Dustless regenerative air sweeper

A closed-loop Regenerative.RTM. air sweeper is provided which constitutes an improvement of that disclosed in U.S. Pat. No. 3,512,206. The sweeper of the latter patent is provided as an integral portion thereof, whereas a conversion, a "dustless" mechanism having first and second chambers into the first chamber of which is directed a portion of the air stream from a pressure conduit associated with a pickup head of the sweeper. Particles of debris are separated by cyclone separators and thereafter by membrane filters after which substantially clean air is discharged to atmosphere. Air entrained particles separated by the cyclone separators and the cartridge filters are returned to a vacuum side of the pickup head thereby maintaining substantially closed-loop air flow of the sweeper. Clean air is controllably exhausted to atmosphere by flue vanes which can be selectively moved under pressure differential sensing means associated with the cyclone separator. The pressure in the two air chambers is also sensed with the read-out thereof being in an instrument panel to permit an operator to monitor and diagnose the system. Pulses of high pressure air are utilized to clean the membrane filter and a pop-off valve serves as an emergency vent to atmosphere under undesired high pressure within the second chamber of the housing. An extremely important aspect of the present invention is that achieved by creating and maintaining a substantially negative pressure at and across the pickup head. The latter is achieved by assuring that the air drawn into the pickup head is approximately a nominal ten percent (10%) and the clean air discharged to atmosphere is maintained at the substantially the same nominal ten percent (10%) through appropriately operating a valve under the control of a pressure differential sensor which measures pressure drop across the cyclone separators.

BACKGROUND OF THE INVENTION 
The closed-loop Regenerative.RTM. air system was invented more than 
twenty-five (25) years ago by Mr. Bernard W. Young, as is evidenced by 
U.S. Pat. Nos. 3,512,206 and 3,545,181 granted on May 19 and Dec. 8, 1970, 
respectively. Tymco, Inc. of Waco, Tex. has manufactured closed-loop 
Regenerative.RTM. air sweepers for more than twenty-five years, and each 
uses the force of a high velocity controlled jet of air created by a 
powerful blower to blast down and across a pickup head onto pavement and 
into cracks thereof forcing up into the air stream of the pickup head 
packed-on heavy debris and fine dust particles. The debris-laden air 
stream is pulled into a large hopper where the air loses velocity and 
larger debris falls to the bottom. A screen at the top of the hopper 
prevents items, such as leaves, paper, cans, rocks and large pieces of 
debris from leaving the hopper and entering a centrifugal dust separator. 
The centrifugal dust separator spins the air along a curved wall of a 
centrifugal separator chamber until small size dust particles are skimmed 
off into the hopper and substantially clean air is returned to the blower 
to continue the closed-loop air cycle of the Regenerative.RTM. air 
sweeper. This closed loop system substantially prevents dirty air from 
being undesirably exhausted into the environment. 
Such Tymco Regenerative.RTM. air sweepers are highly efficient under dry 
conditions and are also relative efficient even under rainy or wet 
conditions. Mechanical sweepers utilizing brooms and vacuum sweepers 
utilizing both brooms and vacuums tend to clog and/or smear while the 
Regenerative.RTM. air sweeper continues to efficiently clean under such 
rainy or wet conditions which means cleaning schedules can be accurately 
maintained and fulfilled. 
While such Regenerative.RTM. air sweepers have performed admirably over the 
years and were originally intended for use in hazardous environments, 
applications have grown to include virtually all dustless operations in 
such environments as tunnels, building interiors and most any other uses 
where water for dust suppression is not an option (cement plants, freezing 
climates, etc.) The Environmental Protection Agency (EPA) has also 
expanded its restrictions concerning dustless operation and a need has 
arisen for a truly substantially "dustless" Regenerative.RTM. air sweeper. 
A truly substantially "dustless" Regenerative.RTM. air sweeper has become 
highly desirable due to more stringent requirements of the EPA, and 
sensitivities involved in substantially dustless operation in such 
environments as noted immediately heretofore, particularly should dust be 
laden with water and/or moisture. 
