Patent Publication Number: US-10323438-B2

Title: Two-point lock

Description:
FIELD 
     The disclosure relates to a locking device, and more particularly to a two-point lock. 
     BACKGROUND 
     A conventional multi-point lock disclosed in U.S. Pat. No. 6,264,252 is for use in a sliding door, and includes two hook members, two rotary operating members, two rod members each of which is pivotally connected between a respective one of the hook members and a respective one of the rotary operating members, and an interlink member that pivotally interconnects the rotary operating members. When one of the rotary operating members is rotated to drive rotation of the corresponding one of the hook members via the corresponding one of the rod members, the other one of the hook members is also driven to synchronously rotate via the interlink member, the other one of the rotary operating members and the other one of the rod members. However, such a structure is relatively complex. Moreover, the hook members may easily be rotated non-synchronously after long term use of the conventional multi-point lock. 
     Referring to  FIGS. 1, 2 and 3 , a conventional two-point lock disclosed in U.S. Pat. No. 8,376,414 is for use in a sliding door, and includes an outer casing  1 , a locking unit  2  movably mounted to the outer casing  1 , and an adjusting unit  3  disposed between the outer casing  1  and locking unit  2  and operable to move the locking unit  2  relative to the outer casing  1 . The locking unit  2  includes a mounting casing  201  that is movable relative to the outer casing  1  in a first direction, two hook members  202  that are pivotally mounted to the mounting casing  201 , an actuating plate  203  (see  FIG. 3 ) that is movable relative to the mounting casing  201  in a second direction transverse to the first direction for driving rotation of the hook members  202 , a rotary operating member  204  that is pivotally mounted to the mounting casing  201 , a link member  205  (see  FIG. 3 ) that is pivotally connected between the actuating plate  203  and the rotary operating member  204 , and a torsion spring  206  (see  FIG. 3 ) that is disposed between the rotary operating member  204  and a rod portion  207  of the mounting casing  201 . Each of the hook members  202  has a driven pin portion  208  (see  FIG. 3 ). The actuating plate  203  has two actuating grooves  209  (see  FIG. 3 ) respectively and slidably engaged with the pin portions  208  of the hook members  203 . 
     When the rotary operating member  204  is rotated to move the actuating plate  203  in the second direction via the link member  205 , the hook members  202  are driven by the actuating plate  203  to perform locking or unlocking operation. However, with particular reference to  FIGS. 1 and 2 , to adjust an extent (H) by which the hook members  202  extend out of the outer casing  1 , the adjusting unit  3  is operated to move the whole locking unit  2  relative to the outer casing  1 . In other words, the conventional two-point lock of U.S. Pat. No. 8,376,414 employs such a structure that includes inner and outer casings (i.e., the mounting casing  201  and the outer casing  1 ) in order to adjust the extent (H) by which the hook members  202  extend out of the outer casing  1 . Such double-casing structure may increase the weight of the whole conventional two-point lock, and increase the manufacturing cost of the conventional two-point lock as well. 
     Moreover, with particular reference to  FIG. 3 , the rotary operating member  204  is simply pivotally connected to the link member  205 , and a lengthwise extending line of the rotary operating member  204  cooperates with a horizontal line to form a relatively small angle (θ, about 35 degrees) therebetween when the hook members  202  are at an unlocking position. As such, in the beginning of the operation of the rotary operating member  204  to move each of the hook members  202  away from the unlocking position, a user needs to rotate the rotary operating member  204  to generate a resultant force (F) much greater than a horizontal component (Fx) thereof that is required for moving the actuating plate  203 . In this case, F=Fx/sin θ=Fx/sin 35°=1.7Fx. More specifically, the user needs to rotate the rotary operating member  204  to generate 1.7 times the required force to move the actuating plate  203 . Such operation is also laborious. In addition, the torsion spring  206  deforms considerably during the operation of the rotary operating member  204 , and may therefore occupy a relatively large space in the outer casing  1 . 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a two-point lock that employs a single element for driving two hook members adjustable in projecting extent independently of each other, and that has a simplified casing structure. 
