METER CASE FOR VEHICLE

Abstract: A vehicle 10, comprising running boards 11 located on the underside of doors 12 and 13, respectively, a light apparatus, and a meter case having a light transmitting tube which is low in weight, excellent in durability, and also capable of easily repairing a light source, wherein the light transmitting tube 1 is installed along the side edge of the running boards 11, one end of the light transmitting tube 1 is connected to a light source unit 16 located in a cabin of the vehicle 10 at the rearmost thereof and, when a light emitting element emits light, light is radiated from the side peripheral surface of the light transmitting tube 1 at the side edges of the running board 11 and the side edges of the running boards 11 looks luminous if they flash; a stop lamp part 120 and a meter case main body 210 also utilizing the light emission of the light transmitting tube.

Description: Field of the Invention The present invention relates to a meter case having a transparent portion for indicating letters, numbers and figures in the body thereof, particularly relates to a meter case having an improved light source apparatus for lighting up the transparent portion from the back of the body of the meter case. Background of the Invention As well known, a meter case installed in an instrument panel of a vehicle is equipped with a speedometer, a tachometer, an odometer, a water temperature gauge of a radiator, a winker lamp, and a lamp for lighting up the front of the meter case, etc. In order to improve visibility at night of indicators such as the speedometer, the meter case is provided with transparent parts made of slit or transparent synthetic resin which are formed in shapes corresponding to scales of the speedometer, numbers, and the like. An electronic circuit unit is installed on the back of the meter case. The electronic circuit outputs driving signals to meters including the speedometer, the tachometer, and the like installed in the meter case, and also checks trouble or failure of the meters. The electronic circuit unit is integrally equipped with a support case consisting of a shield cover and the like, and the support case is fixed to the meter case with screws. The shield cover covers a circuit substrate which is mounted with electronic parts of the circuit unit in order to shield electromagnetic wave. A flexible wire board for the meters is installed on the back of the meter case. The meters in the meter case are electrically connected with the electronic circuit unit by lead wires and connectors. A light bulb for illumination with a socket which permits installation and removal of the bulb is installed on the flexible wire board and is electrically connected with the flexible wire board. It takes a lot of time to change lamps installed on the back of the meter case when these lamps are down, because it is necessary to separate the electronic circuit unit completely from the meter case by removing screws which fix the electric circuit unit to the meter case and by removing connectors, too. Japanese patent publication H9-282918A disclosed a back light system for a meter of a vehicle, which is equipped with a light transfer board, a fluorescent tube along the edge of the light-transfer board, a reflective sheet on the back of the light-transfer board, and a diffuser panel disposed on the front of the light-transfer board. The back light system does not need light bulbs on the back of the meter case. However, the lifetime of the fluorescent tube is relatively short, and it takes considerable time to change the fluorescent tube because it is necessary to remove the meter case from an instrument panel. French patent application 2 761 029 showing the features of the preamble of claim 1 describes an instrument panal for automobile vehicles comprising a case containing at least a rotatory driving unit, a needle mounted on the axis of the driving unit, a scale associated with the needle, and at least an electro-optical display unit disposed behind the needle, characterized in that the scale is formed on a plate forming an optical guide placed between the needle and the electro-optical display. Object and Summary of the Invention The object of the present invention is to provide a meter case which is low in weight and excellent in durability and has a light source which can be repaired easily. This object is achieved with features of claim 1. A meter case according to the present invention has a main body having a transparent part, a light-transfer board installed on the back of the main thereof, and an illuminating apparatus used for applying light to the end of the light-transfer board. The illuminating apparatus has a light transmitting tube and a light source disposed at one end of the light transmitting tube. Light generated from the light source is introduced into the light transmitting tube and emitted from its circumferential surface, and the light enters into the light-transfer board through its end surface. The light emitted from the surface of the light-transfer board