US2253615A - Head lamp - Google Patents

Description

A118- 26, 1941 R. N'. FALGE Erm. 2,253,615

HEAD LAMP Filed Oct. .'51, 1938 4 Sheets-Sheet l Hlm-ill..

,www Gttornegs Aug. 26, 1941.

Filed Oct 31, 1938 4 Sheets-Sheekl 2 LOWER FILAMEHT HIGH BEAM WITHOUT LENS UPPER FILAMENT LOW BEAM WITHOUT LENS LOWER FILAMENT UPPER EAM UPPER FILMENT V I 3mm y laat/plz Z/al @fg j! 6504,45 Ql/I @zz/511k Lowerz BEAM 5l Aug. 26, 1941. R. N. FALGE ETAI.

HEAD LAMP Filed oct. s1. 193e 4 Sheets-Sheet 3 R. N. FALGE ETAL HEAD LAMP Aug. 26, 1941.

Filed Oct. 3l, 1938 4 Sheets-Sheet 4 m7252212 Ql/.Uzzksfll 'L Patented Aug. 26,A `1941 UNITED STATES PATENT oFFlcE 1 nehm N.- rane lanelle: w. ommen, Jr.,

Anderson, Ind., assigner to/General Motors Corporation, Detroit, Mich., a corporation of Delaware Application october s1, 193s, serial No. 237,994

4 Claims.

This invention has to do with headlamps of the type designed to produce different beams by shifting from one filament to the other.

In prior designs of such headlamps it has been customary to locate one filament at or near the focus of the reflector and the other filament above the focus. Upon changing from the filament at focus to the filament above focus the light from the central zone of the reflector, which is sensitive to changes in vertical position of the light source, is depressed and the insensitive light from the top and bottom zones is at all times directed below the tops of the beams by inclining these portions of the refiector downwardly or by providing down-bending prisms on the corresponding sections of the lens. It is thus possible to secure a high beam from the lower or focal fila-v ment and a low beam from the upper filament.

A disadvantage inherent in this design arises from the fact that the upper filament is appre-` y ciably out of focus so that the low beam is less concentrated than the high beam and the distribution of light in it is much less satisfactory. Efforts to improve the beam tend to make the high beam worse so that in all such designs compromise is necessary and the result is frequently a good driving or upper beam and a much less satisfactory lower or passing beam.

We have found it possible by the use of a special reflector, preferably' in combination with a suitable lens, to obtain an improved low beam in combination with an improved high beam. Our design avoids to a considerable degree the losses necessitated by compromise in conventional headlighting equipment.

According to our invention we employ a reflector consisting of a plurality of sections, each preferably substantially half of a paraboloid, arranged one above the other with vertically spaced foci and converging axes, and we arrange one filament at the focus of one section of the reflector and the other filament atthe focus of the other section. We aim the headlamp with the axis of one section at or near horizontal and with the axis of the other section downwardly inclined.

In order to obtain depression of the beam upon going from one filament to the other it is necessary, as in the conventional two-beam design previously referred to, to give a permanent downward tilt to the light from those portions of the reflector that are insensitive to vertical changes in position of the source of light. In our preferred design this is done by means of suitable down-bending prisms on the lens although the (Cl. 24m-41.25)

corresponding portions of the reflector may be tilted downwardly if preferred. In the present instance we prefer to employ down-bending vfprisms as hereinafter disclosed.

In the preferred form of our invention in which the lower section of the reflector is aimed straight ahead and the lower fllamentis at its focus, while the upper filament is at the focus of the upper section, with the lower filament energized all of the light from the lower half of the reector except the bottom zone may be directed straight ahead to form the top of the high beam. All of the light from the upper half of the reflector ex' cept the top zone may be directed substantially straight ahead by giving to this half of the reflector a downward tilt sufficient to overcome or substantially oil'set the upward inclination given to the rays by the fact that the lower filament is below the focus of the upper half of the reflector. With greater inclination of the upper reflector section this light may, of course, be thrown further down in the beam. The light from the top and bottom zones is used for widespread illumination nearer the car.

Upon energizing the upper filament, the light from the upper section of the reflector is directed downwardly by the inclination given to this section while the light from all but the bottom zone of the lower section is directed downwardly because the upper filament is above the focus of this section. Top and bottom zones provide foreground illumination as before.

