US2537289A

US2537289A - Device for heating pieces of work by means of high-frequency alternating currents

Info

Publication number: US2537289A
Application number: US727030A
Authority: US
Inventors: Hendrik Johannes Meerka Embden
Original assignee: Hartford National Bank and Trust Co
Current assignee: Hartford National Bank and Trust Co
Priority date: 1944-04-26
Filing date: 1947-02-07
Publication date: 1951-01-09
Anticipated expiration: 1968-01-09
Also published as: NL61586C; FR925526A

Description

Jan. 9, 1951 H. J. M. VAN EMBDEN 2,537,289

DEVICE FOR HEATING PIECES OF WORK BY MEANS OF HIGH-FREQUENCY ALTERNATING CURRENTS Feb. 7,

Filed H.J. M- VAN EMBDEN v INVENTOR AGENT Patented Jan. 9, 1951 DEVICE FOR HEATING PIECES OF WORK BY MEAN S 01? HiGH-FRE IN G CURRENTS QU @Y ALTErtNAT- Hendrik .1? ohannes Meerkamp van Embden, Bind hoven, Netherlands, assignor to Hartford Na.- tional Bank and Trust Company, Hartford,

001111., as trustee Application February 7, 1947, Serial No. 727,030 In the Netherlands April 2.6, 194d Section 1, Public Law 690, August 8, 1946 Patent expires April 26, 1964 1 Claim.

The invention relates to high-frequency induction heating apparatus.

The known devices for heating metal pieces of work by means of high-frequency alternating currents for the thermal treatment of pieces or work comprise a coil for conducting the high-frequency alternating currents. In the space inside this coil there is produced a high-frequency alternating field by which the outer layer of the piece of work brought into this field is heated through induction of Foucault currents. The efficiency of such a device is highly dependent on that portion of the magnetic alternating field produc'ed in the coil which is used efficiently for the production of Foucault currents in the piece of work, that is to say on the part of the field which crosses this piece of work. As a rule, the coil will have much larger dimensions than the piece of work introduced, since in view of the high voltages to be used it is desirable that the dimensions of the coil and the distance between its turns should be such that in many cases the coil is necessarily of an excessive size. A great portion of the magnetic field produced will therefore not pass through the piece of work. In order to overcome this drawback, it is already known to use flexible turns for the coil producing the highfrequency field, so that these turns may be adapted to pieces of work of difierent shapes. There are, however, objections from the point of View of construction, since these turns generally have to conduct comparatively strong currents and mostly have to be cooled by a water current.

A known solution to meet the above-mentioned drawback of the dimensions of the coil relative to the piece of work while retaining a comparatively large coil consists in the provision of a filling piece of non-magnetic material having a high electrical conductivity between the coil and the piece of work concerned. Such known filling pieces consist of brass or copper bodies provided with a central aperture which communicates with the outer periphery by means of a slot. The Foucault currents produced in this conductive body by the high-frequency alternating field fiow, owing to the wall effect in the external periphery of the body, along the area of the slit and along the internal periphery of the central aperture recessed in the said body. In the central aperture there is thus produced again a high-frequency alternating field in which is located the piece of work to be heated. It is thus possible to treat efiiciently also small pieces of work while retaining a coil of the required dimensions, since the aperture of the filling piece may be adapted to the piece of work. The filling piece acts in this case as a secondary Of a transformer whose primary is formed by the coil. These known conductive bodies have the drawback, however, that for heating pieces of work in which small diameters as well as large diameters occur, the parts with small dimensions may be introduced only if the slot communicating with the external periphery has a width equal to at least this diameter.- The piece of work to be heated is therefore during the heating in the central aperturenot in the alternating field throughout its section. It is possible indeed to give this slot a'small width, but in this case it must always be possible to pass the whole piece of work through the central aperture, which cannot be realised, for example, in the case of crank-shafts and similar complicated pieces of work without giving the central aperture too great a width and hence rendering the body too little effective.

These drawbacks are obviated by the present invention, in an arrangement wherein the conductive body is built up from at least two different parts and the piece of work is located in a portion of the intermediate space between the separate parts. Owing to this measure it is ensured that the conductive body concerned may be opened before the introduction and the removal of the piece of work, so that small diameters of pieces of work may also be surrounded by the conductive body at a small distance therefrom.

In the construction according to the invention care is preferably taken that at least part of the inner surface of the conductive body divided into parts has such a shape and such dimensions that this surface is adapted to the total part of the piece of work that is to be heated. This exact adaptation has the advantage of a minimum leakage field.

In order that the invention may be more clearly understood and readily carried into effect, it will be explained more fully by reference to the accompanying drawing.

Figures 1 and 2 give a plan view and a sectional side view of the device according to the invention.

In Figure 1, the coil 1 contains a body which is constituted by two parts 2 and 3 which parts may be cooled, said body consisting of non-magnetic material of good electrical conductivity, for example of copper.

A high frequency alternating field is produced in the coil I. When the current in the coil flows in the direction of the outer arrows, Foucault currents are produced in the parts 2 and 3, which flow in accordance with the indicated arrows owing to the edge efiect. The piece of Work which must be externally hardened is located in the aperture 4 between the two pieces 2 and 3, about which also flows a high-frequency alternating current, as can be seen from the drawing.

Fig. 2 is a sectional view of a device according to the invention. As before, I is the coil traversed by the high-frequency alternating current. The parts 2 and 3, which in this case are provided with inclined holes 5 and 6, embrace the aperture 4 which can exactly receive the piece of work I, in the present instance a part of a balljoint. The part 8 of this piece of work need not be hardened and is therefore located outside the space 4. As a result of the inclined holes 5 and 6, the current flowing directly about the piece of work is concentrated still further, from which a quicker heating results.

The two parts 2 and 3 are supported by limbs 9 and ill, the piece of Workbearing on a support II. If desired, the piece of work may be rotatably arranged to facilitate a more uniform heating thereof. The whole is fastened on a carrier l 2 which may be moved up and down along the longitudinal axis of the coil. For exchanging the piece of work the carrier I2 may be lowered and the parts 2 and 3 may be turned away round the limbs 9 and [0. Owing to this possibilityof movement of the parts 2 and 3 the additional advantage is obtained that the opening 4 may be adapted to the piece of work better than with the known devices having a filling piece.

-. What I claim is:

High-frequency induction heating apparatus for treating work pieces comprising a solenoid for establishing a high-frequency field, a nonmagnetic cylindrical body of metallic material of high electrical conductivity coaxially disposed within said solenoid, said body being constituted by a pair of spaced longitudinal segments, the work piece to be treated being disposed in the spacing between said segments, the inner surfaces of said segments being shaped to conform substantially to the contour of said work piece, whereby eddy currents induced in said segments results in a flux field threading through said work piece, and a carrier movable relative to the solenoid along the longitudinal axis thereof for holding said workpiece in the spacing between said segments, said carrier including means pivotally supporting said segments to enable insertion and removal of said work piece.

HENDRIK JQOHANNESI MEERKAMP vm, EMBDEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Num er Name Date 1,997,741 Northrup Apr. 16, 1935 2,299,934 Sherman et al Oct.27, 1942 2,408,229 Roberds Sept. 24, 1946 2,442,968 Bierwirth June 8, 1948