The table following summarises the main patents for the PLUS and Sumlock machines. The US patents are listed, as they are the most readily accessible on-line. Copies can be downloaded free of charge via the search form at the US Patents Office.
| Number |
Description |
Inventor |
Submitted |
Granted |
Pages |
| 1538447 | Actuating mechanism | Petter | May 21 1923 | May 19 1925 | 3 |
| 1615033 | Tens transfer (1924) | Petter | May 21 1925 | Jan 18 1927 | 5 |
| 1917732 | Tens transfer (1930) | Petter | Jul 6 1931 | Jul 11 1933 | 8 |
| 1983945 | Improved mechanism | Petter | Jun 26 1931 | Dec 11 1934 | 9 |
| 2142286 | Duplex lever | Petter | Sep 30 1933 | Jan 3 1939 | 5 |
| 2291853 | Improved tens transfer | Webb | Jun 15 1939 | Aug 4 1942 | 8 |
| 2356714 | Overthrow and lockout | Webb | May 24 1939 | Aug 22 1944 | 15 |
| 2569508 | Keyboard mechanism | Webb | Nov 22 1948 | Oct 2 1951 | 6 |
| 2646927 | Keyboard locking mechanism (1938) | Webb | Jan 17 1951 | Jul 28 1953 | 15 |
| 2662690 | Numeral wheel locking | Webb | Nov 22 1948 | Dec 15 1953 | 6 |
| 2662691 | Actuating mechanism | Webb | Nov 22 1948 | Dec 15 1953 | 5 |
| 2756932 | Key-responsive calculator (Electric) | Webb | Dec 22 1951 | Jul 31 1956 | 7 |
| 2773647 | Grand total register (Duolectric) | Webb | Dec 22 1951 | Dec 11 1956 | 5 |
| 2956741 | Caclulator with multiplier (Sumlomatic) | Webb | Jan 12 1955 | Oct 18 1960 | 18 |