Abstract:
The present invention concerns the structure of and methods of constructing indicating instruments with slim profiles. The indicating instrument comprises a meter movement and a circuit board. The main body of the meter movement is situated in an aperture in the circuit board. With this placement, the front end of the body of the meter movement extends a distance in front of the circuit board and the back end of the meter movement body extends a distance behind the circuit board. Through appropriate selection and arrangement of any components on the circuit board, the circuit board can be constructed such that none of its components extend beyond the distance that the meter movement extends on either side of the circuit board. In this manner the space needed for the meter movement and the circuit board and its components collapses into the same area. A light plate may be added to the circuit board and meter movement. The light plate provides a structural framework for the indicating instrument. The circuit board and meter movement may be mounted to the light plate. In this manner, the internal components of the indicating instrument are all held together and can be calibrated and tested without the addition of any further components.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 60/220,456, entitled “Slim Profile Tachometer,” filed on Jul. 24, 2000, which is hereby incorporated by reference as though fully set forth herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to an indicating instrument assembly of any type and more directly to an assembly structure that decreases the depth required for the instrument assembly.  
           [0004]    2. Description of the Related Art  
           [0005]    Indicating instruments are used for numerous applications across a variety of industries and within innumerable types of machines, systems, and vehicles. Indicating instruments can, for example, measure the speed of a vehicle, such as an automobile or airplane, or measure the rotational speed of an engine shaft or turbine to indicate a need to switch to an appropriate gear ratio so that the motor is not overworked. Indicating instruments can also be fuel, pressure, and temperature gauges, which are found, for example, on vehicles, heavy equipment, assembly line apparatuses, and other industrial equipment. Complex vehicles and other equipment may have a variety of other special purpose indicating instruments to measure any recordable or gaugable activity or condition. For example, airplanes and submarines may have altitude and depth gauges, respectively.  
           [0006]    In many situations it is desirable to construct an indicating instrument as small as possible because of size constraints of the environment in which it is used. For example, in an airplane cockpit a large number of instruments must be placed in an extremely limited area. The size of the indicating instrument is considered not only as a factor of its exposed surface area as viewed by an operator, but also in terms of the amount of space taken, for example, under a mounting surface or behind a panel, by the instrument&#39;s functional and mounting components.  
           [0007]    In other instances, it is desirable that the exposed portion of the indicating instrument be quite large so that the operator can easily perceive the presentation of the gauged information. In these situations, although it may be desirable to provide a large display for the information, it may be equally desirable that the indicating instrument be otherwise small in size due to similar constraints of space for housing or mounting the underlying functional components. An example of these competing needs may be seen in the dashboard instruments of an automobile such as speedometers and tachometers where the dial size is desired to be large for easy reading, but the mounting and housing space within the dashboard is limited.  
           [0008]    Indicating instruments may also be manufactured for sale on the “aftermarket,” wherein additional instruments or devices, which were unavailable as options on the vehicle or other equipment at the time of original purchase, are provided for installation by the operator. In the case of aftermarket indicating instruments such as speedometers or tachometers, these gauges may be provided for mounting on top of the dashboard or at another location in the vehicle for ease of viewing by the operator. For example, many aftermarket tachometers are sold to automobile operators involved in stock car racing. In such racing it is important for the operator to know when to shift, but it is imperative that the operator be able to concentrate on the raceway and the competitor vehicles in order to avoid a collision. Many of these racing operators prefer to mount an aftermarket tachometer on top of the dashboard, or otherwise in the area of the windshield, so they do not have to lower their eyes from the road to read an original equipment tachometer mounted within the dashboard.  
           [0009]    Prior art indicating instruments  200 , such as those shown in FIGS. 1A, 1B,  2 A, and  2 B, depict aftermarket tachometers with their own housings for dashboard mounting applications. Because of standard design configurations, these indicating instruments  200  are relatively deep in body thickness from the face of the instrument to the back of the housing. The thickness of these instruments  200  is dictated in large part by the size of the meter movement  210 , the rear end of which is generally mounted to a printed circuit board (PCB)  230 . The meter movement  210  and PCB  230  assembly is then mounted to and within the housing  240  of the indicating instrument  200 , generally by mounting screws  220   a  and  220   b , to provide a firm support for the meter movement  210 , PCB  230 , and related display components of the indicating instrument.  
           [0010]    The indicating instrument of FIG. 2B is configured with dual PCBs  230  and  230 ′, which further increases the necessary depth of the housing to enclose the additional PCB components. Generally a gap is also needed between the PCB  230 ′ and the rear of the housing  240  in order to allow room for the circuit components mounted on and extending from the PCB  230 ′, again deepening the housing. The design of mounting screws  220   a  and  220   b , which extend beyond the housing in FIG. 2B, further increase the overall depth of the indicating instrument.  
           [0011]    In aftermarket applications, such significant depth of an indicating instrument can make it difficult to fit and install on the dashboard of a vehicle, especially in the case of a narrow dashboard or a steep windshield slope. In applications where the indicating instrument is integrated into the original design of the vehicle, machine, or other system control, the prior art designs of indicating instruments require relatively deep spaces to house their functional components.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention concerns the structure of and methods of constructing indicating instruments with slim profiles. What is meant by “slim profile” is that indicating instruments according to this invention are of shallow depth or are relatively thin between the face of the indicating instrument and the rear most component or the back panel of any housing enclosing the indicating instrument.  
           [0013]    At a base level, an indicating instrument according to this invention may comprise a meter movement and a circuit board. In order to achieve the slim profile, the main body of the meter movement is situated in an aperture in the circuit board. With this placement, the front end of the body of the meter movement extends a distance in front of the circuit board and the back end of the meter movement body extends a distance behind the circuit board. Through appropriate selection and arrangement of any components on the circuit board, the circuit board can be constructed such that none of its components extend beyond the distance that the meter movement extends on either side of the circuit board. In this manner the space needed for the meter movement and the circuit board and its components collapses into the same area.  
