Process and device for the junction of the ends of an edge gasket on a sheet of glass

Abstract: Junction of the starting end and the finishing end of an edge gasket on a sheet of glass, for example a windscreen for an automobile, extruded directly onto the glass (2), is carried out by means of a separate supplementary mold applied to the glass, into which a compatible polymerizable compound is poured to complete the gasket.

Description: The present invention relates to a process and a device for performing the connection of a seam of extruded plastic material to a sheet of glass particularly to a fixed windscreen in an automobile, in which the seam of plastic material has the function of an edge gasket. It is known that, in order to reduce the cost of assembling a fixed windscreen to the body of an automobile, a process is used which consists in the extrusion directly onto the glass of a polyurethane seam having a calibrated cross-section, the polyurethane being polymerized by environmental humidity so as to generate a gasket which adheres to the glass itself. Assembly on the body of the automobile is greatly simplified, as it is sufficient to spread an adequate quantity of adhesive on the hardened seam, compatible with the polyurethane used to form the seam itself, and to stick the whole onto the metal of the body. In the manufacture of the seam it is necessary to define the most suitable cross-section shape, in order to respond to the requirements of resistance to vibration and sealing against the infiltration of water. For ease of illustration, in the following description reference will be made to a windscreen for automobile, but it is obvious that the present invention can also refer to any kind of fixed sheet of glass. During extrusion of the polyurethane material onto the sheet of glass, a calibrated nozzle is used, through which an amount of plastic material is delivered with pressure which, in correlation with the translation speed of the nozzle itself, defines the shape and thickness of the seam. The problem to be solved according to the invention is that, as the seam has to join up with itself, it is necessary to connect the starting end, or head, of the seam with the finishing end, or tail, in such a way that this connection is performed in the best possible manner and using the least possible manpower. The size of an extrusion nozzle forms a limit to the perfect union of the head and tail of the seam, in that at the least a gap equal to the width of the nozzle itself will remain between the head and the tail. Furthermore the seam itself often has a cross section of a complex shape which is difficult to join up. A typical complex shape is that made up of two sections connected one to the other, in which the first section rests completely against the glass and the second is cantilevered, connected to the first section at its one end only and projecting from the edge of the glass, with a notably elongated portion. In this case it is difficult to obtain a mechanical connection, as there is also the problem of extrusion of the second projecting part which, due to the flowability of the polyurethane, is unable to maintain the desired shape during polymerization. The present invention has the object of overcoming the above difficulties, allowing mechanical manufacture of the connection. According to EP-A-0 421 833, upon which the preamble of claim 1 is based, a surplus of elastomeric material is extruded in the area of the tail of the seam, and then stamped to the shape of the seam to form the connection between the head and the tail of the seam. According to the invention, the process of laying down the seam is divided into two steps: in the first step a first portion of the seam is laid down by extrusion along the whole edge of the glass, while in the second step a second portion of the seam, which forms the final connection of the entire seam in the part of the edge of the glass free from the first portion of seam, is made by direct molding on the glass using a specially prepared mold. There is also a difference between the materials forming the two portions of the seam: the peripheral seam is formed by polyurethane which polymerizes under environmental humidity, whereas that forming the connection is made using a different type of polyurethane, which polymerizes by heating in a relatively short time. Object of the present invention is therefore a process for performing connection of the ends of a seam laid down by extrusion on the edge of a sheet of glass to form the edge gasket of said sheet of glass, in which said seam comprises a first portion in contact with the sheet of glass and a second portion extending above the plane of the glass and projecting out from the first portion, and in which the extrusion of the seam is performed by means of an extrusion device comprising a calibrated nozzle, from which a flow of plastic material is delivered at a given pressure and with a