 
                 Patent Grant
 Patent Grant
                     4239565
 4239565
                    | Number | Name | Date | Kind | 
|---|---|---|---|
| 1374505 | Hopkinson | Apr 1921 | |
| 2824336 | Weigold et al. | Mar 1953 | |
| 2974714 | Kraft | Mar 1961 | |
| 3364093 | Porter | Jan 1968 | |
| 3374138 | Porter et al. | Mar 1968 | |
| 3388024 | Black et al. | Jun 1968 | |
| 3738893 | Edler | Jun 1973 | |
| 3740292 | Leblond | Jun 1973 | |
| 3867229 | Marra | Feb 1975 | |
| 3909337 | Yabe | Sep 1975 | 
| Number | Date | Country | 
|---|---|---|
| 239897 | Jul 1962 | AUX | 
| 689253 | Jun 1964 | CAX | 
| Entry | 
|---|
| Whittlington's Dictionary of Plastics, Whittington, Lloyd R. Pub. by Society of Plastics Engineers & Technomic Publishing Co., Inc., 750 Summer St., Stamford, Conn., 06902, Copyright 1968, p. 173. |