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FIELD OF THE INVENTION  
       [0001]     The present invention relates to hinge assemblies, and particularly to a hinge assembly for foldable electronic devices such as mobile telephones, electronic notebooks, and so on.  
       GENERAL BACKGROUND  
       [0002]     With the development of the technologies of wireless communication and information processing, portable electronic devices such as mobile telephones and electronic notebooks are now in widespread use. These electronic devices enable consumers to enjoy the convenience of high technology services anytime and anywhere. Foldable electronic devices are particularly favored by consumers for their convenience.  
         [0003]     Generally, foldable electronic devices have most of the electronics in one housing, called the main body. The other housing, called the cover, typically contains fewer electronic components than the main body. Other foldable electronic devices have all the electronics in the main body, with the cover containing no electronics. Various types of hinge assemblies are used to join a main body and a cover of a foldable electronic device, so that the cover can unfold up from and fold down upon the main body. Manufacturers are constantly seeking to reduce the volume, size and weight of portable foldable electronic devices. Thus, it is desirable that the hinge assembly coupling the main housing with the cover is modularized and miniaturized. A modularized hinge assembly has moving parts such as a cam member, a follower, and a spring held together in a unified structure. The structure is easily and quickly attached to the main body and the cover during mass production. A miniaturized hinge assembly has as few parts as possible, with the parts being as small as practicable.  
         [0004]     One kind of conventional foldable electronic device with a hinge assembly is configured as follows. The foldable electronic device is typically a mobile phone. The hinge assembly includes a housing secured to a main body of the mobile phone, a spring received in the housing, a rotary cam rod, and a shaft with a follower and a connecting portion. The rotary cam rod is received in the housing and engages with the housing. One end of the spring contacts an inner wall of the housing, and the other end of the spring resists one end of the rotary cam rod. The shaft is passed through the rotary cam rod and the spring in that order.  
         [0005]     Although the above-described hinge assembly is suitable for some foldable electronic devices, the spring and the rotary cam rod are in direct contact with each other. Dry friction is produced between the spring and the rotary cam rod because of relative rotation therebetween. This wastes energy and causes abrasion of the spring and the rotary cam rod. The abrasion may eventually lead to premature malfunction or failure of the hinge assembly.  
         [0006]     What is needed, therefore, is a hinge assembly which can have a relatively long working lifetime and which is energy efficient and convenient to use.  
       SUMMARY  
       [0007]     In a first preferred embodiment, a hinge assembly is provided for joining a cover to a main body of a foldable electronic device. The hinge assembly includes a shaft, a follower, a cam, a washer, a lubrication mass forming means, and an urging means. The shaft has a securing portion formed at a first end thereof, for connecting to the main body of the foldable electronic device. Preferably, the follower is integrally connected with the shaft. The cam is essentially in the shape of a cylinder, and is for connecting to the cover of the foldable electronic device. The cam includes a cam surface, and defines a cam hole extending therethrough. The cam hole receives the shaft therethrough. The washer defines a center hole, and is located around the shaft. The lubrication mass forming means is disposed between the washer and the cam. A first end of the urging means abuts the shaft, and an opposite second end of the urging means biases the washer. The cam surface of the cam is rotatably and movably engaged with the follower under force of the urging means.  
         [0008]     A main advantage of the above-described hinge assembly is that the lubrication mass forming means is disposed between the cam and the washer. The lubrication mass forming means is rotated in unison with the cam, and rotates relative to the washer. Thereby, a mass of lubrication is formed between the lubrication mass forming means and the washer when the cam is rotated relative to the washer. This reduces friction between the cam and the washer. Accordingly, when the hinge assembly is assembled in a mobile phone, the energy required in opening the cover of the mobile phone is reduced. Furthermore, the working lifetime of the hinge assembly is prolonged.  
         [0009]     In a second preferred embodiment, a hinge assembly is provided for joining a cover to a main body of a foldable electronic device. The hinge assembly includes a shaft, a follower, a cam, a washer, a lubrication mass forming means, and an urging means. The shaft has a securing portion formed at a first end thereof, and a latching portion formed at an opposite second end thereof. The securing portion is for connecting to the cover of the foldable electronic device. Preferably, the follower is integrally connected with the shaft. The cam is essentially in the shape of a cylinder, and is for connecting to the main body of the foldable electronic device. The cam includes a cam surface, and defines a cam hole extending therethrough. The cam hole receives the shaft therethrough. The washer defines a center hole, and is located around the shaft. The lubrication mass forming means is disposed between the washer and the latching portion of the shaft. A first end of the urging means abuts the washer, and an opposite second end of the urging means biases the cam. The follower is rotatably and movably engaged with the cam surface of the cam under force of the urging means.  
