FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - CUT OFF DIE ASSEMBLY FOR PROVIDING
HIGH PRECISION COMPONENTS
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company.
(c)ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to cut off die assembly for providing high precision cut off component. More particularly, the present invention is concerned about eliminating tilting of components during cut-off operation to get high precision cutting of surfaces at the cut off regions so as to maintain accuracy of the components,
BACKGROUND OF THE INVENTION
Press tool mainly consists of two halves, namely fixed bottom half and a moving top half. The fixed bottom half is secured to the stationary bolster plate of mechanical press. It comprises 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 & it comprises a no. of circular & non circular cutting & non cutting elements called punches. The" punches move up & down along with the moving ram of the mechanical press & they are guided in cavities made in a plate called Stripper. During downward movement, the punches penetrate the sheet metal & enter the die cavity thus pushing the sheet metal scrap displaced by the cutting punch into the lower half of the tool. One downward & 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.
Press tool may be of multi-station type (progressive) 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 I coil leading to completion of stamping profile in last stage.
The manufacturing process for sheet metal component or stamping is by processing a sheet metal coil or strip in a press tool. Many times the nominal width of coil or strip is equal to maximum width of stamping to reduce the generation of scrap. The components are taken out of the press tool by cutting operations like Blanking, Parting and Cut off. The sheet metal strip or coil may be of ferrous or non ferrous materials. Many times the nominal width of coil or strip is equal to maximum width of stamping to reduce the generation of scrap. In these cases the blanks or components are produced from the strif) either by cut off operation or by

parting operation. The forward advancement (Pitching) of the strip/coil is maintained uniform bv providing fixed stoppers at the required positions in the tool in both these cases. Parting of blanks/components from the strip/coil also generates scrap. But to get blanks of consistent & accurate length and to get straight surface at the cut regions, parting operation was preferred.
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 & die. The die profile is the female profile intentionally kept bigger than the punch profile by a uniform gap called cutting clearance.
The strip/coil is to be firmly held in the tooling operations. In the blanking operation the entire component/blank periphery is cut out by the blanking punch. In the parting operation the strip/coil is parted out at the parting stage. The component/strip's outer periphery is cut out by the corresponding parting punch. This operation has minimum two cutting surfaces at-either sides of the parting punch and hence the operation is balanced and the parting punch firmly holds the strip/coil.
In cut off operation the cutting is done only on one surface or in other words it is a one side cutting operation. This operation doesn't generate scrap. Since this is not a balanced operation the cut out blanks/components will have tapered surfaces at the die region as well as the punch region. The length of the cut off component is more due to this taper angle. During cut off operation the strip/coil is free to tilt up and down since no die support is available for the strip/blank after the cutting region. Hence due to cutting load the component / blank tilts and the region away from the cutting surface moves upward when the cut off punch separates the component from the strip and pushes the component down. This creates taper angle at the cut regions of the strip and blank/component.
The cut off die normally produces blanks/components which are not accurate in length and have tapered surfaces at the cut off region. The cut off tools were not used for precision components. The figure 1 shows the construction and working of a cut off die which was used prior to the present invention. The component tilting during the cutting operation is highlighted in figure I. During cut off operation, there is a lack of support for the blankVcomponent leads to tilting of the component and results in taper angle at the cut region both on the die and punch. As a result, the length of component is not maintained and is always more than the required length and the appearance of the component is not good as

shown in fig 2. Since it is not possible to control the tilting of blank, the length there is not consistent with the length of cut off blanks.
Thus, there is a need to provide cut off die assembly which could eliminate the undesirable movements as well as tilting of the blank/component during cut off operation thereby providing improvement in the precision of cut of the components. This arrangement prevents tilting of the component during cutting operation due to firm gripping action before start of cutting operation. The present invention provides maintaining accuracy of the component/blanks and eliminating wastage known as scrap, which cannot be avoided in the operations like blanking and parting.
OBJECTS OF THE INVENTION
One of the basic objects of the present invention is to overcome the disadvantages/problems of the prior art.
Another object of the present invention is to provide a cut off die assembly for producing high precision cutting of components/blanks from cut off tool.
Another object of the present invention is to provide a cut off die assembly for producing cut off blanks with proper cut surface.
Another object of the present invention is to provide a cut off die assembly for eliminating tapered cut surface.
Another object of the present invention is to provide a cut off die assembly for preventing the tilting of component during cutoff operation.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a cut off die assembly for providing high precision cut in components, said assembly comprising:
movable top plate;
fixed base plate located in proximity to said top plate, said top and bottom plates being mechanically engaged by means of support means, said top plate being movable along said support means in a vertical plane;

die block means mounted on said base plate
wherein said die block comprises cavity means;
stripper plate means comprising :
a slot to accommodate strip means/component; said stripper plate means being placed on said die block means;
a hole to accommodate a stopper member means adapted to control feeding of said strip means; and
plurality of cavities;
punch means mounted on said top plate such that movement of said top plate operatively provided to and fro vertical movement of said punch means;
an ejector assembly means comprising plurality of ejector members and ejector block means; said ejector block means being movably located by means of said plurality of ejector members such that it performs upward and downward movement during the operation;
wherein said punch means comprises a unique profile and being guided through plural cavities provided in said die block and stripper plate by means of down ward stroke of said top plate and cooperatively engages with said ejector block means providing support to said strip means and cutting said strip means by holding in between said ejector block means and said punch means such that high precision cut is produced in strip means.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates construction and working of a cut off die used in the prior art.
Figure 2 illustrates a cut off blank & taper angle at both the cut regions
Figure 3 illustrates sectional view of the assembly of a cut off die.
Figure 4 illustrates strip layout
Figure 5 illustrates bottom half plan view of cut off die.
Figure 6 illustrates sectional side view of cut off die.
Figure 7 illustrates cut off punch
Figure 8 illustrates die plate

Figure 9 illustrates ejector block
Figure 10 illustrates ejector pins
Figure 11 illustrates fixed stopper pin
Figure 12 illustrates retainer pin
Figure 13 illustrates sectional view of various elements when the tool in the upward stroke condition.
Figure 14 illustrates sectional side of retainer pin in the oblong slot in the ejector block when the tool is in the upward stroke condition.
Figure 15 illustrates sectional view showing the position of various elements when the tool is taking the downward stroke.
Figure 16 illustrates sectional side view of the cut off punch holding the strip/coil against the ejector block during downward stroke.
Figure 17 illustrates fully downward stroke of the press.
Figure 18 illustrates view showing fully downward stroke of the press indicating the position of the retainer pin in the assembly.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS
According to the present invention, the cut off die assembly primarily comprises cut off punch means (3), die block/plate means (7), ejector block means (5), ejector member means (6), fixed stopper pin (4b) and retainer pin (8). Figure 3 shows sectional view of the assembly of a cut off die, in which position of top plate (1) , stripper plate means (4), strip/coil (4a) , fixed stop (4b), die block/plate (7), tapered slot (7b) in the die block/plate (7) , ejector block means (5) and base plate (2) elements are highlighted.
Figure 4 shows strip (4a) layout, which' is indicating component dimensions, cut off region and the fixed stop position.

Figure 5 shows bottom half plan view of cut off die, in which the cut off region, position of ejector block (5) & other elements are highlighted.
Figure 6 shows sectional side view of cut off die, in which various elements cut off punch (3), stripper plate (4), die block (7), ejector block (5), retainer pin (8), ejector pin (6), top plate (1) and base plate (2) are highlighted in assembly.
As shown in fig 7, the cut off punch (3) is a hardened member used for cutting the strip / coil (4a) against a fixed die. This is normally rectangular in shape. This is mounted on to the top plate (1) by means of alien screws and is precisely located my means of dowel pins. This is precisely guided inside the stripper cavities and has two projections at the either side of the bottom surface along the strip (4a) feeding direction. This projection is used for heeling the punch (3) against the die block (7). So the deflection of the punch (3) due to one side cutting load is avoided.
As shown in fig 8, the cut off die is a hardened block. This is firmly fastened to the base plate (2) by means of alien screws and precisely located by means of dowel pins. This has a die cavity (7a). The component/blank is produced by cutting the strip/coil (4a) against the cutting edge (3a) in the die cavity (7a). The ejector block (5) is precisely guided inside the die cavity. Opposite side of the cutting edge (3a) acts as heeling surface (3b) for cut off punch (3). The die block (7) has a tapered slot (7b) provided after the die cavity (7a) to take out the cut off blanks/components. The width of the tapered slot (7b) is bigger than the strip/coil (4a) width. Provision for clamping the retainer pin (8) is provided in the die block (7).
As shown in fig 9, the ejector block (5) is a hardened member and is housed inside the die cavity (7a) in the die block/plate (7). Step surfaces (5b) are provided in the ejector block (5) to accommodate the heeling projections (3c) in the cut off punch (3). The ejector block (5) is precisely guided inside the die cavity (7a). The thickness of the ejector block (5) is decided based on the base plate (2) thickness, thickness of the strip / coil (4a) and the punch entry inside the die. An oblong slot (5a) is provided in the ejector block (5) to accommodate the-retainer pin (8).
As shown in fig 10, the ejector pin (6) is round in shape and is hardened. It has a stepped head at one end to restrict it from falling down after assembling in the base plate (2). Corresponding cavity to accommodate the stepped head is provided in the base plate (2). The

length of the ejector pin (6) is decided based on the travel required for the ejector block (5) and the thickness of the base (2) plate.
As shown in fig II, the fixed stopper pin (4b) is round in shape and is hardened. It is assembled in the hole provided in the stripper plate (4). The position of the hole in the stripper plate (4) is decided based on the length of the component and is precisely maintained from the cutting edge (3a) of the die cavity (7a).
As shown in fig 12, the retainer pin (8) is a manufactured by modifying the standard alien screw. This is mounted in the die block (7) and projects into the oblong slot (5a) in the ejector block (5). This acts as a stopper for ejector block (5). The position of the retainer pin (8) is decided based on the stroke required for the ejector block (5).
Figure 13 illustrates sectional view of various elements when the tool in the upward stroke condition and the positions of ejector block (5) and ejector pins (6) are highlighted. During the upward stroke condition the ejector block (5) is pushed up by the bottom buffer/die cushion (9) by means of ejector pins (6). This ejector block (5) comes up to the die surface. The strip/coil (4a) is fed inside the tool through the guiding slot provided inside the stripper plate (4), When the front end of the strip/coil (4a) touches the fixed stopper pin (4b), the feeding is stopped. The stopper pin (4b) is fixed on the stripper plate (4), The component removal is automatic due to this construction. Figure 14 illustrates sectional side view of retainer pin (8) in the oblong slot (5a) in the ejector block (5) when the tool is in the upward stroke condition
Figure 15 illustrates sectional view of various elements when the tool is taking the downward stroke. During the downward stroke the punch (3) comes in contact with the strip/coil (4a) and holds the component firmly against the ejector block (5). Further downward movement of the press cuts the strip/coil (4a) against the die surface and is pushed down. Figure 16 illustrates sectional side view of the cut off punch (3) holding the strip/coil (4a) against the ejector block (5) during downward stroke and the heeling projections (3c) in the cut off punch (3) is accommodated in the relief provided in the ejector block (5). The component/blank is firmly held against ejector block (5) and cutoff punch (3) all these time. Figure 17 illustrates fully downward stroke of the press showing that the component is separated from the strip/coil (4a) and the ejector block (5) also moves down along with the cut off punch (3). The ejector pins (6) are pushed down below the bottom surface of the base plate (2), This movement in compensated by the bottom buffer/die cushion (9) by means of

compressing the spring in it. Figure 18 illustrates fully downward stroke of the press indicating the position of the retainer pin (8) in the assembly.
When the upward stroke takes place the punch (3) starts moving up with the top half. The separated component/blank is also taken up by ejector block (5) during this time by means of die cushion/bottom buffer. This component / blank falls inside the taper slot (7b) provided in the die block (7) and move out of the tool automatically.
ADVANTAGES OF THE INVENTION
1. Component / Blank will have straight cut region and straight cut band
2. This construction eliminates scrap
3. Accurate blanks/components are produced by this operation
4. Ease of assembly & maintenance.
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The guide means, screw means, die plate, top and base plates as stated do not limit the scope of the present invention. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

WE CLAIM
]. A cut off die assembly for providing high precision cut in components, said assembly comprising:
movable top plate;
fixed base plate located in proximity to said top plate, said top and bottom plates being mechanically engaged by means of support means, said top plate being-movable along said support means in a vertical plane;
die block means mounted on said base plate
wherein said die block comprises cavity means;
stripper plate means comprising :
a slot to accommodate strip means/component; said stripper plate means being placed on said die block means;
a hole to accommodate a stopper member means adapted to control feeding of said strip means; and
plurality of cavities;
punch means mounted on said top plate such that movement of said top plate operatively provided to and fro vertical movement of said punch means;
an ejector assembly means comprising plurality of ejector members and ejector block
means; said ejector block means being movably located by means of said plurality of ejector members such that it performs upward and downward movement during the operation;
wherein said punch means comprises a unique profile and being guided through plural cavities provided in said die block and striper plate by means of down ward stroke of said top plate and cooperatively engages with said ejector block means providing support to said strip means and cutting said strip means by holding inbetween said ejector block means and said punch means such that high precision cut is produced in strip means.

2. The assembly as claimed in claim 1, wherein said punch means having unique profile comprises plurality of heeling projections.
3. The assembly as claimed in claim 1, wherein said ejector block means having unique profile comprises plurality of stepped surfaces to accommodate the heeling projections .
4. The assembly as claimed in claim 1, wherein said ejector block further comprises slot means to accommodate a retainer member means.
5. The assembly as claimed in claim 4, wherein said retainer member means is adapted to control the movement of the ejector block.
6. The assembly as claimed in claim 4, wherein said slot provided in said ejector block is oblong shaped.
7. The assembly as claimed in claim 1 further comprises die cushion adapted to support up and down movement of the ejector member.
8. The cut off die assembly for providing precision component as herein substantially described and illustrated with the accompanying drawings.