Abstract:
An illuminated control for a gas range or the like provides arcuate reflective chambers capped by diffusers to create a substantially continuous glowing circular sector indicating the status of a possibly low visibility gas flames. Line power may be used for direct drive of light emitting diodes illuminating the reflective chambers through the use of discrete series-connected voltage dropping resistors distributed to prevent heat concentration.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application 60/975,358 filed Sep. 26, 2007 hereby incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     BACKGROUND OF THE INVENTION 
     The present invention relates to controls for household appliances and in particular for control providing a visual indication of the setting of the control. 
     Dial controls, for example, those used on a cook top, provide an operator (such as a knob) for controlling the heat setting of the burners of the cook top. Most simply, the position of the knob provides a visual indication to the user of the particular setting selected by the user. 
     Sometimes it may be desirable to provide an electronic display indicating the state of a burner apart from the position of the dial control. For example, a light may be used to indicate that the burner is in simmer mode on a gas-stove top when this might not be apparent from the position of the control dial. More generally, the light may provide a high visibility indication that one or more burners have been left on. 
     Conventional incandescent lamps or gas discharge lamps (e.g. neon lamps) are often used in this application. Such lamps are rugged, can be powered directly with line voltage readily available in the appliance, and are resistant to the high temperatures associated with cook top use. Unfortunately the colors and shapes of such lamps are limited and thereby constrain the ability of the designer of an appliance to produce attractive and functional control consoles. 
     SUMMARY OF THE INVENTION 
     The present invention provides a dial control for an appliance or the like that provides illuminated arcuate segments positioned about the dial operator. Each segment is illuminated by a set of LEDs mounted in a reflective chamber having the desired arcuate shape and capped by a light diffuser. The chamber and diffuser permit uniform, colored illumination of a sector shape by LEDs powered directly from rectified line voltage dropped through a series of discrete resistors. 
     Specifically, the present invention provides an illuminated dial control having a dial operator rotating about an axis and switch circuitry communicating with the dial operator to produce switched electrical signals with rotation of the dial operator. Arcuate, internally reflective chambers are positioned concentrically about the axis and around the dial operator, and light diffusers are positioned on front surfaces of the reflective chambers so as to, together with the reflective chambers, define sectors of a ring about the axis. Light emitting diodes are positioned at a back surface of the reflective chambers and receive the switched electrical signals to evenly illuminate different sectors of the ring with rotation of the dial operator. 
     It is thus one object of at least one embodiment of the invention to provide arcuate illuminated indicators of arbitrary color that can demarcate ranges of a rotary operator. 
     The control may further include a gas valve operated by the dial operator to control a gas burner. 
     It is thus an object of at least one embodiment of the invention to provide a dial control suitable for use with gas ranges. 
     The switch circuitry may illuminate at least one sector at all times when the burner is on. 
     It is thus an object of at least one embodiment of the invention to provide a signal to the user that a flame may be present, particularly for low flame settings. 
     The burner control may further include a rotary encoder communicating with the operator. 
     It is thus an object of at least one embodiment of the invention to provide a control that may produce an electric signal indicating the position of the operator. 
     The chambers may have a height measured from a front surface to a back surface substantially no less than the width of the chamber measured along the radius of the arcuate chambers. 
     It is thus an object of at least one embodiment of the invention to provide for even illumination with a small number of LEDs by providing multiple internal reflections as light passes upward in the chambers. 
     The LEDs may be blue LEDs. 
     It is thus an object of at least one embodiment of the invention to provide a color that reminds users of the possibility of blue gas flames. 
     The invention may employ at least one rectifier receiving line voltage and a resistance element communicating with the rectifier to provide a reduced voltage that may be switched by the switch circuitry to provide the switched electrical signals to the light emitting diodes. 
     It is thus an object of at least one embodiment of the invention to provide an LED-based illumination system that may operate directly on line-voltage eliminating the need for complex power conditioning circuitry. 
     The invention may employ two rectifiers electrically in series and separated by a resistance of the resistive element. 
     It is thus an object of at least one embodiment of the invention to reduce the possibility of excess heat being generated in the resistive element upon a single rectifier failure. 
     The invention may provide a printed circuit board supporting the light diffusers and light emitting diodes on a first surface surrounding the axis and having a hole allowing an operator shaft to pass through the printed circuit board to communicate with a wiper interengaging with a contact set on a second surface of the printed circuit board opposite the first surface, the wiper and contact set forming a portion of the switch circuitry. 
     It is thus an object of at least one embodiment of the invention to provide for simplified manufacture of such a control employing a single printed circuit board. 
