DE69215654T2 - Electric light source with reflector - Google Patents

Description

The invention relates to an electric light source with reflector, comprising:

a socket provided with contacts;

a reflector with a basic shape, which is provided with:

an axis of symmetry and a largest diameter d in a plane P perpendicular to the axis of symmetry;

a first, internally concave, reflecting wall section behind the plane P, which in axial cross-sections on a first side of the axis is curved substantially according to an arc of a circle with a center of curvature in front of the plane P, in an area which lies predominantly on the other side of the axis, the first wall section being close to the base;

a second, internally concave, reflecting wall section in front of the plane P, which in axial cross-sections on the first side of the axis is curved substantially according to a circular arc with a center of curvature behind the plane P, on the other side of the axis;

a light window cut by the axis;

the electric light source being arranged in the reflector near the axis and the plane P and being connected to current conductors which run to the contacts of the base. The invention also relates to a reflector and a glass molding for use therein.

Such an electric light source with reflector and a reflector for use therein are described in EP-A-0 410 525.

Radiation from the light source that hits the first wall section directly is reflected there and thrown out through the window behind the light source. The second wall section does not represent a significant obstacle to this. Radiation from the light source that hits the second wall section directly is reflected to the first wall section and thrown out from there. it is added to the first radiation so that, together with the radiation emitted directly from the light source, it forms the beam of the device. The second wall section does not represent a significant obstacle to the radiation which, after reflection, emerges first from the second wall section and then from the first wall section.

The first and second wall sections thus work closely together to focus the radiation produced, while the second wall section prevents radiation from escaping at large angles to the axis, which could be obstructive or useless for practical purposes.

The light source with reflector described in said patent application and the reflector for use therein form a broad beam of light of more than 50º. The term "light" is intended to mean UV light, visible light and IR light. The reflector may have a first wall section having a first segment remote from the plane P and shaped substantially according to a circular arc, and a second such segment close to the plane P. Said reflector enables the electric lamp to irradiate a field with high homogeneity.

In the device described, the light source can be arranged axially or transversely, for example linearly. An incandescent body such as the light source can, for example, have a compact shape such as the M-shape and be arranged axially or, for example, as a straight cylinder transverse to the axis or as an open polygon around the axis. The contours and the light distribution of the light beam depend only very slightly on the shape and position of the light source. Instead of an incandescent body, which may possibly be arranged in, for example, a tubular envelope and which may possibly be surrounded by a halogen-containing gas, a pair of electrodes in an ionizable medium enclosed in an envelope can also be used as the light source, for example a high-pressure sodium discharge lamp, for example for use in horticulture or for general lighting.

An electric incandescent lamp in which a reflector of similar geometrical structure is integrated with the lamp vessel of the incandescent lamp to form a reflector lamp is known from EP 0 284 117-B1. In this incandescent lamp, a light source, an incandescent body arranged around the axis of the lamp vessel. The reflecting wall sections form a very high intensity beam of light in the centre thereof along the axis. The first and second reflecting wall sections cooperate accordingly to form a beam of small width of approximately 25º.

The well-known lamp is suitable for brightly illuminating objects or areas of limited dimensions and thus provides local light accents.

EP 0 410 525-A1 also describes an electric lamp in which a reflector of similar geometric structure is integrated with the lamp vessel to form a reflector lamp. In this case, a first and a second reflecting wall section work together in a corresponding manner to form a beam of small width. The light source here is an incandescent body or a discharge gap between a pair of electrodes in an ionizable medium and is arranged axially.

A disadvantage of the electric light source with reflector and the electric lamp mentioned is that the radiation reflected from the second wall section to the first wall section can hit the light source on its way. If the light source has its own casing, reflection can occur, which disrupts the beam path and leads to scattered radiation. Another possible consequence is a locally higher heat load on the light source, which can lead to instability of the light source and its premature failure.

