WO2019008495A1 - Method for bending and laminating thin glass with pressing plate - Google Patents
Method for bending and laminating thin glass with pressing plate Download PDFInfo
- Publication number
- WO2019008495A1 WO2019008495A1 PCT/IB2018/054885 IB2018054885W WO2019008495A1 WO 2019008495 A1 WO2019008495 A1 WO 2019008495A1 IB 2018054885 W IB2018054885 W IB 2018054885W WO 2019008495 A1 WO2019008495 A1 WO 2019008495A1
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- WIPO (PCT)
- Prior art keywords
- glass
- pressing plate
- thin glass
- bending
- thin
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
- C03B23/023—Re-forming glass sheets by bending
- C03B23/03—Re-forming glass sheets by bending by press-bending between shaping moulds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
- B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
- B32B17/10009—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets
- B32B17/10036—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets comprising two outer glass sheets
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
- B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
- B32B17/10009—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets
- B32B17/10082—Properties of the bulk of a glass sheet
- B32B17/10119—Properties of the bulk of a glass sheet having a composition deviating from the basic composition of soda-lime glass, e.g. borosilicate
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
- B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
- B32B17/10807—Making laminated safety glass or glazing; Apparatus therefor
- B32B17/1088—Making laminated safety glass or glazing; Apparatus therefor by superposing a plurality of layered products
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
- B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
- B32B17/10807—Making laminated safety glass or glazing; Apparatus therefor
- B32B17/10889—Making laminated safety glass or glazing; Apparatus therefor shaping the sheets, e.g. by using a mould
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
- C03B23/023—Re-forming glass sheets by bending
- C03B23/03—Re-forming glass sheets by bending by press-bending between shaping moulds
- C03B23/0302—Re-forming glass sheets by bending by press-bending between shaping moulds between opposing full-face shaping moulds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
Definitions
- This invention relates to the field of bending and laminating glazings comprising thin glass layers.
- Background In response to the regulatory requirements for increased automotive fuel efficiency as well as the growing public awareness and demand for environmentally friendly products, automotive original equipment manufacturers, around the world, have been working to improve the efficiency of their vehicles.
- One of the key elements of the strategy to improve efficiency has been the concept of light weighting. Often times, more traditional, less expensive, conventional materials and processes are being replaced by innovative new materials and processes which while sometime being more expensive, still have higher utility than the materials and processes being replaced due to their lower weight and the corresponding increase in fuel efficiency.
- Vehicle glazing has been no exception.
- Annealed glass is glass that has been slowly cooled from the bending temperature through the glass transition range to relieve any stress in the glass.
- a laminate two sheets of annealed glass are bonded together using a sheet of thermo-plastic. If the laminated glass should break, the plastic bonding layer holds the shards of glass together, helping to maintain the structural integrity of the glass. The shards of broken glass are held together much like the pieces of a jigsaw puzzle. A vehicle with a broken windshield can still be operated. On impact, the plastic bonding layer also helps to prevent penetration by the occupant or by objects striking the laminate from the exterior. Heat strengthened glass, with a compressive strength in the range of 70 Mpa, can be used in all vehicle positions other than the windshield.
- Heat strengthened (tempered) glass has a layer of high compression on the outside surfaces of the glass, balanced by tension on the inside of the glass. When tempered glass breaks, the tension and compression are no longer in balance and the glass breaks into small beads with dull edges. Tempered glass is much stronger than annealed laminated glass. The minimum thickness limits of the typical automotive heat strengthening process are in the 3.2 mm to 3.6 mm range. This is due to the rapid heat transfer that is required. It is not possible to achieve the high surface compression needed for a full temper with thinner glass using the typical low pressure air quenching systems.
- Glass can also be chemically tempered. In this process, ions in and near the outside surface of the glass are exchanged with ions that are larger. This places the outer layer of glass in compression. The maximum strength of chemically tempered soda lime glass is limited. However, with some other glass compositions, compressive strengths in excess of 700 Mpa are possible. The practice of chemically tempering glass is well known to those of ordinary skill in the art and shall not be detailed here.
- a growing portion of windshields are made by the singlet pressing process. With this process, single sheets of glass are bent using a press to form the glass to shape. The resulting shape is much closer to design and the process can hold tighter tolerances across the surface. Thin glass is difficult to bend using either of these bending process.
- the edges of the thin glass have a tendency to lift and form wrinkles. If the plies of glass are of different compositions, with softening points that are too far apart, it may not be possible to gravity bend the different compositions simultaneously on the same mold as the glass with the lower softening point will become too soft leading to marking and distortion. In this case, the different glass types must be bent separately. Also, due to the low weight of the glass sheets, they do not sag under their own weight in the same predictable and repeatable way that thicker glass does. Another problem is that the glass may begin to sag too soon, before the entire sheet of glass has become soft enough.
- Singlet pressing also has problems.
- the primary one is that as the glass is conveyed through the heating section on rolls it tends to bend under its own weight as it softens resulting in the leading edge hitting the rollers and even falling through.
- Lamination also presents problems. Due to the high strength of the chemically tempered thin glass sheets, it can be difficult to get the glass to conform to and bond to the other glass layers in the laminate if there is even a small mismatch between the surfaces. This can lead to delamination, trapped air, distortion and wrinkles. This is even more of a problem when cold bending flat or partially bent thin glass layers.
- Cold bending is a relatively new technology.
- the glass is bent, while cold to its final shape, without the use of heat.
- a flat sheet of glass can be bent cold to the contour of the part. This is possible because as the thickness of glass decreases, the sheets becomes increasingly more flexible and can be bent without inducing stress levels high enough to significantly increase the long term probability of breakage.
- Thin sheets of annealed soda-lime glass in thicknesses of about 1 mm, can be bent to large radii cylindrical shapes (greater than 6 m).
- the glass to be cold bent is placed with a bent glass layer and with a plastic bonding layer placed between the glass to be cold bent and the bent glass layer.
- the assembly is placed in what is known as a vacuum bag.
