Patent Publication Number: US-7902476-B2

Title: Ignition switch assembly for a gas valve

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Spanish Patent Application No. U200801698, filed Aug. 6, 2008. 
     TECHNICAL FIELD 
     The present invention relates to a gas tap with ignition switch adapted to a household cooker. 
     BACKGROUND 
     There are known gas taps, adapted mainly to a household gas cooker, which comprise a safety valve inserted into a body of the tap, a rotatory shaft and an ignition switch that is operated when the user turns the rotatory shaft in a specific direction to generate the ignition of the flame, whereas when the user turns the rotatory shaft in the opposite direction, the ignition is not generated. 
     U.S. Pat. No. 4,019,855 discloses a gas tap that comprises a rotatory shaft, a cam connected to the rotatory shaft, a plate-type ignition switch with a fixed first terminal and a second terminal that moves, driven by the cam, towards the first terminal to generate the ignition. The cam includes a radial first projection disposed centrally and delimited by two parallel ramps, and a second projection that is disposed adjacent to the first projection, with the result that when the gas tap is turned in a direction of ignition the second terminal is moved by means of the ramp of the cam until the second projection causes the second terminal to come into contact with the terminal. If the tap is turned in an opposite direction to the ignition, the second terminal is moved by means of the ramp of the cam, and does not encounter during its stroke any other projection that moves it towards the first terminal, as a result of which contact is not generated. 
     SUMMARY OF THE DISCLOSURE 
     An object of this invention is to provide an ignition switch assembly or a gas tap with an ignition switch adapted to household cookers as defined in the claims. 
     In one embodiment, an ignition switch assembly that is connectable to a rotary shaft of a gas tap of a cooking device is provided. The ignition switch assembly including a coupling element connectable to the rotary shaft, the ignition switch assembly having a fixed contact, a mobile contact, and a cam coupled to the coupling element which is configured to move the mobile contact relative to the fixed contact, the cam having a guide moveable within a groove of the switch assembly that controls the lateral displacement of the cam in relation to the coupling element, the lateral displacement of the cam controlled such that when the coupling element is rotated in a first direction from a first initial position, the mobile contact is moveable into electrically contact with the fixed contact, whereas when the coupling element is rotated in a second direction opposite the first direction the lateral displacement of the cam is controlled to prevent electrical contact between the mobile and fixed contacts. 
     In another embodiment, a gas tap is provided that comprises a rotatory shaft, an ignition switch coupled to the rotatory shaft, the ignition switch including fixed contact and mobile contact means, and a cam coupled to the rotatory shaft that moves the mobile contact means towards the fixed contact means, the electrical contact being generated when the rotatory shaft is turned in a specific direction from an initial closed position of the gas tap, whereas when the rotatory shaft is turned in an opposite direction the electrical contact of the switch is not generated. 
     To achieve this, the cam comprises a guide or guide means that guides the lateral movement of the cam in relation to the rotatory shaft. This way a simple, optimized and of an easy maintenance gas tap is achieved. 
     These and other advantages and characteristics of the invention will be made evident in the light of the drawings and the detailed description thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a gas tap with an ignition switch according to an embodiment of the present invention. 
         FIG. 2  is a perspective view of the ignition switch shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the gas tap shown in  FIG. 1  in an initial closed position of the gas tap. 
         FIG. 4  is a cross-sectional view of the gas tap shown in  FIG. 1  in a first position when a control of the gas tap is turned in a counter-clockwise direction. 
         FIG. 5  is a cross-sectional view of the gas tap shown in  FIG. 1  in a second position when a control of the gas tap is turned in a counter-clockwise direction. 
         FIG. 6  is a cross-sectional view of the gas tap shown in  FIG. 1  in a first position when a control of the gas tap is turned in a clockwise direction. 
         FIG. 7  is a cross-sectional view of the gas tap shown in  FIG. 1  in a second position when a control of the gas tap is turned in a clockwise direction. 
         FIG. 8  is a perspective view of a cam built into the ignition switch shown in  FIG. 1 . 
         FIG. 9  is a perspective view of an element coupling the ignition switch to the gas tap shown in  FIG. 1   
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  partially shows a gas tap  1  according to an embodiment of the present invention, adapted to a household gas cooker not shown in the figures, which comprises burners, the flow of the air/gas mixture supplying the respective burner and the ignition of the air/gas mixture being controlled by means of an ignition switch assembly of the gas tap  1 . 
     The gas tap  1  comprises a body  2 , a gas valve that is housed inside the body  2  and which controls the flow of the air/gas mixture supplied to the respective burner, a rotatory shaft  3  coupled coaxially to the gas valve and a control knob  14 , coupled at one free end of the rotatory shaft  3 , and by means of which a user may control the flow of the air/gas mixture by means of the rotation of the control knob  14 . 
     In addition, the gas tap  1  comprises an ignition switch  4 , a preferred embodiment shown in detail in  FIG. 2 , which preferably comprises a casing  20  that may be fixed to the household cooker, a fixed contact/fixed contact means  5 , a flexible mobile contact/flexible mobile contact means  6  that is moved towards the fixed contact  5  in order to generate an electrical contact between them, a coupling element  15  connected to the rotatory shaft  3 , and a cam  8 , coupled to the coupling element  15 . The fixed contact  5 , the mobile contact  6 , the cam  8  and the coupling element  15  are housed inside the casing  20 . 
