Note: Descriptions are shown in the official language in which they were submitted.
CA 02267823 1999-04-O1
-2-
Title: PASSIVE VENTING DEVICE
FIELD OF THE INVENTION
This invention relates generally to the field of venting devices,
and in particular, to passive venting devices.
BACKGROUND OF THE INVENTION
Virtually all buildings and enclosures where human activity
takes place require venting of one type of another. The type of venting
device employed will depend on the kind of enclosure to be vented. For
example, bathrooms containing showers typically have active vents with
fans to vent steam to the outdoors. Kitchens, particularly in restaurants and
hotels, similarly have powered vents for removing smoke and steam to the
outdoors.
Other types of enclosures, such as attics and yard sheds, do
not require active venting. However, such enclosures do typically require a
passive vent to allow for air flow from the enclosure to the atmosphere.
Such venting is required, for example, to prevent a buildup of moisture in the
enclosure. Passive vents do not include a mechanism for forcing air out of
the enclosure. Rather, they simply include a vent structure in the form of an
air conduit which allows air flow. Passive vents are well-known and have
been extensively used in the past. Although typically formed of metal, good
results have been achieved more recently with plastic vents.
In addition to the venting of air from attic spaces and sheds,
there are other needs for building enclosures, such as the need for light. In
some cases, wiring is provided for electric lights, but spaces such as attics
and sheds are typically left unwired, thus creating a need for the use of
flashlights and the like.
There have been attempts in the past to provide both functions
through a single structure. For example, U.S. patent number 5,561,952
CA 02267823 1999-04-O1
-3-
teaches a static roof vent comprising a base/flange containing an air conduit,
and a hood. The hood includes a translucent oriel located above the air
conduit. However, this device is difficult and expensive to manufacture, in
that the central oriel is made from an expensive clear material which must
be inserted into specially designed opaque mounts which in turn are
attached to the roof.
U.S. patent number 5,435,780 discloses a ventilated skylight
having a light transmissive dome. The dome is supported by a support ring
which is initially provided in two halves and must be welded together for use.
The support ring is then installed on a soaker tray which is in turn is
attached
to the roof. Separate ventilation tabs are inserted into the underside of the
light transmissible dome to provide ventilation. However, this device is
complicated and expensive to assemble, as it requires many different parts
for operation, some of which must be welded. It is also expensive to
manufacture because of the large number of parts.
U.S. patent number 3,934,383 discloses a roof vent for use in
vans and the like. The roof vent cap is formed of a light-transmissive plastic
resin. The cap is opened by turning a crank, and the cap opens at an angle.
When the cap is closed, there is no venting. However, this device is
expensive and complex to manufacture, requiring a complex cranking and
opening assembly. Furthermore, light transmissive plastic resins typically
degrade from exposure to ultraviolet light in the outdoors, taking on an
unattractive yellow appearance. This patent does not address this yellowing
problem.
U.S. patent number4,730,552 discloses a ventilating skylight.
The device includes a housing having an opaque top wall. The housing
includes front and rear openings through which sunlight may pass when the
door to those openings are open. There is further a transparent dividing wall
below the openings and parallel to the top wall. The transparent dividing
wall has an air flow passage at its centre. However, this device is difficult
and expensive to manufacture, assemble and install. It is fabricated from a
CA 02267823 1999-04-O1
-4-
number of different materials and consists of a large number of pieces,
some of which are attached to one another by hinges, thus increasing the
complexity of manufacture and assembly.
SUMMARY OF THE INVENTION
Therefore, what would be desirable is a passive venting device
which provides adequate illumination to the enclosure being vented, is
simple and inexpensive to manufacture and install, and is equipped to have
an attractive appearance upon installation and in the long term.
Accordingly, the present invention is directed to a passive
venting device for venting a building enclosure comprising a base member
having an outer flange for securing the base member to a surface.
Contained within the base member is a vent structure for permitting gases
and vapours to pass through the base member, the vent structure including
a filter screen to prevent objects from passing through the base member.
The passive venting device further comprises a cap member immovably
mounted to the base member and spaced therefrom sufficiently to permit the
free flow of air between the cap member and the base member through the
vent structure. The cap member is integrally moulded from a translucent
material. With respect to this invention, "translucent" means light
transmissive but not transparent. Ambient light travels through the cap
member, filter screen and vent structure and into the building enclosure
being vented.
In another aspect of the invention, the cap member is
composed of a translucent material having a sufficient light transmission
efficiency such that, at typical daytime ambient light levels, sufficient
light is
transmitted into the enclosure to permit the performance of various seeing
tasks. In particular, at least enough light is transmitted to permit simple
orientation of a person making a short temporary visit. More particularly,
enough light is transmitted to permit occasional performance of a visual task
CA 02267823 1999-04-O1
-5-
and most preferably, enough light is transmitted for the performance of
visual tasks of high contrast or large size.
In still another aspect of the present invention, the cap
member is composed of a translucent plastic resin wherein the translucent
plastic resin includes an additive for inhibiting discoloration where enough
additive is added to inhibit discoloration but not enough to adversely
compromise the light transmissive properties of the roof vent. The preferred
range of light transmissive efficiency is greater than 40 % with the most
preferred range being between about 50 % and 60 %.
10
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will now be made by way of example only, to
drawings of the invention, which illustrate the preferred embodiment of the
invention, and in which Figure 1 is a perspective view of the passive venting
device according to the present invention, and
Figure 2 is a bottom plan view of the passive venting device
of Figure1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
20 Figure 1 illustrates the passive venting device 10 according to
the present invention. The passive venting device 10 is for venting a
building enclosure, and comprises a base member 12 having an outerflange
14 for securing the base member 12 to a surface. The flange 14 may be
secured to the surface in any convenient manner, including clip, nails or
screws. Preferably, the flange 14 includes a plurality of securing holes 16
through the outer flange 14. The securing holes 16 are adapted to accept
nails or screws which can be used to secure the base member 12 to a
surface, which would typically be a roof. The flange 14 may be of any
convenient shape, and the securing holes 16 may be distributed on said
30 flange 14 in any way which will allow the device to be securely fastened to
said surface. Preferably, there are at least 7 securing holes 16 on the outer
CA 02267823 1999-04-O1
-6-
flange 14 spaced about at least three sides of the generally rectangular
outer flange 14. Such a spacing arrangement allows the base member 12
to be adequately secured to the surface. The wide flange permits shingles
to be lapped over the device, so the device is readily attached to a shingled
roof.
The base member 12 further includes a vent structure 18 for
permitting the gases and vapours to pass through the base member 12.
The vent structure includes an aperture 17 (Figure 2) through the base
member 12 through which gases and vapours may pass. The vent structure
18 further includes a filter screen 20 to prevent objects from passing through
the base member 12. Preferably, the filter screen 20 consists of a plurality
of screen members 22 disposed across aperture 17, and spaced apart
sufficiently to allow gases and vapours, as well as light, to pass through the
filter screen 20.
The passive venting device further comprises a cap member
24 immovably mounted to the base member 12, and spaced from the base
member 12 sufficiently to permit the free flow of air between the cap
member 24 and the base member 12 through the vent structure 18.
The cap member 24 may be mounted on the base member 12
in any secure fashion. Examples include screws, nails, clips or glue. The
cap is immovably mounted, meaning that the cap has a single position for
operation of the invention, namely, spaced from the base to permit the free
flow of air. In ordinary operation the cap cannot be opened and closed to
alternately block and unblock the flow of air. In the preferred embodiment,
the cap member 24 is mounted using four cap mounting shafts 26 and four
corresponding cap mounting slots 28 which are open at each end. The cap
mounting shafts 26 are positioned adjacent to each of the four corners of the
cap member 24, which is generally rectangular when viewed from above or
below. The cap mounting slots 28 are positioned so as to correspond with
the cap mounting shafts 26, and are distributed on the vent structure 18
diagonally and radially inwardly from each of the four corners of the outer
CA 02267823 1999-04-O1
-7-
flange 14. The cap mounting shafts 26 are affixed to the cap member 24
extending downward, while the cap mounting slots 28 are formed on the
outside of the vent structure 18, and are shaped to receive the cap mounting
shafts 26.