- the vacuum bag is an airtight set of plastic sheets, enclosing the assembly and bonded together it the edges, which allows for the air to be evacuated from the assembly and which also applies pressure on the assembly forcing the layers into contact.
- the assembly in the evacuated vacuum bag, is then heated to seal the assembly.
- the assembly is next placed into an autoclave which heats the assembly and applies high pressure. This completes the cold bending process as the flat glass at this point has conformed to the shape of the bent layer and is permanently affixed.
- the cold bending process is very similar to a standard vacuum bag/autoclave process, well known in the art, with the exception of having an unbent glass layer added to the stack of glass.
- the thin glass has a thickness of less than about 1.6 mm.
- the female mold 14 may be of the periphery support ring type, as shown in the figures 1A to 1C or of the full surface type as shown in the figures 7 to 10.
- a layer or layers of glass 2, required for the final laminate or as may be required to support the thin glass layer 4 is placed onto the mold prior to the bottom thin glass layer 4.
- the thin glass layers 4 are then placed onto the female mold 14.
- the number of sheets that comprise the stack of thin glass layer that can be bent at the same time will depend upon the type of mold used, the thickness of the glass, the glass composition, the size and the complexity of the shape.
- An innovative process is used to bend a sheet of high bending temperature glass (HBT) to form a pressing plate. This lowers the initial cost of the bending tooling substantially as the cost to fabricate a full surface mold is substantial using conventional materials and methods such as casting and machining metals. Routine maintenance is also substantially reduced as the pressing plate is dimensionally stable and so does not need to be periodically checked for accuracy and adjusted. A method for laminating glazings is also disclosed.
- HBT high bending temperature glass
- the method consists in providing at least one thin glass layer and placing at least one additional thin glass layer, assembling such thin glass layers and a plastic bonding interlayer, placing the pressing plate of the invention such that one of the pressing plate's major faces is in contact with the corresponding major face of the top thin glass layer, enclosing the assembled laminate and evacuating the air from the enclosure and applying heat and pressure to the assembly in a standard lamination process.
- a pressing plate 10 is then placed on the stack of thin glass.
- the male serves to hold the edge of glass down, preventing wrinkling. Additional weight can be added to the male if needed. In addition, clamping can be added.
- the male mold is open to allow for radiant heating of the glass. As the glass is heated and begins to soften, the added mass of the pressing plate aids in the bending of the thin glass layers. The bending can be modified by adjusting the thickness and weight of the pressing plate 10 as may be required.
- the pressing plate is formed by constructing a sand mold to a model of the surface to be bent.
- the sand mold loaded with a sheet of flat HBT glass, is placed in a furnace and bent to shape.
- the present invention also claims a laminate produced by the method for bending and the method for laminating. It is also an object of the invention to provide a vehicle comprising the glazing obtained by the methods of the present invention.
- Figure 1 A shows the isometric view of a bending mold loaded with flat glass and pressing plate.
- Figure IB shows the front view of a bending mold loaded with flat glass and pressing plate.
- Figure 1C shows the rear view of a bending mold loaded with flat glass and pressing plate.
- Figure 2A shows the isometric view of a bending mold with bent glass and pressing plate.
- Figure 2B shows the front view of a bending mold with bent glass and pressing plate.
- Figure 2C shows the rear view of a bending mold with bent glass and pressing plate.
- Figure 3A shows the corner section of a bending mold with bent glass and pressing plate.
- Figure 3B shows the corner detail of a bending mold with bent glass and pressing plate.
- Figure 4A shows the cross section of a bending mold.
- Figure 4B shows the corner detail of a bending mold with glass support layer, thin glass and pressing plate.
- Figure 4C shows the Isometric view of a bending mold with glass support, thin glass and pressing plate.
- Figure 5A shows the exploded view of a laminate with cold bent thin glass layer.
- Figure 5B shows the exploded view of a laminate with thermally bent thin glass layer.
- Figure 6 shows a typical glass laminate cross section.
- Figure 7A shows the isometric view of a male surface master tool.
- Figure 7B shows the isometric view of a male surface master with sand mold box in place.
- Figure 8 shows the isometric view of a filled mold box.
- Figure 9A shows the isometric view of a cast female ceramic mold.
- Figure 9B shows the isometric view of a cast female ceramic mold loaded with flat glass.
- Figure 10A shows the isometric view of a bent pressing plate.
- Figure 10B shows the isometric view of a cast female ceramic mold loaded with bent glass.
- Glass includes but is not limited to: the common soda-lime variety typical of automotive glazing as well as aluminosilicate, lithium aluminosilicate, borosilicate, glass ceramics, and the various other inorganic solid amorphous compositions which undergo a glass transition and are classified as glass included those that are not transparent. Also included are glass like ceramic materials. There are a wide variety of differences in the glass transition temperature range between the various types of glass. The starting point is to pick a glass that has a glass transition range that is sufficiently higher than the glass type that will be bent in the final product. At the forming temperature of the lower temperature glass, the higher temperature glass must retain its shape and strength. In the case of ordinary soda-lime glass or borosilicate glass, an example, certain formulations of lithium aluminosilicate glass meet this criteria.
- the method for bending thin glass of the present invention comprise the steps of: providing a bending mold and a pressing plate; providing a top thin glass layer and a bottom thin glass layer; placing the at least two thin glass layers onto the bending mold; applying the pressing plate over top of the thin glass layers; heating the pressing plate to at least the softening point of the thin glass; and allowing the glass to sag to the desired shape.
- the thin glass 4 will tend to sag under its own weight and even further with the added weight of the pressing plate 10.
- the pressing plate 10 and the thin glass stack will make contact in the central areas. As the thin glass is shielded from much of the radiant heat by the pressing plate 10, the area in direct contact with the pressing plate will heat faster than the edges helping to prevent the early sag problem.
- the pressing plate 10 will help to form the soft thin glass to the desired shape in conjunction with the female mold 14. This is particularly useful when a ring type periphery support mold is used as there is not contact between the female mold and the glass otherwise. With the pressing plate 10, we can achieve improved dimensional quality.
- the pressing plate 10 and the thin glass 4 will be in direct contact across the entire surface of the glass. This helps to reduce any thermal gradients that may be present and assists in reducing residual stress as the glass is annealed. The more uniform heating improves the dimensional quality of the finished part as bending tends to be more accurate and repeatable. The full surface contact and improved heat pattern also serves to prevent wrinkles from forming.
- HBT high temperature glass
- Sand molds have been in use for well over 100 years in the foundry industry and are well known in the art. There are numerous methods and materials, any of which may be used. As the operating temperature required is lower than the typical mold used for some methods and materials are more economical than others.
- a male surface model is cut from tooling board or any other suitable tooling material.
- the mold is enclosed in a box having an open top and metal or wood sides of sufficient strength to contain the sand that will be used to fill the box.
- the box is then filled with the sand mix, tamped firmly into place to eliminate voids and then cured.
- the sand mold is inverted, the box and the male model are removed, leaving a female sand mold.
- a sheet of flat HBT is loaded onto the mold and the mold is then heated to the forming temperature of the HBT and allowed to soak for a period of time sufficient to allow the flat HBT to bend to and take on the shape of the sand mold. The glass is allowed to slowly cool and anneal. The HBT is removed and then used as the pressing plate of the invention.
- a typical automotive laminate is comprised of two layers of glass, the exterior or outer, 201 and interior or inner, 202 that are permanently bonded together by a plastic bonding interlayer 6 (Figure 6).
- the glass surface that is on the exterior of the vehicle is referred to as surface one 101 or the number one surface.
- the opposite face of the exterior glass layer 201 is surface two 102 or the number two surface.
- the glass 2 surface that is on the interior of the vehicle is referred to as surface four 104 or the number four surface.
- the opposite face of the interior layer of glass 202 is surface three 103 or the number three surface. Surfaces two 102 and three 103 are bonded together by the plastic bonding interlayer 6.
- the plastic bonding layer 4 has the primary function of bonding the major faces of adjacent layers to each other.
- the material selected is typically a clear thermoset plastic.
- the most commonly used bonding layer 4 (interlayer) is polyvinyl butyral (PVB).
- PVB has excellent adhesion to glass and is optically clear once laminated. It is produced by the reaction between polyvinyl alcohol and n-butyraldehyde. PVB is clear and has high adhesion to glass. However, PVB by itself, it is too brittle.
- Plasticizers must be added to make the material flexible and to give it the ability to dissipate energy over a wide range over the temperature range required for an automobile. Only a small number of plasticizers are used.
- a typical automotive PVB interlayer is comprised of 30-40% plasticizer by weight.
- ethylene vinyl acetate (EVA), cast in place (CIP) liquid resin and thermoplastic polyurethane (TPU) can also be used.
- Automotive interlayers are made by an extrusion process with has a thickness tolerance and process variation. As a smooth surface tends to stick to the glass, making it difficult to position on the glass and to trap air, to facilitate the handling of the plastic sheet and the removal or air (deairing) from the laminate, the surface of the plastic is normally embossed contributing additional variation to the sheet. Standard thicknesses for automotive PVB interlayer at 0.38 mm and 0.76 mm (15 and 30 mil).
- the pressing plate may be formed by press bending, ring type mold gravity bending or by any other means that had the capability to produce the desired shape.
- the process of fabrication of the present invention provides a full surface pressing plate comprising: a glass sheet having a sufficiently higher glass transition temperature range than the final product composition, such that the pressing plate will maintain its shape at the temperature that the final glass composition is formed; a full surface bending mold of the glass surface; and bending the high temperature glass to the shape on the mold. It should be noted that the difference in temperature between the glass sheet and pressing plate will depend on the glass type of the glass sheet is used. For instance, if Soda Lime is used for the glass sheet, the pressing plate should be a glass of higher transition temperature.
- the foregoing embodiments will also describe in detail the steps of the method for laminating glazings having thin glass layers.
- the method of laminating glazings comprises:
- Embodiment 1 In first embodiment a ring type female mold 14 is first loaded with 5 sheets of thin 0.7 mm clear aluminosilicate glass 4 cut to size. A 6 mm soda lime glass pressing plate 10 is then placed over top of the thin glass 4. The pressing plate 10 is cut slightly larger than the thin glass to make sure that the thin glass 4 is completely covered. After bending, the thin glass 4 is chemically tempered. 2.1 mm soda-lime glass 2 is press bent to shape separately. A laminate is prepared comprising the 2.1 mm bent soda-lime glass 2 outer layer 201 and with an 0.7 mm aluminosilicate inner layer 202. A layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers.
- PVB polyvinyl butyl
- the bent pressing plate covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the surface 204 of the 0.7 thin glass 4 layer 202.
- the assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. Upon completion of the lamination processed, the pressing plate 10 can be reused.
- Embodiment 2 is a diagrammatic representation of Embodiment 1:
- a full surface female mold is first loaded with 10 sheets of thin 0.4 mm clear aluminosilicate glass 4 cut to size.
- An 8 mm infra-red absorbing soda lime glass pressing plate 10 is then placed over top of the thin glass 4.
- the present invention may include a pressing plate comprised of an infrared absorbing glass composition.
- the thin glass 4 is chemically tempered.
- 2.1 mm soda-lime glass 2 is press bent to shape separately.
- a laminate is prepared comprising the 2.1 mm bent soda-lime glass 2 outer layer 201 and with the 0.4 mm aluminosilicate inner layer 202.
- a layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers.
- the bent pressing plate covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the surface 204 of the thin glass 4 layer 202.
- the assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. Upon completion of the lamination process, the pressing plate 10 can be reused.
- Embodiment 3 Embodiment 3:
- a ring type female mold 14 is first loaded with 4 sheets of thin 1.2 mm clear aluminosilicate glass 4 cut to size.
