A crane, in particular a mobile crane, having a closed hydraulic circuit in which a hydraulic pump is hydraulically connected to at least one hydraulic motor via a feed and a discharge, and in which the feed is hydraulically connected to the discharge via at least one bypass which bypasses the at least one hydraulic motor, wherein the at least one bypass includes a continuously adjustable valve for variably controlling the fluid flow bypassing the at least one hydraulic motor. In addition, a corresponding control device and a corresponding crane control program for actuating a closed hydraulic circuit of a crane are provided.

A work machine capable of preventing cavitation more effectively. The work machine includes a work device, a variable displacement hydraulic pump, a hydraulic actuator, a posture detector, a control valve, an operation unit, an operation detector, and a controller. The controller judges whether or not a work operation detected by the operation detector is a low-pressure operation based on posture information acquired by the posture detector, and increases the pump capacity of the hydraulic pump when judging that the work operation is the low-pressure operation.

A work machine capable of preventing cavitation more effectively. The work machine includes a work device, a variable displacement hydraulic pump, a hydraulic actuator, a posture detector, a control valve, an operation unit, an operation detector, and a controller. The controller judges whether or not a work operation detected by the operation detector is a low-pressure operation based on posture information acquired by the posture detector, and increases the pump capacity of the hydraulic pump when judging that the work operation is the low-pressure operation.

A mobile working machine includes a lower structure, an upper structure, a boom assembly, and a hydraulic system including a hydraulic pump, a work line, a hydraulic consumer, a volume control valve to regulate hydraulic fluid flow in the work line connected to the consumer in order to control the consumer, and a bypass to bypass the volume control valve. An anti-cavitation device with a replenishment function is provided in the bypass such that when a pressure in the work line is greater than a predetermined pressure, the bypass is closed, and when the pressure in the work line is equal to or less than the predetermined pressure, the bypass is open and the work line or the hydraulic consumer connected to the work line can suck in hydraulic fluid via a supply line. The anti-cavitation device includes an emergency stop function or device to close the line in the bypass or the supply line when a leak is detected in the work line.

A mobile working machine includes a lower structure, an upper structure, a boom assembly, and a hydraulic system including a hydraulic pump, a work line, a hydraulic consumer, a volume control valve to regulate hydraulic fluid flow in the work line connected to the consumer in order to control the consumer, and a bypass to bypass the volume control valve. An anti-cavitation device with a replenishment function is provided in the bypass such that when a pressure in the work line is greater than a predetermined pressure, the bypass is closed, and when the pressure in the work line is equal to or less than the predetermined pressure, the bypass is open and the work line or the hydraulic consumer connected to the work line can suck in hydraulic fluid via a supply line. The anti-cavitation device includes an emergency stop function or device to close the line in the bypass or the supply line when a leak is detected in the work line.

A hydraulic system for use during reduced gravity flight including: a reservoir; a hydraulic device; a supply line providing fluid communication between the reservoir and the hydraulic device; a return line providing fluid communication between the hydraulic device and the reservoir; a supply valve located on the supply line between the reservoir and the hydraulic device and selectively configurable in an open or closed position; and a return valve located on the return line between the reservoir and the hydraulic device and selectively configurable in an open or closed position; and wherein the supply valve is adapted to prevent fluid communication between the reservoir and the hydraulic device when in the supply valve closed position; and wherein the return valve is adapted to prevent fluid communication between the reservoir and the hydraulic device when in the return valve closed position.

A hydraulic system includes: a first bi-directional pump connected to a head-side chamber of a single-rod cylinder by a head-side line and connected to a rod-side chamber of the single-rod cylinder by a rod-side line; and a second bi-directional pump connected to the head-side line by a supply/discharge line, the second bi-directional pump being a variable displacement pump. The hydraulic system further includes a low-pressure selection valve connected to the head-side line by a first discharge line and connected to the rod-side line by a second discharge line, wherein the low-pressure selection valve allows the second discharge line or the first discharge line to communicate with a relief line on which a relief valve is located.

A hydraulic system includes: a first bi-directional pump connected to a head-side chamber of a single-rod cylinder by a head-side line and connected to a rod-side chamber of the single-rod cylinder by a rod-side line; and a second bi-directional pump connected to the head-side line by a supply/discharge line, the second bi-directional pump being a variable displacement pump. The hydraulic system further includes a low-pressure selection valve connected to the head-side line by a first discharge line and connected to the rod-side line by a second discharge line, wherein the low-pressure selection valve allows the second discharge line or the first discharge line to communicate with a relief line on which a relief valve is located.