U.S. patent number 3,865,022 [Application Number 05/338,871] was granted by the patent office on 1975-02-11 for exhaust fume treatment apparatus.
Invention is credited to Willard K. Ahlrich.
United States Patent |
3,865,022 |
Ahlrich |
February 11, 1975 |
EXHAUST FUME TREATMENT APPARATUS
Abstract
An exhaust fume treatment apparatus for removing suspended or
entrained material from a gas including a substantially cylindrical
housing having a peripheral wall and inlet and outlet openings in
opposite end walls. A suction blower coupled to the outlet of the
housing has a rotatably driven shaft extending into the housing. A
slinger wheel is rotatable on and with the shaft within the housing
adjacent the inlet. The slinger wheel has an open face opposed to
the inlet and a plurality of circumferentially spaced blades angled
so the radially outer edge of each trails its radially inner edge
during normal rotation of the shaft. Fumes drawn into the housing
inlet by the suction blower pass outwardly through the blades and
outlet. Materials in the gas are deposited on and thrown
substantially radially outwardly by the blades toward the
peripheral wall of the housing for collection. Embodiments of the
invention shown disclose integration of the housing and suction
blower with an exhaust hood having an air curtain. In one
embodiment, an air curtain supply blower and the cylindrical
housing and suction blower utilize coaxial conduits for
communicating with an air curtain chamber and exhaust chamber,
respectively, in the hood. In another embodiment, the air curtain
supply blower shares a common shaft axis and drive motor means with
the suction blower and cylindrical housing.
Inventors: |
Ahlrich; Willard K.
(Winterhaven, FL) |
Family
ID: |
23326499 |
Appl.
No.: |
05/338,871 |
Filed: |
March 7, 1973 |
Current U.S.
Class: |
126/299D;
55/DIG.36; 55/406; 55/408 |
Current CPC
Class: |
F24C
15/20 (20130101); B01D 45/14 (20130101); Y10S
55/36 (20130101) |
Current International
Class: |
B01D
45/12 (20060101); B01D 45/14 (20060101); F24C
15/20 (20060101); F23j 011/02 () |
Field of
Search: |
;98/115K,115LH
;55/406,407,408,409,401,467,DIG.36,DIG.40 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
1,205,723 |
|
Feb 1960 |
|
FR |
|
977,657 |
|
Apr 1951 |
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FR |
|
Primary Examiner: Antonakas; Manuel A.
Assistant Examiner: Devinsky; Paul
Attorney, Agent or Firm: Woodhams, Blanchard & Flynn
Claims
The embodiment of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. Exhaust fume treatment apparatus for removing contaminant
materials from a gas, comprising in combination:
a substantially cylindrical extractor housing having a peripheral
wall and an inlet and an outlet in opposite end walls thereof;
suction blower means coupled to the outlet of said housing for
drawing gas therethrough and having a rotatably driven shaft
extending into said housing;
a slinger wheel on and rotatable by said shaft and located in said
housing, said slinger wheel having an open face adjacent said inlet
and having a plurality of circumferentially spaced gas contacting
blades each angled so that the radially outer edge thereof trails
the radially inner edge thereof during normal rotation of said
shaft, the opposed downstream ends of said slinger wheel and
housing being spaced by an open air passage unoccupied except by
said shaft; and
a shield spaced closely radially inboard of the said peripheral
wall of said housing by a dead air space and being spaced remotely
radially outwardly of said slinger wheel by a reduced gas velocity
zone, the radial extent of said reduced gas velocity zone being at
least several times that of said dead air space, said shield at
least partially circumferentially surrounding said slinger wheel,
said shield being pierced by a plurality of holes for receiving
contaminant masses thrown outwardly by said slinger wheel and
admitting same to said dead space between said shield and said
housing peripheral wall;
means for increasing axial uniformity of material build up on said
blades comprising a radially extending air deflector disk fixed to
said shaft axially within said slinger wheel, the periphery of said
disk being spaced radially intermediate the shaft and inner slinger
blade edges.
2. The apparatus of claim 1 in which said slinger wheel blades are
radially narrow and substantially spaced from said shaft, the
upstream ends thereof being joined by a common annular end plate
adjacent said extractor housing inlet, the cross section of said
blades being curved to provide a concave trailing face adapted to
continuously collect and periodically outwardly throw off
contaminate material masses, said suction blower means having a
bladed wheel similar to said slinger wheel but of opposite hand,
whereby gas movement through said suction blower blades is
accelerative and gas movement through said slinger wheel blades is
not.
3. The apparatus of claim 2 including motor means coupled to said
shaft for maintaining slinger wheel blade tip speeds in the range
of 2,100 to 2,200 feet per minute.
4. The apparatus of claim 1 in which the spacing of the slinger
wheel radially from the peripheral wall of the housing
substantially exceeds the spacing of said wheel from said inlet,
the axial width of said open air passage between said slinger wheel
and downstream housing end wall being a substantial fraction of the
width of said slinger wheel.
5. The apparatus of claim 1 in which the holes are skewed and the
axis of each has at least a component substantially aligned with a
tangent to the periphery of the wheel whereby contaminant masses
thrown from the wheel tend to pass axially through said holes.
6. The apparatus of claim 5 in which said shield extends axially
beyond said slinger wheel toward said downstream end wall of said
housing, the axes of said skewed holes in said shield having a
further component angled longitudinally of said shield and
corresponding to the migration axially of the slinger wheel of
contaminant masses thrown from the slinger wheel due to exhaust air
movement from said slinger wheel toward said downstream end wall of
said housing, whereby to provide alignment of said holes in said
shield with the path of contaminant masses thrown from said slinger
wheel despite migration thereof with air from said slinger
wheel.
7. The apparatus of claim 1 in which said shield is substantially
horizontal and including means defining a contaminant outlet at a
low point in the peripheral wall of said housing for receiving
contaminant masses entrapped between said shield and said housing
peripheral wall.
8. The apparatus of claim 7 including a collection trough fixed to
said housing in communication with said contaminant outlet for
receiving contaminant masses therefrom, said contaminant outlet and
trough extending axially along said housing substantially the width
of said shield and radially opposed thereto.
9. The apparatus of claim 8 including a conduit communicating with
a low point in said trough and wherein said suction blower means
includes a housing and including a conduit communicating between a
low point on said suction blower means housing and said trough for
draining to said trough any contaminant material escaping from said
extractor housing into said suction blower means housing.
10. The apparatus of claim 1 in which said suction blower means
comprises a centrifugal blower having a housing through which said
shaft extends, a centrifugal, open-faced blower wheel mounted on
said shaft for rotation therewith and within said blower housing,
an inlet opening in the side of said blower housing, said
open-faced blower wheel having an air inlet opening of diameter
substantially less than the diameter of said extractor outlet and
means defining a convexly curved inlet cone interposed between said
extractor outlet and blower wheel air inlet opening for smoothly
correspondingly reducing air flow cross section therebetween during
normal rotation of said shaft, said extractor housing and blower
housing being located in coaxial, close-spaced relation, said
extractor outlet and blower housing inlet opening being in
coaxially aligned communication and including annular flange means
extending between said housing and surrounding said last-mentioned
openings for defining a transfer passage shorter than said wheels
between said lastmentioned openings.
11. The apparatus of claim 10 in which said annular flange means
comprises a pair of snugly telescoped flanges extending from said
extractor housing and blower housing, respectively, and including a
web extending across the inner one of said annular flanges and a
bearing on said web, said bearing supporting said shaft and said
slinger wheel in cantilevered relation within said extractor
housing.
12. The apparatus of claim 1 including an exhaust hood, an elongate
equipment enclosure spaced from said hood and an exhaust conduit
interconnecting said hood and an intermediate portion of said
elongate equipment enclosure, said extractor housing and suction
blower means lying within and having their common shaft extending
along one end portion of said elongate equipment enclosure from an
extractor inlet coupling with said exhaust conduit to a
substantially horizontally directed suction blower means outlet at
one end of said elongate enclosure, the other end portion of said
elongate enclosure defining an air inlet.
13. The apparatus of claim 1 including an exhaust hood having inner
wall means defining a downwardly opening exhaust chamber and outer
wall means defining a downwardly opening air outlet chamber for
establishing an air curtain, said extractor housing and suction
blower means being disposed within said hood between said inner and
outer wall means and for communicating said extractor housing inlet
with said exhaust chamber.
14. The apparatus of claim 1 including an air supply blower having
a shaft portion coaxial with and coupled to said shaft and common
drive means for rotatably driving said shaft and shaft portion.
15. The apparatus of claim 14 including a further extractor housing
and a further slinger wheel within said further extractor housing
and mounted on said shaft portion for rotation therewith, said
further extractor housing being coupled to the inlet of said air
supply blower and an air curtain-exhaust hood having an air curtain
chamber communicating with the output of said air supply blower and
an exhaust chamber communicating with the inlet of said
first-mentioned extractor housing, whereby ambient air is cleaned
before being applied to the air curtain portion of said housing and
exhaust air from said hood exhaust chamber is cleaned before
release from said suction blower means.
Description
BACKGROUND OF THE INVENTION
This invention relates to exhaust fume treatment apparatus and,
more particularly, relates to apparatus for removing materials from
an entraining exhaust gas utilizing a rotating wheel and housing to
effect such separation.
Although use in other environments is contemplatd, the present
invention arose in connection with the development of exhaust hood
systems and integrated exhaust hood-air curtain systems usable in a
variety of situations in which fumes produced by a device are to be
exhausted from an enclosure in which the device is located and in
such a way as to protect personnel or the like adjacent such device
from deleterious or unpleasant effects which might be caused by
such fumes. Cook tops or the like in food preparation
establishments including restaurants, hamburger stands, etc.,
provide one example of situations to which the present invention is
directed.
In such establishments, the air above such cooking apparatus (for
example, griddles, grills, open deep fat frying vats, kettles,
pressure cookers, etc.) may frequently carry objectionable
quantities of fatty or greasy materials in suspension or
entrainment. It has been common in the past to exhaust such fumes
from a collecting exhaust hood directly or substantially directly
to the atmosphere and without treatment to remove suspended or
entrained grease or other objectionable materials.
Recently increased public and governmental concern with degradation
of environmental qualities, specifically with air pollution, has
resulted in proposal and passing of statutes and ordinances at
various governmental levels restricting outputs of air, containing
objectionable or harmful pollutant materials, from a variety of
business enterprises, including not only industrial concerns but
other business enterprises as well. Food preparation establishments
are at least a potential subject for such legislation. Thus, the
present invention, in materially reducing or substantially
eliminating the level of foreign materials, such as grease
particles or the like, from air exhausted therethrough is intended
to improve environmental quality.
Known prior art devices have not been fully satisfactory in
providing convenient and effective removal of foreign materials,
particularly sticky or liquid-like particles from air, particularly
as heretofore used in connection with exhaust hoods. For example,
it has been known to provide in the exhaust chamber of an exhaust
hood, fixed filter devices including random strand mats or a series
of plates defining a labyrinthian passage. Among their
disadvantages, such devices tend to clog, are difficult and time
consuming to clean and frequently cannot be relied on for removal
of an acceptably high percentage of contaminant particles from the
air passing therethrough. Attempts have been made in more
generalized forms of gas-solid or gas-liquid separation to utilize
movement of a member with respect to particle laden gas to effect
separation of gas and particle. However, those of which I am aware
suffer disadvantages including, for example, difficulty of
integration with exhaust hoods and the like, undue complexity,
excessive cost, or ineffectiveness in removing a high percentage of
contaminant particles from air passing therethrough.
Therefore, the objects of this invention include provision of:
1. An exhaust fume treatment apparatus which removes solid or
liquid particles from an exhaust gas preparatory to releasing same
to the atmosphere.
2. Apparatus, as aforesaid, particularly adapted for use in
combination with exhaust hood constructions, with or without air
curtain devices.
3. Apparatus, as aforesaid, capable of removing substantial
percentages, such as 80 to 95 percent of contaminant material from
a suspending or entraining exhaust gas and which has been found
particularly effective for removing fatty or greasy materials from
such gas.
4. Apparatus, as aforesaid, particularly adapted to close
integration with a conventional exhaust blower particularly of the
centrifugal blower type which is capable of utilizing a rotating
drive shaft and motor means with such exhaust blower.
5. Apparatus, as aforesaid, which may be relatively inexpensively
constructed in large or small scale production from commonly
available materials and/or components.
6. Apparatus, as aforesaid, which is capable of effective operation
over long periods of time without attention, which tends to be
self-cleaning in use, which provides for convenient elimination of
contaminant materials extracted from exhaust air flowing
therethrough and which provides for positive entrapment of material
particles removed from the exhaust gas to prevent re-entry of such
particles into the exhaust gas flow.
Other objects and purposes of this invention will be apparent to
persons acquainted with apparatus of this general type upon reading
the following specification and inspecting the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary, partially broken oblique view of an
exhaust hood, air curtain assembly incorporating the present
invention.
FIG. 2 is a central cross-sectional view taken from the side of the
extractor, exhaust blower apparatus of FIG. 1. FIG. 3 is a
sectional view substantially taken on the line III--III of FIG.
2.
FIG. 4 is an enlarged sectional view substantially taken on the
line IV--IV of FIG. 2.
FIG. 5 is a fragmentary sectional view substantially taken on the
line V--V of FIG. 4.
FIG. 6 is a central cross-sectional view of a modified apparatus
embodying the invention.
FIG. 7 is a fragmentary oblique view of the apparatus of FIG. 6
with the top and front portions of the outer hood wall indicated in
broken lines.
FIG. 8 is a modified fragment of FIG. 2.
Certain terminology will be used in the following description for
convenience in reference only and will not be limiting. The words
"up," "down," "right" and "left" will designate directions in the
drawing to which reference is made. The words "front" and "rear"
will refer to the direction of gas flow through the apparatus,
forwardly being the normal flow direction. The words "in" and "out"
will refer to directions toward and away from, respectively, jthe
geometric center of the device and designated parts thereof. Such
terminology will include derivatives and words of similar
import.
