Micromechanical shock sensor

• US 6,737,979 B1
• Filed: 12/04/2001
• Issued: 05/18/2004
• Est. Priority Date: 12/04/2001
• Status: Expired due to Fees

• Current Assignee: United States Secretary of the Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Fan, Lawrence, Jean, Daniel L., Smith, Gabriel L., Balestrieri, Ralph E.
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Previl, Daniel
• Application Number:
  US10/021,700
• Time in Patent Office: 896 Days
• Field of Search: 340/665, 340/666, 340/669, 340/670, 340/671, 340/672, 340/673, 340/674, 340/682, 340/683, 340/689, 340/686.6, 340/691.7, 340/571
• US Class Current: 340/665
• CPC Class Codes: G08B 21/18 Status alarms G08B21/02 takes precedence
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 2001/0047 operable only by mechanical latching
• CPC Class Codes: H01H 35/14 Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch wherein the liquid constitutes a contact of the switch H01H29/002

Abstract

The invention comprises a micromechanical shock sensor that is formed on the surface of a micro-substrate. A moveable proof mass is formed on the surface with at least one spring connected to the proof mass and the surface. The spring allows the proof mass to move a predetermined distance. Latching means are formed on the surface the predetermined distance from the proof mass. When the sensor is subjected to a sufficient shock, the proof mass moves and contacts the latching means. An indicator means is provided to allow this contact to be readily known by the user.

Claims

1. A micromechanical shock sensor device, comprising:

a substrate having a surface;

a moveable proof mass formed upon the surface;

at least one spring formed upon and attached to the surface, and attached to the proof mass wherein the proof mass may move a predetermined distance when subjected to a force of a predetermined magnitude;

latching means formed upon and attached to the surface the predetermined distance from the proof mass wherein the proof mass moves the predetermined distance and contacts the latching means when the proof mass is subjected to the force of a predetermined magnitude; and

,

indicator means to indicate that the proof mass has contacted the latching means.

2. The micromechanical shock sensor device of claim 1, wherein the indicator means comprises an electrical switch so that the contact by the proof mass and the latching means completes a circuit for the electrical switch.

3. The micromechanical shock sensor of claim 2, further comprising a plurality of springs formed upon the surface attached to the proof mass.

4. The micromechanical shock sensor of claim 3, further comprising a plurality of latching means formed upon and attached to the surface the predetermined distance and a plurality of proof masses formed upon the surface wherein the plurality of proof masses move the predetermined distance toward any of the plurality of latching means when subjected to the force of a predetermined magnitude.

5. The micromechanical shock sensor of claim 1, wherein the latching means comprises a plurality of levels wherein the latching means holds the proof mass proximate to a different level dependent upon a predetermined amount of force applied to the proof mass.

6. The micromechanical shock sensor of claim 5, wherein the indicator means may indicate which of the plurality of levels the proof mass is held proximate to.

7. The micromechanical shock sensor of claim 1, wherein the latching means holds the proof mass proximate to the latching means after the proof mass contacts the latching means.

8. The micromechanical shock sensor of claim of claim 7, further comprising an unlatching means to release the proof mass from the latching means wherein the proof mass returns to the predetermined distance from the latching means.

9. The micromechanical shock sensor of claim 8, wherein the unlatching means comprises at least one electronically activated actuator.

10. The micromechanical shock sensor of claim 7, further comprising damping means proximate to the proof mass wherein the proof mass does not contact the latching means as a result of a build up of small vibrations or resonance.

11. The micromechanical shock sensor of claim 2, wherein the latching means comprises a thin beam wherein the proof mass breaks the thin beam upon contact and opens the electrical switch.

12. The micromechanical shock sensor of claim 1, further comprising:

a second proof mass formed on the surface at an angle to the first proof mass;

a second spring formed on the surface at the angle of the second proof mass wherein the proof mass may move the predetermined distance;

a second latching means formed on the surface, the predetermined distance from the second proof mass and at the angle of the second proof mass wherein the second proof mass moves the predetermined distance as a result of the force of a predetermined magnitude and contacts the second latching means; and

,

a second indicator means to indicate that the second proof mass has contacted the second latching means wherein the shock sensor operates in a plane substantially parallel to the proof mass and in a plane substantially parallel to the second proof mass.

13. The micromechanical shock sensor of claim 1, wherein the spring comprises one or more beams wherein the beams may be selected from straight, folded or curved.

14. The micromechanical shock sensor of claim 1, wherein the sensor may detect a shock from about 1 gravity to about 50,000 gravities.

15. The micromechancial shock sensor of claim 1, wherein the force of a predetermined magnitude comprises from about 1 micronewton to about 10 micronewtons.

16. The micromechanical shock sensor of claim 1, wherein the predetermined distance comprises from about 50 microns to about 300 microns.

17. The micromechanical shock sensor of claim 1, further comprising a mass from about 0.1 milligrams to about 50 milligrams.

18. The micromechanical shock sensor of claim 1, further comprising a coating applied to the substrate wherein the increases the conductance of the substrate.

19. A method for detecting shock applied to packages, comprising the steps of

providing a micromechanical shock sensor comprising a substrate having a surface, a moveable proof mass formed upon the surface, at least one spring formed upon and attached to the surface, and attached to the proof mass wherein the proof mass may move a predetermined distance when subjected to a force of a predetermined magnitude, latching means formed upon and attached to the surface the predetermined distance from the proof mass wherein the proof mass moves the predetermined distance and contacts the latching means when the proof mass is subjected to the force of a predetermined magnitude, and, indicator means to indicate that the proof mass has contacted the latching means;

and,

attaching the shock sensor to the package.

20. The method of claim 19, further comprising four springs formed upon and attached to the surface, and attached to the proof mass.