Abstract:
Disclosed is a handheld electronic device including a sliding mechanism configured to interconnect a first body and a second body such that the first and second bodies are slidable with reference to the other. The sliding mechanism includes a first sliding member configured to be secured to the first body and a second sliding member configured to be secured to the second body, the second sliding member slidably engaged with the first sliding member and slidable relative to the first sliding member between a first position and a second position. The device further has a spring comprising an undulating portion interposed between a first point and a second point of the spring&#39;s wire. The first point is secured to the first sliding member, and the second point is secured to the second sliding member. The undulating portion is configured to be compressed and released as the first sliding member slides between the first and second positions.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application is a continuation application under 35 U.S.C. §365(c) of International Application No. PCT/KR2005/003155, filed Sep. 23, 2005 designating the United States. International Application No. PCT/KR2005/003155 was published in English as WO2007/035008 A1 on Mar. 29, 2007. This application incorporates herein by reference the International Application No. PCT/KR2005/003155 including the International Publication No. WO2007/035008 A1 in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to a sliding mechanism, and more particularly, to a sliding mechanism for use in a handheld electronic device. 
         [0004]    2. Discussion of the Related Technology 
         [0005]      FIG. 33  schematically shows a typical sliding type opening and closing apparatus mounted to a portable telephone. Referring to  FIG. 33 , a portable telephone  12   a  comprises first and second units  14   a  and  16   a  that are shown in dotted lines. In general, the first unit  14   a  is provided with a keypad, while the second unit  16   a  is provided with a liquid crystal display. The first and second units  14   a  and  16   a  are movably coupled with each other by means of an opening and closing apparatus  10   a.  The opening and closing apparatus  10   a  includes a support  20   a  fixed to the first unit  14   a,  two movable rods  40   a  serving as two sliders fixed respectively to both sides of the second unit  16   a,  and a torsion spring  50   a.  Although it has not been shown in detail, guide rails are provided on both sides of the support  20   a  and the two movable rods  40   a  are fitted into the relevant guide rails to be linearly moved along the guide rails. Two connecting portions of the torsion spring  50   a  are connected to the support  20   a  and the movable rod  40   a,  respectively. As the two movable rods  40   a  are linearly moved along the guide rails of the support  20   a,  the keypad of the first unit  14   a  is exposed or closed. At this time, the torsion spring  50   a  allows the second unit  16   a  to be automatically opened or closed after the second unit  16   a  is moved by a predetermined degree. 
         [0006]    The foregoing discussion is to provide general background information, and does not constitute an admission of prior art. 
       SUMMARY 
       [0007]    One aspect of the invention provides a handheld electronic device comprising a sliding mechanism configured to interconnect a first body and a second body such that the first and second bodies are slidable with reference to the other, wherein the sliding mechanism may comprise: a first sliding member configured to be secured to the first body, a second sliding member configured to be secured to the second body, the second sliding member slidably engaged with the first sliding member and slidable relative to the first sliding member between a first position and a second position; and a spring comprising an undulating portion interposed between a first point and a second point of the spring&#39;s wire, the first point being secured to the first sliding member, the second point being secured to the second sliding member, wherein the undulating portion is configured to be compressed and released as the first sliding member slides between the first and second positions. 
         [0008]    In the foregoing device, the undulating portion may comprise a plurality of alternating hills and valleys, wherein two immediately neighboring hills form a first gap therebetween, and two immediately neighboring valleys form a second gap therebetween. At least part of the hills and valleys may comprise a U-turn of the wire. At least part of the hills and valleys may comprise a circular turning of the wire. The hills and valleys may be generally in the same size. At least one of the hills and valleys may have a size significantly different from another of the hills and valleys. The undulating portion may be configured such that the second gap becomes smaller as the undulating portion is compressed. The undulating portion may be configured such that the first gap becomes larger as the second gap becomes smaller. At least one of the hills may comprise a circular turning of the wire. The first gap may be the largest when the first sliding member is at the first or second position. 
         [0009]    Still in the foregoing device, the undulating portion may further comprise a plurality of extensions, each between a hill and a valley immediately neighboring the hill. The plurality of extensions may be in generally the same length. At least one of the plurality of extensions may have a length significantly different from another of the plurality of extensions. At least part of the plurality of extensions may be substantially straight. At least two of the plurality of extensions may be generally curved while generally parallel with each other. 
         [0010]    Further in the foregoing device, the spring may comprise the undulating portion substantially throughout between the first and second points. The undulating portion may be only a part between the first and second points of the spring. The spring may comprise at least one additional undulating portion between the first and second points. The spring may further comprise at least one circular turning between the first and second points. The undulating portion may comprise a plurality of first U-turns and a plurality of second U-turns generally in an opposite direction of the plurality of first U-turns, wherein the plurality of first and second U-turns may be alternatingly arranged such that two neighboring first U-turns form a first gap therebetween and two neighboring second U-turns form a second gap therebetween. The wire of the spring may be press-produced. The undulating portion may be substantially in a single plane. The undulating portion may be configured to be compressed and released while substantially staying in the single plane. The spring may comprise another undulating portion interposed between the second point and a third point of the spring&#39;s wire, the third point being secured to the first sliding member, wherein the additional undulating portion may be configured to be compressed and released as the first sliding member slides between the first and second positions. 
         [0011]    An aspect of the present invention is to provide a sliding type opening and closing apparatus capable of opening or closing at least portions of two units by allowing the two units to be coupled with each other and to be slid relative to each other. Another aspect of the present invention is to provide a sliding type opening and closing apparatus for use in a portable telephone with improved durability. A further aspect of the present invention is to provide a sliding type opening and closing apparatus that is accurately operated. A still further aspect of the present invention is to provide a sliding type opening and closing apparatus of small thickness. 
         [0012]    An aspect of the present invention provides a sliding type opening and closing apparatus for coupling first and second units moved relative to each other and causing at least a portion of the first or second unit to be opened or closed through a relative sliding movement between the first and second units. The opening and closing apparatus comprises a first linking member linked to the first unit; a second linking member linked to the second unit and slid with respect to the first linking member; a movable member movably connected to the first and second linking members; and a resilient member for imparting a force to the movable member in a direction substantially perpendicular to a direction in which the first and second link members are slid, wherein the first linking member includes a first guide track extending in a direction substantially perpendicular to the sliding direction of the first and second linking members to guide the movement of the movable member with respect to the first linking member, and the second linking member includes a second guide track extending between two points along the sliding direction of the first and second linking members to guide the movement of the movable member with respect to the second linking member and being inclined toward a direction of the force imparted by the resilient member with respect to the sliding direction as the second track runs toward its opposite ends. 
         [0013]    The first linking member may further include a third guide track spaced apart from the first guide track in a direction perpendicular to the sliding direction while the second linking member may further include a fourth guide track spaced apart from the second guide track in a direction perpendicular to the slide movement direction, and the apparatus further comprises another movable member interacting with the third guide track of the first linking member and the fourth guide track of the second linking member. Preferably, the resilient member is a tensile coil spring and both ends of the tensile coil spring are connected to the two movable members, respectively. 
         [0014]    Another aspect of the present invention provides a sliding type opening and closing apparatus for coupling first and second units moved relative to each other and causing at least a portion of the first or second unit to be opened or closed through relative movement between the first and second units. The opening and closing apparatus comprises a first linking member linked to the first unit; a second linking member linked to the second unit and slid with respect to the first linking member, the second linking member including a rack extending in a sliding direction of the second linking member; a pinion gear engaged with the rack; and a torsion spring including both ends connected respectively to the pinion gear and the first linking member, whereby a distance between both ends can be changed as the pinion gear rotates. Preferably, a rotating shaft of the pinion gear is coupled to the first linking member. 
         [0015]    The second linking member may further include a second rack formed to face the rack, and the opening and closing apparatus may further comprise a second pinion gear engaged with the second rack of the second linking member and the pinion gear and formed with a rotating shaft thereof coupled with the first linking member. The first linking member may include a third rack formed opposite to the rack of the second linking member and engaged with the pinion gear. 
