The composite profile according to the invention is characterized by the presence, in the intermediate connection element, of elastic attachment elements which ensure an efficient join with the inner element, even when the environmental conditions are particularly unfavorable, also without the use of glues.

BACKGROUND OF THE INVENTION There are known composite profiles of a mixed type, with wood and aluminium, to make doors, windows, wings or similar. Such composite profiles are assembled together to make frames on which panels are usually mounted with a covering and/or plugging function.

Such composite profiles normally consist of an outer element made of metal, usually aluminium or alloys thereof, an inner element made of wood or alternative materials, such as for example covered or veneered profiles, and an intermediate connection element, normally made of plastic material such as PVC, polyamide, nylon or similar. The inner element is advantageously of the inter-changeable type.

The function of the metal outer element is to provide adequate resistance, both mechanical and also to the atmospheric agents, ensuring that the frame is kept in substantially unchanged conditions for a long time. The inner element allows to obtain a high level of aesthetics,

when the frame is observed from the inside, and a good level of heat insulation. Finally, the plastic intermediate element contributes to the heat insulation between the inside and outside of the frame, and also makes possible to avoid a direct connection between the wood and the metal, which could entail damage in correspondence with the join zones.

The join between the wooden inner element and the intermediate connection element is usually made by means of non-deformable hooks or fins which are normally further attached, in order to guarantee greater stability to the join, with gluing means such as glues, putty, resins, silicone or other adhesives.

During the storage period which follows production and assembly, and thereafter, during use, the profiles which constitute the frame are subjected to the action of the atmospheric agents. To be more exact, the profiles can be subject to environmental conditions, possibly extreme, of cold, heat, great differences in temperature, especially if the frame is used in particular geographic areas, or when it is repeatedly opened between an inside environment and an outside environment.

In profiles of this type, as known in the state of the art, the use of glues prevents the elements made of different materials such as, in this case, plastic and wood, from dilating independently. Since these materials behave differently when subjected to variations in temperature, due to their different heat dilation coefficient, the presence of reciprocal glue causes considerable tensions and mechanical stresses in correspondence with the join areas, and are even greater if the join is made continuously over the whole length thereof.

Such mechanical stresses cause deformation and undulation

on the elements, which alter the linearity thereof, and not only compromise the aesthetics of the assembled frame but also entail a loss of water-tight seal and mechanical resistance.

It must also be considered that the use of glues entails risks of environmental pollution, the need to provide systems during the production process to take in and filter the toxic fumes and vapors, and also potential risks for the workers.

FR-A-2. 082.933 discloses a plastic insert able to couple each other two metal profiles for frames. It does not refer to the coupling between an intermediate plastic element and an inner wooden element, so it does not dealt with to the problem of different deformations of these elements caused mainly by heat stresses. The plastic fins have their extremities perpendicularly angled to the development of the fin itself; each of this extremity couples with a mating surface perpendicularly angled to the axis of a seating provided in the metallic profile. These extremities insert themselves without play in the relative seating, so they cannot slide during use or storage of the frame to compensate heat or mechanical stresses to which the frame is subjected.

WO-A-9110801 discloses an elastic coupling between a metal profile and an intermediate plastic element in which the tooth-like extremity of the fin is perpendicularly angled to the axis of the fin itself and couple without play with a surface perpendicularly angled to the axis of an aperture provided in the metal profile.

DE-A-3107810 and EP-A-392342 disclose similar arrangements to couple some inserts or seals to profiles of a frame.

However, these documents do not disclose solutions to couple a wooden element to a plastic element of a frame allowing a

reciprocal movement to compensate heat or mechanical stresses to which the frame is subjected.

The present Applicant has devised and embodied this invention to overcome these shortcomings of the state of the art and to obtain further advantages.

SUMMARY OF THE INVENTION The invention is set forth and characterized essentially in the main claim, while the dependent claims describe other innovative characteristics of the invention.

The purpose of the invention is to achieve a composite profile for frames wherein the join between elements made of different materials does not provide to use glues, in order to be able to allow said elements to dilate in a differentiated manner in the event of variations in temperature and great temperature differences.

The invention is applied to composite profiles of the type used to make mixed structures of wood and aluminium, comprising at least an outer element made of metal material, an inner element made of wooden material, or similar, and an intermediate connection element made of synthetic material such as plastic or similar.

