Note: Descriptions are shown in the official language in which they were submitted.
The invention is generally related to apparatus for
cleaning air, and is specifically directed to an air cleaner
for use with internal combustion engines which are operated
under extremely dusty conditions or in an environment contain-
ing substantial particulate matter of varying size.
The conventional approach to the cleaning of intake
air for internal combustion engines is filtration; e.g.,
causing the air to flow through a pGrOuS medium to remove
particles by interception, impaction and diffusion. Although
filtration can be a highly efficient process in the cleaning of
fluids, a problem does arise in extremely dirty environments
because the filtered particulate matter tends to clog the
filter element very quickly. This results in the frequent
replacement or cleaning of the filter element, or an inadequate
supply of fluid due to the increased pressure drop across the
clogged element.
Because of this problem, it has long been the practice
to preclean the air by separation, in which a force field is
applied to a fluid containing particulate matter in such a way
that the applied force can be overcome by the fluid, but not
by some of the particulate matter. In this way, the efficiency
of the filter element is prolonged, and the requirement for
replacement or maintenance is less frequent.
More recently, air cleaners which utilize both separa-
tion and filtration in a single unit have been developed and
advanta~eously used, and this invention is directed to an improve-
ment in such devices. More specifically, we have been concerned
with the development of an air cleaner in which air taken in
from a dusty environment is more efficiently precleaned by
separation, and then thoroughly filtered by passing it through
a porous medium for delivery to an internal combustion engine.
An additional and necessary objective, which arises from space
-- 1 --
limitations encountered in the area of use, is that the unit be
of compact size without compromising its overall effectiveness.
It has been ascertained that maintaining the uncleaned
air at a uniform or, preferably, increasing velocity as it
passes through the separation stage enahles separation to uni-
formly and effectively occur over the entire length of the
separation stage. Although this has been recoynized in prior
art apparatus, the means for accomplishing a uniform or in-
creasing velocity require an additional structural element
which occupies a significant amount of space within the unit.
In addition, the resulting unit is more difficult to assemble
and more costly to manufacture~
Other prior art structuxes have recognized the need
for both separation and filtration in a single unit, but this
has been accomplished at the expense of separation or filtration
efficiency, or without serious regard to economy or space limi-
tations.
The improved and inventive air cleaner combines the
advantages of separation and filtration in a single unit which
is extremely compact in size. As pointed out ahove, maintaining
uniform or increasing velocity throughout the separation stage
gives rise to extremely efficient separation; and this is
accomplished with structure which also uniquely enables the
unit to be of lesser size than prior art devices. ~ore speci-
fically, in the preferred embodiment we provide a cylindrical
casing having an inlet for uncleaned air at one axial end and a
first outlet for scavenged particulate matter at the opposite
axial end. A ~enerally fxustoconical wall member is disposed
within the casing, defining a flow path for the inlet air which
converges toward the outlet. A plurality of louvers are formed
through the frustoconical wall member and ~paced over its length.
Each of the louvers extends radially inward and at the same
-- 2
~V~9~
time in the downstream direction, so that it is necessaxy for
air to partially reverse its downstream direction in order to
pass through the conical wall member. However, the particulate
matter, which is of greater density than the air, builds up an
inertial force which is of such magnitude as to preclude the
particles from reversing direction as they pass through the
converging flow path, and separation of the particulate matter
from a substantial portion of the air is thus effected. The
converging flow path maintains the air at a uniform or increas-
in~ flow velocity by compensating for the loss of air through
upstream louvers, and this enables the spaced louvers to have
equal effectiveness at any point on the conical separation
surface. As such, highly efficient separation occurs within a
very small area, with the scavenged particulate matter passing
out of the device through the axial outlet.
A filter element, preferably of the pleated, dry por-
ous paper type is disposed radially outward of the frustoconical
wall member. In order to take full advantage of the uniform
flow velocity, the pleated filter element also takes a generally
frustoconical form which receives the precleaned air from the
spaced louvers and filters the air as it passes through the por-
ous medium. As is well known in the art, the pleated medium sub-
stantially increases the filtration surface of the element as
well as provides it with increased structural strength.
