Patent Publication Number: US-11042193-B2

Title: Foldable mobile terminal, foldable mechanism for foldable mobile terminal, and foldable unit for foldable mobile terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application is a continuation application of International (PCT) Patent Application No. PCT/CN2018/086595, filed on May 11, 2018, which claims foreign priorities to Chinese Patent Application No. 201710349442.0, filed on May 17, 2017, and Chinese Patent Application No. 201720552311.8, filed on May 17, 2017, the entire contents of all of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of electronic devices, and in particular to a foldable mobile terminal, a foldable mechanism for a foldable mobile terminal, and a foldable unit for a foldable mobile terminal. 
     BACKGROUND 
     A flexible display screen may have a property of being foldable. Therefore, a smart mobile terminal, such as a smart phone, which carries a flexible display screen may be transformed between a folded state and an unfolded state. A customer may consider purchasing a mobile terminal if the mobile terminal can provide an indication to the customer during transforming between the folded state and the unfolded state, such that the customer may feel by hand that the mobile terminal is folded or unfolded to an appropriate position. 
     SUMMARY 
     A foldable mobile terminal may include: a flexible display screen; a shell assembly, including a first shell and a second shell, wherein the flexible display screen is arranged on the first shell and the second shell; a first rotation assembly, at least partially received in the first shell and able to slide towards or away from the first shell, wherein the first rotation assembly has one or more first grooves; a second rotation assembly, at least partially received in the second shell and able to slide towards or away from the second shell; and a first roller and a first spring, disposed between the first rotation assembly and the first shell, wherein when the first rotation assembly slide towards or away from the first shell, the first roller is able to move into or out of the one or more first grooves. 
     A foldable mechanism for a foldable mobile terminal may be provided. The mobile terminal may include a first shell and a second shell connected to each other. The foldable mechanism may include: a first rotation assembly, capable of being at least partially received in the first shell and able to slide towards or away from the first shell, wherein the first rotation assembly has a first groove; a second rotation assembly, capable of being at least partially received in the second shell and able to slide towards or away from the second shell; wherein the second rotation assembly has a second groove; and a first roller and a first spring, capable of being disposed between the first rotation assembly and the first shell, wherein when the first rotation assembly slide towards or away from the first shell, the first roller is able to move into or out of the first groove. 
     A foldable unit for a foldable mobile terminal may be provided and include: a shell assembly, including a first shell and a second shell; a first rotation assembly, at least partially received in the first shell and able to slide towards or away from the first shell, wherein the first rotation assembly has a first groove; a second rotation assembly, at least partially received in the second shell and able to slide towards or away from the second shell; a first roller and a first spring, disposed between the first rotation assembly and the first shell, wherein when the first rotation assembly slide towards or away from the first shell, the first roller is able to move into or out of the first groove; and a second roller and a second spring, disposed between the second rotation assembly and the second shell, wherein when the second rotation assembly slide towards or away from the second shell, the second roller is able to move into or out of the second groove. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a foldable mobile terminal in an unfolded state according to some embodiments of the present disclosure. 
         FIG. 2  is an exploded perspective view of the foldable mobile terminal shown in  FIG. 1 . 
         FIG. 3  is an exploded perspective view of the foldable mobile terminal shown in  FIG. 1 , but shown from a different aspect. 
         FIG. 4  is a perspective view of a foldable mechanism in a foldable mobile terminal in an unfolded state according to some embodiments of the present disclosure. 
         FIG. 5  is a front view of the foldable mechanism shown in  FIG. 4 . 
         FIG. 6  is a perspective view of the foldable mechanism of  FIG. 4  with portions omitted. 
         FIG. 7  is an exploded perspective view of the foldable mechanism of  FIG. 4 . 
         FIG. 8  is an exploded perspective view further illustrating a partial structure of  FIG. 7 . 
         FIG. 9  is an exploded perspective view of a partial structure of  FIG. 7 , but shown from a different aspect. 
         FIG. 10  is a perspective view of a foldable mobile terminal with a flexible display screen omitted according to some embodiments of the present disclosure. 
         FIG. 11  is a front view of a partial structure shown in  FIG. 10 . 
         FIG. 12  is a cross sectional view taken along a line A-A of  FIG. 11 . 
         FIG. 13  is a cross sectional view from a back of the structure shown in  FIG. 10 . 
         FIG. 14  is a schematic view of the structure shown in  FIG. 11  with some elements of the foldable mechanism omitted. 
         FIG. 15  is a back view of the structure shown in  FIG. 14 . 
         FIG. 16  is view of an elastic sheet of a foldable mechanism. 
         FIG. 17  is a perspective view of a first decoration component or a second decoration component. 
         FIG. 18  is a perspective view of the first decoration component or the second decoration component, but shown from a different aspect. 
         FIG. 19  is a perspective view of a foldable mobile terminal in a folded state according to some embodiments of the present disclosure. 
         FIG. 20  is a perspective view of the foldable mobile terminal shown in  FIG. 19  with a flexible display screen omitted. 
         FIG. 21  a perspective view of the foldable mobile terminal shown in  FIG. 4  in an unfolded state. 
         FIG. 22  is a front view of the foldable mechanism shown in  FIG. 21 . 
         FIG. 23  is a sectional view of a partial structure of a foldable mobile terminal in an unfolded state according to some embodiments of the present disclosure. 
         FIG. 24  is a sectional view of a partial structure of a foldable mobile terminal in a semi-folded (or a semi-unfolded) state according to some embodiments of the present disclosure. 
         FIG. 25  is a sectional view of a partial structure of a foldable mobile terminal in a folded state according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, in which the same or similar reference numbers throughout the drawings represent the same or similar elements or elements having same or similar functions. Embodiments described below with reference to drawings are merely examples and used for explaining the present disclosure, and should not be understood as limitation to the present disclosure. 
     The directional terms used here are only for better and more clearly describing and understanding the present disclosure, and are not intended to indicate or imply that the devices or the elements are disposed to locate at the specific directions or are structured and performed in the specific directions, which could not to be understood as limiting the present disclosure. In addition, terms such as “first”, “second”, and the like are used herein for purposes of description, and are not intended to indicate or imply relative importance or significance or to imply the number of indicated technical features. Thus, the feature defined with “first”, “second”, and the like may include one or more of such a feature. In the present disclosure, a plurality may indicate two or more, unless specified otherwise. 
     The mobile terminal provided in the present disclosure may include, but not be limited to, a device receiving/transmitting communication signals by wired connection (such as a public switched telephone network (PSTN), a digital subscriber line (DSL), a digital cable, a direct cable connection, and/or another data connection/network), and/or by a wireless interface (such as a wireless interface of a cellular network, a wireless local area network (WLAN), a digital television network such as a DVB-H network, a satellite network, an AM-FM broadcast transmitter, and/or another communication terminal). A communication terminal configured to communicate by a wireless interface may be referred as a “wireless communication terminal”, a “wireless terminal”, and/or a “mobile terminal”. The mobile terminal of the present disclosure may include, but may be not limited to a satellite or cellular radiotelephone telephone, a terminal of personal communications system (PCS) that may combine cellular radiotelephone with data processing, fax, and data communication capabilities, a personal digital assistant (PDA) equipped with a radiotelephone, a pager, an internet/intranet access, a web browser, a notepad, a calendar, and/or a global positioning system (GPS) receiver, a conventional laptop and/or a palm receiver, other electronic device including a radiotelephone transceiver and the like. 
     According to an aspect of the present disclosure, a foldable mobile terminal may include: a flexible display screen; a shell assembly, including a first shell and a second shell, wherein the flexible display screen is arranged on the first shell and the second shell; a first rotation assembly, at least partially received in the first shell and able to slide towards or away from the first shell, wherein the first rotation assembly has one or more first grooves; a second rotation assembly, at least partially received in the second shell and able to slide towards or away from the second shell; and a first roller and a first spring, disposed between the first rotation assembly and the first shell, wherein when the first rotation assembly slide towards or away from the first shell, the first roller is able to move into or out of the one or more first grooves. 
     In some embodiments, the second rotation assembly has one or more second grooves; the foldable mobile terminal further includes a second roller and a second spring disposed between the second rotation assembly and the second shell; and when the second rotation assembly slide towards or away from the second shell, the second roller is able to move into or out of the one or more second grooves. 
