A louver has vertical blades arranged in a frame alternately in a staggered relation from front to back in a front and a rear row. The blades in at least the front row have a web oriented substantially perpendicularly to the plane of the frame and substantially parallel to the jambs, a pair of front flanges extending in opposite directions generally laterally from a front edge of the web, and a pair of rear flanges extending in opposite directions generally laterally from a rear edge of the web. The webs subdivide the air flow volume within the frame into flow channels, each of which is partially blocked laterally by the front flanges and the rear flanges of the blades of the front row. The blades of the rear row have flanges that block the portions of the channels between the extremities of the flanges of the blades of the front row. The flanges of the adjacent blades overlap so that there is no straight path through the flow channels along which air and water entrained in the air can pass perpendicularly to the plane of the frame and the air flows along a tortuous flow path of approximately constant area. The flanges are configured to control and trap water impinging on them.

BACKGROUND OF THE INVENTION 
It is often desirable in a louver installation to prevent to the utmost 
extent wind-driven rain water from passing through the louver (i.e., to 
prevent "water carry-over") from the outside environment into a duct or a 
space on the opposite side of the louver from the environment. Often, 
horizontal blade louvers of the drainable type are used, inasmuch as they 
have relatively low air flow pressure drops. In particular, they can be 
designed to minimize turbulence, a major source of pressure drop. 
Vertical blade louvers can be designed to minimize water carry over by 
causing the flow to change direction as it passes through the louver and 
in so doing cause the rain drops to impinge upon and be captured by blade 
surfaces that generally face a portion of the flow path. One or more 
portions of the blades of vertical blade louvers can have projecting 
flanges to capture water driven along an adjacent surface and provide a 
vertical gutter along which the captured water flows to the sill. An 
unavoidable trade-off for inducing changes in the direction of flow 
through a louver is an increased pressure drop. In many situations, the 
trade-off is an acceptable one. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a vertical blade louver 
that is highly effective in preventing water carry over. 
The foregoing and other objects are attained, in accordance with the 
present invention, by a louver that includes a rectangular frame having a 
header, a sill, and jambs joining opposite ends of the sill and header, 
the frame defining a volume open at parallel front and rear planes for 
passage of air through the louver. A multiplicity of laterally 
spaced-apart front blades extend between and are joined to the sill and 
header, each front blade being of substantially uniform cross-section 
throughout its length and including a web extending vertically between the 
sill and header and oriented generally perpendicular to the front and rear 
planes. The webs subdivide the volume within the frame into channels. A 
pair of front flanges extend in opposite directions generally laterally 
from a front part of the web, and a pair of rear flanges extend in 
opposite directions generally laterally from a rear part of the web. The 
flanges partially block the channels in the transverse direction. A 
multiplicity of laterally spaced apart rear blades, which also extend 
vertically between and are joined to the sill and header, have flanges 
that block the remainder of each channel between the webs of the front 
blades in the lateral direction. In that regard, the front and rear blades 
are positioned with respect to each other laterally such that the flanges 
of each rear blade partially overlap the front flanges of the adjacent 
front blades. 
The configuration and arrangement of the blades in two rows, one staggered 
with respect to the other and with the flanges of adjacent blades 
overlapping has several effects. First, there is no unobstructed straight 
path perpendicular to the front and rear planes of the flow volume along 
which air and entrained water drops can pass directly through the louver. 
In addition, the air passing through the louver must change direction and 
in so doing will tend to divert entrained water drops with a component of 
velocity in a lateral direction. The momentum of the laterally diverted 
water drops will carry them toward a blade surface, on which they will 
impinge and be captured. Second, all air entering the louver, regardless 
of the angle at which it enters, will encounter the surface of a blade of 
either the front row or the rear row. Rain drops entrained in the air 
impinge on the blade surfaces, lose velocity, and fall by gravity. Some of 
the water will be captured by blade surfaces upon which they first 
impinged. To some extent, depending on the direction in which they 
impinge, drops will become re-entrained in the flow, and they will splash 
and be thereby formed into smaller droplets. The re-entrained drops and 
droplets will, however, encounter additional blade surfaces by virtue of 
the tortuous flow path produced by the overlapping of the flanges of each 
adjacent pair of blades between the front and rear planes and will 
eventually be captured on a surface and flow by gravity onto the sill, 
from which the water is drained away. Third, the velocity of the air flow 
is quickly reduced upon encountering a succession of blade surfaces along 
the tortuous flow path. As the flow velocity is reduced and small eddy 
currents are formed as a result, re-entrainment of water diminishes and 
water capture on blade surfaces increases. 
In preferred embodiments, adjacent blades are configured and positioned 
with respect to each other such that the extremities of their flanges 
define flow path areas that are of generally equal size. That is 
accomplished by maintaining approximately equal spacings between the 
portions of the flanges of each adjacent pair of blades that are closest 
to each other. A generally equal flow area will minimize losses and 
enhance air flow efficiency. 
