Pivot mechanism for seats

#The invention relates to a pivot mechanism for height-adjustable seats.

#In the conventional pivot mechanisms for chairs and armchairs, the pullback springs utilized are mechanical, hydraulic and pneumatic springs of varying designs. The pullback springs are installed with pretensioning; the spring characteristic and thus the resetting force acting on the back of the sitting furniture when a person seated on the latter leans back and leans forward can be varied in dependence on the adjustable pretensioning of the pullback springs. Such tilt mechanisms known, for example, from German Utility Model No. 84 17 429 are very complicated in their technological aspects and require a relatively large volume of space for installation below the seat, whereby the appearance of the chair is impaired.

#The invention is based on the object of developing a pivot mechanism for seats which is distinguished over the conventional pivot mechanisms by a substantially simpler structure and a less expensive manufacturing cost.

#The invention and its additional advantages will be described in detail below with reference to a swivel armchair shown in the accompanying drawing in a lateral view.

#The swivel armchair (1) exhibits a base (2) equipped with casters (3), this base carrying the base tube (4) with a gas-pressure spring (5) installed therein for the height adjustment of the seat (6) and the back (7) which latter (6, 7) are mounted to the underframe (8) to be pivotable in synchronism. Two armrests (9) are articulated to the back (7). The seat (6) has a seat pad (10) resting on spring elements (11), which latter constitute an essential functional part of the pivot mechanism of the swivel armchair (1).

#The spring elements (11), designed as tension springs and consisting, for example, of coil springs or spring belts, and serving simultaneously to support the seating surface, are attached, on the one hand, by way of a guide roller (12) arranged at the front end of the underframe (8) and by way of a tensioning element (13) designed as a turnbuckle, to the underframe (8) and, on the other hand, at (A) to the back (7) above the pivot axle (14--14) of the latter, arranged in the underframe (8).

#In case the user of the swivel armchair (1) assumes an upright sitting position, the back (7) is maintained in the vertical or almost vertical position (7') by the spring force provided by the pretensioned spring elements (11), and the seat (6) assumes the almost horizontal position (6'). The pretensioning of the spring elements (11) can be adjusted by the tensioning element (13) designed as a turnbuckle.