CN118102949A - Support surface - Google Patents

Abstract

A support surface (5) comprising an opening (25) on a bottom surface of the support surface (5). The openings (25), which may include a plurality of openings, provide controlled structural collapse of the support surface by varying the stiffness of the cross section. That is, the area where the opening (25) is located is more prone to collapse than the peripheral area of the support structure, thereby making the area with the opening feel softer. The opening (25) may reduce peak pressure on a user's body part (e.g., a user's ischial tuberosity) located above the opening. The support surface may also include a low friction interface extending above a top surface of the support surface.

Description

Support surface

Cross Reference to Related Applications

The present application claims priority and benefit from U.S. provisional patent application No. 63/351,191 entitled "seat support surface [ SEAT SUPPORT SURFACE ]" filed on day 6 and 10 of 2022; and claims priority and benefit from U.S. provisional patent application No. 63/221,657 entitled "SUPPORT SURFACE" filed on 7.14 of 2021; the entire contents of both of these patent applications are hereby incorporated by reference in their entirety.

Background

Seat cushions are typically made of durable cushion materials such as foam, gel, or inflatable bladders. Foam is typically used in seats because it is more resilient and durable than other options such as padding with polyester padding or feather/down pads. Foam mats are typically cast, injection molded, or milled to form mats having a finished or desired shape. Alternatively, the foam cushion may be cut from a larger foam block to the contour of the desired cushion shape.

While foam cushions are the most popular choice for durable and economical seats, foam cushions can be uncomfortable for users sitting for long periods of time. In particular, single density foam cushions can result in high sitting pressures (typically measured in mm Hg) and cause high shear forces. These high sitting and shearing strains may lead to the stimulation of nociceptors, in particular mechanoreceptors, of the user and trigger pain signals in the brain. The signal is sent up the spinal cord, into the brain, modulated, and the perception of pain is given to the individual who takes action (e.g., adjusts to a new location) when needed. High sitting and shearing forces are often simply handled as "too uncomfortable" by the user's brain, especially if the user sits for a longer period of time than 5 minutes to 10 minutes. The ischial tuberosities (IT or ischial bones) of the user are very sensitive and in a self-protected mode are very sensitive to pain in the seat to prevent tissue rupture. If left uncontrolled, tissue disruption may lead to necrosis, creating pressure or shear strain damage.

Disclosure of Invention

The support surface described herein is designed to reduce stress on the user's IT, which allows the user to sit more comfortably for longer periods of time without sitting restless or repositioning himself on the seat. The example support surface may also be easily manufactured using relatively inexpensive materials. Thus, the support surface may be used for a variety of different purposes and (as compared to existing support surfaces that reduce peak pressure to a level similar to the example support surface) may be used by a larger portion of the population.

The example support surfaces described herein include an opening (cutoff) on a bottom surface of the seat support surface. The openings provide controlled structural collapse of the support surface by varying the stiffness of the cross section. That is, the area where the openings are located is more prone to collapse than the peripheral area of the support structure, thereby making the area with the openings feel softer. The opening reduces peak pressure of a user's body part (ideally IT) located above the opening. The support surface further includes a low friction interface extending above the top surface of the support surface, the low friction interface being located between the opening on the bottom surface and the user's bony prominence, wherein the low friction interface is a low friction fabric. The low friction interface extending over the support surface and the low friction fabric reduces shear strain in the seating plane of the user. The support surface may also or alternatively include a cut (cut) extending through the support surface between the opening on the bottom surface and the user's bony prominence, with the low friction fabric disposed within the cut. The cuts extending through the support surface and the low friction fabric reduce shear strain in the seating plane of the user.

An example chair including a support surface is described herein. The support surface includes a top surface and a bottom surface, the top surface being contoured to receive the pelvis of the user. The openings on the bottom surface provide controlled structural collapse of the support surface by varying the stiffness of the cross section.

As mentioned above, the support surface may be used in a variety of different applications in addition to the described chair. Such applications may include, but are not limited to, vehicle seats (including bus seats or train seats or any other public transportation seat), aircraft seats, farm equipment seats or any other possible use of a support surface. The concept of an opening in a support surface for reducing peak pressure in an area of the body may also be applied to wheelchairs, mattresses or other furniture.

The support surface may also or alternatively include a low friction interface extending over the top surface of the support surface, the low friction interface being located between the opening on the bottom surface and the bony prominence of the user, wherein the low friction interface is a low friction fabric. The low friction interface extending over the support surface and the low friction fabric reduces shear strain in the seating plane of the user.

The support surface may also or alternatively include a cutout extending through the support surface between the opening on the bottom surface and the bone protrusion of the user, wherein the low friction fabric is positioned within the cutout. The cuts extending through the support surface and the low friction fabric reduce shear strain in the seating plane of the user.

Drawings

Various examples of embodiments of systems, devices, and methods according to the present invention will be described in detail with reference to the following drawings.

FIG. 1 depicts a perspective view of an example seat support surface.

Fig. 2 depicts a bottom view of the seat support surface of fig. 1.

Fig. 3 is a cross-sectional view of the seat support surface of fig. 1.

Fig. 4 depicts a bottom view of an alternative example seat support surface similar to the seat support surface of fig. 1.

Fig. 5 is a cross-sectional view of the seat support surface of fig. 4.

FIG. 6 is a bottom view of an alternative example seat support surface similar to the seat support surface of FIG. 1.

Fig. 7 is a cross-sectional view of the seat support surface of fig. 6.

Fig. 8 depicts a cross-sectional view of an example user about to sit on a seat support surface similar to the seat support surface described in fig. 1-5.

FIG. 9 depicts an example user sitting on the seat support surface of FIG. 8.

Fig. 10 depicts a perspective view of the support surface of fig. 1-7 in an example seat pan.

Fig. 11 depicts the support surface of fig. 1-7 in an example office chair including the seat pan of fig. 10.

Fig. 12 depicts an alternative version of the support surface of fig. 1-7 made of a gel material.

Fig. 13 depicts a perspective view of an example support surface including shear reduction features.

Fig. 14 depicts a cross-sectional side view of the support surface of fig. 13.

Fig. 15 depicts a cross-sectional side view of an example support surface including the shear reduction feature of fig. 13 and the pressure reduction feature described in connection with fig. 4 and 5.

Fig. 16 depicts a cross-sectional side view of an example support surface including the shear reduction feature of fig. 13 and the pressure reduction feature described in connection with fig. 6 and 7.

Fig. 17 depicts a perspective view of an example support surface including an alternative shear reduction feature.

Fig. 18 depicts a cross-sectional side view of an example support surface including the shear reduction feature of fig. 17 and the pressure reduction feature described in connection with fig. 6 and 7.

Fig. 19 depicts a cross-sectional side view of an example support surface including alternative shear reduction features and pressure reduction features described in connection with fig. 6 and 7.

FIG. 20 depicts an example interface map of pressure and shear using a support surface similar to that of FIG. 19.

Fig. 21 depicts an example volumetric strain distribution of compressive and shear tissue strain on a user sitting on a support surface similar to the support surface of fig. 19.

FIG. 22 depicts example results of a pressure mapping test performed according to ISO 16840-6:2015, clause 14.

It should be understood that the figures are not necessarily drawn to scale. In some instances, details that are not necessary for an understanding of the present invention or that render other details difficult to perceive may have been omitted. Of course, it is to be understood that the invention is not necessarily limited to the specific embodiments illustrated herein.

