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Mechanical Engineering Home >Info: Useful Links > Patent > Basics

Wanda Dent

March 11, 1994

(Revised 1/17/95)

United States patents have been regularly granted since 1790, and now number over 5 million. Aside from the public search room located in the U.S. Patent office in Washington, there are public Patent Depository Libraries located throughout the United States which have U.S. patents filed in numerical sequence so that the public may have access to information contained in these patents. This paper will describe what a patent is, and what can be patented. It will also describe the basics of performing a patent search at Minnesota's Patent Depository Library located at the Minneapolis Public Library.

There are four basic types of intellectual property that are protected by state or federal government: patent, trademark, copyright and trade secret. [2] "Although there are some resemblances in the rights of these four kinds of intellectual property, they are different and serve different purposes." [4]

A patent for an invention is a grant of property right by the Government to the inventor. It provides an inventor with the right to exclude others from making, using, or selling an invention for a limited period of time. Patents will be further described below.

"A trademark is a word, name, symbol, or device used by a manufacturer or merchant to identify his or her goods and distinguish them from others." [2] "Trademark rights may be used to prevent others from using a confusingly similar mark but not to prevent others from making the same goods or selling them under a non-confusing mark." [4]

"A copyright protects the writings of an author against copying." [4] It covers literary, dramatic, musical and artistic works, and in some instances performing and recording rights. A copyright covers the form of expression instead of the subject matter of the writing. [4]

"A trade secret is any formula, pattern, device, process, tool, mechanism, or compound of peculiar value to its owner which is not protected by a patent and is not known or accessible to others." [2] There is no limit to time that a trade secret may be kept confidential; however, no action may be taken against anyone discovering a trade secret by inspection and analysis of the product. [2]

A patent gives its owner (generally an individual unless assigned to a company) the right to exclude others from making, using, or selling his or her invention for a period of 14 or 17 years depending on the type of patent granted. The patent is only in effect so long as certain maintenance fees are paid.

Patents are issued in three types: plant patents, design patents, and utility patents. With the exception of the earliest patents issued between 1780 and 1836, patents are issued in numerical order. [1]

Plant patents comprise only 0.1% of the patents granted. These are issued for certain new varieties of asexually reproducing plants. These patents are issued in numerical sequence beginning with the letters "PL". [1]

Design patents comprise nearly 5% of the patents granted. [1] Design patents are available for anyone who invents any new, original, and ornamental design for an article of manufacture. In other words, design patents cover only the specific appearance of the article, rather than the concept of the article itself. Patents for designs are granted for a term of 14 years. [2] These patents are issued in numerical sequence beginning with the letter "D". [1]

Utility patents comprise the remaining 95% of the patents granted. [1] Utility patents are issued on an invention's utilitarian or functional aspects. In other words they are granted for inventions which function in a unique way to provide a useful result. As with the first two patent types, utility patents are issued in numerical sequence but with no prefix. However, "if a utility patent is withdrawn by the inventor for certain technical reasons, and is reissued by the Patent Office, it is given a reissue number which begins with the letters "Re"." [1] Utility patents are granted for an unrenewable term of 17 years. [2]

There are four basic requirements an invention must meet before patent protection can be obtained. These requirements apply mainly to utility patents.

First the invention must fit into one of these categories of patented subject matter: [2]

1. Process: Must be a process, art, or method. This may also be defined as one or more steps or acts performed on materials to produce a result (DDT to kill insects, threshing wild rice, etc.).

2. Machine: Mechanical devices or combinations which perform some function and produce a certain effect or result (carburetors, vacuum cleaners, lawn mowers).

3. Manufactured Article: Any product or thing make by industry or man (carpets, toothbrushes, purses, etc.).

4. Composition: Matter formed by the mixture of two or more ingredients (drugs, insecticides, adhesives, etc.).

5. Improvement: An improvement to any of the above. This may be an addition, a simplification, or a variation relating to existing processes, machines, manufactured articles, or compositions.

