Patent Publication Number: US-10773291-B2

Title: Universal radius forming system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/510,593 filed May 24, 2017, which is hereby incorporated by reference in its entirety herein. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present disclosure relates generally to female press brake dies for use with large, heavy duty powered metal forming equipment, and more specifically to bottom die elastomers for radius forming on a sheet metal bending machine or press brake. 
     II. Description of the Prior Art 
     Press brakes are conventionally used in metal forming, particularly for forming bends in relatively large and/or thick sheets of metal. Such brakes are almost universally actuated by hydraulics, but may be powered by other means (mechanical, electromechanical, etc.) as desired. These brakes commonly have a relatively fixed lower table or bed which carries a metal forming die (or series of dies), and a relatively movable upper ram which holds a series of complementary punches. When the machine is actuated, the ram with its punches is forced downwardly into the die or dies, bending any metal placed therebetween. 
     More particularly, in order to bend sheet metal on a press brake, the conventional method is to use a steel punch with a matching steel bottom die. The punch is usually the upper portion, convexly shaped with a radius slightly smaller than the desired inside radius of a sheet metal being bent. The mating die is usually the bottom portion, concavely shaped with a radius equal to the radius of the matching punch plus the thickness of the sheet metal being bent. Typically, such matching punch and die are made from tool steel machined for each specific radius on a given type (i.e. stainless steel, mild steel, aluminum, etc.) or thickness of sheet metal. Machining of these matching convex and concave shapes is very expensive. 
     Additionally, while bending a large radius by such tooling, it will be understood that the radius at the closed position of the punch and die determines the radius of the bend, however, when the pressure is released the sheet metal may spring back to end up with a larger radius. The amount of spring back is related to the tensile strength and the hardness of the sheet metal being bent. If the size after spring back is not the desired size, then both the punch and die have to be re-machined to produce the desired radius on the part being bent. This too is a very expensive process. 
     Conventionally, and as shown in prior art  FIGS. 1 and 2 , to bend a radius shape on a press brake  10 , a steel convex shape punch  12  and a concave shaped die  14  are used as a matching set to position the sheet metal  16  in between. At the bottom of the stroke of the machine, the sheet metal gets bent to the desired shape. The punch has a radius  18  and the die has a radius  20 . The die radius is that of the punch plus the thickness  22  of the metal to be shaped. When the pressure is released, the sheet metal likely springs back and the finished radius  24  on the sheet metal will be larger than the radius of the punch. If the sheet metal radius after spring back is not the same as the desired radius of the part being formed, both the punch and the die will have to be re-machined. This, again, is a very expensive process, mostly because the machining of the concave shape is very time consuming. This method requires making a matching punch and die for each radius size, and possibly re-machining both if the size does not match the desired size of the part. 
     A newer version of the radius bending application is shown in the prior art  FIG. 3  wherein a steel punch  26  with the calculated radius, allowing for the spring back of the metal and placing a sheet metal on top of a sheet of rubber or urethane  28  and applying pressure on the punch pushing the sheet metal into the sheet of rubber or urethane, deforming it to take the shape of the punch and thus bending the sheet metal. Deflector bars  30  made of steel or aluminum are placed below the sheet of rubber or urethane to provide relief below the pad, so the sheet deflects into the air gap thus created. The complete assembly is to be placed inside a welded U-shaped steel box  32  functioning as a retainer. This method requires high tonnage, set up is very heavy to handle and is also very expensive for the limited size range that can be formed. 
     A further improved version of radius bending systems is shown in the prior art pad system of  FIG. 4 , which utilizes a molded rectangular urethane pad  34  with multiple relief holes  36  molded to the full length of the pad, thus reducing the forming tonnage. The pad is positioned inside a steel channel retainer  38  and block  40  sitting on top of deflector pads  42  made of hard grade urethane, in order to create air space for the main pad to deflect into. During use, filler rods or tubes  44  may be used within the relief holes  36 , but they must be used in symmetry. This pad system works reasonably well. The problem is that the areas molded between the molded holes tend to crack easily which leads to failure of the forming pad. Additionally, the total stack height of this pad sitting on top of the deflector bars, and all of these fitting inside a steel channel retainer is an issue. Many machines do not have the open height on the press brake to accommodate this stack height. 
     The present disclosure overcomes the problems associated with the aforementioned conventional radius bending applications. Accordingly, it is a general object of this disclosure to provide an improved radius forming system for sheet metal. 
     It is another general object of the present disclosure to provide a universal radius forming system for bending virtually any radius in many thicknesses and types of metals, using the same bottom bending die. 
     It is a more specific object of the present disclosure to provide a bending die comprising a specific shape of urethane forming pad designed to form a variety of radii using the same pad as the bottom die on a sheet metal bending machine commonly known as a press brake. 
     It is another more specific object of the present disclosure to provide a pressure pad layered on top of the forming pad to enable multiple forming pressures as well as wear resistance for the forming pad. 
     These and other objects, features and advantages of this disclosure will be clearly understood through a consideration of the following detailed description. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present disclosure, there is provided a radius forming system for bending sheet metal with a press brake that has a punch and a bottom die retainer. The system includes a pair of cooperating urethane pads whereby the bottom larger pad is dimensioned to fit within the bottom die retainer and includes a bottom cavity sized relative the size of the punch and the top flat pad is a heavier durometer and sits upon the larger pad. The pads are coupled to one another on one of the sides of the bottom pad 
     According to another embodiment of the present disclosure, these is provided a sheet metal forming system for use in a bending machine having a press punch and a bottom die bed. The system includes a pair of cooperating urethane pads whereby the bottom larger pad is dimensioned to fit within the bottom die bed and includes a bottom cavity sized relative the size of the punch and the top flat pad is a heavier durometer and sits upon the larger pad. The pads are coupled to one another through the middle centerline of the press punch. 
     According to another embodiment of the present disclosure, there is provide a radius forming device for bending sheet metal with a press brake having a punch and a bottom die retainer. The system includes a pair of cooperating urethane pads whereby the bottom larger pad is dimensioned to fit within the bottom die retainer and includes a bottom cavity sized relative the size of the punch and the top flat pad is a heavier durometer and sits upon the larger pad. The pads are coupled to one another through the middle centerline of the press punch. The device is capable of heavier tonnage via the use of optional reinforcement rods located on the top of the first pad. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will be more fully understood by reference to the following detailed description of one or more preferred embodiments when read in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the views and in which: 
         FIG. 1 a    cross-sectional frontal view of the component parts of a conventional prior art press brake in the pressed position. 
         FIG. 1 b    is a perspective view of the press brake of  FIG. 1   a.    
         FIG. 2 a    is a cross-sectional frontal view of the press brake of  FIG. 1  in the released position. 
         FIG. 2 b    is a perspective view of the press brake of  FIG. 2   a.    
         FIG. 3 a    is a cross-sectional frontal view of the component parts of another prior art press brake. 
         FIG. 3 b    is a perspective view of the press brake of  FIG. 3   a.    
         FIG. 4  is a cross-sectional frontal view of the component parts of yet another prior art press brake. 
         FIG. 5 a    is a cross-sectional partially exploded frontal view of the universal radius forming system according to the principles of an embodiment of the present disclosure. 
         FIG. 5 b    is a perspective view of the radius forming system of  FIG. 5   a.    
         FIG. 6 a    is a cross-sectional partially exploded frontal view of the universal radius forming system according to the principles of another embodiment of the present disclosure. 
         FIG. 6 b    is a perspective view of the radius forming system of  FIG. 6   a.    
         FIG. 7 a    is a frontal view of the universal radius forming system of  FIG. 6 a    in the released position. 
         FIG. 7 b    is a frontal view of the universal radius forming system of  FIG. 7 a    in the pressed position. 
         FIG. 8 a    is a cross-sectional partially exploded frontal view of the universal radius forming system according to the principles of another embodiment of the present disclosure. 
         FIG. 8 b    is a perspective view of the radius forming system of  FIG. 8   a.    
