US3864598A

US3864598A - Incandescent lamp with internal fuse

Info

Publication number: US3864598A
Application number: US384744A
Authority: US
Inventors: Jr John G Cardwell
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1973-08-01
Filing date: 1973-08-01
Publication date: 1975-02-04
Anticipated expiration: 1992-02-04
Also published as: NL7409961A; JPS5038974A; JPS573185B2; GB1469968A; CA1015394A; BE817876A; DE2434983A1

Abstract

An incandescent lamp having a coiled-coil filament connected to at least one formed spud, which is embedded in a pinch seal, contains at least one fuse member internal to the lamp envelope. The fuse member has a coiled portion which is connected to the spud and a leg portion which is connected to a lead-in conductor.

Description

United States Patent Cardwell, Jr. Feb. 4, 1975 [54] INCANDESCENT LAMP WITH INTERNAL 3,211,943 10/l965 Cardwell 315/74 X FUSE 3,211,950 10/1965 Cardwell ,1 315/74 3,346,768 10/1967 Patsch 315/74 [75] Inventor: J01lll G. Cardwell, .lr., Kirtland,

Ohm Primary Examiner-Gerard R. Strecker [73] Assignee: General Electric Company, Attorney, Agent, or Firm-Emi1 F. 805, Jr.; Lawrence Schenectady, N.(. R. Kempton; Frank L. Neuhauser [22] Filedi Aug. 1, 1973 [21] App]. No.: 384,744 1 ABSTRACT I An incandescent lamp havmg a coded-coil filament connected to at least one formed spud, which is em- [52] U.S.Cl. 315/74, 313/315 bedded in a pimh Sea], contains at one fuse [51] I111. C1. T1011: 1/66 member internal to the lamp envelope. The fuse [58] Fltld of Search 315/74, 313/315 ber has a coiled portion which is cnnnected to [he [5 e e ce Cited zgltilcj'igre leg portion which is connected to a lead-in UNITED STATES PATENTS 3,211,942 10/1965 Wiley 313/315 7 3 1 INCANDESCENT LAMP WITH INTERNAL FUSE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates generally to incandescent lamps. More particularly, the invention relates to incandescent lamps having a fuse member internal to the lamp envelope.

2. Description of the Prior Art It has been common practice to provide a fuse for certain high efficiency tungsten-halogen type lamps because these lamps have a tendency to develope an ionized are which causes a flow of high current as is more fully described in Wiley U.S. Pat. No. 3,21 I942. Two such fuse devices are described in Cardwell US. Pat. Nos. 3,2l 1,943 and 3,2l l ,950, assigned to the assignee of the present invention. Both fuse constructions referred to above are internal to the lamp envelope which means that any are which occurs at lamp filament failure will be quenched inside the envelope.

By contrast, there are lamp constructions having external fuse designs such as illustrated in US. Pat. No. 3,274,426. The disadvantages of this type of construction are the number, complexity and expense of the parts which must be assembled and the necessity for the are which commences inside the lamp to continue through the lamp pinch seal before it is interrupted by the fuse located in the base, external to the envelope.

Certain lamp applications require a very fine small diameter wire to make a coiled-coil. The same applica tions also require a small diameter wire fuse. Prior art fuse constructions mentioned above are not readily adaptable to these fine wire type lamps. Because of the delicate nature of the filament wire, it might easily break while in transit or during other handling. Furthermore, wire which is very thin does not lend itself for threading a fuse member onto a coiled'coil, such as an overwind, as shown in Cardwell US. Pat. No. 3.2l L943.

Consequently, formed spuds, such as .I-hooks or helispuds, are inserted into the ends of the coiled-coil to give stability to the fine wire filament. J-hook spuds or supports are more fully described in US. Pat. Nos. 3,44l,772 and 3,441,776. These spuds are metal conductors with a curved portion which fits inside a portion of the first secondary turn of the coiled-coil or a primary leg. Although the formed spud is a good conductor and gives mechanical support to the filament, this construction has the disadvantage of conducting heat back into the seal area thereby causing foil shaling and other forms of seal failure. Another problem with formed spuds is because of their relatively large diameter the spud makes a good electrode to conduct the are when the filament fails.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a lamp with an internal fuse which will protect the lamp circuit from high amperage damage. A further object of the invention is to provide a fuse internal to the lamp envelope so that any are may be terminated at the earliest possible moment. Still another object of the invention is to provide a fuse construction with a minimum number of parts and a minimum number of manufacturing steps to assemble the lamp. Yet another object of the invention is to provide an internally fused lamp with a formed spud construction which gives good mechanical support and precise location to the filament.

