Patent Description:
The present invention relates to a crawler vehicle, in particular used for the preparation of ski runs.

Generally speaking, a crawler vehicle of the kind identified above comprises a frame; a pair of motorized tracks; and a working tool coupled to the frame at the back thereof.

In case the crawler vehicle is used for the preparation of ski runs, the working tool comprises a tiller assembly, which is dragged by the crawler vehicle on a snowpack of the ski run and comprises a rotary shaft provided with a plurality of teeth to process the snowpack.

As it is known, the ideal preparation of a ski run involves processing the snowpack by means of the tiller assembly carried by the crawler vehicle, in order to eliminate possible unevenness of the snowpack and make it aesthetically appreciable.

During the processing of the snowpack, in order to follow the conformation of the ski run as efficiently as possible, the crawler vehicle needs to make turns, which can have an extremely variable radius.

Therefore, known crawler vehicles comprise a connection between the frame and the working tool, which allows the working tool to rotate relative to the frame, so as to prevent the working tool from creating resistances along bends, thus determining a scarce snowpack finishing quality.

<CIT> discloses a control system to selectively control the angular position of the working tool connected to the crawler vehicle at the back thereof along bends. In particular, the control system described therein, in response to a steering command, automatically causes the rotation of the working tool around a yaw axis, so that the working tool follows the same trajectory as the crawler vehicle in order to make it easier for it to steer.

However, the control system of <CIT> is particularly complicated to be used and installed on a known crawler vehicle and is scarcely reliable, especially in case the crawler vehicle is used for the preparation of a ski run on a slope.

An object of the invention is to provide a crawler vehicle, in particular for the preparation of ski runs, which reduces the drawbacks of the prior art discussed above.

In particular, an object of the invention is to provide a crawler vehicle provided with a working tool, which can be used in a simple and reliable fashion for the preparation of ski runs on a slope, so as to ensure an ideal quality of the processed snowpack.

According to the invention, there is provided a crawler vehicle, in particular for the preparation of ski runs; the crawler vehicle comprising:.

the control device being configured to calculate a value of the steering radius of the crawler vehicle and to control the actuation system so as to selectively perform at least one of the following actions:.

Thanks to this invention, the position of the working tool with respect to the frame can selectively be blocked/released in an automatic, simple and reliable manner, with no need for an intervention of the driver of the crawler vehicle.

Furthermore, due to the simplicity and reliability of the control device, said control device can be installed on known crawler vehicle.

More in detail, in case the crawler vehicle is used for the preparation of a ski run on a slope and proceeds along a straight trajectory, keeping the position of the working tool blocked, the working tool can be prevented from falling to the side because of its own weight, thus jeopardizing the quality of the processing of the snowpack.

On the contrary, in case the crawler vehicle is used for the preparation of a substantially flat ski run and/or proceeds along a curved trajectory, the free oscillation of the working tool around the frame allows the working tool to follow the same trajectory as the one covered by the crawler vehicle, this avoiding the lateral dragging of the working tool on the snowpack.

A further object of the invention is to provide a method to control a crawler vehicle, which reduces the drawbacks of the prior art discussed above.

According to the invention, there is provided a method to control a crawler vehicle as set forth in appended claim <NUM>.

Further features and advantages of the invention are defined in the appended dependent claims and will be best understood upon perusal of the following description of a non-limiting embodiment, with reference to the accompanying figures, wherein:.

With reference to <FIG>, number <NUM> defines, as a whole, a crawler vehicle, in particular used for the preparation of ski runs.

The crawler vehicle <NUM> comprises a frame <NUM> extending along a longitudinal axis A; a track <NUM> and a track <NUM>, which are both motorized; a speed sensor <NUM> and a speed sensor <NUM>, each associated with a respective track <NUM>, <NUM> in order to detect a speed signal indicative of the speed of said track <NUM>, <NUM>; a tilt sensor <NUM> configured to detect a tilt signal indicative of the inclination of the crawler vehicle <NUM>; a working tool <NUM>, which extends transversely and symmetrically with respect to a longitudinal axis A2 and is hinged at the rear of the frame <NUM> around a yaw axis A3; and an actuation system <NUM>, which is configured to act between the working tool <NUM> and the frame <NUM>.

