Abstract:
A gauge which uses a prism or other type of reflector to illuminate a single graphic or icon on a dial such that only one graphic on the dial is shown during the operation of the gauge. All of the remaining graphics have a dead front appearance, and cannot be viewed, such that the gauge presents only one discrete value at a time. The dial is beneath a lens, and the prism is beneath the dial. An actuator is mounted to a PCB, and an LED is also mounted to the PCB to allow the prism to transmit light to the desired area of the dial. The dial also includes a central graphic, or icon, and the gauge is able to display different values, while the central graphic remains constantly illuminated in the center of the gauge.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to a gauge having a dial with several graphics, where only one of the graphics is illuminated at a time, while the remainder of the graphics have a dead front appearance. 
     BACKGROUND OF THE INVENTION 
     Gauges are commonly used in different applications to convey information to a driver about various operating conditions of a vehicle. Several gauges may be included as part of an instrument cluster to provide information to the driver relating to vehicle speed, engine speed, amount of fuel used, engine temperature, fuel economy, and the like. Gauges are also used for applications other than for automotive use, such as air compressors, boilers, and the like. When used in a vehicle, typical gauges receive information from a device such as the vehicle&#39;s electronic control unit (ECU). These gauges include a pointer which rotates and aligns with various portions of a scale, and the pointer moves to various locations along the scale, depending upon the information received from the ECU. 
     However, most of these types of gauges have a pointer that is in front of the scale, and the pointer rotates about an axis. The pointer typically is mounted near the center of the gauge, and extends outwardly, overlapping with part of the scale. The pointer is calibrated to properly align with the portion of the scale when the gauge is viewed substantially perpendicularly. The reading provided by the gauge may have a margin of error when viewed from various angles. Also, the pointer takes up space on the front of the gauge, which limits the amount of information that may be displayed on the scale. 
     Accordingly, there exists a need for a gauge which is viewable from different angles, provides an accurate reading, and improves the reading of the scale. 
     SUMMARY OF THE INVENTION 
     The present invention provides a gauge which uses a prism or other type of reflector to illuminate a single graphic on a dial such that only one graphic on the dial is shown during the operation of the gauge. All of the remaining graphics have a “dead front” appearance, and are not visible. In one embodiment, the present invention is a pointerless gauge having a housing, a printed circuit board (PCB) mounted within the housing, an actuator mounted to the PCB, and a shaft extending through the actuator. A light emitting diode (LED) is mounted on the PCB in proximity to the shaft, such that light passes through the shaft when the LED is activated. A tube portion is mounted on an end of the shaft, a prism connected to the tube portion, and a dial is mounted in the housing in proximity to the prism. A plurality of graphics is located on the dial, and each of the plurality of graphics represents a measurement of an operating parameter. A lens is mounted in the housing in proximity to the dial such that the lens is on the opposite side of the dial in relation to the prism. 
     The actuator rotates the shaft to position the prism in proximity to one of the plurality of graphics representing a measurement of the operating parameter, and light emitted from the LED passes through the shaft and is directed through one of the plurality of graphics by the prism. 
     Instead of having a pointer which moves through the use of a mechanical device towards one of several values always displayed on a scale, the gauge of the present invention presents only one discrete value at a time. The dial is behind the lens, and the prism is behind the dial. In one embodiment, the actuator is a stepper motor located on top of the PCB, and the LED is placed below the shaft of the stepper motor so the prism transmits the light to the desired area of the dial. The dial also includes a central graphic, or icon which may vary depending upon the type of application for which the gauge is used. The gauge is able to display different values, while the icon remains constantly illuminated in the center of the gauge. 
     Beneath the dial, a prism (or in alternate embodiment, a reflector) is moved by the shaft of the gauge. The shaft rotates the prism to place the prism under the graphic representing the desired value of the dial, illuminating only that graphic and making it visible to the user. Also, the prism continuously illuminates a graphic located in the center of the dial. This invention is applicable to any of the gauges in an instrument cluster, or other applications. 
     One of the advantages of the gauge of the present invention is that there is more space in the dial, which provides a cleaner design and improved viewing of the gauge. The dial being located closer to the lens improves its visibility from different viewing angles. The gauge of the present invention also has a reduced number of parts compared to typical gauges, reducing the cost. Furthermore, the gauge of the present invention is shorter in length than typical gauges, allowing the gauge of the present invention to meet more stringent packaging requirements. 
