Patent Publication Number: US-2021188052-A1

Title: Air treatment apparatus

Description:
BACKGROUND 
     Field 
     The present invention relates to an air treatment apparatus, in particular to an air treatment apparatus for an operator environment or cab of an agricultural vehicle or a similar vehicle. 
     Description of Related Art 
     Agricultural vehicles are known to operate in environments in which many different kinds of particulate or contaminant are present. This creates a requirement for filtration of the air for operators of such vehicles when in use. The particulates may be of different sizes and of different natures, for example larger particulates such as dust, pollen and the like and smaller contaminants such as fumes, aerosols and vapours. 
     It is known to provide separate air filters to provide selective filtering of the air supply to a vehicle operator. For example a first filter may be used when the predominant contaminant in the working environment of the agricultural vehicle is relatively large (for example when traversing a field) and a second filter is used when the predominant contaminant in the working environment is relatively small (for example when applying a herbicide, pesticide or similar). 
     Also, legislation in various countries now requires the use of filters of a particular rating to filter out particular contaminants from the air which would otherwise be introduced into the operator environment or cab of the agricultural vehicle. For example in the EU, EU Standard EN 15695 provides for four categories of filter for cabin protection, where Category 2 (hereinafter “CAT2”) protects only against dust but does not protect against aerosols and vapours, Category 3 (CAT3) protects against dust and aerosol, but not vapours and Category 4 (CAT4) protects against dust, aerosols and vapours. In this context, CAT3 filters tend to be more expensive than CAT2 filters, with CAT4 being most expensive. Accordingly, it is beneficial to the working life of the higher rated filters if they can be cleaned rather than replaced. It is a further advantage if such filters can be cleaned when in service on the agricultural vehicle rather than being removed while being cleaned (requiring replacement during cleaning or enforced downtime of the agricultural vehicle). 
     BRIEF SUMMARY 
     According to a first aspect of the present invention there is provided an air treatment apparatus for an operator environment of an agricultural vehicle in which air to be filtered is drawn into an air filtration system, filtered and directed to an agricultural vehicle HVAC system, in which the HVAC system comprises an inlet plenum, at least one blower, other HVAC components and an outlet to the operator environment; 
     wherein the air filtration system comprises: 
     at least one external inlet; 
     a first filtration device having a first coarser level of filtration located between the external inlet and the HVAC inlet plenum; 
     a second filtration device having a second finer level of filtration located between the external inlet and the HVAC inlet plenum; 
     a first air filtration system blower connected to the HVAC inlet plenum; 
     a valve mechanism selectively to connect either the first filtration device to the HVAC inlet plenum or the second filtration device to the inlet HVAC plenum; and 
     for each filtration device, a respective bypass permanently connected with an inlet end downstream of the valve mechanism and an outlet end upstream of the valve mechanism and adjacent the respective filtration device such that in use a portion of an air flow downstream of the valve mechanism may be recirculated to purge the respective filtration device, and each bypass includes a respective non-return valve opposing transit of air from the outlet to the inlet ends. The outlet end of each bypass is preferably located between the respective filtration device and the valve mechanism. 
     Suitably, the inlet end of each bypass may be connected to draw air directly from the operator environment. In a first alternative arrangement, where the apparatus has first and second air filtration system blowers connected in series, with the first blower being located between the valve mechanism and the second blower, and the second blower being configured to produce a higher throughput of air than the first blower, the inlet end of each bypass may be connected to draw air directly from the output of the first blower. In a further alternative arrangement, where the apparatus has first and second air filtration system blowers connected in series, with the first blower being located between the valve mechanism and the second blower, and the second blower being configured to produce a higher throughput of air than the first blower, the inlet end of each bypass may be connected to draw air directly from the output of the second blower ahead of the other HVAC components. 
     In one of the alternative arrangements of the preceding paragraph, where the apparatus has first and second air filtration system blowers connected in series, with the first blower being located between the valve mechanism and the second blower, and the second blower being configured to produce a higher throughput of air than the first blower, a recirculation line may be provided having an inlet drawing air from the operator environment and an outlet in the line between the first and second air filtration system blowers. A third filtration device may be provided in the recirculation line. 
     The valve mechanism preferably selectively connects either the first filtration device to the HVAC inlet plenum or the second filtration device to the HVAC inlet plenum such that in use an air flow is directed from one or the other of the filtration devices to the HVAC inlet plenum. 
     Preferably, the first filtration device is adapted to filter dust particles and conforms to CAT2. Preferably, the second filtration device is adapted to filter dust, aerosols and vapour and conforms to CAT4. 