In particular, the speed sensors <NUM> and <NUM> are configured to detect a speed difference between the track <NUM> and the track <NUM>.

According to a non-limiting embodiment of the invention, each speed sensor <NUM>, <NUM> is a pressure sensor configured to detect the pressure of a fluid supplied to a respective drive wheel, which determines the movement of a respective track <NUM> and <NUM>.

In particular, the tilt sensor <NUM> is configured to detect a pitch of the crawler vehicle <NUM> around an axis perpendicular to the longitudinal axis A1 and to the yaw axis A3 and to detect a roll of the crawler vehicle <NUM> around the longitudinal axis A1.

According to a non-limiting embodiment of the invention, the tilt sensor <NUM> is a gyroscope.

Furthermore, the crawler vehicle <NUM> comprises a shovel <NUM> mounted at the front on the frame <NUM>; a cabin <NUM> mounted on the frame <NUM>; and a command unit <NUM>, which is arranged inside the cabin <NUM>, can be operated by an operator of the crawler vehicle <NUM> and is configured to impart a steering command.

In the example described and shown herein, the command unit <NUM> comprises a joystick <NUM>.

The actuation system <NUM> comprises a pair of actuators <NUM> configured to act in an opposite manner. In particular, each actuator <NUM> is a pneumatic cylinder hinged, at an end, to the frame <NUM> and, at the other hand, to the working tool <NUM>.

In particular, the working tool <NUM> comprises an elongated arm <NUM>, which extends along the longitudinal axis A2 and is hinged, at an end, to the frame <NUM> around the yaw axis A3.

In the non-limiting embodiment of the invention described and shown herein, the working tool <NUM> comprises a tiller assembly <NUM> to process a snowpack of a ski run. In particular, the tiller assembly <NUM> comprises a rotary shaft, which is not shown in the accompanying figures, provided with a plurality of teeth, which are not shown in the accompanying figures, to process the snowpack.

In the configuration shown in <FIG>, the crawler vehicle <NUM> basically is a snow groomer.

More in detail, the crawler vehicle <NUM> is used for the preparation of ski runs for Alpine skiing and/or ski runs for cross-country skiing and/or ramps for ski jumping and/or half-pipes and/or snow-parks.

According to a further embodiment which is not shown in the accompanying figures, the crawler vehicle <NUM> can be used in agricultural operations, such as for example the harvesting and/or the handling of agricultural products and/or the ensilage of fodder and/or the harvesting and/or the handling of bagasse. In this configuration, the working tool <NUM> is configured to process the agricultural products laid on the ground.

Furthermore, according to a further embodiment which is not shown in the accompanying figures, the crawler vehicle <NUM> comprises a mulcher arranged on the front side of the vehicle and can be used to mulch plants.

With reference to <FIG>, the crawler vehicle <NUM> comprises a control device <NUM>, which is in communication with the one speed sensors <NUM> and <NUM> and with the tilt sensor <NUM> and comprises a memory <NUM> configured to store a reference interval for a steering radius of the crawler vehicle <NUM>.

The control device <NUM> is configured to calculate a value of the steering radius of the crawler vehicle <NUM>, in order to preferably vary the stored reference interval in real time as a function of the detected tilt signal, and to control the actuation system <NUM> so as to selectively:.

In particular, the command unit <NUM> is in communication with the control device <NUM> so as to transmit, to the control device <NUM>, a steering signal indicative of the imparted steering command.

With reference to <FIG>, the control device <NUM> is configured to calculate the value of the steering radius as a function of the speed signals detected by the speed sensors <NUM> and <NUM> and to control the actuation system <NUM> as a function of said speed signals.

Furthermore, the control device <NUM> is configured to vary the stored reference interval in real time as a function of the speed signals detected by the speed sensors <NUM> and <NUM>.

With reference to <FIG>, the control device <NUM> is configured to control the actuation system <NUM> so as to selectively bring the working tool <NUM> gradually back into alignment with the frame <NUM> when the value of the calculated steering radius does not fall within the reference interval.

