Abstract:
Each of a plurality of LED lamp modules includes a base, an LED drive circuitry mounted on the base, and a cover coupled with the base to cover the LED drive circuitry. The LED lamp modules are stacked one on another. A single flat cable is extending through the LED lamp modules so as to have at least one first portion disposed outside the LED lamp modules and a plurality of second portions disposed inside the LED lamp modules to be electrically connected to the LED drive circuitry in each of the LED lamp modules. The first portion of the flat cable is sandwiched between the base of an upper one of the LED lamp modules and the cover of a lower one of the LED lamp modules.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a small-sized illuminator provided with an LED (light-emitting diode) which is used as a room light or a map light of a vehicle to illuminate the cabin and the interior of a container for small items such as a console box, a glove compartment, an accessory pocket, or an ash tray. It may also illuminate a cup holder or the area of passengers&#39; feet. 
     FIG. 6  shows a first example of a related-art illuminator which is disclosed in Japanese Patent Publication No. 9-272377 (cf., pages 2–4, FIG. 1). 
   In this example, an illuminator  60  is capable of illuminating the interior of containers for small items such as a console box  66  with adequate luminance at low power consumption. The illuminator comprises a main body  61 , a circuit board  63  attached to the main body  61 , and a lens  65  which covers the circuit board  63 . 
   The main body  61  is formed in a box-shaped general configuration using a synthetic resin material. A mount  62  for mounting the illuminator  60  to a surface of a wall of the console box  66  is provided in a lower part of the main body  61 . Each of the circuit board  63  and the lens  65  is securely held on the main body  61  using an engagement member. 
   A plurality of LED chips  64  are mounted on the circuit board  63 . The LED chips  64  are arrayed and connected to an alternator and a battery through branch lines  66  so that the emitted light linearly. The circuit board  63  is also provided with electronic components such as a rectifier diode for preventing noises and a current limiting resistor which are not shown. 
   The lens  65  is formed in a box-shaped configuration from a highly transparent synthetic resin material. Therefore, light emitted from the LED chips  64  is converged as it passes through the lens  65  to illuminate the interior of the console box  66  with high luminance. 
   With such a configuration, since a large number of LED chips  64  are mounted, an illuminator can be provided which can illuminate the interior of a container for small items with sufficient luminance and which consumes small power. 
   In this example, since ends of the two branch lines  66  are connected to the circuit board  53 , a new branch line  66  must be formed on the trunk line to provide an additional illuminator. This is troublesome and costly, and a problem arises in that an additional illuminator cannot be easily provided. 
   Further, since the plurality of LED chips  64  is mounted on the circuit board  63 , a problem arises in that the main body  61  is therefore large-sized and cannot be mounted to a container for small items which has only a small space therein. For example, the lamp may not be mounted to an ash tray or cup holder. When the intervals between the plurality of LED chips  64  are decreased to reduce the size of the illuminator  60 , a problem arises in that the temperature in the illuminator  60  increases because of poor heat radiation to reduce light-emitting efficiency. In particular, a red LED chip may undergo an abrupt reduction of light-emitting efficiency at a high temperature. 
   When the illuminator  60  is used in a container for small items such as an ash tray or cup holder, it will sufficiently work with a small number of LED chips  64  because high luminance is not required. When the illuminator  60  is used in a console box or a glove compartment or used as a map light, it must have a large number of LED chips  64  because high luminance is required. While the number of the LED chips  64  depends on the size of the container for small items or the place to be illuminated, the illuminator  60  cannot accommodate an increase or decrease in the number of the LED chips  64  with flexibility. It is therefore required to redesign the main body  61 , the circuit board  63 , and the lens  65  to satisfy such a requirement, which results in the problem of an increase in total cost including tooling costs. 
     FIG. 7  shows a second example of an related-art illuminator. In this example, illuminators  70  which are mounted in containers for small items such as a console box and glove compartment in a way similar to that in the first example. The illuminators  70  are connected to a wire harness  75  provided in a vehicle through joint connectors  71 , branch lines  72 , and module-side connectors  73  in a manner so-called bus-type connection. 
   When an additional illuminator  70  is to be provided, a new joint connector  71 , branch line  72 , and module-side connector  73  are prepared and are arranged along the wire harness  75  similarly to the other illuminators  70  in parallel with them. 
   In this example, although it is advantageous in that connecting operations are simple because the illuminators  70  are connected to ends of the branch lines  72  using connectors, there is a problem in that the illuminators cannot be made small. Further, since the illuminators  70  are connected to the wire harness  75  through the joint connectors  71 , the branch lines  72 , and the module-side connectors  73 , there is a problem in that a large number of components are involved to result in a high total cost. Further, since the illuminators  70  are connected to ends of the branch lines, not intermediate portions of the same in a manner similar to that in the first example, there is a problem in that it is uneasy and troublesome to provide an additional illuminator  70 . 
