US2633552A - Lamp, filament therefor and method - Google Patents

Description

March 31,'1953 N. J. RAlNoNE 2,633,552

LAMP, FILAMENT THEREFOR AND METHOD Filed June 4, 1951 iff-g. INVENToR A'TTORN EY Patented Mar. 31, LA1953 LAMP, FILAMENT THEREFOR AND METHOD Nicholas J. Rainone, Passaic, N. J., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania- Application June 4, 1951,- Serial No. 229,759

Claims. l

This invention relates to lamps and, more particularly, to filaments for projection lamps.

The conventional filament for an incandescent electric lamp, such as a projection lamp, isa biplane ten-section iilamentary translation device having the first and last sections for mounting, the second and third and eighth and ninth sections as outer sections, and the remaining four sections as inner or center sections. Y

v Before the development of coil bending machines as disclosed in U. S. Patent No. 2,449,653, issued September 21, 1948, such sectional laments were differentially wound on a coil winding machine with three to live mm. spaces or open turns between sections. The laments were hand formed by bending this open turn between sections over a hot knife. By this method it was possible, through the use of the proper cam arrangement on the coil winding machines, to wind the outer sections with a closer pitch than the center sections of the filament.

However, because of the relatively large space between sections on such a differentially wound filament, it is not possible at present to bend the sections on the new coil bending or forming machine. A continuously wound coil having an overall length undesirably longer than the differential coil is used. The machine-forming method is extremely desirablev in the production of filaments, as the rate is three times that of the hand forming method.

In projection lamp operation, the center or inner sections of the filament are mutually heated by one another and by the adjacent outer sections. Also, the outer sections are cooled to a greater extent than the innerV sections by conduction through and convection currents in the gas in the enclosing bulb or envelope. Hence, the center sections tend to operate at a higher temperature than the outer sections, thereby giving both non-uniform lament temperature and resultant screen illumination. In addiiton, such center sections tend to develop hot spots which shorten the life of the lamps. Further, a nonuniform light source is difficult to focus and ciecreases the screen intensity.

` This defect was formerly compensated for and reasonably corrected by the differentially wound lament having a smaller Vpitch and consequently more turns in: the'outer sections having the same length as the centersections ofthe fila-vr ment. However, with the newcoil forming 0r bending machines, the 'diiferentially wound sectional filament'` has not beenusable. "Hence, it hasbeen' found advantageous, ac-

(Cl. S13-344) cording to my invention, to employ the following methods of filament manufacture which permit use of the desirable machine-forming method and give a more uniformly heated lamentary light source which will increase screen intensity and uniformity, facilitate focusing, and give a longer lamp life:

1. The method of sectional filament manufacture comprising machine winding a differential coil having a smaller pitch in the outer sections than in the inner sections and only small breaks between sections, and machine forming the coil into a biplane sectional lament.

2. The method of continuous filament manufacture comprising machine winding a continuous coil having a pitch which is desired in the later formed outer sections, machine bending the coil into a biplane iilament having more turns in the outer sections than in the center sections, and stretching while hot the center sections to the same length as the outer sections.

3. The method of continuous filament manufacture comprising machine winding a continuous coil having a pitch which is desired in the later formed center sections, machine bending the coil into a biplane filament having more turns in the outer sections than the center sections, and compressing while hot the outer sectionsto the same length as the center sections.

4. The methodof continuous filament manufacture comprising machine winding a continuous coil at a pitch Which is desired in the later formed outer sections, selecting from each end of the coil a sufficient number of turns to comprise the respective outer sections, stretching while hot the middle of the coil to give the desired larger pitch in the center sections, and machine-forming the coil into a biplane sectional filament.

, In its general aspect, the present invention has the object of producing a biplane sectional filament as a uniformly heated light source for a projection ,lamp `which will increase screen intensity and uniformity, facilitate focusing, and give a longer lamp life.

Y Specifically, an object of the present invention is a method of filament manufacture which permits use of the desirable machine-forming method.

Another specific ,object is the method of sectional filament manufacture comprising machine winding a differential coil having a smaller pitch in the outer sections than in the inner sections fand only a small-break between sections, and machine forming .the coil into abiplane sectionalii1ame'r1t."""'`- An additional object is the method oi continuous lament manufacture comprising machine winding a continuous coil having a pitch which is desired in the later formed outer sections, machine bending the coil into a biplane filament having more turns in the outer sections than in the center sections, and stretching the inner` or center sections to thev same length as:l the outer sections.

Another object is the method of continuous lament manufacture comprising machine wind"-v ing a continuous coil having a pitch which. is. desired in the later formed center sections, ma-

chine bending the coil into a biplane` izllament` having more turns in the outer sections thanv the center sections, and compressing` under heat the outer sections to the same length as the center sections.

A further object is the method of continuous iilament manufacture comprising machine winding a continuous coil at a. pitch which is desired inthe later formed; outer sectionsselectinggfrom each end of thecoit asuiiicient; number Qi turns to comprise the respective outer sectionsi stretch* ing-while hot theA middle. of: the coii to'. give the. desired larger ptchn the center sections, andmachine forming the coil into a bi-plane fila..b ment.

Other objects. and? advantages.. ot' the invention will' appearv to those: skilled in the; art. to which it` appertains as the. descriptionproceeds', both bydirect-recitation-andi byV implicationirom the context. A

Referringtovthe.E accompanying drawingr 1n which likev numerals of vreference refer to similar partsv throughout:

Fig'. l is an elevational view-- of." a projection lamp embodying my invention.;

Fig; 2' is an elevational viewf of. a biplaneV sec;- tional filamenti-or the projection lampY ofFig;l;

Fig. 3 is a topviewf of the iilamentofy 2;

Fig. 4" isan# eleva-tional: view: oi" a differentially wound sectional coil; prior to machine. bending;

Fig. 5v is an elevational view: ci.` a. portion'. of the coil-winding machine;

Fig. 6 is an elevationallviewof a iiiament for the projectionlamp of Fig. l', after machine bending but prior tostretching;

Fig; is-anV elevational view oiacontinuously wound coilI for the fila-ment' of Fig; 6;

Fig. 8; is-an' elevational view off-a filament of the projection-lamp-of-'Fig ll,y aftermachine bending but prior to compressing while hot;

Fig. 9 isarr elevational viewl of a continuously Wound coil vafterv stretching the middleof said coil.

Referring to the` drawings in detail7 thereAVV is shown a projection lamp I-I designated'iorfbasedown operation and comprising a vitreous envelope I2 with its upper closed`- end painted black for alight shield anda base I3', and' enclosing a mount I4.

The mount I4- comprises` a stem i51 sealed to the envelope i^2-andprovided with an exhaust tube I6 opening through-a' pressA IR leading-in and supporting conductors i8 and- I-Sl extending through the pressirom-thebase I-B; atop bridge i9, a iioatingbridgeA 219; two iiiamentleg; inserts 2l and a filament 40.

The supportingconductcrs i8 and It;suitably five-piece leads, have theirnormally vupper --ends bentto a, JV-shaped configuration with the elongatedbottom section oitheili' suitably parallel to the axis ofthe lamp as illustrated` in Fig: 1; The upper or free ends of` conductorslj and Y I'S 4 are suitably nickel to facilitate the connection of the top bridge I9 thereto.

This bridge I9 consists of a short vitreous cane insulator 22 having two outer support wires 23, suitably nickel, for afixing said bridge to the upper ends of conductors I8 and I9 and three to lament supports 24, suitably molybdenum. Wires 23 and supports @have their upper ends embedded`v in insulator 22 and: are insulated thereby from each other. The lower ends of supports 2@ are hooked, as illustrated in Fig. l, to provide top support for thecoiled filament 40. The number of supports 24 is determined by the number of coiled'sectionsa in. filament 40.

In the presenti embodiment, this filament 40 comprises 10 coiled sections which are connected. by interrsection uncoiled loops and staggered so that five are disposed in one normally/*vertical plane parallel to that of the conductors I8 and I9 and iive in a normally vertical plane. parallel thereto.` The sections. are. so spaced that.in.planas;shown in Pig;v 3;,.they'lie at the vertices of isoscelesl triangles.

In this. showing the numerals; 4; and 42; re,- spectivelydesignate the rst and: tenth'l sections oilament 40, as the.v fragmentary termnalsec.- tions; thenumerals 43, 44;,45 and. 46; respectively designate the second,l third, eighth'.l and: ninth. sections, that is,.rthe. outer sections; and the: ninV morals. 41, 48, 49' and.- 50; respectivelyV designate the; fourth, fth.. sixth and seventh sections;that is., the; inner. sections.

The upper inter-section,uncoiled4 loops-of: the filament, d. are draped over: ther hookediendsiof: tcpY lament support. wires.- 245 and; the terminal. portions 40. and 41| are respectivelyn electrically connectedzto; conductors 1 8: and i9? by means of theiilament leginsertsf. 2I

The; filament leg. insertsi eachconsists; of.` an; ebliquely L-shaped lead. wire.. suitably nickel; around which has; been Wound; an appropriate coil. having the same: pitch. as; terminal sections 4-.If anddfofla-men-t 40:.. 'helowerrend of; eachinsert 2l is. screwed into the respective termina-l section of. the lament` 40e.. The ytree;` or: upper end .of` eachinsertZ-.I` isf secured, as by welding. to the. upper. or free..end-o.` supporting-conductors I8. and.Y IS..

In order toV position lament 40 between con.- ductors [8a-nd. I9. and allow for expansionv and contraction, a floating bridgeN-issprovided.

The lower uncoiled portions of the connected sections. of. filament. 4D- arev secured by hooks inthe. upper end ot the lower.V lament supports 25 of said bridge` 20. In this showinggthereare four lower supports 25.` This bridge. 2.9. comprises. a vitreous cane. insulator 2s. into. which. the. lower ends of' supports 25' areY embedded. and insulated from each, other,y two, floating. bridge. side. guides 2' anda. fioating bridge. bottom.,guide. 28. The side guidesZ'I', suitably thinmetallic. wires have. their inner ends embeddedfin the. ends. of. the. in.- sulator 2b an their upper ends, looped" about Ieading-in conductors IB and I 9i with. freedom to. slide thereon. The. bottom. guide.v 228,. similar to guides 2T, has its upper. end' embedded. suitablyin the. underside of'insulatcr Z6V and. its, lower end projecting through the top. loop` of. spud 294 which' extends upwardly` from press il' in which its. lower endV is embedded'. Aitor, insertion through. the loop of. spud,29, the.. end. of. bottom guide 28 is bent over to prevent. disengagement.

After a suitable exhaust.' vwhichmay consistof a bake, ii'ush with inert.- gas, such. as nitrogen; and a nal fili of'agassuch asnitrogerr atthe land 46b than in said center sections.

conventional pressure, the lamp is tipped off and the base I3 is applied.

According to my invention, the filament 49 may be manufactured by first machine-winding a differential sectional coil 35, as shown in Fig. 4, having a smaller pitch in the terminal sections 4l and 42 and outer sections 43, 44, 45, 4S than in the inner sections 4l, 48, 49 and 5i] and only a small break or one open turn, such as 0.3 to 0.5 mm., between sections. This may be accomplished by a suitable cam arrangement (not shown) on thecoil-winding machine by feeding the filament wire 30 from a reel 3|, as shown in Fig. 5, over rollers 32 and 33, and winding said wire 30 on a filament mandrel 34.

The differential sectional coil 35 is thenv machine-formed on the bending machine by the method and filament-forming apparatus dis.- closed in U. S. Patent No. 2,449,653, issued September 21, 1948, so that five sections, namely terminal section 4I, outer sections 44 and 43 and center sections 48 and 59 are in a normally vertical plane parallel to a second normally vertical plane in which the other five sections lie. The sections are so spaced that in plan, as shown in Fig. 3, they lie at the vertices of isosceles triangles. While a ten section differential coil is shown as a specific, embodiment of the present invention, it will be understood that my method may be used in making a filament of any desired number of sections.

