The present invention relates to a displacement extensometer for measuring the linear displacement of an object to be measured, the displacement extensometer comprising: a first bracket installed at a reference point so as to provide support force; a second bracket fixed to an object to be measured; a displacement meter body fixed to the first bracket and including a center rod connected to the second bracket, so as to detect displacement while the center rod horizontally moves according to positions of the object to be measured; a first link connecting the displacement meter body to the first bracket; a second link connecting the center rod of the displacement meter body to the second bracket; and a friction compensation member provided in the displacement meter body so as to compensate for the friction due to sagging of the center rod while providing physical stress to the center rod.

TECHNICAL FIELD

The present invention relates to a displacement extensometer for displacement measurement used in a structural integrity test of a containment building of a nuclear power plant, and more particularly, to a displacement extensometer in which a displacement meter body may be easily installed in a horizontal state and which may enhance precision by canceling frictional force caused by sagging of a center rod measuring displacement.

BACKGROUND ART

In general, as one of the structural integrity tests (SITs) for containment buildings installed in nuclear power plants, there is a displacement test using a displacement measuring device.

A displacement measuring device generally called a displacement extensometer refers to a device that measures or meters the movement distance or position of an object, and its measurement range is commonly zero to a few millimeters (mm) or centimeters (cm).

A representative example of such a displacement measuring device is a magnetic sensor using the magnetic principle.

Specifically, a magnetic sensor using the magnetic principle is an element that converts magnetism into electricity and is a transducer in which a mechanical displacement causes a change in the magnetic flux generated between the primary coil and the secondary coil, that is, mutual inductance. Such a transducer is called a linear variable differential transformer (LVDT).

Here, LVDT refers to a type of electrical transducer that measures the linear distance difference. Three solenoid coils are positioned around a tube, and the middle coil is a main one, and the other two are positioned outside.

In this case, a cylindrical magnet core moves along the center of the tube to indicate the position value of the measurement object. Therefore, the LVDT, which converts mechanical displacement into an electrical signal, is a transducer that changes the magnetic flux induced from the primary coil to the secondary coil by the movement of the core or armature, that is, the mutual inductance. In proportion to the displacement of the core which is mechanically or electrically separated and movable, an electrical output is generated. The position of the valve is controlled according to the amount of the output.

However, in such a conventional displacement measuring device, if the wire connected to the measurement object is long, the wire may sag so that the center rod where the core installed sags, causing friction with the housing.

Accordingly, the conventional displacement measuring device may cause an error in measurement due to the frictional force of the center rod, deteriorating precision.

Further, the conventional displacement measuring device has the problems that it is cumbersome to fix the displacement meter body to the measurement object, especially in the horizontal state of the displacement meter body.

Therefore, a need exists fora new technique to address such issues.

As a prior art document in the technical field to which the present invention pertains, there is Korean Patent Application Publication No. 10-2012-93382.

DETAILED DESCRIPTION OF THE INVENTION

Technical Problems

The present invention was created to address the foregoing problems of the prior art and aims to provide a high-resolution displacement extensometer that may minimize errors in displacement measurement by cancelling out the frictional force caused by sagging of the wire or the center rod connected to the object for displacement measurement.

Specifically, an object of the present invention is to provide a high-resolution displacement extensometer capable of canceling the frictional force of the center rod by periodically providing vibrations to the center rod inside the displacement meter body.

Further, an object of the present invention is to provide a high-resolution displacement extensometer that may firmly and easily fix the first bracket and the second bracket fixed to the measurement object, and in particular, guide the first bracket and the second bracket to be installed in a horizontal state while fixing them.

MEANS TO ADDRESS THE PROBLEMS

To achieve the foregoing objectives, according to an embodiment of the present invention, a displacement extensometer measuring a linear displacement of a measurement object may comprise a first bracket installed at a reference point to provide a supporting force; a second bracket fixed to the measurement object; a displacement meter body fixed to the first bracket, including a center rod connected to the second bracket, and detecting a displacement as the center rod is horizontally moved according to a position of the measurement object; a first link connecting the displacement meter body with the first bracket; a second link connecting the center rod of the displacement meter body with the second bracket; and a friction compensation member provided in the displacement meter body and providing physical stress to the center rod to cancel a frictional force due to sagging of the center rod.

In this case, the displacement extensometer may further comprise a first fixing member detachably fixing the first bracket to the reference point; a second fixing member detachably fixing the second bracket to the measurement object; and a centering member guiding the first bracket to be horizontal with the second bracket while visually guiding an installation position of one of the first bracket and the second bracket to the other.

Further, the friction compensation member may include at least one vibration motor built in the displacement meter body, connected to the center rod, and vibrating the center rod in a preset period.

