Technical field

The invention relates to a seed press wheel of the type having the features stated in the preamble of the main claim .

Technical background

In precision seeders it is known to use a wheel disposed downstream of the seed drop pipe so as to gently press each seed to the bottom of the sowing furrow. Each wheel is subject to numerous problems, such as the fact that it must resist wear and damage resulting from contact with the ground to be sown, and at the same time must have a certain resilience so as to be able to ensure, by deforming, that adhesion of the soil to the mantle or the flanks of the wheel is avoided.

Among the documents that are relevant in this technical field, the document "DuraLok Seed Wheels" (available at https://www.exapta.com/2034-2/ ^' ) describes a seed press wheel which is made of a highly wear-resistant polymer material, has a streamlined profile, and is equipped with replaceable pads.

In particular, the above-mentioned document describes the use of "Duralok", an industrial highly wear-resistant polyvinyl chloride, as a material which forms a solid-disc seed press wheel for the purpose of creating a device that can last for a very long time without having to be frequently replaced due to cuts or damage caused by the ground during use. It is also demonstrated that the increased wear resistance reduces the adhesion of mud to the disc itself and thus also reduces the possibility of sowing failure and of the sowing unit becoming clogged. This technical solution, however, has a number of disadvantages, as discussed below.

It is known that the furrows produced by the sowing unit of a seeder can have a discontinuous shape that is not perfectly regular and varies in terms of direction and conformation, depending for example on unexpected hard elements contained in the ground (rocks, roots, etc.) and/or variations in the gradient of the ground itself.

Since DuraLok is a polyvinyl chloride disc that has high wear-resistance, this makes it impossible for said disc to deform extensively or quickly so as to effectively follow the shapes or directions of the furrows in which the seeds are sown.

It should also be noted that, as asserted by the manufacturer, this property of wear resistance does not necessarily result in a reduced amount of mud adhered to the disc, this being dependent on different parameters, such as surface wettability (according to a chemical analysis) and/or the possibility of mud adhering to/residing on the surface of the disc (according to a morphological and/or mechanical analysis). The aforementioned disc therefore does not have a self-cleaning function that substantially reduces the amount of mud that becomes adhered, and therefore is not able to effectively prevent possible sowing failures or prevent the seeder unit from becoming clogged.

Description of the invention

The object of the present invention is to provide a seed press wheel that overcomes one or more of the disadvantages of the identified prior art. Within the scope of this objective, one object of the invention is to provide a seed press wheel that has a greater capability for correctly positioning the seed within the furrow created by a sowing unit of a precision seeder.

The product provided in accordance with the present invention is a seed press wheel for sowing units for precision seeders, comprising a solid tyre in the shape of a disc that has a hole or central axis for mounting said tyre on a hub, said solid tyre comprising a first portion extending radially from said central hole and a second portion extending radially from said first portion. The first portion is preferably made of a first material having a first modulus of elasticity value, and the second portion is made of a second material having a second modulus of elasticity value, said first modulus of elasticity value being different from said second modulus of elasticity value.

In this way it is possible to provide two zones having different mechanical behaviour: this condition will allow the solid tyre to deform differently in different zones and to therefore more efficiently follow the conformations and variations of the furrow in which the seed is optimally positioned.

In addition, another advantage deriving directly from the aforementioned technical features of the product produced in accordance with the present invention is that the different deformations that are created in different parts of the solid tyre depending on the different moduli of elasticity produce local variations in elongation and contraction of the material, said variations preventing the adhesion of mud and earth. The first portion close to the hub defines a relatively rigid ring so that the wheel does not slip from the hub, whereas the second portion defines a soft peripheral ring, which can thus deform so as to promote the detachment of the ground and prevent retention of the seeds, which retention results in irregularities in the sowing distance.

This condition also improves the functionality of the solid tyre, and therefore of the seed press wheel, keeping it cleaner and consequently increasing the efficacy thereof, allowing it to follow the conformation of the furrow in the ground more accurately and to position the seed in the desired position in the furrow.

In accordance with one embodiment, the first modulus of elasticity value is between 2.5 and 3.5 MPa, and the second modulus of elasticity value is between 0.5 and 1.5 MPa.

The applicant has demonstrated that it is possible in this way to improve the self-cleaning effect of the solid tyre, whilst maintaining its optimal features of resistance to the forces applied during use by mechanical elements that connect the solid tyre to the sowing unit or by the ground. In accordance with a further aspect of the invention, the first material preferably has a modulus of elasticity of 3.2 MPa, and the second material has a modulus of elasticity of 0.9 MPa.

In this way, it is possible to obtain improved local deformability, and therefore the maximum capability for following the conformation of the furrow and the best condition of local deformation in order to activate the self-cleaning feature of the solid tyre, together with optimal resistance on the part of the solid tyre to the forces applied during use.