An alternative method for manufacturing a filament comprises machine winding, as shown in Fig. 5, a continuous coil 36, as shown in Fig. 7, having a pitch which is desired in the later formed four outer sections, namely 43, 44, 45, and 46. Coil 36 is machine bent into filament 40, as shown in Fig. 6, having more turns in said outer sections than in the center sections, namely 41, 48a, 49, and 50a. The four inner or center sections are then stretched downwardly While hot to the same length as the outer sections, thereby forming a filament equivalent to that designated 40.

A further alternative method of manufacture of a filament comprises machine winding a continuous coil 36h, similar to the coil shown in Fig. 7, except having the pitch of the later formed four center sections, namely 41, 48, 49 and 50. Coil 3Bb is then machine bent into filament 40h, as shown in Fig. 8, having more turns in the outer sections, namely 43, 44, 45b The outer sections are compressed under heat to the same length as the center sections, thereby forming a filament equivalent to that designated 40.

A still further method of producing a 'filament comprises machine winding a continuous coil 36 having the pitch of the later-formed outer sections, namely 43, 44, 45 and 46 (not shown). From each end of the coil 36, the required number of turns is selected to form the two outer sections 43 and 44 and 45 and 46 on each end, and terminal sections 4l and 42. The middle of coil 36 is then stretched while hot to give the desired center sections pitch. Coil 38, as shown in Fig. 9, is machine formed into lament equivalent to that designated 40, as shown in Fig. 2.

While preferred embodiments of my invention have been disclosed, it will be understood that modifications may be made Within the spirit and scope of the appended claims. Y

I claim:

1. A filament for an incandescent electric lamp having a plurality of coiled sections comprising terminal sections, outer sections and center sections united by looped portions, said outer sections having the same pitch as said center sections and a different length than said center sections whereby said filament may be distorted so as to make said center and outer sections corresponding in length and simultaneously the pitch of the center sections different from that of said outer sections.

2. A filament for an incandescent electric lamp having a plurality of coiled sections comprising terminal sections, outer sections and center sections united by looped portions, said sections so spaced that half of the sections are in a normally vertical plane parallel to the remaining sections in a normally vertical plane and that in plan said sections lie at the vertices of isosceles triangles, said outer sections having the same pitch as said center sections and a different length than said center sections whereby said filament may be distorted so as to make said center and'outer sections corresponding in length and simultaneously the pitch of said center sections diferent from that of said outer sections.

3. A filament for an incandescent electric lamp having a plurality of coiled sections comprising terminal sections, outer sections and center sections united by looped portions, vsaid outer sections having the same pitch as said center sections and a longer length than said center sections whereby said center sections may be stretched to corresponding length so as to simultaneously make the pitch of the center sections larger than that of the outer sections.

4. A filament of an incandescent electric lamp having a plurality of coiled sections comprising terminal sections, outer sections and center sections united by looped portions, said outer sections having the same pitch as said center sections and a longer length than said center sections whereby said outer sections may be compressed to corresponding length so as to simultaneously make the pitch of the outer sections smaller than that of the center sections.

5. A filament for an incandescent electric lamp having a plurality of coiled sections comprising terminal sections, outer sections and center sections joined together at their ends, said outer sections having the same pitch as said center sections and a different length than said center sections whereby said filament may be distorted so as to make said center and outer sections correspond in length and simultaneously the pitch of the center sections different from that of said outer sections.

' NICHOLAS' J. RAINO'NE.

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

UNITED STATES PATENTS Number Name Date v 1,632,769 Severin June 14, 1927 1,726,480 Fehse Aug. 27, 1929 2,167,765 McGowan Aug. 1, 1939 2,434,478 Allen Jan. 13, 1948 2,449,653 Isaac et a1. Sept. 21, 1948 2,449,679 Van Horn Sept. 21, 1948 Y

Images