Abstract:
A system or apparatus that in one implementation includes an electromagnetic valve having an actuator rod with a first coil and a second coil positioned at different longitudinal locations on the actuator rod and being situated electrically parallel to one another in an electrical circuit. The electromagnetic valve is constructed to induce a first voltage in the second coil when the electromagnetic valve is in the open position and to induce in the second coil a second voltage lower than the first voltage when the electromagnetic valve is in the closed position. A switch changeable between a first position and a second position is located in the electrical circuit. When the switch is in the first position the electrical circuit is configured to allow current from a power source to be delivered to the second coil. When the switch is in the second position the electrical circuit is configured to not allow current from a power source to be delivered to the second coil. A control device situated in series with the second coil in the electrical circuit is adapted to detect the open or closed position of the first electromagnetic valve based on the induced voltage of the second coil. The control device is adapted to act upon the switch to change it between the first and second positions. In one implementation, upon detecting that the electromagnetic valve is in the closed position, the control device is configured to act upon the switch to cause it to assume the first position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 12/508,448 filed Jul. 23, 2009, which is a continuation-in-part of U.S. application Ser. No. 12/343,283 filed on Dec. 23, 2008, which claims priority to Spanish Patent Application No. P200802834, filed Oct. 2, 2008. 
    
    
     TECHNICAL FIELD 
     The present invention relates to control systems for the ignition of a gas burner, and more specifically to a burner used in domestic gas appliances such as cookers, driers and furnaces. 
     BACKGROUND 
     Different control systems for the ignition of a burner in domestic gas appliances are already known. In some of the systems an incandescent element or an igniter (a glowbar) is used for such a purpose. The incandescent element is disposed adjacent to the burner and is heated up to a temperature suitable for gas combustion, the incandescent element causing, when it reaches the temperature, the gas that reaches the burner to light. 
     U.S. Pat. No. 3,826,605 discloses a control system of this type, the control system comprising a thermoelectric valve to enable the passage of gas towards the burner. The thermoelectric valve comprises a bimetallic element and a resistive element that keeps the passage of gas closed at ambient temperature, this being opened when the bimetallic element is heated by the power supply current of the igniter. The choice of material of the elements and their arrangement is essential in ensuring the system functions correctly and that the valve does not open too early, for example, or open too late after the incandescent element has reached the combustion temperature. In addition, as it is dependent upon the temperature of the elements in order to close, the thermoelectric valve may remain open for a period of time after the command to switch off the burner has been sent, with gas reaching the burner during the period of time. In a second embodiment disclosed in the document, the control system also comprises an electromagnetic valve, it being necessary for both the thermoelectric and the electromagnetic valve to be open to enable the passage of gas. The thermoelectric valve continues to control the opening of the passage of gas, whereas the electromagnetic valve controls the closure of the passage. 
     SUMMARY OF THE DISCLOSURE 
     It is an object of the invention to provide a control system for the ignition of a gas burner, as described herein and as set forth in the claims. 
     The control system for the ignition of a gas burner in one implementation comprises at least one incandescent element that is designed to be heated until it reaches the gas combustion temperature and which is disposed adjacent to a burner in order to light the gas that reaches the burner, a power source for powering the incandescent element and thereby cause it to heat up, an electromagnetic valve to allow the passage of gas towards the burner, and an activation coil associated to the electromagnetic valve in order to open the valve. 
     The control system also comprises an additional coil associated to the electromagnetic valve and disposed electrically in series with the incandescent element, the additional coil and the incandescent element forming a branch electrically parallel to the activation coil, the valve being closed when power no longer reaches the additional coil. 
     When the incandescent element reaches the gas combustion temperature and both coils are powered; the electromagnetic valve opens to allow the passage of gas to the burner. The burner may be switched off by preventing power from being supplied to the coils, and, as the electromagnetic valve is not dependent upon the temperature as it would be if it were a thermoelectric valve, the valve thus is closed preventing the passage of gas towards the burner. 
     As a result, the use of a thermoelectric valve is not necessary in order to control the point at which the passage of gas towards the burner is opened, the control being performed through the electromagnetic valve that also controls the point at which the passage is prevented. Thus, the control system requires fewer elements and may also be more compact. 
     In accordance with one embodiment, a control system for the ignition of a gas burner is provided that includes an electromagnetic valve having an open position and a closed position for controlling the flow of a gas to a burner, the electromagnetic valve having a first coil and a second coil, the electromagnetic valve configured to assume the open position to permit the flow of gas through the electromagnetic valve to the burner when a current that passes through the first coil reaches a first predetermined amount and when a current that passes through the second coil reaches a second predetermined amount; at least one ignition element for igniting the gas burner when the ignition element reaches a combustion temperature of the gas, the ignition element being disposed electrically in series with the first coil, the first coil and ignition element forming a first branch; an auxiliary electromagnetic valve having an open position and a closed position for controlling the flow of a gas to the burner, the auxiliary electromagnetic valve having a coil and being configured to assume the open position to permit the flow of gas through the auxiliary electromagnetic valve to the burner when a current that passes through the coil reaches a third predetermined amount, the flow of gas towards the burner being allowed when both the electromagnetic valve and the auxiliary electromagnetic valve are open; and a switch adapted to cause the second coil of the electromagnetic valve to be electrically in parallel to the first branch in a first position, or to cause the coil of the auxiliary electromagnetic valve to be electrically in parallel to the first branch, in a second position. 
