Track unit for work vehicle

Abstract

The present application relates to a track unit comprising a belt track (4) driven by a drive sprocket (3) and guided by a guide wheel (5) and a support roller (6). The belt track comprises a core (10) with drive lugs (11) on the inner surface of the core and two rows of ground lugs (15) arranged in parallel on the outer surface (13) of the core. Each ground contact lug comprises a load bearing portion (15a) defined as a portion of the lug located within one of the contact strips (25) of the core, where the contact strips are lateral portions of the core, in direct contact with the guide wheels (5) and / or the support rollers (6) when the belt track is moving. According to a set of embodiments, the ground bumps (15) have uniform elasticity, without or substantially without overlapping a central portion (26) of the core between the contact strips (25). According to other embodiments, the ground bump (15) includes a non-load-bearing portion (15b) overlapping the central portion, where the non-load-bearing portion is at least partially thinner or more elastic than the load-bearing portion.

Description

Technical Field

[0001] The present invention relates to work vehicles, mainly but not limited to agricultural work vehicles such as tractors, combine harvesters or forage harvesters. The present invention particularly relates to a crawler unit for such work vehicles. Background Art

[0002] Due to the increasing size of currently developed agricultural vehicles, it is often necessary to replace two or all four traditional wheels of these machines with crawler units in order to reduce ground compaction, increase traction and / or prevent the vehicle from getting stuck in the mud.

[0003] Therefore, such a crawler unit needs to be able to withstand huge forces without serious damage during a relatively long service life. Considering the cost and time required to replace the belt-type crawler, premature damage to the belt-type crawler of the crawler unit is particularly undesirable. Summary of the Invention

[0004] The present invention relates to a crawler unit as described in the appended claims and a work vehicle equipped with the crawler unit. The crawler unit includes a belt-type crawler driven by a drive sprocket and guided by a guide wheel and support rollers. The belt-type crawler includes a core, on the inner surface of the core there are drive lugs, and on the outer surface of the core there are two rows of ground contact lugs arranged in parallel. The ground contact lugs are sometimes also referred to as tread bars. Each ground contact lug includes a load-bearing portion, which is defined as the portion of the lug located within one of the contact strips of the core, where the contact strip is a lateral portion of the core that directly contacts the guide wheel and / or support rollers when the belt-type crawler moves. According to a set of embodiments, the ground contact lugs have uniform elasticity and do not overlap or substantially do not overlap with the central portion of the core, the central portion being defined as the portion of the core that extends between the contact strips. According to other embodiments, the ground contact lugs include a non-load-bearing portion that overlaps with the central portion of the core, where the non-load-bearing portion is at least partially thinner than the load-bearing portion, or where the non-load-bearing portion is more elastic than the load-bearing portion.

[0005] One of the guide wheels can also act as a drive sprocket. The crawler can also be driven by friction drive rather than by a sprocket.

[0006] A more elastic portion is a portion that is more easily compressed and / or more easily flattened under the same load compared to a less elastic portion, and / or a portion that wears faster and / or is more easily worn compared to a less elastic portion.

[0007] The present invention makes the ground contact lugs wear evenly in the portion where they directly bear the weight of the work vehicle via the guide wheel and / or support rollers, thus solving the problem of uneven wear of the prior art belt-type crawler in the direction perpendicular to the center line of the belt-type crawler.

[0008] The invention also relates to a work machine, such as a tractor, which comprises an even number of track units according to the invention, such as two track units and two wheels, or four track units.

[0009] The invention also relates to a work machine, such as a combine harvester or a forage harvester, which comprises an even number of track units according to the invention, such as two track units and two wheels, or four track units.

[0010] The invention also relates to a method of converting a belt track into a track unit according to the invention by at least partially removing the ground engaging lugs where they overlap the central part of the core. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 An example of a work machine is shown, in which the work machine is a tractor, where the wheels have been replaced by track units.

[0012] Figure 2 The main components of a track unit known in the prior art are shown.

[0013] Figure 3 A cross-section and a plan view of the ground engaging side of a belt track of the prior art are shown, and also the position of a set of support rollers in cross-section is shown.

[0014] Figure 4 Are more detailed cross-sections and plan views showing a number of specific features of a track of the prior art.

[0015] Figure 5 and Figure 6 Show a first embodiment of a track unit according to the invention.

