Abstract:
A valve stem position sensor for a gas range provides a slotted housing, wiper assembly, and printed circuit board that may be aligned to allow the sensor to be installed on the valve stem from the side of the valve stem rather than over the end of the valve stem permitting the valves to be partially installed in the gas range with the valve stems extending through the console for mechanical support during the remainder of the assembly process.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This Non-Provisional Application is national phase of PCT/US2010/052312 filed Oct. 12, 2010, and claims benefit to U.S. Provisional Application Ser. No. 61/254,084 filed Oct. 22, 2009 hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to cooking ranges having gas burners and specifically to a rotation sensor for sensing a position of a burner control valve. 
     BACKGROUND OF THE INVENTION 
     Gas ranges which cook using the combustion of natural gas or the like are prized by chefs who value their fast response and high heat output. Such gas ranges may use gas valves which meter gas to individual burners according to rotation of the valve stem communicating with an internal valve mechanism. Control of the gas valves by a consumer is provided by rotation of a control knob fitting over an end of the valve stem as it passes through a console on the front of the range. By controlling the volume flow of gas to the burner, the output of the burner may be adjusted. Many modern gas ranges include electronic igniters that may be triggered by initial movement of the valve detected by a sensor switch to automatically ignite the gas at the burner. 
     Low heat ranges for simmering or the like are not always easily obtained with a gas range because low rates of gas flow are difficult to control to a steady level and/or low gas flow rates do not reliably support a flame. For this reason, high-end gas ranges may employ a strategy for low heat ranges in which heat output is controlled not by adjusting the continuous rate of gas flow but by pulsing the gas flow on and off according to a schedule to control an average treated gas flow producing the desired heat. Electrical igniters ignite the gas at the beginning of each pulse cycle. 
     This technique of heat control requires a rotational encoder attached to the gas valve to relay its rotational position by an electrical signal to a controller that may effect the desired pulse schedule turning the gas valve on and off and that may appropriately control the igniter. This rotary encoder, for example, may be a potentiometer having a rotating element through which the valve stem is threaded so that the rotating element turns with the valve stem and provides a variable voltage (or resistance) indicating the rotational position of the valve stem. 
     Assembly or replacement of the rotary encoder on the gas valve can be difficult, requiring installation or removal of the rotary encoder before the valve stem is inserted through a hole in the console and thus before the valve stem is securely positioned to the range. Early installation of the rotary encoder risks damage to the encoder during mechanical assembly of the valves to the manifold and gas piping of the range and prevents pre-assembly of the valves to a frame before they are identified to a particular range feature set. 
     SUMMARY OF THE INVENTION 
     The present invention provides a rotary encoder designed to be installed on the stem of a gas valve in a direction perpendicular to the axis of the stem. In this way, the rotary encoder may be slipped onto the valve stem “sideways” eliminating the need to have access to the end of the valve stem. In this way the present invention improves manufacturability of the range by permitting partial assembly of the console before the installation of the rotary encoders. The invention further permits improved field repair by eliminating the need for complete disassembly of the console for the replacing of one encoder. 
     Specifically, the present invention provides a rotary encoder for use with a gas valve on a range, the gas valve having a valve stem. The rotary encoder includes a housing having a slot extending from one edge of the housing to a central portion so that the housing may be installed around the valve stem along an axis perpendicular to an axis of rotation of the valve stem, the housing sized to fit between a valve body and a control knob attachable on an end of the valve stem. A printed circuit board fits within the housing and has a corresponding slot aligned with the slot of the housing and has electrical conductors on at least a first surface. A wiper assembly fits within the housing against the first surface of the printed circuit board to contact the electrical conductors on the first surface with rotation of the wiper assembly. The wiper assembly further has a slot corresponding to the slot of the housing and the slot of the printed circuit board and aligned therewith at a predetermined rotational orientation. 
     It is thus a feature of at least one embodiment of the invention to provide a rotary encoder that may be installed or removed while the valves are partially or fully assembled to the range. 
