FIELD OF THE INVENTION
The present invention generally relates to a turbogenerator, in particular a stator
body of the turbogenerator. More particularly, the invention relates to an
improved device for drilling of holes on insert cover of a stator body.
BACKGROUND OF THE INVENTION
A turbo generator consists of two main parts a first part is a Stator and a second
part rs a Rotor. The Rotor is a rotating part and the stator is a static part having
an insert cover with a plurality of drilled holes.
According to the existing process of drilling holes in an insert cover of a Stator,
comprises a control marking of the Stator body, machining in a horizontal boring
machine the marked stator body including End Shield seating surface and Insert
cover seating surface; and drilling insert cover holes by a pneumatic drill
Machine. A pneumatic drilling machine is necessary because the outer plate of
the end shield having an inner diameter less than the pitch-circle-diameter (PCD)
of the insert cover holes, thereby obstructing the tooboperation of the horizontal
boring machine to drill the holes.
Figure 1 shows a sequence of machining operation for drilling holes on the insert
cover according to prior art.
During the operation of drilling/tapping of holes in the insert cover according to
prior art, the following problems are encountered :
1. Shifting in holes location ; As the holes are done by hand drill
machine, access to these holes are very difficult, resulting the frequent
shifting of holes;
2. Ovalitv in holes ; Application of uniform load on the drill machine due to
very narrow working area, the drilled holes become oval. Further the
threads in the oval holes become defective;
3. High cvcle time : As the working area is very narrow the time cycle for
drilling and tapping becomes quite high.
OBJECTS OF THE INVENTION :
It is therefore an object of the invention to propose an improved device for
drilling of holes on insert cover of a stator body, which eliminates shifting of hole
locations.
Another object of the invention is to propose an improved device for drilling of
holes on insert cover of a stator body, which avoids ovality the drilled holes.
A still another object of the invention is to propose an improved device for
drilling of holes on insert cover of a stator body, which allows increase the
productivity by reducing cycle time.
A further object of the invention is to propose an improved device for drilling of
holes on insert cover of a stator body, which enables drilling of standard holes on
the insert cover to make the insert cover interchangeable for various stator
SUMMARY OF THE INVENTION
According to the invention, there is provided an improved device for drilling of
holes on insert cover of a stator body in a turbogenerator comprising : a base
plate; a arm rotatably fixed at the centre of the base body; a balance weight to
counterbalance the weight of other components, so as to ensure a free rotation
of the arm; a clamping plate to lock the position of the arm during drilling
operation; a gear arrangement to turn the rotation of the arm; an electric motor
to operate the device; and a centering pin to flexibly lock the arm on the base
plate. Wherein the arm of the device is enabled to rotate around the centering
pin such that the device is aligned at a center of the bore of the end shield
seating surface to allow drilling of holes on the insert cover.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 : Prior Art Process Mapping chart for drilling operation.
Figure 2 : Shows a prior art turbogenerator Stator body.
Figure 3 : Shows Insert Cover holes of the stator body.
Figure 4 : Drilling of holes by pneumatic drill machine according to the prior art.
Figure 5 : Shows an improved device for drilling holes on insert cover of a stator
body according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The device of the invention is used in TG Stator Body. Stator Body is one of the
major component of a Generator. Stator Body holds major components such as
Stator Core. End Shields. Terminal Box and coolers. Stator core remains fixed
with the Stator Body. The Rotor remains at the center of the core supported
from ends by bearing mounted on the End Shields. A Stator Body of TG is shown
in Figure 2. Rotor rotates at high rpm and current is induced in the Stator core.