Several efforts have been made toward achieving dustless debris collection, 
as is evidenced by U.S. Pat. Nos. 4,870,489; 4,006,511 and 4,457,043 
issued respectively on Mar. 11, 1975; Feb. 8, 1977 and Jul. 3, 1984. Each 
of these patents discloses a sweeping machine which desirably seeks to 
prevent dust-entrained air from being exhausted to atmosphere. For 
example, in U.S. Pat. No. 4,457,043 air is drawn from a main mouthpiece 
through a suction pipe into a coarse separator arranged in front of a 
cyclone separator with air being recycled through a fan and another 
conduit to the main mouthpiece. A portion of the air stream from the fan 
is diverted to another separator through which air is exhausted by a 
separate fan. The latter prevents the overall system from being truly 
"closed" because a substantial portion of the air and any entrained debris 
beyond the separator is evacuated into atmosphere by the associated 
evacuation fan. A similar auxiliary blower associated with the mobile 
street sweeper of U.S. Pat. No. 4,006,511 prevents the system from being 
essentially "closed." However, these and other similar patents, such as 
U.S. Pat. No. 3,870,489, reflect common usage of bag house filtering units 
and/or cyclone filtering units associated with street sweepers, though 
none in association with a Regenerative.RTM. air sweeper which maintains 
substantially 100 percent air flow through its closed-loop air system 
absent debris being forcefully or otherwise exhausted to atmosphere. 
SUMMARY OF THE INVENTION 
In keeping with the foregoing, a novel, "dustless" Regenerative.RTM. air 
sweeper is provided which essentially maintains the closed-loop air system 
of such Tymco manufactured street sweepers, while at the same time 
providing maximum filtration under both dry and wet conditions absent any 
substantial air loss and absent debris-laden air exhaust to atmosphere. 
The "dustless" Regenerative.RTM. air sweeper preferably includes the 
conventional components of Tymco's closed-loop Regenerative.RTM. air 
sweepers, such as a high velocity fan or blower, a high pressure conduit 
for delivering high pressure air to an inlet of a pickup head along which 
the air flows to achieve optimum pickup, an outlet conduit from the pickup 
head for delivering debris to a main hopper, a filter in the main hopper 
for segregating relative large debris from an air stream, and a 
centrifugal filter for separating smaller debris from the air stream 
followed by the return of the air stream to the fan and the continuation 
of the closed-loop air flow. However, either as a conversion to such a 
conventional Regenerative.RTM. air sweeper or as an integral unit, the 
"dustless" Regenerative.RTM. air sweeper of the present invention includes 
a transfer tube or conduit which delivers a portion of the debris-laden 
air stream from the pressure conduit to a small particle separator which 
in turn delivers still smaller particle-ladened air to dust filters from 
which clean air flows and is exhausted to atmosphere. The small particle 
separator delivers small particles entrained in an air stream to the 
suction or vacuum side of the sweeper, while the smallest filtered 
particles are also returned to the suction side or vacuum conduit for 
eventual separation by the main centrifugal dust separator. Since the 
system is entirely substantially "closed," the only air exhausted is clean 
air exiting the filters. 
In further accordance with the invention, the filters are pulsed-cleaned 
automatically and relatively rapidly to assure that all small 
particles/dust are substantially cleaned from filtering surfaces of the 
filters which inherently assures that only clean air will be exhausted to 
atmosphere. 
The small particle separator is also bridged by a pressure-differential 
sensor to control associated flue plates or vanes downstream of the 
filters to assure that a constant volume of clean air is exhausted to 
atmosphere. 
The entire system is preferably encased in a housing, and at any 
over-pressure downstream of the filters, a pop-up valve will automatically 
move to an open position thereby preventing dirt-laden air from exhausting 
to atmosphere, damaging the housing, and/or components within the housing. 
Finally, another pressure differential gauge is provided in the air stream 
bridging a filtering manifold or chamber and a clean air manifold or 
chamber with a read-out therefrom being located in the cab of the vehicle 
which allows continued operator surveillance and manual shut-down of the 
system should such be found necessary. 
