FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the Invention. - METHOD OF SILVER PLATING OF COMPONENTS USING A VERTICAL AXIS TROLLEY
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY: An Indian Company.
(c) ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a method of silver plating. More particularly the present invention relates to a method of Silver plating of components using a vertical axis trolley thereby improving thermal and electrical conductivity.
BACKGROUND AND THE PRIOR ART
Second time VAT (Vertical Axis Trolley) plating is not done in a conventional plating process. Vertical axis trolley is a method of carrying the components to the plating bath, the other method being barrel and the method of plating using Vat is termed as VAT plating. Because of rising prices of silver, plating the component only at functional surfaces is now looked into by companies that require silver plating of components for better thermal and electrical conductivity. Hence there is a need for second time VAT plating.
With the existing process when the components are plated using VAT, occurrences of white patches on already plated surface is observed. The components with the patches show poor tarnish resistance and no aesthetic appeal. Thus there is a need to provide an improved process of component surface finish as compared to the conventional/prior process. Conventionally a component is not plated second time unless and otherwise for re-works. The present invention describes an improved plating process wherein patches which occur normally after second time plating are eliminated.
Present invention therefore provides a new and improved process to do VAT plating twice on the same component without occurrences of patches and with better quality of plating. With a small modification in the existing plating process,

two stages VAT silver plating without any patches is achieved with better quality and aesthetic appeal.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide a method by which second phase VAT plating process can be done to get better surface finish of component.
Yet another object of the present invention is to provide an improved process where economies of scale can be achieved for differential silver plating, helping in saving precious silver metal.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
There is provided a method of silver plating of components.
According to the present invention, there is provided method of Silver plating of components using a vertical axis trolley thereby improving thermal and electrical conductivity, wherein said method comprising the steps of providing first stage plating of said components; providing vibratory finishing operation ensuring removal of passive layer formed on said components during said first stage plating; putting said components in plating line; chemical cleaning operation of said components by switching off ultrasonic and completely preventing

electrochemical process of anodic cleaning; and continuing the plating cycle of said components.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 illustrates the principle method steps used in the silver plating process.
Fig. 2 illustrates the method steps used in the silver plating process.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Reference is first invited to Fig 1 where the three principle steps used in silver plating is provided. It shows vibratory finishing operation, switching off ultrasonic and switching off current in anodic cleaning process.
Fig. 2 shows different method steps used in implementing present method of silver plating.
The invention therefore provides a method of Silver plating of components using a vertical axis trolley thereby improving thermal and electrical conductivity.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention Figure 1 illustrates the second stage VAT Plating process.

• Vibratory finishing operation for 30-40 minutes (process 2)
• Switch off ultrasonic in the cleaning process (process 4)
• Switch off current in the anodic cleaning process (process 5)
Figure 2 illustrates the flow chart of the method steps used in the present invention.
Process 1: Second stage VAT plating is done only when
• Components are required to be reworked
• Second stage plating on non functional surfaces after the
first stage plating on functional surfaces.
Process 1 indicates first stage plating of components.
Process2: Partially plated components are then processed for the finishing operation by vibratory finishing for some time. This is done to ensure that the passive layer is removed from the component after first stage plating. The components are kept in for vibratory finishing for 25-35 minutes after first stage plating. Any time less than the above mentioned range, does not improve the quality of the component after plating.
Also, the medium used for finishing depends on the geometry and size of the component. In the present invention, ceramic balls have been used. The idea of proper timing is that the entire plated surface has to be polished before second stage plating.
The present invention describes a process to successfully implement second stage silver plating process using vertical axis trolley. With this process, the component quality after second phase plating is not affected as compared to the quality of the component when this process is not followed.

