Patent Publication Number: US-2021162521-A1

Title: Bidirectional sheet metal cutting tool

Description:
TECHNICAL FIELD 
     The disclosure of the present patent application relates to sheet metal tools, and particularly to a bidirectional sheet metal cutting tool that can be mounted on a bending or folding machine. 
     BACKGROUND ART 
     Cutting of sheet metal and other sheet materials using a single cutting assembly generally requires that the cutting assembly have a capability of acting from one side of the sheet, extend across the entire length of the cut, or deflect the sheet across a part of the cutting assembly. The present disclosure is directed to the latter, i.e., to a cutting assembly that deflects the sheet. 
     The general cutting technique uses a scissors cut configuration, meaning the same assembly applies pressure from both sides of the sheet material or web. The scissors cut can be accomplished by having a cutting blade on both sides or one side of an opposing pair, which can use configurations having at least one of the blades configured as a rotary blade or cutting wheel. When the material being cut passes a connection between the opposing pair, which can be a hinge or a fixed attachment, an extended bypass cutting operation is performed. In the extended bypass cutting operation, the cut material bypasses the hinge or fixed attachment, allowing cutting to continue beyond the dimensional limits imposed by the hinge or fixed attachment. 
     As used herein, such a cutting operation is referred to as a progressive linear cutter, meaning that the cutting operation begins at one end of the length of the cut, and continues or progresses along that length. Such cutting is in some cases along a straight line. However, progressive linear cutting can occur with the cut being other than a straight line, for example curved or following a complex directional pattern. 
     A familiar example of deflecting the material is found in scissors-type cutting mechanisms. If the cut has a length that extends beyond the reach of the scissors, the cut material must deflect away from the hinge as the scissors progresses. The ability of the sheet metal to deflect is in a large part dependent on the sheet metal being flat. In the case of sheet metal, the deflection becomes difficult if the work (the workpiece) is already formed, for example by a sheet metal brake or other metal deforming machine. As a result, once the material is formed, it does not bend as easily, and when it is bent, it is more likely to become deformed. 
     When using a sheet metal bending brake, sometimes called “sheet metal brake”, “bending machine” or “sheet metal folder”, folds are made in the sheet material. The folded or forms in the sheet material often restrict the ability of the sheet metal to deflect, because in effect, the formed material is no longer flat. Thus a progressive linear cutter is difficult to use when a free end of the sheet to be cut is formed to have a non-flat shape. 
     In tools used with sheet material, the designation of “length” and “width” can differ according to the operation. In the case of brakes and similar metalworking tools, “length” can mean the forward progression of the work through the machine, whereas for the cutting operation, the “length” can mean the direction of the cut. If, as is often the case, the length of the cut is orthogonal to the direction of the forward progression of the work through the machine, the term “length” when describing a cut may be orthogonal to the lengthwise direction of the progression of work through the brake or other metalworking tool. 
     The typical approach to using a progressive cutter for sheet metal to be formed is to first use the cutter to cut portions from a larger piece, and then form the portions to a desired shape after the portions are cut. This of course means feeding the individual portions to the brake or other forming machine after individual portions are cut. Such a process of feeding the individual portions can be time consuming and either require additional labor or require additional robotic material handling, especially in the case of producing work products of significant length. 
     A further characteristic of progressive cutters is that it is often necessary to perform the cut in one direction. As a result, if the cut is made along a substantial length of cut, it is necessary for the cutting assembly to be returned “home” to a starting point in order to initiate a subsequent cut. 
     A sheet metal brake, in its simplest form, creates a linear bend in the sheet metal; however, more complex bends and shapes are possible. One particular type of brake is described in U.S. Pat. No. 6,324,882. That brake is configured so that upper and lower beams terminate in clamping tools to support the work, and has at least one tool carrier terminating in a bending tool having a curved pressure surface to press against the work to bend the work against the clamping tools. A lower beam arranged on the brake&#39;s machine frame and an upper beam arranged on the machine frame are configured so that the work can be fixed in position. A bending tool moving device allows a bending tool to be moved, in such a manner that the movements of the bending tool can be effected with bending movements of the bending tool. That type of sheet metal brake or bending tool has a bending nose with a curved pressure surface for acting upon one side of the fiat material. The bending tool is movable by the bending tool moving device between a starting bending position and an end bending position on a path about the respective bending edge which is predetermined in a defined manner such that the curved pressure surface and the side of the fiat material acted upon move relative to one another in the form of an essentially slide-free rolling on one another. This type of brake is sometimes called a “folder” or bending machine because it can easily be used to create folds in the work. 