[0016] Figures 7 to 13 Show an alternative embodiment of a track unit according to the invention. DETAILED DESCRIPTION

[0017] Preferred embodiments will now be described with reference to the accompanying drawings. The detailed description does not limit the scope of the invention, which is defined only by the appended claims.

[0018] Figure 1 A tractor 1 is shown, in which four wheels have been replaced by track units 2. The track units for a tractor with two track units usually at the rear and two wheels usually at the front are similar. In addition, the track units for a combine harvester or a forage harvester with usually two track units at the front and two wheels usually at the rear are similar. Figure 2A more detailed illustration of a track unit 2 currently known in the art is shown. The track unit includes a sprocket 3 configured to be coupled to one of the usually four rotatable shafts of a work vehicle. Rotation of the sprocket 3 drives the movement of a belt track 4, which is guided by front and rear idlers 5 and supported on the ground by support rollers 6. Figure 2 The track unit shown has four support rollers 6, but the present invention is also applicable to track units having a different number of support rollers 6, such as two or three support rollers 6. The idlers 5 and the support rollers 6 are rotatably mounted on a track unit frame 7. A variable length actuator 8 is configured to tension the belt track 4 by actuating a pair of idlers 5.

[0019] In other track units, one of these idlers 5 is a drive sprocket 3. Even in other track units, the drive sprocket drives the belt track by friction, rather than by or not continuously by driving these drive lugs. The present invention is also applicable to these track units, which also have the same problems described below.

[0020] The belt track 4 itself is made of an elastic material such as rubber or any equivalent material. The belt track 4 can include different types of rubber, for example, rubber laminated in different layers, and various fillers can be contained in the rubber, for example, for enhancing certain properties such as wear resistance or thermal conductivity. Figure 3 A cross-section and a plan view of a part of the ground contact side of a prior art belt track 4 are shown. The belt track 4 extends along a longitudinal belt track centerline 9 and includes a reinforcing core 10 formed of an elastic matrix, in which reinforcing elements (not shown) are embedded. These reinforcing elements can include yarns and / or cords / cables made of a high-strength material, usually fibers or filaments, such as aramid fibers, polypropylene, and / or polyethylene fibers and / or steel wires. The yarns or cords / cables can be wound in a serpentine manner along a circumferential section of the core 10, and additional reinforcing pads or braids can reinforce the core. On the inner surface of the core 10, the belt track includes regularly spaced drive lugs 11 configured to engage with the sprocket 3 in the manner of a toothed belt. Figure 3 The cross-section in also shows a pair of idlers 5. The pair of idlers 5 are spaced apart in a direction perpendicular to the belt track centerline 9 to leave space for the passage of the drive lugs 11. The support rollers 6 are arranged equidistantly in spaced pairs, usually mounted on a landing gear (not shown) suspended from the track unit frame 7. The width of the support rollers 6 can be slightly less than the width W1 of the idlers 5.

[0021] The grounding bumps 15 formed of rubber or rubber-like material are attached to or integrally formed with the outer surface 13 of the core 10. This material is elastic, but has a hardness sufficient to enable the bumps 15 to obtain a strong grip on the terrain over which the track unit 2 moves. The grounding bumps 15 are regularly spaced apart, oriented at an inclined angle with respect to the longitudinal belt track centerline 9 of the track, and arranged in two rows extending on both sides of the belt track centerline 9 and staggered with respect to each other. Each grounding bump 15 is formed as a uniform volume structure, which includes a ground contact surface 16 oriented parallel to the outer surface 13 of the core 10 and inclined side walls 17 on four sides of the surface 16. This arrangement of the grounding bumps 15 ensures a strong grip on the terrain when the track unit 2 moves forward or backward. The thickness of the grounding bump 15 is defined as the distance between the outer surface 13 of the core 10 and the ground contact surface 16.

[0022] The reinforcing structure in the core can also extend into the drive bumps 11 and / or the grounding bumps 15.

[0023] Also refer to Figure 4 , which shows a more detailed illustration of the cross-section and plan view of the grounding side of a prior art track. In the plan view, only two grounding bumps 15 are shown on both sides of the belt track centerline 9 to illustrate a plurality of specific features. In addition to engaging with the sprocket 3, the drive bump 11 also has the function of restricting the lateral movement of the belt track 4 relative to the guide wheel 5 and the support roller 6. However, the gap 18 between the drive bump 11 and the guide wheel 5 is small, which enables the belt track 4 to make a limited lateral movement relative to the track unit frame 7 during the movement of the belt track, called "snaking" movement. Therefore, in practical applications, on the one hand, the contact between the guide wheel 5 and / or the support roller 6 and on the other hand the belt track 4 is made on two contact strips 25 on both sides of the drive bump 11, and the contact strips 25 have a width W2, as Figure 4 shown. The contact strip 25 is herein defined as the lateral part of the core 10 of the belt track 4, located on both sides of the central part 26 of the core 10, with a boundary 27 between the contact strip 25 and the central part 26.

[0024] From Figure 4 the cross-section of, it can be seen that the width W2 of the contact strip 25 is smaller than the projected width of the grounding bump 15 (i.e., the projection of the grounding bump in Figure 4(width of the planar projection of the figure in). Thus, the grounding bump 15 can be divided into two parts, separated by the boundary 27 of one of the contact strips 25: the load-bearing part 15a and the non-load-bearing part 15b, including the ground contact surfaces 16a and 16b respectively. The load-bearing part 15a is the part of the bump located within the boundary of the contact strip 25. Therefore, this part 15a directly bears the vehicle load force acting through the guide wheel 5 and the support roller 6. The non-load-bearing part 15b extends outside the contact strip 25 and overlaps with the central part 26 of the core 10, and does not directly bear the vertical weight component through the guide wheel 5 and the support roller 6, so it is called "non-load-bearing", which does not mean that no load acts on this part, but to distinguish this part from part 15a. However, the load borne by the load-bearing part 15a of the bump 15 is higher than that borne by the non-load-bearing part 15b. This may cause uneven wear of the grounding bump 15: in the area corresponding to the contact strip 25, the grounding bump 15 wears faster, while the central part of the bump wears slower. Especially when driving on the road, this type of wear may occur. Usually, it is found that the thickness of the grounding bump 15 increases from the side of the belt track 4 to the center line 9. This uneven wear may cause lateral bending of the track 4, which generates great pressure on the core of the belt track 4, especially in the area near the boundary 27. Every time the belt track 4 bears the weight of the vehicle and pushes on the ground, lateral bending occurs when it passes under the support roller, but when the belt track 4 bypasses the guide wheel and crosses the sprocket again, this lateral bending is more or less released again. This periodic bending in the area near the boundary 27 may cause the temperature of the belt track 4 in this area to rise, rubber degradation, rubber cracking, and even cause the reinforcement structure in this area to be pulled out of the belt track 4.

[0025] According to the present invention, the first way to solve this problem is to make the grounding bump 15 have an elastically uniform load-bearing part, but the grounding bump 15 does not overlap or substantially does not overlap with the central part 26 of the core 10 between the contact strips 25. Figure 5 A first example of this embodiment is shown. The grounding bumps 15 are formed of a uniform material and have a constant thickness defined by the distance between the ground contact surface 16 and the outer surface 13 of the core 10, but they are shorter than the bumps of the prior art belt track and are located within the boundary of the contact strip 25, that is, the bumps 15 do not overlap with the central part 26 of the core 10. Therefore, the bumps 15 are uniformly stressed on their contact surface 16 with the terrain and will also wear evenly over time.

[0026] As described, the lug 15 according to this embodiment does not overlap or substantially does not overlap with the central portion 26 between the contact strips 25. The term "substantially" is intended to include such endless tracks in which a small portion of the ground engaging lug 15 does overlap with the central portion 26, but does not overlap with a majority of the central portion, for example, according to a particular embodiment, more than 25% of the width of the central portion 26, or according to a further embodiment, more than any of the following percentages of the width: 20%, 15%, 10% or 5%. For example, in Figure 6 the endless track shown, the ground engaging lug 15 overlaps with the central portion 26 to a very small extent, but the endless track still complies with the embodiment of the present invention, according to which the ground engaging lug "substantially does not overlap with the central portion". In this case, the load bearing portion 15a of the lug is located within the boundary of the contact strip 25, while the small non-load bearing portion 15b extends beyond the boundary 27 between the contact strip 25 and the central portion 26 of the core. More generally, on any track unit according to this embodiment, a majority of the central portion of the endless track is not covered by the ground engaging lugs. Thus, these solutions reduce the grip on the terrain to some extent. However, for certain types of work machines operating on a particular type of terrain, this may be acceptable.