     The present invention further provides an agricultural vehicle comprising an operator environment, and an air treatment apparatus as recited above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example only, in which 
         FIG. 1  shows a utility vehicle in the form of a farm tractor including an air filtration apparatus; 
         FIG. 2  shows a schematic view of a first embodiment of an air filtration apparatus in accordance with the present invention in a first operating condition; 
         FIG. 3  shows a schematic view of the air filtration apparatus of  FIG. 2  in a second operating condition; 
         FIG. 4  shows a schematic view of a second embodiment of an air filtration apparatus in accordance with the present invention; 
         FIG. 5  shows a schematic view of a third embodiment of an air filtration apparatus in accordance with the present invention; 
         FIGS. 6A and 6B  illustrate a non-return valve used in the present invention; and 
         FIG. 7  schematically represents the layout of components of the air filtration apparatus installed in the roof of the tractor of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description. 
     Referring to  FIG. 1 , an agricultural/utility vehicle in the form of a tractor  10  is shown having an operator environment in the form of a cab  12  and an engine compartment  14 . A chassis  16  which is partly visible connects front wheel suspension and steering assembly  18  and rear axle assembly  20 . The cab  12  has a roof assembly  22  within which is mounted an air filtration apparatus  24  and HVAC (heating, ventilation and air conditioning) unit  26 . Two inlets (represented by arrows  28 ) for the air filtration apparatus and HVAC unit are located under an eaves overhang on a side of the roof assembly  22 , although it will be appreciated that a single inlet may alternately be provided. Openable covers  40 C,  34 C in a side wall of the roof assembly  22  enable user access for inspection and/or replacement of respective filtration devices, as described further below. 
     With reference to  FIGS. 2 and 3 , a schematic view of a first embodiment of an air filtration apparatus is shown comprising the air filtration system indicated generally at  24  (to the left of the figure) connected to the HVAC system indicated generally at  26  (to the right of the figure) for the operator environment or cab  12  of the agricultural vehicle  10 . 
     The external inlet or inlets  28  feed a first vent or duct  30  and a second vent or duct  32  by which air to be filtered is drawn into the filtration system. As mentioned above, the first and second vents or ducts  30 ,  32  may be provided with individual external inlets  28  in a preferred arrangement, or may share a common inlet. 
     The first vent or duct  30  is directed to a first filtration device  34  having a first coarser level of filtration. The first filtration device  34  is conveniently suitable for extracting dust particles and the like from the externally fed air. By way of example, this may be a Category 2 (CAT2) dust filter. The first filtration device  34  is provided with an outlet  36 . The outlet  36  is connected to a first inlet side of a valve mechanism  38 . 
     The second vent or duct  32  is directed to a second filtration device  40  having a second finer level of filtration. The second filtration device  40  is conveniently suitable for extracting dust, aerosols, vapour and the like from the externally fed air. By way of example, this may be a Category 4 (CAT4) filter. The second filtration device  40  is provided with an outlet  42 , which outlet  42  is connected to a second inlet side of the valve mechanism  38 . 
     The valve mechanism  38  is provided with an outlet conduit  44 . The valve mechanism allows air flow from the second filtration device  40  to the outlet conduit  44  while isolating the first filtration device  34  or, alternatively allows air flow from the first filtration device  34  to the outlet conduit  44  while isolating the second filtration device  40 . 
     The valve mechanism  38  may be operated by any convenient means, for example automatically following a suitable signal received from a suitable sensor, automatically following actuation of a suitable device for example a sprayer, or by the direct action of a driver actuating suitable means within the cab. 
     The outlet conduit  44  is connected to an inlet plenum of a first fan or air impeller device, pressurisation blower  46 , the output of which is connected to the input of a second fan or air impeller device, main blower  48 , of the HVAC system  26 . 
     The HVAC system typically includes additional components downstream of the main blower  48 , such as by way of example a evaporator  50  and a heater  52  (see also description of  FIG. 7  below), the output of which directs the treated air flow to the cab  12  by way of a cabin air supply duct  63 . 
     In this first embodiment, a first (inlet) end of a first bypass channel or passage  54  is connected to an outlet of the pressurisation blower  46 . A second (outlet) end of the first bypass channel or passage  54  is located between the second filtration device  40  and the valve mechanism  38 . A non-return valve  54 V is provided in the bypass channel  54  opposing the flow of air from the second to the first ends. 
