FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - FLOATING PUNCH ARRANGEMNET IN PRESS TOOLS (PROGRESSIVE DIES) FOR BENDING OPERATION
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 generally to the field of pressing tools. More particularly the present invention relates to an improved press tool assembly for progressive punching operation and a method thereof.
BACKGROUND AND THE PRIOR ART
Press tools are used for processing coils/strip in Progressive punching operations. The strip or coil is punched, formed, bent, notched, Flared (push through holes) and made to different shapes. Finally the component is separated from the strip / coil either by blanking or by parting operation.
Separate die inserts and die buttons are provided in the main die plate for individual operations like piercing, notching, lancing, flaring, bending etc. The die inserts are either kept projecting above the die level or are kept below the die level for performing these operations in progressive dies. So it is required to lift strip /coil to a certain height (above the die inserts or to the height to bring bent/flared/formed regions to above the die surface). Otherwise the die inserts and the bent/flared/formed features which are a part of the coil/strip, will become an obstruction for further feeding/pitching. So sufficient number of spring loaded strip/coil lifters are provided to lift the strip/coil all over the feeding region, to facilitate the coil/strip advancement or pitching or feeding.
Some of the prior arts in the present field of invention are as follows:
CN201720334 discloses a bending-type bar stock punching die, which comprises two support blocks, a bar floating block is arranged between the two support blocks; a forming punch is arranged above the bar floating block; a guiding insert is arranged between the forming punch and the bar floating block; and an ejector rod is arranged at the upper end of the forming punch. When the bending-type bar stock stamping die is used, a bar stock is placed on the two support blocks, is then punched by pressing down the forming punch under the action of the ejector rod, and is formed under the action of the forming punch and the bar floating block, then the forming

punch upwardly moves, the bar stock is separated from the forming punch after passing through the guiding insert, therefore the whole punching process is completed. By adopting the punching die to perform punching, the obtained bar stocks are seamlessly connected, the die stock layout is simple, the design workload is small, and the processing period and the design period are short.
US537741S provides an improved sheet metal punch including a second class lever system compounded with a hybrid first-third class lever system. A nutcracker-like tool employs two lever arms that are linked at the ends thereof by a fulcrum link and opposing fulcrum points, one on each of the lever arms, to actuate a hybrid first-third class lever system to drive a floating punch into a guide-stripper plate and die matrix assembly that are rigidly fixed to one of the levers. The punch assembly consists in a plate having a plurality of easily removable/replaceable cylindrical tools projecting there from and which are used in combination with the die matrix to perforate sheet materials such as sheet metal, fibre glass and other relatively thin, planar substances.
US3611498 provides a press for forming a pulverulent material to which a floating die carrying plate is resiliently supported to yield during compression , a punch support plate is placed below the die carrying plate on a fixed bed, a lifting device provided for punch support plate, a core plate below the punch support plate and movable parallel with compression axis, a plate below core support plate, supported by a lifting device and coupled to floating punch support plate by rods passing through core supporting plate and punch support plate, stop limiting the minimum distance of the punch support plate and the core support plate.
US4442691 provides a double action mechanical press, especially for performing a blanking operation and a forming operation on each cycle thereof, having a first slide and a second slide, wherein the slides have separate strokes. The slides are reciprocated by means of a crankshaft and connecting rod assembly comprising a single crankshaft and a plurality of connecting rods wherein the throws of the crankshaft can be differently dimensioned and angularly offset relative to each other so as to provide different stroke lengths for the slides and to cause one slide to lead the other. A guide bushing assembly is connected to one of the press slides, and a blanking punch is received in the guide bushing for reciprocating movement relative to the bushing along

