U.S. patent number 3,791,281 [Application Number 05/227,031] was granted by the patent office on 1974-02-12 for exhaust fan assembly.
This patent grant is currently assigned to Emerson Electric Co.. Invention is credited to Robert E. Steiner.
United States Patent |
3,791,281 |
Steiner |
February 12, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
EXHAUST FAN ASSEMBLY
Abstract
An improved exhaust fan assembly is provided in which a fan and
damper are mounted in a frame, the damper being mounted at the fan
outlet, within an exhaust fan housing structure. Two springs are
utilized to hold the damper closed. The damper opens by the force
of air exerted during fan operation. During that operation, the
springs exert a force which helps to hold the damper open. At least
one spring has a top extension that contacts a pin on the damper,
keeping the over-center force from becoming so great to hold the
damper open permanently. The fan and damper are self-contained with
respect to the rest of the fan housing and the length of the
exhaust fan housing can be varied for differing thicknesses of wall
through which the housing is to extend.
Inventors: |
Steiner; Robert E. (St. Louis,
MO) |
Assignee: |
Emerson Electric Co. (St.
Louis, MO)
|
Family
ID: |
22851461 |
Appl.
No.: |
05/227,031 |
Filed: |
February 17, 1972 |
Current U.S.
Class: |
454/350; 49/386;
454/353 |
Current CPC
Class: |
F24F
7/013 (20130101) |
Current International
Class: |
F24F
7/013 (20060101); F24f 007/00 () |
Field of
Search: |
;98/43,119,116
;49/197,386 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: O'Dea; William F.
Assistant Examiner: Ferguson; Peter D.
Attorney, Agent or Firm: Polster and Polster
Claims
Having thus described the invention, what is claimed and desired to
be secured by Letters Patent is:
1. An exhaust fan unit comprising:
a housing including an external section and a blower mounting frame
adjustably mounted with respect to said external section, said
mounting frame having an inlet side and an outlet side;
a blower mounted to said mounting frame so as to direct a volume of
air from said inlet side to said outlet side;
a back draft damper mounted to the outlet side of said mounting
frame, said damper being mounted for pivotal movement with respect
to said frame, about a pivot axis, between closed and opened
positions;
a spring stop connected to said damper;
a spring anchor mounted to said damper, said spring anchor being
offset, toward the inlet side, from said pivot axis when said
damper is closed; and
at least one spring element attached to said spring anchor having a
serpentine contour between a first end and a second end, one of
said first and said second ends of said spring element being
attached to said housing and the other of said first and said
second ends being free and projecting towards the outlet side, the
said free end and said spring stop being positioned to abut when
the damper is opened, thereby limiting the opening of the
damper.
2. The fan unit of claim 1 wherein the opening of the damper moves
the spring anchor to a point just short of over-centering, whereby
the effect of the bias of the spring is reduced in the damper-open
position.
3. A through wall exhaust fan unit comprising:
a housing, said housing including a blower mounting frame having an
inlet side and an oulet side;
a blower mounted to said blower mounting frame so as to direct a
volume of air from said inlet side to said outlet side;
a back draft damper mounted to the outlet side of said mounting
frame, said damper being mounted for pivotal movement with respect
to said frame, about a pivot axis, between closed and opened
positions;
a spring anchor mounted to said damper, said spring anchor being
offset, toward the inlet side, from said pivot axis when said
damper is closed;
at least one spring element having a first end and a second end,
one of said first and said second ends being attached to said
blower mounting frame and the other of said first and said second
ends being free and projecting toward the outlet side, said spring
element being attached to said spring anchor between said first and
said second ends; and
a spring stop mounted to said damper, said free end of said spring
and said spring stop being arranged to abut in at least one open
position of said damper to limit opening of said damper.
4. The fan unit of claim 3 wherein said housing is further
characterized by an external portion and a shell portion, said
blower mounting frame, said shell portion and said external portion
being adjustably mounted to one another, said external portion
having a pyramidal silhouette having three walls, at least one of
said walls having a plurality of louvered openings in them.
