Note: Descriptions are shown in the official language in which they were submitted.
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1 1~ 5~37
In the art of gas cleansing by eIectrostatic
precipitation it is well known to provide'laterally spaced
apart and opposi~ely charged discharge'and collector
electrode means within an electrostatic precipitator for
the purpose of arresting particulate matter from a stream
of gas passed therethrough.' Among conventional discharge
electrode means are the so-called pole or mast type
electrodes which typically have been characterized by their
elongated~ formed struc~ure including variously formed
protrusions ~hereon to promote efficient corona discharge,
for example as shown in ~.SO patents 3,gg5,524, 3,200,566,
3,616,608, 3,158 9 453, 3,158,454 and 3,257,779 among many
others.
A~though ~nown mast or pole type discharge
' electrodes ~ave generally served the intended purposes they
have nevertheless often been subject to serious deficien-'
, cies. For example, conventional electrode structures and
particularly those formed in relatively thin sheet metal
often have been subject to considerable lateral deflection
' 20 as a result of periodic rapping or by their tendency to
act as airfoils thus causing a pressure differential in the
gas flowing at high velocity over the electrode. Excessive
electrode deflection may result in arcing between adjacent
discharge and collector electrodes thereby degrading dust
collecting efficiency or causing localized burning of the
electrodes. In the prior art, the requisite structural
rigidity in such electrodes has been provided by such means
as the use of heavier gauge sheet metal than would other-
wise be required or by affixing additional structural
members to the electrode. This approach seriously
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complicates electrode fabrication, results in unduly
heavy and cumbersome electrodes and is unnecessarily
wasteful of materials. Additiona:Lly, many prior mast or
pole type discharge electrodes have included integrally
formed stiffener means adjacent the electrode edqes from
which corona discharge emanates. Thus the design con-
siderations for desirable corona discharge and for required
structural rigidity have often been in conflict and the
difficult of optimizing the electrode design has been
correspondingly increased.
Furthermore, the formed protrusions on prior
electrodes constitute, in effect, point sources of corona
emission whereby the resulting distribution of corona
emission over the length of the electrode is quite non-
uniform.
These and other deficiencies of prior mast
type discharge electrodes are alleviated by the present
invention according to which there is provided an elongated,
formed discharge electrode having support or stiffener
means formed integral therewith intermediate the corona
emitting electrode edge portions. The electrode of this
invention additionally offers improved corona propagating
means and enhanced durability and simplicity of fabrication.
In accordance with the present invention, therefore,
there is provided in an electrostatic dust filter apparatus
for electrostatic precipitation of contaminants from gas
wherein a gas flow path is defined within such filter
apparatus to accommodate the passage of gas therethrough
and the filter apparatus includes a corona generating means
having at least one collector electrode extending adjacent
such gas flow path and at least one axially elongated
discharge electrode spaced transversely from the collector
csm/~
electrode across a portion of such flow path whereby the
corona generating means is cooperable with a power means
to provide corona discharge in such portion of such gas
flow path, the discharge electrode comprising: an
elongated substantially unitary electrode body extending
axially of the discharge electrode; the body including
a pair of axially elongated laterally spaced body edge
portions extending longitudinally thereof; the body including
an axially elongated formed intermediate portion extending
laterally intermediate the pair of edge portions and
including a pair of laterally spaced axially extending
side portions and axially extending formed stiffener means
disposed intermediate the side portions and protruding
transversely outwardly with respect to the side portions;
and corona discharge means extending longitudinally adjacent
at least one of the body edge portions.
These and other objects and advantages of the
: invention are more fully specified in the following
description with reference to the accompanying figures,
in which:
Fig. 1 is a schematic cross section of an
electrostatic precipitator including discharge electrode
means of the present invention;
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5~137
Fig. 2 is an enlarged fragmentary portion of
Fig. 1 showing an upper end portion of a discharge
electrode according to one preferred embodiment of the
invention;
Fig. 3 is a transverse section of the electrode
of Fig. 2 taken on line III-III of Fig. 2;
Fig. 4 is a transverse section similar to
Fig. 3 showing a variation of the embodiment of Fig. 3;
Fig. 5 is a transverse section similar to Figs. 3
and 4 showing yet another variation of the embodiment of
Fig. 3;
Fig. 6 is a partial side elevation taken on
line VI-VI of Fig. 5;
Fig. 7 is a partial side elevation of another
preferred embodiment of the invention;
Fig. 8 is an elevation taken on line 8-8 of
Fig. 7;
Fig. 9 is a transverse cross section taken on
line 9-9 of Fig. 7; and
Fig. 10 is an elevation similar to Fig. 7 showing
a variation of the embodiment of Fig. 7.
