Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2003-01-13
2004-08-03
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S410000, C428S425600, C428S451000, C428S920000
Reexamination Certificate
active
06770375
ABSTRACT:
The invention concerns a glazing which can be subjected to high levels of thermal stress, in particular for fire-resistant glazing, and comprising a glass body.
In accordance with the fire resistance classes, fire-resistant glazings, including the framework and gripping mechanisms, must withstand thermal stress according to the standard fire curve (ISO fire curve) according to DIN 4102 (and/or ISO 834) for between 30 minutes and up to 180 minutes and prevent the passage of fire and smoke.
Moreover, additional requirements are often placed on building glazings. For example, glazings in doors must guarantee protection against fire as well as the safety of the users. To achieve this, the glazings must meet the requirements of applicable safety glass standards (e.g., single-pane safety glass DIN 1249, part 12).
These requirements are met in different fashions in the case of the known fire-resistant glazings, although all known systems have specific disadvantages.
For example, fire-resistant glazings are known (DE 38 17 240 A 1), in the case of which tempered glasses (lime/soda or borosilicate glasses) having appropriate thicknesses are used. They are, for example, lime/soda glasses having thicknesses of 6-15 mm for 30 or 60 minutes fire resistance, or borosilicate glasses having thicknesses of 5-8 mm for 30 to 120 minutes fire resistance. These tempered glasses have the disadvantage, however, that they exceed their softening temperature at a relatively early point in time (before the 60
th
minute) during the thermal stress occurring when exposed to fire according to the ISO fire curve, and the previously solid, elastic glasses change to a low-viscosity, plastic state. It was made known in DE 43 31 082 C 1 to provide the lime/soda glass pane, before tempering, with a TiO2 or ZrO3 layer that is covered with an SiO2 layer and that changes the physical properties of the glass and reinforces the pane in fire situations.
The softening of the glasses (softening temperature), however, is the main factor that determines whether or not long durations of fire resistance will be achieved. Further influential factors are the pane size, the pane thickness, and the width of the glass bite, as well as the holding force of the pane as well as the nature of the frame (material).
For example, the wider the glass bite of the pane is in the case of the aforementioned glasses, the longer the glasses are prevented from sliding out of the edge region if the glasses have reached their softening temperature while being exposed to fire.
At the same time, however, the width of the covered edge region is a very strong determining factor for the level of the thermal stresses occurring between the hot (exposed) center of the pane and the cold (covered) edge of the pane during exposure to fire.
If the thermally-induced tensions occurring during the warm-up phase—including the tensions resulting from other causes such as frame bending—exceed the strength of the glass, the glass pane invariably breaks and the protective effect of the fire-resistant glazing is therefore lost entirely. It is therefore not immediately possible to select any size of edge covering for the panes in order to achieve the longest duration of fire resistance possible. Other, supplementary measures can serve to achieve these higher fire resistance classes, e.g., reducing the size of the pane or, to a minimum extent, increasing the pane thickness or applying contact pressure to the pane in the edge region of the frame system using glass retaining strips under an appropriate preload, or by using an expanding sealing band.
Another type of fire-resistant glazing uses “multilayer laminated glass systems” to achieve long durations of fire resistance (>60 minutes) with lime/soda glasses. These systems are typically composed of a plurality of lime/soda glass panes (some of which are tempered) with heat-absorbing layers between them. These laminated glasses have the disadvantage, however, that they must have a very large number of glass layers and heat-absorbing layers in order to reach higher fire resistance classes. As a result, these laminated glasses are very costly to produce and are therefore expensive. Additionally, such glasses have a large thickness and, therefore, a very heavy weight and, associated therewith, costly frame systems. As a result, the frame constructions required to install such glasses becomes expensive as well.
The same applies for the laminated fire-resistant plate according to EP 0 524 418 B 1.
A further known fire-resistant glazing, e.g., a glazing according to “General Building Construction Certification Z-19.14-546” describes the use of panes made of glass ceramic.
Panes made of this material have the advantage that they do not soften unless exposed to much higher temperatures. In the case of exposure to fire according to the ISO fire curve, these temperatures are not reached until after a much longer time, so that the panes made of glass ceramic do not soften at all, or only slightly. As a result, these panes have a very low tendency to slide out of the frame system, and very long durations of fire resistance can therefore be achieved.
The disadvantage of these fire-resistant glazings made of glass ceramic lies in the fact that, compared to tempered panes, the corresponding panes made of glass ceramic have only minimal strength and therefore respond sensitively to the bending of the frame systems occurring during exposure to fire. Such panes can only be used in such frame systems in particular that have a very high stability and low bending in fire situations (e.g., special thick-walled or insulated steel or cement profile).
Moreover, such glass-ceramic panes (e.g., according to DIN EN 1748, part 2), due to their lack of tempering, cannot fulfill the requirements of single-pane safety glasses, for example according to DIN 1249, Part 12, without more. In order to fulfill the requirements placed on safety glasses with such panes made of glass ceramic, for example, a plurality of these non-tempered glass-ceramic panes must be combined with suitable Intermediate layers to form laminated safety glasses, as described in EP 0 581 620 A1, for example. These Intermediate layers are typically composed of very tough plastic materials, however, that can negatively influence the behavior of such laminated safety glasses in fire situations.
In addition to fire-resistant glazings, there are further fields of application that require a glass body which can be subjected to high levels of thermal stress. The same applies for these applications.
The invention is based on the object of creating a glazing which can be subjected to high levels of thermal stress, and comprising a glass body, that combines the advantages of glass ceramic to achieve long durations of resistance to stress with the advantages of tempered glasses to fulfill the safety glass requirements while preventing the disadvantages of these glasses from occurring.
This object is attained according to the invention by means of a glazing which can be subjected to high levels of thermal stress and comprising a glass body that contains the following main components in the composition (in percentage by weight, based on oxide)
55-69%
SiO
2
19-25%
Al
2
O
3
3.2-5.0%
Li
2
O
as well as additions of nucleating agents commonly used in the ceramization of glass so that crystalline structures form in the glass body when the glazing is subjected to high levels of thermal stress.
The glazing, which can be subjected to high levels of thermal stress, and comprising a glass body designed according to the invention can be subjected to high levels of thermal stress without any additional mechanical measures. This ability to be subjected to high levels of thermal stress is based on the fact that the glass body forming the glazing, due to its composition, undergoes ceramization when exposed to thermal stress.
In addition to the components forming the glass, the required “nucleating agents” are already contained in this glass body forming the glazing. These nucleating agents allow the glass t
Karschti Thomas
Leroux Roland
Jones Deborah
Savage Jason L
Schott Glas
Striker Michael J.
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