Patent Publication Number: US-11035701-B2

Title: Front pick-up illuminated pointer

Description:
BACKGROUND 
     Cars and trucks have instrument panels, also known as instrument clusters that include gauges and dials, which provide vehicle operation information to a driver. Such gauges and dials can be digital, most drivers prefer “analog” gauges and dials having pointers or indicators that rotate about an axis and “point to” a number, symbol, icon or an area on a dial. 
     Prior art pointers are preferably provided with some type of illumination in order to make them visible in darkness, i.e., at at night. Some such pointers are made from a light-transmissive plastic such as a polycarbonate or acrylic and have a light introduced at one end of the pointer, which is carried throughout the length of it emitted somewhere along the pointer&#39;s length whereat the light is emitted and illumination provided to a localized area of the gauge or dial. Stated another way, prior art light-transmissive pointers provide an illumination that is unevenly distributed and which can adversely affect the ability to see a number, symbol, icon or other indication on a gauge or dial. A pointer that provides a more uniform illumination along its length would be an improvement over the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of an instrument panel or instrument cluster for a motor vehicle; 
         FIG. 2  is a front view of one gauge or dial of the instrument cluster shown in  FIG. 1 ; 
         FIG. 3  is a side view of the gauge or dial depicted in  FIG. 2 , showing a stepper motor that rotates the pointer on a shaft extending through the instrument cluster circuit board and a light source which provides light into the interior of the pointer; 
         FIG. 4  is an isolated side view of a pointer showing light from a source incident on an inclined surface at one end of a first embodiment of a light transmitting pointer body; 
         FIG. 5  is a side view of a second embodiment of a light-transmitting pointer showing an inclined surface at a different angle of inclination as compared to what is shown in  FIG. 4 ; 
         FIG. 6  is a side view of another embodiment of a pointer for an instrument cluster, the pointer shown in  FIG. 6  having two differently-inclined surfaces at one end of the pointer; 
         FIG. 7  depicts a preferred embodiment of a pointer for an instrument cluster having several inclined surfaces, each of them inclined at a different angle; 
         FIG. 8  is a perspective view of an embodiment of a illuminated pointer system for a vehicle instrument cluster showing an arrangement of a light-transmitting prism; and 
         FIG. 9  is an isometric view of an elongated, light-transmitting prism of  FIG. 8  and which is a configured to transmit light provided at a bottom surface and transmitted along the length of the prism body. 
     
    
    
     DETAILED DESCRIPTION 
     The reflection and refraction of light by a surface that separates two different light-transmissive media, such as air and a light-transmissive transparent plastic, is well known. If two light-transmissive media have different indexes of refraction, light that travels through their interface is bent or refracted. Light which strikes an interface between two different media, and which is redirected away from it at the same angle at which it struck the interface, is reflected. 
     As is well known, a reflected ray lies in the plane of its incidence and has an angle of reflection equal to the angle of incidence. A refracted ray of light also lies in the plane of incidence and has an angle of refraction, Θ, (theta) which is related to the angle of incidence theta Θ1 by the well-known equation n1 sin Θ=n2 sin Θ, where n1 and n2 are dimensionless constants referred to as the indices of refraction of each medium through which the light travels. 
     It is well known that light striking an interface between two different light-transmissive media will be totally or completely reflected if the light&#39;s angle of incidence is greater than or equal to a “critical angle” Θ c . The critical angle is defined as the arcsine of the quotient of the index of refraction of the first media, n 1  and the index of refraction of the second media, n 2 . Stated another way, the critical angle for a total internal reflection to occur is: 
     
       
         
           
             
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                   - 
                   1 
                 
               
               ⁢ 
               
                 
                   n 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
                 
                   n 
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                   2 
                 
               
             
           
         
