Patent Publication Number: US-2011051432-A1

Title: LED Lamp

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an LED lamp comprising an elongated housing in which a LED-unit is accommodated. 
     DE 202 19 987 U1 discloses an LED lamp having an LED unit accommodated together with an electronic adaptation circuit in a housing, wherein the housing corresponds to the housing of a conventional light bulb. A collective lens is integrated in the transparent part of the housing. 
     In recent years high-power LEDs have come on the market having an electrical power of up to some Watts. If such a high-power LED is accommodated in a housing, as it is known from DE 202 19 987 U1, there is a strong heat development in the housing, which can result in damage to the high-power LED. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to create an LED lamp by means of a simple design guaranteeing sufficiently high dissipation of heat in order to avoid damage to the LED unit. 
     This object is achieved by an LED lamp which comprises a hollow, preferably cylindrical housing made of metal, preferably brass, in which an elongated cooling body made of ceramic is arranged. The outer surface of the cooling body contacts the inner surface of the housing. An LED unit is mounted at the front end face of the cooling body. At the front end of the housing a lens system is arranged in front of the LED unit. In order to provide an electrical connection between the LED unit and a contact element provided at the rear end of the housing, which contact element can be brought into contact with a power supply, there is a groove formed in the outside of the cooling body, which groove extends in the longitudinal direction of the cooling body, at least one of the connecting lines for the LED unit being arranged in the groove. 
     As the ceramic material for the cooling body, for example, CeramCool® can be used, which is sold by the company of CeramTec AG. 
     By means of the ceramic material the heat can reliably be dissipated from the LED unit. Since the cooling body with its outer surface lies against and contacts the inner surface of the housing made of metal along the whole length of the cooling body , the heat is very well dissipated to the outside, thereby avoiding overheating of the LED unit. In order to guarantee optimal heat transfer between the outer surface of the cooling body and the inner surface of the housing, a heat-conducting paste or a heat-conducting adhesive can be used. 
     Preferably, connections for the LED unit which are in contact with the connecting lines are metallized onto the front end face of the cooling body made of ceramic, for example, by galvanizing. The cooling body made of ceramic can be directly coated and thus be used as a circuit carrier. At the same time the cooling body is reliably electrically insulated. 
     In a preferred embodiment the LED unit is connected to the cooling body through a contact surface metallized onto the front face of the cooling body. A high-power LED often has, in addition to the electrical connections, also a metallic surface through which heat can be dissipated. This metallic surface is connected to the metallized contact surface on the cooling body, thereby guaranteeing a reliable dissipation of heat. 
     Additionally, an electronic circuitry, for example, for regulating the current for the LED unit, can be accommodated in a recess in the cooling body, wherein the recess is preferably formed in the side wall of the cooling body. Circuit paths for the electronic circuitry can also be applied by means of metallization. 
     It is also possible to form the recess in the rear end face of the cooling body. 
     In the case of the embodiments according to the invention where an electronic circuitry is arranged in a recess, a storage choke consisting, for example, of a ferrite core surrounded by a choking coil can be arranged adjacent to the rear face of the cooling body in the housing. 
     The rear face of the housing is preferably closed by an insulating bush in which at least one contact pin is arranged which is connected to at least one connecting line. 
     Depending on the field of application of the LED lamp, the lens system can be formed by a condenser lens, a rod lens or other lenses or, in the simplest case, by a protecting glass. Between the LED unit and the lens system a great variety of aperture elements can be accommodated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention are hereinafter explained in more detail by way of drawings, in which 
         FIG. 1  is a perspective view of a first embodiment of an LED lamp according to the present invention; 
         FIG. 2  shows a longitudinal section of the LED lamp of  FIG. 1 ; 
         FIG. 3  shows a longitudinal section of a second embodiment of the LED lamp according to the present invention; 
         FIG. 4  shows the detail X of  FIG. 3 ; 
         FIG. 5  shows a side view of the cooling body of the LED lamp of  FIG. 3 ; 
         FIG. 6  shows a front view of the cooling body of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The LED lamp  10  shown in  FIGS. 1 and 2  has a generally cylindrical, elongated hollow housing  11  made of metal, for example, brass. The opening at the front end of the housing  11  is closed by a collective lens  12  mounted concentrically to the central axis of the housing  11 . At the rear end the housing  11  has a ring collar  24  extending outwardly. The opening at the rear end of the housing  11  is closed by an insulating bush  22  made of insulating material. The rear end of the insulating bush  22  is flush with the rear end of the housing  11 . The front end face of the insulating bush  22  extends in a radial plane to the central axis of the housing  11 . An elongated, generally cylindrical ceramic body  14  abuts with its rear end face against the front end face of the insulating bush  22 . The outer diameter of the ceramic body  14  corresponds to the inner diameter of the housing  11  in this area so that the outer surface of the ceramic body  14  contacts the inner surface of the housing  11  along the whole length of the ceramic body  14 . The front face of the ceramic body  14  is spaced apart from the condenser lens  12  so that a clearance  13  is formed between them. An LED unit  16  is mounted centrally at the front end face of the ceramic body  14 , wherein the front end face of the LED unit  16  is at a short distance to the condenser lens  12 . A first connecting line  21  of the LED unit  16  is connected to the housing  11  through the clearance  13  between the condenser lens  12  and the cooling body  14 . Diametrically opposite this connection there is an outer groove  18  formed in the outer surface of the cooling body  14 , which outer groove  18  extends in the longitudinal direction of the cooling body  14  and over the whole length of the cooling body  14  and thus forms a passage between the clearance  13  and the rear end of the cooling body  14 . 
