FR2464017A1 - PRECISION SIETING - Google Patents

Abstract

THE INVENTION CONCERNS AGRICULTURAL MACHINES. THE ESSENTIAL ELEMENT OF A PRECISION SOWING MACHINE IS A DISC 70 WHICH IS CROSSED BY ORIFICES 94. A DEPRESSION IS ESTABLISHED ON ONE SIDE OF THE DISC AND SEEDS ON THE OPPOSITE SIDE SO THAT THE SEEDS 98 LODGE IN THE ORIFICES, DUE TO A SINGLE SEED PER ORIFICE. THE SEEDS ARE THEN DEPOSITED ONE BY ONE WITH UNIFORM SPACING. APPLICATION TO SOWING IN A NURSERY.

Description

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  The present invention relates to a precision seeder. The term "precision sowing machine" is used herein to refer to a sowing machine which is capable of depositing seeds one by one in seedlings, with predetermined spacings, but which is also capable of sowing seeds with predetermined spacings in unprepared soil. The invention relates to the use of a seed drill for sowing pinus radiata seeds in order to obtain

  shoots in specially prepared seedlings in the nursery.

  It will be noted that if the seeds are sown in groups of two or three, the two shoots, for example, which result in such a way of sowing will tend to kill each other. If the shoots are too close to each other, they also tend to choke

  mutually and if they are too far apart,

  the nursery is adversely affected by the fact that the space used is greater than that

strictly necessary.

  The invention aims to make a contribution

  elimination of the above-mentioned disadvantages and of

  come to the aforementioned desirable conditions.

  We can thus say in a general way that the invention

  This consists of a precision seeder that includes:

  aspiration sampling means which

  take a source of vacuum and several distinct orifices, each of which is designed to receive and retain a single seed, on one side of the orifice considered, when

  the vacuum source is plugged on the other side of this original

  fice; vacuum removal means which, in use, are associated with each port so as to remove the vacuum at a predetermined deletion point, in order to successively release each retained seed; and seed deposition means which in use is associated with the vacuum removal means for successively transferring each seed released from the vacuum removal point to a seedling, with a predetermined spacing from the adjacent seed,

  regardless of the speed of movement of the seed drill.

  The aspiration sampling means preferably comprise a disc which is traversed by axial orifices, and each of these orifices is at the same distance

radial from the center of the disc.

  The vacuum source preferably consists of an annular slot which, during use, coincides with the orifices passing through the disc. This slot

  ring is preferably formed in a housing which defines

  Nit a cylindrical chamber and is on a first -5mtve fore-a configuration such that during use the vacuum attracts the disk against the first

end face.

  The deposition means preferably comprise fins which protrude axially from one face of the disc so as to define with the circumferential face of the

  chamber and with a housing that forms the

  of the chamber, a cell that opens on the inside

  in the radial direction, the means of abolishing the

  empty space being arranged so as to release the seeds

  that they enter the opening of the cell. The point of discharge through which the seeds are discharged out of the cells, radially outward, consists of

  in an opening in the circumferential face of the chamber

  which starts slightly above the bottom dead point, whereby each seed rests against a winglet at

time of evacuation.

  According to one variant, the seed deposition means comprise fins projecting axially from one face of the disk in order to define with the circumferential face of the chamber and with a casing forming the second end face of the chamber, a radially inwardly opening cell and the vacuum removal means are arranged to

  to release the seeds so that they enter this opening.

  the cell. A first evacuation point for evacuation

  seed the seeds radially outwards

  cells consists of an opening in the circumferential

  room of the room; the means of deposition of seed

  additionally take an endless belt which has fins projecting outwards; this belt and these fins are positioned to move in a guide which defines with the fins and the endless belt a series of moving cells; guide

  has an entrance opening which coincides with the opening

  formed in the circumferential face of the chamber and a second discharge point is slightly above the bottom dead center of the lower pulley on which the endless belt passes, whereby each

  seed rests against a fin at the time of evacuation.

