Abstract:
The invention relates to a device approximately defining an L shape and comprising at least two first nested pipes in the foot of the L ( 32 ), and at least one second pipe ( 36 ) provided with at least one opening ( 38 ), in the leg of the L, the first pipes being arranged in such a way as to define a duct between one end ( 34 ) of a first central pipe and said at least one opening ( 38 ) by means of passages defined at the ends of the first pipes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Stage of PCT International Application Serial Number PCT/FR2013052833, filed Nov. 23, 2013, which claims priority under 35 U.S.C. §119 of French Patent Application Serial Number 1261158, filed Nov. 23, 2012, the disclosures of which are incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to a device capable of being integrated within a fireplace. More particularly, the present disclosure relates to such a device enabling to improve the combustion inside of a fireplace. 
     DISCUSSION OF THE RELATED ART 
     Many types of fireplaces are known. Two main types of fireplaces may be distinguished: closed-hearth fireplaces where the hearth is confined in a closed enclosure, and open-hearth fireplaces where at least one wall of the hearth is in contact with free air. 
     Studies have shown that the combustion of wood generates a significant quantity of pollution emission, for example, carbon monoxide or fines which may be noxious for the health and for the environment. In an open-hearth fireplace, the temperature within the fireplace hearth is not sufficient for all effluents to be burnt. Incomplete combustions thus occur. 
     In the case of a closed-hearth fireplace, the high temperature inside of the hearth enables to limit such toxic emissions. Indeed, within a closed hearth, the combustion temperature is generally higher than 573° C., and a more complete combustion than in the case of an open hearth occurs, during which effluents noxious for the environment and for the health are burnt. 
     SUMMARY 
     An object of an embodiment is to provide a device capable of being integrated in a fireplace and enabling to perform a double combustion. 
     Thus, an embodiment provides a device approximately defining an L shape and comprising, in the foot of the L, at least two first nested pipes and, in the leg of the L, at least one second pipe provided with at least one opening, the first pipes being arranged in such a way as to define a duct between one end of a first central pipe and the at least one opening via passages defined at the ends of the first pipes. 
     According to an embodiment, the second pipe comprises a plurality of lateral openings. 
     According to an embodiment, the duct runs through all throughout the volume of the first and second pipes. 
     According to an embodiment, the first and second pipes have a circular cross-section. 
     According to an embodiment, the first and second pipes are made of refractory steel, of stainless steel, of cast iron, or of a metal such as copper. 
     According to an embodiment, the first pipes define duct stages, the stages having a cross-section which increases along with their distance to the center of the first pipes. 
     According to an embodiment, the cross-section of a second pipe is smaller than the cross-section of an outer stage. 
     According to an embodiment, the axes of the first pipes are parallel to one another and coplanar in a plane running through the second pipe, the axis of a first pipe having a first cross-section being located above the axis of a first pipe having a second cross-section if the first cross-section is larger than the second cross-section. 
     According to an embodiment, the device further comprises a third pipe provided with at least one additional opening, the third pipe being parallel to the second pipe, being located at the end of the first pipes opposite to the second pipe, and extending from a first intermediate pipe to form a second duct. 
     According to an embodiment, the device comprises three first pipes. 
     An embodiment further provides a block insertable in a fireplace comprising at least one device such as provided hereabove. 
     According to an embodiment, the block comprises at least two devices such as provided hereabove defining independent ducts, the devices being held in position by means of an armature comprising four lateral walls. 
     According to an embodiment, the block further comprises a removable plate capable of being positioned at the surface of the armature to close the top of the armature. 
     According to an embodiment, one wall of the armature comprises outlets associated with an exhaust duct. 
     According to an embodiment, the exhaust duct is defined along the armature, on the side of the second pipes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, among which: 
         FIG. 1  is a simplified perspective view of an example of an open-hearth fireplace; 
         FIGS. 2 and 3  respectively are a perspective view and a cross-section view of a block according to an embodiment; 
         FIG. 4  is an enlarged cross-section view illustrating an elementary structure of a block according to an embodiment; 
         FIGS. 5A and 5B  illustrate elements for holding an elementary structure according to an embodiment; 
         FIGS. 6, 7, and 8  respectively are two perspective views and a cross-section view of a variation of a device according to an embodiment; and. 
         FIGS. 9A and 9B  respectively show a top view and a front view of a variation of a device according to an embodiment,  FIG. 9A  being a cross-section view along plane A-A of  FIG. 9B . 
