Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With cutting – punching – piercing – severing – or tearing
Reexamination Certificate
2001-07-31
2003-07-08
Gray, Linda L (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With cutting, punching, piercing, severing, or tearing
C156S268000, C156S257000, C065S060300, C065S105000, C065S106000, C065S112000, C264S154000, C427S289000, C427S154000, C083S016000, C083S875000, C083S881000, C083S885000, C428S426000, C428S441000, C428S442000
Reexamination Certificate
active
06588477
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and an apparatus for cutting a laminate made of a brittle material and a plastic with a cutting tool. The cutting of thin glass or glass-ceramic/plastic laminates is a preferred application.
2. Prior Art
Laminates made of a brittle material and a plastic are composite workpieces, the component parts of which consist of materials that differ greatly on account of their mechanical and thermal properties.
Plastics customarily used for the production of these laminates are generally mechanically relatively flexible or ductile and have a high thermal expansion of typically 20 to 80 ppm/K and a low softening temperature of typically 120 to 260° C.
In contrast to this, brittle materials, such as glass, glass-ceramic or ceramic material, used for the production of the above-mentioned laminates are mechanically brittle and generally have a low thermal expansion and a high softening temperature. The thermal expansion of glass is typically around 3.5 to 11 ppm/K and the softening temperature T
G
is typically 500 to 750° C.
Because of the stated very different physical properties of the two materials, until now no method or apparatus has existed for cutting a laminate comprising a brittle workpiece and a plastic with a cutting tool in one operation. The previously known methods and apparatuses relate only to the cutting of the respectively unprocessed material, but not of the composite.
To mechanically cut an unprocessed brittle material, such as glass for example, the glass surface is scored, for example by means of a diamond cutter or a small cutting wheel or a cutting blade made of hard metal. The surface damage produced in this way then represents a rupture joint of the glass, along which the crack runs in a controlled manner under tensile loading. During scoring of the glass, the normal force exerted on the cutting instrument must not exceed a certain value, dependent on the thickness of the glass. Otherwise, this generally leads to an uncontrolled rupture of the glass (H. Jebsen-Marwedel and R. Brückner (editors), Glastechnische Fabrikationsfehler [glass manufacturing defects], Springer-Verlag, Berlin, Heidelberg, New York, 1980, page 577 et seq., Chapter 12.7, F. Kerkhof and B. Gänswein, Das “Schneiden” des Glases [the “cutting” of glass]).
In addition to conventional mechanical cutting, methods in which the inducement of stresses along the cutting line is produced by thermal means have been known for some time. For example, DE 197 15 537 Al discloses a method and an apparatus for severing flat workpieces made of brittle material, in which a laser beam is used to induce a thermomechanical stress along a separating line.
Furthermore, cutting the unprocessed brittle material by means of sand blasting using a mask (JP 06008145 A) or by means of water-jet cutting using an abrasive agent (DE 35 33 340 Al) are known.
In contrast to this, unprocessed plastic films are generally either cut with a shear-action cut, using a shearing action of two sharp-edged hard-metal blades moved against one another, or by using a very sharp cutting knife or cutting wheel.
However, all the methods mentioned above are unsuitable for cutting a laminate of the type mentioned, for example a glass/plastic laminate. It is directly evident that the shear-action cutting of the laminate is possible only when using thin types of glass. However, here too the shear-action cut produced by the shearing action in the thin glass sheet gives rise to uncontrolled brittle cracks transversely to the cutting direction. Although a sharp, scalpel-like cutting knife is capable of severing the plastic film, it is not able to cut through or score the glass. Rather, it would very quickly be blunted on the glass surface.
When cutting with a diamond or a small hard-metal wheel, it is necessary according to the above to keep the loading pressure below a certain limit value to avoid uncontrolled rupture of the glass. The maximum loading pressure of the cutting tool limited in this way is not sufficient, however, to sever the film of the laminate composite reliably. On account of its flexibility, relatively high loading pressures (or normal forces) would be required for severing the plastic film, but for their part would again lead to uncontrolled rupture of the glass.
Because of the foregoing facts, it is not possible with the conventional mechanical cutting methods to cut these laminates in one operation. Alternative methods for cutting these composite pieces have a series of disadvantages.
In the known laser cutting, the apparatus expenditure is significantly greater, on account of the laser and the necessary optical peripherals, resulting in significantly higher costs. Vaporized or even pyrolyzed material may be deposited on the laminate or the optical components.
Water-jet cutting leads to soiling of the surface and to surface defects due to the water and the admixed abrasive agent. Cutting by means of sand blasting likewise leads to soiling of the surface and to surface defects of the laminate. These methods usually entail additional cleaning expenditure.
The introduction of these laminates, such as thin glass/plastic laminates for example, into existing product applications, for example in the display industry as a substitute for thin glass substrates, is facilitated considerably if there is an available cutting method which is as compatible as possible with the conventional cutting techniques, causes low additional costs and, if appropriate, can be implemented in existing glass cutting installations.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and an apparatus for cutting a laminate made of a brittle material, in particular made of glass, glass-ceramic or ceramic material, and a plastic with a cutting tool, whereby the laminate is to be cut as far as possible in one operation, and at the same time a high cutting accuracy and faithfulness to contours as well as rapid cutting are to be made possible.
It is another object of the invention to design the method and the apparatus in such a way that they are compatible with existing cutting methods, that only low additional costs result and that they can, if appropriate, be implemented in existing cutting installations.
According to the invention, these objects are achieved by a method comprising the steps of:
heating the plastic at least in the vicinity of a predetermined cutting line, thereby lowering the viscosity of the plastic,
placing or engaging a cutting tool onto the plastic side of the laminate and adjusting the loading pressure of the cutting tool on the surface of the laminate,
moving the cutting tool relative to the laminate along the cutting line, with severing of the plastic and simultaneous scoring of the brittle material, thereby inducing a mechanical stress, and
additionally increasing, if appropriate, the mechanical stress along the cutting line to exceed the rupture strength of the scored brittle material.
According to the invention, these objects are also achieved by an apparatus comprising
means for heating the plastic at least in the vicinity of a predetermined cutting line, thereby lowering the viscosity of the plastic,
a cutting tool engageable with the plastic side of the laminate with an adjustable loading pressure of the cutting tool on the surface of the laminate,
means for producing a relative movement between cutting tool and laminate along the cutting line, for the purpose of severing the plastic and simultaneously scoring the brittle material, thereby inducing a mechanical stress, and
means for additionally increasing the mechanical stress along the cutting line to beyond the rupture strength of the scored brittle material, if appropriate.
The measures according to the invention make it advantageously possible to cut a laminate made of a brittle material and a plastic, in particular a laminate made of a brittle material laminated on one side with plastic, with a single cutting tool in one operation.
This is
Buerkle Roland
Habeck Andreas
Otto Torsten
Scherer Oliver
Gray Linda L
Schott Glas
Striker Michael J.
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