An air damper having a housing, a strut mounted across the housing, a pair of damper panels hinged on the strut, and swingable between open and closed positions, an adjustable control above the strut, and, linkage on the upper side of each panel extending to the control to cause the panels to swing from one position to the other.

The invention relates to an air supply damper for location at an air 
outlet, and incorporating damper adjustment controls, and optionally 
incorporating heat sensitive means for closing the damper. 
BACKGROUND OF THE INVENTION 
Air supply outlets such as are used for distributing fresh air in an air 
circulating system, usually incorporates some form of damper for 
controlling the flow of air through the outlet. Such air outlets may be of 
various shapes. When the air outlet is located in the ceiling, 
particularly of domestic, or office space or commercial space, or the 
like, a circular form of air distribution outlet is particularly 
preferred. This form of outlet is usually connected by means of a duct 
system of generally circular cross section. 
The design of a damper for use in a connection with such circular duct and 
circular outlet, presents certain problems. It must be adaptable to 
progressively open and close the circular opening, and at the same time it 
must be accessible from the building space beneath the air outlet and 
ceiling itself. 
One form of such a damper which is particularly suitable for the purpose is 
shown in U.S. Pat. No. 3,592,240. That patent discloses a damper having 
two generally semi-circular panels, which are hinged to swing upwardly and 
downwardly about a central strut. 
A worm and linkage, is mounted below the strut, and connects between the 
strut and the hinged panels. 
A suitable tool such as a screwdriver or the like may be inserted to rotate 
the worm and thus adjust the two panels upwardly and downwardly. 
This device works effectively and has proved to be popular and 
satisfactory. 
There are however certain disadvantages with this system. Fire insurance 
and building code regulations are requiring much higher standards of 
resistance to heat and fire, particularly in the construction of ceilings 
in such buildings. A principle area of weakness in such ceilings occurs at 
each air outlet. The ceiling itself may be constructed of panels which are 
substantially fireproof or are at least heat resistant for a sufficient 
length of time to meet the regulations. However, each air outlet 
constitutes a relatively substantial opening through such ceiling. These 
openings provide an easy passage way for heat and possible flames, through 
the ceiling. Thus although the ceiling fabric itself may have the 
necessary fire rating which substantially negates the effectiveness of the 
ceiling in a fire situation. 
Thus in buildings where the construction code or regulations call for a 
fire rated ceiling, it is highly desirable to provide some form of 
automatic fire damper in the ducts immediately above each air outlet. Such 
fire dampers are sensitive to heat and will close automatically in 
response to a pre-determined temperature. 
Fire dampers of rectangular design are well known in the art. Essentially, 
all that is required is simply to place a fire damper in the duct above 
the air outlet and control damper of the type shown in the U.S. Patent 
referred to above. 
In practice however this greatly increases the cost of construction. In 
addition, the installation time required is much greater than the time 
required for installation merely of the outlet and control damper itself. 
A further problem is that the location of a fire damper of conventional 
construction on top of such an air outlet and a control damper, creates an 
excessive height above the ceiling. This may in fact interfere with the 
dead space between the ceiling, and the floor slab of the floor next above 
in the building. 
Most of the existing fire dampers incorporates some form of heat fusible 
link, and one or more blades which is spring loaded, and is held open by 
means of such a link. When the link becomes heated, it melts and releases 
the blades. The blades then snap closed, thereby closing off the duct. 
It might at first appear feasible to modify the damper shown in U.S. Pat. 
No. 3,592,240 to include a spring and a fusible link. 
However, in practice it is found that this will not be satisfactory. The 
location of the worm, and operating linkage on the strut below the level 
of the panels, causes obstruction on the underside of the panels. The 
inclusion of some form of heat fusible member in such linkage will 
therefore present serious difficulties. The linkage will tend to obstruct 
the closure of the panels, in response to a fire situation. 
Nevertheless, it is readily apparent that if the control damper can also be 
used as a fire damper, there would be substantial economies achieved in 
the cost of materials and also even greater economies is the cost of 
installation. In addition, the problems of obstructing the dead space 
between the ceiling and the floor slab will also be eliminated. 
On the other hand, in providing such a multi-mode damper, it is essential 
to avoid increasing the cost to the point where when it is used merely as 
a control damper it has a cost greater than prior art control dampers. 
It is therefore desirable to provide a control damper, which may be used as 
a fire damper, where building regulations have this requirement, and which 
may be used as a control damper, where this requirement is not present. 
BRIEF SUMMARY OF THE INVENTION 
The invention seeks to overcome the forgoing disadvantages, by the 
provision of an air control damper for use in association with an air 
outlet, having an opening of predetermined dimensions, and comprising a 
strut member adapted to be mounted in a generally transverse manner across 
the center of such opening, a pair of damper panels hingedly mounted on 
said strut, and swingable between upright open positions, and generally 
horizontal closed positions, adjustable movement means mounted above said 
strut, and operable by means of a tool, opening means in said strut for 
access of such tool therethrough, whereby said movement means may be 
operated from beneath the said opening, linkage means on the upper side of 
each said panel extending from said panels to said movement means may 
cause said panels to swing from one position to the other. 
More particularly, the invention seeks to provide such a control damper 
wherein the linkage means incorporate at least one link for each said 
panel, such link being formed of heat fusible metal, and spring means for 
each such panel urging same to swing into its generally horizontal closed 
position, upon melting of said link. 
More particularly, it is an objective of the invention to provide such a 
control damper, including thermal barrier means bonded to the upper 
surfaces of each said panel, whereby to resist transfer of heat 
therethrough and prolong the fire rating. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the invention 
.

DESCRIPTION OF A SPECIFIC EMBODIMENT 
As best shown in FIG. 1, a typical ceiling is shown which comprises a 
rectangular frame work of grid of ceiling Tees, suspended from the 
concrete floor slab, or roof structure of a building. Such ceiling Tees 
are shown generally as 10, and are well known in the art. Typically, 
accoustic panels 12 are layed on the ceiling Tees, to provide the 
completed ceiling fabric. 
It will of course be appreciated however, that the invention is not limited 
to such a tile ceiling. Many other forms of ceiling structure are 
available some of which are simply strips of coated sheet metal. Ceilings 
may also be formed of plaster wall board, or plaster material in a wide 
variety of different ways and finishes. The invention is not restricted to 
any particular form of ceiling. 
In order to provide air distribution throughout the building space, air 
outlets are usually provided in the ceiling at regular intervals. Such air 
outlets are shown generally as 14. Air outlets may take a number of 
different forms. In this invention, the air outlets are shown in the form 
of circular openings in the ceiling which are provided with circular air 
distributor blades 16. The blades are adjustable up and down, so as to 
vary the air distribution pattern in the building space. 
In order to equalize air distribution at all of the air flow outlets, it is 
the practise to provide an air flow damper in the ductwork above the 
opening. The damper must be capable of being adjusted from beneath the 
ceiling, by a maintenance man, or by persons occupying the space, so that 
they may insure their own personal comfort. In this form of air 
distribution system, the air ducts in the space above the ceiling are 
usually flexible cylindrical tubular members. Accordingly. it is desirable 
that the dampers shall also be of a generally cylindrical design. 
One form of a damper which has proved to be satisfactory in the past in 
this type of situation is shown in U.S. Pat. No. 3,592,240. 
For the purposes of describing FIG. 1, it will thus be seen that the air 
distributor 14 which is mounted in the ceiling itself is connected to an 
air damper shown generally as 20 which is located immediately above it, 
and this in turn is connected to a flexible air duct 22, which connects 
with the air distribution system provided in the building. Such air 
distribution system and duct form no part of this invention and are 
accordingly not described herein. They are in any event subject to wide 
variation and are well known in the art. 
Referring now to FIGS. 2 to 6, the damper 20 according to the invention 
will be seen to comprise a generally cylindrical housing 24, which in this 
embodiment is formed in two halves, each half having an annular lip 26. 
Between the two annular lips 26, an annular sealing ring 28 is fitted, 
which extends inwardly into the interior of the housing 24. 
Housing 24 defines an upstream end 24a and a downstream end 24b, and air 
flows, namely, from 24a to 24b. 
Spanning the diameter of the interior of housing 24 is a cross member or 
strut 30, which is attached at either end by means of brackets 32 to the 
interior of housing 24. 
Two generally semi-circular damper panels 34--34 are hinged by hinge 
tongues 36, to the sides of member 30. Springs 38 engaging between 
channels 30 and panels 34 urge panels 34 into a normally horizontal closed 
position, in which they contact ring 28. 
In this way, panels 34--34 can completely close off housing 24. 
