RU2169901C2 - Anchor strain gauge - Google Patents

Abstract

FIELD: applicable for measurement of rock pressure manifestations. SUBSTANCE: the gauge has a body with a central hole and flanges at the ends. Positioned on the body outer side are active and compensation resistance strain gauges interconnected according to the bridge circuit, whose branches have equal resistances. The gauge is positioned in a protective housing. The compensation resistance strain gauges are glued on plates made of the body material that are attached to the body by one end. The bridge circuit active branches have two series-connected resistance stain gauges each that are glued on the body in parallel with its axis. The space between the body and housing is filled with sealant. EFFECT: enhanced accuracy and reliability of the gauge, as well as reduced its height. 2 cl, 2 dwg

Description

 The invention relates to mining, in particular to instruments for measuring the manifestations of rock pressure, namely, sensors for measuring the tension of the anchor.

 Known dynamometer for measuring the loads on the lining in the mine workings, consisting of upper and lower covers, bushings, Belleville springs, rubber gaskets. For remote measurement of plate spring strains, it is equipped with a photocell [1].

 The main disadvantage of such dynamometers is the instability of the deformation characteristics of the disk springs during the measurement process, due to the influence of the shape during thermal quenching and significant sensitivity to a slight temperature change.

 A device for controlling the tension of an anchor support is known, consisting of two support washers and a compliance element located between them. A capsule is built into the body of the compliance element, in the cavity of which a system of stripped movable contacts connected to a radio transmitter is installed [2].

 The disadvantage of this device is that it is difficult to combine with a single monitoring network system for monitoring the methane gas content, the condition of the anchor support and the edge array. In addition, an elastic malleable element, for example of vacuum rubber, does not have a time-stable load characteristic due to aging of the rubber. The closest analogue in technical essence is a sensor that includes a housing with a central hole and a flange at the ends, on the outside of which four active and compensation strain gages are glued, connected by a bridge with equal electric shoulders, a protective casing connecting the flanges with rubber cuffs [3] .

 The disadvantage of this sensor is its low accuracy and significant height of the housing. The low accuracy of the sensor is due to the fact that in the case of longitudinal deformation of the housing, its deformation inevitably occurs in the transverse direction, although to a lesser extent. In this case, deformation and compensation strain gages are glued to the body in the transverse direction. In addition, the small base length of the arms of the active strain gages in the bridge circuit also limits the accuracy of the sensor. A simple increase in the base length leads to an increase in the height of the sensor, which is already significant. The height of the sensor is limited by the length of the shank of the anchor on which it is placed. The length of the shank of the anchor is regulated by technical safety rules. In addition, temperature changes often lead to the formation of condensate in the gap between the housing and the protective casing, which often leads to sensor failure.

 The aim of the invention is to increase the accuracy of measurement and the reliability of its operation, as well as reducing the height of the sensor.

 Additionally, the space between the housing and the protective cover is filled with sealant.

 The parallel arrangement of two active, shorter base strain gages allows to reduce the height of the housing while increasing the base length of the active arm of the sensor due to the series electrical connection of these short base gages.

 Increasing the base length of the active shoulders increases the accuracy of measuring the deformation of the body. Reducing the height of the sensor housing achieves a decrease in the length of the shank of the anchor, for which there is a restriction according to safety rules. In addition, this leads to a decrease in the length of the anchor and, consequently, to lower material costs for the anchor and the sensor. Sticking compensation strain gages on a separate, non-deformable plate also improves measurement accuracy.

 All free space between the housing and the housing is filled with elastic, non-curing sealant. This, unlike the prototype, eliminates the possibility of the formation and accumulation of condensate in the cavity, which guarantees the reliability of the operation of the electrical circuit.

 The essence of the proposal is illustrated by drawings.

 In FIG. 1 shows the design of the sensor housing and the arrangement of strain gages on the outer surface of the housing.

 In FIG. 2 is an electrical bridge connection of a strain gauge.

