Method and apparatus for changing tools in an automated machine tool

Apparatus for inserting a first end of an elongated tool of unknown length into a working unit so that a predetermined length of the tool extends from the unit, comprising:

• a gripper device for receiving a second end of the tool and selectively gripping the tool with a relatively high gripping force or a relatively low gripping force;
• means for inserting the second end of the tool in said gripper device so that the first end of the tool extends from the gripper device, with a length of the tool received within the gripper device which is less than the predetermined length;
• means for aligning the gripper device with the working unit;
• means for effecting relative movement between the gripper device and the working unit to insert the first end of the tool into the working unit with said tool being gripped by said relatively high gripping force of said gripper device;
• means for gripping the tool by the working unit and reducing the gripping pressure of the gripper device so that further relative movement of the gripper and the working unit causes sliding movement of the tool in the gripper device;
• means for effecting further relative movement between the gripper device and the working unit to reduce the distance therebetween to cause the tool to slide within the gripper device until said length of the tool received within the gripper device is substantially equal to said predetermined length;
• means of releasing the tool gripping of the tool by the working unit and increasing the gripping pressure of the gripper device;
• and
• means for effecting further relative movement between the gripper device and the working unit to bring the gripper device and the working unit substantially adjacent each other to insert said tool into said working unit with said predetermined length extending from the working unit.

An improved gripper apparatus for an automated tool changer system, comprising:

• a plurality of grip jaws each characterized by a jaw tip;
• means for closing said jaws to exert gripping force on a tool inserted therebetween, said closing means comprising means for selectively applying a relatively high gripping force and a relatively low gripping force;
• means for translating said gripper jaws along a predetermined axis between a first position and a second position;
• and
• sensor means for sensing the condition that a tool has been inserted into the grip of the jaws a predetermined distance from the jaw tips.

A tool changer system for a machine tool characterized by at least one spindle driving a replaceable tool having a shank and a tool end, a workpiece carrier mounted for movement in a plane, the spindle being translatable to effect movement of the tool relative to the workpiece carrier, the system comprising:

• a tool magazine for releasably holding a plurality of said tools, said magazine comprising means for effecting translating movement of said magazine relative to the workpiece carrier;
• a gripper apparatus secured to said workpiece carrier and comprising gripper means for receiving said tools in an inserted position within a tool gripper and selectively gripping said tools with a selectable grip pressure of either a relatively high grip pressure or a relatively low grip pressure to transfer tools between said spindle and said magazine, and means for effecting translating movement of said gripper means relative to said workpiece carrier;
• means for sensing when the tool has been inserted to a predetermined depth in said tool gripper and generating an insertion depth signal indicative of such condition;
• controller means for inserting the tool into the spindle so that a predetermined length of tool extends from the spindle, comprising means for aligning the gripper apparatus with a selected one of the tools in the magazine, and causing translation between the gripper and the magazine to insert the tool into the gripper means so that the length of tool inserted into the gripper means is less than said predetermined length, gripping the tool with the relatively high gripping pressure, thereafter aligning the gripper apparatus with the spindle, translating the gripper means in relation to the workpiece carrier to insert a portion of the exposed tool into the spindle, causing the spindle to securely grip the inserted portion of the tool, reducing the grip pressure of the gripper device, translating the spindle relative to the gripper device to insert more of the tool into the gripper until the insertion depth signal is generated, increasing the gripper device grip pressure and releasing the tool grip by the spindle;
• and translating the spindle toward the gripper device until the spindle is directly adjacent the gripper device so that said predetermined length of tool extends from the spindle;
• and releasing the gripping pressure of the gripper apparatus and causing the spindle to grip the tool in its inserted position.