Floating cushion sub

Abstract From the Canadian patent

A floating cushion sub for connection to the rotary power head of a drill rig has a mandrel section connectable to a drill string and an outer housing section connectable to the power head. The mandrel and the housing have mating axi-, ally extending splines permitting relative axial movement while also transmitting torque from the power head to the mandrel. Mandrel axial movement is limited by a cap member and by an internal shoulder in the housing. A resilient cushion adjacent the shoulder dampens vibrations when the mandrel and housing are compressed together and a similar cushion adjacent the cap member dampens vibrations when the mandrel and housing are at full extension. The axial …