With the above and other objects in view that will hereinafter appear, the 
nature of the invention will be more clearly understood by reference to 
the following detailed description, the appended claims and the several 
views illustrated in the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A novel "dustless" Regenerative.RTM. air sweeper of the present invention 
is fully illustrated in FIGS. 1 and 2 of the drawings and is generally 
designated by the reference numeral 10. 
The sweeper 10 corresponds substantially to that disclosed in U.S. Pat. No. 
3,512,206 granted on May 19, 1970, and most of the specifics thereof are 
incorporated hereat by reference, including a truck T having wheels W and 
a frame F supporting a housing H which defines an inner solids collection 
bin SCB. A pickup head P is floatingly suspended from the frame F and 
extends transversely to the direction of the path of cleaning movement of 
the truck T over and adjacent to the surface to be cleaned. 
A fan or blower B (FIG. 2) discharges air under pressure through a pressure 
duct or conduit 12 to the pickup head P which is so constructed that the 
air under pressure is delivered through orifice means in a forceful flow 
downwardly against the surface to be cleaned under the pickup head and 
flows over that surface both parallel to the direction of cleaning and 
transverse to that direction while drawing a small amount, i.e. ten 
percent (10%) of air from atmosphere into the pickup head, as indicated by 
the air flow arrows AF. The parallel air flow PF through the pickup head P 
is finally discharged from the pickup head through a suction or vacuum 
duct or conduit 13 which delivers air-entrained solids or particulate 
material to the solids collection bin SCB. The air-entrained particulate 
stream reaches the large volume solids collection bin SCB expands, slows 
down, so to speak, and thereby permits a major portion of the 
heavier/larger entrained solids to drop to the bottom of the bin SCB. The 
air, still containing somewhat smaller entrained solids, passes through a 
generally horizontally disposed grate-like filter (not shown) which 
separates still smaller entrained solids from the air flow, and the latter 
is thereafter delivered tangentially into a centrifugal separator CS which 
spins die air and entrained particulate material/dust along a curved wall 
thereof with particles being discharged into the solids collection bin SCB 
and relatively clean air being returned to the blower B to continue the 
Regenerative.RTM. air flow in a continuous closed-loop stream. 
As thus far described, the sweeper 10 operates in accordance with the more 
specific description set forth in U.S. Pat. No. 3,512,206. 
In accordance with the present invention, the sweeper 10 includes as an 
integral part thereof or a conversion, a "dustless" mechanism 20 
associated with the surface sweeping machine 10 which particularly adapts 
the latter for sweeping particulate material under both wet and dry 
conditions. 
The mechanism 20 includes a housing 21 located adjacent a cab C carried by 
the frame F of the sweeper 10 which is defined by a top wall 22, side 
walls 23, 24 (FIG. 2), a front wall 25 (FIG. 2), a rear wall 26 and a 
bottom wall 30. 
Conduit means 32 in the form of a conduit, pipe or duct is connected 
between the pressure conduit 12 and a housing 27 located in a first 
chamber or housing portion 28 of the housing 21 and conducts or transports 
a portion of the air-entrained particulate material from the conduit 12 
into the housing 27 immediately adjacent to the wall 24 and a bank of 
vertically disposed filter means or separator means 35 housed in the 
housing 27. The filter means or separator means 35 are Strata.RTM. panel 
inertial separators each in the form of an individual tube 36 having 
substantially horizontally disposed axes (FIG. 1). Thus, the separator 35 
is essentially a conventional Strata.RTM. panel made up of many individual 
Strata.RTM. tubes 36 with each tube containing specially designed vanes 
that induce a spinning motion to the stream of air entrained particulate 
material which causes the particles to be thrown against outer walls 
(unnumbered) of each tube 36 and removed with a scavenge air flow by way 
of a first air stream which discharges small particles into conduit means 
40 in the form of a duct, pipe or conduit while still smaller particles 
axially exit the tubes 36 in a stream Ss. Thus, small particles Ps exit 
the cyclone separators 35 through the conduit 40, while still smaller 
particles Pss pass through the cyclone separators or tubes 36 entrained in 
the air streams Ss with the still smaller air particles Pss dropping 
downwardly into a hopper portion 41 of the first chamber 28 which includes 
a tapered wall 42 and a conical discharge 43 in fluid communication with 
further conduit means 45 in the form of a conduit, pipe or duct. The 
conduits 40 and 45 are connected to the vacuum or suction conduit 13 (FIG. 
