GB1586796A

GB1586796A - Magnetic field inductors for pressure forming

Info

Publication number: GB1586796A
Application number: GB4569477A
Authority: GB
Original assignee: KHARKOV POLITEKHN I IM VI
Current assignee: KHARKOV POLITEKHN I IM VI
Priority date: 1977-11-03
Filing date: 1977-11-03
Publication date: 1981-03-25

Description

(54) IMPROVEMENTS IN OR RELATING TO MAGNETIC FIELD INDUCTORS FOR PRESSURE FORMING (71) We, KHARKOVSKY POLITEKHNICHE SKY INSTITUT IMENI V.I. LENINA, a Corporation organised and existing under the laws of the Union of Soviet Socialist Republics, of ulitsa Frunze, 21, Kharkov, U.S.S.R., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to inductors for forming metals by the pressure of a pulsed magnetic field.

According to the present invention, there is provided an inductor for forming metals by the pressure of a pulsed magnetic field, comprising a magnetic field concentrator, a coil for inducing eddy currents in the concentrator, said concentrator comprising at least two electrically insulated, relatively movable, dies, and at least one opening in the concentrator such that eddy currents are concentrated on the surface of the opening to induce eddy currents in a workpiece received within the opening, the concentrator being split in a plane extending along said opening, and the coil for inducing eddy currents in the concentrator being located on at least one of said dies which includes an insulating slot located in a plane containing the axis of the workpiece-receiving opening.

Preferably, one of the concentrator dies is stationary and accommodates the coil to induce eddy currents in the concentrator.

In order to equalize the electrodynamic forces acting upon the workpiece, the coil may be located on two dies of the concentrator.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a longitudinal section of an inductor with a concentrator composed of two dies; Figure 2 is a longitudinal section of another embodiment of the inductor with a concentrator composed of four dies; and Figure 3 is a longitudinal section of yet another embodiment of the inductor with a coil located on each of two opposed dies of the concentrator.

In the embodiments to be described the directions of the eddy currents are indicated by arrows in the corresponding figures.

Referring to Figure 1, an inductor for forming metals by the pressure of a pulsed magnetic field comprises an electricallyconducting solid cylindrical concentrator 1 with an axial stepped opening 2, the concentrator being made up of two dies. One die is in the form of a hollow cylinder 3 with an insulating slot 4. The other die is in the form of an electrically conducting disc 5.

The concentrator 1 has an opening 6, the axis of which extends along the plane in which the concentrator is split and which is normal to the axis of the concentrator 1, the axis of the opening 6 and that of the concentrator 1 intersecting each other.

Depending on the range of components be formed, the concentrator to 1 may be provided with more than one such opening. In addition, these openings may vary in diameter.

The concentrator dies are electrically insulated from each other by means of an insulating liner 7 placed between the hollow cylinder 3 and disc 5, the liner made from polyethylencterephthalate, polyfluoroethylene or other suitable insulating materials.

On the outer surface of the hollow cylinder 3, recesses are made to accommodate a coil 8 which induces eddy currents in the hollow cylinder 3.

The slot 4 associates the surfaces of the recesses of the coil 8 with the end surface of the hollow cylinder 3.

The disc 5 is associated, through a rod 9, with a drive 10 which moves the disc 5 along the axis of the concentrator 1.

The coil 8 is coupled to a capacitor 11 via a switch 12.

The above-described inductor operates as follows: A workpiece 13 is inserted into the opening 6, and the switch 12 is closed so that the capacitor 11 discharges into the coil 8. When the coil 8 is energized, eddy currents are induced in the walls of the recesses made in the hollow cylinder 3, the eddy currents forming a closed loop through the slot 4 and over the end surface of the hollow cylinder 3.

The eddy currents over the end surface of the hollow cylinder 3 induce, in turn, eddy currents in the disc 5.

