Office chair

Details Office chair Office chair

2000-01-07

2001-07-10

Brown, Peter R. (Department: 3636)

Chairs and seats

Back movement resiliently opposed in operating position

Back and bottom adjust in a fixed relationship

C297S329000

Reexamination Certificate

active

06257666

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a chair, especially an office chair with a pedestal and a seat carrier that bears a seat element and that is attached to the pedestal.
2. Brief Description of the Prior Art
Office chairs are well known and have a long time been used in offices and the like at desks and computer work stations. Along with the resilient support of the seat element in the vertical direction, one can frequently also resiliently adjust the inclination of the seat surface and the backrest, both with respect to the pedestal and with respect to each other.
An office chair is known from the European Patent No. EP 0 669 819 B1 whose seat element can be swung backward and down in the form of a circle arc of a pivot axis that lies roughly in the foot joint of a person sitting thereupon. In order to facilitate this pivotal motion of the seat element that is derived from the ergonomic conditions when sitting on a chair, the seat element is attached in the area of its forward edge to a circle-arc-shaped seat carrier that extends to the rear and downward corresponding to the desired pivot motion. This seat carrier is guided in a sliding manner in a likewise circular-arc-shaped guide element that is attached to a pedestal so that it can extend into the guide element corresponding to the pivotal motion of the seat element against the force of a pressure spring.
In this known chair, both the generally customary vertical elasticity and the pivotal motion of the seat element into a tension release position facilitate relaxed sitting by means of the circle-arc-shaped seat carrier that is supported resiliently; therefore, this known office chair does not have a definitely detectable upright working position for the user.
The object of the present invention is to provide an additional chair that, in particular, enables the user to assume a stable working position without constantly running the risk of sliding away into a tension release position that is inclined to the rear.
SUMMARY OF THE INVENTION
According to a primary object of the invention, in other words, taking a stool whose seat carrier can be shifted with relation to the pedestal from an initial position against a restoring spring force along a guide track toward a second position that is inclined vertically when compared to the normal user position of the chair, it is provided that the increase in the restoring spring force along the shifting path in a first shifting path segment adjoining the initial position be greater than in a second shifting path segment that is spaced away from the initial position. In this way, when initially sitting down on the chair and when subsequently sitting upon the chair, a user does of course feel the usual resiliency connected with a slight backward inclination of the seat element; nevertheless, a stable sitting sensation is transmitted to him because the restoring force spring that pushes the seat element back into its initial position at first increases relatively powerfully.
The seat element of the chair of the present invention is thus cushioned comparatively hard near its initial position so that the particular user can assume a stable seated position. When a person sitting on the seat leans back in relaxation, then due to the design of the spring characteristic, the person gets a pleasant and soft cushioning effect that facilitates comfortable and relaxed sitting. The variously hard cushioning, provided according to the invention, thus improves the sitting comfort; it does this due to the clear differentiation that the user can detect between the initial swing range determined for the working positions and the subsequently following pressure release swing range.
According to another object of the invention, means are provided that generate the restoring spring force, first and second spring means being arranged parallel to each other in terms of effect between the pedestal and the seat carrier; the second spring means along the second shifting path segment does not deliver any restoring force component. This is done to implement in the simplest possible fashion the increase in the restoring force spring, in other words, the spring constant that depends on the shifting path, which increase in the restoring spring force as a function of the position along the guide track.
A particularly advantageous embodiment of the invention provides the following. One end of the second spring means is supported by cam and follower means and one end of the second spring means supported with the other end in terms of effect on the pedestal or the seat carrier is supported on a pivot lever that is retained by a pivot joint in a fixed manner with respect to the pedestal or the seat carrier and whose free end engages a cam surface on the seat carrier or on the pedestal.
By using cam and follower means, in particular, by using a pivot height that when the seat carrier is shifted with respect to the pedestal is pivoted with the help of a cam surface, it is possible in a particularly simple manner to neutralize the effect of a spring that may be required to generate hard cushioning in the initial sector so that following an initial shifting range of the seat carrier, there will be a relatively soft cushioning. Here, the cam means facilitate the operation of the second spring means needed for initial cushioning upon return from the relaxed sitting position into a working position. The spring means are automatically connected to generate the restoring force so that in spite of the backward movement in the transition area between soft and hard cushioning, the user can detect the constant retention or even a slight rise of the restoring spring force. As a result, the user is informed of the return of the chair into the working position range that surrounds the initial position.
An advantageous development of the invention is characterized as follows: The control surface has a first segment that essentially runs laterally with respect to the guide track for the seat carrier and a second segment that essentially is arranged in the direction of the guide track for the seat carrier.
Prestressing means are provided to set the restoring spring force to enable persons of differing weights to use the chair without any loss of comfort.
It is particularly practical when the seat carrier has a guide rail that for the purpose of fixing the guide track corresponds to a guide element retained on the pedestal; one end of the guide rail of the seat carrier is connected with the latter in the area of a forward edge of the seat element.
A particularly advantageous embodiment of the invention is provided so that one can make not only circular-arc-shaped and linear guide tracks but also other curved guide tracks that correspond to the actual ergonomic conditions. The guide element in the direction of the guide track has mutually spaced first and second guide supports that in a guiding manner engage the guide rail. In this way, one can prevent a linear guide contact between the guide rail and the guide element; instead, one can provide a two-point guide, which makes it possible so to design the guide track that a translation movement can be superposed simultaneously in the pure swing motion of the seat element. The seat element therefore can so move to the rear and down as if a corresponding swing axis were to be shifted simultaneously parallel with respect to itself. In that way, when a person leans back in the invention-based chair, one can consider not only the swing motion of the lower leg around the ankle joint but simultaneously also a stretching, in other words, a reduction of the bending of the knee joint.


REFERENCES:
patent: 2152024 (1939-03-01), Brosset
patent: 3232574 (1966-02-01), Ferro
patent: 4858993 (1989-08-01), Steinmann
patent: 5577802 (1996-11-01), Cowan et al.
patent: 5918935 (1999-07-01), Stulik et al.
patent: 29600821 (1997-07-01), None
patent: 0 669 816 B1 (1995-03-01), None

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