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Ergonomic chair backrestErgonomic chair backrest description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070138851, Ergonomic chair backrest. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] 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 [0002] 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. [0003] 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. [0004] An object of the present invention is to address this problem by providing an improved chair back structure. SUMMARY OF THE INVENTION [0005] 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. [0006] 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. [0007] 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. [0008] 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 [0009] 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: [0010] FIG. 1 is a three-quarter perspective view from the rear and to one side of a chair in accordance with the invention; [0011] FIG. 2 is a vertical sectional view generally on the centreline of the back of the chair in its normal rest position; [0012] FIG. 3 is a view similar to FIG. 2 showing the contour of the backrest when a person leans back in the chair; [0013] FIG. 4 is an exploded perspective view illustrating the struts at the rear of the backrest; and, [0014] FIG. 5 is a perspective view illustrating a parallelogram linkage comprising one of the struts. DETAILED DESCRIPTION OF THE INVENTION [0015] Referring first to FIG. 1, the invention is illustrated in the context of a typical office or "task" chair generally denoted 20. It is, however, to be understood that the invention may equally well be applied to the backs of other types of chair including so-called sit/stand chairs of the type disclosed in U.S. Pat. No. 6,752,459 (Deisig). [0016] With continued reference to FIG. 1, chair 20 includes a base 22 (only part of which is shown) which supports a seat 24 of the chair. The chair also includes a back 26 that is supported from the seat by a pair of L-shaped arm structures 28. These structures include respective struts 30 which are coupled to the seat back as will be described later, and a pair of forwardly extending arms 32 that are secured to support structure 24a of the seat. Though not shown in detail, a conventional tilt mechanism is provided between the base 22 and the seat 24 so that the seat 24 and back 26 can tilt as a unit with respect to the base. The base itself is also conventional and has therefore not been shown in detail. As shown, the base includes a column 22a that supports the seat for adjustment in the vertical direction. A conventional "spider"-type base (not shown) is provided at the bottom of column 22. [0017] Referring now more particularly to FIGS. 2 and 3, the back 26 includes a backrest 34 for contact by the back of a person sitting on the seat 24. The backrest has a contour which follows a generally S-shaped curve as seen in vertical section. That shape continues outwardly to the sides of the back. The backrest may also be curved laterally to partially wrap around the torso of a person seated on the chair. The backrest includes a lower region 34a which is forwardly curved in vertical section for contact by the lumbar area of the person, and an upper region 34b for contact by the upper thorax area of the person. The backrest is flexible so that the contour can be varied under the control of the struts 30 (FIG. 1) as will be described in more detail later. [0018] In this particular embodiment, the backrest 34 is a polypropylene moulding, the normal "as moulded" shape of which is seen in FIG. 2. The moulding is flexible as indicated previously and has spring-like characteristics so that it always tends to return to the normal shape shown in FIG. 2. The moulding has a solid back wall 36 which carries a resilient moulded cushion structure 38 for contact with the back of a person using the chair. A cover 40 is provided over the moulding 34 to provide an appropriate aesthetically pleasing external appearance. In the embodiment illustrated in FIG. 4, the struts 30 are shown external and therefore visible at the exterior of the chair. In an alternative embodiment, the struts could be incorporated within the backrest or enclosed within the cover 40. [0019] Reverting to FIG. 2, the two struts 30 of the chair back are identical and a representative one is shown in FIG. 2. Each strut spans substantially the entire height of the back including the lumbar region 34a and the thorax region 34b. The strut has upper and lower ends 30a and 30b respectively, which are coupled to the backrest 34. The struts are adapted to vary the contour of the profile of the backrest in response to rearward pressure exerted generally in the thorax region 34b by a person leaning back in the chair. The struts confine the backrest to change its contour from the configuration shown in FIG. 2 to the configuration shown in FIG. 3. In FIG. 2, the front face of the backrest is indicated in dotted lines at 34' to show the contour of the backrest in the position of FIG. 3. Continue reading about Ergonomic chair backrest... Full patent description for Ergonomic chair backrest Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Ergonomic chair backrest patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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