In the preferred embodiment, the pleated filter ele-
ment includes an annular inner and outer perforate lining for
additional support, and is integrally formed with the louvered
frustoconical wall member into a separation, filtration element
which is easily replaceable within the cylindrical casing.
The space defined between the outer surface of the
pleated filter element and the inner surface of the cylindrical
casing diverges or increases in flow area from the inlet end to
-- 3 --
the outlet end. The structural configuration is a space saving
feature since the resulting chamber has its smallest dimension
closestto the inlet end, where a lesser volume of filtered
air enters. By the same token, as this outlet chamber increases
in size, it is capable of accommodating a greater volume of air
as it leaves the pleated filter element. A second outlet is
formed in the wall of the cylindrical casing in direct communi-
cation with this outlet chamber.
The unit may also advantageously include a safety
filter element which is also frustoconical in shape and disposed
within the outlet chamber immediately outward of the pleated
filter element. The safety element consists of inner and outer
perforate frustoconical liners and a single layer of dry paper
therebetween which is of greater porosity than that of the
pleated element. As such, the safety filter element is capable
of performing minimal filtration to protect the internal com-
bustion engine should a breakage occur in the pleated element.
According to the invention there is to be provided
an apparatus for cleaning air comprises a general]y cylindrical
casing having first and second axial ends and defining an
internal chamber, the cylindrical casing further comprising
an inlet in the first axial end, a first outlet in the second
axial end for discharging particulate matter, and a second
outlet. The apparatus further comprises a separator comprising
a hollow, frustoconical member disposed within the said chamber
with its larger end sealably encircling the inlet and the
smaller end sealably encircling the first outlet to define a
first flow path for inlet air which decreases in flow area
from the inlet to the first outlet, and louver means formed
in the frustoconical member and defining a second flow path
therethrough, the louver means being constructed to cause air
to partially change direction in order to flow therethrough,
~ _ 4 _
O~
thereby enabling the separation of partlculate matter from the
air. The apparatus further comprises a hollow, frustoconical
filter element disposed in the said chamber in concentric,
encircling relation to the separator with its larger end
sealably engaging the first axial end of the casing and its
smaller end sealably engaging the second axial end of the casing,
the frustoconical filter element diverging relative to the
separator to define a first annular space therebetween which
increases in flow area from the Eirst axial end of the casing
to its second axial end. The frustoconical filter element
further defines a second annular space with the inner surface
of the cylindrical casing that increases in flow area from the
first axial end of the casing to its second axial end. The
second outlet of the cylindrical casing is in fluid communi-
cation with the second annular space to receive filtered air
from the filter element, and to discharge filtered air from
the apparatus.
The inventive apparatus for cleaning air may also
comprise a generally cylindrical casing having first and
second axial ends and defining an internal chamberr the cylin-
drical casing further comprising an inlet in the first axial
énd, a first outlet in the second axial end for discharging
particulate matter and a second outlet. The apparatus further
comprises a separator comprising a hollow frustoconical member
having open axial ends and formed from a plurality of tapered
frustoconical segments, the frustoconical member disposed
within the chamber with its larger end sealably encircling
the inlet and the smaller end sealably encircling the first
outlet to define a first flow path for inlet air which decreases
in flow area from the inlet to the first outlet, with louver
means formed in the frustoconical member and defining a second
flow path therethrough, the louver means being constructed to
~ - 4a -
~ \
-
cause air to partially chan~e direction in order to flow there-
through, thereby enabling the separation o~ particulate matter
from the air. The apparatus further comprises a hollow, frusto-
conical filter element disposed in the chamber in concentric,
encircling relation to the separator, with its large end
sealably engaging the first axial end and its smaller end
sealably engaging the second axial end. Means are also included
for spacing the frustoconical separator fro~ the frustoconical
filter element to define an annular space therebetween. The
frustoconical element further defines a second annular space
with the inner surface of the cylindrical casing that increases
in flow area from the first axial end of the casing to its
second axial end. The second outlet of the casing is disposed
in fluid communication with the second annular space to receive
filtered air from the filter element and to discharge filtered
air from the apparatus.
