Patent Publication Number: US-2005121300-A1

Title: Keyboard keys using marked elastic domes and fabrication method thereof

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to keyboard keys with marked elastic domes and the fabrication method thereof, and in particular to elastic domes with geometric marks for the keys of a notebook computer and the fabrication method thereof.  
      2. Description of the Related Art  
       FIG. 1A  is an exploded view of a conventional keyboard.  FIG. 1B  is a cross section of a key of a notebook computer. In order to simplify the drawing,  FIG. 1A  only shows one key of a conventional keyboard. In  FIG. 1A , the key of a keyboard for a notebook computer includes a key cap  11 , a cap support  12 , an elastic sheet  13 , a circuit membrane assembly  14  and a base sheet  15 .  
      The base sheet  15  is a metal sheet on which two seats  151  and a hook  152  are formed by punching and contacting.  
      The circuit membrane assembly  14  is disposed on the base sheet  15 . It comprises the circuit of the keyboard and a plurality of holes  141  with respect to the seats  151  and the hook  152  of the base sheet  15 .  
      The elastic sheet  13  has a sheet-like body, an elastic dome  131 , a connecting portion  133  and holes  132 . The connecting portions  133  connect the elastic dome  131  and the sheet-like body. Further, the elastic dome  131  has a plunger (not shown) inside to contact the circuit membrane assembly  14  and conduct the circuit thereto.  
      The cap support  12  has a first linking bracket  121  and a second linking bracket  122 . The shaft portions  1221  of the second linking bracket  122  are inserted into the holes  1211  of the first linking bracket  121 , so that the first linking bracket  121  and the second linking bracket  122  are hinged together. This structure is known as a scissors-type support mechanism. Furthermore, the first linking bracket  121  has shaft rods  1212 . The second linking bracket  122  has shaft rods  1222  on its corners.  
       FIG. 1C  is a schematic back view of a key cap of the key in  FIG. 1A . In  FIG. 1C , the key cap  11  has hooks  111  and holding portions  112 ,  113  on its bottom surface.  
      In FIGS.  1 A˜ 1 C, while assembling the conventional keyboard, the circuit membrane assembly  14  and the elastic sheet  13  are put on the base sheet  15 . The seats  151  and the hook  152  of the base sheet  15  protrude through the holes  141  of the circuit membrane assembly  14  and the holes  132  of the elastic sheet  13 . The key cap  11  is mounted on the base sheet  15  via the cap support  12 . The shaft rods  1212  are inserted into the seats  151  so that the first linking bracket  121  is rotatable with respect to the base sheet  15 . The narrow portion  1221  of the second linking bracket  122  is hooked by the hook  152  of the base sheet  15  so that the second linking bracket  122  is also rotatable with respect to the base sheet  15 . The hooks  111  hold the shaft rods  1212  of the first linking bracket  121 , and the holding portions  112 ,  113 , hold the shaft rods  1222  of the second linking bracket  122 . Furthermore, the L-shaped hooks  111  contact the first linking bracket  121  in  FIG. 1C .  
      In operation, the user pushes down the key cap  11  and compresses the elastic dome  131 . Then, the plunger of the elastic dome  131  contacts the circuit membrane assembly  14  so that a completed circuit is induced to send out a corresponding signal.  
      The elastic domes of conventional keyboards are made by molding. An elastic membrane with a plurality of elastic domes is first formed. The elastic domes are separated from the elastic membrane, and then the elastic domes are bonded on the elastic sheet  13  arbitrarily. During the process, however, when elastic domes are broken, it is unknown which mold cavities have defects, or whether the mold or jigs are improperly designed. Thus, there must an additional sifting process during assembly. The broken elastic domes must be sifted out before the adhesion process to avoid producing keyboards with bad keys, and the running cost increases.  
     SUMMARY OF THE INVENTION  
      Accordingly, an object of the invention is to provide marked elastic domes made by a mold with marked mold cavities. The related mold cavities can be checked according to the marks on broken elastic domes. The marked elastic domes thoroughly solve the problem and save time spent in the sifting process.  
      Another object of the invention is to provide a key structure using the elastic dome of the invention. It is easy to trace defects in the mold and jigs, such that the running cost is reduced.  
      The present invention provides a method for fabricating elastic domes. The method first comprises providing a mold having a plurality of mold cavities with markable surfaces. Next, a plurality of different marks is formed thereon. An elastic membrane with marked elastic domes is formed by the mold. The marks on the elastic domes represent the position or a serial number with respect to the mold cavities on the mold. Finally, the marked elastic domes are separated from the elastic membrane.  
      According to the method of the invention, the marks represent the parameters of fabricating the elastic membrane.  
      The present invention also provides a marked elastic dome made by the method provided above. The marked elastic dome has a main body with a markable surface and a plurality of marks disposed therein. The markable surface is divided into a plurality of mark areas to separate the marks into groups. The second marks of each of the mark areas have the same intervals. The marks between each two mark areas are protrusions or recesses, and the figures thereon are different.  