SUMMARY OF THE INVENTION
The objects and purposes of this invention are met by providing an
exhaust fume treatment apparatus for removing suspended or
entrained material from a gas including a substantially cylindrical
housing having a peripheral wall and inlet and outlet openings in
opposite end walls. A suction blower coupled to the outlet of the
housing has a rotatably driven shaft extending into the housing. A
slinger wheel is rotatable on and with the shaft within the housing
adjacent the inlet. The slinger wheel has an open face opposed to
the inlet and a plurality of circumferentially spaced blades angled
so the radially outer edge of each trails its radially inner edge
during normal rotation of the shaft. Fumes drawn into the housing
inlet by the suction blower pass outwardly through the blades and
outlet. Materials in the gas are deposited on and thrown
substantially radially outwardly by the blades toward the
peripheral wall of the housing for collection. Embodiments of the
invention shown disclose integration of the housing and suction
blower with an exhaust hood having an air curtain. In one
embodiment, an air curtain supply blower and the cylindrical
housing and suction blower utilize coaxial conduits for
communicating with an air curtain chamber and exhaust chamber,
respectively, in the hood. In another embodiment, the air curtain
supply blower shares a common shaft axis and drive motor means with
the suction blower and cylindrical housing.
DETAILED DESCRIPTION
FIG. 1 discloses an exhaust hood assembly 10 including an exhaust
hood 11, here including an air curtain device, which may be of any
convenient conventional construction such as that shown in U.S.
Pat. No. 3,645,194, issued Feb. 29, 1972, to Willard K. Ahlrich.
The hood 11 may be supported in any convenient way (not shown) and
is usable in conjunction with a source (not shown) of exhaust gas,
such as a cook top or the like. An equipment enclosure 13 is
supported by any convenient means, here on the roof 14 of a
building housing the hood 11. Coaxial inner and outer conduits 16
and 17 extend from the top of the hood 11 upwardly to the equipment
enclosure 13. An air intake chamber 20 is, in the particular
embodiment shown, provided in the equipment enclosure 13 and opens
through the rightward end 21 thereof. An intake, or air curtain,
blower 23, provided with a motor 24 is mounted within the air inlet
chamber, at the inner end thereof, and has an inlet 25 in
communication with the air inlet chamber. The equipment enclosure
13 includes a central chamber 27 closed by transverse end walls 28
and 29. The outlet 30 of the air curtain blower 23 communicates
through the wall 29 with the central chamber 27. The central
chamber 27 is an upward continuation of the outer conduit 17 and
therewith provides communication between the blower 23 and an air
curtain outlet (not shown) in the hood 11.
An exhaust chamber 32 is provided in the equipment enclosure 13 to
the left of the central chamber 27. The exhaust outlet chamber 32
is closed except as otherwise discussed below. The exhaust outlet
chamber 32 houses an extractor 34 and an exhaust blower 35, both
hereinafter described in more detail. In the particular embodiment
shown in FIG. 1, the inlet 37 of the extractor 34 is coupled
through the wall 28 with a leftwardly angled extension 39 of the
inner, or exhaust, conduit 16. The exhaust blower 35 has an outlet
40 which communicates through a suitable opening in the outer wall
41 of the equipment enclosure 13 with a leftwardly and somewhat
downwardly extending exhaust duct 42 which opens leftwardly to the
atmosphere. A motor 44 is provided for driving the exhaust blower
35 and extractor 34, in a manner hereinafter discussed, and in the
particular embodiment shown is mounted by a bracket 45 on the
scroll 46 of exhaust blower 35.
More particularly, as to the extractor, exhaust blower unit 34, 35
(FIG. 2), the exhaust blower 35 is preferably a conventional single
inlet centrifugal blower comprising a housing 51 having end walls
52 and 53 jointed by a transversely extending, spiral-shaped
peripheral wall 54 and defining therewith a blower outlet 40, which
is here substantially rectangular and opens upwardly. The leftward
wall 53 has an inlet port 56. An annular plate 57 is secured, as by
welding, to the outer face of the sidewall 53 around the inlet port
56 and has secured, as by welding, to the radially inner edge
thereof a radially inwardly and then axially inwardly curved inlet
cone 59 which lies within the blower housing 51. A cylindrical
adaptor 61, coaxial and preferably integral with the cone 59,
extends leftwardly and exteriorly from the blower housing 51.
A blower shaft 63 is supported for rotation by bearings 64 and 65
and extends coaxially through the inlet cone 59. The bearing 64 is
located adjacent a shaft opening (not shown) on the outer face of
the blower wall 52 and the bearing 65 is located adjacent the inlet
cone 59 and adaptor 61 by means hereinafter discussed. The shaft 63
is rotatably driven, here through a pulley 67 fixed to the
rightward end thereof and a drive belt (not shown) from a
corresponding pulley on the shaft of the motor 44 of FIG. 1.
