Patent Publication Number: US-9426906-B2

Title: Bracing piece, back frame, and backlight system of flat panel display device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of displaying techniques, and in particular to a bracing piece, a back frame, and a backlight system of a flat panel display device. 
     2. The Related Arts 
     The state-of-the-art liquid crystal display device comprises a front bezel, a panel, and a backlight module, of which the backlight module comprises a back frame, a reflector plate, a light guide, and a lighting assembly. 
     Currently, a variety of display panels of different sizes are available in the market to meet different needs of general consumers. For example, in the field of television set, the sizes of liquid crystal panels include 31.5, 42, 46, 48, and 55 inches. Different back frame molds are provided for liquid crystal planes of different sizes. 
     Referring to  FIG. 1 ,  FIG. 1  is a schematic view showing a conventional back frame of liquid crystal display device. As shown in  FIG. 1 , the conventional back frame  10  is a unitary back frame, and it is often that a unitary back frame  10  is made with metal stamping or plastic injection molding. The unitary back frame  10  consumes much material and has a high material cost. Further, a large-sized back frame  10  requires large-sized stamping equipment, and the size of mold corresponding to such a back frame  10  is large and the structure complicated, making the expenditure of the back frame mold high. As a consequence, the conventional back frame is of a high cost. 
     SUMMARY OF THE INVENTION 
     The technical issue to be addressed by the present invention is to provide a bracing piece, a back frame, and a backlight system of a flat panel display device, wherein the bracing piece in the back frame is applicable to various mounting heights of mounting holes, can be manufactured together in a unified manner, reduces the cost of mold, and improves manufacturing efficiency. 
     To address the above technical issue, the present invention adopts a technical solution that provides a bracing piece of flat panel display device. The bracing piece comprises a first step surface and a plurality of second step surfaces that integrally formed at one end of the first step surface, the first step surface forming thereon at least one bump, the bump forming a mounting hole, the first step surface being of a different vertical levels with respect to each of the second step surfaces. 
     According to a preferred embodiment of the present invention, the bracing piece further comprises a plurality of third step surfaces integrally formed at an opposite end of the first step surface, the first step surface being of a different vertical level with respect to each of the third step surfaces. 
     According to a preferred embodiment of the present invention, the back frame comprises at least two assembling pieces, the at least assembling pieces being joined to form the back frame, the back frame further comprising a bracing piece, the bracing piece being of a multiple-stepped configuration and mounted to the assembling pieces. 
     To address the above technical issue, the present invention adopts a technical solution that provides a back frame of flat panel display device. The back frame comprises at least two assembling pieces, the at least assembling pieces being joined to form the back frame, the back frame further comprising a bracing piece, the bracing piece being of a multiple-stepped configuration and mounted to the assembling pieces. 
     According to a preferred embodiment of the present invention, the bracing piece comprises a first step surface and a plurality of second step surfaces that integrally formed at one end of the first step surface, the first step surface forming thereon at least one bump, the bump forming a mounting hole, the first step surface being of a different vertical level with respect to each of the second step surfaces, whereby one of the second step surfaces is selected to fix to the assembling pieces according to a mounting height of the mounting hole. 
     According to a preferred embodiment of the present invention, the bracing piece further comprises a plurality of third step surfaces integrally formed at an opposite end of the first step surface, the first step surface being of a different vertical level with respect to each of the third step surfaces, whereby one of the second step surfaces is selected to fix to the assembling pieces according to the mounting height of the mounting hole 
     According to a preferred embodiment of the present invention, the back frame comprises a plurality of primary assembling pieces, the primary assembling pieces being joined to form a main frame structure of the back frame, the primary assembling piece comprising a first primary assembling piece and a second primary assembling piece, the first primary assembling piece having an end forming at least two joint sections, each of the joint sections having a structure mating an end of the second primary assembling piece, the first primary assembling piece using one of the joint sections to join the corresponding end of the second primary assembling piece. 
