Source: https://patents.justia.com/patent/6484387
Timestamp: 2020-02-25 10:56:42
Document Index: 625943865

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US Patent for Progressive stamping die assembly having transversely movable die station and method of manufacturing a stack of laminae therewith Patent (Patent # 6,484,387 issued November 26, 2002) - Justia Patents Search
Justia Patents Dynamoelectric MachineUS Patent for Progressive stamping die assembly having transversely movable die station and method of manufacturing a stack of laminae therewith Patent (Patent # 6,484,387)
Jun 7, 2000 - L. H. Carbide Corporation
The manufacture of parts comprising a stack of interlocked laminae, e.g., stators and rotors for electric motors, or cylindrical cores for ignition system coils such as those used in low voltage ignition systems having spark plug-mounted coils, is known in the art. Apparatuses and methods associated with such manufacture are disclosed, for example, in U.S. Pat. No. 5,755,023 and Pending U.S. patent application Ser. No. 09/152,979, filed Sep. 14, 1998, which are assigned to the present assignee, and the disclosures of which are expressly incorporated herein by reference. Prior art progressive stamping die assemblies in which a plurality of differently shaped laminae are formed from a common piece of strip stock material, which laminae are stacked to form the laminated part, provide a separate stamping die station for each punch and die which forms a lamina having a particular shape and/or size.
FIGS. 1 and 2 illustrate one embodiment of a laminated part which may be produced by the inventive progressive stamping die apparatus inventive method described further herein below. Part 20, which may also be referred to as a “pencil core”, comprises a stack of interlocked laminae which is generally cylindrical; each of the plurality of laminae 22 having a common length L. Laminae 22 are interlocked by means of intermitted tabs 24 and recesses 26 formed on and in all but the bottommost lamina. Tabs 24 of one lamina 22 are received in recesses 26 of the adjacent lamina as shown in FIG. 2. The bottommost lamina in the stack is provided with holes 28 into which tabs 24 of the overlying lamina of the stack are engaged. Further, FIG. 2 shows that part 20 is symmetrical about plane 30 and that it has, at its vertical center, two widest laminae which are located on opposite sides of plane 30. The lateral sides of these two widest laminae 22, and axial end surfaces 32, 34 frictionally engage a choke passageway in the apparatus as described further herein below. Although cylindrical part 20 comprises two widest laminae 22 having side edges which frictionally engage the adjacent choke surfaces, it is envisioned that other long, slender parts which may be produced by the inventive apparatus or method may comprise only a single lamina of greatest width, the side edges of which engage the adjacent choke surfaces. Further it is envisioned that the widest lamina(e) need not be vertically middlemost in the stack, as they are in part 20. Indeed, the widest lamina(e) may be anywhere in the stack and, if a plurality of widest laminae are included, they need not be adjacent to one another.
Referring now to FIGS. 3 and 4, there is shown progressive stamping die assembly apparatus 38. according to one embodiment of the present invention. Apparatus 38 comprises rigid die bed 40 to which first lower die portion 42 and second lower die portion 44 are attached by means of bolts 46. First lower die portion 42 is provided with recesses having collars 48, and second lower die portion 44 includes recesses having collars 50. The recesses and collars form guide bushings which engage guide rods 56, 58 respectively fixed to first upper die portion 52 and second upper die portion 54. The alignments between the upper and lower die portions are maintained by guide rods 56 and 58, as shown, which are slidably received in the guide bushings. Ball bearing cages (not shown) encircle each guide rod and are disposed within the recesses, and have a slight interference fit between the guide rods and the guide bushings. The ball bearing cages are suspended from the guide rods and remain with the upper die portions when they are pulled away from the lower die portions.
As discussed further herein below, the distances die station 84 travels between its successive positions varies. The rate of movement of die station 84 from one of its preselected positions to a different one of its preselected positions may be controlled in response to the steady, controlled incremental movement of the strip stock material in the first direction. Die station 84 and strip stock material 108 should simultaneously assume their respective new predetermined positions to maintain smooth operation of apparatus 38 and a constant part production rate. Apparatus 38 may operate a speeds of approximately 300 to 350 press cycles per second and, with each part 20 comprising 20 laminae, and two parts 20 being produced simultaneously, approximately 35 completed parts per minute can be produced by apparatus 38. Moreover, those skilled in the art will appreciate that the repositioning of the variously sized punches and their respectively mating die holes about strip stock material 108 in die station 84 is done “on the fly” as the strip stock material continuously and intermittently advances through apparatus 38. Movement of strip stock material 108 pausing, or “dwelling”, only during the portion of each press cycle in which the strip stock material is engaged by a pilot pin or punch. Similarly, transverse movement of die station 84 will normally dwell only during those periods, unless two sequentially identical and longitudinally adjacent laminae are being processed through die station 84, such as, for example, with reference to FIG. 2, two endmost laminae 22a or two middlemost laminae 22j, described further hereinbelow. That is, die station 84 may remain transversely stationary for longer than one press cycle while two sequentially identical and longitudinally adjacent laminae are being processed therethrough, but would otherwise remain transversely stationary only for so long as necessary to allow its punches to engage the material. The incremental advancement of strip stock material through apparatus 104 is thus substantially smooth and continuous, and there is no appreciable interruption of the stamping process to introduce new punch and die hole sets into the stamping process at the transversely moveable die station, the movements of die station 84 and the strip stock material being very rapid and closely coordinated.