FR-A-846 188 describes a luminaire with a concave reflector which has a transparent cover at its largest diameter. Opposite the cover there is a socket in which an electric lamp is held.

The reflector has superimposed axial tracks that reflect light falling on the reflector directly to the cover without it crossing the light source of the lamp.

One of the objects of the invention is to provide an electric light source with a reflector of the type mentioned at the outset, which effectively focuses the radiation generated, while at the same time avoiding reflection of radiation onto the light source.

This object is achieved according to the invention in that

the light source has a cylindrical edge with a diameter d1; concentric to the reflector;

the second wall section has superimposed paths that are tilted relative to the basic shape and that run essentially in the axial direction and are curved transversely to their axial direction essentially in accordance with a circular arc with a center of curvature lying on a cylinder coaxial with the axis of symmetry,

the radii of this circular arc touching at most the said coaxial cylinder and this cylinder has a diameter dc which is greater than 0.5 d₁.

Light rays reflected from the second wall section to the first wall section are deflected by the superimposed paths from the corresponding plane through the axis so that they run behind the light source. This prevents reflections on the light source and thus the generation of scattered radiation. It also prevents the light source from being heated unevenly.

The light source can be of different types: a filament, a filament in, for example, a substantially cylindrical casing filled with a gas that may possibly contain a halogen, a discharge gap between electrodes with an ionizable medium in a casing made, for example, of quartz glass or ceramic material. In an axially arranged light source with a casing, the cylindrical edge of the light source coincides at least partially with the outer surface of the casing.

As will be clear from the drawing, rays coming from the second wall section would just graze the light source on their way to the first wall section if the diameter dc were equal to 0.5 d₁.

The measure in the electric light source with reflector according to the invention leads to the expansion of the light beam formed in comparison with the beam of an identical light source with reflector without superimposed paths. If desired, this expansion can be compensated by means of the basic shape of the reflector. If the paths are tilted to the same extent over their entire axial dimension, all light rays reflected therefrom are deflected by the same angle, and rays which travel a longer path to the first wall section receive a larger transverse deviation than rays which travel a shorter path. The former rays lead to a larger expansion of the light beam. In a favorable embodiment, the tracks are twisted: the tracks are tilted relatively slightly at points from which light beams travel a longer path, while they are tilted relatively strongly at points from which light beams travel a relatively short path. In this way, it is achieved that points on the second wall section that are relatively far away from the light source do not deflect light beams more than desired.

It is a favorable property of the light source with reflector that light coming directly from the light source in one axial plane and light coming from the light source in another axial plane, deflected to the second wall section and from this wall section to the first wall section, falls on the first wall section at one and the same point. Therefore, in the reflector, the light is mixed and, if the light source does not emit light of the same color everywhere, the colors are mixed so that the color of the light beam becomes homogeneous.

The light source with reflector may be designed so that all the tracks are tilted in the same direction. Alternatively, the tracks may form an alternating pattern, for example, tilted alternately in one direction and then the other, or tilted in pairs, for example, alternately by +xº, for example +5 or +10º, and -xº. These choices may be relevant depending on the manufacturing processes available. The tracks may have a slope around the axis of the reflector, particularly when tilted in the same direction.

In a favorable embodiment, the first wall section also has superimposed, substantially axially extending tilted tracks. The tracks in this embodiment can be used to counteract or reinforce the deflection of the light rays caused by the second wall section. In the latter case, a beam is obtained which is more broadly spread. In the first case, the deflection caused by the second wall section can be completely eliminated or only partially eliminated. If a relatively narrow beam of light is desired, it is favorable if the second wall section has tracks which deflect incident light rays by an angle of xº and the first wall section has tracks which deflect light rays by half as large, where x is chosen to be small enough to prevent light from returning to the light source in the given geometry. The explanation for this is that the first section of the wall also reflects light that comes directly from the light source and has therefore not yet experienced any deflection that needs to be compensated for. This light is, as mentioned, thrown out through the window without a second reflection.

