Leakproof framed panel curtain wall system

This invention relates to an exterior curtain wall system assembled from multiple framed panels. The design utilizes externally framed panel design with concealed water drainage mechanism within pressure equalized wall cavities to eliminate the dependency of the sealing integrity of the shop and/or field applied sealant lines for watertight performance. The design also eliminates the accumulative thermal movement of the wall surface and facilitates the easiness of replacing an individual facing panel.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to exterior curtain wall system utilizing multiple 
framed panels. Each individual framed panel consists of a facing panel 
supported by four perimeter members. In this type of curtain wall system, 
there are two typical field formed wall joints, namely, horizontal wall 
joint and vertical wall joint. These field formed wall joints are the 
potential sources of water leakage problem. The wall joint designs of this 
invention eliminate the dependency of sealant line integrity for 
watertight performance. In addition, this invention allows thermal 
movement of the facing panel to be unrestrained by the perimeter frame and 
vice versal. Also this invention allows easy replacement of each 
individual facing panel. The facing panel material can be glass panel, 
natural or artificial stone panel, composite honeycomb panel, composite 
foam panel, or metal plate. 
2. Description of the Prior Art 
The mechanism of water leakage phenominon can best be described in the 
following manner. The first step is that the exterior rain water running 
along the exterior wall surface reaches the sealant lines of the field 
formed wall joints. The second step is that if the sealant lines are not 
perfect (i.e. pin holes or small cracks in the sealant lines), the water 
reached the sealant lines will infiltrate through the pin holes or cracks 
in the sealant lines under a positive pressure between the exterior air 
and the interior air. The positive pressure always exists on the windward 
wall due to the wind forces and is sometimes magnified by the suction type 
air exchange system of the building. The prior art systems for solving the 
water leakage problem can be classified into the following four 
generations. 
The first generation of the wall joint design is to seal off the wall 
joints right along the exterior wall surface using field applied caulking. 
The facing panel is structurally supported by an interior wall frame 
system using curable silicone caulking as the structural connection. This 
type of design is an attempt of making a perfect seal in the field (i.e. 
no pin hole or hairline crack in the sealant line is allowed). This 
perfect seal concept requires careful field executions of the following 
items. 
(1) The caulking backer (known as backer rod) must be placed in the proper 
location to give an adequate and uniform caulking depth. 
(2) The caulking bonding surfaces must be free of water, oil, or dirt 
before the application of caulking (i.e. no erection on a rainy day). 
(3) The caulking must be tooled after the application. 
It can be easily seen from the above that this perfect seal concept is 
highly dependent of the field workmanship. In addition, cyclic thermal 
movements of the facing panel surface induce stress reversals within the 
sealant causing latent sealant failure due to stress fatigue. Aside from 
the sealing reliability and durability problems, the caulked wall joints 
are known to have two aesthetic problems, namely, streaking due to 
chemical release and dirt collection due to electrical charge. Another 
drawback of the system is the need of temporary support before the curing 
of the structural caulking and the associated removal of the temporary 
support and the patching of the sealant due to the removal of the 
temporary support. 
The second generation of the wall joint design utilized the concept of 
controlled water leakage. The first design feature is to use interior 
perimeter aluminum extrusion members structurally connected to and sealed 
to the facing panel in the shop to form interlocking tongue-and-groove 
horizontal and vertical panel side joints. The tongue-and-groove joints 
are hidden behind but close to the facing panel and are sealed with 
nonbonding gasket material to allow free thermal movements of the panel 
surface without causing sealant stresses. However, the nonbonding 
contacting surface of the gasket represents a continuous hairline crack 
which will allow water infiltration through the sealant line under 
positive differential pressure, therefore, it requires a second design 
feature to control the water leaked through the gasket line. The second 
design feature is to create a horizontal gutter (known as internal gutter) 
behind the gasket line within the depth of the perimeter aluminum 
extrusion to collect the water leaked through the gasket line and to 
provide drainage holes from the bottom of the internal gutter to the 
exterior horizontal panel joint such that the water collected within the 
internal gutter can be drained to the outside after the positive pressure 
differential has been subsided. In addition, it is required to splice and 
to seal the horizontal internal gutter across the vertical wall joint, to 
seal off the holes at four corner intersections, and to seal between the 
horizontal and vertical gasket lines (known as marriage seal) in the field 
to complete the system. Again, these three field sealing operations must 
rely on careful workmanship in the field. In addition, these field applied 
sealants are subjected to stresses due to thermal movements of the wall 
panel surface. Another drawback of the design is that the exposed drainage 
holes will allow the water to infiltrate freely into the internal gutter 
under positive pressure, therefore, substantial water buildup in the 
internal gutter is expected even in there is no water leakage in the 
gasket line. This high water buildup in the internal gutter necessitates a 
high gutter leg design and increases the risk of water leakage at the 
gutter splice joint. Another drawback of the design is that the potential 
leakage source of the gutter splice is hidden behind the plate, thus, 
repair can only be done from the interior side which usually involves 
costly interior restoration. Additional aesthetic problem is the water 
stain on the panel surface below the drainage holes. 
