Abstract:
A lamp socket for supporting a light source provided with an LED, the lamp socket including a cooling element; a socket housing which includes socket contacts for electrically connecting the light source; and a lamp base which supports an LED connected to a heat conducting element and is insertable in the socket housing and includes base contacts which are connectable with the socket contacts through a contact force for providing power to the LED, wherein the cooling element on the socket side is connected with the heat conducting element on the base side with a contact pressure that promotes heat transfer, wherein the contact pressure is provided through a pressing force in order for the cooling element to absorb heat generated by the LED, wherein the electric contact between the socket contacts and the base contacts is provided so that it does not provide forces opposite to the pressing force.

Description:
RELATED APPLICATIONS 
     This application is a continuation of International application PCT/DE2010/000655 filed on Jun. 9, 2010 claiming priority from German application DE 20 2009 010 577.6 filed on Aug. 5, 2009 and German application DE 10 2009 040 115.6 filed on Sep. 4, 2009. All the above applications are incorporated in their entirety by this reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a lamp socket for supporting a light source provided with an LED, the lamp socket including a cooling element and a socket housing, which includes socket contacts for electrically connecting the LED, and a lamp base which supports an LED connected to a heat conducting element and which is insertable into the socket housing and includes base contacts, which are electrically contactable through the socket contacts through a contact force in order to supply the LED with power, wherein the cooling element on the socket side is connected with the thermally conductive element on the LED side—possibly through a device that promotes heat transfer, such as thermally conductive foil or thermally conductive paste—with a contact pressure that promotes heat transfer, wherein the contact pressure is provided through a contact force produced through a suitable device in order to absorb heat generated by the LED during operations. 
     BACKGROUND OF THE INVENTION 
     Lamp sockets of this type are known in the art. They are typically configured as compact fluorescent lamp sockets and lamp bases, wherein the lamp base is inserted into the socket and fixated through a rotation like a bayonet. Differently from fluorescent tubes, these configurations are designated as one side socket systems. Through the rotation, furthermore the socket and base contacts are connected with one another and the lamp is electrically contacted. This locking principle is also known as twist lock system. Lamp sockets are also known in the art in particular for light sources provided LEDs, where the base is inserted parallel to a surface of a cooling element, wherein this process also includes electrical contacting. 
     In the art it was the object of a lamp socket and a lamp base to mechanically support and electrically contact the lamp. 
     The service life of illuminants based on LEDs, however, depends from an optimum dissipation of the heat generated during operation of the LED. LEDs are particularly temperature sensitive. Therefore, lamp bases of this type include a heat conducting element which contacts a cooling element arranged at the socket. It is evident that a particular contact pressure between heat conducting element and cooling element positively influences heat transfer. Thus, sockets and bases for a light source including at least one LED are characterized in that besides the mechanical support and the electrical support, optimum heat dissipation has to be provided. Thus, sockets and bases for LED illuminants with respect to their configurative requirements greatly differ from their equivalents for compact fluorescent lamps. 
     In arrangements of lamp socket and lamp base according to the prior art, it has become apparent that the contact pressure between a base side heat conducting element and a socket side cooling element is not the sole measure for the quality of the heat transfer. In spite of a contact pressure accordingly provided, many sockets cause premature aging of the LEDs. Tests have shown that an even distribution of the contact pressure over the contact surfaces of heat conducting element and cooling element determines the quality of the heat transfer. 
     BRIEF SUMMARY OF THE INVENTION 
     Thus it is the object of the invention to provide a lamp socket and a lamp base which provide evenly distributed contact pressure over a contact surface between heat conducting element and cooling element. 
