Push button switch using dome spring and switch element thereof

A push button switch comprising:

• a bottom plate;
• a plunger and an associated key top;
• means for mounting said plunger and associated key top for limited, reciprocating movement along a generally vertical axis relative to a generally horizontal orientation of said bottom plate;
• a terminal plate affixed to said bottom plate in a vertical orientation relative to said horizontal orientation of said bottom plate, the terminal plate having a first major surface generally parallel to the vertical axis, an indented surface with a periphery of a predetermined configuration displaced inwardly of and parallel to the major surface in a first horizontal direction relatively to the vertical axis and a central recess within the indented surface, further displaced from the indented surface in the first horizontal direction;
• plural outer contacts fixedly mounted at predetermined positions on said terminal plate within and adjacent the periphery of the indented surface and disposed to protrude toward said first major surface;
• plural inner contacts and means for flexibily mounting said plural inner contacts within the recess in the indented surface of the terminal plate, centrally of the periphery of the indented surface and protruding toward the first major surface, the mounting means resiliently urging the plural inner contacts toward the first major surface and thus in a second horizontal direction, opposite to the first horizontal direction, and permitting limited, resiliently yielding movement of the plural inner contacts in the first horizontal direction;
• a dome spring disposed in a generally vertical orientation and having a convex configuration oriented in the second horizontal direction, said dome spring having a substantially continuous surface normally in the aforesaid convex configuration in the second horizontal direction and being susceptible to a depressing force applied thereto in the first, opposite horizontal direction to snap to a convex configuration oriented in the first horizontal direction and upon release of the force to resiliently return to the second horizontal direction, the periphery of the dome spring being normally in contact with the plural outer contacts in each of the first and second horizontal directions of its convex configuration;
• and
• an actuator interconnecting said plunger and said dome spring and responsive to downward vertical movement of said plunger to apply a depressing force in the first horizontal direction for depressing and causing said dome spring to snap to the first horizontal direction, thereby to complete an electrical connection through said dome spring between said first and second contacts, the actuator comprising a lever having first and second arms extending at right angles from one another in a plane transverse to the main surface of the terminal plate and parallel to the generally vertical axis, the free end of the first arm defining a spring seat aligned with the generally vertical axis, means associated with the second arm of the lever for engaging and applying said depressing force to said dome spring and means for mounting the lever for limited pivotal movement about a pivot axis transverse to the first and second arms and adjacent and parallel to the plane of the indented surface of the terminal plate, the actuator further comprising a coil spring received on the spring seat of the first arm and connected to the plunger.