Method and apparatus of bending glass sheets

Abstract: An apparatus for shaping heat softened glass sheets includes a shaping station to receive a heat softened glass sheet to be shaped; first and second transfer stations positioned along opposing sides of the shaping station, and first and second cooling stations positioned adjacent a corresponding transfer station. An upper vacuum mold having first and second downwardly facing, shaped sheet engaging surfaces moves between the transfer stations and within the shaping station. The sheet engaging surfaces of the vacuum mold each have a shaped configuration generally corresponding to a final desired shaped of a glass sheet to be shaped. Heat softened glass sheets are positioned within the shaping station and lifted into engagement with one of the sheet engaging surfaces to shape the sheet. Vacuum is drawn along the sheet engaging surface to hold the shaped sheet thereagainst. The mold then moves the shaped sheet and engaging surface to one of the transfer stations where the vacuum is discontinued to deposit the shaped sheet a on sheet support. The sheet support then transfers the shaped sheet to one of the cooling stations, where the shaped sheet is controllably cooled.

Description: BACKGROUND OF THE INVENTION This invention relates to bending of glass sheets and in a particular to a glass sheet shaping system which utilizes a double faced vacuum mold arrangement to shape and move heat softened glass sheets from a shaping station to two independent transfer and cooling stations. Shaped glass sheets are widely used as windshields, side windows or rear windows in vehicles such as automobiles and the like. To be suitable for such applications, flat glass sheets must be shaped to precisely define curvatures dictated by the shape and outline of the frames defining the window openings into which the glass windows are installed. It is also important that the windows meet stringent optical requirements and that they be free of optical defects that would tend to interfere with the clear viewing therethrough in their viewing area. During fabrication, the glass sheets may be subjected to thermal treatment to control internal stresses. In particular, glass sheets used for windshields are normally annealed to reduce the internal stresses while glass sheets used for side windows or rear windows are tempered to induce compressive stresses in the major surfaces of the sheets and tensile stresses in the center regions. Tempering strengthens the glass and increases its resistance to damage resulting from impact. In the heating and shaping of glass sheets for windshields, it is common practice to use contoured bending rings that support one or more flat glass sheets and convey it through a heating lehr. As the temperature of the glass increases and approaches its heat softening temperature, it begins to sag under the force of gravity and conforms to the contours of the shaping rails on the mold. If desired, additional presses may be used to shape the glass sheets while supported on the ring. During the commercial production of tempered glass sheets for sidelights and backlights, a glass sheet is generally conveyed along a substantially horizontal path through a tunnel type furnace, heated to its heat softening temperature and transferred into a shaping station adjacent the furnace where the glass sheet is shaped. After shaping, the shaped glass sheet is transferred to a cooling station where it is controllably cooled. The heat softened glass sheet may be shaped, for example, by pressing the sheet between a pair of upper and lower shaping surfaces such as that disclosed in U.S. Patent Nos. 4,272,274, 4,662,925 and 4,830,650. Such shaping means are disclosed in FR-A-2 693 184 and FR-A-2 693 183, wherein shaping stations, transfer stations, first and second cooling stations and a shuttle arrangement are provided. FR-A-2 693 184 additionally discloses an upper mold horizontally movable between the shaping station and two transfer stations and a lower mold vertically movable to lift one of the heat softened glass sheets to be shaped into engagement with the upper mold. The transfer stations between the shaping station and each cooling station comprise bended rolls to transfer the shaped sheets to the cooling stations. Instead of this FR-A-2 693 183 discloses transfer rings provided to move the shaped glass sheets from the shaping stations on each side of the transfer station into the cooling stations. The assembly according to this document provides two vertically movable upper molds. It would be beneficial to have a glass sheet shaping arrangement that provides for high speed shaping of glass sheets while maintaining high optical quality and shape control and in addition allows for the shaping of successive glass sheets to different configurations. SUMMARY OF THE INVENTION This problem is solved by an apparatus according to claim 1 and by a method according to claim 10. The present invention provides an apparatus and method for shaping heat softened glass sheets which includes a shaping station to receive a heat softened glass sheet to be shaped, first and second transfer stations positioned