     According to the disclosure, the two-point lock includes an elongated casing unit, an adjusting unit and a locking unit. The casing unit extends in a first direction. The adjusting unit includes a pair of first adjusting guide plates that are pivoted to and disposed in the casing unit and that are spaced apart from each other, a first adjusting assembly that is disposed to the casing unit, a pair of second adjusting guide plates that are pivoted to and disposed in the casing unit and that are spaced apart from each other, and a second adjusting assembly that is disposed to the casing unit. Each of the first adjusting guide plates has a first arc-shaped groove. The first adjusting assembly includes a first adjusting bolt that is rotatably mounted to the casing unit, and a first nut member that is engaged threadably with the first adjusting bolt and that is coupled to the first adjusting guide plates. The first adjusting bolt is rotatable to move the first nut member so as to rotate the first adjusting guide plates relative to the casing unit. The second adjusting guide plates are spaced apart from the first adjusting guide plates in the first direction. Each of the second adjusting guide plates has a second arc-shaped groove. The second adjusting assembly includes a second adjusting bolt that is rotatably mounted to the casing unit, and a second nut member that is engaged threadably with the second adjusting bolt and that is coupled to the second adjusting guide plates. The second adjusting bolt is rotatable to move the second nut member so as to rotate the second adjusting guide plates relative to the casing unit. The locking unit includes a first hook member that is pivotable between the first adjusting guide plates, a second hook member that is pivotable between the second adjusting guide plates, an actuating guide plate that is disposed between the first adjusting guide plates and between the second adjusting guide plates and that is substantially movable in the first direction, a rotary operating member that is rotatably disposed on the casing unit, and a link member that is connected between the actuating guide plate and the rotary operating member. The first hook member has a first driven pin portion that movably engages the first arc-shaped grooves of the first adjusting guide plates, and a first pivoted pin portion that is pivoted to the first adjusting guide plates. The second hook member has a second driven pin portion that movably engages the second arc-shaped grooves of the second adjusting guide plates, and a second pivoted pin portion that is pivoted to the second adjusting guide plates. The actuating guide plate has a first driving groove that is movably engaged with the first driven pin portion of the first hook member, a second driving groove that is movably engaged with the second driven pin portion of the second hook member, a first guiding groove that extends in the first direction and that is movably engaged with the first pivoted pin portion of the first hook member, and a second guiding groove that extends in the first direction and that is movably engaged with the second pivoted pin portion of the second hook member. The rotary operating member is located outside a space between the first and second hook members, and is adjacent to an end of the casing unit in the first direction. The rotary operating member is operable to move the actuating guide plate in the first direction via the link member, so as to move each of the first and second hook members relative to the casing unit between an unlocking position and a locking position. When the first and second hook members are at the unlocking position, the first and second hook members are located within the casing unit. When the first and second hook members are at the locking position, the first and second hook members extend out of the casing unit. When the first and second hook members move between the unlocking position and locking position, the first driven pin portion of the first hook member moves along the first arc-shaped grooves of the first adjusting guide plates, and the second driven pin portion of the second hook member moves along the second arc-shaped grooves of the second adjusting guide plates. The first adjusting guide plates and the first adjusting assembly are operable to adjust an extent by which the first hook member extends out of the casing unit when the first hook member is at the locking position. The second adjusting guide plates and the second adjusting assembly are operable to adjust an extent by which the second hook member extends out of the casing unit when the second hook member is at the locking position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic side view illustrating a conventional two-point lock disclosed in U.S. Pat. No. 8,376,414; 
         FIG. 2  is another schematic side view illustrating the conventional two-point look; 
         FIG. 3  is still another schematic side view illustrating the conventional two-point look; 
         FIG. 4  is a perspective view illustrating an embodiment of the two-point lock according to the disclosure; 
         FIG. 5  is an exploded perspective view illustrating the embodiment; 
         FIG. 6  is a schematic side view illustrating first and second hook members of the embodiment, each of which is at an unlocking position; 
         FIG. 7  is another schematic side view illustrating the first and second hook members, each of which is at an unlocking position; 
         FIG. 8  is still another schematic side view illustrating the first and second hook members, each of which is at a locking position; 
         FIG. 9  is still another schematic side view illustrating the first and second hook members, each of which is at the locking position; 
         FIG. 10  is a schematic view illustrating operation of the embodiment for moving each of the first and second hook members to the locking position; 
         FIG. 11  is a schematic side view illustrating cooperation of a rotary operating member and a link member of the embodiment; 
         FIG. 12  is a schematic view illustrating operation of the embodiment for moving each of the first and second hook members to the unlocking position; and 
         FIG. 13  is a schematic side view illustrating cooperation of the rotary operating member and the link member. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 4 and 5 , the embodiment of the two-point lock according to the disclosure includes an elongated casing unit  10 , an adjusting unit  20 , a locking unit  30  and a safety unit  40 . 
