Patent Publication Number: US-7217009-B2

Title: Reflector-type light fixture

Description:
FIELD OF THE INVENTION 
     The invention relates to a reflector-type light fixture, such as a floor, ceiling, or wall light, in particular a step light having a reflector having a surface extending along a part-elliptical line and having at least one focal point at which is provided at least one LED set behind a main shield that prevents light from passing directly out of the light through a light-output plane. 
     BACKGROUND OF THE INVENTION 
     Such a reflector-type light fixture is known from German 10 16 742 (U.S. Pat. No. 6,648,490). The known reflector-type light fixture shown in the drawing of DE 101 16 742 has a rotation-symmetrical parabolic reflector from whose surface the light is reflected parallel. The light source is at least one light-emitting diode (LED) that is mounted between a generally radially extending shield arm and the reflector surface so as not to be visible from outside. In the setup where the LED is mounted at the focal point of the parabolic reflector, the reflected light beams extend parallel to the parabola axis. In the setup where the LED is inside the focal-point plane, but spaced from the from the focal point, the reflected light forms an angle to the parabola axis. If several LED&#39;s are provided in the focal-point plane, selective switching of the LED&#39;s allows different patterns to be produced. In this manner the light output can be adjusted without moving the light source. 
     OBJECTS OF THE INVENTION 
     Starting with the reflector-type light fixture of German 101 16 742, it is an object of the invention to provide a reflector-type light fixture that is particularly adapted for the use of LED&#39;s and that can give a wide light output, as for example desired for wall illumination (wall washer) or in lights built into steps (step lights). 
     SUMMARY OF THE INVENTION 
     This object is attained according to the invention the reflector surface is shaped as an ellipse segment along an ellipse, with the minor and major apices being outside the ellipse segment. At the same time the ellipse segment is adjacent the one focal point of the ellipse while the other focal point is outside the reflector-type light fixture. At the focal point that is very close to the ellipse segment, there is the light-emitting surface of the epoxy body of the LED. This light-emitting surface can be planar or nearly planar or convexly lens-shaped. 
     A particularly flat construction of the reflector is achieved according to the invention in that a flatly arcuate portion of the ellipse segment defines the light-output plane and a strongly curved portion of the ellipse segment is close to the LED. 
     According to another feature of the invention the reflector surface extends along a longitudinal straight line so that the reflector has an elongated flat shape that produces the desired wide light output. 
     According to the invention, the LED, that is its light-emitting surface, a straight longitudinally extending free edge of the main shield, and a straight longitudinally extending free edge of the reflector surface or a longitudinally extending straight edge of a secondary shield at or near the outer free edge of the reflector surface lie in a common plane. This feature ensures that the LED cannot be seen from outside and direct blinding by the LED is impossible. According to the invention, if necessary the straight outer free-end edge of the reflector surface can be replaced by a longitudinally extending straight edge of a secondary shield near the outer free end of the reflector surface. 
     In accordance with the instatn invention the light-output plane of the reflector is defined in the following manner: 
     A portion of the common plane lying between the straight free edge of the main shield and the straight free edge of the reflector surface or the region of the common plane lying between the straight free edge of the main shield and the straight free edge of the secondary shield form the light-output plane. 
     According to a very important feature of the invention, the relationship of the reflector surface, in particular the reflector surface effective on the light-output plane, is defined by parameters of the LED. Here it is necessary to distinguish between the actual physical reflector surface and the part of the reflector surface effective on the light-output plane, which is only a portion of the physical reflector surface. The actual physical reflector surface and the portion of significance with respect to emitted light can but do not have to be the same. 
     In particular the relationship between parameters of the LED and the effective reflector surface is as follows: 
     The orientation of the output angle of light emitted by the LED as the reflector surface and/or the size of the output angle, which has a front plane extending at an angle to the light-output plane and a back plane extending away from the light-output plane, determine the position and/or the size of the effective reflector surface at the light-output plane. According to the orientation (angle) of the LED along the reflector surface, the position of the effective reflector surface and the physical reflector surface can be changed or adjusted. For particular uses the size of the effective reflector surface can be influenced by the orientation of the LED, for example such that the LED is inclined one way or the other so that only a part of the light beam it emits falls on the physical reflector surface so that the effective reflector surface is reduced. 
