Shock sensor and devices to which the latter is applied

Details Shock sensor and devices to which the latter is applied Shock sensor and devices to which the latter is applied

1992-02-27

1994-09-27

Williams, Hezron E.

Measuring and testing

Vibration

Sensing apparatus

73510, 73517A, G01D 2100

Patent

active

053498631

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

The present invention relates to a shock or impact sensor and devices to which it is applied. It more particularly applies to the characterization of a shock (determination of the shock spectrum, etc.) and to the measurement of accelerations and speeds.
A complex mechanical structure which is subject to a shock vibrates. The low frequency components of this vibration have an important function in the mechanical effects following the shock, such as the relative displacements of the different parts of the structure. However, their characterization is made difficult by the presence of interfering components having a higher frequency and which in practice do not influence the displacements, but falsify the measurement.
Known shock sensors have a wide passband (a few 10 kHz to a few 100 kHz) and this constitutes a major disadvantage, because the sensitivity of these sensors is proportional to their passband. They provide no information on the low frequency components corresponding to accelerations close to 100 g. The latter are drowned in the numerous high amplitude, high frequency components. The peak accelerations measured during the envisaged shocks are in the range 1000 to 100,000 g.
The object of the present invention is to provide a shock sensor permitting the easy extraction of the low frequency components from the high frequency components and thus permitting the evaluation of the different mechanical effects undergone by the parts of a structure.
Another object of the invention is to provide a device for characterizing a shock to which said sensor is applied, which is easy and inexpensive to use.
Another object of the present invention is to provide a gyrometer to which the present sensor can be applied and which is easy and inexpensive to use.
More specifically, the present invention relates to a shock sensor, which can be fixed to a structure, characterized in that it comprises, along a longitudinal axis perpendicular to the structure, a rod which can be joined to the structure by a first end, a weight joined to a second end of the rod and at least one means for detecting acceleration along an axis perpendicular to the longitudinal axis, said acceleration means being fixed to the weight.
This apparatus constitutes a mechanical oscillator tuned to a fundamental resonant frequency chosen as a function of the type of shock to be dealt with. This oscillator is excited when the structure to which it is fixed is exposed to an impact or shock. The means for detecting acceleration then supplies an electrical signal proportional to the acceleration of the weight in a given direction. Following appropriate processing, this signal makes it possible to determine the speed at the base of the sensor and to deduce the shock spectrum therefrom.
The present invention also relates to apparatuses in which said shock sensor is used and in particular a shock characterizing apparatus and a gyrometer.
The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings, wherein show:
FIG. 1 diagrammatically an apparatus for the characterization of a shock according to the invention.
FIG. 2 diagrammatically a gyrometer according to the invention.
FIG. 1 shows diagrammatically an apparatus for characterizing a shock. The apparatus comprises a shock sensor 10 according to the invention and which is fixed to a structure or frame 14.
Such a shock sensor 10 has a fundamental resonant frequency below 1 kHz. It has a means for removing the harmonic resonant frequencies from the fundamental resonant frequency of the sensor. When the fundamental resonant frequency is fixed, this amounts to raising the value of the harmonic resonant frequencies. An example of such a means is given hereinafter. During the processing of the electrical signals supplied by the sensor, it makes it possible to easily separate the component at the fundamental resonant frequency from the components at the harmonic resonant frequencies.
The shock sensor 10 comprises a cylindrical rod 12 termina

REFERENCES:
patent: 3292977 (1966-12-01), Williams
patent: 3754225 (1973-08-01), Gleason
patent: 4041775 (1977-08-01), McNamee
patent: 4562740 (1986-01-01), Webber et al.

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