Damper blade

Claim 1

A rigid blade for use in a fluid damper, said blade being made by bending a one-piece sheet metal blank into an elongate U-section channel member and bringing the longitudinal edges of the channel together to form a trailing edge of the blade, wherein said longitudinal edges of the channel are of castellated form throughout their length with castellations on one longitudinal edge of said blank being so formed that the gaps between adjacent castellations are in alignment transversely of the blank with the castellations on the other longitudinal edge and are of the same length as the castellations on said other longitudinal edge whereby those edges interlock when brought together to prevent relative movement between the edges, said castellations being first bent into a hook formation whereby U-shaped grooves are formed in the castellations to receive a reinforcing locking rod extending the full length of said blade trailing edge, said hooked castellations thereafter being rolled over to embrace the rod very tightly in order to increase the resistance of the blade to bending and twisting stresses and to avoid the necessity for any welding at the blade trailing edge, the rod thereby being hidden from sight apart from its ends.