A fan includes a stationary portion, a rotating portion, and an impeller arranged to rotate about a central axis together with the rotating portion to produce an axial air current. The rotating portion includes a rotor holder. The impeller includes a cup portion arranged to cover the rotor holder and a plurality of blades arranged on an outer circumference of the cup portion. The cup portion includes a cup cover portion arranged to extend radially outward from the central axis; a cup cylindrical portion being substantially cylindrical in shape, and arranged to extend in an axial direction from an outer edge portion of the cup cover portion; and a cup through hole arranged to extend through the cup portion at a position overlapping with a portion or boundary between the cup cover portion and the cup cylindrical portion.

A fan hub balancing structure includes a hub main body. The hub main body has a top section, a circumferential section extending from the circumference of the top section and a lip section. The lip section is connected with the lower end of the circumferential section. The lip section has at least one residual weight section on the lip section. After the residual weight section is removed from the lip section, a balancing section is formed on the lip section. The balancing structure is able to provide a balancing effect for the hub main body and facilitate the processing of the hub main body.

A vacuum pump and a washer which can reduce vibration of a rotor and the rotor which can reduce the vibration are provided. When an inertia moment ratio which is a ratio between the inertia moment around a z-axis and the inertia moment around an x-axis or a y-axis is larger than 1, a natural frequency ω.sub.2 does not match a rotational frequency Ω.sub.z but goes away from that. When the natural frequency ω.sub.2 matches the rotational frequency Ω.sub.z, the rotor vibrates and thus, a fatigue failure occurs in a rotor blade. When the rotor is to be made larger in a radial direction of a rotating shaft, a value of the inertia moment ratio is set to a value larger than 1.

The driving device for providing assisted ventilation comprises an air inlet (15), an impeller (7) provided with blades (8) rotatably driven by a motor (6), and an air outlet (5), the rotation of said impeller (7) being caused by the air circulation through a duct (4) from the air inlet (15) to the air outlet (5), wherein said blades (8) of the impeller (7) are flexible, vibrating at least one of its ends by the thrust caused by said circulating air.

It reduces noise to improve user comfort.

A turbomachine assembly includes a casing, first and second rotors, and a damper. The first rotor includes a disk and blades and is movable in rotation relative to the casing. The second rotor is movable relative to the casing around a longitudinal axis. The damper damps a movement of the first rotor relative to the second rotor. The damper includes first to third parts. The first part bears on the first rotor in a first area extending over a first angular sector around the longitudinal axis and applies a first centrifugal force on the first rotor. The second part bears on the first rotor in a second area that is smaller than the first angular sector and extends over a second angular sector around the longitudinal axis. The third part bears on the second rotor and applies a second centrifugal force on the second rotor.

An annular parts assembly for mounting onto a shaft of an aircraft engine is provided. The assembly comprises a first annular body having a surface defining a plurality of pulling features extending from a remainder of the surface, the pulling features circumferentially spaced apart on the surface. The assembly comprises a second annular body defining a balancing ring, the balancing ring concentric with the first annular body, the balancing ring having a plurality of protrusions and circumferential spaces between adjacent ones of the plurality of protrusions, the circumferential spaces accommodating the pulling features such that the pulling features of the first annular body and the protrusions intercalate.

A rotating assembly for a gas turbine engine has a balancing ring mounted to a first rotating component having a rotating unbalance about an axis of rotation. The ring is clocked at a circumferential position about the axis to counteract the rotating unbalance. A spacer is axially abutted against the first rotating component to set an axial position of the first rotating component relative to a second rotating component. The balancing ring is locked against rotation relative to the first rotating component in its circumferential position by the dual use spacer.

A vacuum pump includes: a particle transferring portion that functions as a means for transferring a particle in an exhaust direction of the gas particle by increasing or reducing a height of an upstream end of at least a part of rotor blades among a plurality of rotor blades that constitute an uppermost exhaust stage to realize a stepped structure in which heights of the upstream ends differ as the uppermost exhaust stage as a whole, and in a rotating body constituted by the plurality of rotor blades, the particle transferring portion, and a cylindrical portion that supports the plurality of rotor blades, an imbalance created with respect to the rotating body as a whole by a presence of a rotor blade of which a height of the upstream end has become higher than other rotor blades due to the stepped structure has been corrected.

A vacuum pump comprises: a rotary body including a rotor blade and a rotor shaft; a case rotatably housing the rotary body; a motor configured to drive the rotor shaft of the rotary body; a bearing arranged at an end portion of the rotor shaft; and at least three balance correction portions including a first balance correction portion provided on one end side of the rotary body in an axial direction, a second balance correction portion provided on the other end side of the rotary body in the axial direction, and a third balance correction portion provided between the first balance correction portion and the second balance correction portion. Balance correction by an n-plane method, where n≥3, is available such that any of the three balance correction portions is accessible from an outside of the case.

A noise reduction method of a ventilator, comprising the following steps: S1 starting a ventilator and imputing a required wind pressure d at a man-machine interface, and then sending a signal to an actuator through a processor, and adjusting a first blade automatically to a maximum adjustable angle state a′° through the actuator and a second blade to a minimum adjustable angle state b°; S2 regulating a revolution speed, when a wind pressure is d, feeding back a revolution speed c, a conducting noise e.sub.1 and a radiated noise f.sub.1 to the processor through an acquisition device, and after the processor receives a revolution speed information, sending a command to lock the revolution speed to the actuator through the processor. The present disclosure can effectively solve the poor noise reduction function of the present noise reduction hoop, and can effectively reduce the cost and simplify the installation process.