Title of Invention

A NOVEL APPARATUS AND A METHOD FOR SCRAPPING AND REMOVING SOOT DURING DEPOSITION IN A MCVD PROCESS

Abstract This invention is related generally to the field of manufacturing of optical fiber preform and more particularly to removal of soot from the exhaust tube during a MCVD process. The current methods of soot removal are ineffective in terms of ensuring the quality required of the final performs. The present invention provides a novel apparatus and a method to scrape the excess soot deposited inside the exhaust tubes that are used in the MCVD processes deployed in optical fiber manufacturing. The present invention aimed at effectively scrapping and removing the soot deposited inside wall of exhaust tube during the deposition process and to ensure proper flow of reactant gases inside the deposition tube and also through the exhaust tube further to the collection box. The method ensures the safety of the process equipment and the materials used therein, and also help maintain the quality of the final product. The invention comprises a soot remover rod as the inventive apparatus and a method of using the same.
Full Text FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL/COMPLETE SPECIFICATION
(See section 10 and rule 13 )

l. TITLE OF THE INVENTION:: A novel apparatus for scraping and
removing soot during deposition in a MCVD process and a
method of using the same

2. APPLICANT (S)
a. NAME : Sterlite Optical Technologies Limited
b. NATIONALITY : Indian company registered under the Indian Companies Act, 1956.
c. ADDRESS : E-2, Waluj MIDC, Aurangabad 431 136, Maharashtra State, India

3. PREAMBLE TO THE DISCRIPTION
The following specification particularly describes the invention and the manner in which it is to be
performed.







A novel apparatus for scraping and removing soot during deposition in a MCVD process and a method of using the same
Field of Invention
The present invention generally relates to the manufacturing of an optical fiber preform by MCVD process, and more particularly to an apparatus and a method for scraping and removing the excess soot accumulated inside the exhaust tube during the deposition process of MCVD.
Background Of Invention
Conventional methods for manufacturing optical fiber by using the MCVD process involve injecting a chemical reaction mixture gas into a deposition glass tube from its inlet end. There is a heat source that traverses longitudinally along the glass tube in the same direction as that of the injected gas. The reaction mixture reacts in the hot zone to form soot, which flows downstreamm of the moving hot zone. During this process, soot is simultaneously deposited on the inside surface of the glass tube and sintered into glass. Some of the soot finds its way further downstream into the exhaust tube that is attached to the outlet end of the deposition tube.
Different competing methods employed in the manufacture of
silica-based optical fiber are described in "Optical fiber
communication" and the article entitled "Fiber optics" in Kirk-
Othmer Encyclopedia of Chemical Technology, 4th Ed., Vol 10, pp.
125-147(1994).
2

It is of vital importance to ensure that the exhaust tube will not be clogged by the soot accumulating therein during the process of manufacture of optical fiber preform. The clogging of the exhaust tube would result in a pressure anywhere within the manufacturing system including the increase of pressure within the preform, which could darnage the preform. For optimum results the exhaust tube should provide a smooth, continuous flow for the gases escaping from the deposition tube, and also through the exhaust tube further to the soot collection chamber.
Conventionally, the function of keeping the exhaust tube clear of soot is carried out fully manually by scraping off the soot accumulated in this tube called an exhaust tube at regular intervals during the manufacture by means of a glass rod so as to prevent the clogging of the exhaust tube. The clogging of the exhaust tube would result in a pressure increase within the preform and damage the preform.
Several methods are used in the industry to overcome the problem of clogging of the exhaust tube and are known to a person reasonably skilled in the art.
The patent JP-A-5841734 describes an apparatus for removing the excess soot by using a rod that traverses in longitudinal direction. The rod is equipped with a terminal screw with flat helical threads which scrape the interior surface of the exhaust tube to remove the soot which is then collected in a collection chamber. However, this apparatus has a disadvantage that the excess soot can accumulate
between the threads of the screw. This leads to ineffective removal
3

of soot. This can further result in some of the soot that has been removed finding its way back into the deposition tube. This can result into a substandard preform, which might need to be discarded.
Another patent, WO 89/02 419, describes a device that has a screw type structure and a tubular pipe wound in a spiral. The device is further characterized in that the screw structure comprises a gas conduit provided with orifices opening towards the open end of the exhaust tube. When introducing dry gas, such as N2 gas, into the gas conduit, the soot in the exhaust tube is exposed to a gas flow which tends to remove the soot out of the exhaust tube. A disadvantage of this device is that the threads of the tubular screw do not effectively scrape the soot accumulated on the wall of the exhaust tube. This further causes turbulence inside the tube.
The U.S. Patent No. 5,972,115 discloses an apparatus which comprises a hollow helical screw having an outside diameter substantially equal to the inside diameter of the exhaust tube and a cylinder housed in contact with the interior surface of the helix to rotate on its axis in the passage. However it has a disadvantage that the helical screw is continuously rotated along with the rotary seal that is used to contain the chemical gases. This can result in undesirable frictional forces on the rotary seal, ultimately resulting in rupture of the seal and leakage of chemical gases.
There is therefore a need to provide a more effective method of removing excess soot from the exhaust tube without affecting the
4

performance of the manufacturing process and also the quality of the preform.
Objects and advantages of the invention:
Accordingly, the objects and advantages of the present invention are described below.
An object of the present invention is to provide a novel apparatus and a method for scrapping and removing the soot accumulated inside the exhaust tube.
Another objective of the present invention is to provide for smooth, continuous flow for the gases escaping from the deposition tube, and through the exhaust tube.
Yet another objective of the present invention is to provide a method of manufacture of preform wherein the scraped soot does not find its way back into the deposition tube, thereby ensuring a high quality of the preform.
Further objective of the present invention is to provide a method of manufacture of preform wherein the components of manufacturing equipment, such as the rotary seal of the collection chamber remain undamaged.
5

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The principles and features of the present invention will be readily apparent from the following detailed description when read in conjunction with the accompanying drawings.
Figure 1 is a schematic representation of deposition tube with lathe along with the novel apparatus of the present invention, thereby showing the general set up of the MCVD process.
Figure 2 is a schematic representation of the movement of the soot scraper and removal rod of the apparatus inside the exhaust tube.
Figure 3 is a schematic representation of design of the scraper rod.
Figure 4 shows the longitudinal cross sectional view of front-end tip of the scraper rod.
Figure 5 shows the front cross-sectional view of the front end tip of the scraper rod.
Summary of the invention:
The present invention provides a novel apparatus and a method to
scrape the excess soot deposited inside the exhaust tubes that are
used in the MCVD processes deployed in optical fiber
manufacturing. The present invention aimed at effectively
scrapping and removing the soot deposited inside wall of exhaust
tube during the deposition process and to ensure proper flow of
reactant gases inside the deposition tube and also through the
6

exhaust tube further to the collection box. The method ensures the safety of the process equipment and the materials used therein, and also help maintain the quality of the final product. The invention comprises a soot remover rod as the inventive apparatus and a method of using the same.
. DETAILED DESCRIPTION OF THE PRESENT INVENTION:
General:
Figure 1 shows a general set up of the MVCD process. The inlet end of a high purity glass deposition tube 1 is installed on the head stock chuck 2. An exhaust tube 3 is installed on tail stock chuck 4 at the outlet end of the deposition tube 1. During deposition process, a mixture of reactant gases such as SiC14, GelC4, PoC13, Helium and Oxygen is fed into the deposition tube through a delivery tube 6. The deposition tube 1 is rotated along its longitudinal axis along with exhaust tube as shown in Figure 1. An Oxyhydrogen burner 5 is provided to heat the deposition tube 1, which has its forward traverses from the position X of deposition tube to the position Y at the other end thereof.
Hot zone is formed near the position of the burner 5 at any given instant, hence the position of the hot zone moves in synchronization with the burner movement. The gas mixture that is injected into the deposition tube 1 through the delivery tube 6 reacts at hot zone of the deposition tube 1 to form soot and the deposition of soot occurs in the deposition tube 1 downstream of the hot zone. The deposition of soot occurs only during the forward
traverse of the burner 5. A layer of deposition gets added on the
7

inside surface of the deposition tube during every forward traverse. The forward traverses are carried out at certain speed for each layer of deposition. The reverse traverses, from Y to X, are carried out at a much higher speed.
The high temperature generated by the oxyhydrogen burner 5 sinters the deposited soot. Excess soot that doesn't get deposited in the deposition tube finds its way to the exhaust tube and gets deposited on its inside surface. To facilitate a smooth and unobstructed entry of gases from the deposition tube into the exhaust tube, the exhaust tube should generally have a diameter larger than that of the deposition tube 1. The outlet end of deposition tube 1 is therefore shaped, with the help of a graphite tool, into a truncated cone shape to provide an internal diameter at the mating end of the deposition tube 1, same as that of the exhaust tube. As shown in Figure 2, the enlarged end of the deposition tube and the mating end of the exhaust tube are joined together by heating flame of the oxyhydrogen burner 5.
The present invention provides an apparatus and a method to scrape and remove soot from the internal surface of the exhaust
Description of the preferred embodiment:
Accordingly, the preferred embodiment of the present invention
and the apparatus, as shown in Figure 2, comprises a novel soot
scraper and removal rod 7 (referred to hereinafter as the rod). The
rod 7 is hollow with a cylindrical cross section, and comprises an
annular front tip 8, a scraping arm 9, a transition arm 10, and an
operating arm 11. Its wall has a preferable thickness of not less
8

than 2mm. It has a plurality of bends to facilitate the entry into and the movement inside the exhaust tube 3. It also has a plurality of holes orientated and spaced in a manner that facilitates removal of the scraped soot with the help of gas supplied from a gas source 13. According to the novel method of soot removal disclosed in this invention, the rod is moved along the inside surface of the exhaust tube with the help of a movable motor or an actuator.
Referring to Figures 1 and 2, before the process of deposition of the soot inside the deposition tube 1 begins, the front tip 8 of rod 7 is positioned inside the exhaust tube at a location A near the far end of the exhaust tube as shown in Figure 2. After completion of the first layer soot in the deposition tube 1, that is when the burner has reached the position Y as shown in Figure 1, the rod 7 starts traversing along the inside surface of the exhaust tube, from the position A to position B with certain speed and return backs to original position A, as shown in Figure 2. A single cycle of the rod 7, that is from A to B and from B to A is completed in the approximately the same time as a single cycle or the traversing movement of the burner 5, that is from Y to X followed by X to Y. The traverses of the burner 5 are continued until the required preform of required diameter is fabricated.
The traverse speed of the rod 7 is set in such way that the rod 7, due to the longitudinal movement of the rod 7 combined with the rotational movement of the deposition tube 1 and the exhaust tube 3, contacts a substantial portion of inside surface of the exhaust tube 3 over a relatively large portion of the length thereof.
9

A novel feature of the present invention is that the rod 7 is connected with a gas source 13 to remove as shown in Figure 3. The gas source 13 supplies gas (referred to hereinafter as the remover gas) such as nitrogen or oxygen to loosen and carry away the scraped soot. Alternatively, any other inert gas that does not adversely affect the reaction inside the deposition tube may be used. The remover gas is fed at one end of the soot remover rod 7 under a suitable positive pressure, preferably at 1 bar, and comes out of the plurality of holes 12.
As the rod 7 traverses from position A to position B and back from position B to position A, soot particles on the inside surface of the exhaust tube are scraped or dislodged by the rod and carried away by the remover gas flowing out of the holes 12. It is important to note that the remover gas after coming out of the plurality of holes 12 flows in the same direction as the direction of the flow of deposition gas mixture in the deposition tube 1.
The rod traversing is provided with an arrangement to collect the soot inside the soot collection box. A person skilled in the art knows that it is possible under certain circumstances, that the dislodged soot particles can come together to form larger soot particles. These larger soot particles are sometimes difficult to carry away and there is a risk that they can find their way back into the deposition tube. A small negative pressure is maintained at the soot collection box, which along with the positive gas pressure applied inside the rod 7, ensures that soot is effectively carried away from the exhaust tube 3. One of the advantageous features of the present invention is that the remover gas is applied
10

at a pressure which is set at a level such that the dislodged soot particle do not enter back inside the deposition tube 1.
The soot scraped from the exhaust tube 3 is collected inside a soot collection chamber. A sealing mechanism is provided in the soot collection chamber so that the movement of the rod can take place without soot escaping from the chamber. It will be known to a person reasonably skilled in the art that the rotational movement of conventional soot removing devices tends to damage the seals through which they operate. As another advantageous feature of the present invention, the chances of damaging the seal during the traversing motion of the rod are minimal as the rod 7 does not have rotational motion.
In the preferred embodiment of the invention, the soot remover rod 7 is made of stainless steel or aluminum so that it doesn't get rusted quickly when exposed to the corrosive chemical environment inside the exhaust tube. The dimensions and design of the rod 7 are determined so as to be able to remove the soot generated inside the exhaust tube 3 during manufacturing of any size of preform made from MCVD process.
As shown in Figure 3, in the preferred embodiment of the invention, the total length of the soot remover rod is, more preferably, less than 6 meters. The length LI of the operating arm 11 is preferably greater than LI and L3, which are the lengths of the transition and scraping arms 9 and 10 respectively. Furthermore, L2 is more preferably less than LI.
11