     In accordance with another embodiment, a control system for the ignition of at least two gas burners is provided that includes a first electromagnetic valve having an open position and a closed position for controlling the flow of a gas to a first burner, the first electromagnetic valve having a first coil and a second coil, the first electromagnetic valve configured to assume the open position to permit the flow of gas through the first electromagnetic valve to the first burner when a current that passes through the first coil reaches a first predetermined amount and when a current that passes through the second coil reaches a second predetermined amount; at least one first ignition element for igniting the first gas burner when the first ignition element reaches a combustion temperature of the gas to be delivered to the first burner, the first ignition element being disposed electrically in series with the first coil, the first coil and first ignition element forming a first branch; a second electromagnetic valve having an open position and a closed position for controlling the flow of a gas to a second burner, the second electromagnetic valve having a third coil and a fourth coil, the second electromagnetic valve configured to assume the open position to permit the flow of gas through the second electromagnetic valve to the second burner when a current that passes through the third coil reaches a third predetermined amount and when a current that passes through the fourth coil reaches a fourth predetermined amount; at least one second ignition element for igniting the second gas burner when the second ignition element reaches a combustion temperature of the gas to be delivered to the second gas burner, the second ignition element being disposed electrically in series with the third coil, the third coil and second ignition element forming a second branch; an auxiliary electromagnetic valve having an open position and a closed position for controlling the flow of a gas to the first and second burners, the auxiliary electromagnetic valve having a coil and being configured to assume the open position to permit the flow of gas through the auxiliary electromagnetic valve to the first and second burners when a current that passes through the coil reaches a fifth predetermined amount, the flow of gas towards the first burner being allowed when both the first electromagnetic valve and the auxiliary electromagnetic valve are open, the flow of gas towards the second burner being allowed when both the second electromagnetic valve and the auxiliary electromagnetic valve are open; a first switch adapted to cause the second coil of the first electromagnetic valve to be electrically in parallel to the first branch in a first position, or to cause the coil of the auxiliary electromagnetic valve to be electrically in parallel to the first branch, in a second position; and a second switch adapted to cause the fourth coil of the second electromagnetic valve to be electrically in parallel to the second branch in a first position, or to cause the coil of the auxiliary electromagnetic valve to be electrically in parallel to the second branch, in a second position. 
     In accordance with another embodiment, a method for controlling the gas flow to a burner through an electromagnetic valve and an auxiliary electromagnetic valve is provided, each of electromagnetic valve and auxiliary electromagnetic valve having a normally closed position and an open position, the electromagnetic valve having a first coil and a second coil that control the position of the electromagnetic valve, the auxiliary electromagnetic valve having a coil that controls the position of the auxiliary electromagnetic valve, the first coil of the electromagnetic valve being disposed electrically in series with an ignition element that is positioned to ignite the burner when the temperature of the ignition element reaches a combustion temperature of the gas to be delivered to the burner, the first coil and the ignition element forming a branch, the method including delivering a first current through the branch to provide power to the first coil of the electromagnetic valve and to cause the ignition element to heat, and a second current to the second coil of the electromagnetic valve to cause the electromagnetic valve to open; and subsequently delivering a third current to the coil of the auxiliary electromagnetic valve to cause the auxiliary electromagnetic valve to open. 
     In accordance with another embodiment a system or apparatus is provided that comprises an electromagnetic valve having an actuator rod with a first coil and a second coil positioned at different longitudinal locations on the actuator rod and being situated electrically parallel to one another in an electrical circuit, the electromagnetic valve constructed to induce a first voltage in the second coil when the electromagnetic valve is in the open position and to induce in the second coil a second voltage lower than the first voltage when the electromagnetic valve is in the closed position; and a control device situated in series with the second coil in the electrical circuit and adapted to detect the open or closed position of the first electromagnetic valve based on the induced voltage of the second coil. 
     In accordance with another embodiment a system or apparatus is provided that comprises an electromagnetic valve having an actuator rod with a first coil and a second coil positioned at different longitudinal locations on the actuator rod and being situated electrically parallel to one another in an electrical circuit, the electromagnetic valve constructed to induce a first voltage in the second coil when the electromagnetic valve is in the open position and to induce in the second coil a second voltage lower than the first voltage when the electromagnetic valve is in the closed position; a switch located in the electrical circuit, the switch changeable between a first position and a second position, when the switch is in the first position, the electrical circuit is configured to allow current from a power source to be delivered to the second coil and when the switch is in the second position, the electrical circuit is configured to not allow current from a power source to be delivered to the second coil; and a control device situated in series with the second coil in the electrical circuit and adapted to detect the open or closed position of the first electromagnetic valve based on the induced voltage of the second coil, the control device adapted to act upon the switch to change it between the first and second positions, upon detecting that the electromagnetic valve is in the closed position, the control device configured to act upon the switch to cause it to assume the first position. 
