A gas circulation apparatus is applied to a pneumatic apparatus including a solenoid valve apparatus and a cylinder apparatus, and is connected in series between the solenoid valve apparatus and the cylinder apparatus. The gas circulation apparatus includes a valve core structure, a first circulation cavity, and a second circulation cavity. The valve core structure is configured to move in a first direction, so that compressed gas discharged from a first cylinder cavity of the cylinder apparatus and passing through the solenoid valve apparatus is collected and stored by the first circulation cavity, and a second cylinder cavity of the cylinder apparatus is supplied with compressed gas stored in the second circulation cavity together with the compressed gas supplied from the solenoid valve apparatus.

A direction control valve group for a construction machine that controls an amount of pressure oil supplied to a hydraulic actuator from a hydraulic pump that discharges the pressure oil is provided. The direction control valve includes a cylinder port that supplies the pressure oil to the hydraulic actuator, a bridge passage that is switchably connected and disconnected to the cylinder port according to a change in position of a first spool, and an internal passage that supplies the pressure oil discharged from the hydraulic pump to the bridge passage. The first spool is provided in the internal passage.

A valve includes a basic body, control spool, sealing ring, and control cover. The control spool is received in the basic body to be movable along a longitudinal axis. The basic body includes a counter-sealing surface, connecting channel, and tank channel having at least one first annular groove surrounding the control spool. The control cover and at least one end face of the control spool facing toward the longitudinal axis delimits, at least in part, a control space. The control cover includes a sealing surface that abuts the counter-sealing surface of the basic body. At least one of the sealing surface and the counter-sealing surface includes a sealing groove that surrounds the control space in ring-like fashion. The sealing ring is received in the sealing groove. The connecting channel opens out into the tank channel and into the sealing groove.

A valve device having a valve housing (10, 54, 94, 166) and fluid ports (16, 18) disposed therein, which are connected to or separated from one another in a fluid-conveying manner by means of a valve piston (22) displaceable along its longitudinal axis (24) in its various travel positions, and having at least one latching device (26, 28) for latching the valve piston (22) in at least one of its travel positions, wherein individual latching means (30, 38, 170) of said latching device, when it is actuated by an external force, take latching positions spatially different from one another, which is characterized in that, with respect to the longitudinal axis (24) of the valve piston (22), the individual latching means (30, 38, 170) of the latching device (26, 28) take positions differing from one another both in the axial and in the radial direction in the individual latching positions.

An electro-hydraulic servo valve, which has an adjustable null position and can be directly driven by the motor, is provided and includes four parts: a slide valve assembly, a two-dimensional motor, a magnet resetting-to-null mechanism, and a displacement sensor, and the four parts are set coaxially arranged. The slide valve assembly is a conventional two-dimensional servo valve structure. The two-dimensional motor may directly drive the valve core to rotate to further control a size of an opening opened by a valve. The magnet resetting-to-null mechanism is configured to reset the valve to the null position. The displacement sensor may monitor a position of the valve core in real-time and feedback signals to achieve closed-loop controlling.

A hydraulic control system for blowout preventers systems, frack valves and chokes, and related wellhead and control equipment used in oil and gas well drilling operations. The hydraulic control system can include one or more hydraulic control valves or pressure regulators including an internal, linear slider and pairs of seal rings. Lapped and polished surfaces of the seal rings and sliders can form a dynamic metal-to-metal seal within the hydraulic control valves or pressure regulators.

A counter pressure valve arrangement for controlling a pressure level of a hydraulic fluid in a return line from a hydraulic actuator arrangement. The counter pressure valve arrangement comprises a counter pressure valve having: a moveable valve member; a counter pressure regulating port configured for being connected to the hydraulic actuator arrangement via the return line; a tank port configured for being connected to a tank or low pressure reservoir for storing low pressure hydraulic fluid; and a pump port configured for being connected to a source of pressurised hydraulic fluid. A first position of the valve member effects fluid communication between the pump port and the counter pressure regulating port for supplying pressurised hydraulic fluid to the return line, and a second position of the valve member effects fluid communication between the counter pressure regulating port and the tank port for discharging hydraulic fluid from the return line to the tank.

A time delay valve includes a switching valve that switches between a first position and a second position; an urging member that urges the switching valve toward the first position; a driving mechanism that urges the switching valve toward the second position located opposite the first position in the presence of the pressure of a pilot fluid being supplied: a pilot flow channel that introduces the pilot fluid to the driving mechanism; and a delaying mechanism that delays the switching timing of the switching valve. The delaying mechanism includes a first throttle valve provided on the pilot flow channel, a compensation mechanism that urges the switching valve toward the first position in the presence of the pressure of the pilot fluid being supplied, and a compensation flow channel that is branched from the pilot flow channel to introduce a portion of the pilot fluid to the compensation mechanism.

A directional control valve includes: a housing having a cylindrical spool hole communicating with an inlet port letting a fluid from an external supply source at a predetermined pressure and an outlet port flowing the fluid to a working cylinder; a spool movable in the spool hole axially and changing an amount of flow of the fluid; a first solenoid driving section having a first needle coupled to or integral with a first end portion of the spool and driving the spool; and a second solenoid driving section having a second needle coupled to or integral with a second end portion of the spool and driving the spool, the directional control valve including a pressure equalization circuit equally applying a pressure to the end portions.

A selector control that is manually operable by a user for activating or deactivating a primary control or a secondary control. The selector control may include a first state for activating the primary control and deactivating the secondary control, a second state for activating the secondary control and deactivating the primary control, and a failsafe state for deactivating both the primary control and the secondary control. The selector control may be configured to maintain the second state independent of continuous user input being applied to the selector control, and configured to maintain the first state when continuous user input is applied to the selector control. The selector control is normally biased toward the failsafe state such that the selector control automatically selects the failsafe state when the user discontinues applying the user input for maintaining the first state. The selector control has particular application for use in controlling a boom of a work vehicle.