  According to a variant, the seed deposition means comprise an endless belt which comprises fins projecting outwards; the belt and the fins are positioned to move in a guide; the guide defines with the fins and the endless belt a series of moving cells; the guide has an inlet opening; the vacuum removal means associated with the disk are arranged to release the seeds so that they penetrate the opening

  input; and an evacuation opening is light-

  above the bottom dead center of the pulley on which the endless belt passes, thanks to which each seed

  rests against a fin at the time of evacuation.

  The invention will be better understood when reading

  the following description of embodiments, and

  with reference to the accompanying drawings in which: Figure 1 is a vertical section of a sower mounted on a carriage which is towed by an agricultural tractor. Fig. 2 is a side elevational view of a seed sump with the disk in place and with a

  part of the surface torn off to show the function

the seeder.

  Figure 2A is a partial section of a fin

on the disk.

  FIG. 3 represents a part of the sower casing which is fixed to the part which is represented on

Figure 2.

  FIG. 4 is a side elevational view,

  with some parts torn off, of a seed drill corresponding to

  in a second embodiment of the invention.

  FIG. 5 is a plan view from above, with some parts torn off, of a corresponding seeder

  in the second embodiment of the invention which is

shown in Figure 4.

  Referring now to Figure 1 which shows a sower 10 mounted on a carriage behind a tractor. A hopper 11 containing a seed bank is mounted above the seed drill 10. The seed drill is preceded by a depth control wheel 12

  which is height-adjustable thanks to a lower swivel arm

  The sower 10 is mounted between two wheels 14 which roll on the ground. The wheel 14 rotates on a short shaft 16 which protrudes inwards. The shaft 16 is mounted in a housing 17 and carries a chain drive gear which drives a drive chain 18 extending forwards to a chain gear on a main shaft. 20. The gear wheel that is driven by the chain 18 is outside a differential

  in which two parts of the main shaft penetrate 20.

  The purpose of this differential will be described later. A shift shaft 21 is placed immediately above the shaft 20 and carries a chain gear on which a cat 22 passes. The shaft 21 extends outwardly to a gear wheel The outer casing contains an upper gear and a lower gear, and the latter is mounted on a drive shaft 29. The outer gear wheels on the shafts 21 and 29 are interchangeable so as to change the training ratio of the seed drill. A housing 25 is

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  placed on the chain transmission 24, between the shafts 21 and 29. Finally, another chain transmission 26 is mounted

  inside a housing 27 to drive the main shaft

  pal 31 of the seeder. An upper swivel arm 48 constitutes

  kills an additional mounting point for the seed drill 10 and is pivotally mounted on an upper frame member 42. The other end of the frame member 42 pivots at a hinge 46 which is itself mounted on a cross member 44 which ensures rigidity between

  two flanges 28, one of which is shown in FIG.

  A double lifting hook 40 is pivotally mounted on the frame member 42. This piece 40 is hooked onto a lifting beam 36 which is mounted in a pivotal side frame member 32. One end of the element 32 is pivotally mounted on the flange 28 between abutments 34. An additional transverse frame member provides good rigidity. The element 35 also forms a stop for the lifting beam 36. When the latter is raised by the hydraulic arms of the tractor via the chain 38, it first takes off the seeders from the ground and then, if the lifting continues, it lifts the entire mechanism including the drive wheels, which may be necessary to turn

in a limited space.

  A main transom 30 is placed at the front of the chassis. An upper arm 54 and a lower arm 56 extend forward. A crank screw 60 makes it possible to adjust the angle of inclination of the lower arm 56 with respect to the main towing bar 58, in order to adjust the horizontality of the apparatus, in accordance with the indication of a spirit level. 13 which is mounted on the side of the hopper 11. The main towing bar is fixed to a tractor by means of a fixing pin 62. The driving wheel

  64 of the tractor is shown. A flexible suction pipe

  15 is connected to the intake manifold of the tractor to evacuate. The connection is equipped with a spring loaded valve to produce a vacuum sufficient for

  seeders, without impairing the operation of the tractor engine.

