Spacer frame bar for insulated window

Details Spacer frame bar for insulated window Spacer frame bar for insulated window

2000-04-13

2004-11-30

Friedman, Carl D. (Department: 3635)

Static structures (e.g., buildings)

Composite prefabricated panel including adjunctive means

Sandwich or hollow with sheet-like facing members

C052S172000, C052S749100, C052S717020

Reexamination Certificate

active

06823644

ABSTRACT:

BACKGROUND OF THE INVENTION
a. Field of the Invention
The present invention relates generally to insulated windows, and, more particularly, to spacer frame tubing for spacing apart inner and outer panes of an insulated window, the tubing being constructed to accommodate inward and outward movement of the panes in response to changes in atmospheric pressure.
b. Related Art
It is well known in the art to provide insulated windows having more than one pane of glass, the panes being separated by an air space. Typically, the panes are maintained in spaced apart relationship by a frame that is interposed between their edges. The interior space between the panes, which is typically filled with air or other gas, thus serves as an insulator to reduce heat flow through the window. In the prior art it is known to manufacture the frame from a plurality of individual tubes joined at their ends to form a continuous frame, or of a single tube which is bent to form the frame. The tubes are generally made of aluminum alloy, or of molded plastic or other material having sufficient rigidity to maintain the space between the panes; aluminum alloy has the advantages of strength, stability and longevity for this use.
The tubing typically has a somewhat rectangular form so as to provide inner and outer side walls for supporting the glass panes, and the hollow interior of the tubing often contains a supply of desiccant material which removes moisture from the interpane air space. Examples of spacer tubes of this general configuration include those shown in U.S. Pat. Nos. 4,222,213 (Kessler), 4,576,841 (Limgemann), 5,439,716 (Larsen), and 5,581,971 (Peterson); many other examples of spacer frame tubing will occur to those skilled in the art.
Although very successful in most respects, it has been discovered that the configuration of conventional frame tubing may create a long term “weak spot” in many insulated window assemblies, especially those having relatively large, continuous panes of glass, such as are commonly used in office buildings and similar structures.
To illustrate this problem,
FIG. 1
shows an example of conventional spacer frame tubing
10
installed between first and second glass panes
12
,
14
so as to define the interpane air space
16
. As was described above, the spacer tubing has a generally rectangular cross-section with first and second side walls
20
,
22
for supporting the panes and a hollow interior
24
which is filled with granular desiccant material
26
. In the version which is shown in
FIGS. 1-3
, the side walls are formed with raised ribs for minimizing the contact area with the glass panes, so as to minimize thermal transfer through the aluminum alloy material of the spacer. A strip of sealant material
28
is installed outside the spacer tubing, i.e., between the tube and the edges of the panes, so as to form an air tight seal which excludes the surrounding atmosphere and moisture from the interpane space
16
. The sealant strip is normally formed of a polymeric material which has a degree of resilience and surface adhesion when new, but which tends to lose these qualities with age.
FIG. 1
shows the assembly in its initial configuration, with panes
12
,
14
extending parallel to one another and resting more or less flat against the side walls of the spacer tubing and the surfaces of the sealant strip. As soon as the window is installed, however, the panes begin to undergo virtually continuous relative movement due to changes in atmospheric pressure. As was noted above, the window is hermetically sealed by the strip
28
, so that the pressure in the interpane space does not equalize with that of the surrounding air. As a result, an increase in pressure, as is shown in
FIG. 2
, causes the two panes to bow inwardly, in the directions indicated by arrows
30
a
,
30
b
(this movement being somewhat exaggerated in the figures for purposes of illustration), with the greatest amount of inward deflection taking place towards the middle of the unsupported window and away from the spacer tubing
10
. As this happens, the inner surfaces
32
,
34
of the glass panes react and pivot against the side walls
20
,
22
of the spacer tubing, with the result that the edge portions
36
,
38
of the panes which extend beyond the spacer tubing move apart in corresponding, outward directions, as indicated by arrows
40
a
,
40
b
. This motion draws the inner surfaces
32
,
34
of the panes outwardly, away from the surfaces
42
,
44
of the sealant strip, with the result that the sealant eventually separates from the glass around the outer edges of the panes and thereby creates gaps and breaks in the seal, as indicated at arrows
46
and
48
in FIG.
2
.
Conversely, a decrease in atmospheric pressure, as is illustrated in
FIG. 3
, causes the panes
12
,
14
to bow outwardly towards their centers, as indicated by arrows
50
a
,
50
b
. As this happens, the sides
20
,
22
of the spacer tubing again act somewhat in the manner of pivot points (due in part to the adhesion of the sealant material), and the edges
36
,
38
of the panes press inwardly against the sealant strip
28
in the direction indicated by arrows
52
a
,
52
b
. This action tends to draw the inside surfaces of the panes away from the surfaces
42
,
44
of the sealant along the sides of the spacer tubing, eventually causing the formation of additional gaps or openings, as indicated at
54
,
56
. Moreover, the sealant strip
28
resists being compressed between the edges of the glass panes, especially if the strip has hardened and lost it resilience, so much so that the edges of the panes can sometimes fracture and chip so as to leave little or no contact area between the pane and the sealant in the damaged area.
While the actual amounts of movement are comparatively small in absolute terms, they are significant (for example, the “bellows effect” generated by the flexing of the panes is sufficient to be employed to circulate the interpane air into and out of the desiccant material in some types of spacer tubing) and the resulting loads on the components can be quite great. In particular, with a very large window the distance from the unsupported centers of the panes to the spacer tubing around the perimeter of the window creates a very large lever arm as compared with the distance from the tubing to the outer edges of the panes, so that a small amount of movement at the centers of the panes results in comparatively large forces being exerted at the edges of the assembly.
The atmospheric pressure changes which generate these forces occur almost continuously, with pressures often fluctuating up and down several times in a single day, so that a window assembly may experience these forces/motions over several thousand cycles during its lifetime. As a result, the repeated pulling away from the sealant and/or chipping of the panes eventually leads to one or more breaches being formed in the hermetic seal around the edge of the window assembly. This allows moisture to enter the interpane space, so that the window quickly becomes fogged and must be replaced.
Many modern structures, such as large office towers are fitted with a huge number of insulated window assemblies. The cost of having to replace even a few of these window assemblies can be extraordinarily high, and so any improvement which extends the service life of the assemblies can easily translate to large economic savings.
Accordingly, there exists a need for a spacer tubing having a construction which reduces or eliminates the tendency of the outer edges of the glass panes in an insulated window assembly to pull away from and press against the sealant strip at the edge of the assembly as the panes flex inwardly and outwardly in response to changes in atmospheric pressure. Furthermore there exists a need for such a spacer tubing which has a hollow interior for containing a supply of desiccant material therein, and which permits a degree of fluid communication between the interior of the tubing and the interpane space so as to allow the desiccant materia

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