along opposing sides of the shaping station, and first and second cooling stations positioned adjacent a corresponding transfer station. An upper vacuum mold having first and second downwardly facing, shaped sheet engaging surfaces moves between the transfer stations and within the shaping station. The sheet engaging surfaces of the vacuum mold each have a shaped configuration generally corresponding to a final desired shape of a glass sheet to be shaped. Heat softened glass sheets are positioned within the shaping station and lifted into engagement with one of the sheet engaging surfaces to shape the sheet. Vacuum is drawn along the sheet engaging surface to hold the shaped sheet thereagainst. The shaped sheet and engaging surface then move to one of the transfer stations where the vacuum is discontinued to deposit the shaped sheet a on sheet support. The sheet support then transfers the shaped sheet to one of the cooling stations, where the shaped sheet is controllably cooled. In one particular embodiment of the invention, the sheet engaging surfaces of the mold are positioned relative to each other such that when the first engaging surface is in the shaping station, the second engaging surface is in the second transfer station and when the second engaging surface is in the shaping station, the first engaging surface is in the first transfer station. As the mold moves to position the shaped sheet at one of the transfer stations, the next glass sheet to be shaped enters the shaping station and is subsequently lifted into engagement with the other sheet engaging surface to shape the next sheet. DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a preferred embodiment of the invention, with portions removed for clarity. Figure 2 is a schematic view of the invention taken along line 2-2 of Figure 1. DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, an apparatus for shaping and treating heat softenable materials, such as glass but also including plastic and other sheet materials, includes a tunnel type furnace 10 through which a series of glass sheets G is conveyed from a loading station (not shown) at the upstream end of the furnace 10, along a generally horizontal path to a shaping station 12 where a glass sheet G is aligned between an upper vacuum mold assembly 14 and lower mold 16. Vacuum mold assembly 14 includes two glass sheet shaping surfaces 14A and 14B, each shaped to generally correspond to the desired shape of a glass sheet G. Lower mold 16 lifts the glass sheet G and presses it against one of surfaces 14A or 14B as will be discussed later in more detail. The glass sheet G is held against mold 14 by vacuum which then travels to position the shaping surface and glass sheet G within one of two transfer stations 18A and 18B positioned along opposing sides of the shaping station 12. The shaped sheet G is then deposited on sheet transfer means 20A or 20B and transferred to a corresponding cooling station 22A or 22B where it is controllably cooled. More particularly, if the shaped glass sheet is to be used as an automotive side or back window, it will be cooled quickly to impart at least a partial member in the shaped glass sheet. If the shaped glass sheet is to be used in a vehicle windshield, the glass sheet is slowly cooled to anneal the glass. The glass sheet G is then transferred to a cooling conveyor (not shown) for further cooling. If desired, the shaping station 12 and transfer stations 18A and 18B may be enclosed within a heated cavity (not shown) to reduce heat loss during the shaping and transfer operation, as will be discussed later in more detail. Heat may be supplied to the furnace 10 in any convenient manner, for example, from gas heaters or by electrical radiant heaters or a combination of both, which heat supply means is well known in the art. The furnace 10 includes a horizontal conveyor comprising longitudinally spaced transversely extending conveyor rolls 24 of a type well known in the art that define a path of travel which extends through the furnace 10. The exit end of furnace 10 includes conveyor rolls 26 which are arranged in sections so that the speed of the different conveyor sections may be controlled and synchronized in a manner well known in the art, for proper positioning and movement of the glass sheets into shaping station 12 as will be discussed later in more detail. A glass sensing element 28 is located within the furnace 10, as shown in Figure 1, to initiate a shaping, transfer and cooling cycle. The shaping station 12 includes vacuum mold assembly 14, lower shaping mold 16 and a series of spaced support rolls 30 of a type well known in the art, arranged to support the transverse dimension of each heat softened glass sheet G in turn as it exits the furnace 10 and enters the shaping station 12. Mold assembly 14 is preferably composed of a rigid material such as ceramic composite, cast iron, brass or steel, These materials provide a smoothly surfaced contour and good durability despite intermittent contact with hot glass that causes rapid cyclic temperature variations over an extended period. If desired, mold assembly 14 may be covered with a heat resistant cover such as stainless