Spindle clamping device for machine tool

摘要

A machine tool is provided with a spindle clamping device for clamping a spindle assembly supported by a spindle head and composed of an outer spindle rotatably supported by the spindle head and an inner spindle disposed inside the outer spindle to be reciprocal along an axial direction thereof. The inner spindle is inserted into an inner hollow portion of the outer spindle so that a space is formed between an inner peripheral surface of the outer spindle and an outer peripheral surface of the inner spindle. The spindle clamping device comprises a pressure applying member such as a pair of pistons or oil ring disposed in the space between the outer and inner spindles for applying a pressure in an axial direction of the outer and inner spindles. The pressure applying member is provided with an oil chamber, and a pair of clamp rings are disposed in the space axially outside the pressure applying member. Each of the paired clamp rings comprises inner and outer ring elements having tapered surfaces slidably contacting each other. Spring members are disposed in the space axially outside the clamp rings, respectively, for urging the outer ring elements inwardly, and a static pressure pocket is formed in a contacting portion of the spindle head supporting the inner spindle wherein pressurized oil and air is supplied into the oil chamber through the static pressure pocket.