Abstract: A main hydraulic circuit for controlling printing pressure of a printing machine is supplemented by an auxiliary high pressure generating circuit which becomes effective only after the pressure flow reversal in the main hydraulic circuit. The auxiliary circuit includes a pressure transformer or a hand-operated auxiliary pump connected via a back pressure valve to a hydraulic motor in the main circuit, and a second back pressure valve connected in series with a driving pump in the main circuit.

Abstract: A device for sealing surfaces defined between a collar of a motor shaft and a motor cover comprises a pre-stressed sealing ring mounted at the surfaces which extend at right angles relative to each other, a viscous elastic element for prestressing the sealing ring, and a guide ring positioned between the elastic element and the sealing ring. The sealing ring is positioned between the surfaces to be sealed and is pressed by the guide ring which is displaceable by a pressure medium.

Abstract: A hydraulic drive for a multi-color, sheet-fed rotary printing machine assembled of a plurality of consecutively arranged press units each having a set of sheet-processing cylinders and gear trains interconnecting the cylinders, is constituted by the following combination:a plurality of constant-flow, radial piston type hydraulic motors directly connected for driving a cylinder in each press unit;a first hydraulic control means including a main directional control valve and an auxiliary or switching directional control valve connected between the source of pressure fluid and the hydraulic motors; anda second hydraulic control means including a control cylinder-and-piston unit assigned to each operational radial piston of the motors and controlled by the latter so as to overlap in the cross-over position of the motors both the intake port and the discharge port for working fluid.

Abstract: A printing machine which has a plurality of printing units each including several rollers is equipped with a gear train which drives at least one roller of each of the printing units. At least associated two of the gear wheels of the gear train are coaxially mounted on a common shaft, one of them being movable toward and out of contact with the other gear wheel for establishing entraining connection therewith and for permitting angular displacement of the associated gear wheels relative to one another, respectively. The angular position of the associates gear wheels is to be changed when the mode of operation of the printing machine is to be changed from first page printing mode to first and second page printing mode. The arrangement which connects and disconnects the associated wheels includes a plurality of moving units which simultaneously act on the other gear wheel and which are mounted on an annular clamping element mounted on the other side of the one gear wheel from the one gear wheel.

Abstract: A pressure control arrangement for controlling pressure between a printing roller and an offset roller by measuring a force exerted in a bearing of the printing roller when the latter rotates with an angle .psi.. The arrangement includes a piezoelectric pickup positioned on the internal surface of the bearing of the printing roller, a measured pressure value processor for receiving a signal from the piezoelectric pickup, an indicator generating a signal corresponding to a desired pressure value and means to compare the first abovementioned signal with the second mentioned signal. The arrangement also includes a positioner circuit which receives the compared signal and applies the same to a drive member which adjusts the position of the bearing of the offset roller thereby adjusting printing pressure between two contacting rollers for printing on sheets of paper.