Patent Publication Number: US-11383284-B2

Title: Press brake tool engagement system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims benefit under 35 U.S.C. § 119 to the earlier filing date of U.S. Provisional Application No. 62/385,513, filed Sep. 9, 2016, entitled PRESS BRAKE TOOL SAFETY MECHANISM, which is incorporated by reference herein, in its entirety and for all purposes. 
    
    
     BACKGROUND 
     Press brake tool systems are used for forming sheet metal and other workpieces, and commonly include an upper table and a lower table. The upper table can be equipped to move vertically with respect to the lower table. Various forming tools can be mounted to the tables, so that when the tables are brought together, the tools bend or impress a workpiece, such as a piece of sheet metal, placed therebetween. 
     Typically, the upper table will couple with male forming tools, such as press brake and punch tools, and the bottom table will couple with female forming tools, such as dies. In order to perform a variety of forming operations, differently shaped press brake tools and dies are used. Thus, it is often necessary to exchange various forming tools within both the upper table and lower table. 
     Because the forming tools mounted in the lower table are supported from below, they may be substituted with relative ease. The forming tools mounted to the upper table, however, are suspended from above, usually held in place by a clamping mechanism that clamps all of the forming tools simultaneously. Upon loosening, unlocking, or releasing the clamping mechanism, the forming tools mounted to the upper table may be removed by sliding the tools horizontally to an open end of the upper table, or in some instances, by removing the tools vertically. Horizontal exchange of the forming tools can be cumbersome due to the proximity of the forming tools with respect to one another in the upper table, often necessitating the removal of each tool mounted within the upper table when only one tool is being exchanged. Neighboring clamps may also interfere with horizontal removal of the tools. 
     Vertical removal and insertion of the forming tools may not improve the exchange process due to the safety risks associated with handling the often heavy forming tools. In particular, loosening the clamping mechanism of the upper table may result in one or more tools falling and injuring a press brake operator. 
     To prevent the forming tools from accidentally falling from the upper table of a press brake assembly, several safety mechanisms have been developed. One such mechanism may involve a safety tang that protrudes laterally from a surface of the forming tool. Such a safety tang may be shifted into a complementary groove defined by a tool holder in the upper table, thereby securing the tool to the holder until the tool is clamped. This mechanism is problematic, however, because of the manipulation required of the user to actuate the safety mechanism and secure the tool within the holder. Other preexisting safety mechanisms that involve forming tools equipped with a variety of latches, straps, or projections and complementary receiving spaces defined by tool holders are deficient for similar reasons. These designs typically employ a variety of movable external parts and often require a high degree of structural specificity between the design of each forming tool and corresponding tool holder. 
     Thus, there exists a need for improved mechanisms used to secure forming tools to the upper table of a press brake assembly while the clamping mechanism of such an assembly is disengaged, such that heavy forming tools can be quickly exchanged without the risk of accidentally falling. 
     SUMMARY 
     A tool includes a magnetic safety mechanism for operation in a press brake or similar machine apparatus. The mechanism includes a coupling assembly configured to provide a releasable magnetic coupling between the tool and a tool holder. A release is provided to selectively engage and disengage the magnetic coupling with the tool holder, alternately coupling and releasing the tool from the press assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an isometric view of a tool for a press brake apparatus. 
         FIG. 1B  is a front view of the tool. 
         FIG. 1C  is a top view of the tool. 
         FIG. 1D  is an alternate top view of the tool. 
         FIG. 1E  is a section view of the tool, taken along line A-A of  FIG. 1C . 
         FIG. 1F  is a top view of a magnetic coupling assembly for the tool, taken at detail K in  FIG. 1D . 
         FIG. 1G  is a section view of the tool, taken at detail H of  FIG. 1E  and along line A-A of  FIG. 1C . 
         FIG. 2  is an exploded view of the magnetic coupling assembly and an armature. 
         FIG. 3A  is a section view of the tool, taken along line B-B of  FIG. 1D . 
         FIG. 3B  is an alternate section view of the tool with the coupling assembly in a disengaged configuration, taken along line B-B of  FIG. 1D . 
         FIG. 4  is an isometric view of a tool for a press brake apparatus, showing the internal configuration with an alternate magnetic coupling configuration. 
         FIG. 5  is an isometric section view of a tool for a press brake apparatus, in an embodiment having an alternate magnetic coupling assembly. 
         FIG. 6  is an alternate isometric section view of the tool, transverse to  FIG. 5 . 
         FIG. 7A  is an isometric view of the tool of  FIG. 5 , including a magnetic coupling assembly detail. 
         FIG. 7B  is a front view of the tool. 
         FIG. 7C  is a top view of the tool. 
         FIG. 7D  is an alternate top view of the tool. 
         FIG. 7E  is a section view of the tool at detail H, taken along line A-A of  FIG. 7C , showing magnetic flux paths. 
         FIG. 7F  is an alternate section view of the tool. 
         FIG. 7G  is a further section view of the tool, taken along line B-B of  FIG. 7D . 
         FIG. 8A  is an isometric view of the tool, with an external handle mechanism. 
         FIG. 8B  is a top view of the tool showing the handle mechanism. 
         FIG. 8C  is a section view of the handle mechanism, taken along line C-C of  FIG. 8B . 
         FIG. 8D  is a section view of the tool in an engaged position, taken along line B-B of  FIG. 8B . 
         FIG. 8E  is an alternate section view of the tool in a released position. 
         FIG. 9A  is an isometric view of a tool for a press brake apparatus, in a narrow profile configuration. 
         FIG. 9B  is a front view of the tool in  FIG. 9A . 
         FIG. 9C  is a side view of the tool. 
         FIG. 9D  is a top view of the tool. 
         FIG. 9E  is a section view of the tool, taken along line A-A of  FIG. 9D . 
         FIG. 9F  is an alternate section view of the tool at detail H of  FIG. 9E . 
         FIG. 10  is an isometric view of a tool for a press brake or similar machine apparatus, showing an alternate internal magnetic coupling structure and a decoupling member. 
         FIG. 11A  is an isometric view of a tool for a press brake or similar machine apparatus, showing two decoupling members. 
         FIG. 11B  is a top transparent view of the tool of  FIG. 11A . 
         FIG. 11C  is a section view of the tool, taken along line A-A of  FIG. 11B . 
         FIG. 11D  is another section view of the tool, taken along line B-B of  FIG. 11B . 
         FIG. 12A  is a top transparent view of a tool for a press brake or similar machine apparatus, showing alternate decoupling mechanisms. 
         FIG. 12B  is a front transparent view of the tool of  FIG. 12A , showing the internal components of the decoupling mechanisms. 
         FIG. 12C  is a section view of the tool, taken along line A-A of  FIG. 12A . 
         FIG. 12D  is another section view of the tool, taken along line B-B of  FIG. 12A . 
         FIG. 13  is a section view of a tool for a press brake or similar machine apparatus. 
         FIG. 14  is a section view of a press brake punch or tool coupled with a tool holder. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is an isometric view of a tool component  10  for a press brake machine or similar press-type machine apparatus. While generally described as a press brake tool herein, component  10  may alternately be configured as a press brake punch, punch tool, or similar machine tool component. 
     As shown in  FIG. 1A , tool  10  includes a tool end or working end  12  opposite a coupling end or tang  13 . Depending on the particular configuration of tool  10 , working end  12  may be generally positioned beneath coupling end or tang  13 , such that working end  12  is the bottom end and coupling end or tang  13  is the top end. Tang  13  may be mounted within a corresponding tool holder as part of a press brake assembly. In operation, such a press brake assembly may punch, impress, crimp, fold, crease, or otherwise shape various workpieces inserted beneath working end  12  and optionally one or more forming dies. In some examples, a workpiece may include a sheet metal component or other material to be tooled. 
     In these examples, tool  10  may include two load-bearing shoulder portions  16 ,  17  that extend horizontally outward from reference faces  14 ,  15  at the base of tang  13 . Shoulder portions  16 ,  17  may contact complementary surfaces on a tool holder upon inserting tool  10  within the holder, in order to bear or transfer a load between the tool holder and the tool body upon operation of the working end on a sheet metal component or other workpiece. 
     Tool  10  also includes a plurality of magnetic assemblies  18  vertically disposed within tang  13  and tool body  21 . Each magnetic assembly  18  may include one or more magnetic elements, which may include one or more permanent magnets, ferromagnetic components, or combinations thereof. As illustrated, each magnetic assembly  18  may be partially exposed through a top surface  20  of tang  13 . In this particular example, tool  10  includes three magnetic assemblies  18 . In other examples, the number of magnetic assemblies  18  in a given tool  10  may vary, ranging from 1 to about 50 magnetic assemblies  18 . Each magnetic assembly  18  may be removable, adjustable, or fixed within tool  10 . 
     The body  21  of tool  10  may include front and back surfaces  26  and  28 . In examples, surfaces  26 ,  28  may be variously shaped and sized depending on the desired function of tool  10 . Tool  10  may further define a lateral cavity  22 , of which only the opening is visible in  FIG. 1A . Lateral cavity  22  may be configured to slidably receive an armature  24 , which is shown fully inserted within the lateral cavity in  FIG. 1A . In the embodiment shown, armature  24  provides a coupling mechanism configured to modulate the strength of a magnetic flux coupling induced between tool  10  and the holder. In some examples, armature  24  can be adapted for selective disengagement of the coupling end or tang  13  of tool  10  from the holder. Armature  24  contains one or more dynamic or moving elements, which can include one or more magnetic elements, e.g., permanent magnets and/or ferromagnetic components. 
