Symmetric percussion switching device using a head point over-run device

A double percussion snap-acting switching device comprising:

• (i) a bistable dead center over-run device including:
• a toggle arm mounted about a fixed axis for rocking between first and second positions and having a striker part;
• at least first and second stops respectively defining said first and second positions, a control means whose displacement causes rocking of the toggle arm from one to the other of said positions after passing through a dead center and a spring connected between said control means and said toggle arm;
• (ii) first and second switches each comprising a fixed switch contact and a rigid switch arm carrying a movable switch contact and a surface portion on the switch arm disposed for engagement by said striker part after said toggle arm passes the dead center;
• (iii) first and second further spring means respectively biasing the rigid switch arms of the respective switches towards the respective fixed switch contact with an antagonistic force lower than that produced by the toggle arm, said toggle arm exerting on each rigid switch arm a force which is a linear function of the displacement of said toggle arm having a first predetermined slope, whereas each rigid switch arm exerts on said toggle arm a resistance force which is a linear function of said displacement having a second predetermined slope, said first slope being substantially larger than said second slope.