KR101948775B1 - Composite joining apparatus - Google Patents

Abstract

An invention relating to a composite material joining apparatus is disclosed. The disclosed composite material bonding apparatus includes a pair of main body portions having fixing portions for pressing a composite material, and a heating portion mounted on the pair of main body portions, respectively, for applying heat to the point-bonding portions of the composite material do.

Description

COMPOSITE JOINING APPARATUS [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material joining apparatus and a composite material joining method, and more particularly, to a composite material joining apparatus and a composite material joining method capable of point bonding a composite material, .

BACKGROUND ART [0002] Composite materials having both the strength of metals and the lightness and moldability of plastics have recently been developed. Typical examples of such composite materials include fiber reinforced plastic (FRP) and carbon fiber reinforced plastic (CFRP).

Such a composite material is an advanced composite material which is attracting attention as a high-strength and high-elasticity lightweight structural material made of a fiber reinforced material, and has excellent characteristics as a lightweight structural material.

As a typical method of joining composite materials, a composite material and a metal material are mechanically joined using a general rivet, a self-piercing rivet and a bolt.

However, such a joining method increases the manufacturing cost compared to the welding method, the appearance quality of the joining work is not good, the investment cost can be increased due to the change of the joining equipment and the production environment due to the change of the joining composite material, There is a problem in that the structure of the semiconductor device becomes complicated.

BACKGROUND ART [0002] The background art of the present invention is disclosed in Korean Patent Laid-Open Publication No. 10-2015-0002945 (published on Mar. 23, 2017, entitled " Adhesive and composite material bonding method using the same).

SUMMARY OF THE INVENTION The present invention has been conceived to solve the problems described above, and it is an object of the present invention to provide a composite material joining apparatus capable of reducing a bonding time by heating a point junction region of a composite material to be bonded by a heating unit, And a method of joining materials.

A composite material bonding apparatus according to the present invention includes: a pair of body portions having a fixing portion for pressing a composite material; And a heating part mounted on the pair of main body parts, respectively, for applying heat to the point-bonding part of the composite material.

The heating unit may include: a heating body of a heat insulating material coupled to the body; And a heat dissipating unit disposed on one side of the heating body toward the composite material side and formed of a conductive material and radiating heat by power supply.

The plurality of heat dissipating units are provided, and are uniformly arranged with respect to the center of the heating body.

The composite material joining apparatus may further include a guide part surrounding the heat dissipating part and coupled to the heating body and guiding the heat generated from the heating part to the composite material side by opening the composite material side .

Further, the guide portion is characterized in that the inner diameter decreases toward the composite material side in the heating portion.

Further, the guide portion is formed of an insulating material.

The heating unit may include: a heating body coupled to the main body; And a discharge unit rotatably coupled to the heating body and applying heat to the composite material.

In addition, the emitting portion is characterized in that heat is applied to a point junction portion of the composite material by a laser method.

A sensor unit installed at a pair of the fixing units and detecting that each of the fixing units is disposed on a straight line; And a control unit for receiving an electrical signal from the sensor unit and controlling the operation of the driving unit.

According to another aspect of the present invention, there is provided a composite material joining method comprising: a disposing step of disposing a pair of main bodies each having a fixing portion; A heating step of subjecting the composite material to plastic deformation by applying heat to the composite material by a heating unit coupled to the body unit; And a fixing step of driving the main body to press and join the plurality of composite materials to the fixing part.

Further, the disposing step may include a sensing step of sensing that a pair of the fixing parts are arranged on a straight line.

The composite material bonding apparatus and the composite material bonding method using the same according to the present invention have the effect of improving the moldability of the composite material by heating the point junction portion of the composite material due to the heating portion and bonding the composite material to be bonded .

Further, since the heating unit does not require any additional equipment for deforming the composite material into a molded state, the manufacturing process of the parts is reduced and the production cost is reduced.

Further, there is an effect that heat is guided to the composite material side due to the guide portion and heat is prevented from being radiated outside the point junction region of the composite material.

In addition, since the guide portion is formed of the heat insulating material, it is possible to prevent the heat from being lost before the heat is applied to the point junction portion of the composite material.

Further, since the discharge part is rotatably coupled to the heating body, the heating part can be set differently according to the size and position of the joint part of the composite material.

