WO2011075771A1

WO2011075771A1 - Seat cushion

Info

Publication number: WO2011075771A1
Application number: PCT/AU2010/001715
Authority: WO
Inventors: Kevin Brookes
Original assignee: Gregory Commercial Furniture Pty Limited
Priority date: 2009-12-22
Filing date: 2010-12-22
Publication date: 2011-06-30
Also published as: AU2019202821B2; AU2017210637A1; AU2019202821A1; AU2010336014A1

Abstract

A seat cushion (1) including: a pair of primary support portions (5) formed from a relatively firm resilient material and positioned in spaced apart relationship so as respectively to support the ischial tuberosities of a sitter. The seat cushion further includes a forward support portion (10) formed from a softer resilient material and disposed in front of the primary support portions to support the upper thighs (12) of the sitter.

Description

TITLE: Seat Cushion

FIELD OF THE INVENTION

The present invention relates generally to seats and chairs, and more specifically to seat cushions and associated methods of manufacturing. BACKGROUND OF THE INVENTION

The following discussion of the prior art is intended to present the invention in an appropriate technical context and allow its advantages to be properly appreciated. Unless clearly indicated to the contrary, however, reference to any prior art in this specification should not be construed as an express or implied admission that such art is widely known or forms part of common general knowledge in the field.

Seat cushions are well known. They are typically integrated into the generally horizontal support portion of a seat or chair to support a sitter. Many chairs have been designed with the aim of promoting correct posture in the sitter. This involves supporting the sitter with a relatively straight back, such that the lower spine displays a natural concave curvature known as lumbar lordosis.

One example of a chair which positions the occupant for improved posture includes a seat member which slopes forwardly, so as to enhance the lumbar lordosis in the sitter. In one form, to prevent the user from sliding forwardly on the seat, a knee rest is provided. However, it has been found that the resultant pressure exerted on the knees can become uncomfortable after long periods of time. The process of getting into and out of chairs of this type can also be cumbersome and inconvenient.

In another form, which aims to ameliorate these problems, a transverse crevice or ridge is defined between adjacent forward and rearward transverse support portions of differential resiliency, to resist the tendency for the sitter to slide forwardly on the chair. However, these crevice or ridge formations can tend to restrict blood flow through or to the thighs, which again can cause discomfort and other problems linked to compromised blood circulation after prolonged periods of time. Aside from these examples, many different types of seats and seat cushions have been developed over a period of many years. In general, however, those that are aimed primarily at comfort often fail to support the sitter in an ergonomically correct posture, while those intended primarily to improve posture are often uncomfortable, restrict blood flow to certain parts of the body and/or are inconvenient to use.

It is an object of the present invention to overcome or substantially ameliorate one or more of the disadvantages of prior art, or at least to provide a useful alternative.

SUMMARY OF THE INVENTION

Accordingly, in a first aspect, the invention provides a seat cushion including: a pair of primary support portions formed from a relatively firm resilient material and positioned in laterally spaced apart relationship so as respectively to support the ischial tuberosities of a sitter; and

a forward support portion formed from a resilient material that is relatively softer than the primary support portions and disposed in front of the primary support portions to support the thighs of the sitter.

Preferably, the seat cushion includes a rear peripheral support portion extending generally behind the primary support portions and formed from a resilient material that is relatively softer than the primary support portions.

Preferably also, the seat cushion includes an intermediate bridge support portion extending between the primary support portions and formed from a resilient material that is relatively softer than the primary support portions, the bridge support portion being adapted to comfortably support the soft tissues between the ischial tuberosities of the sitter.

In one embodiment, the forward support portion includes a pair of laterally spaced apart thigh support portions extending forwardly from the primary support portions and formed from a resilient material that is relatively softer than the primary support portions, so as comfortably to support the thighs of the sitter without substantially impeding blood flow through the thighs. The forward support portion preferably also includes front peripheral support portions extending respectively on either side of the thigh support portions and formed from a resilient material that is relatively firmer than the thigh support portions. In one embodiment, a front central support portion preferably extends between the thigh support portions.

