Abstract:
A hinge assembly includes a shaft, a tube, two friction members, and a resilient member. The tube is rotatably sleeved on the shaft. One of the shaft and the tube defines two receiving holes. The friction members are positioned in the receiving holes. The resilient member causes the friction member to resist the other one of the shaft and the tube which does not define the receiving holes. A foldable electronic device applying the hinge assembly is also provided.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present disclosure generally relates to hinge assemblies and foldable electronic devices and, particularly, to a hinge assembly used in a foldable electronic device having a top cover and a main body, and a foldable electronic device using the hinge assembly. 
     2. Description of the Related Art 
     Foldable electronic devices, such as notebook computers, are popular for their portability. In the foldable electronic device, a cover is rotatably connected to a main body via a typical hinge assembly. 
     The typical hinge assembly often includes a shaft, a friction member fixed on the shaft, and a rotary member rotatably sleeved on the shaft. The rotary member and the shaft are fixed to the cover and the main body. The rotary member is capable of being positioned in any positions relative to the friction member and the shaft because of friction created between the friction member and the rotary member. Thus, the cover can be opened to any angle relative to the main body, and remain in any position. 
     However, over time, the friction causes the engaging surfaces of the rotary member and the friction member to become abraded, resulting in little or no friction between the rotary member and the friction member. Thus, the cover would be incapable of remaining in any desired position. Therefore, the hinge assembly has a relatively short service life. 
     Therefore, a new hinge assembly and a new foldable electronic device is desired to overcome the above-described shortcomings. 
     SUMMARY 
     A hinge assembly includes a shaft, a tube, two friction members, and a resilient member. The tube is rotatably sleeved on the shaft. One of the shaft and the tube defines two receiving holes. The friction members are positioned in receiving holes. The resilient member causes the friction member to resist the other one of the shaft and the tube which does not define the receiving holes. 
     A foldable electronic device includes a main body, a cover, and a hinge assembly rotatably connecting the cover to the main body. The hinge assembly includes a shaft, a tube, two friction members, and a resilient member. The tube is rotatably sleeved on the shaft. The shaft is fixed to one of the main body and the cover, and the tube is fixed to the other one of the main body and the cover. One of the shaft and the tube defines two receiving holes. The friction members are positioned in the receiving holes. The resilient member causes the friction member to resist the other one of the shaft and the tube which does not have the receiving holes. 
     Other advantages and novel features will become more apparent from the following detailed description of various embodiments, when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present hinge assembly and foldable electronic device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout several views, and all the views are schematic. 
         FIG. 1  is an assembled, isometric view of a first embodiment of a hinge assembly, the hinge assembly being shown attached to a main body and a cover of a foldable electronic device. 
         FIG. 2  is an exploded, isometric view of the hinge assembly of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the hinge assembly of  FIG. 1 . 
         FIG. 4  is a partial, cross-sectional view of a second embodiment of a hinge assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present hinge assembly may be used in foldable electronic devices, such as notebook computers, cell phones, media players, and so on. Referring to  FIG. 1 , for the purposes of conveniently describing the present hinge assembly, a first embodiment of the hinge assembly  10  as used in a notebook computer  100  is described and illustrated. 
     The notebook computer  100  includes two hinge assemblies  10 , a main body  20 , and a cover  30 . The main body  20  includes a receiving portion  21  and a coupling cover  23 . The receiving portion  21  is formed from an edge of the main body  20  and the coupling cover  23  is configured to be coupled to the receiving portion  21 . The receiving portion  21  defines a plurality of screw holes  211  therein. The cover  30  includes two mounting portions  31  and two mounting covers  33 . The mounting portions  31  are formed from an edge of the cover  30  and the mounting covers  33  are configured to be coupled on the mounting portions  31 . The mounting portions  31  define a plurality of screw holes  311  therein. 
     Referring to  FIG. 2  and  FIG. 3 , each hinge assembly  10  includes a hollow cylindrical shaft  11 , a hollow cylindrical tube  13 , two friction members  15 , and a resilient member  17 . 
     The shaft  11  has an outer surface  111  and an inner surface  113 . Two receiving holes  115  are defined in a sidewall of the shaft  11 . The receiving holes  115  are coaxial and opposite to each other. A plurality of connecting ears  117  is formed on the shaft  11 . A connecting hole  1171  is defined in a center portion of each connecting ear  117 . The connecting ears  117  are configured for connecting the shaft  11  to the cover  30 . 
