Abstract:
A safety device ( 61 ) for a lighting valve ( 23 ) of a gas burner, comprising a starting button ( 36 ), a return spring ( 57 ), a cutoff shutter ( 42 ) controlled by the starting button ( 36 ), a control shutter ( 41 ) for a pilot light nozzle, and a holding electromagnet ( 54 ) for the control shutter ( 41 ). The control shutter ( 41 ) is normally closed and is actuatable through the starting button ( 36 ) for the flowing of the gas to the pilot light nozzle, whilst the holding electromagnet ( 54 ) is dependent on the pilot light to hold open the control shutter ( 41 ). The starting button ( 36 ) is provided for rotation and can be depressed only for a given angular start position so that, for starting the lighting, the button ( 36 ) must be rotated up to said start position and subsequently depressed to close the cutoff shutter ( 42 ) and open the control shutter ( 41 ). There are provided a hooking condition and an unhooked condition for the starting button: in the hooking condition, the cutoff shutter ( 42 ) is closed and the control shutter ( 41 ) is open under the control of the holding electromagnet ( 54 ) without being influenced by the starting button ( 36 ); and, in the unhooked condition, the starting button ( 36 ) can return to the lifted position to open the cutoff shutter ( 42 ) for the flowing of the gas to the burner, the unhooked condition requiring a further rotation of the starting button ( 36 ) spaced away from the angular start position.

Description:
PRIORITY CLAIM AND RELATED APPLICATIONS  
       [0001]     This application claims priority to Italian Patent Application No. TO2004A000218 entitled “Dispositivo di sicurezza per valvola d&#39;accension di un bruciatone a gas” filed Apr. 8, 2004, incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a safety device for a lighting valve of a gas burner, exemplarily for water heaters.  
         [0003]     More specifically, the invention relates to a safety device for a lighting valve of a gas burner, exemplarily but not exclusively, for domestic water heaters, comprising a starting button, a control shutter actuatable through the starting button and a cutoff shutter controlled by the starting button, according to the introductory portions of the principal claims.  
       BACKGROUND OF THE INVENTION  
       [0004]     A gas water heater generally provides a control pilot light for the main burner, a regulating device for the burner controlled by manual controls and by the temperature of the water and a safety device, which prevents the flowing of the gas to the burner in the case of turning off the pilot light.  
         [0005]     Although water heaters with burners provided of piezoelectric or electronic type lighting devices are normally on sale, water heaters having flame lighting system for the gas burners are still commonly produced.  
         [0006]     In a safety device for a gas water heater of known type, the cutoff shutter is downstream of the control shutter and upstream of a thermostatic shutter for the main burner. The control shutter is also controlled by a holding, electromagnet, in turn fed by the current of a thermocouple heated by the pilot flame. The thermostatic shutter is adjustable through a knob, which further provides a given start position, of minimum feed, for the gas burner.  
         [0007]     In the condition of rest, the cutoff shutter is open and the control shutter is closed. When is depressed, the starting button closes the cutoff shutter and opens the control shutter. In this condition, the user can light the pilot light whilst, for the action of the thermocouple, the electromagnet holds open the control shutter. A following lifting of the button opens the cutoff shutter and allows the flow of the gas to the burner under the control of the thermostatic shutter and its automatic lighting by the pilot light.  
         [0008]     The known safety device is generally effective to prevent the feeding of the main burner before the lighting of the pilot light, avoiding risks of saturation of the combustion chamber and consequent bursts. Nevertheless, the phase of starting of a lighting valve can be source of problems, particularly in the cases in which the user manually lit the pilot light by means of matches, lighters and free flames. A particular risk arises when the thermostatic shutter is open and the user unintentionally releases the starting button before moving away the hand from the area of the pilot light. A sudden lighting of the main burner during the return to rest of the button can cause fear and burns in the most unfavorable cases.  
         [0009]     However, also if a water heater provides a piezoelectric or electronic system for the lighting of the pilot light, the safety device above described can cause problems. It may depend on improper sequences in the depression/lifting operations of the starting button and/or to anomalies in the functioning of the system, with hazards of leaks of gas in the combustion chamber and consequent hazards of bursts.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the invention is to accomplish a safety device for a lighting valve of gas burners, exemplarily for water heaters, which assures high security standards together with easiness of operations for the user.  
