Abstract:
A gauge with a light transmitting pointer and a light-transmitting dial plate having a surface with indicia for a variable represented by the dial, at least one light source facing a hub of the pointer and positioned rearwardly from the rear surface of the dial plate for illuminating the dial plate. The light-transmitting pointer is mounted for rotational movement about an axis normal to the dial plate. The pointer hub is concentric with the axis, extending through the dial plate and projecting both forwardly and rearwardly from the plate, and an indicator projecting laterally from the hub across a portion of the front surface of the dial plate. The portion of the hub extending rearwardly of the dial plate is shaped to capture light directly from the light source so that light enters the hub and propagates forwardly through the hub, and then laterally from the hub into the indicator to illuminate the indicator.

Description:
[0001]     This application claims priority from U.S. Provisional Application No. 60/675,855, filed on Apr. 29, 2005, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to gauges and, more particularly, to gauges having illuminated dials and pointers such as the gauges used in automotive applications for speedometers, fuel gauges and the like.  
       BACKGROUND OF THE INVENTION  
       [0003]     Gauges with illuminated dials and pointers have been made for many years, and for a variety of different applications. One of the largest applications for such gauges is the automotive industry where gauges having illuminated dials and pointers are used in large numbers, and have been in use for many years. Much effort has gone into the development of such gauges that can be efficiently and economically manufactured and that are aesthetically pleasing. Numerous patents have been issued on various designs and constructions for such gauges, such as U.S. Pat. Nos. 4,163,428; 4,215,647; 4,218,726; 4,274,358; 4,771,368; 5,839,811; 5,915,822; 5,934,782; 6,276,809 and 6,663,251.  
       SUMMARY OF THE INVENTION  
       [0004]     It is one object of the present invention to provide an improved design for a gauge having an illuminated dial and pointer, that can be efficiently manufactured at a relatively low cost because of the simplicity of the construction, and yet still provides good illumination of the dial and pointer and is aesthetically pleasing. In this connection, one specific object of this invention is to provide such an improved gauge that does not require a separate light source for the pointer.  
         [0005]     It is a further object of the present invention to provide such an improved gauge that has relatively few parts and can be made small, compact and lightweight.  
         [0006]     Another object of the invention is to provide such an improved gauge that illuminates the pointer uniformly regardless of the angular position of the pointer.  
         [0007]     A still further object of the present invention is to provide such an improved gauge which generates very little heat.  
         [0008]     It is a further object of the invention to provide an improved gauge that illuminates the pointer and may be implemented in a variety of gauge arrangements.  
         [0009]     A still further object of the invention is to provide an improved gauge in which hot spots are eliminated.  
         [0010]     In accordance with the invention, there is therefore provided a gauge comprising a light-transmitting pointer and a light-transmitting dial plate having a front surface with indicia for a variable represented by the dial, at least one light source facing the pointer hub and positioned rearwardly from the rear surface of the dial plate for illuminating the dial plate. The light-transmitting pointer is mounted for rotational movement about an axis normal to the dial plate. The pointer hub is concentric with the axis, extending through the dial plate and projecting both forwardly and rearwardly from the plate, and an indicator projecting laterally from the hub across a portion of the front surface of the dial plate. The portion of the hub extending rearwardly of the dial plate is shaped to capture light directly from the light source so that light enters the hub and propagates forwardly through the hub, and then laterally from the hub into the indicator to illuminate the indicator. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention will now be described in connection with a preferred embodiment with reference to the following illustrative figures so that it may be more fully understood. It will be understood that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiment of the present invention only, and are presented to provide what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the drawings:  
         [0012]      FIG. 1  is a longitudinal cross-sectional view of an automotive gauge according to one embodiment of the invention;  
         [0013]      FIG. 2  is a longitudinal cross-section view of an automotive gauge according to one embodiment of the invention;  
         [0014]      FIG. 3  is an enlarged longitudinal cross-sectional view of the pointer in the gauge of  FIG. 1 ;  
         [0015]      FIG. 4  is a top plan view of the pointer shown in  FIG. 2 ;  
         [0016]      FIG. 5  is a longitudinal cross-sectional view of a cap for the tail portion of the pointer in the gauge of  FIG. 1 ;  
         [0017]      FIG. 6  is a top down plan view of the cap shown in  FIG. 4 ; and  
         [0018]      FIG. 7  is an exploded perspective of the gauge of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     Referring now to  FIG. 1 , there is shown an automotive gauge having a light-transmitting pointer  10  mounted for rotational movement across the face of a dial plate  11  formed as the end wall of a cylindrical cup  12  that is open at its inner end. The pointer  10  is mounted to maintain a clearance between the dial face and the rear surface of the pointer, and is driven by a small electric motor  13  controlled by electrical circuitry on a printed circuit board (PCB)  15 , illustrated in  FIG. 7 . The motor  13  has an output shaft  16  that fits into a mating hole in a stem  17  extending rearwardly from the pointer  10  and formed as an integral part of the pointer. A stop pin, illustrated in  FIG. 1, 18  may optionally be included to limit the pivoting movement of the pointer  10  across the dial, for precise positioning of the pointer during automatic re-calibration, as is known in the art ( FIG. 2 ).  
