Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to fluid
dampers, and particularly to aix dampers used in building
ventilation systems.
Building air distribution systems require stable and
accurately controllable air valve or air dampers for
control of building heating and air circulation
functions. For maxlmum e-fficiency, large numbers of such
air dampers are usually computer controlled
simultaneously in order to provided the proper heat and
air distribution within the building. Air dampers have
been disclosed having longitudinal blades provided with
sealing gaskets with the blades arranged in a venetian
blind arrangement. Such systems are prone to leakage due
to alignment problems which can arise over time. Other
damper systems employ linkage assemblies having
relatively slow response times.
Yet other systems employ piston driven damper plates
utilizing a pair of guide pins which slide in an open
ended slot and a guide pin slidably mounted in a closed
longitudinal guideway wherein in the fully closed
position pins are located at the closed ends of the
guideway and slot. Systems of this type are disclosed in
U.S. paten~ No. 4,605,198 issued August 12, 1986 to Seal-
Air Control Systems Inc. A drawback to this kind of
arrangement is that backlash problems developing in the
damper plate opening and closing mechanism over time will
cause the seal formed by the damper plate compressed
against a gasket to degrade resulting in leakage. When
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this damper is opened, the guide pins move
translationally along the slots thereby translationally
displacing the damper plate until the pin in the open
ended slot pivots around the pin located at the end
portion of the closed guideway whereupon the damper plate
rotates from a vertical to a substantially horizontal
position. A drawbaclc to this type of movement i.s that it
is very difficult to reproducibly control the motion of
the damper plate as it rotates open. Furthermore, it is
very difficult to control the position of the damper
plate in order to modulate the flow of air through the
duct when the plate is not in the fully open or fully
closed position. In other words, with ~his arrangement,
there is not a desired linear relationship between the
amount of piston movement and the ~mount of air flow
through the system.
According to one aspect of the invention, there is
I provided a fluid damper for controlling fluid flow. The
damper comprises a frame member having an opening for
fluid flow therethrough when the damper is open. A
closure member is movable between a closed position where
the opening is blocked and an open position where the
opening is unblocked. An actuator mechanism for
controlling the movement of the closure member includes
a pair of spaced guide members which are rigidly fixed to
the frame member. The guide members are each provided
with upper and lower arcuate guide slots with the upper
guide slots in the two plates being in registratior. ~nd
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the lower slots being in registration. The actuator
mechanism includes a bracket having a first registration
means mounted in the bracket wherein the first
registration means is movably captive within the upper
guide slots. A second registration means is mounted in
-the bracket and is movably captive within the lower guide
slots. The closure men~er is secured to the bracket and
a bracket moving mechanism is attached to the bracket for
moving the bracket between a firs~ position coxresponding
to the closure member in the closed position and a second
position corresponding to the closure member being in the
open position. Movement of the first and second
registration means through the diverging guide slots
causes the bracket to rotate with respect to the guide
members thereby rotationally moving the closure member
with respect to the frame member.
According to another aspect of the invention, there
is provided a damper apparatus for an air input opening
of an air distribution system comprising a closure member
having a perimeter portion seatable on the edge of said
input opening; means for controlling movement of said
closure member, said control means including a pair of
spaced guide members each provided with first and second
arcuate guide slots the paths of which diverge from one
end thereof to the opposite end thereof, means for
supporting said closure member connected to said closure
member, first and second follower means mounted in or on
said supporting means and each provided with followers
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that are movably captive within the first and second
guide slots respectively; and power means for moving said
supporting means with respect to said guide members so as
to move said closure member between closed and open
portions; wherein during use of the apparatus, movement
of said follower~ along said guide slots from positions
corresponding to the closed position of the closure
member to the open positlon of the closure member causes
said supporting means and closure member to commence and
undergo rotation with respect to the guide members as
said closure member is moved away from said input
opening.
In a preferred aspect of the inventlon, the
diverging portion of the arcuate gulde slots is such thak
at a first intermediate position between the closure
member open and closed positions, one registration means
or follower means reverses direction and at a second
intermediate position the other registration means or
follower means reverses direction.
The invention will now be described, by way of
example only, with reference to the accompanyin~
drawings, in which: ~
Figure 1 is a perspective view partly broken away
of a fluid damper of the subject invention mounted in an
a fluid duct and in the ~ully closed position;
Figure 2 is a sectional side view of a fluid damper
in the fully closed position;
Figure 3 is a sectional side view partly broken
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away showing -the fluid damper in partially open
positions; and
Figure 4 is a schematic side view of a part of the
driver mechanism of a fluid damper of the present
invention showing the relative positioning of various
parts of the driver mechanism during the opening and
closing motions of the damper.