     On the other hand the size of the effective reflector surface is directly dependent on the size of the output angle. Since with respect to the output angle there is to date no standard technical definition, in this context the output angle is the entire angle of the light cone that is emitted by the light-emitting surface of the epoxy body of the LED. 
     While with the reflector according to the invention the reflector surface is elliptical and emits light through a second focal point of the ellipse outside the light fixture so as diverge toward the surface being illuminated, in the reflector-type fixture according to the invention the reflector is parabolic. 
     Furthermore in the reflector-type light fixture of this invention the front plane extends at an angle to the light-output plane, the rear plane extends away from the light-output plane of the output angle of the LED, and both at least generally enclose the effective width of the reflector surface as well as the effective reflector surface along the ellipse segment or along the parabola segment. 
     This means that the effective reflector surface that determines the size of the output angle of the LED at least corresponds to the effective width of the reflector measured generally transversely. In this manner the reflector can optimally be matched to an LED with a particular output angle. 
     In a practical application of the invention it has been determined that the maximum effective width of the reflector surface, that is the effective reflector surface, corresponds to an LED having an output angle of about 90°. This means that with such light fixtures any LED whose output angle is less or larger than 90° can be used equally. Only with an LED with an output angle of more than 90° is some of the light wasted as it cannot be deflected or is difficult to deflect in the desired forward direction. On the other hand even with such reflector-type light fixtures LED&#39;s with an output angle of less than 90° can be so set or adjusted so that the light beam falls on the reflector surface. 
     An optimization of the lighting effect and of the actual width of the reflector can also be achieved according to further features of the invention in that the front plane extending at an angle to the light-output plane of the output angle of the LED lies in the common plane. This means that the front plane tangents the free edge of the main shield. 
     A significant embodiment of the invention is that a row of the LED&#39;s extends longitudinally in the reflector. Here with reflector-type light fixture having an elliptical reflector according to the invention only one row of LED&#39;s is provided. 
     The light fixture with the parabolic reflector corresponding to the invention can alternately have a plurality of adjacent rows of LED&#39;s. In the setup where several rows can be activated, each row produces a parallel light output but the parallel beams of the LED rows outside the focal-point plane are offset from the parabola axis and move out at an angle to the longitudinal direction of the reflector. In this manner particular effects can be achieved so that the LED&#39;s of the rows can be switched on and off individually or jointly or by rows. It is also possible to use different colors in the individual rows of LED&#39;s. With different LED colors there is color mixture where the adjacent beam overlap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Preferred embodiments of the invention are shown in the drawing, wherein: 
         FIG. 1  is a schematic section through a reflector-type light fixture serving as a step light and having an elliptical reflector surface; 
         FIG. 2  is an enlarged view of a detail of  FIG. 1 ; 
         FIG. 3  is a view like that of  FIG. 1  of a step light with a parabolic reflector; 
         FIG. 4  is an enlarged view of a detail of  FIG. 3 ; 
         FIGS. 5 and 6  are variants on the reflector-type light fixture of  FIGS. 1 and 2 ; and 
         FIGS. 7 and 8  are variants on the reflector-type light fixture of  FIGS. 3 and 4 . 
     
    
    
     SPECIFIC DESCRIPTION 
     In the drawing similar parts and elements are identified with the same reference even when of somewhat different construction. 
     The figures show a step light  10 . 
     The step light  10  according to  FIGS. 1 and 2  has a housing  11  of rectangular section that is set in a niche  12  in a wall or a step  13 . The step light fixture  10  serves for illuminating a traffic surface, for example a stair tread  14 . 
     Inside the light housing  11  is a reflector  15  having a reflector surface  16  that is shaped as an ellipse segment  17 . 
     The ellipse segment  17  has two focal points F 1  and F 2 . The focal point F 1  is inside and the focal point F 2  outside the light fixture  10 . 
     The light-emitting part of the epoxy-body LED  18  not shown in detail in  FIG. 1  is at the focal point F 1 . 
     A planar and opaque shield plate A having a matte-black face turned toward the LED  18  extends upward from a lower straight edge  19  at an angle of about 45° to a light-output plane KA-FF. The reflector  15  extends straight longitudinally perpendicular to the plane of the view of  FIGS. 1–8 . Thus the lower straight edge  19  of the shield plate A extends longitudinally as well as the straight edge KA at the free end of the shield plate A. 