2) and the respective particles Ps and Pss are drawn therethrough into and 
maintain intact the closed-loop air stream. 
The Strata.RTM. panel separator 35 and the individual Strata.RTM. cyclone 
separators are preferably of the type manufactured by Donaldson of P.O. 
Box 1299, Minneapolis, Minn. 55440 and the specifics thereof are found in 
Donaldson Bulletin #1020-0344 which is incorporated hereat by reference. 
The efficiencies of such cyclone separators 35 are extremely high, 
particularly in the 0.5 to 7 micron size particle range. Further details 
of the construction of individual cyclone separators collectively 
identified as Strata.RTM. Tube separators or cyclone separators 35 can be 
found in U.S. Pat. No. 4,746,340. Additionally, though a single bank or 
tube panel 35 is illustrated in FIGS. 1 and 2, several such banks can be 
utilized with larger or smaller tubes in substantially aligned 
relationship depending upon the particular cfm/sq. ft. involved and the 
size particles which are to be scavenged from the air stream conducted 
through the conduit 32. The cyclone separators 35 are extremely efficient, 
not only under dry conditions, but particularly under wet conditions and 
tend to avoid clogging or compacting which would otherwise decrease 
overall particle separation efficiencies. 
A plurality of filter means or separator means 50 are also located in the 
housing portion or chamber 28 downstream of the filter means or separator 
means 35, and each filter means 50 is a so-called Torit-Tex.TM. cartridge 
which is essentially tubular and is primarily defined by an exterior 
cylindrical smooth hydrophobic PTFE membrane 51 which provides exceptional 
filtration efficiency (99.999% on 0.5 micron particles). Thus, virtually 
all such particles impinging against the membrane 51 are prevented from 
passing therethrough and substantially clean air axially exits the 
cartridge filters 50 along individual air streams Sc of substantially 
clean air which enter the housing chamber or portion 29 and exit the 
latter through a passage 53 which in turn exhausts to atmosphere through 
an opening 54 in the lower wall 30 of the housing 21. Each Torit-Tex.TM. 
filter 50 is also manufactured by Donaldson, supra, and the exact 
specifications of the desired Torit-Tex.TM. filters 50 utilized in 
conjunction with this invention are those set forth in Form Torit-Tex.TM. 
4/96 entitled "TNERS in GRIME" of Donaldson. The PTFE membrane 51 of 
each of the cartridge filters 50 is particularly advantageous because the 
thousands of microscopic fibers thereof capture dust particles on the 
exterior surface of the medium. The smooth hydrophobic exterior surface of 
each filter 50 easily releases moist, hygroscopic and agglomerative 
particles, particularly damp or wet particles, particularly under 
expansion and flexing of the filter media 51 under high pressure air pulse 
cleaning, as will be described more filly hereinafter. Such filter media 
or membranes 51 can also be washed and reused repeatedly, dry quickly, and 
each can be returned to service immediately thereafter. 
As is best illustrated in FIG. 2 of the drawings, two aligned pairs of 
filters 50 are illustrated and the air streams Sc exit therefrom through 
openings 55, 56, each having an axis in alignment with air jets 65, 66, 
respectively, of a pressurized air manifold 67 located in the housing 
portion or chamber 29. A conventional compressor (not shown) supplies the 
manifold 68 with compressed air and an appropriate conventional timing 
circuit opens valves (not shown) associated with the nozzles 65, 66 at 
desired time intervals (every 15 seconds, for example) to blast high 
pressure air through the openings 55, 56 and into the interiors of the 
filter cartridges 50 causing the filter membranes 51 to flex or bulge 
outwardly. The high pressure internal air and the flexing of the membranes 
51 discharges particles from the exterior surfaces of the membranes 51 and 
these particles also descend downwardly into the conical discharge 43 and 
are eventually conveyed by the conduit 45 to the suction conduit 13 (FIG. 
