Self-cleaning pulsed air cleaner with integral precleaner

An air cleaning method and apparatus is disclosed in several embodiments. In one set of embodiments, there is described an air cleaning method and apparatus in which air to be cleaned is drawn toward and through a filter in a particular direction. Periodically, reverse pulses of air are directed through the filter in a direction opposite to normal flow to interrupt the flow of air and to dislodge collected particles from the uncleaned air side of the filter and to enable migration of the particles toward the downstream lower end of the filter. In accordance with other embodiments of the present invention, there is described the addition of inertial precleaner devices located proximate the unfiltered side of each filter for inertially separating heavy particulate matter from the uncleaned air prior to filtration. In addition, the inertial precleaner devices may have closure means operable during the periodic reverse pulse cleaning to remove the dislodged collected particles and prevent reentrainment on the filter.

TECHNICAL FIELD 
This invention relates to the field of air cleaning by removal of 
particulate matter such as dust, particularly in installations requiring 
treatment of large volumes of air. 
BACKGROUND OF THE INVENTION 
The removal of dust is accomplished by passing the air through a filter of 
material permeable to flow of gas but not to passage of particulate 
matter, which collects on the filter thus gradually filling its pores and 
increasing the restriction of the cleaner, that is, the pressure drop 
across the filter and the load on the air-moving fan or blower. A 
successful air cleaner must accordingly have a large enough area of filter 
medium to reduce the initial restriction to an acceptable level, and must 
be either cleaned or replaced at sufficiently frequent intervals to 
prevent dirt buildup to a point where the restriction is adversely 
affective. 
Means have been devised for cleaning filters, even without interrupting 
system operation, by mechanical shaking or by reverse air jet pulsing. The 
latter cleaning procedure is successful, when the filter medium is pleated 
paper, in releasing the particulate matter from the medium, but the 
resumption of normal airflow through the filter at the end of each pulse 
in large measure draws the particles back against the filter medium, thus 
greatly reducing the cleaning efficiency. This is particularly noticeable 
in installations which because of the large volume of air to be treated 
require large areas of filter medium. 
BRIEF SUMMARY OF THE INVENTION 
One aspect of the present invention relates to an air cleaner with pulse 
jet cleaning in which the filter medium is positioned and the gas flow is 
directed so that particulate matter initially impinging on the filter 
medium is enabled and impelled to "migrate" across the medium during 
successive cleaning pulses and to ultimately reach a scavenge site where 
it can be discharged from the cleaner, always without interruption of the 
cleaning operation. 
Other embodiments of the present invention relate to an air cleaner with 
pulse jet cleaning and an integral precleaner. 
In accordance with one of these embodiments, there is disclosed an air 
cleaner apparatus for removing particulate matter from air comprising a 
housing having an unfiltered air inlet and a filtered air outlet, a filter 
assembly within the housing including a filter having a filtered air side 
and an unfiltered air side, the filtered air side being isolated from 
unfiltered air, inertial precleaner means located proximate the unfiltered 
air side and defining an intermediate space therebetween, the precleaner 
means for reversing the flow of unfiltered air thereby inertially 
separating particulate matter, reverse pulse cleaning means for 
intermittently directing a reverse flow of air toward the filtered side of 
the filter so that particulate matter will become dislodged from the 
unfiltered air side and enter the intermediate space, closure means 
responsive to the reverse flow of air for blocking passages of the reverse 
flow through the inertial precleaner means, and an outlet means in said 
intermedate space for exhausting the reverse flow of air so that 
particulate matter in the flow will not be reentrained on the unfiltered 
side of the filter. 
In accordance with other aspects of the invention, there are disclosed a 
number of embodiments relating to closure means described above and one 
embodiment having the above elements without the inertial precleaner 
means. 
