| Number | Name | Date | Kind |
|---|---|---|---|
| 3939229 | Hechenbleikner et al. | Feb 1976 | |
| 4064100 | Hechenbleikner et al. | Dec 1977 | |
| 4305866 | York et al. | Dec 1981 |
| Entry |
|---|
| Patent Abstracts of Japan, vol. 13, No. 491 (C-650) [3839], Nov. 7, 1989, p. 87 C 650 corresponding with Japanese Reference No. 1-193371 dated Aug. 3, 1989. |