FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION
[See section 10, Rule 13]
A SHEET METAL STAMPING PROCESS AND DEVICE FOR THE SAME;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION
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FIELD OF THE INVENTION
The present invention relates to an arrangement in sheet metal stamping process, and more particularly to an arrangement to avoid distortion of sheet metal components in progressive operations due to lateral forces generated during cutting operations.
DESCRIPTION OF THE BACKGROUND ART
Sheet metal stamping process for manufacturing of various sheet metal related components is well known in the related art. Many a times in a specific sheet metal process, stamping is made from a metallic strip, width of which is equal to the maximum width of the stamping. In order to suit various applications of various industries and to get required shape after stamping, width of the sheet metal strip is reduced from maximum width to a lesser value as a result of various cutting operations employed in the sheet metal stamping process at successive stages, both on front edges (6) and back edges (7) of the strip (as shown in figure 1 labeled as prior art).
Again referring to figure 1, notching operations (2A to 2F) are carried out to remove material from front and back edges of the strip in a progressive strip layout. It is quite well known in the stamping process that due to notching operation side thrust is induced that may cause bow and distortion opposite to notch profile in the metal strip. In case of strips having less strip width, two notches provided as a result of notching operations (2B and 2F) and opposite to each other are provided in the same stage (2C and 2D) to counter and balance the side thrust. A prominent drawback that is usually faced in the aforementioned
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stamping process is that the width of final strip (4) achieved is so small that die
wall between the front and rear notches are weak.
Another drawback of the stamping process employed at present is that, due to
the reduced width of the strip during the stamping process the final strip not only
gets distorted but also defects such as extra burrs are developed which may cause dimensional inaccuracy as well as impose difficulty in locating the stamping in nesting in subsequent press working operations.
Hence there is a need of an arrangement in the stamping process that reduces
the aforementioned defects and drawbacks.
A BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become apparent from the following description in
conjunction with the accompanied drawings in which:
Figure 1 shows the prior art illustrating the conventional strip layout for sheet
metal stamping dyes according to the prior art.
Figure 2 shows the position of the edge supporting round pilot arrangement
according to an embodiment of the present invention.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is an object of the present invention to avoid distortion or defects like burr in the strip during stamping operation.
Another object of the present invention is to avoid any dimensional variation in the final strip during the stamping operation.
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In the following description of the embodiments of the present invention reference is made to the accompanying figure 1, which in conjugation with this detailed description, illustrates and describes working principle of a sheet metal stamping process, and a device incorporated therein with the stamping process to avoid distortion of sheet metal components in progressive operations due to lateral forces generated during cutting operations.
According to an embodiment herein and as referred to figure 2, notching of a metal strip is being done in two stages rather than in one stage as is being currently done in the related art. This in another way avoids weakening of the dies that incorporates a punch assembly. The strip is being stamped and notched in two stages, a first stage and a second stage on opposite sides thereof. Normally, a sheet metal stamping is being done to a metal strip whose width is nearly equal to the width of the stamping. A sufficiently long strip of metal is being made to pass through the stamping process, the said process is categorically divided into two stages. Notching of the strip herein is normally done in two stages wherein the first notch (2B) reduces the width of material and the second notch (2E) without distorting reduces further the width of the strip. Notching operations (2A and 2F) removes the metal both from the front (6) and back (7) edges of the metal strip in a progressive layout. Initially the metal strip is made to pass through the first stage of the die and punch assembly employed therein a machine. As the metal passes over the dye through the first stage (2B), a significant amount of metal is removed from the strip thereby producing a first notch (2B) on one of the sides of the strip. As the metal strip advances towards
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the second stage and as it comes over another dye employed therein to produce
a second notch, the punch assembly punches the metal strip thereby producing
the second notch (2E) on to the opposite side of the strip as to the first notch.
According to another embodiment herein, during the second stage of the stamping process and in order to avoid distortion, dimensional variation and defects like burr on the metal strip after notching, a support is provided in the second notching stage as shown in figure 2. The support is preferably round in shape and spring loaded in order to suit the design requirements. The support is so positioned that its diameter is tangential to the previously notched edge in strip. The position of the support is opposite to the second notching cavity.
The support is guided in the die block for avoiding any deflection due to the side
thrust applied by the second notch (2E) operation. Since, the strip material is supported by the support during notching operation, its distortion and extra burr
development is avoided.
According to another embodiment herein, the support is provided within the punch assembly and as the punch goes down to produce the second notch onto the strip, the support at the same time holds the strip onto the opposite side of the strip and enables the punch to provide a second notch.
Dated this 30th day of March, 2007

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