More particularly, the present invention relates to a gasket for a plate-type heat exchanger that is provided with means for reinforcing the inner areas of the plate which are not encircled by the gasket, which surround the inlet and outlet holes of the fluid that flows within said heat exchanger.

The invention may be mainly applied in the field of thermo-mechanical industry.

BACKGROUND ART Plate-type heat exchanger devices are well known in the art.

These devices are constituted by a fixed and a movable endplate, one or both of them being provided, according to different applications, with inlet and outlet connections for fluids, and with a pack of metallic plates, generally stainless steel plates, disposed between said endplates.

Said metallic plates, which are bored close to their angled edges in order to allow the circulation of the fluids, constitute the surface of thermal exchange between the fluids and are provided with a series of ribs, suitable for increasing the exchange surface and the fluid turbulence, in order to obtain enhanced thermal exchanges.

Furthermore, said ribs are suitable for stiffening the pack of plates, that undergoes very high pressures during its use.

Said ribs are generally disposed according to a herringbone or a so-called laundress-board pattern.

Furthermore, the periphery of such plates is provided with sealing gaskets made of an elastic, rubber- like material, which delimit and physically separate the pair of channels formed inside of the heat exchanger and within which are flowing the fluids.

This type of device is generally used in applications of various kinds, e. g. for instantaneously producing sanitary hot water by means of a boiler, with or without buffers, or for swimming-pool heating by means of a boiler, or for a district-heating network.

The gaskets which are to be placed between respective plates in these heat exchangers have to stand both relatively high temperatures and remarkable temperature differences, since they are designed in order to sealingly delimit and divide from each other volumes inside of which respective hot and cold liquids are assigned to flow.

Moreover, they undergo remarkable operating pressures which may range between some bar and several tens of bar.

Therefore, owing to the wide thermal amplitude and to the elevated pressures, the gaskets work at extreme conditions, sometimes resulting in yieldings and leakages of fluid from the heat exchanger, thereby compromising their main function.

Furthermore, it is known that, in a heat exchanger, the area surrounding the four inlet and outlet holes runs the most risks of fluid leakages, owing to a very high gradient of thermal and dynamic conditions which,

considering a pair of joined plates, the gasket that surrounds a respective pair of the four holes of each plate is supposed to stand.

Referring to fig. 1, that schematically represents a known gasket 10 suitable for being inserted into a peripheral groove of a heat exchanger plate 20, it may be noticed that said gasket 10 comprises a circular portion that completely surrounds an inlet or outlet hole of plate 20, as well as an inner portion 12, that is suitable for physically separating the plate area 22 inside which flows a first fluid, from hole 21 inside of which flows the other fluid.

The inner portion 12 is housed within a further groove of plate 20.

Since the plates of these heat exchangers are symmetrically manufactured, another groove 24, similar to the one that houses gasket portion 12, is provided in correspondance of the other hole 23; said groove 24 is generally empty, since the fluid of area 22 flows towards or from hole 23 above said groove.

The presence of groove 24 determines a possibility of deflection or flexure of the plate while the heat exchanger is operating, since no supporting or bearing elements are provided beneath said groove.

Said flexure often determines the passage and leakage of a given quantity of fluid from area 22 underneath gasket portion 12, and from this point outwards.

Several gaskets are known in the art, which are more or less stable and quick to be installed, such as for instance the gasket disclosed in italian patent application No. VR98A000028 in the name of the present Applicant; however, all of them involve the drawback constituted by possible yieldings in the described inner

areas surrounding the inlet and oulet holes.

In order to stiffen the area close to groove 24, and to avoid then any flexure of the plate in a so delicate area as the one around the fluid inlet and/or outlet holes, a supporting element shaped as metallic blade or plate has been used, said blade being placed inside of groove 24 and being provided with bosses or, in general, protuberances in correspondance of the plate ribs; said bosses or protuberances act as supporting elements for the superimposed plate, and they prevent an excessive flexure of the plate in this area, though allowing the fluid flow.

However, said supporting element involves some disadvantages. In fact, it has to be stored separately in respect of the gaskets and, when assemblying the heat exchanger, it has to be joined to a plate by inserting it into groove 24 and by fastening it to the latter.