     Once inserted into the receiving space defined by a tool holder, tool  10  may be held in place at least temporarily by magnetic forces prior to clamping tool  10  with the holder. In particular, the magnetic elements of magnetic assemblies  18  and armature  24  may align such as to guide a magnetic flux in a circuit further involving a ferromagnetic material, e.g., medium alloy steel, comprising the tool holder. The magnetic flux can urge tool  10  upwardly into the tool holder so as to minimize non-ferromagnetic gaps, e.g., air gaps, between the two components, thus holding tool  10  up against the load-impinging shoulder surfaces of the holder. In some examples, the magnetic flux coupling induced between tool  10  and its tool holder can support the weight of the tool without additional clamping support. By holding tool  10  in place prior to clamping a tool holder around the upper portion of tool  10 , a user&#39;s hands may be free to install additional tools until the holder is activated to lock all tools in place for operation on a workpiece. In some embodiments, the strength of the magnetic flux coupling can secure tool  10  even during operation on a workpiece without additional clamping support. 
       FIG. 1B  is a front view of tool  10 . As illustrated in  FIG. 1B , magnetic assemblies  18  may protrude a distance above top surface  20 . The distance by which magnetic assemblies  18  protrude above top surface  20  may vary. 
     Press brake tool system or apparatus  10  includes a tool body  21  with a working end configured for operation on a workpiece, and a coupling end configured for selective engagement with a tool holder. The working end is spaced from the coupling end along the tool body, e.g. at opposite top and bottom ends. One or more magnetic assemblies  18  can be configured to induce a magnetic coupling between the tool body  21  and the tool holder, where the coupling end of the tool body is magnetically engageable with the tool holder. 
     The magnetic assemblies  18  can include one or more magnets disposed in the tool body  21  for generating magnetic flux to induce the magnetic coupling, one or more ferromagnetic components disposed in the tool body  21  for guiding magnetic flux to induce the magnetic coupling, or a combination thereof. Typically, the magnetic coupling is sufficient to support the weight of the tool body  21  upon engagement of the coupling end with the tool holder. 
       FIG. 1C  is a top view of tool  10 , showing each of the three magnetic assemblies  18  included in this particular example. In other examples, the number, spacing, and arrangement of magnetic assemblies  18  within tool  10  may vary. As shown in  FIG. 1C , each magnetic assembly  18  may include two assembly slugs  30  laterally flanking each side of an end guide  32 . Assembly slugs  30  and end guide  32 , along with other components of each magnetic assembly  18 , may be contained within a housing  19 , which can be fixed within tool  10 . In some examples, such components may be cast or mold into housing  19  to form each magnetic assembly  18 . Housing  19  may be a structural insert that defines the external shape of each magnetic assembly  18  and its internal compartments. Such an insert may be made from various materials including but not limited to one or more plastics or polymer compositions. 
     In embodiments, the number of assembly slugs  30  and end guides  32  may vary. Each assembly slug  30  may be made from various materials including but not limited to a magnetically permeable material, e.g., one or more metals such as steel. In some examples, such magnetically permeable material may be highly permeable. End guides  32  may also be made from various materials including but not limited to iron or steel, e.g., electrical steel.  FIG. 1C  also shows line A-A, which denotes a cross-sectional plane used for illustration purposes. 
       FIG. 1D  is an alternate top view of tool  10 , showing three magnetic assemblies  18  exposed at one end through top surface  20 .  FIG. 1D  also shows line B-B, which denotes a cross-sectional plane, and detail K, used for illustration purposes. 
     The magnetic assemblies  18  can include one or more permanent magnets disposed in the tool body  21 , and configured to form a magnetic coupling between the tool body and the tool holder with the coupling end of the tool body  21  is engaged. One or more non-ferromagnetic components can also be disposed in the tool body, and adapted for modulation of a flux path through the one or more magnetic elements (e.g., where the strength of the magnetic coupling is responsive to the modulation of the flux path). Similarly, a plurality of magnetic sub-assemblies  18  may each include one or more magnets, ferromagnetic elements or non-ferromagnetic components configured to independently induce a magnetic coupling between the coupling end of the tool body  21  and the tool holder. 
     A tang  13  can be defined by the coupling end of the tool body, and adapted for the selective engagement with the tool holder. One or more magnets or ferromagnetic components can be disposed in the tang  13 , and configured to induce the magnetic coupling by generating or guiding magnetic flux between the tang  13  and the tool holder. 
     One or more load-bearing shoulders  16 ,  17  can be defined on the tool body, and configured to bear a mechanical load between the tool holder and the tool body for operation of the working end of the tool body  21  on a workpiece. One or more magnets or ferromagnetic components can also be disposed in the load-bearing shoulder  16 ,  17 , and configured to induce the magnetic coupling by generating or guiding magnetic flux between the load-bearing shoulder  16 ,  17  and the tool holder. 
       FIG. 1E  is a section view of tool  10 , taken along line A-A of  FIG. 1C . This section view illustrates the inner portion of a magnetic assembly  18  and armature  24  inserted therethrough, each component positioned within tool  10 . As shown in this particular view, magnetic assembly  18  can include an assembly magnet  34 , multiple end guides  32  and a return flux guide or loop component  38 , each contained within housing  19 . Armature  24  can include an armature magnet  36 .  FIG. 1E  also shows an outline of the bottom portion of an exemplary tool holder TH (dashed lines) with which tool  10  may be magnetically coupled and clamped into a press brake machine or similar machine apparatus. In various embodiments, tool holder TH can be a preexisting, conventional tool holder lacking discrete magnetic components and made of steel, for example. 
     In some examples, assembly magnet  34  may comprise a permanent magnet made from one or more magnetic materials, e.g., neodymium iron boron (“NdFeB”). Assembly magnet  34  may be a bar magnet. 
     In the particular configuration of  FIG. 1E , armature magnet  36  is included within armature  24  and positioned beneath assembly magnet  34  when armature  24  is inserted within lateral cavity  22 . Like assembly magnet  34 , armature magnet  36  may also be a permanent magnet made of NdFeB. In some embodiments, armature magnet  36  may be made of other magnetic materials. Armature magnet  36  may be magnetized diametrically and oriented such that the north pole of armature magnet  36  is in closest proximity to the south pole of assembly magnet  34 . 
     In the example of  FIG. 1E , end guides  32  are positioned above assembly magnet  34 , and between assembly magnet  34  and armature magnet  36 . In some examples, end guides  32  may be made from various materials including but not limited to one or more metals, e.g., iron or electrical steel. 
     Return flux guide  38  is positioned beneath armature magnet  36  in this example, and is also contained within housing  19  as a sub-component of magnetic assembly  18 . Return flux guide  38  may comprise a magnetically permeable material. In some examples, such material may be highly permeable. 
     In the example depicted in  FIG. 1E , magnetic assembly  18  extends downward through tang  13  and into a vertical cavity  39  defined by tool body  21  to a distance below the horizontal plane of shoulders  16 ,  17 . The distance by which each vertical magnetic assembly  18  extends within tool  10  may vary and may depend on the shape, weight, and/or size of tool  10 , the number of magnetic assemblies  18  included within a given tool  10 , and/or the configuration of the tool holder into which tool  10  is inserted. As further shown, an air gap  33  may be defined beneath the bottom-most surface of flux guide  38  in magnetic assembly  18 , at the bottom of vertical cavity  39 . In these examples, gap  33  may contribute to a desired magnetic flux direction induced by tool  10  and the holder by providing a non-ferromagnetic component positioned to modulate the magnetic flux coupling, e.g., by guiding the magnetic flux or by modifying or disrupting the flux path. 
       FIG. 1F  is a top view of a vertical magnetic assembly  18 , taken at detail K in  FIG. 1D . Detail K illustrates a magnified view of the top of each magnetic assembly  18 . As in  FIG. 1F , each magnetic assembly may include two D-shaped assembly slugs  30  and an end guide  32  exposed at top surface  20 . Housing  19 , also visible at top surface  20 , may laterally partition assembly slugs  30  and end guide  32 . 
       FIG. 1G  is a section view of detail H taken along section A-A. As shown in  FIG. 1G , assembly magnet  34  may define an approximately rectangular cross-sectional shape, and armature magnet  36  may define an approximately circular cross-sectional shape. In other examples, the shape of each magnet may vary. The cross-sectional width of each wall of housing  19  may also vary. In this particular embodiment, the cross-sectional width of each exterior wall of housing  19  may be the greatest near top surface  20 . 
       FIG. 2  is an exploded view of a magnetic assembly  18  and armature  24 . In this example, magnetic assembly  18  defines an aperture  40  configured to slidably receive armature  24  such that magnetic assembly  18  and armature  24  intersect. As shown, aperture  40  may define a lateral through-hole. Aperture  40  may align with lateral cavity  22  of tool  10 , such that armature  24  is configured to slide seamlessly through aperture  40  and tool  10 . 