There have this been outlined rather broadly the more important features of 
the invention in order that the detailed description thereof that follows 
may be better understood, and in order that the present contribution to 
the art may be better appreciated. There are, of course, additional 
features of the invention that will be described hereinafter and which 
will form the subject of the claims appended hereto. Those skilled in the 
art will appreciate that the conception upon which the disclosure is based 
may readily be utilized as a basis for the designing of other structures 
for carrying out the several purposes of the invention. It is important, 
therefore, that the claims be regarded as including such equivalent 
structures as do not depart from the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
The embodiment of the invention shown in FIGS. 1 and 2 comprises an 
airtight housing 20 having a removable or hinged top 21, a bottom 22, 
opposite sides 23 and 24, opposite ends 25 and 26, and a vertical 
partition 27 which divides the housing into a larger chamber 30 and a 
smaller chamber 31. Bottom 22 is configured to provide a scavenge chamber 
32 to which there is connected a scavenge duct 33. An inlet 34 for air to 
be cleaned is provided in top 21 near end 25, which is closed, and a draft 
opening 35 may be provided in top 21 opening into chamber 30 near 
partition 27. An outlet 36 for cleaned air is formed in end 26. Partition 
27 is provided with a plurality of apertures 37, 38, 40 so that a path for 
air flow extends from inlet 34 through chamber 30, apertures 37, 38 and 
40, and chamber 31 to outlet 36, as suggested by the arrows in FIG. 2. 
A plurality of filter assemblies 41, 42 and 43 are mounted on partition 27 
to close openings 37, 38, and 40. To accomplish this an upper rod 180 and 
a lower rod 181 are secured at first ends to partition 27, between filters 
41 and 42, and a second pair of rods are similarly secured between filters 
42 and 43. A clamping frame 182 comprising upper and lower horizontal 
channels 183 and 184 and vertical legs 185 and 186 is secured to the rods 
by nuts 187. Pressure pads 190 are provided between the channels and the 
filters. Legs 185 and 186 are extended downward to rest on bottom 22. 
Deflectors 191 of sheet metal are secured to extend vertically between the 
rods by clips 192, for a purpose presently to be described. 
The filter assemblies are alike, and assembly 41 is shown in FIGS. 3 and 4 
to comprise first and second flat filters 44 and 45 mounted on edge in a 
frame 46 with a tapering space 47 between them to converge toward a first, 
closed end 50 of the frame. The opposite end 51 of the frame is open, and 
is dimensioned to be seated against one of the openings in partition 27 
and be sealed with respect thereto by a suitable gasket 52. A top 53 and 
bottom 54 of frame 46 are closed, and a pair of horizontal partitions 55 
and 56 provide strength and rigidity to the assembly, and divide the 
tapering space 47 between the filters into an upper chamber 60, a middle 
chamber 61, and a lower chamber 62. 
Each of filters 44 and 45 is made up of a body of pleated paper filter 
medium 63, contained between inner and outer sheets 64 and 65 of 
perforated metal or similar material, the whole being unified by stripes 
66 of plastic or cement. The pleats of the filter medium run vertically, 
as is shown. 
It will be apparent that assemblies 41, 42, and 43 divide chamber 30 into 
first and second portions of irregular outline, the first portion being 
that space outside of the filter assemblies, and the latter portion being 
the sum of the tapering spaces inside the filter assemblies. 
Turning again to FIGS. 1 and 2, a horizontal partition 70 is provided in 
chamber 31, so that the space 71 below the partition comprises a reservoir 
for air for cleaning the filter, which air is supplied through a duct 72. 
A number of standpipes 73, 74, 75 equal to the number of filter assemblies 
extend upwardly from partition 70, each supplying air from the chamber to 
a number of valves equal to the number of chambers in the tapered space 47 
of a filter assembly. Thus standpipe 73 is connected to and supports an 
upper valve 76, a center valve 77, and a lower valve 78. The valves 
connect with nozzles 80, 81, and 82 respectively, and are positioned so 
that the nozzles are directed centrally into chambers 60, 61, and 62 of 
the apposed filter assembly 42. Standpipes 74 and 75 are similarly 
equipped with valves and nozzles, of which valves 83 and 84 and nozzles 85 
and 86 are shown in FIG. 2. 
Between the nozzles and partition 27 are mounted a set of diffusers 90, 91, 
and 92, aligned with standpipes 73, 74, and 75 respectively. The 
partitioning of the filter assemblies into vertically arranged chambers, 
the provision of plural nozzles, one for each chamber, and the 
interposition of diffusers between the nozzles and the chambers has been 
found to optimize the efficiency of pulse jets in releasing particulate 
matter from the filters, as will be explained below. 
Preferably valves 75, 76, etc. are normally closed, solenoid valves 
actuated electrically at brief intervals to emit pulses of air through the 
associated nozzles 80, 81, etc. 
By a suitable switching circuit suggested in FIG. 6 and including a timer 
93 the valves are energized so that jets are directed simultaneously into 
the upper chambers of the filter assemblies, then into the center 
chambers, and then into the bottom chambers, in a repeating cycle: the 
length of the cycle and the lengths of the pulses within the cycle and 
their spacing may be varied at the will of the operator, to maximize the 
cleaning effect in dependence on the nature of the particulate matter 
being removed. 
Operation 
In operation top 20 is opened and a pluraltiy of clean filter assemblies 
41, 42, and 43 are inserted and secured in sealed relation to partition 
27. Top 21 is closed, an inlet duct for air to be cleaned is connected at 
34, an outlet duct for clean air is connected at 36, a source of air under 
negative pressure is connected to duct 33, and a source of air under 
positive pressure is connected to duct 72. To set the cleaner in 
operation, electrical energy is supplied to timer 93, and airflow through 
the cleaner is started, ordinarily by a pump or fan connected to outlet 
36. 
Particles of dirt carried by the air entering the cleaner at 34 are 
initially collected on the outer surfaces of the filters in assemblies 41, 
42, and 43. Timer 93 operates to supply a pulse of air from reservoir 71 
through standpipes 73, 74, and 75 and valves 83, 76, and 84 to upper 
nozzles 85, 80, and 86, which project jets of air past diffusers 90, 91, 
and 92 into the upper chambers 60 of the filter assemblies, interrupting 
the flow of air inwards through the filters and momentarily discharging 
dirt particles from the outer surfaces of the filters. Deflectors 191 are 
provided to prevent particles expelled from one of the filters from being 
forcibly jetted across the space between filters to impinge on the 
adjacent filter. The particles start to descend by gravity into the normal 
airflow below, but upon termination of the cleaning pulses normal air flow 
is resumed and the particles are again brought into contact with the 
filters, at sites lower and nearer to partition 27 than initially. Pulses 
of air are then supplied in sequence to the center and the lower chambers 
of the filter assemblies, again dislodging particles of dirt and enabling 
them to move. The downward movement of particles near partition 27 is 
facilitated if a small quantity of ambient air is admitted at draft 
opening 35. The dust particles partake of a motion of migration across the 
surfaces of the filters and ultimately reach scavenge opening 32, from 
which they are extracted by duct 33, together with a small quantity of the 
air entering at 34 and 35. 
In one embodiment of the invention the volume of chamber 71 was one cubic 
foot, cleaning air was supplied at 100 pounds per square inch, and the 
pressure dropped to 65 pounds per square inch during the pulses. These 
dimensions will naturally vary with the size of the installation: the one 
referred to had a capacity of 8,000 cubic feet per minute of air at inlet 
34. 
Structure of the Second Embodiment 
A second embodiment of the invention is shown somewhat schematically in 
FIG. 5 to comprise a housing 100 divided by a partition 101 into a lower, 
larger chamber 102 and an upper, smaller chamber 103. Air to be cleaned is 
admitted to the housing at an inlet 104 near the bottom, and cleaned air 
is taken from the cleaner at an outlet 105, in its top. A reservoir 106 is 
supplied with air for the cleaning function by a duct 107, and standpipes, 
valves, nozzles, and deflectors may be supplied as described above. Filter 
assemblies such as assembly 110 are supported on and sealed to partition 
101, and may be as shown in FIGS. 3 and 4. 
