The present invention relates to the general technical field of agricultural machinery. The invention relates to a device for a self-regulated pneumatic supply from a main reservoir containing product toward at least one auxiliary reservoir according to its filling rate, the supply device comprising a compressed air supply, a tilted duct connected to pipe connections, a bypass air duct having a first channel emerging near the outlet of the main reservoir and a second channel emerging near the inlet of the pipe connections to bring product to the auxiliary reservoir.
Such a self-regulated pneumatic supply device is known from document FR 2 340 031. This device in particular comprises a bypass air duct having a first channel, the convergent of which emerges near the outlet of the main reservoir to carry seeds over an upward journey, and a second channel, the convergent of which emerges near the inlet of the conveying pipe connections to bring the seeds to the auxiliary reservoir. The air flow emitted by the first channel is used to remove the seeds from the main reservoir and drive them over an upward journey. The seeds are then picked up by the air flow emitted by the second channel to be conveyed to the auxiliary reservoirs.
In practice, such a supply device equips a seeder used to plant all types of seeds. This supply device must therefore supply the auxiliary reservoirs, whether the seeds are light or heavy, and easy or difficult to convey. In general, the air flow passing through the second channel is greater than the air flow passing through the first channel. This difference in air flow is obtained by the section difference of the channel necks. In order to adapt to the type of seeds to be distributed, the user changes the pressure and therefore the air flow produced by the compressed air source. Such a modification will affect the extracting flow of the seeds and the conveying flow. The air flow provided by the compressed air source results from a compromise between the extracting flow and the conveying flow. The conveying flow must be sufficient to take the seeds to the auxiliary reservoirs without the extracting flow driving too many seeds toward the pipe connections. With an excessive extracting flow, the supply of seeds to the auxiliary reservoirs is irregular, and it takes place in blocks. Such a supply of seeds in blocks requires frequent starting of the supply device.