FR2750496A1 - Machine tool monitoring vibration sensor - Google Patents

Abstract

The sensor includes a cylindrical box with a central hole which is used to attach the sensor to the equipment to be monitored. The box houses an acceleration gauge connected to a CMS amplification circuit. Filters are inserted in the circuit to eliminate parasitic signals. A temperature sensor can also be mounted inside the box. The box is then filled with rigid resin and covered with a lid. A cable is connected to the box. Two of its wires are used for power supply while the other three deliver the output signal.

Description

The present invention relates to a device for continuously monitoring machines in operation by the vibrations they generate.

Traditionally, vibration monitoring of machines has been limited to expensive and complex equipment. It is carried out either manually, or by various technical means themselves often complex and expensive., Most often requiring human intervention.

The device according to the invention considerably simplifies the monitoring of the machines. It is of very limited size, since it consists of a metal box of limited size, comprising fixing holes and, if necessary, a bonding surface. n is screwed or glued to the machine, permanently or temporarily, its signal transmission wire going to the device for reading and analyzing the sensor signal.

According to the particular embodiments:
The case is cylindrical with a central hole allowing a solid and easy fixing by a simple screwing, ensuring a good behavior and therefore a reliable measurement, not risking to be itself disturbed by the vibrations of the machine with which it forms a body. The case could be of square base or any other useful shape.

The case has a recess at its base, allowing it to be housed in a machining provided for this purpose which keeps it securely in position.

The sensitive element is not of the piezoelectric type, as it already exists. These are indeed fragile and their bandwidth is limited downwards. Such sensors therefore do not detect vibrations of low amplitude. They are also fragile, and themselves sensitive to shocks.

The use of accelerometric type sensors with a glued or diffused gauge, the resistance of which varies and mounted on a strip between two mechanical stops, reinforces the robustness of the sensor against shocks and falls during assembly in particular. H makes it possible to detect from a very low threshold and even from the first movement or shock of the machine.

The slightest sensitivity of this type of sensor has so far eliminated them for this type of monitoring. The device according to the invention combines in the same housing a CMS amplification and conditioning circuit. The signal is therefore adjustable to the sensitivity level appropriate for monitoring, with very high thresholds if necessary. Filters can be easily added to eliminate spurious signals. This type of sensor is also very little sensitive to vibrations transverse to that which one wishes to measure. Being thus designed it is therefore robust and can withstand significant vibrations for very long periods of time, without itself being altered in its performance by vibrations.

The combination of rigorous mechanical positioning, a one-piece housing, complete electronics included and a sensor can be sensitive to shocks but sensitive to low amplitudes constitutes the device of the present invention.

The device has a bearing face at its base. Inside the case, the sensitive element is glued against the internal part of the bearing face. The machining is such that the sensor is strictly parallel to the bearing face of the machine.

A second sensitive element, or even a third, can be mounted inside the case in order to measure the vibrations and shocks along two or even three axes.

All of the electronics are therefore incorporated in the housing. By way of nonlimiting example, the case can measure 30 millimeters in diameter and 25 mm high, with a central hole allowing the passage of a threaded rod MS.

Another monitoring sensor, mainly a temperature sensor can be mounted inside said box, to complete the vibration monitoring with thermal monitoring.

Typically, the output signal is either of low levels, for example from 0 to 60 millivolts, or said of high level, for example 0 to 10 volts or 4 to 20 milliamps, for connection to computer or any other instrument of reception and signal processing.

The housing cover is fixed, like all of the components by gluing. The entire interior of the case is filled with hard glue, to ensure robustness against vibrations, as well as a good transfer of these vibrations from the machine to the sensor. Miniature circuits do not fear overheating of the components. The whole is waterproof and submerged and withstands harsh industrial and military environments.

The output cable has two power wires and two signal output wires. N optionally has two or three temperature sensor output wires. 11 is fixed to the housing by a sealed passage or by bonding.

Claims (1)

CLAIMS:  1) device for monitoring machines in operation by vibrations perceived by a sensitive element mounted in a small monobloc box with signal output by cable. Device according to claim 1 characterized in that the sensitive element begins to perceive vibrations and shocks from the lowest frequencies and meme the first vibratory movement or movement of the machine, or shock it undergoes. Device according to claim 1 characterized in that the sensitive element is mounted on the internal face of the case so as to be completely integral with the case and very close to the frame on which it will be fixed. Device according to claim 1 characterized in that the sensitive element is itself insensitive to shocks and drops in particular before mounting the sensor, due to mechanical stops applied to a metal strip type sensor whose deformation is measured by a gauge pasted or broadcast. Device according to claim 1 characterized in that the sensitive element and all of its electronics are included in a one-piece waterproof housing and embedded in a mass of rigid adhesive. Device according to claim 1 characterized in that a central hole perpendicular to the bonding face of the sensitive element, allowing easy mounting and suitable for the correct transmission of machine vibrations.