Your ability to file and obtain a patent depends on many things. The novelty and non-obviousness of the invention may be foremost in your mind. However, other things are influential as well, such as the skill of the patent attorney drafting the application, the quantity and quality of your disclosure to your patent attorney, the depth of your understanding of the invention, etc. And, very technically, timing also matters. There is a one-year clock that begins ticking when you publicly disclose your invention; if you haven’t filed a patent application by the time that clock runs out, you never can.
This is a painful deadline to miss. If you’ve stalled on filing a patent application beyond the one-year deadline, you can’t file for the original invention. But if you’ve come up with some improvements to the original invention, those have their own one-year clock ticking, so you may be able file applications on those.
Policy mainly drives the one-year deadline. An inventor shouldn’t be able to disclose or sell an item a long period of time, build up commercial interest in the product, and then remove the product by patenting it and demanding a high premium to purchase it. Likewise, the deadline is meant to encourage the prompt disclosure of inventions through patent publications. There are considerations for the inventor as well: the law provides the inventor with a year grace period in which to test the marketability of a product and decide if pursuing a patent is worthwhile.
Patent law places a fairly low bar on what constitutes public disclosure, unfortunately. Public disclosure can be thought of not as disclosing the invention in public, but rather, disclosing it without limitation or obligation of secrecy. To keep an invention secret, all uses of it must be private, under the inventor’s control, and not for commercial purposes.
A disclosure is considered public even if the public cannot see the invention. In one case, an inventor came up with a set of springs to hold a corset together. He gave them to his girlfriend, who used them for ten years. The springs were hidden within the garment itself and so weren’t visible to the outsider. Nevertheless, this use by one single person was enough to constitute a public disclosure and prevent the inventor from obtaining a patent. Likewise, the use of a product containing the invention without any restrictions is a public disclosure.
Restrictions alone are not enough, however. The use must not be for commercial purposes. In another case, the inventor had come up with a process to repair and recondition worn-out metal parts. He used the process privately to recondition old machine parts brought in by customers. The patent on the invention, which was filed more than a year after he first used the process in private on customer’s parts, was invalidated. Although he was using the invention secretly, he was doing so for commercial gain, and that contradicted the policy considerations behind the one-year deadline. The court noted that the inventor had to choose between keeping the invention secret forever or patenting and thus describing it to the public.
There is an experimental use “exception,” but it essentially follows the contours of the law. Activity which would otherwise trigger the one-year clock is disregarded if it is experimental. In a very old case, an inventor had developed a method of making a pavement. He wanted to investigate whether the constructed pavement was any good, so he set up a test section and allowed the public to use. However, he examined the pavement each day and asked users what they thought of it. Further, it had to be tested for a substantial period of time in order to determine whether it worked appropriately. This use was experimental and thus did not trigger the one-year clock. Several factors now weigh into the analysis as to whether an otherwise public use is experimental, such as the extent of use, the duration of use, the presence of secrecy agreements with testers, and others. The experimental use exception is a fairly narrow one and basically follows the logic in deciding whether a use is public or not.
In summary, public disclosure can be avoided. By keeping the invention to yourself, or by spreading it non-commercially only with non-disclosure agreements and requiring secrecy, you can protect your patent rights. However, you should really consult a patent attorney if you are approaching a potential one-year deadline, because failure to protect your invention can be fatal to a patent.