A child patent application is a follow up of a previously filed patent application. The previously filed application is called the parent, whereas the later filed application is called the child. The child application is used to ask the Patent Office for a patent that covers a different variation of the invention, or a patent that provides stronger coverage than the parent.

3 Types of Child Applications

There are 3 types of child applications:

1. Continuation – An application for a patent that covers a broader version or more variations of the previously disclosed invention, without adding new variations or features to the invention. Used to protect more than what the parent covered.
2. Continuation in Part – An application for a patent that covers different newly added variations or features of the invention that were not disclosed in the parent patent application. Used to cover a new version of your invention.
3. Divisional – An application for a patent that covers a variation of the invention that the Patent Office did not allow you to patent in the previous parent patent application. Used to protect a variation of your invention that the Patent Office did not allow you to patent in the parent.

Continuation Application

Let’s say you invent a time machine that is built into a truck, van, or bus. You have made 3 variations. You apply for a patent only for the truck version of your time machine and you don’t ask for a patent for the van or bus variations. The Patent Office approves your patent for the truck variation of the time machine. Now, you want to also get patents for the van and bus versions of your invention. You could file continuation applications for the van and bus variations of your invention and see if the Patent Office will also grant you patents for those variations. The truck version patent would be the parent, and the continuations you file for the van and bus variations would be the child applications. You could also try to file a continuation application to cover the van and bus variations. Alternatively, you could try for a broader continuation application to cover any type of vehicle. For example, since a truck, a van, and a bus are all vehicles, you could remove the requirement that the time machine be built into any specific type of vehicle and instead cover the time machine being built into any type of vehicle. A continuation application can be used to ask for a broader version of the invention, a patent covering a second variation of your invention, or to ask for a patent that covers multiple additional variations. The main stipulation for a continuation application is that you cannot add new information that was not already included in the parent application.

Continuation in Part Application

Let’s say you invent a time machine that is built into a truck, van, or bus. You have made 3 variations. Let’s say the US Patent Office gives you a patent for all 3 variations. However, you then invent a time machine that is built into a plane. The plane version is a new variation that you had not invented when the parent application was filed. You could then file a child application for the time machine that is built into a plane. Because the plane version includes both information that was disclosed in the parent application and features that were invented after the parent application was filed, this child application is called a continuation in part.

Divisional Application

Let’s say you invent a time machine that is built into a truck, van, or bus. You have made 3 variations. You ask the patent office for a patent that covers all 3 variations. The Patent Office decides it is only willing to give you a patent for the truck version, not the van or bus version. The Patent Office wants you to apply for the van and bus versions separately in separate patent applications. You could then file child applications to “divide” out the van and bus versions for the Patent Office to consider separately.

Child applications must be filed before the parent application is granted or abandoned

A child application can only be filed before the previously filed parent application is granted as a patent or abandoned due to rejection by the patent office. If your parent application is rejected, you have time to argue back before it becomes abandoned. A child application must be filed before the parent application is abandoned. If your parent application is approved, you have time before it is printed and granted as a patent. A child application must be filed before the parent application is granted as a patent.

Child applications are used to increase the coverage of your patent protection. Proper strategizing is necessary to determine what type of child application to file and when to file it. Speak to a patent practitioner whenever you create a new variation of your invention, and whenever you have a patent application that is soon to be abandoned or granted as a child application must be filed before then.