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Field of the invention

The present invention relates to a track-wheel convertible unit for vehicles, in particular for high mobility ATVs ("All-Terrain Vehicles"), usable for example in civil emergency or rescue activities, or in agricultural field, or in earth-moving or similar activities. Naturally, the invention herein described is still of general application.

Prior art

A track-wheel convertible unit for vehicles has already been proposed in the past, in particular a track-wheel convertible unit comprising a track engaged on a plurality of rollers carried by a support structure mounted on a unit main shaft, said rollers being each movable between a first operative position corresponding to a track configuration and a second operative position corresponding to a wheel configuration.

A solution of this type is for example described and illustrated in document US 2009/0212623 A1 . In this known solution, the track is extendable, so as to be adapted to provide a lower perimeter length, in which the track covers a wheel and acts as a tread for such a wheel, and a higher perimeter length, in which the track acts as a track properly said, with a track section in contact with the ground which is kept stretched by two rollers which protrude out of the wheel perimeter, in front of the wheel and behind it. A solution of this type requires the provision of a track structure configured to enable a considerable lengthening of the track perimeter, which set great limits for constructive simplification and operation reliability.

Document WO 99/21749 A1 shows a solution of the type indicated above in which the perimeter length of the track remains substantially the same in the aforementioned track configuration and in the aforementioned wheel configuration. However, this known solution is not suitable in order to be used in an ATV vehicle, being not adapted to bear stresses to which the unit is exposed during use. Similar solutions are also known from DE 11 71 755 B and CN 105 774 930 A.

Object of the invention The object of the present invention is to provide a track-wheel convertible unit of the type indicated at the beginning of the present description which has a robust and reliable structure during operation, even in situations of high stress, such as in the case of ATV vehicle applications, and which nevertheless results relatively simple to manufacture, enabling in particular both the use of conventional tracks with links, and tracks of elastomeric material.

Summary of the invention

In view to achieve the aforementioned object, the invention has for subject a track-wheel convertible unit for vehicles, in particular for vehicles of the ATV type, comprising a track engaged on a plurality of rollers carried by a unit support structure, the rollers being each movable between a first operative position corresponding to a track configuration and a second operative position corresponding to a wheel configuration, wherein said first operative position and said second operative position of each of said rollers are arranged in such a way that the perimeter length of the track remains substantially the same in said track configuration and in said wheel configuration, said unit being characterized in that:

- the unit comprises a plurality of track support segments alternated with said rollers and carried by said support structure so as to be radially movable between a first operative position, which is radially inward, corresponding to the track configuration and a second operative position, which is radially outward, corresponding to the wheel configuration,

- said rollers are radially guided by said support structure between a first operative position, which is radially outward, corresponding to the track configuration and a second operative position, which is radially inward, corresponding to the wheel configuration,

- said unit comprises also an actuator device to control a movement of said rollers between said first operative position and said second operative position, and a simultaneous movement of said track support segments between said first and second operative positions.

In a first embodiment, the track-wheel convertible unit according to the invention comprises three rollers and three track support segments alternated with the three rollers. In a first example relative to this embodiment, said actuator device controls each of said rollers by means of an articulated transmission linkage and each of said track support segments by means of a pinion- and-rack transmission.

In a second and preferred example of this embodiment, the actuator device has a first operative position corresponding the operation as a track, in which said rollers are controlled in rotation around the respective axes by a unit central shaft, each by means of a gear drive, and the actuator device has a second operative position corresponding to the operation as a wheel, in which said central shaft is connected in rotation with a central pivotable member which is configured and located so as to pivot the whole roller assembly with the relative transmissions, as a single structure, around the wheel central axis. The pivotable member is connected to the structure carrying said rollers and to said track support segments, in such a way that when the actuator device shifts from its first operative position to its second operative position, the pivotable member moves the rollers and the support segments between their first operative position and their second operative position.

Naturally, the invention is also applicable to cases in which the number of the rollers is different from three. For example, a solution is provided including six rollers distributed in three twin roller assemblies. Each twin roller assembly has a frame which is freely pivotable on the support structure of the track-wheel convertible unit. In this example, the track support segments are completely inoperative in the track configuration, while in the wheel configuration the support segments are shifted parallel to the axis of the main unit shaft in order to support the track in the wheel configuration.