Detailed Description

One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

Fig. 1 is a perspective view of an example seating or support surface 5 (e.g., a cushion) described herein. The example seat support surface 5 is made of foam (e.g., cast foam, injection molded foam, etc.) that may be molded, milled, cut, or otherwise formed into a desired shape for a particular application. The support surface 5 may be used with most any type of seat such as, but not limited to, office chairs, aircraft seats, vehicle seats, industrial equipment seats, stadium seats, theatre seats, residential seats, bus seats, train seats, and the like. The support surface 5 described herein may be covered with virtually any suitable woven or non-woven material that is sufficiently resilient to accommodate the shape change of the support surface 5 using virtually any decorative method. The support surface 5 may be used with or without a covering and may be a self skinning foam such as an EVA injection molded foam or a closed cell resin.

The top surface 10 of the support surface 5 is contoured in a wave, the sides 15 of the support surface 5 are convex, and the front edge 20 of the support surface 5 is tapered (e.g., undercut, relief cut). In addition, the top surface 10 of the undulating profile includes a pelvic recess 12 and an inclined femoral surface 14. The pelvic recess 12 and the inclined surface 14 help provide a force in the posterior direction to stabilize the pelvis and prevent translation on the seat support surface 5 in the anterior direction, thereby positioning the user on the pressure and shear strain relief features. The contour of the top surface 10 may be dependent on the shape of the user's pelvic region. The top surface 10 is contoured to better match the negative surface of a person in a seated position than a flat seating surface. The mating shape helps to greatly reduce the seat pressure below IT and coccyx compared to flat top seating surfaces or cushions. The side 15 may be raised to help guide the user into the centre of the seat. The profile of the convex side 15 also complementarily matches the shape of the user to assist in loading the pelvic side and tissue and muscles along the femoral region. This surface helps to carry the patient's load and redistribute the pressure over a larger sitting area. The anterior edge 20 may taper posteriorly to act as a relief incision that is directed down the calf muscle closer to the popliteal fossa. Relief cuts help alleviate contact with these areas, thereby reducing the chance of restricting blood flow to the lower extremities. For the embodiment of fig. 1-3, the design of the front edge 20 of the support surface 5 allows the front edge 20 of the seat to collapse due to the weight of the user's legs, while the edge of the seat bottom plate (such as the seat bottom plate in fig. 8 and 9) does not contact and stress the user's legs. The front edge 20 of the seat bottom plate may be lower (as compared to conventional seat bottom plates) to allow the foam a lot of room to squeeze under the weight of the user's legs while not contacting the hard front edge of the seat bottom plate, which may cause severe pressure to the user's skin and other tissues, which may lead to pressure damage.

In addition, the support surface 5 described herein reduces peak pressure on the ischial tuberosities of the user due to a plurality of pressure reducing features 25 (e.g., openings) integrated into the bottom side or bottom surface 30 of the support surface 5. The example support surface 5 provides reduced peak pressure compared to prior foam cushions. As mentioned herein, the openings 25 may include holes, recesses, notches, and the like. The openings 25 change the cross-sectional stiffness of the support surface 5 in certain areas, in particular in areas located under the bone projections, such as the areas where ischial tuberosities or coccyx are placed. The reduced cross-sectional stiffness in the region of the support surface 5 where the ischial tuberosities are located reduces the peak pressure experienced by some or all of the ischial tuberosities. For example, peak pressures may be reduced by up to 60mm Hg for a standard-sized male user. Specifically, in at least one variation, the peak pressure is reduced to a value of 77mm Hg using a support surface 5 having openings 25 as described herein, whereas in contrast, a mesh-like seating surface typically has a peak pressure of about 152mm Hg).

The use of the support structure 5 reduces peak pressure because the support surface 5 includes controlled structural collapse built into the support surface 5. That is, the area where the opening 25 is located is more prone to collapse than the peripheral area of the support surface 5, thereby making the area with the opening 25 softer. The opening 25 reduces peak pressure on a user's body part (ideally IT) located above the opening 25. More specifically, the openings 25 and contoured top surface 10 reduce peak pressure because the stiffness of the seat support surface 5 below the bone protrusion is strategically collapsed, allowing the single density substrate to have different stiffness values, typically only by adding foam inserts, viscous or non-viscous gel inserts, or balloon inserts having different (e.g., softer) densities to the cushion. The controlled collapse of the structure is built into the bottom surface 30 of the support structure 5, which enables the support structure 5 to look and feel like an existing mat, except for a reduction in peak pressure on the user. That is, the built-in structural collapse (openings 25) enables the cross-sectional stiffness to be changed in certain areas of the support surface 5 (e.g., in a portion of a certain cross-section) without the mat material in different areas becoming softer or thicker.

Fig. 2 to 7 show three examples of support surfaces 5 comprising openings 25 for reducing peak pressure on ischial tuberosities. Fig. 2 is a bottom view of the support surface, and fig. 3 is a cross-sectional view of the support surface 5, depicting the shape of the opening 25 (e.g., notch) on the bottom surface 30 of the support surface 5. The example opening 25 is substantially dome-shaped or hemispherical such that the top of the opening 25 is rounded, but may be shaped differently (e.g., conical, rectangular prismatic, conical, etc.). For these figures, the opening 25 may have a circular or oval basic shape (as shown in fig. 2), and a semi-circular or semi-elliptical cross-section (as shown in the cross-sectional view of fig. 3) as seen from a side view of the support surface. The opening 25 does not extend to the top surface 10 of the support surface 5, and thus the opening 25 does not open to the top surface 10 of the support surface 5. Because the opening 25 does not extend to the top surface 10 of the support surface 5, the user does not have the sensation of sitting on an open hole when sitting on the support surface 5.

In the example shown, the openings 25 are arranged in a first group located closer to the rear edge 35 of the support surface 5 and in a second group located closer to the front edge 20 of the support surface 5. The first group of examples is ideally located for a user sitting in the rear of a seat or chair and using the backrest of the seat or chair. The second group of examples is ideally located for when the user sits closer to the front edge 20 of the seat support surface 5 (i.e. in the rim position). Users may often prefer to sit more forward, for example, to relieve pressure on their legs from the support surface, to better reach items on their tables or workspaces, or for any other number of reasons or particular tasks. The two sets of openings 25 function similarly to provide controlled structural collapse of the support surface 5 in the region adjacent the ischial tuberosities of the user. The openings 25 are intended to reduce peak pressures common to existing single density materials (e.g., foam, gel, etc. without openings) when a user is properly on the support surface 5.

As shown in fig. 4 and 5, an alternative example support surface 5 may include only a set of openings 25 disposed adjacent the rear edge 35 of the support surface. In some examples, the opening 25 in the support surface 5 of fig. 4 and 5 may be elongated (e.g., may have an oval or elliptical basic shape that extends further toward the front edge 20 of the support surface 5) to accommodate different body shapes of the user or different seating positions of the user. When the user sits only near the rear of the support surface 5, the single set of openings 25 provides a reduction in peak pressure on the same ischial tuberosity as the example support surface 5 with two sets of openings 25 in fig. 2 and 3.

Fig. 6 and 7 depict an example support surface 5 that includes an alternative opening 25 disposed adjacent the rear edge 35 of the support surface. In the example configuration shown, the shape of the opening 25 may be described as a double dome shape or a stacked dome shape. In the example shown, the opening 25 comprises a first dome and a second dome that overlap and/or overlap each other. In the example configuration shown in fig. 7, the double dome shaped opening 25 includes a first region or first dome extending into the support surface 5 to a first distance (e.g., depth) and a second region or second dome extending into the support surface 5 to a second distance. In at least one example, the first dome extends a greater distance into the support surface 5 than the second dome. In the example shown, the first and second domes of the opening 25 are aligned with each other. For example, the center point of the first dome and the center point of the second dome are aligned with each other. In another example, the first dome may overlap only a portion of the second dome. For example, the center point of the first dome and the center point of the second dome are offset from each other. The stacked dome shape may also include rounded edges and/or straight edges.