  6- A large capacity air filter is also inserted in the suction hose 15, between the seed drill and the intake manifold of the engine, to stop any foreign body. The operation of the structure shown in FIG. 1 will now be described. The chassis is mounted behind a tractor and is positioned so that the seed drill 10 is at level A of the seed drill. The main carrier wheel 14 is positioned in the aisle at level B between the seedlings. The coupling chain 38 which is connected to the hydraulic lifting mechanism of the tractor has been lowered and the crossbar or hook 36 has been placed

  in the correct position to allow this operation.

  As the tractor moves forward, the main carrier wheel 14 which rolls on the ground at level B is rotated, which rotates the shaft 16 and transmits the movement of

  rotation to the shaft 20 via the chalne 18.

  The shaft 20 enters a differential, not shown. The differential is used because, although the seedlings are generally not bent, in some cases either of the wheels of the seed drill may begin to spin or spin at a slightly different speed than

  the other wheel. It is very desirable that there be a rela-

  the speed of rotation of the seed drill and the speed of movement of the seed drill on the ground, and the existence of a differential in the transmission between the load wheels and the seed drill contributes to this. An additional factor is the use of tires

  with strong adhesion, for example motorcycle tires.

off-road debt.

  The movement of the differential coupled to the shaft is transmitted by the chain 22 to a gear which drives the shaft 21. extending outside the transmission housing 25. The gear ratios can be selected to accelerate the speed of rotation of the seed drill when sowing seeds closer to one another, Ouc to slow down this speed of rotation

  when you want to sow the seeds with a larger space-

  is lying. The movement is finally transmitted to the sowing tree 31 through the transmission chains 24 and 26 which have been previously described. The depth at which the seed drill operates is controlled by the depth wheel 12 which can be adjusted by means of the

Rotating genome 52.

  In another embodiment, not shown, a combined differential / gearbox could replace the differential and the separate gearbox.

just described.

  The embodiment shown is comprised of a single sower. It should be noted, however, that in normal use a number of seeders corresponding to the width of the seedling are used to form lines of grain along

sowing.

  When multiple seeders are used, each

  of them can be synchronized so as to evacuate the

  at the same time, in order to deposit the seeds in

  perpendicular to the direction of travel of the seeders.

  Each seed drill then has a clearance device on the shaft 31 which, by relaxing the chains when all the seeders are in the fully raised position (frame member 32 against the crossmember 35 and hook 40 hooked on the crossmember 36 by the lower hook among the two (40)), allows to make coincide a reference carried

  on each disc with a mark on the workpiece.

  66. When they are "synchronized" in this way, all the discs rotate together

  seed in each furrow, which

  mence the seed in a square pattern.

  We see in Figure 2 the body 66 of the sower which is generally flat and is made of aluminum

  mold. A cylindrical chamber 68 whose axis is relative-

  short in comparison to its diameter is defined in the body. A series of orifices 78 communicate with each other and with a suction nozzle 76. It will be seen that the

  annular line of these suction ports extends from

  about 4 hours at about 7 o'clock on the circle. There exists a

246 4017

  annular wear surface 80 which is divided on either side of the suction orifices 78 but which is continuous

otherwise.

  The wear surface 80 comprises a cavity 84, the purpose of which will be described later. There is also an air inlet hole 82 which coincides with the orifices 94

  formed in the disk 70 and will be described later.

  A coulter 104 is screwed into the front part of the body 66 and there are coulters 106. It can be seen that a discharge lip 108, inside the cylindrical chamber 68, is at a point slightly above from the bottom dead point of the

  circle. The disc 70 is adjusted without play in the chamber 68.

  It is fixed on the shaft 31 by means of a key.88 so as to turn in clockwise direction (in FIG. 2) with the shaft 31. The outer periphery of the disc 70 carries a series of fins 90 which are riveted with rivets

  92 on the disk 70, as shown in Figure 2A. Originals

  Fices 94 are distributed symmetrically around the disc, the inner side relative to the fins 90. When the disc is in position, the orifices 94 coincide with the suction port 78 and with the air inlet hole 82 which is formed in the body 66. Also shown is a portion 72 of the housing 109 which fits on the body 66. A toothed blade 100 and a scraper blade 102 are mounted radially

  outside and inside the hole 94.

