Abstract:
An illuminated instrument assembly includes an instrument cluster having a graphical image and a pointer moveable relative to the graphical image to indicate a vehicle operating condition. In one example, the pointer has a body and an arm portion. A light source illuminates at least a portion of the pointer. The arm portion of the pointer is at least partially coated with a surface finish comprising a metal substrate to eliminate light bleed and the halo effect that may occur when viewing the graphical image.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This application claims priority to U.S. Provisional Patent Application Ser. No. 60/607,401 filed Sep. 3, 2004. 
     
    
       [0002]     This invention generally relates to an illuminated pointer for an instrument panel, and more particularly to an illuminated pointer that controls light from escaping from an arm portion of the pointer and reflecting onto surrounding surfaces.  
         [0003]     A vehicle instrument panel typically includes several gauges for displaying and conveying information to a driver. The instrument panel typically includes a speedometer along with other gauges such as a tachometer, battery level indicator, and oil pressure gauge. Typically a pointer is mounted to move relative to a fixed graphical image on each gauge.  
         [0004]     The pointer is typically one of two basic types, either a non-active pointer or an active pointer. A non-active pointer is illuminated by a light source mounted to a circuit board positioned behind a light transparent output shaft. Light is reflected into the pointer and scattered to illuminate the pointer. An active pointer includes a light source secured to the moving pointer.  
         [0005]     In each configuration, the pointer includes a body portion that extends from a first end coupled to a motor to a second end that moves relative to the graphical image. One disadvantage with illuminated pointers is that light is often transmitted from the pointer arm to undesirable locations such as toward the viewer. Also, light may reflect onto surrounding gauge surfaces resulting in an undesirable appearance.  
         [0006]     Many illuminated pointers include an opaque-plastic shroud attached to the pointer to eliminate undesirable light transmission. Disadvantageously, a plastic shroud requires additional molding and assembly equipment. Further, plastic shrouds are commonly large and bulky which may cause imbalance of the pointer during movement.  
         [0007]     Accordingly, it is desirable to provide an illuminated pointer that is easy to assemble and that provides light shrouding without a bulky plastic shroud.  
       SUMMARY OF THE INVENTION  
       [0008]     An illuminated instrument panel assembly includes a pointer moveable relative to an instrument cluster. The pointer is at least partially coated with a surface finish that prevents undesirable light emissions.  
         [0009]     In an example pointer according to this invention, the arm portion of the pointer includes a light emitting surface and an internally light reflecting surface. The internally light reflecting surface includes a surface finish applied using a vacuum metallizing process. The light emitting surface does not include the surface finish. In one example, the assembly includes a light source to illuminate at least a portion of the pointer. The illumination exits the pointer only through the light emitting surface of the arm portion of the pointer to light the graphical image.  
         [0010]     The illuminated instrument assembly of the present invention provides a surface finish for an illuminated pointer that is simple to apply and provides a compact appearance. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:  
         [0012]      FIG. 1  illustrates an instrument cluster including a pointer assembly according to the present invention;  
         [0013]      FIG. 2  shows a perspective view of an example pointer with an exemplary surface finish shroud according to the present invention;  
         [0014]      FIG. 3  is a perspective view of a bottom side of the pointer with the surface finish shroud according to the present invention;  
         [0015]      FIG. 4  is a flow chart illustrating a process for providing a surface finish on a pointer according to the present invention; and  
         [0016]      FIG. 5  is a cross-sectional view of an example gauge pointer assembly including the pointer with the surface finish shroud.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     An instrument cluster  10  including at least one gauge pointer assembly  20  is shown generally in  FIG. 1 . The instrument cluster  10  includes a gauge  12  having a graphical image, such as a scale, for example, which is used to indicate a vehicle operating condition. The gauge  12  is mounted to a dash panel or other similar fixed vehicle structure  14 . A pointer  16  is mounted for movement relative to the gauge  12  and is used to indicate the current status of the vehicle operating condition. A light source  18  is mounted behind the instrument cluster  10  and is used to illuminate at least a portion of the pointer  16  so that a vehicle operator can clearly see the vehicle operating condition. The light source  18  can illuminate the length of the pointer  16 , only the tip of the pointer  16 , or any portion thereof. The light source  18  is a light emitting diode [LED]. It is within the contemplation of this invention to utilize any other light source known in the art.  
         [0018]     An example pointer  16  for use within the gauge pointer assembly  20  is illustrated with reference to  FIGS. 2 and 3 . The pointer  16  includes a body  30  and an arm portion  32 . The body  30  includes a shaft  34  protruding transverse to the arm portion  32 . In one example, the shaft  34  is perpendicular to the arm portion  32 . The shaft  34  includes an opening  26  for receiving an output shaft  22  of a motor  24  (See  FIG. 4 ).  
