Patent Publication Number: US-2011073052-A1

Title: Fire tube condensing boiler for generating hot water

Description:
TECHNICAL FIELD 
     The invention relates to a fire tube condensing boiler for generating hot water. 
     BACKGROUND ART 
     The widespread diffusion achieved by fire tube condensing boilers is known; such boilers are provided with a structure that comprises an outer enclosure, which is adapted to delimit a portion of space designed to contain the water to be heated, which is introduced cold by way of an inlet connector that is located proximate to the base of the enclosure and exits hot by way of an outlet connector that is located proximate to the top of such enclosure. 
     In a raised position, the enclosure contains the furnace where combustion occurs, and tubes branch out from the furnace which are designed to convey the exhaust gases that convey heat to the water to be heated before being sent to the flue. 
     All the described elements are advantageously made of carbon steel, which, differently from what occurs for stainless steel, ensures easy joining of the several components by welding, but in this manner such elements are subject to the danger of corrosion by the condensation that, being a condensing boiler, is generated within the exhaust gases as a consequence of the condensation of the water vapor contained in such exhaust gases. 
     The same Applicant has filed patent applications related to protection against the danger of corrosion of exhaust gas conveyance tubes. 
     DISCLOSURE OF THE INVENTION 
     The aim of the present invention is to provide a fire tube condensing boiler in which the furnace is also protected against the risk of corrosion. 
     This aim is achieved by a fire tube condensing boiler for generating hot water according to the invention, characterized in that it comprises the characteristics according to the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the present invention will become better apparent from the description of a preferred but not exclusive embodiment thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein: 
         FIG. 1  is a longitudinal sectional view of the boiler, in which, as in the figures that follow, the exhaust gas conveyance tubes are not shown in cross-section; 
         FIG. 2  is a sectional view, taken along the line II-II of  FIG. 1 ; 
         FIGS. 3 and 4  are respectively views of the details shown in  FIG. 1 . 
     
    
    
     WAYS OF CARRYING OUT THE INVENTION 
     With reference to the figures, the reference numeral  1  generally designates a boiler comprising an outer enclosure  2 , which is adapted to delimit a portion of space  3  for containing the water to be heated, which is introduced cold by way of an inlet connector  3   a  located proximate to the base of the enclosure and exits hot by way of an outlet connector  3   b  that is located proximate to the top of the enclosure. 
     Moreover, the reference numeral  4  designates a furnace where the combustion generated by a burner  5  occurs, and the reference numeral  6  designates tubes designed to convey the exhaust gases in output from the furnace  4  to a chamber  7  for accessing a flue along the arrows of  FIG. 1 . 
     An important feature of the invention is the presence of a thermostatic device, which will be described in detail with reference to  FIG. 4  and is comprised within a stub  8  that is interposed between the outlet connector  3   b  and the portion of space  3  for containment of the water to be heated. Such device is adapted to let the water flow out through the connector  3   b  only when it reaches a preset value of the temperature that allows the accumulation, around the furnace  4 , of a mass of water that is hot enough to prevent condensation on the wall of said furnace of the water vapor contained in the exhaust gases, thus providing protection of the furnace against the risk of corrosion caused by the formation of condensation. 
     Circulation of water through the boiler is in any case ensured by the presence of an external bypass line  9 , which is connected at an end  9   a  to the outlet connector  3   b  downstream of the stub  8  that comprises the thermostatic device, and at an end  9   b  to the portion of space  3  that contains the water to be heated in a position that is interposed between the inlet connector  3   a  of the cold water and a diaphragm  10  that is located below the furnace  4  and is spaced from it and is provided with ports  10   a,    10   b  that are visible in  FIG. 3 , so as to appropriately graduate the passage of water through it. 
     The thermostatic device comprised within the stub  8  is now described with reference to  FIG. 4 . 
     Such device comprises a plate  11 , which is shown in the figure in the position for opening a port  8   a  for the passage of water, which has been moved into such position, overcoming the action of a spring  12 , which abuts against a cross-member  8   b  that is jointly connected to the stub  8 , by the action of a plurality of expanding heat-sensitive elements  13 , which are constituted by known wax-based sensors which comprise a cylinder  13   a  that contains wax and a piston  13   b,  which are arranged in series within a tube  14  that is jointly connected to the plate  11  and act in abutment against a block  15  that is fixed to a cross-member  16  that is jointly connected to the stub  8 . 
     With this arrangement, a multiplication of the strokes of the individual pistons  13   b  is obtained which produces satisfactory values of the stroke of the plate  11 . 
     The described invention is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims: thus, for example, the thermostatic device can be provided in any manner, and the same applies for the diaphragm  10 . 
     The disclosures in Italian Patent Application no. MN2008A000010, from which this application claims priority, are incorporated herein by reference. 
     Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.