U.S. patent number 3,788,207 [Application Number 05/257,148] was granted by the patent office on 1974-01-29 for top discharge roof ventilator.
This patent grant is currently assigned to Doherty-Silentaire. Invention is credited to Lewis S. Doherty, II.
United States Patent |
3,788,207 |
Doherty, II |
January 29, 1974 |
TOP DISCHARGE ROOF VENTILATOR
Abstract
A roof ventilator for exhausting air includes a tapered,
upstanding, hollow stack for sealed securement on a roof at an air
opening therein. A hollow, upstanding and semispherical outlet bell
is telescoped in close spaced radial relation over the upper end of
the stack and has an open upper end. A substantially flat damper
pan normally rests upon and closes the upper stack end. A mounting
sleeve is fixedly supported within the stack. A hollow guide
element, pendently and coaxially fixed to the damper pan, is
slidably located within the mounting sleeve and carries limiting
means coacting with the mounting sleeve for limiting movement of
the damper pan upwardly off the upper stack end, whereby a pressure
drop from the stack to the bell causes the damper pan to lift from
the upper end of the stack to vent the stack into the bell.
Inventors: |
Doherty, II; Lewis S. (Parish
of East Baton Rouge, LA) |
Assignee: |
Doherty-Silentaire (Baton
Rouge, LA)
|
Family
ID: |
22975089 |
Appl.
No.: |
05/257,148 |
Filed: |
May 26, 1972 |
Current U.S.
Class: |
454/362;
137/533.21; 415/148; 415/157; 415/158; 454/348; 454/353 |
Current CPC
Class: |
F04D
25/14 (20130101); Y10T 137/7915 (20150401) |
Current International
Class: |
F04D
25/14 (20060101); F04D 25/02 (20060101); F04d
025/14 () |
Field of
Search: |
;98/42,43,66,74,59,79,116,85,119 ;137/533.21,533.29,543.23
;415/157,158 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: O'Dea; William F.
Assistant Examiner: Ferguson; Peter D.
Attorney, Agent or Firm: Woodhams, Blanchard & Flynn
Claims
I claim:
1. A roof vent device for exhausting air, comprising in
combination:
an upstanding hollow stack for mounting on a roof at a vent
opening, said stack having open upper and lower ends;
a hollow upstanding outlet bell fixed with respect to said stack,
said bell having an open lower end telescoped over the upper end of
said stack and an open upper end, the diameter of said bell
intermediate the ends thereof substantially exceeding the diameter
of the ends thereof;
a damper pan normally closing the upper end of said stack and
located within said bell;
means guiding said damper pan for substantially coaxial movement
away from the stack in response to a pressure drop from said stack
to said bell so as to exhaust air from said roof opening through
said stack and bell.
2. The device of claim 1 in which said bell is substantially
semispherical, having convexly outwardly curved sidewalls extending
radially outwardly from said ends thereof toward the intermediate
portion thereof, said stack being of upwardly tapered frustoconical
form and extending for a minor portion of its length into the
interior of said bell to a level below said intermediate bell
portion, said guiding means including limit means limiting movement
of said damper pan away from said stack to a level approximating
the maximum diameter of said bell.
3. The device of claim 2 in which the diameter of said damper pan
approximates that of the upper end of said stack, said damper pan
having a dependent perimetral flange adapted to overhang said upper
end of said stack and being disposed in close radially spaced
relation to the exterior face of said stack for assisting in
centering said damper pan on said stack as said damper pan is
closed and preventing entry of foreign material into said stack
when said damper pan is closed, said damper pan resting upon the
upper end of said stack when closed.
4. The device of claim 3 in which the lower portion of the curved
sidewall of the bell is spaced downwardly from and radially
outwardly from said flange of said damper pan, said lower portion
of said bell peripheral wall extending upwardly and outwardly in
curved spaced relation past said flange for deflecting air passing
between said damper pan and the upper end of said stack smoothly
outwardly and upwardly through said open upper end of said
bell.
5. The device of claim 4 in which the open lower end of said bell
is fixed in radially outwardly spaced relation to said stack,
whereby rain entering the upper bell end exits at the lower bell
end along the outer face of said stack, the minimum spacing of said
damper pan from the wall of said bell substantially exceeding the
minimum spacing of said bell from said stack whereby to minimize
air flow from said stack downwardly along the peripheral wall of
said stack out of said bell.