Two ends of the stator core are closed by an Insert cover and Gas Baffle Ring
assembly. The Insert covers are mounted of the Stator Body with a plurality of
holes shown in Figure 3. During rotation of the rotor, hydrogen gas filled inside
the stator, get circulated across the stator core. The gas is used for cooling of
the Stator Body and the Rotor. Drilling operation of the Insert cover holes is
carried out by a hand drill machine in prior art as shown in Figure 4. For
machining of the Stator Body, firstly a control marking of the body is done, then
it goes to a H. Boring machine for machining of the complete Stator Body
including the insert cover seating surface. Insert cover holes cannot be
performed on H. Boring machine because of the inaccessibility of the H. B.
machine tool to the surface where the holes are to be made.
As shown in figure 5, an improved device for configureating holes on the insert
cover of a stator body of the turbogenerators (TG). The device comprises :
a base plate (1);
a arm (2) rotatabiy fixed at the centre of the base body (1);
a balance weight (3) to counterbalance the weight of other components, so as to
ensure a free rotation of the arm (2);
a clamping plate (4) to lock the position of the arm during drilling operation;
a gear arrangement (5) to turn the rotation of the arm (2);
an electric motor (6) to operate the device; and
a centering pin (7) to flexibly lock the arm (2) on the base plate (1).
Base Plate (1)
The base plate is used to hold the drilling device at the center of the stator body.
At least four holes (two at each edge) are configured on the base plate (1) is
clamped on end shield seating surface having corresponding holes on the Stator
Body with (1) bolts. At the center of the base plate (1); the arm (2) of the device
is mounted.
Arm ( 2)
The arm (2) is supported at the center of base plate (1) with the help of a pin.
The arm (2) can rotate on the pin in both directions. At one end of the arm there
major components of the device (motor, clamping plate and gear box assembly)
are mounted and at other end a balancing weight (3) is provided.
Balancing weight (3)
A balancing weight (3) is used to counter balance the weight of the motor, gear
box, clamping plate and tool. With the help of the balancing weight (3) the arm
(2) can rotate freely at the center of the base plate (1).
Clamoina plate (4)
The clamping plate (4) is use to lock the position of the arm (2) during drilling
operation. After setting the position of the drill of the device on the location of
hole, the clamping plate (4) is locked on a seating plate of the Insert cover of the
Stator Body by tightening a bolt of the clamping plate (4).
Gear Box (5)
A gear (5) is used to turn the direction of rotation of the arm (2) by 90 degree;
which constitutes a bevel gear arrangement.
Electric Motor (6)
A three phase motor (6) is provided for operation of the Device.
Centering pin (7)
The arm (2) of the device rotates around the centering pin (7). The centering pin
(7) further allows aligning of the drilling device at the center of bore of the End
shield seating surface.
WE CLAIM :
1. An improved device for drilling of holes on insert cover of a stator body in
a turbogenerator comprising :
a base plate (1);
a arm (2) rotatably fixed at the centre of the base body (1);
a balance weight (3) to counterbalance the weight of other components,
so as to ensure a free rotation of the arm (2);
a clamping plate (4) to lock the position of the arm during drilling
operation;
a gear arrangement (5) to turn the rotation of the arm (2);
an electric motor (6) to operate the device; and
a centering pin (7) to flexibly lock the arm (2) on the base plate (1).
Wherein the arm (2) of the device is enabled to rotate around the
centering pin (7) such that the device Is aligned at a center of the bore of
the end shield seating surface to allow drilling of holes on the insert cover.

ABSTRACT

The invention relates to an improved device for drilling of holes on insert cover
of a stator body in a turbogenerator comprising : a base plate (1); a arm (2)
rotatably fixed at the centre of the base body (1); a balance weight (3) to
counterbalance the weight of other components, so as to ensure a free rotation
of the arm (2); a clamping plate (4) to lock the position of the arm during drilling
operation; a gear arrangement (5) to turn the rotation of the arm (2); an electric
motor (6) to operate the device; and a centering pin (7) to flexibly lock the arm
(2) on the base plate (1). Wherein the arm (2) of the device is enabled to rotate
around the centering pin (7) such that the device is aligned at a center of the
bore of the end shield seating surface to allow drilling of holes on the insert
cover.