[sdgsdgsdg]

I cannot understand the logic that could make this kind of contract enforceable.

By this reasoning, the patent office employing Albert Einstein owned the theory of Special Relativity and presumably therefore a stake in subsequent commercialised technological development?

It makes me feel physically sick that this is a thing.

I had a probably similar clause in an old contract, anything I built or indeed thought, in or out of work belonged to the company.