Abstract:
A gas orifice holder for a gas burner includes a gas orifice and a solenoid valve. The solenoid valve is positioned between a gas inlet and the orifice for controlling the gas flow to the orifice.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates in general to a gas orifice holder for a gas burner, in particular to a gas orifice holder having a solenoid valve for controlling the gas flow to the orifice. 
       BACKGROUND 
       [0002]    The operation of gas burners for cookers can be monitored and controlled in a great variety of ways. One widely-used system is the well-known flame re-ignition system. Here, after a main gas valve is opened, a flame at the gas burner is automatically ignited and the presence or the lack of a flame at the gas burner is constantly monitored. In case the flame gets extinguished, the lack of flame is detected and the flame will be re-ignited automatically. 
         [0003]    For example, U.S. Pat. No. 5,961,311 describes a burner re-ignition system having a plurality of flame sensors. Here, once a main valve is opened igniters arranged at the burner are energized to ignite the flame. The presence of the flame is then detected resulting in a change of current flow across the electrodes in the igniters that are dispersed around the flame. If no flame is detected at the electrodes, for example in case of a transient air current, the spark module automatically re-energizes the igniters to re-light the flame. However, the burner re-ignition system is only designed to re-ignite the flame in case of a detected absence of the flame. The burner re-ignition system does not provide for a way to turn-off the gas supply, if re-ignition fails. Thus, hazardous situations might arise in the case of un-ignited gas emerging from the burner. 
         [0004]    Therefore, gas burners with a fail-safe system which is also widely known in the state of the art are used to prevent such dangerous situations. Here, the gas burner ignition system is equipped with a safety-tap. The safety-tap keeps the flow of gas to the burner open as long as the presence of a flame is detected by a sensor at the burner. For example, a control circuit for such gas burners is described in EP 1 070 919 A2. 
         [0005]    However, replacing the main gas valve that is used in conjunction with burner re-ignition systems with a safety tap which is used in fail-safe systems is costly and hence would not be an economically viable option for improving the safety of older cookers having a re-ignition system installed. 
         [0006]    Therefore, there is a need for inexpensively modifying the widely-used burner re-ignition system to automatically turn off the gas supply, if the lack of a flame is detected. 
       SUMMARY 
       [0007]    This need is fulfilled by the gas orifice holder according to independent claim  1 . 
         [0008]    The gas orifice holder according to the present invention which in particular is intended to be used with a gas burner comprises a gas orifice and a solenoid valve. The solenoid valve is positioned between a gas inlet and the orifice for controlling the gas flow to the orifice. 
         [0009]    The gas orifice holder can be part of a gas burner assembly which may further consist of at least a base member and a burner cap. The burner base member may include a number of flame discharge points that are annularly located around a center where the top part of the gas orifice holder extends through. On top of the burner base member the burner cap may be arranged that directs the gas from the gas orifice to the discharge points for creating the gas flames. 
         [0010]    The solenoid valve can be arranged at the gas inlet of the orifice holder to control the gas stream to the orifice. The solenoid valve can be controlled by an electric current through the solenoid, i.e. the coil of the solenoid valve. The solenoid valve shuts-off a gas stream to the gas orifice, if the electric current to the solenoid valve is interrupted. This could be achieved by the plunger of the valve being magnetic, so that it can move when the solenoid is energized. The plunger is preferably coaxial with the solenoid. When the solenoid is not energized, a spring holds the plunger in the closed position. Therefore, if no electric current is applied to the solenoid valve, the gas supply to the orifice can be reliably interrupted. Advantageously, solenoid valves offer fast and safe switching, high reliability, long service life, low control power and a compact design. 
         [0011]    In one embodiment, the solenoid valve is located inside the housing of the gas orifice holder. The solenoid valve may be located in such a manner that the plunger of the solenoid valve seals the gas connection between orifice and gas inlet when the solenoid is not energized and opens the connection between orifice and gas inlet when the solenoid is energized. 
