The invention relates to a process of operating the air conditioning system of a cab of a machine, and a machine, in particular an agricultural machine, comprising a cab equipped with an air conditioning system which is adapted to be operated according to such a process.

It applies in particular to the technical domain of mechanical or pressurized spreading of treatment products, such as phytosanitary products, insecticides or fertilizers, on the harvest plants and/or the plowed soil of an agricultural field, such as a vineyard or an orchard.

To do so, land agricultural machines are known, comprising a motorized support structure which is equipped with a driver station and movable in particular along rows of plants and/or furrows of an agricultural field, a spreading unit being mounted on said structure for straddling at least one of said rows and spreading determined measures of at least one treatment product on said rows.

In particular, such machines are driven by a human operator seating in a closed cab of the driver station for actuating the commands means for moving said machine and/or operating the spreading unit.

Treatment products used in the agricultural domain are generally harmful for the health. In particular, during spreading operations, a quantity of such products may diffuse in the air, in particular in the form of dusts, aerosols and/or vapors, and form air pollutants which, if there are inhaled by the operator, in particular repeatedly, may cause in the long term serious and invalidating professional pulmonary and/or respiratory diseases.

For limiting the risks of exposure of the operator to such air pollutants, cabs are generally equipped with air conditioning systems that are adapted to condition the air circulating in said cabs, in particular by feeding said cabs with air that is mainly free from such pollutants.

In particular, such air-conditioning systems are known, comprising: - a circuit for supplying the cab with air coming from a recycling branch, that is fed with recycled air coming from the interior of said cab, and an exterior branch, that is fed with air coming from the exterior of said cab;

- a blowing device for providing an air flow inside said circuit;

- filtration means for removing pollutants from the air blown in the cab through said circuit;

said air-conditioning systems being operated according to a regular procedure to balance the air supplied by each of the recycling and exterior branches, for example to supply the cab with fresh air comprising approximately 80% of recycled air coming from said recycling branch and approximately 20% of exterior air coming from said exterior branch.

Besides, such air-conditioning systems may comply with strict regulatory texts, such as the European standard EN-15695, in particular as regards the air flow debit, the air pressurization inside the cab and the quality of the filtration means. For example, this standard defines four levels or categories for the security provided to the operator, from a minimum security level (category ) wherein the health risks are minimal, for instance when the machine is driven on a road, to a maximum security level (category 4), wherein said machine is driven on a field to spray highly polluting and volatile products.

However, these requirements are not totally satisfactory, as they cannot efficiently protect the operator in case of a contamination of the cab with air pollutants as described above. Indeed, when polluted air enters into the cab, for example upon opening of an access of said cab by the operator, said polluted air is difficult and slow to evacuate, in particular as the air provided by the air- conditioning system mainly comprises recycled air coming from said cab, i.e. potentially polluted air. The invention aims to improve the prior art by proposing a process of operating the air conditioning system of a cab which allows to protect more efficiently the operator from air pollutants diffused around said cab, in particular in the case of contamination of the interior of said cab with said air pollutants.

For that purpose, and according to a first aspect, the invention relates to a process of operating the air conditioning system of a cab of a machine, said air- conditioning system comprising:

- a circuit for supplying said cab with air coming from a recycling branch fed with air coming from the interior of said cab and an exterior branch fed with air coming from the exterior of said cab;

- a blowing device for providing an air flow inside said circuit;

- filtration means for removing pollutants from the air blown in the cab through said circuit;

said air conditioning system being operable to balance, in the supplied air flow, the amount of air coming from the recycling branch versus the amount of air coming from the exterior branch;

said process comprising a regular procedure wherein the air-conditioning system is operated to balance the air flow to supply air coming from each of the recycling and exterior branches, said process further comprising the monitoring of a signal indicative of a potential contamination of the interior of the cab and, upon the detection of such signal, a flushing procedure wherein the air conditioning system is operated to:

- increase the flow of air supplied into the cab by the blowing device through the circuit;

- balance said flow of air to supply air coming only from the exterior branch by closing the recycling branch; and

- open an exhaust flap within the cab for increasing the flow of air evacuated from said cab;

said flushing procedure being performed for a determined period of time before performing again the regular procedure.