     FIG. 8  shows a third example of an related-art illuminator. The present example is different from the second example in that a plurality of illuminators  80  is serially connected to a branch line  81  which branches from a wire harness. 
   Each of the illuminators  80  is constituted by a case  87  formed by a base  84  and a cover  86  and a connecting circuit. Both of the base  84  and the cover  86  are provided by molding a synthetic resin material having insulating properties. An intermediate section of the branch line  81  is soldered to the connecting circuit. 
   In this example, a redundant part  81   a  of the cable  81  is left between the adjoining illuminators  80  to facilitate the assembly of each of the illuminators  80 . However, if the redundant part  81   a  is too long, the cable can be flapped by vibration of the vehicle when it is running, which results in the problem of the generation of noises and damage of the cable due to interference with its surroundings. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide an illuminator provided with LED chips (hereinafter, simply referred as an LED illuminator) capable of solving the above problems, particularly to prevent a redundant part of an cable from flapping to thereby eliminating the generation of noises and the damaged due to interference with its surroundings. 
   In order to achieve the above object, according to the invention, there is provided an LED illuminator, comprising: 
   a plurality of LED lamp modules, each of which comprises:
         a base;   an LED drive circuitry, mounted on the base; and   a cover, coupled with the base to cover the LED drive circuitry, the LED lamp modules being stacked one on another; and       

   a flat cable, extending through the LED lamp modules so as to have at least one first portion disposed outside the LED lamp modules and a plurality of second portions disposed inside the LED lamp modules to be electrically connected to the LED drive circuitry in each of the LED lamp modules, 
   wherein the first portion of the flat cable is sandwiched between the base of an upper one of the LED lamp modules and the cover of a lower one of the LED lamp modules. 
   With such a configuration, since the plurality of the LED lamp modules connected to the flat cable are stacked one on another, the luminance of the LED lamps can be adequately adjusted depending on the specifications of areas to be illuminated. Since the redundant part (the first portion) of the flat cable is sandwiched between the base of the upper module and the cover of the lower modules, the generation of noises and damage due to flapping of the redundant part of the flat cable can be prevented. 
   Preferably, an outer face of the base is formed with a groove for receiving the first portion of the flat cable. 
   With such a configuration, the redundant part of the cable is securely positioned by being contained in the groove, which prevents a transverse shift of the redundant part. Therefore, the first portion is completely protected from interference with its surroundings. 
   Preferably, the cover comprises a retainer which retains each of the second portions of the flat cable on an inner face of the base. 
   With such a configuration, the flat cable can be prevented from being lifted from the inner face of the base even when the first portion of the flat cable is folded back to be sandwiched by the LED lamp modules. 
   Preferably, each of the LED lamp modules comprises a guide member disposed on an inner face of the base to restrict a lateral movement of each of the second portions of the flat cable. 
   With such a configuration, the flat cable extended along the inner and outer faces of the base can be prevented from being damaged due to the friction caused by the lateral movement. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
       FIG. 1  is a perspective view showing an embodiment of an LED illuminator according to the invention; 
       FIG. 2  is an enlarged perspective view of an groove of the LED illuminator shown in  FIG. 1 ; 
       FIG. 3  is a side view of the LED illuminator in a state in which a cover of the same is removed; 
       FIG. 4  is a wiring diagram of a flat cable which is connected to the LED illuminator; 
       FIG. 5  is an exploded perspective view of one of LED lamp modules which constitute the LED illuminator; 
       FIG. 6  is a sectional view showing an example of an illuminator according to the related-art (a first example of the related-art); 
       FIG. 7  is a sectional view showing another example of an illuminator according to the related-art (a second example of the related-art); and 
       FIG. 8  is a sectional view showing still another example of an illuminator according to the related-art (a third example of the related-art). 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Preferred embodiments of the invention will be described below in detail with reference to the accompanying drawings. 
   An LED illuminator  10  is a small-sized illuminator which is provided by stacking LED lamp modules  34  serially connected to a two-core flat cable  40  and which is used as a room light or a map light of a vehicle for illuminating the cabin and the interior of a container for small items such as a console box, a glove compartment, or an accessory pocket. 
   The plurality of LED lamp modules  34  is disposed at predetermined intervals before they are stacked one on another such that a redundant part  41  of the flat cable  40  is left as seen in the related-art example shown in  FIG. 8 . The flat cable  40  is a single cable which extends through the plurality of LED lamp modules  34 . The number of the LED lamp modules  34  connected to the flat cable  40  may be more than two. 
