Torsional dampers

Claim 1

A multi-stage torsional damper comprising at least two coaxial parts mounted so as to be rotatable relative to one another within pre-determined limits of relative angular movement, first and second torsional damping stages operatively disposed between said coaxial parts, said second stage torsional damping means comprising a plurality of helical springs extending in a substantially tangential direction relative to a circumference of the damper and disposed between said coaxial parts in the circumferential direction, each of said springs being partially housed, without circumferential clearance in a rest configuration of the damper, in an opening formed for this purpose in a first of said coaxial parts, and partially housed with circumferential clearance in said rest configuration, in an opening formed for this purpose in a second of said coaxial parts, said first stage torsional damping means comprising a peg of elastic material arranged inside at least one of said helical springs and housed in an associated opening in said second coaxial part and a bush coaxial with said spring accommodating said peg and being circumferentially slidable relative thereto; and constricting means disposed between said elastic material peg and said bush to impede movement of said peg within said bush and to return said peg to a substantially central rest position after such movement, said bush being held in engagement with said first coaxial part during an initial range of relative angular displacement of said coaxial parts while being slidable relative to said peg to effect first stage damping.