Conducting a Subject Search (continued)

Learn More #4:

Classification Codes

Once we have completed a free-text subject search, we may want to restrict our search to specific classes of inventions. Within the U.S. patent system similar subject matter is brought together in large groupings called classes. There are also international class codes.

Classification Codes are numbers that are assigned to patents by the patent issuing authority. U.S. class codes are searched with the prefix CL=; international class codes use the prefix IC=.

U.S. Class Codes

• U.S. Class Codes are indexed as nine-digit numbers that may be followed by up to three alpha characters.
  
  
• The first three digits represent the class and are zero filled to the left:
  
  
  Example: 36=036
  
  
• The next six digits represent the subclass number. The numbers to the left of the decimal point are zero filled to the left; the numbers to the right of the decimal point are zero filled to the right:
  
  
  Example: 10.55=010550
  
  

  Patent Office Classification	Dialog Conversion
  36	CL=036
  73/432.1	CL=073432100
  75/321	CL=075321

International Class Codes

• International Class Codes are indexed using ten-digit alpha-numeric codes.
  
  
• The first four digits represent the class:
  
  
  Example: G06F
  
  
  
• The next six digits represent the subclass. This needs to be zero-filled to the left both before and after the slash mark.
  
  
  Example: 15/66 = 0015/66
  
  
• Thus, an international class code converted to a Dialog format would look like this:
  
  
  Example: G06F 15/66 = G06F-0015/66

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Learn More #5:

Dates

Dates can be an effective way to narrow a search. We can search on publication/patent year, publication/patent date, or application date and year.

The table below illustrates the different formats.

Note: You can also use a four-digit month: AM=YYYYMM.

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