WO2008131363A1

WO2008131363A1 - Electromagnetic actuator for multiple operations

Info

Publication number: WO2008131363A1
Application number: PCT/US2008/061066
Authority: WO
Inventors: Glenn S. Daehn
Original assignee: Ohio State University
Current assignee: Ohio State University
Priority date: 2007-04-19
Filing date: 2008-04-21
Publication date: 2008-10-30
Anticipated expiration: 2009-10-19

Abstract

An apparatus to electromagnetically form a work piece, wherein the apparatus has a forming assembly and a current source. The forming assembly comprising a forming unit having a plurality of forming cavities, arranged in series, adapted to accommodate a work piece. A medial gap extends through the forming unit intersecting the each of the forming cavities and terminating at one of the forming cavities. The resistance and inductance in the forming cavities is greater than that of the connections between each forming cavity.

Description

ELECTROMAGNETIC ACTUATOR FOR MULTIPLE OPERATIONS

Inventor: Glenn Daehn

[0001] This application claims priority of U.S. Provisional Application No.

60/912,801 , filed April 19, 2007, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to electromagnetic actuators. More particularly, to electromagnetic actuators used for metal forming.

BACKGROUND AND SUMMARY

[0003] The present electromagnetic actuators available offer limited throughput and efficiency. The present invention addresses these limitations and produces a higher output of operations while offering improved efficiency through the use of multiple electromagnetic actuators in series.

[0004] Performing several simultaneous operations with a single discharge to actuators in series allows a much greater throughput. This series circuit may be accomplished by placing the forming spaces along a line, or they may be placed along some other path, depending on the configuration of the part or work flow. Due to charging and discharging considerations of capacitor bank circuitry, it is difficult to run a cycle with a duration of only a few seconds. If many work pieces can be created with a single discharge, one can drastically improve the systems efficiency by increasing the number of forming spaces powered by each discharge. [0005] Efficiency is increased when multiple operations are preformed with multiple actions on one-turn actuators. It is advantageous to use simple, robust, low- inductance single turn actuators. However, these actuators often have a similar inductance in the capacitor bank as is found in the actuator itself, or alternatively, the actuator may have significantly lower inductance. This produces a relatively low efficiency system. The electromagnetic actuator described herein overcomes lower efficiency by providing that the majority of the system inductance is in the work actuator.

[0006] To ensure that a majority of the inductance is in the work actuator, a step-down transformer may be used in the work actuator to increase the current at the work actuator. Another way to increase the inductance in the work actuator is by increasing the number of forming spaces in the actuator. Not only will this increase the inductance in the work actuator, but it will also decrease the discharge energy per operation. In many cases, the discharge current is effectively fixed because bank inductance is much larger than the actuator inductance. In such cases, the same discharge energy may be used to form a small or large number of work pieces using nearly the same discharge currents and characteristics. Thus the electromagnetic actuator described herein provides a large reduction in the energy per operation.

[0007] One such area in which the electromagnetic actuator described herein may be used is bottle cap crimping, such as pharmaceutical bottles for injectable compounds. In this area electromagnetic forming has an advantage over traditional mechanical crimping. As the forming unit makes no contact with the work piece, there is little particulate generated during the process; as opposed to traditional mechanical crimping. This allows the capping operation to take place in the aseptic area of the packaging plant thereby resulting in a cost reduction. [0008] The wrinkling limits of the work piece may be extended by using high velocity techniques as opposed to the wrinkling limits found in traditional mechanical crimping of the same material. [0009] The electromagnetic equipment may be cheaper and simpler to operate than traditional mechanical crimpers. Often, in crimping operations, crimping 600 units per minute is a goal. Currently, no present day capacitor bank system operates at greater than one operation every second or 60 units per minute. The electromagnetic actuator described herein overcomes this limitation and achieves the stated goal of crimping 600 units per minute. Current low inductance capacitor banks in combination with the invention described herein require energies of less than about 500 Joules to form a series of 10 caps.

[0010] Exemplary embodiments of the apparatus for electromagnetically forming a work piece may include: a forming assembly and a current discharge circuitry. The forming assembly may comprise a forming unit having forming cavities arranged in series. Each forming cavity is adapted to accommodate a work piece of a particular geometry. In some instances this is accomplished by sizing the forming cavity slightly larger than the object. The forming unit may also have a medial gap extending from one end of the forming unit to a distal forming cavity. The medial gap intersects the forming cavities. An electrical insulator may be positioned in the medial gap. To maintain efficiency, the resistance and inductance of the area between the forming cavities may be lower than that found in the forming cavities. [0011] In another exemplary embodiment of the apparatus for electromagnetically forming a work piece may include: a forming assembly and a current discharge circuitry. The forming assembly comprises a forming unit having a forming cavities arranged in series. Each forming cavity may be adapted to accommodate a work piece of a particular geometry. The forming unit may have a medial gap separating the first and second portions of the forming unit that extends from one end of the forming unit to the other end. The first and second portions are in electrical communication with one another. An electrical insulator may be positioned in the medial gap. To maintain efficiency, the resistance and inductance of the area between the forming cavities may be lower than that found in the forming cavities.