     In some embodiments, the first rotation assembly includes: a first sliding plate, at least partially received in the first shell and able to slide towards or away from the first shell; a first rotation shaft, arranged on the first sliding plate; and a first connection rod, wherein a first end of the first connection rod is slidably hinged to the first rotation shaft, and a second end of the first connection rod is rotatably connected to the first shell. The second rotation assembly includes: a second sliding plate, at least partially received in the second shell and able to slide towards or away from the second shell; a second rotation shaft, arranged on the second sliding plate; and a second connection rod, wherein a first end of the second connection rod is slidably hinged to the second rotation shaft, and a second end of the second connection rod is rotatably connected to the second shell. 
     In some embodiments, the first rotation assembly further includes a first sliding member, the first sliding member slidably sleeves on the first rotation shaft, and the first end of the first connection rod is rotatably connected to the first sliding member. The second rotation assembly further includes a second sliding member, the second sliding member slidably sleeves on the second rotation shaft, and the first end of the second connection rod is rotatably connected to the second sliding member. 
     In some embodiments, the first sliding plate includes a first substrate and two or more first latches arranged on the first substrate and spaced apart from each other. The first shell has two or more first notches, and the two or more first latches correspond to the two or more notches. The one or more first grooves are formed in a side wall of one of the two or more first latches of the first sliding plate, and the one or more first grooves are facing towards an adjacent first latch. The second sliding plate includes a second substrate and two or more second latches arranged on the second substrate and spaced apart from each other. The second shell has two or more second notches, and the two or more second latches correspond to the two or more second notches. The one or more second grooves are formed in a side wall of one of the two or more second latches of the second sliding plate, and the one or more second grooves are facing towards an adjacent second latch. 
     In some embodiments, the first shell includes a first front shell and a first back shell engaged with each other; the second shell includes a second front shell and a second back shell engaged with each other; the flexible display screen is arranged on the first front shell and the second front shell; and the first front shell has the two or more first notches, and the second front shell has the two or more second notches. 
     In some embodiments, a side wall of one of the two or more first notches of the first shell is recessed inwardly away from a corresponding first latch to form a first cavity. The first roller and the first spring are received in the first cavity, and the first spring is arranged to elastically abut against the first roller such that the first roller is at least partially exposed to an outside of the first cavity. A side wall of one of the two or more second notches of the second shell is recessed inwardly away from a corresponding second latch to form a second cavity. The second roller and the second spring are received in the second cavity, and the second spring is arranged to elastically abut against the second roller such that the second roller is at least partially exposed to an outside of the second cavity. 
     In some embodiments, the number of the one or more first grooves is two, and the two first grooves are formed in the side wall of the one of the two or more first latches at positions corresponding to two terminating positions of the first sliding plate. The number of the one or more second grooves is two, and the two second grooves are formed in the side wall of the one of the two or more second latches at positions corresponding to two terminating positions of the second sliding plate. 
     In some embodiments, a length for which one of the two or more first latches having the one or more first grooves extends towards the first shell is greater than a length for which any other one of the two or more first latches extends towards the first shell. A length for which the one of the two or more second latches having the one or more second grooves extends towards the second shell is greater than a length for which any other one of the two or more second latches extends towards the second shell. 
     In some embodiments, the number of the one or more first grooves is two, and the number of the one or more second grooves is two. At least two sets of first rollers and first springs are arranged, the two first grooves are formed in two opposing side walls of one of the two or more first latches, and each of the two first grooves matches with a first roller. At least two sets of second rollers and second springs are arranged, the two second grooves are formed in two opposing side walls of one of the two or more second latches, and each of the two second grooves matches with a second roller. 
     According to another aspect of the present disclosure, a foldable mechanism for a foldable mobile terminal may be provided. The mobile terminal may include a first shell and a second shell connected to each other. The foldable mechanism may include: a first rotation assembly, capable of being at least partially received in the first shell and able to slide towards or away from the first shell, wherein the first rotation assembly has a first groove; a second rotation assembly, capable of being at least partially received in the second shell and able to slide towards or away from the second shell; wherein the second rotation assembly has a second groove; and a first roller and a first spring, capable of being disposed between the first rotation assembly and the first shell, wherein when the first rotation assembly slide towards or away from the first shell, the first roller is able to move into or out of the first groove. 
     In some embodiments, the first rotation assembly further includes: a first sliding plate, capable of being at least partially received in the first shell and able to slide towards or away from the first shell; a first rotation shaft, arranged on the first sliding plate; and a first connection rod, wherein a first end of the first connection rod is slidably hinged to the first rotation shaft, and a second end of the first connection rod is capable of being rotatably connected to the first shell. The second rotation assembly further includes: a second sliding plate, capable of being at least partially received in the second shell and able to slide towards or away from the second shell; a second rotation shaft, arranged on the second sliding plate; and a second connection rod, wherein a first end of the second connection rod is slidably hinged to the second rotation shaft, and a second end of the second connection rod is capable of being rotatably connected to the second shell. 
     In some embodiments, the first rotation assembly further includes a first sliding member, the first sliding member slidably sleeves on the first rotation shaft, and the first end of the first connection rod is rotatably connected to the first sliding member. The second rotation assembly further includes a second sliding member, the second sliding member slidably sleeves on the second rotation shaft, and the first end of the second connection rod is rotatably connected to the second sliding member. 
     In some embodiments, the first sliding plate includes a first substrate and two or more first latches arranged on the first substrate spaced apart from each other, the first shell has two or more first notches, the two or more first latches are capable of being arranged to correspond to the two or more notches, the first groove is formed in a side wall of one of the two or more first latches of the first sliding plate, and the first groove is facing towards an adjacent first groove. The second sliding plate includes a second substrate and two or more second latches arranged on the second substrate spaced apart from each other, the second shell has two or more second notches, the two or more second latches correspond to the two or more second notches, a second groove is formed in a side wall of one of the two or more second latches of the second sliding plate, and the second groove is facing towards an adjacent second groove. The foldable mechanism further includes a second roller and a second spring, and the second roller and the second spring are capable of being disposed between the second rotation assembly and the second shell. 
     In some embodiments, a side wall of one of the two or more first notches of the first shell is recessed inwardly away from a corresponding first latch to form a first cavity; the first roller and the first spring are received in the first cavity and the first spring is configured to elastically abut against the first roller such that the first roller is at least partially exposed to an outside of the first cavity; a side wall of one of the two or more second notches of the second shell is recessed inwardly away from a corresponding second latch to form a second cavity; and the second roller and the second spring are received in the second cavity and the second spring is configured to elastically abut against the second roller such that the second roller is at least partially exposed to an outside of the second cavity. 
     In some embodiments, the side wall of the one of the two or more first latches has two first grooves at two terminating positions of the first sliding plate; and the side wall of the one of the two or more second latches has two second grooves at two terminating positions of the second sliding plate. 
     In some embodiments, the one of the two or more first latches which has the first groove extends towards the first shell for a length greater than any other one of the two or more first latches extends towards the first shell. The one of the two or more second latches which has the second groove extends towards the second shell for a length greater than any other one of the two or more second latches extends towards the second shell. 
     In some embodiments, at least two sets of first rollers and first springs are arranged, two opposing side walls of one of the two or more first latches have two first grooves, and each of the two first grooves matches with a first roller. At least two sets of second rollers and second springs are arranged, two opposing side walls of one of the two or more second latches have two second grooves, and each of the two second grooves matches with a second roller. 
     According to still another aspect of the present disclosure, a foldable unit for a foldable mobile terminal may be provided and include: a shell assembly, including a first shell and a second shell; a first rotation assembly, at least partially received in the first shell and able to slide towards or away from the first shell, wherein the first rotation assembly has a first groove; a second rotation assembly, at least partially received in the second shell and able to slide towards or away from the second shell; a first roller and a first spring, disposed between the first rotation assembly and the first shell, wherein when the first rotation assembly slide towards or away from the first shell, the first roller is able to move into or out of the first groove; and a second roller and a second spring, disposed between the second rotation assembly and the second shell, wherein when the second rotation assembly slide towards or away from the second shell, the second roller is able to move into or out of the second groove. 
     In some embodiments, the first shell includes a first front shell and a first back shell engaged with each other. The second shell includes a second front shell and a second back shell engaged with each other. The first front shell and the second front shell are configured to arrange a flexible display screen. 