         [0011]     This object is attained by the safety device for lighting valve of a gas burner, exemplarily for domestic water heaters according to the characteristic portions of the principal claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The characteristics of the invention will become clear from the description that follows, provided merely by way of non-restrictive example, with the aid of the accompanying drawings, in which:  
         [0013]      FIGS. 1 and 1   a  show schematic views of a water heater with a relative lighting valve and a gas burner of known type;  
         [0014]      FIG. 2  shows a perspective view, partially sectioned, of a lighting valve of a gas burner with a safety device for the water heater shown in  FIG. 1 , according to the invention;  
         [0015]      FIG. 3  represents a schematic section of the valve of  FIG. 2 ;  
         [0016]      FIGS. 4   a - 4   d  show perspective schematic views of details of the valve of  FIG. 2  in different working configurations;  
         [0017]      FIG. 5  represents, in a perspective view, a component group of the safety device according to the invention;  
         [0018]      FIG. 6  shows a scheme of operation of a detail of the group of  FIG. 5 ;  
         [0019]      FIG. 7  represents an exploded view of the component group of  FIG. 5 ;  
         [0020]      FIG. 8  shows a detail, in enlarged scale, of the group of  FIG. 7 ;  
         [0021]      FIG. 9  is a schematic sectioned view of the component group of  FIG. 5 ;  
         [0022]      FIG. 10  shows a section according to the line X-X of the group of  FIG. 5 ; and  
         [0023]      FIG. 11  shows, in enlarged scale, details of the section of  FIG. 10  in different working configurations. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]      FIG. 1  represents a gas water heater  12  for domestic use of known type. The water heater  12  includes a container  13  and a lighting valve  14  and provides a combustion chamber with a main burner  16  ( FIG. 1   a ), a nozzle  17  for a pilot light and a thermocouple  18  inside the container  13 . The thermocouple is located in the path of the pilot flame and is electrically connected to leads protected by a tubular element “T”. The water heated by the burner  16  is accumulated in a reservoir not shown in the figures and a (not shown) thermostat through a conduit “R” controls its temperature.  
         [0025]     The lighting valve  14  is outside the water heater  12 , whilst the nozzle  17  for the pilot light is accessible through a door  19  of the container  13 . The gas, as methane, liquid gas etc. enters into the valve  14  through an input pipe “G” and the valve  14  feeds the nozzle  17  through a pipe “F” and the burner  16  through a pipe “B”. The valve  14  is connected with the thermocouple  18  and the thermostat through the leads of the element “T” and through the conduit “R”, respectively. In particular, the lighting valve  14  includes a starting button  21  for the feeding of the pilot light and a knob  22  for regulating the temperature of the water in the reservoir.  
         [0026]      FIG. 2  shows a lighting valve  23 , which can replace the known valve  14  of  FIG. 1  and to which the safety device of the invention is applied. The lighting valve  23  includes a valve body  33 , a control knob  34  similar to the knob  22 , and a starting button  36 .  
         [0027]     An inlet  37 , ducts  38  and  39  and a sleeve  40  for the conduit “R” of the thermostat are evident in the valve body  33 . The inlet  37  is connectable with the input pipe “G”, whilst the duct  38  is connectable with the pipe “F” for the nozzle of the pilot light and the duct  39  is connectable with the pipe “B” for the burner. Further, the valve body  23  lodges a control shutter  41 , a cutoff shutter  42  and a thermostatic shutter  43  ( FIG. 3 ), all of disk type.  
         [0028]     The inlet  37 , and the ducts  38  and  39  are connected each the other through an input chamber  44 , an intermediate chamber  46  and a cutoff chamber  47 , respectively. The input chamber  44  is gas connected with the inlet  37 ; the intermediate chamber  46  is interposed between the chambers  44  and  47  and is in gas connection with the duct  38  for the nozzle of the pilot light; and the cutoff chamber  47  is gas connected with the duct  39  for the burner.  
         [0029]     The chambers  44  and  47  lodge the control shutter  41  and the cutoff shutter  42 , respectively. The output of the input chamber  44  and the input of the cutoff chamber  47  are delimited by shutter seats  48  and  49  for the disks of the shutter  41  and of the shutter  42  and these seats put the intermediate chamber  46  in gas connection with the chambers  44  and  47 . The seats  48  and  49  are of circular section, parallel each the other and substantial coaxial.  
         [0030]     The control shutter  41  is in axis with the seat  48  and comprises a gastight disk  51  and a contrast head  52  mounted on a free end of an actuating stem  56 . The disk  51  normally closes the seat  48  for the action of a spring  53 , whereby preventing, in the use, the flowing of the gas from the input chamber  44  to the intermediate chamber  46  and, therefore, to the pilot light nozzle  17  and to the main burner  16  (see  FIG. 1   a ).  
