Chair

The invention relates to a chair having a seat structure formed by a frame member that defines a central opening. A flexible membrane extends across the central opening. A pair of support pads, one disposed on either side of the cross-beam member, is provided and arranged at a level below the central opening of the frame member. The support pads are arranged within the seat structure so as to be rearwardly disposed with respect to the front edge of the frame by a first distance and spaced apart from each other by a second distance, the first and second distances generally corresponding to the positioning of the ischicial tuberosity of a user when the user assumes a seated position engaging the seat structure.

FIELD OF THE INVENTION

This disclosure relates to the field of ergonomic chairs.

BACKGROUND OF THE INVENTION

Ergonomic chairs for reducing various stresses on the body that are often related to sitting for long periods of time and/or due to incorrect posture when in the seated position are known and come in a variety of designs. Mesh chairs that provide a mesh or material covering formed from a resilient material that is arranged over a chair frame for supporting the user in the seated position have gained popularity, at least in part for their modern aesthetics. Mesh chairs are also considered advantageous for allowing air flow through the mesh or material covering enabling the user to remain cool when seated in the chair for long periods of time and for being more easily cleaned and/or sterilized than more traditional chairs that include more fabric and cushioning.

SUMMARY OF THE INVENTION

Forming one aspect of the invention is a chair comprising a base, a support post extending upwardly from said base; and a seat structure attached to said support post. The seat structure comprises: a frame member defining a central opening; a flexible membrane extending across the central opening of said frame member; and a pair of support pads arranged at a level below the central opening of said frame member.

According to another aspect, the support pads can be rearwardly disposed with respect to the front edge of said frame member by a first distance and are spaced apart from each other by a second distance, the first and second distances generally corresponding to the positioning of the ischicial tuberosity of a user when the user assumes a seated position engaging the seat structure.

Forming another aspect of the invention is a chair comprising a base and a seat structure attached to said base. This seat structure includes: a frame member defining a central opening; a flexible membrane extending across the central opening of said frame member; and a pair of support pads arranged at a level below the central opening of said frame member.

Forming yet another aspect of the invention is a chair comprising a base, a seat structure attached to said base to support the buttocks of a user seated thereupon; and a back rest attached to one or more of the base and the seat structure to support the back of the user. The back rest includes: a frame member defining a central opening; a flexible membrane extending across the central opening of said frame member; and a pad arranged behind the central opening and positioned in the manner of a lumbar pad.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now toFIGS. 1 and 2there is shown a chair10according to an exemplary embodiment of the present disclosure. The chair10includes a seat structure12, a back rest14and a base16. The base16includes a plurality of radially spaced apart legs18each of which is provided with a caster or roller20, the base16therefore providing rolling support to the chair10. A support post22extends upwardly from the center of the base16and typically includes a height-adjusting mechanism for allowing the overall height of the seat structure12to be adjusted based on the needs of the individual user in accordance with principles known in the art.

The seat structure12is mounted at the upper end of the support post22. The seat structure12includes a frame member26that forms the periphery of the seat and defines a central opening28therethrough. A cross-beam member30having a generally concave or curved structure extends generally below the central opening28of the frame member6along the midline or centerline27of the seat structure12interconnecting the front and rear edges32,34of the frame member26, the cross-beam member30serving to mount the seat structure12to the upper end of the support post22. The frame member26and cross-beam member30may be integrally formed or may be formed as separate components that are fixed together forming the seat structure. The frame member26and cross-beam member30are formed of molded plastic material.

A pair of cushion supports38extend laterally away from the cross-beam member30, one on either side of thereof. The cushion supports38are rearwardly disposed by a distance D1with respect to the front edge32of the frame member26and extend laterally away cross-beam member30by a distance D2with respect to the midline or centerline27of the seat structure12. The distances D1and D2are predetermined so as to generally correspond to and/or align with the position or general location of the ischicial tuberosity, or sitting bones, of the average user when in a seated position.

