load-bearing elastic bearing

Abstract

Elastic bearing (10) which has the following features: a first fastening element (12); a second fastening element (14); a first plurality (22a) of stiffening elements (20) with a central through-hole (25) located between the first and second fastening members (12, 14), wherein at least one first stiffening element (20a) of the first plurality (22a) of stiffening elements (20) is not parallel to a second stiffening element of the first plurality (22a) of stiffening elements (20), and wherein each of the first plurality (22a) of stiffening elements (20) has a material thickness and a curvature dimension that is greater than the material thickness; and an elastic material which is located between and connected to the stiffening elements (20) of the first plurality (22a) of stiffening elements (20), wherein each stiffening element (20) of the first plurality (22a) of stiffening elements (20) has a circular circumference and is substantially continuous along a circumferential direction of the stiffening element (20), and wherein a radial band of material from the edge of the central through-hole (25) to an outer edge of the stiffening element (20) has a width that is constant in the circumferential direction and has one or more perforations in addition to the central through-hole (25).

Description

Technical area

[0001] The present disclosure relates generally to a bearing, and more particularly to a resilient bearing capable of supporting loads while its mounting surfaces move relative to one another. background

[0002] Bearings with both load-bearing and deflection capabilities have been used in vehicle suspension systems for many years. In some applications, load-bearing suspension bearings, such as elastomeric bearings, are positioned between two vehicle components. These elastomeric bearings are designed to support compressive and tensile loads while allowing the two vehicle components to move linearly and tilt relative to each other. Typically, an elastomeric bearing comprises a cushion of an elastomeric material, such as rubber, sandwiched between two mounting or fixing plates. The fixing plates are generally positioned between the axle and the vehicle frame, allowing movement of the axle relative to the payload frame while transferring static and dynamic loads.This type of load-bearing suspension bearing can be used, for example, in articulated trucks of the type used on off-road construction sites.

[0003] One such known load-bearing elastomeric suspension mount is disclosed in U.S. Patent No. 6,443,439 B1 to Newman (the "'439 patent"). The suspension mount disclosed in the '439 patent has a series of parallel flat rings embedded in an elastomeric material and positioned between two rigid end members. The parallel flat rings increase the stiffness and load-bearing capacity of the mount compared to a pure elastomeric mount by reducing the bulging of the elastomeric material in compression and the necking of the elastomeric material in tension. Thus, these elastomeric mounts can adequately support pure compressive or tensile loads when the rigid end members are moved toward or away from each other. However, they are prone to premature failure in the highly stressed elastomeric material when the rigid end members are tilted with respect to each other (i.e., rotated from parallel).Premature failure of the elastomer material or the bond between the elastomer material and the embedded flat rings could result in the need to frequently replace these load-bearing suspension bearings. Replacement is typically difficult, time-consuming, and expensive.

[0004] Another elastic bearing having stiffening elements is known from DE 103 54 479 A1. Furthermore, US 4 968 010 A discloses an elastic bearing with curved or truncated cone-shaped disc elements surrounded by an elastic material and having a discontinuous shape in the circumferential direction. FR 866 361 A relates to a rubber torsion spring divided by rigid walls 5. Furthermore, WO 94 / 01695 A1 discloses an elastic bearing with curved annular elements made of metal material arranged between end plates and an intermediate ring. The curved annular elements have the same curvature as the end plates and the intermediate ring.

[0005] In suspension technology, particularly with respect to articulated truck suspensions, a robust, maintenance-free load-bearing mount that has sufficient stiffness to transmit large compressive and tensile loads and sufficient flexibility to accommodate the linear movement or translation and the tilting of the mounting surfaces relative to each other may be advantageous. The present disclosure is directed to overcoming one or more of the problems or disadvantages associated with the prior art.

[0006] The object of the present invention is achieved by an elastic bearing according to claims 1, 10 and 21. The subclaims relate to preferred embodiments of the invention.

[0007] The present disclosure describes a resilient mount having a first mounting member and a second mounting member. The mount may include a plurality of stiffening elements located between the first and second mounting members. At least a first stiffening element of the plurality of stiffening elements may be non-parallel to a second stiffening element of the first plurality of stiffening elements. Each of the first plurality of stiffening elements may have a material thickness and a crown dimension greater than the material thickness. Each stiffening element of the first plurality of stiffening elements is substantially continuous along a circumference or circumferential direction of the stiffening element.The bearing may also comprise an elastic material located between and connected to adjacent stiffening elements of the first plurality of stiffening elements.

