Abstract:
A multi-direction switch that is less likely to generate erroneous movement and may reduce fabrication and assembly difficulty includes redesigned metal conductive legs of a joystick and corresponding electrode elements so that the interval between the metal conductive legs and the electrode elements increases to prevent the metal conductive legs from mistakenly connecting the electrode elements when the joystick is depressed thereby to increase oscillation amplitude of the joystick and improve the operation maneuverability thereof.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a miniature switch and particularly to the structure of a multi-direction switch. 
     BACKGROUND OF THE INVENTION 
     Multi-direction switch is one of input devices adopted for use on small electronic devices such as personal digital assistant (PDA) or mobile communication devices. A conventional multi-direction switch provides input commands or instructions that include horizontal “direction instruction” (such as X and Y axes and right up, right down, left up and left down) and a single “button key instruction” (such as the instruction generated when the multi-direction switch is depressed). By means of this multi-direction switch, the cursor of a small electronic device may be controlled or operation of functional items may be executed. 
     Refer to FIGS. 1A,  1 B and  1 C for a conventional multi-direction switch. As shown in FIG. 1A, it has a base dock  10  which has first to fourth electrodes  101 - 104  located respectively at four corners. There is a central electrode  105  in the center surrounding by a common electrode  106  (generally a common ground electrode). The first to fourth electrodes  101 - 104  have respectively a leg  101   a - 104   a  exposed outside the periphery of the base dock  10  to connect a circuit (such as a circuit on a printed circuit board). The central electrode  105  and the common electrode  106  connect respectively to the circuit through legs  105   a  and  106   a  that also are exposed outside the base dock  10 . The main operation element of the multi-direction switch is a joystick  11 . It has four metal contact legs  110  extending horizontally from the periphery thereof. By moving the joystick  11 , the four metal legs  110  may be respectively in contact with the first to fourth electrodes  101 - 104 . The joystick  11  has a bottom end  111  in the center above two overlapped and elastic metal blades  121  and  122  in normal conditions. The metal blade  122  is located at the lower side to be in contact with the common electrode  106  in the normal conditions (also referring to FIG.  1 C). 
     When the joystick  11  is depressed vertically, the two elastic metal blades  121  and  122  are deformed to enable the center point of the lower metal blade  122  in contact with the central electrode  105  so that the central electrode  105  and the common electrode  106  are connected and become conductive through the elastic metal blade  122  to generate a button key instruction. By the same token, when the joystick  11  is moved in the horizontal direction, the metal contact leg  110  in the corresponding direction will be moved to contact any one or more of the first to fourth electrodes  101 - 104  in the corresponding direction. Through the contact of the first to fourth electrodes  101 - 104  and the metal contact leg  110 , the metal contact leg  110  and the elastic metal blades  121  and  122  that in contact with the bottom end  111  of the joystick  11  in normal conditions, and the common electrode  106  may form electric connection. And through signal triggering conditions of the first to fourth electrodes  101 - 104 , a “directional instruction” of the joystick  11  may be determined. 
     The maximum compression displacement of the joystick  11  of such a multi-direction switch is limited by the deformation of the elastic metal blades  121  and  122  (about 0.15 mm). The oscillation amplitude of the joystick  11  at two sides of the axial direction is also restricted in a smaller range. As a result, it causes inconvenience during user operation. Moreover, as the metal contact leg  110  is extended horizontally, when the joystick  11  is moved, in order to ensure that the metal contact leg  110  to connect any one or more of the first to fourth electrodes  101 - 104 , the locations of the first to fourth electrodes  101 - 104  have to be raised to an elevation close to the metal contact leg  110  (as shown in FIG.  1 B). Such a design shrinks the vertical distance between the metal contact leg  110  and the first to fourth electrodes  101 - 104  and is prone to cause erroneous movement. For instance, when the joystick  11  is depressed, a small shaking of the joystick  11  could cause the metal contact leg  110  to mistakenly touch the first to fourth electrodes  101 - 104  and result in erroneous movement and generate a wrong directional instruction. And the small dimension and gap also make fabrication and assembly difficult. 
     SUMMARY OF THE INVENTION 
     Therefore the primary object of the present invention is to provide a multi-direction switch that is less likely to generate erroneous movements. 
     The present invention mainly has redesigned the metal contact legs of the joystick and the corresponding electrode elements to achieve the object mentioned above. The invention has lowered the location of the electrode elements and changed the shape of the metal contact legs to increase the interval of the metal contact legs and the electrode elements. Therefore it can prevent the metal contact legs from mistakenly connecting to the electrode elements when the joystick is depressed. The oscillation amplitude of the joystick during operation increases and operational maneuverability improves. 
     Furthermore, the design of the invention also reduces the difficulty of fabrication and assembly. 
     The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a schematic view of the base dock structure of a conventional multi-direction switch. 
     FIG. 1B is a cross section of a conventional multi-direction switch taken on line  1 B— 1 B in FIG.  1 A. 
     FIG. 1C is a cross section of a conventional multi-direction switch taken on line  1 C— 1 C in FIG.  1 A. 
     FIG. 2A is an exploded view of the multi-direction switch according to the invention. 
     FIG. 2B is a cross section of taken on line  2 B— 2 B in FIG.  2 A. 
     FIG. 3A is a perspective view of the multi-direction switch according to the invention. 