given translation speed of the extruder, the process being characterized by the following steps: arranging the sheet of glass in a vertical or subvertical position, with the area of the edge of the glass left without seam at the bottom thereof; applying to this area of the edge of the glass left without seam a mold of elastic plastic material having a configuration such as to contain the area of the edge and to form a cavity for formation of the seam in this area, the mold being able to have an open and a closed position; pouring into the cavity in the mold in its open position a polymerizable polyurethane composition compatible with the seam, and filling the cavity; closing the mold immediately after pouring, to give the polyurethane material the shape of the seam; polymerizing the polyurethane material; opening the mold; and extracting the sheet of glass from the mold. A further object of the present invention is a mold to be used for the molding operations according to the process described above. Further characteristics of the present invention will be more clearly described with reference to the enclosed drawings, in which: figure 1 is a perspective view in cross section of the seam; figure 2 is a side view of the extrusion nozzle; figure 3 is a cross section view of the mold prepared for the pouring step; figure 4 is a cross section view of the mold prepared for the molding step; and figure 5 is a cross section view of the mold during extraction of the finished product. With reference to figures 1 to 5, the seam 1 is laid on the edge of the sheet of glass 2, and has a cross section formed by a rectangular part 3, by a relief 3a and by an elongated part 4 which extends some way beyond the edge of the glass 2 and which projects outward with respect to the part 3. The calibrated nozzle travels along the edge of the glass and extrudes onto it the seam 1 according to the cross section shown in figure 1. The extrusion nozzle 7 running along the glass 2 creates the seam 1 by means of extrusion of polyurethane material through two separate vertical ducts, not shown in the figure, inside the body of the nozzle 7, one of which feeds the parts 3 and 3a of the seam 1, while the other feeds the part 4. When the nozzle 7 comes close to the head of the seam, it stops the supply of plastic material and moves away from the sheet of glass, so as to avoid unwanted deposits or flashes. This leaves an area of the edge of the glass without seam. Following this, the sheet of glass is placed in a subvertical position by means of a device not shown in the figures, and the part of the edge of the glass left without seam is inserted into a mold 6. On the edge of the glass 2 a thin layer of opaque material 11 is previously laid, having the main job of rendering aesthetically presentable the surface of the sheet of glass opposite that onto which the gasket is extruded. The mold 6 is formed by two rigid plates 8 and 9 opposite each other, and connected by means of an elastic connection, for example a spring 10. This mold has a width such as to cover part of the head and of the tail of the extruded seam, in such a way as to render scarcely visible the difference between extruded seam and molded seam. The mold 6 works like a pair of pincers which normally grip the sheet of glass 2 between the two rigid plates 8 and 9, thanks to the pressure of the spring 10. The part of the two rigid plates 8 and 9 which comes into contact with the edge of the sheet of glass 2 in the area in which the connection of the extruded seam is to take place is provided with an extremely thick coating of silicon rubber which, as shown in figures 3 to 5, forms a single body 12 having on its inside a cavity with a cross section the same as that of the extruded seam, so as to form a mold suitable to create, by pouring, the seam 1. To make said mold 12, the silicon product produced by General Electric and commercially known by the name RTV 664 is preferably used, said product being suitable to form a pouring mold for pourable polyurethane materials. The thickness of the silicon rubber and its elasticity are chosen in such a way that the single body mold 12 allows easy opening of the plates 8 and 9 on the sheet of glass 2 by simple manual pressure. An electric heating element 13 is preferably embedded in the silicon rubber forming the mold 12, to provide the mold with the heat necessary to polymerize the poured polyurethane. The process for performing the connection requires that, immediately after the seam 1 has been laid by extrusion on the edge of the sheet of glass 2, the sheet of glass be inserted, in a subvertical position, into the mold 12, which is held open under the effect of simple manual pressure or in an automatic manner (figure 3). A polyurethane composition compatible with the extruded seam is poured into the mold 12 according to the direction of the arrow F. Following this the mold is closed and the heat generated by the heating