      According to the invention, the elastic dome further includes a datum on the markable surface and separations between each two mark areas. Furthermore, the separations are protrusions or recesses with a figure different from the figure of the second marks.  
      The present invention also provides a key structure using a marked elastic dome made by the method provided above. The linking mechanism of the key movably connects a key cap and a base sheet. An elastic dome has a markable surface with marks and is disposed on the base sheet below the key cap.  
      Moreover, the elastic dome further includes a flange at the bottom portion. The markable surface is the top surface of the flange.  
      Moreover, the elastic dome further includes a contact portion for supporting the key cap. The markable surface is the top surface of the contact portion.  
      A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
       FIG. 1A  is an exploded view of keys of the conventional keyboard as referenced in the Prior Art;  
       FIG. 1B  is a cross section of a key of the key board in  FIG. 1A ;  
       FIG. 1C  is a schematic back view of a key cap of the key in  FIG. 1A ;  
       FIG. 2A  is a top view of the cope of the mold for manufacturing the elastic domes of the invention;  
       FIG. 2B  is a cross section of the line S-S in  FIG. 2A ;  
       FIG. 2C  is a cross section of the drag of the mold for manufacturing the elastic domes of the invention;  
       FIG. 3A  is a partial top view of the elastic membrane with elastic domes;  
       FIG. 3B  is a top view of a marked elastic dome of the invention;  
       FIG. 3C  is a side view of a marked elastic dome of the invention;  
       FIG. 3D  is a table for the marks on the elastic dome in  FIG. 3B ;  
      FIGS.  3 E˜ 3 H are side views of a marked elastic dome of other embodiments of the invention;  
       FIG. 3I  is a top view of a marked elastic dome of another embodiment of the invention;  
       FIG. 4  is a top view of a marked elastic dome of another embodiment of the invention;  
       FIG. 5  is a partial top view of marked elastic domes disposed on the elastic sheet of a keyboard; and  
       FIG. 6  is a flowchart of fabricating the marked elastic domes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In  FIGS. 1A and 1B , the key comprises a base sheet  15 , a linking mechanism  12 , a key cap  11 , and an elastic dome  131 . The linking mechanism  12  of the key movably connects a key cap  11  and a base sheet  15 . The elastic dome  131  is disposed on the base sheet  15  below the key cap  11 .  
     First Embodiment  
      According to the key structure stated above, the diameter of the elastic dome is about 3 to 8 mm. There is not enough area to mark a number on the elastic dome. Thus, the elastic dome of the invention is marked on the flange or the contact portion to show the serial number, or position, of the mold cavities on the mold.  
       FIG. 2A  is a top view of the cope of the mold for manufacturing the elastic domes of the invention.  FIG. 2B  is a cross section of the line S-S in  FIG. 2A .  FIG. 2C  is a cross section of the drag with respect to the cope in  FIG. 2A . In  FIGS. 2A and 2B , the cope  20  of the mold has a plurality of mold cavities  22 . Each mold cavity  22  is numbered by a serial number  21  and has a first markable surface  224  with different first marks  223 . In this embodiment, the marks disposed on the first markable surface  224  include a datum  221 , separations  222 , and a plurality of first marks  223 . The first markable surface  224  is divided into three mark areas by the datum  221  and the separations  222  to distinguish the first marks  223  into three groups. The datum  221 , the separations  222 , and the first marks  223  are recesses. The datum  221  is a tangent short line. The separations  222  are radial short lines. The first marks  223  are circular spots. Furthermore, the first marks  223  of each mark area have the same intervals. The datum  221  is a start point for determining the serial number of each mold cavity  22 . In  FIG. 2C , the drag  230  has protrusions  231 ,  231 ′ with respect to the mold cavities  22  on the cope  20 .  
       FIG. 3A  is a partial top view of the elastic membrane with elastic domes. The elastic membrane in  FIG. 3A  is formed by the mold shown in FIGS.  2 A˜ 2 B. The elastic membrane is rubber. It has a plurality of elastic domes  32 . Each of the elastic domes  32  has a flange  324  at the bottom portion and a serial numbers  31  with respect to the mold cavities  22  on the cope  20  in  FIG. 2A . Each of the flanges  324  has a datum  321 , separations  322  and second marks  323  disposed thereon. The elastic domes  32  are then separated from the elastic membrane  30  by jigs and used in the key structure of the invention.  