     
    
    
     For clarity, the same elements have been designated with the same reference numerals in the different drawings. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example of a fireplace where a block according to an embodiment is capable of being inserted. The fireplace shown in  FIG. 1  is an open-hearth fireplace, that is, the hearth is not isolated by a closed enclosure but is created in an enclosure which is open at least on one of its sides. 
     It should be noted that the block improving the combustion provided herein is also capable of being integrated in a closed-hearth fireplace, or in a stove, to further improve the combustion of noxious effluents which would still be present within such a device. 
     In  FIG. 1 , the fireplace comprises a hearth  10  closed by a back wall  12 , lateral walls  14 , and a horizontal ground  16 . The fireplace is topped by a smoke hood  18  having a cross-section which decreases to reach a fume exhaust duct  20 . 
     In a conventional fireplace, ground  16  may be covered with fire dogs, not shown, having the logs to be burnt arranged thereon. An ash collection system, not shown, is generally provided at the level of the fireplace ground. 
     As seen previously, in a fireplace of the type in  FIG. 1 , that is, an open-hearth fireplace, the wood combustion temperature is limited by the fresh air supply on the side of the fireplace opening. Particularly, in an open-hearth fireplace, the temperature above the flames may be lower than 573° C., which only allows a partial combustion: the noxious effluents released during the main combustion of the wood (also called primary combustion) are not burnt. 
     A device capable of being integrated in a fireplace of the type in  FIG. 1 , but also in a closed-hearth fireplace, is here provided, which enables to perform a double combustion in the hearth, such a double combustion enabling to burn at least part of the noxious effluents resulting from the first combustion. Double combustion, or post-combustion, or secondary combustion, here means a combustion which is created by a supply of fresh air, the secondary air, at the level of the fumes, at a temperature sufficient for noxious gases to burn. In practice, this temperature is greater than or equal to 573° C. 
       FIG. 2  is a perspective view of such a device insertable in the hearth of a fireplace. 
     The device of  FIG. 2  comprises a container  30  defining a volume where the logs to be burnt will be laid. Container  30  for example comprises four lateral walls. The bottom of container  30  is delimited by a set of horizontal elements  32  playing the role of fire dogs. Fire dogs  32  extend between the front and the back of container  30 , that is, they will be placed between the front and the back of the hearth of the fireplace being used. The fire dogs are formed, as will be seen hereafter, of a plurality of pipes, for example, which are cylindrical, nested, and communicating together. 
     Openings  34  are defined on the front surface of container  30 , these openings corresponding to the end of the central pipes of each of fire dogs  32 . Each element of larger cross-section of each of fire dogs  32  is connected, at the back of the device, that is, in the portion which will be arranged at the bottom of the fireplace hearth, to a vertical pipe  36 . Vertical pipes  36  comprise a set of openings  38  preferably defined laterally and on the side of the hearth. 
     All throughout the present description, it will be spoken of horizontal fire dogs  32  and of vertical pipes  36 . It should be noted that these horizontal and vertical directions should be interpreted as being actually substantially horizontal and substantially vertical, that is, with a 10° tolerance relative to the horizontal axis and relative to the vertical axis. Thus, the angle formed between the generating line of each fire dog  32  and the generating line of pipe  36  may vary from 70° to 110°. Further, the general shape, lengthwise, of fire dogs  32  and of pipes  36  may slightly vary with respect to a rectilinear shape. Finally, when numerical applications will be provided in the following description, each of the indicated values should be considered as being given to within 10%. 
     The insertable block provided herein comprises a set of independent elementary structures, each formed of a fire dog  32  and of a vertical pipe  36  held in position with respect to each other. In each of these elementary structures, fire dog  32  plays the role of an air-ember counterflow exchanger so that air, inserted through opening  34 , is heated by means of the embers formed by the logs laid on fire dogs  32 . The heated air then passes through means of communication between each of fire dogs  32  and each of vertical pipes  36 , until it reaches openings  38  and is injected back at the level of the fire formed in the hearth. 
     Advantageously, the secondary air heated within fire dogs  32  and pipes  36  is sent back to the top of the flames, via openings  38 , at a temperature sufficient for the mixture between this air and the gases originating from the flames of the fire present at the level of openings  38  is at a temperature higher than 573° C. Thus, the injection of secondary air via the duct formed between openings  34  and  38  enables to perform a double combustion at the level of openings  38 , and thus to burn the noxious gases which are released by the primary combustion and which have not been burnt at the level of the flames. To reach sufficient temperatures, the inventors have observed that at least a double passage, and preferably a triple passage, should be provided for secondary air along the fire dog length, since a simple passage does not enable to sufficiently pre-heat the secondary air to decrease the pollution. 