According to a second aspect, the invention relates to a machine, in particular an agricultural machine, comprising a cab equipped with an air conditioning system which is adapted to be operated according to such a process. Other aspects and advantages of the invention will become apparent in the following description made with reference to the appended figures, wherein:

- figure 1 represents schematically in a perspective view a cab of a machine according to the invention;

- figure 2 represents schematically in a partial exploded view the air conditioning system of the cab of figure 1 , figure 2a representing in a exploded view the filtration and pressurization set of said system with means for switching between first and second filtration modes according to a first embodiment of the invention;

- figure 3 represents schematically in a top view the operation of the air- conditioning system of figures 1 , 2 during the regular procedure, said air- conditioning system being arranged in a first filtration mode;

- figure 4a represents schematically the steps of the procedure for switching the air conditioning system between the first and second filtration modes, figure 4b representing schematically a filtration and pressurization set with switching means according to a second embodiment of the invention;

- figure 5 represents schematically the steps of a process according to the invention;

- figures 6 represents schematically in a top view the operation of the air conditioning system of figures 1 , 2 which is arranged in a second filtration mode, respectively during the regular procedure (figure 6a) and during the flushing procedure (figure 6b). In relation to those figures, we describe below a machine comprising a cab equipped with an air conditioning system.

The machine is in particular an agricultural machine arranged for the mechanical or pressurized spreading of treatment products, such as phytosanitary products, insecticides or fertilizers, on the harvest plants and/or the plowed soil of an agricultural field, such as a vineyard or an orchard. To do so, the machine comprising a motorized support structure which is equipped with a driver station and movable in particular along rows of plants and/or furrows of an agricultural field, a spreading unit being mounted on said structure for straddling at least one of said rows and spreading determined amounts of at least one treatment product on said rows.

In particular, the spreading unit can be mounted on the support structure permanently or removably, so as to be replaceable by other equipment and accessories, for example harvesting equipment, pruning equipment or equipment for working the soil.

The machine is in particular adapted to be driven by a human operator. To do so, the driver station comprises a closed cab 1 wherein the operator is intended to seat for actuating the commands means for moving said machine and/or operating the spreading unit.

As shown in figure 1 , the cab 1 comprises a front windshield 2 made from a substantially transparent and solid material, for example laminated glass, for protecting the operator from wind and/or rain while ensuring a good visibility to allow said operator to safely drive and operate the machine, as well as a device 3 for remotely controlled washing of said windshield, in particular with an adapted product, for removing dirt that can potentially hinder said visibility. Moreover, the cab 1 comprises at least an access, in particular a lateral access door 4, for allowing the operator to enter and to leave the cab 1 .

Direct contact with treatment products used in the agricultural domain is generally harmful for the health. In particular, during spreading operations, a quantity of such products may diffuse in the air, in particular in the form of dusts, aerosols and/or vapours, and then may form air pollutants which, if they are inhaled by the operator, in particular repeatedly, may cause in the long term serious and invalidating professional pulmonary and/or respiratory diseases. For limiting the risk of exposure of the operator to such air pollutants, the cab 1 is equipped with an air conditioning system 5 that is adapted to condition the air circulating in said cab, in particular by feeding said cab with air that is principally free from such pollutants.

In relation to the figures, the air conditioning system 5 is implemented in the roof of the cab 1 , in particular into a sealed compartment 6 which is fixed, for example by gluing, underneath said roof, and which is accessible from the exterior of the cab 1 by means of an upper removable maintenance cover 7. In particular, the maintenance cover 7 comprises a peripheral edge which is equipped with a sealing gasket 8, so as to ensure the sealed closing of the compartment 6.

In a known manner, the air conditioning system 5 comprises:

- a control board card 21 for steering the operation of said system, in particular upon communication with command means implemented within the cab 1 , according to a predetermined process;

- a circuit 9 which supplies the cab 1 with air coming from a recycling branch 9a fed with air coming from the interior of said cab and an exterior branch 9b fed with air coming from the exterior of said cab;

- a blowing device 10 for providing an air flow inside said circuit;

- filtration means 1 1 for removing pollutants from the air blown in the cab through said circuit.