The set of openings 25 provides a reduction in peak pressure on ischial tuberosities similar to the example support surface 5 in fig. 2-5 when a user sits on the support surface 5. In the example configuration of fig. 6 and 7, the first dome of opening 25 is disposed in an area adjacent to the ischial tuberosity of the user and occupies an interior (or central) area of opening 25. The second dome is disposed in an area surrounding and proximate to the user's IT, particularly surrounding (e.g., enveloping, overlapping, bordering or encircling) the first dome and occupies an outer area of the opening 25. The double dome shape provides a greater reduction in peak pressure and a more precise controlled collapse of the support surface 5 under the ischial tuberosities of the user due to the varying degrees of cross-sectional stiffness. That is, when a user sits on the support surface 5, both the first and second domes of the opening 25 act individually and cooperatively to provide a snug submergence of the user's bone protrusion and tissue into the support surface 5. In one such example, the first dome is configured to provide a first cross-sectional stiffness and is further configured such that an interior region of the opening 25 collapses below the user IT. The second dome is configured to provide a second cross-sectional stiffness and is further configured such that an outer region of the opening 25 collapses under the user's surrounding muscle and gluteus tissue, thereby providing a controlled collapse of the support surface 5 that more closely matches the user's anatomy. The stacked dome-shaped openings 25 provide different cross-sectional stiffness in certain areas, particularly in areas located below the bone protrusion, such as the areas where ischial tuberosities or coccyx are placed.

Fig. 8 depicts a cross-sectional view of an example user 40 about to sit on the support surface 5 (but not yet exerting a downward force on the support surface), and fig. 9 depicts the example user 40 sitting on a support surface 5 similar to the support surface 5 of fig. 4 and 5. As shown in fig. 8 and 9, the openings 25 collapse (e.g., controlled structural collapse), which allows the user 40 to sink further into the support surface 5 and be less resistant to the material (e.g., foam) of the support surface 5, while redistributing the user's seating pressure onto the surrounding tissue area, thereby reducing the risk of pressure injury and/or triggering the risk of IT and nociceptors around the surrounding area in the tissue. When the openings 25 collapse, air is simply expelled from within the openings 25 and no active means are required to remove air from the air chamber formed by each opening 25. The reduced stiffness of the support surface 5 in the ischial tuberosity region 45 causes a reduced pressure on the ischial tuberosity 45 of the user 40. In addition, the user 40 sits deeper in the support surface 5, which helps to cradle the user's pelvis and provide a proper basis for the correct sitting posture of the entire spine. Proper foundations provide pelvic lateral stability and mitigate forward movement, which generally causes shear forces common in surface and deep tissues. Shear forces are one of two ways to cause pressure injury and nociceptive pain to occur. Providing lateral stability and reducing forward shear is the basis required to then apply the appropriate posterior input through the pelvis and up to the cervical spine in an attempt to provide the correct sitting position for any individual.

Although the example openings 25 depicted herein are dome-shaped or double dome-shaped, other shapes of openings 25 may alternatively be used. Other shapes of the opening 25 may include, but are not limited to, a flattened dome, a box, a pyramid, a flattened pyramid, a rectangular prism, a cone, a flattened cone, a cylinder with rounded or tapered sides, any combination thereof, or any other regular or irregular geometry or multiple geometries or stacked geometries that provide controlled collapse in the support surface 5 in the region proximate to the user's ischial tuberosities 45 or at the user's ischial tuberosities 45 to reduce peak pressure on the user's 40 tuberosities 45 without weakening the support surface 5 material to a failure point over time. Some shapes (e.g. domes) are more advantageous for the durability of the support surface 5. In some examples, the shape that is more conducive to the durability of the support surface 5 may vary based on the density or type of material used to construct the support surface 5. Furthermore, although the example support surface 5 is described herein as having one or two sets of openings 25, additional sets may be used in other support surfaces 5. For example, the larger support surface 5 may have more sets of openings 25 and/or each set of openings 25 may include more than two openings 25. In particular, the couch or bench support surface 5 may include multiple sets or zones of openings 25, wherein each set or zone of openings 25 includes two, four, six or more openings 25; however, any suitable number of openings 25 is contemplated within the present disclosure.

In some examples, the additional opening 25 may be disposed in an area below the user's coccyx. In at least one such example, the openings 25 are positioned in an area below the user's coccyx, and centered between and slightly behind the openings 25 for IT. When the user 40 does not have the ability to sit in a neutral position in the pelvis, the coccyx is also a high risk area of pressure injury. The posterior collapse of their pelvis lowers the user's coccyx closer to the support surface 5, causing peak pressures that may lead to pressure injury. The strategic openings 25 in this region may have the same effect in reducing the stiffness of the cross section of the support surface 5 to reduce peak pressure in the coccyx region of the user 40.

In another particular example, a mattress (e.g., foam mattress, gel mattress) may have multiple sets of openings 25, where each set of openings 25 includes one or more openings 25. In an example mattress with openings 25, groups of openings 25 may be organized into zones (e.g., head zone, torso zone, buttocks zone, leg zone), and the openings 25 in each zone may have different sizes and/or shapes to provide an optimal combination of support and reduced peak pressure for each zone. In another example, the zones of the opening 25 are configured for supine, prone, and side-sleeping such that the user 40 may roll into or move into the various zones of the opening 25.

While a few specific alternative examples of support surfaces 5 or other uses of openings 25 on the underside of seats or support surfaces 5 are mentioned above, example openings 25 may be used in any seating or support surface including, but not limited to, vehicle seats, public transportation seats, stadium seats, theatre seats, stand-alone mats, seats in heavy machinery and tractors, seats on golf carts or other recreational vehicles, lawn care carts, office seats, household furniture, and the like. In another particular example shown in fig. 10 and 11, an example support surface is placed in a seat pan 50 of an office chair 55. Fig. 10 depicts a side view of the support surface 5 in the seat pan 50, and fig. 11 depicts an example office chair 55 that may be used with the support surface 5.

Additionally or alternatively, other materials may be used for the example support surface 5. In one particular example shown in fig. 12, a solid gel may be used. The solid gel may be manufactured to have similar stiffness as the foam support surface 5 and may produce similar sitting characteristics thereto. Each of the different materials that may be used for the example seat support surface may have an opening 25 that is slightly different in size. However, the position of the opening 25 below IT is uniform. In particular, the solid gel may be cast into a mold or injection molded into a finished shape, including the openings or domes 25 described herein. In the example support surface of fig. 12, the support surface 5 may be shaped to include a lattice or honeycomb structure as shown on the top surface 10 that provides a first cross-sectional stiffness. Similar to prior foam cushions, a support surface made of solid gel may be provided with example openings 25 to alter the cross-sectional stiffness of the area under the user's bone prominences.

