FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
Apparatus and process for reflective mirror polishing of thin stainless steel sheets.

2. APPLICANT
(a) NAME

Larsen And Toubro Ltd.

(b) NATIONALITY. Indian Company, registered under
the provisions of the Companies Act, 1956.

(c) ADDRESS

L & T House, Ballard Estate, Mumbai 400 038, Maharashtra State, India,

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

Title of the invention: Apparatus and process for reflective mirror polishing of thin stainless steel sheets.
Field of the invention: The present invention relates to the apparatus and process of polishing thin metallic sheets.
Prior art: Mechanical polishing process covers grinding and polishing. These processes are used for improving the surface conditions of a product for decorative or functional purposes. In general, grinding permits far more aggressive abrasion action than polishing. Induced cost, skill labor & finish quality of product is major variable in process. The basic mill plate and sheet metal finishes for stainless steel include five grades that have finishes that are produced mechanically by using abrasive compositions and buffing wheels. Special mechanical polishing procedures are required for preparing metal surfaces for electro polishing. Below table indicates the various polished mill finishes against, the abrasive grit number used to produce them, and the surface roughness readings before and after electro polishing. Electro polishing generally reduces surface roughness readings of a non-electro polished surface by 50 percent as depicted in the table given bellow.

Mill No. Grit No. Surface finish beforeElectro Polishing(Micrometer) Surface finish afterElectro Polishing(Micrometer)
3 60 3.56 max. 1.78 - 2.25
4 120 1.14 max. 0.57 - 0.75


4 180 0.64 max. 0.32 - 0.40
7 240 0.20 - 0.51 0.10 -0.26
8 320 0.15 - 0.38 0.08 - 0.19
8 500 0.10- 0.25 0.05 - 0.13
Existing techniques for polishing
Various methods available in prior art were studied for Polishing of thin sheets and available methods are, i) Wet polishing, ii) Dry polishing, iii) Electro polishing
i) Wet polishing:
This technology is widely used in the industry worldwide. This technology is mainly oriented towards architectural, utensils & decorative purpose & generally for higher thickness. This type polishing is mainly carried out by placing job on glass type mounted flat surface where liquid with chemical is spread on entire surface & top-rotating wheel/s is giving pressure & carrying out polishing simultaneously. Advantages:
0 This types of machines give excellent surface finish. 0 Very accurate & precise control Drawbacks:
0 In case of thin sheets, sheets are unable to hold with their self-weight. Even after lot of efforts, few wrinkles were observed over the entire surface.
0 In case where polishing is to be carried out on thin sheets like 0.1mm thick sheets, it is required to have special clamping arrangements to hold the sheets which in turns requires extra edges for clamping i.e.


wastage of material and time. Even with such arrangements the
wrinkles are observed on polished sheets.
0 Operator takes approx. 30 min. for each side of 1sq.m area (1 hr for
each sheet on both sides).
0 The cost is about twice comparing to Dry Polishing Method.
ii) Dry polishing with handy equipments:
This technology is mainly used for manual applications i.e. with the help
of small handy equipments. In this type of polishing, homogeneous
surface finish is not maintained. As this is being done with handy
equipments, profile shaped items can be polished with this technology.
Also this process is very cheap compare to wet polishing technique.
Drawbacks:
0 Not able to maintain uniform surface finish.
0 Forming of wrinkles on the polished sheets.
0 As handy equipments are used, there are safety hazards in this
process.
iii) Electro polishing: Electro polishing requires smooth & flat surface with initial finish of 10pm Ra and also finish product losses some thickness which have impact further processing like dimple forming by deep drawing process. The results obtained with electro polishing vary for each production run with respect to this.
Thus a need is felt by the industry for an apparatus and the process that can eliminate above drawbacks of the prior art.
Objective of the invention:
The objective of the present invention is to eliminate the drawbacks of the prior art and to meet the desired requirements i.e. polishing of thin