     According to a preferred embodiment of the present invention, the at least two joint sections are arranged to space from each other in a lengthwise direction of the first primary assembling piece 
     According to a preferred embodiment of the present invention, the joint sections comprise recesses formed in a surface of the first primary assembling piece and having a shape corresponding to the end of the second primary assembling piece for receiving the end of the second primary assembling piece. 
     According to a preferred embodiment of the present invention, the joint sections comprise recesses formed in a surface of the first primary assembling piece, the second primary assembling piece having a surface forming protrusions at corresponding positions, the protrusions being receivable in the recesses to join the first primary assembling piece and the second primary assembling piece to each other. 
     According to a preferred embodiment of the present invention, the second primary assembling piece has an end having a surface forming at least two protrusions that are arranged to space from each other in a lengthwise direction of the second primary assembling piece. 
     To address the above technical issue, the present invention adopts a technical solution that provides a backlight system. The backlight system comprises a light source, a light homogenization mechanism, and a back frame; and the back frame carries the light source and the light homogenization mechanism. The back frame is a back frame of the back frame described in the above embodiments. 
     The efficacy of the present invention is that to be distinguished from the state of the art, the present invention provides a back frame and a backlight system of flat panel display device that make the structure of a back frame mold simple, reduce the cost of back frame mold, save the material used for the back frame, and lower down the cost of flat panel display device. Further, the bracing piece of the back frame is applicable to various mounting heights of mounting holes, can be manufactured together in a unified manner, reduces the cost of mold, and improves manufacturing efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing a conventional back frame of liquid crystal display device; 
         FIG. 2  is a schematic view showing a flat panel display device according to a first embodiment of the present invention; 
         FIG. 3  is a schematic view showing a back frame of a flat panel display device according to a second embodiment of the present invention; 
         FIG. 4  is a schematic view showing a back frame of a flat panel display device according to a third embodiment of the present invention; 
         FIG. 5  is a schematic view showing a back frame of a flat panel display device according to a fourth embodiment of the present invention; 
         FIG. 6  is a schematic view showing a joining structure of a flat panel display device according to a fifth embodiment of the present invention; 
         FIG. 7  is a schematic view showing a diagonally-arranged first secondary assembling piece mounted to a main frame structure of a flat panel display device according to a sixth embodiment of the present invention; 
         FIG. 8  is a schematic view showing a first secondary assembling piece and a second secondary assembling piece mounted to a main frame structure of a flat panel display device according to a seventh embodiment of the present invention; 
         FIG. 9  is a schematic view showing joint sections of a back frame of a flat panel display device according to an eighth embodiment of the present invention; 
         FIG. 10  is a cross-sectional view showing a first example of joint section of  FIG. 9 ; 
         FIG. 11  is a schematic view showing a joining structure of a joint section of a back frame of a flat panel display device according to a ninth embodiment of the present invention; 
         FIG. 12  is a schematic view showing a joining structure of a joint section of a back frame of a flat panel display device according to a tenth embodiment of the present invention; 
         FIG. 13  is a schematic view showing a joining structure of a joint section of a back frame of a flat panel display device according to an eleventh embodiment of the present invention; 
         FIG. 14  is a schematic view showing a joint section of a back frame of a flat panel display device according to a twelfth embodiment of the present invention; 
         FIG. 15  is a schematic view showing a joint section of a back frame of a flat panel display device according to a thirteenth embodiment of the present invention; 
         FIG. 16  is a flow chart showing a method for manufacturing a back frame of a flat panel display device according to a fourteenth embodiment of the present invention; 
         FIG. 17  is a schematic view showing a flat panel display device with a touch screen according to a fifteenth embodiment of the present invention; 
         FIG. 18  is a schematic view showing a stereoscopic display device according to a sixteenth embodiment of the present invention; 
         FIG. 19  is a schematic view showing a plasma display device according to a seventeenth embodiment of the present invention; 
         FIG. 20  is a schematic view showing a bracing piece according to an eighteenth embodiment of the present invention; and 
         FIG. 21  is a cross-sectional view of the bracing piece according to the eighteenth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 2-3 ,  FIG. 2  is a schematic view showing a flat panel display device according to a first embodiment of the present invention and  FIG. 3  is a schematic view showing a first embodiment of a back frame of a flat panel display device according to a second embodiment of the present invention. As shown in  FIG. 2 , the flat panel display device  20  according to the instant embodiment comprises: a backlight system  21  and a display panel  22 . The backlight system  21  is arranged on a back side of the display panel  22  and supplies light to the display panel  22 . 
     In the instant embodiment, the backlight system  21  comprises a light source  25 , a light homogenization mechanism  24 , and a back frame  23 . The back frame  23  carries the light source  25  and the light homogenization mechanism  24 . When the backlight system  21  is an edge lighting type, the light homogenization mechanism  24  is a light guide; and when the backlight system  21  is a direct type, the light homogenization mechanism  24  is a diffuser plate. The back frame  23  comprises at least a first primary assembling piece and a second primary assembling piece, and the two of at least a first and second primary assembling pieces constitute a main frame structure  27  of the back frame  23 . 
     Referring also to  FIG. 3 , the back frame  23  of the first embodiment comprises a first primary assembling piece  261  and a second primary assembling piece  262 . The first primary assembling piece  261  has an end joined to an end of the second primary assembling piece  262 , and the first primary assembling piece  261  has another end joined to another end of the second primary assembling piece  262  in order to form the main frame structure  27  of the back frame  23 . The first primary assembling piece  261  and the second primary assembling piece  262  are both aluminum pieces or galvanized steel pieces. In the instant embodiment, the first primary assembling piece  261  and the second primary assembling piece  262  are L-shaped. 
     Referring also to  FIG. 4 , the back frame  23  of a second embodiment comprises a first primary assembling piece  281 , a second primary assembling piece  282 , and a third primary assembling piece  283 . The three primary assembling pieces  281 ,  282 , and  283  are assembled and joined to form a main frame structure  27  of the back frame  23 . The three primary assembling pieces  281 ,  282 , and  283  are all aluminum pieces or galvanized steel pieces. In the instant embodiment, the first primary assembling piece  281  is L-shaped, and the second and third primary assembling pieces  282 ,  283  are straight linear. 
     Further, the back frame  23  further comprises secondary assembling pieces arranged inside and joined to the main frame structure  27 . 
     A detailed description will be given to the back frame  23  of the flat panel display device  20  according to the present invention, which comprises four primary assembling pieces and two secondary assembling pieces. 
     Referring to  FIG. 5 ,  FIG. 5  is a schematic view showing a back frame of flat panel display device according to a fourth embodiment of the present invention. As shown in  FIG. 5 , in the instant embodiment, a back frame  23  comprises: a first primary assembling piece  231 , a second primary assembling piece  232 , a third primary assembling piece  233 , a fourth primary assembling piece  234 , a first secondary assembling piece  235 , a second secondary assembling piece  236 , and bracing pieces  2371 ,  2372 ,  2373 ,  2374 ,  2375 ,  2376 , and  2377 . The first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , and the fourth primary assembling piece  234  are successively joined to each other in an end-to-end manner to constitute a rectangular main frame structure  27  of the back frame  23 . The first secondary assembling piece  235  and the second secondary assembling piece  236 , serving as ancillary assembling pieces, are arranged in the main frame structure  27  and joined to the main frame structure  27 . 
     Specifically, an end of the first primary assembling piece  231  is joined to an end of the second primary assembling piece  232 , another end of the second primary assembling piece  232  is joined to an end of the third primary assembling piece  233 , another end of the third primary assembling piece  233  is joined to an end of the fourth primary assembling piece  234 , and another end of the fourth primary assembling piece  234  is joined to another end of the first primary assembling piece  231  in order to form the rectangular main frame structure  27 . The first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , and the fourth primary assembling piece  234  are all aluminum pieces or galvanized steel pieces. In the instant embodiment, the first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , and the fourth primary assembling piece  234  are straight linear, yet in other embodiments, it is apparent to those skilled in the art to make all the first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , and the fourth primary assembling piece  234  L-shaped, or some being straight linear and the remaining being L-shaped. For example, in  FIG. 3 , the first primary assembling piece  261  and the second primary assembling piece  262  are both L-shaped; in  FIG. 4 , the first primary assembling piece  281  is L-shaped, while the second and third primary assembling pieces  282  and  283  are straight linear. 
