CN216119347U - Display device - Google Patents

Abstract

The utility model provides a display device, which comprises a back plate and a front shell; the front side surface of the back plate is provided with a display panel for displaying image information; the peripheral edge of the back plate is provided with insertion tongues protruding forwards; the inserting tongue is provided with a first clamping part; the front shell is positioned at the outer sides of the back plate and the display panel; the front shell is provided with a limiting structure and a second clamping part; the limiting structure is used for enabling the insertion tongue to stretch into the limiting structure to limit the movement of the front shell along the up-down direction and the left-right direction, and enabling the first clamping portion and the second clamping portion to be matched with each other to limit the front shell to move forwards relative to the back plate. Preceding shell and backplate counterpoint the back, preceding shell moves backward relative to the backplate, and will preceding shell spacing on the backplate, conveniently will preceding quick the installing on the backplate of shell. The installation of preceding shell on the backplate has reduced the use quantity of screw, and simple to operate has improved the efficiency of production, has saved the cost of production.

Description

Display device

Technical Field

The utility model relates to the technical field of display, in particular to a display device.

Background

With the development of society, the labor cost is increased year by year, the proportion of the labor cost of products on the whole production chain is heavier, and more enterprises pay attention to how to reduce the labor cost, improve the production efficiency and ensure the production consistency; particularly in the household appliance industry, the industry competition is more intense, and how to better ensure the quality and the quantity and reduce the cost becomes an important direction for the survival and the development of household appliance enterprises.

In the television industry at present, the connection and fixation of the rear shell and the back plate of the flat-panel television are generally fixed by screws for a long time because of the problems of material characteristics, dimensional tolerance and the like. Flat panel televisions typically employ a plastic front shell design with 4 to 9 screws. With the development of the market, the cost competition of various brands of televisions is more and more intense, and the cost compression space of the low-end computers is smaller and smaller. When the screw fixing method is adopted, screws are locked one by a machine or manually, and the assembling working hour is too long. Even if a robot or a mechanical arm is used for multi-station synchronous screw locking, the equipment cost and the implementation difficulty are higher.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a display device, which is convenient for quickly mounting a front shell on a back plate.

In order to solve the technical problems, the utility model adopts the following technical scheme:

according to one aspect of the present invention, there is provided a display device including a rear panel, and a front case; the front side surface of the back plate is provided with a display panel for displaying image information; the peripheral edge of the back plate is provided with insertion tongues protruding forwards; the inserting tongue is provided with a first clamping part; the front shell is positioned at the outer sides of the back plate and the display panel; the front shell is provided with a limiting structure and a second clamping part; the limiting structure is used for enabling the insertion tongue to extend into the limiting structure to limit the movement of the front shell along the vertical and horizontal directions, and enabling the first clamping portion and the second clamping portion to be matched with each other to limit the front shell to move forwards relative to the back plate.

In some embodiments of the present application, the peripheral edge of the back plate extends outward away from the center of the back plate to form a protrusion; the insertion tongue is formed at an outer end of the protruding part.

In some embodiments of the present application, the front shell includes a vertically disposed front plate, and an outer plate extending rearward from an outer end of the front plate; the limiting structure and the second clamping part are arranged on the outer plate.

In some embodiments of the present application, the limiting structure includes two limiting claws which are spaced and oppositely arranged; the two limiting claws are arranged on the inner surface of the outer plate in a protruding mode; the two limiting claws are respectively abutted against two edges of the inserting tongue and are pressed on the inner surface of the inserting tongue.

In some embodiments of the present application, each of the two limiting claws includes an extending portion protruding from an inner surface of the outer plate, and an abutting portion extending from inner ends of the extending portions toward each other; the extension part is abutted against two edges of the inserting tongue, and the abutting part is abutted against the inner surface of the inserting tongue.

In some embodiments of the present application, the limiting structure further includes a rib protruding from the inner surface of the outer plate, and the rib is located between the two limiting claws; the convex rib is abutted against the outer surface of the inserting tongue.

In some embodiments of the present application, the rib extends in a front-rear direction, and a rear end of an inner surface of the rib is disposed obliquely in a direction away from a center of the back plate.

