An electrostatic precipitator is provided comprising a plurality of spaced apart vertically extending collector plates with an array of vertically extending ionizer wire rods disposed in a space between each of the collector plates. The improvement resides in an ionizer wire rod construction made of a heat resistant alloy, one end portion of which terminates into a plurality of closely packed helically formed loops. The size of the loops as a unit is sufficient to hook onto and freely hang from a connecting portion of an ionizer frame, the other end portion of the rod being also helically formed into a plurality of closely packed loops which are coupled as a unit to an end loop of a helically and tightly wound coil spring of a heat-resistant alloy. The tightly wound coil spring comprises a plurality of active turns, with each active turn adjacently touching the other in the unstretched condition, the coil spring being cylindrically shaped and having a length such as to provide a tension on the ionizer wire of at least about 30 pounds when substantially the total length of the cylindrical coil is activated by stretching to provide and maintain said tension, the coil spring having a connecting loop at its other end for coupling to an opposite portion of the ionizer frame.

This invention relates to electrostatic precipitators and to an improved 
emitter ionizer wire construction. 
STATE OF THE ART 
In conventional precipitators there is a tendency for electrode wires 
(i.e., emitter ionizer wire) to break and fracture at their point of 
anchorage due to fatigue. 
As pointed out in U.S. Pat. No. 2,866,517, in electrical precipitator 
operation, dust and other types of precipitates collect on discharge 
electrodes and are removed by vibration and rapping means which cause 
flexing and vibration of the electrodes. 
For example, in the case where discharge electrodes take the form of 
elongated flat ribbons or bands of an electrically conductive material, it 
has been observed that flexing and vibration of such ribbon type 
electrodes produce substantial stresses which are normally concentrated 
along the attachment edges of the ribbon or band. The same phenomenon 
occurs where the electrode is a wire. U.S. Pat. No. 2,866,517 proposes a 
modified mounting and support structure for the discharge electrode to 
minimize this problem. 
However, the discharge electrode material during use tends to elongate and 
sag at elevated temperatures due to creep. To avoid this, stress is 
continually applied to the electrode by means of weights to keep discharge 
electrode under stress. U.S. Pat. No. 2,867,287 also proposes a modified 
mounting or support for discharge electrodes in which the electrode 
structure includes a flexible anchorage means, such as spring means. While 
such support structures appear to be an improvement over other types of 
anchorage means, the specific anchorage structure employed still had much 
to be desired. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide an electrostatic precipitator 
having improved operational life in the field. 
Another object is to provide an improved emitter ionizer wire construction. 
These and other objects will more clearly appear when taken in conjunction 
with the following disclosure, the claims and the accompanying drawings.

SUMMARY OF THE INVENTION 
One embodiment of the invention resides in an improved ionizer wire 
construction for an electrostatic precipitator. Stating it broadly, the 
ionizer wire rod is preferably comprised of a heat resistant alloy, one 
end portion of the rod terminating helically into a plurality of closely 
packed loops, e.g., two loops, sufficient to provide a free tail portion 
which is bent and wrapped around the wire rod adjacent to the loops, the 
size of the loops as a unit being sufficient to hook freely onto a 
connecting portion of an ionizer frame. The other end portion of the rod 
is also helically formed into a plurality of closely packed loops (e.g., 
two loops) which are coupled as a unit to an end loop of a helically and 
tightly wound coil spring of a heat-resistant alloy. 
The tightly wound coil spring comprises a plurality of active turns with 
each active turn adjacently touching the other in the unstretched 
condition, the coil spring being cylindrically shaped and having a length 
such as to provide a tension on the ionizer wire of at least about 30 
pounds when substantially the total length of the cylindrical coil is 
activated by stretching to provide and maintain the desired tension, the 
coil spring having a connecting loop at its other end for coupling to an 
opposite portion of the ionizer frame. 
In a preferred embodiment, the ionizer wire rod has a diameter of about 
0.05 to 0.125 inch, and the coil spring has a stretch rate of about 3 to 
10 pounds per inch of original coil length when stretched. The cylindrical 
coil spring may have a diameter of about 1/2 to 11/4 inch, and is designed 
to provide a total stress on each of the ionizer wires ranging from about 
30 to 50 pounds when mounted in the stretched condition. 
A preferred stretch rate of the spring ranges from about 4 to 6 pounds per 
inch of original spring length when the ionizer wire is mounted in the 
stretched condition, the total stress on the ionizer wire rod preferably 
ranging from about 35 to 40 pounds. 
The rod and spring may both be made of heat resistant alloy, the alloy 
being selected from the group consisting of nickel-base and iron-base 
alloys. Such alloys are preferred where the temperature of the 
electrostatic precipitator reaches 600.degree. F. or higher, particularly 
where the precipitator is used to remove flue dust resulting from 
metallurgical operations. 
The diameter of the wire from which the spring is made may also range from 
about 0.05 to 0.125 inch. 
The advantage of using a plurality of end loops on the ionizer wire as 
connecting means to the ionizer frame and to the springs is that failure 
by fatigue at such connections is substantially reduced. 
Materials used for the ionizer wire and the springs are disclosed in Volume 
1 of the Metals Handbook, Ninth Edition (Published by the American Society 
for Metals, 1978), reference being made to pages 283 to 292. As stated at 
page 283, extension springs normally are close wound, usually with a 
specified initial tension and, because they are used to resist pulling 
forces, are provided with hook or loop ends to fit the specific 
application. 
Stainless steels are the preferred iron-base alloys and may include Type 
302 stainless consisting essentially of about 17% to 19% Cr, about 8% to 
10% Ni and the balance essentially iron by weight. Another steel is Type 
316 which contains by weight about 16% to 18% of Cr, about 10% to 14% Ni, 
about 2% to 3% Mo and the balance essentially iron. This steel is 
particularly preferred as spring and rod material. It has good heat 
resistance and greater corrosion resistance than Type 302 stainless and 
also good spring temper at temperatures in the neighborhood of about 
600.degree. F. 
Another stainless steel is Type 631, otherwise referred to as 17-7 PH 
steel. This steel contains by weight about 16% to 18% Cr, about 6.5% to 
7.75% Ni, about 0.75% to 1.5% Al and the balance essentially iron. This 
steel also has good spring temper at the aforementioned temperature. 
Nickel-base alloy springs include an alloy identified by the trade mark 
Inconel 600 which contains approximately by weight 76% Ni, 15.8% Cr, about 
7.2% Fe and the balance residuals. This alloy has good corrosion 
resistance at elevated temperatures, e.g., 600.degree. F., and also 
retains its spring temper at such temperatures due to its age hardening 
properties. 
Another nickel-base alloy is one known by the trade mark Inconel X-750 
which contains approximately 73% Ni, 15% Cr, 6.75% iron and the balance 
age hardening elements. This alloy in the age hardened condition has good 
spring temper at elevated temperature. 
Another embodiment of the invention is directed to an electrostatic 
precipitator comprising a plurality of spaced vertically extending steel 
collector plates mounted in a housing in substantially parallel 
relationship. The precipitator also includes a plurality of ionizer wire 
frames each mounted between said collector plates and characterized by a 
top and a bottom frame portion; each having a spaced array of vertically 
extending ionizer wire rods, the frames being coupled for electrical 
excitation opposite in charge to said collector plates which are grounded. 
Each of the wire rods have connecting means at each end thereof in the 
form of a plurality of tightly wound closely packed loops sufficient to 
provide a free tail portion extending from said closely packed loops and 
wrapped around said wire rod adjacent said loops, one end of the wire rod 
being freely coupled via the loops as a unit to the top portion of each 
frame with the other end thereof freely coupled via the loops as a unit to 
one end of a helically tightly wound cylindrically shaped coil spring, 
which spring at its other end is coupled under tension to the lower or 
bottom portion of the frame. The length of the coil spring and the 
diameter of the wire forming the spring in the cold worked tempered 
condition are such as to provide a tension on the ionizer rod of at least 
about 30 pounds when substantially the total length of the helically wound 
coil spring is mounted on the frame in the stretched condition. 
DETAILS OF THE INVENTION 
A typical spring employed in carrying out the invention is illustrated in 
FIG. 1, the helically coiled spring 10 having a diameter of about 7/8 of 
an inch and a length, excluding spring loops 11, 12, of about 7.5 inches 
and from the extreme ends of the loops a length of about 8.25". The spring 
is preferably produced from spring temper Type 316 stainless steel wire of 
diameter of about 0.105 inch. As will be noted from FIG. 1, the spring is 
tightly wound with the turns in very close pack relationship, the spring 
comprising, for example, approximately 65 active turns, the spring when 
stretched having a spring rate of about 6 lbs/inch of original spring 
length. The spring in the stretched condition is shown in FIG. 2, the 
spring being attached to ionizer wire rod 13 which is coupled to spring 
loop 12 via double loop 14 of the ionizer wire having a freely extending 
tail portion 14A which has been bent or wrapped around rod 13, the 
opposite end of rod 13 also terminating into a double loop 15 having a 
freely extending tail portion 15A wrapped around rod 13. 
In one embodiment, the extended or stretched length of spring in FIG. 2 
when installed is about 1 foot - 2 inches from end of spring loop 11 to 
end of spring loop 12, as compared to the unstretched length of about 8.25 
inches, the stretch amounting to approximately 70% of the original coil 
length. In this embodiment, the combined stretch length of spring and rod 
is about 10 feet - 2 inches from spring loop 11 to double loop 15 of the 
rod. The total length prior to stretch being approximately 9 feet - 83/4 
inches. 
