Submarine Patents - What are They and Should I Be Afraid? Episode 108

What Are Submarine Patents?

I found this question on Quora: “Why are submarine patents illegal?”

At first glance, it sounds like the question is asking why patents related to submarines are illegal. But that’s not what it means.

A “submarine patent” refers to a patent application that remains secret for years. It’s called a “submarine” because it stays beneath the surface—hidden from public view.

Are Submarine Patents Illegal?

No, they’re not illegal—but the system has changed to make them much harder to pull off today. To understand why, we need to look at the history of how patents used to work.

Old Rules vs. New Rules

Today, patents generally last 20 years from the filing date. But before 1995, patents lasted 17 years from the issue date. That may not seem like a big difference, but under the old system, if you delayed getting your patent issued, you could essentially extend the total time you had patent protection.

Another big change is that patent applications are now published after 18 months. That wasn’t the case before. Under the old system, applications were kept secret unless they eventually issued as patents.

How Submarine Patents Worked

Here’s an example. Suppose you had an idea that revolutionized the auto industry. You filed a patent, but didn’t let it issue. You kept tweaking the claims and letting it sit in the Patent Office for years. Meanwhile, car companies unknowingly started using your technology, because they couldn’t find any patent covering it. That’s because your application was hidden—like a submarine.

Ten years later, once your invention had become an industry standard, you finally let your patent issue. Then, bam! You sued everyone for infringement.

You now had 17 years of protection from the issue date, even though your application had been around for a decade. Totally legal—but widely viewed as unfair.

The Lemelson Example

One of the most well-known submarine patents came from Jerome Lemelson, one of the most prolific inventors in U.S. history. He kept a patent application related to barcode technology alive for years, then asserted it against the entire barcode industry.

Why It’s Harder Today

There are two big reasons:

1. Applications are published after 18 months, so they’re no longer hidden.

2. Patent terms are now 20 years from the filing date, not the issue date. If you delay too long, you just eat up your own patent life.

The rule changed in 1995, but there are rare exceptions. For example, U.S. Patent No. 10,539,396 issued in 2020 but was filed in 1976. That’s 44 years! It was subject to a secrecy order for missile technology.

Could there still be submarine patents? Maybe—especially if a non-publication request was filed. But it’s rare now, thanks to changes in term length and publication rules.

I'm Adam Diament, and until next time, keep on inventing!