1 is a perspective view illustrating a composite material bonding apparatus according to embodiments of the present invention.
2 is a side view showing a composite material bonding apparatus according to an embodiment of the present invention.
3 is a perspective view showing part A of Fig.
4 is a plan view showing a composite material bonding apparatus according to an embodiment of the present invention.
5 is a side view illustrating a state in which a composite material is heated by a composite material bonding apparatus according to an embodiment of the present invention.
6 is a side view illustrating a state in which a composite material is pressed according to an embodiment of the present invention.
7 is a block diagram showing a sensor unit according to an embodiment of the present invention.
8 is a side view showing a composite material bonding apparatus according to another embodiment of the present invention.
9 is a side view illustrating a state in which a composite material is heated by a composite material bonding apparatus according to another embodiment of the present invention.
10 is a side view showing a state where a composite material is pressed by a composite material bonding apparatus according to another embodiment of the present invention.
11 is a flowchart illustrating a composite material joining method according to an embodiment of the present invention.

Hereinafter, embodiments of a composite material bonding apparatus and a composite material bonding method using the same according to the present invention will be described with reference to the accompanying drawings. In this process, the thicknesses of the lines and the sizes of the components shown in the drawings may be exaggerated for clarity and convenience of explanation.

In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention or custom of the user, the operator. Therefore, definitions of these terms should be made based on the contents throughout this specification.

1 is a perspective view illustrating a composite material bonding apparatus according to embodiments of the present invention. 2 is a side view showing a composite material bonding apparatus according to an embodiment of the present invention. 3 is a perspective view showing part A of Fig. 4 is a plan view showing a composite material bonding apparatus according to an embodiment of the present invention. 5 is a side view illustrating a state in which a composite material is heated by a composite material bonding apparatus according to an embodiment of the present invention. 6 is a side view illustrating a state in which a composite material is pressed according to an embodiment of the present invention. 7 is a block diagram showing a sensor unit according to an embodiment of the present invention.

1 to 7, a composite material bonding apparatus 1 according to an embodiment of the present invention includes a main body 101, a heating unit 200, a driving unit 400, a guide unit 500, Unit 600, and a control unit 700. FIG.

Referring to FIGS. 1 to 3, 5 and 6, a plurality of body portions 101 according to an embodiment of the present invention are provided outside the composite materials M1 and M2, And includes a fixing portion 111.

Referring to FIGS. 2, 5, 6, 9, and 10, the composite materials M1 and M2 according to the present invention include a composite material M1 disposed on the upper side 2 standard). The term " composite material M2 "

In the present invention, the composite material (M1, M2) is a thermoplastic composite material which is plastically deformed by heat (H) to be molded, and hardened and hardened when the temperature is reduced.

1 to 3, 5 and 6, the fixing portion 111 is formed at each end of the pair of body portions 101 by pressing the composite materials M1 and M2.

The fixing part 111 presses the composite materials M1 and M2 as the body part 101 operated by the driving part 400 is moved. The fixing portion 111 is rounded at the contact end portions of the composite materials M1 and M2.

The pressing force is uniformly dispersed toward the composite materials M1 and M2 when the composite materials M1 and M2 are pressed due to rounding of the ends of the fixing portions 111. [ In addition to this, it is possible to prevent the pressing force from concentrating on a specific point on the composite materials M1 and M2 and to prevent breakage of the composite materials M1 and M2 to be bonded.

The fixing part 111 is formed of an insulating material and minimizes the influence of the heat H emitted from the heating part 200 to be described later and the composite material M1 and M2 deformed by the heat H So that it can be prevented from being welded to the portion 111.

In addition, the temperature of the portion of the composite material (M1, M2) in contact with the fixing portion (111) is reduced so that the composite materials (M1, M2) deformed by the high temperature are cooled and cured.

1 to 6, a heating unit 200 according to an embodiment of the present invention is coupled to a pair of body portions 101 and includes a heating body 210, a heat dissipating unit 220, .

2 to 4, the heating unit 200 surrounds the main body 101 and applies heat H toward the composite materials M1 and M2, and the diameter of the heating unit 200 is larger than the diameter (111).

The heating unit 200 according to an embodiment of the present invention is formed in a disc shape but is not limited thereto and may be formed into a polygonal shape or the like depending on the size and position of the heated portion of the composite material M1, And various other modifications can be made.