       
     
     and is thus dependent on the light transmission of the two different media. 
     Because the sine of any angle cannot be greater than one, the index of refraction of the first media cannot be greater than the index of refraction of the second media. Stated another way, total internal reflection cannot occur when the incident light is in a medium having a lower index of refraction than a medium that it strikes. 
     As used herein, the word “prism” refers to solid bodies bounded by two identical or nearly-identical, parallel or substantially parallel, similarly-oriented polygonal bases and at least three lateral faces that are parallelograms. It also includes polyhedrons with two polygonal faces lying in parallel or substantially planes and with the other faces parallelograms. 
     A right prism is a prism, of which the lateral edges are perpendicular or substantially parallel to the bases. 
     A pyramid is a body bounded by a polygonal base and at least three triangular faces converging to a point called the apex or vertex. 
     The adjective form of “elongate” means stretched out or, long and slender. 
     The term “normal” refers to a geometric line, perpendicular to a surface at either a point of reflection or refraction. 
     The term “angle of incidence” refers to a geometric angle measured relative to the normal of a surface on which a light ray is incident. 
     The term “angle of reflection” is also measured relative to the normal of a surface through which a light ray passes. An “angle of refraction” is also measured relative to the normal. 
     The term “trapezoid” refers to a quadrilateral having four sides, only two of which are parallel. 
     It is well known that light waves spread out as they move away from their source. The path of a light wave can nevertheless be approximated as being in a straight line and is thus represented herein by lines or rays in order to depict light transmission, its reflection, refraction and subsequent re-radiation. 
     Referring now to the figures,  FIG. 1  depicts a vehicle instrument panel or cluster  100  having various types of gauges  102 ,  104 ,  106 ,  108  and  110 . A centrally-located gauge  102 , which is a speedometer, comprises a dial  112  on which numbers  113  corresponding to the vehicle&#39;s speed are applied. An “illuminated” pointer  116 , which is connected to a spindle  118 , rotates clockwise and counter-clockwise with the spindle in order to “point to” or indicate the speed at which the vehicle is traveling. The spindle  118  extends upwardly through the dial  112 . 
       FIG. 2  is a front or plan view of the speedometer gauge  102  depicted in  FIG. 1 . The dial  112  and the speed-indicating characters  114  are identified or “pointed to” by the pointer  116  as it rotates on the axis of the spindle  118 . 
     Several broken-line concentric circles identified by reference numeral  119 , and which are centered about a region on the pointer  116 , which is identified by reference numeral  202 , represent a relatively localized maxima of light emitted from the pointer  116 . The light-maxima region  202 , i.e., a region or an area of a relatively brighter light, is formed from light emitted from the bottom of the pointer, which is made from light-transmitting material such as polycarbonate, glass, crystal or the like. 
       FIG. 3  is a side view of the gauge or dial shown in  FIG. 2 . A stepper motor  302  is connected to a motor controller  304  via a conventional cable or bus  306 . Signals from the motor controller  304  to the stepper motor  302  cause the spindle  118  to which the pointer  116  is attached, to rotate either clockwise or counter clockwise as indicated by the arrow  206  in  FIG. 2 . One or more light-emitting diodes (LEDs) or incandescent bulbs, referred to interchangeably as a light source  310 , are connected to a light controller  312  via one or more wires  314 , in order to provide a controlled source of light to the pointer. 
     As mentioned above, light waves from a light source can be approximated by a line or ray and light waves are thus represented in the figures of this disclosure by rays and lines. In  FIG. 2 , light emitted from the LEDs is identified by a line identified by reference numeral  316 . That light  316  enters the light-transmitting pointer  116  at a region  318  on the bottom surface  320  of the pointer  116 . Since the light entry region  318  is substantially flat and substantially orthogonal to the incident light  316 , all of the light  316 , or at least substantially all of it enters a prism  317  formed at the end of the pointer  116  proximate to the spindle  118 . 
     As  FIG. 3 , shows, the light  316  strikes an inclined surface  322  at the rear or second end  324  of the pointer/prism  116  and totally, or near-totally reflected toward the opposite end  326  of the pointer or prism  116 . The material from which the pointer  116  made and the light&#39;s  316  of incidence on the inclined surface  322  are thus chosen or selected in advance, i.e., predetermined, in order to totally reflect the light  316  off the inclined surface  322 . 
