CONDENSING BOILER

TECHNICAL FIELD

The present invention relates to a condensing boiler.

Specifically, the present invention relates to a condensing boiler of the type comprising a burner; a combustion chamber; and a heat exchanger including, in turn, a plurality of plates reciprocally aligned in a given direction and connected to each other to define a first circuit for the water to be heated and a second circuit for the combustion products.

BACKGROUND ART

Generally, the first circuit comprises a plurality of pipes obtained between the plates and connected parallel to each other to an inlet manifold of the water into the heat exchanger and to an outlet manifold of the water from the heat exchanger itself.

Since the pipes of the first circuit are connected parallel to each other, the speed of the water along the pipes themselves is relatively low.

Accordingly, the known condensing boilers of the above-described type display some drawbacks mainly deriving from the fact that the low speed of the water along the pipes of the first circuit may cause the water to boil at the segments of the first circuit lapped by the higher temperature combustion products and may further imply the precipitation of limescale at the

segments of the first circuit lapped by the higher temperature combustion products and, therefore, the obstruction of the pipes, a low heat exchange between the water and the combustion products, and the overheating and damaging of the plates. DISCLOSURE OF INVENTION

It is an object of the present invention to provide a condensing boiler which is free from the above- described drawbacks and which is simple and cost- effective to implement.

According to the present invention, there is provided a condensing boiler as claimed in the appended claims .

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described with reference to the accompanying drawings, which show a non-limitative embodiment thereof, in which: figure 1 is a first diagrammatic perspective view of a preferred embodiment of the condensing boiler of the present invention; figure 2 is an exploded perspective view of the condensing boiler in figure 1; figure 3 is an exploded perspective view, with parts removed for clarity, of a detail in figure 2 ; figure 4 is an exploded perspective view, with parts removed and parts enlarged for clarity, of figure 3; figure 5 is a second diagrammatic perspective view,

with parts in section, of the condensing boiler in figure 1; figure 6 is an enlargement of a detail in figure 5; and figure 7 is a diagrammatic perspective view of a variant of the condensing boiler shown in figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to figures 1 and 2, numeral 1 indicates, as a whole, a condensing boiler, which has a substantially horizontal longitudinal axis 2 and comprises a main heat exchanger 3.

The heat exchanger 3 is provided with a boxed containing body 4, which has a parallelogram-shaped cross section, and comprises a cup-shaped container 5, which is laterally delimited by one side wall 6 extending about the axis 2, is axially limited by a bottom wall 7 substantially orthogonal to the axis 2, and is axially closed by a plate 8 substantially orthogonal to the axis 2 itself. The wall 6 comprises two substantially vertical, parallel side faces 9, an inclined upper face 10, and a lower face 11 substantially parallel to the face 10 itself .

The body 4 accommodates a plurality of shaped main plates 12 therein, which have substantially the shape of the container 5, are reciprocally aligned in a direction 13 substantially parallel to the axis 2, are reciprocally connected, e.g. by welding, and are each

provided with a corresponding peripheral edge 14 , which protrudes from the corresponding plate 12 in the direction 13, extends about a part of the corresponding plate 12 itself, and partially overlaps the edge 14 of one of the adjacent plates 12.

As shown in figure 4, at least a part of the plates 12 and the plate 8 have corresponding upper holes 15, which are reciprocally aligned in the direction 13, are obtained by cutting out the corresponding plates 12, and define a combustion chamber 16 for a burner 17, which protrudes inside the chamber 16, and is provided with a plurality of spark plugs 18.

The chamber 16 has a longitudinal axis 19 parallel to and offset from the axis 2, and is axially closed at one end thereof opposite to the plate 8 by two end plates 12 (hereinafter indicated by numerals 12a and 12b) free from the holes 15, and in which the plate 12b is opposite to the plate 8.

With reference to figures 3, 4, and 5, each plate 12 defines a main first exchanging element 20 defining a part of a first feeding circuit 21 of the water to be heated with one of the adjacent plates 12, and a part of a second feeding circuit 23 of the combustion products radially exiting from the chamber 16 with the other adjacent plate 12.