           [0014]    In a further embodiment, a light plate may be added to the circuit board and meter movement. The light plate may be seen as a structural framework for the indicating instrument. The light plate is a rigid, refractive material, and in one embodiment is a molded plastic plate with boss mounts and boss extensions molded as protrusions from the back side of the light plate. The circuit board is mounted to the boss mounts extending from the light plate. In this way, the boss mounts provide appropriate spacing between the light plate and the circuit board to allow room for the front end of the main body of the meter movement and any components of the circuit board to reside. The meter movement may also be mounted to the back side of the light plate to provide secure positioning of the meter movement relative to the rest of the components of the indicating instrument. In this manner, the internal components of the indicating instrument are all held together and can be calibrated and tested without the addition of any further components. This provides a benefit in that significant disassembly is avoided in the event that a functional component is bad and needs to be replaced.  
           [0015]    In an alternative embodiment, the indicating instrument may have a second circuit board. This second circuit board may be positioned between the light plate and the first circuit board and similarly mounted to boss mounts extending from the light plate. In one embodiment, the terminals of the meter movement may be directly electrically and mechanically attached to the second circuit board.  
           [0016]    Aside from its structural function in this invention, the purpose of the light plate is to transmit light from a light source to the face of an indicating instrument to illuminate the dial. In an embodiment of the present invention the light plate collects light from a light source, for example, a light bulb mounted on the circuit board, via a projection from the back side of the light plate that contains an aperture. The aperture is large enough to surround the light bulb projecting from the circuit board. In this manner, the light bulb need take up no more space than the gap provided between the light plate and the circuit board by the boss mounts and taken up by the meter movement and other circuit board components. The edges of the aperture in the light plate surrounding the light bulb collect the emitted light and transmit it through the light plate to its edge around the dial on the face of the indicating instrument where the light is emitted from the light plate.  
           [0017]    The indicating instrument may further have a pointer that travels over the dial face. The pointer may be attached to a shaft extending from the meter movement through apertures in the light plate and dial face. The pointer may move in a plane above and parallel to the dial face and underneath a lens. The pointer may be halted in its travel by a pointer stop protruding from the dial face. In one embodiment, the pointer stop is a light emitting diode (LED) that further functions as an indicator of a condition of the indicating instrument. The LED is electrically and mechanically connected to the circuit board and protrudes through apertures in the light plate and dial face. The pointer stop extends above the dial face far enough to intersect the sweep of the pointer and stop the movement of the pointer.  
           [0018]    The various components of the indicating instrument may be contained in a housing for protection or for individually mounting the indicating instrument, for example, external to an instrument panel integrated into the machinery for which the indicating instrument is providing measurements. The housing may cover the back of the indicating instrument components and be fitted with a lens through which the face of the indicating instrument may be viewed. In one embodiment, the lens is attached to the housing by a bezel surrounding circumferential edges of the lens and housing, clamping the two together. A gasket may be placed between the lens and both the housing and the edge of the light plate as a cushion and a seal. Also, in one embodiment, the housing may be formed with a circumferential ledge normal to the side wall. The boss extension of the light plate may extend beyond the edges of the circuit board to make contact with the ledge. Due to the clamping pressure of the bezel transferred through the lens and the gasket to the light plat, the light plate, supported by the boss extension, is held firmly against the housing ledge.  
           [0019]    In another embodiment of the invention, the lens of the indicating instrument is constructed with a concentric projection around the edge of the face. This projection supports the bezel and prevents the edge of the bezel from scratching or otherwise damaging, for example, gouging or cracking, the optical surface of the lens. In yet another embodiment of the indicating instrument, the concentric projection of the lens may further be a channel bounded by two walls. Either the first wall or the second wall may provide the support to the bezel. In addition, the lens may have a concentric projection around the edge of the lens opposite the channel. With this lens construction, it is possible to place a lens on a relatively flat surface without scratching the optical surface of the lens. It is further possible to stack lenses on top of each other, for example, during shipping of lenses as individual components, with the projection of the second side fitting into the channel of the first side. In this way, the optical surfaces of the lenses are separated from each other and the lenses are unable to rub against each other, thereby preventing scratching and other damage.  
           [0020]    An indicating instrument with a housing may be mounted on various surfaces and in various configurations through the use of a mounting strap that surrounds the housing. The mounting strap can be tightened or loosened around the housing through the use of a tightening means. The indicating instrument may be rotated within the mounting strap and secured at any position by tightening the tightening means. In one embodiment, the tightening means may be a bolt with a nut that connects two ends of the mounting strap and draws them toward each other, thereby tightening the mounting strap around the housing. Also attached to the mounting strap may be a mounting foot, which can be attached to various surfaces at various angles. In one embodiment the mounting foot can be secured into a particular position by tightening the tightening means. In the particular embodiment wherein the tightening means is a bolt, the mounting foot may similarly be held to the mounting strap by the bolt and secured when the nut is tightened.  
           [0021]    The indicating instrument may further have an external indicator to indicate a condition of the indicating instrument. This may be the same condition or a different condition than the condition indicated by the pointer stop indicator in the embodiment previously described. The external indicator may have a mounting foot that can be held between the mounting strap and the housing of the indicating instrument, wherein the mounting foot is attached to the indicating instrument. In another embodiment, the external indicator can be mounted at a location separate from the indicating instrument, but maintain communication with the indicating instrument, for example, by wires. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    [0022]FIG. 1A is a plan view of the face of a prior art indicating instrument.  
         [0023]    [0023]FIG. 1B is a cross-sectional view of the prior art indicating instrument of FIG. 1A from the right side.  
         [0024]    [0024]FIG. 2A is a plan view of the face of a second prior art indicating instrument.  
         [0025]    [0025]FIG. 2B is a cross-sectional view of the prior art indicating instrument of FIG. 2B seen from the right side showing the use of two circuit boards.  
         [0026]    [0026]FIG. 3A is a plan view of the face of an embodiment of an indicating instrument according to the present invention.  
