US3858040A

US3858040A - Motor vehicle headlamps

Info

Publication number: US3858040A
Application number: US00381555A
Authority: US
Inventors: J Ricard
Original assignee: Cibie Projecteurs SA
Current assignee: Cibie Projecteurs SA
Priority date: 1970-05-14
Filing date: 1973-07-23
Publication date: 1974-12-31
Anticipated expiration: 1991-12-31
Also published as: DE2123844B2; FR2087317A5; JPS555201B1; DE2123844C3; GB1347357A; DE2123844A1

Abstract

A motor vehicle headlamp having a light filament for dipped lighting in which masking of the filament is effected to produce two symmetrical half planes of cutout and prisms in the headlamp glass serve to raise one of the half planes so that the planes are staggered in height and connected by an inclined segment.

Description

United States Patent [191 Ricard MOTOR VEHICLE HEADLAMPS Inventor: Jacques Ricard, Fontenay-sous-Bois,

France Assignee: Cibie Projecteurs, Bobigny, France Filed: July 23, 1973 Appl. No.: 381,555

[30] Foreign Application Priority Data May 14, 1970 France 70.17586 US. Cl 240/41.3, 240/41.4, 240/106.l Int. Cl. F2lv 13/04 Field of Search 240/4l.4, 41.3, 41.35,

References Cited UNITED STATES PATENTS 11/1919 Foster et a1. 240/4l.4 R

[4 1 Dec. 31, 1974 1,430,580 10/1922 Old 240/41.4 R 1,916,514 7/1933 Koubek... 240/4l.4 R 1,950,978 3/1934 Falge 240/4l.4 R 2,122,465 7/1938 Graves 240/4l.4 R 2,142,964 l/l939 Godley 240/4l.4 R

Primary Examiner-Richard L. Moses Attorney, Agent, or Firm-Edward J. Brenner 9 Claims, 12 Drawing Figures PATENTED 1 197-4 3, 858.040

SHEET 2 0F 8 PRIOR ART PRIOR ART Fl'gJb PATENTED I 1974 3, 858,040

sum 30F 8 mwggnma 1 1974 3, 858.040

SHEET 7 UF 8 PATENTED [E63 1 I974 SHEET 8 BF 8 MOTOR VEHICLE HEADLAMPS The present invention relates to the headlamps of motor vehicles.

The problem of obtaining a satisfactory dipped beam (lower beam) is a recognized problem in the manufacture of motor vehicle headlamps. US and European regulations and norms specify the lightintensities admissible at certain points of the beam. There can be mentioned, for example, the norm l-l European Code (rule 8 of Geneva) and the SAE norm. The aim is to obtain a beam which lights the road in front of the vehicle adequately, without any danger of dazzling the driver of an oncoming vehicle. I

In order to do this, it has been the practice to bring about a cut-out of the dipped light beam emitted by each headlamp, this beam appearing essentially as limited by two half planes. These two half planes may be horizontal and symmetrically disposed preferably, however, for headlamps of a vehicle adapted for driving on the right-hand side of the road, one uses a horizontal half plane to the left of the central axis of illumination and an inclined half plane directed upwards to the right of the axis of illumination and from this axis.

As a general rule, in the prior art, the cut-out of the dipped beam is obtained by the choice of relative location of the dipped light filament in relation to the parabolic reflector together with the use of masking elements provided to serve as screen or shield between the filament and the reflector. For a lamp with an axial dipped filament, it is customary for instance to use a substantially semicylindrical cup located below and all around the axial filament, the edges of the cup, parallel to the axis of the headlamp, defining the two half planes of cut-out (French standard N.F. R136 for a symmettis l qt tand-. 13: fqta a ym i out). FlG. la shows schematically the known prior art to obtain an asymmetrical cut-out limit, said cut-out limit appearing on a reference screen S. On said figure, P is a headlamp having a glass A, F the axial filament of its lamp, C the above mentioned cylindrical cup having horizontal edges e. In this case, both edges e are not in the same horizontal plane. FIG. lb shows, with the same references how to obtain a symmetrical cut-out with a cup C having both its edges e in the same horizontal level (French norm R 136-02).

