Patent ID: 7484908

Claim:
A controlled release security locking arrangement for a manhole cover fit into a manhole opening defined by a surrounding enclosure comprising: a lock body assembly secured to the underside of the manhole cover adjacent a perimeter of said cover and including a latch slide mounted to said lock body selectively movable radially; an actuator element drivingly engaged with said latch slide and accessible from the top of said manhole cover to enable outward radial movement of said latch slide to position an outer portion thereof to be engageable with a feature on the inside of said enclosure upon upward movement of said cover to prevent removal of said cover; and a clearance space between said feature and said outer portion of said latch slide sufficient to allow a limited vertical rise of said manhole cover to a position which is clear of said enclosure so as to create a gas venting gap extending around a perimeter of said manhole cover in the event of an explosion.