A snap-action overcenter contact mechanism utilizes a spring-loaded apexed plunger depressibly cammed within a rockable actuator block. The plunger rides in tracks in the block which ensure registered pivotal movement of the block and plunger, and also guides the plunger for depression within the block...http://www.google.ca/patents/US4103127?utm_source=gb-gplus-sharePatent US4103127 - Snap-action overcenter switch having an apexed plunger depressible in a rockable actuator block and operated by a toggle lever having a positive off cam
