A method is provided for determining a gas charge pressure P.sub.calcGC of a hydraulic accumulator within a hydraulic fluid system. The method includes receiving pressure decay data representing the pressure decay within a self-pressurizing hydraulic reservoir of the hydraulic fluid system as the self-pressurizing hydraulic reservoir depressurizes from an operating pressure of the self-pressurizing hydraulic reservoir towards atmospheric pressure. The method also includes calculating the gas charge pressure P.sub.calcGC of the hydraulic accumulator using the received pressure decay data of the self-pressurizing hydraulic reservoir.

An electro-hydraulic actuator system includes a fixed-displacement hydraulic pump and a variable speed electric motor configured in combination to constitute an individual electro-hydraulic unit that is coupled to an actuator, and a bypass valve in parallel to the actuator. The system is configured to enable the actuator to be operated at actuation speeds that are higher than a maximum actuation capability of the pump at the maximum flow capability thereof, and at actuation speeds that are lower than a minimum actuation capability of the pump at the minimum flow capability thereof. The actuation velocity of the actuator may be controlled by controlling the speed of the electro-hydraulic unit and a size of an opening of the bypass valve.

A system for operating a work vehicle includes a hydraulic control assembly and a controller. The hydraulic control assembly includes a pump, accumulator, boom hydraulic cylinder, pin hydraulic cylinder, pin control valve, and ride control valve assembly. The boom hydraulic cylinder moves a boom of the work vehicle. The pin hydraulic cylinder moves a pin on the boom. The ride control valve assembly includes a charge valve and discharge valve. The charge valve is in fluid communication with the pump and the accumulator. The discharge valve is in fluid communication with the accumulator and a reservoir. The controller operates the work vehicle in a ride control mode and pin actuation mode. The pin actuation mode includes opening the charge valve with the discharge valve closed, and directing hydraulic fluid through the pin control valve.

A load sensitive ride system and method is disclosed for a vehicle with an implement movably attached by a boom cylinder. The system includes a payload weight measuring system that measures payload weight and generates a signal indicative of the payload weight, a ride control circuit that adjusts hydraulic flow to and from the boom cylinder; and a controller that receives the signal indicative of the payload weight, and sends compliance commands to adjust ride control compliance based on the signal indicative of the payload weight. The system can include a tire inflation system that adjusts tire pressure. The controller can send inflation commands to adjust tire pressure based on the signal indicative of the payload weight. The compliance commands can depend on the components and compliance adjustment methods of the ride control circuit.

An adjustable ride control circuit and method that includes a head valve that controls flow between a boom cylinder head intake and an accumulator, and a rod float valve that controls flow between a boom cylinder rod intake and tank, where the rod float valve is electronically adjustable and proportionally controls flow restriction. A controller controls ride control activation, and adjustment of the head and rod float valves. When ride control is activated, the head valve allows flow between the head intake and the accumulator, and the controller automatically adjusts the rod float valve. When ride control is deactivated, the head valve blocks flow between the head intake and the accumulator, and the rod float valve blocks flow between the rod intake and tank. An enable valve can control positioning of the head valve. A flow selector can select manual or automatic adjustment of the rod float valve.

A balancing valve includes four ports. While the pressures at a pair of balancing ports of a hydraulic balancing valve are equal, the valve maintains two other ports in a closed position. Upon a pressure differential between the balancing ports, fluid communication can occur between one of the balancing ports and either of the other ports based upon the direction of the pressure differential. A hydraulic ride control system utilizes the balancing valve together with other control valves to provide ride control functionality.

A sheet metal working machine includes a hydraulic drive system to drive a plurality of working tools in a separate and independent manner. The hydraulic drive system includes a plurality of hydraulic cylinders provided with pistons defining thrust chambers and return chambers and associated with corresponding working tools, a reversible first pump connected to the thrust chambers and arranged to send fluid to, or to suck fluid from, at least one of the thrust chambers so as to move the respective piston and the working tool associated therewith, a plurality of valves interposed between the first pump and the thrust chambers of the respective hydraulic cylinders and activable to connect the first pump to the thrust chambers; a hydraulic accumulator connected to the return chambers and arranged for maintaining fluid at a defined preload pressure therein.

A technique facilitates wellbore operations and utilization of wellbore equipment, e.g. equipment comprising actuation devices for downhole tools. According to an embodiment, the system comprises a pump solution for an electrically control device, e.g. an electrically controlled valve. The system may comprise hydraulic circuitry which utilizes bellows to effectively enclose the hydraulic circuitry. Consequently, the system enables an electrically control downhole system having components hydraulically actuated via a closed loop hydraulic system.

Provided is a hydraulic circuit of construction equipment, including a boom cylinder for controlling ascending and descending movement of a boom, which includes a valve unit having a first control valve configured to control a large chamber of the boom cylinder to selectively communicate with a small chamber of the boom cylinder, a second control valve configured to control the large chamber to selectively communicate with an oil tank, a third control valve configured to control the large chamber to selectively communicate with an accumulator, and a fourth control valve configured to control a part of hydraulic oil flowing to the accumulator to selectively flow to an assist motor.

Methods can comprise charging a first hydraulic device of a first hydraulic circuit with a first quantity of hydraulic fluid from a hydraulic fluid source. The methods can further comprise pressurizing a control segment and locking the first quantity of hydraulic fluid from exiting the first hydraulic circuit in response to hydraulic pressure within the control segment. The methods can also include unlocking the first quantity of hydraulic fluid to permit exiting of the first quantity of hydraulic fluid from the first hydraulic device in response to dropping the hydraulic pressure within the control segment after a delay. Hydraulic apparatus can comprise a normally open hydraulic pilot operated control valve that can be configured to hydraulically lock a first hydraulic device in response to a hydraulic pressure within a control segment rising to greater than or equal to an actuation pressure.