The third generation of the wall joint design is that the facing panel is 
structurally sandwiched between an exterior flange and an interior flange 
of the perimeter aluminum extrusion and sealed in between. To reduce the 
probability of water leakage, three different design methods have been 
used in the industry. The first design method is to completely seal the 
gap between the exterior flange and the facing panel using silicone 
caulking. This method has the drawbacks of the first generation design 
except the need of temporary support. The second design method is to use 
gasket with pressure applied by the force of screw known as "pressure bar 
system" to seal the gap between the exterior flange and the facing panel. 
However, the nonbonding contacting surface of the gasket represents a 
continuous hairline crack which will allow water infiltration through the 
sealant line under positive differential pressure, therefore, it requires 
to use the seating surface of the facing panel to act as an internal 
gutter with exposed outward drainage holes. In this arrangement, water may 
overflow the gutter and seep through the interior sealant line under high 
pressure differential. The third design method is to create an internal 
horizontal gutter and down spout drainage system in combination with the 
first or the second method. The third method has a higher rate of success 
in preventing water leakage. However, it costs much more. In addition, the 
required thermal expansion joints of the exposed aluminum members are 
difficult to arrange and to maintain sealing integrity. 
The fourth generation design which is my prior invention (U.S. Pat. No. 
4,840,004) utilizes interior perimeter frame to support the facing panel 
and to create a water drainage system within a pressure equalized wall 
cavity eliminating the dependency of field workmanship for water tight 
performance. However, due to the interior frame arrangement, differential 
thermal movement between the facing panel and the interior frame creates 
stresses within the shop applied sealant line which may result in shop 
applied sealant line failure leading to water leakage problem. Therefore, 
even though this design represents a major improvement of eliminating the 
dependency of field workmanship for watertight performance, it still has 
to depend on the long term integrity of the shop applied sealant line. In 
addition, due to the structural connection between the facing panel and 
the interior frame, replacing an individual damaged facing panel is 
extremely difficult. 
In summary, all the prior art design methods must rely on long term sealing 
integrity of the field and/or shop applied sealant line. It is obvious 
that consistent perfect field or shop applied sealant line is practically 
unachievable. Therefore, the probability of water leakage problem 
continues to exist. 
SUMMARY OF THE INVENTION 
The objectives of this invention include the following items. 
1. To eliminate the dependency of the sealing integrity of the shop and/or 
field applied sealant lines for the watertight performance. 
2. To prevent the interference between the facing panel and the perimeter 
frame due to differential thermal movements. 
3. To allow easy replacement of an individual facing panel. 
4. To use the interior face of the assembled wall panel as the interior 
finished wall surface. 
5. To eliminate the accumulative thermal movement of the wall surface. 
It will become obvious from the description of the preferred embodiments 
that the objectives of this invention are accomplished by the design 
features.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates an exterior curtain wall structure 10 consisting of 
spaced apart vertical mullions 14, multiple framed panels 11. Two types of 
wall joints are formed in the field, namely, horizontal wall joints 12 and 
vertical wall joint 13. 
FIG. 2 shows a typical fragmentary cross-section of the horizontal wall 
joint 12 taken along line 2--2 of FIG. 1 where glass panel is used. Each 
framed panel 11 has a glass panel 19 supported by a top window head member 
20 usually made of aluminum extrusion, and a bottom window sill member 21 
usually made of aluminum extrusion. The head member 20 is secured to the 
face of mullion 14 using screws 22. The head member 20 is designed to have 
an inner structural male spline 25 and to adapt a gutter member 23 and a 
head cover 15 in a snap-on fashion. The gutter member 23 is provided with 
end dams 39 and drainage holes 38. The head cover 15 is designed to have 
an integral horizontal rain screen member 24 and together with head member 
20 and gutter member 23 to form a hidden horizontal drainage tunnel 27. 
