Progressive stamping die assembly having transversely movable die station and method of manufacturing a stack of laminae therewith

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a progressive stamping die assembly apparatus, and more particularly to such an apparatus for the manufacture of stacks of interlocked laminae.

2. Description of the Related Art

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.

In certain applications it is desirable to have a stack of interlocked laminae which is long and slender, and which has a cross-sectional shape having lateral sides defined by the lamina outer edges which do not lie in a substantially common plane; such a stack does not provide a choke-engaging surface which extends substantially along the vertical height of the stack. For example, it is desirable to have an elongate, substantially cylindrically-shaped lamina stack, in which the first, bottommost lamina is narrower than the adjacent, overlying second lamina, which is narrower than the adjacent, overlying third lamina, and so on, with the middlemost lamina(e) defining the widest portion of the substantially circular cross section and subsequent adjacent, overlying laminae each having a reduced width as compared to its adjacent lamina, thus forming a circular cross section, with each of the laminae of the cylindrically-shaped stack interconnected. Notably, the stock material from which a lamina stack may be produced according to the present invention is thin, and the individual laminae stamped therefrom quite flexible. Because the individual laminae of such a stack are long, thin and flexible, and may also not have common choke-engaging edges, the individual laminae tend to inadequately support the stack in the choke opening, rendering the above-described automatic interlocking method unusable for manufacturing such stacks.

It is known to form interlock tabs in the laminae which extend below the generally planar lamina surface. As the laminae of a stack is added to the stack, in the choke passageway located at the blanking station of the die assembly, each interlock tab engages a corresponding slot in the next lower lamina of the stack, generally by the entire thickness of the tab. The choke passageway may contain a plurality of individual laminated parts, themselves stacked upon each other. The bottom lamina of a stack may have the interlock tabs blanked and removed to avoid interlocking the bottom lamina with the next lower lamina which forms the top lamina of the previous stack. The choke passageway is typically configured to generally match the outer perimeter of at least one (i.e., the widest) of the blanked laminae in a stack and may be slightly undersized relative to that at least one lamina, e.g., by 0.001 inch, so that the laminae will be firmly held and accurately positioned within the choke passageway or barrel. The laminae, after they are located in the choke passageway with an interference fit thereby provide backpressure or resistance which facilitates the entry of the interlock tabs of the next lamina when it is pressed into the choke passageway.

These die stations are generally arranged linearly along a die bed of fixed length. Introducing additional die stations into the bed may thus not be easily facilitated. Further, where great variation in lamination shape and/or size is desired, the required length of prior die assembly apparatuses may be substantial, thereby requiring a large facility to accommodate the apparatus.

What is needed is an apparatus and method for producing long, slender, interlocked stacks of flexible laminae in which the laminae are automatically stamped, stacked and interlocked, the stacks having cross-sectional shapes with side surfaces defined by the side edges of the laminae which may or may not commonly engage the adjacent choke surfaces.

SUMMARY OF THE INVENTION

The present invention provides a method of manufacturing a stack of laminae in a progressive stamping die assembly having a choke passageway, means for guiding strip stock material through the die assembly in a first direction, and 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. The method includes the steps of: 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 first lamina from the strip stock material; placing the first lamina into the choke passageway; separating the second lamina from the strip stock material subsequently to placing the first lamina into the choke passageway; placing the second lamina into the choke passageway; and frictionally engaging the choke passageway with at least one of the first and second laminae.

The present invention also provides a progressive stamping die assembly apparatus for manufacturing a stack of laminae from strip stock material, the apparatus including means for incrementally advancing strip stock material through the die assembly apparatus in a first direction, and a transversely moveable die station comprising a plurality of matched punch and die hole sets arranged along opposite second and third directions, the second and third directions substantially perpendicular to the first direction. The transversely moveable die station has a plurality of preselected positions along the second and third directions, a different one of the plurality of matched punch and die hole sets interfaced with the strip stock material in each of the preselected transversely moveable die station positions. Different ones of the preselected transversely moveable die station positions are assumed by the transversely moveable die station substantially simultaneously with the strip stock material assuming an incrementally advanced position in the first direction through the die assembly apparatus.

An advantage of the present invention is that it provides the ability to easily introduce stamping variations without adding to the length of the apparatus.

Another advantage of the present invention is that it provides a shorter apparatus vis-a-vis previous apparatuses which produce similar laminated parts, thereby facilitating attendant facility requirement reductions.

Yet another advantage of the present invention is that, in addition to providing improved ability to introduce stamping variations without adding to the length of the apparatus, indeed, while providing a shorter apparatus, it is comparable in speed to previous progressive stamping die assembly apparatuses. The apparatus of the present invention can achieve 300 to 350 punch strokes per minute while presenting different die tools to the strip stock material between strokes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1

is a perspective view of one embodiment of a laminated part which may be produced by the inventive progressive stamping die assembly apparatus or in accordance with the inventive method;

FIG. 2

is a cross-sectional view of the laminated part of

FIG. 1

, along line

2

—

2

;

FIG. 3

is a perspective view of one embodiment of a progressive stamping die assembly apparatus according to the present invention;

FIG. 4

is a perspective view of the apparatus of

FIG. 3

, with the upper die portions removed;

FIG. 5

is an underside perspective view of the carriage of the apparatus of

FIG. 3

;

FIGS. 6A and 6B

are a fragmentary plan view of the apparatus of

FIG. 4

, showing strip stock material, and cross hatched punches associated with their respective dies;

FIG. 7

is an enlarged, fragmentary plan schematic of the apparatus of

FIG. 6A

;

FIG. 8

is a fragmentary plan view of a blanking station of the apparatus of

FIG. 6B

, showing an stack of interlocked laminae in the choke passageway thereof;

FIG. 9

is a fragmentary sectional end view of the blanking station of

FIG. 8

, along line

9

—

9

, showing the first-produced interlocked stack of interlocked laminae in the choke passageway thereof;

FIG. 10

is a fragmentary sectional end view of the blanking station of

FIG. 8

, along line

10

—

10

, showing a plurality of stacks of interlocked laminae in the choke passageway thereof;

FIG. 11

is a cross sectional view of the die assembly at the blanking station of

FIG. 8

along line

11

—

11

, shown at the beginning of a stamping stroke, a completed and a partially completed stack are shown in the choke passageway;

FIG. 12

is a cross sectional view of the die assembly at the blanking station of

FIG. 8

along line

12

—

12

, shown after the pilot pin has passed through the pilot hole and entered the pilot bore, a completed and a partially completed stack are shown in the choke passageway;

FIG. 13

is a cross sectional view of the die assembly at the blanking station of

FIG. 8

along line

13

—

13

, showing interlock tabs of the lamina being blanked being engaged with the uppermost lamina disposed in the choke passageway, a completed and a partially completed stack are shown in the choke passageway;

FIG. 14

is a cross sectional view of the die assembly at the blanking station of

FIG. 8

along line

14

—

14

, showing the blanking punch separating the lamina from the strip stock material, a completed and a partially completed stack are shown in the choke passageway;

FIG. 15A

is a cross sectional view of the die assembly at one blanking station of

FIG. 6B

along

15

A—

15

A, showing a first embodiment of an alternative choke passageway which may be incorporated thereinto;

FIG. 15B

is a cross sectional view of the die assembly at the other blanking station of

FIG. 6B

along line

15

B—

15

B; and

FIG. 15C

is a cross sectional view of an alternative die assembly to that shown in

FIG. 6B

, showing a second embodiment of an alternative die apparatus having two laterally aligned choke passageways.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention, in several forms, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DESCRIPTION OF THE PRESENT INVENTION

The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise forms disclosed in the following detailed description.

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.

Although part

20

is generally cylindrical, it is to be understood that this part configuration is but one possible embodiment of a stack produced according to the apparatus and method of the present invention; other apparatuses and methods which produce laminated parts having other shapes, but which employ the inventive features disclosed hereinbelow, are to be considered within the scope of the present invention.

Notably, the individual laminae

22

of part

20

are stamped from strip stock material such that length L of each lamina lies along the grain of the material, which substantially lies along the length of the strip stock material. This stamping orientation provides each lamina

22

, and thus part

20

, with magnetic properties which differ from what would result if the laminae were stamped from the strip stock material such that the length of each lamina lies across the grain of the material, i.e., across the strip stock material width. The orientation of the strip stock material grain relative to the length of part

20

may be an important consideration, depending on the application for which the part is used. Further, each lamina in stack

20

may be made of steel and may or may not be coated with a dielectric material. As shown in

FIG. 1

, axial end faces

32

and

34

of part

20

are respectively provided with notched grooves

36

and

37

which extend along the directions normal to plane

30

; each lamina provided with notches which form the grooves. As illustrated, the aligned notches forming groove

34

and

36

have a triangular shape, but may be of another shape (e.g., rectangular or semicircular) suitable to help maintain the correct position of the lamina or the stack within the choke passageway as described further herein below.

