FR2628823A1 - Projection lamp has a parabolic reflector and polyacrylic deflector - for enhanced electro=optical efficiency and reduced weight for directional illumination beacon or signal lamps - Google Patents

Abstract

A lamp (1) for projecting a beam of light from two or more electroluminescent diodes (4) includes a combination of parabolic reflector (3) and of a coaxial deflector in the form of a conical profile (10) of transparent material (I) which will transmit some (deflected) rays R 3 directly while reflecting others (R1) so that the latter emerge (R4) after subsequently encoutering the reflector (3). Pref. the coaxial deflector (4) is approximately centred on the focal point of the other reflector (3). The wall thickness of (10) may vary, pref. increasing as the wall diverges and not necessarily of constant annular thickness. Pref. (I) comprises 'plexiglass' (RTM - an acrylic or methacrylic polymer). Pref. the emitters (4) are mounted directly on a transverse printed circuit board carried on a threaded stud for adjusting the positions of the lamps (4) or the deflector (10) relative to each other and to the reflector (3). USE - Esp. for projection lamps for illumination of selected areas, such as a road obstruction, or a (railway) signal lamp, or a runway beacon. Use of the electroluminous energy, the combination of the type of emitter and the semi- and total reflector profiles makes efficient, e.g. by halving the power consumption necessary for a railway wagon rear lamp and reducing its weight from typically 7 kg to 5 kg through saving weight and size on battery capacity.

Description

FRENCH REPUBLIC Publication No. 2,628,823 (to be used only for

  NATIONAL INSTITUTES Reproduction Orders)

OF INDUSTRIAL PROPRIETY

  OF INDUSTRIAL PROPERTY) National Registration No .: 88 03428 PARIS

Int C41: F 21 K 2/00; F 21 Q 3/00.

  APPLICATION FOR PATENT OF INVENTION A1

  Filing Date: March 17, 1988. Q Applicant (s): New Company of the Power Switch

C.N.A. - FR.

) Priority

(Inventor (s) Maurice Pair.

  Date of the public availability of the

  application: BOPI "Patents" No. 38 of 22 September 1989.

  6 References to other national documents appearing

Qt Holder (s):

Q Agent (s): Office Blétry.

(Light projector.

  (According to the invention, the light projector 1 comprises a light source 2 constituted by a plurality of high-brightness electroluminescent diodes 4 and a reflector 3. The incident radii 3 emitted by the diodes 4 are intercepted by a splitter light 10 such as a cone 11 which reflects and refracts the light rays emitted by the diodes 4. The beam / 7 I 3_ output of the projector 1 is constituted by the radii R4, 3b f7 2; a corresponding to the rays R1 reflected by the reflector 3 and: .- .t3 q- by the radii R3 at the outlet of the cone 11. The position of the cone x; -?, x

  Is it the extension of every ray that is reflected R1.3 -

  pass to the vicinity of focus F of reflector 3. b 00>

IN -. "-

  ao N {O <o. CI ULD Sale of fascicles to NATIONAL PRINTING. The present invention relates to a light projector, of the type comprising a light source and a reflector of generally parabolic shape which reflects a part of the beam emitted by the source, the reflected beam and the beam. unreflected forming a characteristic light beam

predetermined geometries.

  In the context of the invention, the term "light projector" must be understood to mean either an illumination system of a shadow zone for example, or a system for signaling an obstacle or marking a track by example. The light sources used in these projectors are often arc, electric or incandescent lamps, knowing that the choice of the light source, in particular according to the required luminous power, and the geometrical characteristics of the reflector, in particular according to the configuration symmetrical or asymmetrical desired for the output beam,

  vary depending on the intended applications.

  In general, the light sources used emit most often omnidirectional radiation and are located at the focus of the reflector

  to minimize energy losses, this is - & -

  say to have a maximum return which results in a

  light beam output & optimum brightness.

  However, the light projectors using as a light source an electric discharge lamp in a gas, in particular a neon lamp, have some disadvantages inherent to this type of lamp. Indeed, a neon lamp has a relatively short operating time, is fragile and is a high cost resulting in particular from its complexity which imposes delicate manufacturing processes often implemented manually. In addition, a neon lamp requires for its operation a relatively high starting voltage which requires the presence of a

voltage converter.

  In the case of a standalone and portable light projector, there is added an additional drawback related to the power source, such as a battery, which considerably increases the dimensions and the

weight of the projector.