     Fire dogs  32  are preferably arranged so that a space separates them in order for the ashes formed during the wood combustion to fall into an ash collection vessel placed under the device (not shown). As an example, to provide this function, the space between fire dogs  32  may be in the range from 5 to 20 mm, preferably 10 mm. Such a gap enables to keep hot embers above fire dogs  32 , while enabling to discharge the ashes downwards. 
     It should be noted that each system comprising an association of a fire dog  32  and of a vertical pipe  36  operates independently and defines an independent air inlet duct. Thus, the secondary air heated at the fire dogs is distributed on each of vertical pipes  36 , which makes it possible to perform a double combustion over a large surface area at the back of the fireplace. 
       FIG. 3  is a cross-section view from front to back of the device of  FIG. 2 . In this drawing, the structure of fire dogs  32  and their association with vertical pipes  36  are shown in further detail.  FIG. 4  shows this association only, isolated and enlarged. 
     As can be seen in  FIGS. 3 and 4 , each fire dog  32  is formed of an assembly of nested pipes. Although, in the shown example, three nested pipes are shown, it should be noted that less or more than three pipes may be used, preferably an odd number of pipes to promote the air inflow. In this example, fire dog  32  comprises a first central pipe  40 , a second intermediate pipe  42 , and an outer pipe  44 . 
     Central pipe  40  has one end located at the front of the device, which matches with opening  34  of container  30 . At the other end of central pipe  40 , at the bottom of the device, are provided lateral openings  46  which enable air to flow from central pipe  40  into intermediate pipe  42 . In this case, the bottom of central pipe  40  is closed. Preferably, lateral openings  46  are located at the bottom of pipe  40 , that is, opposite to opening  34 , so that air can flow all along central pipe  40  before flowing into intermediate pipe  42 . At the front of the device, that is, on the side of openings  40 , intermediate pipe  42  comprises lateral openings  48  which enable air to flow from intermediate pipe  42  to outer pipe  44 . In this case, the front end of pipe  42  is closed. 
     Vertical pipe  36  is provided to nest into outer pipe  44 , at the back thereof (on the side of openings  46 ) to form a tight assembly. According to how pipes  44  and  36  are assembled, openings  49  may be alternately provided, either in pipe  44 , or in pipe  36 , to enable air to flow between the two pipes. 
     Thus, the device defines a tight duct between air inlet point  34  and lateral openings  38  formed in vertical pipe  36 . 
     Preferably, the axes of pipes  40 ,  42 , and  44  are provided as being parallel and coplanar in a plane running through vertical pipe  36 , the axis of an outer pipe being located above the axis of an inner pipe. This provides heat exchanges of good quality with the blaze. 
     It should be noted that the assembly provided herein for pipes  40 ,  42 , and  44  is an example only, and that other assemblies enabling to perform the same function, that is, to define a duct between one end of a fire dog  32  and openings defined in the vertical pipes by snaking in the different pipes, may be provided. Particularly, pipes  40  and  42  slightly shorter than the length of fire dogs  32  and held by one of their ends may be provided, so that air flows between the pipes via the free ends of pipes  40  and  42  (on the side opposite to the pipe holding system). 
     In use, the logs are placed at the surface of fire dogs  32 . Advantageously, such an arrangement enables to form a very hot area at the surface of fire dogs  32 , which heats the air flowing through the duct formed between inlet  34  and outlets  38 , and first the air in the stage defined between outer pipe  44  and intermediate pipe  42 . Pipes  40 ,  42 , and  44  define counter-flow exchangers in fire dogs  32 . Advantageously, a natural air convection occurs in fire dogs  32  due to such heat exchanges. 
     Further, to improve heat exchanges in counterflow exchanger  32 , it is provided to nest pipes  40 ,  42 , and  44  so that their central axes are not confounded, the center of central pipe  40  being located lower than the center of intermediate pipe  42 , and the center of intermediate pipe  42  being located lower than the center of outer pipe  44 . 
     The cross-section of central pipe  40  (first stage) is further provided to be smaller than that of the second stage (internal cross-section of pipe  42  minus the external cross-section of pipe  40 ) and the latter is provided to be smaller than the cross-section of the third stage (internal cross-section of pipe  44  minus the external cross-section of pipe  42 ). This enables to provide an expansion between each stage, which also slows down the air flow between the different pipes and enables to store a larger amount of heat energy in heat exchanges with the blaze. The air is further compressed at the duct inlet, at the level of opening  34 . 
     Further, the cross-section of the vertical pipe will preferably be smaller than the cross-section of the third stage to create, at the inlet of pipe  36 , a compression and thus a new acceleration of the air flow before it comes into contact with the unburnt combustible gases to cause the double combustion at the level of openings  38 . Such a configuration advantageously helps improving the natural convection of air between inlet  34  and outlets  38 . 
     As an example of numerical application, central pipe  40  may have an inner diameter equal to 9.5 mm and a 2-mm thickness (cross-section of the first stage equal to 70.9 mm 2 ), the intermediate pipe may have an inner diameter equal to 17.3 mm and a thickness equal to 2 mm (cross-section of the second stage equal to 92 mm 2 ), outer pipe  44  may have an inner diameter equal to 36 mm and a 2-mm thickness (cross-section of the third stage equal to 661.6 mm 2 ), and vertical pipe  36  may have an inner diameter equal to 9.5 mm and a 2-mm thickness, that is, a cross-section of this pipe in the order of 70.9 mm 2 . 
     Openings  46  defined between the first stage and the second stage (defined in pipe  40 ) may have a cross-section equal to 84.8 mm 2 , openings  48  between the second stage and the third stage (defined in pipe  42 ) may have a cross-section equal to 115.5 mm 2 , and openings  49  between the third stage and the vertical pipe (defined, for example, in the portion of vertical pipe  36  which penetrates into outer pipe  44 ) may have a cross-section equal to 70.9 mm 2 . Lateral openings  38  defined along the height of pipe  36  may be formed by drilling, and may have a diameter in the range from 3 to 6 mm. It should be noted that opening  34  will advantageously be provided to have a diameter identical to the internal diameter of central pipe  40 . 
     As an example of material, outer pipe  44  and vertical pipe  36  may be, to be compatible with a direct contact with the blaze, made of refractory or stainless steel. Pipes  40  and  42  may also be made of refractory steel or also of stainless steel. In all cases, the pipes, mainly those in contact with the blaze, will be made of a material withstanding high temperatures and having a high heat conductivity, for example, cast iron or a metal such as copper. 
     The walls of container  30  are preferably made of an insulating material, for example, vermiculite. 
       FIGS. 5A and 5B  illustrate a practical embodiment of sleeves intended to be placed at the front and at the back of fire dogs  32  to hold the different pipes  40 ,  42 ,  44  in their position. In this example, pipes  40 ,  42 , and  44  having a circular cross-section are considered. 
     In  FIGS. 5A and 5B , a front sleeve  50  ( FIG. 5A ) is provided on the front portion of fire dog  32 , for example, rigidly attached to container  30 , and a back sleeve  52  ( FIG. 5B ) is provided on the back portion of container  30  to hold pipes  40 ,  42 , and  44  in their position. Front sleeve  50  has an opening of same diameter as opening  34 , intended to be positioned opposite opening  34 . Sleeve  52  is tight. Opposite opening  34 , the back sleeve has a raised circular portion  53 . Crescent moon-shaped raised portions  54  and  55 , of increasing size, are formed on the opposite surfaces of sleeves  50  and  52 . Central pipe  40  is held in position between raised portions  53  and  54 , intermediate pipe  42  is held in position between raised portions  54  and  55 , and the outer pipe is held in position around raised portions  55 . 
     On the outer side of sleeves  50  and  52 , a raised portion or a recessed portion may be provided to hold the sleeves in container  30 . It may in particular be provided for the elements holding the sleeves to ensure a proper positioning thereof, and thus of pipes  40 ,  42 , and  44  (to provide significant heat exchanges with the blaze). 
     Other structures for holding pipes  40 ,  42 , and  44  (not necessarily with a circular cross-section) within fire dogs  32  may be provided. 
       FIG. 6  illustrates an alternative embodiment of the block insertable in a fireplace of  FIG. 2 . In this variation, openings  60  are formed in the back portion of container  30 , above fire dogs  32 . A back piece  62  is placed at the back of openings  60  to form a duct  64  between openings  60  and the upper portion of the fireplace. The structure of openings  60  and of piece  62  enables to exhaust the fumes originating from the fire through duct  64 . This variation is particularly advantageous in a case where the device of  FIG. 2  is desired to be closed. 
     In  FIGS. 6 and 7 , front sleeves  50  can be seen at the front of container  30 . 
       FIGS. 7 and 8  illustrate this state, respectively in perspective and in cross-section view. In this state, a removable plate  70  is placed above the blaze to tightly close container  30 . The fumes originating from the combustion are then exhausted through openings  60  towards duct  64  and are redirected by this duct towards smoke hood  18  of the fireplace. 
     Advantageously, the closing of container  30  by plate  70  may be performed at the end of the combustion, when the fire is being extinguished. This enables to concentrate the heat inside of a stove which would have, in this case, a hearth nearly closed by plate  70 . Other applications can then further be provided for the fireplace, for example, using plate  70  as food cooking means. 
