초록 ▼

A balancing mechanism for manhole covers uses two sets of conical disc springs, one stronger than the other, mounted on a common pull rod, to balance the cover as it moves from the open vertical position to the closed position. This provides a progressive spring force curve that balances the manhole

A balancing mechanism for manhole covers uses two sets of conical disc springs, one stronger than the other, mounted on a common pull rod, to balance the cover as it moves from the open vertical position to the closed position. This provides a progressive spring force curve that balances the manhole in any position between the closed position and the vertical position. The balancing mechanism is also provided with an additional set of disc springs that absorb shock when the cover is opened rapidly. The mechanism is preferably mounted on a nozzle protection ring, which allows the system to be installed on existing glass lined vessels without welding, drilling or similar operations which might damage the lining.

대표청구항 ▼

In a balancing aid for a pivotally mounted manhole cover, comprising a stack of conical disc springs and means to compress said stack of springs as said cover pivots from an open vertical position to a closed position, the improvement wherein said stack of springs comprises a first subset of springs

In a balancing aid for a pivotally mounted manhole cover, comprising a stack of conical disc springs and means to compress said stack of springs as said cover pivots from an open vertical position to a closed position, the improvement wherein said stack of springs comprises a first subset of springs having a first diameter and a second subset of springs having a different diameter, with said first subset having a steeper spring force characteristic curve than said second subset, whereby the overall spring force characteristic curve of said combined stack of springs as said cover pivots from the open vertical position to the closed position is progressive.