Patent Publication Number: US-6706986-B2

Title: Scissors-like linkage structure, key switch including the structure and method of assembling the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Taiwan Patent Application No. 091110478 entitled “Scissors-like Linkage Structure, Key Switch Including the Structure and Method of Assembling the Same”, filed May 20, 2002. 
     FIELD OF INVENTION 
     The present invention generally relates to a scissors-like linkage structure for use with a key switch and a method of manufacturing the same and, more particularly, to a scissors-like linkage structure with a slot having portions of different diameters to accommodate a pivot in different configurations, a key switch including the structure, and a method of assembling the same. 
     BACKGROUND OF THE INVENTION 
     Keyboards are widely used with various devices, such as computers, to input characters and numerals. To make a key on the keyboard easy to depress, the key is usually designed to function no matter where a force is exerted on the key cap. In other words, even though the force is exerted on the edge of the cap, the force is generally equally distributed over the entire surface of the cap using a scissors-like linkage structure for each key. Furthermore, while space is especially an important consideration in designing for keyboards of portable computing devices, key switches with scissors-like linkage structure are often the solution. 
     Typically, a scissors-like linkage structure includes an inner arm and an outer arm, which are formed by the injection mold technique. Connection mechanisms are provided about on the middle portion of the inner and outer arms, so that the inner and outer arms are rotatably connected with each other to form the scissors-like linkage structure. However, in the conventional connection mechanism, the inner arm and the outer arm must be respectively formed on two independent areas by the injection mold process. Therefore, the necessary area for forming the scissors-like linkage structure is relatively large, resulting in the increase of the manufacture cost and the complication of assembling the inner and outer arms. 
     During the assembly of the scissors-like linkage structure, a step of separating the inner arm and the outer arm is firstly performed. Then, the two independent arms are sophisticatedly connected through the connection mechanism to form the scissors-like linkage structure. Therefore, the assembly process is relatively complicated and time-consuming, which induces the high assembly cost. 
     Therefore, there is a need to provide a scissors-like linkage structure to reduce the production cost and simplify the assembly process. 
     SUMMARY OF THE INVENTION 
     It is an aspect of the present invention to provide a scissors-like linkage structure for use with a key switch. The scissors-like structure has a slot including portions of different diameters, which are configured to selectively accommodate a pivot in different configurations. When the structure is formed, the pivot is located in the slot portion of larger diameter, which reduces the necessary area of producing the structure and increases the production yield by one injection mode process, and therefore the production cost per each injection mode process is reduced. By moving the pivot to the portion of smaller diameter to engage with a wall of the smaller portion, the assembly of the structure is completed at a lower assembly cost due to the simplification of the assembly process. 
     It is another aspect of the present invention to provide a scissors-like linkage structure and a key switch having the structure. The scissors-like linkage structure includes a first arm and a second arm. The first arm has a pivot. The second arm has a slot, which has a first portion and a second portion. The first portion is larger than the second portion in diameter. The second portion defines a wall. The pivot of the first arm selectively moves to the first portion and the second portion of the slot of the second arm. When the pivot moves to the second portion to engage with the wall of the second portion, the first arm is rotatably connected with the second arm in a first configuration. When the pivot of the first arm moves to the first portion of the second arm, the first arm and said second arm are in a second configuration. 
     The scissors-like linkage structure further includes a mechanism to enhance the connection when the first and second arms are in the first configuration. In a first embodiment, a protrusion is optionally provided on a sidewall of the first arm or the second arm facing the other. When the first arm and the second arm are in the first configuration, the protrusion exemplarily provided on the sidewall of the first arm contacts the second arm so that the first and second arms are closely connected. In a second embodiment, the first arm and the second arm respectively have corresponding side-edges in a complementary shape. When the first arm and the second arm are in the first configuration, the first arm movably touches the second arm through the side-edges. In a third embodiment, the second arm further includes a seal part provided on a side of the second portion. When the first arm and the second arm are in the first configuration, the seal part is configured to contact an end portion of the pivot. 
