Abstract:
A dual-shaft hinge includes an axle housing, a pivot shaft set including a first pivot shaft and a second pivot shaft respectively pivotally coupled to the axle housing, a transmission mechanism including a first transmission member connected to the first pivot shaft and a second transmission member connected to the second pivot shaft, and a link connected between the first transmission member and the second transmission member in such a manner that the first pivot shaft and the second pivot shaft are rotatable relative to each other and the axle housing is turnable about the second pivot shaft to prevent the problem of a broken component due to overstress, or the problem of a jammed component.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to hinge technology and more particularly, to a dual-shaft hinge, which is practical for use in a dual leaf electronic device to smoothen the pivoting motion of the cover member of the dual leaf electronic device relative to the base member thereof. 
     2. Description of the Related Art 
     Hinges are intensively used in flip-up mobile electronic devices, such as notebooks, smart phones, and etc. to pivotally connect a base member and a cover member together, allowing only a limited angle of rotation between them. Some dual leaf mobile electronic devices allow the cover member to be turned from the top side of the base member to the bottom side thereof, enabling the dual leaf mobile electronic devices to be used as a tablet computer. A hinge for this application is a dual-shaft design. Taiwan Patent Publication Number M460957, equivalent to Chinese Patent CN102261371A, discloses a dual-shaft hinge design. According to this design, a link is used to pivotally couple two pivot shafts in an eccentric manner, wherein rotating one pivot shaft causes the other pivot shaft to be rotated, turning the cover member to the bottom side of the base member. However, using the link to force the two pivot shafts to rotate at the same time can cause concentration of high stress on the connection rods of the two pivot shafts, leading to breaking of the connection rods. Further, because the two pivot shafts are simultaneously rotated, a minor rotation angle deviation can cause a component jam, leading to hinge failure. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a dual-shaft hinge, which uses a link for enabling a first pivot shaft and a second pivot shaft to be rotated relative to each other and an axle housing to be turned about the second pivot shaft to prevent the problem of a broken component due to overstress, or the problem of a jammed component. 
     To achieve this and other objects of the present invention, a dual-shaft hinge of the present invention comprises an axle housing, a pivot shaft set, a transmission mechanism and a link. The axle housing comprises a base, a first bearing portion smoothly curved from a right side of a top wall of the base in direction toward an opposing left side of the top wall, a first pivot shaft chamber defined between the top wall and the first bearing portion, a first gap defined between a distal end of the first bearing portion and the top wall in communication with one lateral side of the first pivot shaft chamber, a second bearing portion smoothly curved from a left side of an opposing bottom wall in direction toward an opposing right side of the bottom wall, a second pivot shaft chamber defined between the bottom wall and the second bearing portion, and a second gap defined between a distal end of the second bearing portion and the bottom wall in communication with one lateral side of the second pivot shaft chamber. The pivot shaft set comprises a first pivot shaft and a second pivot shaft. The first pivot shaft comprises a first shaft body mounted in the first pivot shaft chamber of the axle housing, and a first positioning tip axially extended from one end of the first shaft body. The second pivot shaft comprises a second shaft body mounted in the second pivot shaft chamber of the axle housing, and a second positioning tip axially extended from one end of the second shaft body. The transmission mechanism comprises a first transmission member and a second transmission member. The first transmission member comprises a first connection hole fixedly fastened to the first positioning tip of the first pivot shaft, and a first position-limit rod located at one side thereof adjacent to the first connection hole. The second transmission member comprises a second connection hole fixedly fastened to the second positioning tip of the second pivot shaft, and a second position-limit rod located at one side thereof adjacent to the second connection hole. The link comprises a first position-limit hole and a second position-limit hole respectively disposed near two distal ends thereof and respectively coupled to the first position-limit rod and second position-limit rod of the transmission mechanism. The first position-limit hole defines a first abutment portion near the second position-limit hole, and a second abutment portion remote from the second position-limit hole. Further, the distance between the first abutment portion and the second abutment portion is larger than the outer diameter of the first position-limit rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a dual-shaft hinge in accordance with a first embodiment of the present invention. 
         FIG. 2  corresponds to  FIG. 1  when viewed from another angle. 
         FIG. 3  is an exploded view of the dual-shaft hinge in accordance with the first embodiment of the present invention. 
         FIG. 4  is a front view of the dual-shaft hinge in accordance with the first embodiment of the present invention. 
         FIG. 5  is a rear side view of the dual-shaft hinge in accordance with the first embodiment of the present invention. 
         FIG. 6  is a sectional view taken along line A-A of  FIG. 2 . 
         FIG. 7  is a schematic operational front view of the dual-shaft hinge in accordance with the first embodiment of the present invention (I). 
         FIG. 8  is a schematic operational rear side view of the dual-shaft hinge in accordance with the first embodiment of the present invention (I). 
         FIG. 9  is a schematic operational front view of the dual-shaft hinge in accordance with the first embodiment of the present invention (II). 
         FIG. 10  is a schematic operational rear side view of the dual-shaft hinge in accordance with the first embodiment of the present invention (II). 
         FIG. 11  is a schematic operational front view of the dual-shaft hinge in accordance with the first embodiment of the present invention (III). 
         FIG. 12  is a schematic operational rear side view of the dual-shaft hinge in accordance with the first embodiment of the present invention (III). 
         FIG. 13  is a schematic operational front view of the dual-shaft hinge in accordance with the first embodiment of the present invention (IV). 
         FIG. 14  is a schematic operational rear side view of the dual-shaft hinge in accordance with the first embodiment of the present invention (IV). 
         FIG. 15  is a schematic operational front view of the dual-shaft hinge in accordance with the first embodiment of the present invention (V). 
         FIG. 16  is a schematic operational rear side view of the dual-shaft hinge in accordance with the first embodiment of the present invention (V). 
         FIG. 17  is a schematic operational front view of the dual-shaft hinge in accordance with the first embodiment of the present invention (VI). 
         FIG. 18  is a schematic operational rear view of the dual-shaft hinge in accordance with the first embodiment of the present invention (VI). 
         FIG. 19  is a front view of a dual-shaft hinge in accordance with a second embodiment of the present invention. 
         FIG. 20  is a front view of a dual-shaft hinge in accordance with a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1-6 , a dual-shaft hinge in accordance with a first embodiment of the present invention is shown. The dual-shaft hinge comprises an axle housing  1 , a pivot shaft set  2 , a transmission mechanism  3 , a link  4  and a positioning device set  5 . 
     The axle housing  1  comprises a base  11 , a first bearing portion  12  smoothly curved from one side, namely the right side of a top wall of the base  11  in direction toward an opposite side, namely, the left side of the top wall of the base  11 , a first pivot shaft chamber  13  defined between the top wall of the base  11  and the first bearing portion  12 , a first gap  14  defined between the distal end of the first bearing portion  12  and the top wall of the base  11  in communication with one lateral side of the first pivot shaft chamber  13 , a second bearing portion  15  smoothly curved from one side, namely, the left side of an opposing bottom wall of the base  11  in direction toward an opposite side, namely, the right side of the bottom wall of the base  11 , a second pivot shaft chamber  16  defined between the bottom wall of the base  11  and the second bearing portion  15 , a second gap  17  defined between the distal end of the second bearing portion  15  and the bottom wall of the base  11  in communication with one lateral side of the second pivot shaft chamber  16 , a planar first bearing wall  18  formed integral with the top wall of the base  11 , and a planar second bearing wall  19  formed integral with the bottom wall of the base  11 . 
     The pivot shaft set  2  comprises a first pivot shaft  21  and a second pivot shaft  22 . The first pivot shaft  21  comprises a first shaft body  211 , a first connection bar  212  axially extended from one end of the first shaft body  211 , a first positioning tip  214  axially extended from an opposite end of the first shaft body  211 , a first position-limit flange  213  extended around the periphery of the first shaft body  211  adjacent to the first connection bar  212 , and a first positioning plane  215  axially located on the periphery of the first shaft body  211 . The second pivot shaft  22  comprises a second shaft body  221 , a second connection bar  222  axially extended from one end of the second shaft body  221 , a second positioning tip  224  axially extended from an opposite end of the second shaft body  221 , a second position-limit flange  223  extended around the periphery of the second shaft body  221  adjacent to the second connection bar  222 , and a second positioning plane  225  axially located on the periphery of the second shaft body  221 . Further, the first shaft body  211  of the first pivot shaft  21  is positioned in the first pivot shaft chamber  13  of the axle housing  1 ; the second shaft body  221  of the second pivot shaft  22  is positioned in the second pivot shaft chamber  16  of the axle housing  1 . 
     The transmission mechanism  3  comprises a first transmission member  31  and a second transmission member  32 . The first transmission member  31  comprises a first connection hole  311  cut through opposing front and back sides thereof at the center, and a first position-limit rod  312  located at the front side adjacent to the first connection hole  311 . The second transmission member  32  comprises a second connection hole  321  cut through opposing front and back sides thereof at the center, and a second position-limit rod  322  located at the front side adjacent to the second connection hole  321 . The first connection hole  311  of the first transmission member  31  is fixedly connected to the first positioning tip  214  of the pivot shaft set  2 ; the second connection hole  321  of the second transmission member  32  is fixedly connected to the second positioning tip  224  of the pivot shaft set  2 . 
     The link  4  comprises a first position-limit hole  41  and a second position-limit hole  42 . The first position-limit rod  312  and second position-limit rod  322  of the transmission mechanism  3  are respectively coupled to the first position-limit hole  41  and second position-limit hole  42  of the link  4 . The first position-limit hole  41  defines a first abutment portion  411  at one side near the second position-limit hole  42 , and a second abutment portion  412  at an opposite side remote from the second position-limit hole  42 . Further, the distance between the first abutment portion  411  and the second abutment portion  412  is larger than the outer diameter of the first position-limit rod  312 . 
     The positioning device set  5  comprises a first positioning member  51  and a second positioning member  52 . The first positioning member  51  and the second positioning member  52  are respectively disposed at opposing front and back sides of the axle housing  1 . Further, the second positioning member  52  is set between the axle housing  1  and the transmission mechanism  3 . The first positioning member  51  comprises a first positioning hole  511  and a second positioning hole  512  respectively disposed near two distal ends thereof. The second positioning member  52  comprises a third positioning hole  521  and a fourth positioning hole  522  respectively disposed near two distal ends thereof. The first positioning hole  511  and the third positioning hole  521  are respectively pivotally connected to two opposite ends of the first shaft body  211  of the pivot shaft set  2 . The second positioning hole  512  and the fourth positioning hole  522  are respectively pivotally connected to two opposite ends of the second shaft body  221  of the pivot shaft set  2 . The first positioning member  51  further comprises a stop block  513  located at one side thereof between the first positioning hole  511  and the second positioning hole  512 . The stop block  513  comprises a first abutment surface  514  and a second abutment surface  515  bilaterally disposed adjacent to the first positioning hole  511 , and a third abutment surface  516  and a fourth abutment surface  517  bilaterally disposed adjacent to the second positioning hole  512 . 
     The application of the dual-shaft hinge in accordance with the first embodiment of the present invention is outlined hereinafter with reference to  FIGS. 7-18  and  FIGS. 3 and 6  again. As illustrated in  FIGS. 7 and 8 , the first connection bar  212  and second connection bar  222  of the pivot shaft set  2  are respectively affixed to a top cover member  8  and a bottom cover member  9  (the cover member and base member of a mobile dual leaf electronic device). When the top cover member  8  and the bottom cover member  9  are closed, the top cover member  8  is disposed at the top side of the bottom cover member  9  in a parallel manner. At this time, the first position-limit rod  312  of the transmission mechanism  3  is kept apart from the second abutment portion  412  of the link  4  a distance, the first position-limit flange  213  of the first pivot shaft  21  is stopped against the first abutment surface  514  of the positioning device set  5 , and the second position-limit flange  223  of the second pivot shaft  22  is stopped against the third abutment surface  516  of the positioning device set  5 . As illustrated in  FIGS. 9 and 10 , when the user bias the top cover member  8  toward the bottom side of the bottom cover member  9 , the friction force between the first bearing portion  12  and the first shaft body  211  is larger than the friction force between the second bearing portion  15  and the second shaft body  221  just because the extending direction of the first bearing portion  12  of the axle housing  1  is same as the biasing direction of the top cover member  8  and the extending direction of the second bearing portion  15  of the axle housing  1  is reverse to the biasing direction of the top cover member  8 , allowing the axle housing  1  to be turned about the second shaft body  221  toward the top cover member  8  to move the second position-limit flange  223  away from the third abutment surface  516  toward the fourth abutment surface  517 . At this time, the first pivot shaft  21  is immovable. Further, during rotation of the axle housing  1 , the distance between the first position-limit rod  312  and second position-limit rod  322  of the transmission mechanism  3  is gradually increased. When the first position-limit rod  312  is stopped at the second abutment portion  412  of the first position-limit hole  41 , the distance between the first position-limit rod  312  and the second position-limit rod  322  can no longer be increased, and thus, the axle housing  1  is prohibited from further rotation relative to the second shaft body  221 . As illustrated in  FIGS. 11 and 12 , when the axle housing  1  is stopped from rotation relative to the second shaft body  221 , the first shaft body  211  will be rotated in the first pivot shaft chamber  13  in the biasing direction of the top cover member  8 . During rotation of the first shaft body  211 , the distance between the first position-limit rod  312  and the second position-limit rod  322  is gradually reduced, causing the first position-limit rod  312  to be moved away from second abutment portion  412  toward the first abutment portion  411 . At the same time, the first position-limit flange  213  is moved away from the first abutment surface  514  toward the second abutment surface  515 . As illustrated in  FIGS. 13 and 14 , when a gap appears between the first bearing portion  12  and the first shaft body  211 , the axle housing  1  will be forced to turn about the second shaft body  221  toward the top cover member  8  and the first pivot shaft  21  will be prohibited from rotation due to that the friction force between the first bearing portion  12  and the first shaft body  211  is larger than the friction force between the second bearing portion  15  and the second shaft body  221 . Thus, repeating the aforesaid action enables the top cover member  8  to be turned to the bottom side of the bottom cover member  9 . As illustrated in  FIGS. 15-18 , when the first position-limit flange  213  is stopped against the second abutment surface  515 , the first pivot shaft  21  is prohibited from rotation. At this time, the axle housing  1  will be turned about the second shaft body  221  to the position where the second position-limit flange  223  is stopped at the fourth abutment surface  517 , allowing the top cover member  8  to be biased to the bottom side of the bottom cover member  9  and kept in a parallel relationship relative to the bottom cover member  9 . Thus, the first abutment surface  514  and second abutment surface  515  of the positioning device set  5  limit the rotating range of the first shaft body  211 ; the third abutment surface  516  and fourth abutment surface  517  of the positioning device set  5  limit the rotating range of the second shaft body  221 , i.e., the top cover member  8  can be biased relative to the bottom cover member  9  within a predetermined angle. 