         [0016]    Preferably, two columns protruding in a rotating axis of the pinion gear are provided on opposite sides of the pinion gear, respectively, and the first and second linking members are provided with guide portions which extend in the sliding direction and in which the two columns of the pinion gear are movably received. Preferably, the columns of the pinion gear are caught into opposite ends of the guide portions of the first and second linking members to limit their movements. 
         [0017]    A further aspect of the present invention provides a sliding type opening and closing apparatus for coupling first and second units moved relative to each other and causing at least a portion of the first or second unit to be opened or closed through relative movement between the first and second units. The opening and closing apparatus comprises a first linking member linked to the first unit; a second linking member linked to the second unit and slid with respect to the first linking member; and a resilient member connected to the first and second linking members, wherein the resilient member imparts a force to the linking members in a direction in which its portions connected to the first and second linking members move away from each other. The resilient member may be formed into a zigzag shape and include linear extension portions and curved portions. 
         [0018]    Preferably, the resilient member is a compression spring, both longitudinal ends of the resilient member are connected respectively to both sides of the first linking member on an extension line substantially perpendicular to a direction in which the second linking member is slid with respect to the first linking member, and a middle portion of the resilient member is restrained by the second linking member. 
         [0019]    Preferably, both longitudinal ends of the resilient member are connected respectively to the first and second linking members, and curved portions on one lateral side among a plurality of curved portions formed on both lateral sides of the resilient member are always kept closer than curved portions on the other lateral side as the first and second linking members are moved relative to each other. Preferably, at least one of the curved portions of the resilient member is formed into a coil. 
         [0020]    Preferably, at least one curved portion formed into a coil is arranged in the middle of curved portions formed on the relatively wider lateral side among the plurality of curved portions formed on the lateral sides. Preferably, at least one curved portion formed into a coil is arranged at opposite ends of curved portions formed on the relatively wider lateral side among the plurality of curved portions formed on the lateral sides. 
         [0021]    The opening and closing apparatus of the present invention may further comprise another resilient member connected to the first and second linking members to be crossed with the resilient member, wherein the other resilient member is substantially similar to the resilient member in view of their shapes. The two resilient members may be substantially symmetrical with respect to a central axis extending in a direction in which the linking members are slid relative to each other. 
         [0022]    Preferably, the resilient member includes two extension portions, two first connecting portions are provided respectively to both ends of the two extension portions, a second connecting portion formed into a coil is provided between the two extension portions, and one of the first and second connecting portions is connected to the first linking member while the other is connected to the second linking member. The two extension portions may be curved to be concave on sides facing each other. The two extension portions may be curved into a zigzag shape. 
         [0023]    Preferably, the resilient member includes two or more extension portions substantially parallel to each other which are formed by curving a wire rod, two or more first connecting portions formed into a coil are provided on one side of the extension portions while two or more second connecting portions formed into a coil are provided on the other side of the extension portions, the plurality of extension portions are curved toward an identical direction, and one of the first and second connecting portions is connected to the first linking member while the other is connected to the second linking member. 
         [0024]    Preferably, the resilient member includes an extension portion formed by twisting two wire rods, and first and second connecting portions provided respectively on both ends of the extension portion; and one of the first and second connecting portions is connected to the first linking member while the other is connected to the second linking member. 
         [0025]    Preferably, the resilient member includes a long extension portion, and first and second connecting portions provided respectively at both ends of the extension portion; the extension portion is inclined to gradually move away from a straight line connecting the first and second connecting portions as it goes from the first and second connecting portions toward its middle portion and a concave portion protruding toward the straight line connecting the two connecting portions is formed in the middle of the extension portion; and one of the first and second connecting portions is connected to the first linking member while the other is connected to the second linking member. 
         [0026]    A sliding type opening and closing apparatus capable of opening or closing at least portions of two units by allowing the two units to be coupled with each other and to be slid relative to each other can be provided. The sliding operation of the opening and closing apparatus with a pinion gear can be precise. The opening and closing apparatus with a resilient member made of a thin wire rod can be made thinner. Further, since a resilient member includes a plurality of deformable curved portions to cause elastic force to be uniformly distributed and some of the deformable curved portions are wound in the form of a coil to improve its durability, the opening and closing apparatus with the resilient member can be used for a long time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a perspective view of a portable telephone that is opened and closed in a sliding mode. 
           [0028]      FIG. 2(   a ) to ( c ) are a side view, a bottom view and a sectional view, taken along line C-C′ in  FIG. 2(   b ), of a sliding type opening and closing apparatus according to an embodiment of the present invention, respectively, which is mounted to the portable telephone of  FIG. 1 , when the portable telephone has been completely closed. 
           [0029]      FIG. 3  is a plan view of a first linking member installed to the opening and closing apparatus shown in  FIG. 2 . 
           [0030]      FIG. 4  is a plan view of a second linking member installed to the opening and closing apparatus shown in  FIG. 2 . 
           [0031]      FIG. 5  is an exploded perspective view of a first movable member installed to the opening and closing apparatus shown in  FIG. 2 . 
           [0032]      FIG. 6(   a ) and ( b ) are side and bottom views illustrating a state of the opening and closing apparatus of  FIG. 2 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 2  is in a neutral position where the portable telephone is being opened. 
           [0033]      FIG. 7(   a ) and ( b ) are side and bottom views illustrating a state of the opening and closing apparatus of  FIG. 2 , respectively, when the portable telephone has been completely opened. 
           [0034]      FIG. 8(   a ) to ( c ) are a side view, a bottom view and a sectional view, taken along line D-D′ in  FIG. 8(   b ), of a sliding type opening and closing apparatus according to an embodiment of the present invention, respectively, which is mounted to the portable telephone shown in  FIG. 1 , when the portable telephone has been completely closed. 
           [0035]      FIG. 9(   a ) and ( b ) are side and bottom views illustrating a state of the opening and closing apparatus of  FIG. 8 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 8  is in a neutral position where the portable telephone is being opened. 
           [0036]      FIG. 10(   a ) and ( b ) are side and bottom views illustrating a state of the opening and closing apparatus of  FIG. 8 , respectively, when the portable telephone has been completely opened. 
           [0037]      FIG. 11(   a ) to ( c ) are a side view, a bottom view and a sectional view, taken along line E-E′ in  FIG. 11(   b ), of a sliding type opening and closing apparatus according to an embodiment of the present invention, respectively, which is mounted to the portable telephone of  FIG. 1 , when the portable telephone has been completely closed. 
           [0038]      FIG. 12  is a plan view of a first linking member installed to the opening and closing apparatus shown in  FIG. 11 . 
           [0039]      FIG. 13  is a plan view of a second linking member installed to the opening and closing apparatus shown in  FIG. 11 . 
           [0040]      FIG. 14(   a ) and ( b ) are side and bottom views illustrating a state of the opening and closing apparatus of  FIG. 11 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 11  is in a neutral position where the portable telephone is being opened. 
           [0041]      FIG. 15(   a ) and ( b ) are side and bottom views illustrating a state of the opening and closing apparatus of  FIG. 11 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 11  has been completely opened. 
           [0042]      FIG. 16(   a ) to ( c ) are side, plan and front views of a sliding type opening and closing apparatus according to an embodiment of the present invention, respectively, which is mounted to the portable telephone of  FIG. 1 , when the portable telephone has been completely closed. 
           [0043]      FIG. 17  is a perspective view of a first linking member installed to the opening and closing apparatus shown in  FIG. 16 . 
           [0044]      FIG. 18  is a perspective view of a second linking member installed to the opening and closing apparatus shown in  FIG. 16 . 
           [0045]      FIG. 19(   a ) and ( b ) are side and plan views illustrating a state of the opening and closing apparatus of  FIG. 16 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 16  is in a neutral position where the portable telephone is being opened. 