     The inclined surface  322  has a normal  328 , which as noted above is a geometric line, perpendicular to the inclined surface  322 . The light  316  from the light source  310  that enters the prism strikes the inclined surface  322  at an angle, a (alpha) relative to the normal  328 . The angle of incidence, a and the index of refraction, n, of the material from which the pointer  116  is made, are selected in order to obtain a total internal reflection or near-total internal reflection of the light  316  and a redirection of the reflected light  319  down or along an axis  330  that extends from or between the two opposing ends of the pointer/prism  116 . The reflected light,  319  travels partway down the length of the pointer/prism  116  and exits the pointer/prism at a location identified by reference numeral  322 , which as shown, is approximately half-way between the two opposing ends of the pointer/prism  116 . Light that exits the pointer/prism  116  at that location  322  strikes an area  323  of the surface of the dial  112  and illuminates the area and re-reflected upwardly as another light ray  321 . The inclined surface  322  at the rear end  324  of the pointer/prism  116  thus reflects light toward a relatively localized area or region of the bottom surface  320  of the pointer  116  from which the light from the light source  310  is transmitted or “piped” and provides a relatively localized illumination of the dial. 
       FIG. 4  is an isolated, cross-sectional view of another embodiment of an illuminated pointer  400  for a vehicle instrument cluster, such as the instrument cluster  100  shown in  FIG. 1 . The pointer  400  in  FIG. 4  is also made from a transparent material such as glass, crystal or polycarbonate. 
     The pointer  400  is considered to be an elongate, light-transmitting prism  400 , having a first end  404  and an opposing second end  406 . Between the first and second ends  404 ,  406  respectively are a top face or surface  408  an opposing bottom surface or face  410  and first and second opposing sides  412 , only one side being shown in  FIG. 4  because the other side is substantially coincident to the side depicted in  FIG. 4 . 
     The pointer, which is also a prism  400 , has a geometric axis  416  that extends through the pointer  400 , only a portion of which is shown in  FIG. 4 , however, in the interest of drawing legibility. The axis  416  extends completely through the pointer  400 , including through the first and second ends,  404 ,  406 . The axis  416  thus has no real dimension or size. 
     At the second end  406  of the pointer/prism and near a pointer-rotating spindle  409 , a light wave  422  enters a substantially flat, substantially horizontal portion or area  420  of the bottom surface  410  and travels upwardly through the material from which the pointer  400  is made. The area  420  where the light enters the pointer/prism  400  is considered herein to be a surface through which the pointer illumination light enters the pointer. The area is thus referred to as an “illumination light entry surface.” The light wave entering the illumination light entry surface is represented by a ray or line identified by reference numerals  422 . 
     The light wave  422  is incident on a first inclined surface  424  at an angle of incidence, Θ 1 , measured relative to the normal  428  of the first inclined surface  424 . The inclined surface  424  is itself of course inclined relative to horizontal and which is a different angle, Θ 2  Horizontal is considered to be a geometric plane that is parallel to or coincident with a plane in which the axis  416  of the prism  402  lies. 
     As noted above, total internal reflection of the first light wave  422  will result when the angle of incidence Θ 1  is substantially equal to the arcsine of the quotient of the index of refraction of the material from which the prism  400  is made and air through which the light wave  422  passes when it leaves a light source. Such a reflection, represented by the ray identified by reference numeral  423  can be seen extending from the first inclined surface  424  to a distant location or point identified in the figure by reference numeral  428 . The reflected wave  423  strikes the bottom surface  410  and is refracted (bent) out of the pointer/prism  400 . A localized light “maxima” is thus produced at and around the location where the refracted light wave  423  leaves the bottom surface of the pointer/prism. 
     Refracted light  425  strikes the top surface  430  of a dial and is re-reflected as a separate light wave. A light wave  422  from a light source under the pointer  400  near the spindle can thus be propagated through the light transmitting prism material to strike an inclined face  424 , reflected by the inclined face at an angle, which determines a location to which the reflected light  423 A is transmitted down the length of the pointer/prism and thus provides a relatively localized illumination. 
