Patents are designed to protect creations and designs, but how long a patent lasts for is dependent on a number of factors. The length of time that a patent offers protection, depends largely on what type of patent is issued and whether required maintenance fees are paid to keep the patent active.
Much like copyrights and trademarks, patents are designed to protect the creations of an individual or company from theft or duplication by others. The protection offered by a patent isn't as long as the protection granted by a copyright or trademark, however. So how long does a patent last? It depends largely on what is being patented and the type of patent that is being applied for. Patents won't be granted on natural phenomena, creative works that fall under the domain of copyright, or inventions that serve no actual purpose; for everything else, three different types of patents exist which last for different amounts of time.
When most people ask 'how long does a patent last', they are inquiring about utility patents. A utility patent is the patent granted for new machines, processes, products, and scientific formulas such as medicines or new elemental compounds. Once a utility patent is granted, it is valid for 20 years provided that required maintenance fees are paid. When the patent expires or is allowed to lapse by nonpayment of required maintenance fees, the patent holder is no longer able to enforce the patent on their creation or process and competitors can replicate it without violating the patent. The only way that a patent's protection can be extended is through an act of Congress.
Plant patents are similar to utility patents and likewise are valid for a period of 20 years after being granted. As with utility patents, a maintenance fee must be paid on plant patents to keep the patent protection from lapsing. Plant patents are used to protect new and distinct varieties of plants which are produced asexually, such as custom roses, pest- or disease-resistant varieties of corn, or other flowers or crops. Plants protected by a plant patent cannot be found in a natural state, and cannot be propagated by use of tubers or root stock; they must be fully original plant creations.
Design patents differ from utility and plant patents in two significant ways. Patent protection for design patents only lasts for 14 years after the patent is granted, so they offer six years less protection than other patent types. Unlike plant and utility patents, however, no maintenance fee is required to keep a design patent active. These patents protect products and creations that have only a cosmetic effect, such as fabrics and covers for handheld electronics.
The United States isn't the only country that offers patent protection. When dealing with international patents it's important to ask how long does a patent last from each country; depending on where the patent was issued, it may last for anywhere from 6 to 20 years or longer. To better respect the patents of trading partners, most countries that are members of the World Trade Organization issue 20-year patents similar to utility patents. Patents from other countries are typically acknowledged within any country that has patent laws.
US Patent and Trademark Office - Patents http://www.uspto.gov/inventors/patents.jsp
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