US3727091A

US3727091A - Halogen-cycle incandescent lamp having a platinized interior fuse

Info

Publication number: US3727091A
Application number: US00142303A
Authority: US
Inventors: Caro A De
Original assignee: Westinghouse Electric Corp
Current assignee: Philips North America LLC
Priority date: 1971-05-11
Filing date: 1971-05-11
Publication date: 1973-04-10
Anticipated expiration: 1990-04-10
Also published as: DE2222088A1

Abstract

A halogen-containing single-ended electric lamp of the type used in slide projectors is provided with a platinum-coated fuse wire of nickel or Nichrome alloy which is located within the envelope and connected in series with the tungsten filament. The platinum coating is of such thickness that it protects the wire from the hot corrosive atmosphere within the operating lamp and prevents the fusible core metal from contaminating the lamp and disrupting the halogen-regenerative cycle.

Description

' DeCaro States atent [191 [75]' Inventor: Aristide R. DeCaro, Edison, NJ.

[73] Assignee: Westinghouse Electric Corporation,

. a Pittsburgh, Pa. 9

22 Filed: Mayll, 1971 21 App1.No.:142,303

[52] US. Cl. ..313/222', 313/107, 315/74 [51] Int. (31. ..l-l0lk 1/50, l-lOlk 1/66 [58] Field of Search...' ..3l5/74, 66, 71;

[56] References Cited UNITEDSTATES PATENTS 3,211,943 10/1965 Cardwell, Jr. ..3 1 5/74 X 2,021,758 11/1935 Van Horn 268,270, 11/1882 Nichols 2,859,381 11/1958 Gray et a1 3,445,713 5/1969 Cardwell, Jr. 3,431,448 3/1969 English 2,883,571 4/1959 Fridri ch et a1. 3,325,665 -6/1967* Meijer et al.

3,012,167 Poole ..313/222 UX 51 Apr. 10, 1973 FOREIGN PATENTS OR APPLICATIONS 690,662 7/1964 Canada ..3 13/222 OTHER PUBLICATIONS Primary Examiner-Palmer C. Demeo Attorney-A. T. Stratton, W. D. Palmer and D. S. Buleza 57 ABSTRACT -A halogen-containing single-ended electric lamp of the type used in slide projectors is provided with a I 6 Claims, 2 Drawing Figures PATENTED APR 1 01375 FIG. I

R O T N E V N WITNENESSES Aristide R. DeCcro W QmZ A HALOGEN-CYCLE INCANDESCENT LAMP HAVING A PLATINIZED INTERIOR FUSE CROSS-REFERENCES TO RELATED APPLICATIONS The present application is related to but constitutes an improvement over the subject matter disclosed and claimed in the following copending commonly-owned U.S. applications:

Application Ser. No. 100,665 filed Dec. 22, 1970 by N. J. Rainone et al. and entitled Halogen-Cycle Incandescent Lamp Having An Improved Filament Mount Assembly; and

Application Ser. No. 28,663 filed Apr. 15, 1970 by A. R. DeCaro et al. and entitled Lamp Combination Comprising An Improved Envelope For Tungsten- Halogen Incandescible Projection Lamp, now U.S. Pat. No. 3,648,094.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electric lamps and has particular reference to an improved halogen-cycle incandescent lamp of the type used in film projectors and similar apparatus.

2. Description of the Prior Art Incandescent lamps having built-in fuse elements that are located within the lamp envelope are per se well known in the art. A conventional projection type lamp having such an integral fuse is disclosed in U.S. Pat. No. 2,859,381 issued Nov. 4, 1958 to S. M. Gray et al. Since such conventional projection lamps are filled with an inert gas such as nitrogen or the like, the fuse can be fabricated from any metal that meets the current-carrying requirements and has the proper rigidity and melting point to fulfill the automatic fusing function.

The situation in the case of the so-called regenerative type incandescent lamps is, however, quite different in that such lamps contain a highly-corrosive halogen atmosphere and operate at much higher temperatures in order to sustain the halogen-tungsten cycle which returns vaporized tungsten back to the filament. (This principle is well known and is described in detail in U.S. Pat. No. 2,883,571.) Tests conducted with fusible elements composed of bare copper, nickel, or Nichrome alloy wires have shown that they are not only chemically attacked bythe bromine or other halogen gas used in the lamp but that the wires, when heated to the high temperatures which prevail within the operating lamp, released gaseous and other impurities which contaminated the lamp atmosphere. This, in turn, disrupted the halogen-tungsten cycle and formed discoloring deposits on the lamp envelope which drastically reduced the light output.