         [0027]    [0027]FIG. 3B is a plan view of the right side of the indicating instrument of FIG. 3A.  
         [0028]    [0028]FIG. 4A is a plan view of the face of an embodiment of an indicating instrument according to the present invention.  
         [0029]    [0029]FIG. 4B is a cross-sectional view of the indicating instrument of FIG. 4A taken along line  4 B- 4 B.  
         [0030]    [0030]FIG. 5 is an exploded isometric view of the construction of the face and circuit board assembly of an embodiment of an indicating instrument according to the present invention.  
         [0031]    [0031]FIG. 6 is an exploded isometric view of the components of an embodiment of an indicating instrument according to the present invention.  
         [0032]    [0032]FIG. 7A is a plan view of the front side of a circuit board of an embodiment of an indicating instrument according to the present invention.  
         [0033]    [0033]FIG. 7B is a plan view of the back side of the circuit board of FIG. 7A.  
         [0034]    [0034]FIG. 8 is a cross-sectional view of an embodiment of an indicating instrument utilizing two circuit boards according to the present invention.  
         [0035]    [0035]FIG. 9A is a plan view of the end of a switch shaft component used with an embodiment of an indicating instrument according to the present invention.  
         [0036]    [0036]FIG. 9B is a first plan view of a portion of the surface along the length of a switch shaft component used with an embodiment of an indicating instrument according to the present invention.  
         [0037]    [0037]FIG. 9C is a second plan view of a portion of the surface of a switch shaft component used with an embodiment of an indicating instrument according to the present invention.  
         [0038]    [0038]FIG. 9D is a cross-sectional view of a knob for a switch shaft component used with an embodiment of an indicating instrument according to the present invention.  
         [0039]    [0039]FIG. 9E is a plan view of the bottom of the knob of FIG. 9D.  
         [0040]    [0040]FIG. 9F is a fragmentary view, partially in cross-section, of an embodiment of an indicating instrument according the present invention detailing the placement of a switch.  
         [0041]    [0041]FIG. 10A is a plan view of the front of a pointer used in an embodiment of an indicating instrument according to the present invention.  
         [0042]    [0042]FIG. 10B is a partial cross-sectional view of the right side of the pointer of FIG. 10A.  
         [0043]    [0043]FIG. 11 is a partial view in cross-section of stacked lenses used in an embodiment of an indicating instrument according to the present invention.  
         [0044]    [0044]FIG. 12 is a partial view in cross-section of the assembly of the face of an embodiment of an indicating instrument according to the present invention.  
         [0045]    [0045]FIG. 13A is a plan view of a reflector, prior to assembly, for use in an external indicator of an embodiment of an indicating instrument of the present invention.  
         [0046]    [0046]FIG. 13B is an isometric view of the reflector of FIG. 13A assembled.  
         [0047]    [0047]FIG. 14A is a cross-sectional view of a first configuration of a strap, strap pad, and housing in an embodiment of an indicating instrument according to the present invention.  
         [0048]    [0048]FIG. 14B is a cross-sectional view of a second configuration of a strap, strap pad, and housing in an embodiment of an indicating instrument according to the present invention.  
         [0049]    [0049]FIG. 15 is a plan view of the right side of an embodiment of an indicating instrument according to the present invention, wherein the external indicator is mounted on a surface apart from the body of the indicating instrument.  
         [0050]    [0050]FIG. 16 is a plan view of the back of an embodiment of an indicating instrument according to the present invention with an access plug removed.  
         [0051]    [0051]FIG. 17 is a plan view of the back of the indicating instrument of FIG. 16 with the access plug in place.  
         [0052]    [0052]FIG. 18 is a plan view of the back of an embodiment of an indicating instrument according to the present invention with an alternate wiring and access scheme.  
         [0053]    [0053]FIG. 19 is a plan view of the right side of an embodiment of an indicating instrument according to the present invention with an alternate configuration of the external indicator and the strap pad.  
         [0054]    [0054]FIGS. 20A and 20B are plan views of the right side of an embodiment of an indicating instrument according to the present invention in alternate upside down mounting positions with the mounting foot reversed.  
         [0055]    [0055]FIGS. 20C and 20D are plan views of the right side of an embodiment of an indicating instrument according to the present invention in alternate upside down mounting positions with the mounting foot facing forward.  
         [0056]    [0056]FIGS. 20E, 20F, and  20 G are plan views of the right side of an embodiment of an indicating instrument according to the present invention in alternate mounting positions with the mounting foot facing forward.  
         [0057]    [0057]FIGS. 20H and 20I are plan views of the right side of an embodiment of an indicating instrument according to the present invention in alternate mounting positions with the mounting foot reversed.  
         [0058]    [0058]FIGS. 20J is a plan view of the bottom of an embodiment of an indicating instrument according to the present invention, turned on its right side. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0059]    For the purposes of providing a detailed description of an indicating instrument according to the present invention, an aftermarket automobile tachometer has been chosen as an exemplary embodiment for describing the novel features of the invention. The inventive design as translated in the tachometer is merely one representation of the application of the novel construction techniques for indicating instruments disclosed herein, which are equally applicable to indicating instruments of all types. The tachometer is chosen because of the ease of describing the novel construction techniques as applied to this particular indicating instrument. In addition, an aftermarket embodiment is chosen as a means of detailing a complete set of features (for example, an instrument including a housing), many of which would be inapplicable to an indicating instrument for an integrated application, such as if incorporated into an automobile dashboard display.  
         [0060]    [0060]FIG. 3A shows the face  3  of an indicating instrument  1  (a tachometer) of the novel configuration disclosed herein. Primary elements of the indicating instrument seen in this view include: a housing  2  (FIG. 3B); a bezel  4  that attaches a lens  6  to the housing  2 ; a gasket  8  to cushion the lens  6  and separate it from a light plate  10  (FIG. 4B) and a dial face  14 , which is seen through the lens  6  and is printed with the instrument markings; and a pointer  16  with a pointer cap  20 , the pointer  16  indicating the instrument reading against the markings on the dial face  14 . For an aftermarket automotive application, the face  3  may be of a large diameter for ease of reading by the vehicle operator. While the face  3  may be sizable, the depth of the indicating instrument  1 , as viewed from the side in FIG. 3B, is substantially less than the typical prior art indicating instruments depicted in FIGS. 1B and 2B. The slim profile of the indicating instrument  1  is achieved through the novel component designs and mounting configurations of the present invention.  
         [0061]    [0061]FIG. 4B depicts a cross-sectional view of the indicating instrument  1 , wherein the cut-away of the section presented is indicated by the broken line  4 B- 4 B across the face  3  of the indicating instrument  1  in FIG. 4A and the direction of the view is indicated by the arrows on the ends of line  4 B- 4 B. Other views that may aid the reader with reference to the following discussion may be found in FIGS. 5, 6,  7 A, and  7 B. As is readily seen, while the face  3  of the indicating instrument  1  is quite large for ease of viewing, the housing  2  containing the components of the indicating instrument  1 , in contrast, defines a very slim profile. A significant space savings is achieved through novel designs and arrangements of the components within the housing of the indicating instrument  1 .  
         [0062]    The most significant space saving design feature is an aperture created in the printed circuit board (PCB)  70 , the PCB hole  72 , through which the meter movement  52  is placed, rather than mounting the meter movement  52  behind the surface of the PCB  70  as in prior art designs. The meter movement  52  translates electrical impulses into rotational movement to move the pointer  16  around the dial face  14 . By placing the meter movement  52  so that it extends through the plane of the PCB  70 , a slimmer profile housing  2  can be used. The circuit components  134  (FIGS. 7A and 7B) on each side of the PCB  70  may be chosen to extend no more than the thickness of the meter movement  52  protruding from either side of the PCB  70 , thereby combining two depth intensive components in the same space.  
         [0063]    A second embodiment of an indicating instrument  1  according to the present invention is shown in FIG. 8. In this instance, the diameter of the indicating instrument  1  is required to be smaller, for example because of space constraints on the area allotted to the size of the face  3  in an instrument collection. It is often the case that a second PCB  71  is then needed to accommodate all the circuit components that can no longer fit on a single, smaller-diameter PCB  70 ′. The concept of providing a hole in the PCB  70 ′ to encompass a component (e.g. the meter movement  52 ) can be expanded to the second PCB  71  to achieve a slim profile indicating instrument  1 , even with a decreased diameter. The meter movement  52  may be mounted so that it extends through a hole in the plane of the first PCB  70 ′ and the second PCB  71  may be mounted in front of meter movement  52 , between the meter movement  52  and the light plate  10 .  
         [0064]    The second PCB  71  may have multiple apertures for accommodating various components in the indicating instrument  1 . For example, in the second embodiment depicted in FIG. 8, the second PCB  71  has a light plate hole  73   a  for accepting the extension of the light plate  10  that encircles the lamp  54  to collect the emitted light; a shaft hole  73   b  through which the shaft  106  extending from the meter movement  52  extends to connect with the pointer  16 ; one or more boss mount holes  73   c  allowing the boss mounts  12  to attach to the first PCB  70 , and a pot extension hold  73   d  and a switch extension hole  73   e  through which the pot shaft extension  24  and switch shaft extension  30 , respectively, may extend to protrude above the face  3  of the indicating instrument  1 . The second PCB  71  is held in radial alignment by the protrusion of these various components through these various holes. The second PCB  71  is held in axial alignment by the direct connection of the terminals  53   a ,  53   b  (not shown in FIG. 8), and  53   c  of the meter movement  52  to the PCB  71 . (In the embodiment of FIG. 7A, the terminals  53   a - c  of the meter movement  52  are connected to the PCB  70  by meter movement leads  114   a - c .) Through this novel configuration of the PCBs  70 ′,  71 , the axial length needed for the housing  2  covering the components of the indicating instrument  1  is minimized. In fact, the additional axial length needed may be as little as the thickness of the second PCB  71 .  
         [0065]    As seen in prior art FIGS. 1B and 2B, the common internal mounting structure in the prior art indicating instruments  200  is through the use of long bolts  220   a - b  and spacers  225   a - b  that thread through the PCB  230  and the housing  240 , thereby attaching the components to the housing  240 . The use of these bolts  220   a - b  additionally increases the thickness of the prior art indicating instruments  200  because of the bolt heads and nuts needed to fasten the bolts  220   a - b  in place.  
         [0066]    A second, novel, space-saving technique of the present invention is the use of a light plate  10  as the principle mounting structure in the indicating instrument  1 , as seen in FIG. 4B. Light transmission based on light pipe technology (the use of internally refractive composite materials that can reflect light to travel throughout the materials&#39; structure) is commonly used in indicating instrument construction. Light pipes of various configurations are used in the prior art to transmit light from a light source to illuminate the face of an indicating instrument. In an embodiment of the present invention, light pipe material is fabricated into a generally disk-shaped light plate  10 . The circumferential edges of the light plate  10  are beveled to reflect light, originating from behind the dial face  14 , across the face  3  of the indicating instrument  1 . Lamp  54  interfaces with lamp socket  56 , which is mechanically and electrically connected with PCB  70  through socket aperture  108 , thereby holding the lamp  54  in proper position and providing electrical power to illuminate the lamp  54 . The lamp  54  is positioned within a aperture  110  protruding from the rear of the light plate  10 , whereby the edges of the light plate  10  surrounding the protruding aperture  110  collect the emitted light from lamp  54  and direct it to the face  3  of the indicating instrument  1 .  