In preferred embodiments, the blade flanges are configured to control water 
that collects on them and is carried along their surfaces by the air flow. 
In one form of control, the front flanges of the blades each have a 
lateral edge part that is generally J-shaped in cross-section and includes 
a hook portion, each hook portion having a convex surface facing generally 
away from the web so that water is carried around the convex surface and 
is released from the surface in a direction generally toward the web so 
that it will impinge on the web and be captured. 
In another form of control of water capture by the blades, each of the 
flanges of some or all of the blades has a lateral edge part that is 
generally J-shaped in cross-section and includes a hook portion, each hook 
portion having an opening facing generally toward the front plane and 
serving as a channel to trap water and drain it to the sill. Ordinarily, 
all of the blades have rear flanges of that configuration to ensure that 
water is captured and not blown off the edge of the flange. 
Some or all of the blades may, optionally, have one or more pairs of ribs 
extending generally laterally from the web in opposite directions from 
each other at locations intermediate of the front and rear flanges. Where 
provided, the ribs are located relative to the flanges of adjacent blades 
to further define areas of the flow paths that are approximately equal to 
the areas defined between the flanges of adjacent blades. Similarly, 
except for no more than two blades adjacent each jamb, all adjacent blades 
in each row are, preferably, substantially equally spaced apart laterally 
and the spacing of adjacent blades in the front row is the same as the 
spacing of the blades in the rear row, thereby providing uniform flow 
conditions across the width of the louver. 
It is desirable to provide a flashing member having a base portion under 
the sill and an upright flange portion behind the sill and to configure 
the sill and the flashing so that they define a space and to provide 
drainage holes in the sill near the rear plane for water to drain from the 
upper surface of the sill into the space. Provision is made for water to 
drain from the space under the sill. 
For a better understanding of the invention, reference may be made to the 
following description of exemplary embodiments, taken in conjunction with 
the accompanying drawings.

DESCRIPTION OF THE EMBODIMENTS 
A louver according to one embodiment of the present invention, as shown in 
FIGS 1 to 3, comprises a rectangular frame having a header 10, a sill 12, 
and jambs 14 joining opposite ends of the sill and header. The frame 
defines a volume open at parallel front and rear planes for passage of air 
through the louver. A multiplicity of elongated blades 16 extend 
vertically between and are joined to the sill and header. The design of 
the header, sill and jambs may vary. In the embodiment, the sill and 
header are extruded members of the same cross section and have a 
channel-shaped body portion and a rear flange portion. The jambs 14 are 
also of the same cross section and are channel-shaped. The front flanges 
of the sill, header and jambs have small grooves for a field-placed 
caulking. 
All of the blades 16 of the embodiment of FIGS. 1 to 3 are identical. Each 
blade 16 is of substantially uniform cross-section throughout its length 
and has in cross-section (see FIG. 3) a planar web 161, which is oriented 
substantially perpendicularly to the front and rear planes and 
substantially parallel to the jambs 14, a pair of front flanges 162 
extending in opposite directions generally laterally from a front edge of 
the web, and a pair of rear flanges 163 extending in opposite directions 
generally laterally from a rear edge of the web 161. Each flange 162 and 
163 is generally J-shaped and is oriented with its leg portion (e.g., 
162L) oriented obliquely to the web portion 161 such that the leg portions 
at each end (in cross section) of the web portion form a "V." The 
junctures of the leg portions with the tip portions (e.g., 162L with 162t) 
form a sharp corner edge 162ce. The laterally outermost extremities of 
each flange portion form a smoothly rounded convex surface (e.g., 162cs) 
and each tip portion turns in at the end back toward the web portion in a 
terminal flange portion (e.g., 162fp). 
Screw bosses 164 are formed on the web portion 161 and receive screws (not 
shown) that pass into the bosses though holes in the sill and header. The 
blades of the embodiment of FIGS. 1 to 3 are pieces cut to the desired 
lengths from extrusions, preferably of aluminum. As may be seen in FIG. 2, 
the blades 16 are arranged in staggered relation with respect to the front 
and rear planes, with every other blade being closer to the front plane 
than the remaining blades, and are positioned with respect to each other 
laterally such that the front flanges 162 of adjacent blades partially 
overlap so that there are no straight paths perpendicular to the front and 
rear planes along which air and water entrained in the air can pass 
through the louver unobstructed. In order to maximize the free area, the 
amount of overlap is, preferably kept small, say 1/8th inch. 
FIG. 4 shows a plane P perpendicular to the front and rear planes FP and RP 
of the louver and to the sill and header of the frame. The plane P 
intersects the tips of the front flange ff1 of one blade B1 and the front 
flange ff2 of an adjacent blade B2. 
