US3195335A

US3195335A - Coil construction

Info

Publication number: US3195335A
Application number: US243010A
Authority: US
Inventors: David F Brower; Gamon B Hayward
Original assignee: General Dynamics Corp
Current assignee: General Dynamics Corp
Priority date: 1962-12-07
Filing date: 1962-12-07
Publication date: 1965-07-20
Anticipated expiration: 1982-07-20
Also published as: BE640944A; DE1452658B2; AT243598B; GB994135A; CH416518A; DE1452658A1

Description

y 965 n. F. BROWER ETAL 3,1 95;335

COIL CONSTRUCTION Filed D80. 7, 1962 United States Patent 3,195,335 COIL CONSTRUCTION David F. Brewer, San Diego, and Gannon B. Hayward,

Del Mar, Califi, assignors to General Dynamics Corporation, New York, N.Y., a corporation of Delaware Filed Dec. 7, 1962, Ser. No. 243,010 7 Claims. (Cl. 7256) The present invention relates to a forming device and, more particularly, to an improved forming coil assembly for an electromagnetic forming apparatus.

In recent years, methods and apparatus have been developed for forming material by employing magnetic fields of high flux density. In such apparatus, a magnetic field of high flux density is set up about ashaped conductor by passing a current pulse of high amperage through the conductor. This high density pulsed, magnetic field induces a current in a conductive work piece disposed in the magnetic field, which current is concentrated on the surface of the work piece. This induced current is always in such a direction as to tend to exclude the magnetic field from the work piece. This results in pressure being applied to the work piece, which is equal to the energy density of the magnetic field. This pressure is' made sufficiently high to form the work piece.

' The shape of the conductor or forming coil assembly employed in such apparatus depends upon the shape of the work piece and the desired end product. Because it is desirable to accomplish diverse forming operations with a single forming coil assembly, the coil assembly is preferably designed to accommodate various sizes and shapes of work pieces.

An object of the present invention is the provision of an improved forming coil assembly for an electromagnetic forming apparatus. Another object of the invention is the provision of a forming coil assembly for an electromagnetic forming apparatus, which assembly can be adapted to form diverse shapes of work pieces. A further object is the provision of a forming coil assembly for an electromagnetic forming apparatus, which coil assembly is efficient in operation and has a relatively high strength. Still a further object is the provision of an electromagnetic forming coil assembly which is relatively inexpensive to manufacture and durable in use.

Other objects and advantages of the present inventionwill become apparent with reference to the following description and accompanying drawings.

In the drawings:

FIGURE 1 is a side View of an electromagnetic form ing coil'embodying various features of the present invention, portions of the coil assembly being broken away to better illustrate certain parts thereof;

. FIGURE 2 is a plan View taken along line 22 of FIGURE 1, portions thereof being broken away to better illustrate certain parts thereof;

FIGURE 3 is an enlarged perspective view of a portion of the coil assembly shown in FIGURES 1 and 2; and

FIGURE 4 is a cross sectional view taken generally along line 44 of FIGURE 1.

In the drawings, a forming coil assembly is shown which is adapted to be mounted in an electromagnetic forming apparatus. Generally, the forming coil assembly includes an annular core of conductive material and a coil 12 of conductive material which is disposed about and insulated from the conductive core 10. A generally cylindrical field shaping element 14 of conductive material is removably-disposed within the space defined by the annular core 10. I The field shaping element 14 is provided with an aperture 16 for receiving the work piece to be formed, and a slot 18 extending between the outer surface thereof and the aperture 16. The surface of the field shaping element 14 facing the annular core 10 is pro- 3,125,335 Patented July 20, 1965 ice vided with means 29 for electrically insulating the field shaping element 14 from the core 10.

