Patent Publication Number: US-7589293-B2

Title: Membrane switch circuit and keyswitch using such membrane switch circuit

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a membrane switch circuit and a keyswitch using the membrane switch circuit. 
   2. Description of the Prior Art 
   A keyboard, which is the most common input device, can be found in variety of electronic equipments, such as household computer, laptop computer, personal digital assistance (PDA), or the like. A membrane keyboard has been widespread because it produces less noise while pressing a membrane keyswitch. 
   During the procedures of manufacturing a membrane keyboard, a deformable member is adhered to an insulating layer of a membrane switch circuit. The deformable member is deeply affected by air therein while being pressed. If the keyswitch has a vent, the deformable member will move smoothly when the keyswitch is pressed. Accordingly, the user can use the keyboard with great smoothness. 
   However, it is a critical consideration about where the vent should be disposed. For example, Hu (U.S. Pat. No. 6,191,776) has disclosed a keyswitch structure with a vent. Although the air can be exhausted from the vent, liquids (e.g. water or beverage) may enter the keyboard through the vent since the vent is disposed on a base plate. Consequently, the circuit within the keyboard may be damaged. 
   Therefore, the invention discloses a membrane switch circuit and keyswitch using such membrane switch circuit to solve the aforesaid problems. 
   SUMMARY OF THE INVENTION 
   A scope of the invention is to provide a membrane switch circuit and a keyswitch using the membrane switch circuit. The keyswitch comprises a deformable member disposed on the membrane switch circuit. 
   According to an embodiment of the invention, the membrane switch circuit comprises a membrane circuit, an adhering layer, and an insulating layer. 
   There is a switch disposed on the membrane circuit. The adhering layer is formed on the membrane circuit and surrounds the switch. The adhering layer comprises at least one gap. The insulating layer is formed on the adhering layer. The insulating layer comprises a hole in which the switch is exposed. 
   A bottom of the deformable member is adhered to the insulating layer. In particular, the at least one gap covered by the bottom of the deformable member is utilized as at least one vent. 
   According to another embodiment, the invention discloses a keyswitch comprising a keycap, a substrate, a membrane circuit, an adhering layer, an insulating layer, a deformable member, and a supporting device. 
   The membrane circuit is disposed on the substrate, and there is a switch disposed on the membrane circuit. The adhering layer is formed on the membrane circuit and surrounds the switch. The adhering layer comprises at least one gap. The insulating layer is formed on the adhering layer. The insulating layer comprises a hole in which the switch is exposed. A bottom of the deformable member is adhered to the insulating layer. In particular, the at least one gap covered by the bottom of the deformable member is utilized as at least one vent. 
   The supporting device is movably disposed between the keycap and the substrate. The supporting device supports the keycap to vertically move relative to the substrate, wherein the deformable member is actuated to switch on the switch in response to the movement of the keycap. Air within the deformable member escapes from the at least one vent when the keycap moves toward the substrate. 
   Compared with the prior art, since the membrane switch circuit applied in the keyswitch according to the invention has a vent itself, the deformable member will move smoothly when the keyswitch is pressed. Accordingly, the user can use the keyboard with great smoothness. Besides, since the vent is disposed within the membrane switch circuit, it can prevent liquids from entering the keyboard via the vent. Accordingly, the circuit within the keyboard will not be damaged. 
   The advantage and spirit of the invention may be understood by the following recitations together with the appended drawings. 