The spacings S of the blades in each row (the respective front and back 
rows) are the same, and the front row of blades is arranged with respect 
to the back row of blades such that the closest distances between the 
blade flanges of adjacent blades are approximately the same. That is, the 
spacings S1, S2 and S3 marked on FIG. 5 are nearly the same. The reason 
for this is to maintain as large a free area as possible for any given 
blade size. Similarly, the spacings S4 and S5 between the web of each 
blade and the nearest to it is maintained approximately equal to the 
spacings S1, S2, and S3 between the blade edges. Accordingly, the free 
area of each tortuous flow path formed by each adjacent pair of blades is 
approximately constant throughout its extent through the louver. 
The width of the frame between the jambs 14 can be varied to meet the 
desired size of the opening in which the louver is to be installed by 
changing the spacings of blades nearest each jamb and by using half 
blades. In FIG. 4, the blade B4 immediately adjacent each jamb 14 is 
installed with its flange portions in engagement with the jamb 14. The 
blades B5 and B1 next in from the jamb are placed at any desired spacing 
S6, but always with the small overlap between the front flanges, as 
described above. When the desired size falls between the limits of 
changing the spacing S6, half blades 16H (FIG. 5) are used at each jamb. 
As before, additional width variations are made by changing the spacings 
S7 between the half blade 16H and the next two blades B7 and B8 in from 
it. In all instances, the rest of the blades (all of the blades other than 
one or two blades adjacent each jamb) are installed at the same spacing S. 
The blades 226 of the embodiment shown in FIGS. 6 and 7 are similar in 
configuration to those of the embodiment of FIGS. 1 to 5 but are made by 
brake-forming from sheet metal, such as aluminum sheet. Each blade 
consists of two sheet metal members 226A and 226B, each of generally 
channel-shaped cross section, suitably joined back to back (FIG. 7). The 
overall shapes of the blades and their positions in the frame are 
essentially the same as those of the blades of FIGS. 1 to 5. The blades 
are attached to the sill and header by slitting each end of the blade 
parts to form several tabs (not shown), which are bent out on either side 
of the blade and fastened by rivets or screws to the sill and header. 
In an exemplary design of the louver with extruded blades according to 
FIGS. 1 to 5, the blades are 3.125 inches wide and 4.164 inches deep at 
their extremities and 0.060 inches in thickness throughout and are 
installed at 6.00 inches on center in each row. The break-formed blades 
are 2.84 inches wide by 6.125 inches deep and are made of 0.040 inch thick 
sheet aluminum sheet. They are installed at 5.750 inches on center. 
When wind-blown rain impinges on the louver exactly perpendicular to the 
front plane, much of it impinges directly on a frontal surface of a front 
flange portion 162 of a blade of either the front row or the back row, 
inasmuch as the flanges of the front blades overlap the flanges of the 
back blades. Some of the water collects on the frontal surfaces, and some 
of the water drops are formed into droplets by splashing. Water that 
collects on or splashes into droplets against the surfaces of the 
divergent leg portions 162l is pushed back against the apex at the 
juncture between them and flows down to the sill. Droplets that become 
re-entrained may be picked up in the air flow and will be handled as 
described below. Drops that impinge on the portions 162t are largely 
deflected as splash; most of the water that collects on the portions 162t 
clings to and is blown around the convex surface 162cs and flows down the 
terminal flange portion 162fp to the sill. 
Drops entering the louver that are diverted by the air flow, which acquires 
a lateral component in order to pass between adjacent blade flanges 162, 
and droplets from splash that become entrained in the air flow are carried 
predominantly onto a web portion 161 and a rear flange portion 163 of a 
blade in the front row and cling to and flow down the portion on which 
they impinge to the sill. Any additional splash and any droplets that 
remain entrained after passing the front flange 162 of a blade in the back 
row are diverted in the direction of the web portion 161 and rear flange 
portion 163 of a blade in the back row, where they are captured and flow 
down to the sill. The tip portions 163t of each rear flange 163 of each 
blade form a channel, which catches all water collecting on a web portion 
161 and a rear flange leg portion 163l that is blown along the blade by 
the air flow. The water caught in the channels drains to the sill. 
When the wind is oblique to the front plane of the louver, the rain drops 
and droplets from splash that pass between the front flanges of adjacent 
blades impinge on the web portion 161 of a blade in the front row. Much of 
that water is collected and flows down the web portion or is carried by 
the air flow into the channel formed by the tip portion 163t of a rear 
flange portion of a blade in the front row and flows to the sill. Any 
droplets that become entrained in the air flow impinge on the web portion 
161 or flange portion 163 of a blade in the back row and are collected and 
flow to the sill. The tortuous flow path formed by the four flange 
portions between adjacent webs ensures that no water can reach the space 
behind the louver--there is no water carryover. 