         FIG. 9 a    is a frontal view of the universal radius forming system of  FIG. 8 a    in the released position. 
         FIG. 9 b    is a frontal view of the universal radius forming system of  FIG. 9 a    in the pressed position. 
         FIG. 10 a    is a cross-sectional partially exploded frontal view of the universal radius forming system according to the principles of another embodiment of the present disclosure. 
         FIG. 10 b    is a perspective view of the radius forming system of  FIG. 10   a.    
         FIG. 11 a    is a frontal view of the universal radius forming system of  FIG. 10 a    in the released position. 
         FIG. 11 b    is a frontal view of the universal radius forming system of  FIG. 11 a    in the pressed position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One or more embodiments of the subject disclosure will now be described with the aid of numerous drawings. Unless otherwise indicated, use of specific terms will be understood to include multiple versions and forms thereof. 
     In any event, in the present system, the bottom die is a urethane forming pad with a flat top surface that deflects and applies uniform pressure from the bottom to wrap the sheet metal tightly against the punch. The size and shape of the punch determines the size and shape of the sheet metal part that is bent. The urethane forming pad functions like a bladder of hydraulic fluid that deflects and conforms to the shape of the punch, and in the deflection process, exerts enormous uniform pressure against the punch, thus bending the sheet metal tightly against the radius of the punch. The same urethane pad can be used with a variety of punches to form virtually any radius with the same bottom die. 
     Urethane or polyurethane is the preferred elastomeric material for this application because of a variety of unique engineering properties of this elastomer. For example, high load bearing capacity, excellent wear resistance, elastic memory, excellent impact resistance, superior resistance to abrasion, tearing, cutting and availability in a variety of hardness. Urethane is therefore an ideal material for this application. 
     If the urethane forming pad is too soft, it will not be able to bend tougher and heavier gauge metals, as the metal will kink, instead of bending with a uniform arc radius. If the forming pad is too hard, the required tonnage for deflecting such a forming pad will be very high, especially in larger radius and longer bends. Most press brakes will not have such high tonnage to form tougher longer sheet metal. That said, the forming pad must be flexible in a large area, without requiring a higher amount of tonnage to deflect the pad, and at the same time it should be able to apply enough forming pressure to wrap the sheet metal around the punch. 
     To increase the forming pressure for heavier or tougher metals, a harder grade of urethane pad, a so-called pressure pad or wear pad is layered on top of the forming pad and is held adjacent and/or attached to the forming pad during the forming operation. The complete forming system comprises a forming pad, which is a flexible member shaped specifically to provide a built-in deflecting area for the pad to deflect into when the punch pushes down into this pad; and layered on top of this pad is a pressure or wear pad, usually made of a harder grade urethane designed to provide a much higher forming pressure, and is more wear resistant and able to apply more forming forces bending the sheet metal against the punch. In a preferred embodiment, the system includes a detachable pressure pad that moves with the sheet metal during the forming process and should be replaceable if it is damaged by the sharp edges of the sheet metal. 
     More particularly, and turning now back to the figures to more specifically describe the present disclosure, an embodiment of the universal radius forming system  50  is illustrated in the partially exploded cross-sectional view of  FIG. 5 a    and associated perspective view of  FIG. 5 b   . The urethane forming pad  52  is designed to fit in a preferably standard steel channel  54  to function as a holder or a retainer to position the bottom die on the bed of a press brake. The sides  56  and the bottom  58  of the forming pad are molded (dimensioned) to conform to the shape of the steel channel  54 , which may be a commercially available C-channel retainer. The bottom  58  of the pad  52  has a molded concave shape  60 , with a radius and height generally sized for the maximum size punch that a given pad is designed to bend. More particularly, the space  62  this creates under the pad is sized volumetrically proportional to the volume of the punch that will penetrate the forming pad. The shape of this space  62  is preferably a mirror image of the shape of the largest punch contour that the forming pad is designed to bend. The shape  60  of the bottom of the pad  52  is designed for easy deflection and to provide progressively increasing forming pressure on the punch as it descends into the forming pad  52 . 