With reference to the figures, the air conditioning system 5 comprises a filtration and pressurization set 12 which is arranged upstream the circuit 9, said set comprising a central housing 13, wherein the blowing device 10 is arranged, and two lateral housings 14a, 14b, wherein respectively a first 1 1 a and a second 1 1 b filtration means are arranged. As shown in figure 2a, the central 13 and lateral 14a, 14b housings may be constituted by upper 13u, 14au, 14bu and lower 131, 14al, 14bl housing portions to be assembled together to form said housings. Moreover, figures 2a and 4b represent schematically a filtration and pressurization set 12 according to respectively an embodiment of the invention. The lateral housings 14a, 14b are in fluid communication with the exterior of the cab 1 , so as to allow circulation through said housings of air coming from said exterior and to remove pollutants from said exterior air by means of the filtration means 1 1 a, 1 1 b arranged within said housings.

Further, the central housing 13 is in fluid communication with the lateral housings 14a, 14b, so as to allow the blowing into the exterior branch 9b of an exterior air flow FE that has been filtered by at least one filtering means 1 1 a, 1 1 b. The filtering means 1 1 , 1 1 a, 1 1 b may be adapted to remove pollutants to comply with the requirements of at least the category 2 defined by standard EN-15695 so as to be able to remove at least the dust pollutants from the air flow to be blown into the cab 1 , and more particularly with the requirements of the maximum category 4 of said standard, so as to be able to remove not only dusts, but also aerosol and vapour pollutants from said air flow.

In the embodiment shown, the air conditioning system 5 comprises first 1 1 a and second 1 1 b filtering means that comply with the requirements of respectively the categories 2 and 4 of the standard EN-15695, said filtering means being made for example respectively from paper and from charcoal.

Moreover, the air conditioning system 5 comprises means for selectively switching between two filtration modes corresponding respectively to category 2 and 4 filtration levels, wherein the filtrations means 1 1 a, 1 1 b are selectively put in fluid communication with the blowing device 10 according to the desired level of filtration.

As shown in figures 2a and 4b, the switching means comprise at least one filter selection valve 15 (figure 2a), and in particular two selection valves 15a, 15b (figure 4b), said valves being arranged in fluid communication paths 16 relaying the central housing 13 to respectively the first category 2 14a and the second category 4 14b filtering housings, said valve(s) being operable to be selectively actuated, in particular by means of an actuator 17 to which said valve is linked through a connector (not shown), respectively in category 2 and 4 filtration modes, wherein said valve(s) close(s) - respectively open(s) - the fluid communication between the category 4 filtration housing 14b and the central housing 13 and open(s) - respectively close(s) - the fluid communication between the category 2 filtration housing 14a and said central housing.

Thus, in a particularly advantageous manner, the operator can benefit from a high level of filtration only when required, in particular only during the performing of a spreading operation in an agricultural field, and can switch to a lower level of filtration of category 2 when the risks of air pollution are lower, for example during road transport between an agricultural field and a farm or between fields Such a configuration allows to limit the clogging of the category 4 filtering means 1 1 b and to substantially increase its lifetime, which is quite short in relation to the lifetime of approximately 1 year of the category 2 filters.

In order to assess the saturation or clogging of the filtering means 1 1 a, 1 1 b, each housing 14a, 14b may be provided with a pressure differential sensor S (figure 4b) which is connected by sensor lines to the upstream and downstream ends of the respective lateral housings 14a, 14b. Thus, the pressure differential sensor signal is constantly monitored by the sensors S and, upon the pressure differential exceeding a limit value, the operator is warned that the one or the other filtering means 1 1 a, 1 1 b needs replacement, in particular by activating a communication mean such as a lighting indicator button, a screen or speaker(s), implemented in the cab 1 .

