Patent Publication Number: US-7220931-B2

Title: Switching device with integrated light source

Description:
CROSS-REFERENCE 
   This is a continuation-in-part of PCT application PCT/IB 2003/006343 filed 30 Dec. 2003 which named the United States and which claimed priority from French application 0300267 filed 10 Jan. 2003. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a switching device of the type comprising a casing forming a cavity, a switching mechanism in the casing and an operating member for operating the switching mechanism. A light source carried by the casing is connected to energizing conductors. The light source comprises a LED (light emitting diode) element and at least two connection members extending at least partially through the casing to the energizing conductors. The light source illuminates a control button of the operating member. 
   In order to be visible from the operating region at which the control button is pushed, the light source must be positioned outside the switching mechanism. The LED is commonly constructed with a transparent head that contains a light-emitting semiconductor element. The LED element is connected to a pair of conductors that are embedded in the transparent head and that have free ends forming flat conductive connection areas on a side of the transparent head. Such flat connection areas are suitable for surface mounting on a circuit board by direct soldering to traces on the circuit board. Such LED&#39;s are widely available at moderate cost. 
   In practice, the internal region of the casing of the switching device is occupied by the switching mechanism. In a switching device where the control button is depressed, or pushed down, the presence of the LED can result in a tall switching device. 
   A major object of the invention is to provide a low cost switching device with a light source that is compact in height. 
   SUMMARY OF THE INVENTION 
   The present invention provides a compact switching device with a SMC-type (surface mounted component type) light-emitting diode (LED) element, of the type that has a body and at least two flat, conductive and coplanar connection plates on the body. The switching device includes a pair of contacts, or connection members that each comprises a base portion that is conductively joined (e.g. by solder or an ultrasonic weld) to one of the connection plates of the LED element. Each connection member also has a pin portion that projects deeply into the casing and below the switching mechanism where it connects to an energizing conductor that supplies electricity. The switching device can include one or a plurality of the following characteristics:
     each base portion is ultrasonically welded to the associated connection plate;   each pin portion comprises an arm and comprises a foot extending primarily parallel to each other at a bend of almost 180°, and engaged with one of the energizing conductors;   the casing comprises at least two partition walls which project up into a cavity of the casing and which form channel portions between them into which the pin portions of the connection members are inserted and where they are held;   the foot of each pin portion has a locking tooth that engages one of the casing partitions in order to fix the position of the light source;   the light-emitting diode bears against a top end of at least one partition wall;   each energizing conductor has a perforation, or hole, through which the corresponding pin portion projects and where the pin portion is conductively joined to the energizing conductor.   

