IT202100013397A1 - Method for making double-walled flue elements - Google Patents

Description

DESCRIPTION

Field of application

The present invention refers to the sector of double-walled flues.

Known art

A double wall chimney? essentially formed by two coaxial pipes (also called pipes), respectively an internal pipe and an external pipe, separated by a cavity. The internal pipe (or internal barrel)? designed to contain the fumes to be evacuated; the external pipe (or external barrel) serves to define the interspace which acts as an insulating chamber. The presence of said insulating chamber allows to operate in safety with fumes at high temperatures, for example higher than 200°C. The size of the room, that is? the distance between the walls of the two pipes, ? generally by a few millimeters, for example about 10 mm.

Double wall flues are well known; their realization for? poses some technological problems that are not yet fully resolved. In particular, a problem encountered in making double-walled barrels consists in stably fixing the inner barrel to the outer barrel while maintaining the desired coaxiality. A deviation from coaxiality? would create a region of insufficient width of the insulating gap, cio? with the outer barrel too close to the inner barrel, reducing or nullifying the thermal insulation function.

Various methods are known for industrially manufacturing double-walled barrels, but all of them have contraindications or drawbacks. A first method involves punching the outer barrel inwards, creating a sort of ?boss? of the distance necessary to stably fix the two rods together. Another method involves creating a circular depression (rib) inward in the outer barrel to make it converge at a fixed point on the inner barrel, so as to create a line of contact between the two barrels where they can be fixed by welding or mechanically. Yet another method involves inserting permanent spacers between the two barrels, i.e.? intended to remain in place, with the function of keeping the two pipes concentric and linked together. Said spacers can be made of various metallic or plastic materials.

Methods that involve punching or deforming the outer barrel require specially created molds and machines and a relatively long processing time; consequently they imply a certain manufacturing cost which one would like to reduce. Furthermore, these methods are difficult to apply when the elements to be assembled are not straight, for example they have curves, T-shaped deviations or the like.

The use of spacers permanently inserted between the two flues has the disadvantage of introducing additional elements, and therefore an additional cost, especially for flues of considerable length. Furthermore, the spacers can represent a weak point in the flue, especially if they are not metallic. For example ? known to use non-metallic rubber spacers, which for? they can reduce the bearable temperature of the flue and/or make the flue unsuitable for operating with solid fuels that are subject to soot fire, such as wood, pellets or coal.

Summary of the invention

The invention poses the problem of finding an industrially convenient method for making double-walled flue elements. Furthermore, the invention has the aim of finding a method which allows to make double-walled flue elements resistant to high temperatures, free from flammable elements and free from non-metallic elements. Another purpose of the invention? to propose a manufacturing method for flue elements that does not require expensive equipment or long processing times.

The aims stated above are achieved with a method for making a double-walled flue element in accordance with claim 1.

The method includes the steps of:

providing a first barrel and a second barrel, of such dimensions that the first barrel can be positioned coaxially inside the second barrel;

create a plurality of cuts on the wall of said second barrel, wherein each of said cuts defines a tongue of inwardly bendable material;

positioning said first barrel coaxially inside said second barrel;

prepare one or more removable spacers between said two barrels, said spacers being capable of keeping them stably in a coaxial position;

fold the tabs inwards, towards the first internal barrel;

weld the tabs bent to the first barrel, making cos? the first barrel integral with the second barrel;

remove the spacers previously inserted between the two barrels.

Advantageously, the steps mentioned above are performed in the order indicated. First, the cuts are made on the second barrel, which define the tabs to be used for welding; then the two rods are positioned coaxially; the spacers are arranged to keep the two barrels correctly aligned; fold the tabs inwards; welds are made; finally the spacers are removed.

The subject of the invention is also a flue in accordance with the claims.

The method of the invention ? advantageous since?: the execution? easy and adaptable to any diameter, without the need? of dedicated machinery; makes the product much more convenient in industrial production; eliminates parts that perish at high temperatures; allows the flue to be made in accordance with higher temperature resistance categories and to operate with solid fuels. Thanks to the fact that the two inner and outer barrels are directly welded together, the double wall barrel assembly can be made without spacer elements, which ? cost-effective and eliminates potential weaknesses.

The spacers are temporarily placed between the two barrels, during the process of bending and welding the tabs, and are removed at the end of the process when the two barrels are integral with each other.