A double-ended compact infrared heating lamp having a silica envelope and a seal-structure wherein the portions of the lead-in conductors that extend from the press seals formed at the ends of the envelope and are exposed tothe air are composed of platinum-sheathed tungsten or platinum-sheathed molybednum is described in U.S. Pat. No. 3,012,167 issued Dec. 5, 196] to F. E. Poole. 1

SUMMARY OF THE INVENTION 7 layer of platinum is such that it protects the fuse from the hot halogen atmosphere within the lamp and prevents the nickel or Nichrome core portion of the fuse from releasing contaminants which disrupt the halogen-tungsten cycle. The improved lamp thus operates in the normal fashion and the fuse remains intact until such time that the filament fails and the resulting surge in current causes the fuse to melt and open the circuit.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the invention will be obtained from the following description of the exemplary embodiment shown in the accompanying drawing, wherein:

FIG. 1 is a side elevational view of a halogen-cycle incandescent projection lamp having an internal fuse structure according to the invention; and

FIG. 2 is a cross-sectional view through the based end of the lamp, taken along line II--II of FIG. 1, showing the physical arrangement of the fuse assembly and the sealed-in pin members.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown a representative 500 watt halogen-cycle type projection lamp 10 having a lighttransmitting tubular envelope 12 that is sealed by an end wall formed by fusing a disk or wafer 14 to the rim of the envelope in the usual manner. Four rigid metal pins l5, l6, l7 and 18 (see FIG. 2) are hermetically sealed through the wafer 14 and spaced equal distances from each other around the circumference of the wafer. A concentrated light source such as a planar tungsten filament 20 having a plurality of interconnected coil sections arranged in monoplane or biplane relationship is suspended within the envelope 12 by a mountassembly consisting of a pair of

support wires

22, 24 that are held in spaced-apart relation by a pair of

non-conductive bridges

26 and 28. The

supports

22, 24 are terminated by helical-coiled segments 23 and 25, respectively, that are slipped over and fastened as by spot welding to oppositely disposed

pins

15 and 17, as shown. The planar filament 20 is electrically connected to the

support wires

22, 24 by short end coils 21 that are spot welded in telescoped relation with slip coils force-fitted over the support wires.

Hooked filamentsupport wires

27 and 29 are anchored in the top and

bottom bridges

26 and 28, respectively, and coupled to the uncoiled segments of the filament 20 that join the coil sections. A detailed description of the mount assembly and the manner in which it is fabricated is disclosed in the aforementioned copending application of v The envelope 12 and wafer 14 are composed of quartz or a suitable high-silica content glas's (such as Pyrex" borosilicate glass No. 7740 marketed by the Corning Glass Works) and the envelope contains a mixture of a halogen and an inert fill gas a mixture of bromine and nitrogen at a pressure of about 1,000 torrs for example. The

bridge members

26 and 28 are composed of quartz and all of the metal parts of the mount assembly enclosed within the envelope 12 are composed of tungsten.

A suitable base member such as a metal shell 30 having a keyed post 31 is fastened to the neck of the envelope 12 by a suitable cement 32 in the usual manner.

In accordance with the present invention, a fuse 34 consisting of either a platinum-plated nickel wire or a platinum-plated Nichrome alloy wire is attached to one of the auxiliary conductors and an adjacent main conductor (

pins

16 and 17 in the lamp illustrated in the drawing). The fuse wire 34 is fastened, as by spot welding, to the inner ends of the

pins

16, 17 at locations adjacent to but spaced from the envelope end wall 14. The fuse 34 is thus connected in series with the filament 20 by

pins

16 and 17 which it bridges. The outer ends of pins and 16 accordingly constitute exposed longitudinally-extending terminals for the lamp 10.

A protective sleeve such as a loose-fitting glass tube 36 is desirably placed over the fuse wire 34 to guard against the possibility that molten metal from the activated fuse will strike the envelope walls and cause them to crack when the lamp fails. As will be noted in FIG. 2, the glass tube 36 is locked in such position by the connected segments of

pins

16,17.

In the case of the 500 watt T10 projection lamp 10 lllustrated having a biplane filament designed to operate at a voltage within a range of from 1 10 to 130 volts, satisfactory results have been obtained by spacing the

pins

16 and 17 approximately 11 millimeters apart and using a platinized Nichrome wire 16 millimeters long and approximately 0.4 millimeters in diameter as the fuse 34. The platinum coating or sheath was of such thickness that it protected the Nichrome core from the halogen gas without interfering with the fusing action. Excellent results have been obtained by employing Nichrome wire having a platinum sheath such that the platinum comprises approximately 62 percent by weight of the wire. The thickness of the platinum coating can vary and Nichrome wires wherein the platinum comprises from about 30 to 70 percent by weight of the wire can be used.

