Issued Patents All Time
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 5635061 | Plate shifter mechanism | Leonid B. Gelfand, David J. Spyker | 1997-06-03 |
| 5567327 | Air-assist discharge of filter press cake | Joel D. De Haan, Daniel De Haan, Gregory De Haan, David J. Spyker, David P. McLeod +1 more | 1996-10-22 |
| 5456022 | Batch-type sludge drier | David P. McLeod, David J. Spyker, Daniel De Haan, Greg De Haan, James E. Roelofs | 1995-10-10 |
| 5328617 | Air-assist discharge of filter press cake | Joel D. De Haan, Daniel De Haan, Gregory De Haan, David J. Spyker, David P. Mc Leod | 1994-07-12 |
| D323797 | Electric runabout vehicle | Arunas P. Oslapas | 1992-02-11 |