   
     BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
       FIG. 1  is an exploded view illustrating a membrane switch circuit used in a keyswitch according to an embodiment of the invention. 
       FIG. 2  is a sectional view illustrating the membrane switch circuit  1  shown in  FIG. 1 . 
       FIG. 3  is an exploded view illustrating a keyswitch according to another embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Please refer to  FIG. 1 .  FIG. 1  is an exploded view illustrating a membrane switch circuit  1  used in a keyswitch according to an embodiment of the invention. As shown in  FIG. 1 , a deformable member  2  of the keyswitch (not shown) is disposed upon the membrane switch circuit  1 . 
   As shown in  FIG. 1 , the membrane switch circuit  1  comprises a membrane circuit  10 , an adhering layer  12 , and an insulating layer  14 . 
   In an embodiment, the membrane circuit  10  is substantially made of Polyethylene Terephthalate (PET). 
   There is a switch  100  disposed on the membrane circuit  10 . The adhering layer  12  is formed on the membrane circuit  10  and surrounds the switch  100 . The adhering layer  12  comprises at least one gap. In this embodiment, the adhering layer  12  comprises, but not limited to, one gap. That is to say, in practical application, the adhering layer  12  may comprise more than one gap. 
   In an embodiment, the adhering layer  12  is made of, but not limited to, water-proof glue. 
   Please refer to  FIG. 2 .  FIG. 2  is a sectional view illustrating the membrane switch circuit  1  shown in  FIG. 1 . 
   As shown in  FIG. 2 , the insulating layer  14  is formed on the adhering layer  12 . The insulating layer  14  comprises a hole  140 . The switch  100  is exposed in the hole  140 . In practical application, the insulating layer  14  can be made of resin. 
   A bottom of the deformable member  2  is adhered to the insulating layer  14 . In particular, the at least one gap covered by the bottom of the deformable member  2  can be utilized as at least one vent. Therefore, when the deformable member  2  is depressed, air within the deformable member can escape from the at least one vent to the atmosphere. As a result, the deformable member  2  will move smoothly when being pressed. Accordingly, the user can use the keyboard with great smoothness. 
   Please refer to  FIG. 3 .  FIG. 3  is an exploded view illustrating a keyswitch  3  according to another embodiment of the invention. 
   The keyswitch  3  comprises a keycap  30 , a substrate  32 , a membrane circuit  34 , an adhering layer  36 , an insulating layer  38 , a deformable member  40 , and a supporting device  42 . 
   In an embodiment, the membrane circuit  34  is substantially made of Polyethylene Terephthalate (PET). 
   The membrane circuit  34  is disposed on the substrate  32  and the membrane circuit  34  thereon comprises a switch  340 . 
   The switch  340  comprises a first conductive portion  3400  and a second conductive portion  3402  separated from the first conductive portion  3400 . In practical application, the first conductive portion  3400  and the second conductive portion  3402  can be covered by a carbon paste. 
   The adhering layer  36  is formed on the membrane circuit  34  and surrounds the switch  340 . The adhering layer  36  comprises at least one gap. In this embodiment, the adhering layer  36  has, but not limited to, one gap. 
   In an embodiment, the adhering layer  36  is made of, but not limited to, water-proof glue. 
   The insulating layer  38  is formed on the adhering layer  36 . The insulating layer  38  comprises a hole  380 . The switch  340  is exposed in the hole  380 . A bottom of the deformable member  40  is adhered to the insulating layer  38 . In particular, the at least one gap covered by the bottom of the deformable member  40  is utilized as at least one vent. 
   The supporting device  42  is movably disposed between the keycap  30  and the substrate  32 . The supporting device  42  supports the keycap  30  to vertically move relative to the substrate  32 . The deformable member  40  comprises a contact portion (not shown). As the deformable member  40  is pressed in response to the movement of the keycap  30 , the contact portion (not shown) contacts the first conductive portion  3400  and the second conductive portion  3402  at the same time, so as to switch on the switch  340 . Besides, while the keycap  30  is moving toward the substrate  32 , air within the deformable member  40  escapes from the at least one vent. 
   Compared with the prior art, since the membrane switch circuit applied in the keyswitch according to the invention has a vent itself, the deformable member will move smoothly when the keyswitch is pressed. Accordingly, the user can use the keyboard with great smoothness. Besides, since the vent is disposed within the membrane switch circuit, it can prevent liquids from entering the keyboard via the vent. Accordingly, the circuit within the keyboard will not be damaged. 
   With the example and explanations above, the features and spirits of the invention will be hopefully well described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.