Abstract:
An eyes up instrument having a transparent display is disclosed which is mountable on or above the dashboard of a vehicle to allow the instrument to be read by a vehicle operator without lowering his eyes to the vehicle instrument panel. The display of the instrument is transparent and therefore does not interfere substantially with the view of the operator. The compact design of the instrument and use of a miniature crossed coil gauge supported in the display itself allow it to be mounted unobtrusively on a dashboard even in applications where transparency is not required.

Description:
The present invention is a continuation of U.S. Provisional Patent Application No. 60/064,019, filed Nov. 3, 1997, and priority based on this earlier application is claimed herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed toward a gauge-based instrument for use in a motor vehicle, and more specifically, toward a gauge-based instrument having a transparent display. 
     BACKGROUND OF THE INVENTION 
     Motor vehicles are generally equipped with a variety of instruments for providing information on the status of the vehicle. These instruments often include a speedometer for indicating the speed of the vehicle, a tachometer for showing the speed of the engine, and various other gauges for showing engine temperature and fluid levels, for example. Similar instrumentation is present on aircraft, boats, motorcycles and other vehicles. These instruments often include analogue gauges wherein a needle or pointer is mounted on the rotary output shaft of a gauge motor and assumes different positions based on the control signal received by the gauge. The needle is positioned near a display bearing markings relevant to the condition being measured, and the needle points to various marks as it turns. For example, if the gauge is part of a speedometer, the markings on the display will indicate various rates of speed in miles or kilometers per hour. Sensors measure the rate of speed of the vehicle and send signals proportional to that speed to the gauge causing the needle to point to the appropriate marking on the display. 
     Instrumentation must be visible to a person operating a vehicle, and many of the instruments must be read while the vehicle is in motion. A driver will generally focus on the road in front of him when driving, and thus the most convenient location for placing instrumentation has been directly below the driver&#39;s gaze, on the dashboard of the vehicle. The steering wheel is located between the driver and the instrumentation, and partially obstructs the driver&#39;s view of the dashboard. Furthermore, the most important instruments must be large enough for the driver to read and interpret quickly. A vehicle traveling at 60 miles per hour moves 88 feet per second. Thus a driver takes his eyes off the road for 88 feet every time he looks at an instrument for one second. If the instrumentation is small or cannot be read quickly, an even greater time will elapse. In addition, a person&#39;s eyes take a certain amount of time to adjust when shifting focus from a distant point to a proximate point, and a similar time elapses when attention is returned to the distant point. Changes in lighting between the interior and exterior of the vehicle can also make it difficult to switch focus between the road and the dashboard. A driver moving along a highway, for example, generally focuses on the vehicle in front of him or some other point many feet in front of his car. The instruments on a dashboard, meanwhile, are located perhaps one to two feet from the driver&#39;s eyes. The constant shifting of attention from the road to the instruments and the refocusing of eyes involved in this process can be distracting and had the potential to contribute to the occurrence of accidents. 
     One attempt to overcome this problem was the introduction of so-called “heads-up” displays. These displays use complex optics and controls to project an image of an instrument in front of the driver so that the instrument appears to hover in space somewhere over the hood of the vehicle. Similar technology is used in military aircraft. The price of such displays remains high, and therefore this feature is not generally available in average automobiles. 
     It would therefore be desirable to provide instrumentation that could be read by the driver of a vehicle in a minimal amount of time and with a minimal amount of distraction from driving, that was at the same time easy to use and install and more economical than typical “heads-up” displays. 
     SUMMARY OF THE INVENTION 
     These and other problems are addressed by the present invention which comprises a vehicle instrument with a transparent portion that can be placed in or near a driver&#39;s line of sight without interfering with his view, to allow the instrument to be read with a minimal amount of eye movement and with minimal distraction from the road. Because the instrument can be read without substantially lowering one&#39;s eyes, it may be referred to herein as an “eyes up” instrument or display. For simplicity, the subject invention will be described in terms of an instrument for use in an automobile; however, it could as easily be used in a truck, motorcycle, boat, airplane, or any other vehicle that includes instrumentation located generally in front of the driver. In a preferred embodiment, the subject invention comprises a gauge mounted in a clear display with translucent or partially opaque markings and a pointer connected to the gauge for pointing to the markings on the display in a well-known manner. Significantly, such a display can be mounted on the dashboard of a vehicle in a location that would normally interfere with a driver&#39;s view, but because the display is transparent, the driver can readily look through the instrument or ignore it until such time as it become necessary to take another reading. In this manner, the benefits of a heads-up display are obtained at a fraction of the cost. In a second embodiment, the same general instrument design is used, but the display is enclosed within a housing so that a driver cannot look through the instrument to the road beyond. However, due to the compact size of the display produced in accordance with this invention, and the method of illuminating the display from one edge and/or from beneath, low profile gauges can be provided for mounting on a dashboard so as not to interfere with a driver&#39;s vision. These low profile gauges may be located closer to the driver&#39;s line of sight than instruments mounted in a dashboard in a traditional manner and thus provide many of the advantages of the first embodiment of the invention. In accordance with another aspect of the invention, thin screens are molded into the display or attached to the front or rear of the display in order to control the angle at which light leaves the display to minimize unwanted reflection off the windshield. 
