AN IMPROVED MECHANISM FOR UPWARD LANCING IN A
PROGRESSIVE DIE ASSEMBLY
FIELD OF THE INVENTION
The present invention relates to progressive dies for processing coils / strip in progressive punching / cutting operations. More particularly, the invention is concerned about an improved mechanism for upward lancing in a progressive die assembly
BACKGROUND OF THE INVENTION
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 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.
In a multi-station (progressive) press tool, the strip moves from one end of strip guides to the other. It moves progressively by a fixed distance called pitch after ever stroke of the mechanical press. At each stage of movement of the strip, different punching operations are carried out on strip/ coil leading to completion of stamping profile in the last stage.
Progressive dies are used for processing coils/ strip in progressive punching/ cutting operations. In progressive tools various operations such as piercing, embossing, notching, lancing, bending take place simultaneously at different locations in the tool. The requirement of these operations is decided by features in component / stamping design. The strip layout is the schematic arrangement /representation for sequencing various cutting/ punching operations on metal strip/coil in a progressive die. It has to be designed as per the component / stamping design.
Lancing is cutting along a line in a work piece without detaching the slug from the work piece. Mainly there are two types of construction, such as 1) Lancing punch operates from lower half of tool and 2) Lancing punch operates from top half of tool, by which lancing operation can be performed in a tool. Lancing operation is done in a separate tool with fixed lancing punch arrangement from top half of the tool. This increased handling of component reduces the productivity and yield due to tedious task of loading & unloading the components. US 4,106,422 teaches a method of making open can closures or can tops comprising the steps of piercing, marginally notching, and lancing the web according to a predetermined pattern. The notching, lancing and piercing are said to be done simultaneously by two tools of a single progressive die.
Thus there is a need to overcome the problems of the prior art. The present inventors have developed an improved mechanism for upward lancing in a progressive die assembly to get consistent results with a single progressive tool and safeguarding the safety of lancing punch against breakage as well as avoiding obstruction to feeding of strip / coil.
OBJECTS OF THE INVENTION
An object of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide an improved mechanism for upward lancing in a progressive die assembly
Yet, another object of the present invention is to provide a lever profile for use in the mechanism for upward lancing in a press tool. SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved mechanism for upward lancing in a progressive die assembly, said mechanism comprising:
plurality of springs means;
punch actuator means; lever actuator means positioned in substantially vertical direction; said lever actuator comprises a collar means, and guide means wherein said collar means having a predetermined length and width and substantially a rectangular shape positioned in substantially horizontal direction at a predetermined distance from a top or bottom face of the lever actuator means ; lever means having a substantially oblong shaped being located on a base plate with a hinged hole, said hinge or pin hole means being located substantially at center of the lever;
said lever means at its two ends having two projected arms at a predetermined angle to the horizontal having substantially rounded profile at their ends to define plural point contacts and a plane elevated portion having a predetermined length being located substantially at the center of the lever; said construction of lever means being such that said point contacts being ensured between said lever means and said actuators means all the time; floating insert means comprising a slot means and plurality of edges wherein said slot means being able to accommodate said spring means; and
a stripper insert means comprising a slot means being able to accommodate and guide said floating insert means; wherein during downward stroke, the spring means being compressed so that said lever actuator means pushes the lever means down such that the lever means gets tilted so that the lancing punch actuator means moves in upward direction against the pressure of said springs for lancing operation by said punch means.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 illustrates a sectional view showing mechanism for upward lancing.
Fig 2 illustrates a strip layout showing lancing operation.
Fig 3 illustrates an additional sectional view showing lancing operation.
Fig 4 illustrates an enlarged sectional view of the lancing operation.
Fig 5 illustrates a lancing punch.
Fig 6 illustrates the lancing punch actuator.
Fig 7 illustrates the lever profile.
Fig 8 illustrates the lever actuator.
Fig 9 illustrates the floating insert.
Fig 10 illustrates the stripper insert.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
According to the invention there is provided a mechanism for upward lancing in a press tool. An improved mechanism for upward lancing in a progressive die assembly as shown in figures 1 ,3 and 4 comprises plurality of springs means(la & lb), die insert means (2), holder plate means (3), spacer (4), a lancing punch means (5), lancing punch actuator means (6), lever means (7), lever actuator means (8), floating insert means (9), and stripper insert means (10). Figure 2 shows the strip layout showing lancing operation. It is to be understood that some components which are generally present in a progressive die assembly are not described in details in the present embodiment as it will be quite evident and understood by a person skilled in the art from the figures and descriptions provided in the foregoing description.
As shown in figure 5, the lancing punch (5) is made of hardened steel. The lancing punch (5) is well guided in die insert (2) and floating in holder plate (3).
As shown in figure 6, lancing punch actuator (6) is a hardened spacer with collar construction (6a). The lancing punch actuator (6) has a substantially "T" shaped profile. The bottom face (6b) shown in figure touches the lever (7) and operates with the force of lever mechanism. The collar (6a) is provided to control the movement of lancing punch (5) with the help of spring (lb).
As shown in figure 7, the lever (7) is a hardened material located in base plate with a hinged hole (7b) for tilting action. The hinge member is a cross pin which bears the load acting at both the ends. The lever means (7) is substantially oblong shaped located on a base plate with a hinged hole (7b) which is located substantially at the center of the lever (7). The lever means (7) has been uniquely designed at its two ends having two projected arms at a predetermined angle to the horizontal having substantially rounded profile at their ends. Such unique profile provides plural point contacts (7a) which comes in contact with the lever actuator means (8). The lever is provided with a plane elevated portion having a predetermined length substantially at the center of the lever (7). The construction of lever
means (7) is such that said point contacts (7a) being ensured between said lever means (7) and said actuators means (6 & 8) all the time.. Point contact (7a) also helps in reducing the friction. As shown in figure 8, the lever actuator (8) is a round member with a collar (8a). This member is in the top half of the tool and the collar (8a) rests on spring loaded stripper plate at Top Dead Center (TDC). The bottom face of actuator (8b) touches lever (7) with point contact. The lever actuator means (8) is positioned in a substantially vertical direction. The lever actuator (8) comprises a collar means (8a) , and guide means (8c). The collar means (8a) having a predetermined length and width and substantially a rectangular shape positioned in substantially horizontal direction at a predetermined distance from a top or bottom face of the lever actuator means (8).
As shown in figure 9, a hardened member called floating insert (9) is well guided in stripper insert (9) and as name indicates it is moving against spring pressure. The floating insert means (9) comprises a slot means (9a) and plurality of edges (9b). The slot means (9a) being able to accommodate said spring means (lb); Floating insert (9) performs two main functions such as gripping the strip during downward stroke of press and acts as a die for lancing operation and during upward stroke of press, the spring expands and the insert comes out of bottom surface of stripper plate & removes the lanced portion of strip out of the stripper insert. This prevents sticking of coil to stripper and ensures feeding of strip without obstruction.
As shown in figure 10, stripper insert (10) is a hardened member which guides the floating insert (9). The stripper insert means (10) comprises a slot means (10a) for accommodating and guiding the floating insert means (9).
Initially when the tool is in open condition at Top Dead Center (TDC), lever mechanism spring (la) which is in pre compressed condition and lever actuator (8) is in top position as
this is a floating stripper construction. When the downward stroke takes place, this spring (la) gets further compressed and lever actuator (8) pushes the lever (7) down. The lever (7) gets tilted as it is hinged by a dowel. This pushes the lancing punch actuator (6) in upward direction against the pressure of two springs (l a & l b) and lancing operation takes place. As the Press ram or top bolster moves downward to Bottom Dead Center (BDC), these springs (la & lb) get compressed further without any relative displacement of lancing punch (5). This safeguards the punch (5) against any breakage due to extra load or press stroke variation. In upward stroke i.e. from BDC to TDC, the pressure on these two springs (l a & lb) is released and they push the lancing punch actuator (6) and lancing punch (5) in turn, downwards. The main function of spring (lb) is to control the movement of lancing punch (5) and ensure that lancing punch (5) will not obstruct strip / coil feeding. This construction ensures the balance lancing operation.
ADVANTAGES OF THE INVENTION
1. An improved mechanism takes care of breakage of lancing punch due to press stroke variation and misalignment of Press ram with respect to bottom bolster.
2. This mechanism guides the lancing punch and avoids frequent breakages of the punch due to movement of the lancing punch
3. This mechanism can be also used for upward embossing and upward bending of thin stock.
4. Ease of assembly and maintenance.
5. This mechanism is particularly effective when upward lancing is necessary and thickness of component is less.
6. This mechanism also controls the dimensional accuracy.
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 springs, punch, actuators, floating insert, stripper insert, die insert
and holder plate 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. springs (la & lb),
die insert (2),
holder plate (3),
a lancing punch (5),
lancing punch actuator (6),
collar construction (6a),
the bottom face (6b)
point contact (7a),
hinged hole (7b)
lever actuator (8),
bottom face of actuator (8b),
floating insert (9),
a slot (9a) ,
stripper insert ( 10).
a slot (10a)