The cushion supports38are formed as separate components that are securely fixed to the cross-beam member30. First and second support cushions40are secured to the upper surface42of the cushion supports38and are formed from a suitable padded material to provide a cushioning effect. The cushion supports38and support pads40are selected and/or together have a predetermined overall thickness or height to ensure that the upper surface44of the support cushions40lies at a level below the central opening28of the frame member26when arranged or mounted on the cushion supports38.

As shown inFIG. 2, a thin, flexible membrane50is arranged so as to extend across the central opening28of the frame member26. The membrane50is generally formed from a resilient mesh fabric that is stretched across the central opening28and affixed to the frame member26.

It is generally understood that a person in a seated position rests on the ischicial tuberosity, or sits bones, which extend from the lower, back portion of the pelvis or hip bones. When a person is standing, the ischicial tuberosity is generally covered by large muscle groups that generally provide cushioning or padding to the otherwise bony protrusions of the ischicial tuberosity. However, when a person assumes a seated position, the muscles tend to shift leaving the bony protrusions of the ischicial tuberosity to bear the majority of the weight. Bearing the majority of one's weight on the ischicial tuberosity can be quite uncomfortable especially when one is in a seated position for a long duration of time, as is often typical of an office workplace situation. As well, depending on the size and overall weight of the user, when mesh is utilized, it has been discovered that pressure points may also be created against the backs of the user's legs and/or on their hips or thighs where the edges of the frame member may come into contact with and impinge on the user's body.

In the embodiment shown inFIG. 1andFIG. 2, the cushion supports38and support pads40are strategically arranged in relation to the cross-beam member30in order to reduce the pressure points associated with the membrane50. In particular, the cushion supports38together with the support pads40provide support to the membrane50when the membrane50becomes stretched under the weight of a user. The arrangement of the cushion supports38and support pads40in relation to the cross-beam member30underneath the membrane50also prevents the membrane50from bottoming-out under the weight of a larger and/or heavier individual. Accordingly, should a larger and/or heavier individual assume a seated position on the chair10, the user will end up resting on the support pads40and enjoy the comfort of the padded material forming the support pads40as opposed to bottoming-out the seat structure12and finding themselves resting on the cross-beam member30. Accordingly, cushion supports38and support pads40together provide additional support to the membrane50which allows the seat structure12to provide the benefits associated with a mesh-style chair since the membrane50can stretch and conform to the shape of the user when the user assumes a seated position bearing weight on the membrane50and allow for air-flow through the mesh-material forming the membrane50, but still offers the added benefit of support and cushioning to the sits bones or ischicial tuberosity of the user. The cushion supports38and support pads40also serve to reduce the overall amount of shear stress on the membrane50which reduces the likelihood of the frame member26impinging on the user and creating uncomfortable pressure points that can have an adverse effect on the overall comfort and ergonomic health of the user. It has also been found that incorporating cushion supports38and support pads40underneath the membrane50prevents the user from sinking too low within the central opening28of the frame member26and assuming a less-than-ideal sitting position. As a result, the user is less likely to be inclined to raise the overall height of the seat in an effort to compensate for sinking too low within the central opening28which raised seat height would result in an even less ergonomic sitting position.

A third support pad52is also provided at the front end54of the cross-beam member30proximal to the front edge32of the frame member26. The third support pad52is arranged so as to generally lie between the user's legs when in the seated position on the chair10. Accordingly, the third support pad52provides additional support to membrane50in the area proximal the front edge32of the frame member26along the centreline or midline27of the seat structure12. The third support pad52extends laterally on either side of the centreline or midline27of the seat structure12by a distance D3and is generally sized and arranged below the central opening28of the frame member26so as not to come into contact with the user's legs when seated on the chair10. The third support pad52, therefore, provides support to only the membrane50at the front edge32of the seat structure12. The third support pad52therefore works in combination with the first and second support pads40that are arranged within the central area of the seat structure12to provide a support triangle for providing additional support the membrane50under the weight of a user allowing the membrane50to adopt a more comfortable position without undue shear stresses being created in the material resulting in a more ergonomic and a more comfortable feel for users of various overall weights and/or sizes. Reducing the amount of shear stresses created in the membrane50when under the weight of a user also tends to increase the life of the material forming the membrane50over time.