5. In an exhaust fan unit having a housing, said housing including
a blower mounting frame having an inlet side and an outlet side,
the improvement which comprises a back draft damper pivotally
mounted to said blower mounting frame at said outlet side and
adapted for rotation with respect to said housing about a pivot
axis so as to define at least a closed position, a plurality of
opened positions, and an outermost open position, said damper
comprising a structure having a pair of pivots and a pair of spring
anchors attached to it, one each of said pivots and said spring
anchors projecting outwardly on opposite sides of said damper along
parallel but laterally displaced axis, and at least one spring
element having a first end and a second end, said first end being
operatively connected between said housing and said spring anchor
so as to exert a force tending to open said damper in said
plurality of open positions of said damper, said second end of said
spring coacting with said spring stop to enable said spring to
exert a force tending to close said damper in said outermost open
position of said damper.
6. The improvement of claim 5 wherein said pivot pair, said spring
anchor pair, and said spring stop are integrally formed with said
damper.
7. The improvement of claim 6 wherein said outlet comprises a wall
having an opening in it for defining said outlet side, said opening
having a flange extending about its perimeter, said damper
comprising a flange engaging portion adapted to seal said outlet
opening in a closed position of said damper.
8. In an exhaust fan unit housing having an inlet side and an
outlet side, a blower mounted in said housing, the improvement
which comprises a back draft damper pivotally mounted to said
housing adjacent said blower, said damper being adapted for
rotation with respect to said housing between at least closed and
opened positions, said damper comprising a resilient material
structure having a pair of pivots projecting oppositely outwardly
from said damper along a pivot axis, at least one anchor means
projecting outwardly from said damper along a second axis, said
second axis being parallel to but laterally spaced from said pivot
axis, at least one spring operatively connected between said anchor
means and said housing, and a spring stop mounted to said damper,
said spring stop and said spring coacting to exert a closing force
on said damper in said opened position.
9. The improvement of claim 8 wherein said outlet side comprises a
wall having an opening in it for defining said outlet side, said
opening having a flange extending about its perimeter, said damper
comprising a flange engaging portion adapted to seal said outlet
opening in a closed position of said damper.
10. In an exhaust fan unit having a housing and a back draft damper
rotatably mounted between a closed position, a plurality of open
positions and an outermost open position, the improvement which
comprises means for exerting a force tending to open said damper in
said plurality of open positions of said damper, and means for
exerting a force tending to close said damper in an outermost open
position of said damper, said open force exerting means including a
spring element operatively connected between said housing and said
damper, said closed force exerting means including a spring stop
attached to said damper which coacts with said spring in at least
the outermost open position of said damper to enable said spring
element to exert a force on said damper in a direction of the
closed position of said damper.
11. An exhaust fan unit comprising:
a housing selectively adjustable between a minimum housing length
and a maximum housing length including an external section and a
blower mounting frame adjustably mounted with respect to said
external section, said mounting frame having an inlet side, a wall
having an opening in it attached to said mounting frame, said
opening defining an outlet side for said mounting frame;
a blower mounted to said mounting frame so as to direct the volume
of air from said inlet side to said outlet side;
a back draft damper mounted to the outlet side of said mounting
frame, said damper being mounted for pivotal movement with respect
to said mounting frame between a closed position blocking said
opening in said wall and an open position, said damper being
mounted so as to be surrounded by said housing at all lengths of
said housing and at all positions of said damper;
at least one spring element operatively connected between said
housing and said damper, said spring element having a free end
extending outboard of said wall in the direction of air volume flow
for all positions of said damper; and
means for engaging the free end of said spring element to exert a
closing force on said damper in its closed position.
Description
BACKGROUND OF THE INVENTION
This invention relates to back draft dampers for exhaust fans, and
in particular, to through-wall exhaust fans. Those skilled in the
art, however, will recognize the applicability of the concepts of
this invention to other damper applications.
It is common to use exhaust fans in the construction of houses and
the like in a number of areas.
For example, commonly a new home has a through-wall exhaust fan
near the cooking area of the home to dissipate the heat and odors
generated in food preparation. Conventionally, the exhaust units
have a fan mounted in a housing. the housing extends through the
wall structure of the house and the blower or fan is adapted to
blow air through the housing to the external atmosphere. Because
these units are vented to the outside atmosphere, it is common to
utilize some form of back draft damper in conjunction with the
units to prevent rain, cold air, insects and the like from getting
in. Conventionally, the damper has been installed on the external
side of the through-wall unit.
While these units work well for their intended purposes, they
exhibit inherent disadvantages heretofore unresolved in the prior
art. Prior art dampers conventionally are constructed from sheet
metal and are attached to a sheet metal enclosure. Such
construction presents a highly objectionable noise problem as the
back draft damper tends to close with some force. It is
conventional to line the damper-enclosure contact area with some
form of padding, conventionally of the felt type, to lessen the
metal chatter. Unfortunately, it is difficult to attach the padding
to the damper and have it remain there for any extended period of
time. It also generally is difficult to position the padding
properly.
While recent improvements in damper constructions, for example,
that disclosed in the U.S. Pat. to Steiner No. 3,589,268, issued
June 29, 1971, alleviated cerain objectional features of the
stamped metal damper by utilizing a non-metallic material for the
damper, the use of non-metallic material for damper construction in
certain applications, and in particular, in through-wall
applications, has been heretofore unfeasible because of the
conventional placement of that damper on the outside, along the
outlet of the exhaust fan structure, remote from the impeller of
the blower unit. In some through-wall units, this means that the
damper is exposed to the ravages of the environment, and not all
non-metallic dampers will stand up under the conditions of extreme
heat and cold to which they are liable to be exposed. In addition,
the through-wall unit, to be economically feasible in a large scale
production, must be adaptable to a variety of wall thicknesses.
Heretofore, no reliable non-metallic unit was considered
commercially feasible because the adjustability requirement for the
housing was believed to preclude mounting of the damper at any
point except near the outlet of the exhaust unit.
My invention permits use of a non-metallic back draft damper by
mounting the damper adjacent the unit impeller. A unique system of
back biasing the damper is provided which enables the damper to
close regardless of the thickness of the wall, hence the length of
the housing, thereby retaining the necessary adjustability features
provided by older systems. The damper mounting procedure is
simplified by utilizing a flanged opening at the unit impeller and
by designing the damper to seal about the flange.
One of the objects of this invention is to provide an exhaust unit
having a back draft damper mounted adjacent the impeller of the
blower.
Another object of this invention is to provide such a through-wall
exhaust unit having a non-metallic back draft damper.
Yet another object of this invention is to provide novel means for
back biasing a back draft damper.
Still another object of this invention is to provide a damper
characterized by silent operation.
Yet another object of this invention is to provide increased air
flow in an exhaust unit by utilizing louvers in the external side
of a through-wall exhaust system.
Other objects will be apparent to those skilled in the art in light
of the following description and accompanying drawings.
SUMMARY OF THE INVENTION
In accordance with this invention, generally stated, a through-wall
exhaust unit is provided having a non-metallic back draft damper
mounted adjacent the impeller of the blower. The damper is back
biased by a spring arrangement which prevents the damper from
locking itself in an open position.
In the preferred embodiment, the damper is mounted in a housing
which is adjustable to correspond to a variety of wall thicknesses.
The external portion of the housing is louvered to increase exhaust
fan (blower) output without requiring increased blower
capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, FIG. 1 is a view in perspective of one
illustrative embodiment of exhaust fan unit of this invention;
FIG. 2 is a view in front elevation of a self-contained fan-damper
assembly of the unit shown in FIG. 1;
FIG. 3 is a view in rear elevation taken along the line 3--3 of
FIG. 1;
FIG. 4 is a view in side elevation taken along the line 4--4 of
FIG. 3;
FIG. 5 is a top plan view of the assembly shown in FIGS. 2-4;
FIG. 6 is an enlarged plan view of a bumper unit utilized in
conjunction with the damper shown in its mounted position in FIG.
2;
FIG. 7 is a view in side elevation taken along the line 7--7 of
FIG. 6;
FIG. 8 is an enlarged view in side elevation of a spring utilized
to back bias the damper of FIG. 2; and
FIG. 9 is a view in side elevation taken along the line 9--9 of
FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, reference numeral 1 indicates one
illustrative embodiment of exhaust fan unit of this invention.
Exhaust fan unit 1 includes a blower 2 mounted in a frame 22 which
forms part of an enclosure 3. Also mounted in the frame 22 within
the enclosure 3 is a damper 4.
Blower 2 includes a motor 8. Motor 8 is conventional and includes a
stator assembly 5 having a plurality of windings 6 associated with
it in accordance with conventional motor design theory. In the
embodiment illustrated, the windings 6 are enclosed by a shroud 14.
Stator assembly 5 has an axial opening through it in which a rotor
assembly, not shown, is rotatably mounted. A rotor assembly
includes a shaft operatively connected to it, likewise not shown,
on one end of which is mounted an impeller 7. Motor 8 is attached
to a bracket 9. Bracket 9 is made of sheet metal, rectangular in
plan, U-shaped in side elevation, with integral mounting tabs 15 at
each end, and a central mounting portion 12. The bracket is blanked
out between the tabs 15 and the central mounting portion 12 and
turned up at the edges to form flanged rails 11. Portion 12 has a
square opening 16 in it, through which a cover attaching bolt 13 is
placed. Bolt 13, in the embodiment illustrated, is nothing more
than a conventional, flat headed bolt with a square shank. The
motor 8, when mounted to the bracket 9 locks the bolt 13 within the
opening 16.
Motor 8 is attached to the central portion 12 of bracket 9 by a
conventional nut-bolt combination 10.
Mounting tabs 15 have an opening 17 in them, through which
fasteners are run to attach the motor bracket to the enclosure 3.
In the particular embodiment illustrated, an annular vortex ring 18
is connected to the bracket by spotwelding or the like along the
tabs 15. Ring 18 has a transverse lower wall 19 and a vortex wall
20, tending axially with respect to the axis of rotation of the
fan. The purpose and function of ring 18 is described in detail
hereinafter.
Motor 8 is electrically connected to a cord 21 with two conductors
in it and a male plug connected to them.
In the embodiment illustrated, enclosure 3 comprises a motor
mounting frame 22, telescoping shell 23 and an external portion
24.
Motor mounting frame 22, in the embodiment illustrated, is
substantially square and has a top 25, a bottom 26, and side walls
27 and 28. Motor mounting frame 22 has a open back 29 and a front
wall 30. Front wall 30 has a circular opening 31 through it defined
by an annular flange 32 which projects outwardly with respect to
the motor 8 and is perpendicular to the front wall 30. When the
motor 8 is mounted within motor mounting frame 22, the wall 19 of
the ring 18 abuts the back of the front wall 30 while the wall 20
is adjacent but spaced from the annular flange 32. This arrangement
permits effective sealing of the unit to back drafts, as later
explained.
The front wall 30 has mounting means associated with it for
attaching the bracket 9 to it. Common screws through the opening 17
work well. A connection box 33, with a female socket mounted in it
to receive the male plug on the motor cord may be utilized to
connect the electrical connections 21 for the motor 8 to the
external source of power not shown. In FIG. 1, the connection box
33 is shown as mounted in the lower right hand corner, to show the
female socket. In FIG. 3, it is shown as mounted in the upper left
hand corner. The construction of the frame 22 permits mounting
either place. The top 25 and the bottom 26 have a pair of parallel
slits 34 in them. The slits 34 provide a portion of the adjustable
feature for the exhaust unit 1 as later explained in detail.
Referring now to FIGS. 2, 4 and 5, it is observed that a pair of
legs 35 extend perpendicularly to the front wall 30 from opposite
ends of the top 25. The legs 35 are parallel to one another and
aligned, and have laterally aligned openings defined by integrally
formed journals 48. In the embodiment of FIG. 4, a second pair of
legs extend from the wall 30 near the bottom 26. The legs near the
bottom 26 serve no function, but are shown because the top and
bottom are identical and are obtained in a single punching
operation. For the functioning of my invention, however, only one
pair of legs 35, or their equivalent, need be provided. While the
particular embodiment illustrated has the legs 35 formed integrally
with the top-bottom members of motor mounting section 22, those
skilled in the art will recognize that the legs 35 may be formed
from or with a front wall 30 or individually formed and later
attached to the section 22. The front wall 30 has a pair of
T-shaped openings 36 in it, along each side of the annular flange
32.
