FIELD OF INVENTION
This invention relates to an operation of drilling on taper faces of core press ring
of all types of turbo generators, More particularly, It relates to a device with
clamping and indexing arrangement and a method for the same for vertical
drilling operation on taper surfaces of core press ring of all types of turbo
generators,
BACKGROUND OF THE INVENTION
Core of turbo generator is made of thin Iron sheet stampings coated with
insulated varnished on both the side as shown in fig.11 To make the core a
monolithte mass, the stampings are tightened with long steel bolts passing
through the stampings and core press ring at both the ends. Core press ring is
circular ring having a thickness of 60 mm (fig.2). Core press ring Is a part of
Turbo generator slater used at both the ends of the core to press the stampings,
After matching of both the ends, the operations involved are facing and taper
turning on a vertical boring machine. Then 24 holes Ø40mm with counter of
Ø120mm and 48 holes of M20 X 1,5 mm are dried on the taper portion of core
press ring making the axes of the holes perpendicular to the face. Taper is given
on the face of core press ring to compensate distortion of ring in fully tightened
condition so that the taper face of the ring becomes perpendicular to the bolt
ensuring uniform tightening of the nuts, There are five types of core press ring
with different tapers.
Alter the machining operation, the drilling operation on the taper face of a core
press ring is carried out on a horizontal boring machine which is a very costly
machine and the cost of operation Is very high, The setting of the job on this

machine for drilling operation is not only difficult but also critical. It involves risk
and extremely tiring for operators. It calls for utmost skill and attention of the
operators. Also, dimension and finish of the holes as per requirement is difficult
to achieve. For drilling all holes, the job needs to be shifted by crane after
completion of each hole for doing the operation for next hole. It means crane is
needed 48 times to complete all 72 holes (two holes of M20 being in same
vertical line need shifting by crane 24 times). It is because after completing one
hole the ring is required to be reset for drilling the next hole. It means 48 times
this process of resetting is being done. The total time consumed in drilling
operation of all 72 holes including the use of crane is around 125 to 150 hours.
Since the job is held vertically, the clamping being in vertical position, drilling
operation is carried out at low feed and speed to avoid problem of chattering and
variation in size. Also since the work is being done on an elevated platform, the
frequent setting and use of crank causes a high human fatigue resulting slow
down of work. From safety point of view also this method of operation is
hazardous.
Hence there exists a need to find a suitable device to carry out a process to
undertake this important drilling operation which can eliminate the disadvantages
of prior art as stated above.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device with clamping and
indexing arrangement and a method for the same for vertical drilling operation
on taper surface of core press ring of all types of turbo generator which
eliminates the disadvantages of prior art.

Another object of the invention is to propose a device with clamping and
indexing arrangement and a method for the same for vertical drilling operation
on taper surface of core press ring of all types of turbo generator which clamps
the job horizontally so that a simple vertical drilling operation is performed.
A still another object of the invention is to propose a device with clamping and
indexing arrangement and a method for the same for vertical drilling operation
on taper surface of core press ring of all types of turbo generator which is
capable of indexing the job for performing the drilling operation of each hole one
by one in a single setting.
A further object of the invention is to propose a device with clamping and
indexing arrangement and a method for the same for vertical drilling operation
on taper surface of core press ring of all types of turbo generator which sets the
taper surface of the job perpendicular to machine spindle axes automatically
after indexing.
A still further object of the invention is to propose a device with clamping and
indexing arrangement and a method for the same for vertical drilling operation
on taper surface of core press ring of all types of turbo generator which reduces
the cycle time of operation as well as the human fatigue involved and cost
saving.
SUMMARY OF THE INVENTION
As shown in fig.4, the device (D) of the present invention consists of three rollers
(la,lb,lc) fixed on a T shape base plate (2). The rollers (la,lb,lc) are spaced at
a minimum diameter for example of 2700 mm so that any type of pressing ring
(7) can be fixed on the device (D). All the rollers (la,lb,lc) are inter connected