     As shown in  FIG. 1 ,  FIG. 2 ,  FIG. 3 , and  FIG. 4 , according to some embodiments of the present disclosure, a foldable mobile terminal may be provided. The foldable mobile terminal may include a flexible display screen  10 , a foldable mechanism  20 , and a shell assembly  30 . The shell assembly  30  may include a first shell  31  and a second shell  32 . The foldable mechanism  20  may be connected between the first shell  31  and the second shell  32 . The flexible display screen  10  may be arranged on the first shell  31  and the second shell  32 . The foldable mobile terminal shown in  FIG. 1  may be in an unfolded state, and the first shell  31  and the second shell  32  may be symmetric to each other with respect to the foldable mechanism  20 . As shown in  FIG. 19 , when the first shell  31  and the second shell  32  rotates to reach a completely folded state with respect to the foldable mechanism  20 , the flexible display screen  10  may be arranged at an outside of the mobile terminal. As shown in  FIG. 1 , in the unfolded state, an extending length of a side of the shell assembly  30  facing towards the flexible display screen  10  (the length along a direction parallel to an X-axis shown in  FIG. 1 ) may be substantially equal to an extending length of a side of the shell assembly  30  facing away from the flexible display screen  10  (the length along the direction parallel to the X-axis shown in  FIG. 1 ). However, as shown in  FIG. 19 , the shell assembly  30  itself may have a thickness (the thickness is along a direction parallel to an Y-axis shown in  FIG. 1 ), in a folded state, the extending length of the side of the shell assembly  30  facing towards the flexible display screen  10  may be greater than the extending length of the side of the shell assembly  30  facing away from the flexible display screen  10 . By providing the foldable mechanism  20 , the first shell  31  and the second shell  32  may adapt to a length difference generated while switching between the folded state and the unfolded state. 
     The first shell  31  may include a first front shell  311  and a first back shell  312  connected to each other. The second shell  32  may include a second front shell  321  and a second back shell  322  connected to each other. The connection may be achieved by screwing, adhesion, welding, and the like. The flexible display screen  10  may be disposed on the first front shell  311  and the second front shell  321 . The flexible display screen  10  may have a display region, and the display region may be rectangular or rounded rectangular in the unfolded state. A space may be formed between the first front shell  311  and the first back shell  312  along the direction parallel to the Y-axis. Similarly, a space may be formed between the second front shell  321  and the second back shell  322  along the direction parallel to the Y-axis. The spaces may allow arrangement of a power module, a communication module, and other components. The spaces may further allow the foldable mechanism  20  to slidably extend and retract with respect to the first shell  31  and the second shell  32 ; that is to say, the foldable mechanism  20  is slidable away from or towards the first shell  31  and the second shell  32 . 
     Another space may be formed between the first shell  31  and the second shell  32  along the direction parallel to the X-axis. The foldable mechanism may be arranged within the space between the first shell  31  and the second shell  32  along the direction parallel to the X-axis, and at least a partial structure of the foldable mechanism  20  may be received in the first shell  31  and the second shell  32 . The space between the first shell  31  and the second shell  32  along the direction parallel to the X-axis may be changed during the rotation of the first shell  31  and the second shell around the foldable mechanism  20 . Therefore, during the rotation of the first shell  31  and the second shell  32  around the foldable mechanism  20 , the foldable mechanism  20  may be retracted into the first shell  31  and the second shell  32  at varying levels. As shown in  FIG. 4  and  FIG. 5 , the foldable mechanism  20  may include a first rotation assembly  50  and a second rotation assembly  60 . The first rotation assembly  50  may be connected to the first shell  31 . The rotation assembly  50  may be at least partially received inside the first shell  31 , and may slidably extend and retract with respect to (i.e., slide away from or towards) the first shell  31 . The second rotation assembly  60  may be connected to the second shell  32 . The second rotation assembly  60  may be at least partially received inside second shell  32 , and may slidably extend and retract with respect to (slide away from or towards) the second shell  32 . By the slidable extension and retraction of the first rotation assembly  50  with respect to the first shell  31  and the slidable extension and retraction of the second rotation assembly  60  with respect to the second shell  32 , the first shell  31  and the second shell  32  may adapt to a length difference generated while switching between the folded state and the unfolded state. 
     In some embodiments, the first rotation assembly  50  and the second rotation assembly  60  may have a same structure. The first rotation assembly  50  and the second rotation assembly  60  may be symmetrically distributed about a central axis I-I (shown in  FIG. 5 ) between the first rotation assembly  50  and the second rotation assembly  60 . By arranging the first rotation assembly  50  and the second rotation assembly  60  to be symmetric to each other, the first shell  31  and the second shell  32  may be folded and unfolded symmetrically about the central axis I-I. 
     As further shown in  FIG. 4 ,  FIG. 5 ,  FIG. 6 , and  FIG. 7 , the first rotation assembly  50  may include a first sliding plate  51 , a first rotation shaft  53 , and a first connection rod  54 . The first rotation shaft  53  may be arranged on the first sliding plate  51 . A first end  541  of the first connection rod  54  may be slidably hinged to the first rotation shaft  53 , and a second end  542  of the first connection rod  54  may be rotatably connected to the first shell  31 . The first sliding plate  51  may be at least partially received in the first shell  31 , and slidably extend and retract with respect to (i.e., slide away from or towards) the first shell  31 . While the first shell  31  and the second shell  32  folds and unfolds symmetrically, the first sliding plate  51  together with the first rotation shaft  53  may slidably extend and retract with respect to (i.e., slide away from or towards) the first shell  31 . The second end  542  of the first connection rod  54  may rotate with respect to the first shell  31 . The first end  541  of the first connection rod  54  may slide on the first rotation shaft  53  and rotate with respect to the first rotation shaft  53 . By changing a level at which the first sliding plate  51  is received inside the first shell  31 , it is possible to adapt to a length difference generated during the folding and unfolding of the first shell  31  and the second shell  32 . 
     According to some embodiments shown in  FIG. 2  and  FIG. 3 , two first rotation shafts  53  and two first connection rods  54  may be arranged on the first sliding plate  51 . The two first rotation shafts  53  may be arranged symmetrically about a middle position of the first sliding plate  51  along a direction parallel to a Z-axis, and the two first connection rods  54  may be arranged symmetrically about a middle position of the first sliding plate  51  along the direction parallel to the Z-axis. In some other embodiments, the number of the first rotation shaft  53  may be one or more, and the number of the first connection rod  54  may be one or more. Slidable extension and retraction of the first sliding plate  51  with respect to the first shell  31  may be achieved with various numbers of the first rotation shafts  53  and the first connection rods  54 . 
     As shown in  FIG. 4 ,  FIG. 5 ,  FIG. 6 , and  FIG. 7 , the second rotation assembly  60  may include a second sliding plate  61 , a second rotation shaft  63 , and a second connection rod  64 . The second rotation shaft  63  may be arranged on the second sliding plate  61 . A first end  641  of the second connection rod  64  may be slidably hinged to the second rotation shaft  63 , and a second end  642  of the second connection rod  64  may be rotatably connected to the second shell  32 . The second sliding plate  61  may be at least partially received in the second shell  32 , and slidably extend and retract with respect to (i.e., slide away from or towards) the second shell  32 . While the first shell  31  and the second shell  32  folds and unfolds symmetrically, the second sliding plate  61  together with the second rotation shaft  63  may slidably extend and retract with respect to (i.e., slide away from or towards) the second shell  32 . The second end  642  of the second connection rod  64  may rotate with respect to the second shell  32 . The first end  641  of the second connection rod  64  may slide on the second rotation shaft  63  and rotate with respect to the second rotation shaft  63 . By changing a level at which the second sliding plate  61  is received in the second shell  32 , it is possible to adapt to a length difference generated during the folding and unfolding of the first shell  31  and the second shell  32 . 
     According to some embodiments shown in  FIG. 2  and  FIG. 3 , two second rotation shafts  63  and two second connection rods  64  may be arranged on the second sliding plate  61 . The two second rotation shafts  63  may be arranged symmetrically about a middle position of the second sliding plate  61  along the direction parallel to the Z-axis, and the two second connection rods  64  may be arranged symmetrically about a middle position of the second sliding plate  61  along the direction parallel to the Z-axis. In some other embodiments, the number of the second rotation shafts  63  may be one or more, and the number of the second connection rods  64  may be one or more. Slidable extension and retraction of the second sliding plate  61  with respect to the second shell  32  may be achieved with various numbers of the second rotation shafts  63  and the second connection rods  64 . 