The preferred embodiment of the invention shows two bends with angles 01 and 02 in the rod 7. The angle 02 is preferably approximately ten times greater than 01. The value of angle 01 is determined in relation to the outer diameter ®2 of the rod 7, as shown in Figure 4. It is observed that larger the diameter of the rod 7, smaller is the angle 01 required for effective operation of the rod 7. The diameter 02 of rod 7 is less than 12 mm and more preferably less than 10 mm. The angle of cone at the tip 03 is determined such as to avoid accumulation of the soot at the tip of the rod 7.
The number of holes 12 and the diameter 0l of individual holes 12 are determined to suit the flow rate of the remover gas. The angle 04 of holes is preferably less than 60° and more preferably less than 50°.
The angle 05 between adjacent holes (see Figure 5) is determined such that inert gas flowing out of the plurality of holes 12 is effectively able to carry away the soot scraped from the inside of the wall of exhaust tube 3.
In another embodiment of the present invention, the material of the rod is any material that does not get adversely affected by the corrosive chemical environment inside the exhaust tube and which has requisite strength to withstand forces exerted on it during the scraping action.
In yet another embodiment of the present invention the cross-sectional shape of the rod is selected from a group of shapes
12

comprising rectangular, square, and triangular or any other shape that facilitates scraping action effectively.
The soot remover rod is replaceable after a certain number of core rod fabrication.
While the preferred embodiments of the present invention have been illustrated and described, it should be understood that the present invention has been described through the particular embodiment disclosed herein as the best mode contemplated for carrying out the invention, and that various additional modifications will occur to those skilled in the art within the scope of the invention.
In the view of the above detailed description of the present invention, any person reasonably skilled in the art will understand that the present invention basically comprises the following items:
1. A novel apparatus for scraping and removing soot accumulated in exhaust tube during an MCVD process, comprising:
a. soot scraper and remover hollow tubular rod
comprising a plurality of distinct arms in an angularly
joined relationship, wherein said tubular rod has one
scraping end and another remover gas entry end;
wherein the wall of said tubular rod has a plurality of holes
made in spaced apart relationship, said holes being disposed
near the scraping end of said tubular rod, and
wherein longitudinal axis of each of the said holes is
disposed in a predetermined orientation with predetermined
13

angular relationship with longitudinal axis of respective said distinct arms,
whereby said soot in exhaust tube is effectively removed by scraping by said tubular rod and carrying away by remover gas.
2. A novel apparatus as described in item 1 above, wherein the cross-sectional shape of any of said distinct arms of said hollow tubular rod comprises an annular ring having a shape selected from the group consisting of cylindrical, square, rectangular, trapezoidal, elliptical, and diamond shapes or any combination thereof, preferably cylindrical.
3. A novel apparatus as described in items 1 or 2 above, wherein any of said distinct arms is made of a material selected from the group consisting of steel, aluminium, copper, an alloy or any material unaffected by the gases inside the exhaust tube, or any other combination thereof, preferably stainless steel.
4. A novel apparatus as described in items 1 to 3 above, wherein outer diameter of any of said distinct arms is less than 12 mm, preferably less than 10 mm, and more preferably about 6mm, and wherein the wall thickness of said distinct arms is about 2 mm or more.
5. A novel apparatus as described in items 1 to 4 above, wherein angle 94 between longitudinal axes of said holes and said respective distinct arm containing said holes is preferably less than 60°, more preferably less than 50°, and wherein diameter 03 of said holes is about 1 mm to about 2 mm, preferably 1.2 mm, and wherein said longitudinal axes of said holes are orientated such that overall direction of flow of remover gas coming out of said holes is substantially same
14

as the direction of flow of reactant gases through deposition tube.
6. A novel apparatus as described in items 1 to 5 above, wherein said tubular rod comprises preferably three arms including a scraping arm, a transition arm, and an operating arm, wherein their respective lengths LI, L2, and L3 have predetermined values, and the angles 01, and 02, wherein 01 is the angle between said scraping arm and said transition arm, and 02 is the angle between said transition arm and said operating arm, have predetermined values, and wherein 02 is preferably ten times greater than 01 and LI is preferably greater than the sum of LI and L2, and the total length of said tubular rod is approximately 6 meters, whereby soot removal from said exhaust tube is facilitated.
7. A novel apparatus as claimed in claims 1 to 6 wherein said
holes are disposed near the scraping end of said tubular rod.
8. A novel method of scraping and removing soot deposited
inside an exhaust tube, by using a novel apparatus as
described in items 1 to 6, comprising the steps of:
a. positioning scraping end of said tubular rod of said
apparatus in the exhaust tube,
b. traversing said tubular rod inside and along the
internal wall surface of said exhaust tube at a
predetermined speed in a predetermined mode of
each traverse, such that each traverse of said tubular
rod inside said exhaust tube corresponds to
deposition of one layer of soot in the deposition tube,
15

c. passing a remover gas under a predetermined
pressure, through said tubular rod, simultaneously with
step b above, to effectively remove scraped soot, and
d. continuing steps b and c above till completion of the
work of soot deposition in said soot deposition tube.
9. a novel method as described in item 8, wherein the speed of
traverse in any one cycle is constant for said cycle and is set at
a value which is preferably less than 2 cm/sec, more preferably
less than 1.5 cm/sec.
10. A novel method as described in items 8 and 9 wherein said
remover gas is selected from a group of gases comprising oxygen,
nitrogen, or any other gas that does not adversely affect the
reaction inside the deposition tube, or a combination of any
of these, and wherein the pressure of said remover gas is set
to such value that the scraped soot does not get lodged into
said deposition tube, preferably at 1 bar.
11. A novel apparatus of scraping and removing soot deposited inside an exhaust tube, substantially as hereinbefore described and illustrated in examples and accompanying drawings.
12. A novel method of scraping and removing soot deposited inside an exhaust tube, by using a novel apparatus substantially as hereinbefore described and illustrated in examples and accompanying drawings.
References Cited:
U.S. Pat. No. 4,217,027 12/08/1980 MacChesney et
al,
U.S. Pat. No. 5,972,115 26/10/1999 Maurin et al.,
16

Other Publications
Optical Fiber Communications vol.1, Fiber Fabrication, Academic Press Inc., 1985, pp 1-177
Kirk-Othmer Encyclopedia of Chemical Technology, 4th Edition, Vol 10, pp 125-147(1994)
17

We claim:
1. A novel apparatus for scraping and removing soot accumulated
in exhaust tube during an MCVD process, comprising:
a. soot scraper and remover hollow tubular rod
comprising a plurality of distinct arms in an angularly
joined relationship, wherein said tubular rod has one
scraping end and another remover gas entry end;
wherein the wall of said tubular rod has a plurality of holes
made in spaced apart relationship, and wherein longitudinal
axis of each of the said holes is disposed in a predetermined
orientation with predetermined angular relationship with
longitudinal axis of respective said distinct arms, whereby said
soot in exhaust tube is effectively removed by scraping by said
tubular rod and carrying away by remover gas.
2. A novel apparatus as claimed in claim 1 wherein the cross-sectional shape of any of said distinct arms of said hollow tubular rod comprises an annular ring having a shape selected from the group consisting of cylindrical, square, rectangular, trapezoidal, elliptical, and diamond shapes or any combination thereof, preferably cylindrical.
3. A novel apparatus as claimed in claim 1 or 2 wherein any of said distinct arms is made of a material selected from the group consisting of steel, aluminium, copper, an alloy or any material unaffected by the gases inside the exhaust tube, or any other combination thereof, preferably stainless steel.
4. A novel apparatus as claimed in claims 1 to 3, wherein outer
diameter of any of said distinct arms is less than 12 mm,
18

