Backlight module convenient to assemble

Abstract

The backlight module convenient to assemble comprises a back plate, a light guide plate, a dimming assembly and a fixing frame installed on the back plate, a containing table is arranged in the fixing frame, an annular groove is formed in the containing table, a step structure is arranged on the annular groove, the step structure comprises a plurality of sets of planes which are symmetrically distributed, and the planes are arranged in the containing table. The dimming assembly comprises a diffusion piece, a first brightness enhancement piece, a second brightness enhancement piece and a polaroid which are sequentially arranged in a stacked mode from bottom to top, and one side edge of the diffusion piece, one side edge of the first brightness enhancement piece and one side edge of the second brightness enhancement piece are each provided with an installation part. Each mounting part is placed on a group of planes with the same height of the step structure, a plurality of convex cushion blocks are arranged on the inner side wall of the fixing frame, inclined slope parts are arranged at the end parts of the cushion blocks, and the fixing frame, the cushion blocks and the step structure are of an integrated structure. The utility model has the advantages of convenient assembly, strong stability and the like.

Description

TECHNICAL FIELD

[0001] The utility model relates to display technical field, specifically, relate to a backlight module convenient to assemble. BACKGROUND

[0002] The backlight module is one of the key components of the liquid crystal display panel, and is located behind the liquid crystal display, used for supplying sufficient brightness and uniformly distributed light source for the liquid crystal display, so that it can normally display the image.

[0003] A plurality of optical elements (such as light enhancement sheet, diffusion sheet, etc.) are arranged inside the backlight module, which are usually stacked in the module, and during assembly, since there is no relevant reference, the elements need to be aligned one by one by hand, and placed neatly in the frame, and need to be placed in place, which consumes a lot of energy, and is very troublesome to operate, and since the size of the element is smaller than the frame size of the module, it is easy to shift during assembly and use, and the stability is poor; in addition, the light guide plate needs to be installed in the backlight module, and the light guide plate is used for guiding the light emitted by the light source to the display screen, but since the light guide plate needs to be assembled in the frame of the module, its size is smaller than the frame, so there will be a gap between the frame, which may cause the light guide plate to shift during use, affecting the guiding effect of the light, and further affecting the display effect of the display screen. UTILITY MODEL CONTENTS

[0004] Therefore, in order to solve the above problems, the utility model provides a backlight module convenient to assemble.

[0005] A backlight module convenient to assemble, comprising a back plate, a light guide plate, a light adjusting assembly, and a fixed frame installed on the back plate, the fixed frame is provided with a placing table, the light adjusting assembly and the light guide plate are respectively arranged on both sides of the placing table, the placing table is provided with an annular groove, the annular groove is provided with a stepped structure, the stepped structure comprises a plurality of groups of symmetrically distributed planes, the heights of the plurality of groups of planes change in a stepped manner, the light adjusting assembly comprises a diffusion sheet, a first light enhancement sheet, a second light enhancement sheet and a polarizing sheet which are sequentially stacked from bottom to top, the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet are each provided with a mounting portion on one side, each mounting portion is placed on a group of planes of the same height of the stepped structure, the inner side wall of the fixed frame is provided with a plurality of protruding pads, the end of the pad is provided with an inclined inclined surface portion, and the fixed frame, the pad and the stepped structure are an integral structure.

[0006] In the technical solution, the whole ladder structure is a symmetrical structure, and is formed with multiple groups of planes, each group including two symmetrical planes with the same height, the heights of the planes in each group are different, and the planes are distributed in a stepped manner. The mounting portions are arranged on the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet, the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet can be placed on the planes with the same height in each group through the mounting portions, the ladder structure and the mounting portions can serve as references when assembling, the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet can be placed correspondingly, and the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet can be ensured to be placed in place, so that the convenience of assembly is greatly improved. Meanwhile, the planes with different heights of the ladder structure form end faces, and the end faces formed by the differences can limit and fix the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet, so that the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet are prevented from shaking in the module, and the installation stability is improved. In addition, the inner side wall of the fixed frame is provided with a pad, the pad can limit the light guide plate to prevent the light guide plate from shaking in the module, the end of the pad is provided with a beveled portion, the light guide plate can be directly slid into the beveled portion when the light guide plate is installed, so that the assembly is more convenient and fast.

[0007] It should be noted that the pad and the ladder structure are formed on the fixed frame by integral molding, and the pad and the ladder structure are an integral part of the fixed frame, and do not need to be additionally processed and installed on the fixed frame, so that the installation convenience is improved, and the integral structure can make the assembled stability stronger.