Simultaneously with the advancement of material 108 through apparatus 38, die station 84 advances in the direction of arrows 114 or 116, adjusting to another one of its plurality of predetermined positions about strip stock material 108 to produce the desired lamina portion width characteristics in the material. As shown, each respective set 118a-i of matched punches and die holes in die station 84 comprises three (3) pairs of mating punches and die holes. Set 118a includes center punch/die hole pair 120a, first outlying punch/die hole pair 122a and second outlying punch/die hole pair 124a. The distance between a center punch/die hole pair and each of its two respective outlying punch/die hole pairs defines the widths of two laminae, but not the widest laminae, in part 20. Referring again to FIG. 2, these two laminae will be equidistant from plane 30. Further, it is to be understood that lamina portions for two separate parts 20 are simultaneously formed side-by-side in material 108, and that a lamina portion formed between a center punch/die hole pair 120 and its first outlying punch/die hole pair 122 is included in a part 20 which is stacked in the choke passageway having its opening defined by blanking die hole 72, whereas a lamina portion formed between a center punch/die hole pair 120 and its second outlying punch/die hole pair 124 is included in a part 20 which is stacked in the choke passageway having its opening defined by blanking die hole 74. Those skilled in the art will recognize that with attendant revisions to apparatus 38 and the width of the strip stock material, the number of parts which may be simultaneously produced may be more or less than two as described herein.
Moreover, an outlying punch/die hole pair 122 or 124 is shared between adjacent punch and die hole sets 118, i.e., the first outlying punch/die hole pair of one punch and die hole set 118 comprises the second outlying punch/die hole pair of the adjacent set 118. For example, with reference to FIG. 6A, second outlying punch/die hole pair 124a of set 118a also serves as first outlying punch/die hole pair 122b of set 118b. This sharing of outlying punch/die hole pairs exists between adjacent punch/die hole sets 118a through 118i, thereby minimizing the required width of die station 84 and reducing the distance die station must travel as it advances from one set 118 to an adjacent set 118. The quick adjustment of the die station between its various positions thus facilitated, apparatus 38 may operate a speeds of approximately 300 to 350 press cycles per second, as mentioned above. With each part 20 comprising 20 laminae, and two parts 20 being produced simultaneously, approximately 35 completed parts per minute can be produced by apparatus 38.
Notably, the widest laminae in part 20 are formed at the blanking die station 130 or 132 in die assembly 55 (FIG. 6B), rather than at die station 84. The lamina portions in strip stock material 108 from which the widest lamina are formed pass through blank portion 126 in die station 84. Although blank portion 126 of die station 84 (FIG. 6B) includes no punches or die holes, if the positioning of this die station about material 108 is considered in the context of the positions of the various, aforementioned punch/die hole sets 118a-i, blank portion 126 may be thought of as “punch/die hole set 118j” (FIG. 6A). The strip stock material portion which is disposed in die station 84 when set 118j is aligned with the material (the “idle position”) proceeds through the movable die station without being punched therefrom although the press which engages upper die portion 88 may be cycled as usual.
A normal transverse cycle of die station 84 begins with the cycling of the press(es) to engage strip stock material 108 with punch/die hole set 118a, which forms the narrowest side-by-side lamina portions in the material. These narrowest lamina portions comprise the bottommost lamina 22a in two parts 20, one of which is shown in FIG. 2. Once all of the lower and upper die portions are separated, at the end of the punch cycle, material 108 incrementally advances such that a pair of its pilot holes 112 are moved from its alignment with one pair of pilot pin bores 64 to an alignment with the next successively encountered pair of pilot pin bores 64. As material 108 so advances, die station 84 is simultaneously moved in the direction of arrow 116 to position punch/die hole set 118b over the strip stock material. Relative to moveable die station 84, this process continues, with die station 84 so moved in the direction of arrow 116, until the press(es) have finished a cycle and die station 84 is in its idle position; here, one half of the lamina portions 22 eventually comprising part 20 have been processed through die station 84. At this point, die station has traveled its full distance in the direction of arrow 116.