In one embodiment, each support portion of the seat cushion is formed from a resilient material such as polyurethane foam that is relatively uniform in composition, density, and resiliency. In other embodiments, however, one or more of the support portions may be formed from a combination of materials having different composition, density, or resiliency. In such cases, references to performance parameters such as relative firmness or softness should be interpreted functionally, as relating to the overall or resultant parameter of the relevant combination of materials. Moreover, any reference to a "material" should be interpreted sufficiently broadly to include a combination of materials that collectively exhibit the specified material or performance characteristics. In one embodiment, each of the primary support portions is formed, at least in part, by a plug of material that is relatively firmer than a surrounding matrix material. The plugs defining the respective primary support portions in one embodiment are generally circular in plan view, each having an upper diameter that it preferably at least around 80 mm and more preferably at least 100 mm. In one embodiment, the plugs defining the respective primary support portions are formed from a relatively firm foam material and the surrounding matrix is formed from a relatively softer foam material.

In one embodiment, the plugs forming the primary support portions have tapered sides and more preferably are generally frusto-conical in shape, so as in use to effectively provide a progressive transition in firmness or resiliency between the primary support portions and the surrounding relatively softer support portions of the cushion.

In one embodiment, the primary support portions are formed by the incorporation of a plurality of discrete cores formed from resilient materials having firmness characteristics that are different from those of a surrounding matrix material such that in combination, the cores and the surrounding matrix synergistically exhibit predetermined effective relative firmness characteristics. In one variation of this embodiment, the seat cushion includes a matrix material that is common to substantially all of the support portions, and the specified differences in relative firmness between different support portions result from the use of cores of different shape, firmness and/or different relative spacing. In one embodiment, the cores are formed from foam cylinders, each being less than around 80 mm (and preferably around 50 mm) in diameter, and being positioned at 10 mm (and preferably at least 30 mm) below the upper surface of the seat cushion.

In a further aspect, the invention provides a method of forming a seat cushion as previously defined, the method including the steps of forming the primary support portions from a relatively firm foam material, and positioning the primary support portions within a surrounding matrix formed from a relatively softer foam material, such that the relatively softer foam material forms the forward support portion.

In one preferred form of this method, the primary support portions are positioned so as to be substantially covered by a top layer formed by the relatively softer foam material of the surrounding matrix.

In a further aspect, the invention provides a method of manufacturing a seat cushion as previously defined, the method including the steps of incorporating cores of different firmness or resiliency into a surrounding matrix material, to achieve the specified differences in relative firmness and softness in the respective support portions. In yet another aspect, the invention provides a method of manufacturing a seat cushion having adjacent support portions of different firmness or resiliency, the method including the step of providing an inclined interface between the adjacent support portions, the inclined interface defining an overlapping region to provide a progressive transition in firmness or resiliency between the adjacent support portions. BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a chair incorporating a seat cushion in accordance with a first embodiment of the invention; Figure 2 is a diagrammatic side elevation view showing a sitter on the chair of figure 1;

Figure 3 is a perspective view showing the seat cushion from the chair of figures 1 and 2, with the covering layer removed to reveal the different support portions, including the primary support portions formed by cylindrical plugs;

Figure 4 is a cross-sectional view taken a long line 4-4 of figure 3;

Figure 5 is a perspective view similar to figure 3, showing a second embodiment of the invention with the primary support portions formed by frusto-conical plugs;

Figure 6 is a cross-sectional view taken a long line 6-6 of figure 5; Figure 7 is an underside perspective view of a seat cushion in accordance with a third embodiment of the invention, wherein the support portions are defined by clusters of cores of differing resiliency positioned within a surrounding matrix material;

Figure 8 is a cross-sectional view taken a long line 8-8 of figure 7;

Figure 9 is a perspective view similar to figure 5, showing a fourth embodiment of the invention with the primary support portions formed by elongate plugs; and

Figure 10 is a cross- sectional side elevation showing a fifth embodiment of the invention, incorporating elongate plugs similar to those in the embodiment of figure 9 embedded within a surrounding foam matrix material.

