Electronically controlled pneumatic seeder

The invention provides a pneumatic seeder wherein the various functions are controlled by electronic means. The seed distributors are operated by as many direct current motors, controlled by an electronic device as a function of the forward speed of the seeder, which speed is detected by an encoder. Electronic devices are also used for controlling both the sowing depth and the devices that adjust the seed fall.

FIELD AND BACKGROUND OF THE INVENTION 
The invention relates to a seeder wherein the functions of the main 
components are electronically controlled. 
More specifically, electronic means are employed for adjusting the speed of 
the distributors to the machine forward speed, and for acting upon the 
devices that control the seed fall, with a view to making them evenly 
spread over the ground, and penetrate same at a constant depth. There are 
known pneumatic seeders consisting substantially of a container divided in 
two by a revolving disk, provided with a plurality of holes all over its 
periphery. 
One of the compartments functions as a reservoir for the seeds, while the 
other is a chamber kept under vacuum by suitable suction means. 
By effect of vacuum the seeds adhere to the holes present on the disk, 
which revolves about a horizontal axis. 
During such revolution, the holes pass before an area that is not subjected 
to vacuum, from where the seeds may fall to the ground. In the known 
seeders the distributor disks are rotated by the machine wheels, through 
mechanical transmission gears. 
This system, however, is not free of some drawbacks and inconveniences: 
First of all, the speed of revolution of the distributor is linked to the 
forward speed of the machine by a limited number of fixed ratios. 
Secondly, this system entails as a consequence the building of very heavy 
costly and structurally complicated machines which, in case of wear, 
require considerable maintenance costs. 
Italian patent applcation 20162 A/87 describes a seeder of substantially 
the above kind, but providing electronic devices that allow to adjust the 
speed of revolution of the distributors in a continuous way, so as to make 
it fit moment by moment to the forward speed of the machine. 
SUMMARY OF THE INVENTION 
An object of the present invention is the further exploitment of the 
opportunities offered by electronics with a view to realizing a seeder in 
which other main functions too, such as the adjustment of the depth of 
sowing and the control of the uniform distribution of seeds over the 
ground, are electronically performed. 
This and other aims are achieved by the seeder according to the invention, 
as it is defined by the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The seeder according to the invention consists of a frame, not shown in the 
Figures, comprising a crosspiece or support 1 on which are mounted, and 
lockable at different positions, a plurality of seeding units, one of 
which, being shown at 2 in FIG. 1. 
Each of said seed units comprises a support 3 mounted on the crosspiece 1, 
a supporting arm 4 and a distributor 5. 
The latter is provided, at its upper part, with a hopper 6 wherein the 
seeds to be scattered over the ground are introduced, and is of the 
revolving disk type, like those previously described. 
In the specific case, however, the rotary motion of the disk is controlled 
by a d.c. motor 8, through a reducer 7, e.g. of the bevel gear type. 
Motor 8 is controlled, in a known manner, by an electronic control device 9 
set within the operator's easy reach. 
A support 10 of a wheel 11 resting on the ground is fixed in the proximity 
to an end of crosspiece 1. On the axis of said support is mounted a 
transducer of known kind, e.g. an encoder 12, connected too to the control 
device 9. 
Following the revolution of wheel 11, due to the forward motion of the 
seeder, the encoder 12 generates a series of impulses that are processed 
by the control device which, after it has been opportunely programmed, 
adjusts the speed of motor 8, and accordingly the speed of the 
distributor, to the forward speed of the tractor. 
It is thus possible to simplify the transmission system of the sowing 
machines, to make the motion of the distributing disks perfectly conform 
to the tractor speed without solution of continuity and to make the rotary 
motion of the disks independent, if necessary, from the other parameters, 
by simply making transducer 12 inoperative and by directly controlling the 
operation of motors 8 by means of the control device. Arms 4--to the ends 
of which are mounted the distributors--are hinged each at their relevant 
support 3, and subjected to the action of a hydraulic piston 13 
controlled, through an electrovalve 14, by a second electronic control 
device 15 housed too near the operator. 
The sowing unit 2 carries a sonar 16 which emits waves that are reflected 
by the soil, whereby the distance of the sonar from the ground surface can 
be measured, as a function of the time elapsed between the emission and 
the reception of the wave. 
In this way it is possible, by means of sonar 16, to detect the distance 
from the ground of the sonar itself and, consequently, of the sowing unit, 
so that one is informed moment by moment of the sowing depth. 
Once determined, at the beginning of the operation, the desired sowing 
depth--to which there corresponds a given "P" value representing the 
distance of the sonar from the ground--the device measures the variations 
in such "P" value and, should these ovestep a given limit, it gives off a 
signal that is processed by the control device 15; the latter, through the 
electrovalve 14, actuates the piston 13 in order to adjust the height of 
unit 2, and, consequently, the sowing depth. 
A slidable blade 18, actuated by a step-by-step motor 19, is placed near 
the disk 17 of the distributor, in the proximity to the trajectory 
described by the holes. In correspondence of the holes of disk 17 there is 
also a photocell 20 of known kind capable, when passing before each hole, 
of detecting the seeds--if any--. 
The photocell 20 is connected to a control device 21, through which it is 
possible to act upon the step-by-step motor 19 to the effect of moving the 
blade 18 backwards or forwards, so that the same interfere to a variable 
extent with the trajectory of the holes over the distributor, and therfore 
with the seeds sticking to such holes. 
In this way the disk is revolved, and the blade is moved back until 
photocell 20 detects the presence of a seed in correspondence of each 
hole. 
It is thus possible to position the blade in such a way that, when more 
than one seed adhere to the hole, they are lightly stirred by the blade, 
and the excess ones fall back inside the reservoir, only one seed 
remaining adherent to the hole. 
A different embodiment of the invention, on the contrary, provides a 
photocell 22 set below disk 17, in correspondence of the trajectory 
described by the seeds as they fall down. 
This solution enables the automatic working of the apparatus: in fact, 
thanks to the photocell, the seeds falling from the disk can be counted, 
and this datum can be processed at constant intervals of time by the 
control device 21, in which the required data were originally introduced. 
If the amount of the fallen seeds is greater or lesser than the expected 
amount, the control device will automatically operate in a known manner 
the step-by-step motor 19, that will bring in turn the blade 18 to a 
closer or looser engagement with the hole trajectory. 
An expert in the art can provide for several amendments and variations, 
which should fall, however, within the scope of the present invention.