     Referring to  FIG. 19  and  FIG. 5  again, a dual-shaft hinge in accordance with a second embodiment of the present invention is shown. This second embodiment is substantially similar to the aforesaid first embodiment with the exception that the link, referenced by  6 , comprises a first position-limit hole  61  and a second position-limit hole  62  respectively disposed near two distal ends thereof; the first position-limit rod  312  and second position-limit rod  322  of the transmission mechanism  3  are respectively inserted in the first position-limit hole  61  and the second position-limit hole  62 ; the second position-limit hole  62  defines a first abutment portion  621  adjacent to the first position-limit hole  61  and a second abutment portion  622  remote from the first position-limit hole  61 ; the distance between the first abutment portion  621  and the second abutment portion  622  is larger than the outer diameter of the second position-limit rod  322 ; similarly, a gap can be provided between the second position-limit rod  322  and the second abutment portion  622  of the link  6  for allowing adjustment of the gap between the first position-limit rod  312  and second position-limit rod  322 , thus, the axle housing  1  can be turned about the second pivot shaft  22 , and the first pivot shaft  21  can be rotated in the axle housing  1  relative to the second pivot shaft  22 . 
     Referring to  FIG. 20  and  FIG. 5  again, a dual-shaft hinge in accordance with a third embodiment of the present invention is shown. This second embodiment is substantially similar to the aforesaid first embodiment with the exception that the link, referenced by  7 , comprises a first position-limit hole  71  and a second position-limit hole  72  respectively disposed near two distal ends thereof; the first position-limit rod  312  and second position-limit rod  322  of the transmission mechanism  3  are respectively inserted in the first position-limit hole  71  and the second position-limit hole  72 ; the first position-limit hole  71  defines a first abutment portion  711  adjacent to the second position-limit hole  72  and a second abutment portion  712  remote from the second position-limit hole  72 ; the gap between the first abutment portion  711  and the second abutment portion  712  is larger than the outer diameter of the first position-limit rod  312 ; the second position-limit hole  72  defines a third abutment portion  721  adjacent to the first position-limit hole  71  and a fourth abutment portion  722  remote from the first position-limit hole  71 ; the distance between the third abutment portion  721  and the fourth abutment portion  722  is larger than the outer diameter of the second position-limit rod  322 ; similarly, the design of the first position-limit hole  71  and second position-limit hole  72  allows adjustment of the gap between the first position-limit rod  312  and the second position-limit rod  322  so that the axle housing  1  can be turned about the second pivot shaft  22 , and the first pivot shaft  21  can be rotated in the axle housing  1  relative to the second pivot shaft  22 . 
     In conclusion, the invention provides a dual-shaft hinge that has the technical features as follows: The design and functioning of the first position-limit hole  41  and second position-limit hole  42  of the link  4  allows adjustment of the gap between the first position-limit rod  312  and second position-limit rod  322  of the transmission mechanism  3 ; the design and functioning of the axle housing  1  enables the first pivot shaft  21  and the second pivot shaft  22  to produce different friction forces so that the axle housing  1  can be turned about the second pivot shaft  22  and the first pivot shaft  21  can be rotated in the axle housing  1  relative to the second pivot shaft  22 , preventing the problem of a broken component due to overstress, or the problem of a jammed component. 
     Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention.