A selector control that is manually operable by a user for activating or deactivating a primary control or a secondary control. The selector control may include a first state for activating the primary control and deactivating the secondary control, a second state for activating the secondary control and deactivating the primary control, and a failsafe state for deactivating both the primary control and the secondary control. The selector control may be configured to maintain the second state independent of continuous user input being applied to the selector control, and configured to maintain the first state when continuous user input is applied to the selector control. The selector control is normally biased toward the failsafe state such that the selector control automatically selects the failsafe state when the user discontinues applying the user input for maintaining the first state. The selector control has particular application for use in controlling a boom of a work vehicle.

A safety valve which has two fluidically interconnected safety valves, each of which has a 4/2-way valve function. Each safety valve has a first connecting port and a second connecting port, which are connected to each other in such a way that a fluid flow through the two safety valves, controlled by means of a control valve, to a fluid-actuated drive is prevented if the two safety valves simultaneously adopt a first switching position and such a fluid flow is possible if both valves simultaneously have a second switching state. One safety aspect results from the fact that the above-mentioned fluid flow is also prevented if the two safety valves adopt different switching states.

A valve arrangement has two main valves which are each preloaded by a spring device into a first switching position, and which can each be switched into a second switching position by means of an assigned pilot valve. The pilot medium required for switching is provided with a pilot pressure at a pilot connection of each pilot valve. The main valves are each equipped with a working valve section each of which are fluidically connected to one another. In addition, each main valve contains a monitoring valve section. The monitoring valve sections are designed to provide the venting of at least one pilot connection when the two main valves are in different switching positions. This allows a fluid-actuated actuator to be controlled in accordance with high safety standards.

A selector control that is manually operable by a user for activating or deactivating a primary control or a secondary control. The selector control may include a first state for activating the primary control and deactivating the secondary control, a second state for activating the secondary control and deactivating the primary control, and a failsafe state for deactivating both the primary control and the secondary control. The selector control may be configured to maintain the second state independent of continuous user input being applied to the selector control, and configured to maintain the first state when continuous user input is applied to the selector control. The selector control is normally biased toward the failsafe state such that the selector control automatically selects the failsafe state when the user discontinues applying the user input for maintaining the first state. The selector control has particular application for use in controlling a boom of a work vehicle.

A cross-flow dual valve has a supply path, an exit path, and first and second valve holes through which the supply path and the exit path communicate with each other. The cross-flow dual valve has a first intersecting path through which a supply path side of the first valve hole and an exit path side of the second valve hole communicate with each other. The cross-flow dual valve has a second intersecting path through which a supply path side of the second valve hole and an exit path side of the first valve hole communicate with each other. The cross-flow dual valve includes a first valve and a second valve. The first valve includes a first lower valve body and a first spool. The second valve includes a second lower valve body and a second spool.

An actuating unit for a process valve is described, which comprises a pilot valve unit, a separate removable seal arranged between two parts through which a fluid can flow, and a piston configured for the adjustment of the process valve. The seal has through openings for the passage of fluid, and the adjacent parts have holes, such that different holes are in fluid communication with each other via the through openings or are fluidically separated due to an intermediate wall portion of the seal depending on the fitting position of the seal. A process valve having such an actuating unit is furthermore described.

A cross-flow dual valve has a supply path, an exit path, and first and second valve holes through which the supply path and the exit path communicate with each other. The cross-flow dual valve has a first intersecting path through which a supply path side of the first valve hole and an exit path side of the second valve hole communicate with each other. The cross-flow dual valve has a second intersecting path through which a supply path side of the second valve hole and an exit path side of the first valve hole communicate with each other. The cross-flow dual valve includes a first valve and a second valve. The first valve includes a first lower valve body and a first spool. The second valve includes a second lower valve body and a second spool.

A hydraulic control device for an emergency stop valve of a steam turbine has a module for reducing a hydraulic pressure by rapid opening of an outflow valve and/or unloading or loading an actuator for actuating the emergency stop valve. In an operating medium supply and/or conducting system a control valve arrangement with at least three safety valves is provided, which are hydraulically interconnected such that they open the outflow valve or unload or load the actuator only when a safety circuit by way of at least two safety valves of the control valve arrangement has assumed an emergency stop position. A precontrol valve that is independent from the remaining safety valves is hydraulically connected upstream of each safety valve. A safety valve that is connected downstream of a respective precontrol valve can be hydraulically decoupled from the same during the operation.

A safety valve which has two fluidically interconnected safety valves, each of which has a 4/2-way valve function. Each safety valve has a first connecting port and a second connecting port, which are connected to each other in such a way that a fluid flow through the two safety valves, controlled by means of a control valve, to a fluid-actuated drive is prevented if the two safety valves simultaneously adopt a first switching position and such a fluid flow is possible if both valves simultaneously have a second switching state. One safety aspect results from the fact that the above-mentioned fluid flow is also prevented if the two safety valves adopt different switching states.

An actuating unit for a process valve is described, which comprises a pilot valve unit, a separate removable seal arranged between two parts through which a fluid can flow, and a piston configured for the adjustment of the process valve. The seal has through openings for the passage of fluid, and the adjacent parts have holes, such that different holes are in fluid communication with each other via the through openings or are fluidically separated due to an intermediate wall portion of the seal depending on the fitting position of the seal. A process valve having such an actuating unit is furthermore described.