The present invention relates to a safety device and a safety method for farm machines and to the corresponding farm machine.

In the agricultural sector, farm machines, termed straw balers or round balers, are known which are designed to pick up and bale (and optionally cut up) materials such as straw, hay, forage and the like.

For these purposes, round balers are equipped, frontally along the advancement direction, with an apparatus for picking up the materials cited above, which is typically constituted by a working shaft, which rotates about an axis that is parallel to the ground and is provided with a plurality of teeth capable of picking up and lifting the hay, straw, forage, etcetera.

After being collected (and optionally pressed and cut up by means of a further rotor, or other similar device), the material is rearranged on a central supply channel by the action of screw feeders. From this channel, the material is finally transferred toward a chamber in which the bale is formed, typically (but not exclusively) with a circular shape.

This constructive solution, however, is not without drawbacks.

During operation an occasional excessive build-up of material at a transverse portion of the working shaft may cause the jamming and sudden locking of said shaft even though the power unit (arranged upstream of the power take-off unit with which these farm machines are typically provided) is still active.

Faced with this eventuality, often the operator who controls and drives the round baler stops the advancement of the machine and takes care personally of the removal of the jam.

In order to do this, he gets close to the working shaft and, with his hands or feet, moves the material in order to free the affected portion of the working shaft from the material accumulated therein.

If he, carelessly and in order to shorten working time, performs this activity without having first stopped the drive unit, it is clear that this procedure proves to be highly dangerous. In fact, the removal of the constraint to the rotation of the working shaft restores immediately the transmission of power and therefore causes the restarting of the previously locked elements, with consequent danger of injury or death of the operator.

The Applicant filed on 15 December 2011 Italian patent application BO2011A000716, which describes a safety device capable of partly solving the drawback cited above.

This device provides in fact for the use of a movable retention element and of a complementary retention element, which is keyed on the output shaft of the power take-off (associated with the working shaft).

The retention element can be arranged on command so as to interfere with the path of the complementary retention element, in order to cause, in case of restarting of the rotation of the output shaft (and therefore of the complementary retention element) as a consequence of the removal of the jam, the almost immediate forced stopping of the output shaft itself and of the working shaft with it.

Moreover, the application also describes the presence of a unit for damping the forced locking caused by the abutment of the complementary retention element against the retention element, which can be actuated automatically upon mutual impact, in order to cushion its effects, thus solving other known drawbacks of safety devices of the known type, which expose the involved elements to violent and unwanted stresses.

Moreover, according to the constructive solution described in the cited application of the Applicant, the movement of the pivot, in order to place it in the above-cited interference arrangement, was entrusted to a bar, arranged frontally to the working shaft, so that the operator could easily press it before approaching said shaft, so as to proceed with the attempt to remove the jam only after actuating the safety device.

Even this constructive solution, however, is not free from drawbacks. In this solution, in fact, the operator must take care manually to operate on the retention element, by means of the bar, in order to then proceed with the removal of the jam.

Vice versa, the safety rules with which farm machines such as the one described above must comply require the safety devices to be capable of intervening in advance, in practice "forcing" the operator, who wishes to remove the constraint manually, to work in absolute safety, without the possibility of bypassing the provided safety measures.

On the other hand, a constructive solution that entails the simple stopping of the tractor following the detection of a jam would not be welcomed, because it would force the operator to stop frequently, who would be forced to climb down from his seat to remove the jam manually, with consequent inconveniences, physical efforts and delays, although it is often sufficient for the operator to wait a few seconds, without climbing down from his seat, for the impulses of the drive unit to clear autonomously the rotating shaft from the mass of accumulated material.

The aim of the present invention is to solve the problems cited above, providing a safety device that allows an operator to remove in absolute safety an accidental jamming of the working shaft.

Within this aim, an object of the invention is to propose a safety method that allows an operator to remove in absolute safety an accidental jamming of the working shaft.