In some embodiments of the present application, a locking protrusion protruding away from the back plate is disposed on an outer surface of the insertion tongue to form the first engaging portion; the inner surface of the outer plate is convexly provided with a limiting rib to form a second clamping part; the clamping protrusion is clamped on the front side face of the limiting rib.

In some embodiments of the present application, the outer plate is provided with an observation hole penetrating through the inner and outer surfaces; the insertion tongue is provided with an alignment hole corresponding to the observation hole; the alignment hole is opposite to the observation hole.

In some embodiments of the present application, the insertion tongue is provided in a plurality at intervals along an edge direction of the back plate, and the limiting structure is provided in a plurality corresponding to the insertion tongue.

According to the technical scheme, the utility model has at least the following advantages and positive effects:

according to the utility model, the front shell moves backwards, so that the insertion tongue extends into the limiting structure to limit the movement of the front shell along the vertical and horizontal directions, and the first clamping part and the second clamping part are matched to limit the forward movement of the front shell relative to the back plate. Preceding shell and backplate counterpoint the back, preceding shell moves backward relative to the backplate, and will preceding shell spacing on the backplate, conveniently will preceding quick the installing on the backplate of shell. The installation of preceding shell on the backplate has reduced the use quantity of screw, and simple to operate has improved the efficiency of production, has saved the cost of production.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of a display device of the present invention.

Fig. 2 is an exploded schematic view of an embodiment of a display device of the present invention.

Fig. 3 is an exploded schematic view of a back plate and a front case of an embodiment of a display device of the present invention.

FIG. 4 is a schematic cross-sectional view of a back plate of an embodiment of a display device according to the present invention.

FIG. 5 is a schematic cross-sectional view of another viewing angle of a backplane of an embodiment of a display device according to the utility model.

Fig. 6 is a schematic structural diagram of a front case of an embodiment of a display device of the present invention.

Fig. 7 is an enlarged view at a in fig. 6.

Fig. 8 is a partial cross-sectional view of a back plate and front housing connection of an embodiment of a display device of the present invention.

The reference numerals are explained below: 100. a back plate; 110. inserting a tongue; 120. a bottom wall; 130. a protruding portion; 140. clamping convex; 150. aligning holes; 160. a circumferential wall; 200. a display panel; 300. a front housing; 310. a front plate; 320. an outer plate; 330. a limiting claw; 331. an extension portion; 332. an abutting portion; 340. a rib is protruded; 350. limiting ribs; 360. an observation hole; 400. a rear shell.

Detailed Description

Exemplary embodiments that embody features and advantages of the utility model are described in detail below in the specification. It is to be understood that the utility model is capable of other embodiments and that various changes in form and details may be made therein without departing from the scope of the utility model and the description and drawings are to be regarded as illustrative in nature and not as restrictive.

In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated in a particular manner, and are not to be construed as limiting the present application. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

In the television industry at present, the connection and fixation of the rear shell and the back plate of the flat-panel television are generally fixed by screws for a long time because of the problems of material characteristics, dimensional tolerance and the like. Flat panel televisions typically employ a plastic front shell design with 4 to 9 screws. With the development of the market, the cost competition of various brands of televisions is more and more intense, and the cost compression space of the low-end computers is smaller and smaller. When the screw fixing method is adopted, screws are locked one by a machine or manually, and the assembling working hour is too long. Even if a robot or a mechanical arm is used for multi-station synchronous screw locking, the equipment cost and the implementation difficulty are higher.

For convenience of description and understanding, the state of the display device when the display device is vertically placed for use is taken as a reference, the vertical direction is the up-down direction, the direction facing the user is the front, the direction back to the user is the rear, and the width direction of the display device is the left-right direction; the direction towards the center of the backboard is inward, and the direction away from the center of the backboard is outward.

Fig. 1 is a schematic structural diagram of an embodiment of a display device of the present invention. Fig. 2 is an exploded schematic view of an embodiment of a display device of the present invention.

