Try that argument next time you invent something on a lunch break and want the patent assigned to you :)

I just checked my contract again. If the patent is outside the scope of my work activities, and I don't write up the application while I am at work, I don't see how they could claim it.

But then Americans have these funny "all your intellectual property are belong to us" clauses in work contracts....

Try making the argument that the invention was developed purely over the course of lunch

The larger problem is that the IP assignment clauses are way too broad in the US. When I worked at Microsoft I had one that theoretically covered everything I wrote regardless of when, where, or on what devices. As an hourly worker, though, Microsoft was never going to exercise that due to overtime issues.

I rechecked my contract and under the terms of the contract, if it is specific to my work at my employer, they could claim it, but frankly we prefer to release everything that isn't specific to our industry open source anyway, so.....