Another object of the invention is to propose a farm machine that allows an operator to remove in absolute safety an accidental jamming of the working shaft.

A further object of the invention is to provide a device that offers the operator the possibility of waiting for the automatic removal of the jam.

A further object of the invention is to propose a method that ensures high reliability in operation, in practice preventing the operator from being able to bypass the method. Another object of the invention is to provide a device that can be obtained easily starting from commonly commercially available elements and materials.

Yet another object of the invention is to propose a method that can be performed easily and at low cost.

This aim and these and other objects are achieved by a safety device for farm machines provided with an apparatus for treating materials of the type of agricultural products, equipped with at least one rotating working shaft which faces the ground and is proximate thereto and is provided with means for treating the materials, said device comprising at least one movable element for actuating the interruption of the transmission of power from a drive unit of the working shaft to the working shaft itself, said actuation element being movable from a passive configuration, for free power transmission, to an active configuration, for interruption of power transmission, and vice versa, characterized in that it comprises an automatic apparatus for the timed actuation of the transition of said actuation element from said passive configuration to said active configuration, said automatic apparatus comprising at least first means for detecting the rotation rate of said working shaft and second means for detecting the rotation rate of a driving shaft, comprised in said drive unit, said detection means being controlled by an electronic unit for the control and actuation of a mechanism for the movement of said actuation element, said electronic unit being provided with a module for comparing the rotation rates for the timed sending, after a preset delay time monitored by a respective timer, of the command for transition of said movable element from said passive configuration to said active configuration, following the detection of a variation between the rates that exceeds a preset reference parameter, which represents a jamming of the working shaft, said delay time being shorter than the time estimated for manual intervention by an operator to remove the jam. This aim and these and other objects are achieved also by a farm machine, comprising an apparatus for treating materials of the type of agricultural products, equipped with at least one rotating working shaft which faces the ground and is proximate thereto, is provided with means for treating the materials and has a safety device that comprises at least one movable element for actuating the interruption of the transmission of power from a drive unit of said working shaft to the working shaft itself, said actuation element being movable from a passive configuration, for free power transmission, to an active configuration, for interruption of power transmission, and vice versa, characterized in that said safety device comprises an automatic apparatus for the timed actuation of the transition of said actuation element from said passive configuration to said active configuration, said automatic apparatus comprising at least first means for detecting the rotation rate of said working shaft and second means for detecting the rotation rate of a driving shaft, comprised in said drive unit, said detection means being controlled by an electronic unit for the control and actuation of a mechanism for the movement of said actuation element, said electronic unit being provided with a module for comparing the rotation rates for the timed sending, after a preset delay time monitored by a respective timer, of the command for transition of said movable element from said passive configuration to said active configuration, following the detection of a variation between the rates that exceeds a preset reference parameter, which represents a jamming of said working shaft, said delay time being shorter than the time estimated for manual intervention by an operator to remove the jam.

This aim and these objects are also achieved by a safety method for farm machines provided with an apparatus for treating materials of the type of agricultural products, equipped with at least one rotating working shaft, which faces the ground and is proximate thereto and is provided with means for treating materials, which consists in detecting, in a step a., the rotation rate of the working shaft; in monitoring, in a step b., the rotation rate of a driving shaft, comprised in a drive unit, through a respective kinematic transmission chain, of the working shaft, substantially simultaneously with said detection step a; in performing, in a step c, a comparison between the rotation rates by means of an electronic control and actuation unit provided with a respective comparison module; in sending, in a step d., after a preset delay time from the detection of a variation between the rates that exceeds a preset reference parameter, which is representative of a jamming of the working shaft, the command for activation of a mechanism for moving at least one movable element for actuating the interruption of the transmission of power from a drive unit of the working shaft to the actuation shaft itself, the actuation element being movable from a passive configuration, for free power transmission, to an active configuration, for interrupting the transmission of power, and vice versa, said delay time being preferably shorter than the time estimated for manual intervention by an operator to remove the jam.