         [0031]     The valve body  33  further provides, along the duct  39  and downstream of the cutoff chamber  47 , a chamber and a respective seat, not shown in the figures, for the thermostatic shutter  43 . The shutter  43  is operatively connectable with the thermostat of the water heater  12  through the conduit “R” and with the control knob  34  for controlling the flowing of the gas to the burner  16  as function of the temperature of the water and the position of the knob  34 , in a well known manner.  
         [0032]     The cutoff shutter  42  can be opened solely when the pilot light is on and the starting button  36  is lifted. Specifically, the valve  23  includes an electromagnet  54  for the control shutter  41  which is electrically connectable with the thermocouple  18  through the leads of the element “T”. The electromagnet  54  is such to hold back the disk  51  in an open condition and at an end stop, against the action of the spring  53 , when the pilot light heats the thermocouple according to a known technique.  
         [0033]     In the starting button  36 , the actuation stem  56  is in axis with the seat  49  and supports the cutoff shutter  42  and a return spring  57 . At rest, the spring  57  maintains the starting button  36  in the lifted position and the cutoff shutter  42  in an open condition. Moreover, a free end of the stem  56  is arranged in front of the contrast head  52  of the control shutter  41 . These components are dimensioned so that the complete depression of the button  36  up to the end stop of the electromagnet  54  causes the closing of the seat  49  by the shutter  42  and, in sequence, the shifting of the gastight disk  5 . Thus, the shutter seat  48  will be opened for the feeding of the pilot light nozzle  17  in a condition of cutoff of the gas for the burner  16 .  
         [0034]     With the lighting of the pilot light and the button  36  depressed, the electrical current produced by the thermocouple  18  energizes the electromagnet  54 . It holds open the control shutter  41 , with flowing of the gas into the intermediate chamber  46  and the cutoff chamber  47 . The lifting of the button  36  does not modify the state of the shutter  41  but causes the opening of the cutoff shutter  42  with flowing of the gas to the main burner under the control of the thermostatic shutter  43  and its lighting by the pilot light.  
         [0035]     According to the invention, the safety device, depicted with  61 , has such a structure to start the lighting according to an univocal procedure which ensures conditions of total protection for the user. Specifically, the depression of the starting button  36  is subordinated to a given condition of alignment, through rotation, at a predetermined angular start position. This depression causes a hooking condition, in which the cutoff shutter  42  is closed and the control shutter  41  is under the control of the thermocouple  18 .  
         [0036]     An unhooking condition, in which the starting button  36  is released for its lifting by the return spring  57  is subordinated to a further rotation of the button. In the unhooked condition, the cutoff shutter  42  is open, whilst the control shutter  41  remains under the control of the thermocouple  18 .  
         [0037]     The structure of the invention prevents any uncontrolled lighting of the gas in the chamber of combustion. In fact, also in the case in which the thermostatic shutter  43  is open and the user releases the starting button  36  before moving away the hand from the area of the pilot light, the main burner  16  is isolated from the inlet  37  in view of the hooking condition of the button. With safe, the gas can be lit only after the deliberate action of rotation by the user such to enable the releasing of the starting button  36 .  
         [0038]     In detail and with reference to the  FIGS. 5-8 , the lighting starting button  36  includes a head  62  with a hub  63  fixed to the end of the actuating stem  56  opposite to the free end. The head  62  has a projection  64  which is lined up with an index  66  of the valve body  33  (see  FIG. 10 ) when the button  36  is at the angular start position of the button  36  to give a visual indication of the reached start position.  
         [0039]     The safety device  61  includes a pin element  67  arranged in an angularly fixed position with respect to the starting button  36  and adapted to cooperate with the hub  63  to define the above described procedure of start.  
         [0040]     The device  61  is integrated in a starting group  68  comprising a guide sleeve  69  for the actuating stem  56  and stop elements  71  mounted adjacent to the free end of the stem  56 . The cutoff shutter  42  is slidably mounted on the stem  56  and is arrested against the stop elements  71  by a holding spring  72  opposed by the guide sleeve  69 .  
         [0041]     The hub  63  of the button  36  has a cylindrical surface  73  providing a recessed terminal section  74 , a longitudinal notch  76  and a transversal notch  77 . The recessed section  74  is limited by an annular shoulder  78  (see  FIG. 8 ) and the longitudinal notch  76  begins from the shoulder  78  and continues for a certain portion of the surface  73 . The transversal notch  77  crosses the notch  76  and extends symmetrically through about 30°, whilst the longitudinal notch  76  extends beyond the notch  77  in a final section  79 .  
         [0042]     The longitudinal notch  76  is defined by two sides of guide and by a bottom that begins from the recessed section  74  and proceeds with an inclined ramp-like section toward the surface  73  and with a descending step section  81  to which follows a basis section  82  adjacent to the step section  81 . The inclined section is such that the distance from the longitudinal axis starting button  36  increases in the sense of depression of the button.  
         [0043]     The transversal notch  77  includes two guide margins and a bottom which is defined by the basis section  82  and by two inclined sections  83   a  and  83   b , ascending to the surface  73 . Thus, the distance of the bottom from the longitudinal axis of the button  36  along the transversal notch increases, with the increasing of the distance from the axis of the longitudinal notch  76 . In turn, the guide margin close to the reduced section  74  is substantially coplanar with the step section  81 .  
         [0044]     A seat  84  of the sleeve  69  (see  FIG. 9 ) lodges the pin element  67  with possibility of radial shifting perpendicular to the axis of the starting button  36 . A conventional inside end  86  of the pin  67  cooperates with the hub  63  and an external end  87  cooperates with a radially acting spring  88 , which pushes the pin element  67  toward the longitudinal axis of the button  36 .  
         [0045]     In an initial condition, corresponding to the lifted position of the starting button  36 , the inside end  86  of the pin  67  projects from the seat  84  and engages the recessed terminal section  74  of the hub  63  in front of the annular shoulder  78 . It prevents the depression of the button  36  as represented in the configuration “I” shown in  FIG. 6  and in  FIG. 11 .  
         [0046]     The rotation of the starting button  36  up to a reference start position causes the longitudinal notch  76  to be arranged in front of the pin element  67 , as shown in the configuration “II” of  FIG. 6  and  FIG. 11 , allowing the depression of the same button  36 .  
         [0047]     Now, depressing the starting button  36 , the pin element  67  is forced to reenter in the seat  84  by the ascending section of the notch  76  against the action of the radially acting spring  88 , up to the step section  81 . The depression continuing, the spring  88  snap moves the pin element  67 , positioning the inside end  86  on the basis section  82  and, in sequence, on the final section  79  of the longitudinal notch  76 , according to the configuration “III” of  FIG. 6  and the configurations “III-IV” of  FIG. 11 .  
         [0048]     The following release of the starting button  36  causes a short lifting of the button  36  under the action of the return spring  57  (to see  FIG. 9 ). The lifting is interrupted for the arrest of the step section  81  by the pin element  67  in a hooked position for the button  36 . Here, as shown in the configurations “IV” of  FIG. 6  and “III-IV” of  FIG. 11 , the pin element  67  engages the basis section  82  in the area of intersection between the notches  76  and  77 .  
         [0049]     A limited rotation of the starting button  36  in the hooking condition, out of the angular start position, causes the pin element  67  to reenter partially in the seat  84  for the action of the ascending section  83   a  or  83   b . Anyway, it has no effect in the releasing of the button, in view of the remaining contrast on the pin element  67  practiced by the margin of the notch  77  coplanar to the step section  81 . The rotation continuing over the extension of the transversal notch  77 , the end  86  of the pin element  67  engages the cylindrical surface  73  according to the configurations “V” of  FIG. 6  and “V-VI” of  FIG. 11 , whereby releasing the hub  63 . Now, the return spring  57  moves the button  36  to the lifted position, of rest, as represented in the configuration “VI” of  FIG. 6 .  
         [0050]     In the starting group  68  ( FIGS. 3 and 7 - 10 ), the guide sleeve  69  is constituted by a cylindrical body  90  with a first annular notch  89  in which the seat  84  for the pin element  67  is also defined. The radially acting spring  88  is defined by a resilient annular leaf, shaped as a cut ring, lodged in the notch  89  and having a fold  91  engaged in a hole of the annular notch  89  and an operational section which urges the outside end  87  of the pin element  67 .  
         [0051]     The guide sleeve  69  is locked in a cylindrical hollow  92  of the valve body  33 , whilst an “O” ring  93 , in resilient material, interposed between a second annular notch of the body  90  and the cylindrical hollow  92 , assures the gas seal. The sleeve  69  has a substantially frusto-conical terminal section  94  projecting from the body  90  and a cylindrical vane  96  formed in the body  90 . The terminal section  94  defines the guide for the sliding of the stem  56  and the vane  96  is provided for guiding and receiving a portion of the hub  63 .  
         [0052]     The return spring  57  is partially lodged in the vane  96  ( FIG. 9 ), around the stem  56 , interposed between the bottom of the vane  96  and a seat  97  of the hub  63 . Another “O” ring  98 , in resilient material, lodged in a seat of the terminal section  94  and opposed through a washer by the spring  57  insures the gas seal between the sleeve  69  and the stem  56 .  
         [0053]     The cutoff shutter  42  includes a gastight disk  99 , also in resilient material, and a spring holding disk  101 . The gastight disk  99  has a surface opposed by the stop elements  71  and a hub  102  (see  FIG. 3 ) slidably mounted along the actuating stem  56  and having capability of gastight.  
         [0054]     The disk  101  is shaped for receiving an end of the holding spring  72  and is provided of a hole in which the hub  102  of the disk  99  is lodged. The intermediate portion of the spring  72  is arranged around the frusto-conical section  94  and the other end of the spring  72  is lodged in an annular seat at the base of the section  94 .  
         [0055]     The operation of the valve  23  and of the relative safety device  61  will result evident from the  FIG. 3  and from the  FIGS. 4   a - 4   d.    
         [0056]     In the safety device  61 , as shown in  FIG. 3 , the starting button  36  is at rest in a lifted position in virtue of the return spring  57 . Further, the action of the return spring  57  is prevailing and the spring  57  maintains compressed the holding spring  72 . In the lighting valve  23 , the cutoff shutter  42  is open, whilst the control shutter  41  is closed under the action of the spring  53 . The gas of the input chamber  44  cannot flow in the intermediate chamber  44  and the starting button  36  cannot be depressed for the obstacle constituted by the pin element  67  to the annular shoulder  78  of the hub  63 . It also prevents that the starting button  36  may be operated by child or inexperienced people.  
         [0057]     In  FIG. 4   a  the effects of a clockwise or counterclockwise rotation of the starting button  36  up to the angular start position are in evidence. The longitudinal notch  76  of the hub  63  is lined up with the pin element  67  and the button  36  can be freely depressed. This rotation does not produce effects on the other components, which remain in the same situation of  FIG. 3 .  
         [0058]      FIG. 4   b  shows the components of the device  61  of  FIG. 3  when the starting button  36  is completely depressed beyond the position of start. During the depression, the actuating stem  56  shifts on the guide sleeve  69  toward the control shutter  41 . For the action of the holding spring  72 , the disk  99  of the shutter  42  follows the shift and slides along the stem  56 , jointly with the extension of the holding spring  72 . Reached the seat  49 , the disk  99  is arrested and isolates the cutoff chamber  47 .  
         [0059]     The stroke of the starting button  36  continuing, the actuating stem  56  withdraws the gastight disk  51  from the seat  48  through the head  52 . It puts in communication the intermediate chamber  46  with the input chamber  44 , whilst the spring  72  maintains the gas seal of the disk  99  with the seat  49 . The depression of the button  36  is limited by the end stop condition of the holding electromagnet  64 . Now, the gas feeds the nozzle  17  through the duct  38  and the user can proceed to the lighting of the pilot light in the safe condition of cutoff of the main burner. As consequence of the lighting, the thermocouple energizes the electromagnet  54  with holding of its mobile portion and maintenance of the open condition of the control shutter  41 .  
         [0060]     In  FIG. 4   c,  the starting button  36  has been released but the pin element  67  maintains it hooked. The end of the stem  56  is spaced away from the seat  48  and it cannot practice any action on the head  52  of the gastight disk  51 . The stop elements  71  are moved away from the seat  49 , allowing the holding spring  72  to maintain the disk  99  adherent to the seat  49  and closed the intermediate chamber  47 . In this state, whilst the gas continues to feed the pilot light, the flowing of the gas to the cutoff chamber  47  and the burner is still prevented. A possible turning off of the pilot light will cause only the closing of the control shutter  41  owing to the de-energization of the electromagnet  54 .  
         [0061]     In  FIG. 4   d  the effects of the application of a further clockwise or counterclockwise rotation of the starting button  36  beyond the angle of extension of the transversal notch  77  are shown. The releasing of the hub  63  allows the spring  57  to completely lift the button  36 . The actuation stem  56  has been shifted with respect to the guide sleeve  69  and its end is further spaced away from the control shutter  41 . In turn, the stop elements  71  have withdrawn the disk  99  from the seat  49  and compressed the holding spring  72 , with-consequent opening of the cutoff chamber  47 . Thus, the gas can feed the burner  16  through the duct  39 . As in  FIG. 3 , the pin element  67  is now in front of the shoulder  78  of the hub  63  preventing uncontrolled depressions of the button  36 . Also in this case, a turning off of the pilot light will cause the closing of the control shutter  41  and the isolation of the intermediate chamber and of the duct for the pilot light.  
         [0062]     Naturally, the principle of the invention remaining the same, the embodiments and the details of construction of the safety device for a lighting valve can be widely varied with respect to what has been described and illustrated, by way of non-limitative example, without by this departing from the ambit of the present invention.