With headlamps having a transverse filament, one also knows cut-out means to obtain symmetrical cutout of the lower beam (SAE 1579a).

The present invention aims to obtain a new cut-out for a dipped beam for a car headlamp, which satisfies in a particularly effective manner the standards and regulations in force, and relates to an arrangement of means making it possible to obtain it in a simple and effective manner.

The new cut-out according to the invention is characterized by two horizontal half planes of cut-out connected by an inclined plane, namely a plane inclined at about 45 relative to the horizontal. The horizontal half plane constituting the cut-out of the left-hand part of the beam is preferably slightly below the horizontal plane passing through the axis of the headlamp and its parabolic reflector. The right-hand, horizontal half plane constituting for the main part of the masking limit of the right-hand part of the beam is, preferably, substantially in the horizontal plane passing through the axis of the headlamp.

Naturally, the details given above are for a headlamp adjusted for driving on the right-hand side of the road. It would be necessary to transpose the words right" and left" for a car adjusted for driving on the left.

In the following, in order to simplify the description, we will only consider the case of driving on the right, without this being in any way limiting.

According to the invention, in order to obtain the new, aforesaid cut-out on the one hand, there is associated with the headlamp cut-out means known per se for effecting a horizontal cut-out along two symmetrical half planes of cut out.

on the other hand, there are provided in the path of the light rays of the dipped beam, in particular at the level of the headlamp glass, a plurality of small prismatic, deflection elements,-each of said prismatic elements intersecting a small part of said dipped beam just below said second half plane of cut-out, said small part of said beam projecting with respect to a reference screen a quadrangular image having an upper inside corner and an upper horizontal boundary, said plurality of prismatic elements including a series of stepped prismatic elements, each of said series of prismatic elements deflecting said part of said beam in a vertical direction and also in a transverse direction to translate said corner to coincide on said screen with an oblique segment, all of said prismatic elements intersecting and deflecting different parts of said dipped beam to create finally for said beam a central cut-out limit surface approximating step-by-step-wise on said screen said oblique segment and a lateral horizontal limit surface staggered in height relative to said unchanged first half plane of cut-out.

The location of the prismatic deflection elements, their number, their geometric orientation, their dimensions, are chosen depending on the result to be obtained. These factors may vary in each particular case, but, however, following these general criteria in the case of an axial dipped filament, the location of the prismatic elements must be chosen on both sides of the horizontal plane of symmetry passing through the axis of the reflector in the case of a transverse, dipped filament, i.e., perpendicular to the axis of the headlamp, the location of the elements is chosen in the vicinity of the axial plane of symmetry of the headlamp in both cases, the number of prismatic elements is chosen to be sufficiently great in order that the plane of connection between the two horizontal half plane of cut-out is sufficiently clear In both cases also, the dimension of the prismatic elements depends on a certain maximum admissible tolerance, taking into account the variation of the aberration as one moves away from the axis of the headlamp.

Preferably, the prismatic elements are associated with the headlamp glass, being advantageously moulded with it.

The prismatic regions thus defined are theoretically defined on the glass by arcs of circles centred on the axis of the headlamp. However, in practice simpler shapes are satisfactory and the regions may be limited in the shape by small rectangles or small trapeziums with parallel vertical sides in the case of an axial filament and parallel horizontal sides in the case of a transverse filament.

The following description, referring to the accompanying drawings, given as non-limiting examples, will make it easier to understand how the invention may be realised.

In the accompanying drawings FIGS. la and 1b have already been presented as prior art headlamp including cut-out means.

FIG. 1 is a representation on a reference screen of a dipped beam produced according to the present invention.

FIGS. 2 and 3 show in a similar illustration, the creation of the cut-out by the effect of prismatic zones in a headlamp according to the present invention.

FIG. 4 shows, in front view, a headlamp according to the present invention with an axial filament in which a cut-out is produced by means of prismatic zones.

FIG. 5 is a graph illustratingthe choice of prismatic zones for the headlamp of FIG. 4.

FIG. 6 is an illustration in projection, as in FIGS. 1 to 3 showing the production of the cut-out in the case of the headlamp of FIG. 4.

FIG. 7 is a front view of a headlamp according to the present invention with a transverse filament showing the location of these prismatic zones for producing the cut-out.

FIG. 8 is an illustration, on a screen, similar to that of FIGS. 1, 2, 3 and 6, showing the formation of the cut-out in the case of the headlight of FIG. 7.

FIGS. 9 and 10 are schematic illustrations of the invention for headlamps having respectively an axial and a transverse light filament.

FIG. 1 shows, on a vertical screen located at 25m from the headlamp, perpendicular to its axis, the new type of cut-out which it is desired to obtain. The point H indicates the intersection of the screen and the central, horizontal axis of the headlamp. The reference I corresponds to a length of 25 cm. The new cut-out is constituted by a left-hand half plane AB located slightly below the axis of the headlamp, a half plane DC located substantially at the level of this axis, with an inclined connecting plane BD, preferably at an inclination of 45.

Referring now to FIGS. 2 and 3, the obtention of the new cut-out will now be explained. Firstly, one creates in a known manner 2 symmetrical cut-out constituted by two horizontal half planes Cg and C,,

If one considers a small, individual zone of the reflector, this zone gives an image such as G I J K on the screen (FIG. 2) in which the segment GI is on the righthand half plane Cd.

There corresponds to a small area of the mirror a small area on the glass and an image on the screen, both defined by the shape of the basic beam reflected by the small area of the reflector mirror.

If there is interposed at the level of the glass in the path of the said basic beam-which has just formed an image G I J K a prism with adeflecting effect, a point such as G may be moved to a point G' located on the segment BD previously defined.

With a plurality of areas, for example, four areas GIIIJIKI GgIgJgKg G3I3J3K3 G4I4J4K4, there can thus be produced a plurality of image displacements such that all the points G,G,G G occur at G',, G G;,, G, along the segment BD, the point G substantially coinciding with B, the point G, with D, and the displaced segment G, I, with the half plane of cut-out DC.

There is thus produced (FIG. 3) the desired cut-out by approximation of the rectilinear shape BD by a stepped contour.

Since the general method of obtaining the cut-out has been defined, there will now be described two accurate examples showing the determination of the location and of the dimensions of the prismatic elements within the framework of the invention.

In a first example, we examine the case of a headlamp whose dipped filament is axial.

In this case, and if we refer to the method of forming an image described in relation to FIG. 3, the horizontal limit GI is given, in known manner, by a cup/masking element located around the filament this limitation is thus perfectly well defined.

The limit K] is a little significance for determining the cut-out. It depends on the height of the said region.

The basic limit for the formation of the cut-out is the limit GK. The distance from the point G to the axis of the beam varies according to the distance from the corresponding area of the reflector to the axis of the reflector. In order that the displacements of the image to be produced are not too great, it would be necessary, in principle, to choose the regions as near as possible to the axis of the reflector. In practice, however, one is limited by the presence of the opening provided at the rear of the reflector for the passage of the lamp and due to the fact that near to this aperture, the reflector often has deformations.

On the other hand, in order that the line GK is not blurred, it is necessary to place oneself at a point on the mirror where the aberration is practically constant.

In order to make the explanation still clearer, more details of the example chosen are given, by stating that it is a parabolic reflector mirror having a parameter of 45mm.

FIG. 4 shows a headlamp with a rectangular aperture provided with such a mirror. As previously, A designates its glass, F its light filament, and C its cup constituting the symmetrical cut-out means. The determination and the location of the

prismatic regions

1, 2, 3 and 4 located on its glass will now be discussed.

In the following, in known manner, the z-axis represents the variations in height, the y-axis, the variations in width, the x-axis the variations in depth, these variations being indicated in hundredths of a radian of angular separation.

In the particular example chosen, i.e., with a mirror of 45mm parameter, the variation of the aberration as a function of the distance from the region to the axis of the reflector is shown in FIG. 5. In order that the aberration is practically constant, one solution would be to choose the location of the prismatic regions between the points S and S' of the curve. Such a solution is, however, impossible in practice due to the fact that the proximity of the attachment aperture of the lamp tends to deform the corresponding region of the mirror. In practice, and as can be seen in FIG. 5, the tolerance T which can be allowed in the position of each point such as G, determines the width of the corresponding

areas

1, 2, 3, 4 at the level of the glass. In other words,

areas

1, 2, 3, 4 are chosen as having the same tolerance T as seen on FIG. 5. On FIG. 5, it can be seen that for a tolerance T of 0.2 percent (in hundredths of a radian) the region 1 extends between the radii of aperture 56 and 62mm, the region 2 between the radii of aperture 62 and 68mm, the region 3 between the radii of aperture 68 and 76mm, the region 4 between the radii of aperture 76 and 85mm.