The eddy currents induced on the mating surfaces of the disc 5 and hollow cylinder 3 further induce a current in the workpiece 13 placed in the opening 6. The interaction of the eddy currents induced on the surfaces of the opening 6 and workpiece 13 causes deformation of the latter.

When the forming process is finished, the disc 5 is actuated by the drive 10 via the rod 9 to move along the axis of the concentrator 1, whereby the workpiece 13 is withdrawn from the opening 6.

The inductor shown in Figure 2 has increased capacity over that shown in Figure 1. The inductor comprises a concentrator 14 made up of four dies, one being in the form of a hollow cylinder 15, while the other three are in the form of electrically conducting discs 16, 17 and 18. The concentrator 14 has a stepped opening 19. An insulating slot 20 extends along the hollow cylinder 15 and through the discs 16 and 17.

The concentrator 14 is provided with three openings 21, 22 and 23, the axes of which extend along the plane in which the concentrator 14 is split, between the cylinder 15 and the discs 16, 17 and 18, intersecting the axis of the concentrator 14. These openings accommodate workpieces 24, 25 and 26.

The dies are electrically insulated from one another by linings 27, 28 and 29.

The outer surface of the hollow cylinder 15 contains recesses accommodating a coil 30 inducing eddy currents in the hollow cylinder 15. The coil 30 is connected to a capacitor 31 via a switch 32.

The discs 16, 17 and 18 are linked, via a rod 33, to a drive 34 which actuates the discs 16, 17 and 18 to move along the axis of the concentrator 14.

The above-described inductor operates in the following manner: When the switch 32 is closed, the capacitor 31 discharges into the coil 30. As a result, eddy currents are induced on the surface of the recesses in the hollow cylinder 15, and form a closed loop through the slot 20 and over the end surface of the hollow cylinder 15.

The eddy current over the end surface of the hollow cylinder 15 induces a current on the surface of the electrically conducting disc 16, facing the cylinder 15, which current flows over said surface and through the insulating slot 20 extending through the disc 16 and forms a closed loop on the opposite surface of the disc 16, i.e. on the surface facing the disc 17, and then on the surface of the disc 17 facing the disc 18.

The eddy currents induced on the mating surfaces flow around the openings 21, 22 and 23 accommodating the workpieces 24, 25 and 26, and interact with the eddy currents through the work-pieces 24, 25 and 26 to cause deformation of the workpieces.

Figure 3 shows an inductor in which the electromagnetic pressure on a workpiece can be equalized. To this end, the inductor comprises a magnetic filed concentrator 35 with an axial stepped opening 6. The concentrator 35 is made up of two dies in the form of hollow cylinders 37 and 38, one cylinder 37 being stationary and the other cylinder 38 being coupled, via a rod 39, with a drive 40 which actuates the cylinder 38 to move along the axis of the concentrator 35.

A coil 41 inducing eddy currents in the concentrator 35 is placed in recesses made on the outer surfaces of the cylinders 37 and 38, that is, on both dies of the concentrator.

The coil 41 has a flexible connector 42.

The concentrator 35 is provided with an insulating slot 43 which associates the surfaces of the recesses in the hollow cylinders 37 and 38 with the end surfaces of these cylinders, facing each other.

An opening 44 is made in the concentrator 35, at right angles to its axis, the concentrator 35 being split in a plane angles to its axis, the concentrator 35 being split in a plane containing the axis of the opening 44.

The opening 44 is intended to accommodate a workpiece 45. The mating surfaces of the cylinders 37 and 38 are separated by an insulating liner 46. The coil 41 is connected, via a switch 47, to a capacitor 48.

The coil 41 induces eddy currents, in opposite directions, on the end surfaces of the hollow cylinders 37 and 38 of the concentrator 35. As these currents flow around the opening 44, eddy currents are induced in the workpiece 45. The electrodynamic interaction of the currents causes deformation of the workpiece 45. The geometry and electric parameters of the hollow cylinders 37 and 38 in the plane in which the concentrator is split are identical, whereby equal currents flow over the end surfaces of these cylinders 37 and 38. This ensures uniform deformation of the workpiece 45 over its contour.