In accordance with this purpose, the inner element has at least a clamping means comprising a seating open on its inner side, that is, towards the intermediate connection element, which seating is provided with at least a lateral wider portion. The intermediate connection element comprises in turn at least an elastically deformable fin able to cooperate through interference with the mating lateral wider portion of the seating provided on the inner element.

In a preferential embodiment, the intermediate connection element comprises at least two elastically deformable fins able to cooperate with mating and opposite lateral wider portions provided in said seating of the inner element.

When the composite profile is assembled, the fins are inserted in a direction substantially orthogonal with respect to the plane on which the elements themselves lie.

These fins have a tooth-like extremity, facing outwards with respect to the development of the fin, which is able to be first elastically thrust inwards, due to the interference with the walls of the seating, during the coupling movement of the two elements, and then to be inserted into the relative lateral wider portion of the seating as the fins elastically return.

In this way, the elastic fins cause a snap-in type coupling which thrusts the two elements one towards the other, ensuring that they are reciprocally constrained.

According to a characteristic feature of the invention, the lateral wider portion of the seating provided in the inner element has a first side defined by an inclined plane oriented towards the outside and arranged as a continuation of the wall of the seating. The tooth-like extremity of the elastic fin has a mating conformation with an inclined plane.

With this configuration, during the coupling movement of the two elements of the profile, the elastic fin is progressively moved inside the seating and, when the tooth- like extremity meets the relative wider portion, the two respective inclined planes couple. Thanks to the return of the elastic deformation, the tooth-like extremity of the fin expands itself outwards and progressively slides on the inclined plane of the wider portion of the seating to a stop position defined by the abutment between the two elements, inner and intermediate, of the profile.

According to the invention, this tooth-like extremity of the fin is located with a play inside the respective wider portion of the seating.

During storage and/or use of the profiles, when the frame is subjected to heat stresses, or mechanical or other type of stresses, the sliding coupling of the respective inclined planes of the elastic fin and the relative lateral wider portion, and the presence of a play between the extremity of the fin and the wider portion, allows to withstand these stresses, allowing reciprocal movements of adaptation to the different conditions of deformation. These coupling movements can occur either longitudinally, according to the axis of the elements, or transversely to said axis, thanks to the presence of the mating inclined planes and of the play.

The composite profile according to the invention thus allows to achieve a stable join between the two elements even when there are considerable heat stresses, it allows to totally avoid the use of glues, and it guarantees that the frame cannot be deformed and will hold over time even in extreme environmental conditions.

In a preferential form of embodiment, the intermediate connection element comprises cavities to house inserts made of reinforcing material, to achieve for example steel-clad frames, or of insulating material, to increase the heat insulation properties of the frame.

BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics of the invention will be apparent from the following description of some preferential forms of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein: - fig. 1 shows a lateral sectioned view of a composite profile for frames according to the invention in accordance with a first form of embodiment; - fig. 2 shows an enlarged detail of fig. 1; -fig. 3 is a part view of a composite profile according to

the invention in accordance with a second form of embodiment; - fig. 4 shows a first variant of fig. 3; - fig. 5 shows a second variant of fig. 3.

DETAILED DESCRIPTION OF SOME PREFERENTIAL FORMS OF EMBODIMENT OF THE INVENTION With reference to the attached figures, a composite profile for frames for doors, windows, wings or similar is indicated generally by the reference number 10. Such composite profile 10 comprises, as basic components, an inner lining element 11, possibly interchangeable and made advantageously of wood or similar material, an outer element 23 made advantageously of aluminium or alloys thereof, and an intermediate connection element 12, made advantageously of plastic material or similar, such as for example PVC, polyamide or nylon.

The intermediate element 12, apart from the specific function of connecting the inner element 11 and the outer element 23, also has a partial function of heat insulation between the inside and outside of the frame.

In a first preferential form of embodiment, as shown in figs. 1-2, the inner element 11 comprises, for reciprocal clamping with the intermediate connection element 12, a seating or cavity 14 provided with two lateral wider portions 14a inside the element 11 itself.

Said lateral wider portions 14a are defined by a first surface 16 with an inclined plane, facing outwards with respect to the development of the cavity 14, and a second surface 21 with an inclined plane facing inwards.