     Thus, a bidirectional sheet metal cutting tool solving the aforementioned problems is desired. 
     DISCLOSURE OF INVENTION 
     The bidirectional sheet metal cutting tool is a cutting tool that performs cuts on webbed material in which a length of cut exceeds a physical dimension of the cutting tool, while limiting flexing of the webbed material during a cutting operation. The cutting tool comprises a cutter assembly riding on a guide track, and having upper and lower sections. The upper and lower sections have an offset attachment to each other at an interface, wherein the webbed material passes the offset after cutting in an extended bypass cutting operation. The interface has a curved profile between the upper and lower sections, allowing deflection of the webbed material on at least one side of a cutting direction in the extended bypass cutting operation. At least one pair of cutting wheels engages the webbed material prior to deflection. 
     In one configuration, a sheet metal forming tool is equipped with the cutting tool to allow sequential operations involving cutting sheet metal as the webbed material. The interface has a differentiation in its profile, the differentiation comprising the curved profile and at least one additional profile. The differentiation causes a differential deflection in the sheet metal downstream of the cut as the cutting assembly rides on the guide track. The deflection on one side of the sheet metal downstream of the cut exceeding the deflection of an other side of the metal downstream of the cut allows bypass cutting of sheet metal in a manner that reduces distortion of the sheet metal on a side of the cut in which the sheet metal forming tool had created or changed a profile in the sheet material. 
     These and other features of the present disclosure will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are perspective views showing a multi-station bending machine having a bidirectional sheet metal cutting tool assembly (also referred to herein as a slitter or slitting assembly) mounted thereon. 
         FIG. 2  is a perspective view showing a multi-station bending machine with a unidirectional cutter assembly (or slitter assembly) mounted thereon. 
         FIGS. 3A, 3B, 3C, and 3D  are perspective views showing details of a bidirectional sheet metal cutting tool. 
         FIG. 4  is a perspective view showing details of a single cutter head. 
         FIG. 5A  is a top view of a sheet metal slitter having a bidirectional sheet metal cutting tool assembly mounted thereon. 
         FIG. 5B  is a detail view of area  5 B of  FIG. 5A . 
         FIG. 5C  is a front view of the slitter of  FIG. 5A . 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     BEST MODE(S) FOR CARRYING OUT THE INVENTION 
     The bidirectional sheet metal cutting tool is a slitter or cutter that is configured with a cutting head that causes the cut work (the workpiece) to deflect in opposite directions on opposite sides of the cutting head, where the work on one side deflects more than the work on the other side. This allows the side of the work that is more easily deflected without causing permanent distortion to deflect more, and allows the deflection on a side of the work that would be damaged or distorted by deflection to be deflected less. 
     When used with a sheet metal working tool (other than the cutter), such as a sheet metal brake, the deflection on the side of the cutting head facing the sheet metal working tool can be greater than the deflection on the side of the cutting head facing away from the sheet metal working tool. In that way, the working tool can progressively discharge worked sheet metal past the cutting head, and the major deflection can occur on the side of the cutting head that faces the sheet metal working tool. In one non-limiting example, the sheet metal working tool is a sheet metal brake of the type called a “folder”. In a typical arrangement, the sheet metal is progressively discharged from the bender as successive forming operations are performed. 
     While a sheet metal brake is described, the sheet metal brake is given as a non-limiting example. The disclosed cutter can be used with other types of machines that may or may not be able to grip the work. In addition, the disclosed cutter can be used for types of webbed material other than sheet metal, with the primary motivation being an ability to deflect the webbed material in a bypass operation as the webbed material passes the cutter. Thus, a relatively stiff webbing on a roll can be cut by the disclosed cutter. 
     While bypass cutting is described, the disclosed techniques can also be used for pinch cutting, in which opposing elements create a cut in the work. 
     The deflection of the work on the side of the cutting head facing the sheet metal working tool appears counter-intuitive because the work would be clamped on that side. The reason this is advantageous is that in some cases, which by non-limiting example include sheet metal brakes, the discharged work is formed into non-flat shapes and therefore is not easily deflected without damage. On the other hand, after the shapes are discharged, the sheet metal on the side of the sheet metal working tool is still flat, i.e., not yet formed into non-flat shapes. By spacing the cutter head away from a clamping position, the sheet metal is able to deflect on the clamped side in a sort of waved pattern. Since the sheet metal is flat on that side, the deflection on that side falls well within the elastic deformation limits of the sheet metal. 