         [0067]    In addition to transmitting light to the dial  14 , this invention further utilizes the light plate  10  as a mechanical framework to mount components, align parts, and facilitate the manufacture and functioning of the indicating instrument  1 . To achieve the benefits of a slim profile for the indicating instrument  1 , the light plate  10  may be fabricated to include additional structures such as boss mounts  12  and boss extensions  32 . The boss mounts  12  may be generally cylindrical appendages with either threaded molded holes or self tapping apertures for receiving mounting screws. The boss mounts  12  extend from the rear of the light plate  10  to create a gap between the light plate and PCB  70 . The PCB  70  is attached to the boss mounts  12  with mounting screws  62  through mounting screw apertures  118   a - d  (FIG. 6). The gap between the light plate  10  and PCB  70  is sized to allow sufficient room for circuit components  134  (FIGS. 7A and 7B) on the PCB  70 , the extension of the meter movement  52  through the PCB  70 , and other features to be described herein.  
         [0068]    The boss extensions  32  in the described embodiment may be smaller, shorter extensions from the light plate  10  that are sized to space the light plate  10  away from a ledge  33  in the wall of the housing  2 . The boss extensions  32  provide firm axial alignment of the light plate  10  against the housing  2  and thereby prevent axial movement of the PCB  70 , of the meter movement  52 , and of other components affixed to the light plate  10  within the housing  2 . The measurements of the boss mounts  12 , boss extensions  32 , and housing ledge  33  are all chosen in relation to each other to provide appropriate spacing between components, while still achieving a slim profile for the indicating instrument  1 .  
         [0069]    The light plate  10  further supports and provides a mounting surface for the dial face  14  and the meter movement  52 . The dial face  14  is situated directly upon a flat surface of the light plate  10 . Meter movement mounts  112   a - b  (FIG. 6) extend from the meter movement  52  and are attached to the light plate  10  with dial face screws  76   a - b . The dial face screws  76   a - b  also secure the dial face  14  to the light plate  10  and further act to align the dial face with reference to the other functional and display components on the face  3  of the indicating instrument  1 . In this way, the light plate  10  acts as a framework to hold all functional parts as one assembly. This allows complete calibration and testing of the functional components of an indicating instrument  1  before installing the functional components in the housing  2  or other environment and attaching any associated peripheral parts. The ability to test the functionality of an indicating instrument  1  before it is encompassed in a housing  2  is a great benefit to manufacturing economy, as malfunctioning components can easily be replaced without having to take apart the entire indicating instrument  1 .  
         [0070]    Another function of the light plate  10  is to provide radial and axial alignment of the components with respect to the housing  2 . Radial alignment is provided by the abutment of the exterior circumference of the light plate  10  with the internal wall  74  of the housing  2 . In this exemplary embodiment, PCB  70  also has alignment notches  137   a - b  (FIG. 5) that mate with housing indentions  136   a - b  (FIG. 6) in housing  2  providing additional radial alignment and preventing rotational movement around a center axis A. Since the PCB  70  is attached to the light plate  10 , the conjunction of the alignment notches  137   a - b  and the housing indentions  136   a - b  provide radial stability to all the components of the indicating instrument  1 . Other means of radial alignment of components through an interface with the housing  2  are well known in the art. Axial alignment is provided by the contact between the boss extensions  32  and the housing ledge  33  as described above. Axial alignment may also be augmented by dimple  34  in the rear of the housing  2 , which limits any movement of the meter movement  52  in the housing  2 .  
         [0071]    The light plate  10  also receives holding pressure from the face  3  of the indicating instrument  1 , thereby further preventing axial rotation, by the combination of the lens  6  and a gasket  8 . The gasket  8  may be rubber, or other similar elastic but minimally compressive material, that provides spacing between the dial face  14  on the light plate  10  and the lens  6  to allow room for the pointer  16  to sweep the dial face  14 . The lens  6  is placed opposite the light plate  10 , sandwiching the gasket  8  in between. The lens  6  is held against the gasket  8  by a bezel  4 , which clamps around the circumference of the face  3  of the indicating instrument  1 , clasping the lens  6  along one edge of the bezel  4  and the housing  2  along a second edge of the bezel  4 . The combination of the lens  6 , gasket  8 , light plate  10 , bezel  4 , and housing  2  fixes the entire internal assembly of the indicating instrument  1  in place.  
         [0072]    Additional projections from the light plate  10 , extending in the direction of the face  3  and identified as pot tube  66  and switch tube  68 , also prevent rotation of the various components relative to each other. Pot tube  66  and switch tube  68  may be of unitary construction with the light plate  10  and extend though apertures in the dial face  14  and lens  6 , positively aligning the dial face  14  and the lens  6 . The pot tube  66  and switch tube  68  also provide good bearing surfaces for pot shaft extension  24  and switch extension  30 , which are further described later herein.  
         [0073]    A design feature may be added to the pot tube  66  and switch tube  68  to control unwanted light transmitted through the pot tube  66  and switch tube  68  as they are integral to the light plate  10 . This escaping light is prevented by forming the ends of the pot tube  66  and switch tube  68  projections as conical surfaces  69  (of approximately 45° angles). See FIG. 9F. The conical surfaces refract the light harmlessly inward toward the pot shaft extension  24  and the switch shaft extension  30 . Also, opaque tubing  64   a - b  may be placed over the pot tube  66  and switch tube  68  projections between the dial face  14  and the lens  6  to contain unwanted light.  
         [0074]    It is preferred that lens  6  have smooth polished surfaces with optical clarity. However, this is not a requirement for the functionality of the invention. Prior art indicating instrument  200  lenses  250 , seen in FIGS. 1B and 2B are typically made as flat disks. The lens surfaces are very sensitive to scratching that can result if lenses are allowed to move and touch each other, which is usually the case as prior art lenses are stacked for shipping or for availability during the assembly of the indicating instruments  200 . This can be a very serious problem, which often demands careful individual wrapping of individual lenses for storage and handling before assembly into the indicating instruments  200 . The present invention solves the problem of scratched lenses  6  by forming a concentric channel  5  and a concentric projection  7  around the circumference of each lens  6 , as shown to best advantage in FIG. 11. The concentric projection  7  of a first lens  6  can rest in the concentric channel  5  of a second lens  6 , thereby interlocking in such a way as to provide good separation and to prevent radial movement between each lens  6  when stacked for shipping or use in assembly of indicating instruments  1 . Thus the surfaces of lenses  6  are well protected for bulk handling.  
