Abstract: A quick opening manhole cover assembly is provided which is suitable for use with virtually any shape manhole cover of a pressure vessel. The assembly broadly includes a manhole cover having outer dimensions which are less than the inner dimensions of the manhole so that the cover can pass freely therethrough. The assembly also includes a structure for raising and lowering the cover into and out of the manhole. A sliding lock mechanism is located above the cover and is engageable to prevent axial movement of the cover. A safety mechanism is provided to prevent the lock from disengaging when the vessel is under pressure. Once the lock is engaged, the cover is raised and a seal carried atop the cover provides a fluid tight sealing engagement of the cover. The pressure within the vessel urges the cover further upward to further ensure the integrity of the seal.

Abstract: The invention relates to an improved balancing aid for a pivotally mounted cover for a manhole comprising means for hinging the cover relative to the manhole so the cover may be rotated about the hinge to expose and cover the manhole; and a spring retaining means comprising a rod pivotally secured to the cover, said rod being at least partially encased by a housing, said housing containing a compression spring means which is compressed when the cover is closed; wherein the improvement comprises securing the spring retaining means by attachment means which may be removed only after the spring means is first removed.