     As shown in  FIG. 8  and  FIG. 9 , in some embodiments, the foldable mechanism  20  may include a linkage element  22  connected to the first rotation shaft  53  and the second rotation shaft  63 . The linkage element  22  may have a first through hole  221  and a second through hole  222 . The first through hole  221  and the second through hole  222  may be spaced apart from each other. The first rotation shaft  53  may be arranged to extend through the first through hole  221 , and the second rotation shaft  63  may be arranged to extend through the second through hole  222 . The linkage element  22  may link the first end  541  of the first connection rod  54  and the first end  641  of the second connection rod  64  to move at the same time. That is, by virtue of the linkage element  22 , sliding of the first end  541  of the first connection rod  54  along the first rotation shaft  53  may lead to sliding of the first end  641  of the second connection rod  64  along the second rotation shaft  63 , and vice versa. 
     The linkage element  22  may allow the first connection rod  54  which is slidably hinged to the first rotation shaft  53  and the second connection rod  64  which is slidably hinged to the second rotation shaft  63  to move synchronously. That is, the slidable extension and retraction of the first sliding plate  51  with respect to the first shell  31  is synchronous with the slidable extension and retraction of the second sliding plate  61  with respect to the second shell  32 , such that a symmetric folding and unfolding of the first shell  31  and the second shell  32  may be further achieved. The linkage element  22  may be made of metals or plastics. 
     In other embodiments, functions of the linkage element  22  may be achieved by other components. For example, a component configured to achieve a slidable hinge between the first connection rod  54  and the first rotation shaft  53  and a component configured to achieve a slidable hinge between the second connection rod  64  and the second rotation shaft  63  may be configured as an integral component. By configuring an integral component to achieve the slidable hinge, the first connection rod  54  which is slidably hinged to the first rotation shaft  53  and the second connection rod  64  which is slidably hinged to the second rotation shaft  63  may move synchronously. 
     As shown in  FIG. 7 ,  FIG. 8 , and  FIG. 9 , in some embodiments, the first rotation assembly  50  may further include a first sliding member  52  configured to achieve the slidable hinge between the first connection rod  54  and the first rotation shaft  53 . The first sliding member  52  may be arranged to slidably sleeve on the first rotation shaft  53 , and the first end  541  of the first connection rod  54  may be rotatably connected to the first sliding member  52 . 
     In some embodiments, the first sliding member  52  may include two sleeve tubes  521  and a connection arm  522  connected between the two sleeve tubes  521 . The first rotation shaft  53  may extend through the sleeve tubes  521  of the first sliding member  52 . The first sliding member  52  may slide along the first rotation shaft  53  and rotate with respect to the first rotation shaft  53 . 
     The first end  541  of the first connection rod  54  may be rotatably connected to the connection arm  522  of the first sliding member  52 . Further, the connection arm  522  of the first sliding member  52  may have a first positioning hole  523 , and the first end  541  of the first connection rod  54  may have a first positioning protrusion  543 . The first positioning protrusion  543  may be inserted into the first positioning hole  523 . 
     The second rotation assembly  60  may further include a second sliding member  62 . The slidable hinge between the second connection rod  64  and the second rotation shaft  63  may be achieved by the second sliding member  62 . The second sliding member  62  may be arranged to sleeve on the second rotation shaft  63  in a slidable manner, and the first end  641  of the second connection rod  64  may be rotatably connected to the second sliding member  62 . 
     In some embodiments, the second sliding member  62  may include two sleeve tubes  621  and a connection arm  622  connected between the two sleeve tubes  621 . The second rotation shaft  63  may extend through the sleeve tubes  621  of the second sliding member  62 . The second sliding member  62  may slide along the second rotation shaft  63  and rotate with respect to the second rotation shaft  63 . 
     The first end  641  of the second connection rod  64  may be rotatably connected to the connection arm  622  of the second sliding member  62 . Further, the connection arm  622  of the second sliding member  62  may have a second positioning hole  623 , and a first end  641  of the second connection rod  64  may have a second positioning protrusion  643 . The second positioning protrusion  643  may be inserted into the second positioning hole  623 . 
     In some embodiments, the linkage element  22  may include a first arm portion  223  having the first through hole  221  and a second arm portion  224  having the second through hole  222 . The first arm portion  223  may be arranged between the two sleeve tubes  521  of the first sliding member  52 . The second arm portion  224  may be arranged between the two sleeve tubes  621  of the second sliding member  62 . The first rotation shaft  53  may extend through the first through hole  221 , and the second rotation shaft  63  may extend through the second through hole  222 . The linkage element  22  may serve as a link between the first sliding member  52  and the second sliding member  62 , such that the sliding of the first sliding member  52  along the first rotation shaft  53  may be synchronous with the sliding of the second sliding member  62  along the second rotation shaft  63 . 
     As shown in  FIG. 4 ,  FIG. 5 ,  FIG. 6 , and  FIG. 7 , in some embodiments, the first rotation assembly  50  may further include a first support  56 , and the first rotation shaft  53  may be configured on the first sliding plate  51  through the first support  56 . Further, the first support  56  may be fixed on the first sliding plate  51  by screw fastening. The first rotation shaft  53  may extend through the first support  56 , and the first sliding member  52  may be arranged between the first support  56  and the first sliding plate  51 . By arranging the first support  56 , relative movement of the first sliding member  52 , the first end  541  of the first connection rod  54 , and the first rotation shaft  53  may be restricted within a space between the first support  56  and the first sliding plate  51 , such that a possibility of the first end  541  of the first connection rod  54  detaching from the first sliding member  52  may be reduced. 
     The rotatable connection between the second end  542  of the first connection rod  54  and the first shell  31  may be achieved by a rotatable connection between the second end  542  of the first connection rod  54  and the first front shell  311 . Alternatively, the rotatable connection between the second end  542  of the first connection rod  54  and the first shell  31  may be achieved by a rotatable connection between the second end  542  of the first connection rod  54  and the first back shell  312 . Alternatively, the rotatable connection between the second end  542  of the first connection rod  54  and the first shell  31  may be achieved by rotatably connecting the second end  542  of the first connection rod  54  to the first front shell  311  and the first back shell  312  at the same time. In some embodiments, as shown in  FIG. 8 ,  FIG. 9 , and  FIG. 11 , the first front shell  311  may have a first connection hole  313 , and a first connection protrusion  544  may be arranged at the second end  542  of the first connection rod  54 . The first connection protrusion  544  may be inserted into the first connection hole  313 . Further, as shown in  FIG. 13  and  FIG. 15 , the first rotation assembly  50  may further include a first pressing sheet  55 . The first pressing sheet  55  may be connected to the first front shell  311 , and configured to limit a position of the first connection rod  54 , such that the first connection rod  54  may be disposed between the first pressing sheet  55  and the first front shell  311 . 
     As shown in  FIG. 4 ,  FIG. 5 ,  FIG. 6 , and  FIG. 7 , in some embodiments, the second rotation assembly  60  may further include a second support  66 , and the second rotation shaft  63  may be configured on the second sliding plate  61  through the second support  66 . Further, the second support  66  may be fixed on the second sliding plate  61  by screw fastening. The second rotation shaft  63  may extend through the second support  66 , and the second sliding member  62  may be arranged between the second support  66  and the second sliding plate  61 . By arranging the second support  66 , relative movement of the second sliding member  62 , the first end  641  of the second connection rod  64 , and the second rotation shaft  63  may be restricted within a space between the second support  66  and the second sliding plate  61 , such that a possibility of the first end  641  of the second connection rod  64  detaching from the second sliding member  62  may be reduced. 