     In accordance with another embodiment, a control system for the ignition of a gas burner is provided comprising a first electromagnetic valve and a second electromagnetic control valve disposed in series to one another, each of the first and second electromagnetic valves having an open position and a closed position for controlling the flow of a gas to the burner, the gas deliverable to the burner when the first and second electromagnetic valves are each in an open position, the gas not being deliverable to the burner when one of the first or second electromagnetic valves is in a closed position, the first electromagnetic valve having a first coil and a second coil, the first electromagnetic valve configured to assume the open position to permit a flow of gas through the first electromagnetic valve when a current that passes through the first coil reaches a first predetermined amount and when a current that passes through the second coil reaches a second predetermined amount, the second electromagnetic valve having a third coil and configured to assume the open position to permit a flow of gas through the second electromagnetic valve when a current that passes through the third coil reaches a third predetermined value; at least one incandescent element for igniting the gas burner when the incandescent element reaches a combustion temperature of the gas, the incandescent element being disposed electrically in series with the first coil, the first coil and incandescent element forming a first branch; and an activator comprising a switch and a control device, the control device configured to act upon the switch, the switch changeable from a first position to a second position, when the switch is in the first position the control device being electrically in series with the second coil to form a block with the second coil, the block being electrically parallel to the first branch, when the switch is in the second position the block forms a closed circuit and the third coil is electrically in parallel to the first branch. 
     In accordance with another embodiment, a method for controlling the gas flow to a burner through a first electromagnetic valve and a second electromagnetic control valve disposed in series to one another is provided, each of the first and second electromagnetic valves having an open position and a closed position for controlling the flow of a gas to the burner, the gas deliverable to the burner when the first and second electromagnetic valves are in an open position, the gas not being deliverable to the burner when one of the first or second electromagnetic valves is in a closed position, the first electromagnetic valve having a first coil and a second coil, the first electromagnetic valve configured to assume the open position to permit a flow of gas the first electromagnetic valve when power is supplied to the first coil and to the second coil, the first coil configured to hold the first electromagnetic valve in the open position by itself after the first electromagnetic valve has assumed the open position, the second electromagnetic valve having a third coil and configured to assume the open position to permit a flow of gas through the second electromagnetic valve when power is provided to the third coil, at least one incandescent element for igniting the burner when the incandescent element reaches a combustion temperature of the gas, the incandescent element being disposed electrically in series with the first coil, the first coil and incandescent element forming a first branch, an activator comprising a switch and a control device disposed in a circuit comprising the first coil, second coil, third coil and the incandescent element, the switch changeable from a first position to a second position by being acted upon by the control device, when the switch is in the first position the control device being electrically in series with the second coil to form a block with the second coil, the block being electrically parallel to the first branch, when the switch is in the second position the block forms a closed circuit and the third coil is electrically in parallel to the first branch, the method comprising: causing the switch to be in the first position to enable a power supply to deliver power to the first and second coils to place the first electromagnetic valve in the open position and to cause the incandescent element to heat; and upon or after the incandescent element reaches the gas combustion temperature, or after a predetermined amount of time, acting upon the switch by use of the control device to change the switch to the second position in order to provide power to the third coil to place the second electromagnetic valve in the open position and to deactivate power to the second coil. 
     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  schematically shows a first embodiment of a control system of the invention. 
         FIG. 2  schematically shows a second embodiment of a control system of the invention. 
         FIG. 3  is a perspective view of a domestic gas appliance where a control system of  FIG. 1  or a control system of  FIG. 2  may be used. 
         FIG. 4  shows a configuration of a control module of the domestic gas appliance of  FIG. 3 . 
         FIG. 5  schematically shows another embodiment of a control system having a switch disposed in a first position. 
         FIG. 6  shows the control system of  FIG. 5  with the switch disposed in a second position. 
         FIG. 7  shows a valve arrangement of a domestic gas appliance in one embodiment. 
         FIG. 8  shows a valve: arrangement of a domestic appliance in another embodiment. 
         FIG. 9  schematically shows another embodiment of a control system having a switch disposed in a first position. 
         FIG. 10  shows the control system of  FIG. 9  with the switch disposed in a second position. 
         FIG. 11  shows a valve arrangement of a domestic appliance in another embodiment. 
         FIG. 12  shows exemplary induced voltages in a second coil of an electromagnetic valve. 
