Abstract:
A machine spindle includes a rotatable casing in which a clamping device is mounted. The clamping device includes a drawbar for securing a cutting tool. The drawbar is axially displaced by a gas spring which includes a chamber in which a lubricant-containing gas medium is confined. A piston includes a head slidable within a cylindrical upper portion of the chamber, and a rod extending through a lower portion of the chamber and connected to the drawbar. The lower portion of the chamber is non-cylindrical and widens upwardly to promote the upward travel of lubricant toward the piston and upper seals under the effects of centrifugal force during rotation of the spindle.