Abstract:
A sealed LED light module comprises a base plate, having at least one LED, and a cover providing a base plate support. The base plate is located on the cover to define an inner space which is sealed against the environment. For sealing the cover has at least one sidewall, which defines a trench together with at least one base plate support, and the trench holds a seal which interacts with at least one edge of the base plate and the surface of the trench to seal the inner space against the environment.

Description:
PRIORITY CLAIM 
       [0001]    This application is a continuation of pending International Application No. PCT/EP2013/065806 filed on Jul. 26, 2013, which designates the United States and claims priority from European Application No. 12178841.8 filed on Aug. 1, 2012, both of which are incorporated herein by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a LED (Light Emitting Diode) light unit and specifically to a housing for a LED light unit. 
         [0004]    2. Description of Relevant Art 
         [0005]    In LED light units, a plurality of LEDs may be mounted to a printed circuit board. This circuit board is often covered by a cover which may also act as a lens for guiding light to the outside of the light unit. 
         [0006]    The European patent application publication EP 1 821 030 A1 discloses a LED light unit, where LEDs are mounted to a heat sink. Furthermore, the LEDs are embedded by a cover element and a housing to form an integral part which is water-tight. 
         [0007]    US 2012/0188788 A1 discloses a LED-light assembly. The LED light assembly has a housing with a transparent front cover being screwed to a back cover. A sealant may be inserted in an annular through between the front cover and the back covering after the screws have been fastened. At the rear side of the back cover are fins rendering the back cover into a heat sink. The housing accommodates a printed circuit board, the latter supporting LEDs. 
         [0008]    A disadvantage of these LED light units is their respective complex and thus expensive design. With respect to EP 1 821 030 A1 the cover element embeds the LEDs which may affect optical characteristics. 
       SUMMARY OF THE INVENTION 
       [0009]    The problem to be solved by the invention is to design a sealed LED light module which is sealed against dust, dirt, water and/or humidity, which has excellent long term stability and which can be manufactured by an automated process in large volumes at low costs. 
         [0010]    The problem is solved by an embodiment with a base plate supporting at least one LED and/or further electronic components which may be required for driving/controlling the at least one LED. The base plate may be a printed circuit board. It may also comprise a printed circuit board. Preferably, the base plate is a heat conducting plate which may be made of a metal, like aluminum, and which further preferably comprises laminated electrically isolating and current-conducting structures. Preferably, the base plate is at least essential planar, as expressed in the word “plate”. The base plate is positioned on a cover through which light may be emitted from the at least one LED to the outside of the light module. The cover may have at least one lens for guiding and/or directing the light emitted by the at least one LED. Preferably, the cover is made of a clear and/or transparent and/or semitransparent material, preferably a plastic material. The cover preferably has at least one base plate support. Such a base plate support may be a strut or a protrusion from the inner surface of the cover. 
         [0011]    Preferably, the base plate support is a bar or a barrier, preferably surrounding at least a part of the base plate. It is further preferred, if the cover has at least one sidewall which forms a trench together with the at least one base plate support. Most preferably this trench is surrounding the baseplate and/or the cover. 
         [0012]    At least one edge of the base plate, preferably all edges of an e.g. rectangular base plate are held within a sealing. The sealing seals a slit between the base plate and the cover and preferably fixes the base plate to the cover. In other words, the mechanical connection of the base and the cover is provided by said sealing. The base plate and the cover are so to speak attached to each other by said sealing. The sealing preferably is the only connecting means between the base plate and the cover. Accordingly there is no screw, rivet or clip in between or surrounding the base plate and the cover. The sealing may be a mold or cast or glue. It preferably is at least a semi-elastic plastic material. Preferably, the sealing is contained within the trench defined by at least one base plate support and a sidewall of the cover. Preferably the sealing is processed by low pressure injection molding. It may be a hot-melt which may be based on polyamide. 
         [0013]    Preferably, the base plate and the cover form a hermetically sealed unit which preferably is water tight and which preferably cannot be opened and need not to be opened for service. This prevents the penetration of dust and debris into the optical system which also extends lifetime and improves quality. Most preferably the base plate has no further holes or openings except holes which are sealed and ventilation holes. Due to the elastic properties of the seal, different thermal expansion of the base plate and the cover may be equalized, therefore preventing cracks or even bending of the unit at extreme temperatures. 