     If the deflection on the sheet metal working tool of the cutting head is too great to be limited to elastic deformation of the work, then the cutting head is positioned further from the clamping position, thus allowing cutting to take place without the deflection causing plastic deformation of the work. This positioning is expected to be necessary if the bends themselves are close to the edge of the final form, so after a cutting operation, it may be necessary to retract the un-formed part of the sheet metal for a subsequent forming operation, such as a subsequent bending operation by the above-described sheet metal brake. 
     It is expected in some operations, the side of the cutting head with the greater deflection would be faced away from the sheet metal forming machine, but this presumes that the part of the work furthest away from the sheet metal forming machine has the greatest ability to deflect. 
       FIGS. 1A and 1B  are perspective views showing a sheet metal folding brake  100  with a cutting wheel assembly mounted. The sheet metal folding brake is given as a non-limiting example, as it is only necessary for the work to be supported in some manner while being cut. Depicted is chassis  101 , which functions as a frame and has fixed thereto a plurality of stations  111 - 115 . Since the stations  111 - 115  are fixed to the chassis  101 , the stations  111 - 115  are mechanically and functionally part of the chassis  101 . Also mounted to the chassis  101  is a machine controller  130 , which provides automated machine control functions, for example, by use of a processor and an associated memory. 
     Of note, the nomenclature of the machine (brake  100 ) and of the work results in a difference in which direction is described as the “length” and “width”. The width of the brake  100  is indicated by stations  111 - 115 , whereas the length of the work extends across the same stations  111 - 115 . Thus, the width of the work is often orthogonal to the width of the machine. 
     A brake of this type is intended to perform bending and folding work on long pieces of metal, for example, 7 meters (21 ft.) long. The multiple stations  111 - 115  accommodate that length across the width of the brake  100 . 
     Cutter assembly (or slitter assembly)  140 , shown at one end of the brake  100 , is caused to traverse in front of the brake  100  along track  145 , in order to cut a portion of the work after the work is formed by the brake  100 . The cutter assembly  140  comprises cutter head  141 , which is used to cut sheet metal forming the work. The track  145  is mounted to the chassis  101 , and the cutter assembly  140  rides on the track  145  to traverse in front of the brake  100 . 
     In the usual circumstance, the brake  100  forms a width of the work by bending and folding, and then discharges the formed width out the front. According to the disclosed technology, after discharging the formed width of the work, the formed width of the work extends past cutter head  141 . As a result, the formed part of the work is positioned past the path of the cutter head, as defined by the path of the cutter assembly  140  along the track  145 . In order to perform a cut, the cutter assembly  140  is driven along track  145  across the width of the brake  100  by a cutter assembly drive (not separately shown). 
     In order to cut the work, cutter head  141  must either extend around the work or otherwise move the work out of the way. In the disclosed configuration, cutter head  141  causes the work to deflect, so it is not necessary for the cutter head  141  to extend around the work. This deflection comprises a major deflection on the side of the work that is substantially flat, and a minor deflection on the side of the work that has been formed. In one non-limiting example, the side of the work that is substantially flat is on the side of brake  100 , the major deflection is 9.525 mm or ⅜ inch, and the minor deflection is 3.175 mm or ⅛ inch. These figures would vary for the same cutter head configuration, depending on the physical nature of the work. 
     The deflection of the work at the cutter head  141  allows the use of a dual cutting wheel configuration in which two sets of opposing wheels are provided on the cutting head  141 . The use of two sets of opposing wheels on the cutting head is facilitated by the deflection of the work because the deflection of the work also allows the work to clear a set of cutting wheels not in use during the cut. Since the configuration of  FIGS. 1A and 1B  allows cutting in two directions, the cutter assembly  140  is able to perform sequential cuts in opposite directions, thereby avoiding a need for the cutter assembly  140  to return to a home position on a particular side of the brake  100 . 
     It is also possible to configure the cutter  140  so that all deflection occurs on one side of the cutter head  141 . However, in the case of a dual cutter head, it would be necessary to either accept engagement with the trailing set of opposing wheels or otherwise configure the cutter head  140  to allow the trailing set of opposing wheels to clear the work. Alternatively, it would be possible to shift the cutter head  141  to reduce or avoid engagement of the cut portion of the work with the trailing set of opposing wheels. 
