Patent Publication Number: US-2013233140-A1

Title: Blanking die

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Italian patent application MI2012A000356 filed on Mar. 7, 2012, which is incorporated herein by reference in its entirety. The present application may also be related to U.S. application Ser. No. 13/474,511 filed on May 17, 2012, and U.S. patent application Ser. No. 13/554,374 filed on Jul. 20, 2012, both of which are also incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present disclosure relates to a blanking die assembly with an anti-seizure braking device in accordance with the introduction to the main claim. 
     BACKGROUND 
     Common blanking die assemblies are known, for example for producing magnetic laminations and/or magnetic lamination packs for electric motors and generators. These die assemblies usually present a lower part and an upper part. These two parts are mutually aligned by guide columns. The upper and lower parts of the die assembly present corresponding substantially flat portions known respectively as the flat lower portion or die plate and the flat upper portion or punch guide plate or punch stripping plate. With the die assembly open, sheet metal in the form of a strip is fed to the die assembly, to rest on the die plate. The die assembly upper part presents a plurality of punches which project from the punch guide plate during blanking, when the die assembly is closed by the action of the press. The punches then blank the laminations. For blanking purposes, recesses are provided in the die plate in positions corresponding with the punches, to receive said punches in order to implement the blanking operation. 
     On closing the die assembly, the punches press on the sheet metal in positions corresponding with the portion under which the relative recesses lie. Blanking is then achieved by cutting forces which the punches generate on the sheet metal at the recesses. 
     The die assembly presents at least one detachment die, with a relative brake, to detach the laminations from the sheet metal fed to the die assembly and to slidingly house the blanked laminations (or alternatively to brake the loose laminations by friction). This brake is in the form of a portion of the die assembly positioned below the detachment die. The brake presents a cavity coaxial with that of the detachment die. During lamination blanking, the brake enables the laminations to undergo braking (generally by interference), such that the laminations blanked in succession can be stacked together (or simply braked by friction). This stacking is implemented by suitable clips/seats present on the individual laminations, which enable the laminations to be connected together, to consequently generate a lamination pack of the required thickness. 
     A solution of the aforesaid type presents however various drawbacks related to possible seizure of the laminations within the accumulation brake. 
     To prevent the packs from undergoing seizure within the brake, emulsifiable cooling oils are normally sprayed into the sheet metal strip and/or the brakes are lubricated with suitable oils. 
     Because of the standard of cleaning demanded for the blanked product, this solution is not satisfactory in that such products leave oily residues/deposits on the lamination surfaces. 
     SUMMARY 
     An aspect of the present disclosure is to provide a blanking die assembly able to overcome the aforesaid drawbacks and to solve the relative technical problems. 
     A particular aspect of the present disclosure is to avoid seizure of the pack or of the individual laminations within the brake, while at the same time generating a braking effect which enables the blanked laminations to be secured together (by means of said clips/seats). 
     A further aspect of the present disclosure is to reduce as much as possible the quantity of cooling and/or lubricant oil used to prevent seizure. 
     In particular, according to an aspect of the present disclosure, a sheet metal blanking die assembly is provided, comprising: a lower part, an upper part and guide columns for maintaining the parts aligned during movement of the upper part relative to the lower part in order to close or open the die assembly or to blank the sheet metal to obtain relative blanked laminations, the die assembly upper part and lower part comprising flat parallel mutually opposing upper and lower horizontal portions, the lower flat portion being adapted to receive the sheet metal, the upper flat portion comprising a plurality of punches which project downwards from the upper flat portion at the moment of blanking when, by the action of a press, the die assembly is closed onto said flat lower portion, blanking recesses to receive respective punches, at least one detachment die comprising a detachment die through cavity, a brake positioned below said at least one detachment die, said brake comprising a brake through cavity positioned coaxial to the detachment die through cavity, said brake through cavity enabling blanked laminations to be stacked, the brake comprising a plurality of contact zones arranged to brake fall of the blanked laminations and possibly to enable formation of a lamination pack, and cooling and/or lubrication means to cool and/or lubricate just the contact zones between the blanked laminations or the lamination pack and the brake. 
