"Modular tubular element"

DESCRIPTION

Technical field of the invention

The present invention relates to a modular tubular element for duct construction.

More in detail, the present invention relates to a modular tubular element for the construction of flues. The following description will make explicit reference to this particular application without however the invention being restricted thereto.

Prior art

As is known, flues are normally composed of a series of modular tubular elements of circular section which are mutually engaged one in the other so to form a vertical conduit through which the discharge gases produced by a boiler may flow. Of course the tubular modular elements must be manufactured in material resistant to the high temperatures typical of the discharge gases exiting from the boiler, and must be appropriately structured so to facilitate the correct outflow of such gases through the flue without losses at the connections between adjacent modular tubular elements .

More in detail, according to the most recent safety regulations, the tubular elements must be manufactured in metallic material so to be able to resist both the high temperatures and the typical chemical attacks of the boiler discharge gases. Moreover they must be structured so that the coupling between the terminal ends of two consecutive modular tubular elements builds a gastight connection,

ensuring no losses due to pressure differences between the inside and outside of the flue duct up to 0.1 bar.

In the presently known flues, the safety regulations are satisfied by manufacturing modular tubular elements of predetermined length which have both opposite ends shaped such to present a helical profile groove which wraps at constant pitch around a corresponding portion of the side wall of the tubular element. In addition to that described above, the opposite endes also have different diameter. A first end has a diameter which is substantially equal to the nominal diameter of the tubular element, while a second opposite end is flared so to have a diameter which is slightly greater than the diameter of the first end. The second end of a modular tubular element can thus be engaged on the first end of an adjacent modular tubular element by superimposing its own helical profile groove on that of the first end of the adjacent modular tubular element.

In this manner it is possible to screw the first end of a tubular element in the second end of the immediately adjacent tubular element, obtaining a mechanical coupling which guarantees the necessary structural stiffness.

To ensure the gastight seal required by the current safety regulations, each tubular element of the flue is provided with an annular seal in plastic material which is positioned on its first end at the end of the side wall portion which has the helical profile groove. After that two adjacent modular tubular elements are engaged, such annular seal is flattened between the cylindrical side walls of the two modular tubular elements so to close in a gastight seal the hollow space present between such side walls and to therefore prevent the accidental escape of discharge gases at the connection between the adjacent modular tubular elements.

Unfortunately, the modular flue thus obtained has shown large seal problems over the long term, almost entirely due to the wear and the premature aging of the material which forms the annular seal. To overcome such drawback it has been proposed to use more resistant and costly plastic materials .

However, these materials, in addition of considerably increasing the production costs of the modular tubular elements, they are also subjected to a certain wear and aging over the long term, thus requiring their periodical replacement for ensuring the desired gas seal.

Summary of the invention

The problem underlying the present invention is therefore that of providing a modular tubular element for the duct, in particular flue, construction, which is reliable and can ensure gas seal over the long term and which is at the same time easy and economical to produce and to maintain, thus overcoming the drawbacks set forth with reference to the prior art.

According to the present invention, a modular tubular element is provided for duct construction comprising a circular section tubular conduit of predetermined length which is structured so to have a first male terminal portion and a second female opposite terminal portion, both portions being shaped in complementary manner to each other so that the first male terminal portion of a first modular tubular element may be engaged in the second female terminal portion of a second modular tubular element, obtaining a gastight connection between said first and second modular tubular elements; said modular tubular element being characterized in that said first male terminal portion of said circular section tubular conduit

comprises a threaded portion provided at end thereof, corresponding to a first end of the circular section tubular element, and an adjacent inner sealing portion shaped substantially in barrel form; said second female opposite terminal portion of said circular section tubular conduit comprises a substantially cylindrical portion provided at an end thereof, corresponding to a second opposite end of the circular section tubular conduit, and an adjacent inner threaded portion.

Advantageously, according to the present invention, the barrel-shaped inner sealing portion of said first male terminal portion of the circular section tubular conduit has at least one section, preferably a central section, with a diameter greater than the diameter of said adjacent threaded end portion, said at least one section being preferably of substantially cylindrical shape. Preferably, said inner sealing portion of said first male terminal portion of the circular section tubular conduit is embossed.

Advantageously, according to the present invention, said cylindrical end portion of said second opposite female terminal portion of the circular section tubular conduit is sized so to have a diameter which is greater than the diameter of the threaded end portion but slightly smaller than the diameter of said at least one section of the barrel-shaped inner sealing portion of said first male terminal portion.

Preferably, the cylindrical end portion of said second opposite female terminal portion of the circular section tubular conduit has a predetermined length so as to guarantee that, when two adjacent modular tubular elements (1) are coupled, at least a part of said cylindrical end portion overlaps said at least one section of the barrel-

shaped inner sealing portion of said first male terminal portion when the adjacent threaded inner portion is engaged with the threaded end portion of said first male terminal portion.

The present invention will now be described with reference to the attached drawings, which illustrate a not limiting embodiment thereof, wherein:

figure 1 is an exploded view of a modular flue obtained by means of modular tubular elements according to the present invention;

figure 2 illustrates a detail of figure 1, in enlarged scale and with sectional parts; while

figures 3 and 4 illustrate two consecutive steps of the coupling of two modular tubular elements illustrated in figures 1 and 2.

Detailed description

With reference to figures 1-4, numeral 1 generally indicates a modular tubular element, which has particularly advantageous use in the construction of pressure ducts and, more in particular, in the construction of flues, i.e. discharge conduits preferably but not necessarily of vertical extension, through which the discharge gases produced by a boiler, stove, fireplace etc. flow during its normal functioning.

The modular tubular element 1 is composed of a circular section tubular conduit 2 of predetermined length, which is preferably but not necessarily manufactured in metallic material (such as, for example, stainless steel) and is structured such to have a first male terminal portion 2a and a second female opposite terminal portion 2b. Both

portions 2a, 2b are shaped in complementary manner to each other so that the first male terminal portion 2a of a first modular tubular element 1 may be engaged in the second female terminal portion 2b of a second modular tubular element 1, obtaining a gastight connection between said first and second modular tubular elements 1.

More in detail, the first male terminal portion 2a of said circular section tubular conduit 2 comprises a segment 3 composed of a threaded portion 5 provided at end thereof, corresponding to a first end of the circular section tubular element 2, and an adjacent inner sealing portion 6 shaped substantially in barrel form. The second female opposite terminal portion 2b of said circular section tubular conduit 2 comprises a segment 4 composed of a substantially cylindrical portion 7 provided at an end thereof, corresponding to a second opposite end of the circular section tubular conduit 2, and an adjacent inner threaded portion 8.

In other words, segments 3, 4 are shaped in complementary manner with respect to each other such that one may be engaged in the other in a gastight connection, or more precisely, so that the segment 3 of a circular section tubular conduit 2 of a first modular tubular element 1 may be coupled with the segment 4 of an immediately adjacent circular section tubular conduit 2 of a second modular tubular element 1, thus obtaining a gastight seal capable of satisfying current safety regulations .

With reference to figures 1 and 2, the segment 3 of the circular section tubular conduit 2 has a predetermined length Ll, wherein the threaded end portion 5 has a length L2 which has a substantially cylindrical shape. The threaded end portion 5 has an external, peripheral, thread 5a, which extends till the end of the circular section

tubular conduit 2, corresponding to one end of the side wall of the modular tubular element 1, for a predetermined length L4, which is preferably but not necessarily less than the overall length L2 of the threaded end portion 5. The threaded end portion 5 has (nominal) diameter Dl preferably but not necessarily equal to the (nominal) diameter DO of the tubular element 1, i.e. of the central portion of the circular section tubular conduit 2.