Detailed description of the invention

Further features and advantages of the invention will become apparent from the following description with reference to the annexed drawings, given purely by way of non-limiting example, in which:

- figure 1 is a diagrammatic perspective view of a first embodiment of the track-wheel convertible unit according to the invention, in the wheel configuration,

- figure 2 is a rear perspective view of the unit of figure 1 , - figure 3 is a partially cross-sectioned perspective view of the unit of figure 1 ,

- figures 4,5 are perspective views of details of the unit of figure 1 ,

- figure 6 is a perspective view of the unit of figure 1 in the track configuration,

- figure 7 is a rear perspective view of the unit in the configuration of figure 6,

- figure 8 is a partially cross-sectioned view of the unit of figure 6,

- figure 9 is a diagrammatic perspective view of a second embodiment of the track-wheel convertible unit of the invention,

- figure 10 is a further perspective view of some parts of the unit of figure 9,

- figure 1 1 is a perspective view of the unit of figure 9 in the wheel configuration,

- figure 12 shows some parts of the unit of figure 9, in the wheel configuration of figure 1 1 ,

- figure 13 is a perspective view of a further embodiment of track- wheel unit according to the invention, in the wheel configuration,

- figure 14 is a further perspective view of the unit of figure 13, with a cover removed,

- figure 15 is a view corresponding to figure 14, which shows the unit in the track configuration,

- figure 16 is a perspective view of the transmission system associated to the unit three rollers,

- figure 17 is a further perspective view of the system of figure 16, with some envelopes removed,

- figure 18 is a partially cross-sectioned perspective view of the unit of figure 15,

- figure 19 is an exploded perspective view of the main components of the unit, and

- figure 20 is a functional diagram of the unit.

Figures 1 -8 show a first embodiment of a track-wheel convertible unit for vehicles. The unit is generally designated with reference 1 and comprises a track 2 of any known type, for example made of elastomeric material, engaged on three rollers 3 carried, in the way that will be described in detail hereinafter, by a support structure 4 (see figure 2) which is mounted on a main shaft 5.

The three rollers 3 are each movable between a first operative position (shown in figure 6) corresponding to a track configuration, and a second operative position, shown in figure 1 , corresponding to a wheel configuration.

In the wheel configuration, the whole unit 1 operates as a single wheel guided in rotation by the unit main shaft (figure 2), which acts as a wheel shaft. This shaft (not shown) is coaxial to the cylindrical body 5 of an actuator device 6 (described in detail in the following), and receives the motion by means of a transmission of any known type (not shown in the drawing) by an engine of any known type associated to the vehicle on which the unit 1 is mounted.

In the track configuration shown in figure 6, the three rollers 3 impart to the track 2 a triangular configuration, with an upper vertex and a base side in contact with the ground. One or more of the rollers 3 is a roller provided internally with a motor and provided with an outer toothed surface, engaged with a corresponding toothed inner surface of the track 2 (not shown in the drawings) for driving a movement of the track 2 around the three rollers 3.

In particular with reference to figures 2 to 3, with reference 5 is designated the cylindrical body of an actuator device 6, which is supported by the support structure 4 coaxially to the unit 1 . In the illustrated example, the actuator device 6 is a fluid device comprising a plunger 60 slidably mounted within the cylindrical hollow body 5 and connected to a rod 61 slidably mounted within the support structure 4. The rod 61 controls sliding of an actuator member 62.

As can be seen in figure 4, each roller 3 is mounted on a shaft 300 which is slidably mounted within a radial slot 301 of a plate 400 which is a part of the support structure 4. The two chambers 62,63 of the actuator device 6 selectively receives fluid in pressure by means of the movement of the actuator member 6 between a first operative position (which is shown in figure 3) and a second operative position (shifted to the right with reference to figure 3), in which the shafts 300 of the three rollers 3 move radially outwardly up to reach the position shown in figures 6-8. The actuator member 62 controls moving of the of the roller shafts 300 by means of three articulated transmission linkages 66.

Again with reference to figures 1 -8, track support segments 7 are alternated with the rollers 3 and said track support segments 7 are radially movable between a first operative position corresponding to the track configuration (shown in figure 6) and a second operative position shown in figure 1 .

The radial movement of the three track support segments 7 between their operative positions is controlled by the actuator member 62 simultaneously with the radial movement of the three rollers 3, by means of three pinion-and-rack transmissions which are generally designated with reference 8 in figure 3. As can be seen in particular in figure 5, the actuator member 62 carries at its free end three pairs of racks 80. With reference to figure 4, frontally with respect to the plate 400, the support structure 4 comprises a cylindrical body 401 for guiding the actuator member 62. The cylindrical body 401 carries three pairs of radial flanges which freely support in rotation three shafts carrying respective pinion assemblies. Each pinion assembly includes two end pinions 81 and an intermediate pinion 82 which is interposed between the two end pinions 81 , the two pinions 81 and the pinion 82 being all connected in rotation with a respective shaft (not shown in figure 4) which is freely rotatably mounted on the respective pair of radial flanges 402 of the cylindrical body 401 .