The method of the present invention allows the production of flue elements resistant up to 1000 ?C to thermal shock (in the case of soot fire) and up to 600 ?C to normal operation, which can be used with equipment that uses fuels solids such as wood, pellets, coal.

Description of the invention

The first flue and the second flue denote pipes of the type that can be used for flues. Typically these are steel pipes of small thickness and variable diameter according to the needs. In most practical applications the outside diameter of the double wall barrel is ? between 80 mm and 300 mm but the invention? equally applicable to larger or smaller diameters. The internal diameter (passage section available for the fumes) for example? about 20 mm more? small than the outside diameter.

It should be noted that a flue according to the invention generally has a circular section but in some embodiments it may have a non-circular section, for example elliptical.

The flues are made with modular elements, which can be straight, curved, T-shaped, etc. Therefore, in the present description and in the claims, the reference to a flue must be to be understood equally as a module or element of a flue. The cuts which create the foldable and weldable tabs are preferably made essentially in the shape of a U or in the shape of a C. In a preferred embodiment each of said cuts has two parallel sections, which are straight or substantially straight, and a section curve that connects said two parallel sections.

Said cuts are preferably arranged so as to form at least one circumferential ring on the wall of the second barrel. The cuts forming a ring are preferably arranged at regular angular intervals.

In a preferred embodiment said cuts are made on the second (outer) barrel in correspondence with an area of maximum width of the first barrel more? internal. Said zone of maximum width of the first barrel? for example an area for housing a gasket at a joint between flue elements.

Obtaining the tabs in an area of maximum width of the internal barrel? advantageous since? corresponds to an area of minimum distance between the walls of the two flues.

Said cuts can be arranged in symmetrical pairs, where the two cuts forming a pair are substantially symmetrical or specular with respect to a central axis of symmetry and parallel to the axis of the barrel.

Said cuts have a thickness which depends on the cutting method. Some cutting methods that can be used, but are not limited to, include mechanical cutting, plasma cutting, laser cutting, water jet cutting. Generally, by way of example and not as a limitation, the thickness of the cuts can be less than 1 mm, for example from 0.01 mm to 0.5 mm and preferably from 0.2 mm to 0.5 mm.

The tabs, by way of example, can have a shape suitable for the purpose, depending on the material used and the thickness of the same or the cutting means or the type of welding used for fixing/hooking to the internal barrel. By way of example and not limitation, in preferred applications the width of each tab can? be between 4 mm and 30 mm and preferably between 5 mm and 15 mm or between 8 mm and 12 mm.

The welding of the tabs to the first barrel? preferably performed with an induction welding process. The folding of the tabs can? be done directly with a spot welder for welding so as to use only one tool for bending and welding.

Preferably folding ? performed in such a way as to deform the tabs into an S or Z shape, creating a support area on the inner barrel which lends itself suitably to welding.

The welding of the tabs to the inner barrel generates welding points which make the two barrels integral, creating the desired double wall barrel structure.

The number of cuts made on the external tube, and consequently of welding points, will be able to be determined based on diameter and/or specific application requirements, to ensure adequate stability? mechanics of the double wall structure and maintain the desired coaxiality.

The first barrel and the second barrel can be made of stainless steel, preferably AISI 304 or AISI 316, or other metallic material. For some applications ? It is possible to make the two rods in different materials, including non-metallic ones.

The distance between the inner barrel and the outer barrel, cio? width of the interspace, pu? vary according to the application; generally it is between 5 cm and 15 cm, preferably 10 cm.

L? interspace normally ? an air gap; however, the invention does not exclude the provision of an insulating material inside the interspace itself. The dimension of the interspace could? vary according to the degree of insulation required, the operating temperature or other requirements.

Are the spacers to be temporarily inserted between the rods, to keep them in a coaxial position during the execution of the method, are they spacers in themselves? known and need not be further described.

Description of the figures

Fig. 1 shows a double wall flue element according to one way of carrying out the invention.

Fig. 2 represents a section of the flue of Fig. 1, according to an inclined sectional plane as shown by line II-II of Fig. 1.

Fig. 3 ? a detail of Fig. 2.

Fig. 4 schematically shows one of the cuts made on the surface of the outer barrel of the element of Fig. 1, to obtain the welding tabs.

Fig. 5 shows a preferred arrangement of the cuts and corresponding welding tabs.

