Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~ his invention relates to shut-o~f damper~, that is to
say, dampers which are used to allow the flow of air through
a duct or, in their closed position, to shut off o~ stop that
flow completely. More specifically, the in~ention relates to
shut-o~f dampers of the kind comprieing a li~e o~ blade~ which
can be swung about parallel æes to open or close an opening in
a frame supporting the blades, the frame being adapted to be
mounted in an air duct. ~he~low of air through the frame can
thus be varied by varying the angle through which the blades
æ e rotated. -
In some shut-off damper~ of this general con~truction,
the blades are linked together in such a way that they all move
in uni~on with eaoh other and alway~ in the same direction or
~en~e as ea¢h other. In other shut-of~ dampers, the linkage
between the blades is such that pairs of blades ~o~e towards and
;l awa~ from each other as the blades are rotated about their respec-
tive a~e30 In other word~, adjacent blades move in opposite
senses or direction~ to each other. ~he effect however in both
forms of damper i9 the same, namely, that swinging movement of
the blades about their axes moves them either towards their
closed position or towards their open po~ition.
~ he presen~ invention i9 primarily concerned with a
shut-o~ damper of the second type mentioned above, iOe., it has
pair~ of blades which mo~e towards and away from each other. It
is to be understood, howe~er, that the i~ention can also be
applied to the fir t ~orm of construction in which the blades
move always in the same direction .~nd sense as each other.
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From one aspect, the present invention is directed to
a shut-off damper comprising a hollow metal frame defining an
opening for the passage of fluid therethrough9 a line of hollow,
sheet-steel, aerofoil-section, open-ended blades arranged in
said opening of said frame with each blade having a leading edge
and a trailing edge, a plurality of blade bearing components,
one at each end of each blade, to support the blades on said
frame for rotation about parallel axes extending longitudinally
of the blades, said blades being swingable about said axes to
open and close the said opening in the frame, a shaft on each
blade bearing component and a respective aperture in said frame
to rotatably receive said shaft, an intermediate flange on each
blade bearing comp~nent, a surface on said ~lange opposing the
adjacent open end of the respective blade, a spigot projecting
from said flange ~urface and shaped in cross-3ection to enter
the ~aid adjacent open end of the blade and to support that end
of the blade for rotation about the longi-tudinal axes of the
blade, a pair of spaced~art flange-like ridges projecting from
said flange surface of said blade bearing component to snugly
receive the extreme end-portion of the blade between them9 the
ridges being in sealing contact with said extreme end portion to
give additional support to the blade end and to provide a seal
at the blade end, a plurality of ro-tary elements, one for each
blade, keyed onto the blade bearing components at one side of
said frame ~or the purpose of ef~ecting swinging movement of the
blades about their parallel axe~, the said rotary elementæ being
rotatable in unison to cause corresponding swinging movement of
the blades between their fully-open and fully-closed positions,
and fludid sealing means extending along the tralling edge of
each blade whereby a seal is formed between adjacent blades when
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the blades are in their closed positions, said trailing edge
sealing means comprising a compressible sealing member faætened
. to the trailing edge of the respective blade, there also being
additional fluid sealing means interposed between the flange on
` each blade bearing component and the said frame.
From another aspect9 the invention is also directed
to a shut-off damper comprising a hollow metal frame defining
an opening for the passage of fluid therethrough, a line of
hollow, sheet-steel, aerofoil-section, open-ended blades
arranged in said opening of said frame with each blade having
a leading edge and a trailing edge, a plurality of` blade bear-
ing components, one at each end of each blade, to support the
blades on said frames for rotation about parallel axes extend-
; i.ng longitudinally to the blades, said blades being swingable
about ~aid axes to open and close the said openlng in the
frame, a sha~t on each blade bearlng component and a respective
aperture in said frame to rotatably receive said shaft, an
: intermediate flange on each blade bearing component, a surface
on said flange opposing the adjacent open end of the respective
blade, a pair of spaced-apart flange-like ridges projecting .
from said flange surface of said blade bearing component to
snugly receive the extreme end-portion of the blade between :.
them, the ridges being in sealing contact with said extreme
end-portion to provide a seal at -the blade end, a plurality of
rotary elements, one for each blade, keyed onto the blade bear-
ing components at one side of said frame for the purpose of
effecting swinging movement of the blades about their parallel
axe~, the said rotary elements being rotatable in unison to
cause corresponding swinging movement of the blades between their
fully-open and fully-closed positions, and fluid sealing means
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extending along the trailing edge of each blade whereby a seal
is formed between adjacent blades when the blades are in their
closed positions, said trailing edge sealing means comprising a
compressible sealing member fastened to the trailing edge of
the respective blade, there also being additional fluid sealing
- means interposed between the flange on each blade bearing
component and the said frame.