         [0019]     The arm portion  32  of the pointer  16  includes a light emitting surface  40  and a plurality of internally light reflecting surfaces  42 . The light emitting surface  40  preferably faces the direction of a driver in a passenger compartment of a vehicle. The arm portion  32  of the pointer  16  includes one light emitting surface  40  and three internally light reflecting surfaces  42  to form a four-sided arm portion  32 . The arm portion  32  could be comprised of additional numbers of surfaces.  
         [0020]     The plurality of internally light reflecting surfaces  42  are coated during a secondary process with a surface finish shroud  50 . The surface finish shroud  50  is preferably applied through a vacuum metallized process. The surface finish shroud may also be applied through other known processes such as by painting or chrome plating, for example.  
         [0021]     With reference to  FIG. 4 , a process for coating a pointer  16  through a vacuum metallization process is demonstrated. The process begins by masking the light emitting surfaces  40  of a plurality of pointers  16  as indicated at  200 . The pointers  16  may be masked in any known manner to prevent the surface finish shroud  50  from being applied to the light emitting surface  40 . The plurality of pointers  16  are placed into a fixture as indicated at  210 . Advantageously, a large amount of pointers  16  may be coated with the surface finish shroud  50  simultaneously. The fixture is then placed inside of a vacuum chamber as indicated at  220  along with an amount of nearly pure aluminum. The vacuum chamber is then pressurized and vacuum sealed as indicated at  230 .  
         [0022]     Next, the aluminum is heated until it liquefies as indicated at  240 . As the aluminum liquefies and begins to flow, the vacuum chamber enters a spin cycle as indicated at  250 . The spin cycle circulates the fixtures within the vacuum chamber such that all parts within the fixtures are properly exposed to the aluminum. The aluminum begins to vaporize as indicated at  260 , and upon contacting the pointers  16 , the vaporized aluminum molecules penetrate the light reflecting surfaces  42  of the pointers  16  to provide the surface finish shroud  50  as indicated at  270 . The light emitting surface  40  of the pointer  16  will not include the surface finish shroud  50  because the light emitting surface  40  is masked prior to the vacuum metallization process.  
         [0023]     Referring to  FIG. 5 , a light receiving tube  60  is received within the opening  26  of the shaft  34  of the body  30 . The light receiving tube  60  receives light from the light source  18  and communicates the light to a light reflecting surface  62  ( FIG. 2 ) within the body  30 . The light reflecting surface  62  provides internal reflection. In one example, the light receiving tube  60  is a clear, hollow shaft. The light received within the light receiving tube  60  is reflected off of the light reflecting surface  62  into the arm portion  32 . The light reflecting surface  62  comprises flat surfaces angled at 45°. A worker skilled in the art would understand how to configure the length, angle and shape of the light reflecting surface  62  to direct light along a desired path through the arm portion  32  of the pointer  16 . The light emitting surface  40  does not include the surface finish shroud  50 . Therefore, as light from the light source  18  is emitted through the light receiving tube  60  and into the arm portion  32  of the pointer  16 , the light escapes only through the light emitting surface  40  and is prevented from escaping through the internally light reflecting surfaces  42 . The light that attempts to leak through the internally light reflecting surfaces  42  is reflected back toward the light emitting surface  40 .  
         [0024]     In operation, the opening  26  of the shaft  34  of the pointer  16  is received on the output shaft  22  of the motor  24  in an interference fit, however other attachment methods could be used. The pointer  16  is driven by the motor  24  and is rotated to a desired position relative to the gauge  12  including the graphical image.  
         [0025]     The pointer  16  is illuminated by the light source  18  that is mounted behind the instrument cluster  10 . In one example, the light source  18  is mounted to a printed circuit board (PCB)  100  and positioned adjacent to the motor  24 . The output shaft  22  of the motor  24  is preferably a translucent shaft. Therefore, the light that is emitted from the light source  18  passes through the output shaft  22  and enters the pointer  16  through the light receiving tube  60 , where light is propagated and scattered into the arm portion  32  to illuminate the gauge  12 . The light exits only through the light emitting surface  40  of the arm portion  32 .  
         [0026]     The present invention improves upon the prior art by providing an illuminated gauge pointer assembly  20  that includes a surface finish shroud  50  on at least a portion of the pointer  16 . The surface finish shroud  50  may be applied by a vacuum metallization process which provides the benefits of a less costly shrouding process and the ability to shroud a multitude of pointers  16  simultaneously. The surface finish shroud  50  effectively eliminates light bleed from the pointer  16  (without a bulky appearance) that may occur when viewing the gauge  12 .  
         [0027]     The foregoing shall be interpreted as illustrative and not in a limiting sense. A worker of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.