Vacuum-type circuit interrupter with means for protecting its bellows against mechanical damage

A vacuum-type circuit interrupter comprising:

• a. an evacuated envelope,
• b. a pair of relatively movable contacts within said envelope,
• c. a conductive contact rod projecting through a wall of said envelope and carrying one of said contacts at one end of the rod,
• d. a flexible metal bellows of a generally tubular configuration projecting into said envelope and surrounding said contact rod, said bellows containing annular convolutions axially-spaced along its length,
• e. means for joining the inner end of said bellows to said contact rod and for joining the outer end of said bellows to said envelope wall,
• f. a guide for said contact rod comprising a tubular metal sleeve surrounding said contact rod, located within said bellows, and fixed to said envelope wall for guiding said rod for axial movement, said sleeve having an inner end wall so located that some of said convolutions are located axially inwardly thereof,
• g. means forming a slide bearing disposed between said sleeve and said contact rod, and
• h. a coating of self-lubricating plastic material on the outer peripheral surface of said sleeve and on the inner end surface of said sleeve, which coating is sufficiently close to the internal surface of said bellows as to be contacted by said convolutions when said contact rod is axially moved during operation of the interrupter, the lubricating properties of said coating reducing friction between said convolutions and said coated sleeve.