Hydraulically operated cover, e.g. vehicle door or roof, has actuator applying relatively high closure force to cover in final closure region

摘要

The hydraulic actuator (10) for moving the cover is designed to apply a higher closure force to the cover in a third closure region than in a second closure region, the third region corresponding to that in which the cover is finally completely closed. The cover is opened and closed using a hydraulics system comprising a twin-action hydraulic actuator. The actuator casing (11) contains a cylinder space containing a piston device (12, 13) defining a closure chamber (14) and an opening chamber (15), each chamber being connected to lines for supplying and removing hydraulic fluid. Supplying fluid to the closure chamber causes the actuator to close the cover and supplying fluid to the opening chamber causes the actuator to open the cover. The force applied to the cover by the actuator in the second closure region is less than that applied in the first closure region.