An objection to the employment of reflectors such as described consisting of sections of paraboloids or the like having spaced foci is that, as ordinarily produced, there is a step between the sections of the reflectors. We have found it possible to avoid rthis step by making the reflector punch of two identical paraboloidal sections. Each section consists of slightly more than a semi-paraboloid and terminates in a parting line lying in a plane slightly inclined to the axis of the paraboloid and intersecting the axis forwardly of the focus. When two such paraboloids are placed together they fit exactly since their meetstruction reierred'to aboveand atthe sametlme obtain compact beams with high intensity hot spots at the top', it is necessarygto design thereilector with the locus ofthe upper haii' not only above but also to the. lett oi the focus of thelowerhali'. Whilethiscouldbedoneby rotating the upper halrvabout a vertical line connectlng the foci. a break or step would be formed betwemthepartinglinesotthesecticnsorelse acurvedpartinglinewouldbeobtainedi'romthe intersection or the parabcloida Steps and curved,

parting lines are objectionable in that they introduee complications in manufacture. These found it best to use horizontal coiled filaments so astoobtainahot spot ofminimum depth.

'l'hereiiector designedasdescribedisusedin combination withalenstheprincipaltunctionot whichistospreadthelightacroestheroadfor .the-reilectoritselftakescareotalargepartoi' the vertical and lateral tilt which must be given tolightiromvariouspartsofthelamptoget the desired result. Lateral spreading oi.' light is accomplished by ilutes on the lens in accordance with usual practice. However, we have also found it advantageous to provide the lens with down-bending prisms where necessary or desirable to improve the beam pattern. We have also employed some side-bending prisma here and theretosmoothupthebeams. Roadtestspcint toward the desirability of providing light above the cutoi! in the upper beam to illuminate the highway for a greater distance ahead when ears are not approaching and to provide better illumination in hilly country. We have provided light above the cutoi! fromregions of the reflector where the images move through a comiderable number of degrees in response to changes in vertical position ot the light source so that this light will fall below the top of the lower beam. Where necessary up-bending prisms are employed to bring this fast-moving light above the normal cuto of the upper beam.

Details of the invention as well as various modiilcations are described ln the following speciilcation taken in connection with the accompanying drawings in which:

Figure 1 is a front view of our improved reilector showing the position oi' the bulb and its filaments. f

Figure 2 is a side view showing the two halves of the reector pimch iitted together and with their axes in a vertical plane. v

Figure 3 is a side elevation of the punch rotated to bring the axes of the sections in the desired inclined plane and with the punch sections secured to a mounting plate ready for use in the press.

Figure 4 shows the beam patterns 'obtained from the reflector shown in Figure 1 with the lower filament energized.

Figure 5 shows the beam patterns obtained from the same reilector with the upper i'llament energized.

Figure 6 is a vertical section through our com-I plete headlamp.

Figure 7 is a iront view of the headlamp.

line and withthelensseetions markodto'sbow the upward or downward tilt'siven bytheprisms incorporated in them.

Figure l'isasideviewot'one oftheoptil elements making up the lens.

Fleurelisasectiononlineit-Ilotlilure l2.

il indicates a reilector comprising paraboloidal andalowerparaboloidal lhe focusoiparaboloidai section Il'isindicatedatlandthsto! Il'isindicated atl". 'Iheaxisofparaboloid'alsectionll'is indicatedbydottedlineA-A'andthea'liso parabcloidal section I4' is'indicatedbylineH'. Itwillbenotedthattheplaneinwhichparting line-ll-II lies bisectg the angle between mg?- section i2' is tilted downwardly and to the In the illustrated embodiment of our invention the reflector has a focal length oi' 11/4" and the spacing between illaments is on the order o! Vs". In general. in der to obtain two satisfactory concentrated beams with our design oi.' headlamp it is desirable that the distance between the foci should be not in excess of 15% of the focal length of the reflector. The minimum distance between foci is. of course, determined by limitations of incandescent lamp design.

In the -illustrated embodiment the alle betweentheaxesofthe reneetorsectionsison the :,asaeis order of 3. :Menem it will be round ont but results in the use of our invention are obtained parte are distinguished on the drawing by simiwhere the angle between these axes is not in exv cess of for with greater angles it is no longer possible to obtain two smooth. concentrated beams. y

In Figure 4 we have shown the beam patterns produced by energizing the lower filament in our reflector. because the filament is laterally elongated. The pattern 23 is projected by the lower reflector section. It is aimed straight ahead with the top slightly above the horizontal. The pattern Il comes from the upper reflector section. This pattern is less concentrated than pattern 2l because the lower filament is not at the focus of this section of thereector. The pattern extends higher above the horizontal for the same reason and also because the lower filament is below the focus of the upper section of the reflector.

In Figure 5 are shown the beam patterns produced by energizing the upper filament. Pattern 26 is produced by the lower reflector section. The pattern 2l is larger than pattern 2l oi.' Figure 4 because the upper filament is not at the focus of this section of the reflector. The top of pattern 26 is but very little lower than the top of pattern 23 because the light from the bottom zone changes but little in direction in going from one filament to the other. Some of this top light is also due to the tilting of' filament images from parts of the reflector near the parting line. It will also be noted that pattern 2S is displaced to the right of pattern 23 as a. consequence of the upper iilament lying to the left of the lower filament.

Pattern 2l, Figure 5, is produced by the upper reflector section. It is compact because the upper filament is at the focus of this section. It is depressed below horizontal because the upper reflector section is tilted downwardly. The pattern is displaced toward the right because this reflector section is aimed in that direction as well as down.

By providing our reflector with conventional properly designed spreading flutes lt would be possible to obtain two horizontally spread beams, each having a well defined hot spot, the hot spot of the lower beam being from 11/2 to 2 below the hot spot of the high beam and displaced toward the right. The provision of good hot spots in both beams is an important advantage of our design. Such a low beam, Ihowever, would have the objection that the top of the beam is higher than is desirable for passing. Such a high beam would also lack the desired light above ,the cutoff for fast driving or driving in hilly country. More light is also desirable in the foreground and it is also necessary to provide a smooth graduation of intensity in both beams both laterally and vertically. While this could be done by properly shaping the reflector this is diiilcult to do in practice and lt is preferred to accomplish the desired shift in the light by employing a lens having flutes and prisms to accomplish'the desired result.

The details of the lens design are shown in Figures 8 and 9. In Figure 8 the dotted lines define sections of the lens provided with prisms to give the approximate vertical tilts indicated.I The remaining sections have little or no tilt.

Referring to Figure 9 the hot spot of the high beam is made up of light from the sectionsof The patterns are laterally elongatedv the lamp indicated by the following reference' 75 characters: 2A, IA, IC, IA, IA and IB. These larcrosshatching. Itwlllbe noted thatallot these sectlonslieintheoentralroneof thereiiector so that'upon goingto the upper filament the lightfrom them is depressed. It will also be noted that sections 4A. IA, IB and the lower part of section 3A lie over the lower half of the rehector so that the light passing through them when the lower filament is energized is directed straight ahead. The remaining hot spot sections !A. 8C and part of 3A lie over portions of the upper half of the reflector. The light from theseportionsgoestothetopofthebeambecause the eii'ect of the downward tilt given to this section of the reflector is overcome bythe eect of the location ot the lower filament beneath the focus of the upper reflector section. ence to Figure 8 it will be observed that these high beam hot spot sections are given little or no up or down tilt by prisms on the lens. 'me light from these hot spot sections is likewise given but slight spread, varying from 0 to 16 so as to concentrate the light down the center of the road.

Sections 2A and IC. Figure 9, provide the hot spot in the low beam. The light from these sections is projected downwardly below horizontal when the upper filament is energized because of the downward tilt given to the upper half of the reflector.

Light is provided above the horizontal in the upper beam from sections 3B, IC. ID and 4E which are given like crosshatching on Figure 9. It will be noted that these sections lie close to the filaments so that the light from them is shifted a considerable number-.of degrees in going from one filament to the other. To bring light from section 4C above the horizontal in the high beam it is necessary to give it a substantial upward tilt by means of prisms on the lens. 'nils tilt may be on the order of '1t/2 as indicated on Figure 8. Sections 3B, 4D and 4E lie over the upper reflector section and the light from these sections is projected above horizontal because the lower filament is below the axis of thissection. However,A it will be found desirable to provide some of these sections with upbending prisms as shown in Figure 8 to throw light further above the cutoff.