     The object is achieved by a lamp socket and a lamp base with a cooling element, a socket housing which includes socket contacts for electrically connecting a light source, and a lamp base which supports an LED connected to a heat conducting element and is insertable in the socket housing and includes base contacts which are connectable with the socket contacts through a contact force for providing power to the LED. The cooling element on a socket side is connected with the heat conducting element on a base side (optionally through a device that promotes heat transfer, such as heat conducting foil or heat conducting paste) through a contact pressure that promotes heat transfer. The contact pressure is provided through a pressing force produced through a suitable device in order for the cooling element to absorb heat generated by the LED during operation, and the electrical connection between the socket contacts and the base contacts is provided through a contact configuration and/or a contact support that does not provide forces opposite to the pressing force. In particular the object is achieved with the electrical contacting between the socket contacts and the base contacts is provided by configuring and/or supporting the contacts without an opposite force to the contact force. 
     The invention uses the finding that already small force components that are oriented against the contact force providing the contact pressure significantly change the pressure distribution. Based on this, the invention prevents electrical contacting in which the contact forces are oriented against the pressing force through appropriate configuration of socket and base contacts or their support in the socket housing or at the lamp base. 
     An embodiment is advantageous in particular which is characterized in that the contact force between the socket contacts and the base contacts includes a force component which is oriented transversal to the effective direction of the pressing force. 
     Alternatively, it is conceivable that the contact force between the socket contacts and the base contacts has a force component that is oriented in the effective direction of the pressing force and does not influence an even distribution of the contact pressure. 
     Both recited embodiments provide that the effective direction of the contact forces does not negatively influence the pressing force and an even distribution of the pressing force. 
     It is even conceivable that the contacting between the socket contacts and the base contacts is provided in a manner that increases the pressing force. 
     A particular embodiment provides that the base contacts are configured as contacts which protrude from the base towards the cooling element, in particular as contact pins, wherein the contact force between the socket contacts and the base contacts is oriented transversal to the effective direction of the pressing force. 
     As a supplement thereto, it can be provided that the base contacts are configured as contact clamps which support the base contacts, in particular support the contact pins between two contact arms. It is particularly advantageous that the contact clamps which receive the base contacts between one another provide secure electrical contacting. 
     Alternatively it is conceivable that the base contacts are configured as contacts laterally protruding from the base circumference, in particular contacts oriented transversal to an effective direction of the pressing force like, for example, flat blade contacts and the contact forces between the socket contacts and the base contacts have an identical effective direction as the pressing force. With an even distribution of the flat blade contacts over the base circumference, this embodiment does not negatively influence an even contact pressure distribution on the contact surfaces of the heat conducting element and the cooling element. 
     However, it is also conceivable to provide a contact arrangement in which contact forces are provided which are oriented against the effective direction of the pressing force without the contact forces that are negative with respect to the effective direction of the pressing force influencing the contact pressure between the heat conducting element and the cooling element. An embodiment of this type is characterized in that the socket contacts are configured as a contact clamp and receive the socket contacts, in particular the flat blade contacts between one another and the contact forces of the contact arms receiving the socket contacts between one another are oriented opposite to one another and are oriented parallel to the effective direction of the pressing force, wherein the socket contacts are supported floating in the socket housing parallel to the effective direction of the pressing force and/or the socket contacts are supported parallel to the effective direction of the pressing force and are supported floating in the lamp socket. 