At the end of each cap mounting shaft 26 is a lip 32 (Figure 2).
When the cap mounting shaft 26 is inserted into the cap mounting slot 28,
the lip 32 compresses slightly. The lip 32 is then pushed through the cap
mounting slot 28 and expands when it exits the opposite end of the slot, thus
immovably mounting the cap member 24 by anchoring it onto the cap
mounting slot.
The vent structure 18 when viewed from above is preferably
generally rectangular, with three of its sides parallel to the sides of the
outer
flange 14. However, the fourth side of the vent structure 18 is slightly bent
or angled, forming a peak 30 in the middle of the fourth side. When the
passive venting device 10 is mounted on a sloped roof, the passive venting
device 10 is positioned such that the peak 30 is pointed up the slope. This
positioning prevents waterfrom pooling against the side of the vent structure
18.
In accordance with the present invention, the cap member 24
is integrally composed of a translucent material which is preferably a
mouldable plastic. In Figure 1 the translucent nature of the cap member 24
is illustrated as the vent structure outline is visible through the cap member
24. Use of a plastic allows for cost effective and simple manufacturing using
a moulding process.
In being integrally composed of a translucent material, the cap
member may be of one piece or more, but the one piece construction is
preferable because of the benefit of simpler construction and use. It will now
be appreciated that because the cap member's material is moulded
(preferably in one step) into a generally uniform translucent material, there
is no need for a central clear plastic piece mounted and separately sealed
against weather to an opaque plastic base piece as taught in the prior art.
CA 02267823 1999-04-O1
_$_
Rather, the preferred one piece cap member of the present invention is
composed of a sufficiently translucent material such that light transmission
is provided to the enclosure.
The base member 18 need not be translucent for operation of
the present invention. Rather, the present invention may be employed with
the screen members 22 spaced apart sufficiently to allow light to pass
through the filter screen 20 and base member 12 into the building enclosure
being vented. However, if the screen members are more widely spaced
there is a risk that unwanted objects will penetrate the vent, such as pests
and the like. Thus, most preferably, the base member 12 is integrally
composed of the same translucent plastic resin as the cap member 24.
From Figure 2 it is also apparent that the base member 12 is translucent,
meaning that the outline of cap member 24 is visible through the base
member 12. This allows for cheaper and easier manufacture, as there is
only one raw material which is purchased in bulk and fed into, for example,
an injection moulding machine. Also, manufacturing the base member 12
from the same plastic resin allows for greater light transmission into the
enclosure while hiding from view the unattractive rough cut edges of the hole
that is made in the roof beneath the passive venting device to provide
access to the building enclosure.
To provide adequate illumination within the enclosure being
vented, the moulded plastic must have a sufficient light transmission
efficiency such that, at typical daytime ambient light levels, sufficient
light is
transmitted into the enclosure being vented. "Light transmission efficiency"
in respect of the present invention means the percentage of incident light
hitting the device which is transmitted through the device. Typical
enclosures for which the passive venting device would be used are, for
example, attics and sheds. It is preferable to provide within such an
enclosure sufficient illumination for simple orientation by a person making
a short temporary visit. This is because such enclosures are usually used
for storage of tools, equipment and other articles which must periodically be
CA 02267823 1999-04-O1
_g_
located. It would be more preferable to provide sufficient illumination for
the
occasional performance of a visual task inside such an enclosure. Most
preferably, sufficient illumination is provided for the performance of visual
tasks of high contrast or large size. Of course, it will be understood by
those
skilled in the art that the present invention relates to a passive venting and
lighting device, which relies on the amount of light outside being sufficient
to be transmitted through the device to perform the tasks as set out above.