     The casing unit  10  extends in a first direction (X), and includes two side walls  11  that are spaced apart from each other, a first axle portion  12  that is disposed between the side walls  11 , a second axle portion  13  that is disposed between the side walls  11  and that is spaced apart from the first axle portion  12 , a surrounding wall  14  that is integrally connected to one of the side walls  11 , and an end wall  15  that is integrally connected to the one of the side walls  11  and the surrounding wall  14 . It should be noted that, in the drawings of this disclosure, the first direction (X) is illustrated as a horizontal direction. However, in general use, the two-point lock is mounted to a sliding door (not shown), and the first direction (X) extends vertically. 
     In this embodiment, each of the side walls  11  has a first height limiting groove  111 , and a second height limiting groove  112  that is spaced apart from the first height limiting groove  111 . Each of the first and second axle portions  12 ,  13  integrally extends from the one of the side walls  11  and connected to the other one of the side walls  11 . The end wall  15  has two through grooves  151 . 
     Referring to  FIGS. 5, 6 and 7 , the adjusting unit  20  includes a pair of first adjusting guide plates  21  that are pivoted to and disposed in the casing unit  10  and that are spaced apart from each other, a first adjusting assembly  22  that is disposed to the casing unit  10 , a pair of second adjusting guide plates  23  that are pivoted to and disposed in the casing unit  10  and that are spaced apart from each other, and a second adjusting assembly  24  that is disposed to the casing unit  10 . 
     The first adjusting assembly  22  includes a first adjusting bolt  221  that is rotatably mounted to the end wall  15  of the casing unit  10 , and a first nut member  222  that is engaged threadably with the first adjusting bolt  221 . 
     In this embodiment, each of the first adjusting guide plates  21  has a first pivoted end portion  211  that is pivoted to the casing unit  10 , a first adjusting end portion  212  that is coupled to the first nut member  222  of the first adjusting assembly  22 , a first intermediate portion  213  that is connected between the first pivoted end portion  211  and the first adjusting end portion  212 , a first arc-shaped groove  214  that is formed in the first intermediate portion  213 , a first pivot hole  215  that is formed in the first intermediate portion  213 , a first axle hole  216  that is formed in the first pivoted end portion  211 , and a first engaging groove  217  that is formed in the first adjusting end portion  212 . For each of the first adjusting guide plates  21 , the first pivot hole  215  is located at the center of curvature of the first arc-shaped groove  214 . The first axle hole  216  of each of the first adjusting guide plates  21  permits the first axle portion  12  of the casing unit  10  to rotatably extend therethrough, so that the first adjusting guide plates  21  are pivotable about the first axle portion  12  of the casing unit  10 . 
     In this embodiment, the first nut member  222  of the first adjusting assembly  22  movably engages the first engaging groove  217  of each of the first adjusting guide plates  21 . The first adjusting bolt  221  is rotatable to drive the first nut member  222  to move in a second direction (Z) that is perpendicular to the first direction (X), so as to rotate the first adjusting guide plates  21  relative to the casing unit  10 . 
     The second adjusting assembly  24  includes a second adjusting bolt  241  that is rotatably mounted to the end wall  15  of the casing unit  10 , and a second nut member  242  that is engaged threadably with the second adjusting bolt  241 . 