A conventional open end centrifugal blower wheel 69 includes a
rightward end plate 71 coaxially fixed to the shaft 63 by a
conventional hub structure 72 and an annular leftward end plate 73
located closely adjacent the inlet collar 59 and supported on the
rightward end plate 71 by means of a plurality of circumferentially
spaced axially extending blower blades 75. Thus, rotation of the
blower wheel 69 in one rotational direction will move air
rightwardly through the collar 59 and outwardly past blades 75
through the blower outlet 40.
The extractor 34 includes a substantially cylindrical extractor
housing 81 comprising coaxial, circular rightward and leftward end
walls 82 and 83. End walls 82 and 83 lie in spaced, substantially
radial planes and are connected at their peripheries by a
circumferentially continuous peripheral wall 84. Openings 86 and 87
are provided in the end walls 82 and 83, respectively, coaxially
with the peripheral wall 84. The blower shaft 63 includes a
leftward end extension 89 which extends coaxially through the
opening 86 into the interior of the cylindrical extractor housing
81.
The housings 81 and 51 are spaced adjacent each other. An annular
flange 91 is fixed as by welding to the wall 82 at the edge of the
opening 86 and snugly telescopes within the adaptor 61 of the
exhaust blower 35 for defining a transfer passage 93 from the
extractor housing 81 to the inlet of the blower 35. In the
particular embodiment shown, a transverse web 95 extends chordally
across the transfer passage 93 near the center thereof and fixedly
supports the bearing 65, the web 95 being secured to the interior
of the flange 91 by any convenient means, such as welding.
An axially short, circularly cylindrical inlet collar 98 extends
coaxially through the opening 87 in the leftward extractor housing
wall 83 and is fixed, as by welding, to an annular flange 101
secured to the exterior face of the wall 83, here by screws 102
(FIG. 3).
A slinger wheel 106 (FIGS. 2-4) includes a rightward end plate 107
coaxially fixed to the leftward end extension 89 of the shaft 63 by
a hub structure 108. The rightward end plate 107 is located within
the extractor housing 81 in spaced relation between the bearing 65
and inlet collar 98, the outer peripheral edge thereof being spaced
radially inwardly from the peripheral wall 84. The slinger wheel
106 includes an annular leftward end plate 110 coaxial with the
rightward end plate 107 and located closely adjacent the inlet
collar 98. The annular leftward end plate 110 is supported on the
rightward end plate 107 by a plurality of preferably identical,
circumferentially spaced and axially extending blades 111. In the
particular embodiment shown, the blades 111 are provided with end
flanges 112 secured to plates 107 and 110, as by rivets 114, and,
particularly in larger-size units, suitable diagonal bracing rods
116 (FIG. 3) may be provided between hub 108 and the annular flange
10.
In the normal direction of rotation of the shaft 63, (here
counter-clockwise as indicated by the arrow R in FIGS. 3 and 4, as
viewed from the inlet collar 98 of the extractor 34), wherein the
blower wheel 69 acts in a conventional manner to draw air through
the blower inlet cone 59 and impel same out the blower outlet 40,
the outer edges 118 of the slinger wheel blades 111 trail the
radially inner edges 119 thereof. Thus, the slinger wheel blades
111 are arranged so that each lies at a shallow angle to a radius
of the slinger wheel passing therethrough. In the preferred
embodiment shown, the blades as seen in cross section in FIG. 4,
are slightly curved so that the trailing face 120 of each blade is
somewhat concave. However, this curvature of the blades 111 has not
been found absolutely essential to effective operation of the
extractor, though it is helpful. Although the invention is by no
means so limited, it has been found, in several embodiments of the
invention which have been constructed, that the slinger wheel 106
may be a conventional open face blower wheel but of opposite hand
to that of suction blower wheel 69, that is, a conventional blower
wheel intended for rotation in a direction opposite to that in
which the shaft 63 actually rotates during operation of the
extractor, exhaust blower unit 34, 35. In contrast, it has been
found by experimentation that use of a conventional blower wheel in
its intended direction of rotation as a blower wheel, in place of
slinger wheel 106 (that is, a wheel of the same hand as suction
blower wheel 69) is singularly ineffective for extracting particles
from gas flowing through the extractor.
A cylindrical shield 123 (FIGS. 2 and 4) is coaxially interposed
between the slinger wheel 106 and the peripheral wall 84 of the
extractor housing 81. The shield 123 is radially remote from the
periphery of the wheel and circumferentially close spaced from the
peripheral wall 84. The shield 123 is preferably fixed to the
peripheral wall 84 by a plurality of suitable spacers 124 (FIG. 4)
and coacting nut and bolt connections 125 distributed
circumferentially and axially thereof. The shield 123 preferably
extends axially from about the leftward edge of the slinger wheel
106 rightwardly to a point intermediate the rightward end plate 107
and rightward end wall 82 of the extractor.
