Aspects of the present disclosure relate to fail open or fail close actuator assemblies and related methods for valve systems. In one implementation, an actuator assembly for valves includes an outer housing that includes an inner surface at least partially defining an internal volume. The actuator assembly includes one or more first fluid openings formed in the outer housing, one or more second fluid openings formed in the outer housing, and one or more ambient openings formed in the outer housing. The actuator assembly includes a valve stem disposed at least partially in the internal volume, and a first piston disposed in the internal volume and coupled to the valve stem. The actuator assembly includes a second piston disposed in the internal volume and disposed about the valve stem.

A hydraulic actuator includes two or more cylinder parts that nest inside each other, each cylinder part including a piston and piston rod forming an operating element and a cylindrical component, inside which the operating element is arranged, the piston of the inner cylinder part being inside the piston rod of the outer cylinder part, chambers formed for each cylinder part, a pressure-medium feed arrangement creating work-movement in the operating element by the pressure medium led to the chambers, a pressure-difference-controlled valve controlling operation of the hydraulic actuator between a first ducting and a second ducting, controlling the feed of the pressure medium among the chambers and a pressure-difference-controlled spool valve including a housing, connecting chambers and a spool arranged to move backwards and forwards in the housing to open and close the connections creating a work movement alternately by the operating element of the inner or outer cylinder part.

A hydraulic actuator includes two or more cylinder parts that nest inside each other, each cylinder part including a piston and piston rod forming an operating element and a cylindrical component, inside which the operating element is arranged, the piston of the inner cylinder part being inside the piston rod of the outer cylinder part, chambers formed for each cylinder part, a pressure-medium feed arrangement creating work-movement in the operating element by the pressure medium led to the chambers, a pressure-difference-controlled valve controlling operation of the hydraulic actuator between a first ducting and a second ducting, controlling the feed of the pressure medium among the chambers and a pressure-difference-controlled spool valve including a housing, connecting chambers and a spool arranged to move backwards and forwards in the housing to open and close the connections creating a work movement alternately by the operating element of the inner or outer cylinder part.

A hydraulic cylinder comprising a cylinder, a piston element movably guided in the cylinder in a working direction and comprising an active surface, and a first opening for feeding a fluid into a cylinder chamber by the active surface. A working pressure of the fluid acting on the active surface drives the piston element in the working direction. The active surface includes a first partial surface and at least one second partial surface, the cylinder chamber being divided into a first sub chamber with the first opening by the first active surface and a second partial surface with a second opening by the second partial surface, and the partial surfaces are hydraulically separated from each other at least in a selectable operating mode.

A hydraulic cylinder comprising a cylinder, a piston element movably guided in the cylinder in a working direction and comprising an active surface, and a first opening for feeding a fluid into a cylinder chamber by the active surface. A working pressure of the fluid acting on the active surface drives the piston element in the working direction. The active surface includes a first partial surface and at least one second partial surface, the cylinder chamber being divided into a first sub chamber with the first opening by the first active surface and a second partial surface with a second opening by the second partial surface, and the partial surfaces are hydraulically separated from each other at least in a selectable operating mode.

An artificial muscle stack that includes a plurality of artificial muscle layers. Each artificial muscle layer includes one or more artificial muscles having a housing with an electrode region and an expandable fluid region, a dielectric fluid housed within the housing, and an electrode pair having a first and second electrode positioned in the electrode region. The first and second electrodes each include two or more tab portions and two or more bridge portions. The two or more bridge portions interconnects adjacent tab portions. At least one of the first and second electrode includes a central opening positioned between the tab portions and encircling the expandable fluid region. The plurality of artificial muscle layers are arranged such that the expandable fluid region of the artificial muscles of each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles of an adjacent artificial muscle layer.

A method of controlling a hydraulic actuator, wherein the hydraulic actuator includes a linear double-acting output member, and at least three working chambers in fluid connection with the output member, the working chambers having respective effective areas with a non-binary relationship; wherein the method includes selectively fluidly connecting each working chamber to either a high-pressure side or a low-pressure side to provide a plurality of discrete pressurization states of the hydraulic actuator; determining at least one of the pressurization states as a prevented pressurization state; and transitioning between a plurality of allowed pressurization states among the pressurization states while preventing transition to the at least one prevented pressurization state. A hydraulic actuator and a hydraulic system are also provided.

A method of controlling a hydraulic actuator, wherein the hydraulic actuator includes a linear double-acting output member, and at least three working chambers in fluid connection with the output member, the working chambers having respective effective areas with a non-binary relationship; wherein the method includes selectively fluidly connecting each working chamber to either a high-pressure side or a low-pressure side to provide a plurality of discrete pressurization states of the hydraulic actuator; determining at least one of the pressurization states as a prevented pressurization state; and transitioning between a plurality of allowed pressurization states among the pressurization states while preventing transition to the at least one prevented pressurization state. A hydraulic actuator and a hydraulic system are also provided.

Disclosed is a piston-cylinder assembly of a hydraulic press, which includes a basic cylinder and a first and second piston. A ring cylinder is formed above the basic cylinder as a continuation of the cylinder structure. The first piston is located inside the basic cylinder in the bottom part of the basic cylinder and the second piston is located above the first piston in the top part of the cylinder structure. The piston-cylinder assembly has a first hydraulic fluid space below the first piston and a second hydraulic fluid space below the second piston and the piston-cylinder assembly includes a unified hydraulic fluid channel in flow connection to the first hydraulic fluid space in order to provide a pressure effect in the first piston and to the second hydraulic fluid space in order to provide a pressure effect in the second piston.

An artificial muscle stack that includes a plurality of artificial muscle layers. Each artificial muscle layer includes one or more artificial muscles having a housing with an electrode region and an expandable fluid region, a dielectric fluid housed within the housing, and an electrode pair having a first and second electrode positioned in the electrode region. The first and second electrodes each include two or more tab portions and two or more bridge portions. The two or more bridge portions interconnects adjacent tab portions. At least one of the first and second electrode includes a central opening positioned between the tab portions and encircling the expandable fluid region. The plurality of artificial muscle layers are arranged such that the expandable fluid region of the artificial muscles of each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles of an adjacent artificial muscle layer.