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, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
A core building fixture
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Vaidya Sameer Sharadchandra of Crompton Greaves Ltd, Tl Division, Crompton Greaves Ltd, Kanjur (E), Mumbai 400042, 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 a core building fixture. BACKGROUND OF THE INVENTION
The core of a power transformer is formed by a plurality of core laminations stacked one upon the other in a core building fixture. The core building fixture usually comprises a frame of a shape of the core including the windows. Upstanding guide rods in a spaced apart relationship are provided on the frame portion corresponding to the top and bottom yokes of the core. Corresponding holes are also provided on the core laminations to be placed on such platform portions. After the core laminations corresponding to the top and bottom yokes are placed on their corresponding frame portions through their respective guide rods, core laminations corresponding to the three limbs are placed on their respective frame portions. Thereafter, a second layer of core lamination is placed on the first layer as described above and so on. Usually, the ends of the laminations are mitered and hence mitre joints are formed between two laminations. Therefore, it is critical that each core lamination is aligned accurately and placed properly. The guide rods ensure that the inter and intra layer alignment of the core laminations is accurate. However, holes on the core laminations is one of the factors responsible for magnetic flux leakage. In the event the holes are not provided on the core laminations, guide rods cannot be used during the formation of the core stack in the core building fixture. Consequently, aligning the placement of laminations gets cumbersome and extremely difficult. Even if the alignment is achieved for one layer, retaining the same while the other layers are formed upon the other is very difficult and impractical.

OBJECTS OF THE INVENTION
An object of the invention is to provide a core building fixture. Another object of the invention is to provide a core building fixture for building a core comprising of hole less core laminations.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, there is provided a core building fixture comprising a frame corresponding to the shape of the core, at least one vertical member placed within the frame in the area corresponding to the window of the core, a movable horizontal arm fixed perpendicularly to each vertical member, the horizontal arm being movable along its axis and the axis of the vertical member; and at feast one support link for supporting and locking the position of the horizontal arm on the vertical member.
Preferably, a level gauging instrument such as a spirit level is provided at one end of the horizontal arm. The support link is a rod, one end of which is fixed to the horizontal arm and the other end fixed to the vertical member.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig 1 is a schematic view of a core building fixture.
Fig 2 is a schematic view of a core building fixture with the core being partially formed thereupon.
Fig 2a is an enlarged view of the encircled portion on Fig 2.
Fig 3 is a schematic view of a core building fixture with the core being formed thereupon.

Referring to the figures, the core building fixture comprises of a frame 1, two vertical members 2, a horizontal arm 3 for each vertical member 2 and a plurality of support links 4 for each horizontal arm 3. The frame 1 is more or less rectangular in shape and corresponds to the shape of the core 5 i.e. having a bottom yoke portion 6, top yoke portion 7, three limbs 8, 9, 10 and a window 11 & 12 on the either sides of the central limb 9. The width of the surface on the frame 1 is provided large enough to cater to core of different sizes. The frame 1 remains elevated from the ground by means of pillars or through other mechanisms well known in the art. In each window 11 & 12, there remains disposed a vertical member 2, preferably nearer to the bottom yoke portion 6 of the frame 1. The vertical member 2 is bolted to the surface on which the frame 1 is supported. A pair of line of holes 13 & 14 parallel to each other runs along the length of the vertical member 2. The horizontal arm 3 comprises of holes 15 running along its length and is fixed perpendicularly to the vertical member 2 by inserting a pin into a set of aligned holes 13, 14 & 15 of the horizontal arm 3 and vertical member 2. Thus the length of vertical member 2 at which the horizontal arm 3 is fixed thereto is changeable. Similarly, the portion of the horizontal arm 3 remaining disposed on either sides of the vertical member 2 is also changeable. Owing to the position of the vertical member being nearer to the bottom yoke portion 6 of the frame 1, one end 16 of the horizontal arm 3 is also proximal to the bottom yoke portion 6 of the frame 1. This end 16 works as a pointer. On the other end 17, a level gauging instrument 18 such as a spirit level is mounted for testing the perpendicularity of the horizontal arm 3 with respect to the vertical member 2. To retain the perpendicularity and to support the horizontal arm 3, a plurality of support links 4 are provided which supports the horizontal arm 4 at its different lengths. Each support link 4 is a rod like structure of increasing lengths, respective ends 19 & 20 of which are connected to the

horizontal arm 3 and vertical member 2 by means of set screws. To change the position of the horizontal arm 3, support links 4 are required to be removed first.
For building the core 5, a core lamination corresponding to the bottom yoke portions 6 are first placed on the frame. To do that, the position of the edge of a core lamination having the smallest width to be placed on the bottom yoke portions 6 of the frame 1 on the either sides of the central limb 9 is pre-determined. These positions are marked by placing the pointer ends 16 of the horizontal arms 3 in each window 11 & 12 against thereof. The corresponding core laminations are then placed on the bottom yoke portions 6 of the frame 1. Thereafter, core laminations corresponding to the top yoke and limb portions are placed on the respective frame portions 7, 8, 9 & 10. Thus one layer of core is placed on the frame 1. The second layer of core laminations is larger than the first layer core laminations and placed thereupon. The size of each lamination layer keeps on increasing till the central layer and keep on decreasing therefrom till the topmost layer. To place the second layer on the first layer, the above steps are repeated. The position of the horizontal arms 3 is easily changeable as described above. Owing to a many number or layers and the difference of size between two layers being very small, the marking of the pre-determined position by the horizontal arm 3 can be done after a frequency of four or five layers. Upon building the entire core 5, subsequent known manufacturing processes follows such as binding the core laminations together, making them upright, curing etc.
The shape of the frame may not be necessarily rectangular and can be of any shape corresponding to the shape of the core. The mechanism of holding the horizontal arm against the vertical member may not be necessarily as described above and some other means well known in the art may be used. Such also stands true for connecting the support links to the horizontal arm and vertical members. Further, the

support links may not be necessarily connected to the vertical member. They may be supported on the ground or on the surface on which the frame is supported.
According to the invention, inter and intra layer alignment of core laminations is made feasible even without guiding rods on the frame. Such a fixture may also be used for cross checking the alignment even if guiding rods are made available.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the scope of the invention as defined in the appended claims.

We claim:
1. A core building fixture comprising
a. a frame corresponding to the shape of the core
b. at least one vertical member placed within the frame in the area
corresponding to the window of the core,
c. a movable horizontal arm fixed perpendicularly to each vertical
member, the horizontal arm being movable along its axis and the axis
of the vertical member; and
d. at least one support link for supporting and locking the position of the
horizontal arm on the vertical member;
2. A core building fixture as claimed in claim 1, wherein a level gauging instrument such as a spirit level is provided at one end of the horizontal arm.
3. A core building fixture as claimed in claim 1, wherein the support link being a rod, one end of which fixed to the horizontal arm and the other end fixed to the vertical member.
4. A core building fixture as claimed in claim 1, wherein the support link being a rod, one end of which fixed to the horizontal arm and the other end fixed to the ground.