Further, although part

20

comprises laminae which are interlocked to one another within the apparatus, those skilled in the art will appreciate that the method and apparatus for its manufacture herein described may be adapted to produce a stack of laminae which are not interlocked by means of tabs

24

received in recesses

26

or holes

28

. Rather, the individual laminae may not include such tabs, recesses and/or holes, and may be attached to one another to form a laminated part by means of, for example, bonding, gluing or welding in a manner known in the art.

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.

In the manner well-known in the art, the upper die portions are cyclically moved downward, toward the lower die portions, and upward, away from the lower die portions, by means which include a rotating, double eccentric crank (not shown) which drives the slide or ram of the press.

First lower die portion

42

includes die plate

60

in which are located die holes

62

which engage, with each cycle, or stroke, of the press, mating punches (not shown) attached to upper die portion

52

. Die plate

60

also includes pilot pin bores

64

which slidably engage, with each cycle of the press, pilot pins (not shown) which depend from first upper die portion

52

. Similarly, die plate

66

of second lower die portion

44

includes pilot pin bores

64

which slidably engage, with each punch cycle, pilot pins which depend from second upper die portion

54

.

Further, second lower and upper die portions

44

and

54

are provided with die stations

68

and

70

at which tabs

24

and holes

28

are respectively formed in the laminae as described further hereinbelow. Die plate

66

includes blanking die holes

72

and

74

which define the opening of the two separate choke passageways within which parts

20

are formed. As shown in

FIG. 3

, the individual parts

20

, once completed, are received from apparatus

38

via chutes

76

and

78

which are attached to die bed

40

and extend beneath second lower die portion

44

and the choke passageways.

Second upper die portion

54

is provided with blanking punches which engage blanking die holes

72

,

74

with each cycle of the press, as will be described further hereinbelow. Further, second upper die portion

54

is provided with shear blade

80

which slidably engages, with each cycle of the press, shear die

82

, which is attached to die plate

66

. As second upper die portion

54

cycles relative to second lower die portion

44

, strip stock material having been fed through apparatus

38

is engaged by the shear to chop the scrap material up into small, easily disposable pieces

83

.

From the foregoing, it can be clearly understood that first mating die portions

42

and

52

, referred to hereinbelow as first die assembly

53

(FIG.

3

), and second mating die portions

44

and

54

, referred to hereinbelow as second die assembly

55

(FIG.

3

), are horizontally fixed relative to die bed

40

, and that the locations of their respective die stations do not move. Intermediate first and second die assemblies

53

and

55

is transversely movable die station

84

which is comprised of lower die portion

86

and overlying upper die portion

88

. In the manner described above, lower die portion

86

is provided with recesses having collars

90

, forming guide bushings, and upper die portion

88

is provided with relatively fixed guide rods which slidably engage the guide bushings through ball bearing cages to maintain proper alignment of the upper and lower die portions. Lower die portion

86

includes die plate

94

comprising a plurality of die holes

95

, and upper die portion

88

includes a plurality of punches which engage die holes

95

as a group with each cycle of the press.

Those skilled in the art will appreciate that a common press may be used to cycle upper die portions

52

,

54

and

88

. Alternatively, individual presses may be provided for actuating these upper die portions, but it is envisioned that such individual presses will cycle substantially simultaneously. Further, it should be noted that second upper die portion

54

may be provided with a cam mechanism (not shown) by which die station

68

or

70

may be selectively actuated, such that the holes

28

are provided only in the bottommost lamina of a part

20

at die station

70

, each of the other lamina in a part

20

being provided with tabs

24

and recesses

26

at die station

68

.

With each punch cycle, a number of blanks

104

may be removed from the strip stock material as the material passes through moveable die station

84

. These blanks are removed from apparatus

38

via chute

106

which is attached to lower die portion

86

.

Movable die station

84

is controllably moved transversely to the direction of strip stock material advancement by means of servomotor

96

, best shown in FIG.

