Swing-door drive

摘要

An automatic swing-door drive having a hydaulic piston/cylinder unit 7, 8 with closer spring 10 and an opener motor, consisting of an electric motor 5 and hydraulic pump 4, is described. It is a so-called servo-closer. Provided in the hydraulic system is a safety relief valve 20 which responds when the door is jammed during opening or is forcibly pushed shut during closing. In order to prevent damage to the drive caused by overloading pressure surges, the safety relief valve 20 is especially designed as a slide valve 20 with a piston-shaped valve member 21 which is loaded by the closer spring 10.