     In the instant embodiment, the back frame  23  of the flat panel display device  20  is formed by joining connection. As shown in  FIG. 6 , an illustrative example is given for the connection of an end of the first primary assembling piece  231  to an end of the second primary assembling piece  232 , wherein the end of the second primary assembling piece  232  is joined to the end of the first primary assembling piece  231  by means of for example screwing, fastening, or welding, to have the end of the second primary assembling piece  232  connected to the end of the first primary assembling piece  231 . 
     In the instant embodiment, the first secondary assembling piece  235  and the second secondary assembling piece  236  are arranged in the main frame structure  27  of the back frame  23 . An end of the first secondary assembling piece  235  is joined to the first primary assembling piece  231  and another end of the first secondary assembling piece  235  is joined to the third primary assembling piece  233 ; and an end of the second secondary assembling piece  236  is joined to the first primary assembling piece  231  and another end of the second secondary assembling piece  236  is joined to the third primary assembling piece  233 . Further, the second primary assembling piece  232 , the fourth primary assembling piece  234 , the first secondary assembling piece  235 , and the second secondary assembling piece  236  are arranged parallel to each other. In other embodiments, those skilled in the art may arrange at least one secondary assembling piece in the main frame structure  27 . For example, only the first secondary assembling piece  235  is arranged in the main frame structure  27 . Further, the two ends of the first secondary assembling piece  235  can be selectively joined to at least two of the primary assembling pieces of the first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , and the fourth primary assembling piece  234 . For example, the first secondary assembling piece  235  is set diagonally in the main frame structure  27 , as shown in  FIG. 7 . Similarly, the two ends of the second secondary assembling piece  236  can be selectively joined to at least two of the primary assembling pieces of the first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , and the fourth primary assembling piece  234 . For example, the two ends of the first secondary assembling piece  235  are respectively joined to the first primary assembling piece  231  and the second primary assembling piece  232  that are adjacent to each other and the two ends of the second secondary assembling piece  236  are respectively joined the third primary assembling piece  233  and the fourth primary assembling piece  234  that are adjacent to each other, as shown in  FIG. 8 . 
     In the instant embodiment, the back frame  23  comprises seven bracing pieces  2371 ,  2372 ,  2373 ,  2374 ,  2375 ,  2376 , and  2377 . The bracing piece  2371  is fixed to the fourth primary assembling piece  234 ; the bracing pieces  2372 ,  2373  are both fixed to the first secondary assembling piece  235 ; the bracing piece  2374  is fixed to the second secondary assembling piece  236 ; the bracing piece  2375  is fixed to the second primary assembling piece  232 ; and the bracing pieces  2376 ,  2377  are each fixed, at two ends thereof, to the first secondary assembling piece  235  and the second secondary assembling piece  236 . In practice, the bracing pieces can be fixed to one or more of the first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , the fourth primary assembling piece  234 , the first secondary assembling piece  235 , and the second secondary assembling piece  236 . In other embodiments, those skilled in the art may mount bracing pieces of any other numbers to the back frame  23 , such as one or more bracing pieces. Further, the bracing pieces can be releasably fixed to one or more of the first primary assembling piece  231 , the second primary assembling piece  232 , the third primary assembling piece  233 , the fourth primary assembling piece  234 , the first secondary assembling piece  235 , and the second secondary assembling piece  236 . 
     The bracing pieces  2371 ,  2372 ,  2373 ,  2374 ,  2375 ,  2376 , and  2377  may be provided with bumps (not labeled) so that the back frame  23  may fix components, such as circuit boards, with such bumps. 