is directed to the transparent part of the main body of the meter case. In each of these meter cases, the light transmitting tube can be extended so that the light source is positioned in a place which is far from the meter case and in which the light source can be maintained easily. The light transmitting tube can be equipped with a tubular cladding and a core made of a material having higher refractive index than that of the tubular cladding. The light transmitting tube may be equipped with a belt-like reflective layer formed between the tubular cladding and the core along the longitudinal direction of the tubular cladding so that a light passing through the core is allowed to be reflected and scattered by the reflective layer and emitted from the side surface opposite to the reflective layer of the cladding. In the light transmitting tube having the belt-like reflective layer formed between the tubular cladding and the core along the longitudinal direction of the tube, a strong light passing through the core (having the greatest capacity for transmitting light than the other portions in the light transmitting tube) is reflected by the belt-like reflective layer, and the strong light having a high directivity is emitted from a part of the outer surface area of the tube opposite to the reflective layer. As a result, the brightness of light emitted from the light transmitting tube is considerably high and thus the light transmitting tube emits a highly bright light. The tubular cladding can be made of a (meth-)acrylic polymer, the core is made of a polystyrene, a polycarbonate, or a styrene-(meth-)acrylic copolymer, and the reflective layer is made of a (meth-)acrylic polymer containing a white color pigment or a light scattering material. The light transmitting tube can be manufactured with high productivity and at low cost by the following method: a multiple color extrusion molding machine, for example, a three-color extrusion molding machine having three screw sections, is used; a material for the core (core material), a material for the cladding (cladding material), and a reflective material containing a white color pigment or a light scattering material are simultaneously introduced into each nozzle on the extrusion molding machine; in a simultaneous manner, the core material is extruded to be formed into a solid cylindrical core member, the reflective material is extruded into plural belt-like reflective layers formed on the outer surface of the solid cylindrical core member, the cladding material is extruded into a tubular member covering the solid cylindrical core member and the belt-like reflective layers, so that belt-like reflective layers are formed between the tubular cladding and the core in the longitudinal direction thereof. The light transmitting tube may be made only of a polymethyl (meth-)acrylate (PMMA), or may be equipped with a core made of PMMA and belt-like reflective layers formed on the outer surface of the core in the longitudinal direction thereof. The light transmitting tube may also be provided with grooves or concave holes which penetrate the reflective layer to reach the core. The core can be formed by extrusion molding method, injection molding method, cast molding method, and the like. It is preferred that the reflective layer includes TiO 2 , BaSO 4 , silica, and the like. The reflective layer can be formed by extrusion molding, coating, printing, and the like. The core may have concave portions such as grooves and concave holes on the outer surface thereof instead of the reflective layers. The concave portions are preferably arranged in the longitudinal direction of the core. Brief description of the drawings Fig.1 is a perspective view showing a light transmitting tube according to the present invention. Fig.2 is a sectional view taken along II-II line in Fig.1. Fig.3 is a sectional view taken along III-III line in Fig.2. Fig. 4 is a front view of a meter case according to an embodiment. Fig.5 is an explanatory drawing illustrating arrangement of a light transmitting tube of the meter case in Fig. 4. Fig.6 is a sectional view taken along XV-XV line in Fig. 4. Fig. 7 is a sectional view showing a part of a meter case according to another embodiment. Fig. 8 is an enlarged view of XVII part in Fig. 7. Fig. 9 is a perspective view of another light transmitting tube according to the present invention. Fig.10 is a sectional view taken along 19-19 line in Fig. 9. Fig.11 is a perspective view of further another light transmitting tube according to the present invention. Fig.12 is a sectional view taken along 21-21 line in Fig.11. Fig. 13 is a perspective view of a light transmitting tube according to the present invention. Fig.14 is a sectional view taken along 23-23 line in Fig.13. Fig.15 is a perspective view of a light transmitting tube according to the present invention. Fig.16 is a sectional view taken along 25-25 line in Fig.14. Fig.17 is an enlarged view showing a surface of the light transmitting tube in Fig.15. Fig.18 is an enlarged view showing a surface of another