     The valve stem may provide a key surface received by a corresponding key surface at the end of the slot of the wiper assembly to cause the valve stem and wiper assembly to rotate together when the wiper assembly is installed on the valve stem. In one example, the key surface may be a flat on the valve stem and corresponding flat on the end of the slot of the wiper assembly aligned generally with one wall of the slot of the wiper assembly. 
     It is thus a feature of at least one embodiment of the invention to provide an interlocking between the valve stem and the wiper assembly that may accommodate installation of the valve assembly through a slot. 
     The slot in the wiper assembly may be substantially a width of the valve stem. 
     It is thus a feature of at least one embodiment of the invention to maximize the available angular surface of the printed circuit board for rotary encoding. 
     An end of the slot in the wiper assembly may provide a partial collar extending along the axis of the valve stem to partially surround the valve stem. 
     It is thus a feature of at least one embodiment of the invention to offset the decrease contact surface of the slot of the wiper assembly with the valve stem through an augmenting collar. 
     The wiper assembly may have a substantially circular outer periphery received by corresponding arcuate guides in the housing so that the wiper assembly is constrained to rotate with respect to the housing about a center point aligned with the end of the slot of the housing and the wiper assembly. 
     It is thus a feature of at least one embodiment of the invention to preserve rotational alignment of the components of the rotary encoder before they are installed on the valve stem. 
     The wiper assembly and housing may include stop surfaces limiting rotation of the wiper assembly with respect to the housing. 
     It is thus a feature of at least one embodiment of the invention to prevent damage to the wiper arms before or during installation. 
     The wipers may connect to a resistive ladder on the printed circuit board to provide a variable resistance with rotation of the valve stem. 
     It is thus a feature of at least one embodiment of the invention to provide a simple electrical interface standard relying on voltages or resistances. 
     The housing may include alignment pins engaging with corresponding bores of the valve stem when the housing is moved along the axis of rotation of the valve stem. At least one alignment pin may include a resilient barb for releasably retaining the alignment pin within a corresponding bore of the valve stem. 
     It is thus a feature of at least one embodiment of the invention to permit the housing to be simply attached to the valve by axial motion without the need for separate connectors or the access space for installing those connectors. 
     The housing may include at least one alignment surface engaging outer surfaces of the valve stem when the housing is moved along the axis of rotation of the valve stem. 
     It is thus a feature of at least one embodiment of the invention to provide an increased resistance to rotational torque between the valve and the housing beyond that which may be provided by pre-existing valve bores. 
     The housing may further include a releasable electrical connector half receiving a corresponding connector along an engagement axis generally parallel to the rotational axis of the valve stem. The electrical connector may receive the corresponding electrical connector from a side of the housing removed from a side of the housing closest to the control knob when installed on the valve stem. 
     It is thus a feature of at least one embodiment of the invention to permit ready electrical connection of the rotary encoder after installation on the valve. 
     Generally, the present invention enables a method of manufacturing a gas range comprising the steps of installing a valve manifold providing a gas pipe and a least one gas valve to a portion of the range behind a console so that valve stems of the gas valve extend through apertures within the console and then sliding a valve stem rotational sensor as described above onto the valve stems behind the console along an axis substantially perpendicular to an axis of rotation of the valve stem. 
     It is thus a feature of at least one embodiment of the invention to substantially simplify manufacture and repair of a gas range. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a gas range having multiple controls showing an exploded view of one such control and a sideways mounting of a rotary encoder on a valve stem of the valve associated with the control; 
         FIGS. 2   a - 2   c  are a sequence of perspective views of the rotary encoder being installed on the stem of the valve; 
         FIG. 3  is a front elevational view in partial exploded form showing a wiper assembly and printed circuit board of the rotary encoder of  FIG. 1  within a housing, both having corresponding slots for sideways assembly; 
         FIG. 4  is a cross-sectional view through the control of  FIG. 1  as assembled showing the two steps of sliding the rotary encoder into place and then locking it to the valve without full disassembly of the control console. 
