Round Manhole Cover

Concern:

The cover for an opening that is rectangular (e.g., a ground excavation), can be turned sideways and fall into the opening. People working underneath inside the opening would be in harm’s way.

Countermeasure:

A manhole cover is round because a round cover cannot fall through a circular opening of at least the same diameter, no matter how it is positioned.

Limitation:

 

Categories: , , , ,

Additional information

Triz Description

14.1: Instead of using rectilinear parts, or forms, surfaces, use curvilinear ones; move from flat surfaces to spherical ones; from parts shaped as a cube (parallelepiped) to ball-shaped structures.
Image sources

(McCarthy (2015-01-07) “Why Are Manhole Covers Round?” mentalfloss.com/article/60929/why-are-manhole-covers-round 19 OCT 2016).

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