light transmitting tube. Detailed Descriptions of the Preferred Embodiments Hereinafter, the present invention will be described in detail with reference to the drawings. Fig. 4 is a front view of a meter case according to an embodiment, Fig.5 is an explanatory drawing illustrating arrangement of a light transmitting tube of the meter case in Fig. 4 , Fig. 6 is a sectional view taken along XV-XV line in Fig. 4, Fig. 7 is a part of a meter case according to another embodiment, and Fig. 8 is an enlarged view of XVII part in Fig. 7. The meter case shown in Figs. 4-6 has a main body 210, a speedometer 211, a tachometer 212, a hydraulic meter 213, and a radiator water temperature gauge 214 which are installed in the front of the main body 210. The meters 211-214 have needles 211a, 212a, 213a and 214a and sets of scales 211b, 212b, 213b and 214b, respectively. In each set, the scales are arranged in such a manner that the distance between each scale and the axis of rotation of the needle is the same. These sets of scales 211b, 212b, 213b, 214b are composed of transparent resin parts which penetrate the main body 210. Light transmitting tubes 221, 222, 223 are arranged along the back of these scales, respectively. Each of these light transmitting tubes 221-223 is so constituted that the tube emits light from a part of the circumferential surface which part faces the back of the main body 210. The detailed structure of the light transmitting tube will be described later with reference to Figs.1-3. The main body 210 of the meter case is equipped further with winker indication parts 215, 216. On the back of them, light transmitting tubes 225, 226 are installed, respectively. These light transmitting tubes 221, 222, 223, 225, 226 (hereinafter, referred to as "221-226") are extended out of the under part or side of the meter case and enter into a light source unit (not shown), respectively. The unit is positioned apart from the meter case. The light source unit has light-emitting elements such as LED and driving circuits, in which the light-emitting elements face the top ends of the light transmitting tubes 221-226, respectively, and the driving circuits drive the light-emitting elements, separately. When each light-emitting element such as LED lights up or flashes on and off, the light from the element is introduced into the light transmitting tube of which the top end faces the element, and emitted from the circumferential surfaces of the tube. Then, the light goes through the sets of scales 211b-214b or the winker indication parts 215, 216 and is recognized visually by a crew. Maintenance of the light source unit can be carried out easily because the unit in disposed in a place far from the meter case where maintenance of the light source unit can be carried out easily The light transmitting tube is low in weight even when the light transmitting tube is long. Because only light passes through the light transmitting tube, a short circuit does not occur even if the tube is in contact with water or the tube breaks. Because each of these light transmitting tubes 221-226 is needed to emit light from its outer surface facing the body 210 of the meter case (particularly, from a part located at the back of the scales or indication parts), other part may be made of a light transmitting tube which does not emit a light from its outer surface area. A circuit substrate 230 is installed at the back of the body 210 of the meter case. The circuit substrate 230 is equipped with a circuit for driving needles 211a-214a and an actuator 231 for driving them. The meter case shown in Figs. 7, 8 has a light-transfer board 240 which covers almost the whole back area of the body 210 of the meter case. The light-transfer board 240 has a transparent main board 241, a reflective layer 242 formed on the back surface of the main board 241, and a light scattering layer 243 formed on the front surface of the main board 241. A light transmitting tube 1 is disposed along one end of the light-transfer board 240. The light transmitting tube 1 is so constituted that it emits a light from its circumferential surface toward the one end of the light-transfer board 240. The light transmitting tube 1 is extended out of the meter case and extended into the aforementioned light source unit. A light emitting element such as LED faces one end of the light transmitting tube 1. Other end of the light-transfer board 240 is overlaid with a reflective layer. The construction of the light transmitting tube 1 is the same as those of the aforementioned light transmitting tubes 221, 222, 223, 225, 226. The construction of the light transmitting tube 1 will be described in detail with reference to Figs.1-3. Fig.1 is a perspective view of the light transmitting tube 1, Fig.2 is a sectional view along II-II line in Fig.1, and Fig.3 is a view along III-III line in Fig.2. The light transmitting tube 1 is composed of a core 2, a tubular cladding 3 covering the core 2, and belt-like light reflective layer 4 formed between the inner surface of the cladding 3 and the core 2. The