2 and 3, the heating body 210 according to an embodiment of the present invention is coupled to the main body 101 and is formed of a heat insulating material.

Thus, the main body 101 can be prevented from being deformed and damaged by the heat H generated from the heat dissipating unit 220 to be described later.

2 and 3, the heat dissipating unit 220 according to the embodiment of the present invention is installed on one side of the heating body 210. [ 2, the heat dissipating unit 220 is disposed on the upper surface of the heating body 210 disposed on the lower side (reference in FIG. 2) of the composite materials M1 and M2 ).

3 and 4, the heat dissipating unit 220 according to an embodiment of the present invention is protruded toward the composite material M1 and M2 (upper side in FIG. 3) on the upper surface of the heating body 210 But the present invention is not limited to this but may be applied to one side of the heating body 210 facing the composite materials M1 and M2 (upper side in FIG. 3) (Not shown) may be formed so that the insertion grooves 220 are inserted.

When the plurality of composite materials M1 and M2 are joined by the heat dissipating unit 220, heat H is applied to the point junctions of the composite materials M1 and M2, M1, and M2 are intensively generated.

Referring to FIGS. 1 to 4, the heat dissipating unit 220 according to an embodiment of the present invention is formed of a conductive material. The heat dissipating unit 220 may be disposed on the side of the composite materials M1 and M2 And radiates heat (H).

3 and 4, the heat dissipating unit 220 according to an exemplary embodiment of the present invention is formed in a net shape through which current flows, and radiates the heat H, but not limited thereto, Various modifications are possible.

Referring to FIGS. 3 and 4, a plurality of heat dissipating units 220 according to an embodiment of the present invention are equally arranged with respect to the center of the heating body 210.

3 and 4, the fixing unit 111 is disposed at the center of the heating body 210 according to an embodiment of the present invention and the heat dissipating unit 220 is disposed at the side of the composite materials M1 and M2 (H) is uniformly applied to the point bonding region when the composite materials (M1, M2) are bonded due to the uniform positioning of the fixing unit 111 on one side (upper side in FIG. 3) The materials M1 and M2 can be stably bonded.

Referring to FIGS. 1 and 7, a driving unit 400 according to an embodiment of the present invention provides power to the main body 101 so that the main body 101 presses the composite materials M1 and M2. The driving unit 400 may be formed by a motor type and may be supplied with power from the outside to drive the main body 101.

Referring to FIGS. 1 to 6, a guide unit 500 according to an embodiment of the present invention includes a heat dissipating unit 220 and a heating unit 210. The heating unit 200 includes a heating unit 200, The heat H generated in the diverging portion 220 is guided to the composite materials M1 and M2.

The guide part 500 opens the side of the composite materials M1 and M2 and guides the heat generated in the heating part 200 toward the composite materials M1 and M2.

5, the guide unit 500 according to an exemplary embodiment of the present invention includes a guide member 500 for guiding heat H generated in the heating unit 200 disposed on the upper side of the composite materials M1 and M2 (Refer to FIG. 5) of the heating unit 200 and guides the composite material to the composite materials M1 and M2 (reference lower side in FIG. 5).

5, the guide unit 500 according to an embodiment of the present invention is configured to guide the heat H generated in the heating unit 200 disposed below the composite materials M1 and M2 (Refer to FIG. 5) of the heating unit 200, and guides it to the side of the composite materials M1 and M2 (upper side of FIG. 5).

This prevents the heat H generated in the heating unit 200 from concentrating on the composite materials M1 and M2 and from being transmitted to the body 101 disposed outside the heating unit 200, It is possible to prevent the main body 101 from being damaged by the heat H of the main body 101. [

3 to 5, the guide unit 500 according to an embodiment of the present invention is characterized in that the inner diameter of the guide unit 500 decreases toward the composite materials M1 and M2 in the heating unit 200. FIG.

Referring to FIG. 4, the guide part 500 is formed to have a diameter smaller than that of the heating part 210, specifically, the heating part 200.

The heat H generated in the heating part 200 is moved to the point bonding part of the composite materials M1 and M2 along the guide part 500 and the point bonding part can be heated, Is changed in shape by the row (H), so that joining is possible.