Further, the displacement meter body may include a displacement meter housing having a first end connected with the first link and a second end having a withdrawal hole through which the center rod is drawn out; a load plate fixed to the center rod while being movably built in the displacement meter housing and horizontally moving along with the center rod; a plurality of guide rods installed along a length direction of the displacement meter housing to movably guide the load plate; return springs provided on the guide rods and elastically compressed by a movement of the load plate and returning the load plate to an original position; a plurality of solenoid coils built in the displacement meter housing, positioned outside the center rod, and generating a magnetic field; and a magnetic body installed in the center rod, positioned between the solenoid coils, and providing, along with the solenoid coils, to an electrical output according to the displacement while moving along with the center rod, and wherein the vibration motor is attached to the load plate and operates to vibrate the load plate.

Further, the second link may include an invar wire connected to the second bracket; and a turnbuckle connecting the invar wire and the center rod and adjusting an interval between the invar wire and the center rod.

Further, the first link may include a first fork fixed to the first bracket; a second fork fixed to the displacement meter body while being orthogonal to the first fork; and a tilting block provided between the first fork and the second fork to allow tilting in upper and lower directions and left and right directions of the displacement meter body.

Effects of the Invention

According to an embodiment of the present invention, in the displacement extensometer, as the vibration motor constituting the friction compensation member operates in a preset period to provide vibration to the center rod, the frictional force due to sagging of the center rod may be canceled, reducing an error rate due to frictional force.

In particular, according to an embodiment of the present invention, in the displacement extensometer, the vibration motor is attached to the load plate fixed to the center rod, so that the vibration generated by the vibration motor may be smoothly provided to the center rod as well as the invar wire to cancel the friction force.

Further, according to an embodiment of the present invention, in the displacement extensometer, the first bracket and the second bracket may be firmly and easily fixed to the object by the first fixing member and the second fixing member. In particular, since one installation position is visually guided to the other by the centering member while the first bracket and the second bracket are installed, the first bracket and the second bracket may be accurately installed in a horizontal state with each other.

Further, according to an embodiment of the present invention, the displacement extensometer may easily adjust the distance between the measurement object and the displacement meter body because the second link includes the turnbuckle.

Further, according to an embodiment of the present invention, in the displacement extensometer, the first link includes a pair of forks facing each other orthogonally to each other, thus allowing tilting of the displacement meter body in the upper and lower directions and left and right directions and hence keeping the displacement meter body horizontal.

Other objects of the present invention are not limited to the foregoing objects, and other objects will be apparent to one of ordinary skill in the art from the following detailed description.

MODE TO PRACTICE THE INVENTION

Hereinafter, embodiments of the disclosure are described in detail with reference to the accompanying drawings. The same references may be used to denote the same or similar elements throughout the drawings and the specification, and no duplicate description is given of the elements. As used herein, the terms “module” and “unit” are provided solely for ease of description and these terms may be used interchangeably but rather than being distinct in meaning or role.

When determined to make the subject matter of the present invention unclear, the detailed description of the known art or functions may be skipped. The accompanying drawings are provided merely for a better understanding of the disclosure and the technical spirit or the scope of the invention are not limited by the drawings.

The terms coming with ordinal numbers such as ‘first’ and ‘second’ may be used to denote various components, but the components are not limited by the terms. The terms are used to distinguish one component from another.

It will be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “adjacent to” another element or layer, it can be directly on, connected, coupled, or adjacent to the other element or layer, or intervening elements or layers may be present. In contrast, when a component is “directly connected to” or “directly coupled to” another component, no other intervening components may intervene therebetween.

The displacement extensometer according to the present invention may be mainly used in building structures and, particularly, is suitable for, but not limited to, nuclear power plant SITs.

Hereinafter, for convenience of description, a displacement extensometer for a SIT of a nuclear power plant is described as a main example.

FIG.1is an exploded perspective view illustrating a displacement extensometer according to an embodiment of the present invention.FIG.2is a perspective view illustrating a displacement meter body according to an embodiment of the present invention.FIG.3is a perspective view illustrating the displacement meter body ofFIG.2as viewed in the opposite direction.FIG.4is a front view illustrating a displacement extensometer for a SIT of a nuclear power plant according to an embodiment of the present invention.

According to an embodiment of the present invention, the displacement extensometer is a device for measuring the linear displacement of a measurement object, e.g., a device for measuring a change in the distance between the measurement object and a reference point in a tensile test of the measurement object.

Specifically, according to an embodiment of the present invention, the displacement extensometer may include a first bracket100, a second bracket200, a displacement meter body300, a first link400, a second link500, and a friction compensation member600.

The first bracket100may form a reference point for displacement measurement while supporting a first end of two opposite ends in the length direction of the displacement meter body300to be described below and may provide a supporting force for installation of the first end of the displacement meter body300while being installed at the reference point.