Between the two elements 20 of each pair of adjacent elements 20 there are arranged two shaped secondary plates 24, each of which faces the lower

portion of a corresponding plate 12, is coupled to the corresponding plate 12 and to the other plate 24, e.g. by means of welding, is obtained from the machining scrap deriving from the cutting out of the corresponding plate 12, and defines a secondary exchanging element 25 of the circuit 21 with the other plate 24 and a part of the circuit 23 with the corresponding plate 12.

Furthermore, the plates 12, 12a, and 24 have corresponding lower holes 26, which are obtained at the lower vertexes of the plates 12, 12a, and 24, are reciprocally aligned in the direction 13, and define an inlet channel 27 of the circuit 21. The channel 27 has a longitudinal axis 28 parallel to the axis 19 and is provided with an inlet joint 29 obtained on the plate 8 to allow the water to enter into the boiler 1.

Furthermore, the plates 12, 12a, and 24 have corresponding intermediate slots 30, which are obtained between the holes 15 and 26, have substantially the shape of a circular sector, are reciprocally aligned in the direction 13, and define a collection manifold 31, which has a longitudinal axis 32 parallel to the axis 28, and hydraulically communicates with the manifold 27 by means of a plurality of pipes 33, which are reciprocally and parallelly connected to the manifolds 27, 31, and are obtained both between the lower portions of the plates 12 of the elements 20 and the plates 24 of the elements 25.

Furthermore, at the element 20 defined by the

plates 12a and 12b, the manifold 31 is connected to an outlet channel 34, which is provided with an outlet joint 35 obtained on the plate 8 to allow the water to exit from the boiler 1, and comprises a plurality of pipes 36, which are each obtained between the upper portions of the plates 12 of a corresponding element 20, and are reciprocally connected in series.

Each pipe 36 comprises a substantially circular segment 36a, which extends about the axis 19 and about the combustion chamber 16, and a segment 36b, which extends through the plates 12 of the corresponding element 20 in the direction 13, is obtained at the upper vertex of the corresponding element 20, is arranged on the opposite side of the corresponding slots 30 with respect to the corresponding holes 15, and is coaxial with a longitudinal axis 38 which is common to all segments 36b and parallel to the axis 32.

Each segment 36b is provided with a baffle member 39, which is accommodated inside the segment 36b itself, and is selectively positionable either in a first operating position, in which all the water fed to the inlet of the segment 36b is firstly conveyed along the segment 36a and then to the outlet of the segment 36b itself, or in a second operating position, in which the segment 36a and the segment 36b are reciprocally and parallelly connected and the water fed to the inlet of the segment 36b is conveyed in part along the segment 36a and in part directly to the outlet of the segment

36b itself.

In either case, the pipes 36 are always reciprocally connected in series and all the water circulating in the exchanger 3 is fed along the pipes 36 of all the elements 20, both when the members 39 are arranged in their first operating positions, and when the members 39 are arranged in their second operating positions .

Therefore, in use, the water to be heated (diagrammatically shown by the dark arrows in figure 4) enters the exchanger 3 through the inlet joint 29, is conveyed along the inlet channel 27, is distributed along the pipes 33, is discharged into the collection channel 31, is conveyed along each pipe 36 of the outlet channel 34 from the element 20 defined by the plates 12a and 12b, and is finally exhausted outside the exchanger 3 through the outlet joint 35.

The circuit 23 of the combustion products (diagrammatically shown by the light arrows in figure 4) includes a plurality of pipes 40, which are reciprocally and parallelly connected to the combustion chamber 16, alternate with the segments 36a of the- pipes 36 and with the pipes 33, and are laterally limited by the peripheral edges 14 of the plates 12 so as to extend downwards from the chamber 16 firstly between the elements 20 and about the collection manifold 31, then between each element 20 and the corresponding element 25, and finally about the inlet channel 27.

At the outlet of the pipes 40, the combustion products are conveyed upwards along an outlet pipe 41, which extends upwards between the external surface of the exchanger 3 and the container 5, is substantially tangent to the plates 12 and to the container 5, and allows to exhaust the combustion products outside by means of an outlet joint 42 obtained on the upper face 10 of the side wall 6 of the container 5 itself .

