a first speed, produce a noise at a second harmonic when it rotates at a second speed, etc. The blocks can be spaced to disrupt such harmonic waves and thus further aid in noise reduction.

[0043] Figure 3B is a side view of the noise damper 150. As can be seen in this view, the blocks are equally spaced on the first tier 150a. The height of each block is substantially the same as the height of the first tier 150a. Each of the blocks has substantially the same height.

[0044] Figure 4 is a side view of an alternative embodiment of a noise damper 400. The damper 400 is substantially the same as the damper 150 described above, except for the differences described herein. The damper 400 may be placed in a tire cavity according to any of the manners described above.

[0045] The damper 400 includes a first tier 410a and a second tier 410b that is formed by a plurality of blocks. In this embodiment, the blocks are pitch sequenced. In other words, the spacing between the blocks varies. The spacing may be selected based on the harmonics of the tire, or for purposes of balancing the weight of the tire.

[0046] In the illustrated embodiment, the height of the second tier 410b is greater than the height of the first tier 410a, and each block has substantially the same height. In an alternative embodiment, the height of the second tier is the same as the height of the first tier, and each block has substantially the same height. In another alternative embodiment, the heights of the blocks vary.

[0047] Figure 5 is a side view of another alternative embodiment of a noise damper 500. The damper 500 is substantially the same as the damper 150 described above, except for the differences described herein. The damper 500 may be placed in a tire cavity according to any of the manners described above.

[0048] The damper 500 includes a first tier 510a and a second tier 510b that is formed by a plurality of blocks. In this embodiment, the blocks are equally spaced from each other. In an alternative embodiment, the blocks may be pitch sequenced.

[0049] In the illustrated embodiment, the second tier 510b is formed by two block types, including blocks having a first height and blocks having a second height. The block types are alternated, such that a tall block is disposed between two short blocks. In an alternative embodiment, blocks of three or more heights are employed. The blocks of multiple heights may be arranged in any order. The arrangement of the blocks may be selected based on the harmonics of the tire or to balance the weight of the tire.

[0050] Figure 6 is a side view of yet another alternative embodiment of a noise damper 600. The damper 600 is substantially the same as the damper 150 described above, except for the differences described herein. The damper 600 may be placed in a tire cavity according to any of the manners described above.

[0051] The damper 600 includes a first tier 610a and a second tier 610b that is formed by a plurality of blocks. In this embodiment, the blocks are equally spaced from each other. In an alternative embodiment, the blocks may be pitch sequenced.

[0052] In the illustrated embodiment, the second tier 610b is formed by blocks having a triangular cross-section. Each block has substantially the same height, and the blocks are taller than the first tier 610a. In an alternative embodiment, the blocks have the same height as the first tier 610a. In another alternative embodiment, the blocks have a height less than the height of the first tier 610a. In yet another alternative embodiment, the height of the blocks vary.

[0053] Figure 7 is a side view of still another alternative embodiment of a noise damper 700. The damper 700 is substantially the same as the damper 150 described above, except for the differences described herein. The damper 700 may be placed in a tire cavity according to any of the manners described above.

[0054] The damper 700 includes a first tier 710a and a second tier 710b that is formed by a plurality of blocks. In this embodiment, the blocks are equally spaced from each other. In an alternative embodiment, the blocks may be pitch sequenced.

[0055] In the illustrated embodiment, the second tier 710b is formed by a first plurality of blocks having a triangular cross-section and a second plurality of blocks having a rectangular cross-section. In the illustrated embodiment, the blocks are arranged in an alternating pattern, such that a rectangular block is disposed between two triangular blocks. In alternative embodiments, the blocks may be arranged in any desired order.

[0056] Each block has substantially the same height, and the blocks are taller than the first tier 710a. In an alternative embodiment, the blocks have the same height as the first tier 710a. In another alternative embodiment, the blocks have a height less than the height of the first tier 710a. In yet another alternative embodiment, the height of the blocks vary.

[0057] Figure 8 is a side view of yet another alternative embodiment of a noise damper 800. The damper 800 is substantially the same as the damper 150 described above, except for the differences described herein. The damper 800 may be placed in a tire cavity according to any of the manners described above.

[0058] The damper 800 includes a first tier 810a and a second tier 810b that is formed by a plurality of blocks. In this embodiment, the blocks are equally spaced from each other. In an alternative embodiment, the blocks may be pitch sequenced.

[0059] In the illustrated embodiment, the second tier 810b is formed by blocks having a trapezoidal cross-section. In the illustrated embodiment, each block has the same geometric cross-section. In an alternative embodiment, the cross-sections of the blocks may vary.

[0060] Each block has substantially the same height, and the blocks are taller than the first tier 810a. In an alternative embodiment, the blocks have the same height as the first tier 810a. In another alternative embodiment, the blocks have a height less than the height of the first tier 810a. In yet another alternative embodiment, the height of the blocks vary.

[0061] In any of the above-described embodiments, one or more of the blocks may have a leading edge constructed of a different material. The leading edge material may be a polymer with a Rockwell hardness of up to 100 HRR. The leading edge material may be polyethylene, polypropylene, or another polymeric material. The leading edge may have pores. In one particular embodiment, the leading edge includes flaps.

