FI62595B - TRYCKMAETNINGSGIVARE - Google Patents

Description

62595

The invention relates to a pressure measuring sensor comprising a base plate fixed to the body by a screw, to which the measuring legs of the measuring plate are welded, disc springs and a sleeve to be mounted between them, and resistance strain strips 5 attached to the measuring legs.

Currently used pressure measuring sensors measure a constant pressure, e.g. liquid pressure. In this case, when measuring an arbitrarily and unevenly distributed pressure, 10 such as ground or ice pressure, correct measurement results are not obtained.

U.S. Patent No. 3,557,612 and DE-A-2,304,027 disclose measuring force by force-induced elongation. The devices disclosed in these publications are expensive to manufacture and are not suitable for measuring both rapid short-term forces and phenomena occurring over long periods of time, nor for measuring arbitrarily and unevenly distributed pressures.

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The object of the invention is to provide an improvement in pressure measuring sensors and to provide a sensor which is particularly suitable for measuring ice and ground pressure. It is also an object to provide a pressure measuring sensor which measures 25 arbitrarily distributed pressures and indicates the average pressure applied to the measuring plate and operates reliably for long periods in humid, highly corrosive conditions.

The object of the invention is achieved by a pressure measuring sensor, which is mainly characterized by what is stated in the claims.

The invention will now be described in more detail with reference to the accompanying drawing, which shows a sectional drawing of a pressure measuring sensor according to the invention.

3,62595

The body 1 is a one-piece machined relatively thick-walled cylindrical shell, the deformations of which under the loading conditions occurring in the measuring environment are insignificant.

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The measuring plate and legs are formed by a one-piece machined thick circular plate and its preferably four thin legs. At least three measuring feet 2 are required for the operation of the sensor, but a minimum number of measuring intervals of four feet is practical for the connection 10 of the resistance strain gauges 7. When manufacturing large sensors, it is practical to make several legs, in which case it is advantageous to select 8, 12, etc. as the number of legs for connection reasons, the number of legs divided by four, but the number of legs 15 can be any of three upwards.

The deflection of plate 2 under the measuring conditions is very small. The measuring feet 2 are compressed by the pressure on the measuring plate 2. The measuring legs 2 are welded 20 to a thick circular plate acting as a base plate 3.

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Between the measuring plate 2 and the base plate 3, disc springs 4 are placed, by means of which the measuring splits 2 are prestressed (pulled). Mounted between the disc springs 4 is a sleeve 5 acting as a fitting-25 piece, the length of which determines the biasing force of the springs.

Attached to each measuring leg'2 are resistance strain gauge strips 7, which are connected so as to measure the sum of the forces acting on the measuring legs 30 4.

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The measuring plate and legs 2, the base plate 3, the disc springs 4 and the sleeve 5 are fastened to the body 1, e.g. by means of a screw 6, so that the measuring legs 2 contact the body 1 tightly.

Between the measuring plate 2 and the body 1 there is a seal 8 made of Teflon or other suitable material, which prevents contact of the metal surfaces of the measuring plate 2 and the body 1 and allows small movement of the metal plate 2 relative to the body 1 without causing significant friction between them.

5 The sensor is filled with oil coming along the filling pipe and hose 11 from the expansion tank 12. The expansion tank 12 is an oil tank 1-2 meters above the ground or ice surface. The hydrostatic pressure of the oil in the sensor and the filling hose 11 keeps the oil pressure 10 in the sensor higher than the ambient water pressure. The 0-ring 9 prevents oil from escaping from inside the sensor.

The wires 11 connected to the resistance strain strips 7 are led out through the filling pipe and hose 10 to the expansion tank 12 and 15 therefrom to the measuring device.

The pressure measuring sensor is placed at the desired depth below the ground or ice surface. Ground or ice pressure is applied against the measuring plate 2. The pressure can be either evenly distributed or overwhelmingly. The measuring plate 2 does not bend under the measuring conditions, but the measuring feet 2 are compressed under the effect of pressure. By means of the resistance-elongation strips 7 attached to the measuring legs 2, the measurement result is the average pressure applied to the measuring plate 2.

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The measuring range of the sensor is determined by the cross-sectional area of the measuring instruments 2. For example, by selecting a large-diameter icy sensor with thin measuring legs, very low pressures can be measured. By biasing the measuring legs 2 by means of the disc springs 4, the measuring range of the sensor can be expanded.

To achieve corrosion resistance, all outer surfaces of the sensor are, for example, hard chrome-plated. In the ice pressure measurements, the chrome-plated outer surfaces are also polished, whereby the sensor is heated as little as possible by solar radiation. In this case, the effect of thermal stresses on the measurement accuracy of the 5 62595 sensor and the effect of the heat collected by the sensor on the surrounding ice are eliminated. If the sensor is not completely sealed, a slightly overpressurized oil will flow out, preventing corrosive moisture from entering the sensor.

The size of the sensor can vary as needed. If required, several pieces of disc spring packs 4 can be installed in large sensors.

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The sensor according to the invention is also suitable, for example, in laboratory use as a force sensor. In this case, the advantage of the sensor is that the load does not have to be central, but can be freely distributed in the area of the measuring plate 2.

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The invention is, of course, not limited to the application example presented above, but may vary considerably in detail within the scope of the claims.

Claims (4)

6 62595 A pressure measuring sensor comprising a base plate (3) fixed to the body (1) by a screw (6), to which the measuring legs (2) of the measuring plate are welded, disc springs (4) and a sleeve (5) mounted therebetween and measuring discs (2) Fixed resistance strain gauge strips (7) characterized in that a seal (8) preventing contact of their metal surfaces is placed between the measuring plate (2) and the body (1), which allows small movement of the measuring plate (2) relative to the body (1) and thin stripping legs (2) prestressed by means of disc springs (4), whereby when the arbitrarily distributed pressure is applied to the measuring plate (2), the measuring legs (2) are compressed and the average value of the pressure is measured by means of the resistance elongation strips (7). Pressure measuring sensor according to Claim 1, characterized in that there are a plurality of measuring legs (2), at least three, most preferably four or a number divisible by four. Device according to Claim 1, characterized in that the sensor is filled with a slightly overpressured oil to combat corrosion. 25