Vacuum circuit breaker with improved means for limiting overtravel of movable contact at end of opening stroke

A vacuum-type circuit breaker comprising:

• a. an evacuated envelope,
• b. a pair of separable contacts within said envelope, one of which is movable relative to the other,
• c. a contact rod extending into said envelope for carrying said one contact,
• d. a flexible metal bellows connected between said contact rod and said envelope for providing a seal about said contact rod,
• e. a wipe mechanism comprising:
• e1. a driven part coupled to said contact rod,
• e2. a driving part through which contact operating force is applied to said driven part, and
• e3. preloaded spring means between said driving and driven parts through which driving force is transmitted from said driving to said driven part during contact-closing motion, said spring means yielding to store energy when said driving part is driven through contact-wipe travel after said contacts engage at the end of a closing operation,
• f. an operating member movable with respect to said driving part but coupled to said driving part and operable through a closing stroke to transmit closing motion to said one contact through said wipe mechanism;
• said operating member and said driving part continuing to move through contact-wipe travel after said contacts engage at the end of a closing stroke, thereby storing energy in said spring means,
• g. said operating memer being operable through an opening stroke to drive said driving part against said driven part to impart contact-opening motion to said driven part,
• h. first stop means for stopping said operating member at the end of its opening stroke with such abruptness that said driven part overruns said driving part following such stopping against the opposition of said preloaded spring means,
• i. second stop means for limiting overrunning of said driven part with respect to said driving part following said stopping of said driving part comprising a stop carried by said operating member for engaging said driven part and thereby blocking said overrunning after a limited amount of such overrunning sufficiently low to prevent damage to said bellows despite thousands of excursions of said driven part through said overrunning travel, said stop being carried on said operating member in such a location that the stop is spaced from said wipe mechanism during contact-wipe travel at the end of a closing stroke.