The press(es) again cycle with die station 84 in its idle position, and as the material is further advanced, die station 84 reverses its initial direction of movement, moving in the direction of arrow 114 to, next dispose punch/die hole set 118i about the strip stock material. This process continues, with die station moving in the direction of arrow 114 until the press(es) have finished a cycle with “narrowest lamina” punch/die hole set 118a disposed about the strip stock material; here, all of the lamina portions 22 eventually comprising part 20 have been processed through die station 84. At this point, die station has traveled its full distance in the direction of arrow 114 and has completed one full transverse cycle.
FIG. 6B is a continuation of FIG. 6A and the two drawings may be linked together by superimposing lines 128-128 thereof. Referring to linked FIGS. 6A and 6B, with transversely movable die station 84 moving in the direction of arrow 114 (second direction), to the right of die station 84 are successively located lamina portions 22 formed in strip stock material 108 by the respectively associated sets of punch/die holes 118 which had previously engaged the material. Hence, lamina portions 22e are shown being formed in die station 84 by punch/die hole set 118e; just previously, rightwardly adjacent lamina portions 22f were formed by adjacent set 118f; prior to that, successively adjacent lamina portions 22g (shown now located at die station 68 at which tabs 24 and recesses 26 are formed in the lamina portions) were formed by successively adjacent set 118g; prior to that, successively adjacent lamina portions 22h (shown now located at die station 70 at which holes 28 are formed in only the widest of the laminae) were formed by successively adjacent set 118h; prior to that, successively adjacent lamina portions 22i (shown at blanking station 130 at which one of the side-by-side lamina portions is separated from the strip stock material and forced into a choke passageway) were formed by successively adjacent set 118i (Here it should be noted that in FIGS. 6A and 6B, parenthesized reference numerals indicating lamina portions 22 along strip stock: material 108 (e.g., “(22i)”) refer to the former location of that particular lamina portion in the material, prior to being separated therefrom.); prior to that, successively adjacent lamina portions 22j, which will each eventually be one of the two widest laminae in a part 20 (FIG. 2), had passed through die station 84 at its idle position; and prior to that, adjacent lamina portions 22j (shown at blanking station 132 at which the other of the side-by-side lamina portions is separated from the strip stock material and forced into a choke passageway), which will each eventually be the other of the two widest laminae in a part 20, had also passed through die station 84 at its idle position. As mentioned above, the width of these widest laminae 22j are defined at blanking stations 130, 132, and their longitudinal side edges 150j, 152j, along with at least portions of part axial end faces 32, 34 frictionally engage the interior side surfaces of the choke passageways. Downstream of blanking station 132, the strip stock material scrap is chopped by shear parts 80, 82 into easily collected pieces 83 (FIG. 3). The trend detailed above continues as material 108 continues to advance in the direction of arrow 114. Once lamina portions 22a have been provided in the material, and die station 84 has returned to its initial position after completing one full transverse cycle, all the side-by-side lamina portions which eventually comprise two parts 20 have been processed through die station 84. The cycle then repeats without interrupting the advancement of material 108 through apparatus 38, with another side-by-side pair of lamina portions 22a being formed by set 118a—these eventually comprising the bottommost laminae in two parts 20. As mentioned above, these two bottommost lamina portions 22a will later have holes 28 formed in them at die station 70, rather than tabs 24 and recesses 26 at die station 68. Die station then proceeds to move transversely in the direction indicated by arrow 116 as the new cycle continues.
Referring now to FIG. 7, there is shown a schematic plan view of transversely movable die station 84, which more particularly points out the distances traveled as punch/die hole sets 118 are successively positioned about strip stock material 108. As shown, die assembly 84 moves in the direction of arrow 116. The total distance traveled by die station 84, as it successively positions punch/die hole sets 118a-j about the strip stock material, is 7.2155 inches. Owing to the differences in width of the center punch/die hole pair 120 and the sharing of outlying punch/die hole pairs 122, 124 as described above, the distances traveled to successively position adjacent successive punch/die hole sets 118 about the strip stock material varies. It can be seen from FIG. 7 that in die station 84, along the second or third direction (respectively indicated by arrows 114 and 116), the distance between center punch/die hole pairs 120a and 120b is approximately 0.6720 inches; the distance between center punch/die hole pairs 120b and 120c is approximately 0.7155 inches; the distance between center punch/die hole pairs 120c and 120d is approximately 0.7480 inches; the distance between center punch/die hole pairs 120d and 120e is approximately 0.7735 inches; the distance between center punch/die hole pairs 120e and 120f is approximately 0.7945 inches; the distance between center punch/die hole pairs 120f and 120g is approximately 0.8115 inches; the distance between center punch/die hole pairs 120g and 120h is approximately 0.8250 inches; and the distance between center punch/die hole pairs 120h and 120i is approximately 0.8355 inches. The distance between center punch/die hole pair 120i to center axis 134 of set 118j (i.e., blank portion 126), which axis is aligned with the center of strip stock material 108 when blank portion 126 is disposed thereabout (i.e., the idle position), is approximately 1.0400 inches. These incremental distances total 7.2155 inches, the maximum distance die station 84 can travel in either the second or the third direction. It is to be understood that the specificity of the distances between punch/die hole pairs is not intended to limit the scope of the present invention in any way. Rather, such specificity is intended to illustrate that the incremental transverse movements of die station 84 between its positions are not necessary equal. Further, it is to be understood that every die placed in station 84 may be different, and that in a given die the sequencing between its various positions need not be sequential and may be easily altered by appropriately altering the program of controller 107.
Referring to FIG. 8, at die station 130 all of the lamina portions are blanked from one lateral side of strip stock material 108 which, for purposes of clarity, is not shown in FIG. 8. A finished part 20 is shown in choke passageway 136, the opening of which is defined by blanking die hole 72 in die plate 66. As mentioned above, the engagement of the blanking punch with its mating die hole 72 defines lateral edges 150j, 152j in the widest laminae in part 20; thus, lamina 22j, once fully formed, has a shape and size which matches those of die hole 72. It is to be understood that the preceding description of the structure and operation of blanking die station 130, and that which follows, correspondingly applies to the structure and operation of blanking die station 132 and its associated choke passageway.
As shown in FIG. 8, choke passageway 136 has end alignment surfaces 142, 144 which correspond with and slidably engage each lamina of part 20 at the lamina's opposed third and fourth axial end edges 154, 156, which lie distance L apart and comprise part axial end surfaces 32, 34 (best shown in FIG. 1). To preclude lamina bowing, there may be no appreciable frictional engagement between edges 154, 156 and choke surfaces 142, 144. Choke passageway 136 also has side alignment surfaces 146, 148 which correspond with and frictionally engage side edges 15Oj, 152j of each widest lamina 22j (best shown in FIG. 2). Alignment surfaces 146, 148 of choke passageway 136 define a choke width therebetween which is equal to or slightly less, e.g., by 0.001 inch total or about 0.0005 inch per side, than the part width defined by side edges 150j, 152j of widest laminae 22j to thereby provide an interference fit engagement with these laminae.
Moreover, the engagement of protrusions 138, 140 and the notches which form grooves 36, 37 ensures that individual laminae 22a-i, which have insufficient width between their respective, opposed first and second edges 150a-i, 152a-i to engage choke passageway side surfaces 146, 148, remain properly positioned laterally in choke passageway 136. The sliding engagement of the notches over protrusions 138, 140 is particularly useful in maintaining the alignment of laminae 22a-i which enter the choke passageway before the lowermost of widest laminae 22j in a part 20 does. For example, with reference to FIG. 2, in producing a part 20, the engagement of the laminae notches on protrusions 138, 140 ensures that a partial stack of laminae consisting only of bottommost lamina 22a up to and including lamina 22i (the lamina which is adjacently below lowermost widest lamina 22j) remains correctly positioned in choke passageway 136. Otherwise, such a partial stack would depend solely on the frictional engagement of partially formed axial end surfaces 32, 34 with adjacent choke end surfaces 142, 144, respectively, for maintaining its proper orientation in the choke passageway. Further, the engagement of grooves 36, 37 over ridges 138, 140 preclude the possibility of a partially formed or a completed part 20 inadvertently rotating about its longitudinal axis within passageway 136. The lamina notches may frictionally engage ridges 138, 140 or, alternatively, the cross sections of the ridges 138, 140 within the choke passageway may be slightly undersized vis-a-vis those provided in blanking die hole 72, thus providing a slight clearance between the notches and the ridges within the choke passageway below die plate 66. Those skilled in the art will recognize that, conversely, a protrusion may instead be provided in opposite sides of the blanking die, and which will mate to notches provided on opposite ends of die hole 72, these notches extending as grooves in choke end surfaces 142, 144. Hence, protrusions rather than notches would be formed in end edges 154, 156 of each lamina, the lamina protrusions slidably received in the grooves formed in choke passageway 136 in the manner described above, for maintaining proper orientation of the laminae or stacks in the choke passageway.