with the universal joints (4) so that movements of all rollers remain the same.
White giving manual rotation to one roller by a handle (6), correct directional
rotation to all three rollers simultaneously Is achieved through three gears (3).
Movement of the rollers (la,lb,lc) are given by a handle (6) which is provided
on one roller (la) and is manually operated. Job is supported on rollers
(laflb,lc) and clamped near the location of hole to be drilled in such a way that
the taper portion of the ring on which hole is to be drilled becomes parallel to the
horizontal plane and thus perpendicular to the vertical drill axes of the radial drill
machine. The clamping arrangement of the centering device (5) is made to hold
the job at Its internal diameter with the help of bolts (8) which are tightened
against the internal diameter of the job rigidly. After drilling one hole, the job Is
indexed for drilling of next hole by manually rotating the roller (la) with the
handle (6) when the position of taper portion of the ring (7) automatically comes
parallel to horizontal plane, All the required holes as shown in fig,2 are drilled
one after another by rotating the ring by the handle (6) when the ring (7)
remains clamped during drilling. During the whole operation crane is required
only two times, one for loading of the ring (7) on the device (D) and other for
finally unloading the complete job, The ring (7) is then undamped and rotated to
drill the next hole.
BRIEP DESCRIPTION OP THE ACCOMPANYING DRAWINGS
Fig.l - shows stator core and core pressing ring having taper faces
Fig.2 - shows the core pressing ring and 72 nos. drilled holes on it
Fig.3 - shows the Job on the device before drilling
Fig.4 - shows the device for drilling operation according to invention
Fig.5 - shows a photograph of the core ring

An exemplary embodiment of the invention as depicted in the accompanying
drawings will now be explained in details. However there can be several other
embodiments ail of which are deemed covered by this specification.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in fig.4, the indexing cum clamping device (D) for carrying out the
drilling operation on taper surfaces of core press ring consists of a T-shaped
steel plates fabricated base (2) having three threaded holes (9) for jacking near
each end of three arms (10) of the base (2). Three taper roller assemblies
(la,lb,lc) are also being mounted on each of the three arms of the same base
(2). The threaded holes (9) are used for taper setting of the device (D), Before
starting the drilling operation of first hole on the radial drill machine, the device
(D) with ring (7) set on it, is set with the help of screw (11) in screw Jacking
holes (9) on the base (2) such that the ring (7) surface exactly under the
machine spindle is perpendicular to its axis. Base (2) of the device (D) is not kept
parallel to the machine bed but is set according to the taper of the ring surface.
This setting is done only once for a particular type of ring and once the initial
taper setting is complete, the ring (7) is rotated manually with the handle (6). All
holes to be drilled as shown in fig.2 are marked before the drilling operation. The
ring is rotated to bring the marked position under the machine spindle, when the
surface of the ring (7) comes automatically perpendicular to the axis of machine
spindle. Mounting of taper roller assemblies (la,lb,lc) on each of the three arms
(10) of the base (2) is done in such a way that these can tilt in vertical plane
along the radial line. The ring (7) is placed on the device (D) and rested on
rollers (la,lb,lc) as shown in fig.3. One roller assembly for example, la, is fitted
with the arrangement to rotate the roller (la) in clockwise or anticlockwise
direction manually with the help of a handle (6). An assembly of three gears (3)

is fitted to this arrangement which transmits the motion to the other two rollers
(lb,lc) with the help of universal joints (4) in such a way that all rollers move in
one direction either in clockwise or anticlockwise direction resulting required
indexing of the ring (7). Tilting provision is provided to the roller assemblies
(la,lb,lc) so that rollers are capable of adjusting automatically with the weight
of the ring (7) according to the taper on the surface of the ring (7) in such a way
that whole length of the rollers is in contact with the ring (7). This helps In
providing stability during drilling operation, reducing wear of the rollers and
transferring rotational movement to the job (7). Rollers (la,lb,lc) are
specifically designed in taper shape so that during rotational movement of the
job (7), the tendency of the roller assembly is to push the job (7) towards the
center of the fixture (D) where a centering device (5) restricts all movement.
Therefore the job or ring (7) remains in set position during drilling operation. The
job centering device (5) is mounted on the base (2) at the geometric centre of
the base (2). This centering device (5) consists of axel, ring and three arms (10)
with adjusting bolts (8) at the end. The centering device (5) is used to set the
ring (7) concentric with the fixture or device (D) when arms (10) of the centering
device (5) are placed on the inner diameter of the ring (7) and adjusting bolts
(8) are set accordingly to clamp the ring (7) at its inner diameter. Equal length of
each arm (10) with adjusted length of bolts (8) ensures concentric setting of the
ring (7). The Job or ring (7) is set concentric to the device (D) only once before
starting the drilling operation of first hole on radial drill machine. To arrest
vibration and subsequent disturbance of the job (7) during drilling operation, a
clamp is provided near the location of hole to be drilled. This clamp is loosened
while rotating the job (7) for indexing the next hole and retightened again before
drilling. This vertical drilling operation are done on a simple radial drilling
machine instead of a costly and critical horizontal boring machine as in prior art.

