Патент USA US2110590код для вставки
lvlarch~ 8, 1938. J, F, CQQK, JR 2,110,590 REFLECTING INCANDESCENT LAMP Filed Sept. 11, 1936 . 1770621502" by W// 7(mgk/1/W ‘I? QM. viormjgs Patented Mar. 8, 1938 " 2,110,590 UNITED STATES PATENT ‘ OFFICE ’ 2,110,590 REFLECTING INCANDESCENT LAMP Joseph Francis Cook, Jr., West Roxbury, Mam, assignor to Birdseye Electric Corporation, Dover, DeL, a corporation 01 Delaware Application September 11, 1936, Serial No. 100,285 7 Claims. (Cl. 176-34) This invention relates to' improvements in the design and construction of incandescent lamps and particularly incandescent lamps having a part of the bulb surface coated with a re?ecting 5 material arranged to re?ect a large part of the rays from the‘ incandescent source and concen Fig. 4 is a sectional‘ plan view showing the loca tion and shape of the V-shaped ?lament. One satisfactory re?ecting medium for lamps of my invention is metallic silver deposited upon the inner surface of the bulb in accordance with 5 the process of Pincus Deren disclosed in applica trate and direct them on the area of useful work. tion Ser. No. 42,227, but the invention is in no The particular improvements of this invention concern the shape and curvature of that part of 10 the lamp bulb which determines the shape of the re?ecting surface. I have discovered that im proved results in certain ?elds may be secured by shaping a re?ecting portion of-the bulb as a sense limited to the employment of metallic silver nor to locating the re?ecting medium upon the paraboloid of revolution, expanded until its focus, or the locus of its focal points, constitutes a circle of appreciable diameter and employing in the bulb an extended ?lament concentrically or symmetrically disposed with respect to such circle. An incandescent lamp so designed and 20 constructed is e?ective to throw a very bright spot of light on the center of the area to be illu minated, and a gradually diminishing amount of inner surface of the lamp bulb. For purposes of 10 illustration, however, two lamps are shown which are provided with an inner coating of silver form ing re?ecting areas. The bulb of the lamp herein shown is sym metrical about its axis and the re?ecting surface is therefore also symmetrical, and may be ac 5 curately described as a surface of revolution, formed by rotating the trace l0—l2 in Fig. l, for example, about the axis of the bulb. The trace of this re?ecting surface, however, was not devel- 0 oped about the axis of the lamp. It bears a de?nite relation to this axis, and can be de?ned That is, the area by a mathematical equation using the bulb axis , around the spot is brightly illuminated—less as one of the rectangular co-ordinates, according 25 brightly than the spot however-and the inten sity in this larger area of reduced illumination gradually fades out at the far edge of the illu ever, it is much simpler to de?ne the curvature of ' light on the surrounding area. minated area. ‘ Such lamps are useful in large store windows, for example, where the central 30 exhibits require bright spots of light, and where the rest of the window requires .a reduced inten sity of illumination, or in lighting gasoline ?lling stations, where much light is required near the Q Li pumps and a reduced amount elsewhere in the yard. The gradually reduced intensity of the outer zone permits these lamps to be grouped so that the light patterns overlap, without produc ing unsightly rings or bands of light and shade. These and other features of the invention will 40 be best understood and appreciated from the fo1 lowing description of preferred embodiments thereof, selected for purposes of illustration and shown in the accompanying drawing in which, Fig. ‘1 is a view of the lamp shown somewhat conventionally in cross section, Fig. 2 is a similar view of a lamp of somewhat ' different design, Fig. 3 is a polar diagram of the light emitted by the lamp of Fig. 2, and to the practice of analytical geometry. How- 25 the re?ecting surface in terms of the method by which it was designed. The trace of the re?ect ing surface from l@--l2 in Fig. 1, forexample, is a portion of a true parabola; however the 30 re?ecting surface is not a paraboloid of revolu-v tion about the axis 20-22 of the parabolaas are the ordinary parabolic re?ectors, such as those used in automobile headlights, for example. Such parabolic re?ectors are designed to operate 35 with a source of light ‘thatis as nearly as possible a point source, and which is located in the main axis of the paraboloid of revolution and at its focus. In the production of commercial lamps of high wattage-from 100 watts and above—it is 40 impossible to make use of ?laments that ap proximate a point source, since even pure tung sten would melt under such conditions. Gen~ erally a ?ne coil of fine tungsten or other'suit able wire is suspended in loops or in a circle of about 1/2" in diameter to several times this size in lamps of high wattage. If such a ?lament is suspended at or near the focus of a true para bolic re?ector, generated by revolving a half, parabola about its axis, there is obtained not a 50 9,1 1o,soo spot-light but a mottled arrangement of brilliant and less brilliant light directly in front of the parabolic re?ector with much "scattered and mottled light over a considerable area. In the lamp of my invention I desired a strong spot of light directly in front of the re?ecting bulb-in line with the axis of the lamp-sur rounded by a ?eld of diminishing intensity. However, no part of the field should be mottled 10 with light of varying intensity, and for practical reasons a point source can not be used. To accomplish this desired‘ result I have de signed the outer or lower part of the re?ecting surface of my new lamp so that it is generated 15 by revolving the parabola l0—-|2, Fig. 1, about the axis of the mount, and therefore the axis of the bulb itself, but while maintaining the focus of the parabola in the circle of the ?la ment, the axis of the parabola being maintained 20 parallel to the axis of the mount. Thus the shape of the parabolic portion of the re?ecting surface with respect to each point on the ?la ment however, is limited in extent in each case to a line lying in a plane determined by the point in question on the ?lament and the axis of the lamp. ‘Those areas of the bulb-and therefore re?ecting surface-lying adjacent to this line are approximately parabolic with respect to this same point on the‘ ?lament and for an appreci able re?ecting area surrounding this line approximately focus the light from this source. 10 The rest of the re?ecting surface, located above the plane of the ?lament re?ects light falling on it from this same point source in a more and more widely divergent direction, divergence in creasing with the distance from the parabolic 15 axis, and this divergent light, from the in?nite number of point sources which compose the cir cular ?lament comes an important part of the total used to illuminate the larger ?eld of gradu ally diminishing intensity, surrounding the cen 20 tral brightly illuminated spot. Thus it will be seen that the re?ecting sur surface becomes a paraboloid of revolution in which each element has been displaced outward . face, with the parabolic trace, below the plane of the ?lament concentrates a considerable part of ly with reference to the axis of the mount a dis 25 tance equal to the radius of the circle of the the light falling on it in a spot directly in front of 25 the lamp and in a line with the axis of the bulb ?lament. It will be seen that under these cir cumstances the locus of the focal points of all and tends to surround this spot with a ?eld of the displaced elements of this paraboloid of gradually diminishing intensity. ‘Added to this effect is the direct light from the revolution lie in the circle which also contains ?lament that passes through the transmitting 30 30 the ?lament: or that the mraboloid has been ex panded until its focal point becomes a locus of portion 28 of the bulb, which, without any re?ec tion, fans out with constantly diminishing in points which is a ring coinciding with the gen eral contour of the ?lament or circumscribing tensity, on a plane surface perpendicular to the axis of the lamp, being brightest at a point the ?lament. 35 It will be understood that by a circular type nearest to and directly in front of the lamp, on 35 ?lament I mean one which lies in a plane and the axis of the bulb, thus actually aiding in pro which is approximately a circle or inscribed in or ' ducing, the desired effect. The rest of the re?ecting surface within or circumscribed about a circle so that the distance between the wire of the ?lament and the nearest 40 point in the bulb is as uniform as possible. Such a circumscribing circle is shown in dot and dash lines in Fig. 4 and this may also represent the above the plane of the ?lament requires special consideration. One of the great dimculties in using a true parabolic re?ecting surface in con nection with a ?lament operating under a rela focal circle of the parabolic re?ecting portion of tively high wattage-400 watts for example-and the bulb. Obviously there must be an open 45 space where the end of the circular ?lament joins the lead-in wires, and which cannot be closed without short circuiting the ?lament. A V-shaped ?lament, or a ?lament of almost any other shapeof which all parts are located in a with the ?lament located at the focus, is the fact that in parabolic re?ectors of reasonable design, 50 single plane perpendicular to the axis of the mount, and disposed within the limits of the circle which is the locus of the focal points of the paraboloid and which are substantially uni formlyspread over the area of this circle, will 55 produce satisfactory and substantially accurate results with the re?ecting surfaces disclosed, since, as has already been stated the purpose of the lamp of this invention is to produce a bright spot surrounded by a ?eld of gradually diminish ing intensity of illumination rather than to pro duce a clear-cut light spot. The coiled ?lament has two traces I4 and I 6 where it cuts the plane of the paper, as shown in the drawing Fig. 1. The ?lament trace I4 is 65 at the focus ofthe partial parabola l?-IZ, and the dotted curved line It indicates the completed half-parabola, having an axis 20-22 extending through the focus l4 and parallel to the main axis 24—26 of the bulb. The other trace ii of 70 the ?lament bears the same relation to the par tial parabola on the near side of the drawing. Thus it will be noted that for each point on the ?lament there is a true parabolic re?ecting sur face, approximately at the focus of which lies 75 that point of the ?lament. This true parabolic the focus is very close to the apex of the re?ector. It is well understood that a parabola may vary in shape depending on the mathematical for mula for the particular curve in question. It may be slender and narrow, or it may be broad and ?at. A narrow, slender parabola has its focus much closer to the apex of the parabola than a broad ?at parabola, and the broad ?at type are not desirable for use in re?ecting lamps of this type for several reasons, although it would be possible to use a broad ?at parabolic re?ector, the focus of which was at a sufficient distance from the apex of the paraboloid so that an incandescent ?lament of relatively high watt age could be used without injuring the glass. Such broad ?at parabolas, used as the basis of a bulb for a re?ecting incandescent lamp, would make much too large and bulky a bulb for prac tical purposes-much larger than the normal vol ume requirements for a given wattage, and this effect would be greatly exaggerated if the par abolic surface were extended soas to hood the ?lament, and produce a cone of light, the outside edge of which would make some desirable angle with the axis of the cone, of say, 60 or 75°. In the 70 past, efforts to avoid this dii?culty with a par abolic re?ecting lamp have resulted in an arbitrary enlargement of the lamp bulb at the apex of the parabolic cone, simply to make greater the distance, between the bulb and the .15. 2,110,000 ?lament at the focus of the parabolic part of 3 ' ly re?ected through the opposite ?lament trace the re?ecting surface. In the case of a‘ re I 4. All other rays leaving trace ii on the ?lament . ' ?eeting type lamp, this would result in a hit will be re?ected by the globular part of the re ?ecting surface through points near the trace l4, and at gradually increasing distances from II or miss re?ection of the light falling on this part of the re?ecting surface, and the generally desired true spot light'would not be obtained. as the angle of the plane containing the ray In the lamp of the present invention the globu lar part of the re?ecting surface, above the plane of the ?lament is designed as a particular surface 10 with respect to the circular ?lament, and in such under consideration makes a greater and greater angle with the plane of the paper. On allrother planes through the axis of the lamp. there will‘ be two traces similar to I‘ and I6, and to light a way- that the're?ected rays from this part of . from this in?nite number of point sources on the the re?ecting surface act as much as possible in substantially the same wayv as those from the parabolic part, and actually serve to reinforce the 15 e?ect of the re?ected light from the parabolic surface. Moreover, by this design, although from neither part of the re?ecting surface is all of the re?ected light sent out in parallel rays, a large circular ?lament can be applied this same dis; cussion. Thus it will be seen, that light re?ected from the globular part of the re?ecting surface, is in part accurately emitted as parallel rays to 15 produce a centrally located brilliant spot of light, and the rest of the light will be distributed over a larger area, and at an intensity which gradually part of the re?ectedlight is so emitted, thus form diminishes as the distance from the central spot of light increases. This gradually diminishing in 20 20 ing the desired spot at the center of the illumi nated area, and all the rest of the light from the tensity feature of the larger area around the cen ?lament is emitted in a larger surrounding cone tral spot is of great importance, and it is apparent of gradually diminishing intensity, brightest at that any abrupt ‘changes in re?ecting angles of the center and diminishing to a low valueat the the re?ecting rays, from any point source on the N, GI edge of the cone. As has been pointed out above,’ ?lament under consideration, as they gradually 25 this gradual diminution of intensity toward the edge of the illuminated ?eld, without mottling, diverge from the direction that produces parallel is a most important characteristic of this partic changing intensity, and a mottled illuminated area would result. ular lamp. The direct light from the ?lament, as 30 is well understood, meets this requirement; that from the parabolic part of the re?ector does, also, as has been explained above; and the re?ected light from the globular part of the re?ecting sur face also does, since it is used to reinforce the re?ected light from the parabolic part ‘of the re?ector, as is shown directly below. The globular part of the re?ecting surface is rays, would tend to produce an area of rapidly ' . Thus it is apparent that the re?ected light from 80 the globular re?ecting surface tends to reinforce the effect from the parabolic portion, and that light from these two surfaces together with the direct light from the ?lament all contribute to the desired ?nal result of a bright spot, centrally 35 located, surrounded by a larger area of gradually diminishing intensity, and without any abrupt composed partly of the re?ecting surface