US2617062A - Electric incandescent lamp - Google Patents

Description

J. RUNDERS ELECTRIC INCANDESCENT LAMP Nov. 4, 1952 2 SHEETSSHEET 1 Filed April 11, 1950 INVENTOR J-OHANNES RIJNDERS AGENT Nov. 4, 1952 J. RIJNDERS ELECTRIC INCANDEISCENT LAMP Filed April 11, 1 950 JOHANNES R 188% Patented Nov. 4, 1952 UNITED STAT ES PAT EN T" OFFICE ELECTRIC .INCANDESCENT' LAMP Johannes Rijnders; Eindhoven; Netherlands assignor to' Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application April 11, 1950,-Serial l\lo.-1 55 ,238

Inthe Netherlands April13p1949 This invention relatesto electric incandescent 1amps,. particularly for. use in vehicle lighting, which comprise .at least onefilament and a cupshaped screen, andlin which the filament" is located between at least two lateral edges of the screen.

Such lamps are arranged in a spotlightv or headlight in such manner. thatthe filament extends substantially in the optical axis of'the optical system of the spotlight. This optical system usually consists of- 'a reflector shapedin the form of a parab'oloid of revolution. The screen serves to prevent light from-falling on one side of. the reflector, thusobtainin'g the so-called dipped? lighting, when the. light is directed solely below the horizontal plane extending through the lamp. Thescreengenerallyconsists of a metal. cup-shaped hoodgfor. example, of nickel, arranged in close proximity to the filament in the lamp. The. screen is, generally of a small size, in order to intercept a minimum quantity of light from a secondl'filament generally provided in the lamp, calledlthe main filament herein, which produces..the.undipped or. normal beam. The firstrfilament is calledthe dipping filament herein. If only the latter is-provided in the lamp, there .isgenerallyi no objection to makingthe screen considerably larger and applying it, for exampleinthe formv of'a mirror or a layer of lacquer, on to the lampbulb.

If a screen isiarranged transversely of the optical axis of thelightbeam and atawdi'stancaior example m., in. front oisthela'mpaa patch of light viz. the beam pattern is.projected.thereon. By operating alternatively one filament. or the other, a so-called main and la .dipped? beam is produced respectively, thebeam patterns of 'most lamps being substantially circular,.semi-circular or approximately elliiaticaL. It is to be noted that in the present case referenceismade only to co-operation of the lamp with. an optical system having rotationalsymmetry, suchlasthe aforesaid refiectoninorder to make the properties of the lamp better understood. Consequently no reference is made. to the .use. ofimeans, such-as ribbed refiectorsof' front glasses, for directing the light.

The well-known lamps produce a' dipped beam pattern having. a comparatively large radius, 1. e. that a greatly diffused beam is produced ina ,verticaldownward direction, a large part of the light flux produced'bythe dipping? filament being projected Ontotheroad at a comparatively short distance infront of thevehicle. As. a resultof this illumination thesensitiveness of a drivers" eyes-"'adiiists"itself to thisbri'ght illuminationoccupying a considerable part of his field of view, so that he is handicapped inobserving' more remoteobstaclesfi The inventionhas forits obje'c't inter aliato mitigate this limitationand to" provide a construction of lamp which gives-fdipped lighting and permits'th'e light 't'obe radiated in thfo'rm of a beam, whichisccmp'aratively litt l-e 'difi iised, and at a considerabledistancein iron-tot the vehicle:

According to the-invention} the filament is located-between atleast two-side walls of the screen; is'V-shaped"and"extends in aplane which is parallel to or-coincides'with the plane through the edges of the-screen: Iiia" normalheador spot-light comprisin'gf'a reflector in the-former a paraboloid of revolution, this lamp should be arrangedsuch' that the" plane of the" filament extends horizontally" slightlyabove the axis of the reflector'and 'the top of the v shaped filament is near the focus'of therefl'ectbr, the limbs ofthev extending on-eitherside-above the axis. This resultsiir a beam pattern; the sectional area" of whichis approximately" se'mi elliptical with a' small elevation: the highest luminous intensity being just below'the upper boundary: It is this luminous intensity whicnenab'les obstacles to bemade-visible at'a great-'di'stancein front of the vehicle.