[0008] In an embodiment, a protruding clamping block is arranged on the side wall of the annular groove, and a clamping groove matched with the clamping block is arranged on the diffusion sheet, the first light enhancement sheet and the second light enhancement sheet.

[0009] In the technical solution, the clamping block is matched with the clamping groove, and the clamping groove and the clamping block are used to limit the installed diffusion sheet, first light enhancement sheet and second light enhancement sheet.

[0010] In an embodiment, a reflective sheet is mounted on the bottom of the inner side of the back plate, and the edge of the reflective sheet is upwardly bent.

[0011] In the technical solution, the reflective sheet is mounted on the bottom of the back plate, and the light leaking to the bottom of the backlight module can be reflected back to improve the light utilization efficiency. Meanwhile, the reflective sheet can also enhance the brightness of the reality. The edge of the reflective sheet is upwardly bent to cover the side wall of the back plate, so that the light falling on the side wall can also be reflected back to improve the reflection effect.

[0012] In an embodiment, a flexible circuit board is further arranged, and the flexible circuit board is mounted on the outer bottom of the back plate.

[0013] In the technical solution, the flexible circuit board is used to control the brightness, color and other parameters of the backlight module.

[0014] In one embodiment, a clearance groove is provided on the outer wall of the fixed frame, and one end of the flexible circuit board is bent and installed in the clearance groove.

[0015] In the above technical solution, one end of the flexible circuit board is bent and passes through a clearance groove, so that the flexible circuit board is installed together with the back plate and the fixing frame. By setting a clearance groove on the fixing frame to allow the flexible circuit board to pass through, the overall structure can be made more compact and the installation gap can be reduced.

[0016] In one embodiment, a light strip is installed inside the fixing frame, the light strip is located on one side of the light guide plate, the light strip includes a connecting part, the fixing frame is provided with a connecting groove for the connecting part to pass through, and the light strip is electrically connected to the flexible circuit board.

[0017] In the above technical solution, the light strip is provided with a bent connecting part, which passes through the connecting groove on the fixed frame and is connected to the fixed frame to ensure stable installation. The light strip is electrically connected to the flexible circuit board to control the light emission of the light strip. The light strip is located on the side of the light guide plate. The light emitted by the light strip is guided by the light guide plate and then reaches the display screen after passing through the dimming component above.

[0018] In one embodiment, the sidewalls of both the fixing frame and the back plate are provided with a plurality of snap-fit ​​blocks and snap-fit ​​grooves, and the fixing frame and the back plate are detachably fastened together through the snap-fit ​​blocks and snap-fit ​​grooves.

[0019] In the above technical solution, the fixed frame and the back plate are connected by snap-fit ​​blocks and snap-fit ​​slots, which facilitates assembly.

[0020] In one embodiment, a faceplate is provided on the outer side of the back plate, and the faceplate is detachably connected to the back plate to limit the dimming components stacked on the fixed frame.

[0021] In the above technical solution, after the fixed frame and the back plate are assembled, the faceplate is then installed on the fixed frame to limit the dimming component and prevent it from falling out of the fixed frame.

[0022] In one embodiment, the faceplate is detachably assembled from four fixing strips, each of which is mounted on one side of the backplate.

[0023] In the above technical solution, the faceplate consists of four fixing strips. During installation, the back plate is first assembled with the fixing frame, and then the four fixing strips are installed on the four sides of the back plate in turn.

[0024] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0025] This utility model features a stepped structure on the fixed frame and corresponding mounting parts on the diffuser, the first brightening sheet, and the second brightening sheet. The stepped structure and mounting parts serve as references, making it easy to place the diffuser, the first brightening sheet, and the second brightening sheet in place during assembly, greatly improving the ease of assembly. At the same time, the end face formed by the drop on the stepped structure can also play a limiting and fixing role, preventing the components from shaking inside the module and greatly improving the stability of the installation.

[0026] This utility model has a pad on the inner side wall of the fixed frame. The pad can limit the light guide plate and prevent it from shaking inside the module. In addition, the end of the pad has a beveled part, which can guide the light guide plate when it is installed. The light guide plate can slide directly in through the beveled part, making the assembly more convenient and quick.

[0027] This invention uses an integrated molding process to fabricate a stepped structure and pads on the fixed frame, eliminating the need for additional fabrication and subsequent installation onto the fixed frame. This improves installation convenience and reliability, and the integrated structure also enhances the stability after assembly. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is an exploded view of a backlight module according to an embodiment of this application.

