Abstract:
A method and apparatus for progressively cutting, piercing, bending, stacking, and interlocking lamination assemblies from a strip of laminate. The stacked laminations are mechanically interlocked with a staple-style interlock that secures all the laminations in the stack together. All the steps in the process of forming, stacking and interlocking are done within the tool and die assembly, eliminating the need for additional equipment to stack and interlock assemblies.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates generally to systems for forming laminations used in electrical devices, such as those used in the windings for D.C. motor armatures or A.C. rotors and stators. More particularly, the present invention relates to a method and apparatus for automatically producing interlocked laminations from blanks, or strips.  
           [0002]    Typically, laminations are created from continuous sheets that are fed through progressive cutting, punching, and bending steps in a tool and die assembly until the desired end configuration is obtained. Once cut to the desired configuration, laminations are typically stacked, or piled together to achieve the required thickness of laminations.  
           [0003]    It is desirable to retain the laminations together in a stack of the desired height in some way so the stack of laminations can be moved together in order to undergo further processing.  
           [0004]    Various methods and apparatus have been used to fasten the laminations together, including the use of tabs in the laminations which extend below a surface of the lamination and are inserted into a slot formed in the next adjacent lamination. As each lamination is cut out of the blank, or carrier strip, it is pushed out the end of the die and positioned adjacent to the next lower lamination in the stack. Typically, at least the bottom lamination in the stack has the interlock tabs removed to prevent a stack of laminations from becoming interlocked with another stack of laminations.  
           [0005]    This method of securing laminations together works fairly well, but part of the assembly method must include a way to align each lamination coming out the end of the die with the laminations in the stack so that the tabs align with the slots in the adjacent lamination. This typically requires piling the disconnected laminations on a spindle, or in a barrel type mechanism that rotates the lamination until the tab is aligned with the slot on the adjacent lamination and drops into that slot. In many situations, once the stack has been made, additional processing must be done to compress the laminations together so the tabs are firmly seated in the slots in order to keep the stack secured together. This step of aligning the laminations in the stack is time-consuming, and often results in decreased output from the manufacturing process. Attempts to speed up this step generally result in an increased number of misaligned laminations, and therefore a higher number of rejected parts.  
           [0006]    Accordingly, a continuing search has been directed to the development of a method which can increase the throughput of lamination stacks, while consistently providing stacks that are accurately aligned and properly secured.  
           [0007]    Therefore, what is needed is an improved system and method for manufacturing and interlocking laminations.  
         SUMMARY OF INVENTION  
         [0008]    Accordingly, the system of the present invention provides a method of interlocking a lamination that is still attached to the carrier strip to at least one lamination that has already been disconnected from the carrier strip. Performing this interlocking step while a lamination is still attached to the carrier strip eliminates the need for the extra step of having to align the laminations before they can be interlocked. Because the lamination being interlocked is still connected to the carrier strip, it is in a known, fixed position, and can be accurately aligned with the adjacent lamination. Elimination of the time-intensive step of aligning the laminations speeds up production throughput, and reduces failures due to misalignments.  
           [0009]    One aspect of the present invention is a method for manufacturing lamination assemblies from a strip of laminate, wherein at least one first lamination and at least one second lamination are cut in the strip, with at least one hole cut in each first lamination and at least one interlock tab in each second lamination. The first lamination is detached from the strip, and the strip is then moved so that the second lamination, still attached to the strip, is positioned adjacent to the disconnected first lamination. The interlock tab on the second lamination, which is inserted through the hole on the second lamination, is bent so that the interlock tab contacts the side of the first lamination in the stack that is opposite to the side adjacent to the second lamination, interlocking the at least one first lamination and the second lamination. The second lamination, which is now interlocked to the at least one first lamination, is then disconnected from the strip.  
           [0010]    Another aspect of the present invention is a method for manufacturing lamination assemblies from a strip of laminate, wherein at least one first lamination and at least one second lamination are cut in the strip, with at least one interlock tab on each second lamination. The first lamination is detached from the strip, and the strip is then moved so that the second lamination, still attached to the strip, is positioned adjacent to the disconnected first lamination. The interlock tab on the second lamination is bent around the periphery of each first lamination and the interlock tab is crimped such that it contacts the side of the first lamination in the stack that is opposite to the side adjacent to the second lamination, interlocking the at least one first lamination and the second lamination. The second lamination, which is now interlocked to the at least one first lamination, is then disconnected from the strip.  