5

. Simultaneously with the incremental advancement of strip stock material through the apparatus, the servomotor rotates drive screw

98

in one direction or the other. The external thread of screw

98

is engaged with the internally threaded portion of carriage

100

. Carriage

100

is attached to the underside of lower die portion

86

, which slides along ways or runners

102

disposed between rigid die bed

40

and lower die portion

86

. The mating threads of screw

98

and carriage

100

are of high precision, and in conjunction with the precisely controlled rotation of the screw, provide very fine control over the transverse position of die station

84

relative to the strip stock material. Die station

84

assumes its new position substantially simultaneously with the strip stock material assuming an incrementally advanced position in the first direction.

Basically, there are four functions (A, B, C and D) which are coordinated in operation of the inventive die stamping apparatus: (A) the rate and positioning of the strip stock material as it is fed through apparatus

38

; (B) the cycling rate of the press(es); (C) if the apparatus is so configured, the actuation of the cam which selectively alternates between die stations

68

and

70

(FIG.

4

); and (D) the rotation of screw

98

by servomotor

96

. These four functions may be controlled by a single controller

107

(FIG.

3

).

Alternatively, in lieu of a single controller

107

, functions A and B may be controlled by a first, known, separate and dedicated punch press controller (not shown) as provided by the various punch press manufacturers; and functions C and D may be controlled by a second, separate controller (not shown) which is coordinated with the punch press controller. The second controller is fully programmable with respect to the servo motion profile governing the action of the transversely moveable die station and all cammed operations of the apparatus. Further, the second controller permits production of any and all widths of laminae for which tooling is present, in any order, and in any multiple. Moreover, the second controller can also control and coordinate more than one transversely moveable die station, and in that case lamina stacks can be sized and configured independently; i.e., the parts assembled in the choke associated with blanking die hole

72

(

FIG. 4

) may not be identical to the parts assembled in the choke associated with blanking die hole

74

.

The functions of the separate first and second controllers may be similar to those of controllers

72

and

190

described in U.S. Pat. No. 4,619,028, issued Oct. 28, 1986; U.S. Pat. No. 4,738,020 issued Apr. 19, 1988; U.S. Pat. No. 5,087,849 issued Feb. 11, 1992; and U.S. Pat. No. 5,123,155 issued Jun. 23, 1992, the disclosures of which are each expressly incorporated herein by reference. Indeed, these first and second controllers may be based on referenced controllers

72

and

190

. A thickness measurement of the incoming strip stock material may also be performed, and the second controller is capable of increasing or decreasing the number of laminae in the stack in response to changes in stock material thickness, thereby providing a means of ensuring a finished part of consistent exterior dimensions, rather than of a particular number of laminae, if desired.

Moreover, it is envisioned that single controller

107

, or the second controller of the above-described alternative control means, may also control a backpressure and unload device operatively communicating with each of the choke passageways. Such a device is described further hereinbelow, with reference to

FIGS. 15A-C

.

Notably, a stepper motor (not shown) having appropriately defined angular steps may be substituted for servomotor

96

and its attendant feedback system, a means of control common to servomotors. A servomotor system, however, provides greater flexibility vis-a-vis a more powerful and precise stepper motor, and can more easily accommodate changes to part

20

or provide the ability to run parts of various designs through apparatus

38

by merely revising its controlling program. It is envisioned that any such changes to the part or the running of parts having various designs may require a stepper motor having windings which provide a different step angle specification.

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

22

a

or two middlemost laminae

22

j,

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.

Strip stock material

108

is fed through apparatus

38

by known feeder roll means (not shown) along the first direction indicated by arrow

110

. Pilot holes

112

are formed in material

108

at die station

113

(

FIG. 4

) comprising die holes

62

and their mating punches. The pilot pins associated with upper die portions

52

,

54

engage the strip stock material through pilot holes

112

and extend therethrough into pilot pin bores

64

provided in the respective die plates

60

,

66

on which the strip stock material slides. As shown in

FIG. 6A

, transversely movable die station

84

moves in opposed second and third directions indicated by arrows

114

and

116

, respectively, the second and third directions being perpendicular to the first direction indicated by arrow

110

.

As strip stock material

108

advances through apparatus

38

, that portion of the strip stock material which lies between upper and lower die portions

86

,

88

of die station

84

may be engaged by one of the plurality of matched punches and die holes

95

or, as described below, pass through die station

84

without being punched. As one of the plurality of matched punch and die sets engages the strip stock material, blanks

104

are removed from material

108

, resulting in elongate lamina portions having variable widths between first and second longitudinally extending edges

150

,

152

being left in the strip stock material as it continues through apparatus

38

from die station

84

.

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

118

a-i

of matched punches and die holes in die station

84

comprises three (3) pairs of mating punches and die holes. Set

118

a

includes center punch/die hole pair

120

a,

first outlying punch/die hole pair

122

a

and second outlying punch/die hole pair

124

a.

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

124

a

of set

118

a

also serves as first outlying punch/die hole pair

122

b

of set

118

b.

This sharing of outlying punch/die hole pairs exists between adjacent punch/die hole sets

118

a

through

118

i,

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.

6

B), 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

118

a-i,

blank portion

126

may be thought of as “punch/die hole set

118

j

” (FIG.

6

A). The strip stock material portion which is disposed in die station

84

when set

118

j

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

118

a,

which forms the narrowest side-by-side lamina portions in the material. These narrowest lamina portions comprise the bottommost lamina

22

a

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

118

b

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

118

i

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

118

a

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.

6

A 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

22

e

are shown being formed in die station

84

by punch/die hole set

118

e;

just previously, rightwardly adjacent lamina portions

22

f

were formed by adjacent set

118

f;

prior to that, successively adjacent lamina portions

22

g

(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

118

g;

prior to that, successively adjacent lamina portions

22

h

(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

118

h;

prior to that, successively adjacent lamina portions

22

i

(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

118

i

(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., “(

22

i

)”) 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

22

j,

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

22

j

(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

22

j

are defined at blanking stations

130

,

132

, and their longitudinal side edges

150

j,

152

j,

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

22

a

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

22

a

being formed by set

118

a

—these eventually comprising the bottommost laminae in two parts

20

. As mentioned above, these two bottommost lamina portions

22

a

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

118

a-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

120

a

and

120

b

is approximately 0.6720 inches; the distance between center punch/die hole pairs

120

b

and

120

c

is approximately 0.7155 inches; the distance between center punch/die hole pairs

120

c

and

120

d

is approximately 0.7480 inches; the distance between center punch/die hole pairs

120

d

and

120

e

is approximately 0.7735 inches; the distance between center punch/die hole pairs

120

e

and

120

f

is approximately 0.7945 inches; the distance between center punch/die hole pairs

120

f

and

120

g

is approximately 0.8115 inches; the distance between center punch/die hole pairs

120

g

and

120

h

is approximately 0.8250 inches; and the distance between center punch/die hole pairs

120

h

and

120

i

is approximately 0.8355 inches. The distance between center punch/die hole pair

120

i

to center axis

134

of set

118

j

(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

150

j,

152

j

in the widest laminae in part

20

; thus, lamina

22

j,

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

15

O

j,

152

j

of each widest lamina

22

j

(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

150

j,

152

j

of widest laminae

22

j

to thereby provide an interference fit engagement with these laminae.

Notably, end edges

154

,

156

of at least one lamina of a part precisely hold the longitudinal position of the part in the choke, and there may be only a close clearance between these edges and the respective adjacent surfaces of the choke; frictional engagement therebetween is not necessary.

Further, as the engagement of the blanking punch with its mating die hole

72

severs lamina portions

22

from the strip stock material, the notches which form grooves

36

and

37

in respective axial end faces

32

and

34

of part

20

are simultaneously formed in each lamina

22

. Choke passageway

136

is provided with protrusions or ridges

138

and

140

, which extend into grooves

36

and

37

to prevent undesirable rotation of part

20

in the choke passageway, thereby helping to ensure the proper angular orientation of the part. The interference fit engagement of each of the laminae, in combination with the engagement of protrusions

138

,

140

and grooves

36

,

37

, maintain the laminae in a properly aligned position within the choke passageway. The interference fit engagement of each of the laminae and the side walls of the choke passageway also resists the movement of the laminae therethrough, which facilitates the pressing of tabs

24

of a subsequently blanked lamina into interlocked engagement with recesses

26

or holes

28

of a lamina already in the choke passageway.

