A method for the manufacture of a sealing gasket on the rim of a sheet of glass

Abstract: A method of manufacture of a sealing gasket on the rim of a sheet of glass is provided, in which a preformed sealing gasket is fixed to the rim of glass by polymerization in situ of a polyurethane material in a modified mold in which the pre-formed sealing gasket is positioned, the sealing gasket also forming a sealing junction to avoid leaking of the polymer material.

Description: The present invention relates to a method for the manufacture of a sealing gasket on the rim of a sheet of glass, particularly of a sheet of glass to be used as glazing on a vehicle or a fixed installation. The method is well known of manufacturing a sealing gasket for a sheet of glass directly on the outer rim of the glass. Italian patent 1178437 in particular describes a process comprising the step of injecting a thermosetting polyurethane material into the cavity of a mold placed all around the rim of the sheet of glass to be provided with the sealing gasket. The injected polyurethane material polymerizes at determined temperature and pressure conditions and it adheres to the rim of the glass thus taking the shape of the cavity into which it was injected. Italian patent 1178177 describes a mold for carrying out the process according to the above mentioned patent. The mold comprises two portions complementary one to the other, which, on closing one on the other, define a cavity to receive the polyurethane material injected through a hole. A sealing junction placed in a determined position in each of the mold portion and around the cavity is used to prevent the injected material from pouring onto the glass surface. By means of the above mentioned process it is possible to manufacture in one step the entire sealing gasket on the sheet of glass, the sealing gasket serving the purpose of supporting and sealing the glass on the structure to which it is assembled, as well as aesthetically merging the glass surface into the same structure. JP-A-61-189182 describes a sealing gasket formed of two elements, namely a molding and a part obtained by filling the cavity with an injectable material. JP-A-61-235760 describes a molding operation of a sealing gasket on the edge of a glass, in which a braiding is used to prevent faulty moulding. JP-A-55-75290 describes a molding operation of a sealing gasket on the edge of a window glass in which a metallic frame is used to be inserted within the molded gasket. The above mentioned known prior art shows, however, some disadvantages. The polyurethane material forming the sealing gasket does not withstand weathering satisfactorily, so that the strip surface which, after assembling, is in contact with the outer environment, tends to degrade. Consequently a further operation after injection and polymerization is provided, which consists in painting the exposed surface with an opaque paint. The two complementary half-molds have to be provided with a sealing junction in the areas in which they are in contact with the glass. These sealing junctions are subjected to wear and/or to damage so that they have to be replaced from time to time. Since the half-mold forming the outer part of the sealing gasket should provide the gasket with a particular finishing and precision working, as this also has an aesthetic function, such half-mold has to be carefully cleaned after each cycle of molding, to prevent unacceptable surface defects. The inner surface of both half-molds should be treated regularly with anti-adhesive products to avoid that, during the molding, portions of the sealing gasket remain glued to the mold, which would result in a production of waste and further loss of time for the cleaning of the mold. An object of the present invention is to provide a method of manufacture of sealing gasket resistant to weathering, thus avoiding the painting operation and also eliminating the need to clean the lower half-mold after each working cycle. A further object of the present invention is to reduce the use of an anti-glueing substance. Last but not least, an object of the present invention is to provide a method of easy and cheap performance. According to this process the operation for the manufacture of the sealing gasket is divided into two parts. In the first part a weathering strip is produced having characteristics such as to make it adapted to be used in the outside environment, in the second part the operation is carried out of application in situ of the polyurethane material, the prefabricated weathering strip then being sealed to the glass. Object of the present invention is a method for the manufacture of a sealing gasket on the edge of a fixed glazing on a vehicle having a surface to be exposed to the ouside environment, comprising the steps of providing a prefabricated weathering strip having an outer surface on one side and an inner surface on the other side, said inner surface including a sealing edge, the surface of which is capable of sealing on the surface of the sheet of glass; placing said prefabricated weathering strip in a first half mold such that said inner surface of the prefabricated weathering strip defines a surface of a molding cavity; placing the edge of said sheet of glass in contact with said prefabricated weathering strip at said sealing edge thereof, such that said edge of said sheet of glass projects into said molding cavity and additionally defines said molding cavity together with said inner surface of the prefabricated weathering strip; injecting a polymerizable material into said molding cavity under polymerizing conditions and under pressure to obtain a finished sealing gasket comprising said prefabricated weathering strip and said seam of polymerized material, said