     When the user opens the gas tap  1 , rotating the rotatory shaft  3  in a counter-clockwise direction from an initial closed position of the gas tap, as shown in  FIG. 3 , the cam  8  moves the mobile contact  6  towards and into contact with the fixed contact  5 , thereby creating an electrical contact between them. On the contrary, when the user turns the rotatory shaft  3  in a clockwise direction, an electrical contact between mobile contact  6  and fixed contact  5  is not obtainable. Thus, when a user operates the gas tap by turning the rotary shaft in one direction an ignition is achievable, whereas when the rotary shaft is rotated in the opposite direction an ignition is not achievable. As a result, in the event that the flame goes out at any given moment and gas continues to flow through the gas tap, the user may close the gas tap  1  with no danger of the ignition switch  4  generating sparks, with the subsequent risk of explosion, as the ignition switch  4  only operates in the direction of opening of the gas tap  1 . 
     The coupling element  15 , shown in detail in  FIG. 9 , is preferably substantially cylindrical and preferably comprises a base  11  that is supported on the casing  20 , the coupling element  15  being fixed in connection to the rotatory shaft  3 . 
     In addition, the cam  8 , shown in detail in  FIG. 8 , is an eccentric cam that is supported on the base  11  of the coupling element  15 , and includes a closed eccentric or wide hole  16  inside which the coupling element  15  is tightly housed, the cam  8  being capable of moving in relation to the coupling element  15  and, therefore, to the rotatory shaft  3  all the way along the hole  16 . 
     The cam  8  also includes a protrusion or stop  12  that extends radially in relation to the rotatory shaft  3  or peripheral surface of the cam, and which is configured to move the mobile contact  6  towards the fixed contact  5 . In one embodiment, the protrusion/stop  12  is delimited by a first surface  12   a  that extends in a radial direction and a second curved surface  12   b  continuous to the first surface  12   a.    
     The cam  8  comprises a guide/guide means  9  that guides the lateral movement of the cam  8  in relation to the rotatory shaft  3  or coupling element  15 . The guide  9  comprises a projection  10  that extends in the axial direction of the rotatory shaft  3  or coupling element  15 , and the base  11  of the coupling element  15  includes a closed and preferably curved groove  7  in which the projection  10  is housed, the projection  10  being guided as it moves in the groove  7  when the rotatory shaft  3  or coupling element  15  is rotated. 
     In one embodiment, the fixed contact  5  comprises a fixed metallic member or plate  17  that includes a first end  17   a  that is inserted in the casing  20 , an intermediate part  17   b  that is preferably disposed substantially orthogonal to the rotatory shaft  3  and which includes a contact area  18  that may project out in relation to the intermediate part  17   b,  and a second end  17   c  that preferably forms a substantially 45° angle in relation to the intermediate part  17   b  and which acts as a stop against a support  13  that projects out of the casing  20  in the axial direction. In the initial closed position of the gas tap, shown in  FIG. 3 , the intermediate part  17   b  and the contact area  18  are preferably disposed substantially orthogonal to the rotatory shaft  3 . 
     In one embodiment, the mobile contact  6  comprise a flexible metallic member or plate  19  that includes a first end  19   a  that is preferably inserted substantially orthogonal in relation to the rotatory shaft  3  in the casing  20 , an intermediate part  19   b  that forms an angle in relation to the first end  19   a,  and a second end  19   c  that is preferably substantially orthogonal to the intermediate part  19   b.    
       FIG. 3  shows the gas tap  1  closed, with the projection  10  of the cam  8  positioned on a first end  7   a  of the groove  7  in the base  11  of coupling element  15 . Starting from this position, when the user turns the control knob  14  in a counter-clockwise direction, the first surface  12   a  of the protrusion/stop  12  comes into contact with the intermediate part  19   b  of the flexible metallic member  19 , thereby moving it until the second end  19   c  of the flexible metallic member  19  comes into contact with the contact area  18  of the fixed metallic member  17 , thereby enabling the generation of an ignition. At the same time, the projection  10  of the cam  8  is guidely displaced along the groove  7  to a second end  7   b,  and the cam  8  moves in relation to the rotatory shaft  3  or coupling means  15  all the way along the hole  16 , as shown in  FIG. 4 . 
     Starting from the position shown in  FIG. 4 , if the user continues turning the control knob  14  in a counter-clockwise direction, the flexible metallic member  19  separates from the fixed metallic member  17  and the projection  10  of the cam  8  is guidely displaced along the groove  7  positioning itself again on the first end  7   a  of the groove  7 , as shown in  FIG. 5 . 
       FIGS. 6 and 7  show how the gas tap  1  works when the user turns the control knob  14  in a clockwise direction in the direction of closure of the gas tap  1 . Starting from the position shown in  FIG. 5 , when the user turns the control knob  14  in a clockwise direction, the second surface  12   b  of the protrusion/stop  12  of the cam  8  comes into contact with the second end  19   c  of the flexible metallic member  19 , thereby moving it towards the fixed metallic member  17 , without losing contact with the second surface  12   b.  At the same time, the projection  10  of the cam  8  remains fixed in relation to the rotatory shaft  3  or coupling element  15  and as a result, even though the flexible metallic member  19  moves towards the fixed metallic member  17 , the electrical contact between mobile contact  6  and fixed contact  5  is not achieved, as shown in  FIG. 7 . 
     In other embodiments not shown here, the ignition switch  4  may be built into the body  2  of the gas tap  1 . 
     Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.