Some examples of shut~off dampers in accordance w~th
the invention are shown in the accompanying drawings, in which :-
Figure 1 is a perspective view of one form of shut-off
damper with a small portion shown in section;
Figure 2 is an exploded view in perspective of paxt of
the shut-o~f damper ~hown in Figure l;
Figure 3 i9 an enlarged si.de view o~ a bearing com-
ponent for supporting an end o~` a blade;
Figure 4 i~ a ~ection taken on the lineIV-IV in
~igure 3;
Figure 5 is an end view of the bearing component as
seen from the line V-V in Figure 3;
Figure 6 is a section taken on the line VI-VI in
~igure 5;
Figures 7 and 8 are enlarged diagrammatic sectional
views showing the blades in their open and closed position~
respectively;
Figure 9 is a greatly-enlarged section through the
: trailing edge portion of one of-the blades of the damper;
~: Figure 10 is a sectional view, on a reduced scale,
showing the damper of Figure 1 mounted in an air duct;
,r Figureg 11~ 12 and 13 are views corresponding to
Figures 1, 2 and 10 of a second form of shut-off damper; :
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Fig~re 14 is a perspective view illu~trating a modi~ica- -~
tion to the damper of ~igure~ 11 and 12; ænd
~ igures 15-19 illustrate ~ive ~urther alterna~ive ~orms
of sealing mean3 provided on the traili~.g edge~ c~ de~
~ he ~hut-off damper shown in ~igures 1 and 2 comprises
a roll-formed galvani~ed sheet steel outer ~rame 10 o~ girder ~.
section and a sheet steel inner frame 12. ~he outer frame 10
- has continuously-welded corners and has elongated holes 14 punehed
in it to permit the damper to be bolted to the flanges of a~ air
duct and to be adju~ted for height on tho~e ~langes. ~e attach-
ment by welding, bolting, rivetting or other means o~ the ~nner
and outer ~rames together prod~ces a double-skin air-tight oasing
o~ high rigidity and substantial strength.
As will be see~ from ~igure 2, the in~er frame 12 has a
series o~ holes 16 punohed in its two vertioal ~ides, the punching
operation being ~uoh that the holes 16 have a length greater than
the actual thiokness of the metal. ~he holes 16 serve to support
the shafts 18 o~ blade bearing oomponent3 19 which fit into and
onto the ope~ ends of blades 20 wh~oh are thus mounted for rot2-
tion in the frame about parallel aæes. ~he blade3 20 are low- :.
profile aspeot ratio aerofoil stainless steel blades to provide
low re~istance to air or other gaseous fluid flowing through the
d~mper, especially when the blades are in their ~ully open posit-
ions (i.e~, the posltions o~ the blade~ shown in ~igure 1 of the ~.
dra~hng~ he aerofoil ~ecti~n of the blades also reduces tur~
bulence and ~oise a~d provides excellent protection again t
corro~ion re~ulting from the presence o~ corroQi~e paxticles in
~ the air stream. Another ad~antage is that the narrow blade w1dth
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readil~ pe~mits the withdrawal o~ the complete damper ~rom a
duct, regardless of the positions o~ the blades within the damper
casing, without materially disturbing the ~low o~ alr through the
duct ~rame as a whole~
Rotation of the blades 20 about their respective axes can ~-
be e~fected either masuall~ or through power-operated mean~. In
Figure 2, a masually-rotated control knob 22 mounted on the out-
~ide of the outer ~rame 1Q has a ~ha~t 24 ~ixed to it, and this
sha~t is provided with a ~mall gear wheel 26 meshing ~ith a larger
gear wheel 28 on a sha~t 30 to provide a low-torque 4:1 rotation
gear. ~hs sha~t 30 passes through a hole 32 in a ba~e-plate 34
attached to the outer ~rame 10. ~he hole 32 is i~ alignment with
a hole 35 ~n the outer ~rame 10 so as to permit the keyed end 36
o~ the sha~t 30 to enter a rectangular-section hole 38 in the shaft
18 o~ one of the blade be æing components 19. In 90 doing, the
sha~t 30 passes through a gear wheel 40 which is keyed on to the
same sha~t 18. Each blade has a re~pective gear wheel 42 o~ the
same diameter and co~struction as the said gear l~heel 40, the ge æ
wheels 42 and the gear wheel 40 being arranged in meshing engage-
ment a~d disposed in a line vertically of the damper.