     The rotatable connection between the second end  642  of the second connection rod  64  and the second shell  32  may be achieved by a rotatable connection between the second end  642  of the second connection rod  64  and the second front shell  321 . Alternatively, the rotatable connection between the second end  642  of the second connection rod  64  and the second shell  32  may be achieved by a rotatable connection between the second end  642  of the second connection rod  64  and the second back shell  322 . Alternatively, the rotatable connection between the second end  642  of the second connection rod  64  and the second shell  32  may be achieved by rotatably connecting the second end  642  of the second connection rod  64  to the second front shell  321  and the second back shell  322  at the same time. In some embodiments, as shown in  FIG. 8 ,  FIG. 9 , and  FIG. 11 , the second front shell  321  may have a second connection hole  323 , and a second connection protrusion  644  may be arranged at the second end  642  of the second connection rod  64 . The second connection protrusion  644  may be inserted into the second connection hole  323 . Further, as shown in  FIG. 13  and  FIG. 15 , the second rotation assembly  60  may further include a second pressing sheet  65 . The second pressing sheet  65  may be connected to the second front shell  321 , and configured to limit a position of the second connection rod  64 , such that the second connection rod  64  may be disposed between the second pressing sheet  65  and the second front shell  321 . 
     As shown in  FIG. 8  and  FIG. 9 , the foldable mechanism  20  may further include a first shaft sleeve  24   a  and a second shaft sleeve  24   b . The first shaft sleeve  24   a  may be disposed at one end of the first rotation shaft  53  and one end of the second rotation shaft  63 , and may be connected to both the first rotation shaft  53  and the second rotation shaft  63 . The second shaft sleeve  24   b  may be disposed at the other end of the first rotation shaft  53  and the other end of the second rotation shaft  63 , and may be connected to both the first rotation shaft  53  and the second rotation shaft  63 . The first and the second shaft sleeves  24   a  and  24   b  may be configured to fix the first rotation shaft  53  on the first support  56 , and fix the second rotation shaft  63  on the second support  66 . The first support  56 , the second support  66 , the first rotation shaft  53 , and the second rotation shaft  63  may be provided with equal number. In some embodiments, the number of the first supports  56  and the number of the second supports  66  may both be two. Each first support  56  may be arranged at a corresponding end of the first sliding plate  51  along the direction parallel to the Z-axis, and each second support  66  may be arranged at a corresponding end of the second sliding plate  61  along the direction parallel to the Z-axis. 
     In some embodiments, as shown in  FIG. 4  and  FIG. 7 , the foldable mechanism  20  may further include a supportive strip  26 . The supportive strip  26  may be arranged between the first rotation assembly  50  and the second rotation assembly  60 . The supportive strip  26  may be configured to support the flexible display screen  10 . The supportive strip  26  may extend for a certain length along the direction parallel to the Z-axis in order to be arranged in a gap between the first sliding plate  51  and the second sliding plate  61 . According to some embodiments provided with the first support  56  and the second support  66 , the supportive strip  26  may further extend into a gap between the first support  56  and the second support  66 . The supportive strip  26 , the first sliding plate  51 , the second sliding plate  61 , the first support  56 , the second support  66 , the first front shell  311 , and the second front shell  321  may cooperatively support the flexible display screen  10 . 
     As shown in  FIG. 8  and  FIG. 9 , the linkage element  22  may have a receiving recess  226 . At least a partial structure of the supportive strip may be received in the receiving recess  226 . In some embodiments, the linkage element  22  may include a connection portion  225  connecting with the first arm portion  223  and the second arm portion  224 , and the receiving recess  226  may be formed on the connection portion  225 . 
     As shown in  FIG. 8  and  FIG. 9 , in other embodiments, at least one of the first shaft sleeve  24   a  and the second shaft sleeve  24   b  may also have a receiving recess  241 , and at least a partial structure of the supportive strip  26  may be received in the receiving recess  241 . At least one of the connection between the supportive strip  26  and the first shaft sleeve  24   a  and the second shaft sleeve  24   b  and the connection between the supportive strip  26  and the linkage element  22  may be achieved by welding or other means. 
     As shown in  FIG. 20 ,  FIG. 23 ,  FIG. 24 , and  FIG. 25 , a top face  261  of the supportive strip  26  faces towards the flexible display screen  10 , and the top face  261  of the supportive strip  26  may be a curved face. When the foldable mobile terminal is in a semi-folded state as shown in  FIG. 24  or in a folded state as shown in  FIG. 25 , as the supportive strip  26  has a curved face, a curvature of a contour of the mobile terminal may not be changed sharply during the folding of the first shell  31  and the second shell  32 . Therefore, the flexible display screen  10  may be better supported. 
     As shown in  FIG. 7 ,  FIG. 8 , and  FIG. 9 , in some embodiments, the first rotation assembly  50  may further include a first elastic sheet  57  arranged on the first sliding plate  51 . The first end  541  of the first connection rod  54  may reach two extreme positions along a direction of sliding, the first elastic sheet  57  may include two first engaging portions  571 . Each of the two first engaging portions  571  may correspond to each of the two extreme positions. In the embodiments provided with the first support  56 , the first elastic sheet  57  may be fixed on the first sliding plate  51  through the first support  56 , and the first elastic sheet  57  may be disposed inside the first support  56 . 
     The two first engaging portions  571  of the first elastic sheet  57  may respectively correspond to two ends of a sliding path of the first end  541  of the first connection rod  54  while the first end  541  slides along the first rotation shaft  53 . To some extent, interference may be generated between each first engaging portion  571  and the first end  541  of the first connection rod  54 , such that the first engaging portion  571  may apply a clamping force to the first end  541  of the first connection rod  54 , and the position of the first connection rod  54  may not be changed randomly. Therefore, the first sliding plate  51  may be arranged at a stable position with respect to the first shell  31 , that is, the foldable mobile terminal may stably remain in the folded or unfolded state. 
     In some embodiments, the first positioning protrusion  543  at the first end  541  of the first connection rod  54  may extend through two opposing sides of the first end  541 . An end of the first positioning protrusion  543  may be engaged in the first positioning hole  523  of the first sliding member  52 , and an opposing end of the first positioning protrusion  543  may be inserted into the first engaging portion  571  of the first elastic sheet  57 . The first engaging portion  571  may clamp the first positioning protrusion  543  to apply a certain clamping force to the first connection rod  54 . 
     In some embodiments, the first elastic sheet  57  may further include a first damping portion  572  disposed between the two first engaging portions  571 . When the first end  541  of the first connection rod  54  slides from the first engaging portion  571  to the first damping portion  572 , a resistance may be increased. Increasing of the resistance may be achieved as a clamping force applied to the first positioning protrusion  543  by the first damping portion  572  is greater than the clamping force applied to the first positioning protrusion  543  by the first engaging portion  571 . For example, the first elastic sheet  57  may be stadium-shaped with an opening at an end and closed at an opposing end. The two first engaging portions  571  may be arranged at the two opposite ends of the first elastic sheet  57 , and the first damping portion  572  may be arranged at a middle portion of the first elastic sheet  57 . A first gap  572   a  formed in the first damping portion  572  for the first positioning protrusion  543  to extend through may be smaller than a second gap  571   a  formed in the first engaging portion  571  for the first positioning protrusion  543  to extend through. Therefore, during the sliding from the first engaging portion  571  to the first damping portion  572 , the first connection rod  54  may receive an increased resistance. By arranging the first elastic sheet  57  in such manner, when rotating the first shell  31  and the second shell  32  of the foldable mobile terminal, a user may feel the resistance more obviously. 
     In some other embodiments, the first elastic sheet  57  may be in shape of a closed loop. Further, in yet other embodiments, the first elastic sheet  57  may include two separated strips. Two ends of each of the two separated strips may be fixed on the first sliding plate  51  through the first support  56  or other components (or by other means), such that the first connection rod  54  may be applied with different resistances when the first connection rod  54  is at various positions of the sliding path along the first rotation shaft  53 . 
     As shown in  FIG. 9 , the first support  56  may have a first receiving cavity  560 , and the first elastic sheet  57  may be received in the first receiving cavity  560 . After the first support  56  is fixed on the first sliding plate  51 , the first sliding plate  51  may close the first receiving cavity  560 , such that the first elastic sheet  57  may be fixed inside the first receiving cavity  560 . 
     Further, the first receiving cavity  560  may include two first positioning cavities  561  and a first releasing cavity  562 . Each of the two first positioning cavities  561  may correspond to each of the first engaging portion  571  of the first elastic sheet  57 . The first releasing cavity  562  may be formed between the two first positioning cavities  561 . A size of the first releasing cavity  562  may be greater than a size of each first positioning cavity  561 . After the first engaging portion  571  is arranged in the first positioning cavity  561 , the first engaging portion  571  may be fixed to be unmovable. The first damping portion  572  arranged between the two first engaging portions  571  may be correspondingly arranged in the first releasing cavity  562 . The first releasing cavity  562  may offer a space allowing the first damping portion  572  to be elastically deformed. 