The shield 123 is perforated, having in the preferred embodiment
shown a multitude of holes therethrough of about 1/8-inch diameter
spaced on about 1/2-inch centers. As seen in FIGS. 4 and 5, the
holes 127 do not extend radially through the shield but rather
extend therethrough in a sloped, or angled, manner. Such holes may
be provided, for example, by drilling a radial hole through the
shield and then using a punch or the like to upset the material at
the rim of the hole so that one portion of the hole is pulled
radially inwardly toward the wheel and the opposed portion is
pushed radially outwardly toward the peripheral wall 84. In the
preferred shield shown, the net inclination of the holes 27 is at
about 60.degree. to a radius drawn from the shaft extension 89 or
in other words, to about 30.degree. to a plane tangential to the
shield at the hole. Further, the direction of upset of the holes is
preferably at about a 30.degree. angle to a radial plane of the
shaft 68. By this means, the effective axis of each of the holes
127 is substantially aligned with the path which particles tend to
take when thrown from the outer edges of the rotating slinger
wheel.
A collection trough 131 (FIGS. 2 and 3) is fixed, by any convenient
means such as welding, to the bottom of extractor housing 81 and
extends axially therealong at least for a distance exceeding the
axial dimension of the shield 123. A preferably downwardly flanged
waste outlet opening 132 is provided in the bottom of the extractor
housing peripheral wall in communication with the open top of the
trough 131, the opening 132 being almost coextensive with the top
of the trough 131 in the preferred embodiment shown. In the
preferred embodiment shown the blower housing 51 communicates at
the bottom of peripheral wall 54 and near the leftward edge
thereof, through a conduit 136 (FIG. 2), with the rightward end of
the trough 131. The trough 131 is provided with an outlet conduit
138, here adjacent the leftward end thereof, which may be
terminated as desired.
The extractor 34 may be constructed in a wide range of sizes. The
particular embodiment shown, for example, used a 24-inch external
diameter slinger wheel 106 and an extractor housing 81 of about
36-inch diameter. The radial spacing from the tips of the blades of
the slinger wheel to the shield 123 was about 5 inches and the
radial spacing of the shield from the peripheral wall 84 of the
extractor housing was about one-half inch. The axial spacing
between the slinger wheel 106 and the rightward end wall 82 of the
extractor housing is preferably a substantial fraction of the
slinger wheel width, for example, 60-90 percent and in the
particular embodiment shown was about 71/2 inches with a wheel
width of about 121/2 inches. Thus, a substantial volume is provided
between the slinger wheel and the peripheral and rightward walls of
the extractor housing for air passing radially outwardly from the
slinger wheel.
In the particular embodiment shown, the slinger wheel 106 is
somewhat larger in diameter than the blower wheel 69. However, this
has been found not to be absolutely essential and, for example,
satisfactory performance has been obtained with blower wheel
diameters of about 80-100 percent of the slinger wheel diameter and
even somewhat beyond.
OPERATION
Where the hood 11 includes provision for an air curtain, as in the
embodiment of FIG. 1, energization of the intake, or air curtain,
blower 23 causes intake air flow through the rightward end 21 of
the equipment enclosure 13, thence through the blower 23 and
downwardly into the air curtain section of the hood through the
central chamber 27 and outer conduit 17.
To exhaust air from the hood 11, motor 44 is energized to inturn
energize the exhaust blower 35 and extractor 34. Impurity laden
exhaust air, for example, containing grease particles or the like
in suspension or entrainment, is thus drawn from the hood 11
upwardly through inner conduit 16 and thence into the inlet 37 of
the extractor housing 34.
As seen in FIG. 2, energization of the motor 44 rotates pulley 67,
shaft 63 and shaft extension 89, such rotation being
counterclockwise as seen from the inlet 37 of the extractor
housing. Wheels 69 and 106 rotate with the shaft 63. Rotation of
the blower wheel 69 draws air from the inlet 37 of the extractor
housing 81 through the slinger wheel 106 and thence rightwardly
through the transfer passage 93 into the interior of the blower
wheel 69, whereafter the blades 75 of the rotating blower wheel 69
propel such air outwardly through the blower outlet 40.
More particularly, particle laden exhaust air indicated by the
arrows L and L' enters the interior of the slinger wheel 106
through the inlet collar 98. The particle laden air decelerates in
moving radially outwardly past the blades 111 of the slinger wheel,
moving at a much reduced speed radially outwardly from the slinger
wheel and then rightwardly therefrom toward the transfer passage
93. The moist or sticky particles in such exhaust air (which may
include particles of oil, water, or grease, for example) tend to
accumulate, or floculate, on the trailing faces of the slinger
wheel blades near the outer edges thereof, as indicated at G on one
of the blades in FIG. 4. The amount of build-up G tends, in
practice, to be somewhat greater toward the rightward end, as seen
in FIG. 2, of the blades 111. The tip speed of the blades,
resulting from rotation of the slinger wheel 106, is sufficient
that the accumulated masses of particulate material G are
periodically released from their positions on the blades and
impelled substantially tangentially outwardly, as indicated by for
example the arrow G' in FIG. 4, toward the perforated shield 123.