The light from these sections is given but little spread, preferably on the order of 10 so that this highlight may be confined to the distance roadway.

The light from the remainder of the lamp that is, the portions not crosshatched in Figure 9. is employed to illuminate the road nearer the car and to provide a gradual change in the illumination between the hot spot and the rest of the beam both1 laterally and vertically. To accomplish this these sections are provided with flutes giving a wider spread to the light, for example, on the order of from 24 to 38.

As previously pointed out, it is necessary to give the light from bottom zone of the lower half 0i.' the reector a substantial downward tilt for the light from this section is insensitive to vertical changes in the filament position and would not shift down upon going to the upper filament. p

Consequently, as shown in Figure 8, this zone is given a substantial downward tilt, preferably on the order of 4, by means of prisms on the lens. The zone next above is likewise preferably given a substantial downward tilt. It has been found desirable to give a greaterdegree of downward 4 Yarmateur tilt to zone 6 than to zone IA in-order to smooth up the beams.

It will be noted that a substantial amount'of downward tilt is given to the sone I of the renector to bring this insensitive light into the lower part of the beam.

Attention is also called to the substantial downward tilt about 6 given to sone IG of therefiector. This light would otherwise fall between the hot spot of the high beam and the top of the light above the horizontal 'and so would make the top of the hot spot less well dehned and thereby interfere with aiming in service. Hence it -was ioundA desirable to use prisms to place this light further down in the beams.

Figure .10 illustrates how the light from `the various sections of the lamp'. as iust described. cooperates. to produce the desired high beam. The light pattern Il providing light above the cutoff, comes from sections IB. IC, ID and IE as described. The hot spot light Il from the lower section of the lens comes from sections of the lamp marked IA, IA, IB and part of IA on lll'ig-y ure 9. 'Ihe'hot spot- II from the upper section of the lens comes from lsections of the lamp indicated at 2A, IC andpart of IAon the same ligure.

The remaining wide spread pattern II comes from the remaining sections of the lamp.

Figure l1 indicates the beam .produced by the upper filament. Thepatterns II, Ii, II and II 30 have now become patterns II', Il'. II' and II' respectively. It will be noted that the hot spots Il and I2' are shifted substantially entirely to the right of the center line, and the top of the lower beam lies from 1 to 1% below horizontal. Attention is also called to the fact that the pattern II' is aimed lower than pattern II and is more concentrated. The complete lower beam provides a smooth, concentrated passing light with the hot spot depressed and aimed toward thev base in xed relation to the filaments. The bulb with the ring 6I is carefully positionedin the reflector with the illaments in their proper optical positions and then the ring l is secured in the opening 6I in the reflector by soldering or other suitable means. This method of mounting the bulb in the reector is the subject of copending application for patent illed by Robert N. Falge, under Serial No. 286,819, on July 27, 1939.

The parts shown in Figure 6 constitu@ a sealed headlighting unit which may be suitably mounted in housing I indicated in dotted lines in Fig- 'ure 6.

We have not pictured the details of lens design on the drawings because of the considerable number of sectional views required instead we have shown in Figure 12 a side elevation of one of the rectangular units making up the lens, and indicated by dotted lines on Figures 7 and 8. We have chosen for this purpose one of the units making up section IG of the lens. It will be noted from Figure 8 that this lens element includes a 6 down-bending prism and as shown Itwillbeunderstoodthatthelensismadeup of similar elements, each given the vertical tilt indicated on Figure 8 andl the spread 4indicated in the foregoing description.

It has also been found desirable to incorporate side-bending prisms in certain portions of the lens providing light for the hot spots or light above the horizontal so as to insure that this light is concentrated down the center of the 10 road. The amount of lateral bending is comparatively slight, ranging from if -to 3.

In general, the light from such portions over the lower half of the reflector is-inclined toward the left, while the light from portions over the 5 upper half is inclined toward the right.

o that we do not limit ourselves to any particular selection of precise angles or spreads. The important feature of our invention consists in so designing our headlamp as to provide concen- Jtrated light at the top of both beams rather than one concentrated beam and one brokenup,'unconcentrated beam as is so often the result of present designs.

Our inventionis capable of considerable modification. In some cases it may be desirable to employ paraboloidal sections fitted together with a-step between them. This may be especially desirable where more than half of the reector is used to provide highly concentrated light in one of the beams, for example, the high beam.