Fig. 13 and 14 depict perspective and cross-sectional side views of an example seat support surface 5 including a shear reduction feature 60. Example shear reduction features may include cuts 65 (e.g., apertures, holes, slots, slits) and low friction or smooth material 75 (e.g., a material having a low coefficient of friction or low COF), the cuts 65 being disposed adjacent to but spaced apart from the rear edge 35 of the support surface 5. The example cutout 65 extends through the width of the support surface 5 (e.g., from the left edge 72 to the right edge 74). In the example shown, the cutout 65 extends in a horizontal plane and is substantially parallel to the bottom surface 30 of the support surface 5. Alternatively, the cuts 65 may extend in a plane substantially parallel to the inclined femoral surface. The cross-section of the incision 65 described herein is straight when viewed in the sagittal plane. However, the cut-out 65 may be any suitable shape and may additionally or alternatively include, for example, a curved portion or a bent portion. In one such example, the incision 65 may be curved such that the cross-section of the incision 65 mimics or follows the contours of the pelvic cavity and the inclined femoral surface.

In the figures, the example cutout 65 includes a first surface 80 and a second surface 85 opposite the first surface 80. Each of the first surface 80 and the second surface 85 includes a low friction material 75 (e.g., lycra, silicone coated nylon (tear resistant), etc.). The low friction material 75 is preferably a fabric having a low COF, and in particular, a fabric having anisotropic properties. That is, the low friction material or fabric 75 is manufactured (woven, stitched, or knitted) such that the fibers or fiber patterns extend longitudinally on a first side or face and transversely (e.g., perpendicular to each other) on a second side. The low friction fabric 75 is a tightly knit fabric including fine ribs (rib pattern), such as a lycra spandex knit. The first/major face or side of the low friction fabric 75 comprising fine ribs may be referred to as the low friction side and may have a shiny tint. The second side of the low friction fabric includes a rib or stitch direction extending perpendicular to the rib or stitch direction of the low friction side and may exhibit a dull or matte finish. In at least one example configuration, the low friction material 75 may stretch or expand in all directions (e.g., length and width). In the example configuration shown, the first surface 80 and the second surface 85 are provided with a low friction fabric. When joined together, the low friction fabrics exhibit a low coefficient of friction. In particular, the low friction and/or shiny sides of the low friction fabric 75 are placed against each other such that the fiber or rib directions (e.g., weave or knit directions) extend perpendicular to each other, thereby forming a smooth and/or low friction interface between the surfaces 80, 85 due to the minimization of surface area contact between the first surface 80 and the second surface 85. Although a vertical orientation is preferred, the low friction fabric 75 need not be so precisely arranged.

When a user sits on the support surface 5 in the area above the shear-reducing feature 60, the low friction material 75, and thus the two surfaces 80, 85 of the cutout 65, can move relative to each other with very little friction. Thus, the multidirectional (e.g., superior/inferior, left-right, anterior/posterior) shear stress or shear force below the bone prominence is reduced as compared to conventional mats. Reducing shear stress in the seating plane results in increased user comfort. Specifically, decreasing shear stress and increasing immersion in the seating plane reduces the triggering reaction of mechanoreceptors (called Lu Feini cells), which react negatively to tensile and shear stress.

The cutout 65 of the example support surface 5 may be formed at the time of manufacturing the support surface 5. In some examples, the mold for the support surface 5 comprises a plate at the location of the cut-out, and the foam is poured into the mold (and thus around the plate). The low friction material 75 is wrapped around the plate during this process before the foam is poured. When the foam is removed from the mold, the plate is removed from the support surface, leaving the cut-out 65 and the low friction material 75 within the cut-out and on the surfaces 80, 85. Alternatively, the slit 65 may be cut through the support surface 5 after the support surface 5 is removed from the mold, and the low friction material 75 is inserted using a plate corresponding to the shape/size of the slit 65. In a further alternative example, a cut-out may be made from the rear edge 35 of the support surface 5, which cut-out extends into the support surface 5 for a desired distance. The flat tube of low friction material 75 is then placed into the cutout. The rear edges of each surface of the cutout may be attached to each other (e.g., using an adhesive or other mechanical fastener).

In another particular example, the support surface 5 may include an alternative shear reduction feature 60, the alternative shear reduction feature 60 having an opening or slot adjacent to but spaced apart from the rear edge 35 of the support surface 5. In one such example, the support surface 5 may include an upper portion having a first major surface (interface) 80 and a lower portion separated from the upper portion and having a second major surface or interface 85 disposed opposite the first interface 80. That is, the support surface 5 may be two separate pieces, with the lower portion having an opening and the upper portion configured to fill the opening such that the first and second major surfaces 80, 85 are proximate to one another, thereby forming an interface within the support surface 5 (similar to the cut-out 65). In line with the cut-out 65 depicted in fig. 13 and 14, an opening or slot extends from the left side edge 72 to the right side edge 74. The first and second surfaces of the opening or slot further comprise a low friction fabric 75. In other words, the low friction material is provided on the adjacent (main) surfaces 80, 85 between the upper and lower portions of the support surface 5. As with the cut-out 65 depicted in fig. 13, the opening or slot enables the first and second surfaces of the slot to move relative to each other with very little friction, thereby reducing the shear stress when a user sits on the support surface 5. In at least one example configuration, the first and second surfaces of the opening extend in a horizontal plane substantially parallel to the bottom surface 30 of the support surface 5. In another example, the opening may alternatively extend in a plane substantially parallel to the inclined femoral surface. The cross-section of the opening described herein is straight when viewed in the sagittal plane. However, the openings (and thus the respective shapes of the upper and lower portions) may be of any suitable shape such that the first and second major surfaces 80, 85 (corresponding to the upper and lower portions of the support surface 5) form a low friction interface below the bone prominence of the user. For example, the first and second major surfaces 80, 85 of the opening or slot may be rectangular, circular, or any suitable shape. The cross-section of the opening or slot may additionally or alternatively comprise, for example, a curved or bent portion. In one such example, the opening may be curved such that a cross-section of the opening mimics or follows the contours of the pelvic recess and the inclined femoral surface.

Similar to the formation of the cutout 65, the opening of the example support surface 5 may be formed at the time of manufacturing the support surface 5. In some examples, the mold for the support surface 5 includes a plate at the location of the opening or slot, and the foam is poured into the mold (and thus around the plate). During this process, a low friction material 75 is wrapped around the plate. When the foam is removed from the mould, the plate is removed from the support surface 5, leaving a cut and a low friction material 75 in the cut and on the surface. Alternatively, a slot may be cut through the support surface (e.g., a slot formed from left edge 72 to right edge 74) after the support surface 5 is removed from the mold, and a low friction material 75 placed on each surface of the cut and attached (e.g., using an adhesive).

Although the example support surface 5 shown in fig. 13 and 14 includes only shear reduction features 60, the support surface may additionally or alternatively include pressure reduction features described in connection with fig. 1-7. An example support surface 5 having the aforementioned pressure reducing features 25 and shear reducing features 60 is shown in fig. 15 and 16. In the illustrated configuration of fig. 15, the example support surface 5 includes a set of openings 25, similar to the example support surfaces depicted in fig. 4 and 5. The set of openings 25 are disposed adjacent the rear edge 35 of the support surface and below the shear reduction feature 60; however, the position of the opening 25 below IT is uniform. In some examples, the opening 25 in the support surface 5 may be elongated (e.g., may have an oval or elliptical basic shape that extends further toward the front edge 20 of the support surface 5) to accommodate different body shapes of the user or different seating positions of the user. As shown in fig. 16, an example support surface 5 may include a shear reduction feature 60 and a set of openings 25 having a double dome shape. Although depicted in a horizontal plane, in alternative examples, the shear reducing features 60 of fig. 15 and 16 may extend through the support surface in any suitable plane or at any suitable angle such that the shear reducing features 60, or a portion thereof, are located between the top surface 10 of the support surface 5 and the opening 25.

