Abstract:
A slide rail assembly includes first and second rails. The second rail, slidable relative to the first rail, has a mounting hole. A connecting device includes first and second units, an engaging element, and an adjusting element. The second unit has a transverse guiding portion located at its counterpart of the first unit. The engaging element, connected to the second unit, has an engaging portion partially located in the mounting hole to connect the connecting device to the second rail. The adjusting element is connected to both units. The second unit is displaceable in response to rotation of the adjusting element, thereby enabling displacement of the engaging portion relative to the mounting hole.

Description:
FIELD OF THE INVENTION 
     The present invention relates to slide rails and more particularly to a slide rail system and a connecting device used therein for connecting a slide rail assembly. 
     BACKGROUND OF THE INVENTION 
     Undermount drawer slides are a type of hidden slide rails. Typically, an undermount drawer slide is mounted on the bottom of a drawer so that, when the drawer is pulled out with respect to a frame (e.g., a cabinet), the undermount drawer slide stays hidden at the bottom of the drawer and is not exposed to view. Such an undermount drawer slide generally has an L-shaped bracket and a slide rail. The bracket is mounted on a wall surface of a cabinet, and the slide rail is arranged on the bracket and longitudinally slidable relative to the rail on the bracket. A drawer mounted on the slide rail can be pulled out with respect to the cabinet or pushed back into the cabinet via the slide rail. 
     However, due to minor errors in the mounting process or some external factors, the connecting device of the drawer may have problem being mounted to the slide rail. 
     To solve this problem, US Patent Application Publication No. 2012/0292465 A1, titled “Coupling device having side adjustment for a drawer”, discloses a coupling device configured for a drawer and featuring transverse adjustability. The coupling device (5) serves mainly to detachably couple a drawer to an extendable rail. The relationship between the spiral disk (15) of the adjusting wheel (8) of the coupling device (5) and the tooth-shaped holding elements (21) of a mounting plate (16) is such that, when the adjusting wheel (8) is adjusted, the latching portion (10) of the coupling device (5) is driven, allowing abutment surfaces (10a, 10b, 10c) of the latching portion (10) to be adjusted in position relative to the carcass rail (3c) of an extension guide (3). In other words, the drawer (2) is transversely adjustable in position relative to the carcass rail (3c) of the extension guide (3) to eliminate minor mounting errors between the drawer and the carcass rail. 
     In addition, US Patent Application Publication No. 2012/0319548 A1, titled “Pull-out guide for a drawer”, discloses in paragraph [0081], FIG. 2b, and FIG. 4 of its specification a holding element (5) mounted at the rear end of the extension rail (3a) of an extension guide (3). The holding element (5) has a holding nose (15) mounted in a bore of a drawer rear wall (2d). According to paragraphs [0082, 0083] and FIG. 5a of the specification, when a pivotal movement of an adjusting lever (18) is transmitted to lateral abutment surfaces of the holding element (5), a connecting element (7) and the holding nose (15) are displaced along a pair of guide bars (14). Therefore, the holding nose (15) of the extension rail (3a) can be adjusted in position relative to the drawer (2) in a transverse direction to eliminate mounting errors, which if existing may hinder installation of the drawer (2) on the holding nose (15) of the extension rail (3a). However, the numerous components of the holding element (5)—namely an adjustment device (11), a support element (17), a holding portion (19), and guide pins (14), in addition to the adjustment lever (18), the connecting element (7), and the holding nose (15) of the connecting element (7)—are to the disadvantage of the overall production cost and manufacturing process; in other words, the holding element (5) still leaves room for improvement. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a slide rail system which allows the connecting position of a drawer to be adjusted relative to a slide rail in a transverse direction. The present invention also relates to a connecting device used in the slide rail system to connect a slide rail assembly. 
     According to one aspect of the present invention, a slide rail system includes a slide rail assembly and a front connecting device. The slide rail assembly includes a first rail and a second rail. The second rail is longitudinally slidable relative to the first rail. The second rail has a longitudinally extending main body, a front portion, and a mounting hole adjacent to the front portion. The front connecting device includes a first unit, a second unit, an engaging element, and an adjusting element. The first unit has at least one transverse guiding portion. The second unit has at least one transverse guiding portion located at the transverse guiding portion of the first unit. The engaging element is connected to the second unit and has an engaging portion. At least a portion of the engaging portion is located in the mounting hole of the second rail. The adjusting element has an adjusting portion and a screw rod. The screw rod is connected to the first unit and the second unit. The second unit is displaceable relative to the second rail in response to rotation of the adjusting portion of the adjusting element so that the engaging portion of the engaging element can be displaced relative to the mounting hole of the second rail. 