  The inclined surface 102 and the protruding surface 72, which appear more clearly in FIG. 3, define with the disc 70 a zone for receiving seeds from

  the feed inlet through the hopper, 74 (-figure 3).

  Optionally, nylon bristles, 96, may alternate with orifices 94 to agitate seeds 98 that originate from the hopper, to help isolate

the seeds one par.une.

  - Figure 3 shows the housing 109 which adjusts

  against the body 66 to close the chamber 68 of the sower.

  We also see coultre 104 and soc 106 which leave the body 66. The toothed blade 100 can be adjusted with a screw 103. Similarly, the scraper blade 102 can

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  to be adjusted by loosening a bolt 105 which is housed in a slot in the center of the blade 102. A top-level surface 110 and a recess portion 113 face the housing 109. Also shown is the inlet 74 which communicates with the hopper 11. An air inlet 112 is formed so that there is a greater pressure difference between the side of the disc 70 which communicates with the atmosphere and the side of the disc from which the vacuum is evacuated, This makes it possible to better retain the seeds 98 in the orifices 94. The inlet 112 is provided with a vertical tube so that the air which is sucked into the seed drill comes from a zone of clean air situated clearly beyond above the seedling surface, and may be equipped (if necessary) with an air filter

  lightweight to avoid the risk of dust suction.

  Inspection windows 114 and 115 are formed so

  an operator can check the positioning of the

  A wear plate 116, which may be made of Teflon or other suitable material, is placed at the point where the seeds fall into the respective cells from the orifices 94. The wear plate 116 is positioned to urge the disc against the annular wear surface 80 around the cavity 84 to increase the wear on the cavity.

  vacuum applied to the orifice 78 which holds the seed 98.

  We will now describe the operation of the

  seeder itself, considering figures 2 and 3.

  A vacuum source, such as the air intake pipe of a tractor, is connected by the flexible pipe 15 (FIG. 1) to the suction manifold 76.

  depression in the suction ports 78, in the chamber

  When the carrier wheels 14 are pulled forward, the shaft 31 rotates counter clockwise. The flap of the hopper 11 is open to allow the passage of seeds 98 which descend to the feed inlet 74. After passage of agitators, the seeds, generally single seeds 98, are received and retained in the orifices 94 by the pressure difference that exists because there is a depression on one side and an air inlet on the other side. The seeds 98 may have a regular or irregular shape. In the case of pinus radiata, the seeds are occasionally long and pointed and thus a hole 94 sometimes holds two seeds, as shown for the seeds 99. When this hole passes the toothed blade 100 and the blade scraper 102, the seeds are dislodged and a single seed continues to rotate with the disc, from this point. Once the seeds have passed at the end of the suction inlet 78, at about 7 o'clock, and the associated suction holes 94 coincide with the cavities 84 formed in the wear plate 80, these seeds fall into each of the cells that are defined

  by the disc 70, the fins 90, the circumferential surface

  room 68 and the outer casing 109. We can see

  that there is only one seed in each cell. In posi-

  making the discharge lip 108 slightly above or below the bottom dead point, each seed can slide in

  back in his cell against the wing 90.

  This ensures a uniform spacing between all the seeds.

  The height of the lip 108 is, however, reduced to a minimum so as to reduce the effect of the bouncing of the seed

when it falls in the furrow.

  When the disk 70 continues to rotate, each hole 94 momentarily coincides with the air inlet hole 82. The air jet passing through each port 94 eliminates dust or other foreign particles. who could lodge in the hole. The foreign material that one usually encounters is constituted by

seed coatings.

  Under ideal conditions where there is little or no dust, the air inlet hole could be removed.82. However, under more conditions

  normal it is desirable to have net-to-

  An alternative would be to use

  an annular slot surrounding three or four orifices 94.

  Such a structure would preferably be accompanied by a

  wear plate similar to the plate 116.

  Seedlings were tested in seedlings using pinus radiata seeds. Table I presents the results of part of this test. It can be seen that the seeder sows only one seed at a time in more than 90% of cases, and that the variation in mean spacing is minimal.