element 13 provides hardening of the poured mixture 14 (figure 4). On completion of the hardening phase, the mold 12 is re-opened and the sheet of glass 2 is removed in the direction of the arrow G, with the connection 14 shaped and hardened and intimately bound to the head and tail of the extruded seam 1 (figure 5). With the above arrangement the following advantages are obtained: excellent surface finishing of the connection; the mold, which closes onto itself without openings in the tongue area, avoids the presence of flashes on visible parts of the gasket; the aesthetic appearance of the extruded seam and that of the molded one are almost totally identical. The above advantages give notable reduction of manufacturing costs. A preferred composition of polyurethane material will now be described for use in the connecting process described above, which enables pouring and polymerizing times to be obtained compatible with the process as a whole and also resulting in a molded connection which is entirely similar in appearance to that of the extruded gasket. The preferred polyurethane composition is characterized in that it comprises: A) as the polyole component from 0% to 66% of a polyole having primary OH number equivalent to about 25 mg KOH/g and having a molecular weight equivalent to about 4000; from 5% to 80% of an amine polyole mixture with OH equivalent to about 92 mg KOH/g; from 0% to 40% of a polyetheric mixture with OH equivalent to about 165 mg KOH/g; from 0% to 25% of a plastifying agent stable under ultraviolet light, of the type diisodecyladipate; from 0% to 2% of an organometallic catalyzer; from 0% to 1% of an organometallic catalyzer of the dibutyldilauryl lead type; B) as the isocyanate component the following isocyanates are used together or separately: 4,4'-diphenylmethane-diisocyanate modified with 23% NCO; isoforon-diisocyanate with 38% NCO; isoforon-diisocyanate polyadduct with 30,5% NCO: the isocyanates being chosen in such a way that the ratio NCO:OH be comprised between 1,01 and 1,1. By variation of the percentages of the polyole part and suitable choice of the type or types of isocyanate, a range of composition is obtained having similar final characteristics but with substantial differences as regards the pouring time, the demoulding time, the processing temperature. The features of the present invention will be more clearly illustrated in the following example of realization of the composition. EXAMPLE 1 100g of a polyole mixture produced by the company BAYER and known as VP PU 0784A, having a number of OH equal to approximately 92, are mixed with: 20g of a polyether produced by the company HULS and known as Lab A 2499, having a number of OH equal to approximately 156; 40g of a low viscosity plastifying agent stable under UV, of the type diisodecyladipate; 3g of an organometallic catalyzer of the type Thorcat 535 produced by the company THOR CHEMICAL; 1g of dibutyldilauryl lead. After thorough stirring, the following are added rapidly to the compound: 10.2 g of Desmodur VP PU 0743 produced by the company BAYER with a percentage of NCO of 23% and 23.8g of a polyadduct of IPDI produced by the company HULS and known as Lab B 2499 containing 30.8% NCO. The amounts of isocyanate indicated above include the increase to obtain an NCO index equal to 1.05. The thus obtained mixture has a flow time at 23°C of approximately 35-40 seconds, a delivery time at 90°C of 15' and a Shore A hardness of the hardened product equivalent to 66 units. EXAMPLE 2 The following are intimately mixed together: 2 g of a 92% OH polyole produced by BAYER and known as VP PU 0784A; 10 g of a polyether mixture produced by HULS and known as Lab A 2499 containing 155.7% OH; 5 g of Tecnothane 1371 with an OH percent equivalent to 25; 1.5 g of diisodecyladipate; 0.2 g of Thorcat 535. There are then added 6.5 g of an MDI produced by BAYER of the type Desmodur VP PU 0743 with 23% NCO so as to obtain an NCO index equal to 1.03, and the mixture is rapidly poured into the mold (the flow time at 23°C is approximately 40''). After 15' at 40°C a material is delivered which, on completion of the reaction, has a shore hardness of 56 units. EXAMPLE 3 15 g of Tecnothane 1371 with a % OH equal to approximately 25 and 5 parts of a polyole formulated by the company BAYER and known as VP PU 0784A with OH equal to 92 are mixed, and to this mixture are added 2.9g of Desmodur BAYER VP PU 0743 at 23% NCO (the NCO index will be equal to 1.08). For this mixture the flow time is approximately 30'' at 23°C, the delivery time is 5' at 40°C and the final hardness results approximately 60 Shore A units. EXAMPLE 4 The following are mixed: 10 g of BAYFLEX VP PU 0784A; 1.3 parts of diisoldecyladipate; 0.25 g of Thorcat 535; 0.08 g of dibutyldilauryl lead; 1.9 parte of IPDI by the company HULS at 38% NCO. This composition has a flow time of approximately 2 minutes, a delivery time of 7' at 120°C and a Shore hardness of 70 units.