  An autonomous and portable projector with a neon lamp light source is used in particular in railways as a signaling system called lantern. These lanterns are used to signal the back of a train, especially of goods, in circulation or at a standstill. The use of neon lamps in these lanterns is essentially justified by the characteristic of a neon lamp which is to emit radiation whose wavelength corresponds to a red-orange color that comes closest to the red color imposed for this type of signaling. To obtain this imposed red color, each lantern is equipped with a red color correction filter which, on the one hand, makes it possible to restore the correct wavelength for the output beam of the lantern and, on the other hand, allows to obtain a visual effect of red color during the extinction of the lamp. However, the use of this correction filter has the disadvantage of absorbing about 30% of the energy of the radiation emitted by the lamp, which decreases the brightness of the output beam which, nevertheless, must be sufficient to make the lantern visible at a distance of about 1 km under conditions

normal atmospheric conditions.

  In general, the object of the invention is to design a light projector based on the use of directional light-emitting diodes, known per se, to obtain, at least at equal luminous power, an output light beam similar to that obtained in a light projector equipped with an omnidirectional radiation lamp. For this purpose, the invention proposes a light projector of the aforementioned type and characterized in that the light source is formed by at least one directional light-emitting diode, and in that it comprises a light distributor having at least one less a semi-reflective surface on which the incident beam emitted by the diode projects, the extension of each ray of light reflected by the splitter and projected onto the passing reflector

  substantially by the focus of the latter.

  As a result of this orientation of the beam reflected by the light distributor, the light-emitting diode, brought globally to a point light source, and the focus of the reflector are substantially symmetrical to each other with respect to the semi-reflective surface. of the light distributor. Under these conditions, the second reflection made by the reflector is such that the reflected beam, forming part of the output light beam of the

  projector, has a maximum brightness.

  According to another embodiment of the invention, the incident beam emitted by the diode is reflected in part by the semi-reflecting surface of the light distributor, while the other part of the incident beam passes through, by refraction, the distributor to give at the output a beam which, combined with the beam reflected by the reflector, forms the output beam

of the projector.

  According to one embodiment of the invention, the light source is formed of a plurality of electroluminescent diodes parallel to each other, arranged on a ring axially aligned with the optical axis of the reflector, the incident rays emitted by the diodes being substantially parallel to the optical axis, the reflector is of parabolic shape with the focus located on the optical axis, and the light distributor is formed by a transparent hollow cone substantially axially aligned with the optical axis, the apex of the cone

  being directed towards the inside of the reflector.

  According to another embodiment of the invention, the geometrical configuration of the output beam of the headlamp is obtained by varying the geometry of the reflector and / or on the respectively external and internal faces of the cone, in particular on their degree.

  tilt relative to the optical axis of the projector.

  Thanks to these different arrangements, a light projector according to the invention has many advantages resulting in particular from the use of light emitting diodes, in particular their low power consumption, their reliability, their operating time, their robustness and their cost of manufacturing which is significantly lower than that of a neon lamp for example. These advantages can be particularly highlighted in comparison to a light projector whose light source is formed by a neon lamp, as in the case of a lantern signaling used in railways. Consumption is reduced by about half, the voltage converter is removed and, for the same light power, it is possible to increase the life of the projector by increasing the operating time of the power source constituted by batteries. , or to reduce to autonomy equals the weight, and consequently the price of the batteries. Concretely, a conventional lantern with a weight of 7 kg for example can be reduced to 5 kg, which greatly facilitates the operations of hooking the lantern in the back of a car. Finally, it is possible to choose high-luminescent diodes that emit radiation at the wavelength corresponding to the red color imposed by the railways. Under these conditions, the red corrector filter which nevertheless equips the projector to give a red visual appearance when the diodes are extinguished, does not play its proper role filter, that is to say, it does not absorb of power, so that at equal power, a higher brightness is obtained for a projector equipped with light-emitting diodes than for a

  projector equipped with a neon lamp.

  Other advantages, features and details

  will emerge from the explanatory description which will follow

  Referring to the accompanying drawings given solely by way of example and in which: - Figure 1 is a partial front view of a light projector according to the invention, - Figure 2 is a longitudinal sectional view of the optical axis of a preferred embodiment of a light projector according to the invention, Figure 3 is an enlarged partial sectional view of the light distributor of Figure 2 to illustrate the principle of operation, and FIGS. 4 and 5 show schematically the sectional cross-section of the light distributor

  following two variants.