The adjacent inner sealing portion 6 of the segment 3 has instead a length L3 and is shaped substantially in barrel form so to have at least one section, preferably a central section 6a, with a (nominal) diameter D2 greater than the

(nominal) diameter Dl of the adjacent threaded end portion

5 and than the (nominal) diameter DO of the modular tubular element 1. The central section 6a is preferably of substantially cylindrical shape. The adjacent inner sealing portion 6 of the segment 3 also has two side sections 6b,

6c of substantially frustoconical shape which connect the central section 6a with the remaining parts of the circular section tubular conduit 2 with smaller diameter i.e. the threaded end portion 5 and the central portion of the circular section tubular conduit 2, respectively.

In the illustrated example, the central section 6a of the inner sealing portion 6 extends for a length L5 along the inner sealing portion 6 of segment 3, which is preferably but not necessarily less than the length L4 of the thread 5a of the threaded end portion 5. While the side section 6b of the inner sealing portion 6 connecting the central section 6a with the threaded end portion 5 is shaped substantially in funnel form and has a length L6 which is preferably greater than the length L5 of the central section 6a.

The threaded end portion 5 is preferably obtained by

moulding directly on the circular section tubular conduit 2 with diameter Dl, providing a helical profile groove which wraps at constant pitch at the end of the circular section tubular conduit 2 for a length L4, while the inner sealing portion 6 is obtained by moulding directly on the corresponding segment of the circular section tubular conduit 2, providing an annular projection of length L3. In other words, an embossed inner sealing portion 6 is provided.

With reference to figures 1 and 2, segment 4 of the second female opposite terminal portion 2b of the circular section tubular conduit 2 has a predetermined length L7, while the substantially cylindrical end portion 7 has a length L8 and the adjacent inner threaded portion 8 has a length L9. The substantially cylindrical end portion 7 has a (nominal) diameter D3 which is slightly smaller than the diameter D2 of the central section 6a of the inner sealing portion 6 of segment 3. The diameter D3 of the cylindrical end portion 7 of segment 4 is also sized so to have a diameter which is greater than the diameter Dl of the threaded end portion 5 of segment 3.

The length L8 of the substantially cylindrical end portion 7 preferably satisfies the following equation: L8>= L6+ (L2- L4) . Other said, the length L8 of the substantially cylindrical end portion 7 must preferably be greater than or equal to the length L6 of the side section 6b of the inner sealing portion 6 of the segment 3 plus the difference between the length L2 of the threaded end portion 5 and the length L4 of the thread 5a of the same threaded end portion 5 of the segment 3.

In other words, the substantially cylindrical end portion 7 of a first modular tubular element 1 must have a predetermined length L8 sufficient to ensure that at least

a part thereof is superimposed on, i.e. overlaps, the central section 6a of the inner sealing portion 6 of the male terminal portion 2a of a second modular tubular element 1 when the threaded inner portion 8 of the female terminal portion 2b of the first modular tubular element 1 is engaged (screwed) with the thread 5a of the threaded end portion 5 of the male terminal portion 2a of the second modular tubular element 1.

In addition to that described above, the length L8 of the substantially cylindrical end portion 7 must be preferably but not necessarily less than the sum of the length L2 of the threaded end portion 5 and the length L6 of the side section 6b of the inner sealing portion 6 of the segment 3. Or other said, the length L8 of the substantially - cylindrical end portion 7 must preferably satisfy the following equation: L8 < L6 + L2.

The threaded inner portion 8 of segment 4 of the female terminal portion 2b has preferably a cylindrical shape with a (nominal) diameter D4, which is slighter greater than the (nominal) diameter D3 of the threaded end portion 5 of segment 3 of the male terminal portion 2a. The threaded inner portion 8 has a thread 8a which is sized so that it may be coupled with the thread 5a of the threaded end portion 5, thus to permit the coupling and locking by screwing of the segment 4 of a tubular element 1 on the segment 3 of a further, immediately adjacent, tubular element 1.