     Molds for making the back frame  23  will be described. In the instant embodiment, the first primary assembling piece  231  and the third primary assembling piece  233  are of the same size and shape so that they can be made by stamping with the same mold. The second primary assembling piece  232 , the fourth primary assembling piece  234 , the first secondary assembling piece  235 , and the second secondary assembling piece  236  are of the same size and shape so that they can be made by stamping with the same mold, making it possible to share the mold. Thus, the back frame  23  of the present invention can be made by stamping with only two small-sized molds, and compared to the conventional back frame  10  that requires a large-sized mold, the molds for making the back frame  23  of the present invention are simple in structure and small in size and thus the cost of mold for the back frame  23  can be lowered. Further, compared to the whole back frame structure of the conventional back frame  10 , the back frame  23  of the present invention can significantly save material used and thus reduce the manufacturing cost of the flat panel display device  20 . 
     Referring to  FIG. 9 ,  FIG. 9  is a schematic view showing joint sections of a back frame of a flat panel display device according to an eighth embodiment of the present invention. As shown in  FIG. 9 , in the instant embodiment, an end of the first primary assembling piece is provided with two joint sections, and the joint sections have a structure mating an end of the second primary assembling piece so that the first primary assembling piece can be joined to a corresponding end of the second primary assembling piece. 
     Specifically, the first primary assembling piece  231  has an end forming joint sections  2311 ,  2312 , and the joint sections  2311 ,  2312  are arranged in a spaced manner in a lengthwise direction of the first primary assembling piece  231 . The joint sections  2311 ,  2312  are formed by forming recesses having a shape mating an end of the second primary assembling piece  232  in the first primary assembling piece  231  in order to receive the end of the second primary assembling piece  232  therein. As shown in  FIG. 10 , the joint sections  2311 ,  2312  are recesses that do not extend through opposite surfaces of the end of the first primary assembling piece  231  and the recesses are of a rectangular shape with the second primary assembling piece  232  being straight linear. 
     To assemble a large-sized back frame  23 , the joint section  2311  that is close to the very end of the first primary assembling piece  231  is first taken and a second primary assembling piece  232  having a corresponding width is selected. Afterwards, an end of the second primary assembling piece  232  is positioned in the recess of the joint section  2311 . And then, means, such as screwing, fastening, or welding, is applied to join and fix the end of the second primary assembling piece  232  to the joint section  2311 . To assemble a small-sized back frame  23 , the joint section  2312  that is distant from the very end of the first primary assembling piece  231  is first chosen and a second primary assembling piece  232  having a corresponding width is selected. Afterwards, an end of the second primary assembling piece  232  is positioned in the recess of the joint section  2312 . And then, means, such as screwing, fastening, or welding, is applied to join and fix the end of the second primary assembling piece  232  to the joint section  2312 . Specifically, for example the second primary assembling piece  232  forms a protrusion at a corresponding location on a surface thereof, and the protrusion of the second primary assembling piece  232  is embedded in the recess the first primary assembling piece  231  at a corresponding location in order to join the first primary assembling piece  231  and the second primary assembling piece  232 , as shown in  FIG. 11 . Further, the second primary assembling piece  232  may form, on one end thereof, at least two protrusions that are spaced in the lengthwise direction of the second primary assembling piece  232 , such as two, three, or four protrusions. 
     Furthermore, the recess of the first primary assembling piece  231  can be a recess of a multi-stepped configuration and the second primary assembling piece  232  forms, at a corresponding location, a protrusion having a multi-stepped configuration corresponding to the recess, as shown in  FIG. 12 . Further, as shown in  FIG. 13 , taking the joint section  2311  as an example, the recess of the first primary assembling piece  231  forms, in a bottom thereof, a first through hole  2313 , and the second primary assembling piece  232  forms, at a location corresponding to the joint section  2311 , a second through hole  2321 . The back frame  23  further comprises a fastener  240 . The fastener  240  extends through the first through hole  2313  and the second through hole  2321  to joint the first primary assembling piece  231  and the second primary assembling piece  232  to each other. 
     As shown in  FIG. 14 , in another embodiment of the back frame of flat panel display device according to the present invention, the recesses of the joint sections  2311 ,  2312  of the first primary assembling piece  231  are of a circular shape. Yet, in other embodiments, those skilled in the art may arrange the shape of the recesses to be other polygonal configurations, such as triangle. 