[0008] Further, the present disclosure describes an elastic mount comprising a first fastening member, a second fastening member, and an elastic material connected to the first and second fastening members. The mount may also comprise a first plurality of non-planar elements, each non-planar element being at least partially embedded in the elastic material and having a camber dimension. At least a first of the non-planar elements may be non-parallel to a second of the non-planar elements, wherein the camber dimension of at least one first non-planar element differs from the camber dimension of at least one second non-planar element. Each stiffening element of the first plurality of stiffening elements is substantially continuous along a circumference or circumferential direction of the stiffening element.

[0009] Furthermore, the present disclosure describes a resilient mount comprising a first fastening element, a second fastening element, and a first plurality of stiffening elements located between the first and second fastening members. At least a first stiffening element of the first plurality of stiffening elements may be non-parallel to a second stiffening element of the first plurality of stiffening elements. Each of the first plurality of stiffening elements may have a material thickness and a camber dimension greater than the material thickness. Each stiffening element of the first plurality of stiffening elements may be substantially stiff to substantially limit deformation of the stiffening elements under load. The mount may also comprise a resilient material located between and connected to adjacent stiffening elements of the first plurality of stiffening elements. Short description of the drawings

[0010] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary disclosed embodiments and, together with the description, serve to explain certain aspects associated therewith. Fig. 1a is a side view of an exemplary embodiment of a resilient mount according to certain disclosed embodiments; Fig. Figure 1b is a cross-sectional view through section AA of the exemplary embodiment of the Fig. 1a; Fig. 2a is a side view of another exemplary disclosed embodiment of an elastic mount; Fig. Figure 2b is a cross-sectional view through section BB of the exemplary embodiment of the Fig. 2a; Fig. 3a-e are cross-sectional side views of exemplary configurations of a stiffening element according to certain aspects of the disclosure; Fig. 3f is a plan view of an exemplary stiffening element according to certain disclosed embodiments. Detailed description

[0011] The Fig. 1a and Fig. 1b are illustrations of an exemplary embodiment of a resilient mount 10 according to certain disclosed embodiments. The resilient mount 10 includes a first mounting member 12 and a second mounting member 14. An elastic material 16 is provided between the first and second mounting members 12, 14, and a plurality 22 of stiffening elements 20 are embedded in the elastic material 16. The resilient mount 10 would typically be positioned between two machine or vehicle components (not shown).

[0012] Both the first fastening member 12 and the second fastening member 14 may be flat plates with a square, rectangular, circular, or other regular or irregularly shaped perimeter. Alternatively, one or both of the first and second fastening members 12, 14 may be non-flat, for example, concave, as best shown by the second fastening member 14 in Fig. 1b, have convex or other regular or irregular non-planar shapes. The first and second fastening members may be provided with a central through-hole 17.

[0013] Additionally, the first and second fastening members 12, 14 are adapted to be secured to vehicle components between which the resilient mount 10 is positioned. The first fastening member 12 may have a mounting surface 13 that supports a mounting surface of the corresponding vehicle component (not shown), and the second fastening member 14 may have a mounting surface 15 that supports a mounting surface of the other vehicle component (also not shown). For example, the first fastening member 12 may have a square perimeter with a screw hole at each corner for securing the corresponding vehicle component. Other fastening methods known to those skilled in the art may be used.

[0014] The elastic material 16 is positioned between the first and second fastening members 12, 14. The material 16 is formed from any suitable elastic material, such as an elastomeric material. Such materials typically bulge when subjected to compressive loads and contract when subjected to tensile loads. The elastic material 16 may be molded onto, bonded to, or otherwise attached to the first and second fastening members 12, 14 to more efficiently transfer loads between these fastening members 12, 14.

[0015] Additionally, the elastic material 16 may be molded, bonded with an adhesive, or otherwise attached to the plurality 22 of stiffening elements 20. The elastic material 16 may be formed from a single piece of elastic material, as best shown in Fig. 1b. As shown, the elastic material 16 may, for example, be molded or partially molded around the stiffening elements 20. Alternatively, the elastic material 16 may form a plurality of pieces 16a that are inserted between the plurality of stiffening elements 20 and molded or bonded thereto, as best shown in Fig. 2b shown.

[0016] As in the Fig. 1a and Fig. As shown in Figure 1b, a plurality 22 of stiffening elements 20 are positioned between the first and second fastening members 12, 14. The stiffening elements 20 are stacked on top of each other, spaced apart from each other, and a layer of elastic material is located between them. Each stiffening element 20 is formed from a thin plate with a plate thickness t. The plate thickness t does not have to be uniform. For example, as shown in Fig. 3a, the plate thickness t may vary from a thickness t0 at the perimeter of the stiffening element 20 to a second thickness t1 closer to the center of the stiffening element 20. The stiffening elements 20 may have a circular perimeter, however, other perimeter shapes, such as square, rectangular, oval, or other shapes, could be used to assist in more efficient response to loads transmitted by the elastic bearing 10. Furthermore, not every stiffening element 20 of the plurality 22 needs to have the same perimeter shape, nor does every stiffening element 20 of the plurality 22 need to be the same size.

[0017] How best to Fig. 1b, 2b and 3a-3e, the stiffening elements 20 may not be planar, ie the stiffening elements 20 may have a dimension deviating from the plane or curvature dimension d which is greater than the plate or material thickness t. As shown in Fig. 1b, the camber dimension d need not be the same for each of the plurality 22 of stiffening elements 20 in any one elastic bearing 10. For example, the camber dimension d may vary across the stack of stiffening elements 20, from a minimum camber dimension d0 for a first stiffening element 20a at one end of the stack of stiffening elements 20 to a maximum camber dimension d1 for a last stiffening element 20b at the opposite end of the stack. As another example, as shown in Fig. As shown in Figure 2b, the camber dimension d can vary from a minimum camber dimension d0 for a stiffening element 20a near the center of the stack of stiffening elements 20 to a maximum camber dimension d1 for the stiffening elements 20b at each end of the stack of stiffening elements 20. Other arrangements of stiffening elements 20 with their associated camber dimensions d can be provided, for example, to vary the load-bearing capacity or stiffness of the elastic mount 10.

[0018] Also as in Fig. 2b, one or more of the stiffening elements 20 may be planar, ie the curvature dimension d may be substantially the same as the plate thickness t. In Fig. 2b, the central stiffening element 20c is planar. A plurality 22a of stiffening elements 20 is arranged on one side of the central stiffening element 20c, and a second plurality of stiffening elements 22b is arranged on the other side of this central planar stiffening element 20c.

[0019] How best to Fig. 3a-3e, the non-planar stiffening elements 20 may have any of a variety of cross-sections. For example, Fig. 3a a stiffening element 20 with a conical shape, ie with a "V-like" cross-section. In this particular example, the stiffening element 20 has a truncated cone shape with a central through-hole 25. In addition, the element of the Fig. 3a a plate thickness t which is greater towards the center than towards the edge. Fig. Figure 3b illustrates a stiffening element 20 with a spherical shape, i.e., with a circular cross-section. In other words, the plate forming the stiffening element has a constant radius of curvature. In this particular example, the plate thickness t is essentially constant, and the element has no central through-hole. Fig. Figure 3c illustrates a stiffening element 20 with a parabolic cross-section, i.e. the plate curvature is greater in the center than at the edges, and the plate generally follows a parabolic curvature. As in Fig. 3b, the plate thickness t is essentially constant and as in Fig. 3a, the stiffening element has a central through hole 25. Fig. Figure 3d illustrates a stiffening element 20 with an elliptical cross-section, i.e., the plate forming the stiffening element has a radius of curvature that is larger at the periphery than towards the center, and the plate generally follows an elliptical curvature. Again, the plate thickness t, as shown in the Fig. 3b and Fig. 3c, essentially constant. As in the Fig. 3a and Fig. 3c the element has a central through hole 25. Fig. Figure 3e illustrates a stiffening element 20 with a polygonal cross-section, ie the plate cross-section is formed from a series of substantially straight line segments. The size and shape of the Fig. The cross-sections illustrated in Figure 3e are merely exemplary and are not intended to be limiting. It is contemplated that additional and / or different shapes than those illustrated in the figures and described herein may be associated with the stiffening element 20. For example, a stiffening element 20 may have a substantially flat cross-section in one direction and a substantially circular cross-section in a second direction perpendicular to the first direction, i.e., a drum- or cylindrical-shaped element may be formed.