The objects of the invention are achieved by providing a lamp comprised of a vitreous envelope of glass or quartz having a pinch seal at least at one end thereof. Contained within the envelope is a filament preferably of tungsten and preferably of the coiled-coil variety. At least one end of the filament is connected to a formed spud through the insertion ofa curved end of the spud into a portion of the primary turn of the filament.

The other end of the formed spud is sealed into the pinch seal to prevent any movement. A fuse member containing a coiled portion and a leg portion is positioned on the spud by inserting a straight section of the spud into the coiled portion of the fuse and by attaching the coiled portion to the straight section by a process such as welding. The leg portion of the fuse is then attached to a lead-in conductor, a portion of which is usually a foliated piece of molybdenum. The lamp is then exhausted and filled with an inert gas and a halogen.

BRIEF DESCRIPTION OF THE DRAWING FIG. I of the drawing is a front elevation view of a lamp of the invention having one fuse;

FIG. 2 is a front elevation of a section of the lamp shown in FIG. I; and

FIG. 3 is a front elevation view of another embodiment of the invention utilizing two fuses and a support.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 of the drawing, lamp I0 is comprised of a tubular envelope II having pinch seals 12 and I8 at each end. Even though the preferred embodiment is shown as a double-ended lamp containing two pinch seals, it should be remembered that a singleended lamp, one pinch seal, may also successfully utilize the invention. Coil-coiled tungsten filament I3 is connected to formed spuds, helispuds, l4 and 15. These spuds are preferably made of tungsten. The spuds are inserted into the secondary turns of the fila ment, as shown at 16 and 17. The end of the spud is curved so that when it is inserted it will penetrate about one-half turn of the secondary coil.

Helispud I4 is sealed in insulating relationship to molybdenum foil 19 which is hermetically sealed in pinch seal I8. Molybdenum foil I9 is connected to outer lead 20 which makes electrical contact to a power source. not shown, through tab 2]. Insulating base 22 is held firmly in place on pinch seal 18 by a quantity of cement 23.

At the other end of envelope ll, helispud 15 which is attached to coiled-coil I3 at location I6 is connected to foil 29 in pinch seal 12. Referring now to both FIGS. 1 and 2, fuse member 25 is comprised of coiled section 26 and leg portion 27. Coiled section 26 should have more than one turn of wire to facilitate supporting the formed spud and making electrical contact with it. Although not entirely necessary to practice the invention, several of the coiled segments are attached to the spud to further facilitate contact and support as shown at 28 in FIG. 2.

Leg portion 27 extends into pinch seal 12 and is attached to molybdenum foil I9. The foil in turn is connected to outer lead-in conductor 20 and tab 2l. Insulating base 22 is attached to the tab and pinch seal by cement 23.

Test data from lamps of the construction illustrated in FIG. 1 indicates that lamps using a helispud and fuse member such as 25 have improved life over a construction which does not utilize the fuse but merely utilizes helispuds attached directly to foil leads. Most of the improvement appears to be due to the reduction in foil failures caused by excessive heat being conducted back to the foil from the relatively heavy helispud.

One of the lamp types used in testing is a LOGO-watt. IZO-volt design known as a DXW. In this lamp, the fuse was made of tungsten wire with a 0.0l5-inch diameter, and it was attached as shown at 28 to a helispud of approximately 0.032-inch diameter. The particular fuses used had a minimum of five turns in the coiled section 26. With five turns, this allows welding of one or more turns to the spud but at the same time keeps a number of turns available if the welded turns would fracture due to tungsten embrittlement. The other turns could continue to support and make contact with the helispud.

A further improvement in lamp life was noticed when lamps similar to the construction of lamp 40, shown in FIG. 3. had two fused helispuded ends instead of one. The lamp shown in FIG. 3 is basically the same as that shown in FIGS. 1 and 2, and like parts are designated by like numerals except the numbers in FIG. 3 are followed by the letter a.