     The second adjusting guide plates  23  are spaced apart from the first adjusting guide plate  21  in the first direction (X). In this embodiment, each of the second adjusting guide plates  23  has a second pivoted end portion  231  that is pivoted to the casing unit  10 , a second adjusting end portion  232  that is coupled to the second nut member  242  of the second adjusting assembly  24 , a second intermediate portion  233  that is connected between the second pivoted end portion  231  and the second adjusting end portion  232 , a second arc-shaped groove  234  that is formed in the second intermediate portion  233 , a second pivot hole  235  that is formed in the second intermediate portion  233 , a second axle hole  236  that is formed in the second pivoted end portion  231 , and a second engaging groove  237  that is formed in the second adjusting end portion  232 . For each of the second adjusting guide plates  23 , the second pivot hole  235  is located at the center of curvature of the second arc-shaped groove  234 . The second axle hole  236  of each of the second adjusting guide plates  23  permits the second axle portion  13  of the casing unit  10  to rotatably extend therethrough, so that the second adjusting guide plates  23  are pivotable about the second axle portion  13  of the casing unit  10 . 
     In this embodiment, the second nut member  242  of the second adjusting assembly  24  movably engages the second engaging groove  237  of each of the second adjusting guide plates  23 . The second adjusting bolt  241  is rotatable to drive the second nut member  242  to move in the second direction (Z), so as to rotate the second adjusting guide plates  23  relative to the casing unit  10 . 
     The locking unit  30  includes a first hook member  31  that is pivotable between the first adjusting guide plates  21 , a second hook member  32  that is pivotable between the second adjusting guide plates  23 , an actuating guide plate  33  that is disposed between the first adjusting guide plates  21  and between the second adjusting guide plates  23  and that is substantially movable in the first direction (X), a rotary operating member  34  that is rotatably disposed on the casing unit  10 , a link member  35  that is connected between the actuating guide plate  33  and the rotary operating member  34 , and a positioning resilient plate  36  that is disposed between the rotary operating member  34  and the casing unit  10 . 
     In this embodiment, the first hook member  31  has a base portion  311 , a hook portion  312  that extends from the base portion  311 , a first driven pin portion  313  that is disposed at the base portion  311  and that slidably engages the first arc-shaped grooves  214  of the first adjusting guide plates  21 , and a first pivoted pin portion  314  that is disposed at the base portion  311 , that rotatably engages the first pivot holes  215  of the first adjusting guide plates  21 , and that slidably engages the first height limiting grooves  111  of the side walls  11  of the casing unit  10 . 
     In this embodiment, the second hook member  32  has a base portion  321 , a hook portion  322  that extends from the base portion  321 , a second driven pin portion  323  that is disposed at the base portion  321  and that slidably engages the second arc-shaped grooves  234  of the second adjusting guide plates  23 , and a second pivoted pin portion  324  that is disposed at the base portion  321 , that rotatably engages the second pivot holes  235  of the second adjusting guide plates  23 , and that slidably engages the second height limiting grooves  112  of the side walls  11  of the casing unit  10 . 
     In this embodiment, the actuating guide plate  33  has a first plate portion  330  that corresponds in position to the first hook member  31 , a second plate portion  331  that corresponds in position to the second hook member  32 , an intermediate portion  332  that is connected between the first and second plate portions  330 ,  331 , an extension portion  333  that extends from the second plate portion  331  away from the first plate portion  330  in the first direction (X), a first driving groove  334  that is formed in the first plate portion  330  and that is slidably engaged with the first driven pin portion  313  of the first hook member  31 , a second driving groove  335  that is formed in the second plate portion  331  and that is slidably engaged with the second driven pin portion  323  of the second hook member  32 , a first guiding groove  336  that extends in the first direction (X) and that is slidably engaged with the first pivoted pin portion  314  of the first hook member  31 , a second guiding groove  337  that extends in the first direction (X) and that is slidably engaged with the second pivoted pin portion  324  of the second hook member  32 , a safety limiting groove  338  that is formed in the extension portion  333 , and a through groove  339  that is formed in the intermediate portion  332  and that permits the second nut member  242  to extend therethrough for preventing the actuating guide plate  33  from interfering with some components. 
     The first driving groove  334  has a first groove portion  3341  that extends in the first direction (X), and a second groove portion  3342  that is substantially perpendicular to the first groove portion  3341 . The second driving groove  335  has a first groove portion  3351  that extends in the first direction (X), and a second groove portion  3352  that is substantially perpendicular to the first groove portion  3351 . The first guiding groove  336  is formed in the first plate portion  330 . The second guiding groove  337  is formed in the second plate portion  331 . 
     In this embodiment, the link member  35  has an imaginary reference line  350 , a first end portion  351  that is pivotally connected to the first plate portion  330  of the actuating guide plate  33 , a second end portion  352  that is opposite to the first end portion  351 , and an elongated groove  353  that extends along the imaginary reference line  350  and that is proximate to the second end portion  352 . 
     The rotary operating member  34  is located outside a space between the first and second hook members  31 ,  32 , and is adjacent to an end of the casing unit  10  in the first direction (X). In this embodiment, the rotary operating member  34  has an input end portion  341  that is pivoted to the side walls  11  of the casing unit  10 , an output end portion  342  that is opposite to the input end portion  341 , a guiding pin portion  343  that is disposed at the output end portion  342  and that slidably engages the elongated groove  353  of the link member  35 , and an imaginary reference line  344  extending along the output end portion  342 . The input end portion  341  is formed with first and second positioning surfaces  345 ,  346 . 
     In this embodiment, the rotary operating member  34  is operable to move the actuating guide plate  33  in the first direction (X) via the link member  35 , so as to move each of the first and second hook members  31 ,  32  relative to the casing unit  10  between an unlocking position (see  FIGS. 6 and 7 ) and a locking position (see  FIGS. 8 and 9 ). 
     Referring to  FIGS. 6 and 7 , when each of the first and second hook members  31 ,  32  is at the unlocking position, the first and second hook members  31 ,  32  are located wholly within the casing unit  10 , the first driven pin portion  313  of the first hook member  31  engages the second groove portion  3342  of the first driving groove  334 , the second driven pin portion  323  of the second hook member  32  engages the second groove portion  3352  of the second driving groove  335 , the first positioning surface  345  is in abutment with the positioning resilient plate  36  so as to position the rotary operating member  34  relative to the casing unit  10 , and the second positioning surface  346  is spaced apart from the positioning resilient plate  36 . 
     Referring to  FIGS. 8 and 9 , when the each of first and second hook members  31 ,  32  is at the locking position, the hook portions  312 ,  322  of the first and second hook members  31 ,  32  extend out of the casing unit  10  through the through grooves  151 , respectively, the first driven pin portion  313  of the first hook member  31  engages the first groove portion  3341  of the first driving groove  334 , the second driven pin portion  323  of the second hook member  32  engages the first groove portion  3351  of the second driving groove  335 , the first positioning surface  345  is spaced apart from the positioning resilient plate  36 , and the second positioning surface  346  is in abutment with the positioning resilient plate  36  so as to position the rotary operating member  34  relative to the casing unit  10 . At this time, the first driven pin portion  313  of the first hook member  31  is prevented from moving into the second groove portion  3342  of the first driving groove  334 , and the second driven pin portion  323  of the second hook member  32  is prevented from moving into the second groove portion  3352  of the second driving groove  335 , unless the actuating guide plate  33  is moved. More specifically, the first driven pin portion  313  of the first hook member  31  is positioned within the first groove portion  3341  of the first driving groove  334  so that the first hook member  31  is prevented from rotating about the center of the first pivoted pin portion  314  thereof, and the second driven pin portion  323  of the second hook member  32  is positioned within the first groove portion  3351  of the second driving groove  335  so that the second hook member  32  is prevented from rotating about the center of the second pivoted pin portion  324  thereof. As a result, the two-point lock of this disclosure is prevented from being picked by directly applying force on the hook portions  312 ,  322  of the first and second hook members  31 ,  32  when each of the first and second hook members  31 ,  32  is at the locking position. 