As regards the above, it is worth specifying that: the axes 19, 28, 32, and 38 are reciprocally aligned and coplanar with a major symmetry plane P of the exchanger 3 ; the pipes 33, the segments 36a of the pipes 36, and the pipes 40 are substantially symmetric with respect to the plane P; since the circuit 21 extends upwards from the inlet channel 27 and the circuit 23 extends downwards from the combustion chamber 16, the paths of the water to be heated and of the combustion products are substantially counter flowing and thus promote the heat exchange between the water to be heated and the combustion products themse1ves ; the inclination of the upper face 10 of the container 5 allows to exhaust outside substantially all the combustion products by means of the outlet joint 42; the cross section of the pipes 40 decreases in a feeding direction of the combustion products along the pipes 40 themselves so as to at least partially

' compensate for the reduction of volume of the combustion products deriving from the decrease of their temperature ; the heat exchanging surface increases in a feeding direction of the combustion products along the pipes 40 due to the concurrent presence of the elements 20 and 25; the connection in series of the pipes 36 guarantees a relatively high speed of the water along the outlet manifold 34, thus preventing the water from boiling at the manifold 34 itself, i.e. at the portion of the circuit 21 lapped by the higher temperature combustion products; and the position of the combustion chamber 16 with respect to the longitudinal axis 2 of the boiler 1 allows the combustion products to cool mainly underneath the burner 17, thus preventing condensate from falling onto the flame of the burner 17 itself.

Furthermore, the container 5 and the pipe 41 of the circuit 23 define a part of a secondary heat exchanger

44 for heating the combustion-promoting air fed to the burner 17 by means of the combustion products exiting from the exchanger 3.

Furthermore, the exchanger 44 includes a cup-shaped container 45, which has a parallelogram-shaped cross section, is laterally limited by a side wall 46 extending about the side wall 6 of the container 5, is axially limited by a bottom wall 47 substantially

orthogonal to the axis 2 , is axially closed by the plate 8, and has a length, measured parallelly to the direction 13 , greater than the length of the container 5, also measured parallelly to direction 13. The wall 46 includes two substantially vertical side faces 48 parallel to each other and to the faces 9, an upper inclined face 49 parallel to the face 10, and a lower face 50 parallel to the face 11, and is provided with an inlet joint 51, which allows the combustion- promoting air into the exchanger 44, and is obtained on the face 49 so as to be coaxial and concentric to the outlet joint 42 of the circuit 23.

With reference to figures 2 and 6, the exchanger 44 further comprises an intermediate plate 52, which is mounted between the walls 7 and 47 orthogonally to the direction 13, and defines, along with the containers 5 and 45, a combustion-promoting air suction pipe 53 adjacent to the combustion product outlet pipe 41.

The pipe 53 defines a part of a pneumatic feeding circuit 54 further including a mixing pipe 55 (figures 1 and 2) , which is connected to the pipe 53 by means of the interposition of a suction fan 56, and feeds the burner 17 with a mixture consisting of the combustion- promoting air aspirated by the fan 56 along the pipe 53 and of a combustible gas fed in a known manner to the pipe 55 itself.

As regards the above, it is worth specifying that: the inclination of the face 11 allows to collect,

at the lower part of the container 5, substantially all the condensate generated by the cooling of the combustion products on the plates 12 , 24 and on the walls 6 and 7 of the container 5, and to exhaust such a condensate outside the boiler 1 by means of an exhaust pipe 57 protruding downwards from the face 11 through the face 50; and the intermediate plate 52 allows to establish a correct heat exchange between the combustion-promoting air of the pipe 53 and the combustion products of the pipe 41 regardless of the length of the container 45 and of the number of plates 12, 24 of the exchanger 3. According to some variants (not shown) : the outlet joint 42 of the combustion products from the container 5 and the inlet joint 51 of the combustion-promoting air into the container 45 are parallel and reciprocally side-by-side; the intermediate wall 52 is eliminated and the container 45 has a length, measured parallelly to the direction 13, approximating by excess the length of the container 5, also measured parallelly to the direction

13 ; and the side wall 6 and/or the bottom wall 7 of the container 5 may be eliminated and replaced by corrugated walls adapted to increase the heat exchanging surface of the exchanger 44.

According to the variant shown in figure 7, the secondary heat exchanger 44 and the containers 5 and 45

are eliminated and replaced by a container 58, which defines the exhaust pipe 41, and is provided with the outlet joint 42 and with the condensate exhaust pipe 57, and the combustion-promoting air inlet joint 51 is made directly on the fan 56.