METHOD AND APPARATUS FOR STACKING LAMINAS

Abstract: Individual laminas (14) are blanked from sheet strip material 12) and stacked to form a lamina stack (16) for use in electric motor or generator rotors or stators. The thickness of each lamina (14) is measured prior to stacking, and the individual lamina thickness measurements (37) are supplied to a controller (30). The controller (30) monitors the increase in stack height as the individual laminas (14) are stacked and compares the increase in stack height to an operator entered preselected stack height. Individual laminas (14) are stacked as long as the height of the lamina stack (16) is less than an operator entered preselected stack height. Individual laminas (14) are continually stacked until the addition of another lamina would cause the lamina stack height to exceed the preselected stack height. Slotted openings (28) are blanked in each lamina (14) to form a slot in the stacked laminas which is skewed to the stack axis by a constant skew angle by providing that the lamina stack (16) is rotated an angular increment determined by the thickness of the lamina (14) prior to stacking the lamina (14).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to method and apparatus for stacking laminas, and more particularly, to a method and apparatus for controlling the height of a lamina stack formed from individually blanked laminas and controlling the skew angle between a stack axis and a conductor slot axis wherein the conductor slot axis is formed from individual laminas of unequal thickness. 2. Description of the the Prior Art It is well known to form electric motor rotors and stators from individually blanked laminas stacked to form a lamina stack. The individual laminas are blanked from sheet strip material and then stacked together to form a rotor or stator which is pressed on a motor armature shaft. The devices disclosed in U.S. Patent Nos. 2,562,254; 3,202,851; 3,457,445; 3,652,889 and 4,204,314 disclose various types of rotors, stators or electromagnetic cores formed from individual laminas. It is also known to form a lamina stack in which individual laminas in the stack are interlocked to adjacent laminas to form an interlocked lamina stack. Examples of known interlocked lamina stacks are disclosed in U.S. Patent Nos. 3,110,831; 3,203,077; 4,110,895 and 4,160,182. U.S. Patent No. 3,590,208 discloses a method for forming a lamina stack which includes stamping a number of laminations to form projections and recesses at points around a circle. Each projection is formed in mating configuration with one of the recesses but is displaced in the circumferential direction around the circle with respect thereto. It is stated that the indi­ vidual laminations are stacked so that the projections of one lamination engage a recess in the adjacent lamination. As a consequence, each lamination will be angularly displaced, about the common axis formed by all of the circles of the individual laminations, with respect to its adjacent laminations. The stacked laminations are welded together by passing a current through them from one end lamination to the other. Since the individual laminations are separated by the weld projections, all the current will be constrained to flow through these projections, causing them to melt and fuse the laminations together. U.S. Patent No. 4,445,272 discloses a method and apparatus for con­ structing a laminated rotor. The apparatus consists of a rotatable carousel having a plurality of rotatable work stations each of which is carried to a plurality of operating stations. Lamina are punched from sheet metal stock and brought back into the stock and held in a friction fit. Sheet stock is then advanced to a stacking station where the lamina is forced onto a rotor shaft. It is stated that the height of the lamina accumulated on the shaft is sensed to determine completion of the rotor. U.S. Patent No. 4,619,028 discloses apparatus for the manufacture of laminated parts. Stock strip material is blanked to form interlocking laminas for electric motor or generator rotors or stators at successive blanking stations. At a final assembly station the laminas are stacked and pressed into interlocking relationship. In response to an operator input, a predeter­ mined number of reversals or half turns about the stack axis of the previously stacked lamina are provided in order to compensate for nonuniform strip thick­ ness to obtain a rotor or stator of substantially uniform height with respect to the parallelism between the top and bottom laminas in the stack. Rotor con­ ductor slots formed in the stacked laminas are skewed to the stack axis by providing arcuate indexing of each lamina relative to the next preceeding lamina in the stack by an arcuate increment that is determined in response to operator inputs relative to the stack height, the skew angle, nominal lamina thickness and skew direction. However, the thickness of each individual lamina is not taken into account when arcuately indexing the lamina stack prior to stacking the next individual lamina. As a result, if lamina stacks having a given skew angle are mass produced, there is no skew angle uniformity between completed stacks having different numbers of laminas. While it has been suggested by the prior art devices to stack individ­ ually blanked laminas to form a completed lamina stack and to form conductor slots in the stacked laminas which are skewed to the stack axis, there is a need for an improved method and apparatus for forming a lamina stack that is computer controlled to form a lamina stack of preselected stack height. The apparatus must be capable of