         [0020]     The entire gauge mechanism and control circuitry is enclosed in a cylindrical housing  20  having a closed back end  21  and an open front end for receiving a lens  22  and a bezel  23  covering the outer peripheries of the lens  22  and the open front end of the housing  20 . The lens  22  is supported on a retainer ring  24  that rests on the open end of the housing  20  and extends downwardly to the face of the dial plate  11 . A sealing ring  25 , illustrated in  FIG. 7 , fits inside the bezel  23  to provide a seal between the bezel  23  and the adjacent surfaces of the housing  20 , lens  22  and retainer ring  24  to prevent ambient moisture and particulate matter from entering the interior of the gauge.  
         [0021]     To illuminate the dial face, the cup  12  that forms the dial plate  11  is made of a light-transmitting material such as a clear plastic and is illuminated by light radiated from several side-fire light-emitting diodes (“LEDs”)  26  mounted on a second PCB  30 . The number of LEDs is chosen to best suit the illumination needs of the implementation. The LEDs  26  are positioned around the perimeter of the PCB  30  and face towards a pointer hub  10   a . Further, the LEDs  26  are selected to provide light at the desired angle (i.e., wide angle LEDs may be use). The LEDs  26  are positioned rearwardly from the rear surface of the dial plate  11 , and receive electrical power from connectors (not shown) that pass through the printed circuit board  15  to a power connection at the back end of the housing  20 . The LEDs  26  are mounted at intervals around the central axis of the gauge, which is normal to the plane of the dial plate  11  and is also the axis of the pointer stem  17  and the output shaft  16  of the motor  13 . The LEDs  26  may be spaced around the PCB  30  equally or randomly. The spacing may be predetermined to provide illumination best suited for the implementation.  
         [0022]     Provided between the cup  12  and PCB  30  is a light ring  18 . The light ring  18  directs light from the perimeter of the PCB  30  towards the pointer hub  10   a . The light ring  18  also serves to limit the hot spots created by the close proximity of the LEDs  26  to the dial face. The width  19  of the light ring  18  is selected relative to the angle of the light emitted from the LEDs  26  to eliminate hot spots while still allowing light to reach the dial. Additionally, the light ring  18  may be formed to selectively illuminate portions of the dial face in a variety of shape and size arrangements. Alternatively if a non-transparent dial face is used, the light shield  18  is not necessary.  
         [0023]     Light from the LEDs  26  is picked up by the inside surfaces of the dial-plate cup  12  and propagated throughout that cup so as to illuminate the dial plate  11  that forms the base plate of the dial face. A thin opaque face plate  31  is attached to the surface of the illuminated plate  11  to form the desired indicia on the dial face by covering portions of the plate  11  so that only the non-covered portions of the illuminated plate  11  are visible.  