     Preferably, the second unit further includes a first sidewall with a hanging hole, and the first unit further includes a sidewall with a threaded hole. The screw rod of the adjusting element is threadedly connected to the threaded hole while the second unit hangs on a neck of the screw rod via the hanging hole. The second unit preferably further includes a second sidewall which is opposite the first sidewall and which has a wall hole. The engaging portion of the engaging element corresponds in position to the wall hole. 
     Preferably, the engaging element further includes an elastic arm. When the adjusting portion of the adjusting element is rotated, the second unit is displaced relative to the second rail, the engaging portion of the engaging element if not yet corresponding in position to the mounting hole of the second rail is pressed against a sidewall of the second rail and pivoted by a predetermined angle such that the elastic arm stores an elastic energy, and the engaging portion of the engaging element, once corresponding in position to the mounting hole, enters the mounting hole due to the elastic energy released by the elastic arm. Preferably, the engaging element further includes a slot, and the front connecting device further includes a disengaging element pivotally connected to the second unit. The disengaging element has a disengaging portion located in the slot. When the disengaging element is pivoted, the disengaging portion of the disengaging element drives the engaging element via the slot and thereby pivots the engaging element; consequently, the engaging portion of the engaging element is displaced relative to the second rail and separates from the mounting hole. 
     Preferably, the second rail further has a rear portion opposite the front portion, and the rear portion is provided with a rear connecting device. The rear connecting device includes a main body, a locking element, and a movable element. The main body includes a supporting portion and a transverse portion substantially perpendicularly connected to the supporting portion. The locking element is pivotally connected to the supporting portion of the main body and includes a head and a locking rod connected to the head. The locking rod has a contact portion. The movable element is movably provided between the main body and the locking element. The movable element includes a first plate portion and a second plate portion substantially perpendicular to the first plate portion. When the head of the locking element is rotated to a first position, the contact portion of the locking rod is pressed against the first plate portion of the movable element such that the movable element is positioned on the main body. Once the head of the locking element is rotated from the first position to a second position, the contact portion of the locking rod is no more pressed against the first plate portion of the movable element, and the movable element is therefore allowed to be displaced relative to the main body. 
     Preferably, the supporting portion of the main body of the rear connecting device includes a first vertical wall and a second vertical wall, and the transverse portion of the main body of the rear connecting device has two opposite lateral sides respectively and substantially perpendicularly connected to the first vertical wall and the second vertical wall. Each of the first vertical wall and the second vertical wall has a through hole, and the through holes correspond in position to each other. 
     The locking rod of the locking element extends through the through holes of the first vertical wall and the second vertical wall. The movable element preferably has a width less than a width between the first vertical wall and the second vertical wall so that the movable element can be displaced between the first vertical wall and the second vertical wall. Preferably, the transverse portion of the main body of the rear connecting device includes a plurality of fixing portions which are arranged at intervals, and the first plate portion of the movable element includes a fixing portion corresponding in position to one of the fixing portions of the transverse portion of the main body of the rear connecting device. When the head of the locking element is rotated to the first position, the contact portion of the locking rod is pressed against the first plate portion of the movable element such that the fixing portion of the first plate portion of the movable element is engaged with one of the fixing portions of the transverse portion of the main body of the rear connecting device. Once the head of the locking element is rotated from the first position to the second position, the contact portion of the locking rod is no more pressed against the first plate portion of the movable element, and the fixing portion of the first plate portion of the movable element is therefore disengaged from the one of the fixing portions of the transverse portion of the main body of the rear connecting device. 
