FIELD OF INVENTION
The present invention relates to a universal re-rolling machine to convert large spools of
insulation tapes into smaller and handy rolls to be used for the insulation of stator bars
of generators.
BACKGROUND OF THE INVENTION
Generator bars of 500 MW and 210 MW are manufactured in the plant at various work
centers. After giving final shape to the stator bar, it is transported to other work
centers for insulation. Insulation of bars is done in different stages. First, the surface
of the conductors is cleaned with acetone to remove greasy substance and dust
particles. Then, mica paper tape of size 0.15 x 35 mm is wrapped through out the bar
with 50 % overlap. 0.9 x 8 mm copper strip is put and brazed on one strand of the bar
in over hang portion near slot. Conducting tape of size 0.36 x 60 mm is then wrapped
on slot portion of the bar with 50 % overlap. One layer of mica paper is again applied
throughout the length. Few layers of Mica Splitting tape of size 0.18 x 35mm are
wrapped throughout the length. Finally fine mica paper tape of size is wrapped
throughout the bar. Final insulated bar is now protected from any dust & scratches
during transport to Impregnation center by applying a perforated released film. During
impregnation, perforation in the release film allows flow of hot resin inside the layers of
insulation tape. After impregnation bar is loaded on pressing wagon. Purpose of this
wagon is:
a) Holding for hydraulic pressing of stator bars.
b) To shift the bar inside oven for curing and backing.
After curing process, finishing operation of bar is carried out to maintain dimensions.
Then finishing bars are sent to other work centers.
The difficulties in Insulation Taping process are:
1. Initially 3 layers of insulation tape of size 0.15 x 35 mm are wrapped manually
and subsequent layers are wrapped with CNC machine. But in the event of
machine break down all layers of insulation tapes are wrapped manually.
2. Supplied rolls for manual wrapping and that with machine are of same size
(diameter 250 mm). These rolls are more suitable for wrapping machine.
3. While doing manual wrapping, it is difficult to handle large size tape rolls.
4. In some cases roll gets unreeled damaging the insulation tape.
5. Rolls of large size are reduced to smaller size manually. In one shift only 8
large size rolls could be converted to smaller size.
6. After manual wrapping operation is completed, bars are shifted to next work
center for further insulation with CNC machine. If the machine is in working
order otherwise the whole operation is done at the same work center.
7. Interruption in wrapping operation and difficulties in handling causes delay in
work.
8. Delayed delivery for next operation affects final testing schedule which leads to
customer's dissatisfaction.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a universal re-rolling machine to
convert large spools of insulation tapes into smaller and handy rolls which enables
sufficient number of small rolls readily available for manual wrapping of insulation tape
on generator bars.
Another object of the invention is to propose a universal re-rolling machine to convert
large spools of insulation tapes into smaller and handy rolls, which requires only one
man to carry out the work instead of three as in prior art.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The invention can now be described in detail with the help of the figure of the
accompanying drawing in which:
Figure 1 shows a re-rolling machine.
DETAILED DESCRIPTION OF A PREFERRED
EMBODIMENT OF THE INVENTION
Therefore, there existed a need to find a way to overcome the problem of handling
large size rolls. The problem has been overcome by converting large size rolls to
smaller size which are easy to handle. For this a new universal rolling machine is
developed as shown in Figure 1.
The machine / device (1) is constructed on a platform and supporting structure (2).
The device (1) consists of a driven axle (3) and driving axle (4). The driven axle (3) is
the spool roll holder on which large size tape spool on a tape roll cover (5) is mounted
for re-rolling. The tape guide (6) holds the fast moving tape in position during re-
rolling operation so that tape (7) is wrapped to give uniform thickness of the roll. There
are separate tool guides according to the width of the tape. An electric motor (8) of 0.5
hp and 1410 rpm provides rotary motion to the axel (4) on which empty spool is
mounted for re-rolling of the insulation tape. Empty spools are collected after tape
holes are exhausted. These empty spools are used for re-rolling of tape. An easy to
approach starter (9) enables operator to start or stop motor as per requirement.
A large roll is mounted on driven axle (3). Loose end of the tape (7) is passed through
tape guide (6) and few turns are manually wrapped on empty spool mounted on driving
axle (4). Now starter (9) is switched on to run the motor for re-rolling. Re-rolling starts
at high speed. Tape guide (6) ensures uniform re-rolling of the tape. When it is
observed that re-rolled spool has been almost same size to that of unrolled tool, motor
is switched off. It takes about five minutes for re-rolling of one spool.
