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 power press tool
APPLICANT
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Chandrashekhar Ramakant Keluskar and Jayprakash Maharana of Stamping Division, Crompton Greaves Ltd, Kanjur Marg, Mumbai, Maharashtra, India, both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in
which it is to be performed:

FIELD OF THE INVENTION
[001] The present invention relates generally to power presses and more
particularly, to power press tools for punching out rotor dampers from sheet materials.
DESCRIPTION OF THE BACKGROUND ART
[002] Power punch presses are commonly known and are highly useful
for producing various types of cutouts in sheet-like work pieces of metal, plastic, composite materials and the like in one stroke of the punching section against the die bed. Generally, the punch has a protruding cutting profile extending therefrom and the die has a similar passage therein conforming the punch. A sheet is positioned on the die bed and the punching section, which moves along a punching axis, strikes the sheet with an impact resulting in creation of a profile on the sheet material. Such power punch presses find immense application in formation of dampers capable of being used within alternators. Such dampers are positioned at each end of the rotor core laminations and tied together.
[003] Typically, in industries where a larger dampers throughput is
required power punching presses of larger capacity is used. Such, presses have large die section as well as punch section wherein during one stroke on the sheet material one damper is formed. On manipulating the frequency of the strokes on the sheet material, a particular requirement of dampers can be quite easily met. A factor that must be considered in punch design is that the width of the punch must be at least as great as, and preferably greater than, the thickness of the sheet material. If not, the punch is subject to breakage. Moreover, polygonal punches wear more rapidly in cutting sheet material than does a tool of circular cross

section, and this is particularly significant as thicker sheet material is being punched.
[004] However, the problem arises when the requirement of dampers are
not that large. In such a scenario, usage of large die and section assembly is not a cost effective option. Even reducing the size up to acceptable levels will still not be enough to save on costs. Thus, there is a need to find a solution of small and medium scale industries where requirement of larger churning out of dampers is not there and cost of die and punch assembly is more.
SUMMARY OF THE INVENTION
[005] Accordingly.disclosed herein is a power press tool for punching out
rotor dampers, wherein each of the dampers comprising a central body having a central hole and a plurality of limbs radially extending from the central opening, the plurality of limbs arranged in spaced apart relationship with each other, each of the limbs having a substantially T-shaped profile with an arcuate outer end, and wherein the tool including a horizontally extending punch segment fixedly attached to a punch holder, the punch segment having an arcuate cutting portion and a cutting protrusion extending inwardly from the arcuate cutting portion, the cutting protrusion resembling space between any two immediate limbs, and a die segment fixedly attached to a die bed and supporting a sheet material, the die segment having a slug passage formed therethrough that conforms the arcuate cutting portion and the cutting protrusion of the punch segment, the die bed and the punch holder being relatively movable along a punching axis and cooperating with other to punch the sheet material, wherein a corner area of the sheet material is positioned over the slug passage and punched so as to allow the arcuate cutting portion of the punch segment to knock out the outer end of the limb and to allow

the cutting protrusion to knock out space between any two immediate limbs, other corner areas being sequentially rotated and punched thereby forming the plurality of limbs of the damper.
[006] According to some embodiments, the punch segment further
includes a plurality of projections formed on the arcuate cutting portion, and wherein the slug passage of the die segment having conforming serrations formed therethrough, the plurality of projections of the punch segment knocking out serrations on the arcuate outer end of the limb of the damper.
[007] According to some embodiments, the punch holder includes at least
one punching rod protruding outwardly from a surface thereof and disposed adjacent to the punch segment, and wherein the die segment having a hole conforming the punching rod, the punching rod creating a mounting hole within the damper.
[008] According to some embodiments, the die segment further including
a support pad attached to an edge of the die segment, the die pad supporting the sheet material during punching operation.
[009] It is to be understood that both the foregoing general description
and the following detailed description of the present Embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention.

A BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The above-mentioned and other features and advantages of the
various embodiments of the invention, and the manner of attaining them, will become more apparent and will be better understood by reference to the accompanying drawings, wherein:
[0011] FIG. 1 is a front side perspective view of a punch holding plate
having a punch segment attached thereon, according to an embodiment of the present invention;
[0012] FIG. 2 is a front side perspective view of a punch holder having the
punch holding plate of FIG. 1;
[0013] FIG. 3 is a front perspective view of a die bed having a die segment
attached thereon according to an embodiment of the present invention;
[0014] FIGS. 4a-4d illustrate a typical punching operation on a sheet
material positioned on the die segment of FIG. 4 according to an embodiment of the present invention; and
[0015] FIG. 5 shows a front view of a rotor damper formed out of the
sheet material after completion of the punching operation as shown in FIGS. 4a-
4d.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] FIG. 1 shows a punch segment 100 and a back-up plate 102 fixedly
attached to a punch holding plate 104 according to an embodiment of the present invention. The punch segment 100 is fixedly attached to the back-up plate 102 via known means, for example welding. Similarly, the back-up plate 102 is also fixedly attached to a top surface 106 of the punch holding plate 104. Both the

punch segment 100 and the back-up plate 102 are designed to have similar shape and horizontally extend over the top surface of the punch holding plate 104. As seen in FIG. 1, the punch segment 100 has an arcuate cutting portion 108 of a sufficient length and a cutting protrusion 110 extending inwardly from the arcuate cutting portion 108 on the punch holding plate 104. The arcuate cutting portion 108 is defined a pair of arcuate cutting edges 112 defining the outer periphery of the arcuate cutting portion 108. Preferably, the cutting protrusion 110 is of a hexagonal shape defined by six cutting edges 114. When the punch segment 100 rams on to a sheet material 116 placed on a die (See FIGS. 4a-4d), all of the cutting edges of the punch segment 100 as well as the cutting protrusion 110 cut the sheet material 116 so as to form shape of the punch segment 100 thereon. Preferably, one of the arcuate cutting edges 112 has a plurality of projections 118 evenly formed thereon. When the punch segment 100 strikes the sheet material 116, it creates serrations 150 of similar shape as that of the plurality of projections 118. It should be, however, understood that the plurality of projections 118 may have any shape according to the final cutting required on the sheet material 116.
[0017] FIG. 2 shows a front perspective view of a punch holder 120
holding the punch holding plate 104 thereon. Preferably, a pair of punch holding plates 104 is fixedly attached to the punch holder 120 by known means. Preferably, the punch holding plate 104 is rectangular in shape and at least four circular hollow tubes 124 extends from a top surface 126 of the punch holder 120 plate. Two of the circular hollow tubes 124 are positioned on one side 128 of the punch holder 120, whereas the other two of the circular hollow tubes 124 are positioned on the opposite side 130 of the punch holder 120. Additionally, there is also a pair of punch rods 132 extending from centre of the top surface. As shown

in FIG. 2. the punch plate 104 that has a pair of corresponding holes 134 to receive the pair of punch rods 132 therein. These pair of punch rods 132 when rammed into the sheet material 116 creates a pair of holes 136 thereon (See FIGS. 4a-4d, 5). During punching operation, the punch holder 120 is turned up side down and operatively attached to a moving carriage (not shown) that guidingly moves the punch holder 120 along a punching axis towards the die.
[0018] Referring to FIG. 3, a die bed 138 having a die segment 140
fixedly disposed a top surface 142 of the die bed 138 is shown. Preferably, the die segment 140 is fixedly attached to a die plate 144 which in turn is fixedly disposed on the top surface of the die bed 138. The die segment 140 has a slug passage 146 formed therethrough that allows the punch segment 100 to be received therein during punching operation for creating profiles on the sheet material 116. As seen in FIG. 3, the die also has an identical slug passage 146 formed therethrough. Shape of the slug passage 146 of both the die segment 140 and the die plate 144 are identical. The shape of the slug passage 146 conform the shape of the punch segment 100 so that when the punch segment 100 rams the sheet material 116 placed on the die bed 138, a profile similar to that of the punch segment 100 is created thereon. A pair of holes 148 is also formed on the die segment 140 for receiving a corresponding pair of punching rods therein. Preferably, one of the edges of the slug passage 146 has serrations 150 formed therein conforming the shape of the plurality of protrusions on the punch segment 100. According to another embodiment of the present invention and as seen in FIG. 3, a support pad 152 is also attached to an edge 154 of the die segment 140. The support pad 152 supports the sheet material 116 when positioned thereon during punching operation.

[0019] The die bed 138, which is preferably rectangular in shape, has a
slug passage 146 formed therein. Outer boundary of the slug passage 146 matches the slug passages 146 of the die segment 140 and the die plate 144. Preferably, the die bed 138 has at least four guide rods 156 protruding outwardly therefrom with each of the guide rods 156 has a bulging portion 158 on its free end 160. Preferably, a pair of the guide rods 156 is disposed at one side 162 of the die bed 138 whereas the other pair of guide rods 156 is disposed at the opposite side 164 of the die bed 138. Each of the guide rods 156 is capable of being received within a corresponding circular tube of the punch holder 120. The guide rods 156 are movably connected within the circular hollow tubes 124 so as to allow the die bed 138 to move against the punch holder 120. The punch holder 120 is movable against the die bed 138 along a punching axis. In the above various embodiments of the present invention, the punch holder 120 and the die bed 138 may be used within a power press punching machine (not shown) that punches out rotor dampers.
[0020] Referring now to FIGS. 4a-4d, a process of the punching out rotor
dampers is shown, according to an embodiment of the present invention. Before the operation starts the sheet material 116 is positioned on the die segment 140 in such a manner that a first corner portion 166 of the sheet material 116 lies over the slug passage 146 of the die segment 140. The sheet material 116, as can be seen in FIGS. 4a- 4d, has a central opening 168 formed therein. The central opening 168 is pre-formed in the sheet material 116 by known means. The punch holder 120 then rams onto the sheet material 116 in known mariner thereby allowing the arcuate cutting portion 108 and the cutting protrusion 110 of the punch segment 100 to enter into the slug passage 146 of the die segment 140 thereby cutting the

sheet material 116. The arcuate cutting edges 112 having the plurality of protrusions formed thereon cuts the sheet to form serrations 150 thereon whereas the cutting protrusion 110 cuts a hexagonal shape on the sheet material 116. The hexagonal shape represents shape of the cutting protrusion 110 of the punch segment 100. Once, the first ramming of the punch holder 120 is done, the sheet material 116 is turned in anticlockwise direction so as allow the other corner area to be positioned on top of the slug passage 146. This positioning is shown in FIG. 4b where a partial first limb 170 of the sheet material 116 is formed. Thereafter, the punch holder 120 is rammed onto a second corner portion 172 for the second time. Due to the second-time punching of the punch segment 100, a similar serrations 150 and hexagonal profile is formed on the sheet material 116. A skilled person would easily make out that after the second punching a complete first limb 170 is formed whereas a partial second limb 174 is created.
[0021] As shown in FIG. 4c, the second-time punched sheet material 116
is further rotated in anti-clockwise direction so that a third corner portion 176 is positioned on the slug passage 146 and punched thereby fully creating the second limb 174 and partially creating a third limb 178. Accordingly, FIG. 4d shows a fourth punching operation wherein a fourth corner portion 180 of the sheet material 116 is punched thereby fully creating the third limb 178 and partially creating the fourth limb 182. A further stroke of the punch segment 100 creates all the four limbs accordingly. A fully complete damper 184 with four limbs and the central opening 168 obtained at the end of the punching process. The damper 184 obtained is shown in FIG. 5. The damper 184 has four T-shaped limbs radially extending from the central opening 168 and having a T-shaped profile 186. Each of the T-shaped profile 186 is arranged in spaced apart relationship

from each other. An end of the T-shaped limb has an arcuate out end 188 and the space between any two of the limbs has a shape of the cutting protrusion of the punch segment 100.
[0022] It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

We Claim:
1. A power press tool for punching out rotor dampers, wherein each of the dampers comprising a central body having a central hole and a plurality of limbs radially extending from the central opening, the plurality of limbs arranged in spaced apart relationship with each other, each of the limbs having a substantially T-shaped profile with an arcuate outer end, and wherein the tool comprising:
a horizontally extending punch segment fixedly attached to a punch holder, the punch segment having an arcuate cutting portion and a cutting protrusion extending inwardly from the arcuate cutting portion, the cutting protrusion resembling space between any two immediate limbs; and
a die segment fixedly attached to a die bed and supporting a sheet material, the die segment having a slug passage formed therethrough that conforms the arcuate cutting portion and the cutting protrusion of the punch segment, the die bed and the punch holder being relatively movable along a punching axis and cooperating with other to punch the sheet material, wherein
a corner area of the sheet material is positioned over the slug passage and punched so as to allow the arcuate cutting portion of the punch segment to knock out the outer end of the limb and to allow the cutting protrusion to knock out space between any two immediate limbs, other corner areas being sequentially rotated and punched thereby forming the plurality of limbs of the damper.
2. The power press tool according to claim 1, wherein the punch segment further includes a plurality of projections formed on the arcuate cutting portion, and wherein the slug passage of the die segment having a conforming serrations formed

therethrough, the plurality of projections of the punch segment knocking out serrations on the arcuate outer end of the limb of the damper.
3. The power press tool according to claim 1, wherein the punch holder includes at least one punching rod protruding outwardly from a surface thereof and disposed adjacent to the punch segment, and wherein the die segment having a hole conforming the punching rod, the punching rod creating a mounting hole within the damper.
4. The power press tool according to claim 3, wherein a corresponding rotor damper is rotatably positioned on opposite ends of rotor core laminations, each of the rotor core laminations having a corresponding at least one mounting hole, a rod being passed through the mounting hole of the damper and the rotor core laminations so as to bind them together.
5. The power press tool according to claim 1, wherein the punch segment is fixedly attached to a back-up plate, the back-up plate being fixedly attached to the punch holder.
6. The power press tool according to claim 1, wherein the die segment further including a support pad attached to an edge of the die segment, the die pad supporting the sheet material during punching operation.