     As further shown in  FIG. 2 , the sub-assemblies of magnetic assembly  18  and armature  24  may include numerous distinct components. In particular, assembly magnet  34 , return flux guide  38 , each end guide  32 , and each assembly slug  30  may be separate sub-components of each magnetic assembly  18 , arranged to generate a magnetic circuit upon assembly with armature  24  and insertion within a tool holder. Housing  19  may define one or more internal compartments for containing each of the internal components of magnetic assembly  18 . In this embodiment, housing  19  is cylindrical, but the shape of housing  19  may vary in other examples. 
     Each armature  24  can include a plurality of dynamic elements, such as armature magnets  36 , which can be permanent magnets in various embodiments. In this particular example, armature  24  includes three armature magnets  36  each flanked by a pair of D-shaped armature slugs  31 . The armature slugs  31  can comprise ferromagnetic wedges. When inserted within tool  10 , armature magnets  36  and slugs  31  can align with the magnetic elements included within each magnetic assembly  18 . In embodiments, armature  24  can include one or more permanent magnets, electromagnets, ferromagnetic components, and/or non-ferromagnetic components collectively arranged to strengthen or support a magnetic circuit between tool  10  and the holder. Armature  24  may further include an end portion  42  that may be manually engaged by a user of tool  10  to insert and remove armature  24  therefrom. In some examples, end portion  42  may comprise a handle, knob, protrusion, or other feature graspable by a user. 
       FIG. 3A  is a section view of tool  10 , taken along line B-B of  FIG. 1D . In this example, tool  10  may define an internal lateral cavity  22  configured to slidably receive armature  24 . A bias member  46 , e.g., a spring, may be secured at a stop end  48  of cavity  22 , protruding laterally within cavity  22  such that armature  24  contacts bias member  46  upon insertion into cavity  22 . Cavity  22  may define a receiving end  50  positioned opposite stop end  48 . Receiving end  50  may define a greater cross-sectional height and/or width to accommodate armature end portion  42 . 
     As further shown in  FIG. 3A , assembly slugs  30  may be laterally partitioned from each end guide  32 , assembly magnet  34 , armature magnet  36 , and flux guide  38  by housing  19 . An assembly slug  30  and armature slug  31 , in combination, may extend vertically from top surface  20  to the top plane of flux guide  38 . 
     Armature  24  may be inserted to various depths within cavity  22 . The depth at which armature  24  is inserted may determine whether tool  10  is in an engaged, locked position or a disengaged, unlocked position. In some examples, movement of armature  24  can switch the strength of the magnetic flux coupling between two bi-stable states: an engaged state in which the magnetic flux coupling between tool  10  and the holder is established, and a disengaged state in which the magnetic flux coupling between tool  10  and the holder is diminished or absent.  FIG. 3A  depicts the locked position, in which armature  24  contacts, but may not compress, bias member  46 . Accordingly, the locked position may represent a relaxed position. In this configuration, armature  24  functions as a button that can be manually pressed to various depths within cavity  22  by exerting various amounts of lateral force against armature end portion  42 . As shown in the locked position of  FIG. 3A , armature end portion  42  is inserted within cavity  22  such that its end surface is flush with the end surface of tool  10 . 
     In the locked position, assembly magnet  34  included in each magnetic assembly  18  may be magnetically oriented the same as each armature magnet  36 . In these examples, each assembly magnet  34  is oriented such that its north pole is positioned above its south pole, and each armature magnet  36  is similarly oriented such that its north pole is oriented above its south pole. In this orientation, assembly magnet  34  armature magnet  36 , surrounded by the additional ferromagnetic components of tool  10  and its corresponding tool holder, may form a magnetic circuit that generates a magnetic flux  52  that passes vertically through each end guide  32 , loops through a ferromagnetic material comprising the tool holder when tool  10  is in the locked position within a receiving space defined by the holder. It may be desirable that magnetic circuit involves the shoulders of the tool holder: first to hold tool  10  firmly against such shoulders so that tool  10  is in an ideal position for clamping by a press brake or similar machine apparatus, and secondly because the gap between the tang  13  and the inside of the holder is designed as clearance and may therefore not be a precise or sufficiently small gap that it could be depended upon to form a reliable part of the magnetic circuit. 
     After passing through the tool holder, magnetic flux  52  may be guided back down into each assembly slug  30 , which, together with each armature slug  31 , may function as a ferromagnetic wedge that propagates magnetic flux  52  downward through each magnetic assembly  18 . At the bottom of each armature slug  31 , magnetic flux  52  may loop horizontally, via return flux guide  38 , and back upward through the south pole of armature magnet  36 . 
     As further shown in  FIG. 3A , air gaps  33  and  56  may be present at the bottom of each vertical aperture  39  and receiving end  50 , respectively. Gaps  33  and  56  may function as non-ferromagnetic gaps to prevent magnetic flux  52  from dissipating within body  21  of tool  10  beneath vertical aperture  39  and receiving end  50 , thereby maintaining an upward flux direction. 
       FIG. 3A  also shows that the body of armature  24  may be made from aluminum. In other examples, the body of armature  24  may be made from various different and/or additional materials. In this example, each flux guide  38  is made from a high permeability soft magnetic material. Other magnetic materials may also be suitable, depending upon flux density and other application-specific considerations. 
       FIG. 3B  is a section view of tool  10  in an unlocked configuration, taken along line B-B of  FIG. 1D . In the unlocked configuration, armature  24  may be urged a greater distance within lateral cavity  22 , thereby compressing bias member  46 . The magnetic poles of each assembly magnet  34  and armature magnet  36  are misaligned, creating a conflicting, and therefore much weaker, magnetic circuit. The reduced flux  52  generated within such a circuit may reduce the holding force between tool  10  and a corresponding tool holder, allowing manual insertion and removal of tool  10  with respect to the holder. In some examples, gravity alone may cause tool  10 , in the unlocked configuration, to fall from a corresponding tool holder. 
     The release mechanism can include any suitable armature  24  having one or more magnets or ferromagnetic components  36  configured to modulate a strength of the magnetic coupling by motion with respect to the flux path defined by disposition of the one or more magnetic elements  34  in the tool body. The armature  24  can rotate the magnets or ferromagnetic components  36  with respect to the flux path, or with respect to the poles of the magnetic elements  34  defining the flux path. The armature  24  can also be configured for lateral motion of the one or more magnets or ferromagnetic components  36  with respect to the magnetic elements  24  and the flux path defined by the magnetic elements  34 . A lever, knob or push button actuator can be engaged with the tool body  21 , and mechanically coupled to the magnetic armature  24  for manipulation of the magnets or ferromagnetic elements  36  by the user to modulate the strength of the magnetic coupling. The release mechanism may also comprise a plurality of armature members  24 , each having one or more of the magnets or ferromagnetic elements  36  configured to modulate the strength of the magnetic coupling by rotational or lateral motion with respect to one or more flux paths defined by disposition of the one or more magnetic elements  34  of the magnetic assembly  18  within the tool body  21 . 
     Additional Tool Configurations 
       FIG. 4  is an isometric view of an upper portion of tool  60  for a press brake or similar machine apparatus. As shown in  FIG. 4 , tool  60  may include a t-shaped magnetic circuit assembly with a sliding armature. The example of  FIG. 4  includes two top magnets  62  included within tang  71 . A portion of each top magnet  62  may be exposed at the top surface  65  of tool  60 . Tool  60  further includes side magnets  64  within tang  71 , each exposed at reference face  66 . 
     Top and side magnets  62 ,  64  can be fixed within tool  60 . Each top magnet  62  may be vertically oriented such that its north pole is positioned above its south pole. In some examples, top magnet  62  may be arranged in the opposite polar orientation. Each side magnet  64  may be oriented such that its north pole is positioned on the left side and its south pole on the right side, or vice versa. With respect to the magnetic orientation of top magnets  62 , side magnets  64  may thus be oriented in an opposing orientation. Regardless of the specific polar orientation, each side magnet  64  may include a magnetic pole facing the exterior of tool  60 , and a magnetic pole facing the interior of tool  60 . In any or all of the various examples included herein, the polar orientation of each magnet may be reversed, provided that the polarity of each magnet relative to the other magnets comprising the magnetic circuit remains the same. 
     Armature  68  can provide a coupling mechanism configured to modulate the strength of the magnetic flux coupling between tool  60  and the holder. Armature  68  is shown inserted within parallel lateral cavities defined by tool  60 . In particular, tool  60  includes two lateral cavities: an upper cavity  70  positioned above a lower cavity  72 . First or upper arm  74  of armature  68  may be slidably inserted into upper cavity  70 , and second arm  76  may be slidably inserted into lower cavity  72 . First arm  74  and second arm  76  may be connected at one end by a vertical or transverse armature member  77 . While the particular arrangement of upper cavity  70  and/or lower cavity  72  may vary,  FIG. 4  illustrates that upper cavity  70  may be defined within tang  71 , and lower cavity  72  may be defined below the plane of shoulders  73 ,  75  that demarcate the lower boundary of tang  71 . The exterior surface of transverse member  77  may remain accessible upon insertion of armature  68  within tool  60  such that transverse member  77  may be manually engaged by a user to insert armature  68  within tool  60 , and to adjust the lateral depth at which armature  68  extends into tool  60 . Upper arm  74  and lower arm  76  of armature  68  can each include one or more dynamic or moving elements, which may include permanent magnets and/or ferromagnetic components. 
