U.S. Additional Improvement Patents

Under the Patent Act of 1836, an inventor who had made improvements to his patented invention could apply to have the improvements added to his original patent. These documents were known as additional improvement (AI) patents. Approximately 320 AI patents were issued from 1837 through 1861. The Patent Act of 1861 required inventors to file a new patent application for each improvement to their inventions.

Table 1. U.S. Additional Improvement Patent Numbers, 1837-1861

Year 1st Number Related Patent
1861 AI310 27,681
1860 AI261 20,545
1859 AI215 21,256
1858 AI184 15,654
1857 AI158 16,244
1856 AI131 NA
1855 AI118 10,655
1854 AI107 9,796
1853 AI104 5,438
1852 AI100 8,006
1851 AI97 7,531
1850 AI93 5,960
1849 AI88 6,409
1848 AI85 4,249
1847 AI82 3,042
1846 AI78 3,016
1845 AI72 3,185
1844 AI67 3,292
1843 AI65 2,568
1842 AI50 1,798
1841 AI35 239
1840 AI29 1,472
1839 AI21 1,044
1838 AI2 364
1837 AI1 X8,849

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