The present invention relates to heating radiator elements to be joined to one another in a battery.

The invention also relates to a method for manufacturing said radiator elements, and to a joining method for joining said radiator elements in a battery.

The invention preferably (but not necessarily) applies to the sector of radiators made of aluminium, in particular die-cast aluminium, to which specific reference is made in the following description, without excluding the possibility of use for radiators made of other (metal) materials .

BACKGROUND ART

Indoor heating radiators known in the prior art may consist of a battery of radiator elements, produced individually, for example by means of an aluminium die- casting process, and then joined to one another.

A typical radiator element (for example, but not necessarily, made of die-cast aluminium) has a substantially tubular body, provided with an inner chamber for water circulation, and a plurality of heat exchanger fins and/or plates, variously connected to one another and/or to the body. The radiator element is provided, at respective opposite longitudinal ends, with respective pairs of transverse joint sleeves for connection to other similar radiator elements and/or to a hydraulic circuit. The radiator elements are arranged side by side and are joined by means of the joint sleeves.

The radiator elements must be joined so as to guarantee a secure mechanical joint and adequate fluidtightness .

Two joint sleeves of adjacent radiator elements are usually joined by means of a nipple, i.e. a tubular member with an external thread which engages two threaded portions formed on the inside of the joint sleeves. The two joint sleeves to be joined are aligned with one another and placed so as to come into contact with one another via their respective front annular faces; as the nipple is tightened, the two joint sleeves are tightened together, specifically their respective front faces are pressed against one another; gaskets are inserted between the front faces of the joint sleeves, or inside these, to make the joint fluidtight.

In the case of die-cast aluminium radiator elements, the sealing surface of each joint sleeve, defined by the surface of its front face which comes into contact with the corresponding front face of the adjacent joint sleeve, is obtained by means of a mechanical process in which material is removed (milling) ; indeed, when the part leaves the casting die its surface is not suitable for joining.

The milling process generally removes a surface layer of a few tenths of a millimetre (roughly, between 0.7 and 1.00 mm) and is performed on each side of the radiator element (that is to say, on each joint sleeve) .

In addition to the waste of material, this method has some further drawbacks.

Firstly, it removes the material with the best hardness and compactness properties: owing to the characteristics of the die-casting process, the surface layer of the part has the best mechanical properties.

Furthermore, the joint sleeves are the most solid parts of the radiator element (since they are the thickest parts), which means the material inside them, again as a consequence of the die-casting process, is more porous (contains air bubbles and pockets) ; the removal of material to prepare the sealing surface, by removing the hardest and most compact surface layer, could thus expose porous areas which, in use, could undermine the tightness of the seal.

Lastly, following the mechanical removal of material, the surface is generally slightly undulated and/or has some areas where the material is "torn", and is not perfectly plane and even.

Similar problems occur with radiator elements made of other metal materials.

Ultimately, the mechanical machining process normally used to prepare the sealing surfaces of the joint sleeves of radiator elements, as well as wasting material, produces surfaces that are not perfectly plane, and which are uneven and porous; to compensate for these surface defects, special gaskets have to be used and a relatively high tightening torque has to be applied to the nipples, with the consequent possible deformation of the threads.

DISCLOSURE OF INVENTION

One purpose of the present invention is to provide radiator elements, for example made of aluminium and in particular die-cast aluminium, to be joined to one another in a battery, a manufacturing method for producing said radiator elements, and a joining method for joining said radiator elements in a battery, which overcome the drawbacks of the prior art described above.

The present invention thus relates to a radiator element, a method for manufacturing radiator elements, and a joining method for joining radiator elements in a battery, as respectively defined in the appended claims 1, 12 and 24.

According to the invention, the sealing surfaces of the joint sleeves of the radiator elements are prepared for joining by means of a roller burnishing process, which does not involve the removal of any material.

Roller burnishing is a surface finishing process generally performed at room temperature and without removing any chippings; the surface to be treated is pressed using specific metal rollers (usually made of hardened steel) that are extremely smooth and hard (made of a material that is harder than the material of the surface to be treated) ; the rollers exert a pressure which produces a plastic deformation of the material of the treated surface .

The method according to the invention achieves significant savings of raw material compared to the prior art methods .

Moreover, the method according to the invention does not envisage the removal of material, thus eliminating the need for chippings to be removed and recycled.

Furthermore, it prevents the loss of the material (on the surface) with the best mechanical properties (harder and more compact) .

Roller burnishing produces plane, even surfaces, and also closes the underlying pores better.

The surfaces that are obtained are entirely suitable as the sealing surfaces of the joint sleeves. The joint sleeves can be joined with or without inserting a gasket; in any case, thanks to the improved characteristics of the sealing surfaces, if gaskets are used these can be of a simple and economical type.

According to one aspect of the invention however, the use of gaskets can be avoided altogether. The two joint sleeves to be joined have, respectively, a plane surface and at least one protruding annular projection, which is also obtained by means of roller burnishing. When the two joint sleeves are pressed together, by tightening the nipple inserted inside them, the annular projection slightly deforms the opposite surface to create a fluidtight joint.

This effect is achieved by applying a lower tightening torque (approximately, less than 90 Nm) than the tightening torque normally applied when using traditional methods (usually more than 100 Nm) .

In this way, the method according to the invention achieves further advantages in terms of energy saving, in addition to the fact that it altogether eliminates the need for gaskets (which results in savings in the cost of components and simplification and reduction of assembly operations) .

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will become clear from the description of the following non-limiting embodiments thereof, with reference to the figures of the accompanying drawings, in which:

- figures 1 and 2 are partial views from respective opposite sides of a heating radiator element according to the invention;

- figure 3 is a partial cross-sectional view of two radiator elements joined to one another according to the invention, shown during their assembly;

- figure 4 is an enlarged scale view of the detail A highlighted in figure 3;

- figure 5 is an enlarged scale view of the detail B highlighted in figure 3, with parts removed for the sake of clarity;

- figure 6 is an enlarged scale view of the detail B highlighted in figure 3, with parts removed for the sake of clarity, according to an alternative embodiment of the invention .

BEST MODE FOR CARRYING OUT THE INVENTION

In figures 1 to 3, denoted as a whole by reference numeral 1 is a heating radiator element (for heating buildings) made of a metal material, in particular of aluminium (said term also comprising aluminium alloys) and precisely of die-cast aluminium (thus produced by means of an aluminium die-casting process) . In figures 1 and 2 only a lower end part of the element 1 is shown for the sake of simplicity; figure 3 shows the lower end parts of two elements 1 arranged side by side to form a battery 2 of radiator elements (possibly along with further elements 1 which are not illustrated) .

The element 1 (that is to say, each element 1) has a substantially tubular, preferably monolithic, body made of a metal material (of die-cast aluminium in the example described herein) and provided with an internal chamber 4 through which water flows; the body 3 and the element 1 as a whole extend longitudinally along an axis X which, with reference to the normal position of use of the element 1, is substantially vertical.

The element 1 is provided with a plurality of heat exchanger fins and/or plates 5 variously connected to one another and/or to the body 3.

The element 1 is provided, at respective opposite longitudinal ends (only the lower longitudinal end is illustrated in figures 1-3), with two pairs of transverse joint sleeves 6a, 6b for connection to other radiator elements and/or to a hydraulic circuit.

For the sake of simplicity, in figures 1-3 only the sleeves 6a, 6b arranged at the lower longitudinal end of the element 1 are shown.

The sleeves 6a, 6b of each pair (thus arranged at each longitudinal end of the element 1) extend on opposite sides of the body 3 and are aligned along a transverse axis Y perpendicular to the axis X.

Preferably, the sleeves 6a, 6b are obtained as an integral part of the body 3 so as to form a monolithic piece 7.

Each sleeve 6a, 6b extends from the body 3 and has a free open end 8 provided with an opening 9 communicating with the chamber 4; in particular, each sleeve 6a, 6b has a lateral wall 10 substantially orthogonal to the body 3 and ending with a free end lateral edge 11. As illustrated in detail in figure 4, the lateral wall 10 has an inner lateral surface 12 provided, at the free end 8, with a threaded portion 13.

The openings 9 of the sleeves 6a, 6b are aligned along the axis Y and are delimited by respective front perimeter edges 14a, 14b having respective front annular surfaces 15a, 15b substantially transversal with respect to the axis Y.

According to the invention, the front annular surfaces 15a, 15b of the edges 14a, 14b delimiting the openings 9 are roller burnished surfaces, that is to say, surfaces polished by means of a roller burnishing process, preferably a cold roller burnishing process, described more in detail below. Owing to the roller burnishing process, the surfaces 15a, 15b consist of a work-hardened material having a density and a hardness greater than the material below the surfaces 15a, 15b.

In particular, each of the surfaces 15a, 15b includes a surface layer 16 in which the material of the sleeve 6a, 6b is work-hardened and has a density and a hardness greater than the material below the surface layer 16, that is to say the material of the rest of the respective sleeve 6a, 6b.

In other words, the material (aluminium or aluminium alloy, or other metal material) of which the sleeves 6a, 6b are made is harder and has a greater density on the surfaces 15a, 15b, in particular in the surface layer 16, than in the rest (of the inside) of the sleeves 6a, 6b, in particular the lateral walls 10.

According to the embodiment illustrated in figures 1- 3, the surfaces 15a, 15b of the two sleeves 6a, 6b are both roller burnished, but have different shapes.

As illustrated in particular in figures 1 and 4, the surface 15a of the sleeve 6a is a substantially plane, smooth and flat surface; the surface 15a thus has no projections or protuberances and is flush with the free end lateral edge 11 of the sleeve 6a; advantageously, the surface 15a is perfectly plane and orthogonal to the axis Y.

As illustrated in figures 2, 4 and 5, the surface 15b of the sleeve 6b has instead at least one projection 17 projecting axially (along the axis Y) beyond the free end lateral edge 11 of the sleeve 6b. In particular, the surface 15b comprises: a substantially plane, smooth and flat base portion 18, advantageously perfectly plane and orthogonal to the axis Y, flush with the free end lateral edge 11 of the sleeve 6b; and at least one continuous annular projection (closed around the axis Y) which projects axially from the base portion 18 and protrudes axially beyond the base portion 18 and beyond the free end lateral edge 11 of the sleeve 6b.

In the example that is illustrated, the projection 17 has a pointed vertex. In particular, the projection 17 has a substantially triangular cross-section and two sides converging in a vertex.

It is nonetheless understood that the projection 17 may be of a different shape (in particular, it may have a different cross-section) , for example the cross-section could be triangular, polygonal, curved semi-circular or as an arc of a circle, etc.

According to the alternative embodiment illustrated in figure 6, the projection 17 is a convex curved projection, defined by the shape of the surface 15b (or a part thereof) ; in particular, the surface 15b is a convex surface protruding with respect to the lateral wall 10, specifically beyond the free end lateral edge 11 of the sleeve 6b.

For example (but not necessarily) the projection 17 protrudes by a few tenths of a millimetre or even by less than a tenth of a millimetre (for example by 0.05-0.5 mm) with respect to the lateral wall 10 and to the free end lateral edge 11.

According to alternative embodiments that are not illustrated, instead of being provided with a single projection 17 as shown, the sleeve 6b may be provided with two or more concentric projections 17 around the axis Y and radially spaced from one another.

According to a further alternative embodiment, the surfaces 15a, 15b of the sleeves 6a, 6b are instead the same, being for example both substantially plane, smooth and flat surfaces and with no projections and protuberances, in particular parallel to one another and orthogonal to the axis Y.

According to other embodiments that are not illustrated, both of the surfaces 15a, 15b are provided with one or more projections 17; preferably, the projections 17 on the surfaces 15a, 15b are radially staggered . The method for manufacturing the element 1 will now be described.

First, the monolithic piece made of a metal material (for example, aluminium or aluminium alloy) defining the body 3 provided with the sleeves 6a, 6b is produced, preferably (but not necessarily) by means of a die-casting process .

The surfaces 15a, 15b of the sleeves 6a, 6b are then subjected to a roller burnishing process, preferably a cold roller burnishing process, using a roller burnishing machine provided with rollers made of a metal material that is harder than the material of the surfaces 15a, 15b, for example work-hardened steel.

The surfaces 15a, 15b are pressed and plastically deformed without removing any material, in order to work- harden the material of the surfaces 15a, 15b and thus increase their hardness and density. The surface layer 16 is thus produced, in which the material of the sleeves 6a, 6b (metal material, in particular aluminium or aluminium alloy) has a density and a hardness greater than the material below the surface layer 16.

The projection 17 is also obtained by means of a roller burnishing process, plastically deforming the surface 15b.

The roller burnished surfaces 15a, 15b constitute the respective sealing surfaces of the sleeves 6a, 6b, to be joined to respective sealing surfaces of other similar elements 1 to form the battery 2 and thus a heating radiator of appropriate dimensions.

To join two elements 1, the two elements 1 are arranged side by side with the sleeve 6a of a first element 1 facing and aligned along the axis Y with the sleeve 6b of a second element 1 (figures 3 and 4) .

The surface 15a of the sleeve 6a of the first element 1 faces and is aligned along the axis Y with the surface 15b of the sleeve 6b of the second element 1.

A nipple 20 is inserted into the adjacent sleeves 6a, 6b; the nipple 20 is provided with an external thread 21 such as to engage the threaded portions 13 of the sleeves 6a, 6b.

Tightening the nipple 20 in the sleeves 6a, 6b, the sleeves 6a, 6b move closer together along the axis Y and the surfaces 15a, 15b are pressed against each other and joined.

Cptionally, especially if both of the surfaces 15a, 15b are flat and parallel and have no projections, an annular gasket made of a polymeric material (not illustrated) may be inserted between the surfaces 15a, 15b.

However, the use of the gasket can also be avoided, especially if at least one of the surfaces 15a, 15b is provided with at least one projection 17. In that case, when the nipple 20 is tightened and the surfaces 15a, 15b are thus pressed against one another, the surfaces 15a, 15b are plastically deformed as they come into contact with one another, as the projection 17 on the surface 15b penetrates the surface 15a.

This creates a mechanical and fluidtight joint between the two surfaces 15a, 15b, even without the use of gaskets.

It is understood that further modifications and variations can be made to the radiator elements, the manufacturing method thereof and the joining method for joining the radiator elements in a battery described and illustrated herein without departing from the scope of the invention as set forth in the appended claims.