[0062] To the extent that the term "includes" or "including" is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term "comprising" as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term "or" is employed (e.g., A or B) it is intended to mean "A or B or both." When the applicants intend to indicate "only A or B but not both" then the term "only A or B but not both" will be employed. Thus, use of the term "or" herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms "in" or "into" are used in the specification or the claims, it is intended to additionally mean "on" or "onto." Furthermore, to the extent the term "connect" is used in the specification or claims, it is intended to mean not only "directly connected to," but also "indirectly connected to" such as connected through another component or components.

[0063] While the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail.

Claims

1. A tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) comprising: a tire (105), wherein the tire (105) comprises: a first annular bead (135a) and a second annular bead (135b), a body ply (145) extending between the first annular bead (135a) and the second annular bead (135b), an innerliner, disposed radially under the body ply (145) and extending axially across a portion of the body ply (145), an annular belt package (125), disposed radially upward of the body ply (145) and extending axially across a portion of the body ply (145), a circumferential tread (115) disposed radially upward of the annular belt package (125) and extending axially across a portion of the body ply (145), and a first sidewall (140a) extending between the first annular bead (135a) and a first shoulder, the first shoulder being associated with the circumferential tread (115), and a second sidewall (140b) extending between the second annular bead (135b) and a second shoulder, the second shoulder being associated with the circumferential tread (115); and a noise damper (150; 400; 500; 600; 700; 800) made of an open cell foam and having a continuous circumferential upper tier (150a; 410a; 510a; 610a; 710a; 810a) and an interposed circumferential lower tier (150b; 410b; 510b; 610b; 710b; 810b) including blocks and voids, wherein the interposed circumferential lower tier (150b; 410b; 510b; 610b; 710b; 810b) has a radial height that is 1.5-14.0% of a section height of the tire (105) and an axial width that is 20-80% of a tread width of the tire (105), wherein the continuous circumferential upper tier (150a; 410a; 510a; 610a; 710a; 810a) has a radial height that is 1.5-14.0% of the section height and an axial width that is 20-80% of the tread width, characterised in that each of the blocks has an axial width that is 80-120% of the axial width of the continuous upper tier (150a; 410a; 510a; 610a; 710a; 810a), and the blocks span 20-40% of the continuous circumferential upper tier's (150a; 410a; 510a; 610a; 710a; 810a) inner circumference and the voids span 60-80% of the continuous circumferential upper tier's (150a; 410a; 510a; 610a; 710a; 810a) inner circumference.

2. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of claim 1, wherein the interposed circumferential lower tier (150b; 410b; 510b; 610b; 710b; 810b) has a radial height that is 6.0-10.0% of the section height.

3. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of claim 1 or claim 2, wherein the open cell foam is polyurethane.

4. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of any one of claims 1-3, further comprising an adhesive that secures the continuous circumferential upper tier (150a; 410a; 510a; 610a; 710a; 810a) to the interposed circumferential lower tier (150b; 410b; 510b; 610b; 710b; 810b).

5. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of any one of claims 1-4, further comprising an adhesive that secures the noise damper (150; 400; 500; 600; 700; 800) to the tire (105).

6. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of any one of claims 1-5, wherein the blocks are pitch sequenced.

7. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of any one of claims 1-6, wherein the noise damper (150; 400; 500; 600; 700; 800) has a trapezoidal cross section.

8. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of any one of claims 1-7, wherein the noise damper (150; 400; 500; 600; 700; 800) further includes fibers.

9. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of any one of claims 1-8, wherein the open cell foam has a sound absorption coefficient between 0.7 and 1.2.

10. The tire (105) and noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) of any one of claims 1-9, wherein the noise damper (150; 400; 500; 600; 700; 800) assembly (100; 200) reduces noise having a frequency between 180-220 Hz.

11. A method of making a noise damper (150; 400; 500; 600; 700; 800), the method comprising: forming a first tier (150a; 410a; 510a; 610a; 710a; 810a) of a first open cell foam; forming a plurality of blocks of a second open cell foam; adhering the plurality of blocks to the first tier (150a; 410a; 510a; 610a; 710a; 810a) of the first open cell foam in a spaced fashion, such that the plurality of blocks form a second tier (150b; 410b; 510b; 610b; 710b; 810b) of the second open cell foam and such that each of the plurality of blocks has an axial width that is 80-120% of the axial width of the continuous upper tier (150a; 410a; 510a; 610a; 710a; 810a); and forming the first tier (150a; 410a; 510a; 610a; 710a; 810a) of the first open cell foam and the second tier (150b; 410b; 510b; 610b; 710b; 810b) of the second open cell foam into an annular shape, such that the blocks span 10-30% of the first tier's (150a; 410a; 510a; 610a; 710a; 810a) inner circumference.

12. The method of claim 11, wherein the first open cell foam and the second open cell foam are the same material.

13. The method of claim 11, wherein the first open cell foam is made of polyurethane and the second open cell foam is made of melamine.

14. The method of any one of claims 11-13, wherein the plurality of blocks are formed with a height of 1.5-3.0 cm.

15. The method of any one of claims 11-14, wherein the forming of the plurality of blocks of the second open cell foam includes forming at least one of the plurality of blocks of the second open cell foam with a triangular cross-section.