Robot protection system

A method for automatically preventing damage, due to improper operation, to a machine for moving workpieces with a SMIF apparatus having a robot transfer mechanism with a workpiece gripper, and a workpiece elevator, comprising the steps of:

• providing a first sensor for detecting whether the robot transfer mechanism is in a first selected condition or not, and producing a first indicative output,
• providing a second sensor for detecting whether the workpiece gripper is in a second selected condition or not and producing a second indicative output;
• providing a third sensor for detecting whether the workpiece elevator is in a third selected condition or not, and producing a third indicative output;
• inputting said first, second, and third indicative outputs to a logic circuit to determine whether said transfer mechanism, said workpiece gripper, and said workpiece elevator, are all in said selected conditions;
• and
• outputting a signal disabling said SMIF apparatus when at least one of said transfer mechanism, workpiece gripper, and workpiece elevator is not in its selected position.

Apparatus for avoiding damage, due to improper operation, to a machine for moving semiconductor-wafer-carrying cassettes into a clean room environment with a SMIF apparatus, having a cassette elevator and a robot transfer arm with a cassette gripper, and comprising:

• a first sensor for detecting whether the robot transfer arm is in the out position or not, and producing an indicative output signal;
• a second sensor for detecting whether the cassette gripper on the transfer arm is open or closed and producing an indicative output signal;
• a third sensor for detecting whether the cassette elevator is "home" or not, and producing an indicative output signal;
• wherein the improvement comprises:
• a logic circuit comprising a NAND gate and an OR gate;
• means for inputting said three indicative output signals to said logic circuit to determine whether said robot transfer arm, said cassette elevator, and said cassette gripper are all in selected conditions, said inputting means comprising:
• means for inputting said first and second indicative outputs from said transfer arm and said cassette elevator sensors to said NAND gate;
• and
• means for inputting said third indicative output from said cassette gripper sensor to said OR gate along with the output of said NAND gate;
• means for disabling said robot transfer arm;
• and
• means for outputting a signal disabling said robot arm when at least one of said robot arm, cassette elevator, and cassette gripper is not in its selected position, said disabling signal outputting means comprising means for inputting the output of said OR gate to said disabling means.