     The printed circuit board may further include at least one rectifier diode receiving a line voltage and the switch circuitry may further include at least one set of series connected discrete resistors communicating with the rectifier diode and providing a reduced voltage connectable directly to light emitting diodes by the switch circuitry. 
     It is thus an object of at least one embodiment of the invention to provide line voltage operation in a manner consistent with the thermal limits of a printed circuit board. 
     The series connected resistors and at least one diode may be arrayed on a second surface of the printed circuit board opposite the LEDs. 
     It is thus an object of at least one embodiment of the invention to provide a control having heat-dissipating components removed from a front panel. 
     The printed circuit board may further include a secondary contact set interengaging with the wiper to provide a signal independently indicating operator position. 
     It is thus an object of at least one embodiment of the invention to fully integrate various control aspects onto a single printed circuit board. 
     The light emitting diodes may be arranged along an arc of constant radius with their axes rotated corresponding to the position along the arc. 
     It is thus an object of at least one embodiment of the invention to provide for radial symmetry in illumination variations to make any variations less noticeable. 
     The light emitting diodes for each sector may be in series. 
     It is thus an object of at least one embodiment of the invention to reduce the necessary voltage drop across the resistive elements and thus the heat dissipation in any one location. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of the dial control of the present invention having a rotating operator communicating with a wiper assembly engaging contacts on a printed circuit and attached to a gas valve, the dial control further providing arcuate reflective chambers surrounding the dial operator; 
         FIG. 2  is a cross section through a reflective chamber showing its operation shaping light from the LEDs into sector-shaped indicators; 
         FIG. 3  is a cross-sectional view along lines  3 - 3  of  FIG. 1  showing a molded reflective chamber assembly receiving an LED board carrier and sitting on top of a printed circuit board; 
         FIG. 4  is a bottom plan view of the circuit board of  FIG. 3  showing conductive traces that form part of an LED switching circuit and that form an electrical encoder, and showing a distribution of discrete resistors for operation on line voltage; 
         FIGS. 5   a - 5   c  are views of the control of the present invention from a user&#39;s point of view showing sequence of the illuminated sectors during use; 
         FIG. 6  is an electrical schematic of the switching circuitry used in the present invention; and 
         FIG. 7  is a fragmentary plan view of the LED board carrier showing orientation of the LEDs. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , the dial control  10  of the present invention includes an operator  12 , for example, a knob  14  having a shaft  16  extending along an axis  18 . The shaft  16  may pass through a hole  19  in a molded lamp housing  32  and a printed circuit board  26  to attach to a wiper plate  20  holding a first set of electrical wipers  22 . The wiper plate  20  rotates with the shaft  16  and electrical wipers  22  may connect with a set of electrical contacts  24  on the bottom of a printed circuit board  26  in the manner of a rotary switch. The lower end of shaft  16  may also connect with a shaft  27  of a gas valve  30  to provide control of a gas line (not shown) directed to a gas burner of a cook top. 
     Referring now to  FIGS. 2 and 3 , the molded lamp housing  32  may fit against the top of the printed circuit board  26  and provides upwardly extending arcuate chambers  34  and  36  together defining an arc extending slightly over 180° about axis  18  to surround the periphery of the knob  14 . Chamber  36  extends approximately 30° and chamber  34  extends approximately 120° of the arc. 
     The chambers  36  and  34  are open along their bottom to receive an arcuate LED carrier card  40  forming a bottom of the chambers  34  and  36  and holding on its upper surface blue LEDs  42 . The LED carrier card  40  may be electrically connected to other circuitry on the printed circuit board  26  by electrical vias or pins (not shown). 
     The inside of the chambers  34  and  36  is defined by upwardly extending walls  44  providing an internally reflective surface. The height of the walls  44  measured generally along the axis  18  is desirably no less than the width of the separation of the walls  44  perpendicular to that direction along a radius about axis  18  so as to pen-it internal reflections  46  within the chambers  34  and  36  serving to diffuse the light from the LEDs  42 . A plastic suitable for molding the walls  44  of the chambers  34 ,  36  is PPO or polyphenylene oxide. 
     An upper edge of the chambers  34  and  36  is fitted with a diffuser  50  formed in the shape of a sector of a circle and being constructed, for example, from a translucent thermoplastic material to provide for diffusion  53  improving the uniformity of the illumination. 
     Referring now to  FIG. 7  the dies of the LEDs  42  may be mounted on the LED carrier card  40  so that their axes are rotated to provide a constant orientation with respect to the axis  18  so that any unevenness in illumination is really symmetric. The dies of the LEDs  42  are otherwise positioned in separation to promote uniformity of illumination of the diffuser  50  to produce an effect of a solid evenly illuminated sector. 