         [0075]    The lens  6  may also be protected from the sharp edge of the bezel  4  upon assembly to prevent damage to the lens  6 . Prior art indicating instruments  200 , as seen in FIGS. 1B and 2B, typically add a spacer  260  between the bezel  270  and lens  250 . The present invention provides for a proper spacing between the sharp edge of the bezel  4  and the optical surface of the lens  6  as shown in FIG. 12. By spacing the walls forming the concentric channel  5  to support the bezel  4  and designing the interior wall forming the concentric channel  5  with a conical surface  9  to mate with the angle of the bezel  4 , the edge of the bezel  4  may be spaced apart from the surface of the lens  6 . Designing the concentric channel  5  to support the bezel  4  fulfills the need of protecting the optics of the lens  6  without the cost of an extra part (i.e., a spacer) and its handling in production.  
         [0076]    As shown, for example in FIGS. 4A and 4B, wherein the indicating instrument  1  is a tachometer, the lens  6  is constructed with two apertures, a pot shaft aperture  25  and a switch shaft aperture  31 , through which the pot tube  66  and switch tube  68  extending from the light plate  10  pass, respectively. In the embodiment depicted, pot tube  66  and switch tube  68  extend no further than the exterior surface of the lens  6 . A pot shaft extension  24  and a switch shaft extension  30  extend from a pot  42  and a switch  36 , respectively, mounted on the PCB  70 , through the pot tube  66  and switch tube  68 , respectively, and extend above the exterior surface of the lens  6  for actuation by a user. This design eliminates the need for additional, bulky interface structures  275  externally attached to the indicating instrument  200  for user control, as seen in prior art FIGS. 1A and 2A. It may be desirable to provide user accessible controls on the face  3  of other types of indicating instruments  1 , and the techniques and configurations described herein with reference to the example tachometer are not meant to be limited to only that embodiment, but may be used to provide other types of control mechanisms to various embodiments of indicating instruments  1 .  
         [0077]    In the case of an indicating instrument  1  that is a tachometer, as in this example embodiment, the pot  42  and switch  36  enable a user to set an RPM limit, at which point a shift indicator  26  is activated to signal to a driver that the chosen RPM has been reached. When the switch  36  is depressed, current from the pot  42  (e.g., a potentiometer) is allowed to pass to the meter movement  52  and sweep the pointer  16  to a desired RPM limit. By varying the pot, and the current through it, a desired RPM limit can be set. A clutch engagement  43 , as seen in FIGS. 4B and 5, is used between the pot shaft extension  24  and the pot  42  to prevent accidental re-setting of an indicator trigger point. This invention incorporates a hard, smooth clutch ball  46  between a clutch spring  44  and a clutch base  48 , all of which are contained in a cavity in the pot  42 . The clutch base  48  interfaces with the pot shaft extension  24 , but the clutch ball  46  and clutch spring  44  eliminate possible torque transmittal to the pot  42  without depression of the pot shaft extension  24 , and thereby accidental resetting of the indicator  26  limit, at very low cost. When the pot shaft extension  24  is depressed and rotated, the clutch base  48  pushes against the clutch ball  46  and depresses the clutch spring  44 , whereby a dog  50  on the pot shaft extension  24  engages a second dog  49  on the clutch base  48 , thereby transmitting rotation from the pot shaft extension  24  to the pot  42  for setting the RPM limit.  
         [0078]    Attached to the external ends of the pot shaft extension  24  and the switch shaft extension  30  are a pot knob  22  and a switch knob  28 , respectively, for ease of grasp by a user, allowing a user to manipulate and control the pot  42  and switch  36  functions. Prior art typically uses setscrews or holding clips for knob to shaft attachment. The present invention uses a novel knob to shaft attachment system that is shown in detail in FIGS.  9 A-F in exemplary fashion with respect to the switch knob  28  and switch shaft extension  30 , but equally applicable to the pot knob  22  and pot shaft extension  24 , or any other knob to shaft attachments in any application.  
         [0079]    The switch knob  28 , which may be made of rubber or other minimally compressive elastic material, has axial keys  125  molded integrally within a cavity  126  within the shift knob  28 . The switch shaft extension  30  has mating axial keyways  124  molded in place. The switch shaft extension  30  also has a series of concentric barbs  122  that allow easy installation of the switch knob  28  on the switch shaft extension  30 . While the installation of the shift knob  28  on the switch shaft extension  30  is easy, the interference between the walls of the shift knob cavity  126  and the concentric barbs  122  on the switch shaft extension  30  prevent the easy removal of the shift knob  28 . This knob to shaft system results in secure fixing of knobs on shafts at a low manufacturing cost.  
         [0080]    Most indicating instruments with a sweeping pointer require a pointer stop. Prior art pointer stops  280 , as seen in prior art FIG. 2A, typically employ a small metal post riveted to the dial in the vicinity of the zero mark to ensure that pointer  285  is at the zero position when there is no power or no signal condition. An embodiment of the present invention, as shown, for example, in FIGS. 3A, 4A, and  4 B, utilizes a shift indicator  26 , which may be a light emitting diode, and which connects to the PCB  70 , extending through an aperture  27  in the light plate  10 , and protruding through the dial face  14 . The shift indicator  26  may be placed in an appropriate location near the zero mark on the dial face  14  to act as a stop for the pointer  16 . This eliminates the cost of a metal post and its assembly to the dial face  14 , while providing a valuable signaling feature to the user.  
