Tool turret for a machine tool, in particular a lathe

Tool turret for a machine tool, in particular a lathe, with a turret head mounted on a turret head carrier for rotation about a turret axis and having a plurality of tool stations, said turret head having at each of a plurality of its tool stations a receiving means for the insertion of a tool holder for a tool adapted to be rotatably driven, said tool holder having a tool spindle, with at least three annular locking elements concentric to the turret axis for locking the turret head against rotation about the turret axis in relation to the turret head carrier, a first locking element being securely connected to the turret head carrier and a second locking element to the turret head, a third locking element being displaceable in the direction of the turret axis between an operative and an inoperative position and the three locking elements being designed such that in each angular position of the turret head in which one of its tool stations is located in a working position the third locking element being in its operative position engages positively in the first and second locking elements such that the turret head is non-rotatable relative to the turret head carrier, with a multifunctional shaft rotatably mounted on the turret head carrier and drivable by a motor provided both for rotating the turret head and driving a tool spindle, an indexing shaft rotatably mounted on the turret head carrier for rotating the turret head, a tool drive shaft drivable by the multifunctional shaft, said tool drive shaft being rotatably mounted in a bearing stationary in relation to the turret head carrier and the turret head being rotatable about the turret axis in relation to said tool drive shaft, and with an actuatable turret indexing coupling between the multifunctional shaft and the indexing shaft, characterized in that the tool drive shaft (38) is arranged such that it defines a working position for the tool stations (28a-28l), that a tool drive coupling (54) is provided for establishing a rotary drive connection between the tool drive shaft (38) and the tool spindle of a tool holder (30) located in working position, said tool drive coupling having at least two coupling elements (50, 52) separable from one another, a first coupling element (50) being in rotary drive connection with the tool drive shaft (38) and the second coupling element (52) being arranged on the tool spindle, wherein the two coupling elements (50, 52) are designed such that by rotating the turret head (26) about the turret axis (24) the second coupling element (52) of a tool spindle located in working position is releasable from the first coupling element (50) and the second coupling element (52) of a tool spindle located out of the working position is adapted to be brought into engagement with the first coupling element (50) by displacing the tool spindle about the turret axis (24) into the working position, that the turret head (26) is rotatable in relation to a tool spindle blocking element (100) concentric to the turret axis (24), a tool spindle not located in working position being secured against rotation about the spindle axis by said blocking element, that an actuatable separation coupling (87', 89') is provided between the multifunctional shaft (21') and the tool drive shaft (38), and that a drive shaft blocking coupling (86', 88') with two coupling halves is provided for locking the tool drive shaft (38) against rotation when the turret head (26) is unlocked, a first half (88') of said blocking coupling being non-rotatably connected to the turret head carrier (10) and the second half (86') being non-rotatably connected to the tool drive shaft (38).