| Number | Name | Date | Kind |
|---|---|---|---|
| 2451077 | Emsig | Oct 1948 | |
| 3816200 | McKenna | Jun 1974 | |
| 4120054 | Lemelson | Oct 1978 | |
| 4823948 | Bonar | Apr 1989 | |
| 5409740 | Brann | Apr 1995 | |
| 5824413 | Schell | Oct 1998 |
| Number | Date | Country |
|---|---|---|
| 2841442 | Apr 1980 | DE |
| 22561437 | Jul 1992 | GB |
| WO98 08777 | Mar 1998 | WO |
| Entry |
|---|
| Plastic News, USA, 6, No. 11, p 38, May 1994. |