Referring to fig. 1 and 2, the present embodiment provides a display device, which mainly includes a back plate 100, a display panel 200 mounted on a front side of the back plate 100, a front case 300 disposed below the back plate 100, and a rear case 400 detachably mounted on a back surface of the back plate 100. The display device is a television, a computer monitor, or the like, and the following description will be given taking a television as an example.

The display panel 200 is disposed on the front side of the backplate 100 for displaying image information for a user to watch. The outer peripheral edge of the rear panel 100 is further provided with a center frame (not shown) and a front case 300 to dispose the display panel 200 on the front side of the rear panel 100 through the center frame or the front case 300. There is a space between the front side of the back plate 100 and the back side of the display panel 200, and an optical film set and a light source are disposed in the space, and light emitted from the light source passes through the optical film set to display image information on the display panel 200.

In this embodiment, the front case 300 is disposed at the bottom ends of the rear panel 100 and the display panel 200 to connect the display panel 200 and the rear panel 100, and to close the bottom ends of the rear panel 100 and the display panel 200.

The electronic component mainly comprises a mainboard, a power panel, a sound assembly and a power strip. The electronic components are fixed on the rear surface of the rear panel 100 and are located within the coverage of the rear case 400 to protect the electronic components with the rear case 400. The main board is mainly used for operating the control system and correspondingly outputting related operation instructions. The main board is fixed between the rear surface of the rear panel 100 and the rear case 400.

In some embodiments, the power board is integrated on the motherboard, and is mainly used for providing a driving voltage or a stable operating voltage to the motherboard and keeping an output current of a circuit on the motherboard stable during operation. The sound component is disposed on the back side, left side, right side, or front side of the main board, and is mainly used for generating corresponding sound in cooperation with the interface displayed on the display panel 200.

The power strip is provided with a plurality of interfaces of different types for connecting external equipment. To receive signals from or output signals to an external device.

The rear case 400 is mounted on the rear surface of the rear panel 100, and covers and shields the electronic components to protect the electronic components on the rear surface of the rear panel 100. The rear case 400 is detachably fitted to the rear surface of the rear panel 100, so that the electronic components on the rear surface of the rear panel 100 can be repaired and inspected after the rear case 400 is detached.

In some embodiments, the display device further includes a base fixed to the rear surface of the rear panel 100 for supporting the rear panel 100, thereby supporting the entire display device. In other embodiments, the base is disposed on the rear case 400. In other embodiments, the display device is not provided with a base, and the back of the display device is provided with a hanger to hang the display device on a wall.

Fig. 3 is an exploded schematic structure diagram of a back plate 100 and a front case 300 of an embodiment of a display device of the present invention. Fig. 4 is a schematic cross-sectional view of a back plate 100 of an embodiment of a display device according to the present invention. Fig. 5 is a schematic cross-sectional view of another perspective of a back plate 100 of an embodiment of a display device according to the utility model.

Referring to fig. 2 to 5, the back plate 100 is disposed on a rear side of the display panel 200 for supporting the display panel 200 and corresponding electronic components.

The peripheral edge of the rear plate 100 is provided with forwardly extending insertion tongues 110 for cooperating with the front case 300 to fix the front case 300 to the peripheral edge of the rear plate 100. In this embodiment, the front case 300 is a lower front case and is located at the bottom end of the back plate 100. In other embodiments, the front case 300 is located at the upper end or left and right edges of the rear panel 100.

In this embodiment, the peripheral edge of the back plate 100 protrudes forward to form a bottom wall 120. The bottom wall 120 partially protrudes away from the center of the rear plate 100 to form a protruding portion 130, and the latch 110 is formed at an outer end of the protruding portion 130 and protrudes forward. The insertion tongue 110 extends outward beyond other portions of the bottom wall 120 to facilitate the insertion of the insertion tongue 110 and the front housing 300. In some embodiments, the protruding portion 130 is not disposed on the back plate 100, and the insertion tongue 110 is formed at the front end of the bottom wall 120.

The back plate 100 is made of metal material, so as to ensure the structural strength of the back plate 100, and thus the structural strength of the tongue 110.

