DESCRIPTION

METHOD FOR MANUFACTURING PRE-INSULATED

CONDUITS WITH CIRCULAR OR ELLIPTIC SECTION FOR

THE SUPPLY OF CONDITIONED AIR AND THE CONDUIT

THEREBY OBTAINED.

Technical field

The present invention relates to a method for manufacturing pre- insulated conduits with circular or elliptic section for the supply of conditioned air and the conduit obtained through the said method. Background Art

The vast majority of pre-insulated conduits are currently manufactured with a square or rectangular section, as it is possible to manufacture stubs by using plane panels composed of rigid foamed polyurethane slabs coated with thin aluminium or stainless steel sheets.

For this purpose, at least three V-shaped slots are made on the surface of a plane panel to obtain folding lines; the panel is then folded along the said folding lines, in order to form a trunk with a quadrangular section.

Suitable angular sealing means are provided for fixing the two end edges of the slab together, usually along a corner of the trunk.

This kind of manufacturing allows a marked decrease in the complexity of conduit production methods, as well as transport costs,

since the transport involves panels which are pre-slotted along folding lines are plane.

However, conduits with a quadrangular section present problems if compared with conduits with circular section, such as: reduced aesthetic impact in exposed conduit applications; greater capacity loss for the same section area. The same Applicant has filed Italian patent applications IT TO2000A000761 and TO2002A000220, which refer to methods and systems for the manufacturing of conduits with circular section in rigid foamed polyurethane.

The manufacturing of these conduits is rather complex and, in particular, the joining of the semi-shells which comprise the conduit requires quite a long time and, moreover, it is carried out on the building site.

In addition, the said joining does not assure perfect sealing, therefore air leakage often occurs, which causes a decrease in the actual system delivery and the supply of conditioned air in rooms where it is not required.

In fact, Italian patent application TO 2002A000220 provides for the application of an adhesive to the ends of the two semi-conduits, which are formed with a projecting male-female connection. Thereinafter, a first semi-conduit is overlapped - upside down - to a second semi- conduit in order to couple the male and female connections. Subsequently, a sealing adhesive tape is applied to the two semi- conduit joint and finally the conduct is wrapped with at least one sealing and/or fixing band.

All these operations are carried out on the building site and require a large amount of time.

Disclosure of Invention

The aim of the present invention is to eliminate the abovementioned problems, in particular by manufacturing circular conduits with a perfect seal at the joints of the elements which comprise them.

The said aim is achieved by the method for manufacturing pre-insulated conduits with circular or elliptic section for the supply of conditioned air and the conduit thereby obtained, according to the present invention, whose features are provided for in the following claims, forming an integral part of the present description.

The advantages obtained through the method according to the present invention are fewer transport and fitting costs for these conduits with circular or substantially elliptic section.

The aims and advantages of the present invention will better emerge in the description that follows related to a preferred production sequence of the conduits, as well as in the enclosed drawings of a conduit manufactured according to the said method, in which: figures 1 and 2 illustrate two phases of the method for manufacturing the conduit; figure 3 illustrates a conduit detail according to a further embodiment; figure 4 illustrates a slab for the riveting coupling the two semi- conduits.

With reference to the figures, the first phase of the method provides for the manufacturing of two semi-conduits Ia and Ib obtained by injecting

polyurethane resins between two metal sheets 2 and 3, which are pre- bent in a semi-circular fashion and kept apart until the resin hardens. Steps 4 are subsequently realised, by milling, on the free ends of the two semi-conduits and, more precisely, one step 4a on the internal side of the semi-conduit Ia and one step 4b on the external side of the same semi-conduit. The two steps are identical and their depth is equal to half the conduit's thickness, which generally ranges from 25 to 30 mm. The joining of the two semi-conduits is carried out by inserting mechanical joints made of aluminium or steel along the two longitudinal edges on which the steps are obtained. In the example shown in figure 2, the joint of the two semi-conduits is realised by inserting a section bar 5 along the whole longitudinal edge of one of the two semi-conduits, the said section bar 5 being described in technical jargon as a "chair-shaped" and shown in figure 2a. Figure 2 shows how the section bar 5 is inserted and, more precisely, how the portion 5 a surrounds the step 4a while the portion 5b abuts the metal sheet 3 of both semi-conduits. The section sides surrounding the step have a certain roughness in order to exercise a gripping action on the polyurethane and aluminium of the external sheet 3. Naturally, the section bar 5 is inserted into both steps 4a to ensure a better seal; according to a possible embodiment variant, a layer of adhesive 6 can be spread on the two sides of the opposing steps which are not surrounded by the portion 5a of the section. With the type of joint described above, a very efficient system is obtained, as the internal conduit pressure simply pushes the two overlapped steps closer, thus improving the overall seal.

According to a further possible variant of the joining phase for the two semi-conduits, their coupling can be realised by inserting a riveted sheet 7 into the polyurethane in the internal step area, as illustrated in figure 4.

The said sheet 7 causes an efficient coupling by penetrating the polyurethane layer of both the semi-conduits (see fig. 3).

Both the semi-conduit coupling methods can be realised on the building site, thanks to their easy and fast implementation.

The two semi-conduits thereby obtained, which represent the starting point in obtaining the final conduit, are perfectly identical and therefore can be manufactured on the same milling line, using the same machines and tools, which will also remove any material from the inside or outside faces of the semi-conduit.

If the manufacture of substantially elliptic conduits is desired, two plane panels can simply be inserted between the two semi-conduits described above, these panels being of the desired width and featuring the same steps as the semi-conduits.

It should be noted that the insertion of the mechanical joints is realised by simply pressing the said joints onto either the polyurethane or the polyurethane and/or aluminium insulating sheet, these operations being executed on the building site with no special equipment.

The conduit 1 thereby obtained has two parallel longitudinal bands corresponding to the portion 5b of the joining element 5, or a single separation line between the two semi-conduits in the case of joining according to figure 3.