     
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof are meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a gas range  10  may include one or more burners  12  exposed at an upper cooking surface  14  of the gas range  10 . Gas to the burners  12  may be controlled by means of associated controls  16  accessible to a user at a front console  17 . Each of the controls  16  may provide a knob  18  of conventional design having indicia indicating a setting of the control  16 , for example, in a range from “off” to “high” and including a “low heat” range. 
     A knob  18  may be attached to a valve stem  20  passing through an aperture  19  in the front console  17 , the valve stem  20  connected with a gas valve  22  behind the front console  17 . The front console  17  may be, for example, a plate of enameled steel or the like. 
     Generally, rotation of the knob  18  and the valve stem  20  controls a flow of gas through the gas valve  22  to a burner  12  over a range that corresponds to the range of “off” to “high”. In the “low heat” range. The gas valve  22  may provide both a range of constant flow rates dictated by the angle of the valve stem  20  and electrically control the gas flame on and off as will be described. 
     In the present invention, a rotary encoder potentiometer  24  is attached to the valve stem  20  to measure rotation of the valve stem  20 . The rotary encoder potentiometer  24  may be installed on the valve stem by movement of the rotary encoder potentiometer  24  along an installation axis  26  generally perpendicular to an axis  28  about which the valve stem  20  rotates. For this purpose, the rotary encoder potentiometer  24  may include a slot  29  generally aligned with the installation axis  26  allowing a passage for the valve stem  20  so that the valve stem  20  may move from an edge of the rotary encoder potentiometer  24  to an assembled position at centerpoint  21  roughly centered within the rotary encoder potentiometer  24 . 
     An electrical connector  30  on the rear of the rotary encoder potentiometer  24  may mate with a corresponding connector  32  communicating with a control board  34  providing for electronic circuitry that may read signals from the rotary encoder potentiometer  24  to deduce the rotational orientation of the valve stem  20 . The control board  34  may execute a control program based on this rotational orientation to control an igniter  36  associated with a burner  12  controlled by the control  16  and a solenoid valve  38  also associated with the burner  12  controlled by the control  16 . The solenoid valve  38  may, for example, be incorporated into the gas valve  22  according to techniques well known in the art. The solenoid valve  38  is actuated when the control  16  is in the “low heat” range to provide for pulsed operation having periods when the burner flame is on and periods when the burner flame is off The pulsing may change in its duty cycle to control average heat without decreasing gas flow beneath a tractable amount. 
     Referring now to  FIG. 2   a , the rotary encoder potentiometer  24  may provide a generally rectangular housing  40  having a narrow thickness measured along an axis  28  of the valve stem  20  so as to fit easily between a flange  70  of the valve  22  and the console  17  through which the valve stem  20  passes by means of an aperture  19 . The housing  40  may be placed above the valve stem  20  behind the console  17  with the valve stem  20  aligned with the opening of the slot  29  in a lower edge of the housing  40 . 
     As shown in  FIG. 2   b , the housing  40  may then be moved downward as indicated by arrows  31  along the installation axis  26  in a direction generally perpendicular to axis  28  until the valve stem  20  is aligned with the centerpoint  21  at the center of the housing  40 . 
     Referring to  FIGS. 2   a  and  2   b , extending from a face of the housing  40  toward the valve  22  above and below the centerpoint  21  are attachment pins  65  and alignment pin  67 . The attachment pins  65  are displaced vertically above and below the centerpoint  21  to be generally aligned with bores  68  in the flange  70  of the gas valve  22  when the valve stem  20  is at the centerpoint  21 . 
     Referring now to  FIG. 2   c , with the valve stem  20  positioned at the centerpoint  21 , axial movement as indicated by arrow  71  engages the attachment pins  65  with the bores  68  to lock the valve  22  and the housing  40  together against torsion about axis  28 . The attachment pins  65  may include end barbs  69  which may protrude through the bores  68  to expand on the opposite side of the flange  70  to lock the housing  40  against the flange  70  with respect to axial forces along axis  28 . Alignment pin  67  slides against one side of the flange  70  to provide further resistance against torsion. 
     The slot  29  may have a dogleg path, that is a path having a diagonal portion between two generally parallel vertical portions allowing the slot  29  to avoid the lower attachment pin  65 . 
     Referring now to  FIG. 3 , the housing  40  may enclose a printed circuit board  42  mounted to be stationary with respect to the housing  40 . The printed circuit board  42  may support on its rear surface the electrical connector  30  which may communicate via traces on the printed circuit board  42  with one or more ring-shaped electrical traces  44  on a front surface of the printed circuit board  42  and, in a preferred embodiment, discrete resistors  46 . The ring-shaped traces  44  are concentric about the centerpoint  21  through which the valve stem  20  will pass when the rotary encoder potentiometer  24  is assembled to the valve  22  as described. A central aperture  48  at the centerpoint  21  joins to a generally radially extending slot  52  identical to slot  29  which then passes downward to a lower edge of the printed circuit board  42  cutting through the ring-shaped traces  44 . When the printed circuit board  42  is assembled to the housing  40 , the slots  29  and  52  are perfectly aligned. 
     A circular rotary wiper assembly  56  may fit in the housing against the front surface of the printed circuit board  42 . The ring-shaped traces  44  of the printed circuit board  42  may be selectively interconnected by wiper springs  54  flexibly extending rearward from the rotary wiper assembly  56  with rotation of the rotary wiper assembly  56 . The wiper assembly  56  has a central aperture  58  which is keyed by a flat  60  to conform with a similar keying flat  62  on the valve stem  20  shown displaced from the centerpoint  21  for clarity. A slot  64  passes from an edge of the wiper assembly  56  to join to aperture  58 , the slot  64  conforming in shape to the slot  52  of the printed circuit board  42  and a slot  29  of the housing  40  when the rotary wiper assembly  56  is properly aligned for assembly. In this position, the valve stem  20  may pass through the slots  29 ,  52  and  64  to be received by the aperture  58  in the rotary wiper assembly  56 . As so received, rotation of the valve stem  20  will provide identical rotation of the wiper assembly  56  as a result of an interfacing between the key surfaces  62  and  60 . A technique for manufacture of an adjustable resistor array suitable for this purpose is described in U.S. application Ser. No. 12/133,731 entitled: “Dial Control With LED Light Ring” filed Jun. 5, 2008 and now published as U.S. Application 2009/0080176, assigned to the assignee of the present invention and hereby incorporated by reference. 
     The housing  40  may include guides  66  that constrain the wiper assembly  56  to rotate in alignment with the printed circuit board  42  so that apertures  48  and  58  are concentric at the centerpoint  21 . A stop  59  may be formed in one or both of the housing  40  and wiper assembly  56  to limit rotational travel of the two. It will be understood that with rotation of the wiper assembly  56 , various interconnections may be made between the traces of  44  in the manner of a rotary switch. These interconnections may connect various resistors  46  attached to the traces  44  to provide an effective variable resistor having a resistance value, or a voltage divider value, producing a voltage value functionally related to the rotational position of the valve stem  20 . This signal may be provided through the connector  30  to the control board  34 . 
     Referring now to  FIG. 4 , as described above, after the rotary encoder potentiometer  24  is installed on the valve stem  20  along an axis  26  with the slots  64  and  52  aligned as shown in  FIG. 2   a , rotary encoder potentiometer  24  may be moved rearward so that rearwardly extending retention barbs  69  are received in corresponding open ended bores  68  of a flange  70  of the gas valve  22 . The barbs  69  are passed through the bores  68  to snap in place and thereby retain the housing  40  against rotation about axis  28  or displacement along axis  28 . Removal of the rotary encoder potentiometer  24  for servicing or the like may be obtained by simply prying the housing  40  of the rotary encoder potentiometer  24  away from the flange  70  and removing the potentiometer along axis  26 . 
     Variations and modifications of the foregoing are within the scope of the present invention. It is 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. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
     Various features of the invention are set forth in the following claims.