Notably, it may not be necessary for choke passageway side surfaces 146, 148 to continuously contact side edges 150j, 152j of widest laminae 22j, as shown in FIGS. 9 and 10. Indeed, choke passageway 136 may be provided with downwardly-extending grooves or carbide bar inserts (not shown) which define intermittent side surfaces 146, 148 which contact side edges 150j, 152j of widest laminae 22j only at longitudinally spaced contact areas. Such spaced contact of the choke side walls 146, 148 with edges 150j, 152j of the widest laminae may be designed to provide part 20 with the proper resistance to movement along choke passageway 136 and to prevent possible buckling, bending or rotation of the stack or individual laminae while in the choke passageway. Further, as seen in FIG. 8, the junctures of side surfaces 146, 148 and end surfaces 142, 144 of choke passageway 136 may be provided with reliefs 158 which extend into side surfaces 146, 148 to ensure that the longitudinal ends of widest laminae 22j contact the choke passageway only at their end edges 154, 156, allowing better control of the part's resistance to movement through the choke.
Choke passageway 136 ordinarily contains a plurality of parts 20, and, as will be discussed further hereinbelow, for each part 20 in the choke passageway, the frictional engagement of its end surfaces 32, 34 with respective choke end surfaces 142, 144, and the portions of side edges 150j, 152j of its widest laminae 22j with choke side wall surfaces 146, 148 contribute a portion of the overall frictional resistance which holds the topmost lamina in the choke passageway in place for interlocking with an overlying lamina of the same part. Resistance to downward movement in the choke barrel provides the back pressure necessary to engage the interlock tabs of the laminae when the overlying lamina is pressed into engagement with the remainder of a partially formed stack in choke passageway 136.
Referring to FIG. 9, during the manufacture of the initial part 20, the back pressure otherwise provided by a plurality of completed stacks within choke passageway 136 may be provided by an appropriately numbered plurality of widest laminae 22j, which comprise plug 160. Plug 160 is formed by first running apparatus 38 with die station 84 positioned such that its blank portion 126 is disposed over the strip stock material for a number of press cycles appropriate to form plug 160. It is envisioned that the laminae of plug 160 will not be interlocked, and rather will merely abut. Controller 107 may be provided with a special routine which permits widest laminae 22j to be run without being provided with interlocking features in forming plug 160. Alternatively, the plug may be a unitary, preformed part (not shown) made of plastic, wood or other suitable material of sufficient circumferential size and thickness that once forced into choke passageway 136, sufficient resistance to movement of the individual laminae and parts 20 is provided for the tabs and slots to interlock. Another alternative would be to provide a hydraulic or pneumatic backpressure device (not shown), such as known in the art, may be used in lieu of plug 160 or the abovementioned unitary, preformed plug to provide resistance to movement of the laminae of the initial stacks until a sufficient plurality of stacks has been accumulated in passageway 136.
Once choke passageway 136 is completely filled with a plurality of parts 20, which provide sufficient frictional engagement with the engaging surfaces of the choke to create sufficient back pressure for interlocking the tabs and slots of the individual parts 20, plug 160 will drop out of the choke passageway, no longer needed. A new plug 160 would be formed the next time the process begins with a clear choke passageway. The number of widest laminae 22j in plug 160, the number of parts 20 which are to be contained within passageway 136, the resistance to movement through passageway 136 each part 20 provides, and the resistance necessary to interlock the tabs and slots of the laminae are characteristics which may be varied to suit the particular apparatus and/or the stacks it produces.
The process of stacking of one of a plurality of laminae which form a part 20 is sequentially illustrated in FIGS. 11-14, which shows blanking die station 130 at which an individual lamina 22 (here 22c) is severed from strip stock material 108 and automatically stacked within choke passageway 136 during a single die stroke. As described above, the width of all laminae which comprise lamina part 20, except for widest laminae 22j, are established prior those lamina portions reaching the blanking die stations. These laminae are attached to strip stock material 108 at their longitudinal ends, which are severed by blanking punch 164 to form end edges 154, 156 thereon. Each of edges 150j, 152j, 154j and 156j are formed on widest laminae 22j at the blanking die stations.
As noted above, strip stock material 108 includes pilot pin holes 112 which form apertures in the carrier portion of the strip stock material, i.e., that portion of strip stock material which is not used to form laminae. Pilot pin holes 112 are used to maintain the strip stock material in a desired position relative to the die stations as it is stamped during its advancement through the die assembly. As can be seen in FIGS. 11-14, pilot pin 166 passes through pilot pin hole 112 and enters pilot pin bore 64 to properly locate strip stock material 108 and lamina portion 22c attached thereto relative to blanking station 130 prior to stamping the strip stock material. During each stroke of the press(es), ail pilot pins 166 of apparatus 38 engage their respective mating bores 64 through holes 112 in the strip stock material to maintain the material in proper alignment during stamping operations.
