Patent GB-781361-A (GB)
Title: Method and apparatus for edge sealing glass sheets
IPC: B32B17/10
Filed: 1955-11-14
Abstract: 781,361. Compound transparent sheets. LIBBEY-OWENS-FORD GLASS CO. Nov. 14, 1955 [Nov. 19, 1954], No. 32435/55. Class 140. [Also in Group XI] In a method of sealing the marginal area of a laminate comprising a pair of glass sheets and an interposed sheet of thermo-plastic material, air is evacuated from between the sheets, pressure is applied to the laminate, and the marginal area of the thermoplastic sheet is heated to a higher temperature than that of the adjacent glass sheet to cause the thermoplastic sheet to become adhesive and effect a seal between the glass sheets. A fixed platen 17 is mounted on a support on a frame 21 directly beneath a movable platen 16 supported by rods 22 connected to a support secured to the frame 21 and vertically movable by hydraulic cylinders 23. The platen is guided by a shoe 26 sliding in guides 25. A laminate comprising two layers of bent glass with a layer of thermoplastic material between is placed on the lower platen. The lower platen comprises a thin member 27 with a thickened rim 28. A flexible air impervious diaphragm 29 is placed on the platen on spaced notched rubber strips 41. Over the platen is placed an electrode 44 and a continuous metal bar 30 secured to the rim by bolts 31. The upper platen similarly has a diaphragm 34, an electrode 43 with spaced extensions 45 and insulating blocks 35 secured by insulated blocks 36. The blocks 35 are separated by metallic plates 38 secured by bolts 39 in metallic bushings. A resilient tube 46 acts as a seal between the ends of the platen. The electrodes 43, 44 contact the edges of the glass and are connected to a high-frequency generator or dielectric heater to fuse the thermo-plastic and unite the glass layers. To prevent unequal heating tuning inductances are connected to the electrodes. Conducting clips 69 are connected between electrode extensions 45 and the diaphragm 34 and each one contacts a member 70 which is connected by a bolt 72 insulated in the rim 28 to one end of an inductance coil 74 surrounding a movable core 75. The other end of the coil is secured to a bolt 31 situated midway between a pair of plates 38 of the upper platen. All parts of the rim are equally heated by varying the position of the core 75 in the coil to vary the impedance to tune to resonance. The electrode 44 is connected to a U-shaped conductor 65. The outer member 67 of a coaxial cable connected to the highfrequency generator is connected to the conductor 65 and the inner member 62 is connected to a metallic T-bar 63 supported on insulator blades 64 on member 65. A member 68 connected to an electrode extension 45 contacts the member 63 and closes the transmission line. A two-armed member 79 is bolted to the member 65 and contacts a clip 69. The position of a sliding contact 81 on the member 78 is varied to vary the inductance. In operation the space between the diaphragms is evacuated by ports 49, 50 through exhaust pipes 51. To aid the evacuation increased pressure is applied to spaces 53, 54 through ports 55, 56. Heat is then applied to soften the adhesive and bond the layers. Atmospheric air is then applied between the diaphragms and the air pressure in spaces 53, 54 is reduced to atmospheric pressure. The laminate is then removed and placed in an autoclave. In a modification the outwardly extending clips 69 and members 70 are eliminated. As shown in Fig. 13, a conducting bolt 86 passes through insulated bushes 84, 85 in the rib 33 of the upper platen and secures the electrode. A bolt 91 passes through insulated bushings 89, 90 in the rim 28 of the lower platen and secures the electrode but is insulated therefrom. The ends of bolts 86, 91 contact when the platens are in position. A metallic bar 93 is between and spaced from the bolts 91 and is clamped to the electrode by bolts 94. The upper platen has a similar bar 95 secured by bolts 96. The bar has a wire clip 97 part of which contacts the bar 93 when the platens are in position. The coil 74 is connected between the bolts 94 and a bolt 91. Instead of tuning to resonance to obtain uniform heating, heating may be effected to a greater extent at one part than another.