     According to another aspect of the present invention, a connecting device used for a slide rail assembly includes a first unit, a second unit, an engaging element, and an adjusting element. The first unit has at least one transverse guiding portion. The second unit has at least one transverse guiding portion located at the transverse guiding portion of the first unit. The engaging element is connected to the second unit and has an engaging portion. The adjusting element has an adjusting portion and a screw rod, wherein the screw rod is connected to the first unit and the second unit. The second unit is displaceable in response to rotation of the adjusting portion of the adjusting element so that the engaging portion of the engaging element can be displaced. 
     Preferably, the at least one transverse guiding portion of the first unit includes a transverse guiding hole, and the at least one transverse guiding portion of the second unit includes a protruding block. 
     Preferably, the second unit further includes a first sidewall with a hanging hole, and the first unit further includes a sidewall with a threaded hole. The screw rod of the adjusting element is threadedly connected to the threaded hole while the second unit hangs on a neck of the screw rod via the hanging hole. The second unit preferably further includes a second sidewall which is opposite the first sidewall and which has a wall hole. The engaging portion of the engaging element corresponds in position to the wall hole. 
     Preferably, the engaging element further includes an elastic arm and a slot, and the connecting device further includes a disengaging element pivotally connected to the second unit. The disengaging element has a disengaging portion located in the slot. 
     One technical feature of the embodiments of the present invention is that an operator can adjust the connecting position of a drawer with respect to the slide rail assembly in a transverse direction by means of the adjusting element of the front connecting device. Another technical feature is that the locking element of the rear connecting device makes it possible for the operator to adjust the mounting position of the slide rail assembly with which the drawer is to align. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as well as a preferred mode of use and the advantages thereof will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is an assembled perspective view showing how a drawer is mounted on slide rail assemblies by means of connecting devices according to an embodiment of the present invention; 
         FIG. 2   a  is an exploded perspective view of the slide rail assembly and front connecting device on a single side of  FIG. 1 ; 
         FIG. 2   b  is an exploded perspective view of the rear connecting device and second rail (only a rear portion thereof is shown) on a single side of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the first front connecting device in  FIG. 1 ; 
         FIG. 4   a  is a schematic drawing in which mounting errors between the engaging portion of the front connecting device and a mounting hole of the slide rail assembly prevent the front connecting device from being properly connected to the mounting hole in the second rail of the slide rail assembly; 
         FIG. 4   b  is another schematic drawing in which mounting errors between the engaging portion of the front connecting device and a mounting hole of the slide rail assembly prevent the front connecting device from being properly connected to the mounting hole in the second rail of the slide rail assembly; 
         FIG. 5   a  is a schematic drawing in which the adjusting portion of the adjusting element has been adjusted to adjust the distance between the second unit and the second rail of the slide rail assembly; 
         FIG. 5   b  is a schematic drawing in which the adjusting portion of the adjusting element has been adjusted, allowing the engaging portion of the engaging element of the front connecting device to be mounted in the mounting hole in the second rail of the slide rail assembly; 
         FIG. 6   a  is a schematic drawing in which the disengaging element of the front connecting device has yet to be adjusted; 
         FIG. 6   b  is a schematic drawing in which the disengaging element in  FIG. 6   a  has been adjusted such that the engaging element is pivoted by a predetermined angle; 
         FIG. 7  is an exploded perspective view of an embodiment of the rear connecting device in the present invention; 
         FIG. 8   a  is a schematic drawing showing operation of the rear connecting device in  FIG. 7  after assembly; 
         FIG. 8   b  is another schematic drawing showing operation of the rear connecting device in  FIG. 7  after assembly; 
         FIG. 9  schematically shows how the movable element of the rear connecting device in  FIG. 7  can be adjusted in position; 
         FIG. 10  schematically shows how the first plate portion of the movable element in an embodiment of the present invention is aligned with a positioning hole in the back panel of a drawer; 
         FIG. 11   a  is a schematic drawing showing operation of the second embodiment of the rear connecting device in the present invention; 
         FIG. 11   b  is another schematic drawing showing operation of the second embodiment of the rear connecting device in the present invention; 
         FIG. 12   a  is a schematic drawing showing operation of the third embodiment of the rear connecting device in the present invention; and 
         FIG. 12   b  is another schematic drawing showing operation of the third embodiment of the rear connecting device in the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows how a drawer  10  is mounted on a first slide rail assembly  16  and a second slide rail assembly  18  by means of a first front connecting device  12  and a second front connecting device  14 . The first slide rail assembly  16  includes a front portion  20   a  and a rear portion  20   b  opposite the front portion  20   a . The second slide rail assembly  18  includes a front portion  22   a  and a rear portion  22   b  opposite the front portion  22   a.    