steel or fiber glass fabric. In addition, the mold assembly 14 may include a sheet engaging surface cooling arrangement (not shown) to cool the shaped glass sheet G while held thereagainst. This would be particularly useful in the shaping of glass sheets for windshields, wherein the sheets are subsequently annealed after shaping. As discussed above, mold assembly 14 includes shaping surfaces 14A and 14B. Although not required, it is preferred that mold assembly 14 be constructed such that when surface 14A is in shaping station 12 aligned above lower mold 16, surface 14B is in transfer station 18B, and when surface 14B is in shaping station 12 aligned above lower mold 16, surface 14A is in transfer station 18A, Referring to Figure 1, mold assembly 14 may incorporate the two surfaces into a single structure which is constructed so that vacuum may be independently drawn and released along each surface. As an alternative, mold assembly 14 may include two separate, spaced apart molds that move as a unit as assembly 14 shuttles through shaping station 12 and between transfer stations 18A and 18B. Vacuum is drawn along surface 14A and 14B through evacuation pipes 32A and 32B which connect assembly 14 through a suitable valve arrangement (not shown) to a vacuum source (not shown). The assembly 14 may also be provided with a pressurized air source which provides a positive pressure along surfaces 14A and 14B to help separate the heat softened glass sheet from the assembly 14 when the vacuum is released. The valves for the vacuum and pressurized air lines may be synchronized according to a predetermined time cycle in any convenient manner well known in the glass sheet bending art. If desired, the rolls 24, 26 and/or 30 may be replaced with a gas hearth support arrangement of a type well known in the art. Although not limiting in the present invention, in the embodiment illustrated in Figures 1 and c2, lower mold 16 includes a flexible ring 34 capable of assuming a flat shape when unstressed and a deformed shape that conforms to the curvature of shaping surface 14A or 14B during pressing, as taught in U.S. Patent No. 4,830,650 . The flexible ring 34 is supported on a mounting plate 36 by compliant support assemblies 38 of the type known in the art. If desired, additional pressing pads 40 may be positioned within the periphery of the ring 34 to help lift center portions of the glass sheet G and press it against surfaces 14A and 14B of the assembly 14. Mounting plate 36 is secured to an elevator means 42 so that the flexible ring 34 may be vertically reciprocated from an initial position, wherein the sheet engaging surface of the flexible ring 34 is positioned below support rolls 30 in shaping station 12, to a second position above the support rolls 30 wherein the ring 34 lifts the heat softened glass sheet off the roll 30 and presses it against surface 14A or 14B. Support assemblies 38 allow the flexible ring 34 to engage and conform to the downwardly facing shaping surfaces 14A and 14B of the mold assembly 14. It should be appreciated that as an alternative to moving ring 34 upward between the rolls 30 to transfer the glass sheet G onto ring 34, the rolls 30 may be moved downward below ring 34 to affect the transfer. Ring 34 would then move upward and/or assembly 14 would move downward to press the heat softened glass therebetween. Glass sheet lifting and pressing arrangements other than those illustrated in Figs. 1 and 2 may be used to lift and press the glass sheets G against surfaces 14A and 14B of mold assembly 14, For example, the lower mold may be a non-deformable ring having a fixed shape corresponding to the final desired peripheral configuration of the glass sheet, a slotted mold as disclosed in U.S. Patent No. 4,272,274 or an articulating ring as disclosed in U.S. Patent No. 4,496,386. Furthermore, the lower mold 16 may be eliminated by using air jets of the type disclosed in U.S. Patent No. 4,204,854 to lift the glass sheet into contact with the mold assembly 14. In addition, it should be appreciated that although the shaping surfaces of the molds in the shaping station 12 are configured to shape the glass sheet G into a convex downward configuration, as shown in Figures 1 and 2, they may also be shaped to form the glass to other desired curved configurations. As shown in Figures 1 and 2, the vacuum mold assembly 14 is horizontally movable via a shuttle arrangement 46 (shown in Figure 1 only) along rails 48 (only one shown) between shaping station 12 and transfer stations 18A and 18B. In the particular embodiment illustrated in Figure 1, shuttle arrangement 46 includes a timing belt 50 secured to assembly 14 and extending between pulleys 52 and 54. The outer surface of pulleys 52 and 54 are configured to enmesh with the toothed configuration of the belt 50. If desired, belt 50 and pulleys 52 and 54 may be replaced by a drive chain and sprocket arrangement. Reversible drive 56 is positioned at pulley 52 to drive belt 50 and move assembly 14. If desired, a second drive 58 may be positioned at pulley 54 and drives 56 and 58 may work in combination to alternately shuttle assembly 14 in such a manner that drive 56 moves assembly 