in the figures , there is generally designated 1 a pneumatic seed - drill which is schematically illustrated in terms of only the main components . the seed - drill 1 comprises a receptacle 2 , in which the granular material to be distributed is contained , a fan 3 or other type of air compressor , a device for pneumatic transport 4 with a venturi tube ( venturi below for the sake of brevity ), in which the flow of air generated by the fan 3 flows together , a rotary distributor 5 , in particular provided with a bladed impeller 51 , and a diffusor 6 which receives the flow of air mixed with granular material to be distributed and supplies it to sowing elements which are illustrated by means of discharge conduits 7 which are connected to the diffusor by means of a tubular channel 71 . as illustrated more clearly in fig2 and 2a , the relationship between the above - mentioned components is such that the granular material contained in the receptacle 2 falls owing to gravitational force into the distributor 5 and is dispensed thereby in a through - conduit 8 which extends between the outlet of the distributor and a mixing chamber 41 of the venturi 4 ( and optionally including the venturi itself ), where it is mixed with an air flow and transported to the diffusor 6 . in particular , there is defined in the mixing chamber a through - hole 42 which is constructed in the region of a partition wall 15 between the transport device 4 and the distributor 5 and which opens in the through - conduit 8 in such a manner as to place them in communication with each other . there is further provided in the through - conduit 8 a calibration aperture 9 which is normally closed by a gate 10 in the form of a blade which is articulated at one end to the conduit 8 and which can be pivoted away from and towards the aperture 9 in order to open or close it . springs 12 or other locking devices retain the gate 10 in a closed position which is also indicated as the distribution position , restoring the continuity of the through - conduit 8 . a linear actuator 11 of the electromechanical type is active between the fixed structure of the conduit 8 and the gate 10 in order to move it between the closed position mentioned and an open position which is also indicated as the calibration position , in which the granular material is dispensed through the aperture 9 , thereby bringing about the calibration step previously illustrated . the operative distribution and calibration configurations , with the gate 10 in the respective position , are illustrated in fig2 and 2a , respectively , with a broken line ( gate closed — distribution position ) and solid line ( gate open — calibration position ). as may be noted from those figures , in the present embodiment when the gate 10 is in the open position , the flow of granular material is redirected by the gate 10 itself towards the aperture 9 , further preventing the flow from reaching the chamber 41 . consequently , in the present embodiment , the gate 10 acts as a deflector of the flow . alternatively , there may be provision for the aperture 9 to be arranged in a position below an outlet of the conduit 8 , in such a manner that , when the gate 10 is open , the granular material is directed towards the aperture 9 simply owing to the effect of gravitational force . in that case , therefore , an action for redirecting the flow will not be necessary . in the actuator 11 , there are integrated a first and a second travel limit detector . those travel limit detectors , which may also alternatively be constructed by means of external sensors , allow detection of whether the gate is in the open or closed position , consequently giving or not giving authorization for the calibration step of the distributor or for distribution over the whole field . those authorization signals are provided by means of suitable connection to a control unit which is not illustrated in the figures and which , once the appropriate authorization has been received , allows or prevents the functions mentioned . there is provision for the actuator 11 to be able to be of the electromechanical type , as in the present embodiment , or hydraulic , pneumatic , linear or rotary . there is further provision for it to be able to be unidirectional and for the opposite travel to actuation travel to be controlled by resilient return means , such as helical springs or the like . it must further be understood that , in the case of use of stepping motors , it may not be necessary to provide travel limit sensors , because such control is implicit in that type of actuation . it is also known that the locking function brought about by the spring 15 may be brought about by the same actuator which may be controlled in such a manner as to keep the gate 10 locked in a closed position during normal operation of the seed - drill . still as an alternative to the spring , or in combination with the spring , there may be provision , as a locking device , for a hook which is not illustrated in the figures and which keeps the gate 10 locked in the closed position . finally , there is further provision for the distributor of the seed to