This operation needs to be repeated many times for every single plate until the whole heat exchanger is assembled, thereby causing important losses of working time during the assemblying operation.

Furthermore, the plates of heat exchangers may have the most different dimensions; consequently, a plurality of different supporting elements needs to be stored, whereby the organisation of the elements to be assembled together is still more difficult and it is subjected to mistakes.

DESCRIPTION OF THE INVENTION The present invention aims to set aside the inconveniences and drawbacks which are typical of the background art, and to provide, thus, for a supporting element that is specifically suitable for being inserted into the inner groove of the area surrounding a fluid inlet or outlet hole of a plate of a heat exchanger, said

supporting element being made integral to the gasket, whereby it can be assembled together with the gasket into the groove that is provided in the plate.

More particularly, a purpose of the present invention is to provide for an element which can implement a reliable and safe sealing action in proximity of the inlet and/or outlet areas of the fluids, said areas being generally subjected to a larger stress in respect to other portions of the plate.

Another purpose of the present invention is that to provide for a gasket for a plate-type heat exchanger provided with a protection in proximity of the fluid inlet and/or outlet holes, whereby said gasket can be stocked in an orderly way, so that it is quick to be found and preventing an assemblying operation of several separated pieces in several working steps, when the gaskets of a heat exchanger are placed on the plates.

This is achieved by means of a gasket having the features disclosed in the main claim.

The dependent claims outline particularly advantageous forms of embodiment of the present invention.

The gasket for plate-type heat exchangers according to the present invention is provided with a bearing element that is preferably made of a metallic material and that is embedded, in correspondance of its two ends, into predetermined locations of said gasket.

Consequently, it is fastened to the gasket in an irremovable way and it can be placed into a groove located in proximity of a fluid inlet or outlet hole.

Said element is provided with protuberances or bosses in correspondance of the ribs which are present on the plate that receives said gasket.

This configuration allows a plurality of bearing

points to be defined between two superimposed plates, preventing plate deflections and thereby lowering the risk of leakages through the gasket and increasing the intrinsic strength of the whole pack of plates.

ILLUSTRATION OF DRAWINGS Other features and advntages of the invention will become apparent by reading the following description of a form of embodiment of the invention, given as a non- limiting example, with the help of the figures illustrated in the attached drawings, in which: -fig. 1 shows a schematic plan view of a known gasket for plate-type heat exchanger, as placed on a corresponding plate; -fig. 2 shows a schematic plan view oof a gasket according to the invention, as placed around an inlet or outlet hole of a plate of a heat exchanger; -fig. 3 shows an enlarged plan view of the encircled area of fig. 2; -fig. 4 shows a view sectioned along line A-A of fig.

3.

DESCRIPTION OF A FORM OF EMBODIMENT With reference to figures 2,3 and 4, reference sign 30 indicates a gasket made of a gummy material for a plate of a heat exchanger according to the present invention.

As known in the art, the area surrounding the fluid inlet or outlet hole is provided with a series of ribs 31 and corresponding depressions which are obtained by pressing the plate.

Gasket 30 lays inside a groove that is realised in the plate and it is preferably fixed to the latter by means of protuberances 32, e. g. as described in italian patent application No. VR98A000028, which are engaged in notchings of a corresponding shape, realised in said

plate.

A supplementary groove 24 (see also fig. 1) surrounding the fluid inlet or outlet hole receives a bearing element constituted by a generally metallic small blade or plate 33, whose ends 34,35 are irremovably embedded in two different locations of gasket 30.

Particularly referring to fig. 3, the small plate is provided with protuberances 36 which advantageously match in a perfect way with ribs 31 of the plate, so that the continuity of the bearing action is never interrupted.

In this way, as previously mentioned, small plate or blade 33 forms a bearing element that, in operation, stiffens the structure of plate 20 which does not undergo any excessive deflection.

Consequently, the leakage problems in the areas in proximity of the inlet and/or outlet holes, which are typical of the known heat exchangers, are avoided.

Furthermore, the fact that the small plate or blade is made integral to the gasket allows any problems of double storing and assemblying mistakes to be avoided.

Thus, the assemblying time is considerably reduced.