More in detail, the threaded inner portion 8 is provided with an inner thread 8a which extends towards the central portion of the circular section tubular conduit 2 for a length L9 which is preferably greater than the length L5 of the central section 6a of the inner sealing portion 6 of the segment 3. Preferably but not exclusively, such length

L9 is also greater than the length L4 of the thread portion 5a of the threaded end portion 5.

In the illustrated example, the inner thread 8a extends towards the central portion of the circular section tubular conduit 2 for a length L9 which is equal to the overall length of the threaded inner portion 8.

The substantially cylindrical end portion 7 is preferably obtained by moulding, flaring the circular section tubular conduit 2 until the diameter D3 is attained. The threaded inner portion 8 is preferably obtained by moulding directly on the corresponding part of the circular section ^' tubular conduit 2 of diameter Oi, obtaining a helical profile groove which wraps at constant pitch around the entire length L9 of the threaded inner portion 8. Such helical groove is of course sized so that it may be superimposed on the helical thread 5a present on the threaded end portion 5 of the segment 3 of the circular section tubular conduit 2.

The operation of the tubular element 1 may be easily inferred from that described and illustrated above and does not therefore require further explanation.

On the other hand, regarding the coupling between two consecutive modular tubular elements 1, i.e. the connection between the male terminal portion 2a of a first modular tubular duct 1 with the female terminal portion 2b of a second modular tubular element 1, the following is noted with reference to figures 3 and 4.

The segment 3 of a first tubular element 1 is inserted within the segment 4 of an immediately adjacent second tubular element 1, until the edge (end) 3a of the segment 3 abuts on the edge of the thread 8a of the threaded inner portion 8 of segment 4, i.e. on the border line which separates the substantially cylindrical end portion 7 from

- li ¬

the threaded inner portion 8 (figure 3) .

In this position, the edge (end) 4a of the segment 4, i.e. the edge (outer end) of the substantially cylindrical end portion 7, is arranged immediately in front of the central section 6a of the inner sealing portion 6 of the segment 3 which, as already described above, has a diameter D2 slightly greater than the diameter D3 of the substantially cylindrical end portion 7 of the segment 4.

At this point (figure 4), screwing the segment 3 of the first modular tubular element 1 in the segment 4 of the immediately adjacent modular tubular element 1, it is possible to force the edge 4a of the section 4 to pass over (overlap) the central section 6a of the inner sealing portion 6 of the segment 3, bringing the substantially cylindrical end portion 7 of the section 4 above the threaded end portion 5 of the segment 3. At the same time, the threaded inner portion 8 of the segment 4 is brought above the threaded end portion 5 of the segment 3. The above overlapping induces a plastic deformation of the substantially cylindrical end portion 7 of the immediately adjacent tubular element 1 on the central section 6a of the inner sealing portion 6 of the first modular tubular element 1.

In view of the plastic deformation of the substantially cylindrical end portion 7 of the tubular modular element 1 on the central section 6a of the inner sealing portion 6 of the adjacent modular tubular element 1, the side walls of the two corresponding circular section tubular conduits 2 remain perfectly adherent, providing a gastight connection (seal) which is able to fully satisfies the requirements in force in the current safety regulations.

The advantages resulting from the above described modular

tubular element 1 according to the present invention are many, among them it is worth citing that the modular tubular elements 1 for flue construction or, more in general, for the construction of pressure ducts, do not require any annular seal in plastic material to obtain the necessary gastight seal between adjacent modules thus improving the their reliability and at the same time reducing the production and maintenance costs with respect to the prior art modular elements.

The flue obtained by the tubular elements 1 according to the present invention is furthermore much easier and quicker to install, permitting therefore a reduction in the laying costs as well.

The invention thus conceived may be susceptible to variations and modifications, all falling within the scope of protection defined in the following claims.