Damper assembly 4 comprises a damper 37 and a pair of mounting
springs 38. Damper 37 is constructed of a vibration absorbing,
synthetic material and includes a front 38, a side wall 39 and a
back 40. The side wall 39 extends about the perimeter of the damper
37 and is perpendicular to the front 37 and back 40, extending
rearwardly, toward the motor 8, from the back 40. Side wall 39 has
a pair of oppositely disposed, integral bosses 42 from which pivot
pins 41 project, on opposite sides of the damper. The pivot pins 41
are aligned on an axis along a top edge 43 of the side wall 39.
Spaced below the bosses 42, on both sides of the damper, spring
anchors 44 project from the side wall 39. They are aligned
transversely of the damper and are offset rearwardly with respect
to the axis of the pivot pins 41 when the damper is closed, as
shown in FIG. 4. Spring anchors 44 are formed integrally with the
wall 39. In the embodiment shown, they are cylindrical and have an
annular channel in them as may best be seen in FIG. 2.
Side wall 39 also has a spring stop 45 extending outwardly from it
on one side of the damper. Spring stop 45 is a cylindrical section
formed integrally with side wall 39.
Side wall 39 has a plurality of fastening bosses 46 formed
integrally with and extending outwardly from it. Fastening bosses
46, in the embodiment illustrated, are made up of facing angles
defining an inverted T-shaped channel. Fastening bosses 46 are
intended to receive a resilient stop 47, described in detail
hereinafter.
The pivot pins 41 are rotatably mounted in the pair of fixed
journals 48 formed in each leg 35. Placement of pivot pins 41
within journals 48 pivotally mounts damper 37 at the opening 31.
The side 39 is adapted closely but freely to surround annular
flange 32 while resilient stops 47 are sized to abut front wall 30
in the closed position of the damper 37 illustrated in FIG. 4.
Spring 38 is a broad band, serpentine design, best illustrated in
FIGS. 8, 2 and 4. As can be seen by comparing those Figures, the
spring is inverted in FIG. 8, with respect to its orientation in
use. Spring 38 has a free outer end 49, an attaching crook 51, a
compression loop 50, and an inner mounted end 52. The end 52, in
the embodiment illustrated, has notches 53 in it to define a
T-shaped end. As is best illustrated in FIGS. 2 and 4, one spring
38 is frictionally mounted to each spring anchor 44 by snapping the
attaching crook 51 over it. The spring 38 on the side of the damper
from which the spring stop 45 projects is so positioned that the
end 49 abuts spring stop 45 when the damper is opened. This
abutment is important in the operation of the damper, as is
explained in detail hereinafter. Although only one spring stop 45
is illustrated in the drawings, those skilled in the art will
recognize that two can be provided and both of the springs will be
so positioned.
The inner end 52 of each spring is inserted in the opening 36
against the bias of the spring, and the notches 53 permit the end
to go into the stem of the T, with the cross of the T of the end 52
behind the front wall 30. The downward bias of the spring keeps it
in place.
Resilient stop 47 is thin and flat, and dart shaped in plan, as
best illustrated in FIGS. 6 and 7. As there shown, stop 47 has a
wedge-shaped blunt end 54 and a base 55 joined by a reduced part
56. The part 56 is caged within the channel of the fastening bosses
46. End 54 strikes the front wall 30 when the damper is closed.
Telescoping shell 23 is square in front elevation and includes a
top 57, a side wall 58 and 59, and a bottom 60. Top 57 and bottom
60 have a pair of openings 61 for receiving conventional metal
screws 62. The openings 61 are positioned so as to align with the
slits 34 of the motor mounting frame 22. The opening defined by the
walls of the telescoping shell 23 is large enough to permit
insertion of motor mounting frame 22.
External portion 24 includes a rectangular frame 63, a flange part
64 and a pyramidal section 65.
Rectangular frame 63 has four walls, a top 66, sides 67 and 68 and
a bottom 69. Top 66 and bottom 67 have a pair of slits 70 in them.
