The OTT-Jakob power drawbar from Advanced Machine and Engineering is held securely in the spindle taper with gripper fingers. The fingers are pulled into the taper with the spring pack of the power drawbar, and an intensifying mechanism multiplies the pull-in force. The spring force applied to the clamping sleeve pushes the balls outward. The angle design of the clamping ring and cylinder shoulder increases the spring force. To securely lock the tool, the cam inside the spindle closes the gripper fingers.
Loss or reduction in hydraulic pressure will not release the tool. The power-off design requires pressure applied to the hydraulic piston and transmitted through the rod to push the clamping sleeve down and unlock the intensifying mechanism. After clearing the cam, the gripper fingers open, and the face of the holder ejects the tool with a controlled stroke.
The power drawbar features a compact design to minimize rotating mass. Other advantages include no load on the spindle bearings during tool change and a low tool release force, the company says.