[0020] According to one embodiment, except for the portion associated with the central through-hole 25, the stiffening element 20 may be substantially continuous. In the case of a stiffening element with a circular circumference, the radial band of material from the edge of the central through-hole 25 to an outer edge of the stiffening element 20 may be substantially constant along the circumference of the stiffening element 20. In the case of stiffening elements having non-circular circumferences, the substantially continuous extension of the element may be maintained by providing a radial band of material that substantially limits the bending, flattening, or deformation of the stiffening element 20, thereby maintaining the shape of the element and preventing significant flexion or deflection thereof.

[0021] According to a further embodiment, the stiffening element 20 may, in addition to the through-hole 25, have one or more perforations or holes between the edges of the radial band of material. It is contemplated that these holes may be provided such that the stiffness of the stiffening elements having holes between the edges of the radial band is substantially similar to the stiffness of the stiffening elements that do not have holes, thereby substantially preventing deformation or bending of the stiffening element under load. Accordingly, stiffening elements 20 having holes may be used to reduce material and manufacturing costs associated with the stiffening elements 20 while maintaining the structural integrity of the element.

[0022] According to a further embodiment, the stiffening element 20 may be substantially rigid, so that the deflection or deformation of the stiffening element 20 due to a load is substantially limited. Alternatively and / or in addition to the general continuity, the stiffening element 20 may be constructed of a rigid or semi-rigid material, which, in cooperation with the elastic material 16, can limit and / or prevent the structural deformation of the stiffening element.

[0023] In addition, the elastic bearing 10 may have at least one stiffening element 20 which is not parallel to a second stiffening element 20. As in Fig. 1b, the stiffening element 20a has a relatively flat profile, while the stiffening element 20b has a cross-sectional profile inclination angle that is approximately 15 to 20 degrees from the horizontal. The cross-sectional profiles of the stiffening elements 20 stacked between the elements 20a and 20b have inclination angles that increase over the extension of the plurality of stiffening elements 20 from element 20a to element 20b. Thus, in the embodiment of Fig. 1b not all stiffening elements are parallel to each other. Similarly, in the Fig. 2a and Fig. 2b, wherein the stiffening elements 20 have a circular cross-section, the radius of curvature varies from element to element. The first plurality 22a of stiffening elements 20 are not parallel to each other; the second plurality 22b of stiffening elements 20 are not parallel to each other, nor to the stiffening elements in the first plurality 22a. Furthermore, the central planar stiffening element 20c is not parallel to all of the other stiffening elements 20. Thus, again, the stiffening elements are not parallel to each other. It is also contemplated that other arrangements of non-parallel stiffening elements are within the scope of the invention.

[0024] In addition, the elastic bearing 10 could have a combination of non-parallel stiffening elements and parallel stiffening elements. For example, a Fig. 2 shown embodiment may be an alternative embodiment that second or third planar stiffening elements 20c are provided, which are located adjacent to the single central planar stiffening element 20c, which is already shown in Fig. 2b. All of the planar stiffening elements 20c are parallel to each other; all other stiffening elements, ie the stiffening elements 20a, 20b, etc., are not parallel to each other. Alternatively, each stiffening element 20 could be arranged within the Fig. 1b and Fig. 2b, the two parallel stiffening elements can be paired with a similar parallel stiffening element. Thus, for example, a pair of parallel stiffening elements 20b could be located adjacent to a pair of parallel stiffening elements 20a, with the stiffening element 20b not being parallel to the stiffening element 20a.

[0025] A tension-bearing element 32, such as a centrally extending screw or threaded rod with nuts at one or both ends, as best shown in the Fig. 1b and Fig. 2b, can be used to control the maximum extent of the separation between the first and second fastening members 12, 14. The tensile load-bearing element 32 would typically carry tensile loads, i.e., loads acting to move the first fastening member 12 away from the second fastening member 14, thereby stretching the elastic material 16. Although the tensile load-bearing element 32 would not typically carry compressive loads, i.e., loads acting to move the first fastening member 12 toward the second fastening member 14, thereby compressing the elastic material 16, the member 32 can carry compressive loads in certain applications. Additionally, the tensile load-bearing element 32 can be preloaded. Alternatively, more than one tensile load-bearing element 32 can be used, and these elements need not be centrally located.For example, a pair of tension-bearing elements (not shown) may be arranged at opposite edges or corners of the first and second fastening members 12, 14. Industrial applicability