     Also, a first (inlet) end of a second bypass channel or passage  56  is connected to an outlet of the pressurisation blower  46 . A second (outlet) end of the second bypass channel or passage  56  is located between the first filtration device  34  and the valve mechanism  38 . As for the first bypass, a non-return valve  56 V is provided in the bypass channel  56  opposing the flow of air from the second to the first ends. 
     A air recirculation path  58  is provided by a conduit extending between the cab  12  and the inlet to the main blower  48  as will be described further below. The further air recirculation path  58  suitably includes a dust filter  60  (preferably in the form of a simple cartridge filter easily replaceable by a user) to prevent dust from the ambient air within the cab  12  from being passed to the main blower  48  and downstream components  50 ,  52  and thereby reintroduced to the cab. 
     The typical operating position of the valve mechanism  38  is that shown in  FIG. 2 , with inlet air drawn through the first coarser CAT2 filtration device  34 . However, when there is a need to extract aerosols, vapour and the like the system is switched to the configuration shown in  FIG. 3  with inlet air drawn through the second finer CAT4 filtration device  40 . 
     To adopt the configuration shown in  FIG. 3 , the valve mechanism  38  is moved to the position shown and the pressurisation and main system blowers  46 ,  48  are also actuated. Air is drawn into the air filtration system through the second vent or duct  32  and drawn through the second CAT4 filtration device  40  to remove dust, aerosols, vapour and the like entrained in the air. The air is directed through the valve mechanism  38  to the outlet conduit  44  and then drawn by the pressurisation and main blowers  46 ,  48  into the HVAC system and onward via the additional components  50 ,  52  to the cab air supply duct. In this position, the valve mechanism  38  prevents communication between the first filtration device  34  and the blowers  46 ,  48 . 
     In addition, due to the overpressure of a portion of the air drawn into the HVAC system is drawn or recirculated through the bypass channel or passage  56  to the region between the first filtration unit  34  and the ventilation mechanism  38  where, due to the closed state of the valve, the recirculated air is directed back through the first filtration device  34 , thereby removing trapped dust and the like from the first filtration device  34  and directing these back out through vent or duct  30  and inlet  28 . For this reason, separate inlets  28  for the ducts  30 ,  32  are preferred to reduce the risk of ejected particulate matter from one filter being drawn into the other. 
     This arrangement has as an advantage that the air filtered by the second filtration device  40  is used to clean the first filtration device  34 . It can be seen that the first filtration device  34  is being cleaned whenever the second filtration device  40  is in operation. It is a further advantage, with the second filtration device  40  connected to the HVAC system, that the use of the portion of the treated air to clean the first filtration device  34  results in a gentler cleaning action than if the pressurisation blower  46  was simply reversed to drive air back through the first filtration device  34 . This results in a prolonged life for the first filtration device  34 . 
     Once the need to extract aerosols, vapour and the like has passed, the valve mechanism  38  is caused to adopt the position shown in  FIG. 2 . In this position, the valve mechanism  38  prevents air flowing from the second filtration device  40  to the pressurisation blower  46  and on to the inlet plenum of the main blower  48 . 
     Air is drawn into the air filtration system from the inlet  28  through the first vent or duct  30  and directed through the first filtration device  34  to remove dust and the like entrained in the air. The air passes through the valve mechanism  38  to its outlet conduit  44  and is then drawn by the pressurisation and main blowers  46 ,  48  into the HVAC system and (via components  50 ,  52 ) out through the cab air supply duct. 
     As before, due to the overpressure a portion of the air drawn into the HVAC system by the pressurisation blower  46  is drawn or recirculated through the second bypass channel or passage  56  to the region between the second filtration unit  40  and the valve mechanism  38 , where, due to the closed state of the valve, the recirculated air is directed back through the second filtration device  40 , thereby removing trapped dust, vapour and aerosol particles and the like from the second filtration device  40  and directing these back out through vent or duct  32  and inlet  28 . 
     This has as an advantage that the air filtered by the first filtration device  34  is used to clean the second filtration device  40 . It can be seen that the second filtration device  40  is being cleaned whenever the first filtration device  34  is in operation. As before it is a further advantage that the use of the portion of the treated air to clean the second filtration device  40  results in a gentler cleaning action than if the pressurisation blower  46  associated with the second filtration device  40  was simply reversed to drive air back through the second filtration device  40 . This results in a prolonged life for the second filtration device  40 . 
     A second embodiment of an air treatment apparatus in accordance with the present invention is shown in  FIG. 4 . Like reference numerals are used to refer to like parts. The difference in this embodiment is that the inlets to the two bypass channels  54 ,  56  are fed from the main blower  48  (rather than the plenum blower  46 ). 