Furthermore, the second material, preferably, comprises mud release agents, for example having a fluorinated or silicone base, in order to increase the self-cleaning effect and also make a chemical contribution towards reducing any potential adhesion of the mud to the surface of the solid tyre. In accordance with one embodiment, the first portion has annular conformation and can be found in a bead zone of said solid tyre, and the second portion is annular and defines an intermediate zone between said bead zone and a tread zone of said solid tyre, said bead zone, said intermediate zone and said tread zone being contiguous in pairs and respectively being radially arranged from closest to furthest away with respect to said central hole.

In this way, the optimal spatial arrangement of the elements having different moduli of elasticity is achieved : in fact, the first portion, which preferably has a modulus of elasticity greater than that of the second portion, is found in a bead zone of the solid tyre, in which the forces associated with the mechanical elements of the sowing unit or of the seeder (hub, shaft, etc.) are normally applied; the second portion, which preferably has a modulus of elasticity lower than that of the first portion, is found in an intermediate zone between the bead portion and the tread portion of the solid tyre, in which there is a greater deformability for the purpose of being able to follow the conformation of the furrow to the best possible extent and for greater deformation for the purpose of more easily detaching any adhered mud.

The annular conformation of the first and second portions also makes it possible to implement circularly uniform mechanical and tribological behaviour, which is thus more easily supported by the disc-shaped seed press wheel.

In this context, the bead zone is a zone that defines an interface portion between the solid tyre and a portion of a hub or of a shaft of the sowing unit of the seeder. This bead zone of the solid tyre is that which interacts most with the hub and/or with the shaft and which is subject to the forces associated with these types of constraints. In addition, in this context, the tread zone is the portion of the solid tyre comprising the surface distanced radially furthest from the central hole and intended for contact with the surface of the ground. Lastly, the intermediate zone in this context is the portion of the solid tyre between the bead zone and the tread zone. It is clear that this intermediate zone produces a connection between the bead zone connected to the hub and/or the shaft of the sowing unit and the tread zone, which interacts mostly with the ground in which the seed is positioned.

The seed press wheel preferably comprises a third portion that has annular conformation and is made of a third material having a third modulus of elasticity of between said first modulus of elasticity value and said second modulus of elasticity value.

On account of this technical solution, a third portion is created which acts as an interface between the first and second portions, allowing a more gradual variation of the modulus of elasticity values and therefore gentler and less jerky behaviour on the part of the seed press wheel.

In accordance with one embodiment, the intermediate zone has tapered conformation so as to converge away from said bead zone and is made of, or of a material similar to, said second material or third material.

In this way it is possible to further optimise the deformability of the seed press wheel, making the full insertion of the seed press wheel into the furrow easier and more effective, the tapered part initiating this insertion, and therefore able to better adapt to the conformation of the furrow itself. In accordance with one embodiment, the intermediate zone having tapered conformation comprises shoulders having connection surfaces between said intermediate zone and said tread zone, and the angle formed between said shoulders is 22°.

In this context the shoulders define connection surfaces that can have a curvature for the purpose of optimally connecting the intermediate zone and the tread zone and provide a mechanical resistance so as to allow interaction with the ground such that no damage is sustained during use. The applicant has demonstrated that the angle of 22° between the shoulders is an optimal angle for allowing the solid tyre to enter the furrow effectively, even in conditions of irregular conformation of the ground and of the furrow itself.

The first material preferably has a hardness between 60 and 80 Shore A, and the second material preferably has a hardness of between 35 and 50 Shore A.

In this way it is ensured that the solid tyre has a sufficiently increased tribological resistance, in particular for the portion within the bead zone. In accordance with one embodiment, the solid tyre is in the shape of a disc and has a dimensional ratio between its maximum diameter and its maximum thickness of between 5 and 15.

In this way, the solid tyre has a shape having a greater dimension of extent in the radial direction relative to the central hole and is thus able to bend significantly by way of elastic deformation in directions substantially parallel to the axis of rotation, so as to be able to follow the conformations of the furrow in an optimal manner.

In accordance with one embodiment, the present invention is directed to a seeder that comprises a seed press wheel comprising a solid tyre in the shape of a disc that comprises a central hole and comprising a first portion, which is made of a first material having a first modulus of elasticity value, and a second portion, which is made of a second material having a second modulus of elasticity value, said first modulus of elasticity value being different from said second modulus of elasticity value.

The aforementioned seed press wheel intended for a seeder is preferably obtained in accordance with a production method comprising : providing a mould for producing a solid tyre comprised in said seed press wheel, injecting or pouring a first material into said mould in order to produce a first portion of said solid tyre having a first modulus of elasticity value, injecting or pouring a second material into said mould in order to form a second portion of said solid tyre having a second modulus of elasticity value that is different from said first modulus of elasticity value, and finishing forming said solid tyre and extracting it from said mould.