[0026] While the load-bearing elastic bearing of the Fig. 1 and Fig.2 has a wide variety of applications, the described bearing could equally well be suited for use with an articulated vehicle. For example, this load-bearing elastic bearing could be used for the rear suspension of an articulated dump truck. In the articulated dump truck, the rear suspension transfers very high loads from the frame to the rear axles. For example, in an articulated dump truck with two rear axles, equalizing beams could transfer the weight of the payload to the rear axles through four elastic bearings, two per equalizing beam. The elastic bearings would typically be attached to the ends of the equalizing beams and would allow independent movement of the axles. At the same time as the rear suspension transfers these large loads, it undergoes large oscillations or deflections while maintaining traction over rough terrain.In these situations, the load-bearing elastic bearing would carry high compressive and tensile loads while its mounting surfaces move and tilt relative to each other in a straight line.

[0027] Because the resilient bearing includes stiffening elements that are substantially stiff under loading conditions, the presently disclosed bearing may be particularly well-suited for load-bearing applications that require the bearing to support vertical loads without significant deflection of the stiffening elements, while permitting tangential and / or radial movement. The stiffness of the bearing may be further improved by providing stiffening elements that are substantially continuous (e.g., having a width that is substantially constant at the periphery or in the circumferential direction), thereby limiting the extension or deformation of the bearing under loading conditions and potentially increasing the load-bearing capabilities of the bearing.

[0028] For those situations where one elastic bearing may not have the desired load carrying capacity, a pair of elastic bearings could be mounted side by side in a parallel load carrying configuration.

[0029] It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed load-bearing elastic mount. Other embodiments of the present disclosure will become apparent to those skilled in the art from consideration of the specification and from practice of the present disclosure. It is intended that the specification and examples be considered exemplary only, with a true scope of the present disclosure being indicated by the following claims and their equivalents.

