Control valve system for the hydraulic work system of a work vehicle

A valve system for the hydraulic work system of a work vehicle, comprising:

• an elevating drive system for raising and lowering a load, the elevating drive system including a control valve, a hydraulic cylinder and a hydraulic line extending between the control valve and the hydraulic cylinder;
• a tilting drive system having a hydraulic cylinder and a control valve, with admission and discharge lines in flow communication with the tilting drive system control valve;
• a check valve located in the hydraulic line extending between the elevating drive system control valve and hydraulic cylinder, the check valve including a control surface that acts in a direction of an opening position, which control surface is pressurizable by a load pressure of the elevating drive system, and a control pressure chamber that acts in the direction of a closing position, which control pressure chamber is pressurizable by the load pressure of the elevating drive system and is in flow communication with a reservoir when the elevating drive system control valve is actuated to a descent position:
• a pressure relief valve, wherein the control pressure chamber is in flow communication with the pressure relief valve which is a seat valve and is in flow communication with a reservoir, wherein the relief valve is movable into a closed position by a load pressure of the elevating drive system, and into an open position when the control valve of the elevating drive system is actuated into the descent position in which the control pressure chamber of the check valve is in communication with the reservoir;
• and
• a stepper motor connected to the control valve of the elevating drive system, wherein the stepper motor is connected with the relief valve and moves the relief valve into the open position when the elevating drive system control valve is actuated into the descent position;
• wherein the control valve of the elevating drive system is a longitudinal slide valve with a valve slide, and the stepper motor is connected to a control piston of the elevating drive system control valve by a transmission, wherein the valve slide is mounted non-rotationally but so that it is movable longitudinally in a housing boring, and wherein a spring device holds the valve slide in a middle position in a non-actuated status, and
• wherein the relief valve has a valve body which is effectively connected with the valve slide of the control valve of the elevating drive system by an actuator element.

A valve system for the hydraulic work system of a work vehicle, comprising:

• an elevating drive system for raising and lowering a load, the elevating drive system including a control valve, a hydraulic cylinder and a hydraulic line extending between the control valve and the hydraulic cylinder;
• a tilting drive system having a hydraulic cylinder and a control valve, with admission and discharge lines in flow communication with the tilting drive system control valve;
• and
• flow regulators having open and closed positions located in the tilting drive system admission and discharge lines, wherein the flow regulators are pressurized toward the closed position by a pressure upstream of a throttle point of the tilting drive system control valve and toward an open position by a pressure downstream of the throttle point of the tilting drive system control valve and a spring, and wherein the flow regulator in the admission line is controlled by a pressure decrease at an admission-side throttle point of the control valve and the flow regulator in the discharge line is controlled by a pressure decrease at a discharge-side throttle point of the control valve.