     As further shown in  FIG. 4 , a bias member  78  may be secured to a stop end  80  defined by lower cavity  72 . In this example, bias member  78  comprises a spring. In a locked or engaged configuration, bias member  78  may not be compressed, or may be only slightly compressed, by second arm  76  of armature  68 . Tool  60  also includes two vertical cavities  81 . In some examples, the number of vertical cavities may vary and may depend on the number of top magnets  62  needed to form a magnetic circuit with armature  68  strong enough to at least temporarily secure tool  60  within a tool holder. 
     Adjusting the position of armature  68  can modulate the strength of the magnetic flux coupling between tool  60  and the holder. For example, inserting armature  68  to a greater depth within tool  60  by compressing bias member  78  can cause misalignment between the magnetic poles of the dynamic elements of the armature and the magnetic poles of the top magnets  62  and side magnets  64 , thus disrupting the magnetic flux coupling between tool  60  and the holder and allowing for release of the tool. By contrast, when the magnetic elements included in armature  68  are magnetically aligned with top and side magnets  62 ,  64  fixed within tool  60 , a magnetic circuit can be established, thereby inducing a magnetic flux guided from tang  71  through reference face  66  into a ferromagnetic shoulder portion of a tool holder coupled with tool  60 . Sliding armature  68  in this manner can gradually modulate the strength of the magnetic flux coupling between tool  60  and the holder. 
       FIG. 5  is an isometric section view of a tool  100  for a press brake or similar machine apparatus, taken along the length or longitudinal direction of tool  100 . Tool  100  may include a cross-shaped circuit assembly with a rotating armature. In the particular configuration of  FIG. 5 , tool  100  includes two vertical magnetic assemblies  101 , each assembly  101  including a first magnet  102  and a second magnet  103 . First magnet  102  may be exposed at top surface  115 , positioned above a lateral cavity  105  defined by tool  100 . Second magnet  103  may be positioned below lateral cavity  105 . As further shown in the figure, focal wedges  104  may be sandwiched between each first magnet  102  and lateral cavity  105 , as well as between each second magnet  103  and lateral cavity  105 . 
     Tool  100  also includes a rotating armature  116 , which provides a coupling mechanism configured to modulate the strength of the magnetic flux coupling between tool  100  and the holder. By rotating, armature  116  may adjust the polar orientation of one or more dynamic elements, e.g., permanent disc magnets  106  and ferromagnetic collar  113 , contained in the armature and inserted within lateral cavity  105 . Rotating the dynamic elements of rotating armature  116  may gradually modulate the strength of the magnetic flux coupling along a spectrum from high strength to low or zero strength. This particular example includes two disc magnets  106  and one ferromagnetic collar  113 , but the number of dynamic magnetic components can vary depending upon tool size and application. 
     As further shown in  FIG. 5 , tool  100  may also include an upper gear member  108 , which includes an elongate body  109  that extends through at least a portion of lateral cavity  105 . Upper gear member  108  may rotatably engage an adjacent pinion  110  via a plurality of complementary grooves, or mechanical teeth  117 , protruding outward from the perimeter of both gear member  108  and pinion  110 . Together, pinion  110  and gear member  108  comprise gear assembly  112 . An idler gear  111  may be also positioned at the radial center of pinion  110 . Pinion  110  may rotatably engage rack  114  via a plurality of complementary grooves or mechanical teeth also protruding from rack  114 . 
     In operation, lateral movement of rack  114 , e.g., sliding, may drive rotation of armature  116 . Specifically, lateral movement of rack  114  may cause pinion  110  to rotate, thereby causing rotation of upper gear member  108 . Because body  109  of upper gear member  108  is secured within the radial center of each disc magnet  106 , rotation of body  109  also drives rotation of each disc magnet  106 , thereby adjusting the polarity of each disc magnet  106  with respect to first magnets  102  and second magnets  103 . 
       FIG. 6  is an isometric section view taken along the width of tool  100 , transverse to the view of  FIG. 5 . As further detailed in  FIG. 6 , tool  100  may include one or more side magnets  118 ,  119 . A lateral focal wedge  120  may be sandwiched between each side magnet  118 ,  119  and disc magnet  106 . In this particular example, disc magnet  106  is magnetized axially such that it includes four magnetic poles. 
       FIG. 7A  is an isometric view of tool  100 . As shown in  FIG. 7A , tool  100  may include an exterior button  122 . In this example, button  122  protrudes outward from front surface  123 , where it may be manually engaged by a user, for example. To rotate armature  116 , thereby either releasing or locking tool  100  within a corresponding tool holder, button  122  may be pushed. Pushing button  122  causes rack  114  to move laterally, thus causing pinion  110  and upper gear member  108  to rotate. Disc magnets  106  secured to gear member  106  may then be rotated, causing a shift in magnetic alignment within tool  100 . 
       FIG. 7B  is a front view of tool  100 . As shown in  FIG. 7B , each first magnet  102  may protrude above the plane defined by top surface  115 . Button  122  is positioned beneath tang  125 , within body  107  of tool  100 . 
       FIG. 7C  is a top view of tool  100 .  FIG. 7D  is an alternate top view of tool  100 , showing section B-B. 
     As shown in  FIGS. 7B and 7C , a first set of magnets  102  may be exposed at top surface  115 . This particular embodiment includes two vertical magnetic assemblies  101 . In other examples, the number, size, and/or arrangement of magnetic assemblies  101  may vary. Button  122  is shown protruding laterally outward from tool  100 .  FIG. 7C  also shows line A-A, which denotes a cross-sectional plane used for illustration purposes. 
       FIG. 7E  is a section view of detail H, taken along section A-A of  FIG. 7C . With button  122  in a relaxed position, tool assembly  100  is in a locked or engaged configuration with respect to the tool holder. In the locked position, tool assembly  100  may form two magnetic circuits comprised of separate pathways of magnetic flux: flux pathway f 1  and flux pathway f 2 . As shown in  FIG. 7E , flux pathway f 1  is guided in a counterclockwise direction through disc magnet  106  to first magnet  102 , through top surface  115  of tang  125  into a ferromagnetic portion of a tool holder TH, and back through one of side magnets  118 . The alternating magnetic poles of disc magnet  106 , top magnet  102 , and side magnet  118  in this configuration may generate the closed magnetic circuit defined by flux pathway f 2 . 
     Similarly, flux pathway f 2  is generated by the alternating magnetic poles of disc magnet  106 , side magnets  118 , and second magnet  103 . As shown in the figure, flux pathway f 2  may be guided in a clockwise direction, passing from disc magnet  106  to second magnet  103 , through a ferromagnetic shoulder portion of a tool holder TH, and back through side magnet  118 . 
     In combination, flux pathways f 1  and f 2  may generate a strong upward force to at least temporarily secure tool  100  within a corresponding tool holder. By generating two circuits that work in cooperation, tool  100  may drive a magnetic flux through a larger portion of tool holder TH relative to other tool and punch designs. 
     As further shown in  FIG. 7E , first magnet  102  may be an NdFeB disc, which may also be large, while side magnets  118  may be smaller, axially magnetized NdFeB discs. Disc magnet  106  may also be an NdFeB magnet. Disc magnet  106 , however, may be magnetized radially. Focal wedges  104  and lateral focal wedges  120  may each be made of iron-nickel compositions in one example. 
       FIG. 7F  is a section view of tool  100 , taken along section A-A of  FIG. 7C .  FIG. 7F  shows tool  100  in a release position caused by pressing button  122 . As shown in  FIG. 7F , pressing button  122  causes disc magnet  106  to rotate. In some examples, disc magnet  106  will rotate up to about 90°. Armature  116  may resist the rotation of disc magnet  106  beyond 90° such that no internal bias member, e.g., spring, may be necessary. In some examples, a bias member may be included to prevent over-rotation of armature  116 . Rotation of disc magnet  106  causes the magnetic poles between disc magnet  106 , first magnet  102 , second magnet  103 , and each side magnet  118  to misalign, thereby nearly cancelling magnetic circuits x and y. Without a magnetic flux through tool  100  and a tool holder, the force urging tool  100  upward into a tool holder may be diminished, allowing removal of tool  100  from the tool holder. 
     As further shown in  FIG. 7F , non-ferromagnetic sleeves  124  may house magnetic assemblies  101  and side magnets  118  within tool  100 . 
       FIG. 7G  is a section view of tool  100  taken along line B-B of  FIG. 7D . In this example, body  109  may extend the entire length of lateral cavity  105 . 
       FIG. 8A  is an isometric view of tool  60  for a press brake or similar machine apparatus. As shown in  FIG. 8A , tool  60  includes an external handle mechanism  85 . In this particular embodiment, handle mechanism  85  includes a slidable handle component that protrudes from front surface  59  of tool  60 . Handle mechanism  85  may be shaped to be graspable by a user. By moving handle mechanism  85  laterally, armature  68  may be moved laterally within tool  60 . Thus, handle mechanism  85  may be engaged to alternate tool  60  from a locked to an unlocked configuration. 
       FIG. 8B  is a top view of tool  60 . As shown in  FIG. 8B , handle mechanism  85  protrudes laterally outward from tool  60  for user access. 