preferably less than 10 mm, and more preferably about 6mm, and wherein the wall thickness of said distinct arms is about 2 mm or more.
5. A novel apparatus as claimed in claims 1 to 4, wherein angle 04 between longitudinal axes of said holes and said respective distinct arm containing said holes is preferably less than 60°, more preferably less than 50°, and wherein diameter 03 of said holes is about 1 mm to about 2 mm, preferably 1.2 mm, and wherein said longitudinal axes of said holes are orientated such that overall direction of flow of remover gas coming out of said holes is substantially same as the direction of flow of reactant gases through deposition tube.
6. A novel apparatus as claimed in claims 1 to 5, wherein said tubular rod comprises preferably three arms including a scraping arm, a transition arm, and an operating arm, wherein their respective lengths LI, L2, and L3 have predetermined values, and the angles 91, and 92, wherein 01 is the angle between said scraping arm and said transition arm, and 92 is the angle between said transition arm and said operating arm, have predetermined values, and wherein 92 is preferably ten times greater than 91 and LI is preferably greater than the sum of LI and L2, and the total length of said tubular rod is approximately 6 meters, whereby soot removal from said exhaust tube is facilitated.
7. A novel apparatus as claimed in claims 1 to 7 wherein said
holes are disposed near the scraping end of said tubular rod.
19

8. A novel method of scraping and removing soot deposited
inside an exhaust tube, by using a novel apparatus as
claimed in claims 1 to 7, comprising the steps of:
a. positioning scraping end of said tubular rod of said
apparatus in the exhaust tube,
b. traversing said tubular rod inside and along the
internal wall surface of said exhaust tube at a
predetermined speed in a predetermined mode of
each traverse, such that each traverse of said tubular
rod inside said exhaust tube corresponds to
deposition of one layer of soot in the deposition tube,
c. passing a remover gas under a predetermined
pressure, through said tubular rod, simultaneously with
step b above, to effectively remove scraped soot, and
d. continuing steps b and c above till completion of the
work of soot deposition in said soot deposition tube.
9. a novel method as claimed in claim 8, wherein the speed of
traverse in any one cycle is constant for said cycle and is set at a
value which is preferably less than 2 cm/sec, more preferably less
than 1.5 cm/sec.
10. A novel method as claimed in claims 8 and 9 wherein said
remover gas is selected from a group of gases comprising oxygen,
nitrogen, or any other gas that does not adversely affect the
reaction inside the deposition tube, or a combination of any
of these, and wherein the pressure of said remover gas is set
to such value that the scraped soot does not get lodged into
said deposition tube, preferably at 1 bar.
20

11. A novel apparatus of scraping and removing soot deposited inside an exhaust tube, substantially as hereinbefore described and illustrated in examples and accompanying drawings.
12. A novel method of scraping and removing soot deposited inside an exhaust tube, by using a novel apparatus substantially as hereinbefore described and illustrated in examples and accompanying drawings.
Dated this 28th Day of February 2005

(Sharatchandra Dattatraya Tase) Patent Agent for the Applicant Registration Number IN/PA 879
To,
The Controller of Patents
Patents Office Branch at Mumbai,
Todi Industrial Estate, Sun Mills Compound,
Lower Parel (w), Mumbai 400 013
21

A novel apparatus for scraping and removing soot
during deposition in a MCVD process and a method
of using the same
Abstract:
This invention is related generally to the field of manufacturing of optical fiber preform and more particularly to removal of soot from the exhaust tube during a MCVD process. The current methods of soot removal are ineffective in terms of ensuring the quality required of the final performs. The present invention provides a novel apparatus and a method to scrape the excess soot deposited inside the exhaust tubes that are used in the MCVD processes deployed in optical fiber manufacturing. The present invention aimed at effectively scrapping and removing the soot deposited inside wall of exhaust tube during the deposition process and to ensure proper flow of reactant gases inside the deposition tube and also through the exhaust tube further to the collection box. The method ensures the safety of the process equipment and the materials used therein, and also help maintain the quality of the final product. The invention comprises a soot remover rod as the inventive apparatus and a method of using the same.
2 8 FEB 2005



FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL/COMPLETE SPECIFICATION
(See section 10 and rule 13 )

l. TITLE OF THE INVENTION:: A novel apparatus for scraping and
removing soot during deposition in a MCVD process and a
method of using the same

2. APPLICANT (S)
a. NAME : Sterlite Optical Technologies Limited
b. NATIONALITY : Indian company registered under the Indian Companies Act, 1956.
c. ADDRESS : E-2, Waluj MIDC, Aurangabad 431 136, Maharashtra State, India

3. PREAMBLE TO THE DISCRIPTION
The following specification particularly describes the invention and the manner in which it is to be
performed.







A novel apparatus for scraping and removing soot during deposition in a MCVD process and a method of using the same
Field of Invention
The present invention generally relates to the manufacturing of an optical fiber preform by MCVD process, and more particularly to an apparatus and a method for scraping and removing the excess soot accumulated inside the exhaust tube during the deposition process of MCVD.
Background Of Invention
Conventional methods for manufacturing optical fiber by using the MCVD process involve injecting a chemical reaction mixture gas into a deposition glass tube from its inlet end. There is a heat source that traverses longitudinally along the glass tube in the same direction as that of the injected gas. The reaction mixture reacts in the hot zone to form soot, which flows downstream of the moving hot zone. During this process, soot is simultaneously deposited on the inside surface of the glass tube and sintered into glass. Some of the soot finds its way further downstream into the exhaust tube that is attached to the outlet end of the deposition tube.
Different competing methods employed in the manufacture of
silica-based optical fiber are described in "Optical fiber
communication" and the article entitled "Fiber optics" in Kirk-
Othmer Encyclopedia of Chemical Technology, 4th Ed., Vol 10, pp.
125-147(1994).
2