According to another aspect of the invention, the
frustoconical separator is separate from the pleated filter
element and formed from a stack of annular members of progress-
ively decreasing diameter which are held in relative positionby a plurality of longitudinal stringers. The relationship
of the annular members one to another defines the desired
louvered configuration.
The frustoconical separator can be constructed by
other manufacturing methods, such as spiral winding, which
simultaneously forms the louvers, or by molding the entire unit.
According to yet another aspect of the invention, a
reversed outlet tube is provided for the scavenged particulate
matter, and means including a high pressure nozzle are included
in cooperation with the outlet tube to assist in the removal
of scavenged matter.
- 4b -
Brie~ Description of the Drawings
Figure l is a view in side elevation of air cleaning
apparatus embodying the subject invention, portions thereof
broken away and shown in section;
Figure 2 is an exploded perspective view of the re-
placeable separator/filter assembly for the air cleaning
apparatus;
Fi~ure 3 is an enlarged end view of the frustoconical
separator of the separator/filter assembly;
Figure ~ is a fragmentary view in side elevation of
an alternative embodiment of the invention with portions there-
of broken away and shown in section;
Figure 5 is a side elevational view which is dimin-
ish~ed in size of the frustoconical separator of the alternative
embodiment;
Figure 6 is an end view of the alternative frusto-
conical separator; and
Figures 7-9 are views taken in longitudinal section
of alternative embodiments of the invention, each of which
specifically discloses the variation in the outlet treatment
of scavenged particulate matter.
Description of the Preferred Embodiment
With initial reference to Figure 1, an air cleaner
embodying the inventive concept is represented generally by the
numeral ll. Cleaner ll comprises a cylindrical casing 12 having
a longitudinal axis, and which, in unassembled form, is open at
both axial ends. The inlet end (the right end of Figure l) of
casing 12 has an annular flange 13 secured thereto which receives
an end cap 14 in a manner described in greater detail herein-
below. Cap 14 defines a central axial opening 15 which servesas the inlet for uncleaned air to the cleaner ll.
At the opposite or outlet end, a cap 16 is secured to
, ~ ~
the casing 12 as by welding, the cap 16 defining a central axial
opening 17 of smaller diameter than opening 15, and which serves
as an initial outlet for the device. The opening 17 empties into
a cylindrical collector 18 of short axial dimension and which
includes an outlet tube 19 which extends radially outward for
venting scavenged pa~ticulate matter.
Casing 12 also has a large, generally circular opening
formed through its side adjacent the outlet end to which an out-
let 20 for clean air is rigidly and sealably secured.
With additional reference to Figures 2 and 3, a sepa-
rator/filter assembly for the device 11 is represented generally
by the numeral 21. Assembly 21 comprises a separator 22 which
is the innermost component~ Generally speaking, separator 22
defines a wall or partition which converges from the inlet 15
to the outlet opening 17, thus presenting a flow path of pro-
gressively decreasing area to the uncleaned air entering the
device. Specifically, separator 22 is a truncated cone formed
from a plurality of frustoconical segments 23. To this end,
each of the segments 23 is arcuate in section and tapered as a
function of the progressively decreasing cone diameter. As
best shown in Figure 3, each of the segments 23 is formed with
an upturned side 23a which in assembled form extends radially
outward to form a longitudinal spacer rib. The opposite side
of each segment is formed to define a step 23b which extends
radially inward an amount approximating the thickness of the
segment so that it receives the opposite side of the adjacent
segment while at the same time continuing the circular configu-
ration as viewed in transverse cross section~ As constructed,
the overlapping, fitted sides of ad~acent segments 23 are
welded or epoxied together to define the frustoconical shape.
With reference to Figures 1 and 2, each of the
segments 23 is formed with a plurality of louvers 24 which
-- 6 --
. ~ .
~3t~9(~
are disposed in two longitudinal rows. In assembled form, the
louvers of each segment 23 are aligned with the louvers of other
segments to define circumferential rows. In the preferred
embodiment, the louvers 24 are punched from the body of the
se~ment 23, thus creating edges which project radially inward.