Moreover, the engagement of protrusions

138

,

140

and the notches which form grooves

36

,

37

ensures that individual laminae

22

a-i,

which have insufficient width between their respective, opposed first and second edges

150

a-i,

152

a-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

22

a-i

which enter the choke passageway before the lowermost of widest laminae

22

j

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

22

a

up to and including lamina

22

i

(the lamina which is adjacently below lowermost widest lamina

22

j

) 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

150

j,

152

j

of widest laminae

22

j,

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

150

j,

152

j

of widest laminae

22

j

only at longitudinally spaced contact areas. Such spaced contact of the choke side walls

146

,

148

with edges

150

j,

152

j

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

22

j

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

150

j,

152

j

of its widest laminae

22

j

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

22

j,

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

22

j

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

22

j

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.

To minimize the risk of undesirable bowing, alignment surfaces

142

,

144

,

146

and

148

of choke passageway

136

utilize a relatively light interference fit which exerts a reduced pressure on each individual lamina but which develops that pressure over a relatively greater vertical depth to thereby provide an adequate total back pressure for engagement of the interlock tabs. For example, in an application wherein a conventional interference fit might involve a 0.001 inch interference fit and a choke depth of 1.25 inches, the present application might utilize a 0.0002 to 0.0005 inch interference fit and a choke depth of 3 inches. Resistance to downward movement within the choke is needed to facilitate the engagement of the interlock tabs of the lamina being blanked with the interlock slots of the uppermost lamina in the choke passageway. The pressure exerted on the individual laminae not only provides resistance to downward motion through the choke passageway, but also helps maintain the laminae in proper alignment.

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

22

c

) 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

22

j,

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

150

j,

152

j,

154

j

and

156

j

are formed on widest laminae

22

j

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

22

c

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.

FIGS. 11-14

illustrate a portion of upper die portion

54

and die plate

66

, the latter of which is attached to lower die portion

44

(FIG.

4

). As mentioned above, upper die portion

54

reciprocates vertically, together with pilot pin

166

and blanking punch

164

, to stamp the laminae from the strip stock material. Blanking punch

164

severs each lamina portion from the remainder of strip stock material

108

and pushes that lamina into engagement with the uppermost lamina layer disposed in choke passageway

136

.

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

22

b.

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.

The thickness of the lamina is designated

174

in

FIG. 11

, and is approximately 0.010 to 0.015 inch, although stacks made according to the present invention may comprise thicker (or thinner) laminae. The distance by which tabs

24

extend below the lower lamina surface is designated

176

in FIG.

11

and is equivalent to the distance

170

by which staking punch

168

extends below blanking punch

164

. Because these laminae are rather thin, distance

176

may be equivalent to lamina thickness

174

or even greater to ensure proper engagement of tabs

24

with their mating recesses

26

in the adjacent lamina. The length designations shown in

FIG. 11

are included merely to provide a convenient mechanism for graphically identifying the lengths and spatial relationships discussed herein and are not necessarily to scale.

As discussed above, staking punches

168

are used to ensure engagement of interlock tabs

24

into interlock recesses

26

or holes

28

, and to prevent tabs

24

from being forced upwardly into the horizontal plane of the remainder of the lamina when tab

24

engages the uppermost lamina in choke passageway

136

. Distance

170

which staking punches

168

extend below the bottom surface of blanking punch

164

is equivalent to the depth it is desired to have interlock tabs

24

enter interlock recesses

26

or holes

28

of the lower adjacent lamina, and generally will be equivalent to distance

176

which interlock tabs

24

extends below the lower surface of strip stock material

108

when tabs

24

are formed at die station

68

.

Stock lifters

178

are used to prevent tabs

24

from being biased upwardly into the horizontal plane of the strip stock material

108

or from being snagged on die plates

60

,

94

or

66

during the progressive movement of strip stock material

108

in the first direction, indicated by arrow

110

. Stock lifters

178

are biased upwards by springs

180

and lift strip stock material

108

above upper surface

162

of die plate

66

when the strip stock material is being advanced between die stamping strokes. The strip stock material is lifted by stock lifters

178

a distance designated

182

in FIG.

11

. Lifter distance

182

is usually equivalent to approximately 1.5 times the thickness

174

of strip stock material

108

, or tab depth

176

, whichever is greater, to provide ample clearance. Illustrated stock lifters

178

are cylindrical, but other types of stock lifters, such as bar type lifters, are known in the art and can also be used in apparatus

38

.

