GB2248854A

GB2248854A - Induction hardening apparatus.

Info

Publication number: GB2248854A
Application number: GB9113882A
Authority: GB
Inventors: Friedhelm Emde
Original assignee: AEG Elotherm GmbH
Current assignee: SMS Elotherm GmbH
Priority date: 1990-07-02
Filing date: 1991-06-27
Publication date: 1992-04-22
Anticipated expiration: 2011-06-27
Also published as: GB2248854B; FR2663952A1; GB9113882D0; DE4021025C1

Description

-)2483-:)4 1 INDUCTION HARDENING APPARATUS This invention relates to

apparatus for hardening the surface of workpieces which are of different dimensions in respect of length and/or diameter, comprising two clamping heads, a rotary drive for clamping and rotating the workpiece that is to be hardened, inductors for electro- inductive heating of the workpiece surface, and a quenching spray, in which respect at least two inductors, each having two parallel conductor portions and end portions elbowed at a right angle, a respective end portion of each extending arcuately or polygonally over the workpiece to connect the two parallel conductor portions together, are arranged so as to be displaceable relative to one another for adaptation to the respective workpiece length.

In the case of such electro-inductive hardening apparatus problems occur when, successively, workpieces of different length and different diameter have to be hardened using the same apparatus. Frequently, the edges of the workpieces remain unhardened in order to reduce the risk of edge break-offs. For this purpose, to date, the inductors have always had to be changed so that those of the respectively desired length are brought into use. This requires, on the one hand, maintenance of a correspondingly large stock of different size inductors and, furthermore, long conversion times, which are lost as dead time from the production time and also tie up operating personnel who carry out the conversion.

The aim of the invention is to provide an inductor for the electroinductive heating of metal workpieces which will have a sharp separation between the portion that is to be heated and the adjacent portions which are not to be co-heated, so as to make it possible to harden 2 workpieces of different length and/or diameter without changing inductor.

German Patent Specification DE-PS 38 43 457 discloses induction hardening apparatus with which it is possible to harden workpieces of different lengths, but in the case of this inductor the current loss occurring as a result of voltage drop at the supply leads is comparatively high. The present invention, therefore, seeks to provide an inductor which has less inductivity, and therewith less voltage drop and current loss than the one described in DE-PS 38 43 457.

In accordance with the present invention the connection ends of each of the two inductors are disposed in the region of influence of branches, having current flowing therethrough in the opposite direction, of loops between active conductor and return conductor of the respective other inductor.

With such an arrangement of the inductors relative to each other in the region of their connection ends, minimization of the voltage drop is ensured irrespective of the relative positioning of the inductors in the longitudinal direction of the workpiece because the stray magnetic fields of the loop branches, which have current flowing therethrough in opposite directions, mutually cancel each other out so they are not effective outwardly and towards the workpiece.

The return conductors of the inductors, which have current flowing therethrough in opposite directions, preferably lie so close to each other side-by-side or one above the other that, here too, compensation of the magnetic fields around the conductors occurs and there is no magnetic field effective outwardly. If the return conductors lie one above the other in the radial direction of the workpiece it is possible, by means of a

4 3 swivel mechanism, to move the active conductors of the inductors towards one another in order to adapt to workpieces of different diameter. Thus, but also adaptation to different diameters of workpieces that are to be hardened is feasible in addition to adaptation to different lengths.

The invention will be explained in more detail with reference to the drawings, in which:

Fig. 1 is a schematic plan view of a preferred embodiment of the induction hardening apparatus of the invention; Fig. 2 is a section along the line A - B of Fig.

Fig. 3 is a section along the line C - D of Fig.

Fig. 4 is a section along the line E - F of Fig. 1; Fig. 5 is a section similar to A - B of Fig. 1, but of a modified embodiment with return conductors lying one above the other instead of side-by-side; Fig. 6 is a partial perspective representation of one end portion of one version of apparatus in accordance with the invention; and Fig. 7 is a partial perspective representation of one end portion of a modified version of apparatus in accordance with the invention.

Identical parts are provided with the following identical reference numbers in the various illustrations:

1, 10 la, 10a - Inductor Active conductor 4 2a, 2b 3 4 5, 50 6, 60 61, 611, 601, 60 7, 70 - 8, 80 9, 90 - 11 Return conductor Longitudinal axis Workpiece End portion Loop IT - Branches Looping conductor Transformer Current source Bundle of laminations The exemplary induction hardening apparatus of the invention, as shown in Fig. 1, comprises two separate inductors 1, 10, which are identical in design, are arranged oppositely to one another and are connected to separate current supplies, consisting, in each case, of a respective transformer 8, 80 and current source 9, 90. Each inductor 1, 10 has an active conductor la, 10a as outgoing conductor, which is arranged adjacent a surface of the workpiece 4 parallel to the longitudinal axis 3 thereof and heats the workpiece, during rotation of same about its longitudinal axis 3, in an electro-inductive manner.