- a 6 mm Lithium Silicate glass pressing plate 10 is then placed over top of the thin glass 4. The pressing plate is cut slightly larger than the thin glass to make sure that the thin glass is completely covered.
- the thin glass 4 is chemically tempered.
- 2.1 mm soda-lime glass 2 is press bent to shape separately.
- a laminate is prepared comprising the 2.1 mm bent soda-lime glass 2 outer layer 201 and with the 1.2 mm aluminosilicate inner layer 202.
- a layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers.
- the bent pressing plate covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the surface 204 of the 0.7 thin glass 4 layer 202.
- the assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. Upon completion of the lamination process, the pressing plate 10 can be reused.
- Embodiment 4 is a diagrammatic representation of Embodiment 4:
- the method used bend the laminate of embodiment 2 is modified with the addition of a 3 mm layer of aluminosilicate glass placed on the mold to provide additional support and to prevent marking of the thin glass.
- the support layer is discarded after bending.
- Embodiment 5 is a diagrammatic representation of Embodiment 5:
- a ring type female mold 14 is first loaded with 5 sheets of thin 1.2 mm clear aluminosilicate glass 4 cut to size.
- a 6 mm Lithium Silicate glass pressing plate 10 is then placed over top of the thin glass 4. The pressing plate is cut slightly larger than the thin glass to make sure that the thin glass is completely covered.
- the 1.2 mm thin glass 4 is chemically tempered.
- a sheet of 0.4 mm aluminosilicate glass is cut to size and then chemically tempered while flat.
- a laminate is prepared comprising the 1.2 mm bent aluminosilicate 4 outer layer 201 with an 0.4 mm aluminosilicate inner layer 202.
- a layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers.
- the bent pressing plate covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the flat surface 204 of the 0.4 thin glass 4 layer 202.
- the assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. The pressure and vacuum bend the flat glass to the desired bent shape. Upon completion of the lamination process, the pressing plate 10 can be reused.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Joining Of Glass To Other Materials (AREA)
- Laminated Bodies (AREA)
- Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
Abstract
Thin glass is finding increasing application in laminates. However, conventional processing methods have short coming when applied to very thin glass. The present invention provides for an improved method of bending and laminating thin glass layers. The present invention allows to multiple sheets or layers of thin glass to get stacked onto a single mold. A male full surface pressing plate, comprising a bent sheet of thicker glass, is placed over the sheets of thin glass. As the glass is heated the added mass of the pressing plate aids in bending. The pressing plate can also be used in the lamination process to prevent wrinkles during laminate. The pressing plate is comprised of a glass composition having a higher glass transition point than the thin glass such that the pressing plate will not soften or deform as the thin glass is bent. The pressing plate is formed by conventional glass bending methods.
Description
METHOD FOR BENDING AND LAMINATING THIN GLASS WITH PRESSING
PLATE
Field of Invention
This invention relates to the field of bending and laminating glazings comprising thin glass layers. Background In response to the regulatory requirements for increased automotive fuel efficiency as well as the growing public awareness and demand for environmentally friendly products, automotive original equipment manufacturers, around the world, have been working to improve the efficiency of their vehicles. One of the key elements of the strategy to improve efficiency has been the concept of light weighting. Often times, more traditional, less expensive, conventional materials and processes are being replaced by innovative new materials and processes which while sometime being more expensive, still have higher utility than the materials and processes being replaced due to their lower weight and the corresponding increase in fuel efficiency. Vehicle glazing has been no exception.
For many years, the standard automotive windshield had a thickness of 5.4mm. In more recent years, we have seen the typical thickness decrease to 4.75 mm. Today, windshields with a 2.1 mm outer ply, a 1.6 mm inner ply and a 0.76 mm plastic interlayer, totaling just under 4.5 mm in total thickness, are becoming common. This is at or very near the limits of how thin an annealed soda- lime glass windshield can be while still retaining safety and durability.
Annealed glass is glass that has been slowly cooled from the bending temperature through the glass transition range to relieve any stress in the glass. In a laminate, two sheets of annealed glass are bonded together using a sheet of thermo-plastic. If the laminated glass should break, the plastic bonding layer holds the shards of glass together, helping to maintain the structural integrity of the glass. The shards of broken glass are held together much like the pieces of a jigsaw puzzle. A vehicle with a broken windshield can still be operated. On impact, the plastic bonding layer also helps to prevent penetration by the occupant or by objects striking the laminate from the exterior.
Heat strengthened glass, with a compressive strength in the range of 70 Mpa, can be used in all vehicle positions other than the windshield. Heat strengthened (tempered) glass has a layer of high compression on the outside surfaces of the glass, balanced by tension on the inside of the glass. When tempered glass breaks, the tension and compression are no longer in balance and the glass breaks into small beads with dull edges. Tempered glass is much stronger than annealed laminated glass. The minimum thickness limits of the typical automotive heat strengthening process are in the 3.2 mm to 3.6 mm range. This is due to the rapid heat transfer that is required. It is not possible to achieve the high surface compression needed for a full temper with thinner glass using the typical low pressure air quenching systems.
Glass can also be chemically tempered. In this process, ions in and near the outside surface of the glass are exchanged with ions that are larger. This places the outer layer of glass in compression. The maximum strength of chemically tempered soda lime glass is limited. However, with some other glass compositions, compressive strengths in excess of 700 Mpa are possible. The practice of chemically tempering glass is well known to those of ordinary skill in the art and shall not be detailed here.
Unlike heat tempered glass, chemically tempered glass breaks into shards rather than beads. This property allows for its use in windshields. However, in standard windshield thicknesses chemically strengthened glass would actually be too strong. In the event of a crash and a head impact, the windshield must break, absorbing the energy of the impact rather than the head of the occupant. Therefore, depending upon the tempered strength, thicknesses of 1.6 mm or less must typically be used. The majority of the vehicles on the road today have windshields that were made using the gravity bending process. In this process, the plies of glass that form the laminate are placed onto a ring type mold which supports the glass near the edges, or a full surface mold and heated. The glass softens and sags to shape under the forces of gravity. Sometimes, for more complex shapes, gravity is assisted by pneumatic pressure and/or a partial or full surface pressing. As the plies of glass to be laminated are bent in sets, the surfaces, while they may have substantial variation from windshield to windshield, are a near perfect match.