Further characteristics and advantages of the invention will become more apparent from the description of a preferred but not exclusive embodiment of the safety device and of the farm machine according to the invention, illustrated by way of non- limiting example in the accompanying drawings, wherein:

Figure 1 is a perspective view of the safety device according to the invention and of some components of the farm machine on which is installed;

Figure 2 is a top view of the safety device of Figure 1 ;

Figure 3 is a perspective view of a detail of Figure 1 ,

Figure 4 is a top view of the detail of Figure 3 ;

Figure 5 is a front elevation view of the detail of Figure 3;

Figure 6 is a lateral elevation view of the detail of Figure 3;

Figure 7 is a schematic lateral elevation view of the farm machine according to the invention;

Figure 8 is a schematic view of a possible method of operation of the electronic unit.

With reference to the cited figures, the safety device according to the invention, generally designated by the reference numeral 1, is designed (preferably, but not exclusively) to be installed on farm machines 2, of the type that comprises an apparatus 3 for treating materials of the type of agricultural products, equipped with at least one rotating working shaft 4 which in turn faces the ground and is proximate thereto and is provided with means 5 for treating said materials.

It is useful to note right now that according to the preferred but not exclusive application of the present invention, the farm machine 2 is of the type of straw balers, round balers and the like, which are designed to pick up materials such as hay, straw and forage, by means of said apparatus 3, and to then transfer them and press them, by means of a conveyance unit typically provided with mutually opposite screw feeders that surmount the apparatus 3, and with other pressing and shredding rotors, to a chamber 6 for forming the bale, which is arranged at the rear of the apparatus 3.

According to this preferred application, therefore, the working shaft 4 is arranged parallel to the ground (and at right angles to the advancement direction of the machine 2) and is provided with treatment means 5 constituted by a plurality of teeth 7, capable of picking up and lifting the hay and straw that the machine 2 encounters progressively during its advancement.

With further reference to the preferred application, the farm machine

2 is designed to be towed by a tractor or other motorized vehicle, to which the machine 2 can be anchored stably by brackets 8 or other engagement elements.

It is noted that the installation of the device 1 according to the invention (which in any case falls within the protective scope claimed herein) in other types of farm machines 2 (even provided with independent motor drive) or in different fields of application, depending on the specific requirements, is not excluded.

The device 1 comprises at least one movable element for actuating the interruption of the transmission of power from a drive unit of the working shaft 4 to the working shaft 4 itself; more precisely, said actuation element is movable from a passive configuration, for free power transmission, to an active configuration, for interruption of power transmission, and vice versa.

It is therefore possible (and within the protective scope claimed herein) to use the safety device 1 on farm machines 2 provided with any type of actuation element (for example, a clutch, a brake, or other type of disengagement element), in any case capable of operating in order to decouple the drive unit from the working shaft 4, even according to known methods.

In the paragraphs that follow, a brief description will be given of a possible embodiment of the actuation element and of the other components associated therewith, as illustrated in the accompanying figures and substantially in analogy to what is described in the already cited Italian patent application BO201 1A000716 filed by the same Applicant, to which reference should be made for further details.

More precisely, according to this constructive solution, the safety device 1 comprises therefore an actuation element constituted by a retention element 9, which can move on command from a passive configuration to an active configuration, and vice versa, and operates on a complementary retention element 10, which can be functionally associated with a kinematic transmission chain 1 1 , which is interposed between the already cited drive unit of the working shaft 4 and the working shaft 4 itself, in order to place the working shaft 4 under the control of the complementary retention element 10.

Reference will be made repeatedly in the continuation of present description to the constructive solution that entails an actuation element constituted by the retention element 9, but, as already observed, devices 1 that entail the use of different types of actuation elements fall within the protective scope claimed herein.

