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 method and a progressive stamping tool for use in a press system for manufacturing rotor and stator laminations.
APPLICANTS
Crompton Greaves Limited, CG House. Dr Annie Besant Road. Worli, Mumbai 400 030. Maharashtra, India, an Indian Company
INVENTOR
Chandrashekhar Ramakant Keluskant of Stamping Division, Crompton Greaves Ltd, Kanjur Marg, Mumbai. Maharashtra. India, 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

The present invention relates to a method and a progressive stamping tool for use in a press system for manufacturing rotor and stator laminations.
BACKGROUND OF THE INVENTION
Press systems are used to manufacture rotor and stator laminations for alternators and generators. These systems generally employ a progressive stamping operation to obtain rotor and stator laminations that are stacked together later to form a rotor and a stator.
Progressive stamping operation generally encompasses punching, coining, bending several other ways of modifying a metal sheet. In progressive stamping operation a metal sheet is controllably fed through a stamping tool that comprises of a die plate and punch plate. The metal sheet proceeds through multiple stages in the progressive stamping operation in which a die plate and punch plate repetitively stamp out portions of metal in each stage of operation. As the metal sheet moves incrementally though each stage, the die plate and the punch plate close on each other and perform the stamping of the metal sheet until a finished metal part(s) is formed.
In a factory operation for manufacturing rotor and stator laminations that use high speed press systems, it is desirable to optimize the stamping tool of the press system so as to increase the efficiency of the progressive stamping operation. An example of such an optimization may include a reduction in the stamping tool size in a way such that the same

number of finished parts is obtained per stamping operation. A smaller stamping tool also
effectively requires a lesser area of metal sheet per stamping operation, thereby reducing the
effective metal requirement.
OBJECTS OF THE INVENTION
An object of the invention is to provide for a method of progressive stamping of a metal
sheet to obtain rotor and stator laminations of an alternator.
Another object of the invention is to provide a reduced size stamping tool to be used in progressive stamping of a metal sheet to form rotor and stator laminations. DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, disclosed herein is a method and a progressive stamping tool to obtain rotor and stator lamination.
According to an inventive method, rotor and stator laminations are progressively stamped out of a metallic sheet in a press system. In a single cycle of operation, rotor and stator laminations are simultaneously punched out from a metallic sheet that undergoes a progressive stamping in a sequence of three stages. A rotor lamination is formed in the first and second stages whereas, a stator lamination is formed in the third stage.
In one embodiment of the invention, a progressive stamping tool comprises of a die plate having a first rotor die and a second rotor die and a stator die; a punch plate having a first rotor punch a second rotor punch and a stator punch, the punch plate being aligned with the die piate and provided a guided motion that is synchronized with a continuous feed of metal

sheet such that the corresponding die operates with the corresponding punch at regular intervals of time to stamp out metallic portions from the metallic sheet.
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
Figure I illustrates a progressive stamping tool according to an embodiment of the present invention.
Figure 2 illustrates a metallic sheet and the stages involved in a cycle of operation of progressive stamping according to an embodiment of the present invention.
Figure 1 illustrates a progressive stamping tool, which is to be used in a press system (not shown) that comprises of a die plate 1 and a punch plate 2. The die plate 1 and the punch plate 2 perform a progressive stamping operation on a metal sheet that is positioned between them. The metal sheet proceeds through multiple stampings by different portions of the die plate 1 and punch plate 2 in a single cycle of operation. Each portion of die plate 1 and a corresponding portion of punch plate 2 define a stage of progressive stamping in the single cycle of operation. According to the present invention the rotor and the stator lamination are obtained in three stages of the progressive stamping of metal sheet. Die plate 1 is shown having a rotor die 1001, a rotor die 1002 and a stator die 1003. Punch plate 2 is shown having a rotor punch 2001, a rotor punch 2002 and a stator punch 2003. Rotor die 1001 and rotor punch 2001 form the first stage of stamping operation. Rotor die 1002 and rotor punch 2002

form the second stage of stamping operation. Stator die 1003 and stator punch 2003 form the third stage of stamping operation.
The punch plate 2 and the die plate 1 coordinate with each other in a manner such that the respective die portions and corresponding punch portions press against each other thereby causing the progressive stamping of the metal sheet between them. The die portions on die plate 1 and corresponding punch portions punch plate 2 define geometries of the metal sheet portion removed in each of the three stages of operation. The die plate 1 is provided holes 10 within which vertical members 201 are firmly fixed. The punch plate 2 has holes 20 through which the vertical members 201 are disposed. A press system moves the punch plate 2 upwardly and downwardly limited by a stroke length that is equal to the length of the vertical members 201. The vertical members 201 help in providing a guided and aligned motion for the punch plate 2 over die plate 1, which is held stationary relative to the punch plate 2.
In the first stage of progressive stamping operation rotor die 1001 and rotor punch 2001 form a part of the required rotor lamination. Rotor die 1001 has four holes represented by 11 and the rotor punch 2001 has four pins represented by 21 that form pilot holes on the metallic sheet. The pilot holes that are formed are used to locate the portion of the metallic sheet that need to operate upon in the second stage of operation. The hollow portion 13 and protruding portion 23 represents respective portions in rotor die 1001 and rotor punch 2001 that are used to remove identical circumferential portions of a required radius for the rotor lamination from the metallic sheet to form the required number of pole sections for the rotor lamination. Although that the geometry of hollow portion 13 and 23 figure 1 illustrate the structure for

the rotor die 1001 and rotor punch 2001 to form 4 pole sections, a person of average skill in the art would be aware of the required geometry for a hollow portion 13 and a protruding portion 23 to obtain required number of pole sections.
Rotor die 1001 is shown having a four sets of five holes represented by 12 and are required to provide for holes in a rotor lamination required by damping rods. The holes required for damping rods are provided for by four sets of five pins represented by 22. The hollow portion 14 and the protruding portion 24 represents respective portions in the rotor die 1001 and rotor punch 2001 that is used to remove a portion from the metallic sheet for the central hole for a rotor shaft bore. The first stage of progressive stamping operation as mentioned above results in formation of a part of the rotor lamination on the metal sheet that proceeds further to be processed in the second stage of operation in the next cycle of progressive stamping operation.
In the second stage of progressive stamping operation rotor die 1002 and rotor punch 2002 form the required rotor lamination. In the second stage rotor punch 2002 locates the metallic portion to operate upon by locating the pilot holes 34 formed in the first stage by means of four pins 26 and blanks a circular portion of the required radius of the rotor lamination. The protruding circular portion in the rotor punch 2002 blanks a circular portion of the metal sheet of the required radius to form the rotor lamination with required number of pole sections. The rotor laminations as formed are stacked together such that the pole sections of the laminations are aligned together to result in a rotor.

Stator die 1003 and stator punch 2003 form the third stage of progressive stamping operation and forms the stator lamination. The ring shaped portion is decided by an outer edge 27 and inner edge 26 in the stator punch 2003 and a corresponding outer edge 17 and inner edge 16 in the stator die 1003. The stator punch 2003 forms the stator lamination by blanking a ring shaped portion having the inner edge 26 of a required radius, that is almost the same as the radius of the rotor lamination formed in the second stage, with identical serrations 28 that are equally spaced along the inner edge 26. Stator die 1003 has hollow portion 18 that corresponds to the identical serrations 28 in the stator punch 2003 .The stator laminations formed are stacked together form a stator and the identical serrations aligned with each other form winding slots in the stator.
The three stages of progressive stamping is illustrated in, the next figure for a progressive stamping tool that stamps out a rotor lamination having four pole sections.
Figure 2 illustrates a metallic sheet that undergoes the progressive stamping operation and the stages involved in a cycle of operation. Metallic sheet portion 3001-3003 represents the fist stage, second stage and the third stage of progressive stamping in a single cycle of operation in which the shaded portions represent the metal portions removed in each stage of operation. 3001 is formed by a rotor die 1001 and rotor punch 2001. Rotor die 1001 is shown having four holes represented by i 1 and the rotor punch 2001 is shown having four pins represented by 21 that form pilot holes on the metallic sheet. The pilot holes that are formed are used to locate the portion of the metallic sheet that need to operate upon in the second stage of operation. The four vacant portions 33 represent identical circumferential portions of

a required radius to form four pole sections for the rotor lamination and are formed by hollow portion 13 of rotor die 1001 and protruding portion 23 of rotor punch 2001. Four sets of five holes each represented by 32 are formed by four sets of five holes in rotor die 1001 represented by 12 and four sets of five pins represented by 22 in rotor punch 2001. Vacant portion 34 represents the metallic portion removed for the central vent hole for a rotor shaft bore and is formed by the hollow portion 14 and the protruding portion 24 represents respective portions in the rotor die 1001 and rotor punch 2001.
3002 represents the second stage of stamping operation and is formed by a rotor die 1002 and rotor punch 2002. The metallic portion to operate upon is identified by first locating the pilot holes 14 as formed in the first stage. The 4 pilot holes are located by the four pins 15 present in rotor punch 2002. Rotor punch 2002 blanks a circular portion of a radius of the required rotor lamination.
3003 represents the third stage of stamping operation and is formed by stator die 1003 and stator punch 2003. The stator punch 2003 forms a stator lamination by blanking a ring shaped portion having an outer edge 37 of a required radius and an inner edge 36 with identical serrations 38 that are equally spaced along its surface. The stator lamination is by blanking the ring shaped portion having the inner edge 36 of a required radius that is almost the same as the radius of the rotor lamination. The stator laminations formed are stacked together form a stator pack and the serrations aligned with each other form winding slots in the stator.
We Claim:

1. A method for punching out rotor and stator laminations simultaneously from a metallic sheet in a progressive stamping press system wherein the press system operates in a sequence of three stages in a cycle of operation and the rotor is formed in the first and second stages and the stator is formed in the third stage.
2. The method of claim 1, wherein
the first stage of operation on the metallic sheet comprising of removing identical circumferential portions of a first pre-determined radius from the metallic strip that correspond to a desired number of pole sections in the rotor lamination; piercing a central hole in the for a rotor shaft bore; piercing a plurality of pilot holes; piercing for a plurality of damping holes;
wherein the second stage of operation comprises of locating the metallic sheet to operate upon by identifying the pilot holes; blanking a round circular portion having the first predetermined radius to obtain the rotor lamination; and
wherein the third stage of operation comprises of blanking a ring shaped portion having an inner edge defined by a pre-determined inner radius and with a plurality of identical serrations that are equally spaced along the inner edge, to obtain the stator lamination.
3. The method of claim 1 where in the press system is an H frame press system.
4. A progressive stamping tool for use in a press system, the tool comprising of a die plate having a first rotor die and a second rotor die and a stator die; a punch plate having a first rotor punch a second rotor punch and a stator punch, the punch plate being aligned with the die plate and provided a guided motion that is synchronized with a continuous feed of metal sheet such that the corresponding die operates with the

corresponding punch at regular intervals of time to stamp out metallic portions from the metallic sheet.
5. The progressive stamping tool of claim 4,
wherein the geometry of first rotor die and the first rotor punch is such that it forms desired number of pole sections in a rotor lamination by removing identical portions from the metallic sheet;
wherein the geometry of second rotor die and second rotor punch is such that it removes the rotor lamination from the metallic sheet; and
wherein the geometry of the stator die and the stator punch is such that it removes a ring shaped element with a plurality of identical serrations that are equally spaced along the inner edge thereby forming a stator lamination from the metallic sheet.
6. The progressive stamping tool of claim 4, wherein the press system is an H frame press
system.