Snap action mechanism and pressure switch employing it

A pressure switch in accordance with the present invention includes an external force transmission mechanism for separating a cover and a housing from each other. A chamber defined by the above-mentioned cover and the above-mentioned external force transmission mechanism serves as a first pressure chamber, and a chamber defined by the above-mentioned housing and the above-mentioned external force transmission mechanism serves as a second pressure chamber. In the second pressure chamber, a movable piece having first and second movable members arranged opposite to each other and one or more fixed contacts are disposed. The first and second movable members are connected to each other via a flat spring. A contact is disposed on the second movable member and functions as a movable contact. The above-mentioned external force transmission mechanism applies an external force to the first movable member to displace the first movable member, and the second movable member is reversed at the operating point of the first