Automatic tool change mechanism for machine tool

Claim 1

A MACHINE TOOL FOR AUTOMATICALLY PERFORMING A SERIES OF SUCCESSIVE MACHINING OPERATIONS WITH DIFFERENT CUTTING TOOLS COMPRISING A TOOL HEAD, A TURRET ROTATABLY SUPPORTED ON SAID TOOL HEAD, A PAIR OF SPINDLES JOURNALED FOR ROTATION IN SAID TURRET WITH THEIR AXES DISPOSED IN SPACED, PARALLEL RELATION AND NORMAL TO THE AXIS OF ROTATION OF SAID TURRET BUT OFFSET BY EQUAL AMOUNTS ON OPPOSITE SIDES THEREOF, POWER DRAW BAR MEANS ASSOCIATED WITH THE REAR END OF EACH OF SAID SPINDLES FOR SECURING A CUTTING TOOL IN THE FORWARD END THEREOF, MEANS FOR INDEXING SAID TURRET ON SAID HEAD MOVE ONE SPINDLE THEREON FROM AN OPERATING STATION TO A TOOL CHANGE STATION AND THE OTHER SPINDLE THEREON FROM THE TOOL CHANGES STATION TO THE OPERATING STATION, A TOOL DRUM SUPPORTED FOR ROTATION ON SAID TOOL HEAD, A PLURALITY OF RECEPTACLES DISTRIBUTED AROUND THE PERIPHERY OF THE DRUM FOR HOLDING THE DIFFERENT CUTTING TOOLS, SELECTION MEANS FOR ROTATING THE DRUM TO BRING A SELECTED RECEPTACLE INTO A TOOL CHANGES POSITION, MEANS TO TRANSFER A CUTTING TOOL FROM THE SPINDLE AT THE TOOL CHANGE STATION TO ITS RECEPTACLE IN SAID TOOL DRUM AND VICE VERSA, AND MEANS FOR CONTROLLING THE OPERATION OF SAID SELECTION MEANS AND SAID TRANSFER MEANS TO CAUSE THE OLD TOOL CARRIED BY THE SPINDLE AT THE TOOL CHANGE STATION TO BE RETURNED TO SAID TOOL DRUM AND REPLACED WITH A NEW TOOL THEREFROM WHILE A MACHINING OPERATION IS BEING PERFORMED BY THE TOOL IN THE SPINDLE AT THE OPERATING STATION.