The released masses normally strike the shield 123 at about a
30.degree. angle to a tangential plane of the peripheral face of
the shield.
Although the clean air leaving the slinger wheel 106 and flowing as
indicated by the arrows C and C' toward the transfer passage 93 is
moving at a relatively slow velocity, the fact that there is a net
air movement rightwardly tends to cause the particulate masses G'
released from the slinger wheel to migrate somewhat rightwardly as
they move tangentially outwardly toward the shield 123. As a
result, the shield 123 extends rightwardly beyond the wheel
sufficiently to be struck by the rightwardmost of such particulate
masses G' and the skewed openings 127 in the shield are
correspondingly inclined axially, as seen in FIG. 5, so that the
paths of the masses G' are closely aligned with the axes of the
skewed openings 127, thus facilitating entry of the particulate
masses G' through such openings. Each material mass G', upon
striking the inner face of the shield directly enters, or has
sufficient velocity as to move on such face until it enters, one of
the multitude of openings 127. Each mass thus passes into the
annular space between the shield and the peripheral wall 84 of the
extractor housing. Particle masses within this space tend to drain
by gravitation downwardly along the opposed faces of the shield and
peripheral wall 88 to the bottom of the extractor housing and
thence through the outlet 132 into the collection trough 131,
wherefrom they may continuously drain through suitable outlet
conduit such as indicated at 138.
Cleaned air, indicated by arrows C and C', accelerates as it moves
rightwardly and radially inwardly into the transfer passage 93 and
inlet cone 59 of the exhaust blower 35 and thence is driven
outwardly through the exhaust blower blades 75. The cleaned air
emerges from the exhaust blower outlet 40.
For best performance with, for example, grease laden exhaust air,
slinger wheel tip speeds in the range of 1,800 to 2,500 feet per
minute have been found satisfactory, with speeds of 2,100 to 2,200
feet per minute being preferred. In one embodiment, built according
to the present invention, given operation to provide about 3,000
feet per minute exhaust air velocity into the extractor inlet 37,
exhaust air deceleration through the slinger wheel blades area
resulted in exhaust air speed of about 1,400 feet per minute
outside the slinger wheel (between the slinger wheel blade and
shield 123), the air then accelerating into the transfer passage 93
and through the blower wheel 69 to achieve a velocity of about
3,000 feet per minute.
Measurements have indicated that the pressure drop from the inside
to the outside of the slinger wheel is small but that a substantial
pressure drop takes place at the transfer passage 93 and the inlet
cone 59 of the exhaust blower which may range from, for example,
1/2-inch static pressure drop to several times that amount
depending upon the particular embodiment under test.
Further testing was carried out to determine extraction efficiency.
In one embodiment, utilizing a 16-inch diameter slinger wheel,
cooking oil was sprayed into the inlet 37 utilizing a standard oil
burner nozzle under 100 pounds of pressure at a rate of 1.1 gallons
per hour at a temperature of 375.degree.F. Measurement determined
that about 92 percent of the oil introduced into the unit was
recovered at the collection outlet of the extractor housing. Other
testing was done, using a 13-inch diameter slinger wheel, with
water introduced into the inlet 37 as a spray at about 1 gallon per
hour, and no evidence was found of any water moving into the
exhaust blower and collecting in the blower housing.
Further testing involving various modifications of the structure
disclosed in FIGS. 2-5, resulted in degraded performance. For
example, removal of the exhaust blower 35 from its position shown
in FIG. 2 and substitution of a remote suction source for drawing
air through the extractor housing resulted in a substantial
reduction in extraction efficiency, in one test reducing extraction
efficiency from about 90 percent (on oil as above discussed) to
about 75-80 percent. Similarly, tests involving a substantially
closer radial spacing between the peripheral wall 84 of the
extractor housing and the periphery of the slinger wheel (with a
13-inch diameter slinger wheel reducing extractor housing diameter
from 17 inches to 15 inches) increased air velocity between the
outside of the slinger wheel and the inside of the extractor
housing and tended to keep portions of the oil contaminant
air-borne rather than letting it travel, as intended, outwardly
toward the peripheral wall 84 for collection.
Other testing variations including, as examples, slinger wheel
blades oriented reversely of the orientation shown in FIG. 4, or
providing movement of exhaust air from outside the wheel inwardly
therethrough have been found ineffective.
MODIFICATION
FIGS. 6 and 7 disclose a modified exhaust hood assembly 150.
Portions of the modified hood assembly 150 corresponding to similar
parts of the assembly 10 of FIG. 1 will carry the same reference
numerals with the suffix A added thereto.