stainless steel sheets (e. g. 0.1mm Thk. or the like) with highly reflective finish (mirror finish) conforming to finish no. 8 as per ASTM A480/480M and Ra surface finish of _0.04 urn from _0.25 urn raw surface finish which otherwise can not be obtained by prior art methods and apparatus.
Another objective of the present invention is to eliminate the drawbacks of dry polishing technique with handy equipments & wet polishing technique particularly for polishing the thin metallic sheets and providing polishing apparatus and process for better control over thickness, uniformity, & rejection.
Yet another objective of the present invention is to eliminate the thickness variation as it is obtained in the electro polishing process. Yet another objective of the present invention is to increase the productivity of the polishing process for the thin metallic sheets.
Summary of invention: The present invention comprises of a reciprocating table dry polishing apparatus with a fixture for clamping the sheet. The apparatus is provided with a frame on which a main motor is mounted; this supplies power to buffing wheel set. The buffing wheel set comprises multiple buffing wheels mounted on a horizontal shaft. Said buffing wheels with horizontal shaft are fixed on a vertical slide. A drive motor is provided to impart rotary motion to the horizontal shaft and thus to the set of buffing wheels fixed on the same. A dust collector is provided to collect all the dusts generated during polishing process. A gear motor is provided to supply power for moving the fixture along the length of the machine. When a fixed rotary buffing wheel set is used for polishing the thin sheets, scratch like lines are observed on the polished sheet. A pneumatic cylinder is provided to impart oscillatory motion to buffing wheel set across the length of the


machine, which eliminates the said scratch like lines on the polished sheet. The said fixture is guided on two rods, the said rods passing through guide holes provided in the blocks provided on the fixture on its bottom side. The said holes are provided with self lubricating bearings for smooth motion of the fixture. The said fixture can thus be provided with reciprocating motion by means of the drive motor for the same; along the said guide rods. Thin metallic sheet of the order of 0.1mm thickness to be polished is clamped on Fixture. The said fixture comprises of a rigid fixture base, said four guide blocks being provided at the bottom of the said base. The said guide blocks are provided with holes of the size of the said guide rods aligned with the same so that the fixture can be guided during its motion by the said guide rods. A sheet-fixing tray is provided on the upper side of the said fixture base to support the sheet to be polished, which is fixed in fixing tray. For escape of air that is trapped between sheet and fixture, carpet is provided below the metallic sheet. Also density of threads in carpet plays important role in polishing. Fixing clamps are provided to clamp the sheet to be polished on the fixing tray. After clamping of sheet on fixing tray, minor waviness is observed on the sheet before polishing. To remove the waviness lever arrangement is provided on sheet fixing tray.
A sheet to be polished is mounted on the sheet fixing tray. The fixture placed on the two rods with the help of four blocks. As the fixture moves to and fro over these two rods the said four blocks are equipped with self-lubricating bearing to give a smooth movement over rods. A geared motor provides motion to the fixture. Set of buffing wheels that are clamped on the said shaft and the shaft is supported by a vertical slide. The buffing wheel set can be set up or down to give required buffing pressure on the sheet by adjusting the same vertically by means


of this slide. Two motions are provided to the shaft i.e. rotary motion by means of drive motor and oscillatory motion across the length of the machine by means of pneumatic cylinder. Thus sheet, which is moving to and fro below the buffing wheels, gets evenly polished. Due to abrasion action between buffing wheels and metallic sheet, lot of dust is generated. If this dust is allowed to settle on the metallic sheet, scratches are observed on the polished sheet.
To avoid above difficulty, dust collectors are provided for the polishing apparatus. These dust collectors are mounted on vertical slide and near the buffing wheel. These dust collectors suck all the dust. Above machine is made as per L&T's specifications. The result obtained is highly reflective finish (mirror finish) conforming to finish no. 8 as per ASTM A480/480M and Ra surface finish of 0.05 urn (max.) from 0.25 urn raw surface finish which otherwise can not be obtained by prior art methods and apparatus. The sheets are then wrapped with protective film for handling and transportation.
Description of figures:
Fig. 1 shows the side view of the polishing machine according to present
invention.
Fig. 2 shows a perspective view of the sheet mounting fixture according
to present invention.
Description:
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention as described bellow in the preferred embodiment.