There is generally indicated at 10 in Fig. 1 an
electrostatic precipitator including discharge electrode
means constructed according to the principles of the
present invention. For purposes of illustration the
precipitator 10 is shown in simplified schematic form and
of course it is to be understood from the outset that such
simplification is not intended to unduly limit the scope
of the invention described.
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~'~f~ 5~:37
Precipitator 10 comprises a closed housing 12
which encloses a space 14 and includes gas inlet and
outlet means 24, 26, respectively~ whereby a flow of
gas may be directed through space 14 as indicated by
arrows 28 for cleansing. Within space 14 there is
carried at least one discharge'electrode bank 21 assembled
from a plurality of discharge'electrodes 20r Electrodes
20 are carried in generally vertically extending, parallel
orientation by respective pairs of upper and lower elec~
trode support members 15, 30 such that the electrodes 20
extend transversely across the gas flow path ~ith the
plane of each electrode 20 generally aligned with the'
direction of gas flow. Members 15, 30 supportingly and
electrically conductively engage respective upper and
lower end portions of the electrodes 20. The upper suppor~
members 15 are suitably secured to a rigid support frame
16. Frame 16 in turn is carried by and electrically
insulated from housing 12 as by an elongated upwardly
extending frame hanger member 17 which is supportingly
engaged by a well known compression insulator 18 such
that frame 16 and the electrode bank 21 carried thereby
are suspended within the flow path of gas passed through
space 14. Adjacent the lower ends of respective electrodes
20, the lower support memebrs 30 are suitably secured to
a base frame 22 which is electrically insulated from hous-
ing 12 as by the surrounding-air space.
As is well known, there may be provided a
plurality of generally parallel, laterally spaced
electrode banks 21 within space'14 with conventional
grounded collector electrode plates 23 also carried within
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space 14 intermediate respective pairs of adjacent
discharge electrode banks 21 and parallel thereto whereby
the discharge electrodes 20 may ~e electrîcally energized
by any suitable means (not shown) to set up corona
discharge therefrom in the space ~etween each discharge
electrode 20 and the respective adjacent collectors 23.
Accordingly, in practice the gas stream passed through
space 14 is cleansed by electrical precipitation of
entrained particulate contaminants and deposition thereof
on the collector electrode plates 23 in the well known
mannerv Conventional rapping techniques are employed
to dislodge the accumulated contaminants from collector
electrodes 23 for disposal. Inasmuch as electrostatic
precipitators such as described hereina~ove and the
operation thereof are well ~nown to those versed in the
art, further detailed description thereof if considered
unnecessary for an understanding of the present invenion.
According to one preferred embodiment of the
invention as shown in Figs. 2 and 3, each electrode 20
includes an elongated, generally planar and substantially
unitary electrode body 36 formed as by roll forming or
similar processes and comprising: a central axially
extending elongated stiffener or support portion 38 formed
intermediate the transversely opposed longitudinal edges
58 of the body 36 and corona discharge portions shown as
elongated tabs 40 formed adjacent respective adges 58 to
define respective lines of corona emission extending
therealong. Supporting web portions 42 extend inter-
mediate respective tabs 40 and stiffener portion 38. The
electrode portions 38, 40 and 42 ordinarily may be
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coextensive throughout substantially the entire length
of body 36.
Stiffener portion 38 is so formed as to define
a longitudinally extending opening 50 substantially co-
extensive therewith. The opening 50, shown as having
a circular cross section9 is adapted to have secured
therewithin the cooperably formed support members~15 and
30 adjacent respective opposed end portions of body 36
(only the upper end portion is shown in Fig. 2) as by weld-
ments 60 whereby members 15 and 30 are electrica~ly con-
ducti~ely affixed to body 36. ~s shown in Figs. ~ and 3~
body 36 is comprised of two identical and generally planar
~- elongated, formed plates 44, each being formed for
example from NoO 16 gauge steel to have a thickness of
approximately 0.04 to ~.08 inches. Each plate 44 includes
a longitudinally extending semi-circular outward bend 48
intermediate the longitudinal edges thereof which forms
one half of the stiffener portion 38, and a plurality
of the longitudinally spaced tabs 40 transversely to
one side of bend 48 adjacent one longitudinal edge of
each plate 44. In each plate 44, a longitudinal web
portion 42a extends transversely intermediate the bend
48 and tabs 40, and a second elongated web portion 42b
extends transversely outward from bend 48 generally
coplanar with and in the opposite direction from web 42a.
