A high-pressure unit (HPU) skid for greasing and actuating a frac tree valve includes one or more hydraulic pumps, a grease pump, a hydraulic reservoir, and two or more accumulators all of which are mounted on a portable frame. The HPU skid further includes fluidic connections to connect the frac tree valve to an output of the grease pump and fluidic connections to connect the frac tree valve to at least one of the two or more accumulators. The hydraulic pumps are configured to withdraw hydraulic fluid from the hydraulic reservoir for charging the accumulators, operating the grease pump, or charging the accumulators and operating the grease pump at a same time.

A hydraulic system for controlling an implement on a work machine may include a hydraulic reservoir, a hydraulic pump in fluid communication with the reservoir, a central valve in fluid communication with the pump and configured for controlling the implement, a pressure relief system arranged in fluid communication with the hydraulic pump and the central valve, and a controller. The controller may be configured for controlling the hydraulic pump, the central valve and the pressure relief system and selecting between operating the hydraulic system at a first pressure and a second pressure based on a factor relating to implement position.

A construction machine including a variable displacement pump, and a boom cylinder including a rod operable to extend and retract to move a boom of the construction machine. A first chamber of the boom cylinder is configured to be supplied with fluid from the pump during rod extension while fluid is removed from a second chamber of the boom cylinder. The second chamber of the boom cylinder is configured to be supplied with fluid from the pump during rod retraction while fluid is removed from the first chamber of the boom cylinder. The construction machine has an active ride control mode in which a valve between the boom cylinder and the pump remains open, and the pump is configured to actively damp pressure fluctuations in the boom cylinder by variation of a displacement setting.

A hydraulic system includes: an arm hydraulic cylinder; a first hydraulic pump and a second hydraulic pump; an arm first direction switching valve; an arm second direction switching valve; and a controller that controls an operation of the arm second direction switching valve when the arm hydraulic cylinder is extended and operated. Further, the arm first direction switching valve incorporates an arm regeneration passage capable of supplying oil when the arm hydraulic cylinder is extended and operated, and the controller monitors a pressure state of the arm hydraulic cylinder, and when determining that oil flow through the arm regeneration passage is possible, the controller blocks oil flow between the arm hydraulic cylinder and the arm second direction switching valve, and otherwise, the controller operates the arm second direction switching valve so that oil can be supplied from the second hydraulic pump to the bottom chamber.

A working machine includes a machine body, a first hydraulic actuator mounted on the machine body, a first control valve that controls the first hydraulic actuator, a controller that controls the first control valve, and a second hydraulic actuator that is different from the first hydraulic actuator. When the second hydraulic actuator and the first hydraulic actuator are operated in combination, the controller reduces the amount of change in the flow rate of a hydraulic fluid supplied from the first control valve to the first hydraulic actuator with respect to changes in a manipulation amount to operate the first hydraulic actuator to a value smaller than that when the first hydraulic actuator is solely operated.

A valve device that changes the direction of flow of a hydraulic fluid supplied to and discharged from a cylinder mechanism to actuate the cylinder mechanism, the valve device including: a control valve including a main spool axially movable between different positions; a lock valve including a plunger and a pressure chamber; and a selector valve including a selector spool operable in conjunction with the main spool to axially move between different positions, the selector spool being located adjacent to the main spool and having an axis crossing an axis of the main spool.

A hydraulic system for a working machine, the hydraulic system includes: a hydraulic fluid reservoir; a boom actuator having an ascending chamber and a descending chamber; a first pump; a first directional control valve comprising a first ascending state configured for moving the boom in the ascending direction, a descending state configured for moving the boom actuator in the descending direction, and a first neutral state; a second pump; a second directional control valve comprising a second ascending state configured for moving the boom actuator in the ascending direction, and a second neutral state; wherein the second directional control valve further comprises a float state configured to connect at least one of the ascending and descending chambers to the hydraulic reservoir for permitting the boom to move freely in the descending and/or descending directions.

A hydraulic unit includes a hydraulic circuit fluidly connected to a hydraulic actuator, and a control device to control the hydraulic circuit. The hydraulic circuit includes a hydraulic oil tank, a hydraulic pump that supplies the hydraulic oil to the hydraulic actuator from the hydraulic oil tank, a discharge flow path fluidly connecting a discharge side of the hydraulic pump to the hydraulic actuator, a valve that blocks a flow of the hydraulic oil in the discharge flow path, and a pressure sensor that detects a pressure of the hydraulic oil the discharge flow path. In a pressure holding state, when a rotational frequency of the hydraulic pump exceeds a predetermined first determination rotational frequency or when a discharge flow rate of the hydraulic pump exceeds a predetermined first determination discharge flow rate, the control device determines that the hydraulic circuit is abnormal.

A pressurizing device includes: a pressurizing unit that pressurizes a pressurized object by supplying a working fluid; a first cylinder mechanism that supplies the working fluid in a first cylinder to the pressurizing unit by output of a first drive source; a second cylinder mechanism that supplies the working fluid in a second cylinder to the pressurizing unit by output of a second drive source; and a control device that controls the first drive source and the second drive source, in which the control device performs transition control to transition to a second supply state of supplying the working fluid from the second cylinder mechanism to the pressurizing unit when satisfying a remaining amount condition of the working fluid in the first cylinder of the first cylinder mechanism in a first supply state of supplying the working fluid from the first cylinder mechanism to the pressurizing unit.

Provided is a work machine which can achieve both of excellent operability when an operator manually operates a machine body or a work device and an accuracy of control of the machine body or the work device when a controller performs automatic control. The controller is configured to, in a case where the automatic control function selector switch gives an instruction to disable the automatic control function, adjust an opening amount of a bleed-off valve to a maximum opening amount or an opening amount corresponding to input amounts of control levers, and in a case where the automatic control function selector switch gives the instruction to enable the automatic control function, adjust the opening amount of the bleed-off valve, in at least part of an operation region of the control levers, so as to be smaller than the opening amount with the instruction to disable the automatic control function being given.