         [0024]     In accordance with one aspect of the present invention, the pointer, illustrated in  FIG. 3 , is made of a transparent or translucent material, preferably colored, and is illuminated by the light from the same light source that illuminates the dial face. Thus, in the illustrative embodiment of  FIG. 1 , light from the LEDs  26  is captured by a tapered transition  40  on the pointer stem  17 , rearwardly of the dial plate  11 . This tapered transition  40  is located between a narrow distal portion  41  of the stem  17  and a wide proximal portion  42  that extends forwardly through the dial plate  11 . The transition is located such that a portion of the light radiating from the LEDs  26  impinges on the tapered transition  40 , as illustrated by the dashed line in  FIG. 1 . Light thus enters the wide portion  42  of the transparent or translucent stem  17  via the tapered transition  40  and propagates forwardly through the wide portion  42  of the stem  17 .  
         [0025]     The tapered transition  40  is coaxial with the stem  17  and is uniform around the entire circumference of the stem  17 , so that the exterior surface of the transition captures substantially the same amount of light regardless of the angular position of the pointer. This arrangement illuminates the pointer without the use of a separate light source dedicated to the pointer, and illuminates the pointer with a brightness that is consistent and non-fluctuating regardless of the angular position of the pointer. The surface of the transition  40  forms an angle with respect to the axis of the stem  17 . The contour of the transition  40  is selected to propagate light through the pointer  10 . The preferable angles of the transition  40  is between 15° and 60°, however the invention is not limited to this angular range. Further, the transition  40  is not limited to the tapered transition construction illustrated in  FIG. 1 . The transition  40  may be implemented using a variety of transition designs including the spherical shaped transition  40  illustrated in  FIG. 2 . The key feature of each transition contour construction is the ability to capture light from the LEDs  26 . Other configurations of the pointer  10  are contemplated, including a pointer stem  17  of a constant width over the entire length of the pointer stem  17 . The exterior surface of the transition  40  is preferably a highly polished surface, which may be achieved by molding the pointer from a polymeric material in a mold in which that portion of the mold surface that forms the transition  40  is treated to form a very smooth surface.  
         [0026]     To direct the light that propagates forwardly through the stem  17  laterally into the pointer  10 , a recess  43  in the upper surface of the pointer hub  10   a  forms a reflecting surface  44  extending at a 45° angle to the axis of the stem  17 . The forwardly propagating light impinges on this surface  44  and is reflected laterally (downwardly as viewed in  FIG. 2 ) toward the free end of the indicator portion  10   b  of the pointer  10 , thus illuminating the indicator portion  10   b . The rear surface  45  ( FIG. 3 ) of the indicator portion  10   b  of the pointer is preferably coated with a reflective material, such as an opaque white paint, to improve the uniformity of illumination of the indicator portion and to increase the amount of light that reaches the top and side surfaces of the indicator portion.  
         [0027]     To conceal the pointer stem  17 , an opaque cap  50 , illustrated in  FIGS. 4-6 , fits over the front of the hub portion  10   a  and tail portion  10   c  of the pointer  10 . This cap  50  is notched to fit over the indicator portion  10   b  that extends laterally from the hub portion  10   a , so that only the indicator portion  10   b  is visible from the front of the gauge, even though the hub and tail portions of the pointer are also illuminated beneath the opaque cap  50 . If desired, the cap  50  can be made of a translucent material to reveal the entire illuminated pointer, including the hub and tail portions  10   a  and  10   c , with the cap  50  serving to attenuate light from the brightest regions of the pointer and thereby make the illumination more uniform along the entire length of the pointer  10 . The cap  50  can also be made of a color different from that of the pointer  10 . A notch  51  formed in the tail side of the recess  43  reflects more light into the tail portion  10   c  when it is desired to illuminate that portion of the pointer.  
         [0028]     One advantage of the above described invention is that it allows for the space between the LEDs  26  and the back of the dial face plate  11  to be reduced. The compact design of the gauge allows for the gauge to be used in a wider variety of implementations, and particularly an implementation in which space is limited. Further, the spacing of the LEDs  26  provides the ability for the invention to be implemented in variety of gauge arrangements, including either as a full or short sweep gauge.  
         [0029]     It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes, which come within the meaning and range of equivalency of the claims, are therefore intended to be embraced therein. What is claimed as new and desired to be protected by Letters Patent of the United States is: