FIELD OF THE INVENTION
The present invention relates to Electrostatic Precipitator (ESP), which is a
pollution control equipment widely used for collecting dust particles from flue gas
exhausted by thermal power plants, cement plants, steel plants and glass plants.
More particularly, the invention relates to an improved drive device for rapping
mechanism in Electrostatic Precipitators to allow effective rapping of collecting
electrode.
BACKGROUND OF THE INVENTION
An Electrostatic Precipitator (ESP) is a particulate collection device that removes
particles from a flowing gas (such as air) using the force of an induced
electrostatic charge. Electrostatic precipitators are highly efficient filtration
devices that minimally impede the flow of gases through the device, and can
easily remove fine particulate matter such as dust and smoke from the air
stream.
The dust laden particles are electrically charged and in the presence of high
electric field between the electrodes the charged dust particles experience a
force which causes the particles to move towards the collecting electrodes and
finally get deposited over collecting plate. The deposited dust particle is
dislodged to a hopper through a rapping mechanism.
Rapping mechanism consists of a round solid shaft mounted with a plurality of
rapping hammers. A rapping motor is coupled axially to the rapping shaft
through clutches and coupling.

The efficiency of an ESP is enhanced by rapping the collecting electrode
sequentially to avoid building-up of dust layer. By this, the collecting surface
areas are available for sustained electrostatic precipitation. In the prior art
rapping arrangement, the geared motor is axially coupled with the rapping shaft
to drive the rapping shaft effectively. The motor is connected to the rapping
shaft through the clutch and coupling, which is having complex manufacturing
process and high procurement lead time. During operation of the ESP, the
coupling sometimes get dis-engaged from the clutches and false information is
transmitted to control room on running of the rapping shaft. This phenomenon
leads to non-removal of ash layer from the collecting electrode, hence non-
performance of the ESP. And also, this arrangement requires more space for
locating the motor along with the shaft.
In an electrostatic precipitator, the flue gas laden with fly ash is sent through a
box structure having negatively charges plates which give the particles a
negative charge. The particles are then routed past positively charged plates or
grounded plates, which attract the now negatively charges ash particles. The
particles stick to the positive plates until they are collected. The flue gas that
leaves the plates constitutes clean gas and free of harmful pollutants.
The collected dust particles is dislodged by rapping forces exerted by a rapping
hammer. The rotation of a rapping shaft is effective by a rapping motor.
According to the prior art, the rapping motor is axially coupled to the rapping
shaft to have an effective drive of the shaft. However, this occupies more space
for maintenance, accordingly ESP foot print is being increased.

OBJECT OF THE INVENTION
It is therefore an object of the invention to propose an improved drive device for
rapping mechanism in Electrostatic Precipitators to allow effective rapping of
collecting electrode.
Another object of the invention is to propose an improved drive device for
rapping mechanism in Electrostatic Precipitators to allow effective rapping of
collecting electrode, which substantially reduces the space requirement leading
to an optimized platform width even with prior art geared motor.
A still another object of the invention is to propose an improved drive device for
rapping mechanism in Electrostatic Precipitators to allow effective rapping of
collecting electrode, which eliminates clutches and coupling components of prior
art axial orientation drive device leading to avoid procurement process.
A further object of the invention is to propose an improved drive device for
rapping mechanism in Electrostatic Precipitators to allow effective rapping of
collecting electrode, which substantially reduces structural weight of platforms,
ESP roof coverage, and associated duct length.
A still further object of the invention is to propose an improved drive device for
rapping mechanism in Electrostatic Precipitators to allow effective rapping of
collecting electrode, which reduces ESP foot print thereby reducing pitching of
boiler.

Yet another object of the invention is to propose an improved drive device for
rapping mechanism in Electrostatic Precipitators to allow effective rapping of
collecting electrode, which allows smooth and effective rotation of rapping
hammer in absence of clutch and coupling .
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved drive device for rapping mechanism
in Electrostatic Precipitators to allow effective rapping of collecting electrode.
Thus, the improved drive device is enabled to transmit motion perpendicularly,
thereby reducing platform width effectively. The prior art use of coupling and
clutch is replaced with a pin wheel arrangement which eliminates the complexity
of disengagement of coupling and clutch during operations. According to the
invention, one pin wheel is coupled with the motor shaft, and another pin-wheel
is coupled with the rapping shaft with keyway.
To reduce ESP foot print, according to the invention, the effective motion of
motor is transmitted to the rapping shaft perpendicularly, by using the same
motor and introducing at least two pin-wheel assembly in between the motor
and shaft. Following are the advantages with new drive device :
• Optimised ESP footprint (ESP width reduced by 3.0M for four pass ESPs
configuration and 5.0M for Six pass ESPs configuration
• Optimised platform width leading to weight reduction.