Housing 100 is provided with a vertical partition 113 to define a scavenge 
plenum 114, connected to a scavenge duct 115, and a plurality of apertures 
116, 117, 120, and 121 provide communication between chamber 102 and 
plenum 114. 
Operation 
The operation of the second embodiment of the invention is as described 
earlier. Particles of dust initially collecting on the surfaces of the 
filters, are momentarily released by the cleaning jets, and migrate across 
the filter surfaces. In this embodiment upward movement is caused by the 
normal flow of the air into the housing, and movement to the left is 
caused by the negative pressure maintained in scavenge plenum 114. The 
drawing shows that no draft opening is provided in this housing, so the 
cleaner can be used in a system where air is forced into inlet 104 rather 
than being drawn from outlet 105. In both of the embodiments the matter 
removed in the scavenge duct is disposed of in conventional fashion. 
Alternate Embodiments Including Integral Precleaner 
Alternate embodiments of the present invention including an integral 
precleaner are shown in FIGS. 7-22. Several alternative embodiments within 
this group of figures are shown and will be explained hereinafter. 
The embodiment shown in FIGS. 7-13 comprises an airtight housing 220 having 
a hinged section 222 for intake of unfiltered air which pivots on hinge 
224 and is held in a closed position by locking means 226. FIG. 7 shows 
left wall 228 and right wall 230 while FIG. 8 shows the top wall 232 and 
the bottom wall 234. Portions 236 and 238 form the side and bottom walls 
of the hinge section 222. 
Within housing 220 are located a plurality of filter assemblies 240, 242, 
and 244. The filter assemblies are held in housing 220 by bolts 246 and 
plates 250 and 252 at their respective ends. Plate 252 includes apertures 
254, 256, and 258. Located proximate apertures 254-258 are pulse jets 
260a-c, 262a-c, and 264a-c. Their relative orientation can best be seen in 
FIG. 9. Each pulse jet 260-264 is designed to supply a high velocity 
stream of air for reverse pulse cleaning of the filter assemblies. The 
pulse jets are of the same general nature as those in the earlier 
embodiment designated generally by the numbers 73, 76, and 80; however, a 
diffuser 90 used in the previous embodiment is optional. The pulse jets 
are connected to conduits 266, 268, and 270, which direct the air 
therethrough. 
Hinge section 222 includes a plurality of passageways 272, 274, 276 which 
are formed of a plurality of partitions 278, 280, 282, and 284, and which 
are curved as shown in FIG. 8. The conduits are aligned so as to provide a 
flow of unfiltered air to the filter assemblies, as will be explained 
hereinafter. 
Turning temporarily to the individual filter assemblies, attention is 
directed to FIGS. 10-12. Basic components of the filter assemblies 240-244 
are the same as assembly 41 shown in FIGS. 3 and 4 of the previous 
embodiment. To the extent variations are not explained herein, reference 
should be had to those figures for a detailed description. 
All of the filter assemblies are alike. Filter assembly 240 is shown in 
FIGS. 10-12 to comprise first and second flat filters 286 and 288 (each 
having a filtered and unfiltered face 287a and 287b respectively) mounted 
on edge in a frame 290 with a tapering space 292 between them to converge 
toward a first closed end 294. The opposite end 296 is opened and is 
dimensioned to be seated against one of the openings 254-258 in plate 252 
preferably with a gasket seal 298 to ensure an airtight connection. The 
top 300 and bottom 302 of frame 290 are closed, thereby enclosing the 
"filtered" side of the filter assembly, and a pair of horizontal 
partitions 304 and 306 provide strength and rigidity to the assembly as 
well as dividing space 292 into an upper chamber 292a, middle chamber 
292b, and lower chamber 292c. Each of filters 296 and 288 is made up of a 
body of pleated paper filter medium 306 contained between inner and outer 
sheets 308 and 310 of perforated metal or similar material. 