Coiled-coil 13a is connected to helispuds 14a and 1511 through insertion of a curved portion of the helispuds into the secondary turns such as at 160. The other ends of helispuds 14a and 150 are embedded in pinch seals 12a and 18a in insulating relationship to foil

conductors

19a and 29a.

Fused members 250 are attached to the helispuds by welding. for example. at locations 280. Coiled section 26a of the fuse is shown as having a plurality of turns generally more than five. Fuse legs 27a are attached to foil conductors 19a and 290 which in turn make electrical contact with

tabs

21a and 31a through outer conductors a and 30a. Insulating bases 22a and 32a are held to the pinch seals and tabs by cement 23a and 33a. Coil support 35 is used to give the filament additional stability and to prevent sagging. The ends of the support are anchored in the respective pinch seals.

As indicated earlier, the presence of two fuses in the lamp improves the life over lamps using one or no fuses, presumably because foil seal temperatures are low ered and the probability of premature seal failure is greatly reduced.

A lamp construction using two fuses is desirable for ("ill yet another reason. When two fuses are used. they are connected in series and therefore each fuse has only half the voltage across it. This in turn reduces the tendency of arcing at the fuse itself.

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

I. An electric incandescent lamp comprising an envelope of vitreous material having at least one pinch seal at one end of the envelope, an incandcscible filament of the coiled-coil type made of fine wire connected at one end to a formed spud. said spud having its opposite end sealed in said pinch seal in insulating relationship to a lead-in conductor, and a fuse member electrically connected to the spud at one end and a lead-in conductor at the other end. said fuse member comprising a coiled portion fitted over the formed spud which is sealed in said pinch seal and a leg portion, said leg portion being attached to a foliated section of the lead-in conductor, said filament being unsupported by said fuse member.

2. An incandescent lamp as claimed in claim 1 wherein said coiled portion of said fuse has five or more turns.

3. An incandescent lamp as claimed in claim I wherein said coiled-coil filament is supported by a coil support which has its ends sealed in said pinch seals.

4. An incandescent lamp as claimed in claim 1 wherein said coiled portion of said fuse has more than one full wire turn.

5. An incandescent lamp as claimed in claim I wherein a part of said coiled portion of said fuse is attached to the formed spud.

6. An electric incandescent lamp comprising a tubular envelope of vitreous material having pinch seals at each end, an incandescible coiled-coil filament made of fine wire, said filament connected at each end to a formed spud, the opposite ends of the spuds being sealed in said pinch seals in insulating relationship to lead-in conductors. and fuse members connected to each spud at one end and a lead-in conductor at the other end. said lead-in conductor being hermetically sealed in said pinch seals, said fuse members comprising a coiled portion fitted over the spuds and a leg portion. said leg portion being attached to said hermetically sealed lead-in conductors. said filament being unsupported by said fuse members.

7. An incandescent lamp as claimed in claim 6 wherein said coiled-coil filament is supported by a coil support which has its ends sealed in said pinch seals.

Claims

1. An electric incandescent lamp comprising an envelope of vitreous material having at least one pinch seal at one end of the envelope, an incandescible filament of the coiled-coil type made of fine wire connected at one end to a formed spud, said spud having its opposite end sealed in said pinch seal in insulating relationship to a lead-in conductor, and a fuse member electrically connected to the spud at one end and a lead-in conductor at the other end, said fuse member comprising a coiled portion fitted over the formed spud which is sealed in said pinch seal and a leg portion, said leg portion being attached to a foliated section of the lead-in conductor, said filament being unsupported by said fuse member.

3. An incandescent lamp as claimed in claim 1 wherein said coiled-coil filament is supported by a coil support which has its ends sealed in said pinch seals.

5. An incandescent lamp as claimed in claim 1 wherein a part of said coiled portion of said fuse is attached to the formed spud.

6. An electric incandescent lamp comprising a tubular envelope of vitreous material having pinch seals at each end, an incandescible coiled-coil filament made of fine wire, said filament connected at each end to a formed spud, the opposite ends of the spuds being sealed in said pinch seals in insulating relationship to lead-in conductors, and fuse members connected to each spud at one end and a lead-in conductor at the other end, said lead-in conductor being hermetically sealed in said pinch seals, said fuse members comprising a coiled portion fitted over the spuds and a leg portion, said leg portion being attached to said hermetically sealed lead-in conductors, said filament being unsupported by said fuse members.