     More specifically, the first front connecting device  12  and the second front connecting device  14  are respectively arranged on two lateral sides of the bottom of the drawer  10 . The first front connecting device  12  is mounted at the front portion  20   a  of the first slide rail assembly  16 , and the second front connecting device  14  is mounted at the front portion  22   a  of the second slide rail assembly  18 . In addition, the rear portion  20   b  of the first slide rail assembly  16  is mounted with a first rear connecting device  24 , and the rear portion  22   b  of the second slide rail assembly  18  is mounted with a second rear connecting device  26 . 
     In one preferred embodiment, one of the first front connecting device  12  and the second front connecting device  14  has an adjusting element  28 . With the adjusting element  28 , an operator can adjust the connecting position of the drawer  10  relative to the corresponding slide rail assembly (e.g., the first slide rail assembly  16  or the second slide rail assembly  18 ) in a transverse direction. Also, one of the first rear connecting device  24  and the second rear connecting device  26  has a locking element  30 . With the locking element  30 , the operator can adjust the mounting position of the corresponding slide rail assembly (e.g., the first slide rail assembly  16  or the second slide rail assembly  18 ) with which the drawer  10  is to align. 
     In practice, only one of the slide rail assemblies (e.g., the first slide rail assembly  16  or the second slide rail assembly  18 ) is required to be equipped with the front connecting device and the rear connecting device to achieve the aforesaid effects. 
     The first slide rail assembly  16  is now described in more detail with reference to  FIG. 2   a  and  FIG. 2   b . The first slide rail assembly  16  includes a first rail  32  and a second rail  34 . The first rail  32  has a wall portion  36  provided with at least one positioning hole  38  so that the first rail  32  can be mounted to a frame (e.g., a cabinet) by passing a fastener (not shown) through the positioning hole  38 . 
     In one preferred embodiment, a third rail  40  is further provided between the first rail  32  and the second rail  34 . The third rail  40  is configured to extend the sliding distance of the second rail  34  relative to the first rail  32 , thus allowing the drawer  10  to be displaced farther from the frame. In practice, however, the third rail  40  is optional, meaning that the first rail  32  and the second rail  34  alone are sufficient to enable displacement of the drawer  10  relative to the frame. 
     More specifically, the first rail  32  has a longitudinally extending main body  42 . The second rail  34  can slide longitudinally relative to the first rail  32 . The second rail  34  has a longitudinally extending main body  44 , the front portion  20   a , the rear portion  20   b  opposite the front portion  20   a , and a mounting hole  46  adjacent to the front portion  20   a.    
     The first front connecting device  12 , which includes the aforesaid adjusting element  28 , is connected to the second rail  34  via the mounting hole  46 . The first rear connecting device  24 , which includes the aforesaid locking element  30 , is arranged at the rear portion  20   b  of the second rail  34 . 
     Referring to  FIG. 3  and  FIG. 4   a , the first front connecting device  12  includes a first unit  48 , a second unit  50 , an engaging element  52 , and a disengaging element  54 , in addition to the adjusting element  28 . 
     The first unit  48  includes a main body  56 , a front wall  58  located at a front portion of the main body  56 , and a sidewall  60  located at a lateral side of the main body  56 . 
     The main body  56  of the first unit  48  has at least one transverse guiding portion  62  which is substantially parallel to the front wall  58 . The at least one transverse guiding portion  62  of the first unit  48  may be formed as one or more transverse guiding holes. Here, the at least one transverse guiding portion  62  of the first unit  48  is implemented by a first transverse guiding hole  64   a  and a second transverse guiding hole  64   b  by way of example. In an embodiment which is not shown, however, the at least one transverse guiding portion  62  of the first unit  48  is one or more protruding blocks. It should be noted that the “transverse” direction refers to a direction perpendicular to the longitudinally extending main body  42  of the first rail  32  or the longitudinally extending main body  44  of the second rail  34 . 
