Switch Device

A switch device, comprising:

• a base board having a face on which a fixed contact is provided;
• and
• an elastic sheet that covers the face of the base board,
• wherein the elastic sheet includes:
• a contact dome part that covers the fixed contact to form a hollow contact chamber between the base board and contact dome part and is elastically deformed by receiving an operating force;
• a movable contact that is provided on the contact dome part so as to face the fixed contact and contacts with the fixed contact when the contact dome part is elastically deformed;
• a first recessed part that forms a hollow air accumulating chamber between the base board and the first recessed part;
• a second recessed part that forms a hollow foreign material accumulating chamber between the base board and the second recessed part;
• a guide groove that has a straight part connected to the first recessed part and a circular arc part connected to the second recessed part at a position deviating from an extending line of the straight part to form a guide passage between the base board and the guide groove for communicating the air accumulating chamber with the foreign material accumulating chamber;
• a nonreturn part provided inside the circular arc part in a connecting part of the second recessed part and the circular arc part of the guide groove;
• and
• a vent groove connected to the contact dome part and the guide groove to form a vent passage between the base board and the vent groove for communicating the contact chamber with the guide passage.