US Patent 6935466 Lift pin alignment and operation methods and apparatus

A lifting mechanism includes a plurality of lift pins which may be driven separately and independently upward to engage an alignment surface of the chamber using ambient atmospheric pressure as the chamber is evacuated by a pump. In the illustrated embodiment, each lift pin includes a piston which is exposed to the internal chamber pressure on one side of the piston, and is exposed to the external ambient pressure on the other side of the piston. As the pump evacuates the chamber, the internal chamber pressure decreases, causing each lift pin piston to drive the associated lift pin upward. Once all the lift pins have securely engaged the alignment surface, the lift pins may be clamped to a linking mechanism to permit a motor to actuate the lift pins during processing operations.