By making the sha~t 30 longer, a~ shown at 30a, an hydraulic,
pneumatic, electric or electro-magnetic motor (not shown) ma~ be
connected to the shaft so as to turn it. Remote control o~ the
blade~ then becomes possible.
It will there~ore be seen that, by rotating -the knob 22 to
rotate the gear wheel 26 and thus the gear wheel 28, or, alte~nat-
ively, by actuating a motor coupled to the shaft 30, the sha~t 30
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will be made to rota~e the particular blade 20 to which it is
connected as well as the gear wheel 40. Rotation of the gear
wheel 40 will cause rotation of all the gear wheels 42 so that
all the blades 20 will move together about their respective a~es.
However, alternate gear wheels 40, 42 will rotate in opposite
senses so that adjacent pa~rs o~ blades will likewi~e rotate in
opposite senses or directions to open or close the central pa~sage
through the damper according to which way the shaft 30 is rotated.
In order to lock the blades in a selected setting ~rhere
rotation o~ the shaft 30 is ef~ected ma~ually, a c~li~drical
locking nut 44 is provided on the sha~t 24 which carries a screw-
thre~d 46 fox this purpose. A window 48 is also provided ad~acent
the knob 22 on the co~er plate 50 80 that the setting o~ the blades
betwee~ their ~ully-open and their ~ully-closed positions can be
obsexved. ~here rotation of the 3ha~t 30 i9 e~ected by a motor,
the latter ca~ be provided with suitable locking means to lock the
sha~t. ~lso, visual indicat~ng means can be associated with a
moving part o~ the motor to indicate the positions of the blades.
In order that the v æ ious gears a~d bearings may be quiet
in operation and ha~e high strength, low weight and long li~e wlth
sel~-lubricating properties~ the gear wheels and bearings are
pre~erabl~ all made o~ a sel~-lubricating synthetic plastics
material such as mol~bdenum disulphide-impregnated nylon or poly-
e~ter. Such gear wheels and bearings can be precision-moulded and
are then totally enclosed and completely shut o~f from the ai~
stream thro~gh the damper by the outer and inner ~rames 10 and 12.
~hi~ e~sures that the gear wheels and bearing~ do not become dirty
~A or contaminated~with impurities in the alr stream.
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Figures 3-6 illustrate the detailed construction of the
blade be æing components 19 ~hich support the ends of the blades
20. As already described abo~e9 the sha~t 18 of each component 19
has a rectangular-section hole 38 90 that any selected one of the
components 19 ca~ be used to receive the keyed end 36 of the sha~t
30. ~he keying of the gear wheels 40 a~d 42 on their respective
shaIts 18 is effected by providing each sha~t 18 with two longitud-
inally-extending external slots 52 as shown in ~igures 3 and 49 the
said gear wheels being pro~ided with internal keys which enter those
slot.~ to lock the ge æ wheels against rotation on their shafts.
~ he shaft 18 of each component 19 leads up to an intermediate
flange 54 on the component which forms a sur~ace 56 opposing the
ad~ac0~t end o~ its respective blade 20. Projecting from that
surface 56 of the flange 5~ is a spigot 58 which is specially shaped
in cross--section (see ~igure 5) to enter the adjacent open end o
the blade 20 and to support that end of the blade for rotation
about an axis parallel to the leading and trailing edges o~ the
blade~ A pair of ridges 60 and 62 are also formed on the flange 54
of the blade bearing component to receive the egtreme end-portion
of the blade between them. ~hese ridges give additional support
to the blade Qnd and also give the latter a neat appearance while
ha~ing a beneficial sealing e~fect.