14 to the right, as viewed in Figure 1, into transfer station 18B and drive 58 moves assembly 14 to the left into transfer station 18A. As an alternative, shuttle arrangement 46 may also be of the type disclosed in U.S. Patent Nos. 4,662,925 and 4,767,434 or any other arrangement known in the art. Transfer station 18A is similar in construction to transfer station 18B, sheet transfer means 20A is similar in construction to sheet transfer means 20B and cooling station 22A is similar in construction to cooling station 22B. The following discussion will be directed toward transfer station 18A, sheet transfer means 20A and cooling station 22A with the understanding that corresponding transfer station 18B, sheet transfer means 20B and cooling station 22B most likely are, but not required to be, identical. Referring to Figure 1, sheet transfer means 20A is provided at transfer station 18A to move the shaped glass sheets G from the transfer station 18A into the cooling station 22A. In the particular embodiment illustrated in Figure 1, sheet transfer means 20A is a transfer ring 60A, e.g. as disclosed in U.S. Patent No. 4,285,715, which includes a support rail 62 with a sheet supporting surface that follows the contours of the shaped glass sheet spaced slightly inward of the sheet's periphery. The glass sheet supporting surface of the rail 62 is preferably a non-metallic material that can support the hot glass sheet without leaving a mark on the glass sheet surface. The ring 60A is mounted on a carriage 64 which moves the ring 60A along guide rail 66 from a load position where the ring 60A is positioned in the transfer station 18A beneath shaping surface 14A to receive a shaped glass sheet, to a cooling position where the ring 60A is positioned between air nozzles in the cooling station 22A. The cooling station 22A includes longitudinally spaced, transversely extending rows of spaced nozzles 68 extending downward from an upper platen 70 and in an opposing position to longitudinally spaced, transversely extending rows of bar nozzles 72 on a lower platen 74, e.g. as disclosed in U.S. Patent No. 4,285,715. The bar nozzles 72 are spaced vertically below the upper nozzles 68 to provide clearance for moving the ring 60A along a path therethrough. The lower ends of the rows of the upper nozzles 68 and the upper ends of bar nozzles 72 are located along a curved surface complimenting the curved shape of the shaped glass sheet transferred therebetween. In operation, each glass sheet G in turn is conveyed through the furnace 10 and heated to its heat softening temperature while supported across it entire width on rolls 24. Sensor 28 senses the position of a glass sheet in the series, e.g. its leading or trailing edge, and sends this information to a controller (not shown) which controls the conveying rates of rolls 24, 26 and 30. While it is possible to preset any desired program of rotational speeds for conveyor rolls 24, 26 and 30, in one particular embodiment, the program involves rotating conveyor rolls 24 within the furnace 1 G at a rate of rotation sufficient to transport a series of glass sheets through the furnace 10 at a constant speed on the order of 400-450 inches (10.2-11.4 m) per minute. As each glass sheet G approaches the end of the furnace 10, the rolls 26 and 30 accelerate in sequence to increase the glass sheet's speed to a speed on the order of 1200 inches (30.5 m) per minute for transfer of the shaped glass sheet G from furnace 10 to the shaping station 12. As the glass sheet G approaches the shaping position within shaping station 12, i.e. aligned below shaping surface 14A or 14B, which in turn is aligned above lower mold 16, the rolls 30 decelerate in unison to a glass sheet speed on the order of 700 inches (17.8 m) per minute or less at the moment the glass sheet is lifted by lower mold 16 into engagement with the mold assembly 14. Decelerating the rate of rotation of the support rolls 30 to a speed less than the accelerated speed of transfer from the furnace 10 to the shaping station 12 before the glass sheet G is lifted by lower mold 16 into engagement with and pressed against shaping surface 14A or 14B of vacuum mold assembly 14 insures a smaller variation of glass sheet position from sheet to sheet when lifted off support rolls 30. When a glass sheet G exits furnace 10 and enters shaping station 12, the assembly 14 is positioned so that one of its engaging surfaces is at a shaping position within the shaping station 12 while its other engaging surface is at a unload position at one of the transfer stations. Referring to Figure 2, assembly 14 is shown with engaging surface 14A at a shaping position within shaping station 12 while engaging surface 14B is at transfer station 18B. When a heat softened glass sheet G is in the proper position within shaping station 12 between engaging surface 14A and lower mold 16, the sheet G is lifted by mold 16, pressed against shaping surface 14A, and held thereagainst by vacuum drawn along surface 14A. The assembly 14 then moves to position the glass sheet G at an unload position in one of the transfer stations. More particularly, assembly 14 and the heat softened glass sheet G