Abstract:
A flame atmosphere analyzer is described, for operation with combustible gases, including a tube in which an intake and air and gas mixing chamber is formed, a first gas supply nozzle and means for supplying primary combustion air opening into said intake chamber, and a flame burner in fluid communication with the intake and mixing chamber for supplying an air and gas mixture, formed in the chamber, to the burner. The analyzer includes a second gas supply nozzle, which is slidably guided in the tube, and an actuator provided on the tube and operable from outside the tube, for moving the second nozzle between an inoperative first position, in which the gas is supplied through the first nozzle, and an operational second position, in which the gas is supplied through the second nozzle, the first nozzle having no effect on the supply of the gas in the second position.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a flame atmosphere analyser having the characteristics stated in the preamble to claim  1 , which is the principal claim. 
       TECHNOLOGICAL BACKGROUND  
       [0002]    The invention relates particularly, although not exclusively, to the field of flame atmosphere analysers used for controlling the ignition of gas burners. Typical applications are those in which the burners are provided in apparatus with open combustion chambers for space heating or for domestic water heating. 
         [0003]    These analysers are used not only for ignition and flame monitoring, for the purpose of preventing leakage of unburnt gases, but also for intercepting the gas supply when the oxygen content in the combustion air falls below a safe level, or when the content of carbon dioxide increases. These analysers are designed for use with air and gas mixing ratios which create a relatively unstable flame, which may become detached when the oxygen content of the air varies. 
         [0004]    There is also a known way of using flame atmosphere analysers of the aforesaid type in burners for use with combustible gases of different types, such as natural gas and liquefied gas; these gases differ in their characteristics and combustibility and consequently require different calibrations or configurations of the analyser for operation with one or other of the gases. 
         [0005]    In particular, a separate nozzle is required for each type of gas used, and a specific and different quantity of primary air has to be conveyed to the region for mixing with the gas to ensure correct combustion at the burner. 
         [0006]    In some known solutions, the nozzle is changed to suit the gas which is used, but this operation has to be performed by specialist personnel who must check the choice of components and their assembly for correct operation of the device. In another known solution, opposing tubes are used, each tube being dedicated to use with a specific combustible gas, but this design is rather complicated and expensive as regards the components required and their assembly. 
         [0007]    There is also a known way of providing a Y-shaped analyser tube structure, in other words a structure with a tube provided with passages converging in a common end region, but this design is also complicated and expensive. 
       DESCRIPTION OF THE INVENTION 
       [0008]    The primary object of the invention is to provide a flame atmosphere analyser which is structurally and functionally designed so as to be rapidly convertible in use with gases of different kinds, and which is safe, without requiring any replacement of components, thus ensuring safe operation of the apparatus without the need for adjustment by the operator. 
         [0009]    The invention achieves this object by means of a flame atmosphere analyser made in accordance with the following claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Other features and advantages of the invention will become clear from the following detailed description of a preferred example of embodiment thereof, illustrated, for the purpose of illustration and in a non-limiting way, in the attached drawings, in which: 
           [0011]      FIG. 1  is a perspective view of a flame atmosphere analyser made according to the present invention, 
           [0012]      FIG. 2  is an exploded perspective view of the analyser of  FIG. 1 , 
           [0013]      FIG. 3  is a view in axial section of the analyser of the preceding figures, 
           [0014]      FIG. 4  is a plan view of the analyser of  FIG. 3 , 
           [0015]      FIGS. 5 and 6  are views in axial section of the analyser of the preceding figures in different operating positions, 
           [0016]      FIGS. 7 and 8  are enlarged sectional views of details of  FIGS. 5 and 6  respectively. 
       
    
    
     PREFERRED EMBODIMENT OF THE INVENTION 
       [0017]    With reference to the aforesaid drawings, the number  1  indicates the whole of a flame atmosphere analyser made according to the present invention. 
         [0018]    The analyser  1  comprises a support  2  on which are fixed a tube  3 , a thermocouple flame detection device  4  and a spark igniter  5  for igniting the flame. 
         [0019]    The tube  3  has an internally hollow tubular shape and is provided at one of its axial ends with a first combustible gas supply nozzle  6  having a corresponding delivery orifice  6   a . The tube opens at its opposite end into a gas inlet section  7  and is extended at the opposite end into a tubular conduit  8  on which a burner head  9  with a flame nozzle  9   a  is fitted. 
         [0020]    An intake and mixing chamber  10  is formed in the tubular conduit  8 , at the position of the nozzle  6 , this chamber being coaxial with the nozzle  6  and in fluid communication therewith, and having a pair of holes  11  passing through the shell of the conduit  8  and positioned on diametrically opposite sides, the primary air being supplied through these holes into the intake and mixing chamber  10 . The analyser  1  also comprises, according to a principal feature of the invention, a second nozzle  12 , having a corresponding supply hole  12   a , mounted slidably in the tube  3  and coaxial therewith, as described more fully below. 
         [0021]    The second nozzle  12  is provided at one end of an internally hollow tubular body  13  whose opposite axial end is in contact with a cam-shaped surface profile  14  of an actuator means, indicated as a whole by  15 , which is supported rotatably in the tube and by means of which the tubular body, together with the nozzle  12 , can be moved between an inoperative first position, in which the gas is supplied through the first nozzle  6 , and an operational second position in which the gas is supplied through the second nozzle  12 , the first nozzle  6  having no effect on the gas supply in this operational second position. 