seam being bonded to said prefabricated weathering strip and to said sheet of glass, and said seam embedding the projecting edge of said sheet of glass, characterized in that: a second half mold is overlaid on said first half mold to form a molding cavity therebetween defined by said inner surface of said weathering strip, said edge of the sheet of glass and said second half mold, with the exclusion of said first half mold; said polymerizable material is polyurethane; and said prefabricated weathering strip being made from a material compatible with polyurethane and adapted to be exposed to the outside environment. A further object of the present invention is a method for the manufacture of a sealing gasket on the edge of a fixed glazing on a vehicle having a surface to be exposed to the ouside environment, comprising the steps of providing a prefabricated weathering strip having an outer surface on one side and an inner surface on the other side, said inner surface including a sealing edge the surface of which is capable of sealing on the surface of the sheet of glass; placing said prefaricated weathering strip in a half mold such that said inner surface of the prefabricated weathering strip defines a surface of a molding cavity; placing the edge of said sheet of glass in contact with said prefabricated weathering strip at said sealing edge thereof, such that said edge of said sheet of glass projects into said molding cavity and additionally defines said molding cavity together with said inner surface of the prefabricated weathering strip, characterized in that: a polymerizable polyurethane material is extruded on said molding cavity under polymerizing conditions from an extrusion nozzle, said extrusion nozzle sliding along said molding cavity and having a cross-sectional configuration such as to provide a seam of a desired cross-sectional shape to obtain a finished sealing gasket comprising said prefabricated sealing gasket and said seam of polymerized polyurethane material, said seam being bonded to said prefabricated sealing gasket and to said sheet of glass, and said seam embedding the projecting edge of said sheet of glass; said prefabricated weathering strip being made from a material compatible with polyurethane and adapted to be exposed to the outside environment. The invention is illustrated in further detail hereinafter with reference to the accompanying drawing, which represents an illustrative embodiment thereof. Figure 1 is a cross section along a vertical plane of the main body of the mold unit, in which the process according to the invention is carried out. The drawing shows a unit formed with two complementary molds, in which mold 1 is closed on mold 2, thus forming a cavity 6. The sheet of glass 3, around the edge of which the polyurethane material has to be injected, is supported by a fixture not shown in the drawing. A braiding 5 is inserted in a housing provided in the mold 1 and it ensures the system being sealed with respect to a polyurethane material leaking towards the upper surface of the glass. The sheet of glass 3 is previously coated on a peripheral strip, with an, opaque layer 7 also containing a chemical bridge substance enhancing the adhesion of glass and polyurethane material. According to the present invention, in the mold 2 a weathering strip 4 is housed along the whole periphery of the glass 3, which is preformed and made of a material compatible with polyurethane and at the same time treated so as to be resistant to weathering. The weathering strip 4 remains exposed to the outside environment after the glass has been assembled on the structure of destination. The weathering strip 4 adheres to the glass 3 in correspondence with the surface 8 thus exploiting a sealing action on it. The manufacture of the sealing gasket according to the present invention comprises two successive steps. The first step is the manufacture of the weathering strip 4 to be exposed to the outside environment, in the second step the injection of polyurethane between the preformed weathering strip 4 and the glass 3, is carried out, so that the glass 3 and the weathering strip 4 are sealed by a seam of polymer material which takes the same size and shape as the cavity 6. In this way the aesthetic function, as well as the function of resistance to weathering are accomplished by the prefabricated weathering strip 4 with no need of a further painting step. Moreover the mold 2 will result in being particularly inexpensive, in that a sealing junction is not required any more, as this function is accomplished by the same preformed weathering strip 4. In addition to this the mold 2 no longer requires an antiglueing treatment, in that it will only come in contact only with the preformed weathering strip 4 which can be provided chemically inert with respect to the mold. A further advantage is that as the mold is not subject to any flowing of the molding material, it will not be excessively worn and it can thus be made of a less expensive material. In a modification of the present invention, the injecting operation of the polyurethane material can be substituted by an extrusion operation of the same material along the rim of the glass. The mold 2 in this case supports the prefabricated weathering strip and the mold 1 is substituted by an extrusion nozzle having the same configuration as mold 1. The nozzle, on horizontally sliding on the mold 2 will lay, on the sealing gasket 4 and the glass 3, a seam of polyurethane material having the same cross-section as the cavity 6, this material being polymerized and set by air humidity and sealing the glass 3 and weathering strip 4 one to the other. This modification can be advantageously used in order to apply a weathering strip having a particular shape.

Claims: A method for the manufacture of a sealing gasket on the edge of a fixed glazing on a vehicle having a surface to be exposed to the ouside environment, comprising the steps of providing a prefabricated weathering strip (4) having an outer surface on one side and an inner surface on the other side, said inner surface including a sealing edge, the surface (8) of which is capable of sealing on the surface of the sheet of glass (3); placing said prefabricated weathering strip in a first half mold such that said inner surface of the prefabricated weathering strip defines a surface of a molding cavity (6); placing the edge of said sheet of glass in contact with said prefabricated weathering strip at said sealing edge thereof, such that said edge of said sheet of glass projects into said molding cavity and additionally defines said molding cavity together with said inner surface of the prefabricated weathering strip; injecting a polymerizable material into said molding cavity under polymerizing conditions and under pressure to obtain a finished sealing gasket comprising said prefabricated weathering strip and said seam of polymerized material, said seam being bonded to said prefabricated weathering strip and to said sheet of glass, and said seam embedding the projecting edge of said sheet of glass, characterized in that: a second half mold is overlaid on said first half mold to form a molding cavity (6) therebetween defined by said inner surface of said weathering strip, said edge of the sheet of glass and said second half mold, with the exclusion of said first half mold; said polymerizable material is polyurethane; and said prefabricated weathering strip being made from a material compatible with polyurethane and adapted to be exposed to the outside environment. A method as claimed in claim 1, in which a braiding (5) is placed between said second half mold and the surface of the sheet of glass. A method for the manufacture of a sealing gasket on the edge of a fixed glazing on a vehicle having a surface to be exposed to the ouside environment, comprising the steps of providing a prefabricated weathering strip (4) having an outer surface on one side and an inner surface on the other side, said inner surface including a sealing edge the surface (8) of which is capable of sealing on the surface of the sheet of glass (3); placing said prefaricated weathering strip in a half mold such that said inner surface of the prefabricated weathering strip defines a surface of a molding cavity (6); placing the edge of said sheet of glass in contact with said prefabricated weathering strip at said sealing edge thereof, such that said edge of said sheet of glass projects into said molding cavity and additionally defines said molding cavity together with said inner surface of the prefabricated weathering strip, characterized in that: a polymerizable polyurethane material is extruded on said molding cavity under polymerizing conditions from an extrusion nozzle, said extrusion nozzle sliding along said molding cavity and having a cross-sectional configuration such as to provide a seam of a desired cross-sectional shape to obtain a finished sealing gasket comprising said prefabricated sealing gasket and said seam of polymerized polyurethane material, said seam being bonded to said prefabricated sealing gasket and to said sheet of glass, and said seam embedding the projecting edge of said sheet of glass; said prefabricated weathering strip being made from a material compatible with polyurethane and adapted to be exposed to the outside environment.

Inventors: LEONE MASSIMO, PAUDICE CIRO, LEONE, MASSIMO, PAUDICE, CIRO
Applicants: SIV SOC ITALIANA VETRO, SOCIETA' ITALIANA VETRO - SIV - S.P.A.
Application year: 1989
Main classification: B29C67
IPC codes: B29C70, B60J10, B29C45, B29C33