         [0012]    In another embodiment, the solenoid valve is detachably attached to the gas orifice holder. This manner of connecting the valve to the orifice holder allows to quickly upgrading existing orifice holders with a solenoid valve. An adapter piece that contains the solenoid valve may be simply plugged between the gas pipe and the gas inlet of the orifice holder. Alternatively, the gas orifice holder can also have an empty opening for the solenoid valve. This empty opening can be sealed by a dummy plug or some other filing material when a solenoid valve is not installed. Advantageously, existing systems can be upgraded more easily. 
         [0013]    In yet another embodiment, the solenoid valve opens a gas supply from the gas inlet to the orifice for as long as the solenoid valve is energized by a power source. The solenoid valve can be energized by an electric current provided by the power source through the solenoid. This in turn leads to a retracting movement of the plunger of the solenoid valve against the force of a spring which is arranged around the plunger. The spring normally holds the plunger extended in the closed position. Once the power source is shut off the solenoid force created by the energized coil rapidly decreases and the spring moves the plunger to close the gas supply from the gas inlet to the orifice. Therefore, if the power source is switched on, the gas supply to the orifice can be opened for as long as the electric current is kept switched on. 
         [0014]    In one embodiment, the gas orifice holder further comprises a valve switch for energizing and de-energizing the solenoid valve by the power source. The valve switch can be directly or indirectly via the power source electrically connected to the solenoid valve and can be located inside or outside the housing of the gas orifice holder. In a further embodiment de-energizing the solenoid valve is delayed by a time period which is adjustable at a timer module that is connected between the solenoid valve and the valve switch. The timer module can be located in the same housing as the power source or can be located in a separate housing. The timer module can delay the de-energizing of the solenoid valve by first detecting that the valve switch was actuated to de-energize the solenoid-valve, and secondly energizing the solenoid valve to keep the gas supply open for a predetermined time period. The time period can be adjusted by the user at the timer module. 
         [0015]    In another embodiment the valve switch is located at a main valve and energizes the solenoid valve when the main valve at a main switching unit is opened and de-energizes the solenoid valve when the main valve at the main switch is closed. Thereby, the power source can be controlled to provide a current to the solenoid valve when the main valve at the main switching unit is opened and switched off when the main valve at the main switching unit is closed. Advantageously, a high level of security can be provided by disconnecting the gas flow at two places in the gas feed. Alternatively, the power source can also be switched at some point in time after the main valve had been opened and alternatively, or additionally, switched off at some point time after the main valve had been closed. The main switching unit can be the main switching unit of a burner re-ignition system. The solenoid valve and at least one igniter can be connected to the main switching unit as well. The main switching unit could be located at the main gas inlet and can have a mechanically operated main valve by which the gas flow to the burner can be manually controlled. Further, the main switching unit may include a spark module which generates the electric current for the at least one igniter and a flame sensing module to detect the presence of the flame at the burner. This may be done by measuring the current flow across the spark gap of the at least one igniter, where the presence of a flame creates a conductive path which becomes more and more resistive with the absence of the flame. Advantageously, after having detected that the flame is extinguished and after having tried to re-light the gas that is streaming out from the burner with the at least one igniter, the main switching unit can disconnect the power to the solenoid valve, so that it interrupts the gas path in the gas orifice holder to the gas orifice and no more gas can uncontrollably emerge from the gas burner. Advantageously, the timer module can be utilized for adjusting the time interval between detecting that the flame is extinguished and the moment when any further re-igniting attempts are abandoned by disconnecting the power to the solenoid valve, and thereby interrupting the gas flow to the burner. 