In the passive configuration, the retention element 9 is spaced from the complementary retention element 10, so as to allow the free rotation of the complementary retention element 10 and of the working shaft 4 and therefore the free transmission of power.

Vice versa, in the active configuration (shown in the accompanying figures), the retention element 9 is arranged so as to interfere with respect to the path of the complementary retention element 10, so as to cause, in ways that will be described in more detail hereinafter, the forced locking of the complementary retention element 10 itself and consequently of the working shaft 4 (with consequent interruption of the transmission of power).

Moreover, at least one of the retention element 9 and the complementary retention element 10 is associated with a unit 12 for damping the above-mentioned forced locking of the complementary retention element 10 and of the working shaft 4 (but more generally of all the functional units arranged downstream of the complementary retention element 10), which can be actuated automatically upon the impact of the retention element 9 with the complementary retention element 10, in order to cushion this impact and avoid the danger of subjecting the elements involved to violent stresses.

It should be noted furthermore that the possibility is not excluded of providing safety devices 1 according to the invention that have different types of retention elements 9, complementary retention elements 10 and damping units 12, as a function of the specific requirements, without thereby abandoning the protective scope claimed herein.

With reference to the constructive solution proposed in the accompanying figures, therefore, the retention element 9 is substantially constituted by an arm 13, which can be articulated to a supporting plate 14a about a first pivot 15 and can therefore oscillate from the passive configuration, in which the arm 13 is spaced from the complementary retention element 10, to the active configuration, and vice versa.

In the active configuration, a first end portion of the arm 13, which is substantially opposite the first pivot 15, is arranged along the stroke of at least one shoulder 16, which protrudes externally from a rotating disk 17, which substantially constitutes the complementary retention element 10 and can be keyed on the output shaft of the power take-off 18 of the farm machine 2: the output shaft is comprised in the above-cited kinematic transmission chain 11 and therefore is also designed to transmit the motion to the working shaft 4, for example by means of a subsequent main transmission shaft 1 1a, arranged downstream of the output shaft and associated therewith by means of suitable gears.

In fact, as is known, the power take-off 18 is the element by means of which the drive unit of the tractor or of another motorized vehicle (to which, according to the solution proposed and described herein by way of non- limiting example, the machine 2 can be anchored thanks to the brackets 8) can actuate the various functional units that operate on the farm machine 2 coupled thereto, by means of a mechanical rotary movement and thanks to a Cardan transmission shaft 18a.

In the active configuration, therefore, the retention element 9 is capable of stopping forcibly the rotation of the complementary retention element 10 (of the disk 17) and therefore the rotation of the output shaft of the power take-off 18, thus stopping the transmission of power to all the functional units of the machine 2, including, as mentioned earlier, the working shaft 4.

More particularly, in the solution proposed in the accompanying figures, the disc 17 has a pair of shoulders 16, formed by opposite parts of its circumferential rim: in this manner, a rotation of the disk 17, when the arm 13 is arranged in the active configuration, brings one of the shoulders 16 into abutment with the first end portion cited above, with the consequent forced locking of the disk 17 and, consequently, of the working shaft 4.

In practice, therefore, when the arm 13 is arranged in the active configuration, the disk 17 is allowed only a rotation equal to the angular distance between two consecutive shoulders 16 provided on its rim.

Usefully, the supporting plate 14a cited above is articulated to a fixed body of the farm machine 2 about a second pivot 19: upon the abutment (impact) of one of the shoulders 16 at the first end portion, the plate 14a and the arm 13 (before their forced stopping) are thus entrained in oscillation by the disk 17 (about the second pivot 19) up to a stroke limit, on which the forced locking of the disk 17 occurs.

The damping unit 12 comprises therefore at least one elastic element, associated with the arm 13, the elastic reaction of which contrasts said stroke in order to soften the forced locking of the working shaft 4 and of the other functional units associated with the kinematic chain 11 and/or arranged downstream of the power take-off 18.