     In one preferred embodiment, the main body  56  of the first unit  48  further includes at least one transverse guiding groove between the first transverse guiding hole  64   a  and the front wall  58 . Here, the at least one transverse guiding groove is implemented by a first transverse guiding groove  66   a  and a second transverse guiding groove  66   b , wherein the first transverse guiding groove  66   a  and the second transverse guiding groove  66   b  are arranged substantially in a line. In addition, the main body  56  of the first unit  48  is provided with an aperture  68  between the first transverse guiding hole  64   a  and the second transverse guiding hole  64   b . Moreover, the front wall  58  of the first unit  48  is provided with a mounting portion (e.g., mounting holes  70 ) which, together with a mounting element (not shown), allows the first unit  48  to be mounted to the drawer  10 , and yet the mounting method of the first unit  48  is not limited to the above. The sidewall  60  of the first unit  48  includes a threaded hole  72 . 
     The second unit  50  includes a main body  74 , a first sidewall  76  located at a lateral side of the main body  74 , and a second sidewall  78  located at the opposite lateral side of the main body  74  and facing the first sidewall  76 . 
     The main body  74  of the second unit  50  corresponds in position to the main body  56  of the first unit  48 . The main body  74  of the second unit  50  has at least one transverse guiding portion  80  corresponding in position to and located at the transverse guiding portion  62  of the first unit  48  so as to be guided by the transverse guiding portion  62  of the first unit  48 . Here, the at least one transverse guiding portion  80  of the second unit  50  is implemented by a first protruding block  82   a  and a second protruding block  82   b  by way of example. Thus, with the first protruding block  82   a  and the second protruding block  82   b  of the second unit  50  corresponding in position to the first transverse guiding hole  64   a  and the second transverse guiding hole  64   b  of the first unit  48  respectively, the second unit  50  can slide smoothly relative to the first unit  48 . In an embodiment which is not shown, however, the at least one transverse guiding portion  80  of the second unit  50  is one or more transverse guiding holes corresponding in position to one or more protruding blocks (i.e., the at least one transverse guiding portion  62 ) of the first unit  48 . 
     In one preferred embodiment, the main body  74  of the second unit  50  further includes a transverse hole  84  whose dimensions, in particular the transverse width, are greater than those of the aperture  68  of the first unit  48 . A first connecting element  86  is passed through the transverse hole  84  of the second unit  50  and the aperture  68  of the first unit  48  to connect the first unit  48  and the second unit  50 . Moreover, the first connecting element  86 , once positioned in the transverse hole  84  and the aperture  68 , serves to guide and facilitate the sliding action of the second unit  50  relative to the first unit  48 . 
     Preferably, a front portion of the main body  74  of the second unit  50  further includes an edge  88  to be pressed against the first transverse guiding groove  66   a  and the second transverse guiding groove  66   b  of the first unit  48 . The edge  88  of the main body  74  of the second unit  50  includes a protruding portion  90  for indicating the displacement distance of the second unit  50  relative to the first unit  48 . In addition, the first sidewall  76  of the second unit  50  includes a hanging hole  92 , and the second sidewall  78  of the second unit  50  has a wall hole  94 . 
     The engaging element  52  is connected to the second unit  50 . The engaging element  52  has a main body  96 , an engaging portion  98  located at a lateral side of the main body  96 , an elastic arm  100  located at the opposite lateral side of the main body  96 , and a slot  102  in the main body  96 . In one preferred embodiment, the engaging element  52  is pivotally connected to the second unit  50  via a second connecting element  104 . Thus, when subjected to a rotating force, the engaging element  52  can be pivoted relative to the second unit  50  by a predetermined angle. 
     At least a portion of the engaging portion  98  is located and mounted in the mounting hole  46  of the second rail  34  (as can be seen more clearly in  FIG. 5   b ). More specifically, when the engaging element  52  is pivotally connected to the main body  74  of the second unit  50 , the engaging portion  98  of the engaging element  52  corresponds in position to the wall hole  94  in the second sidewall  78  of the second unit  50  and can be adjusted in position by means of the adjusting element  28 . The engaging portion  98  of the engaging element  52 , once extending through the wall hole  94  of the second unit  50 , can be engaged in the mounting hole  46  of the second rail  34  to connect the first front connecting device  12  to the second rail  34 . 