6. The device of claim 1 in which the diameters of said damper pan
and the open upper end of said top bell are approximately equal,
the diameter of said bell intermediate its ends substantially
exceeding the diameter of said damper pan for providing ample cross
sectional area for relatively high volume and low velocity air flow
in an annular zone between said damper pan and the peripheral wall
of said bell.
7. The device of claim 6 in which the upwardly facing surface of
said damper plate is substantially flat for preventing accumulation
of rain water thereon, whereby said pressure drop is substantially
uniform despite varying weather conditions.
8. The device of claim 1 in which said bell comprises a bowl-like
lower bell portion and a bowl-like upper bell portion removably
securable thereto by means including an overlapping flange, said
overlapping flange being located substantially at the maximum
diameter of said bell, said bell portions and stack being compactly
nestable when disassembled, said stack and bell portions being
dimensioned to allow inverted reception of said upper bell portion
in said lower bell portion and inverted reception of said stack in
said upper bell portion, said pan being nestable therewith.
9. The device of claim 1 wherein said means quiding said damper pan
comprises a guide element coaxially fixed to and dependent from
said damper pan, a hollow sleeve coaxially located within said
stack adjacent the upper end thereof, arms fixed to the peripheral
wall of said stack and extending inboard thereof, said arms fixedly
carrying said sleeve therebetween, said arms and sleeve being
spaced below and adjacent said damper pan when said damper pan
rests upon the top of said stack.
10. The device of claim 9 in which the length of said guide element
approximates the height of said stack, said guide element having
means adjacent the lower end thereof for coacting with the lower
end of said sleeve to limit upward movement of said damper pan to a
height corresponding to the maximum diameter of said bell.
11. The device of claim 1 in which said stack is upwardly tapered
and substantially frustoconical in form, said bell having a
dependent flange at the open lower end thereof, said flange
tapering in substantial parallelism to said stack and lying in
close spaced relation thereto for defining an annular water drain
opening therebetween for said bell, a plurality of fastening
devices connecting said flange to said stack for supporting said
bell, said fastening devices being distributed around the periphery
of said stack, washerlike elements on said fastening devices
disposed between said flange and said stack for maintaining said
drain opening.
12. A roof vent device for exhausting air, comprising the
combination:
an upstanding hollow stack adapted to be secured in sealed relation
on a roof for venting an opening therethrough and having open upper
and lower ends;
a hollow weather shield fixed with respect to said stack, said
weather shield having an open lower end overhanging the upper end
of said stack, an open upper end above said stack and a widened
intermediate portion;
a damper pan normally closing the upper end of said stack and
located within said weather shield;
means guiding said damper pan substantially coaxially upwardly from
the stack to a full open position adjacent the widened intermediate
portion of said weather shield in response to an increasing
pressure drop from said stack to said weather shield, for
maximizing exhaust air flow from said roof opening upwardly through
said weather shield.
Description
FIELD OF THE INVENTION
This invention relates to a roof ventilator and more particularly
relates to a top discharge roof ventilator.
BACKGROUND OF THE INVENTION
Prior roof ventilators have in general been relatively complex, and
hence expensive in construction, particularly as to the arrangement
of damper members and baffling therefor. Prior roof ventilators
have frequently been of relatively high silhouette, which combined
in many instances with a generally displeasing appearance, has
degraded the appearance of the building on which they are mounted.
The construction of such prior roof ventilator devices as in
certain instances been such that portions thereof are susceptible
to vibration or rattling in use and/or to deflection in moderate or
high winds. Further, dampers often used on prior art roof
ventilator devices have been relatively heavy, have been supported
in a relatively unbalanced way and/or have been provided with
friction mounting arrangements, requiring a substantial pressure
drop from the building to the atmosphere in order to open, and
thereby requiring the use of a closely adjacent, normally
structurally coupled, exhaust fan. Frequently, there is a
substantial drop in pressure, or air flow loss, across open or
partially open prior art damper structures. In many instances prior
upwardly opening devices have provided inadequate protection from
entrance of rain, hail or the like past the damper unit,
particularly where the damper is open or partially open and air
flow rates are relatively low. Further, such prior constructions
have often been susceptible to opening of damper members by wind,
allowing back drafts into the building.
Accordingly, the objects of this invention include provision
of:
1. A top opening discharge ventilator device, or exhaust valve, for
discharge of air from the interior of a building structure adapted
for mounting on the roof of such structure.
