Devices, systems, and methods for damping vibration of a structural component or power-transmission shafts are disclosed. Damping devices, systems, and methods utilize a lightweight damping device, which is targeted at reducing the resonant amplitude of the first several beaming modes and/or torsional modes of bending a structural component comprising a hollow shaft or strut. The damping device includes a stiff concentric tube with damping elements disposed at each end. The device is inserted within the original structural component or shaft and attached thereto. When the primary shaft undergoes bending due to modal characteristics, the damping elements react to dissipate energy, which effectively reduces the resonant amplitude.

A structure for preventing vibration of a solenoid valve includes: a plunger which opens and closes a flow path by moving inside the solenoid valve; a yoke attached to an inner surface of a valve core; and a friction member disposed along an outer circumferential surface of the plunger between the plunger and the yoke, in which the friction member presses the yoke between the yoke and the plunger.

A damper includes a piston provided with a rod, and a housing storing the piston, and generates a braking force by an operation of the piston. The piston is provided with a seal member relative to an inner wall of the housing; and a slider provided slidably relative to the piston, and contacting the inner wall of the housing with a predetermined frictional force. When the braking force is generated, the slider presses against the seal member, and a portion contacting the inner wall of the housing in the seal member deforms outwardly toward the housing.

A connector for connecting two structural components. The connector has a casing engaged and to move with a first of said structural components. The casing is of an elongate constant cross section interior within which is operative in a frictional sliding engagement a spring and damper assembly. This comprising of at least one damper to move with a second of said structural components and contacting the interior of the casing and able to slide in frictional contact with the casing. A spring is able to be elastically deformed by and between the damper and the casing when the damper and casing are in relative motion to bias the two structural components towards their initial relative position.

A damping device has a pin member inserted slidably in a cylindrical case member. The bottom of the case member has: a hole forming section in which an insertion hole is formed; and a slit for allowing the hole forming section to be expanded and deformed. The outer peripheral surface of the pin member and/or the inner peripheral surface of the hole forming section has a tapered section tilted relative to the axial direction. The movement of the pin member of being pressed into the insertion hole from the inside causes the outer peripheral surface of the pin member and the inner peripheral surface of the hole forming section to slide on each other along the tapered section, and as a result, the insertion hole is expanded.

An improved recoil reduction system comprises a forward body, a friction spring, a rear body, a bolt, and, optionally, a bumper. When in forward battery, the said friction spring is compressed to a preloaded operating point by the bolt. In embodiments, when a weapon equipped with the improved recoil reduction system is fired, the front body is impacted by the bolt carrier group of the weapon and the rear body moves aft and strikes the rear of the shoulder stock of the weapon, compressing the friction spring. During compression, the tapered mating surfaces of the friction spring generate friction and thereby dissipate the energy generated from firing the weapon in the form of heat, thus reducing the felt recoil of the weapon.

A damper includes a piston provided with a rod, and a housing storing the piston, and generates a braking force by an operation of the piston. The piston is provided with a seal member relative to an inner wall of the housing; and a slider provided slidably relative to the piston, and contacting the inner wall of the housing with a predetermined frictional force. When the braking force is generated, the slider presses against the seal member, and a portion contacting the inner wall of the housing in the seal member deforms outwardly toward the housing.