How to write a patent application

Many components go into writing a patent application.  For example, a patent application usually includes a description that covers the technology in detail, claims that define the invention and drawings.  This guide will provide you with the basic tools to do this yourself.  It is not intended to be legal advice, simply a guide for those who wish to write a patent application themselves.  Please consult with an experienced patent attorney if you have any questions or concerns.

1. Making the drawings

They say that a drawing speaks a thousand words.  There is simply no way that words can cover the same amount of ground as a good drawing, and that holds true when you write a patent application.  Patent drawings do however have to comply with certain space requirements and readability.  Drawing sheets are 8-1/2 x 11 inches.  In addition, the drawings have to fit within certain margins for them not to be rejected by the patent office – top and left margins should be at least 1 inch, a right margin should be at least 5/8 inch, and a bottom margin should be at least 3/8 inch.  In order to comply with the space requirements while at the same time disclosing as much as possible of the design and how it works, the following three categories of drawings can be included when you write a patent application for an electrical, mechanical and software invention.

1.1. System overview drawings

These drawings help the reader to understand the system at a high level.  They help you when you write a patent application because they provide an entry into to showing the technology before getting into the finer detailspar

1.2. System detail drawings

System detail drawings can be used to show specific sub-components of the system.  It may be important when making system detail drawings to show how the components are connected to one another.  More on that later.

1.3. Drawings showing how the system works

The description write-up will include a description of how the system works.  It may be useful to include drawings showing how the system works.  These drawings could be complex flowcharts, interactive charts, time charts, or snapshots showing the system at sequential moments in time.

2. Writing the claims for the patent application

2.1. Writing a main system claim

2.1.1. Objectives


There are conflicting interests when writing the first claim for a patent application. On the one hand, the claim should be as broad as possible. On the other hand, the claim should not be so broad that it fails to describe something that is new, which will result in the claim being rejected by the Patent Office.  By the same token, a claim that is too broad can describe something that is obvious and be rejected.  Broad terms can also lack clarity, which can result in a rejection.

2.1.2. Step-by-step Think away all structure

When writing a patent application’s main system claim, it is usually tempting to focus on the components of the system to determine what components should go into the system claim.  Remember, however, that patents are for inventions and an invention relates to the way that something works.  Moreover, the system, at least at its highest level, is just the object that works on an external subject.  A corn stripper functions to strip corn from the cob.  A prism separates white light into its frequencies.  You get the idea.  We always want to identify the high level functioning first. Make a drawing showing the input on the left and the result on the right

Focusing on the subject, make a drawing showing the input on the left and the result on the right – corn-on-the-cob on the left / stripped corn on the right; white light on the left / different frequencies of light on the right. Starting with verbs, write down every step necessary to transform the input into the result
Start with verbs

It is important to start each step with a verb.  The verbs are functional steps, after all, which begin the process of describing how the invention works.

Write down every step

The reason why it is important to not to skip any steps is because it will go a long way toward writing a claim that will be for something new.  Skipping steps will ultimately result in a claim that will cause that examiner to include prior art documents that are from unrelated fields.

Don’t write down unnecessary steps

Only write down the steps that are necessary to transform the input into the result.  If you include more than the necessary steps, the claim will likely be too narrow and it will be easy for a competitor to avoid infringement. Write down the result

What you have accomplished can be written as the result (e.g., strip corn; split light frequencies).  Note that the result starts with a verb. Use the result to craft a title.

You can now use the result to craft a title.  “Strip corn” can become “A corn stripper”; “Split light frequencies” can become “A light frequency splitter”. Extract the structure

It is now time to extract the structure (nouns) from the language that you have created.  You will need the nouns in order to write a claim for a system. Split the structure into positively and inferentially claimed elements

You can now begin to focus on the components of the subject that are needed.  Positively claimed elements are the ones of the subject that you have identified.  They can be the corn holder, corn remover, corn ejection bucket. Or the prism body with is first refractive surface and second refractive surface.  Inferentially claimed elements are usually the pieces of the object.  They could include the corn-on-the-cob, the cob, husk and corn seed.  Or the white light and different frequencies of light. We do not want to only claim elements of the object inferentially, and not positively, because a seller of the subject (the corn husker; the light prism) will not include the object (the corn-on-the-cob; the white light). Connect the structure with the remaining language

After you have extracted the structure from the language that you have created you will notice that there is still a fair amount of language that is left over.  You can now use that language to connect the structural components to one another.  By connecting all the pieces of the structure together in this manner you will ensure that the claim is a single unit, and you can avoid a rejection based on lack of novelty, obviousness or lack of clarity. Clarity test – can you draw it?

