Floating cushion sub

Abstract From the Canadian patent

A cushion sub for absorbing both axial and torsional vibration in modern drilling techniques. The cushion sub includes an outer casing connectable at one end to a section of a drill string, usually the upper section being actually the output of the rotary drive and an inner, piston reciprocally mounted in a cylinder within the casing the piston has a shaft projecting, from the other end of the casing connectable to another section of the drill string. The cylinder includes a first cushion device at opposite ends thereof for engagement by the piston to absorb axial vibrations and thereby prevent their transmission between the piston and the cylinder. A spline type connection prevents …