The air conditioning system 5 further comprises additional filtering means 19 that may be arranged at the fluid communication path between the interior of the cab 1 and the outlet of the recycling branch 9a, so as to remove possible air pollutants from the recycled air flow coming from said cab interior. In the embodiment shown, the additional filtering means 19 are provided at the inlet of the recycling branch 9a. The air conditioning system 5 further comprises a recycling valve 27 located in the recycling branch 9a, e.g. downstream of the additional filtering means 19, for selectively opening and closing said recycling branch. Moreover, the air conditioning system 5 comprises a HVAC device 20 (for Heating, Ventilation and Air Conditioning) which is arranged downstream of the circuit 9 for conditioning the air flow blown in the cab 1 through said circuit, said HVAC device comprising an inlet into which both of the circuit branches 9a, 9b end for feeding said HVAC device with the air flow to be conditioned and blown into the cab 1 . The HVAC device 20 comprises heat exchangers for cooling or heating the passing air and a circulation blower for blowing the conditioned air into the interior of the cab 1 .

With reference to the figures, we describe now a process of operating the air conditioning system 5.

In particular, the process comprises a filtration mode selection procedure wherein the switching means are operated to select one filtration mode, either upon manual activation of an appropriate means by the operator in the cab 1 , for example a button or a switch on a control board within said cab, or upon automatic detection of an appropriate signal corresponding to the actuation state of the spreading unit.

More precisely, the filtration mode selection procedure provides a first step A, in which the system assesses whether the cab 1 is provided with both category 2 and category 4 filtering means 1 1 a, 1 1 b and puts the selection valves 15, 15a, 15b in the category 2 filtration mode. The recycling valve 27 is in its default position, which is the open state to allow the flow FR of interior air through the recycling branch 9a to the HVAC device 20.

Afterward, the filtration mode selection procedure provides a second step B, wherein the air conditioning system 5 may be operated to put the selection valves 15, 15a, 15b in the category 4 filtration mode. Here, the selection procedure provides for the monitoring of appropriate signals, for example the manual actuation of a command means in the cab 1 or the actuation/deactivation of the spreading unit, and to perform switching from one filtration mode to another, according to the results of said monitoring.

In an advantageous manner, the process can provide for performing the filtration mode selection procedure upon initial actuation I of the air conditioning system 5. In particular, as shown in figure 5, the category 2 mode selection step A is performed just after the initial actuation step I, so as to put by default the filtration and pressurization set 12 in the category 2 filtration mode.

Afterwards, the process provides for monitoring an appropriate signal as described above and for performing the category 4 mode selection step B upon the detection of such signal. In particular, the process can provide for informing the operator that the filtration and pressurization set 12 is in the category 4 filtration mode, in particular by lighting an indicator button 23 and/or displaying an icon on a screen in the cab 1 .

The process then automatically proceeds to a step E for performing a regular procedure, described with reference to figures 3 and 6a. Herein, the air conditioning system 5 is operated to balance the air supplied by each of the recycling 9a and exterior 9b branches of the circuit 9, whatever the filtration mode selected. In particular, the air conditioning system 5 is operable to balance, in the supplied air flow, the amount of air coming from the recycling branch 9a versus the amount of air coming from the exterior branch 9b. Moreover, the regular procedure can provide for operating the air conditioning system 5 to supply the cab 1 with a total flow of air comprising approximately 80% of a flow F of recycled air coming from the recycling branch 9a and approximately 20% of a flow FE of exterior air coming from the exterior branch 9b. Moreover, to comply with the requirements of at least the category 2 defined by standard EN-15695, the regular procedure can provide for operating the air conditioning system 5, and in particular the blowing device 10, so that the air flow FE from the exterior branch 9b supplied in the cab 1 presents a flow rate of at least 30m ³ /h with an overpressure in said cab of at least 20Pa.

As illustrated in figure 5, the process provides for performing the regular procedure upon initial actuation I of the air conditioning system 5, the steps A, B of the filtration mode selection procedure being performed during said regular procedure just after the initial actuation step I.

Thus, during the regular procedure, the cab 1 is regularly supplied with a flow of fresh air F , FE coming from both the interior and the exterior of the cab 1 , said flow being previously filtered by appropriate filtration means 1 1 , 1 1 a, 1 1 b, 19 for removing pollutants generated in particular by the spreading product before being blown into said cab.