A growing portion of windshields are made by the singlet pressing process. With this process, single sheets of glass are bent using a press to form the glass to shape. The resulting shape is much closer to design and the process can hold tighter tolerances across the surface.
Thin glass is difficult to bend using either of these bending process.
When gravity bending is used, due to the low weight of the thin glass sheets, the edges of the thin glass have a tendency to lift and form wrinkles. If the plies of glass are of different compositions, with softening points that are too far apart, it may not be possible to gravity bend the different compositions simultaneously on the same mold as the glass with the lower softening point will become too soft leading to marking and distortion. In this case, the different glass types must be bent separately. Also, due to the low weight of the glass sheets, they do not sag under their own weight in the same predictable and repeatable way that thicker glass does. Another problem is that the glass may begin to sag too soon, before the entire sheet of glass has become soft enough.
Singlet pressing also has problems. The primary one is that as the glass is conveyed through the heating section on rolls it tends to bend under its own weight as it softens resulting in the leading edge hitting the rollers and even falling through.
Lamination also presents problems. Due to the high strength of the chemically tempered thin glass sheets, it can be difficult to get the glass to conform to and bond to the other glass layers in the laminate if there is even a small mismatch between the surfaces. This can lead to delamination, trapped air, distortion and wrinkles. This is even more of a problem when cold bending flat or partially bent thin glass layers.
One approach used to solve these problems is cold bending. Cold bending is a relatively new technology. As the name suggest, the glass is bent, while cold to its final shape, without the use of heat. On parts with minimal curvature a flat sheet of glass can be bent cold to the contour of the part. This is possible because as the thickness of glass decreases, the sheets becomes increasingly more flexible and can be bent without inducing stress levels high enough to significantly increase the long term probability of breakage. Thin sheets of annealed soda-lime glass, in thicknesses of about 1 mm, can be bent to large radii cylindrical shapes (greater than 6 m). When the glass is chemically or heat strengthened the glass is able to endure much higher levels of stress and can be bent along both major axis. The process is primarily used to bend chemically tempered thin glass sheets (<=1 mm) to shape.
The glass to be cold bent is placed with a bent glass layer and with a plastic bonding layer placed between the glass to be cold bent and the bent glass layer. The assembly is placed in what is
known as a vacuum bag. The vacuum bag is an airtight set of plastic sheets, enclosing the assembly and bonded together it the edges, which allows for the air to be evacuated from the assembly and which also applies pressure on the assembly forcing the layers into contact. The assembly, in the evacuated vacuum bag, is then heated to seal the assembly. The assembly is next placed into an autoclave which heats the assembly and applies high pressure. This completes the cold bending process as the flat glass at this point has conformed to the shape of the bent layer and is permanently affixed. The cold bending process is very similar to a standard vacuum bag/autoclave process, well known in the art, with the exception of having an unbent glass layer added to the stack of glass.
As can be appreciated, a better process would be beneficial. Brief Description of the invention. Multiple sheets of thin glass 4 are bent simultaneously using a single bending mold 14. The thin glass has a thickness of less than about 1.6 mm. The female mold 14 may be of the periphery support ring type, as shown in the figures 1A to 1C or of the full surface type as shown in the figures 7 to 10. A layer or layers of glass 2, required for the final laminate or as may be required to support the thin glass layer 4, is placed onto the mold prior to the bottom thin glass layer 4. The thin glass layers 4 are then placed onto the female mold 14. The number of sheets that comprise the stack of thin glass layer that can be bent at the same time will depend upon the type of mold used, the thickness of the glass, the glass composition, the size and the complexity of the shape.
An innovative process is used to bend a sheet of high bending temperature glass (HBT) to form a pressing plate. This lowers the initial cost of the bending tooling substantially as the cost to fabricate a full surface mold is substantial using conventional materials and methods such as casting and machining metals. Routine maintenance is also substantially reduced as the pressing plate is dimensionally stable and so does not need to be periodically checked for accuracy and adjusted. A method for laminating glazings is also disclosed. The method consists in providing at least one thin glass layer and placing at least one additional thin glass layer, assembling such thin glass layers and a plastic bonding interlayer, placing the pressing plate of the invention such that one of the pressing plate's major faces is in contact with the corresponding major face of the top thin glass layer, enclosing the assembled laminate and evacuating the air from the enclosure and applying heat and pressure to the assembly in a standard lamination process.
A pressing plate 10 is then placed on the stack of thin glass. The male serves to hold the edge of glass down, preventing wrinkling. Additional weight can be added to the male if needed. In addition, clamping can be added. The male mold is open to allow for radiant heating of the glass. As the glass is heated and begins to soften, the added mass of the pressing plate aids in the bending of the thin glass layers. The bending can be modified by adjusting the thickness and weight of the pressing plate 10 as may be required.
Most windshield bending glass layers use electric radiant heating in the roof of the furnace. The pressing plate 10 absorbs the radiant heat. The heat is then transferred to the thin glass layers by conduction.
One of the problems that it is encountered when bending thin glass is that the glass sometimes starts to bend too soon. As most of the curvature is typically located towards the center of the glass sheet, the center needs to run hotter than the edges. If the edges heats too fast and soften while the center is still stiff, the shape will be wrong.
The pressing plate is formed by constructing a sand mold to a model of the surface to be bent. The sand mold, loaded with a sheet of flat HBT glass, is placed in a furnace and bent to shape. The present invention also claims a laminate produced by the method for bending and the method for laminating. It is also an object of the invention to provide a vehicle comprising the glazing obtained by the methods of the present invention.
Some advantages of the present invention can be listed as follows.
· Prevents thin glass wrinkles during bending.
• Prevents thin glass wrinkles during lamination.
• Controls the thin glass temperature during bending preventing it from sagging too soon.
• Reduces thermal gradients.
• Reduces residual stress.
· Improves dimensional surface control.
• Provides and efficient means of bending thin glass.
• Allows for bending of different glass compositions for use in the same laminate.
• Improves lamination quality and yields.
Brief Description of the Several Views of the Drawings
Figure 1 A shows the isometric view of a bending mold loaded with flat glass and pressing plate. Figure IB shows the front view of a bending mold loaded with flat glass and pressing plate. Figure 1C shows the rear view of a bending mold loaded with flat glass and pressing plate. Figure 2A shows the isometric view of a bending mold with bent glass and pressing plate.
Figure 2B shows the front view of a bending mold with bent glass and pressing plate.
Figure 2C shows the rear view of a bending mold with bent glass and pressing plate.
Figure 3A shows the corner section of a bending mold with bent glass and pressing plate.
Figure 3B shows the corner detail of a bending mold with bent glass and pressing plate.
Figure 4A shows the cross section of a bending mold.
Figure 4B shows the corner detail of a bending mold with glass support layer, thin glass and pressing plate.
Figure 4C shows the Isometric view of a bending mold with glass support, thin glass and pressing plate.
Figure 5A shows the exploded view of a laminate with cold bent thin glass layer.
Figure 5B shows the exploded view of a laminate with thermally bent thin glass layer.
Figure 6 shows a typical glass laminate cross section.
Figure 7A shows the isometric view of a male surface master tool.
Figure 7B shows the isometric view of a male surface master with sand mold box in place.
Figure 8 shows the isometric view of a filled mold box.
Figure 9A shows the isometric view of a cast female ceramic mold.
Figure 9B shows the isometric view of a cast female ceramic mold loaded with flat glass.
Figure 10A shows the isometric view of a bent pressing plate.
Figure 10B shows the isometric view of a cast female ceramic mold loaded with bent glass.
Reference Numerals of Drawings
2 Glass sheet
4 Thin glass layer
6 Plastic bonding interlayer
8 Support glass plate
10 Pressing Plate
12 Bending mold base
14 Bending mold female ring
51 Male master
52 Mold box
53 Sand/Castable ceramic
54 Cast female mold
55 Flat high bending temperature glass
57 Mold frame
101 Exterior side of glass layer 1, number one surface.
102 Interior side of glass layer 1 , number two surface.
103 Exterior side of glass layer 2, number 3 surface.
104 Interior side of glass layer 2, number 4 surface.
201 Vehicle exterior layer
202 Vehicle interior layer
Detailed Description of the Invention
There are many materials that are classified as glass. Glass, as used in this document, includes but is not limited to: the common soda-lime variety typical of automotive glazing as well as aluminosilicate, lithium aluminosilicate, borosilicate, glass ceramics, and the various other inorganic solid amorphous compositions which undergo a glass transition and are classified as glass included those that are not transparent. Also included are glass like ceramic materials. There are a wide variety of differences in the glass transition temperature range between the various types of glass. The starting point is to pick a glass that has a glass transition range that is sufficiently higher than the glass type that will be bent in the final product. At the forming temperature of the lower temperature glass, the higher temperature glass must retain its shape and strength. In the case of ordinary soda-lime glass or borosilicate glass, an example, certain formulations of lithium aluminosilicate glass meet this criteria.
The method for bending thin glass of the present invention comprise the steps of: providing a bending mold and a pressing plate; providing a top thin glass layer and a bottom thin glass layer; placing the at least two thin glass layers onto the bending mold; applying the pressing plate over top of the thin glass layers; heating the pressing plate to at least the softening point of the thin glass; and allowing the glass to sag to the desired shape.
Due to the herein before mentioned method, the thin glass 4 will tend to sag under its own weight and even further with the added weight of the pressing plate 10. When initially placed on the thin glass 4, the pressing plate 10 and the thin glass stack will make contact in the central areas. As the thin glass is shielded from much of the radiant heat by the pressing plate 10, the area in direct contact with the pressing plate will heat faster than the edges helping to prevent the early sag problem.
As the thin glass 4 sags to shape, the pressing plate 10 will help to form the soft thin glass to the desired shape in conjunction with the female mold 14. This is particularly useful when a ring type periphery support mold is used as there is not contact between the female mold and the glass otherwise. With the pressing plate 10, we can achieve improved dimensional quality.
Near the end of the bending cycle, the pressing plate 10 and the thin glass 4 will be in direct contact across the entire surface of the glass. This helps to reduce any thermal gradients that may be present and assists in reducing residual stress as the glass is annealed. The more uniform heating improves the dimensional quality of the finished part as bending tends to be more accurate and repeatable. The full surface contact and improved heat pattern also serves to prevent wrinkles from forming. To precisely form the high temperature glass (HBT), a sand mold is made. Sand molds have been in use for well over 100 years in the foundry industry and are well known in the art. There are numerous methods and materials, any of which may be used. As the operating temperature required is lower than the typical mold used for some methods and materials are more economical than others.
A male surface model is cut from tooling board or any other suitable tooling material. The mold is enclosed in a box having an open top and metal or wood sides of sufficient strength to contain the sand that will be used to fill the box. The box is then filled with the sand mix, tamped firmly into place to eliminate voids and then cured. The sand mold is inverted, the box and the male model are removed, leaving a female sand mold.
Note that other materials and processes can be used including but not limited to castable ceramics, all of which can be used to produce equivalent bent HBT shapes.
A sheet of flat HBT is loaded onto the mold and the mold is then heated to the forming temperature of the HBT and allowed to soak for a period of time sufficient to allow the flat HBT to bend to and take on the shape of the sand mold. The glass is allowed to slowly cool and anneal. The HBT is removed and then used as the pressing plate of the invention.