The drainage tunnel 27 is open at both ends where vertical joint is 
formed. The sill member 21 has an inner structural groove with sealing 
material 28 to cause structural engagement with the spline 25 of the 
window panel below. The weight of the glass panel 19 is supported by the 
sill member 21 with the protection of the setting blocks 67. Drainage 
holes 68 and a downwardly extended leg 34 are provided in the sill member 
21. The glass panel 19 is secured within the aluminum frame using the 
exterior gasket 54 and the interior gasket 55. It can be seen from the 
construction that most of the wind driven water will be repelled by the 
rain screen member 24 and spilled over water will be guided into the 
external gutter 26 by the leg 34. Since both the external gutter 26 and 
the drainage tunnel 27 are pressure equalized, the drainage of water from 
the external gutter 26 into the drainage tunnel 27 through the drainage 
holes 38 will be instantaneous and there will be no water buildup in the 
external gutter 26. It becomes obvious that it is impossible for the 
exterior water to get to the interior gasket 55 or the field formed 
horizontal sealed joint using gasket 28. Any water seeped through the 
exterior gasket 54 will drain to the outside through the drainage holes 
68. The drainage holes 68 also help to equalize the pressure in the frame 
cavity surrounding the glass panel 19. The installation procedures include 
the following steps: (1) putting the framed panel 11 in position to cause 
bottom joint engagement; (2) securing the head member 20 to mullion 14; 
(3) snap-on gutter member 23; (4) snap-on the head cover 15. 
FIG. 2a is a possible variation of FIG. 2. The glass panel 19 is replaced 
by an opaque panel 74 which can be natural stone, honeycomb panel, 
composite foam panel, etc.. The insulation board 71 with an interior skin 
72 can be shop assembled into the framed panel 11 to provide thermal 
insulation value. Structural thermal break material 70 is provided within 
the frame members 20 and 21 using pour-and-debridge process. Loosely 
packed glass fiber insulation 73 can be used to further improve the 
thermal efficiency. An interior snap-on cover member 75 can be used to 
facilitate the replacement of the insulation board 71 from inside. The 
skin 72 can be used as the finished interior surface with many variations 
such as painted metal skin, painted drywall, wooden panel, or drywall with 
wall paper. This will eliminate the need of building a separate interior 
finished wall resulting in significant savings of time and money. 
FIG. 3 shows a typical fragmentary cross-section of the vertical window 
joint taken along line 3--3 of FIG. 1. The jamb members 40 are profiled to 
miter-match with the top perimeter member 20 and the bottom perimeter 
member 21 at the corners of the window frame. Sealant 41 contained in a 
cavity on the face of the mullion 14 forms the vertically sealed line and 
it can be either shop applied or field applied. The vertical rain screen 
member 42 is field installed continuously across the horizontal panel 
joint 12 by snapping into engagement with the holding rib 43 of member 40 
on one side. The material for member 42 should be flexible such that it 
will not be damaged by thermal movement of the exterior frame. Gasket type 
of material would be suitable for member 42. The outer vertical cavities 
45 serve as the drainage down-spout. The inner vertical cavity 46 is 
interconnected with the horizontal open cavities 26 (shown on FIG. 2) at 
each horizontal window joint and thus is pressure equalized to the 
exterior air. Due to the fact of pressure equalized cavity 46, it becomes 
obvious that the exterior rain water will be confined to the front of the 
vertical joint flowing downwardly within cavity 45. Therefore, it is 
impossible for the exterior rain water to reach the vertical sealant 41 
which can be a shop installed sponge gasket. Anti-walk blocks 80 can be 
installed near the top of the glass panel 19. The pocket occupied by the 
block 80 should be deep enough to allow the replacement of the glass panel 
19 without disassembling the framed panel. To replace the glass panel 19, 
the following steps are required: (1) unzip the gasket 54; (2) un-snap 
member 15; (3) take out blocks 80; (4) take out the old glass panel 19; 
(5) place the new glass panel 19; (6) place blocks 80; (7) snap on head 
cover 15; (8) place gasket 54 and caulk the corners. It can be easily seen 
from the details that differential thermal movement between the facing 
panel and the perimeter frame can be easily absorbed within the frame 
cavity. It can also be seen from the details that each field formed 
horizontal or vertical wall joint represents a thermal expansion joint, 
therefore, the thermal movements of the framed panel will not accumulate 
and grow no matter how tall or how wide the building is. 
FIG. 3a is a possible variation of FIG. 3 where opaque facing panel 74 
instead of the glass panel 19 is used and the insulation board 71 with 
interior skin 72 is added. The details are similar to those explained in 
FIG. 2a. 
From the above descriptions, it is obvious that all the five objectives of 
this invention are accomplished. 
While I have illustrated and described several embodiments of my invention, 
it will be understood that these are by way of illustration only and that 
various changes and modifications may be contemplated in my invention and 
within the scope of the following claims.