Patent Publication Number: US-6220736-B1

Title: Headlight for a vehicle

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to headlights for vehicles. 
     One of such headlights is disclosed for example in the German patent document DE 32 18 703 A1. This headlight has a reflector, a light source, a lens through which the light reflected by the reflector passes. Moreover, the headlight has a light permeable element which surrounds the lens at least over a part of its periphery, so that the light emitted by the light source and not caught by the reflector can pass and be reflected. For this purpose the element has prisms which deviate the passing light. With this design of the element, when the light source is turned on, the illuminated surface of the reflector relative to the surface of the lens increases, so that no or a little subjective blinding is caused by the reflector. When the light source is turned off, the element becomes dark and the headlight has an undesirable, non uniform appearance. Moreover, with the prisms of the element, only a part of the light passing through the element can be captured. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a headlight for vehicles which avoids the disadvantages of the prior art. 
     In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a headlight for a vehicle, in which the element is formed at least locally as a Fresnel lens with ring-shaped optical profiles. 
     When the headlight is designed in accordance with the present invention, the light emitted by the light source, due to the design of the element as a Fresnel lens, is collected during passage through the element with high efficiency. 
     In accordance with a feature of present invention, the headlight in the turned off position has a brilliant appearance. Due to the collecting action of the fresnel lens, despite the partial screening of the light passing through the element, because of the layer a sufficient illumination of the region around the lens is obtained. 
     In accordance with still a further feature of present invention a coating can be applied on the profile in a simple manner without covering the entire surface of the element by the coating. 
     In accordance with still a further feature of the present invention, the distribution of the light passing through the element can be influenced. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing a headlight in a vertical longitudinal section in accordance with a first embodiment of the present invention; 
     FIG. 2 is a view showing a section of the headlight in a vertical longitudinal section in accordance with a second embodiment of the invention; 
     FIG. 3 is a view showing a section of the headlight in a vertical longitudinal section in accordance with a third embodiment of the present invention; 
     FIG. 4 is a view showing the headlight as considered in direction of the arrow  4  in FIG. 3; 
     FIG. 5 is a view showing a section of the headlight in a vertical longitudinal section in accordance with a fourth embodiment of the invention; 
     FIG. 6 is a view showing a portion of the headlight of FIG. 5 identified with reference numeral  5 ; 
     FIG. 7 is a view showing a portion of the headlight as seen in direction of the arrow  7  in FIG. 5; 
     FIG. 8 is a view showing the headlight in accordance with the modified embodiment; and 
     FIG. 9 is a view showing a headlight in a vertical longitudinal section in accordance with the fifth embodiment. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     A headlight for vehicles shown in FIGS. 1-9, and in particular for motor vehicles, is formed preferably in accordance with a projection principle and serves for producing at least one dim light. The headlight has a reflector  10  composed of a synthetic plastic material or metal. A light source  12  is inserted in its apex region. The light source  12  can be an incandescent lamp, a gas discharge lamp, or another suitable lamp. As seen in a light outlet direction  14 , a lens  16  composed of glass or synthetic plastic material is arranged after the reflector  10 . The lens for example has a flat side  18  facing the reflector  10  and a convex curved side  20  which is opposite to the flat side. The lens  16  is held in a supporting element  22  which can be connected with a front edge  24  of the reflector  10  facing in the light outlet direction  14 . The reflector  10  and the lens  16  can be arranged in a housing  15  provided with a light outlet opening. The light outlet opening is covered  15  by a light-permeable member  17  which can be formed as a disk and composed of glass or synthetic plastic material. The cover member  17  can be smooth so that the light passes through it without being affected. Alternatively, it can be provided at least locally with optical elements which deviate the light passing through it, for example disperse the light. 
     The light emitted by the light source  12  is reflected by the reflector  10  as a converging light bundle which passes through the lens  16  and thereby is deviated. The lens  16  is formed as a collecting lens, and the light passing through it is refracted to the optical axis  11  of the reflector  10 . The reflector  10  can have at least approximately an ellipsoidal shape, and ellipsoid-like shape or a numerically determined shape which is derived from the characteristic of the light bundle to be reflected by the reflector  10 . A light-permeable orifice  26  can be arranged between the reflector  10  and the lens  16 , which is arranged substantially under the optical axis  11 , so that only a part of the light bundle reflected by the reflector  10  passes along it. The light bundle passing on the orifice  26  contains a bright-dark limit determined by the upper edge of the orifice  26 . It is formed by the lens  16  as the bright-dark limit of the dim light bundle exiting the headlight. Alternatively, the orifice  26  can be dispensed with when the shape of the reflector  10  is determined so that the light bundle reflected by it already has the required bright-dark limit formed for the lens  16 . 