The resulting louver surfaces are inclined toward the outlet;
or, stated otherwise, they converge in the general direction of
uncleaned air flow. As shown in Figure 1, the flow of air
through the louvers 24 is permitted only upon a partial reversal
of flow direction. For a substantial amount of particulate
matter, which is of greater density than the air, the buildup
of inertia is too large to permit such partial reversal, and
the particulate matter is thus swept through the entire length
of the separator 22 for discharge through the outlet.
Separa~or/filter assembly 21 further comprises a
pleated filter element 25 sandwiched between inner and outer
liners 26, 27, respectively. Filter element 25 is made from
porous paper, and, as is well known in the art, pleated to
increase the filtration surface as well as to strengthen the
element itself. Inner and outer liners 26, 27 are made from
thin metal or plastic to provide additional strength to the
filter element 25, and include large perforations to permit the
unobstructed flow of air.
As shown in ~igure l, the sandwich of filter element
25 and liners 26, 27 also takes the form of a truncated cone,
although it diverges slightly with respect to the separator 22.
This divergence may be observed with the increasing radial
dimension of the single spacer side 23a shown in Figure 1. The
divergence is included to increase the size of the inner diameter
of the filter element 25, while at the same time permitting the
outlet opening 17 to be small. The opening 17 must be sufficient- -
ly small relative to the inlet 15 to permit sufficient convergence
an~ thereby control the flow veLocity, and the separator 22
must converge smoothly to the opening 17 without abrupt changes
to insure maximum effectiveness. However, were the inner dia-
meter of the smaller end of filter element 25 to correspond more
closely to the outlet opening 17, the pleats would be too close
together to permit full and efficient filtration, and the con-
centration of pleats could also create the possibility of struc-
tural defects. The spacing effect of the sides 23a thus enables
the filter element 25 to assume more desirable dimensions.
It is intended that the separator/filter assembly 21 be
easily removed and replaced as a unit, and the several elements
are therefore held in relative position by end caps 28, 29.
~ach of the end caps 28, 29 is annular in shape and cupped to
receive the component ends. The caps are secured to the elements
by an adhesive material.
It is also preferable that the device 11 include a
safety filter element, which is represented by the numeral 31
in Figure 1. Safety element 31 consists of inner and outer
linings 32, 33 which are similar to the linings 26, 27 but for
the difference in diameter. A single layer of paper 34 is sand-
wiched between the linings 32, 33, the porosity of which is ,
greater than that of the filter element 25, but which is suffi-
cient to perform minimal filtration should a break occur in the
element 25. Safety element 31 further includes an annular cap
35 at its smaller end which is adhered to the elements 32-34.
An end cap 36 having a radial flange is adhered to the larger
end, the flange serving to mount the safety element 31 in
proper position.
The separator/filter assembly 21 and safety element
31 are sealably mounted within the device 11 through the use of
gaskets 37, which are adhesively secured to the respective end
caps 14, 16 of the device for engagement with the end caps 28,
-- 8 --
29 and 35, 36. For assembling purposes, the inlet cap 14 is
removed, and the safety element 31 is initially inserted with
its tapered sides in engagement with the cylindrical casing 12
at the inlet end (see Figure 1). This has the effect of center-
ing the element 31, and the subsequent insertion of the separa-
tor/filter assembly 21 is thus centered by the engagement of its
end caps with those of the element 31. The cap 14 is then
placed over the inlet end of the unit and secured in place with
a nut and bolt assembly.
~ bracket 39 is mounted to the casing 12 for mounting
the device.
In operation, uncleaned air is admitted through the
inlet 15, passing through the longitudinal flow path defined
within the separator 22. Depending on the selected degree of
convergence of the frustoconical separator, the flow of the air
is maintained at a uniform or increasing velocity; and separa-
tion of a substantial amount of the particulate matter therefore
occurs uniformly over its length. In this regard, we have found
that optimum separation efficiency occurs when the flow velocity
at the scavenge outlet is more than two times greater than the
flow velocity at the dirty air inlet. As pointed out above,
separation occurs because the particles are of greater density
than the air, and are unable to reverse the essentially straight
flow path due to the buildup of inertia. The scavenged parti-
culate matter thus passes entirely through the separator 22,
entering the collector 18 from the opening 17 and passing to
atmosphere from the outlet tube 19.
