| Number | Name | Date | Kind |
|---|---|---|---|
| 2664132 | Leverte | Dec 1953 | |
| 2744185 | Cawley | May 1956 | |
| 2869094 | Francis | Jan 1959 | |
| 3790922 | Normann | Feb 1974 | |
| 4407042 | Schramme et al. | Oct 1983 | |
| 4640478 | Leigh-Monstevens | Feb 1987 | |
| 4687446 | Birch et al. | Aug 1987 | |
| 4743210 | Schild et al. | May 1988 |
| Entry |
|---|
| A Drawing of a "Conventional System", Filed on 2-23-90, Discussed Under the Background Section of the Instant Specification. |