FORM 2

THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
A MECHANISM FOR BENDING SHEET-METAL COMPONENTS;
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
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
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Field of Invention
The present invention relates to the field of sheet metal bending and more particularly to the mechanism for bending thin sheet-metal components.
Background
Countless varieties of products made of sheet metal are found in everyday life. The characteristics of sheet metal such as ability to be bent, cut and easily deformed to give desired shapes are utilized in manufacture of these products. Various processes are utilized for such purposes, which include stretching, drawing, bending etc. Bending is considered one of the most important manufacturing processes during the production of sheet metal components. This involves bending the sheet metal components by pressing them in a bend press or power press.
Broadly the types of power press may be classified as mechanical and hydraulic press based on the driving force utilized in their operation. Among which mechanical presses are considered to be cheap, fast, easy to maintain and operate as compared to the hydraulic press. Further, the mechanical presses may be of two types namely C-Frame type and Gantry type presses. C-Frame type presses are the most commonly used power presses, since, they are cheap, easy to operate and maintain and occupy less space as compared to gantry press. Gantry type presses are more costly and occupy more space.
However, C-Frame type presses have inherent disadvantage of slight frame opening during the operation and variation in stroke as they are based on slider crank type of mechanism as shown in figure 1. The stroke of C-Frame type presses is set manually with the help of a screw and nut arrangement; hence the stroke depends on the
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operator skill. While setting the stroke and adjusting the ram manually, there is possibility of oversetting or under setting. Also in slider crank mechanism, over a period of time, clearances between the joints increase because of which, stroke may also change during operation, leading to inaccurate bending results.
Also, during the normal bending operations it is preferred to squeeze the component near the bending edge as shown in figure 2. The operation of squeezing the sheet metal component helps in providing a plastic deformation so that bend does not open. Also, the squeezing also takes care of the stroke variation or over setting of the press. However the operation of squeezing is usually applicable to thick sheet-metal components, where such squeezing is very less as compared to material thickness.
As shown in fig.3, a conventional bending tool comprises of a fixed part (1) and a moving part (3). In the fixed part of the tool, a housing (304) & Die Blocks (306a and 306b) are mounted on a Base Plate (302) with the help of screws and dowels. An ejector block (308) is provided to slide between the housing (304) and die blocks (306a, 306b). Ejector Pin (309) may be guided in the housing and supports the ejector block (308). The fixed part is connected to a bottom bolster of the press and ejector pins rest on the spring-loaded buffer.
The moving part (3) is connected with the ram of the press. The ram of the press may be connected to a shank fitted on a shank plate (104) provided in the moving part. The moving part of tool usually comprises of a punch (106) connected to a top plate (102) with screws and dowels, which, in turn is fixed rigidly to the shank plate (104).
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The bending of the sheet metal component in the press is carried out by placing the sheet-metal component on the ejector block. The ram may then be fired pushing the punch (106) against the component and ejector block (308). The movement of the elector block is held by the die blocks 306a and 306b. The movement of the sheet-metal component downwards pushes the ejector pin, which are resting on the spring-loaded buffer. At the end of stroke, when the ejector block rests on the base plate (1), squeezing of the component takes place where metal is pressed against the metal. When the ram moves up, spring-loaded buffer pushes ejector block up applying the force through the ejector pin towards the ejector block and the component gets ejected.
In case of thin sheet metal components squeezing is not possible and hence, it is not possible to take care of stroke variations and over setting of the press. Hence, it becomes most important for the operator to set the stroke accurately to avoid over setting. This requires highly skilled operators and time to set. Due to these inherent disadvantages of presses, it becomes difficult to bend thin sheet metal components on the press.
There is therefore a requirement of a mechanism for bending thin sheet-metal components with ease and overcoming the squeezing and biting of thin sheet-metal components.
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Summary
A mechanism for a sheet-metal bending press is provided. The mechanism allows
bending of thin sheet-metal components with ease of operation. The mechanism is usable
in C-Frame type sheet-metal bending press. Further, the mechanism is usable in other
sheet-metal bending presses also.
In one embodiment of the present invention, to provide the flexibility in the sheet-metal
bending press to overcome setting imbalances by the operator, spring means is provided.
The mechanism provides a convenient yet effective system for avoiding squeezing of thin
sheet-metal components during bending. Further, the compression of the mechanism to
absorb the oversetting of the press prevents breakage of the ejector block.
Brief Description of the Drawings
Figure 1 illustrates the slider crank mechanism of a power press as present in the prior
art.
Figure 2 illustrates the squeezing of the thick components to retain the shape.
Figure 3 illustrates a bending tool as present in the prior art.
Figure 4 illustrates the invention as per one embodiment of the present invention, during
the top most position of the punch.
Figure 5 illustrates the invention as per one embodiment of the present invention, during
the contact of the punch with the sheet-metal component.
Figure 6 illustrates the invention as per one embodiment of the present invention, during
the bottom position of the punch.
Figure 7 illustrates the invention as per one embodiment of the present invention, during
the compression position.
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Detailed Description of the Invention
The present invention provides mechanism for a sheet-metal bending press. The mechanism allows bending of thin sheet-metal components with ease of operation. The mechanism is usable in C-Frame type sheet-metal bending press. Further, the mechanism is usable in other sheet-metal bending presses also.
Fig.4 illustrates a mechanism for sheet-metal bending press as per one embodiment of the present invention. The mechanism may comprise of a shaft plate (10), which may be attached to a ram of the sheet-metal bending press. The shaft plate (10) moves in unison with the ram. A top plate (20) may be provided to which is fixed a punch (40). The punch may be fixed to the top-plate (20) with help of screws and dowels. The punch during the bending operation comes in contact with the sheet-metal component to be bent. The force is transferred from the ram to the punch, which is applied, on the sheet-metal component, which is bent.
In order to provide the flexibility in the sheet-metal bending press to overcome setting imbalances by the operator, a spring means (32) is provided in form of a spring. The spring may be a compression spring. A spring retainer means (34) may be provided between the shaft-plate (10) and the top-plate (20). One end of the spring retainer means may be fixed to the shaft plate (10), while another end is fixed to the top plate (20). Spring means (32) may be provided over the spring retaining means (34) such that, the movement of the top-plate with respect to the shaft plate is made possible.
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An auxiliary pillar (36) may be provided between the top-plate (20) and the shaft-plate (10). One end (36a) of the auxiliary pillar may be provided to be fixed to the shaft plate (10). A free end (36b) is provided to be slidable in and out of the top-plate (20). A hole (20a) may be provided in the top-plate (20). The free end (36b) of the auxiliary pillar slides through the hole (20a). Bush (26) may be provided in the inner periphery of the hole for smooth movement of the free end (36b) in the top-plate (20).
A fixed part of the sheet-metal bending press may be provided to have a base plate (62). A housing (64) may be provided around a die block (66a, 66b). Further, an ejector block is provided one end, of which is in contact with the sheet-metal component which required to be bent. The other end of the ejector block is connected to an ejector pin (69) that may be further attached to a spring-loaded buffer present in the bottom bolster of the press.
As seen in figure 4, the position of the punch is the initial position. The punch (40) is at the top most position. During the sheet bending operation, sheet-metal component (70) required to be bent may be placed on the die blocks (66a, 66b).
Referring to figure 5, the position of the mechanism during the contact of the punch with the sheet-metal component is shown as per one embodiment of the present invention. In response to the movement initiated by the ram the mechanism is lowered. The punch (40) comes in contact with the part on one face of the sheet-metal component (70). The ejector
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block (68) is at the upper position where one end of the ejector block is in contact with another face of the sheet-metal component (70).
Referring to figure 6, the position of the mechanism during the bottom position of the punch is shown as per one embodiment of the present invention. The punch bends the sheet-metal component (70) owing to the force initiated by the ram. The ejector block (68) is forced downwards. This pushes the ejector pin (69) downwards, and towards the spring-loaded buffer of the sheet-metal bending press.
Referring to figure 7, the position of the mechanism during the compression position is shown as per one embodiment of the present invention. The provision of spring means (32) enables absorption of excess force, which may be caused due to oversetting of the press. This is achieved when compression of spring means (32) occurs, sliding the top-plate (20) in the free end (36b) of the auxiliary pillar (36). The movement of the spring may be guided by the spring retainer means (34).
The mechanism thus provides a convenient yet effective system for avoiding squeezing of thin sheet-metal components during bending. Further, the compression of the mechanism to absorb the oversetting of the press prevents breakage of the ejector block.
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WE CLAIM
1. A mechanism for sheet-metal bending press comprising:
a shank-plate connected to a ram;
a top-plate movable towards and away from the shank-plate;
a punch fixed on the top-plate;
a spring means between said shank-plate and the top-plate allowing movement of
the top-plate with respect to the shank-plate.
2. The mechanism of claim 1, further comprising:
an auxiliary pillar;
one end of said auxiliary pillar attached to said shank-plate;
a free end of the auxiliary pillar slidable in and out of said top plate.
3. The mechanism of claim 1, wherein the spring means is a compression spring.
4. The mechanism of claim 3, wherein the pre-compressed load of the spring means is greater than the maximum load of the bottom buffer of the sheet-metal bending press.
5. The mechanism of preceding claims, further comprising:
a spring retainer means between said shank-plate and said top-plate. Dated this 15th day of February, 2007

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Abstract
A mechanism for a sheet-metal bending press is provided. The mechanism allows bending of thin sheet-metal components with ease of operation. In one embodiment of the
present invention, to provide the flexibility in the sheet-metal bending press to overcome setting imbalances by the operator, spring means is provided in the mechanism.
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