That portion of the air flow which separates from the
main stream by passing through the louvers 24 then moves essen-
tially radially outward through the filter element 25. The pre-
cleaned and filtered air then passes through the safety element
31 and into an outlet chamber 40 r from which it leaves through
~/
the ou-tlet 20 ~or use in the internal combustion engine. The
chamber 40 increases in size toward the outlet end of the
device, commensurate with the volume of flow delivered from the
assembly 21 over its length.
A vacuum assist may be used in conjunction with the
outlet l9 to enhance the removal of particulate matter, and/or
with the outlet 20 to assist in the separation and filtration
processes.
With reference to Figures 4-6, an alternative air
cleanin~ device is represented generally by tne numeral 41.
In these figures, like numerals represent structure identical
to that of the device ll, and additional numerals represent new
or modified structure.
The principal difference between devices 41 and ll
resides in the separation and filtration stages. Rather than
an integral assembly, the device includes a separate separator
42 and a separate filter element 43, along with the identical
safety element 31.
With specific reference to Figures 5 and 6, separator
42 comprises a plurality of annular rigid bands 44, each of
which takes the form of a truncated cone having a large diameter i
as compared with its axial dimension. The rigid bands 44 are
of progressively decreasing diameter in the direction of air
flow; and, in order to define the necessary louvered passages,
the smallest diameter of each band is smaller than the largest
diameter of the adjacent band, thus creating a flow passage
therebetween. The plurality of bands 44 are arranged in a
stacked relationship and commonly secured by four longitudinal
stringers 45O
At the inlet end of the separator 42, a larger rigid
band 46 of greater axial dimension and converging in the opposite
direction is secured to the first band 44 and defines an inlet
-- 10 --
~or the separator 42. A cruci~orm 47, consistin~ of a pair of
orthogonal blades 48, extends into the inlet of the separator
42 and is secured to the inner surface of the larger band 46.
The cruciform 47 assists in maintainin~ straight, axial flow
through the separator 42, which results in better separation of
the particulate matter.
At the outlet end of separator 42, a cylindrical
outlet sleeve 49 is secured to the smallest rigid band 44.
An annular flange 50 extends radially outward from ~he outlet
sleeve 49. The outer diameter of sleeve 4g corresponds to the
inner diameter of outlet opening 17, permitting a sliding rela-
tion. ~n additional gasket 37 is positioned on outlet cap 16
for sealing engagement with the flange 50, as shown in Figure 4.
With continued reference to Figure 4, the filter ele-
ment 43 consists of the same pleated element 25 and liners 26,
27, but includes modified end caps 52, 53 which do not accommo-
date the separator 42.
The construction of device 41 is otherwise essentially
the same as device 11. The stacked construction of separator 42
creates an increased louvered passage flow area. It will also
be appreciated that the separate construction of the separator
42 and filter element 43 enables them to be individually removed
and replaced from the device 41.
Figures 7-9 disclose three further embodiments which
include means for assisting in the removal of scavenged parti-
culate matter, and which are particularly useful in extremely
dusty and dirty conditions. In Figure 7, an air cleaning device
represented generally by the numeral 61 comprises a cylindrical
casing 62 which is open at both ends and formed with a peripheral
flange 63 at the inlet end. Casing 62 also includes an outlet
64 for cleaned air which opens from its side approximately the
outlet end. A removeable cap 65 is sealably secured to the
~3ti9U~l
casing 62 by nut and bolt assemblies 66 and an 0-ring 67.
Inlet cap 65 is formed with a large inlet 68 which admits
uncleaned air to the device 61.
