Chairs and seats – Back movement resiliently opposed in operating position – Back adjusts independent of seat
Patent
1993-07-12
1995-06-20
Brown, Peter R.
Chairs and seats
Back movement resiliently opposed in operating position
Back adjusts independent of seat
297302, 297320, 297353, A47C 1032
Patent
active
054255660
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a chair, especially a working/office chair, comprising a seat-supporting frame, a seat rotatably mounted in the frame about a first axis, a back support pivotally mounted in the frame about a second axis behind the first one, and a coupling means connected between the seat and the back support behind said axes to cause a synchronous movement of the seat in relation to the back support.
A chair of the above-mentioned type is, for example, known from U.S. patent specification No. 4,143,910.
There are previously known many different types of adjustable chairs based on different principles with respect to "sitting technique". With the pure tilting chair, wherein the seat and back are formed in one piece, the chair can be regulated backwards without the person sitting in the chair having the possibility to vary the "body angle", i.e. the angle between the thighs and the upper part of the body. An opening of the "body angle" is favourable, i.a. with a view to a better blood circulation.
In the type of chair having an angularly adjustable back and a fixed seat, one achieves the advantage that the body angle can be opened in a position of rest. The drawback of a fixed seat is, however, that the body tends to slide forwards (and off the chair) in the position of rest.
In a chair of the type stated in the introduction, i.e. a chair having a synchronous adjustment of the seat and back, one achieves the advantage that the body angle can be opened in the position of rest, at the same time as the seat is readjusted synchronously backwards in a certain ratio (e.g. 1:2) to the back. This prevents that one slides off the chair when the back is tilted backwards.
As stated in the introduction, a chair of this type includes separate axes of rotation for the seat and back, and the coupling means between the seat and the back may consist of a link arm or a linkage. Springs for the return of seat and back are disposed in the axis of rotation of these members, or at another suitable location dependent on the type of spring which is used.
An important function, especially in working or office chairs, is the seat angle adjustment forwards. This is particularly important in connection with larger height adjustment ranges. In a traditional chair having a synchronous adjustment, a seat adjustment forwards will cause a too large angular change of the back of the chair forwards (in the ratio 2:1 or more). It is possible to provide an extra adjustment (double seat) having a separate adjustment between the seat and the seat member of the mechanism. However, this would be a complicated solution, and in addition cumbersome to the user which all the time would have to operate an additional handle.
It is an object of the invention to provide a chair of the type in question with which one achieves a synchronous adjustment of the seat and back backwards and a separate angular adjustment of the seat forwards without having to operate a handle.
The above-mentioned object is achieved with a chair of the introductorily stated type which, according to the invention, is characterized in that the coupling means consists of a means having a length which can be readjusted with a certain inertia for adjustment of the relative position of the seat and the back support, so that the position of the seat in relation to the back can be readjusted by the exertion of a torque on the seat while the back support simultaneously is kept essentially stationary in relation to the frame.
In a preferred embodiment the coupling means consists of a hydraulic cylinder.
In the chair according to the invention the seat and the back can be adjusted in accordance with the desired body posture in a particularly simple and user-friendly manner, the user not being in need of operating adjustment knobs or handles, and the structural solution being suitable for small as well as large chair sizes. The position of the seat in relation to the back can be readjusted in that the user in a sitting position only holds on to the seat and exerts a suitable
REFERENCES:
patent: 3989297 (1976-11-01), Kerstholt
patent: 4198094 (1980-04-01), Bjerknes et al.
patent: 4575150 (1986-03-01), Smith
patent: 4763950 (1988-08-01), Tobler
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