       FIG. 8C  is a section view of handle mechanism  85 , taken along line C-C of  FIG. 8B . Handle mechanism  85  may be coupled, attached, or otherwise secured to armature  68  via transverse member  77 . In some examples, handle mechanism  85  may be directly or indirectly coupled to armature  68 . For instance, handle mechanism  85  may be inserted into an aperture or cavity defined by transverse member  77 . As depicted in  FIG. 12C , handle mechanism  85  may be secured to the outer surface of transverse member  77 . In other embodiments, handle mechanism  85  may be integrally formed with transverse member  77 . 
       FIG. 8D  is a section view of tool  60 , taken along line B-B of  FIG. 8B .  FIG. 8D  illustrates tool  60  in a latched, engaged or “locked” configuration in which handle mechanism  85  is not urged laterally in a direction against the lateral force exerted by bias member  78 . Thus, bias member  78  remains uncompressed, and the polarity of the magnets  34 ,  36  within armature  68  remain aligned with side magnets  64 . 
     In this example, handle mechanism  85  may be coupled with transverse member  77  of armature  68 . With handle  85  protruding laterally outward with from front surface  59 , armature  68  may not need to be directly engaged by a user. Thus, in this particular embodiment, tool  60  may lack external openings exposing transverse member  77 . As shown in  FIG. 8D , end wall  83  may provide a barrier to the exposure of transverse member  77 . 
       FIG. 8E  is a section view of tool  60  taken along line B-B of  FIG. 8B .  FIG. 8E  shows tool  60  in a release, or unlocked, configuration in which handle  85  has been slid or otherwise urged to the left and bias member  78  is at least partially compressed, causing the magnets  34 ,  36  to misalign with side magnets  64 , thus weakening the magnetic flux coupling between tool  60  and its corresponding tool holder. As shown in  FIG. 8E , movement of armature  68  directly corresponds to movement of handle  85 . 
       FIG. 9A  is an isometric view of tool  130  for a press brake or similar machine apparatus. Tool  130  may be smaller in profile relative to other tool configuration. Thus, tool  130  may only require two magnets to create a magnetic flux sufficient to at least temporarily hold tool  130  within a corresponding tool holder. As shown in  FIG. 9A , tool  130  may include a top magnet  134  within tang  132 . A bottom magnet  136  may be positioned beneath tang  132 , laterally exposed at surface  133 . Tool  130  may further include one or more air gaps positioned to divert a magnetic flux toward the shoulders of a tool holder. In this particular configuration, tool  130  includes a first air gap  137 , a second air gap  138 , and a third air gap  139 , each defined by openings in surface  133 . 
       FIG. 9B  is a front view of tool  130 . As shown in  FIG. 9B , one or more top magnet components  134  may be exposed at reference face  131  of tool  130 . 
       FIG. 9C  is a side view of tool  130 , showing surface  133 . Air gaps  137 ,  138 , and  140  may be arranged in vertical fashion. The air gaps illustrated in  FIG. 9C  are each circular or semicircular. In some examples, the size and/or shape of each air gap may vary.  FIG. 9C  also shows bottom magnet  136 , exposed at surface  133  and overlapping with air gaps  137  and  138 . 
       FIG. 9D  is a top view of tool  130 . As shown in  FIG. 9D , no magnetic assemblies or sub-assembly components may be visible on top surface  144 . 
       FIG. 9E  is a section view of tool  130 , taken along line A-A of  FIG. 9D . As shown in  FIG. 9E , top magnet  134  may be housed within a non-ferromagnetic housing or sleeve  135 . Sleeve  135  may be made from various materials, including but not limited to aluminum or brass. Each of top magnet  134  and bottom magnet  136  may be an NdFeB magnet. Top magnet  134  may be axially magnetized, while bottom magnet  136  may be diametrically magnetized. As further shown in  FIG. 9E , each air gap  137 ,  138 ,  140  may comprise a lateral through-hole. Tool  130  may be inserted into tool holder TH. 
       FIG. 9F  is a section view of tool  130  at detail H, taken along line A-A of  FIG. 10D .  FIG. 9F  shows magnetic flux F that may be generated by the arrangement of top magnet  134 , bottom magnet  136 , and the ferromagnetic components of tool holder TH. In particular, top magnet  134  may be axially magnetized and oriented such that its north pole is to the left of its south pole in the embodiment depicted. Bottom magnet  136  may be oriented such that its south pole is positioned to the left of its north pole. In this configuration, magnetic flux F may be guided through top magnet  134 , a portion of tool holder TH, and down to bottom magnet  136 . After passing through bottom magnet  136 , the magnetic flux may be guided upward toward top magnet  134 , after passing through another portion of tool holder TH. 
     In these examples, lower magnet  136  may be ring-shaped and circumferentially encompassed by tube  148 . Tube  148  may be made from various materials, including but not limited to brass or aluminum. 
       FIG. 10  is an isometric view of a tool  150  for a press brake or similar machine apparatus, showing internal structure. As shown in  FIG. 10 , tool  150  may contain a plurality of fixed magnet island assemblies  152  and a release lever  154 . Tool  150  also includes a plurality of horizontal magnets  156  that collectively increase frictional holding of tool  150  within a corresponding tool holder. To facilitate removal of tool  150  from a tool holder, release lever  154  may be urged downward at distal end  155 , thereby causing protrusion  157  to pivot about pin  158  and exert an outward force against an inner surface of the tool holder, effectively prying tool  150  away from the holder. Such prying may weaken the magnetic circuit generated by magnetic island assemblies  152  and the holder by urging the coupling end of the tool body  150  from the tool holder, creating an air gap in the magnetic flux path between the tool body  150  and the tool holder. Other decoupling members, in addition or alternatively to lever  154 , may be implemented in various examples. Each decoupling member can be configured to mechanically urge tool  150  away from a tool holder by creating an air gap therebetween, thereby allowing removal of tool  150  from the holder. 
     The release or decoupling mechanism can include one or more pry bar or lever members  154  engaged with the tool or tool body  150 . As shown in  FIG. 10 , each pry bar or lever member  154  extends from a first end  155  to a second end or protrusion  157 , with the second end  157  configured to selectively disengage the coupling end of the tool body  150  from the tool holder upon actuation of the first end. The first end  155  of the pry bar or lever member  154  may be accessible by a user, e.g., with the coupling end of the tool body  150  engaged in the tool holder, with the second end  157  of the pry bar or lever member  154  configured to protrude from the tool body  150  to selectively disengage the coupling end from the tool holder upon manipulation of the first end  155  by the user. A biasing element can be configured to bias the second end  157  of the pry bar or lever member  154  in a position disposed within the tool body  150 , absent manipulation of the first end  155 , or when the first end  155  is released. 
       FIG. 11A  is an isometric view of a tool  160  for a press brake or similar machine apparatus. Tool  160  includes a plurality of fixed magnetic island assemblies  162  disposed within a load-bearing shoulder  164  of the tool. Two levers  166  protrude from their respective access windows  168  at a front surface  169  of the tool. Each lever  166  defines an actuating end  167  and a decoupling end  172 . Shoulder  164  defines two decoupling windows  170 , through which the decoupling end  172  of each lever  166  protrudes various distances depending on the position of each lever  166 . 
     In operation, magnetic island assemblies  162  can be configured to induce a magnetic flux coupling with a tool holder. Each magnetic island assembly  162  may include one or more permanent magnets, ferromagnetic components, and/or non-ferromagnetic components configured to induce a magnetic flux coupling with a tool holder. The magnetic elements comprising each magnetic island assembly can be non-adjustable, such that the strength of the magnetic flux coupling depends only on the proximity of the upper portion of the tool  160  with a tool holder. 
     To disrupt the magnetic flux coupling and remove tool  160  from its tool holder, a user can manipulate one or both levers  166 . Moving lever  166  downward, for example, causes the decoupling end  172  of the lever to move upward through decoupling window  170 . Because the surface of shoulder  164  can be pressed flat against a receiving shoulder of a tool holder when the two components are coupled, upward motion of a decoupling end  172  through decoupling window  170  mechanically urges tool  160  away from the tool holder by creating an air gap therebetween. As the size of the air gap increases, the strength of the magnetic flux coupling decreases, such that tool  160  may be removed from the tool holder, either by gravity or user-assisted removal. 
       FIG. 11B  is a top transparent view of tool  160 . As shown, each lever  166  can rotate about a rotational axis defined by a pin  174 . The pins  174  extend into the body of tool  160 , anchoring the levers  166  to the body of the tool. In the embodiment shown, the coupling components, e.g., magnetic island assemblies  162 , and decoupling components, e.g., decoupling ends  172 , are each exposed at the surface of shoulder  164 , thus positioned to engage with the same mating surface of a tool holder. 
       FIG. 11C  is a cross-sectional view of tool  160 , taken along section A-A of  FIG. 11B . As shown, lever  166  may be approximately L-shaped, with decoupling end  172  oriented approximately perpendicular to the actuating end  167 . Lever  166  is shown in a resting or coupling configuration, in which the actuating end  167  is perpendicular to the front surface  169  of the tool and decoupling end  172  does not protrude from the surface of shoulder  174  through decoupling window  170 . 
       FIG. 11D  is a cross-sectional view of tool  160 , taken along section B-B of  FIG. 11B . Lever  166  is shown in a disengaged or decoupling configuration, in which actuating end  167  of lever  166  has been pushed downward, thus forcing decoupling end  172  upward through decoupling window  170 . In this configuration, tool  160  may be mechanically urged from its tool holder. In some examples, each lever  166  must be in the decoupling configuration to effect release of tool  160  from the holder. In other examples, movement of one lever  166  to the decoupling configuration can suffice to urge tool  160  away from its tool holder. 
