Patent Publication Number: US-2009225560-A1

Title: Aircraft External Illumination Lamp

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims the benefit of priority of Japanese Patent Application No. 2008-056784, filed on Mar. 6, 2008, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an aircraft external illumination lamp having a discharge bulb as a light source. More particularly, the present disclosure relates to an aircraft external illumination lamp having a waterproof structure in which a power supply socket having a discharge-bulb actuation circuit embedded therein is mounted on a plug portion located on the rear end side of a discharge bulb and projecting rearward from a bulb insertion hole of a reflector serving also as a lamp body. 
     BACKGROUND 
     An aircraft external illumination lamp is attached to an airframe and is used to illuminate a runway during landing, to illuminate a predetermined region of a road surface for loading and unloading work, and the like. An example is disclosed in Japanese Patent Application Laid-Open (Kokai) No. 2001-266603, which discloses an aircraft searchlight in which a reflector having a discharge bulb inserted therein and a bulb actuation circuit are integrally accommodated in a cylindrically-shaped lamp body having a translucent cover attached to its front side. 
     However, the foregoing searchlight is structured so that the reflector having the discharge bulb inserted therein, the bulb actuation circuit, and the like are accommodated in the lamp body having a waterproof structure. Accordingly, the a large number of components are required and thus the overall size is increased. 
     SUMMARY 
     The present invention provides a compact aircraft external illumination lamp having a discharge bulb as a light source and ensuring a waterproof property. 
     For example, in one aspect, an aircraft external illumination lamp includes: a container-shaped reflector serving also as a lamp body; a translucent front cover attached to a front opening of the reflector; and a discharge bulb inserted in a bulb insertion hole formed in the reflector. A power supply socket is attached to a back side of the reflector so that a peripheral edge of the power supply socket covers a peripheral edge of the bulb insertion hole. The power supply socket thus longitudinally fits on a plug portion of a rear end side of the discharge bulb which projects rearward of the bulb insertion hole, whereby electric connection with the plug portion is ensured. The power supply socket has an actuation circuit embedded therein for actuating the discharge bulb. A socket main body having a plug-portion fitting hole formed on a front side thereof is covered with a resin mold layer. 
     The reflector serves also as a lamp body and the discharge bulb actuation circuit is embedded in the power supply socket which is connected (e.g., fittingly mounted) to the plug portion of the discharge bulb by attaching the power supply socket to the back side of the reflector. Accordingly, the number of components of the lamp can be made smaller than that of a conventional illumination lamp, which makes the illumination lamp compact and facilitates assembly. 
     By pressing the power supply socket onto the reflector so that the plug-portion fitting hole of the socket main body aligns with the plug portion of the discharge bulb which projects rearward from the bulb insertion hole, the plug-portion fitting hole of the socket main body fits on the plug portion of the discharge bulb. As a result, the power supply socket (socket main body) and (the plug portion of) the discharge bulb are electrically connected to each other. The power supply socket (socket main body) and (the plug portion of) the discharge bulb are electrically disconnected from each other by removing the power supply socket from the reflector. The power supply socket can thus be attached and detached easily. 
     In some implementations, the peripheral edge of the bulb insertion hole is structured by a rearward extending cylindrical portion, and a peripheral edge of the power supply socket is structured so as to fit on an outer periphery of the cylindrical portion. 
     In some lamps, alignment between the plug-portion fitting hole in the power supply socket (socket main body) and the plug portion of the discharge bulb is difficult because it is hard to see these elements from outside. However, the plug-portion fitting hole of the socket main body fits on the plug portion of the discharge bulb simultaneously when the peripheral edge of the power supply socket is fitted onto the peripheral edge of the bulb insertion hole (e.g., a rearward extending cylindrical portion). Accordingly, the power supply socket can be assembled easily to the peripheral edge of the bulb insertion hole of the reflector without the need to visually align the plug-portion fitting hole and the plug portion of the discharge bulb. 
     In some implementations, the resin mold layer is made of a polyamide resin, and the peripheral edge of the power supply socket is structured by two layers, that is, an outer resin mold layer and an inner second resin layer having a higher melting point than that of the resin mold layer and having excellent heat resistance. 