  The light projector 1 as shown in Figure 1 comprises essentially a light source 2 and a reflector 3 generally funnel-shaped, the inner side wall 3a substantially of parabolic shape is a reflective surface. According to the invention, the light source 2 is constituted by light-emitting diodes 4 which, in the example considered here, are six in number regularly distributed on a ring centered on the optical axis X'X of the projector 1 passing substantially

  by the axis of symmetry of the reflector 3.

  Referring more particularly to Figure 2, the diodes 4 are mounted in a ring on one side of a printed circuit board 5. The other side of the wafer 5 supports the various electrical connections (not shown) between the diodes 4 and has two input-output terminals connected by two electrical conductors 6a, 6b to a power source (not shown), such as a battery by

example.

  The diodes 4 are interconnected between the input-output terminals of the wafer 5 in a parallel or series-parallel arrangement to prevent the failure of a diode 4 causing the total extinction of the light source 2. Finally, the diodes 4 are arranged on the printed circuit board 5 so that the different directional radiations emitted by the different diodes propagate substantially parallel to the optical axis X'X of the projector 1. In other words, the diodes 4 are mounted parallel between they, the angle of opening of the light beam emitted by each diode being understood

between 5 and 10 o'clock.

  The printed circuit board 5 is integral with a base 7 forming a base. The base 7 is in the form of a hollow cylindrical element 7a open at one end and the other end opposite 7b has a central opening extended axially by a tubular portion 7c internally threaded. A threaded element such as a threaded rod 8 is screwed inside the tubular portion 7c and has a length such that it projects on either side of this tubular portion 7c. The printed circuit board 5 has a central hole through which it is freely engaged on the threaded rod 8 to abut against the free end surface of the tubular portion 7c of the base 7. The printed circuit board 5 is fixed in position by means of two nuts 9 engaged respectively by the two ends of the threaded rod 8 to abut, on the one hand, against the printed circuit board 5 and, on the other hand, against the inner wall of the end

7b of the base 7.

  The light projector 1 is completed, in accordance with the invention, by a device 10 called a light distributor which, in the example considered here is a transparent hollow cone 11 made of plexiglass for example and whose open apex is extended axially by a tubular portion 12 threaded internally by which it is screwed onto the threaded rod 8 on the side adjacent to the diodes 4. The top of the cone It abuts, if necessary, by one or more spacers washer 13 against the nut 9 resting on the printed circuit board 5. The dimensions of the cone 11 are such that the radiation emitted by the diodes 4 is intercepted by the outer surface 11a of the cone 11, the spacer washer (s) 13 serving to adjust the position of the cone 11 relative to the focus F of reflector 3, as

this will be described later.

  In a general way, the cone 11 in the application

  envisaged to a variable thickness (Figure 3), that is to say

  that the angles of inclination of the outer surface 11a and the inner surface 11b with respect to the optical axis X'X are different from each other and, in particular, the angle of inclination of the inner surface llb is lower than that of the outer surface 11a for reasons which will be

explained further.

  The light source 2 thus formed forms an assembly which is then fixed to the reflector 3. For this purpose, the reflector 3, which is substantially of parabolic shape, is open at its top and is extended axially by a tubular element 3b of barely larger diameter. to that of the base 7 of the light source 2, so as to receive it by press fitting, for example, while allowing them to separate from one another. After this assembly, the diodes 4 and the cone 11 are located inside the reflector 3, the axis of the cone 11 being substantially coincident with the axis X'X of the parabola formed by the

  internal surface 3a of the reflector 3, which axis forms the axis.

  1. The diodes 4 mounted substantially parallel to the threaded rod 8 emit each radiation whose main direction is substantially parallel to the optical axis X'X. The structure of the projector 1 is completed by a plate 15 which, in the example considered here, is tinted red for the application envisaged thereafter. This plate 15, for example made of polycarbonate, is attached and fixed, removably, against the free end surface of the reflector 3, thus trapping the

  light source 2 inside the reflector 3.

  Referring to FIG. 3, the principle of the light distributor 10, that is to say the way in which it modifies the trajectory of the radiation, will be described.

  emitted by the diodes 4 not shown in this figure.

  By considering an incident ray Il which is emitted by a diode 4, this incident ray II, for example parallel to the optical axis X'X, strikes the outer surface 1a of the cone 11 at an angle of incidence of 45 'by example, knowing that the angle of inclination of the outer surface 11a with respect to the optical axis X'X is also 45 ', while the angle of inclination of the inner surface 11b of the cone 11 makes an angle lower, of the order of 40 'relative to this axis X'X

in the example considered.

  The semi-reflecting surface 11a of the cone 11 has the effect of splitting the incident ray I1 into a reflected ray R1 and a refracted ray R2. The incident ray falling at an angle of incidence of 45 'relative to the normal N1 at the surface 11a is reflected at an angle of 45', that is to say along a radius R 1 perpendicular to the axis X'X optical. The refracted ray R2 is at an angle r1 with respect to the normal N1 defined by the formula ni sin il = n2 sin r1, where n is the index of refraction of the air equal to unity and n2 the refractive index of the cone which, in the case of plexiglass, is equal to 1.49. By applying this formula, the refraction angle r1 is equal to 28 'with respect to the normal N1, that is to say that this refracted radius R 2 approaches this one since it passes from a medium that is less refractive to a more refractive medium. The refracted ray R2 passes through the thickness of the cone II and, in contact with the inner surface 11b of the cone 11, it will refract again to give an output radius R3. The incident refracted ray R2 falls into contact with the surface 11b of the cone 11 at an angle of incidence 12 of 33 'with respect to the normal N 2 at the surface 11b, given that this surface 11b is at an angle of 40' to the optical axis X'X. By applying the above formula, the refractive angle r2 is equal to 55 ', i.e., the exit radius R3 deviates from the normal N2 to form a divergent exit beam since the two surfaces 11a, 11b of the cone are not parallel to each other and that the inner surface 11b is inclined with respect to the optical axis X'X at an angle less than that of the

outside face lia ..

  Referring again to FIG. 2, the reflected ray R1 through the cone 11 is reflected again by the reflecting surface 3a of the projector 3 to give an output radius R4 whose direction is a function of the shape of the reflecting surface 3a. at the point of impact of the incident ray R1. According to the invention, the shape of the reflecting surface 3a is such that the extension of the reflected ray R1I by the cone 11 passes substantially through the focus F of the. reflector 3. If the reflective surface 3a was actually a parabola, the exit radius R4 reflected by the surface

  reflective 3a would be parallel to the optical axis X'X.

  In the example considered here, the reflective surface 3a does not have the exact shape of a parabola in order to obtain a substantially divergent output beam R4, so that the extension of the reflected rays R1 by the cone 11 substantially passes through the focus F reflector 3, just adjust the position of the cone 11 on the rod

  threaded 8 possibly by inserting the washers-

  spacers 13 which make it possible to adjust the position of the

  cone 11 with respect to the focal point F of the reflector 3.

  In the example considered here, the thickness e of the cone 11 is not uniform but increases in a continuous manner between the vertex and the base of the cone 11, this non-constant thickness making it possible to obtain a divergent beam R3, as this is schematically illustrated in Figure 4. Alternatively, as shown in Figure 5, the cross section of the reflective surface 11a of the cone 11 may be circular, while the cross section of the inner surface 11b of the cone 11 may be elliptical thus giving different thicknesses e1, e2 to obtain a non-uniform divergent output beam. Alternatively also, it is possible to invert the structure of Figure 5 with an elliptical section on the outside and a circular section on the inside. In addition, it is also possible to give the outer surfaces lia and

  Inner 11b of the cone 11 a convex or concave shape.

  The intended application for the projector 1 according to the invention and as described above relates to a lantern signaling used in railways. The diverging beam formed by the reflected rays R4. by the reflector 3 and the diverging beam formed by the radii R3 at the outlet of the cone 11 make it possible to obtain an output beam having a vertical aperture of approximately 10 and a lateral opening of approximately 15 'in accordance with the imposed standards.

for such a lantern.

  The plate 15 mounted at the outlet of the reflector is red so as to obtain the color imposed for such a lantern. Since the high-luminosity light-emitting diodes 4 emit radiation whose wavelength substantially corresponds to the imposed red color, the plate 15 does not act as a filter, that is to say that it does not it absorbs no energy, its role being limited to giving a red color to the lantern when the diodes are extinguished. Thus, it is possible thanks to the light-emitting diodes to obtain an output beam with a minimum loss of energy because of the wavelength of the radiation emitted by the diodes 4 and the fact that the extensions of the reflected light rays R1 by the cone They pass near the focus F

reflector 3.