     The generally flat wear pad  64  is dimensioned to lay and is positioned on top of the forming pad  52  and is designed to provide a harder wear resistant forming surface. This wear pad is made of a material harder than the forming pad. The thickness  66  of the wear pad can be changed and is dependent on the thickness and the tensile strength of the sheet metal being formed. The wear pad  64  includes an overlapping curved loop section  68 , having a thinner cross-section to provide easy deformation and allowing the wear pad  64  to flow into the forming arc length of the punch contour. The wear pad further includes a rectangular key  70  and a circular key  72  that are both molded integral with the wear pad  64 . Matching rectangular slot  74  and circular slot  76  are molded integral with the forming pad  52 . A deformation slot  77  which is rectangular in cross section with a half round bottom is also molded in the forming pad  52  provides easy deformation into the forming area without the wear pad pulling out of the key slots ( 74 ,  76 ). 
     Finally, the steel punch  78  is attached to the ram  80  of the press brake and the tang  82  mounts the steel channel  54  retainer to the bed  84  of the press brake. In use, the press brake compresses the aforementioned component parts as the ram  80  and bed  84  are pressed together down the centerline  86 . 
     As such, the present disclosure pertains to bending sheet metal (stainless steel, mild steel, brass, bronze, copper, aluminum, etc.) into radius shapes using a universal bottom die. A plethora of radii can be formed with the same bottom die by merely changing the top steel punch radius. The maximum width of punch that can penetrate the forming pad is limited by the width of the forming pad. Staying within such a limitation, the desired radius is formed in one hit to form a ninety-degree (90°) bend or in three hits to form a U-shape or any size very large radii can be formed in sections by progressive bump forming hits. In any event, all forming hits are accomplished without any bump lines between formed sections. Since the sheet metal outside is being formed by urethane, there are no marks or damage of any kind to the finish of the sheet metal. So, pre-finished, pre-polished or pre-painted sheet metal can be formed without any damage to the outside finish. Accordingly, there is no need for secondary finishing operations. Even when forming perforated metal with large percentage openings, the sheet metal can be formed to the desired radial shapes without any kinks or distortions of the weak areas of the sheet metal. 
     Another embodiment of the universal radius forming system of the present disclosure will be described through  FIGS. 6 and 7 . It will be noted that  FIG. 6  is generally the same as  FIG. 5  but for the added pair of molded holes  88  in the main forming pad  52 . These holes are preferably symmetrically placed and shaped as tear-drops (or belt-drive shaped) with a larger diameter hole  90  towards the centerline  86  of the pad  52  and a smaller diameter hole  92  towards the outside edge of the pad. These holes  88  provide additional deflection space for the pad to deform for various sizes of punches that push into the forming pad  52 . If in the teardrop shape, the larger diameter  90  closer to the center line  86  will deflect more easily to the descending radius punch, and the smaller diameter  92  towards the outer edge of the punch will be exerting a progressively increasing forming pressure against the descending punch. It will be appreciated that there are many possible shapes and locations for these relief holes that can be molded to accomplish the same purpose. If for some application, there is a need for higher forming pressure, these holes (and in the illustrated teardrop shape the smaller diameter  92 ) can be filled with urethane (or otherwise) rods, and the like, of the same or harder durometer. Essentially, this embodiment enables the forming pad  52  to deflect easily requiring less tonnage to deflect the forming pad, as compared to the embodiment shown in  FIG. 5 , while adding flexibility and adjustability of forming pressures. 
     In any event, and once again, the main forming pad  52  is molded in a cast urethane compound shaped and sized to fit inside a steel channel retainer  54 . The top surface  94  of the pad  52  is flat, and the bottom side  60  has a molded concave shape that provides a cavity  62  for the forming pad  52  to deflect into when the punch penetrates. Positioned on top of the forming pad  52  is a pressure pad  64 , which is made of a higher grade of urethane. The pressure pad  64  is held anchored in the backside of the forming pad by a combination rectangular  70  and round  72  key molded in the wear pad, which are in turn press fit into the matching shapes ( 74 ,  76 ) molded in the forming pad  52 . 
