US1929212A

US1929212A - Induction heating

Info

Publication number: US1929212A
Application number: US520008A
Authority: US
Inventors: O'neill George Dean
Original assignee: Hygrade Sylvania Corp
Current assignee: Hygrade Sylvania Corp
Priority date: 1931-03-04
Filing date: 1931-03-04
Publication date: 1933-10-03
Anticipated expiration: 1950-10-03

Description

Oct. 3, 1933.

G. D. ONEILL INDUCTIOli HBATIHQ Filed March 4. 1931 Patented Oct. 3 1933 INDUCTION HEATING George Dean ONeill, Beverly, Mass, assignor to Hygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Application March 4, 1931. Serial N 0. 520,008

13 Claims.

In the art of heat treatment by induction it is often desirable to heat certain parts without correspondingly heatingan adjacent part or parts but inasmuch as the induction is effected by core- 5 less coils whose fields spread widely it has not been possible to establish a very definite or distinct boundary for the heat zone. For example, in the manufacture of radio tubes and the like containing getters it is desirable to heat all the metal parts within the tubes during the evacuating process to liberate occluded gases but the getters must be maintained at a comparatively low temperature until time for flashing; and owing to the close grouping of the parts within the restricted spaces of the tubes it has been difficult if not impossible adequately to heat the electrodes and other metallic parts without prematurely flashing the getters.

Objects of the present invention are to provide 29 a method and apparatus by which the heat zone may be sharply bounded at least on one side and/or two juxtaposed parts may be treated effectively while maintaining an intermediate part at a comparatively low temperature, to attain these results without insulating barrier-sand generically to improve the art of heat treatment by vinduction. More particular objects are to heat interior parts of electron discharge tubes having getters without flashingthe getters and at the 30 same time to make the heat treatment thoroughly effective in parts close to the getters.

In one aspect the present invention comprises creating in offset but overlapping relationship to the usual induction field, a counterfield which varies synchronously therewith so that the two fields tend to neutralize each other in the overlapping zone, whereby heating is inhibited in said zone. In case parts are to be heated on each side of the relatively cool zone the counter field may also be utilized for heating purposes by suitably regulating its magnitude and distribution.

In another aspect the invention comprises induction apparatus having the novel characteristics setforth hereinafter and illustrated by way 45.. of example in the accompanying drawing in which:

Fig. 1 is an axial section of a heating coil for heat treatment of radio tubes, a typical tube being shown in elevation with the parts broken away;

Fig. 2 is a top plan view of the parts shown in Fig. 1; and

Fig. 3 is a diagram illustrating the theory of? operation.

The particular embodiment of the invention chosen for the purpose of illustration comprises upper and lower coils C and C' joined together by an intermediate part I. These coils may be of any suitable type as for example of the type comprising copper tubing flattened so that with a given spacing between turns more turns may be accommodated within a given axial dimension. By interconnecting the coils by means of tubing the cooling water may be circulated through the coils in series, the water entering or leaving at the lower end A of the lower coil and leaving or entering at the upper end B of the upper coil. The source of current may also be connected to the ends A and B.

r The particular tubes shown in the figures comprises electrodes and other metallic parts (indicated generally by the reference character D) in the upper part of the tube and a metallic clamp E surrounding the reentrant stem of the tube for supporting certain of the parts D. A getter-holder is shown at G. From the foregoing it will be understood that in the process of evacuating tubes such as shown at 1 it is desirable to heat the parts D and E to a relatively high temperature without correspondingly heat ing the getter G.

As will be evident from Figs. 1 and 2 the turns of the coils C and C progress from top to bottom or vice versa in opposite directions around the common axis of the coils; that is, viewing the coils from the top, the turns of the upper coil C progress from top to bottom in a clockwise direction and the turns of the lower coil progress from top to bottom in a counterclockwise direc tion. Thus when the coils are operated in series from the same source the fields inside the res ective coils are always in opposition as ted in Fig. 3. Consequently, the region between the two coils near the common axis, in which the getter G is located, is relatively free from heating effects. Thus the parts D and E may be heated to a relatively high temperature without flashing the getter G.

It will of course be understood that this inven tion has many other applications than that chosen for the purpose of illustration and that the invention as defined by the appended ciaims may be carried out in many difierent ways. For example the coils may be connected either in series or in parallel and the turns of the respective coils may progress either in the same or opposite directions depending upon the manner in which the coils are connected to the source or sources of current.

I claim:

1. In the manufacture of radio tubes and the like which contain parts to be heated by induction during evacuation and a juxtaposed getter which, to avoid flashing during evacuation, must be maintained at a comparatively low temperature, the method which comprises heatingsaid parts by induction with a variable field in the locality of said parts and at the same time creating a counter field in the region of the getter, whereby heating is inhibited in the getter;

2. The method of localizing heat treatment by induction which comprises creating a variable field in the desired locality and at the same time creating in offset but overlapping relationship to said field a counter field, the two fields varying synchronously and tending to neutralize each other in the overlapping zone, whereby heating is inhibited in said zone.

lhe method of effecting heat treatment in two juxtaposed locations while maintaining a comparatively low temperature in the intermedi:- ate zone which comprises prmzlucing in said locations opposed synchronous fields which overlap in said zone.

4. Induction heating apparatus comprising coils arranged in juxtaposition so that when energized their fields are in part coextensive and means for energizing the coils oppositely so that the fields tend to counteract each other in at least a part of their coextensive zone.

5. Induction heating apparatus comprising approximately coaxial coils arranged in iuxtaposition so that when energized their fields are in part coextensive, and means for energizing the coils oppositely so that the fields tend to counteract each other in at least a part of their coextensive zone.

6. Induction heating apparatus comprising coils arrangedend to end so that when energized their fields are coextensive in a zone therebetween, and means for energizing the coils oppositely so that the fields tend to counteract each other in said zone.

'7. Induction heating apparatus comprising approximately coaxial coils arranged end to end so that when energized their fields are coextensive in a zone therebetween, and means for energizing the coils oppositely so that the fields tend to counteract each other in said zone.

8. Induction heating apparatus comprising coils arranged in juxtaposition so that when energized their fields are in part coextensive, the coils being connected in series but having their turns progressing oppositely so that the fields tend to counteract each other in at least a part of their coextensive zone.

9. Induction heating apparatus comprising approximately coaxial coils arranged in juxtaposition so that when energized their fields are in part coextensive, the coils being connected in series but winding in opposite directions around their common axis so that the fields tend to counteract each other in at least a part or their coextensive zone.

10. Induction heating apparatus comprising coils arranged end to end so that when energized their fields are coextensive in a zone therebe tween, the coils being connected in series but winding in opposite directions so that the fields tend to counteract each other in said zone.

11. Induction heating apparatus comprising approximately coaxial coils arranged end to end so that when energized their fields are coextensive in a zone therebetween, the coils being connected in series but winding in opposite directions so that the fields tend to counteract each other in said zone.

12. The method of selectively heating a body by induction which comprises subjecting said body to opposed fields which overlap to maintain a portion of said body comparatively cool, and adjusting the magnitude of one of said fields to control the heating of another portion 0! said body.

13. The method of selectively heating a body by induction which comprises subjecting said body to opposed fields which overlap to a predetermined extent to maintain a predetermined portion of said body comparatively cool, and adjusting the distribution of one of said fields to control the heating of another portion of said body.

GEORGE DEAN ONEIIL.