A hydraulic system for a construction machine having a protection device is disclosed, which can limit a flow rate of hydraulic fluid that is discharged from a hydraulic pump in accordance with a hydraulic fluid temperature and notify an operator of information on the hydraulic fluid temperature. The hydraulic system for a construction machine includes a hydraulic actuator operated by hydraulic fluid that is supplied from a hydraulic pump; a control valve installed in a flow path between the hydraulic pump and the hydraulic actuator to control a flow rate of the hydraulic fluid that is supplied from the hydraulic pump to the hydraulic actuator; an oil cooler installed in a return flow path from the control valve to an hydraulic fluid tank to cool the hydraulic fluid; a hydraulic fluid temperature sensor detecting in real time a hydraulic fluid temperature of the hydraulic fluid tank; a hydraulic pump regulator controlling a discharge flow rate of the hydraulic pump through adjustment of an inclination angle of a swash plate of the hydraulic pump; and a controller comparing the hydraulic fluid temperature detected by the hydraulic fluid temperature sensor with a predetermined hydraulic fluid temperature, and outputting a control signal to the hydraulic pump regulator so as to limit the discharge flow rate of the hydraulic pump to or below a predetermined flow rate if the detected hydraulic fluid temperature is equal to or lower than a predetermined lower limit value, or equal to or higher than a predetermined upper limit value.

The invention relates to a hydraulic cylinder, for example for use in a hydraulic tool, comprising at least one piston/cylinder combination composed of a cylinder body and a piston accommodated in said cylinder body and provided with a piston rod that projects from said cylinder body, wherein the cylinder body and the piston body define a first cylinder chamber while the cylinder body, the piston body and the piston rod define a second cylinder chamber, and wherein during operation the piston performs alternating forward and return operational cycles under the influence of a fluidum under pressure that is conducted to the first and the second cylinder chamber through a first and a second line, respectively, and a control valve which regulates the supply of a fluid under pressure through the first or the second line to the piston/cylinder combination.

A manifold structure for a fluid reclamation apparatus incorporated into a hydraulic system having inner and outer fluid lines and with annular containment space between the inner and outer fluid lines for capturing fluid leaking from the inner fluid line, the manifold structure being connected to least one end the inner and outer fluid lines and contains a chamber for receiving leaked fluid from the annular space and including a manifold inner sleeve to which the inner fluid line is coupled, the inner sleeve being retained within a manifold outer sleeve to which the outer fluid line is coupled and having a lateral bore extending from the chamber and through the outer sleeve for delivering leaked fluid into a reclamation line and back into the hydraulic system, the inner sleeve being rotatably mounted within the outer sleeve by at least one O-ring seated in a groove around the inner sleeve and sealingly abutting the inner surface of the outer sleeve.

An actuator includes a housing that defines a first inlet to receive a fluid, a second inlet to receive the fluid and a chamber. The actuator includes an actuator rod movably coupled to the housing. The actuator rod includes a head. A first face of the head is responsive to the fluid from the first inlet, and a second face of the head is responsive to the fluid from the second inlet to move the actuator rod. The head defines at least one cross-bore. The actuator includes at least one plug coupled to the cross-bore to inhibit a flow of the fluid through the cross-bore in a first state such that the plug fluidly isolates the fluid from the first inlet from the fluid from the second inlet. The plug is to enable the flow of the fluid through the at least one plug in a second state.

A control line operating system includes a first piston having a first pressure face and a second pressure face, a first control line in operable communication with the first pressure face of the first piston, a second piston having a third pressure face and a fourth pressure face and a second control line in operable communication with the third pressure face of the second piston. Both the first piston and the second piston are in operable communication with a tool such that pressure increases in either the first control line or the second control line can cause actuation of the tool, the first control line is in operable communication with the fourth pressure face of the second piston and the second control line is in operable communication with the second pressure face of the first piston.

A pneumatic control device includes a functional assembly that has an interruption valve device for the selective opening or interruption of at least one main working channel used for the pneumatic control of a pneumatic actuator. The functional assembly also contains a manually actuatable valve device that is connected to the interruption valve device by means of at least one auxiliary working channel and which enables manual pneumatic control of the connected actuator, if the at least one main working channel is interrupted by the interruption valve device at the same time. A process control device can also be equipped with a control device of this type.

A pneumatic control device includes a functional assembly that has an interruption valve device for the selective opening or interruption of at least one main working channel used for the pneumatic control of a pneumatic actuator. The functional assembly also contains a manually actuatable valve device that is connected to the interruption valve device by means of at least one auxiliary working channel and which enables manual pneumatic control of the connected actuator, if the at least one main working channel is interrupted by the interruption valve device at the same time. A process control device can also be equipped with a control device of this type.

A proportional pressure controller includes a body having inlet, outlet, and exhaust ports. A fill valve communicates with pressurized fluid in the inlet port. A dump valve communicates with pressurized fluid from the fill valve. An inlet poppet valve opens by pressurized fluid through the fill valve. An exhaust poppet valve when closed isolates pressurized fluid from the exhaust port. An outlet flow passage communicates with pressurized fluid when the inlet poppet valve is open, and communicates with the outlet port and an exhaust/outlet common passage. An isolation valve assembly selectively isolates fluid flow to and from the inlet port or the exhaust port to achieve a zero pressure condition.

A system uses a two-stage electrohydraulic servo valve that includes an additional control port that commands a fail-fixed valve to lock the position of a device in the last commanded position. The additional port is modulated by an existing land on the EHSV valve element, adding little to no complexity. Major technical benefits of the disclosed system are that it adds little to no cost, complexity, size, or weight the device being controlled. The disclosed configuration allows for the use of a relatively small and simple fail-fixed valve, and the control ports on the controlled device keep “drift” to a minimum, when transitioning between normal operating mode and fail-fixed operating mode.

In a steam valve driving apparatus according to an embodiment, a control valve permits or blocks a flow of hydraulic oil from a supply port to an opening direction piston chamber. A dump valve blocks or permits the flow of the hydraulic oil from the opening direction piston chamber to a discharge port. A blocking valve permits or blocks a flow of the hydraulic oil from an accumulator to a closing direction piston chamber. The control valve permits the flow of control oil from the closing direction piston chamber to the discharge port in a state where the flow of hydraulic oil from the supply port to the opening direction piston chamber is permitted.