Distributing tower of an agricultural distributing machine and method for series cut-off on such a distributing tower

An improved shut-off device for a distribution tower of an agricultural distribution machine for spreading granular distribution goods with a riser pipe for supplying the distribution goods to a distributor head connected at the top to the riser pipe, with the distributor head serving for dividing the air volume flow of granular distribution goods into a multitude of partial air volume flows of granular distribution goods corresponding to a number of outflows distributed along a circumference of the distributor head, wherein each of said outflows has one of the shut-off devices associated therewith, wherein each shut-off device has a track switch through which an air volume flow of granular distribution goods can be guided toward a seed tube connection associated with the shut-off device or toward a return section associated with the shut-off device;

• wherein a return device connects to the return section;
• wherein the return device surrounds the riser pipe or is formed as part of said riser pipe;
• and wherein the riser pipe has openings extending therethrough, in flow communication with the return device, the openings serving for receiving the granular distribution goods returned through the return device, wherein, in the improved shut-off device, the riser pipe, the return device, and the return section, as well as the seed tube connection are permanently pneumatically connected, independently of the position of the track switch, by a bypass pneumatically connecting the return section to the seed tube connection, the bypass including a separator section extending vertically from an opening between the bypass and the return section, whereby a pressure level P1 results in the return device, and a pressure level P2 and P3 result in the return section and in the bypass respectively, wherein P1 is less than or equal to P2 and P3 respectively.

A distribution tower for an agricultural distribution machine for spreading granular distribution goods, the distribution tower comprising a riser pipe for supplying an air volume flow of granular distribution goods to a distributor head connected to the riser pipe with the distributor head dividing the air volume flow of granular distribution goods into a plurality of partial air volume flows of granular distribution goods corresponding to a number of outflows distributed along a circumference of the distributor head, wherein at least one of the outflows has a shut-off device connected thereto;

• wherein the shut-off device includes a seed channel, a bypass channel and a return channel formed therein with the seed channel connected between an inlet passage and a seed channel outlet, the return channel connected between said inlet passage and a return channel outlet, and the bypass channel connected between the seed channel and the return channel;
• a track switch is pivotably mounted within the shut-off device and pivotable between an open position in which the track switch closes off the return channel from the inlet passage while leaving the seed channel open to the inlet passage such that a partial air volume flow of granular distribution goods entering the inlet passage is guided from the inlet passage through the seed channel toward a seed tube connection of the shut-off device and a closed position in which the track switch closes off the seed channel from the inlet passage while leaving the return channel open to the inlet passage such that the partial air volume flow of granular distribution goods entering the inlet passage is guided from the inlet passage through the return channel toward a return connection of the shut-off device to which a return line is connected for delivering the partial air volume flow of granular distribution goods to a return device surrounding the riser pipe and wherein the riser pipe has openings extending therethrough, in flow communication with the return device through which the granular distribution goods in the partial air volume flow from the return channel re-enter the riser pipe, wherein the riser pipe, the return device, the return channel and the seed channel are pneumatically connected through the bypass channel independent of the position of the track switch.