Beside many intangible gains through this present invention like reduction of
machine time cycle, a operator friendly process, reduction in inventory tool cost,
good quality product, the tangible gains are as follows:

WE CLAIM
1. A device with clamping and indexing arrangement for vertical drilling
operation on taper surface of core press ring of all types of turbo
generators comprising:
a T-shape steel plates fabricated base (2);
a plurality of threaded holes (9) near each end of three arms (10) of the
base (2);
a plurality of rollers (la,lb,lc) being fixed to the base (2) and assembled
with each other through universal joints (4);
a gear assembly (3) with plurality of gears being attached to the roller
assembly (la) for transmitting the motion of the roller assembly (la) to
other rollers (lb,lc);
a handle (6) for manually moving the roller assembly (la);
a plurality of universal joints being fixed to the gear assembly (3) and
rollers (lb,lc);
a centering device (5) having a plurality of arms (10) and a plurality of
adjustable bolts (8) for holding the ring (7) at its inner diameter and for
setting it concentric with the device (D);
Characterised in that a plurality of jack screws (11) are provided in the
threaded holes (9) for setting the taper of the core ring (7) surface
perpendicular to machine spindle axes.
2. A device with clamping and indexing arrangement for vertical drilling
operation on taper surface of core press ring of all types of turbo
generators as claimed in claim 1, wherein three jack screws (11) are used
in three threaded holes (9) for setting the taper of the core ring surface
(7).

3. A device with damping and indexing arrangement for vertical drilling
operation on taper surface of core press ring of all types of turbo
generators as claimed in claim 1, wherein three rollers (la,lb,lc) are used
in roller assembly.
4. A device with clamping and indexing arrangement for vertical drilling
operation on taper surface of core press ring of all types of turbo
generators as claimed in claim i, wherein two universal joints (4) fixed to
the gear assembly having three gears are used to move the rollers.
5. A method of the device (D) for vertical drilling operation on taper surface
of core press ring of all types of turbo generators comprising;
placing the device (D) with T-shape base (2) and a plurality of taper rollers
(la,lb,lc) on machine bed;
placing the core press ring (7) on the device (D) such that the ring (7)
rests on a plurality of taper rollers (la,lb,lc);
centering the ring (7) concentric with the device (D) with a plurality of
adjustable bolts (8) of the centering device (5);
clamping the ring (7) with adjustable bolts (8) at the inner diameter of the
ring (7);
setting the device (D) by a jack screw (11) to set the taper surface of the
ring (7) perpendicular to machine spindle axis;
indexing the core press ring (7) manually rotating the handle (6) till the
marked hole position coming under the spindle;
clamping the job near the location of the marked hole to be drilled;
carrying out drilling operation of a marked hole; and
unclamping the ring indexing is done to bring the next marked hole position
under the spindle.

6. The method of the device (D) for vertical drilling operation on taper
surface of core press ring of all types of turbo generators as claimed in
claim 2 wherein, the clamping and setting of the ring (7) concentrically
with the device (D) is done only once for the entire operation.
7. The method of the device (D) for vertical drilling operation on taper
surface of core press ring of all types of turbo generators as claimed in
claim 2 wherein, manual rotation of a handle (6) rotates a plurality of
rollers simultaneously in one direction only through a plurality of gears.

A device (D) with clamping and indexing arrangement for vertical drilling
operation on taper surface of core press ring of all types of turbo generators
consists of a T-shape steel plates fabricated base (2) having three threaded
holes (9) near each end of three arms (10) of the base (2) on which three
rollers (1a,1b,lc) are fixed. Three rollers (1a,1b,1c) are assembled with each
other through universal joints. A gear assembly (3) of three gears is attached
to the roller assembly (la) for transmitting the motion of the roller assembly
(1a) to other rollers (1b,1c). A handle (6) is provided for moving the roller
assembly (ia,lb,lc) manually. A centering device (5) having three arms (10)
and three adjustable bolts (8) holds the ring (7) at its inner diameter and sets
it concentric with the device (D). Three jack screws (11) are provided in the
threaded holes (9) for setting the taper of the core ring (7) surface
perpendicular to machine spindle axis.