Once you have filed a first non-provisional patent application and until that first application issues or is abandoned, you can file additional applications “related” to that first one. No matter when you actually file one of these “continuing” applications, everyone will treat the application as if you filed it on the same day as the very first application. The downside is that these applications have short life spans because they also expire at the same time as that first application. So why file one?
Smart use of continuations can save a company money. For example, you might file an extremely detailed first application that would support claims to a number of different aspects of your invention. You might choose to file the application with a small subset of the claims – perhaps the ones most relevant to your company at the time of filing – and then you only have to pay for the PTO to examine that focused subset of claims (and for you/your lawyer to respond to the PTO’s initial rejections). Once you get a patent allowed you’re 4-7 years out from time of filing and in a different place as a company, both from a funding perspective and from a business perspective. Maybe you’ve long since moved on to another venture – no need to have spent money on those other aspects of the invention. Or maybe the focus of your company has changed to one of those other aspects and you’re thrilled that you can now protect the methods / products that have become relevant to your business. Either way, you’ve bought yourself the time you need to make more informed decisions.
Additionally, filing continuations can be useful when licensing the technology. If you have continuations that are each directed to different aspects or implementations of the invention, you have much more granular control over what rights you license out. Say you have a patent that supports X, Y, and Z, where Z is the least relevant to your business model. You may want to license out Z to a company that is going to be able to use Z and send you substantial royalty fees – but you may not want to enable them to compete with you in areas X and Y. Continuations can help you do that.