According to a possible constructive solution, as shown in the accompanying figures, the plate 14a is articulated to a reference complementary plate 14b, which can be fixed to the chassis of the machine 2 and with respect to which the plate 14a itself can thus rotate (by oscillating).

For example, said elastic element can be constituted by at least one Belleville spring 20 (or by a plurality thereof, depending on the specific constructive requirements), which is fixed with its base (which defines said stroke limit) to the chassis of the farm machine 2 and can abut, at the opposite end, against a transverse plate 14c, which protrudes from both sides of the plate 14a.

It is specified, moreover, that the possibility of providing devices 1 in which the damping unit 12 is of a different type is not excluded and is in any case within the protective scope claimed herein.

In any case, once the arm 13 has been moved into this active configuration, if the operator subsequently manages to clear the working shaft 4, removing the unwanted build-up of material, any sudden restarting of the rotation of said working shaft 4 is almost instantaneously and forcibly stopped. In fact, the rotation of the disk 17 moves quickly one of its shoulders 16 into abutment against said first end portion 13a of the arm 13, thereby causing the locking of the rotation of the disk 17 and of the working shaft 4.

Normal operation can therefore be restored by stopping the drive unit in order to then proceed with the transition of the retention element 9 from the active configuration to the passive configuration.

According to the invention, the safety device 1 comprises an automatic apparatus for the timed actuation of the transition of the actuation element (for example constituted by the retention element 9) from the passive configuration to the active configuration; more precisely, said automatic apparatus comprises, first of all, at least first means for detecting the rotation rate of the working shaft 4 and second means for detecting the rotation rate of a driving shaft (arranged upstream of the working shaft 4 and of the output shaft already described), comprised within the working assembly.

The detection means described above (a possible embodiment of which that is non-limiting of the application of the invention will be described in the continuation of the present description), are controlled by an electronic control and actuation unit, constituted for example by an electronic controller (which can be part of the main one, which controls the entire farm machine 2, or a separate controller dedicated to the specific task described herein).

In turn, the electronic unit is capable of controlling and actuating a mechanism 21 for moving the retention element 9 (or other actuation element); the electronic unit is therefore provided with a module for comparing the rotation rates cited above, so as to be able to perform the timed sending, after a preset delay time monitored by a respective timer, of the command for transition of the retention element 9 from the passive configuration to the active configuration, following detection of a variation between the rates that exceeds a preset reference parameter and represents a jam of the working shaft 4.

In fact, in case of a jam (caused for example by an unwanted and excessive build-up of straw, hay and the like, between the teeth 7) that involves the working shaft 4, a deviation occurs between the rates of rotation of the working shaft, which stops, and the rate of rotation of the driving shaft, which instead remains active (because said driving shaft is arranged, as already noted, upstream of the clutch that takes care of the uncoupling between the working shaft 4 and the drive unit following the jam).

More precisely, the disengagement can be provided by a normal radial pin clutch that operates on the working shaft 4 (and is interposed between the working shaft 4 and the driving shaft), capable of disengaging it from the drive unit upon detection of a limit torque that corresponds to a jam that involves the working shaft 4.

It is possible therefore to monitor in each instant the two rotation rates, conveniently fixing a reference parameter in order to detect immediately a difference between the number of rotations (that corresponds to the undesired stopping of the working shaft 4) that occurs due to a jam.

For reasons that will become more apparent in the following paragraphs, this delay time is chosen preferably to be shorter than the time estimated for manual intervention by an operator to remove the jam.

In particular, the preset delay time is chosen preferably in an interval comprised between 5 seconds and 10 seconds and even more preferably is equal to 8 seconds. The choice of the duration of the delay time, before the safety device 1 operates on the retention element 9, causing, as already shown, its transition into the active configuration, is made so as to leave available to the operator the seconds (indeed just a few) needed in order to wait for an optional self-restarting of the working shaft 4 (if, under the thrust of the driving shaft, which is still active, the material that has built up is not removed automatically).