     The power supply socket can be manufactured by an insert molding process in which resin is injected with the socket main body inserted in a mold. Since the resin mold layer covering the socket main body is made of a polyamide resin (the molding temperature is as low as about 120° C.), heat that is generated in the mold during molding of the power supply socket does not become high enough to damage the discharge bulb actuation circuit (e.g., a printed board having mounted thereon electronic parts such as a transformer, a spark gap, a capacitor, a diode, and a resistor) embedded in the socket main body. 
     Moreover, the inside of the peripheral edge of the power supply socket which fits on the outer periphery of the peripheral edge of the bulb insertion hole (a cylindrical portion of the reflector side) and is in direct contact with the reflector is structured by the second resin layer having a higher melting point than that of the polyamide resin and having excellent heat resistance. The heat resistant strength of the peripheral edge of the power supply socket is thus ensured. 
     In some implementations, the power supply socket is structured by a molded body that forms the second resin layer and a polyamide resin molded body formed by insert-molding the socket main body. 
     The second resin layer can be formed as a molded body before the power supply socket is formed by an insert molding process in which a polyamide resin is injected with the socket main body inserted in a mold. The second resin having a high melting point will, therefore, not be injected in the state in which the socket main body is inserted in the mold. Accordingly, heat that is generated in the mold during molding of the power supply socket (e.g., injection molding of the polyamide resin) does not become high enough to damage the discharge bulb actuation circuit (e.g., a printed board having mounted thereon electronic parts such as a transformer, a spark gap, a capacitor, a diode, and a resistor) embedded in the socket main body. 
     As noted above, the number of parts of the illumination lamp can be made small. This makes the illumination lamp compact and facilitates assembly of the illumination lamp. Moreover, as the illumination lamp becomes compact, the illumination lamp is less likely to interfere with other members. As a result, the degree of design choice with respect to the installation position is increased. 
     By fitting the peripheral edge of the power supply socket onto the peripheral edge of the bulb insertion hole (e.g., a rearward extending cylindrical portion), the socket main body of the power supply socket and the plug portion of the discharge bulb are electrically connected with each other. Accordingly, this simplifies the operation of attaching the power supply socket to the reflector. 
     The portion of the power supply socket which is in direct contact with the reflector of the power supply socket and is heated to a high temperature can be made of the second resin layer having excellent heat resistance. Durability of the power supply socket can, therefore, be ensured. 
     Preferably, the discharge bulb actuation circuit embedded in the socket main body is not affected by the heat generated during molding of the power supply socket. Accordingly, an aircraft external illumination lamp in which discharge-bulb actuation characteristics are ensured is provided. 
     Other features and advantages will be readily apparent from the detailed description and the accompanying drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view showing an example of an aircraft external illumination lamp according to the present invention. 
         FIG. 2  is an enlarged sectional view showing detail of a discharge bulb inserted in a bulb insertion hole and a power supply connecter. 
         FIG. 3(   a ) is an enlarged perspective view of a bulb fixing holding member, and  FIG. 3(   b ) is a front view of the bulb fixing holding member. 
         FIG. 4  is a front view of the power supply connecter. 
         FIG. 5  is a block diagram showing a lighting control circuit of the illumination lamp (e.g., discharge bulb). 
         FIG. 6  is a structural diagram of an igniter circuit as an actuation circuit embedded in a socket main body. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
       FIGS. 1 through 6  show an example of an aircraft external illumination lamp according to the present invention. 
     In these figures, reference numeral  1  denotes an external illumination lamp that is attached by a screw  3  to an airframe outer plate  2  of an aircraft. The external illumination lamp includes: a reflector  10  serving also as a lamp body and having a circular container shape when viewed from the front; a translucent front cover  16  attached to a front opening of the reflector  10 ; and a discharge bulb  20  inserted in a bulb insertion hole  12  provided at the rear top of the reflector  10 . A power supply socket  40  is attached to the reflector  10  through an O-ring  44  as a sealant so as to cover a peripheral edge of the bulb insertion hole  12  located on the back side of the reflector  10 , and is thus fitted on a plug portion  30  located on the rear end side of the discharge bulb  20  and projecting rearward from the bulb insertion hole  12 . Electric connection between the power supply socket  40  and the plug portion  30  is thus ensured. In  FIG. 1 , reference numeral  4  denotes a bracket for screwing with the fitting screw  3 . The bracket is provided at three positions evenly spaced apart from each other in a circumferential direction on the outer peripheral edge of the front opening of the reflector  10 . Reference numeral  90  denotes an output cord that is led out from a lower end of the power supply socket  40  and extends to a ballast circuit unit  80  (see  FIG. 5 ) fixed to the airframe  2 . Reference numeral  98  denotes a tube covering an output-cord lead-out portion  41  at the lower end of the power supply socket  40 . The tube can be made, for example, of a thermosetting resin and has a sealing function. 
