Abstract: A screw press has a friction clutch for coupling the driving flywheel to the press spindle. The clutch is engaged by a hydraulic piston. To maintain a constant piston stroke as the friction clutch wears, a metering piston and cylinder are interposed between the clutch operating piston and the pressure fluid supply to trap pressure fluid in the clutch operating cylinder and to top it up as required, so that the operating piston stroke corresponds essentially to the fixed stroke of the metering piston. Fluid flow to the operating cylinder bypassing the metering piston is controlled by a normally closed valve arranged to be opened positively in dependence on the position of the metering piston, as the metering piston approaches the end of its stroke in the direction for pressurizing the clutch operating piston to engage the clutch. This arrangement ensures that the clutch cannot be inadvertently locked in an engaged condition.

Abstract: A screw press has a flywheel rotationally connected to the press spindle by way of a friction coupling. The spindle is displaced axially in a nut mounted in the upper cross member of the press frame, and the flywheel has external toothing with a width corresponding to the maximum pressing stroke plus the width of the driving pinions. A plurality of pinions engaging in the said toothed rim are each driven by an oil-hydraulic axial piston motor or by a pair of oil-hydraulic axial piston motors and the axial piston motors together with the pinions are disposed on a platform surrounding the upper cross member of the press frame. In order to reduce the structural expenditure and to increase the operational reliability, each axial piston motor or pair of axial piston motors associated with a pinion has associated with it on the platform a controllable pump which is driven by a respective electric motor and is reversible with respect to the flow direction.