     A contact pin  26  is inserted coaxially in the insulating bush  22 , wherein the contact pin  26  with its front end lies against the rear end face of the cooling body  14  and the rear end of the contact pin  26  protrudes over the insulating bush  22 . A radial groove  28  is formed in the front face of the insulating bush  22 , wherein the radial groove  28  is in contact with the outer groove  18  in the cooling body  14  and leads to the contact element  26 . A second connecting line  20  of the LED unit  16  is with its one end in contact with the LED unit  16  and with its other end with the contact element  26  and extends via the clearance  13  through the outer groove  18  and the radial groove  28 . 
     In the LED lamp  10  shown in  FIGS. 1 and 2  no electronic circuitry for the LED unit  16  is accommodated. The electronic circuitry (not shown) is arranged outside and is in contact with the LED unit  16  through the contact pin  26  and the housing  11 . 
     The LED unit  16  has at its rear side a metallic surface  15  which is connected to a contact surface  17  galvanized onto the front face of the cooling body  14 , for example, by soldering, whereby an excellent heat transfer is guaranteed between the LED unit  16  and the cooling body  14 . 
     It is also possible to connect the connecting lines  21  and  20  to contact surfaces metallized onto the front face of the cooling body  14 , wherein the contact surfaces in turn are in contact with connections of the LED unit  16 . 
     It is also possible to apply a high-power LED chip directly onto the ceramic body and to bond the connections of the chip directly to the metallized connecting surfaces of the ceramic body. 
     The LED lamp shown in  FIG. 3  differs from the LED lamp  10  of  FIGS. 1 and 2  essentially in that an electronic circuitry  37  is integrated in the LED lamp  30 . Elements which correspond to the ones in the embodiment of  FIG. 1  are referred to by the same reference numerals. An outer groove  34  extends in the longitudinal direction of the cooling body  32  and over the whole length of the cooling body  32  and thus forms a passage between the clearance  13  and the rear end of the cooling body  32 . The electronic circuitry  37  is arranged in a recess  36  in the cooling body  32 , which recess  36  is formed by an enlarged portion of an outer groove  34  formed in the outer surface of the cooling body  32  between a front portion  34   a  and a rear portion  34   b  of the outer groove  34 . The circuitry paths for the electronic circuitry  37  are galvanized in the recess  36  onto the material of the cooling body  32 . Here, too, the first connecting line  21  of the LED unit  16  can be in contact with the housing  11 . The second connecting line  38  is in contact with a connecting line  39  metallized by galvanization onto the front end face of the cooling body which in turn is connected to the LED unit  16 . The second connecting line  38  extends via the front portion  34   a  of the outer groove  34  into the recess  36 . 
     The rear end of the housing  11  is closed by an insulating bush  52 . A storage choke  44  formed by a ferrite core  42  surrounded by a choking coil  40  is arranged between the front face of the insulating bush  52  and the rear face of the cooling body  32 . 
     The choking coil  40  is in contact with the electronic circuitry  37  via two connecting lines guided through the rear portion  34   b  of the outer groove  34 . 
     Three contact pins  46 ,  48 ,  50  are inserted in the rear face of the insulating bush  52 , which contact pins  46 ,  48 ,  50  are in contact with the electronic circuitry via connecting wires. Herein one connection can be used for supplying current, another one, for example, for fast switching on and off the LED with chronological synchronism, and another one, for example, for adjusting brightness. The number of the connections can vary depending on the control signals required. A serial bus connection for the various settings and control functions can also be realized. The connections can be designed as contact pins, as shown, but also as a multipolar miniature connector.