As already indicated in the introductory p æ t of the
Speci~ication, the shut-off damper of the present invention has
been devised to provide low resistance to air flow by the blades,
especially when they are i~ their fully-open positions, and, at
the same time, to ensure that there is a minimum or negligible
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le~kage of air past the blades when they are in their fully-closed
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positions. In this connection, it needs to be borne in mind
that shut-off dampers as used in air ducts do not generall~ ha~e
to cope with high pressure air but, in the great majority of
cases, only with air at comparatively low pressure.
~ o prevent leakage at the longitudinal edges o~ the blades,
each blade 20 has fluid sealing means exte~ding along it~ trailing
edge so that a good seal is foxmed betwee~ adjacent blades when
they are in their closed positions. ~he sealing means and the
precise shape o~ the blade trailing edge c~n take various ~orms -
as will be seen ~rom the description c~ alternati~e constructions
described below - but the pre~erred blade shape ~d seal~ng means
is illustrated in ~igures 7 to 9. From these figures it will be
~een that, after the blade has been bent into blade-shape ~rom a
~lat rectangular sheet of stainless steel, it is sealed by being
welded, bra~ed, rivetted or otherwise connected alo~g a zone 64
~see Figure 9) adjacent its ~railing edge~ At the same time, its
trailing edge portions 66 and 68 are "opened-out" to ~orm a V-
section fish tail portion which is thus adapted to embrace the
respective rounded leading edge portions o~ ad~acent blades when
the latter are in their closed positions. ~his is illustrated i~
~igure 8. It will be noted that, whereas the "turned-out" trail-
ing edge portion 68 i~ entirely straight, the trailing edge portion
66 is straight ~or part o~ its total area and is then curved
æ cuately over the remaining part ~or an angul æ distance o~ 60.
~hi~ permitæ the tralling edge portion 68 to conform clo~ely to
the rounded leading edge of an a~jacent blade whe~ the blades æ
in their closed position~.
Bonded or otherwise fastened along the trailing edge o~
each blade is a tubular sealing member 70 as ~hown in ~igure 9
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and the fo~r uppexmosl blades in Figures 7 and 8. Alternatively,
a solia strip 72 of sealing material as exemplified by the lower-
most blade in Figures 7 and 8 c2n be used instead of the tubular
sealing member 70. The sealing tube 70 or the sealing strip 72
can be made of neoprene, polyvinyl chloride, foamed synthetic
plastics material, or some other rubbe~y or resilient sealing
material. ~ecause the sealing tube 70 or the sealing strip 72 is
located partially within the V of the fish-tail portion, the tube
70 or the strip 72 will be highly compressed by the leading edge of
an adjacent blade when the blades are in the poæitions shown in
Figure 80 By this means 7 leakage o~ air at the leading and trailing
edges of the blades can be reduced~ in practioe, to a negligible
amount.
~ o æeal the leading edge of the uppermost blade 20, a sealing
~trip or tube 7~ of the ~ame mater~al as the tube 70 or the strip
72 is bonded along the upper inner surface of the inner frame 12 as
shown in Figure 8. Alternatively, springy metal sealing strips 72a
and 73a can be used in place of the sealing strips 72 and 73.
~ he damper illu~trated in ~igure~ 9 is designed to be in-
serted in a duct by ha~ing the flanges 74 of the outer casing 10
bolted to corresponding flanges 76 of the duct by bolts 77 as shown
in ~igure 10, In other words, the damper is inserted in a "break"
in the duct so that the inner frc~me 12 is substanbially flush with
the internal surfaces 78 of the duct. Howe~er, in certain coun-
tries - particularly the United States of America - it is customary
to position dampers entirely within a duct. Figures 11 and 12
illustrate a damper having a frame 80 ~hich permits this to be
done. ~he frame 80 iæ, in effect, the 3ame as the inner ~rame 12
in ~ig~lre 2 except that the frame 80 has
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flanges 82 which lie against the inner surface 84 of a duct as
shown in ~igure 13a The duct itself therefore form~ an outer
frame for the damper so that the outer frame 10 of ~igure 1 is no
longer needed. Apart from thi~s e~d the omi~sion of the base-plate
34 shown in ~igure 2 7 the damper shown in Figures 11 and 12 is
essentially the same as that shown in Figures 1-97 and the same
reference numerals have been applied to like parts.