[0027] For a tractor, grip is usually very important because it will determine the maximum tractive force. The greater the tractive force, the more mould boards the plough can use and the fewer passes across the field are required for ploughing, thus increasing the efficiency of the farmer. In addition, for other applications, the tractive force may determine the maximum working width, such as for sowing. However, harvesters such as combine harvesters and forage harvesters are not used to pull things across the field and therefore do not require a large tractive force. The benefits of using track units for harvesters are that the track units have a larger footprint, reducing the ground compaction caused by the heavy harvester, and the track units also prevent the harvester from getting stuck in the field under adverse conditions (such as in very muddy fields). The harvester also requires a certain amount of grip to move the heavy harvester forward. Therefore, a track unit with a weaker grip but a longer service life, due to more uniform wear of the ground engaging lugs, may reduce or even avoid the problem of lateral bending and may provide more value to harvester users.

[0028] Alternative embodiments of the present invention do take into account the effect on grip by providing such ground engaging lugs that include a non - load - bearing portion which does overlap with the central portion 26 of the core 10, but which is at least partially thinner and / or more elastic than the load - bearing portion. A more elastic portion is a portion that is more compressible and / or more squashable under the same load compared to a less elastic portion, and / or a portion that wears faster and / or more readily compared to a less elastic portion. Figure 7 A first embodiment in accordance with the above description is shown in Figure 7 . The ground engaging lug 15 also includes a load - bearing portion 15a and a non - load - bearing portion 15b. The load - bearing portion 15a has a constant thickness defined by the distance from the ground - engaging surface 16a to the outer surface 13 of the core 10, and is integrally formed from a material having an elasticity of the same order of magnitude as that of the ground engaging lugs in prior - art belt tracks. The non - load - bearing portion 15b is formed from a material that is more elastic than the load - bearing portion 15a, that is, the non - load - bearing portion 15b is more compressible and / or more squashable than the load - bearing portion 15a under the same load, and / or wears faster and / or more readily than the load - bearing portion 15a, while having sufficient stiffness to provide sufficient grip on the terrain. In this case, portions 15a and 15b coincide exactly with two portions of the lug that have different elasticities, and are fixed to each other along the interface 28 by bonding or any other equivalent attachment means, thereby forming a single ground engaging lug 15. The non - load - bearing portion 15b has the same thickness as the load - bearing portion 15a, defined by the ground - engaging surface 16b. Due to the different elasticities, when the load - bearing portion 15a wears and thins, the non - load - bearing portion 15b either wears at the same rate or faster than the load - bearing portion; if not, it would be compressed under the weight of the load. Whichever way it is, the load - bearing portion 15a wears evenly, thus solving the problem of uneven wear in the prior art. At the same time, compared with the embodiments of Figure 5 and Figure 6 it can also better maintain the grip on the terrain.

[0029] In Figure 7 the embodiment, the interface 28 between the portions of the ground engaging lug 15 having different elasticities is perpendicular to the outer surface 13 of the core 10 and coincides with the boundary 27 of the contact strip 25. The latter is not an essential limitation of the scope of the invention. Figure 8a and Figure 8b An embodiment where this is not the case is shown in Figure 8b . Now, the interface 28 between the portions having different elasticities is perpendicular to the longitudinal direction of the lug itself. However, the definition of the load - bearing portion 15a and 15b remains the same: the dividing line between these portions is the boundary 27 of one of the contact strips 25, as shown in Figure 8bIllustrated by the representation of these portions 15a and 15b of a convex bump 15. In this case, it can be clearly seen from this figure the difference between the portions 15a and 15b separated by the boundary 27 and the portions 31 and 32 with different elasticities separated by the interface 28. It can be seen that the load-bearing portion 15a is mainly formed of a material with higher hardness and lower elasticity, except for the small corner portion 20, while the non-load-bearing portion 15b is mainly formed of a material with higher elasticity, except for the corner portion 21. However, generally speaking, the non-load-bearing portion 15b is more elastic than the load-bearing portion 15a. Therefore, this embodiment provides the same advantages as Figure 7 the embodiment. To some extent, as long as the said advantages remain valid, the interface 28 can be oriented differently while being perpendicular to the outer surface 13 of the core 10 and Figure 7 or any of the versions shown in FIG. 8, and / or the said interface 28 can be entirely located on one side or the other side of the boundary 27 of the contact strip 25. In any of the above embodiments, the non-load-bearing portion 15b at least partially coincides with the more elastic portion (e.g. Figure 8a and Figure 8b portion 32 in the embodiment of) of the two portions included in each grounding bump 15.