shuttle to the left, as viewed in Figure 2, into transfer station 18A to position surface 14A and glass sheet G at an unload position above transfer ring 60A while surface 14B of the assembly 14 moves from an unload position within transfer station 18B to a shaping position within shaping station 12. When the glass sheet G is in proper alignment above ring 60A, the vacuum along surface 14A is terminated to deposit the sheet onto the ring 60A which then transfers the shaped glass sheet G to cooling station 22A where it is controllably cooled in a manner as discussed earlier. As the assembly 14 moves the shaped sheet from the shaping station 12 to transfer station 18A, the next glass sheet exits the furnace 10 and moves towards shaping station 12. The movement of assembly 14 between transfer stations 18A and 18B and conveyance of the glass sheets G into shaping station 12 is coordinated such that the sheet engaging surfaces 14A and 148 are positioned within the shaping station 12 whenever a heat softened glass sheet arrives at the shaping station 12 above lower mold 16. As a result, the next glass sheet G arrives below surface 14B which is at its shaping position above mold 16 at approximately the same time as the previous glass sheet is being deposited at a transfer station 18A. Mold 16 then lifts sheet G and presses it against shaping surface 14B and vacuum is drawn along surface 14B to hold glass sheet G thereagainst. The assembly 14 then shuttles to the right, as viewed in Figure 2, to move surface 14B and shaped glass sheet G from shaping station 12 to its unload position above transfer ring 60B in transfer station 18B. As the assembly 14 moves to the right, surface 14A moves from its unload position at transfer station 18A to its shaping position within shaping station 12 to receive the next heat softened glass sheet G. Vacuum is then terminated along surface 14B to deposit the shaped glass sheet G on transfer ring 60B at transfer station 18B which then transfers the shaped glass sheet to cooling station 22B where it is controllably cooled as the next glass sheet G enters shaping station 12 and is positioned between surface 14A and lower mold 16 of assembly 14. The cycle is repeated to shape successive glass sheets at shaping station 12 and alternately transfer the glass sheets to transfer stations 18A and 18B. It should be appreciated that although optimal cycle time may be achieved by depositing a shaped glass sheet from one of the sheet engaging surfaces at one of the transfer stations at the same time the next heat softened sheet is lifted and pressed against the other engaging surface, operating constraints or other conditions may result in a time delay between the arrival of one of the engaging surfaces within the shaping station 12 and the arrival of the next glass sheet G from the furnace 10. This condition however will not create a problem since there will always be an engaging surface waiting for the next glass sheet at the shaping station. As a result, the sheet may be lifted off rolls 30 and pressed to shape against one of the sheet engaging surfaces as soon as it is in the proper position within the shaping station 12. It should be appreciated that, if desired, additional shaping of the glass sheet G may be performed in the transfer stations. More particularly, the temperature of the glass sheet G may be maintained and/or the distance the sheet G drops from engaging surfaces 14A or 14B to rings 60A or 60B, respectively, may be such that when vacuum is terminated along the engaging surfaces of assembly 14, there is additional shaping of the sheet G as it contacts the rings of the sheet transfer means. This type of shaping arrangement is commonly referred to as drop forming and is disclosed in U.S. Patent No, 4,233,049. It should also be appreciated that the surfaces 14A and 14B of assembly 14 may have different glass sheet shaping configurations as shown in Figure 2. For example, surface 14A may correspond to the shaped configuration for the outer glass sheet of a laminated windshield, while surface 14B corresponds to the configuration for the inner glass sheet. It is expected that with a flexible lower mold 16 of the type discussed earlier, the shapes of the inner and outer glass sheets are similar enough that the mold 16 may be used to lift and shape both glass sheets against the different shaping surfaces. As shown in Figures 1 and 2, the glass sheets G travel in a generally straight path from the shaping station to the transfer station to the cooling station, If desired, the cooling stations may be oriented 905 ○ relative to the transfer stations to form a "tuning fork" arrangement as is known in the art. This arrangement is particularly useful when fabricating inner and outer glass sheets for a laminated windshield since it keeps the glass sheets in close proximity to each other so that they may be mated after cooling to form a doublet pair that is further processed to form the windshield. The forms of the invention shown and described in this specification represent illustrative preferred embodiments and it is understood that various changes may be made without departing from the scope of the claims.