Surrounding frame 290 is the precleaner enclosure 312 which surrounds frame 
290 on face 287a. Between enclosure 312 and frame 290 there is defined an 
intermediate space 314. Enclosure 312 includes two louvered panels 316a 
and 316b which are mirror images of each other and which are joined by a 
second end panel 318. The remaining portions of enclosure 312 abut frame 
290 at gasket 298. 
Louvered panels 316a and 316b can be more clearly seen in FIG. 13 of the 
drawings. In view of the symmetry of panels 316a and 316b, only one will 
be discussed in detail. Panel 316a includes a plurality of successive 
louvers 319 which are preferably stamped out of a planar sheet so as to 
create the overall shapes most clearly shown in FIG. 12, having a rising 
portion 320 and side sloping portions 322. The angle of inclination of 
portion 320 relative to the planar sheets 316a and 316b may be 
predetermined according to desire at manufacture to enhance the 
precleaning effect according to particular gas densities and pressures to 
be applied to this device. 
Each louver provides a passageway 324 between the intermediate chamber 314 
and interior space 221 within housing 220. 
Affixed to the other side of plate 312, proximate space 314, by fasteners 
326 and flaps 328. Flaps 328 are preferably made of a flexible material, 
such as rubber or plastic, so that they may move from a position blocking 
the passageways 324 to a position extending into intermediate space 314 
thus opening the passageways in response to air pressure changes within 
the intermediate space. When flaps 328 are in a blocking position, there 
will be contact between the flap and end portion 330 of each louver 320. 
As can be seen in FIG. 10, within the interior space 314, proximate end 
318, a scavenge outlet 332 is provided. The scavenge outlets for each 
filter assembly 240-244 are collected by a manifold 334 as shown in FIG. 
7. As a scavenging outlet for air within the interior space 221, ports 336 
are provided (as seen in FIG. 7), which connect to manifold 338, which is 
ultimately exhausted to the outside environment. 
Operation 
This embodiment of the present invention effectively provides a dual 
filtration of uncleaned air and a superior means for reverse pulse 
cleaning of the filter element. 
The first filtration of uncleaned air is accomplished by inertial 
separation. Uncleaned air enters conduits 272-276 (FIGS. 7 and 8) and 
enters interior space 221 of housing 220. Arrows 400 in conduits 272-276 
indicated the direction of air flow. The air within space 221 will travel 
in a direction generally toward ports 336. As the air passes through 
louver 318, it will reverse directions approximately 180.degree. so as to 
enter passageway 324 as shown by arrows 402 in FIGS. 7 and 13. Because the 
particulate matter, which is of a greater mass than air, inertial forces 
of such magnitude are achieved so as to preclude the particles from 
reversing direction as they pass the louvers, a substantial portion of the 
heavier particulate matter will be separated out and continue to flow in a 
linear direction into ports 336. Therefore, the air entering passageways 
324 will be precleaned. 
The air now enters intermediate space 314 in the direction shown by arrows 
404 in FIG. 13. The filtering medium 286 removes most of the remaining 
particulate matter and allows the air to exit the filter in the direction 
shown by arrows 406 in FIG. 13. Finally, the clean air will exit the 
filter through apertures 254-258 in the direction shown by arrows 408 in 
FIG. 7. 
As the filter medium 286 becomes filled with particulate matter, it will be 
necessary to purge the medium with a reverse pulse of air from pulse jets 
260-264. This reverse flow of air is shown by arrows 410 in FIG. 10 and 
FIG. 13. 
During the period when the reverse pulse of air is activated, particulate 
matter will be blown off the surface of filter medium 286 into 
intermediate space 314. This reverse pressure will immediately cause flap 
328 to become biased against edge 330, thereby closing passageway 324 
(FIG. 13). The only remaining path for the reverse pulse of air will then 
be toward port 332 and into manifold 334. This will effectively sweep this 
particulate-laden purging air flow out of the system to prevent the major 
portion of the particulate matter from being relodged on the filter 
medium. Because flaps 328 are flexible and preferably slightly curved, 
they will tend to deflect the reverse flow in the direction of port 332 
shown by arrows 412. In addition, their flexibility will tend to allow the 
formation of a greater curvature during the period when they are in the 
process of closing passageway 324. 