         [0010]     A main advantage of the above-described hinge assembly is that the lubrication mass forming means is disposed between the washer and the latching portion of the shaft. The lubrication mass forming means is rotated in unison with the latching portion, and rotates relative to the washer. Therefore a mass of lubrication is formed between the lubrication mass forming means and the washer when the latching portion is rotated relative to the washer. This reduces friction between the washer and the latching portion. Accordingly, when the hinge assembly is assembled in a mobile phone, the energy required in opening the cover of the mobile phone is reduced. Furthermore, the working lifetime of the hinge assembly is prolonged.  
         [0011]     Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is an isometric view of a flip type mobile phone including a cover, a main body, and a hinge assembly according to a first preferred embodiment of the present invention, the hinge assembly being shown with dashed lines;  
         [0013]      FIG. 2  is an enlarged, exploded, isometric view of the hinge assembly of  FIG. 1 ;  
         [0014]      FIG. 3  is similar to  FIG. 2 , but viewed from another aspect;  
         [0015]      FIG. 4  is an enlarged, assembled view of the hinge assembly of  FIG. 1 ;  
         [0016]      FIG. 5  is similar to  FIG. 4 , but showing the hinge assembly in another state;  
         [0017]      FIG. 6  is an enlarged, schematic, side view of part of the hinge assembly shown in  FIG. 2 , showing a pushing block thereof in a parallel position;  
         [0018]      FIG. 7  is similar to  FIG. 6 , but showing the pushing block in an inclined position; and  
         [0019]      FIG. 8  is an exploded, isometric view of a hinge assembly according to a second preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]     Referring now to the drawings,  FIG. 1  shows an electronic device like a flip type mobile phone  200 , which includes a hinge assembly  10  according to a first preferred embodiment of the present invention. The mobile phone  200  has a main body  202  and a cover  204 . The main body  202  and the cover  204  are pivotally connected to each other via the hinge assembly  10 . It should be noted that the hinge assembly  10  is also able to be used to interconnect components like a main body and a cover of any of various different kinds of foldable electronic devices other than the mobile phone  200 .  
         [0021]     Referring now to  FIGS. 2 and 3 , the hinge assembly  10  includes a shaft  20 , a cam  30 , a plurality of pushing blocks  40 , a washer  50 , a spring  60  functioning as an elastic urging means, and a clip  70 . In the illustrated embodiment, there are three pushing blocks  40 . The shaft  20  extends through the cam  30 , the washer  50 , the spring  60 , and the clip  70 , thereby integrating the hinge assembly  10 .  
         [0022]     The shaft  20  includes in sequence a securing portion  21  formed at a first end thereof, a follower  22  adjacent the securing portion  21 , a large diameter portion  23 , a neck portion  24 , and a small diameter portion  25 . The securing portion  21  is for engaging with the main body  202  of the mobile phone  200 . The follower  22  includes an enlarged cylindrical portion  221 , and two symmetrically opposite finger portions  222  extending in an axial direction and adjoining one end of the large diameter portion  23 . The small diameter portion  25  has a latching portion  26  formed at one end thereof. A diameter of the latching portion  26  is larger than that of the small diameter portion  25 .  
         [0023]     The cam  30  is a generally cylindrical body and defines a cam hole  31 . The cam  30  has a cam surface  32  formed at a first end thereof, and a plurality of hemispherical bulges  33  formed on an opposite second end thereof. In the illustrated embodiment, there are three bulges  33 . The bulges  33  are symmetrically spaced apart from each other around the cam hole  31 . The bulges  33  can alternatively be partially hemispherical, arc-shaped relative to a central axis of the cam  30 , substantially semicircular relative to the central axis of the cam  30 , or have another suitable shape. Further, the bulges  33  can alternatively be a single substantially semicircular bulge, a single substantially circular bulge, or a single bulge having another suitable shape. The cam surface  32  includes two valleys  322 , two peaks  324 , two moderate inclined planes  326 , and two steep inclined planes  328 . Preferably, the valleys  322  are located 180 degrees opposite from each other, and the peaks  324  are located 180 degrees opposite from each other. The cam  30  has a protrusion  34  formed on an outer peripheral wall thereof, the protrusion  34  being oriented parallel to the central axis of the cam  30 . The protrusion  34  is for engaging with the cover  204  of the mobile phone  200 .  