A special embodiment is one in which both wall sections have tracks that are tilted alternately in one direction and the other. This embodiment can be used to obtain a product with a relatively wide beam or a product with a relatively narrow beam when manufacturing the light source with reflector by aligning the two wall sections relative to each other. In a further development of this embodiment, the first wall section is rotatably connected to the second wall section so that the user can change the beam width.

The basic shape of the reflector may be rotationally symmetrical, but alternatively the basic shape may form another closed configuration in cross-sections transverse to the axis.

The electric light source may be firmly connected to the reflector to form a unit supporting a base.

The electric light source can, for example, be accommodated in a lamp vessel with which the reflector is integrated to form a reflector lamp provided with a base. Wall sections of the lamp vessel are then shaped and mirrored to form the reflector. The lamp vessel can be made of glass. The lamp vessel then has a seam, for example in the plane P. In this case it is constructed from a first and a second molded part which contain the first and second wall sections respectively. The second molded part can also comprise a wall section which forms the light window. A lamp vessel can have a neck-shaped part supporting the base opposite the light window. Alternatively, however, the base can be supported by the first molded part itself. The two molded parts can be rigidly connected to one another or can be rotated relative to one another or even detached, for example if the light source is replaceable.

The light source can alternatively be installed in a reflector, for example a Metal reflector to form a lamp/reflector unit carrying a base. The light window can possibly be closed with a translucent, e.g. transparent, pane.

Mirroring of wall sections of the reflector can be achieved with a metal layer deposited, for example, from the vapor phase, such as aluminum, aluminum and copper, gold, chrome, or with a dichroic filter, such as a filter that reflects visible light and allows thermal radiation to pass through.

Alternatively, the reflector can form a lamp together with a lamp holder in which the light source can be accommodated when the base is placed in the lamp holder. The invention also relates to such a reflector. The reflector can be divisible in the plane P in order to facilitate the introduction of a light source into it. The parts of the reflector can be rotatably attached to one another in order to provide, for example, adjustability for the width of the beam.

It will be clear that the same arrangement of optical elements and the same interaction for focusing generated radiation while avoiding undesirable reflections are realized in these embodiments.

Various basic shapes of the reflector are possible, for example one in which the first reflecting wall section in each axial cross-section on the first side of the axis has a centre of curvature which lies in an area which lies predominantly on the other side of the axis and is bounded, for example, by lines which form an angle β and an angle γ of 23 and 39º respectively with the plane P and which intersect the plane P at the point where the first reflecting wall section intersects the plane P on the first side of the axis;

the second reflecting wall section has a centre of curvature which lies in an area which has the shape of an ellipse Q, the major axis of which has a first end in the plane P at a distance of 0.02 d from the axis of symmetry and a second end at a distance of 0.07 d from the plane P and 0.13 d from the axis of symmetry, the major axis of the ellipse being 6.8 times the length of the minor axis. A reflector with such a basic shape produces a wide beam of 50º or more, for example 60 or 70º. One advantage is that there is great freedom with regard to the positioning of the light source and its shape. The light source can thus be arranged axially or transversely, for example linearly. A filament such as the light source can, for example, have a compact shape, such as an M-shape, or can be a straight cylinder and arranged axially or transversely. Alternatively, however, a filament can also be arranged around the axis as an open polygon. It has been shown that the contours and the light distribution of the light beam to be formed have a very low dependence on the shape and position of the light source.