     During the forming process, the punch  78  makes contact with the sheet metal first on the centerline  86 , and as it pushes the sheet metal down, the sheet metal as well as the pressure pad are deformed into an arc shape, and the pressure pad and the sheet metal are dragged into the formed arc shape. The length of the wear pad from the centerline to the outside edge of the arc at the bottom of the stroke is considerably more than the length at the beginning of the forming process when the pressure pad was flat. The extra length of the pressure pad is provided in the shape of a loop  68  at the backside. As the pressure pad is dragged into the forming area, because of the retractable design of the loop  68 , the extra material in this loop  68  moves into the forming area as the punch pushes the sheet metal into the forming pad. The vertical molded slot  77  in the back of the forming pad helps in the deflection of the main pad, without the pressure pad pulling out of the retaining key slots. 
       FIG. 7  illustrates the embodiment of  FIG. 6  in use. In particular,  FIG. 7 a    shows the press brake and the universal radius forming system in the released position while  FIG. 7 b    shows the press brake and universal radius forming system in the pressed position. The ram  80  directs the punch  78  towards the tang  82  and bed  84  of the press brake through the universal radius forming system positioned within the channel retainer  54 . The universal radius system starts in the released/ready position/state of  FIG. 7 a   , is temporarily transformed during the pressed/bending position/state of  FIG. 7 b   , and then returns to the state of  FIG. 7 a    for the next use of the brake. As the sheet metal  16  is pressed in  FIG. 7 b    the forming pad  52  is compressed and the cavity  62  and relief holes  88  are squeezed while the wear pad  64  and loop  68  are deformed as previously described. 
     In order to bend sheet metal of a heavier gauge or of a higher tensile strength, which requires more forming pressure to bend the sheet metal or plate, the embodiment of  FIG. 8  may be utilized. Such heavier sheet metal may have sharp edges that can cut into and damage the forming pad during the bending operation. As such, a urethane wear pad (or pressure pad) of a harder durometer urethane than the forming pad is designed for reducing the damage to the main forming pad. This pressure pad has to be flexible enough to deflect and bend along with the forming pad to bend the sheet metal against the exact contour of the steel punch, and then must return to its original position after the forming pressure is released. To accomplish this continuous and flexible engagement, a circular key-way is molded at the bottom of the pressure pad, along the centerline of the pressure pad, so that it snaps into a matching circular shaped groove that is molded in the forming pad. This design enables the deflecting of the pressure pad in conjunction with the radius shape of the punch, where the contact between the forming punch and the bottom die pad start as a line contact along the center line, and as the punch descends into the forming die, the urethane pressure pad wraps the sheet metal tightly against the punch, progressively moving outwards from the centerline. The forming pad has to be flexible and the pressure pad has to be rigid enough to uniformly bend the sheet metal around the punch. Depending on the tensile strength of the metal being formed, the hardness and the thickness of the pressure pad can be varied to accomplish the desired forming pressure. The harder grade of the pressure pad is also more wear resistant for forming sheet metals with higher thicknesses or with sharp edges or odd shapes. This design is a preferred method for providing a pressure pad, anchored in the middle wherein a much harder grade of pressure pad is required. Harder pressure pads will be required when bending sharper edged sheet metal or odd shaped sheet metal, or sheets with cut-outs within the sheet. 