In another particular example, the example support surface 5 may include shear reduction features 60 located on the top surface 10 of the support surface 5. Fig. 17 depicts an example support surface 5 including an alternative shear reduction feature 60. In the example configuration shown, the shear reduction feature 60 or low friction interface is generally rectangular and is disposed on the top surface 10 adjacent to but spaced apart from the rear edge 35 of the support surface 5 and extends from the left edge 72 to the right edge 74. However, the shear reducing features 60 may be any suitable shape. The shear reduction features 60 are provided on the support surface 5 in the region below the user's bony prominences, in particular below the user's ischial tuberosities. In the example shown, the shear reduction feature includes a first interface 85 of the low friction material 75 disposed proximate the top surface 10 of the support surface 5 and a second interface 80 of the low friction material 75 disposed opposite the first interface 85. In at least one example configuration, the low friction material is a tightly knit fabric having a first fiber or rib direction on a first side and a second fiber or rib direction on a second side extending perpendicular to the first fiber direction. In the example shown in fig. 17 and 18, the first interface 80 and the second interface 85 of the low friction material 75 are oriented such that the low friction sides of the first interface 80 and the second interface 85 are opposite and arranged such that the rib directions are perpendicular to each other, thereby forming a low friction interface on the top surface 10 of the support surface 5.

In the example shown in fig. 17 and 18, the shear reducing features 60 are provided in an area adjacent the rear edge 35 of the support surface 5, however, the shear reducing features may also be provided across the entire top surface 10. Fig. 19 depicts an example support surface 5 including an alternative shear reduction feature 60. In the example configuration shown, the shear reduction features 60 or low friction interfaces are disposed across and/or on top of the top surface 10 of the support surface 5. In the depicted configuration, the shear reduction features include a first interface 85 of the low friction material 75 disposed proximate the top surface 10 of the support surface 5 and a second interface 80 of the low friction material 75 disposed opposite the first interface 85. Consistent with the example constructions discussed herein, the low friction material 75 is preferably a fabric having a low COF, and in particular, a fabric having anisotropic properties. When joined together, the low friction fabrics exhibit a low coefficient of friction. In particular, the shiny sides of the low friction fabric are placed against each other such that the fiber or rib directions (e.g., weave or knit directions) extend perpendicular to each other, thereby forming a smooth and/or low friction interface between the surfaces 80, 85.

In some examples, the shear reduction feature 60 may be provided in the form of a housing (e.g., wrap, bag, tube) having a first interface 85 and a second interface 80 of the low friction material 75 opposite the first interface. In at least one such example configuration, the shear reducing features 60 may encapsulate the support surface 5; in other examples, the shear reduction feature 60 may enclose only a portion of the support surface 5. The housing or bag of low friction material 75 may have an open end and a closed end. For ease of manufacture, the housing may cover the entire support surface 5. In particular, the open end of the housing may be slid over (or enveloped over) the front edge 20 of the support surface 5 and secured to the rear edge 35 using any suitable decorative method. In another example, the shear reduction feature 60 may comprise a single interface of the low friction material 75.

The example support surface 5 described in connection with fig. 13-19 may further include a covering (e.g., a seat cushion covering, a decorative covering, and/or a fabric covering) disposed over and/or atop the shear reducing features 60. In at least one configuration, the shear reducing features 60 may be sewn into the trim cover such that the shear reducing features are located near the top surface 10 of the support surface 5, thereby separating the support surface 5 from the bottom surface of the trim cover. When a user sits on a support surface having only a conventional decorative covering, shear strain is induced on the user's tissue (Lu Feini small) in areas where the decorative covering and support surface exhibit a high COF (e.g., under the user's bony prominences), thereby causing the decorative covering to bite and thereby preventing the user from freely sinking into the support surface. By implementing a low friction interface (shear reducing feature 60) between the support surface 5 and the underside of the trim cover, the friction barrier can be separated, allowing a user to sink into the support surface and/or adjust the position in the support surface without inducing shear strain in the plane of the support surface. In other examples, the shear reducing features 60 may be fastened in another manner (e.g., staples, rivets, or any suitable decorating method), however, the location of the shear reducing features 60 on top of the support surface 5 and below the decorating cover is consistent. Additionally or alternatively, the shear reduction feature 60 may be secured to both the support surface 5 and the decorative covering; however, the low friction interface (shear reducing feature 60) is consistent in location between the support surface 5 and the decorative covering. In other words, the shear reducing feature 60 is disposed proximate to the (top) surface of the support surface 5 and is further disposed adjacent to but separate from the tissue of the user, and the decorative covering separates the shear reducing feature 60 from the user.

Any of the example shear reduction features 60 described herein may be used with the pressure reduction features 25 described above in connection with fig. 1-11. The use of both the shear reducing feature 60 and the pressure reducing feature 25 may be desirable to create a more immersive and thus comfortable seating surface for the user. In particular, the shear reducing features 60 and the pressure reducing features 25 act separately and in concert to provide a snug submergence into the support surface 5 to reduce peak pressure and shear strain acting on the user while the user is seated. For example, the structure of the pressure reduction feature 25 functions to receive the shape of the user and in particular to provide controlled collapse of the support surface 5, thereby reducing peak pressure on the user's IT. The shear reduction feature 60 functions to allow the user to smoothly or freely sink and/or sink into the support surface 5 while preventing the user's body from seizing or biting into the support surface 5 (e.g., preventing the user's body from experiencing shear pressure or strain in the plane of the support surface). In contrast, a support surface having only a conventional decorative covering can cause shear pressure and shear strain on a user while sitting due to the frictional interface between the support surface and the decorative covering. When a user sits on a support surface with a conventional decorative covering, shear strain is induced on the user's tissue (Lu Feini small) in areas where the decorative covering and support surface exhibit a high COF (e.g., thereby preventing the user from freely sinking into the support surface). By implementing a low friction interface between the support surface and the decorative covering, the friction barrier may be separated, allowing a user to sink into the support surface and/or adjust the position in the support surface without causing shear in the plane of the support surface. While both the pressure reducing feature 25 and the shear reducing feature 60 are described in connection with a seat support surface, the respective features 25, 60 may also be implemented on, for example, a working chair, all support surfaces in a mattress, or any suitable support surface below a bone protrusion, such as a lateral support surface, an inferior support surface, a medial support surface, a anterior support surface, or a posterior support surface. That is, the pressure reducing features 25 and shear reducing features 60 may facilitate proper submersion of the support surface against collapse in the coronal (anterior), transverse (top) and sagittal (side) planes, respectively.

By using shear reduction and/or peak pressure reduction, the example seat support surface 5 reduces the amount and/or strength of mechanoreceptors related to pressure (merck plates) and shear strain (Lu Feini small). Reducing mechanoreceptors activation causes less discomfort to the user, allowing the user to have greater comfort for the duration of sitting on the example seat support surface 5.

An initial analysis is performed to evaluate the submersion and performance characteristics of the example support surface 5 and, in particular, the pressure reduction feature 25. The kinematic study included subjecting the support surface to an average simulated load (e.g., a user of height 1.80 meters, weight 78 kilograms) in an upright position and tilting the support surface in space from the upright position to a first or six degree tilt position and a second or twelve degree tilt position. Sensors located on the seating plane of the support surface are used to measure the maximum of compressive pressure and compressive shear and the maximum of compressive strain and shear strain. A dispersion mapping of the seat plane across the support surface 5 is performed. Fig. 20 depicts an example resulting pressure map and shear map recorded for the support surface 5. For example, the tissue strain points under the ischial tuberosities of the user are quantified using a Volumetric Strain Distribution (VSD). Fig. 21 shows an example distribution of compressive and shear strains observed during the study.

