Tuned ground motion detector utilizing principles of mechanical resonance
First Claim
1. A tuned resonant ground motion sensor comprising:
- a. housing means;
b. oscillatory mass means mounted in said housing for harmonic movement from a neutral position to a signaling position in response to applied vibrational forces falling within a predetermined frequency range; and
c. viscous damping means contained in said housing for impeding the natural harmonic motion of said mass means to broaden the range of frequencies to which said mass means responds, said viscous damping means comprising a viscous fluid in which said mass means is partially immersed, and wherein at least a portion of said mass means confronts a conforming surface of said housing across a narrow gap, said gap being completely occupied by said fluid.
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Abstract
A mechanically resonant ground motion sensor having a frequency response which is "tuned" to discriminate between applied vibrational forces which are destructive and those which are not. The basic operating principle of the sensor is that of an oscillating mass whose dynamic response to applied forces takes the form of viscously damped harmonic motion. The disclosed embodiments include a horizontal ground motion detector based on the movement of a pendulum in a viscous fluid and a vertical ground motion detector utilizing a vertically sprung dashpot cylinder moving through a viscous fluid. The detector is tuned to trigger a tripping mechanism in response to accelerations above a threshold value and within the critical range of destructive frequencies. Tuning is accomplished through appropriate selection of the various design parameters including the active surface area upon which the viscous force acts, the fluid gap between moving and stationary surfaces, the weight of the moving element and the fluid viscosity. The sensor may be used to disable or deactivate systems such as elevators or gas lines which may become life endangering during a destructive earthquake.
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Citations
10 Claims
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1. A tuned resonant ground motion sensor comprising:
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a. housing means; b. oscillatory mass means mounted in said housing for harmonic movement from a neutral position to a signaling position in response to applied vibrational forces falling within a predetermined frequency range; and c. viscous damping means contained in said housing for impeding the natural harmonic motion of said mass means to broaden the range of frequencies to which said mass means responds, said viscous damping means comprising a viscous fluid in which said mass means is partially immersed, and wherein at least a portion of said mass means confronts a conforming surface of said housing across a narrow gap, said gap being completely occupied by said fluid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification