Patent Description:
"Heat exchange cell" means a unit comprising at least one heat exchanger mounted in a respective containment casing and configured to actuate a heat exchange between a first heat-transfer fluid circulating inside the exchanger, and a second heat-transfer fluid circulating inside the containment casing.

For example, the heat exchanger is of the type comprising a duct wound in a spiral on a plurality of overlapping coils adapted to be traversed by the first heat-transfer fluid which is then circulated in the heating system, and in which such duct forms a central space in which a combustion occurs, adapted to heat the second heat-transfer fluid.

In the heating boiler industry, the employment of a heat exchange cell comprising a containment casing and a heat exchanger mounted thereinside is well known.

The use of an exchanger comprising a duct, or tube, wound in a spiral according to a plurality of overlapping coils so as to form an internal or central space adapted to host a combustion is also known.

Such exchanger has a front end coil facing towards the outside of the casing and an opposite back end coil, which, in use, faces towards the inside of the casing. The front end coil, therefore, has a front surface which is not flat but helical.

During the assembly, the exchanger is inserted into the casing, which is closed by means of a closing flange having a central opening aligned with the internal space so as to allow access to the exchanger for maintenance operations.

Some embodiments are known in which the flange comprises elements made from a molded sheet metal, assembled to one another so as to take advantage of the thermal inertia of the sheet metal which is lower with respect to that of an element obtained by die-casting, by virtue of the reduced thickness thereof.

A known cell further comprises a closing door adapted to be mounted to the casing, in particular to the flange, to close the opening while in use.

The door comprises a disc made from refractory insulating material, centrally fastened with respect thereto. Such disc is configured to be arranged, in use, into the opening of the flange near the radially internal edge of the flange.

A heat exchange cell is known having a flange having a main body made from a sheet metal, having a radially internal edge arranged around the flange opening, a radially external edge fastened to the casing, and an intermediate flange portion which connects them to one another, wherein the intermediate portion is flat and orthogonal to a flange axis.

The radially internal edge is flat and lying on a plane orthogonal to the flange axis.

To allow the door to close the opening, it has a face adapted to be facing towards, and in abutment against, the radially internal edge of the flange, also.

To obtain a seal between the flange and the door, the aforesaid embodiment according to the background art requires the use of at least one annular gasket which remains axially interposed, and axially pressed, between the flange and the door.

Such gasket, according to the background art, may not be interposed between the insulating disc and the flange, since the planarity of the radially internal edge and the orthogonality thereof with respect to the flange opening axis do not allow the gasket to be interposed radially between the edge and the insulating disc, but only axially between the flange and the door.

Thereby, a high amount of heat is transmitted from the combustion area to the radially internal edge of the flange, since no gasket may be interposed therein.

On the contrary, according to the background art, the gasket may only be arranged in a position more external radially with respect to the radially internal edge. Such a solution, therefore, does not allow the radially internal end of the internal edge of the flange to be protected from the high temperatures reached by the combustion. Such edge, in fact, remains directly exposed towards the combustion chamber.

The at least one gasket is arranged near such internal edge, and, therefore, in an area with high thermal stress.

This produces a rapid deterioration of the gasket itself.

The need is therefore felt to provide a heat exchange cell which allows to thermally insulate the door from the combustion area in a manner more efficient with respect to the background art. At the same time, the need is felt to further protect both the thermal barrier and the fume seal from the high thermal stresses.

For the cell to properly operate, a fume seal shall be provided between the front end coil and the internal surface of the flange.

To this end, the internal surface of the flange shall adhere to the front end coil.

However, in an exchanger wound according to a plurality of helical coils, also the front end coil is helical, thus offering a surface facing on the front towards the flange which is not flat but is shaped according to a helicoid.

For the surface of the flange facing towards such surface of the front end coil to provide a seal therewith, it shall adhere thereto.

An attempt is known to solve this problem by means of an additional element shaped as a helicoid, separated from the flange and fastened to the flange in a manner spaced therefrom.

Such additional element allows to provide a seal between the end coil and the additional element itself, but is not free from disadvantages.

For example, this background art with additional element requires to provide a remarkably complicated flange structure, in which the additional element is manufactured separately and subsequently fastened to the flange. This directly translates into high production costs. However, worse than that, this increases the mass of the flange-element assembly, increasing the thermal inertia thereof, which negatively affects the thermal efficiency of the cell. In fact, since the additional element is separated from the flange, it does not contribute to the optimal cooling of the end coil, but only provides the fluid seal between the combustion area and the peripheral space arranged externally to the exchanger.

Another attempt, known to make the surface of the front end coil adhere to the flange, is to deform the end coil by modifying the straight section along the development axis of the coil so as to provide a flat shape to a wall portion of the coil facing towards, and in contact with, the flat flange.

The variation of the straight section of the front end coil negatively affects the flow of the fluid passing through it, moving the flow behavior away from the laminar motion. In fact, due to the section variation, the fluid is subjected to variations in speed and pressure along the path thereof, which may lead to turbulent motion, load loss, or cavitation. These effects result in a reduction in the thermal efficiency of the cell. Furthermore, the execution of an end coil deformation step is an indisputable additional production cost.

The need is therefore felt to improve the thermal efficiency of a heat exchange cell having a flange made from a sheet metal, limiting the production costs of the cell itself.

In particular, none of these known solutions proposes a heat exchange cell having a flange made from a sheet metal which allows to satisfy all the aforesaid requirements at the same time, and, specifically, to improve the thermal insulation of the door with respect to that of the combustion area, protecting both the thermal barrier and the fume seal from the high thermal stresses, thus extending the useful life thereof, and to improve the thermal efficiency of the cell, while still minimizing production costs.

A heat exchange cell according to the preamble of claim <NUM> is known from <CIT>.

It is an object of the present invention to devise and provide a heat exchange cell which allows to satisfy the aforesaid requirements and to obviate at least partially the drawbacks complained here above with reference to the background art.

In particular, it is an object of the present invention to provide a heat exchange cell having a flange made from a sheet metal which allows to thermally insulate the door from the combustion area in a manner more efficient with respect to the background art.

It is also an object of the present invention to provide a heat exchange cell which allows to further protect both the thermal barrier and the fume seal from the high thermal stresses originating from the combustion area.

It is another object of the present invention to provide a heat exchange cell capable of improving the thermal efficiency of the cell itself.

It is a further object of the present invention to provide a heat exchange cell capable of limiting the production costs of the cell itself.

It is also an object of the present invention to provide a heat exchange cell having a flange made from a sheet metal which allows to satisfy all the aforesaid requirements at the same time, and, specifically, to improve the thermal insulation of the door with respect to that of the combustion area, protecting both the thermal barrier and the fume seal from the high thermal stresses, thus extending the useful life thereof, and to improve the thermal efficiency of the cell, while still minimizing production costs.

These and further objects and advantages are achieved by means of a heat exchange cell in accordance with claim <NUM>.

Further objects, solutions and advantages are shown in the embodiments described below and claimed in the dependent claims.

The invention will be illustrated below with the description of some embodiments thereof, given by way of explanation and not by way of limitation, with reference to the accompanying drawings in which:.

With reference to the Figures, a heat exchange cell for a heating boiler in accordance with the invention is generally indicated with reference numeral <NUM>.

The heat exchange cell <NUM> comprises a casing <NUM> comprising a side wall <NUM> enclosing an internal space, said side wall <NUM> having an open front end <NUM> surrounded by an annular edge <NUM>' of the front end of the casing.

The cell further comprises an annular closing flange <NUM> made from a sheet metal having a flange through opening <NUM> to allow the access to the inside of the casing <NUM>.

The closing flange <NUM> defines a radially internal flange edge <NUM> surrounding the through opening <NUM>, a radially external flange edge <NUM> arranged around the radially internal edge <NUM>, an intermediate flange portion <NUM> connecting the radially external flange edge <NUM> and the radially internal flange edge <NUM> to one another.

The radially internal edge <NUM> has an annular shape, preferably circular.

The radially external edge <NUM> has an annular shape, preferably circular or polygonal, preferably with rounded vertices.

The radially external flange edge <NUM> is connected to the side wall <NUM> of the casing along the annular edge <NUM>' of the front end of the casing.

In accordance with an embodiment, the cell comprises a door <NUM> configured to be removably fastened to said closing flange <NUM> to close the through opening <NUM>, the door <NUM> comprising an insulating disc <NUM> comprising a refractory insulating material.

The door <NUM> may comprise a door plate <NUM>, preferably made of metal, on which the insulating disc <NUM> is fastened.

The insulating disc <NUM> is delimited by a side disc surface <NUM>.

The radially internal edge <NUM> defines a radially internal surface <NUM>, a radially external surface <NUM> arranged around the radially internal surface <NUM>, a front edge surface <NUM> connecting said radially internal surface <NUM> and said radially external surface <NUM> to one another.

In accordance with an embodiment, the radially internal surface <NUM> is configured to surround and to externally embrace the side disc surface <NUM> and to allow an axial sliding of said disc <NUM> with respect to said radially internal surface <NUM>.

The front edge surface <NUM> lies on a lying plane PA.

Such lying plane PA defines an axial direction A orthogonal to the lying plane PA and a radial direction R orthogonal to the axial direction A.

The axial direction A is arranged passing through the opening <NUM>.

The radially internal surface <NUM> extends parallel to the axial direction A in a manner protruding towards the outside of the cell <NUM> with respect to said intermediate flange portion <NUM>.

In other words, the radially internal edge <NUM> is shaped as a collar extending in the axial direction A towards the outside of the cell <NUM>.

Again in other words, the radially internal edge <NUM> has a tubular or a sleeve shape, with an axis arranged according to the axial direction A, and defined by the radially internal surface <NUM> and by the radially external surface <NUM>, and axially ending towards the outside with the front edge surface <NUM>.

In accordance with an embodiment, the radially internal surface <NUM> of the radially internal edge <NUM> and the side surface <NUM> of the insulating disc <NUM> are complementary to one another and radially arranged, in use, at a minimum distance from one another when the door <NUM> is mounted on the flange <NUM>.

In accordance with an embodiment, the cross-section orthogonal with respect to the axial direction A of the radially internal surface <NUM> is constant along the axial direction A.

In accordance with an embodiment, the radially internal surface <NUM> is substantially cylindrical, or prismatic, with a central axis arranged according to the axial direction A. Preferably, also the side surface <NUM> of the insulating disc <NUM> is substantially cylindrical, or prismatic, with the central axis arranged according to the axial direction A.

In accordance with an embodiment, the radially internal surface <NUM> and the radially external surface <NUM> are defined by two respective sheet metal portions, folded with one another in a superimposed double layer.

Such two sheet metal portions are, for example, cylindrical.

In accordance with another embodiment, the radially internal surface <NUM> and the radially external surface <NUM> are defined by two opposite faces of a single sheet metal portion.

In accordance with an embodiment, the radially external surface <NUM> surrounds the radially internal surface <NUM> and is parallel to the radially internal surface <NUM>.

In accordance with an embodiment, as shown, for example, in <FIG>, the cell <NUM> comprises a thermal barrier device <NUM> and a fume seal device <NUM>, separate from one another and interposed between the closing flange <NUM> and the door <NUM> along the radially internal edge <NUM>.

The presence of two distinct devices, respectively, a thermal barrier and a seal device, allows to optimize the specific features required for both.

In accordance with some embodiments, shown in <FIG> and <FIG>, the thermal barrier device <NUM> is interposed in the axial direction A between the front edge surface <NUM> and the door <NUM>.

In other words, the thermal barrier device is arranged at an external end of the radially internal edge, opposite to an end thereof facing towards the combustion area. Since the radially internal surface embraces the side surface of the insulating disc, the latter partially protects it from thermal stress. By virtue of this arrangement, the temperature of the radially internal edge, at the axially external end thereof, is lower than the temperature thereof at the axially internal end thereof. Consequently, the thermal barrier device <NUM> is partially protected by means of the insulating disc <NUM>.

In accordance with an embodiment, for example, shown in <FIG>, the thermal barrier device <NUM> comprises, or is formed by, an annular peripheral protrusion <NUM> of the disc <NUM>, protruding in the radial direction R from the side surface <NUM> of said insulating disc <NUM>.

Such annular protrusion <NUM>, may be made in one piece with the insulating disc <NUM>.

The annular peripheral protrusion <NUM> forms an abutment surface <NUM> lying on a plane orthogonal to the axial direction A and configured to axially adhere to the front edge surface <NUM> of the closing flange <NUM>.

Thereby, the insulating disc <NUM> itself operates as a thermal barrier, allowing to avoid the use of any other thermal barrier device.

As shown in <FIG> and <FIG> themselves, the fume seal device <NUM> may be interposed in the radial direction R between the radially external surface <NUM> of the radially internal edge of the closing flange and a peripheral radial seal edge <NUM> of said door <NUM>.

In other words, the fume seal device <NUM> is received by and/or fastened to the radially external surface <NUM> of the radially internal edge of the closing flange.

The feature of the radially internal surface <NUM> of embracing the side surface of the insulating disc <NUM> is also particularly advantageous so as protect the fume seal device from the high temperatures. In fact, the disc <NUM>, whose side surface <NUM> is at a minimum distance from the radially internal surface <NUM>, also protects the radially external surface <NUM> of the radially internal flange edge <NUM> on which the fume seal device <NUM> is mounted, from the high temperature.

In accordance with another embodiment, shown for example in <FIG>, the thermal barrier device <NUM> is interposed in the radial direction R between the radially internal surface <NUM> of the closing flange <NUM> and the door <NUM>.

Thereby, such thermal barrier device <NUM> is arranged axially upstream of the fume seal device <NUM>.

The fume seal device <NUM> may be interposed, for example, in the axial direction A between the front edge surface <NUM> and the door <NUM>.

Also in accordance with this embodiment, the feature of the radially internal surface <NUM> of embracing the side surface of the insulating disc <NUM> is also particularly advantageous so as protect the fume seal device from the high temperatures. In fact, the insulating disc <NUM>, whose side surface <NUM> is at a minimum distance from the radially internal surface <NUM>, also protects the radially external surface <NUM> of the radially internal flange edge <NUM> on which the fume seal device <NUM> is mounted, from the high temperature.

In accordance with an embodiment, the thermal barrier device <NUM> comprises a gasket <NUM>, selected among a ceramic fiber cord gasket, or a glass fiber cord gasket, or a graphite gasket.

In accordance with an embodiment, the fume seal device <NUM> comprises a gasket <NUM> selected between a rubber gasket or a silicone gasket.

The cell <NUM> comprises a heat exchanger <NUM> mounted inside the casing <NUM>.

The exchanger <NUM> is of the type comprising at least one tubular duct <NUM> helically wound about a coincident helix axis arranged along the axial direction A according to a plurality of coils ending with a front end helical coil <NUM> facing towards said closing flange <NUM>.

The intermediate annular flange portion <NUM> is shaped so as to adhere with continuity to the front end helical coil <NUM>.

Thereby, the flange <NUM>, and in particular the intermediate flange portion <NUM>, has a double function: facilitating the fume seal between the flange and the front end coil <NUM> of the exchanger <NUM>, and cooling down the intermediate flange portion <NUM> by means of the contact with the front end coil <NUM>.

In fact, such front end coil <NUM> is placed at the outlet of the exchanger and is traversed by a heated fluid, preferably water, which is then fed into the heating system.

Such heated fluid which traverses the front end coil <NUM> has a temperature of about <NUM>-<NUM>, which is much lower with respect to that of the central space of the exchanger in which the combustion occurs and which the door faces, which has a temperature of about <NUM>-<NUM>.

Therefore, the adherence of the intermediate flange portion to the front end coil <NUM> allows to reduce the flange temperature from <NUM>-<NUM> to <NUM>-<NUM>, thereby protecting the thermal barrier device and the fume seal device from the high temperatures.

The intermediate annular flange portion <NUM> is shaped according to a single helicoid ring joined at the ends thereof by means of a step portion <NUM>. <FIG> shows in cross-section an example of such step portion.

The axis of the helicoid is preferably arranged in the axial direction A, preferably coincident with the central axis of the casing C-C.

Such helicoid ring ends with a first end <NUM>' in a position axially more external to the cell, and with a second end <NUM>" axially more internal to the cell, in which such first end <NUM>' and second end <NUM>" are connected to one another by the step portion <NUM>, preferably in a radiused manner.

In accordance with an embodiment, the tubular duct <NUM> has a constant cross-section along the extension thereof, in which such cross-section is flattened and has opposite upper <NUM> and lower sides <NUM> of the cross-section, evaluated according to the axial direction, substantially straight.

In such case, the intermediate annular flange portion <NUM> is shaped as a flat helicoid.

In accordance with an embodiment, for example, shown in <FIG>, the diameter of the opening of the flange D1 is substantially equal to the internal diameter D2 of the exchanger.

In accordance with an embodiment, for example, as shown in <FIG>, the closing flange <NUM> comprises axial protrusions <NUM> extending from the radially internal edge <NUM> towards the inside of the cell <NUM>, in which such axial protrusions <NUM> form a centering of the exchanger <NUM> with respect to the closing flange <NUM>.

In accordance with an embodiment, for example shown in <FIG>, the closing flange <NUM> comprises at least one flat portion <NUM> which preferably lies on a plane orthogonal to the axial direction A.

In accordance with an embodiment, the at least one flat portion extends from the radially external edge <NUM> towards the radially internal edge <NUM>.

Each of such flat portions <NUM> is adapted to support a respective fastening pin <NUM> to fasten the door <NUM> to the closing flange <NUM>, arranged according to the axial direction A.

In accordance with an embodiment, the cell <NUM> comprises removable fastening means <NUM> to fasten the door <NUM> to the closing flange <NUM>.

The removable fastening means <NUM> comprise at least one aforesaid fastening pin <NUM>, fastened to the closing flange <NUM> at the at least one flat portion <NUM>, and arranged with the axis thereof in the axial direction A, and protruding from the closing flange <NUM> towards the outside of the cell <NUM>, and at least one corresponding through hole <NUM> made in the door <NUM> to slidingly receive the fastening pin <NUM> to perform the assembly of said door <NUM> to the flange <NUM>.

In accordance with an embodiment, the intermediate flange portion <NUM> comprises at least one annular channel <NUM> internally facing the cell <NUM>, adapted to receive a sealing material in a manner interposed between the intermediate flange portion <NUM> and the end helical coil <NUM> of the exchanger.

In accordance with an embodiment, the cell <NUM> comprises a sealing material interposed between the intermediate flange portion <NUM> and the end helical coil <NUM> of the exchanger, so as to ensure the seal between the intermediate flange portion <NUM> and the end helical coil <NUM> of the exchanger.

Such sealing material is preferably arranged in the aforesaid at least one annular channel <NUM>.

In accordance with an embodiment, the closing flange <NUM> comprises an orientation and anti-rotation protrusion <NUM> adapted to engage in a corresponding seat <NUM> made in the casing <NUM> to correctly orient the closing flange <NUM> with respect to the casing <NUM>.

In accordance with an embodiment, the radially external edge <NUM> of the closing flange <NUM> is fastened to the second side wall end <NUM> of the casing by means of the folding of a peripheral portion <NUM>' of said radially external edge <NUM> around an annular edge <NUM>' of the second side wall end <NUM> of the casing <NUM>.

In accordance with an embodiment, the radially external edge of the flange <NUM> lies on a plane parallel to the lying plane PA of the front edge surface <NUM>.

In accordance with an embodiment, the radially external edge <NUM> is circular and concentric, or coaxial, with respect to the radially internal edge <NUM>.

In accordance with an embodiment, the casing <NUM> comprises two half-casings <NUM>, <NUM> which may be assembled together to form said casing <NUM> by converging them along a radial direction R.

In accordance with an embodiment, the two half-casings <NUM>, <NUM> may be separated from each other by means of a separation plane parallel to the axial direction A, or comprising the axial direction A.

In accordance with an embodiment, the side wall <NUM> is substantially cylindrical with the central axis of the casing C-C arranged parallel to the axial direction A, and the casing <NUM> comprises a back wall which closes a back end of the side wall <NUM>.

In accordance with an embodiment, the casing <NUM> is made from plastic material.

In accordance with an embodiment, the casing <NUM>, the exchanger <NUM>, the flange <NUM>, the radially internal surface <NUM>, the door <NUM> and the disc <NUM> are all coaxial to one another with an axis coincident with the central axis of the casing C-C of the side wall <NUM>.

The flange <NUM> is entirely formed in one piece from a single piece of sheet metal by plastic deformation.

Thereby, a plurality of advantages is obtained, among which those described below.

For example, the closing flange made from a single sheet metal molded by plastic deformation, or deep-drawn, allows to avoid a large number of manufacturing and assembly operations of different elements. Although, the economic advantage is not the only one.

In fact, making the radially internal edge <NUM> and the intermediate flange portion <NUM> as a single piece allows to easily obtain a structural continuity therebetween, avoiding areas of internal stresses which would derive from a weld. Among other things, such a flange allows to withstand variations in the temperatures involved, which, in the case of different pieces assembled together, would lead to different thermal expansions, and therefore, to greater mechanical stresses between such pieces.

Similarly, the feature according to which all parts of the flange are made in one piece from a single starting sheet metal allows the flange to perform a plurality of functions without having to add further components thereto.

In fact, the radially internal surface <NUM> contributes to the thermal insulation of the door by cooperating with the side surface <NUM> of the insulating disc <NUM> and may support a radial thermal barrier device <NUM>, the radially external surface <NUM> may house a fume seal device, or gasket, in a manner protecting it from heat, the front edge surface <NUM> may cooperate to form a thermal barrier <NUM> or a fume seal <NUM>.

Furthermore, the intermediate flange portion <NUM> may adhere to the front end coil <NUM> of the exchanger <NUM> to cool down the flange <NUM>.

The radially external edge <NUM>, made from a folded sheet metal, facilitates the non-removable assembly of the flange to the side wall of the casing, simply by means of a plastic rolling deformation step.

The flange <NUM> entirely formed in one piece from a single piece of sheet metal by plastic deformation, allows to obtain, exclusively by means of plastic deformation and with a reduced number of moldings, all the following portions of the flange: radially internal edge <NUM> and radially external edge <NUM>, intermediate portion <NUM> shaped as a helicoid, the flat portions <NUM>, the axial protrusions <NUM>, between which a total structural continuity is ensured.

According to another aspect not falling within the scope of the present invention, the aforesaid objects and advantages are satisfied by a door <NUM> for a heat exchange cell <NUM> as described above.

The aforesaid heat exchange cell <NUM> comprises a casing <NUM> comprising a side wall <NUM> enclosing an internal space, said side wall <NUM> having an open front end <NUM>.

An annular closing flange <NUM> made from a sheet metal, fastened to the side wall <NUM> to close the open front end <NUM>, is associated with the casing <NUM>.

The closing flange <NUM> has a flange through opening <NUM> surrounded by a radially internal flange edge <NUM> of a tubular shape, protruding towards the outside of said cell <NUM>.

The door <NUM> comprises an insulating disc <NUM> comprising a refractory material.

The insulating disc <NUM> defines a door axial direction AP and a door radial direction AR with respect to said insulating disc <NUM>.

The insulating disc <NUM> is laterally delimited by a closed side disc surface <NUM>.

The door <NUM> further comprises a door plate <NUM> on which the disc <NUM> is fastened and defines a substantially flat door coupling surface <NUM> extending along a closed contour around the side disc surface <NUM>.

The door coupling surface <NUM> is arranged orthogonal to the side disc surface <NUM>.

The door comprises a thermal barrier device <NUM> and a fume seal device <NUM>, in which at least one between the thermal barrier device <NUM> and the fume seal device <NUM> is arranged so as to cooperate with the door according to the radial direction AR.

In accordance with an embodiment, the thermal barrier device <NUM> is arranged to cooperate with said door <NUM> in the door radial direction AR, and the fume seal device <NUM> is arranged to cooperate with the door <NUM> in the door axial direction AR. For example, <FIG> and <FIG> show such embodiment.

In accordance with an embodiment, the thermal barrier device <NUM> comprises an annular thermal gasket <NUM> housed in a radial slot which enters into the door from the side surface <NUM> of the disc in the door radial direction AR, and wherein said fume seal device <NUM> comprises an annular seal gasket <NUM> housed in an axial slot which enters into the door plate <NUM> in the door axial direction AR.

In accordance with an embodiment, the thermal barrier device <NUM> is arranged to cooperate with said door <NUM> in the door axial direction AR, and said fume seal device <NUM> is arranged to cooperate with said door <NUM> in the door radial direction AR. For example, <FIG>, <FIG>, <FIG> show such embodiments.

In accordance with an embodiment, the thermal barrier device <NUM> is formed by an annular protrusion <NUM>, radially protruding towards the outside from said side surface <NUM> of the insulating disc <NUM>, and wherein said fume seal device <NUM> comprises a seal gasket adapted to act radially on said door in the door radial direction AR against an annular edge <NUM> axially protruding with respect to said door coupling surface <NUM>.

In accordance with an embodiment, the thermal barrier device <NUM> is formed by an annular protrusion <NUM> radially protruding towards the outside from said side surface <NUM> of the insulating disc <NUM>, and in which the fume seal device <NUM> is housed in an annular slot which enters into the door plate <NUM> in the door radial direction AR.

In accordance with an embodiment, the thermal barrier device <NUM> comprises a thermal gasket <NUM> housed in an axial slot which enters into the door plate <NUM> in the door axial direction AR, and in which said fume seal device <NUM> comprises a seal gasket adapted to act radially on said door in the door radial direction AR against an annular edge <NUM> axially protruding with respect to said door coupling surface <NUM>.

In accordance with an embodiment, said thermal barrier device <NUM> and said fume seal device <NUM> are both arranged so as to cooperate with said door in the door radial direction AR. <FIG> show this embodiment.

In accordance with an embodiment, the thermal barrier device is formed by the side wall <NUM> of the disc <NUM> when placed at a minimum distance from the radially internal flange edge <NUM>, and in which the fume seal device <NUM> comprises a fume seal gasket <NUM> adapted to act radially on said door in the door radial direction AR against an annular edge <NUM> axially protruding with respect to said door coupling surface <NUM>.

In accordance with an embodiment, the thermal barrier <NUM> comprises an annular thermal gasket <NUM> housed in a radial slot which enters into the door from the side surface <NUM> of the disc in the door radial direction AR, and in which the fume seal device <NUM> comprises a fume seal gasket <NUM> adapted to act radially on said door in the door radial direction AR against an annular edge <NUM> axially protruding with respect to said door coupling surface <NUM>.

In accordance with an embodiment, the thermal barrier device <NUM> comprises a thermal gasket <NUM>, selected among a ceramic fiber cord gasket, or a glass fiber cord gasket, or a graphite gasket.

An expert, to satisfy contingent needs, may modify, adapt and replace elements of the embodiments of the device described above with other functionally equivalent, without departing from the scope of the following claims. Each of the features described as belonging to a possible embodiment may be achieved independently from the other embodiments described.

Claim 1:
A heat exchange cell (<NUM>) for a heating boiler, comprising:
- a casing (<NUM>) comprising a side wall (<NUM>) enclosing an internal space, said side wall (<NUM>) having an open front end (<NUM>) surrounded by an annular edge (<NUM>') of the front end of the casing,
- an annular closing flange (<NUM>) made from a sheet metal having a flange through opening (<NUM>) to allow the access to the inside of the casing (<NUM>), said closing flange (<NUM>) defining a radially internal flange edge (<NUM>) surrounding said through opening (<NUM>), a radially external flange edge (<NUM>) arranged around said radially internal edge (<NUM>), an intermediate annular flange portion (<NUM>) connecting the radially external flange edge (<NUM>) and the radially internal flange edge (<NUM>) to one another, said radially external flange edge (<NUM>) being connected to said side wall (<NUM>) of the casing along said annular edge (<NUM>') of the front end of the casing,
- a heat exchanger (<NUM>) mounted inside the casing (<NUM>), said exchanger (<NUM>) comprising at least one tubular duct (<NUM>) helically wound about a helix axis arranged along a axial direction (A), according to a plurality of coils, said plurality of coils ending with a front end helical coil (<NUM>) facing towards said closing flange (<NUM>);
- wherein said intermediate annular flange portion (<NUM>) is shaped so as to adhere with continuity to said front end helical coil (<NUM>), and
- wherein said flange (<NUM>) is entirely formed in one piece from a single piece of sheet metal by plastic deformation;
- wherein the intermediate annular flange portion (<NUM>) is in direct contact with the front end coil (<NUM>), and
characterized in that said intermediate annular flange portion (<NUM>) is shaped according to a single helicoid ring joined at the ends thereof by means of a step portion (<NUM>).