The plurality of insertion tongues 110 are arranged at intervals along the edge direction of the back plate 100, and the arrangement of the plurality of insertion tongues 110 makes the connection of the back plate 100 to the front shell 300 more stable and reliable.

In this embodiment, the outer surface of the tongue 110 is provided with a protruding part 140 protruding away from the back plate 100 to form a first engaging part. The snap protrusions 140 are adapted to cooperate with the front housing 300 to limit the forward movement of the front housing 300 relative to the back plate 100. The front side of the catching protrusion 140 is a slope inclined backward in the inward-outward direction, and the slope is used for guiding.

In some embodiments, the outer surface of the tongue 110 is provided with a fastening hole to form a first fastening portion. In other embodiments, the first engaging portion is a protruding portion 140 or a hole disposed on an inner surface of the tongue 110.

In this embodiment, the insertion tongue 110 is provided with an alignment hole 150, and the alignment hole 150 is used for matching with a corresponding structure of the front housing 300 to observe the assembling condition of the insertion tongue 110 and the front housing 300. The alignment hole 150 penetrates both the inner and outer sides of the insertion tongue 110.

The inner surface or the outer surface of the tongue 110 is convexly provided with the annular circumferential wall 160 at the edge of the alignment hole 150, and through the arrangement of the circumferential wall 160, the structural strength of the tongue 110 caused by the arrangement of the alignment hole 150 can be prevented from being weakened, and the overall structural strength of the tongue 110 can be enhanced. In this embodiment, the annular wall 160 is protruded from the inner surface of the tongue 110, and the annular wall 160 on the inner surface does not interfere with the fitting of the outer surface of the tongue 110. In some embodiments, the circumferential wall 160 is disposed on an outer surface of the tongue 110.

Fig. 6 is a schematic structural diagram of a front case 300 of an embodiment of a display device of the present invention. Fig. 7 is an enlarged view at a in fig. 6. Fig. 8 is a partial sectional view showing the connection of the rear plate 100 and the front case 300 according to the embodiment of the display device of the present invention.

Referring to fig. 2 to 8, the front case 300 is disposed outside the rear panel 100 and the display panel 200 to close a gap between the outside of the display panel 200 and the outside of the rear panel 100. The front case 300 is disposed along an edge direction of the rear plate.

The front case 300 extends entirely along the peripheral edge direction of the rear panel to connect and block the outer edges of the rear panel 100 and the display panel 200. In this embodiment, the front case 300 is a lower front case extending in the left-right direction and covering the bottom edges of the rear panel 100 and the display panel 200.

In this embodiment, the front case 300 includes a front plate 310 vertically disposed, and an outer plate 320 formed by extending rearward from an outer end of the front plate 310; the outer panel 320 is connected to the outer end of the rear panel 100 and shields the outer side of the rear panel 100 and the outer side of the display panel 200. The front plate 310 is attached to the edge of the front side of the display panel 200 to sandwich the display panel 200 between the front case 300 and the rear panel 100.

The front shell 300 is provided with a limiting structure; the limiting structure is used for being clamped on the insertion tongue 110 backwards to limit the movement of the front shell 300 along the up-down and left-right directions. The front shell 300 is further provided with a second clamping portion, and the first clamping portion is matched with the second clamping portion to limit the front shell 300 to move forwards relative to the back plate 100, so that the insertion tongue 110 is prevented from being separated from the limiting structure, and the connection reliability of the front shell 300 and the back plate 100 is ensured.

The front housing 300 moves backwards, so that the insertion tongue 110 extends into the limiting structure to limit the movement of the front housing 300 along the up-down and left-right directions, and the first clamping portion and the second clamping portion are matched to limit the forward movement of the front housing 300 relative to the back plate 100. After the front housing 300 and the back plate 100 are aligned, the front housing 300 moves backward relative to the back plate 100, and the front housing 300 is limited on the back plate 100.

In this embodiment, the limiting structure and the second engaging portion are disposed on the outer plate 320. The front plate 310 covers the front side of the stopper structure and the second engaging portion. In some embodiments, the front housing 300 does not include the front panel 310, and only includes the outer panel 320.

The limiting structure comprises two limiting claws 330 which are arranged at intervals and oppositely and a convex rib 340 arranged between the two limiting claws 330. The two limiting claws 330 are arranged at intervals along the edge direction of the back plate 100 to limit the movement of the back plate 100 of the tongue 110 in the edge direction, the convex rib 340 abuts against the outer surface of the tongue 110, the inner surface of the tongue 110 also abuts against the limiting claws 330, and the movement of the tongue 110 in the inner and outer directions is limited by the matching of the limiting claws 330 and the convex rib 340. In some embodiments, the limiting structure is an opening with an opening at the rear end, and the periphery of the tongue 110 abuts against the inner peripheral wall of the opening to limit the movement of the tongue 110.

In this embodiment, the two limiting claws 330 are convexly arranged on the inner surface of the outer plate 320; the two limiting claws 330 respectively abut against two edges of the tongue 110 and are pressed on the inner surface of the tongue 110. The two restricting claws 330 each include an extending portion 331 provided on the inner surface of the outer plate 320 in a protruding manner, and an abutting portion 332 extending from the inner end of the extending portion 331 toward each other; the extension 331 abuts against two opposite edges of the tongue 110, and the abutment 332 abuts against an inner surface of the tongue 110.

The two limiting claws 330 are spaced in the left-right direction and are oppositely arranged, so that the abutting portions 332 of the two limiting claws 330 have a space in the edge direction of the back plate, and do not interfere with the annular peripheral wall 160 on the inner surface of the tongue 110.

The front ends of the extension 331 and the abutment 332 are connected to the front plate 310 to secure the structural strength of the restricting pawl 330. The rear end of the abutment portion 332 projects rearward beyond the extension portion 331 so that the abutment portion 332 and the inner end of the tongue 110 have a larger abutment area, enhancing the stability of the connection between the spacing pawl 330 and the tongue 110.

The rear ends of the opposing faces of the two extending portions 331 of the two restricting claws 330 are arranged back-to-back in the front-to-back direction for guiding and increasing the distance between the rear ends of the two restricting claws 330 in the left-right direction.

The limiting structures are arranged in a plurality of corresponding inserting tongues 110, and the limiting structures are arranged at intervals along the edge direction of the back plate 100 and correspond to the inserting tongues 110 one by one.

The rib 340 is protruded from the inner surface of the outer plate 320 and located between the two limiting claws 330, and the rib 340 abuts against the outer surface of the tongue 110, so as to clamp the tongue 110 between the rib 340 and the abutting portion 332 in the inward and outward directions.

In some embodiments, the limiting structure does not include the rib 340, and the outer surface of the tongue 110 abuts against the upper inner surface of the outer plate 320.

The rib 340 extends in the front-rear direction, and the rear end of the inner surface of the rib 340 is disposed obliquely in a direction away from the center of the rear plate 100 so that the front end of the tongue 110 is inserted between the rib 340 and the abutment portion 332. The rear end of the outer surface of the abutment portion 332 is disposed obliquely inward. The ribs 340 and the rear end of the abutment portion 332 are inclined to provide a guiding function.

When the rib 340 abuts against the outer surface of the tongue 110, a space is formed between the outer surface of the tongue 110 and the inner surface of the outer plate 320, so that the clamping protrusion 140 on the outer surface of the tongue 110 can be inserted.

In this embodiment, the inner surface of the outer plate 320 is protruded with a limiting rib 350 to form a second engaging portion; the locking protrusion 140 is locked on the front side of the limiting rib 350, so that the insertion tongue 110 is limited from being released from the limiting structure, and the front shell 300 is limited from moving forward relative to the back plate 100. The rear side of the inner surface of the stopper rib 350 is disposed obliquely outward for guiding.

The outer plate 320 is provided with an observation hole 360 which runs through the inner side and the outer side; the observation hole 360 corresponds to the alignment hole 150; the alignment hole 150 is opposite to the observation hole 360, so that the front shell 300 and the back plate 100 can be observed to be clamped at a preset position through the alignment hole 150 and the observation hole 360, and the clamping position of the alignment hole 150 and the observation hole 360 is accurate and reliable.