TABLE I

  SPACING (BETWEEN CENTER ALONG THE SILLON (in cm) FOR PINUS SEEDS

RADIATA COATED DI.'ARASAN-42S

  DISTANCE TOURS COVERED (cm) * Mean Spacing Distance Spacing PERCENT DISK between seeds total seed distribution SEPARATION medium One Two None Total GR-AINES Quarter Turns Quarter Turns cm seed only (12 seeds) (12 seeds ) (48 holes seed seed receiving reception fans 1st 2nd 3rd 4th 1st 2nd 3rd 4th cm of Eraine) __ __ _ _

  FIRST 68.4 67.0 67.4 67.6 5.70 5.58 5.62 5.63 270.4 5.633 87.50% 6.25% 6.25% 100%

  SECOND 67.1 66.7 66.5 67.2 5.59 5.56 5.54 5.60 267.5 5.573 95.83% 2.08% 2, 08% 100%

  THIRD 66.5 67.7 67.9 66.9 5.54 5.64 5.66 5.57 269.0 5.60 85.50% 2, 10% 0.40% 100%

  FOURTH 64.5 67.7 66.6 67.2 5.37 5.64 5.55 5.60 266.0 5.542 91.66% 4, 17% 4.17% 100%

  FIFTH 66.8 66.4 68.0 66.8 5.57 5.53 5.67 5.57 268.0 5.583 89.60% 8, 30% 2.10% 100%

  AVERAGE 66.7 67.1 67.3 67.1 5.56 5.59 5.61 5.59 268.2 5.587 90.40% 4.60% 5.00% 100%

  * Note: Determined by the distance covered by the main carrier wheel rolling along the driveway between seedlings, and not directly to

the surface of the seedling.

4N oas P> 0% -

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  Figures 4 and 5 show a second embodiment of the invention. This mode can be used

  with a device in which the vertical distance

  that the seeds must travel is greater than that corresponding to the embodiment of Figures 1 to 3. The sower 120 comprises a hopper 122 which feeds

  a sub-hopper 126, as in the previous embodiment

  tooth. The main element of the first part of this embodiment of the seeder is constituted by the disc of

  seed separation, 130, which is mounted on a tree 128.

  In a preferred embodiment, this disk 130 has the same structure as the disk 70 which is shown in Figures 1 to 3. A series of fins 131 project axially from the face of the disk. The suction ports 129 are aligned with an annular slot. There may be

  nylon bristles, 133, but these are optional.

  It has been found that by establishing a high vacuum in the suction hose 124, it is not necessary to use the fins 131 and 133. In addition, by using a higher vacuum the hole diameter can be reduced. suction 129 relative to the suction holes

  94 of the disc 70 of the embodiment of Figures 1 to 3.

  The disc 130 is mounted on a driven shaft 128, as before. The main modification of the seed drill consists in the existence of an endless belt 134 from which a series of fins 135 rise. This belt circulates in a housing or guide 137 and a series of moving cells are defined. between the belt, the fins and the housing. Each of these cells carries a seed. These cells are synchronized to align with

  the orifices 129 of the disk 130. The alignment can be easily

  by the use of fins 131, but these are optional. The release of seeds from disc 130 is performed in the same manner as the release of the seeds.

seeds from the disc 70.

  The endless belt 134 passes over a driven gear 132 and an idler gear 152. The driven gear 132 is mounted on the shaft 166 via a flange which extends from a crosshead U-shaped main gear 136. The gear 132 may be driven by a driven shaft 138 which drives a chain 139. Alternatively, the gear 132 may drive the disk 130,

  equipped with teeth appropriate to its circumference.

  The frame on which the seed drill is mounted is similar to that shown in FIG.

  slot 143 is formed in the main lateral flange 140.

  A bar 142 is placed in the slot 143 to lift

  the device, as indicated by the big arrow.

  The crazy gear 152 is mounted on a bar

  voltage 144 which may be remote from the gear 132.

  In another embodiment, an endless chain such as a saw chain can be used and the idle gear 152 and the tension bar 144 replaced by a

saw guide.

  The soc 146 is intended to dig the groove in which the seeds must be sown. It can be seen that the inner part of the casing 137, behind the plow 146, passes beyond the bottom dead center and rises slightly to form a lip 147 which ensures a uniform deposit of seeds 148,

  as will be explained below. The product control wheel

  foundry 150 is intended to define the depth to which

the seeds are sown.

  Referring to Figure 5, it can be seen that the main drive shaft 156 is mounted in a bearing 154 which is on the side flange 140. Two mounting members 159 are mounted on the cross member 136 and their positions are controlled at using the blocking wheel 158, as will be explained below. There is an auxiliary mounting member 160 for a seeder. An auxiliary drive wheel 162 drives the seeder. An electric motor 164 drives the wheel 162 to make it turn on the shaft 163.

  Another drive shaft 166 carries a series of gears 168. These gears mesh with a gear 170 which is mounted on the main drive shaft 156 to drive the shaft 166. This embodiment of the invention operates in a manner very similar to that of the first embodiment. The sower 120 is mounted on a carriage which is towed by a motor vehicle such as a tractor. The sub-hopper 126 is fed with the seeds 148 which are in the hopper 122, in the same manner as the sub-hopper 74 in the embodiment of FIGS. 1 to 3. The disc 130 rotates clockwise in the embodiment shown in Fig. 4. The seeds 148 are picked one by one into the orifices 129 and rotate until they occupy positions exactly above the point where the edge of the disk is located. 130 coincides with the orifice 141 which passes through the housing 137. The seed release means of the disc 130, which are identical to those of the other embodiment of the invention, release the seeds one by one into the orifice 141 to enter a single cell which is formed by two fins 135, the housing 137 and the belt 134. The fins 131 facilitate the alignment of the seeds with a cell of the belt but we see that they are not

  essential to the operation of the disk 130.

  In another embodiment corresponding to the invention, the disk 130 and the conveyor belt 134 are synchronized so that a seed falls in every other cell. A second disc is positioned at a certain point on the path of the belt 134 so as to also deposit a seed in every second cell, the timing being such that there is a seed in each cell. This mode of operation can be used

  to double the speed relative to the ground.

  The toothed wheel 132 shown in FIG. 4 rotates counterclockwise, as shown in FIG.

  the arrow. The seeds 148 found in the cells

  then descend them along the lower run of the chain to a position behind the share 146 to which the chain begins to rise. The seeds are applied

  by gravity against the fins 135 which ensures their posi-

  uniformity. The fins 135 thus fulfill a function identical to that of the deposition of the seeds by the fins 90 above the lip 108 on the disc 70 in

  the embodiment previously considered.

  b The purpose of the mounting element 161 is to allow removal of the upper seed drill for maintenance or adjustment. The gear wheel 162 rotates

  the seed drill in an unobstructed position regardless of any movement

  in advance of the machine or the motor vehicle. This allows an operator to make adjustments to the seeder, on the restriction plate which controls the

  seed transfer rate from the hopper to the sub-

  hopper 126, and other settings. The hopper 122 'is

  felt in this position in Figure 5.

  The diameters of the sampling orifices were measured

  the suction of the discs, with the vacuum produced by a domestic vacuum cleaner as well as with a depression of -1.75 kPa. Table II below indicates the diameters that have been determined to be useful. These diameters are

expressed in millimeters.

- Table II

  Aspiration Orifice Suction Diameters (mm) Seed Aspirator -1.75 kPa But 4.0 2.8 Sunflower 2.8 1.6 Pinus Radiata 1.8 1.0 Of course many modifications can be made to the device described and shown,

  without departing from the scope of the invention.

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Claims (17)

  A precision sowing machine, characterized in that it comprises: aspiration sampling means which comprise a vacuum source and a plurality of distinct orifices, each of them being designed to receive and retain a single seed of the one of its sides, when the vacuum source is connected to its other side; vacuum removal means which operates in association with each port so as to suppress the vacuum at a point of   predetermined deletion, so as to release   each seed retained; and seed deposition means operative in association with the vacuum removal means for successively transferring each seed released from the control point to a seedling, with a predetermined spacing from the adjacent seed, regardless of the seed speed. moving from the seeder.   2. Precision seeder according to claim 1,   characterized in that the suction sampling means   comprise a circular disc which has orifices passing through it axially, and all the orifices   are at the same radial distance from the center of the disc.   3. Precision seeder according to any one of   claims 1 or 2, characterized in that the source   vacuum consists of an annular slot which, during operation, coincides with the orifices passing through the disc.   4. Precision seeder according to any one   claims 1 to 3, characterized in that   also carries a seed separating aid one by one which cooperates with the orifices of the disc to agitate the seeds which are associated with these orifices, to help remove excess seeds from finding in the orifices.   5. Precision seeder according to claim 4, characterized in that the seed separation aid comprises a toothed element which is placed on the side of the seed. 24640 17   outside relative to the disk orifices radially, and a blade which is positioned on the inside   of these orifices, in the radial direction.   6. Precision seeder according to any one of   Claims 3 to 5, characterized in that the slot   annular is formed in a housing which defines a cylindrical chamber, this slot is on a first end face of the housing, and the configuration is such that during use the vacuum attracts the disc against the first end face.   Precision seeder according to claim 6, characterized in that the annular gap extends over less than 3600 around the first end face and the vacuum removal means comprises a cavity which is formed in the first face of the end to allow   the air inlet on the side of the disc to which the vacuum is applied.   8. Precision seeder according to any one   claims 6 or 7, characterized in that the means   deposition include fins that protrude axially-   from a face of the disk to define with the circumferential face of the chamber - and with a housing which forms the second end face of the chamber, a radially open cell on the inner side; the vacuum removal means are placed so as to release the seeds so that they penetrate the opening of the cell; and the discharge point at which the seeds are discharged radially outward from the cells is an opening in the circumferential face of the chamber which is slightly above the bottom dead point, whereby each seed rests against a fin at the time of evacuation.   9. Precision seeder according to claim 8, characterized in that the fins have a curved section. in radial view.   10. Precision seeder - according to any one   Claims 6 to 9, characterized in that the means   seed deposition comprise fins which protrude axially from one face of the disc so as to define with the circumferential face of the chamber and with a housing which forms the second end face of the chamber, a cell open towards radially inside the vacuum removal means are arranged to release the seeds so that they enter the opening of the cell; a first discharge point for discharging the seeds out of the cells, radially outwards, consists of an opening in the face   concordential of the chamber; the means of deposit   additionally take an endless coutriage which has fins projecting outwards; this belt and these fins are positioned to move in a guide which defines with the fins and the endless belt a series of moving cells; and the guide   has an entrance opening which coincides with the opening   which is formed in the circumference of the   chamber, and an evacuation opening which is slightly   above the bottom dead center of the lower pulley on which the endless belt passes, thanks to which each   seed rests against a fin at the time of evacuation.   11. Precision seeder according to any one of   Claims 1 to 7, characterized in that the means   seed deposition include an endless belt this belt has fins that protrude outwardly; the belt and the fins are positioned to move in a guide which defines with the fins and the endless belt a series of moving cells; the guide comprises an inlet opening, the vacuum removal means being arranged so as to release the seeds so that they penetrate into the opening   entrance, and an escape opening which is slightly   above the bottom dead center of the lower pulley over which the endless belt passes, whereby each   seed rests against a fin at the time of evacuation.   12. Precision seeder according to any one of   claims 1 to 11, characterized in that it comprises   a coulter and lateral coulters that are associated with the seed drill to form a furrow in which the seeds are 2 46 4017   sown. Precision seeder according to claim 12, characterized in that the associated sower and coulter   are preceded by a depth control wheel.   14. Precision seeder according to any one of   Claims 1 to 13, characterized in that it is   mounted on a chassis between a pair of wheels that roll On the ground.   Precision seeder according to claim 14, characterized in that the frame is adjustable   to have a constant orientation with respect to the ground.   16. Precision seeder according to any one of   claims 14 or 15, characterized in that   includes differential transmission means between the wheels which roll on the ground and the seed drill to cause the latter to be driven with a gear ratio of constant transmission.   17. Precision seeder according to any one of   claims 1 to 16, characterized in that the source   of vacuum is constituted by the intake manifold of a tractor pulling the seeder.