           [0011]    Yet another aspect of the present invention is a tool and die apparatus for manufacturing an interlocked stack of laminations from a strip of material, comprising a series of dies and punches. At least one die is used for cutting holes in a first lamination, removing the material that is cut. At least one die is used for cutting at least one hole in a second lamination. A die is used for parting at least one first lamination from the strip of material. A stacker positions the second lamination adjacent to the first lamination parted from the strip of material. A punch presses the material from the hole on the second lamination into the corresponding hole on each first lamination and bends the material against the side of the first lamination that is opposite to the side adjacent to the second lamination. A die parts the second lamination, now interlocked to the first lamination, from the strip of material.  
           [0012]    In yet another aspect of the present invention a tool and die apparatus is used for manufacturing an interlocked stack of laminations from a strip of material, comprising a series of dies and punches. At least one die is used for cutting at least one first lamination. At least one die is used for cutting at least one second lamination having at least one tab extending from the periphery. A die is used for parting at least one first lamination from the strip of material. A stacker positions the second lamination adjacent to the first lamination parted from the strip of material. A punch bends the tab on the second lamination next to the periphery of each first lamination and against the side of the first lamination that is opposite to the side adjacent to the second lamination. A die parts the second lamination, now interlocked to the first lamination, from the strip of material.  
           [0013]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0014]    For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 is a plan view of a piece of laminate strip stock as it appears as it is progressively formed in the punch and die assembly of an embodiment;  
         [0016]    [0016]FIG. 2 is a side elevation view of the laminate strip stock during the steps of formation of FIG. 1; and  
         [0017]    [0017]FIG. 3 is an enlarged view of the last portion of the steps of formation of FIG. 1. 
     
    
     DETAILED DESCRIPTION  
       [0018]    As described in further detail below, the present invention utilizes a multi-station punch and die assembly adapted for use in an automatic cycling press, in which a strip of material is moved through a progressive die assembly which performs a further processing step on the material at each station of the unit. The punches and dies may be selectively activated to perform the desired function on only specific laminates.  
         [0019]    In the discussion of the FIGURES, the same reference numerals will be used throughout to refer to the same or similar components. In the interest of conciseness, various other components, such as punches, dies, and the like necessary for the manufacture of laminations are considered to be well-known and therefore have not been shown or discussed.  
         [0020]    Referring to FIG. 1 of the drawings, a strip of laminate sheet  10  is fed into a tool and die assembly (not shown) in the direction of the arrow  102  and progressively formed within various punches and dies of the tool and die assembly to form a stack of laminations  20  from the strip of laminate  10 . The particular tool and die assembly from which the stack of laminates  20  shown results is a preferred embodiment, used to produce staple-interlocked cupped laminations  20  for electrical motor cores. The tool and die assembly comprises a series of individual punches and dies, as described below. The tool and die assembly described below is one preferred embodiment, for which each step in the formation of the particular stack of staple-interlocked cupped laminations  20  for electrical motor cores, is described. However, it is understood that various arrangements and configurations of a tool and die assembly can be used to achieve different end-product laminations, and that all possible combinations are not discussed herein.  
         [0021]    At a first station  110  in the tool and die assembly, a center hole  22  for the motor core is pierced, and alignment notches  12  are cut in the strip of laminate  10 . These alignment notches  12  correspond with pins (not shown) located at each station in the tool and die assembly. As the strip  10  advances through the stations of the tool and die assembly, the notches  12  are aligned with the pins at each station to ensure the strip  10  is properly positioned for further processing at that station.  
         [0022]    At a second station  112 , part of the outer shape of the lamination  20  is cut, leaving braces  14  that hold the lamination  20  to the strip  10  during processing. At station  114 , the material between subsequent laminations  20  on the strip  10  is cut and removed.  
