Pitch system for a wind turbine blade

Abstract

A pitch actuator for a wind turbine pitch system, the pitch actuator having an actuator rod, a drive end of which is defined by a clevis fork arrangement having first fork member and a second fork member that extend in a direction along a rod axis and terminate at a tip end. The first and second fork members define respective clevis openings for receiving a clevis pin therethrough, said clevis openings each having an opening perimeter profile comprising: a first perimeter section defined by a leading circular arc that is centred on the rod axis and oriented in the direction of the tip end of the fork members, the circular arc defining a nominal radius and a central angle of less than 120 degrees, and second and third flared perimeter sections that flank respective sides of the first perimeter section, each of which define an enlarged clearance zone with respect to at least part of an imaginary circle defined by the nominal radius of the first perimeter section. A benefit of the invention is that the enlarged clearance zones defined by the flared perimeter sections create an area where there is no contact between the perimeter of the openings and the outer surface of the clevis pin. This provides a stress relieving function since deformation of the openings in use, due to force applied along the axis of the actuator rod, does not create a point of stress combined with sliding or rubbing movement with the sides of the clevis pin, thereby reducing wear and fatigue. The invention extends to a pitch system including such a pitch actuator and a wind turbine incorporating such a pitch system.