The control device <NUM> is basically configured to align the longitudinal axis A2 of the working tool <NUM> with the longitudinal axis A1 of the frame <NUM>.

In particular, the control device <NUM> is configured to calculate a theoretical steering trajectory as a function of the imparted steering command and of the detected speed signals and to control the actuation system <NUM> so as to selectively bring the working tool <NUM> back into alignment with the frame <NUM> following said calculated theoretical trajectory when the calculated value of the steering radius does not fall within the reference interval.

More in detail, the control device <NUM> is configured to calculate, as a function of the detected speed signals, a time delay interval, which elapses between the time instant in which the calculated value of the steering radius falls within the reference interval and the time instant of activation of the actuation system <NUM> to bring the working tool <NUM> back into alignment with the frame <NUM>. The control device <NUM> is configured to control the actuation system <NUM> with a delay equal to the calculated time delay interval.

In use and with reference to <FIG>, a reference interval for a steering radius of the crawler vehicle <NUM> is stored in the memory <NUM> (block <NUM>). In particular, said reference interval is defined for the purpose of preventing the activation of the actuation system <NUM> with every small steering correction by a driver of the crawler vehicle <NUM>.

While the crawler vehicle <NUM> proceeds on a ski run to be processed, the speed sensors <NUM> and <NUM> detect the speed of the tracks <NUM> and <NUM> respectively (blocks <NUM> and <NUM>) and the tilt sensor <NUM> detects the inclination of the crawler vehicle <NUM> (block <NUM>). In particular, the inclination sensor <NUM> detects a pitch angle and a roll angle, each defined with respect to a Cartesian reference system having two axes belonging to an ideal horizontal plane.

The control device <NUM> calculates a moving speed (block <NUM>) of the crawler vehicle <NUM> and a steering radius value (block <NUM>) of the crawler vehicle <NUM> as a function of the detected speeds of the tracks <NUM> and <NUM>.

Subsequently, starting from the stored reference interval, the control device <NUM> calculates a variation in the reference interval (block <NUM>) as a function of the detected inclination of the crawler vehicle <NUM> and of the calculated speed of the crawler vehicle <NUM>.

By way of example, when the crawler vehicle <NUM> proceeds downhill along a ski run on a slope, the control device <NUM> reduces the reference interval with respect to the situation in which the crawler vehicle <NUM> moves along a substantially flat ski run, so as to prevent the working tool <NUM> from falling to the side because of its own weight.

On the contrary, as the moving speed of the crawler vehicle <NUM> increases, the control device <NUM> widens the reference interval in order to avoid excess stresses for the working tool <NUM>.

At this point, the control device <NUM> compares the calculated steering radius value with the reference interval (block <NUM>).

In case the calculated value of the steering radius is outside the reference interval, the control device <NUM> controls the actuators <NUM> so as to keep the position of the working tool <NUM> with respect to the frame <NUM> blocked (block <NUM>). In particular, the actuators <NUM> keep the longitudinal axis A2 of the working tool <NUM> aligned with the the longitudinal axis A1 of the frame <NUM>.

On the contrary, in case the calculated value of the steering radius is within the reference interval, the control device <NUM> controls the actuators <NUM> so as to allow the working tool <NUM> to freely oscillate around the yaw axis A3 (block <NUM>).

With reference to <FIG>, in case the calculated value of the steering radius is outside the reference interval, the control device <NUM> evaluates whether the longitudinal axis A2 of the working tool <NUM> is aligned with the longitudinal axis A1 of the frame <NUM> (block <NUM>).

If it is, the control device <NUM> controls the actuators <NUM> so as to keep the position of the working tool <NUM> with respect to the frame <NUM> blocked (block <NUM>).

If it is not, the control device <NUM> detects the steering command (block <NUM>) imparted by the command unit <NUM>.

Subsequently, the control device <NUM> calculates a theoretical steering trajectory (block <NUM>) and a time delay interval (block <NUM>) as a function of the speed signals detected by the speed sensors <NUM> and <NUM> and as a function of the detected steering command.

