TRACK UNIT FOR GROUND WORK VEHICLE

A track unit for ground work vehicle, which comprises a structure for supporting a driving wheel that transmits motion to a ground resting track; the track unit is designed to be mounted as an alternative to a wheel at the end of at least one axle of the work vehicle that is provided with a motor drive unit designed with such characteristics as to give the machine correct values of the transmission ratio, i.e., of the travel speed in the configuration in which wheels are mounted at the ends of the axle; the track unit further comprises a speed-increasing gear system interposed between a hub, designed to be connected to a flange of the axle of the work vehicle, and the driving wheel that moves the track.

The present invention relates to a track unit for ground work vehicle.

As is known, in the use of ground work vehicles, such as for example tractors or machines that harvest agricultural products, such as combine harvesters or the like, it is often necessary, due to functional reasons linked to the characteristics of the ground or to the type of operations to be performed, to mount alternately, at the ends of at least one axle of the machine, simple wheels or track units.

Typically, the track units used on these machines comprise a supporting structure for a driving wheel, which is designed to move a track arranged in contact with guiding wheels and ground resting rollers which are associated with the same supporting structure.

Ground work vehicles of the type cited above are normally provided with a motor drive unit which is structured to give the machines values of the transmission ratio, i.e., of the translation speed, that are correct when the machines are in the configuration with simple wheels.

Upon transition, in the alternation cited above, to the presence of track units according to the background art, the transmission ratio of the axle is reduced considerably due to the reduction of the diameter of the driving wheel of the track units with respect to the diameter of the wheels, with consequent reductions of the maximum forward travel speed and incorrect synchronization between the axles of the machine when the original wheels are mounted on at least one of them, as in the typical case of track units mounted only on the rear axle of the tractor.

The aim of the present invention is to provide a track unit that can be mounted detachably on the end flanges of an axle of a ground work vehicle as an alternative to a simple wheel without the interposition of transmission boxes and without touching the motor drive unit of the machine, any variations of the transmission ratio of the machine remaining substantially absent.

Within this aim, an object of the present invention is to provide a track unit that is capable of offering the greatest assurances of reliability and safety in operation.

Another object of the invention is to provide a track unit that has a simple structure and is competitive from the economic standpoint.

This aim, as well as these and other objects that will become better apparent hereinafter are achieved by a track unit for ground work vehicle, according to the invention, as defined in claim1.

With reference to the figures, the reference numeral1designates an axle of a work vehicle, with which two mirror-symmetrically identical track units2are associated.

The axle1is designed to be rotationally actuated about its own axis by a motor drive unit connected to the work vehicle.

Each track unit2comprises a supporting structure3for a driving wheel4that is designed to move a track5, which is arranged in contact with guiding wheels6and ground resting rollers7, which are associated, according to one possible embodiment, with the structure3.

With reference in particular toFIG. 2, each track unit2is provided with a corresponding hub8in order to allow its connection to the axle1.

More particularly, the axle1, as per se known, is provided, at its two opposite ends, with flanges1a,1b, which are entrusted with the function of supporting a respective track unit2, by means of the coupling with the corresponding hub8, as an alternative to simple wheels, without, it is important to note, undergoing any change.

With reference toFIG. 3, the hub8is designed to support the structure3of the track unit2by means of bearings10and is connected to the driving wheel4by means of an angular speed-increasing gear system, constituted advantageously, according to the example ofFIG. 3, by an epicyclic gear system9, which has the function of increasing the rotation rate from the hub8of the track unit2, which constitutes its input, to the driving wheel4, which constitutes its output.

In greater detail, the epicyclic gear system9advantageously has a sun gear9a,which is integral with the structure3, a ring gear9b,which is substantially coaxial to the hub8and integral with the driving wheel4of the track unit2, and at least one pair of planet gears9c,which mesh with the sun gear9aand with the ring gear9b.With reference again to the example ofFIGS. 2 and 3, the planet gears9care advantageously supported, at the corresponding rotation pivot, by the hub8.

The presence of the epicyclic gear system9allows to compensate the reduction factor of the transmission ratio, i.e., of the translation speed of the work vehicle, in the configuration with track units2with respect to the configuration with simple wheels, which is due to the smaller diameter of the driving wheel4of the track units2with respect to the diameter of the wheels, thus achieving a substantial equality of the values of the transmission ratio, i.e., of the speed, in the two configurations.

With reference again toFIG. 3, the sun gear9aof the epicyclic gear system9, being its reaction element, can advantageously be rendered integral with the structure3of the track unit2with the interposition of a torque limiter safety coupling11, shown schematically inFIG. 5, in order to eliminate the motor moment peaks that might cause damage to the internal transmission teeth of the track5.

For example, the safety coupling11can be constituted by a pack of disks which are preloaded axially according to the maximum transmissible torque.

It should be noted that in general the safety coupling11can be associated with at least any one of the elements that constitute the angular speed-increasing gear system.

Operation of the truck unit according to the invention is as follows.

The axle1turns the hubs8of the track units2that have been connected detachably to the flanges1a,1b,arranged at its opposite ends, as an alternative to simple wheels.

The meshing of the sun gears9awith the corresponding planet gears9cof the epicyclic gear systems9associated with the track units2and the driving of the rotation pins of the planet gears9cby the hubs8causes the rotation of the ring gears9bthat are integral with the driving wheels4with a higher angular velocity than the angular velocity of the axle1, with a consequent multiplication of the rotation rate and compensation of the reduction of the transmission ratio in the transition from the configuration with simple wheels to the configuration with the track units2.

In practice it has been found that the invention is capable of achieving fully the intended aim and objects.

All the characteristics of the invention indicated above as advantageous, convenient or the like may also be omitted or be replaced with equivalents.

The individual characteristics presented with reference to general teachings or to particular embodiments may all be present in other embodiments or may replace characteristics in these embodiments.

Thus, for example,FIGS. 4 and 5show a constructive variation in which, as a supporting element of the track unit2, there is a hub8that has a spindle-like shape, instead of the hub8with an open configuration of the preceding example.

According to a third constructive variation, shown inFIGS. 6 and 7, if the driving wheel4must be arranged off-axis with respect to the input of the transmission, i.e., to the axle1of the work vehicle, the angular speed-increasing gear system can be constituted by an ordinary gear system12, for example with three shafts.

More particularly, the ordinary gear system12conveniently comprises a first shaft12a,which is provided with a first gear and is integral with the hub8that is connected to a respective flange1a,1bof the axle1, a second shaft12b,which is supported by a supporting body13which is connected, conveniently, to the structure3of the track unit2and is provided with a second gear that engages the first gear connected to the hub8, and a third shaft12c,which is integral with the driving wheel4and is provided with a third gear that engages the second gear.

In a further embodiment, shown inFIG. 8, there is a structure3for supporting a driving wheel4that is provided with an angular speed-increasing gear system, such as for example an ordinary gear system12, and is not supported by a second supporting structure14of the guiding wheels6and ground resting rollers7, the reaction of the gear system being absorbed by a coupling element, constituted for example by a reaction arm15, which is associated with the work vehicle and is connected to the supporting body13or to the structure3.

In practice, the materials used, so long as they are compatible with the specific use, as well as the shapes and dimensions, may be any according to the requirements.

All the details may furthermore be replaced with other technically equivalent elements.

The disclosures in Italian Patent Application No. 102015000057497 (UB2015A004182) from which this application claims priority are incorporated herein by reference.