the same direction of reciprocating movement as the slides. A preloaded antifriction bearing is positioned between the punch and bushing assembly, and serves to maintain the proper clearance between the punch and the corresponding cutting edge on the lower die half. A forming die is received in the guide bushing assembly for reciprocating movement relative thereto and is connected to the other press slide. The other portion of the punch is formed as a piston and is urged downwardly by pressurized air. The travel of the punch against the pressurized air enables the punch to abut the top of the strip material until the blanking slide strikes it and causes it to blank out the part. Meanwhile, the forming die draws the blanked out part, which is continued to be held by the pressure of the punch against the lift out ring. Thus, the action of the floating punch simulates the dwell provided by a cam driven punch.
While the prior art provides for different floating punch arrangement for pressing they have their own limitations. The components of prior art have complicated features and have multiple bends. Normally, these types of components are processed by stage tooling. These bends are completed in a sequential manner in a progressive die. The formerly (earlier) bend features becomes an obstruction for the next sequential bend or strip feeding or upward travel of the punch. The earlier bend feature goes inside the punch opening and goes up along with the punch. This causes difficulty in further strip advancement and also results in damage to the components or tooling elements. Thus, there is a need to provide an arrangement in the bottom half of the press tool to support the bending operations and at the same time, facilitate smooth feeding of coil/ strip inside the tool.
In conventional arrangement, the multiple bends are provided with the help of side cams acting sideways. The removal of slug after flaring operation was a problem in this construction. Also, the maintenance and assembly of side cam and bending elements from the sides was difficult. The tool construction and tool assembly is also very difficult.
When quantity required was less similar components were produced in stage tooling. Separate tools for Blanking and bending operations were used. In stage tooling the component removal after final bending was also difficult. In contrast, the present construction can work on any

mechanical press & any value of Press stroke. The undercut formation does not create hindrance to feeding of strip or coil during movement in progressive operations.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the invention is to provide a floating punch arrangement in mechanical pressing tools for bending operations.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
There is provided a floating pin arrangement for a mechanical pressing tool used in bending operation.
According to one aspect of the present invention there is provided an improved press tool assembly for progressive punching operation, said assembly comprising a plurality of bending punches fastened to a retainer plate adapted to perform bending operation; a holder block fastened and doweled to a die plate wherein said holder block having a pair of substantially threaded holes to anchor a pair of spring loaded sleeve means that guide and restrain movement of said floating punch in upward direction; a relief slot provided on said punches and open towards feeding direction adapted to facilitate feeding of a coil/strip for performing bending operation; a spring means housed between said retainer plate and said holder block adapted to facilitate movement of said floating punches; at least one clamping plate; a washer means provided between a socket head cap screw and said sleeve means thereby ensuring a resting surface for both said socket head cap screw and said sleeve means; a spacer means; at least one dowel means; wherein said sleeve means, said washer means and said socket head cap screw

together fastened between said retainer plate and said holder block thereby acting as a stopper for upward movement of said punch; wherein during the downward stroke of said press tool, a wear plate/stripper presses the strip/coil and further pushes a spacer which in turn pushes said retainer plate.
Other aspect of the present invention provides a method for progressive punching using an improved press tool assembly, said method comprising the steps of providing an upward stroke to a press tool assembly thereby projecting a bending punch downwards up to lifting height of a strip/coil; lifting said strip/coil using a strip lifting means and a floating bending punch during said upward stroke of said press tool assembly; blocking upward movement of a die insert when a washer comes in contact with a retainer plate; feeding a strip/coil above bottom surface of said punch; providing a downward stroke to said press tool assembly during which said bending punch is pushed down; wherein during upward stroke said spring means comes to pre compressed stage and pushes said bending punch below to the strip lifting height; wherein during downward stroke condition said spring means comes to fully compressed stage when a spacer is pushed down by top half; wherein said bending punch pushing the bending die down and the bottom surface of the bending die touches the backing plate thereby restricting downward movement of the bending punch and areas which are formed/bend/flared in previous stages go inside a relief slot in said bending punch thereby completing bending operation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
FIG .1 illustrates a component with multiple bends
FIG .2 illustrates a component with multiple bends

FIG.3 illustrates strip layout showing various operations performed at various stages in a progressive tool
FIG .4 shows a sectional view showing the various elements of a progressive tool with floating bending punch.
FIG .5 shows a bottom half plan view of a progressive die with floating bending punch and position of various elements of the tool
FIG .6 shows a sectional view of the floating bending punch &. various elements related are highlighted.
FIG .7 illustrates an enlarged view of the floating die region
FIG .8 illustrates a bending punch
FIG.9 illustrates a holder block
FIG. 10 illustrates a sleeve
FIG.11: shows a sectional view showing the positions and conditions of various elements in the upward stroke condition.
FIG. 12 shows a sectional view showing the fully downward stroke of the press DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention there is provided a floating punch arrangement in pressing tools for bending operations. The different element used and their working are explained as under-

Press working;
The manufacturing process for sheet metal component or stamping is by processing a sheet metal coil or strip in a press tool. The sheet metal strip or coil may be of ferrous or non ferrous materials. 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.
Press Tool:
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 / coil leading to completion of stamping profile in last stage.
The strip / coil is punched, formed, bend, flared and made to different shaped inside the tool at various locations at each pitching in progression. Sometimes the operations which are performed

earlier become an obstruction for further pitching and feeding. So strip/coil is lifted to the desired height, with the help of spring loaded lifters. This facilitates pitching and further feeding.
Sometimes components have multiple bends or an acute angle. After bending operation (normally 90°) , these regions (which are formed/flared/bent earlier) become an obstruction to strip lifting and further advancement of strip/coil.
Spring loaded punches (floating bending punches) are provided in these regions. These punches are precisely guided inside the holder block and springs are provided between retainer plate and blind pocket in holder block. Provision or relief for previously performed operation (bending/forming/flaring etc.) is given in the punches. The punches are pushed downward for bending operation and again pushed back to the same height of strip lifting. The relief slot is open towards the feeding direction. This facilitates the feeding of the coil/strip and further pitching. Smooth progressive feeding and tooling operations are performed in the tool with this mechanism.
CONSTRUCTION:
Floating punches may be rectangular in shape or may be of any shape according to the features. These are precisely guided in the holder block which is fastened and doweled to the die block. Floating punch is fastened to the retainer plate and the retainer plate is fastened with the holder block. The spring is provided between the retainer plate and the holder block . The spring is in the pre compressed condition during the upward stroke condition of the press. The punch projects upward to the lifting height of the strip/coil. A sleeve, washer and socket head cap screw (SHCS) assembly is fastened between the retainer plate and the holder block which acts as a stopper for the upward movement of punch.
The strip/coil is fed above the bottom surface of the punch. During the downward stroke of the press, the wear plate/stripper presses the strip/coil down from the top. The further downward movement of the top half of the press pushes spacer which in turn pushes the retainer plate. Since the retainer plate is fixed to the bending punch, the punch also goes down and completes the bending operation. The areas which are formed/bend/flared in the previous stages goes inside the

relief slot of the bending punch.
During the upward stroke, the top half of the press tool moves up. The compressed spring between the retainer plate and the holder block pushes the bending punch upward and it is taken up to the feeding height of the strip i.e. the height of the lifter pins. The strip is advanced forward before the next stroke. The areas which are formed/bend/flared in the previous stages are easily taken out of the bending punch in the feeding direction during feeding.
The assembly consists of:
1. Bending Punch
2. Holder Block
3. Clamping Plate
4. Sleeves
5. Socket head cap screw
6. Spacer
7. Springs
8. Dowels
Bending Punch may be rectangular in shape or may be of any shape according to the features and the area available in the tool. These are precisely guided in the Holder block which is fastened to the die plate. Bending punch projects down up to the lifting height of the strip/coil with the help of a compression spring provided between the holder block and the retainer plate. Relief slots for the previously completed operations (like forming, bending, flaring etc) are provided in the die insert. These relief slots are made open as a channel along the feeding direction.
HOLDER BLOCK
The holder block is aligned & clamped to the die block with a pair of dowel pins & SHC screws. It has a slot in the middle to guide & support the bending punch during operation. It also has two threaded holes to anchor a pair of spring loaded sleeve assemblies which guide & restrain the movement of bending punch in the upward direction.

SPRING
Spring is housed between the holder block and the retainer plate. During upward stroke condition the spring conies to the pre compressed stage and pushes the bending punch below up to the strip lifting height. During downward stroke condition the spring comes to the fully compressed stage, when the spacer is pushed down by the top half. The spring is selected according to the stroke and load required.
SLEEVE
Sleeve is provided between the washer and the block holder. A SHC screw is inserted through the sleeve and is clamped to the holder block. The length of the sleeve is maintained based on the travel required for the bending punch and the spring selected.
WASHER
Washer is provided between the Socket head cap screw and sleeve. The washer provided ensures
proper resting surface for both Socket head cap screw and sleeve.
WORKING:
During the upward stroke condition of the press, the bending punch projects downward up to the lifting height of the strip/coil. The strip/coil is fed below the bottom surface of bending punch. (Or in other words, the strip/coil is lifted by the strip lifting pins and the floating bending punch during the upward stroke of the press). The spring comes to the pre compressed state and the further upward movement of the die insert is stopped when the washer comes in contact with the retainer plate. Feeding of the strip/coil is done at this condition.
During the downward stroke of the press, the wear plate/stripper holds the strip/coil from the top. The further downward movement of the top half of the press pushes the bending punch down, in turn the bending punch pushes the bending die down and the bottom surface of the bending die touches the backing plate. This restricts the further downward movement of the bending punch. The spring above the bending punch is in the compressed stage at this stage. The bottom surface of the bending punch is flush with the top surface of the strip at this stage. Thus the punches come below and complete the bending operation. The areas which are formed/bend/flared in the

previous stages go inside the relief slot in the bending punch. This completes the bending operation
During the upward stroke, the top half of the press tool moves up. The compressed spring between the holder block and the retainer plate pushes the bending punch downward and it is taken up to the lifting height of the lifter pins. The strip is advanced forward before the next stroke. The areas which are formed/bend/flared in the previous stages are easily taken out of the bending punch in the feeding direction during feeding. The finished component is either parted or blanked out of the strip in the subsequent progressive operations.
Advantages:
1. The strip is positively lifted up to the lifting height with this arrangement.
2. The construction takes care of previously performed operations and does not disturb the same during working.
3. Ease of assembly and maintenance.
4. Spring load and travel can be adjusted according to the requirement.
5. Avoid further stage tool for upward bend.
6. Tool can run at any press and at any stroke.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM:
1. An improved press tool assembly for progressive punching operation, said assembly comprising:
a plurality of bending punches fastened to a retainer plate adapted to perform bending operation;
a holder block fastened and doweled to a die plate wherein said holder block having a pair of substantially threaded holes to anchor a pair of spring loaded sleeve means that guide and restrain movement of said floating punch in upward direction;
a relief slot provided on said punches and open towards feeding direction adapted to facilitate feeding of a coil/strip for performing bending operation;
a spring means housed between said retainer plate and said holder block adapted to facilitate movement of said floating punches;
at least one clamping plate;
a washer means provided between a socket head cap screw and said sleeve means thereby ensuring a resting surface for both said socket head cap screw and said sleeve means;
a spacer means;
at least one dowel means;
wherein said sleeve means, said washer means and said socket head cap screw together fastened between said retainer plate and said holder block thereby acting as a stopper for upward movement of said punch.
wherein during the downward stroke of said press tool, a wear plate/stripper presses the strip/coil and further pushes a spacer which in turn pushes said retainer plate.

2. Assembly as claimed in claim 1 wherein said retainer plate is fastened to said holder block.
3. Assembly as claimed in claim 1 wherein said holder block having a slot to guide and support said bending punch,
4. Assembly as claimed in claim 1 wherein said spring means selected according to the stroke and load required.
5. Assembly as claimed in claim 1 wherein at least one socket head cap screw inserted through said sleeve means and clamped to said holder block.
6. Assembly as claimed in claim 1 wherein at least one sleeve means provided between said washer means and said block holder.
7. A method for progressive punching using an improved press tool assembly, said method comprising the steps of:
providing an upward stroke to a press tool assembly thereby projecting a bending punch downwards up to lifting height of a strip/coil;
lifting said strip/coil using a strip lifting means and a floating bending punch during said upward stroke of said press tool assembly;
blocking upward movement of a die insert when a washer comes in contact with a retainer plate;
feeding a strip/coil above bottom surface of said punch;

providing a downward stroke to said press tool assembly during which said bending punch is pushed down;
wherein during upward stroke said spring means comes to pre compressed stage and pushes said bending punch below to the strip lifting height;
wherein during downward stroke condition said spring means comes to fully compressed stage when a spacer is pushed down by top half;
wherein said bending punch pushing the bending die down and the bottom surface of the bending die touches the backing plate thereby restricting downward movement of the bending punch and areas which are formed/bend/flared in previous stages go inside a relief slot in said bending punch thereby completing bending operation.
8. An improved press tool assembly for progressive punching operation as herein described and illustrated with reference to accompanying drawings.
9. A method for progressive punching using an improved press tool assembly as herein described and illustrated with reference to accompanying drawings.