The first bracket100may be coupled to the displacement meter body300via the first link400to be described below.

Specifically, the first link400may include a first fork410, a second fork420and a tilting block430as shown inFIGS.1and4.

The first fork410may be fixed to the first link400and include fork portions divided to two opposite sides to rotatably receive the tilting block430described below between the fork portions.

The second fork410has fork portions divided in the same manner as those of the first fork410and is fixed to the displacement meter body300while forming a state of being orthogonal to the first fork410. The second fork410may rotatably receive the tilting block430described below, between the fork portions.

The tilting block430is a component that is coupled between the first fork410and the second fork420and allows tilting of the displacement meter body300in the upper and lower directions and left and right directions while rotating in the upper and lower directions or the left and right directions.

In other words, the tilting block430is formed in the shape of a rod having a predetermined length, so that one end of the tilting block430may be coupled to the first fork410in the upper and lower directions, and the other end thereof may be rotatably coupled to the second fork420in the left and right directions, allowing tilting of the displacement meter body300fixed to the second fork420in the left and right directions and upper and lower directions.

The second bracket200is a component that is fixed to the measurement object and supports a second end of the two opposite ends in the length direction of the displacement meter body300.

In other words, the second bracket200is fixed to an object to be measured for displacement while horizontally facing the first bracket100and supports the second end of the displacement meter body300.

The second bracket200may be coupled to the displacement meter body300via the second link500to be described below.

Specifically, the second link500may include an invar wire510and a turnbuckle520as shown inFIGS.1and4.

The invar wire510is a component that connects the second bracket200and the displacement meter body300and is formed of a wire having a predetermined length while being formed of a material having a small coefficient of expansion to enhance measurement precision. A first end of the invar wire510is fixed to the second bracket200while a second end thereof is fixed to the displacement meter body300via the turnbuckle520described below.

The turnbuckle520is a component that adjusts the tension of the invar wire510by adjusting the interval between the invar wire510and the displacement meter body300.

Specifically, the turnbuckle520may be coupled to the invar wire510and the center rod300aof the displacement meter body300through screw rods screwed to two opposite ends thereof. The turnbuckle520closes the screw rods by forward rotation or opens the screw rods by reverse rotation, thereby adjusting the interval between the interval between the invar wire510and the center rod300aof the displacement meter body300.

The displacement meter body300is a component for detecting and measuring the displacement of the measurement object and is installed between the first bracket100and the second bracket200to measure the displacement of the measurement object through the horizontal movement of the center rod300aconnected to the second bracket200.

As shown inFIGS.2and3, the displacement meter body300may include a displacement meter housing310, a load plate320, guide rods330, return springs340, solenoid coils340, and a magnetic body360.

The displacement meter housing310constitutes the body of the displacement measuring device and is formed in a cylindrical shape and includes an installation space formed therein.

This displacement meter housing310is provided with the above-described second fork420at a first end and is connected to the tilting block430and fixed to the first bracket100. The above-described center rod300ais drawn out of a second end of the displacement meter housing310and is fixed to the above-described turnbuckle520.

Further, the displacement meter housing310is provided with a connector311for connecting a power source and it is provided with a laser pointer312to irradiate a laser beam to the measurement object to for zeroing during installation.

Further, the displacement meter housing310is provided with a variable resistor313to convert the horizontal displacement caused by the horizontal movement of the center rod300ainto a change in electrical resistance.

The load plate320is a member that moves together with the center rod300a. As shown inFIGS.2and3, the load plate320is movably embedded in the displacement meter housing310and fixed to the center rod300aand moves along with the center rod300aaccording to the displacement of the measurement object.

The guide rods330movably guide the load plate320and are fixed along the length direction of the displacement meter housing310to be fitted into the load plate320so that the load plate320is movable.

In other words, when the displacement of the measurement object increases, the load plate320, along with the center rod300a, moves toward the measurement object along the length direction of the guide rods300.

The return springs340are coupled along the length direction of the guide rods330and are elastically compressed by the movement of the load plate320and return the load plate320to its original position.

In other words, when the displacement of the measurement object increases, the load plate320, together with the center rod300a, moves while compressing the return springs340of the guide rods330and, when the displacement of the measurement object decreases, the load plate320is returned to its original position by the elastic force of the return springs340.

The solenoid coils350are built in the displacement meter housing100to generate a magnetic field. The solenoid coils350are operated by power applied through the connector311of the displacement meter housing310to generate a magnetic field.

The magnetic body360is positioned between the solenoid coils350while being installed on the center rod300a. As the displacement of the measurement object increases, the magnetic body360, together with the center rod300a, moves, generating, together with the solenoid coils350, an electrical output.

In other words, the displacement extensometer according to the present invention may measure the displacement through the position of the magnetic body360moving together with the center rod300aaccording to the displacement of the measurement object.

Meanwhile, as the distance from the measurement object increases, the invar wire510sags, the center rod300adoes not remain in the horizontal state but is inclined to sag and contacts the through hole of the displacement meter housing310, causing a frictional force.

The friction compensation member600may cancel the friction force that occurs as the center rod300sags. The friction compensation member600may cancel the frictional force by providing physical stress to the center rod300a.

For example, the friction compensation member600may be formed of a vibration motor that is built in the displacement meter body300to vibrate the center rod300a. Preferably, the friction compensation member600may vibrate the center rod300awhile operating in a preset period, thereby canceling the friction to thereby reduce an error rate during displacement measurement.

Specifically, the vibration motor constituting the friction compensation member600may be attached to the above-described load plate320to periodically vibrate the load plate320. In this case, the vibration generated by the vibration motor may be transferred up to the displacement meter body300and the invar wire510, as well as to the center rod300a, thereby canceling the frictional force.

In other words, the vibration motor may cancel the friction of the center rod300awith the through hole of the displacement meter housing310by vibrating the center rod300athrough its periodic operation and may prevent friction by spacing the center rod300aapart from the through hole through vibration.

Thus, the displacement extensometer according to an embodiment of the present invention may be free from a reduction in measurement current even when the invar wire510is long and may reduce in the stratified behavior and residual deviation phenomenon, thus reducing an error rate.

Meanwhile, according to an embodiment of the present invention, the displacement extensometer further may include a first fixing member150, a second fixing member250, and a centering member700as shown inFIG.1.

The first fixing member150is a component for detachably fixing the first bracket100to the reference point.

For example, the first fixing member150may be formed of a fixing bolt that passes through the first bracket100and is fastened to the reference point.

Alternatively, the first fixing member150may be configured as a suction plate that is suctioned and fixed to the reference point while being detachably fixed to the rear surface of the first bracket100.

Alternatively, the first fixing member150may be configured as a magnet that is provided as the same body as the first bracket100and is fixed to the reference point of the metal material through magnetic force.

The second fixing member250is a component for detachably fixing the second bracket200to the measurement object.

For example, the second fixing member250may be formed of a fixing bolt that passes through the second bracket200and is fastened to the reference point.

Alternatively, the second fixing member250may be configured as a suction plate that is suctioned and fixed to the reference point while being detachably fixed to the rear surface of the second bracket200.

Alternatively, the second fixing member250may be configured as a magnet that is provided as the same body as the second bracket200and is fixed to the reference point of the metal material through magnetic force.

The centering member700is a component that guides the center of the first bracket100and the center of the second bracket200to form a horizontal state with each other.

Specifically, the centering member700visually guides the installation position of one of the first bracket100and the second bracket200to the other, thereby allowing the center of the first bracket100to be horizontally aligned with the center of the second bracket200.

In other words, the first bracket100and the second bracket200may be fixed through the first fixing member150and the second fixing member250while forming a horizontal state with each other by the centering member700.

Here, the centering member700may include a pointer710that is provided on one of the first bracket100and the second bracket200to irradiate light to the other and a light receiving portion720that is provided on the other one of the first bracket100and the second bracket200in a position corresponding to the pointer710to receive the light from the pointer710to thereby provide a reference point.

For example, as shown inFIG.1, the pointer710which is provided on the second bracket200radiates light to the first bracket100, thereby visually guiding the installation position of the second bracket200.

Further, as shown inFIG.1, the light receiving portion720may be provided on the first bracket100in a position corresponding to the pointer710to receive the light from the pointer710.

Thus, the user may install the first bracket100and the second bracket200in a state of being horizontal to each other by aligning the light from the pointer710to the light receiving portion720while installing the first bracket100after installing the second bracket200.

As described above, according to an embodiment of the present invention, in the displacement extensometer, as the vibration motor constituting the friction compensation member600operates in a preset period to provide vibration to the center rod300a, the frictional force due to sagging of the center rod300amay be canceled, reducing an error rate due to frictional force.

Although embodiments of the present invention have been described with reference to the accompanying drawings, It will be appreciated by one of ordinary skill in the art that the present disclosure may be implemented in other various specific forms without changing the essence or technical spirit of the present disclosure. Thus, it should be noted that the above-described embodiments are provided as examples and should not be interpreted as limiting. Each of the components may be separated into two or more units or modules to perform its function(s) or operation(s), and two or more of the components may be integrated into a single unit or module to perform their functions or operations.

It should be noted that the scope of the present invention is defined by the appended claims rather than the described description of the embodiments and include all modifications or changes made to the claims or equivalents of the claims.

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