stacking laminas until the stacking of one additional lamina causes the lamina stack height to exceed a preselected stack height. There is also need for a stamping and blanking apparatus in which the thickness of each lamina determines the positioning of the lamina stack relative to each individ­ ual lamina to provide a slot in the stacked laminas that forms a continuous linear slot axis. By utilizing the thickness of each lamina to be stacked to determine the positioning of the lamina stack, a constant skew angle is maintained regardless of the number of laminas in the stack. SUMMARY OF THE INVENTION In accordance with the present invention there is provided apparatus for controlling the height of a lamina stack formed from individual laminas blanked from sheet strip material that includes blanking means for blanking from sheet strip material individual laminas each having a preselected configuration. The individual laminas are stacked to form a lamina stack having a stack axis substantially perpendicular to the laminas. Measuring means determines the increase in height of the lamina stack. A controller is connected with the measuring means and has operator entry means for receiving an operator entered preselected stack height. The controller continually determines the height of the lamina stack and stops the stacking of individual laminas on the stack when the lamina stack height substantially equals and does not exceed the preselected stack height. Further in accordance with the present invention there is provided appar­ atus for limiting the height of a lamina stack formed from individual laminas blanked from sheet strip material that includes means for blanking from sheet strip material individual laminas each having a preselected configuration. The individual blanked laminas are stacked to form a lamina stack having a stack axis substantially perpendicular to the laminas. Measuring means is provided for determining the increase in height of the lamina stack. A con­ troller, connected with the measuring means, has an operator entry means for receiving an operator entered preselected stack height. The controller contin­ uously determines the height of the lamina stack to continue stacking individual laminas when the increase in lamina stack height is less than the preselected stack height, and to stop stacking of individual laminas before the increase in lamina stack height exceeds the preselected stack height. Additionally in accordance with the present invention there is pro­ vided a method for blanking from sheet strip material individual laminas to form a lamina stack comprising the steps of stamping a slot in sheet strip material and blanking from the sheet strip material individual laminas having a presel­ ected configuration including a slot. The method includes stacking the blanked laminas to form a lamina stack having a stack axis substantially perpendicular to the laminas. The method includes the further steps of measuring the thick­ ness of each lamina, positioning the lamina stack relative each lamina and controlling the positioning of the lamina stack relative each lamina determined by the thickness of each lamina so that the slots in the stacked laminas form a continuous linear slot axis skewed to the stack axis. Accordingly, the principal object of the present invention is to provide apparatus for controlling the height of a lamina stack formed from individual laminas blanked from sheet strip material. Another object of the present invention is to provide apparatus for limiting the height of a lamina stack formed from individual laminas blanked from sheet strip material. An additional object of the present invention is to provide a lamina stack having a continuous linear slot formed from individual slotted openings in which the linear slot axis is skewed to the stack axis by a constant skew angle determined by the thickness of each lamina in the lamina stack. Providing a constant skew angle determined by the thickness of each lamina in the stack ensures skew angle uniformity between completed stacks where it is desired to mass produce lamina stacks each having the same preselected skew angle, regard­ less of the number of laminas in the completed stack. These and other objects of the present invention will be more com­ pletely disclosed and described in the following specification, the accompanying drawings, and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an isometric view of an apparatus for controlling the height of a lamina stack formed from individually blanked laminas which is the subject of this invention. Fig. 2 is an elevational view of a blanking apparatus taken along line II-II of Figure 1, illustrating the arrangement for rotating a die knock-out chamber and stacking individual blanked laminas. Fig. 3 is an enlarged fragmentary elevational view of a stack of laminas having slotted openings skewed to an axis perpendicular to the lamina plane as disclosed in the prior art. Fig. 4 is an enlarged fragmentary elevational view of a stack of laminas having slotted openings skewed to an axis substantially perpendicular to the lamina plane which is the subject of this invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings and particularly to Figures 1 and 2, there is illustrated apparatus generally designated by the numeral 10 for blanking from sheet strip material 12 individual laminas 14 to form a completed lamina stack 16 for use in electric motor or generators. The stamping and blanking apparatus generally designated by the numeral 10 includes die shoe assembly 18 and punch assembly 20. Punch assembly 20 is positioned above and securely attached to the die shoe assembly 18. Punch assembly 20 is mounted for reciprocal vertical movement on die shoe assembly 18 by mounting posts schematically illustrated by the numerals 34. As illustrated in Figure 2, the sheet strip material 12 is passed through stamping and blanking apparatus 10 to progressively blank from sheet strip material 12 individual laminas 14 to form completed lamina stack 16. Stamping and blanking apparatus 10 includes a plurality of individual stamping and blanking stations numbered 1 through 5. Although five stamping and blanking stations are illustrated, it should be understood that stamping and blanking apparatus 10 may include any number of stamping and blanking stations required to stamp the desired openings in sheet strip material 12. It should be further understood that the stamping and blanking apparatus generally designated by the numeral 10 is itself known in the art and is described herein only as it relates to the present invention. The general operation of stamping and blanking apparatus 10 is as follows. At Station No. 1, interlock tab openings 22 and armature shaft pilot hole 24 are blanked. At station No. 2, arcuate interlocked tabs 26 are lanced from sheet strip material 12 and then depressed below the lower strip surface. At station no. 3, slot openings 28 are blanked. At station no. 4, a lamina 14 is blanked from sheet strip material 12 and shaft hole 30 is simultaneously blanked, after which lamina 14 is pushed back into the plane of sheet strip 12. At station no. 5, lamina 14 is pushed through sheet strip material 12 and into die knock-out chamber 36. As sheet strip material 12 is passed through stamping and blanking apparatus 10, it is maintained in its relative position with respect to die shoe assembly 18 by means of a pair of guides 32, broken away to better illustrate station no. 5. Referring to Figure 2, there is illustrated a rotating apparatus generally designated by the number 52 for providing rotation of die knock-out chamber 36 within die shoe assembly 18. As will be explained later in greater detail, die knock-out chamber 36 is rotated with die shoe assembly 18 a preselected incremental angular amount to provide a preselected amount of skew between slotted openings 28 in the individual laminas 14 in completed lamina stack 16. The rotating apparatus generally designated by the numeral 52 includes a bevel ring gear 50 suitably secured to die knock-out chamber 36 to rotatably drive die knock-out chamber 36 within die shoe assembly 18. Bevel pinion gear 48 is positioned in driving engagement with ring gear 50 and in turn is con­ nected through shaft 46 and coupling 44 to motor 42. Motor 42 may be a stepper motor or, for greater torque and rotational speed requirements, a direct current servo motor may be utilized. However, in all cases, a motor which tends to dissipate heat through its housing should be utilized to minimize the adverse temperature effects due to motor 42 heating on die shoe assembly 18. Individual laminas 14 blanked from sheet strip material 12 form a lamina stack within die knock-out chamber 36. As laminas 14 are forced into die knock-out chamber 36 by operation of punch assembly 20, arcuate interlock tabs 26 blanked in each lamina 14 at station no. 3 cause adjacent laminas 14 to interlock to form a lamina stack 16 of interlocked laminas 14 known in the art. As additional laminas 14 are forced into die knock-out chamber 36 by operation of punch assembly 20, the completed lamina stacks 16 are forced through the bottom of die knock-out chamber 36 and are deposited on the conveyor schemat­ ically illustrated as 54 or onto any suitable receiver. It is apparent that the bottom laminas 14 in a lamina stack 16 do not include arcuate interlock tabs 26. Since the bottom lamina 14 in a lamina stack 16 does not include arcuate interlock tabs 26, a plurality of lamina stacks 16 of preselected height may be retained within die knock-out chamber 36. Referring to Figure 1, sheet strip material 12 fed from a supply coil or other supply (not shown) passes through the thickness measuring appar­ atus generally designated by the numeral 37 before entering stamping and blank­ ing apparatus 10. The thickness measuring apparatus generally designated by the numeral 37 includes thickness gauge 38 mounted above sheet strip material 12 and thickness gauge 40 mounted below sheet strip material 12. Thickness gauges 38 and 40 may be secured in their respective positions in any suitable manner. Thickness gauges 38 and 40 are of the contacting type of displacement measuring devices known to those skilled in the art. Thickness gauges 38 and 40 include rollers 41 and 43 which contact the top and bottom surfaces respectively of sheet strip material 12. Thickness gauge 38 provides a signal to controller 30 on line 39, and thickness gauge 40 provides a signal to controller 30 on line 45. Thickness gauges 38 and 40 operate together to measure the thickness of sheet strip material 12 for each lamina stack 16 formed. As previously described, rollers 41 and 43 mounted on thickness gauges 38 and 40 contact the top and bottom surfaces respectively of sheet strip material 12. The distance between rollers 41 and 43 corresponds to the thickness of sheet strip material 12. A preselected number of individual thickness measurements are taken at each point measured, and these thickness measurements are supplied to controller 30 which averages the thickness readings taken to obtain an average thickness measurement for sheet strip material 12. To practice the present invention, sheet strip material 12 is fed from a supply coil or other supply to stamping and blanking