FR2496237A1 - FILTER DEVICE FOR AIR CIRCULATION INSTALLATION - Google Patents

Abstract

AIR CONDITIONING SYSTEM SUPPLIED BY A SOURCE OF FRESH AIR FROM A AMBIENT A AND BY RECYCLED AIR R TREATED PRIORLY. THE INSTALLATION INCLUDES TWO FILTERS 30, 32 WHICH ARE MOUNTED TO COOPERATE WITHIN AN ASSEMBLY 28 WHICH DIRECTS THE AIR FROM THE FIRST SOURCE THROUGH THE TWO FILTERS 30, 32, AND A CHAMBER 90 WHICH MIXES THE RECYCLED AIR R WITH THE ROOM AIR AND DIRECTS IT THROUGH THE SINGLE SECOND FILTER 32. THE BEDROOM OFFERS A 100 PASSAGE OF SUFFICIENT SIZES TO CONSTANTLY ENSURE SUFFICIENT AIR FLOW INTO THE AIR CONDITIONING SYSTEM. THE FILTER ASSEMBLY INCLUDES ASSEMBLY GUIDES 64, 66 WHICH ALLOW THE EASY MAINTENANCE OF THE FILTERS FROM A COMMON MAINTENANCE POINT WITHOUT THE RISK OF DESTROYING THE GASKETS 44 THAT ARE FIXED ON EACH FILTER TO PREVENT THE INTAKE OF AIR WHICH HAS NOT BEEN FILTERED. APPLICATION TO THE AIR CONDITIONING OF EARTH MOVING VEHICLES.

Description

 The present invention generally relates to a filter device for an air circulation installation and more particularly to the way in which several filters are arranged and mounted inside a heating and air-conditioning system.

 In heating and air-conditioning systems such as those used in the cab of an earth moving vehicle, for example, it is common practice to suck in a unit of heating and cooling the ambient air from from outside the cabin. Before entering the cabin, the air passes through a filter to prevent the entry of dust, etc., into the cabin. It is also common practice to return the air that is already in the cabin through the heating and conditioning unit for recycling. This air is often passed through a second filter for further cleaning before it enters the unit. These facilities typically include a filter for each separate source. These filters are mounted independently of each other and are often arranged in separate locations or in locations that are not readily accessible.

Such an installation is described in the patent of
No. 3,868,896. Another installation with a similar filter device is disclosed in US Patent 3,742,684 assigned to the applicant of the present patent application. In patent No. 3,868,896, the filter which is intended for recycled air is mounted on an articulated panel at the upper and rear part of the cabin. This panel serves as an access cover in a pressure chamber in which the fresh air and the recirculated air are mixed, and the two air sources are introduced into the circulation system by a blower which is mounted to the chamber. inside the pressure chamber. Inside the pressure chamber is also installed the new air filter. To install or remove the new air filter, it must be maneuvered around the blower and through the narrow access cover. This tends to lead to the proper placement of the filter. In the above-mentioned patent No. 3,742,684, the filters intended for the two air sources are situated in two distinct places, one being accessible from inside the cabin and the other being accessible from outside the cabin. .

 In other air circulation installations such as those described in United States Patent No. 3 59 846 and in U.S. Patent No. 4,120,527 assigned to the Applicant of US Pat. In the present patent application, a single filter is provided for the fresh air flow and for the recycled air stream. The ability of the filter to effectively purify both air sources, particularly in a dusty environment that is common in the implementation of a earth moving vehicle, is relatively limited.

The present invention aims to solve one or more of the problems set forth above
According to one of the aspects of the present invention, there is provided a filter device for an air circulating installation having two sources of air flow.

The filters are arranged so that the combined current of the two air sources passes through one of the filters while the other filter is provided only in the flow path of one of the air sources.

 According to another aspect of the invention, the two filters are mounted so as to cooperate by forming a passage in which the two air sources are formed, as well as means for directing the flow of air into the air. one of the filters.