More specifically, the illustrated forming coil assembly is adapted to be clamped in position on an electromagnetic forming apparatus (not shown). One such electromagnetic forming apparatus is disclosed and claimed in a pending application, Serial No. 171,333, filed February 6, 1962,

now U.S. Patent No. 3,114,585. The apparatus generally includes a source of pulsed current and a control circuit therefor. A clamp is also included in the apparatus which clamp is designed to clamp the herein disclosed forming coil assembly in position on the forming apparatus. The clamp is also designed to make a ground connection and a high voltage connection with the forming coil assembly.

In the illustrated embodiment, the forming coil assembly includes the coil or solenoid 12 which is formed of a tubular conductor 22 composed of a material such as copper, beryllium copper, etc. The

end portions

24 and 26 of the conductor 22 extend generally radially from the coil 12.

I water through the conductor 22.

3 by a suitable plug 30. The other end 26 of the conductor 22 is provided with a coaxial coupling 32 which is adapted to connect the tube to a source of coolant (not shown) which may be included in the forming apparatus. Thus a continuous path for the cooling medium is provided which extends from the coupling 32 through the annularpassage provided between the tube 28 and the conductor 22 to the plugged end 24 and then back through the tube 28 to the coupling 32.

The magnetic field established by a pulsatory current passing through the coil 12 is concentrated by a flux concentrating means 34, which includes the annular core 10 and the removable, generally cylindrical field shaping element 14 disposed within the space defined by the annular core 10. The annular core 10 is made of a high strength conductive material, such as beryllium copper, copper, etc., and is disposed within the coil 12 with the outer surface thereof in contact with the coil 12. To reduce the repulsion force between the coil 12 and the core 10 and also to provide a close electrical coupling between the core and the coil, the coil 12 is disposed within a helical groove 36 provided in the exterior surface of the annular core 10. The coil 12 is insulated from the annular core 10 by a tube 38 of insulating material disposed on the conductor 22.

The annular core 10 is provided with a radially extending slot 40 to provide a path for the current induced in the core to flow between the external surface and the internal surface thereof. A piece of insulating material 42,.

such as fiber glass reinforced plastic, is disposed within the slot 41) to maintain the desired size of the slot. As

shown particularly in FIGURE 1 the coil 12 is struc element 14 is disposed within the space defined by the annular core 10. The illustrated field shaping element 14 is generally cylindrical in outline and is made slightly smaller in diameter, than, the internal diameter of the.

annular core 10. The field shaping element 14 is made of a conductive material, such as copper, beryllium copper, etc. The element 14 is electrically insulated from the core. by means 263 which includes a wrapping of high.

. shown) to be formed. One end of the element 14 is provided with a circular cavity 52 which is larger in diameter than the aperture 16 so that the forming of the work piece is accomplished only at the other end portion of the element 14. This other end portion of the element 14 is provided with additional structural reinforcement by providing the outer surface thereof with a groove 54, which groove is filled with the wrapping 20 of plastic-impregnated fiber glass roving. The slot 18 which extends from the external surface of the element Bite the internal surface thereof, is provided in the element 14 to provide a pathfor the currentinduced in the external surface to flow to and from the internal surface thereof. The slot 18 is filled with an insulating material 58, such as plastici-rnpregnated fiber glass, to

prevent the wrapping of fiber glass roving from reducing v shaping element 14 is retained Within the annular core by a pair of

retaining rings

60 and 62. Each. of the

rings

60 and 62 .is made of an insulating materiahsuch as plastic-impregnated fiber glass, and is suitably secured to the end of the core 10, as by bolts 6 The internal diameter of the

rings

60 and 62 is made slightly less than the external diameter of the element 14 so as to thereby retain the element 14 in place and yet not interfere with the insertion of the work piece in the element 14.

The shape and size of the aperture in the field shaping element 14 depends upon the work piece to be formed and the final product desired. For other shapes or sizes of work pieces, other field shaping elements having appropriate apertures which may be, for example, square or triangular in cross section, are substituted fo the described field shaping element.