apparatus 10 to blank from sheet strip material 12 individual laminas 14 which are stacked in die knock-out chamber 36. The various openings and tabs 22-28 are blanked in laminas 14 at stations 1-5 in preselected locations for specific applications. Before sheet strip material 12 passes through the various stations numbered 1-5, the thickness of sheet strip material 12 is measured by thickness measuring apparatus 37 and the thickness measurement readings are provided to controller 30. Thickness measurement readings are taken between operations of punch assembly 20 to minimize thickness measurement errors due to vibration. The system operator provides to controller 30 the desired preselected height of the completed lamina stack 16 to be formed within die knock-out chamber 36 and a value corresponding to the distance between measuring apparatus 37 and station no. 5. Given the value corresponding to the distance between measuring apparatus 37 and station no. 5, controller 30 automatically calcu­ lates the number of laminas 14 of predetermined diameter to be blanked from sheet strip material 12 between measuring apparatus 37 and station no. 5. Thickness measurements are provided to controller 30 by thickness measurement apparatus 37 to provide that the thickness measurement of each successive individual lamina 14 to be blanked from sheet strip material 12 between measure­ ment apparatus 37 and station no. 5 are entered into controller 30. In this manner, the controller identifies the number of laminas 14 between measurement apparatus 37 and station no. 5 and the thickness of each individual lamina 14. As individual laminas 14 are stacked in die knock-out chamber 36 by operation of punch assembly 20, the thickness measurements of each individual lamina 14 provided by measurement apparatus 37 are added together within controller 30 to determine the increase in stack height of the individual laminas 14 in die knock-out chamber 36. Controller 30 continually compares the height of the laminas 14 in die knock-out chamber 36 to the preselected stack height entered into controller 30 by the operator. Controller 30 provides a signal to punch assembly 20 to allow punch assembly 20 to continue blanking from sheet strip material 12 laminas 14 and stacking the laminas 14 in the die knock-out chamber 36 as long as the stack height of the stacked laminas 14 is less than the operator entered preselected stack height. As previously described, controller 30 adds the thicknesses of each individual lamina 14 in die knock-out chamber 36 to determine the increase in stack height. Controller 30 also has calculated and stored the number of laminas 14 to be blanked from sheet strip material 12 between measurement apparatus 37 and station no. 5 and the thickness of each lamina yet to be blanked. Given the above information, controller 30 calculates the number of additional laminas 14 which may be blanked from sheet strip material 12 and stacked in die knock-out chamber 36 to provide that the height of completed lamina stack 16 does not exceed the preselected height. The continual addition and comparison process within controller 30 provides that a completed lamina stack 16 having a height which does not exceed the preselected stack height is formed. As previously described, stamping and blanking apparatus 10 includes means for rotating die knock-out chamber 36. Die knock-out chamber 36 may be rotated before each individual lamina 14 is stacked. Referring to Figures 2 and 4, the rotating apparatus generally designated by the numeral 52 rotates die knock-out chamber 36 before each individual lamina 14 is stacked so that the slotted openings 28 in the stacked laminas 14 form slot 56 having a slot axis 60 which is skewed to stack axis 58 by a desired skew angle for purposes well known in the art. The skew angle may be left handed or right handed with respect to stack axis 58 depending on whether slot axis 60 crosses stack axis 58 from left to right or right to left as one moves down slot axis 60. Referring to Figure 3, there is illustrated a stack of laminas 14 having slotted openings 28 which form conductor slot 56. Conductor slot 56 has a slot axis 60 skewed to stack axis 58. As seen in Figure 3 and disclosed in the prior art devices, die knock-out chamber 36 is rotated an equal angular distance prior to stacking each individual lamina 14 to form conductor slot 56. In the prior art devices, die knock-out chamber 36 is rotated an equal angular distance prior to stacking each individual lamina 14 without considering the thickness of each individual lamina 14 in the lamina stack. Since the thickness of sheet strip material 12 varies, the thicknesses of the individual laminas 14 blanked from sheet strip material 12 will also vary. Rotating die knock-out chamber 36 an equal angular distance prior to stacking laminas 14 having unequal thicknesses will form a conductor slot 56 having a nonlinear slot axis 60 skewed to stack axis 58 by a skew angle which is also nonlinear. Since the thickness of each lamina 14 is not taken into account when rotating die knock-­ out chamber 36, if lamina stacks having a given skew angle are mass-produced, there is no skew angle uniformity between completed stacks 16 when completed stacks 16 have different numbers of laminas 14. Figure 4 illustrates a stack of laminas 14 having slotted openings 28 which form slot 56. Conductor slot 56 has a slot axis 60 which is skewed to stack axis 58. As seen in Figure 4, slotted openings 28 in laminas 14 form a slot 56 having a linear slot axis 60. Linear slot axis 60 is formed by rotating die knock-out chamber 36 by an angular amount dependant upon the