This eventuality in fact occurs frequently, and it would be therefore very inconvenient for the operator to have to climb down every time from his driving seat, when, indeed, waiting a few seconds often proves to be a solution to the problem.

First of all, therefore, the delay time is kept sufficiently long to allow the automatic reactivation of the normal operation of the machine 2.

However, as anticipated in the previous paragraphs, the delay time is preferably chosen to be shorter than the time that one estimates necessary for the operator to climb down to take care of the manual removal of the built-up material, which prevents free rotation.

In this manner, the safety device 1 according to the invention allows an operator to solve in absolute safety an accidental jam of the working shaft 4: in fact, if he decides to remove manually the excess material, the delay time after which the electronic unit arranges the retention element 9 in the active configuration is still shorter than the time that the operator needs to climb down from his seat and approach the working shaft 4, which operates therefore in absolute safety, achieving thereby the intended aim, even without the operator having to carry through any particular action in this regard.

According to the preferred constructive solution, which is non- limiting for the application of the invention, the first means comprise a first sensor for detecting the rotation rate of a first phonic wheel, which can be keyed on the working shaft 4, and likewise the second means comprise a second sensor for detecting the rotation rate of a second phonic wheel, that can be keyed in turn on the driving shaft.

It is noted that the protective scope claimed herein includes the use of any known type of phonic wheel (and consequently of corresponding specific types of detecting sensors): for example, the detection means can comprise phonic wheels of the inductive type, or optical phonic wheels, capacitive phonic wheels, etcetera, and likewise the use of other components adapted to detect the rotation rate of the working shaft 4 and of the driving shaft is not excluded.

Whatever the choice of detection means adopted, the sensors are controlled by the controller (or other electronic unit), so as to send in each instant respectively the values of the rotation rate of the working shaft and of the driving shaft, in order to allow the desired comparison, and the intervention already described, in case of a jam.

Usefully, with further reference to the preferred solution, which does not, however, limit the application of the invention, the movement mechanism 21 is constituted substantially by an electromagnetic actuator

22, which is controlled by the electronic unit and is provided with a piston 23 fixed at one of its ends to the retention element 9. It is useful to note that the possibility is not excluded, and is in any case within the protective scope claimed herein, to use different types of movement mechanisms 21 : for example, the movement mechanism 21 might be constituted by a hydraulic cylinder, provided with a respective electric valve, or by a different element, as a function of the specific requirements of application.

With further reference to the solution that entails the use of a piston

23, said piston can slide (inside the actuator 22) between a first limiting position, in which the retention element 9 is arranged in the already cited passive configuration, and a second limiting position, in which the retention element 9 is arranged correspondingly in the active configuration (illustrated in the accompanying figures), and vice versa, in ways that will be illustrated in more detail in the following paragraphs.

Usefully, the safety device 1 comprises an elastic element, of the type of a helical spring 24 and the like, which is coupled to the retention element 9 and capable therefore of keeping it elastically in the active configuration upon shutdown of the electronic unit.

The sequence of the movements of the retention element 9 under the operation of the piston 23 and of the helical spring 24 is therefore as follows: when the controller is off or deactivated, the helical spring 24 keeps the retention element 9 in the active configuration (and therefore the piston 23 in the second limiting position).

This prevents the farm machine 2 from operating without having first activated the controller (and therefore without having reached the safety conditions offered thereby and described above), because the retention element 9 can only move to the passive configuration when the controller is on.

When the controller is activated, in fact, it actuates the transition of the piston 23 from the second limiting position to the first limiting position, thus moving the retention element 9 to the passive configuration and allowing therefore the normal operation of the farm machine 2.

At a subsequent jam of the working shaft 4, the electronic unit actuates the new transition of the retention element 9 from the passive configuration to the active configuration simply by deactivating the operation of the piston 23, thus releasing the retention element 9 itself, which, under the action of the helical spring 24, returns to the active configuration (entraining the piston 23 into the second limiting position), so as to interfere with the complementary retention element 10 and prevent its immediate restarting once the problem has been solved.

