| Number | Name | Date | Kind |
|---|---|---|---|
| 3210030 | Ramsey et al. | Oct 1965 | |
| 3632069 | Thayer | Jan 1972 | |
| 4509710 | Cooper et al. | Apr 1985 | |
| 4795114 | Usui et al. | Jan 1989 | |
| 4844389 | Nimtz | Jul 1989 | |
| 4865280 | Wollar | Sep 1989 | |
| 4865281 | Wollar | Sep 1989 | |
| 4911388 | Unger et al. | Mar 1990 | |
| 4942644 | Rowley | Jul 1990 | |
| 4953801 | Oikawa | Sep 1990 | |
| 4993669 | Dyer | Feb 1991 |
| Number | Date | Country |
|---|---|---|
| 1296316 | May 1962 | FRX |
| 1507263 | Dec 1967 | FRX |
| Entry |
|---|
| Japanese Utility Model SHO-52-136198. |