The invention relates to a height adjustment device of a vehicle seat, which comprises a control valve means serving for controlling the degree of filling of at least one compressed air actuator holding the seat body at a desired height and thereby providing a vertical elastic supporting action, such control valve means being so provided with at least one actuating member for cooperation with at least one control cam slide that in accordance with use dependent alteration of the weight to be borne by the at least one compressed air actuator a relative switching over movement causing the switching over of the control valve means takes place between a component bearing the control cam slide and another component bearing the associated actuating member.
The invention furthermore relates to a vehicle seat fitted with such a height adjustment device, comprising a seat body, which is arranged on a seat bracket fitted with a height adjustment device, such seat bracket having at least one compressed air actuator, with the aid of which the seat body may be set at different heights and is able to be vertically resiliently supported at the respectively set height, the seat bracket having at least two support elements changing the distance between them during vertical movement of the seat body, one support element of the seat bracket being kinematically coupled with at least one control cam slide, which so cooperates with at least one actuating member kinematically coupled with the other support element and associated with a control valve means serving for control of the degree of filling of the at least one compressed air actuator that in the case of an alteration in the use dependent weight carried by the at least one compressed air actuator a relative switch over between the at least one control cam slide and the components bearing the actuating member associated with the control cam slide and the actuating member associated with it.
Such a height adjustment device with an associated vehicle seat is disclosed in the German patent publication DP 4335199. The seat bracket of the vehicle seat in this case comprises two support elements, coupled together to form a scissor-like structure, which alter their angular position when the height of the seat body changes, for example owing to a varying weight load. The change in angle is detected by two control valves, whose actuating members control cam slide down two curved control cam slides while performing an arcuate switching over movement and, if they are deflected sufficiently, cause compressed air to be supplied to the compressed air actuator or let off therefrom. Accordingly it is possible to ensure that the seat height is automatically set to the right height independently of weight.
Owing to their quite complex structure the known height adjustment devices appear to be in need of improvement. This also applies for alternative designs of height adjustment devices and the vehicle seats fitted with them, which are described in the German patent publications DE 19705010 A1, DE 3517503 C2 and DE 3517505 C2.