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

22

c

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

22

c,

which is about to be blanked. Shortly after staking punches

168

enter recesses

26

, blanking punch

164

engages the upper surface of lamina portion

22

c.

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

22

c

from the remainder of strip stock material

108

. As shown, tabs

24

of lamina portion

22

c

are already partially engaged with recesses

26

of lamina

22

b,

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

22

c

from the remainder of the strip stock material.

To accomplish the engagement of tabs

24

of lamina portion

22

c

and recesses

26

of lamina

22

b

prior to the complete severing of the blanked lamina layer from the strip stock material, the lamina

22

b

must be positioned in choke passageway

136

near upper surface

162

of die plate

66

. Lamina

22

b

is positioned a distance

184

(

FIG. 11

) below the entrance of choke passageway

136

located in upper surface

162

of die plate

66

.

Distance

184

is determined by the distance blanking punch

164

enters choke passageway

136

at the end of the die press downstroke as shown in FIG.

14

. Punch entry distance

184

is typically greater than thickness

174

(

FIG. 11

) of the strip stock material in conventional die assemblies. For example, for a strip stock thickness

174

equivalent to 0.015 inch, a conventional die assembly would often have a punch entry between 0.020 and 0.025 inch.

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.,

22

c

) are engaged with recesses

26

of a first, lamina (e.g.,

22

b

) which is already in the choke passageway prior to completely severing second lamina

22

b

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.

It is to be understood that in practicing the present invention, partial interlocking of a first lamina already disposed in the choke and a second lamina not yet completely severed from the strip stock material is not necessary in all cases. Notably, with reference to

FIGS. 1 and 8

, the notches in each lamina, which collectively form grooves

36

,

37

in respective surfaces

32

,

34

of a part

20

, slidably engage protrusions

138

,

140

of the choke passageway. This engagement prevents lateral movement of an individual lamina, or an interlocked stack of laminae, in the choke. Further, the sliding engagement of lamina edges

154

,

156

or of part surfaces

32

,

34

with adjacent choke surfaces

142

,

144

, maintain the longitudinal position of the individual lamina, or stack of laminae, in the choke. Because the lateral and longitudinal movement of each lamina or stack of laminae are so restrained, there is no need, in the case of part

20

, to partially engage the interlocking features of the first and second laminae prior to severing the second lamina from the strip stock material as described immediately above.

Blanking punch

164

severs the longitudinal ends of lamina portion

22

c

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

22

c

into further engagement with uppermost lamina

22

b

in choke passageway

136

and pushing lamina

22

c

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

22

d

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

22

j

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

136

a

is that associated with blanking die station

130

(FIG.

6

B), and choke passageway

136

b

is that associated with blanking die station

132

(FIG.

6

B). As shown in

FIG. 15A

, backpressure device

190

a

comprises first, horizontally actuating pneumatic or hydraulic/pneumatic cylinder

192

a

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

192

a

to ensure that stacks

20

in choke passageway

136

a

are securely clamped between fixed choke sidewall surface

146

a

and moveable choke sidewall surface

148

a,

which is biased towards the fixed sidewall surface by compression springs

194

. Notably, surface

148

a

may be defined by separate, upper and lower choke sidewall portions

196

a,

198

a,

respectively, only one of which (as shown, lower portion

198

a

) is engaged with cylinder

192

a.

With reference to

FIG. 15B

, backpressure device

190

b

and choke passageway

136

b

each have a respectively similar structure and operation to device

190

a

and passageway

136

b,

and are correspondingly marked. Notably, cylinders

192

a

and

192

b

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

200

a

or

200

b,

which is positioned to strike support anvil

202

a

or

202

b.

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.

