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Mechanism for a chair

Mechanism for a chair description/claims

The invention relates to a chair mechanism, in particular for a rotatable office chair with a pneumatic spring which is arranged vertically in the substructure and is intended for adjusting the height of the seat. As a result of the chair mechanism, the seat surface is lowered in the rearward direction synchronously with the rearward inclination of the backrest, which the user initiates by shifting his weight.

Many synchronizing mechanisms for chairs are known, e.g. from patent publications EP 0 592 369 B1, EP 0 839 478 B1, EP 1 039 816 B1, EP 1 358 821 A1 and WO 2005/120291 A1, and have become a standard feature for comfortable commercially available chairs for the workplace.

In relation to the known prior art, it is an object of the invention to propose a further-improved chair mechanism which responds more sensitively to shifts in weight. A further object is to facilitate the adjustment of the prestressing of the mechanism for relatively light and relatively heavy individuals. An additional object is to render the mechanism more universal, in order to make it possible for a backrest and armrest to be attached in different ways.

The mechanism is intended for a chair, in particular for a rotatable office chair with a pneumatic spring which is arranged vertically in the substructure and has a telescopically extensible piston rod for adjusting the height of a seat. The inclining adjustment of the seat is synchronous with the inclining adjustment of a backrest. The mechanism has a fixed base, through which a fixed first axis of rotation extends and on which an inclinable seat carrier is mounted. Arranged between the base and the seat carrier is a front connecting means, which is articulated along a fixed third axis of rotation on the base and along a movable fourth axis of rotation. A rear connecting means is articulated, on the one hand, along a movable sixth axis of rotation and, on the other hand, along a movable further axis of rotation. The mechanism contains at least one first spring element which acts between the base and the seat carrier and is articulated along the fourth axis of rotation. The first spring element is also articulated along a movable eighth axis of rotation, which can be changed in position by means of a gear mechanism which can be actuated by the user from the outside.

Specific embodiments of the invention will be defined hereinbelow: the gear mechanism is articulated along a fixed second axis of rotation, which extends through the base, along the eight axis of rotation and along a movable ninth axis of rotation. In the rest position, with the seat positioned, at least in principle, horizontally and the backrest located vertically, the second axis of rotation, the eighth axis of rotation and the ninth axis of rotation are located at least essentially vertically one above the other. In the relaxed position, with the seat inclined up to a maximum extent and the backrest inclined up to a complementary maximum extent, the eighth axis of rotation is displaced, in the direction of the third axis of rotation, in front of the second axis of rotation and the ninth axis of rotation moves, in the opposite direction, behind the second axis of rotation.

The first spring element is a pneumatic spring with a cylinder and a telescopically extensible piston rod which is extended to the greatest extent in the rest position, with the eighth axis of rotation moved all the way downward, and is retracted to the greatest extent in the relaxed position, with the eighth axis of rotation moved all the way upward. The piston rod is articulated along the fourth axis of rotation by means of an intermediate component.

The mechanism contains, within it, pairs of spring units which are supported, on the one hand, in a bearing of the base, and, on the other hand, beneath bearing strips, in bearing blocks, the bearing strips being joined to the base from both sides. The bearing strips preferably consist of plastic and thus form self-lubricating bearing locations along with the joined-on, preferably metallic components.

The front connecting means is designed as a plate-like lever, through which the third and fourth axes of rotation extend. The rear connecting means comprises a sixth axial rod and a sleeve component, which is connected thereto via arms, or a sixth axial rod and a seventh axial rod, which is connected thereto via arms, the associated fifth, sixth and seventh axes of rotation extending through these axial rods.

A backrest carrier can be articulated along the first axis of rotation, within the base, or a pair of side members can be articulated outside the base, in order for the backrest to be fastened thereon. The bearing strips have stubs for penetrating into the front lever and the intermediate component. The bearing strips also have mounts for accommodating the ninth axial rod, which passes through the gear mechanism, and for accommodating the sixth axial rod.

An arresting element, which can be actuated by the user, is arranged on the intermediate component for blocking the pneumatic spring with optional switching functions. The arresting element acts on a valve stem which is guided in the piston rod of the pneumatic spring.

In the drawings:

FIG. 1A shows a perspective view from beneath of a chair with the mechanism according to the invention, using side members;

FIG. 1B shows a side view of the chair according to FIG. 1A in the rest position;

FIG. 1C shows a side view of the chair according to FIG. 1A in the relaxed position;

FIG. 2A shows an exploded view of the essential subassemblies of the mechanism;

• Provisional Patent
• Utility Patent

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