It is of vital importance to ensure that the exhaust tube will not be clogged by the soot accumulating therein during the process of manufacture of optical fiber preform. The clogging of the exhaust tube would result in a pressure anywhere within the manufacturing system including the increase of pressure within the preform, which could darnage the preform. For optimum results the exhaust tube should provide a smooth, continuous flow for the gases escaping from the deposition tube, and also through the exhaust tube further to the soot collection chamber.
Conventionally, the function of keeping the exhaust tube clear of soot is carried out fully manually by scraping off the soot accumulated in this tube called an exhaust tube at regular intervals during the manufacture by means of a glass rod so as to prevent the clogging of the exhaust tube. The clogging of the exhaust tube would result in a pressure increase within the preform and damage the preform.
Several methods are used in the industry to overcome the problem of clogging of the exhaust tube and are known to a person reasonably skilled in the art.
The patent JP-A-5841734 describes an apparatus for removing the excess soot by using a rod that traverses in longitudinal direction. The rod is equipped with a terminal screw with flat helical threads which scrape the interior surface of the exhaust tube to remove the soot which is then collected in a collection chamber. However, this apparatus has a disadvantage that the excess soot can accumulate
between the threads of the screw. This leads to ineffective removal
3

of soot. This can further result in some of the soot that has been removed finding its way back into the deposition tube. This can result into a substandard preform, which might need to be discarded.
Another patent, WO 89/02 419, describes a device that has a screw type structure and a tubular pipe wound in a spiral. The device is further characterized in that the screw structure comprises a gas conduit provided with orifices opening towards the open end of the exhaust tube. When introducing dry gas, such as N2 gas, into the gas conduit, the soot in the exhaust tube is exposed to a gas flow which tends to remove the soot out of the exhaust tube. A disadvantage of this device is that the threads of the tubular screw do not effectively scrape the soot accumulated on the wall of the exhaust tube. This further causes turbulence inside the tube.
The U.S. Patent No. 5,972,115 discloses an apparatus which comprises a hollow helical screw having an outside diameter substantially equal to the inside diameter of the exhaust tube and a cylinder housed in contact with the interior surface of the helix to rotate on its axis in the passage. However it has a disadvantage that the helical screw is continuously rotated along with the rotary seal that is used to contain the chemical gases. This can result in undesirable frictional forces on the rotary seal, ultimately resulting in rupture of the seal and leakage of chemical gases.
There is therefore a need to provide a more effective method of removing excess soot from the exhaust tube without affecting the
4

performance of the manufacturing process and also the quality of the preform.
Objects and advantages of the invention:
Accordingly, the objects and advantages of the present invention are described below.
An object of the present invention is to provide a novel apparatus and a method for scrapping and removing the soot accumulated inside the exhaust tube.
Another objective of the present invention is to provide for smooth, continuous flow for the gases escaping from the deposition tube, and through the exhaust tube.
Yet another objective of the present invention is to provide a method of manufacture of preform wherein the scraped soot does not find its way back into the deposition tube, thereby ensuring a high quality of the preform.
Further objective of the present invention is to provide a method of manufacture of preform wherein the components of manufacturing equipment, such as the rotary seal of the collection chamber remain undamaged.
5

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The principles and features of the present invention will be readily apparent from the following detailed description when read in conjunction with the accompanying drawings.
Figure 1 is a schematic representation of deposition tube with lathe along with the novel apparatus of the present invention, thereby showing the general set up of the MCVD process.
Figure 2 is a schematic representation of the movement of the soot scraper and removal rod of the apparatus inside the exhaust tube.
Figure 3 is a schematic representation of design of the scraper rod.
Figure 4 shows the longitudinal cross sectional view of front-end tip of the scraper rod.
Figure 5 shows the front cross-sectional view of the front end tip of the scraper rod.
Summary of the invention:
The present invention provides a novel apparatus and a method to
scrape the excess soot deposited inside the exhaust tubes that are
used in the MCVD processes deployed in optical fiber
manufacturing. The present invention aimed at effectively
scrapping and removing the soot deposited inside wall of exhaust
tube during the deposition process and to ensure proper flow of
reactant gases inside the deposition tube and also through the
6

exhaust tube further to the collection box. The method ensures the safety of the process equipment and the materials used therein, and also help maintain the quality of the final product. The invention comprises a soot remover rod as the inventive apparatus and a method of using the same.
. DETAILED DESCRIPTION OF THE PRESENT INVENTION:
General:
Figure 1 shows a general set up of the MVCD process. The inlet end of a high purity glass deposition tube 1 is installed on the head stock chuck 2. An exhaust tube 3 is installed on tail stock chuck 4 at the outlet end of the deposition tube 1. During deposition process, a mixture of reactant gases such as SiC14, GelC4, PoC13, Helium and Oxygen is fed into the deposition tube through a delivery tube 6. The deposition tube 1 is rotated along its longitudinal axis along with exhaust tube as shown in Figure 1. An Oxyhydrogen burner 5 is provided to heat the deposition tube 1, which has its forward traverses from the position X of deposition tube to the position Y at the other end thereof.
Hot zone is formed near the position of the burner 5 at any given instant, hence the position of the hot zone moves in synchronization with the burner movement. The gas mixture that is injected into the deposition tube 1 through the delivery tube 6 reacts at hot zone of the deposition tube 1 to form soot and the deposition of soot occurs in the deposition tube 1 downstream of the hot zone. The deposition of soot occurs only during the forward
traverse of the burner 5. A layer of deposition gets added on the
7

inside surface of the deposition tube during every forward traverse. The forward traverses are carried out at certain speed for each layer of deposition. The reverse traverses, from Y to X, are carried out at a much higher speed.
The high temperature generated by the oxyhydrogen burner 5 sinters the deposited soot. Excess soot that doesn't get deposited in the deposition tube finds its way to the exhaust tube and gets deposited on its inside surface. To facilitate a smooth and unobstructed entry of gases from the deposition tube into the exhaust tube, the exhaust tube should generally have a diameter larger than that of the deposition tube 1. The outlet end of deposition tube 1 is therefore shaped, with the help of a graphite tool, into a truncated cone shape to provide an internal diameter at the mating end of the deposition tube 1, same as that of the exhaust tube. As shown in Figure 2, the enlarged end of the deposition tube and the mating end of the exhaust tube are joined together by heating flame of the oxyhydrogen burner 5.
The present invention provides an apparatus and a method to scrape and remove soot from the internal surface of the exhaust
Description of the preferred embodiment:
Accordingly, the preferred embodiment of the present invention
and the apparatus, as shown in Figure 2, comprises a novel soot
scraper and removal rod 7 (referred to hereinafter as the rod). The
rod 7 is hollow with a cylindrical cross section, and comprises an
annular front tip 8, a scraping arm 9, a transition arm 10, and an
operating arm 11. Its wall has a preferable thickness of not less
8

than 2mm. It has a plurality of bends to facilitate the entry into and the movement inside the exhaust tube 3. It also has a plurality of holes orientated and spaced in a manner that facilitates removal of the scraped soot with the help of gas supplied from a gas source 13. According to the novel method of soot removal disclosed in this invention, the rod is moved along the inside surface of the exhaust tube with the help of a movable motor or an actuator.
Referring to Figures 1 and 2, before the process of deposition of the soot inside the deposition tube 1 begins, the front tip 8 of rod 7 is positioned inside the exhaust tube at a location A near the far end of the exhaust tube as shown in Figure 2. After completion of the first layer soot in the deposition tube 1, that is when the burner has reached the position Y as shown in Figure 1, the rod 7 starts traversing along the inside surface of the exhaust tube, from the position A to position B with certain speed and return backs to original position A, as shown in Figure 2. A single cycle of the rod 7, that is from A to B and from B to A is completed in the approximately the same time as a single cycle or the traversing movement of the burner 5, that is from Y to X followed by X to Y. The traverses of the burner 5 are continued until the required preform of required diameter is fabricated.
The traverse speed of the rod 7 is set in such way that the rod 7, due to the longitudinal movement of the rod 7 combined with the rotational movement of the deposition tube 1 and the exhaust tube 3, contacts a substantial portion of inside surface of the exhaust tube 3 over a relatively large portion of the length thereof.
9

A novel feature of the present invention is that the rod 7 is connected with a gas source 13 to remove as shown in Figure 3. The gas source 13 supplies gas (referred to hereinafter as the remover gas) such as nitrogen or oxygen to loosen and carry away the scraped soot. Alternatively, any other inert gas that does not adversely affect the reaction inside the deposition tube may be used. The remover gas is fed at one end of the soot remover rod 7 under a suitable positive pressure, preferably at 1 bar, and comes out of the plurality of holes 12.
As the rod 7 traverses from position A to position B and back from position B to position A, soot particles on the inside surface of the exhaust tube are scraped or dislodged by the rod and carried away by the remover gas flowing out of the holes 12. It is important to note that the remover gas after coming out of the plurality of holes 12 flows in the same direction as the direction of the flow of deposition gas mixture in the deposition tube 1.
The rod traversing is provided with an arrangement to collect the soot inside the soot collection box. A person skilled in the art knows that it is possible under certain circumstances, that the dislodged soot particles can come together to form larger soot particles. These larger soot particles are sometimes difficult to carry away and there is a risk that they can find their way back into the deposition tube. A small negative pressure is maintained at the soot collection box, which along with the positive gas pressure applied inside the rod 7, ensures that soot is effectively carried away from the exhaust tube 3. One of the advantageous features of the present invention is that the remover gas is applied
10

at a pressure which is set at a level such that the dislodged soot particle do not enter back inside the deposition tube 1.
The soot scraped from the exhaust tube 3 is collected inside a soot collection chamber. A sealing mechanism is provided in the soot collection chamber so that the movement of the rod can take place without soot escaping from the chamber. It will be known to a person reasonably skilled in the art that the rotational movement of conventional soot removing devices tends to damage the seals through which they operate. As another advantageous feature of the present invention, the chances of damaging the seal during the traversing motion of the rod are minimal as the rod 7 does not have rotational motion.
In the preferred embodiment of the invention, the soot remover rod 7 is made of stainless steel or aluminum so that it doesn't get rusted quickly when exposed to the corrosive chemical environment inside the exhaust tube. The dimensions and design of the rod 7 are determined so as to be able to remove the soot generated inside the exhaust tube 3 during manufacturing of any size of preform made from MCVD process.
As shown in Figure 3, in the preferred embodiment of the invention, the total length of the soot remover rod is, more preferably, less than 6 meters. The length LI of the operating arm 11 is preferably greater than LI and L3, which are the lengths of the transition and scraping arms 9 and 10 respectively. Furthermore, L2 is more preferably less than LI.
11

The preferred embodiment of the invention shows two bends with angles 01 and 02 in the rod 7. The angle 02 is preferably approximately ten times greater than 01. The value of angle 01 is determined in relation to the outer diameter ®2 of the rod 7, as shown in Figure 4. It is observed that larger the diameter of the rod 7, smaller is the angle 01 required for effective operation of the rod 7. The diameter 02 of rod 7 is less than 12 mm and more preferably less than 10 mm. The angle of cone at the tip 03 is determined such as to avoid accumulation of the soot at the tip of the rod 7.
The number of holes 12 and the diameter 0l of individual holes 12 are determined to suit the flow rate of the remover gas. The angle 04 of holes is preferably less than 60° and more preferably less than 50°.
The angle 05 between adjacent holes (see Figure 5) is determined such that inert gas flowing out of the plurality of holes 12 is effectively able to carry away the soot scraped from the inside of the wall of exhaust tube 3.
In another embodiment of the present invention, the material of the rod is any material that does not get adversely affected by the corrosive chemical environment inside the exhaust tube and which has requisite strength to withstand forces exerted on it during the scraping action.
In yet another embodiment of the present invention the cross-sectional shape of the rod is selected from a group of shapes
12

comprising rectangular, square, and triangular or any other shape that facilitates scraping action effectively.
The soot remover rod is replaceable after a certain number of core rod fabrication.
While the preferred embodiments of the present invention have been illustrated and described, it should be understood that the present invention has been described through the particular embodiment disclosed herein as the best mode contemplated for carrying out the invention, and that various additional modifications will occur to those skilled in the art within the scope of the invention.
In the view of the above detailed description of the present invention, any person reasonably skilled in the art will understand that the present invention basically comprises the following items:
1. A novel apparatus for scraping and removing soot accumulated in exhaust tube during an MCVD process, comprising:
a. soot scraper and remover hollow tubular rod
comprising a plurality of distinct arms in an angularly
joined relationship, wherein said tubular rod has one
scraping end and another remover gas entry end;
wherein the wall of said tubular rod has a plurality of holes
made in spaced apart relationship, said holes being disposed
near the scraping end of said tubular rod, and
wherein longitudinal axis of each of the said holes is
disposed in a predetermined orientation with predetermined
13

angular relationship with longitudinal axis of respective said distinct arms,
whereby said soot in exhaust tube is effectively removed by scraping by said tubular rod and carrying away by remover gas.
2. A novel apparatus as described in item 1 above, wherein the cross-sectional shape of any of said distinct arms of said hollow tubular rod comprises an annular ring having a shape selected from the group consisting of cylindrical, square, rectangular, trapezoidal, elliptical, and diamond shapes or any combination thereof, preferably cylindrical.
3. A novel apparatus as described in items 1 or 2 above, wherein any of said distinct arms is made of a material selected from the group consisting of steel, aluminium, copper, an alloy or any material unaffected by the gases inside the exhaust tube, or any other combination thereof, preferably stainless steel.
4. A novel apparatus as described in items 1 to 3 above, wherein outer diameter of any of said distinct arms is less than 12 mm, preferably less than 10 mm, and more preferably about 6mm, and wherein the wall thickness of said distinct arms is about 2 mm or more.
5. A novel apparatus as described in items 1 to 4 above, wherein angle 94 between longitudinal axes of said holes and said respective distinct arm containing said holes is preferably less than 60°, more preferably less than 50°, and wherein diameter 03 of said holes is about 1 mm to about 2 mm, preferably 1.2 mm, and wherein said longitudinal axes of said holes are orientated such that overall direction of flow of remover gas coming out of said holes is substantially same
14

