Here's one way to counter that argument: let's say you run a car manufacturer. You don't happen to know about the Kearns patent, but one day while driving home in an intermittent rainstorm, you find yourself wishing your wipers didn't have to run continuously. When you get to work the next day you stop by the engineering department and say "Hey, Joe, stick a 555 timer in that windshield relay circuit, would you?"
Five years and several million cars later, Kearns jumps out of the bushes and whacks you in the kneecap with a lawsuit. What should your penalty be? Do you agree with the judge that you owe some guy $10,000,000 for a trivial idea that he happened to have before you did?
Without having read any docs or patents, I'd say some sort of bimetallic strip: two metals, different resistances/heat expansion constants. It's how they used to make turn signal timers.
Sigh. OK, let's work on the 'abstraction' thing a bit.
Given almost any mechanical or electrical technology, there exists means of using that technology to control the duty cycles of machines. The 555 was just an example of what you might use to implement an intermittent wiper.
As I understand it, accessories like windshield wipers originally operated from manifold vacuum, so the patent probably describes some sort of vacuum-based contraption which would be as obvious to MEs as a timer circuit is to EEs.
Another point being, even if it were a novel concept when implemented with vacuum lines and valves, it certainly wouldn't be novel or unexpected when cheap solid-state electronics did arrive on the scene. But chances were good that the patent claims were broad enough to hold sway over future implementations. (Disclaimer: I haven't read it.)
So fast-forward your 8-track to the early 70s: windshield wipers are now run from the car's electrical system, and wow, hey, cool, here's the 555... and meanwhile the goofy patent's still in force.
We shouldn't ignore the effect of hindsight. Lot of ideas that we think today as obvious or straight forward, may not have been all that obvious before it got popular. In that movie, Ford and Chrysler engineers apparently had trouble duplicating his model.
That said, Its not about how simple or how hard an idea is right? Its about how much value it adds.
EDIT: In your example, as long as it is not willful infringement and as long as he started making them before he patented it, there will not be any penalty. But in case of ford and Chrysler, its willful infringement.
There's still a penalty for non-willful infringement; if nothing else, the inventor can request an injunction that shuts down your whole production line. That's the scary thing about patents... unless you have comprehensive knowledge of every patent in your field of endeavor, they are financial time bombs.
If the plaintiff can show that you did know about the patent and infringe it willfully, the damages are tripled.
Well, that is why patent law keeps lots of lawyers busy. There is a principle of "nonobviousness" in patent law that requires enough engineering or science knowledge that most patent lawyers are persons with undergraduate degrees in engineering or science.
Five years and several million cars later, Kearns jumps out of the bushes and whacks you in the kneecap with a lawsuit. What should your penalty be? Do you agree with the judge that you owe some guy $10,000,000 for a trivial idea that he happened to have before you did?