FIELD OF THE INVENTION
The invention relates to an apparatus for joining of heavy thick plate/pipe with a
motorized narrow gap torch for submerged arc welding process.
BACKGROUND OF THE INVENTION
Welding/Joining of heavy thick plate/pipe made components are best done using
submerged arc welding. To improve the rate of production, the conventional
wide groove is converted to narrow groove. The narrow groove demands
customized torch designs. A special type of torch designed for such high
thickness applications is the narrow gap torch. This enables the arc movement of
the torch through an apparatus which interalia demands mechanization for finer
control. Therefore, a mechanized form of torch movement may allow the torch to
navigate through the gap without touching the side wall and also enable weld
deposit to be made in required dimensions without any defects.
Indian Patent No. 216941 granted (March 2008) titled 'An improved torch
assembly for narrow gap welding using single and tandem wire techniques in
submerged arc welding' discusses an improved torch assembly for narrow gap
welding using single and tandem wire techniques in submerged arc welding.

It comprises a torch holder fitted to the wire feeder at the top end and to a torch
positioner at the bottom and fixed with a lock nut for a support of pivotal
movement transverse to the welding direction, said positioner has a nozzle at the
lower end and said assembly of positioner and the torch holder is provided with
a tilting means comprising a tilting frame mounted on an adjustable screw with a
handle. However, there is no controller design associated with this torch
assembly.
Indian Patent 218881 granted (April 2008) titled "Method for welding railroad
rails" discusses a method and system for automatically filing the narrow gap
between facing end walls of adjacent first and second railway rails by depositing
vertically spaced layers of molten metal in the gap with an electric arc welding
torch using a robotic mechanism. This however is not related to the design of
controller for narrow gap torch or the assembly.
Indian Patent 248111 granted (June 2011) titled 'A Device for configurating and
feeding a uniformly bent Wire with a preset pitch and amplitude to oscillate a
welding arc in Narrow Gap Gas Metal Arc Welding procedure' discusses a
compact device for producing and feeding uniformly bent wire for oscillating the
arc in narrow gap gas metal arc welding procedure, the device comprising a wire
spool accommodating a continuous straight wire. A wire-feeder drawing the wire
from the wire-spool via a wire- guide for feeding the wire into a wire-bending
means, the wire-bending means configurating the fed wire into a sinusoidal wave
form. Here again, the design does not relate to the design of controller for
regulating the torch movement.

United States Patent 6596969 dated July 22, 2003 (Sakurai et al.) titled "Method
for guiding arc by laser and arc guiding welding and device by the method"
discusses in an arc welding method and apparatus, a plasma in generated at a
welding intended position on a base material by a laser irradiated to the base
material. This patent however does not relate to the SAW process or design of
controller for arc welding processes.
United States Patent 4,591,685 dated May 27, 1986 (Hinger et al.) titled "Narrow
gap welding torch" discusses a narrow gap welding torch using a twisted wire
center electrode. This corresponds to the design of a narrow gap torch and no
controller design is extended.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose an apparatus with a
motorized narrow gap torch for joining of heavy thick plate/pipe in submerged
arc welding process.
Another object of the present invention is to propose an apparatus with a
motorized narrow gap torch for joining of heavy thick plate/pipe in submerged
arc welding process which allows producing butt joint of different materials
reducing the cycle time.

A still another object of the present invention is to propose an apparatus with a
motorized narrow gap torch for joining of heavy thick plate/pipe in submerged
arc welding process which allows mechanical manipulation and control of the
narrow gap torch for saw process.
A further object of the present invention is to propose an apparatus with a
motorized narrow gap torch for joining of heavy thick plate/pipe in submerged
arc welding process which provides the mechanized control of the narrow gap
torch with limited internal movement within the gap.
SUMMARY OF THE INVENTION
Accordingly, there is provided an apparatus for joining of heavy thick plate/pipe
with a motorized narrow gap torch for submerged arc welding process
comprising a mounting assembly having a helical screw gear; a torch head
assembly; a sensor/encoder; a micro controller; a plurality of limit switches; and
a D.C motor.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 - A schematic representation of an apparatus for joining of heavy thick
plate/pipe with a motorized narrow gap torch for submerged arc
welding process according to the invention.

DETAIL DESCRIPTION OF THE INVENTION
In a first embodiment of the invention, as shown in Figure 1, an apparatus for
joining of heavy thick plate/pipe with a motorized narrow gap torch for
submerged arc welding process is disclosed. The apparatus comprises a DC
motor (1) which has sufficient torque to support the load of a wire feeder (3),
and a torch head assembly (5). The torch head assembly includes a housing
arrangement, a torch mounting assembly, and a power contact (4). The torch
head is connected to the DC motor through a helical screw gear (2) driving the
narrow gap torch. The position of the torch (5) is sensed by an encoder/sensor
an sent to a controller. The signal from the encoder is used in conjunction with a
plurality of limit switches to limit the movement of the torch to ±15°. The limit
switches cut off the supply to the DC motor from driving the torch any further.

WE CLAIM :
1. An apparatus for joining a heavy thick plate/pipe with a motorized narrow
gap torch for submerged arc welding process, comprising a mounting
assembly having a helical screw gear; a torch head assembly; a
sensor/encoder; a micro controller; a plurality of limit switches; and a D.C
motor.
2. An apparatus as claimed in claim 1, wherein the micro controller limits the
movement of the torch within the narrow gap to ±15°.
3. An apparatus as claimed in claim 1, wherein the sensor measures the
current position of the torch in the gap, and transmits the measured value
as a digital signal to the controller.
4. An apparatus as claimed in claim 1, wherein the limit switches are
activated to start and stop the movement of the narrow gap torch, the
controller transmitting the signal to the limit switches to move the torch or
to stop the torch.

5. An apparatus as claimed in claim 1, wherein the torch head assembly
comprises a flexible arrangement to house the mounting assembly
including the narrow gap torch to the D.C. motor and the sensor/encoder.
6. An apparatus as claimed in claim 1, wherein the controller compares the
current position of the torch from the encoder signal and initiates an
ON/OFF action of the limit switches for control of the torch position.

ABSTRACT

The invention relates to an apparatus for joining of heavy thick plate/pipe
with a motorized narrow gap torch for submerged arc welding process to an
extent of ±15°. Joining of high thickness components is done using SAW
process. Different joint designs used in the SAW process demand different
torch designs for optimal utilization. A narrow gap torch therefore has to
negotiate a very small space in the welding groove and has to be controlled
through an external controller. Hence, an apparatus to measure the current
position, generate the signal for the movement of the torch through the
groove. The movement of the torch is controlled by limit switches on either
side of the torch. Thus, the controller provides an option to mechanize the
torch assembly for SAW process.