Abstract: For the drive of a vehicle having at least one driven axle, in particular a rail vehicle, a secondarily controlled hydrostatic drive is provided which is connected to a pressure network with impressed pressure. The respective travelling direction and the acceleration and retardation is set at a desired value pickup or generator which is part of a speed control circuit. The circuit arrangement according to the invention solves the problem of avoiding slipping of the drive wheels on acceleration and retardation. In addition, the determined acceleration and retardation values can be superimposed to avoid inadmissible wheel slip and obtain optimum accelerations and retardation operations. For this purpose the circuit arrangement employs a ramp former to which as control voltage various voltages proportional to different operating parameters are supplied, in particular a voltage dependent on the speed of rotation.

Abstract: For setting and guiding a band running round two rolls the bearings of the roll on either side are each adjustable by a hydraulic or lifting cylinder. Each hydraulic cylinder comprises a position control circuit. The position desired value applied jointly to the position control circuits is varied by a tension-dependent control in such a manner that in the position adjustment a maximum admissible tension force is not exceeded. Furthermore, the position desired value has superimposed thereon a correction control by which the center setting of the band is monitored. The arrangement is preferably provided for positioning and tension-dependent adjustment of the encircling metal band of a sheet casting apparatus.

Abstract: For a drive system comprising a hydrostatic adjustable machine an electrical control is provided with which the actuator of the machine is driven so that for acceleration, retardation and braking, i.e. when the machine moves from motor mode to pump mode, a predetermined operating behavior of the machine necessarily results. The particular input desired value for the speed is transformed so that suddenly occurring abrupt acceleration, retardation and braking operations are avoided and in particular on abrupt entry of desired values increased safety against operating errors is achieved.

Abstract: The electrode of an electric arc melting furnace is adjusted in height by a hydraulic cylinder having an operating chamber which is connected via a servo valve to a hydraulic pressure source or, respectively, to a reservoir. The servo valve is actuated by a control signal which is produced by a comparison of the actual value of the electric arc current and a predetermined desired current value. Additionally, the pressure in the operating chamber of the cylinder is measured and supplied to the control circuit as a feedback value. An important advantage deriving from the present invention is the ability to provide a control of the electrode motion by virtue of the measured pressure even before the electric arc is ignited and to steadily hydraulically support the electrode under any condition of operation. Accordingly, uncontrolled motions of the electrode are prevented which motions might result in an increased danger of breakage, in overcurrents or short-circuits.