         [0016]    In yet another embodiment the valve switch is arranged at the gas burner and energizes the solenoid valve when cookware is located on the gas burner. The valve switch can be used to sense the presence of cookware, such as a pot, kettle, pan, etc. on the burner and can, thus, energize the coil of the solenoid valve which causes the solenoid valve to remain open for as long as cookware is located on the burner. Advantageously, the gas supply is automatically interrupted when the cookware is removed from the burner. In one embodiment the valve switch is a mechanical switch. Such a switch may have, for example, a lever that is moved by the mass of the cookware. In yet another embodiment the valve switch is a light barrier. Advantageously, a light barrier can sense the presence of cookware on the burner without having to be mechanically actuated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the following the gas orifice holder according to the present invention is further described by reference to the schematic illustrations shown in the figures, wherein: 
           [0018]      FIG. 1  is a view of an embodiment of a gas orifice holder according to the invention mounted as part of a gas burner assembly; 
           [0019]      FIG. 2   a  is a cross-sectional view of a gas orifice holder according to the invention mounted as part of a gas burner assembly with the solenoid valve in a closed position; 
           [0020]      FIG. 2   b  is a cross-sectional view of a gas orifice holder according to the invention mounted as part of a gas burner assembly with the solenoid valve in an open position; and 
           [0021]      FIG. 3  is a schematic view of a gas orifice holder according to the invention mounted as part of a gas burner assembly used in a burner re-ignition system. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  shows an embodiment of a gas orifice holder  3  with a solenoid valve  4 , a gas orifice  5  and a gas inlet  6  according to the invention. In the here shown embodiment the gas orifice holder  3  is mounted as part of a gas burner assembly. As shown in  FIG. 1 , the gas burner assembly, for example, comprises three main components, namely the gas orifice holder  3 , a base member  2  and a burner cap  1 . However, this example shall not be limiting and it is evident for a person skilled in the art that the gas orifice holder  3  according to the invention is also suitable to be used with other gas burner assemblies that consist of more or less components. 
         [0023]    In the here shown embodiment the gas orifice holder  3  is mounted under an opening in a surface, such as for example the surface of a cook top. The gas orifice holder  3  also has a gas inlet  6  to which a pipe originating from a manifold or from a main valve can be connected. In the example shown in this figure the solenoid valve  4  is located opposite the gas inlet  6  to control the gas supply to the gas orifice  5 . Also, a valve switch  17  is connected to the solenoid valve  4  to control the power supply to the solenoid valve  4 . 
         [0024]    As it can be seen better in  FIGS. 2   a  and  2   b  the gas orifice holder  3  has a central opening extending towards the cook top in which a corresponding sleeve of the burner base  2  can be fitted from the top side of the cook top. Around the annular top part of the burner base  2  that rests on the cook top, gas discharge ports in the form of projections are arranged, where gas is directed through. These projections form with corresponding recesses in the burner cap  1  gas channels, where gas flows through to establish gas flames. 
         [0025]      FIGS. 2   a  and  2   b  show cross-sectional views through the gas orifice holder  3  with the solenoid valve  4  according to the invention mounted as part of a gas burner assembly.  FIG. 2   a  shows the solenoid valve in the not-energized state, where the plunger  8  is in the closed position. In the example shown in  FIG. 2   a  a spring  7  that is arranged around the plunger  8  pushes the sealing cap  9  of the plunger  8  into the closed position to block the passage between gas inlet  6  and gas orifice  5  of the gas orifice holder  3 . The sealing cap  9  of the plunger can be made of rubber and/or any magnetic material to achieve improved sealing of the passage between gas inlet  6  and gas orifice  5 . 
         [0026]    In  FIG. 2   b  the solenoid valve  4  is shown in an energized state. In the here shown example, the plunger  8  is made of a magnetic material, so that the energized solenoid retracts the plunger  8  by electromagnetic force against the force of the spring  7  to open the passage between gas inlet  6  and gas orifice  5 . Also, the valve switch  17  is shown that is connected to the solenoid valve  4  to control the power supply to the solenoid valve  4 . 
         [0027]      FIG. 3  is a schematic view of the gas orifice holder  3  according to the invention mounted as part of a gas burner assembly and used with a burner re-ignition system. 
         [0028]    The burner re-ignition system which is exemplarily shown in  FIG. 3  has a main switching unit  14  that is traditionally mounted on a wall on top of a gas pipe that is connected to the gas inlet  13  of the main switching unit  14 . In the example shown in  FIG. 3  the main switching unit  14  has also a main valve  16  that can be operated manually by means of a handle or a similar operating device. Once the main valve  16  is manually opened by the operator gas starts to flow through the pipe  11  to the gas burner where it is directed through the gas channels of the burner cap  1 . At the same time a spark module  15  that is in the here shown example also located in the housing of the main switching unit  14  generates an electric current for at least one igniter  10  to ignite the gas at the gas burner. In another example, the spark module  15  can also be arranged outside the main switching unit  14 . 