of the ' changes in the intensity of illumination of the 40 ?oor area, for example, below the lamp. ‘The globular portion of the bulb has also the 40 bulb, indicated by the trace l0--30 in Fig. 1, and partly of the re?ecting barrier, 32, which is preferably a bright white metal upwardly con important function of spacing the re?ecting coat vex disk supported in any desired manner in the ing sufl‘lciently from the incandescent ?lament to location suggested in Figs. 1 and 2. The curve of this combined re?ecting surface is continuous, except for a small space between the bulb walls and the re?ecting barrier 32, and the curve is a somewhat ?attened circle and may be considered to be an ellipse of which two points M and I6 are the two foci, these points also being the trace of the circular type ?lament with the plane of the paper. It is well understood that a re?ector shaped in the curve of an ellipse and receiving an incident ray from a source located at one focus will re?ect the my back to the other focus. In (:1 LI any case the curve as shown and as used for this symmetrical globular portion of the re?ecting sur face is such that light striking. it in the plane of the paper, for example, from trace l6 of ‘the ?lament will be re?ected back through trace l4 (50 and vice versa. Thus such a ray, after being re?ected by the globular portion of the, re?ecting surface will appear to emerge from a point on the ?lament directly opposite the point on the ?lament where it was originally generated. It will thus act merely to reinforce the light coming from the point on the ?lament directly opposite and will either appear to emerge through the transmitting portion of the bulb as a direct ray or be re?ected a second time from the parabolic part of the re?ecting surface, and, for example, emerge as one of the parallel rays forming the centrally located bright spot. \ In the elliptical re?ector- of my invention, it is apparent that only the rays leaving the ?lament trace l6 in the planeof the paper will be accurate permit convection currents of gas to pass across the re?ecting surface and by the distance and cooling effect thus provided to obviate damage to 45 the coating which might otherwise be caused by over-heating. ‘ I do not desire to be limited in my invention to the exact design, shape and measurements shown in the accompanying drawing, since it is apparent that larger sizes, for example, or lamps giving a'larger bright spot, or a less marked dif ference in illumination between the bright spot and the surrounding less brilliant area, could readily be designed and manufactured from the 55 disclosure given and without departing from the actual invention. The lamp shown in Fig. 2 is of slightly dif- ' ferent shape from that illustrated in Fig. 1 but it corresponds in construction thereto. The por 60 tion generated by revolving parabolic trace 50-52 about the axis 64-66 of the bulb is provided with an internal coating 5| of metallic silver. The parabolic axis of this trace is shown at 60-62. The small circles 54-56 indicate the traces with the plane of the paper of a ring shaped ?lament which is the locus of the focal points of all the parabolic elements of this sur face. The portion of the bulb generated by re volving the trace 50-10 about the axis of the 70 bulb, together with the upwardly convex re ?ecting barrier 12 constitute a ?attened spherical re?ecting surface acting upon the light rays as already explained in connection with the lamp of Fig. 1. The ?attened transmitting portion 4 9,110,590 with a mount therein, and a ?lament coiled in Bl may be clear or frosted as desired and, of course, may have a greater or lesser radius of curvature than as illustrated. The stem, mount helical fashion and arranged as a ?at loop, a por tion of the surface of the bulb serving as an e?icient re?ecting surface and being divided into and lead-in wires are omitted in Figs. 1 and 2 since they may be of any conventional or com mercial construction. two parts, one a paraboloid of revolution which is a surface generated by revolving a partial parabola about the axis of the bulb and at a - As one example of a bulb of satisfactory shape to accomplish the results above discussed, the constant distance from said axis, so that the focus ‘of the parabola transcribes a circle about - dimension of that shown in Fig. 2 may be as fol said axis, and said circle determining the posi 10 10 lows, where it is assumed that the "diameter of the circular axis of the ?lament is 0.86, inch: - statlon Distance 0 tion of said filament, and a second re?ecting portion beyond the ?rst, the surface of which is a ?attened hemisphere and shaped to re?ect the Outside to station bulb radius light from one or more points on the ?lament back to the ?lament at a point directly across 15 from the point of emission, said second re?ecting ~ 15 0.15 0.50 0.25 0.00 0.25 0.50 0.15 1.00 1.25 1.50. 1.15 2.00 2.25 2.50 20 25 2.68 0. 00 1.04 1.15 portion thereby shaped to reinforce the light fall ing on the parabolic re?ecting surface. 4. A re?ecting incandescent lamp having a 1.21 1.38 1.54 1.00 1.81 1.04 2.05 2.11 2.21 2. 31 2. 