Erector for holding a leaf-flap in various opening settings

An erector for holding a leaf-flap in opening settings relative to a frame, comprising a continuously length-variable dynamic unit operatively supported with respect to the leaf-flap and the frame and having a hollow cylinder and a piston movable via a piston rod and slidably guided in the hollow cylinder to divide an interior space of the hollow cylinder into two pressure-medium chambers which are overflow-connected with each other, a flow regulator operatively interposed between the two chambers and configured to have a direction-reversible, through-flow depending upon an advancement direction of the piston, the flow regulator comprising a flow-duct system having two valves configured to be pushed open by a pressure-medium column and respectively operatively arranged at an associated overflow duct such that the respective overflow duct is capable of being shut off against through-flow in one direction by the valve associated therewith, one of the two valves being a control valve configured as a step valve to flow-block, when closed, the associated overflow duct in both directions, and the flow regulator being configured to be moved under pressurization by the pressure-medium column flowing through an associated control duct, against a return force in which it is maintained up to a pressure level of the pressure-medium which is significantly lower than a control pressure of the step, valve which comprises a differential piston axially displaceable against a spring load, whereby control pressure of the pressure- medium acts upon a first piston surface of the differential piston and whereby the pressure-medium which is in force in the pass-through setting acts upon a second piston surface of the differential piston, wherein the step valve is arranged to be constantly flow-connected via the associated control duct to one of the pressure-medium chambers, the flow-duct system further comprising an equalization duct, via which a cylinder space of the step valve, on a side thereof opposite the control duct, is constantly flow-connected to the other of the pressure-medium chambers.