2. A device, as aforesaid, of low silhouette and pleasing
appearance shaped to minimize wind resistance, which is
structurally stable under high wind or variable wind conditions
with little or no flutter, vibration, etc. and has little or no
tendency to lift or change position or configuration under high
wind conditions.
3. A device, as aforesaid, of simple and lightweight construction
which, particularly in its exterior elements, is of substantial
strength and stability of configuration and which is adapted for
mounting on a roof without need for reinforcement of such roof and
which indeed may be installed on an existing roof surface by a
simple mopping-in operation.
4. A device, as aforesaid, which is of inexpensive construction and
is manufacturable of commonly available materials in large or small
quantities, in which major elements are particularly adaptable for
production by a spinning operation from sheet aluminum, which is
capable of being stored and shipped in a compact disassembled
condition with the elements thereof in nested relation and
occupying a volume not substantially exceeding the volume not
normally occupied by the larger ones of such elements and which can
readily be assembled by persons of little skill or experience with
manipulation of a minimal number of fastening devices and in
relatively little time.
5. A device, as aforesaid, including an openable damper member or
valve which is of relatively lightweight, has relatively low
opening friction and is capable of opening in response to a
relatively small pressure drop from within the supporting building
structure to the outside atmosphere, which is openable in response
to the pressure created within the building by an adjacent fan or
the like or, alternatively, by other remotely located means,
including for example air conditioners, window fans, etc. and in
which air flow loss caused by the damper or valve along or in inner
action with the surrounding exterior element is minimized.
6. A device, as aforesaid, which though upwardly opening prevents
entry of rain, hail or the like therethrough into the building
whether the damper valve is open or closed, which provides for
drainage of water due to rain or the like from the upwardly opening
element thereof while minimizing or eliminating downward or
sideward direction of exhausting air toward the supporting
roof.
7. A device, as aforesaid, in which the damper or valve is not
susceptible to opening by ambient winds, for example when exhaust
air flow is small or absent.
8. A device, as aforesaid, which eliminates the need for a sealing
shutter or valve within the building structure in the air flow path
through the device. 9. A device, as aforesaid, in which the
pressure drop required to open the damper, and the air flow through
the device, is substantially unchanged despite rain or the like
entering the open upper end of the device and striking the damper
member.
Other objects and purposes of this invention will be apparent to
persons acquainted with apparatus of this general type upon reading
the following specification and inspecting the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial view of a roof ventilator device embodying
the present invention and installed on the roof of a building.
FIG. 2 is an enlarged central cross-sectional view, in elevation,
of the device of FIG. 1 and showing same installed in conjunction
with a motor driven fan.
FIG. 3 is a sectional view substantially taken on the line III--III
of FIG. 2.
SUMMARY OF THE INVENTION
The objects and purposes of the invention are met by providing a
roof ventilator for exhausting air which includes a tapered
upstanding hollow stack for sealed securement to a roof at an air
opening therein. A hollow upstanding and semispherical outlet bell
is telescoped in close spaced radial relation over the open upper
end of the stack and has an open upper end. A substantially flat
damper pan normally rests upon and closes the upper stack end. A
mounting sleeve is fixedly supported within the stack. A hollow
guide element, pivotally and coaxially fixed to the damper pan, is
slidable within the mounting sleeve and carries limiting means
coacting with the mounting sleeve for limiting movement of the
damper pan upwardly off the upper stack end, whereby a pressure
drop from the stack to the bell causes the damper pan to lift from
the upper end of the stack to vent the stack into the bell.
DETAILED DESCRIPTION
The ventilator device 10 embodying the invention is adapted to be
supported upon a roof structure, generally indicated at 12, of a
building.
The device 10 includes a hollow, open ended stack 14. The stack 14
has a peripheral wall 15 which is upwardly tapered and of generally
frustoconical form. A radial flange 16 extends outwardly from the
lower end of the peripheral wall 15 and is adapted to be supported
upon and secured to the roof structure 12. An opening 17 in the
roof structure 12 provides communication between the interior of
the building covered by the roof structure 12. The opening 17 is
preferably coextensive in size and coaxial with the open lower end
of the stack 14. The upper end of the peripheral wall 15 is
preferably provided with a reinforced edge 18, in the preferred
embodiment shown an outwardly rolled lip.
