FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
An improved shield fixing mechanism for bushings of a transformer, and an improved bushing thereof
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Awkale Ramesh Ramkrushna of Crompton Greaves Limited, S1 -R&D Division, Switchgear Complex, A3, Ambad, Nashik, Maharashtra, India; an Indian National.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
This invention relates to the field of transformers and transformer bushings.
Particularly, this invention relates to an improved shield fixing mechanism for bushings of a transformer, and an improved bushing thereof.
BACKGROUND OF THE INVENTION:
A transformer is an electrical device which transfers electrical energy from one circuit to another. This is achieved through inductively coupled coils or windings. It includes primary windings and secondary windings along with a core. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding.
Larger transformers may have heavy bolted terminals, bus bars or high-voltage insulated bushings made of polymers or porcelain. A bushing is a hollow insulating liner through which a conductor may pass. A large bushing can be a complex structure since it must provide careful control of the electric field gradient without letting the transformer leak oil.
The bushing is separately transported and installed at a customer facility having a transformer. The bushing has a transformer side end which mates with the transformer. The bushing may have a shield at the connection end. This end enters a transformer tank in order to get connected to the leads from the transformer coil. The bushing shield needs to be removed from the bushing and inserted on

transformer leads. Bushing is mounted on transformer tanks and leads are connected to bushing bottom terminal through assembly hole on tank. After connection of leads, shield is to be fixed with bushing bottom by two screws. Fixing of shield is not possible through assembly hole. An operator has to enter inside the transformer tank through inspection hole for shield fixing, which is not a safe operation. Space for shield screw fixing is not a safe operation, according to prior art mechanisms and methods. Space for shield screw fixing is also very less and not easy for assembly.
Hence, there is a need for an improved shield fixing mechanism for bushings of a transformer.
OBJECTS OF THE INVENTION:
An object of the invention is to provide an improved shield and shield fixing mechanism for bushings of a transformer where no tools require for assembly.
Another object of the invention is to provide an improved shield and shield fixing mechanism for bushings of a transformer which is easy for assembly.
Another object of the invention is to provide an improved shield and shield fixing mechanism for bushings of a transformer which require less time for assembly.
Another object of the invention is to provide an improved shield and shield fixing mechanism for bushings of a transformer which is safe for operator.

Another object of the invention is to provide an improved shield and shield fixing mechanism for bushings of a transformer which has secure mechanism.
SUMMARY OF THE INVENTION:
According to this invention, there is provided an improved shield fixing mechanism for bushings of a transformer, said mechanism comprises:
b) an annular concentric inner ring with J-slots provided around said ring on the wall of said ring such that each of said slots includes an opening from an operative top side of the ring, wherein, each of said slots are adapted to receive a correspondingly positioned pin on a bushing end;
c) spring loaded guide pin located concentrically interior to said ring in order to receive said bushing and to guide said pins through said pin into a locking position and to remove said pin from said locking position by spring mechanism.
According to this invention, there is also provided an improved bushing with an improved shield fixing mechanism for bushings of a transformer, said bushing comprises:
a) pins at the operative bottom of said bushing; and
said shield fixing mechanism comprises:
b) an annular concentric inner ring with J-slots provided around said ring on the wall of said ring such that each of said slots includes an opening from an operative top side of the ring, wherein, each of said slots are adapted to receive a correspondingly positioned pin on a bushing end; and
c) spring loaded guide pin located concentrically interior to said ring in order to receive said bushing and to guide said pins through said pin into a locking

position and to remove said pin from said locking position by spring mechanism.
Typically, said bushing includes pins at the operative bottom of said bushing such that said pins are in corresponding numbers with respect to said J-slots.
Typically, said mechanism includes lateral screws to screw together bushing lead to transformer lead.
Typically, said mechanism includes locking pins from lateral sides of said ring.
Typically, said shield fixing mechanism is a bushing shield.
Brief Description of the Accompanying Drawings:
Figure la illustrates a schematic view of a bushing mated with a transformer, according to the prior art;
Figure lb illustrates an enlarged view of the shield and shield fixing mechanism which assists in the mating of the bushing with the transformer according to Figure 1; and
Figure 2 illustrates a front view of the shield used in the mating bushing with transformer.
The invention will now be described in relation to the accompanying drawings, in which:

