In the industrial branch of refrigerator profiles equipped with a magnetic sealing gasket, sealing systems of a type such as described in the U.S. Pat. No. 4,167,759 and in the European patent 319.087 by the same Applicant are known.
These systems have the common characteristic of assembling, manually or in an automated manner, a rigid profile fitted with a soft gasket co-extruded with the same, an inner door shell on one side and an outer door on the other, and of producing, after the assembly, a foamed material in the hollow space formed between the inner and outer door in order to achieve the thermal insulation of the same.
One of the drawbacks arising in such sealing systems is that in order to produce the foaming material inside an appropriate mold the soft part of the gasket is subjected to a squashing action, which may, in the event of an anomalous positioning inside the foaming mold, even produce a permanent deformation of the mentioned gasket.
On the other hand, different sealing systems have recently been developed, where the need of having a rigid profile of a rather complex geometric shape to allow supporting the soft sealing element on one side and to achieve the coupling of the inner and outer door as well as to fit an alternative gasket on the opposite side has been eliminated.
This has become possible by configuring the same outer door with a groove, generally arranged along the perimeter and capable of functioning as a seat to receive a soft gasket.
The system radically differs from the one discussed above in reference to the patents by the same Applicant, due to the fact that it is in this case possible to arrange for an inner/outer door assembly by executing the thermally insulating foaming step inside the hollow space formed between them prior to installing the gasket.
In other words, this system first produces a complete door, meaning a fully assembled and foamed-out door leading to the additional effect of holding the inner and outer doors permanently coupled to each other, and subsequently provides for mounting the soft gasket by a fastener element, for instance an anchor or leg capable of penetrating and latching by interference into the perimeter hollow with which the outer door has been molded.
A gasket installed according to a technology of this kind is shown in FIG. 1 of the drawings attached to this description.
With reference to this FIG. 1, a gasket of the known art is indicated by G and operatively assumes the configuration shown by a full line.
In this operating condition, the gasket G is installed across an anchoring leg E inside a groove 10 provided along the perimeter of an outer door 30. The latter is assembled with the plate of an inner door 30, where the inner door 30 and the outer door 30 are held together by a thermally insulating roamed material used to fill the hollow space formed between them.
This gasket is produced from a single type of soft plastic material and fitted at its upper end with a seat for a magnetic material M.
As can be seen, in the lower part a fastening element E projects from a base D produced with a thickness greater than that of the remainder of the gasket, so as to attain an adequate stability against the stresses induced by the door's opening and closing motions, and therefore by the traction of the magnet on the part of the refrigerator chest.
These stresses basically result into two forces, as shown in FIG. 1 by the vectors A and B which are basically acting vertically to each other.
The effect of a continuous application of such forces A and B on the gasket G is to generate some deformations, as shown in a simplified manner by a dashed line in FIG. 1.
As can be seen, these deformations are substantially due to a lifting action of the base D in the outer lateral area of the system, accompanied by a corresponding lifting action of the sealing strip C, which should in an operating position fit against the outer door (30) so as to achieve a lateral seal.
The deformation caused by the gasket's stretching under the effect of the magnetic traction is considerable. In order to attempt reducing this deformation, the only possible solution is to try to increase the thickness of the base D, which adversely affects the production costs.
Moreover, such a solution is incapable of preventing the deformations generated in this manner. The magnetic attraction also results in a constant lifting action of the anchoring leg E inside the outer door's groove 10. This entails the need to size this fastening leg E with a considerable thickness, which again affects the costs and at any rate fails to prevent the constant shifting action of the leg inside the groove 10, and consequently even runs the risk that such an anchoring leg may sooner or later jump off its seat.