         [0014]    To easy assembly, the cover may be placed with its inside up on a flat surface. Then, the base plate may be placed on the cover. The base plate is preferably held at a correct distance to the cover by the at least one base plate support. There may be further notches or holes in the base plate, interacting with protrusions in the base plate support to ensure a correct location of the base plate on the cover. After placement of the base plate on the cover, sealing is filled and/or molded to the edges of the base plate, preferably filling the at least one trench. Here, the at least one trench may act as a molding form which holds the sealing when it is in a semi-liquid or liquid condition. 
         [0015]    In a further preferred embodiment, there is at least one sealing sidewall located between the cover and the base plate for sealing the inner space between the cover and the base plate containing the at least one LED against the outer environment. The sealing sidewall may enclose an area within which a further hole or opening may be provided in the base plate and/or the cover. Such an opening may be used for contacting an electrical connector and/or for inserting a screw. The sealing sidewall may be extending from the cover and may be of the same material as the cover. In an alternative embodiment, the sidewall may be of a material which is the same as the sealing. There may be any combination of the sealings disclosed herein with a connector. Generally such a sealed opening prevents any debris or contamination from the connector to penetrate into the optical system. 
         [0016]    In a further embodiment, there may be an upper sealing which further seals parts of the outer side of the base plate. This upper sealing preferably is of the same material as the first sealing. To simplify molding, it may be connected by at least one bar to the first sealing. The upper sealing may also extend from the outside of the base plate through the inner space between the base plate and the cover to the inner side of the cover, therefore also sealing the inner space against the environment. 
         [0017]    In a further embodiment, there are cut-outs and/or protrusions at the edges of the base plate. 
         [0018]    In another embodiment, the edges of the base plate are bent to further in-crease mechanical strength of the connection to the sealing and to increase the mechanical stability of the mechanical contact between the base plate and the sealing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment and with reference to the drawings. 
           [0020]      FIG. 1  shows a sectional view of the sealed LED light module. 
           [0021]      FIG. 2  shows a sectional view with sealing sidewalls extending from the cover to the surface of the base plate. 
           [0022]      FIG. 3  shows a different embodiment of the sealing sidewall. 
           [0023]      FIG. 4  shows an embodiment providing a cut-out in the cover. 
           [0024]      FIG. 5  shows an embodiment with an upper sealing to seal the outer side of the base plate. 
           [0025]      FIG. 6  shows a further sealing protruding to the cover. 
           [0026]      FIG. 7  shows a modified upper sealing protruding to the cover. 
           [0027]      FIG. 8  shows an embodiment with a base plate having bent sidewalls is dis-closed. 
           [0028]      FIG. 9  shows an embodiment of bent sidewalls of the base plate. 
           [0029]      FIG. 10  shows a top view of the light module. 
       
    
    
       [0030]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    In  FIG. 1 , a sectional view of a first embodiment of the invention is shown. A cover  100  holds a base plate  200 , whereas fixing and sealing between the cover and the base plate is done by a sealing  300 . The base plate has an outer side (on top in the figure) and an inner side directed towards the cover, the inner side holds at least one LED (Light Emitting 
         [0032]    Diode)  210 ,  220 , and optionally further electronic components. The LEDs radiate light from the bottom side through the cover  100  to the outside of the light module. For better holding of the base plate, preferably at least one base plate support  130 ,  131  are provided within the cover. They are preferably protruding from the surface of the cover. Furthermore, it is preferred, if the cover has at least one sidewall  110 ,  111 , which preferably forms at least one trench  141  which may be filled with sealing  300  which preferably seals the edges  206 ,  207  of the base plate  200 . Between the base plate  200  and the cover  100 , there is a sealed inner space  140 . Furthermore, there is at least one sealing sidewall  150 ,  151  between the cover  100  and the base plate  200 . This at least one sealing sidewall encloses a section of the base plate which may contain an opening  230 , through which a connecting plate  260  may penetrate to enter into electric contact with at least one electrical connector ( 240 , 250 ). By this way, electrical connection may be made from the LEDs at the base plate to an external power supply. In combination with an opening in the cover  100 , which may be similar to opening  180  from  FIG. 4 , but with shortened inner walls, to allow access to the base plate  200 , a connector may be inserted from the front side of the cover. This may allow external access e.g. for diagnosis or control like dimming of the lamp and/or the power supply. The connector may also be extending from the power supply though the base plate to be accessed from the front side of the cover. It is further preferred to have guiding elements for the connector at least in one of the cover, base plate or inner walls. Preferably these guiding elements allow insertion of the connector from at least one side, preferably from both sides. 