As mentioned above, the scope of the present invention should not be construed as including an apparatus or method which necessarily includes integrally interlocking the individual laminae 22 through tabs 24 and recesses 26 or holes 28, as illustrated. The herein described means for attaching the individual laminae of a part produced in accordance with the present invention is but one way of doing so. Other means in accordance with the present invention for attaching the individual laminae of a part together include, for example, banding, welding, or the use of external fasteners or adhesives. As depicted, however, blanking punch 164 of apparatus 38 includes staking punch inserts 168 which extend below the bottom surface of the blanking punch by a distance designated 170 in FIG. 11. Staking punches 168 correspond to the locations of the interlock tabs and recesses in the lamina portions, and enter recesses 26 of the lamina portion being blanked from strip stock material 108 to positively engage the respective lamina tabs 24 of the lamina being blanked with the respective interlock recesses 26 of the uppermost lamina layer disposed in choke passageway 136, here consisting of lanina 22b.
Staking punch inserts 168 are held in a fixed position relative to blanking punch 164 and each include head 172 which is seated in a counterbore in blanking punch 164. A grind collar (not shown) may be located below head 172 to permit the lowering of staking punch 168 relative to blanking punch 164. Lowering of the staking punch might be necessary due to chipping or wear of staking punch 168 or to accommodate different interlock tab depths. A number of different interlock tab designs are known in the art and the tab design will influence the selection of the appropriate tab depth. In the illustrated embodiment, part 20 utilizes a design in which no portion of interlock tab 24 is completely severed from the surrounding lamina material. Instead, interlock tab 24 is partially blanked from the surrounding material, deforming, but not severing, the material at the edges of interlock tab 24, and extend below the bottom of the remainder of the lamina by approximately ½ to ⅓ the thickness of the lamina layer. As noted above, alternative embodiments of the present invention may employ alternative interlock styles or have the interlock tabs extend a greater or less distance below the remainder of the lamina.
FIG. 11 illustrates the relative positions of upper die portion 54, punches 164, 168, die plate 66 and strip stock material 108 at the initiation of a stamping stroke at blanking die station 130. FIG. 12 illustrates the die assembly during the downstroke after pilot pin 166 has extended through pilot pin hole 112 and has entered pilot bore 64 to thereby properly locate strip stock material 108 and lamina portion 22c attached thereto. Shortly after pilot pins 166 have properly aligned strip stock material 108, and the lanina portions attached thereto, staking punches 168 enter the recesses 26 of lamina portion 22c, which is about to be blanked. Shortly after staking punches 168 enter recesses 26, blanking punch 164 engages the upper surface of lamina portion 22c.
In FIG. 12, stock lifter spring 180 has been compressed and strip stock material 108 is pressed against upper surface 162 of die plate 66. Strip stock material 108 may be pressed against die plate 66 by engagement with the downwardly moving punches or by another suitable mechanism, such as a spring stripper (not shown), attached to upper die portion 54, which presses the strip stock material against die plate 66 prior to the engagement of punches 164, 168 with the strip stock material.
FIG. 13 illustrates the blanking station after blanking punch 164 has begun to sever lamina portion 22c from the remainder of strip stock material 108. As shown, tabs 24 of lamina portion 22c are already partially engaged with recesses 26 of lamina 22b, the uppermost lamina layer in choke passageway 136. The partial engagement of tabs 24 and recesses 26 occurs prior to the complete separation of lamina portion 22c from the remainder of the strip stock material.
To accomplish the engagement of tabs 24 of lamina portion 22c and recesses 26 of lamina 22b prior to the complete severing of the blanked lamina layer from the strip stock material, the lamina 22b must be positioned in choke passageway 136 near upper surface 162 of die plate 66. Lamina 22b is positioned a distance 184 (FIG. 11) below the entrance of choke passageway 136 located in upper surface 162 of die plate 66.