         FIG. 13  shows a valve arrangement of a domestic appliance in another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  in combination with  FIGS. 3 and 4  show embodiments of the control system  100  for the ignition of a gas burner according to different implementations, which preferably comprise at least one incandescent element or glow bar  1 , which is designed to be heated until it reaches the gas combustion temperature and which is disposed adjacent to a gas burner  5 , a power source  2  for powering the incandescent element  1  and thereby cause it to heat up, and an electromagnetic valve  3  for allowing or preventing the passage of gas to the burner  5 , the incandescent element  1  causing the combustion of the gas when gas passes through the electromagnetic valve  3  and when the incandescent element  1  has reached the gas combustion temperature. The gas reaches the burner  5  from a fuel source (not shown in the Figures) through a fuel pipe  6 , and the valve  3  allows the passage of gas through the pipe  6  from the fuel source to the burner  5  when it is open, or prevents the passage when it is closed. 
     The control system  100  is designed for domestic gas appliances  200 , such as a cooker as shown in  FIG. 3  or a drier (not shown in the Figures). The appliances  200  may comprise a single burner or a plurality of burners  5 , the control system  100  preferably comprising, in the embodiments of  FIGS. 1 ,  2  and  4 , an incandescent element  1  and a valve  3  for each burner  5 , the valve  3  being designed to allow or prevent the passage of gas to the corresponding burner  5 , and the power source  2  being adapted in order to power and heat the incandescent elements  1 . In the embodiments, the appliances  200  may also comprise, generally, a control circuit board (not shown in the Figures) by means of which the power of the burners  5  is controlled, for example, and through which the appliances  200  are powered. Thus, the power source  2  of the control system  100  is preferably disposed on the control circuit board. 
     In one embodiment, the electromagnetic valve  3  comprises a rod  10  upon which at least two coils  41  and  42  are wound. When the coils  41  and  42  are activated or powered with sufficient current, the rod  10  is moved, thereby opening the valve at the same time. Thus, in one embodiment, the control system  100  comprises activation coils  41  and  42  associated to the valve  3  in order to open the valve  3 , the opening enabling the valve  3  to allow the passage of gas to the burner  5 . As shown in the  FIGS. 1 ,  2  and  4 , coil  41  is disposed electrically in series with the incandescent element  1 , the coil  41  and the incandescent element  1  forming a branch R 1  electrically parallel to the activation coil  42 . As a result, if the incandescent element  1  breaks down, the current stops circulating through the coil  41  due to the fact that it is disposed on the same branch as the incandescent element  1 , and the valve  3  closes preventing the passage of gas to the burner  5 . 
     In the embodiment of  FIG. 1 , the valve  3  is designed to open once the incandescent element  1  has reached the gas combustion temperature, the gas that reaches the burner  5  thus being lit, with the result that in order to open, it also depends on the current that passes through the coil  41 , this being dependent on the temperature of the incandescent element  1 . Thus, it is necessary that the current increases along with the temperature of the incandescent element  1 . For example, in one embodiment the incandescent element  1  displays NTC (negative temperature coefficient) behaviour, in which the resistance of the incandescent element  1  reduces as its temperature increases, thus increasing the current that passes through the incandescent element  1  and, therefore, through coil  41 . 
     The burner  5  may be switched off by turning off the power supply, thereby preventing power from being supplied to the coils  41  and  42 , the valve  3  thus closing straightaway, preventing the passage of gas to the burner  5 . 
     In the embodiment, the control system  100  may also operate without the activation coil  42 , although the additional coil  41  would have to be adapted in order to allow it to open the valve  3  by itself, which would involve a much larger size of coil, preventing the obtaining of a compact control system  100  as is the case with the activation coil  42 . 
     In a second embodiment shown in  FIG. 2 , the valve  3  is designed so that the additional coil  41  may keep the valve  3  open by itself but may not open it by itself. In order to light the burner  5 , in a first moment power is supplied to the additional coil  41  and the incandescent element  1 , but not the activation coil  42 , it being necessary to power it afterwards in order to open the valve  3  and allow the passage of gas to the burner  5 . In this case, the opening of the valve  3  depends, lastly, upon the activation coil  42 , the use of a specific type of incandescent element  1  not being necessary, an incandescent element with NTC (negative temperature coefficient) or PTC (positive temperature coefficient) behaviour, or another type of behaviour, being capable of being used. For this purpose, the control system  100  comprises an activator to power the activation coil  42 , powering it once the incandescent element  1  has reached the gas combustion temperature. 
     The activator preferably comprises a switch  61  disposed electrically in series with the activation coil  42 , forming, along with the activation coil  42 , a second branch R 2  parallel to the branch R 1  formed by the additional coil  41  and the incandescent element  1 . In one embodiment, the switch  61  is normally open, preventing the activation coil  42  from being powered, and closing when the burner  5  is to be lit and the incandescent element  1  has reached the gas combustion temperature. The switch  61  preferably comprises a triac as shown in  FIG. 2 . 
     The activator may also comprise a control device  60  that acts on the switch  61  when a predetermined time equal to or greater than the time necessary for the incandescent element  1  to reach the gas combustion temperature has elapsed, the switch  61  allowing the activation coil  42  to be powered. This guarantees that the valve  3  opens when the incandescent element  1  has reached the gas combustion temperature. 
     The control device  60  acts on the switch  61 , preferably by means of an activation pulse, the switch  61  allowing the activation coil  42  to be powered only during the activation pulse, given that the additional coil  41  may keep the valve open by itself. In addition, if the incandescent element  1  breaks down, for example, the additional coil  41  is no longer powered and as power is prevented from reaching the activation coil  42 , the valve  3  closes so as to not allow the passage of gas to the burner  5 . The control device  60  may also generate, for example, at least one additional pulse for the purposes of safety to ensure that the valve  3  has opened. 
     In the embodiments of  FIGS. 1 ,  2  and  4 , instead of a control device  60  and a triac, the activator may comprise, for example, a temperature sensor (not shown in the Figures) that activates the switch  61  when it detects that the incandescent element  1  has reached the gas combustion temperature, thus allowing power to be supplied to the activation coil  42 , the valve  3  being opened. 
     In the embodiment, preferably, in order to switch the burner  5  off, the power supply is switched off, thereby preventing power from being supplied to the coil  41 , the valve  3  thus closing straightaway, preventing the passage of gas to the burner  5 . 
     In the embodiments of  FIGS. 1 ,  2  and  4 , the control system  100  may be comprised in the domestic gas appliance  200  in a variety of different arrangements. In a first arrangement shown in  FIG. 4 , a control module  7  comprises the electromagnetic valve  3  and the coils  41  and  42 , the control module  7  comprising two power inputs through which the power supply reaches the additional coil  41  from the power source  2  which may be disposed on the control plate of the appliance  200 , and an additional input for carrying the power supply to the activation coil  42 , by means of the activator disposed, preferably, on the control circuit board of the appliance  200 . 
     In a second arrangement not shown in the Figures, the appliance  200  may comprise a control module  7  that comprises the valve  3 , the coils  41  and  42  and the activator. The control module  7  may comprise two power inputs through which the power supply reaches the coils  41  and  42  and the activator from the power source  2  which may be disposed on the control plate of the appliance  200 . 
     In a third arrangement not shown in the Figures, the control module  7  comprises only the coils  41  and  42  and the switch  60  of the activator, the control module  7  comprising two or three power inputs through which the power supply reaches the coils  41  and  42  and the switch means from the power source  2  which may be disposed on the control plate of the appliance  200 , and an additional input for carrying the activation pulse or the signal generated by the control means  60  to the switch means. 
       FIGS. 5 to 7  show other embodiments of a control system  300  for the ignition of a gas burner  305 . Control system  300  includes a gas ignition element  301  positioned in proximity to a gas burner  305  and comprises one or more heating elements such as, for example, one or more incandescent elements or glow bars which are designed to be heated to a gas combustion temperature of a gas to be delivered to burner  305 . In one embodiment, the control system  300  includes a power source  302 , such as a transformer connected to a mains supply, for powering the control system  300  and which is used to cause an electrical current to pass through the ignition element  301  to cause it to heat. Control system  300  also includes an electromagnetic valve  303  and an auxiliary electromagnetic valve  330  for allowing or preventing the passage of gas to the burner  305 , the ignition element  301  causing the combustion of the gas when gas passes through the electromagnetic valves  303  and  330  and when the ignition element  301  has reached the gas combustion temperature of the gas being delivered to burner  305 . Gas is delivered to burner  305  from a fuel source (not shown in the Figures) through a fuel pipe  306  and the electromagnetic valves  303  and  330 . As shown in  FIG. 7 , electromagnetic valves  303  and  330  are serially disposed in the gas flow path from the gas source and burner  305  and allow the passage of gas through the pipe  306  from the fuel source to the burner  305  when both valves  303  and  330  are open, or prevent the passage of gas when at least one of the valves  303  or  330  is closed. 
     In one embodiment, electromagnetic valve  303  has the same or similar configuration of the electromagnetic valve  3  of the previous embodiments described herein and comprises a rod  310  upon which at least two coils  341  and  342  are wound. When the coils  341  and  342  are activated or powered with sufficient current, the rod  310  is moved to cause the valve  303  to open to permit the flow of gas through the valve. The auxiliary electromagnetic valve  330  comprises a coil  331  and a rod  332  upon which the coil  331  is wound. When the coil  331  is activated or powered with sufficient current, the rod  332  is moved to cause the auxiliary electromagnetic valve  330  to open to permit a flow of gas through the valve. A flow of gas towards burner  305  is allowed when both the electromagnetic valve  303  and the auxiliary electromagnetic valve  330  are in an open position. 
     In the embodiment shown in  FIGS. 5 and 6 , the electromagnetic valve  303  is designed so that the first coil  341  may keep the electromagnetic valve  303  open by itself but may not open it by itself, powering of both the first coil  341  and the second coil  342  being necessary to open the electromagnetic valve  303 . As discussed above, in order to provide gas flow to burner  305  it is also necessary to power the coil  331  of the auxiliary electromagnetic valve  330  in order to open the auxiliary electromagnetic valve  330 . As shown in  FIG. 5 , in a first moment power is supplied to coils  341  and  342  to cause electromagnetic valve  303  to open, and also to the ignition element  301 , but not to coil  331 . Because coil  331  is not powered, valve  330  remains closed to impede the flow of gas towards burner  305 . In this case, the allowance of the flow of gas towards the burner  305  depends, lastly, upon the activation of coil  331  which may occur anytime after the ignition element  301  reaches the gas combustion temperature of the gas to be delivered to burner  305 . In this, and other embodiments, the use of a specific type of ignition element  301  is not necessary. For example, an incandescent element with NTC (negative temperature coefficient) or PTC (positive temperature coefficient) behaviour, or another type of behaviour, may be used. 
     Control system  300  includes an activator comprising a switch  371  that in a first position P 1  is adapted to cause the second coil  342  of the electromagnetic valve  303  to be electrically in parallel to the branch R 1 ′ formed by the first coil  341  and the ignition element  301 , as shown in  FIG. 5 . When in a second position P 2 , as shown in  FIG. 6 , the switch  371  is adapted to cause the coil  331  of the auxiliary electromagnetic valve  330  to be electrically in parallel to the branch R 1 ′. In one embodiment, switch  371  is normally in the first position P 1  when the ignition element  301  is initially powered to prevent the coil  331  from being powered. The switch  371  adapted to change to the second position P 2  when the ignition element  301  has reached the gas combustion temperature of the gas to be delivered to burner  305  to permit the flow of gas to burner  305  and the ignition thereof. In one embodiment, switch  371  comprises a dual electromechanical relay. 
     As discussed above, in one embodiment switch  371  is normally in the first position P 1  when power is initially supplied to the ignition element  301 . In one embodiment the control system  300  further includes a control device  380  that is configured to act upon the switch  371  to take it to the second position P 2  after a predetermined amount of time after power is supplied to the ignition element  301 . In one embodiment, the time is pre-calculated to be sufficient for the ignition element  301  to reach the gas combustion temperature. The amount of time needed to reach a gas combustion temperature of a particular gas is generally substantially constant for ignition elements  301  exhibiting PTC behaviour. Further, depending on the power source, the amount of time to reach the gas combustion temperature is relatively short (e.g., in the range of about 5 to 15 seconds). On the other hand, the amount of time needed to reach a gas combustion temperature of a particular gas is generally variable and longer (e.g., in the range of about 30-60 seconds) for ignition elements  301  exhibiting NTC behaviour and will depend at least in part on the temperature of element  301  when it is initially powered. For this reason, an ignition element  301  that exhibits PTC behaviour is preferred, but not necessary. 
     In another embodiment, the control device  380  is configured to act upon the switch  371  to take it to the second position P 2  when the current through the ignition element  301  has reached a predetermined value after power is initially supplied to it. For that purpose, in such an embodiment the control system  300  includes a current detection device incorporated within control device  380  or separately provided for detecting the current through the ignition element  301 . In one embodiment, the current detection device is adapted to measure the voltage of a point P′ between the ignition element  301  and the first coil  341  of the electromagnetic valve  303 , and determines the current through the ignition element  301  by taking into account the measured voltage and the resistance of first coil  341 . 
     In one embodiment control device  380  is disposed electrically in series with block B′ formed by the switch  371 , the second coil  342  of the electromagnetic valve  303  and the coil  331  of the auxiliary electromagnetic valve  330 , so that the control device  380  and block B′ form a second branch R 2 ′ that is electrically in parallel with branch R 1 ′. In another embodiment, control device  380  is also disposed electrically in parallel to branch R 1 ′ and to block B′. 
     In an embodiment where the appliance comprises two burners  305 , such as that show in the appliance of  FIG. 3  (e.g., one burner  305  for grilling and the other for baking), a variety of control system configurations is possible. In one arrangement each burner  305  has associated with it its own a control system  300 . However, in another arrangement, as shown in  FIG. 8 , each burner  305  can comprise separate control systems similar to the embodiments of  FIGS. 5 to 7  with the control systems having in common the auxiliary electromagnetic valve  330 . 
     For the purpose of safety, in another embodiment the electrical characteristics of the second coil  342  of the electromagnetic valve  303  and of the coil  331  of the auxiliary electromagnetic valve  330  are dependent on each other, such that in a fault condition, if both coils  331  and  342  are electrically connected in series due to a short circuit for example, the current through them is not sufficient to open both the corresponding electromagnetic valve  303  and the auxiliary electromagnetic valve  330 . 