     In some embodiments, the second rotation assembly  60  may further include a second elastic sheet  67  arranged on the second sliding plate  61 . The first end  641  of the second connection rod  64  may reach two extreme positions along a direction of sliding, and the second elastic sheet  67  may include two second engaging portions  671 . Each of the two second engaging portions  671  may correspond to each of the two extreme positions. In the embodiments provided with the second support  66 , the second elastic sheet  67  may be fixed on the second sliding plate  61  through the second support  66 , and the second elastic sheet  67  may be disposed inside the second support  66 . 
     The two second engaging portions  671  of the second elastic sheet  67  may respectively correspond to two ends of a sliding path of the first end  641  of the second connection rod  64  while the first end  641  slides along the second rotation shaft  63 . To some extent, interference may be generated between each second engaging portion  671  and the first end  641  of the second connection rod  64 , such that the second engaging portion  671  may apply a clamping force to the first end  641  of the second connection rod  64 , and the position of the second connection rod  64  may not be changed randomly. Therefore, the second sliding plate  61  may be arranged at a stable position with respect to the second shell  32 , that is the foldable mobile terminal may stably remain in the folded or unfolded state. 
     In some embodiments, the second positioning protrusion  643  at the first end  641  of the second connection rod  64  may extend through two opposing sides of the first end  641 . An end of the second positioning protrusion  643  may be engaged in the second positioning hole  623  of the second sliding member  62 , and an opposing end of the second positioning protrusion  643  may be inserted into the second engaging portion  671  of the second elastic sheet  67 . The second engaging portion  671  may clamp the second positioning protrusion  643  to apply a certain clamping force to the second connection rod  64 . 
     As shown in  FIG. 4 ,  FIG. 5 ,  FIG. 21 , and  FIG. 22 ,  FIG. 5  illustrates the sliding mechanism  20  in the unfolded state, and the second positioning protrusion  643  arrange at the first end  641  of the second connection rod  64  may be inserted into one of the second engaging portions  671 , as shown in  FIG. 5 .  FIG. 22  illustrates the sliding mechanism  20  in the folded state, and the second positioning protrusion  643  arrange at the first end  641  of the second connection rod  64  may be inserted into the other one of second engaging portions  671 , as shown in  FIG. 22 . 
     In some embodiments, the second elastic sheet  67  may further include a second damping portion  672  disposed between the two second engaging portions  671 . When the first end  641  of the second connection rod  64  slides from the second engaging portion  671  to the second damping portion  672 , a resistance may be increased. Increasing of the resistance may be achieved as a clamping force applied to the second positioning protrusion  643  by the second damping portion  672  is greater than the clamping force applied to the second positioning protrusion  643  by the second engaging portion  671 . For example, the second elastic sheet  67  may be stadium-shaped with an opening at an end and closed at an opposing end. The two second engaging portions  671  may be arranged at two ends of the second elastic sheet  67 , and the second damping portion  672  may be arranged at a middle portion of the second elastic sheet  67 . A third gap  672   a  formed in the second damping portion  672  for the second positioning protrusion  643  to extend through may be smaller than a fourth gap  671   a  formed in the second engaging portion  671  for the second positioning protrusion  643  to extend through. Therefore, during the sliding from the second engaging portion  671  to the second damping portion  672 , the second connection rod  64  may receive an increased resistance. By arranging the second elastic sheet  67  in this manner, when rotating the first shell  31  and the second shell  32  of the foldable mobile terminal, the user may feel the resistance more obviously. 
     In some other embodiments, the second elastic sheet  67  may be in shape of a closed loop. Further, in yet other embodiments, the second elastic sheet  67  may include two separated strips. Two ends of each of the two separated strips may be fixed on the second sliding plate  61  through the second support  66  or other components (or by other means), such that the second connection rod  64  may be applied with different resistances when the second connection rod  64  is at various positions of the sliding path along the second rotation shaft  63 . 
     As shown in  FIG. 9 , the second support  66  may have a second receiving cavity  660 , and the second elastic sheet  67  may be received in the second receiving cavity  660 . After the second support  66  is fixed on the second sliding plate  61 , the second sliding plate  61  may close the second receiving cavity  660 , such that the second elastic sheet  67  may be fixed inside the second receiving cavity  660 . 
     Further, the second receiving cavity  660  may include two second positioning cavities  661  and a second releasing cavity  662 . Each of the two second positioning cavities  661  may correspond to each second engaging portion  671  of the second elastic sheet  67 . The second releasing cavity  662  may be formed between the two second positioning cavities  661 . A size of the second releasing cavity  662  may be greater than a size of each second positioning cavity  661 . After the second engaging portion  671  is arranged in the second positioning cavity  661 , the second engaging portion  671  may be fixed to be unmovable. The second damping portion  672  arranged between the two second engaging portions  671  may be arranged in the second releasing cavity  662 . The second releasing cavity  662  may offer a space allowing the second damping portion  672  to be elastically deformed. 
     As shown in  FIG. 10 ,  FIG. 11 , and  FIG. 12 , in some embodiments, the foldable mobile terminal may further include a joining sheet  70  and two pressing elements  71 . The joining sheet  70  may cross over the first rotation assembly  50  and the second rotation assembly  60 , and each end of the joining sheet  70  may be rotatably connected to the first shell  31  and the second shell  32  through each of the two pressing elements  71  respectively. A change of the length generated during the rotation of the first shell  31  and the second shell  32  may adapt by the extension and retraction of the first rotation assembly  50  and the second rotation assembly  60  of the sliding mechanism  20  with respect to the first shell  31  and the second shell  32 , respectively. In this way, a contour of the foldable mobile terminal may be uniform and complete during folding and unfolding. By arranging the joining sheet  70 , the first shell  31  and the second shell  32  may be protected from being overly stretched, and a possibility of the flexible display screen  10  being damaged by the stretching may be reduced. 
     As shown in  FIG. 16 , a first end  701  of the joining sheet  70  may have a first elongated hole  703 , and a second end  702  of the joining sheet  70  may have a second elongated hole  704 . One of the pressing elements  71  may extend through the first elongated hole  703 , and be further fixedly connected to the first shell  31 , and the other of the pressing elements  71  may extend through the second elongated hole  704 , and be further fixedly connected to the second shell  32 . When the first rotation assembly  50  slides towards and away from the first shell  31  and the second rotation assembly  60  slides towards and away from the second shell  32 , the joining sheet  70  may move with respect to the pressing elements  71  along a direction to which the first elongated hole  703  and the second elongated hole  704  elongate, that is, the joining sheet  70  may move with respect to the first shell  31  and the second shell  32 . As shown in  FIG. 12 , when the foldable mobile terminal is in the unfolded state, an outer end of the first elongated hole  703  and an outer end of the second elongated hole  704  of the joining sheet  70 , that is, an end of the first elongated hole  703  away from the first rotation assembly  50  and an end of the second elongated hole  704  away from the second rotation assembly  60 , may abut against the corresponding pressing element  71 . In this way, a possibility of the first shell  31  and the second shell  32  departing from each other continually may be reduced, and the first shell  31  and the second shell  32  may be protected from being overly stretched. During folding, by virtue of space of the first and the second elongated holes, the joining sheet  70  may slide with respect to the first shell  31  and the second shell  32  to adapt to the length change of the first and the second shells  31  and  32 . In some embodiments, holes in other shapes may be formed to replace the first elongated hole  703  and the second elongated hole  704 , and two pressing elements  71  may be connected to the first or second shells in other means. 
     The joining sheet  70  may include two joining portions  705  respectively located at the first end  701  and the second end  702 , and a supportive portion  706  connected between the two joining portions  705 . Each of the two joining portions  705  may be connected to each pressing element  71 , and the supportive portion  706  may be configured to support the flexible display screen  10 . 