Fig. 6 schematically shows, in section, the welding between the two concentric rods of the element of Fig. 1.

With reference to the figures, Fig. 1 shows an element 1 of a double-walled flue. Element 1 shown ? straight and has extremity? male/female 1A, 1B for connection to other elements, so as to form a flue.

The double-walled element 1 ? essentially formed by an inner barrel 2 and an outer barrel 3, which are made for example of stainless steel. Said barrels 2 and 3 are joined by welding at tabs 4 which are obtained on the surface of the outer barrel 3, bent towards the inner barrel 2 and welded to the latter, for example with induction welding.

Said folded and welded tabs are better visible in Figs. 2 and 3. It can be seen that the tabs 4 are formed in correspondence with a portion 5 of increased width of the inner barrel 2. Between the barrels 2 and 3 ? defined as an air gap 8.

Fig. 4 shows the execution of one of the tabs 4 in a preferred form. ? a U-shaped cut 6 is made on the surface of the outer barrel 3, with a thickness s for example of 0.3 mm. It is understood that said cut 6 defines the tab 4, which can? be folded along a baseline 7.

The 4 tabs can be arranged along a circumference or a ring, such as ? shown in Fig. 1 . For example in Fig. 1 the tabs 4 are located in region 1B.

Fig. 5 shows a preferred arrangement in mirror-image pairs of the cuts 6 and, consequently, of the tabs 4.

Fig. 6 schematically shows the joining principle between the outer barrel 3 and the inner barrel 2. The tab 4 (that is, the surface portion of the outer barrel 3) bent inwards in an S shape has a contact base 10 against the surface of the inner barrel 2, where a weld 9 is made.

Repeating the operation in a plurality? points you get a stable connection between the rods 2 and 3, with a welding for each tab 4, the cio? a double-walled structure as desired.

Claims (10)

1) Method for making a double-walled flue element (1), the flue element comprising a first flue (2) and a second flue (3) arranged coaxially and separated by a cavity, the method comprising: providing a first barrel and a second barrel, of such dimensions that the first barrel can be positioned coaxially inside the second barrel, the barrels being of a weldable material, preferably steel; create a plurality of cuts (6) on the wall of said second barrel, wherein each of said cuts defines a tongue (4) of material which can be folded inwards; positioning said first barrel (2) coaxially inside said second barrel (3); prepare one or more removable spacers between said two barrels, said spacers being capable of keeping the barrels (2, 3) stably in a coaxial position; fold the tabs (4) inwards, towards the first internal barrel (2); weld the folded tabs (4) to the first barrel (2), thus making? the first barrel (2) integral with the second barrel (3) and forming a double wall structure; remove the spacers previously inserted between the two barrels. 2) Method according to claim 1 wherein said cuts (6) are made essentially in the shape of a U or in the shape of a C. 3) Method according to claim 1 or 2 wherein each of said cuts has two parallel sections, which are straight or substantially straight, and a curved section which joins said two parallel sections. 4) Method according to one of the preceding claims, wherein said cuts form at least one circumferential ring on the wall of the second barrel, preferably with the cuts arranged at regular angular intervals. 5) Method in accordance with one of the preceding claims, in which said cuts are made on the second barrel (3) in correspondence with an area of maximum width (5) of the first barrel (2) wider? internal, said region of maximum width of the first barrel preferably being a region for housing a gasket. 6) Method according to one of the preceding claims, wherein said cuts are arranged symmetrically in pairs. 7) Method according to one of the preceding claims wherein said cuts have a thickness comprised between 0.01 mm and 0.5 mm, wherein said cuts are performed so as to define tabs (4) having a width comprised between 4 mm and 30 mm, preferably between 8 mm and 12mm. 8) Method according to one of the preceding claims, wherein the welding of the tabs to the first barrel ? induction welding. 9) Method according to one of the preceding claims, in which the inward bending of the tabs? impressed with a spot welder for welding, using the spot welder both for bending and for subsequent welding. 10) Double-walled flue element (1) obtainable with a manufacturing method according to any one of the preceding claims, comprising a first flue (2) and a second flue (3) arranged coaxially and separated by a cavity (8) , with the first barrel inside the second barrel, in which the two barrels are integrally joined by tabs (4) made on the second barrel, bent inwards towards the first barrel and welded to the latter, said tabs being obtained in correspondence with the cuts (6) made on the second barrel.