belt-like light reflective layer 4 extends in the longitudinal direction of the tube 1. The reflective layer 4 may be formed in such a manner that it invades slightly into the inside of the outer surface of the core 2. As a material for forming the core 2, a transparent material having a higher refractive index than a material which composes the tubular cladding 3 is used. Generally, the material to be employed is suitably selected from the group consisting of a plastic material, an elastomer material, and the like, according to objects. Examples of the core material are transparent materials made of a polystyrene, a styrene, a methyl methacrylate copolymer, a (meth-)acrylic resin, a polymethyl pentene, an allyl glycol carbonate resin, spiran resin, an amorphous polyolefin, a polycarbonate, a polyamide, a polyarylate, a polysulfone, a polyallylsulfone, a polyether sulfone, a polyether imide, a polyimide, a diallyl phthalate, a fluororesin, a polyester carbonate, norbornene resin(ARTON), cycloaliphatic acrylic resin, a silicon resin, an acrylic rubber, a silicon rubber, and the like, where "(meth-)acrylic" means "acrylic" or "methacrplic". A cladding material can be selected from transparent materials having low refractive index. For example, organic materials such as a plastic material and an elastomer material can be used. Examples of the cladding materials are a polyethylene, a polypropylene, a polymethyl methacrylate, and polymethyl methacrylate fluoride, a polyvinyl chloride, a polyvinylidene chloride, a polyvinyl acetate, a polyethylene-vinyl aceate copolymer, a polyvinyl alcohol, a polyethylene-polyvinyl alcohol copolymer, fluororesin, a silicon resin, a natural rubber, a polyisoprene rubber, a polybutadiene rubber, a styrene-butadiene copolymer, a butyl rubber, a halogenated butyl rubber, a chloroprene rubber, an acryl rubber, a ethylene-propylene-diene copolymer (EPDM), an acrylonitrile-butadiene copolymer, a fruorine-contained rubber, a silicon rubber, and the like. Among the above materials, from the viewpoint of optical properties such as transparence and refractive index, and workability of co-extrusion, a polystyrene, a polycarbonate, a styrene-(meth-)acrylic copolymer (MS polymer), and the like, are suitable for the core material, and (meth-)acrylic polymer and the like are suitable for the cladding material. A reflective layer is preferably made of a (meth-)acrylic polymer containing a white pigment or a light scattering material. As a white pigment or a light scattering material, one or more than two among organic polymer particles such as silicone resin particles and polystyrene resin particles, metallic oxide particles such as Al 2 O 3 , TiO 2 and SiO 2 , sulfate particles such as BaSO 4 , and a carbonate particle such as CaCO 3 can be used. In case of considering a reflective efficiency and workability of co-extrusion, an average particle size of these white pigments or light scattering materials is preferably 0.1-200 µm, more preferably 0.5-50 µm, and the content of these white pigments or light scattering materials in a material for forming a reflective layer (reflective material) is preferably 0.5-20 wt.%, more preferably 1-10 wt.%. The a thickness of the reflective layer 4 is not limitative and is preferably 10-200 µm, more preferably 50-100 µm. If the reflective layer 4 is too thin, the amount of light to be reflected by the reflective layer 4 is too less, and thus the brightness of light to be emitted from the light transmitting tube 1 is too low. On the other hand, if the reflective layer 4 is thick, the amount of light to be reflected by the reflective materials 4 is large, and thus the brightness of light to be emitted from the light transmitting tube 1 is high. However, these phenomena are found out only at a part of the light transmitting tube 1 relatively near the light source. That is, there are cases where the brightness of light to be emitted from the light transmitting tube 1 becomes too low at a place relatively far from the light source in case of using the reflective layer 4 having too large thickness. The diameter of the core 2 is not limited and it is generally taken as 2-30 mm, preferably 5-15mm. The thickness of the tubular cladding 3 is generally taken as 0.05-4mm, particularly 0.2-2mm. The light transmitting tube may have a reflective protection layer formed on the outer surface of the tubular cladding 3 so as to cover a part of the circumferential surface thereof, which part does not emit a light. In such a light transmitting tube with the reflective protection layer, in case that the reflective layer 4 has flows such as pinholes, the reflective protection layer reflects the light which passes through the flows to leak into the back of the reflective layer 4 or leaks from the side of the reflective layer 4. Therefore the reflective protection layer decreases light loss and thus improves the brightness of light to be emitted from the portion of the tube opposite to the reflective layer 4. It is desirable that a part of the light transmitting tube which part is