The invention concerns a sowing machine of the type defined in the introductory portion of claim 1.

Such sowing machines make it possible in practice

2 continuously to read the number of seeds sown per m so that the percentage sown too much or too little with respect to the desired one can be readily determined, and the machine can be adjusted accordingly.

However, sowing of exactly the desired amount of seeds per unit of area is conditional upon the counted number of seeds being correct, which is often not the case when two or more seeds pass the. seed counter at the same time and are therefore counted by the counter as a single seed.

The object of the invention is to provide a sowing machine of the present type which ensures more accurate counting of the seeds sown.

This object is achieved in that the sowing machine is constructed as stated in the characterizing portion of claim 1 because the spreading of the seeds eliminates or at any rate minimizes the risk of two or more seeds passing the seed counter at the same time.

The spreading means may be formed by one or two air nozzles, as stated in claims 2, 3 and 4, or by a rotary brush, as stated in claim 5.

The invention will be explained in more detail below with reference to the drawing, in which

fig. 1 is a schematic vertical section through parts of an embodiment of the sowing machine of the invention,

fig. 2 is a perspective view of a chute with an air nozzle to spread the seeds,

fig. 3 is a vertical section through a seed counter incorporated in the machine,

fig. 4 is a schematic vertical section through parts of another embodiment of the sowing machine of the invention, and

fig- 5 is a perspective sectional view of a channel section with two air nozzles to spread the seeds.

In the drawing the numeral 10 designates the seed box of a sowing machine, said box extending in the full width- of the machine and containing the seed corn 11 to be sown. As shown, the lower portion of the seed box is hopper-shaped in cross-section and has a plurali¬ ty of bottom openings 12 defined between the inclined bottom wall 13 and the lower edge of a seed shutter 14, which is associated with each opening and is slidably mounted on the inclined rear wall 15 of the seed box. A bottom flap 17 is pivotally mounted on a bracket 16 below each bottom opening and has a curved top side forming an elongation of the bottom wall 13. Between the rear edge of each bottom flap 17 and the lower edge of the corresponding seed shutter 14 is mounted a seed roller 18, which is designed in a generally known manner and has circumferentially arranged pockets to receive and feed the seeds. All seed rollers are firmly mounted on a common, rotatable shaft 19. When the seed roller is rotated in the direction shown by an arrow 20, it carries seeds upwards above the edge of the bottom flap 17 from which they drop down to

a trough-shaped chute 21. The spacing between the bottom flap edges and the seed rollers can be adjusted in a known and not shown manner by joint rotation of all the bottom flaps, and, additionally, each individual bottom flap can be separately adjusted by means of a screw 22.

The seed corn drops down from the chute 21 in a seed tube 23 associated with the outlet in question and leading to its respective coulter (not shown). One or more of the seed tubes 23 accomodate a seed counter 24, which is shown in more detail in fig. 3 and will be described more fully below with reference to this figure. To eliminate or at any rate minimize the risk of two or more seeds passing the seed counter at the same time and of consequently being counted as one seed, their speed .is increased with a consequent spreading of the seeds by means of a weak air flow applied through a downwardly directed nozzle 25, which is disposed above the chute 21 and is connected to a source (not shown) of compressed air.

Fig. 2 shows an amended location of the air supply tube in connection with a special embodiment of the chute 21. This chute has a bottom portion 26 with a cross-section in the shape of an open V and with a downwardly decreasing width as well as two substantially vertical side walls 27 extending upwardly from the side edges of the V-shaped portion. The air supply tube, which is designed by 28 here, is passed through the bottom of the V-shaped portion 26 and is bent down- wardly towards this bottom.

The seed counter 24 shown in fig. 3 consists of a substantially cylindrical sleeve 29 with an upper and a lower end portion 30 and 31, respectively, having a diameter so reduced as to fit in a seed tube. The hole

32 extending through the sleeve is frusto-conical at the top and cylindrical on the remaining portion and has a diameter adapted to the size of the seeds to be sown. The outer side wall of the sleeve is formed with a relatively wide, annular groove 33, and a transverse hole 34 extends from the bottom of the groove diametrically through the sleeve. At one end of this hole 34 there is mounted a transmitter 35 for infra¬ red light and at the other end a receiver 36 for the same. The transmitter and the receiver are mechanically insulated from the central hole 32 by means of a glass tube 37 inserted in the hole. The groove 33, which may contain electronic equipment (not shown) to actuate the transmitter and the receiver and. to amplify the signals emitted from the latter, is closed outwardly by means of a jacket 38. The sleeve can optionally be formed with another transverse hole 39, shown in broken lines, with a transmitter and receiver (not shown) .

The amplified counting signals are applied to a recording apparatus in a computer (not shown), which also receives signals from a conventional area meter (not shown) and is thus able to display both the number of seeds sown at any time per m 2 and the total seed rate.

The embodiment shown in fig. 4 differs from that of fig. 1 only in that it has a rotary brush 40 instead of the air nozzle 25 to spread and accelerate the seeds. This brush is so mounted on a shaft 41 parallel with the seed roller shaft 19 that the bristles sweep the bottom and the chute 21 during rotation.

The channel section of fig. 5, which is generally designated by 40, can be incorporated in a channel equipped with a seed counter, instead of the chute 21, figs-. 1 and 2. It consists of a block 41 of a suitable moulding material, e.g. plastics, with a curved front side 42,

along which the rear edge of the bottom flap 17 can move, an .angular top side 43 and a plane, rectangular rear side 44. The through-going channel consists of an inlet portion 45 with a rectangular cross-section which tapers in the flow direction and a cylindrical outlet portion 46 in whose rear end 47 the inlet portion terminates. The bottom of the inlet portion is stepped, comprising three steps. Air channels 49 terminate in the end faces 48 of the two first steps, said air channels emerging from a third channel 50 communicating with a threaded hole 51 formed in the underside of the block 41 to receive a threaded plug (not shown), by means of which the air channels can be connected to a source (not shown) of compressed 'air.

During passage through the channel section 40, the seeds are thu-s subjected to the action of an air jet two times in succession. This double action ensures effective spreading of the seeds.

The details of the sowing machine of the invention can be arranged in other ways than those shown in the drawing and described in the foregoing. For instance, the transmitter and receiver of the seed counter may be arranged to transmit and to receive other forms of beams than infra-red light. It is also possible to have the seed counter control the adjusting means of the sowing machine to adjust the seed rate per m 2 automatical¬ ly through suitable, generally known control circuitry.