FIG. 3 is a schematic of one embodiment of an electrostatic precipitator 16 
comprising a housing 17 with gas inlet means 18 and gas exit means 19, the 
housing being partially broken away as shown to reveal collector plate 
elements 20 coupled to upper and lower frame members 21, 22, the collector 
plates being partially broken away to reveal emitter ionizer wires 23 
behind the plates, each wire being hooked to upper frame member 24 via 
hook 25 and lower frame member 26 via spring 27, the springs 27 being 
hooked to lower frame or mid-frame member 26. Frame member 24 is 
electrically coupled to a source of electricity 30 via insulated mounting 
30A. 
The ionizer wires comprise two sets, one above the other as shown, one 
group being coupled between frame members 24, 26 and the other between 
frame members 26, 26. The term "upper and lower ionizer frame members" is 
meant to include a mid-frame member which can serve as an upper or lower 
frame member. 
The lower part of housing 17 extends to a hopper 28 which receives the 
precipitated dust. Rapper means 29, 29A are provided to vibrate the frame 
members supporting ionizer wire rods 23 via insulated upper arms 29A 
attached to frame member 24 as shown. Rapper means not shown are generally 
used to vibrate or shake the frame supporting the collector plates. 
A more detailed schematic is shown in the embodiment of FIG. 4 which is a 
cross section of a housing 31 showing in elevation an alternate 
arrangement in parallel of collector plates 32 and ionizer wire rods 33. 
The collector plates 32 extend from the top 34 of the housing 31 to the 
bottom thereof at 35, while the alternately ranged wire rods 33, 33A are 
disposed and attached between upper, intermediate and lower frame portions 
36, 37, 38 using coupling hooks as shown. 
With regard to ionizer wires 33, they extend from frame 36 to frame portion 
37 via connecting springs 40 in the one instance and from frame portion 37 
to frame portion 38 via connecting springs 40A. 
The ionizer wire rod frame members are vibrated via rapper means 42 and 42A 
as shown, the spring members being disposed at the lower end of the 
ionizer wire, this arrangement being the more preferred use of the 
springs. 
FIG. 5 is illustrative of a side-by-side arrangement of a collector 
plate-ionizer wire rod assembly which is supported in a housing not shown. 
The assembly is partially broken away to show ionizer wire rods 44 
disposed behind collector plates 43, the collector plates being supported 
between top frame member 45 and lower frame member 46, the ionizer wire 
rod 44 being supported between frame member 47 and intermediate frame 
member 48 and between frame member 48 and member 49, and coupled thereto 
at the bottom end via springs 50 and 50A, respectively, as shown. Two 
ionizer wires are associated with each collector plate element. 
A detail of the collector plate elements is shown in FIG. 6, the element 51 
being formed of mild steel strip with the longitudinal edges 52, 52A being 
cold formed to provide a stiffened flanged structure as shown. Hook means 
53 is provided at the top thereof for hooking onto the top frame member 45 
fixed within the housing (FIG. 5), and means 54 at the bottom thereof for 
attachment to the bottom frame portion 46 of the housing. 
Referring to FIG. 5 which shows a side-by-side arrangement of two collector 
plates/ionizer wire rod assemblies, it will be noted that the collector 
plate elements 43 are connected to the bottom frame member 46 via tongue 
or bracket 54A which corresponds to bracket 54 of FIG. 6. The connection 
is also shown in the side view of FIG. 5 in which the tongue or bracket 
54A is shown passing through frame member 46 and held thereby. The term 
"upper and lower frame member" holding the collector plate elements is 
meant to include all the frame members alternately arranged as shown in 
FIG. 4. 
Referring back to FIG. 5, a plate rapper mechanism 55 is shown at the side 
of the lower frame portion comprising a pivotally mounted hammer 56 
(actuated by means not shown) striking the end of frame 46 as shown, the 
frame being supported by mounts 57 and 57A. The end of the frame is struck 
on an intermittent basis to dislodge the collected dust. 
Tests carried out experimentally in the field under actual conditions for a 
period of over about two years resulted in a markedly improved life of the 
ionizer wire--spring assembly, during which period there was an occasional 
wire failure as compared to consistent wire failures in a much shorter 
time period when the novel spring support of the invention was not used. 
Although the present invention has been described in conjunction with 
preferred embodiments, it is to be understood that modifications and 
variations may be resorted to without departing from the spirit and scope 
of the invention as those skilled in the art will readily understand. Such 
modifications and variations are considered to be within the purview and 
scope of the invention and the appended claims.