This invention relates to an air filter for an industrial vehicle.
Industrial vehicles are known to normally comprise a filter unit
for the engine intake air consisting of a filter chamber housing a porous means
for separating the particles suspended in the air, and means for pretreating the
air upstream of the filter chamber to separate water and coarse particles from
the air. These pretreatment means generally comprise a vertical intake pipe or
"snorkel" provided with an upper air inlet at a large distance from the ground,
and means for separating water and powdery particles, such as cyclones and the
A filter unit known from the document FR-A-2 605 271 is provided
with a plurality of cyclones each one including a set of inclined radial leafs
to cause an helicoidal movement of the air. The cyclones are arranged in a pretreatment
chamber, which is positioned side-by-side with a filter chamber and communicates
Another filter unit known from the document FR-A-2 599 272 is provided
with an inner filter chamber coaxial with an outer pretreatment chamber, this latter
being divided in two portions by a coaxial annular wall for reducing the acoustic
waves. Two different centrifugal units formed of a plurality of helicoidal leafs
are provided upstream and downstream of this wall to centrifuge the air.
These known filter units have certain drawbacks. Firstly, they result
in substantial pressure drop in the intake air, resulting in higher fuel consumption
and a more smoky engine; they are also rather bulky and costly.
The object of the present invention is to provide an air filter unit
for an industrial vehicle which is free of the aforesaid drawbacks of known units.
Said object is attained according to the present invention by an
air filter unit for an industrial vehicle, of the type comprising an outer casing
defining a pretreatment chamber provided with an upper inlet port and with interception
and channeling means arranged substantially to separate the water from the intake
air, and a filter chamber housing a hollow cylindrical filter and provided with
an upper outlet port communicating with a central cavity of said filter, said
pretreatment and filter chambers communicating with each other through a first
aperture, said interception and channeling means comprising a first partition disposed
vertically inside said pretreatment chamber and defining therein a first compartment
communicating with said inlet port and a second compartment communicating with
said first aperture, said first and second compartments communicating to each
other through another aperture formed between the lower edge of said first partition
and a lower wall of said pretreatment chamber, characterised in that said filter
chamber is positioned externally to and side-by-side with said pretreatment chamber,
said first aperture being provided in a wall of said pretreatment chamber facing
said filter chamber; and in that said interception and channeling means also comprise
a second partition extending from said facing wall below said first aperture to
the interior of said second compartment.
The present invention will be more apparent from the detailed description
of a preferred embodiment thereof given hereinafter by way of non-limiting example
with reference to the accompanying drawing, which is an elevation view thereof
shown in partial section.
In the accompanying drawing, the reference numeral 1 indicates an
air filter unit for an industrial vehicle.
The unit 1 comprises an outer casing 2 constructed in several parts
conveniently of pressed sheet metal or moulded plastics, to define overall a pretreatment
chamber 3 and a filter chamber 4 which are disposed side-by-side and communicate
with each other. In particular, the chamber 4 is substantially of barrel shape,
whereas the chamber 3 is of parallelepiped shape with a height less than the chamber
4, and is bounded laterally by three substantially flat walls 5 and by a concave
wall 6 which substantially reproduces the profile of a portion 7 of a lateral
wall of the chamber 4, which it faces.
From the upper wall 8 of the casing 2 there branch, both in a horizontal
direction, an air intake pipe stub 9, and an air delivery pipe stub 10 to be connected
to the engine feed pipe.
The intake pipe stub 9 communicates with a zone of the chamber 3
which is external to the chamber 4 and has its mouth cross-section of elongated
form in a horizontal and downwardly inclined direction. The delivery pipe stub
10 communicates through a circular aperture 15 with a central zone of the filter
chamber 4 which houses a hollow cylindrical filter 16 of conventional type. Said
filter 16 therefore defines an axial duct 17 which faces the aperture 15.
The chambers 3 and 4 communicate with each other through a horizontal
oblong aperture 18 provided in proximity to the upper wall 8.
According to the present invention, the chamber 3 is divided transversely
by a partition 19 which extends downwards from the upper wall 8 of the chamber
3, which is therefore divided into a first compartment 20 communicating with the
intake pipe stub 9 and a second compartment 21 communicating with the aperture
18. The partition 19 is provided with a lower rounded edge 24 having a cross-section
shaped substantially as a droplet inclined towards the compartment 21, to define
with the lower wall 25 of the chamber 3 an aperture 26 giving communication between
the first compartment 20 and the second compartment 21.
Within the aperture 18 there is fixed a hollow pipe stub 27 of corresponding
section, which projects into the second compartment 21 and terminates with an outwardly
rounded edge 28.
From the wall 6 of the chamber 3, below the pipe stub 27, there projects
a downwardly inclined flow breaker partition 29 which projects into the compartment
21 for a length slightly greater than the pipe stub 27.
In proximity to the opposing side ends of the lower wall 25 of the
chamber 3 there are disposed two bleed valves 30 of known type, of which only
one is partly visible in Figure 1.
Finally, a projection 33 forming a drip ledge described hereinafter
projects into the compartment 21 from the upper wall 8 of the casing 2.
The operation of the unit 1 is as follows. Air enters the unit 1
through the intake port 14 of the pipe stub 9 and passes into the compartment 20
of the chamber 3. The purpose of the vertical partition 19 is to prevent any direct
entry of water into the chamber 4 and to determine, within the chamber 3, a U-shaped
path (compartment 20 - aperture 26 - compartment 21) which is able to separate
the water droplets by centrifugal action onto the lower wall 25 of the chamber
The purpose of the lower rounded edge 24 is to reduce the local pressure
drop caused by breaking up the fluid flow. The air then passes into the compartment
21, and most of the droplets which remain after the centrifugal action are entrained
upwards by the fluid flow along the wall 6. These droplets are then intercepted
by the flow breaker partition 29, from which they precipitate onto the bottom
wall 25. The air, now almost free of water, proceeds upwards passing beyond the
flow breaker wall 29. Any minute droplets still present in suspension tend to concentrate
on the upper wall 8, again by centrifugal effect, and to run along it to the drip
ledge 33, which concentrates them into droplets of larger mass so that they fall
The rounded edge 28 of the pipe stub 27 has the double purpose of
reducing pressure drop through the mouth and to form a collection channel for
conveying downwards by gravity the water which adheres to the outer walls of the
pipe stub 27, including by the effect of the drip ledge 33. The substantially "dry"
air then passes through the pipe stub 27 and into the chamber 4 in which it is
filtered by the filter 16, which retains the suspended impurities, after which
it flows through the duct 17 and pipe stub 10 to the vehicle engine.
The water which collects on the base wall 25 of the chamber 3 is
evacuated through the valves 30, provided for this purpose in the regions of low
The advantages of the unit 1 constructed in accordance with the present
invention are apparent from an examination of its characteristics.
Firstly, the shape and arrangement of the internal elements of the
chamber 3 (vertical partition 19, flow breaker partition 29, pipe stub 27, drip
ledge 33) ensure almost total separation of the water or mud before the proper
filtration. This means that the filter clogging problems are eliminated and that
the snorkel can be dispensed with. Said effects combined with particular expedients
in the construction of the elements (edge 24 of the partition 19, edge 28 of the
pipe stub 27) result in considerable overall reduction of the intake pressure drop.
The partitions 29 and 19, conveniently dimensioned in relation to
the dimensions of the chamber 3, provide an effective silencing of the engine
Further advantages are the constructional simplicity and reduced
overall cost of the filter unit.
Finally, it is apparent that modifications can be made to the unit
1 which do not leave the scope of protection of the present invention. For example,
a partition can be placed in the chamber 4 between the pipe stub 27 and that portion
of the filter 16 facing it, to prevent rapid clogging of that zone. In addition,
the unit 1 can comprise a conventional snorkel either in place of the intake pipe
stub 9 or connected to it.