Abstract: An improved adjustability and functional reliability of a device for time-dependent control of a duration of regeneration of an air dryer including a piston, which is longitudinally guided, displaceably counter to a resistance, in a cylinder by the force of a spring. The cylinder is closed by a cap, on which means for adjusting the prestressing force of the spring, supported at least indirectly on the cap, are provided. These means comprise a screw-wedge connection, which joins the cylinder and the cap to one another in such a way that by twisting the cap, an axial displacement of the cap relative to the cylinder is brought about. The device can be used for instance in air dryers for compressed air systems of motor vehicles.

Abstract: An apparatus for time dependent control of a regeneration time of an air-dryer. The control apparatus has a shutoff valve, which is disposed in a line between a tank that furnishes regeneration air and an air dryer that can be regenerated by the countercurrent method. For the regeneration of the air dryer, the shutoff valve is switched into an open position by a control pressure and is returned to its closing position by spring force counter to a pneumatic delay device which concludes the regeneration. In the pneumatic delay device, air is displaced through a throttle restriction in the form of a permeable membrane, for instance of porous polytetrafluoroethylene. The apparatus for time-dependent control of the regeneration time of an air dryer is intended in particular for compressed air systems of motor vehicles.