     Eventually an embodiment is conceivable which is characterized in that contact fields are configured at the socket or at the base where the base contacts or the socket contacts contact, wherein the contact forces are oriented transversal to the effective direction of the pressing force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the invention are described based on embodiments with reference to drawing figures, where like numerals are used in for technically equivalent or identical components, wherein: 
         FIG. 1 : illustrates an exploded view of the lamp socket and the lamp base according to the invention; 
         FIG. 2 : illustrates a view according to  FIG. 1  with a socket housing sectioned vertically in the plane of the base contacts; 
         FIG. 3 : illustrates a detail view according to the detail circle III in  FIG. 2 ; 
         FIG. 4 : illustrates a view according to  FIG. 2  without the socket housing; 
         FIG. 5 : illustrates a detail view according to detail circle V in  FIG. 4 ; 
         FIG. 6 : illustrates a side view according to  FIG. 2 ; 
         FIG. 7 : illustrates a detail view according to the detail circle VII in  FIG. 6 ; 
         FIG. 8 : illustrates a second embodiment of the invention in a perspective view with a socket housing that is vertically sectioned in the plane of the socket contacts; 
         FIG. 9 : illustrates a view according to the detail circle IX in  FIG. 8 ; 
         FIG. 10 : illustrates a view according to  FIG. 8  without the socket housing; 
         FIG. 11 : illustrates a detail view according to the detail circle XI in  FIG. 10 ; 
         FIG. 12 : illustrates another embodiment of the invention in a perspective view and an illustration of the socket housing in a vertical sectional view along a sectional plane through the socket contacts; 
         FIG. 13 : illustrates a detail view according to the detail circle XIII in  FIG. 12 ; 
         FIG. 14 : illustrates a view according to  FIG. 12  omitting the socket housing; 
         FIG. 15 : illustrates a view according to the detail circle XV in  FIG. 14 ; 
         FIG. 16 : illustrates another embodiment of the invention in a perspective view with a socket housing vertically sectioned in the plane of the socket contacts; 
         FIG. 17 : illustrates a detail view according to the detail circle XVII in  FIG. 16 ; 
         FIG. 18 : illustrates a view according to  FIG. 16  omitting the socket housing; 
         FIG. 19 : illustrates a detail view according to the detail circle IXX in  FIG. 18 ; and 
         FIGS. 20 through 23 : illustrate schematic views of additional embodiments of the invention depicting force effective directions. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the figures, an arrangement of lamp socket and lamp base is designated overall with the reference numeral  10 . 
     A lamp socket  11  is illustrated which includes a cooling element  12  on which a socket housing  13  is arranged which is provided with socket contacts  14 . The cooling element can also be an integral element, for example, of a lamp housing. 
     The surface of the cooling element  12  that is oriented towards the socket housing  13  is configured planar. The cooling element  12  is provided with a plurality of cooling ribs  15  on its bottom side arranged opposite to the socket housing  13  in order to increase the surface area and in order to improve heat dissipation. 
     The socket housing  13  includes a base receiver  16  which is configured in the present embodiment as a central circular recess. The lamp socket  17  includes optics  18  oriented away from the cooling element, wherein one or plural LEDs are arranged in a transition portion of the lamp base  17  and the optics  18 . The lamp base  17  is configured in the embodiment with a contour that is congruent with the base receiver  16  and therefore configured as a circular cylinder. Support cams  19  radially protruding from the lamp socket  17  penetrate through locking grooves  20  when inserting the lamp base  17  into the socket housing  13  and reach behind accordingly configured wall sections of the socket housing  13  like a bayonet lock. In the first embodiment according to  FIGS. 1 through 7 , the base  17  includes radially protruding base contacts  21  configured as contact pins  22 . The base contacts penetrate insertion grooves  23  when inserting the lamp base  17  into the socket housing  13  and thus move into the interior of the socket housing  13 . When the lamp base  17  is turned in locking direction V and when reaching the end stop with respect to the bayonet type lock the contact pins  22  come into engagement with the socket contacts  14 . 
     In the arrangement  10  including the lamp socket  11  and the lamp base  17 , the lamp socket  11  is considered as a lower component and the lamp base  17  is considered as an upper component. 
     As can be derived from  FIGS. 1 through 7 , the socket contact  14  is configured as a contact clamp  24  with two contact arms  25  that are arranged opposite to one another and preloaded relative to one another. 
     In  FIG. 2 , the arrangement  10  of lamp socket  11  and lamp base  17  is illustrated in its entirety again, wherein the socket housing  13  that is sectioned along a plane defined by the socket contacts  14  facilitates a view of the contact arrangement. 