     The tube  13  has an outer surface  131  and an inner surface  132 . The tube  13  defines two angular slots  133  in a sidewall of the tube  13 . A connecting ear  135  is formed adjacent to each end of each angular slot  133 . A connecting hole  1351  is defined in a center portion of each connecting ear  135 . The connecting ears  135  are configured for connecting the tube  13  to the main body  20 . An inner diameter of the tube  13  is substantially the same as or slightly larger than an outer diameter of the shaft  11 . 
     The friction member  15  includes a shaft portion  151  and a head portion  153  formed at an end of the shaft portion  151 . The head portion  153  includes a friction surface  1531  at an end opposite to the shaft portion  151 . The friction members  15  are configured to be received in the receiving holes  115  of the shaft  11 . 
     In the illustrated embodiment, the resilient member  17  is a helical, compression spring. The resilient member  17  is configured for positioning between the friction members  15 . When the resilient member  17  is in a free state (normal state), part of the friction members  15  protrude out of the receiving holes  115  of the shaft  11 . 
     Referring to  FIG. 3 , the resilient member  17  is received inside the shaft  11  with the axes of the resilient member  17  and the receiving holes  115  aligned in a same line. The friction members  15  are positioned in the receiving holes  115  of the shaft  11  such that the resilient member  17  is positioned between the friction members  15 . Ends of the resilient member  17  are sleeved on the shaft portions  151  of the friction members  15 . The tube  13  is sleeved on the shaft  11 , thereby pushing the friction members  15  to move inwards toward the receiving holes  115 , compressing the resilient member  17 , and forming the hinge assembly  10 . The compressed resilient member  17  creates an elastic force that pushes the friction surfaces  1531  of the friction members  15  to resist the inner surface  132  of the tube  13 . 
     When the hinge assemblies  10  are applied in the notebook computer  100 , the cover  30  is moved close to the main body  20  to position the receiving portion  21  between the mounting portions  31 . The hinge assemblies  10  are put in the receiving portion  21  and the mounting portions  31 . A plurality of screws  40  are inserted in the connecting holes  1351  of the tubes  13  and screwed in the screw holes  211  of the main body  20 , thus fixing the tubes  13  to the main body  20 . A plurality of screws  50  are inserted in the connecting holes  1171  of the shafts  11  and screwed in the screw holes  311  of the cover  30  to fix the shafts  11  to the cover  30 . The coupling cover  23  is coupled on the receiving portion  21  and the mounting covers  33  are coupled on the mounting portions  31  for protecting the hinge assembly  10 . 
     The friction members  15  continuously resist the tubes  13  because of the elastic force created by the resilient members  17 , even after the hinge assemblies  10  are used for a long period of time. Thus, the hinge assemblies  10  have a long service life. In use, when the cover  30  is rotated to move relative to the main body  20 , the shafts  11  are rotated relative to the tubes  13 . Friction is created between the friction members  15  positioned in the shafts  11  and the tubes  13 , retains the cover  30  in any position relative to the main body  20 . 
     In another embodiment, each shaft  11  may define only one receiving hole  115 . In that case, only one friction member  15  is assembled in each hinge assembly  10 . In addition, three or more friction members  15  may be positioned in each shaft  11  and each hinge assembly  10  may include three or more friction members  15 . As such, two or more resilient members  17  should be adopted in each hinge assembly  10 . A first end of the resilient member  17  resists the friction member  15 , and a second end opposite to the first end of the resilient member  17  resists the sidewall of the shaft  11 . Furthermore, the shafts  11  may be solid cylinders fixed to the main body  20 , and the tubes  13  may be fixed to the cover  30 . Moreover, the notebook computer  100  may adopt only one hinge assembly  10 . 
     Referring to  FIG. 4 , a second embodiment of a hinge assembly  80  includes a shaft  81 , a tube  83 , a friction member  85 , and a resilient member  87 . The tube  83  defines one or more receiving blind holes  835  at an inner surface of the tube  83 . Accordingly, the hinge assembly  80  may include one or more friction members  85  received in the receiving holes  835 . The resilient member  87  and the friction member  85  are received in the receiving hole  835 , with the resilient member  87  positioned between the sidewall of the tube  83  and the friction member  85 . An end of the friction member  85  resists an outer surface of the shaft  81 . 
     Finally, while various embodiments have been described and illustrated, the disclosure is not to be construed as being limited thereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the disclosure as defined by the appended claims.