Abstract: A negative control type hydraulic system in which the use of a pilot pump and a load pressure generator between a hydraulic pump and a control valve is not required to prevent a power loss.

Abstract: A hydraulic circuit for heavy equipment is disclosed, which utilizes a hydraulic fluid supplied from a hydraulic pump for driving a cooling fan, as a pilot signal pressure, without installing a separate constant displacement pilot pump for supplying the pilot signal pressure to a control valve for controlling the hydraulic fluid to be supplied to a working device such as a boom.

Abstract: A pressure control valve for heavy equipment. The pressure control valve can smoothly operate a working device having a high load pressure by limiting a supply of hydraulic fluid to a working device having a low load pressure in the case of simultaneously operating a plurality of working devices in a hydraulic circuit in which a plurality of control valves (e.g., a boom control valve and a bucket control valve) are connected in parallel to a single hydraulic pump.

Abstract: A negative control type hydraulic system is provided, in which the use of a pilot pump and a load pressure generator between a hydraulic pump and a control valve is not required to prevent a power loss.

Abstract: A hydraulic circuit for heavy equipment is disclosed, which utilizes a hydraulic fluid supplied from a hydraulic pump for driving a cooling fan, as a pilot signal pressure, without installing a separate constant displacement pilot pump for supplying the pilot signal pressure to a control valve for controlling the hydraulic fluid to be supplied to a working device such as a boom.

Abstract: A pressure control valve for heavy equipment is disclosed, which can smoothly operate a working device having a high load pressure by limiting a supply of hydraulic fluid to a working device having a low load pressure in the case of simultaneously operating a plurality of working devices in a hydraulic circuit in which a plurality of control valves (e.g., a boom control valve and a bucket control valve) are connected in parallel to a single hydraulic pump. The pressure control device includes a valve body, a spool slidably installed in the valve body and shifted to connect an input port to an output port or to disconnect the input port from the output port, and a signal pressure port for applying a signal pressure to a diaphragm of the spool located in a third back chamber formed in the valve body, disconnecting the input port from the output port, and returning the pressure in the output port to the drain port.

Abstract: Disclosed is a relief valve, in which a flow rate of hydraulic fluid is not greatly changed even when temperature is changed, and thus providing smooth operation and preventing foreign materials contained in the hydraulic fluid from being introduced into the relief valve. The relief valve is comprised of a sleeve provided with a high-pressure inlet and a tank fluid channel; a main poppet provided with an inflow fluid passage and a back pressure chamber; an annular fluid passage provided on a front end of the main poppet; a seat provided with a seat fluid channel communicating with the back pressure chamber; and a pilot poppet communicating the seat fluid channel with the tank fluid channel.

Abstract: The present invention discloses a structure for mounting a coin-filter filtering foreign materials contained in hydraulic fluid on a fixing groove formed at an inlet side of an orifice without using O-ring. A coin-filter mounting structure according to the present invention comprises a body having a fixing groove formed at an inlet side of an orifice, and a holder supporting the border of a coin-filter filtering out foreign materials contained in hydraulic fluid flowing through the orifice, and fixed to the fixing groove through plastic deformation after being mounted on the fixing groove.

Abstract: Disclosed is a flow control apparatus for construction heavy equipment capable of maintaining constant set flow rate regardless of changes in load pressure and pump pressure. The flow control apparatus is composed of a control valve, a flow control valve, and a load check valve. The control valve has a parallel passage, a housing provided with a first load passage and a second load passage, and a control spool provided to be movable in the housing. The flow control valve having a logic check valve provided to be openable between the first load passage and the parallel passage, and a logic control valve controlling a flow rate supplied to a back pressure chamber of the logic check valve. The load check valve is provided between the second load passage and the parallel passage to restrict backflow from the second hydraulic cylinder.

Abstract: Disclosed is a pilot operated relief valve, in which a balance system is provided to offset a tank pressure exerted on a piston, so that a setting pressure of a pilot poppet is not changed even when the tank pressure is changed, and thus a function of the relief valve can be stably performed. The pilot operated relief valve is comprised of a sleeve, a main poppet provided to be movable in the sleeve, a seat provided in the sleeve, a housing connected to a rear end of the sleeve, a pilot poppet provided to be movable in the housing, a piston moved by a pilot signal pressure, and the balance system offsetting the tank pressure exerted on the piston.

Abstract: Disclosed is a pilot operated relief valve, in which a balance system is provided to offset a tank pressure exerted on a piston, so that a setting pressure of a pilot poppet is not changed even when the tank pressure is changed, and thus a function of the relief valve can be stably performed. The pilot operated relief valve is comprised of a sleeve, a main poppet provided to be movable in the sleeve, a seat provided in the sleeve, a housing connected to a rear end of the sleeve, a pilot poppet provided to be movable in the housing, a piston moved by a pilot signal pressure, and the balance system offsetting the tank pressure exerted on the piston.