A method and apparatus for dithering hydraulic valves to mitigate static friction (“stiction”) associated with the hydraulic valves. A first hydraulic valve and a second hydraulic valve are dithered to mitigate stiction associated with those valves. The dithering of the first and second hydraulic valves also cause dithering of a main hydraulic valve associated with the first and second hydraulic valves. Accordingly, stiction of three hydraulic valves of a hydraulic system is mitigated.

A hydraulic system for controlling bleed down and retraction of a boom within a safety envelope includes a backup battery power supply, and at least a first boom lift hydraulic cylinder configured to raise and lower the boom. The first boom lift hydraulic cylinder includes a solenoid bleed valve electrically connected to the backup battery power supply. The hydraulic system also includes an input device controllable by an operator of the boom. The input device may, for instance, be used by the operator to initiate bleed down and retraction of the boom from an elevated position. To accommodate independent failsafe features of the system, the input device is configured to selectively actuate the solenoid bleed valve using electrical power supplied from the backup battery power supply.

A valve actuator system includes a valve actuator assembly having a body defining an interior cavity and a piston coupled to a piston rod and movable within a piston cylinder provided within the interior cavity. The piston cylinder has a first chamber on a first side of the piston and a second chamber on a second rod side of the piston. One or more electronic components are disposed within the interior cavity and include at least one processor. The one or more electronic components are configured to move the piston via controlled air pressure and to continuously monitor and/or determine a position of the piston rod relative to the piston cylinder. A fail-safe reservoir is coupled to a source of air and is connected to both the first chamber and the second chamber to provide operating air thereto. A controller is configured to communicate with the processor of the one or more electronic components remote from the body and to selectively monitor and control functions of the valve actuator systems from the controller. The first chamber is maintained at a substantially constant pressure and the second chamber is varied in pressure to move and/or to hold the position of the piston to place the piston rod at a desired position relative to the piston cylinder.

One object is to reduce a weight of a fluid actuator. The fluid actuator includes: a cylinder having an inner space and a first mounting portion, the inner space being partitioned into a first fluid chamber and a second fluid chamber, the first mounting portion being disposed on an end portion of the cylinder on an axial direction A side; and a piston rod configured to reciprocate in accordance with pressures in the fluid chambers. A wall portion defining the first fluid chamber in the cylinder is made of an iron-based alloy. A wall portion defining the second fluid chamber in the cylinder is made of an aluminum alloy. The piston rod is made of an iron-based alloy.

A control device and method for controlling a disengaging actuator (1) of a tool attachment, the device comprising a three-state switch (2), with a middle neutral position (20), a first end position (21), and a second end position (22), a control unit (3, 3′) having an input corresponding to an activation of the first end position (21), an electro-valve (4) coupled hydraulically to the disengaging actuator (1), having a coil (40), a first control line (41) and a second control line (42) coupled respectively to first and second terminals of the coil (40) of the electro-valve, wherein one of the first and second control lines is coupled to the second end position (22) of the three-state switch and the other of the first and second control lines is coupled to an output of the control unit, such that both control lines have to be activated to allow disengagement.

A method for monitoring the condition of a hydraulic system of a metal forming plant is presented. The hydraulic system is coupled to or provided with a pump drivable by a drive motor for providing a working fluid and with a heat exchanger. With the presented method, the following steps are initiated or carried out by a condition-monitoring device during the operation of the hydraulic system: Determining a current cooling power of the heat exchanger; determining a current conveying power of the pump; and determining a current maintenance urgency and/or a current ageing condition of the hydraulic system on the basis of the determined current cooling power of the heat exchanger. Furthermore, a condition-monitoring device designed to carry out the presented method is presented.

A method of controlling a hydraulic valve includes putting a first control chamber under pressure and putting a second control chamber to return so as to cause a slide to move into one of two end positions, putting a second control chamber under pressure and putting the first control chamber to return, thereby causing the slide to move into the other one of the two end positions. An intermediate step of applying pressure to the one of the first or second control chamber that was connected to return can be provided so that both control chambers are maintained simultaneously under pressure for a determined length of time.

A hydraulic leak detection system includes a leak detection switch responsive to a level of hydraulic fluid in a tank used by a hydraulic mowing circuit and a lift and lower circuit of a grass mowing machine. The system includes a controller that activates a warning indicator if the leak detection switch indicates the level of hydraulic fluid in the tank is low, but allows the hydraulic mowing circuit and the lift and lower circuit to continue operating until the lift and lower circuit reaches a fully raised position. A solenoid valve may control the level of hydraulic fluid in the tank based on temperature of the hydraulic fluid.

A method and apparatus for dithering hydraulic valves to mitigate static friction (“stiction”) associated with the hydraulic valves. A first hydraulic valve and a second hydraulic valve are dithered to mitigate stiction associated with those valves. The dithering of the first and second hydraulic valves also cause dithering of a main hydraulic valve associated with the first and second hydraulic valves. Accordingly, stiction of three hydraulic valves of a hydraulic system is mitigated.

One object is to reduce a weight of a fluid actuator. The fluid actuator includes: a cylinder having an inner space and a first mounting portion, the inner space being partitioned into a first fluid chamber and a second fluid chamber, the first mounting portion being disposed on an end portion of the cylinder on an axial direction A side; and a piston rod configured to reciprocate in accordance with pressures in the fluid chambers. A wall portion defining the first fluid chamber in the cylinder is made of an iron-based alloy. A wall portion defining the second fluid chamber in the cylinder is made of an aluminum alloy. The piston rod is made of an iron-based alloy.