Secondly, an invention must be "new" in order to be considered for patent protection. The "invention must not have been known or used by others in the United States, or patented or described in a publication in the United States or any foreign country, before the invention was made by the applicant." [2]

The forth requirement for patentability is that the subject matter must be "useful". This refers to the condition that the subject matter has a useful purpose, is operative, and is of some beneficial use. For instance, a machine which will not operate to perform the intended purpose would not be called useful, and therefore would not be granted a patent. [4]

Finally, the fourth requirement is that the product or process be considered "not obvious". Not obvious means that even if the invention is something that has never before existed, it may be rejected by the Patent Office if they determine that any expert in that particular field of technology would have obviously known how to develop the same process or invention. This requirement is the most common reason for Patent Office rejection, and is the requirement that most often necessitates patent searching. [2]

The way in which a search is conducted depends somewhat on the goal to be achieved. The three most common types of searches are: State-of-the-Art Searches, Patentability or Novelty Searches, and Infringement Searches. Infringement searching is out of the scope of this paper.

The State-of-the-Art search is designed to give the inventor up to date information on technology in the particular area of interest. It enables the inventor to build upon already existing technology rather than invest considerable time and money to reinvent it. This is, in fact, one of the primary purposes of the patent system; to make current technological information available to the public so that future inventions can be developed which improve on this technology. This reduces time and money spent duplicating previously conducted research. A State-of the-Art search can also be used so an inventor can keep informed of a competitor's developments in a particular technical field.

In conducting a State-of-the-Art search, the newest patents are of interest since they contain the most recent technologies (or the "state of the art"). Often times one need only search a small fraction of the total patent collection since the State-of-the-Art search only applies to the period during which the technology existed.

The Patentability Search is directed to an entirely different goal. In a Patentability Search , the searcher attempts to locate patent references at any time in the past patent records which either show the invention itself, or would render the invention to be an obvious variation of a prior invention.

The Patentability search is often useful in that if the search results in determination that if the particular invention is not new and considered obvious the inventor will know that the patent is likely to be rejected and will save the time and money expended in applying for a patent. An inventor can often locate evidence of unobviousness by finding previous patents that recommend against their product, method, or formula as a solution. Additionally, a search can help inventors determine just how original their ideas are.

"Because any patent reference is relevant in a Patentability search regardless of its age, and because combinations of patents must be considered, the scope of such a search increases substantially" over that of the State-of-the-Art Search. It is recommended to search the patent file back at least 50 years, preferably more, for mechanical inventions. Technological fields which are often times more recently developed may require searching more than 25 years back.

United States patents are typically comprised of the following:

A front page (see Figure 1). This contains the patent number, filing and issue dates, inventor name and address, classifications, other references cited, and a short abstract describing the invention.

Drawings (if applicable).

A body of the patent. This contains the background and summary of the patent, detailed descriptions, drawing descriptions (if applicable), and the patent claims.

One of the recommended approaches to doing a State-of-the-Art or Patentability search is by manual means. The search starts by locating class and subclass in an "Index to the US Patent Classification System". The range of subclass listings can be further narrowed down by referencing the "Manual of Classification". With a narrow field of subclass listings, the searcher can find actual numbers for related patents using the "U.S. Patent Classifications Subclass Listing". Patents are filed numerically on microfilm. They can be viewed on microfilm, and copied if desired.

Once applicable patents are located, the searcher should continue the search by inspecting the patents for cross-references to other patents or subclass listings which may or may not apply to the subject of interest.

In order to conduct a search of a specified field of invention from the over 5 million patents issued, the U.S. Patent and Trademark office has developed a system of classes and subclasses which divides technology into narrow fields. A book entitled "Index To The U.S. Patent Classification" is used to enter the Patent Office's classification system. This Index is an alphabetical listing providing class and subclass listings for thesearcher's chosen field.

Since technological fields may not use standard terminology it is necessary to come up with as many synonyms and related fields as possible to conduct a thorough search.

A page from the Index to Classification is shown in Figure 2. From this page the searcher can note the Class which is cited as the general class, and the subclass which appears to be closest to specific area of interest. A "+" after the subclass number indicates that there may be several subclasses which are related.

Once the searcher has determined a likely class and subclass, the next step is to narrow down the field of subclasses using the "Manual Of Classification". The Manual gives a listing of all subclasses within each main class and in numerical order. This Manual is a large loose-leaf book which is updated as frequently as patents are reclassified.