Claims: An apparatus for shaping heat softened sheet material, including a shaping station (12) to receive the heat softened sheets(G) to be shaped, an upper vacuum mold (14) having first and second downwardly facing, said sheet engaging surfaces (14A, 14B) to shape and secure heat softened sheets to be shaped thereagainst, each of said engaging surfaces having a shaped configuration generally corresponding to a final desired shape of each of the sheets to be shaped; first and second transfer stations (18A, 18B) positioned along opposing sides of said shaping station (12); first and second cooling stations (22A, 22B) positioned adjacent a corresponding transfer station; a movable mold (16) to lift one of said heat softened sheets to be shaped into engagement with one of said sheet engaging surfaces within said shaping station; and a shuttle arrangement (46) to move said upper mold between said transfer stations and said shaping station, characterized in that shaped sheet supports (60A, 60B) having a sheet supporting surface contoured similar to the shaped glass sheet are positioned on each side of the upper mold (14) to support and transfer, and preferably additionally shape, said sheet from said one of said transfer stations to a corresponding one of said cooling stations. The apparatus as in claim 1 wherein said shuttle arrangement (46) comprises a timing belt (50) secured to the vacuum mold (14) and motors (56, 58) acting on the belt (50) to position the sheet engaging surfaces (14A, 14B) of said mold (14) relative to said shaping station (12) such that when said first engaging surface (14A) is in said shaping station (12), said second engaging surface (14B) is in said second transfer station (18B) and when said second engaging surface (14B) is in said shaping station (12), said first engaging surface (14A) is in said first transfer station (18A). The apparatus as in claim 1 wherein said first sheet engaging surface (14A) has a shaped configuration different from said second sheet engaging surface (14B). The apparatus as in claim 1 further including conduits (32A, 32B) connected to said mold (14) through which a vacuum is applied to said sheet engaging surface at said shaping station while said movable mold (16) moves toward the engaging surface at the shaping station and no vacuum is applied to the other of said sheet engaging surfaces at one of said transfer stations. The apparatus as in claim 1 wherein said first and second transfer stations (18A, 18B) include first and second shaped sheet supports being support rings (60A, 60B), respectively, to receive said shaped sheet deposited at said respective transfer station, each of said support rings having a configuration generally corresponding to the desired peripheral shape of said shaped sheet. The apparatus as in claim 1 wherein said shaping station (12) further includes a set of longitudinally spaced, transversely extending support rolls (26) forming a sheet support surface and said movable mold (16) is a lower mold vertically aligned below each of said sheet engaging surfaces when said sheet engaging surfaces are within said shaping station, said lower mold being movable from a recessed position below said sheet supporting surface to a raised position above said sheet supporting surface. The apparatus as in claim 5 wherein said lower mold (16) includes a ring (34) having a curve configuration generally corresponding to the desired peripheral shape of said sheet which engages a marginal edge portion of said sheet as said lower mold lifts said sheet off said sheet support surface and presses said sheet against one of said sheet engaging surfaces of said upper mold. The apparatus as in claim 5 wherein said ring (34) is a flexible outline shaping ring (34) having a flat configuration which engages a marginal edge portion of said sheet as said lower mold lifts said sheet off said sheet support surface, and a shaped configuration when said lower mold presses said sheet against one of said sheet engaging surfaces of said upper mold to conform said marginal edge portion of said sheet to a corresponding portion of said one engaging surface. The apparatus as in claim 1 wherein said movable mold (16) includes a plurality of members (40) each having gaseous jets within said members (40) positioned below said ring (34) when said engaging surfaces (14A, 14B) of said mold (14) are within said shaping station to direct air at a lower major surface of said heat softened sheet and lift said sheet into engagement with said one sheet engaging surface. A method of shaping heat softenable sheet material, comprising: (a) heating a series of sheets (G); (b) positioning first and second transfer stations (18A, 18B) on opposing sides of a shaping station (12); (c) providing an upper vacuum mold (14) having first and second sheet engaging surfaces (14A, 14B), each of the sheet engaging surfaces being shaped to a configuration generally corresponding to the final desired configuration of a sheet to be shaped; (d) positioning said mold such that said first sheet engaging surface (14A) is within said shaping station; (e) conveying a first sheet (G) into said shaping station; (f) lifting said first sheet (G) into engagement with said first sheet engaging surface (14A) of said vacuum mold (14); (g) drawing a vacuum along said first sheet engaging surface to secure said