JP3427173B2 - Strain gauge protection device and tension sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain gauge protective device used for various stress measurements, and more specifically, it is equipped with a protective device suitable for protecting a strain gauge used in a natural environment and the protective device. The present invention relates to a tension sensor.

[0002]

2. Description of the Related Art For example, in an overhead power transmission line, it is important for safety management to grasp how much tension is actually applied to the power transmission line. Normally, a part of the power transmission line is set as a test line. Then, attach the strain gauge in advance to the suspension fitting that supports the insulator on which this test line is hung on the steel tower,
A tension sensor using the hanging metal fitting as one strain element is assembled, and the tension applied to the power transmission line is checked by the tension sensor over time.

By the way, the tension applied to the power transmission line changes due to external factors such as snow accretion, and therefore, it is necessary to regularly perform a tension confirmation test throughout the four seasons. in this case,
It is indispensable to protect the strain gauge from the outside world and to maintain the sensor performance permanently.Therefore, conventionally, the strain gauge is wrapped with an insulating coating layer attached to the hanging metal fitting as a strain-generating body. A vinyl tape was wrapped around it to double protect the strain gauge.

[0004]

However, according to the above-mentioned conventional protective structure, the vinyl tape deteriorates relatively early under the influence of sunlight, especially ultraviolet rays, and the strain gauge also deteriorates accordingly. However, there is a problem that the sensor life is shortened. In addition, the chance of damage to the vinyl tape and the coating layer increases due to the influence of wind and rain and flying objects, and from this aspect, there is a problem that it is difficult to perform a stable follow-up test for a long period of time.

The present invention has been made to solve the above-mentioned conventional problems. The object of the present invention is to provide a strain excellent in weather resistance and also excellent in protection against wind and rain and flying objects. An object of the present invention is to provide a gauge protection device and a tension sensor equipped with this protection device.

[0006]

In order to achieve the above-mentioned object, a strain gauge protection device according to the present invention covers a strain gauge adhered to a strain gauge that causes strain in one direction. Insulating coating layer, and a cover made of metal that surrounds the strain-generating body including the coating layer, the cover, the front and rear side plates intersecting the strain direction of the strain-generating body, It is characterized in that it is formed from at least two free pieces, and the free end of each free piece is elastically brought into contact with the flexure element.

In the protective device thus constructed,
The metal cover blocks ultraviolet rays from reaching the coating layer and prevents wind and rain and flying objects from directly colliding with the coating layer, so the deterioration and damage of the coating layer as well as the strain gauge wrapped in the coating layer can be prevented. To be prevented. Moreover, since the cover only elastically contacts the free ends of the free pieces forming the both side plates to the flexure element, the expansion or contraction of the flexure element is restrained by the cover, or the flexure element is deformed by the cover. The body is not hurt.

In the present strain gauge protection device, the cover is divided into two parts in a plane parallel to the strain direction of the flexure element, and each of the division elements has a free piece so that they are superposed on each other in the division surface. The structure may be integrated. By dividing the cover in this way, the assemblability with respect to the flexure element is improved, and in addition, the shim of an appropriate thickness is provided at the mating portion of the dividing element, and the dimensional variation of the flexure element is increased. Can be easily absorbed.

In the strain gauge protection device of the present invention, it is desirable that the cover is made of austenitic stainless steel, which not only improves the durability of the cover itself but also enhances the protection performance against noise.

Further, in the strain gauge protection device of the present invention, the cover may be filled with a resin, preferably a silicone resin, so that not only the displacement of the cover is surely prevented but also the strain gauge is prevented. It also ensures the protection of the coating layer containing.

On the other hand, the tension sensor according to the present invention is provided with the above-mentioned strain gauge protection device, uses a suspension fitting of an overhead power transmission line as a strain-generating body, and a plurality of strain gauges are adhered to the suspension fitting to cover it. In the above, a cable take-out member for taking out a cable in which leads connected to the plurality of strain gauges are bundled is provided. In the tension sensor configured in this way, the suspension fittings of the overhead power transmission line function as they are as strain generating elements, and the multiple strain gauges attached to them are reliably protected by the protective device, so they are stable over the long term. Then, the tension acting on the overhead power transmission line can be measured.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4 show a strain gauge type tension sensor according to the present invention. This tension sensor is for measuring the tension of a power transmission line of an overhead power transmission line, and uses a plate-shaped hanging metal fitting 1 for supporting an insulator of the overhead power transmission line on a steel tower or connecting the insulators to each other as a strain body. The strain gauges 2 are attached to the front and back surfaces of the hanging metal fitting 1, and further the protective device 3 surrounding the strain gauges 2 is provided on the hanging metal fitting 1. The hanging metal fitting 1 includes a large-diameter disk portion 5 at both ends of a connecting portion 4 extending with a constant width.
Has a mounting hole 6 for mounting insulators, etc.
Strain is generated in the extension direction of the connecting portion 4. Two strain gauges 2 are attached to each of the front and back surfaces of the connecting portion 4, and the leads extended from each strain gauge 2 are bundled into one cable 7 (FIG. 3) and provided on the protection device 3. It is adapted to be taken out through the cable taking-out member 8.