       FIG. 12A  is a top transparent view of a tool  180  for a press brake or similar machine apparatus. Like tool  160 , tool  180  includes a plurality of fixed magnetic island assemblies  182  exposed at a surface of a load-bearing shoulder  184  of the tool. Tool  180  also includes two decoupling actuators  186 . Each decoupling actuator  186  is coupled to a pushbutton or slidable shaft or pin member  188 , which when moved to a decoupling position, mechanically urges a tool holder away from tool  180 . 
     Movement of the shaft or pin member  188  can be effected by movement of multiple movable components operationally coupled with each decoupling actuator  186 . In operation, rotation of decoupling actuator  186  is translated into rotation of an inner portion  190  of the decoupling actuator that protrudes within the body of the tool. Rotation of each inner portion  190  causes rotation of internal gear member  192 . Internal gear member  192  rotatably engages the shaft or pin  188  via a plurality of complementary grooves defined by the gear member and the pushbutton. 
       FIG. 12B  is a front transparent view of tool  180 , showing magnetic island assemblies  182 , each pin or shaft member  188 , and each decoupling actuator  186 . In the decoupling configuration shown, each member  188  protrudes above the top surface of shoulder  184 , thereby mechanically urging tool  180  away from its corresponding tool holder. As further shown, each member  188  moves bi-directionally within a pushbutton cavity  194 , a portion of which is vacant upon displacement of the pushbutton above the top surface of the shoulder. The distance by which each member  188  protrudes from shoulder  184  may vary, and may depend at least in part on the strength of the magnetic flux coupling induced by tool  180  and a corresponding tool holder. For example, a stronger magnetic flux coupling may necessitate greater extension of each shaft or pin member  188  to mechanically urge tool  180  away from its tool holder, forming an air gap in the magnetic flux coupling. 
     Each decoupling actuator  186  may be manipulated by a user. In the specific embodiment shown, each decoupling actuator  186  comprises a rotatable knob. Alternative configurations of the decoupling actuators  186 , e.g., pushbuttons, levers, pins, switches, etc., are also within the scope of this disclosure. 
       FIG. 12C  is a section view of tool  180 , taken along section A-A of  FIG. 12A . As shown, a portion of decoupling actuator  186  may protrude from tool  180  for user engagement, while inner portion  190  may extend a distance within the body of the tool. In some examples, inner portion  190  may anchor decoupling actuator  186  to tool  180 . 
       FIG. 12D  is a section view of tool  180 , taken along section B-B of  FIG. 12A . Gear member  192  is shown, along with pushbutton cavity  194 . By engaging with complementary grooves defined by the shaft or pin member  188 , rotation of gear member  192  causes linear movement of member  188 . In this manner, rotation of decoupling actuator  186  causes linear movement of member  188 , which can release tool  180  from the tool holder. 
     Suitable release mechanisms include a longitudinal shaft or pin member  188  engaged with the tool body  180 , the longitudinal shaft or pin member  188  extending from a first (e.g., bottom) end configured for actuation by a user to a second (e.g., top) end configured to selectively disengage the coupling end of the tool body  180  from the tool holder upon actuation of the first end. The longitudinal shaft or pin member  188  can be disposed in sliding engagement within the tool body  180 , e.g., with the second end configured to extend from the tool body  180  to selectively disengage the coupling end from the tool holder upon actuation of the first end. 
       FIG. 13  is a section view of tool  170  for a press brake or similar machine apparatus. As shown in  FIG. 13 , tool  170  includes a magnetic coupling assembly MG with two isolated “island” magnetic assemblies configured for holding tool  170  within a tool holder TH (dashed lines), e.g., where tool holder TH utilizes a side-clamping mechanism. 
     Tool  170  includes first magnetic assembly  174  and second magnetic assembly  176  that together form a magnetic circuit or circuits through tang  180  of tool  170  and the adjacent portion of tool holder TH, sufficient to at least temporarily secure tool  170  to tool holder TH. As further shown in the figure, first magnetic assembly  174  may be secured to tool  170  via first fastener  175 . Similarly, second magnetic assembly  176  may be secured to tool  170  via second faster  177 . 
       FIG. 14  is a section view of a press brake punch or tool  10  (or similar machine tool component  10 ,  60 ,  100 ,  130 ,  150 ,  160 ,  170 ), with a magnetic coupling mechanism MG disposed in tang end  13 , opposite working end  12  of tool  10 . Coupling mechanism MG is configured for selective engagement of tool  10  within tool holder TH, as described herein. 
     Suitable examples of tool holder TH are described, for example, in U.S. Publication No. 2007/0144232 to Shimota et al., which is incorporated by reference, in the entirety and for all purposes. In any of the embodiments described herein, tool holder TH may comprise a preexisting tool holder lacking defined stationary or movable magnetic elements. As described herein, at least a portion of tool holder TH may comprise a ferromagnetic material. Tool  10  may additionally be secured by a bolt BO or similar mechanical fixture, as known in the art. 
     Applications 
     As described above, a safety latch mechanism is applied to Folding Press or Press Brake Tooling to hold the Punch up until it is clamped in place. 
     Press Brake punches with a safety latch which can selectively hold the punch up into the holder until the holder clamping is activated, are useful for installing large punches or multiple punches. There are various mechanisms for facilitating a releasable safety latch, one of which is a straight-in pushbutton and latch-pawl. There are additional latching mechanisms not described in the prior art; this document describes such mechanisms. 
     Suitable applications of the present safety mechanism include, but are not limited to, improved safety mechanism for tooling machinery described in U.S. Pat. Nos. 5,245,854, 6,467,327; 6,732,564; 6,928,852; 7,004,008; 7,021,116; 7,661,288; 7,810,369, each of which is incorporated by reference herein, in the entirety and for all purposes. 
     More specifically, a magnetic safety latch mechanism is applied to a folding press or press brake punch, for example where a protrusion at the top of the punch fits into a receiving, downward-facing cavity in the punch holder. Such systems may have an actuating mechanism in the upper tool holder or punch holder, which clamps all of the punches simultaneously, for securely holding said punches in place while folding or forming the work-piece, which is typically sheet metal. Such tool holder systems have the advantage of simplicity, but make it awkward to deploy multiple punches without some mechanism to hold some punches in place, temporarily, while others are being installed. Conventional safety tang designs, for their part, may require the punches to be installed in the correct order, and slid into the holder from one end. Other traditional safety latch mechanisms are known, such as laterally sliding or pivoting latches. 
     The present disclosure provides a magnetic assembly within the upper portion of each punch, to hold said punches safely in place, temporarily, so that the user&#39;s hands are free to install additional punches until the punch holder is activated to lock all of the punches in place for operation. Such magnetic assembly would ideally be comprised of an arrangement of strong (such as, but not limited to, NdFeB) permanent magnet assembly arranged within the punch such that the ferromagnetic properties of the punch itself are used to guide the magnetic flux in a circuit further involving the ferromagnetic or other material of the punch holder (e.g., typically medium-alloy steel), so that the punch will be urged upward by said magnetic flux so as to minimize non-ferromagnetic gaps (e.g., air) thus holding said punch up against the load-impinging shoulders of said punch holder. 
     It may be desirable that the magnetic circuit involves the shoulders of the punch holder: first to hold said punch firmly against said shoulders so that the punch is in an ideal position for clamping by the press, and secondly because the gap between the top of the punch tang and the inside of the holder is designed as clearance and is therefore not a precise or sufficiently small gap that it could be depended upon to form a reliable part of the magnetic circuit. Some embodiments can incorporate a movable part or movable parts of the magnetic circuit, e.g., permanent magnets or ferromagnetic components, which can be moved from one position with the magnetic circuit in a magnetically coupled or locked state, with a continuous flux path, and another position with the magnetic circuit in a magnetically decoupled or weakened (unlocked) state, e.g., by moving one or more components apart to create an air gap along the flux path, or by orienting a pair magnetic poles in opposition along the flux path. 
     Other variations of the magnetic assembly could use vertically aligned magnets or magnetic assemblies pressed into holes in the top of the tang, thus simplifying the machining needed to adapt stock punch material for receiving said assemblies, which assemblies would also protrude slightly from the top of the tang. A single or plural arrangement of press-fit, switchable magnetic assemblies could be deployed with an optimal protrusion from the punch tang to minimize the deficiency of the unknown gap at the tang top by using said resistively slidable magnetic assemblies which would thus adapt to the aforementioned gap variability. The magnetic assemblies could be made switchable by various mechanism including that of having part of the magnetic circuit involve a slidable permanent magnet with poles alternately in alignment, favorably, with the magnetic circuit, creating a latched position, or opposing so as to weaken or even cancel the magnetic attraction to the punch holder, creating the released position. 
     Similar magnetic work-piece clamping systems can also be used as part holders for such machines as surface grinders, as well as the use of a magnetic tool-holder for press-brake tooling as described here. Other variations could employ magnets or magnetic assemblies installed in the top of the punch shoulder of the tang. 