40 symmetrical bulb, a mount and a ?lament ar faces of which the principal surface is formed by revolving a parabola about the axis of the mount at a constant distance therefrom so that 25 __________ -_ 2.15 0.00 s. 25 3.50 s. 05 the focus of the parabola describes a circle about the axis of the mount and this circle coincides substantially with the circle bounding the ?la ment, the said parabolic surface having its fo cus relatively close to its apex and terminating at the level of the plane containing the ?lament, 2 45 2.20 1.00 1. 01 0.00 30 In Fig. 3 is shown a polar diagram showing the distribution and intensity of the light emitted by the lamp of Fig. 2. This indicates a very high the secondary portion of the re?ecting surface being globular in shape and located between the ?lament and the base of the lamp. intensity of light within a cone having an in 35 cluded angle of 26°, a concentric cone of rapidly 5. A re?ecting incandescent lamp including in 35 decreasing intensity out to an included angle of its structure a bulb having a ?lament arranged in a plane at right angles to the main axis of the bulb, the bulb being shaped and coated to pre sent an integral and continuous re?ecting sur 76° and an outer concentric cone of less rapidly decreasing intensity out to an included angle of 100°. It will be understood that the light dis face including a substantially parabolic portion 40 truncated and terminated approximately at its focal plane and supplementediby an enlarged globular portion located between the ?lament and the base of the lamp, the plane of said ?la ment coinciding substantially with the focal plane of the parabolic portion of the bulb and both portions of the bulb cooperating to direct the light of the lamp in a concentrated beam, while the'globular portion furnishes space for 40 tribution‘ indicated in this diagram is merely typ= ical of that derived from one lamp constructed in accordance with my invention, and that the angles mentioned may be varied within a con siderable range by appropriate modi?cation of 45 the bulb dimensions. ' Having thus described my invention, what I claim as new and desire to secure by Letters Patentof the United States is,— 1. A re?ecting incandescent lamp having a bulb 50 shaped and coated to present a re?ecting surface convection currents of gas tending to cool the re which is a paraboloid of revolution expanded until the locus of its focal points constitutes a circle .of appreciable diameter, a ?lament located in the plane of the focal points of said parabola, 55 and a concave globular re?ecting surface of dif ?ecting coating of the bulb ‘and so prevent dam age from overheating. 6. A re?ecting incandescent lamp including in its structure a symmetrical bulb having a para bolic outer portion and a bulging elliptical inner - ferent curvature located behind the focal plane portion, a mount, and a ?lament disposed in a of the parabolic portion of the bulb and shaped single plane which is perpendicular to the axis so as to ‘aid in re?ecting rays from the lamp in of the mount and which includes the focus of said a'cone of divergent rays of intensity diminishing 60 from the center outwardly. 2. A re?ecting incandescent lamp having a bulb shaped and coated to present a re?ecting surface which is a paraboloid of revolution expanded until the locus of its focal points constitutes a circle 65 of appreciable diameter, a ?lament located in the plane of the focal points of said parabola and acting to supply a reinforced beam of light as substantially parallel rays, and a ?attened hemi spheric-a1 re?ecting surface located behind the 70 focal plane of the parabolic portion of the bulb and shaped to re?ect rays from the ?lament so that these re?ected rays reinforce the partial focusing action of said parabolic portion of the parabolic portion, the bulb providing a re?ecting surface formed by revolving about the axis of the 75 re?ecting surface. 3. A re?ecting incandescent lamp having a bulb 20 ranged concentrically with respect to the bulb, the bulb presenting cooperating re?ecting sur 50 mount, and at a distance therefrom, a compound continuous curve, the outer part of which is a partial parabola and the inner part of which is a partial ellipse, the two parts of such curve having a common focal point which lies in the said plane~ 65 of the ?lament of the lamp and describes a circle in the revolution of said compound curve. 7. A re?ecting incandescent lamp including in v its structure a bulb having a coiled ?lament ar ranged in a plane at right angles to the main ' axis of the bulb, the bulb being shaped and coated to present an integral and continuous re?ecting surface including a substantially parabolic por tion truncated and terminated approximately at its focal plane and supplemented by an enlarged 2,110,690 5 globular portion located between the ?lament ' convection currents of gas tending to cool the re ?ecting coating of the bulb and so prevent dam age from overheating, and’ a re?ecting disk lo plane of the parabolic-portion of the bulb and - cated in the bulb as a substantial continuation'of ' ' 5 both portions of the bulb cooperating-to direct said globular portion. and the base of the lamp, the plane of-said ?la ment coinciding substantially with the focal the light of the lamp in a concentrated beam, ' while the globular portion furnishes space for _ JOSEPH FRANCIS COOKJIRY.