Clearly, the greater the outer light levels, the more light will be
transmitted
to the interior. Thus, in considering the above criteria it is to be kept in
mind
that the starting conditions are assumed to be the ambient light on a
reasonably bright day.
Daylight levels may vary widely according to a number of
variables, including latitude, time of day, time of year and weather
conditions. The amount of such daylight entering the enclosure and its
distribution therein depend on other factors as well, such as the angle of the
venting device and the direction of any incident daylight. In a publication
entitled "Daylight Availability Data for Selected Cities in the United States"
complied for the U.S. Department of Energy in September 1982 by Claude
Robbins et al. of the Solar Energy Research Institute of Golden, Colorado,
values of daylight are given for various cities in the U.S. at different times
of
day, times of year and weather conditions. For the purposes of illustration,
certain typical values of daylight illuminance are provided. The average
global illuminance from an overcast sky in Chicago, Illinois on an April day
at 1:00 p.m. is 2455 footcandles; on a July day, 1919 footcandles. The
average global illuminance in San Diego, California at the same time of day
and under overcast conditions is 1796 footcandles; in July, 1590
footcandles. Thus according to the preferred form of the present invention,
the range of tasks identified above are able to be performed with at least
about 1500 footcandles of ambient light.
In preferred form of the invention, the cap member 24 and
base member 12 are both moulded from a plastic resin into a light
CA 02267823 1999-04-O1
-10-
transmissive plastic suitable for mass produced injection moulding.
Adequate results have been obtained with a random copolymer propylene
plastic. Ordinary polypropylene is typically a highly crystalline plastic, in
which the crystallinity has the effect of reducing light transmission
efficiency.
Further, typically, polypropylene is dyed to be opaque for outdoor plastic
applications. Random copolymer polypropylene has a reduced level of
crystallinity which has the effect of increasing light transmission
efficiency.
On the other hand, the reduced crystallinity of random copolymer
polypropylene typically makes it less resistant to impact and cracking than
ordinary polypropylene. In the present invention, the use of random
copolymer polypropylene resulted in a device having a superior light
transmission efficiency, while still having sufficient resistance to impact
and
cracking to be securable to a roof with nails. Adequate results have been
achieved with a resin supplied by ACLO Compounders Inc. of Cambridge,
Ontario, Canada. It will be appreciated by those skilled in the art that the
present invention comprehends other forms of plastic. What is required is
a plastic which can be easily moulded, for example by injection moulding,
which is light transmissive, which can be protected from UV degradation and
which is still suitable for nailing or the like to a shingle roof.
Adequate illumination results have been obtained with a
moulded plastic having a light transmission efficiency of at least forty
percent. Most preferably, the mouldable plastic will have a light
transmission efficiency of between about fifty and sixty percent. Higher
values are also comprehended by the present invention, but are not
generally preferred because to achieve the same requires reduced
protection against discoloration by reducing the anti-discoloration additive
as set out below.
Also in accordance with the present invention, the plastic resin
which is moulded into a translucent plastic includes an additive for
inhibiting
and preventing early discoloration. The additive is preferably present in
sufficiently large quantity to inhibit discoloration of the moulded plastic
due
CA 02267823 1999-04-O1
-11-
to degradation over time and yet in sufficiently small quantity for the
plastic
to maintain its translucence or light transmission efficiency at acceptable
levels.
Typically, a translucent plastic exposed to the outdoor
elements would begin to discolour within about five years by turning yellow.