     More particularly, and turning now to  FIG. 8 , the main forming pad  52  is molded in a preferably cast urethane compound and is shaped and sized to fit inside a steel channel retainer  54 . The top surface of the forming pad is flat and the bottom has a molded concave shaped air cavity  62  that provides a space for the forming pad to deflect into when the punch  78  penetrates the forming pad  52 . This air cavity  62  below the pad is sized volumetrically proportional to the volume of the largest size punch that will penetrate the forming pad  52 . Indeed, this air cavity below the forming pad is a mirror image of the shape of the largest size punch contour that the forming pad is designed to bend. The concave shape of the bottom side  60  of the pad is for easy deflection of the pad  52  as well as to provide a progressively increasing forming pressure on the punch  78  as it descends into the pad  52 . The wear pad  64  is positioned on top of the forming pad  52  and is designed to provide a harder wear resistant forming surface. This wear pad  64  is made of a material harder than the forming pad  52 . The thickness  66  can be varied as is dependent upon the thickness and tensile strength of the sheet metal that is being formed. A circular key-way  96  is molded at the bottom of the pressure pad, along the centerline of the pressure pad, so that it snaps into a matching circular shaped groove  98  that is molded in the forming pad. The hardness of the pad can be changed to vary the forming pressure as well as the wear resistance characteristic of the pad. During the forming process, the punch  78  makes contact with the sheet metal first on the centerline  86  and as it pushes the sheet metal down, the sheet metal is deformed into an arc shape starting at that centerline and going outwards. 
       FIG. 9  illustrates the embodiment of  FIG. 8  in use. In particular,  FIG. 9 a    shows the press brake and the universal radius forming system in the released position while  FIG. 9 b    shows the press brake and universal radius forming system in the pressed position. The ram  80  directs the punch  78  towards the tang  82  and bed  84  of the press brake through the universal radius forming system positioned within the channel retainer  54 . The universal radius system starts in the released/ready position/state of  FIG. 9 a   , is temporarily transformed during the pressed/bending position/state of  FIG. 9 b   , and then returns to the state of  FIG. 9 a    for the next use of the brake. As the system is pressed in  FIG. 9 b    the forming pad  52  is compressed and the cavity  62  is squeezed while the wear pad  64  is deformed as previously described. 
     In order to bend sheet metal of an even heavier gauge or of an even higher tensile strength, which requires more forming pressure to bend the sheet metal or plate, the embodiment of  FIG. 10  may be utilized. The main pad  52  is molded in a flexible and softer cast urethane compound shaped and sized to fit a steel channel retainer  54 . The top surface of the forming pad  52  includes molded circular slots  100  which may house steel rods  102 . In order to further increase the forming pressure, these round tool steel rods  102  are inserted into the round cavities  100  and have a small gap between each rod so that when the top surface of the forming pad flexes, these rods will also flex and at the same time apply high forming pressure against descending punch. During the forming process, the punch makes contact with the sheet metal first on the centerline and as it pushes the sheet metal down the sheet metal as well as the pressure pad and the full row (if inserted) of steel rods below the pressure pad are deformed into an arc shape and the pressure pad along with the steel rods and the sheet metal are progressively formed into the arc shape, starting with the centerline and going outwards. Once again, in this embodiment, in order to protect the top surface of the pad  52  from cutting by sharp edges, a wear or pressure pad  64  made of a very hard grade urethane can be used. As before, this wear pad  64  has a molded key  96  that snaps into a key slot  98  molded in the center line of the forming pad  52 . This key  96  and matching slot  98  enables compressively holding the pressure pad in place during the forming/bending operation. 
       FIG. 11  illustrates the embodiment of  FIG. 10  in use. In particular,  FIG. 11 a    shows the press brake and the universal radius forming system in the released position while  FIG. 11 b    shows the press brake and universal radius forming system in the pressed position. The press directs the punch  78  through the universal radius forming system. The universal radius system starts in the released/ready position/state of  FIG. 11 a   , is temporarily transformed during the pressed/bending position/state of  FIG. 11 b   , and then returns to the state of  FIG. 11 a    for the next use of the brake. As the system is pressed in  FIG. 11 b    the forming pad  52  is compressed and the cavity  62  is squeezed while the wear pad  64  is deformed as previously described. 
     Yet another embodiment consists of a thin layer of a harder grade pressure pad molded integral with the forming pad. This pad is molded when the two urethane compounds are in a liquid state so that they do not separate from each other during the bending process. The harder grade pressure pad has a shorter pot life (time to harden) than the softer grade forming pad. Accordingly, it will be practical to cast the harder grade first on a leveled mold and before this layer hardens completely, the other compound is poured on top of this layer so that there is a good bond therebetween. 
     The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom. Accordingly, while one or more particular embodiments of the disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the present disclosure.