This invention is illustrated in the accompanying drawings, through out which like reference letters indicate corresponding parts in the various figures.
According to the present invention "apparatus and process for reflective mirror polishing of thin stainless steel sheets" the said apparatus shown as (I) in Fig 1 comprises of a frame (la) provided with mounting blocks, which does not need foundation facilitating easy shifting of the apparatus from one place to the another. On the said frame there is provided main motor (1) to supply power to buffing wheel set (2). The said buffing wheel set (2) comprises plurality of buffing wheels (10), which are mounted on shaft (11). The said shaft is supported by two bearings at its both ends (not shown in the drawings) on frame (la). Rotary motion is imparted to the said shaft (11) by main motor (1) through a belt drive. The said buffing wheel set (2) with horizontal shaft (11) is fixed on the vertical slide (3) so that the buffing wheel set (2) can be adjusted in vertical direction. This adjustment is made in accordance with the requirement of buffing pressure depending on the condition of the raw sheet surface to be polished. When this surface is rough the buffing wheel set (2) is set at lower level thus increasing the buffing pressure on the sheet. To collect all the dust generated during polishing, dust collector (4) is provided near the buffing wheel set (2) nearest to the dust generation point mounted on the vertical slide (3). This dust otherwise gets trapped between the buffing wheels and the sheet under polishing process and cause undesirable scratches on the sheet being polished, damaging the finish of the sheet surface. Pneumatic cylinder (6) is provided to give oscillatory motion to buffing wheel set in the direction across the length of the polishing apparatus. Two rods (7) with smooth surface are provided along the length of the polishing apparatus to guide the fixture (8) on which, the sheet to be


polished is fixed. The said two rods (7) are parallel to each other. The fixture reciprocates on said two rods (7). Geared motor (5) is provided to supply power to reciprocating motion of the said fixture (8) along the length of the polishing apparatus (I).
Thin sheets are mounted on the fixture (8) for polishing. As thin metallic sheet of the order of thickness 0.1mm does not have in-built strength, fixing of sheet on the table so as to resist rotary and oscillation motion of buffing wheel is provided. The fixture (8) is designed such that it will take min. time for clamping and unclamping to increase productivity and high speed of processing.
Clamping arrangement and function of Lever: One edge of sheet is fixed between two metallic strips and these two metallic strips are bolted together. On another edge of sheet, a rod is fixed and this rod is connected to the lever. Two metallic strips are also fixed at this edge and sheet is bolted in between these strips. After bolting two edges in the metallic strips, still minor waviness observed in the sheet. To remove this waviness, lever is rotated by approx 20-25°. This lever in turn rotates the rod and waviness generated during clamping is removed.
The surface of fixture is made flat to provide uniform support to sheet. The weight of fixture is kept low for easy handling. The sheet clamping arrangement for fixture is made to allow wrinkle free fixing of sheet and also to avoid generation of air pockets between sheet and fixture by sandwiching a piece of the carpet having same size as the sheet to be polished.
Now the fixture (8) is described here with reference to Fig. 2. Fixture (8) is provided with a rigid fixture base (B), at the bottom side of which,


are provided four guide blocks (A). The said guide blocks (A) are provided with holes (H) aligned along the length of the polishing apparatus (I) and cooperating with the cross section of two guide rods (7). The holes (H) are provided with self lubricating bearings (J) so that the fixture, when supported on the two rods (7), with the two rods (7) passing through the bearings (J) in the holes (H), can move along the said two rods (7) smoothly and precisely with least friction. Sheet-fixing tray (C) is provided on the fixture base (B). A sheet to be polished (E) is fixed in fixing tray (C). A piece of carpet (D) is provided under the sheet (E) for escape of air that is trapped between sheet (E) and sheet fixing tray (C) on the fixture (8). The density of threads in carpet plays important role in polishing. Fixing clamps (F) are provided on the fixing tray (C) for fixing the sheet (E). Lever (G) is provided on fixing tray (C) to eliminate minor waviness that is observed on the sheet (E) before polishing, after clamping of sheet (E) on fixing tray (C).
Process of polishing:
The process of polishing thin metallic sheet is given bellow with
Reference to Fig 1.
0 Sheet (E) to be polished is mounted on the fixture (8) on its fixing
tray (C) with fixing clamps (F). The waviness on the sheet is removed
by using liver (G) and the fixture is mounted on two rods (7) with help
of holes (H) in the four blocks (A). The fixture (8) is then connected to
geared motor (5).
0 The fixture moves to and fro over these two rods powered by the
geared motor (5). The holes (H) in the said four blocks (A) are equipped
with self-lubricating bearings to give a smooth movement over rods.


0 Geared motor (5) is mounted below the said fixture (8). This drive motor provides motion to table.
0 Sets of buffing wheels (2) are clamped on a shaft (11) and the said shaft (11) is supported by the vertical slide (3). The main motor (1) and pneumatic cylinder are switched on. Two motions are provided to the shaft i.e. rotary motion by the drive motor with gearbox (5) and oscillatory motion by the reciprocation of the pneumatic cylinder (6) across the length of the apparatus (I) while the sheet (E) is moving to and fro along the length of the apparatus (I) below the buffing wheels. 0 Due to abrasion action between buffing wheels and metallic sheet, lot of dust is generated. If this dust is allowed to settle on the sheet (E), scratches are observed on the polished sheet. To avoid this difficulty, dust collectors are specially designed for the polishing apparatus (I) according to the present invention. These dust collectors are mounted on vertical slide and above the buffing wheel. These dust collectors suck all the dust and save the sheet (E) from getting scratched. The sheets are then wrapped with protective film for handling and transportation.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment.
Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to


employ the present invention in virtually any appropriately detailed system, structure or matter.
The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention; which is defined by the scope of the following claims.


We claim,
1) "Apparatus for reflective mirror polishing of thin stainless steel sheets" comprises of a frame (la) provided with mounting blocks, on the said frame (la) there is provided main motor (1) to supply power to buffing wheel set (2); the said buffing wheel set (2) comprises plurality of buffing wheels (10), which are mounted on shaft (11); the said shaft is supported by two bearings at its both ends (not shown in the drawings) on frame (la); rotary motion is imparted to the said shaft (11) by main motor (1) through a belt drive; the said buffing wheel set (2) with horizontal shaft (11) is fixed on the vertical slide (3) so that the buffing wheel set (2) can be adjusted in vertical direction; dust collector (4) is provided near the buffing wheel set (2) nearest to the dust generation point mounted on the vertical slide (3); pneumatic cylinder (6) is provided to give oscillatory motion to buffing wheel set in the direction across the length of the polishing apparatus; two rods (7) with smooth surface are provided along the length of the polishing apparatus to guide the fixture (8) on which, the sheet to be polished is fixed; the said two rods (7) are parallel to each other; the fixture reciprocates on said two rods (7); geared motor (5) is provided to supply power to reciprocating motion of the said fixture (8) along the length of the polishing apparatus (I); thin sheets are mounted on the fixture (8) for polishing; as thin metallic sheets does not have in-built strength, fixing of sheet on the table so as to resist rotary and oscillation motion of buffing wheel is provided; the fixture (8) is designed such that it will take minimum time for clamping and unclamping to increase productivity and high speed of processing.


2)"Apparatus for reflective mirror polishing of thin stainless steel sheets" as claimed in claim 1 wherein fixture (8) is provided with a rigid fixture base (B), at the bottom side of which, are provided four guide blocks (A); the said guide blocks (A) are provided with holes (H) aligned along the length of the polishing apparatus (I) and cooperating with the cross section of two guide rods (7); the holes (H) are provided with self lubricating bearings (J) so that the fixture, when supported on the two rods (7), with the two rods (7) passing through the bearings (J) in the holes (H), can move along the said two rods (7) smoothly and precisely with least friction; sheet-fixing tray (C) is provided on the fixture base (B); a sheet to be polished (E) is fixed in fixing tray (C); a piece of carpet (D) is provided under the sheet (E) for escape of air that is trapped between sheet (E) and sheet fixing tray (C) on the fixture (8); the density of threads in carpet plays important role in polishing; fixing clamps (F) are provided on the fixing tray (C) for fixing the sheet (E); lever (G) is provided on fixing tray (C) to eliminate minor waviness that is observed on the sheet (E) before polishing, after clamping of sheet (E) on fixing tray (C); the surface of fixture (8) is made flat to provide uniform support to sheet; the weight of fixture (8) is kept low for easy handling.
3)"Apparatus for reflective mirror polishing of thin stainless steel sheets" as claimed in claim 1 wherein the sheet clamping arrangement for fixture is made to allow wrinkle free fixing of sheet and also to avoid generation of air pockets between sheet (E) and fixture (8) by sandwiching a piece of the carpet (D) having same size as the sheet to be polished; one edge of sheet (E) is fixed between two metallic strips and these two metallic strips are