With the development and use of the re-rolling machine, there has been many
advantages over the prior art. They are,
1. Two employees out of three as used earlier are free to carry out other
productive work.
2. Sufficient numbers of small rolls are readily available for manual
wrapping of insulation tape on generator bars.
3. With the help of this machine, large size rolls are converted into small
rolls at many times faster than manual rolling. Before introducing
universal rolling machine, only 8 numbers of rolls were being converted
into small size rolls in one shift with collective effort of three employers.
But now one roll can be divided into 2 small and equal rolls within 5
minutes.
4. Scrap generation of insulation is under control because small size rolls
are easy to prevent unreeling during wrapping operation.
5. Commitments for deliveries are met which has generated confidence in
the customers.
6. Ease in handling has made wrapping operation comfortable and has also
increased the output.
7. Small size rolls can be safely and easily handle from one place to other
and are prevented from unreeling due to better grip.
8. Operation of re-rolling to smaller size on developed rolling machine is
also fatigueless and user friendly.
Financial Benefit
1. For stator bars:
A) Manual method of insulation re-rolling of tape:-
number of person involved for re-rolling tape = 2
Length of tape re-rolled per shift = 2000 mts
Length of tape required per shift = 12000 mts
Number of shifts needed for re-rolling tape = 12000/2000 = 6
for one set
Man hour consumed -2x8x6 =96
B. Rolling on developed re-rolling machine:-
Time consumed in re-rolling tape for one set = 5 hrs.
Time save per set (96-5) =91 hrs
Man hour rate = Rs. 200
Savings per set = 91 x 200
= Rs. 18200
Number of sets manufactured in one year = 22 x 18, 200
= Rs.400, 400
2. For bus bars:-
A. Old method:
Number of shift required for re-rolling of 20, 000 M
of tape 30, 000/2000 =15
Man hours per bus bar (2 x 8 x 15) = 240
B. New method:-
Man hours consumed per set = 75
Hours saved per set (240 - 75) = 165
Savings per set 165 x 200 = Rs. 33, 000
Number of bus-bars manufactured in one year = 8
Total saving in bus-bars = 33, 000 x 8
= Rs. 2, 64, 000
3. Cost of re-rolling machine if manufactured
from outside agency on the basis of our invention = 4, 00, 000
Expenditure on machine developed in the plant = Rs. 50, 000
Total annual saving = 1+2+3
4, 00, 400/+ 2, 64, 000 + 3, 50, 000 = Rs. 10, 14, 400/-
Out of this, recurring savings (1+2) = 6.64 lacs
Non-recurring savings (3) = 3.50 lacs
WE CLAIM
1. A universal re-rolling machine to convert large spools of insulation tapes
into smaller and handy rolls comprising:
- a driven axle (3) for holding a large size tape spool for re-rolling;
- a driving axle (4) connected to an electric motor (8) through belt and
pulley (10) for re-winding;
Characterized in that,
the loose end of the tape (7) is passed through tape guide (6) for
manually wrapping few turns on empty spool mounted on driving axle (4)
when the tape guide (6) holds the fast moving tape in position during re-
rolling operation so that tape (7) is wrapped to give uniform thickness of
the roll.
2. A machine as claimed in claim 1, wherein separate tool guides are
provided according to the width of the tape (7).
3. A machine as claimed in claim 1, wherein axles (3, 4) are supported on
bearings, housed in the platform (2) of the machine.
4. A machine as claimed in claim 1, wherein a 0.5 hp and 1410 rpm electric
motor driven the axle (4) for re-rolling of the insulation tape.

A universal re-rolling machine to convert large spools of insulation tapes into smaller
and handy rolls consists of a driven axle (3) for holding a large size tape spool for rerolling
and a driving axle (4) connected to an electric motor (8) through belt and pulley
(10) for re-winding. The loose end of the tape (7) is passed through tape guide (6) for
manually wrapping few turns on empty spool mounted on driving axle (4) when the
tape guide (6) holds the fast moving tape in position during re-rolling operations so that
tape (7) is wrapped to give uniform thickness of the roll.