pulled out of the body of a vehicle is covered with the reflective protection layer all around its circumferential surface. A material for the reflective protection layer is preferably so constituted that the reflective protection layer does not allow light leaked from the reflective layer 4 to pass through and does not absorb the light but reflect the light effectively. For example, metal foils or metal sheets made of silver, aluminum, etc., and coating films in which the aforementioned light scattering particles are dispersed can be used. The light transmitting tube can be manufactured by the following method: a multi-color extrusion molding machine, for example, a three-color extrusion molding machine having three screw sections is used; a core material, a cladding material, and a reflective material containing a white color pigment or a light scattering material are introduced into the extrusion molding machine; in a simultaneous manner, the core material is extruded to be formed into a solid cylindrical core member, the reflective material is extruded into plural belt-like reflective layers formed on the outer surface of the solid cylindrical core member and the cladding material is extruded into a tubular member covering the solid cylindrical core member and the belt-like reflective layers. With the use of the above method, three kinds of materials having different refractive index and different physical properties may be extruded simultaneously so as to be formed into a laminated structure having three different functions, during only one operation. Since this method allows the laminated structure to be formed at a high speed, and since the different layers are allowed to be laminated together while they are still in a soft state, it is allowed to manufacture a light transmitting tube having an excellent adhesion between different layers at high efficiency. The reflective protection layer may be formed by adhering a metallic foil or metallic sheet to the outer surface of the cladding or by coating the outer surface of the cladding with a coating material in which light scattering particles are dispersed. The reflective protection layer may also be formed by extruding simultaneously. Another light transmitting tube which is used suitably in the present invention will be illustrated with reference to Figs. 9-18. A light transmitting tube 300 shown in Figs. 9, 10 is composed of a core made of a polymethyl (meth-)acrylate (PMMA) and a reflective body 301 installed at the end of the core. Because the PMMA absorbs light in small amount, the brightness of the circumferential surface of the tube is high. The reflective body 301 may be omitted. The diameter of the core is preferably 2-30 mm, more preferably 5-15mm. Though not illustrated, a cladding made of fluororesin may be installed at the outersurface of the core made of the PMMA. The cladding made of fluororesin encloses the whole circumferential surface like the above cladding 3. The thickness of the cladding made of the fluororesin is preferably 0.05-4mm, more preferably 0.2-2mm. A light transmitting tube 310 shown in Figs. 11, 12 has a core 311 made of PMMA, a reflective body 301 installed at the end of the core 311, and a reflective layer 312 installed on the circumferential surface of the core 311. The reflective layer 312 extends in the longitudinal direction of the core 311. A light passing through the core 311 is reflected and scattered by the reflective layer 312 so that the light is emitted from the circumferential surface of the core 311 except for the area on which the reflective layer 312 is installed. The reflective layer 312 is preferably made of (meth-)acrylic polymer including a white pigment or a light scattering material. As a white pigment or a scattering material, one or more than two among organic particles such as silicon resin particles and polystyrene resin particles, metallic oxide particles such as Al 2 O 3 , TiO 2 and SiO 2 (silica), sulfate particles such as BaSO 4 , and carbonate particles such as CaCO 3 can be used. Particularly, among them, TiO 2 , SiO 2 and BaSO 4 are suitable. When taking account of reflection efficiency and workability of simultaneous extrusion, an average particle size of the white pigment or light scattering material is preferably 0.1-200µm, more preferably 0.5-50µm, and the amount of the white pigment or light scattering material in a material for composing the reflective layer (reflective material) is preferably 0.5-20 wt.%, more preferably 1-10 wt.