METHOD AND APPARATUS FOR FORMING A REFERENCE PRESSURE WITHIN A CHAMBER OF A CAPACITANCE SENSOR

• US 20060075823A1
• Filed: 10/07/2004
• Published: 04/13/2006
• Est. Priority Date: 10/07/2004
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Grudzien, Chris P.
• Granted Patent: US 7,137,301 B2
• Time in Patent Office: Days
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

The present invention is directed at methods and apparatuses for facilitating the establishment of a reference pressure within a reference chamber of a pressure transducer. The transducer has a housing and a cover, the housing defining a reference chamber and an aperture. A meltable sealing material is disposed on at least one of the cover and the housing. The apparatus includes a pressure chamber that is rotatable between a first position and a second position, a pressure source that is connected to the pressure chamber, a guide that is attachable to the transducer near the aperture, and a heater for selectively heating the pressure chamber to a temperature sufficiently high to melt the sealing material. The cover is positioned in an internal space of the guide. The guide is attached to the transducer near the aperture. The transducer, cover and guide are placed in the pressure chamber, the pressure chamber is rotated to the first position and a pressure is generated in the pressure chamber via the pressure source. After a reference pressure has been established in the reference chamber, the pressure chamber is rotated to the second position. Gravity causes the cover to move within the space towards the aperture when the pressure chamber is rotated to the second position. The heater then heats the pressure chamber to melt the sealing material. Upon cooling, the sealing material forms a seal that seals the reference pressure in the reference chamber of the transducer.

Claims

1. A method for establishing a reference pressure within a reference chamber of a capacitive pressure transducer assembly, the method comprising:

providing a pressure transducer assembly having an aperture;

providing an aperture cover;

depositing a sealing material on at least one of a sealing area that surrounds the aperture and a sealing area of the aperture cover;

positioning the aperture cover in a space that is defined by a guide;

coupling the guide to a portion of the transducer assembly that is adjacent to the aperture;

placing the pressure transducer assembly, the aperture cover and the guide in a pressure chamber of a housing, the aperture providing a fluid pathway between the reference chamber of the pressure transducer assembly and the pressure chamber of the housing;

generating a pressure in the pressure chamber;

rotating the transducer assembly and the guide so that gravity moves the aperture cover towards the aperture;

melting the sealing material; and

allowing the sealing material to cool.

2. The method of claim 1, wherein the transducer assembly is capable of measuring an absolute pressure and wherein the pressure that is generated in the pressure chamber is a vacuum pressure.

3. The method of claim 2, wherein the pressure is substantially equal to 10⁻

8 Torr or less.

4. The method of claim 2, further comprising:

activating a getter element that is in fluid communication with the reference chamber.

5. The method of claim 2, the aperture being defined by a tube and wherein the aperture cover is sealed to an end of the tube.

6. The method of claim 1, wherein the transducer assembly is capable of measuring a gauge pressure.

7. The method of claim 1, further comprising:

providing a slidable mass in the space, the aperture cover being positioned between the slidable mass and the aperture.

8. The method of claim 1, further comprising:

subjecting the housing to a first temperature which causes at least some contaminants that are contained within the transducer assembler to become vaporized;

subjecting the housing to a second temperature to melt the sealing material, wherein the first temperature is lower than the second temperature.

9. An apparatus for facilitating the establishment of a reference pressure within a reference chamber of a capacitive pressure transducer assembly, the apparatus comprising:

a pressure housing that defines an air-tight pressure chamber, the pressure housing comprising an upper housing, a lower housing, a pressure port and a rotation pin;

a support assembly, the support assembly comprising a support bracket having a hole that can accommodate the rotation pin of the pressure housing;

a guide frame having a closed distal end and an open proximal end and an internal cavity that extends therebetween;

wherein a pressure transducer assembly having an aperture and a reference chamber can be secured in the pressure chamber of the pressure housing and an aperture cover can be disposed in the interior cavity towards the proximal end of the guide frame, the aperture providing a fluid pathway between the reference chamber of the pressure transducer assembly and the pressure chamber of the housing;

wherein a sealing material can be deposited on at least one of a sealing area that surrounds the aperture and a sealing area of the aperture cover;

wherein a proximal end of the guide frame can be coupled to a portion of the transducer assembly that is adjacent to the aperture;

wherein a pressure line connected to a pressure source can be coupled to the pressure port, the pressure source being capable of establishing a pressure condition in the pressure chamber via the pressure line and the pressure port;

wherein when the rotation pin is engaged with the hole, the pressure housing can be rotated from a first position to a second position; and

wherein a gap exists between the aperture cover and the aperture when the pressure housing is in the first position and wherein the aperture cover moves towards the aperture when the pressure housing is rotated to the second position.

10. The apparatus of claim 9, further comprising:

a weight, wherein the weight is disposed in the internal cavity towards the distal end of the guide frame.