     Additionally, magnets or magnetic assemblies could be installed horizontally in the punch tang to hold or help hold the punch up with the friction created by the magnetic force between the punch tang vertical sides and the vertical walls inside the punch holder. Also encompassed is the application of a permanent magnet or magnets, in the punch or punch holder, without a switching mechanism or release state, which would be especially practical for smaller punches wherein the magnetic forces holding the punch in the holder could be easily overcome by hand. 
     EXAMPLES 
     Suitable examples and embodiments of the mechanisms and techniques described in this disclosure include, but are not limited to the following. 
     A punch for a folding press or press brake, with a top protrusion or tang that fits into a cavity in said press brake&#39;s upper tool holder, with a safety mechanism for temporarily holding said punch in said press brake using a switchable or adjustable permanent magnet assembly to urge or retain the punch upward into a holder receiving cavity for placement or staging until said holder is activated, thus clamping said punch solidly in place for use, the punch thus having a locked position where said punch is safely restrained in said punch holder, or an unlocked setting, where said punch can be manually installed in or removed from said punch holder. 
     The safety mechanism, where an assembly of permanent magnets and ferromagnetic parts are arranged to work cooperatively in a magnetic circuit, with some magnet(s) or part(s) made to be selectively moveable such that said magnetic circuit can be debilitated or weakened (as for punch installation or removal) or alternatively positioned so as to be optimized or enabled, to facilitate secure retention of punch in the holder until said holder is activated to clamp said punch solidly in the holder for folding operation. 
     The safety mechanism, where the magnetic assembly includes one or more electromagnets which could be switchable to selectively aid or conflict with the magnetic circuit, to effect retention or release of said punch. The safety mechanism, where the magnetic assemblies consist of two or more parallel circuits of combinations of magnets and ferromagnetic parts such that one switchable or adjustable assembly is thus scalable for higher magnetic forces to compensation. The safety mechanism, provided with a mechanism for directly leveraging or prying the punch away from the holder. 
     The safety mechanism, where one or more magnetic assemblies or permanent magnets are arranged along the length of a punch. The safety mechanism, where such magnetic assembly or assemblies employs a bi-stable or non-momentary locked and unlocked state. The safety mechanism, where the selectively moveable part or parts move slidably. The safety mechanism, where the selectively moveable part or parts move rotatably. 
     A safety mechanism for holding a punch in a folding press or press brake using a permanent magnet assembly or permanent magnet or array of magnets to urge or retain the punch upward into a holder receiving cavity for placement or staging until said holder is activated to grip said punch solidly in place for use, such non-adjustable magnetic assembly being practical for smaller punches, where the forces encountered would be low enough that said punches could be manually installed or removed to or from said holder without further mechanical adjustment or rearrangement of the magnetic circuit. 
     The safety mechanism, provided with a mechanism for directly leveraging or prying the punch away from the holder. The safety mechanism, where the magnets or magnetic assemblies are held in place with set-screws, glue, spring-pins, or such as are obvious variations of methods for securing said magnets or magnetic assemblies to the punch. The safety mechanism, where the magnet or magnets are installed in the punch shoulder or tang with additionally assembly features. 
     A safety mechanism for holding a punch in a Folding Press or Press Brake using a permanent magnet assembly to urge the punch upward into a holder receiving cavity for placement or staging until said holder clamps said punch solidly in place for use, with non-adjustable magnets but with a mechanism for debilitating the magnetic circuit via an increasing gap or gaps in said magnetic circuit by leveraging or prying apart some part(s) within said magnetic circuit. 
     The safety mechanism, with a selectable mechanism for dissipating magnetic flux away from the productive magnetic circuit by introducing a magnet or magnets or ferromagnetic part or parts to diverge some of the flux away from assisting in the punch-holding work of the magnetic circuit thus providing a selectably locked and unlocked state. 
     A press brake tool comprising: a tool body having a working end configured for operation on a workpiece and a coupling end configured for selective engagement with a tool holder, the working end disposed generally opposite the coupling end; a magnetic assembly comprising one or more magnetic elements configured to generate a magnetic flux coupling adapted for the selective engagement of the coupling end of the tool body with the tool holder; and a coupling mechanism configured to manipulate at least one of the magnetic elements to modulate a strength of the magnetic flux coupling, where the coupling mechanism is adapted for selective disengagement of the coupling end of the tool body from the tool holder. 
     The press brake tool, further comprising a tang formed on the coupling end of the tool body and adapted for the selective engagement with the tool holder, where the magnetic assembly is configured to generate the magnetic flux coupling between the tang and a magnetic component of the tool holder. The press brake tool, where the magnetic assembly comprises one or more permanent magnets disposed in the tang and configured to generate the magnetic flux coupling with the tool holder through one or both of a top surface and a side surface of the tang. The press brake tool, where the coupling mechanism comprise a magnetic armature configured to modulate the strength of the magnetic flux coupling by relative motion with respect to the one or more permanent magnets. The press brake tool, where the relative motion comprises transverse location of the armature with respect to the one or more permanent magnets. The press brake tool, further comprising a pushbutton type biasing member configured to retain the armature in alternate locked and unlocked positions, where the coupling end of the tool body is selectively engaged with and disengaged from the tool holder, respectively. 
     The press brake tool, where the relative motion comprises rotation of the magnetic armature with respect to the one or more permanent magnets. The press brake tool, further comprising gear member configured for rotation of the armature between alternate locked and positions, where the coupling end of the tool body is selectively engaged with and disengaged from the tool holder, respectively. The press brake tool, further comprising a pushbutton coupled to the gear member via a rack and pinion assembly and adapted for rotation of the armature thereby. 
     The press brake tool, further comprising a lever coupled to the armature for rotation thereof. The press brake tool, where the armature comprises transversely oriented magnetic elements configured for selective interaction with corresponding transversely oriented permanent magnets in the tang. The press brake tool, where the transversely permanent magnetics in the tang are adapted to generate the magnetic flux coupling through top surface and the side surface of the tang, respectively. 
     A machine tool comprising: a first end configured for operation on a workpiece; a second end configured for engagement with a tool holder; a plurality of magnetic elements configured to generate magnetic flux couplings adapted for the engagement of the second end of the tool body with the tool holder; and a coupling mechanism configured to modulate the magnetic flux couplings, where the second end of the tool body is selectively disengaged from the tool holder. 
     The machine tool, where the coupling mechanism comprises first and second magnetic armatures joined together by a transverse member. The machine tool, where first and second magnetic armatures have transversely oriented magnetic components. The machine tool, where the first and second magnetic armatures are configured for modulating the magnetic flux coupling by selective interaction with different respective permanent magnet elements disposed in the second end of the machine tool. The machine tool, where the different permanent magnet elements are disposed to generate the magnetic flux coupling through a top surface and one or more side surfaces of the second end of the machine tool, respectively. 
     The machine tool, further comprising a magnetically permeable material disposed adjacent at least one of the magnetic elements and adapted to substantially magnetically isolate the at least one elements from others of the magnetic elements. The machine tool, where the magnetically permeable material is disposed adjacent a first set of the magnetic elements disposed to generate a first component of the magnetic flux couplings through a top surface of the second end of the machine tool, substantially isolated from a second set of the magnetic elements disposed to generate a second component of the magnetic flux couplings through at least one side surface of the second end of the machine tool. The machine tool, further comprising one or more magnetic gaps disposed adjacent at least one of the plurality of magnetic elements, the magnetic gaps adapted to modulate at least one of the magnetic flux couplings by manipulation of the coupling mechanism with respect thereto. 
     Tool Systems and Methods of Use 
     Suitable press brake tool systems can include a tool body having a working end configured for operation on a workpiece and a coupling end configured for selective engagement with a tool holder, the working end spaced from the coupling end along the tool body; and one or more magnetic elements configured to induce a magnetic coupling between the tool body and the tool holder, where the coupling end of the tool body is magnetically engageable with the tool holder. 
     The magnetic elements can include one or more magnets disposed in the tool body for generating magnetic flux to induce the magnetic coupling, one or more ferromagnetic elements disposed in the tool body for guiding magnetic flux to induce the magnetic coupling, or a combination thereof. The magnetic coupling can be sufficient to support a weight of the tool body upon engagement of the coupling end with the tool holder. 
     The press brake tool systems can include a mechanism configured for selective disengagement of the coupling end of the tool body from the tool holder. The mechanism can comprise an actuator engaged with the tool body, the actuator configured to urge at least a portion of the coupling end from the tool holder to define an air gap therebetween. 
     The mechanism can comprise a pry bar or lever member engaged with the tool body, the pry bar or lever member extending from a first end to a second end, the second end configured to selectively disengage the coupling end of the tool body from the tool holder upon actuation of the first end. The first end of the pry bar or lever member may be accessible by a user, e.g., with the coupling end of the tool body engaged in the tool holder, and where the second end of the pry bar or lever member is configured to protrude from the tool body to selectively disengage the coupling end of the tool body from the tool holder upon manipulation of the first end by the user. A biasing element can be configured to bias the second end of the pry bar or lever member in a position disposed within the tool body, absent manipulation of the first end. 
     A load-bearing shoulder can be configured to bear a mechanical load between the tool holder and the tool body upon operation of the working end, where the second end of the pry bar or lever member is configured to protrude from the load-bearing shoulder to selectively disengage the coupling end from the tool holder. A pin or hinge element can be disposed between the first end of the pry bar or lever member and second end of the pry bar or lever member, e.g., where the pry bar or lever member is pivotably engaged with the tool body by the pin or hinge element. In some examples, the pry bar or lever member comprises a longitudinal portion extending from the first end to the pin or hinge element and a transverse portion extending transversely from the longitudinal portion, e.g., between the pin or hinge element and the second end. 