%. Though the thickness of the reflective layer is not limited, it is preferably 10-200 µm, more preferably 50-100 µm. If the reflective layer 4 is too thin, the amount of light to be reflected by the reflective materials 4 is too less, and thus the brightness of light to be emitted from the light transmitting tube 1 is too low. On the other hand, if the reflective layer 4 is thick, the amount of light to be reflected by the reflective materials 4 is large and thus the brightness of light to be emitted from the light transmitting tube 1 is high. However, these phenomena are found out only at a part of the light transmitting tube 1 relatively near the light source. That is, there are cases where the brightness of light to be emitted from the light transmitting tube 1 becomes low at a place relatively far from the light source in case of using the reflective layer 4 having too large thickness. The light transmitting tube may have a reflective protection layer formed on the outer surface of the tubular cladding 3 so as to cover the reflective layer 312. In such a light transmitting tube with the reflective protection layer, in case that the reflective layer 312 has flaws such as pinholes, the reflective protection layer reflects the light which passes through the flaws to leak into the back of the reflective layer 312 or leaks from the side of the reflective layer 312. Therefore the reflective protection layer thereby decreases light loss and thus improves the brightness of light to be emitted from the portion of the tube opposite to the reflective layer 312. It is desirable that a part of the light transmitting tube pulled out of the body of a vehicle is covered with the reflective protection layer all along its circumferential surface. A material for the reflective protection layer is preferably so composed that the reflective protection layer does not allow a light leaked from the reflective layer 312 to pass through and does not absorb the light but reflect the light effectively. For example, metal foils or metal sheets made of silver, aluminum, etc., and coating films in which aforementioned light scattering particles are dispersed can be used. Alight transmitting tube 320 shown in Figs.13, 14 have notch-like grooves 313 on its reflective layer 312. These grooves 313 penetrate through the reflective layer 312, so as to notch the core 311. It is desirable that each of these grooves 313 is provided so as to extend in the circumferential direction of the light transmitting tube 320 (that is, perpendicular to the extending direction of the light transmitting tube 320). For example, these grooves 313 can be formed by pushing a spur gear-like rotator against the circumferential surface of the light transmitting tube. These grooves 313 scatter a light passing through the core 311 of the light transmitting tube 320 and coming into the reflective layer 312 so that the light is emitted from the circumferential surface of the core 311. An extremely small amount of light is emitted from these grooves 313 toward the outside of the light transmitting tube. However, the amount of the light emitted out from these grooves is so small that the loss of light is very small. It is desirable that the groove 313 has a V-shaped cross section, in which the angle of divergence between the slopes thereof is 30-60°, for example, 45°. The clearance between these grooves 313 is preferably 1 to 5 mm, more preferably 2 to 4 mm. However, the shape of the grooves 313 is not limited to the V-shaped cross section. For example, the grooves 313 may have a half-round cross section. Other constructions of the light transmitting tube shown in Figs.13, 14 are the same as those of the light transmitting tube shown in Figs.11, 12, in which the same numerals show the same portions. A light transmitting tube 330 shown in Figs.15, 16 and 17 has a lot of concavities 314 in a reflective layer 312. These concavities 314 penetrate through the reflective layer 312 so as to form concavities on the surface of the core 311. These concavities 314 are provided in a line(s) along the longitudinal direction of the core 311 at specified intervals. It is desirable that two or more lines of these concavities 314 are provided. Though these concavities 314 have a cylindrical shape as shown in Fig.17, concavities 315 may have a conical shape as shown in Fig.18. These concavities 315 also penetrate through the reflective layer 312 and cut into the surface of the core 311. These concavities 314, 315 scatter a light passing through the core 311 of the light transmitting tube 320 and coming into the reflective layer 312 so that the light is emitted from the circumferential surface of the core 311. An extremely small amount of light is emitted from these concavities 314, 315 toward the outside of the light transmitting tube. However, the amount of the light emitted out from the sets of the concavities 314, 315 is so small that the loss of light is very small. Aforementioned grooves 313 and concavities 314, 315 may be provided on the core which does not have a reflective layer 4. Examples of light transmission properties of the light transmitting tubes in Figs. 9-18 will be illustrated in the following. Example 1 The core No.1 is made of polystyrene. The core No.2 is made of styrene-acryl copolymer including 70wt.