     In the case of a use such as that provided in  FIGS. 6, 7, and 8 , a trap door system enabling to avoid for fumes coming out of duct  64  to be brought back into the living room may be provided in smoke hood  20  of the fireplace. To achieve this, conventional trap door systems integrated in the fireplace may be used. 
     Specific embodiments have been described. Various alterations and modifications will occur to those skilled in the art. It should in particular be noted that the cylindrical shape of fire dogs  32  and of pipes  40 ,  42 , and  44  is not limiting. Indeed, these elements may have other cross-sections, for example, rectangular, triangular, hexagonal or other, and may not necessarily all have the same cross-section. Indeed, only the ratio between the cross-sections of the different elements, and their relative positioning, has an influence upon the efficiency of the device. 
     Similarly, pipes  36  may have a non-circular cross-section. Further, the number of structures comprising a fire dog  32  associated with a pipe  36  may vary. Indeed, this system may be adapted to fires of variable magnitude and of variable surface areas. Similarly, it may be provided to place structures allowing the double combustion at the center of the blaze only. It may also be provided to integrate a single structure comprising an association of a fire dog  32  and of a vertical pipe  36  in a fireplace. 
     Further, the structure of container  30  is not limiting, and even the use of this structure is not compulsory. Indeed, the elementary structures formed of a fire dog  32  and of a pipe  36  may be held together by any other means than the structure of container  30  provided herein. 
     Finally, although a system where each fire dog  32  comprises three nested pipes has been discussed herein, more than three pipes, or even two pipes, may be provided. Indeed, a fire dog structure comprising two nested pipes may be provided if it is sufficient to heat the secondary air up to a temperature capable of implying the second combustion. In the case of a structure with two nested pipes, the secondary air inlet into the fire dog may be provided at the back of the device. In this case, an additional duct portion allowing such an air inflow may also be provided at the back of the device. In all cases, the cross-sections of the different stages formed by the pipes in fire dogs  32  will be provided to have increasing sizes from the center to the outside, to cause the above-mentioned air expansion and compression phenomena. 
     Additional hot secondary air outlets may also be provided at the front of the device. In this case, additional vertical pipes, for example shorter than pipes  36  to avoid disturbing the loading of the wood, may be provided at the front of the device, the air flowing through these additional pipes originating from an intermediate pipe formed in the fire dogs. 
     Structures where the vertical pipes are provided to be arranged on one of or on the walls of the hearth instead of at the back thereof may also be provided. In this case, the elementary structure provided herein may be equipped with ducts for transferring the secondary air inlets to the front of the fireplace. 
     Further, pipes  36  have been shown herein as being formed of independent cylinders. It should be noted that other structures may be provided for pipes  36 , and that it may in particular be provided to integrate these pipes in a block placed at the back of the device. Such a block where vertical ducts are defined may for example be provided, openings of communication with the outer pipe of each fire dog and openings for extracting the hot air at the level of the blaze being provided in this block. 
       FIGS. 9A and 9B  respectively show a top view and a front view of a variation of an example of a device where pipes  36  are integrated to a fireplace back plate,  FIG. 9A  being a cross-section view along plane A-A of  FIG. 9B . A fireplace back plate, partially shown, is designated with reference numeral  80 . Pipes  36  are defined by the cooperation between a sheet metal fixed (for example, soldered) to the back of the fireplace plate and the fireplace plate. According to a first variation, illustrated to the left of  FIG. 9A , a continuous sheet metal  82  is used. According to a first variation, illustrated on the left-hand side of  FIG. 9A , a continuous sheet metal  82  is used. According to a second variation, illustrated on the right-hand side of  FIG. 9A , a series of folded sheet metals  83  is used. To define openings  38 , the plate comprises slots  85  or aligned openings  86 . Holes  88  in plate  80  enable to assemble the plate and the pipe-shaped fire dogs. 
     Finally, although pipes  36  having outlets  38  all along their height have been shown, it may be provided to form pipes  36  with openings  38  defined at desired locations only. Particularly, in the case of the variation of  FIGS. 6 to 8 , it may be provided not to define openings  38  in pipes  36  opposite openings  60 . It may also be provided not to define lateral openings in pipes  36 , but only to leave the upper end of each of pipes  36  open, the air extraction then occurring through this opening. A slight curving of this end towards the blaze may be provided. 
     Various embodiments with different variations have been described hereabove. It should be noted that those skilled in the art may combine various elements of these various embodiments and variations without showing any inventive step.