US1650605A

US1650605A - Filament for incandescent lamps or similar articles

Info

Publication number: US1650605A
Application number: US153665A
Authority: US
Inventors: Percy A Campbell
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1926-12-09
Filing date: 1926-12-09
Publication date: 1927-11-29
Anticipated expiration: 1944-11-29
Also published as: GB282066A; DE614767C; FR645389A

Description

Nov. 29, 1927. 0 1,650,605

, Y P. A. CAMPBELL FILAMENT FOR INCANDESCENT LAMPS 0R SIMILAR ARTICLES Filed Dec. 9-, 1926 JNSZ'ENTUR. REE CY A. CAMPBELL,

firs ATI'UHNEYI STATES PT 2: 1;

PERCY A. CAMPBELL, 01 EAST CLEVELAND, OHIO,.ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION NEW YORK.

FILAMENT FOR INCANDESGENT LAMPS 0R SIMILAR ARTICLES.

Application filed December 9, 1926. Serial No. 153,665.

My invention relates to filaments forelectric incandescent lamps and similar devices, and to methods of their manufacture. St1ll more particularly my invention relates to coiled metal filaments, and particularly those filaments which are subjected during use to high temperatures and tend to warp and twist out of shape. ()ne of the objects of my invention is to overcome this difficulty. Another object of my invention is to facihtate the mounting of filaments and to minimize the chances for distortion of the filament during the mounting operation.

According to the present practice where a mandrel wire is used in the coiling of filaments, such mandrel wire is removed usually immediately after the coiling and the mandrelless filament coil-is afterwards mounted on the lamp stem and the ends thereof united to the leading-in conductors of the lamp as by welding or clamping. The handling of a mandrelless wirecoil is comparatively difficult and such practice does not lend itself'to the use of automatic filament mounting machinery. When such filaments are mounted by hand, on account of their extreme flexibility they may be very easily distorted by the operator. According to my invention, the mandrel wire is not removed until after i 30 the filament has been mounted, on the lamp stem and its ends united to the leading-in conductors. This has the great advantage that the filament is easily handled and distortion during the mounting operation is prevented. According to my invention, the mandrel wire is finally removed after the mounting of the filament, preferably by dis-.

solving in acid." i

It is the practice with coiled filaments to give the filament a preliminary set by raising to a high temperature. This has been done by firing the mandrelless' filament coils at a high temperature approaching 1600 C. in cases where-the'filament is subjected to exceptionally high temperaturesin use. While in the case of my invention, this treatment may be given to the mandrel containing the filament before mounting, it may als'o be given to the-filament after mounting and before the mandrel has been removed. This has an additional advantage in that the final set is given to'the filament while it is still held firmly in a definite position.

In the drawing, Fig. 1 is an elevation of a filament coiled upon a mandrel wire; Fig. 2

i'nanufacturc of a modified form of filament;-

Fig. 5 is an end elevation thereof; and Fig. 6

is an elevation of an electric incandescentlamp comprising said modified filament.

As shown in Fig. 1, the filament wire 10 is coiled upon a mandrel wire 11 which may be any wire which may be dissolved or otherwise removed. I prefer to use molybdenum or other wire which will stand a fairly high temperature. The filament coil 12 with its mandrel is preferably given a heat treatment to set the coil, and this may be done be fore or after mounting the filament. The filament is mounted upon a stem 13 which, as shown, comprises the comparatively rigid conducting supports 1415 which are preferably united to the ends of the filament by welding, as shown'in Fig. 6, although as hereinafter explained, they may be united by clamping as shown in Fig. 2. The sup port wires 14c15 may be of chromium treated nickel. In Fig. 4 the mandrel containing the coiled filament is wound upon a man drel 16 and ordinarily it is not necessary to leave this mandrel in place, but a filament may be stripped therefrom before mounting. However, it lends to greater definlteness in filament form to allow said second mandrel to remain until after mounting of the filament. In such case it is preferable to have such second mandrel to be composed of molybdenum or other lugh heat resisting metal, whereas if the second mandrel is re electric current through the mandrel and filament with the mount placed for instance, in a hydrogen bottle.

The removal of the mandrel is preferably accomplished by means of an acid which dissolves. it. One solution which may be candescent lamps comprising used is four parts of nitric acid, four parts of water, and one part sulphuric acid. Another solution which may also be used consists of four parts nitric acid and one part sulphuric acid. In using these solutions it is necessary to use support wires of a material which is not readily attacked by these solutions. Tungsten is a suitable material. If the leading-in conductors are subjected to the acid, they also should be of tungsten or-other metal which is not afiected by the acid although the operation may be performed by dipping only the filament and a portion of the supports in the acid, and in such cases only the supports proper would have to be of acid resisting metal. Nickel may be used as a support or leading-in conductor, but in such case care would have to be t align tgflpreyent its being attacked too much by the mandrebdiesolvingaci,d.

Chromized nickel, nickel or a steel containing chromium or otherwise protected by chromium, 's preferable to pure nickel for this purpose.

In Figs. 3 and 6 are shown electric inbulbs 17' in which are sealed the mounts comprising the stems 13. In each case the filament coil 12 is shown in its final shape after the mandrel has been removed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of manufacturin and mounting coiled filaments for incandescent lamps and similar'devices which consists in coiling the filament upon a mandrel wire, uniting the end of the filament to the conductive supports of a mount and afterwards removing the mandrel.

2. The method of manufacturing and mounting coiled filaments for incandescent lamps and similar devices which consists in coiling the filament upon a mandrel wire, uniting the end of the filament to the conductive supports of a mount, and dissolving out the mandrel.

3. The method of manufacturing and mounting coiled filaments for incandescent lamps and similar devices which consists in coiling the filament on a mandrel, mounting the filament and then removing the mandrel, said filament being given a heat treatment while still on the said mandrel.

In witness whereof, I have hereunto set my hand this 6th day of December, 1926.

PERCY A. CAMPBELL.