| Number | Name | Date | Kind |
|---|---|---|---|
| 1946222 | Mandt | Feb 1934 | A |
| 2488292 | Hilkemeier | Nov 1949 | A |
| 3053367 | Lynch | Sep 1962 | A |
| 3456769 | Prichard et al. | Jul 1969 | A |
| 3542179 | Prichard | Nov 1970 | A |
| 4498568 | Christenson | Feb 1985 | A |
| 4919249 | Alexander | Apr 1990 | A |
| 5660260 | Bareiss | Aug 1997 | A |
| Number | Date | Country |
|---|---|---|
| 731010 | Jun 1955 | GB |
| Entry |
|---|
| Schwing America drawings (6 sheets) of device on sale in the U.S. prior to Aug. 24, 2001. |