Self-closing gate valve system and external self-closing actuator mechanism therefor

A gate valve system of the type having a closure disc that is mounted within a valve body with a valve seat and an outlet opening and is displacable by a hand lever between a closed position, in which the closure disc is seated against the valve seat blocking the outlet opening, and an open position, in which the closure disc is shifted radially relative to the closed position, and having an external self-closing actuator mechanism, wherein said self-closing actuator mechanism comprises:

• (A) an operating rod pivotally connected to the hand lever, said rod being displacable in a first direction corresponding to a valve closing direction of movement of said hand lever and in an opposite, second direction corresponding to a valve opening direction of movement of said hand lever;
• (B) spring means for applying a force to said operating rod in said first direction;
• (C) securing means for releasably securing said spring means in a stressed readiness condition;
• and
• (D) thermally responsive releasing means for releasing said securing means in response to exposure to a temperature above a predetermined minimum value;
• wherein said spring means is operable for moving said operating rod in said first direction into a position corresponding to a valve closed position of said hand lever when released by said securing means;
• and wherein said operating rod is freely displacable in said first and second directions when said spring means is secured in said readiness condition;
• wherein said spring means comprises a spring and a spring retainer, said spring retainer being mounted with clearance about said operating rod and being engageable against an abutment stop thereon when said spring means is released;
• wherein said securing means comprises retaining clips, resilient means for applying a force acting to move said retaining clips to a position radially outward of said spring retainer, and releasable retaining means, acting on said thermally responsive means, for displacing said retaining clips against the force of said resilient means radially inwardly into a position blocking movement of said spring retainer for holding the spring means in its readiness condition.