[0012] In other exemplary embodiments of the apparatus for electromagnetically forming a work piece may include: a forming assembly and a current discharge circuitry. The forming assembly comprises a forming unit having forming cavities arranged in series. Each forming cavity may be adapted to accommodate a work piece of a particular geometry. The forming unit may comprise a first and second field shaper. A primary coil may be located between the first and second field shaper, and have greater number of turns than the first and second field shapers. An electrical insulation material may be placed between the first and second field shapers, the forming unit, and the primary coil.

[0013] In addition, the electromagnetic actuator described herein may have tapered edges in the forming spaces to increase current density (and therefore pressure) where it is most needed on the work piece. The forming cavity may take any shape, and the forming cavity largely mirrors the shape of the object to be crimped.

[0014] In other embodiments, the forming unit may open to allow cap insertion and removal. This may be done either by elastic displacement of the coil or by an electrical contact region that is broken and reconnected with the other end of the coil possessing a hinge. Significant pressure may be needed to maintain such connections for current flow if an openable circuit is used.

[0015] In other embodiments, a transformer may be used to increase efficiency. A transformer may be interposed between the capacitor bank output and the work coil that increases the current at the driven end. In some embodiments, a separate transformer is utilized. In others, the work end of the coil is used as a field shaper in a multi-turn coil. It should also be noted that the series arrangement may also be applied to expansion and other forming operations.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0016] The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.

[0017] Figure 1 is a perspective view of a forming unit

[0018] Figure 2 is a top perspective view of a forming unit.

[0019] Figure 3 is a cross-sectional view of a forming cavity illustrating a means for increasing the current density.

[0020] Figure 4 is a top perspective view of forming unit having a first and second portion.

[0021] Figure 5 is a top perspective view of a forming unit surrounded by a primary coil.

[0022] Figure 6 is a perspective view of two halves of a forming unit having a primary coil interposed between a first field shaper and a second field shaper. [0023] Figure 7 is a perspective view of an assembled forming unit having a primary coil interposed between a first and second field shaper. [0024] Figure 8 is a diagram illustrating an exemplary embodiment for use in expansion and sheet metal forming operations connected in series.

DETAILED DESCRIPTION OF THE EXEMPLARY E M BO D I M E NT(S) [0025] Figures 1 and 2 illustrate an exemplary embodiment of a forming assembly 10. The forming assembly comprises a forming unit 12 defining a plurality of separately spaced forming cavities 14 and a plurality of bores 16. The forming unit 12 may be constructed from a high strength and high conductivity material such as copper beryllium or other suitable conductive material. The plurality of bores 16 serving as attachment point, wherein the forming unit 12 may be fixed to a nonconductive support to decrease deformation of the forming unit 12. Further, the forming unit may have a first end and second end. A current discharge circuitry 80 in electrical communication with the forming assembly. The first end of the forming unit 12 may have contact portions to receive current from the current discharge circuitry. [0026] The plurality of forming cavities 14 may be separately spaced and arranged in series. Each forming cavity 14 may be adapted to accommodate a work piece of a particular geometry. If the work pieces have a rectangular shape the plurality of forming cavities 14 may also have a rectangular design. Likewise, if the work pieces have a circular design, the plurality of forming cavities 14 may also have a circular design. Similarly, the forming cavities 14 may mirror nearly any work piece shape.

[0027] The forming unit may also have a medial gap 18 extending from a first end of the forming unit 12 and intersecting each forming cavity 14. The medial gap 18 may terminate at the distal forming cavity 14. An electrical insulator (not shown in the Figures) may also be positioned in the medial gap 18. In exemplary embodiments, the medial gap 18 may be about 2 to 3 times the width of the current path in the forming unit. In other exemplary embodiments, the medial gap 18 may be about 500 microns to 10 millimeters. The portions of the medial gap 18 located between the forming cavities 14 may have a lower electrical resistance and inductance than those found in the forming cavities 14. This decreased resistance and inductance may be maintained by adjusting the width and shape of the medial gap 18. Still in other embodiments, an insulating material may cover the entire forming unit 12.

[0028] The plurality of forming cavities 14 may also be adapted to increase the local current density; thus increasing the electromagnetic field in said forming cavities 14. The local current density is increased in the forming cavities 14 by decreasing the current path in the forming cavities 14. Figure 3 is a cross-sectional view of a forming cavity 14 adapted to increase current density. The interior surface of the forming cavity 14 has been shaped so as to decrease the current path. Figure 3 illustrates a forming cavity 14 having a beveled interior surface 30 which decreases the width of the inner most surface of the forming cavity 14. The beveled interior surface 30 may have an angle α. In some embodiments α is approximately 135°. One of ordinary skill in the art will recognize the need to adjust the angle α depending on the strength of field needed. In some embodiments, the interior surface of the forming cavities 14 may not be beveled but straight, curved, or any other shape suitable to increase current density. In this manner, the interior surface of the forming cavities 14 may be adapted to best suit the work piece. [0029] In other exemplary embodiments, a conductive insert (not shown in the

Figures) may be positioned in the interior of a forming cavity 14. The conductive insert may be adapted to increase the current density in the same manner as described above. In some embodiments, the conductive insert may be removably attached to the interior surface of the forming cavity 14. By providing a removable insert, a greater variety of work pieces may be formed using a single forming unit. The conductive insert may be constructed from a material having differing electrical properties than the forming unit so as to increase current density. [0030] In other exemplary embodiments, the medial gap 18 may extend from the first end of the forming unit 12 and terminate at a second end of the forming unit 12, so as to define first portion 40 and second portion 42 of the forming unit 12. An electrically conductive connection 44 may be disposed at the second end of the forming unit 12. The electrically conductive connection 44 is in electrical communication with the first and second portion 40 and 42 of the forming unit 12, so as to maintain the flow of current. The electrically conductive connection 44 allows the first and second portions 40 and 42 to move relative to one another. This movement allows the forming unit 12 to open to receive new work pieces and/or to release finished work pieces. By allowing the forming unit 12 to open to receive work pieces, the gap between the work piece and the forming unit 12 may be reduced during operation. The reduction of this gap increases the efficiency of the forming assembly 10. In exemplary embodiments, the electrically conductive connection 44 may be a hinge or other suitable conductive connection allowing movement of the first and second portions 40 and 42.

[0031] Figure 5 illustrates a multi-turn coil 50 positioned around the outside of the forming assembly 10. The multi-turn coil 50 may act as a transformer. The leads from the current discharge circuitry 80 may be connected directly to the multi- turn coil 50 instead of being connected directly to the forming unit 12 as described above. This may increase the efficiency of the forming assembly 10. [0032] Figure 6 illustrates another exemplary embodiment having a first field shaper 60, a second field shaper 62, and a primary coil 64 interposed between the first and second field shaper 60 and 62. Although shown in a circular configuration, the first and second field shapers 60 and 62 may be linear or any other suitable shape. The leads from a current discharge circuitry (shown in Figure 8) may be connected directly to the primary coil 64. The number of turns in the primary coil 64 may be greater than the number of turns in the first and second field shapers 60 and 62.

[0033] The first and second field shapers 60 and 62 each define a portion of a forming cavity 14. After the first and second field shapers 60 and 62 are brought into complimentary communication 80 forming a first actuator 72 (shown in Figure 7), a complete forming cavity 14 is formed. Although shown having a single forming cavity 14, other exemplary embodiments may have a plurality of forming cavities 14 arranged in a series. A plurality of forming cavities may provide greater efficiency on an energy-per-work piece basis and also provide greater throughput. [0034] Referring now to Figure 7, the first and second field shapers 60 and 62 are placed in complimentary communication. The primary coil 64 may be used to induce a current on both the first and second field shapers 60 and 62. This allows the use of the transformer effect to obtain larger currents and current densities in the vicinity of the work piece 70. This transformer effect may provide greater efficiency in the forming process. Another advantage of this exemplary embodiment is that the current paths in the first field shaper 60 and the current in the second field shaper 62 may be equal. The ability to have substantially similar current paths through the first and second field shapers 60 and 62 may ensure a more uniform crimping or forming of the work piece.

[0035] Figure 8 illustrates an exemplary embodiment that may be used with the multiple expansion and sheet metal forming operations. A current discharge circuitry 80 may be in electrical communication with a series of forming units 82, wherein the connections between the forming units 82 may have low inductance relative to the forming units 82. The current discharge circuitry 82 may be a capacitor bank comprising at least one capacitor 84, an inductor 86, and a resistor

88.

[0036] In some embodiments, the forming units 82 may be expansion coils.

The series of expansion coils may be inserted into a series of tubes or cans to expand them. The local current density is adjusted to induce the desired local pressure to produce the desired expansion. Altering the forming unit's 82 coil winding locally modifies the local current density. Exemplary embodiments or the expansion coils may have a circular shape or any other suitable shape dictated by the work piece.

[0037] In other embodiments, the forming units 82 may be constructed of copper wire or cut copper plate embedded in a non-conductive medium. The medium may be G-10, cast urethane, epoxy, or other suitable non-conductive material. More particularly, the forming unit 82 may be constructed using interlocking pieces of G-10 and copper utilizing waterjet cutting.

