VACUUM SYSTEM FOR USE IN MANUFACTURING LAMINATED GLASS

Abstract: A vacuum system (10) for evacuating the space between individual laminae (13) of a laminated glass assembly (14). A sealing ring (16) surrounds the peripheral edges of a stacked arrangement of individual laminae (13) adapted to form the laminated glass assembly (14) and communicates with a source of vacuum (20) by a suitable conduit (18a, 18b, 18c). A sensing device (30) is coupled to monitor the pressure within the conduit (18c) and is adapted to prevent communication between the sealing ring (16) and the vacuum source (20) in the event the pressure within the conduit (18c) increases to a predetermined amount. In the preferred embodiment of the invention, the sensing means includes a solenoid valve (24) connected in the conduit (18a, 18b, 18c) between the vacuum source (20) and the sealing ring (16), and a vacuum switch (30) coupled to monitor the pressure in the conduit section (18c) between the solenoid valve (24) and the vacuum source (20) for operating the solenoid valve (24).

Description: Description Vacuum System for Use in Manufacturing Laminated Glass Technical Field The present invention relates generally to a vacuum system utilized for evacuating the space between at least two laminae of a laminated assembly and, in particular, to a vacuum system which is utilized in the manufacturing process of a laminated windshield assembly. Background Art In the early stages of the automobile industry, single sheets of ordinary glass were employed as windshields. As it became evident that this type of windshield presented a considerable safety hazard, the single sheets of ordinary glass were replaced with single sheets of heat treated or tempered glass. Thereafter, as laminated safety glass was developed to reduce the severity of lacerative injuries, its use in automotive windshields greatly increased until today, when almost all automotive windshields are constructed of some type of laminated glass. Typically, a sheet of laminated glass of the type utilized in vehicle windshields consists of two sheets of glass bonded together with a thin plastic interlayer, such as a sheet of polyvinyl butyral, for example. In the event of an impact on a laminated glass windshield OMH sufficient to break the glass, the plastic interlayer functions to bind the glass fragments together, thus reducing the risk of injury to a driver or passenger as a result of flying glass or contact with the windshield. Recently, it has been found that the addition of a second plastic layer applied to the inner surface of the windshield further increases the effec iveness of the laminated glass. However, one of the problems in manufacturing this type of glass is related to the assemblying and bonding techniques utilized to fabricate a windshield of this type with good optical quality. Disclosure of Invention The present invention relates to a vacuum system for use in evacuating the space between individual laminae in the manufacturing of a laminated glass assembly. More specifically, the system includes a sealing means which surrounds the peripheral edges of a stacked arrangement of individual plastic and glass laminae to be bonded into a laminated glass assembly. A source of vacuum communicates with the sealing means through a line means and is adapted to evacuate the space between the individual laminae in order to urge the individual laminae toward one another. In accordance with the present invention, a sensing means is responsive to a predetermined increase in pressure in the line means to prevent communication between the sealing means and the vacuum source. The sensing means can include, for example, a solenoid valve connected in the line means and a vacuum switch coupled to monitor the pressure in the line means and connected to operate the solenoid valve. In the preferred embodiment of the invention, the stacked arrangement of individual laminae having the sealing means attached thereto is positioned within a heated, pressurized chamber which simultaneously applies pressure to the exterior of the stacked laminae to further assist in urging the individual laminae toward one another, while the heat causes the plastic laminae to be bonded to the adjacent glass surfaces. In the event a leak occurs in the sealing means, the pressure within the chamber causes an increase in the line pressure which could possibly damage the vacuum source. The sensing means of the present invention monitors this increase in pressure and disconnects the vacuum source from the seal means, thereby preventing any possible damage to the vacuum source. Brief Description of the Drawings The above, as well as other advantages of the present invention, will become readily apparent to one skilled in the art from reading the following detailed description in conjunction with the attached drawings, in which: Fig. 1 is a block diagram illustrating the vacuum system of the present invention; and Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1 and illustrating the sealing means coupled around a peripheral edge portion of a stacked arrangement of individual laminae adapted to form a laminated glass assembly . Modes for Carrying Out the Invention Referring to Fig. 1, there is shown a block diagram of a vacuum system 10 embodying the features of the present invention. It should be noted at the outset of this description that, while the vacuum system is described for use in the manufac uring process of a laminated glass assembly, it will be appreciated that the vacuum system can be utilized in the manufacturing of other types of laminated assemblies. The vacuum system 