The sensor (Fig. 1) consists of a housing 1 made in the form of a cylindrical sleeve with an axial bore for a load-bearing rod of the anchor. The ends of the housing 1 are made with flanges. On the outer surface of the housing 1 are glued strain gauges connected to a bridge electrical circuit (Fig. 2). Active strain gages A ₁₁ and A _{12 of} one shoulder of the bridge circuit are glued on one side of the cylindrical surface of the housing 1, and strain gages A ₂₁ and A _{22 of the} other shoulder are glued on the opposite side of the housing 1. Moreover, the strain gages A ₁₁ and A _{12 are} connected in series in an electrical circuit and glued to the housing 1 along the generatrix of the cylindrical surface in parallel. In this case, the short base of the strain gages is extended with a small height of the sensor housing.

The active strain gages A ₂₁ and A _{22 of the} other arm of the bridge on the opposite side of the housing 1 are connected and glued in the same way. The compensation strain gages K ₁ and K _{2 are} glued to the plates 2 made of the material of the housing 1 to which they are glued at one end. In this case, when the housing 1 is deformed, the plates 2 do not deform and, accordingly, the compensation strain gauges.

 The flanges of the housing 1 are interconnected by a hard protective casing 3, designed to protect the electrical circuit from mechanical damage.

 A plug 5 is connected to the casing 3 through the boss 4, to the contacts of which an electric bridge circuit of the sensor is connected. The space between the casing 3 and the housing 1 is filled with sealant 6. The sealant 6 is designed to prevent the formation of condensate in the gap between the housing 1 and the casing 3 and to isolate the electrical circuit.

 To measure the imbalance of the bridge during deformation of the sensor housing along the axis, the bridge circuit is connected through a plug to the measuring device.

The sensor operates as follows. In the unloaded state, the housing 1 is not subject to deformation. The electrical resistance of the shoulders of the bridge circuit is balanced to the ^3rd sign. In the process of deformation in the axial direction of the sensor housing 1, the active strain gauges A ₁₁ , A ₁₂ , A ₂₁ , A ₂₂ are also deformed. The compensation strain gauges K ₁ and K ₂ glued to the plates 2 do not deform and do not change the electrical resistance. Deformed strain gages change their electrical resistance, and the imbalance of the bridge occurs, which registers the device. The imbalance of the bridge is proportional to the magnitude of the deformation of the active strain gauges and housing 1.

 Due to the fact that the acting forces have a linear relationship with the body deformations within the elastic deformation, then the magnitude of these forces is judged by the change in the unbalance of the bridge. For this, the sensor is pre-calibrated before use. Based on the results of four times the load build calibration schedule, which is an integral part of the product passport. During operation, this calibration schedule is used to determine the tension of the anchors according to the measurement of the unbalance of the bridge circuit.

 The device for measuring the imbalance of the bridge is connected through a plug connector 5, which is connected to the protective casing 3 through the boss 4.

 The proposed solution will reduce the height of the housing by more than 1.5 times while increasing the measurement accuracy and increasing the reliability of the sensor for a long time.

Sources of information:
1. A.S. USSR 474671, MKI G 01 B 5/30.

 2. A.S. USSR 191448, MKI G 01 B 5/30.

 3. A. D. Shirokov "Theory and practice of using anchor support", M, "Nedra", 1981, p. 318-319 (prototype).

Claims (2)

 1. A sensor for measuring the tension of the anchor, comprising a housing with a central hole and flanges at the ends, on the outside of which active and compensating strain gages are connected, connected by a bridge circuit, the shoulders of which have equal electrical resistance, a protective casing, characterized in that the compensation strain gages are glued to plates of housing material, which are attached to the housing at one end, and the active shoulders of the bridge circuit contain two series-connected strain gages, a cat Some are glued to the housing parallel to its axis.  2. The sensor according to claim 1, characterized in that the space between the housing and the casing is filled with sealant.

Images