In particular, the time delay interval elapses between the time instant in which the calculated value of the steering radius falls within the reference interval and the time instant of activation of the actuation system <NUM> to bring the working tool <NUM> back into alignment with the frame <NUM>. Said time delay interval has the function of preventing the working tool <NUM> from going back into alignment with the frame <NUM> too quickly, thus determining a scarce quality of processing of the snowpack.

Once the time delay interval and the theoretical steering trajectory have been calculated, the control device <NUM> activates the actuators <NUM> so as to bring the working tool <NUM> back into alignment with the frame <NUM> (block <NUM>) following said theoretical trajectory calculated with a delay that is equal to the calculated time delay interval.

At this point, the control device <NUM> controls the actuators <NUM> so as to block the position of the working tool <NUM> with respect to the frame <NUM> (block <NUM>).

<FIG> shows the crawler vehicle <NUM> while driving along a bend with a steering radius R, which is comprised within the reference interval. In this operating configuration, the working tool <NUM> is free to oscillate around the yaw axis A3 so as to follow the trajectory of the bend.

<FIG> shows the crawler vehicle <NUM> while moving along a given trajectory having a plurality of segments T1, T2, T3 and T4.

In particular, along the straight segment T1, the actuation system <NUM> keeps the position of the working tool <NUM> blocked with respective to the frame <NUM>. Under this circumstance, the longitudinal axis A2 of the working tool <NUM> is aligned with the longitudinal axis A1 of the frame <NUM>.

Along the curved segment T2, the value of the steering radius is within the reference interval and the control device <NUM> controls the actuation system <NUM> so as to allow the working tool <NUM> to freely oscillate around the yaw axis A3.

When shifting from the curved segment T2 to the straight segment T3, the value of the steering radius is outside the reference interval. Under this circumstance, the control device <NUM> controls the actuation system <NUM> so as to gradually bring the working tool <NUM> back into alignment with the frame <NUM>. In particular, the control device <NUM> controls the actuation system <NUM> so as to bring the working tool <NUM> back into alignment with the frame <NUM> following a calculated theoretical trajectory and with a delay that is equal to a calculated time delay interval.

Once they are aligned, the actuation system <NUM> keeps the position of the working tool <NUM> blocked with respect to the frame <NUM> for the entire length of the straight segment T3.

Along the segment T4, the value of the steering radius goes back to falling within the reference interval and, as a consequence, the control device <NUM> controls the actuation system <NUM> so as to allow again the working tool <NUM> to freely oscillate around the yaw axis A3. In this way, the working tool <NUM> is capable of following the trajectory determined by the series of bends in succession of the segment T4.

Claim 1:
A crawler vehicle, in particular for preparing ski runs; the crawler vehicle (<NUM>) comprising:
- a frame (<NUM>) extending along a first longitudinal axis (A1)
- a first and a second motorized track (<NUM>, <NUM>);
- at least one speed sensor (<NUM>; <NUM>) to detect a speed difference between the first track (<NUM>) and the second track (<NUM>);
- a working tool (<NUM>), which extends transversely and symmetrically with respect to a second longitudinal axis (A2) and is hinged at the rear of the frame (<NUM>) about a yaw axis (A3) ;
- an actuation system (<NUM>), which is configured to act between the working tool (<NUM>) and the frame (<NUM>); and
- a control device (<NUM>), which is in communication with the at least one speed sensor (<NUM>; <NUM>)
characterised in that <NUM>
the control device (<NUM>) comprises a memory (<NUM>) configured to store a reference interval for a steering radius of the crawler vehicle (<NUM>);
the control device (<NUM>) being configured to calculate a value for a steering radius of the crawler vehicle (<NUM>) and to control the actuation system (<NUM>) so as to selectively perform at least one of the following actions:
- allowing the free oscillation of the working tool (<NUM>) about the yaw axis (A3) when the calculated value of the steering radius is comprised within the reference interval;
- keeping the position of the working tool (<NUM>) blocked with respect to the frame (<NUM>) when the calculated value of the steering radius is outside the reference interval, preferably so that the second longitudinal axis (A2) of the working tool (<NUM>) is aligned with the first longitudinal axis (A1) of the frame (<NUM>) .