The slits 70 are parallel and designed to align with at least a
pair of openings 61 in top 57 and bottom 60 of telescoping shell
23.
Flange 64 extends outwardly about the perimeter of the frame 63 and
may be formed integrally with either frame 63 or section 65, or may
be constructed separately and attached to either part. In the
embodiment illustrated, the flange 64 is formed integrally with the
section 65 and the frame 63 is flared along an end 70 for
attachment therewith. Section 65 includes a front wall 71 and a
first and a second side 72 and 73 respectively. The sides 72 and 73
have a plurality of louvers 74 lanced in them. The pyramidal
section 65 is open bottomed.
As thus described, enclosure 3 comprises three sheet metal units
which may be varied in length to correspond to a plurality of wall
thicknesses. That is, motor mounting frame 22, telescoping shell
23, and external portion 24 are telescopically mounted to one
another and may be adjusted for a variety of wall thicknesses
ranging, in the embodiment illustrated, between four and ten
inches. The various parts are adjusted along the slots 34 and slots
70 by loosening the middle screws 61 and 75 along both the upper
and lower portions of the enclosure 3. Once installed, the flange
64 abuts the external wall covering and the pyramidal section 65
extends outwardly therefrom. Motor mounting frame 22 is positioned
so that the back 29 opens within the building. Back 29 may be
closed by a decorative grill which also serves as an inlet to the
blower 2. The outlet of the blower 2 is the opening 31 in the front
wall 30 of motor mounting section 22. As previously indicated, it
is at that location that the damper 37 is mounted. The damper 37
will always be so mounted regardless of the position of the frame
and housing elements of the enclosure 3.
In operation, air is forced against damper 37 by the impeller 7
which causes the damper 37 to swing out, around the axis of the
pins 41. As the damper 37 opens, the spring anchor 44 swings
outwardly with respect to the plane of the pivot pins 41 and the
springs 38 would tend to exert a force to hold the damper open were
it not for the abutment of the spring stop 45 and the end 49 of the
spring. The damper is prevented from being biased open permanently
under the influence of the springs by the restraining action of end
49 of the spring. The end 49 and stop 45 not only prevent the
damper and spring from over-centering completely but resiliently
bias the damper toward closing when the fan is turned off. Thus,
the spring keeps the damper firmly closed when the fan is off, and
tends to counter balance the damper to permit it to be and remain
opened wide by the fan, the amount of opening being regulated by
the end 49. The resilient stops 47 cushion the closing of damper 37
as the fan is turned off.
The construction thus described provides a highly versatile unit.
The placement of the damper adjacent the impeller permits the use
of non-metallic damper material, thereby permitting extremely quiet
damper operation. Removal of the damper from attachment with
external unit 24, permits use of the louvers 74 in the sides 72.
Dampers in the prior art generally were arranged to close the open
bottom of the pyramidal section 65. Louvers in the sides of the
section 65 were then impractical because their use defeated the
purpose of the damper. With the placement of the damper as
described above, louvers can in fact be used. Such use greatly
increases the efficiency of the blower 2 by relieving pressure on
the impeller 7.
Numerous variations, within the scope of the appended claims, will
be apparent to those skilled in the art in light of the foregoing
description and accompanying drawings. Thus, various parts
described as integrally constructed may be constructed separately
and later attached. The shape of the enclosure 3 may be varied.
Thus, while I find it convenient to utilize three elements for the
enclosure 3, other element combinations may be used. External
portion 24 may be altered. While I find the use of louvers 74
extremely effective, other embodiments of my invention may
eliminate them, alter their size or shape or change their
positioning. Other forms of resilient stops 47 may be used in place
of stops shown or in conjunction with them. For example,
conventional felt padding may be utilized along the interior
portion of side wall 39 and back 40 of damper 37 in place of or in
conjunction with the resilient stops 47 illustrated in the drawings
and described above. I prefer the use of the stops 47 because of
the difficulties in placing and maintaining the position of the
felt and the hazards inherent in the use of felt. The design and
configuration of the springs 38 may be varied. These variations are
merely illustrative.
* * * * *