Note: Descriptions are shown in the official language in which they were submitted.
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The prcsent invention relates to an isolation damper for
gas ducts and more particularly to an isolation damper of the
slide type.
Isolation dampers are used to close off a gas duct. A
valve member of some type in the damper is brought into
sealing engagement with the seat of the damper, or some other
sealing element, to form a gas tight seal preventing gas
leakage past the damper. Conventional dampers are of three
types viz., the poppet type wherein a flexible sheet of steel
is deformed onto the seat of the damper under system pressure
or negative pressure; the slide type in which an inflexible
steel plate is slid across the duct and into sealing
engagement with sealing means on the damper seat and the
butterfly type in which two pivotably connected inflexible
plates are folded into or out of sealing engagement with the
sealing means on the damper seat. Ihe poppet type valve
cannot be conveniently used as an isolation damper
intermediate the ends of a gas duct. The slide type suffers
from the disadvantages that, firstly, a secondary seal
system, which is susceptible to wear, is required to make
sealing contact with the slide and, secondly, a housing is
required to hold the plate when it has been withdrawn from
the duct which is both unsightly and expensive to build.
The present invention is directed to a slide type
isolation damper which does not have the disadvantages of
known slide type dampers while having the advantage of the
poppet type valve.
The present invention consists in an isolation damper
for a gas duct comprising a damper blade, a pair of guide
m0mbers adapted to guide the damper blade along a path
transverse to the gas duct, and means to move the damper
blade along the said path between a first position in which
the damper blade extends across the duct and a second
position in which it is substantially withdrawn from the
duct, the arrangement being characterised in that the damper
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blade is relatively thin and flexible such that when in the
first position and under an applied gas pressure it can
elastically deform to enter into sealing engagement with the
guide members and in that there is disposed intermediate the
guide members, and in close juxtapostion with at least one
side of the path of the damper blade, a plurality of support
elements against which the damper plate can bear when
pressure is applied to the face of the damper blade distal to
the support elements.
The use of a thin, flexible damper blade allows the
blade to be elastically deformed onto the guide members,
which constitute the damper seat, without the need for a
secondary sealing system. The flexibility of the blade also
allows the blade to follow a non-linear path as it is
introduced into, and drawn out of, the duct. The blade
could, for instance lie in a plane parallel to and slightly
above the gas duct and be turned through 90 just before
entering the duct. In this way the isolation damper could be
made more cheaply and would be less unsightly.
The damper blade is preferably formed of a material such
as stainless steel and preferably has a thickness of no more
than 5 mm., preferably no more than 3 mm. The use of such a
thin damper blade facilitates the movement of the blade into
and out of the duct as the thin blade can cut through any
duct accumulation which occurs in the guide means.
The support elements preferably comprise an array of
parallel bars or rods, however a grid of such bars or a
perforate plate could also be used provided that the flow of
gas through the duct is not unduly impeded. The support
elements are preferably provided on each side of the damper
blade path such that the damper blade will be supported
against undue deformation upon the application of a positive
pressure to either of its faces.
Hereinafter given by way of example only is a preferred
embodiment of the invention described with reference to the
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accompanying drawings in which:-
Fig. 1 is vertical sectional view through an isolationdamper according to this invention, and
Fig. 2 is a view along A-A of Fig. 1.
The isolation damper 10 is mounted in a gas duct 11, the
gas moving through the duct in the direction of the arrow B
of Fig. 1. The damper comprises a damper blade 12, a frame 13
surrounding the duct 11 which frame includes a pair of
channel shaped side members 14 constituting guide members for
the damper blade 12, and drive means 15 to move the damper
blade 12 into and out of the duct 11.
The damper blade 12 comprises a sheet of stainless steel
3 mm. thick which is connected at its end remote from the
duct to the drive means 15 as hereinafter described. The
blade extends horizontally at the point of its connection to
the drive means 15, it then turns through 90 before
entering the guide slots 16 defined by side members 14.
The frame 13, in addition to the side members 14,
includes a base member 17 and a top member 18. The base
member 17 includes a longitudinally extending slot 19 in
alignment with slots 16 in the side members 14, and into
which the lower end of the damper blade 12 slides when the
damper is fully closed. A flap 20 is hingedly connected to
the underside of the base member 17 and can be opened to
release dust which has lodged in the frame. A plurality of
support bars 21 extends between the base member 17 and the
top ~ember 18 on either side of the path traversed by the
damper blade 12. The bars 21 are formed of mild steel or
erosion resistant steel and may have an aerodynamically
efficient cross sectional shape if desired.
The top member 18 may be formed with a removable top
cover 22 such that the slot 23 in the top member through
which the damper blade 12 is introduced into the frame 13 may
be closed when the damper blade 12 is completely removed from
the frame 13.
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The drive means 15 comprises a reversible motor 24 which
drives a pair of endless chains 25 about drums 26. The
chains are connected to the free end of the damper blade 12.
Upon actuation of the motor 24 the damper blade 12 can be
moved into or out of the duct 11.
If the damper blade 12 is introduced fully into the duct
11 and a force applied to one side of the blade 12 it will be
elastically deformed against the edges of the slots 16, 19
and 23 of the frame 13 and will sealingly engage therewith in
view of the relatively thin, flexible, nature of the damper
blade 12. As the blade 12 is forced against the edges of the
slots it will similarly be forced against the support bars 21
on the side of the slots opposite the direction from which
the force is applied to the blade 12. The support bars 21
give to the damper blade 12 the structural integrity lacking
due to its flexible nature.