For further safety, it is possible to provide the safety device 1 with a control microswitch, arranged on the retention element 9, which checks its correct position upon controller power-on. As already observed, in fact, when the controller is off the retention element 9 must be in the active configuration: the purpose of the control microswitch is indeed to verify this condition, and only when it is met (which corresponds to correct operation of the safety device 1 according to the invention) does the controller ensure movement of the piston 23 to the first limiting position and therefore of the retention element 9 to the passive configuration.

Advantageously, the safety device 1 also comprises an actuation element 25, which can be activated manually by an operator, for the transition of the retention element 9 from the passive configuration to the active configuration.

In particular, the actuation element 25 is constituted preferably by an oscillating bar 26, which can be arranged in front of and parallel to the working shaft 4 and is associated with a microswitch for actuating the forced transition of the retention element 9 from the passive configuration to the active configuration.

This oscillating bar 26 (thanks to the actuation microswitch, connected to the electronic unit) can thus allow the operator to proceed directly with the movement of the retention element 9, for example in order to remove partial jams (that do not involve the entire length of the working shaft 4).

Positively, the electronic unit is provided with a function for resetting the count of the preset delay time (by the above-mentioned timer), which can be activated automatically when the electronic unit itself detects the stopping and subsequent restarting of the drive unit.

The possibility offered by the function described above allows the operator to defer the actuated transition of the retention element 9 from the passive configuration to the active configuration, in order to wait thus for a higher number of seconds for the possible automatic restarting of the rotation shaft 4. Obviously, in order to make use of this possibility, the operator, who is sitting in his driving seat, is called upon to actuate a lever (or other actuation element usually provided in farm machines 2) designed to turn on and off the drive unit responsible for the movement of the working shaft 4 and of the other functional units, before the entire delay time passes (for example, therefore, within 5-6 seconds from the stopping of the working shaft 4).

In this manner, following a jam, and after a few seconds, the operator can turn off and on again the drive unit to reset its timer and have additional seconds available in order to wait for a possible automatic restart, substantially according to the diagram shown in Figure 8, which shows the viewer 27 of the electronic unit, which reports the seconds missing before the actuated transition of the retention element 9 from the passive configuration to the active configuration.

Moreover, this function can be deactivated automatically, by the electronic unit itself, as a consequence of the detection of a time interval, between the stopping of the drive unit and the subsequent restarting, that is longer than a preset safety time.

For example, said preset safety time is chosen preferably in an interval comprised between 5 seconds and 15 seconds and even more preferably is chosen to be equal to 9 seconds (as indeed shown in the accompanying Figure 8), in any case substantially shorter than the time interval required (by the operator) to disassemble the controller and climb down from the driving seat, taking the controller with him, in order to bypass the provided safety features.

In fact, if the operator had the possibility of resetting the timer at will, without further controls, he might decide to bypass the provided safety features by stopping first the drive unit before the delay time has elapsed (thus preventing the controller from moving the retention element 9 to the active position). Then he might disassemble the controller, in order to bring it to the ground while he manually removes the jam, using at the same time other controls, arranged typically on the rear fender of farm machines 2 of the known type, to restart the drive unit with consequent resetting of the count, avoiding indefinitely the transition of the retention element 9 from the passive configuration to the active configuration.

Indeed to prevent this improper use of the safety device 1 according to the invention, the safety time is chosen equal to a few seconds: this safety time is in fact shorter than the one needed to disassemble the controller, climb down from the driving seat and arrange oneself proximate to the working shaft 4; once this safety time has elapsed, a subsequent restarting of the drive unit would be detected as abnormal by the electronic unit, causing immediately (or at most after 8 seconds) the transition of the retention element 9 from the passive configuration to the active configuration.