         [0024]     The pushing blocks  40  are arc-shaped, and together form part of a same imaginary ring. Each pushing block  40  defines a generally hemispherical but eccentric concavity  42  in a first surface portion thereof. The bulges  33  of the cam  30  can movably engage in the concavities  42  of the pushing blocks  40 . An opposite second surface of each pushing block  40  resists the washer  50 . Further, the concavities  42  can alternatively have other shapes and configurations, corresponding to the above-described alternative shapes and configurations of the bulges  33 .  
         [0025]     The washer  50  is circular and defines a center hole  52 . A first main surface of the washer  50  resists the second surface of the pushing blocks  40 , and an opposite second main surface of the washer  50  resists the spring  60 .  
         [0026]     The spring  60  is helical and preferably metallic, with an inner diameter larger than a diameter of the large diameter portion  23  of the shaft  20 . Thus the spring  60  can be located around the shaft  20 . A second end of the spring  60  resists the second main surface of the washer  50 , and an opposite first end of the spring  60  resists the clip  70 .  
         [0027]     The clip  70  is C-shaped, and is made of an elastic material. A first main surface of the clip  70  resists the spring  60 , an opposite second main surface of the clip  70  resists the latching portion  26  of the shaft  20 .  
         [0028]     Referring to  FIGS. 4 and 5 , in assembly of the hinge assembly  10 , firstly, the shaft  20  is passed through the cam hole  31  of the cam  30 , the center hole  52  of the washer  50 , and the spring  60  in that order. The pushing blocks  40  are received between the cam  30  and washer  50 . The clip  70  is snappingly engaged around the small diameter portion  25  of the shaft  20 , such that the spring  60  is slightly compressed. The bulges  33  of the cam  30  movably engage in the concavities  42  of the pushing blocks  40 , and the second surfaces of the pushing blocks  40  abut against the first main surface of the washer  50  under force of the spring  60 . The second main surface of the washer  50  resists the second end of spring  60 . The first end of the spring  60  resists the first surface of the clip  70 . The latching portion  26  of the shaft  20  resists the second surface of the clip  70 , and prevents the clip  70  from falling off from the shaft  20 . The cam surface  32  of the cam  30  always contacts the finger portions  222  no matter what rotational position the cam  30  is in, because of urging force of the spring  60 . The hinge assembly  10  is thus completely assembled. Finally, lubricant is applied generally between the pushing blocks  40  and the second end of the cam  30 , and between the pushing blocks  40  and the first main surface of the washer  50 . The lubricant may for example be lubricating oil. The hinge assembly  10  is thus completely assembled.  
         [0029]     Referring also to  FIG. 6 , in use, the protrusion  34  is engaged in a cavity (not shown) of the cover  204  of the mobile phone  200 , and the securing portion  21  of the shaft  20  is engaged in the main body  202  of the mobile phone  200 . When the cover  204  of the mobile phone  200  is in a fully open position (or fully closed position), the finger portions  222  of the shaft  20  are located in the valleys  322  of the cam  30  and engage with the valleys  322 . The pushing blocks  40  may initially be oriented generally parallel to both the second end of the cam  30  and the washer  50 .  
