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 punch holder
APPLICANTS
Crompton Greaves Limited, CG House, Dr. Annie Besant Road, Worli, Mumbai - 400 030, Maharashtra, India, an Indian Company
INVENTORS
Sangwikar Sudhir Dattatraya of Crompton Greaves, of M-6 Stamping Division, Kanjur Marg (East), 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 punch holder. BACKGROUND OF INVENTION
Finishing stampings of a stator core and lamination of a rotor is usually done by means of a press tool comprising of a top and bottom assembly. The bottom assembly and the top assembly are fitted to a lower bed and upper arm of the of the press tool respectively. The bottom assembly holds the die and the top assembly holds the collared punches. Usually, the punches are collared before being mounted to the top assembly of the press tool. The collars to be formed on the punches are ought to be of precise size and shape for obtaining a fine stamping and lamination of the rotor. To obtain collars, the punches are first clamped to a vice or a magnet before being grinded by a grinding wheel. Such a method of holding the punch while being grinded invariably leads to a deflection in its position thereby requiring constant monitoring and realigning thereof during its grinding thereby requiring a greater time in the formation of the collar. Such a monitoring is also a skilled process. Further, in a progression press tool, 24 to 58 numbers of collared punches are mounted on the top assembly. Formation of collars on such a large number of punches by above process is time consuming and cumbersome. Incase of grooving punches, wedges needs to be formed on the punches for clamping thereof thereby weakening the punch and increasing the possibility of its crack at a minimum cross-section during punching.

OBJECTS OF THE INVENTION
An object of the invention is to provide a punch holder which holds the punch firmly and obviates the need of repositioning and realigning the punch during its grinding to form a collar thereon.
Another object of the invention is to provide a punch holder wherein inserting and removing the punch there from is easy and simple.
Another object of the invention is to provide a punch holder by which the turn around time in formation of a collar thereon is substantially less. DETAILED DESCRIPTION OF THE INVENTION
In order to achieve the aforesaid and other objectives, a punch holder is provided for holding a punch and machining thereof. The punch comprises of an oblong body having a plurality of spaced projections extending along the length thereof. The punch holder comprises an elongated body having a bore extending along the length thereof and corresponding to the periphery of the oblong punch body, the bore periphery having oblong slots along the length thereof contiguous with the bore and corresponding to the projections of the punch, the bore further having an oblong slit extending along at least one surface of the punch holder and contiguous with the bore and matching with a projection of the punch.
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 shows an isometric view of a punch holder.
Fig 2a shows an isometric view of a punch without collars.
Fig 2b illustrates a punch without collars being inserted into a punch holder for grinding thereof.
Fig 2c shows a schematic layout of the grinding operation of a punch.
Fig 2d illustrates a collared punch being removed from the punch holder.
Fig 2e shows an isometric view of a collared punch.
Fig 1 shows an isometric view of a punch holder 1 being a rectangular block open from three sides. A. bore 2 is provided within the punch holder 1 and extending along the length of the punch holder 1. The bore 2 corresponds to the periphery of a punch 4 (as shown in Fig 2a) and comprises of oblong slots 3 provided along the length of the bore 2. The size and shape of the slots 3 corresponds to projections 5 (as shown in Fig 2a) of the punch 4. Further, an oblong slit 6 extends along the upper surface of the punch holder 1, contiguous with the bore 2 of the punch 4 so as to protrude out a projection 5a (as shown in Fig 2b) of the punch holder 1. The shape and size of the bore periphery and the bore 2 is such that the punch 4 is held firmly within the punch holder 1 as well as be easily slid in and out there from.
Fig 2a shows an isometric view of a punch 4 without collars. The punch 1 comprises of an oblong body having a plurality of spaced projections 5 extending along the length thereof. The punches 4 are to be collared before mounting them onto a press tool (not shown in fig). To form collars on the punch 4, it is first slid into the bore 2 of the punch holder 1 as shown in Fig 2b such that the projection 5a (as shown in Fig 2b) protrudes from the slit of the punch holder 1. The punch holder 1 is then placed on a

magnetic table 7 of a grinding machine. Fig 2c depicts a schematic layout of the grinding operation of the punch 4. The punch holder 1 is supported on its side by means of support blocks 8 to render extra rigidity. A grinding wheel 9 is then rolled over the projection 5a protruding out of the punch holder 1 for machining a collar thereupon. Thereafter, to form a collar on the correspondingly opposite side of the collared projection (not shown in the fig), the punch 4 is slid out of the punch holder 1 and reinserted such that the correspondingly opposite side of the collared projection protrudes from the slit of the punch holder 1. A grinding wheel 9 is then rolled over the projection protruding out of the slit of the punch holder 1 for machining a collar thereupon. The punch 4 is held firmly within the punch holder 1 all the while being grinded to form a collar thereupon. Finally, the collared punch 4a is slid out of the punch holder 1, as shown in Fig 2d. Fig 2e shows an isometric view of the collared punch 4a. The collared punch 4a, as shown in Fig 2e, is then mounted to the top assembly of a press tool machine.
The punch holder may include lids, permanent or otherwise, on either sides of the fixture to prevent the punch from sliding further or locking it. The punch within the punch holder may be reinforced further by means of flat end screws or by any other means.
According to the invention, any need for repositioning or realigning the punch during the grinding thereof is eliminated once it is inserted in the punch holder leading to an increased efficiency and accuracy in the grinding of the punch for formation of a collar thereupon. The turn around time in the formation of collars on the punch is reduced substantially. The placement and alignment of the punch within the fixture is easy and simple. Further, the fixture can be designed to hold a punch of any size and shape.

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 spirit or scope of the invention as defined.

We claim:
7
1. A punch holder for holding a punch for machining the punch comprising an oblong body having a plurality of spaced projections extending along the length thereof, the punch holder comprising an elongated body having a bore extending along the length thereof and corresponding to the periphery of the oblong body of the punch, the bore periphery having oblong slots along the length thereof contiguous with the bore and corresponding to the projections of the punch, the bore further having an oblong slit extending along at least one surface of the punch holder and contiguous with the bore and matching with a projection of the punch.