     In alternate embodiments, the prism or reflector may be different shapes, providing illumination of the values of the dial with LEDs. Additionally, illumination of the values of the dial may be achieved with a light beam form a different light source or a display. 
     In other alternate embodiments, the actuator may be mounted on different sides of the PCB, such as either the top or the bottom side, and still perform the functions as described above. When the actuator is mounted on the bottom side of the PCB, light from the LED passes directly into the tube portion, instead of passing through the shaft. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a sectional view of a gauge, according to embodiments of the present invention; 
         FIG. 2A  is a first front view of a gauge, according to embodiments of the present invention; 
         FIG. 2B  is a second front view of a gauge, according to embodiments of the present invention; 
         FIG. 3  is a third front view of a gauge, with all of the graphics visible, according to embodiments of the present invention; 
         FIG. 4  is a perspective view of a gauge with the housing removed, according to embodiments of the present invention; 
         FIG. 5  is a perspective view of an alternate embodiment of a gauge with the housing removed, according to embodiments of the present invention; and 
         FIG. 6  is a sectional view of an alternate embodiment of a gauge, according to embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     An embodiment of a gauge according to the present invention is shown in  FIGS. 1-4 , generally at  10 . The gauge  10  includes a housing  12  having an outer sidewall  14 . Formed as part of the sidewall  14  is a ledge portion  16 , and mounted on the ledge portion  16  is a printed circuit board (PCB)  18 . Mounted on the PCB  18  is various circuitry necessary for the operation of the gauge  10 , as well as an actuator, shown generally at  20 , which in this embodiment is a stepper motor. However, it is within the scope of the invention that other types of actuators may be used. 
     The stepper motor  20  includes various components which are used for rotating a shaft  22 , and the shaft  22  protrudes outwardly away from the stepper motor housing  24 . Mounted on an end  26  of the shaft  22  is a tube portion  28 , and connected to the tube portion  28  is a light directing device, which in this embodiment is a prism  30 . The prism  30  is rotated by the shaft  22 , and the stepper motor  20  rotates the shaft  22 . The prism  30  is located in proximity to a dial  32 , and the dial  32  has various graphics, or icons,  34  which provide an indication of various ranges of operating conditions, as shown in  FIG. 3 . 
     The housing  12  also includes an inner step portion  36 , and the dial  32  is mounted on the inner step portion  36 , as shown in  FIG. 1 . The lens  38  is positioned in the housing  12  on top of the dial  32  such that light projecting from the prism  30  penetrates through the dial  32  and the lens  38 . The lens  38  and the dial  32  are secured to the inner step portion  36  by a bezel, shown generally at  40 . The bezel  40  has a first flange portion  42  integrally formed with a body portion  44 , and a second flange portion  46 , which is also integrally formed with the body portion  44 . During assembly, the first flange portion  42  and second flange portion  46  are deformed, or “crimped,” to the shape shown in  FIG. 1 , to attach the bezel  40  to the housing  12 . Formed as part of the housing  12  is an outer lip portion  48 , and the second flange portion  46  is deformed such that the diameter  50  of the outer lip portion  48  is larger than the innermost diameter  52  of the second flange portion  46 . The deformation of the flange portions  42 , 46  and the difference in size between the two diameters  50 , 52  provides for a secure connection between the bezel  40  and the housing  12 , and prevents the bezel  40  from becoming detached from the housing  12 . The secure connection between the bezel  40  and the housing  12  also secures the location of the dial  32  and the lens  38 . 
     In the embodiment shown in  FIGS. 1-4 , the prism  30  and the tube portion  28  are integrally formed as a single component. However, it is within the scope of the invention that the prism  30  and tube portion  28  may be formed separately, and connected together during assembly. The prism  30  protrudes outwardly away from the tube portion  28  towards the outer diameter  54  of the dial  32 . The end  26  of the shaft  22  partially extends into the tube portion  28 . Disposed on the PCB  18  is a light source, which in this embodiment is a light emitting diode (LED)  56 . A lower end  58  of the shaft  22  receives light from the LED  56 , and the light is transferred through the shaft  22  towards the prism  30 . 