The heating unit 200 according to an embodiment of the present invention is formed of an insulating material. This prevents the heat H generated in the heating unit 200 from being absorbed and lost by the guide unit 500 and prevents the heat H from being diverted to the outside of the heating unit 200 .

1 to 7, a sensor unit 600 according to an embodiment of the present invention is installed in a pair of fixing units 111, and each of the fixing units 111 is arranged on a straight line Detection. The sensor unit 600 may be formed to detect that the point junctions of the composite materials M1 and M2 are arranged between the fixing units 111 and the fixed unit and the point junctions are arranged on a straight line.

2 to 5, the sensor unit 600 according to an embodiment of the present invention includes an end portion of the fixing portion 111 on the side of the composite materials M1 and M2, specifically, an upper portion of the composite material M1 and M2 (Refer to FIG. 2) of the fixing part 111 disposed on the lower side (reference in FIG. 2) of the fixing part 111 (refer to FIG. 2) Respectively.

2 to 5, the sensor unit 600 according to the embodiment of the present invention is installed at the center of each of the fixing portions 111. Specifically, the center of the fixing portion 111 disposed on the upper side (reference in FIG. 2) of the composite materials M1 and M2 and the center of the fixing portion 111 disposed on the lower side of the composite materials M1 and M2 The center is formed to face each other.

The sensor unit 600 according to an embodiment of the present invention senses that the fixing portions 111 on the upper and lower sides of the composite materials M1 and M2 are arranged on a straight line, The pressing positions of the materials M1 and M2 coincide with each other and warping or the like can be prevented at the time of bonding the composite materials M1 and M2.

Referring to FIG. 2, signals between the sensor units 600 formed at the ends of the fixing unit 111 disposed on the upper and lower sides (reference in FIG. 2) of the composite materials M1 and M2 are exchanged, 111 are coincident with each other.

The sensor unit 600 according to an exemplary embodiment of the present invention senses whether or not each of the fixing units 111 is center-aligned through a current, but the present invention is not limited thereto. And the like.

Referring to FIG. 7, the controller 700 according to an embodiment of the present invention receives an electrical signal from the sensor unit 600 to control the operation of the driving unit 400.

The controller 700 according to an exemplary embodiment of the present invention may be configured such that the sensor unit 600 matches the centers of the fixing units 111 disposed on the upper and lower sides of the composite materials M1 and M2 The controller 400 receives the electrical signal from the sensor unit 600 and operates the driving unit 400 so that the main body 101 presses the composite materials M1 and M2.

The controller 700 according to an embodiment of the present invention may be configured such that the sensor unit 600 does not match the centers of the fixing units 111 disposed on the upper and lower sides of the composite materials M1 and M2 Upon sensing, the driving unit 400 receives an electrical signal from the sensor unit 600 and blocks the operation of the driving unit 400.

Hereinafter, the operation principle and effects of the composite material bonding apparatus 1 according to one embodiment of the present invention will be described.

1 to 8, a composite material bonding apparatus 1 according to an embodiment of the present invention includes a main body 101, a heating unit 200, a driving unit 400, a guide unit 500, (600), and a control unit (700).

The composite material joining apparatus 1 according to an embodiment of the present invention joins composite materials M1 and M2 made of carbon fiber or the like rather than metal such as steel. Composite materials (M1, M2) are thermoplastic composite materials (M1, M2), which are heated by heat (H) to cause plastic change, and when cooled, they are reversibly cured.

The pair of body portions 101 are disposed outside the composite materials M1 and M2 to be bonded. The body portion 101 is provided with a fixing portion 111 for pressing and pressing the composite materials M1 and M2.

5, the heating unit 200 is coupled to the pair of body portions 101 and applies heat H to the point-bonding portions of the composite materials M1 and M2. A current is caused to flow through the heat dissipating unit 220 provided on the side of the composite material M1 and M2 of the heating body 210 of the heat insulating material and the heat dissipating unit 220 is formed of a conductive material, And heat H is applied to the composite materials M1 and M2.

It is possible to heat the point bonding portions of the plurality of composite materials M1 and M2 to be bonded due to the heating portion 200, thereby causing plastic deformation of the thermoplastic composite materials M1 and M2.

A plurality of heat dissipating units 220 are provided and are uniformly arranged with respect to the center of the heating body 210 so that the heat H applied to the point bonding sites is uniformly concentrated on the composite material M1 , M2 can be heated.

5, the guide unit 500 surrounds the heat dissipating unit 220 and is coupled to the heating body 210 to guide the heat H toward the composite materials M1 and M2 to form a composite material M1 The heat H can be prevented from being radiated to the upper side of the heating unit 200 disposed on the upper side of the composite materials M1 and M2 (Refer to FIG. 5) of the heating section 200 disposed in the heating section 200 (see FIG. 5).

As a result, the heat H generated in the heating unit 200 is concentrated at the point-bonding sites of the composite materials M1 and M2, and the heat H is prevented from being transmitted to the body 101, It is possible to prevent the body 101 from being damaged.

5, when the guide unit 500 is heated from the heating unit 200 toward the composite materials M1 and M2, the heat generated by the heating unit 200 is transmitted to the heating unit 200, It is possible to heat the point junction portions of the composite materials M1 and M2 through the end portion of the guide portion 500 having a diameter smaller than the diameter of the guide portion 500. [

The guiding portion 500 is formed of a heat insulating material to prevent the heat H from being absorbed by the guide portion 500 and reduce the loss of the heat H transmitted to the composite materials M1 and M2 .

5 and 6, the composite material M1 and M2 are plastically deformed by heat of the composite material M1 and M2 generated in the heating unit 200, The main body 101 presses the composite materials M1 and M2.

The fixing portion 111 presses the composite materials M1 and M2 to be plastically deformed and the temperature of the composite materials M1 and M2 to be bonded decreases with time and is cured and bonded to each other.

Referring to FIGS. 5 and 6, since the ends of the fixing portions 111 contacting the composite materials M1 and M2 are round-processed, stress is prevented from concentrating on specific portions of the composite materials M1 and M2 , The pressing force is uniformly distributed to the contact portion so that the composite materials (M1, M2) are bonded.

The heat H generated in the heating part 200 prevents the bonding part of the composite material M1 and M2 from being transmitted to the fixing part 111 when heating the bonding part of the composite material M1 and M2 , And the pressing force against the composite materials (M1, M2) plastically deformed at a high temperature can be maintained.

5 to 7, a sensor unit 600 according to an embodiment of the present invention is installed in a fixed portion 111 formed in a pair of body portions 101, It detects that it is disposed in a straight line.

When the sensor unit 600 senses that the centers of the fixing units 111 are aligned with each other, the control unit 700, which transmits an electrical signal to the control unit 700 and receives an electrical signal from the sensor unit 600, (101) presses the composite material (M1, M2) to be bonded.

Alternatively, when the sensor unit 600 senses a mismatch between the centers of the fixing units 111, the controller 700 transmits an electrical signal to the controller 700 and receives an electrical signal from the sensor unit 600, The driving unit 400 is stopped so that the portion 101 does not press the composite materials M1 and M2 to be bonded.

Thereby, it is possible to improve the reliability of the bonding of the composite materials M1 and M2 by matching the bonding portions of the composite materials M1 and M2.

Hereinafter, the configuration, operation principle, and effects of the composite material bonding apparatus 1 according to another embodiment of the present invention will be described.

1 is a perspective view illustrating a composite material bonding apparatus according to embodiments of the present invention. 8 is a side view showing a composite material bonding apparatus according to another embodiment of the present invention. 9 is a side view showing a state in which a composite material is heated by a composite material bonding apparatus according to another embodiment of the present invention. 10 is a side view showing a state where a composite material is pressed by a composite material bonding apparatus according to another embodiment of the present invention.

The heating unit 300 according to another embodiment of the present invention is coupled to a pair of body portions 103 and has a point junction region And the heating body 310 and the emitting portion 320 by applying heat H to the heating body 310. [

8 and 9, the heating body 310 according to another embodiment of the present invention is coupled to the main body 103. In another embodiment of the present invention, the heating body 310 is formed into a disk shape However, the present invention is not limited thereto, and various modifications can be made in the shape of a leg portion (not shown) so that the discharge portion 320 to be described later is rotatably coupled.

Referring to FIGS. 8 to 10, the discharge part 320 according to another embodiment of the present invention is rotatably coupled to the heating body 310 and injects heat. As a result, the composite material M1 and M2 The injection direction can be set differently according to the size and position of the joint portion.