thickness of the each lamina 14 to be placed on the lamina stack. Referring to Figures 1 and 2, the thickness of sheet strip material 12 measured by thickness measuring apparatus 37 is provided to controller 30. As previously described, since thickness measuring apparatus 37 is placed a preselected distance from station no. 5, controller 30 calculates the number of individual laminas 14 of preselected diameter to be blanked from sheet strip material 12 between thickness measuring apparatus 37 and station no. 5 and also stores the thickness of each lamina 14 to be blanked between measuring apparatus 37 and station no. 5. Before each lamina 14 is blanked from sheet strip mater­ ial 12 at station no. 5 and forced into die knock-out chamber 36 by operation of punch assembly 20, controller 30 provides a signal to motor 42 on line 47 to rotate die knock-out chamber 36 a preselected angular distance dependant upon the thickness of the lamina 14 to be placed in the lamina stack 16. In this manner, the amount of angular rotation of die knock-out chamber 36 and lamina stack 16 is controlled by the thickness of each lamina 14 to be placed on lamina stack 16 to provide that the slotted openings 28 in the stacked laminas 14 form a continuous linear slot 56 having a continuous linear slot axis 60 skewed to stack axis 58 by a constant skew angle. As previously described, die knock-out chamber 36 may be rotated in either a clockwise or counterclockwise direction to provide either a right handed or left handed skew axis with respect to stack axis 58. Any desired skew angle may be provided to meet particular application requirements. According to the provisions of the patent statutes, I have explained the principal, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. However, it should be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

Claims: 1. An apparatus for controlling the height of a lamina stack formed from individual laminas blanked from sheet strip material comprising, blanking means, said blanking means including means for blanking from a sheet strip material individual laminas each having a preselected configuration, means for receiving and stacking said individual blanked laminas to form a lamina stack having a stack axis substantially perpendicular to said laminas, measuring means for determining the increase in height of said lamina stack, and controller means connected with said measuring means and having adding means and operator entry means for receiving an operator entered presel­ ected stack height, said controller means continuously determining the height of said lamina stack to stop said stacking of said individual laminas when said lamina stack height substantially equals and does not exceed said preselected stack height. 2. An apparatus for controlling the height of a lamina stack formed from individual laminas blanked from sheet strip material as set forth in claim 1 in which said measuring means includes, means for measuring the thickness of each said lamina before each said lamina is added to said lamina stack. An apparatus for controlling the height of a lamina stack formed from individual laminas blanked from sheet strip material as set forth in claim 1 in which, said measuring means is positioned for measuring the thickness of each said lamina at substantially the center of each said lamina. 4. An apparatus for controlling the height of a lamina stack formed from individual laminas blanked from sheet strip material as set forth in claim 1 in which said controller adding means includes, means for adding the thicknesses of said laminas in said lamina stack to determine the height of said lamina stack. 5. An apparatus for blanking from sheet strip material individual laminas to form a lamina stack comprising, stamping means for stamping a slot in a sheet strip material, blanking means for blanking from said sheet strip material individual laminas having a preselected configuration, each said lamina including said slot, means for receiving and stacking said individual blanked laminas to form a lamina stack having a stack axis substantially perpendicular to said laminas, measuring means for measuring the thickness of each said individual lamina, positioning means for positioning said lamina stack relative each said individual lamina, and controller means connected with said measuring means and said posi­ tioning means for controlling the positioning of said lamina stack relative each said individual lamina, said thickness of each said lamina determining the positioning of said lamina stack relative each said individual lamina so that said slots in said stacked laminas form a continuous linear slot axis skewed to said stack axis. 6. An apparatus for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 5 in which said positioning means includes, means for positioning said lamina stack while said individual laminas are maintained in a fixed position relative said lamina stack. 7. An apparatus for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 5 in which, said lamina stack is positioned prior to stacking said individual laminas. 8. An apparatus for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 5 in which said positioning means includes, means for providing incremental angular rotation of said lamina stack about said stack axis for each of said laminas. 11. An apparatus for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 5 in which said controller means includes, means for controlling the degree of incremental angular rotation of said lamina stack relative each of said laminas. 