Abstract:
Gasket for refrigerator cabinets for providing seal-tight closure between cabinet ( 32 ) and door ( 17 ) composed of an outer door ( 30 ) and inner door ( 31 ), comprising a soft bellows portion ( 11 ), characterized in that said soft bellows portion ( 11 ) is interposed in an extensible manner between at least a pair of magnets ( 9, 15 ) one of which is operatively coupled to said door and the other is coupled to said cabinet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a 371 of PCT/EP2011/071881, filed Dec. 6, 2011, which claims priority to Italian Application No. MI2010A002272, filed Dec. 10, 2010, the disclosures of which are incorporated herein by reference and made a part of this application. 
     FIELD OF THE INVENTION 
     The present invention relates to a gasket for refrigerator cabinets of the kind comprising a soft bellows portion for effecting a seal-tight closure between cabinet and door. 
     PRIOR ART 
     The door consists of a shell, defined by an outer door and an inner door, filled with a heat-insulating material, for example polyurethane foam. Suitable gaskets are described for example in EP 146994, EP 319087 and EP 1129319 of the same applicant, in which the gasket is in that case assembled corresponding to said base with outer door and inner door before the step of foaming of the shell, therefore this type of gasket is generally called foamed in place. 
     On the opposite side relative to the base, the extensible bellows gasket has a magnetic bar which, with the door in the closed position, is coupled by magnetic attraction to the flat face of the edge of the cabinet. 
     The applicant is also the holder of patents in which a different technique is adopted for assembly of the gasket, press-fitting it in a suitable seat arranged on the shell that is already assembled and foamed, in particular on the inner door. If this seat is formed as a slot on the inner door, this is called push in assembly, for example of the type described in EP 1129319. If this seat is formed as a projection on the inner door, this is called push on assembly, for example of the type described in EP 1466129. 
     Regarding the foamed in place type, the gaskets of push-in and push-on type have on the one hand the advantages of easier assembly on a door that is already assembled, and of being able to be replaced easily, when worn out, with a spare part, because being a press-fit, they can be removed from the door by an operative merely by pulling, without the aid of mechanical means. 
     On the other hand the limitations of this technology relate to the difficulties connected with forming of the seat for the gasket on the inner door, whether it is a slot or a projection. 
     This seat is in fact formed during thermoforming of the inner door, making it difficult to ensure correct dimensional uniformity of this seat on its whole length. 
     A further complication arises when the assembled outer door/inner door shell is submitted to filling with heat-insulating material, for example by expansion of polyurethane foam. The pressure of the foam, combined with the heat generated by the reaction of expansion, can in fact further deform the seat geometry, whether with a slot or a projection, especially near smaller thicknesses. 
     In particular for compensating a seat that is often imperfect, gaskets of the push-in and push-on type must therefore have assembly tolerances on dimensions, which we try to reduce for example with a combination of coextruded soft and rigid materials, as in EP 1129319. Nevertheless, the tolerances are still present. 
     SUMMARY OF THE INVENTION 
     A first object of the present invention is to preserve, if not improve, a substantial ease of assembly and disassembly of the gasket on a door already assembled, which therefore avoids the foamed in place system, while also avoiding the dimensional problems typical of push-in and push-on systems, whether these relate to the moulding of the gasket seat or to the assembly tolerances. 
     A further object of the present invention is to provide a gasket with characteristics such that, for meeting the now prevalent requirements on improved thermal insulation for reducing the power consumption of refrigerators, it can be mounted within an outer door/cabinet distance (called hinge height) that is as small as possible. In fact, with less space between the cabinet and the door to be sealed, there is less possibility of heat exchange between the interior of the refrigerator and the outside. 
     To achieve these objects, and other advantages that will be described hereunder, the present invention proposes a gasket for refrigerators for a seal-tight closure between a refrigerator cabinet and a door composed of an outer door and inner door, comprising a soft bellows portion, characterized in that the gasket comprises at least a pair of magnets one of which is operatively coupled to said door and the other is operatively coupled to said cabinet, said soft bellows portion being interposed in an extensible manner between said magnets. 
     This extensible bellows gasket therefore comprises at both ends at least one magnetic bar which, with the door in the closed position, is able to be coupled by magnetic attraction to a suitable flat face provided not only on the edge of the cabinet but also on the edge of the door, avoiding the typical structural complications relating to an inner door and outer door mentioned above with respect to the prior art. 