     In one preferred embodiment, the engaging portion  98  of the engaging element  52  has a step-like structure to adapt to mounting errors between the first front connecting device  12  and the mounting hole  46  of the second rail  34 . For example, if a first mounting error (or a first distance error) exists between the engaging portion  98  of the engaging element  52  and the mounting hole  46  of the second rail  34 , the first front connecting device  12  can be mounted in the mounting hole  46  of the second rail  34  via a first stage of the step-like structure. Similarly, if a second mounting error (or a second distance error) exists between the engaging portion  98  of the engaging element  52  and the mounting hole  46  of the second rail  34 , the first front connecting device  12  can be mounted in the mounting hole  46  of the second rail  34  via a second stage of the step-like structure. It should be understood, however, that the engaging portion  98  of the engaging element  52  may adapt to the mounting errors between the first front connecting device  12  and the mounting hole  46  of the second rail  34  in ways other than described above. The elastic arm  100  extends from a portion of the main body  96  of the engaging element  52  and is located on the lateral side of the main body  96  that is opposite the engaging portion  98 . The elastic arm  100  is generally U-shaped and has an end portion to contact against the second unit  50 . 
     The disengaging element  54  is pivotally connected to the main body  74  of the second unit  50  via a third connecting element  106 . The disengaging element  54  has a disengaging portion  108  located in the slot  102  of the main body  96  of the engaging element  52 . The disengaging portion  108  is substantially an elliptic cylinder (but is not limited thereto) and is in contact with the wall surface of the slot  102 . 
     The adjusting element  28  has an adjusting portion  110  and a screw rod  112 . The screw rod  112  is connected to the first unit  48  and the second unit  50 . More specifically, the screw rod  112  of the adjusting element  28  is threadedly connected to the threaded hole  72  of the first unit  48 , and the second unit  50  hangs on the neck  114  of the screw rod  112  via the hanging hole  92 . 
     Referring to  FIG. 4   a  and  FIG. 4   b , the first unit  48  is marked with a plurality of characteristic marks, including a first characteristic mark K 1 , a second characteristic mark K 2 , a third characteristic mark K 3 , a fourth characteristic mark K 4 , and a fifth characteristic mark K 5 . If a mounting error S 1  (distance error) exceeding an allowable range exists between the engaging portion  98  of the engaging element  52  of the first front connecting device  12  and the mounting hole  46  of the second rail  34  of the first slide rail assembly  16  (at which time the protruding portion  90  of the second unit  50  is located at the third characteristic mark K 3 , indicating a first position of the second unit  50 ), the engaging portion  98  of the engaging element  52  of the first front connecting device  12  cannot extend, let alone be mounted, into the mounting hole  46  of the second rail  34  of the first slide rail assembly  16  without the operator rotating the adjusting portion  110  of the adjusting element  28 . In other words, unless the adjusting portion  110  of the adjusting element  28  is rotated, the first front connecting device  12  in this position cannot be connected to the second rail  34  of the first slide rail assembly  16 . 
     With reference to  FIG. 5   a , when the adjusting portion  110  of the adjusting element  28  is rotated, the second unit  50  is displaced relative to the second rail  34  of the first slide rail assembly  16 . As the engaging element  52  is connected to the second unit  50 , the distance between the engaging portion  98  of the engaging element  52  and the mounting hole  46  of the second rail  34  is adjusted with the displacement of the second unit  50 . More specifically, when the adjusting portion  110  of the adjusting element  28  is rotated (at which time the protruding portion  90  of the second unit  50  is displaced from the third characteristic mark K 3  to the fifth characteristic mark K 5 , meaning that the second unit  50  is moved from the first position to a second position), the second unit  50  is displaced stably toward the first slide rail assembly  16  due to, referring back to  FIG. 3 , the guiding relationships between the first protruding block  82   a  of the second unit  50  and the first transverse guiding hole  64   a  of the first unit  48 , the guiding relationship between the second protruding block  82   b  of the second unit  50  and the second transverse guiding hole  64   b  of the first unit  48 , the guiding relationship between the first connecting element  86  and the transverse hole  84 , and the guiding relationship between the edge  88  of the second unit  50  and the first and second transverse guiding grooves  66   a ,  66   b  of the first unit  48 . When displaced along with the second unit  50 , the engaging portion  98  of the engaging element  52  is first pressed against a sidewall of the second rail  34  of the first slide rail assembly  16 . As a result, the engaging element  52  is pivoted by the predetermined angle due to the second connecting element  104 . In the meantime, the elastic arm  100  of the engaging element  52  is compressed and stores an elastic energy. 
