| Number | Name | Date | Kind |
|---|---|---|---|
| 1827442 | Stokes | Oct 1931 | |
| 1851518 | McGovern | Mar 1932 | |
| 1865159 | Adamson | Jun 1932 | |
| 2015202 | Stokes | Sep 1935 | |
| 2111157 | Stokes | Mar 1938 | |
| 4608038 | Virta et al. | Aug 1986 | |
| 5108355 | Walsh | Apr 1992 |
| Entry |
|---|
| Opcon Advertizement "Have Your Sensors Reached Their Limits?" Machine Design Oct. 1984. |