Varying apparent mass accelerometer

• US 5,604,313 A
• Filed: 11/23/1994
• Issued: 02/18/1997
• Est. Priority Date: 11/23/1994
• Status: Expired due to Fees

• Current Assignee: Tokyo Gas Company Limited
• Original Assignee: Tokyo Gas Company Limited
• Inventors: Nakamura, Kenichi, Cahill, Sean S.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US08/346,263
• Time in Patent Office: 818 Days
• Field of Search: 73/517 AV, 73/514.18, 73/514.24, 73/514.32, 73/514.38, 73/514.16, 73/514.35, 361/280, 361/283.1, 361/283.2
• US Class Current: 73/514.38
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: G01V 1/01 Measuring or predicting earthquakes

Abstract

A varying apparent mass accelerometer 1 for detecting earthquake vibrations includes a frame 2 vibrating with an earthquake wave, a mass 51 supported on the frame 2 via a spring 52, electrodes 6 and 7 disposed above and below the mass 51, power sources 8 each applying a voltage across the electrodes 6 and 7, and a capacitance detector 9 for detecting changes in capacitance between the electrodes. The accelerometer 1 exerts a signal only when an acceleration exceeds a threshold.

Claims

1. A varying apparent mass accelerometer, comprising:

a frame vibrating with a vibrating wave;

a mass supported on said frame via a spring;

electrodes disposed above and below said mass;

power sources for applying voltages to said electrodes;

means for detecting the position of the mass when the mass is moved beyond a threshold by an exceeded vibration force; and

wherein the upper and lower electrodes are each divided into a plurality of sectors of electrode plates located in respective pairs above and below the electrode plates, and wherein a voltage V0 is applied across a center one of said pairs, a voltage V1 is applied across a second one of said pairs which is adjacent said center one of said pairs, a voltage V2 is applied across a third one of said pairs which is adjacent said second one of said pairs, and a voltage V3 is applied across a forth one of said pairs which is outside of said center, second and third pairs, and wherein V0>

V1>

V2<

V3.

2. A varying apparent mass accelerometer, comprising:

a frame vibrating with a vibrating wave;

a mass supported on said frame via a spring;

electrodes disposed above and below-said mass;

power sources for applying voltages to said electrodes;

means for detecting the position of the mass when the mass is moved beyond a threshold by an exceeded vibration force; and

wherein the potentials on the top and bottom electrodes are of opposite polarities, and voltages applied across respective upper and lower electrode pairs vary in a lateral direction.

3. A varying apparent mass accelerometer according to claim 2, including means for establishing magnitudes of attractive forces based on said voltages applied which exhibit a pattern so as to locate the mass, at rest, between central ones of the electrodes, and to locate the mass between outermost electrodes when the acceleration exceeds the threshold.