         [0030]     Referring also to  FIG. 7 , when the cover  204  of the mobile phone  200  is rotated between an open position and a closed position (or vice versa), the cam  30  rotates along with the cover  204 , while the shaft  20  remains fixed in the main body  202  of the mobile phone  200 . As a result, the finger portions  222  ride along the moderate inclined planes  326  of the cam surface  32  from the valleys  322  to the peaks  324 , with the cam  30  moving toward the clip  70  and compressing the spring  60 . At the same time, the pushing blocks  40  rotate in unison with the cam  30 , and thereby rotate relative to the washer  50 . The cam  30  and the washer  50  resist each other via the pushing blocks  40 , and the bulges  33  of the cam  30  engagingly receive the concavities  42  of the pushing blocks  40 . When the spring  60  is compressed as described above, corresponding same ends of the pushing blocks  40  are inclined toward the washer  50  by the applied force because of the eccentric configurations of the concavities  42 . Thus the lubricant between the pushing blocks  40  and the washer  50  is reformed into a generally cuneiform mass. This reduces friction between the pushing blocks  40  and the washer  50 , and thus reduces friction between the cam  30  and the washer  50 . Once the finger portions  222  pass over the peaks  324 , the spring  60  decompresses and drives the cam  30  back toward the cylindrical portion  221 , with the finger portions  222  riding along the steep inclined planes  328  from the peaks  324  to the valleys  322 . When the spring  60  decompresses as described above, said ends of the pushing blocks  40  are inclined toward the cam  30  by the expansion force exerted by the spring  60  and because of the eccentric configurations of the concavities  42 . Thus the lubricant between the pushing blocks  40  and the washer  50  is reformed into another generally cuneiform mass. This reduces friction between the pushing blocks  40  and the washer  50 , and thus reduces friction between the cam  30  and the washer  50 . According to the above-described process, the cover  204  is rotated automatically to the fully open position (or fully closed position) under the decompression force of the spring  60 . That is, the cover  204  is moved 180 degrees relative to the main body  202 , with the finger portions  222  once again mating in the valleys  322 . In this way, the cover  204  is opened (or closed). Preferably, the structures of the cover  204  and the main body  202  are adapted to control the degree of rotation of the hinge assembly  10 , such that the finger portions  222  can be held in one or more particular locations between the valleys  322  and the peaks  324 .  
         [0031]     In further alternative embodiments, the follower  22  can be a separate element that is not integrally formed with the shaft  20 . In such case, the follower  22  defines a shaft hole, and has a cam surface or finger portions. The cam  30  can define a plurality of concavities, and the pushing blocks  40  can form a plurality of bulges. The spring  60  can be made of nonmetallic material such as plastic. Further, the spring  60  can instead be another kind of elastic element or urging means known in the art, such as a resilient cylinder. The clip  70  can be omitted, in which case the spring  60  directly resists the latching portion  26 . There can be more than one protrusion  34 .  
         [0032]     Referring to  FIG. 8 , a hinge assembly  10 ′ according to a second preferred embodiment of the present invention is similar to the hinge assembly  10 , except that the hinge assembly  10 ′ has a cam  80  and a clip  90 . The cam  80  has a cam surface  82  formed at one end thereof. One surface of the clip  90  facing the spring  60  has a plurality of hemispherical bulges  92  formed thereon. In the illustrated embodiment, there are three bulges  92 . The hinge assembly  10 ′ can be used to pivotally connect the main body  202  and the cover  204  of the mobile phone  200 . However, the securing portion  21  of the shaft  20  is used to connect with the cover  204 , and a protrusion  84  of the cam  80  is used to connect with the main body  202 . In such case, there is no relative rotation between the cam  80  and the spring  60 , whereas there is relative rotation between the clip  90  around the shaft  20  and the spring  60 . Accordingly, the washer  50  and pushing blocks  40  are disposed between the spring  60  and the clip  90 . Lubricant between the pushing blocks  40  and the washer  50  can be reformed into a generally cuneiform mass, in much the same way as described above in relation to the hinge assembly  10  of the first preferred embodiment. This reduces friction between the pushing blocks  40  and the washer  50 , and thus reduces friction between the clip  90  and the washer  50 .  
         [0033]     In an alternative embodiment, the clip  90  can be omitted. In such case, the washer  50  and the pushing blocks  40  are disposed between the spring  60  and the latching portion  26  of the shaft  20 . The hinge assembly  10 ′ may have other alternative embodiments, similar to the alternative embodiments described above in relation to the hinge assembly  10 .  
         [0034]     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Summary:
A hinge assembly ( 10 ) includes a shaft ( 20 ), a follower ( 22 ), a cam ( 30 ), a washer ( 50 ), a lubrication mass forming means, and an urging means. The shaft has a securing portion ( 21 ) formed at one end thereof. The follower connects with the shaft. The cam essentially is in the shape of a cylinder, and includes a cam surface ( 32 ) and defines a cam hole ( 31 ) extending therethrough. The cam hole receives the shaft therethrough. The washer defines a center hole ( 52 ), and is located around the shaft. The lubrication mass forming means is disposed between the washer and the cam. One end of the urging means abuts the shaft, and an opposite end of the urging means biases the washer. The cam surface of the cam is rotatably and movably engaged with the follower under force of the urging means.