Helix Technology Corporation

Texas Instruments Corporation

Donald A Olsen

Peter W Gaudet

Michael J Eacobacci

Steven A Bender

David Edward Roche

Robert J Lepofsky

John T Harvell

Henry J Boulanger

In a cryogenic vacuum pump, after determining that a power fail recovery mode is on, and that the temperature is below a setpoint, the cryopump is automatically cooled. If the power fail recovery mode is on, and the temperature is above the setpoint, a regeneration cycle is started automatically. If the power fail recovery mode is off, the cryopump may be maintained in an off state. When a command to turn on a pressure sensing thermocouple (TC) gauge is received, the TC gauge is turned on only if there is not a sufficient amount of gas to ignite. When a command to turn on a roughing valve is received, an additional command must be received before the roughing valve is turned on. When a temperature-sensing diode is faulty, temperature control is automatically turned off. During a regeneration cycle, a purge test is performed. If the purge test passes, heaters are turned on. If the purge test fails, the heaters are turned on only if the temperature reaches a threshold within a predetermined period. Otherwise, the regeneration is aborted.

Electronically controlled cryopump

A cryogenic vacuum pump includes, in an integral assembly, temperature sensors and heaters associated with the first and second stages of the cryopumping array, a roughing valve and a purge valve. An electronic module removably coupled in the assembly responds to all sensors and controls all operations of the cryopump including regeneration thereof. System parameters are stored in a nonvolatile memory in the module. Included in the regeneration procedures are an auto-zero of the pressure gauge, heating of the array throughout rough pumping, and a change in pressure rate test to determine stall in rough pumping. The electronic module also restarts the system after power failure, limits use of a pressure gauge to safe conditions, provides warnings before allowing opening of the valves while the cryopump is operating and stores sensor calibration information. Control through a control pad on the pump may be limited by a password requirement. Password override is also provided.

Electronic process controller having password override

The refrigerator of a cryopump is positioned within an insulating vacuum and the two stages of the refrigerator are selectively thermally coupled to first and second stage cryopanels. After initial rough pumping by an air ejector, rough pumping is completed during startup by coupling the cold first stage of the refrigerator to a first stage adsorption cryopanel. The second stage of the refrigerator is thereafter coupled to the second stage cryopanel. Thermal coupling of the refrigerator to the cryopanels is by means of spring biased thermal contacts brought into position by movement of the refrigerator. The thermal contact elements are provided with sufficiently large thermal masses to handle the large thermal loads of system startup.

Cryopump and method of starting the cryopump

An oil free vacuum system 10 which comprises a high thermal capacitance cryopump 12 and air ejector 38. The air ejector 38 is used to reduce load lock chamber 16 pressure to an intermediate vacuum. Cryopump 12 further evacuates chamber 12 to the operating vacuum of a work chamber 14. The work chamber 14 is maintained at high vacuum by a main cryopump 20. The main cryopump can be started in an oil free manner through the use of air ejector 38 and high thermal capacitance cryopump 12. A high themal capacitance, high thermal conductance cryopanel is formed of a lead/copper sandwich.

Oil free vacuum system

In a cryopump, condensation of gases such as argon, oxygen and nitrogen on surfaces other than the second stage array 38, 40 is avoided to prevent cross over hang up and pressure instability. To prevent condensation of argon, oxygen and nitrogen on the frontal cryopumping array 46, that array is held to a temperature of at least 50.degree. K. A heat load to the first stage increases as the temperature of the first stage drops. That heat load is provided by a high emissivity radiation shield 44 or by a thermal switch 56, 58. Condensation of argon and other gases on the second stage refrigerator cylinder 32 is avoided by a close fitting sleeve 52 positioned over the refrigerator cylinder 32 in thermal contact with the second stage heat sink 30 but out of thermal contact with the cylinder 32.

Cryopump with rapid cooldown and increased pressure

A time delay relay has a switch assembly, a spring terminal assembly, and an electrical resistance heater unit of an inexpensive construction held together in a reliable and economical manner by a pair of easily mounted metal spring clips. The clips have opposite ends each securely hooked over portions of the terminal assembly and resiliently engaged with respective, oppositely-facing surfaces of the switch and terminal assemblies so that the heater unit is firmly held in a predetermined position in the relay with opposite electrical poles of the unit resiliently engaged with respective terminals in the terminal assembly for directing electrical current through the heater, so that a thermally-responsive dished thermostatic disc is disposed in close heat-transfer relation to the heater unit at a location where it is free to move at a precisely predetermined temperature as it is heated by the heater unit, and so that a motion transfer pin is guided for free movement in response to the disc movement to provide snap-acting opening and closing of electrical contacts in the switch assembly.

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Millis, MA, United States of America

Donald A Olsen