FIELD OF THE INVENTION
5
The present invention relates to utilization of solid state relays in welding
machines and more particularly replacing the expensive and less reliable gold and silver
coated relay of capacitor discharge welding machine with reliable and cheap solid state
Thyristor by a suitable modification in the circuitry of the welding machine.
10
BACKGROUND OF THE INVENTION
In a capacitor discharge welding machine, a bank of Capacitors is charged to a
15 preset voltage and then discharged through a gold or silver coated relay. This machine
is used for welding dissimilar metals, projection welding and thin sheet spot welding
where very high current passed in very short time results in the welding of the joints.
The main drawbacks of using the gold and silver coated relays are that it is expensive
as well as frequently replacement (10-15 welding events) depending upon the
20 requirements.
With present invention, said relay is replaced by solid state thyristor with suitable
modification in the circuitry of the Welding machine.
25
SUMMARY OF PRESENT INVENTION
In accordance with one aspect of present invention is to provide a replacement
30 for the gold and silver coated relay used for discharging the charged capacitor bank in a
Capacitor Discharge Welding Machine.
In accordance with second aspect of present invention is to provide a cheap
replacement of this expensive relay.
In accordance with another aspect of present invention is to provide a much
35 more reliable replacement for the relay of the Capacitor Discharge Welding machine.
Annexure‐II
In accordance with yet another aspect of present invention is to provide a
replacement for relay which withstands the welding current requirements.
In accordance with yet another aspect of present invention is to provide a
replacement 5 for relay without much complicated changes in circuitry of the capacitor
discharge welding machine.
In accordance with yet another aspect of present invention is to provide a
replacement for relay which can be easily fitted at the place of the relay.
10 Briefly, the present invention is a cheap, reliable and uncomplicated replacement
to the expensive and short aged gold and silver coated relay in a Capacitor discharge
Welding machine.
15
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention will become more apparent
and descriptive in the description when considered together with figures/flow charts
20 presented:
Fig. 1 is a Block diagram of a Capacitor Discharge Welding machine with Gold
and Silver Coated Relay.
Fig. 2 is a Block Diagram of a capacitor Discharge Welding machine with solid
state Thyristor.
25
30
35
Annexure‐II
5
DETAILED DESCRIPTION
10 Referring to figure1, a Capacitor Discharge Welding machine consists of bank of
Capacitors (3) which is charged to a preset voltage and then discharged through a gold
or silver coated relay (1). This machine is used for welding dissimilar metals, projection
welding and thin sheet spot welding where very high current passed in very short time
results in the welding of the joints. The main drawbacks of using the gold and silver
15 coated relays are that it is expensive as well as frequently replacement (10-15 welding
events) depending upon the requirements.
Referring figure 1, the mains supply of 220V and 50 Hz is supplied to the welding
machine which then passes through a block of switches for operating the Capacitor
20 Discharge Welding machine. The circuitry is divided into two sections through
transformers. One of the circuitry is having rectifier and filter circuits which then
connected to the capacitor bank (3). This capacitor bank (3) is responsible for storage of
charges into them and discharged when welding is to be carried out. The capacitor bank
discharge through a relay (1) which is gold or silver coated. The second part of the
25 circuit is consisting of Rectifier, filter and switching circuit (4). The Working / Foot
operated switch connected to the switching circuit (4) is responsible for operating the
hydraulics and activating the relay (1).
Referring to figure 2, the present invention is the replacement of the gold and silver
30 coated expensive and small aged relay (1) by durable, reliable and cheap solid state
thyristor and resistance circuit (2) with suitable modification in the circuitry of the
Capacitor Discharge Welding machine. The use of thyristor and resistance circuitry (2)
has the same output as that of using the relay (1) in a Capacitor discharge welding
machine. The working of Capacitor discharge welding machine using thyristor
35 resistance circuitry is having more efficient then using the gold and silver coated relay.
Annexure‐II
The thyristor and resistance circuitry (2) is activated by switching ON the switching
circuit (4). When ever the Foot operated switch is pressed the signal goes to the
hydraulics which when touches the job completes the current path for discharging the
Capacitor Bank (C) through 5 rough the activated Thyristor. Thus a large current flow in few
milliseconds through the Thyristor circuitry completes the welding operation effectively.
This invention is very beneficial for the projection welding, dissimilar metal welding and
thin sheet spot welding. The application of this welding machine may be in automobile
10 components, auto electrical, sheet metal fabrication, stainless steel cookware and
kitchenware, Leak proof welds, fabricated stainless steel impellers, switchgears, white
goods (refrigerator, washing machine, microwaves), control panel and cabinets, hollow
metal doors and clean rooms, aeronautics, heavy duty transformers, batteries,
hydraulics, name plate welding, semiconductors, super market displays, diamond tools
15 etc.
The replacement of gold and silver coated relay (1) with Thyristor and resistance
circuitry (2) make the Capacitor discharge welding machine much more efficient and
reliable. Briefly, this replacement is non expensive and long life span and is easy to
assemble at the place of the relay (1).

WE CLAIMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. We Claim

1. The present invention wherein, a solid state device like thyristor and resistance circuitry in place of relay for discharging the charged capacitor bank in a Capacitor Discharge Welding machine is used.

2. The Circuitry in claim 1 wherein, the thyristor’s gate is activated by switching circuitry of the Capacitor discharge welding machine.

3. The circuitry in claim 1 wherein, the path for discharging the charged capacitor bank is completed through thyristor when the capacitor discharge welding pin touches the job to be welded.

4. The circuitry in claim 1 wherein, thyristor is able to withstand the current requirements of the welding machine.

5. The circuitry in claim 1 wherein, the unused relay of the switching circuit of the Capacitor discharge welding machine is utilized by thyristor resistance circuit.

6. The circuitry in claim 1 wherein, the solid state thyristor is operated for few milliseconds to pass the high discharge current through it. ,TagSPECI:As per Annexure-II