         [0023]    Station  116  is preferably an idle station, wherein no processing is performed on the strip  10 . Two different laminations  20   a  and  20   b  are alternated to form the stack of staple-interlocked cupped laminations  20  of the preferred embodiment described. In order to generate the different laminations  20   a  and  20   b  from a single strip  10 , operations that are specific to one lamination  20   a  or the other lamination  20   b  are performed at different stations in the tool and die assembly. While some of the operations can be done simultaneously at different stations on the different laminations  20   a  and  20   b , there must be two partially formed laminations ready for simultaneous processing. When the first lamination  20   a  has been partially formed, it waits in the idle station  116  while the second lamination  20   b  is being formed at station  114 . Station  118  is also preferably an idle station.  
         [0024]    At station  120 , staple interlock holes  24  are pierced in the first lamination  20   a , the material cut away to form the holes  24  is trimmed off, and additional trimming on the arms  26  is performed. The arms  26  on the first lamination  20   a  are shorter than those on the second lamination  20   b . While this work is being performed on the first lamination  20   a , the second lamination  20   b  is waiting in idle station  118 .  
         [0025]    At station  122 , staple interlock holes  24  are pierced in the second lamination  20   b . As can be seen in FIG. 2, the tabs  28  (the material that was cut to form the holes  24 ) remain attached to the lamination  20   b , but are bent at the attachment point to descend in a plane below the lower surface of the lamination  20   b . While the staple interlock holes  24  are being pierced in the second lamination at station  122 , the arms  26  on the first lamination  20   a  are being bent down at station  124 . As can be seen in FIG. 2, the arms  26  descend below the lower surface of the carrier strip  10 .  
         [0026]    Station  126  is an idle station, wherein preferably no processing is performed on the strip  10 . The two different laminations  20   a  and  20   b  have been partially formed, and at station  126  are now ready to undergo further processing, as described below.  
         [0027]    At station  128 , the arms  26  on the second lamination  20   b  are bent down. As viewed in FIG. 2, the arms  26  descend below the lower surface of the carrier strip  10 . Because the arms  26  on the second lamination  20   b  have not been trimmed, they descend slightly lower than the arms  26  on lamination  20   a , as can be seen in FIG. 2. While the arms  26  are being bent on the second lamination  20   b  at station  128 , at station  130 , a notch  30  is being cut into the first lamination  20   a.    
         [0028]    As shown in detail in FIG. 3, at station  132 , the first lamination  20   a  is seated on a horn (not shown) in the tool and die assembly, and the braces  14  that hold the first lamination  20   a  to the carrier strip  10  are removed. While the braces  14  are being removed from the first lamination  20   a  at station  132 , a notch  30  is cut into lamination  20   b  at station  130 . At station  132 , the second lamination  20   b , which is still attached to the carrier strip  10  is positioned on top of the first lamination  20   a , which is seated on the horn (not shown) at station  132  of the die. As seen in FIG. 2, the tabs  28  that were cut in the second lamination  20   b  at station  122  are pressed down into the staple interlock holes  24  that were cut in the first lamination  20   a  at station  120 , and the tabs  28  are bent up like a staple against the underside of the first lamination  20   a , as viewed in FIG. 2. The lamination stack  20 , formed by the second lamination  20   b , to which the first lamination  20   a  is now stapled is moved to station  134  of the tool and die assembly.  
         [0029]    As can also be seen in FIG. 3, at station  134  the lamination stack  20 , formed by the second lamination  20   b , to which the first lamination  20   a  is now stapled, is disconnected from the carrier strip  10  by removal of the braces  14 . The lamination stack  20  is then blown out, pushed, or otherwise removed from, the end of the tool and die assembly.  
         [0030]    It is understood that the present invention can take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or the scope of the invention. For example, this process may be used on other laminations than cupped laminations. Similarly, this invention may be used with a lamination stack comprised of numerous laminations that are all substantially similar, rather than the first and second laminations being slightly different, as described in the preferred embodiment, above. With a stack of substantially similar laminations, the only variation between laminations is that the top lamination in the stack is the only one on which the tabs which are interlocked to the lower lamination remain attached. Alternatively, this invention may be used with a lamination stack comprised of numerous laminations that differ in shape and/or size, but are still cut from the same strip and stacked together. In yet another arrangement of the tool and die assembly of the present invention, the stations may be arranged so that the stack of laminations comprises more than one first lamination interlocked to a second lamination. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.  
         [0031]    Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.