In assembly, two plates 44 are positioned adjacent one
another so as to extend in generally parallel coplanar
relation with the inner or concave sides of the bends 48
coaxially aligned and facing each other, and with the tabs
40 of each pla~e 44 being spaced laterally in opposite
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s~
directions as shown in Fig. 3. The two plates 44 are
affixed rigidly together in the position described as by
a plurality of resistance weldments 52 spaced long;tudinally
at intervals to rigidly secure together adjacent web
portions 42a and 42b such that the juxtaposed outward bends
48 form the stiffener portion 38 and opening 50. Of
- course, any suitable alternative fastening means may be
employed in lieu weldments 52, for example o~her types
of welding, threaded fasteners or rivets.
Longitudinally adjacent ones of tabs 40 are
shown as being formed by intervening slots 39 and as
shown may be bent or outstruck alternately in oppos;te
directions from the plane of web portion 42 at an angle
of approximately 45 degrees, for example such that alter-
nate tabs 40 provide corona emission to the collector
plates 23 on opposite sides of the discharge electrode 20.
Of course, the particular angle, shape and size of tabs
40 may be varied to achieve the most desirable and
efficient pattern of corona emission therefrom. For
example, in another preferred embodiment of this
invention which is described in detail hereinbelow tabs
40 may be substantially coplanar with web 42 such that
corona will propagate from each tab to the collector
plates 23 on both sides of the discharge electrode. In
any case, one desirable property in the discharge electrode
of this invention is that the pattern of corona discharge
to collectors on opposite sides of the discharge electrode
be generally symmetrical about the plane of the discharge
electrode. By this it is meant that approximately equal
corona discharge propagates from one edge of the electrode
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20 to each of the adjacent collector electrodes 23.
Fig. 4 illustrates a variation of the
embodiment of Figs. 2 and 3 wherein eIectrode body 36
is comprised of a generally p'Lanar elongated formed plate
44' having a ormed semi-circular outward bend 48' which
extends longitudinally of plate'44' and is located
centrally intermediate opposed longitudinal edges 58
thereof. Corona d;scharge means such as outstruck tabs
40 are formed adjacent the edges 58 of plate 44' and
identical coplanar web portions 42' extend inter-
mediate ~he bend 48l and respective tabs 40~ According
to this embodiment an elongated stiffener portion 38',
including an elongated cylindrical opening 50' adapted
to receive support mem~ers 15 and 3~, is formed by bend 48'
in cooperation with an elongated, formed means shown as
a member 54 having an alongated semi-circular outward
bend 62 formed intermediate transversely extending coplanar
web portions 64 thereof. The members 44' and 54 are
positioned with the respective inner or concave sides of
bends 48' and 62 facing each other and coaxially aligned
' to form the stiffener portion 38' and opening 50' in
the manner indicated hereinabove for the first described
embodiment, and the respective web portions 64 and 42'
are affixed rigidly together in any suitable manner as
hereinabove described to form the substantially unitary
body 36'. Elongated means 54 may be comprised of a
plurality of distinct members affixed at longitudinally
spaced intervals along the member 44' if desired.
Another variation on the embodiment of Figs. 2
and 3 is shown in Figs. 5 and 6 wherein electrode body 36''
,,,
~ 37
comprises a single, elongated, generally planar formed
member 44''having an elongated stiffener portion 38''
and identical, coplanar web portions 42'' extending
transversely in opposite directions therefrom. Tabs
40 are formed adjacent respective opposed outer edges
58 of member 44''. According to this embodiment, a
cylindrical opening 50" to receive support members 15
and 30 is formed by a plurality of longitudinally adjacent
segments ~6 of stiffener portion 381~ being outwardly formed
alternately in opposite directions.
~n each of ~he hereinabove and herei~below
described variatio~s, the stiffener portions 38-38''
are suitably formed and dimensioned to provide the
structural rigidity considered sufficient to xender the
electrode body 36-36l' substantially self-supporting
in that only the end support members 15 and 30 are
needed to support the electrode and that portion of the
electrode body extending longitudinally intermediate the
respective electrode body ends has no support means other
than its own formed structure. The openings 50-50'' as
described may be substantially coextensive with stiffeners
38-38'' whereby if desired the support members 15 and 30
may be longitudinally opposed end portions of a single
elongated member disposed within the opening 50 and extend-
ingthrouhgout thelength of body 36 to provide added struc-
tural rigidity therefor. If members 15 and 30 engage only
the opposed end portions of the body 36, the stiffener
portion 38 intermediate the end portions engaging members
15 and 30 need not necessarily be formed to include the
opening 50, for example as in the hereinbelow described
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embodiment.