as the direction of flow of reactant gases through deposition tube.
6. A novel apparatus as described in items 1 to 5 above, wherein said tubular rod comprises preferably three arms including a scraping arm, a transition arm, and an operating arm, wherein their respective lengths LI, L2, and L3 have predetermined values, and the angles 01, and 02, wherein 01 is the angle between said scraping arm and said transition arm, and 02 is the angle between said transition arm and said operating arm, have predetermined values, and wherein 02 is preferably ten times greater than 01 and LI is preferably greater than the sum of LI and L2, and the total length of said tubular rod is approximately 6 meters, whereby soot removal from said exhaust tube is facilitated.
7. A novel apparatus as claimed in claims 1 to 6 wherein said
holes are disposed near the scraping end of said tubular rod.
8. A novel method of scraping and removing soot deposited
inside an exhaust tube, by using a novel apparatus as
described in items 1 to 6, comprising the steps of:
a. positioning scraping end of said tubular rod of said
apparatus in the exhaust tube,
b. traversing said tubular rod inside and along the
internal wall surface of said exhaust tube at a
predetermined speed in a predetermined mode of
each traverse, such that each traverse of said tubular
rod inside said exhaust tube corresponds to
deposition of one layer of soot in the deposition tube,
15

c. passing a remover gas under a predetermined
pressure, through said tubular rod, simultaneously with
step b above, to effectively remove scraped soot, and
d. continuing steps b and c above till completion of the
work of soot deposition in said soot deposition tube.
9. a novel method as described in item 8, wherein the speed of
traverse in any one cycle is constant for said cycle and is set at
a value which is preferably less than 2 cm/sec, more preferably
less than 1.5 cm/sec.
10. A novel method as described in items 8 and 9 wherein said
remover gas is selected from a group of gases comprising oxygen,
nitrogen, or any other gas that does not adversely affect the
reaction inside the deposition tube, or a combination of any
of these, and wherein the pressure of said remover gas is set
to such value that the scraped soot does not get lodged into
said deposition tube, preferably at 1 bar.
11. A novel apparatus of scraping and removing soot deposited inside an exhaust tube, substantially as hereinbefore described and illustrated in examples and accompanying drawings.
12. A novel method of scraping and removing soot deposited inside an exhaust tube, by using a novel apparatus substantially as hereinbefore described and illustrated in examples and accompanying drawings.
References Cited:
U.S. Pat. No. 4,217,027 12/08/1980 MacChesney et
al,
U.S. Pat. No. 5,972,115 26/10/1999 Maurin et al.,
16

Other Publications
Optical Fiber Communications vol.1, Fiber Fabrication, Academic Press Inc., 1985, pp 1-177
Kirk-Othmer Encyclopedia of Chemical Technology, 4th Edition, Vol 10, pp 125-147(1994)
17

We claim:
1. A novel apparatus for scraping and removing soot accumulated
in exhaust tube during an MCVD process, comprising:
a. soot scraper and remover hollow tubular rod
comprising a plurality of distinct arms in an angularly
joined relationship, wherein said tubular rod has one
scraping end and another remover gas entry end;
wherein the wall of said tubular rod has a plurality of holes
made in spaced apart relationship, and wherein longitudinal
axis of each of the said holes is disposed in a predetermined
orientation with predetermined angular relationship with
longitudinal axis of respective said distinct arms, whereby said
soot in exhaust tube is effectively removed by scraping by said
tubular rod and carrying away by remover gas.
2. A novel apparatus as claimed in claim 1 wherein the cross-sectional shape of any of said distinct arms of said hollow tubular rod comprises an annular ring having a shape selected from the group consisting of cylindrical, square, rectangular, trapezoidal, elliptical, and diamond shapes or any combination thereof, preferably cylindrical.
3. A novel apparatus as claimed in claim 1 or 2 wherein any of said distinct arms is made of a material selected from the group consisting of steel, aluminium, copper, an alloy or any material unaffected by the gases inside the exhaust tube, or any other combination thereof, preferably stainless steel.
4. A novel apparatus as claimed in claims 1 to 3, wherein outer
diameter of any of said distinct arms is less than 12 mm,
18

preferably less than 10 mm, and more preferably about 6mm, and wherein the wall thickness of said distinct arms is about 2 mm or more.
5. A novel apparatus as claimed in claims 1 to 4, wherein angle 04 between longitudinal axes of said holes and said respective distinct arm containing said holes is preferably less than 60°, more preferably less than 50°, and wherein diameter 03 of said holes is about 1 mm to about 2 mm, preferably 1.2 mm, and wherein said longitudinal axes of said holes are orientated such that overall direction of flow of remover gas coming out of said holes is substantially same as the direction of flow of reactant gases through deposition tube.
6. A novel apparatus as claimed in claims 1 to 5, wherein said tubular rod comprises preferably three arms including a scraping arm, a transition arm, and an operating arm, wherein their respective lengths LI, L2, and L3 have predetermined values, and the angles 91, and 92, wherein 01 is the angle between said scraping arm and said transition arm, and 92 is the angle between said transition arm and said operating arm, have predetermined values, and wherein 92 is preferably ten times greater than 91 and LI is preferably greater than the sum of LI and L2, and the total length of said tubular rod is approximately 6 meters, whereby soot removal from said exhaust tube is facilitated.
7. A novel apparatus as claimed in claims 1 to 7 wherein said
holes are disposed near the scraping end of said tubular rod.
19

8. A novel method of scraping and removing soot deposited
inside an exhaust tube, by using a novel apparatus as
claimed in claims 1 to 7, comprising the steps of:
a. positioning scraping end of said tubular rod of said
apparatus in the exhaust tube,
b. traversing said tubular rod inside and along the
internal wall surface of said exhaust tube at a
predetermined speed in a predetermined mode of
each traverse, such that each traverse of said tubular
rod inside said exhaust tube corresponds to
deposition of one layer of soot in the deposition tube,
c. passing a remover gas under a predetermined
pressure, through said tubular rod, simultaneously with
step b above, to effectively remove scraped soot, and
d. continuing steps b and c above till completion of the
work of soot deposition in said soot deposition tube.
9. a novel method as claimed in claim 8, wherein the speed of
traverse in any one cycle is constant for said cycle and is set at a
value which is preferably less than 2 cm/sec, more preferably less
than 1.5 cm/sec.
10. A novel method as claimed in claims 8 and 9 wherein said
remover gas is selected from a group of gases comprising oxygen,
nitrogen, or any other gas that does not adversely affect the
reaction inside the deposition tube, or a combination of any
of these, and wherein the pressure of said remover gas is set
to such value that the scraped soot does not get lodged into
said deposition tube, preferably at 1 bar.
20

11. A novel apparatus of scraping and removing soot deposited inside an exhaust tube, substantially as hereinbefore described and illustrated in examples and accompanying drawings.
12. A novel method of scraping and removing soot deposited inside an exhaust tube, by using a novel apparatus substantially as hereinbefore described and illustrated in examples and accompanying drawings.
Dated this 28th Day of February 2005

(Sharatchandra Dattatraya Tase) Patent Agent for the Applicant Registration Number IN/PA 879
To,
The Controller of Patents
Patents Office Branch at Mumbai,
Todi Industrial Estate, Sun Mills Compound,
Lower Parel (w), Mumbai 400 013
21