The results are recorded in table 1 below.

Table 1 interfacial pressure and tissue strain analysis.

A conventional seating surface (such as a mesh seating surface) typically causes a peak compressive pressure of about 152mm HG on the user's tissue and does not provide a submerged support surface. In an example study, various embodiments of the support surface 5 successfully reduced the peak pressure by more than 60mm HG. Specifically, in at least one variation, the peak compression pressure is reduced to a value of 77mm Hg when configured in an upright position using a support surface 5 having an opening 25 as described herein. When the user sits in an inclined posture, a further reduction in peak pressure is observed. In the inclined position, the example support surface 5 works with support surfaces adjacent to the lumbar and thoracic regions to cradle the pelvis of the user and provide a proper basis for the correct sitting posture of the entire spine.

In addition to reducing peak pressure, the results of the study further demonstrate that the opening 25 can successfully reduce compressive shear, thereby relieving the tissue strain experienced by the user. Referring to fig. 9, when the user 40 sits on the support surface 5, the opening 25 collapses under the user's bony prominence. Although in the example shown, the opening 25 is collapsed in a vertical plane or dimension; in some examples, however, the opening may collapse in three dimensions (including torsional deformation and translational deformation). In the test, the opening 25 exhibited uneven collapse, which varied between the three sitting postures. The support surface 5 with the superimposed dome-shaped openings 25 shows a slight improvement in every index recorded. Studies have shown that the varying degrees of cross-sectional stiffness formed by the openings 25 provide non-uniform controlled collapse, allowing the openings to deform in a manner that reduces the tension in the support surface 5, which in turn reduces the tissue strain experienced by the user 40.

A second series of kinematic studies was conducted to evaluate the performance and sink characteristics of the example support surface 5 compared to a competitor support surface. In each example, a series of studies was conducted using three variants of the seat support surface 5, each variant including a pressure reduction feature 25. The first variant of the support surface 5 comprises the shear reducing feature 60 and an existing decorative covering, the second variant of the support surface 5 comprises only an existing decorative covering, and the third variant of the support surface 5 is tested without any decorative covering.

Published standards for seat cushion (support surface) provide standardized terms and methods for characterizing performance. Ten ISO 16840 seat standards have been published and information provided by these voluntary standards can be used by manufacturers to evaluate and benchmark their products, by consumers and clinicians to compare and select products, and by regulatory authorities, purchasers, and third party payors in terms of regulatory and purchasing policies. These criteria are modified and applied to the example support surface 5 and the competitor support surface. The results of four example studies conducted in accordance with ISO 16840 are depicted in tables 2-6 and fig. 22 and described further herein.

Example 1

Proper submergence and holding of the user's pelvis and buttocks significantly helps reduce tissue strain in the area adjacent the bony prominences. A number of standardized tests can be used to demonstrate the effect of the pressure and shear force reducing features 25, 60, used alone and in combination, with respect to the extent of immersion into the support surface and the stability of the support surface under live loads. ISO 16840-2 provides guidance for determining the physical and mechanical properties of the support surface intended to manage tissue integrity and should be referred to for more information about the procedure described in connection with the study conducted in example 1.

Load profile depth and overload deflection tests were performed (following ISO 16840-2:2018, clause 11) to assess the ability of the support surface to properly submerge into the user. The submergence is defined as the depth to which a person submerges into the mat (support surface). Mats with higher additional submersion under overload conditions have higher safety margins against bottoming out (i.e., higher safety margins against peak pressures). The following procedure was followed:

1) Applying a nominal load of 135N to the mat for 300 seconds;

2) Applying an overload of 33% greater than the nominal load to the mat for 60 seconds and measuring the additional submersion as an overload deflection of 1 (mm); and

3) An additional overload of 66% greater than the nominal load was applied to the mat for 60 seconds and the additional submersion was measured as overload deflection 2 (mm).

The loading contour depth and overload deflection method is used to verify CMS encoding. CMS is different from the ISO load profile depth of universal mats that were tested using a 25-mm mat load ram (CLI) at a nominal load of 140N and an overload of 187N. The skin protection mats were tested using an ISO 40-mm mat loading ram. According to the requirements set forth in CMS wheelchair seat-policy clause (a 52505), if for all three loading profile depth test trials there is contact between the rotor button of the mat loading ram and the mat and a median overload deflection 1 of greater than or equal to 5mm (when rounded to the nearest 5 mm) is exhibited, the mat (support surface) passes the test. The mat should pass this test before (front) and after (rear) the simulated aging procedure to meet official code verification requirements.

Each support surface was tested according to the ISO test method using a 40-mm indenter and was tested using the CMS PDAC test method using a 25-mm indenter. Three key achievements were evaluated: rotor contact at nominal load, overload deflection 1 and overload deflection 2. Contact was assessed 300 seconds after nominal load was applied. The overload deflection 1 is the additional sink when the load is increased by 33% from the nominal load. Overload deflection 2 is the additional sink when the load is increased 66% from the nominal load. The results of the support surface group using the ISO test method and a 40-mm cushion loading ram can be seen in Table 2. The results of the CMS PDAC test method using a 25-mm mat loading ram for a universal mat are shown in table 3.

Table 2. LCD and OD using ISO test method and 40-mm pad loading ram.

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Table 3. LCD and OD using CMS PDAC test method and 25-mm mat loading ram.

While most support surfaces pass the loading profile depth and overload deflection test, the extent of submersion is slightly different. The support surface exhibiting a higher additional submersion under overload conditions demonstrates a higher safety margin against causing pressure damage. The support surface 5 described herein exhibits the strongest submersion mass.

Of particular note is the assessment of the differences in the amount of immersion of the three variants of the example seating surface 5. In both analyses, the support surface 5 without the decorative covering exhibited the greatest degree of submersion, whereas the support surface 5 with the conventional decorative covering only produced the lowest degree of submersion. The difference in the amount of immersion can be explained as being due to the frictional interface between the support surface 5 and the conventional decorative covering. When a user sits on a support surface with a conventional decorative covering, shear strain is induced on the user's tissue (Lu Feini small) in areas where the decorative covering and support surface exhibit a high COF (e.g., under the user's bony prominences), thereby causing the decorative covering to bite into the user and thereby preventing the user from freely sinking into the support surface. By implementing a low friction interface between the support surface and the decorative covering, the friction barrier may be separated, allowing a user to sink into the support surface and/or adjust the position in the support surface without inducing pressure or shear strain on the plane of the support surface. The effect of the shear reduction feature 60 can be clearly observed when compared to variants without this feature.

Example 2

Maintaining the pelvis within a neutral alignment range of three degrees helps promote proper posture when seated. The example support surface 5 is configured such that the pelvic recess 12 and the inclined surface 14 help provide a force in a rearward direction to stabilize the pelvis and prevent translational or shear strain on the seat support surface 5 in a forward direction, thereby positioning the user on the pressure and shear strain relief features. The top surface 10 is contoured to better match the negative surface of a person in a seated position than a flat seating surface. The mating shape helps to greatly reduce the seat pressure below IT and coccyx compared to flat top seating surfaces or cushions. The contour of the convex side 15 also complementarily matches the shape of the user to help carry the pelvic side and tissue and muscles along the femoral region. This surface helps to carry the patient's load and redistribute the pressure over a larger sitting area. A horizontal stiffness test was performed to quantify and characterize the reaction of the support surface to slight horizontal movement in the anterior direction, indicating resistance to pelvic movement. The procedures in ISO 16840-2:2018 appendix C are followed and described herein:

1) The mat was loaded to 500N using a rigid mat loading ram;

2) Pulling the loaded ram 10mm in a forward direction and measuring the peak force (N) of the pulling ram; and

3) This position is maintained and the tension (N) is recorded again after 60 seconds.

