Seeder Unit Feed Mechanisms

Belt feed (Fig. 30)A small, endless rubber belt which has holes punched in it carries seed from the hopper to the outlet point. A repeller wheel, turning in the opposite direction to the belt, helps to ensure that only one seed is carried in each hole. The belt is stretched slightly at the outlet point and the seeds drop through the holes into a shallow furrow made by the coulter. Seed rate and spacing are altered by:

1. Changing the seed belts. A range of belts is available with holes punched at different intervals.

2. Belts with different size holes are used to suit a variety of seeds. Belt speed can be changed on master wheel seeder units. A gearbox drive provides a range of belt speeds. Only one set of belts may be needed to give a full choice of seed rates and spacings for a particular crop. The choke controls seed flow from the hopper.

Figure 31. Cell wheel seeder units on a toolbar illustrating different types of press wheel.

Figure 32. Cell wheel feed mechanism.

Cell wheel feed (Fig. 31) Holes in the rim of the cell wheel collect single seeds from the hopper. A repeller wheel, which turns in the same direc­tion as the cell wheel, sweeps spare seeds away to ensure that only one is carried in each hole. The seed is carried in the cell wheel to the outlet point where an ejector plate prises them from the holes and they fall to the ground.

Seed rate and spacing are changed in the same wav as belt feed. The cell wheels are changed as required and different sized holes cater for various sizes of seed.

Vacuum feed. (Fig. 33)This increasingly popular feed mechanism has a power take-off driven fan on the toolbar which creates a vacuum in each seeder unit. The feed mechanism consists of a flexible disc with regularly spaced holes which turns in a housing under the hopper. The vacuum pulls individual seeds against the holes in the disc which carries them to a discharge slot above the coulter. Here a blanking plate cuts off the vacuum and the single seeds fall to the ground. Airflow from the fan keeps dust away from the seed disc housing and cleans the seed holes.

Flexible seed discs with one, two or three circles of holes can be used to drill seeds in single rows, closely spaced double rows or in triple rows for such crops as carrots. Vacuum feed is suitable for many seeds including celery, parsnip, parsley and cabbage.

Figure 33. Vacuum feed mechanism.

Seed spacing is altered by changing the speed of the feed disc with the master land wheel drive gearbox.

Seeder unit performance monitor. The seeder units are connected to a control box in the tractor cab which monitors their opera­tion. Rotation of the seed belts or cell wheels causes lights to flash on the control panel to inform the driver that the units are working correctly. A separate sensor and warning light alerts the driver when the seed hoppers need re-filling. The hopper with this sensor should have less seed than the others, to ensure that none of them are emptied before the warning light flashes. Some precision drills have an audible warning which sounds when the seed hoppers are nearly empty or a seeding mecha­nism develops a fault.

Figure 34. Computer-assisted monitoring and-control.

Figure 34 shows the switchboard and monitor for electronic tramline shifting of an air-seeder. The shifting sequence is manually put in; accordingly each marker change causes a switch forward. Activating the markers is triggered by the hydraulic lift at the headlands. When the adjusted point in the shifting sequence is attained, the respective tube inlets at the circular deflector plate are closed or opened by magnets.

Further possibilities for computer-assisted monitoring result from sensors, which register the seed level in the hoppers or record the travel distance. Thus the need for refilling and the acreage done can be indicated.

Using precision seeders. Before attaching a precision drill to a tractor, the track setting should be set so that the wheels do not run directly in front of a seeder unit and compact the soil. The wheel track is usually set at a multiple of the row width of the crop being drilled. The tractor wheels would, for example, be set at 1.5 m (60 in) when drilling sugar beet in rows spaced at 500 mm.

Marker setting is calculated in the same way as for a grain drill. However, if the total drilling width is less than the wheel track then distance В is subtracted from distance A (see Figure 26).

Figure. 35. This 18-row seeder is end towed when taken on the road.

The headlands are normally drilled first and accurate joins between the bouts are important for inter-row work and harvesting. It is usual to drill in multiples of the number of rows lifted at a time by the harvester. A toolbar with 6, 12 or 18 seeder units would be used for a crop to be lifted with a six-row harvester (Fig. 35).

Precision seeder toolbars which are too wide to be taken along the road on the tractor linkage are either end towed in a similar way to grain drills or the units are attached to a two-part toolbar which is folded with hydraulic rams.

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