US 4,180,372 AGranted

Wind rotor automatic air brake

AssigneeGrumman Corporation

InventorJoseph Lippert, Jr.

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Abstract

A spring-loaded pivoting end plate that is hinged such that it is deployed by centrifugal force into the airstream to thereby act as an aerodynamic brake for wind turbines in overspeed conditions. The brake has a stationary portion fixed on the tip of the turbine rotor and a pivoting portion hinged for movement with respect to the fixed portion. The longitudinal centerline of the brake coincides with the chord line of the turbine blade and the pivoting movement is about a hinge axis that is normal to the rotational plane of the turbine. The planform of the brake has a low aspect ratio shape with the ratio of the fore and aft chordwise length to the width being one or greater. The edges of the brake in the normal running condition extend beyond the contour of the turbine blade to serve as an end plate such that the aerodynamic efficiency of the blade is improved thereby.

Claims13

Dependent claims

In a wind-driven motor having a rotor supported for rotation about an axis, an aerodynamic brake mounted on the tip of each blade of said rotor, each of said brakes comprising:

a brake plate pivotally attached to the tip of said blade for relative pivotal deployment therewith;
means responsive to centrifugal forces resulting from overspeed conditions of said rotor for pivotally deploying said plate between a stowed position in which the planform surfaces thereof are substantially parallel to the circumference generated by said blade tip to various deployed positions which extend greater surface areas of said plate into the relative airstream to create levels of drag proportional to said centrifugal forces whereby the rotational speed of said rotor is affected thereby such that the rotor overspeed condition is remedied, said means responsive to centrifugal forces comprising a brake plate weight distribution in which the greater mass is forward of the pivot hinge line of said plate and in the direction of rotation of said rotor blade;
and
means for restoring said plate from said deployed positions to said stowed position in response to reductions in said centrifugal forces.

1 more element

Dependencies are inferred from the claim text.