In order to provide for continuous operation of the filter, it is not 
possible to provide reverse pulse cleaning of all sections of the filter 
simultaneously. By specifically sequencing the portions of each filter 
assembly which shall be purged, it is possible to cause a general 
migration of particulate matter in a direction shown by arrows 414 in FIG. 
8. By utilizing this migrating effect, the filter assemblies tend to be 
self-cleaning by ultimately siphoning off the accumulated particulate 
matter through apertures 332 at the bottom of the intermediate space 314 
(see FIGS. 8-10) and by sweeping this matter away through conduit 334 as 
shown by arrow 344. 
Alternate Embodiment 
The embodiment disclosed in FIGS. 19-21 is considered the preferred 
embodiment at this time. Many of the features of this embodiment are 
identical with those of the previous embodiments and will therefore not be 
reiterated. The changes made in this embodiment over the previous 
embodiment are shown in FIGS. 19-21. In order to simplify the air flow 
within intermediate chamber 314a as shown in FIG. 20 and eliminate port 
332, flaps 328a have been reversed (see FIG. 13 for comparison). In FIG. 
20, it can be seen that each of flaps 328a is fixed to the next leading 
louver 319a so that the curl of the flap is reversed. As mentioned 
previously, it is this curvature or curl which aids in urging the reverse 
air pulse shown by arrows 412a in flowing in a particular direction during 
the time and after passageways 324a are closing. As can be seen in FIG. 
20, the air flow of uncleaned air outside the louvers indicated by arrows 
414 and the air flow of the reverse air pulse indicated by arrows 412a is 
generally in the same direction. This aspect allows for simplification of 
the scavenging system for intermediate space 314a. As seen in FIG. 22, the 
termination of plate 312a proximate gasket 298a has been altered as 
compared with the previous embodiment shown in FIG. 10. In this 
embodiment, in FIG. 22, ports 416 at the ends of intermediate space 314a 
provide an outlet passage (FIG. 21) for this flow of air which is 
collected in manifold 338a. The direction of air flow is indicated by 
arrows 422 in FIG. 21. It is noted that manifold 338 is the same manifold 
which collects the heavy particulate matter initially separated in space 
221 during the first phase of precleaning. Manifold 338a corresponds 
substantially to manifold 338 in the previous embodiment shown in FIG. 7. 
Thus, by reversing the direction of air flow within intermediate chamber 
314a, shown by arrows 412a, as a consequence of the orientation of flaps 
328a, it is possible to eliminate port 332 and manifold 334 which were 
employed in the previous embodiment. The present embodiment uses manifold 
338 to collect scavenged air during reverse pulse jet cleaning. 
Alternate Embodiment Having Adjustable Louvers 
This embodiment of the present invention contains many of the features and 
elements shown in the previous two embodiments, and to the extent these 
features or elements are not repeated, they should be considered to be 
generally the same. 
This embodiment allows for the mechanical adjustment of the angle of 
inclination of the louvers either by mechanical or electromechanical 
means. This adjustability feature may allow for the elimination of flaps 
328 or 328a by mechanically closing louvers 319b (FIGS. 14, 15, and 18) at 
the appropriate time. In addition, the adjustability of louvers allows 
selection of the proper angle of inclination to most effectively separate 
particulate matter of a particular mass carried in a gas at a particular 
air flow or pressure. 