       FIG. 5  shows an alternate embodiment of an illuminated pointer  500 . The pointer  500  depicted in  FIG. 5  differs from the pointer  400  depicted in  FIG. 4  by the inclination angle of the inclined surface  502  at the second end  506  of the elongate, light-transmitting prism  508 . The normal  510  of the inclined surface  502  is at a much steeper angle relative to horizontal, the inclination angle Θ2, being the angle of incidence of a light wave  512  incident on the inclined surface  502 . 
     As with the pointer  400  depicted in  FIG. 4 , the index of refraction of the material from which the prism  508  is made, and the angle of incidence Θ2, are selected, i.e., predetermined, in order to achieve a total or at least near-total reflection of the light  512  from a light source  514 . 
     As can be seen in  FIG. 5 , the relative steep angle of inclination of the inclined surface  502  causes a reflected wave  513  to travel farther down the length L of the prism toward the second end  516 . The reflected wave  513  is shown as intersecting the bottom surface  518  at a point  520  that is separated or distant from the second end by a shorter distance D 2 . The distance that the light travels through the prism  508  is thus determined by the inclination angle of the inclined surface  502  at the second end  506  of the prism  508 . 
       FIG. 6  shows a third embodiment of an illuminated pointer  600  for a vehicle instrument cluster. In this figure, light waves  602 , (represented by rays or lines) pass through an illumination light-entry surface  604 , which is on the bottom surface  606  of the light-transmitting prism  600 . 
     The light wave  602 A strikes a “first” inclined surface  610  at the rear or second end  612 . A second light wave  602 B strikes a “second” inclined surface  614 . Both inclined surfaces  610  and  614  have corresponding normal, identified by reference numerals  616  and  618  respectively. 
     The first light wave  602 A strikes the first inclined surface  610  at a first angle of incidence denominated as β 1 . The second light wave  602 B strikes the second inclined surface  614  at a second angle of incidence denominated as β 2 . The first light wave  602 A is reflected. The reflected version of the first light wave is identified by reference numeral  603 A. The reflected version of the second light wave  602 B is also reflected and identified as  603 B. Both reflected light waves  603 A and  603 B enter the elongated portion of the prism, past the axle  620  on which the prism rotates. 
     As can be seen in  FIG. 6 , the first reflected wave  603 A travels farther down the length, L, of the prism toward the second end  630 , than does the second reflected light wave  603 B due to the fact that the inclined surfaces are at different inclination angles. The first reflected light wave  603 A strikes or impinges upon the bottom surface  606  at a “first” distance, D 3 , away from the second end  630 . The second reflected wave  603 B strikes the bottom surface closer to the axle  620  and farther from the second end  630  at a distance D 4 . 
     Waves  603 A,  603 B that are incident on the bottom surface  606 , are refracted out of the material from which the pointer is made. Stated another way, the two inclined surfaces  610  and  614  reflect light incident upon them at different angles and thus produce light maxima  605 A and  605 B at two different locations along the length L of the pointer  600 . 
       FIG. 7  shows yet another embodiment of an illuminated pointer for a vehicle instrument cluster. In  FIG. 7 , only the second end  701  of the pointer is depicted in order to better illustrate multiple planar inclined surfaces  702 A- 702 D, each of which reflects or at least partially reflects light waves  704 A- 704 D incident on them after entering a illumination light entry surface  718  on the bottom surface  708  of the light-transmitting prism  700 . 
     Each of the incident light waves  704 A- 704 D is reflected and propagates down the length of the pointer as reflected waves  705 A- 705 D. Each reflected wave,  705 A- 705 D travels along a different inclined path through the prism and impinges on the bottom surface  708  of the pointer at different locations  710 ,  712 ,  714  and  716 . The differently-inclined surfaces  704 A- 704 D thus produce light maxima at differently locations where each reflected wave  705 A- 705 D strikes or impinges upon the bottom surface  708 . 
     Those of ordinary skill in the art should recognize that providing multiple planar inclined surfaces at one end of a light-transmissive prism and to which light is provided from a light source, will produce a corresponding number of refracted light maxima along the bottom surface of the prism and thus better-distribute light from the light source along the entire length of a pointer fabricated from a light-transmissive material. Those of ordinary skill in the art might also recognize that obtaining a total internal reflection from each of the inclined surfaces might not be possible without providing a reflective surface. Accordingly, alternate embodiments include a thin, light-reflective material layer  720  applied to the backside or outside surfaces of the inclined surfaces  704 A- 704 D in order to insure that each of them can provide a total or near-total internal reflection of incident light. 
