Elastomeric helicopter rotor head with dynamic and static blade coning and droop stops

Claim 1

An articulated helicopter rotor including: A. a rotor hub adapted to be mounted for rotation, B. at least one helicopter blade projecting substantially radially from said hub and having a pitch change axis, a leadlag axis and a flapping axis intersecting at a common point, C. means supporting said blade from said hub for universal motion about the intersection of said axes, D. a ring member mounted on said blade for rotation relative thereto about said pitch change axis and at a station radially outward of said point of intersection and having: 1. a conically shaped surface positioned to move toward said hub as said blade droops downwardly, E. a droop stop member including: 1. a frame means connected to said hub, 2. dynamic droop stop means supported by said frame means and having a barrel shaped surface concentric with respect to the lead-lag axis and positioned and shaped to matingly engage said conically shaped surface of said ring member when said blade droops downwardly to a selected first angle, and so that said matingly engaged surfaces will continue in mating engagement without affecting blade pitch or downward droop angle as the blade moves in lead-lag motion about the lead-lag axis, due to the continuous rolling contact between said matingly engaged surfaces of said rotatable ring member and said dynamic droop stop means, 3. static droop stop means loosely pivotable on and supported from said frame means or dynamic droop stop means for movement with respect thereto and including: a. a cam member having a conically shaped surface and positionable to matingly engage said conically shaped surface of said ring member when said blade droops downwardly to a second selected angle, and being concentric with respect to the lead-lag axis so that said matingly engaged surfaces of said rotatable ring member and said cam surface remain in mating engagement without affecting blade pitch, blade downward flap or droop angle, and without preventing independent blade pitch change as said blade moves in leadlag motion about said lead-lag axis, due to the continuous rolling contact established between said matingly engaged surfaces of said ring member and said cam surface, b. a barrel shaped surface corresponding in shape to said barrel shaped surface of said dynamic droop stop means, c. counterweight means connected to said cam member so that when said blade is operating at low rotational speed or is stopped, said conically shaped surface of said cam member matingly engages the conically shaped surface of said rotatable ring member when said blade and rotatable ring member flap downwardly to said selected first angle so as to, due to the loose pivot connection between said static droop stop means and said frame means, or dynamic droop stop means to thereby cause said barrel shaped surface of said cam member to engage said barrel shaped surface of said dynamic droop stop means in mating engagement so that blade loading is imparted through said static droop stop means and said dynamic droop stop means and said frame means to said hub, and so that when rotor speed increases, said counterweight means will cause said cam member to move in response to centrifugal force from between said conically shaped surfaces of said ring member and said dynamic droop stop means to permit a greater degree of downward blade droop motion to a second selected angle before said conically shaped surfaces of said ring member and said dynamic droop stop means barrel shaped surface matingly engage to impart blade loads through said dynamic droop stop means and said frame means to said hub.