     The mechanism can comprise a longitudinal shaft or pin member engaged with the tool body, the longitudinal shaft or pin member extending from a first end configured for actuation by a user to a second end configured to selectively disengage the coupling end of the tool body from the tool holder upon actuation of the first end. The longitudinal shaft or pin member may be disposed in sliding engagement with the tool body, e.g., with the second end configured to extend from the tool body to selectively disengage the coupling end from the tool holder upon actuation of the first end. 
     The mechanism can comprise an armature having one or more magnets or ferromagnetic components configured to modulate a strength of the magnetic coupling by motion with respect to a flux path defined by disposition of the one or more magnetic elements in the tool body. The armature may be configured to rotate the one or more magnets or ferromagnetic components with respect to the flux path, or with respect to the poles of the magnetic elements defining the flux path. The armature may be configured for lateral motion of the one or more magnets or ferromagnetic components with respect to the flux path defined by magnetic assembly. A lever, knob or push button actuator can be engaged with the tool body, and mechanically coupled to the magnetic armature for manipulation of the one or more magnets or ferromagnetic components by the user to modulate the strength of the magnetic coupling. The mechanism may also comprise a plurality of armature members, each having one or more of the magnets or ferromagnetic components configured to modulate the strength of the magnetic coupling by rotational or lateral motion with respect to one or more flux paths defined by disposition of the one or more magnetic elements in the tool body. 
     The magnetic elements may comprise one or more permanent magnets disposed in the tool body, the one or more permanent magnets configured to form the magnetic coupling between the tool body and the tool holder with the coupling end of the tool body engaged therein. One or more non-ferromagnetic elements may be disposed in the tool body and adapted for modulation of a flux path through the one or more magnetic elements, e.g., where the strength of the magnetic coupling is responsive to the modulation of the flux path. 
     The one or more magnetic elements may comprise a plurality of magnetic sub-assemblies. Each magnetic sub-assembly may comprise one or more magnets or ferromagnetic elements configured to independently induce a magnetic coupling between the coupling end of the tool body and the tool holder. 
     A tang can be defined by the coupling end of the tool body, and adapted for the selective engagement with the tool holder. One or more magnets or ferromagnetic elements may be disposed in the tang, and configured to induce the magnetic coupling by generating or guiding magnetic flux between the tang and the tool holder. 
     A load-bearing shoulder can be defined on the tool body, and configured to bear a mechanical load between the tool holder and the tool body for operation of the working end of the tool body on a workpiece. One or more magnets or ferromagnetic elements may be disposed in the load-bearing shoulder, and configured to induce the magnetic coupling by generating or guiding magnetic flux between the load-bearing shoulder and the tool holder. 
     Suitable methods of use and operation include disposing a tool body with respect to a tool holder, the tool body having a working end configured for operation on a workpiece, a coupling end spaced from the working end along the tool body, and one or more magnetic elements configured to induce a magnetic coupling; and engaging the working end of tool body with the tool holder, where the magnetic coupling is induced between the tool body and the tool holder. The magnetic elements may comprise one or more permanent magnets disposed in the tool body for generating magnetic flux to induce the magnetic coupling, one or more ferromagnetic elements disposed in the tool body for guiding magnetic flux to induce the magnetic coupling, or a combination thereof. The magnetic flux coupling may be sufficient to support a weight of the tool body upon engagement of the coupling end with the tool holder. 
     An actuator mechanism may be engaged with the tool body, and operated to selectively disengage the coupling end of the tool body from the tool holder. Operating the actuator mechanism may comprise manipulating a knob, lever or pushbutton device coupled to the tool body, and mechanically engaged with a shaft or lever member configured to urge at least a portion of the coupling end of the tool body from the tool holder to define an air gap therebetween. 
     Operating the actuator mechanism may comprise manipulating a pry bar or lever pivotally engaged with the tool body, the pry bar or lever configured to selectively disengage at least a portion of the coupling end of the tool body from the tool holder. Operating the actuator mechanism may also comprise accessing a first end of a lever or pry member engaged with the tool body, where the coupling end of the tool body is engaged in the tool holder; and manipulating the first end of the lever or pry member such that a second end of the lever or pry member protrudes from the tool body to selectively disengage the coupling end from the tool holder. 
     Upon releasing the first end of the lever or pry member, the second end may be biased into a position disposed within the tool body. The second end of the lever or pry member may protrude from a load-bearing shoulder of the tool body upon manipulation of the first end, the load-bearing shoulder configured to bear a mechanical load between the tool holder and the tool body upon operation of the working end. 
     Operating the actuator mechanism can comprise manipulating a longitudinal shaft in sliding engagement with the tool body. The longitudinal shaft can be configured for urging the coupling end of the tool body from the tool holder, e.g., when manipulated by a user. 
     Operating the actuator mechanism can comprise manipulating one or more magnetic armatures with respect to a flux path defined by disposition of the one or more magnetic elements in the tool body. Manipulating the one or more magnetic armatures may comprise rotation or lateral motion of one or more magnets or ferromagnetic components with respect to the flux path, or with respect to the poles of the magnetic elements defining the flux path. A lever, knob or push button actuator can be manipulated, e.g., by a user, to provide rotation or lateral motion of the one or more magnetic armatures with respect to the flux path. 
     Suitable methods include selectively engaging a tang on the coupling end of the tool body with the tool holder, where the magnetic coupling is induced by one or more of the magnetic elements disposed in the tang. Additional methods include selectively engaging a load-bearing shoulder defined on the tool body with the tool holder, where the magnetic coupling is induced by one or more of the magnetic elements disposed in the load-bearing shoulder. 
     A press brake tool system can include a tool body having a working end configured for operation on a workpiece and a coupling end configured for selective engagement with a tool holder; a magnetic assembly configured to induce a magnetic coupling between the coupling end of the tool body and the tool holder; and a mechanism configured for selective disengagement of the magnetic coupling. The magnetic assembly may comprise one or more magnets disposed in the tool body for generating magnetic flux to induce the magnetic coupling, one or more ferromagnetic elements disposed in the tool body for guiding magnetic flux to induce the magnetic coupling, or a combination thereof. The magnetic coupling may be sufficient to support a weight of the tool body upon engagement of the coupling end with the tool holder. 
     The mechanism can comprise a pry bar or lever actuator engaged with the tool body, the pry bar or lever actuator configured to urge at least a portion of the coupling end from the tool holder to define an air gap therebetween. The pry bar or lever actuator may comprise a first end accessible by a user and a second end configured to extend from the tool body to selectively disengage the coupling end from the tool holder upon manipulation of the first end by the user. 
     The pry bar or lever actuator may comprise a longitudinal portion extending from a first end and a transverse portion extending transversely from the longitudinal portion to the second end. A pin or hinge may pivotably engage the pry bar or lever actuator with the tool body. A biasing element may bias the second end of the pry bar or lever actuator within the tool body, absent manipulation of the first end. 
     A load-bearing shoulder can be configured to bear a mechanical load between the tool holder and the tool body upon operation of the working end. The second end of the pry bar or lever member may protrude from the load-bearing shoulder to selectively disengage the coupling end from the tool holder. 
     The mechanism can comprise a longitudinal shaft or pin member disposed in sliding engagement with the tool body, and configured for actuation by a user to selectively disengage the coupling end of the tool body from the tool holder. The longitudinal shaft or pin member may comprise a first end mechanically engaged with an actuator and a second end configured to extend from the tool body to selectively disengage the coupling end from the tool holder upon manipulation of the actuator. 
     The mechanism can comprise one or more magnetic armatures configured to modulate a strength of the magnetic coupling by motion with respect to a flux path defined by the magnetic assembly. The one or more magnetic armatures may each comprise one or more magnets or ferromagnetic components configured for rotation or lateral motion with respect to the flux path, or with respect to the magnetic elements defining the flux path. An actuator may be engaged with the tool body, and mechanically coupled to the one or more magnetic armatures for manipulation of the magnets or ferromagnetic components by a user to modulate the strength of the magnetic coupling. 
     The magnetic assembly can comprise two or more magnetic subassemblies. The subassemblies may be configured to independently induce two or more respective magnetic couplings between the coupling end of the tool body and the tool holder. 
     A tang may be defined by the coupling end of the tool body and adapted for the selective engagement with the tool holder, e.g., where the magnetic assembly comprises one or more magnets or ferromagnetic elements disposed in the tang to induce the magnetic coupling between the tang and the tool holder. A load-bearing shoulder may be defined on the tool body to bear a mechanical load between the tool holder and the tool body upon operation of the working end, e.g., where the magnetic assembly comprises one or more magnets or ferromagnetic elements disposed in the load-bearing shoulder to induce the magnetic coupling between the load-bearing shoulder and the tool holder. 
     While this invention has been described with respect to particular examples and embodiments, changes can be made and substantial equivalents can be substituted in order to adapt these teaching to other configurations, materials and applications, without departing from the spirit and scope of the invention. The invention is not limited to the particular examples that are disclosed, but encompasses all the embodiments that fall with the scope of the claims.