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 fixture for holding a laminated stator pack
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company.
INVENTORS
Kulkarni Abhijit of Crompton Greaves Ltd, Engineering Department, Stamping Division, B HO, MIDC, Ahmednagar, Maharashtra, India and Singhai Mrigandra of Crompton Greaves Ltd, Advance Material Processing Technology Center, Global R&D, Kanjur Marg, Maharashtra, India, both Indian Nationals
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 fixture for holding a laminated stator pack. BACKGROUND OF THE INVENTION
During the manufacturing of a finished laminated stator core of an electric machine such as motors, alternators etc, the laminated stator packs are subjected to annealing for improving its magnetic properties and removing stresses and strains present therein due to the punching operation on the stators of the stator pack. For annealing, individual laminated stators are stacked one upon another with their stampings aligned, held together by means of a wire and loaded on a meshed grid of the furnace for heating at very high temperatures typically in the range of 700-1400 degree Celsius. The meshes of the grid do not provide a uniform support the stator packs of all sizes. It is also not economically feasible to change the furnace grid according to the size of the stator pack to provide uniform support thereto. Factors such as change in the properties of the stator material due to heating, a considerably large surface area and a thin cross-section of each stator induce warpage therein. Due to the self-weight of the stator pack and a non-uniform support by the meshed grid to the stator pack, bending and misalignment in the stampings of the stators thereof is caused. Such warpage, bending and misalignment may cause the shape of the so annealed stator pack to be distorted beyond acceptable limit and render them unusable. OBJECTS OF THE INVENTION
An object of the invention is to provide a fixture for holding a laminated stator pack in a furnace during annealing thereof.
Another object of the invention is to provide a fixture for holding a laminated stator pack in a furnace through which minimal warpage is induced in the stator pack.

Another object of the invention is to provide a fixture for holding a laminated stator pack in a furnace which provides uniform support to the stator pack in the furnace.
Another object of the invention is to provide a fixture for holding a laminated stator pack in a furnace wherein the stampings of the stators in the stator pack remain aligned during annealing of the stator pack in the furnace. DETAILED DESCRIPTION OF THE INVENTION
According to the invention, there is provided a fixture for holding a laminated stator pack having an outer circumference and a central hole therein defining an inner circumference, the fixture comprising a base having an outer circumference and a central hole defining an inner circumference, a plurality of upright members projecting from the inner circumference of the base in radially spaced apart relationship with one another, the inner circumference of the stator pack corresponding to the outer edges of the upright members and the surface of the base between the outer circumference thereof and outer edge of the upright member corresponding to the surface of the stator pack for supporting the stator pack on the base uniformly, the upright member each having a clamp pivoted at its free end.
Preferably, the base comprises a plurality of open slots at the inner circumference thereof corresponding to the profile of the upright members and radially spaced apart offset with the upright members.
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 la is an isometric view of a fixture for holding a laminated stator pack.
Fig lb is an isometric view of a fixture of Fig la holding the laminated stator pack.
Fig 2a is an isometric view of two fixtures mounted one upon the other for holding a laminated stator pack in each of them.
Fig 2b is an isometric view of the two fixtures of Fig 2a mounted one upon the other holding the laminated stator pack in each of them.
Fig 3 illustrates the fixtures of Fig lb and 2b placed on a meshed grid of a furnace.
Fig la is an isometric view of a fixture for holding a laminated stator pack whereas Fig 2a is an isometric view of two fixtures of Fig la mounted one upon the other. For sake of better representation, above figures la and 2a are shown without the stator packs being held therein. Figures lb and 2b shows the fixtures of figures la and 2a with the stator pack being held therein. The fixture 1 comprises of a base 2 and three upright members 3. The base 2 formed of stainless steel is a ring-shaped structure having an outer circumference 4 and a central hole defining an inner circumference 5. Holes 12 are provided on the base for transfer of heat. The upright members 3 of pre-determined length and profile are welded to the inner circumference 5 of the base 2 in an equidistant relationship with each other. The length of the upright members 3 depends on the height of the laminated stator pack 6 to be held in the fixture 1. As shown in fig lb and 2b, the inner circumference 7 of the stator pack 6 corresponds to the outer edge 8 of the upright members 3. Thus, the stator pack 6 is held against the outer edges 8 of the upright members 3. To support the stator pack 6 uniformly on the base 2, the surface of the base 2 between the outer circumference 4 thereof and outer edge 8 of the upright member 3 corresponds to the surface of the

stator pack 6. However such surface of the base may also be provided a slightly greater than the surface of the stator pack 6. On the free end of each upright member 3, a clamp 9 is provided adapted to slide in and slide out in a horizontal plane. On the inner circumference 5 of the base 2, three open slots 10 are provided in an equidistant relationship with each other and offset from the upright members 3 such that there is an open slot 10 between two upright members 3 and at equidistance therefrom. The size and shape of the open slots 10 corresponds to that of the profile of the upright members 3. The purpose of the open slots 10 in the fixture 1, as shown in Fig lb, is to accommodate the upright members 3 of another fixture disposed therebelow so as to have the fixtures mounted one upon another with stability. It is obvious that such open slots 10 are not required in the bottommost fixture 1 or when the fixture 1 is used individually without any fixture 1 being mounted thereupon. It will also be appreciated by a person skilled in the art that the word 'circumference' does not imply that the shape of the base/stators or the central holes of the base/stators is necessarily circular. They may be of other shapes and such should be contemplated within the spirit of the invention.
Fig 3 illustrates fixtures of Fig lb and 2b placed on a meshed grid 11 of a furnace. The fixtures 1 of figures 1b and 2b with their respective clamps 9 slide in over the laminated stator pack 6 are loaded in the furnace disposed on the meshed grid 11. Although the fixtures 1 are non-uniformly supported on the grid 11, the stator packs 6 are held and supported uniformly by the respective fixtures 1. Normal process of annealing is carried out thereafter.
The base may be formed of some other material other than stainless steel. Holes may or may not be provided. Similarly, the upright members may be made up of a suitable material. The number of upright members may not be necessarily three.

Correspondingly, the number of slots may also not be necessarily three and depends on the number of upright members in the fixtures disposed therebelow. The upright members may be affixed to the base by way of means other than welding. They may also be fabricated integrated to the base.
According to the invention, the fixture minimizes undue warpage and bending of the stator pack during annealing thereof. The clamps lock the alignment of the stator slots thereby rendering the same profile of the stator slots as it was before annealing. All the above renders increased manufacturing efficiency of the finished stator packs.
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 fixture for holding a laminated stator pack having an outer circumference and a central hole therein defining an inner circumference, the fixture comprising a base having an outer circumference and a central hole defining an inner circumference, a plurality of upright members projecting from the inner circumference of the base in radially spaced apart relationship with one another, the inner circumference of the stator pack corresponding to the outer edges of the upright members and the surface of the base between the outer circumference thereof and outer edge of the upright member corresponding to the surface of the stator pack for supporting the stator pack on the base uniformly, the upright member each having a clamp pivoted at its free end.
2. The fixture as claimed in claim 1, wherein the base comprises a plurality of open slots at the inner circumference thereof corresponding to the profile of the upright members and radially spaced apart offset with the upright members.
3. The fixture as claimed in claim 1 or 2, wherein the clamp is a strip.
4. The fixture as claimed in claim 1 or 2 wherein the base comprises a plurality of holes for heat transfer.