11. The apparatus of claim 10, wherein the internal cavity of the guide frame defines a cylindrical volume and wherein the weight is a ball that is comprised of high-density, high-temperature material.

12. The apparatus of claim 11, wherein the high-density, high-temperature material is either Tungsten Carbide or Silicon Nitride.

13. The apparatus of claim 11, wherein the aperture of the transducer assembly is defined by a tube and the internal cylindrical volume of the guide frame is sized to accommodate a portion of the tube.

14. The apparatus of claim 9, the support assembly further comprising an upper support and a lower support, wherein a portion of the pressure housing rests on the lower support when the pressure housing is in the first position and a portion of the pressure housing rests on the upper support when the pressure housing is in the second position.

15. The apparatus of claim 9, the pressure housing further comprising a cable that can be used to rotate the pressure housing from the first position to the second position.

16. The apparatus of claim 9, further comprising an actuator motor and an actuator rod that can be coupled to the pressure housing to control the rotational position of the pressure housing.

17. The apparatus of claim 9, the guide frame having holes that are located between the proximal end and the distal end.

18. The apparatus of claim 9, the guide frame having tightening screws that are located near the proximal end coupling the guide frame to the portion of the transducer assembly that is adjacent to the aperture.

19. An apparatus for facilitating the establishment of a reference pressure within a reference chamber of a capacitive pressure transducer assembly, the apparatus comprising:

a vacuum housing that defines an air-tight vacuum chamber, the vacuum housing comprising an upper housing, a lower housing, a vacuum port and a rotation pin;

a support assembly, the support assembly comprising a support bracket having a hole that can accommodate the rotation pin of the pressure housing;

a guide having a closed distal end and an open proximal end and an internal cavity that extends therebetween;

wherein a pressure transducer assembly having an aperture and a reference chamber can be secured in the vacuum chamber of the vacuum housing and an aperture cover can be disposed in the interior cavity towards the proximal end of the guide, the aperture providing a fluid pathway between the reference chamber of the pressure transducer assembly and the vacuum chamber of the housing;

wherein a sealing material can be deposited on at least one of a sealing area that surrounds the aperture and a sealing area of the aperture cover;

wherein a proximal end of the guide can be coupled to a portion of the transducer assembly that is adjacent to the aperture;

wherein a vacuum line connected to a vacuum source can be coupled to the vacuum port, the vacuum source being capable of establishing a vacuum pressure condition in the vacuum chamber via the vacuum line and the vacuum port;

wherein when the rotation pin is engaged with the hole, the vacuum housing can be rotated from a first position to a second position; and

wherein a gap exists between the aperture cover and the aperture when the vacuum housing is in the first position and wherein the aperture cover moves towards the aperture when the pressure housing is rotated to the second position.

20. The apparatus of claim 19, further comprising:

a weight, wherein the weight is disposed in the internal cavity towards the distal end of the guide.

21. The apparatus of claim 20, the weight being a ball, the aperture of the transducer assembly being defined by a tube and wherein the internal cavity of the guide defines a cylindrical volume that is sized to accommodate at least a portion of the tube.

22. The apparatus of claim 21, wherein the ball is comprised of high-density, high-temperature material.

23. The apparatus of claim 22, wherein the high-density, high-temperature material is either Tungsten Carbide or Silicon Nitride.

24. The apparatus of claim 19, the support assembly further comprising an upper support and a lower support, wherein a portion of the vacuum housing rests on the lower support when the pressure housing is in the first position and a portion of the vacuum housing rests on the upper support when the pressure housing is in the second position.

25. The apparatus of claim 19, the pressure housing further comprising a cable that can be used to rotate the vacuum housing from the first position to the second position.

26. An apparatus for use in constructing a pressure transducer, the transducer having a housing and a cover, the housing defining a reference chamber and an aperture, a meltable sealing material being disposed on at least one of the cover and the housing, the apparatus including:

a chamber, the chamber being rotatable between a first position and a second position, the chamber being sufficiently large to house the transducer;

a vacuum pump connected to the chamber, the vacuum pump being capable of establishing a vacuum in the chamber;

a guide disposed within the chamber, the guide being attachable to the transducer near the aperture, the guide defining an interior space sufficiently large for housing the cover, gravity causing the cover to move within the space away from the aperture when the chamber is in the first position, gravity causing the cover to move within the space towards the aperture when the chamber is in the second position; and

a heater for selectively heating the chamber to a temperature sufficiently high to melt the sealing material.

27. The apparatus of claim 26, further including:

a weight disposed within the space, the cover being disposed between the aperture and the weight.

28. The apparatus of claim 27, the weight being a ball.

29. The apparatus of claim 27, the weight being comprised of at least one of Tungsten Carbide and Silicon Nitride.

30. The apparatus of claim 26, further including a cable coupled to the chamber for rotating the chamber between the first and second positions.