Chair, in particular office chair

Details Chair, in particular office chair Chair, in particular office chair

1999-06-29

2001-05-22

Barfield, Anthony D. (Department: 3624)

Chairs and seats

Back movement resiliently opposed in operating position

Back and seat adjust simultaneously

C297S300700

Reexamination Certificate

active

06234573

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a chair, in particular an office chair comprising a seat top with at least one front seat support arm and at least one rear seat support arm projecting at the underside of the seat top, a seat carrier which is securely connected to a central chair column or several chair legs, and a backrest which is arranged at a backrest carrier firstly extending under the seat top backwards and thereafter upwards with the backrest carrier supported by means of a crosswise horizontally extending backrest carrier swivelling joint with the front seat support arm articulately connected to the seat carrier through at least one lever wherein the rear seat support arm offset backwards from the backrest carrier swivelling joint is articulately connected to the backrest carrier by means of a crosswise horizontally extending rear seat joint, and wherein a spring arrangement is provided under the seat top with the spring arrangement exerting a biasing force upwards upon the seat top and forwardly upon the backrest.
A chair of the type mentioned is known from DE 43 13 301 C2. The spring arrangement provided for this chair consists of a pressure spring which is arranged between the seat carrier and the seat top. By the arrangement of the single parts of this chair as explained above the chair offers the user the opportunities to selectively sit upwards on this chair or in a reclined position. In the reclined position the seat top will lower in the rear part, whereby at the same time the backrest with the backrest carrier will pivot backwards.
It is a disadvantage of this known chair that it offers no possibility to adapt the force acting upon the back of the user to the user, in particular to the body weight thereof. Therefore the known chair is only a compromise regarding the force acted upon the back of the user by the backrest, which in many cases is not optimal, in particular when the chair is used by light weight or heavy weight users.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a chair of the type mentioned above which avoids the disadvantages mentioned, and wherein the force acted upon the back of the user by the backrest may be adapted to the body weight of the user, wherein an automatic adaption must be possible.
For attaining this object, a chair of the type mentioned above is proposed characterized in that the lever connecting the front seat support arm with the seat carrier is designed as a two-arm swivelling lever, pivotable around a crosswise horizontally extending swivelling axis, and supported at the seat carrier, with the one lever arm of the swivelling lever articulately connected to the front seat support arm, and with the other lever arm of the swivelling lever connected to one end of the spring arrangement. The other end of the spring arrangement is connected to the backrest carrier in spaced relation from the backrest carrier swivelling joint.
It is essential for this novel chair that the single pressure spring acting directly onto the seat top used in the state of the art is replaced by a spring arrangement with the biasing force thereof variable by means of the two-arm swivelling lever, wherein the variation is automatically attained by the weight load of the seat top by the user of the chair. Without a manual operation it is thereby attained that with light weight users of the chair, the backrest exerts only a smaller force upon the back of the user, and that with heavy weight users of the chair, the backrest exerts a larger force upon the back of the user, such that depending upon the weight of the user of the chair, the back of the user is always supported with an adequate and suitable force by the backrest. At the same time, the mechanical effort for realizing this adaption of the force of the backrest is relatively small, such that the chair according to the invention may be manufactured at low cost, and may be produced in a stable, safe, and durable way without much effort.
In the first embodiment of the chair according to the invention it is provided that at least one tension spring is the spring arrangement, wherein the second lever arm of the swivelling lever connected to the front end of the tension spring points backwards, and wherein the connection of the rear end of the tension spring with the backrest carrier is offset upwards from the backrest carrier swivelling joint. With this arrangement of the spring arrangement the required function is attained in a technically simple and reliable fashion. Furthermore the production costs are kept low, and it is only relatively little space required for the accommodation of the spring arrangement.
Furthermore, it is preferably provided that the swivelling lever is designed as a strain lever or as a lever angled up to 45° at maximum. This design of the swivelling lever has the advantage that the lever may be easily manufactured, and that a flat construction of the parts of the chair mechanism arranged under the seat top is possible. This will reduce the room requirement for the chair mechanism under the seat top, and improves the optical appearance of the chair, in particular when viewed from the side.
In order to willingly influence and vary the support force acted upon the back of the user of the chair by the backrest, optionally the force of the tension spring acted upon the backrest may be adjustable.
For this reason, in a further embodiment it is provided that the connection point of the rear end of the spring arrangement at the backrest carrier is adjustable in the distance from the backrest carrier swivelling joint. By this means, the lever arm between the spring arrangement and the backrest carrier may be varied in the length thereof, which takes care of the required change of the backrest force.
Furthermore, it is preferably provided that the rear end of the spring arrangement is connected to the backrest carrier through a pivotable adjusting lever which may be locked. By this design, the biasing force of the spring arrangement is hardly changed, however, the lever effect between the spring arrangement and the backrest carrier is varied in dependence from the corresponding position of the adjusting lever.
Preferably at least one helical leg, torsion bar, gas pressure, rubber or elastomer spring is provided as the spring arrangement wherein such springs are cheap and easily accessible construction members which may be purchased in the market without any problems.
To lock the chair in at least one base position when not in use, and in case that the user of the chair wants to use it in a fixed position, and e.g., does not want the reclined position, it is provided that the backrest carrier pivotable around the backrest carrier swivelling joint may be locked in continuous or stepped swivelling positions.
A first embodiment of the chair with the locking capability of the backrest carrier mentioned before provides that at least one one-arm catch lever pivotable around a horizontal swivelling axis is connected to the backrest carrier in vertically spaced relationship from the back-rest carrier swivelling joint with the catch lever substantially extending horizontally to the seat carrier, and freely displaceable in its longitudinal direction in relation to the seat carrier in a first, automatically occupied release position, and in a locking fashion engaging a locking element in a second locking position occupied by adjusting an actuating element, wherein the locking element prevents a displacement of the catch lever in relation to the seat carrier. When the catch lever is in its release position the movements of the seat top and the backrest in relation to the seat carrier are not hindered, only when the catch lever takes its locking position by adjusting the actuating element a further movement of the seat top at the backrest in relation to the seat carrier and in relation to each other is prevented.
A preferred further development provides that the locking element is at least one bolt extending through an elongated hole in the c

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