       FIG. 8  is a cut-away perspective view of an illuminated pointer, light source and drive mechanism for use with a vehicle instrument cluster, such as the one depicted in  FIG. 1 . The assembly  800  is mounted to a conventional circuit board  802  attached to which are light-emitting diodes  804 . 
     A housing  806  has a relatively cylindrical-shaped exterior surface  810  and a substantially conical-shaped interior surface  812 . The interior of the housing  806  is hollow and preferably coated with a white or nearly-white color reflective paint or coating to enhance transmission of light from the LEDs  804  into the bottom  814  of the second end  816  of a light-transmitting prism  818  having a first end  820  that is proximate to or “points” to legends or demarcations on a dial of a gauge forming part of an instrument cluster. 
     A stepper motor  824 , also attached to the circuit board  802  has an output shaft  826  that extends upwardly through the conical-shaped interior of the housing  806  and is attached to the second end of the light-transmitting prism  818 . Electrical signals provided to the stepper motor  824  cause the prism  818  to rotate clockwise or counter clockwise thereby indicating different quantities or providing other information by virtue of the angular displacement of the stepper motor  824  around its vertically-oriented axis, not shown. 
     As described above, light from the LEDs  804  enters an illumination light surface area  815  on the bottom of the pointer and above the LEDs  804 . The light from the LEDs strikes multiple inclined surfaces  826  and  828  at the second end of the light-transmitting prism  818 . Light incident on those inclined surfaces  826  and  828  propagates downwardly along the axis  830  of the prism  818  and impinges upon the bottom surface  814  at different locations  832  and  834  producing at least two different-location light maxima  822 ,  824  on the bottom surface  814 . 
       FIG. 9  is a perspective view of the light-transmitting prism  818  shown in  FIG. 8 , arranged to better illustrate the second end  816  of the light-transmitting pointer/prism  818 . The second end  816 , is “sized, shaped and arranged” to provide multiple inclined surfaces, the normals of which are inclined at different angles but nevertheless directed downwardly or along the axis  830  of the prism. Two “separate prisms  904  and  906  formed at the second end  816  of the prism  818  each have light-reflecting panels or surfaces  910  and  912 , which are inclined at different angles. The reflecting panels  910  and  912  can also have a pitch or rotation by which light reflected off of them will impinge on the sides  916  and  918  of the prism  818  as the reflected light travels down and along the axis  830 . 
     The angles of incidence of the reflected light waves traveling down the length of the light-transmitting prism body  818  and the indices of refraction are selected such that there is a total reflection along the length of the body as the body tapers or narrows from its second end  816  to its first end  820 . 
     Referring again to  FIG. 7 , those of ordinary skill in the art should recognize that as the number of inclined planar surfaces increases toward infinity, the shape of the second surface eventually becomes elliptical or semi-circular. In such an embodiment, i.e. having an elliptical surface joined seamlessly to the bottom, top and side surfaces of the light-transmitting prism, an even more-uniformly distributed light can be generated from the bottom surface of the portion of the prism that extends beyond the axle on which the light-transmitting prism is mounted. 
     Those of ordinary skill in the art should recognize that the elongate, light-transmitting prisms may be formed from a transparent solid material(s) having an index of refraction less than air when combined to form the prism. Those of ordinary skill in the art should recognize that the elongate, light-transmitting prisms having such shape as described and shown herein will result in a cross-sectional shape, which is substantially trapezoidal-shaped. 
     Those of ordinary skill in the art should recognize that the elongate, light-transmitting prisms used to provide an illuminated pointer are solid, i.e., not hollow, bodies of materials that will transmit light. In order to insure total internal reflection of incident waves on an inclined surface at shallow angles, alternate embodiments employ a thin reflective film that is deposited onto the outside surfaces of the solid, light-transmitting prism. In  FIG. 7 , such a surface, which can be made of silver or other similar metal, is depicted as being applied to one of the outside surface of one of the inclined panels  702 D and identified by reference numeral  720 . 
     The foregoing description is for purposes of illustration only. The true scope of the invention is set forth in the following claims.