It is pointed out that v -snaped filaments are frequentlyused" as main filament lamps for vehicle lighting: Thisshape has' al'sobeenused for'the dipping filament but, fbfthis purpose, not" combined with" a screen, andin a: difierent position (British patent specification440g956aiid American" patent specification" 2,214,472) The filamentsarranged betweenthe edgesof 'a screen were" generallyre'ctilinear' (for example" British patent specifications" 442;939and "393386) v Inorder that theinventionmaybe readily carried into efiect', a" number of "examples will now be described more" fully" with reference to the accompanyingdrawings, in which:

Figs". 1 and' l. are diagrammatical vertical sectionsiof headlights comprising a" lampiofkno'wn type'and of avarlant thereof respectively;

Figs." 2 and 5""areplan'viewsof these lamps;

Figs: Band "(ishdwth'e beam'pa'tterns produced by $11 lamps?" Fig. '7 is a diagrammatical lioi'izoiital-sectionof a lamp according to the invention without screen and dipping filament;

Figs 8 and l0 show diftrentforms of a 'dipping filament according tothe invention Fig. 11 is a diagrammatical vertical section of a headlight comprising a lamp according to the invention;

Fig. 12 is a plan view of the lamp according to Fig. 11;

Fig. 13 shows the beam pattern of the lamp according to Fig. 11;

Fig. 14 is a diagram of the light distribution produced by a known lamp and by a lamp according to the invention;

Fig. 15 shows the beam pattern of an incandescent lamp comprising an asymmetrical V-shaped filament;

Fig. 16 is a plan view and Fig. 1'7 a side view of an incandescent lamp and a screen of a lamp according to the invention;

Figs. 18 to 20 are a plan view and two side views respectively of the filament body and the screen of a lamp in a modified embodiment and Fig. 21 is a plan view of a filament and screen in a third embodiment.

The lamp shown in Figs. 1 and 2 comprises a bulb l, a main filament 2, a dipping filament 3, a screen 4, a cap 5 and a few parts (not shown) such as supporting wires for the filaments and the screen, and the pinch in which these wires are secured. The lamp is arranged in a reflector 6 having the shape of a paraboloid of revolution. The lamp is adjusted in a manner such that the main filament 2 is located at the focus F.

A light ray I from the main filament 2 will extend, subsequent to reflection by the reflector E, parallel to the optical axis 8 of this reflector. A ray 9 from that part of the clipping filament 3 which is nearest to the focus F, extends, subsequent to reflection, in a slightly slanting downward direction, whilst a ray in from that end of the clipping filament body which is most remote from the focus F has a steeper slope.

In the present case, the filament 3 is located between the edges H, l2 and 13 of the screen 4 (Fig. 2). These edges extend approximately in one plane with the filament. Only the edge 14 does not extend in the plane but extends in a higher plane, in order to prevent light directly from the filament 3 from shining on approaching trafiic. These edges form the upper boundary of the side walls.

Where in the present specification reference is made to a filament extending in a plane, it should be considered that a filament naturally has certain dimensions and cannot coincide mathematically with a plane, so that such reference is to be taken colloquially.

The beam pattern produced by this known lamp consists of the images formed by various parts of the reflector of the filament. These images may be shown separately by shielding off the remaining reflector parts. Thus, vertically below the point of intersection B of the optical axis 8 with the screen, a series of images 15 is formed by the reflector parts located in or near the vertical plane through the optical axis 8. The series of images 16 and I! through the said axis on either side of the lamp (i. e. under or above the plane of the drawing in Fig. 1). The reflector parts located between these limits form series of images, for example, the series 18 and I9. The whole light falls, however, below the horizontal plane through 0, owing to the presence of the screen 4 which prevents light from falling on the lower reflector part and owing to the position of the filament 3 in front of the focus F and slightly above the axis 8.

From the foregoing it will be seen that the diameter D of the dipping beam is substantially proportional to the length of the dipping filament L (Figs. 3 and 1). Due to the comparatively great length of such a filament, the beam has such a diameter that a great part of the light flux is projected on to the road at a short distance in front of the vehicle.

If the dipping filament is arranged transversely of the axis at the focus F, as shown in Figs. 4 and 5, this would yield the beam pattern shown in Fig. 6. The reflector parts located in or near the vertical plane through the axis 3 form elongated, horizontal images 20 of the filament 3; reflector parts located in or near the horizontal plane through the axis 8 produce comparatively short, compact images 2! near the axis passage 0. The intermediate reflector parts, consequently located in oblique planes through the axis, produce a number of oblique images 22 located in part above the horizontal plane through the axis. This proves that, in spite of the presence of the screen 4, a pure dipped lighting is not produced. Furthermore it is obvious that this effect is the more troublesome, according as the filament 3 (Fig. 5) is longer and protrudes more on either side of the axis.

On the other hand it appears from Fig. 1 that the reflected light from part of the filament is more reflected downward as this part is more located in front of the focus (see for example light rays I, 9 and I0 in Fig. 1). The oblique images 22 (Fig. 6) can thus be prevented from extending above the horizontal plane by placing the filament body 3 at an adequate distance in front of the focus.

In this event, however, the images 26 also descend, so that an unduly strong front illumination is produced.

The invention is based on the recognition that the optimum beam pattern is produced, if the filament is kept within the limits of an angle 23 (Fig. 7), the apex of which is at the focus F and which extends on both sides of the axis 8. The ideal shape of the filament would consequently be a triangular luminous surface. Although such a filament is feasible, for example, in the form of a tungsten plate which is heated to a high temperature by the passage of current or by gas discharge, a suificient approximation is obtained in practice with the use of a normal coiled filament which is bent with two limbs forming the said angle 23, as shown in Fig. 8. If the angle formed by one of the limits of the angle and the axis 9 be 18 (Fig. '7), it is found from experiments with different conventional reflectors that this angle may be between 60 and 15 (Figs. 9 and 10). In a very suitable form, a=30 (Fig. 8). The V-shaped filament will usually be arranged symmetrically with respect to the axis of the lamp, but sometimes a nonsymmetrical arrangement may be advantageous, for example to cause more light to shine on one road half than on the other road half.

Figs. 11 and 12 show diagrammatically the use of such a lamp in a reflector. The reference numerals correspond to those used in Figs. 1, 2, 4 and 5.

Fig. 13 shows the beam pattern produced by several parts of the reflector. The reflector parts located in or near the vertical plane through the axis produce a series of images 24. They are magnified images of the V-shaped filament. The reflector parts located in or near the horizontal plane through the axis are facing, as it a civpac 5. were; the side of the gv shapeda filament-and coni sequently do not reproduce Vj 'b itarectangle so that two series of images 25 are'produced to the left and to the right of the axis 0, of which onlyone series is-shown. -The intermediate reflector parts View.v as it were, the filament body in an oblique direction so that the V is shortened with a smaller .apex;.than.the.virtualone. Such reflector parts produce, for example, aseriesof images 26,. l

The better light distribution ensured by the use of a lamp according to the inventioni's illustrated- Fig. 14-. The 1 diagram shows 'the measuring resultsof the illumination intensity on ascreen arranged at rightangles to the axis of this beamlight and at ajistance of, ill n. in front'l l etbof. The distances" 'Qve and; below thefaxi areindicated' m c The 'beamligh't is arranged at the height of'l m. The light striking the screen 20 cms. below would strike the road at a distance of 50 m. in front of the vehicle, and the light striking the screen 80 cms. below 0 would strike the road at a distance of 12.5 m. in front of the vehicle.

The full line 21 indicates the illumination obtained with the use of a lamp hitherto employed, in which the straight "dipping filament extends just above the optical axis (wire 3 shown in Figs. 1 and 2), whereas the broken line 28 indicates the illumination obtained with the use of a V-shaped dipping filament according to the invention (the wire 3 shown in Figs. 11 and 12). As appears from the points of intersection with the lines 29 and 30, which indicate the illumination intensity at distances of 50 and 12.5 m. respectively in front of the vehicle on the road, the former has become twice as high and the latter has decreased to one half.

The beam pattern shown in Fig. and the diagram shown in Fig. 4 are obtained with the use of V-shaped filaments, the lengths of the limbs being equal. If the length of one of the limbs is increased relatively to that of the other, the diameter of the beam pattern again increases. This increase is generally undesirable, but in view of the fact that the radius of the beam pattern in one direction increases more than in the other, it may in some circumstances be an advantage to use an asymmetrical v, for example ii. it is desired to direct a stronger light flux to one side of the road. The beam pattern produced by such a lamp is shown in Fig. 15. The reflector parts located in or near the vertical plane through the axis produce a series of images 24' of the filament two of which are shown. The reflector parts extending in or near the horizontal plane through the axis produce two series of images 25' and 25" which are asymmetrical, similarly to the filament. The reflector parts extending in oblique planes through the axis produced series of image '26 and 26". From the figure it appears that the vertical diffusion is still smaller than that of a suitable filament (Fig. 3), and show that an improvement in luminous intensity is obtained close below the horizontal outline of the beam.

