Patent Publication Number: US-8110764-B2

Title: Key structure

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of Taiwan Patent Application No. 097120433, filed on Jun. 2, 2008, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to a key structure and in particular to a key structure with a metal link. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional key structure primarily comprises a substrate B, a key cap C, an elastic dome D, a first link L 1 , and a second link L 2 , wherein the first and second links L 1  and L 2  are pivotally connected to each other. 
     When the key cover C is depressed by an external force, the elastic dome D exerts a recovery force on the key cap C. When the external force is released, the key cover C can return to the initial position by the recovery force, as the arrows indicate in  FIG. 1 . However, since the first and second links L 1  and L 2  are usually made of plastic, robust structural strength and miniaturization of key structures are difficult to achieve. 
     BRIEF SUMMARY OF INVENTION 
     The invention provides a key structure including a substrate, a key cap, a first link, and a second link pivotally connected to the first link. The first and second links movably connect the key cap with the base. The key cap comprises a first surface and a guiding portion extended along a first direction, wherein the guiding portion has a second surface. The first link is made of metal and has a sliding end forming a first curved portion and a second curved portion. The first and second curved portions are respectively adjacent to the first and second surfaces and slidable along the guiding portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a perspective diagram of a conventional key structure; 
         FIG. 2  is an exploded diagram of a key structure according to an embodiment of the invention; 
         FIG. 3  is a sectional view of a key structure according to an embodiment of the invention; 
         FIG. 4  is a large view of the first link and the guiding portion in  FIG. 3 ; and 
         FIG. 5  is a sectional view of a key structure according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to  FIG. 2 , an embodiment of key structure primarily comprises a key cap  10 , a first link  21 , a second link  22 , a circuit board  30 , and a substrate  40 . The first link  21  is made of metal, and the second link  22  is made of metal or plastic. The first link  21  comprises a pair of pivots P rotatably received in the holes H of the second link  22 , such that the first and second links  21  and  22  are pivotally connected to each other. 
     As shown in  FIG. 2 , the first and second links  21  and  22  extend through the openings  31  of the circuit board  30  and movably connect the key cap  10  with the substrate  40 . Here, a sliding end  211  of the first link  21  is movably connected to a guiding portion  11  of the key cap  10 , and a connection end  221  of the second link  22  is pivotally connected to a recess  12  of the key cap  10 . Additionally, the connection ends portions  212  and  222  of the first and second links  21  and  22  are movably connected to the connection portions  41  and  42 , so that the key cap  10  is vertically movable via the first and second links  21  and  22 . 
     When the key cap  10  is depressed from a first position to a second position by an external force, a contact portion  213  of the first link  21  descends and contacts a switch W on the circuit board  30  ( FIG. 2 ). The key structure may further comprise an elastic member E disposed on the circuit board  30 , such as a rubber dome or spring, which provides a recovery force to return the key cap  10  to the first position when the external force is released. 
     Referring to  FIGS. 2 and 3 , the sliding end  211  of the first link  21  is bent to form a first curved portion R 1  and a second curved portion R 2 . The first and second curved portions R 1  and R 2  are respectively adjacent to a first surface S 1  of the key cap  10  and a second surface S 2  of the guiding portion  11 . When the key cap  10  vertically moves along a Z axis, the first and second curved portions R 1  and R 2  slide along the guiding portion  11 , as the arrows indicate in  FIG. 3 . In this embodiment, the first and second curved portions R 1  and R 2  can facilitate smooth contact when sliding along the guiding portion  11 . 
     Referring to  FIG. 4 , the guiding portion  11  is extended substantially along a first direction (X axis). Specifically, the first and second curved portions R 1  and R 2  have a first curved surface R 1 ′ and a second curved surface R 2 ′, wherein the first curved surface R 1 ′ defines a first curvature center C 1 , and the second curved surface R 2 ′ defines a second curvature center C 2 . In this embodiment, the first curvature center C 1  substantially coincides with the second curvature center C 2 . As shown in  FIG. 4 , the first and second surfaces S 1  and S 2  are spaced apart a distance h, substantially equal to a maximum width of the first and second curved portions R 1  and R 2 , such that the sliding end  211  can stably slide along the guiding portion  11 . 
     Referring in  FIG. 5 , another embodiment of the sliding end  211  of the first link  21  is bent to form a Z-shaped configuration, wherein the first and second curved portions R 1  and R 2  constitute the angled structures of the Z-shaped sliding end  211 . As shown in  FIG. 5 , the first and second curved surfaces R 1 ′ and R 2 ′ are respectively adjacent to the first and second surfaces S 1  and S 2 . In this embodiment, the first and second curvature centers C 1  and C 2  are separated from each other, and a straight normal line connecting the first and second curvature centers C 1  and C 2  is substantially perpendicular to the X axis. However, positions of the first and second curvature centers C 1  and C 2  can be adjusted depending on design considerations. 
     As shown in  FIGS. 2 and 3 , the first link  21  comprises two flattened fringes  214  and  215 , and the second link  22  comprises two stoppers  216  and  217  corresponding to the fringes  214  and  215 . When the key cap  10  returns to the first position, the fringes  214  and  215  respectively abut the stoppers  216  and  217 , so as to prohibit rotation between the first and second links  21  and  22 . Thus, the key cap  10  can be restricted in the first position. 
     The invention provides a key structure comprising a first link movably connecting a substrate with a key cap, wherein the first link is made of metal. Compared with conventional key structures, the metal first link can provide better structural strength and facilitate miniaturization of the key structure. A sliding end of the first link is bent to form two curved portions for smooth sliding and rotation with respect to a guiding portion on an inner side of a key cap, such that the key cap is vertically movable relative to the substrate. 
     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements.