Abstract: A manhole cover assembly configured to behave as a relief valve in an explosion event, opening so that fluid, such as air or explosive gas, may vent from an underground area. The manhole cover assembly may include a manhole cover and a frame, and may be configured to limit movement of the manhole cover with respect to the frame in response to increased pressure on the manhole cover. In one embodiment, the manhole cover may include legs having angled surfaces adapted to substantially center or guide the manhole cover in the frame while the manhole cover displaces to release pressure. In another embodiment, one or more legs may be at least one of pivotable with respect to the manhole cover and slidable within the manhole cover to enable configuring the manhole cover between a restraint mode and a removal mode.

Abstract: A manhole cover assembly includes a frame that includes a central opening and a safety stop portion, and a cover hingedly attached to the frame such that the cover is pivotable between a closed position covering the central opening and an open position providing access to the central opening. A safety device is connected to the frame and the cover for locking the cover in the open position. Movement of the cover to the open position automatically moves the safety device to a locked position in which said safety device engages the safety stop portion and prevents movement of the cover to the closed position. When the cover is open, the safety device is manually movable between the locked position and an unlocked position in which the safety device is disengaged from the safety stop and permits movement of the cover to the closed position.

Abstract: A manhole cover assembly includes a frame that includes a central opening and a safety stop portion, and a cover hingedly attached to the frame such that the cover is pivotable between a closed position covering the central opening and an open position providing access to the central opening. A safety device is connected to the frame and the cover for locking the cover in the open position. Movement of the cover to the open position automatically moves the safety device to a locked position in which said safety device engages the safety stop portion and prevents movement of the cover to the closed position. When the cover is open, the safety device is manually movable between the locked position and an unlocked position in which the safety device is disengaged from the safety stop and permits movement of the cover to the closed position.

Abstract: A lift-assisted manhole cover assembly with a flush surface and external pivot shaft. The cover includes a mounting tab that extends beyond the general periphery of the cover. The mounting tab may be connected to a shaft that is threadedly engaged with the frame. A spring may be mounted between the frame and the mounting tab, for example, in a sleeve, to provide a mechanical assist in lifting the cover. The sleeve may be disposed outside the manhole opening where it does not block access to the manhole opening.

Abstract: A lift-assisted manhole cover assembly with a flush surface and external pivot shaft. The cover includes a mounting tab that extends beyond the general periphery of the cover. The mounting tab may be connected to a shaft that is threadedly engaged with the frame. A spring may be mounted between the frame and the mounting tab, for example, in a sleeve, to provide a mechanical assist in lifting the cover. The sleeve may be disposed outside the manhole opening where it does not block access to the manhole opening.