Light actuating force elevator drive mechanism

In an electron beam writing system for beam writing on a work piece, said system including:

• a vacuum chamber,
• an elevator mechanism within said chamber to one side of the beam writing area, said mechanism including a workpiece bearing elevator platform and an elevator drive shaft assembly fixed to said platform and mounted to said chamber for vertically displacing said elevator platform within said chamber,
• actuating means coupled to said shaft assembly for vertically raising and lowering said elevator drive shaft assembly and said platform carried thereby, between a first raised position and a second lowered position,
• said vacuum chamber including wall means bearing a closable opening for permitting entry of workpieces into the vacuum chamber through said opening,
• means for subjecting said elevator mechanism to system vacuum pressure when said chamber is sealed off such that said vacuum pressure within said vacuum chamber tends to pull the elevator platform up, while when said wall opening means open, gravity effect on the elevator mechanism tends to pull said elevator platform downwardly within said vacuum chamber,
• the improvement comprising:
• load force counterbalancing means connected to said elevator drive shaft assembly for applying balancing forces for balancing out the vacuum pressure tending to pull the elevator platform up when the opening in the chamber wall means is sealed under chamber vacuum conditions and in the opposite direction to overcome the gravity force tending to pull the elevator platform down when said vacuum chamber is subjected to atmospheric pressure through said wall means opening, thereby placing said elevator mechanism in a condition of substantially zero mass under both vacuum chamber atmospheric and vacuum pressure conditions, thereby permitting rapid movement of said elevator platform by said elevator actuating means with minimal force and with minimal vibration and shock to said system during stoppage such that a first workpiece may be moved by the elevator mechanism while simultaneously electron beam writing may be effected on a second workpiece within said vacuum chamber, thereby increasing workpiece throughput.