Magnetic blow-out arc extinguishing device

Claim 1

A magnetic blow-out arc extinguishing device comprising: two pairs of separable contacts connected electrically in series including a stationary contact having a ring-shaped contact surface, a movable contact having a ring-shaped contact surface and a semi-stationary support member interposed between said stationary and movable contacts and having a first ring-shaped semi-stationary contact surface confronting and cooperating with said ring-shaped contact surface of said stationary contact to form a first pair of contacts and a second ring-shaped semi-stationary contact surface cooperating with said ring-shaped contact surface of said movable contact to form a second pair of contacts, said first and second ring-shaped semi-stationary contact surfaces being connected electrically and mechanically to each other, actuating means for moving said movable contact towards the separated position of said pairs of separable contacts, means for moving said semi-stationary support member to follow said movable contact along a predetermined stroke for separating said first pair of contacts just before said second pair of contacts is separated and drawing arcs between both pairs of contacts, a blow-out coil having a longitudinal axis extending parallel to the path followed by said arcs, said coil having a pair of terminals connected across said first pair of contacts so as to be energized at the appearance of an arc-voltage between the contacts of said first pair and developing a magnetic blow-out field, said ring-shaped contact surfaces on said stationary, semi-stationary and movable contacts being disposed coaxially with the longitudinal axis and outside said coil so that said magnetic field directed substantially radially between said ring-shaped surfaces causes rotation of the arc drawn between the separated contacts of said first pair and of the arc drawn between said second pair of contacts.