Vacuum-type interrupter having an annular insulator

A vacuum-type interrupter comprising:

• a stationary contact member;
• a second contact member axially movable with respect to said stationary contact member;
• a contact stud associated with said second contact member;
• a bellows soldered to said contact stud with one end of the bellows in the immediate vicinity of said second contact member;
• a housing surrounding said stationary contact member, said second contact member and said bellows, said housing including,
• a first cap-like metal part allocated to said contact stud,
• a second cap-like metal part, and
• an annular insulator being disposed concentrically with respect to said bellows and having a wall thickness substantially equal to an axial length of the annular insulator in, area of an end face wherein said second cap-like metal part is joined to said annular insulator by a knife-edge soldered joint, and
• a cap-shaped protective shield open toward an arc gap and disposed at a base of the second contact member, said protective shield including a rim surrounding said base of said second contact member, a radial clearance of the rim from a periphery of said second contact member amounting to approximately 2 to 4 and a height of the shield rim in an axial direction of said second contact member amounting to at least about 4 mm, and being so dimensioned that any partial arcs that might be struck, in which roots of the arcs at an outer wall of the movable contact member tend to migrate toward the contact stud, are confined to a zero-field space formed by the cap-shaped protective shield.