     FIG. 3B is a cross section taken on line  3 B— 3 B in FIG.  3 A. 
     FIG. 3C is a schematic view of the operation condition according to FIG. 3B, showing a conductive contact leg connecting to a direction electrode when the joystick is oscillating. 
     FIG. 4A is a cross section of taken on line  4 A— 4 A in FIG. 3A showing the joystick not being depressed. 
     FIG. 4B is a schematic view of the multi-direction switch according to the invention in an operation condition showing the joystick depressed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please referring to FIG. 2A, the multi-direction switch according to the invention includes: 
     a base dock  20  which is substantially a box type element with a bottom and an opening directing upwards. It has a plurality of electrode elements located therein. Referring to FIG. 2B, the electrode elements include: 
     a first to a fourth direction electrodes  31 - 34  located on a bottom side  201  of the base dock  20 . In a preferred embodiment, they are located at four corners of the bottom side  201 . The four direction electrodes  31 - 34  are flat conductive elements (generally made of metal plate), and have respectively a leg  311 ,  321 ,  331  and  341  extending outside the base dock  20  to connect to a circuit (such as a circuit of a printed circuit board); 
     a compression electrode  35  located in the center of the base side  201 . It also is a flat conductive element and has a leg  351  extending outside the base dock  20  to connect to the circuit (such as the circuit of the printed circuit board); 
     a common electrode  36  (generally a common ground electrode) located around the compressing electrode  35 . It also is a flat conductive element and has a leg  361  extending outside the base dock  20  to connect to the circuit (such as the circuit of the printed circuit board); 
     a first conductive elastic blade  41  and a second conductive elastic blade  42  (referring to FIG. 2A) that are overlapped with each other and formed in a shape as a portion of a spherical surface. They have a center point P located above the compression electrode  35 . The center point P and the compression electrode  35  are not in contact with each other in normal conditions (referring to FIG.  4 A). The second conductive elastic blade  42  has a peripheral bottom sinking into a trough formed on the bottom side  201  above the common electrode  36  (referring to FIG.  3 B). The elastic blade  42  is in contact with the common electrode  36  in normal conditions. The center point P of the second conductive elastic blade  42  may be in contact with the compression electrode  35  when subject to compression (referring to FIG.  4 B). In that condition the compression electrode  35  is connected to the common electrode  36  through the second conductive elastic blade  42  that generates a corresponding compression instruction signal through the electronic device connecting to the leg  351 ; 
     a joystick  50  which has an operation stem  55  extending vertically upwards and first to fourth conductive legs  51 - 54  fixedly located around the operation stem  55 . The first to fourth conductive legs  51 - 54  are connected to the common electrode  36  through a bottom end  501  (being conductive) of the joystick  50  that is in contact with the first conductive elastic blade  41  in normal conditions. The main feature is that first to fourth conductive legs  51 - 54  have distal ends extending respectively in a biased manner towards the first to fourth electrodes  31 - 34 . However, in normal conditions, they are not in contact with the first to fourth electrodes  31 - 34  (as shown in FIG.  4 A). When an user moves the operation stem  55  of the joystick  50  (referring to FIG.  3 C), one or more of the first to fourth conductive legs  51 - 54  in the corresponding direction will be moved accordingly to connect to one or more of the first to fourth electrodes  31 - 34  corresponding to the moving direction of the joystick  50 . Therefore, through the connection of the first to fourth conductive legs  51 - 54 , and the first conductive elastic blade  41  that is in contact with the bottom end  501  of the joystick  50  in normal conditions, and the second conductive elastic blade  42 , it is connected to the common electrode  36 , and through detecting the signal triggering conditions of the first to fourth electrodes  31 - 34 , the “directional instruction” input by the joystick  50  may be determined; and 
     an upper cap  60  has a flat surface  61  and an opening  62  formed in the center of the flat surface  61  to allow the operation stem  55  of the joystick  50  to pass through. There are a plurality of latch lugs  63  formed on the periphery of the flat surface  61  each has an aperture  631  engageable with a reverse hook  21  extending from the periphery of the base dock  20 . Therefore the upper cap  60  can encase the joystick  50 , and the first and second conductive elastic blades  41  and  42  on the base dock  20  (referring to FIG.  3 A). 
     As the first to fourth direction electrodes  31 - 34  are located at the four corners of the bottom side  201  of the base dock  20 , whatever the downward displacement of the center point P of the first and second conductive elastic blades  41  and  42 , the biased distal ends, either extended at a sloped angle or a gradient, of the first to fourth conductive legs  51 - 54  can be moved towards the first to fourth direction electrodes  31 - 34 . Hence the interval problem between the distal ends of the first to fourth conductive legs  51 - 54  and the first to fourth direction electrodes  31 - 34  may be improved. As a result, erroneous movements from the joystick  50  that cause mistaken contact between the first to fourth conductive legs  51 - 54  and the first to fourth direction electrodes  31 - 34  may be avoided. 
     Due to the distal ends of the first to fourth conductive legs  51 - 54  are designed in a biased manner, the interval between them and the first to fourth direction electrodes  31 - 34  may reach 0.3 mm or more in normal conditions. Thus the oscillation amplitude of the joystick  50  may increase, and operation maneuverability improves, and fabrication and assembly difficulty may be reduced.