The limits of the regions at the level of the glass are theoretically arcs of circles concentric to the glass, but for reasons of simplifying the equipment, it is possible, as shown in FIG. 4 to provide the

prismatic surfaces

1, 2, 3, 4 on the glass in the form of small rectangles having the previously defined width limits in the transverse plane passing through the axis of the headlamp.

If we consider the

regions

1, 2, 3, 4 thus defined, their outlines correspond to a series of images, the limits GK of which are represented in FIG. 6 (limits G K G K G K It is a question of ascertaining the prisms to be associated with the

regions

1, 2, 3, 4 of the mirror in order to cause the displacement of the images shown in FIG. 6 in order that the points G G G G move to G,, G',, G';,, G., to come into the plane of cut-out inclined at 45 BD previously defined.

It should be noted that the lines GK are not straight vertical lines but curves which have the advantage of minimizing the stepped appearance of the inclined cutout.

The regions g g g g, of FIG. 6 are the useful parts of the initial regions G I J K In order that their heights are similar, one chooses

initial regions

1, 2, 3, 4 of different heights.

In the example chosen, the

region

1 and 2 are mm above the axis of the

regions

3 and 4 are 3mm above.

In order to pass from a point such as G to a point such as G in each process of forming an image, the displacements in width and in height are the following Lateral Vertical Displacement Displacement From G to G 0.5 1 From G to G 0.5 0.7 From G to G, 0.6 0.4 From G, to G, 0.6 0.2

The above displacements are made in hundredths of a radian of angular separation relative to the headlamp, more precisely relative to the plane of its glass.

Under these conditions, the nature of the prismatic elements to be associated with each of the regions of the glass is easily established as follows Line of the Greatest Angle slope relative to the 9 horizontal prism Region 1 65 115 Region 2 50 62' Region 3 38 50' Region 4 18 45 We have thus shown, by means of FIGS. 4, 5 and 6, the practical use of the invention in the case of a headlamp with an axial filament, using an accurate numerical example.

There will now be described by means of another example, and with reference to FIGS. 7 and 8, the use of the invention in the case of a headlamp with a transverse filament (standard cut-out norm SAE J 579A).

In order to obtain horizontal images from a transverse filament, there are used (FIG. 7) the

regions

1, 2, 3, 4 which are substantially on the vertical axis of the headlamp.

In FIG. 8, the curves such as GK (i.e., G K Gl(,, G K,) represent as previously, the limits of the regions l, 2, 3, 4 which are chosen so as to be as near as possible to a cut-out of 45.

As previously, the points G G G are displaced to G',,, 6' 6' by means of prismatic elements associated with each of the regions. The references used are the same as previously.

The accurate determination of the prismatic elements and of the regions is within the scope of the man skilled in he art, taking into account the details which were given as regards the first example.

FIGS. 9 and 10 sum up schematically the teachings of the invention, for headlamps P having known per se symmetrical cut-out means cooperating with an axial and a transverse filament, respectively.

One sees on a reference screen the above indicated formation of quadrangular images 1 thanks to prismatic elements p.

It is to be understood that the number of regions is not necessarily equal to 4 and that the shape of the cutout finally obtained is not necessarily constituted by two horizontal half planes connected by a segment inclined at 45, other inclinations being possible without departing from the scope of the invention. Similarly, the regions on the glass may have any desirable optical shape in order to achieve this or that particular cut-out effect, in particular for suppression or increasing the stepped effect.

It should be understood that the prismatic elements which have been described as preferably connected to certain regions of the glass could just as well be connected to homologous regions of the mirror, or to homologus regions of an intermediate transverse plane located between the reflector mirror and the glass, taking into account the correspondance which has been made explicit between a region of the mirror, a region of the glass and an image region, all three located in the same basic beam reflected by the reflector.