When a single electric light source with reflector is used to illuminate a field, while it is also desirable to illuminate this field with a high degree of uniformity, it is advantageous if the first reflecting wall section has a first segment remote from the plane P which is curved substantially in accordance with a circular arc whose center of curvature lies in an area having the shape of an ellipse S, the major axis of which has a first end on the first side of the axis of symmetry at a distance of 0.20 d from the plane P and 0.03 d from the axis of symmetry and a second end on the other side of the axis of symmetry at a distance of 0.50 d from the plane P and 0.12 d from the axis of symmetry, the major axis of this ellipse being 33.3 times as long as the minor axis, and

a second segment near the plane P which is curved substantially according to a circular arc, the centre of curvature of which lies in a region on the other side of the axis and which has the shape of an ellipse T, the major axis of which has a first end at a distance of 0.32 d from the plane P and 0.10 d from the axis of symmetry and a second end at a distance of 0.49 d from the plane P and 0.33 d from the axis of symmetry, the major axis of this ellipse being 11.3 times as long as the minor axis. In this case the light beam has a higher luminous flux at acute angles with the axis than along the axis. The luminous flux is then substantially proportional to cos⊃min;³α at an angle α to the axis of symmetry up to relatively large angles.

Another basic form of a reflector has a first wall section which is curved in axial cross sections essentially according to a circular arc and which extends essentially in the transverse direction behind the plane P, the centre of curvature being in front of the plane P on the other side of the axis of symmetry and a second wall portion which is curved in axial cross-sections substantially according to a circular arc and extends substantially in the axial direction in front of the plane P, the centre of curvature lying behind the plane P, on the other side of the axis of symmetry.

Another basic shape of a reflector is similar to that mentioned in the previous section, but the first wall section has a center of curvature lying in front of the plane P in an area that runs on either side of the axis of symmetry.

These and other aspects of the electric light source with reflector according to the invention are shown in the drawing. They show:

Fig. 1, Fig. 2 and Fig. 3 show a first, a second and a third embodiment, respectively, in axial cross-section;

Fig. 4 schematic transverse cross sections along the line IV-IV in a modification of Fig. 1; and

Fig. 5 Views along the line V in modifications of Fig. 1.

In Fig. 1, the electric light source with reflector has a base 1 provided with contacts 2 and a reflector 10 with a basic shape with an axis of symmetry 11 and a largest diameter d in a plane P transverse to the axis of symmetry.

The reflector has a first internally concave reflective wall section 12 behind the plane P which, in axial cross sections on a first side of the axis, is curved substantially according to a circular arc 13 with a center of curvature 14 in front of the plane P, the first wall section being located near the base 1. The reflector 10 also includes a second internally concave reflective wall section 22 in front of the plane P which, in axial cross sections on the first side of the axis 11, is curved substantially according to a circular arc 23 with a center of curvature 24 behind the plane P.

A light window 30 of the reflector 10 has a largest diameter of less than 0.8 d, here 0.68 d, and is intersected by the axis 11.

A light source 3, a high pressure sodium lamp in the figure: an enclosure in which an electrical discharge can be generated between electrodes in a filling of sodium, mercury and noble gas is arranged axially in the reflector 10 near the axis 11 and the plane P and is connected to current conductors 4 which run to the contacts 2 of the base 1.

In the figure, the first reflecting wall section 12 has in axial cross-section on the first side of the axis 11 a centre of curvature 14 which lies in an area which lies predominantly on the other side of the axis and which is bounded by lines 15, 16 which form an angle β and an angle γ of 23 and 39º respectively with the plane P and which intersect the plane P at the point 17 where the first reflecting wall section 12 intersects the plane P on the first side of the axis.

The center of curvature 14 in the figure lies in an area which has the shape of an ellipse R, the major axis of which has a first end 14' on the first side of the axis of symmetry 11 at a distance of 0.23 d from the plane P and 0.04 d from the axis of symmetry and a second end 14" on the other side of the axis of symmetry at a distance of 0.38 d from the plane P and 0.07 d from the axis of symmetry. The major axis of the ellipse R is 10.4 times as long as the minor axis.

The second reflecting wall section 22 has a center of curvature 24 which lies in an area having the shape of an ellipse Q, the major axis of which has a first end 24' in the plane P at a distance of 0.02 d from the axis of symmetry 11 and a second end 24" at a distance of 0.07 d from the plane P and 0.13 d from the axis of symmetry, the major axis of said ellipse being 6.8 times as long as the minor axis.