     The light passing out of the shaft  22  enters the tube portion  28 , where a portion of the light passes out of the tube portion  28  towards the dial  32 , and a portion of the light passes through the prism  30 . The prism  30  directs light outwardly towards the dial  32 . The portion of the dial  32  that is illuminated by the light projecting from the prism  30  varies, depending upon the position of the prism  30 . Referring to  FIGS. 2A and 2B , different portions of the dial  32  are shown as being illuminated. In  FIG. 2A , a first graphic, shown generally at  60 , is shown illuminated, along with a center graphic or icon, shown generally at  62 , and the remaining portions of the dial  32  are dark, essentially having a “dead front” appearance. In  FIG. 2 , a second graphic, shown generally at  64 , is shown illuminated, along with the center graphic  62 . The first graphic  60  is illuminated as shown in  FIG. 2A  when the prism  30  is positioned behind the area of the dial  32  where the first graphic  60  is located, and the second graphic  62  is illuminated as shown in  FIG. 2B  when the prism  30  is positioned behind the area of the dial  32  where the second graphic  62  is located. When the prism  30  is aligned with one of the graphics  60 , 64 , that graphic  60 , 64  is illuminated. There are also other various graphics which are located on the dial  32  that allow light to project through, which are illuminated when the prism  30  is in proper alignment with that particular graphic. 
     Additionally, the center graphic  62  is constantly illuminated when the LED  56  is illuminated. This is a result of the light from the LED  56  passing through the shaft  22  and through the tube portion  28  to illuminate the center graphic  62 . The center graphic  62  remains in constant illumination because the area of the tube portion  28  being in alignment with the center graphic  62 . The area of the tube portion  28  which projects light remains in alignment with the center graphic  62  regardless of how the prism  30  is rotated by the shaft  22 . This results in the center graphic  62  remaining in constant illumination regardless of the position of the prism  30  or which area of the dial  32  is being illuminated. 
     The gauge  10  of the present invention allows for viewing a correct reading at almost any viewing angle relative to the lens  38 . The illumination of only one of the graphics  60 , 64 , and the alignment of the prism  30  behind the dial  32  ensures that only one reading is taken from the gauge  10 , and there is no confusion when looking at the gauge  10  from different angles. The addition of the center graphic or icon  62  also provides for the gauge  10  to have additional functionality. The center graphic  62  is used as an indicator of what type parameter the gauge  10  provides, such as temperature or pressure. However, the center graphic  62  of the gauge  10  could also be used for other purposes, such as a warning indicator. 
     Referring again to  FIG. 2B , the second graphic  64  also includes warning graphics  66 , which are also illuminated to provide an indication that the reading provided by the gauge  10  indicates that an operating parameter has reached an undesired or unsafe operating condition. For example, the second graphic  64  shown in  FIG. 2B  indicates that exhaust temperature has reached an undesirable level. In various other embodiments, the dial  32  may be changed to have different graphics  60 , 64 , such that the gauge  10  may be used to provide a reading for other operating conditions. 
     In the embodiment shown in  FIGS. 1-4 , the stepper motor  20  is shown as being mounted on a top surface  68  of the PCB  18 , such that the stepper motor  20  is located between the PCB and the dial  32 . An alternate embodiment of the invention is shown in  FIGS. 5-6 , with like numbers referring to like elements. In this embodiment, the stepper motor  20  is shown mounted on a bottom surface  70  of the PCB  18 , such that the stepper motor  20  is located between the bottom surface  70  and a lower wall  72  of the housing  12 . In the embodiment shown in  FIG. 5 , the LED  56  is still located on the top surface  68  of the PCB  18 , but the LED  56  in this embodiment is round and includes an aperture  82 , and the shaft  22  extends through the aperture  82 , as shown in  FIG. 6 .  
     Also included in this embodiment is a reflector, shown generally at  74 , mounted to top surface  68  of the PCB  18 . The reflector  74  includes a reflective surface  76  and a cylindrical portion  78 . The cylindrical portion  78  is hollow, and has an inner diameter  80  which is larger than the diameter of the tube portion  28 . The inside surface  84  of the cylindrical portion  78  is also reflective, and directs light from the LED  56  towards the tube portion  28  and the prism  30 , such that the prism  30  and tube portion  28  direct light outwardly through the dial  32  and the lens  38 . 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.