       FIGS. 9 to 11  show other embodiments of control systems for the ignition of a gas burner. In accordance with one implementation, the control system  400  includes a gas ignition element  401  positioned in proximity to a gas burner  405  and comprises one or more heating elements such as, for example, one or more incandescent elements or glow bars which are designed to be heated to a gas combustion temperature of a gas to be delivered to burner  405 . The control system  400  includes a power source  402 , such as a transformer connected to a mains supply, for powering the control system  400  and which is used to cause an electrical current to pass through the ignition element  401  to cause it to heat. Control system  400  also includes an electromagnetic valve  403  and an auxiliary electromagnetic valve  430  for allowing or preventing the passage of gas to the burner  405 , the ignition element  401  causing the combustion of the gas when gas passes through the electromagnetic valves  403  and  430  and when the ignition element  401  has reached the gas combustion temperature of the gas being delivered to burner  405 . Gas is delivered to burner  405  from a fuel source (not shown in the Figures) through a fuel pipe  406  and the electromagnetic valves  403  and  430 . As shown in  FIG. 11 , electromagnetic valves  403  and  430  are serially disposed in the gas flow path from the gas source and burner  405  and allow the passage of gas through the pipe  406  from the fuel source to the burner  405  when both valves  403  and  430  are open, or prevent the passage of gas when at least one of the valves  403  or  430  is closed. 
     The electromagnetic valve  403  has the same or similar configuration of the electromagnetic valves  3  and  303  of the previous embodiments described herein and comprises a rod  410  upon which at least two coils  441  and  442  are wound. When the coils  441  and  442  are activated or powered with sufficient current, the rod  410  is moved to cause the valve  403  to open to permit the flow of gas through the valve. The auxiliary electromagnetic valve  430  comprises a coil  431  and a rod  432  upon which the coil  431  is wound. When the coil  431  is activated or powered with sufficient current, the rod  432  is moved to cause the auxiliary electromagnetic valve  430  to open to permit a flow of gas through the valve. A flow of gas towards burner  405  is allowed when both the electromagnetic valve  403  and the auxiliary electromagnetic valve  430  are in an open position. 
     The electromagnetic valve  403  is designed so that the first coil  441  may keep the electromagnetic valve  403  open by itself but may not open it by itself, powering of both the first coil  441  and the second coil  442  being necessary to open the electromagnetic valve  403 . As discussed above, in order to provide gas flow to burner  405  it is also necessary to power the coil  431  of the auxiliary electromagnetic valve  430  in order to open the auxiliary electromagnetic valve  430 . As shown in  FIG. 9 , in a first moment power is supplied to coils  441  and  442  to cause electromagnetic valve  403  to open, and also to the ignition element  401 , but not to coil  431 . Because coil  431  is not powered, valve  430  remains closed to impede the flow of gas towards burner  405 . In this case, the allowance of the flow of gas towards the burner  405  depends, lastly, upon the activation of coil  431  which may occur anytime after the ignition element  401  reaches the gas combustion temperature of the gas to be delivered to burner  405 . The use of a specific type of ignition element  401  is not necessary. For example, an incandescent element with NTC (negative temperature coefficient) or PTC (positive temperature coefficient) behaviour, or another type of behaviour, may be used. 
     In one implementation control system  400  includes an activator comprising a switch  471 , and a control device  480  that is configured to act upon the switch  471 . When the switch  471  is in a first position P 1  the control device  480  is electrically in series with the second coil  442  of the electromagnetic valve  403 , forming a block B 4 , the block B 4  being connected electrically in parallel to the power source  402  and to the branch R 1  as shown in  FIG. 9 . When the switch  471  is in a second position P 2 , as shown in  FIG. 10 , the coil  431  of the auxiliary electromagnetic valve  430  is electrically in parallel to the branch R 1  and the block B 4  forms a closed circuit CC. In one embodiment, switch  471  is normally in the first position P 1  when the ignition element  401  is initially powered to prevent the coil  431  from being powered. The switch  471  adapted to change to the second position P 2  when the ignition element  401  has reached the gas combustion temperature of the gas to be delivered to burner  405  to permit the flow of gas to burner  405  and the ignition thereof. In one embodiment, switch  471  comprises a dual electromechanical relay. 
     As discussed above, in one embodiment switch  471  is normally in the first position P 1  when power is initially supplied to the ignition element  401 . In one embodiment the control device  480  is configured to act upon the switch  471  to take it to the second position P 2  after a predetermined amount of time after power is supplied to the ignition element  401 . In one embodiment, the time is pre-calculated to be sufficient for the ignition element  401  to reach the gas combustion temperature. The amount of time needed to reach a gas combustion temperature of a particular gas is generally substantially constant for ignition elements  401  exhibiting PTC behaviour. Further, depending on the power source, the amount of time to reach the gas combustion temperature is relatively short (e.g., in the range of about 5 to 15 seconds). On the other hand, the amount of time needed to reach a gas combustion temperature of a particular gas is generally variable and longer (e.g., in the range of about 30-60 seconds) for ignition elements  401  exhibiting NTC behaviour and will depend at least in part on the temperature of element  401  when it is initially powered. For this reason, an ignition element  401  that exhibits PTC behaviour is preferred, but not necessary. 
     In another embodiment, the control device  480  is configured to act upon the switch  471  to take it to the second position P 2  when the current through the ignition element  401  has reached a predetermined value after power is initially supplied to it. For that purpose, in such an embodiment the control system  400  includes a current detection device incorporated within control device  480  or separately provided for detecting the current through the ignition element  401 . In one embodiment, the current detection device is adapted to measure the voltage of a point P′ between the ignition element  401  and the first coil  441  of the electromagnetic valve  403 , and determines the current through the ignition element  401  by taking into account the measured voltage and the resistance of first coil  441 . 