The illustrated forming coil assembly is connected to the ground connection and is supported within the clamping device of the electromagnetic forming apparatus by a radially extending generally fiat, rectangular mounting bracket 66. As shown in FIGURE 2, the mounting bracket 66, which is of laminated construction is connected to the annular core 10 by an integral extension Til of a relatively thick outer or structural layer 68 of the.

bracket 66, which layer 68 is made of structural and conductive material, such as brass, etc. The extension '70 is curved to correspond to the core ill and is mounted to.

the core 10 by suitable means, such as bolts 72. The inner surface of the extension 70 is provided with a recess for receiving the plastic-impregnated fiber glass roving 44 surrounding the coil 12.

The supply end 26 of the coil 12 is extended through:

an aperture 74 in the extension 70 and the coupling 32 is electrically and mechanically secured thereto, as by of the structural layer 68. The end portion 24 is insulated from the structural layer 68 by an insulating layer '78 of insulating material, such as plastic-impregnated fiber glass.

The insulating layer F8 is generally rectangular in shape and is slightly larger than the structural layer 63. The inner surface of the structural layer 68 is provided with a rectangular channel 38 adiacent the closed end portion 24 which receives a corresponding projection fill on the insuiating layer 73'. An aperture 92is provided in the insulating layer 7% parallel to the'projection 9i) for affording passage therethrough of the end portion 2 The insulating layer 78 is suitably connected to the structural layer es, as by bolts 93.

As shown in FTGURES 1 and 4, the face of the insulating layer73 is provided with a generally rectangular recess 94 for receiving a plate contact member 96 which makes Contact with the high voltageconnection of the clamping device. The plate member 96 is formed of two parallel plate members 93 and Mid which are provided withopposed grooves 1&1 for receiving the closed end portion 24 of the coil 12. The plate members 9% and ltitl arerclamped tightly about the uninsulated end portion 24 by suitable means, as by bolts 3:92. The plate member 9 6 is provided with an elongated rectangular projection lfi-iwhich extends parallel to the end portion 24 and is received in a corresponding recess 106 in the insulating layer 78. The thickness of the plate member 96 is made slightly greater than the depth of the recess 94 in'the insulating layer 73 so that the surface, of the plate member 96 extends beyond the surface of the insulating layer '78 and makes good contact with the high voltage connection.

The disclosed forming. coil assembly has a relatively high strength and is relatively efficient in operation. In this connection, there is a close coupling between the coil and the fiux concentrating means. In addition, each of the parts which is under mechanical strain,-is reinforced by a high strength material. Also, the .field shaping element may be easily removed and replaced by other elements.

1 Various changes and modifications may be made in the above identified forming coil assembly without departing or deviating from the spirit or scope of the present invention.

Various features of the present invention are set forth in the accompanying claims.

- What is claimed is:

1. In an electromagnetic forming apparatus, a forming coil assembly comprising a slotted annular core of conductive material, an insulated coil of conductive material disposed on said core, a generally cylindrical field shaping 2. In an electromagnetic forming apparatus, aforming coil assembly comprising a slotted annular core of conductive material, said core having a helical groove on the outer surface thereof, an insulated coil of conductive material disposed in said groove, a generally cylindrical field shaping element of conductive material removably disposed in said core, said element having an aperture therein and a slot extending between the outer surface of said element and said aperture, anda wrapping of electrically insulating material disposed on said field shaping element for electrically insulating said field shaping element from said core.

3. In an electromagnetic forming apparatus, a forming coil assembly comprising a slotted annular coreof conductive material, an insulated coil of conductive material disposed on said core, a generally cylindrical field shaping element of conductive materialremovably disposed in said core, said element having an aperture therein and a slot extending between the outer surface of said element'and said aperture, a Wrapping of insulating and structural material on said coil, and a second Wrapping of insulating and structural material on said field shaping element.

