A hydraulic control assembly includes means for holding pressure in a cylinder to inhibit boom or arm drop of a machine in the event that a hose between the cylinder and a main control valve (MCV) ruptures. The pressure holding means of the hydraulic control assembly include a hydraulic valve and a parts-in-body check assembly both configured for insertion into a valve cavity defined by a valve body. The hydraulic valve comprises a proportional piloted valve that controls pressure.

In accordance with an example embodiment, a hydraulic system may include a pump, reservoir, accumulator, hydraulic cylinder, ride control valve assembly, and controller. The ride control valve assembly may include a charging valve, discharging valve, and a head ride control valve. The controller may open the head ride control valve when a ride control feature has been activated, or open the charging valve if the ride control feature has not been activated and a hydraulic fluid warmup is to be performed.

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic actuator (110), first and second counter-balance valves (300, 400), first and second control valves (700, 800), and first and second blocking valves (350, 450). A net load (90) is supported by a first chamber (116, 118) of the hydraulic actuator, and a second chamber (118, 116) of the hydraulic actuator may receive fluctuating hydraulic fluid flow from the second control valve to produce a vibratory response (950) that counters environmental vibrations (960) on the boom. The first blocking valve prevents the fluctuating hydraulic fluid flow from opening the first counter-balance valve. The first blocking valve may drain leakage from the first counter-balance valve.

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic cylinder (110), first and second counter-balance valves (300, 400), first and second control valves (700, 800), and a selection valve set (850). The selection valve set is adapted to self-configure to a first configuration and to a second configuration when a net load (90) is supported by a first chamber (116, 118) and a second chamber (118, 116) of the hydraulic cylinder, respectively. When the selection valve set is enabled in the first and second configurations, the second and first control valve may fluctuate hydraulic fluid flow to the second and first chamber, respectively, to produce a vibratory response (950) that counters environmental vibrations (960) of the boom. When the selection valve set is not enabled, the first and second counter-balance valves are adapted to provide the hydraulic cylinder with conventional counter-balance valve protection.

A milling machine is disclosed. The milling machine may have a frame, first and second tracks connected to a first end of the frame, a third track connected to a second end of the frame, and a milling drum attached to the frame. The milling machine may have first, second, and third actuators connecting the frame and the first, second, and third tracks, respectively. Each actuator may adjust a height of the frame relative to a respective one of the first, second, and third tracks. The milling machine may include a damper assembly attached to each of the first and second actuators. The damper assembly may have an accumulator connected to a respective one of the first and second actuators and a control valve for controlling a flow of fluid between the accumulator and the respective one of the first and second actuators.

A hydraulic system of construction machinery includes: a boom cylinder divided; a first boom hydraulic line serving to supply a hydraulic oil to the boom cylinder during an ascending operation of a boom; a second boom hydraulic line serving to supply the hydraulic oil to the boom cylinder during a descending operation of the boom; a regeneration line serving so that the hydraulic oil discharged from the head side of the boom cylinder flows during the descending operation of the boom; a circulation line connected to the second boom hydraulic line; an accumulator connected to the regeneration line and serving to accumulate the hydraulic oil discharged from the boom cylinder; a boom regeneration valve including a first regeneration spool and a second regeneration spool; and a control unit serving to adjust opening areas of the first regeneration spool and the second regeneration spool during the descending operation of the boom.

A controller for a hydraulic excavator includes a first speed computation section that calculates a first speed of an arm cylinder from a value detected by an operation amount sensor; a second speed computation section that calculates a second speed from a value detected by a posture sensor and a third speed computation section calculates a third speed that is used as the speed of the arm cylinder in an actuator control section adapted to execute MC (machine control). The third speed computation section calculates the first speed as the third speed during the period between the detection of an input of operation for an arm by the operation amount sensor and predetermined time to, the third speed as a speed calculated from the first speed and the second speed during the period between t0 and time t1, and the second speed as the third speed at and after time t1.

In a vibration suppression control OFF state, a signal pressure supply control valve stops supplying a first signal pressure, a pressure-regulating valve is in first position where a supply/discharge port connects to a pump port, and an open/close signal pressure is not supplied to an open/close control valve, so an open/close valve is closed. When the OFF state switches to ON state, the signal pressure supply control valve allows supplying the first signal pressure, and the pressure-regulating valve is in second position where the supply/discharge port connects to a tank port, so the pressure of a pressure accumulator decreases. In the ON state, when the pressure of the pressure accumulator is equal to pressure of a pressure chamber, the pressure-regulating valve is in third position where the supply/discharge port is blocked, and the open/close signal pressure is supplied to the open/close control valve, so the open/close valve is opened.

A motor grader having ride control for dampening machine bounce using a DCM assembly rotatably coupled to and suspended from a frame of the motor grader is disclosed. Each lift cylinder for the DCM may have an associated ride control circuit with an accumulator, a ride control conduit fluidly connected to a carry end of the lift cylinder and having a flow restriction element, and a ride control accumulator valve fluidly connected to the accumulator and the ride control conduit and operable to either block or allow fluid communication between the carry end and the accumulator through the flow restriction element. Each rid control circuit may also include a head end valve fluidly connected to between the head end of the lift cylinder and a low pressure fluid reservoir and operable to block or allow fluid communication between the head end and the low pressure fluid reservoir.

Provided is a swing-back preventing apparatus capable of preventing a hydraulic actuator in a stop state from operating by undesired load. The swing-back preventing apparatus includes a housing, a piston, and a pair of biasing members. First and second spaces are formed between the piston and the housing, and the piston includes a pair of communication passages that are communicable with first and second spaces. When the piston is located at a first offset position, the first space is blocked from a first port. When the piston separates from the first offset position, the first space is connected to the first port. When the piston is located at a second offset position, the second space is blocked from a second port. When the piston separates from the second offset position, the second space is connected to the second port. When the piston is located at a position on the first offset position side of a neutral position, a first communication passage is connected to the first space. When the piston is located in a range from the neutral position to the second offset position, the first communication passage is blocked from the first space. When the piston is located at a position on the second offset position side of the neutral position, a second communication passage is connected to the second space. When the piston is located in a range from the neutral position to the first offset position, the second communication passage is blocked from the second space.