In each of the embodiments described the insulating slot 4 (Figure 1), 20 (Figure 2), or 43 (Figure 3), is located in a plane containing the axis of the workpiece-receiving slot or slots.

The inductors particularly described can most advantageously be used in assembly operations, in particular, in joining components having a closed contour by squeezing (for example joining of pipes, joining of elongate components), as well as in forming components with a developed end portion (for example for achieving a permanent connection of a cable thimble with a cable).

The embodiment described with reference to Figure 3 provides improved power characteristics of the inductor (the inductor efficiency is increased by 20%), rules out the possibility of fusion of the concentrator dies simplifies operation of the inductor, prolongs its surface life, and increases its output capacity.

The inductors particularly described permit magnetic forming to be effected on a wide range of components (including long components and components having a closed contour), and provide improved quality and accuracy of forming.

WHAT WE CLAIM IS: 1. An inductor for forming metals by the pressure of a pulsed magetic field, comprising a magnetic field concentrator, a coil for inducing eddy currents in the concentrator, said concentrator comprising at at least twd electrically insulated, relatively movable, dies, and at least one opening in the concentrator such that eddy currents are concentrated on the surface of the opening to induce eddy currents in a workpiece received within the opening, the concentrator being split in a plane extending along said opening, and the coil for inducing eddy currents in the concentrator being located on at least one of said dies which includes an insulating slot located in a plane containing the axis of the workpiece-receiving opening.

2. An inductor as claimed in claim 1, wherein one of the concentrator dies is stationary and accommodates the coil for inducing eddy currents in the concentrator.

3. An inductor as claimed in claim 1, wherein the coil for inducing eddy currents in the concentrator is located on two opposed dies of the concentrator.

4. An inductor for forming metals by the pressure of a pulsed magnetic field, substantially as hereinbefore described with reference to Figure 1, Figure 2, or Figure 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. opposite directions, on the end surfaces of the hollow cylinders 37 and 38 of the concentrator 35. As these currents flow around the opening 44, eddy currents are induced in the workpiece 45. The electrodynamic interaction of the currents causes deformation of the workpiece 45. The geometry and electric parameters of the hollow cylinders 37 and 38 in the plane in which the concentrator is split are identical, whereby equal currents flow over the end surfaces of these cylinders 37 and 38. This ensures uniform deformation of the workpiece 45 over its contour. In each of the embodiments described the insulating slot 4 (Figure 1), 20 (Figure 2), or 43 (Figure 3), is located in a plane containing the axis of the workpiece-receiving slot or slots. The inductors particularly described can most advantageously be used in assembly operations, in particular, in joining components having a closed contour by squeezing (for example joining of pipes, joining of elongate components), as well as in forming components with a developed end portion (for example for achieving a permanent connection of a cable thimble with a cable). The embodiment described with reference to Figure 3 provides improved power characteristics of the inductor (the inductor efficiency is increased by 20%), rules out the possibility of fusion of the concentrator dies simplifies operation of the inductor, prolongs its surface life, and increases its output capacity. The inductors particularly described permit magnetic forming to be effected on a wide range of components (including long components and components having a closed contour), and provide improved quality and accuracy of forming. WHAT WE CLAIM IS:

1. An inductor for forming metals by the pressure of a pulsed magetic field, comprising a magnetic field concentrator, a coil for inducing eddy currents in the concentrator, said concentrator comprising at at least twd electrically insulated, relatively movable, dies, and at least one opening in the concentrator such that eddy currents are concentrated on the surface of the opening to induce eddy currents in a workpiece received within the opening, the concentrator being split in a plane extending along said opening, and the coil for inducing eddy currents in the concentrator being located on at least one of said dies which includes an insulating slot located in a plane containing the axis of the workpiece-receiving opening.