10 of Fig. 1 is specifically adapted for use in conjunction with an autoclave unit 12. The autoclave unit 12 includes a heated and pressurized chamber 12a for receiving a stacked arrangement of individual plastic and glass laminae 13 adapted to form a O PI laminated glass assembly. The pressure within the chamber 12a, generally within the range of 225 psi to 275 psi, functions to urge the individual laminae 13 toward one another, while the heat, generally a temperature within the range of 200°F. to 300°F., causes the plastic laminae to bond to the adjacent glass laminae. The vacuum system 10 of the present invention is utilized to evacuate the space between the individual laminae 13 to further urge the individual laminae toward one another. A seal means 16 surrounds the peripheral edge portions of the laminae 13 and is coupled to the vacuum system 10. As shown in Fig. 2, the laminae 13 comprises a windshield assembly 14 and a cover sheet 15. The windshield assembly 14 includes an outer glass sheet 14a, an inner glass sheet 14b, a plastic interlayer 14c positioned between the glass sheets 14a and 14b, and a second plastic layer 14d positioned on the surface of the inner glass sheet 14b opposite the plactic interlayer 14c. The cover sheet 15 is positioned adjacent the plastic layer 14d and is utilized as a press mold to bond the plastic layer 14d to the inner surface of the glass sheet 14b. The surface of the cover sheet 15 adjacent the plastic layer 14d is provided with a suitable wax coating to prevent the layer 14d from bonding to the cover sheet. The seal means 16 is adapted to sealingly engage the outer surfaces of the sheets 14a and 15 to define an enclosed chamber 16a. The enclosed chamber 16a is connected to a conduit section 18a which communicates with a vacuum pump 20 through a manual valve 22, a conduit section 18b, a solenoid valve 24, and a conduit section 18c. A vacuum switch 30 is connected to monitor the pressure in the conduit section 18c through a manual valve 26. The switch 30 generates a signal on a line 30a to either open or close the solenoid valve 24, depending on the pressure in the conduit section 18c. When the pressure in the conduit section 18c increases to a predetermined amount, the switch 30 generates a signal on a line 30a which causes the solenoid valve 24 to close, thereby disconnecting the vacuum pump 20 from the seal means 16. A vacuum gauge 32 is connected to the conduit section 18c through a manual valve 28 to provide the operator with an indication of th vacuum level in the conduit section 18c. It has been found desirable to provide a vacuum switch 30 of the type which will open automatically on a pressure increase above a predetermined set point, but must be manually reset to close on a pressure decrease below the predetermined set point. For example, the switch 30 can be manually set to close and generate a signal to open the solenoid valve when the pressure in the conduit section 18c falls below atmospheric pressure. Thus, before the vacuum pump 20 is activated, the vacuum switch 30 is open and the solenoid valve 24 is closed and, when the vacuum pump 20 is activated, the vacuum switch 30 will sense the pressure drop below above atmospheric pressure and close to generate a signal on the line 30a, thereby causing the solenoid valve 24 to open and apply a vacuum within the chamber 16a of the seal means 16. In the event a leak occurs within the sealing means or the associated connections thereto, the vacuum switch 30 will sense the pressure increase above atmospheric pressure and will open to cause the solenoid valve 24 to close, thus preventing the relatively high pressure within the autoclave unit 12 from entering the conduit section 18c protecting the vacuum pump and the vacuum gauge. In order for the switch 30 to operate again, the switch must then be manually reset. The manual valves 22, 26 and 28 can be used to isolate various sections of the vacuum system in order to assist in detecting the location of a vacuum leak. In accordance with the provisions of the patent statutes, the principles and mode of operation of the present invention have been described in what is considered to represent its preferred embodiment. However, it should be understood that the invention may be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.

Claims: AMENDED CLAIMS [received by the International Bureau on 12 April 1985 (12.04.85); original claim 1 amended; claims 2 and 3 unchanged (1 page)] 1. (Amended) A system for evacuating the space between at least two laminae of a laminated assembly comprising: sealing means surrounding the peripheral edges of the laminated assembly; a source of vacuum; means providing communication between said sealing means and said source; and sensing means associated with said communication means and responsive to a predetermined increase in pressure to discontinue communication between said sealing means and said source and prevent damage to the latter. 2. A system according to claim 1, characterized in that said sensing means includes a valve means located in said communication means between said seating means and said source. 3. A system according to claim 2, characterized in that said sensing means includes a vacuum switch means coupled to monitor the pressure in said communication means, said switch means responsive to a predetermined increase in pressure in said communication means for closing said valve means. OMPI

Inventors: CHAMBERS SCOTT W, CHAMBERS, SCOTT, W.
Applicants: LIBBEY OWENS FORD CO, LIBBEY-OWENS-FORD COMPANY
Application year: 1984
Main classification: B32B31
IPC codes: B32B17, B32B37, B32B43