This will therefore obstruct all air flow from the duct to the air outlet 
14. 
In order to regulate and control the air flow, provision is made for the 
adjustable movement of panels 34 so that they may be positioned at any 
angular position between their upstream open position and their transverse 
closed position. 
Such adjustment means will be seen best in FIG. 4 and comprises an 
elongated worm gear 40, mounted centrally on the upper side of cross 
member 30, and supported at its lower end on such cross member. The upper 
end of the worm 40 is mounted in a hat shaped bracket 42, which is 
fastened to the cross member 30 on either side of the worm 40, and 
provides a further journal 44 for the upper end of the worm 40. 
The worm 40 has a central opening 40a for receiving a tool 46. The central 
opening will have some form of key way (not shown) by means of which 
torque from the tool can be transmitted to the worm. 
A tool opening 45 is also provided through member 30, to permit the tool to 
be inserted from below, through passage 47, in air distributor 14. 
A plate member 48 has a central opening 50, which fits around the worm. The 
opening 50 is formed in such a way that it engages the threads of the 
worm. The plate member is dimensioned so that its side edges ride inside 
the hat shaped bracket. Thus when the worm is rotated, the plate member is 
driven either up or down the worm, and its held against rotation by means 
of the hat shaped bracket. 
On either side of the plate member 48, a connecting bracket 52 extends 
outwardly with respect to the hat-shaped bracket, and is bent upwardly 
generally perpendicular to the plate. 
Each of the brackets 52 is pivotally connected to a connecting link 54. 
Each link 54 is in turn connected by means of an attachment bracket 56 to 
respective panels 34, also in a pivotal manner. 
Each of the panels is thus operated and controlled by means of the worm and 
plate member. As the worm is rotated to force the plate member upwardly 
the panels will swing upwardly thereby opening the damper. As the worm is 
rotated in the opposite direction the plate member will move downwardly 
thereby swinging the panel down in to their closed position. 
By suitably adjusting the worm, the air flow through the damper can be 
balanced with respect to other dampers and air outlets in any building 
space. 
Where this is the only action or function that is required of the damper, 
then the links 54 may simply be one piece members stamped out of sheet 
metal such as steel. 
In this case, the damper will simply function as a damper, and will not 
function as a fire damper in an emergency. 
However, where it is desired to provide an emergency fire damper mode of 
opertion, then the links 54 may be replaced by heat fusible link members 
60 (FIG. 5). Links 60 are well-known for use in other applications, such 
as the operation of emergency fire extinguishers and the like. They are of 
a variety of different designs. Typically, there will be two link portions 
62, bonded by fusible metal typically of some low temperature melting 
alloy such as white metal or the like. 
When subjected to a predetermined elevated temperature such as might arise 
in an emergency, the fusible metal melts, allowing the two link portions 
to separate. 
Where this action takes place in the present invention, the springs 38 will 
then immediately urge the panels 34 to swing into their closed position 
thereby shutting off the damper. 
It will clearly be seen that movement of the two panels, under the 
influence of such springs, causes the two link portions of the two fusible 
links, to fly apart, and the two panels are free to close without 
obstruction by the link members or any other associated mechanism. 
This advantage is a result of locating the worm, and plate and bracket 
above the cross-member 30, and is the result of locating the entire 
operating linkage for the panels on the upstream side of the panels. 
It will thus be seen that by the use of the invention a multi mode damper 
is provided, in which in one mode a simple air control damper function is 
provided, and in the other mode, an air control damper and fire damper 
mode of operation is provided. The change over from one mode of operation 
to the other is achieved merely by substituting one form of link for the 
other without in any way changing any of the tooling or any of the other 
parts required. 
Where an extended fire rating is desired, a thermal barrier panel 66 may be 
loosely attached to panels 34--34 as shown in FIG. 2. 
The panel 66 is of flexible heat resistant felt-like material. It fits 
loosely over the panels 34, and also the cross member 30 and operating 
mechanism 50. It will be flexible enough to permit normal operation of the 
panels 34 for adjustment, and will not impede emergency closure as 
described. 
In this way a fully flexible design is provided, having a broad sales 
appeal in a variety of different functions. 
The foregoing is a description of a preferred embodiment of the invention 
which is given here by ways of example only. The invention is not to be 
taken as limited to any of the specific features as described, but 
comprehends all such variations thereof as come within the scope of the 
appended claims.