     When the first coil  441  of the electromagnetic valve  403  is powered an induced force is generated, which causes an induction current through the second coil  442  of the electromagnetic valve  403 , the second coil  402  comprising a voltage V 442  due to the induced current through it. The value of the voltage V 442  depends on if the electromagnetic valve  403  is open, allowing the flow of gas through it, or closed, impeding the flow of gas through it. When the electromagnetic valve  403  is closed an air-gap AG is present, and part of the induced force generated by the first coil  441  is lost in the air-gap AG, the induced current through the second coil  442  being smaller than when the electromagnetic valve  403  is open, situation in which no air-gap AG is present, and little or no induction force is lost. As the induced current through the second coil  442  is smaller, the voltage V 442  is also smaller when the electromagnetic valve  403  is closed rather than when the electromagnetic valve  403  is open.  FIG. 12  illustrates an example of this situation, the value Vo corresponding with the value of the voltage V 442  when the electromagnetic valve  403  is open, and the value Vc corresponding with the value of the voltage V 442  when the electromagnetic valve  403  is closed. 
     With the switch  471  in the second position P 2 , due to the closed circuit CC formed and due to the presence of the voltage V 442  in the second coil  442  of the electromagnetic valve  403 , the voltage in the control device  480  is equal to the voltage V 442 . Hence, if the voltage V 442  changes due to a change in the position of the electromagnetic vale  403  (from an open position to a closed position or vice-versa), the voltage in the control device  480  is also changed, and the control means can determine that the electromagnetic valve  403  has changed its position. If an increase in the voltage V 442  has occurred, then the control device  480  is able to determine that the electromagnetic valve  403  has been open, allowing the flow of gas through it, and if a decrease in the voltage V 442  has occurred, then the control device  480  is able to determine that the electromagnetic vale  403  has been closed, impeding the flow of gas through it. 
     In the event that the power from the power supply  402  suffers a power-dip, the first coil  441  of the electromagnetic valve  403  loses power during the power-dip resulting in the electromagnetic valve  403  passing from an open position to a closed position. The input of conventional control device  408  typically includes a rectifier bridge and a filter (not illustrates in the Figures). The rectifier bridge is adapted for rectifying the alternating voltage from the power source  402 , and the filter generally comprises at least one capacitor for filtering the rectified voltage coming from the rectifier bridge, the control device  480  being powered with the rectified voltage. This type of control device has the risk that, with the switch  471  in the second position P 2 , the control device  480  may not be able to determine the presence of a power-dip since as a result of the presence of the capacitor if the duration of the power-dip is short, the capacitor compensating momentarily for the loss of voltage so that the rectified voltage not affected. As a result, even though the electromagnetic valve  403  has closed due to the lack of power in the first coil  441  during the power-dip, the switch  471  is maintained in the second position P 2  making it not possible to open again the electromagnetic valve  403 . 
     This problem is solved in the control system  400  due to the closed circuit CC formed by the control device  480  and the second coil  442  of the electromagnetic valve  403 . When the electromagnetic valve  403  is closed due to a power-dip, the voltage V 442  in the second coil  442  of the electromagnetic valve  403  is changed causing the alternating voltage powering the control device  480  to also change along with the rectified voltage. As a result of the control device  480  being able to detect this voltage change, it may also then determine that the electromagnetic valve  403  has been closed and in response act upon the switch  471  to take it to the first position in order to permit the electromagnetic valve  403  to be opened again. 
     Another advantage of system  400  is that the control device  480  may also detect problems associated with the glow bar/igniter  401 , such as whether it has been damaged or not by virtue of detecting a change in voltage V 442 . For example, if the igniter  401  is damaged, the branch comprising the first coil  441  of the electromagnetic valve  403  and the igniter  401  is opened, the first coil  441  not being powered with the result that the electromagnetic valve  403  is closed. The control device  480  detects this situation and takes the switch  471  to the first position P 1  in order to power the first coil  441  and to open the electromagnetic valve  403 . When the switch  471  is again taken to the second position P 2  the control device  480  is able to detect that the voltage V 442  does not correspond to a value indicative of the valve  403  being in an open position, determining then that the electromagnetic valve  403  has not been opened. As a result, a determination that the igniter  401  is possibly damaged may be made. 
     In an embodiment where the appliance comprises two burners  405 , such as that show in the appliance of  FIG. 3  (e.g., one burner  405  for grilling and the other for baking), a variety of control system configurations is possible. In one arrangement each burner  405  has associated with it its own a control system  400 . However, in another arrangement, as shown in  FIG. 14 , each burner  405  can comprise separate control systems similar to the embodiments of  FIGS. 9 to 11  with the control systems having in common the auxiliary electromagnetic valve  430 . 
     Although the present invention has been disclosed in the context of certain 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.