In the drawings and discussion, the following terminology is used to describe the configuration of a laminated glazing. A typical automotive laminate is comprised of two layers of glass, the exterior or outer, 201 and interior or inner, 202 that are permanently bonded together by a plastic bonding interlayer 6 (Figure 6). The glass surface that is on the exterior of the vehicle is referred to as surface one 101 or the number one surface. The opposite face of the exterior glass layer 201 is surface two 102 or the number two surface. The glass 2 surface that is on the interior of the vehicle is referred to as surface four 104 or the number four surface. The opposite face of the interior layer of glass 202 is surface three 103 or the number three surface. Surfaces two 102 and three 103 are bonded together by the plastic bonding interlayer 6.
The plastic bonding layer 4 (interlayer) has the primary function of bonding the major faces of adjacent layers to each other. The material selected is typically a clear thermoset plastic. For automotive use, the most commonly used bonding layer 4 (interlayer) is polyvinyl butyral (PVB). PVB has excellent adhesion to glass and is optically clear once laminated. It is produced by the reaction between polyvinyl alcohol and n-butyraldehyde. PVB is clear and has high adhesion to glass. However, PVB by itself, it is too brittle. Plasticizers must be added to make the material flexible and to give it the ability to dissipate energy over a wide range over the temperature range required for an automobile. Only a small number of plasticizers are used. They are typically linear dicarboxylic esters. Two in common use are di-n-hexyl adipate and tetra-ethylene glycol di-n-heptanoate. A typical automotive PVB interlayer is comprised of 30-40% plasticizer by weight.
In addition to polyvinyl butyl, ionoplast polymers, ethylene vinyl acetate (EVA), cast in place (CIP) liquid resin and thermoplastic polyurethane (TPU) can also be used. Automotive interlayers are made by an extrusion process with has a thickness tolerance and process variation. As a smooth surface tends to stick to the glass, making it difficult to position on the glass and to trap air, to facilitate the handling of the plastic sheet and the removal or air (deairing) from the laminate, the surface of the plastic is normally embossed contributing additional variation to the sheet. Standard thicknesses for automotive PVB interlayer at 0.38 mm and 0.76 mm (15 and 30 mil).
While a vacuum bag process is used in the discussion and the preferred embodiments, other methods such as a vacuum ring and other means may be used and are considered as equivalent and do not deviate from the intend of the invention. In the same manner, the pressing plate may be formed by press bending, ring type mold gravity bending or by any other means that had the capability to produce the desired shape. The process of fabrication of the present invention provides a full surface pressing plate comprising: a glass sheet having a sufficiently higher glass transition temperature range than the final product composition, such that the pressing plate will maintain its shape at the temperature that the final glass composition is formed; a full surface bending mold of the glass surface; and bending the high temperature glass to the shape on the mold. It should be noted that the difference in temperature between the glass sheet and pressing plate will depend on the glass type of the glass sheet is used. For instance, if Soda Lime is used for the glass sheet, the pressing plate should be a glass of higher transition temperature.
The foregoing embodiments will also describe in detail the steps of the method for laminating glazings having thin glass layers. The method of laminating glazings comprises:
a) providing at least one thin glass layer and placing at least one additional thin glass layer;
b) assembling the at least two thin glass layers and a plastic bonding interlayer between the at least two thin glass layers;
c) placing a pressing plate produced by the method of Claim 1 such that one of the pressing plate's major faces is in contact with the corresponding major face of the top thin glass layer;
d) enclosing the assembled laminate and evacuating the air from the enclosure; and e) applying heat and pressure to the assembly in a standard lamination process.
Embodiment 1: In first embodiment a ring type female mold 14 is first loaded with 5 sheets of thin 0.7 mm clear aluminosilicate glass 4 cut to size. A 6 mm soda lime glass pressing plate 10 is then placed over top of the thin glass 4. The pressing plate 10 is cut slightly larger than the thin glass to make sure that the thin glass 4 is completely covered. After bending, the thin glass 4 is chemically tempered. 2.1 mm soda-lime glass 2 is press bent to shape separately. A laminate is prepared comprising the 2.1 mm bent soda-lime glass 2 outer layer 201 and with an 0.7 mm aluminosilicate
inner layer 202. A layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers. The bent pressing plate, covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the surface 204 of the 0.7 thin glass 4 layer 202. The assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. Upon completion of the lamination processed, the pressing plate 10 can be reused.
Embodiment 2:
In a second embodiment a full surface female mold is first loaded with 10 sheets of thin 0.4 mm clear aluminosilicate glass 4 cut to size. An 8 mm infra-red absorbing soda lime glass pressing plate 10 is then placed over top of the thin glass 4. It should be noted that the present invention may include a pressing plate comprised of an infrared absorbing glass composition. After bending, the thin glass 4 is chemically tempered. 2.1 mm soda-lime glass 2 is press bent to shape separately. A laminate is prepared comprising the 2.1 mm bent soda-lime glass 2 outer layer 201 and with the 0.4 mm aluminosilicate inner layer 202. A layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers. The bent pressing plate, covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the surface 204 of the thin glass 4 layer 202. The assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. Upon completion of the lamination process, the pressing plate 10 can be reused. Embodiment 3:
In a third embodiment a ring type female mold 14 is first loaded with 4 sheets of thin 1.2 mm clear aluminosilicate glass 4 cut to size. A 6 mm Lithium Silicate glass pressing plate 10 is then placed over top of the thin glass 4. The pressing plate is cut slightly larger than the thin glass to make sure that the thin glass is completely covered. After bending, the thin glass 4 is chemically tempered. 2.1 mm soda-lime glass 2 is press bent to shape separately. A laminate is prepared comprising the 2.1 mm bent soda-lime glass 2 outer layer 201 and with the 1.2 mm aluminosilicate inner layer 202. A layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers. The bent pressing plate, covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the surface 204 of the 0.7 thin glass 4 layer
202. The assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. Upon completion of the lamination process, the pressing plate 10 can be reused.
Embodiment 4:
In a forth embodiment, the method used bend the laminate of embodiment 2 is modified with the addition of a 3 mm layer of aluminosilicate glass placed on the mold to provide additional support and to prevent marking of the thin glass. The support layer is discarded after bending.
Embodiment 5:
In a fifth embodiment a ring type female mold 14 is first loaded with 5 sheets of thin 1.2 mm clear aluminosilicate glass 4 cut to size. A 6 mm Lithium Silicate glass pressing plate 10 is then placed over top of the thin glass 4. The pressing plate is cut slightly larger than the thin glass to make sure that the thin glass is completely covered. After bending, the 1.2 mm thin glass 4 is chemically tempered. A sheet of 0.4 mm aluminosilicate glass is cut to size and then chemically tempered while flat. A laminate is prepared comprising the 1.2 mm bent aluminosilicate 4 outer layer 201 with an 0.4 mm aluminosilicate inner layer 202. A layer of 0.76 mm transparent polyvinyl butyl (PVB) thermo plastic is placed between the two glass layers. The bent pressing plate, covered with a layer of fine mesh fiberglass cloth to prevent scratching, is placed in contact with the flat surface 204 of the 0.4 thin glass 4 layer 202. The assembled laminate and pressing plate 10 are placed in a plastic "bag", the bag is sealed and a vacuum is drawn. This bag is then processed through a standard autoclave process where heat and pressure are applied. The pressure and vacuum bend the flat glass to the desired bent shape. Upon completion of the lamination process, the pressing plate 10 can be reused.
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 spirit of the invention as defined in the following claimed subject matter.
Claims
2. A method for bending thin glass, comprising the steps of:
a) providing a bending mold and a pressing plate;
b) providing at least one thin glass;
c) placing the at least one thin glass onto the bending mold;
d) applying the pressing plate over top of the thin glass layers;
e) heating the pressing plate to at least the softening point of the thin glass; and f) allowing the glass to sag to the desired shape.
3. The method of Claim 1 further comprising the step of placing one or more sheet of glass onto the mold prior to the thin glass.
4. The method of Claim 1 further comprising the step of chemically tempering the thin glass before bending the glass layers.
5. The method of Claim 1 wherein a full surface female mold is used.
6. The method of Claim 1 wherein female pressing plate is used.
7. The method of Claim 1 wherein the thin glass has a thickness of less than about 1.6 mm.
8. The method of Claim 1 wherein the size of the pressing plate is slightly larger than the thin glass.
9. The method of Claim 1 wherein the pressing plate is comprised of a glass composition having a higher glass transition temperature than that of the thin glass.
10. The method of Claim 1 wherein the pressing plate is comprised of an infrared absorbing glass composition.
11. The method of Claim 1 wherein the thin glass is an aluminosilicate glass composition.
12. The method of Claim 1 wherein the thin glass is a borosilicate glass composition.
13. A method for laminating glazings having thin glass layers comprising the steps of: a) providing at least one thin glass layer and placing at least one additional thin glass layer;
b) assembling the at least two thin glass layers and a plastic bonding interlayer between the at least two thin glass layers;
c) placing a pressing plate produced by the method of Claim 1 such that one of the pressing plate's major faces is in contact with the corresponding major face of the top thin glass layer;
d) enclosing the assembled laminate and evacuating the air from the enclosure; and e) applying heat and pressure to the assembly in a standard lamination process.
14. The method of Claim 12 wherein the thin glass is flat.
15. The method of Claim 12 wherein the thin glass is partially bent.
16. The method of Claim 12 wherein the thin glass is cold bent to the desired shape.
17. The laminate produced by the method of Claim 1.
18. The laminate produced by the method of Claim 12.
19. A vehicle comprising the glazing of Claim 16.
20. A vehicle comprising the glazing of Claim 17.
21. A fabrication process of a full surface pressing plate, comprising:
a) providing at least one glass sheet;
b) providing a pressing plate having a sufficiently higher glass transition temperature range than the at least one glass sheet, such that the pressing plate will maintain its shape at the temperature that the final glass sheet is formed;
c) providing a full surface bending mold of the glass surface; and
d) bending the high temperature glass to the shape on the mold.
22. The pressing plate produced by the process of Claim 20.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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DE112018003400.3T DE112018003400T5 (en) | 2017-07-02 | 2018-07-02 | METHOD FOR BENDING AND LAMINATING THIN GLASS WITH A PRESSING PLATE |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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US201762528129P | 2017-07-02 | 2017-07-02 | |
US62/528,129 | 2017-07-02 | ||
CONC2017/0009263A CO2017009263A1 (en) | 2017-09-13 | 2017-09-13 | Method for bending, curving and rolling thin glass with a plate press |
CONC2017/0009263 | 2017-09-13 |
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WO2019008495A1 true WO2019008495A1 (en) | 2019-01-10 |
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PCT/IB2018/054885 WO2019008495A1 (en) | 2017-07-02 | 2018-07-02 | Method for bending and laminating thin glass with pressing plate |
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CO (1) | CO2017009263A1 (en) |
DE (1) | DE112018003400T5 (en) |
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Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0351739A2 (en) * | 1988-07-18 | 1990-01-24 | Asahi Glass Company Ltd. | Method of and apparatus for bending glass plates for a laminated glass |
-
2017
- 2017-09-13 CO CONC2017/0009263A patent/CO2017009263A1/en unknown
-
2018
- 2018-07-02 WO PCT/IB2018/054885 patent/WO2019008495A1/en active Application Filing
- 2018-07-02 DE DE112018003400.3T patent/DE112018003400T5/en not_active Withdrawn
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0351739A2 (en) * | 1988-07-18 | 1990-01-24 | Asahi Glass Company Ltd. | Method of and apparatus for bending glass plates for a laminated glass |
Non-Patent Citations (1)
Title |
---|
ANONYMOUS: "Laminated glass", 11 May 2017 (2017-05-11), XP055514248, Retrieved from the Internet <URL:https://en.wikipedia.org/w/index.php?title=Laminated_glass&oldid=779810554> [retrieved on 20181010] * |
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CO2017009263A1 (en) | 2018-01-31 |
DE112018003400T5 (en) | 2020-03-12 |
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