[0038] Forming units 82 constructed in this manner may be robust and used for a number of applications including, but not limited to: cutting, flanging, hemming, bulging, and embossing along a line. In other embodiments, a local transformer (not shown in Figure 8) may be used to improve the process efficiency, as described above.

[0039] While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.

Claims

What is claimed is:

1. An apparatus for electromagnetically forming a work piece, comprising: a forming assembly comprising: a forming unit defining a plurality of separately spaced forming cavities arranged in series, each said forming cavity adapted to accommodate a work piece, said forming unit having a medial gap extending from a first end of said forming unit and intersecting each said forming cavity, said medial gap terminating at one of said plurality of forming cavities; an electrical insulator positioned in said medial gap; wherein the forming unit has a relatively low electrical resistance and inductance between each said forming cavity compared to said electrical resistance and inductance in each said forming cavity; and a current discharge circuitry in electrical communication with the forming assembly.

2. The apparatus of claim 1 , wherein at least one forming cavity is adapted to increase the local current density.

3. The apparatus of claim 2, wherein an interior surface of each forming cavity is beveled.

4. The apparatus of claim 1 , wherein an multi-turn actuator transformer is located around the outside of the forming assembly and electronically interposed between the forming unit and the current discharge circuitry, such that leads from the current discharge circuitry are in electrical communication with the multi-turn actuator transformer.

5. The apparatus of claim 1 , wherein the width of the medial gap is about 2-10 times the width of a current path in the forming unit.

6. The apparatus of claim 5, wherein the width of the medial gap is about 500 microns to 10 millimeters.

7. The apparatus of claim 1 , wherein the forming unit is covered by an electrically insulating material.

8. The apparatus of claim 1 , wherein the forming unit is copper beryllium.

9. The apparatus of claim 1 , further comprising a conductive insert disposed in a forming cavity so as to increase local current density.

10. An apparatus for electromagnetically forming a work piece, comprising: a forming assembly comprising: a forming unit defining a plurality of separately spaced forming cavities arranged in series, each said forming cavity adapted to accommodate a work piece, said forming unit having a medial gap extending from a first end of said forming unit and terminating at a second end of said forming unit so as to define a first and second portion of said forming unit, said forming unit additionally comprising an electrically conductive connection disposed at said second end of said forming unit that is in electrical communication with said first and said second portions of said forming unit,; an electrical insulator positioned in said medial gap; wherein the forming unit has a relatively low electrical resistance and inductance between each said forming cavity compared to said electrical resistance and inductance in each said forming cavity; and a current discharge circuitry in electrical communication with the forming assembly.

1 1. The apparatus of claim 10, wherein said electrically conductive connection allows said first portion and second portion to move relative to one another.

12. The apparatus of claim 10, wherein at least one forming cavity is adapted to increase the local current density.

13. The apparatus of claim 12, wherein an interior surface of each forming cavity is beveled.

14. The apparatus of claim 10, wherein an multi-turn actuator transformer is located around the outside of the forming assembly and electronically interposed between the forming unit and the current discharge circuitry, such that leads from the current discharge circuitry are in electrical communication with the multi-turn actuator transformer.

15. The apparatus of claim 10, wherein the width of the medial gap is about 2-10 times the width of a current path in the forming unit.

16. The apparatus of claim 10, wherein the width of the medial gap is about 500 microns to 10 millimeters.

17. The apparatus of claim 10, wherein the forming unit is covered by an electrically insulating material.

18. The apparatus of claim 10, wherein at least one of the first and second portions of said forming unit is copper beryllium.

19. The apparatus of claim 10, further comprising a conductive insert disposed in at least one forming cavity so as to increase local current density.

20. An apparatus for electromagnetic forming a work piece, comprising: a forming unit comprising: a first and second field shaper designed to come into complimentary communication, forming a first actuator defining a plurality of forming spaces arranged in series, each forming space adapted to receive a work piece; a primary coil located between the two actuators, wherein the number of turns in the primary coil is greater than the number of turns in the first actuator; an electrical insulation material interposed between the first and second field shapers and between the first actuator and the primary coil; and a current discharge circuitry in electrical communication with the primary coil.

21. The apparatus of claim 20, wherein at least one forming space is adapted to increase local current density.

22. The apparatus of claim 21 , wherein an inside portion of at least one forming space is beveled.

23. The apparatus of claim 20, wherein the plurality of forming spaces are adapted to receive a conductive insert, the conductive insert being adapted to increase the current density.

24. The apparatus of claim 20, wherein the forming unit is copper beryllium.

25. The apparatus of claim 20, wherein the first and second field shapers and the primary coil are individually covered in an insulating material.