The farm machine according to the invention comprises an apparatus

3 for treating materials of the type of agricultural products that is equipped with at least one rotating working shaft 4 which faces the ground and is proximate thereto and is provided with means 5 for treating the materials.

The farm machine 2 has, moreover, a safety device 1 that comprises at least one movable actuation element (for example a retention element 9 of the type described on the preceding pages) for actuating the interruption of the transmission of power from a drive unit of the working shaft 4 to the working shaft 4 itself. Said actuation element is movable from a passive configuration, for free power transmission, to an active configuration, for interrupting the transmission of power, and vice versa.

According to the invention, the safety device 1 comprises an automatic apparatus for the timed actuation of the transition of the actuation element from the passive configuration to the active configuration. This automatic apparatus comprises at least first means for detecting the rotation rate of the working shaft 4 and second means for detecting the rotation rate of a driving shaft, comprised within the working assembly. The detection means are controlled by an electronic unit for the control and management of a mechanism 21 for moving the actuation element. In this manner, the electronic unit, which is provided with a module for comparing the rotation rates, can proceed with the timed sending, after a preset delay time monitored by a respective timer, of the command for the transition of the actuation element from the passive configuration to the active configuration, following the detection of a variation between the rates that exceeds a preset reference parameter.

This variation corresponds preferably to a jam of the working shaft 4, and this delay time is preferably shorter than the time estimated for manual intervention by an operator to remove the jam.

The safety method for farm machines 2 provided with an apparatus 3 for treating materials such as farm products and equipped with at least one rotating working shaft 4, which faces the ground and is proximate thereto and is provided with means 5 for treating materials consists, in a first step a., in detecting the rotation rate of the working shaft 4 (for example according to the methods already described).

Moreover, the method entails, in a step b. (to be performed substantially simultaneously with the above-mentioned step a.), monitoring the rotation rate of a driving shaft, which is comprised in a drive unit of the working shaft 4, with which it is associated by means of a respective kinematic transmission chain 11.

The method according to the invention entails then, in a step c, comparing the rotation rates by means of an electronic control and management unit provided with a respective comparison module.

If a deviation between the rates that exceeds a preset reference parameter representative of a jam of the working shaft 4 is detected, the safety method according to the invention entails then, in a step d., sending, after a preset delay time, the command for activation of a mechanism 25 for moving at least one movable element (for example the retention element 9 already described) for actuating the interruption of the transmission of power from a drive unit of the working shaft 4 to the working shaft 4 itself.

This delay time is preferably shorter than the time estimated for manual intervention by an operator to remove the jam.

The actuation element is movable from a passive configuration, for free power transmission, to an active configuration, for interrupting the transmission of power, and vice versa.

In practice it has been found that the device, the machine and the method according to the invention fully achieve the intended aim and objects, since by resorting to the automatic apparatus for timed actuation described on the previous pages, if the operator wishes to intervene manually on the working shaft 4 of a farm machine 2 he will find himself inevitably operating in absolute safety conditions, with the actuation element arranged in a configuration that prevents power transmission from the drive unit to the working shaft, therefore making it impossible to witness a dangerous and sudden restarting of the rotation of the working shaft 4.

After the transition of the retention element 9 (or other actuation element) from the passive configuration to the active configuration, in fact, only by stopping the drive unit is it possible to proceed with the manual reactivation of the active configuration and therefore with the restarting of the normal operation.

Moreover, the choice of a delay time equal to a few seconds makes it possible to wait for any automatic restart of the rotation of the working shaft 4, avoiding therefore a useless waste of time by the operator, who might climb down from his seat just when the jam is automatically removed.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may furthermore be replaced with other technically equivalent elements. In the exemplary embodiments, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other exemplary embodiments.

In practice, the materials used, as well as the dimensions, may be any according to the requirements and the state of the art.

The disclosures in Italian Patent Application No. BO2012A000193 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.