A method is proposed for establishing termination criteria for a partial stroke test on a safety valve, including: a) A partial stroke test is carried out when the safety valve is operational. b) Position of the valve member and pressure in the drive fluid are recorded. c) A first relation is derived, which relates position of the valve member, time, pressure of the drive fluid, and/or control deviation to one another. d) This relation is defined as a safety valve reference curve. e) A second relation is defined, which has a predetermined distance from the reference curve. f) Termination criterion include: If the partial stroke test is repeated on the same valve, the same data are recorded and a third relation is derived for the reference curve, the partial stroke test is not passed if the third relation has a greater distance to the reference curve than the second relation.

A hydraulic system for a rear gate of a baler implement includes a fluid circuit having a first portion connected to and disposed in fluid communication with a first fluid port of a hydraulic cylinder. A flow bypass assembly is disposed in the first portion of the fluid circuit. The flow bypass assembly includes a flow rate control valve selectively moveable between a first position allowing fluid communication therethrough at a first flow rate, and a second position blocking fluid communication therethrough. The flow bypass assembly further includes a bypass passageway for circulating the fluid when the flow rate control valve is closed. A flow restriction is disposed within the bypass passageway to provide a second flow rate that is less than the first flow rate.

A work machine control system includes: a pump; a cylinder operating a working equipment element in a movable range based on hydraulic oil supplied from the pump; a first path connected to the pump; a second path branching from the first path; a control valve adjusting the flow rate of the oil supplied to the cylinder via the first path; a bleed valve adjusting the flow rate of the oil discharged to a tank via the second path; a sensor detecting a posture of the element in the range; and a control device outputting a first command for adjusting the flow rate of the oil supplied to the cylinder and a second command for adjusting the flow rate of the oil discharged to the tank when element is determined to be present in an end section of the range based on detection data of the sensor.

A pneumatic control device of auto door includes a first directional control valve configured to control a direction of a compressed air supplied to a door cylinder for opening and closing a door, a door detection sensor configured to detect an open/close state of the door, first and second exhaust lines respectively connected to first and second outlet ports of the first directional control valve, and second directional control valves installed in the first and second exhaust lines respectively to operably exhaust the compressed air exhausted from the first and second outlet ports according to an emergency stop signal, and capable of changing positions to reduce an exhaust speed of the compressed air in case that the door is not completely open or closed when an operation signal is generated after the emergency stop signal.

A construction machine that makes it possible for an operator to linearly push a bucket simply by operating an arm in a pushing direction is provided. A controller 50 is configured to, in a case where a straight locus is selected by a bucket locus selecting device 52, calculate a constant flow rate ratio α according to a boom initial angle that is an angle of a boom 2 sensed by a boom angle sensor 33 at a time point when an arm 4 is operated in a pushing direction by an operation device 51, and control the delivery flow rate of a first hydraulic pump 12 such that a hydraulic fluid is discharged from a cap chamber 1a of a boom cylinder 1 at a flow rate Qb obtained by multiplying a flow rate Qa of a flow supplied to a cap chamber 3a of an arm cylinder 3 by the flow rate ratio α while the arm 4 is operated in the pushing direction by the operation device 51 and there is not an instruction for operation of the boom 2.

A system for adjusting actuator pressure on an agricultural implement includes a fluid-driven actuator configured to adjust a position of a tool of the implement relative to the implement frame, with the fluid-driven actuator defining a fluid chamber. Furthermore, the system includes a valve configured to control a flow of a fluid to the fluid-driven actuator. In addition, the system includes a fluid conduit fluidly coupled between the valve and the fluid chamber. Moreover, the system includes a computing system is configured to determine the current position of the tool relative to the implement frame based on the data captured by a position sensor. Additionally, the computing system is configured to determine a current volume of the fluid chamber and the fluid conduit based on the determined current position. Furthermore, the computing system is configured to control the operation of the valve based on the determined current volume.

A hydraulic drive apparatus includes a flow-path selector valve and a flow-path switching control unit that operates the valve. The flow-path selector valve has a first position for a single operation state and a second position for a combined operation state, configured to, at the first position, form a first flow path connected to a first pump, a second flow path connected to a second pump, and a connecting flow path providing communication between the first flow path and the second flow path. When a driving state of a work actuator is deviated from an allowable range in the combined operation state, the flow-path switching control unit reduces an opening area of the connecting flow path as compared with that when the driving state is within the allowable range.

Disclosed is a hydraulic control apparatus including a flow-path selector valve that switches a supply flow path and a flow-path switching control unit that operates the same, a regeneration valve and a regeneration release valve capable of the regenerative operation, and a regeneration control unit that operates the same. The flow-path switching control unit makes the flow-path selector valve form a flow-path providing communication between first and second pumps in a combined operation state. The regeneration control unit judges the propriety of the regenerative operation on the basis of the second pump pressure which is the discharge pressure of the second pump in a single operation state and judges the propriety of the regenerative operation on the basis of whether or not the driving state of the work actuator is within an allowable range corresponding to the target work operation amount in the combined operation state.

An actuator system includes a piston-cylinder arrangement including a piston that is movable with respect to a cylinder. A first flow path is in fluid communication with the piston-cylinder arrangement and a second flow path is in fluid communication with the piston-cylinder arrangement. A control system is operable to fluidly connect the first flow path to a source of high-pressure fluid and to connect the second flow path to a drain to move the piston in a first direction. A pressure sensor is fluidly connected to the first flow path and is operable to measure sufficient pressure data during the movement of the piston to generate a pressure versus time curve. The control system is operable to compare the generated pressure versus time curve to a known standard pressure versus time curve stored in the control system to determine the condition of the piston-cylinder arrangement.

The subject matter of this specification can be embodied in, among other things, an electrohydraulic positioning control system that includes a shuttle valve configured to direct fluid flow between a selectable one of a first fluid port and a second fluid port, and a fluid outlet configured to be fluidically connected to a fluid actuator, a first servo valve controllable to selectably permit and block flow between the first fluid port, a fluid source, and a fluid drain, a second servo valve controllable to selectably permit and block flow between the second fluid port, the fluid source, and the fluid drain, a first servo controller configured to provide a first health signal and control the first servo valve based on a second health signal, and a second servo controller configured to provide the second health signal and control the second servo valve based on the first health signal.