Patent Publication Number: US-2011056817-A1

Title: Key module and manufacturing method for keycap thereof

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to key modules, and particularly to a key module with reduced height. 
     2. Description of Related Art 
     Generally, keyboards utilized in electronic devices, such as desktop computers, notebook computers and mobile phones, tend to be ultra-thin and elegant. However, keycaps of the keyboard, typically have a certain size and height and are made of plastic, therefore the thickness of the keyboard cannot be decreased any further. 
     Therefore, what is needed is to provide a key module, which can address the problem described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with reference to the following 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 embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the two views. 
         FIG. 1  is a cross-sectional view of a key module in accordance with an exemplary embodiment. 
         FIG. 2  is a flowchart of a manufacturing method for a keycap of a key module in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a key module  100  according to an exemplary embodiment is illustrated. The key module  100  may be used as an input device in an electronic device (not shown), such as a portable computer, a mobile phone, and a personal digital assistant (PDA). The key module  100  is operable for inputting commands and/or information to the electronic device. 
     The key module  100  includes a keycap  112 , a scissor-type connection mechanism  113 , a fixing plate  130 , an elastic assembly  140 , a membrane circuit board  150 , a spacer sheet  160 , and a circuit board  180  for mounting the above-mentioned components thereon. 
     The keycap  112  is resiliently supported on the circuit board  180  by the elastic assembly  140 . The keycap  112  includes a body  10  and an oxide film  20 . The oxide film  20  is attached on the body  10 , and configured for protecting the body  10 . 
     The keycap  112  is made of a first type of metal. The oxide film  20  is made of a second type of metal. In this embodiment, the first type of metal is the same as the second type of metal. In other embodiments, the first type of metal can be different from the second type of metal. As the same type of metal, the combination between the oxide film  20  and the body  10  is enhanced. 
     Comparing with a traditional keycap made of plastic, the keycap  112  is thinner. In this embodiment, the first type of metal is aluminum alloy. In other embodiments, the first type of metal can be aluminum, or other metal, or other metal alloy. Because the keycap  112  is made of metal, the keycap  112  has a pleasant appearance and is resilient and comfortable. 
     The oxide film  20  is formed by anodizing. So the surface of the oxide film  20  includes a plurality of holes, the holes are for the surface to adsorb dyes and coloring matter. The ability for decorating the keycap  112  is improved. In addition, the oxide film  20  has a compact structure, and does not tarnish or rust easily. In other embodiments, the oxide film  20  can be further processed by hot water, or high-temperature water vapor, or nickel salts, the processed oxide film  20  will have good abrasion and corrosion resistance. 
     The keycap  112  includes a first surface  11 , a second surface  13  opposite to the first surface  11 , and a sealed side surface  15  is connected between the first surface  11  and the second surface  13 . The first surface  11  is capable of receiving an external force from pressing. The first surface  11  includes a decoration  30 , such as a letter “D”. The decoration  30  is etched into the first surface  11  by laser. Compared with a traditional decoration formed on the plastic keycap by printing, the decoration  30  in the metal keycap  112  has better abrasion resistance. The second surface  13  is for transmitting the external force from the first surface  11 . A recess  14  is defined in the second surface  13 . 
     The scissor-type connection mechanism  113  includes a first support leg  115  and a second support leg  117  intersecting with each other. Each support leg  115  and  117  has a first end pivotably connected to the fixing plate  130 , and a second end slidably received in the recess  14  and connected to the keycap  112 . 
     The circuit board  180  has one surface including at least a first conductive portion  182 . The first conductive portion  182  may be a contact or a trace. In this embodiment, the circuit board  180  is a printed circuit board (PCB). 
     The membrane circuit board  150  is made of elastic material, such as mylar. The membrane circuit board  150  deforms when an external force is applied to it. The membrane circuit board  150  has one surface including at least a second conductive portion  152  aligned with (facing towards) the first conductive portion  182 . The second conductive portion  152  may also be a contact or a trace. 