Parallel to each active conductor la, 10a, the respective return conductor 2a, 2b is likewise arranged parallel to the longitudinal axis 3 of the workpiece 4,. In this respect, the return conductors 2a, 2b are arranged in the region of influence of each other (i.e. in the region of mutual influence) and have current flowing therethrough in opposite directions, as indicated by the arrows, so that the magnetic fields around the return conductors 2a, 2b mutually cancel each other out.

Each active conductor la, 10a and its return conductor 2a, 2b are connected together by way of a respective looping conductor 7, 70, which extends transversely to A the longitudinal axis of the workpiece 3, and thus transversely to the active and return conductors, and a respective conductor loop 6, 60 which has parallel portions 61, 61', 601, W' positioned parallel to the respective conductor end portions 5, 50 which have current flowing therethrough in opposite direction.

The looping conductors 7, 70 extend arcuately or polygonally over the workpiece 4, at a spacing therefrom, or over a defined area in which the workpiece is situated, in that they are arranged in their own longitudinal direction outside the workpiece 4. Since, as already stated, the parallel branches 61, 611, 601, 60'' of the conductor loops 6, 60 have current flowing therethrough in opposite.direction to the end portions 5, 50 of the inductors 1, 10, here too the magnetic fields forming around the conductors mutually cancel each other out, so that no magnetic field is effective outwardly.

Figures 2 to 5 illustrate in cross-section respective positions of the active and return conductors, in which respect the return conductors 2a, 2b can lie either side-by-side, as shown in Figures 2 to 4, or one above the other, as shown in Fig. 5. In the latter case it is possible to design the inductors so as to be swingable towards one another, in order to be able to harden workpieces of different diameter with the same induction hardening apparatus. In order to be able to harden workpieces 4 of different lengths, the inductors 1, 10 are displaceable relative to one another in the direction of the longitudinal axis 3 of the workpiece.

Figures 6 and 7 illustrate in perspective representations the position of the conductor portions of the inductors. The current direction is indicated by the respective arrows. The active conductors may have bundles of laminations 11 arranged over their entire 1 6 length to focus the magnet field acting on the workpiece that is to be hardened.

e 7

Claims

1. Apparatus for hardening the surface of workpieces which are of different dimensions with respect to length and/or diameter comprising two clamping heads, a rotary drive for clamping and rotating the workpiece that is to be hardened, with inductors for electro-inductive heating of the workpiece surface and a quenching spray, in which respect at least two inductors, each having two parallel conductor portions and end portions elbowed at a right angle, a respective end portion of each extending arcuately or polygonally over the workpiece to connect the two parallel conductor portions together, are arranged so as to be displaceable relative to one another for adaptation to the respective workpiece length, characterised in that each of the inductors possess portions which extend in the direction of the longitudinal extent of their active conductors and parallel to parallel branches of a loop between the active conductor and the associated return conductor of the respective other inductor.

2. Apparatus as claimed in Claim 1 wherein the inductors, for adaptation to the diameter of the workpiece, are rotatable, swivellable or displaceable relative to one another transversely to their longitudinal extent.

3. Apparatus as claimed in Claim 1 or 2 wherein the respective return conductors which have current flowing therethrough in opposing directions to each other are arranged parallel and adjacent to one another, one above the other or side by side, so that the magnetic fields forming around them cancel each other out.

4. Apparatus for hardening the surface of workpieces which are of different dimensions with respect to length 8 and/or diameter comprising at least two inductors, each having two substantially parallel conductor portions and angled end portlons which extend over the workpiece to connect the two parallel conductor portions together, these inductors being mutually displaceable to adapt to different lengths of workpiece, and being so arranged that each has an end portion, extending in the same longitudinal direction as its substantially parallel conductor portions, which lies substantially parallel and adjacent to at least one parallel branch of a loop between the active and associated return conductor portions of the respective other conductors, the currents flowing in opposite directions in the said end portion and the adjacent loop branch so that inductive effects thereof mutually cancel each other out.

5. Apparatus for hardening the surface of workpieces substantially as hereinbefore described with reference to and as illustrated by Fig. 1, or Fig. 6 or Fig. 7 of the accompanying drawings.