Machine tool

Abstract

A machine tool is provided in which a movable member guided by a hydrostatic slideway is held in a predetermined attitude. A vertical machining center as the machine tool includes a spindle head supported on a front face of a column in a vertically movable manner. A hydrostatic slideway for guiding the spindle head includes a slide rail provided on the spindle head and a slide guide provided on the front face of the column. A pocket is provided in a lower end portion of a slideway of the slide guide on the side of the column. Pressurized oil is supplied into the pocket at a pressure which is gradually increased according to a downward movement distance of the spindle head from the uppermost position.

What is claimed is:  
     
         1 . A machine tool comprising a hydrostatic slideway for guiding a movable member for movement of the movable member, the hydrostatic slideway comprising opposed slideways between which a pressurized fluid is supplied, one of the slideways of the hydrostatic slideway having an independent pocket provided in one of opposite end portions thereof with respect to a sliding direction, wherein the pressurized fluid is supplied into the pocket at a pressure which is continuously varied according to a movement distance of the movable member from a reference position.  
     
     
         2 . A machine tool comprising a hydrostatic slideway for guiding a spindle head for up and down movement of the spindle head, the hydrostatic slideway comprising opposed slideways between which a pressurized fluid is supplied, wherein one of the slideways of the hydrostatic slideway has an independent pocket provided in one of lower and upper end portions thereof, wherein the pressurized fluid is supplied into the pocket at a pressure which is gradually increased according to a downward movement distance of the spindle head.  
     
     
         3 . A machine tool as set forth in  claim 2 , wherein a pressure increase of the pressurized fluid supplied into the pocket is varied linearly with respect to the downward movement distance of the spindle head.  
     
     
         4 . A machine tool as set forth in  claim 2 , wherein a pressure increase of the pressurized fluid supplied into the pocket is varied nonlinearly with respect to the downward movement distance of the spindle head.  
     
     
         5 . A machine tool as set forth in  claim 2 , wherein a pressure increase of the pressurized fluid supplied into the pocket is varied quadratically with respect to the downward movement distance of the spindle head.  
     
     
         6 . A machine tool as set forth in  claim 2 , wherein a pressure increase of the pressurized fluid supplied into the pocket is varied logarithmically with respect to the downward movement distance of the spindle head.