[0030] Figure 9 Another embodiment is shown in. The load-bearing portion 15a of the grounding bump 15 has the same thickness and elasticity as the grounding bumps of the prior art, but now the thickness of the non-load-bearing portion 15b of the grounding bump is less than that of the load-bearing portion 15a. The elasticity of the non-load-bearing portion 15b can be equal to that of the load-bearing portion 15a. The effect of this is that the load-bearing portion 15a will wear evenly, while the non-load-bearing portion 15b can still provide a certain degree of grip on the terrain. As in the previous embodiment, the dividing line between the higher and lower portions of the thickness of the bump does not necessarily coincide with or be parallel to the boundary 27 of one of the contact strips 25.

[0031] Figure 10 Another embodiment is shown in. The load-bearing portion 15a of the grounding bump 15 has the same thickness and elasticity as the grounding bumps of the prior art, but now the non-load-bearing portion 15b includes a groove 29 over a large part of its thickness. The elasticity of the material of the non-load-bearing portion 15b can be the same as or higher than that of the material of the load-bearing portion 15a. The groove 29 can maintain the grip of the central portion 26 of the core on the terrain, but at the same time reduce the contact area with the soil. Compared with the solid load-bearing portion 15a, the reduced contact area may accelerate wear. In this way, the risk of the above-mentioned uneven wear is reduced. In the illustrated embodiment, the groove 29 is parallel to the longitudinal direction of the belt track 4, but this orientation can be different, for example, perpendicular to the longitudinal direction of the grounding bump 15 itself. The number of grooves 29 and the depth of the grooves 29 are not limited to Figure 10The example shown. In the illustrated embodiment, the groove 29 is linear, but the groove 29 can also be zigzag or curved. The depth and width of the groove can also vary across the width of the track belt 4 and / or along the circumference of the track belt.

[0032] Figure 9 and Figure 10 The two embodiments shown actually define the same feature, namely that the non-load-bearing part 15b is at least partially thinner than the load-bearing part 15a, i.e., thinner than the load-bearing part in at least one or more regions of the non-load-bearing part 15b. In Figure 9 the case where, the thickness of the non-load-bearing part 15b is constant and lower than the thickness of the load-bearing part 15a, while in Figure 10 the case where, within the region defined by the groove 29, the thickness of the non-load-bearing part 15b is lower than the thickness of the load-bearing part 15a. Other embodiments also fall within this general feature of "at least partially thinner", for example, in at least a part of the non-load-bearing part 15b, the thickness of the non-load-bearing part gradually decreases or increases.

[0033] Figure 11 Another embodiment is shown, in which the non-load-bearing part 15b is more elastic than the load-bearing part 15a. The load-bearing part 15a and the non-load-bearing part 15b have the same thickness. However, the grounding lug 15 is formed as a mass consisting of a first part 35 and a second part 36, the first part 35 being formed of a material having, for example, an elasticity of the same order of magnitude as that of the grounding lugs of the prior art, and the second part 36 being formed of a more elastic material, wherein the first part 35 and the second part 36 have complementary wedge-shaped configurations. The second part 36 is fixed on top of the first part 35 along an interface 37 that forms a downward slope from the side of the load-bearing part 15a to the side of the non-load-bearing part 15b, said slope passing through the boundary 27 between one of the contact strips 25 and the central part 26 of the core 10. Thus, the load-bearing part 15a is not a solid body formed of a single material, but its elasticity is lower than that of the non-load-bearing part 15b mainly formed of a more elastic material, thereby achieving the same beneficial effect as the embodiments described previously.

[0034] In any embodiment according to the present invention, the load-bearing part 15a of the lug includes a ground contact surface parallel to the outer surface 13 of the core 10, wherein the distance between the ground contact surface and the outer surface of the core defines the thickness of the load-bearing part 15a. In the above embodiment, the ground contact surface 16a is defined by one of the boundaries 27 of the contact strip 25, since the thickness of the load-bearing part 15a is constant before this boundary.

[0035] However, as Figure 12a and Figure 12bAs shown, the latter is not a limitation on the scope of the present invention. This is an example of the ground engaging lug 15 of the crawler unit according to the present invention, wherein the non-load bearing portion 15b is thinner than the load bearing portion 15a because the inclined surface 40 is inclined from the section 41 of the lug towards the end section 42 of the lug. The section 41 is slightly to the left of the boundary 27, that is, the section 41 is located within the load bearing portion 15a. The load bearing portion 15a now has a ground contact surface 16' parallel to the outer surface 13 of the core 10, wherein the ground contact surface 16' is smaller than the ground contact surface 16a shown in the previous embodiment. However, as long as the ground contact surface 16' is large enough to support the load of the work vehicle, then this embodiment falls within the scope of the present invention. In this embodiment, the thickness of the load bearing portion 15a is defined by the distance between the surface 16' and the outer surface 13 of the core 10.

[0036] When it is stated in the claims that two rows of ground engaging lugs 15 are arranged in two rows so as to extend on both sides of the center line 9 of the belt track of the belt type crawler, this is not limited to the shown embodiment, wherein the lugs do not overlap the center line 9 of the belt track. Figure 13 An embodiment is shown in which the lugs have a lesser degree of overlap with the center line 9 of the belt track. If the non-load bearing portion 15b of the lugs is thinner or more elastic than the load bearing portion 15a, then this arrangement also falls within the scope of the present invention. In Figure 13 the embodiment is such that the lugs are the same as those in Figure 8a and include a relatively rigid portion 31 and a relatively elastic portion 32 attached along the interface 28, and the non-load bearing portion 15b partially coincides with the relatively elastic portion 32.

[0037] The present invention is not limited to Figure 1 and Figure 2 the type of crawler unit shown, and it is also applicable to other types of crawler units, which include a crawler having a core 10, with drive lugs 11 on the inner surface of the core and two rows of parallel arranged ground engaging lugs 15 on the outer surface of the core. For example, another type of crawler unit to which the present invention is applicable is a crawler unit that does not include a drive sprocket 3 centrally located above the idler 5 as in the units shown in Figure 1 and Figure 2 but in which the drive sprocket is mounted between two spaced idlers 5 or in place of the idler. The crawler can also be driven by friction drive instead of by a sprocket. Therefore, compared with the triangular unit shown in Figure 1 and Figure 2 this type of unit is flatter.

Claims

1. A crawler unit for a work vehicle (1), the crawler unit comprising a crawler unit frame (7), a drive sprocket (3), a belt crawler (4) having a longitudinal belt crawler centerline (9), the belt crawler comprising a core (10) having an outer surface (13) and an inner surface, the crawler unit further comprising front and rear guide wheels (5) and support rollers (6) rotatably mounted on the crawler unit frame (7) for guiding and supporting the belt crawler (4), wherein: The belt crawler (4) comprises regularly spaced drive lugs (11) on the inner surface of the core (10) for engaging the drive sprocket (3) and spaced ground contact lugs (15) on the outer surface (13) of the core (10), the ground contact lugs being arranged in two rows extending on either side of a belt crawler centre line (9), The front and rear guide wheels (5) and the support rollers (6) are spaced apart and arranged in pairs in a direction perpendicular to the center line (9) of the belt crawler to leave space for the driving lugs (11) to pass through. The guide wheels (5) and / or support rollers (6) are configured to contact the belt crawler on two contact strips (25) of the core (10), the contact strips extending on both sides of the drive lug (11), the central part (26) of the core (10) extending between the contact strips (25), Each ground bump (15) comprises a load-bearing portion (15a) located within the boundaries of one of the contact strips (25), the load-bearing portion comprising a ground contact surface (16a, 16') oriented substantially parallel to the outer surface (13) of the core, wherein the distance between the ground contact surface (16a, 16') and the outer surface (13) of the core (10) defines the thickness of the load-bearing portion (15a), Features: The load-bearing portion (15a) has uniform elasticity, and the grounding protrusion (15) does not overlap or substantially does not overlap with the central portion (26) of the core (10), Alternatively, the ground bump (15) further comprises a non-load-bearing portion (15b) overlapping the central portion (26) of the core, wherein the non-load-bearing portion (15b) is at least partially thinner and / or more elastic than the load-bearing portion (15a).

2. A crawler track unit according to claim 1, wherein the drive sprocket (3) is mounted above the front and rear guide wheels (5) and centrally between the front and rear guide wheels.

3. The crawler unit according to claim 1, wherein one of the guide wheels (5) is the drive sprocket (3).

4. A crawler unit according to any one of the preceding claims, wherein the drive sprocket (3) drives the belt crawler by friction.

5. A crawler unit according to any one of claims 1 to 4, wherein the ground contact lug (15) includes the non-load-bearing portion (15b) overlapping the central portion (26) of the core (10), and wherein the ground contact lug (15) is formed by a first portion (15a, 31) having a first elasticity and a second portion (15b, 32) more elastic than the first portion, the second portion being fixed to the first portion along an interface (28) perpendicular to the outer surface (13) of the core (10), and wherein the non-load-bearing portion (15b) at least partially overlaps within the second portion.

6. A crawler unit according to any one of claims 1 to 4, wherein the ground contact lug comprises the non-load-bearing portion (15b) overlapping the central portion (26) of the core (10), and wherein the non-load-bearing portion (15b) has a constant thickness that is smaller than the thickness of the load-bearing portion (15a).

7. A crawler unit according to any one of claims 1 to 4, wherein the ground contact lug (15) comprises the non-load-bearing portion (15b) overlapping the central portion (26) of the core (10), and wherein the non-load-bearing portion (15b) has a gradually decreasing thickness.

8. A crawler unit according to any one of claims 1 to 4, wherein the ground contact lug comprises the non-load-bearing portion (15b) overlapping the central portion (26) of the core (10), and wherein the non-load-bearing portion (15b) comprises one or more grooves (29) such that in the grooves, the non-load-bearing portion (15b) is thinner than the load-bearing portion (15a).

9. A crawler unit according to any one of claims 1 to 4, wherein the ground contact lug includes the non-load-bearing portion (15b) overlapping the central portion (26) of the core (10), and wherein the ground contact lug (15) is formed by a first portion (35) having a first elasticity and a second portion (36) more elastic than the first portion, the second portion being fixed on the top of the first portion along an interface (37), the interface forming a downward slope from one side of the load-bearing portion (15a) to one side of the non-load-bearing portion (15b), the slope passing through a boundary (27) between one of the contact strips (25) and the central portion (26) of the core (10).

10. A work vehicle comprising an even number of track units according to any one of the preceding claims.

11. A tractor comprising an even number of track units according to any one of claims 1 to 9.

12. A combine harvester or forage harvester comprising an even number of track units according to any one of claims 1 to 9.

13. A method of converting a belt crawler (4) for use in a crawler unit (2) according to any one of claims 1 to 4, The crawler unit comprises a crawler unit frame (7), a drive sprocket (3), a belt crawler (4) having a longitudinal belt crawler centerline (9), the belt crawler comprising a core (10) having an outer surface (13) and an inner surface, and the crawler unit further comprises front and rear guide wheels (5) and support rollers (6) rotatably mounted on the crawler unit frame (7) for guiding and supporting the belt crawler (4); The belt crawler (4) comprises regularly spaced drive lugs (11) on the inner surface of the core (10) for engaging the drive sprocket (3) and spaced ground contact lugs (15) on the outer surface (13) of the core (10), the ground contact lugs being arranged in two rows extending on either side of a belt crawler centre line (9), The front and rear guide wheels (5) and the support rollers (6) are spaced apart and arranged in pairs in a direction perpendicular to the center line (9) of the belt crawler to leave space for the driving lugs (11) to pass through. The guide wheels (5) and / or support rollers (6) are configured to contact the belt crawler on two contact strips (25) of the core (10), the contact strips extending on both sides of the drive lug (11), the central part (26) of the core (10) extending between the contact strips (25), Each ground bump (15) comprises a load-bearing portion (15a) located within the boundaries of one of the contact strips (25), the load-bearing portion comprising a ground contact surface (16a, 16') oriented substantially parallel to the outer surface (13) of the core, wherein the distance between the ground contact surface (16a, 16') and the outer surface (13) of the core (10) defines the thickness of the load-bearing portion (15a), The method is characterized in that it comprises at least partially removing the ground bump (15) where the ground bump overlaps the central portion (26) of the core (10). 14 . The method of claim 13 , further comprising adding material where the ground bump is removed, such that the added material is more elastic than a material from which the ground bump is made.

Images