first sheet thereagainst and shaping said first sheet; (h) moving said mold such that said first sheet engaging surface and said first sheet move from said shaping station to said first transfer station (18A); (i) terminating said vacuum applied to said first sheet engaging surface to deposit said first sheet onto a first shaped sheet support (60A) at said first transfer station (18A); (j) transferring said shaped sheet and sheet support to a first cooling station (22A); (k) controllably cooling said first shaped sheet; (l) positioning said second sheet engaging surface (14B) within said shaping station (12); (m) conveying a second sheet into said shaping station; (n) lifting said second sheet into engagement with said second sheet engaging surface of said vacuum mold; (o) drawing a vacuum along said second sheet engaging surface to secure said second sheet thereagainst and shaping said second sheet; (p) moving said vacuum mold such that said second sheet engaging surface and said second sheet move from said shaping station (12) to said second transfer station (18B); (q) terminating said vacuum applied to said second sheet engaging surface to deposit said second shaped sheet onto a second shaped sheet support (60B) at said second transfer station; (r) transferring the second shaped sheet and sheet support to a second cooling station (22B); and (s) controllably cooling said second sheet. The method as in claim 10 wherein the practice of said step (l) is started prior to the completion of the practice of said step (k). The method as in claim 11 wherein said positioning step (d) and moving step (p) locate said first sheet engaging surface (14A) within said shaping station (12) and said second sheet engaging surface (14B) within said second transfer station (18B) and said moving step (h) and positioning step (l) locate said first sheet engaging surface (14A) within said first transfer station (18A) and said second sheet engaging surface (14B) within said shaping station (12). The method as in claim 12 wherein said steps (m) and (n) are practiced during the practice of said steps (h) and (i), and the practice of said steps (p) and (q) are practiced during the practice of said steps (e) and (f). The method as in claim 10 wherein said lifting steps (f) and (n) each include the step of pressing a sheet against one of said vacuum mold engaging surfaces. The method as in claim 10 wherein said lifting steps (f) and (n) each include the steps of engaging a marginal edge portion of a sheet and of pressing said sheet so engaged against one of said sheet engaging surfaces of said upper mold. The method as in claim 10 wherein the practice of said lifting step (f) shapes said first sheet to a first configuration and the practice of said lifting step (n) shapes said second sheet to a second configuration different from said first configuration. The method of claim 10 wherein: (t) practicing steps (d) and (p) by positioning said mold such that said first sheet engaging surface (14A) is within said shaping station (12) and said second sheet engaging surface (14B) is within said second transfer station (18B); (u) practicing steps (h) and (l) by moving said mold such that said first sheet engaging surface and said first shaped sheet move from said shaping station (12) to said first transfer station (18A) and said second sheet engaging surface moves from said second transfer station (18B) to within said shaping station while conveying a second heat softened sheet into said shaping station; (v) practicing step (i) by terminating said vacuum applied to said first sheet engaging surface (14A) to deposit said first shaped sheet on a first shaped sheet support at said first transfer station while step (n) is practiced to move said second sheet into engagement with said second sheet engaging surface (14B) of said mold to shape said second sheet and step (o) is practiced to draw a vacuum along said second sheet engaging surface (14B) to secure said second shaped sheet thereagainst; (w) practicing step (p) by moving said mold (14) such that said second sheet engaging surface and said second shaped sheet move from said shaping station (12) to said second transfer station (18B) while practicing the further step of moving said first sheet engaging surface from said first transfer station to said shaping station while said steps (d) and (e) are practiced, wherein step (e) is practiced to convey a next heat softened sheet into said shaping station (12); (x) practicing step (q) by terminating said vacuum along said second sheet engaging surface (14B) to deposit said second shaped sheet on a second shaped sheet support (608) at said second transfer station (18B) while practicing said steps (f) and (g) to move said next sheet into engagement with said first sheet engaging surface (14A) of said mold (14) to shape said next sheet and draw a vacuum along said first sheet engaging surface (14A) to secure said next shaped sheet thereagainst; (y) practicing steps (r) and (s) to transfer said second shaped sheet and said second sheet support to a cooling station (22B) to controllably cool said second sheet, and further including (z) repeating steps (t) through (y).

Inventors: FRANK ROBERT GEORG, FRANK, ROBERT GEORG
Applicants: PPG IND OHIO INC, PPG INDUSTRIES OHIO, INC.
Application year: 1995
Main classification: C03B23
IPC codes: C03B23, C03B35