Before, it is observed that the components were having patches after plating. These patches occur in those areas where the first layer of silver was plated and then another layer is plated on top of it. These patches are not removed after putting the components for vibratory finishing after second phase plating was over.
In the present invention, vibratory finishing is introduced before the second phase plating. This ensures that the component surface is made clean of the passive layer that was formed during first phase plating.
The present invention combines vibratory finishing with the plating process in such a manner as making second stage VAT plating process feasible. Vibratory finishing is a type of mass finishing manufacturing process used to debar, radius, de-scale, burnish, clean, and brighten a large numbers of relatively small work pieces.
Vibratory finishing is used to remove the rust and dirt and debar the component before it goes through the plating cycle. If vibratory finishing is not used in the present invention, the passive layer on the plated surfaces will result in formation of patches during the second stage of plating. These patches are very dull and less
resistant to tarnish.
A major point to be noticed is the stage at which the vibratory finishing operation has been used in this invention. This process is undertaken after the first stage plating, prior to second stage plating.
The main feature of using the vibratory finishing technique in the present invention is only to remove the passive layer on the plated surfaces.

Surface finishing is not the end result that is expected from this process. In order to get a great quality plated component, the invention employs the vibratory finishing technique.
The two important parameters in the vibratory finishing process are the time and the finishing media used. Eliminating the steps 4 & 5 without adding step 2 would be futile too. From this invention, the implementation of vibratory finishing process in differential plating field can be established.
Process3: This process refers to the already existing plating cycle. The components after vibratory finishing operation are put into the existing plating line.
Process4: Ultrasonic cleaning is a very essential during plating process. It is a process by which, components are cleaned by sound waves produced by a transducer. It removes all dirt and rust from the surface of the component. Ultrasonic cleaning bath consists of a chemical bath with transducers on the sides.
But this invention supports the fact that the ultrasonic has to be switched off during second stage plating process. This is mainly due to the fact that, ultrasonic make the existing layer of silver deposit (from 1st stage plating) very feeble and susceptible to peel off. At the same time, the chemical cleaning in the bath is very essential to the un-plated copper surface.
Process5: Anodic cleaning is another cleaning process which is mandatory in the plating cycle. This process works on the reverse idea of electroplating. In this process, the components are kept as anodes and SS plates connected as cathodes. When current is passed, material flows from anode to cathode. Hence, this process removes dirt, rust and other particles from the component surface for a better plating cycle. According to the present invention, anodic cleaning process needs

to be modified during the second time VAT plating process i.e. current is not passed in this bath.
Thus the electrochemical process is stopped and only the chemical cleaning is done. During anodic cleaning process (with current ON), there is a tendency for the deposited silver to separate from the component surface thereby defeating the very idea of differential plating.
Process6: This refers to the rest of the plating cycle after anodic cleaning. No changes are required in these processes. So process 6 is not in the scope of the invention, but mentioned only for understanding purpose only.
Thus, this invention lays down process by which second stage VAT plating can be made possible. The sequence of operations/processes mentioned above has to be followed to get a good quality plated component.
Advantages:
• Improved method of component surface finish as compared to the conventional methods.
• Possibility of second stage VAT plating for differential plating
• Improved quality of plating.
• Better tarnish resistance of components after plating.
• Improved method to save silver during plating of a component.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM
1. A method of Silver plating of components using a vertical axis trolley
thereby improving thermal and electrical conductivity, wherein said
method comprising the steps of:
providing first stage plating of said components;
providing vibratory finishing operation ensuring removal of passive layer formed on said components during said first stage plating;
putting said components in plating line;
chemical cleaning operation of said components by switching off ultrasonic and completely preventing electrochemical process of anodic cleaning; and
continuing the plating cycle of said components.
2. Method as claimed in claim 1 wherein said vibratory finishing operation
performed using a plurality of ceramic balls.
3. Method as claimed in claim 1 wherein during said first stage plating
entire surface of said components is polished.
4. Method as claimed in claim 1 wherein said vibratory finishing operation
performed for approximately 25-35 minutes.

5. Method as claimed in claim 1 wherein said method step of preventing electrochemical process of anodic cleaning is performed by switching off current in electrochemical bathe.
6. A method of Silver plating of components using a vertical axis trolley thereby improving thermal and electrical conductivity as herein described and illustrated with reference to accompanying drawings.