An end cap 69 is permanently and sealably secured to
the outlet end of casing 62. As shown, end cap 69 is formed
with a cylindrical recess which receives the smaller end of a
frustoconical separator/filter assembly 71. The assembly 71
comprises a frustoconical separator 72 having louvers 73 and a
pleated dry paper filter element 74 which is also frustoconical
in shape. The separator 7~ and filter element 74 are integrally
held by end caps 75, 76, the former of which includes a peri-
pheral flange which is clamped between the end cap 65 and flange~
63 of casing 62. A flat annular seal 77 is disposed between end
caps 76 and 69 for air tight operation. An outlet stack 78 is
secured to and supported by the inlet cap 65, projecting vir-
tually to the outlet end of the separator 72 to define a separa-
tion flow passage 79 and an outlet flow passage 80 which are
concentric. It will be observed that the end cap 76 for the
separator/filter assembly 71 is a solid circular cap, as dis-
tinguished from the annular configuration of end cap 75, so thatthe scavenged particulate matter and carrier air flow do not
leave from the bottom o~ the device 61 as shown in Figure 7.
The end cap 76 is formed with an annular, concave recess 76a
which conforms generally to the annular, rounded lower end of
the outlet stack 78, so that the scavenging air flow from sepa-
ration passage 79 to outlet passage 80 is smoothly reversed.
It will be further observed that the outlet passage 80 `
initially assumes a constant diameter and then expands to a
larger flow area before curving outwardly for issuance through
the side of inlet cap 65. To this end, outlet stack 78 is
formed from an outer lining 81 which is generally c~lindrical
and an inner lining 82 which defines the expanding flow passage.
- 12 -
,, .`j ,~.',~
. ,,j . , .
The connection between the linings 81, 82, designated by refer-
ence numeral 83, initially conforms to the shape of the lower-
most louver 73 and is then rounded to effect the smooth reversal
of flow as noted above.
To assist in the rapid and efficient removal o~
scavenged particulate matter, an air nozzle 8~ is introduced
through the end cap 76, projecting axially into the inlet of
outlet passage 80. Air nozzle 84 is sealably clamped against
the end cap 76 through the use of an O-ring 85, and is adapted
for connection to a high pressure air source through the use
of an enlarged fitting 86.
Separation and fil~ration of the air cleaner 61 is
much the same as air cleaner 11, although it will be noted that
incoming air must pass around the outlet stack 78 into the -
annular separation flow passage 79. This passage is convergent
to maintain a uniform flow velocity to achieve efficient separa-
tion.
As the particulate matter and its carrier flow leave
the separation passage 79, a smooth flow reversal takes place
which is significantly assisted by the high velocity flow issuing
from air nozzle 84. Nozzle 84 creates a flow pressure within
outlet passage 80 which is lower than that within separation
passage 79, and which draws the scavenged particulate matter into
the outlet passage and out of the outlet stack 78. This in-
creased flow significantly improves the separation capability
of the device 61 and is th~s well adapted to extremely dusty
environments.
Figure 8 discloses an air cleaner which is essentially
the same as device 61, with the exception of a modified outlet
stack 91. Stack 91 comprises an outer lining 92 which has a
progressively increasing diameter as it approaches the lower
end of the separator 72, thus increasing the degree of conver-
13 -
gence of a separator flow passa~e 93. An inner lining 94 is
cylindrical in shape, thus defining an outlet passage 95 of
constant cross sectional area. The outlet end of stack 91 bends
radially outward through the side of the inlet cap as shown.
In figure 9, an outlet stack 101 is defined by a
cylindrical outer lining 102 and a cylindrical inner lining 103
to define a separator ~low passage 104 having a lesser degree of
convergence and an outlet passage 105 o~ constant cross sectional
area. The upper end of outer lining 102 terminates in a dome 106
which is disposed in the inlet of the device to assist in smoothly
dividing the flow into the annular separation passage 104. The
inner lining 103 bends radially outward through the outer lining
102 and the side o~ the inlet cap to discharge the scavenged
particulate matter.
The space defined between inner and outer linings 81~
82, 92-94, and 102-103 is dead space and is not exposed to flow.
The embodiments of Figure 7-9 are somewhat schematic
for purposes of clarity, and do not disclose any support for the
outlet stacks 78, 91 and 10~ other than the support provided by
the associated inlet cap. It is possible to include radial
struts between the stack and the inlet cap or associated
separator if necessary for additional support.
- 14 -
