Patent Publication Number: US-2021168992-A1

Title: Scraper wheel for sowing

Description:
The invention relates to an agricultural wheel and more particularly to a wheel which forms the accessory of a seed drill disc. 
     A seed drill is an agricultural machine that is used in a field to seed grain therein. This machine conventionally takes the form of a hitch which is moved across the field using a tractor or the like. A seed drill can have a fairly complex constitution, made of several portions, each of these portions being adapted to a specific operation. Conventionally, a seed drill thus comprises a portion intended to open one or more furrows in the ground, for example by means of coulters, discs or teeth, a portion intended to deposit seed or grains in these furrows and a portion intended to close these furrows or compact the soil, after the seed or the grains have been deposited therein. 
     To open the furrows, some seed drills are equipped with disc-shaped tools, generally mounted in pairs on the hitch, which, by rolling, penetrate the ground so as to spread the soil. 
     It is known to add to these discs, as an accessory, an agricultural wheel comprising a body carrying a rim and a tire slipped on the body, around this rim. This wheel allows to adjust the working depth of the discs, keeping their active portion at a substantially constant depth when the seed drill is moved. This is referred to as “gauge wheel” in the art. 
     Most often, the tire is of the type called “semi-hollow” type. Such a tire comprises a case made of flexible material around a chamber left empty. One or more orifices through this case maintain the chamber in fluid communication with the outside of the tire. As a result, the case has a high capacity for deformation during work, a deformation which contributes to cleaning the tire, or at least to preventing soil from accumulating therein. 
     In at least some circumstances, soil tends to accumulate on the seed drill discs when they are working, making them less efficient. To clean these discs, it is known to use gauge wheels with semi-hollow tires, the profile of which comprises a lip which protrudes, at least axially, from the rest of the case. This lip is arranged so as to rub against a disc of the seed  drill, or to scrape it, taking advantage of a relative rotational movement between the gauge wheel and the disc. 
     Examples of lip tires of this type, a lip that can be described as a “scraper”, are disclosed by FR 2 885 008 A1 and FR 3 017 265 A1 in the name of the applicant, and also U.S. Pat. No. 5,533,793 in the name of Walker. 
     These tires are generally satisfactory. 
     Under some working conditions, however, for example when the ground is composed of clayey or sticky soil, the scraper lip is not fully satisfactory, in particular because of its flexibility. The cleaning effect produced by such a lip may prove to be insufficient. 
     Under such conditions in particular, it is a known practice to use, as a replacement for the scraper lip, a rigid crown, usually metallic, integral with the gauge wheel. The tire then generally has no scraper lip. This crown can be attached to the body of the gauge wheel, by means of a part which occupies the dish of this wheel. The crown can also be integrated into the rim, as an axial portion thereof, in the continuation of the seat, as in AR053781 A1 in the name of Pierobon for example. This allows to preserve the wheel dish, which can remain hollow, at least in part. 
     The use of a rigid crown significantly improves the cleaning of the seed drill discs. However, this use induces a difficulty: since the portion of the rim comprised between the scraper crown and the tire contacts the ground, the soil also tends to accumulate therein, so that it is necessary to provide a sealing between the tire and the rim, at least near the crown. To this is added the soil possibly detached from the discs, which, due to a generally frusto-conical shape of the rim in the vicinity of the crown, is also found on the portion of the rim in question. 
     To this end, AR053781 A1 uses a tire whose case has no sidewall on the side of this tire oriented towards the crown. The tread is directly connected to the sheath. There the tire has an annular lip which protrudes axially towards the crown. This lip rests on the frusto-conical portion of the rim, which portion supports the crown. In a certain way, AR053781 A1 changes the conventional use of such a lip, from a scraper function to that of sealing.  
     The applicant has identified some disadvantages to the wheel according to AR053781 A1. 
     The lip is very exposed and remains static even when the wheel is working, which considerably weakens it. This lip deteriorates prematurely, faster than the rest of the tire wears out. 
     The lip also tends to leave the rim when the tire deforms. The interface between this lip and the rim opens when the wheel is working, and the soil tends to enter therein. The sealing loses its effectiveness. 
     To overcome these disadvantages, it is possible to use harder elastomers, which make the tire more rigid as a whole, and in particular its annular lip. However, this results in a tire which can no longer, or only poorly, be cleaned, because the deformation capacity of the case is reduced. 
     The invention aims at improving the situation. 
     An agricultural wheel forming an accessory for a seed drill disc is provided. This wheel comprises a body comprising a rim generally of a shape of revolution around a central axis and a semi-hollow-type tire comprising a flexible case around a hollow chamber, this flexible case comprising a sheath and a tread. This tread has a profile domed towards the outside of the tire. The rim comprises an axial section shaped as a seat, suitable for receiving the tire, and an axial section shaped as a tool, suitable for scraping the seed drill disc. The case includes at least a first sidewall, close to the tool section, connecting the sheath to the tread, this first sidewall generally extending radially or slightly inclined radially. The rim comprises an intermediate axial section which connects the tool section to the seat section. This intermediate section is shaped as an axial stop for the tire which is form fitted with the first sidewall. The tire being mounted on the seat section by means of the sheath in an axially stressed state which maintains the first sidewall in contact against the stop.  
     In this wheel, a sealing is created between the rim and the tire in the stop section, by placing the first sidewall in surface contact with this section. This contact is made under pressure because the tire is mounted on the seat in a state of lateral stress. 
     This contact is created as soon as the tire is mounted on the seat. When working, due to its domed shape, the tread transfers the reaction force of the ground, generally directed radially, at least on the first sidewall, in a way which tends to deform it axially, towards the stop section. This increases the contact pressure between the stop section and the first sidewall. The sealing is more effective when the wheel is working. 
     The tire can be produced with a flexible case, since the deformation of this case contributes to the effectiveness of the seal. Therefore, a tire with a high deformation capacity can be maintained, which is beneficial for cleaning the tire. 
     Optional, complementary or substitute features of the invention are set out below. 
     The axial stop and the first sidewall each have a rectilinear profile. 
     The flexible case comprises one or more portions which protrude radially from the sheath or from the tread into the hollow chamber, these portions being shaped as at least one radial stop for the tread. 
     At least one of these protruding portions projects from the sheath or from the tread by a height close, by greater values, to the height of the first sidewall. 
     At least two of the protruding portions facing one another project respectively from the sheath and from the tread and by a cumulative height close, by greater values, to the height of the first sidewall. 
     The tread has a top portion and the case has a median plane, and the top portion is offset from the median plane, in a direction away from the first sidewall.  
     The tool section comprises two generally frusto-conical axial sections from an axial edge of the rim to the axial stop, and that of these sections which is closest to said axial edge is more inclined than the other relative to a radial direction. 
     The wheel body comprises a first flange and a second flange mounted on top of each other, and the first flange comprises at least the tool section and the axial stop section, and the second flange comprises at least a portion of the seat section. 
     The first flange further comprises at least a portion of the seat section and the second flange comprises the rest of the seat section. 
     The flexible case includes a second sidewall, remote from the tool section, connecting the sheath to the tread. 
     The second sidewall generally extends radially or slightly inclined radially. 
     The second sidewall is in part at least significantly thicker than the first sidewall. 
     The tire has an annular groove, formed in the second sidewall, and the rim has a curved edge, engaged in the annular groove. 
     The seat section comprises at least one generally frusto-conical section which widens towards the tool section. 
     The body comprises a first flange and a second flange mounted on top of each other, the first flange including at least the tool section, the axial stop section and at least one generally frusto-conical section of the seat section. 
     The tire comprises an annular bead which projects from the flexible case where the first sidewall is connected to the tread. 
    
    
     
       Other features and advantages of the invention will become apparent upon reading the detailed description below, made in relation to the drawings, wherein:  
         FIG. 1  shows a seed drill module, seen from the front; 
         FIG. 2  shows the module of  FIG. 1 , seen from the left; 
         FIG. 3  shows the module of  FIG. 1 , seen from behind; 
         FIG. 4  shows the module of  FIG. 1 , seen in isometric perspective; 
         FIG. 5  shows an accessory wheel according to a first embodiment, seen from the front; 
         FIG. 6  shows the wheel of  FIG. 5 , in section along a line VI-VI; 
         FIG. 7  shows the wheel of  FIGS. 5 and 6 , in isometric perspective; 
         FIG. 8  shows the wheel of  FIGS. 5 to 7  exploded; 
         FIG. 9  shows a detail IX of  FIG. 6 ; 
         FIG. 10  shows a detail X of  FIG. 9 ; 
         FIG. 11  is equivalent to  FIG. 6  for a variant of the first embodiment; 
         FIG. 12  shows a detail XII of  FIG. 11 ; 
         FIG. 13  shows a detail XIII of  FIG. 12 ; 
         FIG. 14  is equivalent to  FIG. 6  for another variant of the first embodiment; 
         FIG. 15  shows a detail XV of  FIG. 14 ; 
         FIG. 16  shows a detail XVI of  FIG. 15 ; 
         FIG. 17  is equivalent to  FIG. 6  for a second embodiment of the accessory wheel;  
         FIG. 18  shows a detail XVIII of  FIG. 17 ; 
         FIG. 19  is equivalent to  FIG. 6  for a variant of the second embodiment; 
         FIG. 20  shows a detail XX of  FIG. 19 ; 
     
    
    
     The drawings and the description below essentially contain elements that are certain. They can therefore not only be used to better understand the present invention, but also contribute to its definition, if necessary. 
     The term “wheel body” (or “body”) refers here to the practically undeformable portion of a wheel, as opposed to its essentially deformable portion constituted by the tire or the pneumatic tire. The term “wheel rim” (or “rim”) refers to the peripheral portion of the wheel body intended in particular to support the tire or the pneumatic tire. The rest of the wheel body can be called a “dish” (“disc”, “wheel disc”, or else “wheel dish”). The wheel body thus consists of the rim and the dish. 
     Unlike the use which is sometimes made of it, the term “rim” does not designate here the entire wheel body. 
     Reference is made to  FIGS. 1 to 4 . 
     A seed drill assembly  100  comprises a pair of similar rotary tools  101 , mounted symmetrically relative to a vertical plane on a support. Each tool  101  comprises a respective seeding disc  105 , mounted rotationally free on the frame of a machine or of a tool towed/pushed by such a machine, and a respective accessory wheel  107 , mounted rotationally free around an axis  109 , on an arm  103  which connects the wheel  107  to the frame in question. The disc  105  and the wheel  107  of a respective tool  101  are free to rotate relative to each other. 
     The arm  103 , or at least a portion thereof adjacent to the wheel  107 , is interposed between the disc  105  and the wheel  107 . 
     In each tool  101 , the axis of rotation  109  of the wheel  107  relative to the arm  103  is eccentric from the axis of rotation of the seeding disc  105 . This eccentricity comprises a  non-zero vertical component so that the axis of rotation of the disc  105  relative to the arm  103  is located lower than that of the wheel  107 . The eccentricity in question further comprises a non-zero horizontal component so that the axis of rotation of the disc  105  relative to the arm  105  is at the front of that of the wheel  107 , with reference to a direction of advance  111  of the assembly  100 . 
     For its assembly, the disc  105  of each tool  101  comprises a hub (not shown) equipped with one or more bearings, of the rolling type in particular. This hub protrudes from the disc  105 , or at least from one face of this disc  105  oriented towards the wheel  107  of the tool  101 . This hub is located at least in part in a space of the wheel  107  comprised between two large lateral faces thereof. 
     Each wheel  107  comprises a body (not referenced) with a central portion forming a hub and a peripheral portion forming a rim. The rim is equipped with a semi-hollow tire  113 , produced in the form of a deformable case. This case comprises a portion forming a tread by means of which the wheel  107  rests on the ground. The tire  5  is made of a flexible material of the rubber or elastomer type. 
     In a semi-hollow tire, the case delimits a space empty of material, like a chamber, maintained in fluid communication with the outside, most often by means of one or more holes through the case. The air pressure inside the chamber tends to correspond to atmospheric pressure. For this reason, a semi-hollow tire can also be described as non-inflatable and/or non-inflated. The term “pneumatic tire” is sometimes preferred to that of “tire” because a semi-hollow tire has a profile which may resemble what is conventionally called a “pneumatic tire”. 
     The discs  105  of the assembly  100  are mounted on the arm  103  in an inclined manner relative to a vertical plane, with a first angular toe, and to the plane of symmetry, with a second angular toe. These discs  105  approach each other, on the one hand, in the direction of advance  111  and, on the other hand, in a vertically downward direction. The assembly  100  has a configuration called “V” configuration relative to the vertical direction and to the direction of advance  111 . The first toe angle and/or the second toe angle are for example close to 5°. The first toe angle may differ from the second one.  
     The wheels  107  are oriented similarly to the discs  105 . The first and second toe angles of the wheels  107  may differ from those of the discs  105 . 
     When the assembly  100  is working, the discs  105  penetrate the ground so as to create a furrow therein, intended for example for the burying of grains or seeds, while the assembly  100  rests on the ground by means of the wheels  107 , in particular the tread of the tire  113 . The working depth of the discs  105  is fixed thanks to the wheels  107  and corresponds to the vertical offset of the axis of rotation  109  of the wheels  107  relative to that of the discs  105 , i.e. to the vertical component of the eccentricity of these axes. The discs  105  can thus work the ground at a substantially constant depth, even when a field has unevenness. 
     The tire  113  has an annular lip  115 , which radially and axially protrudes from the rest of the case outwardly of the tire  113  and from the rim of the wheel body. 
     When the assembly  100  advances, the lip  115  of each wheel  107  rubs against the proximal face of a neighboring disc  105  by scraping it. This scraping has the effect of cleaning the discs  105  of anything that may have adhered thereto, such as mud or debris for example. 
     The tire  113  of  FIGS. 1 to 4  is of a known type, for example from FR 3 017 265 A1 in the name of the Applicant. Other forms of hollow lip tire are known, in particular from FR 2 885 008 A1. 
     For some applications, for example when the ground is composed of clayey and/or sticky soil, a lip of the type of the annular lip  115 , made of flexible material, may not be fully satisfactory. The cleaning effect produced by such a lip may prove to be insufficient. 
     Reference is made to  FIGS. 5 to 10 . 
     These figures show a wheel  1  of a new type, suitable for replacing the accessory wheel  107  in the assembly  100  described in relation to  FIGS. 1 to 4 . 
     The wheel  1  comprises a wheel body  3  of a general shape of revolution, around a central axis which coincides with a central axis  5  of the wheel  1 . The body  3  comprises a central portion shaped as a hub  6  and a peripheral portion shaped as a rim  7 . The wheel  1  is  equipped with a semi-hollow-type tire  9 , which fits around the rim  7 . The tire  9  comprises a flexible case of a generally toroidal shape, a central axis of which coincides with the central axis  5  of the wheel  1  when the tire  9  is mounted on the body  3 . The case of the tire  9  defines a chamber  13 . This chamber  13  is hollow and non-inflatable, typically due to the fact that one or more holes pass through the case of the tire  9  (not shown). 
     The tire  9  is made of a flexible material, of the elastomer type, preferably of natural or synthetic rubber, optionally mixed with one another. This material preferably has a Shore hardness comprised between 50 and 70. The case has a significant capacity to deform and resume its initial shape, due to the combination of a flexible material and a hollow interior space, such as the chamber  13 , in fluid communication with the outside. The case is deformed in particular when the wheel  1  is working, biased by a reaction force from the ground. This force is exerted mainly radially towards the central axis  5  of the wheel  1 . 
     The tire  9  includes a generally tubular inner sheath  15 , shaped so as to fit closely on the outer surface of the rim  7 , or at least over an axial portion thereof. The portion of the tire  9  corresponding to the sheath  15  is sometimes called the “sole”. The sheath  15  corresponds to the radially inner portion of the tire  9 . The sheath  15  carries an inner face  17  of the tire  9 . This inner face  17  is generally oriented substantially radially towards the central axis of the tire  9 . Essentially, the inner face  17  comprises surfaces oriented substantially radially towards the central axis of the tire  9  or the orientation of which comprises a radial component oriented towards this axis. 
     The tire  9  further includes a portion of the case radially opposite to the sheath  15  and which forms a tread  19 . The tread  19  corresponds to a radially outer face of the tire  9 , i.e. essentially oriented radially opposite to the central axis of the tire  9 . 
     The tread  19  is connected to the sheath  15  by two portions of the case which are axially opposite to each other and which form the sidewalls of the tire  9 : an outer sidewall  21 , on the right of the chamber  13  in  FIG. 6 , and an inner sidewall  23 , on the left. 
     The outer sidewall  21  and the inner sidewall  23  extend generally in the radial direction of the tire  9 . Alternatively, at least one of the outer sidewall  21  and the inner sidewall  23   generally extends in a direction slightly inclined relative to the radial direction, of the order of a few degrees and 15 degrees at most. 
     This inclination can be positive, when the sidewall is spaced from the radial direction axially outwardly of the tire  9  as it moves away from the axis of the tire  9 , or negative, when this spacing is in the direction axially inwardly of the tire  9 . 
     For the inner sidewall  23  at least, a negative inclination relative to the radial direction is favored over a positive inclination, in that a negative inclination is accompanied by more effective sealing and preserves the inner sidewall  23  from weakening. 
     The tread  19  has a profile which is generally domed towards the outside of the tire  9  (convex), continuously from the outer sidewall  21  to the inner sidewall  23 . This profile has a top portion  20 , the distance from the central axis of the tire  9  of which corresponds to a half outside diameter OD of this tire  9 . Here, for example, the diameter OD is close to 405 millimeters. This top  20  is located here in a median plane MP of the tire  9 , or close thereto. The plane MP of the tire  9  is perpendicular to the central axis of this tire  9  and is located axially at an equal distance from the outer sidewall  21  and the inner sidewall  23 . The spacing between these sidewalls, i.e. the distance separating their respective outer surface in the axial direction, corresponds to a width W of the tire  9 . 
     When a force is exerted on the tread  19  which is essentially directed radially towards the central axis of this tire  9 , the case of the tire  9  tends to deform in such a way that the outer sidewall  21  and the inner sidewall  23  are each biased axially towards the outside of the tire  9 . Such a force typically results from the reaction of the ground when the wheel  1  is working. The domed shape of the tread  19  causes the force exerted on this tread  19  to bear on the outer sidewall  21  and the inner sidewall  23  with an axial resultant. The outer sidewall  21  and the inner sidewall  23  are biased in an approximately similar manner to each other due to the symmetry of the tread  19 . 
     Here, the outer sidewall  21  is substantially thicker than the inner sidewall  23 . This allows to increase the resistance of the outer sidewall  21 , in particular to wear, relative to the inner sidewall  23 . In work, the outer sidewall  21  is more exposed that the inner sidewall  23 . Furthermore, this wheel  1  is intended to work at a cross angle relative to the direction of  advance, which angle exposes the outer sidewall  21 . This extra thickness can reach 20 percent. 
     For example, a thickness of the inner sidewall  23  may be comprised between 8 and 12 millimeters while the thickness of the outer sidewall  21  may be comprised between 8 and 15 millimeters. 
     The outer sidewall  21  and the inner sidewall  23  have outer diameters which are close to each other. 
     The body  3  has a first large face, or front face  25 , on the right in  FIG. 6 , and a second large face, or rear face  27 , on the left, opposite to the front face  25 . 
     The wheel  1  is intended to be mounted in an agricultural tool, for example of the type of the assembly  100  described in relation to  FIGS. 1 to 4 , so that the rear face  27  of the body  3  is located in part at least facing a tool in the shape of a disc, such as the disc  105  of  FIGS. 1 to 4  for example. The front face  25  of the body  3  is then oriented opposite to this disc. This front face  25  of the body  3  is directed towards the outside of an assembly of the type of the assembly  100  of  FIGS. 1 to 4 , the rear face  27  towards the inside. 
     The rim  7  comprises a first axial section shaped as a seat  29  adapted to the sheath  15 , or at least to the portion of this sheath  15  which corresponds to the inner face  17  of the tire  9 . This seat  29  has a shape which essentially corresponds to the inner face  17  of the tire  9 . The tire  9  is held on the rim  7  by means of a bearing of its inner face  17  against the seat  29 , over most of the axial extent of this face  17 . 
     The seat  29  is generally oriented substantially radially towards the outside of the body  3 , or its orientation comprises a radial component oriented towards the outside of the body  3 , optionally in portions in the axial direction of the body  3 . The seat  29  includes mostly surfaces oriented substantially radially towards the outside of the body  3 , or the orientation of which comprises a radial component oriented towards the outside of the body  3 . When the tire  9  is mounted on the body  3 , its inner face  17  is in contact, for its greater part at least, with the seat  29 . Here, the seat  29  ends axially on the front face  25  of the body  3 . The  seat  29  receives the radially inner portion of the tire  9 , which extends from the inner sidewall  23  to the outer sidewall  21 . 
     The rim  7  further comprises a second axial section shaped as a scraper tool  31  and which extends axially from the rear face  27  of the body  3 . The scraper tool  31  comprises an end surface  33  in the shape of a crown, which extends radially and by means of which the tool  31  is intended to rub against the disc of a seed drill, typically the disc  105  described in relation to  FIGS. 1 to 4 . This end surface  33  is carried by a section of the tool  31  shaped as a ledge of the rim  7 , or inner ledge  35 . The inner ledge  35  is generally frusto-conical and widens radially, in the direction of the end surface  33 . 
     The inner ledge  35  ends in a sharp ridge  37 , which forms the outer edge of the crown  33 . The ridge  37  is intended to scrape the surface of a seeding disc, for example of the type of the disc  105  of  FIGS. 1 to 4 . The end surface  33  can be seen as a relief surface relative to the ridge  37 . A radially outer surface of the inner ledge  35  can be seen as a scraping surface, as the soil which is detached from the disc by the action of the ridge  37  tends to follow this surface of the inner ledge  35 . 
     The distance from the ridge  37  to the axis  5  in the radial direction of the body  3  corresponds to half of the outside diameter TOD of the tool  31 . For example, the diameter TOD can reach 410 millimeters. 
     The distance which separates, in the axial direction of the body  3 , the crown  33  from an end remote from the additional section  40  corresponds to a width TW of the tool  31 . For example, the width TW can reach approximately 20 millimeters. 
     As shown in the figures, the inner ledge  35  is inclined at an angle A 35  of about 20 degrees relative to the radial direction of the body  3 . Other values of inclination can be considered. An inclination comprised between 10 and 45 degrees is beneficial in the evacuation of soil, or the like, detached from the disc with which the wheel  1  cooperates. 
     The rim  7  further comprises an intervening axial section  38 , which connects the section carrying the seat  29  to that forming the tool  31 . This intervening section  38  is shaped so as to carry a bearing surface  39  adapted to the inner sidewall  23  of the tire  9 . This bearing  surface  39  forms an axial stop on the body  3  against which the tire  9  is mounted. The bearing surface  39  is shaped to be form fitted with the inner sidewall  23 , or at least the outer surface thereof. This bearing surface  39  cooperates with the inner sidewall  23  over the entire extent of the latter. The radial extent of the bearing surface  39  and that of the inner sidewall  23  are close to each other. The bearing surface  39  does not project radially from the inner sidewall  23 . This inner sidewall  23  does not project radially from the bearing surface  39 . The bearing surface  39  extends over the entire intervening section  38  of the rim  7 . An optimal cooperation is thus obtained between the bearing surface  39  and the inner sidewall  23 . 
     The bearing surface  39  could extend radially outwardly of the body  3  beyond the inner sidewall  23 . However, this would result in an area between the rim  7  and the tire  9  where the latter would be unlikely to deform and where, as a result, debris or soil could accumulate. With a bearing surface  39  and an inner sidewall  23  of similar heights, any accumulation of soil or the like is avoided at the junction of the tool  31  to the tread  19  of the tire  9 . 
     A connection is obtained between the tool  31  and the tire  9  widely open to the outside and rather fluid in shape. This prevents the fouling of this connection and reduces the impact of the wheel  1  on the field, near the furrow. 
     The bearing surface  39  begins radially where the sheath  15  connects to the inner sidewall  23 . The bearing surface  39  ends radially where this inner sidewall  23  connects to the tread  19 . 
     The tool  31  further comprises an axial section of the rim  7  which connects the ledge  35  to the intermediate section  38 , or additional section  40 . This additional section  40  is generally frusto-conical. The inclination of the additional section  40  relative to the direction which is radially opposite the axis  5  is much greater than that of the ledge  35 . 
     The inclination of the additional section  40  is identified by the angle A 40  made by this additional section  40  with the axial direction. This inclination allows to prevent the accumulation of soil on the tool  31 .  
     An additional frusto-conical section  40  tends to be cleaned better than a cylindrical section. An inclination of this additional section  40  greater than that of the ledge  35  is beneficial. Such an inclination gives the region of the wheel  1  comprised between the ledge  35  and the tread  19  a configuration which is radially open outwards (concave). Such an opening thwarts the accumulation of soil in this region. The angle A 40  is comprised between 10 and 45 degrees is preferred here. Such an inclination provides, on the one hand, a clear break in profile between the ledge  35  and the intermediate section  40  and a fluidity of the profile of the region grouping the tread  19  and this intermediate section  40 . Here, this inclination is close to 30 degrees. 
     The ledge  35  and the additional section  40  form therebetween an angle A 354  greater than 90 degrees. Here, the angle A 354  between the extension of the ledge  35  and that of the additional section  40  is comprised between 100 and 120 degrees. Such an angle promotes the evacuation of the soil detached from the disc. 
     This association, in the tool  31 , of two frusto-conical sections of different inclinations improves the performance of the wheel  1 . It allows to separate, in the tool  31 , the portion involved in the scraping of the disc and the portion in contact with the ground. This association increases the rigidity of the tool  31  and consequently its efficiency. A configuration of the tool  31  in a single frusto-conical surface is however not excluded. This configuration would result, all other things being equal, in a greater inclination of the ledge  35  relative to the radial direction. A configuration of the tool  31  in three or more frusto-conical surfaces complicates its manufacture and tends to create a stepped profile that is less efficient for the evacuation of the soil and more damaging to the ground. Above all, such a profile is accompanied by an axial bulk of the tool  31  which makes it impractical. The ledge  35  and the additional section  40  here have a rectilinear profile. Without departing from a general frusto-conical shape, the ledge  35  and the additional section  40  could have a slightly curved, in particular concave profile. 
     The inclination of this additional section  40 , relative to the axial direction for example, can be close to that of the tread  19 , at least in the vicinity of the connection of this tread  19  to the inner sidewall  23 . Here, it is about imparting to the corresponding portion of the wheel  1  a valley shape which is useful from an agronomic point of view. Indeed, the portion in question is in contact with the ground when the tool is working. Preferably, the angle A 419   formed between the direction of extension of the additional section  40  and the tread  19 , at least in the vicinity of the inner sidewall  23 , is greater than 100 degrees, while remaining less than 150 degrees. 
     The rim  7  consists of an axial section shaped as a tool  31 , an axial section shaped as a seat  29  for the tire  9  and an intervening axial section  38  which connects the tool  31  to the seat  29 . This intervening section  38  forms an axial stop  39  against which the tire  9  rests as soon as it is assembled. The tool  31  consists of an axial section shaped as a ledge  35  and an additional section which forms an open angle on the outside of the wheel  1 . 
     Unlike conventional pneumatic tires, in particular those described in the aforementioned publications, the tire  9  has no lip, in particular where the tread  19  is connected to the inner sidewall  23 . The tread  19  can be connected to the inner sidewall  23  in a sharp ridge or a rounding, which mark a break in the directions of the outer surfaces of these portions of the case. 
     Here, this connection is shaped as a bead  41 . This bead  41  is formed by a slight inflection of the curvature of the tread  19  in the vicinity of the end of the latter which is connected to the inner sidewall  23  and by a portion the profile of which forms a slight rounding at the end of the inner sidewall  23 . The bead  41  projects substantially from the rest of the outer surface of the inner sidewall  23 , the profile of which is rectilinear and extends purely radially. This projection is very limited: of the order of 5 millimeters at most. 
     The bearing surface  39  is connected to the tool  31  by a portion of the rim  7  shaped as a rounding  43 . The bearing surface  39  is connected to the seat  29  by a rim portion  7  whose profile forms a fillet  45 . 
     The tire  9  has a rounded edge  47  where the sheath  15  is connected to the inner sidewall  23 . This rounded edge  47  is arranged form fitted with the fillet  45  between the seat  29  and the bearing surface  39 . The rounding of the bead  41  is form fitted with the rounding  43  of the rim  7 . This improves the cooperation between the inner sidewall  23  and the intervening section  38  of the rim.  