PREFERRED EMBODIMENTS OF THE INVENTION Referring initially to figures 1 to 4 of the drawings, the invention provides a seat cushion 1 which in this embodiment is adapted for use as part of the main support member of a chair 2, which also includes a backrest 3. As best seen in figures 3 and 4, the cushion 1 includes a pair of primary support portions 5 formed from generally cylindrical plugs 6. The plugs 6 are composed of a relatively firm resilient material such as polyurethane foam and are positioned in laterally spaced apart relationship, so as respectively to support the ischial tuberosities 7 of a sitter 8 (see figure 2). The plugs each have a diameter of at least around 80 mm and more preferably at least 100 mm. The cushion further includes a forward support portion 10 disposed in front of the primary support portions to support the thighs 12 of the sitter and formed from a resilient material which, at least in the vicinity of the sitter's thighs, is relatively softer than the primary support portions 5. A rear peripheral support portion 14 extends generally behind the primary support portions 5 and is formed from a resilient material that is relatively softer than the primary support portions. An intermediate bridge support portion 15 extends between the primary support portions 5 and is formed from a resilient material that is relatively softer than the primary support portions. The bridge portion 15 is thereby adapted to comfortably support the soft tissues between the ischial tuberosities of the sitter.

More specifically, the forward support portion 10 includes a pair of laterally spaced apart longitudinally oriented thigh support portions 18, extending forwardly from the respective primary support portions. These thigh support portions 18 are formed from a resilient material that is relatively softer than the primary support portions, so as comfortably to support the thighs of the sitter from below without substantially impeding blood flow through the thighs.

The forward support portion preferably also includes front peripheral support portions 20 extending on either side of the thigh support portions and formed from a resilient material that is relatively firmer than the thigh support portions. In this embodiment, the rear peripheral support portion 14 and the front peripheral support portions 20 form an effectively continuous U-shaped rim of intermediate resiliency, extending around the back and sides of the cushion, to help locate the sitter centrally, and in the optimal ergonomic position with the ischial tuberosities correctly located substantially centrally on the primary support portions 5. A front bridge portion 21 also extends longitudinally between the thigh support portions 18 to help locate the thighs in the optimal position on the cushion. A relatively rigid base 22 provides overall structural integrity and support for the various support portions.

In this embodiment, each support portion of the seat cushion is formed from a resilient material such as polyurethane foam that is relatively uniform in composition, density and resiliency. Thus, the cylindrical plugs 6 defining the primary support portions 5 are formed from a relatively firm foam material, while the thigh support portions 18 are formed from a substantially softer foam material, and the front peripheral and rear peripheral support portions 20 and 14 are formed from foam materials of intermediate firmness or resiliency. It should be appreciated, however, that in other embodiments, one or more of the respective support portions may be formed from a combination of materials having different composition, density, or resiliency. Such combinations of materials can be readily tailored so as synergistically to produce the desired overall or resultant characteristics in terms of firmness, resiliency, or resistance to deformation.

It should also be appreciated that in some embodiments (such as that shown in figure 4), the different support portions may be obscured from view by a covering layer, which may range from less than 1 mm to several centimetres in thickness. In some embodiments, the covering layer includes a viscoelastic gel or a memory-effect foam material for enhanced comfort. In other embodiments, some or all of the support portions may be readily discernible, or even accentuated, for example by a covering material extending substantially into the join lines between adjacent sections, for enhanced aesthetic and/or ergonomic effect. The aesthetic aspect may also be enhanced, for example, by using contrasting colours in the different support portions.

The average difference in firmness between the primary support portions 5 and the forward or thigh support portions is preferably at least 10%, more preferably at least 20% and in some preferred embodiments is at least 30%. One suitable measure for this firmness parameter is Indentation Force Deflection (IFD). Using this measure, 25% IFD means the force (in Newtons) required to achieve a deflection corresponding to 25% of the thickness of a standard sample of the material. Thus, a seat foam material with a 25% IFD of 80 Newtons (N) would be approximately 30% softer or less firm than a seat foam material with a 25% IFD 120 N. In preferred embodiments, the relatively firm primary support portions are formed predominantly from materials with an effective 25% IFD in the range of 60 to 200 N, while the relatively softer forward or thigh support portions are formed predominantly from materials with an effective 25% IFD in the range of 20 to 120 N.