Referring to FIGS. 11-14, apparatus 38 may, however, utilize a much smaller punch entry which ensures that interlock tabs 24 of a second, blanked lamina (e.g., 22c) are engaged with recesses 26 of a first, lamina (e.g., 22b) which is already in the choke passageway prior to completely severing second lamina 22b from the remainder of strip stock material 108. For example, by utilizing a distance 184 which is smaller than tab depth distance 176 (FIG. 11), tabs 24 will be partially interlocked with recesses 26 when the die assembly reaches the position shown in FIG. 12. Alternatively, distance 184 can be equivalent to distance 170 (as shown in FIGS. 11-14) and tabs 24 will be engaged with recesses 26 or holes 28 as the lamina portion being blanked is being severed from the strip stock material, but prior to their complete separation. It may also be possible to have a distance 184 slightly larger than distance 170 and still provide for the partial interlocking of tabs 24 and recesses 26 prior to complete separation of a lamina portion from the strip stock material. The partial interlocking in such an arrangement, however, would be minimal.
Blanking punch 164 severs the longitudinal ends of lamina portion 22c from the remainder of strip stock material 108 in cooperation with cutting edges on die hole opening 172, forming end edges i 54, 156 thereon. Typically, after blanking punch 164 has sheared the lamina portion to a depth which is approximately ⅓ of the lamina thickness, the lower ⅔ of the strip stock material will fracture and the lamina portion will be completely separated from the strip stock material. The use of a softer, more elastic strip stock material, however, would permit the blanking punch to enter the strip stock material for more than ⅓ of the lamina thickness and produce a lamina with a smaller fracture zone.
Referring to FIG. 14, the downstroke is finished by pushing lamina portion 22c into further engagement with uppermost lamina 22b in choke passageway 136 and pushing lamina 22c to a depth 184 (FIG. 11) below upper surface 162 of die plate 66. After blanking punch 164 is retracted, stock lifters 178 elevate strip stock material 108, which then proceeds in the direction indicated by arrow 110. The blanking cycle is repeated with lamina portion 22d next added to the part 20 being assembled in choke passageway 136.
It is envisioned that the choke passageway may be provided with a side surface (such as surface 146 or 148) which is spring loaded to accommodate a slight growth in part width resulting from wear to the die cutting edges, for it is expected that as the cutting edges dull slightly, the resultant width of laminae 22j may begin to grow. This lamina width change, while slight, could alter the behavior of the stacks in the choke. It is expected that allowing the choke passageway to so expand against the force of a spring (not shown) would help compensate for changes in lamina size as a result of tool wear. Additionally, as mentioned above, single controller 107, or the second controller of the above-described alternative control means, may control the pressure exerted on the stacks in each choke passageway having such spring loaded side surfaces, as well as an unload device operatively communicating with each of the choke passageways.
Referring to FIGS. 15A and 15B, respectively, choke passageway 136a is that associated with blanking die station 130 (FIG. 6B), and choke passageway 136b is that associated with blanking die station 132 (FIG. 6B). As shown in FIG. 15A, backpressure device 190a comprises first, horizontally actuating pneumatic or hydraulic/pneumatic cylinder 192a having either “high” or “low” pressure fluid controllably applied thereto, in coordination with the press cycle. During “up” cycles of the press, as the ram begins its ascent from the bottom of its stroke and the blanking die begins to ascend from the uppermost lamina in the choke passageway, high pressure is applied to cylinder 192a to ensure that stacks 20 in choke passageway 136a are securely clamped between fixed choke sidewall surface 146a and moveable choke sidewall surface 148a, which is biased towards the fixed sidewall surface by compression springs 194. Notably, surface 148a may be defined by separate, upper and lower choke sidewall portions 196a, 198a, respectively, only one of which (as shown, lower portion 198a) is engaged with cylinder 192a. With reference to FIG. 15B, backpressure device 190b and choke passageway 136b each have a respectively similar structure and operation to device 190a and passageway 136b, and are correspondingly marked. Notably, cylinders 192a and 192b may be cycled independently, but because blanking die stations 130 and 132 cycle simultaneously in the depicted embodiment, the cylinders are simultaneously actuated, and may be commonly linked to the controller.
In addition to the above, controlled backpressure variation, immediately below each choke passageway 136 may be provided second, vertically actuated pneumatic or hydraulic/pneumatic cylinder 200a or 200b, which is positioned to strike support anvil 202a or 202b. Anvils 202 move downward as the number of laminae in the choke passageway incrementally increases as a new stack 20 is formed. Cylinders 200 also have either “high” or “low” pressure fluid controllably applied thereto, in coordination with the press cycle. Each anvil 202 is lightly biased upwardly under the influence of a spring (not shown) to keep it in contact with the lowermost stack 20 in the choke passageway. Cylinder 200 and anvil 202 provide a means for “restriking” the bottommost stack 20 in the choke passageway, and ensure that its laminae are completely abuttingly engaged and are fully interlocked.