     The lamp socket  17  supports a heat conducting element which is not designated in more detail which contacts on the one hand side the LED and when arranged in the socket  11  on the other hand side contacts the cooling element  12 . This way, the heat generated through the operation of the illuminant is conducted away from the illuminant and dissipated through the cooling element  12  to the ambient. Thus it is required that the contact surfaces of the cooling element  12  and the base side heat conducting element contact one another with a particular minimum contact pressure. This minimum contact pressure is provided with a contact force which is generated by a device that is not illustrated. Typically, these are spring elements which load the lamp socket  11  and the lamp base  17  relative to one another. The contact pressure provides, possibly using additional devices improving heat transfer like heat transfer foil or heat transfer paste, a full surface even contact of the base side heat conducting element and the cooling element  12 , and therefore provides optimum heat transfer. 
     In order to prevent negative influences upon the contact pressure or its even distribution through electrically contacting base and socket contacts, the invention provides solutions in the subsequently described embodiments, in particular with the described contact configuration and arrangement. 
     The socket contacts  14  configured as contact clamps  24  illustrated in  FIGS. 1 through 7  contact the radially oriented outer surface of the contact pins  22  with its contact arms  25 . The contact forces of the contact arms  25  thus act axially in a direction of the pressing force and also against the direction of the pressing force taking the longitudinal center axis M through the arrangement  10  as a reference. This is clearly apparent from  FIGS. 3 through 5 . In a contact arrangement of this type, there is a risk in principle that a force component of the lower contact arm  25  acting against the pressing force negatively influences the contact pressure, thus reduces the contact pressure. In order to prevent this, the socket contact  14  is supported in its contact cavity  26  axially movable, this means parallel to the center axis  14 . Therefore, the socket contact  14  in a first embodiment according to  FIGS. 1 through 7  cannot be supported in axial direction; this means parallel to the effective direction of the pressing force at the socket housing. An opposite force can in particular not be applied through the lower contact arm  25  against the effective direction of the contact force. The force component oriented against the pressing force between lamp socket  11  and lamp base  17  can therefore be used exclusively for a safe contact between the socket contact  14  and the contact pin  22 , but cannot negatively influence the contact pressure between the cooling element  12  and the base side heat conducting element. The clearance of the socket contact  14  in its contact cavity  26  is sized so that all possibly occurring axial dimensional tolerances at the base  11  and the socket  17  can be bridged/compensated without any force. 
     A second advantageous embodiment of the invention is illustrated in  FIGS. 8 through 11 . The socket contacts  14  are thus configured as approximately V-shaped contacts and are arranged in vertical direction, this means in the direction of the vertical center axis M without clearance in the contact cavity  26  formed by the socket housing  13 . The lamp base  17  forms radially outward oriented contact fields  27  which move in locking direction V after insertion of the lamp base  17  into the lamp socket  11  and contact the V-shaped socket contact  14 . A spring loaded arm  28  of the V-shaped socket contact contacts the contact field  27  for providing an electrical contact. The contact forces imparted by the spring arm  28  are essentially oriented in radial direction towards the lamp socket  17  or transversal to the vertical center axis M or transversal to the effective direction of the contact force. A negative influence of the contact force between the base side heat conducting element and the cooling element  12  is therefore not provided. 
     A third embodiment of the invention is illustrated in  FIGS. 12 through 15 . This is a lamp socket  17  which forms radially protruding flat blade contacts  29  which are in turn configured by socket contacts  14  configured as contact clamps  24  with contact arms  25  acting against one another. Thus, the statements made regarding  FIGS. 1 through 7  also apply; in particular the socket contact  14  is supported also here parallel to the vertical center axis M or parallel to the effective direction of the contact force in a floating manner in the contact cavity  26 . 
