Chairs and seats – Back movement resiliently opposed in operating position – Back adjusts independent of seat
Patent
1993-02-08
1995-01-03
Brown, Peter R.
Chairs and seats
Back movement resiliently opposed in operating position
Back adjusts independent of seat
297302, A47C 1032
Patent
active
053780396
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to a torsion spring and an adjustable mounting for a chair according to the preamble of the claims.
Mountings for chairs and specially office chairs generally provide for the possibility of adjusting the inclination of the seat and the position of the back as well, independently or not. The height of the seat usually is adjusted with the position of the mounting on a central column or the position of the column in a base device.
Mountings of the above mentioned type normally comprise a spring function, thereby making it possible for the user to tilt the back of the chair, the seat or both. Additionally the user may adjust the height and the angles of the seat and the back to a comfortable position for the user.
For designing chairs as such it is advantageous that the mounting is small thereby giving more freedom to design work, also of cosmetic reasons, as a mounting with smaller dimensions may be easily hidden behind the seat.
The torsion spring according to the present invention provides a spring having smaller dimensions as compared to known torsion springs having the same spring force and twisting angle.
The adjustable mounting according to the present invention provides a special motion picture as compared to known mountings as a combination with the way of articulating the seat, the back and the mounting bracket. A very comfortable chair is achieved which easily may be adjusted to a desired angle for the back and the seat of the chair. These advantages are achieved with the torsion spring and the mounting according to the present invention as defined by the features stated in the claims.
The only figure FIG. 1, discloses a side view of the adjustable mounting, disclosing also the position of the seat and the back frames in a relaxed position of the chair.
The drawing discloses a mounting bracket 3 fixed to a center shaft 4 which connection may be adjustable in the height, whereby the center shaft 4 is fixed to a not disclosed base as well known in the art.
It has been discovered that the spring function of a torsion spring may be substantially increased when the torsion spring instead of only one bar comprises at least four rods, all being clamped together at the ends of the spring.
Principally the spring effect of a torsion spring will increase with the spring bar cross section dimension. When increasing the cross section, however, the twisting angle will be limited. Torsion springs having small dimensions make possible larger twisting angles, but will naturally be correspondingly weaker, e.g. the spring force is decreased.
It is found however, that a combination of a plurality of smaller torsion rods give the desired high spring force, thereby substantially maintaining a relatively large twisting angle, as each of the rods will be twisted separately in a helical line.
The friction forces between the single rods in a multi-rod torsion spring to a certain degree also contribute to increase the spring force in relation to one single bar having a cross section corresponding to the total cross section of all rods. The result of the combined effect from torsion forces of the small dimension rods and the friction forces, result in the spring force being achieved with a certain total spring cross section of substantially shorter spring length than is the case with a single rod torsion spring having the same cross section, the torsion spring comprising several single rods, thereby maintaining a desired, relatively large twisting angle.
A torsion spring 5 of the above disclosed type is disclosed in the drawing, arranged in a mounting bracket 3. In the middle between the two side walls of the bracket 3 a tilting lever 9 is clamped to a pipe whose other end is clamped to one end of the torsion spring 5. A second pipe is connected to the other end of the torsion spring 5, the other end of the pipe being connected to a lever against which a screw connected with the bracket 3 is adjustable.
To the upper end of the lever 9 the front portion of a seat frame 1 is articulated or pivot
REFERENCES:
patent: 2424753 (1947-07-01), Herold
patent: 2778626 (1957-01-01), Klepp
patent: 3031164 (1962-04-01), Desanta
patent: 4603830 (1986-08-01), Franck
patent: 4865384 (1989-09-01), Desanta
patent: 4966411 (1990-10-01), Katagiri et al.
patent: 5018287 (1991-05-01), Estkowski et al.
Brown Peter R.
Ring Mekanikk AS
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