     The front cover  16  can be made of glass. An annular gasket  14  having a U-shape in cross section is mounted as a sealant on the peripheral edge of the front cover  16 . The front cover  16  is fixed to the front opening of the reflector  10  by an attachment frame  15   b  screwed  15   a  to the front edge of the reflector  10 . 
     The reflector  10  can be structured by aluminum die casting. The peripheral edge of the bulb insertion hole  12  located on the back side of the reflector  10  is structured by a cylindrical portion  13 , and a cylindrical peripheral edge  42  on the front side of the power supply socket  40  is fitted on the cylindrical portion  13 . An annular stepped portion  13   a  (see  FIGS. 1 and 2 ) is formed on the inner peripheral side of an end of the cylindrical portion  13 , and a focus ring  33  of the discharge bulb  20  side engages in the annular stepped portion  13   a  in a circumferentially aligned manner. On the back side of the reflector  10  are provided heat release fins  17  projecting from the reflector  10 . The heat release fins  17  are provided at predetermined intervals in a lateral direction (a direction vertical to the plane of the paper of  FIG. 1 ), whereby heat that is generated by light emission of the discharge bulb  20  can be released through the reflector  10 . 
     As shown in the enlarged view of  FIG. 2 , the discharge bulb  20  is formed by integrating an arc tube main body  21  with the insulating plug portion  30  made of a polyphenylene sulfide (PPS) resin having excellent heat resistance. The arc tube main body  21  is supported at its both ends by a lead support  31  extending forward from the substantially cylindrical insulating plug portion  30  and a metal support member  32  provided on the front side of the insulating plug portion  30 . Reference numeral  33  denotes a ceramic insulating sleeve though which the lead support  31  is inserted. The insulating sleeve  33  is inserted in an insertion hole  30   c  formed on the front side of the insulating plug portion  30 . 
     The arc tube main body  21  is structured so that a cylindrical ultraviolet shielding shroud glass  22   c  is integrally welded (i.e., sealed) to a quartz glass arc tube  22 . The quartz glass arc tube  22  has tungsten electrode rods  23   a  provided therein so as to face each other, and has a sealed glass bulb  22   b  as a discharging light source in which a metal halide or the like as a light-emitting material is enclosed together with a starting rare gas. Each electrode rod  23   a  is connected integrally with a molybdenum foil  23   b  and a molybdenum lead wire  23   c  ( 23   c   1 ,  23   c   2 ) and is thus structured as an electrode assembly  23 . The electrode assemblies  23  are sealed in respective pinch seal portions  22   a   1 ,  22   a   2  so that the electrode rods  23   a  project in the sealed glass bulb  22   b.  The lead wire  23   c   1  of the front end side which is led out from the pinch seal portion  22   a   1  of the front end side is welded to a bent tip portion of the lead support  31 . The lead support  31  has its rear end welded to a flange portion  38   a  of a belt-type terminal  38  provided on the outer periphery of the rear end side of the insulating plug portion  30 . The lead wire  23   c   2  of the rear end side which is led out from the pinch seal portion  22   a   2  of the rear end side, on the other hand, is welded to a cap-type terminal  39  provided in the middle of the rear end of the insulating plug portion  30 . 