     As shown in  FIG. 15 , in another embodiment of the back frame of flat panel display device according to the present invention, the joint sections  2311 ,  2312  are recesses that do not extend through opposite surfaces of the first primary assembling piece  231 , whereby an end of the second primary assembling piece  232  is movable within the joint sections  2311 ,  2312 . For example, after the end of the second primary assembling piece  232  is set extending beyond and joined and fixed to the joint section  2312 , the portion of extension is then trimmed off so that the length of the second primary assembling piece  232  that serves as a primary assembling piece of the back frame can be adjusted. 
     In a practical application, the other end of the first primary assembling piece  231  and both ends of the third primary assembling piece  233  are all provided with two joint sections having a structure identical to that of the joint sections  2311 ,  2312 . The ends of the second primary assembling piece  232  and the ends of the fourth primary assembling piece  234  may be subjected to specific designs or no design at all according to the application. For example: 
     (1) In a first situation, as shown in  FIG. 10 , the two ends of the second primary assembling piece  232  and the two ends of the fourth primary assembling piece  234  are of no specific design. In other words, the ends are of the same structure as the remaining portions. Under this condition, in making a join with a selected joint section  2311  ( 2312 ) at one end of the first primary assembling piece  231  (the same applicable to the other end), if an attempt is made to change the width of the back frame  23 , then the length of the corresponding second primary assembling piece  232  and fourth primary assembling piece  234  must be selected accordingly. Namely, if the joint section  2311  that is close to the very end of the first primary assembling piece  231  is selected for joining, then no trimming is applied to the second primary assembling piece  232  and the fourth primary assembling piece  234  or the portion that is trimmed off is short; if the joint section  2312  that is distant from the very end of the first primary assembling piece  231  is selected for joining, then the second primary assembling piece  232  and the fourth primary assembling piece  234  are trimmed and the trimmed portion being long or short is according to the distance that the joint section is from the very end of the first primary assembling piece  231  being great or small; and 
     (2) In a second situation, it is similar to the first situation, but as shown in  FIG. 11 , the second primary assembling piece  232  and the fourth primary assembling piece  234  use different protrusions to respectively mate the first primary assembling piece  231  and the third primary assembling piece  233  in order to realize change of width of the back frame  23 ; similarly, if a joint section  2312  other than the first joint section  2311  that is close to the very end of the first primary assembling piece  231  is selected for joining, then before or after joining, excessive portions of the second primary assembling piece  232  and the fourth primary assembling piece  234  may be trimmed off. 
     This also applicable to a main frame structure  27  of the back frame  23  that is formed by joining two L-shaped primary assembling pieces. 
     In summary, the present invention provides a back frame  23  having a first primary assembling piece that is provided with at least two joint sections. The number of the joint section can be selected according to the requirement of customers. In the instant embodiment, a description is given to an example comprising two joint sections  2311 ,  2312 . Thus, to prepare the molds for making the back frame  23 , only two sets of mold are needed, namely one mold for a first primary assembling piece and the other mold for a second primary assembling piece. The first primary assembling piece may be provided with a plurality of joint sections for joining operation in order to form various sizes for the back frame  23 . To assemble the back frame  23 , based on the desired size of the back frame  23 , the corresponding one of the joint sections is selected. With the joint section, the second primary assembling piece is joined to the joint section of the first primary assembling piece and the other joint section of the first primary assembling piece that is located outward of the joining location of the second primary assembling piece is trimmed off to obtain a desired size of the back frame  23 . Compared to the conventional technology that requires different back frame molds for making different sizes of back frame  10 , the back frame of the flat panel display device  23  according to the present invention requires only a mold for the first primary assembling piece and a mold for the second primary assembling piece  28  so that mold sharing among various sizes of product can be realized and the molds used are of simple structures, allowing of reduction of expenditure of the molds for back frames. 
     The present invention also provides a mold for making a back frame of flat panel display device. The back frame mold is provided with a main pattern for forming a primary assembling piece of the back frame and the main pattern comprises a sub-pattern that forms at least two joint sections on an end of the primary assembling piece. The primary assembling piece comprises the previously discussed first primary assembling piece and second primary assembling piece, corresponding to the above mentioned main pattern; and the joint section comprises the previously discussed joint section of the first primary assembling piece, corresponding to the above mentioned sub-pattern. Repeated description is omitted herein. 