         [0022]    The actuator means comprise a sleeve formation  16  mounted rotatably in the tube  3  about an axis of rotation Y, lying perpendicular to the axial direction of development of the tube  3 , indicated by X, the cam profile  14  being formed on the outer shell of the sleeve  16  so as to interact with the corresponding end of the tubular body  13 . The sleeve formation  16  is fixed to a control knob  17  accessible from outside the tube  3 , by means of which the sleeve  16  of the actuator means can be rotated, thus causing, as a result of the rotation of the cam  14 , an axial movement of the nozzle  12  between the aforesaid positions. The number  18  indicates a spring which is provided inside the sleeve  16  and which can press the sleeve against a closure element  19  provided in the tube  3 , with the interposition of a gasket (not shown). The resilient action of the spring  18  serves to position the sleeve formation  16  in the tube, with a gas-tight seal between the inside and outside. 
         [0023]    The number  20  indicates a further spring fitted on the tubular body  13  and acting between a pair of shoulders  21  and  22  provided in the tube  3  and in the tubular body  13  respectively, the spring  20  acting as a return means for the body  13  by holding the latter in contact with the sleeve formation  16 , while also causing, by the resilient return action of the spring, the return of the nozzle  12  into the inoperative first position which is distant from the first nozzle  6 . The nozzle  12  is provided at the end of the tubular conduit  13 , in a portion  13   a  of the conduit which has a conical shape and is housed in a portion  3   a  of the tube which also has an internally conical shape, tapering towards the first nozzle  6 . The cone angles of the facing portions  3   a  and  13   a  are such that, in the inoperative first position (in which the gas is supplied from the nozzle  6 ), the conical portions of the body  13  and of the tube  3  remain spaced apart (as shown in  FIG. 6 ) and gas can flow through the annular volume delimited by the facing conical surfaces. In this condition, the gas flows inside the tube both inside and outside the tubular body  13 , and also through holes  23  and  24  in the tubular body  13 , until it reaches the first nozzle  6 , through which the gas is supplied to the chamber  10 . 
         [0024]    In the operational second position, the cone angles of the aforesaid portions, which are different from each other, are such that the conical portion of the body  13  is in localized surface contact with the inner conical surface of the corresponding portion of the tube  3  (as shown in  FIG. 7 ). In this condition, the whole flow of gas in the tube passes through the nozzle  12 , through which the gas is supplied to the chamber  10 . Since the hole  12   a  of the nozzle  12  has a smaller cross section than the hole  6   a , the nozzle  6  has no effect on the supply in this operational condition. 
         [0025]    The analyser  1  is provided with means for dividing the primary air, indicated as a whole by  25 , which are incorporated into the analyser and connected for operation to the actuator means  15  in such a way that, in the first and second operating positions, they are moved, by the operation of the selection knob  17 , from and towards the holes  11  for the admission of gas into the chamber  10 , to provide a predetermined admission of primary air into the chamber  10 , adapted to the corresponding nozzle activated by the selector knob. 
         [0026]    More particularly, the divider means comprise a pair of holes  26  passing through a strip  27  which has an approximately semicylindrical shape and which is such that it can be fitted and retained slidably on the cylindrical shell of the tube  3 . The strip is extended into a lever  28  whose free end is connected pivotably at  29  to the knob  17 , at a predetermined distance from the axis Y and the pivot point, in such a way that a rotation of the knob  17  is converted into a translation of the strip  27  in the axial direction X, by means of the aforesaid connection of the lever mechanism  28 . 
         [0027]    The passage cross section of the holes  26  is smaller than the cross section of the holes  11 . 
         [0028]    In the first operating position ( FIG. 8 ) in which the gas is supplied from the nozzle  6 , the divider strip  27  is positioned with the holes  26  superimposed on the holes  11 , preferably coaxially, in such a way that the aperture for the admission of the primary air into the chamber  10  is determined by the holes  26 . Conversely, in the second operating position, in which the rotation of the knob activates the nozzle  12  and simultaneously moves the strip  27  away from the holes  11 , without any division of the holes, the admission of the primary air into the chamber  10  takes place through the passage cross section determined by the holes  11 . 
         [0029]    By designing the nozzles  6 ,  12  and the admission holes  11 ,  26  with suitable dimensions, the analyser can be made to operate correctly with different gases. In the example which has been described the nozzle  6  and the holes  26  are chosen for operation with natural gas, while the nozzle  12  and the holes  11  are chosen for operation with liquid gas. 
         [0030]    In operation, the first or second operating position is selected by means of the control knob  17 , these positions being illustrated, respectively, in  FIGS. 6 ,  8  (natural gas) and  FIGS. 5 ,  7  (liquefied gas), the change from one position to the other being made solely by the rotation of the selector knob  17 , which can act simultaneously on the nozzle  12  and the primary air divider means  25  to move them between the aforesaid positions. 
         [0031]    Thus the invention achieves the proposed objects while yielding numerous advantages by comparison with the known solutions. 
         [0032]    A primary advantage is that the analyser can be used with different gases without the need for any substitution of components, which would require corresponding assembly and disassembly; consequently, the change from one operating mode to the other is extremely rapid. 
         [0033]    Furthermore, a change from one function to the other does not require any tests or calibration other than those specified initially, whereas these would be required in the known solutions in which components are changed. 
         [0034]    Because of the invention, the positions assumed in changes between the specified functions are also predetermined and not subject to alteration, and are therefore extremely safe for the use of the analyser with gases of different kinds. 
         [0035]    Additionally, because the movement of the actuator means for activating the chosen nozzle and for moving the divider means is synchronized and is produced with a single selector knob, the analyser setting procedure is simplified and is made safe and rapid for the user.