[0030] Figure 2 for Figure 1 A magnified view of area A in the middle.

[0031] Figure 3 for Figure 1 A magnified view of area B in the middle.

[0032] Figure 4 This is a schematic diagram of the installation of the fixed frame and the dimming assembly (the polarizer in the diagram has been omitted).

[0033] Figure 5 This is a 3D view with a fixed frame.

[0034] Figure 6 This is the bottom view of the fixed frame.

[0035] Figure 7 for Figure 6 A magnified view of region C in the middle.

[0036] Figure 8 This is a schematic diagram showing the installation of the fixed frame, light guide plate, and light strip.

[0037] Figure 9 for Figure 8 A magnified view of region D in the middle.

[0038] Figure 10 This is a bottom view of the backlight module.

[0039] Explanation of the reference numerals in the figure:

[0040] 1-Backplate; 11-Reflector; 12-Snap-on block; 13-Snap-on groove; 14-Face shell; 141-Opening; 2-Light guide plate; 3-Fixing frame; 31-Placement platform; 311-Annular groove; 3111-Snap-on block; 312-Stepped structure; 3121-Stepped block; 3122-Buffer pad; 313-Pad; 3131-Beveled surface; 314-Leaving groove; 315-Connecting groove; 4-Dimming assembly; 41-Diffuser; 42-First brightness enhancement sheet; 43-Second brightness enhancement sheet; 44-Polarizer; 45-Mounting part; 46-Snap-on groove; 5-Flexible circuit board; 6-Light strip; 61-Connecting part. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Example 1

[0044] Please refer to Figures 1 to 10In a preferred embodiment of this utility model, a backlight module is provided, which includes a back plate 1, a light guide plate 2, a dimming component 4, and a fixing frame 3 mounted on the back plate 1. A placement platform 31 is provided within the fixing frame 3. The dimming component 4 and the light guide plate 2 are respectively disposed on both sides of the placement platform 31. An annular groove 311 is provided on the placement platform 31. A stepped structure 312 is provided on one side of the annular groove 311. The stepped structure 312 includes several sets of symmetrically distributed planes, the height of which varies in a stepped manner. The dimming component 4 is enclosed in... The structure includes a diffuser 41, a first brightness enhancement film 42, a second brightness enhancement film 43, and a polarizer 44, which are stacked sequentially from bottom to top. Each of the diffuser 41, the first brightness enhancement film 42, and the second brightness enhancement film 43 has a mounting part 45 on one side. Each mounting part 45 is placed on a set of planes of the same height on the stepped structure 312. The polarizer 44 is placed on the top surface of the placement platform 31. The inner side wall of the fixing frame 3 has a plurality of protruding pads 313, and the end of the pads 313 has an inclined beveled part 3131.

[0045] Specifically, such as Figure 4 and Figure 5 As shown, the stepped structure 312 in this embodiment consists of two stepped blocks 3121. The height of the plane on the stepped block 3121 decreases in a stepped manner towards the other stepped block 3121. To ensure stable installation, the width of the mounting portion 45 on the diffuser 41, the first brightness enhancement film 42, and the second brightness enhancement film 43 increases sequentially to accommodate the different intervals formed between the two stepped blocks 3121. The diffuser 41 is placed directly on the annular groove 311, and its mounting portion 45 is located in the interval between the two stepped blocks 3121. The first brightness enhancement film 42 and the second brightness enhancement film 43 are stacked sequentially on the stepped blocks 3121 from bottom to top. The mounting portions 45 of the first brightness enhancement film 42 and the second brightness enhancement film 43 are each placed on a set of planes of the same height on the two stepped blocks 3121. The polarizer 44 is placed on the top surface of the placement platform 31, covering the diffuser 41, the first brightness enhancement film 42, and the second brightness enhancement film 43 below in the annular groove 311.

[0046] During assembly, the stepped structure 312 and the mounting part 45 can serve as a reference to facilitate the alignment of the diffuser 41, the first brightness enhancement film 42 and the second brightness enhancement film 43, ensuring proper placement and greatly improving the ease of assembly. At the same time, the end faces formed between the planes of different heights of the stepped structure 312 can also limit and fix the diffuser 41, the first brightness enhancement film 42 and the second brightness enhancement film 43, preventing them from shaking inside the module and improving installation stability.

[0047] In addition, such as Figure 6 and Figure 7As shown, a pad 313 is provided on the inner side wall of the fixing frame 3. The pad 313 can limit the light guide plate 2 and prevent it from shaking inside the module. The end of the pad 313 is provided with a beveled part 3131, which can play a guiding role when installing the light guide plate 2. The light guide plate 2 can slide directly in through the beveled part 3131, making the assembly more convenient and quick.