     It is therefore a principal object of the present invention to provide improved instrumentation for vehicles. 
     It is another object of the invention to provide instrumentation that can be viewed by the driver of a vehicle with minimal eye movement. 
     It is a further object of the invention to provide transparent instrumentation that can be placed in or near the line of sight of a driver. 
     It is still another object of the invention to provide instrumentation mounted at or above the dashboard level in a vehicle. 
     It is still a further object of the invention to provide illuminated instrumentation having a transparent display. 
     It is yet another object of the invention to provide an instrumentation cluster of the foregoing character. 
     It is yet a further object of the invention to provide instrumentation having a display that can be readily configured with a variety of different markings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be better understood from a reading and understanding of the following detailed description of several preferred embodiments of the invention together with the accompanying drawings of which: 
     FIG. 1 is a perspective view of an instrument constructed in accordance with the present in invention; 
     FIG. 2 is a front elevational view of the instrument shown in FIG. 1; 
     FIG. 3 is a side elevational view of the instrument shown in FIG. 1 with an optional hood attached thereto; 
     FIG. 4 is a top plan view of a transparent display for use in the instrument of FIG. 2; 
     FIG. 5 is a perspective view of a second embodiment of an instrument constructed in accordance with the present invention; 
     FIG. 6 is an exploded view of a third embodiment of an instrument constructed in accordance with the present invention; 
     FIG. 7 is perspective view showing the instrument of FIG. 6 mounted on the dashboard of a vehicle; 
     FIG. 8 is a top plan view of a circuit board used in practicing the subject invention; 
     FIG. 9 is a circuit diagram of the circuitry for controlling an instrument; 
     FIG. 10 is a side elevational view of an instrument according to the subject invention having parallel screens molded into the instrument display to control the angle of light leaving the display; and, 
     FIG. 11 is a side elevational view of an instrument according to the present invention having venetian-blind-type screens mounted on the front and rear surfaces of the display to control the angle of light leaving the display. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein the showings are for the purpose of illustrating several preferred embodiments of the subject invention only and not for the purpose of limiting same, FIGS. 1 and 2 show an instrument  10  (in this case, a tachometer) comprising a housing  12  having an upper portion  14  for holding a transparent display  16  and a lower portion  18  for holding control circuitry (not shown). Display  16 , which is shown by itself in FIG. 4, comprises a sheet of transparent material such as acrylic or polycarbonate and has an outer edge  20  and a central opening  22 . A miniature crossed-coil gauge  24 , such as the gauge shown and described in U.S. Pat. No. 5,868,832, which is incorporated herein by reference, and is available from Invotronics Manufacturing of Lapeer, Mich., is mounted in opening  22  and connected to control circuitry in housing lower portion  18  using flexible connector  26 . A pointer  28  is mounted to rotate with gauge  24  and travels over display  16  as the gauge turns. The instrument can be used in a variety of settings, however it is particularly well adapted for use on the dashboard of a vehicle because the transparent display does not interfere substantially with a driver&#39;s view, and therefore, the instrument can be mounted closer to a driver&#39;s line of sight than was previously practical. 
     Display  16  is provided with various markings  30 , which markings may include numerals or hash marks, around the periphery thereof which serve as points of reference over which pointer  28  travels while being turned by gauge  24 . The markings are painted or screen-printed on the back of display  16  and are visible to a person viewing the instrument from the front. Under daylight conditions especially, the driver can see through the instrument and needs to shift focus only briefly to take a reading of the instrument. 
     The instrument can also be illuminated so that it can be seen in the dark. The method of illuminating the display can be understood with reference to FIG. 4 which shows display  16  removed from housing  12 . Display  16  includes a projection  32  having an opening  34  which projection extends downwardly into lower portion  18  of housing  12  toward a light source such as light bulb  36  mounted to a circuit board  38 , shown in FIG. 8, in the lower housing. The light bulb is placed in close proximity to opening  34  so that light emitted by the bulb travels through the edges of the opening and into display  16  where it is reflected throughout the interior of the display. Markings  30  printed on display  16  cause light to be emitted from the display in the shape of the markings making these markings visible to a viewer at night. 
     Gauge  24  further includes a second light source, such as LED  40  mounted near the pointer for illuminating the pointer in a well known manner. This LED is mounted under the gauge motor housing  41  and is powered by current that travels through flexible connection  26  from the lower part of housing  18 . Preferably, LED  40  is a different color from light bulb  36  so that the pointer stands out against markings  30 . 
