Abstract: A spool valve (22) controls a hydraulic drive, such as a drive for a fuel pump (18) in an internal combustion engine, in which the hydraulic drive comprises a driving piston (34) journalled in a hydraulic cylinder (33) which through a flow passage (31) is in communication with the spool valve. The spool (38) may occupy a position in which the flow passage is connected with a high-pressure source (29) and another position in which the flow passage is connected with a low-pressure port (30). The spool is settable by means of a positioning means (23) electrically activated by a control unit (16) which determines intended positions of the spool and for a movable part (56) in the positioning member. The movable part has windings (51) positioned in a magnetic field in a slit (60) which is oblong in the longitudinal direction of the spool. A sensor (66) signalizes the actual position of the movable part to the control unit (16).

Abstract: A fluidic power-assisted setting device has a setting motor having an output torque; a threaded spindle supported for rotation; a spindle nut threadedly mounted on the spindle for linear displacement; a setting member attached to the spindle nut for linear travel therewith; a gearing for transmitting the output torque of the setting motor to the spindle; a signalling device coupled to the gearing for generating an output signal when the linear force derived from the output torque of the setting motor is insufficient to overcome an external force opposing linear displacement of the setting member; and a fluidic power device including a hydraulic motor connected to the setting member for applying thereto a linear force to overcome the external force; and a hydraulic control valve hydraulically connecting the hydraulic motor with pressurized hydraulic fluid as a function of the output signal of the signalling device for causing the hydraulic motor to generate a force applied to the setting member for overcoming

Abstract: Fluidic amplifier, particularly a hydraulic linear amplifier for converting a low-energy rotary movement of a control member into a linear setting movement of the piston rod of an operating piston, wherein: the control member is connected with a threaded spindle whose free end extends into an axial bore in the piston rod of the operating piston and mates with a spindle nut provided in the axial bore; the pressure fluid for charging the operating piston to produce the setting movement of the piston rod is controllable by means of an axial deflection of the control piston of a control valve, which deflection is effected by the control member and the threading of the threaded spindle into the spindle nut, and this setting movement causes the control piston to be repositioned to its starting position. A protective device is provided within the amplifier for the automatic separation of the mechanical connection between the operating piston and the control piston during a malfunction.