Claims

[1] Elastic bearing (10) comprising: a first fastening member (12); a second fastening member (14); a first plurality (22a) of stiffening elements (20) having a central through-hole (25) located between the first and second fastening members (12, 14), wherein at least a first stiffening element (20a) of the first plurality (22a) of stiffening elements (20) is not parallel to a second stiffening element of the first plurality (22a) of stiffening elements (20), and wherein each of the first plurality (22a) of stiffening elements (20) has a material thickness and a camber dimension that is greater than the material thickness; and an elastic material which is located between the stiffening elements (20) of the first plurality (22a) of stiffening elements (20) and is connected thereto, wherein each stiffening element (20) of the first plurality (22a) of stiffening elements (20) has a circular circumference and is substantially continuous along a circumferential direction of the stiffening element (20), and wherein a radial band of the material from the edge of the central through-hole (25) to an outer edge of the stiffening element (20) has a width that is constant in the circumferential direction and has one or more perforations in addition to the central through-hole (25). [2] Bearing (10) according to claim 1, wherein an elastic material is arranged between the first fastening member (12) and one of the first plurality (22a) of stiffening elements (20) and is connected thereto, and wherein an elastic material is arranged between the second fastening member (14) and another stiffening element (20) of the first plurality (22a) of stiffening elements (20) and is connected thereto. [3] The bearing (10) of claim 1, wherein the first plurality (22a) of stiffening elements (20) comprises a series of stiffening elements (20) arranged in an order of decreasing camber dimensions. [4] Bearing (10) according to claim 1, wherein the camber dimension of a first plurality (22a) of stiffening elements (20) differs from the camber dimension of a second plurality of stiffening elements (20). [5] Bearing (10) according to claim 1, wherein at least one of the first plurality (22a) of stiffening elements (20) has a V-shaped cross-section, a circular cross-section, a parabolic cross-section, an elliptical cross-section, or a polygonal cross-section. [6] Bearing (10) according to claim 1, further comprising: a second plurality (22b) of stiffening elements (20) having a central through-hole (25) located between the first and second fastening members (12, 14), each stiffening element (20) of the second plurality (22b) of stiffening elements (20) having a material thickness and a camber dimension that is greater than the material thickness; and an elastic material (16) which is located between the stiffening elements (20) of the second plurality (22b) of stiffening elements (20) and is connected thereto, wherein the first plurality (22a) of stiffening elements (20) are arranged in an order of increasing curvature dimensions, and wherein the second plurality (22b) of stiffening elements (20) are arranged in an order of decreasing curvature dimensions. [7] The bearing (10) of claim 6, further comprising at least one planar stiffening element (20c) located between the first plurality (22a) of stiffening elements (20) and the second plurality (22b) of stiffening elements (20). [8] A bearing (10) according to claim 7, further comprising a tension-bearing element (32) extending between the first and second fastening members (12, 14). [9] The bearing (10) of claim 1, wherein each stiffening element (20) of the first plurality (22a) of stiffening elements (20) is substantially rigid to substantially limit deformation of the stiffening element (20) under load. [10] Elastic bearing (10) comprising: a first fastening member (12); a second fastening member (14); an elastic material (16) connected to the first and second fastening members (12, 14); and a first plurality (22a) of non-planar elements (20) having a central through-hole (25), each non-planar element (20) being at least partially embedded in the elastic material (16) and having a curvature dimension, and at least a first of the non-planar elements (20) being non-parallel to a second of the non-planar elements (20), the curvature dimension of at least one non-planar element (20) differing from the curvature dimension of at least a second non-planar element (20), wherein each non-planar element (20) of the first plurality (22a) of non-planar elements (20) has a circular circumference and is substantially continuous along a circumferential direction of the non-planar element (20), and wherein a radial band of the material from the edge of the central through-hole (25) to an outer edge of the non-planar element (20) has a width that is constant in the circumferential direction, and in addition to the central through-hole (25) has one or more perforations. [11] The bearing (10) of claim 10, wherein each of the first plurality (22a) of non-planar elements (20) has a material thickness less than the crown dimension. [12] The bearing (10) of claim 11, wherein at least one of the first plurality (22a) of non-planar elements (20) has a V-shaped cross-section, a circular cross-section, a parabolic cross-section, an elliptical cross-section, or a polygonal cross-section. [13] The bearing (10) of claim 10, wherein the first plurality (22a) of non-planar elements (20) are arranged in an order of increasing crown dimensions. [14] The bearing (10) of claim 10, further comprising a tension member (32) extending between the first and second mounting members (12, 14) and limiting relative movement of the first mounting member (12) away from the second mounting member (14). [15] The bearing (10) of claim 10, further comprising a second plurality (22b) of non-planar elements (20), each non-planar element (20) of the second plurality (22b) of non-planar elements (20) being at least partially embedded in the elastic material and having a camber dimension. [16] The bearing (10) of claim 15, wherein each of the first plurality (22a) of non-planar elements (20) and each of the second plurality (22b) of non-planar elements (20) has a V-shaped cross-section, a circular cross-section, a parabolic cross-section, an elliptical cross-section, or a polygonal cross-section. [17] The bearing (10) of claim 15, wherein the first plurality (22a) of non-planar elements (20) are arranged in an order of increasing crown dimensions, and wherein the second plurality (22b) of non-planar elements (20) are arranged in an order of decreasing crown dimensions. [18] The bearing (10) of claim 17, further comprising at least one planar element (20) located between the first plurality (22a) of non-planar elements (20) and the second plurality (22b) of non-planar elements (20). [19] A bearing (10) according to claim 10, further comprising at least one planar element (20c) located between the first and second fastening members (12, 14). [20] A bearing according to claim 10, wherein each non-planar element (20) of the first plurality (22a) of non-planar elements (20) has a material width extending from an edge of a central through-hole (25) to an outer edge of the non-planar element (20), the width of the material being substantially the same along the circumferential direction of the non-planar element (20). [21] Elastic bearing, which has the following: a first fastening member (12); a second fastening member (14); a first plurality (22a) of stiffening elements (20) having a central through-hole (25) located between the first and second fastening members (12, 14), wherein at least a first stiffening element (20) of the first plurality (22a) of stiffening elements is not parallel to a second stiffening element (20) of the first plurality (22a) of stiffening elements (20), and wherein each of the first plurality (22a) of stiffening elements (20) has a material thickness and a camber dimension that is greater than the material thickness; and an elastic material which is located between the stiffening elements (20) of the first plurality (22a) of stiffening elements (20) and is connected thereto, wherein each stiffening element (20) of the first plurality (22a) of stiffening elements (20) is substantially rigid to substantially limit the deformation of the stiffening element (20) under load, wherein each stiffening element (20) of the first plurality (22a) of stiffening elements (20) has a circular circumference and is substantially continuous along a circumferential direction of the stiffening element (20), and wherein a radial band of the material from the edge of the central through-hole (25) to an outer edge of the stiffening element (20) has a width that is constant in the circumferential direction, and in addition to the central through-hole (25) has one or more perforations.

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