           [0046]      FIG. 20(   a ) and ( b ) are side and plan views illustrating a state of the opening and closing apparatus of  FIG. 16 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 16  has been completely opened. 
           [0047]      FIG. 21(   a ) to ( c ) are side, bottom and front views of a sliding type opening and closing apparatus according to an embodiment of the present invention, respectively, which is mounted to the portable telephone of  FIG. 1 , when the portable telephone has been completely closed. 
           [0048]      FIG. 22(   a ) and ( b ) are side and bottom views illustrating s state of the opening and closing apparatus of  FIG. 21 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 21  is in a neutral position where the portable telephone is being opened. 
           [0049]      FIG. 23(   a ) and ( b ) are side and bottom views illustrating a state of the opening and closing apparatus of  FIG. 21 , respectively, when the portable telephone with the opening and closing apparatus of  FIG. 21  has been completely opened. 
           [0050]      FIG. 24  is a bottom view of a sliding type opening and closing apparatus according to an embodiment of the present invention, which is mounted to the portable telephone shown in  FIG. 1 . 
           [0051]      FIG. 25  is a bottom view of a sliding type opening and closing apparatus according to an embodiment of the present invention, which is mounted to the portable telephone shown in  FIG. 1 . 
           [0052]      FIG. 26  is a bottom view of a sliding type opening and closing apparatus according to an embodiment of the present invention, which is mounted to the portable telephone shown in  FIG. 1 . 
           [0053]      FIG. 27  is a bottom view of a sliding type opening and closing apparatus according to an embodiment of the present invention, which is mounted to the portable telephone shown in  FIG. 1 . 
           [0054]      FIG. 28(   a ) and ( b ) are plan views of another embodiment of a resilient member mounted to the sliding type opening and closing apparatus shown in  FIG. 21 , respectively. 
           [0055]      FIG. 29(   a ) and ( b ) are plan views of a further embodiment of a resilient member mounted to the sliding type opening and closing apparatus shown in  FIG. 21 . 
           [0056]      FIG. 30(   a ) to ( g ) are plan views of a still further embodiment of a resilient member mounted to the sliding type opening and closing apparatus shown in  FIG. 21 , respectively. 
           [0057]      FIG. 31  is a plan view of a still further embodiment of a resilient member mounted to the sliding type opening and closing apparatus shown in  FIG. 21 . 
           [0058]      FIG. 32  is a plan view of a still further embodiment of a resilient member mounted to the sliding type opening and closing apparatus shown in  FIG. 21 . 
           [0059]      FIG. 33  is a schematic plan view of a typical sliding type opening and closing apparatus that is mounted to the portable telephone. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0060]    Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0061]    A sliding type opening and closing apparatus mounted to a portable telephone should have predetermined durability. In particular, a resilient member among parts of the sliding type opening and closing apparatus should have sufficient durability to continuously perform its own inherent operation. Further, the opening and closing apparatus should be accurately operated. Furthermore, the opening and closing apparatus should be thin and compact enough to be suitable for a product such as a portable telephone that will be gradually minimized. 
         [0062]    Referring to  FIG. 1 , a portable telephone  12  comprises a first unit  14  provided with a keypad, and a second unit  16  provided with a liquid crystal display. As shown in the figure, the second unit  16  may also be provided with buttons, if necessary. Referring also to FIG.  2 ( a ) to ( c ), the first and second units  14  and  16  overlap and couple each other through an opening and closing apparatus  10  such that they can be linearly slid relative to each other along a moving axis  100 . 
         [0063]    Referring to  FIG. 1  and  FIG. 2(   a ) to ( c ), the opening and closing apparatus  10  according to an embodiment includes a first linking member  20  linked to the first unit  14  of the portable telephone  12 , a second linking member  40  linked to the second unit  16  of the portable telephone  12 , a first movable member  50 , a second movable member  60 , and a resilient member  70 . Referring to  FIG. 2(   a ) to ( c ) and  FIG. 3 , the first linking member  20  is shaped as a generally rectangular plate and includes a flat base plate  22  and a pair of guide rails  26  extending in a direction parallel to the moving axis  100  on both sides of the base plate  22  and formed to slightly protrude toward the second unit  16 . 
         [0064]    The base plate  22  has first and second guide portions  221  and  222  that are positioned near the guide rails and extend in a direction perpendicular to the moving axis  100 . The first and second guide portions  221  and  222  are positioned on the same extension line  110 . As shown in the figures, the first and second guide portions  221  and  222  are formed into perforated tracks that are formed by perforating the base plate  22  at a predetermined width. The first and second movable members  50  and  60  can be moved along the first and second guide portions  221  and  222 , respectively. Between the first and second guide portions  221  and  222  is provided a connecting portion  223  that perforates the base plate  22  and connects the first and second guide portions  221  and  222 . The width of the connecting portion  223  is smaller than those of the first and second guide portions  221  and  222 . This is to prevent the first and second guide portions  221  and  222  from being moved into the connecting portion  223 . Meanwhile, in a space defined by the connecting portion  223  is positioned the resilient member  70  for connecting the first and second guide portions  221  and  222 . The two guide rails  26  are provided with linking wings  261  which are slightly spaced apart from the surface of the base plate  22  and protrude to face each other. The linking wings  261  are fitted into two linking grooves  42  of the second linking member  40 , respectively, as described later. 
         [0065]    Referring to  FIG. 2(   a ) to ( c ) and  FIG. 4 , the second linking member  40  is shaped as a rectangular plate generally extending along the moving axis  100 . The linking grooves  42  in which the linking wings  261  of the two guide rails  26  of the first linking member  20  can be slid, respectively, are provided on both sides of the second linking member  40  extending in a direction parallel to the moving axis  100 . The two linking wings  261  of the first linking member  20  are fitted into the two linking grooves  42  of the second linking member  40 , respectively, such that the first and second linking members  20  and  40  can be linearly slid relative to each other along the moving axis  100  without being separated from each other. The second linking member  40  is provided with third and fourth guide portions  44  and  46  that are positioned near the linking grooves  42  and substantially extend in a direction parallel to the moving axis  100  to be symmetrical to each other. The third and fourth guide portions  44  and  46  are formed into perforated tracks that are formed by perforating the second linking member  40 . The third and fourth guide portions  44  and  46  have track portions which are slightly inclined from the moving axis  100  such that the track portions can be far away from each other as they run toward their middle points. The first and second movable members  50  and  60  can be moved along the third and fourth guide portions  44  and  46 , respectively. 
         [0066]    Referring to  FIG. 2(   c ) and  FIG. 5 , the first movable member  50  includes a rivet  52 , a support member  54 , two rollers  56  and a coupling ring  58 . The rivet  52  is fitted into the first guide portion  221  of the first linking member  20  and the third guide portion  44  of the second linking member  40  such that a column  521  of the rivet  52  can pass through the first and second guide portions. The rivet  52  is not separated from the first and third guide portions  221  and  44  by means of the head of the rivet  52  and the coupling ring  58  coupled to a tip end of the rivet  52  opposite to the rivet head. The two rollers  56  are fitted around the column  521  of the rivet  52  and roll along the first guide portion  221  of the first linking member  20  and the third guide portion  44  of the second linking member  40  to reduce friction between the roller and relevant guide portion when the second linking member  40  is moved in the first and third guide portions  221  and  44 . The support member  54  is fitted around the column  521  of the rivet  52  at its middle point. The support member  54  is provided with a coupling portion  541  extending toward the second guide portion  222  of the first linking member  20 . To the coupling portion  541  is coupled a coupling rivet  59  to which one end of the resilient member  70  is fixed. 
         [0067]    Since the second movable member  60  has the same configuration as the first movable member  50 , a detailed description thereof will be omitted herein. It can be understood by a person skilled in the art that the first and second movable members  50  and  60  are moved far away from or close to each other along the first and second guide portions  221  and  222  of the first linking member  20  by means of the third and fourth guide portions  44  and  46  of the second linking member  40  when the second linking member  40  is moved along the moving axis  100  with respect to the first linking member  20 . 