         [0029]    In the here shown embodiment, once the flame is ignited, the current flow across the spark gap of the at least one igniter  10  is constantly measured to determine whether the flame is still burning, or the flame got extinguished by a draught or a similar event. Here, a conductive path across the spark gap indicates the presence of a flame and a high resistive path indicates the absence of the flame, so that the spark module  15  in the main switching unit  14  can generate an electric current for the at least one igniter  10  to re-ignite the gas at the gas burner. 
         [0030]    However, if it is not possible to re-ignite the gas, for example due to a power cut, the gas keeps streaming from the gas burner assembly which may lead to potential dangerous situations. Therefore, a gas orifice holder  3  according to the invention is mounted in the gas burner assembly that is used with the above described burner re-ignition system. For example, by de-energizing the solenoid of a solenoid valve  4  the solenoid valve  4  will interrupt the gas flow and, thus, even in the above described case of a power cut, dangerous situations can be avoided. For that reason, at least one of the electric control terminals of the solenoid valve  4  is connected to a first valve switch  17   a  that is in the here shown example arranged in the main switching unit  14  and switches a current from a power source  12 . For example, the power source,  12  can be a battery or can be connected to the in-house mains supply to provide the energy necessary to energize the solenoid valve  4 . The power source  12  can energize the solenoid once the main valve  16  is manually opened and the spark module  15  generates an electric current for the at least one igniter  10  to ignite the gas at the gas burner. The solenoid is kept energized during the entire time the gas burner is in operation and is disconnected from the power source  12  when the main valve  16  at the main switching unit  15  is closed. 
         [0031]    In case that a change in the conductivity across the spark gap of the igniter  10  is sensed which is indicative of the absence of a flame, the current from the power source  12  can be immediately interrupted to shut off the electric current to the solenoid valve  4 . As described above with reference to  FIGS. 2   a  and  2   b  the spring that is arranged around the plunger pushes the sealing cap of the plunger into the closed position to block the passage between gas inlet  6  and the gas orifice  5  from the gas orifice holder  3  and thereby effectively prevents unignited gas leaking from the burner. 
         [0032]    Additionally or alternatively to the first valve switch  17   a  that is arranged in the main switching unit  14 , a second valve switch  17   b  can also be utilized to control the solenoid valve  14 . As shown in  FIG. 3 , a second valve switch  17   b  is arranged near the burner to sense the presence of a piece of cookware on the burner. Advantageously, the coil of the solenoid valve  4  can be energized for as long as cookware is located on the gas burner. Once the cookware is removed the second valve switch  17   b  can interrupt the power supply to the solenoid valve  14  which in turn will close the gas supply. The second valve switch  17   b  can be a mechanical switch where a moveable part is dislocated to switch between two states. However, in another example, the second valve switch  17   b  could also be implemented as a light barrier, where an interrupted light beam indicates the presence of cookware on the gas burner. 
         [0033]    In addition, interrupting the electric current to the solenoid valve  4  can also be delayed for a certain time, for example to allow for a number of re-igniting attempts to take place. As shown in  FIG. 3 , a timer module  18  can be located in the power source  12 . Alternatively, the timer module  18  can also be located outside the power source  12  and just be connected to the valve switch  17   a ,  17   b  and the power source  12 . Thereby, the time instance when the electric current to the solenoid valve  4  is interrupted after the valve switches  17   a ,  17   b  are transitioned into their respective off positions or the absence of the flame is sensed can be freely adjusted at the timer module  18 . 
         [0034]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The foregoing invention has been described in accordance with the relevant legal standards; thus, the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and do come within the scope of the invention. Accordingly, the scope of legal protection afforded this invention can only be determined by studying the following claims.