ERGONOMIC CHAIR BACKREST
A “task” chair intended primarily for a person working at a computer terminal has a back provided with a pair of upright struts that incorporate respective parallelogram linkages operative to increase the curvature of the lumbar region of the seat back while at least substantially maintaining the contour of the upper region of the backrest when a person leans back in the chair.
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This invention relates generally to chairs and is concerned in particular with the chair backs that are designed in accordance with ergonomic principles.BACKGROUND OF THE INVENTION
The invention has been devised in the context of chair designs that are intended to address problems with respect to the posture and comfort of individuals who are required to spend long periods of time in a seated position, for example, working at a computer. However, the invention is not limited in this respect.
In modern office environments, people who work at computers naturally adjust their seating positions from time to time, for example, by leaning back in their chairs. Some people even work leaning back. Such a sitting posture places significant strain on the upper thorax and neck regions of the person. In other words, if the person leans back, while continuing to keep their eyes on the computer screen, they must inevitably compensate by tilting their head forward, causing strain in the neck and/or upper thorax region.
An object of the present invention is to address this problem by providing an improved chair back structure.SUMMARY OF THE INVENTION
A chair in accordance with the invention comprises a base, a seat supported on the base and a back coupled to at least one of the seat and base. The back includes a backrest having a normal contour which includes a lower, lumbar region for contact by the lumbar area of a person seated in the chair and which is forwardly curved, and an upper region for contact by the upper thorax of the person. The backrest is biased to the normal contour and is flexible to vary the contour. The back further includes at least one upright strut spanning the lumbar and upper thorax regions of the backrest, the strut having a lower end which is fixed with respect to the seat and an upper end which is coupled to the upper region of the backrest for back and forward movement therewith in response to rearward pressure exerted by said person leaning back against the backrest, and return to said normal contour. The strut includes a parallelogram linkage operative to increase the curvature of the lumbar region while at least substantially maintaining the contour of the upper region of the backrest in response to said rearward pressure.
In other words, as the person leans back, the contour of the backrest changes to support the lumbar area and the upper thorax and/or neck of the person and thereby at least partly alleviate the strain on the upper thorax and neck region that would otherwise occur, for example, when the person leans back while continuing to look at a computer screen as discussed previously.
Preferably, the normal contour of the backrest follows a gentle S-shaped curve in the upright direction of the backrest (top to bottom) including a forwardly curved lumbar region and an upper region in which the top of the backrest curves slightly forwardly so as to tend to augment the support function in the upper thorax and neck region.
While a single strut may be provided, for example, generally centrally of the backrest, a pair of struts preferably is provided, one at each side of the backrest. The strut or struts may be external to the backrest and therefore visible in use, or may be incorporated into the backrest itself or into a supplementary cover at the rear of the backrest.BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which illustrate a particular preferred embodiment of the invention by way of example, and in which:
Referring first to
With continued reference to
Referring now more particularly to
In this particular embodiment, the backrest 34 is a polypropylene moulding, the normal “as moulded” shape of which is seen in
As noted previously in referring to
Applicant does not intend to be bound by theory. At the same time, it is believed that the invention is based on medically sound principles of emphasing kyphosis in the thorax area of the person to compensate for lordosis in the lumbar area. Lordosis is defined as forward curvature of the spine and kyphosis is rearward curvature, both following the slightly S-shaped curvature of a healthy spine. In a healthy spine, the portion above about the sixth thorax vertebra tends to tilt forward. This tilt is accentuated or supported by the backrest contour that is achieved in accordance with the present invention.
The precise changes in contour that occur of course depend on the relative lengths of the two links 44, 46 and on the relative positions of their pivot points. For example, in the illustrated embodiment, shortening the inner link would have the effect of tending to cause some forward curvature of thorax region 34b of the backrest, tending to increase support in that area.
It will of course be appreciated that the preceding description relates to a particular preferred embodiment of the invention and that a number of modifications are possible, some of which have been indicated previously, while others will be apparent to a person skilled in the art. Obviously, the particular design and configuration of the parallelogram links may change. The manner in which the struts are coupled to the seat of the chair may also change. In the illustrated embodiment, each strut 30 is coupled to the seat support structure 24a of the chair seat by an arm 32 that extends forwardly from the lower end of the strut. The strut itself is then coupled to upper and lower regions of the seat back as shown in
1. A chair comprising a base, a seat supported on the base and a back coupled to at least one of the seat and base, wherein the back comprises a backrest having a normal curved contour as seen from the side including a lower, lumbar region for contact by the lumbar area of a person seated on the chair and which is forwardly curved, and an upper region for contact by the upper thorax of the person, the backrest being biased to said normal contour and flexible to vary said contour, and the back further comprising at least one upright strut spanning the lumbar and upper thorax regions of the backrest, the strut having a lower end which is fixed with respect to the seat and an upper end which is coupled to said upper region of the backrest for back and forward movement therewith in response to rearward pressure exerted by said person leaning back against the backrest and return to said normal contour, the strut comprising a parallelogram linkage operative to increase the curvature of said lumber region while at least substantially maintaining the contour of said upper region of the backrest in response to said rearward pressure.
2. A chair as claimed in claim 1, comprising a pair of struts at respectively opposite sides of the back and each coupled both to said upper region of the backrest and to the backrest at a lower region below said lumbar region.
3. A chair as claimed in claim 2, wherein each said strut is coupled to the base of the chair by an arm that extends forward from a bottom end of said strut.
4. A chair as claimed in claim 1, wherein said parallelogram linkage comprises an inner link and an outer link disposed respectively closer to and further away from said backrest, wherein the outer link is wider than the inner link and includes a slot receiving the inner link for permitting the links to nest together.
5. A chair as claimed in claim 1, wherein said parallelogram linkage is disposed externally with respect to the backrest and is enclosed within a decorative shroud.
6. A chair as claimed in claim 1, wherein said backrest comprises a plastic moulding having an as-moulded shape that represents said normal curved contour of the backrest, and wherein the plastic moulding is resiliently deflectable to permit said contour variation, the moulding inherently providing said biasing to said normal contour.
7. A chair as claimed in claim 6, wherein said moulding comprises a solid back wall which carries a resilient cushion structure for contact with the back of a person using the chair.
International Classification: A47C 7/46 (20060101);