 According to yet another aspect of the invention, there is provided a mounting mode of the two filters that allows each filter to be easily guided to its correct position without having to be careful not to damage the filters. The filters are mounted to cooperate at a location that provides easy access to each of the two filters for simultaneous or separate maintenance.

 The present invention solves the problem of obtaining an insufficiently filtered air supply for a confined space such as the cabin of an earth moving vehicle. The filter device according to the present invention ensures that a minimum amount of filtered air will be introduced into the cabin even if the vehicle is operating in the most dusty environment.

 The elementary filters of the two air sources are arranged in line with each other so that the first air source, which is the most contaminated, is directed through each of the two filters, while the Second source of air, contaminated, is continuously recycled through only one of the two filters. The filters are cooperatively mounted forming a passage between the two filter housings which allows the combination of the second, less contaminated air source with the first air source after the air from the first source has passed through only one of the filters. The passage formed between the two filter housings is of sufficient size to provide a sufficient amount of air to the air conditioning system to effectively adjust the temperature of the cabin.

 Another problem that arises in many air circulation installations lies in the impossibility of access to the location of the filter, and in the difficulty that results to dismantle and replace the elementary filters.

 According to the present invention, the filters are arranged at a location that allows access to both filters from a single point within the enclosed space of the vehicle. The interactive mounting mode allows each filter assembly to be disassembled and maintained separately.

During filter replacement, the mounting mode provides a guide that engages each edge of the filter by pushing the filter into its correct installation position.

On the plates of annexed drawings
Figure 1 is a sectional view of a vehicle cab incorporating the air circulation system according to the present invention.
FIG. 2 is a partial top view of the filtrate device according to the present invention, and a section of 13 abine taken along lines 2-2 of FIG. 1.
Figure 9 is a fragmentary sectional view, taken along lines 3-3, of the filtering disrosite shown in Figure 2; and
Tn Figure S is a partial sectional view similar to Figure 3, showing the filter device according to the present invention in a position to maintain it in state
Referring now to the drawings, and in greater detail in FIG. 1, there is provided an air circulation installation 10 for the cabin 11 of an earthmoving vehicle (not shown), in which an operator sits normally to manipulate the vehicle controls. The cabin comprises a carcass 12 which comprises two tupular uprights 13 arranged in each corner of the cabin. Each upright 13 has an opening or entry la at its upper end. A crossbar 15, which is also tubular, interconnects two vertical uprights by their lower ends and communicates with the inner portion of each upright 13. This crossbar cohort a surface lb, facing inwards, within The carcass of the cabin further comprises a seat bat 18 which supports a seat 19. The seat frame is at a distance within the cross member 15 and has a surface 20; turned rearward, in which is formed an opening 21 arranged to be opposite the opening 17 formed in the cross-piece l.

 In the seat housing 18 is housed a zlimatization installation 22 which serves to regulate the atmosphere of the cabin 11. The term "air conditioning" is used here in its broadest sense to designate any air treatment such as heating, cooling, dehydration, etc. The various constituents of the air conditioning system, including the blowers 23, are arranged inside the air circulation system so as to ensure the treatment of the air at as it is sucked into this installation by the blowers 23 and diffused inside the cabin by the air ducts 24. The blowers suck air from a source A of ambient air through the inlets 14 tubular uprights 13, inside which it descends until it arrives in the crossbar 15. From the inside of the crosspiece, the air exits through the opening 16 and is directed by the opening 21 in the seat frame 18, after which it passes through the constituents of the ins air conditioning system to be processed and distributed.

 Between the crosspiece 15 and the seat frame 18 is disposed a filter assembly, generally designated by the reference 28, which serves to clean the air as it passes through it. The filter assembly (FIGS. 2 and 3) comprises a first filter 30 and a second filter 32 which are mounted respectively on the cross-member 15 and on the seat frame 18.

