FORM 2
The Patents Act 1970
(39 of 1970) &
The Patent Rules 2003 COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:
CENTRALIZER ARRANGEMENT FOR COIL / STRIP

IN PRESS TOOLS

APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra . INDIA.

PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED


A) TECHNICAL FIELD
[0001] The present invention generally relates to a press tool assembly and particularly to press tools for processing coils or strip in progressive punching operations executed during the manufacturing process of sheet metal components used in applications such as electrical/electronic products, automobiles, watches etc. The present invention more particularly relates to a centralizer punch assembly used to centralize the strips or coils in press tools for maintaining the symmetry of holes with respect to coil/strip edges in punching operations.
B) BACKGROUND OF THE INVENTION
[0002] Press working is one of the major processing techniques for converting sheet metal into sheet metal parts of different shapes. The sheet metal parts are required for different applications such as electrical/ electronic products, automobiles, watches etc. The sheet metal is punched between two parts called punch and die. The die profile is the female profile intentionally kept bigger than the punch profile by a uniform gap called cutting clearance.
[0003] The press tool mainly consists of two halves, namely fixed bottom half and moving top half. The fixed bottom half is secured to the stationary bolster plate of mechanical press. The bottom half comprises of an arrangement to guide the strip/coil, die cavities, guide pillars for alignment of both halves etc. The top moving half is

clamped to the moving ram of the mechanical press and it comprises a number of circular and non circular cutting and non cutting elements called punches. The punches move up and down along with the moving ram of the mechanical press and they are guided in cavities made in a plate called Stripper. During downward movement, the punches penetrate the sheet metal and enter the die cavity thus pushing the sheet metal scrap displaced by the cutting punch into the lower half of the tool. One downward and return upward movement of the top half of press tool is called as stroke of press tool. Surrounding metal clings to the body of cutting punches during downward stroke. The same is stripped off by the stripper plate during upward stroke of the punches.
[0004] The press tools are of multi-station type or single station type. In a multi¬station tool, the strip moves from one end of strip guides to the other end. It moves progressively by a fixed distance called pitch after every stroke of the mechanical press. At each stage of movement of strip, different punching operations are carried out on strip / coil leading to completion of stamping profile in last stage.
[0005] Many times the nominal width of coil or strip is equal to maximum width of stamping to reduce the generation of scrap. The stampings have circular and non circular holes placed symmetrically with respect to the width of the stamping. The gap in the strip guides is always kept bigger than the maximum size of strip/coil width for ease of strip/coil feeding. It is not possible to ensure that the strip moves exactly at the middle of the gap between strip guides. The strip would move randomly and the position of the punched holes with respect to edges of coil width will vary randomly. This will not allow the maintenance of the symmetry of holes with respect to the strip/coil width leading to

rejection of stampings by quality control department. Many times, the width of the coil/strip is kept the same as the maximum size of the stamping to save material. In such cases, it is not possible to maintain symmetry of holes with respect to coil / strip edges. This has lead to the development of the said invention.
[0006] In convention press tools, the coil / strip width is more than the component width and the edges of the component were formed by notching operations. Hence an extra material is punched by notching punches to form outer edges of the component. However, this resulted in loss of material in the form of scrap generated by the notching punches.
[0007] Hence there is a need to provide a mechanism to centralize the strip or coils in press tools to ensure that the strip or coil moves exactly in the middle of the gap between the strip guides.
[0008] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECTS OF THE INVENTION
[0009] The primary object of the present invention is to provide a mechanism to centralize the strips /coils in press tools by using single piece or two piece centralizing punches of different sizes feasible, at one or more locations to maintain the symmetry of holes with respect to the coil/strip edges.

[0010] Another object of the present invention is to provide a centraiizer punches in press tools to ensure that the strip or coil moves exactly at the middle of the gap between the strip guides.
[0011] Yet another object of the present invention is to provide a centraiizer punch to maintain the symmetry of holes with respect to the outer coil or strip edges.
[0012] Yet another object of the present invention is to provide centralizers in press tools which is easy to assemble and which requires less maintenance.
[0013] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0014] The various embodiments of the present invention provide a mechanism for centralizing the strip or coils in press tool assembly by utilizing single or two piece centralizing punches of different sizes feasible at one or more locations. According to one embodiment, the centralizers are floating punches which is rectangular in shape and is guided in stripper plate. The centralizing punches are provided to guide the strip or coil exactly at the middle of the gap between strip guides. The centraiizer punch comprises of a taper surface at the bottom and a light spring above the centraiizer punch, a sleeve is

provided above the centrahzer punch. A washer is provided between Allen screw and the sleeve and between the centralizing punch and sleeve.
[0015] According to one embodiment of the present invention, a centrahzer arrangement for coil/strip in a press tool assembly has at least one centrahzer punch held in a punch holder plate which is provided in the press tool assembly. An Allen screw is mounted on the centrahzer punch. A sleeve is provided above the centrahzer punch. A spring is arranged around the sleeve. A first washer is provided between the Allen screw and the sleeve while a second washer is provided between the sleeve and the centrahzer punch. The centrahzer punch has a tapered surface at the end to come in contact with the coil/strip to exert a wedge effect on the coil/strip from both the sides to ensure that the coil/strip is not moved randomly and is kept centralized during the punch process. The tapered surface at the end is made to come in contact with the vertical edges of the coil/strip to exert a wedge effect on the coil /strip from both the sides to force coil/strip into the middle portion of a strip guide provided in a press tool assembly, irrespective of the size of the coil/strip to ensure that the coil/strip is not moved randomly and is kept centralized during the punch process.
[0016] Pluralities of the centrahzer punches are used in the press tool assembly, when the width of the coil/strip is bigger. The pluralities of the centrahzer punches are arranged on either side of the coil/strip at the entry point of the coil/strip before any punching station provided in the press tool assembly. The height of the all the centrahzer punches are identical. The taper angles of the taper surface provided at the centrahzer punches are

same and the point at which the taper surface starts in all the centralizer punches are also identical.
[0017] The spring has a height based on the stroke required for the centralizer punch, shut height of the press tool and the thickness of the coil/strip material. The load of the spring is designed in such a manner to prevent the formation of dent marks on the edges of the coil/strip. The sleeve is provided to reduce the pressure on the spring during fully downward stroke. The sleeve also ensures that the spring is not over tightened beyond the required length and force. The two washers are arranged to provide a resting surface for both the Allen screw and the centralizing punch with the punch holder plate.
[0018] When the pitch (the fixed distance travelled by strip during each stroke of press tool) is larger than the stamping size, one more pair of equalizers is provided in the press tool at a suitable location. Any extra downward movement of top half is compensated by the deflection of the spring above centralizer punch.
[0019] According to embodiment of the present invention, the press tool assembly comprises of a top plate, base plate, a die plate clamped to the base plate, a strip or coil to be guided on the die plate, a stripper plate with a cavity at the centre mounted on the die plate, holder plate clamped to the top plate, a centralizer punch to be guided in stripper cavity, washers, spring and a sleeve.
[0020] According to embodiment of the present invention, the single piece construction of centralizing punch is provided for strip or coil of smaller width and two piece constructions of centralizing punches are provided for strip or coil of larger width.

The single piece centralizer punch is a floating punch which is rectangular in shape and is guided in stripper plate. The single piece centralizer punch includes a taper surface at the bottom centre and a light spring above the equalizer punch, the complete assembly is held in the punch holder plate of the press tool. The sleeve is provided above the centralizer punch. The washers are provided between the Allen screw and the sleeve and between centralizing punch and sleeve. The washer provided ensures proper resting surface for both Allen screw and the centralizing punch. The spring is provided around the sleeve. The spring provided above the centralizer punch is in the pre compressed condition. The load on the spring is very light to avoid the dent marks on the edges of the strip or coil due to tapered surfaces of the centralizer punches. The height of the spring is maintained based on the stroke required for the centralizer unit, shut height of the press tool and the material thickness. The sleeve also ensures that the spring is not over tightened beyond the required length and force.
[0021] When the stroke on the press tool is in fully upward direction there is no gap between the top plate and the washer. Hence the centralizer punches and the punch will not come in contact with the strip or coil. When the stroke on press tool is in fully downward direction, the spring above the centralizer punch is compressed and the tapered surfaces of the centralizer punch come in contact with the strip or coil. This ensures that the strip or coil would not move randomly and will be centralized. Any extra downward movement of top half is compensated by the deflection of the spring above centralizer punch.

[0022] According to one embodiment, the two piece construction of centralizing punches is provided for guiding strip or coil of larger width. The centralizer punchers are located on either side of coil at the entry of strip or coil before any punching station in the press tool. The centralizers include a taper surface at the bottom sides and a light spring above the equalizer punch, the complete assembly is held in the punch holder plate of the press tool. The construction and working of the two piece centralizer punches is same as that of the single piece centralizer punch. When the stroke on the press tool is in fully downward direction, the spring above the centralizer punches is compressed and the tapered surfaces of the equalizer punches come in contact with the vertical edges of strip or coil and exert wedge effect on the strip or coil from both the sides. The wedge effect forces the strip or coil into the middle portion of strip guide gap irrespective of the size of strip or coil width. Hence the strip or coil will not move randomly and will be centralized. The extra downward movement of top half of press tool is compensated by the deflection of the spring above centralizer punch.
[0023] The centralizing punches ensure that the strip or coil moves exactly at the middle of the gap between the strip guides. It helps in maintaining the symmetry of holes with respect to the outer coil or strip edges. The assembling and maintenance of the centralizers are very easy.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
9

[0025] FIG.l shows a sectional view of a press tool assembly provided with a centralizer arrangement according to one embodiment of the present invention.
[0026] FIG. 2 illustrates a top view of strip layout showing symmetrical component profiles in the press tool assembly provided with a centralizer arrangement, according to one embodiment of the present invention.
[0027] FIG.3 shows a sectional view of the press tool assembly with a single piece centralizer punch, according to one embodiment of the present invention.
[0028] FIG. 4 shows a sectional view of a press tool assembly with a two piece centralizer punches when the stroke is in fully upward direction, according to one embodiment of the present invention.
[0029] FIG. 5 shows a sectional view of the press tool assembly with a two piece centralizer punch when the stroke is towards downward direction, according to one embodiment of the present invention.
[0030] FIG. 6 shows a sectional view of the press tool assembly with a two piece centralizer punch when the stroke is towards fully downward direction, according to one embodiment of the present invention.
[0031] FIG. 7 shows a plan view of bottom half of the press tool assembly with the two piece centralizer construction, according to one embodiment of the present invention.

[0032] FIG. 8 shows a plan view of the top half of the press tool assembly two piece centralizer construction, according to one embodiment of the present invention.
[0033] FIG. 9 shows a sectional view of a centralizer punch for single piece construction, according to one embodiment of the present invention.
[0034] FIG. 10 shows a sectional view of a centralizer punch for two piece centralizer construction, according to one embodiment of the present invention.
[0035] FIG. 11 shows a sectional view of a sleeve provided above the centralizer punch, according to one embodiment of the present invention.
[0036] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0037] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

[0038] The various embodiments of the present invention provide a mechanism for centralizing strip or coils in press tool assembly by utilizing single or two piece centralizing punches of different sizes feasible at one or more locations. According to one embodiment, the centralizers are floating punches which is rectangular in shape and is guided in stripper plate. The centralizing punches are provided to guide the strip or coil exactly at the middle of the gap between strip guides. The centralizer punch comprises of a taper surface at the bottom and a light spring above the centralizer punch, a sleeve is provided above the centralizer punch. A washer is provided between Allen screw and sleeve and between centralizing punch and sleeve.
[0039] According to one embodiment of the present invention, a centralizer arrangement for coil/strip in a press tool assembly has at least one centralizer punch held in a punch holder plate which is provided in the press tool assembly. An Allen screw is mounted on the centralizer punch. A sleeve is provided above the centralizer punch. A spring is arranged around the sleeve. A first washer is provided between the Allen screw and the sleeve while a second washer is provided between the sleeve and the centralizer punch. The centralizer punch has a tapered surface at the end to come in contact with the coil/strip to exert wedge effect on the coil/strip from both the sides to ensure that the coil/strip is not moved randomly and is kept centralized during the punch process. The tapered surface at the end is made to come in contact with the vertical edges of the coil/strip to exert a wedge effect on the coil /strip from both the sides to force coil/strip into the middle portion of a strip guide provided in a press tool assembly, irrespective of the size of the coil/strip to ensure that the coil/strip is not moved randomly and is kept centralized during the punch process.

[0040] Pluralities of the centralizer punches are used in the press tool assembly, when the width of the coil/strip is bigger. The pluralities of the centralizer punches are arranged on either side of the coil/strip at the entry point of the coil/strip before any punching station provided in the press tool assembly. The height of the all the centralizer punches are identical. The taper angles of the taper surface provided at the centralizer punches are same and the point at which the taper surface starts in all the centralizer punches are also identical.
[0041] The spring has a height based on the stroke required for the centralizer punch, shut height of the press tool and the thickness of the coil/strip material. The load of the spring is designed in such a manner to prevent the formation of dent marks on the edges of the coil/strip. The sleeve is provided to reduce the pressure on the spring during fully downward stroke. The sleeve also ensures that the spring is not over tightened beyond the required length and force. The two washers are arranged to provide a resting surface for both the Allen screw and the centralizing punch with the punch holder plate.
[0042] When the pitch (the fixed distance travelled by strip during each stroke of press tool) is larger than the stamping size, one more pair of equalizers is provided in the press tool at a suitable location. Any extra downward movement of top half is compensated by the deflection of the spring above centralizer punch.
[0043] According to embodiment of the present invention, the press tool assembly comprises of a top plate, base plate, a die plate clamped to the base plate, a strip or coil to be punched is mounted on the die plate, a stripper plate with a cavity at the centre

mounted on the die plate, holder plate clamped to the top plate, a centralizer punch to be guided in stripper cavity, washers, spring and a sleeve.
[0044] According to embodiment of the present invention, a single piece construction of centralizing punch is provided for strip or coil of smaller width and two piece constructions of centralizing punch is provided for strip or coil of larger width. The single piece centralizer punch is a floating punch which is rectangular in shape and is guided in stripper plate. The single piece centralizer punch includes a taper surface at the bottom centre and a light spring above the equalizer punch, the complete assembly is held in the punch holder plate of the press tool. The sleeve is provided above the centralizer punch. The washers are provided between the Allen screw and the sleeve and between centralizing punch and sleeve. The washer provided ensures proper resting surface for both Allen screw and the centralizing punch. The spring is provided around the sleeve. The spring provided above the centralizer punch is in the pre compressed condition. The load on the spring is very light to avoid the dent marks on the edges of the strip or coil due to tapered surfaces of the centralizer punches. The height of the spring is maintained based on the stroke required for the centralizer unit, shut height of the press tool and the material thickness. The sleeve also ensures that the spring is not over tightened beyond the required length and force.
[0045] When the stroke on the press tool is in fully upward direction there is no gap between the top plate and the washer. Hence the centralizer punches and the punch will not come in contact with the strip or coil. When the stroke is towards fully downward direction, the spring above the centralizer punch is compressed and the tapered surfaces

of the centralizer punch come in contact with the strip or coil. This ensures that the strip or coil would not move randomly and will be centralized. Any extra downward movement of top half is compensated by the deflection of the spring above centralizer punch.
[0046] According to one embodiment, the two piece construction of centralizing punches is provided for guiding strip or coil of larger width. The centralizer punchers are located on either side of coil at the entry of strip or coil before any punching station in the press tool. The centralizer includes a taper surface at the bottom sides and a light spring above the equalizer punch, the complete assembly is held in the punch holder plate of the press tool. The construction and working of the two piece centralizer punches is same as that of the single piece centralizer punch. When the stroke on the press tool is in fully downward direction the spring above the centralizer punches is compressed and the tapered surfaces of the equalizer punches come in contact with the vertical edges of strip or coil and exert wedge effect on the strip or coil from both the sides. This wedge effect forces the strip or coil into the middle portion of strip guide gap irrespective of the size of strip or coil width. This ensures that the strip or coil would not move randomly and will be centralized. Any extra downward movement of top half is compensated by the deflection of the spring above centralizer punch.
[0047] The centralizing punch ensures that the strip or coil moves exactly at the middle of the gap between the strip guides. It helps in maintaining the symmetry of holes with respect to the outer coil or strip edges. The assembling and maintenance of the centralizers are very easy.

[0048] FIG.l shows a sectional view of a press tool assembly, according to one embodiment of the present invention. The press tool assembly mainly consists of two halves, namely fixed bottom half and moving top half. The fixed bottom half is secured to the stationary bolster plate of mechanical press. It comprises of an arrangement to guide the strip/coil, die cavities, guide pillars for alignment of both halves etc. The top moving half is clamped to the moving ram of the mechanical press and it comprises a number of circular and non circular cutting and non cutting elements called punches 8. The base plate 2 is clamped to the fixed bottom part. The die plate 3 is clamped on the base plate 2 with the strip or coil to be punched is guided on the die plate 3. The stripper plate 5 is clamped to the die plate 3. The top plate 1 is clamped to the moving top half. The holder plate 6 is clamped to the top plate 1. The holder plate holds the punches 8. The punches 8 move up and down along with the moving ram of the mechanical press and they are guided in cavities made in a plate called stripper plate 5. During downward movement, the punches 8 penetrate the sheet metal and enter the die cavity thus pushing the sheet metal scrap displaced by the cutting punch into the lower half of the tool. The surrounding metal clings to the body of cutting punches during downward stroke. The same is stripped off by the stripper plate 5 during upward stroke of the punches 8.
[0049] FIG. 2 illustrates a strip layout showing symmetrical component profiles, according to one embodiment of the present invention. With reference to FIG. 2, the centralizing punches are provided on either side to guide the strip or coil exactly at the middle of the gap between strip guides. The strip layout shows a symmetrical component

profiles with the holes required at the centre of the component. The stamping component width is equal to the strip width to reduce the generation of scrap.
[0050] FIG.3 shows a sectional view of the press tool assembly with a single piece centralizer punch 30, according to one embodiment of the present invention. With reference to FIG. 3, the press tool assembly includes fixed bottom half and moving top half. The base plate 2 is clamped to the fixed bottom part. The die plate 3 is clamped on the base plate 2 with the strip or coil 4 to be punched is guided on the die plate 3. The stripper plate 5 is clamped to the die plate 3 with a cavity to guide the centralizer punch 30 and the punch. The moving top half is clamped to the moving ram of the mechanical press. The holder plate 6 is clamped to the moving top half. The holder plate 6 holds the centralizer punch 30 and the cutting punch. With reference to FIG. 3, the centralizer punch 30 is located on the strip or coil before punching in the press tool. The centralizer punch includes a taper surface at the bottom centre and a light spring 12 above the equalizer punch. The complete assembly is held in the punch holder plate 6 of the press tool.
[0051] The centralizer 30 for single piece construction is a floating punch which is rectangular in shape and is guided in stripper plate 5. The single piece construction of centralizing punch 30 is provided for strip or coil 4 of smaller width. The centralizing punch 30 ensures that the strip or coil 4 moves exactly at the middle of the gap between the strip guides. It helps in maintaining the symmetry of holes with respect to the coil or strip edges.

[0052] The sleeve 11 is provided above the centralizer punch 30. The washers 10 are provided between the Allen screw 9 and the sleeve 11 and between centralizer punch 30 and sleeve 11. The washer 10 provides resting surface for both Allen screw 9 and the centralizer punch 30. The spring 12 is provided around the sleeve 11. The spring 12 provided behind the centralizer punch 30 is in the pre compressed condition. The load on the spring 12 is very light to avoid the dent marks on the edges of the strip or coil 4 due to the tapered surface of the centralizer punches 30. The height of the spring 12 is maintained based on the stroke required for the centralizer unit, the shut height of the press tool and the material thickness. This also ensures that the spring 12 is not over tightened beyond the required length and force.
[0053] When the stroke is in fully upward direction, there is no gap between the top plate 1 and the washer 10. Hence the centralizer punch 30 and the punch will not come in contact with the strip or coil 4. When the stroke is towards fully downward direction, the spring 12 above the centralizer punch 30 is compressed and the tapered surfaces of the centralizer punch 30 come in contact with the strip or coil 4. This ensures that the strip or coil 4 will not move randomly and will be centralized. The extra downward movement of top half is compensated by the deflection of the spring 12 above centralizer punch 30.
[0054] FIG. 4 shows a press tool assembly with a two piece centralizer when the stroke is in fully upward direction, according to one embodiment of the present invention. With reference to FIG.4 the press tool assembly includes a fixed bottom half and a moving top half. The base plate 2 is clamped to the fixed bottom part. The die plate 3 is clamped on the base plate 2 with the strip or coil 4 to be punched is guided on the die

plate 3. The stripper plate 5 is mounted on the die plate 3 with a cavity to guide the centralizer punches 7 and the cutting punch 8. The moving top half is clamped to the moving ram of the mechanical press. The holder plate 6 is clamped to the moving top half. The holder plate 6 holds the centralizer punches 7 and the cutting punch 8. With reference to FIG. 4, the centralizer punches 7 are located on either side of strip or coil 4 before punching in the press tool. The centralizer punches 7 includes a taper surface at the bottom side and a light spring 12 above the equalizer punch, the complete assembly is held in the punch holder plate 6 of the press tool.
[0055] The centralizer punches 7 are floating punches which are rectangular in shape and are guided in stripper plate 5. The two piece construction of centralizing punches is used for strip or coil of bigger width. The centralizing punches 7 ensure that the strip or coil 4 moves exactly at the middle of the gap between the strip guides. It helps in maintaining the symmetry of holes with respect to the outer coil or strip edges. The sleeve 11 is provided above the centralizer punches 7. The washers 10 are provided between the Allen screw 9 and the sleeve 11 and between centralizing punch 7 and Sleeve 11. The washer provides resting surface for both Allen screw 9 and the centralizing punches 7. The spring 12 is provided around the sleeve 11. The spring 12 provided behind the centralizer punch 7 is in the pre compressed condition. The load on the spring 12 is very light to avoid the dent marks on the edges of the strip or coil 4 due to tapered surfaces of the centralizer punches 7. The height of the spring 12 is maintained based on the stroke required for the centralizer unit, shut height of the press tool and the material thickness. This also ensures that the spring 12 is not over tightened beyond the required length and force. When the stroke is in fully upward direction there is no gap

between the top plate 1 and the washer 10. Hence the centralizer punches 7 and the cutting punch 8 will not come in contact with the strip or coil 8.
[0056] FIG. 5 shows a sectional view of the press tool assembly with a two piece centralizer when the stroke is towards downward direction, according to one embodiment of the present invention. During downward stroke, the gap between the top plate 1 and the washer 10 increases. Simultaneously the distance between the holder plate 6 and the stripper plate 5 decreases. The spring 12 will be compressed, during this condition the cutting punch 8 is inside the stripper plate 5 and proceeds towards the strip or coil 4 and is about to pierce the strip or coil 4. At the same time, the distanced between the top plate 1 and the base plate 2 also decreases. The centralizer punches 7 centralize the strip/coil 4 and the spring 12 behind the centralizer punches 7 will be compressed. This wedge effect forces the strip or coil into the middle portion of strip guide gap irrespective of the size of strip or coil width. This ensures that the strip or coil 4 would not move randomly and will be centralized. Any extra downward movement of top half is compensated by the deflection of the spring 12 above centralizer punches 7.
[0057] FIG. 6 shows a sectional view of the press tool assembly with a two piece centralizer when the stroke is towards fully downward direction, according to one embodiment of the present invention. In this position, the cutting punch 8 pierces the strip or coil 8 and enter the die. The gap between the top plate 1 and washer 10 further increases. The spring 12 above the centralizer punches 7 are further compressed and the tapered surfaces of the equalizer punches come in contact with the vertical edges of strip or coil 4 and exert wedge effect on the strip or coil 4 from both the sides. This wedge

effect forces the strip or coil 4 into the middle portion of strip guide gap irrespective of the size of strip or coil width. This ensures that the strip or coil would not move randomly and will be centralized. Any extra downward movement of top half is compensated by the deflection of the spring above centralizer punch.
[0058] FIG. 7 shows a bottom half plan view of the two piece centralizer construction, according to one embodiment of the present invention. It shows the cavities 70 on the die plate to receive the centralizer punch, when the stroke on press tool is fully downward. FIG. 8 shows a top half plan view of the two piece centralizer construction, according to one embodiment of the present invention. It shows a centralizer punches 80 on top half of the die plate.
[0059] FIG. 9 shows a centralizer punch 30 for single piece construction, according to one embodiment of the present invention. FIG. 10 shows a centralizer punch 7 for two piece centralizer construction, according to one embodiment of the present invention. The height of all the centralizers used for single piece and two piece constructions are identical. The taper angle on all the centralizers and the point at which the taper starts are identical for all centralizers.
[0060] FIG. 11 shows a sleeve 11 provided above the centralizer punches 7, according to one embodiment of the present invention. The Sleeve 11 is provided above the centralizer punch 7. The sleeve is provided to reduce the pressure on the spring during fully downward stroke. The sleeve also ensures that the spring is not over tightened beyond the required length and force.

G) ADVANTAGES OF THE INVENTION
[0061] The various embodiments of the present invention provide a mechanism for centralizing strip or coils in press tool assembly by utilizing single or two piece centralizing punches of different sizes feasible at one or more locations. The centralizing punches are provided to guide the strip or coil exactly at the middle of the gap between strip guides. It helps in maintaining the symmetry of holes with respect to the outer coil or strip edges. The centralizers are provided such that, it takes care of the variation in the strip or coil width during progressive punching operations. The assembling and maintenance of the centralizers are very easy.
[0062] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0063] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of fall there between.

CLAIMS
What is claimed is:
1. A centralizer arrangement for coil/strip in a press tool assembly comprising:
At least one centralizer punch;
An Allen screw mounted on the centralizer punch;
A sleeve provided above the centralizer punch;
A spring arranged around the sleeve;
A first washer provided between the Allen screw and the sleeve; and
A second washer provided between the sleeve and the centralizer punch;
Wherein the centralizer punch has a tapered surface at the end to come in contact
with the coil/strip to exert wedge effect on the coil/strip from both the sides to
ensure that the coil/strip is not moved randomly and is kept centralized during the
punch process.
2. The arrangement according to claim 1, wherein the tapered surface at the end is made to come in contact with the vertical edges of the coil/strip to exert a wedge effect on the coil /strip from both the sides to force coil/strip into the middle portion of a strip guide provided in a press tool assembly, irrespective of the size of the coil/strip to ensure that the coil/strip is not moved randomly and is kept centralized during the punch process.
3. The arrangement according to claim 1, wherein pluralities of the centralizer punches are used in the press tool assembly, when the width of the coil/strip is bigger.

4. The arrangement according to claim 1, wherein the centralizer punch is held in a punch holder plate which is provided in the press tool assembly.
5. The arrangement according to claim 1, wherein the pluralities of the centralizer punches are arranged on either side of the coil/strip at the entry point of the coil/strip before any punching station provided in the press tool assembly.
6. The arrangement according to claim 1, wherein the height of the all the centralizer punches are identical, when pluralities of the centralizer punches are used in the press tool assembly.
7. The arrangement according to claim 1, wherein the taper angle of the taper surface provided at the centralizer punches are identical, when pluralities of the centralizer punches are used in the press tool assembly.
8. The arrangement according to claim 1, wherein the point at which the taper surface starts in all the centralizer punches are identical, when pluralities of the centralizer punches are used in the press tool assembly.
9. The arrangement according to claim 1, wherein the spring has a height based on the stroke required for the centralizer punch, shut height of the press tool and the thickness of the coil/strip material.

10. The arrangement according to claim 1, wherein the two washers are arranged to
provide resting surface for both the Allen screw and the centralizing punch with
the punch holder plate.
11. The arrangement according to claim 1, wherein the load of the spring is designed
in such a manner to prevent the formation of dent marks on the edges of the
coil/strip.