     The reflector  10  at its front edge  24  has a cross-section Q 1 , and the lens  16  has a smaller cross-section Q 2  opposite to the cross-section Q 1 . The supporting element  22  can have one or several webs  28  which extend starting from the front edge  24  of the reflector  10  to the proximity of the lens  16 , where they can be connected with one another, for example by a ring-shaped portion  30  in which the lens  16  is held with its edge. Openings  32  are left between the webs  28  so that the light emitted by the light source  12  and not captured by the reflector  10  can pass through them. The webs  28  preferably are formed as small as possible to maintain great openings  32  between them so that a corresponding great part of the light emitted by the light source  12  can pass through them. 
     In accordance with the present invention, at least one element  40  which surrounds the lens  16  at over a part of its periphery is provided. In FIGS. 1-8 it is shown in various embodiments. All embodiments have the same feature that the element  40  is composed of a light permeable material, for example glass or synthetic plastic material. The element  40  is at least locally, preferably over its total extension, is formed as a Fresnel lens and has a plurality of ring-shaped, approximately concentric, optically active profiles  42 . The optical profiles  42  can be arranged at the side of the element  40  which faces the reflector  10  as shown in FIGS. 1-5. On the other hand, the optical profiles can be arranged on the side of the element  40  which faces in the light outlet direction  14  and away from the reflector  10 . The optical profiles  24  are formed preferably wedge-shaped. The light passing through the element  40  is deviated by the optical profiles toward the optical axis  11  and thereby collected. The optical profiles  42  can be formed for example so that the light emitted by the light source  12  after passage through them extends substantially parallel to the optical axis  11 . The element  40  can be arranged, as shown in FIG. 1, so that it has substantially the same distance from the reflector  10  as the lens  16  in direction of the optical axis  11 . Alternatively, the element  40  has another distance in direction of the optical axis  11  from the reflector  10  than the lens  16 , and thereby is offset relative to the lens  16 . 
     In the shown embodiments, the optical profiles  42  for forming the Fresnel lens are arranged on the side of the element  40  which faces toward the reflector  10 . The element  40  has an opening  41  for passage of the lens  16 . In the first embodiment shown in FIG. 1, the element  40  is formed substantially flat and at its side facing the light outlet direction  40  is substantially smooth. Alternatively, the profiles  42  can be arranged for forming the Fresnel lens also on the side of the element  40  facing in a light outlet direction  14 , while the side of the element  40  facing the reflector  10  is substantially smooth. 
     In accordance with a further embodiment of the headlight, at least partially reflecting coating  44  can be applied at least locally on the side of the element  40  which faces in the light outlet direction  14 . The coating  44  can be formed so that it is light-impermeable, and then it is arranged only in some regions on the element  40  to make possible a partial passage of the light emitted by the light source  12 . The coating  44  can be formed by lines or rings. The light impinging from outside on the coating  44  is reflected by it. 
     Alternatively, the coating  44  can be formed so that it is partially light permeable and partially reflecting. In this case, the total surface of the element  40  is covered by the coating  44 , or only a part of this surface. The light emitted by the light source  20  can pass partially through the coating  44 , while the light impinging from outside on the coating  44  is partially reflected. The element  40  is arranged substantially at the same distance from the reflector  10  as the lens  16 . The coating  44  is composed preferably of metal, for example aluminum and can be applied with known methods on the element  40 , for example by the evaporation, sputtering, varnishing, printing or impregnating. The light permeability of the coating  44  can be varied by its thickness, and its light permeability can reduce with increasing thickness. For obtaining a partial light permeability of the coating  44 , it is formed with a small thickness, while for obtaining a high reflection degree it is formed with a correspondingly greater thickness. 