The assembly 150 includes a hood 151 having a substantially
rectilinear outer wall construction comprising opposed end walls
153, opposed sidewalls 154 and a top wall 155.
An inner wall construction lies spaced within the outer wall
construction 153-155 and comprises opposed front and rear walls 187
and 188, the upper portion 159 of the front wall 157 being sloped
rearwardly (leftwardly as seen in FIG. 7) toward the rear wall 158.
An inner top wall 161 extends forwardly from the rear wall 158 and
is spaced rearwardly and above the upper edge of the front wall of
the upper portion 159 for defining therebetween an exhaust slot
163. The walls 157, 158 and 161 extend between the end walls 153 of
the outer wall construction. In the particular embodiment shown, a
closure panel 184 connects the lower edges of the walls 154 and
158.
The inner wall construction 157, 158, 161 defines a downwardly
opening exhaust gas collecting chamber 167. A separator plate 169
defines, between the inner and outer wall constructions, a pair of
chambers, more particularly an exhaust transfer chamber 191 and a
downwardly opening air curtain chamber 172, the former
communicating through slot 163 with the exhaust collection chamber
167.
In the embodiment shown, the separator plate 169 is substantially
horizontal and extends between the inclined front wall portion 159
and the forward one of the sidewalls 154 of the outer wall
construction, providing an air seal therebetween. In addition, if
desired, suitable baffles 173 may be provided near the open blower,
or outlet, end of the air curtain chamber 172 for controlling and
directing air flow downwardly thereout of.
An air moving unit generally indicated at 175 is disposed in the
space between the inner and outer wall constructions and supported
with respect to such wall constructions by any convenient means not
shown. In the particular embodiment shown, the unit 175 is disposed
in the exhaust transfer chamber 171. However, it is contemplated
that the unit 175 can be disposed in the air curtain chamber, as
hereinafter discussed.
The unit 175 comprises an extractor 34A and an exhaust blower 35A
preferably similar to the extractor and exhaust blower of FIGS.
1-5. In addition, the unit comprises an air curtain blower 23A
coaxially aligned with the extractor 34A and exhaust blower 35A and
located adjacent the exhaust blower 35A. An intake air extractor
178, preferably similar to the exhaust extractor 34A, coaxially
couples at its outlet to the inlet of air curtain blower 23A. The
outlet portion 183 of the air curtain blower 23A communicates
through a suitable opening 181 in the separator plate 169 with the
air curtain chamber 172. Exhaust air outlet ducting 183 and air
curtain inlet ducting 184 communicate from the outlet of exhaust
blower 35A and inlet of air curtain extractor 178, respectively,
upwardly through the top wall 154 of the outer wall construction
for routing in any conventional manner to, for example, the
exterior of a building housing the assembly 150.
A common drive shaft 187, which may comprise a coaxially coupled
set of separate shafts extends coaxially through the unit 175 for
mounting rotatably driving the wheels, not shown, of the devices
34A, 35A, 23A and 178. A common drive motor, here the exhaust
blower drive motor 44A, is advantageously utilized to rotatably
drive the common shaft 187 and hence the several wheels of devices
34A, 35A, 23A and 178.
It is contemplated that by pivotally repositioning the separator
plate 169 upwardly and rearwardly so that it lies to the rear of
the unit 175, the unit 175 can be housed in the air curtain chamber
172 rather than in the exhaust transfer chamber 171. In doing so,
suitable ducting, not shown, may connect the inlet 37A through a
suitable opening in such moved separator plate (in the manner for
example, of the coupling of the outlet of air curtain blower 23A
with the air curtain chamber 172 shown) so as to admit exhaust air
from the exhaust transfer chamber thereto.
It is additionally contemplated that in certain instances, as
desired, particularly wherein air supply by the ducting 184 is
initially in a relatively clean, contaminant-free condition, that
the intake air extractor 178 may be omitted, ducting 184 thus
connected directly to the input of the air curtain blower 23A.
FIG. 8 discloses a modification of the extractor of FIG. 2, wherein
corresponding parts carry the same reference characters with the
suffix B added. In the FIG. 8 structure, a radially extending air
deflector disk 190 is fixed to the left end portion of shaft 89B,
by a hub 191 and any conventional locking means here including a
set screw 192, for rotation therewith. The disk 190 is spaced from
the right end plate 107B of the slinger wheel 106B.
The disk 190 deflects a portion of the incoming air L'B so that air
flow out of the slinger wheel is more uniformly distributed along
the length of the blades 111B (as seen at D and CB). In
consequence, the particulate material build up on the blades 111B
and the particulate masses H and G'B thrown outwardly from the
blades tend to be more uniformly distributed along the length of
the blades.
Although a particular preferred embodiment of the invention has
been disclosed in detail for illustrative purposes, it will be
recognized that variations or modifications of the disclosed
apparatus, including the rearrangement of parts, lie within the
scope of the present invention.
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