My father worked for Pilkingtons when they patented the float-glass process. Lots of companies tried to copy the process (without licensing the patent). They c

My father worked for Pilkingtons when they patented the float-glass process. Lots of companies tried to copy the process (without licensing the patent). They couldn't, because the patent didn't describe all the know-how needed to make the process work. Companies that licensed the patent got the benefit of an on-site engineer that would help them get their process working. So most "plate" glass was thereafter float glass, made by paying licensees. That is: the invention was really protected not by patents, but by trade secrets. And unlike with the mediaeval guilds, nobody had to be assassinated. So it seems to me that in addition to being harmful, patents really are unnecessary; as long as there is also know-how. If there is no know-how, then I don't think the patent should be issued. Therefore, there is no need for patents.