     The element  40  is shown in FIG. 2 in accordance with a second embodiment of the invention. Here, the element  40 , contrary to the first embodiment, is not flat but instead concavely curved. The element  40  has also the opening  41  for passage of the lens  16 . In the region of its opening  41 , the element  40  has substantially the distance from the reflector  10  as the lens  16 , and starting from the lens  16  extends farther in the light outlet direction  14 . The value of the curvature of the element  40  can be selected in correspondence with the space conditions in the headlight and the desired appearance of the headlight. The element  40  has the optical profiles  42  provided on its side facing the reflector  10  for forming the Fresnel lens. At its side facing in the light outlet direction  14 , it has raised profiles  46 . The profiles  46  can be formed for example rectangular and provided with sides which face in the light outlet direction  14  and have flattenings  48 . 
     A coating  44  can be applied on the element  40 . It can be applied for example on the flattenings  48  of the profiles  46  of the element  40  facing in the light outlet direction  14 . The regions of the element  40  remaining between the profiles  46  are not provided with the coating  44 . The coating  44 , similarly to the first embodiment, can be reflecting, or partially reflecting and partially light-permeable and applied in the same way. The profiles  46  can be also provided as in the first embodiment on the flat element  40 , while the concavely curved element  40  of the second embodiment can be also smooth, or in other words formed without the profiles  46 . 
     A third embodiment of the element  40  is shown in FIG.  3 . In contrast to the second embodiment, it is concavely curved, while the remaining design of the element  40  is the same as in the second embodiment. The element  40  in the region of its opening  41  for the lens  16  has substantially the same distance from the reflector  10  as the lens  16 , and extends starting from the lens  16  opposite to the light outlet direction  14 . Here also the curvature of the element  40  is selected so that a desired appearance of the headlight when looked from outside is provided. 
     Contrary to the preceding embodiment, the element  40  can be also truncated-cone shaped. The element  40  is therefore shaped so that its cross-section increases starting from the lens  16  in the light outlet direction  14  or opposite to the light outlet direction  14 . In FIG. 4 the element  40  in accordance with the above described first, second and third embodiments is shown on a view opposite to the light outlet direction  14 . The lens  16  has a round cross-section, and the element  40  surrounds the lens  16  over its entire periphery and is ring-shaped. The element  40  has a substantially round opening  41  for the lens  16  and a substantially round outer shape which however can be for example oval or cornered. It is also possible that the element  40  surrounds the lens  14  only over a part of its periphery and arranged for example only laterally near the lens  16  or only above and/or below the lens  16 . The side of the element  40  facing in the light outlet direction  14  has the profiles  46  which are arranged over its total surface and formed as at least approximately concentric rings. The light passing through the element  40  is not substantially deviated by the profiles  46 . The profiles  46 , in contrast to the embodiments shown in FIG. 4 can extend in any other way, for example straight or curved. 
     The light passing through the element  40  provides an illumination of the element  40 , so that the illuminated surface of the reflector is increased relative to the surface of the lens  16 . The light passing through the element  40  also forms a light bundle additionally to the light bundle which passes through the light  16 , so as to produce the dim light distribution. In the turned off condition of the headlight the light impinging from outside is reflected by the coating  44  at least partially, so that the element  40  has an approximately brilliant or reflecting appearance as reflector. When the optical profiles  42  for forming the Fresnel lens are arranged on the side of the element  40  facing the light outlet direction  14 , the coating can be also applied on it. 
     In FIGS. 5 and 6, the element  40  is shown in accordance with a fourth embodiment, and is formed substantially as in the first embodiment. The element  40  facing the reflector  10  is provided with the optical profiles  42  for forming the Fresnel lens, and on its side facing in the light outlet direction  14  is formed with the profiles  56 . The profiles  56  are wedge-shaped and at their side facing the light outlet direction  14  have increased flattenings  48  as shown in FIG.  6 . The coating  44  is applied on the flattenings  48 . It can be again reflecting, or partially reflecting and partially light-permeable. Due to the raised shape of the profiles  56  and their flattenings  58 , the coating  44  can be applied in a simple manner, for example for by a printing or impregnating process, onto the flattenings  58 . Without additional expenses, for example covering and other, the regions between the flattenings  58  can be left without the coating  44 . With the wedge-shaped design of the profiles  56 , the light passing through them is deviated. The arrangement and the design of the profiles  56  is selected so that this deviation of the passing light is performed with a predetermined intensity and in predetermined directions. The previously illustrated embodiments of the wedge-shaped profiles  56  can be provided also in the second and third embodiments of the curved element  40 . Moreover, the profiles  42  which form the Fresnel lens can be arranged on the side of the element  40  facing in the light outlet direction and provided with the flattenings on which the coating  44  can be applied. 