Two key results of this test, defined in ISO 16840-2:2018 appendix C, are peak force (N) and force at 60 seconds (N). The peak force is the maximum horizontal force required to displace the loaded mat ram forward by 10 mm. The force at 60 seconds is the final force measured after 60 seconds hold time after displacement. In addition to the procedure and results outlined in ISO 16840-2:2018 appendix C, a shear sensor was attached at the interface between the ram and the mat on the lowest base point (simulated ischial tuberosity) on one side of the ram to obtain a shear force (N) at 60 seconds after displacement. The horizontal stiffness test results can be seen in table 4.

Table 4.10 mm pulled three trials average peak horizontal force (N), horizontal force at 60 seconds (N), shear force at 60 seconds.

Higher peak or final forces (meaning higher "horizontal stiffness" results) may provide more stability as the individual moves slightly across the mat. However, due to the shear forces between the seat cushion and the buttocks, the chance of tissue deformation increases, so a notable combination is a high level of stiffness value and low shear forces. The average peak horizontal force for all trials was 234N, while the average horizontal force after 60 seconds was 187N. Of particular note are differences between the three variants. While all three variants of the support surface 5 exhibited strong stiffness against horizontal forces, the example support surface 5 including the shear reduction feature 60 produced the lowest shear force in all experiments, with significant variation compared to variants of support surfaces that did not include the shear reduction feature.

Example 3

The ability of the support surface to evenly disperse and reduce peak pressure may provide greater comfort and support to a user sitting for a long period of time. The interface pressure may be quantified using a pressure mapping test. The pressure mapping test uses the interface pressure measurements to evaluate the magnitude and distribution of pressure on the loading mat (support surface). Following the following procedure in ISO 16840-6:2015, clause 14:

1) Cushion loading rigid cushion loading ram, loading totaling 500N, pressure map at interface between cushion and ram recorded for 60 seconds;

2) Pressure map and interpretation guidelines for the base region. A representation of the pressure map of the Right Basal Zone (RBZ) and the Left Basal Zone (LBZ) and the sacrum or Central Zone (CZ) is shown.

It should be noted that this method is not a validated and standardized test method and is intended to be used to compare the pressure mapping indicators before and after simulated aging. This standard defines several key results of the interfacial pressure measurement test in relation to the highlighted base region in fig. 22, including: peak pressure index of left and right basal zones; percent total force of the right base region, the left base region, the center base region; a dispersity index; and the contact area. For more information on these indices, please refer to ISO 16840-6:2015, clause 14. BT2-3232-200BodiTrak2 pressure pads with 32x 32 arrays and 47cm x47cm sensing area were used for pressure mapping pressure measurements. Each sensor is 11mm by 11mm with a spacing of 2mm. The maximum recorded value is 200mm Hg.

Dispersion may be defined as the percentage of force supported in a particular area or zone relative to the total force. In other words, the dispersion index quantifies the ability of the mat to disperse peak pressure and is inversely related to the amount of submersion. Thus, a low percentage of dispersion is desirable, meaning that a low percentage of weight/force is transferred to the user tissue in each zone (RBZ, LBZ, CZ). The results of the pressure mapping test strongly indicate the submersion mass for all the support surfaces tested. Referring to fig. 22, the example support surface 5 without the decorative covering exhibited the smallest percentage of dispersion in all experiments, with the remaining variants of the support surface 5 tested behaving comparatively. Similarly, each variation of the support surface 5 exhibits a greater reduction in peak pressure than a competitor support surface.

The ability of the support surface to encapsulate and support the user further demonstrates the powerful submergence capability. Referring again to fig. 22, a comparison of the total contact area between the user 40 and the support surface shows that the example support surface 5 described herein provides the greatest amount of surface area contact, which in turn helps reduce peak pressure and produces a low dispersion percentage. In particular, the example support surface 5 is configured such that the pelvic recess 12 and the inclined surface 14 help provide a force in a rearward direction to stabilize the pelvis and prevent translational or shear strain on the seat support surface 5 in a forward direction. The top surface 10 is contoured to better match the negative surface of a person in a seated position than a flat seating surface. The results indicate that the mating shape helps to greatly reduce the seat pressure below IT and coccyx compared to a competitor seat surface or cushion.

Example 4

As demonstrated in examples 1-3, the submergence and stiffness test provides an important indicator of the ability of the support surface to distribute tissue pressure and hold the pelvis of the user to promote and maintain proper postural alignment. However, these tests do not take into account that the user may tilt from side to side. Lateral stability testing evaluates the ability of the support surface to resist moment at the pelvis. The moment in the test method was developed by applying an eccentric load to a standard indenter simulating the buttocks and upper thigh. The resulting ram tilt angle was measured to characterize the mat reaction. The intended use of this method is to distinguish between stability properties between mat models. The following procedure is followed according to ISO 16840-13:

1) The mat is loaded with a total of 500N live load (the portion of the load that translates in the horizontal plane to move the center of mass (60%) relative to the test mat) and dead load (the portion of the total load that includes the rigid mat loading ram that does not translate in the horizontal plane relative to the test mat);

2) Leveling the pressure head and recording an initial angle;

3) The static load is laterally shifted by 75mm to create a tilt condition; and

4) After the movement was applied, the tilt angle was recorded every 10 seconds for 60 seconds.

The main result of this test is a change in the angle of inclination that indicates the amount of rotation of the ram allowed by the mat. The change in lateral tilt was averaged over five trials and measured every 10 seconds for 60 seconds after the 75mm lateral weight shift was applied. The fore-and-aft tilt (which is a deviation from ISO 16840-13) was measured at 0 seconds and 60 seconds. A second version of the test was performed using a shear sensor placed under IT of RCLI. Shear force (N) and interfacial pressure (mmhg) recordings were made after 60 seconds of oblique application and were averaged over three trials. The lateral stability test results can be seen in table 5. Lateral stability and shear results can be seen in table 6.

Table 5. Average lateral tilt of five trials at each time point.

Table 6.60 shear and interfacial pressure after three trials.

The static tilt angle (referring to the tilt angle maintained over the duration of the test) demonstrates a stable support surface when subjected to eccentric loads. Maintaining a static tilt angle is important to prevent the user from tilting excessively. In these cases, the user may experience increased tissue strain. Thus, a notable combination is the ability of the mat to maintain a static angle of inclination while continuing to uniformly disperse the pressure and maintain minimal variation in shear force. While each variation of the support surface 5 performs well as compared to competitor mats, the results of the lateral stability test indicate that the support surface 5 having the pressure reducing features 25 and shear reducing features 60 described herein provides strong support and minimal shear when subjected to uneven loads. Variations of the support surface 5 that include shear reduction features demonstrate considerable improvements in reducing the shear and thus strain experienced by the user. As discussed herein, the low friction interface provided between the support surface 5 and the trim cover prevents the cover from biting or seizing the support surface, thereby preventing shearing in the plane of the seating surface.

One or more of the disclosed embodiments, alone or in combination, may provide one or more technical effects, including reducing sitting peak pressure on a user, making the user comfortable for a long period of time in a seat having a support surface as described herein. The technical effects and problems of the present specification are illustrative and not restrictive. It should be noted that the embodiments described in the present specification may have other technical effects and may solve other technical problems.