2). 
Sensing means 70 (FIG. 2) are provided to sense pressure and preferably 
pressure differential across the cyclone separators 35 to maintain 
efficient particle separation by automatically controlling the discharge 
of clean air Sc through the passage 53 by varying the size thereof through 
movable flue plates or valves 75 operative through a conventional 
servo-motor or an electric actuator responsive to the output of the 
sensing means 70, such as Series EA Electric Actuators manufactured by 
Barber Colman Company, the specifics of which are disclosed in Bulletin 
No. 1321/IN 3-11 of April 1989 entitled "Installation and Wiring." The 
sensing means 70 is preferably a Photohelic sensor/switch/gauge 
manufactured and sold by Dwyer Instruments, Inc. of P.O. Box 373, Michigan 
City, Ind. 46361, preferably the Series 3000 thereof. These 
switches/gauges 70 function as highly repeatable pressure switches 
combined with a precise pressure gauge for measuring and controlling 
positive, negative or differential pressures and can be adjusted or set 
for control between high and low pressure set points. When pressure 
changes, reaching either set point pressure, a phototransistor signal is 
electronically amplified to actuate a slave relay which in turn operates 
the flue plates 75 to adjustably open or close, partially or fully, the 
latter to regulate the discharge of clean air Sc to the atmosphere, thus 
automatically regulating the total air flow exiting the pressure conduit 
12 into the conduit 32 and exiting the conduits 40, 45 into the suction 
conduit 13. By thus regulating the air flow, the system assures that only 
substantially clean air Sc exits the chamber 29 to atmosphere, and such 
occurs automatically while continually maintaining the entire 
substantially closed-loop air flow of the system. 
Further sensing means 80 substantially identical to the sensing means 70 
are provided to measure the pressure differential in and/or across the 
chambers 28 and 29. The output of the sensing means 80 is read-out from an 
instrument panel of the vehicle so that an operator can visually ascertain 
the operating efficiencies of the system and intervene should he diagnose 
problems. 
Finally, as an emergency precaution, the chamber 29 includes a cylindrical 
exhaust stem carrying a conventional automatic pressure pop-off valve 91 
which in its closed position closes the chamber 29 to atmosphere through a 
tube 90 but can automatically open to the phantom outline position of the 
valve 91 under excessive pressure within the chamber 29. 
The "dustless" Regenerative.RTM. air sweeper 10, including the "dustless" 
mechanism 20 thereof, assures high efficiency performance under all 
conditions, particularly under wet surface conditions, and most notably 
maintains a relatively closed-loop air stream throughout the entire system 
with only substantially clean air being eventually exhausted to atmosphere 
after separation/filtration thereof. 
An extremely important aspect of the present invention is that achieved by 
creating and maintaining a substantially negative pressure at and across 
the pickup head P. The latter is achieved by assuring that the air AF 
drawn into the pickup head P is approximately a nominal ten percent (10%) 
and the air SC discharged through the opening 53 is maintained at 
substantially the same nominal ten percent (10%) through appropriately 
varying the valve 75 under the control of the sensor 70. Accordingly, 
since a slight negative or vacuum is maintained at the pickup head PF and 
no over-pressure occurs within the pickup head PF, the main air flow or 
the primary air flow PF of air in the pickup head P is not discharged to 
atmosphere, thus preventing "puffs" of air from being discharged to 
atmosphere along a lower periphery (not shown) of the pickup head P. Thus, 
in the area of the pickup head P the negative or vacuum pressure truly 
maintains "dustless" operating conditions. Obviously, though a nominal ten 
percent (10%) negative pressure has been mentioned herein, the same is 
merely exemplary and can vary within a range of perhaps substantially ten 
percent (10%)/fifteen (15%), again being controlled by the sensing means 
70 and the adjustment of the opening 53 by the valve 75. 
Although a preferred embodiment of the invention has been specifically 
illustrated and described herein, it is to be understood that minor 
variations may be made in the apparatus without departing from the spirit 
and scope of the intention, as defined the appended claims.