True, a patent confers a sort of monopoly. Also true, one of the intentions of patent law is to reward an inventor with a competitive advantage. But, exactly what does that mean, and is it that easy?
Patent rights are defined by their claims. A competitor infringes a patent if their competing product has each and every recited element of at least one claim of the patent. That competing product will still infringe if it has more elements, but not if it has fewer than recited in that claim. Sometimes, an element in a patent claim can be stretched a bit by a court of law, to cover equivalent structures. So far, so good.
But, there are defenses to allegations of patent infringement. For example, the competitor might be able to show their product is the same as that shown by an expired patent. So, expired patents can provide protection to your competitor, since once a patent expires it becomes part of the public domain. Other defenses may also arise from a competitor's own prior patent. Or, the competitor may be able to invalidate your patent, for example based on other prior art or issues of fraud. Just owning a patent might not be enough in these cases.
Let's say your competitor does infringe, has no valid defenses, and cannot invalidate your patent. Great, right? Not so fast – patent litigation costs real money, sometimes big money, so if you sue it has to be worth it. Small time infringement would likely result in very small damages, and your litigation costs could easily exceed the damages you recover. It may pay to wait until damages have mounted, or it may be necessary to simply overlook small or token infringements.
If a big company infringes in a big way, it may well pay to sue them for patent infringement. Let's say the big company is infringing, is making big money, and has no valid defenses. They still have two main options: offer you a license fee, or engage in a long and protracted litigation and hope you run out of money. The costs of litigation include discovery costs, motions and answers, depositions and interrogatories, and more. That adds up fast, even if your litigation attorney works for free, which is not likely. Contingency litigators are scarce in the patent field, are in high demand, and can command exorbitant rewards if they are successful.
Don't feel a patent is less valuable in light of the above – not so! For there is a flip side. Your competitors have to reckon with the above factors too. No one really wants a lawsuit, especially not one as expensive to defend as a patent lawsuit. A patent can often deter competitors, and this may be true even if the competitor feels they have a valid defense to an allegation of infringement.
No two situations are identical. An experienced patent attorney should be able to help guide you, especially one with litigation experience. Nothing in the above constitutes legal advice; you'll have to see an attorney for that.