     As shown in  FIGS. 6 and 8 , when each of the first and second hook members  31 ,  32  moves between the unlocking position and locking position, the first driven pin portion  313  of the first hook member  31  moves along the first arc-shaped grooves  214  of the first adjusting guide plates  21 , and the second driven pin portion  323  of the second hook member  32  moves along the second arc-shaped grooves  234  of the second adjusting guide plates  23 . The first arc-shaped grooves  214  of the first adjusting guide plates  21 , and the second arc-shaped grooves  234  of the second adjusting guide plates  23  are configured to limit the range of rotation of each of the first and second hook members  31 ,  32 . 
     In addition, as shown in  FIGS. 8 and 9 , the first adjusting guide plates  21  and the first adjusting assembly  22  are operable to adjust an extent (H 1 ) by which the hook portion  312  of the first hook member  31  extends out of the casing unit  10  when the first hook member  31  is at the locking position, and the second adjusting guide plates  23  and the second adjusting assembly  24  are operable to adjust an extent (H 2 ) by which the hook portion  322  of the second hook member  32  extends out of the casing unit  10  when the second hook member  32  is at the locking position. 
     When the first adjusting bolt  221  is rotated, the first nut member  222  is driven to move in the second direction (Z) to rotate the first adjusting guide plates  21  relative to the casing unit  10 , so as to move the first hook member  31  substantially in the second direction (Z). The first height limiting grooves  111  of the side walls  11  of the casing unit  10  are configured to limit the range of the movement of the first hook member  31  in the second direction (Z). Since the first driven pin portion  313  of the first hook member  31  engages the first driving groove  334  and the first pivoted pin portion  314  of the first hook member  31  engages the first guiding groove  336  of the actuating guide plate  33 , the movement of the first hook member  31  results in movement of the actuating guide plate  33  within the casing unit  10 . 
     Similarly, when the second adjusting bolt  241  is rotated, the second nut member  242  is driven to move in the second direction (Z) to rotate the second adjusting guide plates  23  relative to the casing unit  10 , so as to move the second hook member  32  substantially in the second direction (Z). The second height limiting grooves  112  of the side walls  11  of the casing unit  10  are configured to limit the range of the movement of the second hook member  32  in the second direction (Z). Since the second driven pin portion  323  of the second hook member  32  engages the second driving groove  335  and the second pivoted pin portion  324  of the second hook member  32  engages the second guiding groove  337  of the actuating guide plate  33 , the movement of the second hook member  32  results in movement of the actuating guide plate  33  within the casing unit  10 . 
     Referring to  FIGS. 5 and 6 , the safety unit  40  includes a safety rod member  41  that is mounted to the end wall  15  of the casing unit  10  and that is movable relative to the casing unit  10  in the second direction (Z), a safety block  42  that is connected to the safety rod member  41  and that is disposed in the casing unit  10 , and a resilient member  43  that has two opposite ends respectively abut against the safety block  42  and the surrounding wall  14  of the casing unit  10 . In this embodiment, the resilient member  43  is configured as a compression spring. The resilient member  43  resiliently biases the safety block  42  toward the extension portion  333  of the actuating guide plate  33 . When each of the first and second hook members  31 ,  32  is at the unlocking position and when the safety rod member  41  is not pressed, the safety block  42  engages the safety limiting groove  338  of the actuating guide plate  33  (see  FIG. 6 ). When each of the first and second hook members  31 ,  32  is at the locking position, the safety block  42  is separated from the safety limiting groove  338  of the actuating guide plate  33  (see  FIG. 6 ). In use with a door plate (not shown), only when the door plate is closed (i.e., the safety rod member  41  is pressed) the actuating guide plate  33  can be driven by the rotary operating member  34  to move each of the first and second hook members  31 ,  32  between the unlocking position and the locking position. When the doorplate is opened (i.e., the safety rod member  41  is not pressed), the safety block  42  engages the safety limiting groove  338  of the actuating guide plate  33  so as to prevent the actuating guide plate  33  from being driven by the rotary operating member  34 , thereby preventing each of the first and second hook members  31 ,  32  from moving away from the unlocking position to bump into a door frame (not shown). 