         [0081]    In the depicted embodiments, the pointer  16  may be constructed of molded plastic. The pointer  16  is covered by a pointer cap  20 , also of molded plastic, which has a shaft  21  (FIG. 4B) that extends through the pointer  16 , the dial face  14 , and the light plate  10  to engage the shaft  106  extending from the meter movement  52 . A detail of the pointer assembly is shown in FIGS. 10A and 10B. The pointer cap  20  also conceals the pointer counterweight  18 , which balances the pointer  16  as it moves through its sweep. A small hole  98  may be molded into the front of the pointer cap  20  and extend as a cavity through a length of the pointer shaft  21 . A rear cavity  99  in the opposite end of the pointer shaft  21  also extends through a second length of the pointer shaft  21 . In a departure from the prior art, seen in FIG. 1A, in which the pointer  285  is generally metallic with a through-hole for mounting the pointer  285  on a shaft, the hole  98  in the pointer cap  20  and the rear cavity  99  opposite it in the pointer shaft  21  are both blind holes in the present invention, but they come very close to meeting each other. A very thin membrane  100  separates the pointer cap hole  98  from the rear cavity  99  in the pointer shaft  21 . As is known in the injection molding art, molding two blind holes is easier and less expensive than molding one through-hole.  
         [0082]    Aside from being a subtle styling feature, the pointer cap hole  98  has several useful purposes. First, the pointer cap hole  98  can be used with a special “pointer puller,” similar to a gear-puller, to remove the pointer  16  assembly from shaft  106  extending from the meter movement  52  during production if removal and replacement of pointer  16  is needed. Use of a pointer-puller eliminates the possibility of excessive force being placed on the thrust bearing of the meter movement  52  during removal of the pointer  16  from the shaft  106 . From an injection molding standpoint, the pointer cap hole  98  in the center of the pointer cap  20  reduces unsightly sink marks on the flat pointer cap  20  surface that can result from the injection molding process.  
         [0083]    In addition to the shift indicator  26  protruding from the face  3  of the indicating instrument  1 , it may be desirable to provide a user with an external indicator to provide a greater degree of notification of the conditions measured by the indicating instrument  1 . In the example embodiment of the tachometer described herein, an external indicator  77 , shown for example in FIGS. 4A and 4B, is provided as a more visible indicator of when the RPM threshold is reached. The external indicator  77  may comprise a cylindrical housing  78 , which screws into a threaded rear cap  80 . The rear cap  80  may hold a lamp and socket assembly  82 , which illuminates the external indicator  77 , thereby providing the notification to the user. A lens  86  may be held in the indicator housing  78  by a retention ring  84 , for example, a readily available rubber O-ring. Such a retention ring  84  is easy to install, inexpensive, and the elasticity of the rubber compensates for tolerance variations and provides rattle free operation.  
         [0084]    A thin sheet of reflective material may be used for a reflector  87  to improve the light output of external indicator  77 . In one embodiment, a die-cut piece of white or reflective material is rolled into a conical shape and placed in the housing. See FIGS. 13A and 13B. The depicted embodiment includes special die cut ends for the reflector  87 , wherein the tabbed end  102  slips into the slotted end  104 . The die-cut tabbed and slotted ends provide for easier handling of the reflector  87  during production and allow the reflector  87  to more easily stay in position. Once assembled, the conical form of the reflector  87  is securely held together for easy installation.  
         [0085]    As shown in FIGS. 4A, 4B,  15 , and  19 , the external indicator  77  may be alternately mounted to the housing  2  or positioned apart from the rest of the indicating instrument  1 . In the depicted embodiments, the external indicator  77  is attached to a mounting bracket  88 . In the embodiment shown in FIGS. 4, 4A and  4 B, the mounting bracket  88  is secured between the rear cap  80  and the external indicator housing  78 . The mounting bracket  88  is further secured to the housing  2  of the indicating instrument  1  by mounting strap  90 . The bracket foot  89  of the mounting bracket  88  is restrained under mounting strap  90  that is secured around the circumference of the housing  2 . The bracket foot  89  may be arced to fit against the curvature of the housing  2 . FIG. 19 depicts an embodiment wherein the bracket foot  89  is reversed in its attachment to both the external indicator and the housing  2 . In this embodiment, the external indicator  77  is seated further back with respect to the indicating instrument  1 , which could be useful depending upon the space configurations of the environment in which the indicating instrument  1  is to be mounted.  
         [0086]    The embodiment of FIG. 15 shows the mounting bracket  88  mounted at a location remote from the indicating instrument  1 . This embodiment allows the user to locate the external indicator  77  at a more optimal location for conspicuous notice by a user. The bracket foot  89  can likewise be reversed with respect to the external indicator  77  in this embodiment. The bracket foot  89  of the mounting bracket  88  may have one or more apertures  127  (FIG. 4B) to allow for a simple attachment of the external indicator  77  to a surface, such as by one or more screws  128  (FIG. 15) placed through the apertures  127  and secured into the surface.  
         [0087]    A means of communication is needed in order to mount the external indicator  77  remotely from the indicating instrument  1 . In the embodiment depicted in FIG. 15, this communication is accomplished by lead wires  58   a - b  connected to lead connectors  116   a - b  (FIGS. 7B and 16) on the PCB  70  at a first end and connected to the external indicator  77  at a second end. The lead wires  58   a - b  exit the rear of the housing  2  via an aperture  59 , as shown in FIGS. 16 and 17. The aperture  59  is depicted in FIG. 17 with a plug  60  that itself has an aperture  61  allowing the lead wires  58   a - b  to pass through the plug  60  and connect to the external indicator  77 . The plug may be rubber or similar minimally compressive, elastic material. The plug  60  protects the lead wires  58   a - b  from potential damage by the potentially sharp edges of the housing  2  forming the aperture  59 , and also provides a removable seal to access components inside the housing  2 .  
         [0088]    The aperture  59  in the depicted embodiment is a large opening allowing the user to access several functional components of the indicating instrument  1 . As discussed, the aperture  59  provides access for attachment of the lead wires  58   a - b  to the lead connectors  116   a - b  on the PCB  70 . Aperture  59  further allows access to the lamp socket  56  for removal and replacement of the lamp  54 , for instance if the lamp  54  burns out. Aperture  59  may also provide user access to controls for specific configurations of the indicating instrument  1 . In the example embodiment of the tachometer, the aperture  59  provides access to a dip switch  120  for selection of the number of cylinders of the vehicle to provide appropriate timing information to the tachometer so that it can accurately measure the rotations of the engine.  