On the side coupling with the inner element 11, the intermediate connection element 12 has a pair of elastically deformable fins 13, protruding laterally with respect to the abutment surface with said inner element 11. The two fins 13

are substantially parallel or partly diverging.

The abutment surface of the intermediate connection element 12 is defined by knurled or notched segments 17, which increase the mutual hold.

The extremities of said fins 13 are conformed as a tooth 15 facing outwards. Each tooth 15 has a first surface 15a with an inclined plane oriented towards the outside and having an angle greater than 90° with respect to the longitudinal development of the fins 13, and a second surface 15b with an inclined plane oriented towards the inside. When the elements 11 and 12 are coupled, the fins 13 are inserted into the corresponding cavity 14, in the direction indicated by the arrow 24.

During insertion, the tooth-like extremities 15 are thrust inwards due to the interference with the substantially straight walls of the cavity 14, exploiting the elasticity of the fins 13. When said tooth-like extremities 15 arrive in correspondence with the lateral wider portions 14a, the fins 13 snap open, returning elastically; the inclined planes 15a of said tooth-like extremities 15 slide on the mating inclined surfaces 16 of the wider portions 14a, until the abutment portions 17 of the intermediate element 12 stop against the corresponding segments of the inner element 11.

The inclination of the planes 15a and of the surfaces 16 is advantageously comprised between 20 and 50° with respect to the orthogonal to the axis of the fin 13, defining an angle between 110° and 140° with respect to the development of the fin, so that, in conditions when the frame is substantially stable, the elastic coupling of the two elements 11 and 12 is safe and secure enough and accidental detachment is prevented.

In the case where the profile 10 is subjected to particularly severe environmental conditions, for example

heat, cold or very great differences in temperature, the differentiated deformations of the two elements 11 and 12 can be compensated thanks to the possible movements of reciprocal adaptation allowed by the sliding of the respective inclined surfaces 15a and 16 and by the play existing between the tooth extremities 15 and the relative wider portions 14a.

In this way, the two elements 11 and 12, made of different material and with different coefficients of dilation, can be subjected even to extreme environmental conditions without creating tensions, warping or loss of linearity and without cracks being formed.

In this case, the intermediate connection element 12 comprises a through hole 20 wherein an insert made of resistant material can be inserted, for example to make a steel-clad frame, or electrical connection cables can be inserted for possible devices associated with the frame.

Moreover, once the fins 13 have been inserted into the corresponding cavity 14, further reinforcement and stabilizing inserts can be inserted into the cavity 14.

In a second form of embodiment, shown in figs. 3-5, the inner element 11 has two cavities 14, each one with at least a relative lateral wider portion 14a. This solution is used particularly when the profiles 10 to be obtained are particularly long. The cavities 14 can be of different sizes.

In a first embodiment, shown in fig. 3, the intermediate connection element 12 comprises four elastically deformable fins 13 able to be inserted in pairs into a corresponding cavity 14. In this case, only the outermost fins 13 have the respective tooth-like extremities 15 cooperating with relative wider portions 14a, while the two innermost fins 13 are substantially straight and function mainly as insertion

and centering guides.

In the variant shown in fig. 4, in correspondence with one of the two cavities 14 of the inner element 11, the intermediate connection element 12 comprises a single fin 13 provided with the tooth-like extremity 15 able to cooperate with a relative wider portion 14a; in correspondence with the other cavity 14, the intermediate connection element 12 has an outer fin 13 provided with the tooth-like extremity 15 and the other fin 13 is substantially straight.

The coupling of the inner element 11 and intermediate connection element 12 is ensured thanks to the presence of the two outer fins 13, each cooperating with a relative cavity 14 of the inner element 11.

In the further variant shown in fig. 5, for each of the two cavities 14 of the inner element 11, the intermediate connection element 12 has only one respective fin 13, provided with the relative tooth-like extremity 15 cooperating with the relative wider portion 14a. In this case too, the coupling of the two elements 11 and 12 is obtained by the presence of the two outer fins 13 cooperating with different cavities 14. These variants facilitate the assembly of the two elements 11 and 12 and yet obtain in any case a stable and secure coupling.

Modifications and/or additions of parts can be made to the composite profile 10 as described heretofore, without departing from the field and scope of the present invention.