A new design for a bur and stick extractor was developed and evaluated in three laboratory experiments. The new machine, referred to as the multistage extractor, combines three stages of extraction into a single machine that can be located at the most convenient position in a cotton gin's seed cotton cleaning system. The machine utilizes three conventional channel-saw cylinders in series for trash extraction, specially designed grid bar arrangements, a two-saw seed cotton reclaiming system designed to minimize re-entrainment of trash into the cleaned cotton, and other design features identified in past research at this laboratory. Bypass valves are provided at the entrance to each of the three extractor cylinders to bypass a portion of the machine when processing cotton that does require the full complement of extractor cylinders.

Laboratory studies using stripper harvested cotton from the 1988-89 crop indicated that the new machine was substantially more efficient in removing burs and sticks from stripper cotton than was a conventional system composed of two extractors in series. Typical bur and stick contents of conventionally cleaned cotton at the gin stand averaged 2.7% and 1.0%, respectively. Comparable bur and stick contents for cotton cleaned with the multistage system averaged 0.9% and 0.4%. Fine trash content of seed cotton at the gin stand was not affected significantly by extraction method, and was within the range of 1.3% to 1.5% in these tests. Generally, seed cotton cleaned by the multistage extractor contained about one-half as much total trash at the gin stand as that cleaned by conventional machinery. This difference in trash level was also evident in lint samples taken after ginning and lint cleaning, but after lint cleaning the difference in trash level was too small to influence classes's grade index. Bark was not a major problem in any of these experiments, but in one test a significant number of bark penalties (67%) was received for cotton that had not been lint cleaned. Under these conditions the multistage extractor produced substantially fewer bark penalties (17%) than did the conventional extracting arrangement. Fiber length parameters, strength, micronaire, and nep level were not significantly affected by variations in seed cotton extraction method.