| 摘要 |
Vertical adjustment assemblies of the type in question are provided with a drive, consisting of a rack and a gear mechanism, for the extensible rod of a telescopic column. The driving wheel is driven by a spring. In the vertical adjustment assembly according to the invention, a brake device (18) is provided, whose mutually opposite brake shoes (19, 20) are provided with an interrupting vane, which is located in the central region and is fixedly mounted, for limiting the opening movement of the brake shoes. At the upper and lower ends, the brake shoes (19, 20) are connected to one another in an articulated manner by coupling members (25, 26). The brake shoes (19, 20) are actuated via an actuating linkage (22), on which a tension spring (34) which produces the braking force engages at the lower end and at whose upper end a control lever is provided for releasing the brake device (18). The prestress of the spring (42) is so great that the table top is automatically moved upwards when the brake device is released. Furthermore, the brake shoes (19, 20) are offset in height relative to one another in such a way that the brake shoes can still be spread apart by the loading of the weight of the extensible tube (12). <IMAGE>
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