   The LED illuminator  10  is operated by power supplied from a battery through the flat cable  40 . A junction box and a joint connector which are not shown are connected to an upstream side of the flat cable  40 . For example, the junction box is connected to a battery through a wire harness which is not shown, and the joint connector is connected to the junction box through the wire harness. The LED lamp modules  34  are connected to the joint connector through the single flat cable  40 . When the junction box has the function of branching the wire harness which is a trunk line, the flat cable  40  can be branched from the junction box without providing the joint connector. 
   The junction box is a well-known electric connection box made of a synthetic resin containing a circuit board and a wiring board and also having electrical components such as connectors, relays, and fuses connected to the wiring board. For example, the junction box is provided in the engine room of a vehicle or in the neighborhood of an instrument panel thereof. The joint connector is provided downstream of the junction box, e.g., at a front pillar or in the neighborhood of the same. 
   Each of the LED lamp modules  34  is comprised of a base  12 , a bus bar circuit  35  provided with an LED chip  38 , and a cover  25 . A box-shaped case is formed by the base  12  and the cover  25 . 
   The rectangular plate-shaped base  12  is formed by molding a synthetic resin material having insulating properties. As shown in  FIGS. 2  and  5 , the base  12  is formed with an groove  23 , engagement claws  16 , reinforcement ribs  20 , and guide members  22  which are described later in detail. The material of the base  12  is not limited to a synthetic resin, and it may be formed of any other material such as hard silicone rubber or ceramics as long as it has high insulating properties and moldability. 
   The flat cable  40  is constituted by one positive-side cable (power supply line) with insulation coating and one negative-side cable (ground line) with insulation coating which are connected in parallel with each other by a flat insulation band provided therebetween, but two cables are separatable at a desired portion (see  FIG. 5 ). The flat cable  40  extends through the LED lamp modules  34  without any discontinuation while a part of the flat cable  40  is electrically connected to each bus bar circuit  35 . 
   The bus bar circuit  35  has a thin plate-shaped bus bar  36  which is formed by punching a conductive substrate according to a circuit pattern. An LED chip  38  and a constant-current diode  39  are soldered to the bus bar  36 . 
   As shown in  FIG. 5 , the conductive bus bar  36  is formed with pairs of terminals  37  and engagement pieces  45 . The terminals  37  extend upright from an end of the bus bar  36  so that each electric wire of the flat cable  40  is press-fitted into each pair of the terminals  37  to establish the electric contact between the power supply and the flat cable  40 . Since the terminals  37  are connected to the constant-current diode  39  and the LED chip  38  through the bus bar  36 , the power supply current is supplied to the LED chip  38  through the constant-current diode  39 . 
   The engagement pieces  45  are provided in some locations of the bus bar  36  as needed. Those engagement pieces  45  are inserted into recesses  21  formed on the base  12  to secure the bus bar  36  on the base  12  in a single action. 
   The W-shaped guide members  22  are members for keeping the flat cable  40  wired on the inner face  13   a  of the base  12  straight while restricting the lateral movement thereof. Specifically, the positive-side cable  40   a  is held between one of the outer walls  22   a  and a center wall  22   b , while the negative-side cable  40   b  is held between the other one of the outer walls  22   a and the center wall  22   b . An interval between each outer wall  22   a  and the center wall  22   b  is made smaller than an outer diameter of each of the cables  40   a ,  40   b  to securely hold the cables  40   a ,  40   b  on the guide member  22 . 
   The reinforcement ribs  20  extend upright from the inner face  13   a  of the base and disposed between the guide members  22  for reinforcing the terminals  37 . Each pair of the reinforcement ribs  20  is associated with one pair of the terminals  37 . Each pair of the terminals  37  is disposed between one pair of the reinforcement ribs  20  and one guide member  22  as shown in  FIGS. 3 and 5 . With this configuration, the terminals  37  are prevented from being inclined by the reinforcement ribs  20  and the guide members  22  when the press-fitting of the cables  40   a ,  40   b  is performed. 
   The LED chip  38  is a white light-emitting diode of surface-mount type having two terminals, i.e., positive and negative terminals on the bottom surface thereof. The LED chip  38  used in the present embodiment has a rated current of 20 mA and a rated voltage of 3.5V. The battery voltage is decreased by the constant-current diode  39  and adjusted to the rated voltage of 3.5V. While the constant-current diode  39  is advantageous in a case where a voltage fluctuates as can be observed in a vehicle, a current-limiting resistor may alternatively be used when there is no voltage fluctuation. The color of the LED chip  38  is not limited to white, and it may be red, blue or green. 
   The LED chip  38  is characterized in that it consumes small power and has a long life, high directivity, and high luminance. It consumes small power and has a long life because it converts electricity into light with very high efficiency (90%). It has high directivity and high luminance because it emits no diffuse light unlike an incandescent lamp. The invention is not limited to an LED chip  38  as described above, and LED chips having various outputs may be used. Further, the invention is not limited to a surface mount type LED chip  38 , and a bullet-shaped LED chip may be used. 