Nichrome" is the trade name for a series of nickelbased alloys (made by the Driver-Harris Company) which melt at approximately l,350C. and contain from 11 to 22 percent chromium, smaller amounts of silicon or manganese, and optionally some iron. Such alloys are well known in the art and are used extensively as electric-resistance heating elements. A specific example of a suitable Nichrome alloy is one which contains 75 percent nickel, l2 percent iron, ll percent chromium and 2 percent manganese.

Since nickel has only a slightly higher melting point (1,450C) than Nichrome alloy, the same fusing action can also be obtained by using a platinum-coated nickel wire of the same dimensions in place of the abovedescribed platinized Nichrome wire fuse element.

While the fuse 34 as illustrated in the drawing and described is a platinum-clad wire of substantially uniform diameter, a composite multi-section wire which has a medial segment of reduced thickness that is composed of platinized nickel or a platinized Nichrome alloy and serves as the fusible member can also be employed. In any event, the opening in the electrical circuit formed when the fuse melts is greater than the maximum arcing distance for the operating voltage of the filament that is, the gap produced within the lamp envelope by the melted fuse wire when the filament fails is too large to support an arc in the halogencontaining atmosphere of the lamp.

I claim as my invention:

1. In a regenerative-type incandescent lamp having a sealed light-transmitting envelope that encloses a coiled tungsten filament and a halogen-containing atmosphere, the improvement comprising a fuse component that is connected in series with said filament, is located within said envelope, and is composed of a material selected from the group consisting of platinized nickel and a platinized nickel-chromium alloy that contains less than 1 1 percent silicon or manganese.

2. The improvement of claim 1 wherein;

said filament is connected to a pair of elongated rigid main conductors that are embedded in an end wall of said envelope,

- a rigid auxiliary conductor is anchored in said envelope end wall and spaced from each of said main conductors,

said fuse component is connected to said auxiliary conductor and one of said main conductors,

said auxiliary conductor and said one main conductor extend through the end wall of the envelope and thereby constitute a pair of exposed terminals for the lamp, and

the interior portions of said main and auxiliary conductors are composed of tungsten.

3. The improvement set forth in claim 1 wherein platinum comprises from about 30 to percent by weight of the fuse component.

4. The improvement set forth in claim 2 wherein;

said lamp comprises a single-ended projection lamp,

said tungsten filament comprises a planar array of interconnected coil sections,

said main and auxiliary conductors each comprise a tungsten pin, and

said fuse component comprises a wire of predetermined and substantially uniform diameter.

5. The projection lamp of claim 4 wherein;

said envelope is composed of borosilicate glass and contains a mixture of an inert gas and bromine, and

each of said tungsten pins extend through the end all of said envelope.

6. The projection lamp of claim 4 wherein;

said envelope is of tubular configuration and contains a mixture of nitrogen and bromine,

said fuse component comprises a platinum-plated wire of said nickel-chromium alloy wherein platinum constitutes approximately 62 percent by weight of the wire, and

a loose-fitting glass tube is disposed in sleeved-protective relationship with the fuse wire and is retained in such position by the connected portions of the associated pins.

Claims

2. The improvement of claim 1 wherein; said filament is connected to a pair of elongated rigid main conductors that are embedded in an end wall of said envelope, a rigid auxiliary conductor is anchored in said envelope end wall and spaced from each of said main conductors, said fuse component is connected to said auxiliary conductor and one of said main conductors, said auxiliary conductor and said one main conductor extend through the end wall of the envelope and thereby constitute a pair of exposed terminals for the lamp, and the interior portions of said main and auxiliary conductors are composed of tungsten.
3. The improvement set forth in claim 1 wherein platinum comprises from about 30 to 70 percent by weight of the fuse component.
4. The improvement set forth in claim 2 wherein; said lamp comprises a single-ended projection lamp, said tungsten filament comprises a planar array of interconnected coil sections, said main and auxiliary conductors each comprise a tungsten pin, and said fuse component comprises a wire of predetermined and substantially uniform diameter.
5. The projection lamp of claim 4 wherein; said envelope is composed of borosilicate glass and contains a mixture of an inert gas and bromine, and each of said tungsten pins extend through the end all of said envelope.
6. The projection lamp of claim 4 wherein; said envelope is of tubular configuration and contains a mixture of nitrogen and bromine, said fuse component comprises a platinum-plated wire of said nickel-chromium alloy wherein platinum constitutes approximately 62 percent by weight of the wire, and a loose-fitting glass tube is disposed in sleeved-protective relationship with the fuse wire and is retained in such position by the connected portions of the associated pins.