Claims: A process for performing connection of the ends of a seam extruded and polymerized in situ to complete the edge gasket of a sheet of glass in the area of the edge of the glass left without seam, in which said seam comprises a first portion (3) in contact with the sheet of glass (2) and a second portion (4) extending above the plane of the glass and projecting out from said first portion, and in which the extrusion of the seam is performed by means of an extrusion device (7) comprising a calibrated nozzle, from which a flow of plastic material is delivered at a given pressure and with a given translation speed of the extruder, characterized by the following steps: arranging the sheet of glass (2) in a vertical or subvertical position, with said area of the edge of the glass left without seam at the bottom thereof; applying to said area of the edge of the glass left without seam a mold (6) of elastic plastic material (12) having a configuration such as to contain said area of the edge and to form a cavity for formation of the seam in said area, said mold being able to have an open and a closed position; pouring into the cavity in said mold in said open position a polymerizable polyurethane composition compatible with said seam, and filling said cavity; closing said mold (6) immediately after pouring, to give the polyurethane material the shape of the seam; polymerizing said polyurethane material; opening said mold; and extracting the sheet of glass (2) from said mold. A process according to claim 1, in which said mold is kept in the closed position by means of the action of elastic closure means (10), and is opened by means opposing said elastic closure means. A process according to claim 1 or 2, characterized in that said polyurethane composition comprises: as a polyole component, from 0% to 66% of a polyole having a primary OH number equivalent to about 25 mg KOH/g and having a molecular weight equivalent to about 4000; from 5% to 80% of an amine/polyole mixture with an OH number equivalent to about 92 mg KOH/g; from 0% to 40% of a polyether mixture with an OH number equivalent to about 165 mg KOH/g; from 0% to 25% of a plastifying agent stable under ultraviolet light, of the type diisodecyladipate; from 0% to 2% of an organometallic catalyzer; from 0% to 1% of an organometallic catalyzer of the dibutyldilauryl lead type; as an isocyanate component: 4,4'-diphenylmethanediisocyanate modified with 23% NCO; isoforondiisocyanate with 38% NCO; a polyadduct of isoforondiisocyanate with 30.5% NCO. A process according to claim 3, in which the ratio between NCO and OH is from 1.01 to 1.1. A device capable of performing a connection between the ends of an extruded seam and a polymerization in situ by means of a process as described in the preceding claims, said device comprising: two opposed rigid plates (8, 9), a single body (12) of elastic plastic material joined to said two plates and forming a mold, closure means for closing said mold over said area of the edge of the sheet of glass left without seam, said elastic plastic material being shaped with a molding cavity to be filled with polyurethane material. A device according to claim 5, in which an electric heating element is embedded in the single body (12) to supply heat for a rapid polymerization of the polyurethane material. A device according to claims 5 or 6, in which said closure means are elastic and comprise a spring (10) which acts on said rigid plates (8, 9) so as to keep the mold (6) closed around said area of the edge of the sheet of glass left without seam. A device according to any one of claims 5 to 7, in which said elastic plastic material forming the single body (12) of the mold (6) is a silicon rubber.

Inventors: CAPRIOTTI LUIGI, DE LENA OSCAR, CAPRIOTTI, LUIGI, DE LENA, OSCAR
Applicants: SIV SOC ITALIANA VETRO, SOCIETA' ITALIANA VETRO - SIV - S.P.A.
Application year: 1993
Main classification: B29C70
IPC codes: B29C35, B29C33, B29C70, B29C39, B29C65, B60J10