A page from the Manual of Classification is shown in Figure 3. The subclass listings are further divided in the Manual into several sub-subclasses. The dots act much as an outline does in that increasing dots indicate more specific information.

Even after locating what seems to be a good match to the search subject, it is important to also review many of the other subclasses within the specific class to determine which are most relevant. This is because most patents are cross-referenced, or located, in more than one class or subclass. The cross-referencing is useful in finding alternative patents to search.

Once the class and subclass are determined, the searcher can determine patent numbers of those located in a particular subclass.

The numbers of all related patents dating back to 1790 can obtained by consulting the U.S. Patent Classifications Subclass Listing which can be found on microfilm. Figure 4 shows one frame of this microfilm. This microfilm listing is updated every six months.

At the Minneapolis Public Library, patents in their entirety are shelved in numerical sequence on microfilm. Once the desired patent numbers are known, the searcher can consult the proper reel to view each patent of interest. A copy machine is connected to the microfilm reader so that the searcher can make a copy of the patent if desired.

Computers offer an alternative way to do a patent search. The two database systems provided at the Minneapolis Public Library are CASSIS and APS. These systems can either be accessed instead of a manual search (keeping in mind the computer files do not date all the way back in history), or in addition to a manual search.

The databases are only able to access at most the front page of the Patent Document (not including the graphics). For this reason, it is still necessary for the searcher to obtain the microfilm copies of patents to get a total view of the patent subject matter.

As with the manual search, once applicable patents are located, the searcher should continue the search by inspecting the patents cross-referenced to other patents or subclass listings which may or may not apply to the subject of interest.

One way to obtain patent information is to access CASSIS (Classification and Search Support Information System). CASSIS is a CD ROM database which offers an alternative way to obtain class and subclass listings. Since the CASSIS database is updated every two months, it is more current than the "U.S. Patent Classifications Subclass Listing" found on microfilm.

On CASSIS the searcher can enter key words from which a key word search will be done and similar patents located. CASSIS will search titles of patent classifications back to 1968, and will search both abstracts and titles back to 1986.

A second computer database available ( at cost) at the Minneapolis Public Library is the APS (Automated Patent System) Text Search System. APS is a mainframe system which accesses the main Patent and Trademark Office in Washington D.C.

"The APS Text Search function allows a searcher to conduct term (word or number) searches on the patent documents in the APS text database, The APS database contains two searchable files, the largest of which is the USPAT file. The USPAT file contains the text of over a million U.S. patents issued since 1971, and is updated weekly. The second file is the Japanese Patent Abstracts (JPOABS) file. It contains the English language abstracts of published Japanese patent applications. The JPOABS file data is supplied by the Japanese Patent Office and is updated as information becomes available." [3]

This database is more powerful than CASSIS since it searches the full text of patents for sets of words. It is considered to be more difficult to use than the CASSIS system, however, a manual of commands is provided at the APS terminal.

As you proceed in your search, you will be collecting information on many, many patents. Figure 5 shows one way of keeping the pertinent information on a spreadsheet. You may also find it useful to keep a collection of one key picture copied from the patent. Typically, the best picture can be found in the Official Patent Gazette.

This report only taps into a small potion of the Patent information that is available, and is aimed mostly toward those wanting to do a patent search at the Minneapolis Public Library. Patent searching information can be found in the Science and Technology section of the library where the librarians can provide advice on patent searching.. They can direct searchers to the computer terminals, and microfilm files, as well as the Manuals and Indexes needed. Additionally, they offer hour long "How To Do a Patent Search" seminars every other Friday to help the beginner start the search.

[1]. Lasky, Michael B.. A Basic Guide to Patent Searching at a Patent Depository Library. Perimeter, Inc., Minneapolis, MN, 1982.

[2]. A Guide to Intellectual Property Protection. Minnesota Department of Trade and Economic Development, 1992.

[3]. Desktop Reference Guide for Public Users of the APS Text Search System. US Department of Commerce, 1992.

[4]. General Information Concerning Patents. US Department of Commerce, 1989.

Additionally, information was obtained from the Librarians in the Science and Technology department at the Minneapolis Public Library, and from attending their "Patentability Search" seminars.