4. In an electromagnetic forming apparatus, a forming coil assembly comprising a slotted annular core of conductive material, an insulated fluid cooled coil of conductive material disposed on said core, said coil including a tubular conductor closed at one end, a tube of insulating material extending through said conductor to a position adjacent said closed end, and means for coupling said tube and said conductor to a source and sink of cooling fluid, a generally cylindrical field shaping element of conductive material removably disposed in said core, said element having an aperture therein and a slot extending between the outer surface of said element and said aperture, and a wrapping of electrically insulating material disposed on said field shaping element for electrically insulating said field shaping element from said core.

5. In an electromagnetic forming apparatus, a forming coil assembly comprising a slotted annular core of conductive material, said core having a helical groove on the outer surface thereof, an insulated coil of conductive material removably disposed in said groove, a generally cylindrical field shaping element of conductive material disposed in said core, said element having a circular aperture therein and a slot extending between the outer surface of said element and said aperture, said aperture being reduced in diameter adjacent one end of said element, an annular groove in the circumferential surface of said element opposite said one end of said element, and a wrapping of insulating and structural material on said element.

6. In an electromagnetic forming apparatus, a forming coil assembly comprising a slotted annular core of conductive material having a helical groove on the outer surface thereof, an insulated tubular conductor wrapped about said core and disposed in said groove to thereby form a coil, a tube of insulating material disposed within said conductor and extending from one end thereoi to the other, said tube being of a diameter such as to form an annular passage between the same and said tubular conductor, means for closing the one end of said tubular conductor, means for connecting said closed end and said open end of said coil to a source of power, a wrapping of high strength non-conductive material disposed about said coil and said core, a generally cylindrical removable field shaping element of conductive material disposed Within said conductive core, means for retaining said element within said core, said element having an axially extending aperture therein and a slot extending between the outer surface thereof and said aperture, and a wrapping of plastic impregnated fiberglass roving insulating material disposed about said element.

7. In an electromagnetic forming apparatus, a for ing coil assembly comprising a slotted annular core of conductive material having a helical groove on the outer surface thereof, an insulated tubular conductor wrapped about said core and disposed in said groove to thereby form a coil, the ends of said conductor extending generally radially in circumferentially spaced relationship from said core, a tube of insulating materialextending through said conductor and terminating adjacent one end of the conductor, said tube being of a diameter such as to form an annular passage between the same and said tubular conductor, means for closing the one end of said tubular conductor, means for connecting the other end of said conductor and said tube to a source and sink of coolant, means for connecting said other end and said one end of said conductor to a source of power, a wrapping of high strength non-conductive material disposed about said coil and said core, a generally cylindrical field shaping element of conductive material disposed within said conductive core, means for retaining said element within said core, said element having an axially extending aperture therein and a slot extending between the outer surface thereof and said aperture, said aperture being reduced in diameter adjacent one end of said element, the outer surface of said element being provided with an annular groove opposite said reduced diameter portion of said element, and a wrapping of high strength insulating material disposed about said element.

References Cited by the Examiner UNITED STATES PATENTS 3/64 Brewer et al. l5310 OTHER REFERENCES CHARLES W. LANE-1AM, Primary Examiner.

Claims

1. IN AN ELECTROMAGNETIC FORMING APPARATUS, A FORMING COIL ASSEMBLY COMPRISING A SLOTTED ANNULAR CORE OF CONDUCTIVE MATERIAL, AN INSULATED COIL OF CONDUCTIVE MATERIAL DISPOSED ON SAID CORE, A GENERALLY CYLINDRICAL FIELD SHAPING ELEMENT OF CONDUCTIVE MATERIAL REMOVABLY DISPOSED IN SAID CORE, SAID ELEMENT HAVING AN APERTURE THEREIN AND A SLOT EXTENDING BETWEEN THE OUTER SURFACE OF SAID ELEMENT AND SAID APERTURE, AND A WRAPPING OF ELECTRICALLY INSULATING MATERIAL DISPOSED BETWEEN SAID FIELD SHAPING ELEMENT AND SAID CORE.