     The expressions used above “at least a pair of magnets” and “at least one magnetic bar” refer to the possibility of dividing each magnet placed at each end of the soft bellows portion, equivalently, into two or more magnets or magnetic bars side by side. 
     With the invention it also becomes possible to choose whether to assemble the gasket on the door or on the refrigerator cabinet so that, during door opening, the gasket remains coupled to said door or to the cabinet. 
     According to the invention, therefore, during door opening one of the two magnets selected to be positioned on the cabinet or on the door, must remain in the coupling position while the other is detached from said coupling, which occurs correspondingly on the door or on the cabinet. 
     In a preferred embodiment of the invention, this effect is obtained in that the magnet of the pair that is selected to remain in the coupling position exerts a magnetic force of attraction greater than the other, selected for detachment from the coupling position. 
     In another embodiment, this effect can be obtained with a pair of magnets provided with substantially similar magnetic force of attraction, by arranging on the cabinet or on the door, as selected, a suitable means capable of holding the magnet selected for maintaining the corresponding coupling, for example a channeled seat for receiving a complementary projection provided on the magnet, or, conversely, a suitable projecting constraining means that engages with a complementary groove provided on the magnet. 
     In a further embodiment a suitable means capable of holding the magnet selected for maintaining said coupling consists of a third magnet of opposite polarity with respect to said magnet selected for maintaining said coupling. 
     In the embodiment in which, in the coupling position, a magnet m 2  exerts a magnetic force of attraction Fm 2  (expressed in g/cm) greater than Fm 1  of the other magnet m 1 , where m 1  is the magnet selected for detachment from the coupling position during door opening, with the same magnetic material for both magnets a prudent criterion for dimensioning of the two magnets is preferably that Fm 2 /Fm 1  is about  2 . 
     A preferred magnet according to the objects of the invention consists of a flexible bar containing magnetic material, for example ferrite or rare earths, combined with plastic or elastomeric material as binder, to give plastoferrite. The presence of an air gap, given for example by the thickness of the seat of plastic material of the plastoferrite bar provided on the gasket, can affect the force of attraction, so that due account must be taken of this when determining the force of attraction that this magnet must exert. Fm 1  is preferably about 20-40 g/cm, more preferably 25-30 g/cm, measured with an air gap of 0.45 mm. 
     The force of attraction Fm of a magnet according to the invention can be determined and adjusted by varying:
         the magnetic material used, for example isotropic ferrite, anisotropic ferrite, rare earths.   the type of magnetization, axial or multipolar (dipolar, tripolar, quadripolar, etc). Fm in contact increases as the number of poles is increased.   the size of the magnet, with identical magnetic material and polarization.       

     Since a gasket is also subjected to shearing stresses during door opening that imposes a rotation on it, it is preferable that the flat face of the cabinet or of the door on which magnet m 2  of the gasket of the invention, i.e. that with the greater force of attraction, must be coupled is laterally delimited by edges for containing any translation by sliding imparted by said shearing stresses. 
     The gasket of the invention can be produced in a large number of variants. For example in one gasket said bellows portion of soft material is coextruded with a base portion of rigid material consisting of a horizontal section from the end zone of which a pair of vertical sections extend acting as elastically divaricating clips for snap-engaging one magnet of the pair. 
     In another embodiment, in a gasket of the invention said bellows portion of soft material is coextruded with a base portion of rigid material consisting of a horizontal section, from the end zone of which a pair of vertical sections extend, the resulting C-section acting as a seat for one magnet of the pair formed as a plastoferrite bar coextruded within said C-section, as will be described in greater detail in a later example. 
     In another embodiment, a gasket of the invention is formed from a single soft plastic material and said bellows portion comprises a base portion that defines a tubular chamber able to contain one magnet of the pair formed as a plastoferrite bar coextruded within said tubular chamber, as will be described in more detail in a later example. 
     In another embodiment, in a gasket of the invention said bellows portion of soft material comprises a base portion coupled at the bottom to one magnet of the pair by means of an interposed bi-adhesive strip, or a layer of adhesive. 
     A gasket of the invention preferably comprises further means for maintaining the gap between cabinet and inner door as will be described in more detail in later examples, and preferably as described in EP 1869379 of the same applicant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For better understanding of the characteristics and advantages of the invention, non-limiting examples of practical implementation thereof are given below, referring to the diagrams in the appended drawings, in which (except  FIG. 2 ) the gasket of the invention is shown in the operative position when working in conjunction with a refrigerator cabinet and door. 
         FIG. 1  shows a schematic perspective view of a refrigerator in which the gasket is applied on the door, shown in the open position. 
         FIG. 2  shows a cross-sectional view of a gasket of the invention. 
         FIG. 3  shows a cross-sectional view of the gasket of  FIG. 2  applied in the operating position on the refrigerator, in which the operating position shown is that of door closure. 
         FIGS. 4 to 8 ,  10  and  11  show similar cross-sectional views of a gasket according to as many variants of the invention applied in the operating position on the refrigerator, in which the operating position shown is that of door closure. 
     
    
    
     Finally  FIG. 9  shows a cross-sectional view of a gasket according to a variant of the invention in the operating position on the refrigerator, in which the operating position shown is that of door opening. 
     DESCRIPTION OF THE INVENTION 
     It should be explained that in all the figures, including those relating to operating positions, for simplicity the gasket is shown schematically according to its nominal section, at rest. 
     Referring in particular to  FIG. 1  of these drawings, a refrigerator comprises a cabinet  32  with an outer edge  33  and a door  17  consisting of outer door  30  and inner door  31 , which define a shell filled with heat-insulating material. 
     In  FIG. 2 , a gasket  10  according to one embodiment of the invention comprises a bellows portion  11  of soft material, for example plasticized PVC or similar, coextruded with a base portion  12  of rigid material such as for example PVC-U (unplasticized, rigid). This base portion  12  consists of a horizontal section from the end zone of which a pair of vertical sections  13  extend, in the direction of the outer door  30 , acting as lightly elastically divaricating clips, each shaped with a projection  14  directed towards the interior of the space interposed between them. 
     The resulting C-section is able to act as a seat for receiving, in a stable manner, a magnet  15 , for example consisting of a flexible bar of plastoferrite shaped as a pair of recesses complementary to said projections  14 , and snap-engaging therewith by means of clips  13 . In the example shown, magnet  15  is tripolar, NSN (North South North). 
     At the opposite end, the bellows portion  11  terminates at the top with a tubular seat  8  able to contain a second magnet  9 , i.e. a strip or bar of magnetic material, in the example consisting of a bipolar SN plastoferrite bar. 
     Magnet  15  has larger dimensions than magnet  9 . Both for this reason and because of the different magnetization, tripolar compared with bipolar, magnet  15  (m 2 ) exerts a greater magnetic force of attraction than magnet  9  (m 1 ), in the example in question the magnetic material of which it is constituted being the same, for example the same type of ferrite. 
     Referring to  FIG. 3 , the gasket of  FIG. 2  is applied here in the operating position on the refrigerator by coupling of magnet  15  by magnetic attraction to the flat face  29  of the outer door  30  made of sheet metal. Therefore in the operating position of closure in  FIG. 2 , magnet  9  is coupled by magnetic attraction to the flat edge  33  of cabinet  32  made of sheet metal. 
     The flat face  29  of outer door  30  in sheet metal to which magnet  15  of the gasket of the invention is coupled is laterally delimited by a step  3  for containing any translation by sliding that might result from the shearing stresses imposed by the rotational movement of the door. On the opposite side, it is edge  4  of the inner door  31  that contains this possible sliding of the base of magnet  15 . 
     In all the embodiments shown in the drawings, in said bellows portion  11  from said seat  8  of magnet  9 , a tubular chamber, or “bulb”,  7  for maintaining the gap  5  between cabinet  32  and inner door  31 , extends, alongside and towards the internal zone of the refrigerator, and is squeezed in the closed position. Similarly, from the ends of base  12 , a pair of lips  18  and  19  extend, for sealing against the supporting wall for which they are intended in the operating position, whether it belongs to the door or to the cabinet ( FIGS. 8 and 9 ). 
     In the variants in  FIGS. 3 ,  6 ,  7 ,  8 ,  9 , a lip  16  extends from said bulb  7 , as further element for sealing the gap  5  between cabinet  32  and inner door  31  in the direction of the internal zone of the refrigerator. 
     In the variants in  FIGS. 6 and 9 , as an element for hermetically sealing gap  5  between cabinet  32  and inner door  31  in the direction of the internal zone of the refrigerator, gasket  10  includes a further sealing means  6 , as described in EP 1869379 of the same applicant. This is made in the form of a tubular chamber or bulb that extends from an inclined section  20  as termination of the rigid base  12  coextruded with bellows  11 , said inclined section  20  being prolonged in a soft section  21 , coextruded with said rigid section  20 . The bulb  6  constitutes the tubular end of section  21  and has a lengthened section substantially complementary to that of said space  5 , so as to be able to seal this space hermetically, being deformed by squeezing on the edge of the cabinet under the action of door closure. 
     The variant in  FIG. 4  shows a gasket  10  with rigid base  12  coextruded with a bellows portion  11  of soft material. The base portion  12  consists of a horizontal section, from the end zone of which a pair of vertical sections  13  extend in the direction of the outer door  30 . The resulting C-section acts as a seat for a tripolar (NSN) magnet  15 , for example a preformed flexible bar of magnetic material, which during extrusion of the gasket is coextruded with it, or better (being preformed) covered by the C-section of base  12  and sections  13  during passage through the extrusion die for moulding of the gasket. 
     A suitable rigid plastic material of base  12  can be selected for example from PVC-U, PS or PP, depending on the type of soft material selected for forming the bellows portion  11 , for example PVC-P, SEBS or TPO. 
     The magnet  9  at the opposite end of bellows  11  is a tripolar NSN magnet, for example a flexible bar of plastoferrite inserted in the appropriate tubular seat  8 . In this variant, as the polarity of magnets  15  and  9  is the same (NSN) and their dimensions are not substantially different, a greater force of attraction of magnet  15  relative to that of  9  is provided by the nature of the magnetic material used for it, for example a rare earth, a material that is intrinsically capable of exerting a greater magnetic force of attraction than the ferrite used for magnet  9 . 
     In the variant in  FIG. 5 , a gasket  10  is made of a single soft plastic material, selected for example from PVC-P, SEBS or TPO. The base portion  12  consists of a horizontal section, from the end zone of which a pair of vertical sections  13  extend in the direction of the outer door  30 , and are joined together at the bottom by a horizontal wall. As a result, a tubular chamber is defined, which acts as a seat for a magnet  15 . This is a pentapolar NSNSN magnet, for example a preformed flexible bar of plastoferrite, which during extrusion of the soft gasket is coextruded with it, or better (being preformed) is covered by said tubular chamber between 12 and 13 that is defined around it during passage through the extrusion die for moulding the gasket. The magnet  9  at the opposite end of bellows  11  is a tripolar NSN magnet, for example a flexible bar of plastoferrite inserted in a suitable tubular seat  8 . In this variant a greater force of attraction in contact with magnet  15  compared to that of  9  is provided by its pentapolarity in contrast with the tripolarity of magnet  9 , assuming that both consist of the same ferrite and have dimensions that are not very different. 
     In the variant in  FIG. 6 , magnet  15  has larger dimensions than magnet  9 . Both for this reason and because of the different magnetization, pentapolar compared to tripolar, magnet  15  exerts a greater magnetic force of attraction than magnet  9 , assuming that the magnetic material of which they are constituted is the same, for example the same type of ferrite. 
     In the variant in  FIG. 7 , a gasket  10  has similar structure to that of  FIG. 2 , except that the base portion  12  of rigid material is coupled at the bottom to a magnet  15  by means of an interposed bi-adhesive strip  22 . 
     The magnet  15 , for example a flexible bar of magnetic material, is tripolar (NSN). In this embodiment, magnet  9  at the opposite end of bellows  11  is also a tripolar NSN magnet, for example a flexible bar of plastoferrite inserted in a suitable tubular seat  8 . In this variant, as the polarity of magnets  15  and  9  is the same (NSN) and their dimensions are not substantially different, a greater force of attraction of magnet  15  than that of  9  is ensured by the nature of the magnetic material used for this, for example an anisotropic ferrite, a material that is intrinsically capable of exerting a greater magnetic force of attraction than the isotropic ferrite used for magnet  9 . 
       FIGS. 8 and 9  show gaskets already described:  FIG. 8  shows the same gasket as  FIG. 2  (and  FIG. 3 ) while  FIG. 9  shows a gasket of a structure that is not identical but is similar to that in  FIG. 6 . The variants shown here therefore do not refer to the structure per se of gasket  10  but to its operating position. In fact while the variants in  FIGS. 3 and 6  show gasket  10  operatively coupled to the door, specifically to the outer door  30 , corresponding to magnet  15 , which exerts a greater magnetic force of attraction than magnet  9 , in the variants in  FIGS. 8 and 9  the gasket is operatively coupled to the cabinet  32 , preferably to a flat face  34  recessed relative to edge  33 , corresponding to magnet  15 , which exerts a greater magnetic force of attraction than magnet  9 . The flat face  34  to which magnet  15  of the gasket of the invention is coupled is in this case laterally delimited by a pair of steps  35  and  36  forming the edge of cabinet  32  for containing any translation by sliding that might result from the shearing stresses imposed on the gasket by the rotational movement of the door. 
