GASKET

Abstract: A method of providing a door or lid with a microcellular polyurethane gasket (30) moulded in situ on the article (23) to provide a seal between the door and a surface (32). The gasket is formed by reaction injection moulding. The gasket is made integral with the door by chemical bonding or mechanical interlocking. A particular use is to provide a seal between a refrigerator or freezer cabinet and the door.

Description: Title: "GASKET" Technical Field This invention relates to a sealing gasket. The invention will herein be described with particular reference to a gasket providing a seal between a refrigerator or freezer cabinet and the door thereof when the door is in its closed position. The invention is not however limited to gaskets having that purpose. Background Art The operational requirements for the door sealing gasket of a modern refrigerator or freezer door are very demanding. The gasket must provide an effective sealing perimeter, must be sufficiently durable and resilient to form a seal repetitively over years of use, and should be able to withstand repeated pinching or rolling action adjacent to the hinge axis. Preferably the gasket is mounted in such a way as also to prevent ingress of moisture to insulation situated between an inner and outer door panel and provides for hidden mounting to the door. In order to meet the above requirements there have been developed gaskets which extend longitudinally of the perimeter of the door and typically include a flat sealing surface, an air chamber or bellow structure providing a degree of resilience, means adapted to receive magnets, and one or more mounting flanges or flaps to aid unseen mounting of the gasket to the door. Often the gasket fits over an edge of the inner panel of the door so as to provide an edge seal between the panel and a panel mounting flange of the door. Such gaskets have a relatively complex cross-section. They are generally manufactured from polyvinyl chloride ("PVC") by extruding continuous lengths, cutting required lengths, with mitre, cut ends forming a door perimeter gasket by welding four of the cut lengths end to end to form a substantially rectangular perimeter and the rectangular shape gasket so manufactured is then mounted to the refrigerator or freezer door usually by stretching over the edge of a door panel and/or by means of a mounting strip screwed at inch intervals around the perimeter. Gaskets such as described above are in wide-spread use in freezers and refrigerators throughout Australia and elsewhere in the world. However they are costly to manufacture, costly to mount to the door, and are not as satisfactory in performance as is desired. The present invention has as an object to alleviate at least some of the above mentioned disadvantages. Disclosure of Invention According to one aspect the invention consists in a method for manufacture of a gasket adapted to provide a seal between one article and another, said method being characterised by the step of forming a suitable microcellular polyurethane in a predetermined gasket shape in situ on the article. In preferred embodiments the polyurethane is a low density microcellular polyurethane and is formed by reaction injection moulding ("RIM") in the required shape in situ on the article. Desirably the gasket is integral with the article by virtue of chemical bonding or mechanical interlocking therewith and may extend around a rim of the article being in contact with opposite faces adjacent the rim. According to a second aspect the invention consists in an article having a suitable microcellular polyurethane portion formed as an integral part thereof, said part being adapted to provide a sealing gasket between the article and a surface. In a preferred embodiment the article is a door panel of a freezer refrigerator or other appliance, the panel being a high density polyurethane moulding having a low density polyurethane gasket moulded integrally therewith. However the panel need not be of high density polyurethane and may be of metal, thermoplastic or other material. OMPI Brief Description of Drawings Various embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings wherein: Fig. 1 is an isometric drawings of a freezer lid assembly according to the invention, partly shown in scrap cross-section. Fig. 2 shows in more detail a cross-section through an edge portion of the lid of Fig. 1. Fig. 3 shows schematically a second embodiment of the invention. Fig. 4 " shows schematically a third embodiment of the invention. Preferred Embodiments of the Invention A first embodiment of the invention will now be described with reference to Figs. 1 and 2 which shows the insulated door or lid assembly of a top opening domestic freezer cabinet. The lid assembly comprises an outer panel 1, an inner panel or liner 2, and a connecting frame 3. The ' connecting frame 3 provides the front edge 4, rear edge 5, and side edges 6,7 for the lid, and is adapted to hold the outer panel 1 and inner panel 2 in spaced apart arrangement. More particularly _ connecting frame 3 comprises a moulding which in the assembled lid extends around the perimeter of the lid assembly. In profile as shown in Fig. 2, the moulding of connecting frame 3 comprises an upper flange 21, an OMPI outer side 22, a downwardly extending skirt 23, a lower seal engaging formation 25, and a groove 24 extending parallel to the perimeter and defined between skirt 23 and formation 25. Upper flange 21 extends inwardly from inner side surface 26 and serves to frame and retain outer panel 1. Outer side edge 22 slopes outwardly and downwardly then steps outwardly to merge with skirt 23. The inner panel or liner 2 is stepped in profile near the edge and has a flat edge rim 27. A gasket 30 extends around the perimeter of rim 27 of panel 2, a portion 31 of rim 27 being embedded in gasket 30. In the assembly the space enclosed between outer panel 1, inner panel 2 and inner side edge 26-of connecting frame 3 is filled with an insulating material e.g. a foamed plastics material formed in situ and not shown in the drawings. Gasket 30 fulfils the dual role of providing a seal between inner liner 2 and formation 25 of frame 3, and also of acting as a door seal gasket for sealing with the door frame or lip of a freezer cabinet (indicated schematically at 32). Frame 3 is provided with a handle formation and hinge formations or mounting means which are not shown in the drawings. Gasket 30 is endless and is made of microcellular polyurethane foam moulded in situ about the perimeter of inner liner 2. It does not have a mitered joint and it is not required to be stretchable in order for it to be fitted around the perimeter of panel 2. In the present example the connecting frame and the inner and outer panel is each manufactured from high density polyurethane by means of reaction injection moulding. In the RIM technique a composition containing a di-isocyanate, a polyester and/or polyether polyol with a catalyst is injected into a split mould as a liquid and subsequently reacts to form a solid polyurethane in the desired shape. After inner panel 2 has been formed, removed from the mould, and prior to its assembly with the other parts of the door, inner panel 2 is placed in another split mould which is assembled so as to enclose rim 27 of panel 2 and a low density microcellular polyurethane is formed by reaction injection moulding within the mould. There is thus formed gasket 30 which extends around the perimeter of the panel as shown in Figure 2. In another embodiment shown in Fig. 3 inner panel 2 is provided with key formation 33 which provides additional mechanical interlocking with the moulded . gasket 30 formed in situ. While it is preferable that the polyurethane gasket adheres to and is unified with the panel on which it is moulded, the invention embraces constructions in which the gasket is integral with the OM article solely by virtue of mechanical interlocking or solely by virtue of chemical bonding as well as by a combination of the two. In other articles gasket 30 formed in situ need not be unified with the panel. If desired the panel may be provided with a release coating prior to formation of the gasket. The gasket may be retained by mechanical formations or may be adhesively bonded to the article or may be integrally formed with the article. The gasket need not extend around the perimeter of a panel and in other embodiments of the invention the gasket may be of a rectangular or other cross-section and may be formed on a surface of an article. The gasket portion is formed as a low density polyurethane microcellular foam in which for preference the body of the gasket is an open cell foam structure and is formed with a integral outer skin or membrane. Fig. 4 shows schematically in cross section portion of an article 40 moulded from high density polyurethane and having a gasket 30 moulded from low density microcellular foam unified therewith by RIM moulding on the surface of article 40. Gasket 30 is formed with an integral outer skin 41. Compositions suitable for use in RIM machinery to produce high density polyurethane mouldings or thermoplastic mouldings such as may be used for the panel are well known in the art. Compositions suitable for use to produce low density microcellular polyurethanes are also well known in the polyurethane art although believed not previously to have been caused to react in high pressure RIM machinery to give satisfactory gasket properties. Those skilled in the art of formulating compositions to produce polyurethanes will readily understand that properties such as the resilience, hardness, compressibility, tear strength, stiffness and the like of the finished gasket can be adjusted by variation in the composition injected into the mould and by control of the moulding conditions although some experiment may be necessary to produce a gasket having a particularly desired set of properties. By way of example only, a satisfactory gasket was produced using a formulation based on Isocyanate 240 obtained from Upjohn Chemicals and Voranol 5148 from Dow Chemicals together with conventional extenders, catalysts, pigments, blowing agents, surfactants, flame retardant and water. By way of further example, three formulations A, B, which can be used to form the gasket are given in Table 1. TABLE 1 Parts by weight of total composition A B C ISOCYANATE PORTION 1. ISOCYANAT 240 48.000 53.300 2. ISOCYANAT 111 44.000 POLYOL PORTION 3. V5148 66.300 66.300 4. V4701 65.400 5. E. GLYCOL 4.160 4.160 4.080 6. MDEAOH 2.040 7. WATER 0.375 0.375 0.204 8. DC11630 0.110 0.110 # 0.040 9. POLYCAT 8 0.007 10. UL28 0.360 0.007 11. UL29 0.360 12. FYROL PCF 13.540 13. MECL2 10.220 13.810 10.220 14. DABCO 33 LV 0.340 0.340 15. TEOHA 1.040 1.040 __•__.._. Components 1 & 2 are diphenylmethane diisocyanate obtained from Upjohn Chemicals. Components 3 and 4 are Veranol (molecular wt 5148) and Veranol (molecular wt 4701) obtained from Dow Chemicals. Component 5 is ethylene glycol. Component 6 is methyl diethanolamine. Component 8 is a silicone obtained from Dow Corning. Component 9 is a dimethyl cyclohexamine. Components 10 and 11 are dibutyl tin dilaurate. Component 12 is a trichlorotrifluro- β -ethyl-phosphate. Component 13 is methylene chloride. Component 14 is triethylene diammine 33% in dipropylene glyσol. Component 15 is triethanolamine. It will be understood that magnetic material may be incorporated in gaskets formed according to the invention. Whether a gasket bonds chemically or mechanically will be influenced by the nature of the substrate and by use, if desired, of release coatings. Freezer doors according to the invention could readily be provided with a plurality of gaskets for example an inner gasket and an outer gasket, which has hitherto been impracticable because of fixing requirements. Thus the heat losses through the seals could be reduced. The invention has application in providing door frames and window frames having integral seals, for use both in construction and in other industries such as the automobile industry and is generally useful for providing parts with an integral gasket for appliances, machinery, and for many other purposes. Those sTilled in the art will readily appreciate from the teaching hereof how the concept may be applied to other embodiments and such embodiments are incorporated within the scope hereof. OMP

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A method for manufacture of a gasket adapted to provide a seal between one article and another, said method being characterized by the step of forming a suitable microcellular polyurethane in a predetermined gasket shape in situ on the article. 2. A method according to claim 1 wherein the microcellular polyurethane is formed in situ by Reaction Injection Moulding. 3. A method according to claim 1 or claim 2 wherein the microcellular polyurethane when formed is of a shape which is mechanically engaged with an interlocking formation of the article. 4. A method according to any one of the preceding claims wherein the gasket is formed around the perimeter of a panel, and is formed with an edge of the panel embedded in the gasket. 5. A method according to any one of the preceding claims wherein the microcellular polyurethane gasket is unified with the article during its in situ formation. 6. A method according to any one of the preceding claims wherein the article is made from a polyurethane composition having a density differing from that of the gasket shape. 7. A method according to any one of the preceding claims wherein the article is manufactured by Reaction Injection Moulding prior to the step of forming a suitable microcellular polyurethane. 8. A method according to any one of claims 1 to 5 wherein the article is made from a thermoplastic material. 9. A method according to any one of the preceding claims wherein the article is a door for a freezer or refrigerator and the gasket is an edge seal gasket. 10. A method according to any one of the preceding claims wherein the microcellular polyurethane is a low density microcellular polyurethane. 11. A method according to claim 1 and substantially as herein described with reference to the example. 12. An article comprising a microcellular polyurethane gasket moulded in situ on the article. 13. An article according to claim 11 wherein the gasket is formed in a configuration which is mechanically interlocked with the article or a formation of the article. 14. An article according to claim 11 or claim 12 wherein the gasket formed is united with the article. 15. An article according to any one of the preceding claims wherein the microcellular polyurethane gasket has a density which differs from the density of the article. 16. An article according to any one of the preceding claims wherein the article is moulded from a polyurethan . 17. An article according to any one of the preceding claims wherein the article is moulded from thermoplastic material. 18. An article according to any one of the preceding^-^f claims wherein the microcellular polyurethane gasket is formed with a skin at the gasket surface. 19. An article according to any one of the preceding claims wherein the gasket is a low density microcellular polyurethane foam. 20. The invention of any one of claims 11 to 18 wherein the article is a freezer or refrigerator door and the gasket is adapted to provide a seal with the freezer or refrigerator cabinet. 21. A freezer lid comprising an inner panel, an outer panel, an edge frame retaining the outer panel, and sealingly engaging with the inner panel, insulation between the inner and outer panel, the inner panel being provided with gasket moulded in situ at or adjacent an edge and adapted for use as a door seal. 22. A freezer lid according to claim 20 wherein the gasket also provided a seal between the inner panel and the edge frame whereby the insulation is sealed from moisture ingress between the frame and inner panel. 23. An article according to claim 11 and substantially as herein described.

Inventors: HOWARD RONALD JOHN, HOWARD, RONALD, JOHN
Applicants: SIMPSON LTD, SIMPSON LIMITED
Application year: 1984
Main classification: B29G3
IPC codes: B29C39, B29C44, B29C67, B29C70, B29K75, B29K105, B60R13, F25D23