     Another embodiment of the invention is illustrated in  FIGS. 16 through 19 . These FIGs. illustrate a lamp base  17  with flat blade contacts which initially radially protrude with a section from the base but transition into an end section that is angled by 90° towards the cooling element  12  and thus oriented parallel to the vertical center axis or relative to the effective direction of the contact force. A socket contact  14  configured as a contact clamps  24  reaches around the angled end section of the flat blade contact  29  on both sides. Due to the arrangement of the end section of the flat blade contact  29 , the contact forces between the contact arms  25  and the angled end section of the flat blade contact  29  inserted between the contact arms are oriented transversal to the vertical center axis M and thus transversal to the effective direction of the pressing force between the base side heat conducting element and the cooling element  12 . Thus, the contact forces do not have any influence at all upon the contact pressure or its even distribution between cooling element  12  and the base side heat conducting element. 
     Subsequently, the invention is also described in more detail with reference to  FIGS. 20 through 23 . For the embodiments according to  FIGS. 20 through 23 , like numerals are used for identical or technically equivalent components. The arrow directions define the effective direction of the respective forces. 
     An arrangement of lamp socket and lamp base is illustrated which is overall provided with the reference numeral  40 . The lamp socket  42  includes a cooling element  43 , a socket housing which is not illustrated and socket contacts  44 . 
     The lamp base overall designated with reference numeral  41  includes a base housing  45 , wherein a heat conducting element  47  is arranged at the bottom side  46  of the base housing which is oriented towards the cooling element  43 . The heat conducting element  47  contacts the cooling element  43  with a particular contact pressure F A , optionally with a heat transfer paste or a heat transfer foil arranged there between. The contact pressure F A  is generated by a device which is not illustrated in more detail which can include, for example, spring elements which clamp the lamp base  41  together with the cooling element  43 . In the embodiments according to  FIGS. 20 through 23 , the effective direction of the force corresponds to the arrow direction. The force therefore impacts the lamp socket  41  and presses the lamp socket in a direction towards the cooling element  43  and is oriented in the particular embodiment vertical to the upper side of the cooling element  48  oriented towards the lamp base  41 . Other embodiments are conceivable. In particular the force effective direction can also be oriented against the illustration in  FIGS. 20 through 23  which only represents a reversal of the principle of the invention described infra. The contact pressure between the cooling element  43  and the heat conducting element  47  is evenly distributed over the respective contact surfaces. 
     The even contact pressure that is generated through the contact force F A  between the heat conducting element  47  and the cooling element  43  provides optimum transfer of the heat generated by the LED  49  during operation. Thus, the LED contacts the heat conducting element  47  supported in the base housing  45 . 
     It is an important principle of the invention to configure the contact between the socket contacts  44  and the base contacts  50  through an appropriately selected contact configuration and/or appropriately selected contact support in the lamp base  41  or in the lamp socket  42  without an opposite force to the contact force F A . This means that the contact forces F K  between the base contacts  50  supported by the lamp base and the socket contacts  44  which provide secure power supply for the LEDs do not have any force component which acts against the contact force F A . 
       FIG. 20  illustrates a contact arrangement of socket contact  44  and base contact  50  in which the base contact is configured as a contact pin  51  and the socket contact is configured as a contact clamp  52 . The contact clamp  52  includes two contact arms  53  that are oriented against one another and receive the contact pin  51  between one another. 
     The base contact  50  is oriented parallel to the effective direction of the contact force F A  in a direction towards the cooling element  43 . The contact arms  53  of the socket contact  44  are oriented in the same direction. The contact forces F K  act substantially transversally to the pressing force F A . 
     An alternative embodiment is illustrated in  FIG. 21 . The base housing  45  is provided on its outer circumference with a base contact  50  configured as a contact field  54 . The socket contact  44  configured as a spring arm  55  that is preloaded in a direction towards the base housing contacts the contact field  54  through a contact force F K  oriented transversal to the pressing force F A . Also this embodiment provides electric contacting without an opposite force to the pressing force. 
     The embodiment of the invention illustrated in  FIG. 22  includes another very advantageous arrangement of socket contacts  44  and base contacts  50 . 