     The straight longitudinally extending outer edge of the reflector  15  is shown at KF. Similarly the straight longitudinally extending inner edge of the reflector  15  is shown at K 1 . 
       FIGS. 1 and 2  clearly show that the straight free outer edge KF of the reflector surface  16 , the straight free-end edge KA of the shield plate A, and the LED  18 , that is the light-emitting surface of its epoxy body, lie in a common plane KF-KA-F 1  which extends longitudinally, that is perpendicular to the drawing plane of  FIGS. 1 and 2 , which also applies for  FIGS. 3–8 . 
     The reflector surface  16  also extends longitudinally since it is centered on a longitudinal axis and thus has a generally flat, elongated and generally C-section shape. In addition the shield plate A extends longitudinally and perpendicular to the plane of the view. 
       FIGS. 1 and 2  do not show that there is a plurality of LED&#39;s  18  aligned in a straight row along the focal point F 1 . The row of LED&#39;s can be of the same or different colors. When different colors the overlap creates a color mixture. 
     The light-output plane extends as part of the common plane F 1 -KA-KF between the edges KA and KF and is thus identified at KA-KF. 
     The light-emitting surface of the LED  18  projects light at an output angle W which is defined between front and rear edge planes SV and SH. The angle W in the embodiment of  FIGS. 1 and 2  is about 90°. 
       FIGS. 1 and 2  show that the front plane SV tangents both the straight edge KA of the main shield A and the outer free edge KF of the reflector surface  16 . The rear plane SH of the angle W tangents the inner edge k 1  of the reflector surface  16 . Since the reflector surface  16  extending between the edge KF and the edge K 1  receives all the light emitted by the LED  18  and reflects it as shown at LE through the light output KA-KF and through the light output opening  20 , passing through the second focal point F 2  outside to the stair tread  14 . The overall width KF-K 1  of the reflector  15  corresponds in this case to the actual reflector surface  16 . The light-output opening  20  extends between the lower straight edge  19  of the main shield A and the straight edge KF of the reflector  15 . 
     The reflector-type light fixture  10  of  FIGS. 5 and 6  is different from the reflector  15  of  FIGS. 1 and 2  mainly in that the reflector width FK-K 1  is less than in the light fixture according to  FIGS. 1 and 2 . In addition the light-output opening has an upper edge KU defined by a secondary shield  21  which is planar and which is mounted near the outer free edge KF of the reflector surface  16 . The secondary shield  21  prevents direct exposure of the LED  18 . The secondary shield  21  extends longitudinally. The common plane in  FIG. 1  is shown at F 1 -KA-KU. The light-output plane is KA-KU. 
       FIGS. 5 and 6  show that the output angle W between the front plane SV and the back plane SH is also 90°. The front plane SV tangents the outer free edge KF of the reflector surface  16  and is above the edge KA of the main shield A. The back plane SH of the output angle W is not on the reflector surface  16 . For this reason some of the light outputted by the LED  18  is not used. This can be alleviated as shown in  FIGS. 5 and 6  for example by using an LED with a narrower output angle W, whose back plane SH tangents the inner edge K 1  of the reflector surface  16 . 
     In  FIGS. 3 and 4  the reflector light fixture  10  has a parabolic reflector  15  whose parabolic segment  23  reflects out a parallel light beam LP. This light of  FIGS. 3 and 4  has a light-output opening with a dispersing lens  22  which makes the emitted light more uniform. The inner surface of the planar lens plate  22  is structured, for example with a field of recesses or a sculptured or Fresnel-lens surface. 
     Otherwise the embodiment of  FIGS. 3 and 4  corresponds to that of  FIGS. 1 and 2 . 
     The embodiment of  FIGS. 7 and 8  corresponds generally to that of  FIGS. 2 and 3 , but has narrow width KF-K 1  of the reflector surface  16  and also has a secondary shield  21  like in  FIGS. 5 and 6  which was already described and to which reference should be made for  FIGS. 7 and 8 . 
     In the embodiment of  FIGS. 7 and 8  the output angle W of the LED  18  corresponds to the width KF-K 1  of the reflector surface  16  so that in this case the light emitted by the LED  18  is used fully. The output angle W of  FIGS. 7 and 8  is 65° and somewhat less than in the other embodiments. 
     In addition it should be stated that the reflector surface  16  itself is highly reflective. It can also be structured, e.g. faceted.