Patent ID: 8651781

Claim:
A spindle assembly adapted for use at high rotational speeds and including a rotational shaft disposed within a housing and supported by spaced apart bearings which shaft carries a tool holding and releasing collet mechanism operated by a drawbar having first and second ends and axially movable between first and second positions and biased toward said first position by a first spring to secure a tool in said collet which is disposed at said first end of said drawbar, the improvement comprising: an actuator for engaging said second end of said drawbar; a plurality of arms having first and second ends, said first ends being pivotally secured to said housing; a piston disposed in said housing and movable between first and second positions engaging said arms at said second end thereof; each of said arms having a cam surface intermediate said first and second ends engaging said actuator at a contact point; a source of gas under pressure connected to move said piston from said first position to said second position when applied to said piston, said piston rotating said arms about the pivotally secured position thereof when moving from said first position to said second position and applying a force to said actuator at said contact point to overcome the bias of said first spring and move said drawbar to said second position to open said collet to release said tool; and the distance between where said first end of said arms are being pivotally secured to said housing and said contact point of said cam surface on said actuator compared to the distance between where said first end of said arms are being pivotally secured to said housing and said point where said piston engages the second end said arms defining a ratio which magnifies the force being applied by said piston to said actuator.