Electric switching device

An electric switching device, comprising:

• a housing;
• a main contact assembly including two fixed contacts, each formed as a pin and positioned along a common center line axis and each said pin including a confronting plane surface directed to form a wedge-shaped opening, and one movable contact including two plane contact wedge-shaped surfaces conforming to the wedge-shaped opening each of said fixed contacts, said movable contact being movable between a closed position to close an electrical circuit, in which said two fixed contacts are connected, and an open position to open said electrical circuit, in which said two fixed contacts are disconnected, said main contact assembly being disposed in a first cavity in said housing;
• a piston shaft axially movable along an axis perpendicular to said common center line axis, a first end of said shaft carrying said movable contact in said first cavity, a second end of said piston shaft positioned in a second cavity in said housing, said first cavity and second cavity being interconnected through a channel in said housing, said piston shaft carrying a piston with first and second piston cavities on each end thereof;
• an auxiliary contact mechanism connected to said main contact assembly and including two movable hollow contact pins for closing and opening said electrical circuit later than the respective closing and opening of said electrical circuit by operation of said main contact assembly;
• a hydraulic system interconnected with said first cavity and said second cavity for operating said movable contact mechanism and said auxiliary contact mechanism;
• and
• two bistable mechanisms disposed in said second cavity and including at least one piston biased by means of a spring for locking said piston shaft with said movable contact in said open and closed positions in which said movable contact is positioned with a pressure drop in the hydraulic system.