   Other characteristics and advantages of the invention will become apparent from reading the detailed description which follows for the understanding of which reference will be made to the appended drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded isometric view of a switching device according to the invention. 
       FIGS. 2 and 3  are sectional views taken on the planes P 2 —P 2  and P 3 —P 3 , respectively, of the switching device illustrated in  FIGS. 2 and 3 . 
       FIG. 4  is an enlarged isometric view of a first embodiment of a light source for the switching device of  FIGS. 1 to 3 . 
       FIG. 5  is a bottom isometric view of the assembled switching device of  FIGS. 1–3 . 
       FIG. 6  is an isometric view, similar to that of  FIG. 4 , of a variant of the light source according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a switching device  10  that includes a casing  12 , an operating member  14  movable relative to the casing  12 , and a switching mechanism  16  housed in the casing  12 . The switching device also includes a light source  18  and a frame  20  for securing the operating member  14  and the switching mechanism  16  in the casing. A transparent push-button indicated at  23  in  FIG. 2 , is fitted on the operating member  14 , over the light source  18 , to improve visual appearance and facilitate operating when the switching device is installed in an electronic apparatus, particularly a portable telephone. In the drawings, arrows U and D designate upward and downward directions, and it is assumed that the button  22  is pushed downward to operate the switch. 
   The casing  12  is generally of parallelepipedal shape and formed of insulating plastic material. The casing forms a cavity  22  of generally cylindrical shape, closed at one end by a base  24 . Six connection terminals  26 A,  26 B,  26 C,  26 D,  26 E and  26 F ( FIG. 5 ) project laterally from opposite sides of the base  24 , for mounting on a circuit board. Four of the terminals  26 A,  26 C,  26 D,  26 F are connected to a conductor  28  ( FIG. 2 ) lying in the cavity  22  in the vicinity of the base  24 . 
   The switching mechanism  16  ( FIG. 1 ) which lies the cavity  22 , comprises two superposed metal conductor switching plates  30  with central holes  31  that closely receive partitions  60  of the casing. The switching plates are identical and formed of sheet metal, and generally have convex surfaces with one convex surface lying on the base  24 . The switching plates have four radially-projecting arms  32  for contacting conductors  28  ( FIG. 2 ) to close circuits as is known in the prior art. At rest, the arms normally extend away from the conductors  28 . The arms have to be resiliently deflected to be brought into contact with the conductors  28 , which is accomplished by depressing the operating member  14 . 
   The operating member  14  generally has an annular shape defining an axial duct  31  ( FIG. 3 ) for receiving the light source  18 . The operating member  14  can be displaced by sliding it along the axis  33  ( FIG. 2 ) of the cavity  22  to downwardly depress or release the arms of the conductor plates. In a conduction position in which the arms  32  of the plates  30  are in contact with the conductors  28 , terminals  26 A,  26 C are in communication with the terminals  26 D,  26 F, respectively. In a rest position as illustrated in  FIGS. 2 and 3 , the arms of the plates  30  are separated from the conductors  28 . 
   The light source  18  is electrically connected to two current-carrying energizing conductors  40  in the form of inserts at  40 . The inserts are fixed firmly in the casing and connected to the connection terminals  26 B and  26 E by conductors embedded in the casing. The conductive inserts  40  extend on the bases under two recesses  42  that open downward to lower surface of the base  24  of the casing. 
   The light source  18  comprises an SMC-type light-emitting diode element  50  ( FIG. 4 ) and two added contacts, or connection members  52 . The diode element  50  illustrated is of the SMC (surface mounted component) type which is intended to be electrically connected (e.g. by solder) directly to the tracks of a printed circuit board. For this purpose, the diode device comprises flat conductive connection plates  76 . The connection members  52  are suitable for being fixed firmly, in electrical connection joints, to the conductive inserts, or energizing conductors  40  ( FIG. 3 ) that supply electricity to the LED. The inserts  40  extend through a central opening  54  ( FIG. 2 ) in the conductive plates  30 . 
   The casing partitions  60  ( FIG. 3 ) form channel portions  61  and lie above the energizing conductor conductive inserts  40 . The inserts have holes under the channel portions for receiving the connection members  52  of the light source. The upper ends of the partitions  60  lie within the duct  31  of the operating member  14 , and form a support surface for the light source. The facing surfaces  62  of the partitions converge downwardly D towards one another. As shown in  FIG. 4 , the light source  18  includes a generally parallelepipedal, transparent body  70  having a lower surface  74  and two coplanar surface mount connection plates  76  on the lower surface. The lower surfaces of the surface mount plates are flush with the lower surface  74  of the body  70  or project only slightly below the lower surface. The surface mount plates  76  (which are shown as parts of right angle bent sheets) extend in a common plane that is parallel to the lower surface  74 . 
   As shown in  FIG. 4 , the connection members  52  are formed of blanked metal plates. Each connection member  52  has a base portion  82  that is electrically joined (e.g. by soldering, brazing, ultrasonic welding, etc.) to a surface of one of the surface mount plates  76 . The electrical-mechanical joints are not shown. Each connection member also has a pin portion  86  connected by a 90° elbow or bend  88  to the base portion. Each pin portion  86  has an arm  80  and has a foot  83  joined to the arm at a bend  84  of more than 135°, and which approaches 180°.  FIG. 3  shows that when the arm is installed in a channel portion  61  the arm  80  and foot  83  extend largely parallel. At its free end, which is furthest from the bend  84 , the foot  83  forms a tooth  85  diverging away from the arm  80 . 
   The width of the connection pin is reduced in a region  89  ( FIG. 4 ) in the vicinity of the bend  84 . The narrow region  89  is suitable for projecting into a perforation  90  ( FIG. 2 ) formed through the base of the casing and through a hole in an energizing conductor  40 . The pin portions  86  are preferably joined, as by solder, to the conductors  40  at the holes therein. To mount the pin portions  86  of the connection members, the pin portions are pressed down into the channel portions  61  ( FIG. 3 ) of the casing. The arm  80  and foot  82  of each connection member are resiliently deflected closer together and resiliently bear against the downwardly converging surfaces  62  of the partition portions  60 . The tooth  85  adds to resilience and holding. When the pin portions are fully inserted the base portions  82  bear against the upper end of the partitions  60 . The electrical joint between the pin portion and energizing conductor lies entirely in the recess  42 . 
   The use of a light source comprising an SMC-type light-emitting diode and added connection members provides a light source of reduced height. 
     FIG. 6 , shows a variant  118  of a light source which differs from the light source of  FIGS. 1–5  in that the connector members  152  have pin portions  180  that do not have almost 180° bends. The pin portions have tapered parts  160  that fit in tapered channel portions with the bottom of the pin passing through a hole in an energizing conductor that lies under the channel and soldered thereto to the energizing conductor. 
   Although terms such as “up” and “down” have been used to describe the switch device as it is illustrated, the switch device can be used in any orientation. 
   Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.