FIGS. 14 and 15 disclose the electromechanical version of this embodiment 
concerning filter assembly 240b. As in previous embodiments, each filter 
assembly has two louvered panels 316c and 316d which are symmetric with 
respect to each other. The louvers 319b are closed at their lateral ends 
502. Each louver 319b includes a tubular member 503. The members 503 are 
axially aligned with cooperating tubular members 505 fixedly carried by 
panels 316c and 316d. Pivot rods 504 are received within respective 
cooperating tubular members 503 and 505 to pivotally mount louvers 319b. A 
lever member 506 is attached to louver 319b and the pivot points each have 
members 506 pivotably attached to control arm 508. Filter assembly 204b is 
divided into three sections, 261a, b, and c, as in the previous 
embodiment. 
In order to obtain the migrating effect discussed in the previous 
embodiment, it is desirable to reverse pulse clean each section 
sequentially a to c so as to cause particulate matter to migrate towards 
the bottom of the filter. (Note that FIG. 14 is shown upsidedown). To 
accomplish this, the louvers of each section are connected together by an 
individual connecting member 508. Each connecting member is individually 
operated by rack and pinion systems 514, 516, and 518, respectively, one 
of which is shown in detail in FIG. 16. Three pivot rods 504 include 
pinion gears 520, 522, and 524, which have meshing engagement with a rack 
and roller system 526, 528, and 530 respectively. The roller holds the 
rack in place while the rack engages the pinion gear. The rack is 
adjustably connected to solenoid armatures 532, 534, and 538 by means of a 
fastener through a slot in a portion of the armature. The armature resides 
within a solenoid 540, 542, and 544, which is adjustably affixed to the 
filter assembly by means of fasteners in a slotted base. The adjustment of 
the solenoids allows for presetting the angle of inclination of the 
louvers. Pinion gear 520 is coupled to the louvers in filter section 261a 
by pin 546. Similarly pinion gears 522 and 524 are coupled to the next 
succeeding filter sections by pins 548 and 550. The remaining pivot rods 
504 do not rotate themselves and are fixed by pins 552, which pass through 
tubular members 505 and respective rods 504, as seen in FIG. 14. This 
allows their respective louvers to rotate freely in response to movement 
of respective control rods 508. 
The circuit shown in FIG. 17, which is used to operate the pulsed jets, may 
also be coupled to solenoids 540-544 so as to electromagnetically close 
the proper section of louvers when reverse pulse jet cleaning is being 
undertaken. 
In the circumstance where it is not desired to close louvers 319b but 
adjustability is an important factor, the manually adjustable system 240c 
disclosed in FIG. 18 is available. Replacing solenoids 540-544 are plates 
602-606, which have integral handles 608-612. The plate is pivoted on 
pivot points and locking nuts 614-18 as it controls the racks and pinions 
626-30 as at 630-24. 
Either the electromechanical or the simple mechanical louver-adjusting 
system disclosed above may be used in conjunction with either of the air 
flow patterns for the scavenging suggested in the previous embodiment. 
Therefore, in FIG. 15, port 332 drawn in phantom lines may be eliminated 
and ports such as 416 in FIGS. 21, 22 substituted therefor. 
FIG. 17 discloses a simple schematic diagram of the preferred electrical 
hookup of solenoid valves 450, 452, and 454 which control pulse jets 260a, 
262a, 264a (for 450), 260b, 262b, 264b (for 452) and 260c, 262c, 264c 
(for 454) and solenoids 540, 542, and 544 etc. which control the louvers. 
Control box 456 would be in the nature of electronic or electromechanical 
sequencing means to operate the three parallel circuits in a desired 
sequence. 
It is noted that it is also possible to practice this invention without the 
precleaner. The embodiments shown in FIGS. 7-13 would be modified by 
removing the louvers and leaving the passageways and flaps. The device 
would then have the same reverse pulse cleaning and migration properties 
of other embodiments described herein. 
Numerous characteristics and advantages of the invention have been set 
forth in the foregoing description, together with details of the structure 
and function of the invention, and the novel features thereof are pointed 
out in the appended claims. The disclosure, however, is illustrative only, 
and changes may be made in detail, especially in matters of shape, size, 
and arrangement of parts, within the principle of the invention, to the 
full extent of the broad general meaning of the terms in which the 
appended claims are expressed.