A novel apparatus for scraping and removing soot
during deposition in a MCVD process and a method
of using the same
Abstract:
This invention is related generally to the field of manufacturing of optical fiber preform and more particularly to removal of soot from the exhaust tube during a MCVD process. The current methods of soot removal are ineffective in terms of ensuring the quality required of the final performs. The present invention provides a novel apparatus and a method to scrape the excess soot deposited inside the exhaust tubes that are used in the MCVD processes deployed in optical fiber manufacturing. The present invention aimed at effectively scrapping and removing the soot deposited inside wall of exhaust tube during the deposition process and to ensure proper flow of reactant gases inside the deposition tube and also through the exhaust tube further to the collection box. The method ensures the safety of the process equipment and the materials used therein, and also help maintain the quality of the final product. The invention comprises a soot remover rod as the inventive apparatus and a method of using the same.
2 8 FEB 2005

Documents:

220-MUM-2005-ABSTRACT(2-1-2009).pdf

220-MUM-2005-ABSTRACT(22-9-2008).pdf

220-MUM-2005-ABSTRACT(28-2-2005).pdf

220-MUM-2005-ABSTRACT(5-10-2010).pdf

220-mum-2005-abstract(granted)-(4-11-2010).pdf

220-mum-2005-abstract.doc

220-mum-2005-abstract.pdf

220-mum-2005-assignment(2-1-2009).pdf

220-MUM-2005-ASSIGNMENT(22-9-2008).pdf

220-MUM-2005-ASSIGNMENT(28-2-2005).pdf

220-mum-2005-cancelled pages(22-9-2008).pdf

220-mum-2005-cancelled pages(5-10-2010).pdf

220-MUM-2005-CLAIMS(2-1-2009).pdf

220-MUM-2005-CLAIMS(22-9-2008).pdf

220-MUM-2005-CLAIMS(28-2-2005).pdf

220-MUM-2005-CLAIMS(AMENDED)-(5-10-2010).pdf

220-mum-2005-claims(granted)-(4-11-2010).pdf

220-MUM-2005-CLAIMS(MARKED COPY)-(5-10-2010).pdf

220-mum-2005-claims.doc

220-mum-2005-claims.pdf

220-mum-2005-correspondence 1(15-5-2008).pdf

220-mum-2005-correspondence 1(3-3-2009).pdf

220-mum-2005-correspondence 2(22-9-2008).pdf

220-mum-2005-correspondence 2(4-10-2006).pdf

220-mum-2005-correspondence(1-3-2005).pdf

220-MUM-2005-CORRESPONDENCE(2-1-2009).pdf

220-MUM-2005-CORRESPONDENCE(22-9-2008).pdf

220-MUM-2005-CORRESPONDENCE(IPO)-(27-11-2008).pdf

220-MUM-2005-CORRESPONDENCE(IPO)-(3-3-2008).pdf

220-mum-2005-correspondence(ipo)-(31-7-2008).pdf

220-mum-2005-correspondence(ipo)-(4-11-2010).pdf

220-mum-2005-correspondence-received-280205.pdf

220-mum-2005-correspondence-received.pdf

220-mum-2005-descripiton (complete).pdf

220-MUM-2005-DESCRIPTION(COMPLETE)-(2-1-2009).pdf

220-MUM-2005-DESCRIPTION(COMPLETE)-(22-9-2008).pdf

220-MUM-2005-DESCRIPTION(COMPLETE)-(28-2-2005).pdf

220-mum-2005-description(granted)-(4-11-2010).pdf

220-MUM-2005-DRAWING(28-2-2005).pdf

220-MUM-2005-DRAWING(5-10-2010).pdf

220-mum-2005-drawing(granted)-(4-11-2010).pdf

220-mum-2005-drawings.pdf

220-MUM-2005-FORM 1(2-1-2009).pdf

220-MUM-2005-FORM 1(22-9-2008).pdf

220-MUM-2005-FORM 1(28-2-2005).pdf

220-mum-2005-form 13(1)-(5-10-2010).pdf

220-mum-2005-form 13(15-5-2008).pdf

220-mum-2005-form 13(19-10-2007).pdf

220-mum-2005-form 13(2)-(5-10-2010).pdf

220-mum-2005-form 18(5-10-2006).pdf

220-mum-2005-form 2(2-1-2009).pdf

220-mum-2005-form 2(22-9-2008).pdf

220-mum-2005-form 2(28-2-2005).pdf

220-MUM-2005-FORM 2(COMPLETE)-(28-2-2005).pdf

220-mum-2005-form 2(granted)-(4-11-2010).pdf

220-MUM-2005-FORM 2(TITLE PAGE)-(2-1-2009).pdf

220-MUM-2005-FORM 2(TITLE PAGE)-(22-9-2008).pdf

220-MUM-2005-FORM 2(TITLE PAGE)-(28-2-2005).pdf

220-MUM-2005-FORM 2(TITLE PAGE)-(5-10-2010).pdf

220-MUM-2005-FORM 2(TITLE PAGE)-(COMPLETE)-(28-2-2005).pdf

220-mum-2005-form 2(title page)-(granted)-(4-11-2010).pdf

220-MUM-2005-FORM 26(15-5-2008).pdf

220-MUM-2005-FORM 26(2-1-2009).pdf

220-mum-2005-form 26(28-2-2005).pdf

220-MUM-2005-FORM 26(5-10-2010).pdf

220-MUM-2005-FORM 3(2-1-2009).pdf

220-MUM-2005-FORM 3(22-9-2008).pdf

220-mum-2005-form 3(28-9-2005).pdf

220-MUM-2005-FORM 5(2-1-2009).pdf

220-MUM-2005-FORM 5(22-9-2008).pdf

220-mum-2005-form-1.pdf

220-mum-2005-form-2.doc

220-mum-2005-form-2.pdf

220-mum-2005-form-26.pdf

220-mum-2005-form-3.pdf

220-MUM-2005-PETITION UNDER RULE 137(5-10-2010).pdf

220-MUM-2005-REPLY TO EXAMINATION REPORT(5-10-2010).pdf

220-mum-2005-specification(amanded)-(22-9-2008).pdf

220-mum-2005-specification(amended)-(2-1-2009).pdf

220-mum-2005-specification(amended)-(22-9-2008).pdf

220-MUM-2005-SPECIFICATION(AMENDED)-(5-10-2010).pdf


Patent Number 243777
Indian Patent Application Number 220/MUM/2005
PG Journal Number 46/2010
Publication Date 12-Nov-2010
Grant Date 04-Nov-2010
Date of Filing 28-Feb-2005
Name of Patentee STERLITE TECHNOLOGIES LIMITED
Applicant Address E-2 WALUJ MIDC, AURANGABAD
Inventors:
# Inventor's Name Inventor's Address
1 CHANDRAVEER SINGH E1/E2/E3,MIDC, WALUJ, AURANGABAD-431 136,
2 NAGESWARAN SENTHIL KUMAR E1/E2/E3,MIDC, WALUJ, AURANGABAD-431136,
PCT International Classification Number C03B 37/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA