FIELD OF INVENTION:
The invention relates to the field of Gas Metal Arc Welding (GMAW) and Gas Tungsten Arc
Welding (GTAW) process through Straight Tube Butt Welding Machine (STBW) with single
and multi-torches. More particularly, the invention relates to development of contact tip
and contact tip holder cum shielding as facilitator to achieve minimal material damage and
efficient utilization of machine hour and man hour during continuous welding operations
with minimal welding defects.
BACKGROUND OF THE INVENTION:
The Straight Tube Butt Welding Machine (STBW) uses single as well as multi torches to
weld tubes using Gas Metal Arc Welding (GMAW) and Gas Tungsten Arc Welding (GTAW)
process. More particularly, this machine is intended to weld tube with tube butt welding
that forms a part of coil and panel products in boiler applications. In both GMAW and GTAW
process, welding consumable in the form of wire is fed from electrode spool to contact tip
through wire feed guide for continuous welding operations. Being a continuous process with
high heat input, the machine is intended to be used with minimal defect rate, minimal
damaged parts, minimal machine stop-start and minimal time to change the damaged parts
during welding operations to meet the requirements of reduced cycle time and early
delivery of products to customers. In addition, material wastage has to be avoided to
achieve high output through low cost.
Earlier, the contact tip holder cum shielding gas facilitator made of brass connects the

contact tip made of copper using press fit. That is, the contact tip is pressed inside the
contact tip holder where there is slight ovality in both contact tip and contact tip holder.
With this ovality design, the contact tip when pressed inside the contact tip holder and
when rotated in either direction gets tightened and fits inside. The external thread in
contact tip holder cum shielding gas facilitator is connected to torch in the machine. The
welding consumable wire is fed through this assembly for welding.Shielding gas flows
through the pores available.
During continuous welding operations, due to high heat input the contact tip gets burnt and
subsequently damages the contact tip holder due to high thermal conductivity and the
contact tip gets jammed inside the contact tip holder during welding which means this type
of fitting works well only at room temperature and not during continuous welding
operations. This led to incurring high cost by replacing the complete set of parts very
frequently. In addition, more time to change the complete set of parts is needed.Also, the
stick-out of the wire kept varying during the welding process due to this press fit method
which has led to welding defects like incomplete penetration and lack of fusion. This calls
for the need to invent a new design for contact tip and contact tip holder which results in
minimal defect rate, minimal material damage andeasily removable parts replacement
during continuous welding operations.This will facilitate continuous welding process with
effective utilization of machine and man hour and minimal cost incurred in utilization of
material.
Now with the proposed invention, if the contact tip burns or gets damaged due to high heat
input, only contact tip is removed and is replaced whereas the whole assembly of contact

tip and contact tip holder cum shielding gas facilitator had to be replaced earlier. Now the
damage is limited to contact tip alone. This has resulted in saving the cost of procurement.
Also, this has led to minimal stop-start of machine with minimal welding defect rate.
OBJECTS OF INVENTION:
It is therefore an object of invention to develop a contact tip and contact tip holder cum
shielding gas facilitator which causes minimal material damage during continuous welding
operations. Further object of invention is to develop a contact tip that is easily replaceable.
Furthermore, the object of invention is to execute in continuous welding operations through
GMAW and GTAW process using Straight Tube Butt Welding (STBW) machine that results in
minimal welding defect arte, significant material savings through minimal damaged parts,
minimal stop-start time of machine, minimal time to change the damaged parts during
welding operations.
SUMMARY OF INVENTION:
According to the new development of contact tip and contact tip holder cum shielding gas
facilitator is modified in such a way that the contact tip is screwed inside the contact tip
holder with external and internal threads respectively. The contact tip with no thread is now
replaced with contact tip with external thread where both are made of copper. The contact
tip holder with no internal thread at bottom is replaced by contact tip holder with internal
thread at bottom where both are made up of brass.
This will ensure minimal welding defect rate, minimal material wastage and thereby

significant savings through avoiding procurement of new parts when contact tip is damaged
while welding and also result in minimal stop and start of machine, minimal time to change
the damaged parts during welding operations. This will in turn lead to efficient cycle time of
product and effective utilization of machine and labour.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 shows the constructional features of conventional contact tip holder cum shielding
gas facilitator which is made of brass and top view is also shown where the periphery of
contact tip holder is slightly oval.
Figure 2 shows the design of conventional contact tip with no threads which is made of
copper and top view is also shown where the periphery of contact tip is slightly oval.
Figure 3 shows the constructional features of complete assembly of contact holder cum
shielding gas facilitator and contact tip which are connected via press fit.
Figure 4 shows the constructional features of contact tip holder cum shielding gas facilitator
which is made of brass with internal thread at bottom.
Figure 5 shows the constructional features of contact tip with external thread at the top.
Figure 6 shows the constructional features of complete assembly of contact tip holder cum
shielding gas facilitator which are connected via internal and external threads respectively.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
PRESENT INVENTION:
The present invention is explained through figure 6,wherein the modified contact tip holder
cum shielding gas facilitator and contact tip used for GMAW and GTAW process using
Straight Tube Butt Welding Machine have been shown.

An internal thread is formed in the contact tip holder cum shielding gas facilitator to which
the contact tip (08) is attached via external thread (07). This facilitates ease of removal
using spanner seat –II (09) and ensures no jamming of parts in spite of high heat input and
continuous welding. In this design, the ovality in the contact tip and contact tip holder is
eliminated and is kept circular.
Theexternal thread (03) on contact tip holder cum shielding gas facilitator (01) is connected
to the torch of Straight Tube Butt Welding Machine. The pores (02) facilitate the flow of
shielding gas for welding. The internal thread (06) connects the contact tip (08) via external
thread (07) by screwing methodology. As a part of development the contact tip holder cum
shielding gas facilitator is made of brass and contact tip is made of copper. Spanner seat-II
(09) on contact tip is used to screw in during tightening and unscrew at times of damage
using spanner. Spanner seat-II (09) is available on other side of the contact tip also.

WE CLAIM:
1) An assembly (10) of a contact tip holder cum shielding gas facilitator (01) and a
contact tip (08), characterized by,
- An external thread (03) at the top and an internal thread (06) at the bottom of
the contact tip holder cum shielding gas facilitator (01);
- An external thread (07) at the top of the contact tip (08);
- Pores (02) on the contact tip holder cum shielding gas facilitator(01);
- Spanner seat (09) on the contact tip (08).

2) The assembly (10) as claimed in claim (1), wherein the external thread (03) of the
contact tip holder cum shielding gas facilitator is screwed in/out for
connection/disconnection of the assembly (10) to/from the welding machine.
3) The assembly as claimed in claim (1), wherein an external thread (07) of the contact
tip (08) is connected /disconnected with the contact tip holder cum shielding gas
facilitator (01) via internal thread (06).
4) The assembly as claimed in claim (1), wherein the pores (02) facilitate flow of
shielding gas during welding.
5) The assembly as claimed in claim (1), wherein the spanner seat (09) is disposed on
the contact tip (08) for tightening/ removing contact tip in/out to/of the contact tip
holder cum shielding gas facilitator (01).
6) The contact tip holder cum shielding gas facilitator (01) of claim (1) having external
thread (03) and internal thread (06) is made of brass.

7) The contact tip (08) of claim (1) having external thread (07) is made of copper.
8) A method of assembly of a contact tip holder cum shielding gas facilitator (01) and a
contact tip (08) by way of an internal thread (06) and external thread (07) of the
contact tip as described in the preceding claims.