A suitable way of installing the louver in an opening is to provide 
flashing F under the sill (see FIG. 1), the flashing being formed into an 
"L" having a base portion under the sill, an upright rear flange portion 
behind the sill (not visible), and side flange portions FF adjacent the 
lower portion of each jamb. The base portion of the flashing defines a 
drainage space under the jamb, and the jamb has drainage holes 18 (see 
FIGS. 2 and 6) near the rear plane for water to drain from the upper 
surface of the sill into the space between the flashing and the sill. An 
outlet from the space under the sill is provided for water to drain from 
the space. 
The louvers shown in FIGS. 8 to 10 are exemplary of modifications of the 
embodiment of FIGS. 1 to 7 that are possible and that have the main 
features of the invention, namely, two staggered rows of blades, flanges 
at the front of blade in the rear row that overlap the front flanges of 
the blades in the front row so that there is no straight, perpendicular 
flow path from front to rear, blade configurations and spacings that 
provide tortuous flow paths with generally equal areas between the 
extremities of the blade flanges nearest each other and between blade 
extremities and webs nearest to them, and control of surface water flow on 
the blade surfaces. 
The louver of FIG. 8 has a front row of blades 100, which are the same as 
the blades 16 of the embodiment of FIGS. 1 to 5, and a rear row of blades 
102 of a different cross-sectional shape. Each blade 102 has a web portion 
104 and a pair of flat front flanges 106, each of which has at its distal 
end a generally J-shaped edge part 108, the curved portion 108a of which 
has an opening that faces toward the front of the louver to define a 
channel for trapping water blown along the surface of the flange and 
draining it to the sill. Each of a pair of planar rear flanges 110 has and 
edge part 112, which is also generally J-shaped with an opening in the 
hook portion 112a that faces generally toward the web portion to capture 
water and drain it to the sill. 
As a flow of air leaves the edge of a surface, eddies are formed in the 
wake of the surface. The average or main air flow through the louver 
follows the tortuous open paths, but eddies generated at the edges of 
surfaces at the boundaries of the main flow migrate out of the main flow, 
if there is space available for them to migrate into. The blades 102 of 
the rear row have pairs of ribs, which promote formation of small eddies 
at the boundaries of the main air flow, provide surfaces for water 
entrained in the eddies to collect on, and form quiet zones at least 
partially shielded from the main air flow that reduce the tendency of 
water to become reentrained in the air flow. The ribs are configured and 
placed, however, so that their extremities (edges) are spaced apart from 
the edges of the blade flanges nearest to them at approximately the same 
distance as the edges of the blade flanges are spaced from the flanges 
nearest to them, thus to maintain generally the same cross-sectional area 
for the main flow. 
In particular, the blades 102 have a pair of front ribs 114 located 
proximate to the front flanges 106 and a pair of rear ribs 116 located 
proximate to the rear flanges 110. The spacings S8 marked in FIG. 8 are 
approximately the same. The arrowed lines indicating the spacings S8 also 
indicate generally the path of the main air flow. Each rib has an edge 
flange portion 114a, 116a that extends toward the front of the louver and 
promotes capture of water collecting on the surface of the rib and 
drainage down to the sill. The regions marked QZ of each rear blade are 
quiet zones into which eddies can migrate, contact the surfaces bounding 
them, and deposit entrained water drops and droplets on those surfaces. 
The embodiment of FIG. 9 has front blades 200 that are similar to those of 
FIGS. 1 to 7 but have front ribs 202 and rear ribs 204 that serve the 
purposes described immediately above. The rear blades 206 are the same as 
those of FIG. 8. The spacings S9 are generally equal, and the quiet zones 
are marked QZ. 
FIG. 10 illustrates an embodiment in which the front blades 300 are the 
same as the rear blades 110 and 206 of the embodiments shown in FIGS. 8 
and 9 and the rear blades 302 have no web portion or rear flanges. A 
single pair of flanges 304 extend generally laterally from a juncture 306 
and block the spaces between the front flanges of the adjacent front 
blades 300. A pair of ribs 308 extend from the juncture 306 and are 
located in front of portions of the flanges and form quiet zones QZ into 
which eddies formed in the wakes of the tips of the ribs migrate and 
deposit entrained water on the surfaces bounding the quiet zones. Edge 
flange portions 308a on each rib keep water that collects on the fronts of 
the flanges from blowing off the edges of the ribs and promote drainage 
down the ribs to the sill. Each flange 304 has a J-shaped edge portion 
304a that opens generally toward the juncture and serves as a channel for 
capturing water and draining it to the sill. The spacings S10 indicated by 
the arrowed lines are approximately equal in order to maintain a tortuous 
flow path through the louver that is of approximately uniform area.