         [0089]    In the embodiment depicted in FIGS. 16 and 17, the indicating instrument  1  further has a second aperture  39  in the rear wall of the housing  2 . This aperture  39  provides a passage for signal wires  38   a - d  from their connection points on the PCB  70  to connection points in the environment from which they measure data. Signal wires  38   a - d  may also be power transmission wires for providing power to the indicating instrument if needed. In the case of the tachometer example, two of the signal wires, for example  38   a - b  , are used to supply power to the tachometer. A third signal wire, for example  38   c , is used to measure spark firings through which the RPMs are measured. A fourth wire, for example  38   d , is connected to the automobile&#39;s dash board illumination switch and supplies power for illumination of the indicating instrument. The aperture  39  is lined with a grommet  40  that itself has an aperture  37  through which the signal wires  38   a - d  pass. Similar to the plug  60 , the grommet  40  protects the signal wires  38   a - d  from the potentially sharp edges of the housing  2  around the aperture  39 . A conical surface as depicted (FIG. 4B) on the insertion edge of the depicted grommet  40  enables easy installation of the grommet  40  within the aperture  39  by axial pressure.  
         [0090]    In another embodiment of an indicating instrument  1 , as shown in FIG. 18, connections for lead wires  58   a - b  and user setting interfaces may be accessible at the surface of the housing  2  itself, without providing access to the PCB  70 . The indicating instrument  1  of FIG. 18 is an embodiment wherein a selection switch  121  accessible through an aperture in the housing  2  allows the user to make a cylinder number selection for the vehicle. Similarly, a protruding clip connector  117  provides an easily accessible attachment means for the lead wires  58   a - b  . Access to other user options and functionality connections for an indicating instrument  1  may similarly be provided.  
         [0091]    The mounting strap  90  described previously and shown in FIGS. 4B, 14A,  14 B,  15 ,  18 , and  19  may be a metal band formed to fit around the circumference of the housing  2 . The mounting strap  90  may have outturned ends  91  a- b  that are held together around the housing  2  by a mounting bolt  95  and nut  96 . A constant distance may be maintained between outturned ends  91  a- b  by a bolt sleeve  97  placed around the shaft of the mounting bolt  95  between the outturned ends  91  a- b  . Any other conventional means for tightening or clamping the mounting strap  90  around the housing  2 , for example, a clamp, a buckle, and a compressive spring force inherent in the mounting strap  90 , are contemplated within the scope of the invention. A strap pad  92 , for example of rubber or similar minimally compressive, elastic material, designed to wrap around metal strap  90  may additionally be placed on the mounting strap  90 . The wrap-around design of the strap pad  92  covers the potentially sharp edges of the mounting strap  90  providing better safety and appearance. Small ribs  133  may be formed on the bottom side of the strap pad  92 , as shown in FIGS. 4B and 14B, to provide, for example, extra flexibility for good conformance of the mounting strap  90  to irregularities in the housing  2  surface, a high friction interface between the housing  2  and mounting strap  90  preventing movement therebetween, and accommodation for the extra thickness of the bracket foot  89  of the external indicator  77  mounting bracket  88 . The strap pad  92  may be optionally mounted on mounting strap  90  with the ribs  133  facing radially outwards as shown in, for example, FIGS. 14A and 19 for a different aesthetic appearance.  
         [0092]    Once assembled, the mounting strap  90 , strap pad  92 , and mounting bolt  95  assembly holds itself together around the housing  2 . The assembly also allows for easy adjustment of radial position of the indicating instrument  1  within the mounting strap  90  by simply loosening the mounting bolt  95  and rotating the indicating instrument  1 . The design allows the indicating instrument  1  to be rotated 360° in relation to mounting strap  90  and mounting foot  94 . This provides maximum flexibility and adaptability for installation of indicating instrument  1 .  
         [0093]    The mounting foot  94  may be similarly attached to the mounting strap  90  by the mounting bolt  95 , and thereby pivot around the axis of the mounting bolt  90 . The design of the mounting foot  94  offers great flexibility of positioning and use of the indicating instrument  1  as shown in FIGS.  20 A-J. The mounting foot  94  may be attached to point forward, as in FIGS.  20 C-G and  20 J, or to the rear, as in FIGS.  20 A-B and  20 H-I, allowing the indicating instrument  1  varying degrees of tilt in the mounted placement. Any particular angular position of the indicating instrument  1  with respect to the mounting foot  94  may be held by simply tightening the mounting bolt  95  and nut  96 . The mounting foot may similarly be rotated 360° with respect to the indicating instrument housing  2  by rotating the mounting strap  90  around the housing  2 . Such versatility in the mounting foot  94  allows the indicating instrument  1  to be mounted in diverse positions and locations and be placed into many different environments. For example, with a tachometer embodiment, by rotating the mounting foot  94  around the mounting bolt  95  and rotating the mounting foot  94  around the housing  2 , the tachometer could variously be mounted in an automobile, for example, to the dashboard, the underside of the roof, a window column, a reinforcement post, or a roll bar.  
         [0094]    Attachment of the mounting foot  94  to various surfaces may be achieved in a number of ways. The mounting foot may be provided with apertures  132   a - b  in its base for the reception of in attachment means, for example screws. Mounting foot  94  may farther be configured with an arch  93  in its base so that the mounting foot  94  may better conform to a curved surface such as a window column, reinforcement post, or roll bar. The mounting foot  94  may further be provided slots  130  for the acceptance of a band for retaining the indicating instrument  1  against a surface. The band may be for example, a fabric or plastic strap, or even an hose clamp, that may slip thorough the slots  130  and around a mounting surface such as a reinforcement post or roll bar. The mounting foot  94  may further be attached to a surface with an adhesive placed between the mounting foot  94  and the surface.  
         [0095]    Although various embodiments of this invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular embodiments and not limiting. Changes in detail or structure may be made without departing from the basic elements of the invention as defined in the following claims.