However, the regular procedure does not allow to protect the operator from such pollutants when polluted air has already entered into the cab 1 , for example upon opening by the operator of an access 4 of said cab, in particular as the flow of air FR, FE supplied by the air conditioning system 5 mainly comprises a flow of recycled air FR coming from the interior of said cab, i.e. potentially polluted air.

Thus, the process further comprises the monitoring of a signal indicative of a potential contamination of the interior of the cab 1 and, upon the detection of such signal, the process provides for performing a flushing procedure wherein the air conditioning system 5 is operated to remove the contamination by flushing of the air within the cab 1 . In particular, as stated above, the process can provide the monitoring of a signal initiated by the occurrence of an access 4 of the cab 1 , for example the access door 4, as the cab 1 may effectively be contaminated upon entry through an open access 4 of air polluted with the spreading product. In relation to figure 5, the process provides a step C1 wherein the occurrence of an access 4 of the cab 1 is detected, and then a consecutive step D wherein the flushing procedure is performed upon said detection. To do so, the air conditioning system 5 comprises means for monitoring such an occurrence signal, in particular air flow 24 and pressure 25 sensors implemented within the cab 1 for monitoring the changes of air flow and/or pressure within the cab 1 due to a potential opening or closing of an access 4 of the cab 1 . Moreover, the process can provide the monitoring of a signal initiated by a manual activation of an appropriate means by the operator in the cab 1 , for example a button or a switch on a control board within said cab. Thus, in relation to figure 5, the process provides a step C2 wherein the actuation of appropriate means by the operator is detected, the step D of flushing procedure being performed upon said detection.

Generally, the process can provide for checking, during the monitoring steps C1 , C2, the closing of all accesses 4 of the cab 1 before performing the step D or flushing procedure. Indeed, for performing the flushing procedure in the best conditions, it is necessary to stop at first potential entries of polluted air within the cab 1 , said stopping being in particular achieved through the total closing of accesses 4 of said cab.

In particular, in the case of an occurrence of an access 4 of the cab 1 , the process can provide the monitoring of consecutive opening and closing signals of said access, in particular by performing step C1 upon detection of the opening signal and by monitoring the consecutive closing signal during this step C , so as to perform the step D of flushing procedure only upon the detection of said closing signal.

Moreover, in the case of a manual actuation of appropriate means by the operator, the process can provide for checking the closing of all accesses 4 of the cab 1 and, in the case when at least one of said accesses is open, for alerting said operator of such opening, for example through the displaying of an error message on the control board in the cab 1 .

Once all the above mentioned conditions are met, the process provides for performing the step D of flushing procedure. In particular, the process can provide for informing the operator that the flushing procedure is to be performed, in particular by actuating an indicator lighting button 26 on the control board or displaying an icon on a screen in the cab 1 . During the step D, the flushing procedure provides for operating the air conditioning system 5 to increase the flow of air supplied in the cab 1 by the blowing device 10 through the circuit 9, so as to accelerate the evacuation of potentially polluted air within the cab 1 . In particular, the flushing procedure provides for operating the blowing device 10 to supply the cab 1 with an air flow having a flow rate greater than 40 m ³ /h.

Moreover, to avoid recycling of potentially contaminated air coming from the interior of the cab 1 , the flushing procedure provides, as represented on figure 6b, to balance the flow of air FE only in the exterior branch 9b of the circuit 9 by closing the recycling branch 9a.

To do so, the process provides for using the recycling valve 27 located in the recycling branch 9a for selectively opening and closing said recycling branch, the flushing procedure providing to operate said recycling valve for closing said recycling branch.

Besides, to increase the flow of air evacuated from the cab 1 , the flushing procedure provides to open an exhaust flap 28 located in a bottom wall or roof of the cab 1 , through which said flow of air can be guided to the exterior of said cab. At the end of the flushing procedure, the exhaust flap 28 is closed again, to restore the regular procedure conditions. In particular, the process provides for performing the step D of flushing procedure for a determined period of time before performing again the regular procedure, in particular by stopping the step D of flushing procedure after the expiry of said period of time and for relaunching step E for restoring such regular procedure upon said stopping. According to an embodiment, the determined period of time is fixed, in particular comprised between 120 s and 140 s, according to the total volume of the cab 1 and the flow rates of air flow evacuated from said cab.