A part of kinetic energy during lowering of a slide of a press machine is converted into oil hydraulic energy by a first oil hydraulic cylinder, and the converted oil hydraulic energy (hydraulic oil having boosted first system pressure) is stored in a first accumulator. The hydraulic oil having the first system pressure stored in the first accumulator is discharged in knockout process, a second oil hydraulic cylinder that functions as a knockout cylinder is raised to perform knockout operation of a product worked by the press machine. Consequently, it is possible to perform knockout operation without using a dedicated driving source such as an oil pressure source and an air pressure source, and provide a low-cost hydraulic knockout device.

A high-speed hydraulic forging press is disclosed. The high-speed hydraulic forging press includes a forging hammer, a movable beam, a main hydraulic cylinder, a single-rod elevation hydraulic cylinder, a plurality of main hydraulic pumps, a high-pressure energy accumulator, an intermediate-pressure energy accumulator, an oil tank, a programmable logic controller and a valve-regulation system. During a rolling process, when a rolling resistance applied to the forging hammer increases to cause pressure in the main hydraulic cylinder to reach a predetermined value, the programmable logic controller controls the valve-regulation system so that the high-pressure energy accumulator stops supplying the hydraulic oil to the main hydraulic cylinder, and that the hydraulic oil in the main hydraulic cylinder is supplied by at least one of the plurality of main hydraulic pumps. The high-speed hydraulic forging press exhibits remarkable advantages including a reasonable resource allocation, a simple structure, low equipment investment, and high energy utilization.

A pressure-measuring system, including a tube system having at least first and second pressure measuring devices, each including a pressure transducer membrane and a measuring chamber. A first flow regulation device with a perfusion tube section is positioned between the first pressure measuring device and a supply of fluid, and has a first tube clamp that acts on a tube section by squeezing. The system further includes at least one non-perfusion regulation device.

A hydraulic forging press machine and a control method, whereby surging of the forging load or dead zones where the forging speed goes to zero is suppressed, and forging is performed with high precision throughout a wider range than the prior art, from low to high load. Pressure cylinders have a main pressure cylinder configured so working fluid is supplied during forging, and secondary pressure cylinders are configured so supplying and stopping of the supply of working fluid thereto are switched in response to the forging load, head-side hydraulic chambers of the secondary pressure cylinders being connected to a head-side hydraulic chamber of the main pressure cylinder via electromagnetic switching valves. Only the main pressure cylinder is used until the forging load exceeds a set load, and the number of secondary pressure cylinders used is sequentially increased as the forging load increases after the forging load exceeds the set load.

An actuator device includes two drive units for an actuator output element. The first drive unit has a first piston chamber and a first piston displaceable therein and also first hydraulic means for displacing the piston. The second drive unit has a second piston chamber and a second piston displaceable therein and also second hydraulic or pneumatic means for displacing the piston. The second piston is joined to the actuator output element for conjoint movement therewith and can be coupled to the first piston for thrust, so that the second piston is displaceable in an outward direction by the first piston. The first drive unit is configured for a larger thrust force than the second drive unit, while the second drive unit is designed for a greater stroke speed than the first drive unit.

Provided are an efficient energy-saving return cylinder of a hydraulic press and a working method thereof. The efficient energy-saving return cylinder of a hydraulic press comprises a plurality of single-rod return hydraulic cylinders symmetrically distributed at two sides of a main hydraulic cylinder of the hydraulic press, the plurality of single-rod return hydraulic cylinders are divided into several groups, each of the groups consisting of one balancing cylinder and one driving cylinder; a rod chamber of the balancing cylinder is communicated with an accumulator, the pressurized oil in the accumulator is filled into an oil chamber of the balancing cylinder, so that the balancing cylinder balances the weight of a walking beam and a working part of the walking beam; the driving cylinder is differentially connected; in the process of neutral-stroke-rapid-descending and ascending-returning of the walking beam and the working part of the walking beam.

An electro-hydrostatic drive for realizing a rapid movement during a rapid movement phase, a force-building movement during a force-building movement phase. The apparatus comprises a hydro-machine with variable volume and/or rotational speed, driven by an electric motor, for providing a volume-stream of a hydraulic fluid, a first cylinder with a piston chamber, an rod chamber, and a plunger rod, a reservoir, a pressure source, a relief valve, a check valve, a fluid connection between the piston chamber and the hydro-machine, a fluid connection between the rod chamber and the hydro-machine, a fluid connection between the piston chamber and the reservoir, a fluid connection between the rod-chamber-side port of the hydro-machine and the reservoir, a fluid connection, through the relief valve, between the reservoir and the pressure source. The relief valve is for pressure safety of the reservoir, and the check valve has a fluid connection from the pressure source to the rod-chamber-side port of the hydro-machine, during the rapid movement phase, a first part of the hydraulic fluid is piped through the fluid connection between the piston chamber and the hydro-machine and the fluid connection between the rod chamber and the hydro-machine, and a second part of the hydraulic fluid communicates through the fluid connection between the piston chamber and the reservoir, during the force-building movement phase, a first part of the hydraulic fluid is piped through the fluid connection between the piston chamber and the hydro-machine and the fluid connection between the rod chamber and the hydro-machine, and a second part of the hydraulic fluid is piped through the fluid connection between the rod-chamber-side port of the hydro-machine and the reservoir.

An electrohydraulic drive unit is provided, comprising a cylinder-piston assembly having a piston-side first hydraulic working chamber and a piston-rod-side second hydraulic working chamber, a tank, a hydraulic pump, which can be driven at variable rotational speed and which has a tank connection point and a working connection point, a valve assembly, which is connected between the working connection point of the hydraulic pump and the cylinder-piston assembly, and an anti-cavitation valve, which is connected between the tank and the first hydraulic working chamber; and a machine controller. Switching valves of the valve assembly can be switched between loading of the first hydraulic working chamber and loading of the second hydraulic working chamber of the cylinder-piston assembly during pumping operation of the hydraulic pump from the working connection point of the hydraulic pump by the machine controller.

A pressure measuring system, including a tube system having at least one first device for measuring pressure in a fluid. The at least one first device includes a coupling element, at least one pressure transducer and at least one measuring chamber, which can be filled with a fluid. Between the first device and the feed of the fluid, the tube system has a second device for regulating a fluid flow, the second device having a tube section through which fluid can flow and at least one tube clamp, which can be set in the regulation positions open, closed and perfused.

An apparatus including an accumulator and a drive mechanism. The accumulator includes an energy storage apparatus with a first piston face configured to reversibly compress an energy storage medium and a second piston face forming at least part of an inner surface of a corresponding second fluid chamber reversibly expandable by movement of the second piston face. A third piston face forms at least part of an inner surface of a corresponding third fluid chamber reversibly expandable by the third piston face. The first, second and third piston faces are coupled together.