In this way, it is possible to produce a seed press wheel having at least two portions made of materials having different moduli of elasticity and therefore different deformabilities, which thus allows a greater capability of the tyre for following the various conformations of the furrow in the ground and for producing different, locally inhomogeneous deformations that increase the self-cleaning effect of the wheel following any potential adhesion of mud to the surface of the wheel itself.

Brief description of the drawings The features and advantages of the invention will become clearer from the detailed description of an exemplary embodiment, shown by way of non- restrictive example and with reference to the drawings, in which :

Fig. l is a view from the side of a seed press wheel,

Fig.2 is a view from the front of the wheel of Fig. l,

Fig.3 is a sectional view of the wheel of Fig. l in the plane III,

Fig.4 is a view from the side of a solid tyre of the wheel of Fig. l, Fig.5 is a sectional view of the solid tyre of Fig.4 in the plane V.

Detailed description of a preferred embodiment of the invention

In Fig. 1, reference sign 1 denotes a seed press wheel for sowing units of precision seeders, comprising a solid tyre 2 in the shape of a disc and comprising a central hole 3 for mounting said tyre on a hub 4. The solid tyre 2 preferably has a first portion 7 extending radially from the central hole 3 and a second portion 8 extending radially from the first portion 7, said first portion 7 being made of a first material 7a having a first modulus of elasticity value El, and the second portion 8 being made of a second material 7b having a second modulus of elasticity value E2, the first modulus of elasticity value El being different from the second modulus of elasticity value E2.

With reference to Fig. 1, 2 and 3, it is clear that the central hole 3 preferably also has the shape of a disc.

An axis of rotation X of the seed press wheel is preferably found at the centre of the central hole 3.

The first modulus of elasticity value El is preferably greater than the second modulus of elasticity value E2, and, even more preferably, the first modulus of elasticity value El is between 2.5 and 3.5 MPa and the second modulus of elasticity value E2 is between 0.5 and 1.5 MPa. Such values of the first and second moduli of elasticity were calculated in accordance with standard ISO 37:2011 during tensile testing at modulus 100%.

The first material 7a and the second material 7b are advantageously made of synthetic, artificial or natural polymer rubbers, it also being possible to use polyurethane mixtures and/or EPDM compounds.

In accordance with one embodiment, the first material 7a has a modulus of elasticity equal to 3.2 MPa and the second material 7b has a modulus of elasticity equal to 0.9 MPa.

Preferably and with reference to Fig. 1 and 4, the first portion 7 has annular conformation and can be found in a radially inner region of the solid tyre 2 and defines a bead zone T. In addition, the second portion 8 has annular conformation and can be found in an intermediate zone I between the bead zone and a tread zone B of the solid tyre 2, the bead zone T, the intermediate zone I, and the tread zone B being contiguous in pairs and respectively being radially arranged from closest to furthest away with respect to said central hole 3.

With reference to Fig. 1 and 4, the maximum diameter D3 and the minimum diameter DO of the solid tyre 2 can be seen, and it is clear that the first portion 7 is preferably between the minimum diameter DO and a first diameter Dl of the solid tyre 2 and that the second portion 8 is between a second diameter D2 and the maximum diameter D3.

The hub 4 is advantageously fitted inside the central hole 3 onto the first portion 7 of the solid tyre 2.

With reference to Fig. 1 and 2, the aforementioned hub 4 preferably has a disc shape characterised by a hub diameter D4 and is made in a single piece or two parts that can be rigidly connected by means of engaging elements, such as screws, nails, adhesives, etc.

By way of non-restrictive example of one embodiment, the minimum diameter DO is equal to 132 mm, the hub diameter D4 is equal to 150 mm, the first diameter Dl is equal to 175 mm, the second diameter D2 is equal to 200 mm, and the maximum diameter D3 is equal to 300 mm.

As shown in Fig. 3 and 5, the hub 4 preferably comprises circular protrusions 12 which protrude towards the inside of the hub in a direction substantially parallel to the axis of rotation X, and the first portion 7 comprises circumferential grooves 11, formed in walls perpendicular to the axis of rotation X, so as to engage by way of an interference fit with said protrusions 12 and thus increase the reciprocal constraint between the hub 4 and the solid tyre 2.

The seed press wheel 1 preferably comprises a third portion 9 of annular conformation and made of a third material 7c having a third modulus of elasticity E3 of between the first modulus of elasticity value El and the second modulus of elasticity value E2.

With reference to Fig. 4, the third portion 9 is preferably between the first diameter Dl and the second diameter D2 of the solid tyre 2.

