Automatic servo-controlled valve with high-speed opening

An automatic quick-release vent and pressure-relief valve structure comprising, a frame secured in use around an opening through which gases under pressure are vented to relieve the pressure thereof, a cover pivotally mounted on the frame movable to a closed position on the frame for closing the opening and movable to an open position in which said opening is opened, a lock mechanism comprising a locking pin fixed to an underside of the cover to which said gases apply pressure in a direction toward opening the cover, said lock mechanism further including a lock device having a slide bolt overlying the locking pin holding the cover on the frame in a closed position, said lock device having variably adjustable biasing means for variably biasing the slide bolt to an extracted position overlying said locking pin to hold the cover closed, said locking pin and slide bolt having surfaces coactive and effectively in response to pressure of gases on said cover developing a force component axially of the slide bolt against biasing pressure of said biasing means for effecting release in response to said pressure on the underside of the cover, and an automatic a activator biasing the closed clover to an open position automatically opening the cover when said slide bolt is retracted.