     FIG. 7 shows the element  40  in accordance with the fourth embodiment of the present invention in a view opposite to the light outlet direction  14 . The element  40  surrounds the lens  16  which has a round cross-section over its entire periphery and has at least approximately round cross-section. The shape of the cross-section of the element  40  can also deviate from a round shape, and can be for example oval or rectangular. The side of the element  40  facing in the light outlet direction  14  is provided with profiles  56  formed as described hereinabove. In the embodiment of the element  40  in FIG. 7, they are linear and substantially horizontal. The light passing through the element  40  is deviated downwardly by the profiles  56 . Due to this shape of the profiles  56 , it is prevented that the light passing through the element  40  causes an extensive blinding, since it extends above the bright-dark limit of the dim light extending through the lens  16 . 
     In FIG. 8 the element  40  is shown on the view opposite to the light outlet direction  14  in accordance with the modified embodiment. Here the profiles  56  are linear and extend substantially vertically. The light passing through the element  40  is deviated by the profiles  56  in a horizontal direction and thereby dispersed in the horizontal direction. Thereby blinding caused by the light passing through the element  40  is reduced, and moreover, a better visibility of the headlight from lateral directions is provided. 
     The headlight in FIG. 9 in accordance with a fifth embodiment substantially corresponds to the headlights of the previous embodiments. However, the coating  44  is applied here not on the element  40  contrary to the previous embodiments. A light permeable disk  60  arranged after the element  40  in the light outlet direction  14  is provided. It at least partially surrounds the lens  16  over a part of its periphery. The light passing through the lens  16  however does not pass through the disk  60 . The disk  60  has an opening  62  provided for the unobjectionable passage of the light separated by the lens  16 . The disk  60  is formed so that it extends at least over a part of the beam path of the light passing through the element  40  or through its total beam path. The coating  44  is applied at least over a region of the side of the disk  60  facing in the light outlet direction  14  and is formed at least partially reflective. The coating  44 , as in the previous embodiment, can be provided in form of rings or lines on the disk  16 , or adhere to the surface as a partially light permeable coating. The disk  60  can be smooth or provided at least on one side with at least local profiles formed so that the passing light is deviated by them. The coating  44  can be applied on the profile. The disk  60  as shown in FIG. 9, can be flat, however, it can be also concavely or convexly curved, or substantially conical. The disk  60  can have a substantially the same distance from the reflector  10  in direction of the optical axis  11  as the lens  16 , or a different distance than the lens  16  and can be offset relative to the lens. The design of the headlight in accordance with the fifth embodiment makes possible in particular to arrange the element  40  relative to the lens  16  near the reflector  10  and to arrange the disk  60  in the region of the lens  16  or with a greater distance from the reflector  10  between the lens  16  and the cover disk  17 . Thereby, the appearance of the headlight can be improved, since the coating  44  of the disk  60  is well visible from outside when looking in the headlight. 
     In the headlight in accordance with the fifth embodiment shown in FIG. 9, an additional reflector  70  is arranged between the reflector  10 , and in particular its front edge facing in the light outlet direction  14 , and the element  40 . The additional reflector  70  extends at least over a part of the periphery of the reflector  10 , for example substantially over the same periphery as the element  40 . With the additional reflector  70 , a part of the light which is emitted by the light source  12  and not captured by the reflector  10 , is reflected so that this light passes at least partially through the element  40 . The additional reflector  70  can be for example ring shaped and arranged around the front edge of the reflector  10 . The additional reflector  70  in the axial longitudinal sections which contain the optical axis  11  can be flat, or can be concavely or convexly curved in any manner. The additional reflector  70  can be formed of one piece with the reflector  10  or can be held on it as a separate part. Alternatively, the additional reflector  70  can be held for example on the support element  20  or in any other way. Moreover, the light emitted by the light source  12  which is not captured by the additional reflector  70  can pass through the element  40 . At least one additional reflector  70  formed as described hereinabove, can be also provided in the headlights of the first, second, third embodiments. 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in headlight for a vehicle, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 
     What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.