     A recess  30   b  surrounded by a partition wall  30   a  is formed on the front end side of the insulating plug portion  30  in order to accommodate the rear end of the arc tube main body  21 . The focus ring  33  that engages with the annular stepped portion  13   a  of the bulb insertion hole  12  side in a circumferentially aligned state is disposed on the outer periphery of the insulating plug portion  30 . This circumferential alignment is structured by a projecting portion  13   a   1  formed in the annular stepped portion  13   a  and a notch  33   a  formed in the peripheral edge of the focus ring  33 . For example, the projecting portion  13   a   1  and the notch  33   a  engage with each other in an extending direction of the bulb insertion hole  12  (i.e., the lateral direction in  FIG. 2 ). The focus ring  33  engaging with the annular stepped portion  13   a  by inserting the discharge bulb  20  into the bulb insertion hole  12  from the back side of the reflector  10  is fixedly held by a bulb fixing holding plate  70  screwed (screws are not shown) to an end face of the cylindrical portion  13 . 
     As shown in the enlarged views of  FIG. 3A  and  FIG. 3B , the bulb fixing holding plate  70  is structured by a stainless-steel disc-shaped plate main body  71  having a circular hole  72  formed in the middle for insertion of the plug portion. A pair of elastic tongue pieces  73  cut and raised to the front side (i.e., the lower side in  FIG. 3(   a )) and a pair of elastic tongue pieces  74  cut and raised to the back side (i.e., the upper side in  FIG. 3(   a )) are provided on the inner peripheral edge side of the plate main body  71  at such positions that the line connecting the pair of elastic tongue pieces  73  and the line connecting the pair of elastic tongue pieces  74  cross perpendicularly to each other when viewed from the front. Reference numeral  75  denotes an insertion hole for a fastening screw (not shown). When the bulb fixing holding plate  70  is screwed to the end face of the cylindrical portion  13 , the pair of elastic tongue pieces  73  cut and raised to the bulb insertion hole  12  side hold the focus ring  33  of the plug portion  30  while pressing the focus ring  33  against the annular stepped portion  13   a.  The discharge bulb  20  is thus fixedly held in the bulb insertion hole  12 . The pair of elastic tongue pieces  74  cut and raised to the rear side of the reflector  10 , on the other hand, are brought into press-contact with a front edge  50   a  (shown by a shaded part in  FIG. 4)  of a socket main body  50  in the power supply socket  40  described below when the peripheral edge  42  of the power supply socket  40  is fitted on the cylindrical portion  13  of the reflector  12  side. 
     On the rear end side of the insulating plug portion  30  is formed a columnar boss  36  inside a rearward-extending cylindrical outer cylinder portion  34 . The belt-type terminal  38  conducting with the lead support  31  is provided on the outer periphery of the root portion of the outer cylinder portion  34 . The columnar boss  36 , on the other hand, is covered by the cap-type terminal  39 . The lead wire  23   c   2  of the rear end side which is led out from the arc tube main body  21  extends through the columnar boss  36  and is connected to the cap-type terminal  39 . Reference numeral  39   a  denotes a terminal projection as a laser welded portion. 
     The power supply socket  40  has an igniter circuit  58  embedded therein as an actuation circuit for actuating the discharge bulb  20 . The power supply socket  40  is structured so that the socket main body  50  having a plug-portion fitting hole  55  on its front side is covered with a resin mold layer  60 . The peripheral edge  42  on the front side of the power supply socket  40  is formed in a cylindrical shape that axially fits on the outer periphery of the columnar portion  13  of the reflector  10  side. Three brackets  43  each having a screw insertion hole  43   a  is formed on the outer periphery of the front end of the peripheral edge  42 . The power supply socket  40  can thus be fixed to the back side of the reflector  10  by fitting screws  43   b  (see  FIG. 1 ). 
     The resin mold layer  60  can be made of a polyamide resin (e.g., having a molding temperature of about 120° C.) so that the igniter circuit  58  embedded in the socket main body  50  is not damaged by heat that is generated during molding of the resin mold layer  60 . 
     More specifically, the power supply socket  40  can be manufactured by an insert molding process in which resin is injected with the socket main body  50  inserted in a mold. Since the resin mold layer  60  covering the socket main body  50  is made of a polyamide resin (e.g., for which the molding temperature is as low as about 120° C.), heat that is generated in the mold during molding of the power supply socket  40  does not become high enough to damage electronic parts of the igniter circuit  58  embedded in the socket main body  50 . 
