Fluid reaction surfaces (i.e. – impellers) – Articulated – resiliently mounted or self-shifting impeller... – Including movement limit stop or damping means
Reexamination Certificate
2000-04-05
2001-10-30
Ryznic, John E. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Articulated, resiliently mounted or self-shifting impeller...
Including movement limit stop or damping means
Reexamination Certificate
active
06309182
ABSTRACT:
TECHNICAL FIELD
This invention relates to helicopter rotor hub assemblies, and more particularly to a droop stop mechanism for such a helicopter rotor hub assembly.
BACKGROUND OF THE INVENTION
Modern rotorcraft, such as helicopters, include a plurality of rotor blades coupled to a central rotor hub assembly. When the rotor hub assembly stops or rotates at low speed, the lift and centrifugal forces on the rotor blades are less than the weight and stiffness of the blades. As such, the blades tend to droop downwardly. When the rotor hub assembly rotates at normal operating speeds, the lift and centrifugal forces overcome the weight and add to the stiffness of the blades thereby eliminating much of the droop.
To control the droop of the rotor blades in both the static and dynamic states just described, most helicopters are equipped with upper and lower stops. Such upper and lower stops are sometimes referred to in the art as droop stop mechanisms. Prior art droop stop mechanisms have a significant drawback due to their complexity. For example, the droop stop mechanism used in the CH-47 rotor includes approximately fourteen components. The droop stop mechanism used in the AH-64 rotor includes approximately nine components. Such complex designs increase production costs due to piece-part pricing, add weight to the overall structure, and are difficult to install and maintain.
In view of the foregoing, it would be desirable to provide a droop stop mechanism for a rotor hub assembly having a minimum number of components while also providing multipositional stops for controlling both static and dynamic droop.
SUMMARY OF THE INVENTION
In preferred embodiments, the present invention is directed towards a droop stop mechanism. In particular, the preferred embodiment of the present invention provides advantages over prior art techniques including simplified construction, lower piece-part pricing, reduced weight, and ease of installation and maintenance. Advantageously, the preferred embodiment of the present invention provides a multipositional stop for controlling droop in both static and dynamic states.
In one preferred embodiment, the droop stop mechanism of the present invention includes a U-shaped pendulum pivotal between a static mode position and a dynamic mode position. The U-shaped pendulum includes a pair of spaced apart, triangularly shaped arms interconnected at their distal ends by a generally rectangularly shaped, stepped base. The proximal end of each of the arms is pivotally coupled to the body of a rotor hub assembly by a pin. The stepped base includes a first striker portion for abuttingly engaging a tie bar housing of a rotor blade assembly in the static mode position. The stepped base also includes a second striker portion which is axially spaced apart from the proximal ends of the arms to a lesser extent than the first striker portion. The second striker portion abuttingly engages the tie bar housing of the rotor blade assembly in the dynamic mode position.
In another preferred embodiment of the present invention, an axially aligned stop plate is coupled between the arms of the U-shaped pendulum adjacent their proximal ends. A cylindrical spring seat is coupled to the rotor hub body opposite the stop plate. A coil spring is coupled between the spring seat and the stop plate. The bias of the spring urges the pendulum between the static mode position and the dynamic mode position as centrifugal forces acting on the pendulum change. The spring seat doubles as a stop by abuttingly engaging the stop plate when the pendulum is in the dynamic mode position.
In yet another preferred embodiment of the present invention, a striker plate is interposed between the stepped base of the pendulum and the tie bar housing of the rotor blade assembly for increasing durability by serving as a wear protector.
REFERENCES:
patent: 2471681 (1949-05-01), Gluhareff
patent: 3778189 (1973-12-01), Ferris
patent: 3853426 (1974-12-01), Rybicki
patent: 3932059 (1976-01-01), Rybicki
patent: 4368006 (1983-01-01), Ferris et al.
patent: 4419051 (1983-12-01), DeRosa
patent: 4652210 (1987-03-01), Leman et al.
patent: 4808075 (1989-02-01), Pariani et al.
patent: 5007799 (1991-04-01), Mouille et al.
patent: 5951251 (1999-09-01), Mondet et al.
patent: 5951252 (1999-09-01), Muylaert
patent: 491164 (1954-02-01), None
Harness & Dickey & Pierce P.L.C.
Ryznic John E.
The Boeing Company
LandOfFree
Helicopter rotor droop stop mechanism does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Helicopter rotor droop stop mechanism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Helicopter rotor droop stop mechanism will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587115