Patent ID: 6663548
Filing Date: 2003-12-16
Classification: B23B,Y10T

Abstract:
A spindle unit for a numerical controlled machine tool having a spindle housing comprising:a spindle having a rotational axis and rotatably supported in said spindle housing; a tool receiving bore formed directly in the forward end portion of said spindle, the center axis of said tool receiving bore extending along the line of the rotational axis of said spindle; one or more pressure chambers disposed within the forward end portion of said spindle and around said tool receiving bore in spaced relationship from said tool receiving bore by a thin wall, said thin wall forming a sleeve within said tool receiving bore being elastically deformable in a radial direction of said spindle, each said pressure chamber being filled with working fluid to expand said thin wall; a working fluid passage formed entirely within said spindle and in fluid communication with said one or more pressure chambers; and a pressure adjusting device arranged in the rear portion of said spindle unit and connected to said pressure chamber through said working fluid passage, said pressure adjusting device adjustably changing the pressure of the working fluid within said pressure chamber so that said pressure adjusting device can elastically deform said thin wall to enlarge or reduce said tool receiving bore in radius, thereby holding or releasing the tool inserted into said tool receiving bore.