In the embodiment shown, the back rest14is similar in structure to the seat structure12in that it comprises a frame member58that forms the periphery of the back rest14and defines a generally elongated, central opening60. A back support member62extends generally along the centerline or midline of the back rest14interconnecting the top and bottom edges64,66of the back frame member58. A second membrane (not shown) is generally arranged across the top of the frame member58so as to extend across the central opening60defined by the frame member58. Similar to the membrane50used on the seat structure12, the membrane for the back rest is formed by a mesh material that can stretch and conform to the shape of the user's back when the user rests against the back rest14of the chair. The back rest14is mounted to the base16by tilt mechanism in order to permit limited, pre-determined movement of the back rest14(e.g. forward tilt, backwards tilt) with respect to the base independent of the seat structure12. The back rest14may also be provided with additional features such as an adjustable lumbar support mechanism and/or a head rest (not shown) positioned at the upper edge64of the back rest14.

By providing both a back rest14and a seat structure12formed by frame members26,58fitted with a resilient mesh membrane50,63arranged across the central openings28,60of the frame members26,58allows for air-circulation around and through both the seat structure12and back rest14. As well, since membranes used for both the seat structure12and the back rest14are generally spaced apart from the supporting structures (e.g. frame members26,58and cross-beam members30,62) forming both the seat structure12and back rest14, the chair10can be relatively easily cleaned since the components of the seat structure12and back rest14are accessible, which is advantageous in environments requiring a degree of cleanliness. Furthermore, by providing a seat structure12having a combination membrane and support cushion structure as described above, a comfortable and durable chair10is provided that is suited to a wide range of individual users.

A further exemplary embodiment shown inFIG. 3and designated with general reference10A. This embodiment is substantially identical to the embodiment ofFIGS. 1 and 2, differing only in that first and second support pads40are connected by a bridge40A.

Without intending to be bound by theory, it has been found that an advantageous arrangement of the cushion provided by pads40(and52, when present) is associated with support pads providing the maximum amount of support possible without the user feeling the pads in use. Accordingly, the technology can advantageously be deployed with removable pads of differing densities (to enable users to customize the chair by substitution of pads) or with pads having adjustable air bladders or otherwise adjustable in height relative to the frame or adjustable in stiffness.

FIG. 4is a matrix of images showing localized pressure experienced by a user of a leading mesh-only seat [left column], a leading foam-only seat [right column] and a foam-mesh seat according an embodiment of the present invention [central column]. In each column: the uppermost image is a plan view showing localized pressures; the middle age is a side view, which assists in understanding quantum of the pressure differential; and the bottom image is a perspective view. With reference to the left column, it will be seen that, in the leading mesh chair, areas of high pressure exist adjacent the sit bones (the light areas at the top of the uppermost image) and also adjacent under the thighs near the front edge of the chair (the light areas at the bottom of the uppermost image). The leading foam-only seat shows much better distribution, as no areas of very high pressure appear in the images. In the mesh-foam chair tests, the pressure to which the sit bones are exposed has been improved relative to the leading mesh-only chair, and the pressure to which the thighs are exposed at the chair leading edge has been vastly improved relative to the leading mesh-only chair. From the above, it will be evident that significant advantage in pressure distribution can be attained by practising the present invention, but the images shown should be understood to be representative of single samples, only, and are merely included by way of example.

A further embodiment is shown inFIGS. 5A-5Hand designated by general reference numeral100. In this embodiment, each pad is defined by an airless cushion104and the third support pad extends across the entire front edge of the seat, as indicated by106. A lumbar pad102is also provided, and is positioned behind the back opening to function in a manner analogous to the ischicial pads. The seat and back are covered with mesh, indicated by108and110, respectively.

While but three embodiments of the chair and seat structure have been illustrated and described, it will be understood that certain adaptations and modifications can be made. For example, whereas the chairs shown each include a support post, this need not be the case; the chair could be made with four legs and non-swivelling.

Therefore, the above discussed embodiments are considered to be illustrative and not restrictive.