With reference to figures 3,4 and 5, the two racks 80 of each pair of racks 80 (figure 5) mesh with the two end pinions 81 of the respective pinion assembly. In this way, the axial movement of the actuator member 62 causes a rotation of each pair of pinions 81 and, along them, of each pinion assembly. As shown in figure 3, the central pinion 82 of each pinion assembly meshes with a rack 83 of the respective track support segment 7. In this way, the rotation of the central pinion 82 caused by the axial movement of the actuator member 62 leads to a radial movement of each of the three track support segments 7.

As can be seen from the above description, activation of the actuator device 6 causes, by means of the actuator member 62, simultaneous displacement of the three rollers 3 and the track support segments 7 between their operative positions corresponding respectively to the wheel configuration and to the track configuration. In the wheel configuration (figure 1 ) the whole unit is rotated by the shaft connected to the support structure 4 of which the vehicle is provided. In this wheel configuration, the track 2 simply operates as a wheel tread. In the track configuration, one or more of the rollers 3 is driven in rotation around its axis by means of an engine of any known type which is now associated (not shown in the drawings) for moving the track in the configuration of figure 7, so as to ensure proceeding of the vehicle on the ground due to engagement of the track base on the ground.

Figures 9-12 show a second embodiment of the invention. In these figures, the parts which are similar or corresponds to those of figures 1 -8 are designated by the same references.

In the case of the embodiment of figures 9-12, the track 2 is engaged on six rollers 3 located in three assemblies each comprising two rollers. As can be seen in figure 10, each assembly of two rollers 3 comprises a frame 305 which supports in rotation the two rollers 3 of the assembly around two axes parallel one to the other. The frame 305 is also freely pivotably supported around a central axis which is parallel and intermediate between the axes of the two rollers 3 on a support pin which is slidably mounted in a respective slot 405 formed in the plate 400 which is part of the unit support structure 1 . As can be seen in figure 10, the support plate 400 has two slots 405 adjacent to its lower side, the two slots 405 being aligned along a common horizontal direction (with reference to figure 10). The plate 400 has a third slot 405 vertically directed in the symmetry plane of the plate 400. The three slots on which are mounted the support structures 305 of the three roller pairs 3 are slidably mounted in the three slots 405.

The plate 400 has three further guide slots 406, opened outwardly and directed according to substantially radial directions, at alternated positions between the three slots 405. Rods 70 are slidably mounted in the guide slots 406, the rods 70 carrying respectively three track support segments 7. As can be clearly seen in figure 12, each prismatic rod 70 comprises a bushing 71 which axially slidably supports a rod 72 carrying the respective segment 7. In the track configuration shown in figure 9, the segments 7 are maintained in a retracted axially position, at a plane spaced from the general plane of the track 2, in such a way that each segment 7 is totally disengaged out of the track 2. In the wheel configuration shown in figure 1 1 , the segments 7 have advanced axially, so as the segments 7 are engaged against the inner surface of the track 2, following also an outwardly radial movement of the respective rods 70.

Furthermore, in the wheel configuration shown in figure 1 1 , the inner surface of the track 2 is also supported by three further support segments 500 which are each radially slidably supported by the support frame 305 of each pair of rollers 3, whereby in the wheel configuration, each of these auxiliary segments 500 is moved in its retracted position, in order to adequately support the track between the two rollers 3 of the respective pair.

For simplicity, figures 9-12 do not show the actuator means which control movement of the three roller pair assemblies within the slots 405, nor the actuator devices for causing movement of the rods 70 of the track support segments 7 within the respective guide slots 406, nor the actuator devices for causing axial movement of each segment 7 with respect to the support bushing 71 , nor movement of the auxiliary segments 500 carried by each twin roller assembly. These actuator means can be provided in any known type, as will become apparent to the skilled person.

Figures 13-20 refer to a further embodiment of the unit according to the invention.

With reference to figure 13, also in this case the unit 1 comprises a track 2 engaged on three rollers 3, and three track support segments 7 for supporting the track 2 in the wheel configuration.