bolted together; on another edge of sheet, a rod is fixed and this rod is connected to the lever; two metallic strips are also fixed at this edge and sheet is bolted in between these strips; after bolting two edges in the metallic strips, still minor waviness observed in the sheet; to remove this waviness, lever is rotated by approx 20-25°; this lever in turn rotates the rod and waviness generated during clamping is removed.
4) Process for reflective mirror polishing of thin stainless steel sheets comprises of the steps given bellow;
0 Sheet (E) to be polished is mounted on the fixture (8) on its fixing tray (C) with fixing clamps (F); the waviness on the sheet is removed by using liver (G) and the fixture is mounted on two rods (7) with help of holes (H) in the four blocks (A); the fixture (8) is then connected to geared motor (5);
0 the fixture moves to and fro over these two rods powered by the geared motor (5); the holes (H) in the said four blocks (A) are equipped with self-lubricating bearings to give a smooth movement over rods;
0 geared motor (5) is mounted below the said fixture (8); 0 sets of buffing wheels (2) are clamped on a shaft (11) and the said shaft (11) is supported by the vertical slide (3); the main motor (1) and pneumatic cylinder are switched on; two motions are provided to the shaft i.e. rotary motion by the drive motor with gearbox (5) and oscillatory motion by the reciprocation of the pneumatic cylinder (6) across the length of the apparatus (I) while the sheet (E) is moving to and fro along the length of the apparatus (I) below the buffing wheels;


0 due to abrasion action between buffing wheels and metallic sheet, lot of dust is generated; if this dust is allowed to settle on the sheet (E), scratches are observed on the polished sheet; to avoid this difficulty, polishing apparatus (I) according to the present invention is provided with the dust collectors; these dust collectors are mounted on vertical slide and above the buffing wheel; these dust collectors suck all the dust and save the sheet (E) from getting scratched;
the sheets are then wrapped with protective film for handling and transportation.
Dated this 15th February 2008.



Abstract
"Apparatus for reflective mirror polishing of thin stainless steel sheets" comprises of a frame (la) provided with mounting blocks, on the said frame (la) there is provided main motor (1) to supply power to buffing wheel set (2); the said buffing wheel set (2) comprises plurality of buffing wheels (10), which are mounted on shaft (11); the said shaft is supported by two bearings at its both ends (not shown in the drawings) on frame (la); rotary motion is imparted to the said shaft (11) by main motor (1) through a belt drive; the said buffing wheel set (2) with horizontal shaft (11) is fixed on the vertical slide (3) so that the buffing wheel set (2) can be adjusted in vertical direction; dust collector (4) is provided near the buffing wheel set (2) nearest to the dust generation point mounted on the vertical slide (3); pneumatic cylinder (6) is provided to give oscillatory motion to buffing wheel set in the direction across the length of the polishing apparatus; two rods (7) with smooth surface are provided along the length of the polishing apparatus to guide the fixture (8) on which, the sheet to be polished is fixed; the said two rods (7) are parallel to each other; the fixture reciprocates on said two rods (7); geared motor (5) is provided to supply power to reciprocating motion of the said fixture (8) along the length of the polishing apparatus (I); thin sheets are mounted on the fixture (8) for polishing; as thin metallic sheets does not have in-built strength, fixing of sheet on the table so as to resist rotary and oscillation motion of buffing wheel is provided; the fixture (8) is designed such that it will take minimum time for clamping and undamping to increase productivity and high speed of processing.