     The bearing surface  39  generally extends in an essentially radial direction. The direction of extension of this bearing surface  39  may have an axial component. However, this axial component remains low with regard to the radial extension of the bearing surface  39 . The inclination of this bearing surface  39  relative to the radial direction is less than approximately 15 degrees. 
     The inner face  17  of the tire  9  is shaped so as to bear against axial sections of the rim  7  provided with surfaces forming support surfaces which are generally cylindrical and centered on the axis  5 . 
     These cylindrical support surfaces here comprise the outer surface of a first end section of the seat  29 , close to the inside of the rim  7 , or inner edge  49  of the seat  29 , and the outer surface of a second end section of the seat  29  which forms its outer edge  51  and that of the rim  7 . The cylindrical support surfaces also comprise the outer surface of an intermediate section  53  of the seat  29 , located on the outer side of the body  3 . These support surfaces respectively cooperate with surfaces with a shape complementary to the inner face  17  of the tire  9 , located respectively in line with the inner sidewall  23 , the outer sidewall  21  and a portion of the sheath  15  located on the outer side of the plane MP. 
     The inner edge  49  of the seat  29  is connected to the intervening section  38 . The outer edge  51  of this seat  29  ends up on the front face  25  of the body  3 . Sections which are equivalent to the inner edge  49  and to the outer edge  51  are generally referred to as “rim edges” in a conventional wheel body, without a section similar to the tool  31 . 
     The sheath  15  and the rim  7  are here shaped so as to jointly produce a generally frusto-conical support surface, which widens axially towards the inner face of the wheel  1 . This frusto-conical support surface corresponds to a frusto-conical section  55  of the rim  7 , section which is connected to the intervening section  38 . This frusto-conical section  55  is located on the side of the tool  31  relative to the plane MP. This frusto-conical support surface contributes to blocking the tire  9  against the bearing surface  39 . This frusto-conical section  55  further facilitates the mounting of the tire  9  on the body  3 , around the seat  29 . This frusto-conical section  55  facilitates the slipping of the sheath  15  around this portion of the rim  7 , while the bearing surface  39  provides a stop during this slipping. This frusto-conical section  55  further frees up a space inside the body  3  (dish) larger than a portion  with a shape similar to the intermediate section  53  would, for example. This space is freed up where the hub of a seed drill disc usually protrudes, or at least close thereto. 
     The portion of the seat  29  between its inner edge  49  and its outer edge  51  comprises a seat bottom. This seat bottom comprises the intermediate section  53  on one side of the plane MP and the frusto-conical section  55  on the other side. 
     The outer edge  51  of the seat  29  and the intermediate section  53  of the latter connect to one another via a section of the rim  7 , or connection section  57 , which extends substantially radially or in a slightly inclined manner relative to this radial direction. This connection section  57  further provides a stop surface when slipping the tire  9  around the body  3 . The connection section  57  further carries an axial bearing surface for the tire  9 , additional to the bearing surface  39 . Unlike the bearing surface  39 , this additional bearing surface carried by the connection section  57  acts on the portion of the tire  9  corresponding to the sheath  15 . The connection section connects the seat bottom  29  to the outer edge  51  of this seat. 
     The rim  7  is formed in one or more parts produced here by stamping or rolling a sheet metal portion. The rim  7  has a shape of revolution around the axis  5 , with a generally tubular shape and of substantially constant thickness over all the axial sections of the rim  7 , from the inner ledge  35  to the outer edge  51 . 
     The tire  9  is mounted on the body  3  in an axially stressed state, between the surface  39  and the connection surface  57 . When the tire  9  is not mounted on the rim  7 , the spacing from the surface of the inner sidewall  23  which cooperates with the bearing surface  39  of the rim  7  and that of the sheath  15  which cooperates with the connection section  57  in the axial direction is greater than the spacing in the axial direction of the surfaces of the rim  7  which cooperates therewith. A compression comprised between 2 and 5 percent of the axial extension of the tire  9  is generally applied. For example, the axial extension of the tire  9  when mounted on the seat is 2 to 3 millimeters less for a tire  9  of the order of 100 millimeters wide. 
     A sealing is produced to prevent the soil detached by the tool  31  or that of the ground where the tool  31  rolls from being inserted between the seat  29  and the tire  9  when the wheel  1  is working. This sealing is achieved between the tool  31  and the seat  29 ,  exclusively by pressing the bearing of the inner sidewall  23  against the bearing surface  39 . This bearing is implemented when mounting the tire  9 , due to the axially stressed state of this tire  9 . This bearing is maintained and increased during the work of the wheel  1  due to the axially outward bias of the inner sidewall  23 . 
     The sheath  15  has a portion which protrudes radially into the chamber  13  at a stop  58  adapted to the tread  19 . Here, this stop  58  is located axially in line with the top  20  of the tread  19 . The height of this stop  58  is such that the crushing of the tread  19  is limited so as to avoid a bias directed radially towards the inside of the sidewalls. The height of the stop  58  is such that the tread  19  cannot cross a virtual line VL connecting the places of connection of the inner sidewall  23  and the outer sidewall  21  to the tread  19  (neutral fiber). Alternatively, the stop  38  can protrude from the tread  19  radially towards the axis  5 . Further alternatively, the stop  38  can be made in two portions, one protruding radially from the tread  19 , the other from the sheath  15 . For an equal stroke, a stop  38  in two portions allows to reduce the extension of each of these portions and thus improve the manufacture of the tire  9 , in particular its curing (vulcanization). 
     The height of the stop  58  is close, by greater values, to the height of the inner sidewall  23 . When the stop  58  is partially produced, their cumulative height is close, by higher values, to the height of the inner sidewall  23 . 
     This stop  38  finds its full utility in the embodiment described here, where the thickness of the considered case and the hardness of the material thereof make this case very deformable and cleaning. In other embodiments, a harder material, for example with a hardness comprised between 75 and 80 Shore, combined with a greater thickness means that the tire  9  hardly deforms during work. In this hypothesis, the stop  38  could be omitted. 
     The stop  58  extends more substantially in the direction of the inner sidewall  23  than in the direction of the outer sidewall  21  in order to ensure that the inner sidewall  23  is not biased axially inwards as a result of the deformation of the tread  19 . 
     The stop  58  further acts as a stiffener for the sheath  15  and thus helps to hold the tire  9  around the seat  7 . The stop  58  surrounds the sheath  15  around the rim  7 . This further helps to prevent any movement of the tire  9  relative to the body  3  in the axial direction.  
     Here, the sheath  15  has a circular rib  59  which protrudes from the inner face  17  of the tire  9 . The rib  59  is located substantially in line with the stop  58 , between a portion of the sheath  15  which is against the support surface of the frusto-conical section  55  and the support surface of the intermediate section  53 . This rib  59  rigidifies the sheath  15  and thus contributes to maintaining the axial position of the tire  9  relative to the seat  29 . 
     The seat  29  extends between its inner edge  49  and its outer edge  51 , here each supporting a cylindrical support surface. Between the inner edge  49  and the outer edge  51 , the rim  7  has a general bowl profile. The continuous axial section of the rim  7 , the outer surface of which carries a regular surface at least partly in contact with the sheath  15  of the tire  9 , is called seat. The frusto-conical section  55  could be connected directly to the intervening section  38  and the seat  29  has no cylindrical support surface  49  in the vicinity of this intervening section  38 . 
     The body  3  is here formed of a first flange, or outer flange  61 , and of a second flange, or inner flange  63 , mounted on top of each other and held together fixedly to form the wheel body  3 . 
     The outer flange  61  and the inner flange  63  each have a shape of revolution about a respective central axis. These central axes coincide with the axis  5  when the outer flange  61  and the inner flange  63  are assembled in the body  3 . 
     The outer flange  61  has a first large face, or inner face  65  by means of which the outer flange bears against the inner flange  63 . The inner flange  63  has a first large face, or outer face  67 , by means of which the inner flange contacts the outer flange  61 . The outer flange  61  and the inner flange  63  each have a second large face, respectively outer face  69  and inner face  71 , opposite to the inner face  65  of the outer flange  61  and the outer face  67  of the inner flange  63 . 
     The outer flange  61  has a peripheral portion which connects its inner face  65  to its outer face  69 . The inner flange  63  has a peripheral portion which connects its inner face  71  to its outer face  67 . The peripheral portion of the outer flange  61  corresponds to an axial portion of the seat  29 , while the peripheral portion of the inner flange  63  corresponds to the  remaining section of the seat  29 , to the tool  31  and the junction portion  39  between the seat  29  and the tool  31 . 
     The outer flange  61  and the inner flange  63  each have a central portion, which is connected to their respective peripheral portion. These central portions comprise a crown surface,  62  for the outer flange  61  and  64  for the inner flange  63 , by means of which these flanges are bearing against one another. For the rest, the central portion of the outer flange  61  and of the inner flange  63  is largely hollowed out. The outer flange  61  and the inner flange  63  each have a substantially hollow dish. This dish could alternatively be full or receive a part closing it. 
     The outer flange  61  and the inner flange  63  are fastened here reversibly to each other by means of fasteners. In the example described here, these fasteners comprise screw  73  and nut  75  pairs. These screw  73  and nut  75  pairs are distributed in pairs along the periphery of the wheel body. Alternatively or in additionally, other fastening means can be used, for example, clips or rivets. 
     The body  3  includes arms  77 , here three in number, each of which connects the hub  6  to the rim  7 . The arms  77  and the hub  6  are integral. The arms  77  and the hub  6  are attached to the outer flange  61 , here by means of screw  73  and nut  75  pairs. 
     In the illustrated embodiment, the body  3  consists of three elementary parts: the outer flange  61 , the inner flange  61  and the assembly formed of the arms  77  and of the hub  6 . This assembly can be seen as the dish of the wheel  1 . 
     The hub  6  has a general shape of revolution. This hub  6  is suitable for receiving an axle or a spindle in order to support the wheel  1  in rotation, in a loose manner, typically on an arm of the type of the arm  102  described in relation to  FIGS. 1 to 4 . 
     The wheel  1  comprises a rotary bearing  79  housed in the hub  6 , here in the form of a two-row ball bearing. Alternatively, the bearing  79  may take the shape of one or more rollers of a different type or of a plain bearing.  
     The hub  6  has a bore  80  suitable for housing the bearing  79 . The bearing  79  is held therein axially in a conventional manner, for example, on one side by a stop formed in the bore  80  and an elastic ring  81  on the other side. The bore  80  is through. On one side, the bore  80  is partially closed for a cup  82  in the form of a crown, capable of allowing passage of the axis or the spindle. On the other side, the bore  80  is completely closed with a plug  83 , held in place by an elastic ring  85 . 
     In the examples described here, the inner flange  63  and the outer flange  61  are each formed from a respective one-piece part. 
     The bulk, or width, of the wheel  1  is here comprised between 110 and 114 millimeters, for example 112 millimeters. This width corresponds to the sum of the width TW of the tool  31  and the width W of the tire  9 . Here, for example, the width W is close to 92 millimeters. 
     Reference is made to  FIGS. 11 to 13 . 
     The wheel  1  differs from the wheel  1  described in relation to  FIGS. 11 to 13  by the shaping of the section of the seat  29  carried by the outer flange  61  and that of the tire  9  in the portion of the sheath  15  which rests on this seat  29  section. 
     The outer edge  51  of the rim  7  is curved, radially opposite the axis  5  and axially towards the inside of the body  3 , so as to form a collar. In the vicinity of its end, the outer edge  51  of the rim  7  engages into a circular groove  87  made in the outer sidewall  23  of the tire  9 . The section of this groove  87  corresponds to that of the outer edge  51  of the rim  7 . 
     The groove  87  separates the outer sidewalls  21  into a portion which is radially remote from the axis  5 , or high portion  21 A, and a portion which is radially close to the axis  5 , or low portion  21 B. The high portion  21 A of the outer sidewall  21  is shaped in a manner similar to its equivalent portion in the tire  9  of  FIGS. 5 to 10 . The low portion  21 B of the outer sidewall  21  is shaped in a complementary manner to the collar of the outer edge  51 . This low portion  21 B bears by its outer surface against the inside of the collar. 
     The collar formed as a ledge of the rim  7  improves the holding of the tire  9  on the rim  7 , in particular in the axial position and in the stressed state. By reaction of the case of the tire  9   to a reaction force from the ground, the contact pressure between the inner sidewall  23  and the bearing surface  39  is increased. The collar improves the sealing between the tire  9  and the bearing surface  39 . In the vicinity of the opening of the groove  87 , the tire  9  is shaped as a bead  88  adapted to bear against a portion of the collar of the outer edge  51 . 
     Between the support surface corresponding to the intermediate section  53  of the rim  7  and the outer edge  51  of the rim  7 , the seat  29  here has a frusto-conical connection section  57 . This frusto-conical shape further improves the bias on the case so as to push the inner  23  and outer  21  sidewalls axially outwardly of the tire  9 . This shape also facilitates the mounting of the tire  9  on the body  3  around the rim  7 . The inner face  17  of the tire  9  is shaped correspondingly to ensure a tire  9  to rim  7  contact on practically the entire seat  29 , with the exception only of the circular rib  59 . 
     Here, as in the variant of  FIGS. 5 to 10 , the sheath  15  is in contact with the seat  29  of the rim  7  over its entire extent, with the exception of the rib  59 . 
     Reference is made to  FIGS. 14 to 16 . 
     In this variant, the wheel  1  differs from the wheel  1  described in relation to  FIGS. 11 to 13  by the configuration of the tire  9 . 
     Here, the top  20  of the tread  19  is offset from the median plane MP of the tire  9 , axially towards the outer sidewall  23 . This offset preserves the tread from soil comprised between the furrow and the top  20 . It facilitates the closing of the furrow by avoiding to compact the soil therein. This top  20  is located substantially at the portion of the sheath  15  bearing against the cylindrical support surface of the intermediate section  53 . The tread  19  has an asymmetrical shape from the inner sidewall  23  to the outer sidewall  21 . The diameter OD of the tire  9  is greater than that of the embodiments of  FIGS. 5 to 13 , for example 412 millimeters. The tire  9  projects radially from the tool  31 . The tread  19  is less inclined than in the previous embodiments relative to the axial direction. 
     The stop  58  is also axially offset towards the outer sidewall  21 . This offset is adjusted so as to prevent the tread  9 , during work, from crossing the virtual line VL.  
     The outer sidewall  21  has a thickness greater than that of its equivalent in  FIGS. 11 to 13 . This extra thickness results from an enlargement of the outer sidewall  21  towards the chamber  13 , in a regular manner from the tread  19  to the sheath  15 . 
     Reference is made to  FIGS. 17 and 18 . 
     In this second embodiment, the wheel  1  is significantly narrower. For example, the width W is here comprised between 40 and 60 millimeters, or approximately half the width W of the first embodiment. The width of the wheel is for example comprised between 78 and 82 millimeters, typically 80 millimeters. A wheel of this type finds its advantage in use in close-row seed drills, known in the art by the term “twin row” seed drills. A wheel of this type is also useful in the case of seed drill elements disposed closer to each other than in the case of  FIGS. 1 to 4  in particular. 
     The outer edge  51  of the rim  7  is curved as in the embodiment of  FIGS. 11 to 16 . The connection portion  57  is more extended and here cooperates with the low portion  21 B of the outer sidewall  21 . This connection portion  57  extends practically radially. The intermediate portion  53  is frusto-conical and is connected directly to the crown  62  of the outer flange  61 . The axial section of the rim  7  corresponding to this outer flange  61  has no cylindrical support surface. The top  20  of the tread  9  is located axially in line with the outer sidewalls  23 . This outer sidewall  23  has the same shape as in  FIGS. 14 to 16 . 
     Reference is made to  FIGS. 19 and 20 . 
     In this variant, the outer sidewall  21  is generally domed towards the outside of the tire  9 . This domed shape continues that of the tread  19 . There is an outer edge  51  of the rim  7  shaped in a cylindrical support surface. The intermediate section  53  is frusto-conical. It provides a surface extending with an axial component capable of axially blocking the tire  9 . The low portion  21 B of the outer sidewall  21  generally follows this shape so as to have a thickness close to that of its high portion  21 A which is domed. The inner face  17  of the tire  9  is form fitted with the seat. This axial stop improves the distribution of the force exerted on the top  20 . This force is transmitted to the inner sidewall  23  furthermore through the outer sidewall  21  and the sheath  15 . The width of the wheel is for example comprised between 80 and 84 millimeters, typically 82 millimeters  
     A hollow dish body  3  has just been described. The body  3  could be a solid dish body. In particular, the body  3  described here can be transformed into a solid dish body by replacing the arms  77  with a sheet metal plate. 
     An outer sidewall  21  and an inner sidewall  23  which extend in a similar manner from one another, were described. The outer sidewall  21  and the inner sidewall  23  could extend at different inclinations from one another. 
     An intervening section  38  carrying an axial stop surface  39  form fitted with the inner sidewall  23  of the tire  9 , or at least the outer surface of this sidewall  23 , was described. Without departing from their shape complementarity, nor from their extension which is generally annular, the inner sidewall  23  and the axial stop  39 , or the intervening section  38 , could have a profile different from the rectilinear profile shown in  FIGS. 5 to 20 . For example, more complex profiles, for example lobe or wavy-shaped profiles, can be provided.