In some instances it may be desirable to use reflectors of slightly dinerent focal length in order to vary the characteristics of the out of focus light in the beam patterns. Thus, one of the nlaments would be behind the focus of 4o one section of the reilector thereby -causing light from that section to be projected above the hot spot while the other filament would be ahead of the focus ofthe other section of the reflector thereby causing light from that section to be projected below the hot spot. Quite similar results mmf be obtained by using reflector sections of the same focal length but displaced axially with respect to each other.

Where one reflector section is tilted both downwardly and laterally with respect to the other it may be desirable to avoid a step between the sections by using as a parting line the natural intersection between the two paraboloids. This intersection' will often be in the form of a rather wide 8 curve, introducing dimculties in manufacture of reflector punches but this may be oifset by advantages in light utilization and distribution.

It may also in some instances prove desirable to tilt downwardly certain portions of the resirable to laterally tilt certain portions of the reilector sections instead of using side-bending prisms on the lens. Y

The spreading of light by means of ilutes on -the lens may be accomplished by flutes on the reiiector as described in Sumner Brown Patent No. 1,546,281 granted July 14, 1925.

It may also be desirable to apply horizontal flutes to portions of the reector, preferably the top and bottom zones to smooth up the beam in in II it is provided with a wide spreading ilute. v'Iii a vertical direction as disclosed in Patent No.

1,825,084v granted September 29, 1931, to C.` A. Michel. i

It will be understood that terms parabolic and paraboloidal are used in a sense to include not only these precise geometric forms but other conic sections such as paraboloids or hyperboloids or hybrid curves differing but slightly from aparaboloid and giving a similar light distribution.

Various other modications will occur to those skilled in the art.

spaced from each other, said reflector being arranged with one of its axes substantially horizontal and with its parting line inclined with respect to the horizontal and with its foci spaced both vertically and laterally, a concentrated horizontally elongated source of light centered on each of said foci, and means for independently energizing said sources so that upon changing to the upper source the beam is shifted downwardly and to one side, the angle between said axes being sufficiently small so that with either source energized the beams from the two segments of the reflectorl overlap to produce a concentrated beam.

2. A headlamp comprising a reflector made of two parabolic segments joined together with the axis-of one segment tilted downwardly and laterally with respect to the other and with the focus of such segment located above and to one side of the focus of the other, a concentrated light source at each of said foci, means for separately energizing said light sources. said headpair of opposed, substantially seml-paraboloidal segments Joined together along a line inclined to the horizontal so that substantial portions of said segments are vertically opposed to each other while the remaining portions are laterally opposed to each other, said segments having their foci vertically and laterally spaced from each other, the upper segment having a top zone extending forwardly of the focal plane, the lower segment having a bottomv zone extending forwardly of the focal plane, concentrated separately energizable light sources, one at each of said foci, the spacing between foci being so slight that the light from each source is projected from each of said segments in a concentrated beam, the upper segment having its axis tilted downwardly slightly with respect to the axis of the lower segment so as to cause the beam therefrom to overlap the beam from the lower segment whichever lament is energized, said top and bottom zones being downwardly inclined so that upon shifting from the lower filament to the upper nlament the beam is depressed as well as shifted toward one side.

4. In combination. a reflector consisting of two substantially identical paraboloidal segments, each segment consisting of slightly more than a semi-paraboloid, said segments being joined together along a line inclined to the horizontal so' that substantial portions of said segments are vertically opposed to each other while the remaining portions are laterally opposed to each other, said segments having their foci vertically and laterally spaced from each other, the upper segment' having a top zone extending forwardly of the focal plane, the lower segmenthaving a bottom zone extending forwardly of the focal plane, concentrated separately energizable light sources, one at each of said foci, the spacing between foci being so slight that the light from each source is projected from each of said segments in a concentrated beam, the upper segment having its axis tilted downwardly with lrespect to the axis of the lower segment so as to cause the beam therefrom to overlap the beam from the lower segment whichever nlament is energized. said top and bottom segments being downwardly inclined so that upon shifting from the lower iilament to thevupper nlament the beamisdepressedaswellasshiftedtooneside.

ROBERT N. FALGE. GEO. W. ONRBEN, Ja.

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