     Referring to  FIG. 5   b , when the first front connecting device  12  is further moved such that the engaging portion  98  of the engaging element  52  corresponds in position to the mounting hole  46  of the second rail  34  of the first slide rail assembly  16 , the elastic energy stored in the elastic arm  100  is released, and the engaging portion  98  of the engaging element  52  springs into and is thereby mounted in the mounting hole  46  of the second rail  34 . Thus, the problem associated with the mounting error S 1  is solved, allowing the first front connecting device  12  to be securely connected to the second rail  34  of the first slide rail assembly  16 . 
     As shown in  FIG. 5   a  and  FIG. 5   b , once the second unit  50  is displaced relative to the second rail  34  of the first slide rail assembly  16  in response to the rotation of the adjusting portion  110  of the adjusting element  28 , the engaging portion  98  of the engaging element  52  can be displaced relative to the mounting hole  46  of the second rail  34  of the first slide rail assembly  16 . 
     Referring to  FIG. 6   a  and  FIG. 6   b , when it is desired to remove the engaging portion  98  of the engaging element  52  from the position shown in  FIG. 5   b , i.e., from the mounting hole  46  of the second rail  34  of the first slide rail assembly  16 , the operator only has to pivot the disengaging element  54  in such a way that the disengaging portion  108  of the disengaging element  54  is rotated and pressed against the wall surface of the slot  102  of the engaging element  52 , and the disengaging portion  108  will pivot the engaging element  52  by the predetermined angle by means of the wall surface of the slot  102 , allowing the engaging portion  98  of the engaging element  52  to displace relative to and separate from the second rail  34  ( FIG. 6   b  showing the engaging portion  98  of the engaging element  52  retracted into the second unit  50  after being rotated). Thus, the connection between the first front connecting device  12  and the second rail  34  of the first slide rail assembly  16  is cut off. 
     As shown in  FIG. 7 , the first rear connecting device  24  includes a main body  116  and a movable element  118  in addition to the locking element  30 . 
     The main body  116  includes a supporting portion  120  and a transverse portion  122  substantially perpendicularly connected to the supporting portion  120 . In one preferred embodiment, the supporting portion  120  of the main body  116  includes a first vertical wall  112   a  and a second vertical wall  112   b . The first vertical wall  112   a  and the second vertical wall  112   b  are respectively and substantially perpendicularly connected to two opposite lateral sides of the transverse portion  122  of the main body  116 . The first rear connecting device  24  includes at least one connecting hole  124  through which a connecting element (not shown) is passed to mount the first rear connecting device  24  to the rear portion  20   b  of the second rail  34  of the first slide rail assembly  16  (see  FIG. 1 ). Alternatively, the first rear connecting device  24  may be integrally formed with the rear portion  20   b  of the second rail  34  of the first slide rail assembly  16 . 
     In one preferred embodiment, the transverse portion  122  of the main body  116  includes a plurality of fixing portions  126  which are arranged at intervals. Each fixing portion  126  of the transverse portion  122  of the main body  116  is a recess  128 . In addition, each of the first vertical wall  112   a  and the second vertical wall  112   b  has a through hole  130 , and the through holes  130  correspond in position to each other. 
     The locking element  30  is pivotally connected to the supporting portion  120  of the main body  116 . The locking element  30  includes a head  132  and a locking rod  134  connected to the head  132 , wherein the locking rod  134  has a contact portion  136 . The locking rod  134  of the locking element  30  is pivotally provided in the through holes  130  of the first vertical wall  112   a  and the second vertical wall  112   b.    
     The movable element  118  is movably provided between the main body  116  and the locking element  30 . The movable element  118  includes a first plate portion  138   a  and a second plate portion  138   b  perpendicular to the first plate portion  138   a.    