A hollow tubular mounting sleeve 21 is located coaxially within the
stack 14 in close spaced relation to the upper end thereof. The
lower end of the mounting sleeve 21 is substantially spaced from
the lower end of the stack 14. The mounting sleeve 21 is fixed to
the stack by a support here comprising a pair of diametrally
aligned support tubes 22 and 23 extending radially inwardly from
the peripheral wall 15 of the stack to the upper portion of the
guide element 21. The tubes 22 and 23 are spaced below the upper
end of the stack. The ends of the support tubes 22 and 23 are
preferably secured as by welding to the stack peripheral wall 15
and mounting sleeve 21. The radially inner ends of the support
tubes 22 and 23 are preferably flattened in a vertical plane, as
indicated at 25, to provide an increased length of contact axially
of the guide element 21 and thereby a more rigid securement of the
support tubes to the guide element.
A valve element or damper 27 has a diameter slightly exceeding that
of the upper end of the stack 14. When at rest, the damper 27
covers the upper end of the stack for closing same. The damper 27
may be somewhat upwardly convex, but is preferably flat and
panlike. The damper pan 27 has a circumferentially continuous,
pendant flange 29 at the circumferential edge thereof. The flange
29 is preferably sloped, substantially corresponding in taper to
the stack 14. The flange 29 extends downwardly past the reinforced
upper edge 18 of the stack in snugly surrounding but freely
removable relation therewith, thereby overlapping the upper portion
of the stack. The flange 29 preferably terminates in a rolled
reinforcing rim 30.
A preferably tubular guide element 32 coaxially depends from the
underside of the damper pan 27 and is preferably fixed thereto by
welding. The guide element 32 axially slidably extends through the
mounting sleeve 21. The guide element 32 preferably substantially
corresponds in length to the height of the stack 14. A stop element
33, here a cotter pin, extends diametrally through the lower
portion of the guide element 32 for preventing unintended upward
removal of the guide element 32 from the mounting sleeve 21. The
tubular elements 21 through 23 and 32 are preferably thin walled
tubular aluminum stock and the damper pan 27 is preferably spun
from aluminum sheet.
A weather shield member is located above the stack and, in the
preferred embodiment shown, comprises an outlet bell 36 which
extends upwardly from the stack 15 and is substantially
semispherical, that is convexly rounded, in cross-section. The
outlet bell 36 is hollow and has open upper and lower ends
terminating in substantially axially extending flanges 37 and 38,
respectively. The flanges 37 and 38 assist in reinforcing the open
ends of the bell. The upper flange is substantially cylindrical.
The lower flange 38 surrounds the upper end of the stack in close
spaced relation thereto. The lower flange 38 is preferably upwardly
tapered to the same extent as the stack 14.
The outlet bell 36 is fixed at its lower flange 38 to the
peripheral wall 15 of the stack 14, preferably removably, as by a
plurality of circumferentially spaced nut and bolt connections 40.
The lower bell flange 38 is preferably spaced from the stack
peripheral wall 15 by interposition therebetween of washers, or the
like, carried by the bolts 40, to afford a narrow annular drain
opening 41 between the opposed surfaces of the bell and stack.
Thus, rainwater entering the top of the bell 36 drains from the
lower end of the bell along the outside of the peripheral stack
wall 15, through the annular drain opening 41.
The lower bell flange 38 is spaced somewhat below the damper flange
29, here by a distance corresponding substantially to the axial
length of such damper flange. The spacing between the lower bell
flange 38 and stack peripheral wall 15 is preferably substantially
less than the spacing between the lower bell flange 38 and damper
pan flange 29. The radial spacing of the bell 36 from the damper
pan flange 29 preferably substantially corresponds to or exceeds
the axial dimension of such pan flange. Thus, with the damper pan
27 raised somewhat from its closed position of FIG. 2, air from the
stack tends to flow upwardly into the bell rather than downwardly
through the drain opening 41.
In the preferred embodiment shown, the bell 36 is constructed in
two parts, a semispherical upper part 43 and a semispherical lower
part 44. The parts 43 and 44 are snugly joined, preferably at the
maximum diameter 46 of the bell 36 and by means of a radially
outwardly offset depending annular flange 47 on the upper part 43
which overlies the lower bell part 44 with a snug friction fit.
Provision of the bell in two parts, as above discussed, facilitates
formation of the bell by spinning from relatively thin aluminum
sheet material and also enables the device 10 to be knocked down
into a more compact package for shipping or storage.