         [0068]    The resilient member  70  is a tension coil spring and both ends of the resilient member are connected to the first and second movable members  50  and  60 , respectively. Therefore, the first and second movable members  50  and  60  are forced to be close to each other by means of the resilient member  70 . 
         [0069]    Hereinafter, the operation of an embodiment will be described in detail with reference to  FIGS. 2 ,  6  and  7 . Referring first to  FIG. 2(   a ) and ( b ), the portable telephone  12  is completely closed. At this time, the first and second movable members  50  and  60  of the opening and closing apparatus  10  are positioned at ends of the third and fourth guide portions  44  and  46  of the second linking member  40 , respectively, to thereby limit the movement of the first and second movable members  50  and  60  such that the first and second movable members  50  and  60  cannot be moved toward each other. Furthermore, the resilient member  70  pulls the first and second movable members  50  and  60  such that the movable members can be moved toward each other. In order to open the portable telephone  12 , the second linking member  40  linked to the second unit  16  is moved such that the first and second movable members  50  and  60  move away from each other. Thus, the portable telephone  12  is stably kept at a closed state when no external force is exerted thereto. 
         [0070]    In order to open the portable telephone  12  at a state shown in  FIG. 2(   a ) and ( b ), an external force is applied to the portable telephone such that the second unit  16  can be pushed in a direction indicated by the arrow (rightward in this figure). Then, the external force allows the second linking member  40  of the opening and closing apparatus  10  to be moved rightward, and thus, the first and second movable members  50  and  60  can be moved along the first and second guide portions  221  and  222  of the first linking member  20 , respectively, to thereby move away from each other against the resilient force of the resilient member  70 .  FIG. 6(   a ) and ( b ) show a state where the portable telephone  12  continues to be opened and the first and second movable members  50  and  60  are then in a neutral position where the movable members are positioned in the middle of the first and second guide portion  221  and  222  of the first linking member  20 , respectively. If the external force is removed before the first and second movable members  50  and  60  arrives at the neutral position, the resilient force of the resilient member  70  causes the first and second movable members  50  and  60  to be moved towards each other. As a result, the second linking member  40  is automatically moved leftward, and thus, the opening and closing apparatus  10  is also automatically closed. 
         [0071]    If the second unit  16  is pushed rightward from the state shown in  FIG. 6(   a ) and ( b ) to further open the opening and closing apparatus  10 , the first and second movable members  50  and  60  of the opening and closing apparatus  10  pass through the neutral positions, i.e. middle points of the third and fourth guide portions  44  and  46  of the second linking member  40 , to inclined points of the guide portions. Even though there is no external force at this state, the resilient force of the resilient member  70  causes the first and second movable members  50  and  60  to move toward each other and thus causes the second linking member  40  to be automatically moved rightward. If the first and second movable members  50  and  60  move rightward and stop at the left side ends of the third and fourth guide portions  44  and  46  of the second linking member  40 , respectively. Such a state is shown in  FIG. 7(   a ) and ( b ). In order to again close the portable telephone  12  at this state, an external force is applied to the portable telephone until the portable telephone is in a state shown in  FIG. 6(   a ) and ( b ). Then, the portable telephone  12  is automatically closed as described above. 
         [0072]      FIGS. 8 to 10  show an opening and closing apparatus  10   b  according to an embodiment of the present invention. Referring to  FIG. 8(   a ) to ( c ), the opening and closing apparatus  10   b  includes a first linking member  20   b  linked to a first unit  14   b  of a portable telephone  12   b,  a second linking member  40   b  linked to a second unit  16   b  of the portable telephone  12   b,  a first pinion gear  50   b,  a second pinion gear  60   b  and a resilient member  70   b.  If the first linking member  20   b  is compared with the first linking member  20  shown in  FIG. 2 , their configurations are substantially identical to each other except that the first and second guide portions  221  and  222  and the connecting portion  223  are not formed on the base plate of the first linking member  20   b.  Therefore, detailed descriptions thereof will be omitted herein. 
         [0073]    The second linking member  40   b  includes first and second racks  44   b  and  46   b  extending along a moving axis  100   b  at opposite positions on both linking grooves. The first rack  44   b  is engaged with the first pinion gear  50   b,  and the second rack  46   b  is engaged with the second pinion gear  60   b.  If the second linking member  40   b  is compared with the second linking member  40  shown in  FIG. 2 , their configurations are substantially identical to each other except that the third and fourth guide portions are not provided in the second linking member  40   b.  Therefore, detailed descriptions thereof will be omitted herein. 
         [0074]    The first and second pinion gears  50   b  and  60   b  are installed to the first linking member  20   b  such that they can be engaged with each other. The respective rotating centers of the first and second pinion gears  50   b  and  60   b  are located on an extension line  110   b  perpendicular to the moving axis  100   b.  However, the present invention is not limited thereto. The radius of the first pinion gear  50   b  is larger than that of the second pinion gear  60   b.  Although it has been illustrated in  FIGS. 8 to 10  that the first pinion gear  50   b  is larger than the second pinion gear  60   b,  it will be understood by those skilled in the art that the sizes of the first and second pinion gears  50   b  and  60   b  can be changed depending on the widths of the first and second units  14   b  and  16   b  and the traveling distance between the first and second units  14   b  and  16   b.  The first and second pinion gear  50   b  and  60   b  are engaged with the first and second racks  44   b  and  46   b  of the second linking member  40   b,  respectively. If the first and second pinion gears  50   b  and  60   b  are engaged and rotated with each other, the first and second linking members  20   b  and  40   b  are moved relative to each other along the moving axis  100   b.    
         [0075]    The resilient member  70   b  is a torsion spring, and one end of the resilient member  70   b  is rotatably connected to the first linking member  20   b  and the other end thereof is rotatably connected to the first pinion gear  50   b.  It will be understood by those skilled in the art that one end is connected to the first linking member  20   b  to be rotatably fitted around a boss installed on the first linking member  20   b  and the other end is connected to the first pinion gear  50   b  to be rotatably fitted into a hole formed on the first pinion gear  50   b.  An elastic force of the resilient member  70   b  imparts the rotational force to the first pinion gear  50   b.    
         [0076]    Hereinafter, the operation of the opening and closing apparatus  10   b  according to an embodiment will be described in detail with reference to  FIGS. 8 to 10 . First, referring to  FIG. 8(   a ) and ( b ), in a state where the portable telephone  12   b  is completely closed, the direction of the rotational force applied to the first pinion gear  50   b  by the resilient member  70   b  of the opening and closing apparatus  10   b  corresponds to a direction in which the second linking member  40   b  is moved to close the portable telephone  12   b.  However, since the portable telephone  12   b  has been completely closed, it is reliably kept in its closed state in such a manner that its movement is limited by a structure such as a stopper (not shown). 
         [0077]    In order to open the portable telephone  12   b  at a state shown in  FIG. 8(   a ) and ( b ), an external force is applied to push the second unit  16   b  in a direction indicated by an arrow (leftward in this figure). Then, the external force causes the second linking member  40   b  of the opening and closing apparatus  10   b  to be moved leftward, and thus, the first and second pinion gears  50   b  and  60   b  to be rotated. At this time, one end of the resilient member  70   b  which is connected to the first pinion gear  50   b  is also rotated together with the first pinion gear  50   b,  and a distance between both ends of the resilient member  70   b  are decreased.  FIG. 9(   a ) and ( b ) show a state where the second unit  16   b  of the portable telephone  12   b  continues to be pushed leftward and is then in a neutral position where the distance between the both ends of the resilient member  70   b  is minimized. If the external force is removed before the second unit  16   b  is in the neutral position shown in  FIG. 9(   a ) and ( b ), the force for increasing the distance between both ends of the resilient member  70   b  causes the first pinion gear  50   b  to be rotated in the opposite direction, and thus, the second linking member  40   b  to be automatically moved rightward. Therefore, the portable telephone  12   b  can be automatically closed. 
         [0078]    If the second unit  16   b  is pushed leftward to further open the portable telephone  12   b  at a state shown in  FIG. 9(   a ) and ( b ), the resilient member  70   b  applies a force for causing the first pinion gear  50   b  to rotate along a direction in which the second linking member  40   b  is forced to move leftward. This resilient force of the resilient member  70   b  can cause the second linking member  40   b  to be automatically moved leftward without an additional external force. When the portable telephone  12   b  is kept completely open as shown in  FIG. 10(   a ) and ( b ), the second linking member  40   b  is stopped by a structure such as a stopper (not shown). 
         [0079]    Referring to  FIG. 10(   a ) and ( b ), the direction of the rotational force applied to the first pinion gear  50   b  by the resilient member  70   b  of the opening and closing apparatus  10   b  corresponds to a direction in which the second linking member  40   b  is moved to open the portable telephone  12   b.  However, since the portable telephone  12   b  has been already completely opened, it is reliably kept in its open state in such a manner that its movement is limited by a structure such as the stopper (not shown). 
         [0080]      FIGS. 11 to 15  show an opening and closing apparatus  10 c according to an embodiment of the present invention. Referring to  FIG. 11(   a ) to ( c ), the opening and closing apparatus  10   c  includes a first linking member  20   c  linked to a first unit  14   c  of a portable telephone  12   c,  a second linking member  40   c  linked to a second unit  16   c  of the portable telephone  12   c,  a pinion gear  50   c  and a resilient member  70   c.  Referring to  FIG. 11(   a ) to ( c ) and  FIG. 12 , the first linking member  20   c  is generally shaped as a rectangular plate and a first rack  21   c  extending in a direction parallel to a moving axis  110   c  is provided at one side of the first linking member  20   c.  The first rack  21   c  is engaged with the pinion gear  50   c.  The first linking member  20   c  is provided with a first guide portion  22   c  that is formed to extend in a direction parallel to the moving axis  100   c  along a line spaced apart from the first rack  21   c  toward the center of the first linking member. The first guide portion  22   c  is formed by perforating the first linking member  20   c.  One end of a rotating shaft  51   c  of the pinion gear  50   c  is inserted into the first guide portion  22   c.  The first guide portion  22   c  guides and limits the linear movement of the pinion gear  50   c.  The other configurations (for example, guide tracks, linking wings, etc.) of the first linking member  20   c  are identical to those of the first linking member  20   b  of an embodiment shown in  FIG. 8  except that their fixing positions are different from each other as described later. Therefore, detailed descriptions thereof will be omitted herein. 
         [0081]    Referring to  FIG. 11(   a ) to ( c ) and  FIG. 13 , the second linking member  40   c  is provided with a second guide portion  41   c  that has the same shape as the first guide portion  22   c  of the first linking member  20   c.  The second guide portion  41   c  is positioned on the same extension line as the first guide portion  22   c  when the first linking member  20   c  is coupled with the second linking member  40   c.  The other end of the rotating shaft  51   c  of the pinion gear  50   c  is inserted into the second guide portion  41   c.  The second guide portion  41   c  guides and limits the linear movement of the pinion gear  50   c.  The second linking member  40   c  is provided with a second rack  42   c  that extends in a direction parallel to the moving axis  100   c  along a line spaced apart from the second guide portion  41   c  toward the center of the second linking member and faces the first rack  21   c  of the first linking member  20   c.  The second rack  42   c  is engaged with the pinion gear  50   c  together with the first rack  21   c.  The other configurations (for example, linking grooves etc.) of the second linking member  40   c  are identical to those of the second linking member  40   b  of an embodiment shown in  FIG. 8 . Therefore, detailed descriptions thereof will be omitted herein. 
         [0082]    The pinion gear  50   c  is engaged with the first rack  21   c  of the first linking member  20   c  and the second rack  42   c  of the second linking member  40   c.  As the pinion gear  50   c  is rotated, the first and second linking members  20   c  and  40   c  are moved relative to each other along the moving axis  100   c.  Both ends of the rotating shaft  51   c  of the pinion gear  50   c  are inserted into the first guide portion  22   c  of the first linking member  20   c  and the second guide portion  41   c  of the second linking member  40   c,  respectively. When the rotating shaft  51   c  of the pinion gear  50   c  is caught by the longitudinal track ends of the first and second guide portions  22   c  and  41   c,  the relative movement of the first linking members  20   c  and  40   c  is restricted. 
         [0083]    The resilient member  70   c  is a torsion spring. One end of the resilient member  70   c  is rotatably connected to the first linking member  20   c  and the other end thereof is rotatably connected to the first pinion gear  50   c.  A resilient restoring force of the resilient member  70   c  imparts a rotational force to the pinion gear  50   c.  Between the completely closed state of the portable telephone  12   c  shown in  FIG. 11(   b ) and the neutral state where the portable telephone  12   c  is almost half opened and a distance between both ends of the resilient member  70   c  is minimized as shown in  FIG. 14(   c ), the resilient member  70   c  imparts a rotational force to the pinion gear  50   c  in a direction in which the portable telephone  12   c  is prevented from being opened. On the contrary, between the neutral state where the portable telephone  12   c  is almost half opened and the distance between both ends of the resilient member  70   c  is minimized as shown in  FIG. 14(   c ) and the completely open state of the portable telephone  12   c  shown in  FIG. 15(   c ), the resilient member  70   c  imparts a rotational force to the pinion gear  50   c  in a direction in which the portable telephone  12   c  is prevented from being closed. 
         [0084]    Now, the operation of the opening and closing apparatus  10   c  according to an embodiment of the present invention will be described in detail with reference to  FIGS. 11 ,  14  and  15 .  FIG. 11(   a ) and ( b ) show a state where the portable telephone  12   c  is completely closed. At this time, the direction of the rotational force applied to the pinion gear  50   c  by the resilient member  70   c  of the opening and closing apparatus  10   c  corresponds to a direction in which the second linking member  40   c  is moved to close the portable telephone  12   c.  However, since the first guide portion  22   c  of the first linking member  20   c  and the second guide portion  41   c  of the second linking member  40   c  are caught in the rotating shaft  51   c  of the pinion gear  50   c,  they are limited such that they cannot be moved further toward the closing direction. At this state, the portable telephone  12   c  is reliably kept in a closed state of the portable telephone by means of the resilient member  70   c.    
         [0085]    In order to open the portable telephone  12   c  at a state shown in  FIG. 11(   a ) and ( b ), an external force is applied to push the second unit  16   c  rightward. Then, the external force causes the second linking member  40   c  of the opening and closing apparatus  10   c  to be moved together rightward and the pinion gear  50   c  is also moved. A state where the portable telephone  12   c  is almost half opened by continuously moving the portable telephone is shown in  FIG. 14(   a ) and ( b ). The state of the resilient member  70   c  shown in  FIG. 14(   a ) and ( b ) becomes a neutral state where no rotational force is applied to the pinion gear  50   c  by the resilient member  70 . If the external force needed for opening the portable telephone  12   c  is removed before the telephone is in the neutral state, the portable telephone  12   c  is automatically closed by means of the resilient member  70   c.    
         [0086]    If the second unit  16  is pushed rightward to further open the opening and closing apparatus  10   c  at a state shown in  FIG. 14(   a ) and ( b ), the rotational force of the resilient member  70   c  of the opening and closing apparatus  10   c  is applied to the pinion gear  50   c  in a direction in which the portable telephone  12   c  is opened. Thereafter, the portable telephone  12   c  is automatically opened without additional external force and then in a state where the portable telephone  12   c  has been completely opened as shown in  FIG. 15(   a ) and ( b ). At this time, the direction of the rotational force applied to the pinion gear  50   c  by the resilient member  70   c  of the opening and closing apparatus  10   c  still corresponds to a direction in which the second linking member  40   c  is moved to open the portable telephone  12   c.  However, since the first guide portion  22   c  of the first linking member  20   c  and the second guide portion  41   c  of the second linking member  40   c  are caught in the rotating shaft  51   c  of the pinion gear  50   c,  they are limited such that they cannot be moved further toward the opening direction. At this state, the portable telephone  12   c  is reliably kept in its open state by means of the resilient member  70   c.    
         [0087]      FIGS. 16 to 20  show an opening and closing apparatus  10   d  according to an embodiment of the present invention. Referring to  FIG. 16(   a ) to ( c ), the opening and closing apparatus  10   d  includes a first linking member  20   d  linked to a first unit  14   d  of a portable telephone  12   d,  a second linking member  40   d  linked to a second unit  16   d  of the portable telephone  12   d,  and a resilient member  70 d. Referring to  FIG. 16(   a ) to ( c ) and  FIG. 17 , the first linking member  20   d  is substantially shaped as a rectangular flat plate and provided with a base plate  22   d  and sidewalls  26   d  which extend in a direction parallel to a moving axis  100   d  along both sides of the base plate  22   d  and slightly protrude toward the second unit  16   d.  The two sidewalls  26   d  are formed with linking guide grooves  261   d,  respectively, which face each other and extend in the direction parallel to the moving axis  100   d.  Two inserted portions  42   d  of the second linking member  40   d,  which will be described later, are slidably fitted into the linking guide grooves  261   d,  respectively. Both ends of the resilient member  70   d  are connected to middle points of the two sidewalls  26   d  above the linking guide grooves  261   d,  respectively. 
         [0088]    Referring to  FIG. 16(   a ) to ( c ) and  FIG. 18 , the second linking member  40   d  is substantially shaped as a rectangular flat plate which extends along the moving axis  100   d,  and the inserted portions  42   d  are formed respectively at both sides extending in a direction parallel to the moving axis  100   d.  The inserted portions  42   d  are thicker than other portions of the second linking member. The two inserted portions  42   d  are slidably fitted into the two linking guide grooves  261   d  of the first linking member  20   d,  respectively. In the center of the second linking member  40   d  are formed two protrusions  44   d  which protrude toward the second unit  16   d  of the portable telephone  12   d  and are substantially arranged in a longitudinal direction. The two protrusions  44   d  are arranged to be close to each other along the moving axis  100   d.  The middle part of the resilient member  70   d  is fitted and coupled between the two protrusions  44   d.    
         [0089]    Referring to  FIG. 16(   b ) and ( c ), the resilient member  70   d  has a zigzag shape in which a steel wire (a wire rod for spring) extends such that linear extension portions and curved portions are repeated. Accordingly, the resilient member  70   d  includes a plurality of curved portions  72   d  formed at both lateral sides thereof and a plurality of linear extension portions  73   d  which connect the adjacent curved portions  72   d.  The resilient member  70   d  is assembled within the linking member under a compressed state where a distance between the two adjacent curved portions  72   d  is decreased, and thus, the resilient member  70   d  functions as a compression spring. The middle portion of the resilient member  70   d  has a linear extension portion  73   d  shorter than other portions thereof, and the curved portion thereof is fitted and coupled between the two protrusions  44   d  of the second linking member  40   d.  Both ends of the resilient member  70   d  are fixed to the two sidewalls  26   d  of the first linking member  20   d,  respectively. The resilient member  70   d  is in a maximally compressed state when the resilient member  70   d  is substantially positioned perpendicular to the moving axis  100   d  as shown in  FIG. 19(   b ). If the second linking member  40   d  is moved in any direction from the state shown in  FIG. 19(   b ), the resilient member  70   d  imparts an elastic force to the second linking member  40   d  in a direction in which the second linking member  40   d  has been moved. 
         [0090]    Now, the operation of the opening and closing apparatus according to an embodiment will be described in detail with reference to  FIGS. 16 ,  19  and  20 . First,  FIG. 16(   a ) and ( b ) show a state where the portable telephone  12   d  is completely closed. At this time, the resilient member  70   d  is symmetrically curved with respect to the middle portion thereof that is coupled with the second linking member  40   d.  Since the resilient member  70   d  functions as a compression spring, the direction of the elastic force applied to the first and second linking members  20   d  and  40   d  by the resilient member  70   d  corresponds to a direction in which the portable telephone  12   d  is closed. However, since the portable telephone  12   d  has been completely closed, it is reliably kept in its closed state in such a manner that its movement is limited by a structure such as a stopper (not shown). 
         [0091]    In order to open the portable telephone  12   d  at a state shown in  FIG. 16(   a ) and ( b ), an external force is applied to push the second unit  16   d  in a direction indicated by an arrow (rightward in this figure). Then, the external force causes the second linking member  40   d  of the opening and closing apparatus  10   d  to be moved rightward with respect to the first linking member  20   d,  and thus, causes the resilient member  70   d  to be compressed.  FIG. 19(   a ) and ( b ) show a state where the second unit  16   d  of the portable telephone  12   d  continues to be pushed rightward with respect to the first unit  14   d  and the first and second units  14   d  and  16   d  are then in a neutral position where the resilient member  70   d  are compressed to the utmost. If the external force is removed prior to the neutral state shown in  FIG. 19(   a ) and ( b ), a restoring force of the resilient member  70   d  causes the second linking member  40   d  to be automatically moved leftward, and thus, the portable telephone  12   d  is automatically closed. 
         [0092]    If the second unit  16   d  is pushed rightward with respect to the first unit  14   d  to further open the portable telephone  12   d  at a state shown in  FIG. 19(   a ) and ( b ), the resilient member  70   d  exerts a force to move the second linking member  40   d  rightward relative to the first linking member  20   d.  This force of the resilient member  70   d  allows the second linking member  40   d  to be automatically moved rightward without any additional external force. When the portable telephone  12   d  is kept completely opened as shown in  FIG. 20(   a ) and ( b ), the second linking member  40   d  is stopped by a structure such as a stopper (not shown). 
         [0093]    Referring to  FIG. 20(   a ) and ( b ), the resilient member  70   d  is symmetrically curved in a direction opposite to that shown in  FIG. 16(   b ), with respect to the middle portion thereof which is coupled with the second linking member  40   d.  Since the resilient member  70   d  is a compression spring, the direction of the elastic force applied to the first and second linking members  20   d  and  40   d  by the resilient member  70   d  corresponds to a direction in which the first and second linking members  20   d  and  40   d  are moved to open the portable telephone  12   d.  However, the portable telephone  12   d  has been completely opened, and thus, it is reliably kept in its open state in such a manner that its movement is limited by a structure such as a stopper (not shown). 
         [0094]    Since the opening and closing apparatus shown in  FIGS. 16 to 20  employs a thin wire rod as a resilient member, there is an advantage in that the total thickness of the opening and closing apparatus can be decreased. 
         [0095]      FIGS. 21 to 23  show an opening and closing apparatus  10   e  according to an embodiment of the present invention. Referring to  FIG. 21(   a ) to ( c ), the opening and closing apparatus  10   e  includes a first linking member  20   e  linked to a first unit  14   e  of a portable telephone  12   e,  a second linking member  40   e  linked to a second linking member  40   e  of the portable telephone  12   e,  and a resilient member  70   e.  Referring to  FIG. 21(   a ) to ( c ), the first linking member  20   e  is substantially shaped as a rectangular plate and provided with a base plate  22   e  and sidewalls  26   e  which extend in a direction parallel to a moving axis  100   e  along both sides of the base plate  22   e  and slightly protrude toward the second unit  16   e.  A linking hole  23   e  through which one end of the resilient member  70   e  is fitted to protrude outward is provided on a corner of the base plate  22   e.  A portion including this linking hole  23   e  protrudes toward the second linking member  40   e  to provide a slightly recessed space on the external surface of the base plate. One end of the resilient member  70   e  protruding outward through the linking hole  23   e  is placed within the space. The two sidewalls  26   e  are provided respectively with linking guide grooves  261   e  that face each other and extend in a direction parallel to the moving axis  100   e.  Two insertion wings  42   e  of the second linking member  40   e,  which will be described later, are slidably fitted into the linking guide grooves  261   e,  respectively. 