[0048] It is worth mentioning that the pad 313 and the stepped structure 312 are integrally formed on the fixed frame 3. The two are an integral part of the fixed frame 3, so there is no need to process the pad 313 or the stepped structure 312 first and then install them on the fixed frame 3, which improves the convenience of installation. The integral structure can also reduce the number of moving components inside the module, making the overall stability stronger.

[0049] Preferably, as shown in the figure, a buffer pad 3122 is provided on the top of the two stepped blocks 3121 and the gap between them. The buffer pad 3122 forms elastic contact with the diffuser 41, the first brightening sheet 42 and the second brightening sheet 43 to play a buffering role.

[0050] Please refer to Figures 3 to 5 In this embodiment, a protruding locking block 3111 is provided on the side wall of the annular groove 311, and the diffuser 41, the first brightening plate 42 and the second brightening plate 43 are all provided with a locking groove 46 that cooperates with the locking block 3111. The locking groove 46 and the locking block 3111 are used to limit the installation of the diffuser 41, the first brightening plate 42 and the second brightening plate 43.

[0051] Preferably, the annular groove 311 is provided with two locking blocks 3111, which are located on both sides of the annular groove 311. Correspondingly, the diffuser 41, the first brightening plate 42, and the second brightening plate 43 are each provided with two locking slots 46 to improve the stability of the installation.

[0052] Please refer to Figure 4 , Figure 5 and Figure 8 In this embodiment, a light strip 6 is installed inside the fixed frame 3. The light strip 6 is located on one side of the light guide plate 2. The light strip 6 has a bent connecting part 61. The fixed frame 3 has a connecting groove 315 for the connecting part 61 to pass through. The connecting part 61 of the light strip 6 passes through the connecting groove 315 on the fixed frame 3, thereby connecting and installing with the fixed frame 3. The light strip 6 is located on the side of the light guide plate 2. The light emitted by the light strip 6 is guided by the light guide plate 2 and then directed to the dimming component 4 above. After passing through the dimming component 4, it reaches the display screen.

[0053] Please refer to Figure 1 , Figure 4 and Figure 10In this embodiment, a flexible circuit board 5 is mounted on the outer bottom of the back plate 1. A clearance groove 314 is provided on the outer wall of the fixing frame 3 to allow the flexible circuit board 5 to pass through. One end of the flexible circuit board 5 is bent into a U-shape. Through the cooperation between the U-shaped structure and the clearance groove 314, the flexible circuit board 5 is mounted together with the fixing frame 3 and the back plate 1. Furthermore, the flexible circuit board 5 is electrically connected to the internal light strip 6 to control the light emission of the light strip 6. By providing the clearance groove 314 on the fixing frame 3 to allow the flexible circuit board 5 to pass through and be installed, the overall structure can be made more compact, reducing the installation gap.

[0054] Please refer to Figure 1 In this embodiment, a reflective sheet 11 is installed at the bottom of the inner side of the back plate 1. The edge of the reflective sheet 11 is bent upward. The reflective sheet 11 can reflect the light that leaks to the bottom of the backlight module back, thereby improving the light utilization efficiency. At the same time, it can also enhance the brightness of the display. The edge of the reflective sheet 11 is bent upward to cover the side wall of the back plate 1, so as to ensure that the light falling on the side wall can also be reflected back, thereby improving the reflection effect.

[0055] Please refer to Figure 1 and Figure 2 In this embodiment, the side walls of the fixing frame 3 and the back plate 1 are provided with a number of snap-fit ​​blocks 12 and snap-fit ​​grooves 13. The fixing frame 3 and the back plate 1 are connected by snap-fit ​​blocks 12 and snap-fit ​​grooves 13 to form a detachable fastening connection, which facilitates assembly.

[0056] Preferably, since it is necessary to make way for the assembly of the flexible circuit board 5 and the fixing frame 3, a snap-fit ​​block 12 is provided on the right side of the back plate 1 (see reference). Figure 1 (as shown in the direction), and snap-fit ​​holes are provided on the other sides. Correspondingly, snap-fit ​​holes are provided on the right side of the fixing frame 3, and snap-fit ​​blocks 12 are provided on the other sides. The bottom right side of the fixing frame 3 is provided with a straight groove for the right side of the fixing frame 3 to be inserted, so that after the fixing frame 3 is assembled with the back plate 1, the right side of the fixing frame 3 is located outside the right side of the back plate 1, so as not to affect the installation of the flexible circuit board 5.