     It is a further aspect of the present invention to provide a method for assembling the scissors-like linkage structure. The method includes a step of forming the scissors-like linkage structure by one injection mold process. The pivot is located in the first portion of the slot after the process is completed. Then, the pivot is moved in the slot to engage with the second portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 illustrates a scissors-like linkage structure in a first embodiment of the present invention; 
     FIG. 2A illustrates a perspective view of the scissors-like linkage structure of FIG. 1 in a first configuration; 
     FIG. 2B illustrates a side view of the scissors-like linkage structure of FIG. 1 in the first configuration; 
     FIG. 2C illustrates a top view of the scissors-like linkage structure of FIG. 1 in the first configuration; 
     FIG. 3A illustrates a perspective view of the scissors-like linkage structure of FIG. 1 in a second configuration; 
     FIG. 3B illustrates a side view of the scissors-like linkage structure of FIG. 1 in the second configuration; 
     FIG. 3C illustrates a top view of the scissors-like linkage structure of FIG. 1 in the second configuration; 
     FIG. 4 illustrates a scissors-like linkage structure in a second embodiment of the present invention; 
     FIG. 5A illustrates a first modification of the second embodiment of the present invention; 
     FIG. 5B illustrates a second modification of the second embodiment of the present invention; and 
     FIG. 6 illustrates a side view of a key switch having the scissors-like linkage structure of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, in a first embodiment, the present invention provides a scissors-like linkage structure  10  for use with a key switch. The scissors-like linkage structure  10  includes a first arm  12  and a second arm  14 . The first arm  12  exemplarily includes a frame-like structure constituted by two arm parts  1210  and  1212  and two connecting parts  1214  and  1216 . The first arm  12  has a pivot  120  provided about on the middle portion of the arm part  1210  or  1212 . The second arm  14  exemplarily includes a frame structure constituted by two arm parts  1410  and  1412  and a connecting part  1414 . The arm part  1410  or  1412  has a slot  140  with at least two portions of different diameters ( 142  and  144 ). For example, the slot  140  includes a first portion  142  and a second portion  144 . The first portion  142  has a diameter larger than that of the second portion  144 , which defines a wall  1440 . The slot  140  is configured to selectively accommodate the pivot  120  in the first portion  142  and engage the pivot  120  with the second portion  144 . In the exemplary embodiment, the slot  140  includes a first hole  142  and a second hole  144  with a common opening for allowing the pivot  120  to selectively move to the first hole  142  and the second hole  144 . In another exemplary embodiment, the slot can include a first hole, a second hole, and a third portion, such as a groove, which allows the pivot to selectively move to the first hole and the second hole. 
     FIGS. 2A,  2 B, and  2 C respectively are a perspective view, a side view, and a top view of the first arm  12  and the second arm  14  when they are in the first configuration, i.e. the connection configuration. When the pivot  120  moves to the second portion  144  to engage with the wall  1440  of the second portion  144 , the first arm  12  is rotatably connected with the second arm  14  in the first configuration, as shown in FIG.  2 A. In other words, when the first arm  12  and the second arm  14  are in the connection configuration, the radial movement of the pivot  120  is substantially restricted in the second portion  144 . As shown in FIG. 2B, the inner diameter of the second hole  144  of the slot  140  is about the same as the outer diameter of the pivot  120  regardless of the manufacture deviation. 
     FIGS. 3A,  3 B, and  3 C respectively are a perspective view, a side view, and a top view of the first arm  12  and the second arm  14  when they are in the second configuration, i.e. the semi-connection configuration. When the pivot  120  moves to the first portion  142  of the slot  140 , the first arm  12  and the second arm  14  are in the second configuration. In other words, when the first arm  12  and the second arm  14  are in the semi-connection configuration, the pivot  120  is allowed to make radial movement in the first hole  142  because the inner diameter of the first hole  142  is larger than the outer diameter of the pivot  120  (or larger than the inner diameter of the second hole  144 ), as shown in FIG.  2 B. That is, the pivot  120  is loosely accommodated in the first portion  142  of the slot  140 , which can not form an effective support structure for a key switch when it is operated. Furthermore, the space between the first hole  142  and the pivot  120  is provided for positioning the injection mold when the first arm  12  and the second  14  arm are manufactured by one injection mold process. 
     The scissors-like linkage structure  10  further includes a mechanism to enhance the connection when the first and second arms ( 12 ,  14 ) are in the first configuration. In the first embodiment, a protrusion  122  is provided on a sidewall  124  of the first arm  12 , which faces the second arm  14  (as shown in FIG.  1 ). When the first arm  12  and the second arm  14  are in the first configuration, the protrusion  122  contacts the second arm  14  (as shown in FIG.  2 B). Therefore, the first arm  12  and the second arm  14  are rotatably closely connected to each other. It is noted that the protrusion  122  can be a portion of the first arm  12  or the second arm  14  and optionally located on a sidewall either facing the first arm or the second arm to enhance the connection of the first and second arms when they are in the first configuration. 