With reference to the exploded view of figure 19, the unit comprises a support structure 5 connected to an ATV vehicle structure. For example, the structure 5 can be rigidly connected at the end of a pivoted leg of the

ATV vehicle, which can be provided for example in accordance with one of international patent applications PCT/IB2018/051896 and PCT/IB/2018/051899, yet secret at the priority date of the present application and filed by the same Applicant.

As may be seen in figure 18, the support structure 5 comprises a cylindrical body inside which is rotatably mounted a central shaft 51 which is rotated by an engine (not illustrated) of the vehicle via a transmission shaft 52 (figure 19) and a pair of conical gears 52a,52b (see figure 20) which connect the shaft 52 in rotation with the shaft 51 .

The central shaft 51 is adapted to control the rotation of the three rollers 3 around the respective axes by means of three gear transmission systems better visible in figures 17 and 19. In particular, the central shaft 51 carries a pinion 53 which is coaxial to the central shaft 51 and which meshes with three gear wheels 54 (figure 17) also meshing with three gear wheels 55 rigidly mounted on the shafts 300 of the rollers 3. The transmission gear wheels 54 are rotatably mounted on three radial forks 56 forming part of a member 54 which is rotatably mounted on the unit support structure around the central axis A. In figure 16 are illustrated the envelopes 302 of the gear pairs 54,55 associated with the rollers 3.

The unit support structure includes, in addition to the cylindrical body 5, two side covers 50A,50B rigidly connected thereto, and rigidly connected to each other by means of cross members 80.

With reference to figure 19, the shafts 300 of the rollers 3 have ends protruding from the rollers carrying slides 301 which are slidably mounted on radial guides 58 formed at the inner face of the covers 50A,50B. In this way, the rollers 3 are guided in a radial direction between their first operative position, which is radially outward, corresponding to the track condition, and a second operative position, which is radially inward, corresponding to the wheel condition.

Also in this embodiment, three segments 7 are provided for supporting the track 2 in the wheel configuration. Each of the segments 7 is provided with two parallel lateral arms 70, arranged parallel to each other, which are guided within radial guide slots provided at the inner faces of the covers 50A,50B. Therefore, also the track support segments 7 are guided in a radial direction between a first operative position which is radially inward, corresponding to the track condition, and the second operative position, which is radially outward, in which the segments 7 engage the inner surface of the track, in the wheel configuration.

With reference to figure 18, a fluid actuator cylinder 6 is provided at the central part of the unit, coaxially with the central axis A, said fluid actuator cylinder 6 being adapted to control the axial movement of a front-toothed disc 59 adapted to engage with a front-toothed wheel 60 which is rigidly connected in rotation with the rotating member 57. The actuator 6 is illustrated only diagrammatically, being possible to provide it in any known way.

In the track configuration shown in figure 18, the disc 59 is located in a position which is axially spaced from the wheel 60. In this configuration, the torque transmitted by the transmission shaft 52 is transferred to the central shaft 51 and from this to the rollers 3, by the respective gear transmissions, in such a way that each roller 3 rotates around its axis and causes a corresponding movement of the track 2 which adheres by friction to the rollers 3.

The actuator device 6 can be actuated in order to move the disc 59 from the aforesaid operative condition to an operative condition in which its front toothing engages the wheel 60. In this condition, the torque transmitted by the transmission shaft 52 is transferred to the rotating member 57. In the initial part of its rotation, for an angle of about 45°, the rotating member 57 drives the shafts of the gear wheels 54 (figure 17) in such a way that the shafts move in a position which is translated in a tangential direction, which enables the gear wheels 55 associated to the rollers 3 to move radially inwardly, while the shafts 300 of the rollers are guided in radial direction in the way described above. From this condition on, the further rotation of the rotating member 57 is transmitted to the whole assembly of three rollers 3, with the relative gear transmissions, as a single rotating structure around the central axis A. At the same time, the rotating member 57, by means of three connecting rod arms 71 , which connect the radial forks 56 of the of the rotating member 57 to the segments 7, causes a radial displacement of these segments from their radially inward position to their radially outward position, in which they engage the inner surface of the track giving to the unit the wheel configuration (figure 13,14).

As can be seen, also in the case of these embodiments, the perimeter extension of the track 2 remains identical in the track configuration and in the wheel configuration, so that the track itself can also be made of non-extendable material, for example with links metal material.

Naturally, while the principle of the invention remains the same, the details of construction and the embodiments may widely vary with respect to what has been described and illustrated purely by way of example, without departing from the scope of the present invention.