• Reduction in weight for other structural items like duct, duct structures,
Pipe trestle etc due to reduction in pitching of boiler and ESPs.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Shows an isometric view of a typical Electrostatic Precipitator (ESP)
Figure 2 Shows collecting and emitting electrodes
Figure 3 Shows 2-D drawing of Pin wheel used in motor and rapping shaft
according to the invention.
Figure 4 Shows a prior art drive arrangement, in which the motor is axially
coupled with rapping shaft.
Figure 5 Shows new drive device in which the motor is perpendicularly
coupled with rapping shaft.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The Electrostatic precipitator as shown figures 1 and 2 essentially consists of two
sets of electrodes called Collecting Electrodes and Emitting Electrodes and (also
called discharge electrodes). A unidirectional high voltage is applied between
these two sets of electrodes, connecting its negative polarity to the emitting
electrodes and the positive polarity to collecting electrodes, which are also
earthed. The dust laden flue gas from the boiler passes between rows of
collecting and discharge electrodes.
The high voltage induces ionization of gas molecules adjacent the negatively
charged emitting electrodes. The positive charges of the ions so created, travel
towards the discharge electrodes and the negative charges towards the

collecting electrodes. On their way to the collecting electrodes, the negative
charges of the ions get deposited on the dust particles.
Thus the dust particles are electrically charged. In presence of high electric field
between the electrodes, the charged dust particles experience a force which
causes the particles to move towards the collecting electrodes and finally get
deposited on them. Minor portions of the dust particles, which have acquired
positive charges, get deposited on the emitting electrodes also. Periodically these
are dislodged from the electrodes by a process called Yapping', in which a
rapping mechanism is used. The particles then fall into the hoppers at the
bottom.
Hammers are mounted in the horizontal rapping shaft and the effective forces
are created due to rotation of shaft by a motor. The rapping forces are
transferred to the collecting electrode through a shock bar attached at bottom of
the electrode. According to the invention, Pin (01) is designed and provided to
transmit the torque exerted by the rapping shaft along with the hammer. The
length and number of the pins are decided to allow a smooth engagement and
dis-engagement of the pins. Hole of required diameter is made in a Flange plate
(04) and the pins (01) are inserted to the hole and seal welded. A Rib plate (03)
is provided to avoid local distortion of the flange plate (04) and maintain the
flatness of the flange plate. A Hub (02) is fixed to the flange plate (04) to insert
in the motor shaft and rapping shaft.
The total pin-wheel assembly (05) is connected to a rapping motor (06) at one
end and to rapping shaft (07) at other end. The effective perpendicular motion is
transferred to the rapping shaft from the motor through the pin-wheel assembly
(05).

WE CLAIM :
1. An improved drive device for rapping mechanism in Electrostatic
Precipitators to allow effective rapping of collecting electrode, the
improvement is characterized by :
at least two pin-wheel assembly (05) are formed, each of the pin-wheel
assembly (05) connecting to a rapping motor (06) at its first end, and the
second end of the each pin-wheel assembly is attached to the rapping
shaft (07) to allow transfer of an effective perpendicular motion from the
motor (06) to the rapping shaft (07) via the pin-wheel assemblies (05),
wherein each pin-wheel assembly is formed of a flange plate (04)
configured with a plurality of holes accommodating the pins (01), a rib
plate (03) provided to maintain flatness of the flange plate (04), and
wherein a hub (02) is fixed to the flange plate (04) to enable insertably
connect the motor shaft and the rapping shaft.
2. The device as claimed in claim 1, wherein the dimension and number of
the pins is decided based on desired engagement or disengagement
criteria of the pins.
3. The device as claimed in claim 1, wherein the pins after insertion on the
holes are seal-welded.

4. The device as claimed in claim 1, wherein the pins are case hardened to
enhance wear resistance.

ABSTRACT

The invention relates to an improved drive device for rapping mechanism
in Electrostatic Precipitators to allow effective rapping of collecting
electrode, the improvement is characterized by : at least two pin-wheel
assembly (05) are formed, each of the pin-wheel assembly (05)
connecting to a rapping motor (06) at its first end, and the second end of
the each pin-wheel assembly is attached to the rapping shaft (07) to allow
transfer of an effective perpendicular motion from the motor (06) to the
rapping shaft (07) via the pin-wheel assemblies (05), wherein each pin-
wheel assembly is formed of a flange plate (04) configured with a plurality
of holes accommodating the pins (01), a rib plate (03) provided to
maintain flatness of the flange plate (04), and wherein a hub (02) is fixed
to the flange plate (04) to enable insertably connect the motor shaft and
the rapping shaft.