In Figs. 7, 8 and 9, there is shown another
preferred embodiment of the invention wherein the electrode
body 36''' includes a formed plate member 70 having
a generally serpentine or S-curved longitudinally extending
stiffener portion 72 formed laterally intermediate the
longitudinal edges 74 thereof. Generally coplanar side
portionq 76 of plate 70 are spaced laterally to elther
side of stiffener portion 72 and each has formed therein
corona discharge means such as a plurality of longitudinally
spaced tabs 78 and intervening notches 80. The corona
discharge tabs 78 may be coplanar with each other and with
side portions 76 as shown or may be alternately outstruck
as described hereinbelow. The dimensions and spacing
, of notches 80 may be varied to alter the current-voltage
characteristics and hence the corona discharge characteris-
tics of the electrode. For example, it may be desirable
that the electrode 20 have a current-voltage characteristic
approximating that of a pair of laterally spaced, parallel-
wire discharge electrodes. One suitable configuration is
shown in Fig. 10 wherein the longitudinal extent of tabs 78
is approximately equal to the longitudinal extent ofnotches
80. A similar configuration results from the tabs in the
embodiment of Fig. 3 being of substantially equal longitud-
inal extent and being outstruck in opposite directions. It
should be noted, however, that in general the longer the
notches 80 are in relation to the length of the tabs 78,
the more corona propagation from the electrode will deviate
from longitudinal uniformity. As notches 80 are lengthened
and tabs 78 correspondingly shortened, the corona
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propagation pattern will approach that of plural,
longitudinally spaced discharge points. In a variation
of the Fig. 10 configuration (not shown) the alternate
notches 80 and tabs 78 formed in the opposite edges
74 of plate 70 may be'longitudinally offset or staggered
in such a manner that each tab 78 in one edge'74 is
transversely aligned with a notch 80 formed in the opposite
edge 74~ In an alternate embodiment the corona discharge
means may be comprised of a continuous edge portion of the
discharge electrode ~aving no cutou~s or notches therein.
If corona emission from the discharge electrodes
must be curtailed, as for example to promote the'uniform
current flow or corona discharge to the collectors near the
upper and lower ends of the body 36 whereat edges 74 are
disposed laterally adjacent corresponding edge portions
of collector plates 23, electrically conductive shroud
means 82 may be employed as shown to "soften" the contour
of the elctrode thereat by eliminating exposed edge por-
tions and curtailing corona discharge from the covered edge
; 20 portions. As shown, shrouds 82 may be formed as elongated,
generally tubular members each having a longitudinally
extending through slot 84 which receives the edge 74 of
plate 70 whereby the edges of slit 84 grip plate 70
to secure the shroud 82 thereto.
The formed plate member 70 extends intermediate
~rames 16, 22 and is secured thereto by respective upper
and lower support members 15', 30'. As shown, member 15'
comprises a formed body having a transversely extending
upper body portion 86 by which the support 15' is releas-
ably secured to a cooperably formed lower portion 88 of
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1 1~ 51 ~7
frame 16 as by threaded fasteners 90, and a pair of
inwardly and downwardly converging side'portions 92 the
lower ends of which receive t'he'respective upper ends of
electrode side portions 76 therebetween for securing
thereof as by threaded fasteners 94. In similar fashion
an upwardly extending end portion 96 of generally H-shaped,
elongated, lower alignment support 30~ is secured by
threaded fasteners 98 to the lower ends of respective
electrode side portions 76, and the lower end of support
30' is secured by threaded fasteners 100 to frame 22.
~ccording tu the description hereinabove~
there is provided by the instant invention an improved
discharge electrode of the pole or mast type for
electrostatic precipitators which is uncomplicated in
fabrication and assembly, highly durable and sufficiently
rigid by virtue of integrally formed stiffener portions
therein to resist excess lateral deflections without being
: wasteful of materials in fabrication.
Although only certain preferred embodments of
the invention have been described herein it is to be under-
stood that the invention may be practiced in numerous
alternative embodiments with various modifications thereto
without departing from the broad spirit and scope thereof.
For example: openings may be formed in web portions 42
to provide a lighter weight electrode assembly; the support
members 15 and 30 may comprise tubular members or solid
bars of any suitable cross section with the cross section
of respective openings 50 being cooperably formed; the
tabs 40 may be formed and positioned according to any
of numerous suitable designs, for example, a sawtooth
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configuration; the electrodes may be assembled from plural
elongated electrode portions connected end to end; an
electrode may combine elements of the several described
t~,~
embodiments in a single structure; end--the~ e. These
and other embodiments and modifications have been
envisioned and anticipated by the inventor, this invention
should be interpreted as broadly as permitted by the scope
of the claims appended hereto.
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