A hydraulic press includes a workbench having four corners provided with uprights. The uprights are arranged in two rows front and rear, and the tops of the uprights in each row are connected by an upper beam extending in a left-right direction. Tie rods are inserted in the front and rear of each upright. The tie rods each have an upper end protruding from the top of the upper beam and fixed to the upper beam by an upper nut and a lower end protruding from the bottom of the workbench and fixed to the workbench by a lower nut. A central cylinder is provided at the center of the upper beam. Side cylinders are symmetrically arranged on the left and right of the central cylinder. The lower ends of plungers of the central cylinder and the side cylinders are fixedly connected to a top of a slider.

Pump-controlled hydraulic circuits are more efficient than valve-controlled circuits, as they eliminate the energy losses due to flow throttling in valves and require less cooling effort. Presently existing pump-controlled solutions for single rod cylinders encounter an undesirable performance during certain operating conditions. Novel circuit designs employ use of different charge pressures on a pair of pilot-operated charging-control valves or different piston areas and/or spring constants on a shuttle-type charging control valve to shift a critical loading region in a load-force/actuator-velocity plane to a lower load force range, thereby reducing the undesired oscillations experienced in the response of the typical critical loading region. One or more specialized valves are controlled by fluid pressures to provide throttling in the circuit only within the critical loading region, thereby reducing the oscillatory amplitude while avoiding throttling-based energy losses outside the critical region over the majority of the circuit's operational overall operating area.

A hydraulic actuator includes a piston accommodated to slide hermetically in a hollow cylinder to divide the internal volume of the hollow cylinder into two chambers. The hydraulic actuator includes a first movable element accommodated so that it can slide hermetically in a longitudinal cavity defined inside the piston stem to divide the longitudinal cavity into two portions with the first one connected to one of the two chambers and the second one connectable to a second circuit adapted to feed under pressure a second fluid into the second portion. The second fluid has a coefficient of compressibility and a nominal pressure greater than those of the first fluid to act as a shock absorber and/or damper in case of sudden peaks of pressure in the chamber connected to the first portion of the longitudinal cavity defined inside the piston stem.

Methods and apparatus to control the actuation of regulators including a loading chamber are disclosed. An example apparatus includes a first pneumatic regulator including a loading chamber, the first pneumatic regulator to flow fluid toward a downstream process; a second pneumatic regulator coupled between the loading chamber and the downstream process, the second pneumatic regulator to control an actuation of the first pneumatic regulator during normal operation based on a pressure difference between a first pressure downstream of the first pneumatic regulator and a second pressure within the loading chamber; and a valve coupled between the loading chamber and the downstream process, the valve to control the actuation of the first pneumatic regulator during a shut-down event.

In order to secure a reached extension position of a piston rod (22, 22) of an in particular multi stage operating cylinder device (100) with at least one operating cylinder unit (50) not only through the operating pressure in the cylinder (1, 1) of the operating cylinder unit (50) but additionally mechanically, a mechanical safety through interlocking safety elements (4a, b) in the interior of the operating cylinder device (100) is provided which is activated exclusively by the operating pressure in the first pressure cavity and disengaged by a pressure in a second operating cavity.

A safety module for a process valve and a system comprising a safety module and a process valve are provided. The safety module comprises at least a first interface complementary to a first connection interface of a drive module of the process valve and a second interface complementary to a second connection interface of a process valve actuator of the process valve, such that the safety module can be retrofitted in the process valve. The safety module further comprises at least one safety valve and fluid lines provided for fluidically coupling the safety valve to the drive module and the process valve actuator of the process valve. The at least one safety valve of the safety module is configured for forced venting of the process valve in a safety case.

A hydraulic excavator drive system includes: a control valve for a cylinder that swings a swinging unit; an operation device that outputs an operation signal in accordance with an inclination angle of an operating lever when receiving a first operation of moving the swinging unit closer to a cabin or a second operation of moving the swinging unit farther from the cabin; a solenoid proportional valve connected to a first pilot port of the control valve, the first pilot port being intended for the first operation; and a controller that, when the operation device receives the first operation, controls the solenoid proportional valve such that: a pilot pressure outputted from the solenoid proportional valve is proportional to the operation signal outputted from the operation device until the pilot pressure reaches an upper limit pressure; and the closer the swinging unit to the cabin, the higher the upper limit pressure.

A hydraulic system, wherein an actuating cylinder and an accelerating cylinder each includes a piston, a rod, and a tube. When the rod of the actuating cylinder extends in an unloaded condition, a circuit is configured such that oil discharged from the bottom-side section of the accelerating cylinder is supplied to the bottom-side section of the actuating cylinder through a bottom line. When the rod of the actuating cylinder extends in a loaded condition, a circuit is configured such that oil supplied to the bottom line without passing through the accelerating cylinder is supplied to the bottom-side section of the actuating cylinder. The circuit for the unloaded condition and the circuit for the loaded condition is switched based on a pressure sensing in the bottom line.

In a hydraulic driving system for construction machines, when track motors 3f and 3g are operated and the delivery pressure of a main pump 2 increases to a second value PS2 of the set pressure of a main relief valve 14, the set pressure of a signal pressure relief valve 16 increases from a third value PA1 to a fourth value PA2, which is smaller than the second value PS2 of the set pressure of the main relief valve 14, the difference between the second value PS2 and the fourth value PA2 being smaller than the target LS differential pressure. With such a structure, even if one of actuators reaches the stroke end and the delivery pressure of the hydraulic pump rises to the set pressure of the main relief valve, the other actuators do not stop, and further when the main relief valve is configured to increase the set pressure during operation of a specific actuator, the load pressure of the specific actuator does not increase to the increased set pressure of the main relief valve.

The hydraulic system includes a reservoir configured to store hydraulic fluid, an actuator, a first conduit coupling the reservoir to the actuator, a second conduit having a first end and a second end, a first valve positioned between the first end of the second conduit and the first conduit, a second valve positioned between the second end of the second conduit and the first conduit, and a pump configured to drive the hydraulic fluid from the reservoir to the actuator. The hydraulic fluid flows through the first conduit to the actuator when the first valve is in a first position. The hydraulic fluid flows partially through the first conduit, through the second conduit, back to the first conduit, and to the actuator when the first valve is in a second position.