     Preferably, the first plate portion  138   a  of the movable element  118  includes a fixing portion  140  corresponding in position to one of the fixing portions  126  of the transverse portion  122  of the main body  116 . The fixing portion  140  of the first plate portion  138   a  is a rib  142  corresponding in structure to each recess  128  in the transverse portion  122  of the main body  116 . Moreover, the movable element  118  has a width L 1  less than a width L 2  between the first vertical wall  112   a  and the second vertical wall  112   b  of the main body  116 . This allows the movable element  118  to move between the first vertical wall  112   a  and the second vertical wall  112   b  of the main body  116 . 
     Referring to  FIG. 8   a , when the head  132  of the locking element  30  is rotated to a first position, the contact portion  136  of the locking rod  134  of the locking element  30  is pressed against the first plate portion  138   a  of the movable element  118  such that the rib  142  of the first plate portion  138   a  of the movable element  118  is engaged in one of the recesses  128  of the transverse portion  122  of the main body  116 . It can be known from the above that, by means of the locking element  30 , the first plate portion  138   a  of the movable element  118  can be fixed at the mounting position to enable alignment of the drawer  10  (see  FIG. 1 ), i.e., allowing the back panel of the drawer  10  to align with and be mounted to the first plate portion  138   a.    
     Referring to  FIG. 8   b , when mounting errors prevent the drawer  10  from being aligned with the first plate portion  138   a  of the movable element  118 , the operator can rotate the head  132  of the locking element  30  from the first position to a second position so that the contact portion  136  of the locking rod  134  of the locking element  30  is no longer pressed against the first plate portion  138   a  of the movable element  118 . This allows the rib  142  of the first plate portion  138   a  of the movable element  118  to disengage from the one of the recesses  128  of the transverse portion  122  of the main body  116 , and consequently the movable element  118  to displace relative to the main body  116 . As shown in  FIG. 9 , the movable element  118 , which includes the first plate portion  138   a , can be adjusted in position to adapt to mounting errors between the drawer  10  and the first plate portion  138   a  of the movable element  118 , thereby eliminating the difficulty of alignment therebetween. 
     Referring to  FIG. 10 , once the position of a positioning hole  146  in the back panel  144  of the drawer  10  is determined, the operator can operate the locking element  30  so that, by adjusting the position of the movable element  118 , which includes the first plate portion  138   a , the first plate portion  138   a  is aligned with the positioning hole  146  in the back panel  144  of the drawer  10  to eliminate mounting errors between the back panel  144  of the drawer  10  and the first plate portion  138   a  of the movable element  118 . 
       FIG. 11   a  and  FIG. 11   b  show the second embodiment of the rear connecting device. This embodiment is different from the embodiment in  FIG. 8   a  and  FIG. 8   b  only in that each fixing portion of the transverse portion  202  of the main body  200  is a rib  204 , and that the fixing portion of the first plate portion  208  of the movable element  206  is a recess  210 . As the second embodiment has the same technical effects as the embodiment in  FIG. 8   a  and  FIG. 8   b , further description is omitted here for brevity. 
       FIG. 12   a  and  FIG. 12   b  show the third embodiment of the rear connecting device. This embodiment is different from the embodiments in  FIGS. 8   a ,  8   b  and  FIGS. 11   a ,  11   b  only in that each fixing portion  304  of the transverse portion  302  of the main body  300  is a flat surface (without any rib or recess), and that the fixing portion  310  of the first plate portion  308  of the movable element  306  is also a flat surface (without any rib or recess). The third embodiment has substantially the same technical effects as the embodiments in  FIGS. 8   a ,  8   b  and  FIGS. 11   a ,  11   b.    
     More specifically, referring to  FIG. 12   a , when the head  314  of the locking element  312  is rotated to a first position, the contact portion  318  of the locking rod  316  is pressed against the first plate portion  308  of the movable element  306 ; as a result, the movable element  306  is fixed to the main body  300  by friction. Referring to  FIG. 12   b , once the head  314  of the locking element  312  is rotated from the first position to a second position, the contact portion  318  of the locking rod  316  is no more pressed against the first plate portion  308  of the movable element  306 , and the movable element  306  is therefore allowed to displace relative to the main body  300 . 
     While the present invention has been disclosed through the foregoing preferred embodiments, it is understood that the embodiments are not intended to restrict the scope of the present invention. The scope of the present invention is defined by the appended claims.