The methods of construction of a lamp according to the invention need not depart considerably from the methods used for known lamps comprising a dipping filament. In the latter, one end of the straight filament is usually welded to the screen, while the other end is secured to a terminal wire. The V-shaped filament in the lamp according to the invention may be suspended in the same manner, as shown in Fig. 15.

The scr ee'rrd isi securedi-zat one. side ;,tO. a; supply. conductor -3 I and:- thev shapedi-i filament 35. is. suspended between one oi the edgesof the' screen and a. second:supply.condi1ctor...13-22- The shape of the screen ismatched to that; ofethe filament, so .that i the edges. 1 3:;and I35: extenclz-p'arallell; to the-limbs ofithewirelx A; l furtheri construction is, shown in: Figs. 18'; IQ -andeZOl 'Ihe ends :ofzthe filament 3..areeach secured to a supply conductor 3t: and-132a respec.-. tively; This'apermitsz morelfreedom in. the farrangementofs these ends .than .in. the. constructtionslshown in:.1 'igs.. 16 and I7,- in which oneend invariablyllies. on. :edge of I the-.screen. (At this enda staywire could-, oficourse, be .welded to the screen, but. then: an additional element x is 1'62- quiredJ- v Inuthe-iconstruction shown: in Figs. -18 1:0 20 the screen his: provided at' the rear side and the top. with. a. groove or. indent: which 'is prolonged about the edge formed by the transition of these sides. The stay wire 3| is secured by welding in this groove. In this way the position of the screen is fixed unequivocally prior to the welding operation.

In the construction shown in Fig. 21, the filament body comprises two parallel filaments 3' and 3". The top of the V is connected to the supply conductor 32, the free ends to the screen 4. The screen is again provided with a groove, in which the bent end of the supply conductor 3| is secured.

Such a construction has the advantage that the burning out of one of the limbs of the filament results only in a decrease in light output of the lamp but not in its extinction.

In order to relieve the filament as much as possible of mechanical loads due to vibration of the filament joints, particularly since the supply conductor supporting the screen will vibrate with a frequency and amplitude differing from those of the other supply conductor, it is advisable to provide an insulating, mechanical joint between the ends of these supply conductors, for example in the manner shown in Figs. 1'7 and 18, where a stay rod 33 is welded to one supply conductor 32 and a stay rod 34 is welded in the screen 4. The two rods are connected together by means of an insulating glass bead 35. This construction, which is known per se (for example British patent specification 393,886) may, of course, also be used in the lamps shown in Figs. 18 to 21.

What I claim is:

1. An incandescent lamp for use with a reflector having an optical axis comprising a bulb, a main filament near the focal point of said reflector, a cup-shaped screen within said bulb, a V-shaped filament located between two lateral edges of said screen, each of said main filament, said V-shaped filament and said optical axis lying in the same plane, said V-shaped filament having its apex pointing toward said main filament and the angle between one of the limbs of the V-shaped filament and the optical axis on the side of the V-shaped filament facing away from the reflector being between 15 and 60.

2. An incandescent lamp for use with a reflector having an optical axis comprising a bulb, a cap for said bulb, the axis of said cap being coincident with the optical axis of said reflector, a main filament, a cup-shaped screen within said bulb, a V-shaped filament located between two lateral edges of said screen, each of said main filament, said V-shaped filament and said cap axis lying in the same plane, said V-shaped fila- 7 ment having its apex pointing toward said main filament and the angle between one of the limbs of the V-shaped filament and the axis of the cap on the side of the V-shaped filament facing away from the refiector being between 15 and 60.

3. An incandescent lamp for use with a reflector having an optical axis comprising a bulb, a cap for said bulb, the axis of said cap being coincident with the optical axis of said reflector, a main filament located at the focal point of said reflector, a cup-shaped screen within said bulb on the side of said main filament remote from said reflector, a V-shaped filament located between two lateral edges of said screen, each of said main filament, said V-shaped filament, said lateral edges and said axis lying in the same plane, said V-shaped filament having its apex pointing toward said main filament and the angle between one of the limbs of the V-shaped filament and 8 the axis of the cap on the side of the V-shaped filament facing away from the reflector being between 15" and 60.

JOHANNES RIJNDERS.

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

UNITED STATES PATENTS Number Name Date 2,071,979 Honing Feb. 23, 1937 FOREIGN PATENTS Number Country Date 481,910 Great Britain Mar. 21, 1938 666,004 Germany July 19, 1936 822,808 France Sept. 27, 1937

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