% styrene. The core No.3 is made of PMMA. Each core has a diameter of 12mm and a length of 300mm, and does not have either a reflective layer or a cladding is installed. Each core was measured in its transmittance of light having wavelengths of 400 to 700mm by introducing a white light emitted from LED thereinto from its one end to measure a light volume emitted from another end thereof. The results are shown in Table.1. core light transmittance No.1 63% No.2 72% No.3 83% The results proved that the core made of PMMA has extremely high light transmittance. Example 2 Light transmitting tubes No.4, 5, 6 were prepared by forming reflective layers on the cores No.1, 2, 3 in Example 1, respectively, wherein the reflective layers are made of a metaacryl polymer including 10wt.% TiO 2 pigment, and colored in white, furthermore the reflective layers have a thickness of 20 µm and a width of 3.5mm. The same white light as example 1 was introduced from both ends of each light transmitting tube to measure volumes of light emission at the parts of the circumferential surface thereof spaced 50mm, 150mm and 250mm apart from said one ends, respectively. The results are shown in Table 2. core volume of light emission (cd/m 2 ) 50mm 150mm 250mm No.4 polystyrene 510 460 510 No.5 styrene-acrylic copolymer 600 550 600 No.6 PMMA 760 700 760 As a result from Table 2, it is exemplified that the light transmitting tube No.6 having the core made of PMMA emits a strong light. The reason is because light transmittance of PMMA is extremely high. Example 3 A lot of conic concavities were provided on the reflective layer of the light transmitting tube No.6 to prepare a light transmitting tube No.7. The angle at the corner of the conic concavities is 90 degrees and the depth of the concavities is 0.25mm. The concavities penetrate through the reflective layer and cut into the face of the core. The diameter of the entrance section of the concavities is 1.2mm. The concavities are arranged in two columns extending in the longitudinal direction of the light transmission, in which the concavities are arranged tube at 2.2mm intervals, respectively. These two columns of the concavities are arranged at 2.2mm intervals in the circumferantial direction of the light transmitting tube. Therefore, the clearance between concavities arranged in the longitudinal direction is 1 mm and the clearance between concavities arranged in the circumferential direction is also 1 mm. A lot of grooves each of which extends in the circumferential direction are provided on the reflective layer of the above light transmitting tube No.6 to make the light transmitting tube No.8 shown in Figs. 13, 14. Each groove provided at 2.7mm intervals has a V-shaped cross section and the angle of its comer is 90 degrees. The maximum width of the entrance of each groove is 1.2mm. Therefore, the clearance between these grooves are 1.5mm. A light was introduced into the light transmitting tubes No.7 and No.8 under the same condition as the light transmitting tube No.6 in the above Example 2 and the intensity of the light emitted from the circumferential surface of these was measured. The results are shown in Table 3. Table 3 also shows the data of the light transmitting tube No.6 which has been shown in Table 2. light transmitting tube hollow portions volume of light emission (cd /m 2 ) 50mm 150mm 250mm No.6 none 760 700 760 No.7 conic concavities are arranged at 2.2mm intervals 1100 1000 1100 No.8 grooves are arranged at 2.7mm intervals 930 850 930 As results from Table 3, it is exemplified that the volume of the light emitted from the circumferential surface of the light transmitting tube increases when the concavities are provided. Example 4 A visible light having a wavelength of 400-700nm was introduced into the aforementioned light transmitting tubes No.6, 7, 8, respectively, and the volume of light emitted from another ends of those were measured in order to measure light transmittance of the each cores of those. light transmitting tube light transmittance No.6 36% No.7 25% No.8 28% As shown in Table 4, it is exemplified that the light volume passing through each of the light transmitting tubes No.7 and No.8 from one end to another end is small, while the light volume emitted from its circumferential surface is large. Example 5 The same concavities as those of the aforementioned light transmitting tube No.7 are provided on the light transmitting tube No.3, which is composed only of the core, to make a light transmitting tube No.9. On the circumferential surface of the transmitting tube No.3 composed only of the core, the same grooves as those of the above light transmitting tube No.8 were provided to make a light transmitting tube No.10. A light was introduced into each of the light transmitting tube No.9 and No.10 from its both ends under the same condition as the above Example 3 and the light volume emitted from the circumferential surface was measured. The results are shown in Table 3. Table 3 also shows the data of No.6 which has been shown in Table 2. light transmitting tube light reflective layer hollow portions volume of light emission (cd/m 2 ) 50mm 150 mm 250mm No.6 installed none 760 700 760 No.9 not installed conic concavities 950 900 950 No.10 installed grooves 850 800 850 As shown in Table 5, it is exemplified that the light transmitting tube provided with the concavities or