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US5744696: Thermal isolation system in a chromatograph

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Filing Information

Inventor(s) Tak Kui Wang · James Ward Baker · Terry A. Berger ·
Assignee(s) Hewlett-Packard Company ·
Attorney/Agent(s) Mark Z. Dudley ·
Primary Examiner Hezron E. Williams ·
Assistant Examiner Wiggins; J. David ·
Application Number US8814035
Filing date 03/10/1997
Issue date 04/28/1998
Predicted expiration date 05/31/2015
U.S. Classifications /73  · /73  ·
International Classifications G01N 3108  ·
Kind CodeA
International Classifications 7323.25;23.27;25.01 ·
Related U.S. Application DataCROSS REFERENCE TO RELATED APPLICATION(S)
This is a continuation of copending application Ser. No. 08/456,210 filed on May 31, 1995.
15 Claims, No Drawings


Abstract

Sample analysis in a portable analytical instrument, preferably in the form of a gas chromatograph, benefits from temperature control of one or more thermal zones in the instrument by way of a thermal isolation system that includes a novel pumping assembly to effect a selective amount of thermal isolation of the thermal zone. The pumping assembly includes a pumping element in the form of a tubular or planar palladium structure. The pumping assembly makes use of the unique properties of palladium to allow selective control of a nominal gas pressure within a vacuum cavity. A component system, which may include a separation column and a thermal device for heating and/or cooling the component system, may be provided within the vacuum cavity. The thermal device and the pumping assembly are individually controlled by a control system. The pumping assembly may be operated to allow selective control of the thermal isolation of the thermal zone; alternatively, the component system may be subject to a controlled temperature by operating the thermal device. A sample mixture passing through the separation column may thereby be exposed to a desired temperature profile according to a selected program so that the sample will separate into its components for subsequent detection by a detector.

Independent Claims | See all claims (15)

  1. 1. Apparatus for providing thermal isolation of a component system in a chromatograph, comprising:a housing defining a closed cavity and a cavity volume, said closed cavity being subject to pressurization and thereby having a cavity pressure;means for locating the component system and the housing in a spaced relationship wherein at least a portion of said component system is enclosed within said housing;a pumping assembly operatively connected to the cavity for controlling cavity pressure in response to a pressure control signal; anda controller operatively connected to the pumping assembly for providing said pressure control signal; wherein said controller includes means for determining a selected cavity pressure and means for providing said pressure control signal in response to said determination so as to control the cavity pressure in the closed cavity, whereby the extent of gas phase heat conduction between said portion of the component system and the housing is selectably controlled.
  2. 10. A chromatograph, comprising:a component system having an active device and a thermal device for altering the temperature of the active device;a thermal isolation system for providing temperature control of a thermal zone, said active device being located in the thermal zone, said thermal isolation system including:a. a housing defining a closed cavity and a cavity volume, said closed cavity being subject to pressurization and thereby having a cavity pressure, said housing including means for locating the component system and the housing in a spaced relationship wherein at least a portion of said component system is enclosed within said housing,b. a gas supply system for providing a first flow of hydrogen gas,c. a pumping assembly located with respect to said closed cavity and operable in response to the control signal for establishing a selectable cavity pressure in the cavity volume and thereby establishing a selected amount of thermal isolation of the thermal zone, andd. a controller operatively connected to the pumping assembly for providing said pressure control signal;wherein said controller includes means for determining a selected cavity pressure and means for providing said pressure control signal in response to said determination of a selected cavity pressure so as to control the cavity pressure in the closed cavity, and whereby the extent of gas phase heat conduction between said portion of the component system and the housing is selectably controlled.
  3. 15.15. A method for providing thermal isolation of a component system in a chromatograph, comprising the steps of:providing a control system for supplying first and second control signals;providing a housing defining a closed cavity and a cavity volume, said closed cavity being constructed to accommodate at least a portion of the component system, the closed cavity being subject to pressurization and thereby having a cavity pressure;locating the component system and the housing in a spaced relationship wherein the portion of said component system is enclosed within said housing;operatively connecting a thermal device to the component system and operating the thermal device in response to the first control signal for effecting a thermal zone in the portion of the component system; andoperatively connecting a pumping assembly to the housing and operating the pumping assembly in response to the second control signal for effecting a selective amount of cavity pressure in the closed cavity,whereby the extent of gas phase heat conduction between the portion of the component system and the housing is selectably controlled.

Patent Family

Document NumberAssigneeInventorsIssue/Pub Date
EP0745845 Agilent Technologies, Inc. a Delaware corporation) Tak Kui Wang et al. Jul 2002
DE69622086 AGILENT TECHNOLOGIES INC WANG TAK KUI et al. Aug 2002