 The first filter 30 is mounted within a removable housing 34 which includes a base 36 from which a plurality of walls 38 extend to form an open ended filter receptacle 40. The walls of the receptacle are at a distance inward of the periphery of the pedestal, and form a rim 42 which surrounds the filter receptacle. An opening 43 is formed inside the base, radially inwardly of the walls 38. A seal 44 is fixed to the base along the periphery of the opening 43, on the opposite side of the base relative to the receptacle. 40.

 A closure element 46 (FIG. 3), having a base 47 and three side walls 48, 50 and 52, is provided such that the base 47 overcomes the open end of the receptacle 40, the side walls 48, 50 and 52 being disposed outside and against the three walls 38 of the receptacle 40. In the walls 48 and 52 of the closure element are formed two slots 54 and 56 L-shaped (Figure 4), which receive two rods 58 and 60 from two of the walls 38 of the receptacle 40. When the closure element is arranged such that the rods 58 and 60 rest in two branches 61 and 62 of the slots 54 and 56, the closure element can not be closed. As a result, the filter 30 may be arranged to be trapped by the closure member 46 within the receptacle 40, so that a seal 63, which is arranged along the outer edge of the filter 18, is kept in contact with heel with the base 38 so as not to allow air to pass between the filter 18 and the base 36.

 The filter housing 34 is mounted on the crosspiece 15 by means of two guide elements 6 and 66 (FIG. 2) which are arranged on each side of the opening 17. Since the two guide elements each have identical constituents a single guide element 66 will be described in detail, and is best shown in FIG. 2. The guide means each comprise a first element 68 which runs vertically along the surface 16 of the crossmember and is fixed to it by a plurality of mounting bolts. 72.A second element 74 extends from the element 68 towards the opening 17 and forms a downwardly directed channel 75 which tapers with respect to the surface 16 of the cross-member 15. The upper end 78 (fi 43 of the element 74 is separated from the cross-member by a first distance D, while the lower end 82 of the element 74 is separated from the cross-member by a second distance D1. When the flange 42 of the filter housing 34 is di sposed inside the channels 75, the seal 44 is pushed in contact with the surface 16 of the cross member 15 at the lower end 82 of the channels because the distance D1 is smaller than the total width of the flange 42 and seal 44. The etaneheite seal 44 is pushed into contact with the surface 16 of the crosspiece 15, in its upper position, by a threaded fastener or a wing nut 86 which passes through the flange 42 and is screwed on. on a mounting flange 88, directed to the top of 7a cross member 15.

 The second filter element 32 of the filter assembly 28 is mounted on the seat frame 18 surmounting the opening 21. This filter is disposed inside a chamber 90 formed by several walls 92, 94, 96 and 98 which depart from the rear of the seat frame towards the cross member 15 so as to overlap the end of the filter housing 34.

 The walls 94 and 96 are vertical walls that extend from the seat frame 18 and form an opening or passage 100 between the walls 94 and 96 and each vertical face of the filter housing 34. The wall 98 is a horizontal wall that forms the bottom of the housing. the chamber 90 and which starts from the seat frame to engage on a lower portion of the filter housing 34 via a seal 102 which is interposed between the wall 98 and the filter housing 34. This seal is attached to the wall 98 while the filter housing 34 is pushed into contact with the seal 102 as a result of its mounting on the crossbar 15, as already described. The wall 92 is a horizontal wall which forms the upper wall of the chamber 90 and which is articulated on the seat frame 18 by a hinge 104. The wall 92 is movable between a first position in which it is kept in contact with the edge upper filter housing by a fixing means 106 which will be described in more detail below, and a second position in which the wall 92 has disengaged by pivoting the filter housing leaving exposed the upper part of the chamber 90, as shown in Figure 4. When the wall 92 is in its first position shown in Figure 3, it forms the upper part of the passage 100, and it serves to communicate with the chamber 90 the air from a second source R of recycled air located inside the cabin.