     The cylindrical peripheral edge  42  of the power supply socket  40  which fits on the outer periphery of the cylindrical portion  13  of the reflector  10  side is structured by the outer polyamide resin layer  60  and an inner second resin (e.g., PPS) layer  62  having a higher melting point than that of the polyamide resin and having excellent heat resistance and excellent mechanical strength. The heat resistant strength and the assembly strength of (the peripheral edge  42  of) the power supply socket  40  are thus ensured. The power supply socket  40  can be molded by first preparing as the inner second resin (e.g., PPS) layer  62  a PPS molded body  62 A formed in a predetermined cylindrical shape by an injection molding process, and then performing an insertion molding process in which a polyamide resin is injected with the socket main body  50  and the PPS molded body  62 A being inserted in a mold. As described above, the igniter circuit  58  embedded in the socket main body  50  will not be affected by heat that is generated during injection molding of the power supply socket  40 . The socket main body  50  is structured so that a PPS case  51  accommodating the igniter circuit  58  is covered by an aluminum thin plate cover body  51   a.  On the front side of the socket main body  50 , the plug-portion fitting hole  55  in which the rear end side of the plug portion  30  of the discharge bulb  20  can be engaged in an axial direction is formed by a cylindrical outer cylinder portion  52  and a cylindrical inner cylinder portion  53  which are integrally formed in the case  51 . The aluminum thin plate cover body  51   a  is molded integrally by a press molding process so as to cover the PPS case  51 , and the aluminum thin plate extends to the front end face of the outer cylinder portion  52  (i.e., the front edge  50   a  of the socket main body  50 ). 
     A part of the inner cylinder portion  53  in a circumferential direction is notched in an axial direction. A tongue-shaped contact terminal  54  (a terminal of the igniter circuit  58  side) which extends in an axial direction so as to be in press-contact with the belt-type terminal  38  of the plug portion  30  side of the discharge bulb  20  is provided in the notch  53   a.  A contact terminal  56  (a terminal of the igniter circuit  58  side) which is in press-contact with the terminal projection  39   a  of the cap-type terminal  39  of the plug portion  30  side of the discharge bulb  20  is provided at the bottom of the plug-portion fitting hole  55 . 
     As shown in  FIG. 4 , notches  50   b  respectively connecting to L-shaped guide grooves  52   a  (see  FIG. 2 ) formed in the inner peripheral surface of the outer cylinder portion  52  are provided at four positions evenly spaced apart from each other in a circumferential direction in the front edge  50   a  of the socket main body  50 . A pair of pins  30   d  (see  FIG. 2 ) capable of engaging in the L-shaped guide grooves  52   a  of the outer cylinder portion  52  side are provided on the outer periphery of the plug portion  30  of the discharge bulb  20 . By engagement between the L-shaped guide grooves  52   a  and the pins  30   d,  the socket main body  50  is prevented from being detached from the plug portion  30  of the discharge bulb  20 . 
     By pressing the power supply socket  40  onto the reflector  10  so that the plug-portion fitting hole  55  of the socket main body  50  is aligned with the plug portion  30  of the discharge bulb  20  projecting rearward from the bulb insertion hole  12 , the front edge  50   a  of the socket main body  50  abuts on the pins  30   d  of the plug portion  30  side. In this state, by rotating the power supply socket  40  with respect to the plug portion  30 , the notches  50   b  in the front edge  50   a  of the socket main body  50  engage with the pins  30   d  of the plug portion  30  side. In this state, by further pressing the power supply socket  40  onto the reflector  10  and rotating the power supply socket  40  counterclockwise, the pins  30   d  and the L-shaped guide grooves  52   a  are brought into bayonet engagement. At this time, the plug-portion fitting hole  55  of the socket main body  50  reliably fits on the rear end side of the plug portion  30  of the discharge bulb  20 , and the contact terminal  54  and the contact terminal  56  of the igniter circuit  58  of the socket main body  50  side are respectively in contact with the belt-type terminal  38  and the terminal projection  39   a  of the plug portion  30  side of the discharge bulb  20 . The power supply socket  40  (the socket main body  50 ) and the plug portion  30  of the discharge bulb  20  are thus electrically connected to each other. 