     Referring now to  FIG. 4 , contacts  24  on the bottom surface of the printed circuit board may provide a set of concentric circular traces, including outermost traces  52   a  and  52   b  at a first radius and corresponding in angular extent generally to the angular extent of chambers  36  and  34  respectively. Adjacent ends of outermost traces  52   a  and  52   b  are electrically separate on the printed circuit board  26 . Continuously within these outermost traces  52   a  and  52   b  is trace  54  which may be selectively joined to one of trace  52   a  and  52   b  by a first wiper finger  22   a.    
     Within traces  52  and  54  are a set of electrically independent traces  58  lying along a common radius, each trace  58  connected to a different point on a resistor ladder  59  to have a different electrical voltage. One of these traces  58  may be joined to an internal circular trace  60  by means of second wiper fingers  22   b  so as to provide for an encoder or potentiometer indicating angular position of the shaft  16  by the voltage communicated to internal circular trace  60 . The internal circular trace  60  may join with a conductive finger  61  at the edge of the printed circuit board  26  to provide an output signal to remote circuitry requiring knowledge of the operator position. Other conductive fingers  61  may receive line voltage and ground to provide power to the dial control  10  as will be described. 
     A plurality of high wattage resistors  62   a  and  62   b  may be distributed over the bottom of the printed circuit board  26  with the resistors  62   a  connected in series and resistors  62   b  connected in series. The bottom of the board may also support rectifiers  66  as will be described. 
     Referring now to  FIG. 5   a - 5   c , chambers  34  and  36  may partially surround the knob  14  as described, and when the knob is positioned in the “off” position corresponding to no gas flow (as shown) the diffuser  50  of chambers  34  and  36  will be dark. 
     Referring to  FIG. 5   b  with counterclockwise rotation of the knob  14 , the gas valve is turned on full to aid in ignition of the burner and both chambers  36  and  34  are fully illuminated commensurate with the high flame level that would be expected. 
     As shown in  FIG. 5   c , continued counterclockwise rotation of the knob  14  may move the gas valve to a simmer range in which only chamber  36  is illuminated, the illumination of chamber  36  continuing at all times when gases flowing. 
     Referring now to  FIG. 6 , the switching sequence described above with respect to  FIGS. 5   a - 5   c  is provided by switching circuitry  70  which connects seven LEDs  42  of chamber  34  in series and three LEDs  42  of chamber  36  in series to maximize the voltage drop that will occur across the LEDs  42  reducing the voltage drop across resistors  62 . The cathode end of the series connected LEDs  42  of chamber  36  is connected to trace  52   a  which, as shown, may be connected to ground through a rectifier  66  when wipers  22  bridge trace  52   a  and  54  with the knob  14  being in the position shown in  FIG. 5   c.    
     The anode end of the series connected to LEDs  42  of chamber  36  is connected to the series connected resistors  62   b , which in turn connect at their other end to a second rectifier  66  receiving line power. Thus half-wave rectified voltage having a root mean square value of approximately 54 volts is applied to the series connected resistors  62   b  and LEDs  42  to provide a desired level of illumination of chamber  36 . 
     The cathode end of series connected LEDs  42  of chamber  34  is connected to trace  52   b  which may also be connected to trace  54  through wiper  22  by rotation of the knob  14  to the position shown in  FIG. 5   b . The anode end of the series connected LEDs  42  of chamber  34  is connected to one end of the series connected resistors  62   b , the other end of which connects to line power through rectifier  66 . When trace  52   b  is grounded through wiper  22  and rectifier  66 , LEDs  42  of chamber  34  may be illuminated. In addition, a rectifier  66  and series resistor joins trace  52   a  to  52   b  to allow current flow from  52   a  to  52   b  so that when the wiper  22  connects trace  52   b  to trace  54  current may flow also through the LEDs  42  of chamber  36 . The resistor  62  in this series connected diode bridge between traces  52   a  and  52   b  may be used to permit slightly brighter illumination of chamber  36  when it is illuminated individually and thus to warn of low flame while allowing perfect matching of the illumination of chambers  36  and  34  when both are illuminated. 
     Each of the resistors  62  may for example be 1 W resistors spread about the printed circuit board  26  to prevent concentration of heat and thus excessive temperature rise, in this way permitting a simple reduction of line voltage. The use of two redundant half-wave rectifiers  66  reduces the risk of overvoltage caused by rectifier failure. 
     It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.