Based on the above description, when the front case 300 is mounted on the rear panel 100, the front case 300 is moved to the outside of the rear panel 100, the limiting claws 330 of the front case 300 correspond to the insertion tongues 110 of the rear panel 100, the front case 300 is moved backward, so that the insertion tongues 110 are inserted into and limited between the limiting claws 330 and the ribs 340, the movement of the front case 300 relative to the rear panel 100 in the up-down and left-right directions is limited, and the rear side surface of the front plate 310 of the front case 300 abuts against the display panel 200, so as to limit the backward movement of the front case 300. The locking protrusion 140 is locked on the front side of the limiting rib 350 to limit the front housing 300 from moving forward relative to the back plate 100.

In the present invention, the front housing 300 moves backward, so that the tongue 110 extends into the limiting structure to limit the movement of the front housing 300 along the up-down and left-right directions, and the first engaging portion and the second engaging portion are engaged to limit the forward movement of the front housing 300 relative to the back plate 100. After the front housing 300 and the back plate 100 are aligned, the front housing 300 moves backward relative to the back plate 100, and the front housing 300 is limited on the back plate 100, so that the front housing 300 can be conveniently and quickly mounted on the back plate 100. The installation of the front shell 300 on the back plate 100 reduces the number of screws, is convenient to install, improves the production efficiency, and saves the production cost.

While the present invention has been described with reference to several exemplary embodiments, it is understood that the terminology used is intended to be in the nature of words of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims (10)

1. A display device, comprising:

the front side surface of the back plate is provided with a display panel for displaying image information; the peripheral edge of the back plate is provided with insertion tongues protruding forwards; the inserting tongue is provided with a first clamping part;

a front case located at an outer side of the back panel and the display panel; the front shell is provided with a limiting structure and a second clamping part; the limiting structure is used for enabling the insertion tongue to extend into the limiting structure to limit the movement of the front shell along the vertical and horizontal directions, and enabling the first clamping portion and the second clamping portion to be matched with each other to limit the front shell to move forwards relative to the back plate.

2. The display device of claim 1, wherein a peripheral edge of the back plate extends outward away from a center of the back plate to form a protrusion; the insertion tongue is formed at an outer end of the protruding part.

3. The display device according to claim 1, wherein the front case includes a front plate vertically disposed, and an outer plate formed to extend rearward from an outer end of the front plate; the limiting structure and the second clamping part are arranged on the outer plate.

4. The display device according to claim 3, wherein the limiting structure comprises two limiting claws which are spaced and oppositely arranged; the two limiting claws are arranged on the inner surface of the outer plate in a protruding mode; the two limiting claws are respectively abutted against two edges of the inserting tongue and are pressed on the inner surface of the inserting tongue.

5. The display device according to claim 4, wherein the two stopper claws respectively include an extending portion provided on the inner surface of the outer panel in a protruding manner, and abutting portions extending from inner ends of the extending portions toward each other; the extension part is abutted against two edges of the inserting tongue, and the abutting part is abutted against the inner surface of the inserting tongue.

6. The display device according to claim 4, wherein the limiting structure further comprises a rib protruding from the inner surface of the outer plate, and the rib is located between the two limiting claws; the convex rib is abutted against the outer surface of the inserting tongue.

7. The display device according to claim 6, wherein the rib extends in a front-rear direction, and a rear end of an inner surface of the rib is disposed obliquely in a direction away from a center of the rear plate.

8. The display device according to claim 4, wherein the outer surface of the insertion tongue is provided with a protruding part protruding away from the back plate to form the first engaging part; the inner surface of the outer plate is convexly provided with a limiting rib to form a second clamping part; the clamping protrusion is clamped on the front side face of the limiting rib.

9. The display device according to claim 3, wherein the outer panel is provided with an observation hole penetrating through inner and outer surfaces; the insertion tongue is provided with an alignment hole corresponding to the observation hole; the alignment hole is opposite to the observation hole.

10. The display device according to claim 1, wherein the insertion tongue is provided in plurality at intervals along the edge direction of the back plate, and the limiting structure is provided in plurality corresponding to the insertion tongue.

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