Referring to ~igures 1 and 2, an air damper 10 is
shown mounted within an air duct 12 boundad by walls 14
for controlling air flow therethroughO Fitted in the
duct is a rectangular panel 20 with a central circular
opening 21. The panel 20 is provided with edge flanges
18 for attachment of the panel to the walls 14 by welding
or the use of bolts (not shown). Mounted on or secured
to the circular edge of panel 20 is a gasket 24. A
support frame 26 extends horlzontally across the opening
21 and between the opposi~e vertical walls 14 of duct 12
at a point lower than the vertical midpoint thereof. The
frame 26 can be connected to the panel 20 by means oE
bolts (not shown).
Damper 10 includes a circular closure member or
damper plate 28 which is in the shape of a shallow bowl
- or dish and which has substantially central flat planar
portion 30. Preferably it has a rolled circumferential
edge 31 for increased strength and rigidity. In the
closed position damper plate 28 is vertically disposed
within duct 12 with the peripheral edge of plate 28 in
contact with gasket 24 thereby ~orming an annular seal,
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as represented by the solid lines in Figure 2. Damper 10
also includes a damper plate actuator mechanism shown
generally at 32 for controlling the movement of damper
plate 28. Damper 10 includes a pair of spaced mounting
frame members 34 secured to support frame 26 on which
actuator mechanism 32 is mounted for mounting damper
plate 28 in air duct 12.
Actuator mechanism 32 is provided with a pneumatic
cylinder 36 pivotally mounted on a pivot rod 38 extending
between and secured to frame members 34. The plvotal
connection of cylinder 36 to pivot rod 38 is accomplished
using a bushing 40 mounted within a bracket 42 which in
turn is rigidly attached to the back end of cylinder 36.
Pneumatic cylinder 36 is provided with a shaft 44
attached to the front end thereof which is held firmly in
a colinear relation with cylinder 36 while being
reciprocally movable within cylinder 36.
Referring now to Figures 2-4, actuator mechanism 32
includes a pair of opposed and spaced outer vertical
guide plates or guide members 46 and 48 each rigidly
secured to one of mounting frame members 34 by bolts 50
at a position forward of cylinder 36. Guide plates 46
and 48 are each provided with a pair of downwardly
arcuate or curvilinear guide slots 52 and 54 which are
: 25 preferably closed at each end. The first slots 52 are
located above second slots 54 ln members 46 and 48, in
- addition first and second slots 52 and 54 are of
different lengths with slot 52 being lon~er than slot 54.
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Slots 52 in guide plates 46 and 48 are in registration,
being horizontally matched. Similarly, the second slots
54 in plates 46 and 48 are in registration. Slots 52
have a back end 56 and a front end 58 whtle slots 54 have
a back end 60 and a front end 62. Preferably, the slots
52 and 54 are of uniform width along substantially their
entire length. Slots 52 and 54 are each provided with
horizontally parallel portions 64 and 66 located adjacent
the back end portions 56 and 60 respectively
(substantially in the range between positions A-B in
Figure 4? while slots 52 and 54 diverge relative to one
another in the forward direction- towards the closure
member beyond portions 64 and 66.
Actuator mechanism 32 also includes a rectangular
U-shaped mounting bracket 68 having side walls 70 and 72
and an end plate 74. This bracket 68 constitutes means
for supporting the closure member 28. A pair of spaced
and parallel guide pins 76 and 78 are mounted
horizontally through walls 70 and 72 and project
laterally through slots 52 and 54 respectively and being
of a diameter smaller than the width of the slots so that
they slide within the slots. These guide pins constitute
first and second follower means mounted in or on the
bracket 68. A connector bar 80 extends between walls 70
and 72 and is securely mounted therein. The end of
cylinder shaft 44 is rigidly attached to connector bar
80. End plate 74 is rigidly coupled to the planar
portion 30 of damper plate 28 by a plurality of bolts 82.
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Al~ernatively, end plate 74 and damper plate 28 may be
coupled using other means such as welding or gluing,
depending on the material of construction.
The operation of damper 10 will now be described
with reference to Figures 2-4. The relative positions o~
pins or followers 76 and 78 in guide slots 52 and 54
respectively as cylinder 36 urges bracket 68 forwards and
backwards is illustrated in Figure 4 wherein the
corresponding positions of damper plate 28 are
illustrated. In the closed position, represented by the
solid lines in Figure 2, cylinder 36 and shaft 44 are
angled upwardly from the horizontal while plate 28 is
: sealingly engaged with gasket 24. In the closed position
guide pins 76 and 78 are at the rearmost limit of travel
in slots 52 and 54 and are spaced from the back end of
the respective slots. As cylinder 36 urges the bracket
; or support means 68 forwàrd, the motion of pins 76 and 78
through the horizontally parallel portions of the slots
in the range from A to B results in plate 28 being
ini~ially displaced away from plate 20 as indicated by
the ghost markings in Figure 2. Since slots 52 and 54
begin diverging in the latter portion of the region
: between A and B, guide pin 78 begins dropping relative to
pin 76. Since pins 76 and 78 are rigidly mounted through
walls 70 and 72, the centre-to-centre (cc) distance
. between pins 76 and 78 remains constant. Onc~ pin 78
starts dropping with respect to pin 76, bracket 68 and
hence damper plate 28 begin rotating upwards. Therefore,
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as cylinder 36 urges bracket 68 forward the end of
bracket 68 closest to cylinder 36 begins dropping and
plate 28 undergoes both translational displacement
forward and rotational motion counterclockwise as shown.