This yellowing is largely a result of exposure to ultraviolet light, and
occurs
regardless of the presence of an ultraviolet inhibitor within the resin,
though
such an inhibitor does delay the onset of yellowing. The present invention
comprehends using an additive to inhibit the plastic from taking on a yellow
or discoloured appearance, thus presenting a more aesthetically pleasing
look and a longer-lasting product. Preferably, the additive is a coloured
pigment. According to an aspect of the present invention sufficient pigment
is added to the resin to provide a colored tint to the plastic without
reducing
light transmission efficiency too much. Reasonable results have been
achieved with the addition of a blue pigment in an amount which reduces the
light transmission efficiency of the plastic to no more than about 40 percent.
The reduction is preferably less than that, namely, to within the range of
about 50 to 60 percent.
The invention may be still further illustrated by the following
two examples and tests, which are provided by way of example only.
A light transmissibility study was performed on a Translucent
Roof Vent Model No. 5950C. The dimensions of the outer flange of this
model are 17 inches by 18 inches. The cap member is 12 inches by 12
inches. The study was performed in accordance with the procedures
recommended by the Illuminating Engineering Society of North America. To
counteract the effects of discoloration through yellowing, a blue pigment was
added to the random copolymer polypropylene. Typically, the random
copolymer polypropylene has a light transmission efficiency of about seventy
percent, but the addition of pigment reduces that efficiency. In this case, an
amount of blue pigment sufficient to prevent discoloration was added to the
resin, but, as set out in more detail below, the random copolymer
CA 02267823 1999-04-O1
-12-
polypropylene maintained sufficient translucence and light transmission
efficiency.
A light transmissibility study was performed on this passive
venting device. The test was performed with one thousand footcandles of
incident sunshine striking the passive venting device directly from above
with the passive venting device being disposed horizontally.
The following candle power readings were taken with respect
to light passing through the passive venting device:
CANDLEPOWER SUMMARY
ANGLE MEAN CP LUMENS
0 933
5 786 66
10 511
15 301 84
20 174
25 109 51
30 74
35 53 33
40 39
45 30 23
50 22
55 17 15
60 11
65 7 g
70 4
75 2 3
80 1
85 1 0
90 0
CA 02267823 1999-04-O1
-13-
In the above table, the title "Angle" refers to the angle from the
vertical, with the downward direction being 0° and the horizontal
direction
being 90°. The heading "Mean CP" refers to the intensity of light
exiting
from the passive venting device at various angles. The third heading
"Lumens" measures the amount of light passing through a specified angular
area as it exits the passive venting device. Therefore, for example, 66
lumens of light were found to be in the annular area whose inner radius is
defined by a line extending downward from the passive venting device at an
angle 2.5° from vertical, and whose outer radius is similarly defined
with
respect to the downward extending line angled 7.5° from vertical.
Similarly,
84 lumens were detected in the 12.5° to 17.5° range.
As can be seen from these results, the light scatter
characteristics of the plastic cause some incoming light to be deflected away
from the vertical, despite the incident light being in the vertical direction.
Therefore, for example, only 66 lumens of light are in the 2.5° -
7.5° range,
while 84 lumens of light are in the 12.5° -17.5° range.
Significant quantities
of light are found all the way out to about 60° from the vertical.
The following table records the amount of light in lumens for
each angular zone away from the vertical.
ZONAL LUMENS
AND PERCENTAGES
ZONE LUMENS % SUNSHINE % LUMINAIRE
0 - 30 201 35.75 70.97
0 - 40 234 41.69 82.75
0 - 60 272 48.48 96.24
0 - 90 283 50.38 100.00
40 - 90 48 8.69 17.25
60 - 90 10 1.90 3.76
90 - 180 0 .00 .00
0 - 180 283 50.38 100.00
CA 02267823 1999-04-O1
-14-
In this table the heading "Zone" refers to the angular zone
anywhere between 0° and 180°. The second column refers to the
number
lumens in each angular zone. The next column shows the percentage of the
external incident sunshine that is transmitted through the passive venting
device into the relevant angular zone. The final column indicates the
percentage of the light transmitted through the passive roof venting device
which reaches the relevant angular zone.