As shown in FIG. 1, the protective device 3 includes a rubber coating layer 10 attached to the hanging metal fitting 1 so as to wrap the strain gauge 2, and a metal cover 11 surrounding the coating layer 10. And a resin protective layer 12 that is filled in the metal cover 11 and wraps the coating layer 10. Here, the coating layer 10 is made of butyl rubber having excellent insulation and moisture resistance, and a butyl rubber sheet is wound around the connecting portion 4 of the hanging metal fitting 1 in multiple layers so that the coating layer 10 has a sufficient thickness. Has been formed. The metal cover 11 is made of austenitic stainless steel, and is formed by sheet metal working of a stainless steel plate having a plate thickness of about 1 mm. On the other hand, the protective layer 12
Is made of a silicon-based resin, and the liquid material is filled in the metal cover 11 and then cured as it is to fill the voids in the metal cover 11 with appropriate elasticity.

As shown in FIG. 5, the metal cover 11 has a two-part construction including a box-shaped cover body 13 and a U-shaped lid body 14 here. The cover body 13 and the lid body 14 are the left and right side plates 15 of the cover body 13.
Using the inner flange 16 provided at the lower end of the as a mating surface, a welding nut 17 previously provided on the inner flange 16 and a plurality of bolts 18 through which the lid 14 is inserted are used for fastening and integration. . The pair of front and rear side plates 19 of the cover body 13 are separated from the left and right side plates 15 by the slits 20 to form free pieces. Each free piece (side plate) 19 is formed with a notch 21 for inserting the connecting portion 4 of the hanging metal fitting 1 as the flexure element. The notch 21 has a depth that is slightly shallower than the thickness of the connecting portion 4 of the hanging fitting 1 and a width that is slightly wider than the width of the connecting portion 4. Therefore, the notch 21 connects the hanging fitting 1 to each other. In the state where the portion 4 is housed, one side surface (lower side surface) of the connecting portion 4 comes to project slightly downward from the tips of the free pieces 19 existing on the left and right of the cutout 21. On the other hand, the lid 15 is elastically contacted with the lower surface of the connecting portion 4 in which the standing pieces (free pieces) 22 before and after the lid 15 are integrated with the cover body 13 in the cutout 21. Its height is set so that That is, in the metal cover 11, the free ends of the free pieces 19 and 22 provided on the cover body 13 and the lid body 14 as the dividing elements are elastically brought into contact with the upper and upper side surfaces of the connecting portion 4 of the hanging fitting 1. It is held by the hanging metal fitting 1 in a state where it is allowed to move.

A cable outlet 23 (FIG. 5) is provided on the bottom portion 13a of the cover body 13 of the metal cover 11, and the cable outlet member 8 has a state in which the internal passage is aligned with the cable outlet 23. And the bottom plate 13
It is fastened to a by using a plurality of bolts 24. Also,
The bottom portion 13a of the cover body 13 is provided with an injection port (not shown) for injecting resin.

In order to assemble the above-mentioned tension sensor, a predetermined number (here, 4
3), the sheet of butyl rubber is wound around the connecting portion 4 in multiple layers to form the coating layer 10 having a sufficient thickness. Next, the connecting portion 4 of the hanging metal fitting 1 is covered with the cover body 13 of the metal cover 11, and the notch 21
The connecting portion 4 of the hanging metal fitting 1 is housed in the cover body 13.
And the bolts 18 are fastened and integrated with the cover body 13. Due to this integration, the free ends of the free pieces 19 and 22 provided on the cover body 13 and the lid 14 are attached to the hanging fitting 1.
The metal cover 11 is elastically fixed to the hanger 1 by elastically contacting the upper and upper side surfaces of the connecting portion 4 of the. At this time, a shim having an appropriate thickness is provided at a mating portion (inner flange 16) between the cover body 13 and the lid body 14,
You may make it adjust the contact condition of the free end of the free pieces 19 and 22 with respect to the hanging metal fitting 1. Thereby, even if the hanging metal fitting 1 has a dimensional variation, the elastic force of the said free piece is adjusted appropriately. be able to.

After that, the slit 20 of the cover body 13
The gap between the cover main body 13 and the lid body 14, the gap in the notch 21 formed on the side of the connecting portion 4 and the like are closed with tape or the like,
Then, a silicon resin is injected into the metal cover 11 through an injection port (not shown) provided in the bottom portion 13a of the cover body 13. This resin injection is performed until the voids in the metal cover 11 are filled with the resin, and then the resin cover is left for a predetermined time until the resin hardens, whereby the protective layer 12 is formed in the metal cover 11.

The tension sensor configured as described above is installed in the overhead power transmission line in place of a suspension fitting that supports the insulator on the steel tower or connects the insulators to each other, and is used for measuring the tension of the transmission line set as the test line. Used. In this case, the four strain gauges 2 attached to the hanging metal fitting 1 as the strain-flexing body are incorporated in the measuring unit so as to form a bridge circuit (Wheatstone bridge), and the measuring unit is adapted to the elongation of the hanging metal fitting 1. The tension is measured from the change in the electrical resistance of the strain gauge 2. At this time, the free pieces 19, 22 of the metal cover 11 constituting the protection device 3
However, since it follows the expansion or contraction of the hanging fitting 1 as shown by the chain double-dashed line or the dotted line in FIG. 1, the expansion or contraction of the hanging fitting 1 as a flexure element is restrained by the metal cover 11, or The hanger 1 is not damaged by the cover 11, and as a result, the sensor performance is stably maintained.

Further, since the metal cover 11 and the protective layer 12 block the ultraviolet rays from reaching the coating layer 10 and prevent wind and rain and flying objects from directly colliding with the coating layer 10, the coating layer 10
Of course, the strain gauge 2 wrapped in the strain gauge 2 is prevented from being deteriorated or damaged, and the performance of the tension sensor is permanently maintained. Particularly in the present embodiment, since the metal cover 11 is filled with the silicone resin to form the protective layer 12, not only the displacement of the metal cover 11 is reliably prevented, but also the strain gauge 2 is prevented. The protection of the coating layer 10 including it is also ensured, and the reliability of the tension sensor is significantly improved. Further, since the metal cover 11 is formed of austenitic stainless steel, not only the durability of the metal cover 11 itself is improved, but also the noise protection performance is improved.

[0020]

As described above, according to the strain gauge protection device and the tension sensor equipped with the protection device of the present invention, the weather resistance is excellent and the protection against wind and rain and flying objects is also excellent. Since the protection device prevents the strain gauge from deteriorating, it can be used in an external environment such as an overhead power transmission line, is extremely reliable, and has a great utility value.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a strain gauge protection device according to the present invention.

FIG. 2 is a plan view showing an external shape of a tension sensor equipped with the present protection device.

FIG. 3 is a side view showing the external shape of a tension sensor equipped with the present protection device.

FIG. 4 is a perspective view showing an external shape of a tension sensor equipped with the present protection device.

FIG. 5 is an exploded perspective view showing a structure of a metal case that constitutes the protection device.

[Explanation of symbols]

1 Hanging metal fittings (flexure element) 2 strain gauge 3 protective devices 7 cable 8 Cable extraction member 10 coating layer 11 metal cover 12 Protective layer 13 Case body (dividing element) 14 Lid (dividing element) 19 Free piece of the case body 22 Free piece of lid

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Claims (5)

(57) [Claims] 1. A protective device for protecting a strain gauge adhered to a strain-generating body which causes strain in one direction, comprising: an insulating coating layer adhered to the strain-generating body so as to wrap the strain gauge; A cover made of metal surrounding the flexure element including a coating layer, the cover forming front and rear side plates intersecting the strain direction of the flexure element from at least two free pieces, and A strain gauge protection device, wherein a free end of each free piece is elastically brought into contact with the flexure element. 2. The cover is divided into two parts in a plane parallel to the strain direction of the flexure element, and each of the division elements has a free piece, and they are integrated with each other in the division plane. The strain gauge protection device according to claim 1. 3. The strain gauge protection device according to claim 1, wherein the cover is made of austenitic stainless steel. 4. The strain gauge protection device according to claim 1, wherein the cover is filled with a resin. 5. The strain gauge protection device according to claim 1, wherein a suspension fitting for an overhead power transmission line is used as the strain-generating body, and a plurality of strain gauges are bonded to the suspension fitting. A tension sensor, wherein the cover is provided with a cable take-out member for taking out a cable in which the leads extending from the plurality of strain gauges are bundled.