Multi-spindle head-replacing machine tool

Abstract

In multi-spindle head-replacing type machine tool comprising a machining unit disposed on a base for advancing and retreating movements between an original position and a machining position, a first annular guide rail including a movable rail integral with the machining unit and a stationary rail to surround the machining unit which is located in the original position, a second annular guide rail disposed concentrically with and at a place axially offset from the first guide rail, a plurality of multi-spindle heads travellably carried on each of the first and second guide rails, first and second index mechanisms releasably connected respectively to the multi-spindle heads on the first and second guide rails for driving such multi-spindle heads for angular displacement, and an elevator mechanism disposed sideways from the first and second guide rails at a place offset from the movable rail for providing replacement of the multi-spindle heads between the first and second guide rails, a part of the stationary rail of the first guide rail and a part of the second guide rail are divided as lift rails in a circular arc at a place corresponding to the elevator mechanism, respectively, and the elevator mechanism comprises an elevator connected to each of the lift rails of the first and second guide rails, and lift-drive means connected to the elevator which is to be raised and lowered between the first and second guide rails.