Glass panel

Details Glass panel Glass panel

2000-01-03

2001-10-30

Dixon, Merrick (Department: 1774)

Stock material or miscellaneous articles

Structurally defined web or sheet

Edge feature

C428S200000, C428S034600, C428S058000, C428S630000

Reexamination Certificate

active

06309733

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a glass panel in which spacing members are interposed between a pair of glass sheets and a heat-fusible outer periphery sealing portion is provided along the entire outer periphery of the two glass sheets for sealing the space between the glass sheets under a pressure-reduced condition.
BACKGROUND ART
As a glass sheet having a higher heat insulating performance than a pair of glass sheets, there is known a double glazing comprising a pair of glass sheets combined together with an air layer acting as a heat insulating layer being interposed therebetween. However, this type of glass panel suffers the problem of its own significant thickness which tends to deteriorate the aesthetic appearance including that of a sash. Then, in order to achieve a higher heat insulating performance with a smaller thickness, there has been proposed a glass panel in which a plurality of spacing members are interposed between a pair of glass sheets and a heat-fusible outer periphery sealing portion (e.g. low-melting glass) is provided along the entire outer periphery of the two glass sheets for sealing the space between the glass sheets under a pressure-reduced condition, so that the glass panel may be formed thinner, yet have a lower heat transmission coefficient.
And, for forming the outer periphery sealing portion, paste of low-melting glass is disposed at the outer peripheral edges of the two glass sheets and then heated above the fusing point of the low-melting glass, so that fused low-melting glass is caused to extend over between the outer peripheral edges of the two glass sheets. Then, the temperature is returned to the normal temperature to solidify the low-melting glass, so that this solidified low-melting glass forms the outer periphery sealing portion.
According to a conventional glass panel of the above-noted type, it has been proposed to employ a same kind of glass sheets (e.g. float glass) as the pair of glass sheets or to employ a wire glass as one of the glass sheets in case the panel is to be used in a fire retarding area.
However, the above-described conventional glass panel suffers the following problem.
Namely, the formation of the outer periphery sealing portion requires elevating of the atmosphere temperature of the glass panel and then returning the temperature to the normal temperature, as described above. In the course of this, each of the pair of glass sheets is expanded and contracted, depending on the atmosphere temperature. Such expansion and contraction of glass sheet is affected by its coefficient of linear expansion. For instance, if the coefficients of linear expansion of the pair of glass sheets are different from each other, when the atmosphere temperature is elevated, the amount of expansion will be greater in the glass sheet having the greater linear expansion coefficient.
On the other hand, when the atmosphere temperature is returned to the normal temperature, both of the glass sheets will be contracted respectively to their original dimensions.
When the outer peripheral edges of the pair of glass sheets are joined together at the outer periphery sealing portion, this operation is effected under the atmosphere of the elevated temperature. Hence, the two glass sheets will be combined together while they keep the different amounts of expansion therein. Then, as the atmosphere temperature gradually returns to the normal temperature, the glass sheet having the higher linear expansion coefficient will be contracted more than the other glass sheet.
As a result, the difference between the contraction amounts of the two glass sheets will appear as a flexion, whereby the glass panel may be warped. If the amount of flexion is significant, the glass panel may be broken due to the atmospheric pressure when the inside thereof is pressure-reduced.
With the conventional glass panel described above, if different kinds of glass sheets are employed as the pair of glass sheets, the two glass sheets may be warped and broken. Or, even when they are not broken, a significant internal stress will remain within the two glass sheets, so that a required strength cannot be obtained.
An object of the present invention is to solve the above problem by providing a glass panel comprised of glass sheets having different expansion coefficients, with which panel an appropriate strength may be readily obtained and which functions stably for a long period of time in spite of the pressure-reduced inside thereof.
DISCLOSURE OF THE INVENTION
The characterizing features of a glass panel relating to the present invention will be described next.
According to a glass panel relating to claim
1
, as shown in
FIG. 1
, in a glass panel in which spacing members are interposed between a pair of glass sheets and a heat-fusible outer periphery sealing portion is provided along the entire outer periphery of the two glass sheets for sealing the space between the glass sheets under a pressure-reduced condition, a linear expansion coefficient (&agr;
1
) of one of the glass sheets and a linear expansion (&agr;
2
) coefficient of the other glass sheet are set within a range which satisfies the following relationship; namely,
 (&agr;
1
−&agr;
2
)×&Dgr;T≦6×10
−5
  (1)
where
&agr;
1
>&agr;
2
&agr;
1
: the linear heat expansion coefficient of one glass sheet (/° C.)
&agr;
2
: the linear heat expansion coefficient of the other glass sheet (/° C.)
&Dgr;T: (solidification temperature of the outer periphery sealing portion—environmental temperature at which the glass panel is to be used) (/° C.).
According to the above construction, of the pair of glass sheets, the linear expansion coefficient of one glass sheet and the linear expansion coefficient of the other glass sheet are set within a range which satisfies the expression (1). Hence, even if warping may develop in the two glass sheets due to a change in the atmosphere temperature in the step of forming the outer periphery sealing portion, it is possible to restrict occurrence of excessive residual internal stress in the two glass sheets. As a result, it becomes possible to prevent such inconvenience that the glass sheet is broken in the step of forming the glass panel, especially when the inside thereof is pressure-reduced or significant internal stress remains in the two glass sheets, so that the glass panel may be broken when subjected to only small external force.
Consequently, an appropriate strength for a glass panel may be readily assured, and also the yield of the glass material or the like employed in the manufacture of the glass panel may be improved.
Incidentally, for obtaining the above expression (1), a plurality of glass panels were made from various combinations of glass sheets having different linear expansion coefficients and these were subjected to experiments in which the atmosphere temperature was varied. And, based on the amounts of warp developed in these glass panels, the appropriate stress condition was determined, from which the expression was derived.
According to the present invention relating to claim
2
, in a glass panel in which spacing members are interposed between a pair of glass sheets and a heat-fusible outer periphery sealing portion is provided along the entire outer periphery of the two glass sheets for sealing the space between the glass sheets under a pressure-reduced condition, a linear expansion coefficient (&agr;1) of one of the glass sheets and a linear expansion (&agr;2) coefficient of the other glass sheet are set within a range which satisfies the following relationship; namely,
{(&agr;
1
×L
1
−&agr;
2
×L
2
)×&Dgr;T}/L
1
≦6×10
−5
  (2)
where
&agr;
1
>&agr;
2
&agr;
1
: the linear heat expansion coefficient of one glass sheet (/° C.)
&agr;
2
: the linear heat expansion coefficient of the other glass sheet (/° C.)
L
1
: the length of the one glass sheet (m)
L
2
: the length of the other glass sheet (m)
&Dgr;T: (solidification temperature of the outer periphery sealing por

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