     A third embodiment of an air treatment apparatus in accordance with the present invention is shown in  FIG. 5 . Like reference numerals are used to refer to like parts. The difference in this embodiment is that the inlets to the two bypass channels  54 ,  56  are fed by overpressure from the cab space  12  (rather than directly from the plenum or main blowers  46 ,  48 ). More alternatively the overpressure could be taken from duct  63  connecting the HVAC unit  26  and the cab space  12  as shown in  FIG. 7 . The overpressure may also arise from the cab door being shut. 
     The presence of non-return valve  54 V,  56 V in bypass channels  54 , 56  ensure that no air can pass from air filtration apparatus  24  to HVAC unit  26  through bypass channels  54 , 56  directly in a direction opposite to the direction of the overpressure provided by plenum or main blowers  46 ,  48  or present in cab 12 . 
       FIGS. 6A and 6B  show a suitable configuration for the non-return valves  54 V,  56 V in the respective bypass lines  54 ,  56 . A deformable disc of silicone rubber  64  is positioned over one or more apertures  66  in a surface  68  which otherwise provides an air blockage. As shown in  FIG. 6A , air pressure from a first (lower) side of the surface (being in communication with plenum or main blowers  46 ,  48  or present in cab 12 ) is sufficient to cause the disc  64  to deform, opening the apertures  66  and allowing airflow. However, as shown in  FIG. 6B , air pressure on the second (upper) side (being in communication with outlets  36 ,  42  of filtration device  34 ,  40 ) of the surface  68  serves to hold the disc  64  against the surface  68 , thereby sealing the apertures  66 . Alternatively, non-return valves  54 V,  56 V may be designed as flap-type non-return valve comprising a flap which is kept closed by a biasing spring in one direction while in the other direction, the flap can be opened against the force of the spring. 
       FIG. 7  is a schematic plan, looking down from above, of a preferred layout of the system components within the roof  22 . The front of the tractor  10 , and the usual direction of travel, is indicated by the arrow A. 
     The first and second filters  34 ,  40  are mounted to one side of the roof with the pressurisation blower  46  located between. In this case cylindrical filters with the filter medium arranged in circumferential orientation around an axis indicated with arrow C are installed, whereby the axis C is aligned longitudinal in driving direction A. Inlets  28  to the filters  34 ,  40  are represented by arrows  28 . The physical inlets  28  are positioned below the respective filters in an underside of the roof assembly  22  forming an eaves projection outside of the cab  12 . Openable covers  34 C,  40 C in the sidewall of the roof assembly enable user access to the respective filter devices  34 ,  40  for inspection, maintenance or replacement purposes. Controlled flaps in the conduit linking the filters  34 ,  40  to the pressurisation blower provide the valve mechanism  38  which controllably connects either of the filters  34 ,  40  to the pressurisation blower. 
     Adjacent one of the filters  34 , to the rear of the roof  22 , is the main blower  48  connected to the pressurisation blower  46  via duct  62 . The output from the main blower  48  is passed through the additional components in the form of evaporator  52  and heater  50 , which components extend across the rear of the cab roof, before the treated air enters the cab space  12 . An opening from the cab space  12  into the duct  62  provides the recirculation path  58  as described above. A filter  60  is omitted from the view of  FIG. 7 . 
     The layout of  FIG. 7  provides a first benefit in that the inlets  28  for the first and second filtration devices  34 ,  40  are under an eaves overhang at the side of the roof which tends to being a less dusty environment than the front or rear and helps to reduce the volume of airborne material drawn into the filters. A second benefit of having the filtration system and HVAC components mounted around the periphery of the cab roof  22  is that it enables a clearance area (indicated generally by dashed line  70 ) giving improved user headroom in the centre of the cab. 
     In the foregoing, the applicants have described an air treatment apparatus for an operator environment of an agricultural vehicle in which air to be filtered is drawn into an air filtration system, filtered and directed to an agricultural vehicle HVAC system. The air filtration system comprises first  34  and second  40  filtration devices having respectively coarser and finer levels of filtration. Each filtration device  34 ,  40  is provided with a respective bypass  54 ,  56  permanently connected with an inlet end downstream of a valve mechanism  38  that selects between the filtration devices, and an outlet end upstream of the valve mechanism  38  and adjacent the respective filtration device  34 ,  40 . In use a portion of an air flow downstream of the valve mechanism may be recirculated to purge the respective filtration device, and each bypass  54 ,  56  includes a respective non-return valve  54 V,  56 V opposing transit of air from the outlet to the inlet ends. 
     From reading the present disclosure, other modifications will be apparent to persons skilled in the art.