The various positions of plate 28 are shown in Figure 4
marked A', B' ... to the fully open position marked G',
with these positions correspondin~ to the positions of
the pins or followers marked with the same letters. A5
back end of bracket 68 drops relative to the front end
thereof, piston shaft 44 is pulled down causing cylinder
36 to pivot downwards about pivot rod 38. Both pins 76
and 78 undergo forward motion in the respective slots
until point E is reached. Beyond points E, the distance
between the centre lines of slots 52 and 54 is greater
than the centre-to-centre separation between plns 64 and
66 with the result that both pins can no longer undergo
- forward motion simuItaneously. Consequently, pin 76 in
slot 52 is forced to reverse direction with further
forward urging of bracket 68 and undergoes retrograde or
reverse motion in slot 52. As this occurs, the pin 78
contlnues to move forward and downwards in slot 54 to
point F at whlch time pin 76 has reached point F in slot
52. Once pin 78 reaches point F it reverses direction
and undergoes retrograde motion backwards in slot 54.
When pins 76 and 78 reach positions G in their reSpective
slots they stop moving since shaft 44 has reached the end
of its forward stroke and damper 1~ is in the fully open
position, see Figure 3. When damper plate 28 is in the
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fully open position, cylinder 36 is approximately
horizon~al.
The closing of damper 10 will retrace the opening
procedure, where now pins 76 and 78 begln moving ln the
S forward direction from points G in the slots until pin 78
reaches point F whereupon it reverses direction in slot
54. Pin 76 continues moving Eorward until lt reaches
point F whereupon it reverses direction in slot 52. Both
pins are then pulled backwards towards points A in the
respective slots. Cylinder 36 pivots upwards about rod
38 until the pins reach the horizontally parallel
portions of the respective slots. At this point plate 28
is translationally displaced backwards whereupon ths
peripheral edge of plate 28 is compressed against gasket
lS 24 thereby sealing damper in the closed position. Due to
the fact that in the closed position of the damper pins
76 and 78 are spaced from the front ends of slots 52 and
54, plate 28 will always be compressed against gasket 24
with the same force thereby forming a positive seal.
This circumvents the problem of a seal developin~ leakage
over time due to backlash which may arise when the guide
pins are designed to be positioned adjacent the slot ends
in the closed position.
It will be appreciated that the rate of divergence
- 25 of slots 52 and 54 determines the length of the piston
stroke required to move damper plate 28 from the open to
the closed position. Specifically, the greater the
divergence of the slots in the forward direction, the
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shorter the piston stroke re~uired to move the closure
member between the two extremes. Since the slots
diverge, the pin located in the slot with the steepest
slope will move more rapidly than the other pin thereby
producing a more rapid opening and closing time than
would be obtained for linear slots with the same piston
speed.
It will also be understood that while ~uide slots
52 and 54 are arcuate downwards as disclosed above, they
may be arcuate upwards as well. In this case damper
plate 28 would be rotated clockwise downwards as viewed
in Figure 2. In addition, the direction of divergence of
guide slots 52 and 54 could be reversed and the piston
stroke reversed where again the guide slots may be
arcuate upwards or downwards as desired.
WhiIe the invention as disclosed employs guide
slots which diverge at such a rate that both guide pins
reverse direction between the damper open and closed
position, lt will be understood by those skilled in the
art that the slots could be designed to diverge at such
a rate that only one of the pin~ undergoes retrograde
motion between the open and closed position.
Since the rotational motion of plate 28 occurs for
most of the motion of pins 76 and 78 in the arcuate
slots, it will be apparent that reproducible and stable
control of damper plate 28 in intermediate positions
between the fully open and fully closed position is
achieved. In other words, a damper constructed in
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accordance with the invention is very linear in its
control, that is, for a certain percentage of piston
shaft 44 movement, there is a corresponding percentage oF
total air flow allowed through the circular input opening
21. For example, a movement by the shaft 44 of one third
of its total stroke from the fully retracted position can
be made to produce an air flow of about one third the
total available air flow.
While the present invention has been described and
illustrated with respect to the preferred embodiment, it
will be appreciated that numerous variations of these
embodiments may be made without departing from the scope
of the invention, which is defined in the appended
claims. For example, a reversing relay can be introduced
between the cylinder 36 and the mounting bracket 68. The
closure member 28 is then in the open position when the
piston shaft 44 of the cylinder is fully retracted. The
closure member 28 then starts to close as the shaft 44 is
extended.
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