grooves instead of a reflective layer also emits a large volume of light. Example 6 The brightness of light leaked from the reflective layers of each of the light transmitting tubes No.6, 7,8 was measured. A light was introduced from one end of each light transmitting tube and a light leaked from each tube was measured by using a brightness measuring equipment which was installed at an angle of 45° from the longitudinal direction of the core of the tube. The measurement results are shown in Table 6. The brightness of the light leaked from the concavities or grooves of the light transmitting tubes No.9 and No.10 which have no reflective layer was measured by the same measurement method. The results are shown in Table 6. light transmitting tube reflective layer hollow portions brightness of the leaked light (cd/m 2 ) No.6 installed none 15 No.7 installed conic concavities 10 No.8 installed grooves 10 No.9 not installed conic concavities 300 No.10 notinstalled grooves 400 As shown in Table 6, it is exemplified that the installation of the reflective layer decreases the leakage of light considerably. Industrial Applicability Because the meter case of the present invention has the light transmitting tubes for transmitting light to provide indications with the light, the light source unit can be located in a place which is away from the meter case. As a result, the light source unit can be installed in a place where maintenance of the light source unit can be carried out easily. The light transmitting tube is low in weight and excellent in durability, and has no fear of an electric leak; besides there is no fear of a short circuit in case of deformation by collisions with a vehicle.

Claims: A meter case which has a main body (210) having a transparent part, a light-transfer board (240) installed at the back of the main body (210) and a lighting system for directing a light to the edge of the light-transfer board (240), wherein the lighting system has a light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330), and a light source installed at one end of the light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330), characterized in that the light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330) emits a light from its circumferential surface. A meter case as claimed in claim 1, wherein the light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330) is extended out of the meter case. A meter case as claimed in any one of claims 1 or 2, wherein the light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330) has a tubular cladding (3) and a core (2, 311) made of a material which has a higher refractive index than that of the tubular cladding (3). A meter case as claimed in claim 3, wherein the light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330) has a belt-like reflective layer (4, 312) being formed between the tubular cladding (3) and the core (2, 311) and extending in a longitudinal direction of the tubular cladding (3) so that a light passing through the core (2, 311) is reflected and scattered by the reflective layer (4, 312) and emitted from the outer surface opposite to the reflective layer (4, 312) of the tubular cladding (3). A meter case as claimed in claim 3 or 4, wherein the tubular cladding (3) is made of a (meth-)acrylic polymer and the core (2, 311) is made of a polystyrene, a polycarbonate or a styrene-(meth-)acrylic copolymer. A meter case as claimed in claim 4, wherein the reflective layer (4, 312) is made of a (meth-)acrylic polymer including a white pigment or a light scattering material. A meter case as claimed in any one of claims 1 or 2, wherein the light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330) has a core (2, 311) made of a polymethyl (meth-)acrylate, and has nothing on the circumferential surface of the core (2, 311). A meter case as claimed in any one of claims 1 or 2, wherein the light transmitting tube (1, 221, 222, 223, 225, 226, 300, 310, 320, 330) has a core (2, 311) made of a polymethyl (meth-)acrylate and a belt-like reflective layer (4, 312) formed on the circumferential surface of the core (2, 311) along its length so that a light passing through the core (2, 311) is reflected and scattered by the reflective layer (4, 312) and then emitted from the outer surface opposite to the reflective layer (4, 312) of the tubular cladding (3). A meter case as claimed in claim 7 or 8, wherein plural hollow portions (313, 314, 315) are provided at the outer surface area of the core (2, 311), which are arranged in the longitudinal direction of the core (2, 311) so as to scatter a light passing through the core (2, 311). A meter case as claimed in claim 9, wherein the hollow portions are concave holes (314, 315). A meter case as claimed in claim 9, wherein the hollow portions are grooves (313) each of which extends in the circumferential direction of the core (2, 311).

Inventors: ISHIHARADA MINORU, ISHIHARADA, MINORU
Applicants: BRIDGESTONE CORP, BRIDGESTONE CORPORATION
Application year: 2000
Main classification: B60Q1
IPC codes: B60Q1, B60K37, B60Q3