METHOD OF MANUFACTURING A LOW DENSITY UNDERWATER ACCELEROMETER

• US 20160279749A1
• Filed: 06/06/2016
• Published: 09/29/2016
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Goodemote, John H., Cummiskey, Ryan
• Granted Patent: US 10,448,181 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B23P 19/04 for assembling or disassembling parts
• CPC Class Codes: G01P 15/09 by piezoelectric pick-up
• CPC Class Codes: G01P 15/0907 of the compression mode type
• CPC Class Codes: G01P 15/0915 of the shear mode type
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: H04R 31/00 Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

A method of manufacturing a low density accelerometer comprises the steps of: providing a rigid hollow housing having an upper member and a lower member and forming a groove circumferentially along an inner surface of the rigid hollow housing about a location where the upper member is configured to meet the lower member; providing a sensor assembly including a sensing element affixed to a solid proof mass; disposing the sensor assembly in the lower member of the rigid hollow housing, such that an outer edge of the sensing element engages and is in physical contact with the groove defined in the inner surface of the rigid hollow housing; and placing the upper member of the rigid hollow housing over the lower member of the rigid hollow housing, to enclose the sensor assembly within the rigid hollow housing, wherein the sensor assembly is in physical contact with the rigid hollow housing at the groove.

Claims

1. A method comprising:

providing a piezoelectric element, said piezoelectric element having first and second longitudinal ends;

affixing the first longitudinal end of said piezoelectric element to a base;

affixing the second longitudinal end of said piezoelectric element to a low density proof mass having at least one cavity formed therein;

exposing said piezoelectric element and said low density proof mass to an external medium for sensing an incident pressure wave, said low density proof mass having a density less than a density of said external medium, to cause movement relative to the base and exert a force on said piezoelectric element to generate a voltage in said piezoelectric element indicative of said incident pressure wave.

2. The method of claim 1, wherein said piezoelectric element comprises a piezoelectric ceramic material.

3. The method of claim 1, wherein said external medium is water, and wherein said incident pressure wave is hydrostatic pressure.

4. The method of claim 1, wherein said low density proof mass comprises a hollow spherical shell having an interior volume configured to contain a volume of air within the hollow spherical shell.

5. The method of claim 4, wherein said hollow spherical shell comprises alumina.

6. A method of manufacturing a low density accelerometer comprising the steps of:

providing a rigid hollow housing having an upper member and a lower member and forming a groove circumferentially along an inner surface of the rigid hollow housing;

about a location where the upper member is configured to meet the lower member;

providing a sensor assembly including a sensing element affixed to a solid proof mass;

disposing the sensor assembly in the lower member of the rigid hollow housing, such that an outer edge of the sensing element engages and is in physical contact with the groove defined in the inner surface of the rigid hollow housing; and

placing the upper member of the rigid hollow housing over the lower member of the rigid hollow housing, to enclose the sensor assembly within the rigid hollow housing, the sensor assembly in physical contact with the rigid hollow housing at the groove.

7. The method of claim 6, wherein providing the sensor assembly including the sensing element affixed to the solid proof mass further comprises:

forming the sensing element as a piezoelectric ring;

forming a shoulder portion of the solid proof mass such that the shoulder portion has a form factor that corresponds to an aperture defined in the piezoelectric ring; and

inserting the shoulder portion into the aperture defined in the piezoelectric ring.

8. The method of claim 6, wherein said solid proof mass is affixed to the sensing element using an adhesive.

9. The method of claim 6, wherein the sensor assembly is enclosed within the rigid hollow housing by bonding the upper and lower members of the rigid hollow housing together.

10. A method of manufacturing a low density accelerometer comprising the steps of:

forming a rigid hollow housing, having an upper member and a lower member;

creating a groove circumferentially along an inner surface of the rigid hollow housing at a point where the upper member meets the lower member;

forming a sensor assembly, wherein forming the sensor assembly comprises the steps of;

forming a sensor element as a ring, an outside perimeter of the sensor element configured to engage the groove along the inner surface of the rigid hollow housing; and

affixing a solid proof mass to the sensor element, the solid proof mass being affixed to the sensor element centered at an aperture defining a center of the sensor element ring;

disposing the sensor assembly in the lower member of the rigid hollow housing, such that an outer edge of the sensor element engages and is in physical contact with the groove defined in the inner surface of the rigid hollow housing; and

placing the upper member of the rigid hollow housing over the lower member of the rigid hollow housing, to enclose the sensor assembly within the rigid hollow housing, the sensor assembly in physical contact with the rigid hollow housing at the groove.

11. The method of claim 10, further comprising:

forming a shoulder portion of the solid proof mass, the shoulder portion having a form factor that corresponds to the aperture defined in the sensor element; and

inserting the shoulder portion into the aperture defined in the sensor element.

12. The method of claim 11, wherein said solid proof mass is affixed to the sensor element using an adhesive.

13. The method of claim 12, wherein the solid proof mass is affixed to the sensor element using epoxy.

14. The method of claim 10, wherein affixing the solid proof mass to the sensor element further comprises the steps of:

defining a threaded bore in the solid proof mass;

placing the sensor element, on said solid proof mass such that the threaded bore is positioned approximately central to the aperture defining the center of the sensor element ring;

placing a Belleville washer on the sensor element, wherein the outer edge of the Belleville washer is in contact with the sensor element in an area proximal to an edge of the aperture; and

inserting a threaded fastener through the Belleville washer and the aperture in the sensor element, the threaded fastener engaging the threaded bore in the solid proof mass.