As used herein, the terms "generally," "about," "substantially," and similar terms are intended to have a broad meaning consistent with the general and acceptable usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Those skilled in the art who review this disclosure will appreciate that these terms are intended to provide a description of certain features described and claimed without limiting the scope of such features to the exact numerical ranges provided. Accordingly, these terms should be construed to mean that insubstantial or inconsequential modifications or alterations to the described and claimed subject matter are considered to be within the scope of the invention as described in the appended claims.

It should be noted that references to relative positions (e.g., "top" and "bottom," "left" and "right") in this specification are merely intended to identify various elements as oriented in the figures. It should be appreciated that the orientation of particular components may vary greatly depending on the application in which they are used.

For the purposes of this disclosure, the term "coupled" means that two members are directly or indirectly engaged with each other. Such engagement may be fixed in nature or movable in nature. Such joining may be achieved by integrally forming the two members or the two members and any additional intermediate members as one piece with each other, or by attaching the two members or the two members and any additional intermediate members to each other. Such engagement may be permanent in nature or may be removable or releasable in nature.

It is also important to note that the construction and arrangement of the system, method and apparatus as shown in the various examples of the embodiments is illustrative only and is not limiting. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many different alternatives, modifications, variations, improvements and/or substantial equivalents, whether known or those that are presently or shortly envisioned (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) are possible without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interface may be reversed or otherwise varied, the length or width of the structure and/or members or connectors or other elements of the system may be varied, the nature or number of adjustment positions provided between the elements may be varied (e.g., by varying the number of engagement slots or the size of engagement slots or the type of engagement). The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the various examples of the embodiments without departing from the spirit or scope of the present inventions. Accordingly, the present invention is intended to embrace all known or earlier developed alternatives, modifications, variations, improvements and/or substantial equivalents.

Claims (37)

1. A support surface for a user, the support surface comprising an opening in a bottom surface of the support surface, the opening providing controlled structural collapse of the support surface by varying the stiffness of a cross section of the support surface.

2. The support surface of claim 1, wherein the opening is geometrically shaped, such as selected from the group consisting of: domes, flat domes, pyramids, flat pyramids, boxes, rectangular prisms, cones, flat cones, cylinders, and tapered cylinders.

3. A support surface according to claim 1 or 2, wherein the openings have a stacked geometry.

4. A support surface according to any one of claims 1 to 3, wherein the support surface and the opening are configured such that when the user sits on the support surface, the peak pressure on the user is less than about 81mm Hg.

5. The support surface of one of claims 1 to 4, wherein the openings comprise a pair of identical openings symmetrical about a central plane of the support surface.

6. The support surface of claim 5, wherein the opening is disposed near a rear edge of the support surface.

7. The support surface of claim 6, further comprising an additional opening disposed near a front edge of the support surface, wherein the opening reduces peak pressure on the user when the user sits on the support surface adjacent the front edge.

8. The support surface of one of claims 1 to 7, wherein a top surface of the support surface is contoured according to a shape of a pelvic region of the user.

9. The support surface of one of claims 1 to 8, further comprising a fabric covering the support surface.

10. A device, such as a chair, comprising a support surface as claimed in any one of claims 1 to 9.

11. A support surface for a user, the support surface comprising:

An opening in a bottom surface of the support surface, the opening providing controlled structural collapse of the support surface by varying the stiffness of a cross section of the support surface; and

A low friction interface extending over a top surface of the support surface, the interface being disposed between the support surface and the user's bony prominences, and the interface being a low friction fabric.

12. The support surface of claim 11, wherein the opening is geometrically shaped, such as selected from the group consisting of: domes, flat domes, pyramids, flat pyramids, boxes, rectangular prisms, cones, flat cones, cylinders, and tapered cylinders.

13. A support surface according to claim 11 or 12, wherein the openings have a stacked geometry.

14. The support surface of one of claims 11 to 13, wherein the low friction fabric is an anisotropic fabric having a primary side and a secondary side, the primary side comprising a fine rib and/or a tightly knit rib pattern.

15. The support surface of one of claims 11 to 14, wherein the low friction fabric is a tightly knit fabric having a primary stitch direction and a secondary stitch direction.

16. The support surface of one of claims 11 to 15, wherein the interface comprises a first interface and a second interface of a low friction fabric.

17. The support surface of one of claims 11 to 16, wherein the support surface and the opening are configured such that a peak pressure on the user is less than about 81mm Hg when the user is seated on the support surface.

18. The support surface of one of claims 11 to 17, wherein the openings comprise a pair of identical openings symmetrical about a central plane of the support surface.

19. The support surface of claim 18, wherein the opening is disposed near a rear edge of the support surface.

20. The support surface of claim 19, further comprising an additional opening positioned near a front edge of the support surface, wherein the opening reduces peak pressure on the user when the user sits on the support surface adjacent the front edge.

21. The support surface of one of claims 11 to 20, wherein a top surface of the support surface is contoured according to a shape of a pelvic region of the user.

22. The support surface of one of claims 11 to 21, further comprising a fabric covering the support surface and the low friction fabric.

23. A device, such as a chair, comprising a support surface as claimed in any one of claims 11 to 22.

24. A chair, comprising:

a support surface, the support surface comprising:

A top surface contoured to accommodate a pelvis of a user;

a bottom surface;

An opening between the top surface and the bottom surface, wherein the opening provides controlled structural collapse of the support surface by varying the stiffness of the cross section; and

A low friction interface extending over the top surface of the support surface, the interface positioned between the support surface and a user's bony prominence, wherein the interface is a low friction fabric.

25. The chair of claim 24 wherein the opening breaks the bottom surface.

26. Chair according to claim 24 or 25, wherein the opening is geometrically shaped, such as selected from the group consisting of: domes, flat domes, pyramids, flat pyramids, boxes, rectangular prisms, cones, flat cones, cylinders, and tapered cylinders.

27. A chair as claimed in any one of claims 24 to 26, wherein the openings have a stacked geometry.

28. The chair of any one of claims 24 to 27, wherein the support surface and the opening are configured such that a peak pressure on the user is less than about 81mm Hg when the user is seated on the support surface.

29. A chair as claimed in any one of claims 24 to 28, wherein the openings comprise a pair of identical openings symmetrical about a central plane of the support surface.

30. A chair as claimed in any one of claims 24 to 29, wherein the opening is provided near the rear edge of the support surface.

31. The chair of claim 30 further comprising an additional opening disposed near a front edge of the support surface, wherein the opening reduces peak pressure on the user when the user sits on the support surface adjacent the front edge.

32. Chair according to one of claims 24 to 31, wherein the main face of the low friction fabric comprises a fine rib stitch pattern and/or a tightly knitted rib pattern.

33. The chair of any one of claims 24 to 32, wherein the low friction fabric is a tightly knit fabric having a primary stitch direction and a secondary stitch direction.

34. The chair of any one of claims 24 to 33, wherein the interface comprises a first interface and a second interface of a low friction fabric.

35. The chair of claim 34 wherein the major faces of the first and second interfaces are disposed in a perpendicular orientation proximate to one another.

36. The chair of any one of claims 24 to 35, further comprising a fabric covering the support surface and the low friction fabric.

37. A support surface for a user, the support surface comprising:

an opening in a bottom surface of the support surface, the opening providing controlled structural collapse of the support surface by varying the stiffness of a cross-section of a bone protrusion adjacent the user; and

A cutout extending through the support surface, the cutout disposed between the opening on the bottom surface and the bone projection of the user, wherein a low friction fabric is positioned within the cutout.