Microelectromechanical timer

• US 6,307,815 B1
• Filed: 07/23/1998
• Issued: 10/23/2001
• Est. Priority Date: 07/23/1998
• Status: Expired due to Term

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Plummer, David W., Polosky, Marc A., Garcia, Ernest J.
• Primary Examiner(s): Roskoski, Bernard
• Application Number:
  US09/121,763
• Time in Patent Office: 1,188 Days
• Field of Search: 368/220, 368/47, 368/187, 368/223
• US Class Current: 368/220
• CPC Class Codes: G04C 1/065 by continuous rotating movement
• CPC Class Codes: G04C 23/06 Driving or regulating means
• CPC Class Codes: G04C 23/08 Programming means
• CPC Class Codes: G04C 3/008 Mounting, assembling of components

Abstract

A microminiature timer having an optical readout is disclosed. The timer can be formed by surface micromachining or LIGA processes on a silicon substrate. The timer includes an integral motor (e.g. an electrostatic motor) that can intermittently wind a mainspring to store mechanical energy for driving a train of meshed timing gears at a rate that is regulated by a verge escapement. Each timing gear contains an optical encoder that can be read out with one or more light beams (e.g. from a laser or light-emitting diode) to recover timing information. In the event that electrical power to the timer is temporarily interrupted, the mechanical clock formed by the meshed timing gears and verge escapement can continue to operate, generating accurate timing information that can be read out when the power is restored.

Claims

1. A timing apparatus, comprising:

(a) a coiled mainspring;

(b) a timing gear comprising an optical encoder, and operatively connected to the coiled mainspring for rotation of the timing gear;

(c) an escapement mechanism operatively connected to the timing gear for regulating the rotation of the timing gear;

(d) a silicon substrare whereon the mainspring, the timer gear and the escapement mechanism are located;

(e) an electrostatic motor operatively connected to one end of the mainspring by a ring gear and a reduction gear train to wind the mainspring; and

(f) means for reading out the optical encoder to recover timing information from the rotation of the timing gear.

2. The apparatus of claim 1 wherein the mainspring comprises polycrystalline silicon.

3. The apparatus of claim 1 wherein the motor operates intermittently to wind the mainspring.

4. The apparatus of claim 1 further comprising switch means for starting and stopping rotation of the timing gear.

5. The apparatus of claim 1 wherein the escapement mechanism comprises a verge.

6. The apparatus of claim 1 wherein the means for reading out the optical encoder comprises a light beam incident on the timing gear.

7. The apparatus of claim 6 wherein the light beam comprises a laser beam.

8. The apparatus of claim 6 wherein the light beam comprises a light-emitting diode (LED) beam.

9. The apparatus of claim 1 wherein the optical encoder comprises a plurality of annular trenches or slots formed in the timing gear.

10. A timing apparatus, comprising:

(a) a silicon substrate;

(b) a main gear formed on the silicon substrate;

(c) a coiled mainspring formed on the substrate and operatively connected to the main gear to supply mechanical power thereto;

(d) a plurality of meshed timing gears formed on the substrate and mechanically coupled to the main gear to provide for rotary motion of the timing gears;

(e) an escapement mechanism operatively connected to one of the timing gears to regulate the rotary motion of the timing gears; and

(f) readout means for recovering timing information from the rotary motion of the timing gears.

11. The apparatus of claim 10 further comprising means for winding the mainspring.

12. The apparatus of claim 11 wherein the means for winding the mainspring comprises a first motor mechanically coupled to the mainspring by a reduction gear train driving a ring gear connected to one end of the mainspring.

13. The apparatus in claim 12 wherein the first motor is an electrostatic motor.

14. The apparatus of claim 12 further comprising a counter-rotation pawl to limit the ring gear to a single direction of rotation for winding the mainspring.

15. The apparatus of claim 12 further comprising a plurality of idler gears meshed with the ring gear to laterally constrain the ring gear.

16. The apparatus of claim 10 wherein the mainspring comprises polycrystalline silicon.

17. The apparatus of claim 10 wherein the main gear comprises polycrystalline silicon.

18. The apparatus of claim 10 wherein each gear in the first gear train comprises polycrystalline silicon.

19. The apparatus of claim 10 wherein the escapement mechanism comprises a verge.

20. The apparatus of claim 10 wherein the readout means comprises optical readout means for determining a rotary position of each timing gear.

21. The apparatus of claim 20 wherein the optical readout means further comprises at least one light beam incident on each timing gear for determining the rotary position of each timing gear and thereby recovering the timing information.

22. The apparatus of claim 21 wherein each incident light beam comprises a laser beam.

23. The apparatus of claim 21 wherein each incident light beam comprises a light-emitting diode (LED) beam.

24. The apparatus of claim 20 wherein the optical readout means comprises an optical encoder formed on each timing gear.

25. The apparatus of claim 24 wherein the optical encoder comprises a plurality of annular trenches or slots formed in each timing gear.

26. The apparatus of claim 25 wherein the optical readout means further comprises at least one light beam incident on each timing gear to read out the optical encoder and thereby recover the timing information.

27. The apparatus of claim 26 wherein each incident light beam comprises a laser beam.

28. The apparatus of claim 26 wherein each incident light beam comprises a light-emitting diode (LED) beam.

29. The apparatus of claim 26 wherein the optical readout means further comprises at least one photodetector for detecting a portion of the light beam and generating an electrical signal containing the timing information.

30. The apparatus of claim 10 further including switch means for starting or stopping rotary motion of the timing gears.

31. The apparatus of claim 30 wherein the switch means comprises a catch moveable into or out from contact with a verge of the escapement mechanism.

32. The apparatus of claim 31 wherein the switch means is activated by a second motor.

33. The apparatus of claim 32 wherein the second motor is an electrostatic motor.

34. A timing apparatus, comprising:

(a) a main gear;

(b) a coiled mainspring connected at a first end thereof to the main gear to supply mechanical power thereto;

(c) an electrostatic motor operatively connected to a second end of the mainspring to wind the mainspring and store mechanical power therein; and

(d) a plurality of meshed timing gears driven by the main gear, each timing gear rotating at a substantially constant angular velocity and having an optical encoder formed therein for providing timing information from rotary motion of that timing gear.

35. The apparatus of claim 34 further comprising a substrate whereon each of the main gear, the mainspring, the electrostatic motor, the meshed timing gears and the switch means are formed by surface micromachining.

36. The apparatus of claim 35 wherein the substrate comprises silicon.

37. The apparatus of claim 35 wherein each of the main gear, the mainspring and the meshed timing gears are formed from polycrystalline silicon.

38. The apparatus of claim 34 wherein the substantially constant angular velocity of the timing gears is provided by an escapement mechanism engaged with one of the timing gears.

39. The apparatus of claim 38 wherein the escapement mechanism comprises a verge.

40. The apparatus of claim 34 wherein the operative connection between the electrostatic motor and the second end of the mainspring is provided by a reduction gear train driven by the electrostatic motor, and a ring gear driven by the reduction gear train.

41. The apparatus of claim 34 wherein each optical encoder is read out by at least one light beam.

42. The apparatus of claim 41 wherein each optical encoder comprises a plurality of trenches or slots formed in the timing gear.

43. The apparatus of claim 34 further comprising switch means for starting and stopping