As can be seen again from these results, the light scatter
characteristics of the plastic have the effect (apart from preventing the
plastic from being transparent) of illuminating the enclosure not only
directly
below the passive venting device, but also the enclosed area disposed
radially and downwardly away from the passive venting device. This allows
the enclosure being vented to be more effectively illuminated by the passive
venting device. An aspect of the present invention is the diffuse nature of
the light which is transmitted into the enclosure. By reason of the
translucency, in combination with the multiple surfaces through which the
light travels when passing through the device, the ambient light transmitted
into the enclosure (as opposed to the focussed light of this example) tends
to spread out into the enclosure providing a desirable, even or soft light in
the enclosure.
Note that the second table discloses the overall light
transmission efficiency of the passive venting device. Since all transmitted
light is in the angular range of 0° to 90°, and the percentage
of incident
sunshine transmitted in that range is 50.38%, the light transmission
efficiency of this passive venting device model is 50.38%. This is a decline
in efficiency of approximately 20% as compared with typical random
copolymer polypropylene having no added pigment. Adequate illumination
results have been obtained at this level of light transmission efficiency such
that, under typical daytime ambient light levels, sufficient light is
transmitted
into the enclosure being vented.
CA 02267823 1999-04-O1
-15-
An additional test with the same 1000 footcandles of incident
sunshine was done using a model no. 5975C roof vent. The dimensions of
the outer flange of this model are 19.5 inches by 20.5 inches. The cap is 14
inches by 14 inches. This model was produced from the same resin as
described in the previous example, having the same pigment additive.
The Candlepower Summary and Zonal Lumen tables are
reproduced below.
CANDLEPOWER SUMMARY
ANGLE MEAN CP LUMENS
0 2007
5 1626 132
10 922
15 462 131
20 238
25 143 gg
30 98
35 71 45
40 55
45 44 34
50 34
55 26 23
60 18
65 12 12
70 8 '
75 4 5
80 2
85 1 1
90 0
CA 02267823 1999-04-O1
-16-
ZONAL LUMENS
AND PERCENTAGES
ZONE LUMENS % SUNSHINE % LUMINAIRE
0 - 30 331 39.41 73.39
0 - 40 376 44.82 83.46
0 - 60 433 51.57 96.04
0 - 90 451 53.70 100.00
40 - 90 74 8.88 16.54
60 - 90 17 2.13 3.96
90 - 180 0 .00 .00
0 - 180 451 53.70 100.00
As can be seen from these results, this model, because of its
light scatter characteristics, allows for illumination not only directly below
the
passive venting device, but in areas disposed below and radially away from
the passive venting device.
The light transmission efficiency of this model was found to be
53.7%, a drop of approximately 16% as compared to typical resin with no
pigment added. Adequate illumination results have been obtained at this
efficiency such that, under typical daytime ambient light levels, sufficient
light
is transmitted into an enclosure being vented.
While the foregoing embodiments of the present invention,
including the two examples, have been set forth in considerable detail forthe
purposes of making a complete disclosure of the invention, it will be
apparent to those skilled in the art that various modifications can be made
to the device without departing from the broad scope of the invention as
defined in the attached claims. Some of these variations are discussed
above and others will be apparent to those skilled in the art. For example,
the base member and cap member may be integrally moulded together as
one piece without being outside the scope of the invention. What is
considered important in the present invention is to provide a simple
CA 02267823 1999-04-O1
-17-
mouldable structure which simultaneously provides the passive venting and
passive lighting functions of the present invention. Such a device needs to
obscure the rough edges of a hole cut in the roof of a device, and be easy
to make and install. The preferred form of material is a random copolymer
form of polypropylene, but other materials may also be used provided they
provide the required light transmissive properties in combination with
acceptable durability and material performance.