[0057] Please refer to Figure 1 and Figure 10 In this embodiment, a faceplate 14 is provided on the outer side of the back plate 1. The faceplate 14 is detachably connected to the back plate 1 to limit the dimming component 4 stacked on the fixed frame 3 and the flexible circuit board 5 installed on the outside. After the fixed frame 3 and the back plate 1 are assembled, the faceplate 14 is installed on the fixed frame 3.

[0058] Please continue to refer to Figure 1 and Figure 10In this embodiment, the faceplate 14 is detachably assembled from four fixing strips. Each fixing strip is installed on one side of the back plate 1. During installation, after the back plate 1, the fixing frame 3 and other structures are assembled, the four fixing strips are installed on the four sides of the back plate 1 in sequence.

[0059] Preferably, such as Figure 10 As shown, the bottom of the fixing strip near the side of the relief groove 314 has an opening 141 for the flexible circuit board 5 to pass through. Example 2

[0060] Please refer to Figures 1 to 10 The specific assembly steps for this backlight module are as follows:

[0061] First, the reflector 11 is installed inside the back plate 1. Then, the light guide plate 2 is placed on the placement platform 31 of the fixing frame 3 by the guide of the pad 313. Next, the lamp strip 6 is installed on the side of the light guide plate 2. Then, the fixing frame 3 is fastened to the back plate 1. After fastening, with the stepped structure 312, the locking block 3111 and the locking slot 46 as references, the diffuser 41, the first brightness enhancement film 42 and the second brightness enhancement film 43 are placed in the annular groove 311 in sequence. Then, the polarizer 44 is placed on the top of the placement platform 31. Then, the flexible circuit board 5 is installed on the side of the back plate 1. Finally, the faceplate 14 is installed on the outside of the back plate 1 to fix the overall structure.

[0062] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

[0063] In the description of this utility model, it should be understood that terms such as "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0065] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

Claims

1. A backlight module that is easy to assemble, characterized in that, The device includes a back plate, a light guide plate, a dimming assembly, and a fixing frame mounted on the back plate. A placement platform is provided within the fixing frame. The dimming assembly and the light guide plate are respectively located on opposite sides of the placement platform. An annular groove is provided on the placement platform, and a stepped structure is provided on the annular groove. The stepped structure includes several sets of symmetrically distributed planes, with the height of the planes varying in a stepped manner. The dimming assembly includes a diffuser, a first brightness enhancement film, a second brightness enhancement film, and a polarizer, stacked sequentially from bottom to top. Each diffuser, the first brightness enhancement film, and the second brightness enhancement film has a mounting portion on one side. Each mounting portion is placed on a set of planes of the same height on the stepped structure. Multiple protruding pads are provided on the inner wall of the fixing frame, and the ends of the pads have inclined bevels. The fixing frame, pads, and stepped structure are an integral structure.

2. The easily assembled backlight module according to claim 1, characterized in that, The annular groove has a protruding locking block on its side wall, and the diffuser, the first brightening plate and the second brightening plate are each provided with a locking groove that cooperates with the locking block.

3. The easily assembled backlight module according to claim 1, characterized in that, A reflective sheet is installed at the bottom of the inner side of the back plate, and the edge of the reflective sheet is bent upward.

4. The easily assembled backlight module according to claim 1, characterized in that, It also includes a flexible circuit board, which is mounted on the outer bottom of the back plate.

5. The easily assembled backlight module according to claim 4, characterized in that, The outer wall of the fixed frame is provided with a clearance groove, and one end of the flexible circuit board is bent and installed in the clearance groove.

6. The easily assembled backlight module according to claim 5, characterized in that, A light strip is installed inside the fixed frame. The light strip is located on one side of the light guide plate. The light strip includes a connecting part. The fixed frame is provided with a connecting groove for the connecting part to pass through. The light strip is electrically connected to the flexible circuit board.

7. The easily assembled backlight module according to claim 1, characterized in that, Both the fixing frame and the back plate have several snap-fit ​​blocks and snap-fit ​​slots on their side walls, and the fixing frame and the back plate are detachably fastened together by the snap-fit ​​blocks and snap-fit ​​slots.

8. The easily assembled backlight module according to claim 1, characterized in that, The back plate has a face shell on its outer side, which is detachably connected to the back plate to limit the dimming components stacked on the fixed frame.

9. The easily assembled backlight module according to claim 8, characterized in that, The faceplate is assembled from four detachable fixing strips, each of which is installed on one side of the back plate.

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