     A second LED  42  is provided on circuit board  38  near the outer edge  20  of display  16  which can be activated to alert a driver to the existence of various conditions. For example, where instrument  10  is a tachometer, LED  42  can be activated when the engine exceeds a certain speed to serve as a red-line indicator. The illumination of a red LED  42  at the edge of display  16  causes the entire display to glow red in an eye-catching manner. LED  42  could also be illuminated at lower engine speeds to serve as an indication that a manual transmission should be shifted into the next higher gear. Other uses of second LED  42 , such as an indication of a low fuel level, can readily be imagined. A circuit diagram showing circuitry for controlling the tachometer of the first preferred embodiment is shown in FIG.  9 . 
     One problem encountered when using an edge-illuminated display on a vehicle dashboard at night is that some light leaks out of the display and reflects off the windshield into the driver&#39;s eyes. Light from the front of the display may travel upward to the windshield before being reflected and light from the rear of the display may reflect off the windshield and into the eyes of the driver in a similar manner. This can be distracting at best and dangerous when the reflection interfere with the driver&#39;s vision. Several approaches can be taken to address this problem of reflected light. First, as shown in FIG. 3, a hood  44  can be detachably connected to housing  12  to prevent light from reaching the windshield from the front of the display. Hood  44  snaps easily into place, and can be removed for daytime driving if desired. Next, the light emitted from the back of the display can be minimized by screen-printing black markings over the white markings on the display. This black printing does not prevent light from exiting from the front of the display, but does substantially prevent it from passing from the rear. Because the white print of the markings lies between the black printing and the viewer, the presence of the paint is not easily noticeable, and does not substantially affect the appearance of the instrument. 
     Other alternatives for controlling the direction of light emitted from the display are shown in FIGS. 10 and 11. FIG. 10 shows an instrument  80  comprising a display  82 , gauge  84  and pointer  86  that further includes a plurality of fine shutter-like elements  88  formed in or attached to the front of display  82  to substantially prevent light from traveling upward from the display and reflecting off the windshield into a driver&#39;s eye  85 . Path  90  in FIG. 10 shows the path that such a light ray would take if shutter elements  88  were not used. FIG. 11 shows a display  96  with thin screen elements  98  on the front thereof. These elements function in the manner of venetian blinds to control the angle at which light leaves the display. The screens can be placed on the front and rear surfaces of the display or on one side only, and a suitable screen product for use in this application is available from 3M as “Light Control Filter Polycarbonate LCF-P.” Alternately, a suitable screen could be made by etching fine lines in a thin sheet of stainless steel or similar material. The use of such a screen would cut down the viewing angle of the device, and would also reduce the amount of light transmitted therethrough. 
     A second embodiment of the subject invention is shown in FIG.  5 . In this embodiment, an instrument  50  includes two separately controlled gauges  52  which extend through a display  54  having two separate sets of markings  56 ,  58 . Significantly, this display is not contained within a housing, but instead is mounted directly to the dashboard  55  of a vehicle. In this embodiment, all parts of the instrument are transparent with the exception of the pointer and the gauge, further reducing interference with a driver&#39;s vision. Alternately, if a housing is still desired, a housing and display can be formed from the same clear material, either as two separate parts or molded as an integral unit. The housing portion can then be painted black if desired. 
     A third embodiment of the subject invention is shown in FIGS. 6 and 7. In this embodiment, the display  60  comprises three separate but connected sub-displays,  62 ,  64 ,  66 , each display being associated with at least one gauge to form an instrument cluster. Sub-display  62  supports a first gauge  68 , sub-display  64  supports a second gauge  70 , and sub-display  66  supports a pair of gauges  72 ,  74 . These sub-displays are edge-lighted from beneath in the same manner as the displays of the previous embodiments. In addition, graphics are applied to the sub-displays using an applique  76  bearing markings for each of the gauges. In this manner, the same display can be used in connection with different arrangements of gauges merely by changing the applique applied. The system is also sufficiently versatile that it can be used in connection with a vehicle information system  77  if desired. 
     FIG. 7 shows the instrument cluster described above mounted on dashboard  55 . FIG. 7 also shows a further method for preventing light from the back of the gauges from escaping from the display and reflecting off the windshield. As can be seen from this figure, the instrument cluster includes a housing  78  extending from the top of the display past the backs of the sub-displays to the dashboard. In this manner, the low-profile design of the instruments of the subject invention can be used in applications where transparency is not a primary consideration. 
     The subject invention has been described in terms of several preferred embodiments, it being understood that obvious modifications and additions to these embodiments will become apparent to persons skilled in the art upon a reading and understanding of the foregoing description. It is applicant&#39;s intention that all such modifications and additions be included within the scope of this application to the extent that they are described by the several claims appended hereto.