The light source 3 has a cylindrical edge with a diameter d1, which is concentric with the reflector.

The second wall section 22 has superimposed tracks 25 which are tilted relative to the basic shape and which run essentially in the axial direction and are curved transversely to their axial direction essentially according to a circular arc with a center of curvature lying on a cylinder coaxial with the axis of symmetry 11, the radii of this circular arc touching at most the said coaxial cylinder and this cylinder having a diameter dc which is greater than 0.5 d₁.

The light source 3 is firmly connected to the reflector 10 to form a unit that supports a base 1.

The reflector 10 is integrated with a closed lamp vessel 5 made of pressed glass, whereby a reflector lamp is formed. The lamp vessel consists of a first part, which comprises the first reflecting wall section 12, and a second part, which comprises the second reflecting wall section 22, which reflects, for example, thanks to an aluminum layer, and the window 30. The two parts are connected via a ring 18, for example made of metal, to form a seam which lies in the plane P.

The light rays a are thrown outwards from the first wall section 12. The rays b first hit the second wall section 22, are reflected to the first wall section and then exit the lamp vessel 5. In the beam bundle formed, they combine with the rays that exit outwards without being reflected.

In Fig. 2 and 3, like parts have reference numerals which are each 40 larger than those in the immediately preceding figure.

In the lamp/reflector unit of Figure 2, the light source 43 has an M-shaped axially disposed incandescent body in a vacuum-tight tempered glass envelope containing a halogen-containing inert gas. The light source is mounted in a metal reflector 50 which supports the base 41 and has a riveted seam in the plane P. The centers of curvature and the ellipses Q and R are located as in the previous figure. Both wall sections 52 and 62 have superimposed paths 55 and 65, respectively, which extend substantially in the axial direction, are tilted relative to the basic shape, and are curved transversely to their axial directions substantially in accordance with a circular arc. A number of these paths are shown. The two wall sections can be rotated relative to each other.

In Fig. 3, the reflector 90 has a lamp holder 111 for the base 81 of the separate light source 83 near the first reflecting wall section 92.

The light rays b shown in Fig. 1 are projected into the plane of the drawing; the rays a actually run in the plane mentioned, just as rays b would run if the second wall section 22 were not provided with tracks. The figure shows that the rays b would then graze or hit the light source 3 after reflection on the reflecting circular arc 23. Undesirable irradiation and undesirable reflection would then occur. Depending on the tilting direction of the relevant path 25, the rays b in the reflector lamp shown are guided either above or below the light source 3. Therefore, even after reflection on the wall section 12, they do not run in the plane of the drawing or in any other plane through the axis 11.

In Fig. 4, the modification of the electric lamp with reflector of Fig. 1 has tracks 15 which are superimposed on the first wall section 12.

Fig. 4a shows a large number of rays b, whereby only sections of those parts are shown that run from the second wall section 22 to the first wall section 12 (Fig. 1). All light rays actually originate from the light source 3 and none of the rays shown (a and b, Fig. 1) reach the vicinity of the light source after reflection on the first wall section 12. Since none of the rays shown have already had contact with the first wall section 12, the schematically shown paths 15 have not yet had any influence. In the viewing direction, the rays are deflected to the right, i.e. clockwise, from the second wall section 22. The figure shows a radiation-free zone immediately surrounding the light source. None of the rays hit or even graze the light source.