       FIG. 3B  is a top view of the marked elastic dome of the invention, and  FIG. 3C  is its side view. In this embodiment, the elastic dome  32 ′ has a flange  324  at the bottom portion. The top surface of flange  324  is taken as, a second markable surface with respect to the first markable surface  224  of the mold cavities  22  in  FIG. 2A . The datum  321 , the separations  322 , and the second marks  323  are protrusions with respect to the datum  221 , the separations  222 , and the second marks  223 . As well, the datum  321  is a tangent short line. The separations  322  are radial short lines. The second marks  323  are circular spots. The second markable surface of the flange  324  is divided into three mark areas named area A, area B and area C by the datum  321  and the separations  322 . The second marks  323  are divided into three groups. The second marks  323  of each mark area (area A˜C) have the same angular intervals  0 . The datum  321  is a start point for determining the serial number of each mold cavity  22 . Furthermore, other shapes of protrusions, such as square or triangle, can be replaced the second marks, the datum and the separations.  
       FIG. 3D  is a table for the marks on the elastic dome in  FIG. 3B . In FIGS.  3 B˜ 3 D, the second markable surface of the flange  324  is divided into three mark areas or groups clockwise named areas A, B, and C. The second marks in area A represent the hundreds place of the serial number. As well, the digit in area B represents the tens place, and the digit in area C represents the ones place of the serial number, revealing the serial number of the elastic dome and the related mold cavity. For an example, if the area A of the elastic dome  32 ′ has four protrusions, the area B has no protrusions, and the area C has seven protrusions, the serial number of the elastic dome is  407 . If this elastic dome is broken, the related mold cavity on the mold can be identified to find the defects.  
      According to this embodiment, the second marks, the datum and the separations can be recesses  326  ( FIG. 3E ) or through holes  327  ( FIG. 3H ) on the flange  324 .  
      Furthermore, the elastic dome  32 ′ has a top surface on a contact portion  325  to support a key. The second marks, the datum and the separations can be protrusions  323  ( FIG. 3F ) or recesses  326  ( FIG. 3G ) on the top surface of the contact portion  325  of the elastic dome  32 ′. As well, the second marks can be through holes on the flange of the elastic dome ( FIG. 3H ).  
      In  FIG. 3I , each group of the second marks  328   a ,  328   b , and  328   c  on the flange  324  has different shapes. The datum and the separations are canceled by setting the circular protrusions  328   a  as the start point. Thus, the second marks  328   a ,  328   b , and  328   c  identify the serial number of the elastic dome  32 ′.  
      In this embodiment, the number of the mark areas can be increased or reduced according to the number of the mold cavities on the mold. In addition, the fabricating parameters can be recorded by adding additional mark areas, such as a batch number, a mold number and the temperature or the pressure of molding processes. Moreover, more mold cavities on the mold can be numbered by adding more mark areas.  
     Second Embodiment  
       FIG. 4  is a top view of a marked elastic dome of the second embodiment of the invention. In  FIG. 4 , the top surface of the flange  44  or the contact portion  45  is the second markable surface. There are a datum  41  and a separation  42  dividing the second markable surface into areas D and E. A plurality of the second marks  43  is disposed on the second markable surface. The second marks have the same intervals θ. The second marks  43  in the area D represent the row number of the mold cavities on the mold. The second marks in the area E represent the column number of the mold cavities on the mold. In this embodiment, different second marks  43 , or symbols, represent “ 10 ”, “ 5 ”, and “ 1 ”. In  FIG. 4 , “X” represents “ 10 ”, “V” represents “ 5 ” and the circular spot represents “ 1 ”. Different second marks avoid calculating errors and save time. The serial number of the elastic dome  40 , or mold cavity, is determined by adding the number on the elastic dome  40 . That is ( 17 , 3 ), which means the elastic dome  40  is formed by the mold cavity at the seventeenth row and the third column.  
       FIG. 5  is a partial top view of marked elastic domes disposed on the elastic sheet of a keyboard. In  FIG. 5 , the elastic domes  32 ′ are randomly adhered to the elastic sheet  50 . If the elastic dome  32 ′ is broken, the related mold cavity of the mold or jigs can be checked according to the serial number, revealing problems with the molding fabrication and/or defects in the mold or jigs, while reducing the yield ratio.  
       FIG. 6  is a flowchart of fabricating the marked elastic domes. Referring to FIGS.  2 A˜ 2 C,  3 A and  6 , the present invention provides a method for fabricating elastic domes. The method first comprises providing a mold (S 61 ), including a cope  20  and a drag  230 . The cope  20  has a plurality of mold cavities  22 . Each of the mold cavities  22  has a serial number  21  and a first markable surface  224  with different first marks  223 . The serial numbers  21  are numbered by the position of the mold cavities  22  (S 62 ). The first marks  223  are formed with respect to the serial number  21  of each mold cavity. Next, an elastic membrane  30  with a plurality of marked elastic domes  32  is formed by the mold (S 63 ). The second marks  323  on the elastic domes  32  represent the position or a serial number with respect to the mold cavities  22 . Finally, the marked elastic domes  32  are separated from the elastic membrane  30  (S 64 ). For use in the key structure of keyboards for notebook computers.  
      While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. 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 so as to encompass all such modifications and similar arrangements.