  Of course, the invention is in no way limited to the embodiment described given solely by way of example, but includes all the equivalent technical means of the means described which are within the abilities of those skilled in the art. In particular, the number of diodes 4 used, their arrangement on the printed circuit board 5 and their orientation may be different from the example described. For example, the diodes 4 are not necessarily distributed evenly on the wafer and they can be oriented so that the radiation emitted is not necessarily substantially parallel to the optical axis of the projector. In addition, the threaded rod 8 which assures the mounting of the cone 11 may be replaced by a screw, and positioning elements may be provided for example at the base 7 of the light source 2 to position correctly, on the one hand , the printed circuit board 5 or support of the diodes 4 and, on the other hand, the base 7 relative to the reflector 3, according to the desired configuration for the output beam. Finally, the projector as described may have other applications than the one envisaged, and the output beam can have different dimensions and directions by playing on the geometric shapes of the reflective surfaces of the projector and the shapes and shapes. degrees of inclination of the outer and lower surfaces of the cone, the latter known as a light distribution

different form.

Claims (17)

  1. Light projector, of the type comprising a light source and a reflector of generally parabolic shape which reflects a part of the beam emitted by the source, the reflected beam and the non-reflected beam forming an output light beam with predetermined geometric characteristics, characterized in that the light source (2) is formed by at least one directional light emitting diode (4), and in that it comprises a light distributor (10) having at least one semi-reflecting surface (11la) on which is projected the incident beam emitted by the diode (4), the extension of each light beam (R1) reflected by the splitter (10) and projected onto the reflector (3)   passing substantially through the focus (F) of the latter.   2. Light projector according to claim 1, characterized in that the diode <4) and the focus (F) are substantially symmetrical to each other with respect to   the semi-reflecting surface (11la).   3. Light projector according to claim 1 or 2, characterized in that the light distributor (10) is constituted by a hollow cone (11), the surface   outer surface (la) forming said semi- reflective (lla).   4. Light projector according to claim 3, characterized in that the cone <11) is made of a material transparent, like plexiglass.   5. Light projector according to claim 3 or 4, characterized in that each incident ray (II) emitted by a diode (4) is on the one hand, reflected by the semi-reflecting surface <(la) to give a reflected ray (R1) and, on the other hand, refracted by the cone 11 along a refracted ray (R2) itself refracted to the inner surface (11b) of the cone (11). 6. Light projector according to claim 5, characterized in that the ray reflected (Ri) by the cone (11) is then reflected by the inner surface (3a> of reflector (3).   7.- Light projector according to any one of   Claims 3 to 6, characterized in that the axis of   cone <11) is substantially aligned with the optical axis (X'X) of the projector (1).   8. Light projector according to claim 7, characterized in that the axis of the cone (11) passes   substantially by the focus (F) of the reflector (3).   9.- Light projector according to any one of   Claims 3 to 8, characterized in that the thickness cone (11) is variable.   10. Light projector according to claim 9, characterized in that the inner surface (11b) of the cone (11) makes an angle of inclination with respect to the optical axis (X'X) which is less than that made by the outer surface (la) of the cone (11) relative to this axis.   11.- Projector of light according to any one of   preceding claims, characterized in that the   light source (2) comprises a plurality of light-emitting diodes (4) located on a ring substantially centered on the optical axis (X'X) of the projector (1).   12. Light projector according to claim 11, characterized in that the diodes (4) are arranged on the ring so that the radiation emitted by said diodes (4) are substantially parallel. between them.   13. Light projector according to claim 12, characterized in that the radiation emitted by the diodes (4) is substantially parallel to the optical axis. (X'X) of the projector (1).   14.- Light projector according to claim 12 or 13, characterized in that the diodes (4) are mounted on a printed circuit board (5) mounted   perpendicular to the optical axis (X'X).   15.- Projector of light according to claim 14, characterized in that the printed circuit board <5) is traversed by a threaded rod (8) screwed at one end to a base (7) integral with reflector (3) and on the other end of which is screwed a tubular portion (12) which extends the top of the cone (11).   16.- Projector of light according to any one of   preceding claims, characterized in that the   projector's output beam is a divergent beam. 17.- Lantern signaling, characterized in that it consists of a light projector such   as defined by any of the claims   preceding. 1/2 4 / _ N2 RiXt + FIG.3 NI, R FIG.4 * FIG5 2 FIG ..- 2- R4   liaXR 10 6a 8 6x, - R3 7a 4- R1 1Ib, 15 \ R4 FIG.4.FIG 5 e1 "'./ 11a