     In another embodiment, the first arm  12  and the second arm  14  respectively include a first side-edge  126  and a second side-edge  146 . The first side-edge  126  corresponds to the second side-edge  146  complementarily. As shown in FIGS. 2A and 2C, the first and the second side-edges ( 126 ,  146 ) are formed in a complementary shape. When the first arm  12  and the second arm  14  are in the first configuration, the first side-edge  126  movably touches the second side-edge  146 . In such configuration, when the first arm  12  rotatably connects the second arm  14 , the sway of the scissors-like linkage structure  10  during operation is prevented. 
     Referring to FIG. 4, in a second embodiment, a seal part  148  is provided on a side of the second portion  144  of the slot  140 . The seal part  148  partially or completely covers the second portion  144  on the side, which does not face the first arm  12 . The seal part  148  is configured to contact an end portion  1201  (shown in FIG. 1) of the pivot  120  when the first arm  12  and the second arm  14  are in the first configuration. Therefore, when the first arm  12  and the second arm are in the connection configuration, radial movements and movements along the longitudinal direction of the pivot  120  are substantially restricted in the second portion  144 . 
     Referring to FIG. 5A, in a third embodiment, a modification of the pivot  120  of the first and second embodiments is made to prevent the sway of the first and the second arms ( 12 ,  14 ) during operation. The pivot  150  of the third embodiment has an enlarged end portion, which makes the pivot  150  look like a T-shape pivot. As show in FIG. 5A, the pivot  150  includes a body  152  and a cap-like end portion  154 . When the first arm  12  and the second arm  14  are in the first configuration, the body  152  of the pivot  150  rotatably engages with the wall  1440  of the second hole  144 , and the cap-like end portion  154  passes through the second hole  144  to contact a sidewall of the arm part ( 1410  or  1412 ) of the second arm  14 . In such configuration, the pivot  150  can substantially not make any movement along the longitudinal direction of the body  152  in the second hole  144 . 
     It is noted that in the first or second embodiments the pivot  120  is provided on the first arm  12 , or generally referred as an inner arm, and the slot  140  is provided on the second arm  14 , or generally referred as an outer arm. However, the locations of the pivot  120  and the slot  140  are exchangeable. As shown in FIG. 5B, a second modification of the scissors-like linkage structure  10  is illustrated. In this modification, the pivot  120  is provided on an inner side of the outer arm  14 , which faces the inner arm  12 . The slot  140  is provided on the inner arm  12  corresponding to the pivot  120 . Furthermore, though the first and the second arms ( 12 ,  14 ) are frame like structure constituted by two arm parts and one or two connecting parts, the structures of the first and the second arms are not limited to the exemplary embodiments. 
     Referring to FIG. 6, a key switch  60  having the scissors-like linkage structure  10  is provided. The key switch  60  further includes a cap  62  and a base  64 , which respectively have connection parts for connecting the first arm  12  and the second arm  14  of the scissors-like linkage structure  10 . In the key switch  60 , the scissors-like linkage structure  10  forms a support for the key switch  60  when it is operated. 
     A method for assembling the scissors-like linkage structure  10  is also provided. As shown in FIGS. 3A to  3 C, the method includes the step of forming the scissors-like linkage structure  10  by one injection mold process. The pivot  120  is located in the first portion  142  of the slot  140  after the process is completed. In other words, when the injection mold process is completed, the first arm  12  and the second arm  14  are in the second configuration (semi-connection configuration). At this step, the pivot  120  is allowed to make radial movement in the first portion  142 . Furthermore, the first arm  12  and the second arm  14  are not engaged with each other because of a space  100  therebetween. The space  100  is provided for positioning the injection mold when the first arm  12  and the second  14  arm are manufactured by one injection mold process. Then, the pivot  120  moves in the slot  140  to engage with the second portion  144 , as shown in FIGS. 2A to  2 C. In other words, the pivot  120  moves from the first portion  142  to the second portion  144  to engage with the wall  1440 , and therefore the first arm  12  and the second arm  14  are in the first configuration (connection configuration) and the assembly of the scissors-like linkage structure is completed. 
     It is one advantage of the present invention to locate the pivot  120  in the first portion  142  of the slot  140 , which reduces the necessary area of producing the scissors-like linkage structure  10 , and therefore increases the production yield and reduces the production cost per each injection mode process. Furthermore, when the scissors-like linkage structure  10  is manufactured, it is already in the semi-connection (second) configuration. By moving the pivot  120  to the second portion  144  of the slot  140  to engage with the wall  1440 , the assembly of the structure is completed at a lower assembly cost due to the simplification of the assembly process. 
     Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.