A friction device for a torsional vibration damper includes an axis of rotation, an input side with a first disc and a second disc, and an output side between the first disc and the second disc and rotatable relative to the input side. The output side has a first friction disc, a second friction disc, and a spring element between the first friction disc and the second friction disc. The spring element has first, second and third contact regions. At a first angle of rotation between the input side and the output side, an axial contact force between the first friction disc and the second friction disc is transmittable via the first contact region and the third contact region. At a second angle of rotation, different than the first angle of rotation, the axial contact force is transmittable via the second contact region and the third contact region.

An orifice plate includes a wear-resistant inner diameter surface, an outer diameter surface, a first side surface extending between the wear-resistant inner diameter surface and the outer diameter surface, and a second side surface extending between the wear-resistant inner diameter surface and the outer diameter surface, the second side surface disposed opposite the orifice plate from the first side surface. The orifice plate may comprise a body portion comprising a first material. The wear-resistant inner diameter surface may comprise a second, wear-resistant material.

A rotor assembly has a drive shaft and a bladed rotor mounted to the drive shaft for rotation therewith. A dampening material is bonded to the rotor at a location where there is torsional strain energy present. Shear forces in the damping material are used to convert the torsional strain energy into heat energy, thereby providing torsional vibration damping.

A rotor assembly has a drive shaft and a bladed rotor mounted to the drive shaft for rotation therewith. A dampening material is bonded to the rotor at a location where there is torsional strain energy present. Shear forces in the damping material are used to convert the torsional strain energy into heat energy, thereby providing torsional vibration damping.

A dampener for an exit device may be disposed between a portion of an exit device actuator and an exit device chassis so that the dampener dampens vibrations to reduce noise of the exit device and/or inhibit unintentional movement of the actuator to an actuated position. The dampener may be composed at least partially of a viscoelastic material.

An orifice plate includes a wear-resistant inner diameter surface, an outer diameter surface, a first side surface extending between the wear-resistant inner diameter surface and the outer diameter surface, and a second side surface extending between the wear-resistant inner diameter surface and the outer diameter surface, the second side surface disposed opposite the orifice plate from the first side surface. The orifice plate may comprise a body portion comprising a first material. The wear-resistant inner diameter surface may comprise a second, wear-resistant material.

A rotary damper comprising a fixed structure, a rotor configured to rotate about an axis (R-R), and two opposing bellows. The bellows each extend between the rotor and the fixed structure and are attached thereto. The bellows each define a chamber for holding hydraulic fluid and are configured to expand and contract as the rotor rotates. The damper further comprises a damping orifice extending through the rotor or the fixed structure. The bellows are sealingly engaged around the damping orifice and the damping orifice permits fluid communication between the chambers defined by the bellows.

A linear motion assembly having a static coefficient of friction, S, as measured between an inner component and an outer component, and a dynamic coefficient of friction, .sub.D, as measured between the inner component and the outer component, wherein .sub.S/.sub.D is less than 2.0, such as less than 1.9, less than 1.8, less than 1.7, or even less than 1.6.

A damper assembly includes a main tube disposed on a center axis and defines a fluid chamber for containing a working fluid. A main piston is disposed in the fluid chamber dividing the fluid chamber into a rebound and a compression chamber. A piston rod is attached to the main piston for moving the main piston between a compression stroke and a rebound stroke. An additional piston is attached to the piston rod adjacent to the main piston. The additional piston includes a body having an upper and a lower member defining a groove. A sealing ring is disposed in the groove and being radially expandable in response to a working fluid pressure. The sealing ring includes at least one annular collar extending outwardly from the sealing ring for forming a locking engagement with the upper and lower members to limit the radial expansion of the sealing ring.

A dampener for an exit device may be disposed between a portion of an exit device actuator and an exit device chassis so that the dampener dampens vibrations to reduce noise of the exit device and/or inhibit unintentional movement of the actuator to an actuated position. The dampener may be composed at least partially of a viscoelastic material.