Fig. 4b shows the tilting and curvature of the tracks 15 and 25. The tracks 15a are tilted to the right in the viewing direction according to the arrows next to them, the track 15b lying between them is tilted to the left. The tracks 15 thus form an alternating pattern. In the same way, the tracks 25a and 25b are tilted in an alternating pattern. The tilting directions in the figure are such that the tracks 15 merge smoothly into the tracks 25. The tracks 15 and 25 are curved essentially according to a circular arc transverse to their axial directions. Point L is a point on the axis about which the track 25a is tilted. A radius of the circular arc of this track is designated 25'. The center of curvature is Cc. The radius 25' touches one and the centre of curvature lies on a cylinder which is coaxial with the axis of symmetry 11 and has a diameter dc. In the figure, the diameter dc is equal to d₁, the diameter of the edge of the light source 3, i.e. greater than 0.5 d₁. A light beam b' originating from the light source 3 comes from the point L. The beam now runs just outside the "radiation-free zone" ZRF. It is clear from the figure that if dc had been equal to 0.5 d₁, b' would have grazed the light source 3. The paths 15 end before reaching the vertex of the first wall section. No rays b reach this vertex, so that a path there cannot interact with paths of the second wall section 22.

In Fig. 5, arcs of a circumscribed circle have been drawn for illustrative purposes.

In Fig. 5a, all the tracks 25b are tilted in the same direction. The same applies to the tracks 15a, but in the opposite direction. A track 15a interacts with a track 25b each time to eliminate an initial reflection of the light rays shown.

The same is done in Fig. 5b, but with tracks 25a and 25b or 15b and 15a tilted alternately in one direction and the other. By giving the first wall section 12" an angular rotation relative to the second wall section 22", it is possible to change the deflection of the light rays. If the second wall section is aligned relative to the first to provide the least possible deflection of the light rays, a maximum possible deflection can be realized by means of an angular rotation of the second wall section by 360/nº, where n is the number of tracks of the wall section.

Claims (8)

1. Electric light source with reflector, with: a base (1) provided with contacts (2); a reflector (10) having a basic shape, which is provided with: an axis of symmetry (11) and a largest diameter d in a plane P transverse to the axis of symmetry; a first, internally concave, reflecting wall section (12) behind the plane P, which is curved in axial cross sections on a first side of the axis substantially according to a circular arc (13) with a center of curvature (14) in front of the plane P, in an area which lies predominantly on the other side of the axis, the first wall section being close to the base (1); a second, internally concave, reflecting wall section (22) in front of the plane P, which is curved in axial cross sections on the first side of the axis (11) essentially in accordance with a circular arc (23) with a center of curvature (24) behind the plane P, on the other side of the axis; a light window (30) intersected by the axis (11); wherein the electric light source (3) is arranged in the reflector (10) near the axis (11) and the plane P and is connected to current conductors (4) which run to the contacts (2) of the base (1), characterized in that the light source (3) has a cylindrical edge with a diameter d₁, concentric with the reflector (10); the second wall section (22) has superimposed paths (25) which are tilted relative to the basic shape and which run essentially in the axial direction and are curved transversely to their axial direction essentially in accordance with a circular arc with a center of curvature lying on a cylinder coaxial with the axis of symmetry (11), where the radii of this circular arc do not exceed the said coaxial cylinder and this cylinder has a diameter dc that is greater than 0.5 d₁. 2. Electric light source with reflector according to claim 1, characterized in that the tracks (25) are twisted. 3. Electric light source with reflector according to claim 1 or 2, characterized in that the tracks (25) are tilted in one direction and the other according to an alternating pattern. 4. Electric light source with reflector according to claim 1 or 2, characterized in that the first wall section (52) has superimposed paths (55) running essentially in the axial direction, which are tilted relative to the basic shape and are curved transversely to their axial direction essentially in accordance with a circular arc. 5. Electric light source with reflector according to claim 4, characterized in that the tracks (55) of the first wall section (52) are tilted in order to counteract the deflection of light rays caused by the tracks (65) of the second wall section (62). 6. Electric light source with reflector according to claim 4 or 5, characterized in that the first (52) and the second wall section (62) are rotatably connected to one another. 7. Electric light source with reflector according to one of the preceding claims, characterized in that the light source (3) is firmly connected to the reflector (10) to form a unit which carries a base (1). 8. Electric light source with reflector according to claim 7, characterized in that the reflector (10) is integrated with a closed lamp vessel (5).