1. A method of manufacturing a stack of laminae in a progressive stamping die assembly having means for guiding strip stock material through the die assembly in a first direction, a transversely moveable die station which is moveable in opposite second and third directions substantially perpendicular to the first direction and having a plurality of predetermined positions, and a choke passageway, said method comprising:
stamping a first lamina having a first shape in the strip stock material in the transversely moveable die station while the transversely moveable die station is in a first predetermined position;
substantially simultaneously advancing the strip stock material through the die assembly in the first direction and moving the transversely moveable die station in one of the second and third directions to a second predetermined position;
stamping a second lamina having a second shape in the strip stock material in the transversely moveable die station while the transversely moveable die station is in the second predetermined position, the second shape different than the first shape;
separating the second lamina from the strip stock material subsequently to placing the first lamina into the choke passageway;
frictionally engaging the choke passageway with at least one of the first and second laminae.
2. The method of claim 1, further comprising substantially aligning the first and second laminae along the first direction prior to separating the second lamina from the strip stock material.
stamping at least one first interlock element into the first lamina;
stamping at least one second interlock element into the second lamina; and
at least partially engaging the first and second interlock elements subsequently to placing the first lamina into the choke passageway.
4. The method of claim 1, wherein the first and second laminae are elongate and have generally opposed first and second longitudinally extending edges formed in the moveable die station.
forming, in the first transversely moveable die station position, first and second generally opposed edges in the first lamina;
forming, in the second transversely moveable die station position, first and second generally opposed edges in the second lamina; and
forming third and fourth generally opposed edges in each of the first and second laminae at the blanking die station;
wherein at least one of the first and second edges of the first lamina is not in alignment with either of the first and second edges of the second lamina when the first and second laminae are both in the choke passageway, and wherein the third and fourth edges of the first lamina are in alignment with the respective third and fourth edges of the second lamina when the first and second laminae are both in the choke passageway.
10. The method of claim 9, further comprising frictionally engaging the first and second edges of one of the first and second laminae with the choke passageway.
11. The method of claim 9, further comprising slidably engaging the third and fourth edges of both the first and second laminae with the choke passageway.
12. The method of claim 9, further comprising forming in at least one of the third and fourth edges of each lamina a first one of a notch and a protrusion, providing a surface of the choke passageway adjacent that lamina edge with a second one of a protrusion and a notch which extends along the choke passageway, and slidably receiving the protrusion of one of the choke surface and the lamina edge in the notch of the other of the choke surface and the lamina edge, whereby that lamina edge is restrained from lateral movement relative to the adjacent choke passageway surface.
13. The method of claim 12, further comprising forming in each of the third and fourth edges of each lamina a first one of a notch and a protrusion, providing the surfaces adjacent the third and fourth lamina edges with a second one of a protrusion and a notch, and slidably receiving the protrusions of one of the choke surfaces and the lamina edges in the notch of the other of the choke surfaces and the lamina edges, whereby the lamina is restrained from lateral movement relative to the choke passageway.
14. The method of claim 1, further comprising providing the transversely moveable die station with a plurality of matched punch and die hole sets, and engaging each of the individual matched punch and die hole sets with the strip stock material at selectively different transversely movable die station positions.
15. The method of claim 14, further comprising substantially simultaneously cycling all punches of the transversely moveable die station.
16. The method of claim 14, further comprising substantially simultaneously cycling the punch of the matched punch and die hole set which engages the strip stock material at the transversely movable die station and a blanking punch, and separating a lamina from the strip stock material and placing that lamina into the choke passageway with the blanking punch.
17. The method of claim 14, further comprising providing the transversely moveable die station with an idle position in which no material is stamped from the strip stock material located in the transversely moveable die station.
18. The method of claim 17, further comprising passing a lamina through the transversely moveable die station when the transversely moveable die station is at its idle position, and forming generally opposed first and second edges in that lamina at the blanking die station.
19. The method of claim 18, further comprising frictionally engaging the opposed first and second edges formed in the lamina at the blanking die station with the choke passageway.
4682524 July 28, 1987 Achelpohl
4708042 November 24, 1987 Jung
5193426 March 16, 1993 Dunn
5279197 January 18, 1994 Takeda et al.
5365816 November 22, 1994 Rudy
5604971 February 25, 1997 Steiner
5778749 July 14, 1998 Dunn
6092278 July 25, 2000 Latkow
Patent number: 6484387
Inventors: Barry Andrew Lee (Fort Wayne, IN), Timothy L. Schrank (Fort Wayne, IN)
Application Number: 09/589,238
Current U.S. Class: Dynamoelectric Machine (29/596); Motor Or Generator (29/732); Laminated (29/609)