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 |
Patent Librarian's Notebook 