Michael L Oswald

US Patent:

6837112, Jan 4, 2005

Filed:

Mar 25, 2003

Appl. No.:

10/249238

Inventors:

Robert J. Ferran - San Diego CA, US
Daniel M. Rohrbach - San Diego CA, US
Michael Oswald - San Diego CA, US

Assignee:

Stec Inc.

International Classification:

G01L 912

US Classification:

73718

Abstract:

A capacitance diaphragm gauge (CDG) for measuring pressure includes a flush diaphragm mounted to a body structure via a shim or other raised perimeter portion. The diaphragm and the shim are welded to the body structure while the diaphragm is maintained at an elevated temperature. Contraction of the diaphragm as it cools pretensions the diaphragm to substantially reduce hysteresis effects. An electrode advantageously includes two portions with one portion providing excellent bonding characteristics and the other portion having temperature characteristics corresponding to the body structure and the diaphragm. An alternative CDG includes two identical electrodes with a first electrode positioned proximate to the center of the diaphragm and with a second electrode positioned proximate to the perimeter of the diaphragm. The second electrode provides a second capacitance signal that is used to compensate for changes in capacitance between the diaphragm and the first electrode caused by temperature changes.

US Patent:

20080226480, Sep 18, 2008

Filed:

Jun 20, 2007

Appl. No.:

11/765954

Inventors:

Robert J. Ferran - San Diego CA, US
Michael Oswald - San Diego CA, US
Stephen J. Corbin - Yucca Valley CA, US

Assignee:

ION METRICS, INC. - San Diego CA

International Classification:

F04C 2/02

US Classification:

418 5

Abstract:

A vacuum pump includes first, second, third and fourth pump stages. Each pump stage has a trochoidal-shaped cavity and a rotor that rotates within the respective cavity. Each cavity has a volume determined by the depth of the cavity and a generally corresponding thickness of the rotor. The fourth stage has a largest volume and receives gas at an input pressure. The fourth stage outputs the gas to the third stage at a second pressure higher than the input pressure. The cavity of each successive stage (third, second and first) has a smaller volume and outputs the gas at a higher pressure than the previous stage. The last (first) stage outputs the gas to the atmosphere. The rotors in the stages rotate about a common pump shaft. Each rotor has a multiple vertices that follow the inner perimeter surface of the respective cavity without contact and without requiring additional seals.