     As shown in  FIG. 16 , the present invention also provides a method for making a back frame of flat panel display device. The method comprises the following steps: 
     Step  501 : manufacturing at least first and second primary assembling pieces, in which the first primary assembling piece has an end forming at least two joint sections, each of the joint sections having a structure that mates a corresponding end of the second primary assembling piece; and 
     Step  502 : selecting one joint section of the at least two joint sections according to a size of the back frame to join the corresponding end of the second primary assembling piece. 
     In the instant embodiment, when other joint sections are present between the joining location of the second primary assembling piece and the end of the first primary assembling piece, before or after the step of selecting one joint section of the at least two joint sections according to a size of the back frame to join the corresponding end of the second primary assembling piece, the other joint sections of the first primary assembling piece that are located outward of the joining position of the second primary assembling piece are trimmed off. The first primary assembling piece comprises the previously discussed first primary assembling piece, and the second primary assembling piece comprises the previously discussed second primary assembling piece, and repeated description will be omitted herein. 
     As shown in  FIG. 17 , the flat panel display device  20  of the present invention further comprises a touch screen  29 . The touch screen  29  is arranged on a light exit surface of the display panel  22  of the flat panel display device  20 . The flat panel display device  20  comprises: the backlight system  21  and the above discussed display panel  22 . The backlight system  21  is arranged at the back side of the display panel  22  and supplies light to the display panel  22 . 
     The backlight system  21  comprises a light source  25 , a light homogenization mechanism  24 , and a back frame  23 . The back frame  23  carries the light source  25  and the light homogenization mechanism  24 . When the backlight system  21  is an edge lighting type, the light homogenization mechanism  24  is a light guide; and when the backlight system  21  is a direct type, the light homogenization mechanism  24  is a diffuser plate. The back frame  23  comprises at least a first primary assembling piece and a second primary assembling piece, and the at least one first and second primary assembling pieces constitute a main frame structure  27  of the back frame  23 . 
     It is noted that the flat panel display device  20  of the present invention can be a liquid crystal display device or a liquid crystal television. 
     The present invention also provides a stereoscopic display device  30 , as shown in  FIG. 18 . The stereoscopic display device  30  comprises a liquid crystal lens grating  31 , a backlight system  32 , and a display panel  33 . The liquid crystal lens grating  31  is arranged on a light exit surface of the display panel  33 . The backlight system  32  can be a backlight system of one of the above discussed embodiments, such as the backlight system  32  comprising the back frame  23 . The back frame  23  comprises at least first primary assembling piece and the second primary assembling piece. The at least first and second primary assembling pieces form a main frame structure of the back frame. Repeated description will be omitted herein. 
     The present invention also provides a plasma display device  40 , as shown in  FIG. 19 . The plasma display device  40  comprises a plasma display panel  41  and a back frame  42 . The back frame  42  is arranged at a back side of the display panel  41 . The back frame  42  can be the back frame of any of the previously discussed embodiments and repeated description will be omitted herein. 
     The present invention also provides a bracing piece that is applicable to the each of the above disclosed embodiments, wherein the bracing piece is of a multiple-stepped configuration and is mounted to an assembling piece of each of the above embodiments. 
     Specifically, as shown in  FIG. 20 , a bracing piece  500  comprises a first step surface  501 , and the first step surface  501  comprise bumps  502 ,  503 ,  504  formed thereon. The bump  502 ,  503 ,  504  forms in a center thereof a mounting hole (not shown). The mounting holes of the bumps  502 ,  503 ,  504  are cooperative with fasteners, such as screws, in an assembling operation in order to fix the bracing piece  500  to other component of a back frame, such as a circuit board. 
     The bracing piece  500  further comprises a plurality of second step surfaces  505 ,  506 ,  507  that is integrally formed at one end of the first step surface  501  and a plurality of third step surfaces  508 ,  509 ,  510  integrally formed at an opposite ends of the first step surface  501 . 