         [0096]    Referring to  FIG. 21(   a ) to ( c ), the second linking member  40   e  is substantially shaped as a rectangular plate which extends in the moving axis  100   e,  and each of sides parallel to the moving axis  100   e  is curved toward the first linking member  20   e  to slightly extend in such a direction and then curved once more outward, thereby resulting in the inserting wing  42   e.  The inserting wings  42   e  are slidably fitted and coupled into the two linking guide grooves  261   e  of the first linking member  20   e,  respectively. On the second linking member  40   e  is provided a linking column  44   e  that protrudes slightly toward the first linking member  20   e.  The linking column  44   e  is positioned opposite to the linking hole  23   e  of the first linking member  20   e.  The other end of the resilient member  70   e  is fitted and coupled around the linking column  44   e.  A coupling ring  441   e  for preventing the resilient member  70   e  from being separated is provided at one end of the linking column  44   e.    
         [0097]    Referring to  FIG. 21(   b ) and ( c ), the resilient member  70   e  has a zigzag shape in which a steel wire (a wire rod for spring) extends such that linear extension portions and curved portions are repeated. Accordingly, the resilient member  70   e  includes a plurality of curved portions  72   e,    73   e  and  74   e  formed at both lateral sides thereof and a plurality of linear extension portions  75   e  which connect the adjacent curved portions  72   e,    73   e  and  74   e.  The radii of the curved portions  72   e,    73   e  and  74   e  are relatively larger than those of the curved portions  72   d  of the resilient member  70   d  provided in the opening and closing apparatus  10   d  shown in  FIG. 16 . The curved portion  74   e,  which is positioned in the middle of the curved portions  73   e  and  74   e  on one lateral side among the plurality of curved portions  72   e,    73   e  and  74   e,  is formed into a coil. The resilient member  70   e  is placed within a space defined between the first and second linking members  20   e  and  40   e.  One longitudinal end of the resilient member  70   e  is inserted into the linking hole  23   e  of the first linking member  20   e  to slightly protrudes outward and the protruding end is then bent to prevent the resilient member from being separated from the linking hole. The other longitudinal end of the resilient member  70   e  is curved into a circular shape, fitted and coupled around the linking column  44   e,  and prevented from being separated by the coupling ring  441   e.  A distance between the linking hole  23   e  of the first linking member  20   e  and the linking column  44   e  of the second linking member  40   e  is shorter than an uncompressed length of the resilient member  70   e,  and thus, the resilient member  70   e  whose both ends are connected respectively to the linking hole  23   e  of the first linking member  20   e  and the linking column  44   e  of the second linking member  40   e  is naturally curved. Therefore, an interval or gap between the two adjacent curved portions or valleys  72   e  positioned on one lateral side are relatively smaller than that between the two adjacent curved portions or hills  73   e  and  74   e  positioned on the other lateral side. 
         [0098]    Among the plurality of curved portions  72   e,    73   e  and  74   e  provided on both lateral sides of the resilient member  70   e,  the curved portions  73   e  and  74   e  of one lateral side whose interval has been relatively wider can provide an elastic force for increasing an interval between the adjacent curved portions  72   e  of the other lateral side. Since the radii of the curved portions  73   e  and  74   e  are relatively large and the total deformation of the resilient member  70   e  is distributed to the respective curved portions  73   e  and  74   e  such that stress can be distributed to the respective curved portions  73   e  and  74   e,  durability of the resilient member  70   e  can be improved. Accordingly, the resilient member  70   e  can be used for a long time. The curved portion  74   e  positioned in the middle of the three curved portions  73   e  and  74   e  is formed into a coil, and thus, stress can be further distributed and durability can be further improved accordingly. 
         [0099]    Meanwhile, although it has been described in this embodiment that the curved portion wound by one turn or two or more turns into a coil is positioned in the middle of the resilient member, the present invention is not limited thereto. The configurations in which the curved portions are formed into a coil may be changed. The examples are illustrated in  FIGS. 24 to 26 . Referring to  FIG. 24 , a resilient member  70   f  is configured in such a manner that the two end curved portions among the three curved portions  73   f  positioned on a lateral side whose interval between the adjacent curved portions is relatively larger are formed into a coil. Referring to  FIG. 25 , a resilient member  70   g  is configured in such a manner that one end curved portion and the middle curved portion among the three curved portions  73   g  positioned on the lateral side whose interval between the adjacent curved portions is relatively larger are formed into a coil. Referring to  FIG. 26 , a resilient member  70   h  is configured in such a manner that all curved portions  72   h  and  73   h  are formed into a coil. 
         [0100]    Now, the operation of the opening and closing apparatus according to an embodiment will be described in detail with reference to  FIGS. 21 to 23 . First,  FIG. 21(   a ) and ( b ) show a state where the portable telephone  12   e  has been completely closed. At this time, the linking column  44   e  of the second linking member  40   e  is positioned rightward along the moving axis  100   e  with respect to the linking hole  23   e  of the first linking member  20   e,  as viewed in the figure. The resilient member  70   e  is shaped as a circular arc and curved such that its center of curvature is positioned rightward on the figure. At this time, an elastic restoring force for increasing the interval between the adjacent curved portions  72   e  positioned at a narrow lateral side whose an interval is relatively narrower is provided in a direction in which the portable telephone  12   e  is closed. However, since the portable telephone  12   e  has been completely closed, it is reliably kept in its closed state in such a manner that its movement is limited by a structure such as a stopper (not shown). 
         [0101]    In order to open the portable telephone  12   e  at a state shown in  FIG. 21(   a ) and ( b ), an external force is applied to push the second unit  16   e  in a direction indicated by an arrow (leftward in this figure). Then, the external force causes the second linking member  40   e  of the opening and closing apparatus  10   e  to be moved together leftward with respect to the first linking member  20   e,  and thus, the distance between both ends of the resilient member  70   e  is decreased.  FIG. 22(   a ) and ( b ) show a state where the second unit  16   e  of the portable telephone  12   e  continues to be pushed leftward with respect to the first unit  14   e  and the first and second units  14   e  and  16   e  are then in a neutral position where the distance between both ends of the resilient member  70   e  is minimized. Referring to  FIG. 22(   b ), the linking hole  23   e  of the first linking member  20   e  and the linking column  44   e  of the second linking member  40   e  are positioned on a line substantially perpendicular to the moving axis  100   e.  If the external force is removed prior to the neutral state shown in  FIG. 22(   a ) and ( b ), the elastic force of the resilient member  70   e  causes the second linking member  40   e  to be automatically moved rightward, and accordingly, the portable telephone  12   e  is automatically closed. 
         [0102]    If the second unit  16   e  is pushed leftward with respect to the first unit  14   e  to further open the portable telephone  12   e  from a state shown in  FIG. 22(   a ) and ( b ), the resilient member  70   e  applies a force for causing the second linking member  40   e  to be moved leftward with respect to the first linking member  20   e.  This resilient force of the resilient member  70   e  can cause the second linking member  40   e  to be automatically moved leftward without any additional external force. When the portable telephone  12   e  is kept completely opened as shown in  FIG. 23(   a ) and ( b ), the second linking member  40   e  is stopped by a structure such as a stopper (not shown). 
         [0103]      FIG. 23(   a ) and ( b ) show a state where the portable telephone  12   e  is completely opened. At this time, the linking column  44   e  of the second linking member  40   e  is positioned leftward along the moving axis  100   e  with respect to the linking hole  23   e  of the first linking member  20   e,  as viewed in the figure. The resilient member  70   e  is shaped as a circular arc and curved such that its center of curvature is positioned rightward on the figure. The direction of the elastic force applied to the first and second linking members  20   e  and  40   e  by the resilient member  70   e  corresponds to a direction in which the portable telephone  12   e  is opened. However, since the portable telephone  12   e  has been completely opened, it is reliably kept in its open state in such a manner that its movement is limited by a structure such as a stopper (not shown). 