The upper bell flange 37 is preferably substantially equal in
diameter to the open upper end of the stack 15, and hence is less
in diameter than the lower bell flange 38. The maximum diameter of
the damper pan 27 including its flange and rim preferably
substantially corresponds to the diameter of the lower bell flange
38.
The location of the stop element 33 allows opening, upward movement
of the damper pan 27 to a position at or near the maximum diameter
level 46 of the bell 36 whereby the annular air flow zone defined
between the periphery of the damper pan 27 and the interior side
wall of the bell 36 is maximized with the damper pan fully opened.
The annular air flow path surrounding the periphery of the damper
pan 27 increases in cross section as the damper pan moves upwardly
from the upper end of the stack, by reason of the increase in axial
distance between the damper pan and the upper stack end and also by
reason of the increased radial distance between the damper pan
periphery and the radially opposed portion of the peripheral wall
of the bell 36.
In many instances it will be desired to use the device 10 for
venting a building maintained at a slight pressure above exterior
atmospheric pressure, as by input ventilation fans, air
conditioning or the like. Particularly in such instances, the stack
flange 16 may simply be placed upon the surface of the roof of the
building in coaxially surrounding relationship with a vent hole
therein, corresponding to the hole 17 shown in FIG. 2. Thereafter,
the flange 16 may be secured to the roof as desired and then
covered with a conventional roof sealing membrane, not shown, to
prevent leakage of water radially inwardly along the lower surface
of the flange 16 and into the opening 17.
However, in other instances it may be desired to install the device
10 in direct conjunction with an exhaust fan or the like, such as
generally indicated as 50. Particularly in such instances it may be
desired to mount the device 10 on a raised roof deck portion, as
generally indicated at 51. To this end, the roof 54 of the building
is here disclosed as including an enlarged exhaust opening 55
surrounded by an upstanding laterally closed barrier 56, of any
conventional nature such as a square or rectangular enclosure of
wood, sealed by any convenient means to the roof deck 54. A carrier
plate 58 is fixed to and supported upon the barrier 56 by any
convenient means and may be provided with an integral, or separate,
depending sealing and locating flange 59. The exhaust fan unit 50
may be of any conventional nature and here is illustrated as
including an annular mounting rim 61 having a radial portion 62
fixed by any conventional means to the underface of carrier plate
58 and further having a dependent support portion 63. A motor
mounting member 65 carries an upstanding conventional electric
motor 67, preferably in coaxiality with the device 10. A plurality
of radial arms 68 support the motor mounting member 65 on the rim
61. A fan blade 70 is loosely located within the support portion 63
below the device 10 and is secured to the shaft 71 of the motor 67
for rotation therewith in a conventional manner for impelling air
from the area below the roof 54 up and out through the device
10.
OPERATION
Portions of the device 10 are, when disassembled, readily nested
for storage or shipping. In a preferred nesting arrangement, the
inverted upper bell portion 43 is substantially fully nested within
the lower bell portion 44. The inverted stack 15 is then nested
substantially within the inverted upper bell portion 43. The damper
pan 27 is nested rightside up within the inverted stack 14, the
damper guide element 32 being received in the inverted mounting
sleeve 32. The resulting nested assembly does not substantially
exceed the height of its longest element.
The device 10 is readily assembled, for example from such a nested
condition, by securing the lower bell portion 44 over the narrow
upper end of the stack 14 in the position of FIG. 2 via the nut and
bolt connections 40. The spacers or washers 39 are disposed between
the bell and stack to provide annular drain opening 41. Thereafter,
the guide element 32 of the damper pan may be dropped downwardly
into the mounting sleeve 21 and the cotter pin 33 may be placed on
the guide element 32, the damper pan 27 resting atop the stack 14.
Finally, the flange 47 of the upper bell portion 43 is frictionally
fitted over the open upper end of the lower bell portion 44 as
shown in FIG. 2.
To install the assembled device 10 on a roof or the like, the stack
flange 16 is placed upon the surface, here as shown in FIG. 2 the
surface 58, upon which it is to be supported, in coaxiality with
the exhaust hole 17 therein. The stack flange 16 is then secured by
any convenient means, not shown, such as nails, screws or the like,
to the supporting surface 58 and a suitable waterproofing membrane
may be applied over the flange 16 and the adjacent portion of the
supporting surface 58 in sealed relation therewith. If desired, a
waterproofing adhesive or the like may be used between the flange
16 and surface 58 to provide additional water sealing and/or
securement of the device 10 to the roof. As stated, the device 10
may be installed either on a built-up deck, as shown in FIG. 2, or
on the surface of the roof and with or without an adjacent exhaust
fan unit 50.