     Since a dual cutting arrangement is used for the cutter head  141 , after the cutter assembly  140  is driven across the width of the brake  100 , it is ready to perform a next cut in the opposite direction across the width of brake  100 , using the other set of opposing wheels. This avoids a time delay that would occur if it were necessary for the cutter assembly  140  to return to its original home position, since the cutter assembly  140  would have home positions at each end of the track  145 . This also avoids additional movement of the cutter head  141  between passes, which further has the advantage of avoiding additional movement of machine parts after the completion of a cutting pass. 
       FIG. 2  shows a configuration in which a cutter assembly  240  uses a single cutting configuration for cutting head  241  using a single set of opposing wheels on cutting head  241 . This configuration provides for deflection primarily in one direction of travel of the cutter assembly  240 , so that after each pass, the cutter assembly  240  returns home. This requires a delay resulting from the return operation, during which machine movement is occurring, but makes it easier to configure the deflection of the work on the two sides of the cut. It is anticipated that in some cases, even the small deflection (given in the above example as the minor deflection of 3.175 mm, or ⅛ inch), may be difficult. By using a single set of opposing wheels on the cutting head  241 , the minor deflection can be minimized or perhaps avoided. 
       FIGS. 3A-3D  are perspective views showing a non-limiting example of the construction of the cutter head  141  having a dual cutting arrangement. Depicted are upper and lower wheel carriers  321 ,  322  and a carrier bracket  327 . Wheel carriers  321 ,  322  support upper and lower wheel assemblies  331 ,  332 ,  333 ,  334 , which are configured to rotate from opposite sides of the cutter head  141  according to whether the wheel assemblies are on the upper wheel carrier  321  (wheel assemblies  331 ,  333 ) or on the lower wheel carrier  322  (wheel assemblies  332 ,  334 ). Wheels assemblies  331 - 334  are configured to cut the work as the work progresses past the first pair of wheel assemblies. Since the work will have been cut, the lagging wheel assemblies serve primarily as guides. Therefore, the lead pair of wheel assemblies perform the cutting and are sometimes referred to as “slitter wheels”. The lagging wheel assemblies are also slitter wheels because cutter assembly  140  performs cutting operations in both directions, but do not perform the cutting when they are lagging. 
     Wheel carriers  321 ,  322  have a curved interface  341  such that, on one side of the cutting head  141 , the curved interface  341  allows the work to deflect down, and on the opposite side of the cutting head  141 , the curved interface  341  allows the work to deflect up. In order to assist this deflection and guide the work without scraping the surface of the work, guide rollers  350  are provided along the interface  341 . 
       FIG. 4  is a perspective view showing a non-limiting example of the construction of cutter head  241  having a single cutting arrangement. Depicted are upper and lower wheel carriers  421 ,  422  and carrier bracket  427 . Wheel carriers  421 ,  422  support a single set of upper and lower wheel assemblies  431 ,  432  which are configured to rotate from opposite sides of cutter head  241  according to whether the wheel assemblies are on the upper wheel carrier  421  (wheel assembly  431 ) or on the lower wheel carrier  422  (wheel assembly  432 ). Wheels assemblies  431 ,  432  are configured to cut the work as the work progresses past the first pair of wheel assemblies. Since cutter assembly  240  uses a single cutting configuration, there are no lagging wheel assemblies. 
     Cutter assembly  140  or  240  can be used on a stage in which the primary purpose of the stage with the cutter assembly is to function as a slitter.  FIGS. 5A-5C  are views showing a slitter  500 , in which the cutter head or slitter assembly  140  is used on stage platform  511 .  FIGS. 5A and 5B  are a top view and a detail view, respectively, and  FIG. 5C  is a front view. 
     The platform  511  is provided with suction cups  521 , which apply vacuum from a suction source (not shown) in order to hold work, such as sheet metal, in place on the platform  511 . The work can be progressively moved for sequential cuts by movement of the suction cups  521 , by use of a separate gripper, or manually. 
     While a bidirectional cutter head  140  is shown, it is also possible to use a unidirectional cutter head (e.g., cutter head  240 ). When the bidirectional cutter head  140  is used, sequential cuts can be made without the necessity for the cutting assembly to return “home” to a starting point in order to initiate a subsequent cut. 
     It is to be understood that the bidirectional sheet metal cutting tool is not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed subject matter.