     Referring to  FIGS. 10 and 11 , to move each of the first and second hook members  31 ,  32  from the unlocking position to the locking position, the rotary operating member  34  is first rotated clockwise such that the guiding pin portion  343  thereof moves along the elongated groove  353  of the link member  35  without driving movement of the actuating guide plate  33  until the guiding pin portion  343  moves to an end of the elongated groove  353  which is distal from the first end portion  351  of the link member  35 . At this time, the imaginary reference line  344  of the rotary operating member  34  cooperates with a horizontal line to form a relatively large angle (θ1, about 76 degrees) therebetween. As such, to move the actuating guide plate  33  for moving the first and second hook members  31 ,  32 , a user needs to further rotate the rotary operating member  34  clockwise to generate a resultant force (F 1 ) slightly greater than a horizontal component (Fx 1 ) thereof that is required for moving the actuating guide plate  33 . In this case, F 1 =Fx 1 /sin θ1=Fx 1 /sin 76°=1.03Fx 1 . In other words, the user only needs to rotate the rotary operating member  34  to generate a force that is 1.03 times the required force to move the actuating guide plate  33 . Such operation is relatively labor-saving. 
     Referring to  FIGS. 12 and 13 , similarly, when each of the first and second hook members  31 ,  32  is moved from the locking position to the unlocking position, the rotary operating member  34  is first rotated counterclockwise such that the guiding pin portion  343  thereof moves along the elongated groove  353  of the link member  35  without driving movement of the actuating guide plate  33  until the guiding pin portion  343  moves to an opposite end of the elongated groove  353  which is proximal to the first end portion  351  of the link member  35 . At this time, the imaginary reference line  344  of the rotary operating member  34  cooperates with the horizontal line to form a relatively large angle (θ2, about 59 degrees) therebetween. As such, to move the actuating guide plate  33  and the first and second hook members  31 ,  32 , a user needs to further rotate the rotary operating member  34  counterclockwise to generate a resultant force (F 2 ) slightly greater than a horizontal component (Fx 2 ) thereof that is required for moving the actuating guide plate  33 . In this case, F 2 =Fx 2 /sin θ2=Fx 2 /sin 59°=1.17Fx 2 . In other words, the user only needs to rotate the rotary operating member  34  to generate a force that is 1.17 times the required force to move the actuating guide plate  33 . Such operation is also relatively labor-saving. 
     The advantages of this disclosure are as follows. 
     1. The first and second hook members  31 ,  32  are synchronously moved by a single element (i.e., the actuating guide plate  33 ), so that the mechanism for actuating the first and second hook members  31 ,  32  is simpler than that of U.S. Pat. No. 6,264,252. 
     2. By virtue of the first adjusting guide plates  21 , the first adjusting assembly  22 , the second adjusting guide plates  23  and the second adjusting assembly  24 , the extent (H 1 ) by which the hook portion  312  of the first hook member  31  extends out of the casing unit  10  and the extent (H 2 ) by which the hook portion  322  of the second hook member  32  extends out of the casing unit  10  can be adjusted independently. Compared with the conventional two-point lock of U.S. Pat. No. 8,376,414, the two-point lock of this disclosure employs a single-casing structure (i.e., the casing unit  10 ) for adjusting the first and second hook members  31 ,  32 , so that the weight thereof and the manufacturing cost thereof can be lowered. 
     3. Since the guiding pin portion  343  of the rotary operating member  34  movably engages the elongated groove  353  of the link member  35 , a user only needs to rotate the rotary operating member  34  to generate a force that is slightly greater than the required force to move the actuating guide plate  33  for moving each of the first and second hook members  31 ,  32  between the unlocking position and the locking position. Such operation is relatively labor-saving. 
     4. The positioning resilient plate  36  deforms slightly during the rotation of the rotary operating member  34  for moving the first and second hook members  31 ,  32 , so that the positioning resilient plate  36  only needs to occupy a relatively small space in the casing unit  10 , and the service life thereof is prolonged. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.