The combined top surface area of the primary support portions is preferably less than 50%, more preferably less than 40% and in some preferred embodiments is less than 30% of the total top surface area of the cushion. A further embodiment of the invention is shown in figures 5 and 6, wherein corresponding features are denoted by the same reference numerals. This embodiment is similar to the one previously described, but in this case, the plugs 6 defining the primary support portions 5 are formed in an inverted frusto-conical configuration. The inclined sidewalls 25 of these plugs provide an inclined or tapered interface with the surrounding support portions of the cushion. This results in a region of overlap between the adjoining sections of different firmness, which advantageously provides a progressive transition in firmness or resiliency between the adjacent support portions. It will be appreciated that this concept of an inclined interface, to provide a progressive transition in firmness across an overlapping region or zone, can be applied to the interface between any of the adjacent support portions if desired for ergonomic, manufacturing, aesthetic or other purposes.

It should also be appreciated that although in the embodiments previously described, the plugs forming the primary support portions are substantially circular in shape when viewed in plan, this need not be the case. For example, these plugs could be oval shaped, diamond- shaped, square, rectangular, triangular, hexagonal, octagonal, elliptical or the like. They may be substantially straight- sided, curved, or a combination of both. They may be symmetrical or asymmetrical. More complex three-dimensional shapes such as spheres or oblate spheroids are also envisaged. The primary support portions may also be formed as a combined shape, and/or effectively as a unitary structure. For example, in one embodiment, they may be formed in the shape of a dumbbell with the enlarged ends predominantly forming the respective primary support portions, joined by an interconnecting neck portion. Similar comments apply with respect to the shape of the various other support portions.

A further embodiment of the invention is shown in figures 7 and 8, wherein again similar features are denoted by the same reference numerals. In this case, the primary support portions 5 are formed by the incorporation of the discrete cylindrical cores 30 formed from resilient materials having firmness characteristics that are different from those of a surrounding matrix material such that in combination, the cores and the surrounding matrix synergistically exhibit the desired relative firmness characteristics. In this embodiment, the primary support portions 5 are denoted by dotted circular outlines 5A, each portion being defined by a respective cluster of seven relatively firm cores 30. Similarly, the thigh support portions 18 are denoted by dotted outlines 18 A, each portion being defined by a respective cluster of six relatively soft cores 30. The front and rear peripheral support portions 20 and 14 are similarly defined by a peripheral array of cores 30 of intermediate softness.

As best seen in figure 8, the seat cushion includes a matrix material 32 that is common to substantially all of the support portions, with the specified differences in relative firmness between the different support portions resulting from the use of cores of different firmness and/or different relative spacing. Advantageously, the upper part of the matrix material 32 defines a relatively uniform top layer 33 that extends continuously over all of the different support portions and over the associated cores of different resiliency, so as to provide a relatively smooth transition between the regions of differential firmness, density or resiliency.

In this embodiment, the cores are formed from foam cylinders, each being less than around 80 mm (and preferably around 50 mm) in diameter, and each being positioned at least 10 mm (and preferably around 30 mm) below the upper surface of the seat cushion. It should be appreciated, however, that the cores may be formed in a variety of different sizes, shapes, material compositions, relative spacings and geometrical arrangements (symmetrical or otherwise) so as in combination to achieve the desired variations in resiliency as between the different support portions, as previously defined. In one variation, a more progressive transition between the different support portions is achieved by progressively varying the height or depth of the respective cores, either in conjunction with or as an alternative to variations in firmness, density or resiliency of the constituent materials from which the cores or the surrounding matrix materials are formed. It should also be emphasised that again, the overall shape 5A of each of the primary support portions need not be circular. In some embodiments, the cushion may be formed by initially moulding the matrix material either with the core holes preformed or subsequently cut out, and then installing the cores as a separate process step. In other embodiments, the matrix and the cores may be moulded substantially simultaneously, so as effectively to form a unitary structure. A further embodiment of the invention is shown in figure 9, in which similar features are again denoted by corresponding reference numerals. This embodiment is similar to that shown in figures 5 and 6. In this case, however, the plugs 6 defining the primary support portions are formed with a more elongate, generally oval or egg-shaped profile when viewed in plan, each tapering progressively inwardly toward the front. In certain configurations, this embodiment can distribute the seating pressure more evenly under the legs the sitter, and provide a more progressive transition in firmness from the rear to the front of the seat member, while providing substantial primary support for the ischial tuberosities of the sitter.

In some variations of this embodiment, the maximum length of each primary support plug is at least 10% greater than the maximum width. In some embodiments, the maximum length of each primary support plug is at least 20% greater than the maximum width and in other embodiments, the maximum length is at least 30% greater than the maximum width. In some preferred embodiments, the maximum length of each primary support plug is at least 50% greater than the maximum width. Each plug has an upper minimum width in plan view of at least around 80 mm, and more preferably at least around 100 mm.

Figure 10 shows a further embodiment of the invention, as a variation on the embodiment of figure 9. In this case, the elongate frusto-conical plugs 6 defining the primary support portions 5 are embedded within a surrounding relatively softer matrix material. In this variation, a top layer 33 of the relatively soft matrix material extends substantially continuously above the primary support portions in a manner somewhat similar to that shown in the embodiment of figure 8. This arrangement has the advantage of providing a relatively soft initial impression when the buttocks of the sitter first contact the seat member, while maintaining the relatively firm underlying support of the primary support portions. These are spaced below the top surface, but come into play functionally once the weight of the sitter has been fully transferred the seat.

As an optional enhancement in this embodiment, the primary support plugs 6 and the covering layer 33 of the surrounding matrix material are configured such that the top surface of the seat member protrudes upwardly above the surrounding surface, immediately or approximately above the primary support plugs. This provides a visual cue in the form of a discernible outline on the top surface of the seat member indicative of the location of the primary support plugs, which would otherwise be concealed from view within the surrounding matrix material. This visual cue serves an aesthetic purpose as a distinguishing feature of interest. It also serves a functional purpose in allowing the sitter to position himself/herself in an ergonomically optimal position on the seat, having regard to the precise location of the primary support portions therewithin. In a further variation on this embodiment, the top surface of the seat cushion may be recessed immediately or approximately above the primary support plugs, again to provide a visual cue as to the position of the underlying primary support portions and to assist the sitter with optimal positioning on the seat.

In use, the cushion may be manufactured as an integral part of a seat or chair, may be retro-fitted to an existing seat or chair, or may be substantially self-contained, and adapted to be removably placed on top of a conventional seat, chair or bench. It may also be placed and used directly on the floor or the ground.

Advantageously, in its various preferred embodiments, the cushion promotes good posture by firmly supporting the ischial tuberosities of the sitter, while providing enhanced comfort by supporting the soft tissues of the sitter between the ischial tuberosities and the thighs less firmly. This is counterintuitive with respect to much conventional wisdom, which has hitherto tended to suggest that because the ischial tuberosities are themselves hard and close to the surface of the body, they should be supported by relatively softer more compliant materials. The invention also avoids the need for crevices or ridges under the thighs to locate the sitter properly on the seat cushion, which advantageously minimises any adverse effect on blood circulation. In these and other respects, the invention represents a practical and commercially significant improvement over the prior art.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. In particular, it should be appreciated that the features of any preferred embodiments may be combined with or substituted for the features of other embodiments even if such combinations and substitutions are not explicitly disclosed.

Claims

1. A seat cushion including:

a pair of primary support portions formed from a relatively firm resilient material and positioned in spaced apart relationship so as respectively to support the ischial tuberosities of a sitter; and

a forward support portion formed from a resilient material that is relatively softer than the primary support portions and disposed in front of the primary support portions to support the upper thighs of the sitter.

2. A seat cushion according to claim 1, further including a rear peripheral support portion extending generally behind the primary support portions and formed from a resilient material that is relatively softer than the primary support portions.

3. A seat cushion according to claim 1 or claim 2, further including an intermediate bridge support portion extending between the primary support portions and formed from a resilient material that is relatively softer than the primary support portions, the bridge support portion being adapted to support soft tissue between the ischial tuberosities of the sitter.