         [0104]      FIG. 27  shows an opening and closing apparatus  10   j  according to an embodiment of the present invention. Referring to  FIG. 27 , the opening and closing apparatus  10   j  includes a first linking member  20   j,  a second linking member  40   j,  and first and second resilient members  70   j  and  70   k.  The first linking member  20   j  has the same configuration as the first linking member  20   e  shown in  FIG. 21 , except that a second linking hole  23   k  positioned at a corner opposite to a first linking hole  23   j  is further provided. Therefore, detailed descriptions thereof will be omitted herein. One end of the second resilient member  70   k  is fitted and coupled into the second linking hole  23   k.  The second linking member  40   j  also has the same configuration as the second linking member  40   e  shown in  FIG. 21 , except that a second linking column  44   k  positioned at a side opposite to a first linking column  44   j  is further provided. Therefore, detailed descriptions thereof will be omitted herein. The other end of the second resilient member  70   k  is coupled to the second linking column  44   k.    
         [0105]    Each of the first and second resilient members  70   j  and  70   k  have the same configuration as the resilient member  70   e  shown in  FIG. 21 . That is, both ends of the first resilient member  70   j  are coupled to the first linking hole  23   j  of the first linking member  20   j  and the first linking column  44   j  of the second linking member  40   j,  respectively, in the same manner as shown in  FIG. 21 , i.e. in such a manner that the resilient members cross each other. Both ends of the second resilient member  70   k  are coupled to the second linking hole  23   k  of the first linking member  20   j  and the second linking column  44   k  of the second linking member  40   j,  respectively, in the same manner as the first resilient member  70   j.  The operation of each of the first and second resilient members  70   j  and  70   k  is the same as that of the embodiment shown in  FIG. 21 . However, since the respective forces applied by the two resilient members  70   j  and  70   k  in a direction perpendicular to a moving axis  100   j  are opposite to each other in view of their directions, force balance can be obtained. Further, since two resilient members are employed, a greater elastic force can be provided. Since the other configurations and operations are the same as those of the embodiment shown in  FIG. 21 , detailed descriptions thereof will be omitted herein. 
         [0106]    Since the opening and closing apparatus  10   j  shown in  FIG. 27  has two resilient members  70   j  and  70   k  which symmetrically cross each other, the first and second linking members are well balanced such they are not pushed toward only one side with respect to each other. Accordingly, friction generated between linking portions of the first and second linking members  20   j  and  40   j  between which the opening and closing apparatus  10   j  is interposed is uniform. 
         [0107]      FIG. 28(   a ) and ( b ) show other embodiments of the resilient member installed to the sliding type opening and closing apparatus as shown in  FIG. 21 . Referring to  FIG. 28(   a ), a resilient member  70   m  includes two first connecting portions  72   m  provided on one end thereof, a second connecting portion  73   m  provided on the other end, and first and second extension portions  74   m  and  75   m  for connecting the first and second connecting portions  72   m  and  73   m.  The two first connecting portions  72   m  are formed by circularly winding ends of the two extension portions  74   m  and  75   m.  The first and second extension portions  74   m  and  75   m  are formed from a single wire rod, and the second connecting portion  73   m  is formed by winding the single wire rod into a coil. The first and second extension portions  74   m  and  75   m  are curved in such a manner that their opposite sides are concave. One of the first and second connecting portions  72   m  and  73   m  is connected to the first linking member  20   e  of the opening and closing apparatus  10   e  shown in  FIG. 21 , whereas the other is connected to the second linking member  40   e.  Referring to  FIG. 28(   b ), a resilient member  70   n  is configured in such a manner that first and second extension portions  74   n  and  75   n  are curved into a zigzag shape. The other configurations of the resilient member  70   n  are the same as those of the resilient member  70   m  shown in  FIG. 28(   a ), and thus, detailed descriptions thereof will be omitted herein. 
         [0108]      FIG. 29(   a ) and ( b ) show further embodiments of the resilient member installed in the sliding type opening and closing apparatus as shown in  FIG. 21 . Referring to  FIG. 29(   a ), a resilient member  70   p  is formed from a single wire rod. The resilient member  70   p  includes a plurality of extension portions  74   p  which substantially have the same length as one another and extend in parallel with one another, and a plurality of first and second connecting portions  72   p  and  73   p  which are formed to be circularly wound at both ends of the plurality of extension portions.  FIG. 29(   a ) shows a state where the extension portions  74   p  are maximally stretched but all of the extension portions  74   p  are slightly curved toward a single direction such that all the extension portions  74   p  can be compressed in the same direction.  FIG. 29(   b ) shows a neutral state where the extension portions  74   p  are maximally compressed. One of the first and second connecting portions  72   p  and  73   p  is connected to the first linking member  20   e  of the sliding type opening and closing apparatus  10   e  shown in  FIG. 21 , whereas the other is connected to the second linking member  40   e.    
         [0109]      FIG. 30(   a ) to ( g ) show still further embodiments of the resilient member mounted to the sliding type opening and closing apparatus as shown in  FIG. 21 . Referring to FIG.  30 ( a ), a resilient member  70   g  includes a curved portion  74   g  extending such that it is curved into a zigzag shape, and first and second connecting portions  72   q  and  73   q  provided on both ends of the curved portion  74   q,  respectively. One of the first and second connecting portions  72   q  and  73   q  is connected to the first linking member  20   e  of the sliding type opening and closing apparatus  10   e  shown in  FIG. 21 , whereas the other is connected to the second linking member  40   e.  The embodiments shown in  FIG. 30(   b ) to ( g ) are modified examples of the embodiment shown in  FIG. 30(   a ). Since the resilient member shown in  FIG. 30  is manufactured through a manufacturing process such as a press process using a plate material, there is an advantage in that both productivity and strength can be improved. 
         [0110]      FIG. 31  shows a still further embodiment of the resilient member mounted to the sliding type opening and closing apparatus as shown in  FIG. 21 . Referring to  FIG. 31 , a resilient member  70   r  includes a long extension portion  74   r  and first and second connecting portions  72   r  and  73   r  provided at both ends of the extension portion  74   r.  The extension portion  74   r  is curved to be slightly convex upward and the middle portion of the extension portion  74   r  is curved to be concave downward. That is, the extension portion  74   r  is inclined to gradually move away from a straight line (not shown) connecting the first and second connecting portion  72   r  and  73   r  as it goes from the first and second linking portions  72   r  and  73   r  toward its middle portion. Further, a concave portion  75   r  is formed at the middle portion of the resilient member  70   r  to be curved opposite to extension portion  74   r.    
         [0111]      FIG. 32  shows a still further embodiment of the resilient member mounted to the sliding type opening and closing apparatus as shown in  FIG. 21 . Referring to  FIG. 32 , a resilient member  70   s  includes a long extension portion  74   s  formed by twisting two wire rods in a longitudinal direction, and first and second connecting portions  72   s  and  73   s  provided on both ends of the extension portion  74   s.    
         [0112]    The resilient members mounted to the opening and closing apparatuses according to the respective embodiments shown in  FIGS. 16 to 32  are not limited to the same shape as shown in the figures. It can be understood by those skilled in the art that a resilient member with any shape can be employed so long as a force is applied such that a portion coupled with the first linking member can be moved away from or close to a portion coupled with the second linking member. 
         [0113]    Although it has been described in the aforementioned embodiments that the sliding type opening and closing apparatus is mounted to the portable telephone, the present invention is not limited thereto. It will be understood by those skilled in the art that if two units which are slidably opened and closed are provided, the aforementioned opening and closing apparatus can be applied thereto. 
         [0114]    Although embodiments of the present invention has been illustrated and described, the invention is not limited thereto. It will be understood by those skilled in the art that various modifications and changes can be made thereto without departing from the scope and spirit of the present invention and such various modifications and changes would also be included into the scope of the present invention.