 The filter 32 is immobilized by two other guides 107 and 108 which play the same role as the guides 64 and 66. The guides 107 and 108 are arranged on each side of the opening 21, and since their components are identical only the guide 107 will be described in detail for clarity. The guide 107 includes a first member 110 which is mounted on the seat frame 18 by bolts 114. A second member 116 extends from the first member forming a channel 117 which tapers relative to the seat frame 18. This channel is separated from the seat frame by a first distance d (FIGS. 2 and 4) at an upper end 120 of the member 116, while being separated from the seat frame by a second distance d1 at a lower end 124.A seal 128 is attached to a peripheral cladding 129 which houses the filter element 131 of the filter 32 and, when the filter is disposed inside the guide 107, this seal is pushed into contact with the surface of the seat frame 18, at its lower end, by the lower ends 124 of the guides, whose distance d1 is smaller than the total thickness of the make and the seal. The upper end of the filter 3 is held in sealing contact with the seat frame by a filter retaining member (FIGS. 3 and 4) and mounted on the lower part of the chamber wall 92. retainer 130 includes a downwardly directed flange 132 which is mounted on the underside of the wall 92 at a distance from the seat frame 18 approximately equal to dl. When the wall 92 is tilted towards its first position, the flange 132 engages the rear face 134 of the filter 32. As the wall 92 continues to move, the flange 132 causes the filter 32 and the gasket sealing 128 in contact with the seat frame 18.

 Fastener 106 is composed of two horizontal clamping members 136 and 138. Each clamping member has a pivotally-engaging first end 44, 146 engages threaded rods 148 and 150 extending vertically from filter housing 34. Two threaded fasteners in the form of wing nuts 152 and 154 are engaged on the rods 148 and 150 to vertically adjust the position of the clamping elbows relative to the rods. clamping 136 and 138 is mounted a stopper 160, 162 which engages the upper part of the wall 92 to maintain this wall against the filter housing, and thus the filter 32 in contact with the seat frame 18.

 During the operation of the air-conditioning system 22, when the blower motors 23 are started up, air is sucked into the air conditioning system and circulates inside the cabin in a series of ducts. 25. The ambient air A from outside the cabin is drawn through the opening 14, the carcass post 13, to the opening 17 provided in the cross member 15, after which it enters the cabin. As it passes through the opening 17, it passes through a fresh air filter 30 which provides initial cleaning by removing dust and other particles from the air. At its outlet from the filter 30, the air passes through the chamber 90 and enters the second filter 32 where it is filtered a second time. Moreover, as the air enters the chamber 90, it mixes with the air from the source R which has already circulated inside the cabin. This recycled air enters the chamber 90 through passages 100 which vertically connect the side walls 94 and 96 of the chamber with the first filter housing 34.

In this chamber, it mixes with fresh air entering the chamber from the filter 30 as already described, and is directed through the second filter 32 for further filtering and reprocessing with fresh air.

 If one continues to use the vehicle in which the air conditioning installation is located, the aggressive environment fInit by fouling the filters, especially the filter 30, to a point such that a sufficient amount of fresh air does not can no longer enter the facility. If it happens that the fresh air filter becomes too dirty to ensure proper air circulation, the passages 100 are of sufficient size to allow a sufficient amount of recycled air to pass through the filter 32 and the constituents of the air conditioning system for proper treatment of air in the cabin until the filter assembly 28 can be reconditioned.

To maintain the filters 30 and 32 of the filter assembly 28, the wing nuts 152 and 154 of the fasteners 106 can be loosened from their position for retaining the clamping elements on the threaded rods 148 and 150. sufficient loosening of the wing nuts, the clamping members 136 and 138 can be rotated on their respective rods, to disengage them from the movable wall 92 of the chamber 90, as shown in FIG. 4. The wall can then be tilted. 92 around the hinge 104 in its second position in which the flange 132 of the wall 92 no longer holds the filter 32 against the seat frame 18. This also has the effect of discovering the upper part of the filter 32, thus facilitating its disassembly The wing nuts 86 can then be removed, which releases the upper part of the first filter housing 34 from the crosspiece 15. The entire filter housing 34 can then be dismantled into the pheasant. t Slide up along the frustoconical channels 75. After having disassembled the filter housing 34, the rods 58 and 60 can be disengaged from the slots 54 and 56 formed in the closure element 46 in order to discover the filtering element 30. view of dismantling and cleaning or subsequent replacement
To reassemble the filter assembly 28 one can simply perform in the reverse order the operations of disassembling the filters.After replacing the filter 30 in the filter housing 34, one can place the rim 42 of the housing in the upper or filter receiving ends 78 (FIGS. 3 and 43 of the frustoconical channels 75 of the guides 64 and 56. Since the filter housing 34 will be in sealing contact with the surface 16 of the cross-member 15, the most important is that the integrity of the sealing joint 44 is preserved when the filter housing 34 is brought into position at this spin, the upper ends 78 of the channels 75 are separated from the crossbar by a distance greater than the total width. The housing of the filter 34 and the sealing ring can be placed on the frusto-conical channel 75 of the candle guides bubon was lowered into position, allowing as much as for the seals It is also possible for the housing 44 to remain clear of the surface 16 of the cross member 15 until the housing approaches the inner trenches of the channels after which the seal is pushed into contact only at its lower end. the seal, as the filter rests on the frustoconical channels 75 of the guides 64 and 66, remains clear to prevent that exerted on the face of the seal shear forces that could cause its destruction. Once the lower portion of the housing 34 is in place, the upper portion can be moved to the cross member 15 (out of engagement with the frusto-conical channels 75, except at its lower end) for the seal to come into contact with each other. engage all over its face with the surface 16 of the crosspiece 15.

The wing nut 8G can then be screwed onto the mounting flange to secure the filter housing 34 in its proper position.

 The filter 32 is installed using the same mounting operations as those described for the installation of the filter housing 34, the filter 32 being shown in the partially installed position in FIG. 4. Since it is important not to damage the seal 128 on the filter 132, the filter is guided in position while it rests on the frustoconical channels 117, until it reaches the lower ends 124 of the channel.

Since the spacing of the lower ends 124 is a distance dl chosen in advance, and this distance is smaller than the total width of the filter 32 and the seal 128, the filter and the seal will be in proper contact with the seat frame 18 only at the lower ends 124 of the guides 107 and 108. The filter 32 will rest constantly on the channels 117, until the movable wall 92 is brought into its first position.

By turning to set up, the flange 132 that starts from the lower face of the wall 92 will engage on the face 134 of the filter 32. As the wall continues to move, the filter 32 and the seal sealing 128 are moved towards the seat frame 18 to engage the surface 20. At the end of the displacement of the wall 92, the filter 32 will be in its correct position in which it overcomes the opening 21, around which it will form an airtight seal. The fastener 106 can be reengaged on the wall 92 and secured to wing nuts 152 to complete the assembly.

The filter assembly as described above provides an air circulation facility that allows the most contaminated source to be cleaned by two separate filters placed in line with each other in the air passage. air leading to the components of the air conditioning system. The filters are mounted such that their respective housings mutually cooperate to form a mixing chamber for recirculated air and fresh air, combining the two before they enter the second one.
filter them while skirting the first filter. This ensures that at all times a sufficient amount of air circulates in the air conditioning system.

 The mounting of the filters also allows the maintenance of the two filters because they are both easily accessible from the 3rd point and can be dismantled and reassembled. part of this point. The mounting method further facilitates maintenance by virtue of the presence of frustoconical mounting guides which seal the filters relative to their appropriate housings at a location as far as possible from the point of maintenance in state. and at the same time preserves the integrity of the seal during installation or disassembly.

 Other aspects, objects and advantages of the present invention will become apparent from the study of the drawings, the specification and the appended claims.

Claims (21)

1. Air circulation installation (10) for an enclosed space (11), characterized in that it comprises  a first filter (30  a second filter (32); and  means (28) for circulating the ambient air (A) in series through each of the two filters (30, 32) and through the enclosed space (11), a portion of the air (R) which The enclosed space (11) is recycled through one of said filters (32). Air circulation installation (10) according to claim 1, characterized in that each of said filters (30, 32) has predetermined dimensions, and in that the installation comprises means (64, 66, 107, 108) for removably clamping said filters (30, 32) and having a frustoconical channel (75, 117), said channel (75, 117) having an inlet end portion (78, 120) whose dimensions are larger than said predetermined dimensions of said filters (30, 32), and an opposite filter engaging end portion (82, 124) whose dimensions are smaller than said predetermined dimensions of said filters (30, 32). An air circulating installation (10) according to claim 2, characterized in that it further comprises filter retaining means (86, 130) near the inlet end (78, 120) of said frustoconical channel (75, 117), arranged to removably overlap said filters (30, 32) and having an extension (90) which forms a second air flow path (100) for said recycled air (R) beyond said first filter (30) and through said second filter (32). 4. Air circulation installation (10) for the cabin of a vehicle (11), characterized in that it comprises  a cabin carcass (12)  an air passage (17, 21) formed in said car carcass (15, 18) and connected to a first air source (A) for supplying air to said car (11)  a first filter (34) connected to said carcase (12) and disposed about said passage (17, 21) so as to filter the incoming air from said first air source (A) as it passes through said passage (17, 21);  a second filter (32) connected to said cabin carcass (12) and disposed in said air passage (17, 2 '3 with respect to said first filter (34) so as to refilter the air from said first source of air (A) t and  means (90) for directing recirculated air within said cabin (to send it into said passage (17, 7, 21), forming a second air source (R) downstream of said first filter (34) and upstream of said second filter f322 for said air from both sources (A, R) is filtered by said second en. 5. Installation air circulation (1OJ according to claim 4, characterized in that said passage (17, 21) common with the ambient air outside the space defined by said cabin (1). 6. AIr circulation system (10) according to claim 4, characterized in that said means 6905 for directing the recycled air R) inside said cabin (110 in said passage (17, 21) comprises a plurality of walls (92, 94, 96, 99w defining a chamber (90) disposed around said first and second filters (34, 32) so as to form a passage (100) between said chamber (90) and said first filter (34) The air circulation installation (10) according to claim 6, characterized in that the chamber (90) has a rockable wall portion (92) on which a first filter (130), said wall portion (92) being movable between a first filter holding position in which it is in contact with said first filter (34), and a second non-filter holding position in which it is disengaged, by tilting, said first filter (34). The air circulating installation (10) according to claim 7, characterized in that the bile retaining means (92) engages in said first position on said second filter (32). 9. Device for mounting a filter assembly (32, 34), characterized in that it comprises  a frame (15, 18)  filters (32, 34) having a filter element  (30, 131), a housing (34, 129) along the periphery of the filter element (30, 131), said housing (34, 129) having a selected width  seals (44, 128) attached to said filters (32, 34)  mounting means (64, 66, 107, 108, 86, 130) for fixing said filters (32, 34) on said frame (15, 18), said mounting means (64, 66, 107, 108, 86 , 130) having a first member (68, 110) which engages on the surface of said frame (16, 20), a second member (74, 116) which is connected to said first members (68, 110) and which laterally, said second member (74, 116) having a first (78, 120) and a second end portion (82, 124), said first end portion (78, 120) being separated from said frame (16, 20) by a first predetermined distance (D, d), and said second end portion (82, 124) being separated from said frame by a second predetermined distance (D1, d1), said first predetermined distance (D, d ) being greater than the total width of said filter housing (42, 129) and sealing gaskets (44, 128) attached thereto and said second predetermined distance (D1, d1) being small as the total width of the filter housing (42, 129) and gaskets (44, 128) attached thereto. 10. Mounting device according to claim-9, characterized in that said seals (44, 128) are disposed between said filters (32, 34) and said frame (15, 18). 11. Mounting device according to claim 9, characterized in that said second element (74, 116) of said mounting means (64, 66, 107, 108) narrows relative to said frame (15, 18). 12. Mounting device according to claim 11, ca-act in that said channel (75, 117) places said filters (32, 34) relative to the frame (15, 18), said channel (75, 117). pushing said filters t32, 34) and said seal (44, i28) into contact with said frame (15, 18) while the filters t32, 34) are directed toward said second end portion (82, 124; element (74, 116)  3. A filtering device (28) for an air circulator system (10), characterized in that it comprises:  a first frame member (15) in which a first opening (17) is formed;  a second frame member (18) in which a second opening (21) is formed, said second frame member (18) being disposed at a distance from said first frame member (15), said second opening (21) being disposed opposite said first opening (17);  a first air source (A) in communication with said first and second openings (17, 21) provided with said first and second frame members (15, 18);  a first filter (34) connected to said first frame members (15) and disposed about said first opening (17) for filtering air from said first air source (Aj as it passes therethrough;  means (92, 94, 96, 98) forming a chamber (90j mounted on said second frame member (18), said chamber (90J extending from said second frame member (13) to engage said first filter (34); ) forming a third open (100) between said chamber (90) and the first filter (34);  a second air source (R) in communication with said third aperture (100);  a second filter (32) connected to said second frame member (18) and disposed about said second opening (21) for filtering air from said first and second air sources (A, R); and  mounting means (64, 66, 107, 108, 130, 86) for respectively securing said first and second filters (32, 34) on said first and second frame members (15, 18). 14. filter assembly (28) according to claim 13, characterized in that said first and second filters (32, 34) comprise:  a filter housing (34, 129);  a filter element (30,131) secured within said housing (34,129); and  a seal (44, 128) connected to said filter housing (34, 129) and arranged to engage sealingly with said respective frame member (15, 18). The filter assembly (28) according to claim 13, characterized in that said chamber (90) has a wall portion (92) on which a filter retaining means (130) is disposed, said wall portion (92) being able to switch between a first filter holding position in which it connects said second frame member (18) and said first filter housing (34) forming a portion of said third opening (100), and a second position of non-contact retainer wherein said wall portion (92) is disengaged from said first filter housing (34) to provide access to said second filter (32). 16. filter assembly (28) according to claim 13, characterized in that said second filter (32) is disposed within said chamber (90). The filter assembly 28) of claim 15, characterized in that said filter retaining means (130) has a flange (132) extending from said wall portion (92) and being arranged to engage on said second filter (32) and pushing it into contact with said second frame member (18) when said wall portion (92) occupies said first position. Filter assembly (28) according to claim 13, characterized in that said mounting means (64, 66, 107, 108) comprise frustoconical channels (75, 117) connected to said first and second frame members (15, 18). ), said channels being disposed on each side of said first and second apertures (17, 21). Filter assembly (28) according to claim 18, characterized in that each of said frustoconical channels (75, 117) forms an inlet end portion (78, 120) which is separated from the respective frame member (15, 18) by a distance (D, d) which is larger than the respective filter (32, 34), and an opposite end portion of the filter engagement  (82, 1943 which is separate from said respective frame member  (15, 18) by a distance (D1, d10 which is smaller than said respective filter (32, 34).  Filter assembly (28) according to claim 19, characterized in that each of said filters (322 34) is held in contact with its respective frame member (15, 18) at one end by said terminal engagement portion of filter (82,124) of said frustoconical channel 75,117) and opposite end by filter retaining means (86,130). 21. The filter assembly (28) according to claim 20, characterized in that said filter retaining means (86) is a threaded fastener (86). 22. The filter assembly (28) is in accordance with claim 13, characterized in that said air circulation system (10) is used in the cabin (11) of a vehicle. 23. Filter assembly 1283 according to claim 20, wherein said first air source (A) is the ambient air which is outside enclosed space delimited by the cabin (II). 24. Filter assembly (28) according to claim 20, characterized in that said second air source (R) consists of the air which is inside the enclosed space delimited by the cabin (11). ).