4. A seat cushion according to any one of the preceding claims, wherein the forward support portion includes a pair of laterally spaced apart thigh support portions extending forwardly from the primary support portions and formed from a resilient material that is relatively softer than the primary support portions, so as comfortably to support the thighs of the sitter without substantially impeding blood flow through the thighs.

5. A seat cushion according to claim 4, wherein the forward support portion further includes front peripheral support portions extending respectively on either side of the thigh support portions and formed from a resilient material that is relatively firmer than the thigh support portions.

6. A seat cushion according to claim 4 or claim 5, wherein a front bridge support portion extends longitudinally between the thigh support portions.

7. A seat cushion according to claim 5 or claim 6, further including a rear peripheral support portion.

8. A seat cushion according to claim 7, wherein the rear peripheral support portion and the front peripheral support portions form an effectively continuous generally U- shaped rim of intermediate firmness or resiliency, extending around the back and sides of the cushion, to help locate the ischial tuberosities of the sitter on the primary support portions.

9. A seat cushion according to any one of the preceding claims, wherein each support portion of the seat cushion is formed from a resilient material that is relatively uniform in composition, density, and resiliency.

10. A seat cushion according to any one of the preceding claims, wherein each of the primary support portions is formed, at least in part, by a plug of material that is relatively firmer than a surrounding matrix material.

11. A seat cushion according to any one of the preceding claims, wherein the respective primary support portions are generally circular in plan view, each having an upper diameter of at least around 80 mm.

12. A seat cushion according to any one of claims 1 to 10, wherein the respective primary support portions are generally oval-shaped in plan view, each having an upper minimum width in plan view of at least around 80 mm.

13. A seat cushion according to any one of the preceding claims, wherein each of the primary support portions is formed from a primary support plug have tapered sides, so as in use to effectively provide a progressive transition in firmness or resiliency between the primary support portions and the surrounding relatively softer support portions of the seat cushion.

14. A seat cushion according to claim 13, wherein the primary support plugs are generally inverted frusto-conical in shape and generally circular in plan view.

15. A seat cushion according and 13, wherein the primary support plugs are generally inverted frusto-conical in shape and generally oval- or egg-shaped in plan view.

16. A seat cushion according to any one of the preceding claims, wherein the primary support portions are formed by the incorporation of a plurality of discrete cores formed from resilient materials having firmness characteristics that are different from those of a surrounding matrix material such that in combination, the cores and the surrounding matrix synergistically exhibit effective relative firmness characteristics so as in combination to define the primary support portions and the forward support portion.

17. A seat cushion according to claim 16, wherein the cores are formed from foam cylinders, each being less than around 80 mm in diameter.

18. A seat cushion according to any one of the preceding claims, wherein the forward support portion is at least 10% softer than the primary support portions.

19. A seat cushion according to any one of the preceding claims, wherein the primary support portions define a combined top surface area that is less than around 50% of a total top surface area of the cushion.

20. A seat cushion according to any one of the preceding claims, further including a covering layer extending over the primary support portions and the forward support portion.

21. A seat cushion according to any one of the preceding claims, wherein a top surface of the seat cushion protrudes upwardly above a surrounding surface immediately or approximately above the primary support portions, so as to provide a visually discernible outline on the top surface indicative of the location of the primary support portions.

22. A seat cushion according to any one of claims 1 to 20, wherein a top surface of the seat cushion is recessed below a surrounding surface immediately or approximately above the primary support portions, so as to provide a visually discernible outline on the top surface indicative of the location of the primary support portions.

23. A method of forming a seat cushion according to any one of the preceding claims, the method including the steps of forming the primary support portions from a relatively firm foam material, and positioning the primary support portions within a surrounding matrix formed from a relatively softer foam material, such that the relatively softer foam material forms the forward support portion.

24. A method according to claim 23, wherein the primary support portions are positioned so as to be substantially covered by a top layer formed by the relatively softer foam material of the surrounding matrix.

25. A seat having a seat cushion as defined in any one of claims 1 to 22.

26. A seat cushion formed in accordance with the method of claim 23 or claim 24.

27. A seat cushion substantially as herein described with reference to any one of the embodiments of the invention as illustrated in the accompanying drawings.