By treaty, a US patent application preserves the right to file internationally for only one year. But a PCT application can extend this another 18 months.
Applying for international patents: Most countries maintain their own separate patent and trademark offices. Usually (Europe being a partial exception), patents only operate within national borders. Thus a US patent, for example, covers just the US.
The Paris Convention: Countries have long realized that there needs to be an easier way to file international patents. Over the years, they have filed a number of international treaties. One important treaty, which is still in effect, was the 1880’s era Paris Convention. This established that a foreign patent office will recognize the priority of a US utility patent application (or provisional patent application) for up to 12 months after its initial filing date.
This was a good start. Unfortunately, it often takes more than 12 months to determine if a new invention is commercially important. It is very expensive to file patent applications in many different countries. So for many applicants, 12 months just wasn’t long enough.
The Patent Cooperation Treaty:
To extend this time, in the 1970’s the international community enacted the Patent Cooperation Treaty (PCT). This treaty is a bit complicated. Think of it as a temporary “holding tank” for patent applications. You must file a PCT application within 12 months of the filing date of the original patent application. This extends your ability to file international patents to 30 months from the filing date of the original patent application. Note that the PCT treats both utility patent applications and provisional patent applications in the same way.
After this, 30, however, you then need to make some tough decisions. It typically costs thousands of dollars to file (i.e. enter the national phase) in each separate country. So unless the invention is looking very promising, consider continuing only in the US. Alternatively, only file nationally in a few select countries.
The Patent Prosecution Highway:
Typically, each local (national) patent office will then want to examine the patent application itself. This is both expensive and duplicative of resources. To help streamline the process, in the late 2000’s, the USPTO initiated various Patent Prosecution Highway (PPH) agreements. Unlike the PCT, these were typically on a bilateral (country-to country) basis. Here, if your patent application’s claims are allowed by one (PPH) country, you can ask to have them accepted by other participating PPH offices. The US participates in the PPH, as do a number of other countries. The PPH is great when it works. However it is a patchwork of agreements rather than a comprehensive international treaty. So view the PPH as being in the “pilot” or “beta” stage.
Illustration: PCT international patent treaty countries. World map by Japinderum (CC BY-SA 3.0) license