What is claimed is:

1. In a motor vehicle headlamp comprising a parabolic reflector adapted to be mounted with a horizontal axis on a vehicle, a light filament for dipped lighting located in the vicinity of the focal point of said reflector, a front glass, cut-out means for effecting cut-out of the dipped light beam according to a left and a right horizontal half plane of cut-out on either side of the central axis of said reflector and of said headlamp, the improvement comprising a plurality of juxtaposed, prismatic elements, each of said prismatic elements inter secting a small part of said dipped beam just below said right half plane of cut-out, said small part of said beam projecting with respect to a reference screen a quadragular image having an upper inside corner and an upper horizontal boundary, each of said series of prismatic elements deflecting said part of said beam in a vertical direction and also in a transverse direction to translate said corner to coincide on said screen with an oblique segment, all of'said prismatic elements intersecting and deflecting different parts of said dipped beam to create finally for said beam a central cut-out limit surface approximating step-by-step-wise on said screen said oblique segment and a lateral horizontal limit surface staggered in height relative to said unchanged left half plane of cut-out.

2. A headlamp according to claim 1, wherein the inclined oblique segment is disposed at an angle of 45.

3. A headlamp according to claim 1, wherein the juxtaposed prismatic elements are molded with the front glass. t

4. A headlamp according to claim 2, wherein the filament is located on the axis of the headlamp, the cut-out means comprise a masking cup with horizontal edges, and the prismatic elements are located on the side of the from glass.

5. A headlamp according to claim 2, wherein the dipped filament is located transversely relative to the axis of the headlamp and the prismatic elements are provided at the upper part of the glass in the vicinity of its vertical, axial plane.

6. A headlamp according to claim 1, wherein at least three prismatic elements are provided.

7. A headlamp accordirg to claim 3, wherein the dimension of each prismatic element relative to the size of the glass is such that the oblique segment of cut-out has no noticeable blur.

8. A headlamp according to claim 3, wherein the prismatic elements are delimited by trapezoidal shapes, the parallel sides of which are vertical in the case of an axial filament and horizontal in the case of a transverse filament.

9. A headlamp according to claim 3 wherein the prismatic element are delimited by rectangular shapes, the

parallel sides of which are vertical in the case of an axial filament and horizontal in the case of a transverse

Claims

1. In a motor vehicle headlamp comprising a parabolic reflector adapted to be mounted with a horizontal axis on a vehicle, a light filament for dipped lighting located in the vicinity of the focal point of said reflector, a front glass, cut-out means for effecting cut-out of the dipped light beam according to a left and a right horizontal half plane of cut-out on either side of the central axis of said reflector and of said headlamp, the improvement comprising a plurality of juxtaposed, prismatic elements, each of said prismatic elements intersecting a small part of said dipped beam just below said right half plane of cutout, said small part of said beam projecting with respect to a reference screen a quadragular image having an upper inside corner and an upper horizontal boundary, each of said series of prismatic elements deflecting said part of said beam in a vertical direction and also in a transverse direction to translate said corner to coincide on said screen with an oblique segment, all of said prismatic elements intersecting and deflecting different parts of said dipped beam to create finally for said beam a central cut-out limit surface approximating stepby-step-wise on said screen said oblique segment and a lateral horizontal limit surface staggered in height relative to said unchanged left half plane of cut-out.

2. A headlamp according to claim 1, wherein the inclined oblique segment is disposed at an angle of 45*.

3. A headlamp according to claim 1, wherein the juxtaposed prismatic elements are molded with the front glass.

4. A headlamp according to claim 2, wherein the filament is located on the axis of the headlamp, the cut-out means comprise a masking cup with horizontal edges, and the prismatic elements are located on the side of the front glass.

7. A headlmap according to claim 3, wherein the dimension of each prismatic element relative to the size of the glass is such that the oblique segment of cut-out has no noticeable blur.

9. A headlamp according to claim 3 wherein the prismatic element are delimited by rectangular shapes, the parallel sides of which are vertical in the case of an axial filament and horizontal in the case of a transverse filament.