Provided is a duct damper comprising: a hollow housing provided inside the duct so as to enable ventilation; a blocking plate provided in the housing and opening and closing the hollow; a fastener detachably fixing the blocking plate to the housing; and shape maintaining members respectively provided on the sides of the blocking plate so as to respectively maintain half of the shape formed by the blocking plate. According to the present invention, even if both sides of the blocking plate are bent with a center bar as an axis, since the shape maintaining members half and half support the both sides of the blocking plate, respectively, so as to maintain the shape, vibrations are not generated at either side of the blocking plate, thereby preventing noise.

A stop pin for a check valve includes a first end and a second end and extending from the first end to the second end in a longitudinal direction along a longitudinal axis. The stop pin also includes at least one slot therein extending in said longitudinal direction, said at least one slot defining a respective at least one flexible, cantilevered tongue having a free end and a connected end connected to said stop pin.

A bleed valve includes a valve body, a first flapper body movable relative to the valve body between an open position and a closed position, and a second flapper body movable relative to the valve body between an open position and a closed position. A resilient member biases the first and second flapper bodies to the open position to vent bleed air. The first and second flapper bodies move to the closed position when a pressure load across the first and second flapper bodies exceeds a biasing force of the resilient member. A gas turbine engine is also disclosed.

A check valve comprises a valve housing defining at least one valve opening, and at least one flapper pivotably mounted for rotation relative to the valve housing between an open position in which it permits fluid flow through the respective valve opening and a closed position in which it prevents fluid flow through the valve opening. The valve housing comprises a hinge body which comprising a hinge groove extending in a straight line in a longitudinal direction therethrough from a first end to a second end. The hinge groove has, in a plane transverse to the longitudinal direction, an arcuate profile. The at least one flapper comprises a hinge tongue formed along a proximal edge thereof. The hinge tongue extends in a straight line in a longitudinal direction along the proximal edge of the flapper from a first end to a second end.

A dual plate backflow and breakaway check valve designed to mount above grade. The dual plate check valve includes a barrel assembly having an upper portion, a lower portion and an annular groove. An upper dual valve includes an upper front plate and an upper back plate. A lower dual valve includes a lower front plate and a lower back plate. A lower valve keeper bar moves up from between a plurality of lower valve stay tabs upon breakage of the annular groove thereby allowing the lower front plate and the lower back plate to rotate about a lower valve pin and closing the lower dual valve upon a lower barrel bevel and simultaneously allowing the upper front plate and the upper back plate to rotate about an upper valve pin and closing upon an upper barrel bevel.

A flapper element for a check valve comprises at least one mounting lug configured to receive a shaft for rotation relative thereto and having a row of teeth for engaging complementary teeth on a mounting lug of a similar flapper element. The complementary teeth tie the rotation of the two flapper elements.

A prosthetic heart valve having a pair of cooperating leaflets mounted in a valve body to alternate between an open position where the flow of blood in a downstream direction is permitted and a closed position where the flow of blood in the reverse direction is counteracted. Pivot member sets at diametrically opposite sides of each leaflet guide the leaflets moving between the open and closed positions, each set including an ear or a recess cooperating with an associated cavity or knob of an interior surface of the valve body. Each ear or recess bounds at least one leaflet passageway through that ear or recess and located spaced from upstream and downstream ends of the ear for allowing flow through that ear and the associated cavity, or through that recess, when the leaflets are in the closed positions.

A flapper check valve includes a valve seat body. Two flapper valve portions are each mounted on their own shaft to the valve seat body, and pivotable between open and closed positions. The flapper valve portions pivot in a common rotational direction to the open position and to the closed position. A fluid systems is also disclosed.

A flapper check valve includes a valve seat body. Two flapper valve portions are each mounted on their own shaft to the valve seat body, and pivotable between open and closed positions. The flapper valve portions pivot in a common rotational direction to the open position and to the closed position. A fluid systems is also disclosed.

In accordance with at least one aspect of this disclosure, a system includes a first wire configured to electrically connect a valve stop to a voltage source, a second wire configured to connect a valve pin to a negative terminal of the voltage source, such that the valve stop, and a valve flap operatively connected to the valve pin are configured to create a closed valve circuit when the valve flap is in a fully open position with the valve flap contacting the valve stop, and an open valve circuit when the valve flap is not in the fully open position. A meter is operatively connected to measure an electrical characteristic of the valve circuit to determine when the valve flap is in the fully open position based on an open/closed status of the valve circuit.