During “up” cycles of the press, after high pressure has been applied to first cylinders

192

, high pressure is applied to cylinders

200

which strike anvils

202

to compress the lowermost stack

20

in the choke passageway. After anvils

202

are struck, the pressure in second cylinders

200

is immediately relieved (i.e., it reverts to low pressure); the pressure in cylinders

192

is then also relieved. Those skilled in the art will appreciate that first and second cylinders

192

and

200

may cycle once per cycle, once per stack (e.g., 20 cycles), or as often as desired. The pressurization of first cylinder

192

will prevent stacks from being driven upwards in the choke during the restriking as second cylinder

200

impacts anvil

202

. Because first cylinder

192

can be pressurized at any time between the time that the punch ram reaches its bottommost position and the time that the blanking punch next comes into contact with the strip stock, the opportunity for accomplishing the restrike extends over much of the press crank rotation. The number of restrikes the stacks undergo may be varied by the operator by adjustment to the controller. Those skilled in the art will appreciate that the restriking is performed while the press is in its open, rather than its closed position. The actuation of first cylinder

192

during restriking, to firmly clamp the stacks

20

in the choke passageway, prevents the upward movement of the stacks in the choke.

Previous backpressure and restriking methods may employ a single, vertically oriented cylinder, and are done in the closed die position. These methods rely on the downwardly moving blanking punch to effect the restrike as well as sever the material from the strip stock and at least partially engage the interlocking tabs and recesses. The prior methods require a relatively high pressure on the vertically oriented cylinder, the vertical position of which is controlled with a check valve so that it resists the downward movement of the stacks in the choke passageway, but once overcome and driven downward by the force of the press, holds its new vertical position. If this cylinder is not properly controlled, it will tend to push the stacks back up the choke passageway, which can be very dangerous. The control of such previous cylinders is further complicated when this cylinder is also used as a part unloader device for ejecting the part from the choke.

In accordance with the present invention, once a new, completed stack

20

has been formed in the choke passageway, a third pneumatic or hydraulic/pneumatic cylinder (not shown) may be provided which is actuated as the pressure in second cylinder

200

is relieved, to axially eject the bottommost stack

20

from the choke with greater ease of control vis-a-vis previous part ejectors. Proximity switches (not shown) may be used to sense the vertical positions of anvils

202

, and when these switches indicate that another stack

20

has been completed within the choke, the third cylinder is actuated. Once the bottommost stack has been ejected, the anvil moves upward under the influence of its biasing spring into contact with the new bottommost stack in the choke. The actuation of the third cylinder, like those of the first and second cylinders, is controlled by single controller

107

or the second controller of the above-described alternative control means.

FIG. 15C

illustrates a further alternative structure to those shown in

FIGS. 15A and 15B

. Rather than being configured as shown in

FIG. 6B

, in this second alternative embodiment, two choke passageways

136

′,

136

″ are located laterally adjacent (i.e., perpendicular to first direction

110

) in die plate

66

′. Moveable choke sidewall surfaces

148

′,

148

″ are respectively biased by springs

194

towards fixed choke sidewall surfaces

146

′,

146

″, which are located on opposite sides of a common portion of lower die portion

44

′ located between the two choke passageways. In the manner described above, first, horizontally actuated cylinders

192

′,

192

″ operatively engage lower choke sidewall portions

198

′,

198

″, and second, vertically actuated cylinders

200

′,

200

″ impact anvils

202

′,

202

″. It is envisioned that a single second cylinder and a single, two-headed anvil may be employed in the depicted embodiment.

Those skilled in the art will recognize that the above-described methods and apparatus may be combined to produce elongate stacks having cross sectional shapes having side surfaces formed by lamina side edges which do not engage choke passageway and in which the lamina layers are comprised of a plurality of discrete lamina segments, each segment provided with interlocking means as described herein above.

While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. 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.

Number	Name	Date	Kind
4220062	Blanz	Sep 1980	A
4532843	Miyama	Aug 1985	A
4619028	Neuenschwander	Oct 1986	A
4682524	Achelpohl	Jul 1987	A
4708042	Jung	Nov 1987	A
4738020	Neuenschwander	Apr 1988	A
5087849	Neuenschwander	Feb 1992	A
5123155	Neuenschwander	Jun 1992	A
5193426	Dunn	Mar 1993	A
5279197	Takeda et al.	Jan 1994	A
5365816	Rudy	Nov 1994	A
5604971	Steiner	Feb 1997	A
5755023	Neuenschwander	May 1998	A
5778749	Dunn	Jul 1998	A
5915750	Usher et al.	Jun 1999	A
6092278	Latkow	Jul 2000	A

Progressive stamping die assembly having transversely movable die station and method of manufacturing a stack of laminae therewith

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Term Extension

Abstract

Description

Claims

US Referenced Citations (16)

Foreign Referenced Citations (1)