8 to 10, a discharge unit 320 according to another embodiment of the present invention emits heat in a laser (L) manner, thereby applying heat H toward a point junction, M1, and M2 can be heated.

In addition, there is an effect that the portion of the composite material M1 and M2 outside the point junction region can be prevented from being deformed by heat at high temperature due to the laser L.

The plurality of discharge portions 320 may be provided according to another embodiment of the present invention, thereby shortening the heating time for applying heat to the point-bonded portions of the composite materials M1 and M2, .

In the description of the composite material bonding apparatus 1 according to another embodiment of the present invention, the remaining components, operation principle, and effects except for the heating unit 300 are the same as those of the composite material bonding apparatus 1 according to the embodiment of the present invention. And therefore the description of the overlapping and corresponding portions will be omitted.

11 is a flowchart illustrating a composite material joining method according to an embodiment of the present invention.

A composite material joining method according to an embodiment of the present invention relates to a composite material joining method using a composite material joining apparatus 1 according to embodiments of the present invention. (S1-1) for arranging a plurality of composite materials (M1, M2) between the pair of main body portions (101, 103) and heating portions (200, 300) A heating step S2 of subjecting the composite materials M1 and M2 to plastic deformation by applying heat toward the materials M1 and M2 and driving the body portions 101 and 103 to fix the composite materials M1 and M2 to the fixing portions 111 and 113, (S3) for pressing and fixing the first and second plates (M1, M2).

According to the composite material joining method according to the embodiment of the present invention, the composite materials M1 and M2 are subjected to plastic deformation by applying heat, the composite materials M1 and M2 in a deformable state are pressed and fixed, And the materials M1 and M2 are cured by cooling to be bonded.

In addition, there is an effect that the heat can be intensively applied toward the point junctions of the composite materials M1 and M2.

Referring to Fig. 11, the arrangement step S1-1 includes a sensing step S1-2 for sensing that the fixing portions 111 and 113 are arranged on a straight line.

It is sensed whether or not the fixing portions 111 and 113 provided on the pair of body portions 101 and 103 are aligned with each other due to the sensing step S1-2 so that the pressing portions of the composite materials M1 and M2 are aligned There is an effect of preventing the composite materials M1 and M2 from being twisted when the plurality of composite materials M1 and M2 to be joined are pressed.

11, the sensing step S1-2 according to an embodiment of the present invention is formed after the arranging step S1-1, but the present invention is not limited thereto, and a pair of body parts 101 and 103 And are formed before being disposed outside the composite materials M1 and M2.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. I will understand.

Therefore, the technical scope of the present invention should be defined by the following claims.

1: Composite material bonding device M1, M2: Composite material
H: heat L: laser
101, 103: main body 111, 113:
200, 300: heating part 210, 310: heating body
220: heat dissipating unit 320:
400: driving part 500: guide part
600: sensor part 700: control part
S1-1: Placement step S1-2: Detection step
S2: heating step S3: fixing step

Claims (11)

A pair of main body portions having fixing portions for pressing the composite material;
And a heat dissipating unit disposed on one side of the heating body toward the composite material side and formed of a conductive material and radiating heat by power supply, A heating unit mounted on the main body unit and applying heat to a point junction region of the composite material; And
And a guide portion surrounding the heat dissipating portion and coupled to the heating body, the guide portion opening the composite material side to guide heat generated in the heating portion to the composite material side.
delete The method according to claim 1,
Wherein a plurality of the heat dissipating units are provided and are equally arranged with respect to a center of the heating body.
delete The method according to claim 1,
Wherein the guide portion has a smaller inner diameter toward the composite material side in the heating portion.
6. The method of claim 5,
Wherein the guide portion is formed of an insulating material.
The method according to claim 1,
The heating unit includes:
A heating body coupled to the body portion; And
And a discharge unit rotatably coupled to the heating body and applying heat to the composite material.
8. The method of claim 7,
Wherein the emitting part applies heat to a point junction part of the composite material in a laser manner.
The method according to claim 1,
A sensor unit installed at a pair of the fixing units and sensing that each of the fixing units is disposed on a straight line;
And a controller for receiving an electrical signal from the sensor unit and controlling an operation of the driving unit.
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