   As shown in  FIG. 5 , the box-shaped cover  25  is formed by molding a resin so as to comprise a ceiling wall  26  and circumferential walls  30  which is orthogonal to and contiguous with the edges of the ceiling wall  26 . A space is defined by the ceiling wall  26  and circumferential walls  30  so as to be adapted to cover and protect the bus bar circuit  35 . The circumferential walls  30  are formed with retaining grooves  33 , an window  31 , an inlet  42  and an outlet  44  for the flat cable  40 . The ceiling wall  26  is formed with retainers  43 . 
   The engagement claws  16  extend upright from the inner surface  13   a  of the base  12  in positions associated with the retaining grooves  33  formed on the cover  25 . As shown in  FIG. 3 , a claw member  16   a  is formed on a distal end of each engagement claw  16  so that the engagement claws  16  and the retaining grooves  33  are engaged to combine the base  12  and the cover  25  such that they will not accidentally come apart as shown in  FIG. 2 . 
   The rectangular window  31  releases the light emitted from the LED chip  38  to the outside. The edges of the window  31  are chamfered into slope faces  31   a  so that the released light is allowed to be diffused at a predetermined angle (120 degrees in this embodiment). A reflective material may be applied to a ceiling surface  31  of the light projecting window  31 , the surface of the ceiling wall  26  facing a top face of the LED chip  38  that constitutes a light-emitting surface  38   a  thereof. Thus, light emitted from the light-emitting surface  38   a  is reflected by the reflective material and emitted out of the window  31  with high efficiency. 
   As shown in  FIG. 2 , the outlet  42  and the inlet  44  are recesses communicating the inside and the outside of the circumferential walls  30 , so that the flat cable is allowed to pass therethrough to be led into or out of the module  34 . 
   In this embodiment, as shown in  FIG. 1 , two LED lamp modules  34  connected to the flat cable  40  are stacked one on another to constitute the LED illuminator  10 . Incidentally, as shown in  FIGS. 1 and 4 , the flat cable  40  extends while being sandwiched by the base  12  of the upper module and the cover  25  of the lower module. More specifically, the flat cable  40  wired along an inner face  13   a  of the base  12  of the upper module  34  is led out from an outlet  42  (see  FIGS. 1 and 2 ) and folded back such that the redundant part  41  extends along an outer face  13   b  of the base  12 . The flat cable  40  is again folded back to be led into the lower module  34  through an inlet  44 . That is, as shown in  FIG. 4 , the flat cable  40  is wired like a crank. 
   With such a configuration, since the redundant part  41  located between the adjoining LED lamp modules  34  is sandwiched between the base  12  and the cover  25  of the LED lamp modules  34  stacked one on another, the redundant part  41  will not be exposed to the outside, which prevents the generation of noises and damage due to the flapping of the redundant part. 
   As shown in  FIGS. 1 through 3 , the groove  23  is formed on the outer surface  13   b  of the base  12  so as to contain the redundant part  41  of the flat cable  40 . The groove  23  is formed with a depth equal to or greater than the thickness of the flat cable  40  so that the redundant cable can be completely contained. The groove  23  is formed with a width similar to the width of the flat cable  40  so as to restrict the lateral movement of the redundant part  41 . 
   Thus, the redundant part  41  of the flat cable  40  will not be exposed on the outside of the LED lamp module  34 , which completely prevents damage on the cable due to interference with the surroundings. 
   The retainers  43  extend from the ceiling wall  26  so as to oppose to the outlet  42  and the inlet  44 , respectively. When the base  12  and the cover  25  are combined, the tip ends of the retainers  43  press the flat cable  40  to prevent the flat cable  40  from moving in the longitudinal direction thereof. Further, the retainers  43  prevent the flat cable  40  from being lifted from the inner face  13   a  of the base  12  even when the flat cable  40  led out from the outlet  42  is folded back to be accommodated in the groove  23  as described the above. 
   As thus described, according to the present embodiment, the bus bar circuit  35  mounted on the base  12  is covered by the cover  25  to protect electrical components such as the LED chip  38  and the constant-current diode  39  and to thereby maintain reliability of electrical connections. Since the plurality of LED lamp modules  34  connected to the flat cable  40  are stacked one on another, the luminance of the LED lamps can be adjusted according to the specifications of an area to be illuminated. Since the redundant part  41  of the flat cable  40  is left between the adjoining LED lamp modules  34 , the assembling workability of the LED lamp modules  34  is improved. Since the redundant part  41  of the flat cable  40  is sandwiched between the base  12  of the upper module  34  and the cover  25  of the lower module  34 , the generation of noises and damage due to flapping of the cable can be avoided. 
   Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.