In accordance with an embodiment shown in Fig. 2, 3 and 5, the intermediate zone I has tapered conformation so as to converge away from the bead zone T and is made of the second material 7b or third material 7c. This preferably implies that the intermediate zone is made of a material having a third modulus of elasticity E3 greater than the first modulus of elasticity El.

In this way, the ability of the solid tyre 2 to enter and adapt optimally to the furrow produced in the ground, which generally has a V shape, is also improved.

Advantageously and with reference to Fig. 2, the intermediate zone I has tapered conformation and comprises shoulders 10, comprising connection surfaces between said intermediate zone I and the tread zone B, and the angle formed between the shoulders 10 preferably being equal to 22°.

In accordance with one embodiment, the intermediate zone I and/or the bead zone T comprise lateral surfaces 13, preferably perpendicular to the axis of rotation X, said zones having a thickness, measured in a direction parallel to the axis of rotation X, referred to as the maximum thickness SI.

In accordance with one embodiment, the tread zone B comprises a tread surface 14, substantially parallel to the axis of rotation X, positioned in line with the maximum diameter D3 and intended to enter into contact with the ground of the furrow during use, having a thickness measured in a direction parallel to the axis of rotation X referred to as the tread thickness S3.

By way of non- restrictive example of an embodiment, the maximum thickness

SI is equal to 28 mm and the tread thickness S3 is equal to 13 mm.

The tapered conformation comprising shoulders 10 that connect the lateral surfaces 13 to the tread surface 14 advantageously maintains a substantially uniform inclination of the connection surfaces.

The first material 7a preferably has a hardness between 60 and 80 Shore A and the second material 7b preferably has a hardness between 35 and 50 Shore A. In accordance with one embodiment, the solid tyre 2 is in the shape of a disc and has a dimensional ratio R between its maximum diameter D3 and its maximum thickness SI of between 5 and 15.

With reference to the exemplary embodiment described above, the maximum diameter D3 is equal to 300 mm and the maximum thickness SI is equal to 28 mm, meaning that R is equal to 10.71.

One embodiment of the present invention is directed to a seeder comprising a seed press wheel 1 comprising a solid tyre 2 in the shape of a disc that comprises a central hole 3, the solid tyre 2 comprising a first portion 7, which is made of a first material 7a having a first modulus of elasticity value El, and a second portion 8, which is made of a second material 7b having a second modulus of elasticity value E2, said first modulus of elasticity value El being different from said second modulus of elasticity value E2.

The steps for producing the seed press wheel 1 intended for a seeder that define the production method are described below.

A user provides a mould for forming a solid tyre 2 comprised in the seed press wheel 1.

Depending on the production method used (e.g. injection moulding, casting, thermoforming, etc.) and depending on the physical characteristics of the materials used (e.g. melting point, softening point, glass transition temperature, viscosity, density, etc.), the materials deemed most suitable can be used for the moulds (e.g. moulds made of steel, aluminium alloys, etc.), these being known to a person skilled in the art.

The user then injects or pours a first material 7a into the mould so as to form a first portion 7 of the solid tyre 2 having a first modulus of elasticity value El. This first material 7a is preferably a rubber having the first modulus of elasticity value El between 2.5 and 3.5 MPa.

In accordance with one embodiment, the user injects or pours a second material 7b into the stamp so as to form a second portion 8 of the solid tyre 2 having a second modulus of elasticity value E2 that is different from the first modulus of elasticity value El.

This second material 7b is preferably a rubber having the second modulus of elasticity value E2 between 0.5 and 1.5 MPa.

The relative phases of injection or pouring of the first and second materials can be performed advantageously at the same time, and therefore by means of a bi-injection system, or at two separate moments, and therefore by means of a successive injection system.

In accordance with one embodiment, the user finishes forming the solid tyre 2 and extracts it from the mould so as to be able to use it directly, without the need to remove cores such as those required for the production of hollow tyres. In accordance with an embodiment of the aforementioned method, a third material 7c having a third modulus of elasticity E3 is injected or poured into the mould before or after the injection or pouring of the aforementioned second material 7b.

This third modulus of elasticity E3 is advantageously between the first modulus of elasticity value El and the second modulus of elasticity value E2.

The first portion preferably has annular conformation and can be found in a bead zone of the solid tyre, and the second portion preferably has annular conformation and defines an intermediate zone between the bead portion and a tread zone of the solid tyre, the bead zone, the intermediate zone and the tread zone being contiguous in pairs and respectively being radially arranged from closest to furthest away with respect to said central hole. In accordance with one embodiment of the aforementioned method, the intermediate zone has tapered conformation so as to converge away from the bead zone and is made of, or of a material similar to, the second material or third material.