     Referring to  FIG. 21 , the first step surface  501  is of different vertical levels with respect to the second step surfaces  505 ,  506 ,  507  and also, the first step surface  501  is of different vertical levels with respect to the third step surfaces  508 ,  509 ,  510 . Selection of one of the plurality of second step surfaces  505 ,  506 ,  507  can be according to mounting heights H 1 , H 2 , H 3  of the mounting holes of the bumps  502 ,  503 ,  504  in order to fix the assembling piece and selection is also made to one of the plurality of third step surfaces  508 ,  509 ,  510  to fix an assembling piece. For example, in case the mounting hole requires a mounting height of H 2 , then trimming can be carried out on the second step surface  506  and the third step surface  509  in order to remove the second step surface  507  that is connected to the second step surface  506  and the third step surface  510  that is connected to the third step surface  509  from the bracing piece  500  so that the second step surface  506  and the third step surface  509  can be respectively fixed to the assembling pieces. 
     Similarly, in the mounting hole requires a mounting height of H 3 , then trimming can be carried out on the second step surface  505  and the third step surface  508  to remove the second step surfaces  506  and  507  that are connected to the second step surface  505  and the second step surfaces  509  and  510  that are connected to the third step surface  508  from the bracing piece  500  so that the second step surface  505  and the third step surface  508  can be respectively fixed to the assembling pieces. 
     With the above described manners, trimming of the second step surfaces and the third step surfaces can be carried out according to actual needs for assembling and thus the mounting height of the mounting hole can be adjusted. Certainly, no trimming may be needed if the widths of the corresponding second step surface and third step surfaces are greater than widths of the assembling pieces. 
     The second step surfaces and the third step surfaces can be arranged symmetric or not with respect to the first step surface. In a practical use, the second step surfaces and the third step surfaces are preferably arranged symmetric. Further, the numbers of the second step surfaces and the third step surfaces can be changed according to practical needs and the present invention imposes no specific limitation in this respect. 
     Thus, in the instant embodiment, the bracing piece  500  is provided with a plurality of step surfaces. After the bracing piece  500  is formed by stamping a metal plate, a trimming position can be selected according to a desired mounting height of a mounting hole so that excessive step surfaces can be trimmed off. Commonly used fastening measures, such as welding and riveting, may then be adopted to fix opposite ends of the bracing piece  500  to the assembling pieces, and this is applicable to the mounting heights of all sorts of mounting holes, thereby achieving the purposes that the bracing pieces  500  that are set at different location in a back frame can be of different mounting heights of the mounting holes. Further, since the bracing piece  500  can be made a standard part that may be manufactured together in a unified manner so that the mold cost is reduced and the manufacturing efficiency is improved. 
     It is noted that, in the above described embodiments, the bracing piece  500  are fixed to assembling pieces with the two ends thereof, yet in a backup embodiment of the present invention, the bracing piece  500  can alternatively be provided with only the first step surface and the second step surfaces, or only the first step surface and the third step surfaces. In an arrangement of only the first step surface and the second step surfaces, the one of the second step surfaces that is selected is fixed to an assembling piece so as to realize fixing at one end. Similarly, in an arrangement of only the first step surface and the third step surfaces, the one of the third step surfaces that is selected can be fixed to an assembling piece so as to realize one end fixing. The arrangement of one end fixing described above also provides the same technical effect as that of the above described embodiment of two end fixing. With such arrangements, the back frame and backlight system of the present invention make the structure of a back frame mold simple, reduce the cost of back frame mold, save the material used for the back frame, and lower down the cost of flat panel display device. Further, the bracing piece disclosed in the present invention is applicable to various mounting heights of mounting holes, can be manufactured together in a unified manner, reduces the cost of mold, and improves manufacturing efficiency. 
     Embodiments of the present invention have been described, but are not intending to impose any undue constraint to the appended claims of the present invention. Any modification of equivalent structure or equivalent process made according to the disclosure and drawings of the present invention, or any application thereof, directly or indirectly, to other related fields of technique, is considered encompassed in the scope of protection defined by the claims of the present invention.