Manhole cover security lock with controlled pressure release
OwnerDavid Stadlerinventor
Life of this patent
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Abstract
A controllably releasable security locking arrangement for a manhole cover allows a manhole cover to be locked into position but allows the manhole cover to rise up in stages upon development of upward forces in an explosion to vent gases developed by the explosion. A lock body mounts a latch slide which has an outer end and which can be extended to prevent removal of the manhole cover. When a shear pin fails the lock body pivots down, to a limited extent, and a secondary shear pin can also be included allowing the cover to be blown completely free upon development of pressures of a great magnitude. A slotted skirt directs venting gas flow so as to retard the inflow of free air and attenuate the explosion.
Claims14
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.
Dependencies are inferred from the claim text.