     This operating position in  FIGS. 8 and 9  ensures, during door opening, that gasket  10  remains in the coupling position on cabinet  32 , while magnet  9  is detached from the respective coupling on the outer door  30 , as identified in  FIG. 9 . 
     This situation is opposite to that shown schematically in  FIG. 1  and valid for all the operating positions shown from  FIG. 3  to  FIG. 7 , i.e. in which gasket  10  is operatively coupled to the door, specifically to the outer door  30 , corresponding to magnet  15  that exerts a greater magnetic force of attraction than magnet  9 . In this operating situation, for door opening as shown in  FIG. 1 , gasket  10  remains in the coupling position on the outer door  30 , while magnet  9  is detached from the respective coupling on cabinet  32 . 
       FIG. 10  shows an embodiment of a gasket with structure similar to that of  FIG. 6  in which a suitable means capable of holding the magnet  15  selected for maintaining the respective coupling, consists of a third magnet  37  of opposite polarity, SNS, relative to said magnet selected  15 , NSN, for maintaining the respective coupling. 
     In operation, the gasket is in this case applied to a flat face  38  at the end of inner door  31 , on which magnet  15  is in fact supported. From the opposite side of  38 , thus within the shell of door  17 , a magnet  37  is positioned, whose opposite polarity causes an Fm of attraction relative to  15 . Therefore in this case Fm of magnet  15  and Fm of magnet  9  can be comparable since detachment of magnet  9  from cabinet  32  during door opening is guaranteed by retention of magnet  15  in position on the inner door by the action of attraction of magnet  37 . 
       FIG. 11  shows an embodiment of a gasket with structure similar to that of  FIG. 7  according to a variant forming the outer door  30  according to a geometry capable of retaining a magnet  15  selected for maintaining respective coupling. In particular, outer door  30  has a flat face  29  recessed by a step  3  formed according to a projection  39  that engages with a complementary groove made in magnet  15 . On the opposite side, it is edge  4  of inner door  31  that constitutes a similar projection that engages with a complementary groove made in magnet  15 . This edge  4  is supported on a flat end  40  of the outer door  30 . Therefore again in this case Fm of magnet  15  and Fm of magnet  9  can be comparable since detachment of magnet  9  from cabinet  32  during door opening is ensured by retention of magnet  15  in position on the inner door by the action of constraints  39  and  4  on magnet  15 . 
     Further variants that can use a pair of magnets  15  and  9  having substantially similar magnetic force of attraction Fm can also be provided for those forms of actuation, similar to  FIGS. 6 and 9 , that envisage a further sealing means  6  as described in EP 1869379 of the same applicant, formed as a tubular chamber or bulb. In fact  6  is able to exert an elastic force of repulsion opposing the magnetic force of attraction Fm 1  of the magnet selected for detachment from the coupling position on the door (or cabinet) during door opening. 
     Therefore this elastic force of repulsion must be subtracted from Fm 1  to evaluate the actual magnetic force of attraction applied during opening. This makes it possible to have Fm 1  roughly equal to Fm 2 , knowing that Fm 1  in the operating step of door opening is still lower owing to this effect. 
     In general, with the present invention, a gasket is therefore obtained which, simultaneously, has a reduced hinge height, improves coverage of the tolerances, and simplifies door manufacture. 
     It is in fact possible to continue to use the convenient process of thermoforming and foaming of the doors as used typically for foamed in place gaskets, but without encountering the problem of having to assemble the gasket as well, together with the outer door and the inner door at the same time. 
     Both the inner door and the metallic part of the door, or outer door, can thus be produced more simply by rectilinear flat coupling, without having to check the critical geometry and dimensions for assembly of the gasket. 
     This results in a greatly reduced scrap rate in production. 
     Regarding the aforementioned push-in and push-on systems, the invention improves the steps of assembly and replacement, shortening their schedules. 
     The assembly tolerances of the gasket of the invention will be almost double those of the push-in and push-on kinds. 
     It thus becomes easy to dismantle and refit the refrigerator gasket, so that this can be done, even just for cleaning the gasket or the cabinet, by the user of the refrigerator, without requiring the services of a maintenance engineer.