In operation, with the device 10 in its rest condition shown in
FIG. 2, and thus with a zero or substantially zero pressure drop
from within the stack to within the bell, the damper pan 27 is
seated on the upper end of the stack. This closes the upper end of
the stack against entry of drafts, rain or the like and makes
unnecessary provision of an auxiliary shutter or the like within
the building to close the opening into the stack.
Rain entering the open upper end of the bell 36 runs down the
interior sidewalls thereof and exits through the narrow annular
drain 41 and then runs down along the exterior of the stack 14.
Winds of relatively high velocity do not tend to shift or move the
damper pan 27 from its closing relationship with the stack, the
damper pan being well shielded from such winds by the bell, the
closest open portion of the bell being the narrow annular drain
slot 41. Though of relatively light gauge material, the tapered
configuration of the stack 14 and rounded configuration of the bell
36 substantially strengthens same and, particularly in the case of
the bell, reduces resistance to wind flow therearound. Further, the
configuration of the stack and bell has substantial mechanical
stability and resistance to vibration and hence is substantially
free of flexing and noise production even in high steady or pulsing
winds.
In view of the light weight and low mounting friction of the damper
pan 27, a relatively low pressure drop from the stack 14 to the
bell 36, for example in the nature of a fraction of a pound per
square inch is sufficient to raise the damper pan 27 from the upper
end of the stack. Raising the damper pan 27 opens the upper stack
end and provides venting air flow upwardly out of the building
through the stack 14, past the pan 27 and out the open upper end of
the bell. Despite the downwardly directed flange 29 on the damper
pan 27, a great majority of air flow out the upper end of the stack
is smoothly directed, even at relatively low damper pan openings
and air flow rates, radially outwardly and then smoothly upwardly
by the outwardly and upwardly curving peripheral wall of the lower
bell portion 44. Little, if any, significant portion of exhaust air
flow passes downwardly through the narrow and rather restrictive
annular drain slot 41. Air flow continues in a smoothly curved
manner upwardly into the upper bell half 43 and out the upper end
thereof.
As increasing pressure drops from the interior of the stack to the
interior of the bell, the damper pan 27 rises increasingly greater
distances from the upper end of the stack, thus providing an
increasingly greater cross-section air path between the damper pan
and the upper stack end an lower bell peripheral wall. As relative
pressure in the stack 14 increases, the damper pan 27 eventually
reaches its maximum height, corresponding to the maximum bell
diameter, that is, the region 46 of the bell whereat the radial
spacing between damper pan and the bell wall (and hence the air
flow path cross-section) is maximized.
Even when the damper pan 27 is in a partially or fully opened
conditon (which can be achieved in the inventive device 10 with a
relatively small pressure drop across the pan and a low air flow
rate), rain or the like falling into the open upper end of the bell
does not tend to enter the stack. More particularly, the damper pan
whether open or closed, radially overlies the open upper end of the
stack and thus prevents vertical rain fall from entering the stack.
Further, the surrounding side walls of the bell prevents wind
driven rain or the like, falling on a slope, from entering the
vertical space between the damper pan and the stack.
The upper surface of the damper pan is preferably flat as shown, or
if desired may be somewhat upwardly convex, so that rain water
falling thereon will tend to drain off therefrom at its peripheral
edge. Thus, the relationship of damper pan height to air pressure
in the stack is not influenced by a buildup of rain water or the
like atop the damper pan. Further, the high heat conductivity of
the damper pan tends to prevent any build up of ice or the like
thereon, particularly when venting heated air from the building
interior. The high heat conductivity of the stack 14 tends to keep
the annular drain opening 41 open for removal of snow, sleet or the
like in the form of water.
Upon reduction of the air pressure in the stack 14 to a level equal
or substantially equal to that in the bell, the damper pan falls,
guided by sliding motion of guide element 32 in the mounting sleeve
21, to the top of the stack for closing same again.
Although a particular preferred embodiment of the invention has
been disclosed in detail for illustrated purposes, it will be
recognized that variations or modifications of the disclosed
apparatus including the rearrangement of parts, lie within the
scope of the present invention.
* * * * *