My husband developed patent # us496567..He passed away. Another company is using the procedure..Who owns the rights?
I'm sorry for your loss.
A patent has one or several inventors and one or several owners. Those do not have to overlap. The inventors stay the same, the owners can change as a patent can be treated as normal property and therefore sold.
US496567 is an old patent, it has lapsed (patents only protect an invention for a certain time, 20 years now, at that time it was less), so nobody owns it anymore.
This patent is from 1893, are you sure it is the right one?