     In some embodiments, the pressing element  71  may include a screw or other fastening elements. The screw or other fastening elements of one pressing element  71  may extend through the first elongated hole  703 , and then connect the joining sheet  70  to the first shell  31 . The screw or other fastening elements of the other pressing element  71  may extend through the second elongated hole  704 , and then connect the joining sheet  70  to the second shell  32 . In some embodiments, each pressing element  71  may be cubic, and may include no screw or other fastening elements. One pressing element  71  may be configured to press on the first end  701  of the joining sheet  70 , and the other pressing element  71  may be configured to press on the second end  702  of the joining sheet  70 . An additional fastening element may be configured to extend through one pressing element  71  and the first elongated hole  703  to fasten with the first shell  31 , and another additional fastening element may be configured to extend through the other pressing element  71  and the second elongated hole  704  to fasten with the second shell  32 . For example, the first front shell  311  may include a first mounting portion  314 , the first end  701  of the joining sheet  70  may be slidably connected to the first mounting portion  314  through one of the pressing elements  71 . Similarly, the second front shell  321  may include a second mounting portion  324 , and the second end  702  of the joining sheet  70  may be slidably connected to the second mounting portion  324  through the other of the pressing elements  71 . In some embodiments, the first mounting portion  314  may have a first mounting hole to allow a fastening element to be mounted, such that one pressing element  71  and the first end  701  of the joining sheet  70  may be fastened with the first shell  31 . Similarly, the second mounting portion  324  may have a second mounting hole to allow another fastening element to be mounted, such that the other pressing element  71  and the second end  702  of the joining sheet  70  may be fastened with the second shell  32 . 
     In some embodiments, a bending portion may be formed at an intersection between the supportive portion  706  and each of the two joining portions  705 . As shown in  FIG. 12 , each of the first mounting portion  314  and the second mounting portion  324  may be recessed to engage with the bending portion of the corresponding joining sheet  70  and configured to receive the corresponding pressing element  71 . 
     The joining sheet  70  may have a plurality of through holes  700  with distance apart from each other. In some embodiments, the plurality of through holes  700  may be formed on the supportive portion  706 . The through holes  700  enable the joining sheet  70  to be bent easily, such that the joining sheet  70  may better fit with the first rotation assembly  50  and the second assembly  60 , and a possibility of the joining sheet  70  generating crease to impact the effect of supporting the flexible display screen  10  may be reduced. 
     In some embodiments, a fixing structure  707  connected to the supportive strip  26  may be arranged on the supportive portion  706 . In some embodiments, the fixing structure  707  may be a hole for welding. As the joining sheet  70  crosses over the supportive strip  26 , the joining sheet  70  may be fixedly connected to the supportive strip  26  by welding. In some other embodiments, the fixing structure  707  may be a protrusion, and a hole may be formed on the supportive strip, the protrusion may be adapted to or match with the hole, such that the joining sheet  70  may be fixedly connected to the supportive strip  26  through the fixing structure  707 . 
     In some embodiments, the number of the joining sheets  70  may be two. It may be understood that, in other embodiments, the number of the joining sheets  70  may be increased or decreased as required. 
     As shown in  FIG. 10  and  FIG. 11 , in some embodiments, the foldable mobile terminal may further include a first decoration component  72   a  and a second decoration component  72   b . The first decoration component  72   a  may be disposed at one end of the foldable mechanism  20  along the direction parallel to the Z-axis, further disposed in the gap formed between the first shell  31  and the second shell  32 . The second decoration component  72   b  may be disposed at the other end of the foldable mechanism  20  along the direction parallel to the Z-axis, further disposed in the gap formed between the first shell  31  and the second shell  32 . The first and the second decoration components  72   a  and  72   b  may be configured to cover structures at each end of the foldable mechanism  20 , such that the structures may not be exposed to an outside to impact the appearance. 
     As shown in  FIG. 11 ,  FIG. 13 , and  FIG. 14 , the first front shell  311  may include a first mating portion  315 , and the second front shell  321  may include a second mating portion  325 . Each of the first decoration component  72   a  and the second decoration component  72   b  may be engaged with both the first mating portion  315  of the first front shell  311  and the second mating portion  325  of the second front shell  321 . Each of the first decoration component  72   a  and the second decoration component  72   b  may be disposed at the corresponding end of the first sliding plate  51  and the second sliding plate  61  along the direction parallel to the Z-axis. 
     As shown in  FIG. 17  and  FIG. 18 , a surface of each of the first decoration component  72   a  and the second decoration component  72   b  facing towards the flexible display screen  10  may be substantially flat to allow an easy configuration of the flexible display screen  10 . A connective structure, such as a protruding block  721 , may be arranged on a surface of each of the first decoration component  72   a  and the second decoration component  72   b  facing away from the flexible display screen  10  and connected to the first front shell  311  and the second front shell  321 . A plurality of ridges  722  may be further arranged on the surface of each of the first decoration component  72   a  and the second decoration component  72   b  facing away from the flexible display screen  10 . When the foldable mobile terminal is in the unfolded state, each of the first decoration component  72   a  and the second decoration component  72   b  may be unfolded naturally. A distance between two adjacent ridges  722  may be gradually increased in a direction away from the flexible display screen  10 . When each of the first decoration component  72   a  and the second decoration component  72   b  is bent, that is, when the foldable mobile terminal is in the folded state, the adjacent ridges  722  may contact with each other. 
     As shown in  FIG. 10  and  FIG. 11 , the first shell  31  may have two or more first notches  316  spaced apart from each other. In some embodiments, as shown in  FIG. 14  and  FIG. 15 , each of the two or more first notches  316  may be formed at a side of the first front shell  311  close to the first rotation assembly  50 . Two or more first latches  511  may be configured on the first sliding plate  51  and correspond to the two or more first notches  316 . When the foldable mobile terminal switches between the folded state and the unfolded state, the first sliding plate  51  may be received in the first shell  31  at varying levels. By configuring the latch on the first shell  31  and forming the notches in the first sliding plate  51  correspondingly, empty space between the first shell  31  and the first sliding plate  51  may be reduced, such that the flexible display screen  10  may be supported more stably and a possibility of the flexible display screen  10  having functional damages due to a local stress may be reduced. 
     In some embodiments, as shown in  FIG. 4  and  FIG. 6 , the first sliding plate  51  may include a first substrate  510 , and the first latch  511  may be arranged on the first substrate  510 . The first substrate  510  may be disposed between the first front shell  311  and the first back shell  312  and may slidably extend and retract between the first front shell  311  and the first back shell  312  (that is, slide away from or towards the first front shell  311 ). The first latch  511  and the first front shell  311  may be in a same plane. Herein, the plane may be parallel to a plane defined by the XZ-axes. The first latch  511  and the first front shell  311  may be configured to cooperatively support the flexible display screen  10 . 
     It may be understood that another first notch may further be formed in the first sliding plate  51  between two adjacent first latches  511 , and another first latch may further be arranged on the first front shell  311  between two adjacent first notches  316 . The first latch  511  on the first sliding plate  51  may correspond to the first notch  316  on the first front shell  311 , and the first notch on the first sliding plate  51  may correspond to the first latch arranged on the first front shell  311 . 
     The second shell  32  may have two or more second notches  326  spaced apart from each other. In some embodiments, as shown in  FIG. 14  and  FIG. 15 , each of the two or more second notches  326  may be formed at a side of the second front shell  321  close to the second rotation assembly  60 . Two or more second latches  611  may be configured on the second sliding plate  61  and correspond to the two or more second notches  326 . When the foldable mobile terminal switches between the folded state and the unfolded state, the second sliding plate  61  may be received in the second shell  32  at varying levels. By configuring the latch on the second shell  32  and forming the notches in the second sliding plate  61  correspondingly, empty space between the second shell  32  and the second sliding plate  61  may be reduced, such that the flexible display screen  10  may be supported more stably and a possibility of the flexible display screen  10  having functional damages due to a local stress may be reduced. 
     In some embodiments, as shown in  FIG. 4  and  FIG. 6 , the second sliding plate  61  may include a second substrate  610 , and the second latch  611  may be arranged on the second substrate  610 . The second substrate  610  may be disposed between the second front shell  321  and the second back shell  322  and may slidably extend and retract (that is, slide away from or towards the second front shell  321 ) between the second front shell  321  and the second back shell  322 . The second latch  611  and the second front shell  321  may be in a same plane parallel to a plane defined by the XZ-axes. The second latch  611  and the second front shell  321  may be configured to cooperatively support the flexible display screen  10 . 