10. An apparatus for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 5 in which said positioning means includes, means for rotating said lamina stack about said stack axis in a preselected angular direction for each of said laminas. 11. An apparatus for limiting the height of a lamina stack formed from individ­ ual laminas blanked from sheet strip material comprising, blanking means, said blanking means including means for blanking from a sheet strip material individual laminas each having a preselected configuration, means for receiving and stacking said individual blanked laminas to form a lamina stack having a stack axis substantially perpendicular to said laminas, measuring means for determining the increase in height of said lamina stack, and controller means connected with said measuring means having adding means and operator entry means for receiving an operator entered preselected stack height, said controller means continuously determining the height of said lamina stack to continue stacking of said individual laminas when said increase in lamina stack height is less than said preselected stack height and to stop said stacking of said individual laminas before said increase in lamina stack height exceeds said preselected stack height. 12. An apparatus for limiting the height of a lamina stack formed from indi­ vidual laminas blanked from sheet strip material as set forth in claim 11 in which said measuring means includes, means for measuring the thickness of each said lamina before each said lamina is added to said lamina stack. 13. An apparatus for limiting the height of a lamina stack formed from indi­ vidual laminas blanked from sheet strip material as set forth in claim 11 in which said controller means includes, means for determining said height of said lamina stack, means for determining the height of the next lamina to be placed on said lamina stack, and means for determining if said height of said next lamina plus said height of said lamina stack exceeds said preselected stack height. 14. An apparatus for limiting the height of a lamina stack formed from indi­ vidual laminas blanked from sheet strip material as set forth in claim 11 in which said controller adding means includes, means for adding the thicknesses of each said lamina in said lamina stack to determine the height of said lamina stack. 15. A method for controlling the height of a lamina stack formed from individ­ ual laminas blanked from sheet strip material comprising the steps of, providing sheet strip material, blanking from said sheet strip material individual laminas each having a preselected configuration, stacking said individual blanked laminas to form a lamina stack having a stack axis substantially perpendicular to said laminas, determining the increase in height of said lamina stack, and stopping said stacking of said individual blanked laminas when the height of said lamina stack substantially equals but does not exceed a preselected stack height. 16. A method for controlling the height of a lamina stack formed from individ­ ual laminas blanked from sheet strip material as set forth in claim 15 including the further steps of, measuring the height of said lamina stack, measuring the height of the next lamina to be placed on said lamina stack, and stopping said stacking of said next lamina when said height of said next lamina plus said height of said lamina stack exceeds said preselected stack height. 17. A method for controlling the height of a lamina stack formed from indi­ vidual laminas blanked from sheet strip material as set forth in claim 15 including the steps of, measuring the thickness of each individual lamina, and adding the thicknesses of said individual laminas in said lamina stack to determine the increase in height of said lamina stack. 18. A method for blanking from sheet strip material individual laminas to form a lamina stack comprising the steps of, providing sheet strip material, stamping a slot in said sheet strip material, blanking from said sheet strip material individual laminas having a preselected configuration, each said lamina including said slot, stacking said individual blanked laminas to form a lamina stack having a stack axis substantially perpendicular to said laminas, measuring the thickness of each said lamina, positioning said lamina stack relative each said lamina, and controlling said positioning of said lamina stack relative each said lamina, said positioning being determined by said thickness of each lamina to provide that said slots in said stacked laminas form a continuous linear slot axis skewed to said stack axis. 19. A method for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 18 including, positioning said lamina stack while said individual laminas are maintained in a fixed position relative said lamina stack. 20. A method for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 18 including, positioning said lamina stack prior to stacking said individual laminas. 21. A method for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 18 including, providing incremental angular rotation of said lamina stack about said stack axis for each of said laminas. 22. A method for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 18 including, controlling the degree of incremental angular rotation of said lamina stack relative each of said laminas. 23. A method for blanking from sheet strip material individual laminas to form a lamina stack as set forth in claim 18 including, rotating said lamina stack about said stack axis in a preselected angular direction for each of said laminas.

Inventors: MALLOY, JOSEPH PATRICK
Applicants: OBERG INDUSTRIES INC.
Application year: 1988
Main classification: H02K15
IPC codes: B21D43, H02K15