Figure 3a illustrates a schematic view of a bushing mated with a transformer; Figure 3b illustrates an enlarged view of the shield and shield fixing mechanism which assists in the mating of the bushing with the transformer; and
Figure 4 illustrates a front view of the shield used in the mating bushing with transformer.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure la illustrates a schematic view of a bushing mated with a transformer,
according to the prior art.
Figure lb illustrates an enlarged view of the shield and shield fixing mechanism
which assists in the mating of the bushing with the transformer according to
Figure 1.
Figure 2 illustrates a front view of the shield used in the mating bushing with
transformer.
The bushing (12) is separately transported and installed at a customer facility having a transformer. The bushing has a transformer side end which mates with the transformer. The bushing may have a shield (10), as seen in Figure 2 of the accompanying drawings, at the connection end. This end enters a transformer tank (14) in order to get connected to the leads (16) from the transformer coil. The bushing shield needs to be removed from the bushing and inserted on transformer leads. Bushing is mounted on transformer tanks and leads are connected to bushing bottom terminal through assembly hole on tank. After connection of leads, shield is to be fixed with bushing bottom by two screws. Fixing of shield is not possible through assembly hole. An operator has to enter inside the transformer tank

through inspection hole for shield fixing, which is not a safe operation. Space for shield screw fixing is not a safe operation, according to prior art mechanisms and methods. Space for shield screw fixing is also very less and not easy for assembly.
The bushing is placed above an installation hole (18) in such a way that the screw connection can be made. After that, the bushing is lowered into the transformer tank. At the same time, the transformer lead (22) is pushed upwards until it has reached its final position in the head armature. The shield fixing screws (24) are utilised to screw the bushing end to the end shield lugs (26). Further, lead connection screws (25) are fixed to connect the transformer lead (22) to the bushing lead (28).
According to this invention, there is provided an improved shield fixing mechanism for bushings of a transformer, and an improved bushing thereof.
Figure 3a illustrates a schematic view of a bushing mated with a transformer. Figure 3b illustrates an enlarged view of the shield and shield fixing mechanism which assists in the mating of the bushing with the transformer.
Figure 4 illustrates a front view of the shield used in the mating bushing with transformer.
In accordance with an embodiment of this invention, there is provided an end shield (30) with an annular concentric inner ring (32) with J-slots (34) provided around said ring on the wall of said ring such that the slot includes an opening from the operative top side of the ring.

In accordance with another embodiment of this invention, there are provided pins at the operative bottom of said bushing (12) such that these pins (36) are in corresponding numbers with respect to the J-slots on the ring of the end shield. The end shield is a part of the transformer and the transformer leads (16) enter the end shield (30) from the operative bottom side.
Bushing is mounted on transformer tank and leads are connected to bushing bottom terminal through assembly hole on tank.
The bushing lead (28) and transformer lead (22) are connected and after connection of these leads, the end shield is fixed with bushing bottom by lifting up and rotating to match the slots (34) with locking pin (36).
Further, spring (35) with guide pin (33) is provided on the inner side of the ring in order to receive the bottom side of the bushing.
After matching the slots with pins, the end shield is to be pressed up to get the spring load and rotated to lock with pin. This is a relatively easy and safe assembly mechanism and procedure which can be inspected through inspection hole (18) and operator need not enter in the transformer tank. No tools are required for this assembly.
There are further provided locking pins (37) from lateral sides.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
I. An improved shield fixing mechanism for bushings of a transformer, said mechanism comprising:
b) an annular concentric inner ring with J-slots provided around said ring on the wall of said ring such that each of said slots includes an opening from an operative top side of the ring, wherein, each of said slots are adapted to receive a correspondingly positioned pin on a bushing end;
c) spring loaded guide pin located concentrically interior to said ring in order to receive said bushing and to guide said pins through said pin into a locking position and to remove said pin from said locking position by spring mechanism.

2. A mechanism as claimed in claim 1 wherein, said mechanism includes lateral screws to screw together bushing lead to transformer lead.
3. A mechanism as claimed in claim 1 wherein, said mechanism includes locking pins from lateral sides of said ring.
4. A mechanism as claimed in claim 1 wherein, said shield fixing mechanism is a bushing shield.
5. An improved bushing with an improved shield fixing mechanism for bushings of a transformer,
said bushing comprising:
a) pins at the operative bottom of said bushing; and
said shield fixing mechanism comprising:

b) an annular concentric inner ring with J-slots provided around said ring on the wall of said ring such that each of said slots includes an opening from an operative top side of the ring, wherein, each of said slots are adapted to receive a correspondingly positioned pin on a bushing end; and
c) spring loaded guide pin located concentrically interior to said ring in order to receive said bushing and to guide said pins through said pin into a locking position and to remove said pin from said locking position by spring mechanism.

6. A mechanism as claimed in claim 5 wherein, said bushing includes pins at the operative bottom of said bushing such that said pins are in corresponding numbers with respect to said J-slots.
7. A mechanism as claimed in claim 5 wherein, said mechanism includes lateral screws to screw together bushing lead to transformer lead.
8. A mechanism as claimed in claim 5 wherein, said mechanism includes locking pins from lateral sides of said ring.
9. A mechanism as claimed in claim 5 wherein, said shield fixing mechanism is a bushing shield.