be able to be rotated by an electric motor 52 in accordance with the authorization received by the control unit in order to drive the bladed rotor 51 of the distributor in rotation about its own axis for the number of rotations provided to carry out the calibration step . the operation of the device according to the present invention is therefore schematically illustrated in fig3 a and 3b which illustrate the seed - drill in the calibration step and sowing step , respectively . during the calibration step , the granular material m is transported by means of the rotor 51 towards the through - conduit 8 . in that step , the gate 10 is arranged in the open position , in such a manner as to release the passage towards the calibration aperture 9 , directing the granular material m towards a receiving tank 91 , which is provided with a discharge 92 , illustrated in fig1 , from which the material used for the calibration may be recovered . at the same time , the gate 10 is arranged in such a position as to prevent the passage of the granular material m towards the chamber 41 and , more specifically , is arranged resting on the partition wall 15 , on which there is constructed the through - hole 42 between the through - conduit 8 and the above - mentioned chamber 41 , as can also be seen in fig4 a . as mentioned above , the gate 10 is articulated in the region of an end 101 thereof to the actuator 11 by means of an articulation shaft 13 . furthermore , the gate 10 is additionally articulated by means of abutment between a vertex 102 thereof , or more generally an intermediate position thereof , and an edge of the calibration aperture 9 . it is evident that , as an alternative to abutment , there could be used a different articulation system such as , for example , a pin . the gate 10 which is secured in this manner is therefore able to move by means of actuation involving a piston and crank rod , in which the linear movement of the actuator 11 which coincides with the movement of the piston produces a rotation of the gate 10 with respect to the point of rotation defined by the abutment between the vertex 102 and the edge of the aperture 9 . the movement of the actuator 11 may therefore move the gate 10 by means of a rotation movement in the closed position which is illustrated in fig3 b and 4b . in that position , the through - hole 42 from the conduit 8 towards the chamber 41 is released and , at the same time , it blocks the calibration aperture 9 . the granular material m may therefore continue towards the venturi tube and become mixed with the air flow a therefrom , and thereby be directed to the diffusor 6 . it is known , as better illustrated in fig4 b , that the spring 12 , which is connected at one end to a pin 14 which is fixed to the wall 15 and at the other end to the shaft 13 controlled by the actuator , is maintained in a rest position when the diffusor is in a closed position . conversely , by the actuator 11 being actuated , the spring 12 becomes tensioned in such a manner that , in the absence of other forces , the gate 10 tends to move again into a closed position . the invention described in this manner allows a number of advantages over conventional devices . in particular , the functionality and efficiency of the calibration step are improved and a higher level of safety for the user is ensured . the use of a rotary gate actuated with a piston / rod system further allows a substantial reduction in the risks of the moving members becoming jammed owing to the presence of dust and other similar material present in the working environment . in addition , it is possible with the device according to the present invention to prevent the redirecting gate from blocking or obstructing the air flow from the transport device , this being positionable in the region of the partition wall between it and the distributor . since the gate in the distribution position is maintained in abutment with the partition wall 15 , which delimits the mixing chamber 41 , it is not affected by the air flow produced by the ventilator . furthermore , the rotation of the gate takes place in a direction away from the mixing chamber even in the calibration position . finally , with the distributor and the transport device being kept separate , it is possible to prevent , during the calibration step , a portion of the material from being able to be directed to the diffusor , thereby causing errors in the calibration step .
a device for calibrating the product dispensed by a distributor of granular materials comprises a calibration aperture formed in a through - conduit for the granular material between the distributor of the seed and a device for transporting the material , and a gate associated with the calibration aperture and movable between a calibration position , in which the aperture is open and the material from the distributor is conducted via the aperture , and a distribution position , in which the aperture is closed and the material is conducted therebeyond along the through - conduit , wherein a motorized actuator is connected to the gate so as to make the gate movable between those positions .