     The base contacts  50  protrude relative to the circumferential surface of the base housing  45 , thus they are radially oriented. In particular they are flat blade contacts  56 . These flat blade contacts  46  oriented transversal to the effective direction of the pressing force F A  are contacted by the socket contacts  44  on a top sides of the flat blade contacts, thus on the side oriented away from the cooling element  43 . Consequently, the effective direction of the contact forces F K  is identical with the effective direction of the pressing force F A . In this embodiment, the contact forces F K  therefore reinforce the contact pressure between the heat conducting element  47  and the cooling element  43  when the flat blade contacts  46  are evenly spaced along a circumference. 
     The last embodiment of the invention is illustrated in  FIG. 23 . Also here the base contacts  50  in turn are configured as circumferentially protruding or radially oriented flat blade contacts  56 . The socket contacts, however, are configured as contact clamps whose contact arms  53  contact the flat blade contacts  56  at opposite sides and contact them electrically at least on one side. In the embodiment, a first contact arm  53  like already in  FIG. 22  contacts the top side of the flat blade contact  56  that is oriented away from the cooling element  43 , the second contact arm  53  contacts the bottom side of the flat blade contact at an opposite side of the flat blade contact that is oriented towards the cooling element  43 . This contact arrangement due to the two-sided contact of the contact arms  53  at the flat blade contact  56  has substantial advantages with respect to contact safety which furthermore also apply to the embodiment according to  FIG. 20 . 
     As can be derived from  FIG. 23 , the contact forces act between the flat blade contact  56  and the lower contact arm  53  adjacent to the cooling element  43  against the pressing force F A . As a matter of principle, this force component is configured to act against the pressing force F A  and to reduce the contact force between the cooling element  43  and the heat conducting element  47  which is important for the heat transfer in a disadvantageous manner. In order to prevent this, the socket contact  44  is supported parallel to the effective direction of the pressing force F A  so that it is movable in the socket housing. Consequently, the force component oriented against the effective direction of the pressing force cannot become effective. 
     To sum it all up, the invention illustrates various contact configurations and contact arrangements of the socket and base contacts  44 ,  50 ,  14 ,  21  whose contact forces F K  act without opposite force with respect to the pressing force F A . This is provided in particular in that the contacts are arranged relative to one another so that the contact forces are mostly aligned transversal to the pressing force or in the effective direction of the pressing force. However, when the contact arrangement includes a contact force component that is oriented against the effective direction of the pressing force, the contacts of the lamp socket  42 ,  11  and/or the lamp base  42 ,  17  have to be supported in a decoupled manner. Then this force component cannot develop an effect that is opposite to the pressing force F A . 
     REFERENCE NUMERALS AND DESIGNATIONS 
     
         
         
           
               10  Arrangement of lamp socket and lamp base 
               11  Lamp socket 
               12  Cooling element 
               13  Socket housing 
               14  Socket contact 
               15  Cooling ribs 
               16  Base receiver 
               17  Lamp base 
               18  Optics 
               19  Support cam 
               20  Locking groove of  13   
               21  Base contact 
               22  Contact pin 
               23  Insertion groove of  13   
               24  Contact clamp 
               25  Contact arm of  24   
               26  Contact cavity 
               27  Contact field 
               28  Spring arm 
               29  Flat blade contact 
               40  Arrangement of lamp socket and lamp base 
               41  Lamp base 
               42  Lamp socket 
               43  Cooling element 
               44  Socket contacts 
               45  Base housing 
               46  Bottom side of  45   
               47  Heat conducting element 
               48  Top side 
               49  LED 
               50  Base contact 
               51  Contact pin 
               52  Contact clamp 
               53  Contact arm 
               54  Contact field of  45   
               55  Spring arm of  44   
               56  Flat blade contacts 
             F A  Pressing force 
             F K  Contact forces 
             M Vertical center axis of  10   
             V Locking device