     Alignment between the plug-portion fitting hole  55  in the power supply socket  40  and the plug portion  30  of the discharge bulb  20  is especially difficult because it is hard to see these elements from outside. However, the plug-portion fitting hole  55  of the socket main body  50  fits on the plug portion  30  of the discharge bulb  20  simultaneously when the peripheral edge  42  of the power supply socket  40  is fitted onto the outer periphery of the cylindrical portion  13  on the back side of the reflector  10 . Accordingly, the power supply socket  40  can be assembled easily to the back side of the reflector  10  without the need to visually align the plug-portion fitting hole  55  and the plug portion  30  of the discharge bulb  20 . 
     As shown in  FIG. 5 , a lighting control circuit of the discharge bulb  20  is structured by an AC/DC converter  81  connected to a 115 v, 400 Hz alternating-current power supply through a switch Sw, a DC/DC converter  82  connected to the AC/DC converter  81 , an inverter  83  connected to the DC/DC converter  82 , and an igniter circuit  58  connected to the inverter  83 . A direct current of  400  Hz is supplied to the terminals  38 ,  39  ( 39   a ) of the plug portion  30  side of the discharge bulb  20  through the terminals  54 ,  56  of the power supply socket  40  (socket main body  50 ) side. The AC/DC converter  81 , the DC/DC converter  82 , and the inverter  83  are integrated as the ballast circuit unit  80 . 
     As shown in  FIG. 6 , the igniter circuit  58  is structured by electronic parts such as a transformer T, a spark gap EC 1 , a capacitor C 2 , a resistor R 1 , a diode D 1 , and a coil L and has three inputs, that is, direct-current±(J 1 , J 2 ) and a trigger line J 4 . When a voltage applied to the spark gap EC 1  between J 1  and J 4  exceeds 800 V, charges accumulated in the capacitor C 2  are discharged and a voltage as high as 25 KV is provided between a high-voltage-side terminal HV (i.e., the terminal  56  in the socket main body  50  and the terminal  39   a  of the plug portion  30  side) and a low-voltage-side terminal LV (i.e., the terminal  54  in the socket main body  50  and the terminal  38  of the plug portion  30  side). 
     As shown in  FIG. 2 , the output cord  90  connecting the power supply connecter  40  (the igniter circuit  58  in the socket main body  50 ) and the ballast circuit unit  80  (see  FIG. 5 ) is structured so that three power supply lines  91 ,  92 ,  93  covered with an insulating resin are covered with a metal shield covering layer  94  and a resin external covering layer  95 . One end of the output cord  90  is connected to a connecter connection portion  51   b  of the power supply socket  40  (the socket main body  50 ) through a connector  90   a,  and the other end of the output cord  90  is connected to a connector connection portion (not shown) of the ballast circuit unit  80  side through a connecter (not shown). One end of the metal shield covering layer  94  is solder-welded to an outer-shell portion  51   b   1  of the connecter connection portion  51   b  as a part of the aluminum thin plate cover body  51   a  that forms an outer shell of the socket main body  50  of the power supply socket  40  side. The other end of the metal shield covering layer  94  is connected to an earth terminal of the ballast circuit unit  80  side which conducts with the airframe  2 . The metal shield covering layer  94  thus forms a part of a transmission path of electromagnetic waves generated in the discharge bulb  20 . 
     In other words, when the peripheral edge  42  of the power supply socket  40  is attached to the back side of the reflector  10  so as to fit on the outer periphery of the cylindrical portion  13 , conduction between the aluminum die-cast reflector  10  and the aluminum thin plate cover body  51   a  (which forms the outer shell of the socket main body  50  in the power supply socket  40 ) is ensured through the elastic tongue pieces  74  of the stainless-steel bulb fixing holding ring  70 . The connecter connection portion  51   b  as a part of the aluminum thin plate cover body  51   a,  on the other hand, is connected through the metal shield covering layer  94  of the output cord  90  to the earth terminal (not shown) of the ballast circuit unit  80  side which conducts with the airframe  2 . Therefore, the illumination lamp  1  has an electromagnetic-wave shielding structure in which electromagnetic waves generated in the discharge bulb  20  will not be transmitted to the airframe  2  through the foregoing transmission path and, thus, electromagnetic interference will not occur. 
     Other implementations are within the scope of the claims.