Figure 14 illustrates a small modification to the damper
shown in Figures 11 and 12 in that the cover plate 50 is designed
to be screwed or bolted to the inside or outsiae of a duct 86, the
cover plate having a pair of flanges 88 with bolt or screw holes
90 in it to permit this to be done. A small window 92 is cut in
the wall of the duct 86 to allow the shafts 24 and/or 30a to pro-
ject through that wall and thus enter.the cover plate 50. Screw
or bolt holes 9~ are also provided in the duct wall to match the
holes 90 in the ~langes 88.
In order to strengthen the inner frame 12 of Figure 2 and
the frame 80 of ~igures 12 and 13, I-shaped metal corner pieees 96
are welded 7 rivetted or otherwise fixed to the corners of those
~rames .
Figures 15 to 19 illustrate alternati~e forms of blade 20
and alternative trailing edge sealing means in accordance wlth the
invention, and these will now be described.
In Figure 15, the trailing edge o~ the blade 20 is formed
by the two edge portions 98 and iO0, the edge portion 100 being
~ormed by doubling over the extreme edge o~ the blade O ~he two
edge portions 98 and 100 nip between them a root portion 102 of
a sealing strip 104 fo~med of neoprene or other rubbery sealing
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materialO The said sealing strip has a well-rounded external
surface 106 which faces away ~rom the metal trailing edge o~
the bl~de, and from this 3urface 106 there e~tend~ two webs i08
and 110, one on each side of the blade, so as to provide a smooth
stream-lined surface with the metal portion of the blade 20~ .
~ he sealing strip shown at 112 in ~igure 16 has a stem 102
like that shown in Figure 15 ~ut is here formed with a circular-
section portion 114. ~his construction is not there~ore ~o
stream-lined as the ~ealing ~trip shown in ~igure 15 with itq
lateral webs 108 and 110.
~ igure 17 illustrates another alternative in which the
metal portion of the blade 20 is formed with a flat trailing
edge ~ace 116 which has, bonded to it, the flat face of a DL
section hollow 3ealing strip 118.
~ igure 18 shows a blade 20 ha~ing an edge portion 120
which is be~t over so as to lie ~lat against the outer ~urface
o~ the edge portion 122, the two overlapping portions being spot
welded at regular points along the length of the blade. ~he
sealing means at the trailing edge of the blade compri~e a ~trip
12~ of ~lexible neoprene or other rubbery sealing material whlch
has been folded over in a C~shape and removably held on the
trailing edge portlon o~ the metal blade 20 by a C-section springy
metal clip 126. ~he longitudinal edge~ of this clip 126 are bent
back at 128 and 130 80 as to nip the longitudinal edge portions
132 ~nd 134 of the se~1ing strip.
It has been found that the existence o~ the small shoulder
136 formed by the tur.ned-over edge portion 120 of the metal blade
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is suf~icient to prevent the clip 126 from coming off the bladeO
~aturally, the spring clip 126 will ha~e su~ficient resilience
to grip the blade quite strongl~.
Yet another alternative construction is shown in ~igure 19.
In this case, the sealing strip 124 has its longitudinal edge
portions 138 and 140 ~olded under.neath the longitudin~l edge
portions 142 and 144 of the spring cli.p 126. A further di~fer- ..
ence is that the said edge portions of the spring clip 126 æ e
located inwaxdly of the strip 124 and not externally o~ it as
i~ ~igure 18.
In order tha~ air may not leak round the ends of the
blades when they æe in their ~ully-closed posi-tions, sealing
strip~ or pad~ 146 made o~ felt or other ~eallng material are
provided on the blade bearing component~ as ~hown in ~igure~ 3
5 and 6.
~ he extent to which the blades cc~n be rotated about their
respective axes can be va~ied to suit the requirements of di~fe =
ent customers. ~ormally they will be rotatable through ~0
to provide for maxlmum ~lexibility in use.
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