         [0033]    In  FIG. 2 , a further embodiment is disclosed. Herein, the opening in the base plate  230  is larger and may be used for a different purpose than inserting a connecting plate as disclosed before. In this embodiment, the sealing sidewalls preferably protrude from the cover  100  into the direction of the base plate  200  and end at the inner side of the base plate  200 , which is bearing the at least one LED. It preferably comprises the same material as the cover  100 . 
         [0034]    In  FIG. 3 , a different embodiment of sealing sidewalls  150 ,  151  is disclosed. Here, the sealing sidewalls  150 ,  151  protrude from the cover  100  to the outside of the base plate  200 , therefore providing a better sealing of the base plate. 
         [0035]    In  FIG. 4 , a further embodiment is shown which provides an opening  180  in the cover. For this purpose, the sealing sidewalls  150 ,  151  extend from the cover  100  throughout the base plate  200 . Contact of the sealing sidewalls may also be done as disclosed in  FIG. 2 . Such a cut-out in the cover may be used for gaining access to an electrical contact or to a screw. 
         [0036]    In  FIG. 5 , a further embodiment is disclosed having an upper sealing  190  to seal an area at the rear side of the base plate  200 . To simplify molding and to have a connection between the upper sealing which preferably is made of the same material as the sealing  300 , at least one bar  191  may be provided. This kind of sealing may be combined with any other kind of sealing sidewalls disclosed before. 
         [0037]    In  FIG. 6 , a further sealing is disclosed which protrudes through the cover  100  and therefore seals or encapsulates the whole inner space. 
         [0038]    In  FIG. 7 , a modified upper sealing is disclosed which protrudes through the cover  100  and therefore seals or encapsulates the whole inner space. 
         [0039]    In  FIG. 8 , a modified embodiment is disclosed. Herein, the base plate  200  has bent sidewalls  201 . These bent sidewalls further increase mechanical stability and stiffness of the base plate. They further increase the mechanical retention force of the base plate within the sealing  300  and therefore within the cover  100 , further increasing mechanical stability of the sealed LED light module. It is obvious that this specific embodiment may be combined with all other embodiments shown herein. 
         [0040]    In  FIG. 9 , a top view of a base plate  200  is shown. Herein, there are bars  202  connecting the bent sidewall  201  to the base plate  200 . Between the bars, there are cut-outs  203 . The sealing  300  penetrates through the cut-outs and therefore increases the retention of the base plate  200  within the sealing  300 , further increasing mechanical stability. It is obvious that this specific embodiment may be combined with all other embodiments shown herein. 
         [0041]    In  FIG. 10 , a top view of the light module is shown. The base plate  200  is placed on cover  100  and is sealed by sealing  300 . Here, the second sidewall  111  and a third sidewall  112  can be seen. On top of the base plate  200 , there is an upper sealing  190  connected by a bar  191  to the sealing  300 . There may be a vent hole  205  in the base plate allowing for equalization of air pressure. This hole may have a filter, a membrane or other means for directing or selecting flow of vent exchange of gases, preferably preventing the intrusion of liquids or humidity. First protrusions  172  and second protrusions  174  may be provided for aligning the light module within a lamp case. Furthermore, it is preferred, if at least one clamp  170  is provided to fix the light module within a lamp case. 
         [0042]    It will be appreciated to those skilled in the art having the benefit of this disclosure that this invention is believed to provide a sealed LED light module. Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           100  cover 
           110  first sidewall 
           111  second sidewall 
           112  third sidewall 
           130  first base plate support 
           131  second base plate support 
           140  inner space 
           141  trench 
           150  first sealing sidewall 
           151  second sealing sidewall 
           170  clamp 
           172  first protrusions 
           174  second protrusions 
           180  opening in cover 
           190  upper sealing 
           191  bar 
           200  base plate 
           201  bent sidewall 
           202  bar 
           203  cutout 
           205  vent hole 
           206 ,  207  edges of the base plate 
           210 ,  220  LEDs/components 
           230  opening in base plate 
           240  first connector 
           250  second connector 
           260  connecting plate 
           300  sealing