     The spacer sheet  160  is disposed between the circuit board  180  and the membrane circuit board  150 . The spacer sheet  160  defines at least a first through hole  162  for allowing the first conductive portion  182  to contact the second conductive portion  152 . When the key module  100  is in a free (normal) state, the second conductive portion  152  and the first conductive portion  182  are separated by the thickness of the spacer sheet  160 , thus, forming an open circuit. 
     The elastic assembly  140  is disposed on a surface of the membrane circuit board  150  opposite to the surface having the second conductive portion  152 . The elastic assembly  140  includes a first part formed as a substantially flat plate  146 , and a second part (not labeled) protruding from the substantially flat plate  146 . The second part integrally includes a resilient member  142  and an actuating member  144 . 
     The resilient member  142  is made of non-transparent material, and has an end thereof connected to the keycap  112 . When the keycap  112  is pressed by an external force, the resilient member  142  deforms, and moves along a first direction (see O-X of  FIG. 1 ) substantially perpendicularly to and towards the circuit board  180 . After the external force is released, the resilient member  142  can provide a restoring force for pushing the keycap  112  along a second direction (see O-Y of  FIG. 1 ) opposite to the first direction, to return the keycap  112  to the normal state. 
     When the resilient member  142  deforms, the actuating member  144  can press the membrane circuit board  150 , through the first through hole  162 , so the second conductive portion  152  can contact the first conductive portion  182 , thus, forming a closed circuit. 
     The fixing board  130  is disposed above and parallel to the flat plate  146 . The fixing board  130  is configured for fixing the elastic assembly  140  and connecting the scissor-type connection mechanism  113 . The fixing board  130  defines at least a second through hole  132 . The second through hole  132  is arranged for allowing the resilient member  142  to be displaced (move) towards the membrane circuit board  150  along the first direction. In this embodiment, the fixing board  130  is made of metal to enhance the structural strength of the key module  100 . 
     When assembling, first, the key module  100  is assembled by sequentially mounting the spacer sheet  160 , the membrane circuit board  150 , the elastic assembly  140 , and the fixing plate  130  on the circuit board  180 . The fixing plate  130  is disposed substantially parallel to, and above, the flat plate  146 . The resilient member  142  extends through the second through hole  132  defined by the fixing plate  130 . Second, the resilient member  142  is connected to the keycap  112 , and the scissor-type connection mechanism  113  is coupled between the keycap  112  and the fixing plate  130 . 
     When the keycap  112  is pressed, the resilient member  142  becomes deformed, and displaces the actuating member  144  toward the resilient member  142 , thus, pressing the membrane circuit board  150 . As a result, the membrane circuit board  150  becomes deformed, causing the second conductive portion  152  to electrically contact the first conductive portion  182 , thereby forming a closed circuit and generating a signal indicating that the key module  100  is being pressed. 
     Referring to  FIG. 2 , a flowchart of a manufacturing method for the keycap  112  of the key module  100  in accordance with an exemplary embodiment is shown. The manufacturing method shown includes the following steps. 
     In step S 10 , forming a body using a first type of metal. 
     In step S 12 , forming an oxide film on the body using a second type of metal, the body and the oxide film creating an original keycap. In this embodiment, the first and the second types of metal are aluminum alloys. In other embodiments, the first and the second types of metal can be other metallic alloys or other metal, and the first type of metal can be different from the second type of metal. The oxide film is formed by anodizing. 
     In step S 14 , fixing the original keycap on a tray, the original keycap including a first surface for being pressed, a second surface opposite to the first surface and for transmitting pressure from the first surface, and a sealed side surface for connecting the first surface and the second surface. 
     In step S 16 , etching a decoration in the first surface to form a final keycap. In this embodiment, the decoration is etched in the first surface by laser. 
     The final keycap formed by the manufacturing method has the same advantages as the keycap  112  of the key module  100 . 
     It is to be understood, however, that even though numerous embodiments have been described with reference to particular embodiments, but the present disclosure is not limited to the particular embodiments described and exemplified, and the embodiments are capable of considerable variation and modification without departure from the scope of the appended claims.