An actuator assembly which has a primary force module having a compression spring can be is compressed by a first fluid pressure-operated piston reciprocally mounted in the primary force module. There is a tandem piston module connected to the primary force module which has a second fluid-activated piston. When the spring of the primary force module is compressed, indicating that an attached valve is in the open position, the tandem module is actuated to apply a counter balancing force against the primary piston which allows the spring to expand and move the primary piston to a position which is sufficient to permit movement of the valve element of the actuated valve to indicate the valve is not stuck in an open position.

Combination linear and rotary actuators are disclosed. The linear and rotary actuators have a housing defining a cylindrical interior space and a pair of pistons located inside the cylindrical interior space. An inner bearing cylinder is provided that has spaced-apart ball bearings arranged in a helical pattern on its surface that engage with a structure having an inner surface with helical grooves therein. The structure at least indirectly engages a linear drive piston that is slidably mounted in the housing, and provides rotational movement thereto. The linear drive piston has an input shaft that has ball bearings on its surface, and is inserted inside the output shaft of a revolution piston that has an inner surface with linear grooves. The actuators use hydrostatically charged integral bearing races that activate during operation to reduce friction. Combination linear and rotary actuators with double actuation output shafts are also provided.

In the present invention, both ends of a cylinder are blocked by end caps, two pistons that reciprocate within the cylinder due to fluid pressure are disposed inside the cylinder, and a space surrounded by the two pistons and the inner wall of the cylinder is connected to a fluid supply/exhaust port provided an end cap of the cylinder via a coiling tube position inside the cylinder.

A vehicle stabilization system is disclosed which include two double-acting hydraulic cylinders of the same size, each attached to a vehicle, chassis and the wheel hub assembly on an axle, each cylinder having a top chamber and a bottom chamber, a hydraulic system which includes two compression chambers disposed between the two double acting cylinders, and hydraulic lines coupling the top chamber of one double-acting hydraulic cylinder to the bottom chamber of the other double-acting hydraulic cylinder, and vice versa, and to the two compression chambers disposed therebetween, movement of a first axel of a first chassis with respect to a second axel of the first chassis causes an increase in pressure in one of the two compression chambers and a decrease in pressure in the other of the two compression chambers, thereby providing a hydraulic coupling between the two axels.

In an exemplary method of monitoring performance of a fluid driven actuator for a valve, pressurized fluid is supplied through an actuator supply line to an inlet port of the actuator during a first time period to operate the actuator from a normal position to an actuated position. Pressure changes corresponding to a fluid flow condition in the actuator supply line are measured during the first time period, with the measured pressure changes defining a valve cycle pressure profile including a first inflection point corresponding to movement of the actuator from the normal position to the actuated position. The valve cycle pressure profile is analyzed to identify a non-compliant condition in at least one of the valve and the actuator. An output communicating the identified non-compliant condition is then generated.

In an exemplary method of monitoring performance of a fluid driven actuator for a valve, pressurized fluid is supplied through an actuator supply line to an inlet port of the actuator during a first time period to operate the actuator. Changes corresponding to a fluid flow condition in the actuator supply line are measured during the first time period, and the measured changes are analyzed to identify a non-compliant condition in at least one of the valve and the actuator. An output communicating the identified non-compliant condition is then generated.

A valve controller for controlling a valve and a valve comprising the valve controller are disclosed. The valve has an actuator and a flow controlling unit. The valve controller is configured to execute a setup process and comprises a first pilot valve that can energize the actuator by allowing a first pressurized fluid to enter the actuator and de-energizing the actuator by allowing the fluid to leave the actuator. The valve controller further has an input device by which the setup process can be initiated, and a memory unit for storing setup parameter values. The setup process comprises: determining parameter values indicative of the functionality of at least one of the valve controller, the actuator and the flow controlling unit, and storing the parameter values as setup parameter values in the memory unit.

Manual hydraulic override pumps for use with actuators are described herein. An example apparatus includes a manifold including a reservoir port to be fluidly coupled to a reservoir of fluid, a pump port to be fluidly coupled to a pump, a first actuator port to be fluidly coupled to a first chamber of an actuator, and a second actuator port to be fluidly coupled to a second chamber of the actuator. The example apparatus also includes a rotor disposed in a cavity formed in the manifold. The rotor is rotatable between a first actuating position in which the rotor fluidly couples the first actuator port and the pump port, and a second actuating position in which the rotor fluidly couples the second actuator port and the pump port.

A cylinder device includes: a first piston (8) inserted in a first cylinder hole (4) so as to be movable in an axial direction, a piston rod (7) being hermetically inserted in the first piston (8), the first piston (8) being fixed to the piston rod (7); a second piston (10, 37) inserted in a second cylinder hole (5) so as to be movable in the axial direction, the piston rod (7) being inserted in the second piston (10, 37); and a partition wall (13) dividing a cylinder hole (6) into the first cylinder hole (4) and the second cylinder hole (5), the partition wall (13) being movable in the axial direction.

The invention relates to a self-propelled construction machine, in particular a road milling machine, stabiliser, recycler or surface miner, which has a machine frame 2 supported by at least three running gears 10A, 10B, 11A, 11B, a drive device 14 for driving at least two running gears, and a work roller 4 arranged on the machine frame. The invention also relates to a method for controlling a construction machine of this kind. The drive device 14 comprises adjustable hydraulic motors 15, 16, 17, 18 associated with the drivable running gears, which hydraulic motors have a displacement volume Vg that can be varied by an adjusting device 15A, 16A, 17A, 18A, and comprises at least one adjustable travel drive-hydraulic pump 19 driven by at least one drive motor to supply the hydraulic motors with a variable total volume flow Q of hydraulic fluid. In addition, a controller 28 is provided which is configured in such a way that a partial volume flow Q.sub.1, Q.sub.2, Q.sub.3, Q.sub.4 is determined for each adjustable hydraulic motor 15, 16, 17, 18 from the total volume flow Q provided by the at least one travel drive-hydraulic pump 19, by means of which partial volume flow the particular hydraulic motor is to be operated, and when the speed n of an adjustable hydraulic motor increases as a result of slippage of the running gear associated with the adjustable hydraulic motor, the adjusting device of the adjustable hydraulic motor is controlled in such a way that a displacement volume Vg is set for the adjustable hydraulic motor, at which displacement volume the partial volume flow determined for the adjustable hydraulic motor is maintained. The self-propelled construction machine according to the invention is characterised in that a hydraulic flow divider is not required.