Air Screen Machine for Seed Cleaning
Principles of Cleaning:
The separation of undesirable material and seeds from desirable seeds in an air screen machine is done on the basis of differences in seed size and weight. In some separations, seed shape could also be used. The air screen machine uses cleaned, but which were too large to drop through the second screen, are removed here.
As the crop seed drops off the fourth screen, they fall through the lower air separation. This removes the light seed and trash which was not removed by the upper air and the screens. For efficient cleaning, the lower air blast should be strong enough to blow out a few good seed.
Adjustment of Equipment:
1. Screen Selection:
Screens must be selected according to the shape of the crop seed being cleaned.
Round Seeds: Top screen- Round hole
Bottom screen – Slotted
Oblong Seeds: Top screen- Oblong
Bottom screens- Oblong
Lens – Shaped Seeds: Top screen- Oblong/ rectangular
Bottom screen – Round hole.
2. Rate of Feed:
The feed gate on a feed hopper is adjustable for large change of rate of feed. The basic adjustment is made by increasing, or decreasing, the speed of the feed roll.
3. Screen Knockers and Tappers:
Adjustable knockers, or tapers, to lightly tap the screens installed on the machine vibrate the screens so that the seeds will pass through close and small openings, and will jolt loose long weed seeds that wedge so tightly in the perforations that the brushes cannot remove them.
4. Upper Air Suction:
The upper air suction is regulated by an adjustable damper in the air passage, so as to remove most of the light chaff and dust before the seed reaches the top screen.
5. Variable Screens Shake:
The variable screen shake adjustment permits the operator to adjust the screen vibration speed from slow to very rapid. The rate of vibration , or shake , should be adjusted to induce a desirable action of the seed on the screen, and not to increase capacity by shaking the screen faster.