It is generally a good idea to test the clarity of your system claim by drawing what you have claimed.  Such a practice is not based on any legal foundation, however patent examiners usually follow this process to determine whether a claim is clear. Special considerations for means-plus-function language

Many years ago, having a claim element that read “means for…” used to be the broadest way to claim the element.  Not anymore.  Such claims are now interpreted in light of the specifics that are described and as a result are much narrower than they appear.  When a claim element should be interpreted as a means-plus-function element is highly case dependent.  In general, the following approach can be followed to avoid such an interpretation.

Avoid “means” language

Replace all instances where “means” occurs with another term.  Use “calculation module”, “detection subsystem”, etc.

Avoid “for” language

Replace the word “for” with language such as “to”, “configured to”, etc.

Connect elements structurally

One glaring give-away that an element is a means-plus-function element is if the element does not include any structural connectors.  Above, you have already connected your structural elements with functional language.  Go a step further and connect the structural elements with structural language.  Use “connected to”, “secured to”, etc.  Do not use uncommon terms such as “coupled to” unless it is commonly used in your particular technological field.

2.2. Writing the dependent claims

Once you have written the main system claim, you can proceed to write some dependent claims.  The dependent claims provide further details of the elements of the main claim that you believe to be important.  They can also be used to introduce additional components of your design.  Dependent claims can also be used for claim differentiation purposes, for example the claim refers to wheels but it may be uncertain when enforcing the patent whether wheels cover hexagonal wheels.  For claim differentiation purposes, a dependent claim can be added stating that the wheels are round. Because there is a presumption that the dependent claim further limits the independent claim, the independent claim should be interpreted as covering round wheels and non-round wheels.

3. Writing the “Detailed Description” section

You should now have enough language from writing the claims so that you can write a detailed description of the drawing.  When writing a patent application it is important that the language of the claims can also be found in the “Detailed Description” section.

First you should mark the drawings up with reference numerals.  A good approach is to use a sequential list of reference numerals such as 10, 12, 14, 16… and mark the drawings in the order that you will describe the components.

The following approach can be used when writing this section:

    1. Write a high-level description (one or two sentences) with reference to the first, system-level drawing.
    2. Write a description of each one of the system drawings.
    3. Write a description of the functional drawings.
    4. Discuss some advantages of the invention.

This is by no means the only way to write a description when you write a patent application – there are many ways to skin a cat.  Inventions for chemical processes, for example, may not even have a system drawing.  The drawings and description of a chemical invention may start at step 1 of the process.

4. Writing the “Brief Description of the Drawings” section

The “Brief Description of the Drawings” should include a list of every drawing.  The Patent Office will ask you to correct it if it is wrong.

5. Writing the “Summary” section

The “Summary” section is of less importance.  It is good practice to copy the language of the claims into the Summary and then to change it into more “pretty” English.  Certain patent offices such as the European Patent Office may require a match between the Summary and the Claims, if you decide to foreign file the patent application.  See Patent Foreign Filing.

6. Writing the “Background to the Invention” section

This section provides the reader with some context about the invention.  Remember that the patent application may eventually end up in the hands of lawyers, engineers, patent examiners, jury members and judges.  So it is important to keep a broad target audience in mind when you write a patent application and especially when you write the Background section.  It is also important to keep the Background section somewhat concise, because anything that you say in this section is usually an admission of prior art.  Here are some some components of a good Background

    1. A field of the invention – usually the first line of the independent claim or claims.
    2. A general discussion of the technological field.
    3. A short discussion of existing systems.
    4. The problem associated with existing systems.

7. Writing the “Abstract of the Disclosure” section

Here you can give a reader a quick view into the technology.  This section should be less than 150 words for it not to be rejected.  Bear in mind that the Patent Office will look at this section to determine the classification and examining division for the patent application.

8. The title

Lastly, the patent application will need a title.  Pick a title that will result in a desirable classification by the patent office and a title that you would like others to see when they do a search for you patent online.par

9. Putting it all together

Well that was all backwards, wasn’t it?  The sequence that I have described is almost the reverse of how a patent is constructed.  That’s correct.  Many patent applications are first drafted by starting with the claims or the drawings and then writing the Detailed Description.  That need not always be the case, but it is a practice that is followed by many practitioners.  You now have all the pieces that can be rearranged for you patent application, as follows:

  • Title
  • Summary of the Invention
  • Brief Description of the Drawings
  • Detailed Description of the Drawings
  • Claims
  • Abstract
  • Drawings

10. Conclusion

You are now ready to file your patent application. However, please consult with an experienced patent attorney if you do not feel comfortable with your product. There are many factors that have to be considered when you write a patent application over and above the ones mentioned here.  A patent attorney will know what they are and they are beyond the scope of this guide.

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