     It may be understood that another second notch may further be formed in the second sliding plate  61  between two adjacent second latches  611 , and another second latch may further be arranged on the second front shell  321  between two adjacent second notches  326 . The second latch  611  on the second sliding plate  61  may correspond to the second notch  326  on the second front shell  321 , and the second notch on the second sliding plate  61  may correspond to the second latch arranged on the second front shell  321 . 
     As shown in  FIG. 4 , a gap  512  may be formed between the first latch  511  on the first sliding plate  51  and the second latch  611  of the second sliding plate  61 . At least partial structure of the supportive strip  26  may be received in the gap  512 . 
     As shown in  FIG. 4  and  FIG. 6 , on the first sliding plate  51 , an end of each of the first latches  511  away from the first shell  31  may be connected to each other to form a first supportive beam  513 . On the second sliding plate  61 , an end of each of the second latches  611  away from the second shell  32  may be connected to each other to form a second supportive beam  613 . At least a partial structure of the supportive strip  26  may be disposed on the first supportive beam  513  and the second supportive beam  613 . 
     As shown in  FIG. 13 , the foldable mobile terminal may further include a first roller  58  and a first spring  59 . The first roller  58  and the first spring  59  may be disposed between the first rotation assembly  50  and the first shell  31 . The first rotation assembly  50  may have a first groove  514 . When the first rotation assembly  50  slidably extends and retracts with respect to (that is, slides away from or towards) the first shell  31 , the first roller  58  may move into or out of the first groove  514 , such that the user of the foldable mobile terminal may feel a standstill if the foldable mobile terminal is folded to an appropriate position. In some embodiments, it is possible that the first roller  58  may move into the first groove  514  when the first groove  514  slides away from the first shell  31 , and move out of the first groove  514  when the first groove  514  slides towards the first shell  31 . However, in some embodiments, it is also possible that the first roller  58  may move into the first groove  514  when the first groove  514  slides towards the first shell  31 , and move out of the first groove  514  when the first groove  514  slides away from the first shell  31 . In some embodiments, the first spring  59  may include at least one of a rubber spring, a gas spring, a lead spring, a spiral spring, a torsion rod spring, and the like. In some embodiments, a first elastic rubber may be provided to replace the first roller  58  and the spring  59 , the first elastic rubber may be disposed in the first groove  514  of the first rotation assembly  50  and abut against the first shell  31 . The first elastic rubber may be elastically deformed to reduce mechanical shock generated during sliding of the first rotation assembly  50 . 
     In some embodiments, the first roller  58  and the first spring  59  may be disposed between the first sliding plate  51  and the first back shell  312 . In some other embodiments, the first roller  58  and the first spring  59  may be disposed between the first sliding plate  51  and the first front shell  311 . According to some embodiments shown in  FIG. 4  and  FIG. 13 , the first groove  514  may be formed in a side wall of the first latch  511  of the first sliding plate  51  and face towards an adjacent first latch  511  arranged on the first substrate  510 . 
     As shown in  FIG. 13  and  FIG. 15 , a side wall in the first notch  316  may be recessed inwardly away from a corresponding first latch  511  to form a first cavity  317 . The first roller  58  and the first spring  59  may be received in the first cavity  317 . The first spring  59  may abut against the first roller  58  to allow at least a part of the first roller  58  to be exposed to an outside of the first cavity  317 , such that the first roller  58  may elastically abut against a side wall of the corresponding first latch  511 . 
     Further, the first latch  511  which has the first groove  514  may extend towards the first shell  31  for a distance longer than any other first latch  511  extends towards the first shell  31 , that is, a length for which the first latch  511  having the first groove  514  may extend towards the first shell  31  is greater than a length for which any other first latch  511  may extend towards the first shell  31 . 
     In some embodiments, at least two sets of the first rollers  58  and the first springs  59  may be provided. Each of two opposing side walls of the first latch  511  may have the first groove  514  matching with the first roller  58 . Correspondingly, two opposing side walls of the first notch  316  may be recessed away from the corresponding first latch  511  to form two first cavities  317 . Each of the two first cavities  317  may be formed to receive one set of the first roller  58  and the first spring  59 . 
     In some embodiments, the side wall of the first latch  511  may have two first grooves  514  at two terminating positions corresponding to the first sliding plate  51 . For example, one of the terminating positions may be located at an end of the first latch  511  close to the first shell  31 , and the other one of the terminating positions may be located at an intersection between the first latch  511  and the first supportive beam  513 . When the foldable mobile terminal is in the folded state and the unfolded state, the first roller  58  may respectively enter the first groove  514  of the corresponding one of the two terminating positions. Therefore, the user of the foldable mobile terminal may feel a standstill if the foldable mobile terminal is folded or unfolded to an appropriate position. 
     The foldable mobile terminal may further include a second roller  68  and a second spring  69 . The second roller  68  and the second spring  69  may be disposed between the second rotation assembly  60  and the second shell  32 . The second rotation assembly  60  may have a second groove  614 . When the second rotation assembly  60  slidably extends and retracts with respect to (that is, slides away from or towards) the second shell  32 , the second roller  68  may move into or out of the second groove  614 , such that the user of the foldable mobile terminal may feel a standstill if the foldable mobile terminal is folded to an appropriate position. In some embodiments, the second spring  69  may include at least one of a rubber spring, a gas spring, a lead spring, a spiral spring, a torsion rod spring, and the like. In some embodiments, a second elastic rubber may be provided to replace the second roller  68  and the second spring  69 , the second elastic rubber may be disposed in the second groove  614  of the second rotation assembly  60  and abut against the second shell  32 . The second elastic rubber may be elastically deformed to reduce mechanical shock generated during sliding of the second rotation assembly  60 . 
     In some embodiments, the second roller  68  and the second spring  69  may be disposed between the second sliding plate  61  and the second back shell  322 . In some other embodiments, the second roller  68  and the second spring  69  may be disposed between the second sliding plate  61  and the second front shell  321 . According to some embodiments shown in  FIG. 4  and  FIG. 13 , the second groove  614  may be formed in a side wall of the second latch  611  of the second sliding plate  61 , and face towards an adjacent second latch  611  arranged on the second substrate  610 . 
     As shown in  FIG. 13  and  FIG. 15 , a side wall in the second notch  326  may be recessed inwardly away from a corresponding second latch  611  to form a second cavity  327 . The second roller  68  and the second spring  69  may be received in the second cavity  327 . The second spring  69  may abut against the second roller  68  to allow at least a part of the second roller  68  to be exposed to an outside of the second cavity  327 , such that the second roller  68  may elastically abut against a side wall of the corresponding second latch  611 . 
     Further, the second latch  611  which has the second groove  614  may extend towards the second shell  32  for a distance longer than any other second latch  611  extending towards the second shell  32 . 
     In some embodiments, at least two sets of the second rollers  68  and the second springs  69  may be provided. Each of two opposing side walls of the second latch  611  may have the second groove  614  matching with the second roller  68 . Correspondingly, two opposing side walls of the second notch  326  may be recessed away from the corresponding second latch  611  to form two second cavities  327 . Each of the two second cavities  327  may be formed to receive one set of the second roller  68  and the second spring  69 . 
     In some embodiments, the side wall of the second latch  611  may have two second grooves  614  at two terminating positions corresponding to the second sliding plate  61 . For example, one of the two terminating positions may be located at an end of the second latch  611  close to the second shell  32 , and the other one of the two terminating positions may be located at an intersection between the second latch  611  and the second supportive beam  613 . When the foldable mobile terminal is in the folded state and the unfolded state, the second roller  68  may respectively enter the second groove  614  of the corresponding one of the two terminating positions. Therefore, the user of the foldable mobile terminal may feel a standstill if the foldable mobile terminal is folded or unfolded to an appropriate position. 
     Technical features of the above-mentioned embodiments may be combined by any means. To provide a concise description, not all of the possible combinations of the technical features are described herein. However, as long as no contradiction is generated, any combination of the technical features should be within the scope of the present disclosure. 
     The above mentioned embodiments may illustrate only some implementations of the present disclosure. The description may be quite specific and detailed, but should not be considered to limit the scope of the present disclosure. It should be noted that, any ordinary skilled in the art, without departing from the concept of the present disclosure, may perform various transformation and improvement which should be within the scope of the present disclosure. Therefore, the scope of the present disclosure shall be subject to the claims.