     These and other aspects which will be apparent to the expert of the art are attained by a blanking die assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The teachings of the present disclosure will be more apparent from the accompanying drawings, which are provided by way of non-limiting example and in which: 
         FIG. 1A  is a perspective view of the upper part of a blanking die assembly for laminations; 
         FIG. 1B  is a perspective view of the lower part of the same die assembly as  FIG. 1A ; 
         FIG. 2  is a cut-away perspective view of the lower part of a die assembly; 
         FIG. 3  is a view of just the brake of the detachment die of  FIG. 2 , seen from above; 
         FIG. 4  s a perspective view of the brake of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1A and 1B , a blanking die assembly is indicated overall by  1 . The die assembly  1  usually presents a lower part  3  and an upper part  5 . These two parts are mutually aligned by the guide columns  7  of the die assembly  1 . The columns  7  enable the die upper part  5  to be maintained aligned with the lower part  3  during closure and opening operations and during blanking. In a central portion  9  of the die assembly  1  the die upper part  5  and lower part  3  present substantially flat portions known respectively as the flat upper portion  11  or punch guide plate or punch stripping plate, and the flat lower portion  13  or die plate. With the die assembly  1  open, sheet metal normally in the form of a strip (not shown in the figure) is fed into the die assembly  1  so as to rest on the die plate  13 . 
     The upper part  5  of the die assembly  1  presents a plurality of punches  17  which at the moment of blanking project from said punch guide plate  11  to penetrate into the relative recesses  19  present in the die plate  13 . 
     On closing the die assembly  1 , the punches  17  press onto the sheet metal at that sheet metal portion below which said recesses  19  are positioned. Blanking is then achieved by cutting forces which the punch  17  generates on the sheet metal at the recesses  19 . 
     In particular, the die assembly  1  presents at least one detachment die  20  with a relative brake  23  (see  FIG. 2 ) and a respective punch  21  (see  FIG. 1A ) which detach the laminations  24  and then stack them, to achieve in this manner the formation of a lamination pack  25 . 
     Said brake  23  is in the form of a portion of the die assembly  1  positioned below the detachment die  20 . The brake  23  presents a through cavity  18  coaxial with that of the detachment die  20 . 
     To enable a lamination  25  to be formed (or simply to brake an individual lamination  24 ), the brake  23  ( FIG. 2 ) presents inside the cavity  18  a plurality of contact zones  22 . The contact zones  22  extend parallel to an axis X defined by the conformation of the cavity  18  (hence in accordance with the direction of movement of the blanked laminations  42  within the die  20  and/or brake  23 ). 
     During a blanking step, the lamination  24  blanked in succession and/or the lamination pack  25  slides within the die  20  and within the brake  23 . Inside this latter, the lamination movement is braked by means of the contact zones  22 . Advantageously, the contact zones  22  enable the movement of the lamination  24  and/or of the lamination pack  25  to be braked by interference (more precisely by an interference fit), enabling the blanked laminations  24  to be stacked. In this manner, the brake  23  (see  FIG. 2 ) does not act on the entire lateral surface of the lamination pack  25 , but only at specific points of said lateral surface, i.e. the contact zones  22 . In this manner, the presence of limited contact zones  22  enables the friction surface between the brake  23  and the lateral surface of the lamination pack  25  (or of the individual lamination  24 ) to be reduced, so reducing the possibility of seizure phenomena and also reducing, the risk of deformation of the lamination pack  25  or of the individual laminations  24 , by braking within structurally stronger zones of the lamination pack  25  or of the individual laminations  24 . 
     To prevent seizure of the lamination pack  25  (or of the individual lamination  24 ) inside the cavity  18 , means are present for lubricating and/or cooling just the contact zone between the laminations  24  or the lamination pack  25  and the contact zones  22 . These means are suitable conduits  27  which carry cooling and/or lubricant fluids into specific zones of the contact zone  22 . Lubrication is then carried out in punctual manner, exclusively at points of interference between the contact zones  22  and the lateral surface of the lamination pack  25 . 
     Advantageously this solution enables precise dispensing of the cooling and/or lubricant fluid, such that the quantity of said cooling and/or lubricant fluid is the smallest possible to enable the lamination pack  25  to slide to the seizure limit and at the same time avoid excessive lubrication of the lamination pack  25 . 
     In particular, the conduits  27  ( FIG. 2 ) feed a plurality of apertures  28 , which open into the cavity  18  via suitable secondary conduits  29 . 
     The conduits  27 ,  29  and the apertures  28  enable a cooling and/or lubricant fluid to be transferred from a position outside the brake  23  to a position inside this latter, where the lamination pack  25  is able to slide. 
     In a further embodiment, the contact zones  22  present in the internal cavity are located on projections or ribs present inside the internal cavity  18  of the brake  23 . 
     A number of embodiments of the disclosure have been described. The specific embodiments provided herein are examples of useful embodiments of the disclosure and it will be apparent to one skilled in the art that the disclosure can be carried out using a large number of variations of the devices, device components, methods steps set forth in the present description. As will be obvious to one of skill in the art, methods and devices useful for the present methods can include a large number of optional composition and processing elements and steps. 
     In particular, it will be understood that various modifications may be made without departing from the spirit and scope of the present disclosure. Accordingly, other embodiments are within the scope of the following claims.